English 966h and 972h Whell Loaders (2)

SERV1815 August 2006

GLOBAL SERVICE LEARNING TECHNICAL PRESENTATION

966H AND 972H WHEEL LOADERS

Service Training Meeting Guide (STMG)

966H AND 972H WHEEL LOADERS MEETING GUIDE 815

VISUALS AND SCRIPT AUDIENCE

Level II - Service personnel who understands the principles of machine system operation, diagnostic equipment, and procedures for testing and adjusting.

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 966H and 972H Wheel Loader. This presentation may be used for self-paced and self-directed training.

OBJECTIVES After learning the information in this presentation, the technician will be able to: 1. Locate and identify the major components in the C11 and C13 ACERT™ 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.

GLOBAL REFERENCES 966H Wheel Loader Specalog 972H Wheel Loader Specalog 966H and 972H Wheel Loader Service Manual 966H Wheel Loader Parts Manual (A6D) 972H Wheel Loader Parts Manual (A7D) 966H Wheel Loader Parts Manual (A6G) 972H Wheel Loader Parts Manual (A7G) NPI Vol. 9, No. 1 "966H and 972H Wheel Loader TIM "966G Series II Wheel Loader Power Train" TIM "972G Series II Wheel Loader Power Train" Updated TIM "972G Series II Wheel Loader Command Control Steering" Update TIM "972G Series II Wheel Loader Steering and Braking" Updated Estimated Time: 8 Hour Illustrations: 194 Form: SERV1815 Date: 08/06 © 2006 Caterpillar Inc.

AEHQ5657 AEHQ5658 RENR8840 SEBP3743 SEBP3744 SEBP3747 SEBP3748 SERV7105 SERV2739 SERV2658 SERV2660 SERV2659

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TABLE OF CONTENTS INTRODUCTION ..................................................................................................................7 Component Location.........................................................................................................8 ENGINE................................................................................................................................10 Engine Electrical Block Diagram ...................................................................................11 Engine Right Side ...........................................................................................................14 Engine Left Side .............................................................................................................15 Crankshaft Speed Timing Sensor ...................................................................................16 Engine Speed/Timing Calibration Port...........................................................................19 Fuel System.....................................................................................................................20 Fuel Transfer Pump.........................................................................................................22 Power Derate...................................................................................................................23 Fuel Filter Sensors ..........................................................................................................24 Fuel Temperature Derate ................................................................................................26 High Fuel Filter Restriction Derates...............................................................................27 Engine Inlet Air System..................................................................................................28 Turbo Inlet Pressure Sensor............................................................................................30 Air Inlet Restriction Derate ............................................................................................31 Oil Pressure Sensor.........................................................................................................32 Low Oil Pressure ............................................................................................................33 Coolant Temperature Sensor...........................................................................................34 High Coolant Temperature Derate..................................................................................35 Intake Manifold Sensors .................................................................................................36 Intake Manifold Air Temperature Sensor Derate ...........................................................37 Virtual Exhaust Temperature Derate ..............................................................................38 POWER TRAIN ...................................................................................................................43 Power Train Electrical System .......................................................................................46 Engine Start Switch and Diagnostic Service Tool Connector ........................................49 Transmission Shift Lever................................................................................................50 Transmission Shift Control.............................................................................................51 Transmission Oil Temperature Sensor............................................................................57 Left Brake Pedal Position Sensor ...................................................................................58 Implement Pod Downshift Switch and Remote F-N-R Switch .....................................59 Parking Brake Pressure Switch.......................................................................................60 Back-up Alarm................................................................................................................63 Warning Panel - Left Side ..............................................................................................64 Implement Control Valve - With Ride Control ..............................................................65 Secondary Steering Intermediate Relay..........................................................................66 Engine Start Relay ..........................................................................................................67 Transmission Hydraulic System - NEUTRAL ...............................................................68 Transmission Modulating Valve - No Commanded Signal............................................76 Transmission Modulating Valve - Commanded Signal Below Maximum.....................77 Transmission Modulating Valve - Commanded Signal At Maximum ...........................79 Transmission Modulating Valve - Solenoids..................................................................81

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TABLE OF CONTENTS (continued) Transmission Relief Valve ..............................................................................................83 Variable Shift Control .....................................................................................................89 Integrated Brake System.................................................................................................90 Left Brake Pedal Actions................................................................................................91 Speed Limiter..................................................................................................................93 IMPLEMENT ELECTROHYDRAULIC SYSTEM............................................................94 Implement Electronic Control System ...........................................................................95 Implement Control Levers............................................................................................102 Fine Modulation............................................................................................................104 Autodig Control Arrangement ......................................................................................106 Implement Hydraulic System - HOLD.........................................................................110 Tilt Control Valve - HOLD ...........................................................................................112 Implement Hydraulic System - DUMP ........................................................................113 Pressure Compensator Valve - HOLD..........................................................................114 Load Check Operation ..................................................................................................115 Pressure Compensator Operation..................................................................................116 Implement Hydraulic System - DUMP ........................................................................120 Implement Hydraulic System - RAISE ........................................................................122 Implement Hydraulic System - FLOAT .......................................................................124 Implement Hydraulic System - Tilt Back and Raise ....................................................126 Implement Hydraulic System - RIDE CONTROL AUTO...........................................128 Ride Control Valve - Auto/Travel Below 9.7 km/h (6 mph)........................................130 Ride Control Valve - Auto/Travel More than 9.7 km/h (6 mph)..................................131 Implement Pump and Pump Control Valve ..................................................................134 Pump Control Valve - Engine Off ................................................................................135 Pump Control Valve - Standby .....................................................................................137 Pump Control Valve - Upstroke....................................................................................138 Pump Control Valve - Constant Flow Demand ............................................................139 Pump Control Valve - Maximum System Pressure ......................................................140 Pump Control Valve - Maximum System Pressure with Added Flow Demand ..........141 Implement Valve ...........................................................................................................142 Differential Pressure Relief Valve ................................................................................143 Pressure Reducing Valve ..............................................................................................144 Pressure Reducing Valve - Above the Adjusted Pressure ............................................145 Load Sense Pressure Tap ..............................................................................................146 Signal Duplication Valve ..............................................................................................150 Signal Relief Valve - Below the Adjusted Pressure Setting.........................................151 Signal Relief Valve - Above the Adjusted Pressure Setting.........................................152 Line Relief Valve- Closed.............................................................................................153 STEERING SYSTEM ........................................................................................................158 Steering Pump...............................................................................................................162 Steering Pump with the Engine OFF............................................................................163 Low Pressure Standby ..................................................................................................164

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TABLE OF CONTENTS (continued) Pump Upstroke .............................................................................................................165 Pump Destroke..............................................................................................................166 High Pressure Stall .......................................................................................................167 Steering Control Valve..................................................................................................168 Steering Neutralizer Valves ..........................................................................................169 Steering Neutralizer Valve ............................................................................................170 Steering System Schematic...........................................................................................171 Steering System - Gradual Left Turn............................................................................173 Steering System - Full Left Turn - Steering Neutralized .............................................174 Secondary Steering ......................................................................................................176 Steering Pilot Valve ......................................................................................................183 Steering Pilot Valve - No Turn .....................................................................................185 Steering Pilot Valve - Right Turn .................................................................................186 Steering System - Command Control Steering ............................................................188 BRAKE AND HYDRAULIC FAN SYSTEM COMPONENTS.......................................191 Brake and Hydraulic Fan System - Cut In and Minimum Fan Speed .........................193 Brake and Hydraulic Fan System - Minimum Fan Speed at Cut Out..........................194 Brake and Hydraulic Fan System - Maximum Fan Speed at Cut Out.........................196 Brake and Hydraulic Fan Pump ...................................................................................203 Service Brake Valve - Low Pressure Standby ..............................................................205 Brake and Hydraulic Fan Pump - Upstroke .................................................................207 Accumulator Charge Vale and Hydraulic Fan Solenoid...............................................211 Service Brake Valve......................................................................................................213 Service Brake Valve - Not Activated............................................................................216 Service Brake Valve - Activated..................................................................................217 CATERPILLAR MONITORING SYSTEM ......................................................................219 Fuel Level Sender .........................................................................................................220 Hydraulic Oil Temperature Sensor ...............................................................................222 Brake Pressure Switch ..................................................................................................223 Axle Oil Temperature Sensors......................................................................................224 Filter Bypass Switch in the Right Side Service Bay ....................................................225 Torque Converter Outlet Temperature Sensor..............................................................227 Electrical System ..........................................................................................................228 Action Alarm.................................................................................................................230 Engine Tachometer .......................................................................................................231 CONCLUSION...................................................................................................................232 HYDRAULIC SCHEMATIC COLOR CODE...................................................................233

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NOTES

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966H AND 972H WHEEL LOADERS

© 2006 Caterpillar Inc.

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INTRODUCTION This presentation discusses the component locations and systems operation of the 966H and 972H Wheel Loader. Basic engine and machine component operation will be discussed. The new C11 and the C13 ACERT™ engines, the power train, proportional priority, pressure compensated implement hydraulics, the steering, and braking system operation will be covered. The 966H and 972H are medium wheel loaders in the Caterpillar product line. The serial number prefix for the 966H is A6D Aurora built (A6G Gosselies, A6J Sagami) and the serial number for the 972H Wheel Loader is A7D Aurora built (A7G Gosselies, A7J Sagami). The 966H operating weight is approximately 23,100 Kg (51,000 lbs) and the 972H operating weight is approximately 25,000 Kg (55,400 lbs). The color codes used for hydraulic oil throughout this presentation are: Red

- System or high pressure

Red and White Stripes

- First reduced pressure

Orange

- Pilot pressure

Blue

- Blocked oil

Green

- Tank or return oil

Yellow

- Active component

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WHEEL LOADER COMPONENTS Power Train and Implement ECM

Hydraulic Tank

Fan Pump

Implement Control Levers

Steering Valve Transmission Lift Lift Position Tilt Implement Sensor Cylinder Cylinder Control Valve

Engine C7 Engine ECM

Hydraulic Fan Cooler

Tilt Position Sensor

Air Conditioner Condenser Radiator and ATAAC

Fan Motor

Rear Rear Final Drive Drive Shaft

Accumulator Charging Valve Electrical Components

Steering Cylinder

Torque Implement and Converter Steering Pumps Engine Components

Parking Front Brake Drive Shaft

Front Final Drive

Steering Control Valve Hydraulic Components

Power Train Components

2 Component Location This illustration shows the basic component locations on the 966H and 972H. The component locations on the 966H and 972H are basically the same as in the G series II Wheel Loaders. Power for the 966H is supplied by the C11 ACERT™ and the power for the 972H is supplied by the C13 ACERT™ engine. Power flows from the engine to the torque converter, to the Electronic Clutch Pressure Controlled (ECPC) transmission, through the output transfer gear to front and rear drive shafts. From the drive shafts, power flows to the bevel gears in the differentials, and through the axles. The wheel loader is equipped with a steering pump, steering control valve, and steering cylinders. Also, the machine is equipped with an electrohydraulic implement control with a variable displacement implement piston pump supplying oil to the 3PC hydraulic valve located in the loader frame. The machine may be equipped with an optional electric secondary steering pump that is installed inside the rear frame.

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The wheel loader is equipped with an on demand hydraulic fan system and brake system that share a common variable displacement piston pump and accumulator charging valve. The machine uses a priority valve with the brake system having priority over the hydraulic fan system. The brake system includes the front and the rear service brakes. The parking brake is spring applied, and hydraulically released.

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ENGINE The C11 ACERT™ and C13 ACERT™ engines utilize the A4 Electronic Control Module (ECM) engine control and is equipped with an Air to Air Aftercooler (ATTAC) intake air cooling system. The C11 engine is rated at 175 kW (235 net horsepower). The C13 engine is rated at 198 kW (265 horsepower). The C11 and C13 engines are electronically configured to provide constant net horsepower through the operating ranges. Constant net horsepower automatically compensates for any parasitic loads, allowing the operator to maintain a constant level of productivity. The Engine ECM utilizes the ADEM IV to control the fuel injector solenoid and to monitor fuel injection. The fuel is delivered through a Mechanical Electric Unit Injection (MEUI) system. ACERT™ Technology provides an advanced electronic control, a precision fuel delivery, and refined air management. The C11 engine is an in-line six-cylinder arrangement with a displacement of 11.1 L. The C13 engine is also an inline six-cylinder arrangement with a displacement of 12.5 L. The C11 and C13 ACERT™ engines meet all US Environmental Protection Agency (EPA) Tier III Emission Regulations for North America and Stage IIIa European Emission Regulations.

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C11 / C13 ENGINE ELECTRICAL SYSTEM

Text Reference

Cat Data Link Engine ECM

INPUT COMPONENTS

Caterpillar Monitor Systems

OUTPUT COMPONENTS + 5Volt (Sensors)

Coolant Temperature Sensor

Throttle Sensor Voltage Intake Manifold Air Pressure Sensor

Analog Sensor Voltage

Engine Oil Pressure Sensor

6 Mechanical Electronic Unit Injectors

Atmospheric Pressure Sensor Intake Manifold Air Temperature Sensor

Air Filter Restricted Indicator

Fuel Pressure Sensor

Ether ON Indicator

Fuel Temperature Sensor Ether ON Solenoid Valve Fuel Differential Pressure Switch

Demand Fan Solenoid Valve Auto Reversing Fan Solenoid Valve

Turbo Inlet Pressure Sensor Ground Level Shutdown Switch

Engine Speed To Power Train ECM (CAN)

Throttle Pedal Position Sensor Key Start Switch ON (B+) Auto Reversing Fan Switch Camshaft Speed Timing Sensor Crankshaft Speed Timing Sensor

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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 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 right brake pedal switch, the ether start control solenoid, and the ground level shutdown switch.

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Input Components: Camshaft 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. Crankshaft 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. Atmospheric pressure sensor - This sensor is an input to the Engine ECM and is used as a reference for air filter restriction. Also, the sensor is used to supply information to the Engine ECM during operation at high altitude. Turbo inlet pressure sensor - This sensor is an input to the Engine ECM to supply information about the air restriction before the turbocharger. Intake manifold air temperature sensor - This sensor supplies air temperature data at the intake manifold to the Engine ECM. Fuel differential pressure switch - This switch relays information to the ECM that the fuel pressure at the output of the filter base is restricted in comparison to the inlet pressure. Coolant temperature sensor - This sensor monitors the temperature of the fluid in the coolant system. 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. Fuel temperature sensor - This sensor sends fuel temperature data to the Engine ECM. Engine oil pressure sensor - This sensor is an input to the Engine ECM to supply an information warning for low oil pressure, engine derates for low oil pressure, or a logged event read by ET. Throttle pedal position sensor - This sensor sends the throttle position to the Engine ECM in order to increase or decrease the fuel supply to the injector. Auto reversing fan switch - This switch is an operator input to the Engine ECM. The operator can manually enable the reversing solenoid valve and change the direction of oil flow through the hydraulic fan motor. Key switch ON (+B) - The Key On input to the Engine ECM enables the ECM for operation and is recognized by any ECM on the machine. Ground level shutdown switch - This switch is an input to the Engine ECM. This input disables fuel injection when the engine is running or at engine start-up. Intake manifold air pressure sensor - This sensor is an input to the Engine ECM to supply information about the air pressure into the intake manifold.

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Output Components: +5 Volt - Regulated supply voltage for the sensor inputs to the Engine ECM. Throttle sensor voltage - Voltage supply for the throttle position sensor. Analog sensor voltage - Analog voltage for the turbo inlet pressure sensor. Either ON solenoid valve - Solenoid valve used to apply ether in order to start the engine in cold weather. Auto reversing fan solenoid valve - This solenoid valve is used in order to reverse the oil flow oil through the hydraulic fan motor.. Demand fan solenoid valve - Proportional solenoid valve that controls the signal pressure to the brake and hydraulic fan pump in order to meet the varying cooling requirements of the machine. Air filter restriction indicator - This indicator illuminates in case of a restriction in the inlet air system. Ether On indicator - This indicator illuminates when the ether solenoid valve is initiated.

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Engine Right Side This view shows the right side of the engine accessed from the right side of the machine. Components which can be seen are: - Alternator (1) - Electric fuel priming pump (2) - Secondary fuel filter (3) - Air inlet (4) - Fuel transfer pump (5) - Brake and hydraulic fan pump (6) - Brake accumulator charging valve (7) - Engine ECM (8) - Cam speed sensor and Atmospheric pressure sensor (9)

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Engine Left Side This view shows the left side of the engine accessed from the left side of the machine. Components which can be seen are: - Air inlet (with turbo inlet pressure sensor) (1) - Turbocharger (wastegated) (2) - Coolant regulator housing (3) - Transmission cooler (coolant-to-oil) (4) - Engine coolant pump (5) - Engine oil cooler (coolant-to-oil) (6) - Engine starter (7) - Engine oil filter (8)

5

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Crankshaft Speed Timing Sensor The crankshaft speed timing sensor (1) is located in the front of the engine at the rear of the machine. The crankshaft sensor is the primary speed sensor reporting to the Engine ECM with the engine speed and position of the crankshaft. The speed sensor detects the reference for engine speed and timing from a unique pattern on the respective gear. Normally the crankshaft speed timing sensor identifies the timing during starting and determines when the No. 1 cylinder is at the top of the stroke. When the timing is established, the crankshaft timing sensor is used to relay the engine speed and the camshaft sensor is ignored. If the engine is running and the signal from the crankshaft is lost, a slight change in performance is noticed during change over to the camshaft sensor.

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If the signal from the crankshaft speed timing sensor is lost or intermittent, normally a CID 0190 FMI 08 Engine Speed Abnormal will be logged and can be viewed through Caterpillar ET. Also, the engine speed is shared with the Power Train ECM. Also shown is the brake and hydraulic fan pump (2).

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2

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The atmospheric pressure sensor (1) is located on the left side of the machine on the engine. The Engine ECM uses the sensor as a reference for air filter restriction and derating the engine under certain parameters. All pressure sensors in the system measure absolute pressure and, therefore, require the atmospheric pressure sensor to calculate gauge pressures. The atmospheric pressure sensor is one of the many sensors that require a regulated 5.0 VDC for the sensor supply voltage. The atmospheric pressure sensor outputs a variable DC voltage signal. The Camshaft speed timing sensor (2) is located below the atmospheric pressure sensor. Under normal operation, the camshaft speed timing sensor determines the No. 1 compression timing prior to the engine starting. If the camshaft sensor is lost, a CID 342 MID 08 Secondary engine speed signals abnormal code is active and the crankshaft sensor will time the engine with an extended starting time. The engine will run rough until the Engine ECM determines the proper firing order using the crankshaft sensor only. In the case that the signal from both engine speed sensors is lost, the engine will not start. During a running condition, the engine will shutdown. The sensor serves as a back-up for the crankshaft speed timing sensor. If the crankshaft speed timing sensor fails, the camshaft speed timing sensor allows for continuous operation.

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Engine Speed/Timing Calibration Port The speed/timing calibration port is located on the right side of the machine. The Engine ECM (1) has the ability to calibrate the mechanical differences between the Top Center (TC) of the crankshaft and the timing gear on the camshaft. A magnetic transducer signals the TC of the crankshaft to the ECM when the notch (2) on a counterweight passes by the transducer (not shown). The speed/timing sensor signals the TC of the timing gear to the Engine ECM. Any offset between the TC of the crankshaft and the TC of the timing gear is stored into the memory of the Engine ECM. Remove the plug (3) in order to install the timing probe. NOTE: For additional information in troubleshooting the engine, refer to the Service Manual module Troubleshooting "C11 and C13 Engines for Caterpillar Built Machines" (RENR9318) "Engine Speed/Timing Sensor - Calibrate.

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C11 / C13 ACERT ENGINE FUEL DELIVERY SYSTEM Primary Fuel Filter / Water Separator

Electric Fuel Priming Pump

Fuel Pressure Regulator

Fuel Shutoff Valve Fuel Gallery

(Optional) Fuel Heater Secondary Fuel Filter

Fuel Tank

Fuel Transfer Pump

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Fuel System Fuel is drawn from the fuel tank through the primary fuel filter and water separator by a gear-type fuel transfer pump. The fuel transfer pump then directs the fuel through the secondary fuel filter. The fuel then flows to the cylinder head. The fuel enters the cylinder head and flows into the fuel gallery, where it is made available to each of the six MEUI fuel injectors. Any excess fuel not injected leaves the cylinder head and flows back to the secondary fuel filter. Then, the excess fuel flows past the fuel pressure regulator. The fuel pressure regulator is a check valve that is installed in the secondary fuel filter. The fuel pressure regulator maintains fuel system pressure between the fuel transfer pump and the fuel pressure regulator. From the fuel pressure regulator, the excess fuel flow returns to the fuel tank. The ratio of fuel used for combustion and fuel returned to tank is approximately 3:1 (i.e. four times the volume required for combustion is supplied to the system for combustion and injector cooling purposes).

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A differential pressure switch is installed in the secondary fuel filter base and will alert the operator of a fuel filter restriction. The differential pressure switch compares the filter inlet pressure to the filter outlet pressure. When the difference in the inlet and outlet pressures causes the switch to activate, the Engine ECM will signal the Caterpillar Monitoring System to warn the operator the fuel flow is probably restricted. A fuel temperature sensor is installed in the secondary fuel filter base and will signal the Engine ECM of a high fuel temperature. The effect of high fuel temperature is an engine derate. The fuel system will derate to 12.5% at 91° C (196° F) percent to a maximum derate of 25%. A fuel pressure sensor is installed in the secondary fuel filter base and will signal the Engine ECM of a high fuel pressure. If the fuel pressure exceeds a pressure of 758 kPa (110 psi) the Engine ECM will log a E096 code. In the case of a logged high fuel pressure Event, check the following Fuel System's Components: - Inspect the fuel transfer pump pressure relief valve that is in the body of fuel transfer pump. Check for damage to the spring or to the valve assembly. - Verify that the pressure regulating valve in the fuel filter manifold is operating correctly. Check for damage or for dirt in the valve assembly. - Check the return line from the fuel filter base to the fuel tank for damage or collapse.

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Fuel Transfer Pump The fuel transfer pump is a gear pump that is located near the balancer at the front of the engine and the rear of the machine. The fuel transfer pump is driven by the front gear train. Fuel is drawn from the primary fuel filter and water separator by the fuel transfer pump and then, it is directed to the secondary fuel filter. The fuel transfer pump incorporates a check valve. The check valve allows fuel to flow around the gears of the pump when the fuel system is primed. A relief valve (not shown) is also installed in the fuel transfer pump. The relief valve limits the maximum fuel pressure in the fuel system.

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POWER DERATE Highest Rated Torque Map

Power

50% Derate Derate 100% Derate

Default Torque Map

Engine Speed

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Power Derate The illustration above defines the power derate in relation to the rated torque map and the default torque map. The power derate is a percentage reduction from the rated power at a given engine speed toward the default map at the same rpm. Power is unchanged until the requested power exceeds the derated level. The maximum power during a derate is calculated as: Maximum Power Output = Rated Power - (Rated Power - Default Power) * Derate Percentage For example, if the engine has a maximum rated power of 500 hp and a 100 hp default torque map with a 50% derate, the engine will have 300 hp output power. If 250 hp was needed, then the operator will not notice any change. If however, 400 hp was needed, there would be only 300 hp available due to derates. 300 hp = 500 hp - (500 hp - 100 hp) X 50% (.50)

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Fuel Filter Sensors The fuel system is equipped with two filters, a primary fuel filter/water separator (1) and a secondary filter (2). The primary fuel filter is located on the right side of the machine. The primary filter contains a water separator which removes water from the fuel. Water in a high pressure fuel system can cause premature failure of the injector due to corrosion and lack of lubrication. Water should be drained from the water separator daily, using the drain valve that is located at the bottom of the filter.

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The electric fuel priming pump (4) is integrated into the primary fuel filter base. The priming pump is activated by toggling the fuel priming pump switch (3). The fuel priming pump is used to fill the fuel filters with fuel after they have been replaced. The priming pump will purge the air from the entire fuel system. To activate the fuel priming pump, the key start switch must be in the OFF position. The fuel system is equipped with a secondary high efficiency fuel filter. The fuel regulator (5) is integrated into the secondary fuel filter base. The fuel pressure regulator regulates the the flow of fuel from the fuel gallery. Also, installed on the base is a fuel differential pressure switch (7), a fuel pressure sensor (6) and a fuel temperature sensor (8). The fuel differential pressure switch monitors the difference between the outlet fuel pressure and the inlet pressure. Fuel pressure exceeding 103 kPa (15 psi) will initiate a Level 1 Warning. Then, after 4 hours the Engine ECM initiates a Level 2 Warning and an Engine Derate. The fuel pressure sensor indicator of a fuel return or a pressure control problem. Excessively high pressure in the fuel system can cause problems for the injector. A differential pressure switch is installed in the secondary fuel filter base and will alert the operator of a fuel filter restriction. The differential pressure switch compares the filter inlet pressure to the filter outlet pressure. When the difference in the inlet and outlet pressures causes the switch to activate, the Engine ECM will signal the Caterpillar Monitoring System to warn the operator the fuel flow is probably restricted. A fuel temperature sensor is installed in the secondary fuel filter base and will signal the Engine ECM of a high fuel temperature. The effect of high fuel temperature is an engine derate. The fuel system will derate to 12.5% at 91° C (196° F) percent to a maximum derate of 25%. A fuel pressure sensor is installed in the secondary fuel filter base and will signal the Engine ECM of a high fuel pressure. If the fuel pressure exceeds a pressure of 758 kPa (110 psi) the Engine ECM will log a E096 code. In the case of a logged high fuel pressure Event, check the following Fuel System Components: - Inspect the fuel transfer pump pressure relief valve that is in the body of fuel transfer pump. Check for damage to the spring or to the valve assembly. - Verify that the pressure regulating valve in the fuel manifold is operating correctly. Check for damage or for dirt in the valve assembly. - Check the return line from the fuel filter base to the fuel tank for damage or collapse.

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FUEL TEMPERATURE DERATE 30%

% Derate

25% 20% 15% 10% 5% 0% 89.8 90.0 90.2 90.4 90.6 90.8 91.0

91.2

91.4

91.6

91.8

92.0 92.2

Fuel Temperature C Level 1 Warning

Level 2 Warning / Derat es

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Fuel Temperature Derate This illustration shows the graph for the warning and derates map for the fuel temperature. When the fuel temperature exceeds 90° C (194° F), the Engine ECM will activate a Level 1 Warning. Also, the graph shows, as the fuel temperature increases to 91.0° C (196° F) a Level 2 Warning will be initiated by the Engine ECM. At the same time, the engine will derate to 12.5%. If the fuel temperature exceeds 92° C (198° F), the engine will be derated to 25%. A fuel temperature sensor open circuit will derate the engine to 12.5%. Excessive fuel temperature will cause injector wear.

