Vane pump

A vane pump used as a fluid pressure supply source, comprising:

• a cam ring having a cam surface formed on an inner periphery thereof;
• a rotor provided on the inner periphery of the cam ring and driven to rotate relative to the cam ring;
• a plurality of slits formed in a radial shape in an outer periphery of the rotor;
• a plurality of vanes inserted slidably into the slits such that respective tip end portions thereof can slide against the cam surface;
• a plurality of pump chambers defined between the cam surface and the rotor by the vanes;
• a plurality of back pressure chambers defined between respective base end portions of the vanes and the slits to be capable of biasing the vanes toward the cam surface;
• a plurality of back pressure grooves capable of communicating with the back pressure chambers as the rotor rotates;
• and
• a plurality of connecting grooves connecting back pressure grooves that are adjacent in a circumferential direction of the rotor to each other,
• wherein a connecting groove that communicates with a back pressure groove positioned in a suction region formed above a rotary center of the rotor so as to suction a working fluid into the pump chambers is formed to have a larger passage sectional area than a connecting groove that communicates with another back pressure groove positioned in another suction region formed below the rotary center of the rotor.