Variable displacement pump

摘要

Within a cam ring ( 8 ), a rotor having a plurality of vanes ( 27 ) is eccentrically disposed. A metering orifice ( 136 ) is provided halfway on a discharge passage ( 135 ) of pressure fluid discharged from the pump, and a control valve is activated due to a pressure difference between the upstream and downstream sides of the metering orifice ( 136 ). A fluid pressure of the first fluid pressure chamber ( 21 ) is controlled by activation of the control valve ( 123 ). The second fluid pressure chamber ( 22 ) is shut off from the control valve ( 123 ) to introduce a pressure on the suction side at any time. To return the cam ring ( 8 ) in a direction of expanding a pump chamber ( 11 ), an internal pressure of the cam ring ( 8 ) is applied in the return direction.