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FUEL FILTER RESTRICTION DERATE THE FUEL TEMP ABOVE 30 C (86 F) AND PRESSURE ABOVE 110 kPa (15 psi) 60%

% Derate

50% 40% 30% 20% 10% 0% 0

3 min

1 hr

2 hr

Time Level 1 Warning

3 hr

4 hr

4hr 1 sec

5 hr


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High Fuel Filter Restriction Derates When the fuel differential pressure switch recognizes a fuel pressure of 103 kPa (15 psi) for 3 minutes, the Engine ECM will initiate a Level 1 Warning. When the fuel differential pressure switch recognizes 15 psi across the filter for 4 hours, the Engine ECM will initiate a Level 2 Warning. With the Level 2 Warning initiated a 17.5 % derate is applied to the engine. After 1 second, the Engine ECM will initiate a second derate of 17.5%. The total derate will be 35%. This feature will be disabled when the fuel temperature is below 30° C (86 ° F).

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Engine Inlet Air System In the engine inlet air system, the air enters the compressor section of the turbocharger (4) through the air cleaner (2). The compressor directs the air through the ATAAC (3), the intake manifold, and to the cylinder head. Exhaust exits the cylinder head to the turbine housing. From the turbine housing, the turbine wheel directs the exhaust out of the turbo and out through the muffler (1).

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20

The C11 and C13 ACERT™ engines are equipped with a wastegate turbocharger which provides higher boost over a wide range, improving engine response and peak torque, as well as outstanding low-end performance. All of the exhaust gases go from the exhaust manifold through the turbocharger. The exhaust gases enter the turbocharger and drive the turbine wheel. The exhaust gases exit the turbocharger through the turbine wheel outlet (2) to the muffler. The turbine wheel is connected by a shaft to the compressor wheel. The turbine wheel rotates the compressor wheel at very high speeds. The rotation of the compressor wheel pulls clean air through the compressor housing air inlet (1). Then, the compressor wheel blades force air into the cylinder head to the inlet valves. The increased amount of forced air enables the engine to be able to burn more fuel producing increased power. The engine can operate under low boost conditions. During a low boost condition, the canister closes the wastegate, allowing the turbocharger to operate at maximum performance. Under high boost conditions, the wastegate opens. The open wastegate allows exhaust gases to bypass the turbine side of the turbocharger. The rpm of the turbocharger is limited by bypassing a portion of the exhaust gases around the turbine wheel. NOTE: The wastegate calibration is preset at the factory.

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21

Turbo Inlet Pressure Sensor The turbocharger inlet pressure sensor (arrow) is located in the tube that is between the air filter group and the inlet to the compressor housing. The turbocharger inlet pressure sensor measures restriction of air flow through the air filters and the inlet. Restriction of the air flow to the turbocharger will initiate a warning and engine derate.

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AIR INLET RESTRICTION DERATE 16% 14%

% Derate

12% 10% 8% 6% 4% 2% 0% 0

2

4

6

8

10

12

14

16

Air Restriction kPa Difference Level 1 Warning

Level 2 Warning / Derates

22

Air Inlet Restriction Derate The turbo inlet pressure sensor measures the restriction of the air inlet that is flowing to the inlet of the compressor housing of the turbocharger. When the pressure difference between the turbo inlet pressure sensor and the atmospheric sensor read a difference of 9.0 KPa, the Engine ECM will derate the engine approximately 2%. The Engine ECM will then derate the engine 2% more for every 1 kPa difference up to 10%. Typically, the atmospheric pressure sensor is 100 Kpa at sea level. As the air restriction increases, the difference will increase. The first derate will occur when the difference is approximately (100 kpa minus 91 kpa.= 9 kpa). If the air inlet restriction is 92.5 kPa (a pressure that is between 7.5 kPa and 9 kPa) for 10 seconds, the Engine ECM will initiate a Level 1 Warning. If the air restriction goes to the point that the turbo inlet pressure sensor sees a difference of 91.0 kPa (a pressure that is 9.0 KPa) for 10 seconds, then the Level 2 Warning will occur and the engine will go into the air inlet restriction derate.

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1 2

23

Oil Pressure Sensor The engine oil pressure sensor (1) is located on the left side of the engine and the right side of the machine near the Engine ECM (2). The sensor monitors the pressure of the engine oil. The engine oil pressure sensor is one of the many sensors that require a regulated 5.0 VDC for the sensor supply voltage. The sensor outputs a variable DC voltage signal. The Engine ECM will use the information supplied oil pressure sensor to output warning levels to the Caterpillar Monitoring System and engine derates.

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Text Reference

LOW OIL PRESSURE 180 160

Oil Pressure (kPa)

140 120 35% Derate

100 80 60 40 20 0

500

0

1000

1500

2000

2340

0 Derate

Engine rpm kPa Warning Level 1

kPa Shut down Level 3

35% Derate

24

Low Oil Pressure This illustration shows a graph with the two different warning levels for low oil pressure. When the oil pressure is below (154 kPa @ 1600 rpm) the blue line, the Cat Monitoring System will enable the low oil pressure Level 1 Warning: Change machine operation or perform maintenance to the system. When the oil pressure is below (104 kPa @ 1600 rpm) the red line, the Cat Monitoring System will enable the low oil pressure Level 3 Warning: The operator should immediately perform a safe engine shutdown. Also, with the Level 3 Warning, the Engine ECM initiates a 35% engine derate. If the signal between the Engine ECM and the oil pressure sensor is lost or disabled, the Engine ECM will initiate a low engine oil pressure Level 1 Warning.

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25

Coolant Temperature Sensor The coolant temperature sensor (arrow) is installed at the right front corner of the engine, above the jacket water pump. The coolant temperature sensor monitors the temperature of the fluid in the coolant system. The coolant temperature sensor information sent to the Engine ECM is used for Warning Levels that are sent to the Caterpillar Monitoring System and engine derates.

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HIGH COOLANT TEMPERATURE DERATE 120%

% Derate

100% 80% 60% 40% 20% 0% 110

116

116.5

117

117.5

118

118.5

119

119.5

Coolant Temperature C Level 1 Warning


26

High Coolant Temperature Derate The coolant temperature sensor measures the temperature of the coolant. When the temperature of the coolant exceeds 110° C (230° F), the Engine ECM will initiate a Level 1 Warning. When the temperature of the coolant exceeds 111° C (231° F), the Engine ECM will initiate a Level 2 Warning. At 111° C (231° F) the Engine ECM will initiate a 25% derate. Refer to the illustration for the remainder of the high engine coolant temperature derates. At 100% derate, the engine available power will be approximately 50%.

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1

27 3 2

1 4

28

2

Intake Manifold Sensors The upper illustration shows the intake manifold air pressure sensor (1), and the intake manifold air temperature sensor. The intake manifold air pressure sensor (1) is used to monitor intake manifold air pressure. The intake manifold air temperature sensor (2) is used to monitor the air temperature flowing into the intake manifold. The Engine ECM also uses the temperature sensor as one of the key target temperatures to control the fan speed in the hydraulic fan system. Also, the sensor is used as an input to the Engine ECM for the virtual exhaust temperature derate. Also shown is the Engine ECM (3) and intake manifold (4).

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Text Reference

C11-C32 ENGINE INTAKE MANIFOLD TEMPERATURE DERATE 21% 18%

% Derate

15% 12% 9% 6% 3% 0% 82

86

87

88

89

90

91

92

93

Intake Manifold Temperature C Level 1 Warning


29

Intake Manifold Air Temperature Sensor Derate The intake manifold air temperature sensor measures the temperature of the air that is flowing to the intake manifold. The sensor is used to initiate warning levels and engine derates. After the engine is running for at least 3 minutes and if the intake manifold air temperature goes above 82° C (180° F), the Engine ECM will initiate a Level 1 Warning. After the engine is running for at least 3 minutes and if the intake manifold air temperature goes above 86° C (187° F), the Engine ECM will initiate a Level 2 Warning. With the Level 2 Warning, the Engine ECM signals the engine to initiate a 3% derate. This derate will have a 20% upper limit.

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Text Reference

VIRTUAL EXHAUST TEMPERATURE DERATE Engine Derate Percentage

Barometric Pressure Intake Manifold Air Temperature Engine Speed

Fuel Injection Calibration

Highest Derate Priority Selector

Other Engine Derate Conditions

Engine ECM

30

Virtual Exhaust Temperature Derate An engine derate can occur due to a estimated (virtual) high exhaust gas temperature. The Engine ECM monitors the barometric pressure, the intake manifold temperature, and the engine speed to estimate exhaust gas temperature. The following conditions are monitored to determine if the engine derate should be enabled: - high altitude - high ambient temperatures - high load and full accelerator pedal throttle - barometric pressure - intake manifold air temperature, and engine speed The Engine ECM determines a maximum fuel delivery percentage to maintain safe maximum power output under load. This calculation is new to the off-road Tier III engines and is used in place of the previous altitude compensation derate strategy. This event informs the mechanic that a derate has occurred because of operating conditions. Generally, this situation is normal and requires no service action.

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The Engine ECM will process all derate inputs in the highest derate priority selector. The most critical derate condition input will be used to adjust fuel system delivery limiting engine power to a safe level for the conditions in which the product is being operated, thereby prevent elevated exhaust temperatures. The virtual exhaust temperature derate will log a 194 event code. The derate will enable a Level 1 Warning and eventually a Level 2 Warning. The level of the warning will depend on the conditions that are sent to the Engine ECM. The following conditions must be met in order to initiate a virtual exhaust temperature derate. - No CID 168 01 FMI (low battery voltage to the Engine ECM) are active. - No active intake manifold air pressure sensor faults. - No active atmospheric pressure (barometric) sensor faults - No +5 V sensor voltage codes active. - The virtual exhaust temp derate must be the highest derate. - More fuel is being requested than the virtual exhaust temp derate will allow. This derate is triggered by the information inferred by the Engine ECM, rather than an individual sensor as with the previous single derate strategies. If you think this derate is possibly being imposed incorrectly check for event codes on the high intake manifold air temperature and correct those first. Also, make sure the aftercooler is unobstructed. For additional information about troubleshooting, refer to the troubleshooting manual for the particular engine that is being serviced.

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3

1

2

4

31

The fuel pressure regulator (1) is located in the secondary fuel filter base (3). The fuel pressure regulator is used to maintain fuel pressure in the fuel gallery. Also shown is the electric fuel priming pump (2) that is located on the primary fuel filter base (4).

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ENGINE IDLE MANAGEMENT MODES - Work Mode - Warm Up Mode - Hibernate Mode - Low Voltage Mode 32

Engine Idle Management System (EIMS) sets the engine idle to maximize fuel efficiency. Also, this system uses new and improved software to benefit the customer with reduced sound levels, reduced emissions, machine ability to set machine parameters to the working conditions, machine ability to set machine to working applications, and increased battery durability. Work Mode - This mode allows the working idle to be programmed according to the customer's applications requirements. The work mode idle can be adjusted to a higher or lower rpm through Caterpillar Electronic Technician (ET). The engine idle range is between 650 rpm and 1000 rpm. In order to go into the work mode, the percentage of fan bypass must be less than 23%. Warm up Mode - In a cold weather operation, the default engine rpm will be set to 1100 rpm in order to generate additional engine heat, keeping the engine warmer. This mode monitors the coolant temperature and intake manifold temperature. When the coolant temperature is below 80° C (176° F) or the intake manifold temperature is below 15° (60° F) and the warm mode is enabled, the machine will time out for 10 minutes. After ten minutes, the coolant temperature is below 70° C (158° F) and the machine has been in the warm up mode, the engine will be in warm up mode. If the machine has not been in warm up mode but the intake manifold temperature is less than 5° C (41° F), the engine will go into the warm up mode.

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Also, the transmission speed selector must be in the NEUTRAL position, the parking brake engaged, and the throttle position sensor output less than 5% for the engine to go to the warm up mode idle. Hibernate Mode - This mode is initiated only when the transmission speed selector switch is in the NEUTRAL position, the parking brake is engaged, the throttle position sensor output is less than 5%, the coolant temperature is above the EIMS default, the fan bypass is above 23%, and the implement control levers are not activated. When these parameters are met along with a 10 second period after the parking brake is engaged, the hibernate mode will lower the engine idle to 600 rpm. The engine will idle at 600 rpm until one of the above parameters are no longer met. Low Voltage Mode - In this mode, the engine idle will ramp up to 1100 rpm when the battery voltage drops below 24.5 VDC and he engine has been running for 5 minutes. The low voltage mode feature is standard on all machines with EIMS with high current drain due to heavy electrical loads from custom attachments. When the battery voltage is greater than 24.5 VDC, the engine idle will return to the current working low idle speed. The 24.5 battery voltage is a default and can not be reconfigured in ET.

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Text Reference

POWER TRAIN COMPONENTS ACERT“ Engine

Torque Power Train Transmission and Modulating Valves Converter ECM Upshift, Downshift Direction Switches Output Transfer Gear Case

Rear Rear Final Drive Drive Shaft

Parking Front Brake Drive Shaft

Front Final Drive

33

POWER TRAIN This illustration shows the major components in the power train. Power from the engine flows to a 360 mm (14.5 inch) diameter torque converter. The torque converter output shaft is splined to the input shaft of the electronically controlled power shift transmission. The transmission output shaft is splined to the output transfer gear. The output transfer gear transmits power from the transmission to the front and rear drive shafts. Power from the transmission output shaft flows through the front drive shaft and the parking brake to the front pinion, the bevel gear, the differential and the axles to the final drives. Power from the transmission output shaft also flows through the rear universal joint group to the rear pinion, the bevel gear, the differential and the axles to the final drives. Power train movements and operations are controlled through the Power Train ECM.

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34

The Power Train Electronic Control Module (ECM) is the central component in the transmission electronic control system. The ECM is located at the right rear of the cab. The rear panel must be removed for access to the ECM. The Power Train ECM will be located behind the operator’s seat and have the connectors horizontal to each other. The ECM makes decisions based on switch-type and sensor input signals and memory information. Input signals to the ECM come from the operator's station, the machine, and the transmission. The operator's station input components consist of: the direction and shift switches, the neutralizer and neutralizer override switches, the park brake switch, the key start switch, and the Auto/Manual select switch. Optional switch inputs are the ride control switch and the secondary steer test switch. The machine input components are: the engine speed sensor, the primary steering pressure switch, the optional secondary steering pressure switch, and the Caterpillar Monitoring System message center module. The transmission input components are the transmission oil temperature sensor, the torque converter output speed sensor, and the two transmission output speed sensors. The ECM communicates with other electronic control modules, such as the Caterpillar Monitoring System, the Engine Electronic Control Module (ECM), and the Implement Electronic Control Module (ECM) through the Cat Data Link. The Cat Data Link allows the Transmission ECM to receive and send information.

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The power train uses the A4M1 Electronic Control Module (ECM). To enable the ECM for power train functions, contact (J1-27) is grounded and contact (J1-32) is grounded in order to enable the ECM. 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 with the shift lever. The Power Train ECM interprets the input signals from the shift lever, evaluates the current machine operating status, and energizes the appropriate modulating valve. The Power Train ECM receives three different types of input signals: 1. Switch input: Provides the signal line to battery, to ground, or to 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. 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. The Power Train ECM interprets signals from the shift lever to signal the transmission to perform the following options: Upshift, Downshift, Forward Neutral, and Reverse. 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 Caterpillar Monitoring System.

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Text Reference

POWER TRAIN ELECTRICAL SYSTEM Cat Data Link

Power Train ECM

Caterpillar Monitor System

INPUT COMPONENTS Auto / Manual Speed Selector Switch (CCS Option)

Shift Lever Upshift, Downshift, Forward, Neutral, Reverse

Parking Brake Pressure Switch

Direction Switch Forward, Neutral, Reverse, Upshift, Downshift (CCS Optional)

Left Brake Pedal Position Sensor Ride Control Switch (ON, AUTO)

Key Start Switch

Secondary Steering Test Switch

Variable Shift Control Selector Switch

Transmission Neutralizer Disable Switch

Transmission Output Speed Sensor 1 and 2

Heated Mirror Switch

Torque Converter Output Speed Sensor

Implement Pod Downshift Switch

Transmission Oil Temperature Sensor

+24 Battery Voltage

Auto / Manual Speed Selector Switch (HMU)

Location Code 2 (Ground)

Primary Steering Pressure Switch

Location Code Enable (Ground)

Secondary Steering Pressure Switch

Engine Speed (CAN)

35

Power Train Electrical System This illustration shows the input components which provide power or signals to the Power Train ECM. Power Train ECM Inputs: Shift lever (Forward, Neutral, Reverse, and Gear): Combines control of the transmission shifting to a single input device. The shift lever can be pushed forward, backward, or placed in the middle position for machine direction. The lever is rotated in order to change the speeds of the transmission. This is the standard control for shifting that comes with the Hand Metering Unit (HMU) steering. Direction switch (Forward, Neutral, Reverse, Upshift, and Downshift): Combines control of the transmission shifting with a single input device. The 3 position switch controls direction and the 2 thumb-switches controls upshift and downshift. This is the control for shifting that comes with the Command Control Steering (CCS). Key start switch: Provides a signal to the Power Train ECM when the operator wants to start the engine. The direction switch/shift lever must be in the NEUTRAL position before the Power Train ECM will permit engine starting.

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Variable shift control selector switch: The variable shift control switch is an input of the Power Train ECM. The switch allows the selection of a range of shifting points in the Power Train ECM for each speed. The switch has three inputs to the power train ECM. Transmission output speed sensors: These sensors measure the transmission output speed in the range of 25 to 3000 rpm. By looking at the difference in phase in between these 2 sensors, direction can be derived. Torque converter output speed sensors 1 and 2: Measures the torque converter speed in the range of 25 to 3000 rpm. Auto/manual speed selector switch (HMU): Signals the Power Train ECM which shift mode the operator wants to operate on a standard machine. The operator can select between manual shifting or automatic shifting in the range of gears 4 to 2 or in the range of gears 4 to 1. Maximum gear, if lower gear than 4 is desired, will be determined by the shift lever position. Auto/manual speed selector switch (CCS option): Signals the Power Train ECM which shift mode the operator wants to operate on a machine with the optional Command Control Steering. The operator can select between manual shifting and automatic shifting with maximum gear of 4, 3, or 2 and also a 4 to 1 range shifting mode. Primary steering pressure switch: Sends a signals the Power Train ECM if the primary steering system loses steering oil flow. Secondary steering pressure switch: It tells the ECM if the secondary steering pump is correctly building up pressure. When the pump is running and we still do not see pressure a warning indicator is lit. It is mostly used as feedback for the start-up test and the manual switch test to ensure that the system is working properly. Left pedal position sensor: Signals the position of the torque converter pedal to the Power Train ECM. The position of the pedal is being used to downshift the transmission and neutralize the transmission during operation. Both the downshift and neutralization function of the pedal can be disabled and hence the pedal would function as a brake pedal only. Parking brake pressure switch: Provides a signal to the Power Train ECM when the pressure is adequate to release the parking brake. Ride control switch (ON/OFF/AUTO): Signals the Power Train ECM which mode the operator wants to operate. The operator should never operate in ON mode since this is the service mode. Transmission neutralizer disable switch: Provides an input to the Power Train ECM that will disable the the left pedal neutralization of the transmission. Transmission oil temperature sensor: Provides an input to the Power Train ECM with the temperature of the transmission oil.

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Implement pod downshift switch: The downshift switch provides an input to the Power Train ECM to downshift the transmission. This switch is only used on a HMU steering machine. Engine speed: The Power Train ECM receives the engine speed over the CAN Data Link from the Engine ECM. Location code enable (grounded): The location code enable is a grounded input signal to the Power Train ECM that enables the location code detection feature to become active. J1-32 pin on the Power Train ECM connector is connected. Location code 2 (grounded) : The location code pin number 2 is a grounded input signal that establishes the ECM is dedicated to the Power Train operation. J1-27 pin on the Power Train ECM connector is connected. +24 Volts: Unswitched power supplied to the Power Train ECM from the battery.

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Text Reference

3

1 4

2

36

Engine Start Switch and Diagnostic Service Tool Connector The engine start switch (1) signals the Power Train ECM that the operator wants to start the engine. The ECM determines if the transmission directional switch (not shown) is in the NEUTRAL position. When the directional switch is in the NEUTRAL position and the key start switch (1) is turned to the START position, the ECM energizes the starter relay. The diagnostic service tool connector (2) for a laptop computer using Caterpillar Electronic Technician (ET) are on the front panel on the right side. A laptop computer with ET can be used for: calibrating, checking and clearing fault codes, and monitoring system inputs and outputs for troubleshooting the transmission system. Also shown are the the hazard switch (3), and the 12 Volt adapter socket (4).

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37

Transmission Shift Lever This is a picture of the standard type of transmission shift lever control group (arrow) that is found on the 966H/972H Wheel Loaders. This control group is found on machines with conventional (HMU) steering systems. The shift lever is mounted on the left side of the steering column. The operator moves the shift lever forward to travel in the FORWARD direction or toward the rear to travel in the REVERSE direction. FIRST through FOURTH speeds are selected by rotating the shift lever. When the transmission is in the Manual Mode, the Transmission ECM allows the shift lever to control the transmission. The Transmission ECM shifts the transmission to the exact gear and direction shown on the shift lever. When the transmission is in the Automatic Mode, the shift lever selection is the maximum gear the transmission will obtain. The Power Train ECM will automatically select the correct speed clutches (SECOND, THIRD, or FOURTH) based on the engine and transmission output speeds.

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Text Reference

1

2

38

Transmission Shift Control This illustration shows the transmission shift control for the optional Command Control Steering (CCS). The directional control switch (1), and the upshift/downshift switch (2) are mounted on the left side of the half moon shaped steering wheel. The directional control switch is a three-position switch with which the operator selects either FORWARD (toggle forward), NEUTRAL (center position), or REVERSE (toggle backward) directions. The switch position the operator selects closes (grounds) that contact while the remaining two contacts stay open. Closing a switch contact sends a signal to the Power Train ECM indicating the direction selected by the operator. The upshift switch/downshift switch are identical in construction and operation. When the operator wants to manually shift to a higher or lower gear, the upshift switch or downshift switch is pressed. Each switch has two input connections at the Power Train ECM. When the switches are not activated, one connection is closed (grounded) and the other connection is open. When the operator pushes the upshift or downshift switch, the selected switch momentarily reverses connections to signal the Power Train ECM to change the desired speed.

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1

Text Reference

2

3

4

39

This illustration shows the location of the ride control ON/OFF/AUTO switch (1). The ride control switch has three positions. In the center position, ride control is disabled. In the UP position (as shown) the ride control switch is in the AUTO position. With the switch in AUTO, the ride control system will be enabled when the machine is traveling at least 9.5 km/h (6.0 mph). The SERVICE position (as shown on the switch) is used for service to the ride control system. The transmission neutralization disable switch (2) is used to disable the neutralization of the left brake pedal. Pressing the upper section of the switch will activate the override. When the neutralization is enabled, the left brake pedal will not neutralize the transmission, but will function as a service brake only. The normal, default position of the switch is the lower (released) position The heated mirror switch (3) enables the heated mirror relay that is located behind the operator seat below the Power Train ECM. If the machine is equipped with the optional secondary steering, there will be a secondary steering test switch (4) mounted in the blocked position on the panel. When the switch is depressed it feeds a ground signal to a relay and also to a switch input on the Power Train ECM. The relay turns on the secondary steering pump and motor, which supplies flow for the steering system. The Power Train ECM is monitoring the pressure of the secondary steering hydraulic lines. This action ensures the pressure has increased to an acceptable level while the pump is running.

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If the switch is depressed and the pressure is not increased to the acceptable level within 3 seconds, the secondary steering warning indicator will be illuminated to indicate that the pump is not functioning properly.

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1

2

40

The 966H and 972H Wheel Loaders are equipped with a variable shift control switch (1). The variable shift control uses the engine speed in order to provide optional autoshift points. The Power Train (ECM) uses the position of the variable shift control switch and the engine speed to determine the autoshift points for the transmission. The variable shift control switch has three inputs to the Power Train Electronic Control Module (ECM). The Auto/manual gear selector switch (2) sends a signal to the Power Train ECM to control shifting mode in auto. The Power Train (ECM) shifts the transmission automatically. To regulate transmission shifts, the Power Train ECM evaluates the input that is sent from the engine speed sensor, the transmission speed sensors, the torque converter output speed sensor, and the left brake pedal position sensor. The automatic mode of operation is represented by two numbers that are separated by a dash. The first number indicates the speed of the transmission when the transmission is placed into gear. The second number indicates the highest speed of the transmission when the machine is traveling. For example, place the autoshift control switch into the 2-4 position. The machine will automatically shift into second gear when the transmission is placed into gear. The transmission will automatically upshift into fourth gear as the machine accelerates. The Power Train ECM does not allow an upshift to a speed that is higher than the speed that is selected with the transmission direction and speed control lever. An automatic downshift from second speed to first speed occurs only if the autoshift switch is in the 1-4 position.

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41

This illustration shows the panel with the optional Command Control Steering. The Auto/Manual gear selector switch sends a signal to the Power Train ECM to control shifting mode in auto. In the MANUAL position, the operator is responsible for upshifting and downshift the transmission. The Power Train ECM automatically shifts the transmission if the autoshift switch is in one of the four AUTO positions and the left brake pedal must be released. To regulate transmission shifts, the Power Train ECM evaluates the inputs that are sent from the engine speed sensor, the transmission speed sensors, the torque converter output speed sensor, and the left brake pedal position sensor. When the machine is operating in "AUTO" mode, the transmission speed selector switch can be used in order to downshift the transmission. This switch is normally used to downshift from second speed to first speed in order to load a bucket. The transmission will remain in the downshifted gear for three seconds after the switch is released. Then, automatic shifting will resume. If the transmission is downshifted to first speed, the machine remains there until there is a direction change or a manual upshift. For example, place the autoshift switch into position "3." The machine will automatically shift into second gear when the transmission is placed into gear. The transmission will automatically upshift into third speed when the machine accelerates. An automatic downshift from second speed to first speed occurs only if the autoshift switch is in the 1-4 position. The Power Train ECM does not allow an automatic upshift to a speed that is higher than the speed that is selected with the auto/manual switch. The autoshift switch is used to select the top speed for the transmission when the transmission is in the AUTO mode. There are four modes of automatic operation: 4 position, 3 position, 2 position and 1-4 position.

