SERV1804 July 2005
GLOBAL SERVICE LEARNING TECHNICAL PRESENTATION
994F WHEEL LOADER INTRODUCTION
Service Training Meeting Guide (STMG)
994F WHEEL LOADER - INTRODUCTION MEETING GUIDE 804 AUDIENCE Service personnel who understand the principles of machine systems operation, diagnostic equipment, and testing and adjusting procedures.
CONTENT This presentation describes the location of the basic components on the engine, and the operation of the power train, implement, steering, and brake systems for the 994F Wheel Loader.
OBJECTIVES After learning the information in this presentation, the serviceman will be able to: 1. locate and identify the major components in the engine, power train, implement, steering, and brake systems; 2. explain the operation of each component in the power train, implement, steering, and brake systems; and 3. trace the flow of oil through the power train, implement, steering, and brake systems.
REFERENCES 994F Wheel Loader Specalog 994F Wheel Loader Service Manual 994F Wheel Loader Parts Book Video "994F Wheel Loader - Introduction" TIM "992G Wheel Loader - Steering and Brake Systems "
AEHQ5460 RENR2500 SEBP2793 SEVN4643 SERV2632-01
PREREQUISITES Interactive Video Course "Fundamentals of Mobile Hydraulics" Interactive Video Course "Fundamentals of Machine Electronics"
Estimated Time: 12 Hours Visuals: 210 Illustrations Handouts: 39 line drawings Form: SERV1804 Date: 7/05 © 2005 Caterpillar Inc.pillar Inc.
TEMV9001 TEMV9002
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TABLE OF CONTENTS INTRODUCTION ..................................................................................................................7 Component Location.........................................................................................................8 Similarities and Differences .............................................................................................9 ENGINE ELECTRICAL BLOCK DIAGRAM....................................................................11 Engine Right Side ...........................................................................................................13 Turbocharger Inlet Pressure Sensor................................................................................15 Primary Speed Timing Sensor ........................................................................................16 Rear Pump Drive Lubrication.........................................................................................17 Atmospheric Pressure Sensor .........................................................................................18 Permanent Speed Timing Sensor....................................................................................19 Aftercooler Temperature Sensor.....................................................................................24 Engine Coolant Flow Switch..........................................................................................26 Jacket Water Temperature Sensor...................................................................................27 Crankcase Pressure Sensor .............................................................................................28 ENGINE COOLING SYSTEM............................................................................................30 Turbocharger Cooling System ........................................................................................32 Radiator Group ...............................................................................................................33 Fuel Filter Differential Switch........................................................................................35 Electric Fuel Priming Pump ...........................................................................................36 Fuel System.....................................................................................................................37 Engine Oil System ..........................................................................................................38 Throttle lock....................................................................................................................39 Throttle Lock ..................................................................................................................40 Throttle Lock Circuit ......................................................................................................41 Engine Derates................................................................................................................42 Engine Air Start System .................................................................................................46 Air Start System - De-energized.....................................................................................48 Air Start System - Energized ..........................................................................................49 Service Fill......................................................................................................................50 Oil Renewal System (ORS)............................................................................................51 Service Fill......................................................................................................................53 Oil Renewal Tank ...........................................................................................................54 Metering Valve................................................................................................................55 Variable Clutch Fan Control ...........................................................................................57 POWER TRAIN ...................................................................................................................60 Power Flow .....................................................................................................................60 Power Train Electrical System .......................................................................................61 Power Train Electronic Control System (ECM).............................................................64 Engine Speed Sensor ......................................................................................................66 Reduced Rimpull Selection Switch ................................................................................69
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TABLE OF CONTENTS Torque Converter ...........................................................................................................73 Transmission Oil Filters..................................................................................................77 Torque Converter ............................................................................................................78 Transmission ..................................................................................................................79 Transmission Hydraulic Control Valve...........................................................................83 Transmission Hydraulic Control Valve - NEUTRAL ....................................................84 Power Train Hydraulic System - NEUTRAL.................................................................86 Cold Power Train Engine Speed Limiting .....................................................................98 Auto Lube System ..........................................................................................................99 994F Wheel Loader Torque Strategy............................................................................105 IMPLEMENT HYDRAULIC SYSTEM............................................................................108 Implement Electronic Control System .........................................................................109 Implement Electronic Control Module (ECM).............................................................111 Front Pump Drive Lubrication System.........................................................................120 Front Pump Drive System ............................................................................................121 Implement Pilot Hydraulic System - Hold ...................................................................122 Dead Engine Lower ......................................................................................................124 Implement Pilot System................................................................................................125 Pilot Control Valve .......................................................................................................127 Tilt Pilot Control Valve.................................................................................................128 Lift Pilot Control Valve ................................................................................................129 Implement Hydraulic System Not in Dig Trigger Mode .............................................131 Implement Hydraulic System In Dig Trigger Mode ....................................................132 Variable Implement Piston Pump Control....................................................................140 Implement Hydraulic Oil Cooling System ...................................................................157 Implement Hydraulic Oil Cooling System - Filter Group ...........................................158 STEERING HYDRAULIC SYSTEM................................................................................161 Steering System Components .......................................................................................161 Steering System ............................................................................................................163 Steering Pilot Valve .....................................................................................................173 Steering Hydraulic System ..........................................................................................179 STEERING OIL COOLING SYSTEM..............................................................................184 Steering Oil Cooling System ........................................................................................186 BRAKE SYSTEM ..............................................................................................................188 Brake System Components...........................................................................................188 Brake System Schematic - Engine Not Running - Parking Brake Engaged................189 Brake System Schematic - Engine Running - Parking Brake Disengaged ..................191 Brake System Schematic - Engine Running - Service Brakes Engaged......................192 Hydraulic Brake System Control..................................................................................193 Service Brake Valve OFF ............................................................................................195
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TABLE OF CONTENTS Service Brake Valve ON...............................................................................................197 Service Brake Valve Balanced......................................................................................198 Brake Pump...................................................................................................................201 Parking Brake ...............................................................................................................205 Brake Oil Cooler System..............................................................................................208 Service Brake Cooling Screen Group...........................................................................213 Vital Information Management System (VIMS) ..........................................................214 Vital Information Management System (VIMS) ..........................................................216 CONCLUSION...................................................................................................................229 HYDRAULIC SCHEMATIC COLOR CODE...................................................................230 HANDOUTS.......................................................................................................................231
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994F WHEEL LOADER INTRODUCTION
© 2005 Caterpillar Inc.
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INTRODUCTION This presentation discusses the component locations and systems operation of the 994F Wheel Loader. Basic engine and machine component locations will be discussed. Also, the operation of the power train, the implement hydraulics, the steering, and the braking system’s component location will be covered. The 994F Wheel Loader is the largest wheel loader in the Caterpillar product line. The loading capacity is matched with the 785 Off-highway Truck (Standard Machine), the 789 Off-highway Trucks (High Lift) and 793 Off-highway Truck (Super High Lift). The new 994F Super High Lift can be equipped with a 35.9 cubic meter (47 cubic yard) coal application bucket. The 994F Wheel Loader operating weight is approximately 160,200 Kg (429, 300 lbs) for a Standard Machine, 160,800 Kg (430,900 lbs) for the High Lift, and 174,300 Kg (467,000 lbs) for the Super High Lift. The serial number prefix for the 994F Wheel Loader is 442.
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994F WHEEL LOADER COMPONENT LOCATION Steering Pump Rear Pump Drive Brake Pump
Input Input Auxiliary Transmission Drive Shaft Transfer Gear Drive Shaft Pilot Pump Front Pump Drive Implement Pumps Tilt Cylinders
Radiator Group and Coolers
Hydraulic Tank Implement Valve
3516B HD Engine
Spring Coupling
Final Torque Transmission Secondary Output Drive Converter Pump Steering Transfer Gear Pump
Engine
Moving Parts
Parking Brake
Power Train
Drive Shaft
Final Drive
Hydraulics
2 Component Location This illustration shows the basic component locations on the 994F. The component locations on the 994F are basically the same as the 994D but are restated as a reminder. Power for the 994F is supplied by the 3516B High Displacement (HD) engine. The engine is connected to the rear pump drive with a spring coupling. Power flows from the rear pump drive to the torque converter, to the input drive shaft, and through the input transfer gear to the transmission. Power from the transmission flows through the output transfer gears to the drive shafts, to the bevel gears in the differentials, and then to the double reduction final drives. The 994F also has an auxiliary drive shaft that turns the front pump drive. The front pump drive is located in the loader frame. The secondary steering pump is splined to the output transfer gears. The secondary steering pump is ground driven.
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SIMILARITIES AND DIFFERENCES FEATURES
DIFFERENT
SIMILAR
Machine Appearance
SAME X
Operator's Station
X
Engine
X
Transmission
X
Implement Hydraulic System
X
Steering System
X
Brake System
X
Monitoring System
X
Maintenance Items
X
3 Similarities and Differences This illustration compares the basic features of the 994F Wheel Loader to the previous 994D Wheel Loader. The machine appearance and the implement hydraulic system are basically the same as the 994D with the addition of a variable displacement piston pump in tandem with the center fixed displacement piston pump on the front pump drive. The main relief pressures have been increased from 30400 kPa (4400 psi) on the 994D to 32775 kPa (4750 psi) on the 994F. The 994F is equipped with a 3516B HD EUI as compared to the 3516B EUI in the 994D. The new engine delivers 1,436 horsepower. This is an increase of 14%. The 994F features new turbochargers, high-capacity air filters, and dual 80-amp alternators. Access to the implement pump case drain filters and the transmission and torque converter filters has improved from the previous version of the 994D. The 994F is installed with a lift linkage position sensor supporting in the cab control of the variable lift kickouts. Also, the 994F is equipped with remote pressure taps for the various hydraulic systems.
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The 994F has both starter and transmission lockout switches and an engine shutoff switch at ground level for easy access. Also, the 994F has the optional Oil Renewal System (ORS) which offers a means to reduce the amount of oil changes and increased machine availability. The power train difference between the 994F and 994D is the removal of the free wheel stator and the torque converter outlet relief valve. The 994F power train is now equipped with two additional air-to-oil coolers in order to increase cooling of the power train system. The 994F has a fully modulated impeller clutch torque converter with flexibility of reducing rimpull using the left brake pedal. The pedal fully modulates the rimpull through the range of 100% to 35%. Also, the 994F power train has remote pressure taps installed. The braking system on the 994F has increased circuit pressure and now features a split control system. The operator station on the 994F has a larger cab with an approximate 75dBa sound level. A Caterpillar seat with state of the art suspension is installed. Also, the cab has a trainer seat with a padded seat and back. The new cab has 50% more glass area increasing visibility. The 994F retains the Steering and Transmission Integrated Control (STIC) power train which enables the operator to use small movements of a single hand to steer the machine and make direction/gear changes. The maintenance items on the 994F are similar to the 994D. The major changes in the maintenance are access to the filters on the 994F. The 994F is equipped with the latest Vital Information Management System (VIMS) that is similar to the 994D. NOTE: For more information on the VIMS refer to the VIMS Service Manual RENR6318
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994F BASIC ENGINE BLOCK DIAGRAM J2
16 Electronic Unit Injectors
J1
Engine ECM
Ground Bolt Jacket Water Temperature Sensor
Primary Speed Timing Sensor
Aftercooler Coolant Temperature Sensor
Fuel Filter Differential Switch Oil Level Add Switch
Permanent Speed Timing Sensor
Coolant Flow Switch
Crankcase Pressure Sensor
Left Exhaust Temperature Sensor
Turbocharger Outlet Pressure Sensor
Right Exhaust Temperature Sensor
Filtered Oil Pressure Sensor Unfiltered Oil Pressure Sensor
Cooling Fan Speed Sensor (Attachment)
Left Turbocharger Inlet Pressure Sensor
Atmospheric Pressure Sensor Right Turbocharger Inlet Pressure Sensor Main Power Relay Coil Ground Level Shutdown Switch Engine Shutdown Relay To EUI Cooling Fan Proportional Valve (Attachment)
Machine Interface Connector
Machine Interface Connector
4 ENGINE ELECTRICAL BLOCK DIAGRAM This block diagram of the engine electrical system shows the components that are mounted on the engine which provide input signals to and receive output signals from the Engine Electronic Control Module (ECM). Based on the input signals, the Engine ECM energizes the injector solenoid valves to control fuel delivery to the engine, and energizes the cooling fan proportional solenoid valve to adjust pressure to the optional cooling fan clutch. The two machine interface connectors provide electrical connections from the engine to the machine including the Cat Data Link. Some of the components connected to the Engine ECM through the machine interface connectors are: the throttle pedal position sensor, the throttle lock switches, the throttle lock enabled indicator, the right brake pedal switch, the ether start control solenoid, and the ground level shutdown switch.
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Input Components: Primary speed timing sensor - The speed timing sensor sends a fixed voltage level signal to the Engine ECM in order to determine the engine speed, direction, and timing. Oil level switch - The oil level switch (lower) is a float type switch mounted in the side of the engine oil sump. The Engine ECM monitors the engine oil level switch to alert the operator when the oil level is low. Coolant flow switch - The coolant flow switch mounts in the coolant passage near the engine coolant pump. When the coolant is flowing past the switch the paddle moves and closes the switch contacts. The Engine ECM alerts the operator when there is no coolant flow while the engine is running. Exhaust temperature sensors - The exhaust temperature sensors communicate the exhaust temperature to the Engine ECM. Permanent speed timing sensor, cooling fan speed sensor (if equipped), - These speed sensors are passive speed sensors that provide a signal similar to a sine wave that varies in amplitude and frequency as speed increases. The permanent speed timing calibration sensor monitors the speed and position of the flywheel. Jacket water temperature sensor, aftercooler coolant temperature sensor - These temperature sensors are analog temperature sensors that provide a signal to the Engine ECM. Crankcase, atmospheric, turbocharger outlet, filtered and unfiltered oil, left and right turbocharger inlet pressure sensors - These sensors are analog sensors that provide a voltage signal to the Engine ECM. The signal varies to a level that corresponds with a calibrated pressure. The Engine ECM calibrates the pressure sensors to the atmospheric pressure when the key start switch is moved to the ON position for 10 seconds without the engine running. Fuel filter differential switch - The fuel filter differential switch is a pressure switch. The contacts open when there is a restriction in the fuel line from the secondary fuel filters. Note: The cooling fan proportional valve and the cooling fan speed sensor are attachments. The valve and the sensor are installed with the variable speed cooling fan system (Rockford Fan System).
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Engine Right Side This view shows the right side of the engine that is accessed from the left side of the machine. Components which can be seen are: - Turbocharger (1) - Coolant regulator housing (2) - Engine oil cooler (3) - Electric fuel priming pump filter (4) - Alternator (5) - Transmission cooler (coolant-to-oil) (6) - Permanent speed timing sensor (7) - Crankcase pressure sensor (8)
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This illustration shows the machine controls that are located at the rear of the machine. The following is a list of the ground level components: - Ground level shutdown (1) - Hood lamp (2) - Ground level stair lamp (3) - VIMS key switch (4) - VIMS serial download port (5) - Hour meter (6) - Start lockout indicator (7) - Transmission lockout LED (8) - Transmission lockout switch (9) - Start lockout switch (10) - Locks (11)
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Turbocharger Inlet Pressure Sensor This illustration shows the left turbocharger inlet pressure sensor (2) and right turbocharger inlet pressure sensor (3). The illustration shows the sensors on the turbochargers (1) that are installed on the front of the engine (located toward the rear of the machine). These analog sensors read the pressure in the turbo inlets and send a corresponding signal to the Engine ECM. The left turbocharger inlet pressure sensor (2) and the right turbocharger inlet pressure sensor (3) communicate with the Engine ECM. The Engine ECM provides an input to the VIMS module informing the operator of an air filter restriction. When an air filter becomes plugged and restricts air available for combustion resulting in elevated exhaust temperatures, the Engine ECM sends a signal to the injectors to decrease the flow of fuel. The Engine ECM receives signals from the turbocharger inlet pressure sensors and determines inlet air restriction by subtracting the turbocharger inlet air pressure that is measured by the turbocharger inlet air pressure sensors from the atmospheric air pressure. The Engine ECM derates the power by 1% when the inlet air restriction reaches 6.5 kPa (25 inches of water). This derate will increase at a rate of 2% kPA of restriction until the maximum derate of 20% is reached. The engine will default to a maximum derate of 20% if the Engine ECM detects a fault in the circuits for the left or right turbocharger inlet pressure sensors. Also shown are the inlet tubes (4).
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8 Primary Speed Timing Sensor The primary speed timing sensor (1) is positioned near the rear of the left camshaft. The sensor signals the speed, direction, and the position of the camshaft by counting the passing teeth and measuring the gaps between the teeth on the timing wheel that is mounted on the camshaft. The primary speed timing sensor receives has an input voltage of 12 VDC. If the Engine ECM does not receive an input signal from the sensor, the engine will not start. Also shown is the Engine ECM (2).
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REAR PUMP DRIVE LUBRICATION
From Transmission Oil Coolers
9 Rear Pump Drive Lubrication The rear pump drive is attached to the engine and drives the steering pumps, brake pump, the steering and brake cooling pump, and the brake cooling pump. The rear pump drive is lubricated with oil from the torque converter outlet that has been cooled by air-to-oil coolers or the coolant-to-oil coolers. The oil lubricates the bearings and gears in the rear pump drive.
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10 Atmospheric Pressure Sensor The atmospheric pressure sensor (1) is located towards the rear of the machine next to the Engine ECM (2). The Engine ECM uses the atmospheric sensor as a reference for calculating boost pressure, and air filter restriction. The sensor also is used to supply information to the Engine ECM to derate the engine at high altitudes. The atmospheric pressure sensor uses 5 VDC that is supplied by the Engine ECM. The sensor is used for altitude derate. If the machine is operating above 10,000 feet, the engine will derate 1% for every kPa of atmospheric pressure below 70 kpa or 3% per 1,000 foot increments above 10,000 feet. If the Engine ECM detects a loss of the signal from the atmospheric pressure sensor, the ECM will derate the engine to a maximum derate of 24%. The Engine ECM uses the atmospheric pressure sensor as a reference when calibrating the pressure sensors. The pressure sensor calibration receives an auto calibration enable command 10 seconds after ECM power-up. The auto calibration will occur when auto calibration is enabled and engine speed is 0 rpm. All pressure sensors will be sampled at 30 msec. The calibration function will then perform a 2 second average on the individual sensors for calibration.
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11 Permanent Speed Timing Sensor The permanent speed timing sensor is used for timing calibration through Electronic Technician (ET). The permanent speed timing sensor is located on the left side of the machine and installed in the torque converter housing.
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This illustration shows two engine oil level switches. Oil level switch (3) communicates with the Engine ECM. This switch opens the circuit when the oil level is below the necessary level. Oil level switch (2) communicates with the VIMS module. The oil level switch (2) signals that oil should be added to the engine. If the machine is equipped with the optional Oil Renewal System (ORS), level switch (2) will disable the ORS when the oil level is low. Also shown is the engine oil filler tube (1).
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This illustration show the right side turbo inlet exhaust temperature sensor (1). The engine is also equipped with a turbo inlet exhaust temperature sensor on the left side (not shown). The sensors communicate with the Engine ECM. The Engine ECM provides an input signal to the VIMS module to inform the operator of the exhaust temperature. Some causes of high exhaust temperature may be faulty injectors, plugged air filters, or a restriction in the turbochargers. When the highest temperature of the right or left turbine inlet temperatures goes above 750º C (1382º F) for 15 seconds, the torque map is reduced by 2%. If the measured temperature does not return to below 750º C (1382º F) within a 15 second interval, the torque map will be reduced by 2%. This will continue in 2% steps with each step lasting 15 seconds until the temperature drops below 750º C or the maximum derate of 20% is reached. The last derate level reached will remain active until the engine is powered down. If a failure is detected in either the left or right exhaust temperature sensor circuits, the Engine ECM will default to the maximum derate value of 20%. An exhaust temperature derate occurrence will log an Engine Event in the Engine ECM that requires a Level 3 password to clear.
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The illustration above shows the location of the Engine ECM (1) and the atmospheric pressure sensor (2). The Engine ECM is an ADEM III module and is equipped with two 70 pin connectors. The Engine ECM (1) is mounted on the engine on the right side of the machine. The engine ECM is accessed from below the machine. The Engine ECM makes decisions based on control program information in memory, switch inputs, analog input signals, and sensor input signals. The Engine ECM responds to machine control decisions by sending a signal voltage to the appropriate circuit which creates an action. For example, as the operator depresses the throttle pedal, the Engine ECM interprets the input signal from the throttle pedal position sensor, evaluates the engine status, and sends a signal to the injectors to increase fuel. The Engine ECM receives three different types of input signals: 1. Switch input: Provides the signal line to battery, ground, or open. 2. PWM input: Provides the signal line with a square wave of a specific frequency and a varying positive duty cycle. 3. Speed signal: Provides the signal line with either a repeating, fixed voltage level pattern signal or a sine wave of varying level and frequency.
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The Engine ECM has three types of output drivers: 1. ON/OFF driver: Provides the output device with a signal level of +Battery voltage (ON) or less than one Volt (OFF). 2. PWM solenoid driver: Provides the output device with a square wave of fixed frequency and a varying positive duty cycle. 3. Controlled current output driver: The ECM will energize the solenoid with 1.25 amps for approximately one half second and then decrease the level to 0.8 amps for the duration of the on time. The initial higher amperage gives the actuator rapid response and the decreased level is sufficient to hold the solenoid in the correct position. An added benefit is an increase in the life of the solenoid. The Engine ECM receives signals from the speed timing sensors, oil level switch, coolant flow switch, exhaust temperature sensors, coolant temperatures sensors, engine pressure sensors, and the current engine operating status. The Engine ECM interprets signals and determines the appropriate output signals to the engine. Different conditions of the inputs affect the output conditions. The Engine ECM communicates through the CAT Data Link. The CAT Data Link allows high speed proprietary serial communications over a twisted pair of wires. The CAT Data Link allows different systems on the machine to communicate with each other and also with service tools such as Caterpillar Electronic Technician (ET). The Engine ECM has built-in diagnostic capabilities. As the Engine ECM detects a fault condition developed by the engine, The ECM logs the faults in memory and displays them on the VIMS. The fault codes can also be accessed using the ET service tool. VIMS software can be used to view faults logged by the VIMS. INSTRUCTOR NOTE: Engine ECM faults displayed on the VIMS relating to the Engine ECM will have a Module Identifier (MID) of "36." For more information, refer to the Service Manual module "Engine, Systems Operation Testing and Adjusting" (Form RENR2211).
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15 Aftercooler Temperature Sensor The aftercooler temperature sensor (arrow) is located at the rear of the engine at the firewall. The sensor reads the temperature of the coolant that is flowing through the aftercooler. The sensor sends an analog signal voltage to the Engine ECM. The sensor along with the water jacket temperature sensor to control the engine timing and cold mode functions. If the aftercooler temperature sensor exceeds 107° C (226° F), the Engine ECM will log an event that requires a factory password to clear.
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This is a partial view of the front right side of the engine. The illustration is showing the location of the following components on the right front side of the engine: Components which can be seen are: - Electric fuel priming pump filter (1) - Alternator (2) - Air conditioning compressor (3) - Engine oil cooler (4) - Fuel transfer pump (5) - Coolant flow switch (6) - Coolant pump for jacket water (7)
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17 Engine Coolant Flow Switch The coolant flow switch monitors the amount of coolant that is flowing from the water pump through the various oil coolers. The coolant flow switch (1) sends an input to the Engine ECM. and the ECM provides an input signal to the VIMS module informing the operator of the coolant flow status. If the ECM detects a low coolant flow condition, a low coolant flow event will be logged. A factory password is required to clear the event. Jacket water coolant samples can be taken at the Scheduled Oil Sampling (S•O•S) port (2).
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Jacket Water Temperature Sensor In this illustration, the jacket water temperature sensor (1) is located on the right side of the machine in the end of the jacket water. The sensor sends an analog signal to the Engine ECM. Then, the Engine ECM sends a signal to the VIMS module displaying the engine coolant temperature. The Engine ECM uses the coolant temperature information for cold mode functions such as: a timing change, elevated idle, cold cylinder cut-out, and ether injection. If the jacket water cooling system temperature exceeds 107° C (226° F), the Engine ECM will log an event that requires a factory password to clear. Also shown is the turbocharger outlet pressure sensor (2).
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Crankcase Pressure Sensor The crankcase pressure sensor (arrow) is located on the right side of the engine above the engine oil cooler. The sensor provides an input to the Engine ECM, which informs the operator of the crankcase pressure. High crankcase pressure may be caused by worn piston rings or cylinder liners. The crankcase pressure sensor initiates an event when the crankcase pressure is above 3.6 kPa (0.5 psi) for three seconds. No factory password is required to clear the event
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This illustration shows the left side of the 3516B HD engine which can be accessed from the right side of the machine Components that can be seen include: - Left side alternator (1) - S•O•S port for the Separate Circuit After Cooler (SCAC) coolant (2) - Fuel filters (3) - Engine oil filters (4) - Air compressor (5) - Separate Circuit After Cooler (SCAC) water pump (6) - Engine oil fill tube (7)
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994F ENGINE COOLING SYSTEM NEXT GENERATION MODULAR RADIATOR (NGMR) Separate Circuit Aftercooler (SCAC) Radiator
Engine Coolant Radiator Regulator Housing
Direction of Air Flow
Aux. Coolant Pump
Radiator Bypass Direction of Air Flow
Main Coolant Pump
Brake Oil Cooler Aftercoolers To / From Service Brakes Hottest
To / From Transmission
Engine Oil Cooler
Increasing Coolant Temperature
Power Train Oil Cooler
Coldest Hot SCAC Coolant
21 ENGINE COOLING SYSTEM This illustration shows the flow of the engine coolant from the main coolant pump through the radiator, the engine, the oil coolers. Also, the machine is equipped with a Separate Circuit After Cooler (SCAC) coolant through the after coolers. The 994F has been updated with Next Generation Modular Radiator (NGMR) two-pass cores for both the engine coolant and the SCAC. In the engine cooling system, the main coolant pump draws the cooled coolant from the radiator, or the regulator housing when the regulators are in bypass, and sends coolant through the engine oil cooler, the brake oil cooler, the power train oil cooler, and then into the engine block. The engine coolant flows through the engine coolant passages and exits the engine block through the regulator housing. The radiator bypass circuit allow coolant flow through the engine and coolers when the engine is below operating temperature. When the temperature of the coolant approaches 81° C (179° F) to 84° C (183° F), the water regulator begins to open. At 92° C (199° F) the water regulator is fully opened. The flow of coolant is sent through the radiator for cooling.
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The SCAC radiator cores are NGMR radiator cores. The hot coolant enters the split bottom tank and flows up through the tube in the dual pass radiator cores nearest the back of the machine. The coolant then flows down through the same cores to the half of the bottom tank nearest the engine after the coolant has been cooled. The location of the brake oil cooler has not changed. The cooler is mounted below the engine on the inside of the left rear frame rail. The brake oil cooler is an oil to coolant cooler and cools the oil from the service brake cooling circuit not the brake application hydraulic oil.
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994F TURBOCHARGER COOLING NEXT GENERATION MODULAR RADIATOR (NGMR) SCAC Coolant Radiator
Hottest
Engine Coolant Radiator
Direction of Air Flow
Radiator Bypass
Regulator Housing
Increasing Coolant Temperature
Main Coolant Pump
Brake Oil Cooler
Coldest
To / From Service Brakes Turbochargers To / From Transmission
Engine Oil Cooler Power Train Oil Cooler
22 Turbocharger Cooling System This illustration shows the coolant flow through the turbochargers. The coolant flow from the pump through the oil coolers, the engine, and the regulator housing. From the regulator housing, the coolant flows through tubes along the engine and is connected to the turbochargers. From the turbochargers, the coolant flows to a tee that is connected to the return tube for the radiator.
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Radiator Group The illustration shows the radiator cores that are used to cool the engine. The Next Generation Modular Radiator cores are divided into two groups. Each core has nine fins per inch with two pass coolant travel. The five cores (1) on the left make up the Separate Circuit Aftercooler (SCAC) Radiator. The SCAC cools the aftercoolers. The 13 cores (2) on the right side are used to cool the engine. Also, included in the radiator group are the engine oil cooler, the brake oil cooler, and the power train oil coolers that are not shown in the illustration. These coolers are located between the cooling cores and the fan blade.
