GEAR-OIL PUMP 3P7785 - Caterpillar

Piston Pump
Illustration 1 g01425529
(1) Actuator piston (2) Feedback lever (3) Solenoid valve (4) Passage (5) Servo valve (6) Pressure override valve (POR Valve) (7) Port for the drive loop (8) Input shaft (9) Swashplate (10) Piston (11) Barrel (12) Spring (13) Port plate (14) Port for the drive loop (15) Charge pumpThe pump for the winch hydrostatic system is a variable displacement piston pump. The winch pump is mounted to the back of the right rear drive pump. The input shaft of the winch pump engages a coupling from the rear pump in order to drive the winch pump.When the engine is running, shaft (8) and barrel (11) are rotating. There are nine piston (10) in barrel (11). Port plate (13) and swashplate (9) are stationary within the pump housing. Port plate (13) and swashplate (9) do not rotate. Spring (12) maintains a force against barrel (11) and port plate (13). When barrel (11) is rotating, each piston (10) follows the angle of swashplate (9) .If the angle of swashplate (9) is zero, pistons (10) do not move in and out of barrel (11) and there is no oil flow. Charge oil from charge pump (15) maintains oil pressure in the pump in order to perform the following tasks:
Keep barrel (11) full of oil.
Lubricate the pump components.
Provide makeup oil for internal loss of oil that is due to leakage.
Provide pilot oil to servo valve (5) in order to shift actuator piston (1) and change the angle of swashplate (9) .For additional information, refer to "Charge Pump".The position of swashplate (9) is determined by actuator piston (1). The winch control lever that is located on the right console sends signals to the electronic control module (ECM). The ECM interprets the signals and the ECM sends pulse width modulated signals to solenoids (3) on either side of servo valve (5). As servo valve (5) is shifted to either direction, signal oil from passage (4) is directed to the corresponding end of actuator piston (1) .As actuator piston (1) begins to move, the angle of swashplate (9) begins to increase. As pistons (10) follow swashplate (9), pistons (10) begin to move in and out of barrel (11). As piston (10) moves out of barrel (11), oil is drawn from the passage from port (7) of the drive loop through port plate (13). As piston (10) follows swashplate (9) and the piston moves into barrel (11), the oil is pushed through port plate (13) into the passage to port (14) of the drive loop.As the angle of swashplate (9) increases, the output flow of the pump also increases.Charge Pump
Illustration 2 g01424827
Charge pump (1) Pressure override valve (POR valve) (2) Orifice (3) Passage (4) Crossover relief valve (5) Oil filter (6) Passage (7) Passage (8) Passage (9) Ring gear (10) Passage (11) Supply passage for the charge pump (12) Filter bypass valve (13) Passage (14) Resolver (15) Charge relief valve (16) Passage (17) Crossover relief valve (18) Supply passage for the charge pump from the