KENR5827-00-01-ALL imp

KENR5827 March 2008

Systems Operation 993K Whe Wheel Loader Electrohydraulic Electrohydraulic System LWA1-Up (Machine) Z9K1-Up (Machine) Z9K1-Up (Machine)

SAFETY.CAT.COM

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Important Safety Information Most accidents that t hat involve product operation, maintenance and repair are caused by failure to observe basic safety rules or precautions. An accident can often be avoided by recognizing potentially hazardous situations before an accident occurs. A person must be alert to potential hazards. This person should also have the necessary necess ary training, skills and tools to perform these functions properly. Improper operation, lubrication, maintenance or repair of this product can be dangerous and could result in injury or death. Do not operate or or perform any lubrication, maintenance or repair on this product, until you have read and understood understood the operation, operation, lubrication, maintenance and repair information. information. Safety precautions and warnings are provided in this manual and on the product. If these hazard warnings are not heeded, heeded , bodily injury or death could occur to you or to other persons. The hazards are identi fied by the “Safety Alert Symbol” and followed by a “Signal Word” such as “DANGER”, “WARNING” or “CAUTION”. The Safety Alert “WARNING” label is shown below.

The meaning of this safety alert symbol is as follows: Attention! Attention! Become Become Alert! Your Safety is Involved. The message that appears under the warning explains the hazard and can be either written or pictorially presented. Operations Operations that that may cause product damage are identi fied by “NOTICE” labels on the product and in this publication. Caterpillar cannot anticipate every possible circumstance that might involve a potential hazard. The warnings warnings in this publication and on the product are, therefore, not all inclusive. If a tool, procedure, work method or operating technique that is not speci fically recommended by Caterpillar is used, you must satisfy yourself that it is safe for you and for others. You should also ensure that the product will w ill not be damaged or be made unsafe by the operation, lubrication, maintenance or repair procedures that you choose. The information, information, specifications, and illustrations in this publication are on the basis of information that cations, torques, torques, pressures, pressures, was availabl available at the time that the publication was written. The speci fications, measurements, adjustments, illustrations, and other items can change at any time. These changes can affect the service that is given to the product. Obtain the complete and most current information before you start any job. job. Caterpillar dealers have the most current information available.

When replacemen replacementt parts parts are requir required ed for this product Caterpillar recommends using Caterpilementt parts parts or parts parts with equival equivalent ent lar replac replacemen specifications cations including, but not limited to, physical dimensions, type, strength and material. material. Failure to heed this warning can lead to premature failures, product damage, personal injury or death.

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Table of Contents Systems Systems Operation Operation Section Graphic Color Codes .................. ............................. ....................... ............... ... 4 General General Information Information .................. .............................. ........................ ................ .... 4 Electrical Electrical Input Components ......................... ................................. ........ 10 Electronic Electronic Control Control Module ....................... ................................... .............. .. 15 Electrical Electrical Output Components Components ...................... .............................. ........ 15 Electrohydrau Electrohydraulic lic System System ....................... ................................... ............... ... 18 Pilot Hydraulic System ...................... .................................. .................... ........ 21 Main Hydraulic System ..................... ................................. .................... ........ 24 Piston Pump (Implement) ..................................... 28 Electrohydrau Electrohydraulic lic System Operation ..................... ....................... 30 Hydraulic Hydraulic System Operation Operation ...................... ................................. ........... 35 Ride Control System ............................ ........................................ ................. ..... 45 Hydraulic Hydraulic Fan System ..................... ................................ ..................... ............ 48 Rear Access Egress System System (Operator Lift) ......... 54 Oil Coolers and Cooling System Operation .......... 56

Index Section Index ....................... ................................... ........................ ........................ ...................... .......... 63

3 Electrohydraulic System Table of Contents Contents

4 Electrohydraulic System Systems Operation Section

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Systems Operation Section i02891046

Graphic Color Codes SMCS Code: 5050

Color Codes f or Illustrations

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Illustration 1

(A) Red color – Main pump system pressure

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(B) Red stripes – First reduction of supply pressure

General Information

(C) Red dots – Second reduction of supply pressure

SMCS Code: 5050

(D) Orange color – Signal pressure

Electrohydraulic System Components

(E) Orange stripes – First reduction of signal pressure (F) Orange dots – Second reduction of signal pressure (G) Green color – Suction line, return line, and case drain (H) Blue color – Blocked oil

The electrohydraulic system is electrically controlling the pilot operated system. The pilot system controls the functions of the main control valves. The pilot system consists of an electronic system and a hydraulic system. The electronic system is composed of the following components:

(I) Yellow color – Moving parts and activated valve envelopes

• solenoid valves for the variable displacement

(J) Gray color – Surface area

• implement electronic control module (ECM)

piston pumps

• electrohydraulic control • lift linkage position sensor

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• tilt linkage position sensor • solenoids for the pilot control actuators • hydraulic lockout solenoid valve • solenoids for the float valves The electrohydraulic control consists of the following components:

• lift control lever • tilt control lever • lift control position sensor

Illustration 3

• tilt control position sensor

(4) Implement electronic control module (ECM)

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Lower right side of cab

Implement ECM (4) is located in the electronics bay that is on the lower right side of the cab.

Illustration 2

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Pump compartment (1) Implement pump (180 cc (11.0 in 3)) (2) Implement pump (250 cc (15.3 in 3))(right) (3) Implement pump (250 cc (15.3 in 3))(center)

Implement pumps (1, 2, 3) are located in the center and the right side of the pump compartment that is behind the cab. Implement pump (1) and implement pump (2) have solenoid valves that are mounted on the lower right side of each pump. Implement pump (3) has a solenoid valve that is mounted on the lower left side of the pump.

Illustration 4

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Right side of operator seat (5) Electrohydraulic control (6) Tilt control lever (7) Lift control lever

Electrohydraulic control (5) is located to the right of the operator seat inside the cab. Electrohydraulic control contains lift control lever (7), tilt control lever (6), the lift control position sensor, and the tilt control position sensor.


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Illustration 7

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Main control valves (front view) (10) Pilot control actuators

Illustration 5

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A-pin joint (8) Lift linkage position sensor

Lift linkage position sensor (8) is located at the A-pin joint on the right side of the loader frame.

Illustration 8

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Main control valves (rear view) (10) Pilot control actuators

Pilot control actuators (10) are located on the main control valves. The main control valves are located inside the loader frame.

Illustration 6

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Inside of F-pin joint (9) Tilt linkage position sensor

Tilt linkage position sensor (9) is located on the inside of the F-pin joint on the right tilt lever.

Illustration 9 Inside of loader frame (11) Hydr aulic lockout solenoid valve

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Hydraulic lockout solenoid valve (11) is located on the inside of the loader frame to the left of the main control valves.

Illustration 10

The pilot hydraulic system consists of pilot/axle oil cooler pump (13) and pilot pressure reducing valve (14). Pilot control actuators (10) and hydraulic lockout solenoid valve (11) are also part of the pilot hydraulic system. Pilot/axle oil cooler pump (13) is located on the right rear of the pump drive. Pilot pressure reducing valve (14) is located on the right wall of the pump compartment.

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Inside of loader frame (12) Float valves

Float valves (12) are located on the inside of the loader frame to the right of the main control valves.

Illustration 13

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(15) Tilt cylinders

Illustration 11

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Pump compartment (13) Pilot/axle oil cooler pump

Illustration 14 (16) Left lift cylinder

Illustration 12 Right side of pump compartment (14) Pilot pressure reducing valve

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8 Electrohydraulic System Systems Systems Operation Operation Section

Illustration 15

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(17) Right lift cylinder

The main hydraulic system consists of implement pumps (1, 2, 3), main control valves, tilt cylinders (15), and lift cylinders (16, 17).

Illustration 16

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(18) Hydraulic tank

Implement hydraulic tank (18) is common to the pilot hydraulic system and to the main hydraulic system.

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Electronic Control System Components

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Illustration 17 Block Diagram of the Implement Electronic Control System

The implement electronic control module (ECM) receives input signals from various sensors and from various various switches. switches. The implement implement ECM processes the input and a corresponding output is provided to the solenoids. solenoids. The implement implement ECM also communicates communicates with other electronic control systems via the CAT Data Link.

• Switch (hydraulic lockout)

The implement electronic control system consists consists of the following following components: components:

• Tilt linkage position sensor

•

Implement Implement electronic control module (ECM)

• Lift lever position sensor • Tilt lever position sensor

• Tilt kickout switch • Lift/lower kickout switch • Lift linkage position sensor

Pressure sensors for supply oil oil and pilot oil • Pressure

• Solenoid valve (hydraulic lockout) • Solenoid valves (pump control)

10 Electrohydraulic System Systems Systems Operation Operation Section

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valves) • Solenoid valves ( float valves)

• Tilt back solenoids • Dump solenoids • Lower solenoids • Raise solenoids • CAT Data Link i02942702

Components Electrical Input In put Components SMCS Code: 1400; Code: 1400; 5050

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Illustration 18


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12 Electrohydraulic System Systems Operation Section The electronic control of the system for the Power Train Electric Drive System will utilize a variety of different types of devices that provide input data to the Machine ECM, the Generator ECM and the Motor ECM. Each ECM will use this information to determine the correct output responses that are needed to control the power train functions based on memory and software parameters. All of the system input components that supply inputs to the ECM fall into one of the following groups: sensor type inputs and switch type inputs. The ECM will monitor most of the circuits of the input components for diagnostics. If the ECM determines that an abnormal condition exists in one of the circuits, the ECM will log a Diagnostic Code or an Event Code f or the involved component circuit.

Sensor Inputs Sensors provide an electrical signal to the ECM that constantly changes. The sensor input to an ECM can be one of the several different types of electrical signals. The types of sensor signals are:

Pule Width Modulated (PWM) Sensors When power ed up, the these types of sensors continuously send a Pulse Width Modulated (PWM) square wave signal to the ECM. The voltage of the signal ranges between 0.0 VDC and 5.0 VDC. The ECM monitors the voltage and the duty cycle of the signal. The PWM duty cycle is the percentage of time that the signal is high as compared to the time interval of one complete square wave cycle (hertz). The voltage of the signal corresponds to the duty cycle of the signal. A higher duty cycle results in a higher signal voltage. The oper ating frequency of the signal for most PWM position sensors is approximately 500 ± 80 hertz, however, some PWM senors operate at a frequency of appr oximately 5000 hertz. An ECM will monitor the duty cycle, the voltage and the frequency of the PWM signal. The duty cycle is most commonly used by the ECM as an indication of the sensor signal. Position sensors are the most commonly used type of PWM sensor. Any movement on the axis that is attached to the sensor will change the duty cycle and the voltage of the sensor output signal. The signal frequency can also change slightly, but the frequency change should not be great. The duty cycle of the PWM sensor signal changes according to the direction and amount of movement on the axis.

