Manual Caterpillar 992g Wheel Loader Electro Hydraulic Implement System Components 1u1j6o
This document was ed by and they confirmed that they have the permission to share it. If you are author or own the copyright of this book, please report to us by using this report form. Report r6l17
Overview 4q3b3c
& View Manual Caterpillar 992g Wheel Loader Electro Hydraulic Implement System Components as PDF for free.
More details 26j3b
- Words: 9,946
- Pages: 65
STMGXXX 4/97
- 60 -
ELECTRO-HYDRAULIC IMPLEMENT SYSTEM
40
ELECTRO-HYDRAULIC IMPLEMENT SYSTEM Introduce system
This portion of this presentation discusses the component locations, systems operation, and testing and adjusting procedures for the ElectroHydraulic Implement System on the 992G Wheel Loader. When discussing systems operation, both sectional view and graphic symbol schematics will be used. The systems will be explained by tracing oil flow from the tank, through the system and back to the tank.
STMGXXX 4/97
- 61 -
ELECTRO-HYDRAULIC IMPLEMENT SYSTEM VARIABLE PUMP PILOT SOLENOID VALVE RELIEF VALVE IMPLEMENT HYDRAULIC PUMPS
ELECTRONIC CONTROL MODULE
PILOT PUMP
PILOT CONTROL LEVER MODULE MAIN CONTROL VALVE ASSEMBLY
HYDRAULIC TANK
LIFT LINKAGE POSITION SENSOR
TILT CYLINDER
LIFT TILT LINKAGE CYLINDER POSITION SENSOR
ELECTRONIC SYSTEM
MAIN HYDRAULIC SYSTEM
HYDRAULIC PILOT SYSTEM
COMMON TO BOTH SYSTEMS
41 Identify components: - Pilot electronic system - Pilot hydraulic system - Main hydraulic system - Common to both systems
Shown are the major components of the electro-hydraulic implement system. The electro-hydraulic implement system is pilot operated. The pilot system controls the functions of the main control valve. The pilot system consist of an electronic system and a hydraulic system. The electronic system components (orange) are the pilot control lever module (includes the tilt lever, lift lever, tilt sensor, lift sensor, bucket kickout detent solenoid, lift kickout detent solenoid, lower kickout detent solenoid and implement lockout switch), the implement electronic control module (ECM), the tilt linkage position sensor, the lift linkage position sensor, the pilot control valve solenoids, the pilot on/off valve solenoid (part of the main control valve assembly) and the torque valve.
STMGXXX 4/97
- 62 -
The pilot hydraulic system (brown) consist of the pilot pump, the pilot relief valve, the pilot on/off valve (part of the main control valve assembly) and the pilot control valves (part of the main control valve assembly). The main hydraulic system (green) consists of the fixed pump, the variable pump, the fixed pump relief valve (part of the main control valve assembly), the variable pump relief valve (part of the main control valve assembly), main control valve assembly, two lift cylinders and the tilt cylinder. The hydraulic tank (red) is common to both systems.
INSTRUCTOR NOTE: The color codes used for hydraulic oil throughout this presentation are: Red
- System or high pressure
Red and White Stripes
- Reduced pressure
Orange
- Pilot pressure
Blue
- Blocked oil
Green
- Tank or return oil
STMGXXX 4/97
- 63 -
IMPLEMENT ELECTRONIC CONTROL MODULE (MAC-14)
ELECTRONIC IMPLEMENT CONTROL SYSTEM
CAT DATA LINK INPUT COMPONENTS
LIFT LEVER SENSOR
OUTPUT COMPONENTS PILOT ON/OFF SOLENOID
TILT LEVER SENSOR
VARIABLE PUMP SOLENOID TILT RACKBACK SOLENOID NO. 1 TILT RACKBACK SOLENOID NO. 2
IMPLEMENT LOCKOUT SWITCH
TILT DUMP SOLENOID NO. 1
LIFT/LOWER/TILT KICKOUT SWITCH
TILT DUMP SOLENOID NO. 2 LIFT LINKAGE SENSOR
LIFT LOWER SOLENOID NO. 1 LIFT LOWER SOLENOID NO. 2
TILT LINKAGE SENSOR
LIFT RAISE SOLENOID NO. 1 LIFT RAISE SOLENOID NO. 2 LIFT LOWER KICKOUT DETENT SOLENOID LIFT RAISE KICKOUT DETENT SOLENOID BUCKET KICKOUT DETENT SOLENOID
42 Explain diagram
Electronic Implement Control System Shown is a block diagram of the Electronic Implement Control (EIC) System. The ECM receives input signals from the various sensors and switches (shown in blue). The ECM processes the inputs, makes decisions and provides a corresponding output to the pilot solenoid valves and kickout solenoids (shown in yellow). The ECM also communicates with other electronic control systems through the CAT Data Link. The Electronic Implement Control System consists of the following components:
STMGXXXx 4/97
- 64 -
Lift lever position sensor: Tells the ECM the position of the lift pilot control lever. Tilt lever position sensor: Tells the ECM the position of the tilt pilot control lever. Lift linkage position sensor: Tells the ECM the position of the lift arm relative to the machine. Bucket linkage position sensor: Tells the ECM the position of the bucket relative to the lift arm. Implement lockout switch: Tells the ECM that the operator wants the pilot control levers disabled. Kickout set switch: Used to set the bucket tilt, lift raise and lift lower kickout positions. Pilot on/off solenoid valve: Used to disable and enable the pilot hydraulic system. Bucket dump actuator: Directs pilot oil from the main control valve to tank. Bucket tilt actuator: Directs pilot oil from the main control valve to tank. Raise actuator: Directs pilot oil from the main control valve to tank. Lower actuator: Directs pilot oil from the main control valve to tank. Raise kickout solenoid: Holds the raise/lower lever in the raise position.
STMGXXX 4/97
- 65 -
Lower kickout solenoid: Holds the raise/lower lever in the lower position. Bucket kickout solenoid: Holds the tilt /dump lever in the tilt back position. CAT Data Link: Communication path to and from other electronic control modules.
STMGXXX 4/97
- 66 -
ELECTRO-HYDRAULIC IMPLEMENT SYSTEM
TILT CYLINDER
RIGHT LIFT CYLINDER
ELECTRONIC SYSTEM COMPONENTS
LEFT LIFT CYLINDER
SHUTTLE VALVE IMPLEMENT LOCKOUT SWITCH
RAISE/LOW/TILT KICKOUT SET SWITCH
PRESSURE REDUCING VALVE
TILT LINKAGE POSITION SENSOR
ELECTRONIC CONTROL MODULE
CAT DATA LINK
BUCKET KICKOUT DETENT SOLENOID
LIFT LINKAGE POSITION SENSOR
LIFT KICKOUT DETENT SOLENOID
TILT LEVER SENSOR
IMPLEMENT CONTROL VALVE
CHECK VALVE
PILOT ON/OFF VALVE
LOWER KICKOUT DETENT SOLENOID LIFT LEVER SENSOR
IMPLEMENT CONTROL VALVE
FIXED PUMP
RELIEF VALVE
RELIEF VALVE
PILOT RELIEF VALVE
PILOT PUMP
VARIABLE PUMP SOLENOID VALVE
VARIABLE PUMP
43 Identify components: - Implement lockout switch - Raise/lower/tilt kickout set switch - Electronic control module - Tilt linkage position sensor - Lift linkage position sensor - Tilt control lever - Bucket kickout detent solenoid - Lift control lever - Lift kickout detent solenoid - Pilot control actuators - Pilot on/off valve solenoid - Variable pump torque valve solenoid
Electronic Implement Control System Components The electronic system components (orange) are the implement lockout switch, the raise/lower/tilt kickout set switch, the electronic control module, the tilt linkage position sensor, the lift linkage position sensor, the tilt control lever, the bucket kickout detent solenoid, the lift control lever, the lift kickout detent solenoid, the lower kickout detent solenoid, the pilot control actuators, the pilot on/off valve solenoid and the variable pump torque valve solenoid.
STMGXXX 4/97
- 67 -
7 6 5 8
1
9 2 3 4
44
Identify components: 1. Implement hydraulic control levers 2. Tilt lever position sensor 3. Horn 4. Right armrest control lever 5. Reduced rim pull switch 6. Throttle lock set switch 7. Throttle resume switch 8. Implement hydraulic lock switch 9. Control lever cover
The implement hydraulic control levers (1) are attached to the right armrest assembly and move forward and rearward with the right armrest. When the operator moves the tilt control lever, the tilt control lever position sensor (2) sends a Pulse Width Modulated (PWM) signal to the ECM. Also shown are the horn (3), the right armrest control lever (4), the reduce rim pull switch (5), the throttle lock set switch (6), the throttle resume switch (7) and the implement hydraulic lock switch (8). Located beneath the control lever cover (9) are the lift control lever position sensor, the bucket kickout detent solenoid, the lift kickout detent solenoid and the lower kickout detent solenoid.
STMGXXX 4/97
- 68 -
10
11
12
13
7
8
9
14
1
2
3
4
5
6
45
Identify components:
The raise, lower and tilt kickout switch (1) is located in the right side
1. Raise, lower and tilt kickout switch 2. Dash lights switch 3. Work lights switch 4. Key pad 5. Electronic diagnostic connector 6. +12V connector 7. Rim pull selector 8. Stairway switch 9. Quick shift switch 10. Heater and a/c fan switch 11. Heater and a/c control 12. Start aid switch 13. Throttle lock switch 14. Ride control switch
. Depress the top of the switch to set the TILT kickout. Depress the bottom of the switch to set the RAISE and LOWER kickouts. When setting the bucket TILT kickout, move the bucket to the desired position. Return the tilt lever to the HOLD position. Depress the top of the kickout set switch for about 1 second and release. When setting the RAISE kickout, raise the lift arm to the desired position. Return the lift lever to the HOLD position. Depress the bottom of the kickout switch for about 1 second and release. When setting the LOWER kickout, lower the lift arm to the desired position. Return the lift lever to the HOLD position. Depress the bottom of the kickout switch for about 1 second and release.
STMGXXX 4/97
- 69 -
Also shown are the dash lights switch (2), the work lights switch (3), the key pad (4), the electronic diagnostic connector (5), the +12V connector (6), the rim pull selector (7), the stairway switch (8), the quick shift switch (9), the heater and a/c fan switch (10), the heater and a/c control (11), the start aid switch (12) and the throttle lock switch (13) and the ride control switch (14). (The ride control switch is no longer in that position. The ride control is currently located at the third position from the right.)
STMGXXX 4/97
- 70 -
2 1
46 Identify components: 1. Lift linkage position sensor 2. Tilt linkage position sensor
The lift linkage position sensor (1) is bolted to the left side of the front frame near the left side lift cylinder attachment pin. The lift linkage position sensor constantly monitors the position of the lift linkage and sends lift linkage position information to the ECM Module. The tilt linkage position sensor (2) is bolted to the right side of the lift arm near the tilt linkage attachment pin. The tilt linkage position sensor constantly monitors the position of the tilt linkage and sends tilt linkage position information to the ECM Module. When the operator moves the lift lever or the tilt lever, the ECM analyze the signal from the lift linkage position sensor and the signal from the tilt linkage position sensor. The ECM then sends a proportional signal to the respective control valve solenoid.
STMGXXX 4/97
- 71 -
6
5
7
4 3 2
1
47
Identify components: 1. Electronic Control Module 2. Fuse 3. Key start relay 4. Main relay 5. VIDS/VIMS interlock module No 1 6. VIDS/VIMS main module 7. Transmission ECM
The Electronic Control Module (1) is located beneath the platform on the right side of the cab. Also shown are the fuse (2), the key start relay (3), the main relay (4), the VIDS/VIMS interlock module No 1 (5), the VIDS/VIMS main module (6) and the Transmission ECM (7).
STMGXXX 4/97
- 72 -
4
2
1
3
48
Identify components: 1. On/off solenoid 2. Pilot control actuators 3. Float valve 4. Fixed pump relief valve
The on/off solenoid valve (1) is located in the front bottom section of the main control valve center manifold. When the on/off solenoid is DE-ENERGIZED, pilot oil is blocked at the on/off solenoid valve. When the on/off solenoid is ENERGIZED, pilot oil flows to the pilot control actuators. Also shown are the float valve (3) and the fixed pump relief valve (4).
STMGXXX 4/97
- 73 -
3
1
2
49
Identify components: 1. Pilot control solenoid 2. Lift cylinder rod end line relief valve 3. Tilt cylinder rod end line relief valve
The pilot control solenoids (1) control the movement of the pilot control actuators. When the operator moves a control lever, the control lever position sensor sends a pulse width modulation (PWM) signal to the ECM. The ECM analyze the signals from the control lever position sensor, the lift linkage position sensor and the tilt linkage position sensor. the ECM then sends a proportional signal to ENERGIZE the respective pilot control actuator solenoid. Also shown are the lift cylinder rod end line relief valve (2) and the tilt cylinder rod end line relief valve(3).
STMGXXX 4/97
- 74 -
4
1
2
3
50
Identify components: 1. Variable pump torque valve 2. Pump torque valve solenoid 3. Implement pilot relief valve 4. Implement pilot oil pressure tap
The variable pump solenoid valve (1) is located on the inside left frame and to the rear of the implement pilot relief valve (3). The variable pump solenoid valve controls pilot pressure to the load limiting control valve on the variable pump control. The ECM energizes the variable pump valve solenoid (2) whenever the key start switch is ON. The ECM signal to the variable pump solenoid valve controls the pressure in the load limit control valve. When the variable pump pressure increases to 80% of maximum pressure, the load limit control valve moves and sends oil pressure to the large actuator to destroke the pump. Also shown is the implement pilot oil pressure tap (4).
STMGXXX 4/97
- 76 -
ELECTRO-HYDRAULIC IMPLEMENT SYSTEM PILOT SYSTEM COMPONENTS
TILT CYLINDER
RIGHT LIFT CYLINDER
LEFT LIFT CYLINDER
SHUTTLE VALVE IMPLEMENT LOCKOUT SWITCH
RAISE/LOW/TILT KICKOUT SET SWITCH
PRESSURE REDUCING VALVE
TILT LINKAGE POSITION SENSOR
ELECTRONIC CONTROL MODULE
CAT DATA LINK
BUCKET KICKOUT DETENT SOLENOID
LIFT LINKAGE POSITION SENSOR
LIFT KICKOUT DETENT SOLENOID
TILT LEVER SENSOR
IMPLEMENT CONTROL VALVE
LOWER KICKOUT DETENT SOLENOID LIFT LEVER SENSOR
IMPLEMENT CONTROL VALVE
PILOT ON/OFF VALVE
CHECK VALVE
CHECK VALVE
RELIEF VALVE
PILOT RELIEF VALVE
PILOT PUMP
FIXED PUMP
RELIEF VALVE
FILTER VARIABLE PUMP SOLENOID VALVE
VARIABLE PUMP
51 Identify components: - Tank - Pilot pump - Pilot relief valve - Pilot on/off valve - Check valve - Pressure reducing valve - Pilot control actuators
Hydraulic Pilot System The hydraulic pilot system components (brown) are the tank, the pilot pump, the pilot relief valve, the pilot on/off valve, the check valve, the pressure reducing valve and the pilot control actuators.
STMGXXX 4/97
- 77 -
7
8
9
10
6
1
5
2
4
3
52
Identify components: 1. 2. 3. 4. 5. 6. 7.
Hydraulic tank Deck plate Fill cap Vent valve Alternator breaker Main circuit breaker Starting/charger analyzer connector 8. Service tool connector 9. Running lamp breaker 10. Key breaker
The implement hydraulic tank (1) is below the forward hinged deck plate (2) on the right side of the machine. The tank has a fill cap (3) for filling and adding oil and a vent valve (4) that protects the tank from excessive pressure and/or vacuum. The tank also has (not shown) three screen for return oil, an ecology-type drain valve for changing the oil and a sight glass for checking the oil level. Also shown are the alternator breaker (5), the main circuit breaker (6), the starting/charger analyzer connector (7), the service tool connector (8), the running lamps breaker (9) and the key breaker (10). NOTE: Oil change intervals and procedures are covered in the Operation and Maintenance section of the Service Manual.
