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| Illustration 1 | g06233564 |
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Component locations (1) Electro-hydraulic control (2) Implement electronic control module (3) Implement hydraulic pumps (4) Hydraulic Oil Cooler (5) Hydraulic tank (6) Main control valve (7) Regeneration valve (8) Tilt cylinder (9) Lift cylinders (A) Electronic system (B) Main hydraulic system | |
The electro-hydraulic system is electrically controlling the pilot operated system. The pilot system controls the functions of the main control valve (6). The pilot system consists of an electronic system (A) and a hydraulic system (B).
The electronic system is composed of the following components: Implement electronic control module (2), electro-hydraulic control (1), a lift linkage position sensor, a tilt linkage position sensor and left and right pump control solenoids. Also, two components from main control valve are part of the electronic system: pilot control valve solenoids and solenoid valve (hydraulic lockout).
Electro-hydraulic control consists of the following components: lift control lever, tilt control lever, lift control position sensor, tilt control position sensor, detent coil (tiltback), detent coil (lower), detent coil (raise), and switch (hydraulic lockout).
The pilot hydraulic system consists of pilot pump and pilot relief valve. Also, two components from main control valve are part of the pilot hydraulic system: pilot control actuators and solenoid valve (hydraulic lockout).
The main hydraulic system consists of following components. Implement hydraulic pumps (3), main control valve (6), regeneration valve (7), tilt cylinder and lift cylinders (8) and (9).
Implement hydraulic tank is common to the pilot hydraulic system and to the main hydraulic system.
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| Illustration 2 | g01442764 |
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Hydraulic system operation (HOLD position) (1) Lift cylinders (2) Regenerative valve (dump) (3) Tilt cylinder (4) Shuttle valve (dead engine lower) (5) Pressure reducing valve (dead engine lower) (6) Rod end line relief valve for lift cylinders (7) Head end line relief valve for lift cylinders (8) Rod end line relief valve for tilt cylinders (9) Head end line relief valve for tilt cylinder (10) Main relief valve (left) (11) Main relief valve (right) (12) Pilot control actuator (lower) (13) Pilot control actuator (tilt back) (14) Pilot control actuator (tilt back) (15) Pilot control actuator (lower) (16) Tilt cylinder rod end dual pressure relief (17) Solenoid valve (hydraulic lockout) (18) Lift stem (left) (19) Tilt stem (left) (20) Tilt stem (right) (21) Lift stem (right) (22) Manual lowering valve (23) Pilot control actuator (raise) (24) Pilot control actuator (dump) (25) Pilot control actuator (dump) (26) Pilot control actuator (raise) (27) Pilot relief valve (28) Float valves (29) Pilot oil filter (30) Pilot oil accumulator (31) Implement pump ( (32) Implement pump ( (33) Pilot pump (34) Hydraulic oil tank | |
In the pilot hydraulic system, pilot pump (33) draws oil from hydraulic oil tank (34) and supplies pilot oil to the following components: pilot relief valve (27), hydraulic lockout solenoid valve (17), ride control valve (if equipped), main control valves and the solenoid valves for the center variable piston pump and the right variable piston pump.
Pilot relief valve (27) maintains the pilot pressure at
The hydraulic lockout solenoid valve (17) is controlled by the hydraulic lockout switch. When the hydraulic lockout switch is in the LOCKED position, the implement ECM will not energize the hydraulic lockout solenoid valve. The flow of oil is blocked to the pilot control actuators (12), (13), (14), (15), (23), (24), (25), and (26). When the hydraulic lockout switch is in the UNLOCKED position, the implement ECM will energize the hydraulic lockout solenoid valve. The pilot oil flows past the hydraulic lockout solenoid valve to pilot control actuators (12), (13), (14), (15), (23), (24), (25), and (26). Certain system faults may cause the Implement ECM to turn off the hydraulic lockout solenoid even when the lockout switch is in the locked position.
