| 摘要 |
PROBLEM TO BE SOLVED: To secure good sealing performance and to extend the service life of a lip seal at a low cost in a vacuum pump. SOLUTION: A relieving hole 53 is formed in the upper wall 332 of a gear housing 33. The relieving hole 53 comprises a small diameter part 531 and a female screw part 532 having a large diameter. An air vent filter 55 is mounted on a step between the small diameter part 531 and the female screw part 532. The filter 55 has air permeability and oil repellency. A male screw 54 is screwed to the female screw part 532, and the filter 55 is interposed between the male screw 54 and the step. A thin relieving hole 541 is drilled in the axial center part of the male screw 54.
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