STMGXXX 4/97
- 78 -
2 1
3 4
5
53
Identify components:
The implement pilot pump (1) is a gear-type pump mounted on the front
1. Pilot pump 2. Implement variable piston pump 3. Pilot pump inlet hose 4. Pilot pump outlet hose 5. Pilot pump pressure tap
of the implement variable piston pump (2). Tank oil flows through the pilot pump inlet hose (3) to the implement pilot pump. Pump supply oil flows through the outlet hose (4) to the implement pilot filter. Also shown is the pilot pump pressure tap (5).
STMGXXX 4/97
- 79 -
2 3
6
1
5
4
54
Identify components: 1. Implement pilot oil filter 2. Oil filter bracket 3. ROPS mounting plate 4. Oil filter inlet hose 5. Oil filter outlet hose 6. Oil filter by switch
The implement pilot oil filter (1) bracket (2) is bolted to the right r ROPS mounting plate (3). Pressure oil from the pilot pump flows through the oil filter inlet hose (4), the pilot filter and the oil filter outlet hose (5) to the pilot relief valve (not shown). The oil filter by switch (6) alerts the VIDS when the filter is bying.
STMGXXX 4/97
- 80 -
4
3
1
5
2
7
6
55
Identify components: 1. 2. 3. 4. 5. 6. 7.
Pilot relief valve Torque valve Inlet hose Outlet hose Outlet hose Return hose Pilot relief valve pressure sensor
The pilot relief valve (1) is bolted to the inside left frame forward of the torque valve (2). Pilot oil from the pilot filter flows through the inlet hose (3) to the pilot relief valve. The pilot relief valve maintains pilot oil pressure at 2520 kPa (365 psi). Pilot pressure oil flows through the outlet hose (4) to the on/off solenoid valve. Pilot pressure oil also flows through the outlet hose (5) to the torque valve. Pilot relief valve return oil flows through the return hose (6) to the tank. The pilot relief valve pressure sensor (7) supplies pilot oil pressure information to the VIDS/VIMS.
STMGXXX 4/97
- 81 -
7 5 6 1 3 2 4 8
56
Identify components: 1. Pilot control solenoid valves 2. Pilot on/off valve solenoid 3. Lift rod end line relief valve 4. Lift head end line relief valve 5. Tilt rod end line relief valve 6. Tilt head end line relief valve 7. Fixed pump relief valve 8. Float valve
The pilot control solenoid valves (1) controls pilot oil flow from the ends of the main control valve spools to the tank. Also shown are the pilot on/off valve solenoid (2), the lift rod end line relief valve (3), the lift head end line relief valve (4), the tilt rod end line relief valve (5), the tilt head end line relief valve (6), the fixed pump relief valve (7) and the float valve (8).
STMGXXX 4/97
- 82 -
ELECTRO-HYDRAULIC IMPLEMENT SYSTEM MAIN HYDRAULIC SYSTEM COMPONENTS
TILT CYLINDER
RIGHT LIFT CYLINDER
LEFT LIFT CYLINDER
SHUTTLE VALVE IMPLEMENT LOCKOUT SWITCH
RAISE/LOW/TILT KICKOUT SET SWITCH
PRESSURE REDUCING VALVE
TILT LINKAGE POSITION SENSOR
ELECTRONIC CONTROL MODULE
CAT DATA LINK
BUCKET KICKOUT DETENT SOLENOID
LIFT LINKAGE POSITION SENSOR
LIFT KICKOUT DETENT SOLENOID
TILT LEVER SENSOR
IMPLEMENT CONTROL VALVE
LOWER KICKOUT DETENT SOLENOID LIFT LEVER SENSOR
IMPLEMENT CONTROL VALVE
PILOT ON/OFF VALVE
CHECK VALVE
CHECK VALVE
RELIEF VALVE
FIXED PUMP
PILOT RELIEF VALVE
RELIEF VALVE
FILTER
PILOT PUMP
VARIABLE PUMP SOLENOID VALVE
VARIABLE PUMP
57 Identify components: - Tank - Fixed pump - Fixed pump relief valve - Fixed pump implement control valve - Variable pump - Variable pump relief valve - Variable pump implement control valve - Shuttle valve - Lift cylinders - Tilt cylinder
Main Hydraulic System The hydraulic pilot system components (green) are the tank, the fixed pump, the fixed pump relief valve, the fixed pump implement control valve, the variable pump, the variable pump relief valve and the variable pump implement control valve, the shuttle valve, the lift cylinders and the tilt cylinder.
STMGXXX 4/97
- 83 -
4
7
6
8
5
2 1
3
58
Identify components: 1. 2. 3. 4. 5. 6. 7. 8.
Fixed pump Suction hose Supply hose Variable pump Suction hose Supply hose Case drain Pump drive housing
The main hydraulic system contains a fixed displacement, piston-type pump (1) and a variable displacement piston-type pump (4). Oil flows from the tank through a suction tube (2) to the fixed displacement pump. Pump pressure oil flows through a supply hose (3) to the fixed pump implement control valve. Oil flows from the tank through a suction tube (5) to the variable displacement pump. Pump pressure oil flows through a supply hose (6) to the variable pump implement control valve. Also shown are the case drain (7) and the pump drive housing (8).
STMGXXX 4/97
- 84 -
VARIABLE PUMP SOLENOID VALVE TO PILOT SYSTEM
VARIABLE IMPLEMENT PUMP LESS THAN 2400kPa (350 psi)
TO TANK PILOT RELIEF VALVE
TO IMPLEMENT CONTROL VALVE PRESSURE CUTOFF
PILOT FILTER
FLUID SAMPLING PORT
LOAD LIMIT CONTROL
SHUTTLE VALVE
SMALL ACTUATOR PILOT PUMP
PUMP
LARGE ACTUATOR
59 Explain schematic
Variable Pump Control Schematic This schematic shows the oil flow in the variable pump control when the variable pump pressure is less than 2400 kPa (350 psi). The pilot pump pulls oil from the tank and sends oil flow through the filter to the pilot system. The pilot relief valve maintains pilot system oil at 2400 kPa (350 psi). When the key switch is in the ON position, the variable pump torque valve solenoid is ENERGIZED. Pilot oil flows through the variable pump torque valve to the load limit control. Pilot oil also flows to the shuttle valve. When the variable pump oil is not being used, the variable pump pressure is less than the pilot pressure. Pilot oil flows through the shuttle valve and into the small actuator spring chamber. The combined force of the pilot pressure and the small actuator spring holds the variable pump swash plate at maximum angle.
STMGXXX 4/97
- 85 -
VARIABLE PUMP SOLENOID VALVE TO PILOT SYSTEM
VARIABLE IMPLEMENT PUMP LESS THAN 28,940 kPa (4200 psi)
TO TANK PILOT RELIEF VALVE
TO IMPLEMENT CONTROL VALVE PRESSURE CUTOFF
PILOT FILTER
FLUID SAMPLING PORT
LOAD LIMIT CONTROL
SHUTTLE VALVE
SMALL ACTUATOR PILOT PUMP
PUMP
LARGE ACTUATOR
60 Explain schematic
When the variable pump oil is being used and the oil pressure is between 2400 kPa (350 psi) and 28,940 kPa (4200 psi), variable pump oil moves the shuttle valve and blocks the pilot system oil. Variable pump oil flows through the shuttle valve and into the small actuator spring chamber. The combined force of the variable pump oil pressure and the small actuator spring holds the variable pump swash plate at maximum angle.
STMGXXX 4/97
- 86 -
VARIABLE PUMP SOLENOID VALVE TO PILOT SYSTEM
VARIABLE IMPLEMENT PUMP MORE THAN 28,940 kPa (4200 psi)
TO TANK PILOT RELIEF VALVE
PILOT FILTER
FLUID SAMPLING PORT
TO IMPLEMENT CONTROL VALVE PRESSURE CUTOFF LOAD LIMIT CONTROL
SHUTTLE VALVE
SMALL ACTUATOR PILOT PUMP
PUMP
LARGE ACTUATOR
61 Explain schematic
When the variable pump oil pressure is more than 28,940 kPa (4200 psi), oil pressure overcomes the force of the pressure cutoff valve spring and moves the pressure cutoff valve. The pressure cutoff valve opens a age to send variable pump oil to the large actuator. The oil pressure in the large actuator overcomes the force of the small actuator (oil pressure and the small actuator spring) and moves the swash plate to the minimum angle.
STMGXXX 4/97
- 87 -
1 2
6
3
4
5
62
Identify components: 1. Main control valve assembly 2. Implement control valve 3. Tilt cylinder rod end hose 4. Lift cylinders rod end hose 5. Lift cylinders head end hose 6. Tilt cylinder head end hose
The main control valve assembly (1) is located in the front frame below the boom. The right side control valve (2) receives oil from the variable implement pump. Also shown are the hose (3) to the tilt cylinder rod end, the hose (4) to the lift cylinders rod end, the hose (5) to the lift cylinders head end and the hose (6) to the tilt cylinder head end.
STMGXXX 4/97
- 88 -
2 1
5
4
3
63
Identify components: 1. 2. 3. 4.
Lift cylinder Tilt cylinder Bucket position Front right brake housing 5. Front right final drive housing
When an implement is activated, oil from the implement control valve is directed to the lift cylinders (1) and/or tilt cylinder (2). Also shown are the bucket position sensor (3), the front right brake housing (4) and the front right final drive housing (5).
STMGXXX 4/97
- 89 -
ELECTRO-HYDRAULIC IMPLEMENT SYSTEM
TILT CYLINDER
RIGHT LIFT CYLINDER
HOLD
LEFT LIFT CYLINDER
SHUTTLE VALVE IMPLEMENT LOCKOUT SWITCH
RAISE/LOW/TILT KICKOUT SET SWITCH
PRESSURE REDUCING VALVE
TILT LINKAGE POSITION SENSOR
ELECTRONIC CONTROL MODULE
CAT DATA LINK
BUCKET KICKOUT DETENT SOLENOID TILT LEVER SENSOR
IMPLEMENT CONTROL VALVE
LIFT LINKAGE POSITION SENSOR
LIFT KICKOUT DETENT SOLENOID
PILOT ON/OFF VALVE
CHECK VALVE
CHECK VALVE
LOWER KICKOUT DETENT SOLENOID LIFT LEVER SENSOR
IMPLEMENT CONTROL VALVE
FIXED PUMP
RELIEF VALVE
PILOT RELIEF VALVE
RELIEF VALVE FILTER
PILOT PUMP
VARIABLE PUMP SOLENOID VALVE
VARIABLE PUMP
64 Explain schematic
Electro-Hydraulic Schematics When the implement lockout switch is in the ON position, the ECM energizes the pilot on/off valve solenoid. The pilot on/off valve solenoid opens the pilot on/off valve. The pilot pump pulls oil from the hydraulic tank and sends oil flow through the pilot on/off valve to the pilot control actuators at each end of the control valve spools. Pilot oil pressure increases to the relief valve pressure setting. The relief valve opens and maintains a constant pressure in the pilot system. The control valve spools are hydraulically locked in the HOLD position. In the HOLD position, the control valve spools block oil flow to the lift and tilt cylinders. Oil from the fixed pump and the variable pump flows past the respective control valve spools to the tank.
STMGXXX 4/97
- 90 -
ELECTRO-HYDRAULIC IMPLEMENT SYSTEM
TILT CYLINDER
RIGHT LIFT CYLINDER
SLOW TILT
LEFT LIFT CYLINDER
SHUTTLE VALVE IMPLEMENT LOCKOUT SWITCH
RAISE/LOW/TILT KICKOUT SET SWITCH
PRESSURE REDUCING VALVE
TILT LINKAGE POSITION SENSOR
ELECTRONIC CONTROL MODULE
CAT DATA LINK
BUCKET KICKOUT DETENT SOLENOID
LIFT LINKAGE POSITION SENSOR
LIFT KICKOUT DETENT SOLENOID TILT LEVER SENSOR
IMPLEMENT CONTROL VALVE
PILOT ON/OFF VALVE
CHECK VALVE
CHECK VALVE
LOWER KICKOUT DETENT SOLENOID LIFT LEVER SENSOR
IMPLEMENT CONTROL VALVE
FIXED PUMP
RELIEF VALVE
PILOT RELIEF VALVE
RELIEF VALVE FILTER
PILOT PUMP
VARIABLE PUMP SOLENOID VALVE
VARIABLE PUMP
65 Explain schematic
When the tilt control lever is moved to the SLOW TILT position, the tilt control lever sensor sends a PWM signal to the ECM. The ECM analyzes the tilt control lever sensor signal and the signals from the lift linkage position sensor and the tilt linkage position sensor. The ECM then sends a proportional signal to ENERGIZE the tilt pilot control valve solenoid on the fixed pump implement control valve. The solenoid moves the pilot control valve and sends pilot oil at the tilt end of the tilt/dump control valve spool to drain. This reduces the pilot oil pressure at the tilt end of the control valve spool. The oil pressure on the dump end of the control valve spool moves the valve spool to the TILT position.
STMGXXX 4/97
- 91 -
The fixed pump oil flows past the tilt/dump control valve spool to the rod end of the tilt cylinder. Tilt cylinder head end oil flows past the tilt/dump control valve spool to the tank. The variable pump oil is not needed for slow tilt operation. The ECM does not energize the variable pump tilt control valve solenoid. The variable pump oil flows through the variable pump implement control valve to the tank. With exception of the FLOAT position, the ECM uses the oil from the fixed pump for all implement operations until the operational demand for oil is greater than the fixed pump can supply. The ECM will then use oil from the variable pump to satisfy the demand.
STMGXXX 4/97
- 92 -
ELECTRO-HYDRAULIC IMPLEMENT SYSTEM
TILT CYLINDER
RIGHT LIFT CYLINDER
FAST TILT
LEFT LIFT CYLINDER
SHUTTLE VALVE IMPLEMENT LOCKOUT SWITCH
RAISE/LOW/TILT KICKOUT SET SWITCH
PRESSURE REDUCING VALVE
TILT LINKAGE POSITION SENSOR
ELECTRONIC CONTROL MODULE
CAT DATA LINK
BUCKET KICKOUT DETENT SOLENOID
LIFT LINKAGE POSITION SENSOR
LIFT KICKOUT DETENT SOLENOID TILT LEVER SENSOR
IMPLEMENT CONTROL VALVE
PILOT ON/OFF VALVE
CHECK VALVE
CHECK VALVE
LOWER KICKOUT DETENT SOLENOID LIFT LEVER SENSOR
IMPLEMENT CONTROL VALVE
FIXED PUMP
RELIEF VALVE
PILOT RELIEF VALVE
RELIEF VALVE FILTER
PILOT PUMP
VARIABLE PUMP SOLENOID VALVE
VARIABLE PUMP
66 Explain schematic
When the tilt control lever is moved to the FAST TILT position, the tilt control lever sensor sends a PWM signal to the ECM.. The ECM analyzes the tilt control lever sensor signal and the signals from the lift linkage position sensor and the tilt linkage position sensor. The ECM sends a signal to ENERGIZE the tilt pilot control actuator solenoid on the fixed pump implement control valve and a signal to ENERGIZE the tilt pilot control actuator solenoid on the variable pump implement control valve. The signals may be of different proportion. The solenoids move the pilot control actuators and send pilot oil at the tilt ends of the tilt/dump control valve spools to drain. This reduces the pilot oil pressure at the tilt ends of the control valve spools. The oil pressure on the dump ends of the control valve spools move the valve spools to the FAST TILT position.
STMGXXX 4/97
- 93 -
The fixed pump oil flows around the tilt control valve spool in the fixed pump implement control valve to the rod end of the tilt cylinder. The variable pump oil flows around the tilt control valve spool in the variable pump implement control valve to the rod end of the tilt cylinder. The tilt cylinder head end oil flows past both tilt control valve spools to the tank. The return oil flow past each valve spool is proportion to the supply oil flow past the valve spool. The desired tilt cylinder speed determines the difference in oil flow between the fixed pump and the variable pump. A slow tilt cylinder speed will cause a larger difference in oil flow between the two pumps than a fast tilt cylinder speed.