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When an axis is moved, the ECM will interpret a specific duty cycle as a speci fic axis position. The ECM will determine the position based on the detected travel limits of the axis and the PWM duty cycle for those limits. The ECM determines the axis limits either by a manual calibration procedure that is performed by an operator or by an automatic calibration procedure that is performed by the ECM usually at machine start up. The percentage of duty cycle signal from a typical position sensor that the ECM will recognize as valid is 10 ± 5 percent to 90 ± 5 percent at the extreme ends of the axis movement. A joystick, pedal or actuator that is in the center or neutral position would result in a duty cycle signal of approximately 50 ± 5 percent. An internal pull up voltage is present at all PWM input circuits in the ECM. If the voltage signal is interrupted due to an open circuit or poor connections or if the power supply to the sensor is interrupted, the signal circuit will be pulled high and the ECM will activate a “voltage above normal” diagnostic code.

Voltage Input Sensors Voltage input (active analog) type sensors provide a voltage input signal to the ECM that usually ranges between 0.0 VDC to 5.0 VDC. Active analog sensors are usually used for measuring pressure. The ECM will associate a specific voltage to a speci fic value for the medium that is being measured. Most active analog sensors are powered by the ECM 5.0 VDC power supply and return circuits. An internal pull up voltage is present at all analog input contacts on the ECM. If the voltage signal is interrupted due to an open circuit or poor connections or if the power supply to the sensor is interrupted, the signal circuit will be pulled high and the ECM will activate a “voltage above normal diagnostic” code.

Resistive Input Sensors Passive analog type sensors provide a resistive input signal to the ECM. the ECM also monitors the voltage of the circuit. This type of sensor is usually used for temperature sensors. The ECM will associate a speci fic circuit resistance to a speci fic temperature value for the medium that is being measured Most passive analog sensors are powered by the ECM 5.0 VDC power supply and return circuits.

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An internal pull up voltage is present at all analog input contacts on the ECM. If the voltage signal is interrupted due to an open circuit or poor connections or if the power supply to the sensor is interrupted, the signal cir cuit will be pulled high and the ECM will activate a “voltage above normal” diagnostic code.

Frequency Inputs Speed sensors provide a frequency input signal to the ECM. Most of the speed sensors that are used on late model machines are “ fixed mount” type speed sensors. No adjustment of the sensor is required once the sensor is installed. A magnetic coil in the sensor creates a square wave voltage signal every time that a ferrous metal object, generally a gear tooth, is passed under the sender tip. The ECM will determine the number of square wave signals (frequency) of the sensor circuit in order to determine the speed of the gear that is being monitored.

Switch Inputs Switches provide input signals to the ECM. When a switch is moved to a position that will cause the switch contacts to close, an open signal, a grounded signal or a voltage signal will be detected on the ECM input circuit.

Switch to Ground / Voltage Inputs

13 Electrohydraulic System Systems Operation Section Switch to ground type input circuits have an internal ECM “pull up voltage” that is present at the ECM contacts. An above normal voltage is internally connected to the ECM input circuit through a resister. This allows the ECM to detect a problem in the switch circuit. During normal operation, the switch signal will hold the circuit low, however, circuit conditions such as a disconnection or an open circuit will allow the circuit to be pulled high by the ECM pull up voltage. This will result in an above normal voltage condition at the ECM contact. If this occurs when the ECM is expecting the circuit to be low, the ECM will activate a diagnostic code for the circuit. Switch to battery type input circuits have an internal ECM “pull down voltage” that is present at the ECM contacts. A below normal voltage is internally connected to the ECM input circuit through a resister. This allows the ECM to detect a problem in the switch circuit. The circuit will be held high when the switch contacts are closed to a system voltage source. If the circuit is open or has a bad connection, the pull down voltage will pull the circuit low. If this occurs when the ECM is expecting the circuit to be high, the ECM will activate a diagnostic code for the circuit. Many switches often provide two inputs to the ECM. Generally, the two inputs are switch to ground type inputs. In each switch position, one of the inputs will be grounded and the other input will be fl oating. If the ECM determines that both of the inputs are grounded or that both of the inputs are fl oating at the same time, the ECM will activate a diagnostic code for the switch.

Switches will provide one of the following types of input signals to the ECM:

Switches

• An open signal

Switches will provide one of the following types of inputs to the ECM:

• A ground signal

• Open

• A voltage signal

• Ground

The contacts of a switch have two contact states. The switch contacts are open or the switch contacts are closed.

• When switch contacts are open, no signal is

provided to the corresponding input of the ECM. This “no signal” condition is also referred to as floating.

• When switch contacts are closed, either a ground signal or voltage signal is passed through the switch contacts to the corresponding input of the ECM.

• +Battery Switches are devices that have two contact states. The switch contacts are open or the switch contacts are closed.

• When switch contacts are open, no signal is

provided to the corresponding input of the ECM. This “no signal” condition is also referred to as floating.

• When switch contacts are closed, either a ground signal or +battery signal is provided to the corresponding input of the ECM.


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When a switch provides two inputs to the ECM, the ECM will almost always monitor the switch circuits for diagnostics. If a switch provides only one input to the ECM, the ECM will not monitor the circuit for diagnostics. For connections and wire numbers for any of the following switches, refer to Troubleshooting, “System Schematic” in the back of this manual or refer to the complete machine Electrical System Schematic in the service manual.

Switch (Hydraulic Lockout)

Illustration 19

When the switch is in the LOCKED position, the ECM outputs a power signal through the solenoid switch pole in order to energize the hydraulic lockout solenoid. The solenoid is located on the hydraulic relief valve. When the solenoid is energized, pilot pressure for the implement system will be blocked. Note: Two cir cuits for each switch are used for diagnostic purposes. The circuits are Normally Closed and Normally Open. If the two circuits are in the same state, a circuit failure is present and the ECM will activate a diagnostic code for the switch.

Kickout Set Switch

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Illustration 20

The hydraulic lockout switch informs the ECM that the operator wants to lockout the hydraulics or unlock the hydraulics for the implements. The switch is a two-pole double-throw rocker switch. The switch is located on the right hand console in the cab. The common switch contact 5 for the input pole is connected to frame ground. The N/C contact at switch contact 4 and the N/O contact at contact 6 provide two inputs to the ECM. When the switch is in the LOCKED position, the ECM input at switch contact 4 is switched to ground. This indicates to the ECM that the switch is in the LOCKED position. When the switch is in the UNLOCKED position, the ECM input at switch contact 6 is switch to ground. This indicates to the ECM that the switch is in the UNLOCKED position.

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Kickout Set Switch

The kickout set switch is a momentary rocker switch that is located in the operator compartment. The kickout set switch is used by the operator to set the kickout positions for the lift lower, the lift raise, and the bucket tilt. When the switch is pushed, the ECM records the current position of the lift arm. The ECM uses the recorded position for the lift 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 tiltback will be set.

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The switch has two input connections to the ECM. Switch terminal (1) connects to location (J1-40). Switch terminal (3) connects to location (J1-35). Both of these connections are normally open. When the switch is in the LIFT position, switch terminal (3) is closed to ground. Switch terminal (1) is open or floating. When the switch is in the TILT position, switch terminal (1) is closed to ground. Switch terminal (3) is open or floating.

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Electronic Control Module SMCS Code: 7610-II

IMPLEMENT ECM

Table 1

Status for the Kickout Set Switch Switch Position

(J1-40 NO)

(J1-35 NO)

Lift

Open

Ground

Center

Open

Open

Tilt

Ground

Open

Sensors Illustration 22

Lift/Tilt Lever Position Sensor

Illustration 21

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The Implement electronic control module (ECM) makes decisions that are based on input information and memory information. After the Implement ECM receives the input information and memory information, the Implement ECM sends a corresponding response to the outputs. The inputs and outputs of the Implement ECM are connected to the machine harness by two 70 contact connectors. The ECM is located to the right of the cab under the floorplate that covers the electronics bay of the machine. There are no visual indicators on the ECM. Information from the Implement ECM is shown on the Caterpillar Electronic Technician. The ECM sends the information to the Caterpillar ET via the Cat Data Link. g01337660

The lift sensor measures lift arm angle relative to the NEEF. The sensor is mounted on the RH side of the machine over the A pin, with the housing fi xed to the NEEF and the sensor shaft pointing towards the LH side. The sensor is mounted such that Boom Raise causes a clockwise rotation of the sensor shaft. The tilt sensor measures angle of the tilt lever structure (EFD) relative to the lift arm. The sensor is mounted on the RH side of the machine with the sensor shaft pointing towards the LH side. The sensor housing is fixed to the lift arm and centered over the F pin. The sensor is mounted such that Bucket Rackback causes a clockwise rotation of the sensor shaft.

Note: The ECM is not serviceable. The ECM must be replaced if the ECM is damaged. The ECM must be replaced if the ECM is diagnosed as being faulty. Prior to replacing an ECM, always contact your dealership’s Technical Communicator for possible consultation with Caterpillar. This consultation may greatly reduce repair time. If the ECM must be replaced, refer to Testing and Adjusting, “Electronic Control Module (ECM) - Replace”. i02942703

Electrical Output Components SMCS Code: 1400; 5050


Illustration 23

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Pilot On/Off The pilot solenoid is an ON/OFF valve controlled by the ECM. It is controlled by the Implement Lockout Switch in the cab or from one of the Failure Mode Effects Analysis (FMEA) modes.

Float Valve The Float valve solenoid is activated during a lower kickout and it remains active for 80ms after the lever moves out of detent during a kickout or until the kickout is manually deactivated. Float control is provided to assist the operator in maintaining a level grade while dozing or during cleanup operation. The lift arm will operate as if the lift cylinder was disconnected from the linkage. The bucket will fl oat over any obstacles that are underneath the bucket.

Raise Solenoid The solenoid controls the pilot control actuator for the raise end of the main control spool.

Lower Solenoid The solenoid controls the pilot control actuator for the lift lower end of the main control spool.

Dump Solenoid The solenoid controls the pilot control actuator for the tilt dump end of the main control spool. The pilot control actuator directs the pilot oil from the dump end of the main control spool to the hydraulic tank.

Rack Solenoid When the rack kickout control is activated the loader tilt linkage stops at a previously set rack kickout position without operator intervention.



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Electrohydraulic System SMCS Code: 1400; 5050

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Illustration 24 Implement Electronic Control System (1) Tilt cylinder (2) Lift cylinder (3) Switch (hydraulic lockout) (4) Lift/lower kickout switch (5) Tilt kickout switch (6) Shuttle valve (7) Pressure reducing valve (8) Tilt linkage position sensor (9) Lift linkage position sensor

(10) Main control valve (left) (11) Float valve (left) (12) Float valve (right) (13) Main control valve (right) (14) Cat Data Link (15) Implement electronic control module (ECM) (16) Hydraulic lockout valve (17) Tilt lever position sensor

(18) Lift lever position sensor (19) Pilot pump (20) Implement pump (180 cc (11.0 in 3)) (21) Implement pump (250 cc (15.3 in 3))(right) (22) Implement pump (250 cc (15.3 in 3))(center) (23) Hydraulic tank

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19 Electrohydraulic System Systems Operation Section Kickout set switches (4, 5) are located on the control console on the right side of the operator compartment. The kickout set switches are used to set the kickouts to the desired positions. To set the bucket kickout position, tilt the bucket to the desired LOADING position. When the tilt control lever returns to the HOLD position, press the top of tilt kickout switch (5) for approximately two seconds. Then, release the switch. To set the lower kickout position, lower the bucket to the desired position below the midway point. When the lift control lever returns to the HOLD position, press the bottom of lift/lower kickout switch (4) for approximately two seconds. Then, release the switch.

