| 摘要 |
PROBLEM TO BE SOLVED: To minimize the wear and deformation and to release generated static electricity by forming at least one of a bearing member and a shaft of ceramics having a specified volume natural resistance value, and providing a dynamic pressure generating groove on its surface. SOLUTION: A shaft 1 has a herringbone-like dynamic pressure generating groove 1a on the side surface to constitute a radial hydrodynamic bearing between the inner circumferential surfaces of a sleeve 3 forming a bearing member. On the other hand, a thrust directional bearing member 2 is provided in a position opposed to the end surface of the shaft 1, and a spiral dynamic pressure generating groove 2a is formed on its surface to constitute a thrust directional hydrodynamic bearing having thrust rigidity. The bearing member 2 is formed of zirconia ceramic having a volume natural resistance value of 10<5> -10<9>Ω.cm. The shaft 1 end surface and the bearing member 2 are rotated in contact to each other in the start/stop or low-speed rotation of the bearing, and laid in non-contact state in the high-speed rotation thereof. Thus, since a static electricity can be removed at a proper speed, even if the static electricity is generated in the contact rotation, to provide excellent sliding property, the mutual abrasion loss can be minimized.
|