STMGXXX 4/97
- 94 -
ELECTRO-HYDRAULIC IMPLEMENT SYSTEM
TILT CYLINDER
RIGHT LIFT CYLINDER
SLOW LIFT
LEFT LIFT CYLINDER
SHUTTLE VALVE IMPLEMENT LOCKOUT SWITCH
RAISE/LOW/TILT KICKOUT SET SWITCH
PRESSURE REDUCING VALVE
TILT LINKAGE POSITION SENSOR
ELECTRONIC CONTROL MODULE
CAT DATA LINK
BUCKET KICKOUT DETENT SOLENOID
LIFT LINKAGE POSITION SENSOR
LIFT KICKOUT DETENT SOLENOID TILT LEVER SENSOR
IMPLEMENT CONTROL VALVE
PILOT ON/OFF VALVE
CHECK VALVE
CHECK VALVE
LOWER KICKOUT DETENT SOLENOID LIFT LEVER SENSOR
IMPLEMENT CONTROL VALVE
FIXED PUMP
RELIEF VALVE
PILOT RELIEF VALVE
RELIEF VALVE FILTER
PILOT PUMP
VARIABLE PUMP SOLENOID VALVE
VARIABLE PUMP
67 Explain schematic
When the operator moves the lift control lever to the SLOW LIFT position, the lift control lever sensor sends a PWM signal to the ECM. The ECM analyzes the lift control lever sensor signal and the signals from the lift linkage position sensor and the tilt linkage position sensor. The ECM then sends a proportional signal to ENERGIZE the lift pilot control actuator solenoid on the fixed pump implement control valve. The solenoid moves the pilot control actuator and sends pilot oil at the lift end of the lift/lower control valve spool to drain. This reduces the pilot oil pressure at the lift end of the control valve spool. The oil pressure on the lower end of the control valve spool moves the valve spool to the LIFT position.
STMGXXX 4/97
- 95 -
The fixed pump oil flows past the lift/lower control valve spool to the head end of the lift cylinders. Lift cylinder rod end oil flows past the lift/lower control valve spools to the tank. The variable pump oil is not needed for slow lift operation. The ECM does not energize the variable pump lift control actuator. The variable pump oil flows through the variable pump implement control valve to the tank.
STMGXXX 4/97
- 96 -
ELECTRO-HYDRAULIC IMPLEMENT SYSTEM
TILT CYLINDER
RIGHT LIFT CYLINDER
FAST LIFT
LEFT LIFT CYLINDER
SHUTTLE VALVE IMPLEMENT LOCKOUT SWITCH
RAISE/LOW/TILT KICKOUT SET SWITCH
PRESSURE REDUCING VALVE
TILT LINKAGE POSITION SENSOR
ELECTRONIC CONTROL MODULE
CAT DATA LINK
BUCKET KICKOUT DETENT SOLENOID
LIFT KICKOUT DETENT SOLENOID TILT LEVER SENSOR
IMPLEMENT CONTROL VALVE
LIFT LINKAGE POSITION SENSOR
PILOT ON/OFF VALVE
CHECK VALVE
CHECK VALVE
LOWER KICKOUT DETENT SOLENOID LIFT LEVER SENSOR
IMPLEMENT CONTROL VALVE
FIXED PUMP
RELIEF VALVE
PILOT RELIEF VALVE
RELIEF VALVE FILTER
PILOT PUMP
VARIABLE PUMP SOLENOID VALVE
VARIABLE PUMP
68 Explain schematic
When the lift control lever is moved to the FAST LIFT position, the lift control lever sensor sends a proportional PWM signal to the ECM. The ECM analysis the lift control lever sensor signal, the signal from the lift sensor and the signal from the tilt sensor. The ECM sends a signal to the lift actuator solenoid on the fixed pump implement control valve and to the lift actuator solenoid on the variable pump implement control valve. The signals may be of different proportion. The solenoids move the pilot control actuators and send pilot oil at the LIFT ends of the lift/lower valves to drain. This reduces the pilot pressure at the lift ends of the control valve spools. The oil pressure on the lower ends of the control valve spools move the valve spools to the FAST LIFT position. The fixed pump oil flows around the lift control valve spool in the fixed pump implement control valve to the head ends of the lift cylinders.
STMGXXX 4/97
- 97 -
The variable pump oil flows around the lift control valve spool in the variable pump implement control valve to the head ends of the lift cylinders. The lift cylinders rod end oil flows past both lift control valve spools to the tank. The return oil flows past each valve spool in proportion to the supply oil flow past the valve spool. The desired lift cylinder speed determines the difference in oil flow between the fixed pump and the variable pump. A slow lift cylinder speed will cause a larger difference in oil flow between the two pumps than a fast lift cylinder speed.
STMGXXX 4/97
- 98 -
IMPLEMENT HYDRAULIC SYSTEM SLOW TILT
PRESSURE REDUCING VALVE
LIFT CYLINDER
TILT CYLINDER
LIFT CYLINDER
SHUTTLE VALVE
LOWER
TILT
TILT
LOWER
RIDE CONTROL
PILOT ON/OFF VALVE
VARIABLE PUMP SOLENOID VALVE RAISE
DUMP
DUMP
RAISE
FAN MOTOR
PILOT RELIEF VALVE
FAN SPEED
PRESSURE CUTOFF COOLER SHUTTLE VALVE
FLUID SAMPLING PORT
FIXED PUMP
LOAD LIMIT CONTROL
FAN DRIVE PUMP
SMALL ACTUATOR LARGE ACTUATOR
VARIABLE PUMP
PILOT PUMP
69 Explain schematic
Implement Hydraulic Schematics This schematic shows the oil flow in the implement pilot system and the implement hydraulic system when the engine is running and the control valves are in the HOLD position. In the pilot system, the pilot pump pulls oil from the tank and sends oil flow to the pilot relief valve, the variable pump control, the variable pump torque valve, the ride control valve (optional) and the pilot on/off valve. The pilot relief valve maintains pilot system at 2514 ± 205 kPa (365 ± 30 psi).
STMGXXX 4/97
- 99 -
When the variable pump oil is not being used, pilot oil pressure assists the small actuator spring in the variable pump control and moves the swash plate to maximum angle. When the variable pump torque valve solenoid is ENERGIZED, pilot oil flows to the load limit control valve in the variable pump control and prevents movement of the load limit control valve until the variable pump oil pressure increase to 0000 ± 000 kPa (0000 ± 000 psi). When oil pressure reaches 0000 ± 000 kPa (0000 ± 000 psi), the load limit control destrokes the pump and decreases flow by approximately 20%. As pressure increases, the load limit control valve will maintain flow at approximately 80% of maximum until pump pressure reaches 28925 kPa (4200 psi). When pump pressure increase to 28925 kPa (4200 psi), the pressure cutoff valve destrokes the pump and maintains pump pressure at a maximum of 28925 kPa (4200 psi). The pilot on/off valve solenoid is controlled by the implement lockout switch (not shown). When the implement lockout switch is in the OFF position, the ECM (not shown) will not energize the pilot on/off valve solenoid. Pilot oil is blocked at the pilot on/off valve. When the implement lockout switch is in the ON position, the ECM energizes the pilot on/off valve solenoid. Pilot oil flows past the pilot on/off valve to the pilot control solenoid valves. In the implement fixed pump hydraulic system, the fixed pump pulls oil from the tank and sends oil flow to the left side main control valve. When the control valve spools are in the HOLD position, oil flows past the fixed pump relief valve and through the open-centered control valve to the tank. The fixed pump relief valve constantly senses pressure at the fixed pump and opens to the tank when the pressure reaches the maximum setting of 31000 kPa (4500 psi).
STMGXXX 4/97
- 100 -
The implement variable pump hydraulic system, the variable pump pulls oil from the tank and sends oil flow to the right side main control valve. When the control valve spools are in the HOLD position, oil flows past the variable pump relief valve and through the open-centered control valve to the tank. Variable pump pressure is controlled by the variable pump compensator valve. The variable pump relief valve serves as a backup in case of a compensator valve failure. The variable pump relief valve is set at 31000 kPa (4500 psi) In the HOLD position, oil flow to and from the cylinders are blocked at the control valve spools.
STMGXXX 4/97
- 101 -
IMPLEMENT HYDRAULIC SYSTEM SLOW TILT
PRESSURE REDUCING VALVE
LIFT CYLINDER
TILT CYLINDER
LIFT CYLINDER
SHUTTLE VALVE
LOWER
TILT
TILT
LOWER
RIDE CONTROL
PILOT ON/OFF VALVE
VARIABLE PUMP SOLENOID VALVE RAISE
DUMP
DUMP
PILOT RELIEF VALVE
RAISE
FAN SPEED PRESSURE CUTOFF SHUTTLE VALVE
FLUID SAMPLING PORT
FIXED PUMP
LOAD LIMIT CONTROL SMALL ACTUATOR LARGE ACTUATOR
VARIABLE PUMP
PILOT PUMP
70 Explain schematic
When the tilt/dump control lever (not shown) is moved to the SLOW TILT position, the tilt/dump control lever sensor (not shown) sends a PWM signal to the ECM (not shown). The ECM analyzes the tilt/dump control lever sensor signal and the signals from the lift linkage position sensor (not shown) and the tilt linkage position sensor (not shown). The ECM then sends a proportional signal to ENERGIZE the tilt pilot control valve solenoid on the fixed pump implement control valve. The solenoid moves the pilot control valve and sends pilot oil at the tilt end of the tilt/dump control valve spool to drain. This reduces the pilot oil pressure at the tilt end of the control valve spool. The oil pressure on the dump end of the control valve spool moves the valve spool to the TILT position.
STMGXXX 4/97
- 102 -
The tilt/dump control valve spool blocks the flow of fixed pump oil to the tank and opens the age to the tilt cylinder. The fixed pump oil flows past the tilt/dump load check valve and past the tilt/dump control valve spool to the rod end of the tilt cylinder. Oil from the head end of the tilt cylinder flows past the tilt/dump control valve spool to the tank. The variable pump oil flows through the right side implement control valve to the tank.
STMGXXX 4/97
- 103 -
IMPLEMENT HYDRAULIC SYSTEM FAST TILT
PRESSURE REDUCING VALVE
LIFT CYLINDER
TILT CYLINDER
LIFT CYLINDER
SHUTTLE VALVE
LOWER
TILT
TILT
LOWER
RIDE CONTROL
PILOT ON/OFF VALVE
VARIABLE PUMP SOLENOID VALVE
RAISE
DUMP
DUMP
FAN MOTOR
PILOT RELIEF VALVE PRESSURE CUTOFF FIXED PUMP
LOAD LIMIT CONTROL
FAN DRIVE PUMP
SMALL ACTUATOR LARGE ACTUATOR
FAN SPEED
COOLER SHUTTLE VALVE
FLUID SAMPLING PORT
RAISE
VARIABLE PUMP
PILOT PUMP
71 Explain schematic
When the tilt/dump control lever (not shown) is moved to the FAST TILT position, the tilt/dump control lever sensor (not shown) increases the PWM signal to the ECM (not shown).. The ECM analyzes the increased tilt/dump control lever sensor signal, the lift linkage position sensor signal (not shown) and the tilt linkage position sensor signal (not shown). The ECM increases the signal to the TILT solenoid on the fixed pump tilt/dump control valve. The ECM also sends a signal to ENERGIZE the TILT solenoid on the variable pump tilt/dump control valve. Often the signal voltage is different to the two pumps. On the fixed pump control valve, the increased ECM signal increases the TILT pilot control valve solenoid magnetic field.
STMGXXX 4/97
- 104 -
The stronger magnetic field moves the TILT pilot control valve further against the spring enlarging the drain age. The additional oil drain decreases the oil pressure at the TILT end of the tilt/dump control valve spool. The oil pressure on the DUMP end of the tilt/dump control valve spool moves the valve spool to the FAST TILT position. In the FAST TILT position, the fixed pump oil flow is increased to the rod end of the tilt cylinder. The increase in oil flow allows the bucket to travel faster. The tilt cylinder head end oil flows past the tilt/dump control valve spool to the tank. On the variable pump control valve, the ECM signal ENERGIZES the TILT solenoid on the tilt/dump control valve . The TILT solenoid moves the pilot control valve and opens a age for pilot oil to drain to tank. This reduces the pilot oil pressure at the TILT end of the tilt/dump control valve. The pilot oil pressure on the DUMP end of the control valve spool moves the control valve spool to the TILT position. In the FAST TILT position, the tilt/dump control valve spool blocks the oil flow to the tank and opens the age to the rod end of the tilt cylinder. The variable pump oil flows past the tilt/dump load check valve, past the tilt/dump control valve spool and s with the oil from the fixed pump. The combined oil flows to the rod end of the tilt cylinder. The tilt cylinder head end oil flows past the tilt/dump control valve spool to the tank. The return oil flow past each valve spool is proportion to the supply oil flow past the valve spool.
STMGXXX 4/97
- 105 -
IMPLEMENT HYDRAULIC SYSTEM SLOW LOWER
PRESSURE REDUCING VALVE
LIFT CYLINDER
TILT CYLINDER
LIFT CYLINDER
SHUTTLE VALVE
LOWER
TILT
TILT
LOWER
RIDE CONTROL
PILOT ON/OFF VALVE
VARIABLE PUMP SOLENOID VALVE
RAISE
DUMP
DUMP
FAN MOTOR
PILOT RELIEF VALVE PRESSURE CUTOFF FIXED PUMP
LOAD LIMIT CONTROL
FAN DRIVE PUMP
SMALL ACTUATOR LARGE ACTUATOR
FAN SPEED
COOLER SHUTTLE VALVE
FLUID SAMPLING PORT
RAISE
VARIABLE PUMP
PILOT PUMP
72 Explain schematic
When the raise/lower control lever (not shown) is moved to the SLOW LOWER position, the raise/lower control lever sensor (not shown) sends a PWM signal to the ECM (not shown). The ECM analyzes the raise/lower control lever sensor signal, the lift linkage position sensor signal (not shown) and the tilt linkage position sensor signal (not shown). The ECM then sends a proportional signal to ENERGIZE the fixed pump raise/lower control valve lower solenoid. The lower solenoid moves the pilot control valve and opens a age for pilot oil at the raise/lower control valve LOWER end to drain to tank. This reduces the pilot oil pressure at the LOWER end of the raise/lower control valve. The pilot oil pressure on the RAISE end of the control valve spool moves the control valve spool to the SLOW LOWER position.
STMGXXX 4/97
- 106 -
The raise/lower control valve spool blocks the flow of fixed pump oil to the tank and opens the age to the lift cylinders. The fixed pump oil flows past the raise/lower load check valve and past the raise/lower control valve spool to the rod ends of the lift cylinders. Oil from the head end of the lift cylinders flow past the raise/lower control valve spool to the tank. The variable pump oil flows through the right side implement control valve to the tank.
STMGXXX 4/97
- 107 -
IMPLEMENT HYDRAULIC SYSTEM FAST LOWER
PRESSURE REDUCING VALVE
LIFT CYLINDER
TILT CYLINDER
LIFT CYLINDER
SHUTTLE VALVE
LOWER
TILT
TILT
LOWER
RIDE CONTROL
PILOT ON/OFF VALVE
VARIABLE PUMP SOLENOID VALVE
RAISE
DUMP
DUMP
RAISE
PILOT RELIEF VALVE
FAN MOTOR PRESSURE CUTOFF
COOLER
SHUTTLE VALVE
FLUID SAMPLING PORT
FIXED PUMP
LOAD LIMIT CONTROL
FAN DRIVE PUMP
SMALL ACTUATOR LARGE ACTUATOR
FAN SPEED
VARIABLE PUMP
PILOT PUMP
73 Explain schematic
When the raise/lower control lever (not shown) is moved to the FAST LOWER position, the raise/lower control lever sensor (not shown) increases the PWM signal to the ECM (not shown).. The ECM analyzes the increased raise/lower control lever sensor signal, the lift linkage position sensor signal (not shown) and the tilt linkage position sensor signal (not shown). The ECM increases the signal to the LOWER solenoid on the fixed pump raise/lower control valve. The ECM also sends a signal to ENERGIZE the LOWER solenoid on the variable pump raise/lower control valve. Often the signal voltage is different to the two pumps. On the fixed pump control valve, the increased ECM signal increases the LOWER pilot control valve solenoid magnetic field.