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This illustration shows the left side of the engine near the front. This side of the engine can be accessed by the right side of the machine. The illustration shows the following components: - Secondary fuel filters (1) - Electric fuel priming pump switch (2) - Fuel differential pressure switch (3) - Oil pressure sensor filtered (4) - S•O•S fluid sampling oil port (engine oil) (5) - Engine oil dipstick (6) - Oil pressure sensor unfiltered (behind the secondary fuel filters) (7) - Engine oil filters (8)
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25 Fuel Filter Differential Switch The fuel filter differential switch (1) is located on the filter base above the secondary filters. The pressure switch sends an input signal to the Engine ECM. If the fuel pressure exceeds 138 kPa (20 psi) due to a restriction in the secondary fuel filters, an open circuit signal will be sent to the Engine ECM. Then, the Engine ECM will send an input to the VIMS module informing the operator that the secondary fuel filters are probably restricted. An event will be logged but no factory password is required to clear the event. This is a switch to ground input to the Engine ECM. Also shown are the fuel priming pump switch (2) and the secondary fuel filters (3).
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Text Reference
1
2
26 Electric Fuel Priming Pump The electric fuel priming pump (1) is located on the electric fuel priming pump filter base. The filter base and the pump are located on the right side of the engine and the left side of the machine. The electric fuel priming pump is used to fill the filters after the filters have been changed. The electric fuel priming pump is activated by a switch that is shown in Illustration 25 on the fuel filters base. In order to activate the electric fuel priming pump, the engine start switch must be in the OFF position and the disconnect switch in the ON position. 24 ± 2 VDC is the normal operating voltage.
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Text Reference
FUEL SYSTEM
Engine Block Engine Oil Renewal Solenoid (Optional)
Fuel Pressure Regulator
Cylinder Head
Fuel Transfer Pump
Fuel Heater (Optional)
Electric Fuel Priming Pump Switch Electric Fuel Priming Pump
Secondary Fuel Filters Primary Fuel Filter
Fuel Filter Differential Switch
Cylinder Head
Fuel Pressure Legend
Fuel Tank
Engine Oil
Return Fuel
Supply Fuel
Suction Fuel
27 Fuel System Fuel is drawn from the tank through a fuel heater (if equipped), by the fuel transfer pump. Fuel flows from the fuel transfer pump to the secondary fuel filters. Fuel flows from the secondary fuel filter base through the fuel injectors in the cylinder heads. Return fuel from the injectors flows through the fuel pressure regulator before returning through the fuel heater to the fuel tank. The fuel system is equipped with an electric fuel pump. The secondary fuel filter base is equipped with a switch controlling the voltage to the electric fuel priming pump that is located on the primary filter base. If the engine is equipped with a Oil Renewal System (ORS), engine oil flows from the engine block through an oil filter to the engine oil renewal system manifold. A small amount of used engine oil flows from the engine oil renewal system manifold into the return side of the fuel pressure regulator. The engine oil returns to the fuel tank with the return fuel. The engine oil mixes with the fuel in the tank and flows with the fuel to the injectors to be burned. The engine is equipped with a electric fuel priming pump. When the filters are replaced or service to the fuel system is completed, the priming pump is used to fill the system.
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Text Reference
ENGINE OIL SYSTEM
Engine Oil Renewal System Solenoid (Optional)
Scavenge Pump
To Fuel Tank
Bypass Valve Engine Oil Filters
Engine Oil Cooler Engine Oil Pump
28 Engine Oil System The engine oil pump draws oil from the oil pan through a screen. The engine also has a scavenge pump at the rear of the engine to transfer oil from the rear of the oil pan to the main sump. Oil flows from the pump through an engine oil cooler bypass valve to the engine oil cooler. The bypass valve for the engine oil cooler permits oil flow to the system during cold starts when the oil is thick or if the cooler is plugged. Oil flows from the engine oil cooler to the oil filters. The oil flows through the filters and enters the engine cylinder block to clean, cool, and lubricate the internal components and the turbochargers. Some wheel loaders are equipped with an optional engine oil renewal system. Engine oil flows from the engine block through an oil filter to an engine oil renewal system manifold. A small amount of oil flows from the engine oil renewal system manifold into the return side of the fuel pressure regulator. The engine oil returns to the fuel tank with the return fuel.
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Text Reference
1
29
2 3 4
30
5
Throttle Lock The throttle lock enable switch (1) is located in the dash. The throttle lock switches that are mounted in the cab to the right of the operator's seat are the set/decelerate (2) and the resume/accelerate switch (3). Also shown are button (4) for the horn and control levers (5).
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Text Reference
1 3
2
31
Throttle Lock The throttle lock lamp (1) is lit when the throttle lock switch is in the enable position. Depressing the right brake pedal (2) will cause the desired engine speed to return to low idle. An invalid brake switch signal will also cause the desired engine speed to return to low idle. The throttle pedal (3) is used in order to select the desired engine speed. The throttle position sensor is located on the throttle pedal. The sensor provides the signal to the Engine ECM. The throttle position sensor receives a regulated 8.0 VDC from the Engine ECM. The throttle position sensor output is a pulse width modulated signal that is expressed as a percentage between 10% and 90%.
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Text Reference
THROTTLE LOCK CIRCUIT Engine ECM
Right Brake Pedal Switch J1
998-BR
F722-OR F721-GY
998-br
998-BR
Throttle Lock Set / Deceleration Sw
998-BR
Throttle Lock Resume / Acceleration Sw
998-BR
998-BR F717-YL F718-BU F719-BR
21 22 5 64 61 62
Throttle Lock Rh Brake (NO) Throttle Lock Rh Brake (NC) Digital Return Throttle Lock Set / Decelerate Throttle Lock Resume / Accelerate Throttle Lock On / Off
Throttle Lock Sw
200-BK or Ground F706-PU 113-OR Batt+ Throttle Lock Lamp
32 Throttle Lock Circuit The Throttle Lock feature is very similar to a cruise control system used on automotive and truck applications. The main difference is that this system uses engine speed as its reference instead of vehicle speed. Therefore, engine speed is maintained, unlike other applications which control ground speed. The Throttle Lock control is within the Engine ECM. The other components are: - Throttle Lock Enable Switch - Set/Deceleration Switch - Resume/Acceleration Switch - Right Brake Pedal Switch - Throttle Lock lamp does not communicate with the engine ECM. The Throttle Lock Lamp ON/OFF is controlled by the Throttle Lock Enable Switch.
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3516B HD ENGINE DERATES - Exhaust Temperature - Altitude Compensation - Air Inlet Restriction
33
Engine Derates The 994F derates for the 3516B HD Engine are as follows: - Exhaust Temperature Derate - Altitude Compensation Derate - Air Inlet Restriction Derate
Text Reference
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Text Reference
EXHAUST TEMPERATURE DERATE 22 20 18
Engine Derate (%)
16 14 12 10 8 6 4 2 0 0
15
30
45
60
75
90
105
120
135
150
165
180
195
Time (Sec)
34 Exhaust Temperature Derate: The engine power will be derated when the turbine inlet temperatures reach a critical level that may cause engine damage. The Engine ECM measures the turbo inlet temperatures using the signals from the left and right exhaust temperature sensors. In the illustration above, 0% engine derate equates to a temperature of 750º C (1382º F) or below with 15 seconds as the trigger for the derate. When the highest of the right or left turbine inlet temperatures goes above 750º C (1382º F) for 15 seconds, the torque map is reduced by 2%. If the measured temperature does not return to below 750º C (1382º F) within a 15 second interval, the torque map will be reduced by 2%. This will continue in 2% steps with each step lasting 15 seconds until the temperature drops below 750º C or the maximum derate of 20% is reached. The last derate level reached will remain active until the engine is powered down. If the condition reoccurs and the Engine ECM has not been powered down, the fuel will be limited in the same manner starting from the previous derate level. If a failure is detected in either the left or right exhaust temperature sensor circuits, the Engine ECM will default to the maximum derate value of 20%. An exhaust temperature derate occurrence will log an Engine Event in the Engine ECM requiring a Level 3 password to clear.
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Text Reference
ALTITUDE COMPENSATION DERATE 22 21 20 19 18 17 16 15 Engine Derate (%)
14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 0
2
4
6
8
10
12
14
16
18
20
22
24
1 Division = 1000 Ft of Altitude
35 Altitude Compensation Derate: The Engine ECM derates engine power according to operating altitude in order to reduce exhaust temperatures. The engine ECM calculates the operating altitude of the machine based on the signal received from the atmospheric pressure sensor. The Engine ECM derates the engine power approximately 3% per 305 m (1000 ft) when the machine is operated above 3050 m (10,000 ft). The maximum altitude derate for the engine is 18% at 5180 m (17,000 ft). Altitude compensation derate does not log an event in the Engine ECM.
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Text Reference
Engine Derate (%)
AIR FILTER RESTRICTION DERATE 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Inlet Restriction (kPa)
36 Air Inlet Restriction Derate: The Engine ECM derates engine power when the air inlet or filter becomes plugged and restricts air available for combustion resulting in elevated exhaust temperatures. The above illustration shows the engine derates in relation to the air inlet restriction. The Engine ECM determines inlet air restriction by subtracting the turbocharger inlet air pressure that is measured by the turbocharger inlet air pressure sensors from the atmospheric air pressure. The Engine ECM derates the power by 1% when the inlet air restriction reaches 6.5 kPa (25 inches of water). This derate will increase at a rate of 2% kPA of restriction until the maximum derate of 20% is reached. The engine will default to a maximum derate of 20% if the Engine ECM detects a fault in the circuits for the left or right turbocharger inlet pressure sensors or the atmospheric pressure sensor. An air inlet restriction event will be logged in the Engine ECM when the engine starts derating. A password is not required to clear an air inlet restriction event. NOTE: Multiple engine derate percentages can add up and result in a total engine power derate greater than 20%.
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Text Reference
1
2 3 4
5
6
7
8
9 10
37 Engine Air Start System This illustration shows the location of the engine air start components on or near the the rear frame. Components that can be seen include: - Air dryer (1) - Air horns (2) - Air start tank (3) - Air horn solenoids (4) - Air compressor (5) - Air start motor (6) - Air start solenoid (7) - Air relay (8) - Gauge (service fill) (9) - Socket (service fill) (10)
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Text Reference
1 2
38
This illustration shows the air engine starter (1) and the air starter solenoid valve (2). This photo shows the air engine starter from under the machine on the right side. The air engine starter solenoid valve receives starting current from the Power Train ECM (not shown).
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Socket (Service Fill)
Text Reference
994F WHEEL LOADER ENGINE AIR START SYSTEM SOLENOIDS NOT ENERGIZED
Air Dryer Check Valve Pressure Switch Air Compressor
Drain Valve
Air Start Tank
Pressure Protection Valve
Air Horn Relay
Relay Valve
Air Horn Relay
Air Start Motor
Gauge (Service Fill) Air Start Solenoid
39 Air Start System Schematic - De-energized This illustration shows the air start tank charged with air pressure and the solenoids de-energized. The engine air start system supplies the required amount of air in order to turn the air start motor. At initial start-up, the air start tank is bled down, or through leakage the air tank will need to be charged to the adequate pressure. The socket located in the service fill area is used to provide the required air to pressurize the tank. The air from the socket flows around the air dryer and into the air tank. The air in the tank will charge the line going to the relay valve. Also, air flows to the air horn solenoids, the gauge, the air start solenoid, and to the unloading valve on the air compressor. When the air compressor has fully charged the tank and the lines, the unloading valve will signal the air compressor to stop. The pressures switch communicates with the VIMS module informing the operator of a low air pressure in the tank. If the pressure on the unloading line (between the air tank and the air compressor) decreases, the unloading valve will signal the compressor to resume supplying air for the air tank. At this time, no air pressure is directed to the air start motor or to the air horns.
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Socket (Service Fill)
Text Reference
994F WHEEL LOADER ENGINE AIR START SYSTEM AIR START SOLENOIDS ENERGIZED
Air Dryer Check Valve Pressure Switch Air Compressor
Drain Valve
Air Start Tank
Pressure Protection Valve
Air Horn Relay
Air Start Motor
Air Horn Relay
Relay Valve
Gauge (Service Fill) Air Start Solenoid
40 Engine Air Start System - Energized This illustration shows the air start tank charged with air pressure and the air start solenoid energized. When the engine start switch is turned to the ON position, a signal is sent to the Power Train ECM. Then, the Power Train ECM sends a voltage signal to the coil on the air start solenoid to open and allow air to pass through the solenoid valve. The air will flow through the air solenoid valve and flow to the air start motor. The pinion (not shown) will move into the fly wheel. Then, the air flows to the relay valve to signal the relay valve to open and allow air to flow directly from the tank to the air start motor. When the engine is started, release the key and the Power Train ECM will de-energize the air start solenoid valve. Also, the Power Train ECM will de-energize the air start solenoid valve when the ECM gets a signal that the engine is rotating at least 400 rpm for 10 seconds.
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Text Reference
1
2
41 Service Fill The air start system is equipped with a socket (2) in the service fill. The socket is used to recharge the air start tank if the supply is depleted for an initial startup or in the case of a air leak. The service bay is equipped with a gauge (1) for checking the air pressure in the air start tank.
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1
Text Reference
2
3
42 Oil Renewal System (ORS) The Oil Renewal System (ORS) is intended to increase the time between oil changes without shortening the life of the engine. Also, the system will decrease the amount of required disposable used engine oil. The ORS removes used engine oil from the engine sump and meters that oil into the fuel return line. The used oil will be consumed by the engine during the normal process of combustion. Normal oil analysis will help to determine whether the engine oil should be changed. The Oil Renewal System is an integrated system that requires the installation of additional components on the machine. The Engine ECM monitors fuel rate for 5 minutes. Then, the ECM determines how much oil to inject. The ORS valve has a fixed injection of oil per "pulse." The Engine ECM calculates how many times it must drive the ORS valve. Each injection last only a few seconds so the actual oil injections based on the previous 5 minute fuel cycle last approximately 30 seconds. The Engine ECM waits until the next 5 minute fuel cycle to start another set of oil injections. The target concentration for this operation is approximately 0.5% oil to fuel.
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Text Reference
There are several parameters that are monitored to determine if it is appropriate to inject oil. If any of these are not true then operation of the ORS strategy is halted until all conditions are met or the ECM power is recycled. The parameters that are monitored are as follows: - Engine Speed must be greater than 1100 rpm. If engine speed exceeds 1100 rpm, oil will be injected at the end of the 5 minute sampling period. - Engine must be running for 5 minutes - Coolant Temperature must be between 63° C and 107° C before ORS start up - Coolant Temperature sensor fault check (open or short to ground) - Oil pressure sensor fault check (open or short to ground) - Oil pressure Event check (active or inactive) - Fuel Level must be equal or greater than 10% - Fuel Level sender fault from VIMS - Engine Oil Level Status The following callouts are locations of the components for the Oil Renewal System. - Renewal tank (1) - Metering valve (2) - Service fill (3) To install the Oil Renewal System, the ORS will be configured through the Power Train ECM. This will take a factory password. Also, the enabling the ORS is configured through the Power Train ECM. Configuration of the Oil Renewal Rate setting is performed through the Engine ECM. The CID code for the ORS solenoid valve is 2271. The code is read in the Engine ECM and relayed to the VIMS module for display. FMI O5 Open circuit/Short to + battery FMI O6 Short to ground
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Text Reference
1 2
43 Service Fill The tank for the Oil Renewal System is filled at the service fill located on the right side of the rear frame near the articulation hitch. The tank filler (1) is used in order to fill the renewal tank (not shown). LED (2) will light when the upper level switch in the renewal tank (not shown) is activated. Access the tank filler by opening the cover over the service fill. The illustration shows the cover removed.
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Text Reference
1
2
3
44 Oil Renewal Tank The renewal tank (1) holds oil which will eventually be metered into the engine sump. The tank is equipped with two separate level switches. The upper level switch (2) is used to illuminate the blue LED in the service fill. The lower level switch (3) communicates with the VIMS module giving a signal the oil renewal system tank is empty. VIMS does display a warning saying ORS OIL LVL LO but does not instruct the operator to take any action. NOTE: The Oil Renewal System will not be shut down until the upper level switch for the engine oil sump shows a low level event.
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Text Reference
1
45
3
46
2
Metering Valve The metering valve (1) draws clean, pressurized oil from a port on the engine block and sends that oil to to the fuel return line. That oil flows through the fuel line to the fuel tank to mix with the fuel. At the same time, the engine oil sump is back filled with oil from the renewal tank. The metering valve is made up of a check valve (3), a shuttle valve and a solenoid valve. When the solenoid valve (2) is energized, pressurized engine oil from the crankcase fills the used oil side of the valve moving the shuttle. Then, forcing oil in the new oil side of the shuttle to the engine sump. When the shuttle is completely shifted to new oil side, no more oil is moving.
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Text Reference
When the solenoid is de-energized, a spring moves the shuttle back which sends the oil from the used oil side of the shuttle to the fuel return line and draws oil form the make-up tank to the new oil side of the shuttle. When the shuttle is shifted completely to the used oil side, no more oil is moved.
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Text Reference
1 2
3
4
47 Variable Clutch Fan Control The variable clutch fan control is used to meet the changing cooling requirements, thus reducing the horsepower that is used to drive the fan in cooler ambients or light duty cycle work conditions. The Rockford fan controls and limits fan speed by proportionally modulating engine oil pressure to the clutch. The speed of the fan will increase or decrease to compensate for a temperature change through feedback from the temperature sensors. The Engine ECM receives feedback from three sensors: the hydraulic oil temperature sensor, coolant temperature sensor, and the aftercooler temperature sensor. Each sensor has a target temperature programmed into the ECM. When one or more of the sensors read a temperature above the key target temperature, the ECM will will send a reduced current to the solenoid. This will increase the oil pressure to the fan clutch and decrease slipping of the clutch. If the temperatures at the sensors are all below the key target temperatures, full current is sent to the the solenoid and reduce the oil pressure to the fan clutch. The fan speed will reduce to minimum. The variable clutch fan is equipped with a speed sensor within the clutch assembly. The speed sensor monitors the speed of the fan and send feedback to the Engine ECM that the fan is rotating at the required speed.
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The following is a list of components in the variable clutch fan control. - Fan clutch (1) - Control valve (2) - Engine oil pressure supply port (3) - Return to the engine sump port (4)
Text Reference
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From Engine Oil Pressure Port
Proportional Solenoid Valve
Text Reference
VARIABLE CLUTCH FAN SYSTEM SPEED REDUCTION
To Engine Sump
To Fan Clutch
Coil Assembly Engine Oil Pressure Port
Fan Clutch
Engine Sump Engine Oil Pump
48 The variable clutch fan system system has two different engine oil circuits. The lubrication circuit is the flow of engine oil from the engine oil pressure port (brown) through the clutch and back to the engine sump through the line (green) at the bottom of the clutch. The engine oil pressure port is located on the front engine cover. The oil pressure in the front cover is supplied by oil from the engine oil pump that is drawn from the engine sump. This circuit is used mainly to cool the fan clutch. In the second circuit (control), oil (red) is taken from the engine oil pressure port in the front cover. The oil flows into the pressure port in the variable control valve, through the orifice, and out of the valve output to the clutch piston (not shown) With no current, the maximum oil flows out of the valve and maximum pressure is acting on the clutch piston. The maximum pressure on the clutch piston develops a force on the clutch plates rotating the fan at maximum speed. In case of a voltage loss in the electrical system, the valve will shift to the open position and the fan is defaulted to maximum fan speed. As the current to the coil assembly starts to increase, the oil flow through the control valve is decreased proportionally to the increase in current and a small amount of oil will flow over the tank orifice to the engine sump through the tank line (green) assisting in decreasing the fan speed.
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Text Reference
994F WHEEL LOADER POWER TRAIN POWER FLOW Rear Pump Drive
Input Torque Converter Drive Shaft
Input Transfer Gear Transmission
3516B HD Engine Spring Coupling
Final Drive
Transmission Pump
Secondary Steer Pump
Parking Brake
Drive Shaft
Final Drive
49 POWER TRAIN Power Flow Power from the 3516B HD engine is sent from the flywheel through the spring coupling to the rear pump drive. The rear pump drive is splined to the torque converter. Other components (not shown on this illustration) that are driven by the rear pump drive are: the two steering pumps, the brake actuation pump, the brake cooling pump, and the steering cooling pump. Two universal joints and the input drive shaft connect the torque converter to the transmission input transfer gear. The input transfer gear is splined to the transmission input shaft. The transmission output shaft is splined to the output transfer gear. Power from the output transfer gear is sent through the front drive shaft and it’s respective pinion, bevel gear, differential carrier, and axles to the front final drives and similarly to the rear final drives.
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POWER TRAIN ELECTRICAL SYSTEM
Text Reference
Cat Data Link Power Train ECM
INPUT COMPONENTS
Control and Monitor Systems
OUTPUT COMPONENTS
STIC Upshift, Downshift, Forward, Neutral, Reverse
Air Start Solenoid Reduced Rimpull Indicator Lamp
Key Start Switch
Clutch 1 Reverse Solenoid
Reduced Rimpull Selection Switch
Clutch 2 Forward Solenoid
Engine Speed Sensor Parking Brake Pressure Switch
Clutch 3 3rd Gear Solenoid
Parking Brake Position Switch
Clutch 4 2nd Gear Solenoid
Steering / Transmission Lock Switch
Clutch 5 1st Gear Solenoid
Lockup Clutch Enable Switch
Impeller Clutch Solenoid
Torque Converter Pedal Position Sensor
Lockup Clutch Solenoid
Auto Lube Pressure Sensor
Bumper Transmission Lockout LED
Torque Converter Output Speed Sensor Transmission Output
Back-up Alarm
Impeller Clutch Auto Lube Solenoid Bumper Transmission
50 Power Train Electrical System This illustration of the Power Train Electrical System shows the components which provide input signals to the Power Train ECM. Based on the input signals, the Power Train ECM energizes the appropriate transmission control valve solenoids for speed and directional clutch engagement. The Power Train ECM also energizes the starter relay when starting the machine and the back-up alarm when the operator selects a reverse gear. When required, the Power Train ECM energizes the impeller clutch control valve solenoid, the lockup clutch control valve solenoid, and the reduced rimpull indicator lamp. The CAT Data Link connects the Power Train ECM to the Engine ECM. The data link also connects the ECMs to the Vital Information Management System (VIMS) and electronic service tools such as Caterpillar Electronic Technician (ET).
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Text Reference
Power Train ECM Inputs: STIC: Combines control of the vehicle steering system and the transmission shifting system in a single input device. Key Start switch: Provides a signal to the Power Train ECM when the operator wants to start the engine. The STIC directional switch must be in the NEUTRAL position before the Power Train ECM will permit engine starting. Reduced rimpull selection switch: The rotary selection switch sends an input signal to the Power Train ECM requesting the desired maximum rimpull torque. Park brake pressure switch: Monitors the park brake hydraulic pressure and the Power Train ECM can determine when pressure is applied to release the park brake. Parking Brake Position Switch: Provides an input to the Power Train ECM to signal whether the parking brake is engaged or disengaged. Lockup clutch enable switch: When in the ON position, enables the lockup clutch to ENGAGE when the machine operating conditions are correct. The lockup clutch enable lamp is turned on by electrical contacts in the switch whenever the lockup clutch is enabled. Steering and transmission lock switch: When in the LOCK position, causes the Power Train ECM to shift the transmission to NEUTRAL. Torque converter pedal position sensor: Signals the position of the torque converter pedal to the Power Train ECM. The Power Train ECM uses the position information to vary torque to the drive train through the impeller clutch. The actual value of torque reduction is determined by a combination of different input signals. Torque converter speed sensor: Provides a signal the Power Train ECM uses to determine the output speed and direction of the torque converter. Transmission speed sensors: Provides a signal the Power Train ECM uses to determine the output speed of the transmission. Impeller clutch pressure sensor: Provides a pulse width modulated signal the Power Train ECM uses to determine the impeller clutch hydraulic pressure. Bumper Transmission Lockout Switch: Provides a ground level input to the Power Train ECM that will neutralize the transmission until the switch is moved to the UNLOCK position. Engine Speed Sensor: A passive speed sensor that uses the passing teeth of the flywheel to provide a frequency input to the Power Train ECM. Auto Lube Pressure Sensor: Provides a signal to the Power Train ECM to determine the status of the auto lube pressure.
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Text Reference
Power Train ECM Outputs: Air Start Solenoid: The Power Train ECM energizes the air start solenoid valve when the appropriate conditions to start the machine have been met. Reduced rimpull indicator lamp: The Power Train ECM illuminates the reduced rimpull indicator lamp when the appropriate machine operating conditions are met and the Power Train ECM is providing reduced rimpull. Clutch solenoids: The solenoids control oil flow to the speed and directional control spools. Impeller clutch solenoid: The Power Train ECM energizes the impeller clutch modulating valve in order to control hydraulic pressure to the impeller clutch. Lockup clutch solenoid: The Power Train ECM energizes the lockup clutch modulating valve in order to control pressure to the lockup clutch when the correct machine conditions have been met. Back-up alarm relay: The Power Train ECM energizes the back-up alarm when the operator selects the REVERSE direction with the STIC. The backup alarm relay energizes the two backup alarms. Auto Lube Solenoid: The energizes the auto lube solenoid for the next lube cycle. Bumper Transmission Lockout LED: The Power Train ECM illuminates the bumper transmission lockout LED when the bumper transmission lockout switch is in the LOCKED position.
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Text Reference
1
51
Power Train Electronic Control Module (ECM) The Power Train ECM (1) is located on the left side of the machine under the door on the platform (cover must be removed). The Power Train ECM makes decisions based on control program information in memory and switch and sensor input signals. The Power Train ECM responds to machine control decisions by sending a signal to the appropriate circuit which initiates an action. For example, the operator selects an upshift using the STIC. The Power Train ECM interprets the input signals from the STIC, evaluates the current machine operating status and energizes the appropriate solenoid valve. The Power Train ECM receives three different types of input signals: 1. Switch input: Provides the signal line to battery, ground, or open. 2. PWM input: Provides the signal line with a square wave of a specific frequency and a varying positive duty cycle. 3. Speed signal: Provides the signal line with either a repeating, fixed voltage level pattern signal or a sine wave of varying level and frequency.
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Text Reference
The Power Train ECM has three types of output drivers: 1. ON/OFF driver: Provides the output device with a signal level of +Battery voltage (ON) or less than one Volt (OFF). 2. PWM solenoid driver: Provides the output device with a square wave of fixed frequency and a varying positive duty cycle. 3. Controlled current output driver: The ECM will energize the solenoid with 1.25 amps for approximately one half second and then decrease the level to 0.8 amps for the duration of the on time. The initial higher amperage gives the actuator rapid response and the decreased level is sufficient to hold the solenoid in the correct position. An added benefit is an increase in the life of the solenoid. The Power Train ECM controls the transmission speed and directional clutches and the operation of the impeller clutch and lockup clutch. The Power Train ECM interprets signals from the STIC, the torque converter pedal position sensor, the lockup clutch enable switch, and the current machine operating status to determine the appropriate output signals to the systems. Different conditions of the inputs affect the output conditions. These conditions will be discussed later. The Power Train ECM communicates through the CAT Data Link. The CAT Data Link allows high speed proprietary serial communications over a twisted pair of wires. The CAT Data Link allows different systems on the machine to communicate with each other and also with service tools such as Caterpillar Electronic Technician (ET). The Power Train ECM has built-in diagnostic capabilities. As the Power Train ECM detects fault conditions in the power train system, it logs the faults in memory and displays them on the VIMS. The fault codes can also be accessed using the ET service tool. VIMS software can be used to view faults logged by the VIMS. INSTRUCTOR NOTE: Power Train ECM faults displayed on the VIMS relating to the Power Train ECM will have a Module Identifier (MID) of "81." For additional information, refer to the Service Manual module "994F Wheel Loader Power Train, Troubleshooting, Testing and Adjusting" (Form RENR6306).
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Text Reference
1
2 3
52 Engine Speed Sensor The engine speed sensor (1) is a passive two wire speed sensor that is positioned on the top of the flywheel housing. The sensor uses the passing teeth of the flywheel to provide a frequency output. The sensor sends the the engine speed signal to the Transmission ECM. Also shown are the primary speed timing sensor (2) and the Engine ECM (3).
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Text Reference
6
3
4
2 6
1 5
53
The STIC (1) is bolted to the seat at the front of the left armrest. The transmission directional control switch (2) is a three position rocker switch that the operator uses to select NEUTRAL, FORWARD, or REVERSE. The transmission speed upshift switch (3) and the transmission speed downshift switch (4) are momentary contact switches that the operator uses to select the desired speed. When the operator selects REVERSE by depressing the top of the directional control switch, the Power Train ECM energizes the reverse directional solenoid. The Power Train ECM also activates the back-up alarm. When the operator selects FORWARD by depressing the bottom of the directional control switch, the Power Train ECM energizes the forward directional solenoid. When the operator selects NEUTRAL by placing the directional control switch in the center position, the Power Train ECM de-energizes both the forward and the reverse directional solenoids. After two seconds, the Power Train ECM energizes speed solenoid No. 3 and the transmission is in NEUTRAL until the operator selects a different gear. When the operator presses the upshift switch, the Power Train ECM energizes the appropriate speed clutch solenoid to select the next higher gear, and the transmission upshifts. When the operator presses the downshift switch, the Power Train ECM energizes the appropriate speed clutch solenoid to select the next lower gear, and the transmission downshifts. The switches must be released and pressed again to continue shifting. If the operator presses and holds the upshift or the downshift switch, the transmission will shift once and remain in that speed until the switch is released and pressed again.
