STRUCTURE AND FUNCTION HYDRAULIC PUMP OPERATION 3 2 5 B A E 1C 1D 1G D E F C G RKS00180 The oil from the charge pump (2) that rotates with the engine flows through a orifice (3) that is installed in the main piston pump. And the oil always flows to pump charge circuit. Charge pump (2) is fixed capacity pump, so that discharge flow is proportionate to engine rotation speed. With the oil from the charge pump (2) passed through the orifice, differential pressure is generated at port A and port B . This differential pressure actuates the differential pressure sensing valve ( 1G ) and makes hydraulic force F .
By the hydraulic force F , the differential pressure sensing valve ( 1G ) is moved direction. That makes a change of spring ( 1D ) load. In port C , the AS valve output pressure that is balanced with spring ( 1C ) and ( 1D ) load is generated by reducing from charge pressure of port G . So the AS valve outputs pressure correspond with charge flow that is changed by engine (5) revolution. 10-30 SK818-5 SK820-5 turbo