Patent ID: 8006555

Claim:
A cap member for covering a sensor unit, the cap member comprising: a cylindrical wall; a bottom end wall closing one axial end of the cylindrical wall, a thickness of the bottom end wall being thinner than that of the cylindrical wall; and an open end positioned opposite to the bottom end wall, the open end to be closed with a closing member after the sensor unit is disposed in the cap member, wherein: the cap member is formed by molding a resin material, using a molding die having an outer die and an inner die; either a projected portion or a depressed portion is formed on an outer surface of the cylindrical wall, the projected portion or the depressed portion prevents the cap member from being moved in the axial direction together with the inner die when the inner die is separated from the cap member after the molding is completed; and the projected portion or the depressed portion is formed in a form of a belt around a center axis of the cylindrical wall.