| 摘要 |
PURPOSE:To simplify a composition, prevent dust generation and lengthen a service life with extremely low torque by a method wherein a magnet is provided on a supporting member, a fixing radial bearing face is smaller in diameter than a large diameter face of a middle part, a non-magnetic shaft has a protrusion larger in diameter than the radial bearing face and magnetic fluid is interposed in a bearing. CONSTITUTION:When a protrusion 8 larger in diameter than radial bearing faces 5a, 5b provided on a shaft 3 moves to the right in a supporting member 1, since a pressure in the supporting member 1 is higher at both ends of an axial direction than a middle part, the protrusion 8 is pushed back to the left. Thus since the shaft 3 is supported by magnetic fluid 2, the protrusion 8 of the shaft 3 and the supporting member 1 are kept in no contact with each other. In addition, when the shaft 3 moves downward, the pressure of the magnetic fluid 2 in radial bearing slits 9a, 9b is higher at a lower section than at an upper section due to difference in flux density to push back the shaft 3 upward. Thus since the shaft 3 is supported in a radial direction by the magnetic fluid 2, the radial bearing faces 5a, 5b and radial receiving faces 7a, 7b are kept in no contact with each other. |