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Text Reference

3

1 2

42

The Power Train ECM receives inputs from three speed sensors on the transmission. The sensors are: - No. 1 output speed sensor (1) - No. 2 output speed sensor (2). - Torque converter output speed sensor (3) The output speed sensors (1 and 2) are positioned out of phase with each other. The Power Train ECM uses the phasing of the input data to determine the direction of rotation of the intermediate and output gears. The torque converter output speed sensor measures torque converter output speed in the range of 25 to 3000 rpm. The Power Train ECM has no direct feed back information to determine if clutch engagement and disengagement is completed. The Power Train ECM uses the speed sensor information, including the engine speed sensor data, to measure expected clutch slippage and planetary speeds to ensure the transmission is shifting according to the application program stored in the ECM memory. The speed sensor information is also used by the Power Train ECM to set and adjust transmission shift points.

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43

44

Transmission Oil Temperature Sensor The transmission oil temperature sensor (arrow) is a two-wire passive temperature sensor that is located on the left side of the machine. The sensor is an input to the Power Train ECM. The oil temperature sensor information is used to adjust transmission clutch fill times. The transmission oil temperature sensor information is also sent by the Power Train ECM to the Caterpillar Monitoring System over the Cat Data Link.

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45

Left Brake Pedal Position Sensor The left brake pedal position sensor (arrow) is located in the cab as part of the left brake pedal. The position sensor (left brake pedal) sends an input to the Power Train ECM. The sensor continuously generates a 500 Hz PWM signal. The duty cycle varies in proportion to the position of the left brake pedal position sensor. The left pedal position sends a change in the input signal to the Power Train ECM. The ECM measures the duty cycle in order to determine the position of the pedal for downshifting the transmission and neutralizing the clutches.

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1

Text Reference

2

46

Implement Pod Downshift Switch And Remote F-N-R Switch The downshift switch (1) is located on the implement pod. If the machine is equipped with a joystick, the downshift switch will be located on the joystick handle. When the Power Train ECM is operating in the Manual Mode, depressing the downshift switch will cause a downshift from SECOND speed to FIRST speed. In the Manual mode, the downshift switch will not shift from FOURTH to THIRD speed or from THIRD to SECOND speed. The transmission will remain in FIRST speed until one of the following conditions occurs: 1. A directional shift is made. 2. The shift lever is moved to NEUTRAL before selecting a speed. 3. The shift lever is turned to FIRST speed and then to another speed. When operating in the Automatic mode, depressing the downshift switch causes the Transmission ECM to downshift the transmission at a higher than normal ground speed. Pressing and immediately releasing the downshift switch causes the Transmission ECM to immediately downshift the transmission one speed range. A downshift will occur only if the machine speed and engine speed will not result in an engine overspeed. Automatic shifting is disabled for five seconds after the downshift switch is pressed. After five seconds, automatic shifting, based on speed sensor inputs, is reactivated. NOTE: The remote F-N-R switch (2) is only installed on the machines that are equipped with the standard HMU steering.

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1

47

2

3

48

Parking Brake Pressure Switch The parking brake pressure switch (1) is a normally closed switch with the parking brake engaged. When the parking brake is engaged, the parking brake indicator light (3) will be illuminated. When the parking brake knob is pushed to the IN position, the parking brake valve (2) will direct oil pressure to the parking brake release cylinder. The parking brake pressure switch will open, turning the parking brake indicator light OFF. Then, the Power Train ECM will receive a signal that the parking brake is disengaged.

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Text Reference

POWER TRAIN ELECTRICAL SYSTEM Cat Data Link Power Train ECM


OUTPUT COMPONENTS Engine Start Relay

Clutch 1 Reverse Solenoid

Low Fuel Level Warning Indicator LED

Clutch 2 Forward Solenoid

Transmission Oil Filter Bypass Indicator Led

Clutch 3 4th Speed Solenoid

Transmission Neutralizer Disabled Indicator LED

Clutch 4 3rd Speed Solenoid

Ride Control ON Indicator LED

Clutch 5 2nd Speed Solenoid

Secondary Steering Intermediate Relay

Clutch 6 1st Speed Solenoid

Ride Control Antidrift Solenoid (RE)

Back-up Alarm

Ride Control Solenoid (Balance)

+24 Voltage

Ride Control Antidrift Solenoid (HE) Heated Mirror Relay

49

Based on the input signals, the Power Train ECM energizes the appropriate transmission control modulating valve 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. The Cat Data Link connects the Power Train ECM to the other machine ECMs. The Cat Data Link also connects the ECM to the Caterpillar Monitoring System and electronic service tools such as Caterpillar Electronic Technician (ET). Power Train ECM Outputs: Engine start relay: The Power Train ECM energizes the key start relay when the appropriate conditions are met to start the engine. Controls the current between the key start switch and the starter relay. Transmission oil filter bypass indicator LED: The Power Train ECM illuminates the indicator LED when the oil is bypassing the transmission filter. Low fuel level warning indicator LED: The Power Train ECM illuminates the indicator LED when the fuel level in the tank is below 10% of total fuel tank volume as read by the fuel level sensor (input to EMS-III communicated over Cat Data Link).

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Text Reference

Ride Control ON indicator LED: The Power Train ECM illuminates the indicator LED when ride control is active. Either in AUTO mode when driving above the threshold speed or when in service mode. Clutch solenoids: The solenoids control the oil flow through the respective speed and directional modulating valves. Secondary steering intermediate relay: The Power Train ECM energizes the relay when the loss of steering pressure is detected by the Power Train ECM. The ECM energizes the relay and power is supplied to the secondary steering pump. Back-up alarm: The Power Train ECM energizes the back-up alarm when the operator selects the REVERSE direction. Heated mirror relay: The Power Train ECM energizes the relay to send current to the coil to warm the mirror. Ride Control Solenoid valve (RE): The Power Train ECM energizes the solenoid valve that controls the opening of the antidrift valve which allows flow between the rod end of the lift cylinders and tank. Ride Control Solenoid valve (HE): The Power Train ECM energizes the solenoid valve that controls the opening of the antidrift valve which allows flow between the accumulator and the head end of the lift cylinders. Ride Control Solenoid valve (Balance): At engine start-up, the Power Train ECM energizes the solenoid valve 2. When the Power Train ECM recognizes the ground speed in AUTO reaches the default threshold speed value in the Power Train ECM, the ECM de-energizes the ride control balance solenoid valve for a default time designated through Caterpillar ET configuration. The pressure between the head end of the lift cylinders and the accumulator are balanced. Then, the Power Train ECM energizes the head end ride control solenoid valve and rod end ride control solenoid valve.

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Text Reference

50

Back-up Alarm The back-up alarm (arrow) is located on the right hand side of the machine inside the access door. The alarm sounds when the transmission directional switch is placed in the REVERSE position.

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Text Reference

1

3

2

4

5

51

Warning Panel - Left Side This illustration shows the warning panel on the left side of the dash panel. These indicators are driven outputs of the Power Train ECM. The transmission oil filter bypass (1) is located on the top right hand side. This alarm is illuminated when the transmission oil filter is bypassing due to a plugged filter requiring a change. The transmission neutralizer disabled indicator (2) is located in the center of the panel. This indicator is illuminated when the transmission neutralized is disabled. The low fuel filter WARNING indicator (3) is located in the center row on the right side. This indicator is illuminated when the fuel level is below 10% of the total fuel tank volume. The ride control SERVICE indicator (4) is located in the bottom row on left side. This indicator is illuminated when the ride control switch is placed in the SERVICE position. The ride control AUTO indicator (5) is located in the bottom row, center. This indicator is illuminated when the ride control switch is placed in the AUTO position.

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Text Reference

2 1

4 3

52

Implement Control Valve - With Ride Control The ride control system is an option on the 966H and the 972H Wheel Loaders. The optional ride control system provides a means for dampening the bucket forces, which produce a pitching motion as the machine travels over rough terrain. The operation of ride control is initiated by the switch input to the Power Train ECM with outputs to the solenoid valves on the implement control valve (1). On the implement control valve, there are two solenoid valves that controls oil flow over the antidrift valves and one solenoid valve controlling the shifting of the balance valve. Energizing solenoid valve (2) provides a path of oil between the head end of the lift cylinders and the ride control accumulator. Energizing solenoid valve (3) allows the balance spool to shift as the solenoid valve provides a path for the oil on the end of the balance spool to flow to the hydraulic tank passage. Energizing solenoid valve (4) drains the oil pressure off the antidrift valve enabling the valve to raise. Supply oil flows between the rod end of the lift cylinders and the hydraulic tank. The optional ride control is enabled through the Machine Configuration screen with Caterpillar Electronic Technician (ET). When the ride control system is in SERVICE/AUTO, the respective LED is illuminated on the machine status display.

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Text Reference

2

1

53

Secondary Steering Intermediate Relay The secondary steering intermediate relay (1) is an output of the Power Train ECM. When the steering oil pressure at the primary pressure goes below the value of the pressure switch (2), a signal is sent to the Power Train ECM. Then, the ECM sends current to the intermediate relay to energize the secondary steering pump motor. The secondary steering pump will supply oil to the steering system.

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Text Reference

1 54

2 55

Engine Start Relay The engine start relay (2) is located in the left side service center (1). The engine start relay is energized by the Power Train ECM when all the engine starting requirements are met. When the relay is energized, battery voltage flows through the relay to the starter solenoid.

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Text Reference

TRANSMISSION HYDRAULIC SYSTEM NEUTRAL Torque Converter

Main Relief Valve

Torque Converter Outlet Relief Valve Cooler To Transmission Bearing Lubrication

Power Train ECM

Modulating Valve

Modulating Valve

Torque Converter Inlet Relief Valve

4 THIRD SPEED

1 REVERSE

1

4 Modulating Valve

Modulating Valve Filter

5

2 FORWARD

Transmission Pump

SECOND SPEED

2

5 Modulating Valve

Modulating Valve Screen Group Magnet

6

3

FIRST SPEED

FOURTH SPEED

6

3

Tank

56

Transmission Hydraulic System - NEUTRAL This illustration shows the transmission hydraulic system with the engine running and the transmission shift lever in the NEUTRAL position. When the engine is running, flow from the pump is sent through the filter to the six transmission solenoid valves. Pump flow is also sent to the transmission relief valve. The transmission relief valve limits the transmission oil pressure to the modulating valves. When NEUTRAL is selected, the Power Train ECM energizes the No. 3 solenoid. The modulating valve controls the flow of oil to the No. 3 clutch. When the No. 3 solenoid is energized, the electromagnetic force moves the pin against the ball. The ball moves to the right against the seat. The oil flow through the center of the valve spool is blocked. The oil pressure increases at the left end of the valve spool and the valve spool moves to the right against the spring. Then, oil flow is directed to the ports for clutch 3. From the main relief valve, oil flows to the torque converter and the torque converter inlet relief valve. The torque converter inlet relief valve limits the oil pressure to the torque converter. When oil pressure to the torque converter exceeds 900 ± 70 kPa (130 ± 10 psi), the inlet relief valve opens and sends the excess oil pressure to drain.

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Text Reference

Oil in the torque converter flows out of the torque converter through the torque converter outlet relief valve. The outlet relief valve maintains the pressure in the torque converter at a minimum of 415 ± 135 kPa (60 ± 20 psi) at torque converter stall rpm. From the torque converter outlet relief valve, the oil flows through the transmission oil cooler and on to the transmission for cooling and lubrication of the bearings and planetary.

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Text Reference

TRANSMISSION HYDRAULIC SYSTEM FIRST SPEED FORWARD Torque Converter

Main Relief Valve


Power Train ECM

Modulating Valve

Modulating Valve


4

1 REVERSE

THIRD SPEED

1

4


Modulating Valve

2

5 SECOND SPEED

FORWARD

Transmission Pump

2

5 Modulating Valve

Modulating Valve

6

3

Screen Group Magnet

FIRST SPEED

FOURTH SPEED

6

3

Tank

57 This illustration shows the transmission hydraulic system with the engine running and the transmission shift lever in the FORWARD position and the speed selector in FIRST SPEED. When the engine is running, flow from the pump is sent through the filter to the six transmission solenoid valves. Pump flow is also sent to the transmission relief valve. The transmission relief valve limits the transmission oil pressure to the modulating valves. When FIRST SPEED FORWARD is selected, the Power Train ECM energizes the No. 2 solenoid and the No. 6 solenoid. The modulating valve controls the flow of oil to the No. 2 and No. 6 clutches. When the No. 2 and No. 6 solenoids are energized, the electromagnetic force moves the armature against the ball. The ball moves to the right against the seat. The oil flow through the center of the valve spool is blocked. The oil pressure increases at the left end of the valve spool and the valve spool moves to the right against the spring. Then, oil flow is directed to the ports for clutch 2 and clutch 6. From the main relief valve, oil flows to the torque converter and the torque converter inlet relief valve. The torque converter inlet relief valve limits the oil pressure to the torque converter. When oil pressure to the torque converter exceeds 900 ± 70 kPa (130 ± 10 psi), the inlet relief valve opens and sends the excess oil pressure to drain.

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Text Reference

Oil in the torque converter flows out of the torque converter through the torque converter outlet relief valve. The outlet relief valve maintains the pressure in the torque converter at a minimum of 415 ± 135 kPa (60 ± 20 psi) at torque converter stall rpm. From the torque converter outlet relief valve, the oil flows through the transmission oil cooler and then to the transmission for cooling and lubrication of the bearings and planetary.

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Text Reference

TRANSMISSION HYDRAULIC SYSTEM SECOND SPEED FORWARD Torque Converter

Main Relief Valve

Torque Converter Outlet Relief Valve Cooler

Power Train ECM

To Transmission Bearing Lubrication

Modulating Valve

Modulating Valve


4

1 REVERSE

THIRD SPEED

1

4 Modulating Valve


2

5

FORWARD

Transmission Pump

SECOND SPEED

2

5 Modulating Valve

Modulating Valve

66

3

Screen Group Magnet

FIRST SPEED

FOURTH SPEED

6

3 Tank

58 This illustration shows the transmission hydraulic system with the engine running and the transmission shift lever in the FORWARD position and the speed selector in SECOND SPEED. When the engine is running, flow from the pump is sent through the filter to the six transmission solenoid valves. Pump flow is also sent to the transmission relief valve. The transmission relief valve limits the transmission oil pressure to the modulating valves. When FIRST SPEED FORWARD is selected, the Power Train ECM energizes the No. 2 solenoid and the No. 5 solenoid. The modulating valve controls the flow of oil to the No. 2 and No. 5 clutches. When the No. 2 and No. 5 solenoids are energized, the electromagnetic force moves the armature against the ball. The ball moves to the right against the seat. The oil flow through the center of the valve spool is blocked. The oil pressure increases at the left end of the valve spool and the valve spool moves to the right against the spring. Then, oil flow is directed to the ports for clutch 2 and clutch 5. From the main relief valve, oil flows to the torque converter and the torque converter inlet relief valve. The torque converter inlet relief valve limits the oil pressure to the torque converter. When oil pressure to the torque converter exceeds 900 ± 70 kPa (130 ± 10 psi), the inlet relief valve opens and sends the excess oil pressure to drain.

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Text Reference


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Text Reference

TRANSMISSION HYDRAULIC SYSTEM SECOND SPEED REVERSE Torque Converter

Main Relief Valve


Power Train ECM

Modulating Valve Torque Converter Inlet Relief Valve

Modulating Valve

1

4 THIRD SPEED

REVERSE

1

4 Modulating Valve


5

2

SECOND SPEED

FORWARD

Transmission Pump

2

5 Modulating Valve

Modulating Valve Screen Group Magnet

66

3

FIRST SPEED

FOURTH SPEED

6

3

Tank

59

This illustration shows the transmission hydraulic system with the engine running and the transmission shift lever in the REVERSE position and the speed selector in SECOND SPEED. When the engine is running, flow from the pump is sent through the filter to the six transmission solenoid valves. Pump flow is also sent to the transmission relief valve. The transmission relief valve limits the transmission oil pressure to the modulating valves. When SECOND SPEED REVERSE is selected, the Power Train ECM energizes the No. 1 solenoid and the No. 5 solenoid. The modulating valve controls the flow of oil to the No. 1 and No. 5 clutches. When the No. 1 and No. 5 solenoids are energized, the electromagnetic force moves the armature against the ball. The ball moves to the right against the seat. The oil flow through the center of the valve spool is blocked. The oil pressure increases at the left end of the valve spool and the valve spool moves to the right against the spring. Then, oil flow is directed to the ports for clutch 1 and clutch 5. From the main relief valve, oil flows to the torque converter and the torque converter inlet relief valve. The torque converter inlet relief valve limits the oil pressure to the torque converter. When oil pressure to the torque converter exceeds 900 ± 70 kPa (130 ± 10 psi), the inlet relief valve opens and sends the excess oil pressure to drain.

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Text Reference


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Text Reference

TRANSMISSION MODULATING VALVE NO COMMANDED SIGNAL Test Port Valve Spool

Ball Orifice

Solenoid

Pin

Drain Orifice

Spring

From Pump To Tank

To Clutch

60

Transmission Modulating Valve - No Commanded Signal In this illustration, the transmission modulating valve is shown with no current signal applied to the solenoid. The Transmission ECM controls the rate of oil flow through the transmission modulating valves to the clutches by changing the signal current strength to the solenoid. With no current signal applied to the solenoid, the transmission modulating valve is DEENERGIZED and oil flow to the clutch is blocked. The transmission modulating valve is located on the transmission control valve. Pump oil flows into the valve body around the valve spool and into a drilled passage in the center of the valve spool. The oil flows through the drilled passage and orifice to the left side of the valve spool to a drain orifice. Since there is no force acting on the pin assembly to hold the ball against the drain orifice, the oil flows through the spool and the drain orifice past the ball to the tank. The spring located on the right side of the spool in this view holds the valve spool to the left. The valve spool opens the passage between the clutch passage and the tank passage and blocks the passage between the clutch passage and the pump supply port. Oil flow to the clutch is blocked. Oil from the clutch drains to the tank preventing clutch engagement.

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Text Reference

TRANSMISSION MODULATING VALVE COMMANDED SIGNAL BELOW MAXIMUM Test Port Ball

Solenoid

Pin

Valve Spool

Orifice

Drain Orifice

Spring

From Pump To Tank

To Clutch

61

Transmission Modulating Valve - Commanded Signal Below Maximum In this illustration, the modulating valve is shown with a signal to the solenoid that is below the maximum current. Clutch engagement begins when the Transmission ECM sends an initial current signal to ENERGIZE the solenoid. During each stage of the engagement and disengagement cycle, the amount of commanded current signal is proportional to the desired pressure applied to the clutch. The start of clutch engagement begins when the current signal to the solenoid creates a magnetic field around the pin. The magnetic force moves the pin against the ball in proportion to the strength of the current signal from the Transmission ECM. The position of the ball against the orifice begins to block the drain passage of the oil flow from the left side of the valve spool to the tank. This partial restriction causes the pressure at the left end of the valve spool to increase. The oil pressure moves the valve spool to the right against the spring. As the pressure on the right side of the valve spool overrides the force of the spring, the valve spool shifts to the right. The valve spool movement starts to open a passage on the right end of the valve spool for pump supply oil to fill the clutch. Oil also begins to fill the spring chamber on on the right end of the spool.

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Text Reference

In the initial clutch filling stage, the Transmission ECM commands a high current pulse to quickly move the valve spool to start filling the clutch. During this short period of time, the clutch piston moves to remove the clearances between the clutch discs and plates minimizing the amount of time required to fill the clutch. The ECM then reduces the current signal which reduces the pressure setting of the proportional solenoid valve. The change in current signal reduces the flow of oil to the clutch. The point where the clutch plates and discs start to touch is called TOUCH-UP. Once TOUCH-UP is obtained, the Transmission ECM begins a controlled increase of the current signal to start the MODULATION cycle. The increase in the current signal causes the ball and pin to further restrict oil through the drain orifice to tank causing a controlled movement of the spool to the right. The spool movement allows the pressure in the clutch to increase. During the MODULATION cycle, the valve spool working with the variable commanded current signal from the Transmission ECM acts as a variable pressure reducing valve. The sequence of partial engagement is called desired slippage. The desired slippage is controlled by the application program stored in the Transmission ECM.

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Text Reference

TRANSMISSION MODULATING VALVE COMMANDED SIGNAL AT MAXIMUM Test Port Ball

Solenoid

Pin

Drain Orifice

Valve Spool

Orifice

To Tank

To Clutch

Spring

From Pump

62

Transmission Modulating Valve - Commanded Signal At Maximum In this illustration, the modulating valve is shown with a maximum current signal commanded to the solenoid. When the modulation cycle stops, the Transmission ECM sends the maximum specified current signal to fully engage the clutch. The constant current signal pushes the pin firmly against the ball in the solenoid valve. The pin force against the ball blocks more oil from flowing through the drain orifice. This restriction causes an increase in pressure on the left side of the valve spool. The valve spool moves to the right to allow pump flow to fully engage the clutch. In a short period of time, maximum pressure is felt at both ends of the proportional solenoid valve spool. This pressure along with the spring force on the right end of the spool cause the valve spool to move to the left until the forces on the right end and the left end of the valve spool are balanced. The valve spool movement to the left (balanced) position reduces the flow of oil to the engaged clutch. The Transmission ECM sends a constant maximum specified current signal to the solenoid to maintain the desired clutch pressure.

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Text Reference

The different maximum specified pressures for each clutch is caused by different maximum current signals being sent by the Transmission ECM to each individual modulating valve. The different maximum signal causes a difference in the force pushing the pin against the ball to block leakage through the drain orifice in each solenoid valve. The different rate of leakage through the spool drain orifice provides different balance positions for the proportional solenoid valve spool. Changing the valve spool position changes the flow of oil to the clutch and the resulting maximum clutch pressure. The operation of the proportional solenoid to control the engaging and releasing of clutches is not a simple on and off cycle. The Transmission ECM varies the strength of the current signal through a programmed cycle to control movement of the valve spool. The clutch pressures can be changed using Caterpillar Electronic Technician (ET) and the 4C-8195 Service Tool during the calibration procedure. The actual Transmission ECM current cycle and transmission calibration will be discussed later in this presentation.

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Text Reference

63

1

64

2 3 4 5

7

6

Transmission Modulating Valve - Solenoids This illustration shows a view of the transmission modulating valves. The six modulating valves on the top of the transmission are located over the respective clutch. The solenoid valves provide electronically controlled pressure modulation. The transmission shifting function is controlled by the Power Train Electronic Control Module (ECM). The Power Train ECM and the transmission modulating valves provide modulation to each individual clutch. Also shown is the transmission main relief valve (7).

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Text Reference

The main Power Train ECM output is the pulse width modulated current signal that is sent to the six transmission modulating valves. The Power Train ECM analyzes the input signals and memory information and activates current drivers within the ECM. Then, the current drivers send electrical pulse width current to energize the modulating valves that are located on the transmission clutch housing. The varying signal strength sent to each proportional solenoid valve by the Transmission ECM controls the rate of oil flow and the rate of pressure modulation of each clutch. In turn, the solenoid provides electronically controlled clutch filling and pressure modulation. The following Tables show which solenoid is energized for the desired speed and direction: Forward First speed Forward Solenoid

2 and 6

Second speed Forward Solenoid

2 and 5

Third speed Forward Solenoid

2 and 4

Fourth speed Forward Solenoid

2 and 3

Reverse First speed Reverse Solenoid

1 and 6

Second speed Reverse Solenoid

1 and 5

Third speed Reverse Solenoid

1 and 4

Fourth speed Reverse Solenoid

1 and 3

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Text Reference

1

2

65

Transmission Relief Valve Shown is the transmission hydraulic main relief valve (1) which is located on the left side of the machine on the torque converter housing (2). The transmission main relief valve operates as both a pressure relief valve and a priority flow control valve. The main relief valve regulates the supply oil pressure to the six transmission proportional solenoid valves by limiting the supply oil pressure to 2785 ± 70 kPa (404 ± 20 psi) at high idle. The main relief valve also insures the solenoid valves have an adequate oil supply before the torque converter and oil coolers receive oil flow. The torque converter inlet relief valve is located behind the transmission main relief valve. The relief valve must be removed to gain access to the torque converter inlet relief valve. The torque converter inlet relief valve limits torque converter inlet oil pressure to a maximum of 900 ± 70 kPa (130 ± 10 psi).

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Text Reference

TORQUE CONVERTER Turbine

Impeller

Rotating Housing Freewheel Stator

Outlet Output Shaft

Carrier Inlet Flywheel Splines

66

This illustration shows the major components of the torque converter. The rotating housing is shown in red. The rotating housing has a direct mechanical connection to the engine flywheel. The turbine and the output shaft are shown in blue, and are mechanically connected. The free wheel stator and the carrier are shown in green. The impeller is shown in pink. The bearings are shown in yellow. The impeller is bolted to the rotating housing and rotates at engine speed. Charge oil from the torque converter inlet relief valve enters the inlet passage in the carrier and fills the torque converter. The torque converter outlet relief, which is connected to the outlet passage, maintains the minimum pressure in the torque converter. As the impeller rotates, it directs oil against the turbine blades, causing the turbine to rotate. Turbine rotation causes the output shaft to rotate. During NO LOAD conditions, the output shaft rotates at nearly the same speed as the engine flywheel. As load is applied, the output shaft slows down. A decrease in output shaft speed causes the rpm of the turbine to decrease. As the output shaft speed is decreased, the output torque from the torque converter increases. When the output shaft is stalled, the torque converter is applying maximum torque to the output shaft.

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Text Reference

The torque converter is equipped with a freewheel stator. The stator, which is mounted to the torque converter outer housing is stationery. When a load is applied, the output shaft slows down. When the turbine is rotating slower than the impeller, the stator redirects the oil from the turbine, and increases the pressure on the turbine. The increase in pressure on the turbine tends to increase the torque output from the torque converter. When the output shaft is turning at near the same speed as the impeller, the stator will freewheel backwards to reduce the drag and turbulence inside the torque converter. The stator freewheels in light load applications and multiplies torque in heavy load applications.