In the left side of the implement hydraulic system, the implement pump (center) (31) draws oil from hydraulic oil tank (34). Then, the pump sends oil to the main control valve (left). When stems (18) and (19) are in the HOLD position, oil flows through the open centered valve to hydraulic oil tank (34). The main relief valve (left) (10) constantly senses pressure at the variable displacement implement pump. When the oil pressure reaches the maximum adjustment, the main relief valve (left) (10) opens. The maximum pressure adjustment for the main relief valve (left) (10) is
In the right side of the implement hydraulic system, the implement pump (right) (32) draws oil from hydraulic oil tank (34). Then, the pump provides oil to the main control valve (right) (32). When the main control stems are in the HOLD position, oil flows through the open centered valve to the hydraulic oil tank (34). The main relief valve (right) (11) constantly senses pressure in the main control valve (left) (10). When the oil pressure reaches the maximum adjustment, main relief valve (11) opens. The maximum pressure adjustment for the main relief valve (right) (11) is
When the control levers are in the HOLD position, oil flow to cylinders (1) and (2) is blocked at the stems for both main control valves.
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| Illustration 3 | g01443024 |
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Hydraulic system operation (TILT BACK position) (1) Lift cylinders (2) Regenerative valve (dump) (3) Tilt cylinder (4) Shuttle valve (dead engine lower) (5) Pressure reducing valve (dead engine lower) (6) Rod end line relief valve for lift cylinders (7) Head end line relief valve for lift cylinders (8) Rod end line relief valve for tilt cylinders (9) Head end line relief valve for tilt cylinders (10) Main relief valve (left) (11) Main relief valve (right) (12) Pilot control actuator (lower) (13) Pilot control actuator (tilt back) (14) Pilot control actuator (tilt back) (15) Pilot control actuator (lower) (16) Tilt cylinder rod end dual pressure relief (17) Solenoid valve (hydraulic lockout) (18) Lift stem (left) (19) Tilt stem (left) (20) Tilt stem (right) (21) Lift stem (right) (22) Manual lowering valve (23) Pilot control actuator (raise) (24) Pilot control actuator (dump) (25) Pilot control actuator (dump) (26) Pilot control actuator (raise) (27) Pilot pressure reducing valve (28) Float valves (29) Pilot oil filter (30) Pilot oil accumulator (31) Implement pump (center) (32) Implement pump (right) (33) Pilot pump (34) Hydraulic oil tank | |
When the tilt control lever is moved to the TILT BACK position, the position sensor for the tilt control lever sends a pulse width modulated signal (PWM) to the implement electronic control module (ECM). The implement ECM analyzes this signal and the signals from the tilt linkage position sensor and from the lift linkage position sensor. The implement ECM then sends a proportional signal that energizes the solenoid for the pilot control actuator (tilt back) (13) and (14) on the left implement control valve.
The solenoid valve in the pilot control actuators (13) and (14) shifts and the pilot oil at the tilt back end of the control valve stems (19) and (20) is released to the hydraulic oil tank. This release reduces the pilot pressure at the end the control valve stems. The combination of the spring force and the oil pressure on the dump end of the tilt stem begins to shift control valve stems to the TILT BACK position.
The oil from implement pumps (31) and (32) flows around the control valve spool regeneration valve rod end of the tilt cylinders (3). The oil at the head end of tilt cylinder (3) flows around stem (19) to the hydraulic oil tank.
As the tilt control lever is pushed further into the TILT BACK position, the implement ECM will increase the current to the solenoid valves for the implement pumps (31) and (32). This increase in current will cause the implement pumps to up-stroke. Additional oil will be directed to each main control valve. The speed of the tilt back operation will increase.
As the tilt control lever is moved to the DUMP position, operation is similar to the tilt back operation. Solenoid valves on the regeneration valve (dump) (2) and pilot control actuators (dump) (24) and (25) are energized. This reduces the pressure on the dump end of the tilt stems. The tilt stems shift to the DUMP position. Implement supply oil is directed to the head end of the cylinder (3). Oil from the rod of the tilt cylinder (3) is directed to the hydraulic oil tank. The regeneration valve also opens during a dump operation. The flow of oil is diverted from the rod end of the tilt cylinder to the head end of the tilt cylinder.
The regeneration valve is also energized during a dump operation. A portion of the oil from the rod end of the tilt cylinder (3) is diverted to the head end of the tilt cylinder through the regeneration valve. The remaining oil from the rod end is directed to the hydraulic oil tank. The bucket will dump forward.
