Method of manufacturing poly-V-pulley

Abstract

The present invention provides a method of manufacturing a poly-V pulley made of metal sheet, which can be easily produced from a thick flat-plate material. By this method, the poly-V pulley is formed to have a two-part arrangement of poly-V grooves having different diameters, i e., a small diameter and a large diameter. A circular flat-plate material having a boss portion at the center thereof is bent, thereby forming a first forming body whose section is dish-shaped. The first forming body includes a supporting base and a conical peripheral portion consecutively disposed so as to be inclined and widened from the outer peripheral end of the supporting base portion in the outward direction. Next, the conical peripheral wall is extended in the widening end direction so as to decrease the thickness thereof, thereby forming a second forming body whose section is also deep dish-shaped. In the extension step, the supporting base portion has great thickness of a flat-plate material without being extended, in order to keep the thickness thereof intact, thus obtaining a boss portion and the supporting base plate, which ensures the necessary joining strength for joining the shaft therewith. Then, the conical peripheral wall of the second forming body, whose thickness is decreased, is drawn, thereby forming a small-diameter cylindrical portion, a stepped portion and a large-diameter cylindrical portion. It is easy to perform a drawing step, because the thickness of the conical peripheral portion has been decreased in the previous step. Finally, the outer peripheral surface of the small-diameter cylindrical portion and the outer peripheral surface of the large-diameter cylindrical portion are provided with poly-V grooves by roll shaping.

Dependencies are inferred from the claim text.