HOLD Position
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| Illustration 1 | g01428250 |
Hydraulic system (HOLD position) (1) Lift cylinder (2) Tilt cylinder (3) Main relief valve (right) (4) Main relief valve (left) (5) Rod end line relief valve for tilt cylinders (6) Head end line relief valve for tilt cylinders (7) Head end line relief valve for lift cylinders (8) Rod end line relief valve for lift cylinders (9) Shuttle valve (10) Pressure reducing valve (11) Pilot control actuator (lower) (12) Pilot control actuator (tilt back) (13) Pilot control actuator (tilt back) (14) Pilot control actuator (lower) (15) Lift stem (right) (16) Tilt stem (right) (17) Tilt stem (left) (18) Lift stem (left) (19) Pilot control actuator (raise) (20) Pilot control actuator (dump) (21) Pilot control actuator (dump) (22) Pilot control actuator (raise) (23) Float valve (right) (24) Float valve (left) (25) Manual lowering valve (26) Solenoid valve (hydraulic lockout) (27) Check valve group (28) Pilot pump (29) Pilot oil filter (30) Pilot pressure reducing valve (31) Pressure sensor (pilot pressure) (32) Pilot oil accumulator (33) Implement pump (180 cc (11.0 in3)) (34) Implement pump (250 cc (15.3 in3))(right) (35) Implement pump (250 cc (15.3 in3))(center) (36) Hydraulic tank | |
In the pilot hydraulic system, pilot pump (28) draws oil from hydraulic tank (36) and supplies pilot oil to the following components: pilot pressure reducing valve (30) , the solenoid valve (hydraulic lockout) (26) , ride control valve (if equipped) and the solenoid valves for the variable displacement piston pumps.
Pilot pressure reducing valve (30) maintains the pilot pressure at 3450 kPa (500 psi).
The solenoid valve (hydraulic lockout) (26) is controlled by the hydraulic lockout switch. When the hydraulic lockout switch is in the LOCKED position, the implement ECM will not energize the solenoid valve. The flow of oil to pilot control actuators (11, 12, 13, 14, 19, 20, 21, 22) is blocked. When the hydraulic lockout switch is in the UNLOCKED position, the implement ECM will energize the solenoid valve. The pilot oil flows past the solenoid valve (hydraulic lockout) to pilot control actuators (11, 12, 13, 14, 19, 20, 21, 22) .
In the left side of the implement hydraulic system, variable displacement piston pumps (33, 34) draw oil from hydraulic tank (36) . Then, the pumps provide oil to the main control valve (left). When stems (17, 18) are in the HOLD position, oil flows through the open centered valve to hydraulic tank (36) . Main relief valve (4) constantly senses pressure in the main control valve (left). When the oil pressure reaches the maximum adjustment, main relief valve (4) opens. The maximum pressure adjustment for main relief valve (4) is 29500 kPa (4300 psi).
In the right side of the implement hydraulic system, variable displacement piston pumps (33, 35) draw oil from hydraulic tank (36) . Then, the pumps provide oil to the main control valve (right). When the main control stems are in the HOLD position, oil flows through the open centered valve to hydraulic tank (36) . Main relief valve (3) constantly senses pressure in the main control valve (left). When the oil pressure reaches the maximum adjustment, main relief valve (3) opens. The maximum pressure adjustment for main relief valve (3) is 29500 kPa (4300 psi).
When the control levers are in the HOLD position, oil flow to lift cylinders (1) and tilt cylinders (2) is blocked at the stems for both main control valves.
TILT BACK Position
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| Illustration 2 | g01428493 |
Hydraulic system (TILT BACK position) (1) Lift cylinder (2) Tilt cylinder (3) Main relief valve (right) (4) Main relief valve (left) (5) Rod end line relief valve for tilt cylinders (6) Head end line relief valve for tilt cylinders (7) Head end line relief valve for lift cylinders (8) Rod end line relief valve for lift cylinders (9) Shuttle valve (10) Pressure reducing valve (11) Pilot control actuator (lower) (12) Pilot control actuator (tilt back) (13) Pilot control actuator (tilt back) (14) Pilot control actuator (lower) (15) Lift stem (right) (16) Tilt stem (right) (17) Tilt stem (left) (18) Lift stem (left) (19) Pilot control actuator (raise) (20) Pilot control actuator (dump) (21) Pilot control actuator (dump) (22) Pilot control actuator (raise) (23) Float valve (right) (24) Float valve (left) (25) Manual lowering valve (26) Solenoid valve (hydraulic lockout) (27) Check valve group (28) Pilot pump (29) Pilot oil filter (30) Pilot pressure reducing valve (31) Pressure sensor (pilot pressure) (32) Pilot oil accumulator (33) Implement pump (180 cc (11.0 in3)) (34) Implement pump (250 cc (15.3 in3))(right) (35) Implement pump (250 cc (15.3 in3))(center) (36) 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 pilot control actuators (tilt back) (12, 13) on the main control valves.