Illustration 25

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To set the lift kickout position, raise the bucket to the desired position above the midway point. When the lift control lever returns to the HOLD position, press the bottom of lift/lower kickout switch (4) for approximately two seconds. Then, release the switch.

Implement control lever module (3) Switch (hydraulic lockout) (24) Tilt control lever (25) Lift control lever

Tilt control lever (24) and lift control lever (25) are located on the right side of the operator seat. Position sensors (17, 18) for the control levers are located beneath the cover of implement control lever module. Switch (3) is an input to implement electronic control module (15). When switch (3) is in the UNLOCKED position and the engine start switch is in the ON position, the implement ECM energizes hydraulic lockout valve (16). Pilot oil flows to the pilot control actuators on main control valves (10, 13) and the stems in the main control valves can be commanded to move with movement in one of the control levers. If switch (3) is in the LOCKED position, pilot oil to the pilot control actuators is blocked.

Illustration 27 Left side of loader frame (Pin F) (8) Tilt linkage position sensor

Illustration 26 Right side console (4) Lift/lower kickout switch (5) Tilt kickout switch

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The electronics bay is located on the lower right side of the cab.

Illustration 28

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Right side of loader frame (Pin A) Illustration 30

(9) Lift linkage position sensor

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(16) Hydraulic lockout valve

Tilt linkage position sensor (8) is bolted to the left side of the lift arm near the linkage pin (Pin F). Lift linkage position sensor (9) is bolted to the right side of the lift arm near the linkage pin (Pin A). The position sensors constantly monitor the position of the appropriate linkage. This information is sent to the implement ECM. When the operator moves an implement control lever, a pulse width modulated signal (PWM) is sent to the ECM. The ECM analyzes the signal from the following sensors:

• Tilt linkage position sensor (8) • Lift linkage position sensor (9) • Tilt lever position sensor (17) • Lift lever position sensor (18) Then, the ECM sends a proportional current to the respective pilot control actuator.

Illustration 31

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Main control valve (10) Main control valve (left) (13) Main control valve (right) (26) Pilot control actuators

Hydraulic lockout valve (16) is located inside the loader frame on the left side of the machine. When hydraulic lockout valve (16) is de-energized, pilot oil is blocked. When the solenoid is energized, pilot oil is allowed to flow to pilot control actuators (26). Hydraulic lockout valve (16) is energized whenever the engine start switch is in the ON position and the switch (hydraulic lockout) (3) is in the UNLOCKED position. Illustration 29 Electronics bay (15) Implement ECM

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Illustration 32


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Pump drive and implement pumps (top view) (20) Implement pump (180 cc (11.0 in 3)) (21) Implement pump (250 cc (15.3 in 3))(right) (22) Implement pump (250 cc (15.3 in 3))(center) (27) Solenoid valve for variable displacement pump

One solenoid valve (27) is located on each of the variable displacement pumps. This solenoid valve controls the pilot pressure to the control valve for displacement control on the pump control for the variable displacement piston pump. Current to the solenoid valve is increased when the engine speed is greater than 1350 rpm. This decreases pressure on the piston for the displacement control. Reference: For additional information about the operation of the variable displacement piston pump, refer to the Service Manual module Systems Operation, “Pump Control Operation (Variable Displacement)” for the machine that is being serviced. i02861426

Pilot Hydraulic System SMCS Code: 5050


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Illustration 33 Pilot hydraulic system (1) Pilot control actuators (2) Solenoid valve (hydraulic lockout) (3) Check valve (4) Pressure switch ( filter bypass)

(5) Filter bypass (6) Pressure sensor (7) Pilot/axle oil cooler pump (8) Pilot filter

(9) Pressure reducing valve (10) Pilot accumulator (11) Hydraulic tank (A) Implement supply oil

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Illustration 34


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Hydraulic tank (top view) (11) Hydraulic tank (12) Filler cap

Illustration 36

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Pilot/axle oil cooler pump (top view) (7) Pilot/axle oil cooler pump (14) Pump drive

The pump compartment is beneath the access doors in the platform behind the cab. Pilot pump (7) is a variable displacement piston pump that is mounted on the rear of the pump drive on the right side of the machine. The pilot pump provides pilot oil to the implement system.

Illustration 35

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Hydraulic tank (front view) (8) Pilot filter (13) Breaker relief valve

Hydraulic tank (11) is beneath the access door behind the cab. Add oil by removing filler cap (12). Breaker relief valve (13) is used in order to relieve excessive pressure or vacuum from hydraulic tank (11). Hydraulic tank (11) also has nine filters and a sight gauge for checking the oil level.

Illustration 37 Pilot filter (4) Filter bypass switch

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The oil that is provided by the pilot pump flows through pilot fi lter (8). Pilot filter (8) is equipped with a bypass valve in the filter mounting base. When the filter is plugged, the filter bypass valve opens and oil fl ows over the check valve. Then, switch (4) opens and the VIMS main module will activate an alert indicator in the cab so that the operator is aware of the problem.

Pilot control actuators (1) control the flow of pilot oil from the spools in the main control valve back to the hydraulic tank. As current from the implement electronic control module (ECM) is applied to one pilot control actuator, the actuator will begin to shift. Trapped oil from behind the stem in the main control valve will begin to drain pilot oil from the actuator. The spring force on the opposite side of the stem will shift the stem. The movement of the stem is proportional to the current that is applied to the pilot control actuator. Oil that is supplied from the implement pumps to the main control valves will flow to the respective cylinder. As the current to the actuator is removed, the actuator shifts back to the relaxed position. Then, the oil is trapped between the stem and the actuator. The combination of the oil pressure and the spring force to each end of the stem is equalized. i02863854

Main Hydraulic System Illustration 38

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(9) Pressure reducing valve

Pressure reducing valve (9) is fastened to the inside of the pump compartment on the right side of the machine. Pilot oil from the pilot filter flows to the pressure reducing valve. The pressure reducing valve maintains the pressure in the pilot hydraulic system at 3450 kPa (500 psi).

Illustration 39 Main control valve (1) Pilot control actuators

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SMCS Code: 5050

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Illustration 40 Main hydraulic system


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26 Electrohydraulic System Systems Operation Section (1) Lift cylinder (2) Tilt cylinder (3) Main control valve (right side) (4) Float valve (5) Main control valve (left side) (6) Main relief valve

Illustration 41

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(7) Line relief valve (8) Shuttle valve (9) Pressure reducing valve (10) Check valve group (11) Variable displacement pump (180 cc (11.0 in 3))

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Left side of loader frame

Right side of loader frame (1) Lift cylinder

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(2) Tilt cylinder

(1) Lift cylinder

Illustration 42

Illustration 43

(12) Variable displacement pump (250 cc (15.3 in 3))(Right) (13) Variable displacement pump (250 cc (15.3 in 3))(Center) (14) Hydraulic tank

When the lift control lever is activated, oil from the main control valves is directed to lift cylinders (1). When the tilt control lever is activated, oil from the main control valves is directed to tilt cylinders (2).

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KENR5827


Illustration 46

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Pump compartment (11) Variable displacement pump (180 cc (11.0 in 3)) (12) Variable displacement pump (250 cc (15.3 in 3))(Right) (13) Variable displacement pump (250 cc (15.3 in 3))(Center)

Illustration 44

g01426510

The pump compartment is located beneath the access door in the platform behind the cab.

Main control valve (right) (front view) (6) (7) (8) (9)

Oil fl ows from the three variable displacement piston pumps to check valve group (10). The check valve group directs the oil to each of the main control valves.

Main relief valve Line relief valve Shuttle valve Pressure reducing valve

Illustration 45

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Main control valve (left) (front view)

The implement control valve consists of two main control valves (3,5). Left main control valve (3) consists of the following components: main relief valve (6), lift stem, tilt stem, and pilot control actuators. Right main control valve (5) consists of the following components: main relief valve (6), line relief valves (7), lift stem, tilt stem, pilot control actuators, shuttle valve (8), and pressure reducing valve (9).


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i02898432

Piston Pump (Implement) SMCS Code: 5070; 5084; 5455

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Illustration 47 (1) (2) (3) (4) (5)

Pressure sensor Pressure tap Implement pump Bias spring Actuator

(6) Super charger impeller (7) Implement ECM (8) Control spool (9) Coil assembly (A) Implement supply oil

(B) Return oil (C) Pilot supply oil (D) Suction oil

KENR5827

29 Electrohydraulic System Systems Operation Section When a lower pump displacement is desired, the current that is supplied to coil assembly (9) is decreased. This shifts control spool (8) downward. This increases the pilot pressure that is acting against the large end of actuator (5) by closing the path to the case drain of the pump. The force that is generated by pump discharge pressure (A) and bias spring (4) is now less than the modulated pilot pressure and spring force on the large end of the actuator. Actuator (5) shifts upward. This decreases the angle of the swashplate.

Illustration 48

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Pump compartment (10) Implement pump (180 cc (11.0 in 3)) (11) Implement pump (250 cc (15.3 in 3))(right) (12) Implement pump (250 cc (15.3 in 3))(center)

Note: During normal operation, each of the three implement pumps operates in the manner that is described below. Differences in standby operation are noted within the text. The implement pumps are variable displacement axial piston pumps that supply hydraulic oil to the main control valves. Each pump contains a swashplate that is driven by a single actuator (5). The small end of the actuator is connected to system pressure (A) from the discharge of the pump. The small end of the actuator also has bias spring (4) that assists in upstroking the pump during low discharge pressure. The large end of the actuator is connected to modulated pilot pressure that is controlled by control spool (8). The pilot pressure that is used to control the large end of the actuator is externally supplied. The pump displacement is controlled by a proportional current from the implement electronic control module (ECM) (7) to coil assembly (9). When a higher pump displacement is desired, the current that is supplied to coil assembly (9) is increased. This shifts control spool (8) upward. This drains a portion of the pilot pressure that is acting against the large end of actuator (5). The oil drains to the case drain of the pump. The force that is generated by pump discharge pressure (A) and bias spring (4) is now greater than the modulated pilot pressure and spring force on the large end of the actuator. Actuator (5) shifts downward. This increases the angle of the swashplate.