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Text Reference
When the steering and transmission lock lever (5) is moved to the LOCK position (not shown), the STIC is held in the center position and steering is disabled. In the LOCK position, the steering lock lever depresses the steering and transmission lock switch (not visible). The steering and transmission lock switch signals the Power Train ECM to shift the transmission to NEUTRAL. When the steering and transmission lock lever is moved to the UNLOCK position, the steering and transmission functions are enabled. The power train portion of the STIC sends input signals to the Power Train ECM. Certain machine operating conditions will override the operator desired function of the STIC. If the directional switch is in the FORWARD or REVERSE position when the steering and transmission lock lever is moved to the UNLOCK position, the Power Train ECM will not shift from NEUTRAL. The directional switch must first be moved to the NEUTRAL position, then to the direction desired before the Power Train ECM will engage a directional clutch. Also shown is the armrest adjustment lever (6).
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Text Reference
1
54
2 3 4 5 55
Reduced Rimpull Selection Switch The Power Train ECM reduces rimpull by increasing the current to the impeller clutch solenoid, which reduces the hydraulic pressure to the impeller clutch and allows slippage between the impeller and the torque converter housing. By additionally decreasing the impeller clutch pressure, the impeller will slip more resulting in lower torque to the power train. The resulting additional engine horsepower can be used for the implements.
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Text Reference
The reduced rimpull selection switch (1) has four positions. Each position corresponds to a maximum allowable percentage of maximum rimpull. The default values for each position are indicated as follows: - Maximum Rimpull (2) - 85% Rimpull (3) - 70% Rimpull (4) - 55% Rimpull (5)
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Text Reference
1
56
The operator turns the key start switch (1) clockwise to signal the Power Train ECM to start the engine. The key start switch supplies a signal of +Battery to the Power Train ECM. The Power Train ECM energizes the air start solenoid and the air start solenoid supplies air to the starting motor. In order to start the engine, the following conditions must be met before the Power Train ECM will energize the air start solenoid: 1. The key switch is turned to the start position. 2. The transmission directional control switch is in neutral. 3. The system voltage is below +32 Volts. 4. Engine prelube is complete (if equipped). If the machine is equipped with the optional engine prelubrication the Power Train ECM will request prelubrication status from the Engine ECM via the datalink. If the Engine ECM determines the need for prelubrication, the Engine ECM will perform the prelubrication function and signal the Power Train ECM when prelubrication has been completed.
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Text Reference
1
2
57
The Power Train ECM monitors the position of the torque converter pedal (1) with the torque converter pedal position sensor (2) located behind the panel at the pivot for the pedal. As the operator depresses the pedal, the Power Train ECM increases the current to the impeller clutch solenoid and reduces the hydraulic pressure to the impeller clutch. The rimpull will decrease with pedal travel from the reduced maximum setting to the minimum setting. When the operator releases the left pedal, the rimpull will return to the maximum percentage as set by the reduced rimpull selector switch (not shown). When the maximum allowable percentage is in the lower values, the total change of rimpull from maximum to minimum is decreased. This condition results in a more gradual change of rimpull over the travel of the torque converter pedal. If the machine is not in FIRST GEAR, the impeller clutch pressure will remain at the maximum level until the transmission is shifted into FIRST GEAR. The torque converter pedal functions similarly when the maximum rimpull selector switch is in the maximum position, except the maximum allowable percentage is now 100%. NOTE: An increase in current to the impeller clutch solenoid from the Power Train ECM results in a decrease in pressure to the impeller clutch. INSTRUCTOR NOTE: To change the setting for each position of the reduced rimpull selection switch, refer to the Service Manual module "994F Wheel Loader Power Train, Troubleshooting, Testing and Adjusting" (Form RENR6306).
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2
Text Reference
1
3
5
4
58
6
59
Torque Converter The impeller clutch modulating valve (1) is located on the left side of the torque converter housing (3). The Power Train ECM (not shown) monitors the status of the impeller clutch solenoid and can determine certain faults that may affect operation of the impeller clutch. These faults include: a short to +Battery, a short to ground, an open circuit, or the impeller clutch not responding properly. The Power Train ECM receives a signal from the impeller clutch pressure sensor (5) to monitor the impeller clutch pressure. The Power Train ECM can compare the control of the impeller clutch solenoid with the response of the impeller clutch pressure to determine if the impeller clutch is responding properly.
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Text Reference
When a fault is detected, controlled throttle shifting is used. When a directional shift is made above 1100 rpm, the Power Train ECM will request a desired engine speed of 1100 rpm from the Engine ECM for 1.9 seconds if shifting into forward and a desired engine speed of 1100 rpm for 2.5 seconds if shifting into reverse. This feature helps decrease the energies absorbed in the transmission. When the Power Train ECM detects a fault in the impeller clutch solenoid circuit, a fault will be displayed on the VIMS message center (not shown). The torque converter pedal position sensor (not shown) and the impeller clutch solenoid must be calibrated through the VIMS to ensure proper operation. Also shown are the lockup clutch solenoid (2) and the lockup clutch valve. The lockup clutch solenoid and lockup clutch valve looks similar to the impeller clutch solenoid and impeller clutch valve but are different and should not be interchanged. The lockup clutch solenoid is mounted on the lockup clutch valve. The lockup clutch modulating valve is located on the left side of the torque converter housing. The Power Train ECM energizes the solenoid for the lockup clutch in order to allow oil to flow to the lockup clutch. The pressure increases in the lockup clutch, causing it to engage and the machine operates in DIRECT DRIVE. The solenoid for the lockup clutch is a proportional solenoid and is energized by a modulated signal from the Power Train ECM. The Power Train ECM varies the amount of current to control the amount of oil flow through the lockup clutch valve to the lockup clutch. The Power Train ECM receives a signal from the torque converter output speed sensor (4). The speed sensor is mounted on the front of the torque converter housing above the output shaft. The signal is a fixed voltage level, patterned waveform which the Power Train ECM uses to determine the speed and direction of the torque converter output. If the machine is allowed to roll backwards on an incline when a forward gear is selected the torque converter output can turn in reverse. This condition is called reverse turbine and can result in high temperatures inside the torque converter. If the Power Train ECM determines the output of the torque converter is turning in the reverse direction greater than 500 rpm, the Power Train ECM will ignore the left pedal position input and increase the impeller clutch pressure to prevent this condition. The Power Train ECM will also override the reduced rimpull setting if necessary to try to eliminate the reverse turbine. The Power Train ECM monitors the temperature of oil exiting the torque converter with the torque converter outlet oil temperature sensor (6) which is mounted on the front right of the torque converter housing. INSTRUCTOR NOTE: An increase in current to the lockup clutch solenoid from the Power Train ECM results in an increase in pressure to the lockup clutch.
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Text Reference
1
60
The lockup clutch enable switch (1) is located on the right side panel in the cab. When the switch is in the ON (closed) position and the proper conditions have been met, the Power Train ECM will engage the lockup clutch in order to improve the efficiency of the power train. The Power Train ECM first sends a signal to the lockup clutch modulating valve to engage the lockup clutch to a Hold Level for .75 seconds to allow time for the clutch to fill. Then, the current is ramped up to full ON in .65 seconds. During normal operation, the Power Train ECM will ENERGIZE the torque converter lockup clutch solenoid based on the following conditions: 1. Lockup clutch enable switch state: ON (closed). 2. Torque converter output speed: When the torque converter output speed is greater than 1125 ± 50 rpm. 3. Time in gear: The transmission must be in the present speed and direction for at least two seconds. 4. Time since lockup clutch solenoid was de-energized: At least four seconds must have passed since the Power Train ECM de-energized the lockup clutch solenoid. 5. Left pedal and right brake pedal status: Both pedals must be fully released.
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Text Reference
1 2
61
This illustration show the transmission pump that is mounted on the torque converter housing below the output shaft on the rear pump drive. The transmission pump has two sections. The front section (1) (toward the front of the machine) supplies oil to the torque converter. The rear section nearest to the torque converter housing (2) supplies oil to the lockup clutch modulating valve, the impeller clutch modulating valve, and the transmission control valve. Also, return oil from the transmission control valve will flow to the block and join the oil that is flowing into the torque converter.
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Text Reference
1
2
3
62
4
4
63
Transmission Oil Filters The upper illustration shows the location of the power train filters (1) in the rear frame of the machine. The transmission filters can be accessed by raising the door on the platform that is behind the cab. Also shown are the torque converter housing (2) and the transmission (3). The lower illustration shows both filters. The filter on the left (toward the rear of the machine), filters the oil that is supplying the priority valve, the modulating valves, and the transmission control valve. The filter on the right (toward the front of the machine), filters the oil that is flowing to the torque converter. Both filters are equipped with fluid sampling ports (S•O•S) (4).
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Text Reference
TORQUE CONVERTER Clutch Discs
Turbine Clutch Discs
Lockup Clutch Port
Output Shaft
Housing
Torque Converter Oil Port Impeller Clutch Port
Lockup Clutch Stator
Impeller Clutch Impeller
Lockup Clutch Oil
Impeller Clutch Oil Pressure
Converter Oil
64 Torque Converter The Illustration shows a sectional view of the torque converter. The major components include the rotating housing, the impeller, the turbine, the nonfree wheel stator, the impeller clutch, and the lockup clutch. The rotating housing is splined to the engine flywheel and turns with the flywheel. When the impeller clutch port is pressurized, the impeller is connected to the rotating housing through the impeller clutch engagement. The clutch discs are splined to the impeller. The clutch plates are splined to the rotating housing. Pressure oil at the clutch piston will engage the discs and plates. The impeller rotates with the housing. The turbine is splined to the output shaft. In torque converter drive, the turbine is turned by oil from the impeller. In direct drive, the lockup clutch port is pressurized. The lockup clutch connects the turbine to the rotating housing. The lockup clutch discs are splined to the turbine. The lockup clutch plates are splined to the rotating housing. Pressure oil moves the clutch piston to engage the discs and plates. When the clutch is engaged, the turbine, the housing, the impeller, and the output shaft rotate as a unit at engine rpm.
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Text Reference
8
2 1
5
4
3 9 6 7
65 Transmission The basic transmission remains unchanged. The planetary power shift transmission (1) has three FORWARD and three REVERSE speeds. Electronic solenoids located in the hydraulic control valve (2) shift the transmission. The solenoids are actuated by the Power Train Electronic Control Module (ECM) located in the electronics bay in the platform on the left side of the machine. The transmission output speed sensors (3) monitors the transmission output shaft. The signal is sent to the Power Train ECM. The transmission output speed signal indicates when the clutches have engaged and the direction of the ground speed. The two transmission oil screens located in the front of the output transfer gear housing can be accessed by removing the covers (4). The oil sump for the transmission pump is located in the bottom of the output transfer gear case (7). Shown here are the secondary steering pump and diverter valve (5) and the output shaft (6) for the rear drive shaft. The transmission fill tube (8) and the transmission liquid level gauge (9) are also shown.
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Text Reference
Test Port
IMPELLER CLUTCH MODULATING VALVE
Ball
Spring
Valve Spool
Orifice
Spring
IMPELLER CLUTCH SOLENOID DE-ENERGIZED
Armature Assembly
Solenoid
From Pump
To Impeller Clutch Test Port
Ball
Spring
Valve Spool
Orifice
Spring
IMPELLER CLUTCH SOLENOID ENERGIZED
Solenoid
Armature Assembly
From Pump To Impeller Clutch
66 This illustration is a sectional view of the impeller clutch solenoid valve. When the impeller clutch solenoid is DE-ENERGIZED, the spring moves the pin assembly against the ball. The ball blocks the pump flow through the orifice to drain. The oil pressure increases at the left end of the valve spool and moves the valve spool to the right against the spring. The valve spool blocks the passage between the impeller clutch and drain and opens the passage between the impeller clutch and the pump. Pump oil flows past the valve spool to the impeller clutch. When the impeller clutch solenoid is ENERGIZED, the solenoid moves the pin assembly against the spring and away from the ball. Pump oil flows through the center of the valve spool, through the orifice and past the ball to drain. The valve spring moves the valve spool to the left. The valve spool blocks the passage between the impeller clutch and the pump and opens the passage between the impeller clutch and drain. Pump flow to the impeller clutch is blocked. The oil in the impeller clutch flows past the valve spool to drain.
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Text Reference
Test Port
LOCKUP CLUTCH SOLENOID VALVE
Ball
Valve spool
Orifice
Spring
SOLENOID DE-ENERGIZED
Solenoid
Pin
From Pump To Clutch
Test Port
Ball
Valve Spool
Orifice
Spring
SOLENOID ENERGIZED
Solenoid
Pin
From Pump To Clutch
67 This illustration is a sectional view of the lockup clutch solenoid valve. When the lockup clutch solenoid is DE-ENERGIZED, the force that held the pin assembly against the ball is removed. The pump oil flows through the orifice and past the ball to drain. The spring moves the valve spool to the left. The valve spool opens the passage between the lockup clutch and drain and blocks the passage between the lockup clutch and the pump. Pump flow to the lockup clutch is blocked. The oil in the lockup clutch flows past the valve spool to drain. When the lockup clutch solenoid is ENERGIZED, the solenoid moves the pin assembly against the ball. The ball blocks pump oil flow through the orifice to drain. The oil pressure increases at the left end of the valve spool and moves the valve spool to the right against the spring. The valve spool blocks the passage between the lockup clutch and drain and opens the passage between the lockup clutch and the pump. Pump oil flows past the valve spool to the lockup clutch.
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Text Reference
2 1 4
3 5
68
The Power Train ECM shifts the transmission by energizing the solenoid valves that are located in the transmission control valve group on top of the transmission. Two solenoid valves are used to control reverse (1) or forward (2) directional shifts and three solenoid valves are used to control speed shifts: first (5), second (4), and third (3). The solenoid valves are two-position, three-way solenoid valves. The solenoid valves are normally open to drain. When energized, the solenoid valve spool moves to direct pressure oil to one end of the transmission control valve spool. The transmission control valve spool then directs oil to the appropriate clutch. The solenoids are operated by 12VDC max. The Power Train ECM first energizes the solenoids with 12VDC for one second and then decreases the voltage to approximately 8.25 VDC for the remainder of the time that the solenoid is energized. The decreased voltage level is enough to keep pressure oil to the control valve spool to maintain position while extending the service life of the solenoid.
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Text Reference
TRANSMISSION HYDRAULIC CONTROL VALVE
To Torque Converter From Filter
P3
Check Valve
P1
Port to Torque Converter Inlet
Orifice Modulating Relief Valve
Converter Inlet Ratio Valve
Slug Chamber From Solenoid (No. 3 Clutch) From Solenoid (No. 2 Clutch) Passage Clutch No. 3
Slug Chamber Passage Clutch No. 2
Passage Clutch No. 5 P2
Passage Clutch No. 1 Directional Selector Spool
1st and 3rd Speed Selector Spool
Pressure Differential Valve
From Solenoid (No. 5 Clutch) Load Piston
From Solenoid (No. 1 Clutch) From Solenoid (No. 4 Clutch)
2nd Speed Selector Spool Passage Clutch No. 4
69 Transmission Hydraulic Control Valve Modulating relief valve: Limits the maximum clutch pressure. First and third speed selection spool: Directs oil flow to the No. 5 and No. 3 clutches. Load piston: Works with the modulation relief valve to control the rate of pressure increase in the clutches. Second speed selector spool: Directs oil flow to the No. 4 clutch. Pressure differential valve: Controls speed and directional clutch sequencing. Directional selection spool: Directs oil to the FORWARD and REVERSE directional clutches. Converter inlet ratio valve: Limits the pressure to the torque converter. Passage to Clutch No. 1: Passage to the port to energize clutch No. 1 (Reverse). Passage to Clutch No. 2: Passage to the port to energize clutch No. 2 (Forward). Passage to Clutch No. 3: Passage to the port to energize clutch No. 3. (Third Speed) Passage to Clutch No. 4: Passage to the port to energize clutch No. 4. (Second Speed) Passage to Clutch No. 5: Passage to the port to energize clutch No. 5 (First Speed).
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TRANSMISSION HYDRAULIC CONTROL VALVE NEUTRAL
Text Reference
To Torque Converter From Filter
P3
Orifice
Check Valve
P1 Modulating Relief Valve
Port to Converter Inlet Converter Inlet Ratio Valve
Slug Chamber From Solenoid (No. 3 Clutch)
From Solenoid (No. 2 Clutch)
Passage Clutch No. 3
Slug Chamber Passage Clutch No. 2
Passage Clutch No. 5
P2 Passage Clutch No. 1
1st and 3rd Speed Selector Spool
Directional Selector Spool
From Solenoid (No. 5 Clutch)
Pressure Differential Valve Load Piston
From Solenoid (No. 1 Clutch)
From Solenoid (No. 4 Clutch)
2nd Speed Selector Spool Passage Clutch No. 4
70 Transmission Hydraulic Control Valve -NEUTRAL The transmission hydraulic control valve is shown with the transmission in the NEUTRAL position. Supply oil from the transmission filter is directed to either the solenoid valve manifolds (not shown) or at the top of the modulating relief valve. The pressure of the supply oil overrides the check valve (at the inlet). Oil flows through the passage (red) around the modulating valve through the ball check valve and fills the slug chamber (red). The pressure in the slug chamber will override the spring and the modulating valve will move downward. As the modulating valve moves downward, oil will flow around the modulating valve to the cavity (orange). The oil will flow through the passage (orange) to the port for the torque converter inlet (not shown). The supply oil flows through the flow control orifice to the chamber for the 1st and 3rd speed selector spool. In NEUTRAL, the speed selector spool directs oil flow to the clutch No. 3. Also, the oil flows through the passage (red) to the slug chamber of the converter ratio valve and the center of the pressure differential valve. The oil sump for the transmission pump (not shown) is located in the bottom of the output transfer gear case (7). Oil flows around the center of the differential valve and through the orifice to the lower end of the load piston.
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Text Reference
The oil pressure at approximately 380 kPa (55 psi) in the upper cavity of the differential valve shifts the valve downward against the spring. The differential valve moves downward. Oil flows around the differential valve to cavity (P2). When the pressure at P2 reaches 380 kPa (55 psi), the load piston starts moving upward compressing the spring from the lower end. The oil pressure at P2 will always be approximately 380 kPa (55 psi) less than the pressure at P1. The differential pressure between P1 and P2 will ensure that the speed clutch will always engage before the direction clutch. With a directional shift out of NEUTRAL, the directional selector spool will be shifted in either direction and oil in cavity (P2) will be directed to No. 1 clutch or No. 2 clutch.
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Text Reference
TRANSMISSION HYDRAULIC SYSTEM NEUTRAL
Lube - Output Transfer Bearings
Lube - Output Transfer Gear
Transmission Lube
Lube - Rear Pump Drive
Dump Orifice
Pump Pressure 2
3
Impeller Clutch Modulating Valve Priority Valve
1
5
4
Lube - Input Transfer
IC Pressure LUC Pressure
P3
Lockup Clutch Modulating Valve Lube - Rear Pump Drive
P1
P2
Torque Converter Filter
Transmission Filter
3
2
5
Torque Converter Oil to Water Cooler
1
4
Transmission Pump
Transmission Control Valve
Oil to Water Cooler
Air to Oil Cooler Magnetic Screens
Sump Air to Oil Cooler
71 Power Train Hydraulic System -NEUTRAL This illustration shows the components and the oil flow for the power train hydraulic system in NEUTRAL. In this schematic, the engine is running and the transmission is in neutral. With the transmission direction switch in the NEUTRAL position, the Power Train ECM energizes the No. 3 clutch solenoid. The Power Train ECM also de-energizes the lockup clutch solenoid. The transmission pump (a two-section gear pump) draws oil from the sump (located in the bottom of the transmission transfer case) through three magnetic screens that are located in the sump by the transmission pump. Oil from the left section of the transmission pump flows through the transmission filter (red) to the priority valve. From the right side of the priority valve, oil flows to the lockup clutch modulating valve and to the impeller clutch modulating valve. During a shift, the priority valve maintains 2205 kPa (320 psi) oil pressure to the lockup clutch modulating valve and impeller clutch modulating valve. When the transmission is in neutral, the lockup clutch is disengaged. Also, the solenoid for the impeller clutch is de-energized and the impeller clutch is engaged.
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Text Reference
When the transmission pump supply pressure increases above the priority valve setting, the priority valve opens and sends oil flow to the manifold for clutch solenoid valves No. 2 and 3, the manifold for clutch solenoid valves No. 1, 5, and 4, and the inlet passage for the transmission valve. The oil at the clutch solenoid valve manifolds becomes the pilot oil for the transmission speed and directional selector spools. When the No. 3 clutch solenoid is ENERGIZED, the No. 3 solenoid valve sends pilot oil to the upper end of the first and third speed selector spool. The pilot oil pressure overcomes the force of the selector valve spring and moves the spool from its center position. Oil from the inlet passage flows through the orifice, past the speed selector spool, and into the No. 3 speed clutch. When directional solenoids No. 1 and 2 are DE-ENERGIZED, pilot oil is blocked at the directional solenoid valves. The directional clutch selector spool spring centers the spool. Oil flow between the direction selector spool and the the directional clutches is blocked. When the oil requirements of the selector and pressure control valve have been satisfied, the remaining power train pump oil flows to the torque converter. Oil from right side of the transmission pump is directed to the torque converter filter. Oil flows from the filter and joins with the oil from the selector and pressure control valve. The combined oil flows to the inlet of the torque converter. Flow continues through the torque converter to either the sump or the power train coolers. Then the oil flows to various lube points in the transmission lubrication circuit. When the transmission is in NEUTRAL, the Power Train ECM disengages the optional lockup clutch. The turbine is disconnected from the rotating housing. No power is transmitted from the housing through the turbine.
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Text Reference
TRANSMISSION HYDRAULIC SYSTEM FIRST SPEED FORWARD CONVERTER DRIVE
Lube - Output Transfer Gear
Lube - Output Transfer Bearings
Lube - Rear Pump Drive
Transmission Lube Dump Orifice
2
Pump Pressure
102 L/min (27 Gpm)
3
Impeller Clutch Modulating Valve Priority Valve
1
5
4
Lube - Input Transfer IC Pressure
LUC Pressure Lockup Clutch Modulating Valve P3
Lube - Rear Pump Drive P1
Transmission Filter
3
2 P2
Torque Converter Filter
5
Torque Converter Oil To Water Cooler
1
4
Transmission Control Valve
Transmission Pump
Oil To Water Cooler
Air To Water Cooler Magnetic Screens Sump Air To Water Cooler
72 In this illustration, the engine is running and the transmission is in 1st speed forward in torque converter drive. Flow from the transmission pump is directed through the transmission filter to the priority valve, the impeller clutch solenoid valve, and the lockup clutch solenoid valve. The priority valve maintains a minimum oil pressure to the impeller clutch solenoid valve and the lockup clutch solenoid valve during transmission shifts. When the transmission pump supply pressure increases above the spring setting of the priority valve, the priority valve opens and oil is directed to the speed manifold and the direction manifold. Also, pump supply oil is directed past the orifice to the inlet port for the 1st and 3rd speed selector spool and the inlet port for the 2nd speed selector spool. When the operator moves the directional switch and upshift or downshift switch to the 1st speed forward position, the Power Train ECM energizes the impeller clutch solenoid (the impeller clutch solenoid will be energized and then de-energized). The solenoid for the lockup clutch is also de-energized. Then, the No. 5 solenoid is energized first and No. 2 solenoid will be energized next.
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Text Reference
When the No. 5 solenoid is ENERGIZED, oil pressure is directed to the lower end of the 1st and 3rd speed selector spool. The force of the oil pressure overcomes the force of the speed selector spool spring, the spool shifts upwards and No. 5 clutch is engaged. The No. 2 solenoid is ENERGIZED, pilot oil is directed to the upper end of the directional selection spool. The oil pressure overcomes the force of the selector spool spring and the spool shifts downward. The No. 2 clutch will be engaged. When the oil requirements of the selector and pressure control valve have been satisfied, the remaining oil combines with the oil from the transmission pump (orange). The combined oil flows to the torque converter. Flow continues through the torque converter through the power train coolers to the transmission lubrication circuit. When the transmission is in NEUTRAL, the Power Train ECM pressurizes the impeller clutch in response to the engine speed. When the engine speed is less than 1100 rpm, the impeller clutch pressure is maintained at a holding pressure of 550 ± 207 kPa (80 ± 30 psi). When the engine rpm increases from 1100 to 1300 rpm, the Power Train ECM increases the impeller clutch pressure from 550 ± 207 kPa (80 ± 30 psi) to 2580 ± 207 kPa (375 ± 30 psi) for one second. The Power Train ECM then reduces the impeller clutch pressure to 2274 ± 207 kPa (330 ± 30 psi). The impeller clutch pressure remains at 2274 ± 207 kPa (330 ± 30 psi) for all engine speeds above 1300 rpm. The torque converter housing and impeller rotate at engine speed. When the engine rpm decreases from 1300 to 1100 rpm, the Power Train ECM decreases the impeller clutch pressure from 2274 ± 207 kPa (330 ± 30 psi) to 550 ± 207 kPa (80 ± 30 psi). The impeller clutch pressure remains at a holding pressure of 550 ± 207 kPa (80 ± 30 psi) for all engine speeds below 1100 rpm. The low pressure allows the impeller clutch to remain filled without engaging. The torque converter housing rotates with the engine while the torque converter impeller is only partially engaged without transmitting torque. NOTE: The impeller clutch pressure is reduced because the pressure to the impeller clutch is reduced after the first second (1/60 of a minute) of engagement to extend the life of the seals and pistons in the impeller clutch. This can be demonstrated by connecting a pressure gauge to the impeller clutch pressure tap and viewing the gauge during a directional shift. Caterpillar Electronic Technician (ET) can also be used to view the impeller clutch pressure and the impeller clutch solenoid valve current during a directional shift.
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Text Reference
TRANSMISSION HYDRAULIC SYSTEM SECOND SPEED FORWARD CONVERTER DRIVE Lube - Output Transfer Gear
Lube - Output Transfer Bearings
Lube - Rear Pump Drive
Transmission Lube Dump Orifice
Impeller Clutch Modulating Valve Priority Valve 1
5
Lube - Input Transfer
4
Lockup Clutch Modulating Valve P3 SOS
Lube - Rear Pump Drive
SOS
P1 Transmission Filter
3
2 P2 1
Torque Converter Filter
Oil to Water Cooler
5
4
Transmission Control Valve
Torque Converter
Transmission Pump
Oil to Water Cooler
Air to Water Cooler Magnetic Screens
Sump Air to Water Cooler
73 When the transmission is shifted from FIRST SPEED FORWARD to SECOND SPEED FORWARD (speed shift), the Power Train ECM de-energizes the No. 5 clutch solenoid, and energizes the No. 4 clutch solenoid. The Power Train ECM also continues to de-energize the impeller clutch solenoid and the lockup clutch solenoid. When de-energized, the No. 5 clutch solenoid valve interrupts the flow of pilot oil to the speed selector spool and directs the pilot oil to the sump. When energized, the No. 4 clutch solenoid valve sends oil to the end of the 2nd speed selector spool. The force of the oil pressure overcomes the force of the selector valve spring and moves the spool from its center position. Oil from the inlet passage flows through the orifice, into the No. 4 speed clutch. The empty No. 4 clutch causes the pressure at P1 and P2 to be less than 375 kPa (55 psi). The decrease in P1 oil pressure allows the pressure differential valve spring to move the differential valve up. When the differential valve moves up, the differential valve opens a passage for oil in the differential valve spring chamber and the load piston cavity to flow to drain. The transmission control valve then repeats the fill and modulation cycle. During a speed shift, the Power Train ECM maintains maximum pressure in the impeller clutch. The transmission directional clutch picks up the load after a direction shift.
