Abstract: A vane pump in which oil is drawn from at least one side, in an axial direction, of a cam ring and is discharged from at least one side, in the axial direction, of the cam ring, has a portion defined by a groove formed on an inner circumference surface of the cam ring. The groove extends along a circumferential direction of the inner circumference surface of the cam ring and is arranged in a position including a middle of an axial direction width on the inner circumference surface. The groove is arranged in an oil suction section or an oil discharge section of the cam ring.

Abstract: A variable displacement pump includes a pump structural member configured to change volumes of a plurality of working chambers by rotation of a rotor, so as to introduce oil through an inlet port into the working chambers and to discharge the oil through a discharge port, and further configured to oscillate a cam ring by a discharge pressure introduced into a control oil chamber. A first coil spring is provided to force the cam ring in a direction for increasing of a rate of change of the working-chamber volume. A second coil spring is provided to force the cam ring in a direction for decreasing of the rate of change of the working-chamber volume. The first and second coil springs are laid out on both sides of an arm portion of the cam ring in a manner so as to be opposed to each other.

Abstract: In a variable displacement vane pump employing a cam ring, a pump rotor, and a plurality of vanes, each slidably fitted into the rotor, a biasing member is provided to force the cam ring in a direction that a geometric center of an inner peripheral surface of the cam ring and a rotation center of the rotor are spaced apart from each other. A force, by which the cam ring can be oscillated against the biasing member in accordance with a buildup of a pressure in a pump discharge portion, acts on the inner peripheral surface of the cam ring.

Abstract: Fluid inlet and outlet portions are provided for introducing and discharging a hydraulic fluid. The fluid outlet portion includes a plurality of outlet ports. A drive shaft is provided that rotates s about its axis. A plurality of volume variable pump chambers are arranged about the drive shaft and rotated by the same. The pump chambers are arranged between the fluid inlet and outlet portions for compressing the hydraulic fluid from the fluid inlet portion before discharging the same from the fluid outlet portion. The pump chambers are exposed to the outlet ports separately one after another when the pump chambers are rotated by the drive shaft. A discharge rate varying mechanism is provided that varies a fluid discharge rate of each of the outlet ports by varying the amount of the fluid led to the outlet ports.

Abstract: A variable displacement pump includes: a pump section arranged to be driven by an internal combustion engine, and to discharge a lubricant introduced from an induction portion to a plurality of hydraulic chambers, through a discharge portion, by volume variations of the hydraulic chambers; a variable mechanism arranged to move a movable member by using the discharge pressure of the lubricant, and to vary volumes of the hydraulic chambers which are opened to the discharge portion; and an urging section arranged to urge the movable member in a direction to increase quantities of the volume variations of the hydraulic chambers, the urging section having a spring constant which increases as a movement distance of the movable member in a direction to decrease the quantities of the volume variations of the hydraulic chambers increases.