Patent ID: 7766553

Claim:
A ball bearing retainer formed by injection molding of a resin composition containing spherical carbons and reinforcement fibers, comprising: a ring-shaped body entirely composed of the resin composition to be disposed between inner and outer races of a ball bearing; and a plurality of pocket surfaces provided on the body to define a plurality of pockets for retaining balls of the ball bearing, the pocket surfaces each having a concaved spherical shape similar to a shape of the ball of the ball bearing and each defining openings in an inner surface and an outer surface of the ring-shaped body, wherein at least one of the pocket surfaces defining the respective pockets has a projection provided in the vicinity of one of the openings defined in the inner and outer surfaces of the ring-shaped body as projecting from the pocket surface inward of the pocket, wherein at least the resin composition forming the projection contains the spherical carbons, wherein the reinforcement fibers hardly enter the resin composition forming the projection, from the resin composition composing the body, so that the projection has a lower concentration of the reinforcement fibers compared to the body, and wherein an amount of the spherical carbons in the resin composition is 3 wt % to 40 wt % based on the whole amount of the resin composition.