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Text Reference
TRANSMISSION HYDRAULIC SYSTEM SECOND SPEED REVERSE CONVERTER DRIVE Lube - Output Transfer Bearings
Lube - Output Transfer Gear
2
Lube - Rear Pump Drive
Transmission Lube Dump Orifice
Impeller Clutch Modulating Valve
3
Priority Valve
1
5
Lube - Input Transfer
4
Lockup Clutch Modulating Valve P3
SOS
SOS
Lube - Rear Pump Drive
P1
2
3
P2
5
Transmission Filter
Torque Converter Filter
Torque Converter Oil to Water Cooler
1
4
Transmission Control Valve
Transmission Pump
Oil to Water Cooler
Air to Water Cooler Magnetic Screens
Sump Air to Water Cooler
74 When the transmission is shifted from First Speed Forward to Second Speed Reverse (directional shift), the Power Train ECM de-energizes clutch solenoids No. 2 and 5 and energizes clutch solenoids No. 1 and 4. The ECM also energizes the impeller clutch solenoid and de-energizes the lockup clutch solenoid. When the Power Train ECM de-energizes the No. 2 clutch solenoid, the No. 2 clutch solenoid valve blocks the pilot oil flow and sends the pilot oil at the end of the selector spool to drain. The force of the selector valve spring moves the spool to its center position. When the selector spool moves to the center position, oil in the No. 2 clutch flows to the sump. When the Power Train ECM energizes the No.1 clutch solenoid, the No. 1 clutch solenoid valve sends pilot oil to the lower end of the directional selector spool. The force of the oil pressure overcomes the force of the selector valve spring and shifts the spool from its center position. Directional clutch oil flows from the pressure differential valve, past the directional selector spool, and into the REVERSE clutch (No. 1).
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Text Reference
When the Power Train ECM de-energizes the No. 5 clutch solenoid, the No. 5 clutch solenoid valve blocks the flow of pilot oil and sends the pilot oil at the end of the 1st and 3rd selector spool to the sump. The selector spool moves to the center position, oil in the No. 5 clutch flows to the sump. When the ECM energizes the No. 4 clutch solenoid, the No. 4 clutch solenoid valve sends pilot oil to the right side of the 2nd speed selector spool. The force of the oil pressure overcomes the force of the selector spool spring and moves the spool from its center position. Oil from the inlet passage flows through the orifice, past the 1st and 3rd speed selector spool, past the 2nd speed selector spool, and into the No. 4 speed clutch. As the empty No. 1 and 4 clutches fill, they cause the P1 and P2 pressures to decrease to less than 375 kPa (55 psi) momentarily. The momentary decrease in P1 oil pressure allows the differential valve spring to move the differential valve up. When the differential valve moves up, the differential valve opens a passage for oil in the differential valve spring chamber and the load piston cavity to flow to drain. The transmission control valve then repeats the fill and modulation cycle. During a directional shift, the Power Train ECM reduces the pressure in the impeller clutch allowing the impeller clutch to slip. The ECM monitors the torque converter output speed sensor and the transmission output speed sensor to determine when the transmission clutches are engaged. When the transmission clutches are engaged, the ECM engages the impeller clutch in the torque converter. The torque converter absorbs the energy of a directional shift.
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Text Reference
TRANSMISSION HYDRAULIC SYSTEM SECOND SPEED FORWARD DIRECT DRIVE Lube - Output Transfer Bearings
Lube - Output Transfer Gear
Lube - Rear Pump Drive
Transmission Lube Dump Orifice
2
Impeller Clutch Modulating Valve
3
Priority Valve
1
5
4
Lube - Input Transfer
Lockup Clutch Modulating Valve P3
SOS
SOS
Lube - Rear Pump Drive
P1
2
3
P2 1
5
Transmission Filter
Torque Converter Filter
Torque Converter Oil to Water Cooler
4
Transmission Pump
Transmission Control Valve
Oil to Water Cooler
Air to Water Cooler Magnetic Screens
Sump Air to Water Cooler
75 When the machine is operating in torque converter drive, six conditions must be present before the Power Train ECM will energize the solenoid for the lockup clutch and shift the torque converter to direct drive. 1. The transmission is in second or third gear. 2. The lockup clutch enable switch is in the ON position. 3. The torque converter output speed is above 1375 ± 5rpm. 4. The machine has been in the present speed and direction for more than two seconds. 5. Neither brake pedal is depressed. 6. The lockup clutch has been released by the Power Train ECM for at least four seconds.
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Text Reference
When the solenoid for the lockup is energized, the lockup clutch modulating valve opens. The transmission pump oil flows past the lockup clutch modulating valve and fills the lockup clutch. The lockup clutch engages and connects the turbine to the rotating housing. In DIRECT DRIVE, both the impeller clutch and the lockup clutch are engaged. The torque converter rotating housing, the impeller, and the turbine turn as a unit.
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Text Reference
POWER SHIFT TRANSMISSION
Ring Gears
Ring Gear
Input Sun Gears Input Shaft
Output Shaft
Planetary Carrier 5 1
2
3
Output Sun Gears
4
76 This illustration is a sectional view that is showing the transmission planetary group. The planetary group is equipped with two directional and three speed clutches. In this sectional view of the transmission, the input shaft and the input sun gear ar shown in red with the output shaft and the output sun gears shown in blue. The ring gears are shown in green. The planetary carriers are shown in brown while the planetary gears and shafts are shown in orange. The clutch discs, clutch plates, pistons, springs, and bearings are shown in yellow. Stationary components are shown in gray. Speed
Engaged Clutches
First/Forward
No. 2 and No. 5
Second/Forward
No. 2 and No. 4
Third/Forward
No. 2 and No. 3
Neutral
No. 3
First/Reverse
No. 1 and No. 5
Second/Reverse
No. 1 and No. 4
Third/Reverse
No. 1 and No. 3
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Text Reference
2
3
4
1 5
77 The 994F Wheel Loader is equipped with two oil-to-coolant coolers (1) and two oil-to-air coolers (2) and (3). The oil-to-coolant coolers are located on the left side of the engine. These two coolers use engine coolant to cool the transmission oil as the oil passes through the coolers. In line with the transmission oil flow through the two oil-to-coolant, an orifice is installed to divide the flow of oil between the oil-to-coolant and two oil-to-air coolers. Approximately two thirds of the torque converter outlet oil flows through the oil-to-coolant coolers. The two oil-to-air coolers are located in the cooler package at the rear of the machine. Cooler (3) has an orifice (4) that divides the other one-third of the transmission oil in half. One half of the oil flows through cooler (2) and one half of the torque converter oil flows through cooler (3). The oil from the coolers flows back to the transmission and lubricates the transmission bearings before returning to the transmission sump. A second orifice (5) is installed in a junction block that is attached to the frame of the machine.
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Text Reference
78
1
79
2
3
The upper illustration shows the orifice (1) in the smaller of the two coolers. The orifice restricts the flow through the smaller cooler in order to equally divide the flow between both coolers. The lower illustration shows the orifice (2) in the block that is attached to the rear frame (3). Access the block with the orifice from below the machine. The orifice is installed in the block to restrict the flow to approximately one-third of the flow of oil through the air-to-oil coolers.
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Text Reference
COLD POWER TRAIN ENGINE SPEED LIMITING
Power Train ECM
Engine ECM Engine Speed Sensor Cat Data Link
To Injectors
Cat Data Link Key Start Switch
Torque Converter Oil Temperature Sensor
VIMS Module
80 Cold Power Train Engine Speed Limiting The torque converter oil temperature is monitored by the torque converter oil temperature sensor which reports to the VIMS module and the engine speed is monitored by the Power Train ECM. The Power Train ECM will power up before the VIMS module is online, but the Power Train ECM will look for the torque converter oil temperature before limiting the engine acceleration or exiting the cold power train engine speed limiting feature. If the engine is started and the oil temperature at the torque converter oil temperature sensor is below the 40° C (104° F) threshold, the Power Train ECM will request an engine speed limit of 1300 rpm and limit the engine speed acceleration to 5rpms/second. The Power Train ECM will cycle through the loop monitoring for an increase in torque converter oil temperature. In the event of a fault with either sensor (engine speed sensor or torque converter oil temperature sensor), the transmission requested engine speed limit will go to 2500 rpm.
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Text Reference
81
3
82 1
2
4
Auto Lube System The auto lube system (arrow) is located on the left side in the platform. Access the auto lube system by lifting the door panel as shown in the upper illustration. The auto lube sensor (2) is located on the top plate of the tank. The sensor is a 5 kHz sensor that communicates with the Power Train ECM. The auto lube solenoid (1) is an output of the Power Train ECM. The ECM sends a current to the solenoid to cycle the auto lube pump (3). Also shown, is the auto lube tank (4).
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Text Reference
1
2
3
83 This illustration shows the lubrication points on the rear frame of the machine. The auto lube pump and tank assembly (1) is located on the left side of the machine in the platform. The previous illustration shows the components of the auto lube pump. Also shown is the engine fan system and pulley (2). The following is a list of the lube points on the rear. - Fan drive shaft bearing - Pulley (support group alternator) - Rear trunnion (rear axle) (Qty 2) - Front trunnion (rear axle) (Qty 2) - Head end of the steering cylinders (Qty 2) - Lower bearing articulation hitch Hose (3) supplies auto lubrication to the components on the loader frame. NOTE: The upper drive shaft bearing is not an auto lube point. This point is greased manually by the operator.
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Text Reference
84 This illustration shows the location of the auto lube points on the pulley shaft and the fan drive shaft.
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Text Reference
1 2
85 This illustration shows the lubrication points on the loader frame of the machine. The loader arms lube points are be shown in the following illustration. The following is a list of the lube points on the loader frame. - Tilt cylinder head end pins (Qty 2) - Steering cylinder rod end pins (Qty 2) - Lift cylinder head end pins (Qty 2) - Upper bearing articulation hitch Divider block (1) supplies auto lubrication to the left side of the lift linkage and divider block (2) supplies auto lubrication to the right side of the lift linkage. NOTE: The lower drive shaft bearing is not an auto lube point. This point is greased manually by the operator.
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86 The illustration shows the auto lubrication points for the lift and tilt linkage. The following is a list of the lube points on the lift linkage and tilt linkage. - A-Pins for upper end of the lift arms (Qty 2) - B-Pins for the lower end of the lift arms (Qty 2) - C-Pins link assembly to the bucket (Qty 2) - D-Pins lever assembly to the link assembly (Qty 2) - E-Pins lever assembly to the rod end of the tilt cylinder (Qty 2) - K-Pins for the rod end of the lift cylinder (Qty 2) - Center pins for the lever assembly to the lift linkage (Qty 2)
Text Reference
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Text Reference
11 1
12
13
2
3
14
4
15
6
5
10
7 8
17
16
9
18
87 The power train hydraulic system is equipped with remote pressure taps. The remote pressure taps are located in the service bay, behind the cab. The remote pressure taps are: - Rear brake pressure (1)
- Steering cooling pump pressure (10)
- Front brake pressure (2)
- Speed clutch pressure (11)
- Brake cooling pump pressure (3)
- Directional clutch pressure (12)
- Front brake accumulator pressure (4)
- Torque converter inlet pressure (13)
- Rear brake accumulator pressure (5)
- Torque converter outlet pressure (14)
- Implement pilot pressure (6)
- Lock-up clutch control pressure (15)
- Implement cooling pump pressure (7)
- Impeller clutch control pressure (16)
- Left steering pump pressure (8)
- Transmission lube pressure (17)
- Right steering pump pressure (9)
- Transmission fluid sampling port (S•O•S) (18)
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Text Reference
POWER TRAIN TORQUE STRATEGY
Power Train ECM
Torque Converter Output Speed Sensor
Transmission Output Speed Sensors
Engine ECM
Cat Data Link
Torque Converter Pedal Position Sensor
To Injectors
Throttle Pedal Position Sensor
Cat Data Link
Implement ECM
Lift Linkage Position Sensor
Implement Fixed Pump Pressure Sensor
88 994F Wheel Loader Torque Strategy Torque strategy is another feature of the Power Train ECM. The purpose of this feature is to control the torque delivered through the power train while digging. This action allows more available torque to the implement pumps. By controlling engine speed, the Power Train ECM is able to manage the loads on the power train, extending power train life while maintaining digging performance. By decreasing the engine speed, the amount of torque that is delivered to the power train through the torque converter is reduced. Since the implement pump drives are connected directly to the engine, maximum torque is delivered to the pumps when the engine speed decreases. This feature results in a net gain of available torque for the pumps.
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Text Reference
994F WHEEL LOADER TORQUE CURVES FOR POWER TRAIN TORQUE STRATEGY Torque Absorbed by Torque Converter
TORQUE
Torque Available for Pumps
Engine Torque Output
1253
1550
ENGINE RPM
89 Torque strategy is automatically enabled when the Power Train ECM determines machine conditions are appropriate for digging. The conditions are: 1. Transmission in FIRST SPEED FORWARD for at least 1.5 seconds. 2. The B-pin is below the horizontal line of the A-Pin. 3. Ground speed is less than 6.8 km/h (4.25 mph). When torque strategy is initiated, the Power Train ECM uses internal data and information communicated over the CAT Data Link from the implement ECM, and the Engine ECM to determine the torque strategy parameters. The Implement ECM signals hydraulic pressure from the implement fixed displacement pump and signals the lift linkage position as part of the digging status. The Power Train ECM uses the transmission output speed sensors, and the torque converter output speed sensor to determine ground speed. The Power Train ECM also evaluates reduced rimpull status and torque converter pedal position. The Engine ECM uses the throttle pedal position sensor in order to provide the engine rpm signal.
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Text Reference
When torque strategy is activated, the Power Train ECM sends a transmission requested engine speed limit to the Engine ECM over the Cat Data Link. The transmission requested engine speed limit will vary between 1250 and 2500 rpm. The actual value varies based on the engine speed, torque converter output speed, implement fixed pump hydraulic pressure, torque converter pedal position, and reduced rimpull status. When torque strategy is inactive, the Power Train ECM sends a transmission requested engine speed limit of 2500 rpm to the Engine ECM. The Engine ECM high idle of 1700 rpm does not allow the engine speed to exceed 1700rpm. Two different engine stall speeds can be measured during a torque converter stall check. One stall speed (1550) will be measured when torque strategy is active and another (1605) will be measured when torque strategy is inactive. When torque strategy is active: - An increase in the implement fixed pump pressure will lower the transmission requested engine speed limit. - A reduction in the desired rimpull with the reduced rimpull selector switch or the torque converter pedal will increase the transmission requested engine speed limit. When torque strategy is enabled, any of the following conditions will cause torque strategy to be disabled: - Machine speed greater than 7.1 km/h (4.4 mph). - Transmission not in FIRST SPEED FORWARD. - The B-Pin is above the horizontal line of the A-Pin.
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Text Reference
994F WHEEL LOADER IMPLEMENT HYDRAULIC SYSTEM Pilot Pilot Relief Implement Oil Filter Valve Cooling Pump
Pilot Front Control Pilot Pump Valve Pump Drive
Implement Pump Case Drain Filters Implement Pumps Main Relief Valves Main Control Valves
Tilt Cylinders
Implement Cooling High Pressure Oil Filter Oil Screens
Implement Oil Cooler Pilot System
Main System
Lift Cylinders
Implement Hydraulic Tank Cooling System
90 IMPLEMENT HYDRAULIC SYSTEM The 994F Wheel Loader implement hydraulic system consists of two basic systems with an additional common cooling system. The systems are divided in the following color codes: Orange
-
Pilot hydraulic system
Red
-
Main hydraulic system
Green
-
Common cooling system for the implement hydraulic oil
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IMPLEMENT ELECTRONIC CONTROL SYSTEM
Text Reference
Implement Electronic Control Module (ECM) Cat Data Link
Input Components
Output Components
Lift Linkage Position Sensor
Variable Pump Solenoid Valve
Fixed Displacement Pump Pressure Sensor
Lower Kickout Cushion Solenoid Raise Stop Solenoid
Kickout Set Switch
Lower Detent Coil
Bucket Positioner Switch
Raise Detent Coil
Lift Head End Pressure Sensor
Tilt Detent Coil
91 Implement Electronic Control System This diagram of the Implement Electronic Control System shows the components which provide input and output signals to the Implement Electronic Control Module (ECM). The Implement ECM receives input signals from the various sensors and switches on the machine. The Implement ECM processes the input signals, makes decisions, and provides a corresponding signal voltage to the proportional solenoid valves and detent coils. The Implement ECM stores information from the calibrations, machine settings, and operational functions. The CAT Data Link connects the Implement ECM to the Power Train ECM, and to the Engine ECM. The data link also connects the Implement ECM to the Vital Information Management System (VIMS), and electronic service tools such as Caterpillar Electronic Technician (ET).
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Text Reference
The input components to the Implement ECM are: Lift linkage Position Sensor: Sends a PWM signal to the Implement ECM communicating the position of the lift linkage in relation to the loader frame. Kickout set switch: Sends the raise and lower kickout position to the Implement ECM. Bucket positioner switch: Sends a signal to the Implement ECM to de-energize the tilt detent coil at the exact set position. Fixed displacement pump pressure sensor: Sends the fixed displacement pump pressure from the fixed displacement implement pump to the Implement ECM as a pulse width modulated signal. Lift cylinder head end pressure sensor: Sends the lift head end pressure to the Implement ECM. The output components which receive signals from the Implement ECM are: Variable Pump Solenoid Valve: This solenoid valve is an output from the Implement ECM that controls the signal flow from the implement pump. The solenoid valve controls the upstroke and destroke of the variable piston pump. Lower kickout cushion solenoid: This solenoid valve is an output from the Implement ECM. The lower solenoid drains pilot oil in the lower end of the lift stems to the hydraulic tank through an orifice. Raise stop solenoid: This solenoid valve is an output from the Implement ECM. Blocks pilot oil flow to the raise end of the lift stems and drains pilot oil in the raise end of the lift stems to tank. Raise kickout detent coil: The coil is an electromagnetic component that retains the lift control lever in the full raise position. Lower kickout detent coil: The coil is an electromagnetic component that retains the lift control lever in the full lower position. Tilt kickout detent coil: The coil is an electromagnetic component that retains the tilt control lever in the full tilt back position.
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Text Reference
2
1
92
Implement Electronic Control Module (ECM) The Implement ECM (1) is located on the left side of the machine under the door on the platform (cover removed). This illustration shows the location of the Implement ECM in the left side of the machine in the electrical bay. The Implement ECM makes decisions based on control program information in memory and switch and sensor input signals. The Implement ECM responds to machine control decisions by sending a signal to the appropriate circuit which initiates an action. For example, if the operator selects the raise function, the Implement ECM interprets the input signals from the lift linkage position sensor, evaluates the lift linkage position, and energizes the raise stop solenoid valve to stop the lift linkage movement in the raise direction. The Implement ECM receives three different types of input signals: 1. Switch input: Provides the signal line to battery, ground, or open. 2. PWM input: Provides the signal line with a square wave of a specific frequency and a varying positive duty cycle. 3. Speed signal: Provides the signal line with either a repeating, fixed voltage level pattern signal or a sine wave of varying level and frequency.
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Text Reference
The Implement ECM has three types of output drivers: 1. ON/OFF driver: Provides the output device with a signal level of +Battery voltage (ON) or less than one Volt (OFF). 2. PWM solenoid driver: Provides the output device with a square wave of fixed frequency and a varying positive duty cycle. 3. Controlled current output driver: The ECM will energize the solenoid with 1.25 amps for approximately one half second and then decrease the level to 0.8 amps for the duration of the on time. The initial higher amperage gives the actuator rapid response and the decreased level is sufficient to hold the solenoid in the correct position. An added benefit is an increase in the life of the solenoid. The Implement ECM controls the limits of the lift and tilt linkage and the stroking of the variable displacement piston pump. The Implement ECM interprets signals from the lift linkage position sensor, bucket positioner switch, implement pump pressure sensor, the kickout set switch, and the current machine operating status to determine the appropriate output signals to the systems. Different conditions of the inputs affect the output conditions. The Implement ECM communicates through the CAT Data Link. The CAT Data Link allows high speed proprietary serial communications over a twisted pair of wires. The CAT Data Link allows different systems on the machine to communicate with each other and also with service tools such as Caterpillar Electronic Technician (ET). The Implement ECM has built-in diagnostic capabilities. As the Implement ECM detects fault conditions in the implement system, it logs the faults in memory and displays them on the VIMS. The fault codes can also be accessed using the ET service tool. VIMS software can be used to view faults logged by the VIMS. Also shown is the VIMS module (2). NOTE: Implement ECM faults displayed on the VIMS relating to the Implement ECM will have a Module Identifier (MID) of "82." For additional information, refer to the Service Manual module "994F Wheel Loader Implement, Troubleshooting, Testing and Adjusting" (Form RENR6323).
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Text Reference
93
This illustration shows the location of the lift linkage position sensor (arrow). The lift linkage position sensor is located on the right side of the loader frame. The sensor sends a PWM signal to the Implement ECM reflecting the position of the lift linkage. In the event of a failure to the lift linkage position sensor, it is assumed that the lift linkage is below the horizontal line. If the other conditions are met for Dig Trigger and the lift linkage position sensor fails, the variable displacement implement pump will be de-stroked from maximum displacement to minimum displacement. Also, with a failure to the position sensor the lift detent will be inactive. A failure to the position sensor will register a CID 350 code and a message will be displayed in VIMS. NOTE: To calibrate the lift linkage position sensor, refer to the Service Manual module "994F Wheel Loader Hydraulic System, Troubleshooting, Testing and Adjusting Position Sensor (Lift Linkage - (Calibrate)" (Form RENR6323).
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Text Reference
1 2
94
This illustration shows the location of the bucket positioner switch (1). The bucket positioner switch on the right side tilt cylinder. The switch sends a signal to the Implement ECM to de-energize the tilt detent coil (not shown) as the magnet (2) passes under the switch. Normally, the magnet is adjusted in order to position the bucket at the proper dig angle.
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Text Reference
1
95
2
96
The upper illustration shows the implement pump pressure sensor (1). The pressure sensor is located on the right side inside the loader frame. Access the pressure sensor from below the loader frame. The input voltage to the pressure sensor is 24 VDC. The sensor communicates with the Implement ECM with a PWM signal. In the event of a failure to the pressure sensor, the Engine ECM will reduce the engine speed to 1253 rpm. The lower illustration shows the raise/lower kickout set switch (2) on the panel inside the cab. The switch sends the kickout position to the Implement ECM for the raise kickout position and the lower kickout position.
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Text Reference
1
97
2
1
3
4
98
The above illustration shows the location of the variable pump solenoid valve (1) in the loader frame (2). The lower illustration shows the variable pump solenoid valve (1). The valve controls the signal pressure for the variable displacement piston pump (center section). When the solenoid is de-energized, the valve is closed and the pressure in the signal line instructs the pump to go to maximum flow. When the conditions are met to activate Dig Trigger, the Implement ECM sends current to the solenoid valve. The solenoid is energized and the solenoid valve shifts to the OPEN position. The signal oil goes to tank pressure and the variable pump will be destroked. In the event of a solenoid failure, the pump will upstroke to maximum flow. Also shown are the check valve (3) and the selector and pressure control valve (4).
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Text Reference
2 1
99
4
3
100
5
The upper illustration shows the location of both (1) the raise stop solenoid valve and the lower kickout cushion solenoid valve in relation to the transmission control valve (2). The lower kickout cushion solenoid valve (3) controls the flow of pilot oil from the pilot control valve to the main control valves. When the solenoid is de-energized, the pilot oil free flows through the valve. When the solenoid is energized by a signal from the Implement ECM, the implement pilot valve (not shown) will return to the neutral position. This action opens the lower end of the lift stems to tank, blocking a free path through the solenoid valve to tank. The pilot oil in the lower end of the lift stem will drain back to the tank through orifice (5). The orifice slows down the lift stem return to the CENTER position.
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Text Reference
When the lift cylinders approach the raise stop at approximately 20 mm (0.8 inch) away from full extension, the Implement ECM sends a voltage signal to the raise stop solenoid valve (4) to block pilot oil. Then, the pilot oil in the raise end of the lift stems is directed to the hydraulic tank. The lift stem will shift to the CENTER position block supply oil to the head end of the lift cylinders. The lower kickout cushion solenoid valve and the raise stop solenoid valve are outputs of the Implement ECM.
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Text Reference
2 Front of Machine
1
1
1
994F Front Pump Drive
3
5
4 1 2 3 4 5
Fixed Displacement Piston Pumps (Implement) Variable Displacement Piston Pump (Implement) Implement Oil Cooling Pump Implement Pilot Oil Pump Front Pump Drive Lubrication Pump
101 The above illustration shows the location of the pumps on the 994F front pump drive. The implement system has three fixed displacement piston pumps (1) and one variable displacement piston pump (2). The implement oil cooling pump (3), the implement pilot pump (4), and the front pump drive lubrication pump (5) are fixed displacement gear pumps.
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Text Reference
1
102
Front Pump Drive Lubrication System The front pump drive system is located in the loader frame. The front pump drive lubrication system lubricates the bearings and gears and filters the oil in the front pump drive. Access the front pump drive (1) from the articulation hitch area.
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Text Reference
2
1
3
103
4 6
3
104
5 7
Front Pump Drive System The oil is drawn from the front pump drive (1) by the front drive lubrication pump (4) and is sent through the filter (3). The oil from the filter is sent to the divider block (2) and the oil is directed to the individual bearing and gear lubrication points in the front pump drive. The oil filter group consists of the filter base and filter, the S•O•S fluid sampling port (7), filter bypass switch (5), and the temperature sensor (6). The front pump drive oil filter bypass switch and the front pump drive oil temperature sensor communicate with the VIMS module. The temperature sensor uses a 8 VDC and provides a 5 kHz PWM output signal to the VIMS module.
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994F IMPLEMENT PILOT HYDRAULIC SYSTEM
Lift
Tilt
Text Reference
Pilot Valve
HOLD Lower Kickout Cushion Solenoid Valve
Check Valve 1
Lift Stop Solenoid Valve
Selector and Pressure Control Valve
Sequence Valve From Makeup and Vent Valve Selector Valves
From Lift Cylinders
Check Valve 2 Pilot Filter
Pilot Relief Valve
To Implement Cooler
To Lift Control Valves
Pilot Pump
To Tilt Control Valves
Implement Hydraulic Tank
105 Implement Pilot Hydraulic System - Hold This illustration shows a block diagram of the pilot hydraulic system. In this illustration, the engine is running and the control levers are in the HOLD position. The pilot system is a closed-center design. Oil is drawn from the implement hydraulic tank by the pilot pump. Pump oil is directed through the pilot filter group and is divided into two paths. One path of oil flows to the the pilot relief valve and the other path flows to the selector valves. The first path of pilot oil flows to the pilot relief valve. The pressure of the pilot oil will be limited by the relief valve setting. When the pilot pump pressure reaches the relief valve setting, the relief valve opens. Oil over the relief valve flows to the implement oil cooler (not shown) before returning to the hydraulic tank. From the pilot relief valve, the pilot oil flows over an opened check valve 2 to the pilot control valves. The pilot oil will be blocked at the pilot control valves until either the tilt or lift control lever is moved. With the pressure of the pilot relief valve adjusted higher than the adjusted pressure of the selector valve, the pressure at the left side of check valve 1 is higher than the pressure on the right side of check valve 1. The check valve 1 will stay seated.
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Text Reference
Check valve 2 is installed in the pilot system to block any oil from returning back to the pump. The second path of pilot oil directed to the selector valves is for the lift and tilt pilot lines. When the control levers are in the HOLD position, the pressure at each end of the selector valves is equal. The selector valves will be in the CENTER position. Pilot oil flows through the selector valves and through the orifices. The selector valve is used in order to circulate a small amount of warm pilot oil from the pilot pump into the pilot lines when the pilot control valve controls aren't being used to help out with cold weather conditions. As soon as the operator moves either control lever, in either direction, the valve shifts and blocks the flow to the pilot lines. It's called a thermal purge because warm pilot oil is circulated through the pilot system. In the HOLD position, the pilot oil flows back through the tank port on the pilot control valve to the hydraulic tank.
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994F IMPLEMENT PILOT HYDRAULIC SYSTEM
Lift
Tilt
Text Reference
ENGINE NOT RUNNING
Pilot Valve
Lower Kickout Cushion Solenoid Valve
Check Valve 1
Raise Stop Solenoid Valve
Selector and Pressure Control Valve
Sequence Valve From Makeup and Vent Valve Selector Valves
From Lift Cylinders
Check Valve 2
Pilot Filter
Pilot Relief Valve
To Implement Cooler
To Lift Control Valves
Pilot Pump
To Tilt Control Valves
Implement Hydraulic Tank
106 Dead Engine Lower In the event the engine is not running and the bucket is raised, the pilot system will use oil pressure in the head end of the lift cylinders for the necessary pilot pressure. Oil in the head end of the lift cylinders (blue) flows to the selector and pressure control valve. With a non-running engine the pilot pump will not be supplying pilot pressure to the system. The pressure on the left side of check valve 1 will be at zero pressure. When the pressure at the left side of check valve 1 is below the pressure that is flowing through the selector and pressure control valve, the pilot oil will open check valve 1 and flow to the pilot control valves. Check valve 2 blocks the return of pilot oil to the pilot pump. If the oil pressure in the head end of the lift cylinders goes above the adjusted pressure of the selector valve, the valve will shift down. The flow of oil from the head end of the lift cylinders will be blocked. The flow of oil for the pilot system will be reduced to the adjusted pressure of the selector and pressure control valve. Low pressure oil available for use in the pilot system. When the lift control lever is moved in the lower direction, the reduced pilot oil will flow from the lift control valve through the lower kickout cushion solenoid valve to the lower ends of the lift stems (not shown) in the main control valve. The bucket will be lowered to the ground.
