Patent ID: 8727631

Claim:
A retainer comprising two annular retaining plates, each of the two annular retaining plates having semispherical swelling portions arranged at predetermined intervals along a circumferential direction, and the semispherical swelling portions of the two annular retaining plates facing each other and forming pockets for retaining balls, wherein: each of the pockets has ball-facing surfaces each including a ball non-contact portion; the ball non-contact portions are rectangular recessed portions; the rectangular recessed portions are provided on the ball-facing surfaces, the rectangular recessed portions forming rectangular protruding portions on sides of the retainer opposite to the ball-facing surfaces; the rectangular protruding portions are arranged on a pitch circle of the balls; a circumferential length of the rectangular protruding portions is longer than a width dimension of the rectangular protruding portions; each of the rectangular recessed portions includes a bottom surface and side surfaces rising from a peripheral border of the bottom surface; a width of the rectangular recessed portions of the retainer is larger than a depth of the bottom surfaces of the rectangular recessed portions in an axial direction of the retainer; the depth of the bottom surfaces of the rectangular recessed portions is constant along a circumferential direction of the semispherical swelling portions; and the ball non-contact portion of each of the pockets reduces a contact area of each of the pockets by 15% to 30%, to reduce resistance generated when lubricant passes inside the pockets and an amount of oil film to be sheared.