| 摘要 |
PURPOSE:To utilize the magnetic force of a magnet structure so effectively and that make its manufacture so easy enough by making an outer diameter of a yoke plate on one side smaller at least 1mm than that of a yoke plate on the other. CONSTITUTION:A yoke 2b at the side of a housing support surface 4a in a magnet structure 2 is supported on this support surface 4a, while an outer circumferential surface of the yoke 2b is stuck onto a large diametral inner circumferential surface of a magnetic substance housing 4. In addition, an outer diameter of another yoke 2b' is formed to be smaller as much as 1mm than that of the yoke 2b at the support surface side, and there is provided with an interspace of 1mm between the circumference of the yoke 2b' and the large diametral inner circumferential surface of the magnetic substance housing 4. For this space, a magnetic path between a radial outer circumferential part of the yoke 2b' and the magnetic substance housing 4 is cut off, whereby magnetic flux of the magnet structure 2 is prevented from leaking to the outside. In this connection, at the inner circumferential side of the magnet structure 2, such a magnetic path as pound magnet 2a- yoke 2b- turning shaft 1- yoke 2b- pound magnet 2a is formed, and a magnetic fluid 3 is held between these yokes 2b, 2b' and the turning shaft 1. |
