| 摘要 |
PROBLEM TO BE SOLVED: To prevent occurrence of an unnecessary ball change when changing a rotating speed of a spindle motor by inclining a fourth surface outside byθ1 in the direction for separating from a second surface to rotation, and inclining the fourth surface inside byθ2 toward a first surface from an almost central part. SOLUTION: An outer peripheral surface (a fourth surface) 214 being an opposite side surface of a rotary shaft becomes a surface inclining outside byθ1 in the direction for separating from a groove bottom surface (a second surface) 212 and inclining inside byθ2 toward a turntable surface (a first surface) 12 from an almost central part. Thus, since a correcting ball 22 is pressed to an outer peripheral surface by centrifugal force, centrifugal force increases at high speed rotation, push-up force overcomes static friction, and the correcting ball 22 is pushed up up to a position of a central part of the fourth surface 214, so that the correcting ball moves along a V-shaped groove without contacting with the groove bottom surface 212 and the turntable surface 211. Thus, a rolling component rather than a slide becomes dominant in a movement of the correcting ball, and since frictional force is small, the correcting ball can smoothly move to a prescribed position.
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