| 摘要 |
A smooth surface 2 d of a shaft member 2 is divided from an outer circumferential surface 2 a by a step so that its axial length dimension B becomes shorter than the axial length dimension A of a hydrodynamic groove region 8 a formed on the inner circumferential surface of a bearing sleeve 8 , whereby the hydrodynamic groove regions 8 a excluding lower portions of a land 8 c between hydrodynamic grooves 8 b oppose the smooth surface 2 d.
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