| 摘要 |
A sheet metal-made cup-shaped material including a circular base plate portion and a cylindrical portion extends from an outer peripheral edge portion of the base plate portion in one direction along the axis of the base plate portion. An annular groove is formed in an upper end portion of the cylindrical portion, whereby an annular projection that projects in a direction opposite to a direction along which the cylindrical portion extends is formed in the cylindrical portion. The annular projection and the cylindrical portion are clampingly pressed to a degree at which the annular groove at least disappears, whereby the outer circumferential face of the projection and the outer circumferential face of the cylindrical portion are flush with each other. Therefore, the axial length of a sheet metal-made back face pulley is increased, and the whole of the increased axial length can be used as the effective length. |
