Patent ID: 8585384

Claim:
A rotary pump comprising: a shaft that is rotatable; a drive device that generates a rotational drive force to rotate the shaft; an inner rotor that includes a plurality of external teeth and is adapted to be rotated integrally with the shaft by the rotational drive force, which is received from the drive device; an outer rotor that includes a plurality of internal teeth meshed with the plurality of external teeth and is placed eccentric to the inner rotor on a radially outer side of the inner rotor, wherein the inner rotor and the outer rotor form a pressure chamber therebetween, and a volume of the pressure chamber is variable upon rotation of the inner rotor; a first housing that includes: an inlet port, which is communicated with the pressure chamber to supply fluid into the pressure chamber; and an outlet port, which is communicated with the pressure chamber to discharge the fluid from the pressure chamber; and a second housing that includes a pump chamber, which receives the inner rotor and the outer rotor in a rotatable manner, wherein; an axial size of an axial clearance, which is formed between an axial end surface of the pump chamber and an axial end surface of the inner rotor, differs from an axial size of an axial clearance, which is formed between the axial end surface of the pump chamber and an axial end surface of the outer rotor; and the axial size of the axial clearance, which is formed between the axial end surface of the pump chamber and the axial end surface of the inner rotor, is smaller than the axial size of the axial clearance, which is formed between the axial end surface of the pump chamber and the axial end surface of the outer rotor.