| 摘要 |
<p>In the invention, a sheet metal-made cup-shaped material (4) comprising: a circular base plate portion (2); and a cylindrical portion (3) which extends from an outer peripheral edge portion of the base plate portion (2) in one direction along the axis of the base plate portion (2) is prepared, an annular groove (13) is formed in an upper end portion of the cylindrical portion (3), whereby an annular projection (15) that projects in a direction opposite to a direction along which the cylindrical portion (3) extends is formed in the cylindrical portion (3), and the annular projection (15) and the cylindrical portion (3) are clampingly pressed by a rotary lower mold (5e), a rotary upper mold (6d), and a flat-face forming rolling roller (18) to a degree at which the annular groove (13) at least disappears, whereby the outer circumferential face (15a) of the projection (15), and the outer circumferential face (30) of the cylindrical portion (3) are formed to be flush with each other. Therefore, the axial length (h4) of a sheet metal-made back face pulley (11) is increased, and the whole of the increased axial length (h4) can be used as the effective length.</p> |
