| 摘要 |
PROBLEM TO BE SOLVED: To prevent such problems that a bolt falls down, falls, and is insufficiently tightened when the bolt held at the tip of a tool is tightened, and prevent a working efficiency from being lowered. SOLUTION: A differential shaft inner part 22 is connected to the output shaft 18 of a speed reduction mechanism 13 decelerating the rotation of a drive motor 12, the differential shaft inner part 22 is inserted into the tube of a differential shaft outer part 21, the screw part n on the outer peripheral part of the differential shaft inner part 22 is meshed with screw grooves m on the inner peripheral part of the differential shaft outer part 21. Oil is sealed in the tube H of the differential shaft outer part 21. A socket shaft 10 is connected to the tip side of the differential shaft inner part 22. In the initial stage where the drive motor 12 is driven, the differential shaft inner part 22 is made so as to be moved forward while rotating at a low speed. In a stage where the differential shaft inner part 22 is allowed to abut on the differential shaft outer part 21, the differential shaft inner part 22 is made so that the rotation thereof can be switched to a high speed. COPYRIGHT: (C)2003,JPO
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