STMGXXX 4/97
- 108 -
The stronger magnetic field moves the LOWER pilot control valve further against the spring and increases the drain age. The increased oil drain decreases the oil pressure on the LOWER end of the raise/lower control valve spool. The oil pressure on the RAISE end of the raise/lower control valve spool moves the valve spool to the FAST LOWER position. In the FAST LOWER position, the fixed pump oil flow is increased to the rod ends of the lift cylinders. The increase in oil flow allows the lift arm to be lowered faster. The lift cylinders head end oil flow past the raise/lower control valve spool to the tank. On the variable pump control valve, the ECM signal ENERGIZES the LOWER solenoid on the raise/lower control valve . The LOWER solenoid moves the pilot control valve and opens a age for pilot oil to drain to tank. This reduces the pilot oil pressure at the LOWER end of the raise/lower control valve. The pilot oil pressure on the RAISE end of the raise/lower control valve spool moves the control valve spool to the LOWER position. The raise/lower control valve spool blocks the oil flow to the tank and opens the age to the rod ends of the lift cylinders. The variable pump oil flows past the raise/lower load check valve, past the raise/lower control valve spool and s with the fixed pump oil. The combined oil flows to the rod end of the lift cylinders. The lift cylinders head end oil flow past the raise/lower control valve spools to the tank. The return oil flow past each valve spool is proportion to the supply oil flow past the valve spool.
STMGXXX 4/97
- 109 -
IMPLEMENT HYDRAULIC SYSTEM FLOAT
PRESSURE REDUCING VALVE
LIFT CYLINDER
TILT CYLINDER
LIFT CYLINDER
SHUTTLE VALVE
LOWER
TILT
TILT
LOWER
RIDE CONTROL
PILOT ON/OFF VALVE
VARIABLE PUMP SOLENOID VALVE
PILOT RELIEF VALVE
RAISE
DUMP
DUMP
RAISE
FAN MOTOR
FAN SPEED
PRESSURE CUTOFF COOLER SHUTTLE VALVE
FLUID SAMPLING PORT
FIXED PUMP
LOAD LIMIT CONTROL
FAN DRIVE PUMP
SMALL ACTUATOR LARGE ACTUATOR
VARIABLE PUMP
PILOT PUMP
74 Explain schematic
TTo enter the FLOAT position, the wheel loader lift arm must be below the mid position. When the wheel loader lift arm is below the mid position and the raise/lower control lever (not shown) is moved to the FLOAT position, the raise/lower control lever sensor (not shown) sends a PWM signal to the ECM (not shown).. The ECM analyzes the raise/lower control lever sensor signal, the lift linkage position sensor signal (not shown) and the tilt linkage position sensor signal (not shown). The ECM sends a strong signal and ENERGIZES the LOWER pilot control actuator solenoid on the fixed pump raise/lower control valve and the LOWER pilot control actuator solenoid on the variable pump raise/lower control valve. The ECM also sends a signal and ENERGIZES the FLOAT solenoid on the raise/lower control lever assembly (not shown).
STMGXXX 4/97
- 110 -
On the fixed pump control valve, the strong ECM signal creates a strong magnetic field in the LOWER pilot control actuator solenoid. The strong magnetic field moves the LOWER pilot control actuator and fully opens the drain age to the tank. The pilot oil in the LOWER end of the raise/lower control valve spool and the pilot oil in the float valve spring chamber flow to the tank. The pilot oil pressure decreases on the LOWER end of the raise/lower control valve spool. The pilot oil pressure on the RAISE end of the raise/lower control valve spool moves the valve spool to the FAST LOWER position. When the pilot oil pressure decreases in the spring chamber of the float valve. The pilot oil pressure at the opposite end of the float valve overcomes the spring and moves the float valve to the open position. The oil in the spring chamber of the float check valve flows through the float valve to the tank. The float check valve spring chamber pressure is reduced to approximately tank pressure. The fixed pump oil flows past the raise/lower load check valve and past the raise/lower control valve spool to the float check valve. The fixed pump oil pressure lifts the float check valve off its seat. The fixed pump oil flows past the float check valve to the tank. On the variable pump control valve, the strong ECM signal creates a strong magnetic field in the LOWER pilot control actuator solenoid. The strong magnetic field moves the LOWER pilot control actuator and fully opens the drain age to the tank. The pilot oil in the LOWER end of the raise/lower control valve spool flows to the tank. The pilot oil pressure decreases on the LOWER end of the raise/lower control valve spool. The pilot oil pressure on the RAISE end of the raise/lower control valve spool moves the valve spool to the FAST LOWER position.
STMGXXX 4/97
- 111 -
The oil in the variable pump float valve spring chamber combines with the oil from the fixed pump float valve spring chamber. The combined oil flow the sequence valve in the fixed pump control valve to the tank. The variable pump float valve spring chamber pressure is reduced to approximately tank pressure. The variable pump oil flows past the raise/lower load check valve and past the raise/lower control valve spool to the float valve. The variable pump oil pressure lifts the float valve off its seat. The variable pump oil flows past the float valve to the tank.
STMGXXX 4/97
- 112 -
IMPLEMENT HYDRAULIC SYSTEM LOWER ENGINE OFF
PRESSURE REDUCING VALVE
LIFT CYLINDER
TILT CYLINDER
LIFT CYLINDER
SHUTTLE VALVE
LOWER
TILT
TILT
LOWER
RIDE CONTROL
PILOT ON/OFF VALVE
VARIABLE PUMP SOLENOID VALVE
RAISE
DUMP
DUMP
FAN MOTOR
PILOT RELIEF VALVE PRESSURE CUTOFF FIXED PUMP
FAN DRIVE PUMP
LOAD LIMIT CONTROL SMALL ACTUATOR LARGE ACTUATOR
FAN SPEED
COOLER SHUTTLE VALVE
FLUID SAMPLING PORT
RAISE
VARIABLE PUMP
PILOT PUMP
75 Explain schematic
In this schematic, the bucket is being LOWERED with the ENGINE OFF. The weight of the implement creates a high pressure in the head end of the lift cylinders. The high lift cylinder pressure oil flows through the hose and shuttle valve to the pressure reducing valve. The pressure reducing valve reduces the lift cylinder oil pressure to approximately 2070 kPa (300 psi). The reduced pressure oil flows past the check valve to the pilot on/off solenoid valve and becomes the oil supply for the pilot system. When the on/off solenoid is de-energized, pilot oil is blocked at the on/off solenoid valve. When the on/off solenoid is energized (as shown), pilot oil flows through the on/off solenoid valve and pressurizes the pilot solenoid valves.
STMGXXX 4/97
- 113 -
When the lift control lever is moved to the LOWER position, the EIC (not shown) operation is the same as when the engine is on. The lift control spool directs oil in the head end of the lift cylinders to the tank. Tank oil flows through the rod end makeup valves into the rod end of the lift cylinders and prevents cylinder cavitation.
STMGXXX 4/97
- 114 -
IMPLEMENT HYDRAULIC SYSTEM RIDE CONTROL ON
PRESSURE REDUCING VALVE
LIFT CYLINDER
TILT CYLINDER
LIFT CYLINDER
SHUTTLE VALVE
LOWER
TILT
TILT
LOWER
RIDE CONTROL
PILOT ON/OFF VALVE
VARIABLE PUMP SOLENOID VALVE
RAISE
DUMP
DUMP
RAISE
FAN MOTOR
PILOT RELIEF VALVE PRESSURE CUTOFF SHUTTLE VALVE
FLUID SAMPLING PORT
FIXED PUMP
FAN DRIVE PUMP
LOAD LIMIT CONTROL SMALL ACTUATOR LARGE ACTUATOR
FAN SPEED
COOLER
VARIABLE PUMP
PILOT PUMP
76 Explain schematic
This schematic shows the hydraulic flow when the ride control solenoid valve is activated. The ride control solenoid valve is controlled by the transmission ECM. The ride control switch (not shown) allows the operator to select between the ride control ON, the ride control OFF and the ride control AUTO positions. When the ride control switch is in the ON position, the transmission ECM will continually energize the ride control solenoid.
STMGXXX 4/97
- 115 -
When the ride control switch is in the AUTO position, the transmission ECM will ENERGIZE the ride control solenoid when the machine ground speed is above 9.7 km/hr (6 mph) and will DE-ENERGIZE the ride control solenoid when the ground speed is below 8.8 km/hr (5.5 mph). When the ride control solenoid valve is ENERGIZED, pilot pressure at the selector spool flows to the tank. The spring shifts the selector spool to connect the head end of the lift cylinders with the accumulators. A floating piston in the accumulators separate the oil from the nitrogen gas. Introduce and perform Lab A and Lab B Summarize labs by asking questions
Since nitrogen gas is compressible, the gas serves as a spring. Any downward force on the lift arms is transferred through the oil at the head end of the lift cylinders to the accumulators. The force in the oil is transmitted to the accumulator piston which compresses the nitrogen gas. Compressing the nitrogen gas absorbs the pressure spike and the oil displacement caused by the downward force on the lift arms. This operation results in less ground induced shocks on structures and components, reduced tire flexing and a greater payload retention. INSTRUCTOR NOTE: At this time, introduce and perform "Lab A: Implement Hydraulic System Component Identification Quiz" and "Lab B: Implement Hydraulic System Tests." These labs will reinforce the material discussed in the preceding slide presentation.
STMGXXX 4/97
- 116 -
FAN DRIVE SYSTEM
FAN
ENGINE OFF
FAN MOTOR
SCREEN
MAKEUP VALVE FAN DRIVE PUMP
PROPORTIONAL VALVE COMPENSATOR VALVE
IMPLEMENT HYDRAULIC COOLER
OIL COOLER BY VALVE
TANK
77 Identify components: - Hydraulic tank - Fan drive pump - Proportional valve - Fan drive motor - Makeup valve - Fan - Oil cooler - Oil cooler by valve
FAN DRIVE SYSTEM Shown is a schematic of the fan drive system. Components of the fan drive system are: Hydraulic tank: Reservoir for the hydraulic oil supply. Fan drive pump: Pulls oil from the tank and supplies oil to the fan drive motor. Proportional valve: Controls the signal to the pump. Compensator valve: Controls fan speed by controlling pump flow.
STMGXXX 4/97
- 117 -
Fan motor: Works with the fan drive pump to turn the fan. Makeup valve: Prevents cavitation of the fan drive motor. Fan: Circulates air through the radiator, hydraulic system oil cooler, steering and brake systems oil cooler, brake and axle oil cooler and air conditioner condenser. Oil cooler: Cools the oil used in the fan drive and hydraulic systems. Oil cooler by valve: Allows cold oil to by the cooler, usually at engine start-up.
STMGXXX 4/97
- 118 -
3 13 1 4 6 7
10
9
8 11 2 5 12
78
Identify components 1. Fan drive pump 2. Pump drive housing 3. Pump outlet tube 4. Signal pressure outlet 5. Electro-hydraulic proportional valve 6. Proportional valve solenoid 7. Drain tube 8. Signal hose 9. Margin spool adjustment 10. Compensator valve 11. Pressure compensator adjustment 12. Signal pressure test port 13. System pressure test port
Fan Drive System Components The fan drive pump (1) is a variable displacement piston. The pump is mounted to the right front of the pump drive housing (2) opposite the variable displacement implement pump (not shown). Other components of the fan drive pump are the outlet tube (3), the signal pressure outlet (4), the electro-hydraulic proportional valve (5), the proportional valve solenoid (6), the proportional valve drain tube (7), the proportional valve signal hose (8), the margin spool adjustment (9), the compensator valve (10), The pressure compensator valve adjustment (11), the signal pressure test port (12) and the system pressure test port (13).
STMGXXX 4/97
- 119 -
2 1 3 4
79
Identify components 1. 2. 3. 4.
Fan drive motor Intake hose Output hose Case drain hose
The fan drive motor (1) is located at the rear of the machine in front of the engine radiator assembly. Also shown are the motor intake hose (2), the motor output hose (3) and the case drain hose (4).
STMGXXX 4/97
- 120 -
FAN DRIVE SYSTEM
FAN
SOLENOID DE-ENERGIZED
FAN MOTOR
SCREEN
MAKEUP VALVE PROPORTIONAL VALVE
FAN DRIVE PUMP
COMPENSATOR VALVE
IMPLEMENT HYDRAULIC COOLER
OIL COOLER BY VALVE
TANK
80 Explain schematic
Fan Drive System Schematics When the engine is running, the fan drive pump pulls oil from the implement hydraulic tank and sends oil flow to the fan motor. The fan motor turns the cooling fan and sends air flow through the engine radiator, the implement hydraulic cooler, the steering and brake oil cooler, the front and rear axle coolers and the air condition condenser. Oil from the fan motor flows through the implement hydraulic cooler to the implement hydraulic tank. Also, the fan drive pump sends oil flow through the screen to the electrohydraulic proportional valve.
STMGXXX 4/97
- 121 -
The electro-hydraulic proportional valve controls the signal oil to the pump compensator valve. When the engine ECM de-energizes the electro-hydraulic proportional valve solenoid (as shown), the proportional valve internal age to drain is blocked. The signal oil flows through the two orifices to the pump compensator valve.
STMGXXX 4/97
- 122 -
FAN DRIVE SYSTEM
FAN
SOLENOID ENERGIZED
FAN MOTOR
SCREEN
MAKEUP VALVE FAN DRIVE PUMP
PROPORTIONAL VALVE COMPENSATOR VALVE
IMPLEMENT HYDRAULIC COOLER
OIL COOLER BY VALVE
TANK
81 Explain schematic
When the engine ECM energizes the electro-hydraulic proportional valve solenoid, the proportional valve opens the internal age to drain. The size of the opening is proportional to the signal from the engine ECM. When the proportional valve sends some of the signal oil to drain, the proportional valve reduces the signal pressure to the compensator valve. The reduced signal pressure allows the compensator valve to destroke the pump. Destroking the pump decreases pump speed and decreases the horsepower needed to turn the fan. When the engine is operating below 88°C (190°F), the fan will operate at a minimum speed of 375 ± 50 rpm.
STMGXXX 4/97
- 123 -
Above 98°C (208°F), the fan will be at a maximum speed of 885 rpm. If an electrical failure of the system occurs, the fan will go to maximum (100%) speed.
STMGXXX 4/97
- 124 -
FAN DRIVE SYSTEM
FAN
RAPID ENGINE DECELERATION
FAN MOTOR
SCREEN
MAKEUP VALVE FAN DRIVE PUMP
PROPORTIONAL VALVE COMPENSATOR VALVE
IMPLEMENT HYDRAULIC COOLER
OIL COOLER BY VALVE
TANK
82 Explain schematic
In this illustration, the fan motor is being driven by the fan. During normal operation, oil pressure at the fan motor inlet is higher than oil pressure at the fan motor outlet. The higher inlet pressure seats the motor check valve. When the engine is decelerated rapidly from high idle, the inertia of the fan keeps the fan drive motor turning faster than the fan drive pump can supply oil. The oil pressure at the fan motor inlet becomes lower than the oil pressure at the fan motor outlet.
STMGXXX 4/97
- 125 -
The higher outlet pressure opens the check valve and allows oil from the outlet to flow back to the inlet. The combination of oil flow through the check valve and the pump oil flow prevents cavitation of the fan motor. When pump output matches fan speed, the motor inlet oil pressure increases above the motor outlet oil pressure. The higher inlet pressure closes the check valve.
