Patent ID: 7637670

Claim:
A thrust roller bearing comprising rollers and a cage, the cage comprising an annular configuration having one surface and another surface parallel to each other and extending over a plane which intersects a bearing rotation axis, the cage having a plurality of pockets to house said rollers on surfaces which intersect with the bearing rotation axis, wherein a first thickness is defined between the one surface and the other surface parallel to each other, the first thickness being equal to a plate thickness “t” of a plate member forming the cage, the cage further comprising an utmost peripheral region, an inmost peripheral region, a first groove forming region adjacent to the utmost peripheral region and a second groove forming region adjacent to the first groove forming region, the utmost peripheral region and the inmost peripheral region each having the first thickness defined by the one surface and the other surface, the first groove forming region having a first ring-shaped groove extending in a circle and recessed on the one surface, a thickness defined between the bottom surface of the first ring-shaped groove and the other surface being smaller than the first thickness, the second groove forming region having a second ring-shaped groove extending in a circle and recessed on the other surface, a thickness defined between the bottom surface of the second ring-shaped groove and the one surface being smaller than the first thickness, and a first roller contact part is positioned in the first groove forming region and a second roller contact part is positioned in the second groove forming region, the first roller contact part and the second roller contact part are provided on a wall surface of said pocket opposed to an outer periphery of said roller so as to be positioned in a direction of said bearing rotation axis and in a direction of a rotation axis of said roller, said first roller contact part comprises a first roller stopper to prevent said roller from escaping in one direction and a first roller guide surface to guide a rotation of said roller, and said second roller contact part comprises a second roller stopper to prevent said roller from escaping in the other direction and a second roller guide surface to guide the rotation of said roller, wherein a relation between the plate thickness “t” of said cage and a roller diameter “φ” is such that t/φ≧0.6, and said roller diameter “φ” is not more than 2 mm.