Offer ball bearings

In order to solve the problems described above, the present invention provides a Ball Bearings that includes a bearing supporting member that has a hemispherical concave surface, a plurality of small balls disposed freely on the hemispherical concave surface, one large ball retained on the plurality of small balls so as to be rotatable in all directions, and a casing having an aperture through which the upper portion of the large ball projects, the casing accommodating the ball supporting member, the small balls, and the large ball; the small balls include primary small balls contacting the large ball so as to support the large ball, and auxiliary small balls, which are smaller than the primary small balls, for supporting the large ball and not contacting the large ball.

According to the present invention, because, on the hemispherical concave surface of the ball supporting member, in addition to the primary small balls contacting the large ball, auxiliary small balls that are smaller than the primary small balls are provided, the primary small balls are not limited in contacting each other, and a state may occur in which the auxiliary small balls are interposed between the primary small balls. In this region, because ample gaps are provided around the primary small balls, contaminants that have penetrated inside accumulate in these gaps. Therefore, it is possible to prevent interference with the rotation of the small balls due to contaminants adhering to the small B Bearing. In addition, it is possible to prevent interference with the rotation of the large ball due to contaminants adhering directly to the large ball or contaminants being interposed between the large ball and the small balls. Thereby, it is possible to prevent the performance as a ball bearing from degrading.

In addition, there is a possibility that contaminants may be compressed and pulverized between the primary small balls and the auxiliary small balls. However, when a hole is provided at the lowest portion of the ball supporting member, the contaminants, whose size has become small, are readily discharged to the outside through the hole, and it is thereby possible to reduce the amount of the contaminants inside. This feature also enables the prevention of degrading of the performance of the ball bearing to the highest degree.

In the ball bearing described above, preferably, the ball supporting member has a through-hole for discharging the contaminants at the lowest portion thereof.