| 摘要 |
A shaft, a circular plate portion and a cylindrical portion are integrally formed with one another through cutting operations to provide a rotor hub of a motor. An inner region on the lower surface of the circular plate portion is formed continuously with the outer peripheral surface of the shaft, and a hub thrust portion is provided in the inner portion so as to axially face a sleeve thrust portion on a sleeve main body. A stepped portion on the lower surface of the circular plate portion is disposed on the outer side of thrust dynamic pressure grooves on the sleeve thrust portion. In this manner, the stepped portion is disposed in a region where a thrust bearing portion is not provided, so that the hub thrust portion can be formed at a low cost in manufacturing the rotor hub by cutting.
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