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Text Reference

1 3 2

67

Shown in the illustration above, is the torque converter outlet relief valve (1) located on the right side of the transmission and below the torque converter housing (2). The torque converter outlet relief valve controls the pressure inside the torque converter by maintaining a minimum pressure of 550 ± 135 kPa (80 ± 20 psi) at torque converter stall rpm. Also shown is the transmission oil temperature sensor (3).

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2

Text Reference

3

1

68

This illustration shows the service center on the right side of the machine below the platform. Located in the lower half of the service center is the transmission oil filter (1), the power train fluid sampling port (2) , and the transmission oil filter bypass switch (3). The transmission oil filter bypass switch reports to the Caterpillar Monitoring System sending a warning when the transmission oil filter requires service.

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Text Reference

69

This illustration shows the message center (arrow) for the Caterpillar Monitoring System. When the Caterpillar Monitoring System is in the Service Mode (Mode 3), the Message Center shows the fault codes. The fault codes consist of the Module Identifier (MID) followed by the Component Identifier (CID) and Failure Mode Identifier (FMI). The MID tells which electronic control module diagnosed the fault. An MID of 081 means the fault was diagnosed in the Power Train ECM. MID's are listed on the machine electrical schematic in the Service Manual. The CID tells which component is faulty. For example, CID 623 means the fault was diagnosed in the transmission directional switch. The FMI tells the type of failure. For example, an FMI of 05 means the failure is an open circuit or current value is below normal.

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Text Reference

70

VARIABLE SHIFT CONTROL CIRCUIT Power Train ECM Ground

J1-32

Variable Shift Control (E conomy)

J2-32

Variable Shift Control (M id)

J2-33

Variable Shift Control (P ower)

J2-34

BK 18 GN 18 BU 18 BR 18

1 2 3 4

BK 16 BK 16 BK 16 BK 16

71 Variable Shift Control Switch

Variable Shift Control The 966H and the 972H Wheel Loaders feature Variable Shift Control on electrohydraulic machines. Variable Shift Control allows the transmission to shift at lower engine speeds. The variable shift control switch (arrow) is a three-position switch (POWER, MID, ECONOMY) that will change the shift points stored in the Power Train ECM. When the switch is rotated to the ECONOMY position (clockwise), the switch sends a signal to the Power Train ECM to shift the transmission at a lower engine rpm for increased fuel economy. When the switch is rotated to the POWER position (counterclockwise), the transmission shifts when the engine reaches 2100 rpm.

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Text Reference

1

2

72

Integrated Brake System The 966H and the 972H Wheel Loaders are equipped with the Integrated Brake System (IBS). This system allows the operator to downshift the transmission and neutralize the transmission using the left brake pedal. The left service brake pedal (1) is attached to a PWM rotary position sensor (2) and a mechanical linkage (not shown). The position sensor continuously monitors the left brake pedal position. The position sensor sends an input signal to the Power Train ECM indicating left brake pedal position. The mechanical linkage is connected to the brake control valve (not shown) located below the cab. The right service brake pedal (not shown) is also connected to the brake control valve independent of the left brake pedal. NOTE: The amount of brake pedal travel can be displayed on the ET Service Tool screen or the Caterpillar Monitoring System main display module. Pedal travel is displayed as a percentage (%) in ET and by counts (ct.) on the Caterpillar Monitoring System. Three percent of brake pedal travel is about 2 ct. or 1°, and 100 percent of pedal travel is about 66 counts or 33°.

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Text Reference

LEFT BRAKE PEDAL POSITIONS

Deadband Calibrated Initial Brake Pressure Point Initial Mode

Calibrated Neutralization Set Point Maximum Pedal Travel

Normal Mode

Left Brake Position Sensor

Brake Lamp Switch

73

Left Brake Pedal Actions This view shows the actions that occur as the brake pedal is depressed. In approximately the first nine percent of brake pedal travel (dead band), no braking or downshift occurs. Brake pedal travel between the pedal dead band and the calibrated initial brake pressure point is the initial Mode. In the Initial Mode, the transmission downshifts, but the service brakes are not engaged and the transmission is not neutralized. In the Normal Mode, the left brake pedal is further depressed between the calibrated initial brake pressure point and the maximum pedal travel. In the Normal Mode, the transmission downshifts and the service brakes are engaged. When the left pedal is depressed in Initial and Normal Modes, and if the transmission is in third or fourth gear, the transmission will downshift one gear at a time until second gear is reached. Each downshift will occur when the transmission output speed decreases to the shift point of the current transmission speed.

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Text Reference

In the Normal Mode, when the brake pedal reaches the neutralization set point and the transmission neutralizer override switch is in the OFF position, the Transmission ECM will DE-ENERGIZE the direction clutch solenoid to neutralize the transmission when the following conditions exist: - The auto/manual selector switch is NOT in the 1-4 position - The transmission is in 2nd gear - The ground speed is 6.5 mph or - The auto/manual selector switch is in the 1-4 position - The transmission is in 1st gear - The ground speed is 4.5 mph If the left brake pedal is raised 4° above the Neutralization Set Point, a signal is sent to the modulating valve to engage the direction clutch. At this time, the drive train will be re-engaged. Normally, the travel of the left brake pedal will overshoot the Neutralization Set Point. Each time the brake travel overshoots the Neutralization Set point without being released into the dead band zone, the New Neutralization point moves down the point of the overshoot. The Power Train ECM will retain the New Neutralization Point until the left brake pedal is released and the pedal is into the dead band zone. In normal conditions, the best gear for loading trucks is 2nd, or "Second Auto." The operator pushes the bucket into the pile, and then manually shifts the transmission down to Forward 1. When the bucket is full, the operator changes the direction of the machine to Reverse. In Second Auto, the transmission automatically reverses in Reverse 2, instead of Reverse 1. The auto/manual selector switch sets parameters in the ECM that influence the Integrated Brake System. On machines equipped with the optional Command Control Steering (CCS), the switch has 5 positions: 1-4, 2, 3, 4, and MANUAL. The switch position for the smoothest neutralization during truck loading in normal applications is 2. Smoothest means high engine speed with the following limitations: unacceptable jerkiness during slowdown, unacceptable engine overspeed during slowdown, and unacceptable transmission overspeed during slowdown. On machines equipped with the standard Hand Metering Unit HMU steering, the auto/manual selector switch has 3 positions: 1-4, 2-4, and MANUAL. With the speed selector on the steering column in the 2 position, the ideal auto/manual selector switch position for the smoothest neutralization during truck loading in normal applications is 2-4.

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Text Reference

966H-972H SPEED LIMITER ATTACHMENT Transmission ECM

Engine ECM Cat Data Link

Crankshaft Speed / T iming Sensor

Camshaft Speed / Timing Sensor

74

Speed Limiter The Speed Limiter feature limits machine ground speed to 20 km/h (12 mph) on 966H-972H Wheel Loaders. The speed limiter software in the Power Train ECM monitors the machine engine speed, the ground speed, and the acceleration. The Power Train ECM receives the engine speed signal from the crankshaft speed/timing sensor and the camshaft speed/timing sensor. The Power Train ECM calculates machine acceleration from the speed sensor data. The Power Train ECM processes the input signals and sends a requested engine speed signal to the Engine ECM via the Cat Data Link, which controls the engine speed. NOTE: The speed limiter attachment is installed and uninstalled through Cat ET. In order to install or uninstall the attachment, a factory password is required.

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Text Reference

IMPLEMENT SYSTEM COMPONENTS Implement ECM Hydraulic Tank

Implement Control Levers

Lift Position Sensor Tilt Cylinder Lift Cylinder Tilt Position Sensor

Electrical Components

Implement Pump

Hydraulic System Components

3PC Electrohydraulic Valve Ride Control Accumulator

75

IMPLEMENT ELECTROHYDRAULIC SYSTEM The "H" Series Medium Wheel Loader is equipped with a Proportional Priority, Pressure Compensated (3PC) implement electrohydraulic system. The 3PC electrohydraulic system will sense a demand for a flow change and the implement pump will upstroke or destroke in order to provide the demanded flow. The following components make up the 3PC electrohydraulic system: - Implement Electronic Control Module (ECM) - Lift and tilt position sensor - Implement pump - 3PC electrohydraulic control valve - Lift and tilt cylinders - Ride control accumulator (optional) - Implement control levers - Hydraulic tank (hydraulic tank is common to all the hydraulic systems)

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IMPLEMENT ELECTRONIC CONTROL SYSTEM CAT Data Link

Implement ECM


Output Components

Input Components Engine Start Switch

Hydraulic Lockout Valve

Tilt Lever Sensor

Tilt Back Solenoid Valve

Lift Lever Sensor Dump Solenoid Valve

Auxiliary Lever Sensor

Lower Solenoid Valve Hydraulic Lockout Switch Raise Solenoid Valve

Kickout Set Switch Lift / Tilt

Auxiliary Function HE Solenoid Valve

Fine Modulation Switch Auxiliary Function RE Solenoid Valve Lift Linkage Position Sensor

Lower Antidrift Solenoid Valve

Tilt Linkage Position Sensor

Dump Antidrift Solenoid Valve

Lift Head End Pressure Sensor

Autodig Audible Indicator Autodig Operator Trigger Indicator

Autodig Dig Mode Switch

Autodig Record Mode Indicator

Autodig Trigger Switch

Fuel Pressure Indicator Autodig Select Mode Switch

Location Code 4 (Ground) Location Code Enabled (Ground)

Autodig Kickout Set Switch Auxiliary Continuous Flow Switch + 24 Voltage

76

Implement Electronic Control System This diagram of the Implement Electronic Control System shows the components which provide input and output signals to the Implement ECM. The Implement (ECM) receives input signals from the various sensors and switches on the machine, processes the input signals, makes decisions, and provides a corresponding signal voltage to the proportional solenoid valves. The Implement ECM stores information from the calibrations, the machine settings and the operational functions. The Implement ECM monitors diagnostic conditions and reports events to the Cat Monitoring System or to Cat Electronic Technician (ET). Also, the Implement ECM provides a means of calibrating the electrohydraulic components for optimal operation. The Implement ECM shares operational data with the other ECMs and the Cat Monitoring System through the Cat Data Link.

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Text Reference

The input components to the Implement ECM are: Engine start switch: Input to the Implement ECM signaling the ECM to power ON. 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. Tilt linkage position sensor: Sends a PWM signal to the Implement ECM communicating the position of the tilt linkage in relation to the lift linkage. Lift lever position sensor: Sends a PWM signal to the Implement ECM communicating the angle of the lift lever position sensor away from the calibrated HOLD position. Tilt lever position sensor: Sends a PWM signal to the Implement ECM communicating the angle of the tilt lever position sensor away from the calibrated HOLD position. Auxiliary lever position sensor: Sends a PWM signal to the Implement ECM communicating the angle of the auxiliary function lever position sensor away from the calibrated HOLD position. Kickout set switch lift/tilt: Sends an input to the Implement ECM to recognize the desired raise/lower/tilt back kickout position. Autodig trigger switch: Sends an input signal to the Implement ECM when the operator has pressed the switch to indicate that the loading cycle should begin. Autodig select mode switch: Sends an input signal to the Implement ECM to signal if autodig should be off or in which mode it should operate (auto, operator trigger or record). Autodig dig mode switch: Sends an input signal to the Implement ECM to recognize what type of operation is currently desired due to the type of material that is being handled. Autodig kickout set switch: Sends an input signal to the Implement ECM to set the current position of the lift arms to be the position where autodig stops after a completed autodig cycle. Lift head end pressure sensor: Measures the pressure of the head end of the lift cylinder to determine operation of autodig. Fine modulation switch: Sends an input signal to the Implement ECM to reduce the amount of current to the raise solenoid valve. Hydraulic lockout switch: Sends an input signal to the Implement ECM to not energize the pilot solenoid valve to protect from inadvertent movement of the lift arms. Auxiliary continuous flow switch: Sends an input signal to the Implement ECM keep the auxiliary function output to the solenoid valve at the current that was being commanded at the time of the switch being depressed. This mode can be exited by depressing the switch again or moving the auxiliary lever.

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+24 Volts: Unswitched power supplied to the Implement ECM from the battery. Location code enable (grounded): The location code enable is a grounded input signal to the Implement ECM that enables the location code detection feature to become active. J1-32 pin on the Implement ECM connector is connected. Location code 4 (grounded): The location code 4 is a grounded input signal that establishes that the ECM is dedicated to the Implement operation. J1-28 pin on the implement ECM connector is connected. The output components which receive signals from the Implement ECM are: Hydraulic lockout valve: This ON/OFF solenoid valve is an output from the Implement ECM. This valve opens the flow of pilot oil to the pilot valves. Raise solenoid valve: This proportional solenoid valve is an output from the Implement ECM. This solenoid valve sends a proportional amount of pilot oil to the raise end of the lift spool depending on the amount of current applied to the solenoid. Lower solenoid valve: This proportional solenoid valve is an output from the Implement ECM. This solenoid valve sends a proportional amount of pilot oil to the lower end of the lift spool depending on the amount of current applied to the solenoid. Dump solenoid valve: This proportional solenoid valve is an output from the Implement ECM. This solenoid valve sends a proportional amount of pilot oil to the dump end of the tilt spool depending on the amount of current applied to the solenoid. Tilt back solenoid valve: This proportional solenoid valve is an output from the Implement ECM. This solenoid valve sends a proportional amount of pilot oil to the tilt back end of the tilt spool depending on the amount of current applied to the solenoid. Auxiliary HE solenoid valve: This proportional solenoid valve is an output from the Implement ECM. This solenoid valve sends a proportional amount of pilot oil to the head end of the auxiliary spool depending on the amount of current applied to the solenoid. Auxiliary RE solenoid valve: This proportional solenoid valve is an output from the Implement ECM. This solenoid valve sends a proportional amount of pilot oil to the rod end of the auxiliary spool depending on the amount of current applied to the solenoid. Lower antidrift solenoid valve: This ON/OFF solenoid valve is a current output from the Implement ECM. The solenoid valve drains oil from the antidrift valve allowing the poppet to unseat and lift cylinder head end oil to flow through the valve.

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Dump antidrift solenoid valve: This ON/OFF solenoid valve is a current output from the Implement ECM. The solenoid valve drains oil from the antidrift valve allowing the poppet to unseat and tilt cylinder head end oil to flow through the valve. Autodig operator trigger mode indicator: This indicator is illuminated when the Implement ECM recognizes that autodig operator trigger mode is activated. Autodig record mode indicator: This indicator is illuminated when the Implement ECM recognizes that autodig record mode is activated. Autodig audible indicator: This audible indicator beeps when the Implement ECM recognizes that a different autodig mode has been activated and to confirm a setting or to warn about failed autodig operations. Low fuel pressure indicator: This indicator is illuminated when the fuel pressure is reported low from the Engine ECM over CAT datalink. The illumination of indicator is driven by the Implement ECM.

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Text Reference

77

The Implement Electronic Control Module (ECM) is the central component in the transmission electronic control system. The ECM is located at the right side of the cab behind the seat. The rear panel must be removed for access to the ECM. The Implement ECM will be located behind the operator’s seat and have the connectors vertical to each other. The ECM makes decisions based on switch-type and sensor input signals and memory information. Input signals to the ECM come from: the operator's station, the machine, and the transmission. The operator's station input components consist of: the lift/tilt kickout switches, the fine modulation switch, the hydraulic lockout switch to energize the hydraulic lockout valve, and the autodig feature switches. The machine input components are: the linkage position sensor, the lever position sensors, and the Caterpillar Monitoring System message center module. The Implement ECM communicates with other electronic control modules, such as the Caterpillar Monitoring System, the Engine Electronic Control Module (ECM) and the Power Train Electronic Control Module (ECM), through the Cat Data Link. The implement system uses the A4M1 Electronic Control Module (ECM). To enable the ECM for implement functions, contact (J1-28) is grounded and contact (J1-32) is grounded in order to enable the ECM.

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The Implement ECM responds to machine control decisions by sending a signal to the appropriate circuit which initiates an action. For example, the operator selects to set the lift kickout. The Implement ECM interprets the input signals from the switch, evaluates the current machine operating status, and de-energizes the appropriate solenoid valve when the preset duty cycle of the linkage position sensor is met. The Implement ECM receives three different types of input signals: 1. Switch input: Provides the signal line to battery, to ground, or to 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. 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 lift, tilt, and the auxiliary solenoid valves in the main control valve. The Implement ECM interprets signals from the implement control lever to send current to the appropriate solenoid valves in order to perform one or more of the following options: Lift, Lower, Tilt Back, and Dump. Also, the Implement ECM triggers the Autodig operator trigger indicator, the Autodig record mode indicator, and the fuel pressure indicator. 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 power train system, it logs the faults in memory and displays them on the Caterpillar Monitoring System. NOTE: The side panel on the right side of the cab is transparent for viewing purposes.

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1

78

2

79

3

The upper illustration shows the lift linkage position sensor (1). The lift linkage position sensor is located on the right side of the loader frame. The lower illustration shows the location of the tilt linkage position sensor (2). The lift linkage position sensor is located on the right side of the lift linkage. The tilt linkage position sensor shaft is attached to the tilt lever pin (3) reflecting the rotation of the lift lever compared to the lift linkage. NOTE: In order to calibrate the lift or tilt linkage position sensors, refer to the Service Manual module "966H and 972H Wheel Loaders Electrohydraulic System, Troubleshooting, Testing and Adjusting - Position Sensor for the Lift and Tilt Linkage (Electronic Technician) - Calibrate or Position Sensor for the Lift and Tilt Linkage (Operator Monitor) - Calibrate" (Form RENR 8858).

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3 2 1

80

Implement Control Levers The tilt control lever (1), the lift control lever (2), and the auxiliary control lever (3) send a Pulse Width Modulated (PWM) signal with the position of the control lever sensor to the Implement ECM. In the HOLD position, the sensor in each lever sends a 50% duty cycle. The movement of each lever in the forward or reverse direction will increase the duty cycle to 90% or decrease to 10% depending on the direction that the lever is moved. The "H" Series machines are a self-contained single axis lever equipped with a single sensor and no mechanical or electrical detents. The sensor frequency is 500 Hz. The self contained single axis lever is equipped with "Soft Detents." With "Soft Detents" the control levers are no longer held in place mechanically. The detents are software controlled within the Implement ECM. When the control lever is moved in either direction into an area of movement with a slight resistance and the lever is released within 1 second, the actuator will continue to move until the software controlled kickout is reached. During troubleshooting of a control lever or joystick, always move the control lever both fast and slow through lever movement. The duty cycle for the control lever can be viewed through Cat ET.

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1

Text Reference

2

81

The two switches located to the right of the operator’s seat control functions of the implement hydraulic system. The hydraulic lockout switch (1) sends an input to the Implement ECM to shift the hydraulic lockout solenoid valve to the OPEN position. The fine modulation switch (2) is an input to the Implement ECM. The fine modulation switch allows the operator to request a lower ramp up current relative to the standard lever curves during control lever movement. In the final one third of the control lever travel, the commanded current is the same as the standard control lever curve.

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Text Reference

LIFT LINKAGE MODULATION

Lift Command

100%

-100%

-50%

-10 0 10

50%

100%

-100%

Percentage of Lift Lever Position Fine Modulation

Normal Modulation

TILT LINKAGE MODULATION

Tilt Command

100%

-100%

-50%

-10

0 10

50%

100%

-100%

Percentage of Lift Lever Position Normal Modulation

Fine Modulation

82

Fine Modulation Fine Modulation allows the operator to reduce the lever sensitivity for better control of the linkage during small movements. The Fine Modulation feature in the "H" Series Wheel Loaders is no longer adjustable as in the "G" Series Wheel Loader. In the illustration, the vertical coordinates (lift command and tilt command) in each graph show the percentage from minimum to the maximum modulation current directed to the modulating valve on the main control valve. The fine modulation feature can be turned ON and OFF using the fine modulation switch located on the right side of the armrest.

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1

83

The kickout set switch (1) is an input to the Implement ECM. The kickout set switch is a momentary three-position rocker switch located on the operator panel. The kickout set switch is used to set the kickout positions for the raise and lower kickout. When the switch is pushed, the Implement ECM records the current position of the lift arm. The Implement ECM uses the recorded position for the raise kickout position or the lower kickout position. If the upper position of the kickout set switch is depressed and the lift arm is above midway, the kickout will be set for raising the lift arm. If the upper position of the kickout set switch is depressed and the lift arm is midway below halfway, the lower kickout will be set. If the lower position of the kickout set switch is depressed, the rotation of the tilt back will be set.

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1

2

3

4 5 6 7

84 Autodig Control Arrangement Autodig automatically controls the bucket loading cycles. At the same time Autodig limits the tire slippage by keeping the front tires loaded. The three modes that Autodig can operate in are: Automatic Pile Detection Mode, Operator Triggered Mode, and Record Mode. The Autodig select mode switch (2) activates Autodig when the top of the switch is pressed and deactivates Autodig when the bottom of the switch is pressed. When Autodig is ON, the spring-loaded switch is held in the center position. Pressing the top of the switch will allow the operator to toggle between the three operating modes. Autodig is disabled by default when the key start switch is turned ON. The automatic pile detection mode indicator (5), operator triggered mode indicator (6), and the record mode indicator (7) flash ON and OFF to indicate the mode that is currently active.

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The Autodig horn also indicates which mode is active by: - beeping once in the automatic pile detection mode; - beeping twice in the operator triggered mode; and - beeping three times in the record mode. The Autodig horn also sounds to indicate when Autodig begins and ends a bucket loading cycle. The Autodig kickout position set switch (3) is used to set the lift cylinder kickout position when Autodig is activated. The Autodig dig mode switch (1) is a 10 position rotary switch which provides a range of dig modes from the lightest material in position 1, to heavier or larger material in position 9. Position 10 on the Autodig dig mode switch is used for the record/playback position. By default, position 10 is identical to position 9 until the operator has recorded a bucket loading cycle. Autodig will downshift the transmission to an appropriate gear for loading, based on the position of the autodig material selector switch. In positions 1 or 2 (light material), the transmission will downshift only to 2nd gear. The machine will load in 1st gear if already in that gear when bucket loading starts. Regardless of the position of the autoshift selector switch if the machine is in 2nd or 3rd gear, with the Autodig material selector switch in positions 3 through 9, the transmission will automatically downshift to 1st gear upon pile entry. Automatic pile detection mode automatically controls bucket loading. When loading is complete, the bucket and linkage return to the Autodig kickout position. The operator triggered mode is used if the operator wants to control the loading cycle. In the operator triggered mode, Autodig is activated when the operator presses the trigger switch (4) to indicate when the pile has been contacted. After the trigger switch is pressed, the system automatically loads the bucket and returns the bucket and linkage to the Autodig kickout position. Record mode allows the operator to record the bucket loading cycle and replay the cycle if the preprogrammed modes are not acceptable. Autodig records all lever movements while loading the bucket. The lever movements are stored in the record/playback position of the Autodig selector switch.

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AUTODIG OPERATING REQUIREMENTS

Autodig ON

Lift linkage near ground

Bucket angle near level

Machine speed > 0.7 kph and < 12.3 kph

1st, 2nd or 3rd gear forward

No direction changes in last 2 seconds

No gear changes in last 0.5 second

Neutralizer not active

Left and tilt levers centered 85

The following conditions are required to properly load the bucket with Autodig: - Autodig is ON - Lift linkage is less than 2 feet off the ground - Bucket angle is less than 10 degrees from level - Machine speed is greater than 0.7 kph and less than 12.3 kph - Transmission is in 1st, 2nd, or 3rd gear FORWARD - No directional changes in last 2.0 seconds - No gear changes in last 0.5 second - Neutralizer is not active, and has not been active for the last 0.5 second - Lift and tilt levers are centered

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86

The left side of the front dash panel shows the low fuel pressure condition. The illuminated indicator is enabled by an output from the Engine ECM over the Cat Data Link, driven by the Implement ECM.

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"H" SERIES MEDIUM WHEEL LOADER IMPLEMENT HYDRAULIC SYSTEM HOLD

Inlet Manifold

Ride Control Accumulator

Tilt Cylinder Lift Cylinders

Cover Manifold

Head End Solenoid valve

Tilt Antidrift Valve

Manual Lower Valve

Auxiliary Function

Line Relief Valves

Hydraulic Lockout Valve

Lift Ant idrift Valve Rod End Solenoid Valve

Raise Pilot Solenoid Valve

Tilt Back Pilot Solenoid Valve Lift Spool

Pressure Compensat or Valve

Ride Control Relief Valve Auxiliary Spool

Tilt Spool Balance Valve

Pressure Compensator Valve Screen Resolver Valve

Resolver Valve

Signal Duplication Valve

Resolver Valve

Check Valve

Pressure Compensator Valve

Pilot Pressure Reducing Valve

Steering Pilot Supply (CCS Only)

Signal Relief Valve

Lower / Float Pilot Solenoid Valve

Dump Pilot Solenoid Valve

Case Drain Filter

Pilot Accumulator

Auxiliary Head End Solenoid Valve

Choke Check Valve

Min Angle

Ride Control Auxiliary Rod End Solenoid Valve

Margin Relief Valve

Pump and Pump Cont rol Valve

Tank

87

Implement Hydraulic System - HOLD The "H" series Medium Wheel Loaders are now equipped with a Proportional Priority, Pressure Compensated (3PC) implement hydraulic system. The 3PC hydraulic system is load sensing with a signal duplication valve, a signal relief valve, pressure compensator valves, a pressure differential relief valve, a pressure reducing valve, and a resolver network. Also, the 3PC valve has antidrift solenoid valves for the lift and tilt functions. The implement control valve is a closed-center valve. The 3PC hydraulic system will sense a demand for a change in flow and the implement pump will upstroke or destroke to provide the flow. The machine may also be equipped with an optional auxiliary function. The auxiliary section is installed between the ride control valve and the cover manifold.

