VALVE GP-CONTROL 9T6401 - Caterpillar

Hydrostatic System in Forward for the Fast Mode
Illustration 6 g01043483
Hydrostatic System in FORWARD and FAST speed mode (1) Creeper Valve (2) Brake valve (3) Large variable displacement motor (4) Oil line from the oil cooler to the motor case (5) Oil returns to tank (6) Small variable displacement motor (7) Small variable displacement motor group (8) Shuttle valve (9) Motor displacement control (10) Actuator for the motor (11) "M1" Test port for the motor (12) Throttle pin (13) Case drain to tank (14) Charge relief valve (15) Crossover relief valve for Forward (16) Hydraulic oil filter (17) Hydraulic oil filter bypass valve (18) Scheduled oil sampling valve (19) Pump control valve (20) Actuator for the hydrostatic pump (21) Hydraulic oil line from the hydraulic tank (22) Brake and steering pump (23) Implement pump (24) Charge pump (25) Hydrostatic pump (26) Hydrostatic pump group (27) Speed sensing valve (28) "PS" Test port for pump signal pressure (29) Test port for charge pressure (30) Crossover relief valve for Reverse (31) Oil line to the implement pilot system (32) Overspeed valve (32A) Solenoid Group (32B) Spool (33) "OS" Signal pressure for the motor (34) Test port for pressure in the pump case (35) Test port for the high pressure oil of the drive loop (36) Pressure override valve (37) Flushing valve (38) Actuator for the motor (39) "M2" test port for the motor (40) Throttle pin (41) Motor displacement control (42) Large variable displacement motor group (43) Shutoff valve for pilot signal (AA) High pressure oil of the drive loop (BB) Low pressure oil of the drive loop (CC) Charge oil (DD) Speed sensing oil (EE) Return to tank oil (FF) Trapped oil (GG) Active path or moving partWhen the machine is in FORWARD mode and in FAST mode, the hydrostatic system is very similar to the SLOW mode. The main difference between SLOW mode and FAST mode is in the function of the overspeed valve (32). When the operator places the speed control switch in the FAST mode, an electrical signal is sent to the solenoid group (32A) for the overspeed valve. The energized solenoid causes the spool for the solenoid group to move upward. When the spool moves upward, the spool blocks the flow of the charge oil that is flowing to the hydraulic tank. The charge oil causes spool (32B) to shift upward. The charge oil (CC) will be routed in order to shift the motor displacement control (41). The pressure in the line for the charge oil (CC) will also increase because the tank drain is blocked. Because the pressure for the charge oil is increased, the motor displacement control will shift downward.Higher pressure in the line for the charge oil (CC) means that the oil pressure will be higher in the speed sensing valve (27). Because the charge oil is at a higher pressure, the speed sensing oil (DD) will be proportionally higher. When the speed sensing oil is at a higher pressure, the actuator for the