| 摘要 |
PROBLEM TO BE SOLVED: To provide a reliable motor wherein lubricant does not leak from radial dynamic pressure bearing portions even under gyro load testing, and the dynamic pressure does not drop and the NPRO performance is maintained for a long time. SOLUTION: The radial dynamic pressure bearing portions 4A and 4B are formed of a shaft 9 and a sleeve 5. Annular projected portions 3A and 3B which are protruded in the inner face of a through hole 5D into which the shaft 9 is inserted are formed between the bearing portions 4A and 4B and the ends 9A and 9B of the shaft 9. Thus, plain bearing portions 30A and 30B consisting of the annular projected portions 3A and 3B and the shaft 9 are formed. A rotor 60 is rotatably supported in the radial direction by the plain bearing portions 30A and 30B and the radial dynamic pressure bearing portions 4A and 4B. The ratio d/D of the axial width (d) of the projected portions 3A and 3B to the axial width D of the radial dynamic pressure bearing portions 4A and 4B is controlled to a value not less than 0.03 and not more than 0.3. Further, the projected portions 3A and 3B are separated from each other, and their surface hardness is made higher than that of the sleeve 5. COPYRIGHT: (C)2004,JPO
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