| 摘要 |
PROBLEM TO BE SOLVED: To eliminate increase in abnormal wear and noise caused by a minute manufacturing error by opposingly providing ball retention surfaces being formed by an annular slope, and by retaining a ball via a retainer with the opposite ball retention surfaces while the ball can freely revolve and rotate on its own axis. SOLUTION: A ball 5 is retained between a first ball retention surface 3a and a second one via a retainer 6 while the ball can freely revolve and rotate on own axis. A through hole for retaining the ball is provided at specific intervals in the retainer 6. The lower end of the second ball holder 9 is pressed by a spring 10, thus allowing a second ball holder 9 to slide in the direction of a first ball bearing BJ1 on the inner surface of a bearing housing 3, pushing up a first ball holder 4 and a rotary shaft 1 via the ball 5, pressing the ball 5 onto the first ball retention surface 3a via the second ball retention surface of the first ball holder 4, and hence eliminating the backlash of the first ball bearing BJ1 and a second one BJ2.
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