PIN 1113997 - Caterpillar

Illustration 3 g01587793
Cross Section of the Pump (32) Feedback link (33) EDC valve (34) Servo piston (35) Servo piston (36) EDC valve (37) Feedback link (38) Servo springs (39) Swashplate (40) Slipper pad (41) Piston (42) Rotating group (43) Rotating group (44) Piston (45) Slipper pad (46) Swashplate (47) Servo springsEngine rotation turns the pump input shaft, which then rotates the two rotating groups. The rotating groups contain a piston and barrel assembly. The pistons in the groups rotate with each barrel assembly. The slipper pads for the piston allow the pistons to follow the angle of the swashplate. The rotating groups only generate flow when the swashplates are not at zero angle. When the machine electronic control system sends an output signal to an EDC, the corresponding servo piston moves. As the servo piston moves, the action of the control linkage causes the angle of the swashplate to change. The swashplate angle is proportional to the signal from the machine electronic control system.The slipper pads in each rotating group follow the angle of the swashplate. This action causes the pistons to move in and out of the barrel assembly as the input shaft rotates. As a piston moves out of the barrel assembly, oil in the low pressure circuit is drawn into the piston chamber. As a piston moves into the barrel assembly, oil is forced out of the piston chamber and into the high pressure circuit.
Illustration 4 g01587800
Cross Section of the Makeup and Relief Valves (48) Relief poppet (49) Relief poppet (50) Check valve (51) Valve spring (52) Makeup spring (53) Makeup spring (54) Valve spring (55) Check valveOil in the closed loop circuits acts to close the check valve. Oil in the charge circuit acts to open the check valve. Flushing and internal leakage cause pressure in the return side of the closed circuit to decrease. This decrease causes charge pressure to unseat the check valve. When the pressure in the return circuit is low enough, the check valve moves the main relief cartridge against the force of the makeup spring. The check valve opens a passage for charge oil to flow into the return side of the circuit. Charge oil replenishes the oil that is lost from flushing and internal leakage.Pressure in the high pressure circuit acts to open the relief poppet. The combined force from the oil in the charge circuit and the valve spring acts to close the relief poppet. When the pressure in the high pressure circuit reaches the relief setting, the relief poppet compresses the valve spring. In this case, oil from the high pressure circuit is directed into the charge circuit.