- 60 -
ELECTRO-HYDRAULIC IMPLEMENT SYSTEM
40
ELECTRO-HYDRAULIC IMPLEMENT SYSTEM Introduce system
This portion of this presentation discusses the component locations, systems operation, and testing and adjusting procedures for the ElectroHydraulic Implement System on the 992G Wheel Loader. When discussing systems operation, both sectional view and graphic symbol schematics will be used. The systems will be explained by tracing oil flow from the tank, through the system and back to the tank.
STMGXXX 4/97
- 61 -
ELECTRO-HYDRAULIC IMPLEMENT SYSTEM VARIABLE PUMP PILOT SOLENOID VALVE RELIEF VALVE IMPLEMENT HYDRAULIC PUMPS
ELECTRONIC CONTROL MODULE
PILOT PUMP
PILOT CONTROL LEVER MODULE MAIN CONTROL VALVE ASSEMBLY
HYDRAULIC TANK
LIFT LINKAGE POSITION SENSOR
TILT CYLINDER
LIFT TILT LINKAGE CYLINDER POSITION SENSOR
ELECTRONIC SYSTEM
MAIN HYDRAULIC SYSTEM
HYDRAULIC PILOT SYSTEM
COMMON TO BOTH SYSTEMS
41 Identify components: - Pilot electronic system - Pilot hydraulic system - Main hydraulic system - Common to both systems
Shown are the major components of the electro-hydraulic implement system. The electro-hydraulic implement system is pilot operated. The pilot system controls the functions of the main control valve. The pilot system consist of an electronic system and a hydraulic system. The electronic system components (orange) are the pilot control lever module (includes the tilt lever, lift lever, tilt sensor, lift sensor, bucket kickout detent solenoid, lift kickout detent solenoid, lower kickout detent solenoid and implement lockout switch), the implement electronic control module (ECM), the tilt linkage position sensor, the lift linkage position sensor, the pilot control valve solenoids, the pilot on/off valve solenoid (part of the main control valve assembly) and the torque valve.
STMGXXX 4/97
- 62 -
The pilot hydraulic system (brown) consist of the pilot pump, the pilot relief valve, the pilot on/off valve (part of the main control valve assembly) and the pilot control valves (part of the main control valve assembly). The main hydraulic system (green) consists of the fixed pump, the variable pump, the fixed pump relief valve (part of the main control valve assembly), the variable pump relief valve (part of the main control valve assembly), main control valve assembly, two lift cylinders and the tilt cylinder. The hydraulic tank (red) is common to both systems.
INSTRUCTOR NOTE: The color codes used for hydraulic oil throughout this presentation are: Red
- System or high pressure
Red and White Stripes
- Reduced pressure
Orange
- Pilot pressure
Blue
- Blocked oil
Green
- Tank or return oil
STMGXXX 4/97
- 63 -
IMPLEMENT ELECTRONIC CONTROL MODULE (MAC-14)
ELECTRONIC IMPLEMENT CONTROL SYSTEM
CAT DATA LINK INPUT COMPONENTS
LIFT LEVER SENSOR
OUTPUT COMPONENTS PILOT ON/OFF SOLENOID
TILT LEVER SENSOR
VARIABLE PUMP SOLENOID TILT RACKBACK SOLENOID NO. 1 TILT RACKBACK SOLENOID NO. 2
IMPLEMENT LOCKOUT SWITCH
TILT DUMP SOLENOID NO. 1
LIFT/LOWER/TILT KICKOUT SWITCH
TILT DUMP SOLENOID NO. 2 LIFT LINKAGE SENSOR
LIFT LOWER SOLENOID NO. 1 LIFT LOWER SOLENOID NO. 2
TILT LINKAGE SENSOR
LIFT RAISE SOLENOID NO. 1 LIFT RAISE SOLENOID NO. 2 LIFT LOWER KICKOUT DETENT SOLENOID LIFT RAISE KICKOUT DETENT SOLENOID BUCKET KICKOUT DETENT SOLENOID
42 Explain diagram
Electronic Implement Control System Shown is a block diagram of the Electronic Implement Control (EIC) System. The ECM receives input signals from the various sensors and switches (shown in blue). The ECM processes the inputs, makes decisions and provides a corresponding output to the pilot solenoid valves and kickout solenoids (shown in yellow). The ECM also communicates with other electronic control systems through the CAT Data Link. The Electronic Implement Control System consists of the following components:
STMGXXXx 4/97
- 64 -
Lift lever position sensor: Tells the ECM the position of the lift pilot control lever. Tilt lever position sensor: Tells the ECM the position of the tilt pilot control lever. Lift linkage position sensor: Tells the ECM the position of the lift arm relative to the machine. Bucket linkage position sensor: Tells the ECM the position of the bucket relative to the lift arm. Implement lockout switch: Tells the ECM that the operator wants the pilot control levers disabled. Kickout set switch: Used to set the bucket tilt, lift raise and lift lower kickout positions. Pilot on/off solenoid valve: Used to disable and enable the pilot hydraulic system. Bucket dump actuator: Directs pilot oil from the main control valve to tank. Bucket tilt actuator: Directs pilot oil from the main control valve to tank. Raise actuator: Directs pilot oil from the main control valve to tank. Lower actuator: Directs pilot oil from the main control valve to tank. Raise kickout solenoid: Holds the raise/lower lever in the raise position.
STMGXXX 4/97
- 65 -
Lower kickout solenoid: Holds the raise/lower lever in the lower position. Bucket kickout solenoid: Holds the tilt /dump lever in the tilt back position. CAT Data Link: Communication path to and from other electronic control modules.
STMGXXX 4/97
- 66 -
ELECTRO-HYDRAULIC IMPLEMENT SYSTEM
TILT CYLINDER
RIGHT LIFT CYLINDER
ELECTRONIC SYSTEM COMPONENTS
LEFT LIFT CYLINDER
SHUTTLE VALVE IMPLEMENT LOCKOUT SWITCH
RAISE/LOW/TILT KICKOUT SET SWITCH
PRESSURE REDUCING VALVE
TILT LINKAGE POSITION SENSOR
ELECTRONIC CONTROL MODULE
CAT DATA LINK
BUCKET KICKOUT DETENT SOLENOID
LIFT LINKAGE POSITION SENSOR
LIFT KICKOUT DETENT SOLENOID
TILT LEVER SENSOR
IMPLEMENT CONTROL VALVE
CHECK VALVE
PILOT ON/OFF VALVE
LOWER KICKOUT DETENT SOLENOID LIFT LEVER SENSOR
IMPLEMENT CONTROL VALVE
FIXED PUMP
RELIEF VALVE
RELIEF VALVE
PILOT RELIEF VALVE
PILOT PUMP
VARIABLE PUMP SOLENOID VALVE
VARIABLE PUMP
43 Identify components: - Implement lockout switch - Raise/lower/tilt kickout set switch - Electronic control module - Tilt linkage position sensor - Lift linkage position sensor - Tilt control lever - Bucket kickout detent solenoid - Lift control lever - Lift kickout detent solenoid - Pilot control actuators - Pilot on/off valve solenoid - Variable pump torque valve solenoid
Electronic Implement Control System Components The electronic system components (orange) are the implement lockout switch, the raise/lower/tilt kickout set switch, the electronic control module, the tilt linkage position sensor, the lift linkage position sensor, the tilt control lever, the bucket kickout detent solenoid, the lift control lever, the lift kickout detent solenoid, the lower kickout detent solenoid, the pilot control actuators, the pilot on/off valve solenoid and the variable pump torque valve solenoid.
STMGXXX 4/97
- 67 -
7 6 5 8
1
9 2 3 4
44
Identify components: 1. Implement hydraulic control levers 2. Tilt lever position sensor 3. Horn 4. Right armrest control lever 5. Reduced rim pull switch 6. Throttle lock set switch 7. Throttle resume switch 8. Implement hydraulic lock switch 9. Control lever cover
The implement hydraulic control levers (1) are attached to the right armrest assembly and move forward and rearward with the right armrest. When the operator moves the tilt control lever, the tilt control lever position sensor (2) sends a Pulse Width Modulated (PWM) signal to the ECM. Also shown are the horn (3), the right armrest control lever (4), the reduce rim pull switch (5), the throttle lock set switch (6), the throttle resume switch (7) and the implement hydraulic lock switch (8). Located beneath the control lever cover (9) are the lift control lever position sensor, the bucket kickout detent solenoid, the lift kickout detent solenoid and the lower kickout detent solenoid.
STMGXXX 4/97
- 68 -
10
11
12
13
7
8
9
14
1
2
3
4
5
6
45
Identify components:
The raise, lower and tilt kickout switch (1) is located in the right side
1. Raise, lower and tilt kickout switch 2. Dash lights switch 3. Work lights switch 4. Key pad 5. Electronic diagnostic connector 6. +12V connector 7. Rim pull selector 8. Stairway switch 9. Quick shift switch 10. Heater and a/c fan switch 11. Heater and a/c control 12. Start aid switch 13. Throttle lock switch 14. Ride control switch
. Depress the top of the switch to set the TILT kickout. Depress the bottom of the switch to set the RAISE and LOWER kickouts. When setting the bucket TILT kickout, move the bucket to the desired position. Return the tilt lever to the HOLD position. Depress the top of the kickout set switch for about 1 second and release. When setting the RAISE kickout, raise the lift arm to the desired position. Return the lift lever to the HOLD position. Depress the bottom of the kickout switch for about 1 second and release. When setting the LOWER kickout, lower the lift arm to the desired position. Return the lift lever to the HOLD position. Depress the bottom of the kickout switch for about 1 second and release.
STMGXXX 4/97
- 69 -
Also shown are the dash lights switch (2), the work lights switch (3), the key pad (4), the electronic diagnostic connector (5), the +12V connector (6), the rim pull selector (7), the stairway switch (8), the quick shift switch (9), the heater and a/c fan switch (10), the heater and a/c control (11), the start aid switch (12) and the throttle lock switch (13) and the ride control switch (14). (The ride control switch is no longer in that position. The ride control is currently located at the third position from the right.)
STMGXXX 4/97
- 70 -
2 1
46 Identify components: 1. Lift linkage position sensor 2. Tilt linkage position sensor
The lift linkage position sensor (1) is bolted to the left side of the front frame near the left side lift cylinder attachment pin. The lift linkage position sensor constantly monitors the position of the lift linkage and sends lift linkage position information to the ECM Module. The tilt linkage position sensor (2) is bolted to the right side of the lift arm near the tilt linkage attachment pin. The tilt linkage position sensor constantly monitors the position of the tilt linkage and sends tilt linkage position information to the ECM Module. When the operator moves the lift lever or the tilt lever, the ECM analyze the signal from the lift linkage position sensor and the signal from the tilt linkage position sensor. The ECM then sends a proportional signal to the respective control valve solenoid.
STMGXXX 4/97
- 71 -
6
5
7
4 3 2
1
47
Identify components: 1. Electronic Control Module 2. Fuse 3. Key start relay 4. Main relay 5. VIDS/VIMS interlock module No 1 6. VIDS/VIMS main module 7. Transmission ECM
The Electronic Control Module (1) is located beneath the platform on the right side of the cab. Also shown are the fuse (2), the key start relay (3), the main relay (4), the VIDS/VIMS interlock module No 1 (5), the VIDS/VIMS main module (6) and the Transmission ECM (7).
STMGXXX 4/97
- 72 -
4
2
1
3
48
Identify components: 1. On/off solenoid 2. Pilot control actuators 3. Float valve 4. Fixed pump relief valve
The on/off solenoid valve (1) is located in the front bottom section of the main control valve center manifold. When the on/off solenoid is DE-ENERGIZED, pilot oil is blocked at the on/off solenoid valve. When the on/off solenoid is ENERGIZED, pilot oil flows to the pilot control actuators. Also shown are the float valve (3) and the fixed pump relief valve (4).
STMGXXX 4/97
- 73 -
3
1
2
49
Identify components: 1. Pilot control solenoid 2. Lift cylinder rod end line relief valve 3. Tilt cylinder rod end line relief valve
The pilot control solenoids (1) control the movement of the pilot control actuators. When the operator moves a control lever, the control lever position sensor sends a pulse width modulation (PWM) signal to the ECM. The ECM analyze the signals from the control lever position sensor, the lift linkage position sensor and the tilt linkage position sensor. the ECM then sends a proportional signal to ENERGIZE the respective pilot control actuator solenoid. Also shown are the lift cylinder rod end line relief valve (2) and the tilt cylinder rod end line relief valve(3).
STMGXXX 4/97
- 74 -
4
1
2
3
50
Identify components: 1. Variable pump torque valve 2. Pump torque valve solenoid 3. Implement pilot relief valve 4. Implement pilot oil pressure tap
The variable pump solenoid valve (1) is located on the inside left frame and to the rear of the implement pilot relief valve (3). The variable pump solenoid valve controls pilot pressure to the load limiting control valve on the variable pump control. The ECM energizes the variable pump valve solenoid (2) whenever the key start switch is ON. The ECM signal to the variable pump solenoid valve controls the pressure in the load limit control valve. When the variable pump pressure increases to 80% of maximum pressure, the load limit control valve moves and sends oil pressure to the large actuator to destroke the pump. Also shown is the implement pilot oil pressure tap (4).
STMGXXX 4/97
- 76 -
ELECTRO-HYDRAULIC IMPLEMENT SYSTEM PILOT SYSTEM COMPONENTS
TILT CYLINDER
RIGHT LIFT CYLINDER
LEFT LIFT CYLINDER
SHUTTLE VALVE IMPLEMENT LOCKOUT SWITCH
RAISE/LOW/TILT KICKOUT SET SWITCH
PRESSURE REDUCING VALVE
TILT LINKAGE POSITION SENSOR
ELECTRONIC CONTROL MODULE
CAT DATA LINK
BUCKET KICKOUT DETENT SOLENOID
LIFT LINKAGE POSITION SENSOR
LIFT KICKOUT DETENT SOLENOID
TILT LEVER SENSOR
IMPLEMENT CONTROL VALVE
LOWER KICKOUT DETENT SOLENOID LIFT LEVER SENSOR
IMPLEMENT CONTROL VALVE
PILOT ON/OFF VALVE
CHECK VALVE
CHECK VALVE
RELIEF VALVE
PILOT RELIEF VALVE
PILOT PUMP
FIXED PUMP
RELIEF VALVE
FILTER VARIABLE PUMP SOLENOID VALVE
VARIABLE PUMP
51 Identify components: - Tank - Pilot pump - Pilot relief valve - Pilot on/off valve - Check valve - Pressure reducing valve - Pilot control actuators
Hydraulic Pilot System The hydraulic pilot system components (brown) are the tank, the pilot pump, the pilot relief valve, the pilot on/off valve, the check valve, the pressure reducing valve and the pilot control actuators.
STMGXXX 4/97
- 77 -
7
8
9
10
6
1
5
2
4
3
52
Identify components: 1. 2. 3. 4. 5. 6. 7.
Hydraulic tank Deck plate Fill cap Vent valve Alternator breaker Main circuit breaker Starting/charger analyzer connector 8. Service tool connector 9. Running lamp breaker 10. Key breaker
The implement hydraulic tank (1) is below the forward hinged deck plate (2) on the right side of the machine. The tank has a fill cap (3) for filling and adding oil and a vent valve (4) that protects the tank from excessive pressure and/or vacuum. The tank also has (not shown) three screen for return oil, an ecology-type drain valve for changing the oil and a sight glass for checking the oil level. Also shown are the alternator breaker (5), the main circuit breaker (6), the starting/charger analyzer connector (7), the service tool connector (8), the running lamps breaker (9) and the key breaker (10). NOTE: Oil change intervals and procedures are covered in the Operation and Maintenance section of the Service Manual.
STMGXXX 4/97
- 78 -
2 1
3 4
5
53
Identify components:
The implement pilot pump (1) is a gear-type pump mounted on the front
1. Pilot pump 2. Implement variable piston pump 3. Pilot pump inlet hose 4. Pilot pump outlet hose 5. Pilot pump pressure tap
of the implement variable piston pump (2). Tank oil flows through the pilot pump inlet hose (3) to the implement pilot pump. Pump supply oil flows through the outlet hose (4) to the implement pilot filter. Also shown is the pilot pump pressure tap (5).
