Vane pump with a vane ring, a vane ring housing chamber and vane ring opposite pressure chambers

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

a rotor which is driven and rotated;

a plurality of slits which are radially formed in the rotor;

a plurality of vanes which slidably project from the slits;

vane back pressure chambers which are defined between base end parts of the vanes and the slits;

a cam ring with which tip parts of the vanes slide in contact as the rotor rotates;

a pump chamber which is defined among (i) the cam ring, (ii) the rotor and (iii) adjacent vanes;

a vane ring which faces the base end parts of the vanes;

a vane ring housing chamber on which one end of each slit is open and in which the vane ring is housed; and

vane ring opposite pressure chambers on which the other ends of the slits are open and which cause a fluid pressure to act in a direction to push the rotor toward the vane ring;

wherein

slit opening recesses recessed at every opening position of the slit are formed in an end surface of the rotor, and

the vane ring opposite pressure chambers are defined between the slit opening recesses and a side plate with which the rotor slides in contact.

2. The vane pump according to claim 1 , wherein

the vane ring opposite pressure chamber includes a throttle passage allowing communication between adjacent ones of the slit opening recesses.

3. The vane pump according to claim 1 , wherein

the total area of pressure receiving surfaces of the vane ring opposite pressure chambers is equal to the area of a pressure receiving surface of the vane ring housing chamber.

4. The vane pump according to claim 1 , further comprising:

a back pressure port which is open on the side plate, with which the rotor slides in contact, and introduces a pump discharge pressure to the vane back pressure chambers via the vane ring opposite pressure chambers,

wherein the back pressure port is provided only in a suction region where the pump chambers expand.