Patent ID: 7306440

Claim:
A vane pump for compressing fluid, comprising: a casing having a cylindrical inner bore; a rotor disposed in the inner bore with an eccentric relation thereto, forming a circular pump chamber between the inner bore and the rotor; vanes slidably held in the rotor so that one end of each vane slidably contacts the inner bore by a centrifugal force generated by rotation of the rotor, the circular pump chamber being divided by the vanes to thereby form pump chambers each having a capacity changing according to rotation of the rotor; and a driving shaft for rotating the rotor, wherein: the driving shaft is coupled to a rotational center of the rotor with a small gag therebetween; and a gravity center of the rotor is positioned eccentrically with respect to its rotational center by one of shaping and forming said rotor to eccentrically distribute a weight of the rotor with respect to said rotational center.