| 摘要 |
PURPOSE:To reduce wear in the region of high speed revolution, heat generation in the region of low speed revolution and wear of sprag by temporarily shifting the center of gravity in the sprag when a revolutional speed exceeds a predetermined value. CONSTITUTION:A curving surface with a radius of curvature R3 smaller than that of a radius of curvature R2 is formed on the end surface of a sprag 4. The center of gravity G is positioned at the side opposed to a vertex 10 with regard to a segment AO2 and a spring force F1 of a garter spring 9 is applied to the sprag 4. When a revolutional speed increases to make the spring force zero, the spring is vibrated so that the center of gravity is temporarily dispalced. The increase in the revolutional speed in the non-wedging direction of an outer ring 3 reduce the spring force F1 so as to make an wedging in the region of the revolutional speed to zero. As the revolutional speed is subjected to zero, the sprag 4 is vibrated with the idling frictional force and the center of gravity G is shifted on the side to which the spring force F1 is applied so as to be stabilized. Thus, the sprag 4 is separated from an inner ring 2 so that wear is not prevented. On the other hand, the reduction of the revolutional speed increases the spring force F1 so that the moment in the wedging direction is exerted on the sprag 4, thus the wedging being performed. Therefore, it is possible to prevent heat generation and wear of the sprag 4.
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