Vane pump

A vane pump including:

• a housing disposed on a cover member of an engine, having a tubular peripheral wall portion and a bottom wall portion which is disposed at one end of the peripheral wall portion in an axial direction and in which a discharge hole that communicates with an internal space of the cover member is provided to open, and defining a pump chamber communicating with the discharge hole inside the housing;
• a rotor that is disposed in the pump chamber and that is rotatable about a rotational axis of the rotor along with rotation of a camshaft of the engine;
• a vane disposed so as to be slidable with respect to the rotor in a radial direction, the vane partitioning the pump chamber into a plurality of working chambers and causing capacities of the working chambers to increase and decrease along with rotation of the rotor;
• and
• a reed valve that opens and closes the discharge hole to allow air compressed in the working chambers and lubricating oil to be intermittently discharged to the internal space of the cover member,
• wherein a pressure relief groove that is continuous with the discharge hole is disposed in an inner surface of the bottom wall portion, a clearance is provided between an inner surface of the peripheral wall portion and the pressure relief groove such that a radial outer edge of the pressure relief groove is disposed apart from the inner surface of the peripheral wall portion by the clearance over an entire length in an extension direction of the pressure relief groove,
• wherein a pair of the working chambers on both sides of the vane in a rotational direction communicate with each other via the pressure relief groove when the vane overlaps the pressure relief groove during forward rotation of the rotor,
• wherein the pressure relief groove is arranged on an outer side of the rotor in the radial direction of the rotor
• wherein the pressure relief groove extends in a circumferential direction about the rotational axis of the rotor, and
• wherein a position at which a sliding direction of the vane with respect to the rotor is inverted from outward in the radial direction to inward is defined as a reference position, a line extending through the reference position and the rotational axis of the rotor is defined as a division line, and an angle about the rotational axis of the rotor with respect to the division line is defined as a center angle, such that the reference position is at the center angle of 0°, and the pressure relief groove extends between a first side and a second side in the rotational direction with reference to a position directly below the rotational axis of the rotor at the center angle of 90°.