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Text Reference

When the engine is started and the implement control levers are in the HOLD position, the implement pump supplies standby oil flow to the 3PC valve group. The oil flows into the inlet manifold and is divided into two paths. The supply path for the implements flows through the inlet manifold into the tilt section where the flow path is divided again. One path flows to the tilt spool and is blocked. The second path flows to the lift control section, to the ride control section, to the optional auxiliary section, and to the cover manifold. Within the cover manifold, the oil flows to both the pilot pressure reducing valve (PRV) and the differential pressure relief valve. The differential pressure relief valve maintains a difference between the load sensing pressure and the pump supply oil pressure of 3000 kPa (435 psi). When all of the control valves are in the HOLD position, the implement pump is at low pressure standby. The differential pressure relief valve maintains the minimum pressure for low pressure standby. The standby pressure is directed to the pilot pressure reducing valve (PRV). The pilot pressure reducing valve provides a regulated pilot oil pressure to activate the control valves as needed. The pilot oil flows from the PRV through the check valve to the pilot accumulator and the hydraulic lockout solenoid valve. If the wheel loader is equipped with the optional Command Control Steering (CCS), the oil flow will be shared by the implement pilot system and the steering pilot system. The hydraulic lockout solenoid valve is in the CLOSED position until the hydraulic lockout switch in the cab is activated. When the solenoid valve is energized, the solenoid valve opens and pilot oil flows to the various implement function solenoid valves. The second path of oil in the inlet manifold flows through the screen to the signal duplication valve. The signal duplication valve uses highest work port pressure in the resolver network to supply an identical pressure to the pump control valve. When all implement control valves are in the HOLD position, there is no load sensing signal in the resolver network. With no load sensing pressure present, the implement pump supplies low pressure standby.

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Text Reference

"H" SERIES MEDIUM WHEEL LOADER TILT CONTROL VALVE HOLD To Signal Duplication Valve From Signal Duplication Valve

From Resolver Valves

To / From Head End of Cylinder

To / From Rod End of Cylinder Pressure Compensat or Valve


Bridge Passage Line Relief and Makeup Valve

Line Relief and Makeup Valve

Internal Passage Control Spool

Feeder Passage

Rackback Pilot Solenoid Valve


Supply Passage

88

Tilt Control Valve - HOLD With the tilt control valve in the HOLD position, the springs on each end of the control spool keep the spool centered. The control spool blocks the flow of pump supply oil to the pressure compensator valve. The bridge passage is open to tank through the internal passage in the control spool and there is no oil flow to the resolver valve. With no oil flow to the resolver network, there is no signal to the signal duplication valve and the signal pressure to the pump control valve is matching the oil pressure in the resolver network. The implement pump is at low pressure standby.

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"H" SERIES MEDIUM WHEEL LOADER TILT CONTROL VALVE DUMP To Signal Duplication Valve From Signal Duplication Valve

From Resolver Network

From Head End of Cylinder

To Rod End of Cylinder


Pressure Compensat or Valve Bridge Passage




Feeder Passage

Tilt Back Pilot Solenoid Valve


Supply Passage

89

Implement Hydraulic System - DUMP When the tilt lever is moved to the DUMP position, the Implement ECM energizes the dump proportional solenoid and the tilt antidrift valve. As the control valve initially shifts to the left, and there is pressure in the rod end of the tilt cylinder, the pressure goes around the control spool to the bridge passage. The pressure in the bridge passage goes to the resolver network and to the signal duplication valve to upstroke the implement pump. The pressure also goes to the spring chamber in the center of the pressure compensator valve. The lower half of the pressure compensator valve shifts down to block the oil flow from the bridge passage to the feeder passage. As the tilt control spool continues shifting to the left, pump supply oil flows around the center land on the control spool to the feeder passage. Oil pressure in the feeder passage lifts the pressure compensator valve up. Pump supply oil goes through the orifices in the lower end of the compensator valve to the bridge passage. From the bridge passage, the pump flow goes around the control spool into the work port to the rod end of the tilt cylinder. Returning oil from the head end of the tilt cylinder, flows around the tilt antidrift valve to the tank port.

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Text Reference

PRESSURE COMPENSATOR AND LOAD CHECK VALVE HOLD To Signal Duplication Valve From Signal Duplication Valve




Load Check Spool Pressure Compensator Valve


Bridge Passage Line Relief and Makeup Valve


Internal Passage

Feeder Passage

Control Spool



Supply Passage

90

Pressure Compensator Valve - HOLD When the control spool is in the HOLD position, the load check spool and the pressure compensator valve are held down by the spring force on top of the load sense spool. Pump supply oil in the supply passage is blocked by the control spool. No supply oil from the supply passage flows to the feeder passage. Therefore, no load sensing pressure is directed to the implement pump control valve. The implement pump is at low pressure standby.

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Text Reference

PRESSURE COMPENSATOR AND LOAD CHECK VALVE LOAD CHECK OPERATION To Signal Duplication Valve From Signal Duplication Valve





Load Check Spool

Pressure Compensator Valve Bridge Passage




Feeder Passage



Supply Passage

91

Load Check Operation This illustration shows the pressure compensator and load check valve in the load check operation. When the control spool is initially shifted to the left, work port pressure from the rod end of the cylinder (if any) flows around the right end of the control spool into the bridge passage. The pressure goes through the holes between the pressure compensator valve and the load check spool. The pressure moves the pressure compensator spool down and the load check spool up. With the pressure compensator valve shifted down, no pressure can go from the bridge passage to the feeder passage. The pressure compensator valve serves as a load check valve to hold the load up to prevent it from dropping. The pressure in the bridge passage is directed through the resolver network to the signal duplication valve. The signal duplication valve generates a load sensing signal pressure equal to the work port pressure. The load sensing signal pressure is directed to the top of the spring chamber on top of the load sense spool. The load sensing signal pressure is also directed to the pump control valve to upstroke the pump (not shown).

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Text Reference

PRESSURE COMPENSATOR AND LOAD CHECK VALVE PRESSURE COMPENSATOR OPERATION From Signal Duplication Valve

To Signal Duplication Valve From Resolver Network



Tilt Anti-drift Valve

Load Check Spool Pressure Compensator Valve Orifices Bridge Passage




Feeder Passage



Supply Passage

92

Pressure Compensator Operation When the control spool is shifted farther to the left, the pump supply oil in the supply passage is directed around the center land of the control spool to the feeder passage. When pressure in the feeder passage increases to more than the pressure on top of the load sense spool plus the spring force, the pressure compensator valve and the load sense spool shift up. Pump flow in the feeder passage goes through the orifices in the bottom of the pressure compensator valve to the bridge passage. From the bridge passage, the flow goes around the control spool to the passage to the rod end of the cylinder. The tilt antidrift valve is activated allowing flow from the head end of the cylinder to be directed around the left end of the control spool to the tank return passage. During a stall condition, the signal limiter valve in the load sensing signal valve and the margin spool maintains pump discharge pressure approximately 2100 kPa (300 psi) higher than the work port pressure. The pressure compensator valve can direct full pump flow to the bridge passage if demand for flow is great enough.

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Text Reference

PROPORTIONAL PRIORITY, PRESSURE COMPENSATOR OPERATION From Signal Duplication Valve Signal

To Pump and Signal Limiter To Signal Duplication Valve

Resolver Valve

Resolver Valve

Valve A

Bridged Passage

Pump Supply

HOLD

Pressure Differential Relief Valve

Valve B

Spool Bridged Passage Feeder Passage

Pump Supply

Valve C

Feeder Passage

LOW PRESSURE

Spool Bridged Passage

Spool Pump Supply

Feeder Passage

HIGH PRESSURE

93

Three compensators are shown in various states in this illustration. The pressure compensator valve for valve "A" is in HOLD. The circuit with the highest workport pressure keeps the resolver valve closed. The circuit with the highest work port pressure regulates the oil flow through all activated control valves. The highest work port pressure is directed through the ball resolver network to the pump control valve as the load sensing pressure. When a high pressure circuit is activated as shown for valve "C", the control spool is shifted and pump supply oil enters the feeder passage below the pressure compensator valve. Pressure increases and the pressure compensator valve moves up. When the valve moves up, supply oil enters the bridged passage of the control valve. Supply oil in the bridged passage enters the signal network sending the work port pressure to the signal duplication valve.

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Text Reference

The work port oil pressure goes to the signal duplication valve. The signal duplication valve is a shock absorber. The valve uses the work port pressure signal and the pump system pressure signal to generate a stabilized load sensing signal which is sent to the pump control valve. The pump control valve directs a pressure signal to the actuator piston to UPSTROKE the pump. The increased flow lifts the pressure compensator spool up. The flow goes through the bridge passage, around the control spool, and out to the work port. The signal oil also flows to the chamber above the compensator. The signal oil on the top of the pressure compensator valve works against the forces working below the pressure compensator. When the forces are in balance, the supply oil is metered through the crossdrilled holes in the pressure compensator to provide work port oil. The pressure of the signal oil is limited by the signal relief valve. When more than one circuit is activated at the same time, the highest work port pressure is directed to the signal duplication valve. The signal duplication valve sends the signal oil to the chamber at the top of all pressure compensators valves. With the same circuit pressure working on all pressure compensators, the pressure differential across all shifted control stems is the same, as shown in the illustration for the pressure compensator for valve "C" and for valve "B." The pressure differential across the control stems will be the same value whether the pump can supply the flow demand for all activated circuits or not. For example, if the margin pressure is 2100 kPa (300 psi) the pressure differential between the pump supply passage and the feeder passage is approximately 2100 kPa (300 psi) regardless of the circuit pressure. With multiple valves activated, the individual circuit pressures will vary. When the pump cannot meet the flow needs of all activated circuits, the pressure compensators will move down to proportion the pump flow in relation to the amount of control spool travel and pressure for each circuit. The pressure differential will be less than described in the example, but the pressure differential will be the same for all spools. Valve "B" pressure compensator shows what occurs when an additional circuit is activated with a lower circuit pressure than the first activated valve. The pressure compensator valve will respond to changes in the circuit pressure by opening and closing off the passage between the feeder passage and the bridged passage to maintain a constant flow rate for a given control stem displacement. As the compensator opens and closes, the pressure differential across the compensator will vary in order to maintain a constant flow rate to the implement. The pressure differential across the main control spool is the same for all activated main control spools.

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Text Reference

The load signal from the valve "C" pressure compensator is directed to the top of the valve "B" pressure compensator valve with the lower circuit pressure. When the control spool is moved, pressure oil in the feeder passage moves the pressure compensator valve up. The pressure compensator valve does not move up enough to open the resolver valve to the signal network due to the higher forces working on the resolver valve. The pressure compensator valve will respond to changes in the circuit pressure by opening and closing off the passage between the feeder passage and the bridged passage to maintain a constant flow rate for a given control spool displacement. As the compensator opens and closes, the pressure differential across the compensator will vary in order to maintain a constant flow rate to the implement, while the pressure differential across the main control spool is the same for all activated main control spools.

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Text Reference

"H" SERIES MEDIUM WHEEL LOADER IMPLEMENT HYDRAULIC SYSTEM DUMP

Inlet Manifold


Tilt Cylinder Lift Cylinders

Line Relief Valves

Cover Manifold Hydraulic Lockout solenoid Valve

Head End Solenoid Valve


Manual Lower Valve

Auxiliary Function

Lift Ant idrift Valve

Pilot Accumulator Rod End Solenoid Valve




Ride Control Relief Valve


Auxiliary Spool

Tilt Spool Pressure Compensator Valve Screen Resolver Valve

Resolver Valve


Balance Valve


Resolver Valve

Signal Relief Valve



Case Drain Filter

Check Valve

Choke Check Valve

Min Angle


Margin Relief Valve

Pump and Pump Control Valve

Tank

94

Implement Hydraulic System - DUMP When the tilt control lever is moved into the DUMP position, a load sensing signal pressure equal to work port pressure is directed to the resolver network. The signal oil goes through the resolver to the top of the signal duplication valve. The signal duplication valve shifts down. Pump flow goes through the signal duplication valve to the bottom of the duplication valve and the orifice. The duplication valve and the orifice stabilizes the load sensing signal pressure to the pump control, to the spring chamber on each compensator valve, and to the margin relief valve. The load sensing pressure acts on the bottom of the margin relief valve. During the upstroking of the implement pump, the margin relief valve maintains an implement pressure equal to the load sensing pressure and the value of the spring. When the control lever is released, the load sensing pressure goes to approximately zero pressure. The margin relief valve opens to relieve supply oil pressure eliminating pressure spikes in the closed center system. Once the implement pump is destroked, the margin relief valve maintains sufficient oil pressure for the pilot system.

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Text Reference

The pilot pressure reducing valve limits maximum pilot pressure to 3450 ± 170 kPa (500 ± 25 psi). The implement pump oil flows through the cover manifold, regulated pilot oil is directed to the various implement function solenoid valves. The load sensing signal moves the pump load sensing spool in the pump control valve to upstroke the pump. The signal circuit is also equipped with a choke check valve. The valve will allow free flow to the pump control valve. Also, the choke check valve will slow the signal flow return back to the hydraulic tank. With the control lever moved to DUMP direction, the current proportional to the movement of the control lever is directed to the coil on the dump pilot solenoid valve. The solenoid valve sends a proportional amount of pilot oil to the dump end of the tilt spool. The tilt spool begins to shift upward. The lower end of the tilt spool is active. Supply oil flowing through the inlet manifold is directed around the lands of the tilt spool to the load check valve. The check valve unseats. Supply oil flows to the tilt pressure compensator valve. The oil flow through the compensator valve is blocked. As the pressure at the top of the compensator valve increases, the oil pressure shifts the compensator spool downward. The supply oil flows through the compensator valve and back around the tilt spool to the rod end of the tilt cylinder. The supply oil is directed to rod end of the tilt cylinder. Also, as the tilt lever is moved, the solenoid for the tilt antidrift valve is energized. The oil from the head end of the tilt cylinder flows around the load check valve, through the tilt spool and back to tank. Oil directed to the rod end of the tilt cylinder through the bridge passage is also directed to the tilt ball resolver in the resolver network. When the work port pressure increases the pressure in the resolver network, the resolver ball shifts and blocks oil from any other revolvers in the network. The oil pressure at the tilt ball resolver is directed to the top of the signal duplication valve or load sensing pressure. The dump operation is also equipped with a makeup and a line relief valve. The line relief valve regulates the pressure spikes caused by outside forces acting on the work tool. This allows the pressure spike to return to the hydraulic tank. This will prevent high pressure from damaging any components in the work tool or actuator. The line relief valve acts like a makeup valve when the pump can not supply the amount of oil needed to fill the void in the cylinder. When the negative pressure occurs in the tilt cylinder, the valves move off the seat and tank oil flows around the valve to fill the void in the cylinder. NOTE: The pilot line used on the optional Command Control Steering has been removed form the illustration.

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Text Reference

"H" SERIES MEDIUM WHEEL LOADER IMPLEMENT HYDRAULIC SYSTEM RAISE

Inlet Manifold


Tilt Cylinder



Manual Lower Valve

Auxiliary Function

Lift Cylinders

Line Relief Valves

Cover Manifold Hydraulic Lockout Valve

Lift Antidrift Valve

Pilot Accumulator



Rod End Solenoid Valve




Auxiliary Spool

Tilt Spool Balance Solenoid Valve



Screen Resolver Valve

Resolver Valve


Balance Valve

Resolver Valve

Signal Relief Valve Ride Control Lower / Float Pilot Solenoid Valve


Case Drain Filter

Check Valve

Choke Check Valve

Min Angle

Auxiliary Rod End Solenoid Valve

Margin Relief Valve

Pump and Pump Control Valve

Tank

95

Implement Hydraulic System - RAISE When the lift control lever is moved to the RAISE position, the lift lever position sensor sends a proportional electronic signal to the Implement ECM. The Implement ECM sends a corresponding proportional signal to the raise pilot solenoid valve. A proportional amount of pilot oil is directed from the raise pilot solenoid valve to the top of the lift spool. The lift spool shifts downward. Initially, as the lift spool begins to shift, any work port pressure will enter the control valve and is directed around the spool to the feeder passage. The work port oil pressure goes through the holes in the pressure compensator valve to the area between the compensator valve and the load check spool. The oil pressure helps the spring force hold the pressure compensator valve down to function as a load check valve. As the control spool shifts down, supply oil flows through the throttling slots into the supply passage. The pressure compensator valve will move up to the load check spool as the pump discharge pressure increases above the the work port pressure. The pump system oil pressure flows through the orifices in the pressure compensator valve to the feeder passage, around the lift antidrift valve, and to the head end of the lift cylinder.

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Text Reference

The pressure at the work port begin to increase which increases the pressure in the lift resolver network. The ball resolver moves downward and oil flows through the resolver network to the top of the signal duplication valve. The signal duplication valve shifts and sends a matching resolver network pressure out of the duplication valve over the choke check valve to the pump control valve. The implement pump upstrokes to supply the flow demand. Also, matching oil from the signal duplication valve flows to the pressure compensator valve working on the bottom of the compensator valve. As the pressure changes in the head end of the lift cylinders, the pressure compensator valve opens and closes to maintain a constant flow for a given control spool displacement. If the machine is equipped with the optional ride control, the balance valve solenoid will be energized, allowing oil on the right side of the balance valve to go to the hydraulic tank. As the pressure in the head end of the lift cylinders increases to raise, the oil pressure on the left side of the balance valve will force the balance valve to shift to the right. Supply oil flows over the check valve, through the balance valve to the ride control accumulator, charging the accumulator. With ride control not enabled, the head end solenoid valve is de-energized. The accumulator charge oil plus the spring pressure holds the valve closed. The flow of oil between the head end of the lift cylinders and the accumulator is blocked. With the rod end solenoid valve also de-energized, the oil flow through the solenoid valve will be blocked by the spring holding the valve closed. The oil from the rod end of the lift cylinders flows around the lift spool to the hydraulic tank. NOTE: The pilot line used on the optional Command Control Steering has been removed form the illustration.

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Text Reference

"H" SERIES MEDIUM WHEEL LOADER IMPLEMENT HYDRAULIC SYSTEM FLOAT

Inlet Manifold


Tilt Cylinder

Head End Solenoid valve


Manual Lower Valve

Auxiliary Function

Lift Cylinders

Line Relief Valves









Tilt Spool

Auxiliary Spool Pressure Compensator Valve



Resolver Valve


Balance Valve

Resolver Valve

Signal Relief Valve



Case Drain Filter

Check Valve

Choke Check Valve


Margin Relief Valve

Pump and Pump Control Valve Min Angle

Tank

96

Implement Hydraulic System - FLOAT When the lift lever is moved to the FLOAT position, the lift lever position sensor sends a proportional electronic signal to the Implement ECM. The Implement ECM sends a corresponding proportional electronic signal to the lower/float pilot solenoid valve. The Implement ECM also sends a fixed electronic signal to the lift load check valve. Pilot oil flows from the lower/float pilot solenoid valve to the bottom of the lift spool and the lift spool shifts up fully. System oil pressure is blocked. Also, oil flow through the pressure compensator loop is blocked. Oil from the head end and rod end of the lift cylinders along with the oil to the resolver network is open to tank. In the FLOAT position, the pilot oil also flows to the resolver valve in the ride control control section, through the resolver network to the signal duplication valve. A matching signal (pilot pressure) is directed to the pump control valve from the signal duplication valve. The pump is upstroked to meet the demands of the system.

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Text Reference

As the machine moves, the lift cylinders move up and down with the contour of the ground. The check valve allows oil to flow to the lift cylinders when the pressure in the lift cylinders drops below tank pressure.

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Text Reference

"H" SERIES MEDIUM WHEEL LOADER IMPLEMENT HYDRAULIC SYSTEM TILT BACK AND RAISE

Inlet Manifold


Tilt Cylinder

Auxiliary Function

Lift Cylinders Tilt Antidrift Valve

Manual Lower Valve

Line Relief Valves

Lift Ant idrift Valve

Pilot Accumulator Auxiliary Head End Solenoid Valve



Pressure Compensat or Valve


Tilt Spool




Resolver Valve

Check Valve

Balance Valve


Resolver Valve

Signal Relief Valve Ride Control Lower / Float Pilot Solenoid Valve


Case Drain Filter



Margin Relief Valve

Choke Check Valve

Pump Tank

97

Implement Hydraulic System - Tilt Back And Raise When the lift control lever is moved to the RAISE position and the tilt control lever is moved to the TILT BACK position, the lift lever position sensor and tilt lever position sensor send an individual proportional electronic signal to the Implement ECM. The Implement ECM sends a corresponding proportional signal to the raise pilot solenoid valve and the tilt back pilot solenoid valve. A proportional amount of pilot oil is directed from the raise pilot solenoid valve to the top of the lift spool and a proportional amount of pilot oil is directed from the tilt back pilot solenoid valve to the top of the tilt spool. The lift spool shifts downward. Initially, as the lift spool begins to shift, any work port pressure will enter the control valve and is directed around the spool to the feeder passage. The work port oil pressure goes through the orifices in the pressure compensator valve in between the compensator valve and the load check spool. The oil pressure helps the spring force hold the pressure compensator valve down. Identically, as the tilt spool begins to shift, any work port pressure will enter the control valve and is directed around the spool to the feeder passage.

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Text Reference

The work port oil pressure goes through the holes in the pressure compensator valve to the area between the compensator valve and the load check spool. The oil pressure helps the spring force hold the pressure compensator valve down to function as a load check valve. As the cylinders start to move, the pressure at the work ports increase which increases the pressure in the resolver network. The ball resolver with the highest work port pressure moves, seats, and blocks oil flow back through the resolver network. The highest work port pressure flows through the resolver network to the top of the signal duplication valve. The signal duplication valve shifts and sends the matching resolver network pressure out of the duplication valve over the choke check valve to the pump control valve. The implement pump recognizes a demand for increased oil flow and the pump upstrokes to supply the flow demand. Also, matching oil from the signal duplication valve flows to the pressure compensator valve working on the bottom of the load check spool. As the pressure changes in the head end of the lift cylinders, the pressure compensator valve opens and closes to maintain a constant flow for a given control spool displacement. If the machine is equipped with the optional ride control, the balance valve solenoid will be energized, allowing oil on the right side of the balance valve to go to the hydraulic tank. As the pressure in the head end of the lift cylinders begins to raise, the oil pressure on the left side of the balance valve will force the balance valve to shift to the right. Supply oil flows over the check valve, through the balance valve to the ride control accumulator, charging the accumulator. With ride control not enabled, the head end solenoid valve is de-energized. The accumulator charge oil plus the spring pressure holds the valve closed. The flow of oil between the head end of the lift cylinders and the accumulator is blocked. With the rod end solenoid valve also de-energized, the oil flow through the solenoid valve will be blocked by the spring holding the valve closed. The oil from the rod end of the lift cylinders flows around the lift spool to the hydraulic tank. NOTE: The pilot line used on the optional Command Control Steering has been removed form the illustration.

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Text Reference

"H" SERIES MEDIUM WHEEL LOADER IMPLEMENT HYDRAULIC SYSTEM HOLD / AUTO TRAVEL MORE THAN 9.7 KM/H (6 MPH)

Inlet Manifold


Tilt Cylinder



Manual Lower Valve

Auxiliary Function

Lift Cylinders

Line Relief Valves

Pilot Shutoff Valve





Pressure Compensator valve



Tilt Spool





Signal Relief Valve

Check Valve

Balance Valve

Resolver Valve

Ride Control Lower / Float Pilot Solenoid Valve


Case Drain Filter

Resolver Valve


Margin Relief Valve

Choke Check Valve

Pump Tank

98

Implement Hydraulic System - RIDE CONTROL AUTO When the ride control system is in AUTO and the machine reaches the configured ride control ground speed, the ride control balance solenoid valve is de-energized by the Power Train ECM. After the ride control equalization time has expired, the Power Train ECM energizes both the ride control head end solenoid valve and the ride control rod end solenoid valve. The head end solenoid valve connects the head end of the lift cylinders to the ride control accumulator. The ride control accumulator dampens the motion of the lift arms which makes the machine more stable. The rod end solenoid valve allows oil from the tank passage to flow into the rod ends of the lift cylinders when the lift cylinders move down. When the machine is in ride control AUTO, the control levers are in the HOLD position, and the ground speed is more than the 9.7 km/h (6 mph), the control spools are in the HOLD position blocking all oil flow through the implement control valve to the cylinders. The resolver network is at tank pressure and the pump is at low pressure standby.

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Text Reference

When the ground speed reaches the ECM configured value of 9.7 km/h (6 mph), the balance solenoid valve will be de-energized and the balance spool will move in the direction needed to equalize the pressures on each end of the balance spool. During the balancing operation, when the pressure at the right side of the balance spool is lowest, the spool shifts to the right and the implement pump supplies oil flow to equalize the pressure on both ends of the spool. During the balancing operation, when the pressure at the left side of the balance spool is lowest, the spool shifts to the left and the pressure in the oil pressure in the accumulator flows to tank until the pressures on both ends of the spool are equal. The Power Train ECM limits the time to equalize to one second (default). Then, the ECM energizes the balance solenoid valve. The oil pressure on the right end of the balance spool flows through the orifice to the hydraulic tank. The balance spool shifts to the right. Oil in the accumulator is trapped at the check valve. After the one second balancing time, the rod end solenoid and the head end solenoid valves are energized. The oil pressure that holds the check valves locked is released to tank. The oil in the head end of the lift cylinders flows to the ride control accumulator. The accumulator cushions the forward and backward pitching motions of the machine. At a ground speed below the ECM configured valve of 9.7 km/h (6 mph), the rod end solenoid and the head end solenoid valves are de-energized. The check valves close and the spring force and the oil pressure hold the check valves closed. NOTE: The one second balance default time can be reconfigured in the Power Train ECM through Cat ET. Also, the forward and reverse activation speeds can be changed .

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Text Reference

RIDE CONTROL SYSTEM AUTO / TRAVEL LESS THAN 9 km/h (6 mph)

Rod End


Head End


Pilot Operated Check Valve

Balance Valve Solenoid

Accumulator Port

Relief Valve Check Valve

To Tank

Resolver Valve

Supply Balance Passage Spool

To Tank

99

Ride Control Valve - Auto/Travel Below 9.7 km/h (6 mph) The main control valve is equipped with the optional ride control section to dampen the ride during machine travel. This illustration shows a sectional view of the ride control section of the main control valve with the ride control system in AUTO, the bucket off the ground, and the travel speed below 9.7 km/h (6 mph). With the head end solenoid valve de-energized, the oil between the head end of the lift cylinders and the ride control valve is blocked. With the rod end solenoid valve de-energized, the oil between the rod end of the lift cylinders and the valve is also blocked. When the balance solenoid valve is energized, oil flow is blocked from the accumulator port to the left side of the balance spool. The blocked oil on the right side of the balance valve is above the tank pressure on the left side of the balance spool. Then, the balance spool shifts to the left and oil in the accumulator port flows back through the balance spool and is blocked by the check valve. The check valve blocks all oil and any spikes from flowing back to the implement pump and causing damage to the pump. The relief valve installed in the ride control section limits pressure in the accumulator port to 34,500 kPa (5000 psi).

