Patent ID: 8057201

Claim:
A variable capacity vane pump comprising: a pump housing having a rotor chamber therein; a vane pump rotor rotatably mounted in the rotor chamber and having a series of vanes; a pump control ring enclosing the vane pump rotor within said rotor chamber and engaging said vanes, the pump control ring being moveable within the rotor chamber to alter the volumetric displacement of the pump; a first control chamber between the pump housing and the pump control ring, the first control chamber operable to receive pressurized fluid to create a force to move the pump control ring to reduce the volumetric displacement of the pump; a second control chamber operable to receive pressurized fluid to create a force to move the pump control ring to alter the volumetric displacement of the pump; and a biasing spring acting between the pump control ring and the pump housing to bias the pump control ring towards a position of maximum volumetric displacement, the biasing spring acting against the force of at least the first control chamber to establish an equilibrium pressure, pressurized fluid being supplied to the second control chamber to change the equilibrium pressure of the pump, wherein the pump control ring pivots about a pivot pin to alter the volumetric displacement of the pump, the pump control ring including a control structure located opposite the pivot point from the rotor, the forces created in the first and second control chambers acting against the control structure.