POLY-V PULLEY AND MANUFACTURING METHOD THEREFOR

Abstract: A method for manufacturing a poly-V pulley includes a process for slitting and compressing the peripheral edge portion of an essentially flat blank for forming widened and thickened flange wall (13). A series of relatively narrow, deep, V-shaped grooves (12) are cold rolled. The poly-V pulley thus produced has the flange wall with poly-V grooves, from the intermediate portion of which a web (18) extends radially inward. This structure provides good dyna­ mic balance of rotation for the pulley and thus prolong life not only of the pulley per se but also a belt to be put around the pulley. Further, the manufacturing method allows to manufacture relatively small diameter poly-V pulley.

Description: The present invention relates to a poly-V-pulley and to a method for manufacturing such a pulley. A method for manufacturing a poly-V-pulley according to the pre-characterizing part of claim 1 is disclosed in the documents US-A-3 977 264 and US-A-4 273 547. The poly-V-pulley is made by forming a cup-shaped blank with a generally cylindrical annular flange which terminates at its open end in an outturned radial flange. A series of wide opening, shallow, corrugation-like grooves is then cold-rolled in the cylindrical flange by outwardly and inwardly displacing portions of the flange wall to form rounded groove valleys with intervening round crests, and slightly thinning the flange wall metal in the crests and valleys while presenting appreciable groove side wall thinning. The groove walls are then axially squeezed to compress the walls to sinuous shape whine maintaining constant the radial dimensions of the Inner and outer rounded surface of the grooves during axial squeezing. The sinuous formed flange wall is roller worked and compressed to form sharp V-shaped outer groove crests and thickened metal in the groove valley walls. In the disclosed poly-V-pulley, the weight balance on opposite sides of the pulley is not good enough to provide good dynamic balance while rotating. Due to the inadequate dynamic balance, the radius of the flange wall may show deviations, or excess vibrations may occur. This tends to shorten the life not only of the pulley per-se but also of the belt to be put around the pulley, due to the uneven distribution of friction on the belt caused by the deflection or distortion of the pulley. In the disclosed manufacturing process, since the blank has to be pre-machined or pre-prepared into a cup-shape with the generally cylindrical flange by a deep-drawing process, it has been considered difficult to make a poly-V-pulley with a relatively small diameter. On the other hand, the document FR-A-2 254 383 discloses a method for manufacturing a pulley having a single V-shaped groove, wherein the circumferential edge of a disk-shaped blank is split by means of a sharp-edged roller. In a second rolling step, the blank is slit to a greater depth and the material of the blank Is redistributed to form a thinned annular flange wall extending from the inner portion of the blank in a V-configuration. This manufacturing method thus results in a pulley the web portion of which is formed by the inner portion of the blank and extends from the axial center portion of the annular flange wall which defines the single groove. However, the V-shaped flange wall of this pulley is not suitable for being further processed to form a poly-V-pulley by cold-rolling. A poly-V-pulley the web portion of which extends from the axial centre of the annular flange wall is disclosed in "Konstruktionselemente des Maschinenbaues", Part 2, Springer-Verlag, Berlin, Heidelberg, New York, 1979, page 310. This pulley, however, is formed by metal casting. Therefore, it is an object of the present Invention to provide an improved poly-V-pulley manufacturing method which facilitates manufacture of relatively small diameter poly-V-pulleys such as an automotive water pump pulley and the like having a good dynamic balance, and to provide an improved poly-V-pulley in which the plurality of V-shaped grooves are formed by cold-rolling. The manufacturing method according to the invention is specified in claim 1. A poly-V-pulley according to the invention is claimed in separate independent claims 5 for DE, IT and GB on the one hand and for FR on the other hand. Further objects and advantages of the Invention will be understood from the dependent claims and from the detailed description of preferred embodiments given hereinbelow In conjunction with the accompanying drawings. In the drawings: Fig. 1 is a perspectice view of a poly-V-pulley to be manufactured in the preferred embodiment of a manufacturing method according to the present invention. Fig. 2 is a cross-section taken along line II-II of Fig. 1; Fig. 3 is a view similar to Fig. 2 of a modified pulley which is formed into an off-set pulley; Fig. 4 is a perspective view of an another modification of the pulley of Fig. 1; Figs. 5 to 7 are illustrations showing preparation of a blank to be formed into the poly-V pulley of Fig. 4, by forming a base to receive a bearing; Figs. 8 to 11 show the processes for forming the poly-V pulley of Fig. 