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Text Reference

RIDE CONTROL SYSTEM

AUTO/TRAVEL MORE THAN 9.6 km/h (6 mph)

Rod End



Head End

Pilot Operated Check Valve Accumulator Port

Balance Valve Solenoid Check Valve

Relief Valve

To Tank

Resolver Valve

Supply Balance Passage Spool

To Tank

100

Ride Control Valve - Auto/Travel More Than 9.7 km/h (6 mph) This illustration is a sectional view of the ride control valve section with the ride control system in AUTO, the bucket off the ground, and the travel speed more than 9.7 km/h (6 mph). The balance solenoid valve is de-energized by the Power Train ECM and the oil pressure from the accumulator port flows around the solenoid valve to the left side of the balance valve. The balance valve will equalize the pressure between the head end of the lift cylinders and the accumulator port. Supply oil flowing around the balance spool is blocked. After the one second equalization time, the head end solenoid valve and the rod end solenoid valves are energized. The oil passage between the rod end of the lift cylinders and the tank port is open. The energized head end solenoid valve allows the oil that locks the pilot operated check valve closed to flow to the hydraulic tank. The pilot operated check valve opens and oil flows between the head end of the lift cylinders and the accumulator. The head end solenoid valve and the rod end solenoid valve stay energized until either the ride control switch is moved to the OFF position or the machine ground speed is less than 9.7 km/h (6 mph).

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Text Reference

1 2 3

4 8 5

6

7

101

This illustration is a transparent view of the ride control valve section. This view shows the location of the following components that are installed on the exterior and the interior of the section. - Head end solenoid valve (1) - Rod end solenoid valve (2) - Pilot pressure reducing valve (3) - Balance solenoid valve (4) - Balance valve (5) - Ball resolver (6) - Check valve (7) - Ride control relief valve (8)

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Text Reference

1 3 2

102

This illustration shows the location of the ride control accumulator (2) within the loader frame (1). Testing and adjusting and service to the accumulator is completed at the articulation hitch. The charge medium for the accumulator is dry nitrogen. Also shown is the location of the implement control valve (3).

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1

Text Reference

3

2

4 5

103

6

7

1

5 8 104

4 6

Implement Pump and Pump Control Valve The Implement hydraulic pump for the 966H and 972H wheel loaders is a variable displacement piston-type pump. The implement pump is installed on the accessory drive from the torque converter housing. The following is a list of components on the implement pump. - Load sensing port (1)

- Maximum angle adjustment (5)

- Case drain port (2)

- Pump control valve (6)

- Pump inlet (3)

- Pump outlet (7)

- Set screw (do not adjust) (4)

- Load sensing adjustment screw (8)

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Text Reference

PUMP CONTROL VALVE ENGINE OFF

Maximum Angle Stop Adjustment Screw Set Screw

To Implement Control Valve

Pump System Pressure Piston Load Sensing Spool

Orifice

Pump Load Sensing Sleeve Margin Spring

Swashplate Pin

Load Sensing Piston

Actuator Piston

Signal Relief Valve

Load Sensing Adjustment Screw LS Signal from Work Port

Bias Spring

Pump Upstroke

105

Pump Control Valve - Engine OFF This illustration shows the pump control group components with the engine OFF. The swashplate pin connects the actuator piston to the pump swashplate (not shown). The bias spring moves the actuator piston and the pump swashplate to maximum angle. The pump control valve group consists of a load sensing spool assembly, which consists of a load sensing spool and a load sensing sleeve. The load sensing spool is moved up or down by different signal pressures pushing on the piston on each end of the spool. The pump system pressure piston receives an internal signal pressure equal to pump system pressure. The load sensing piston receives a load sensing signal from the implement hydraulic control valve, which is equal to the highest work pressure. The signal relief valve (located in the implement control valve) limits the maximum load sensing signal to the load sensing piston. Pump system pressure is directed through the orifice on the right side of the control valve group to the spring chamber in the upstroke end of the actuator piston and the center lands of the load sensing piston.

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Text Reference

The adjustment screw at the top of the actuator piston is used to adjust maximum angle of the swashplate. The set screw at the top of the load sensing spool is used to hold the load sensing sleeve in position. The adjustment screw at the bottom of the load sensing spool is used to adjust the load sensing margin pressure for the pump. The spring at the bottom of the load sensing spool is the margin pressure spring.

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Text Reference

PUMP CONTROL VALVE STANDBY




Orifice

Pump Load Sensing Sleeve Margin Spring Swashplate Pin

Load Sensing Piston

Actuator Piston

Signal Relief Valve


Bias Spring

Pump Destroke

106

Pump Control Valve - Standby When the engine is started, pump flow goes to the closed-center control valves in the implement control valve group. The flow is blocked in the implement control valve. Pressure in the system increases, and the pump system pressure is directed to the top end of the actuator piston. Pump system pressure on top of the pump system pressure piston moves the piston and load sensing spool down against the force of the margin spring. The spool moves down until the upper opening of the spool opens a path around the load sensing spool to drain. The opening to drain must open sufficiently to provide a pressure differential across the orifice. With reduced pressure on the lower end and full pressure on the top of the actuator piston, the actuator piston moves the swashplate pin toward minimum angle. In STANDBY, the pump is delivering minimum flow to compensate for leakage in the pump, for leakage in the implement control valve, and for the operation of the pump control valve.

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Text Reference

PUMP CONTROL VALVE UPSTROKE




Orifice

Pump Load Sensing Sleeve Margin Spring

Swashplate Pin

Load Sensing Piston

Actuator Piston

Signal Relief Valve

Load Sensing Adjustment Screw LS Signal From Work Port

Bias Spring

Pump Upstroke

107

Pump Control Group - Upstroke When the control lever or levers are moved to activate one or more implements, a load sensing signal, equal to the highest work port pressure, is directed to the lower end of the load sensing piston. The combined forces of the load sensing piston and the margin spring push the load sensing spool up until the center land on the load sensing spool closes the drain passage. The upward movement of the load sensing spool continues until the lower opening of the spool opens a path to the two metering ports. Pump system oil flows through the lower opening of the load sensing spool to the spring chamber of the actuator piston. The combined force on the the larger diameter of the actuator piston and the spring pushes the actuator piston and the swashplate pin up, increasing the swashplate angle to increase pump flow.

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Text Reference

PUMP CONTROL VALVE CONSTANT FLOW DEMAND




Orifice


Load Sensing Piston

Actuator Piston

Signal Relief Valve

Load Sensing Adjustment Screw

Bias Spring

LS Signal from Work Port

108

Pump Control Valve - Constant Flow Demand When the flow demand is met, the force developed by the pump system pressure on top of the pump system pressure piston is equal to the force developed by the load sensing signal on the load sensing piston plus margin spring. When the forces are equal, the pump flow is constant and the load sensing spool is in the CENTER position. The pump flow remains constant until a change in the flow demand occurs.

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Text Reference

PUMP CONTROL VALVE MAXIMUM SYSTEM PRESSURE




Orifice


Load Sensing Piston

Actuator Piston

Signal Relief Valve


Bias Spring

Pump Destroke

109

Pump Control Valve - Maximum System Pressure This illustration shows the pump control valve with the load sense pressure at signal relief with one function activated. When the work port pressure increases to the setting of the signal relief valve, the valve opens to limit the signal pressure to the bottom of the load sensing piston. Pump system pressure will increase to overcome the combination of forces on the bottom of the load sensing piston. The load sensing spool moves down to open the actuator piston spring cavity to drain. The pump system pressure moves the actuator piston and swashplate pin towards minimum angle. The pump destrokes to minimum flow.

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Text Reference

PUMP CONTROL VALVE

MAXIMUM SYSTEM PRESSURE WITH ADDED FLOW DEMAND Maximum Angle Stop Adjustment Screw Set Screw



Orifice


Load Sensing Piston

Actuator Piston

Signal Relief Valve

Load Sensing Adjustment Screw LS Signal From Work Port

Bias Spring Pump Destroke

110

Pump Control Valve - Maximum System Pressure With Added Flow Demand This illustration shows the pump control valve with the load sense pressure at signal relief. When an additional function is activated, the pump system pressure slightly decreases. With less pressure on top of the pump system pressure piston, the force on the bottom of the load sensing piston moves the load sensing spool up. The load sensing spool restricts the flow through the upper opening to drain. The increased pressure on the larger area of the actuator piston plus the bias spring pushes the actuator piston up. The pump upstrokes to meet the added flow demand.

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Text Reference

4 5

2

3 6

1 7

8

9

10

11

12

13

111 Implement Valve This illustration shows a side view of the implement control valve out of the loader frame. The following components can be seen in this view: Pilot accumulator (1)

Pilot pressure reducing valve (8)

Ride control balance solenoid valve (2)

Balance valve (ride control) (9)

Rod end solenoid valve (ride control) (3)

Lower pilot valve housing (10)

Line Relief valve (4)

Lower solenoid valve (11)

Tilt antidrift valve (5)

Tilt back pilot valve housing (12)

Signal relief valve (6)

Tilt back solenoid valve (13)

Signal duplication valve (7)

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Text Reference

MARGIN RELIEF VALVE Load Sensing Signal

From Pump

To Tank 112

Margin Relief Valve During normal working conditions, the pressure difference between the pump delivery pressure and the load sensing signal pressure is maintained at approximately 1960 kPa (285 psi) by the spring in the pump control valve (not shown). When an implement movement has stopped, the spool in the main control valve returns to the HOLD position. At this time, the load sensing signal pressure from the implement circuit to the pump control valve goes to approximately zero. Since the pump has not destroked, any pump supply pressure flowing into the margin relief valve that is above the setting of the margin relief valve will be relieved to tank.

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Text Reference

PRESSURE REDUCING VALVE BELOW 3445 kPa (500 psi) Spool

Orifice

Spring Spring Cavity

Ball Seat Retainer

Spring

Spring Cavity

Adjustment Screw

To Pilot Accumulator

From Implement Hydraulic Tank Pump

113

Pressure Reducing Valve The pressure reducing valve regulates the oil pressure in the pilot system. The pilot oil from the implement pump flows into the valve through the holes in the spool, to the center of the spool. Then, the regulated oil flows out of the left end of the reducing valve to the pilot accumulator. Also, the pilot oil flows through the orifice into the left spring cavity. The force of the oil pressure acting on the ball is not sufficient to override the force of the right spring. The spring on the right holds the ball on the seat. When the oil pressure flowing into the valve is below 3445 kPa (500 psi), the spool blocks the flow of any pilot oil to the hydraulic tank. NOTE: For adjustment procedures for the pressure reducing valve, refer to the Service Manual module (RENR8858) Troubleshooting Testing and Adjusting 966H and 972H Wheel Loaders Electrohydraulic System. Pilot Pressure to the Main Control Valve Check.

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Text Reference

PRESSURE REDUCING VALVE ABOVE 3445 kPa (500 psi)

Spool

Orifice

Spring Spring Cavity

Seat

Ball Retainer

Spring

Spring Cavity

Adjustment Screw

To Pilot Accumulator

From Implement Hydraulic Tank Pump

114

Pressure Reducing Valve - Above The Adjusted Pressure As the oil pressure from the implement pump increases, the reducing valve will regulate the pressure in the pilot system. The pilot oil flows into the center of the spool through the passages in the spool. The pilot oil flows out of the pressure reducing valve from the left end of the spool to the pilot accumulator and then, to the hydraulic lockout solenoid valve. When the solenoid valve is energized and one or more of the control levers are moved, the flow from the implement pump will increase along the pilot pressure. Also, oil flows through the orifice into the spring cavity. When the oil pressure rises above the adjusted setting and and the force of the oil pressure overrides the force of the spring. The ball and retainer is moved off the seat. The oil in the spring cavity to the right is allowed to flow to the hydraulic tank. The force of the oil pressure is greater than the force of the left spring which allowing the spool to override the spring. The spool moves to the right and blocks the supply oil from implement pump. The spool shifts to the right allowing the passages in the spool to be open to the hydraulic tank passage. Sufficient oil flows from the pilot system through the passage to the hydraulic tank regulating the pilot pressure to the adjusted setting.

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Text Reference

115

Load Sensing Pressure Tap The access to the load sensing pressure tap is on the right side of the machine at the articulation hitch near the service bay. This pressure tap is used to measure the load sensing pressure between the pump control valve and the signal duplication valve.

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1

Text Reference

2

3

4 5

6 7

8

9

10

11

116

The following components are located on the implement control valve: - Head end solenoid valve (ride control) (1) - Hydraulic lockout valve (2) - Differential pressure relief valve (3) - Lift antidrift valve (4) - Line relief valve (rod end) (5) - Dump pilot valve housing (6) - Dump solenoid valve (7) - Raise solenoid valve (8) - Raise pilot valve housing (9) - Ride control relief valve (10) - Pilot check valve (11)

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1

Text Reference

3

2

117

The following components can be seen from the left rear of the control valve: - Tilt pressure compensator valve (1) - Lift pressure compensator valve (2) - Head end solenoid valve (ride control) (3)

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Text Reference

1 2 4 118

3

5

1 2

119

3

This illustration shows a transparent view of the inlet manifold on the implement control valve. The signal relief valve (1) limits the signal pressure to the load sensing spool which controls the maximum pump system pressure. The signal duplication valve (3) duplicates the true load signal received from the work port. The orifice (2) is used to stabilize the duplicated load sensing signal that is being directed to the tops of the pressure compensator spools and the load sensing spool in the pump control valve. Also shown are the Implement control valve return to the hydraulic tank (4) and the implement control valve inlet (5).

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Text Reference

SIGNAL DUPLICATION VALVE From Resolver Network

From Pump Supply

To Pump Control and Pressure Compensator Valve

120

Signal Duplication Valve The work port pressure pushes on the right end of the signal duplication valve spool pushing it to the left. When the spool shifts left, a passage allowing pump delivery pressure to enter the outer chamber is opened. At the same time, the drain passage to the hydraulic tank is closed. Pump delivery pressure enters the center passage of the signal duplication valve spool through an orifice and pump delivery pressure pressurizes the center passage of the signal duplication valve. The pressurization of the center passage creates the duplicated work port pressure. The duplicated work port pressure on the left end of the signal duplication valve spool moves the spool to the right. When the signal duplication valve spool moves to the right, the passage for pump delivery pressure partially closes and the drain passage partially opens. The duplicated work port pressure on the left end of the signal duplication valve spool is reduced. True load signal pressure on the right end moves the signal duplication valve spool to the left until the work port pressure and the duplicated work port pressure is equal. The duplicated work port pressure is sent from the left end of the signal duplication valve spool into the load sensing signal network.

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Text Reference

SIGNAL RELIEF VALVE

BELOW ADJUSTED PRESSURE SETTING To Pressure Compensator Valves


Choke Check Valve

Seat

Adjustment Screw

Tank

Spring

Poppet

To Pump Control Valve

121

Signal Relief Valve - Below The Adjusted Pressure Setting When the machine is under a load condition, the signal relief valve operates in the following manner. From the signal duplication valve, the duplicated load sensing signal flows through the orifice in two directions. One direction flows to the pressure compensator valve in each control valve section. The second path flows as a load sensing signal to the signal relief valve, through the choke check valve, and to the pump control valve. In the signal relief valve, load sensing signal oil enters the signal relief valve on the left end. The spring force of the spring being greater than the force of the load sensing signal the poppet is held against the seat.

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Text Reference

SIGNAL RELIEF VALVE ABOVE ADJUSTED PRESSURE SETTING

To Pressure Compensator Valves


Choke Check Valve

Seat

Adjustment Screw

Tank

Poppet

Spring

To Pump Control Valve

122

Signal Relief Valve - Above The Adjusted Pressure Setting When the force of the load sensing oil at the left end of the signal relief valve is above the force of the spring, the poppet moves off the seat, and a small amount of oil drains through the passage to the hydraulic tank. The signal relief valve functions like a signal relief valve. As a result, the load sensing signal is maintained at the adjusted pressure setting of the signal relief valve.

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Text Reference

LINE RELIEF VALVE From Implement Cylinders Seat

CLOSED Shoulder Area

Sleeve

Inner Spring Spool

Outer Spring

Spring

Poppet

123

Line Relief Valve - Closed When the control valves for the cylinders are in the NEUTRAL position, spring force on the poppet and the inner and the outer springs to the right of the piston keep the spool moved to the left in the closed position. When the control valves are energized and an external force acts on one end of the cylinder, the oil pressure increases on the opposite end of the cylinder. The oil pressure also increases in the passage of the line relief valve that is connected to the cylinder. The line relief valves limit the circuit pressure to the specified pressure settings. The pressure between the cylinder and the main control valve pressurizes the line relief valve. The pressure oil flows in the center passage of the spool into the inner spring and outer spring chamber. During normal conditions, the oil pressure is lower than the line relief valve pressure setting. The valve remains in the CLOSED position by the force of the spring on the poppet. The oil pressure in the inner spring chamber and the passage to the cylinder are equal. The surface area of the right side of the spool is larger than the area on the left side of the spool.

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Text Reference

With the oil pressure equal on both sides of the piston, the spring force of the inner spring and outer spring assist in keeping the piston seated. Therefore, the force on the right side is greater than the force on the left side and the piston remains seated to the left. The pressure oil does not flow to the return passages and to the hydraulic tank.

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Text Reference

LINE RELIEF VALVE OPEN From Implement Cylinders Seat

Shoulder Area

Sleeve

Inner Spring Spool

Outer Spring

Spring

Poppet

124

When the high oil pressure in the passage between the main control valve and the cylinder exceeds the line relief valve setting, the line relief valve overcomes the force of the spring on the poppet. The reduced pressurized oil in the spring chamber flows into the poppet chamber and the low pressure oil from there flows into the return passages within the valve and returns to the hydraulic tank. At the same time, the high pressure oil in the passage to the cylinder pushes the piston to the right overcoming the force of the inner spring and the outer spring, until the piston come in contact with the left end of the valve. At this time, the high pressure oil also flows through the opening in the seat to the return passages and back to the hydraulic tank. When the high pressure oil in the passage between the cylinder and the main control valve reach the specified pressure setting of the line relief valve, the spring force on the poppet moves the poppet to the left, seating the poppet. With the poppet seated, the oil pressure in the spring chamber will raise to be equal to that of the main passage. With the oil pressure in the spring chamber equal to that of the main passage pressure, the spring force of the inner spring and outer spring will move the piston to the left blocking the oil flow through the opening in the seat.

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Text Reference

LINE RELIEF VALVE MAKEUP FUNCTION To Implement Cylinders Seat

Shoulder Area

Sleeve

Inner Spring Spool

Outer Spring

Spring

Poppet

125

When oil from one end of the cylinder is discharged through the line relief valve, a vacuum condition is created on the opposite end of the cylinder. Makeup oil is needed to prevent the vacuum condition in the cylinder. Also, during the operation of the machine in certain conditions, it is possible to create a vacuum condition on one end of the cylinder. When the vacuum condition occurs on the end of the cylinder, that vacuum also occurs in the spring chamber of the line relief valve. At this point, the return oil is now at a higher pressure than the oil in the passage between the cylinder and the main control valve. When this event occurs, the higher pressure return oil flows through the return passage into the poppet chamber. The return oil pressure works with the spring acting on the poppet, keeping it seated to the left. Simultaneously, the return oil pushes on the shoulder area of the sleeve pushing it to the right. When the sleeve moves to the right, the piston also moves to the right. However, as the sleeve moves to the right, a passage opens between the return passage to the hydraulic tank and to the passage to the cylinder. Return oil flows from the return passage into the main passage in order to remove the vacuum condition in the cylinder.

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1

2 3

4

6

Text Reference

5

8

7

9

126

This illustration shows the lift section of the implement control valve with the lift body section in transparency. The following is a list of components that are in the interior of the valve. - Pressure compensator valve (1) - Load check spool (2) - Load check spool spring (3) - Check valve (ride control) (4) - Lift antidrift valve (5) - Lower solenoid valve (6) - Lift resolver valve (7) - Lift spool (8) - Raise solenoid valve (9)

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Text Reference

STEERING SYSTEM COMPONENTS HAND METERING UNIT Secondary Steering Diverter Valve Steering Pump

Hand Metering Unit

Hydraulic Tank

Neutralizer Valves

Steering Orifices Secondary Steering Steering Pump and Motor Cylinder Control Valve

127

STEERING SYSTEM This illustration shows the location of the components for the standard HMU steering system for the 966H and the 972H Wheel Loaders. The following is a list of the components: - Hydraulic tank - Steering pump - Steering control valve - Secondary steering diverter valve - Hand Metering Unit - Neutralizer valves - Secondary steering pump and motor - Steering cylinders - Orifices

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Text Reference

STEERING SYSTEM BLOCK DIAGRAM HOLD

Hand Metering Unit Neutralizer Valve Check Valve Steering Pump

Neutralizer Valve Secondary Steering Diverter Valve

Steering Cylinders

Steering Control Valve

Secondary Steering Pump and Motor (Optional) Tank

128

This diagram shows the components and oil flow for the 966H/972H standard steering system. The primary steering system is made up of two basic circuits: the main circuit and the pilot circuit. The steering system includes a third circuit if the 966H/972H is equipped with the optional secondary steering system. The main steering circuit consists of: the steering pump, the steering control valve, the steering cylinders, and the hydraulic oil tank. The variable displacement piston steering pump draws oil from the tank and sends flow to the steering control valve. The steering pilot circuit consists of the metering pump, a check valve, and two neutralizer valves. The supply oil is ported through an orifice in the steering control valve, which supplies pilot oil to the steering pilot circuit. When the steering wheel is moved to the left or right, the metering pump sends pilot oil through the respective neutralizer valve to the selector spool and directional spool in the steering control valve. The pilot oil moves the directional spool and directs pump supply oil to the steering cylinders.

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Text Reference

This diagram shows the system in the HOLD position. The steering supply oil to the steering cylinders is blocked. The optional secondary steering system consists of the secondary steering pump/electric motor and the secondary steering valve. The secondary diverter steering valve contains two check valves: the primary steering pressure switch, and the secondary steering pressure switch. Also, the secondary steering system includes an intermediate relay to run the electric motor. The relay receives current from the Power Train ECM to enable the relay. When the relay is engaged, battery voltage flows to the electric motor.

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Text Reference

1 2

3 4

5

6

7

129

The following are components of the standard Hand Metering Unit (HMU) Steering System: - Hydraulic tank (1) -Hand Metering Unit (2) - Steering pump (3) - Neutralizer valves (4) - Orifices (5) - Steering control valve (6) - Steering cylinders (7)

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1

2

Text Reference

3

4 5

130

Steering Pump The steering pump (2) for the 966H and 972H Wheel Loader is a variable displacement piston pump. The steering pump is equipped with a pump control valve (3). The pump control valve is equipped with both the flow compensator valve (4) and the high pressure cutoff valve (5). Also shown is the implement pump (1).

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Text Reference

STEERING PUMP AND PUMP CONTROL VALVE ENGINE OFF Signal From HMU

Pump Output Large Actuator

Swashplate

Drive Shaft Flow Compensator (Margin Spool)

Pressure Compensator (High Pressure Cutoff)

Small Actuator and Bias Spring

Piston and Barrel Assembly

131

Steering Pump with the Engine OFF This illustration shows a sectional view of the steering pump and the pump control valve. The major components are shown. When the engine is in the OFF position, the bias spring holds the swashplate at maximum angle. Also, the spring force on the flow compensator and the pressure compensator spools keep both the spools in the pump control valve downward against the plugs.

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Text Reference

STEERING PUMP AND PUMP CONTROL VALVE LOW PRESSURE STANDBY Signal From HMU

Pump Output Large Actuator Piston Large Actuator

Swashplate

Spring

Drive Shaft Flow Compensator

Pressure Compensator

Small Actuator and Bias Spring Piston and Barrel Assembly

132

Low Pressure Standby This illustration shows the steering pump in LOW PRESSURE STANDBY. When there is no demand for steering system oil, the pump goes to LOW PRESSURE STANDBY. At that position, the pump produces a sufficient amount of oil flow to compensate for internal leakage and maintain sufficient pressure to ensure instantaneous response when the signal from the HMU commands steering oil flow. At LOW PRESSURE STANDBY, no load sensing pressure signal is detected at the flow compensator spool. Pump supply oil pushes the flow compensator spool up. System pressure is then directed into the large actuator piston. The large actuator piston moves the swashplate towards minimum angle until the cross-drilled hole in the large actuator piston opens to case drain. At this point, the pressure inside the piston decreases and the pump stops destroking. The pump will supply sufficient flow to maintain the standby pressure and to compensate for internal leakage. NOTE: LOW PRESSURE STANDBY is more than margin pressure because of the higher back pressure the blocked oil the closed-center valves create when all of the control valves are in NEUTRAL. The pump supply oil pushes the margin spool up to further compress the margin spring. More supply oil goes to the large actuator piston and flows through the cross-drilled hole in the spool to the pump case.

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Text Reference

STEERING PUMP AND PUMP CONTROL VALVE UPSTROKE Signal From HMU


Swashplate

Spring




133

Pump Upstroke When a demand for increased oil flow in the steering system occurs, a load sensing signal is sent to the pump control valve. The load sensing signal is equal to the steering system pressure. The load sensing signal is directed to the spring chamber of the flow compensator spool. The spring force plus the load sensing signal from the HMU shifts the flow compensator spool downward. The flow compensator spool blocks oil between the pump discharge of the large actuator. The oil in the large actuator piston flows around the pressure compensator spool and the flow compensator spool to case drain. Pump system pressure plus spring force on the small actuator piston moves the pump swashplate toward maximum angle to increase pump flow. As pump flow increases, system pressure will also increase. When system pressure increases to 2400 kPa (350 psi) more than the load sensing signal from the control valve, the flow compensator spool starts to move upward. The center land on the margin spool reaches a balance point where flow is metered to and from the large actuator piston. At this point, flow from the pump remains constant until there is a change in the load sensing signal pressure from the control valve.

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Text Reference

STEERING PUMP AND PUMP CONTROL VALVE DESTROKE Signal From HMU


Swashplate

Spring




134

Pump Destroke This illustration shows the pump and pump control valve in the DESTROKE position. When demand for oil flow in the steering system is decreased, the signal from the HMU is decreased allowing the flow compensator spool to move upward. Oil is allowed to flow around the flow compensator spool and into the large actuator. The large actuator moves to the right and forces the swashplate toward a minimum angle.

