Abstract: A thrust ball bearing includes a pair of races that make an eccentric revolving motion relative to each other. The races are formed with a plurality of opposed annular raceway grooves defined by an outer edge and an inner edge. Balls are received in the respective opposed pairs of raceway grooves. Each of the raceway grooves has a groove bottom pitch circle diameter that is smaller than the amount of offset. The height of the inner edge from the bottom of the groove is set at a predetermined value, and the height of the outer edge from the bottom of the groove is set to be larger than the height of the inner edge from the bottom of the groove. This arrangement prevents the contact ellipse of the ball from riding over the outer edge of the groove.

Abstract: A scroll-type compressor includes a fixed first scroll member, an orbital second scroll member, and a ball coupling provided as a rotation preventing mechanism for the second scroll member. The ball coupling has a pair of integrally formed rolling ball regulating plates and a plurality of balls disposed therebetween. The ball coupling is assembled in the compressor at a condition in that an axial preload is provided. The axial preload is set more than an axial force given by the balls to the rolling ball regulating plates during operation of the compressor for correcting deformation of the rolling ball regulating plates. When the compressor is assembled, an axial gap between the first and second scroll members may be properly adjusted. After the assembly and during the operation of the compressor, the behavior of balls may be stable.