1; Figs. 12 to 15 shows a modified process for forming the poly-V pulley of Fig. 1; Figs. 16 to 18 are explanatory illustrations showing the process of Fig. 14 in more detail; Figs. 19 to 22 show another modification of the preferred embodiment of manufacturing process for forming the poly-V pulley of Fig. 1; Figs. 23 to 25 illustrate the process of Fig. 21 in more detail; Fig. 26 to 28 illustrate the processes of a further midification of the preferred embodiment of a manufacturing process for forming the poly-V pulley of Fig. 1; Fig. 29 is an enlarged cross-section of a workpiece as processed by the step of Fig. 26; and Fig. 30 is an enlarged cross-section of the grooved pulley after the step of Fig. 28. Referring now to the drawings, particularly to Figs. 1 and 2, the preferred embodiment of a poly-V pulley 10 according to the present invention is formed with a plurality of circumferentially extending poly-V grooves 12 of generally V-shaped cross-section in the floor of a flange wall 13 defining a belt recess 14. The flange wall 13 is connected to a generally cylindrical base 16 via a web 18. The base 16 defines an internal cylindrical space 20. A bearing 22 is attached to the inner periphery of the base 16. The axial edges 24 of the base 16 are crimped to retain the bearing 22. It should be appreciated that the number of grooves to be formed in the flange wall 13 may be arbitrarily adjusted to match the shape of the belt 26 to be put around the pulley 10. Furthermore, the pulley can be formed as a kind of offset pulley with the flange wall 13 and base 16 lying in different parallel planes as shown in Fig. 3. Fig. 4 shows another modification of the poly-V pulley to be manufactured by the preferred embodiment of a manufacturing method according to the present invention. The modified poly-V pulley 100 is formed with a series of relatively narrow, deep, V-shaped poly-V grooves in a flange wall 103, similarly to the aforementioned pulley 10 of Fig. 1. On the other hand, a web 104 is bent along a crease 106 to form a bracket 108 for a bearing 110. One end 112 of the bracket 108 extends radially inward to form a retainer for the bearing 110. As in the aforementioned pulley 10 of Fig. 1, the poly-V grooves 102 on the flange wall 103 are formed by a slitting process and a rolling process. As shown in Fig. 5, a metal blank 100a is formed. Figs. 5 to 7 show the preparation process to form the bracket 108 and the bearing retaining end 112. As shown in Fig. 5, a metal blank 100a is, at first, formed into circular dish-shaped workpiece at the initial stage of the preparation processes. The edge of the workpiece denoted by the reference number 100b is where the flange wall with the poly-V grooves are to be formed. A central section 100c is substantially parallel to the edge 100b and offset from the latter. The central section 100c is connected integrally with the edge 100b through a section 100d. In the next process, the section 100d is rolled back along a crease 100e, as shown in Fig. 6. In this process, the workpiece 100a is formed to have a transverse section 100f extending perpendicular to the section 100b and 100c. The section 100f is designed to house the bearing. Finally, a circular central opening 114 is formed in the central section 100c, as shown in Fig. 7. When the opening 114 is formed, a relatively short flange 100g is allowed to remain. The flange 100g serves to retain the bearing on the section 100f. The poly-V grooves 12 or 102 in the flange wall 13 or 103 are formed by a combinated processes of a slitting process and a cold rolling process which will be described in detail with reference to Figs. 8 to 11 illustrating processes necessary to form the poly-V pulley in accordance with the preferred embodiment of the poly-V pulley manufacturing method. With reference to Fig. 8, a metal blank 10a is pre-machined into an annular disc shape before performing the slitting process which is performed in advance of the cold rolling process. When a bearing is provided in the base portion of the pulley as shown in Fig. 1, the circumferential edge portion of the central opening 10b of the metal blank or workpiece 10a may be widened so as to form the base portion receiving the bearing 22. Forming of the base portion 16 may be carried out by per se well-known process, though the drawings do not clearly show the base forming process in a form illustrated in Figs. 1 to 3. The base portion 16 may be formed in the form of Fig. 8 by the processes illustrated in Figs. 5 to 7. It should be noted that, although the poly-V pulley illustrated in Figs. 1 and 4 are illustrated to have the base portion 16 to receive the bearing in order to form an idler pulley, the widened base portion is not always necessary to be formed. The workpiece 10a is positioned so that its outer edge opposes a first roller 30 with a sharp edge 30a. The first roller 30 serves to perform the slitting processes. The plane q bisecting the workpiece is aligned with the plane p bisecting the edge 30a of the roller 30. Both the roller 30 and the workpiece 10a are driven to rotate during the first step of the manufacturing process by appropriate devices such as lathes (not shown). In addition, the workpiece 10 and the first roller 30 are adapted to move toward and away from one another. In the preferred embodiment, the roller 30 moves toward and away from the workpiece 10a during the first slitting process of the groove rolling process. As shown in Fig. 9, the outer edge of the workpiece is divided into two sections 10c and 10d by the first roller 30. The sections 10c and 10d will have approximately the same volume. The first roller 30 also travels toward the workpiece far enough to compress the edges of the workpiece and thus thicken areas 10e and 10f. The travelling distance of the roller 30 may be so determined that the roller divides the edge of the workpiece into two sections and thicken the areas 10e and 10f to a desired thickness. After the first step, a second process is performed by means of a flat-top second roller 32. The second roller 32 has a broad, blunt edge 32a with a tapered section 32b to either side. Similarly to the first roller, the second roller 32 is adapted to move toward and away from the workpiece 10a. As shown in Fig. 10, by means of the second roller 32, the workpiece 10a is formed a flat-bottom recess 10g with peripheral flanges 10h. Then, the grooves 12 are formed in the floor of the recess 10g by means of a third roller 34 as shown in Fig. 11. As will be seen from Fig. 11, the third roller 34 has a plurality of sharp triangular working edges 34a. The number of working edges corresponds to the number of grooves to be formed in the floor of the flange wall. The height H of the edges corresponds to the depth D of the grooves 12. Similarly to the aforementioned first and second rollers, the third roller 34 is able to move toward and away from the workpiece. The tapered surfaces 34b of the edges 34a generally match the tapered surfaces 32b of the second roller 32 and guide the third roller as it moves toward the workpiece. By travel of the third roller 34 toward the workpiece, the material of the floor 10i is divided into triangular-cross-section ridges 12a. As a result, the V-shaped-cross-section grooves 12 are defined by the ridges 12a and the peripheral flanges 10h. As the third roller 34 moves toward the workpiece, it redistributes the material forming the flange wall into the groove 34c between the edges 34a to form the ridges 12a. Therefore, the stroke of the third roller will be approximately half of the desired peak-to-trough depth D of the groove. Since the material is deformed to define the grooves rather than cut or ground, no waste material will be produced. It should be appreciated that, although the shown embodiment concerns a pulley with three grooves, the number of the grooves is may be arbitrarily selected by selecting an appropriate roller for use in the third step. Figs. 12 through 15 illustrate a modification to the manufacturing process of the poly-V pulley. In this modification, the second roller with the flat working edge is replaced with a roller 40 with a number of rounded working edges 40a as shown in Fig. 14, The edges 40a are designed to form rounded ridges 10j and rounded grooves 10k in the workpiece which is first machined by the first roller as shown in Figs. 12 and 13 which are identical to Figs. 8 and 9. Thereafter, the multi-edged roller 34 is used as in the previous method to finish forming the poly-V grooves 12, as shown in Fig. 15, which matches Fig. 11. As shown in Fig. 16, at the beginning of the second process employing the second roller 40, the roller 40 is aligned so that its axis p' is coplanar with the axis q' of the workpiece 10, which has canted surfaces 10m formed in the first slitting process by means of the first roller. At first, only, the left- and right-hand edges 40a come into contact with the surfaces 10m of the workpiece. As the roller 40 is driven slowly into the workpiece, the workpiece is deformed such that some of the material of the workpiece is displaced to either side of the working edges 40a. The roller 40 reshapes the workpiece 10a solely by deformation, i.e. no cutting, grinding or removal of material is necessary. The material 10n displaced to the outside of the right- and left-hand edges 40a forms the outer flanges 10h of the flange wall 13 as shown in Figs. 17 and 18. On the other hand, the material 10p between the outer edges 40a is worked into conformation with the roller 40 to form rounded ridges as shown in Figs. 17 and 18. This second process produces rounded grooves which correspond positionally and volumetrically to the poly-V grooves 12 of the finished pulley. By the end of the predetermined stroke of the second roller the outer circumference of the workpiece is worked into a corrugated surface. As shown in Fig. 15, after this, the third roller 34 which is identical to that in the previous embodiment is applied to the workpiece to form the poly-V grooves 12. First, the planes of the working edges 34a are brought into alignment with the planes of the opposing rounded grooves 10k. As in the previous embodiment, the poly-V grooves 12 are then formed into the circumference of the pulley by means of the third roller. According to this modification, since the material of the