When the implement system is in standby operation, two 250 cc (15.3 in3) pumps (11, 12) are controlled in order to provide the necessary fl ow that lubricates the rotating group. This lubrication also cools the rotating gr oup. Adequate response from the pump is maintained and parasitic load on the engine is minimized. Standby control is active when no command is received from the tilt control lever or the lift control lever. During standby, a proportional current is sent to coil assembly (9). This current shifts control spool (8). This modulates the pilot pressure that is applied to the large end of actuator (5). Pump discharge pressure (A) is read by implement ECM (7) by using pressure sensor (1). Implement ECM (7) adjusts the proportional current in order to maintain a pump discharge pressure of 2500 kPa (360 psi). When the implement system is in standby operation, the output of 180 cc (11.0 in 3) pump (10) is set to the minimum. Standby control is active when no command is received from the tilt control lever or the lift control lever. During standby, no current is sent to coil assembly (9). This applies full pilot pressure to the large end of actuator (5). Actuator (5) is shifted fully upward. The angle of the swashplate and pump displacement are at the minimum. When the implement system is in normal operating mode, the displacement of the pump is controlled in order to provide only the fl ow that is required in order to satisfy the requests that are received from the lift contr ol lever and the tilt control lever. Implement ECM (7) reads the requests by using the tilt lever position sensor and the lift lever position sensor. Implement ECM (7) adjusts the proportional current that is sent to coil assembly (9) in order to provide the appropriate pump flow. During engine start-up, implement ECM (7) commands maximum displacement of the pump in order to purge air from the hydraulic system. Also, the float valves are opened in order to reduce parasitic loads on the engine. Once the engine is running, the implement system enters standby mode.


KENR5827

Suction oil (D) is charged by super charger impeller (6). Also, the pump features internal fl ushing of the case. Charged oil flows from the inlet to the case. Due to the fl ushing feature, fl ow of case drain oil from the pump depends on oil temperature, pump speed, and the pressure differential between inlet pressure and case pressure. An increase in the pump speed, the oil temperature, or the pressure differential will increase the fl ow of case drain oil. i02866373

Electrohydraulic System Operation SMCS Code: 1400; 5050

HOLD Position

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Illustration 49 Electrohydraulic system (HOLD position) (1) Tilt cylinder (2) Lift cylinder (3) Switch (hydraulic lockout) (4) Lift/lower kickout switch (5) Tilt kickout switch (6) Shuttle valve (7) Pressure reducing valve (8) Tilt linkage position sensor (9) Lift linkage position sensor



KENR5827

The implements are controlled by movement of the lift control lever and the tilt control lever. As one of the control levers is moved, a change in the duty cycle from one of the lever position sensors is sent to the implement electronic control module (ECM) (15). From ECM (15), a current that is proportional to the movement of the control lever is sent to the respective pilot control actuators. In the HOLD position, the signals from the lever position sensors are balanced and no current is sent to the pilot control actuators. The pilot pump sends pilot oil to the system. Pilot oil pressure is maintained at 3450 kPa (500 psi) by the pilot pressure reducing valve. Pilot oil is directed to hydraulic lockout valve (16). When switch (3) is in the UNLOCKED position and the engine start switch is in the ON position, implement ECM (15) will energize hydraulic lockout valve (16). Pilot oil fl ows to the pilot control actuators at both ends of each stem in the main contr ol valves. The pressure on each end of the stems is equalized and the stems are hydraulically locked in the HOLD position. When the main control valves are in the HOLD position, the stems in the main control valves block oil fl ow to tilt cylinders (1) and lift cylinders (2). In the HOLD position, hydraulic oil fl ows around the stems to hydraulic tank (23).



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TILT BACK Position

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Illustration 50 Electrohydraulic system (TILT BACK position) (1) Tilt cylinder (2) Lift cylinder (3) Switch (hydraulic lockout) (4) Lift/lower kickout switch (5) Tilt kickout switch (6) Shuttle valve (7) Pressure reducing valve (8) Tilt linkage position sensor (9) Lift linkage position sensor


When the tilt control lever is moved to the TILT BACK position, tilt lever position sensor (17) sends a signal to implement ECM (15). The signal is a pulse width modulated signal. Implement ECM (15) analyzes this signal and the signal from tilt linkage position sensor (8) and lift linkage position sensor (9). Implement ECM (15) then sends a proportional current that energizes each tilt back solenoid on main control valves (10, 13). When the tilt back solenoid is energized, oil drains from the area between the pilot control actuator (tilt back) and the tilt stem in the main control valve. The oil will drain to the hydraulic tank. This reduces the pilot pr essure on this end of the tilt stem. The pilot pressure on the opposite end of the tilt stem shifts the stem. Oil flow is directed to the head end of tilt cylinders (1).


Implement supply oil that was flowing through the valve to hydraulic tank (23) is blocked. Implement supply oil now fl ows around the tilt stem to the head end of tilt cylinders (1). The bucket will move toward the TILT BACK position. Oil from the rod end of tilt cylinder s (1) flows around the tilt stem to hydraulic tank (23). As the tilt control lever is pushed further into the TILT BACK position, implement ECM (15) will increase the current to the solenoid valves for implement pumps (20, 21, 22). This will cause the pumps to upstroke. The amount of oil that is fl owing to each main control valve is increased. The speed of the tilt back operation will increase.

KENR5827


DUMP Position When the tilt control lever is moved to the DUMP position, the system acts in a similar fashion as the tilt back operation. The dump solenoids on the opposite side of the main control valves are energized. This causes the tilt stem to move into the DUMP position. Implement supply oil is directed to the rod ends of the tilt cylinders. The bucket will move toward the DUMP position. Oil from the head ends of the tilt cylinders is directed to the hydraulic tank.

RAISE Position

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Illustration 51 Electrohydraulic system (RAISE position) (1) Tilt cylinder (2) Lift cylinder (3) Switch (hydraulic lockout) (4) Lift/lower kickout switch (5) Tilt kickout switch (6) Shuttle valve (7) Pressure reducing valve (8) Tilt linkage position sensor (9) Lift linkage position sensor


When the lift control lever is moved to the RAISE position, lift lever position sensor (18) sends a signal to implement ECM (15). The signal is a pulse width modulated signal. Implement ECM (15) analyzes this signal and the signal from tilt linkage position sensor (8) and lift linkage position sensor (9). Implement ECM (15) then sends a proportional current that energizes the raise solenoid on each main control valve (10, 13).


When the raise solenoid is energized, oil drains from the area between the pilot control actuator (raise) and the lift stem in the main control valve. The oil will drain to the hydraulic tank. This reduces the pilot pressure on this end of the lift stem. The pilot pressure on the opposite end of the lift stem shifts the stem. Oil fl ow is directed to the head end of lift cylinders (2).

34 Electrohydraulic System Systems Operation Section Implement supply oil that was flowing through the valve to hydraulic tank (23) is blocked. Implement supply oil now flows around the lift stem to the head end of lift cylinders (2). Oil from the rod end of lift cylinders (2) flows around the tilt stem to hydraulic tank (23). As the lift control lever is pushed further into the RAISE position, implement ECM (15) will increase the current to the solenoid valves for implement pumps (20, 21, 22). This will cause the pumps to upstroke. The amount of oil that is flowing to each main control valve is increased. The speed of the raise operation will increase.

LOWER Position When the lift control lever is moved to the LOWER position, the system acts in a similar fashion as the raise operation. The lower solenoids on the opposite side of the main control valves are energized. This causes the lift stem to move into the LOWER position. Implement supply oil is directed to the rod ends of the lift cylinders. Oil from the head ends of the lift cylinders is directed to the hydraulic tank.

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KENR5827


FLOAT Position

g01428252

Illustration 52 Electrohydraulic system (FLOAT position) (1) Tilt cylinder (2) Lift cylinder (3) Switch (hydraulic lockout) (4) Lift/lower kickout switch (5) Tilt kickout switch (6) Shuttle valve (7) Pressure reducing valve (8) Tilt linkage position sensor (9) Lift linkage position sensor


In order to enter the FLOAT position, the lift linkage must be below the midway point. When the lift control lever is moved to the FLOAT position, lift lever position sensor (18) sends a signal to implement ECM (15). The signal is a pulse width modulated signal. Implement ECM (15) analyzes this signal and the signal from tilt linkage position sensor (8) and lift linkage position sensor (9). Implement ECM (15) then sends a proportional current that energizes the lower solenoid on each main control valve (10, 13). Float valves (11, 12) are also energized. When the lower solenoid is energized, oil drains from the area between the pilot control actuator (lower) and the lift stem in the main control valve. The oil will drain to the hydraulic tank. This reduces the pilot pressure on this end of the lift stem. The pilot pressure on the opposite end of the lift stem shifts the stem. Oil flow is directed to the rod end of lift cylinders (2).


Implement supply oil that was flowing through the valve to hydraulic tank (23) is blocked. Implement supply oil now flows around the lift stem to the rod end of lift cylinders (2). Implement supply oil can also travel through internal check valves. This oil returns to hydraulic tank (23). Oil from the head end of lift cylinders (2) flows around the lift stem to hydraulic tank (23). i02867420

Hydraulic System Operation SMCS Code: 5050

HOLD Position


Illustration 53

KENR5827

g01428250

KENR5827


Hydraulic system (HOLD position) (1) Lift cylinder (2) Tilt cylinder (3) Main relief valve (right) (4) Main relief valve (left) (5) Rod end line relief valve for tilt cylinders (6) Head end line relief valve for tilt cylinders (7) Head end line relief valve for lift cylinders (8) Rod end line relief valve for lift cylinders (9) Shuttle valve (10) Pressure reducing valve (11) Pilot control actuator (lower) (12) Pilot control actuator (tilt back) (13) Pilot control actuator (tilt back)

(14) Pilot control actuator (lower) (15) Lift stem (right) (16) Tilt stem (right) (17) Tilt stem (left) (18) Lift stem (left) (19) Pilot control actuator (raise) (20) Pilot control actuator (dump) (21) Pilot control actuator (dump) (22) Pilot control actuator (raise) (23) Float valve (right) (24) Float valve (left) (25) Manual lowering valve (26) Solenoid valve (hydraulic lockout)

In the pilot hydraulic system, pilot pump (28) draws oil from hydraulic tank (36) and supplies pilot oil to the following components: pilot pressure reducing valve (30), the solenoid valve (hydraulic lockout) (26), ride control valve (if equipped), and the solenoid valves for the variable displacement piston pumps. Pilot pressure reducing valve (30) maintains the pilot pressure at 3450 kPa (500 psi). The solenoid valve (hydraulic lockout) (26) is controlled by the hydraulic lockout switch. When the hydraulic lockout switch is in the LOCKED position, the implement ECM will not energize the solenoid valve. The fl ow of oil to pilot control actuators (11, 12, 13, 14, 19, 20, 21, 22) is blocked. When the hydraulic lockout switch is in the UNLOCKED position, the implement ECM will energize the solenoid valve. The pilot oil fl ows past the solenoid valve (hydraulic lockout) to pilot control actuators (11, 12, 13, 14, 19, 20, 21, 22). In the left side of the implement hydraulic system, variable displacement piston pumps (33, 34) draw oil from hydraulic tank (36). Then, the pumps provide oil to the main control valve (left). When stems (17, 18) are in the HOLD position, oil fl ows through the open centered valve to hydraulic tank (36). Main relief valve (4) constantly senses pressure in the main control valve (left). When the oil pressure reaches the maximum adjustment, main relief valve (4) opens. The maximum pressure adjustment for main relief valve (4) is 29500 kPa (4300 psi). In the right side of the implement hydraulic system, variable displacement piston pumps (33, 35) draw oil from hydraulic tank (36). Then, the pumps provide oil to the main control valve (right). When the main control stems are in the HOLD position, oil flows through the open centered valve to hydraulic tank (36). Main relief valve (3) constantly senses pressure in the main control valve (left). When the oil pressure reaches the maximum adjustment, main relief valve (3) opens. The maximum pressure adjustment for main relief valve (3) is 29500 kPa (4300 psi). When the control levers are in the HOLD position, oil flow to lift cylinders (1) and tilt cylinders (2) is blocked at the stems for both main control valves.

