| 摘要 |
PROBLEM TO BE SOLVED: To apply an appropriate orientation pre-load by securing support rigidity in a wide rotation range of a main spindle in a bearing structure. SOLUTION: In this bearing structure rotatably supporting the main spindle 1 to the internal circumference of a housing 3 via angular ball bearings 2A and 2B, an initial pre-load is applied for exhibiting an appropriate support rigidity to the angular ball bearings in assembling, and a pre-load adjusting ring 8 expanding more largely than the increasing extent of a centrifugal expansion and thermal expansion in its increase is interposed in inner ring spacers 7A and 7B. An abutment surface between the pre-load adjusting ring and the inner ring spacer is made to incline toward a surface along the diametrical direction, and the pre-load adjustment ring expands along with the increase in the centrifugal expansion and the thermal expansion of the angular ball bearing so that a distance between the inner rings becomes variable via the inner ring spacer so as to limit the change in the initial pre-load.
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