| 摘要 |
A bearing structure used in a pivot bearing for freely supporting the rotation of a head arm of a hard disk drive (HDD). The bearing structure includes an inner shaft, an outer sleeve, a pair of roller bearings axially spaced and interposed between the inner shaft and the outer sleeve, and a preload spring for exerting a preload on the roller bearings. The roller bearings may be provided with an outer race that is attached to the outer sleeve. Nevertheless, the coefficients of linear expansion of the inner shaft and the outer sleeve are chosen so that they are different in an axial direction. Accordingly, the coefficients of linear expansion of the inner shaft and the outer sleeve are chosen so that the rotation torque derived from the preload becomes higher as the temperature rises and lower as the temperature falls. However, the rotational torque becomes lower as the temperature of a lubricant rises and higher as the lubricant temperature falls. Thus, the changes in the rotational torque as a result of temperature change are cancelled out.
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