Patent ID: 7959422

Claim:
A method of assembling an oil pump, the oil pump including a first housing having a rotation shaft insertion hole, a cam ring disposed on the first housing, the cam ring having a generally cylindrical inner circumferential surface, a pump element that is rotatably disposed within the cam ring and performs suction and discharge of a working oil during rotation, a rotation shaft that rotatably extends through the rotation shaft insertion hole of the first housing and rotatively drives the pump element, and a second housing disposed on the cam ring on a side opposed to the first housing in an axial direction of the rotation shaft, the method comprising: a first step of placing the cam ring on the first housing; a second step of mounting a jig to the first housing and the cam ring which determines a position of the cam ring relative to the rotation shaft insertion hole of the first housing; a third step of fixing the first housing and the cam ring to each other; a fourth step of retreating the jig; a fifth step of assembling the pump element and the rotation shaft into the cam ring; and a sixth step of placing the second housing on the cam ring on the side opposed to the first housing and fixing the first housing, the cam ring and the second housing to one another, wherein the jig has a large diameter portion fitted into the generally cylindrical inner circumferential surface of the cam ring and a small diameter portion fitted into the rotation shaft insertion hole of the first housing.