Patent ID: 6877969

Claim:
A vane pump comprising: a vane pump section composed of a cam ring contained in a pump housing, a rotor rotatably provided in said cain ring with a plurality of slits formed in radial direction, and a plurality of vanes guided to be radially slidable respectively in said slits and brought at radial outermost ends into sliding engagement with a cam surface formed at the internal surface of said cam ring for partitioning a space between the outer circumferential surface of said rotor and said cam surface into plural pump chambers each of which is varied in volume as said rotor rotates; at least one side wall member closing at least one side surface of said vane pump section and enabling said rotor and said vanes to be slidable thereon; and an annular backpressure groove formed on an inside end surface of said side wall member to encircle the rotational axis of said rotor to communicate with innermost end portions of said slits and supplied with pressurized fluid ejected from said pump, wherein within an angular area where each vane is moved radially inwardly while being rotated together with said rotor, the outer circumferential edge of said backpressure groove is deflected to be indented toward the rotational axis of said rotor along a locus on which the radial innermost end of each vane moves so that the radial innermost end of each vane does not protrude radially inwardly beyond a predetermined distance from the indented part of the outer circumferential edge of said backpressure groove, wherein within at least a part of another angular area where each vane is moved radially inwardly from the radial outermost position, a recess portion for preventing a radial innermost part of one side surface of each vane from contacting the inside end surface of said side wall member is further provided on the inside end surface of said side wall member which slidably contacts said rotor and each vane; and the outer circumferential edge of said recess portion is deflected at its rotationally preceding part to be indented toward the rotational axis of said rotor along said locus so that the radial innermost end of each vane does not protrude radially inwardly beyond a predetermined distance from the rotationally preceding part of the outer circumferential edge of said recess portion.