| 摘要 |
PROBLEM TO BE SOLVED: To stably hold lubricating fluid and to prevent optical parts from being soiled by surely preventing the lubricating fluid from being splashed and leaked. SOLUTION: When a rotary shaft 20 is inserted in a sleeve 21 filled with the required quantity of lubricating fluid, the lubricating fluid other than the lubricating fluid required as a dynamic pressure radial bearing is held at an oil pan part 31a with which an oil holding member 31 is provided. When the shaft 20 is rotated, the lubricating fluid positioned at a shallow groove 28 formed at the sleeve 21 functions as the dynamic pressure bearing. On the other hand, the lubricating fluid positioned at the pan part 31a is rotated with the shaft 20 by the centrifugal force of the shaft 20. Besides, when the lubricating fluid cannot stay at the pan part 31a because the lubricating fluid expands by the bubbles of air mixed in at an assembling time or the action of heat generated when the lubricating fluid is rotated as a whole, it oozes in the direction of an aperture part from the bank part 31a. At this time, since the aperture part is provided with an oil holding part 31b, the lubricating fluid at this part is prevented from oozing outside by surface tension with the shaft 20. |