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Text Reference
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7
107
Implement Pilot System The implement pilot system is made up of the following components. The illustration shows the location of the components in the loader frame - Pilot Filter Group (1) - Loader frame (2) - Pilot pump (gear) (3) - Selector and pressure reducing valve (4) - Float sequence valve (5) - Pilot relief valve (6) - Selector valve (thermal bypass) (7) - Selector valve (thermal bypass) (8)
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Text Reference
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3
7
6
108 4
5 8
9 10 11
109
12
The upper illustration shows the pilot filter group that is located in the loader frame (1). The pilot filter group is equipped with a filter (3) that is rated at 6 micron and a differential pressure switch (2). The pressure switch communicates with the VIMS module relaying the pressure drop across the filter group. The lower illustration shows the location of the following pilot components: the selector and pressure control valve (6), check valve (7), check valve (8), float sequence valve (9), pilot relief valve (10), and selector valves (thermal purge) (11) and (12). Also shown are the implement hydraulic tank (4) and the variable pump solenoid valve (5).
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Text Reference
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2
3
110
Pilot Control Valve The pilot control is located in the cab to the right of the operator's seat. The control consists of the tilt control lever (2), the lift control lever (3), and the implement lever lock (1). When the implement lever lock is in the forward position, the control levers are unlocked. When the lever lock is pulled back, the control levers are locked. The pilot control valve is also equipped with detent coils (not shown). The detent coils will hold the lift control lever in the full RAISE position, full LOWER position, and/or the tilt control lever in the full TILT BACK positions until the linkage has reached the set kickout position.
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Text Reference
TILT PILOT CONTROL VALVE HOLD Pivot Plate Upper Plunger (Tilt Back)
Upper Plunger (Dump) Detent Coil
Retainer
Retainer
Upper Centering Spring Upper Centering Spring
Lower Plunger Retainer
Lower Plunger
Metering Spring Retainer
Metering Stem Spring
Lower Centering Spring
To Hydraulic Tank
Metering Stem Spring
From Pilot Pump Tilt Back Metering Stem
Dump Metering Stem To Main Control Valve
111 Tilt Pilot Control Valve This illustration shows a sectional view of the tilt pilot control valve in the HOLD position. When the engine is running and the control lever is in the HOLD position, pilot oil from the pilot pump enters the pilot control valve and is blocked by the dump and tilt back metering stems. The lift pilot control valve operates the same way as the tilt pilot control valve. The tilt pilot control valve is equipped with a detent coil for the tilt back function only. When the tilt control lever is pulled to the DETENT position, the retainer will engage the detent coil. The detent coil will hold the retainer until the current to the detent coil is interrupted. The lift pilot control valve is equipped with a detent coil for both raise and lower functions as shown in the next illustration.
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Text Reference
LIFT PILOT CONTROL VALVE RAISE
Pivot Plate
Detent Coil (Float) Upper Plunger
Detent Coil (Raise)
Upper Retainer Upper Centering Spring Lower Plunger To Hydraulic Tank
Center Retainer Metering Spring
From Pilot Pump
Lower Retainer Metering Stem Spring
Lower / Float Metering Stem
Raise Metering Stem To Main Control Valve
From Main Control Valve
112 Lift Pilot Control Valve This illustration shows a sectional view of the lift pilot control valve in the RAISE position. In the RAISE position, the pilot oil (orange) from the pilot pump enters the control valve. When the operator moves the lift control lever into the raise direction, the pivot plate is rotated and the upper plunger, the upper retainer, lower plunger, metering spring, the lower retainer and the metering stem moves downward. As the metering stem moves downward, the port holes in the stem pass over the oil passage from the pilot pump. Pilot oil flows from the passage through the center of the metering stem to the end of the lift stem in the main control valve (not shown). At the same time, the metering stem spring is adding an upward force against the upper edge of the metering stem. Return oil from the main control valve through the lower metering stem, the center of the metering stem and to the tank port. The objective of the metering stem is to allow movement of the stem in the main control valve proportionally with the movement of the pilot control lever. The metering stem and the metering spring function as a pressure reducing valve and control the pilot oil pressure at the end of the main control valve stem. As the metering stem moves downward, pilot oil flows through the orifice, the center of the metering stem and out to the main control valve.
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Text Reference
At the same time, pilot oil from the main control valve flows back to the hydraulic tank through pilot control valve. The lift pilot control valve operates the same way as the tilt pilot control valve. The lift pilot control valve is equipped with a detent coil for both raise and lower functions. The flow of pilot oil is blocked at the main control valve stem causing the pilot pressure to increase. The pressure increase overcomes the centering spring for the main control valve stem and shifts the stem. Then, supply oil is directed to the actuator. The pressure increase is also sensed against the lower end of the metering stem. When the pressure increase overcomes the applied force, the metering stem moves up and compresses the metering spring. The upward movement restricts the flow of pilot through the orifice in the metering stem. Restricting the pilot oil flow controls the signal pressure at the stem of the main control valve. The metering spring therefore adjusts the pressure at the main control valve stem in proportion to the movement of the pilot control lever. When the lift control lever is moved to full travel and the detent coil is energized, the upper retainer (raise) will be held in position by electromagnetic force of the detent coil. The detent coil will be energized until the position sensor (not shown) recognizes the kickout position. The lever can be removed from a detent position manually. When the operator moves the lift control lever to the full LOWER position, the lower side of the pilot control valve will operate similarly to the raise side and the float detent coil will hold the control valve in the FLOAT position.
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High Pressure Screen Left Implement Pump
994F IMPLEMENT HYDRAULIC SYSTEM VARIABLE DISPLACEMENT PISTON PUMP UPSTROKED NOT IN DIG TRIGGER MODE
Relief Valve Implement Pump Pressure Sensor
High Pressure Screens
Case Drain Filters
Check Valve
Text Reference
Check Valve Relief Valve
Check Valve
Relief Valve
Tandem Implement Pump
Check Valve
High Pressure Screen Right Implement Pump
Relief Valve
Solenoid Valve Control Valve Control Valve (Left side Front Frame) (Right Side Front Frame)
Lift Head End Sensor
Implement Hydraulic Tank
113 Implement Hydraulic System Not in Dig Trigger Mode The implement hydraulic system is equipped with three fixed displacement piston pumps and one variable displacement piston pump. The three fixed displacement pumps and the variable displacement pump draw oil from the implement hydraulic tank. The supply oil is directed through the high pressure screens, the individual relief valves, and the check valves. The relief valve limits the supply oil pressure that is flowing to the left and right control valves. This illustration shows the main control valve with a raise signal from the pilot control valve (not shown). Supply oil is sent to the head end of the lift cylinders from the main control valve. Also, each individual piston pump is equipped with its own case drain filter. Oil flow from the three fixed displacement pumps and the variable displacement pump provide system oil to the lift and tilt cylinders. Oil flow is metered to the cylinders by the stems in the main control valves. The oil flow around the stems is controlled by the movement of the stems in the valve through the pressure that is applied to the ends of the stems. The operator controls the pilot oil flow and pressure that shifts the stems with controlled movement of the pilot control valve. Also, movement of the valve stems opens a passage for the oil in the opposite end of the cylinders to return to the implement hydraulic tank.
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High Pressure Screen Left Implement Pump
994F IMPLEMENT HYDRAULIC SYSTEM
Relief Valve
Implement Pump Pressure Sensor
High Pressure Screens
Case Drain Filters
Check Valve
Text Reference
VARIABLE DISPLACEMENT PISTON PUMP DE-STROKED DIG TRIGGER MODE
Check Valve Relief Check Valve Valve
Relief Valve
Tandem Implement Pump
Check Valve
High Pressure Screen Right Implement Pump
Relief Valve
Solenoid Valve Control Valve Control Valve (Left side Front Frame) (Right Side Front Frame)
Lift Head End Sensor
Implement Hydraulic Tank
114 Implement Hydraulic System In Dig Trigger Mode In this illustration, the graphic shows the machine in dig trigger mode. The machine is in first speed forward, the ground speed is less than 6.8 kmh (4.25 mph), and the B-Pin is below the horizontal line of the A-Pin. The three fixed displacement piston pumps are supplying the oil flow to the implement hydraulic system. The variable displacement piston pump is destroked to zero displacement. The implement pumps draw oil from the implement hydraulic tank. The supply oil is directed through the high pressure screens, past the individual relief valves, and the check valves. The individual relief valve limits the supply oil pressure that is flowing to the left and right control valves. This illustration shows the main control valve with a raise signal from the pilot control valve (not shown). Also, each individual piston pump is equipped with its own case drain filter. A decrease of supply oil will be sent to the head end of the lift cylinders until the implement system no longer meets the criteria for dig trigger.
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Text Reference
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4
5
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6
8
115 The implement hydraulic system is built into the loader frame (1). The following components are shown in the loader frame: case drain filters and bypass switches (2), the implement pumps and pump drive (3), the high pressure screen groups and relief valves (5), (6), (7), (9), and the hydraulic tank (4). High pressure screen (7) filters supply oil from the left side fixed displacement pump. High pressure screen (9) filters supply oil from the right side fixed piston pump. High pressure screen (5) filters supply oil from the variable displacement pump (section of the tandem pump). High pressure screen (6) filters supply oil from the center fixed displacement pump (section of the tandem pump). The implement system has two main control valves: the right control valve (8) and the left control valve (10).
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Text Reference
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116
The implement hydraulic system is equipped with four case drain filters with bypass switches. These filter groups filter the case drain oil from the four implement pumps. The following filter and bypass switch are in line with the following pump. Filter (2) and bypass switch (1) are in line with the left side fixed displacement pump. Filter (4) and bypass switch (3) are in line with the center fixed displacement pump. Filter (6) and bypass switch (5) are in line with the variable displacement pump. Filter (8) and bypass switch (7) are in line with the right side fixed displacement pump.
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Text Reference
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High pressure screen (2) is a 200 micron filter that is between the implement pump and the relief valve group (3). Each individual implement pump is equipped with it own high pressure screen and relief valve. The relief valve pressure is adjusted by rotating the adjustment screw (1). Also, the relief valve group (3) is equipped with a check valve (not shown) with free flow out of the valve.
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2
Text Reference
3
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4
119 5
4
This illustration shows the front pump drive (2) and implement pumps removed from the loader frame. The right fixed pump (1) and left fixed pump (3) are installed on each side of the tandem pump (4). The tandem pump is a combination of a fixed piston pump (nearest to the pump drive) and a variable displacement piston pump. The variable displacement piston pump is equipped with a pump control valve (5) that controls the upstroking and de-stroking of the pump when the machine requirements are met.
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Text Reference
IMPLEMENT PUMP IN DIG TRIGGER MODE Fixed Displacement Piston Pump
Swashplate
Pump Inlet
Lock Stop
Pump Outlet
Pump Control Valve
Impeller Pump
Small Bias Pump Piston Spring Inlet
Large Actuator Piston
Pump Outlet
Lock Stop
Lock Stop
Variable Displacement Piston Pump
Swashplate
120 The 994F Wheel Loader is now equipped with a new center pump on the front pump drive. The new pump is a two-section piston type pump. The tandem pump is equipped with an impeller pump (charge) that draws oil from the implement hydraulic tank (not shown) and directs oil to the inlet cavities of each pump section. The pump section that is located next to the front pump drive is a fixed displacement piston pump. This section will continuously supply oil to the main control valve when the engine is running. The displacement for the fixed pump is predetermined by the locking bolts that retain the swashplate at the fixed angle. The pump section that is away from the front pump drive is a variable displacement piston pump. This section will supply either minimum flow or maximum flow to the main control valve depending on the signal pressure at the pump control valve. The pump control valve will control the output of the variable pump using pump pressure to shift either the remote pressure control spool (not shown) and the pressure compensator spool (not shown). In this illustration showing minimum flow, oil pressure is directed to the large piston and the force against the piston moves the piston rod and the swashplate against the stop. At the same time, the spring and the pressure that is behind the small piston will be overridden. Small piston will allow the swashplate to rotate against the stop. The pump will supply sufficient oil pressure to lubricate the pump and supply instantaneous response to a request for maximum flow.
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Text Reference
VARIABLE PUMP AND PUMP CONTROL VALVE DIG TRIGGER MODE To Hydraulic Tank Variable Pump Solenoid Valve High Pressure Cutoff Spool Orifice 1 Remote Pressure Control Spool
Pump Control Valve
Pump Output
Orifice 2 Small Actuator Piston
To Fixed Displacement Pump
Spring Impeller Pump
Bias Spring Variable Displacement Pump
Large Actuator Piston
121 The signal for the control of the upstroke and destroke of the variable displacement piston pump is through a voltage signal from the Implement ECM to the solenoid valve for the variable displacement piston pump. The solenoid valve opens to relieve or is closed and blocks the oil pressure in the signal line to the pump control valve. In the illustration, the signal oil is relieved to tank pressure. When the oil at the signal line goes to zero pressure, the oil on the left side of the remote pressure spool is at tank pressure. With the orifice installed in the line between the pump outlet and the solenoid valve, the pressure on the right side of the remote pressure spool is greater than the pressure on the left side of the spool. The spring force on the left side of the remote pressure spool is overridden by the force that is developed by the system pressure on the right side of the spool. The remote pressure spool shifts to the left. System pressure is allowed to flow to the large actuator piston. The pressure in the large actuator piston overcomes the combined force of the small actuator and bias spring and shifts the swashplate to zero angle.
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Text Reference
IMPLEMENT PUMP MAXIMUM FLOW Fixed Displacement Piston Pump
Swashplate
Pump Inlet
Lock Stop
Pump Outlet
Pump Control Valve
Impeller Pump
Small Bias Pump Piston Spring Inlet
Large Actuator Piston
Pump Outlet
Lock Stop
Lock Stop
Variable Displacement Piston Pump
Swashplate
122 In this illustration, the pump is showing maximum oil flow. The oil pressure that is behind the large piston is relieved to tank. At the same time, the spring and the pressure that is behind the small piston will override the large piston and the small piston will rotate the swashplate against the lock stop. The variable pump will upstroke to maximum flow. The pump will continue to provide maximum flow until the pressure at the signal pressure at the pump control valve changes.
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Text Reference
VARIABLE PUMP AND PUMP CONTROL VALVE NOT IN DIG TRIGGER MODE To Hydraulic Tank Variable Pump Solenoid Valve High Pressure Cutoff Spool Orifice 1 Remote Pressure Control Spool
Pump Control Valve
Pump Output
Orifice 2 Small Actuator Piston
To Fixed Displacement Pump
Bias Spring
Variable Displacement Pump
Impeller Pump
Large Actuator Piston
123 Variable Implement Piston Pump Control This illustration shows the schematic with the machine not in dig trigger mode and the variable displacement piston pump upstroked. The signal for the control of the upstroke and destroke of the variable displacement piston pump is through a voltage signal from the Implement ECM to the variable pump solenoid valve. The solenoid valve opens and relieves oil pressure or is closed and blocks the oil pressure in the signal line from the pump control valve. In this illustration, the signal oil pressure is blocked at the solenoid valve. When the oil at the signal line is blocked at the solenoid valve, the pressure on both sides of the remote pressure control spool is equal. The combination of the spring force and the system pressure on the left side of the remote pressure control overrides by the force that is developed by the system pressure on the right side of the control. The control spool shifts to the right. The oil pressure at the large actuator piston flows over the remote pressure control spool and the high pressure cutoff spool to the tank. The oil that is behind the large actuator piston is at tank pressure. The force of the bias spring and the system pressure on the small piston enables the small piston to override the large piston and the swashplate will rotate to maximum angle.
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Text Reference
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4
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10 11 12
124 This illustration shows the components in the right side implement control valve. The control valve is accessed from the articulation hitch. The following is a list of the components. - Inlet port for the right fixed displacement implement pump (1) - Tilt rod end port (2) - Tilt load check valve (3) - Check valve (4) - Tilt head end port (5) - Check valve (6) - Lift rod end port (7) - Lift head end port (8) - Check valve (9) - Makeup and vent valve (10) - Lift load check valve (11) - Hydraulic tank port (12)
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Text Reference
1
125 This illustration shows the back side of the right implement control valve. Port (1) is the inlet connection for the center fixed displacement piston pump.
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Text Reference
RIGHT CONTROL VALVE RIGHT SIDE IN FLOAT From Right Fixed Displacement Pump
To Float Sequence Valve
FLOAT A3
From Rod End Cylinder
A2 A1
From Center Fixed Displacement Pump
To Tank To Float Sequence Valve
MAKEUP
To Rod End Cylinder
From Head End cylinder
To Hydraulic Tank
To Rod End Cylinder
From Tank
126 The 994F Wheel Loader main implement system is made up of two control valves, the right control valve and the left control valve. The above illustration shows the right side control valve in the float position including the makeup and vent valve. The makeup and vent valve is shown in both the makeup and float operation. In the makeup operation, the pressure in the hydraulic tank exceeds the pressure in the rod end of the lift cylinder. Lowering the bucket faster than the pump can fill the rod end of the lift cylinder the piston displacement causes a vacuum in the rod end of the lift cylinders. The makeup valve allows oil from the tank line to flow into the rod end of the lift cylinders and fill the void. In the float operation, the makeup and vent valve allows the oil that is holding the vent valve against the seat to flow through the float sequence valve (not shown) to the hydraulic tank. The small orifices in the base of the vent valve (in the left control vent valve) allows lift cylinder rod end pressure, along the with the spring force, to keep the makeup and vent valves for both the right and left control valves to remain seated. Both the left and right control valve makeup and vent valve spring chambers are connected. Once the oil that is behind the float sequence is opened to tank, the oil flows through the float sequence valve (not shown). The pressure in the spring chamber drops to tank pressure.
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Text Reference
The pressure of the supply oil that is flowing to the rod end of the lift cylinders acts against the vent valve and the force overrides the spring and the valve opens. When the vent valve shifts to the OPEN position and the supply oil flows to the hydraulic tank. At that time, both ends of the lift cylinders will be open to the tank. This will allow the bucket to follow the contour of the ground. With the differential areas of the makeup and vent valve, the force that is produced by the lift rod end pressure is enough to move the valve off the seat. When the vent valve moves off the seat, the oil from the implement pumps flows past the vent valve to the hydraulic tank. Both ends of the lift cylinders are open to the hydraulic tank allowing the bucket to float along the contour of the ground. With the make up and vent valve used in the float position, the following explanation describes how the forces with in the make up and vent valve effect the float operation. A1 = The Tank Pressure Effective Area, A2 = The Lift Rod End Effective Area, and A3 = The Spring Chamber Effective Area. When the float sequence valve (not shown) is blocked: (Tank Pressure)*A1 + (Lift Rod End Pressure from the right control valve)* A2 is less than the Spring Force + (Lift Rod End Pressure connected from the left control valve)*A3. The vent valve stays seated. When the float sequence valve (not shown) is in the OPEN position: (Tank Pressure)*A1 + (Lift Rod End Pressure from the right control valve)* A2 is greater than the Spring Force + (Tank Pressure opened through the float valve) *A3. The vent valve moves off the seat and opens the lift rod end pressure to the implement hydraulic tank.
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3
Text Reference
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6
5
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9 11
12
13
14
127 This illustration shows the components in the left side implement control valve. The control valve is accessed from the articulation hitch. The following is a list of the components. - Inlet port for the left fixed displacement implement pump (1) - Check valve (2) - Lift head end drain port (3) - Tilt load check valve (4) - Relief and makeup valve (5) - Tilt head end port (6) - Tilt rod end port (7) - Relief and makeup valve (8) - Lift rod end port (9) - Lift head end port (10) - Makeup and vent valve (11) - Relief and makeup valve (12) - Lift load check valve (13) - Hydraulic tank port (14)
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Text Reference
1
128 This illustration shows the back side of the left implement control valve. Port (1) is the inlet connection for the center variable displacement piston pump.
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Text Reference
LEFT CONTROL VALVE LEFT SIDE IN FLOAT To Float Sequence Valve
From Left Fixed Displacement pump
From Head End Lift Cylinders
FLOAT A3
From Rod End Cylinder
Additional Stem
A2 From Center Variable A1 Displacement Pump
To Tank To Float Sequence Valve
MAKEUP
Lift Stem To Rod End Cylinder
Makeup and Vent Valve To Rod End Cylinder
From Head End cylinder
From Tank
129 The 994F Wheel Loader implement system is made up of two control valves, the right control valve and the left control valve. The above illustration shows the left side control valve in the float position including the makeup and vent valve. The makeup and vent valve is shown in both the makeup and float operation. Lowering the bucket faster than the implement pump can fill the rod end of the lift cylinder causes a void in the rod end of the lift cylinders. In the makeup operation, the pressure in the hydraulic tank side of the vent valve exceeds the pressure in the rod end of the lift cylinder. The vent valve moves upward and allows oil from the tank line to flow into the rod end of the lift cylinders and fill the void. In the float operation, the oil that is holding the vent valve against the seat is allowed to flow through the float sequence valve (not shown) back to the hydraulic tank. The small orifices in the base of the vent valve allows lift cylinder rod end pressure, along with the spring force, to keep the makeup and vent valves for both the right and left control valves to remain seated. Both the left and right control valve makeup and vent valve spring chambers are connected. Once the oil behind the float sequence valve (not shown) is open to the hydraulic tank, the pressure in the spring chamber drops to tank pressure. With the differential areas of the makeup and vent valve, the force that is produced by the lift rod end pressure is enough to move the valve off the seat.
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Text Reference
When the vent valve moves off the seat, the oil from the implement pumps flows past the vent valve to the hydraulic tank. Both ends of the lift cylinders are open to the hydraulic tank allowing the bucket to float along the contour of the ground. With the make up and vent valve used in the float position, the following explanation describes how the forces within the makeup and vent valve effect the float operation. A1 = The Tank Pressure Effective Area, A2 = The Lift Rod End Effective Area, and A3 = The Spring Chamber Effective Area. When the float sequence valve (not shown) is blocked: (Tank Pressure)*A1 + (Lift Rod End Pressure from the left control valve)* A2 is less than the Spring Force + (Lift Rod End Pressure connected through the orifice and connected to the right control valve vent valve spring chamber)*A3. The vent valve stays seated. When the float sequence valve (not shown) is in the OPEN position: (Tank Pressure)*A1 + (Lift Rod End Pressure from the right control valve)* A2 is greater than the Spring Force + (Tank Pressure open through the float valve) *A3. The vent valve moves off the seat and opens lift rod end pressure to the implement hydraulic tank.
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LEFT CONTROL VALVE LOWER
Text Reference
From Left Fixed Displacement pump
From Head End Lift Cylinders
Addit ional St em
From Cent er Variable Displacement Pump
To Rod End Cylinder
From Head End cylinder
130 The left control valve on the 994F Wheel Loader is now equipped with an additional stem that uses pilot oil pressure from the lower pilot valve to control when the stem will be shifted. When the lower pilot oil reaches the required pressure, the force that is developed by the pilot oil pressure will override the springs on the right side of the additional stem. The additional stem will start to shift to the right. Return oil from the head end of the lift cylinders will be allowed to flow around the additional stem through the passage in the valve to the hydraulic tank. This will help to decrease the lower cycle time by approximately 10%.
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Text Reference
9 9 4 F WHEEL LOADER IMPLEMENT HYDRAULIC SYSTEM HOLD / VARIABLE PISTON PUMP UPSTROKED
Pilot Control Valve Tilt
Lift
Orifice Raise Stop Solenoid Valve
Check Valve Selector And Pressure Control Valve
Lower Kickout Cushion Solenoid Valve
Float Lift Tilt Sequence Selector Selector Valve Valve Valve
Left Side Cont rol Valve
Right Side Cont rol Valve Lower Sequence
Variable Pump Solenoid Valve
Check Valve
Case Drain Filter Pilot Relief Valve
Pilot Oil Filter
Fixed Displacement Pump
High Pressure Screen
Pilot Pump
Case Drain Filter
Relief Valve
RAISE
Tilt St em
Relief Valve
High Pressure Screen
LOWER
LOWER
Lift St em High Pressure Screen
Fixed Displacement Pump
TILT BACK
Line Relief Valves
Pressure Sensor
Fixed and Variable Displacement Pump
Case Drain Filter
DUMP
DUMP
Tilt St em
Case Drain High Pressure Screen Filter
To Implement Oil Cooler
TILT BACK
Relief Valve
Makeup and Vent Valves
RAISE
Lift St em
Relief Valve
Implement Oil Level Sensor
Lift Head End Sensor
Liquid Level Gage
Breaker Relief Valve
Implement Hydraulic Tank Expansion Tank
Expansion Tank
131 This schematic shows the hydraulic flow with the control levers in the HOLD position. When the engine is running, pilot oil that flows from the pilot pump through the pilot relief valve and is blocked at the pilot control valve. At the same time, oil from the pilot pump flows through the tilt selector valve and lift selector valve. With no signal pressure at either end of the selector valves, the selector valves are in the CENTER position. The pilot oil that is flowing out of the selector valves passes through the orifices. Then, the oil flows back through the pilot control valves to the hydraulic tank. The three fixed displacement piston pumps and the variable displacement piston pump draw oil from the hydraulic tank. Each implement pump directs system oil through the individual high pressure screens, past the individual relief valve, over the individual check valve and supply hydraulic oil to the main control valve. The main control valve is an open-centered valve. With no pilot control valve movement, the open-center valve directs the supply oil through the main control valve and returns the oil to the hydraulic tank. The solenoid valve for the variable displacement piston pump is de-energized and the signal oil to the pump is blocked. At this time, the variable displacement piston pump is upstroked and supplying oil to the hydraulic system.
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Text Reference
994F WHEEL LOADER IMPLEMENT HYDRAULIC SYSTEM RAISE / VARIABLE PISTON PUMP DESTROKED
Pilot Control Valve Tilt
DIG TRIGGER MODE
Lift
Orifice Raise Stop Solenoid Valve
Check Valve Selector and Pressure Control Valve
Lower Kickout Cushion Solenoid Valve
Tilt Float Lift Sequence Selector Selector Valve Valve Valve
Right Side Control Valve
Left Side Control Valve Lower Sequence
Variable Pump Solenoid Valve
Check Valve
Case Drain Filter Pilot Relief Valve
Pilot Oil Filter
Fixed Displacement Pump
High Pressure Screen
Pilot Pump
Dump
Dump
Tilt Stem
Case Drain High Pressure Screen Filter
To Implement Oil Cooler
Tilt Back
Relief Valve
Tilt Stem
Relief Valve
Raise
Lower
Lower
Lift Stem High Pressure Screen Case Drain Filter
Fixed Displacement Pump
Line Relief Valves
Pressure Sensor
Fixed and Variable Displacement Pump Case Drain Filter
Tilt Back
Lift Stem Makeup and Vent Valves
Relief Valve
High Pressure Screen
Raise
Relief Valve
Implement Oil Level Sensor
Lift Head End Sensor
Liquid Level Gage
Breaker Relief Valve
Implement Hydraulic Tank Expansion Tank
Expansion Tank
132 This illustration shows the hydraulic oil flow with the variable displacement piston pump destroked and the power train strategy in dig trigger mode. When the machine is in dig trigger mode, the following conditions are active. The transmission is in first speed forward, the ground speed is below 7.1 k/h (4.25 mph), and the B-Pin is below the horizontal line of the APin. When the lift control lever is in the RAISE position and the machine is in dig trigger mode, pilot oil is directed through the lift stop solenoid valve to the raise ends of the individual lift stems in the main control valve. Also, as the pilot oil pressure to the right side of the lift selector valve increases, the lift selector valve shifts to the left. The flow of pilot oil through the lift selector valve is blocked. All the pilot oil is directed to the ends of the raise end of the lift stems. The force of the oil pressure on the lift stems causes the spools to move against the centering springs. The lift stems shift to the RAISE position. At this time, the lift stems direct supply oil flow to the head end of the lift cylinders. The variable pump solenoid valve is also energized. The pilot oil between the solenoid valve and variable displacement pump is drained to tank. The variable displacement pump will destroke and supply no flow to the main hydraulic system.