STMGXXX 4/97
- 79 -
2 3
6
1
5
4
54
Identify components: 1. Implement pilot oil filter 2. Oil filter bracket 3. ROPS mounting plate 4. Oil filter inlet hose 5. Oil filter outlet hose 6. Oil filter by switch
The implement pilot oil filter (1) bracket (2) is bolted to the right r ROPS mounting plate (3). Pressure oil from the pilot pump flows through the oil filter inlet hose (4), the pilot filter and the oil filter outlet hose (5) to the pilot relief valve (not shown). The oil filter by switch (6) alerts the VIDS when the filter is bying.
STMGXXX 4/97
- 80 -
4
3
1
5
2
7
6
55
Identify components: 1. 2. 3. 4. 5. 6. 7.
Pilot relief valve Torque valve Inlet hose Outlet hose Outlet hose Return hose Pilot relief valve pressure sensor
The pilot relief valve (1) is bolted to the inside left frame forward of the torque valve (2). Pilot oil from the pilot filter flows through the inlet hose (3) to the pilot relief valve. The pilot relief valve maintains pilot oil pressure at 2520 kPa (365 psi). Pilot pressure oil flows through the outlet hose (4) to the on/off solenoid valve. Pilot pressure oil also flows through the outlet hose (5) to the torque valve. Pilot relief valve return oil flows through the return hose (6) to the tank. The pilot relief valve pressure sensor (7) supplies pilot oil pressure information to the VIDS/VIMS.
STMGXXX 4/97
- 81 -
7 5 6 1 3 2 4 8
56
Identify components: 1. Pilot control solenoid valves 2. Pilot on/off valve solenoid 3. Lift rod end line relief valve 4. Lift head end line relief valve 5. Tilt rod end line relief valve 6. Tilt head end line relief valve 7. Fixed pump relief valve 8. Float valve
The pilot control solenoid valves (1) controls pilot oil flow from the ends of the main control valve spools to the tank. Also shown are the pilot on/off valve solenoid (2), the lift rod end line relief valve (3), the lift head end line relief valve (4), the tilt rod end line relief valve (5), the tilt head end line relief valve (6), the fixed pump relief valve (7) and the float valve (8).
STMGXXX 4/97
- 82 -
ELECTRO-HYDRAULIC IMPLEMENT SYSTEM MAIN HYDRAULIC SYSTEM COMPONENTS
TILT CYLINDER
RIGHT LIFT CYLINDER
LEFT LIFT CYLINDER
SHUTTLE VALVE IMPLEMENT LOCKOUT SWITCH
RAISE/LOW/TILT KICKOUT SET SWITCH
PRESSURE REDUCING VALVE
TILT LINKAGE POSITION SENSOR
ELECTRONIC CONTROL MODULE
CAT DATA LINK
BUCKET KICKOUT DETENT SOLENOID
LIFT LINKAGE POSITION SENSOR
LIFT KICKOUT DETENT SOLENOID
TILT LEVER SENSOR
IMPLEMENT CONTROL VALVE
LOWER KICKOUT DETENT SOLENOID LIFT LEVER SENSOR
IMPLEMENT CONTROL VALVE
PILOT ON/OFF VALVE
CHECK VALVE
CHECK VALVE
RELIEF VALVE
FIXED PUMP
PILOT RELIEF VALVE
RELIEF VALVE
FILTER
PILOT PUMP
VARIABLE PUMP SOLENOID VALVE
VARIABLE PUMP
57 Identify components: - Tank - Fixed pump - Fixed pump relief valve - Fixed pump implement control valve - Variable pump - Variable pump relief valve - Variable pump implement control valve - Shuttle valve - Lift cylinders - Tilt cylinder
Main Hydraulic System The hydraulic pilot system components (green) are the tank, the fixed pump, the fixed pump relief valve, the fixed pump implement control valve, the variable pump, the variable pump relief valve and the variable pump implement control valve, the shuttle valve, the lift cylinders and the tilt cylinder.
STMGXXX 4/97
- 83 -
4
7
6
8
5
2 1
3
58
Identify components: 1. 2. 3. 4. 5. 6. 7. 8.
Fixed pump Suction hose Supply hose Variable pump Suction hose Supply hose Case drain Pump drive housing
The main hydraulic system contains a fixed displacement, piston-type pump (1) and a variable displacement piston-type pump (4). Oil flows from the tank through a suction tube (2) to the fixed displacement pump. Pump pressure oil flows through a supply hose (3) to the fixed pump implement control valve. Oil flows from the tank through a suction tube (5) to the variable displacement pump. Pump pressure oil flows through a supply hose (6) to the variable pump implement control valve. Also shown are the case drain (7) and the pump drive housing (8).
STMGXXX 4/97
- 84 -
VARIABLE PUMP SOLENOID VALVE TO PILOT SYSTEM
VARIABLE IMPLEMENT PUMP LESS THAN 2400kPa (350 psi)
TO TANK PILOT RELIEF VALVE
TO IMPLEMENT CONTROL VALVE PRESSURE CUTOFF
PILOT FILTER
FLUID SAMPLING PORT
LOAD LIMIT CONTROL
SHUTTLE VALVE
SMALL ACTUATOR PILOT PUMP
PUMP
LARGE ACTUATOR
59 Explain schematic
Variable Pump Control Schematic This schematic shows the oil flow in the variable pump control when the variable pump pressure is less than 2400 kPa (350 psi). The pilot pump pulls oil from the tank and sends oil flow through the filter to the pilot system. The pilot relief valve maintains pilot system oil at 2400 kPa (350 psi). When the key switch is in the ON position, the variable pump torque valve solenoid is ENERGIZED. Pilot oil flows through the variable pump torque valve to the load limit control. Pilot oil also flows to the shuttle valve. When the variable pump oil is not being used, the variable pump pressure is less than the pilot pressure. Pilot oil flows through the shuttle valve and into the small actuator spring chamber. The combined force of the pilot pressure and the small actuator spring holds the variable pump swash plate at maximum angle.
STMGXXX 4/97
- 85 -
VARIABLE PUMP SOLENOID VALVE TO PILOT SYSTEM
VARIABLE IMPLEMENT PUMP LESS THAN 28,940 kPa (4200 psi)
TO TANK PILOT RELIEF VALVE
TO IMPLEMENT CONTROL VALVE PRESSURE CUTOFF
PILOT FILTER
FLUID SAMPLING PORT
LOAD LIMIT CONTROL
SHUTTLE VALVE
SMALL ACTUATOR PILOT PUMP
PUMP
LARGE ACTUATOR
60 Explain schematic
When the variable pump oil is being used and the oil pressure is between 2400 kPa (350 psi) and 28,940 kPa (4200 psi), variable pump oil moves the shuttle valve and blocks the pilot system oil. Variable pump oil flows through the shuttle valve and into the small actuator spring chamber. The combined force of the variable pump oil pressure and the small actuator spring holds the variable pump swash plate at maximum angle.
STMGXXX 4/97
- 86 -
VARIABLE PUMP SOLENOID VALVE TO PILOT SYSTEM
VARIABLE IMPLEMENT PUMP MORE THAN 28,940 kPa (4200 psi)
TO TANK PILOT RELIEF VALVE
PILOT FILTER
FLUID SAMPLING PORT
TO IMPLEMENT CONTROL VALVE PRESSURE CUTOFF LOAD LIMIT CONTROL
SHUTTLE VALVE
SMALL ACTUATOR PILOT PUMP
PUMP
LARGE ACTUATOR
61 Explain schematic
When the variable pump oil pressure is more than 28,940 kPa (4200 psi), oil pressure overcomes the force of the pressure cutoff valve spring and moves the pressure cutoff valve. The pressure cutoff valve opens a age to send variable pump oil to the large actuator. The oil pressure in the large actuator overcomes the force of the small actuator (oil pressure and the small actuator spring) and moves the swash plate to the minimum angle.
STMGXXX 4/97
- 87 -
1 2
6
3
4
5
62
Identify components: 1. Main control valve assembly 2. Implement control valve 3. Tilt cylinder rod end hose 4. Lift cylinders rod end hose 5. Lift cylinders head end hose 6. Tilt cylinder head end hose
The main control valve assembly (1) is located in the front frame below the boom. The right side control valve (2) receives oil from the variable implement pump. Also shown are the hose (3) to the tilt cylinder rod end, the hose (4) to the lift cylinders rod end, the hose (5) to the lift cylinders head end and the hose (6) to the tilt cylinder head end.
STMGXXX 4/97
- 88 -
2 1
5
4
3
63
Identify components: 1. 2. 3. 4.
Lift cylinder Tilt cylinder Bucket position Front right brake housing 5. Front right final drive housing
When an implement is activated, oil from the implement control valve is directed to the lift cylinders (1) and/or tilt cylinder (2). Also shown are the bucket position sensor (3), the front right brake housing (4) and the front right final drive housing (5).
STMGXXX 4/97
- 89 -
ELECTRO-HYDRAULIC IMPLEMENT SYSTEM
TILT CYLINDER
RIGHT LIFT CYLINDER
HOLD
LEFT LIFT CYLINDER
SHUTTLE VALVE IMPLEMENT LOCKOUT SWITCH
RAISE/LOW/TILT KICKOUT SET SWITCH
PRESSURE REDUCING VALVE
TILT LINKAGE POSITION SENSOR
ELECTRONIC CONTROL MODULE
CAT DATA LINK
BUCKET KICKOUT DETENT SOLENOID TILT LEVER SENSOR
IMPLEMENT CONTROL VALVE
LIFT LINKAGE POSITION SENSOR
LIFT KICKOUT DETENT SOLENOID
PILOT ON/OFF VALVE
CHECK VALVE
CHECK VALVE
LOWER KICKOUT DETENT SOLENOID LIFT LEVER SENSOR
IMPLEMENT CONTROL VALVE
FIXED PUMP
RELIEF VALVE
PILOT RELIEF VALVE
RELIEF VALVE FILTER
PILOT PUMP
VARIABLE PUMP SOLENOID VALVE
VARIABLE PUMP
64 Explain schematic
Electro-Hydraulic Schematics When the implement lockout switch is in the ON position, the ECM energizes the pilot on/off valve solenoid. The pilot on/off valve solenoid opens the pilot on/off valve. The pilot pump pulls oil from the hydraulic tank and sends oil flow through the pilot on/off valve to the pilot control actuators at each end of the control valve spools. Pilot oil pressure increases to the relief valve pressure setting. The relief valve opens and maintains a constant pressure in the pilot system. The control valve spools are hydraulically locked in the HOLD position. In the HOLD position, the control valve spools block oil flow to the lift and tilt cylinders. Oil from the fixed pump and the variable pump flows past the respective control valve spools to the tank.
STMGXXX 4/97
- 90 -
ELECTRO-HYDRAULIC IMPLEMENT SYSTEM
TILT CYLINDER
RIGHT LIFT CYLINDER
SLOW TILT
LEFT LIFT CYLINDER
SHUTTLE VALVE IMPLEMENT LOCKOUT SWITCH
RAISE/LOW/TILT KICKOUT SET SWITCH
PRESSURE REDUCING VALVE
TILT LINKAGE POSITION SENSOR
ELECTRONIC CONTROL MODULE
CAT DATA LINK
BUCKET KICKOUT DETENT SOLENOID
LIFT LINKAGE POSITION SENSOR
LIFT KICKOUT DETENT SOLENOID TILT LEVER SENSOR
IMPLEMENT CONTROL VALVE
PILOT ON/OFF VALVE
CHECK VALVE
CHECK VALVE
LOWER KICKOUT DETENT SOLENOID LIFT LEVER SENSOR
IMPLEMENT CONTROL VALVE
FIXED PUMP
RELIEF VALVE
PILOT RELIEF VALVE
RELIEF VALVE FILTER
PILOT PUMP
VARIABLE PUMP SOLENOID VALVE
VARIABLE PUMP
65 Explain schematic
When the tilt control lever is moved to the SLOW TILT position, the tilt control lever sensor sends a PWM signal to the ECM. The ECM analyzes the tilt control lever sensor signal and the signals from the lift linkage position sensor and the tilt linkage position sensor. The ECM then sends a proportional signal to ENERGIZE the tilt pilot control valve solenoid on the fixed pump implement control valve. The solenoid moves the pilot control valve and sends pilot oil at the tilt end of the tilt/dump control valve spool to drain. This reduces the pilot oil pressure at the tilt end of the control valve spool. The oil pressure on the dump end of the control valve spool moves the valve spool to the TILT position.
STMGXXX 4/97
- 91 -
The fixed pump oil flows past the tilt/dump control valve spool to the rod end of the tilt cylinder. Tilt cylinder head end oil flows past the tilt/dump control valve spool to the tank. The variable pump oil is not needed for slow tilt operation. The ECM does not energize the variable pump tilt control valve solenoid. The variable pump oil flows through the variable pump implement control valve to the tank. With exception of the FLOAT position, the ECM uses the oil from the fixed pump for all implement operations until the operational demand for oil is greater than the fixed pump can supply. The ECM will then use oil from the variable pump to satisfy the demand.
STMGXXX 4/97
- 92 -
ELECTRO-HYDRAULIC IMPLEMENT SYSTEM
TILT CYLINDER
RIGHT LIFT CYLINDER
FAST TILT
LEFT LIFT CYLINDER
SHUTTLE VALVE IMPLEMENT LOCKOUT SWITCH
RAISE/LOW/TILT KICKOUT SET SWITCH
PRESSURE REDUCING VALVE
TILT LINKAGE POSITION SENSOR
ELECTRONIC CONTROL MODULE
CAT DATA LINK
BUCKET KICKOUT DETENT SOLENOID
LIFT LINKAGE POSITION SENSOR
LIFT KICKOUT DETENT SOLENOID TILT LEVER SENSOR
IMPLEMENT CONTROL VALVE
PILOT ON/OFF VALVE
CHECK VALVE
CHECK VALVE
LOWER KICKOUT DETENT SOLENOID LIFT LEVER SENSOR
IMPLEMENT CONTROL VALVE
FIXED PUMP
RELIEF VALVE
PILOT RELIEF VALVE
RELIEF VALVE FILTER
PILOT PUMP
VARIABLE PUMP SOLENOID VALVE
VARIABLE PUMP
66 Explain schematic
When the tilt control lever is moved to the FAST TILT position, the tilt control lever sensor sends a PWM signal to the ECM.. The ECM analyzes the tilt control lever sensor signal and the signals from the lift linkage position sensor and the tilt linkage position sensor. The ECM sends a signal to ENERGIZE the tilt pilot control actuator solenoid on the fixed pump implement control valve and a signal to ENERGIZE the tilt pilot control actuator solenoid on the variable pump implement control valve. The signals may be of different proportion. The solenoids move the pilot control actuators and send pilot oil at the tilt ends of the tilt/dump control valve spools to drain. This reduces the pilot oil pressure at the tilt ends of the control valve spools. The oil pressure on the dump ends of the control valve spools move the valve spools to the FAST TILT position.
STMGXXX 4/97
- 93 -
The fixed pump oil flows around the tilt control valve spool in the fixed pump implement control valve to the rod end of the tilt cylinder. The variable pump oil flows around the tilt control valve spool in the variable pump implement control valve to the rod end of the tilt cylinder. The tilt cylinder head end oil flows past both tilt control valve spools to the tank. The return oil flow past each valve spool is proportion to the supply oil flow past the valve spool. The desired tilt cylinder speed determines the difference in oil flow between the fixed pump and the variable pump. A slow tilt cylinder speed will cause a larger difference in oil flow between the two pumps than a fast tilt cylinder speed.