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| Illustration 4 | g01443041 |
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Hydraulic system operation (RAISE position) (1) Lift cylinders (2) Regenerative valve (dump) (3) Tilt cylinder (4) Shuttle valve (dead engine lower) (5) Pressure reducing valve (dead engine lower) (6) Rod end line relief valve for lift cylinders (7) Head end line relief valve for lift cylinders (8) Rod end line relief valve for tilt cylinders (9) Head end line relief valve for tilt cylinders (10) Main relief valve (left) (11) Main relief valve (right) (12) Pilot control actuator (lower) (13) Pilot control actuator (tilt back) (14) Pilot control actuator (tilt back) (15) Pilot control actuator (lower) (16) Tilt cylinder rod end dual pressure relief (17) Solenoid valve (hydraulic lockout) (18) Lift stem (left) (19) Tilt stem (left) (20) Tilt stem (right) (21) Lift stem (right) (22) Manual lowering valve (23) Pilot control actuator (raise) (24) Pilot control actuator (dump) (25) Pilot control actuator (dump) (26) Pilot control actuator (raise) (27) Pilot pressure reducing valve (28) Float valves (29) Pilot oil filter (30) Pilot oil accumulator (31) Implement pump ( (32) Implement pump ( (33) Pilot pump (34) Hydraulic oil tank | |
When the lift control lever is moved to the RAISE position, the position sensor for the lift control lever sends a pulse width modulated signal (PWM) to the implement electronic control module (ECM). The ECM analyzes this signal and the signals from the tilt linkage position sensor and from the lift linkage position sensor. The implement ECM then sends a proportional signal that energizes the solenoid for pilot control actuators (23) and (26) on the main control valves.
The solenoid valves in the pilot control actuators (23) and (26) shift and the pilot oil at the raise end of the lift stems (18) and (21) is released to the hydraulic oil tank. This reduces the pilot pressure at the end of lift stems (18) and (21). The combination of the spring force and the oil pressure on the lower end of the lift stems begins to shift lift stems (18) and (21) to the RAISE position.
The oil from implement pumps (31) and (32) flows around the control valve spool to the head end of each lift cylinder (1). The oil at the rod end of each lift cylinder (1) flows around stem (18) and (21) to the hydraulic oil tank (34).
As the lift control lever is pushed further into the RAISE position, the implement ECM will increase the current solenoid valves for implement pumps (31) and (32). This will cause the implement pumps to upstroke. Additional oil will be directed to each main control valve. The speed of the raise operation will increase.
When the lift control lever is moved to the LOWER position, operation is similar to the raise operation. Solenoid valves for pilot control actuators (lower) (12) and (15) are energized. This reduces the pressure on the lower end of the tilt stems. The lift stems shift to the LOWER position. Implement supply oil is directed to the rod end of each lift cylinder (1). Oil from the head end of each lift cylinder is directed to the hydraulic oil tank (34).
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| Illustration 5 | g01443120 |
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Hydraulic system operation (float position) (1) Lift cylinders (2) Regenerative valve (dump) (3) Tilt cylinder (4) Shuttle valve (dead engine lower) (5) Pressure reducing valve (dead engine lower) (6) Rod end line relief valve for lift cylinders (7) Head end line relief valve for lift cylinders (8) Rod end line relief valve for tilt cylinders (9) Head end line relief valve for tilt cylinders (10) Main relief valve (left) (11) Main relief valve (right) (12) Pilot control actuator (lower) (13) Pilot control actuator (tilt back) (14) Pilot control actuator (tilt back) (15) Pilot control actuator (lower) (16) Tilt cylinder rod end dual pressure relief (17) Solenoid valve (hydraulic lockout) (18) Lift stem (left) (19) Tilt stem (left) (20) Tilt stem (right) (21) Lift stem (right) (22) Manual lowering valve (23) Pilot control actuator (raise) (24) Pilot control actuator (dump) (25) Pilot control actuator (dump) (26) Pilot control actuator (raise) (27) Pilot pressure reducing valve (28) Float valves (29) Pilot oil filter (30) Pilot oil accumulator (31) Implement pump ( (32) Implement pump ( (33) Pilot pump (34) Hydraulic oil tank | |
Moving the lift lever into the lower detent position will put the machine into FLOAT.