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Text Reference

STEERING PUMP AND PUMP CONTROL VALVE HIGH PRESSURE STALL Signal From HMU

Pump Output Spring

Large Actuator Large Actuator Piston

Swashplate




135

High Pressure Stall This illustration shows the pump and pump control valve at HIGH PRESSURE STALL. When steering system pressure reaches the pressure setting of the pressure compensator, the force on the bottom of the cutoff spool will shift the cutoff spool upward. System pressure is then directed into the large actuator piston. The large actuator piston moves the swashplate towards minimum angle until the cross-drilled hole in the large actuator piston opens to case drain. When system pressure decreases to less than the pressure setting of the pressure compensator, spring force pushes the cutoff spool down and the margin spool again controls flow from the pump.

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Text Reference

4 3 2 1

5

6

8

9

7

136

Steering Control Valve Shown is the steering control valve. This valve is mounted above the transmission between the operator's station and the engine. This illustration shows the location of the following components: - Right neutralizer valve (1) - Left neutralizer valve (2) - Right return to tank orifice(3) - Left return to tank orifice (4) - Steering control valve (5) - Crossover relief valve (6) - Back-up relief valve (7) - System pressure port (8) - Return flow port (9)

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Text Reference

1

2

3

4

137

Steering Neutralizer Valves The steering neutralizers are a plunger-type valve. The neutralizer valve is used to block the pilot oil that is flowing from the HMU to both the pilot control spool and the main steering control spool. As the machine is articulating to the left and the neutralizer valve (1) meets the striker (2), the the pusher will move inward and block the pilot oil flow to the steering control valve. The left articulation will stop. As the machine is articulating to the right and the neutralizer valve (3) meets the striker (4), the the pusher will move inward and block the pilot oil flow to the steering control valve. The right articulation will stop.

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Text Reference

LESS THAN MAXIMUM TURN

NEUTRALIZER VALVE

From To Steering HMU Control Valve Orifice

Spring

To Tank

Valve Spool

MAXIMUM TURN

Center Passage

From To Steering HMU Control Valve Spring

Orifice

To Tank

Valve Spool

Center Passage

138

Steering Neutralizer Valve This illustration shows a sectional view of the neutralizer valve. During a less that maximum turn, oil from the HMU flows through the valve to the pilot end of the spool in the steering control valve. When the striker comes in contact with the neutralizer valve, the valve spool shifts and oil flow to the steering control valve is blocked. Steering pilot oil flows back through the orifice in center passage in the spool to drain. Pilot oil from the neutralizer valve to the steering control valve (not shown) is blocked. The centering springs in the steering control valve return the spool to the HOLD position and steering supply oil to the steering cylinders is blocked. The machine will stop articulating until the steering wheel is turned in the opposite direction.

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Text Reference

STEERING SYSTEM HOLD

Right Neutralizer Valve

Left Neutralizer Valve

Selector Spool

Crossover Relief Valve

Steering Pump Secondary Steering Diverter Valve Orifices

Hand Metering Unit

Secondary Steering Pump and Motor

Flow Control Orifice

Back-up Relief Valve

Directional Spool

Mechanical Linkage

139

Steering System Schematic When the engine is running and the steering system is in HOLD, oil is drawn from the hydraulic tank by the steering pump. The oil flows past the secondary steering diverter valve to the back-up relief valve and the directional spool in the steering control valve. Also, the oil flows through the flow control orifice to the hand metering unit. At this time, the oil is blocked from flowing through the HMU. With the HMU in the center position, a small amount of oil then flows through the orifice and back to the hydraulic tank. The HMU and the steering pump are connected by a signal line. A sense of change in the signal pressure at the HMU will send a reflected change in signal pressure to the pump control valve demanding a change in the output flow of the steering pump. If the pressure of the signal oil decreases, the steering pump will destroke. If the pressure of the signal oil increases, the steering pump will upstroke. In the HOLD position, the flow of pressure oil from the steering pump to the steering cylinders is blocked at the directional spool in the steering control valve. In the HOLD condition, there is no signal pressure sensed at the compensator valve on the steering pump. The steering pump goes to the LOW PRESSURE STANDBY position.

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Text Reference

In LOW PRESSURE STANDBY, the pump supplies an adequate amount of flow to compensate for any system leakage and to maintain sufficient system pressure to provide instantaneous response when the steering wheel is turned.

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Text Reference

STEERING SYSTEM

Steering Cylinders

GRADUAL LEFT TURN



Selector Spool



Hand Metering Unit




Directional Spool

Mechanical Linkage

140

Steering System - Gradual Left Turn During a GRADUAL LEFT TURN with the engine running, the steering pump sends supply oil past the secondary steering diverter valve to the steering control valve and the hand metering unit. When the steering wheel is turned counterclockwise to make a LEFT TURN, pilot oil from the hand metering unit flows past the left neutralizer valve to the steering control valve to the selector spool. The selector spool shifts down, and oil flows to the end of the directional spool. The directional spool shifts down against the force of the centering spring. When the directional spool moves down, main steering pump oil flows through the directional spool to the rod end of the left steering cylinder and the head end of the right steering cylinder. At the same time that oil flows into the two steering cylinders, return oil flows from the head end of the left steering cylinder and the rod end of the right steering cylinder through the directional spool and back to the hydraulic tank. The machine articulates to the left for a left turn.

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Text Reference

STEERING SYSTEM FULL LEFT TURN (STEERING NEUTRALIZED)



Selector Spool

Steering Cylinders



Hand Metering Unit




Directional Spool

Mechanical Linkage

141

Steering System - Full Left Turn - Steering Neutralized During a FULL LEFT TURN with the engine running, the left striker contacts the left neutralizer valve. The neutralizer valve moves to the closed position, and oil flow from the hand metering unit to the steering control valve is blocked at the left neutralizer valve. The steering selector spool and the steering directional spool return to the center position. Flow to the steering cylinders is blocked at the directional spool in the steering control valve, and the machine stops turning. The neutralizer valves prevent the machine loader frame from contacting the machine rear frame when articulating fully to the right or left.

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Text Reference

STEERING SYSTEM GRADUAL LEFT TURN / SECONDARY STEERING



Selector Spool

Steering Cylinders



Hand Metering Unit




Directional Spool

Mechanical Linkage

142 If the steering pump or the engine fails, the primary pressure switch will sense the low pressure in the steering system. The primary steering pressure switch closes and sends a signal to the monitoring system which causes a Category 3 Warning to occur. After a one second delay, the Power Train ECM energizes the intermediate relay for the secondary steering pump and the electric motor actuates. At the same time, the secondary steering indicator on the monitoring system display illuminates. The secondary steering pump draws oil from the hydraulic tank. The oil then flows to the secondary steering valve, which causes the check valve in the hydraulic line from the steering pump to close and the check valve in the hydraulic line from the secondary steering pump to open. The closed check valve prevents pressure oil from flowing to the steering pump. Oil from the secondary steering pump flows past the secondary steering valve to the steering control valve and hand metering unit. Pilot oil from the hand metering unit flows past the left neutralizer valve and moves the steering selector spool. The oil then flows through the steering selector spool and moves the directional spool, allowing the secondary steering oil to flow to the rod end of the left steering cylinder and to the head end of the right steering cylinder. Secondary steering provides a method to steer the machine to a safe location if a failure occurs in the primary steering pump or in the engine.

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Text Reference

1

4

2

5

3

143

Secondary Steering This illustration shows the location of the secondary steering components in the rear frame (1). If the steering pump or the engine fails, the primary pressure switch will sense the low pressure in the steering system. The primary steering pressure switch closes and sends a signal to the monitoring system which causes a Category 3 Warning to occur. After a one second delay, the transmission electronic control module energizes the intermediate relay (4) for the secondary steering pump and the electric motor actuates. At the same time, the secondary steering indicator on the monitoring system display turns ON. The secondary steering pump (3) draws oil from the hydraulic tank. The oil then flows to the secondary steering diverter valve (2), which causes the check valve in the hydraulic line from the steering pump to close and the check valve in the hydraulic line from the secondary steering pump to open. The closed check valve prevents pressure oil from flowing to the steering pump. The secondary steering motor will be de-energized when either the ground speed is 0 rpm or a faulted TOS sensor signal for more than five seconds.

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Text Reference

NOTE: The secondary steering pump does not produce the same amount of flow as the main steering system pump. Secondary steering operations are reduced compared to normal operation. Secondary steering provides a method to steer the machine to a safe location if a failure occurs in the primary steering system or in the engine.

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Text Reference

6

3 2 7

1

8

4

5

144

The secondary steering diverter (1) valve directs oil from the secondary steering oil to the steering control valve when the primary pressure switch (3) senses a loss of oil pressure in the primary steering system and the ground speed is greater than 0 rpm. The primary pressure switch sends a signal to the Power Train ECM and the ECM enables the secondary steering pump motor. When the engine is running and the steering pump is supplying oil to the steering system, oil flows into the diverter valve through the line (6) and oil also flows over the check valve (5) through the line (8) to the steering control valve (not shown). At this time, the oil pressure in the primary steering system holds the check valve (4) against the seat. When the primary steering pressure switch senses a loss of oil pressure in the primary system, the secondary system is initiated. At this time, the primary pressure switch is closed and illuminates the primary steering warning LED. Oil flows into the diverter valve through the line (7), over the check valve (4), and out to the steering control valve through the line (8). At this time, the check valve (5) is seated. When the Power Train ECM enables the secondary steering pump motor, the secondary pressure switch (2) measures the oil pressure in the secondary steering system and sends a signal to illuminate the secondary steering warning LED.

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Text Reference

STEERING SYSTEM COMPONENTS COMMAND CONTROL STEERING

Steering Pump Steering Pilot Valve

Hydraulic Tank

Neutralizer Valves Steering Screened Secondary Steering Secondary Steering Steering and Diverter Valve Pump And Motor Cylinder Control Valve Orifice Manifold Quad Check Valves

145

This illustration shows the location of the components for the optional CCS steering system for the 966H and the 972H Wheel Loaders. The hydraulic tank is common to all hydraulic systems on the machine. INSTRUCTOR NOTE: The color codes used for hydraulic oil throughout this presentation are: Red

- System or high pressure

Red and White Stripes

- Reduced pressure

Orange

- Pilot pressure

Blue

- Blocked oil

Green

- Tank or return oil

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Text Reference

COMMAND CONTROL STEERING HYDRAULIC SYSTEM

From Implement Control Valve

Pilot Control Valve Quad Check Valve

Shuttle Valve

Neutralizer Valve Neutralizer Valve Steering Control Valve

Steering Pump

Screened Orifice Manifold

Steering Cylinders

146

This diagram shows the components and oil flow for the 966H/972H Command Control Steering system. The primary steering system is made up of two basic circuits: the main system and the pilot system. The steering system includes a third circuit if the 966H/972H is equipped with the optional secondary steering system. The main steering circuit consists of: the steering pump, the steering control valve, the steering cylinders, the back-up relief valve, and the hydraulic oil tank. The variable displacement piston steering pump draws oil (green) from the tank and sends flow (red) to the steering control valve. The steering valve is equipped with a directional spool which directs oil to the head end of one steering cylinder and to the head end of the other steering cylinder for machine articulation. Also, the steering control valve sends load sensing oil (green) to the pump control valve on the steering pump to control upstroking and destroking. This diagram shows the system in the HOLD position. The oil (blue) to the steering cylinders is blocked.

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Text Reference

The steering pilot circuit consists of: the steering pilot control valve, the steering quad check valve, the screened orifice manifold, and two neutralizer valves. The pilot system supply oil comes from the implement control valve. When the steering wheel is moved to the left or right, the steering pilot control valve supplies oil through the quad check valve. Then, oil flows through the respective neutralizer valve to the end of the respective directional spool in the steering control valve. The directional spool directs pump supply oil to the correct ends of the steering cylinders. The optional secondary steering system (not shown) consists of: the secondary steering pump and motor and the secondary steering valve. The secondary steering valve contains two check valves, the primary steering pressure switch, and the secondary steering pressure switch.

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Text Reference

QUAD CHECK VALVE LEFT TURN Check Valves

From Pilot Control Valve

Lower Setting

Higher Setting

To Main Control Valve

147

This graphic shows the position of the quad check valve during a left turn. Oil flows from the steering pilot control valve through one side of the quad check valve. The quad check valve consists of four check valves in two sets of two valves each. In each set of two valves, one check valve has a higher cracking pressure than the other valve. One set of check valves are for left turns and the other set of check valves are for right turns. The purpose of the steering quad check valve is to provide an alternative path for pilot oil returning from the non-activated side of the main control valve spool. The normal path for this oil returning to the tank is through the screened orifice manifold (not shown). The check valves with the lower setting prevent return oil from the non-activated spool end to flow through the quad check valve back to the steering pilot valve and to the tank. If the normal path for return pilot oil is blocked in the screened orifice manifold, the return oil will unseat the check valves with the higher setting and allow the oil to return through the steering pilot valve to the tank.

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Text Reference

148

1 2

3

5

4 149

Steering Pilot Valve The Command Control Steering (CCS) pilot control valve (1) is identical to the valve used on the "G" Series II machines. The steering pilot control valve consists of the directional control valve section and the pressure regulating valve section. Also shown is the pilot oil in pressure tap (2) and the pilot lines (3) to the steering control valve In the Command Control System (CCS) on the "H" Series machines, the pilot oil flows to the pilot control valve through the hose (4) that is connected to the implement control valve in the front frame. Also shown in the lower illustration is the location of the quad check valve (5) in the loader frame.

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Text Reference

1

150

2

3

4 151 8 7

5 6 Located in the front frame is the steering drive shaft (1) for the pilot control valve. This shaft is connected to the input shaft on one end with the other end connected to the steering wheel shaft. Also shown in the upper illustration is the neutral pilot pressure tap (2) located remotely on the loader frame right side. Neutral pilot pressure is the oil pressure in the directional control valve section of the pilot valve in the NO TURN position. The lower illustration shows the screen orifice manifold (7) located on the rear frame between the upper and lower hitch pins. The manifold includes the block, the screens (5), and the orifices (6). Attached to the tees are the right pressure tap (3) and left pressure tap (4). The pressure taps are for measuring the output pressure to each end of the spool in the steering control valve. The tubing connected to the manifold is a drain line to the hydraulic tank. Also shown is the steering control valve (8).

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Text Reference

STEERING PILOT VALVE NO TURN

A

To Steering Control Valve To Steering Control Valve

To Steering Control Valve

Pilot Oil Ports

Input Shaft Connected to Steering Wheel

Directional Control Valve

A


Cam

Plunger

Regulating Spring From Implement Control Valve Body Piston

Pressure Regulating Valve

To Hydraulic Tank


Adjustment Screw


Section A-A

152

Steering Pilot Valve - No Turn This illustration shows the components in the steering pilot valve. When the input shaft that is connected to the steering wheel is in the NO TURN position, the flow of pilot oil through the steering pilot valve is blocked by the pressure regulating valve.

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Text Reference

STEERING PILOT VALVE RIGHT TURN To Steering Control Valve

A



Pilot Oil Ports

Input Shaft Connect ed t o St eering Wheel


A


Cam Plunger Orifice Regulating Spring From Implement Control Valve Body

Pressure Regulating Valve

Piston

To Hydraulic Tank


Adjustment Screw Directional Control Valve

Section A-A

153

Steering Pilot Valve - Right Turn When the steering wheel is turned to the right, the steering wheel causes rotation of the steering column, the steering shaft, the input shaft, the cam and the directional control valve. The cam moves the plunger against the spring and the pressure regulating valve spool. Pilot oil from the pump flows between the pressure regulating valve spool and the valve body, which function as an orifice. As the regulating valve moves down, the size of the orifice increases. The larger orifice creates a smaller pressure drop which increases the pressure of the pilot oil to the directional control valve. Also, the pilot oil flows through the orifice in the pressure regulating valve. The force of the pilot oil pressure between the piston and the regulating valve pushes up the regulating valve against the spring. The flow of the pilot oil is proportional to the downward movement pressure regulating valve spool. The pilot pressure controls the steering speed. Increasing the flow of pilot oil between the body and the pressure regulating valve will increase the steering cycle time.

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Text Reference

As the steering wheel is rotated, the directional control valve also rotates. This movement directs pilot oil from the pressure regulating valve to the quad check valve, the neutralizer valves, to the ends of the directional spool in the steering control valve. When the pilot pressure moves the steering control valve directional spool to the RIGHT TURN position, the steering control valve directs main pump oil to the head end of the left steering cylinder and the rod end of the right steering cylinder. The machine articulates to the right. When the steering wheel is returned to the CENTER position, the flow of pilot oil to the steering control valve directional spool is blocked. The centering spring in the steering control valve moves the directional spool to the neutral position and the machine stops articulating. NOTE: The machine turning speed depends on the rotational position of the steering wheel. The farther the steering wheel is turned, the faster the machine will turn. The turning speed of the machine does not depend on how fast the steering wheel is turned.

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Text Reference

STEERING HYDRAULIC SYSTEM (CCS) HOLD

Pump Group To Implement Circuit

Steering Cylinders

From Implement Circuit


Cylinder Crossover Relief Valve

Steering Pilot Valve

Shuttle Valve


Makeup Ball Check Valves

Screened Orifice Manifold Quad Check Valve

Directional Spool

Neutralizer Valves Pressure Reducing Valve Secondary Steering Pump and Motor


Shuttle Valve

M


Secondary Steering Diverter Valve From Implement Control Valve

154

Steering System - Command Control Steering This illustration shows the optional Command Control Steering (CCS) schematic in the HOLD position. When the engine is running and the steering system is in HOLD, oil is drawn from the hydraulic tank by the steering pump. The oil flows past the secondary steering diverter valve to the back-up relief valve and is blocked at the directional stem in the steering control valve. Also, the oil flows through the pressure relief valve At this time, the pressure setting of the reducing valve is lower than the pressure of the pilot oil. The pilot oil pressure shifts the shuttle valve to the right, blocks the oil from the steering control valve at the shuttle valve, and pilot oil flows to the steering pilot valve. The pilot oil is blocked at the steering pilot valve. The signal pressure sensed at the pump control valve on the steering pump is same as the blocked oil at the right and left steering cylinders. The steering pump will be upstroked to the signal demanded at the pump control valve.

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Text Reference

STEERING HYDRAULIC SYSTEM LEFT TURN

Pump Group To Implement Circuit

Steering Cylinders



Cylinder Crossover Relief Valve

Steering Pilot Valve



Shuttle Valve

Makeup Ball Check Valves

Screened Orifice Manifold Quad Check Valve

Directional Spool

Neutralizer Valves Pressure Reducing Valve Secondary Steering Pump and Motor

Pump Back-up Relief Valve

Shuttle Valve

M

Secondary Steering Diverter Valve From Implement Control Valve

155

This illustration shows the optional CCS system in a LEFT TURN. When the operator turns the steering wheel to the left, torque is transmitted through the steering column and the steering shaft to the steering pilot valve input shaft. The pilot valve located in the loader frame directs pilot oil through the quad check valve, through the neutralizer, and to the directional spool in the steering control valve. Turning the steering wheel to a greater angle from the neutral position increases the flow of pilot oil to the directional spool in the steering control valve. Increased flow of pilot oil to the steering control valve moves the directional spool further from the neutral (blocking) position and allows greater flow of steering pump oil to the steering cylinders. When the pilot oil shifts the directional spool to the LEFT TURN position, steering pump oil is sent to the head end of the right steering cylinder and to the rod end of the left steering cylinder. The machine articulates to the left for a left turn. The pressure in the steering cylinders is also sent to the shuttle valve. The cylinder pressure moves the shuttle valve up and becomes the signal pressure to the steering pump control valve. The signal pressure is sensed in the margin spool spring chamber of the control valve. The signal pressure combines with the force of the margin spring and causes the pump to UPSTROKE.

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Text Reference

The supply oil from the steering pump flows over the back-up relief valve. If the pressure exceeds 23500 kPa (3400 psi), the back-up relief valve opens and excess oil flows to the hydraulic tank. Also, the steering control valve is equipped with a pressure reducing valve. The reducing valve will supply pilot oil to the steering pilot valve if the pilot oil supply is lost. The steering control valve is also equipped with a crossover relief valve. In case of a pressure spike above 25600 kPa (3700 psi) as the machine is articulating, the crossover relief valve will open and send the excessive oil pressure to the hydraulic tank. When the machine fully articulates, the stop mounted on the loader frame contacts the neutralizer valve mounted on the rear frame. This action stops the flow of pilot oil from the pilot valve to the directional spool. The directional spool shifts to the CENTER position and the steering oil to the cylinders is blocked. Also, when the steering wheel is returned to the CENTER position, the flow of pilot oil to the directional spool is blocked. The centering spring in the steering control valve returns the directional spool to the neutral position, and the machine stops turning. The pilot valve is mounted on the front frame while the steering wheel and shaft are mounted on the rear frame. As the machine begins to turn, the shaft for the steering pilot valve begins to rotate back to the neutral position. As the shaft rotates closer to the neutral position, the turning speed of the machine is reduced due to lower pilot pressure to the steering control valve directional spool. However, the machine will continue to turn until the steering wheel returns to the center position. As long as the pilot directional valve is rotated from the neutral position and the neutralizer valves are not closed, pilot oil will flow to the steering control valve directional spool. NOTE: The machine turning speed depends on the rotational position of the steering wheel. The farther the steering wheel is turned, the faster the machine will turn. The turning speed of the machine does not depend on how fast the steering wheel is rotated.

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Text Reference

BRAKE AND HYDRAULIC FAN SYSTEM COMPONENTS

Brake and Hydraulic Fan Pump

Engine ECM

Brake Pedal

Hydraulic Tank

Parking Brake Valve And Pressure Switch

Hydraulic Fan Motor

Service Brake Valve

Hydraulic Oil Cooler

Accumulator Charging Valve, Brake Pressure Switch and Fan Solenoid Valve

Rear Service Brakes

Accumulators

Parking Brake

Front Service Brakes

156

BRAKE AND HYDRAULIC FAN SYSTEM COMPONENTS Shown are the brake and hydraulic fan system components on the 966H and 972H Wheel Loaders. The brake system and the hydraulic fan system share the same pump. The hydraulic tank is common to both the brake system and the hydraulic fan system. The brake system components are: - Accumulator charging valve and brake pressure switch - Brake accumulators - Service brake valve - Front and rear service brakes - Parking brake valve and parking brake pressure switch - Parking brake - Brake and hydraulic fan pump - Service brake pedal

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The hydraulic fan system components are: - Accumulator charging valve and fan solenoid valve - Hydraulic fan motor - Hydraulic oil cooler - Engine Electronic Control Module (ECM) - Brake and hydraulic fan pump

Text Reference

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Text Reference

BRAKE AND HYDRAULIC FAN HYDRAULIC SYSTEM ACCUMULATORS CUT IN REDUCED FAN SPEED Left Brake Pedal

Right Brake Pedal

Rear Service Brakes

Parking Brake Valve


Parking Brake Actuator

Hydraulic Fan Motor

Rear Brake Accumulator Accumulator Charging Valve and Fan Solenoid Valve

Service Brake Valve


Parking Brake

Front Brake Accumulator

Relief Valve

Inverse Shuttle Valve

Brake Pressure Switch

Fan Solenoid Valve

Cut In Valve Cut Out Valve

Resolver Valve

Pump Control Valve

Check Valve Screen Priority Valve

Oil Cooler

Flow Control Spool Pressure Cutoff Spool

Actuator Brake and Hydraulic Fan Pump

Filter

Min Angle

Case Drain Filter

Hydraulic Tank

157 Brake And Hydraulic Fan System - Cut In And Minimum Fan Speed This illustration shows the brake system and hydraulic fan system schematic. In the schematic, the accumulator charge pressure has dropped below 12175 kPa (1760 psi). The cut-in valve is shifted to the left. The brake and hydraulic fan pump draws oil from the hydraulic tank and directs the flow of oil to the accumulator charging valve and fan solenoid valve. The charge pressure for the brake accumulators is below 12175 kPa (1760 psi), the cut-in valve is shifted to the left, and the system oil flows to the resolver valve. The resolver valve allows the higher of the two pressures between the signal from the fan solenoid and from the cut-in valve to flow to the flow control spool of the pump control valve. In this instance the oil from the cut-in valve is at a higher pressure. The flow control spool controls the displacement of the brake and hydraulic fan pump. At this time, the pump will upstroke. Also, oil also flows to the lower port on the priority valve, which shifts the priority valve upward and partially blocks the flow of oil to the hydraulic fan motor. Oil also flows past the screen, the check valve, and the orifice to the inverse shuttle valve. The oil flowing into the inverse shuttle valve continues until both the accumulators are charged. The inverse shuttle valve maintains equal pressure between both brake accumulators. The system is also equipped with a relief valve to limit the brake system pressure.

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Text Reference

BRAKE AND HYDRAULIC FAN HYDRAULIC SYSTEM MINIMUM FAN SPEED AT CUT OUT

Left Brake Pedal

Right Brake Pedal

Rear Service Brakes

Parking Brake Valve



Hydraulic Fan Motor


Service Brake Valve


Parking Brake


Relief Valve

Inverse Shuttle Valve Brake Pressure Switch

Fan Solenoid Valve

Cut In Valve Cut Out Valve

Resolver Valve

Pump Control Valve


Oil Cooler

Flow Control Spool Pressure Cutoff Spool

Actuator Brake and Hydraulic Fan Pump

Filter

Min Angle

Case Drain Filter

Hydraulic Tank

158

Brake And Hydraulic Fan System - Minimum Fan Speed At Cut Out This illustration shows the brake system and hydraulic fan system schematic. In the schematic, the accumulators are charged and the parking brake is disengaged. In the system, the brake and hydraulic fan pump draws oil from the hydraulic tank and directs the flow of oil to the accumulator charging valve and fan solenoid valve. This system is designed for the brake system to have priority over the hydraulic fan system. The supply oil has charged the accumulators to 15165 kPa (2200 psi). The cut-out valve momentarily dropped downward to exhaust the oil from the right side of the cut-in valve to tank. The cut-in valve shifts to the right. The oil that was directed through the resolver valve as a signal to the pump control valve drops to tank level. The resolver valve shifts and the oil from the fan solenoid valve is directed to the pump control valve.

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Text Reference

The amount of oil that is flowing into the hydraulic motor is determined by the fan solenoid valve which controls pressure back to the pump control valve through the load sense line. When the brake accumulators are charged (as shown), the pressure from the pump overrides the force of the priority valve spring. The priority valve opens and the supply oil is directed to the hydraulic motor. If all the key target temperatures are below the default values of the particular sensors, the hydraulic fan pump will supply sufficient oil flow to rotate the hydraulic fan motor at minimum fan speed. The minimum fan speed is calibrated through Caterpillar Electronic Technician (ET).