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Text Reference
9 9 4 F WHEEL LOADER IMPLEMENT HYDRAULIC SYSTEM RAISE / VARIABLE PISTON PUMP UPSTROKED
Pilot Cont rol Valve Tilt
Lift
Orifice Raise St op Solenoid Valve
Check Valve Select or and Pressure Cont rol Valve
Lower Kickout Cushion Solenoid Valve
Tilt Float Lift Sequence Select or Select or Valve Valve Valve
Right Side Cont rol Valve
Left Side Cont rol Valve Lower Sequence
Variable Pump Solenoid Valve
Check Valve
Pilot Relief Valve
Case Drain Filt er Pilot Oil Filt er
High Pressure Screen
Fixed Displacement Pump
Pilot Pump
Case Drain Filt er
Relief Valve
Implement Hydraulic Tank
Tilt St em
RAISE
LOWER
LOWER
Lift St em High Pressure Screen
Fixed Displacement Pump
TILT BACK
Line Relief Valves
Pressure Sensor
Fixed and Variable Displacement Pump
Case Drain Filt er
DUMP
DUMP
Tilt St em
Case Drain High Pressure Screen Filt er To Implement Oil Cooler
TILT BACK
Relief Valve
Makeup and Vent Valves
Relief Valve
High Pressure Screen
RAISE
Lift St em
Relief Valve
Implement Oil Level Sensor
Lift Head End Sensor
Liquid Level Gage
Breaker Relief Valve Expansion Tank
Expansion Tank
133 This illustration shows the hydraulic oil flow when the control lever is moved to the RAISE position and the variable displacement piston pump upstroked. When the pilot control lever is in the RAISE position, pilot oil is directed through the lift stop solenoid valve to the raise ends of the lift stems. Also, the pilot oil that is flowing to the lift selector increases in pressure, the lift selector valve shifts to the left. The flow of pilot oil through the lift selector valve is blocked. All the pilot oil is directed to the raise end of the lift stems. The force of the oil pressure on the lift stems pushes the lift stems to move against the centering springs to the RAISE position. The lift stems send supply oil flow to the head end of the lift cylinders. When the lift cylinders are at approximately 70 mm (2.75 inch) from the end of stroke, the Implement ECM energizes the raise stop solenoid valve and the flow of pilot oil to the end of the lift stems is blocked and all pilot oil in the lift stems are drained back to the hydraulic tank through the raise stop solenoid. The lift stems will shift to the CENTER position. The supply oil to the head end of the lift cylinders will be blocked.
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Text Reference
9 9 4 F WHEEL LOADER IMPLEMENT HYDRAULIC SYSTEM LOWER / VARIABLE PISTON PUMP UPSTROKED
Pilot Cont rol Valve Tilt
Lift
Orifice Raise St op Solenoid Valve
Check Valve Select or and Pressure Cont rol Valve
Lower Kickout Cushion Solenoid Valve
Tilt Float Lift Sequence Select or Select or Valve Valve Valve
Left Side Cont rol Valve
Right Side Cont rol Valve Lower Sequence
Variable Pump Solenoid Valve
Check Valve
Case Drain Filt er Pilot Relief Valve
Pilot Oil Filt er
Case Drain Filt er
To Implement Oil Cooler
High Pressure Screen
Fixed Displacement Pump
DUMP
DUMP
Tilt St em High Pressure Screen
Pilot Pump
Case Drain Filt er
Relief Valve
RAISE
Tilt St em
Relief Valve
High Pressure Screen
LOWER
LOWER
Lift St em High Pressure Screen
Fixed Displacement Pump
TILT BACK
Line Relief Valves
Pressure Sensor
Fixed and Variable Displacement Pump
Case Drain Filt er
TILT BACK
Relief Valve
Makeup and Vent Valves
RAISE
Lift St em
Relief Valve
Implement Oil Level Sensor
Lift Head End Sensor
Liquid Level Gage
Breaker Relief Valve
Implement Hydraulic Tank Expansion Tank
Expansion Tank
134 This illustration shows the hydraulic flow when the lift control lever is moved to the LOWER position and the pilot pressure is greater than 900 kPa (130 psi). When the lift control lever is in the LOWER position, pilot oil is directed to the lower end of the lift stems. Also, the pilot oil that is flowing to the lift selector increases in pressure, the lift selector valve shifts to the right. The flow of pilot oil through the lift selector valve is blocked. All the pilot oil is directed to the lower end of the lift stems. The lift stems shift and the lift stems open passages for oil flow from the implement pumps to the rod end of the lift cylinders to lower the bucket. The position of the lift stem also opens a passage for the oil in the head end of the lift cylinders to flow to the implement hydraulic tank. When the pilot pressure is greater than 900 kPa (130 psi) pilot oil pressure, the lower sequence stem starts to shift to the right. Oil in the head end of the lift cylinder is allowed to flow through the sequence stem, through the main control valve, and return to the implement hydraulic tank. This will increase the cycle time for lowering the lift linkage. The lower circuit is equipped with a lower kickout cushion solenoid valve. When the lift linkage is lowered to a predetermined position that is set by the lower kickout, the Implement ECM energizes the solenoid and de-energizes the lower detent.
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Text Reference
The lower kickout cushion solenoid valve shifts downward and blocks the path of pilot oil to the lift stem. Then, the lower pilot oil behind the lower end of the lift stem flows through the orifice to the hydraulic tank. All the pilot oil flows through the orifice slowing down the lower pilot oil drain to the hydraulic tank. Restricting the flow of pilot oil back to the hydraulic tank slows the shifting of the lift stems to the HOLD position. The lift cylinders are cushioned as the bucket nears the kickout position.
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Text Reference
9 9 4 F WHEEL LOADER IMPLEMENT HYDRAULIC SYSTEM FLOAT / VARIABLE PISTON PUMP UPSTROKED
Pilot Cont rol Valve Tilt
Lift
Orifice Raise St op Solenoid Valve
Check Valve Select or and Pressure Cont rol Valve
Lower Kickout Cushion Solenoid Valve
Tilt Float Lift Sequence Select or Select or Valve Valve Valve
Left Side Cont rol Valve
Right Side Cont rol Valve Lower Sequence
Variable Pump Solenoid Valve
Check Valve
Case Drain Filt er Pilot Relief Valve
Pilot Oil Filt er
Fixed Displacement Pump
High Pressure Screen
Pilot Pump
Case Drain Filt er
Relief Valve
RAISE
Tilt St em
Relief Valve
High Pressure Screen
LOWER
LOWER
Lift St em High Pressure Screen
Fixed Displacement Pump
TILT BACK
Line Relief Valves
Pressure Sensor
Fixed and Variable Displacement Pump
Case Drain Filt er
DUMP
DUMP
Tilt St em
Case Drain High Pressure Screen Filt er
To Implement Oil Cooler
TILT BACK
Relief Valve
Makeup and Vent Valves
RAISE
Lift St em
Relief Valve
Implement Oil Level Sensor
Lift Head End Sensor
Liquid Level Gage
Breaker Relief Valve
Implement Hydraulic Tank Expansion Tank
Expansion Tank
135 This illustration shows the hydraulic oil flow when the lift control lever is moved to the FLOAT position. When the lift control lever is in the FLOAT position, pilot oil is directed to the lower end of the lift stems. The force that is developed by the pilot oil pressure causes the lift stems to move against the centering springs to the LOWER position. The lift stems open passages for supply oil flow from the implement pumps to flow to the rod end of the lift cylinders. With the lift control lever is in the FLOAT position, the oil pressure in the pilot line develops a force on the spool in the sequence valve. The sequence valve shifts, and allows the oil in the spring cavity for the makeup and vent valve to flow through the sequence valve and back to the hydraulic tank. The makeup and vent valve shifts to allow oil that is directed to the rod end of the lift cylinder to flow to the hydraulic tank. When the makeup and vent valves move off their seats, oil intended for the rod end of the lift cylinders flows past the makeup valves to the tank. At this time, both ends of the lift cylinders are open to the tank allowing the bucket to float along the ground. Also, the position of the lift stem opens a passage for the oil in the head end of the lift cylinders to flow to the implement hydraulic tank. The detent coil will hold the lift control lever in the FLOAT position until the lever is moved from the FLOAT position or the current to the detent coil is interrupted.
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Text Reference
9 9 4 F WHEEL LOADER IMPLEMENT HYDRAULIC SYSTEM DUMP / VARIABLE PISTON PUMP UPSTROKED
Pilot Cont rol Valve Tilt
Lift
Orifice Raise St op Solenoid Valve
Check Valve Select or and Pressure Cont rol Valve
Lower Kickout Cushion Solenoid Valve
Tilt Float Lift Sequence Select or Select or Valve Valve Valve
Left Side Cont rol Valve
Right Side Cont rol Valve Lower Sequence
Variable Pump Solenoid Valve
Check Valve
Case Drain Filt er Pilot Relief Valve
Pilot Oil Filt er
Fixed Displacement Pump
High Pressure Screen
Pilot Pump
Case Drain Filt er
Relief Valve
RAISE
Tilt St em
Relief Valve
High Pressure Screen
LOWER
LOWER
Lift St em High Pressure Screen
Fixed Displacement Pump
TILT BACK
Line Relief Valves
Pressure Sensor
Fixed and Variable Displacement Pump
Case Drain Filt er
DUMP
DUMP
Tilt St em
Case Drain High Pressure Screen Filt er To Implement Oil Cooler
TILT BACK
Relief Valve
Makeup and Vent Valves
RAISE
Lift St em
Relief Valve
Implement Oil Level Sensor
Lift Head End Sensor
Liquid Level Gage
Breaker Relief Valve
Implement Hydraulic Tank Expansion Tank
Expansion Tank
136 This illustration shows the hydraulic flow when the tilt control lever is moved to the DUMP position and the variable displacement piston pump is upstroked. When the tilt control lever is in the DUMP position, pilot oil is directed to the dump end of the tilt stems. Also, pilot oil is flowing to the tilt selector valve. As the pilot pressure at the tilt selector valve increases, the tilt selector valve shifts to the right. The flow of pilot oil through the tilt selector valve is blocked. All the pilot oil is directed to the dump end of the tilt stems. The force of the oil pressure on the tilt stems cause the stems to move against the centering springs to the DUMP position. The tilt stems send supply oil flow to the rod end of the tilt cylinders. The dump circuit is equipped with makeup valves. As the speed of the bucket rotating around the B-Pin increases, the effect of gravity on the bucket changes the force from the rod end of the tilt cylinder to the head end. The implement pumps are not able to supply the required oil. There will be void in the rod end of the tilt cylinder. The pressure in the dump circuit will decrease. The pressure on the tank side of the makeup valve will be greater than the pressure on the tilt rod end. The poppet will come off the seat and return oil from the head end of the tilt cylinder flows into the rod end to fill the void.
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Text Reference
2
1 3
137
4 5 6
7
8
9
10
138
11
Implement Hydraulic Oil Cooling System The upper illustration shows the components of the implement hydraulic oil cooling system in the loader frame. In the system, the implement oil cooling gear pump (1) on the front pump drive (2) draws hydraulic oil from the hydraulic tank (4) and directs the oil to system bypass valve (3). Also, the tank oil from the pilot relief valve (5) is directed to the system bypass valve (3). The combined oil flows out of the system bypass valve to the implement oil filter (7), through cooler bypass (11), through the implement oil cooler (10) in the lower illustration rear frame. Then, the oil flows back through cooler bypass (11) to the hydraulic tank (4). Also shown is the hydraulic tank (9) for the brake oil cooler system and the main control valve (6). The filter group is equipped with a bypass switch (8) that communicates with the VIMS module.
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Text Reference
1 2
139 3
4
5
6
Implement Hydraulic Oil Cooling System - Filter Group The upper illustration shows the filter group. In the filter group are the filter (1) and the filter bypass switch (3). Also shown are the steering and brake hydraulic tank (2) and the brake cooler tank (4). The filter bypass switch communicates with the VIMS module. The lower illustration shows the location of the implement hydraulic oil cooler (5) within the radiator package (6).
140
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Text Reference
141
1
3
2 4 6 8
5 7 142 9
The upper illustration shows the location of the diagnostic ports on the loader frame. The lower illustration shows the location for the following pressure taps. - Parking brake pressure (1) - Center variable displacement pump (2) - Left fixed displacement pump (3)
- Center fixed displacement pump (4)
- Right fixed displacement pump (5)
- Lift head end pressure (6)
- Tilt head end pressure (7)
- Lift rod end pressure (8)
- Tilt rod end pressure (9)
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1
Text Reference
2
3
4
5
6 7
143 This illustration is a view from the left side of the machine. Also, the illustration shows the location of the expansion tanks, the implement hydraulic tank, and the lines in relation to the loader frame and the rear frame. The following are the components for the implement hydraulic tank expansion system. - Loader frame (1)
- Rear frame (2)
- Breaker relief valve (3)
- Expansion tanks (4)
- Hydraulic oil sight gauge (5)
- Hydraulic tank (6)
Receiver assembly (7) for the external oil fill for the implement hydraulic tank is also shown. The operation of the expansion system is to give extra air for the implement hydraulic tank to keep cyclic pressures to a minimum when the implements are operated for adequate tank life. The expansion tanks are installed on the platform assembly higher than the implement hydraulic tank. The difference of height between the expansion tanks and the implement hydraulic tank will allow gravity to assist in returning the hydraulic oil back to the implement hydraulic tank through the lower hose assembly.
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Text Reference
994F WHEEL LOADER STEERING SYSTEM Steering Cooling Pump
Steering Cooling Filter
Steering Hydraulic Tank
Compensator Valve Group
Steering Control Valve
High Pressure Screens Pilot Valve
Neutralizer Valves
Steering Pumps
Steering Coolers
Case Drain Filters
Diverter Valve
Secondary Steering Pump
Steering Cylinder
Pressure Reducing Valves
144 STEERING HYDRAULIC SYSTEM Steering System Components This illustration shows the components in the steering hydraulic system on the 994F Wheel Loader. The color codes for the components in the steering hydraulic system are: Orange
-
Steering pilot system
Red
-
Main steering system
Green
-
Steering cooling system
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To The Articulation Hitch
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Text Reference
1 2
2
994F Rear Pump Drive
3
1 2 3 4
4
Service Brake Cooling Pump Steering Hydraulic Oil Pumps Steering Oil Cooling Pump Brake Pump
145 This illustration shows the location of the pumps on the 994F rear pump drive as viewed from above. The pump locations are the same as the 994D. The service brake cooling pump (1) and the steering and brake oil cooling pump (3) are fixed displacement gear pumps. The steering hydraulic oil pumps (2) and the brake application oil pump (4) are variable displacement piston pumps.
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2
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3
Text Reference
6
5
4
1 7
8
9
146 Steering System The steering system is made up of the following components that are located on the rear frame (1). - Neutralizers and quad check valves (2) - High pressure screens (3) - Steering Valves (control and reducing) (4) - Case drain filters (5) - Steering and brake hydraulic tank (6) - Right steering cylinder (7) - Left steering cylinder (8) - Steering pumps (9)
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Text Reference
1 2
5
3
4
6
147
The steering neutralizers and quad check valve are located at the articulation hitch between the cab and the rear frame (1). The bracket for the strikers (2) and (5) are attached to the loader frame. The neutralizer valve is normally open between the pilot control valve (not shown) and the quad check valve. Pilot oil is allowed to flow through the neutralizer valve when the operator moves the pilot valve to articulate the machine. When the adjusted striker makes contact with the neutralizer, the valve will block pilot oil through the neutralizer valve. The machine will stop articulating. In a right turn, neutralizer (3) will contact striker (2). In a left turn, neutralizer (6) will contact striker (5). Quad check valve (4) is between the neutralizer valves and the ends of the stem in the steering control valve (not shown). The quad check valve has two check valves for each pilot line. One check valve allows flow through to the steering control valve, while preventing return tank pilot flow. When pilot oil is directed to the steering control valve, the pilot oil flows through the free flow check valve. When the pilot control valve is returned to the HOLD position, the free flow check valve will seat and block pilot oil between the check valve and the steering control valve forcing pilot oil to return through the purge orifice in the steering control valve (not shown). The stem in the steering control valve will be held in the HOLD position until the pilot control valve is moved in either direction. The second check valve will allow the trapped pilot oil to flow back to the pilot control valve when the valve is moved to the opposite direction.
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Text Reference
LESS THAN MAXIMUM TURN
Orifice
To Steering Control Valve
NEUTRALIZER VALVE
From Steer Lever Spring
To Tank
Valve Spool
MAXIMUM TURN
Center Passage
Orifice
To Steering Control Valve
From Steer Lever Spring
To Tank
Valve Spool
Center Passage
148 This illustration shows a sectional view of the neutralizer valve. During a less than maximum turn, oil from the steering control lever flows through the neutralizer valve to the steering control valve. When the striker comes in contact with the neutralizer valve spool, the valve stem shifts and oil flow to the steering control valve is blocked. Pilot oil at the steering control valve flows back through the orifice and center passage in the spool valve to drain. The centering spring centers the steering control valve and stops the machine from articulating further. The machine will continue to turn until the steering pilot control valve is shifted in the opposite direction.
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1
2
Text Reference
4
3
149
150 5
6
7
The upper illustration shows the case drain filters that are located in the pump bay. The lower illustration show the high pressure screens. Access to the filters and screens is gained through the doors in the platform behind the cab. The steering hydraulic system is equipped with two case drain filters (1) and (3). They filter the oil that is in the steering pump case that will flow back to the steering hydraulic tank. Each filter is equipped with a bypass switch (2) and (4). The switch will send a signal to the VIMS module if one of the filters becomes plugged. High pressure screens (5), and (6) strain the system oil that is flowing from the steering pumps to the inlet port on the steering control valve. Also shown is the pump drive shaft (7).
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1
- 167 -
2
Text Reference
3
4
5
6
151 This illustration shows the location of the following components of the steering hydraulic system that are located on the inside of the right frame. Access these components through the door that is behind the cab in the platform. Steering control valve (4) sends system oil supplied by the two steering pumps to the steering cylinders (not shown) when a pilot oil signals the valve to shift. The steering control valve also sends a signal to the margin spool in each pump control valve on the steering pumps. Selector and pressure reducing valve 1 (6) reduces oil that is supplied by the steering pump to the diverter spool in the secondary steering control valve (not shown) and the primary steering pressure switch (5). Orifice (3) meters the reduced oil that flows to the primary steering pressure switch (5). The pressure switch sends a signal to the VIMS module if the primary steering pressure is lost. Adapter (2) is equipped with an orifice that restricts the flow of steering pump oil to tank in order build up pressure behind the orifice to shift the diverter spool in the secondary steering valve. Also, the orifice opens a free path to discharge the oil between the reducing valve and the diverter valve to drain in case of a loss of steering pump oil. Selector and pressure reducing valve 2 (1) reduces the pressure of the steering oil pressure to the pilot pressure level. Then, that oil is directed to the pilot control valve.
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Text Reference
STEERING PUMP AND PUMP CONTROL VALVE
From Steering Control Valve
ENGINE OFF
Flow Compensator Spool Pressure Compensator Spool
Pump control Valve Swashplate
To Steering Control Valve
Maximum Angle Stop
Large Actuator Piston
Steering Pump
Minimum Angle Stop
Bias Spring Large Actuator Piston To Steering Control Valve
Small Actuator Piston From Steering Control Valve
Flow Compensator Spool
Small Actuator Piston
Pressure Compensator Spool
152 Shown is a schematic and sectional view of the steering pump and pump control valve. The pump has two actuator pistons which work together to continually adjust the angle of the swashplate. The small actuator piston that is assisted by the bias spring is used to upstroke the pump. The large actuator piston is used to destroke the pump. The pump control valve consists of a flow compensator (margin) spool and a pressure compensator (cutoff) spool. The valve keeps the pump flow and pressure at a level needed to fulfill the demands of the steering system. The margin compensator spring maintains the pump supply pressure at 2100 ± 105 kPa (305 ± 15 psi) above the signal pressure. The pressure compensator spring limits the system pressure to 29000 ± 350 kPa (4200 ± 50 psi). When the engine is OFF, the bias spring in the small actuator piston moves the swashplate to maximum angle.
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From Steering Control Valve
Text Reference
STEERING PUMP AND PUMP CONTROL VALVE LOW PRESSURE STANDBY
Flow Compensator Spool Pressure Compensator Spool
Pump control Valve
Swashplate
To Steering Control Valve Maximum Angle Stop
Large Actuator Piston
Steering Pump
Minimum Angle Stop
Bias Spring Large Actuator Piston To Steering Control Valve
Small Actuator Piston From Steering Control Valve
Flow Compensator Spool
Small Actuator Piston
Charge Pump
Pressure Compensator Spool
153 At machine start-up, the small actuator spring holds the swashplate at maximum angle. When the steering control valve is in the HOLD position, pump flow is blocked at the steering control valve and no signal pressure is generated. As the pump produces flow, the system pressure begins to increase. This pressure is felt at the lower end of both the flow compensator spool and the pressure compensator spool. The flow compensator spool moves up against spring force and permits system oil to go to the large actuator piston. The oil pressure at the large actuator piston overcomes the combined force of the bias spring and system oil pressure at the small actuator piston. The large actuator piston moves the swashplate to the LOW PRESSURE STANDBY position. In LOW PRESSURE STANDBY, the pump produces enough flow to compensate for system leakage at sufficient pressure to provide instantaneous response when the steering control valve is moved.
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STEERING PUMP AND PUMP CONTROL VALVE
Text Reference
From Steering Control Valve
DESTROKE Flow Compensator Spool Pressure Compensator Spool
Pump Control Valve
To Steering Control Valve Large Actuator Piston
Steering Pump
Small Actuator Piston
Bias Spring
154 When the load on the steering system decreases, signal oil pressure at the right end of the flow compensator valve decreases. This decreased pressure causes the force (flow compensator valve spring plus signal oil pressure) at the right end of the flow compensator spool to decrease below the pump supply pressure at the left end of the spool. The decreased pressure at the right end of the flow compensator spool causes the spool to shift and allows more flow to the large actuator causing the pressure in the large actuator piston to increase. The increased pressure in the large actuator piston overcomes the combined force of the small actuator and bias spring and moves the swashplate to a reduced angle. As pump flow decreases, supply pressure also decreases. When the supply pressure decreases and equals the sum of the oil pressure at the right end of the flow compensator spool and spring force, the flow compensator spool moves to a metering position and the system stabilizes.
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STEERING PUMP AND PUMP CONTROL VALVE
Text Reference
From St eering Cont rol Valve
UPSTROKE Flow Compensator Spool Pressure Compensator Spool
Pump Control Valve
To St eering Cont rol Valve Large Actuator Piston
Steering Pump
Small Actuator Piston
Bias Spring
155 During a turn, signal pressure at the steering control valve increases. This increased pressure causes the force (flow compensator valve spring plus signal oil pressure) at the right end of the flow compensator spool to become greater than the pump supply pressure at the left end of the spool. The increased pressure at the right end of the flow compensator spool causes the spool to shift left. The spool reduces or blocks pump output oil flow to the large actuator piston, and opens a passage to drain. Reducing or blocking oil flow to the large actuator piston reduces or eliminates the pressure acting against the large actuator piston. When the pressure in the large actuator piston decreases, the bias spring and small actuator piston move the swashplate to an increased angle causing the pump to UPSTROKE.
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STEERING PUMP AND PUMP CONTROL VALVE
Text Reference
From Steering Control Valve
HIGH PRESSURE CUTOFF Flow Compensator Spool Pressure Compensator Spool
Pump Control Valve
To St eering Cont rol Valve Large Actuator Piston
Steering Pump
Small Actuator Piston
Bias Spring
156 The pressure compensator spool limits the maximum system pressure for any given pump displacement. The pressure compensator spool is held in the left position during normal operation by spring force. When steering hydraulic system pressure is at maximum, pump supply pressure increases and the pressure compensator spool moves right against spring force. The pressure cutoff spool blocks oil in the large actuator piston from returning to the tank and allows supply oil to go to the large actuator piston. The increase in pressure allows the large actuator piston to overcome the combined force of the small actuator piston and spring to destroke the pump. The pump is now at minimum flow and pump supply pressure is at maximum. Maximum system pressure is adjusted by turning the pressure compensator adjustment screw.
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Text Reference
1
2
3
157
Steering Pilot Valve The steering pilot valve (2) for the steering system is mounted below the STIC (1) on the left side of the operator's seat. When the steering pilot valve is moved side to side, the valve directs pilot oil through the neutralizer valves (not shown) to one of the ends of the directional control valve stem in the steering valve body (not shown). The STIC lock lever (3) is shown in the LOCKED position. At this time, the STIC will not move. Push the STIC lock lever forward to the UNLOCK position in order to shift the steering pilot valve.
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Handle
Text Reference
STEERING PILOT VALVE NO TURN
Cam Follower Linkage
Left Port Plunger Centering Spring Right Port Plunger
Regulating Spring Drain Passage Return Spring Pilot Oil Passage Pilot Stem
Pilot Stem
Orifice
Orifice
Right Port Left Port
158 This illustration shows the major components in the steering pilot valve. The steering pilot valve directs pilot oil to both ends of the stem in the steering control valve. With the engine running and the control lever in the HOLD position, pilot oil enters the pilot oil passage and is blocked by the pilot stems. Any return pilot oil in the lines that is between the steering control valve and the steering pilot valve will be vented to the drain passage through the center of the metering stems.
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Text Reference
Handle
STEERING PILOT VALVE Cam Follower Linkage
LEFT TURN
Left Port Plunger Right Port Plunger
Centering Spring
Regulating Spring Drain Passage
Return Spring Pilot Oil Passage
Pilot Stem
Orifice
Orifice
Left Port
Right Port
159 When the handle for the steering pilot valve is moved to the left, the cam follower linkage pushes the left port plunger downward against the regulating spring. The force of the regulating spring is greater than the return spring so the pilot stem moves downward. At the same time, the return spring adds an upward force against the pilot stem to stabilize the movement. When the hole through the pilot stem moves over the port from the pilot oil passage, the pilot oil flows through the center of the pilot stem. Then, the pilot oil flows through the orifice to the quad check valve and then to the end of the stem in the steering control valve. As the handle is moved further to the left more pilot oil is allowed to flow through the pilot stem. The pilot oil that is directed to the end of the stem will build up pressure and override the force of the centering spring in the steering control valve (not shown) in order to move the stem. The pressure will build up a force in the center of the pilot stem. The combination of the return spring and that force will push upward against the regulating spring. The oil flow between the hole in the pilot stem and the pilot oil passage will be blocked. The pilot stem will act like a reducing valve. As more articulation speed is required, the regulating spring force pushing down must be increased by more handle movement. As the stem in the steering control valve is shifted, return pilot oil will be directed through the orifice in the right port, through the center of the pilot stem.
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Text Reference
The force that is developed by the pressure of the return oil will override the regulating spring. The pilot stem will move upward far enough to allow the return oil to flow out of the drain passage. NOTE: The shims that were previously used to change the adjustment of the capsules at the base of the valve have been removed. Also, the adjustment procedure has been changed. To adjust the capsules, loosen the bolts that hold the steering control valve and raise the bracket. Then, rotate the capsules to the desired amount, lower the bracket over the capsules and tighten the bolts. The recommended amount of movement of the steering lever in both directions before the machine starts to turn is 15 ± 3 mm (0.59 ± 0.120 inch).
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Text Reference
Back-up Relief Valve
STEERING CONTROL VALVE HOLD
Right Turn Pilot Cavity
Spring Cavity
Poppet
Control Stem
Cross Over Relief Valve
Centering Spring
Left Turn Pilot Cavity
Ball Resolver To Steering Pump Control Valves
160 This sectional view of the steering control valve identifies the various components. The control valve is in the HOLD position. When system oil from the steering pumps enters the steering control valve, the oil is blocked by the control stem. The oil flows through the hole in the relief valve and into the spring cavity. The pressure in the spring cavity will be equal to the pressure at the inlet of the control valve. The relief valve will block any oil flow between the inlet of the control valve and the tank port. The function of the control stem is to direct oil to the respective ends of the steering cylinders when making a turn. When the steering control valve is in the HOLD position, the oil between the steering cylinders and the control valve will be blocked. System oil flow entering the steering valve is blocked by the control stem. The steering control valve is equipped with a backup relief valve. The pressure adjustment of the relief valve is set higher than the pressure adjustment of the high pressure cutoff of the steering pumps.
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Text Reference
Back-up Relief Valve
STEERING CONTROL VALVE LEFT TURN
Right Turn Pilot Cavity
Spring Cavity
Poppet
Control Stem
Cross Over Relief Valve
Centering Spring
Left Turn Pilot Cavity
Ball Resolver To Steering Pump Control Valves
161 This sectional view shows the steering control valve with the control stem shifted for a left turn. When the steering control lever is moved to the left, pilot oil is directed to the left turn pilot cavity. Then, the control stem is shifted to the left. System oil from the inlet of the valve flows around the control stem to the head end of the right cylinder and the rod end of the left cylinder. Also, the system oil flows to the ball resolver. The ball shifts to the left and system oil flows around the ball resolver to the pump control valve on each steering pump. The oil flow to the pump control valve signals the steering pumps to either upstroke or destroke. When an external force acts on the wheels when the control stem is in the HOLD position, a hydraulic spike is induced in the steering system. At this time, the pressure at the crossover relief valve will open and allow the higher pressure to flow back to the opposite cylinder.
