| 摘要 |
PROBLEM TO BE SOLVED: To provide a stage difference part sufficient to hook a tooth edge of a spline inner gear tooth of a synchronous sleeve in a spline outer gear tooth formed in a synchronous hub so as to prevent the loose-out of the gear of a synchronous switching mechanism without reducing the thickness of the gear teeth. SOLUTION: A spline outer gear tooth 24a of a synchronous hub 24 to be engaged with a spline inner gear tooth 31a of a synchronous sleeve is formed of a small gear tooth thickness part 35 and a large gear tooth thickness part 36, and the large gear tooth thickness part 36 is displaced to an abutment gear tooth surface 35a of the small gear tooth thickness surface 35 for abutting on the spline inner gear tooth 31a so as to form a level difference part 37 projected at a projection quantity t1. When the spline inner gear tooth 31a is moved in a gear loose-out direction (right direction in figure), a tooth edge of the spline inner gear tooth 31a is hooked on the level difference part 37 so as to prevent the loose-out of the gear. Since the level difference part 37 is secured by eccentrically placing the large gear tooth thickness part 36 in a direction of the abutment gear tooth surface 35a, the level difference part is hardly formed on the non-abutment gear tooth surface 35b side, and the projection quantity t1 of the level difference part 37 can be secured without reducing the gear tooth thickness of the small gear tooth thickness part 35 more than the necessity.
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