| 摘要 |
PROBLEM TO BE SOLVED: To increase rotation precision in high speed rotation and a bearing life by providing a cylindrical shaft body and a hollow cylindrical bearing body opposed to the shaft body at an interval in the radius direction and providing at least one clearance variation part with a predetermined clearance changing rate in the clearance between them. SOLUTION: This structure is provided with a cylindrical shaft body 1 and a hollow cylindrical shaft bearing body 2 opposed to the shaft body 1 at a certain interval in the radius direction. A clearance 3 between the shaft body 1 and the shaft bearing body 2 is provided with at least one clearance variation part 31. In the clearance variation part 31, thickness of the clearance 3 is varied with respect to the center angle corresponding to the circumference along the outer circumference of the shaft body 1. When a diameter of the shaft body 1 is represented by D1 , a thickness changing quantity of the clearance 3 is represented byΔh, and a changing quantity of the center angle is represented byΔθ, a clearance changing rateαis represented by an equation:α=(Δh/D1 )/Δθ[/ deg.]. The clearance changing rateαis within a range of 1.0×10<-4> <=α<=10.0×10<-4> .
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