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Text Reference

BRAKE AND HYDRAULIC FAN HYDRAULIC SYSTEM MAXIMUM FAN SPEED AT CUT OUT

Left Brake Pedal

Right Brake Pedal

Rear Service Brakes

Parking Brake Valve


Hydraulic Fan Motor Parking Brake


Service Brake Valve




Relief Valve

Inverse Shuttle Valve Brake Pressure Switch

Fan Solenoid Valve

Cut In Valve

Resolver Valve

Pump Control Valve


Oil Cooler

Flow Control Spool Pressure Cutoff Spool Actuator

Brake and Hydraulic Fan Pump

Filter

Cut Out Valve

Min Angle

Case Drain Filter

Hydraulic Tank

159 Brake and Hydraulic Fan System - Maximum Fan Speed At Cut-Out In this illustration, the brake accumulators are charged and there is no demand for oil from the brake system. In the Brake and Hydraulic Fan System, the brake and hydraulic fan pump draws oil from the hydraulic tank and directs the flow of oil to the accumulator charging valve and fan solenoid valve. With no demand by the brake system for oil, the hydraulic fan system has priority. The amount of oil that is flowing into the hydraulic fan motor is determined by the fan solenoid valve, which feeds pressure back to the pump control valve through the load sense line. When the brake accumulators are charged, the oil supplied by the pump overrides the force of the priority valve spring. The priority valve opens and the supply oil is directed to the hydraulic motor. As one or more of the key target temperatures rise above the default values of the particular sensors, the current to the solenoid valve decreases. The fan solenoid valve shifts upward proportionally current reduction. The increase in oil flowing through the fan solenoid valve will increase the force on the flow control spool. The flow control spool shifts proportionally to the left and oil from behind the large actuator is allowed to flow to the hydraulic tank. The brake and hydraulic fan pump will upstroke, increase the fan speed, and move more air through the radiator group. The pump supplies sufficient oil flow to rotate the hydraulic fan motor at maximum fan speed.

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Text Reference

The maximum fan speed is controlled by the Engine ECM and calibrated through Caterpillar Electronic Technician (ET). If the current to the fan solenoid valve is interrupted, the fan solenoid valve shifts totally upward. The flow control spool shifts to the left and drain off all the oil from behind the actuator. The swashplate to move to maximum angle and the fan motor rotates at maximum rpm. The pump discharge pressure will raise until the pressure at the cutoff spool overrides the spring force. The pressure cutoff spool shifts to the right. Pump discharge oil flows to the right side of the actuator and shifts the swashplate (not shown) to minimum angle, destroking the pump.

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Text Reference

HYDRAULIC FAN SYSTEM CONTROL Caterpillar Monitoring System

Engine ECM

Cat Data Link

15 10 5

2

20 25 X100

0

MPH km/h

30

44

INPUT COMPONENTS

INPUT COMPONENTS

Hydraulic Oil Temperature Sensor

Intake Manifold Air Temperature Sensor Engine Coolant Temperature Sensor OUTPUT COMPONENT Fan Solenoid Valve

160

In the hydraulic fan system, the speed of the fan and the output of the brake and hydraulic fan pump is directly controlled by the Engine ECM through the fan solenoid valve. The Engine ECM interprets signals from the three sensors on the machine. Then, the Engine ECM sends a proportional current to the hydraulic fan solenoid valve. The following sensors report directly to the Engine ECM: - Intake manifold air temperature - Engine coolant The sensor for the intake manifold air temperature is a passive sensor that is used to measure temperature. The sensor sends an analog signal to the Engine ECM. The analog signal will increase in voltage as the temperature of the air increases. The engine coolant temperature sensor is a passive sensor that is used to measure the temperatures of liquids. The sensor sends an analog signal to the Engine ECM. The analog signal will increase in voltage as the temperature of the engine coolant increases. The hydraulic oil temperature sensor is used for the measurement of liquid temperatures. The sensor sends an analog output signal to the Caterpillar Monitoring System. The analog signal will increase in voltage as the temperature of the oil increases. Then, the Cat Monitoring System sends the temperature signal to the Engine ECM over the Cat Data Link.

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Text Reference

When the engine is started, the brake and hydraulic fan pump will run at minimum fan speed until one of the temperature sensors read higher than the key target temperature. The following conditions must be met, in order to run the fan system at minimum fan speed: - The intake manifold air temperature is below 49° C (120° F). - The hydraulic oil temperature is below 90° C (195° F). - The engine coolant temperature is below 89° C (192° F). As one or more of the sensors reads a temperature that is above the key target temperature, the Engine ECM interprets a demand for additional cooling. The Engine ECM starts sending a reduced amount of current from the Engine ECM to the solenoid valve. The solenoid valve will move proportionally, in the de-energized direction. Then, a load sense signal will be sent to the pump control valve and the brake and hydraulic fan pump will upstroke proportionally. The minimum speed of the fan and the maximum speed of the fan are held in the Engine ECM. The set limits for speed of the hydraulic fan can be changed through Caterpillar Electronic Technician. For additional information regarding the calibration of the hydraulic fan system, refer to the Testing and Adjusting, "Hydraulic Fan System - Test and Adjust."

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DEMAND FAN CIRCUIT

Engine ECM

J2

Analog Temperature Sensor Return

30

Coolant Temperature Signal Main Display Module 2

Text Reference

Intake Manifold Air Temperature

BU 18 PK 18 13

56

Cat Data Link

Ground

Signal Ground

Engine Coolant Temperature Sensor BU 18 PK 18

1 2

Signal Ground

Intake Manifold Air Temperature Sensor

J1 10

1 2

Hyd Temp Sensor

GY 18 BK 18

1 2

Signal Ground

Variable Speed Fan Control

43

Variable Speed Fan Control

51

YL 18 BR 18

1 2 Variable Speed Fan Solenoid

Hydraulic Oil Temperature Sensor

161

The Engine ECM receives input signals from the engine coolant temperature sensor and the intake manifold air temperature sensor. Hydraulic oil temperature sensor signals are sent to the Caterpillar Monitoring System main display module and transmitted over the Cat Data Link to the Engine ECM. The Engine ECM processes the input signals and sends corresponding output signals to the variable speed fan solenoid valve. NOTE: The variable speed fan control feature can be enabled, disabled, and calibrated using the ET Service Tool. The variable speed fan default setting is enabled.

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Text Reference

162

1

2

3

163

The coolant temperature sensor (1) is installed in the jacket water and located on the front of the engine and the rear of the machine. The sensor sends an input to the Engine ECM (3) with the temperature of the engine coolant. The intake manifold air temperature sensor (2) is located in the intake manifold on the left side of the machine. The sensor also sends an input to the Engine ECM (3) with the temperature of the air in the intake manifold.

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Text Reference

2

1 164

3

4

165

The hydraulic oil temperature sender (1) is located on the bottom of the hydraulic tank (2) behind the cab. The sender sends an input to the Engine ECM (not shown) with the temperature of the hydraulic oil. The hydraulic fan solenoid (3) is installed on the accumulator charging valve and solenoid valve (4). The solenoid valve is an output from the Engine ECM. The valve controls the signal oil to the pump control valve.

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Text Reference

3 2

1

166

Brake and Hydraulic Fan Pump The brake and hydraulic fan pump is (1) located on the left side of the machine. The pump is installed on the engine and is driven by the gear train in the front cover. The pump is a variable displacement piston pump that is upstroked when the demand for more oil flow is commanded by the pump control valve. Located on the engine is the accumulator charging valve and fan solenoid. The valve is also located on the same side of the engine as the pump. Also installed on the engine is the Engine ECM (3). The Engine ECM is an A4E4 with a 120 pin connector and a 70 pin connector. The Engine ECM reads key target temperatures and sends current to the solenoid valve on the accumulator charging valve and fan solenoid (2). These temperatures will determine the amount of oil sent to the hydraulic fan motor in order to cool the machine components.

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Text Reference

BRAKE AND HYDRAULIC FAN PUMP ENGINE OFF

Pump Discharge

Signal

Large Actuator

Swashplate

Drive Shaft

Margin Spring

Flow Compensator Spool

Pressure Compensator Spool Piston and Barrel Assembly

Small Actuator and Bias Spring

167

When the engine is OFF, the bias spring holds the swashplate at maximum angle. When the engine is started, the pump drive shaft starts to rotate. Oil is drawn into the piston bore from the pump inlet. As the pistons and barrel assembly rotate, the oil is forced out the pump discharge.

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Text Reference

BRAKE AND HYDRAULIC FAN PUMP LOW PRESSURE STANDBY Signal Pressure

Pump Discharge

Large Actuator

Swashplate

Margin Spring


Pressure Compensator Spool Small Actuator Bias Spring

168

Brake And Hydraulic Fan Pump - Low Pressure Standby When no flow is demanded, no signal pressure is generated. Flow generated by the pump creates "low pressure standby." The pump produces sufficient flow to compensate for system leakage at low pressure standby to provide instantaneous implement response when an implement is actuated. At machine start-up, the bias spring holds the swashplate at maximum angle. As the pump produces flow, system pressure begins to increase because the flow is blocked in the system. This pressure is felt under both the flow compensator spool and the pressure compensator spool. The flow compensator spool moves up against the margin spring and permits system oil to flow around the pressure compensator spool to the large actuator piston. As pressure in the large actuator piston increases, the large actuator piston overcomes the force of the bias spring and the pressure in the small actuator piston and moves the swashplate to a reduced angle. The large actuator piston will move to the right until the cross-drilled passage in the spool is uncovered. Oil in the large actuator piston can then drained to the pump case. At this minimum angle, the pump will produce sufficient flow to make up for system leakage.

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Text Reference

NOTE: Low pressure standby is usually higher than margin pressure. This characteristic is due to the oil flow being blocked by the closed-centered control valves when all the valves are in HOLD. The blocked pump supply oil pushes the margin spool up and compresses the margin spool spring more when the pump is at low pressure standby than during a constant flow condition (which will be discussed later in detail).

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Text Reference

BRAKE AND HYDRAULIC FAN PUMP UPSTROKE Signal Pressure

Pump Discharge Large Actuator

Reduced Pressure

Swashplate

Margin Spring



169

Brake And Hydraulic Fan Pump - Upstroke When the demand for flow is increased, a signal pressure equal to the work port pressure is sent to the margin spring chamber. This signal pressure increases the force (margin spring plus signal pressure) at the top of the flow compensator spool to become higher than the supply pressure at the bottom of the spool. The spool then moves down, blocks oil to the large actuator and opens a passage to drain. Pressure at the large actuator piston is reduced or eliminated, which allows the bias spring and small piston to move the swashplate to an increased angle. The pump will upstroke to produce the required increase in flow.

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Text Reference

BRAKE AND HYDRAULIC FAN PUMP Signal Pressure

CONSTANT FLOW Pump Discharge Large Actuator

Constant Pressure

Swashplate

Margin Spring



170

As pump flow increases, pump supply pressure also increases. When the pump supply pressure increases and equals the sum of the signal pressure plus the margin spring pressure, the flow compensator spool moves to a metering position and the system becomes stabilized.

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Text Reference

BRAKE AND HYDRAULIC FAN PUMP DESTROKE Signal Pressure


Increased Pressure

Swashplate

Margin Spring



171

When less flow is needed, the pump is destroked. To destroke the pump, the force at the bottom of the flow compensator spool becomes higher than at the top. The flow compensator spool then moves up directing more pressure and flow to the large actuator piston. The large actuator piston then overcomes the combined force of the small actuator and bias spring and moves the swashplate to a reduced angle. The pump will now supply less flow.

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Text Reference

BRAKE AND HYDRAULIC FAN PUMP HIGH PRESSURE CUTOFF Signal Pressure


Increased Pressure

Swashplate

Margin Spring



172

The pressure compensator spool is in parallel with the flow compensator spool. The pressure compensator limits the maximum system pressure for any given pump displacement. The spool is forced down during normal operation by the pressure compensator spring. During a stall condition or when system pressure is at maximum, signal pressure is equal to pump supply pressure. The combination of the signal pressure and the margin spring force moves the margin spool down. This movement of the margin spool normally opens a passage in the pump control valve for the oil in the large actuator piston to drain and causes the pump to upstroke. However, since the supply pressure is high enough, the pressure cutoff spool is forced up against the spring. This movement of the pressure compensator spool directs pump system pressure 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 bias spring to destroke the pump. The pump is now at minimum flow and pump supply pressure is at maximum. This feature eliminates the need for a main system relief valve in this brake and hydraulic fan system. Maximum system pressure is adjusted by turning the adjustment screw for the pressure compensator spool.

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1

Text Reference

2

3 4 5 6 7

12 11 8 10

9

173

Accumulator Charge Valve and Hydraulic Fan Solenoid The accumulator charge valve and hydraulic fan solenoid is a priority valve. The operation of the valve determines the oil flow for the hydraulic fan system and the braking system. The amount of flow going to the hydraulic fan motor is determined by a solenoid valve, which feeds pressure back to the load sense line to the pump control valve. A priority valve in the fan drive portion determines whether or not to send flow to the fan. Whenever the brake accumulators are adequately charged, the priority valve will be open, allowing full flow to the fan. However, when brake accumulator pressure is low, the priority valve will be shut off by the brake charge cut-in valve, forcing the majority of the flow to the brake charge section of the block. The brake charge section of the block will send the flow to the brake accumulators to charge them. The two halves are separated by a brake charge check valve, intended to hold the oil pressure within the brake charge section of the block.

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Text Reference

The following components are located on the fan control and brake accumulator charging valve: - Signal line to the fan and brake pump (1) - Fan solenoid valve, an electronic output of the Engine ECM which controls the speed of the cooling fan (2) - Relief valve, limits the maximum pressure in the brake system (3) - Cut-in valve, maintains minimum brake accumulator pressure (4) - Return hose to the hydraulic tank (5) - Cut-out valve, maintains maximum brake accumulator pressure (6) - Brake pressure switch, warns the operator when brake accumulator pressure is low (7) - Inverse shuttle valve, maintains equal charge pressure in both accumulators (8) - Accumulator ports (9) - Pump inlet port (10) - Hydraulic fan motor outlet port (11) - Priority valve, blocks flow to the hydraulic fan motor when the brake accumulators are charging (12)

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1

Text Reference

2

3

174

Service Brake Valve This illustration shows the service brake valve (1). The service brake valve is located under the cab at the articulation hitch. The pressure tap (2) is for the rear brakes and the pressure tap (3) is for the front brakes.

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Rear Brake Accumulator

Front Brake Accumulator To Power Train ECM

Left Brake Pedal

Text Reference

BRAKE SYSTEM

PARKING BRAKE RELEASED

Right Brake Pedal Brake Lights

Rear Axle Brakes

Hydraulic Fan Motor

Service Brake Valve

Accumulator Charging Valve



Front Axle Brakes

Parking Brake Valve


Brake and Hydraulic Fan Pump Parking Brake Tank

175

This illustration shows the brake system with the parking brake disengaged. The parking brake actuator is spring applied and hydraulically released. When the operator pushes the parking brake knob inward, the parking brake valve is shifted mechanically downward allowing brake oil to flow to the parking brake actuator. The springs are compressed and the lever moves the arm downward releasing the parking brake. At this time, the parking brake pressure switch sends a signal to the Power Train ECM informing the ECM that the parking brake is disengaged and the transmission can be shifted to FORWARD or REVERSE. Also, the Power Train ECM turns off the parking brake LED.

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Rear Brake Accumulator

Front Brake Accumulator To Power Train ECM

Left Brake Pedal

Text Reference

BRAKE SYSTEM

PARKING BRAKE RELEASED SERVICE BRAKES APPLIED

Right Brake Pedal Brake Lights

Rear Axle Brakes

Accumulator Charging Valve

Hydraulic Fan Motor

Service Brake Valve



Front Axle Brakes

Parking Brake Valve


Brake and Hydraulic Fan Pump Parking Brake Tank

176

This illustration shows the brake system with the engine running and the parking brake disengaged. The parking brake actuator is spring applied and hydraulically released. When the operator pushes the parking brake knob inward, the parking brake valve is shifted mechanically downward allowing brake oil to flow to the parking brake actuator. The springs are compressed and the lever moves the arm downward releasing the parking brake. At this time, the parking brake pressure switch sends a signal to the Power Train ECM informing the ECM that the parking brake is disengaged and the transmission can be shifted to FORWARD or REVERSE. Also, the Power Train ECM turns off the parking brake LED. Also, this illustration shows the service brakes applied. The right brake pedal is depressed and the service brake valve shifts downward and the charged brake oil is directed to the service brakes. If the machine is equipped with stop lights, the lights will be illuminated.

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Text Reference

SERVICE BRAKE VALVE NOT ACTIVATED

Boot Plunger Return Spring

Plunger Springs Shims

Ball Retainer Ball

Check Valve

Upper Spool Front Brake Port

Tank Port

System Pressure Port Lower Spool

Upper Spool Orifice Upper Spool Passage Tank Port

Rear Brake Port

System Pressure Port

Upper Spool Orifice Lower Spool Passage

Lower Return Spring

177

Service Brake Valve Not Activated The service brake valve has two individual brake ports. Also, the brake valve has two individual spools which control the flow of oil to the 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 upper brake port is 207 kPa (30 psi) higher than the pressure at the lower brake port. Also, the spring force will be proportional to the plunger movement. The brake control valve is equipped with a check valve. The check valve prevents spikes in the tank port from entering the cavity with the plungers springs and acting on the the plunger and eventually transferring to the brake pedal. The brake control valve is also equipped with shims that are between the ball retainer and the plunger spring. 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 BRAKES ACTIVATED

Boot Plunger Return Spring

Plunger Springs Shims

Ball Retainer Ball

Check Valve

Upper Spool Front Brake Port

Tank Port

System Pressure Port Lower Spool

Upper Spool Orifice Upper Spool Passage Tank Port

Rear Brake Port

System Pressure Port Lower Spool Orifice Lower Spool Passage Lower Return Spring

178

Service Brake Valve - Activated In order to initiate the operation of the service brake valve, the operator depresses the brake pedal (not shown). The brake pedal contacts the plunger. The plunger is pushed in the downward direction against the plunger and return springs. The plunger spring puts a downward force on the ball retainer, the ball, the upper spool down, 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 and the upper spool passage into the cavity between the upper spool and the lower spool. The oil pressure on the bottom area of the upper piston puts an upward force on the upper spool pushing the spool against the plunger spring. The upper spool moves the lower spool downward compressing the lower return spring. The rear brake port will then be open to flow from the system pressure port (from the rear brake accumulator). At this time, the oil flows through the lower spool orifice and the lower spool passage into the lower spool spring cavity. The oil pressure on the bottom area of the lower spool puts an upward force on the lower spool pushing the spool against upper spool and the plunger spring. The spool movements are equalized.

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Text Reference

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 combination of the return springs and the upward force on the upper and lower spools move the spools upward. When the service brake pedal is fully released, the service brake ports will be open to the tank ports.

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Text Reference

CATERPILLAR MONITORING SYSTEM Gauge Cluster Module

Speedometer/ Tachometer Module

12

MPH km/h

Main Display Module

Action Lamp

° CkPa Miles KM RPM LiterSERV CODE X10

3F Action Alarm

Input Components

Display Data Link

Cat Data Link

Transmission ECM

Implement ECM Input Components

Engine ECM

Input Components

Input Components

179

CATERPILLAR MONITORING SYSTEM This illustration shows the the relationship of the Caterpillar Monitoring System to the other ECMs on the "H" Series Wheel Loaders. Information displayed on the Caterpillar Monitoring System is sent to the main display module from input components in the monitoring system. Information is also received by the monitoring system from the Transmission ECM, Engine ECM, and Implement ECM over the CAT Data Link. The "H" Series Wheel Loaders use a programmable Caterpillar Monitoring System main display module, which enables installation of updated software that may include future control system features.

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Text Reference

180

Fuel Level Sender The fuel level sender is located on the top of the fuel tank on the right side at the rear of the machine. The sender can be accessed by raising the engine hood. The sender measures the depth of fuel in the tank. The fuel level sender has an internal resistance between 28 and 250 Ohms and is connected to pin 9 and the Cat Monitoring System ECM. The quad gauge displays the fuel level. The depth of the fuel in the tank determines the position of the sender float. As the float rotates upward and downward on the sender arm, the resistance of the sender varies according to the level. The output resistance decreases as the fuel level increases and the output resistance increases as the fuel level decreases. NOTE: The fuel level sender can be service separately from the float assembly.

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Text Reference

181

The fuel level indicator is located on the left side of the dash panel. This indicator illuminates when the fuel level is low.

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Text Reference

182

Hydraulic Oil Temperature Sensor The hydraulic oil temperature sensor is located in the lower end of the hydraulic tank. The sensor is a passive temperature sensor with a thermistor at the tip. The voltage output will decrease as the temperature increases in the tank. The signal from the sensor is connected to the Cat Monitoring System ECM.

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Text Reference

2

3

1

183

Brake Pressure Switch The brake pressure switch (1) is located on the right side of the machine below the Engine ECM (2) and next to the engine oil pan (3). The pressure type switch contacts are normally open. When the engine is running, the switch makes contact as the brake accumulator oil pressure increases to approximately 8270 kpa (1200 psi). If the brake pressure decreases to approximately 6890 kPa (1000 psi), the contacts will open the ground path for pin 20 on the Cat Monitoring System ECM. The brake oil pressure alert will begin flashing on the main display module.

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Text Reference

1

184

2

185

Axle Oil Temperature Sensors The above illustrations show the location of the axle oil temperature sensors. The sensor (1) is located in the front differential. The sensor (2) is located in the rear differential. The sensors are passive temperature sensors with a thermistor at the tip. The voltage output of the sensor will decrease as the oil temperature in the respective differentials increases. The front axle temperature sensor is connected to the Cat Monitoring System ECM. The rear axle temperature sensor is connected to the Cat Monitoring System ECM.

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Text Reference

1

2

186

3

4 5 6

7

1 187

5

Filter Bypass Switches In The Right Side Service Bay These illustrations show the locations of the power train filter pressure bypass switch (2) and the hydraulic oil filter bypass switch (7) in the service bay. The power train filter bypass switch (2) is a pressure differential switch which will give a Level 3 Warning when the filter is bypassing. The Cat Monitoring System will announce the warning when the transmission oil temperature is at normal operating temperature. The hydraulic oil filter bypass switch (7) is located on the filter base (1) base. The switch signals for illumination when the pressure is above 138 kPa (20 psi).

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Text Reference

The hydraulic oil S•O•S port (4) (Blue) is located on the filter base (1) and the power train S•O•S port (6) (Purple) is located on the power train filter base (3). Also shown is the brake accumulators (5)

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188 2

3

189

Torque Converter Outlet Temperature Sensor The torque converter outlet temperature sensor (1) is a passive sensor that sends an input temperature signal to the Cat Monitoring System ECM. The monitoring system interprets the temperature signal and moves the needle for the transmission oil temperature indicator (3) to reflect the oil temperature. Also shown is the Engine ECM (2).

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2

3 191

Electrical System The indicator (1) for the electrical system will illuminate when there is a malfunction in the electrical system. The system voltage is too high for normal machine operation or the system voltage is too low for normal machine operation. If the electrical loads are high with low engine speed, the alternator output is increased. If the alert indicator for the electrical system turns off within one minute, the electrical system is operating normally. Overloading may occur during periods of low engine speeds. Revise the operating cycle in order to avoid overloading the electrical system. Overloading the electrical system could result in discharging the batteries.

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Text Reference

If this procedure does not cause the alert indicator to turn off, stop the machine and investigate the cause of the fault. The fault may be caused by an alternator belt that is loose or broken. Also, the cause of the fault might be faulty batteries. If the indicator remains on or near normal operating speeds and with light electrical loads, stop the machine and investigate the cause of the fault. The fault may be caused by an alternator belt that is loose or broken. Also, the cause of the fault maybe the batteries or the alternator . The electrical indicator is connected to the "R" (3) contact on the alternator (2).

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Text Reference

2

1

192

Action Alarm The action alarm (1) is an output of the Cat Monitoring System (pin 4). When the action alarm is audible, the machine needs immediate attention. A safe machine shutdown is required. The main display module will sound the action alarm whenever a warning category 3 problem exists. An alarm for a warning category 3 is a pulsating sound. The alarm for a warning category 2S is a continuous tone. The action alarm does not operate when the engine is stopped. The main display module uses functions in order to determine when the engine is running. The following functions are examples: the engine oil pressure, the alternator speed, and the engine speed. If necessary, the action alarm SOUNDS when the main display module decides that the engine is running. The action alarm is located behind the operator’s seat next to the Implement ECM (2).

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193

Engine Tachometer The tachometer located on the front dash panel shows an analog display of the engine speed in both rpm and km/h. The engine speed is determined by the information sent to the Cat Monitoring System module over the Cat Data Link from the Engine ECM. The crankshaft speed timing sensor and the camshaft speed timing sensor initiate the input signals to the Engine ECM. The Cat Monitoring System also sends the Module Clock signal and the Data signal to the tachometer module.

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CONCLUSION This presentation has provided information on the machine systems for the 966H Wheel Loader that is equipped with a C11 ACERT™ Engine and the 972H Wheel Loader equipped with a C13 ACERT™ Engine. Understanding the information and features accessible using Cat ET can make troubleshooting, diagnosis, and testing easier and more accurate. Always use the latest Service Information to ensure that the most current specifications and test procedures are used. NOTE: For additional information in troubleshooting the engine, refer to the Service Manual module Troubleshooting "C11 and C13 Engines for Caterpillar Built Machines" (RENR9318).

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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, Charge or Torque Converter Oil

Cat Yellow - (Restricted Usage) Identification of Components within a Moving Group

Orange / White Stripes - Reduced Pilot, Charge, or TC Oil Pressure

Brown - Lubricating Oil

Orange / Crosshatch - 2nd Reduction in Pilot, Charge, or TC Oil Pressure

Green - Tank, Sump, or Return Oil

Blue - Trapped Oil

Green / White Stripes Scavenge / Suction Oil or Hydraulic Void

HYDRAULIC SCHEMATIC COLOR CODE This illustration identifies the meanings of the colors used in the hydraulic schematics and cross-sectional views shown throughout this presentation.

English 966h and 972h Whell Loaders (2)

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