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Text Reference
Diverter Valve Secondary Steering Pump
Steering Cylinders Ball Resolver Valve
Crossover Relief Valve
St eering Cont rol Valve Control Stem
HOLD
Relief Valve Direction Control Spool
Back-up Relief Valve High Pressure Screen Right Pump Control Valve
Quad Check valve
Left Neutralizer Valve
Unloader Spool
STEERING SYSTEM
Check High Pressure Valve Screen Right Neutralizer Valve
Left Pump Control Valve
Check Valve Small Actuator Large Actuator
Small Actuator Large Actuator Steering Pilot Valve
Right Left Piston Piston Pump Pump
Steering Selector Warning and Pressure Switch Reducing Valve 1
Selector and Pressure Reducing Valve 2
Case Drain Filter Case Drain Filter Steering and Brake Tank
162 Steering Hydraulic System When the engine is running and the STIC is in HOLD position, pilot oil that is supplied by the right steering pump flows to the selector and pressure reducing valve 2. The selector valve 2 reduces the pilot oil to the appropriate pressure. The pilot oil is blocked at the steering control valve spool. The two steering pumps draw oil from the steering and brake tank. Oil from the left and right steering pumps flows through the respective check valves, through the high pressure screen to the steering control valve. With no pilot oil acting on the ends of the control stem in the steering control valve, the control stem blocks oil flow to the steering cylinders. The hydraulic oil that is between the steering cylinders and the steering control valve is blocked. No increase in system pressure is sensed through the ball resolver at the pilot control valve of each steering pump. The pilot control valve distributes oil to the large actuator and small actuator to control the output flow of the steering pumps. In the HOLD position, the force of the large actuator overrides the force of the small actuator and the swashplate moves to the LOW PRESSURE STANDBY position. In LOW PRESSURE STANDBY, the pump produces adequate flow to compensate for system leakage and sufficient pressure to provide for instantaneous response when the steering control valve is moved.
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Text Reference
The pilot steering system receives system oil from the output of the steering pumps. System oil flows from the steering pumps to the selector and pressure reducing valve 2. The selector valve reduces the system pressure to pilot pressure and pilot oil flows to the steering pilot valve. From the steering pilot valve, the pilot oil flows through the neutralizer valves over the quad check valve. Then, the pilot system flows to the pilot ports on the steering control valve.
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Text Reference
Diverter Valve
Right Turn
Secondary Steering Pump
Steering Cylinders Ball Resolver Valve
Crossover Relief Valve
Unloader Spool
GRADUAL RIGHT TURN
Relief Valve Direction Control Spool
Back-up Relief Valve
St eering Cont rol Valve Cont rol St em
Right Pump Cont rol Valve
Quad Check valve
Left Neutralizer Valve
STEERING SYSTEM
High Pressure Screen Check High Valve Pressure Screen
Right Neutralizer Valve
Left Pump Control Valve
Check Valve Small Act uat or Large Act uat or
Small Act uat or Large Act uat or Steering Pilot Valve
Steering Selector Warning and Pressure Switch Reducing Valve 1
Right Left Piston Pist on Pump Pump
Selector and Pressure Reducing Valve 2 Steering and Brake Tank
163 When the STIC is gradually moved to the right, increased pilot oil flows through the pilot control valve and the right neutralizer valve to the left side of the steering control spool. Pilot oil pressure shifts the stem in the steering control valve to the right. The two steering pumps draw oil from the steering and brake tank. Oil from the left and right steering pumps flows through the respective check valves, through the high pressure screen to the steering control valve. Then, the system oil flows around the control stem to the steering cylinders. As pressure increases in the steering cylinders, a signal pressure is sensed in the control valve on each pump. System pressure is flowing through the orifice to the the small actuator. At the same time, signal oil is shifting the pump control spools and oil is relieved out from behind the large actuator through the orifice. The small actuators on both steering pumps have more force than the large actuators. On the right steering pump, the large actuator shifts to the left and the swashplate angle increases. On the left steering pump, the large actuator shifts to the right and the swashplate angle increases. The increased angle of both swashplates will upstroke the steering pumps and increase the flow to the steering valve. If the need for more oil pressure in the steering system increases, the signal pressure increases and the pump control valve signals the steering pump for increased flow.
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Text Reference
Divert er Valve
Right Turn
Secondary St eering Pump
St eering Cylinders Ball Resolver Valve
Crossover Relief Valve
St eering Cont rol Valve Cont rol St em
FULL RIGHT TURN
Relief Valve Direct ion Cont rol Spool
Back-up Relief Valve High Pressure Screen Right Pump Cont rol Valve
Quad Check valve
Left Neut ralizer Valve
Unloader Spool
STEERING SYSTEM
High Check Pressure Valve Screen Right Neut ralizer Valve
Left Pump Control Valve
Check Valve Small Act uat or Large Act uat or
Small Act uat or Large Act uat or St eering Pilot Valve
Steering Selector Warning and Pressure Switch Reducing Valve 1
Right Left Piston Pist on Pump Pump
Select or and Pressure Reducing Valve 2 Steering and Brake Tank
164 When the STIC is moved to the right, increased pilot oil flows through the pilot control valve to the right neutralizer valve. The right neutralizer comes in contact with the right striker and pilot oil is blocked and all pilot oil in the right turn pilot cavity is drained to tank. With no pilot pressure on left side of the control stem, the control stem goes back to the center. The oil is blocked between the steering control valve and the steering cylinders. The two steering pumps draw oil from the steering and brake tank. Oil from the left and right steering pumps flows through the respective check valves, through the high pressure screen to the steering control valve. With no pilot pressure to left side of the control stem, no oil flows through the steering control valve. The hydraulic oil that is between the steering cylinders and the steering control valve is blocked. No increase in system pressure is sensed through the ball resolver at the pilot control valve of each steering pump. The pilot control valve distributes oil to the large actuator and small actuator to control the output flow of the steering pumps. In the HOLD position, the force of the large actuator overrides the force of the small actuator and the swashplate moves to the LOW PRESSURE STANDBY position. The neutralizer valves prevent the machine front frame from contacting the machine rear frame when turning FULL RIGHT or FULL LEFT. Refer to the Service Manual Testing and Adjusting (994F Wheel Loader Steering System, RENR6325) for the correct procedures.
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Text Reference
Diverter Valve
Right Turn
Secondary Steering Pump
Steering Cylinders Ball Resolver Valve
Crossover Relief Valve
Unloader Spool
Relief Valve
STEERING SYSTEM SECONDARY STEERING
Direction Control Spool
Back-up Relief Valve
St eering Cont rol Valve Cont rol St em
Right Pump Cont rol Valve
Quad Check valve
Left Neutralizer Valve
High Pressure Screen
Check High Valve Pressure Screen Right Neutralizer Valve
Left Pump Control Valve
Check Valve Small Act uat or Large Act uat or
Small Act uat or Large Act uat or Steering Pilot Valve
Steering Selector Warning and Pressure Switch Reducing Valve 1
Right Left Piston Pist on Pump Pump
Selector and Pressure Reducing Valve 2 Steering and Brake Tank
165 The illustration shows the 994F steering system when the secondary steering system is active. If the engine is not running, the steering pumps will not be supplying steering system oil. The oil flow through selector and pressure reducing valve 1 is at tank level. The unloader spool senses the lack of pressure in the primary steering system, the unloader spool directs secondary steering oil to the steering system. The bi-directional secondary steering pump is splined to the output transfer gears and turns whenever the machine is rolling. The diverter valve is equipped with a secondary steering relief valve that limits the maximum pressure in the secondary steering system. The diverter valve directs oil from the tank to the input side of the pump and the oil from the output side of the pump to the main steering system depending on if the machine is rolling FORWARD or REVERSE. The secondary steering oil flows over the check valve to the steering control valve. The oil flow from the secondary steering pump is blocked from going to the steering pumps by their respective check valves. Also, the secondary steering oil flows to the selector and pressure reducing valve 1 for pilot oil supply. In the illustration, the pilot control valve is moved to the right. Pilot oil that is supplied by the secondary steering pump flows through the right neutralizer valve, and by the quad check valve to the left end of the control stem. The machine will articulate to the right.
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Text Reference
The steering warning switch senses the main steering system pressure after the selector and pressure control valve. The steering warning switch is monitored by the VIMS module. When the main system pressure drops, the switch opens. The VIMS alerts the operator with a Level 3 warning that the main steering system pressure is low.
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To Articulation Hitch
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Text Reference
1 2
2
994F Rear Pump Drive
3
1 2 3 4
4
Service Brake Cooling Pump Steering Hydraulic Oil Pumps Steering Oil Cooling Pump Brake Pump
166 STEERING OIL COOLING SYSTEM The above illustration shows the location of the pumps on the 994F rear pump drive. The pump locations are the same as the 994D. The service brake cooling pump (1) and the steering and brake oil cooling pump (3) are fixed displacement gear pumps. The steering hydraulic oil pumps (2) and the brake application oil pump (4) are variable displacement piston pumps.
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Text Reference
Oil Cooler Cooler Bypass Valve
Filters
Filter Bypass Switch Filter Bypass Valve
Breather
994F STEERING OIL COOLING SYSTEM
Fluid Sampling Valve Steering and Brake Oil cooler Pump
Steering and Brake Tank Filter
167 Shown is a block diagram of the steering and brake hydraulic oil cooling system. The gear pump draws oil from the steering and brake hydraulic tank. Pump oil flows past the fluid sampling valve, through the filter, through the oil cooler core, and back to the steering and brake hydraulic tank. The cooler bypass valve allows pump oil to bypass the coolers at machine start-up or when the oil is cold. The cooler bypass valve is set to open at approximately 345 kPa (50 psi).
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Text Reference
1
2 3
4
6
5
168 Steering Oil Cooling System This illustration shows the location in the rear-frame of the components that are used to cool the hydraulic oil for the steering system and brake system. In the cooling system, oil is drawn from the steering/brake hydraulic tank (1) by the gear pump (4). The oil is directed through the filter group (2) and then through the steering/brake oil cooler (radiator group) (3) and back to the hydraulic tank. Also shown are the left steering cylinder (5) and the torque converter housing (6).
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Text Reference
1 169
2
3
4
170
5
The upper illustration shows the components that are in the area of the rear pump drive. The gear pump (1) and the fluid sampling port (2) are located on the rear pump drive towards the rear of the machine. The filter group is located on the right side of the machine next to the steering and brake oil tank. Installed on the filter is the bypass switch (4). The steering oil cooler filter bypass switch communicates with the VIMS module. Also shown is the implement hydraulic oil cooler filter. In the lower illustration, the steering and brake oil cooler (5) is located in the radiator group at the rear of the machine.
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Text Reference
994F WHEEL LOADER BRAKE COMPONENTS Brake Accumulators
Parking Brake Knob Parking Brake Valve Service Brake Valve
Steering and Braking Tank
Brake Pump
Rear Pump Drive
Service Brakes
Parking Brake
Service Brakes
Brake System
171 BRAKE SYSTEM Brake System Components This illustrations shows the brake component locations on the 994F Wheel Loader. The axle components are retained from the 994D Wheel Loader. The service brakes now feature an increased circuit pressure and a split control system.
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Text Reference
994F BRAKE SYSTEM ENGINE NOT RUNNING PARKING BRAKE ENGAGED SERVICE BRAKES NOT ENGAGED
Left Front Service Brake
Left Rear Service Brake
Brake Low Pressure Warning Switches Brake Pedals
Parking Brake
Brake Accumulators Service Brake Valve
Right Rear Service Brake
Parking Brake Valve Pressure Control Valve
Variable Displacement Piston Pump
Check Parking Valve Brake Interlock Switch
Parking Brake Pressure Switch
Right Front Service Brake
Brake Oil Cooler Core Group
Brake Cooling Pump
Bypass Valve
Pump Actuator
Brake Cooling Oil Tank
Breather Steering and Brake Hydraulic Oil Tank
172 Brake System Schematic - Engine Not Running - Parking Brake Engaged This illustration shows a schematic of the brake system with the engine not running and the pumps not rotating. The brake system component functions are: Brake pump: The brake pump is a variable displacement piston pump with a pressure compensated pump control valve. The pump draws oil from the steering and brake hydraulic oil tank and sends supply oil through the check valves to the accumulators. Check valves: Allow oil flow in one direction between the brake pump and the accumulators. Brake accumulators: When the engine is running, the front and rear brake accumulators supply oil within a controlled pressure range to the brake valve and to the parking brake valve. If the engine stops running, the accumulators provide an emergency oil supply to provide braking. The accumulators are shown charged with nitrogen. Service brake valve: Controls the flow of brake oil to the front and rear service brakes. Parking brake valve: Controls the engagement and disengagement of the parking brake.
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Text Reference
Pressure switch: Sends a signal to VIMS when the case drain filter begins to bypass. Parking brake: Prevents the machine from moving when parked. Parking brake pressure switch: The pressure switch sends a signal to the Power Train ECM if a low pressure event occurs at in the parking brake circuit. Parking brake interlock switch: The proximity switch sends a signal to the Power Train ECM indicating that the parking brake is engaged. Brake low pressure warning switches: The pressure switch sends a signal to the VIMS module if a low pressure event occurs at either brake accumulator. Bypass Valve: The bypass valve allows oil to flow back to tank if the brake oil cooler core becomes restricted.
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Text Reference
994F BRAKE SYSTEM ENGINE RUNNING PARKING BRAKE DISENGAGED SERVICE BRAKES NOT ENGAGED
Left Front Service Brake
Left Rear Service Brake
Brake Low Pressure Warning Switches Brake Pedals
Parking Brake
Brake Accumulators Service Brake Valve
Right Rear Service Brake
Parking Brake Valve Pressure Control Valve
Check Valve Parking Brake Interlock Switch
Variable Displacement Piston Pump
Right Front Service Brake
Parking Brake Pressure Switch Brake Cooling Pump
Brake Oil Cooler Core Group Bypass Valve
Pump Actuator
Brake Cooling Oil Tank
Breather Steering and Brake Hydraulic Oil Tank
173 Brake System Schematic - Engine Running - Parking Brake Disengaged The illustration is a schematic for the service brake system, the parking brake system, and the brake cooling system. In the illustration, the parking brake is disengaged and the service brakes are not engaged. The brake pump draws oil from the steering and brake hydraulic oil tank and supply oil to the parking brake valve, the brake accumulators and eventually the service brake valve. The service brake valve is now split control. The service brakes are not engaged. Also, the illustration shows the parking brake valve shifted and directing brake oil to the parking brake. The brake oil pressure will override the force of the springs and disengaging the parking brake. The brake cooling pump draws oil from the brake cooling oil tank, directs oil to the brake oil cooling core, and directs cooling oil to each service brake. Then, the oil returns to the brake cooling oil tank.
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Text Reference
994F BRAKE SYSTEM ENGINE RUNNING PARKING BRAKE DISENGAGED SERVICE BRAKES ENGAGED
Left Front Service Brake
Left Rear Service Brake
Brake Low Pressure Warning Switches Brake Pedals
Parking Brake
Brake Accumulators Service Brake Valve Parking Brake Valve Pressure Control Valve
Right Rear Service Brake
Parking Brake Pressure Switch Brake Cooling Pump
Check Valve Parking Brake Interlock Switch
Variable Displacement Piston Pump
Right Front Service Brake
Brake Oil Cooler Core Group Bypass Valve
Pump Actuator
Brake Cooling Oil Tank
Breather Steering and Brake Hydraulic Oil Tank
174 Brake System Schematic -Engine Running - Service Brakes Engaged The illustration is a schematic for the service brake system, the parking brake system, and the brake cooling system. In the illustration, the parking brake is disengaged and the service brakes are engaged. The brake pump draws oil from the steering and brake hydraulic oil tank and supplies oil to the parking brake valve, the brake accumulators, and eventually the service brake valve. The new split control service brake valve is being activated and accumulator oil is directed to each service brake. The service brakes are engaged. Also, the illustration shows the parking brake valve shifted and directing brake oil to the parking brake. The brake oil pressure is overriding the force of the springs and disengaging the parking brake. The brake cooling pump draws oil from the brake cooling oil tank, directs oil to the brake oil cooler core, and directs cooling oil to each service brake. Then, the oil returns to the brake cooling oil tank.
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1
Text Reference
3
2
4
5
6
7
175
Hydraulic Brake System Control The hydraulic brake system control consists of the following components: - Steering and brake hydraulic tank (1) - Service brake control valve (2) - Parking brake control valve (3) - Brake pump (4) - Brake accumulators (5) Also shown for relationship of the brake components on the machine are the left side steering cylinder (6) and the rear frame (7).
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2
Text Reference
1
3
4 5
6
8
7
9
176
This illustration shows the service brake valve (3) and the parking brake control valve (4). The service brake control is attached below the cab frame at the articulation hitch. The parking brake valve group is located on rear frame at the articulation hitch. Installed on the parking brake control valve group is the parking brake interlock switch (7) and the parking brake pressure switch (5). These two switches communicate with the Power Train ECM. Service brake low pressure switches (1) and (2) are installed in the brake lines between the service brake control valve and the brake accumulators (not shown). Front brake pressure switch (2) and the rear brake pressure switch (1) communicate a drop in pressure to the VIMS module. Also, hose (8) is connected to the rear service brakes in the rear frame (not shown), hose (9) is connected to the front service brakes in the loader frame (not shown), and hose (6) is connected to the parking brake in the loader frame (not shown).
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Text Reference
SERVICE BRAKE VALVE BRAKES OFF Plunger Plunger Springs
Return Spring
Shims
Ball Check Valve
Ball Retainer
Orifice
Upper Spool
Tank Port Upper Piston
Front Brake Port
Retainer
System Pressure Port
Check Valve
Return Spring Orifice Lower Spool
Tank Port Lower Piston
Rear Brake Port
Check Valve System Pressure Port
177 Service Brake Valve OFF The 994F Wheel Loader is equipped with a new service brake control valve. The valve has two individual brake ports. The upper brake port is for the front service brakes and the lower brake port is for the rear service brakes. With the service brake valve, the pressure at the ports for the service brake ports will be equal to the pressure developed by the two plunger springs. Also, the spring force will be proportional to the plunger movement. The brake control valve is equipped with check valves. The top check valve prevents spikes in the tank port from entering the cavity with the plungers springs and acting on the the plunger. The two lower check valves also prevent spikes in the tank line from acting on the upper and lower spools and eventually transferring to the brake pedal. The brake control valve is also equipped with shims that are between the ball retainer and the springs. These shims are used to adjust the maximum pressure that is directed to the service brakes.
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Text Reference
SERVICE BRAKE VALVE Plunger
BRAKES ON Plunger Springs
Return Spring
Shims
Ball Check Valve Ball Retainer Orifice Upper Spool
Tank Port
Front Brake Port
Upper Piston Retainer
System Pressure Port
Check Valve
Return Spring Orifice Lower Spool
Tank Port Lower Piston
Rear Brake Port
Check Valve System Pressure Port
178 Service Brake Valve ON In order to initiate the operation of the service brake valve, the operator depresses the brake pedal. The plunger is pushed in the downward direction against the plunger springs. The springs push the ball retainer, ball, the upper spool, and the upper piston down against the retainer and the lower spool. The front brake port will be blocked from the upper tank port. The front brake port will then be open to flow from the system pressure port (from the front brake accumulator). Also, the system oil flows through the orifice into the cavity between the upper spool and the upper piston. The upper spool, upper piston and retainer moves the lower spool downward compressing the lower return spring and the lower piston is bottomed out. The rear brake port will then be open to flow from the system pressure port (from the rear brake accumulator). Also, the oil flows through the orifice into the cavity that is between the lower spool and the lower piston.
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Text Reference
SERVICE BRAKE VALVE BRAKE PORTS BALANCED Plunger
Plunger Springs Shims
Return Spring
Check Valve
Ball Ball Retainer
Orifice
Upper Spool
Tank Port Upper Piston
Front Brake Port
Retainer
System Pressure Port
Check Valve
Return Spring Orifice Lower Spool
Tank Port Lower Piston
Rear Brake Port
Check Valve System Pressure Port
179 Service Brake Valve Balanced In the upper section, the oil pressure in the cavity is equal to the pressure at the service brake port. Due to the area of the upper piston, the upper spool is shifted upward compressing the plunger springs. The upper spool moves up to block the flow of oil between the upper pressure port and the front brake port. This creates a balance between the force of the plunger springs and the front brake port pressure. At the same time, the pressure in the lower cavity is equal to the pressure at the rear brake port. Due to the area of the lower piston, the lower spool is pushed up and the lower spool blocks the flow of oil between the lower system pressure port and the rear brake port This creates a balance between the upper piston force an the lower brake port pressure. Increasing the downward movement of the plunger will increase the spring force and cause pressure at the service brake ports to increase until maximum pressure is reached. Decreasing the downward movement of the plunger will decrease spring force and cause pressure at the service brake ports to decrease. The return springs move the upper and lower spools up when the pedal is fully released opening the service brake ports up to the tank ports.
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1 2
3
4
5
6
180
This illustration shows the service brake accumulators and the check valves. Accumulator (2) and check valve (4) are in the circuit for the front service brakes. Accumulator (1) and check valve (6) are in the circuit for the rear service brakes. The accumulators are piston type that are charged with dry nitrogen. The charge pressure for the accumulators at 160° C (70° F) is 5520 ± 280 kPa (800 ± 40 psi). Also, hose (3) is the supply line that is feeding the two accumulators. The hose is installed between the brake pump (not shown) and the divider block (5).
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Text Reference
2
1
3
4
5
6
7 8
9
181
This illustration shows the location of the brake pump (4) and the check valve (9) on the rear pump drive (6). The brake pump is a pressure compensated piston pump that is adjusted to supply 16000 ± 345 kPa (2300 ± 50 psi) pressure. The check valve has a cracking pressure of 448 ± 55 kPa (65 ± 8 psi). Also shown is the steering and brake hydraulic tank (1) and brake cooling tank (5). Installed on the steering and brake hydraulic tank are the temperature sensor (3) and the liquid level switch (2) (the liquid level switch is located on the opposite side of the tank). The temperature sensor for the steering and brake hydraulic oil (3) communicates with the VIMS module. The liquid level switch (2) for the oil in the steering and brake hydraulic tank communicates with the VIMS module. Also shown are the steering and brake oil cooling pump (8) and the hose (7) that is connected to the dividing block for the brake accumulators (not shown).
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Text Reference
BRAKE PUMP LOW PRESSURE Control Piston
Spring
Pump Servo Valve
Barrel Control Piston Passage
Outlet Passage
Drive Shaft
Inlet Passage Piston Assembly
Swashplate
182 Brake Pump Shown in this illustration are the main components of the brake pump. The components are: - Pump control valve - Control piston - Spring - Swashplate - Piston assembly - Barrel - Drive shaft When pressure in the brake system is less than 16000 ± 345 kPa (2300 ± 50 psi), the spring keeps the swashplate at maximum angle. The pump piston stroke is longest and pump displacement is maximum. A small amount of pressure oil from the outlet passage flows to the pressure compensator. A spool in the pressure compensator blocks the flow of oil to the control piston passage.
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Text Reference
PUMP CONTROL VALVE LOW BRAKE SYSTEM PRESSURE
To Control Piston
HIGH BRAKE SYSTEM PRESSURE
From Pump Outlet
Adjustment Bolt
Adjustment Bolt
Locking Nut
Pressure Compensator Spool
Locking Nut
To Control Piston
From Pump Outlet
Pressure Compensator Spool
183 This illustration shows the main components and the operation of the pump control valve. The components are: - Adjustment bolt - Locknut - Spring - Pressure compensator pool The left illustration shows the operation of the pressure compensator valve when the brake system pressure is less than 16000 ± 345 kPa (2300 ± 50 psi). Pump output oil flows around the right land of the pressure compensator spool and into the chamber at the right end of the spool. When the brake system pressure increases to 16000 ± 345 kPa (2300 ± 50 psi), the pressure of the oil in the chamber is high enough to move the spool against the spring. Movement of the spool permits oil to flow past the spool to the control piston in the pump. For the correct adjustment procedure for the pump control valve, refer to the Testing and Adjusting Module, Piston Pump (Brake) Pressure-Test and Adjust (RENR6326).
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Text Reference
BRAKE PUMP HIGH PRESSURE Pump Servo Valve
Control Piston
Spring
Barrel
Control Piston Passage
Outlet Passage Drive Shaft
Inlet Passage Piston Assembly
Swashplate
184 When the brake system pressure reaches 16000 ± 345 kPa (2300 ± 50 psi), oil from the pump control valve fills the chamber in the control piston. As the brake system pressure increases above 16000 ± 345 kPa (2300 ± 50 psi), the oil pressure from the pump control valve moves the control piston against the control spring. This movement decreases the angle of the swashplate, the stroke of the pistons, and the displacement of the pump. The amount of oil per pump revolution is decreased to the amount that is required to maintain the system pressure at 16000 ± 345 kPa (2300 ± 50 psi).
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Text Reference
185
This illustration shows the brake pads and spacers being assembled into the final drive.
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Text Reference
2
3
1 186
Parking Brake This illustration shows the location of the parking valve group (1) with the parking brake pressure switch (2) and the parking brake position switch (3). The parking brake valve group is located between the cab and the top of the rear frame at the articulation hitch. The parking brake is spring applied with hydraulic pressure release. The parking brake pressure switch sends a signal to the Power Train ECM that the oil pressure is high enough to disengage the parking brake. The parking brake position switch sends an input to the Power Train ECM giving the ON/OFF position of the parking brake control
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Text Reference
1 2
4 3
187
The parking brake assembly (2) is located at the articulation hitch on the loader frame (1). The parking brake is spring activated and hydraulic oil pressure released through cylinders (3). The cylinders are equipped with air purge screws (4).
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Text Reference
2
1
3 4
5 6 7 8 188 This illustration is showing a transparency view of the parking brake. The parking brake is spring applied and hydraulically released. When the parking brake knob (not shown) in the cab is pulled out, the parking brake valve has blocked the flow of oil to the parking brake. Springs (1) put a force on plate (6) squeezing plates (2), discs (3) against the parking brake housing plate. The drive shaft that is splined to the discs (3) will not be allowed to rotate. When the parking brake knob is pushed in, the parking brake valve directs oil to the parking brake cylinders (4). The oil pressure develops a force on the piston (5) in the cylinders and moves the piston to the left. The piston pushes pin (7) against plate (6) and the force compresses the springs. Plate (6) is disengaged from both the plates and discs. The discs and the drive shaft are free to rotate. The plate (6) and plates (2) are held in line by the rods (8).
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Text Reference
1 2
5
3
4
189
Brake Oil Cooler System The hydraulic brake system control consists of the following components: - Brake oil cooler tank (1) - Brake cooler pump (2) - Brake oil cooler (3) - Rear frame (4) Also shown is the transmission (5).
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1
Text Reference
2 3
4
5
190
This illustration shows the line routing through the loader frame The brake oil cooler system in the loader frame consists of two hoses that are connected to the front axle (not shown). Hose (5) directs flow to the divider block (not shown) on the front axle. Hose (4) is the return line to the brake oil cooler tank that is located in the rear frame. Also shown is the implement hydraulic oil tank (1) and the front pump drive (2) on the loader frame (3).
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Text Reference
191
The screens (1) for the front brake cooling system are mounted to the front axle housing. Each screen has a check valve not shown to prevent oil from flowing in the reverse direction. The brake cooling screens are canister type screens with replaceable 500 micron elements.
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Text Reference
192
This view shows the screen (arrow) for the right rear wheel brake cooling circuit. It is mounted to the axle housing between the axle housing and the trunnion. The rear brake cooling screens are also equipped with check valves (not shown) to prevent the oil from flowing in the wrong direction. The rear brake cooling screens are also canister type screens with replaceable 500 micron elements.
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Text Reference
193
This illustration shows the screen (arrow) for the rear left wheel brake cooling circuit. It is mounted to the axle housing between the axle housing and the trunnion. The rear brake cooling screens are also equipped with check valves (not shown) to prevent the oil from flowing in the wrong direction.
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Text Reference
SCREEN GROUP To Brake Oil Cooling Tank
Screen Spring Washer
Snap Ring
From Service Brakes
194 Service Brake Cooling Screen Group The 994F Wheel Loader is equipped with four service brake cooling screens, one for each service brake. Each service brake is equipped with its own screen group that filters the oil that is returning to the brake cooling tank. This illustration shows the direction of oil flow through the screen group. The return oil flows from the service brakes, through the screen and out of the center of the screen. From the inside of the screen oil flows out of the canister to the brake oil cooling tank.
