PURPOSE: To control the direction of resin flow in a molding process by providing a thick boss for forming gate outside the bearing housing made integrally with and end bracket on the opposite side of a fan, and connecting the boss with the bearing housing with a thin rib.

CONSTITUTION: The both ends of the shaft 18 of a rotor 15, constituting a motor 11 together with a stator 14, are supported rotatably by ball bearings 16 and 17, and a fan 19 is fixed to the projected portion of a shaft 18 projected through an end bracket 12. The bearing 17 on the fan side is fixed to the bearing housing 12b of the end bracket 12 by means of press-fitting, etc., and the bearing 16 on the opposite side of the fan is loosely held by the bearing housing 13a of the end bracket 13, and a pre-pressure is given to the bearing 16 by means of an wave washer 21. A thick boss 23 for forming gate is provided outside the bearing housing 13a, and the boss 23 and the housing 13a are connected to each other with a thin rib 24.