Patent ID: 7837391

Claim:
A bearing retainer unit, for application in an electric motor furnished with a rotor that rotates centered on a rotational axis, the bearing retainer unit comprising: a metal bearing bushing of cylindrical form including a bushing inner surface and a bushing outer surface, and defining a communicating hole extending laterally therethrough and by which the inside and outside of the bushing communicate; and a molded part having a molded cylinder portion covering the bushing outer surface, a cylindrical bearing-positioning portion disposed inside of the bushing and covering the bushing inner surface, and a linking portion that closes off the communicating hole and links the molded cylinder portion and the bearing positioning portion, the cylindrical bearing-positioning portion having upper and lower end surfaces facing in opposite directions axially with respect to the cylindrical bearing-positioning portion, and frustum-shaped inner circumferential surfaces extending into the cylindrical bearing-positioning portion from the upper and lower end surfaces, respectively, the frustum-shaped inner circumferential surfaces meeting along a die-parting line which extends circumferentially along an axially inner part of the cylindrical bearing-positioning portion, and wherein the inner diameter of the cylindrical bearing-positioning portion is smallest at the die-parting line; whereby said molded part can be formed and integrated with said bearing bushing by an insert molding technique employing at least a pair of mold dies made up of a first die having a frustum-shaped outer circumferential surface corresponding to one of the inner frustum-shaped inner circumferential surfaces of said bearing positioning portion, and a second die having a frustum-shaped outer circumferential surface corresponding to the other of the inner frustum-shaped inner circumferential surfaces of said bearing positioning portion, such that positioning said bearing bushing in an inner space formed by the first and second dies, and closing the pair of dies to ready the mold positions an abutment of the first and second dies radially inward of said bearing bushing, and injecting a molten material into the inner space to form said molded part forms the die-parting line on the inner circumferential surface of said bearing positioning portion, at the radially outer side of the abutment.