The solenoid valves in the pilot control actuators (12, 13) shift, and the pilot oil at the tilt back end of the tilt stems (16, 17) is released to the hydraulic tank. This shift reduces the pilot pressure at the end of stems (16, 17) . The combination of the spring force and the oil pressure on the dump end of the tilt stems begins to shift stems (16, 17) to the TILT BACK position.
The oil from variable displacement piston pumps (33, 34, 35) flows around the control valve spool to the head end of each tilt cylinder (2) . The oil at the rod end of each tilt cylinder (2) flows around stem (16, 17) to the hydraulic tank.
As the tilt control lever is pushed further into the TILT BACK position, the implement ECM will increase the current to the solenoid valves for variable displacement piston pumps (33, 34, 35) . This increase will cause the pumps to upstroke. Additional oil will be directed to each main control valve. The speed of the tilt back operation will increase.
DUMP Position
When the tilt control lever is moved to the DUMP position, operation is similar to the tilt back operation. Solenoid valves for pilot control actuators (20, 21) are energized. This action reduces the pilot pressure on the dump end of the tilt stems. The tilt stems shift to the DUMP position. Implement supply oil is directed to the rod end of each tilt cylinder. Oil from the head end of each tilt cylinder is directed to the hydraulic tank.
RAISE Position
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| Illustration 3 | g01428536 |
Hydraulic system (RAISE position) (1) Lift cylinder (2) Tilt cylinder (3) Main relief valve (right) (4) Main relief valve (left) (5) Rod end line relief valve for tilt cylinders (6) Head end line relief valve for tilt cylinders (7) Head end line relief valve for lift cylinders (8) Rod end line relief valve for lift cylinders (9) Shuttle valve (10) Pressure reducing valve (11) Pilot control actuator (lower) (12) Pilot control actuator (tilt back) (13) Pilot control actuator (tilt back) (14) Pilot control actuator (lower) (15) Lift stem (right) (16) Tilt stem (right) (17) Tilt stem (left) (18) Lift stem (left) (19) Pilot control actuator (raise) (20) Pilot control actuator (dump) (21) Pilot control actuator (dump) (22) Pilot control actuator (raise) (23) Float valve (right) (24) Float valve (left) (25) Manual lowering valve (26) Solenoid valve (hydraulic lockout) (27) Check valve group (28) Pilot pump (29) Pilot oil filter (30) Pilot pressure reducing valve (31) Pressure sensor (pilot pressure) (32) Pilot oil accumulator (33) Implement pump (180 cc (11.0 in3)) (34) Implement pump (250 cc (15.3 in3))(right) (35) Implement pump (250 cc (15.3 in3))(center) (36) 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 implement ECM analyzes this signal and the signals from the tilt linkage position sensor and from the lift linkage position sensor. The implement ECM then sends a proportional signal that energizes the solenoid for pilot control actuators (raise) (19, 22) on the main control valves.
The solenoid valves in the pilot control actuators (19, 22) shift, and the pilot oil at the raise end of the lift stems (15, 18) is released to the hydraulic tank. This action reduces the pilot pressure at the end of stems (15, 18) . The oil pressure on the lower end of the lift stems begins to shift stems (15, 18) to the RAISE position.
The oil from variable displacement piston pumps (33, 34, 35) flows around the control valve spool to the head end of each lift cylinder (1) . The oil at the rod end of each lift cylinder (1) flows around stem (15, 18) to the hydraulic tank.
As the lift control lever is pushed further into the RAISE position, the implement ECM will increase the current to the solenoid valves for variable displacement piston pumps (33, 34, 35) . This increase will cause the pumps to upstroke. Additional oil will be directed to each main control valve. The speed of the raise operation will increase.
LOWER Position
When the lift control lever is moved to the LOWER position, operation is similar to the raise operation. Solenoid valves for pilot control actuators (11, 14) are energized. This action reduces the pilot pressure on the lower end of the lift stems. The lift stems shift to the LOWER position. Implement supply oil is directed to the rod end of each lift cylinder. Oil from the head end of each lift cylinder is directed to the hydraulic tank.
