| 摘要 |
PROBLEM TO BE SOLVED: To provide a small-sized and lightweight spindle motor having a simple structure, which has a single-end retaining type shaft for a small-sized storage device capable of realizing high storage capacity. SOLUTION: A shaft 32 is constituted of high rigidity ceramics of small specific gravity, and shaft vibration during rotation is reduced. Thereby the shaft, wherein a both-ends retaining type is necessary in the case of a steel shaft, is made a single-end retaining type, and larger storage medium 6 can be accommodated in this state. A ratio (Ds/Dh) of an outside diameter Ds of the shaft 32 to on outside diameter Dh of a rotor hub 34 is made at least 0.4, thereby ensuring superior rigidity. In the case of a hollow bearing, the radial thickness is reduced to about 2 mm to ensure desired rigidity. In the case of fluid dynamic pressure bearing, the peripheral speed can be reduced by using small diameter ceramics, and oil temperature rise can be avoided.
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