STRUCTURE AND FUNCTION HYDRAULIC PUMP 2. PC VALVE 1) When pump controller is normal a. When the load on the actuator is small and pump pressure PP is low (1) Action of PC-EPC solenoid (1) The command current from the pump controller flows to PC-EPC solenoid (1). This command current acts on the PC- EPC valve and outputs the signal pressure. When this signal pressure is received. the force pushing piston (2) is changed. On the opposite side to this force pushing piston (2) is the spring set pressures of springs (4) and (6) and pump pressure PP pushing spool (3).
Spool (3) stops at a position where the combined force pushing spool (3) is balanced, and the pressure (pressure of port C ) output from the PC valve changes according to this position. The size of command current X is de- termined by the nature of the opera- tion (lever operation), the selection of the working mode, and the set value and actual value for the engine speed. 10-49