| 摘要 |
PROBLEM TO BE SOLVED: To prevent the abnormal abrasion caused by the releasing of pre-load or the increase of pre-load caused by the change of a temperature by controlling each coefficient of linear expansion of at least an inner ring, an outer ring, a rolling element, a shaft and a rotor within predetermined ranges with respect to their average values. SOLUTION: A rolling element should have a function same as that of a ceramic ball in the view point of quietness, appearance or the like in the rotation when a temperature rise of a bearing device is below 70 deg.C, and the surface hardness of the rolling element satisfies Vickers hardness of above 1000. It is effective that a value obtained by dividing a coefficient of linear expansion of each element by its average value is set within a range of 0.7-1.3 times to prevent the releasing of pre-load, when the pre-load amount at 70 deg.C is disposed on the basis of the relationship between an average valueαx of the coefficient of linear expansion of each each element, and preferably within a ranage of 0.7-1.2 times to prevent the remarkable lowering of the pre-load.
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