| 摘要 |
PURPOSE:To prevent occurrence of cracks due to strain by stress in both end parts of an inner cylindrical section, by making the inner diameter of the inner cylindrical section of a pulley body uniform over the entire axial width thereof and substantially equal to the outer diameter of the outer race of a roller bearing. CONSTITUTION:A pulley body A1 is formed with a relatively cheap polyacetal having a high cool-contraction and a low electric charge capability, integrally with an inserted roller bearing B1, the thickness of outer and inner cylindrical sections 1, 2, an annular joint section and reinforcing ribs 4 being substantially equal to each other. In this arrangement, since dies 41 therefore are formed such that the inner diameter of the inner cylindrical section is made to be uniform over the entire axial width thereof, and substantially equal to the outer diameter of the outer race 11 of the roller bearing B1, there is produced no strain by stress in both end parts of the inner cylindrical section 2 due to axial contacting force. Thus, it is possible to prevent occurrence of cracks in the both end parts of the inner cylindrical section.
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