| 摘要 |
PROBLEM TO BE SOLVED: To control a swing arm at higher speed with higher precision by setting the linear expansion coefficient of an inner ring larger than the linear expansion coefficients of a rolling body and an outer ring, and/or setting the linear expansion coefficient of a shaft larger than the linear expansion coefficient of a housing, and using oil as lubricant. SOLUTION: The linear expansion coefficient of an inner ring 1 is set larger than the linear expansion coefficients of a ball 5 and an outer ring 2, and/or the linear expansion coefficient of a shaft 2 is set larger than the linear expansion coefficient of a housing 4. Further, as the lubricant of a ball bearing 6, oil 8 is used. Since the oil 8 is apt to get into a moving contact surface and dispersible of heat, the initial scattering of the lubricant can be minimized. The deterioration of the ball bearing 8 in operation is also minimized to minimize the torque fluctuation of a bearing device. Since the linear expansion coefficients of the inner ring 1 and the shaft 3 are larger than those of the outer ring 2 and the housing 4, the bearing clearance is never increased at a high temperature, so that the reduction in resonance frequency by preload release can be prevented, and satisfactory positioning performance can be provided.
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