STMGXXX 4/97
- 94 -
ELECTRO-HYDRAULIC IMPLEMENT SYSTEM
TILT CYLINDER
RIGHT LIFT CYLINDER
SLOW LIFT
LEFT LIFT CYLINDER
SHUTTLE VALVE IMPLEMENT LOCKOUT SWITCH
RAISE/LOW/TILT KICKOUT SET SWITCH
PRESSURE REDUCING VALVE
TILT LINKAGE POSITION SENSOR
ELECTRONIC CONTROL MODULE
CAT DATA LINK
BUCKET KICKOUT DETENT SOLENOID
LIFT LINKAGE POSITION SENSOR
LIFT KICKOUT DETENT SOLENOID TILT LEVER SENSOR
IMPLEMENT CONTROL VALVE
PILOT ON/OFF VALVE
CHECK VALVE
CHECK VALVE
LOWER KICKOUT DETENT SOLENOID LIFT LEVER SENSOR
IMPLEMENT CONTROL VALVE
FIXED PUMP
RELIEF VALVE
PILOT RELIEF VALVE
RELIEF VALVE FILTER
PILOT PUMP
VARIABLE PUMP SOLENOID VALVE
VARIABLE PUMP
67 Explain schematic
When the operator moves the lift control lever to the SLOW LIFT position, the lift control lever sensor sends a PWM signal to the ECM. The ECM analyzes the lift control lever sensor signal and the signals from the lift linkage position sensor and the tilt linkage position sensor. The ECM then sends a proportional signal to ENERGIZE the lift pilot control actuator solenoid on the fixed pump implement control valve. The solenoid moves the pilot control actuator and sends pilot oil at the lift end of the lift/lower control valve spool to drain. This reduces the pilot oil pressure at the lift end of the control valve spool. The oil pressure on the lower end of the control valve spool moves the valve spool to the LIFT position.
STMGXXX 4/97
- 95 -
The fixed pump oil flows past the lift/lower control valve spool to the head end of the lift cylinders. Lift cylinder rod end oil flows past the lift/lower control valve spools to the tank. The variable pump oil is not needed for slow lift operation. The ECM does not energize the variable pump lift control actuator. The variable pump oil flows through the variable pump implement control valve to the tank.
STMGXXX 4/97
- 96 -
ELECTRO-HYDRAULIC IMPLEMENT SYSTEM
TILT CYLINDER
RIGHT LIFT CYLINDER
FAST LIFT
LEFT LIFT CYLINDER
SHUTTLE VALVE IMPLEMENT LOCKOUT SWITCH
RAISE/LOW/TILT KICKOUT SET SWITCH
PRESSURE REDUCING VALVE
TILT LINKAGE POSITION SENSOR
ELECTRONIC CONTROL MODULE
CAT DATA LINK
BUCKET KICKOUT DETENT SOLENOID
LIFT KICKOUT DETENT SOLENOID TILT LEVER SENSOR
IMPLEMENT CONTROL VALVE
LIFT LINKAGE POSITION SENSOR
PILOT ON/OFF VALVE
CHECK VALVE
CHECK VALVE
LOWER KICKOUT DETENT SOLENOID LIFT LEVER SENSOR
IMPLEMENT CONTROL VALVE
FIXED PUMP
RELIEF VALVE
PILOT RELIEF VALVE
RELIEF VALVE FILTER
PILOT PUMP
VARIABLE PUMP SOLENOID VALVE
VARIABLE PUMP
68 Explain schematic
When the lift control lever is moved to the FAST LIFT position, the lift control lever sensor sends a proportional PWM signal to the ECM. The ECM analysis the lift control lever sensor signal, the signal from the lift sensor and the signal from the tilt sensor. The ECM sends a signal to the lift actuator solenoid on the fixed pump implement control valve and to the lift actuator solenoid on the variable pump implement control valve. The signals may be of different proportion. The solenoids move the pilot control actuators and send pilot oil at the LIFT ends of the lift/lower valves to drain. This reduces the pilot pressure at the lift ends of the control valve spools. The oil pressure on the lower ends of the control valve spools move the valve spools to the FAST LIFT position. The fixed pump oil flows around the lift control valve spool in the fixed pump implement control valve to the head ends of the lift cylinders.
STMGXXX 4/97
- 97 -
The variable pump oil flows around the lift control valve spool in the variable pump implement control valve to the head ends of the lift cylinders. The lift cylinders rod end oil flows past both lift control valve spools to the tank. The return oil flows past each valve spool in proportion to the supply oil flow past the valve spool. The desired lift cylinder speed determines the difference in oil flow between the fixed pump and the variable pump. A slow lift cylinder speed will cause a larger difference in oil flow between the two pumps than a fast lift cylinder speed.
STMGXXX 4/97
- 98 -
IMPLEMENT HYDRAULIC SYSTEM SLOW TILT
PRESSURE REDUCING VALVE
LIFT CYLINDER
TILT CYLINDER
LIFT CYLINDER
SHUTTLE VALVE
LOWER
TILT
TILT
LOWER
RIDE CONTROL
PILOT ON/OFF VALVE
VARIABLE PUMP SOLENOID VALVE RAISE
DUMP
DUMP
RAISE
FAN MOTOR
PILOT RELIEF VALVE
FAN SPEED
PRESSURE CUTOFF COOLER SHUTTLE VALVE
FLUID SAMPLING PORT
FIXED PUMP
LOAD LIMIT CONTROL
FAN DRIVE PUMP
SMALL ACTUATOR LARGE ACTUATOR
VARIABLE PUMP
PILOT PUMP
69 Explain schematic
Implement Hydraulic Schematics This schematic shows the oil flow in the implement pilot system and the implement hydraulic system when the engine is running and the control valves are in the HOLD position. In the pilot system, the pilot pump pulls oil from the tank and sends oil flow to the pilot relief valve, the variable pump control, the variable pump torque valve, the ride control valve (optional) and the pilot on/off valve. The pilot relief valve maintains pilot system at 2514 ± 205 kPa (365 ± 30 psi).
STMGXXX 4/97
- 99 -
When the variable pump oil is not being used, pilot oil pressure assists the small actuator spring in the variable pump control and moves the swash plate to maximum angle. When the variable pump torque valve solenoid is ENERGIZED, pilot oil flows to the load limit control valve in the variable pump control and prevents movement of the load limit control valve until the variable pump oil pressure increase to 0000 ± 000 kPa (0000 ± 000 psi). When oil pressure reaches 0000 ± 000 kPa (0000 ± 000 psi), the load limit control destrokes the pump and decreases flow by approximately 20%. As pressure increases, the load limit control valve will maintain flow at approximately 80% of maximum until pump pressure reaches 28925 kPa (4200 psi). When pump pressure increase to 28925 kPa (4200 psi), the pressure cutoff valve destrokes the pump and maintains pump pressure at a maximum of 28925 kPa (4200 psi). The pilot on/off valve solenoid is controlled by the implement lockout switch (not shown). When the implement lockout switch is in the OFF position, the ECM (not shown) will not energize the pilot on/off valve solenoid. Pilot oil is blocked at the pilot on/off valve. When the implement lockout switch is in the ON position, the ECM energizes the pilot on/off valve solenoid. Pilot oil flows past the pilot on/off valve to the pilot control solenoid valves. In the implement fixed pump hydraulic system, the fixed pump pulls oil from the tank and sends oil flow to the left side main control valve. When the control valve spools are in the HOLD position, oil flows past the fixed pump relief valve and through the open-centered control valve to the tank. The fixed pump relief valve constantly senses pressure at the fixed pump and opens to the tank when the pressure reaches the maximum setting of 31000 kPa (4500 psi).
STMGXXX 4/97
- 100 -
The implement variable pump hydraulic system, the variable pump pulls oil from the tank and sends oil flow to the right side main control valve. When the control valve spools are in the HOLD position, oil flows past the variable pump relief valve and through the open-centered control valve to the tank. Variable pump pressure is controlled by the variable pump compensator valve. The variable pump relief valve serves as a backup in case of a compensator valve failure. The variable pump relief valve is set at 31000 kPa (4500 psi) In the HOLD position, oil flow to and from the cylinders are blocked at the control valve spools.
STMGXXX 4/97
- 101 -
IMPLEMENT HYDRAULIC SYSTEM SLOW TILT
PRESSURE REDUCING VALVE
LIFT CYLINDER
TILT CYLINDER
LIFT CYLINDER
SHUTTLE VALVE
LOWER
TILT
TILT
LOWER
RIDE CONTROL
PILOT ON/OFF VALVE
VARIABLE PUMP SOLENOID VALVE RAISE
DUMP
DUMP
PILOT RELIEF VALVE
RAISE
FAN SPEED PRESSURE CUTOFF SHUTTLE VALVE
FLUID SAMPLING PORT
FIXED PUMP
LOAD LIMIT CONTROL SMALL ACTUATOR LARGE ACTUATOR
VARIABLE PUMP
PILOT PUMP
70 Explain schematic
When the tilt/dump control lever (not shown) is moved to the SLOW TILT position, the tilt/dump control lever sensor (not shown) sends a PWM signal to the ECM (not shown). The ECM analyzes the tilt/dump control lever sensor signal and the signals from the lift linkage position sensor (not shown) and the tilt linkage position sensor (not shown). The ECM then sends a proportional signal to ENERGIZE the tilt pilot control valve solenoid on the fixed pump implement control valve. The solenoid moves the pilot control valve and sends pilot oil at the tilt end of the tilt/dump control valve spool to drain. This reduces the pilot oil pressure at the tilt end of the control valve spool. The oil pressure on the dump end of the control valve spool moves the valve spool to the TILT position.
STMGXXX 4/97
- 102 -
The tilt/dump control valve spool blocks the flow of fixed pump oil to the tank and opens the age to the tilt cylinder. The fixed pump oil flows past the tilt/dump load check valve and past the tilt/dump control valve spool to the rod end of the tilt cylinder. Oil from the head end of the tilt cylinder flows past the tilt/dump control valve spool to the tank. The variable pump oil flows through the right side implement control valve to the tank.
STMGXXX 4/97
- 103 -
IMPLEMENT HYDRAULIC SYSTEM FAST TILT
PRESSURE REDUCING VALVE
LIFT CYLINDER
TILT CYLINDER
LIFT CYLINDER
SHUTTLE VALVE
LOWER
TILT
TILT
LOWER
RIDE CONTROL
PILOT ON/OFF VALVE
VARIABLE PUMP SOLENOID VALVE
RAISE
DUMP
DUMP
FAN MOTOR
PILOT RELIEF VALVE PRESSURE CUTOFF FIXED PUMP
LOAD LIMIT CONTROL
FAN DRIVE PUMP
SMALL ACTUATOR LARGE ACTUATOR
FAN SPEED
COOLER SHUTTLE VALVE
FLUID SAMPLING PORT
RAISE
VARIABLE PUMP
PILOT PUMP
71 Explain schematic
When the tilt/dump control lever (not shown) is moved to the FAST TILT position, the tilt/dump control lever sensor (not shown) increases the PWM signal to the ECM (not shown).. The ECM analyzes the increased tilt/dump control lever sensor signal, the lift linkage position sensor signal (not shown) and the tilt linkage position sensor signal (not shown). The ECM increases the signal to the TILT solenoid on the fixed pump tilt/dump control valve. The ECM also sends a signal to ENERGIZE the TILT solenoid on the variable pump tilt/dump control valve. Often the signal voltage is different to the two pumps. On the fixed pump control valve, the increased ECM signal increases the TILT pilot control valve solenoid magnetic field.
STMGXXX 4/97
- 104 -
The stronger magnetic field moves the TILT pilot control valve further against the spring enlarging the drain age. The additional oil drain decreases the oil pressure at the TILT end of the tilt/dump control valve spool. The oil pressure on the DUMP end of the tilt/dump control valve spool moves the valve spool to the FAST TILT position. In the FAST TILT position, the fixed pump oil flow is increased to the rod end of the tilt cylinder. The increase in oil flow allows the bucket to travel faster. The tilt cylinder head end oil flows past the tilt/dump control valve spool to the tank. On the variable pump control valve, the ECM signal ENERGIZES the TILT solenoid on the tilt/dump control valve . The TILT solenoid moves the pilot control valve and opens a age for pilot oil to drain to tank. This reduces the pilot oil pressure at the TILT end of the tilt/dump control valve. The pilot oil pressure on the DUMP end of the control valve spool moves the control valve spool to the TILT position. In the FAST TILT position, the tilt/dump control valve spool blocks the oil flow to the tank and opens the age to the rod end of the tilt cylinder. The variable pump oil flows past the tilt/dump load check valve, past the tilt/dump control valve spool and s with the oil from the fixed pump. The combined oil flows to the rod end of the tilt cylinder. The tilt cylinder head end oil flows past the tilt/dump control valve spool to the tank. The return oil flow past each valve spool is proportion to the supply oil flow past the valve spool.
STMGXXX 4/97
- 105 -
IMPLEMENT HYDRAULIC SYSTEM SLOW LOWER
PRESSURE REDUCING VALVE
LIFT CYLINDER
TILT CYLINDER
LIFT CYLINDER
SHUTTLE VALVE
LOWER
TILT
TILT
LOWER
RIDE CONTROL
PILOT ON/OFF VALVE
VARIABLE PUMP SOLENOID VALVE
RAISE
DUMP
DUMP
FAN MOTOR
PILOT RELIEF VALVE PRESSURE CUTOFF FIXED PUMP
LOAD LIMIT CONTROL
FAN DRIVE PUMP
SMALL ACTUATOR LARGE ACTUATOR
FAN SPEED
COOLER SHUTTLE VALVE
FLUID SAMPLING PORT
RAISE
VARIABLE PUMP
PILOT PUMP
72 Explain schematic
When the raise/lower control lever (not shown) is moved to the SLOW LOWER position, the raise/lower control lever sensor (not shown) sends a PWM signal to the ECM (not shown). The ECM analyzes the raise/lower control lever sensor signal, the lift linkage position sensor signal (not shown) and the tilt linkage position sensor signal (not shown). The ECM then sends a proportional signal to ENERGIZE the fixed pump raise/lower control valve lower solenoid. The lower solenoid moves the pilot control valve and opens a age for pilot oil at the raise/lower control valve LOWER end to drain to tank. This reduces the pilot oil pressure at the LOWER end of the raise/lower control valve. The pilot oil pressure on the RAISE end of the control valve spool moves the control valve spool to the SLOW LOWER position.
STMGXXX 4/97
- 106 -
The raise/lower control valve spool blocks the flow of fixed pump oil to the tank and opens the age to the lift cylinders. The fixed pump oil flows past the raise/lower load check valve and past the raise/lower control valve spool to the rod ends of the lift cylinders. Oil from the head end of the lift cylinders flow past the raise/lower control valve spool to the tank. The variable pump oil flows through the right side implement control valve to the tank.
STMGXXX 4/97
- 107 -
IMPLEMENT HYDRAULIC SYSTEM FAST LOWER
PRESSURE REDUCING VALVE
LIFT CYLINDER
TILT CYLINDER
LIFT CYLINDER
SHUTTLE VALVE
LOWER
TILT
TILT
LOWER
RIDE CONTROL
PILOT ON/OFF VALVE
VARIABLE PUMP SOLENOID VALVE
RAISE
DUMP
DUMP
RAISE
PILOT RELIEF VALVE
FAN MOTOR PRESSURE CUTOFF
COOLER
SHUTTLE VALVE
FLUID SAMPLING PORT
FIXED PUMP
LOAD LIMIT CONTROL
FAN DRIVE PUMP
SMALL ACTUATOR LARGE ACTUATOR
FAN SPEED
VARIABLE PUMP
PILOT PUMP
73 Explain schematic
When the raise/lower control lever (not shown) is moved to the FAST LOWER position, the raise/lower control lever sensor (not shown) increases the PWM signal to the ECM (not shown).. The ECM analyzes the increased raise/lower control lever sensor signal, the lift linkage position sensor signal (not shown) and the tilt linkage position sensor signal (not shown). The ECM increases the signal to the LOWER solenoid on the fixed pump raise/lower control valve. The ECM also sends a signal to ENERGIZE the LOWER solenoid on the variable pump raise/lower control valve. Often the signal voltage is different to the two pumps. On the fixed pump control valve, the increased ECM signal increases the LOWER pilot control valve solenoid magnetic field.
