RETAINER 4J0713 - Caterpillar

Illustration 1 g00800485
(1) Piston pump (brake) (2) Piston (3) Piston (4) Plunger (5) Swashplate (6) Pump control valve (7) Springs (8) Spool (9) Spool (10) Springs
Illustration 2 g00800738
Piston pump (1) and pump control valve (6) are mounted on the left side of the engine.Piston pump (1) is a variable displacement pump. The output of the piston pump is determined by the angle of swashplate (5). A greater swashplate angle produces a greater output as the stroke of pistons (3) is increased. Pressure within the pump output line is transmitted to pump control valve (6) which is bolted to the piston pump.The output of the piston pump is controlled by spool (9). The spool can be moved against springs (10) by the system pressure that is generated due to the output from the piston pump. The springs and the spool control the maximum pressure of the system.When the system is below maximum pressure, spool (9) is held by springs (10). System pressure and spring force act on plunger (4) and the chamber inside piston (2) is connected to the tank through an orifice. Swashplate (5) is moved to the maximum angle.When the system reaches maximum pressure, spool (9) is moved against springs (10). System pressure and spring force still act on plunger (4) but pressure is also transmitted past the spool and into piston (2). Movement of the piston moves the swashplate toward the minimum angle and maximum system pressure is maintained.Note: Springs (7) and spool (8) do not contribute to the system.