When the lift control lever is moved forward to the FLOAT (lower detent) position, the lift lever position sensor sends a signal to the electronic control module (ECM). The signal is a pulse width modulated signal (PWM). The implement ECM analyzes this signal and the signal from the lift linkage position sensor. The implement ECM then sends a proportional current that energizes the solenoid for pilot control actuators (lower) (12) and (15) on the main control valves. The implement ECM also sends a signal that energizes the solenoid for the float valves (28). If the linkage is above the lower kickout position, the implement ECM will continue energizing the solenoids for pilot control actuators (lower) on the main control valve, the solenoid for the float valves until the lower kickout position is reached. If the linkage is below the lower kickout position, the solenoids for the pilot control actuators (lower) (12, 15) on the main control lever will remain energized. The hydraulic system will remain in float until the float feature is canceled. The float feature can be canceled by moving the lift control lever out of center.
The solenoids in the pilot control actuators shift and the pilot oil at the lower stems for both stems is relieved to hydraulic tank (34). This reduces the pilot pressure at the end of the stem for the lower function. The combination of spring force and the oil pressure on the ends of both stems (lift) (18) and (21) shift the stems to the LOWER position.
Implement supply oil will flow through the load check valve in each main control valve, around the tilt stems, and to the fault check valves. Float valves (28) are energized. This releases the oil pressure that is trapped between the float valves and the float check valves. The float check valves open. Implement supply oil that would be flowing to the lift stems for lowering the lift linkage is allowed to drain to the hydraulic oil tank (34).
LOWER Position (Non-running engine)
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| Illustration 6 | g01443142 |
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Hydraulic system operation (LOWER position) (non-running engine) (1) Lift cylinders (2) Regenerative valve (dump) (3) Tilt cylinder (4) Shuttle valve (dead engine lower) (5) Pressure reducing valve (dead engine lower) (6) Rod end line relief valve for lift cylinders (7) Head end line relief valve for lift cylinders (8) Rod end line relief valve for tilt cylinders (9) Head end line relief valve for tilt cylinders (10) Main relief valve (left) (11) Main relief valve (right) (12) Pilot control actuator (lower) (13) Pilot control actuator (tilt back) (14) Pilot control actuator (tilt back) (15) Pilot control actuator (lower) (16) Tilt cylinder rod end dual pressure relief (17) Solenoid valve (hydraulic lockout) (18) Lift stem (left) (19) Tilt stem (left) (20) Tilt stem (right) (21) Lift stem (right) (22) Manual lowering valve (23) Pilot control actuator (raise) (24) Pilot control actuator (dump) (25) Pilot control actuator (dump) (26) Pilot control actuator (raise) (27) Pilot pressure reducing valve (28) Float valves (29) Pilot oil filter (30) Pilot oil accumulator (31) Implement pump ( (32) Implement pump ( (33) Pilot pump (34) Hydraulic oil tank | |
When the bucket is off the ground with the engine in the OFF position, the lift linkage can be lowered. The weight of the lift linkage creates pressure in the head end of lift cylinders (1) that can be used for pilot pressure in order to lower the lift linkage. The pressure oil in the head end of the lift cylinders flows through shuttle valve (4) to pressure reducing valve (5). The pressure in the pilot system will increase to approximately
With the key start switch in the ON position, the reduced pilot oil flows to the solenoid valve (hydraulic lockout) (17). This oil becomes the supply oil for the pilot system. The pilot oil will pressurize all the pilot control actuators.
When the lift control lever is moved to the LOWER position, the solenoid valve in pilot control actuator (12) and (15) will shift and this will allow the oil pressure against the lift stem in the HOLD position to shift. The pilot oil is relieved to hydraulic tank (34). Lift stems (18) and (21) shift and this will allow the trapped oil in the head end of lift cylinders (1) to return to hydraulic oil tank (34). The pilot control actuators will have an adequate amount of pilot pressure if there is pressure in the head end of lift cylinders (1).