| 摘要 |
A vane pump is composed of a rotor that is rotatably disposed in a cam ring attached to a housing, a plurality of vanes that are slidably disposed in corresponding slits formed in the rotor in which the vane is projected from the slit upon rotation of the rotor, a pair of sidewall members that close both side portions of the cam ring to form a cavity defined by the cam ring and said sidewall members, a plurality of annular backpressure grooves that is depressively formed on contact surfaces of the sidewall members with the rotor in which adjacent two of the backpressure grooves are communicated with each other through a communication passage to introduce discharged pressure into an inside end portion of each of the slits, and depressions that are formed on at least one of the contact surfaces of the sidewall members with the rotor in which the depressions are not contacted with a part of side surface of each of the vanes.
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