| 摘要 |
PURPOSE:To improve the durability of a gear part by making an action for restraining the thrust displacement of a worm wheel generated by the impact force of a motor device provided with a worm gear or placing both directional changes of a meshed area by the displacement in the increasing direction. CONSTITUTION:A holder 20 is installed on the outer peripheral upper edge of a worm wheel 12 so as to be arranged to prevent any relative displacement in an axial direction by means of the stop ring 17 of a boss 7 and installed in parallel with a cover 18 at a minute clearance thereto and the maximum outer diameter of a part having the minute clearance is made a gear effective diameter or less of the worm wheel 12. |
