Patent ID: 6530752
Filing Date: 2003-03-11
Classification: F04C

Abstract:
A variable displacement pump comprising:a rotor fixable to a pump shaft inserted to a pump casing and receiving a plurality vanes in a groove so as to be movable in a radial direction, the rotor being rotatable and drivable; an adapter ring fitted to a fitting hole in the pump casing; a cam ring fitted to the adapter ring so as to form a pump chamber between the cam ring and an outer peripheral portion of the rotor, being movable and displaceable within the adapter ring and separately forming first and second fluid pressure chambers between the cam ring and the adapter ring; a switch valve operated due to a pressure difference between an upstream side and a downstream side in a metering orifice provided in a pump discharge side passage, and controlling the amount of fluid pressure supplied to the first and second fluid pressure chambers in correspondence to a discharge flow amount of a pressurized fluid discharged the pump chamber so as to move the cam ring and change a capacity of the pump chamber, thereby making it possible to control the discharge flow amount discharged from the pump chamber; and a relief valve relieving excessive fluid pressure in the pump discharge side, wherein the switch valve and the relief valve are provided separately, said relief valve is constituted by a pilot drive type relief valve comprising a pilot valve to a main valve, the fluid pressure in the downstream side of the metering orifice provided in the pump discharge side passage is applied to the pilot valve, and the main valve is capable of opening and closing the downstream side passage of the metering orifice with respect to a drain passage.