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Text Reference
994F VITAL INFORMATION MANAGEMENT SYSTEM (VIMS) BLOCK DIAGRAM
Quad Gauge, Tachometer, Message Center
SPI Data Link
Cat Data Link J2 J1
VIMS Module ECM
Ground Bolt
- Inputs -
- Inputs VIMS Service Connector
VIMS Keypad
Lift Head End Pressure Sensor
VIMS Store Switch
Brake Cooling Tank Temperature Sensor
Lift Linkage Position Sensor
Ambient Air Temperature Sensor
Service Tool Connector
Front Pump Drive Temperature Sensor
- Outputs -
Steering And Brake Oil Temperature Sensor
VIMS Service lamp
Implement Oil Temperature Sensor
+12 VDC Instrument Supply
Front Pump Drive Temperature Sensor
Horn Solenoid
Torque Converter Oil Temperature Sensor
VIMS Action Lamp
Rear Axle Temperature Sensor
VIMS Action Alarm
Front Axle Temperature Sensor
Key Off Voltage +8 VDC Digital Supply
System Air Pressure Sensor
Key On Voltage
195 Vital Information Management System (VIMS) This diagram of the VIMS module shows the components which provide input and output signals to the machine. The VIMS module receives input signals from the various sensors and switches, and the VIMS keypad. The VIMS module processes the input signals, supplies event codes to the operator, and provides a corresponding voltage and signal voltages to the action lamps and/or the VIMS service lamp. The VIMS module monitors diagnostic conditions and reports events to the Cat Data Link or to Cat Electronic Technician. The input components to the VIMS module are: Lift linkage Position Sensor: Sends a PWM signal to the VIMS module communicating the position of the lift linkage in relation to the loader frame. Temperature sensor: The VIMS module receives inputs from the temperature sensors that are located in the three hydraulic tanks and the front and rear axles. The VIMS module report an event when the oil is above the operating temperature of the individual sensor. VIMS keypad: Sends operator commands to the VIMS module.
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Text Reference
System air pressure sensor: Sends an event to the VIMS module when the air in the system is below the required starting pressure Lift cylinder head end pressure sensor: Sensor relays the amount of pressure in the lift cylinder head end to the VIMS module. VIMS store switch: Pressing the store switch clears the payload count on the display prior to starting to load the next truck. VIMS service connector: Connector used to load and down load VIMS PC Service tool connector: Connector available for Caterpillar Electronic Technician (ET) The output components which receive signals from the VIMS module are: VIMS Action lamp: The action lamp is an LED that is located within the operator's viewing area. The FLASHING action lamp warns the operator that a condition exists. The condition will require changing the operation of the machine. The VIMS electronic control module FLASHES the action lamp whenever a warning category 2, 2S, or 3 problem exists. VIMS Action alarm: The VIMS module will enable an intermittent sound for a category 3 alarm and a continuous sound for a category 2 alarm. The engine must be running in order to sound the action alarm. VIMS Service lamp: The service lamp is located outside the cab in an area that is easily seen by someone that is a distance away from the machine. The service lamp is turned ON in order to warn the service personnel that the VIMS electronic control module has detected an active event ("data or machine"). A flashing service lamp indicates that the event could be damaging to the machine. If the event becomes inactive, the service lamp is turned OFF. However, the event is stored in the memory of the VIMS electronic control module. Key on voltage: Voltage available when the key start switch is in the ON position. Key off voltage: Voltage available when the key start switch is in the OFF position.
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Text Reference
994F VITAL INFORMATION MANAGEMENT SYSTEM (VIMS) BLOCK DIAGRAM
Quad Gauge, Tachometer, Message Center
SPI Data Link
Cat Data Link J2 J1
Front Brake Accumulator Pressure Switch
VIMS Module ECM
Ground Bolt
Rear Brake Accumulator Pressure Switch
Fuel Level Sender
Brake Cooling Tank Level Switch
Engine Oil Level Switch
Steering Tank Level Switch
Lower Oil Renewal Level Switch
Primary Steering Pressure Switch
Implement Case Drain Bypass Switch RH
Steering Case Drain Bypass Switch RH
Implement Case Drain Bypass Switch CF
Steering Case Drain Bypass Switch LH
Implement Case Drain Bypass Switch CR
Steering Oil Cooler Filter Bypass Switch
Implement Case Drain Bypass Switch LH Implement Cooling Filter Bypass Switch
Front Pump Drive Filter Bypass Switch
Implement Pilot Filter Bypass Switch
Rear Transmission Filter Bypass Switch Front Transmission Filter Bypass Switch
Implement Cooler Filter Bypass Switch Implement Tank Level Switch
196 Vital Information Management System (VIMS) This diagram shows the components which provide input signals to the VIMS module. The VIMS module receives input signals from senders, pressure switches, liquid level switches, and filter bypass switches. The VIMS module processes the input signals, supplies event codes to the operator, and provides a corresponding voltage and signal voltages to the action lamps and/or the VIMS service lamp. The VIMS module monitors diagnostic conditions and reports events to the Cat Data Link or to Cat Electronic Technician. Level switch: The VIMS module receives inputs from the implement hydraulic tank, the steering and brake tank, the brake cooling tank, the engine oil, the Oil Renewal System (if equipped) and the fuel tank. The VIMS module records an event if one or more of the tanks are below the necessary level. Filter bypass switch: The VIMS module receive inputs from the differential switches and reports an event if one or more of the filters are bypassing. Fuel level sender: The VIMS module receives an analog signal from the fuel level sender reporting the fuel level in the fuel.
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Text Reference
Pressure switch: The VIMS module receives inputs from the pressure switches for the front accumulator or the rear accumulator. The VIMS module reports an event when the oil from the accumulators is below the necessary pressure. Primary steering pressure switch: The VIMS module receives an input from the pressure switch in the main steering system. The VIMS module reports an event when the main steering system has lost oil flow and the secondary steering pump is supplying oil to the steering system.
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Text Reference
1
2
197
The VIMS module (1) is located on the left side of the machine under the door on the platform (cover must be removed). This illustration shows the location of the VIMS module and the Implement ECM (2) in the left side of the machine in the electrical bay. The VIMS module makes decisions based on switch and sensor input signals. The VIMS module responds to machine inputs by sending a signal to the quad gauge, speedometer/tachometer, message center, or the action alarms. The VIMS module receives three different types of input signals: 1. Switch input: Provides the signal line to battery, ground, or open. 2. PWM input: Provides the signal line with a square wave of a specific frequency and a varying positive duty cycle. 3. Speed signal: Provides the signal line with either a repeating, fixed voltage level pattern signal or a sine wave of varying level and frequency.
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Text Reference
The VIMS module has three types of output drivers: 1. ON/OFF driver: Provides the output device with a signal level of +Battery voltage (ON) or less than one Volt (OFF). 2. PWM solenoid driver: Provides the output device with a square wave of fixed frequency and a varying positive duty cycle. 3. Controlled current output driver: The ECM will energize the solenoid with 1.25 amps for approximately one half second and then decrease the level to 0.8 amps for the duration of the on time. The initial higher amperage gives the actuator rapid response and the decreased level is sufficient to hold the solenoid in the correct position. An added benefit is an increase in the life of the solenoid. The VIMS module receives input signals from sensors, switches, and senders, manages the information, and sends outputs to the quad gauge, the speedometer/tachometer, and the message center. The VIMS module communicates through the CAT Data Link. The CAT Data Link allows high speed proprietary serial communications over a twisted pair of wires. The CAT Data Link allows different systems on the machine to communicate with each other and also with service tools such as Caterpillar Electronic Technician (ET). The VIMS module has built-in diagnostic capabilities. As the VIMS module detects fault conditions on the machine, it logs the faults in memory and displays them on the message center. The fault codes can also be accessed using the ET service tool or through a keypad entry. VIMS software can be used to view faults logged by the VIMS. Also shown is the Implement ECM (2).
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Text Reference
1
2
198
The ambient air temperature sensor (1) is located below the cab in the rear frame near the upper articulation hitch pin. The temperature sensor sends the temperature of the air around the machine back to the VIMS module. Also shown is the parking brake valve (2).
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Text Reference
1
2
3
199 The implement hydraulic tank (1) is located in the loader frame. Installed in the rear of the tank is the implement oil level switch (2) and on the right side of the hydraulic tank is the implement oil temperature sensor (3).
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Text Reference
1
2
200 The lift head end pressure sensor (2) is located on the left side of the loader frame. Access the sensor from the articulation hitch. Also shown is the pin (1) for the rod end of the left steering cylinder.
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Text Reference
1
2 201
3
4
5 6
202
The upper illustration shows the steering and brake oil tank (1). Installed on the tank is the steering tank level switch (2) and steering and brake oil temperature sensor (3). The sensor and level switch report to the VIMS module. The lower illustration shows the brake cooling oil tank (4). Installed on the tank is the brake cooling tank level switch (5) and brake cooling tank temperature sensor (6). The sensor and level switch report to the VIMS module.
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1
Text Reference
2
203
The rear transmission filter is equipped with a rear transmission filter bypass switch (1). The front transmission filter is equipped with a front transmission filter bypass switch (2). Both bypass switches report to the VIMS module.
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Text Reference
1
204
The fuel level sender (1) is located in the fuel tank. Access the switch through the hole in the rear frame cross beam.
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Text Reference
205 1 2 3
4
5
6 206
The upper illustration shows the dash panel with the quad gauge (1), the speedometer/tachometer (2), the message center (3), and the action alarm (4). The lower illustration shows the right side panel with the VIMS keypad (5). Also shown is the service tool connector (6) for Caterpillar Electronic Technician (ET).
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Text Reference
1
207
The VIMS (payload) store switch (1) is located on the implement control on the right side of the operator's seat.
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Text Reference
208 1 2
209
3
4
The front axle (1) and the rear axle (3) are equipped with temperature sensors. The temperature sensor (2) and the temperature sensor (4) report the temperature of the respective axles to the VIMS module through a PWM signal. The VIMS module interprets the information and reports a warning if necessary to the operator panel.
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Text Reference
210 CONCLUSION This concludes this presentation on the 994F Wheel Loader. This presentation described the location of the basic components on the engine, the operation of the power train, the implement, the steering, and the braking systems for the 994F Wheel Loader. Always check the Service Manual for the latest service information and specifications when servicing, testing and adjusting, or making repairs.
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Text Reference
HYDRAULIC SCHEMATIC COLOR CODE Black - Mechanical Connection. Seal
Red - High Pressure Oil
Dark Gray - Cutaway Section
Red / White Stripes - 1st Pressure Reduction
Light Gray - Surface Color
Red Crosshatch - 2nd Reduction in Pressure
White - Atmosphere Or Air (No Pressure)
Pink - 3rd Reduction in Pressure
Purple - Pneumatic Pressure
Red / Pink Stripes - Secondary Source Oil Pressure
Yellow - Moving or Activated Components
Orange - Pilot, Signal or Torque Converter Oil
Cat Yellow - (Restricted Usage) Identification of Components Within a Moving Group
Orange / White Stripes Reduced Pilot, Signal or TC Oil Pressure
Brown - Lubricating Oil
Orange / Crosshatch - 2nd Reduction In Pilot, Signal or TC Oil Pressure
Green - Tank, Sump, o r Return Oil
Blue - Trapped Oil
Green / White Stripes Scavenge / Suction Oil or Hydraulic Void
210 Hydraulic Schematic Color Code The table above shows the color code for hydraulic schematics and cross-sectional views that are shown in this presentation.
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Laboratory Exercises
Lab A: 994F Component Identification Worksheet Directions: Use these worksheets during the presentation to take notes on the location of each components. During the lab exercise, match the tag attached to the component with the correct name. ______ Radiator and Coolers Location: ______ 3516 B HD Engine Location: ______ Spring Coupling Location: ______ Rear Pump Drive Location: ______ Brake Application Pump Location: ______ Service Brake Valve Location: ______ Service Brakes Location: ______ Brake Cooling Pump Location: ______ Steering Pump Location:
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Laboratory Exercises
Lab A: 994F Component Identification Worksheet (continued) ______ Steering Cooling Pump Location: ______ Steering, Steering Cooling, and Brake Application Hydraulic Tank Location: ______ Brake Cooling Hydraulic Tank Location: ______ Auxiliary Drive Shaft Location: ______ Front Pump Drive Location: ______ Pilot Pump Location: ______ Implement Pumps Location: ______ Implement Hydraulic Tank Location: ______ Implement Control Valve Location: ______ Lift Cylinders Location:
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Laboratory Exercises
Lab A: 994F Component Identification Worksheet (continued) ______ Tilt Cylinders Location: ______ Torque Converter Location: ______Transmission Pump Location: ______Torque Converter Pump Location: ______Input Drive Shaft Location: ______Input Transfer Gear Location: ______Transmission Location: ______Output Transfer Gear Location: ______Steering Control Valve Location: ______Secondary Steering Pump Location:
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Laboratory Exercises
Lab A: 994F Component Identification Worksheet (continued) ______Steering Cylinders Location: ______Parking Brake Valve Location: ______Parking Brake Location: ______Driveshafts Location: ______Differentials Location: ______Final Drives Location:
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Laboratory Exercises
Lab B: 3516B HD Engine Component Identification Worksheet Directions: Use these worksheets during the presentation to take notes on the location and function of each components. During the lab exercise, match the tag attached to the component with the correct name. ______Engine ECM Function: Location: ______Primary Fuel Filter Function: Location: ______Fuel Transfer Pump Function: Location: ______Electronic Priming Pump Function: Location: ______Secondary Fuel Filters Function: Location: ______Electronic Unit Injector Function: Location:
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Laboratory Exercises
Lab B: 3516B HD Engine Component Identification Worksheet (continued) ______Fuel Pressure Regulating Valve Function: Location: ______Engine Speed Sensor (Reports to Engine ECM) Function: Location: ______Permanent Timing Calibration Sensor Function: Location: ______Engine Jacket Water Pump Function: Location: ______Engine Jacket Water Flow Switch Function: Location: ______Jacket Water Temperature Sensor Function: Location:
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Laboratory Exercises
Lab B: 3516B HD Engine Component Identification Worksheet (continued) ______Radiator Cores Function: Location: ______Separate Circuit Aftercooler Water Pump Function: Location: ______Separate Circuit Aftercooler Water Temperature Sensor Function: Location: ______Separate Circuit Aftercooler Cores Function: Location: ______Engine Oil Pressure Sensor (unfiltered) Function: Location: ______Engine Oil Filters Function: Location:
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Laboratory Exercises
Lab B: 3516B HD Engine Component Identification Worksheet (continued) ______Engine Oil Pressure Sensor (filtered) Function: Location: ______Oil Level Switch (Reports to VIMS ECM) Function: Location: ______Oil Level Switch (Reports to Engine ECM) Function: Location: ______Engine Oil Cooler Function: Location: ______Engine Air Filters (Primary and Secondary) Function: Location: ______Intake Manifold Temperature Sensor Function: Location:
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Laboratory Exercises
Lab B: 3516B HD Engine Component Identification Worksheet (continued) ______Right and Left Turbo Inlet Pressure Sensors Function: Location: ______Turbo Outlet Pressure Sensor Function: Location: ______Left and Right Exhaust Temperature Sensors Function: Location: ______Atmospheric Pressure Sensor Function: Location: ______Crankcase Pressure Sensor Function: Location: ______Air Tank Function: Location:
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Laboratory Exercises
Lab B: 3516B HD Engine Component Identification Worksheet (continued) ______Air Compressor Function: Location ______Air Starter Function: Location: ______Air Starter Solenoid Valve Function: Location: ______Air Horns Function: Location: ______Air Horns Solenoid Valves Function: Location: ______Throttle Lock Enable Switch Function: Location: _____Throttle Set/Decelerate Switch Function: Location:
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Laboratory Exercises
Lab B: 3516B HD Engine Component Identification Worksheet (continued) ______Throttle Resume/Accelerate Switch Function: Location: ______Oil Renewal System (ORS) Reservoir Function: Location: ______Oil Renewal System (ORS) Level Switches Function: Location: ______Oil Renewal System (ORS) Solenoid Valve Function: Location: ______Rockford Fan Function: Location: ______Rockford Fan Solenoid Valve Function: Location: ______Rockford Fan Speed Sensor Function: Location:
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Laboratory Exercises
Lab C: Power Train Component Identification Worksheet 1 Directions: Use these worksheets during the presentation to take notes on the location and function of each components. During the lab exercise, match the tag attached to the component with the correct name. ______Transmission ECM Function: Location: ______Engine Speed Sensor (Reports to Transmission ECM) Function: Location: ______Rear Pump Drive Function: Location: ______Torque Converter Function: Location: ______Torque Converter Outlet Speed Sensor Function: Location: ______Torque Converter Outlet Temperature Sensor (Reports to VIMS ECM) Function: Location:
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Laboratory Exercises
Lab C: Power Train Component Identification Worksheet 1 (continued) ______Impeller Clutch Solenoid Function: Location: ______Impeller Clutch Pressure Sensor Function: Location: ______Torque Converter Pedal Function: Location: ______Torque Converter Pedal Position Sensor Function: Location: ______Reduced Rimpull Selection Switch Function: Location: ______Reduced Rimpull Indicator Lamp Function: Location: ______Lockup Clutch Solenoid Function: Location:
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Laboratory Exercises
Lab C: Power Train Component Identification Worksheet 1 (continued) ______Lockup Clutch Enable Switch Function: Location: ______Torque Converter Pump Function: Location: ______Torque Converter Oil Filter Function: Location: ______Transmission Pump Function: Location: ______Transmission Oil Filter Function: Location: ______Transmission Oil Coolers (Water Cooled) Function: Location: ______Transmission Oil Coolers (Air Cooled) Function: Location:
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Laboratory Exercises
Lab C: Power Train Component Identification Worksheet 1 (continued) ______Input Driveshaft Function: Location: ______Input Transfer Gears Function: Location: ______Transmission Function: Location: ______Directional Solenoids Function: Location: ______Speed Solenoids Function: Location: ______Transmission Control Valve Function: Location: ______Output Transfer Gears Function: Location:
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Laboratory Exercises
Lab C: Power Train Component Identification Worksheet 1 (continued) ______Transmission Output Speed Sensors Function: Location: ______STIC Lever Function: Location: ______Steering/Transmission Lock and Steering/Transmission Lock Switch Function: Location: ______F-N-R Switch Function: Location:
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Laboratory Exercises
Lab C: Power Train Component Identification Worksheet 1(continued) ______Upshift Switch Function: Location: ______Downshift Switch Function: Location: ______Driveshafts Function: Location: ______Differentials Function: Location: ______Final Drives Function: Location: ______Transmission Lockout Switch (Bumper) Function: Location:
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Laboratory Exercises
Lab C: Power Train Component Identification Worksheet 1 (continued) ______Autolube Solenoid Function: Location: ______Autolube Pressure Sensor Function: Location:
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Laboratory Exercises
Lab C: Power Train Pressure Tests Worksheet 2 Directions: Locate and record the specifications from the service manual in the appropriate area of the worksheet for each test. Perform the tests and record the actual readings on the worksheet.
Lab C: Power Train Pressure Tests Pressure P1 Power Train Pump/ Speed Clutch P2 Directional Clutch P3 Torque Converter Inlet Torque Converter Outlet Power Train Lube Impeller Clutch Lockup Clutch
Low Idle (Specification)
Low Idle (Observed)
High Idle (Specification)
High Idle (Observed)
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Laboratory Exercises
Lab D: Implement Component Identification Worksheet 1 Directions: Use these worksheets during the presentation to take notes on the location and function of each components. During the lab exercise, match the tag attached to the component with the correct name. ______Implement ECM Function: Location: ______Front Pump Drive Function: Location: ______Front Pump Drive Lubrication Pump Function: Location: ______Front Pump Drive Lubrication Oil Filter Function: Location: ______Pilot Pump Function: Location: ______Pilot Oil Filter Function: Location:
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Laboratory Exercises
Lab D: Implement Component Identification Worksheet 1 (continued) ______Fixed Displacement Hydraulic Pumps Function: Location: ______Variable Displacement Hydraulic Pump Function: Location: ______High Pressure Screens Function: Location: ______Hydraulic Pump Case Drain Filters Function: Location: ______Fixed Displacement Pump Pressure Sensor (Reports to Implement ECM) Function: Location: ______Variable Displacement Pump Solenoid Valve Function: Location: ______Implement Hydraulic Oil Tank Function: Location:
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Laboratory Exercises
Lab D: Implement Component Identification Worksheet 1 (continued) ______Hydraulic Oil Temperature Sensor (Reports to VIMS ECM) Function: Location: ______Hydraulic Oil Level Switch (Reports to VIMS ECM) Function: Location: ______Implement Cooling Pump Function: Location: ______Implement Cooling Pump Filter Function: Location: ______Implement Oil Cooler Function: Location: ______Main Control Valves Function: Location: ______Lower Kickout Cushion Solenoid Function: Location:
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Laboratory Exercises
Lab D: Implement Component Identification Worksheet 1 (continued) ______Raise Stop Solenoid Function: Location: ______Lift Cylinders Function: Location: ______Lift Cylinder Head End Pressure SEnsor ( Reports to VIMS) Function: Location: ______Lift Position Sensor Function: Location: ______Tilt Cylinders Function: Location: ______Tilt Position Sensor Function: Location: ______Implement Oil Cooler Function: Location:
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Laboratory Exercises
Lab D: Implement Component Identification Worksheet 1 (continued) ______Pilot Control Valves Function: Location: ______Lift Kickout Position Set Switch Function: Location: ______Lower Detent Magnet Function: Location: ______Raise Detent Magnet Function: Location: ______Tilt Detent Magnet Function: Location: ______Implement Lockout Lever Function: Location:
Tilt Cylinder Rackback Line Relief
Tilt Cylinder Dump Line Relief
Low Idle (Specification)
Low Idle (Observed)
High Idle (Specification)
High Idle (Observed)
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Lift Cylinder Raise Line Relief
Left Fixed Displacement Pump - Main Relief
Center Variable Displacement Pump Main Relief
Center Variable Displacement Pump High Pressure Cutoff
Center Fixed Displacement Pump - Main Relief
Right Fixed Displacement Pump - Main Relief
Pilot
Pressure
Lab D: Implement Pressure Tests
Directions: Locate and record the specifications from the service manual in the appropriate area of the worksheet for each test. Perform the tests and record the actual readings on the worksheet.
Lab D: Implement Pressure Tests Worksheet 2
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Implement Pump Sol. Current
Double Torque Stall
Impeller Clutch Sol. Current
Impeller Clutch Pressure
Implement Position
100%
85%
70%
1st Speed FORWARD
Various Rimpull Settings
55%
Torque Stall
(4760 ± 50 psi)
32820 ± 350 kPa
(1000 ± 50 psi)
POWER DOWN TO MAIN RELIEF
POWER DOWN TO MAIN RELIEF
POWER DOWN TO MAIN RELIEF
POWER DOWN
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Double Torque Stall 3rd Speed FORWARD Max. Rimpull Bucket powered down
Bucket Powered Down
Max. Rimpull
1st Speed FORWARD
6900 ± 350 kPa
Implement Pump Pressure
POWER UP TO MAIN RELIEF
Actual Engine Speed (RPM)
Double Torque Stall 1st Speed FORWARD Max. Rimpull Bucket powered up
Transmission Requested Engine Speed Limit (RPM)
BELOW HORIZONTAL
Desired Engine Speed (RPM)
Double Torque Stall 1st Speed FORWARD Max. Rimpull Bucket powered down
P.T. Hyd.
Oil Temp.
BELOW HORIZONTAL
Torque Control Active?
Single Torque Stall 1st Speed FORWARD Max. Rimpull
Machine Condition
Lab D: Power Train Torque Control Strategy
Directions: Locate and record the specifications from the service manual in the appropriate area of the worksheet for each test. Perform the tests and record the actual readings on the worksheet.
Lab D: Power Train Torque Control Strategy Worksheet 3
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Laboratory Exercises
Lab E: Steering and Steering Oil Cooling Component Identification Worksheet 1 Directions: Use these worksheets during the presentation to take notes on the location and function of each components. During the lab exercise, match the tag attached to the component with the correct name. ______Rear Pump Drive Function: Location: ______Steering Pumps Function: Location: ______High Pressure Screens Function: Location: ______Steering Pump Case Drain Filters Function: Location: ______Steering Control Valve Function: Location: ______Pressure Reducing Valves Function: Location:
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Laboratory Exercises
Lab E: Steering and Steering Oil Cooling Component Identification Worksheet 1 (continued) ______Quad Check Valve Function: Location: ______Neutralizer Valves Function: Location: ______Pilot Control Valve Function: Location: ______Steering Cylinders Function: Location: ______Secondary Steering Pump Function: Location: ______Steering/Brake Hydraulic Tank Function: Location:
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Laboratory Exercises
Lab E: Steering and Steering Oil Cooling Component Identification Worksheet 1 (continued) ______Primary Steering Pressure Switch (Reports to VIMS ECM) Function: Location: ______Steering/Brake Oil Level Switch (Report to VIMS ECM) Function: Location: ______Steering/Brake Oil Temperature Sensor (Report to VIMS ECM) Function: Location: ______Steering Oil Cooling Pump Function: Location: ______Steering Oil Cooling Filter Function: Location: ______Steering Oil Cooler Function: Location:
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Laboratory Exercises
Lab E: Steering Pressure Tests Worksheet 2 Directions: Locate and record the specifications from the service manual in the appropriate area of the worksheet for each test. Perform the tests and record the actual readings on the worksheet.
Lab E: Steering Pressure Tests Pressure Standby Margin High Pressure Cutoff Backup Relief Valve
Low Idle (Specification)
Low Idle (Observed)
High Idle (Specification)
High Idle (Observed)
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Laboratory Exercises
Lab F: Brake Component Identification Worksheet 1 Directions: Use these worksheets during the presentation to take notes on the location and function of each components. During the lab exercise, match the tag attached to the component with the correct name. ______Rear Pump Drive Function: Location: ______Brake Application Pump Function: Location: ______Brake Accumulators Function: Location: ______Service Brake Valve Function: Location: ______Service Brakes Function: Location: ______Parking Brake Control Function: Location:
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Laboratory Exercises
Lab F: Brake Component Identification Worksheet 1 (continued) ______Parking Brake Valve Function: Location: ______Parking Brake Function: Location: ______Parking Brake Position Switch (Reports to Transmission ECM) Function: Location: ______Parking Brake Pressure Switch (Reports to Transmission ECM) Function: Location: ______Steering/Brake Oil Level Switch (Report to VIMS ECM) Function: Location:
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Laboratory Exercises
Lab F: Brake Pressure Tests Worksheet 2 Directions: Locate and record the specifications from the service manual in the appropriate area of the worksheet for each test. Perform the tests and record the actual readings on the worksheet.
Lab F: Brake Pressure Tests Pressure High Pressure Cutoff Front Service Brakes Rear Service Brakes Parking Brakes
Low Idle (Specification)
Low Idle (Observed)
High Idle (Specification)
High Idle (Observed)
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Laboratory Exercises
Lab G: Brake Cooling Component Identification Worksheet Directions: Use these worksheets during the presentation to take notes on the location and function of each components. During the lab exercise, match the tag attached to the component with the correct name. ______Rear Pump Drive Function: Location: ______Brake Cooling Pump Function: Location: ______Brake Cooling Hydraulic Tank Function: Location: ______Brake Cooling Oil Level Switch (Report to VIMS ECM) Function: Location: ______Brake Cooling Oil Temperature Sensor (Report to VIMS ECM) Function: Location: ______Brake Oil Cooler Function: Location:
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Laboratory Exercises
Lab G: Brake Cooling Component Identification Worksheet (continued) Front and Rear Brake Screens Function: Location:
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Laboratory Exercises
Lab H: VIMS Monitoring System Information Access Worksheet 1 Directions: Using the keypad and message center, list the number of DATA and MAINTENANCE events currently stored in the VIMS memory.
MAINTENANCE __________ EVENTS: DATA __________
Keypad Entry Used _______________
Directions: Using the keypad and message center, identify the five most recent events stored in the VIMS memory. List the parameter name, service meter hours, event duration, and identify the event as a maintenance or data event.
PARAMETER NAME
SMH
EVENT DURATION
MAINT.
DATA
1. 2. 3. 4. 5.
Keypad Entry Used _______________
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Laboratory Exercises
Lab H: VIMS Monitoring System Information Access Worksheet 2 Directions: Using the keypad and message center, identify the first five displayed parameters. List the parameter name, parameter number, and actual parameter value. PARAMETER NAME
PARAMETER NO.
ACTUAL VALUE
1. 2. 3. 4. 5.
Keypad Entry Used _______________
Directions: Using the keypad and message center, identify the first five displayed maintenance events. List the MID, CID, and FMI identifiers.
EVENT NAME
MID
CID
FMI
1. 2. 3. 4. 5.
Keypad Entry Used _______________
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Laboratory Exercises
Lab H: VIMS Monitoring System Information Access Worksheet 3 Directions: Using the keypad and message center, list the actual parameter values and units for the following parameters.
PARAMETER NO. 1.
790
2.
123
3.
140
4.
500
5.
802
ACTUAL VALUE
UNITS
Keypad Entry Used _______________
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Laboratory Exercises
Lab H: VIMS Monitoring System Information Access Worksheet 4 Directions: Using the keypad and message center, list the machine calibrations that can be performed by the operator or service technician using the keypad and message center. (Do not include Payload Calibrations.) MACHINE CALIBRATION NAME 1. 2. 3. 4.
5. 6. 7. 8. 9. 10. 11. 12. 13.
Keypad Entry Used _______________