STMGXXX 4/97
- 108 -
The stronger magnetic field moves the LOWER pilot control valve further against the spring and increases the drain age. The increased oil drain decreases the oil pressure on the LOWER end of the raise/lower control valve spool. The oil pressure on the RAISE end of the raise/lower control valve spool moves the valve spool to the FAST LOWER position. In the FAST LOWER position, the fixed pump oil flow is increased to the rod ends of the lift cylinders. The increase in oil flow allows the lift arm to be lowered faster. The lift cylinders head end oil flow past the raise/lower control valve spool to the tank. On the variable pump control valve, the ECM signal ENERGIZES the LOWER solenoid on the raise/lower control valve . The LOWER solenoid moves the pilot control valve and opens a age for pilot oil to drain to tank. This reduces the pilot oil pressure at the LOWER end of the raise/lower control valve. The pilot oil pressure on the RAISE end of the raise/lower control valve spool moves the control valve spool to the LOWER position. The raise/lower control valve spool blocks the oil flow to the tank and opens the age to the rod ends of the lift cylinders. The variable pump oil flows past the raise/lower load check valve, past the raise/lower control valve spool and s with the fixed pump oil. The combined oil flows to the rod end of the lift cylinders. The lift cylinders head end oil flow past the raise/lower control valve spools to the tank. The return oil flow past each valve spool is proportion to the supply oil flow past the valve spool.
STMGXXX 4/97
- 109 -
IMPLEMENT HYDRAULIC SYSTEM FLOAT
PRESSURE REDUCING VALVE
LIFT CYLINDER
TILT CYLINDER
LIFT CYLINDER
SHUTTLE VALVE
LOWER
TILT
TILT
LOWER
RIDE CONTROL
PILOT ON/OFF VALVE
VARIABLE PUMP SOLENOID VALVE
PILOT RELIEF VALVE
RAISE
DUMP
DUMP
RAISE
FAN MOTOR
FAN SPEED
PRESSURE CUTOFF COOLER SHUTTLE VALVE
FLUID SAMPLING PORT
FIXED PUMP
LOAD LIMIT CONTROL
FAN DRIVE PUMP
SMALL ACTUATOR LARGE ACTUATOR
VARIABLE PUMP
PILOT PUMP
74 Explain schematic
TTo enter the FLOAT position, the wheel loader lift arm must be below the mid position. When the wheel loader lift arm is below the mid position and the raise/lower control lever (not shown) is moved to the FLOAT position, the raise/lower control lever sensor (not shown) sends a PWM signal to the ECM (not shown).. The ECM analyzes the raise/lower control lever sensor signal, the lift linkage position sensor signal (not shown) and the tilt linkage position sensor signal (not shown). The ECM sends a strong signal and ENERGIZES the LOWER pilot control actuator solenoid on the fixed pump raise/lower control valve and the LOWER pilot control actuator solenoid on the variable pump raise/lower control valve. The ECM also sends a signal and ENERGIZES the FLOAT solenoid on the raise/lower control lever assembly (not shown).
STMGXXX 4/97
- 110 -
On the fixed pump control valve, the strong ECM signal creates a strong magnetic field in the LOWER pilot control actuator solenoid. The strong magnetic field moves the LOWER pilot control actuator and fully opens the drain age to the tank. The pilot oil in the LOWER end of the raise/lower control valve spool and the pilot oil in the float valve spring chamber flow to the tank. The pilot oil pressure decreases on the LOWER end of the raise/lower control valve spool. The pilot oil pressure on the RAISE end of the raise/lower control valve spool moves the valve spool to the FAST LOWER position. When the pilot oil pressure decreases in the spring chamber of the float valve. The pilot oil pressure at the opposite end of the float valve overcomes the spring and moves the float valve to the open position. The oil in the spring chamber of the float check valve flows through the float valve to the tank. The float check valve spring chamber pressure is reduced to approximately tank pressure. The fixed pump oil flows past the raise/lower load check valve and past the raise/lower control valve spool to the float check valve. The fixed pump oil pressure lifts the float check valve off its seat. The fixed pump oil flows past the float check valve to the tank. On the variable pump control valve, the strong ECM signal creates a strong magnetic field in the LOWER pilot control actuator solenoid. The strong magnetic field moves the LOWER pilot control actuator and fully opens the drain age to the tank. The pilot oil in the LOWER end of the raise/lower control valve spool flows to the tank. The pilot oil pressure decreases on the LOWER end of the raise/lower control valve spool. The pilot oil pressure on the RAISE end of the raise/lower control valve spool moves the valve spool to the FAST LOWER position.
STMGXXX 4/97
- 111 -
The oil in the variable pump float valve spring chamber combines with the oil from the fixed pump float valve spring chamber. The combined oil flow the sequence valve in the fixed pump control valve to the tank. The variable pump float valve spring chamber pressure is reduced to approximately tank pressure. The variable pump oil flows past the raise/lower load check valve and past the raise/lower control valve spool to the float valve. The variable pump oil pressure lifts the float valve off its seat. The variable pump oil flows past the float valve to the tank.
STMGXXX 4/97
- 112 -
IMPLEMENT HYDRAULIC SYSTEM LOWER ENGINE OFF
PRESSURE REDUCING VALVE
LIFT CYLINDER
TILT CYLINDER
LIFT CYLINDER
SHUTTLE VALVE
LOWER
TILT
TILT
LOWER
RIDE CONTROL
PILOT ON/OFF VALVE
VARIABLE PUMP SOLENOID VALVE
RAISE
DUMP
DUMP
FAN MOTOR
PILOT RELIEF VALVE PRESSURE CUTOFF FIXED PUMP
FAN DRIVE PUMP
LOAD LIMIT CONTROL SMALL ACTUATOR LARGE ACTUATOR
FAN SPEED
COOLER SHUTTLE VALVE
FLUID SAMPLING PORT
RAISE
VARIABLE PUMP
PILOT PUMP
75 Explain schematic
In this schematic, the bucket is being LOWERED with the ENGINE OFF. The weight of the implement creates a high pressure in the head end of the lift cylinders. The high lift cylinder pressure oil flows through the hose and shuttle valve to the pressure reducing valve. The pressure reducing valve reduces the lift cylinder oil pressure to approximately 2070 kPa (300 psi). The reduced pressure oil flows past the check valve to the pilot on/off solenoid valve and becomes the oil supply for the pilot system. When the on/off solenoid is de-energized, pilot oil is blocked at the on/off solenoid valve. When the on/off solenoid is energized (as shown), pilot oil flows through the on/off solenoid valve and pressurizes the pilot solenoid valves.
STMGXXX 4/97
- 113 -
When the lift control lever is moved to the LOWER position, the EIC (not shown) operation is the same as when the engine is on. The lift control spool directs oil in the head end of the lift cylinders to the tank. Tank oil flows through the rod end makeup valves into the rod end of the lift cylinders and prevents cylinder cavitation.
STMGXXX 4/97
- 114 -
IMPLEMENT HYDRAULIC SYSTEM RIDE CONTROL ON
PRESSURE REDUCING VALVE
LIFT CYLINDER
TILT CYLINDER
LIFT CYLINDER
SHUTTLE VALVE
LOWER
TILT
TILT
LOWER
RIDE CONTROL
PILOT ON/OFF VALVE
VARIABLE PUMP SOLENOID VALVE
RAISE
DUMP
DUMP
RAISE
FAN MOTOR
PILOT RELIEF VALVE PRESSURE CUTOFF SHUTTLE VALVE
FLUID SAMPLING PORT
FIXED PUMP
FAN DRIVE PUMP
LOAD LIMIT CONTROL SMALL ACTUATOR LARGE ACTUATOR
FAN SPEED
COOLER
VARIABLE PUMP
PILOT PUMP
76 Explain schematic
This schematic shows the hydraulic flow when the ride control solenoid valve is activated. The ride control solenoid valve is controlled by the transmission ECM. The ride control switch (not shown) allows the operator to select between the ride control ON, the ride control OFF and the ride control AUTO positions. When the ride control switch is in the ON position, the transmission ECM will continually energize the ride control solenoid.
STMGXXX 4/97
- 115 -
When the ride control switch is in the AUTO position, the transmission ECM will ENERGIZE the ride control solenoid when the machine ground speed is above 9.7 km/hr (6 mph) and will DE-ENERGIZE the ride control solenoid when the ground speed is below 8.8 km/hr (5.5 mph). When the ride control solenoid valve is ENERGIZED, pilot pressure at the selector spool flows to the tank. The spring shifts the selector spool to connect the head end of the lift cylinders with the accumulators. A floating piston in the accumulators separate the oil from the nitrogen gas. Introduce and perform Lab A and Lab B Summarize labs by asking questions
Since nitrogen gas is compressible, the gas serves as a spring. Any downward force on the lift arms is transferred through the oil at the head end of the lift cylinders to the accumulators. The force in the oil is transmitted to the accumulator piston which compresses the nitrogen gas. Compressing the nitrogen gas absorbs the pressure spike and the oil displacement caused by the downward force on the lift arms. This operation results in less ground induced shocks on structures and components, reduced tire flexing and a greater payload retention. INSTRUCTOR NOTE: At this time, introduce and perform "Lab A: Implement Hydraulic System Component Identification Quiz" and "Lab B: Implement Hydraulic System Tests." These labs will reinforce the material discussed in the preceding slide presentation.
STMGXXX 4/97
- 116 -
FAN DRIVE SYSTEM
FAN
ENGINE OFF
FAN MOTOR
SCREEN
MAKEUP VALVE FAN DRIVE PUMP
PROPORTIONAL VALVE COMPENSATOR VALVE
IMPLEMENT HYDRAULIC COOLER
OIL COOLER BY VALVE
TANK
77 Identify components: - Hydraulic tank - Fan drive pump - Proportional valve - Fan drive motor - Makeup valve - Fan - Oil cooler - Oil cooler by valve
FAN DRIVE SYSTEM Shown is a schematic of the fan drive system. Components of the fan drive system are: Hydraulic tank: Reservoir for the hydraulic oil supply. Fan drive pump: Pulls oil from the tank and supplies oil to the fan drive motor. Proportional valve: Controls the signal to the pump. Compensator valve: Controls fan speed by controlling pump flow.
STMGXXX 4/97
- 117 -
Fan motor: Works with the fan drive pump to turn the fan. Makeup valve: Prevents cavitation of the fan drive motor. Fan: Circulates air through the radiator, hydraulic system oil cooler, steering and brake systems oil cooler, brake and axle oil cooler and air conditioner condenser. Oil cooler: Cools the oil used in the fan drive and hydraulic systems. Oil cooler by valve: Allows cold oil to by the cooler, usually at engine start-up.
STMGXXX 4/97
- 118 -
3 13 1 4 6 7
10
9
8 11 2 5 12
78
Identify components 1. Fan drive pump 2. Pump drive housing 3. Pump outlet tube 4. Signal pressure outlet 5. Electro-hydraulic proportional valve 6. Proportional valve solenoid 7. Drain tube 8. Signal hose 9. Margin spool adjustment 10. Compensator valve 11. Pressure compensator adjustment 12. Signal pressure test port 13. System pressure test port
Fan Drive System Components The fan drive pump (1) is a variable displacement piston. The pump is mounted to the right front of the pump drive housing (2) opposite the variable displacement implement pump (not shown). Other components of the fan drive pump are the outlet tube (3), the signal pressure outlet (4), the electro-hydraulic proportional valve (5), the proportional valve solenoid (6), the proportional valve drain tube (7), the proportional valve signal hose (8), the margin spool adjustment (9), the compensator valve (10), The pressure compensator valve adjustment (11), the signal pressure test port (12) and the system pressure test port (13).
STMGXXX 4/97
- 119 -
2 1 3 4
79
Identify components 1. 2. 3. 4.
Fan drive motor Intake hose Output hose Case drain hose
The fan drive motor (1) is located at the rear of the machine in front of the engine radiator assembly. Also shown are the motor intake hose (2), the motor output hose (3) and the case drain hose (4).
STMGXXX 4/97
- 120 -
FAN DRIVE SYSTEM
FAN
SOLENOID DE-ENERGIZED
FAN MOTOR
SCREEN
MAKEUP VALVE PROPORTIONAL VALVE
FAN DRIVE PUMP
COMPENSATOR VALVE
IMPLEMENT HYDRAULIC COOLER
OIL COOLER BY VALVE
TANK
80 Explain schematic
Fan Drive System Schematics When the engine is running, the fan drive pump pulls oil from the implement hydraulic tank and sends oil flow to the fan motor. The fan motor turns the cooling fan and sends air flow through the engine radiator, the implement hydraulic cooler, the steering and brake oil cooler, the front and rear axle coolers and the air condition condenser. Oil from the fan motor flows through the implement hydraulic cooler to the implement hydraulic tank. Also, the fan drive pump sends oil flow through the screen to the electrohydraulic proportional valve.
STMGXXX 4/97
- 121 -
The electro-hydraulic proportional valve controls the signal oil to the pump compensator valve. When the engine ECM de-energizes the electro-hydraulic proportional valve solenoid (as shown), the proportional valve internal age to drain is blocked. The signal oil flows through the two orifices to the pump compensator valve.
STMGXXX 4/97
- 122 -
FAN DRIVE SYSTEM
FAN
SOLENOID ENERGIZED
FAN MOTOR
SCREEN
MAKEUP VALVE FAN DRIVE PUMP
PROPORTIONAL VALVE COMPENSATOR VALVE
IMPLEMENT HYDRAULIC COOLER
OIL COOLER BY VALVE
TANK
81 Explain schematic
When the engine ECM energizes the electro-hydraulic proportional valve solenoid, the proportional valve opens the internal age to drain. The size of the opening is proportional to the signal from the engine ECM. When the proportional valve sends some of the signal oil to drain, the proportional valve reduces the signal pressure to the compensator valve. The reduced signal pressure allows the compensator valve to destroke the pump. Destroking the pump decreases pump speed and decreases the horsepower needed to turn the fan. When the engine is operating below 88°C (190°F), the fan will operate at a minimum speed of 375 ± 50 rpm.
STMGXXX 4/97
- 123 -
Above 98°C (208°F), the fan will be at a maximum speed of 885 rpm. If an electrical failure of the system occurs, the fan will go to maximum (100%) speed.
STMGXXX 4/97
- 124 -
FAN DRIVE SYSTEM
FAN
RAPID ENGINE DECELERATION
FAN MOTOR
SCREEN
MAKEUP VALVE FAN DRIVE PUMP
PROPORTIONAL VALVE COMPENSATOR VALVE
IMPLEMENT HYDRAULIC COOLER
OIL COOLER BY VALVE
TANK
82 Explain schematic
In this illustration, the fan motor is being driven by the fan. During normal operation, oil pressure at the fan motor inlet is higher than oil pressure at the fan motor outlet. The higher inlet pressure seats the motor check valve. When the engine is decelerated rapidly from high idle, the inertia of the fan keeps the fan drive motor turning faster than the fan drive pump can supply oil. The oil pressure at the fan motor inlet becomes lower than the oil pressure at the fan motor outlet.
STMGXXX 4/97
- 125 -
The higher outlet pressure opens the check valve and allows oil from the outlet to flow back to the inlet. The combination of oil flow through the check valve and the pump oil flow prevents cavitation of the fan motor. When pump output matches fan speed, the motor inlet oil pressure increases above the motor outlet oil pressure. The higher inlet pressure closes the check valve.
Related Documents 171j1w
Manual Caterpillar 992g Wheel Loader Electro Hydraulic Implement System Components 1u1j6o
January 2022 0
950h Wheel Loader Hydraulic System 6l3i1h
October 2022 0
Course-steering-system-components-power-train-wheel-loader-992g-caterpillar.pdf 3dw64
May 2020 7
992k And 993k Caterpillar Wheel Loader Hydraulic System 3j6bh
April 2020 8
Manual-caterpillar-992g-wheel-loader-steering-brakes-components-layout-operation-testing-adjusting.pdf 5w1w1q
January 2022 0