HOLD Position
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| Illustration 1 | g01442764 |
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 (250 cc (15.2550 in3)) (center) (32) Implement pump (250 cc (15.2550 in3)) (right) (33) Pilot pump (34) Hydraulic tank | |
In the pilot hydraulic system, pilot pump (33) draws oil from hydraulic 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 3500 kPa (508 psi).
The solenoid valve (hydraulic lockout) (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 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 solenoid valve. The pilot oil flows past the solenoid valve (hydraulic lockout) 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 variable displacement piston pump (center) (31) draws oil from hydraulic tank (34). Then, the pump provides 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 tank (34). The main relief valve (left) (10) constantly senses pressure at the variable displacement piston 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 31000 kPa (4500 psi).
In the right side of the implement hydraulic system, the variable displacement piston pump (right) (32) draws oil from hydraulic 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 hydraulic 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 31000 kPa (4500 psi).
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.
TILT BACK Position
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| Illustration 2 | g01443024 |
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 (250 cc (15.2550 in3)) (center) (32) Implement pump (250 cc (15.2550 in3)) (right) (33) Pilot pump (34) Hydraulic 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 tank. This release reduces the pilot pressure at the end of stems (19) and (20). The combination of the spring force and the oil pressure on the dump end of the tilt stem begins to shift stems (19) and (20) to the TILT BACK position.
The oil from variable displacement piston 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 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 variable displacement piston pumps (31) and (32). This increase in current will cause the pumps to upstroke. Additional oil will be directed to each main control valve. The speed of the tilt back operation will increase.
DUMP Position
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 (2) and pilot control actuators (24, 25) are energized. This energization 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 each cylinder. Oil from the rod end of each tilt cylinder is directed to the hydraulic 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 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 tank. The bucket will dump forward.
RAISE Position
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| Illustration 3 | g01443041 |
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 (250 cc (15.2550 in3)) (center) (32) Implement pump (250 cc (15.2550 in3)) (right) (33) Pilot pump (34) Hydraulic 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 tank. This reduces the pilot pressure at the end of 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 stems (18) and (21) to the RAISE position.
The oil from variable displacement piston 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 tank.
As the lift control lever is pushed further into the RAISE position, the implement ECM will increase the current solenoid valves for variable displacement piston pumps (31) and (32). This will cause the pumps to upstroke. Additional oil will be directed to each main control valve. The speed of the raise operation will increase.
LOWER Position
When the lift control lever is moved to the LOWER position, operation is similar to the raise operation. Solenoid valves for pilot control actuators (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. Oil from the head end of each lift cylinder is directed to the hydraulic tank.
Float Position
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| Illustration 4 | g01443120 |
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 (250 cc (15.2550 in3)) (center) (32) Implement pump (250 cc (15.2550 in3)) (right) (33) Pilot pump (34) Hydraulic 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. 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 (12, 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 (12, 15) 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 (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 (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 tank (34) .
LOWER Position (Nonrunning engine)
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| Illustration 5 | g01443142 |
Hydraulic system operation (LOWER position) (nonrunning 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 (250 cc (15.2550 in3)) (center) (32) Implement pump (250 cc (15.2550 in3)) (right) (33) Pilot pump (34) Hydraulic 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 1650 kPa (240 psi). Pressure reducing valve (5) will shift and this will block the flow of oil through pressure reducing valve (5). Pressure reducing valve (5) reduces the pressure that is used by the pilot system to approximately 1650 kPa (240 psi).
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). Stems (18), (21) shift and this will allow the trapped oil in the head end of lift cylinders (1) to return to hydraulic 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) .