| 摘要 |
PURPOSE:To secure the deflection accuracy of an upper cylinder by fitting the upper cylinder by projecting one part of a thrust receiving member from the edge surface of a sleeve and directly guiding the upper cylinder by the thrust receiving member. CONSTITUTION:The upper part of a thrust receiving member 48 projects from a sleeve 40, and a circular hole 62 of an upper cylinder 60 is fitted with the projection part. When the upper cylinder 60 is revolved, a revolution side rotary trans 68, thrust receiving member 48, and a sleeve 40 revolve integrally. Therefore, a radial gap and thrust gap can be formed between a fixed shaft 20 and the sleeve 40 and the thrust receiving member 48 by the action of the dynamic pressure generating grooves 22 and 24 on the outer peripheral surface of a fixed shaft 20 and the dynamic pressure generating groove formed on the undersurface of the thrust receiving member 48, and the deflection accuracy can be secured.
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