| 摘要 |
PROBLEM TO BE SOLVED: To make it possible to decrease stages, etc., to surely prevent the splashing and leaking out of lubricant fluid inexpensively in terms of a cost, to stably hold the lubricant fluid in a dynamic pressure bearing and to eliminate the possibility of staining optical parts by interposing grease between an oil holding part or near the aperture of the oil holding part and a shaft. SOLUTION: When the revolving shaft 3 rotates, the lubricant fluid existing in shallow grooves 9 formed at a sleeve 4 acts as the dynamic pressure bearing. On the other hand, the lubricant fluid existing in parts exclusive thereof, for example, an oil sump part 12, are co-rotated by the centrifugal force of the revolving shaft 3 and the expansion, etc., of the bubbles of the air intruding into the lubricant fluid at the time of assembly and the entire part of the lubricant fluid by the heating of the rotation occur. When the volume of the lubricant fluid increases greater than the volume of the oil sump part 12, the lubricant fluid oozes toward the aperture of a sleeve 4. At this time, the aperture is provided with the oil sump part 13 and further the grease A is interposed therein and, therefore, the lubricant fluid tending to ooze may be shut off. then, the oozing of the lubricant fluid to the outside of the sleeve 4 may be prevented. |