(27) Check valve group (28) Pilot pump (29) Pilot oil filter (30) Pilot pressure reducing valve (31) Pressure sensor (pilot pressure) (32) Pilot oil accumulator (33) Implement pump (180 cc (11.0 in 3)) (34) Implement pump (250 cc (15.3 in 3))(right) (35) Implement pump (250 cc (15.3 in 3))(center) (36) Hydraulic tank

TILT BACK Position


Illustration 54

KENR5827

g01428493

KENR5827


Hydraulic system (TILT BACK position) (1) Lift cylinder (2) Tilt cylinder (3) Main relief valve (right) (4) Main relief valve (left) (5) Rod end line relief valve for tilt cylinders (6) Head end line relief valve for tilt cylinders (7) Head end line relief valve for lift cylinders (8) Rod end line relief valve for lift cylinders (9) Shuttle valve (10) Pressure reducing valve (11) Pilot control actuator (lower) (12) Pilot control actuator (tilt back) (13) Pilot control actuator (tilt back)


When the tilt control lever is moved to the TILT BACK position, the position sensor for the tilt control lever sends a pulse width modulated signal (PWM) to the implement electronic control module (ECM). The implement ECM analyzes this signal and the signals from the tilt linkage position sensor and from the lift linkage position sensor. The implement ECM then sends a proportional signal that energizes the solenoid for pilot control actuators (tilt back) (12, 13) on the main control valves. The solenoid valves in the pilot control actuators (12, 13) shift and the pilot oil at the tilt back end of the tilt stems (16, 17) is released to the hydraulic tank. This reduces the pilot pressure at the end of stems (16, 17). The combination of the spring force and the oil pressure on the dump end of the tilt stems begins to shift stems (16, 17) to the TILT BACK position. The oil from variable displacement piston pumps (33, 34, 35) flows around the control valve spool to the head end of each tilt cylinder (2). The oil at the rod end of each tilt cylinder (2) fl ows around stem (16, 17) to the hydraulic tank. As the tilt control lever is pushed further into the TILT BACK position, the implement ECM will increase the current to the solenoid valves for variable displacement piston pumps (33, 34, 35). This will cause the pumps to upstroke. Additional oil will be directed to each main control valve. The speed of the tilt back operation will increase.

DUMP Position When the tilt control lever is moved to the DUMP position, operation is similar to the tilt back operation. Solenoid valves for pilot control actuators (20, 21) are energized. This reduces the pilot pressure on the dump end of the tilt stems. The tilt stems shift to the DUMP position. Implement supply oil is directed to the rod end of each tilt cylinder. Oil from the head end of each tilt cylinder is directed to the hydraulic tank.

RAISE Position



Illustration 55

KENR5827

g01428536

KENR5827


Hydraulic system (RAISE position) (1) Lift cylinder (2) Tilt cylinder (3) Main relief valve (right) (4) Main relief valve (left) (5) Rod end line relief valve for tilt cylinders (6) Head end line relief valve for tilt cylinders (7) Head end line relief valve for lift cylinders (8) Rod end line relief valve for lift cylinders (9) Shuttle valve (10) Pressure reducing valve (11) Pilot control actuator (lower) (12) Pilot control actuator (tilt back) (13) Pilot control actuator (tilt back)


When the lift control lever is moved to the RAISE position, the position sensor for the lift control lever sends a pulse width modulated signal (PWM) to the implement electronic control module (ECM). The implement ECM analyzes this signal and the signals from the tilt linkage position sensor and from the lift linkage position sensor. The implement ECM then sends a proportional signal that energizes the solenoid for pilot control actuators (raise) (19, 22) on the main control valves. The solenoid valves in the pilot control actuators (19, 22) shift and the pilot oil at the raise end of the lift stems (15, 18) is released to the hydraulic tank. This reduces the pilot pressure at the end of stems (15, 18). The oil pr essure on the lower end of the lift stems begins to shift stems (15, 18) to the RAISE position. The oil from variable displacement piston pumps (33, 34, 35) flows around the control valve spool to the head end of each lift cylinder (1). The oil at the rod end of each lift cylinder (1) fl ows around stem (15, 18) to the hydraulic tank. As the lift control lever is pushed further into the RAISE position, the implement ECM will increase the current to the solenoid valves for variable displacement piston pumps (33, 34, 35). This will cause the pumps to upstroke. Additional oil will be directed to each main control valve. The speed of the raise operation will increase.

LOWER Position When the lift control lever is moved to the LOWER position, operation is similar to the raise operation. Solenoid valves for pilot control actuators (11, 14) are energized. This reduces the pilot pressure on the lower end of the lift stems. The lift stems shift to the LOWER position. Implement supply oil is directed to the rod end of each lift cylinder. Oil from the head end of each lift cylinder is directed to the hydraulic tank.

Float Position



Illustration 56

KENR5827

g01428539

KENR5827


Hydraulic system (FLOAT position) (1) Lift cylinder (2) Tilt cylinder (3) Main relief valve (right) (4) Main relief valve (left) (5) Rod end line relief valve for tilt cylinders (6) Head end line relief valve for tilt cylinders (7) Head end line relief valve for lift cylinders (8) Rod end line relief valve for lift cylinders (9) Shuttle valve (10) Pressure reducing valve (11) Pilot control actuator (lower) (12) Pilot control actuator (tilt back) (13) Pilot control actuator (tilt back)


In order to enter the FLOAT position , the lift linkage must be below the midway point. When the lift arms are below the midway point and the lift control lever is moved forward to the FLOAT position, the position sensor for the lift control lever sends a pulse width modulated signal (PWM) to the implement electronic control module (ECM). The implement ECM analyzes this signal and the signals from the tilt linkage position sensor and from the lift linkage position sensor. The implement ECM then sends a signal that energizes the solenoids for pilot control actuators (11, 14) on the main control valves. The implement ECM sends a signal that energizes the solenoids for the fl oat valves (23, 24). Also, the implement ECM sends a signal that energizes the detent coil for the lift control lever. The solenoids in the pilot control actuators shift and the pilot oil at the lower end of each stem is relieved to hydraulic tank (36). This reduces the pilot pressure at the end of the stem for the lower function. The oil pressure on the opposite end of each stem (15, 18) shifts the stems to the LOWER position. Implement supply oil flows through the load check valve in each main control valve, around the tilt stems, and to float check valves. Float valves (23, 24) are energized. This releases the oil pressure that is trapped between the float valves and the float check valves. The float check valves open. Implement supply oil that would be fl owing to the lift stems for lowering the lift linkage is allowed to drain to hydraulic tank (36).

Lower Position (Nonrunning Engine)



Illustration 57

KENR5827

g01428554

KENR5827


Hydraulic system (LOWER position)(engine in OFF position) (1) Lift cylinder (2) Tilt cylinder (3) Main relief valve (right) (4) Main relief valve (left) (5) Rod end line relief valve for tilt cylinders (6) Head end line relief valve for tilt cylinders (7) Head end line relief valve for lift cylinders (8) Rod end line relief valve for lift cylinders (9) Shuttle valve (10) Pressure reducing valve (11) Pilot control actuator (lower) (12) Pilot control actuator (tilt back) (13) Pilot control actuator (tilt back)


When the bucket is off the ground with the engine in the OFF position, the lift linkage can be lowered. The weight of the lift linkage creates pressure in the head end of lift cylinders (1) that can be used for pilot pressure in order to lower the lift linkage. The pressure oil in the head end of the lift cylinders fl ows through shuttle valve (9) to pressure reducing valve (10). The pressure in the pilot system will increase to approximately 1580 kPa (230 psi). Pressure reducing valve (10) will shift and this will block the flow of oil through pressure reducing valve (10). Pressure reducing valve (10) reduces the pressure that is used by the pilot system to approximately 1580 kPa (230 psi). With the key start switch in the ON position, the reduced pilot oil fl ows to the solenoid valve (hydraulic lockout) (26). This oil becomes the supply oil for the pilot system. The pilot oil will pressurize all the pilot control actuators. When the lift control lever is moved to the LOWER position, the solenoid valve in pilot control actuator (11, 14) will shift and this will allow the oil pressure against the lift stem in the HOLD position to shift. The pilot oil is relieved to hydraulic tank (36). Stems (15, 18) shift and this will allow the trapped oil in the head end of lift cylinders (1) to return to hydraulic tank (36). The pilot control actuators will have an adequate amount of pilot pressure if there is pressure in the head end of lift cylinders (1). i02852372

Ride Control System SMCS Code: 5004



Illustration 58

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g01423155

KENR5827


Implement hydraulic system with ride control switch in the ON position (1) Lift cylinders (2) Ride control accumulators

(3) Ride control valve (A) Pilot pressure

(B) Implement supply pressure

Note: The ride control solenoid valve allows hydraulic oil to fl ow between the head end of the lift cylinders (1) and ride control accumulators (2). 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. Ride control is activated by the ride control switch. The ride control switch sends an input to the power train electronic control module (ECM). The switch will be in one of following three positions. OFF position, ON position, and AUTO position

Illustration 61

g01438178

Hitch Area (2) Accumulator. Illustration 59

g01420773

Control panel (4) Ride control switch

The ride control switch allows the operator to select the following positions: ON, OFF, and AUTO. Note: The ride control system should be switched to the AUTOMATIC position or to the OFF position during the loading cycle. This is especially important during the bucket down operation. Failure to position the switch for the ride control system in the recommended position could result in machine damage.

