To provide a retainer for a ball bearing which can simultaneously achieve the reduction of the torque of the ball bearing and the improvement of durability and life, and can prevent deterioration in the support capability of the ball bearing as much as possible.
The retainer 5 for the ball bearing is formed into an annular shape and has a plurality of bottomed pockets 5a for holding balls 4 in circumferential directions at equal intervals. Circumferential grooves N1, N2 which straddle the adjacent two pockets 5a, 5a in the circumferential directions are formed on the outer-diameter surface and the inner-diameter surface of the retainer 5, respectively, the contact area between the ball opposing face 5a1 of the pocket 5a and the ball 4 is reduced and a volume of the retainer 5 is also reduced. The circumferential groove N1 is formed by forming a first notch 5e at the end outer diameter of the bottom side of the pocket 5a. The circumferential groove N2 is formed by forming a second notch 5f at the end inner diameter of the opening side of the pocket 5a.
Kunihiko Shiromura
Tsuyoshi Kumano