| 摘要 |
PURPOSE:To only conform each one part of the ball rolling grooves of a worm and a worm wheel to each other, prevent floating up of a ball on the position being not conformed to each other, and smoothly drive the device, by providing a frame ring to prevent large floating-up of a ball from a first groove due to large clearance against a second groove, on the outer circumferential face of the end part of the worm. CONSTITUTION:When a worm 10 is rotated, the power is transmitted to the meshing part with a worm wheel 11 through balls 12, so as to rotate the worm wheel 11. Because the end part of the worm 10 and the worm wheel 11 are not closely contacted with each other when the ball 12 is detached from a second groove 27, the ball is apt to largely float up from a first groove 14. But, by providing a frame ring 10a on the outer circumferential face of the end part of the worm 10, large floating-up of the ball 12 from the first groove 14 can be prevented. Consequently, from the design, the ball rolling groove of the worm 10 and the ball rolling groove of the worm wheel are conformed to each other at only each one part, and hence the movement at driving can be performed smoothly. |
