Patent Publication Number: US-6338197-B1

Title: Method of manufacturing multi-stage pulley

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a method of manufacturing a multi-stage pulley having a plurality of groove sections with which a driving belt is engaged. 
     2. Description of the Related Art 
     Concerning the method of manufacturing a multi-stage pulley, for example, Japanese Unexamined Patent Publication No. 63-63544 discloses a method in which a workpiece used for manufacturing a multi-stage pulley is plastically deformed by a groove forming roller in which a plurality of groove forming sections are arranged coaxially and integrally with each other so that the groove sections can be formed. 
     SUMMARY OF THE INVENTION 
     Each groove section of a multi-stage pulley is formed when a workpiece of the multi-stage pulley is plastically deformed by a groove-forming roller. Therefore, a shearing force is given to an end of the groove forming roller according to the plastic deformation. For the above reasons, there is a high possibility that the groove-forming roller is damaged in the process of forming the grooves by the method disclosed in the above patent publication. 
     In order to solve the above problems, the present inventors made investigation into a means for successively forming a plurality of grooves at different positions so as to prevent the groove-forming roller from being damaged. As a result of the investigation, it was possible to prevent the groove-forming roller from being damaged, however, the following new problems were encountered. Unlike the case described in the above patent publication in which formation of a plurality of grooves is conducted by a groove-forming roller having a plurality of groove-forming sections which are coaxially arranged, it is impossible to simultaneously form the plurality of groove sections by the means which was attempted in the investigation. Accordingly, a groove, which is adjacent to a groove being formed now, is deformed in the process of groove formation. 
     Due to the foregoing, the yield of manufacturing the multi-stage pulleys is deteriorated, and the manufacturing cost is raised. 
     In view of the above circumstances, the present invention has been accomplished. It is an object of the present invention to provide a method of manufacturing a multi-stage pulley by which the manufacturing cost can be reduced without coaxially arranging a plurality of groove forming sections. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cross-sectional view of a multi-stage pulley of the present invention; 
     FIG. 2 is a schematic illustration showing a model of a chucking process; 
     FIG. 3 is a schematic illustration showing a model of a spinning process; 
     FIG. 4 is a schematic illustration showing a model of an annular groove forming process; 
     FIGS. 5 and 6 are schematic illustrations showing a model of a first groove forming process on section A—A in FIG. 9; 
     FIGS. 7 and 8 are schematic illustrations showing a model of a second groove forming process on section B—B in FIG. 9; and 
     FIG. 9 is a schematic illustration showing a method of manufacturing a multi-stage pulley. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In order to accomplish the above object, the following technical means are provided by the present invention. 
     According to the described invention, a plurality of groove sections ( 103 ) are formed while a space between portions of the circumferential outer wall section of the substantially cup-shaped workpiece (W 2 ), corresponding to the groove sections ( 103 ), is being pushed. A portion of workpiece (W 2 ) pushed by the groove forming roller ( 206 ,  207 ) in the case of forming one groove section ( 103   a ) and a portion of workpiece (W 2 ) pushed by the groove forming roller ( 206 ,  207 ) in the case of forming the other groove section ( 103   b ) are shifted from each other in the circumferential direction of workpiece (W 2 ), and one groove section ( 103   a ) and the other groove section ( 103   b ) are simultaneously formed. 
     Due to the foregoing, it is possible to suppress the deformation of the groove sections ( 103 ) which are being successively formed one by one and also suppress the deformation of the groove sections ( 103   a ,  103   b ), which are adjacent to the groove sections ( 103 ). Therefore, it is possible to enhance the yield of manufacturing the multi-stage pulleys ( 100 ) without using a groove forming roller in which a plurality of groove forming sections are coaxially arranged. Therefore, it is possible to reduce the cost of manufacturing the multi-stage pulley ( 100 ). 
     It is possible to enhance the dimensional accuracy of the multi-stage pulley ( 100 ) and to prevent the groove-forming roller ( 206 ,  207 ) from being damaged. It is also possible to enhance the yield of manufacturing the multi-stage pulley ( 100 ). 
     In this connection, as described in the present invention, workpiece (W 2 ) may be formed by conducting spinning on a sheet-shaped workpiece (W 1 ) to manufacture a multi-stage pulley. 
     In this connection, reference numerals in parentheses correspond to the specific means of the embodiments described later. 
     EXAMPLE 
     FIG. 1 is a cross-sectional view of a multi-stage pulley  100  manufactured by the method of manufacturing a multi-stage pulley of this embodiment. This multi-stage pulley  100  includes: a circumferential outer wall section (rim section)  102  of a substantially cup-shaped pulley body  101 ; and two groove sections  103   a ,  103   b  with which a driving belt (not shown) is engaged, wherein the circumferential outer wall section  102  and the two groove sections  103   a ,  103   b  are integrated into one body. These two groove sections  103   a ,  103   b  will be referred to as a groove section  103  in this specification hereinafter. 
     The method of manufacturing the multi-stage pulley  100  will be described below according to the manufacturing processes. 
     There is provided a disk-shaped workpiece W 1  to manufacture a multi-stage pulley. In this embodiment, workpiece W 1  is made of iron. As shown in FIG. 2, a first die  201  and a second die  202  push workpiece W 1  from both sides in the thickness direction, so that workpiece W 1  to manufacture a multi-stage pulley can be chucked. This process is referred to as a chucking process. 
     In this connection, on an outer circumference of the second die  202 , there is provided a step portion  202   a  which is formed along an inner circumference of the rim section  102  of the multi-stage pulley  100 . 
