| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide durabilily against high speed rotation usage by shifting a pitch circle of a rolling element toward the center of a bearing and specifying a ratio of thickness of a raceway track groove bottom of a fixed side outer ring to that of a raceway track groove bottom of a rotary side inner ring and the thickness of the raceway track groove bottom of the rotary side inner ring. SOLUTION: A ratio of the thickness of a raceway track groove bottom of an outer ring 1 serving as the fixed side to that of a raceway track groove bottom of an inner ring serving as the rotary side is set to be 2.0-2.75 to 1.0. That is, the thickness of the raceway track groove bottom of the inner ring 2 is set to be thinner than that of the raceway track groove bottom of the outer ring 1, and centrifugal stress working on the inner ring 2 due to centrifugal force is reduced, and at the same time, a revolution radius of a rolling element such as a ball 3 is reduced advantageously for high speed rotation. In concrete, in an ordinary size main shaft, the thickness of the raceway track groove bottom 2' of the inner ring 2 is set to be 2.5-4.4mm. As the raceway track groove bottom thickness of the inner ring is 2.5mm or more, strength is maintained and a cemented layer of 0.5-1.0mm can be secured, while deformation of the raceway track wheel is generated because of centrifugal force and seizure is caused if thickness of the raceway track groove of the inner ring exceeds 4.4mm.</p> |