Float Position
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| Illustration 4 | g01428539 |
Hydraulic system (FLOAT position) (1) Lift cylinder (2) Tilt cylinder (3) Main relief valve (right) (4) Main relief valve (left) (5) Rod end line relief valve for tilt cylinders (6) Head end line relief valve for tilt cylinders (7) Head end line relief valve for lift cylinders (8) Rod end line relief valve for lift cylinders (9) Shuttle valve (10) Pressure reducing valve (11) Pilot control actuator (lower) (12) Pilot control actuator (tilt back) (13) Pilot control actuator (tilt back) (14) Pilot control actuator (lower) (15) Lift stem (right) (16) Tilt stem (right) (17) Tilt stem (left) (18) Lift stem (left) (19) Pilot control actuator (raise) (20) Pilot control actuator (dump) (21) Pilot control actuator (dump) (22) Pilot control actuator (raise) (23) Float valve (right) (24) Float valve (left) (25) Manual lowering valve (26) Solenoid valve (hydraulic lockout) (27) Check valve group (28) Pilot pump (29) Pilot oil filter (30) Pilot pressure reducing valve (31) Pressure sensor (pilot pressure) (32) Pilot oil accumulator (33) Implement pump (180 cc (11.0 in3)) (34) Implement pump (250 cc (15.3 in3))(right) (35) Implement pump (250 cc (15.3 in3))(center) (36) Hydraulic tank | |
In order to enter the FLOAT position , the lift linkage must be below the midway point.
When the lift arms are below the midway point and the lift control lever is moved forward to the FLOAT position, the position sensor for the lift control lever sends a pulse width modulated signal (PWM) to the implement electronic control module (ECM). The implement ECM analyzes this signal and the signals from the tilt linkage position sensor and from the lift linkage position sensor. The implement ECM then sends a signal that energizes the solenoids for pilot control actuators (11, 14) on the main control valves. The implement ECM sends a signal that energizes the solenoids for the float valves (23, 24) . Also, the implement ECM sends a signal that energizes the detent coil for the lift control lever.
The solenoids in the pilot control actuators shift and the pilot oil at the lower end of each stem is relieved to hydraulic tank (36) . This action reduces the pilot pressure at the end of the stem for the lower function. The oil pressure on the opposite end of each stem (15, 18) shifts the stems to the LOWER position.
Implement supply oil flows around the tilt stems, through the lift check valve and to float check valves. Float valves (23, 24) are energized. This action releases the implement supply pressure that is trapped between the float valves and the float check valves. This action also creates a pressure drop across the float check valves, which overcomes the bias spring keeping the float valve closed. The pressure drop created causes the float check valves to open. Implement supply oil that would be flowing to the lift stems for lowering the lift linkage is allowed to drain around the float check valves and to hydraulic tank (36) . As the bucket is allowed to ride along the contour of the ground, rod end oil from lift cylinder (1) will be able to drain to hydraulic tank (36) .
Lower Position (Nonrunning Engine)
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| Illustration 5 | g01428554 |
Hydraulic system (LOWER position)(engine in OFF position) (1) Lift cylinder (2) Tilt cylinder (3) Main relief valve (right) (4) Main relief valve (left) (5) Rod end line relief valve for tilt cylinders (6) Head end line relief valve for tilt cylinders (7) Head end line relief valve for lift cylinders (8) Rod end line relief valve for lift cylinders (9) Shuttle valve (10) Pressure reducing valve (11) Pilot control actuator (lower) (12) Pilot control actuator (tilt back) (13) Pilot control actuator (tilt back) (14) Pilot control actuator (lower) (15) Lift stem (right) (16) Tilt stem (right) (17) Tilt stem (left) (18) Lift stem (left) (19) Pilot control actuator (raise) (20) Pilot control actuator (dump) (21) Pilot control actuator (dump) (22) Pilot control actuator (raise) (23) Float valve (right) (24) Float valve (left) (25) Manual lowering valve (26) Solenoid valve (hydraulic lockout) (27) Check valve group (28) Pilot pump (29) Pilot oil filter (30) Pilot pressure reducing valve (31) Pressure sensor (pilot pressure) (32) Pilot oil accumulator (33) Implement pump (180 cc (11.0 in3)) (34) Implement pump (250 cc (15.3 in3))(right) (35) Implement pump (250 cc (15.3 in3))(center) (36) 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 (9) to pressure reducing valve (10) . The pressure in the pilot system will increase to approximately 1580 kPa (230 psi). Pressure reducing valve (10) will shift and this position will block the flow of oil through pressure reducing valve (10) . Pressure reducing valve (10) reduces the pressure that is used by the pilot system to approximately 1580 kPa (230 psi).
With the key start switch in the ON position, the reduced pilot oil flows to the solenoid valve (hydraulic lockout) (26) . This oil becomes the supply oil for the pilot system. The pilot oil will pressurize all the pilot control actuators.
When the lift control lever is moved to the LOWER position, the solenoid valve in pilot control actuator (11, 14) will shift and this action will allow the oil pressure against the lift stem in the HOLD position to shift. The pilot oil is relieved to hydraulic tank (36) . Stems (15, 18) shift and this shift will allow the trapped oil in the head end of lift cylinders (1) to return to hydraulic tank (36) . The pilot control actuators will have an adequate amount of pilot pressure if there is pressure in the head end of lift cylinders (1) .