Abstract: An annular groove portion is formed between portions corresponding to groove portions and thereafter the groove portions are formed while the annular groove is pressed. Consequently, since the stress produced due to a plastic deformation in forming the groove portions can be absorbed by the annular groove having a smaller rigidity than the groove portions, no undesirable plastic deformation of the groove portions occurs and hence the accuracy of the finished size of the multi-stage pulley can be improved. Furthermore, the capital investment in groove forming rollers can be reduced and the manufacturing cost of the multi-stage pulley can be reduced.

Abstract: The manufacturing cost of a multi-stage pulley is reduced without coaxially arranging a plurality of groove forming sections. While a portion between groove sections 103 is being pushed by a pushing roller 204, the groove sections 103 are successively formed. While a portion of workpiece W2 pushed by a groove forming roller 206 to form one groove section 103a and a portion of workpiece W2 pushed by a groove forming roller 207 to form the other groove section 103b are being shifted from each other in the circumferential direction, one groove section (103a) and the other groove section (103b) are simultaneously formed. Due to the foregoing, when the groove sections 103 are formed, it is possible to prevent the deformation of the groove section 103 and the groove section 103 which is adjacent to it. Accordingly, it is possible to enhance the yield of the multi-stage pulley 100 without coaxially arranging a plurality of groove forming sections.

Abstract: An annular groove portion is formed between portions corresponding to groove portions and thereafter the groove portions are formed while the annular groove is pressed. Consequently, since the stress produced due to a plastic deformation in forming the groove portions can be absorbed by the annular groove having a smaller rigidity than the groove portions, no undesirable plastic deformation of the groove portions occurs and hence the accuracy of the finished size of the multi-stage pulley can be improved. Furthermore, the capital investment in groove forming rollers can be reduced and the manufacturing cost of the multi-stage pulley can be reduced.

Abstract: A disk material is plastic-formed to form an inner cylindrical portion of a rotor and a cover member which covers an end side of the rotor. After that, the disk material is slit inwardly from an outside thereof in a radial direction of the disk material to form an outer cylindrical portion of the rotor and a pulley corresponding portion which will be the pulley. Finally, the pulley corresponding portion is plastic-formed to form a pulley groove. Thereby, even when the location of the pulley relative to the outer cylindrical portion are different, same processes can be applied to these different type pulley integrated rotors until the disk material is slit. That is, many different type pulley integrated type rotors can be manufactured with low cost while maintaining high concentric accuracy between the pulley and the rotor.

Abstract: In forming a multi-grooved V pulley by roll forming, a preliminary forming method is disclosed for preventing the occurrence of a top roll accompanied by a crack along each annular ridge of the pulley. A preliminary form roller is pressed against an annular material to fabricate a preliminary form having, in a sectional view, a corrugation including linear flat root portions and ridges alternating with them on the bottom surface of a wide annular groove. Next, a finish form roller having a plurality of annular V-shaped protrusions is pressed against the linear flat root portions of the preliminary form to thereby finish roll the preliminary form. The forward end of each V-shaped protrusion is kept off from the slopes of the corrugation ridges, and therefore is not broken under a bending moment.

Abstract: A multi-stepped pulley, and a method and apparatus for manufacturing the same, wherein the mechanical strength is increased while keeping down an increase of mass and a rise of manufacturing costs by pressing against portions of a surface of a hollow metal material having a circular cross-section corresponding to a connection portion of a plurality of pulleys by pressing rollers and simultaneously crushing the material in an axial direction so as to integrally form first and second rims, first and second webs, and a connection portion thereof.

Abstract: A workpiece W2 is grasped by inserting a first jig into a concave portion which is formed in a rotor forming process, and by interfitting a second jig to a convex portion which is also formed in the rotor forming process. Thereby, the workpiece W2 is firmly grasped, and a groove-forming roller can be strongly pressed into the workpiece W2. A time for forming a pulley groove is shortened, and a manufacturing cost thereof is reduced.