Abstract: A multipoint contact ball bearing in constructed to prevent damage to rolling surfaces of the balls and to ensure durability while maintaining radial load capacity. An inner raceway has a complex curved surface including a pair of side surface sections having a generating line shape with a radius of curvature larger than 50% of the ball diameter, and an inner raceway bottom section connecting inside end edges in the width direction of the side surface sections. The inner raceway bottom section is a concave curved surface having a generating line shape with a radius of curvature less than 50% of the ball diameter. The edges of both sides in the width direction of the inner raceway bottom section and the inside end edges of the inner raceway side surface sections are smoothly continuous, and finishing is performed on the inner raceway bottom section and the inner raceway side surface sections.

Abstract: The present invention achieves construction of a multipoint contact ball bearing that is able to prevent the rolling surfaces of the balls 4 from becoming damaged and can keep the durability of the bearing from decreasing while maintaining the radial load capacity even when large radial loads act and the rolling surfaces of the balls 4 coming in contact with the inner raceway bottom section 8a. The inner raceway 5a is complex curved surface that comprises a pair of inner raceway side surface sections having a generating line shape with a radius of curvature that is larger than 50% the diameter of the balls 4, and an inner raceway bottom section 8a that connects the edges of the inside end in the width direction of the pair of inner raceway side surface sections 7a; with the inner raceway bottom section 8a big a concave curved surface having a generating line shape with a radius of curvature R8 that is less than 50% the diameter of the balls 4.

Abstract: A ball bearing has an inner ring fitted on a rotational shaft and including an inner ring raceway on an outer circumferential surface thereof, an outer ring including an outer ring raceway on an inner circumferential surface thereof, a plurality of balls rotatably provided between the inner ring raceway and the outer ring raceway and a crown resin cage for retaining the balls at equal intervals in a circumferential direction. A bore diameter of the inner ring is 100 mm or more, and a radial clearance resulting in a state that the inner ring is assembled to the rotational shaft is 20 ?n or more.

Abstract: A ball bearing has an inner ring fitted on a rotational shaft and including an inner ring raceway on an outer circumferential surface thereof, an outer ring including an outer ring raceway on an inner circumferential surface thereof, a plurality of balls rotatably provided between the inner ring raceway and the outer ring raceway and a crown resin cage for retaining the balls at equal intervals in a circumferential direction. A bore diameter of the inner ring is 100 mm or more, and a radial clearance resulting in a state that the inner ring is assembled to the rotational shaft is 20 ?n or more.