workpiece and especially the region of the displaced material 10p, is preprocessed into corrugations by the second roller 40, the stresses created in the final process step, especially at the peaks of the ridges 10j will be greatly reduced. As a result, crest fold or crack in the foregoing manufacturing process can be successfully avoided. Figs. 19 to 25 show another modification of the above-mentioned first embodiment. In this modification, the first process, in which the edge of the workpiece 10a is slitted to form a crotch wide enough to receive the second roller 42, is separated into two substeps in order to speed up the overall process. First, a starting roller 36 with a relatively acutely pointed ridge 36a is used to slit the edge of the blank 10a as shown in Fig. 19. Subsequently, a flaring roller 38 with a broader ridge 38a than the first roller 30 can be used to quickly widen the groove around the edge of the workpiece 10a as shown in Fig. 20. In the second process of this modification, a modified second roller 42 is used in exactly the same way as in the previous modification. The second roller 42 is modified to provide four grooves in the final product and more importantly, it is modified to reduced the height of the central ridge, and so the volume of material in the central rounded ridge in the partially fabricated flange wall. Specifically, the modified second roller 42 can be viewed as having three working edges 42a, the central edge 42a-3 of which is actually the synthesis of two relatively low peaks. Thus, the center edge 42a-3 is wider and shallower than the left and rightmost edges 42a-1 and 42a-2. Preferably, the width of the center edge 42a-3 is approximately twice of that of the edges 42a-1 and 42a-2. After completion of the second process, the workpiece is further machined with the third roller 34 to have the desired number of V-shaped grooves 12. This shown modification is especially adapted to form an even number of grooves which implies an odd number of ridges 10q and 10j. The third roller 34 is selected to have the same even number of edges 34a. With the foregoing modification, a pulley with an even number of grooves can be manufactured without crest fold or crack on the central ridge. Fig. 26 to 28 illustrate a further modification of the preferred embodiment of the poly-V pulley manufacturing method in accordance with the present invention. The workpiece 10a is subjected to a process for forming the poly-V grooves in the flange wall on the periphery thereof. In this modification, the first roller of the aforementioned embodiments is replaced with a roller 50, as shown in Fig. 26. The roller 50 has a stepped edge 52. The stepped edge 52 is provided with a plurality of steps 52a which extend essentially parallel to the rotational axis of the pulley. The roller 50 with the stepped edge 52 is adapted to distribute material at positions coinciding with ridges between the V-shaped grooves to be formed, in such a way that after completing of slitting and compressing, the volume of material delineated by the positions of the finished ridges essentially match those of corresponding regions of the finished pulley. In the shown modification, the edge 52 is further provided with a sharp working edge 52b lying in the central plan q of the roller 50. Each step 52a is so arranged as to correspond to the position of a corresponding working edge 34a of the third roller 34. For instance, as shown in Figs. 26 and 29, the positions of the steps 52a coincide with the positions at which the finished poly-V grooves will be formed. Therefore, each of the edges 34a of the roller 34 will be aligned with one of the steps in the workpiece 10a formed by means of the roller 50. However, the working edges 34a will not necessarily be centered over the corresponding steps but rather will be so aligned that the volume of material finally distributed to either side of each working edge will corresponding to the volumes of the ridges and other features to be formed in the final product. As will be appreciated from Figs. 29 and 30, the volumes a, b, c, d, e and f of the regions A, B, C, D, E and F of the flange wall of Fig. 29 as formed by means of the roller 50 approximate the volumes a1, b1, c1, d1, e1 and f1 of the regions A1, B1, C1, D1, E1, and F1 of the finished pulley of Fig. 30. A roller 54 has one or more rounded working edges 54a similar to the rollers 40 and 42, as shown in Fig. 27. As described previously, the material of the workpiece 10a is redistributed by the rounded edges 54a. Then, the workpiece is worked into its final form by means of the third roller 34 with the sharp working edges 34a, the positions of which correspond to those of the rounded edges of the roller 54. According to this second embodiment, since the material which will eventually form the features of the flange wall is preliminarily distributed by means of the roller 120, an even final distribution of the material is ensured. As a result, the depths of the grooves, or alternatively the heights of the ridges can be matched. Therefore, the present invention satisfactorily and successfully fulfills all of the objects sought therefor.

