| 摘要 |
In the present invention, without forming a rotational shaft ( 30 ) per se in an eccentric manner, the eccentric structure is provided to the whole structure including a ball bearing ( 50 ). Accordingly, in place of cutting a side of the rotational shaft ( 30 ), the eccentric ball bearing ( 50 ) is joined to a shaft portion of the straight rotational shaft ( 30 ) so as to obtain an eccentric portion. That is, the eccentric portion is constituted of the shaft portion which has an axis aligned with an axis of the rotational shaft ( 30 ) and the eccentric ball bearing ( 50 ) which is joined to the shaft portion. As the eccentric ball bearing, it is optimum to adopt a mode in which an inner side thereof having a smaller diameter is formed in an eccentric manner. The eccentric ball bearing ( 50 ) is constituted of an inner lace ( 52 ) which is arranged eccentric with respect to the axis of the rotational shaft ( 30 ), an outer lace ( 54 ) which surrounds an outside of the inner lace ( 52 ) and balls ( 55 ) which are supported between the outer lace ( 54 ) and the inner lace ( 52 ).
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