VALVE GP- 3516332 - Caterpillar

Electrohydraulic Control
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(8) Proportional solenoid valve
(9) Servo piston
(18) Control spool The electrohydraulic control is based on the hydraulic remote control.The actuation of control spool (18) is made by pilot pressure acting on servo piston (9). Pilot pressure is controlled by proportional solenoid valves (8).
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Detail A1
(8) Proportional solenoid valve
(28) Solenoid stem
(29) Port
(30) Piston
(31) Port
(32) Pilot valve
(33) Spring Refer to Detail A1. When proportional solenoid valve (8) is not energized, piston (30) and solenoid stem (28) are pushed into the top position by the compression of spring (33). The spring cavity of servo piston (8) is open to port (29). The springs in the servo cylinder keep the servo piston in neutral.
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Detail A2
(8) Proportional solenoid valve
(28) Solenoid stem
(29) Port
(30) Piston
(31) Port
(32) Pilot valve
(33) Spring
(H) Hydraulic force
(M) Magnetic force Refer to Detail A2. When the solenoid is energized by a preselected current, magnetic force (M) is applied to solenoid stem (28). This force presses piston (30) downward. The oil flows from port (31) into the servo cylinder until a corresponding pressure builds up in the chamber at spring (33). This creates hydraulic force (H) that is equivalent to magnetic force (M) on pilot valve (32). The servo piston will then achieve a position that corresponds to the oil pressure. The servo piston will then adjust the swashplate angle by that amount.
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Detail A3
(8) Proportional solenoid valve
(28) Solenoid stem
(29) Port
(30) Piston
(31) Port
(32) Pilot valve
(33) Spring
(H) Hydraulic force
(M) Magnetic force Refer to Detail A3. When magnetic force (M), hydraulic force (H) and the spring forces are balanced on piston (30), the piston grooves are in the zero position. The control pressure is constant in the servo cylinder. This will set the swashplate angle of the pump.All Wheel Drive In The ON Position
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(1) Gear pump
(2) Line to the AWD piston motor
(3) Piston pump
(4) Line to the AWD piston motor
(5) Passage
(6) Passage
(7) Passage
(8) Proportional solenoid valve
(9) Servo piston
(10) Proportional solenoid valve
(11) AWD filter
(12) Makeup and line relief valve
(13) Makeup and line relief valve
(14) Actuator piston
(15) Pump displacement controls
(16) Actuator piston
(17) Lever
(18) Control spool
(19) Swashplate
(20) Passage
(21) Passage
(22) Passage
(23) Relief valve
(24) Makeup valve
(25) Spring
(26) Relief valve
(27) Spring When the all wheel drive system is in the ON position, but the machine is in the PARK position or the NEUTRAL position, there is no electrical current to proportional solenoid valve (8) and proportional solenoid valve (10). Passage (7) is at the charge pressure. If there is no signal oil pressure to the spring chambers of servo piston (9), the servo piston stays in NEUTRAL position. This also keeps lever (17) and control spool (18) in the NEUTRAL positions. When control spool (18) is in the NEUTRAL position, charge oil pressure in passage (21) is stopped and oil in passage (20) and passage (22) is blocked. With blocked oil in passage (20) and passage (22), the centering spring force keeps swashplate (19) in the NEUTRAL position. When the swashplate is in the NEUTRAL position, there is no oil output from the pump.All Wheel Drive In The