| 摘要 |
PROBLEM TO BE SOLVED: To prevent damage of a bearing due to a foreign matter, such as wear powder and to perform stable operation of a rotary shaft or a reduction mechanism for a long period. SOLUTION: By setting the outside diameter D of a nut member 46 larger than the diameter (d) of an outer ring 16B, the upper side of the upper bearing 16 is covered with a nut member 46 and a taper surface 47 is formed on the upper surface of the nut member 46. This constitution flies a foreign matter A, settled in lubrication oil to the outer peripheral side of the nut member 46 along the taper surface 47 by the centrifugal force of the nut member 46 rotated together with an output shaft 18, and captures the foreign matter in a recessed groove 45 formed in the shaft support part 44 of a lower housing 43. As a result, the upper bearing 16 is prevented from damage due to mixture of the foreign matter A, mixed in the lubrication oil, in the upper bearing 16.
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