Abstract: A pump device includes: a main pump and a sub pump; and a switching valve that switches so as to supply the hydraulic oil discharged from the sub pump to the hydraulic device, or to return the hydraulic oil discharged from the sub pump to the suction side. The main pump and the sub pump each include: a rotor, a discharge port into which the hydraulic oil discharged from a pump chamber is led, and a groove-shaped discharge-side notch formed from an opening edge of the discharge port toward a direction opposite to a rotation direction of the rotor. The switching valve switches according to a rotation speed of the drive shaft. At least one discharge-side notch of the sub pump is formed so that a resistance applied to the flow of the hydraulic oil passing therethrough is greater than that of the discharge-side notch of the main pump.

Abstract: A variable displacement vane pump includes: a control orifice that imparts resistance to a flow of working oil discharged from pump chambers; a flow-amount control valve that operates in accordance with an upstream-downstream differential pressure of the control orifice and controls a flow amount of the working oil discharged from the pump chambers; a variable control valve that is operated by the working oil that has passed through the control orifice and controls an amount of eccentricity of a cam ring with respect to a rotor by controlling a pressure difference between a first fluid pressure chamber and a second fluid pressure chamber; and a return passage that is connected to the flow-amount control valve and circulates a part of the working oil discharged from the pump chambers through a suction passage.

Abstract: A pump device includes a flow control valve that returns a part of working fluid discharged from a pump to the suction side, and the flow control valve includes a valve body, a first fluid pressure chamber that is provided so as to face against a first-side end surface of the valve body and that is communicated with a discharge channel, a second fluid pressure chamber that is provided so as to face against a second-side end surface of the valve body and that is communicated with the discharge channel, a biasing member that is accommodated in the second fluid pressure chamber for biasing the valve body in the valve-closing direction, and a pressure regulator that is provided in a communicating passage through which the discharge channel is communicated with the second fluid pressure chamber and that adjusts pressure in the second fluid pressure chamber.

Abstract: A pump device includes a pump, a flow control valve having a spool that returns a part of working fluid discharged from the pump to a suction side, and a differential pressure adjusting device that adjusts a differential pressure acting on both end portions of the spool to a target differential pressure, and the differential pressure adjusting device includes a pressure regulating chamber that communicates with a second fluid pressure chamber and a pilot chamber into which pressure in the discharge channel is guided: and a pressure in the pressure regulating chamber is adjusted such that a differential pressure between the pressure in the pressure regulating chamber and a pressure in the pilot chamber becomes the target differential pressure.