When the ride control switch is in the ON position, the transmission ECM will continually energize the ride control solenoid and oil will fl ow between lift cylinder and the ride control accumulators. When the ride control switch is in the OFF position, the transmission ECM will de-energize the ride control solenoid. At this time, the fl ow of oil between lift cylinder and the ride control accumulators will be blocked. When the ride control switch is in the AUTO position, the transmission ECM will energize the ride control solenoid during machine ground speeds above 9.7 km/h (6 mph) and the transmission ECM will de-energize the ride control solenoid during machine ground speeds below 8.8 km/h (5.5 mph). When the ride control solenoid is energized, pilot pressure at the selector spool in ride control valve (3) fl ows to the hydraulic tank. The spring moves the selector spool in order to connect the head end of lift cylinders (1) with ride control accumulators (2). A floating piston in each accumulator separates the oil from the nitrogen gas. Since the nitrogen gas can be compressed, the nitrogen serves as a cushion. Any downward force on the lift arms is transferred through the oil at the head end of the lift cylinders to the accumulators.

Illustration 60 Upper articulation hitch (3) Ride control valve

g01438165


KENR5827

The force on the oil is transmitted to the accumulator pistons. This compresses the nitrogen. Compressing the nitrogen gas absorbs the displaced oil and the pressure spike that is caused by the downward force on the lift arms. This results in fewer shocks on structures and on components, reduced fl exing of the tires, and greater load retention. i02864552

Hydraulic Fan System SMCS Code: 1386; 1387

Hydraulic Fan System

g01426992

Illustration 62 Schematic for hydraulic fan system (1) Check valve (hydraulic oil cooler bypass) (2) Hydraulic oil cooler (3) Hydraulic fan motor (4) Makeup valve (hydraulic fan)

(5) Pressure sensor (6) Solenoid valve (hydraulic fan) (7) Pressure switch (8) Hydraulic tank

(9) Hydraulic fan pump (10) Pump control valve

KENR5827

49 Electrohydraulic System Systems Operation Section Hydraulic fan pump (9) is a variable displacement piston pump. In the hydraulic fan system, the hydraulic fan pump supplies the oil flow that generates the necessary pressure in order to turn the fan motor. The oil flow and pressure allow the fan motor to achieve the desired fan speed. The hydraulic fan pump adjusts the displacement according to the load sensing signal pressure that is supplied to the load sensing port of pump control valve (10). Solenoid valve (6) controls the load sensing pressure for the pump. Solenoid valve (6) is a proportional solenoid. As current to solenoid valve (6) increases, the pressure that is supplied to the load sensing port decreases. This causes the pump to destroke in order to meet demand. When the current to solenoid valve (6) decreases, the pressure that is supplied to the load sensing port increases. The pump upstrokes in order to meet demand.

Illustration 63

g01427031

Pump compartment (6) Solenoid valve (hydraulic fan) (9) Hydraulic fan pump

Flow of air is supplied to the cooling system by a hydraulically driven fan that is controlled by an on demand fan control system. The on demand fan control system controls the amount of oil flow that is provided to the fan motor. Increasing or decreasing the oil fl ow causes the pressure at the inlet port of the motor to increase or decrease accordingly. The increasing or decreasing pressure proportionally affects the torque that is available to the fan motor in order to turn the fan. Fan speed and flow of air increase as available torque increases. Fan speed and flow of air decrease as available torque decreases. This will maintain key system temperatures. During heavy machine usage or high ambient temperatures, the on demand fan control system will increase the fan to the maximum speed. During light usage and lower ambient temperature, the on demand fan control system will maintain a lower fan speed. This can result in lower horsepower requirements. The hydraulic fan system consists of the following components. hydraulic fan pump (9), the solenoid valve (demand fan) (6), hydraulic fan motor (3), and hydraulic oil cooler(2)

The amount of current that is supplied to solenoid valve (6) is controlled by the engine ECM. The engine ECM receives inputs from the hydraulic oil temperature sensor, the intake manifold air temperature sensor, and the engine coolant temperature sensor. If the engine ECM determines that the f an speed should be minimum, then the maximum current is sent to solenoid valve (6). If one of the three sensors shows that there is a demand f or more cooling, then the engine ECM will reduce the amount of current to solenoid valve (6). By decreasing the current to solenoid valve (6), the pump will upstroke. The pump will provide more fl ow in order to achieve the pressure that is commanded by the ECM. Fan speed and fl ow of air will increase in order to provide more cooling capacity. The maximum output that is provided by fan pump (9) is controlled by the adjustment of the high pressure cutoff in the pump control valve (10). The fan motor is a fixed displacement motor that is equipped with makeup valve (4). Makeup valve (4) allows the fan motor to stop gradually when the engine is shut down. The makeup valve allows the hydraulic oil to fl ow from the fan motor outlet through the makeup valve back to the fan motor inlet. This flow will prevent cavitation in the motor. When the engine is first started and the hydraulic oil is cold, the oil from the piston motor can not easily flow through the hydraulic oil cooler. The oil pressure will increase in the hydraulic oil cooler. The check valve for the hydraulic oil cooler bypass will open. The check valve limits the maximum oil pressure in the oil cooler to 345 ± 45 kPa (50 ± 7 psi). As the hydraulic oil temperature increases, the pressure of the oil through the oil cooler will decrease. The force of the spring in the check valve (hydraulic oil cooler bypass) is greater than the force of the oil pressure. Then, the check valve will close. The hydraulic oil will flow through the oil cooler into the hydraulic tank.

50 Electrohydraulic System Systems Operation Section When the engine is started, all temperatures for the three sensors are below the key target temperatures. The engine ECM sends the maximum current to the solenoid valve. Signal oil to the fl ow control spool is open to the hydraulic tank through the solenoid valve. Supply oil is directed to the actuator piston in order to destroke the pump. The angle of the pump swashplate is at a minimum. The pump will produce a minimum flow.

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Piston Pump (Hydraulic Fan)

As one of the temperatures of the three sensors increases above the key target temperature, the engine ECM sends a proportional reduction in current to the solenoid valve. The solenoid valve will start to shift. This will allow some of the supply oil to fl ow to the compensator spool. The compensator spool starts to shift to the left. A proportional amount of oil that is on the right side of the actuator piston will fl ow back to the hydraulic tank. As the pressure behind the actuator piston begins to decrease, the actuator spring will increase the swashplate angle. The pump output fl ow will increase. The fan speed will increase. As the temperatures of the machine continue to increase, the engine ECM will continue to reduce the current that is sent to the solenoid valve. The solenoid valve will continue to close. This will increase the hydraulic signal to the compensator spool. The compensator spool will shift more to the left in order to continue to drain oil that is behind the actuator piston. The swashplate moves more toward a maximum angle and the pump fl ow continues to increase. The fan speed continues to increase. As the speed of the hydraulic fan motor approaches the maximum fan speed, the pressure of the pump output also increases. The increase in pressure of the pump supply oil will work on the left side of both the compensator spool and the pressure cutoff spool. The compensator spool will stay to the left. The pressure on the left side of the cutoff spool will overcome the spring. The cutoff spool will start to shift to the right. This will allow some of the pump supply oil to flow to the actuator piston. This will slightly destroke the pump in order to reduce pump output flow. Once the desired fan speed is reached, the pressure cutoff spool will meter the flow of supply oil to the actuator piston and from the actuator piston. The adjustment of the cutoff spool can be adjusted for the maximum. The maximum pressure setting corr esponds to the maximum fan speed that can be achieved. The cutoff spool is similar to a relief valve. If the motor would lock up, the cutoff spool would destroke the pump to a minimum angle. Then, the pump would produce minimum flow.

Illustration 64

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Fan pump (10) Pump control valve (11) Housing (12) Actuator piston (13) Piston (14) Cylinder barrel (15) Spring (16) Port plate (17) Drive shaft (18) Swashplate (19) Piston shoe (20) Shoe plate (21) Actuator piston (22) Head

Fan pump (9) is a variable displacement pump with load sensing control. The pump senses the pressure signal at the load sensing port of pump control valve (10). The pump then upstrokes or the pump destrokes accordingly in order to meet the pressure demand. The movement of pistons (13) in the pump draws oil from the hydraulic tank(8). Then, the pump provides oil fl ow to hydraulic fan motor (3). When the engine is running and drive shaft (17) is rotating, the components that rotate are cylinder barrel (14), pistons (13), piston shoes (19), and shoe plates (20). Within barrel (14), there are nine piston assemblies (13). The components of the pump that remain are fastened to pump housing (11). Oil from hydraulic tank (8) fl ows into pump head (22) at the inlet passage. Then, the oil fl ows from the inlet passage into port plate (16). When drive shaft (17) rotates, the openings in cylinder barrel (14) move toward the passages in port plate (16).

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Each piston (13) inside cylinder barrel (14) is held against swashplate (18) by shoe plate (20). Swashplate (18) can be at any angle between the maximum angle and the minimum angle. The angle of swashplate (18) determines the displacement of oil that is pushed out of each cylinder barrel (14).

The flow of oil for the hydraulic fan system is regulated by pump control valve (10). Pump control valve (10) maintains the correct oil flow that is provided by the fan pump. Pump flow and pump pressure cutoff are maintained by either sending or draining actuator piston (21).

As pistons (13) follow the angle of swashplate (18), the pistons move in and out of cylinder barrel (14). When pistons (13) move out of cylinder barrel (14), oil is pulled into cylinder barrel (14).

Actuator piston (21) and spring (15) work against each other in order to determine the angle of swashplate (18). The discharge pressure of the pump is 2100 ± 100 kPa (305 ± 15 psi) above the signal pressure. The difference between discharge pressure and signal pressure is referred to as the margin pressure.

As cylinder barrel (14) rotates, the angle of swashplate (18) pushes pistons (13) into cylinder barrel (14). Then, pistons (13) push oil out of cylinder barrel (14) and oil fl ows through the outlet passages of port plate (16). The minimum angle is perpendicular with drive shaft (17). The discharge of oil is greater when the angle of swashplate (18) is greater. Oil is discharged through port plate (16) to the outlet passage. When swashplate (18) is at the maximum angle, the pump is at the maximum displacement. The swashplate angle is controlled by spring (15) and actuator piston(21). Actuator piston (21) is activated by oil pressure from the compensator valve.

Pressure Control Valve (Hydraulic Fan Pump)

Pump control valve (10) has the ability to limit pressure. Pump control valve (10) prevents overloading the hydraulic fan system. When pump outlet pressure exceeds 20500 ± 350 kPa (2950 ± 50 psi), pressure cutoff spool (29) overrides flow compensator spool (24). Pressure acts on the left side of spool (24). Then, spool (29) is shifted to the left. Then, the oil fi lls the cavity behind actuator piston (21). As the pressure behind piston (21) increases, actuator piston (21) begins to move. Then, swashplate (18) rotates in the clockwise direction. The pump destrokes and the pump maintains an output pressure of 20500 ± 350 kPa (2950 ± 50 psi).

Upstroking Upstroking increases the pump displacement. Upstroking occurs when one or more of the temperature sensors sense a higher temperature. When a higher temperature is sensed, a signal is sent to the engine electronic control module (ECM). The engine ECM interprets the data. The ECM determines the proper amount of current that should be sent to solenoid valve (6). Solenoid valve (6) increases the signal pressure that is sent to pump control valve (10) through the load sensing line.