     Next, as shown in FIG. 3, while a portion of workpiece W 1  which is pushed by both dies  201 ,  203  is used as a bottom portion, and while a spinning roller  203  is being rotated together with both dies  201 ,  202  and workpiece W 1 , the spinning roller  203  is moved from the first die  201  side to the second die  202  side. In this way, spinning is conducted on workpiece W 1  so that workpiece W 1  can be formed into a substantial cup shape along the step portion  202   a . This process is referred to as a spinning process. 
     Next, as shown in FIG. 4, a pushing roller  204  to push a space between portions corresponding to the groove sections  103  is made to come into contact with workpiece W 2  formed in the spinning process. This process is referred to as a pushing roller contact process. At the same time, in order to prevent workpiece W 2  from being plastically deformed unnecessarily in the axial direction of the multi-stage pulley  100  (both dies  201 ,  202 ), workpiece holding rings  205   a ,  205   b  are moved toward workpiece W 2 . 
     As shown in FIGS. 5 and 6, while the pushing roller  204  is being pushed against workpiece W 2 , preliminary groove forming rollers  206   a ,  206   b  are simultaneously pushed against the circumferential outer wall section of workpiece W 2 , so that two groove sections  103  can be successively formed one by one. This process is referred to as a first groove forming process. The preliminary groove forming roller  206   a  pushes a portion which will become one groove section  103   a  shown in FIG. 1, and the preliminary groove forming roller  206   b  pushes a portion which will become the other groove section  103   b  shown in FIG.  1 . 
     Next, as shown in FIGS. 7 and 8, in the same manner as that of the first groove forming process, while the pushing roller  204  is being pushed against workpiece W 2 , finishing groove forming rollers  207   a ,  207   b  are simultaneously pushed against the circumferential outer wall section of workpiece W 2 , so that two groove sections  103  can be successively finished one by one. This process is referred to as a second groove forming process. In this case, the finishing groove forming roller  207   a  pushes a portion which will become one groove section  103   a , and the finishing groove forming roller  207   b  pushes a portion which will become the other groove section  103   b.    
     At this time, the first and the second groove forming processes are conducted as follows. Without distinction of the preliminary groove forming process and the finishing groove forming process, as shown in FIG. 9, the first and the second groove forming processes are conducted so that portions, at which both groove forming rollers  206   a ,  206   b ,  207   a ,  207   b  push workpiece W 2  in the case of forming one groove section  103   a  (shown in FIG.  1 ), and portions, at which both groove forming rollers  206   a ,  206   b ,  207   a ,  207   b  push workpiece W 2  in the case of forming the other groove section  103   b  (shown in FIG.  1 ), can be shifted from each other in the circumferential direction and so that one groove section  103   a  and the other groove section  103   b  can be simultaneously formed. 
     Next, characteristics of this embodiment will be described below. 
     According to the method of manufacturing the multi-spate pulley  100  of this embodiment, the groove section  103  is formed under the condition that a portion between the groove sections  103  is pushed by the pushing roller  204 . Accordingly, it is possible to prevent the groove section  103 , which is being formed, and the groove section  103 , which is adjacent to it, being deformed when the groove sections  103  are successively formed one by one. Accordingly, it is possible to enhance the dimensional accuracy of the finished multi-stage pulley  100  and also it is possible to enhance the yield of manufacturing the multi-stage pulley  100  without using a groove forming roller in which a plurality of groove forming sections are coaxially arranged. Therefore, it is possible to reduce the cost of manufacturing the multi-stage pulley  100 . 
     As shown in FIGS. 6 and 7, the circumferential outer wall section (rim section  102 ) of workpiece W 2  is prevented from being unnecessarily plastically deformed, by the engaging sections formed in both workpiece holding rings  205   a ,  205   b . Therefore, it is possible to enhance the dimensional accuracy of the finished multi-stage pulley  100 . As a result, the yield of the multi-stage pulley  100  can be enhanced. Consequently, the cost of manufacturing the multi-stage pulley  100  can be reduced. 
     In this embodiment, the first die  201  and the second die  202 , which were used in the chucking process, are used even in the second groove forming process (final process) for chucking. Therefore, unlike the method disclosed in Japanese Unexamined Patent Publication No. 61-132238, it is unnecessary to change the die for chucking in each process. Accordingly, an amount of equipment investment for the die can be reduced, and the cost of manufacturing the multi-stage pulley  100  can be reduced. 
     In this connection, as a result of the investigation made by the present inventors, the following facts were confirmed. In the first and the second groove forming processes, unless a portion, in which workpiece W 2  is pushed when one groove section  103   a  is formed by both groove forming rollers  206 ,  207 , and a portion, in which workpiece W 2  is pushed when the other groove section  103 b is formed, are shifted from each other in the circumferential direction, and unless one groove section  103   a  and the other groove section  103   b  are simultaneously formed, an amount of deformation of workpiece W is increased, and an amount of plastic fluidity of material is increased. Accordingly, there is a high possibility that the tools (both groove forming rollers  206 ,  207 ) are damaged. 
     According to this embodiment, while the tools (both groove forming rollers  206 ,  207 ) can be prevented from being damaged, the dimensional accuracy of the finished multi-stage pulley  100  and the yield of manufacturing the multi-stage pulley  100  can be enhanced. 
     In this embodiment, the substantially cup-shaped workpiece W 2  is formed by means of spinning, however, it should be noted that the present invention is not limited to the above specific embodiment. The substantially cup-shaped workpiece W 2  may be formed by pressing a sheet material or a pipe material.