Patent ID: 7374411

Claim:
An oil pump comprising: a cam ring made of a material having a first line expansion coefficient; a pump element rotatably disposed in the cam ring and smaller in axial length than the cam ring; a drive shaft for driving the pump element; a first housing member disposed on one of axially opposite sides of the cam ring, made of a material having a second line expansion coefficient larger than the first line expansion coefficient and having a first abutment surface in abutting engagement with one of opposite axial end surfaces of the cam ring and a second abutment surface in abutting engagement with one of opposite axial end surfaces of the pump element; a second housing member disposed on the other of the axially opposite sides of the cam ring, made of a material having a third line expansion coefficient larger than the first line expansion coefficient and having a third abutment surface in abutting engagement with the other of the opposite axial end surfaces of the cam ring and a fourth abutment surface in abutting engagement with the other of the opposite axial end surfaces of the pump element; an intake port formed in one of the first housing member and the second housing member at a position corresponding to an intake range of the pump element; and a discharge port formed in one of the first housing member and the second housing member at a position corresponding to a discharge range of the pump element.