Illustration 65 Pressure control valve (23) Plug (24) Flow compensator spool (25) Seat (26) Port (load sensing signal) (27) Cavity ( flow compensator) (28) Spring (29) Pressure cutoff spool (30) Port passage to the pump outlet (31) Port passage to the actuator piston (32) Port passage for case drain (33) Seat (34) Cavity (pressure compensator) (35) Spring

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The load sensing signal pressure enters through port (26) which fills the pressure cavity (27). The signal pressure and the force of spring (28) shifts compensator spool (24) to the left. The oil behind actuator piston (21) flows through passage (31) to the passage (case drain) (32). The force of spring (15) overrides the force of the oil pressure behind actuator piston (21). Then, the angle of swashplate (18) proportionally increases. When the angle of swashplate (18) increases, the pump upstrokes and the displacement of the pump increases.

52 Electrohydraulic System Systems Operation Section As the speed of fan motor (3) increases, the pressure that is needed to keep the fan motor rotating at that speed will increase. When the pump supply pressure reaches the spring setting of the pressure cutoff spool (29), the oil pressure behind the pressure cutoff spool will override cutoff spring (28). Pressure cutoff spool (29) shifts to the right. When pressure cutoff spool (29) moves to the right, the land on the cutoff spool will block the oil flow from actuator piston (21) to hydraulic tank (8). At the same time, pump supply oil is meter ed around the cutoff spool (29) by the land on the spool. The metered oil supply flows behind actuator piston (21). The oil pressure behind the actuator piston and spring (15) are equalized. The swashplate is at the angle for the adjusted maximum pressure. The pump will provide the fan system with the maximum fl ow in order to maintain the maximum fan speed. The maximum fan speed can be changed by adjusting force on spring (35) for cutoff spool (29).

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Piston Motor (Hydraulic Fan )

Destroking If the temperature of the sensors is dropping toward the key target temperatures, the engine ECM sends an increase in current to solenoid valve (6). Solenoid valve (6) shifts. The solenoid valve opens a path for oil that is above spool (24) in order to be metered out to the hydraulic tank. Solenoid valve (6) decreases the signal pressure to pump control valve (10) through the load sensing line. The force that is behind the left end of spool (24) works against spring (28) and control pressure in cavity (27). As signal oil from cavity (27) is released, the spool will move further to the right. As the spool begins to move to the right, pump supply oil will fl ow around the land on spool (24). The oil flows through pump control valve (10), through passage (31) and to actuator piston (21). The oil pressure increases at the actuator. The actuator moves to the left against the swashplate. The swashplate will override spring (15) and the swashplate moves to a reduced angle. The output of the pump will decrease. If the signal pressure does not change, flow compensator spool (24) will remain in the metering position. When fl ow compensator spool (24) is in the metering position, the fan circuit is equalized.

Illustration 66

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Hydraulic fan motor (36) (37) (38) (39) (40) (41) (42) (43)

Shaft Case Retainer plate Pistons (seven) Pin (pivot) Barrel Port plate Head

Hydraulic fan motor (3) is a bent axis piston-type motor. The motor has a fixed displacement of oil per revolution. The fan drive motor is mounted on a frame in front of the radiator. The fan is mounted to the motor shaft. The components of the motor that turn are shaft (36), retainer plate (38), pistons (39) and barrel (41). The parts that do not turn are case (37), port plate (42), and head (43). When shaft (36) turns, shaft (36) turns the fan blade at the same speed. Any internal leakage drains back to the hydraulic tank through the drain passage. The fan motor turns the fan at a speed that meets the cooling system requirements. When the requirements of the cooling system are met, the power demand on the engine may be decreased.

Solenoid Valve The hydraulic fan valve is located on the left side of the pump compartment. Refer to Illustration 63.

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53 Electrohydraulic System Systems Operation Section The engine ECM receives a signal from the intake manifold air temperature sensor, the hydraulic oil temperature sensor, and the engine coolant temperature sensor. The engine ECM will then send a current to pr oportional solenoid valve (6). As the temperature increases, the amount of current going to the proportional solenoid valve decreases. Poppet (46) is seated and the signal pressure in passage (47) increases. As the signal pressure increases, the pump upstrokes and the fan speed increases.

Electrical Control In the on demand fan control system, the speed of the fan and the output of the hydraulic fan pump is directly controlled by the engine ECM through solenoid valve (6). The engine ECM interprets signals from the three sensors on the machine. Then, the engine ECM sends a proportional amount of current to solenoid valve (6). Illustration 67

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Solenoid valve (demand fan) (6) Solenoid valve (demand fan) (44) Manifold (45) Passage to the hydraulic tank (46) Poppet (variable ori fice) (47) Passage (signal pressure) (48) Orifice (49) Passage (hydraulic pump pressure)

The solenoid valve (demand fan) (6) is located in the pump compartment behind the cab. The solenoid valve (demand fan) (6) is made up of the solenoid valve and manifold (44). The discharge pressure from the hydraulic fan pump flows into passage (49), through ori fice (48), and into passage (47). The oil then fl ows from passage (47) into the load sensing port of pump control valve (10). The solenoid valve controls the pump discharge pressure by modulating the flow of oil between passage (47) and passage (45). The engine ECM receives a signal from the intake manifold air temperature sensor, the hydraulic oil temperature sensor, and the engine coolant temperature sensor. The engine ECM will then send a current to solenoid valve (6). As the temperature decreases, the current to solenoid valve (6) is increased. When solenoid valve (6) is energized, poppet (46) is allowed to raise. Then, oil from the passage (signal pressure) (47) is allowed to flow to the passage (hydraulic tank) (45). This flow causes the signal pressure in passage (47) to decrease. As the signal pressure decreases, the pump destrokes and the fan speed decreases. In the hydraulic fan system, the amount of oil that is allowed to fl ow from the signal line to the hydraulic tank is proportional to the amount of current change that is sent by the engine electronic control module (ECM).

The sensor for the aftercooler temperature is a temperature sensor. The sensor sends a signal to contact J2-15 through wire A751-YL on the engine ECM. The hydraulic oil temperature sensor is used for the measurement of liquid temperatures. The sensor sends an output to the engine ECM. The duty cycle will change as the temperature of the oil increases. The signal is carried to contact J2-45 of the Vital Information Management System (VIMS) by wire 442-GY. From the VIMS, data is sent to the engine ECM through the Cat Data Link. The engine coolant temperature sensor is a sensor that is used to measure the temperatures of liquids. The sensor sends a signal to contact J2-9 on the engine ECM through wire 995-BU. The signal will change as the temperature of the engine coolant increases. When the engine is started, the hydraulic fan pump will be instructed to run at minimum fan speed. The following conditions must be met, in order to run the fan system at minimum fan speed.

• The aftercooler temperature is below 68 °C (154 °F).

• The hydraulic oil temperature is below 70 °C (158 °F).

• The engine coolant temperature is below 88 °C (190 °F).


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As one of the sensors reads a temperature that is above the key target temperature, the engine ECM interprets a demand for more cooling. The engine ECM starts sending a reduced amount of current from J2-19 on the engine ECM through wire F700-BU to solenoid valve (6). The solenoid valve will move proportionally, toward the de-energized direction. i02878185

Rear Access Egress System (Operator Lift) SMCS Code: 7011 Illustration 69

The optional operator lift attachment (Rear Access Egress System) consists of an electrohydraulically controlled platform that can be used to raise or lower an operator from the ground to the bumper level of the machine. The parking brake must be engaged and the transmission must be in the NEUTRAL position in order to lower the lift. The machine cannot be moved until the lift returns to the raised position. A warning will be activated in the cab if the switch for the lift is placed in the LOWER position and the transmission is in gear. A warning will also be activated if the transmission is placed in gear and the lift is not fully raised.

Illustration 68 Switch on bumper on left side of machine

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Switch on platform

The lift is operated with one of two switches. One switch is on the bumper on the left side of the machine. The other switch is on the platform. Refer to Illustration 68 and Illustration 69. The function of the two switches is identical. Pushing the switch in the upward direction will raise the platform. Pushing the switch in the downward direction will lower the platform. When the lift system is in operation, an alarm will sound and a beacon will activate.

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Illustration 70 Lift system with switch in RAISE position

When the switch is in the RAISE position, pump (1) supplies oil to the lift system. When the pressure in the system reaches 552 ± 28 kPa (80 ± 4 psi), valve (2) will shift. Oil passes through valve (3) and check valve (4). Oil enters the rod end of cylinder (5). Cylinder (5) retracts. This raises the platform. Return oil from the head end of the cylinder flows through valve (11). The return oil will pass through filter (13). The oil then returns to hydraulic tank (12). When the platform is fully raised, latch (15) will hold the platform in the RAISE position.

Illustration 71

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Operator lift (bottom view) (16) Limit switch

When the platform is fully raised, limit switch (16) is also closed. The limit switch must be closed in order to place the transmission in gear. When the platform is lowered, the limit switch will open.


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If the platform becomes overloaded, relief valve (6) will open at 2070 ± 104 kPa (300 ± 15 psi). This will allow supply oil to drain to the hydraulic tank.

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Illustration 72 Lift system with switch in LOWER position

When the switch is in the LOWER position, solenoid valve (9) is energized. Solenoid valve (9) allows supply oil to flow to the ends of valves (3, 11), check valve (4), and latch (15). Valves (3, 11) will shift. Check valve (4) will open in order to allow reverse flow through the valve. Latch (15) will open in order to allow the platform to descend. Relief valve (7) allows system pressure to rise to 2070 ± 207 kPa (300 ± 30 psi) in order to release latch (15). Supply oil flows through valve (2) and to valve (3). Valve (3) directs the oil to the head end of cylinder (5). Cylinder (5) extends. This platform lowers. If the platform encounters an obstruction during lowering, relief valve (14) opens at 1379 ± 79 kPa (200 ± 10 psi). Oil from the rod end of cylinder (5) flows through check valve (4). The oil fl ows through valve (11) and filter (13). The oil then returns to hydraulic tank (12). Relief valve (10) limits the pressure in the system to 6200 ± 310 kPa (900 ± 45 psi).

Hand pump (8) allows the system to be operated without electrical power. Solenoid valve (9) can be manually activated in order to allow the platform to lower. i02910865

Oil Coolers and Cooling System Operation SMCS Code: 1350; 1353; 1365; 1374; 1375; 1378

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Illustration 73 Cooling system (1) Shunt tank for radiator (2) Bypass (3) Water regulator housing (4) Radiator cores (5) Turbocharger

(6) Turbocharger oil lines (7) Transmission oil cooler (8) Rear axle oil cooler (9) Engine oil cooler (10) Water pump

Water pump (10) draws coolant directly from radiator (4). The coolant is pumped through engine oil cooler (9). The oil then fl ows through rear axle oil cooler (8) and transmission oil cooler (7). From the transmission oil cooler, coolant fl ows through the engine block.

