| 摘要 |
A rotary shaft and a rotation driven member are connected as to transmit motive power when the rotary shaft rotates relatively to the rotation driven member. A roller gets displaced to a first position where a frictional force with an outer race and the rotation driven member decreases, thereby permitting transmission of a rotational force from the rotary shaft to the rotation driven member. When the rotation driven member rotates relatively to the rotary shaft, the roller gets displaced to a second position where the frictional force with the outer race and the rotation driven member increases, thereby rotationally fixing the rotation driven member with respect to the outer race. The power transmission from a brake apparatus to an electric motor can be hindered while permitting the power transmission to the brake apparatus from the electric motor by using either a worm exhibiting a relatively low transmission efficiency or a worm wheel. |
