VARIABLE DISPLACEMENT VANE PUMP

摘要

In a hydraulic pump, a cam ring 21 is provided in a cylindrical adaptor 13 for movement in a radial direction, and a differential pressure control valve 31 is provided to control internal pressure and load pressure at the front and back sides of a variable orifice 54 to be introduced into action chambers 51a and 51b formed at the opposite sides of the cam ring for controlling a discharge amount of the pump in accordance with the rotation speed of the pump. The differential pressure control valve is operated under the internal pressure and load pressure respectively introduced into action chambers 52a and 52b and the load of a thrust spring 33 biasing the differential pressure control valve toward the internal pressure chamber 52a. The load of the thrust spring is increased or decreased in accordance with an increase or a decrease of the load pressure. The increase or decrease of the load pressure is effected by a load pressure responsive piston 40 loaded by a thrust spring 41 and engaged with the differential pressure control valve at one end thereof in the internal pressure chamber. <IMAGE>