| 摘要 |
PROBLEM TO BE SOLVED: To increase the service life of the bearing by preventing the scattering of the oil of an oil-impregnated sintered bearing. SOLUTION: A bearing surface 9 to support a rotary shaft 3 is formed at a part of the bearing hole of an oil-impregnated sintered bearing 4. The part from the bearing surface 9 to the bearing hole is made in a diameter expansion part extended at the taper angleθ2 deg. to 10 deg., and in the width at least more than 1/ 3 of the width of the bearing surface 9 in the axial direction. The oil spread from the bearing surface 9 is stored in the diameter expansion part 10. As the whirl countermeasure of a rotary shaft 3, plural grooves extending in the axial direction are provided on the bearing surface 9, and the form of the bearing surface 9 is made in a step form repeating the projection and the recess in the peripheral direction. And, in order to stabilize the rotation accuracy, the surface hole opening rate of the step form bearing surface 9 can be made large at the projection parts, and small at the recess parts. In this case, in the surface area rate, the hole opening ratio is made within the scope 3 to 15% at the projection surface, and within the scope 0 to 10% at the recess surface.
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