| 摘要 |
PROBLEM TO BE SOLVED: To sufficiently ensure the strength of a housing to prevent a large torque fluctuation from appearing in a bearing unit by equalizing the thickness of the housing over the axial direction with a specified ratio to the wall thickness of an outer ring. SOLUTION: The inner rings 11 and shafts 5 of two ball bearings 3 are fixed by press-in with a fastening margin of 2-20μm. Outer rings 13 are pressed into a hollow cylindrical housing 9 having no irregularities on the surface with a fastening margin of 2-20μm, and the housing 9 is formed of a thin straight housing having a thickness of 5-20% of the wall thickness of the outer ring 13. A seat 7 between outer rings is provided between the outer rings 13 of both the ball bearings 3 so as to determine the axial space between the ball bearings 3, and its inside surface 7d is set slightly closer to the shaft 5 side from the outer ring 13 inside surface to compensate the strength of the housing 9. Accordingly, the constraining force of the housing 9 to the outer rings 13 is minimized, so that the torque in rotation is not increased, and the outer diameter of a unit 1 can be thus minimized. Further, since the possibility of inserting the bearing 3 obliquely is low, the torque fluctuation is also minimized.
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