(11) Inlet tube (radiator) (AA) Unregulated coolant (BB) Regulated coolant

58 Electrohydraulic System Systems Operation Section The coolant fl ows around the cylinder liners, through the water directors, and into the cylinder heads. The water directors send the fl ow of coolant around the exhaust valves and the passages for exhaust gases in the cylinder heads. The coolant then goes to the front of the cylinder heads and into water regulator housing (3). When the coolant is inside of housing (3), two water temperature regulators control the direction of coolant fl ow within housing (3).

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Radiator Assembly

When the coolant temperature is below 81 °C (178 °F), water temperature regulator (3) will be closed. The path for the coolant return to radiator (4) is blocked. The coolant fl ows through regulator housing (3). Then, the coolant is fed back to the inlet of water pump (10). As the coolant temperature reaches 82° ± 1°C (180° ± 2°F), water temperature regulator (3) starts to open. Coolant begins to flow to tube (11). When the coolant temperature reaches 92 °C (198 °F), the coolant is at normal operating temperature. Water temperature regulator (3) is fully open and the flow of coolant to bypass (2) is blocked. The path for the coolant to radiator (4) through tube (11) is open. The temperature of the returned coolant will be reduced as the coolant fl ows through radiator (4). Note: Water temperature regulator (3) is an important part of the cooling system. Water temperature regulator (3) divides the coolant fl ow between radiator (4) and bypass (2) in order to maintain normal operating temperature. If the water temperature regulator is not installed in the system, the fl ow of coolant is not regulated. Most of the coolant will go through the bypass (2) and bypass radiator assembly (4). The engine, the transmission, and the hydraulic oil may overheat during high ambient temperatures.

Coolant for the Turbocharger Turbocharger (5) has one inlet and one outlet. Turbocharger oil lines (6) are connected to the turbocharger at these ports. Pressurized engine oil flows from the crankcase of the engine into turbocharger (5) through turbocharger oil lines (6). This engine oil is used for lubrication of the bearings in the turbocharger and for cooling the turbocharger. The oil then drains through turbocharger oil lines (6) into the oil pan on the bottom of the engine.

Illustration 74 Radiator assembly (front view) (12) Aftercooler (13) Hydraulic oil cooler for the steering system (14) Hydraulic oil cooler (15) Refrigerant condenser (16) Fuel cooler

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59 Electrohydraulic System Systems Operation Section The radiator is made up of fourteen cores. Each core contains three tubes in the rear and three tubes in the front. The rear tubes and the front tubes are connected by a crossover tank at the top of each core. As the coolant fl ows into the rear section of the bottom tank, the coolant is pushed up the rear tubes of each core. As the coolant reaches the top of the cores, the coolant fl ows through the crossover tank. Then, the coolant fl ows through the front tubes into the front section of the bottom tank. As the coolant fl ows through the radiator cores in both directions and the air is pulled around the radiator cores, the temperature of the coolant is reduced.

Transmission Oil Cooler and Rear Axle Oil Cooler

Illustration 75

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Radiator cores (front view) (4) Radiator cores (17) Radiator bottom tank

The radiator assembly is the source of coolant for the cooling system. The radiator is made up of radiator cores (4) and radiator bottom tank (17). Also, the radiator assembly includes two air aftercoolers (12), two hydraulic oil coolers (14), one hydraulic oil cooler for the steering system (13), refrigerant condenser (15), and fuel cooler (16). Reference: For additional information about the refriger ant condenser, refer to the Service Manual module Systems Operation, SENR5664, “Air Conditioning and Heating R-134a for All Caterpillar Products”. Illustration 76

Reference: For more information about cooling the hydraulic system, refer to the Service Manual module Systems Operation, “Hydraulic Fan System” for the machine that is being serviced. Radiator bottom tank (17) is divided into two sections. Coolant fl ows from water temperature regulator (3) into the rear section of the bottom tank.

Left side of engine (7) Transmission oil cooler (8) Rear axle oil cooler (9) Engine oil cooler (10) Water pump (18) Bonnet (19) Inlet for axle oil cooler (20) Outlet for transmission oil cooler (21) Inlet for transmission oil cooler (22) Outlet for axle oil cooler (23) Bonnet

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Engine coolant from water pump (10) fl ows through engine oil cooler (9). Coolant fl ows from the engine oil cooler (9) into bonnet (23). Bonnet (23) directs the flow of coolant into rear axle oil cooler (8). The coolant fl ows through long tubes inside the oil cooler to bonnet (18). Coolant flows through bonnet (18) and into transmission oil cooler (7). Coolant flows through long tubes inside the transmission oil cooler to bonnet (23). The coolant then fl ows through bonnet (23) and into the engine cylinder block. High temperature transmission oil flows from the torque converter outlet to transmission oil cooler (7). This oil flows through inlet (21) to the inside of the oil cooler. As the oil flows through the inside of the cooler, heat is transferred from the oil to the coolant that is fl owing through the tubes. The cooled oil fl ows out of the cooler through outlet (20). The oil then flows through a line in order to lubricate the planetary group. High temperature oil from the rear axle is pumped to rear axle oil cooler (8). This oil flows through inlet (19) to the inside of the oil cooler. As the oil flows through the inside of the cooler, heat is transferred from the oil to the coolant that is fl owing through the tubes. The cooled oil fl ows out of the cooler through outlet (22). The oil then fl ows back to the rear axle.

Front Axle Oil Cooler

Illustration 77 Front axle oil cooler (right side view) (24) Front axle oil cooler (25) Pump and motor

Illustration 78

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Front axle oil cooler cores (bottom view) (26) Outlet for axle oil (27) Inlet for axle oil

Front axle oil cooler (24) is mounted inside the loader frame above the front axle. Pilot hydraulic oil drives a hydraulic motor which turns pump (25) for the front axle oil cooler. The pilot oil then fl ows into the top rear port of the cooler core assembly. The pilot oil flows through long tubes inside each core. When the oil reaches the bonnet at the front of the assembly, the oil fl ows through the outlet on the top of the bonnet. The pilot oil returns to the main hydraulic tank. Pump (25) sends axle oil from the front axle to inlet (27). The axle oil fl ows through the cooler core on the left side of the assembly. As the axle oil fl ows through the cores, heat from the axle oil is transferred to the pilot oil that is flowing through the tubes. When the oil reaches the front of the core, the oil passes through a tube into the cooler core on the right side of the assembly. At the rear of the right cooler core, the cooled oil passes through outlet (26) and fl ows to the front axle.

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Air-to-Air Aftercooler

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Illustration 79 Air-to-ai r aftercooler (left side view) (5) Turbocharger (12) Aftercooler core (28) Air cleaner

(29) Muf fler (30) Air intake manifold (CC) Inlet air

Note: The left side muf fler has been removed for clarity in Illustration 79.

(DD) Exhaust gases

62 Electrohydraulic System Systems Operation Section The air-to-air aftercooler system provides cooled air to air intake manifold (30) on top of the engine. Air is drawn in through air cleaners (28) and into the compressor side of turbocharger (5). The air is compressed by the turbocharger. This causes a rise in the temperature of the air. The air is sent through the tube into aftercooler core (12). The air is cooled in the aftercooler core. From core (12), the air fl ows into air intake manifold (30) on the top of the engine. The air flow from the inlet port into the cylinders is controlled by inlet valves. Each cylinder has inlet valves and exhaust valves in the cylinder head. The inlet valves open when the piston moves downward on the inlet stroke. When the inlet valves open, cooled compressed air from the inlet port within the inlet manifold is pulled into the cylinder. The inlet valves close when the piston begins to move up on the compression stroke. The air in the cylinder is compressed and the fuel is injected into the cylinder when the piston is near the top of the compression stroke. Combustion begins when the fuel mixes with the air. The force of combustion pushes the piston downward on the power stroke. The exhaust valves open and the exhaust gases are pushed through the exhaust port. Exhaust gases from the exhaust manifold flow into the turbine side of the turbocharger (5). The high pressur e exhaust gases cause the turbocharger turbine wheel to rotate. The turbine wheel is connected to the shaft that drives the compressor wheel. Exhaust gases from turbocharger (5) pass through the exhaust outlet, through a muf fler (29), and through an exhaust stack. The ef ficiency of the engine will increase due to the cooler inlet air. This helps to provide lowered fuel consumption, increased horsepower output, and improved emissions. Reference: For additional information about the turbocharger, refer to the Service Manual module Systems Operation/Testing and Adjusting, “Air Inlet and Exhaust System” for the engine that is being serviced.

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63 Electrohydraulic System Index Section

Index E

M

Electrical Input Components.................................. 10 Sensor Inputs..................................................... 12 Sensors.............................................................. 15 Switch Inputs...................................................... 13 Switches............................................................. 13 Electrical Output Components............................... 15 Dump Solenoid .................................................. 17 Float Valve ......................................................... 17 Lower Solenoid .................................................. 17 Pilot On/Off ........................................................ 17 Rack Solenoid.................................................... 17 Raise Solenoid................................................... 17 Electrohydraulic System........................................ 18 Electrohydraulic System Operation ....................... 30 DUMP Position................................................... 33 FLOAT Position.................................................. 35 HOLD Position ................................................... 30 LOWER Position ................................................ 34 RAISE Position .................................................. 33 TILT BACK Position ........................................... 32 Electronic Control Module ..................................... 15 IMPLEMENT ECM ............................................. 15

Main Hydraulic System.......................................... 24 O Oil Coolers and Cooling System Operation........... 56 Air-to-Air Aftercooler .......................................... 61 Coolant for the Turbocharger ............................. 58 Front Axle Oil Cooler.......................................... 60 Radiator Assembly............................................. 58 Transmission Oil Cooler and Rear Axle Oil Cooler............................................................... 59 P Pilot Hydraulic System........................................... 21 Piston Pump (Implement) ...................................... 28 R Rear Access Egress System (Operator Lift).......... 54 Ride Control System.............................................. 45

G General Information............................................... Electrohydraulic System Components............... Electronic Contr ol System Components ............ Graphic Color Codes............................................. Color Codes for Illustrations...............................

4 4 9 4 4

S Systems Operation Section ................................... 4 T

H Hydraulic Fan System ........................................... 48 Electrical Control................................................ 53 Hydraulic Fan System........................................ 48 Piston Motor (Hydraulic Fan ) ............................ 52 Piston Pump (Hydraulic Fan) ............................. 50 Pressure Control Valve (Hydraulic Fan Pump) .. 51 Solenoid Valve ................................................... 52 Hydraulic System Operation.................................. 35 DUMP Position................................................... 39 Float Position ..................................................... 41 HOLD Position ................................................... 35 LOWER Position ................................................ 41 Lower Position (Nonrunning Engine) ................. 43 RAISE Position .................................................. 39 TILT BACK Position ........................................... 37 I Important Safety Information ................................. 2

Table of Contents...................................................

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KENR5827-00-01-ALL imp

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