Patent ID: 7862305

Claim:
A variable displacement vane pump, comprising: a pump body; a driving shaft supported on the pump body; a rotor disposed within the pump body and rotatably driven by the driving shaft, the rotor including a plurality of vanes arranged in a circumferential direction of the rotor; an annular cam ring disposed within the pump body so as to be swingable around a swing fulcrum, the cam ring cooperating with the rotor and the vanes to define a plurality of pump chambers on an inner circumferential side of the cam ring; a first support member disposed at one axial end of the cam ring; a second support member disposed at an opposite axial end of the cam ring; a suction port and a discharge port which are disposed on at least one of the first and second support members, the suction port being open to a suction area in which a volume of each of the pump chambers is gradually increased with the rotation of the rotor, the discharge port being open to a discharge area in which the volume of each of the pump chambers is gradually decreased with the rotation of the rotor; a seal disposed on an outer circumferential side of the cam ring so as to divide a space on the outer circumferential side of the cam ring into a first fluid pressure chamber and a second fluid pressure chamber, the first fluid pressure chamber being defined in a swing direction of the cam ring in which the cam ring is swung to cause increase in a flow rate of a working fluid which is discharged from the discharge port, the second fluid pressure chamber being defined in a swing direction of the cam ring in which the cam ring is swung to cause decrease in the flow rate of the working fluid which is discharged from the discharge port, the second fluid pressure chamber receiving a suction pressure; and a plunger which biases the cam ring from a side of the second fluid pressure chamber toward a side of the first fluid pressure chamber.