Variable displacement pump

A variable displacement pump comprising:

• a rotor fixable to a pump shaft inserted to a pump casing and receiving a plurality of 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 from 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 upstream 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 upstream side passage of the metering orifice with respect to a drain passage.

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 metering orifice in communication with said second fluid chamber,
• a metering orifice spring biasing the cam ring in the direction of a maximum flow position,
• the cam ring being movable against the bias of the movable orifice spring under the influence of a biasing differential pressure between the first fluid pressure chamber and the second fluid pressure chamber,
• the cam ring being arranged and constructed to throttle the metering orifice as the biasing differential pressure moves the cam ring against an opposing force of the movable orifice spring, thereby controlling the discharge pressure of fluid delivered to a discharge passage,
• 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 from 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 throttled region disposed in a communication channel between the switch valve and the first fluid pressure chamber, and a throttled region disposed in a communication channel between the switch valve and the second fluid pressure chamber,
• a relief valve relieving an 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.

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 metering orifice in communication with said second fluid chamber,
• a metering orifice spring biasing the cam ring in the direction of a maximum flow position,
• the cam ring being movable against the bias of the movable orifice spring under the influence of a biasing differential pressure between the first fluid pressure chamber and the second fluid pressure chamber,
• the cam ring being arranged and constructed to throttle the metering orifice as the biasing differential pressure moves the cam ring against an opposing force of the movable orifice spring, thereby controlling the discharge pressure of fluid delivered to a discharge passage,
• 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 from 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 throttled region disposed in a communication channel between the switch valve and the first fluid pressure chamber, and a throttled region disposed in a communication channel between the switch valve and the second fluid pressure chamber,
• a relief valve relieving an 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 upstream 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 upstream side passage of the metering orifice with respect to a drain passage.