Claims: A method for forming a poly-V-pulley having an annular flange wall with a plurality of V-shaped grooves and a web extending radially and inwardly from said annular flange wall, wherein said V-shaped grooves are cold-rolled on said annular flange wall, characterized by the steps of supplying a substantially flat metal blank in a circular disk form with a predetermined thickness, slitting the peripheral edge of said metal blank essentially at its axial center and thickening the peripheral edge by means of a first roller, compressing and widening said slitted peripheral edge of said blank by means of a second roller to form said flange wall, in such a manner that the slitted and thickened peripheral edge has an axial length substantially corresponding to the axial length of said flange wall and that said web is positioned essentially at the axial center of the flange wall, and finish rolling the compressed and widened edge by means of a third roller such as to obtain a finished flange wall with said plurality of V-shaped grooves. The method as set forth in claim 1, which further comprises a step of distributing the material of said widened edge of said blank into regions having volumes corresponding the volume of ridges between the V-shaped grooves to be formed and to the volumes of the lateral edges of the flange wall to be formed, said distributing step being performed between the step in which the circumferential edge is widened and the step in which the grooved flange wall is formed. The method as set forth in claim 1, which further comprises a step of forming essentially U-shaped ridges on the widened circumferential edge of said blank, said U-shaped ridge-forming step being performed before the step in which the grooved flange wall is formed. The method as set forth in claim 2, wherein said distributing step includes the step of forming a series of annular steps in said widened edge concentric about the rotational axis of said blank, the axial position of each of said annular steps coinciding with that of one of the grooves to be formed in the flange wall. A poly-V-pulley made from a substantially flat metal blank, characterized by a substantially annular web section (104) and an outer cylindrical section formed by slitting an outer peripheral edge of said metal blank, widening and thickening the slitted peripheral edge for forming an annular Range section (103) extending along an outer peripheral edge of said web section, and cold-rolling a plurality of grooves (102) in said annular flange section, said web joining said annular flange section at the axial center thereof. A poly-V-pulley as set forth in claim 5, comprising a bearing rest (108) integrally formed with said web section by bending, said bearing rest having an axially extending first section for setting a bearing (110) and a radially extending section inwardly extending from said first section for restricting axial displacement of said bearing, said bearing rest being formed along an inner peripheral edge of said web section. Claims for the following Contracting States: FR A method for forming a poly-V-pulley having an annular flange wall with a plurality of V-shaped grooves and a web extending radially and inwardly from said annular flange wall, wherein said V-shaped grooves are cold-rolled on said annular flange wall, characterized by the steps of supplying a substantially flat metal blank in a circular disk form with a predetermined thickness, slitting the peripheral edge of said metal blank essentially at its axial center and thickening the peripheral edge by means of a first roller, compressing and widening said slitted peripheral edge of said blank by means of a second roller to form said flange wall, in such a manner that the slitted and thickened peripheral edge has an axial length substantially corresponding to the axial length of said flange wall and that said web is positioned essentially at the axial center of the flange wall, and finish rolling the compressed and widened edge by means of a third roller such as to obtain a finished flange wall with said plurality of V-shaped grooves. The method as set forth in claim 1, which further comprises a step of distributing the material of said widened edge of said blank into regions having volumes corresponding the volume of ridges between the V-shaped grooves to be formed and to the volumes of the lateral edges of the flange wall to be formed, said distributing step being performed between the step in which the circumferential edge is widened and the step in which the grooved flange wall is formed. The method as set forth in claim 1, which further comprises a step of forming essentially U-shaped ridges on the widened circumferential edge of said blank, said U-shaped ridge-forming step being performed before the step in which the grooved flange wall is formed. The method as set forth in claim 2, wherein said distributing step includes the step of forming a series of annular steps in said widened edge concentric about the rotational axis of said blank, the axial position of each of said annular steps coinciding with that of one of the grooves to be formed in the flange wall. A poly-V-pulley made from a substantially flat metal blank comprising a substantially annular web section (104) an outer cylindrical section formed by slitting an outer peripheral edge of said metal blank, widening and thickening the slitted peripheral edge for forming an annular flange section (103) extending along an outer peripheral edge of said web section and cold-rolling a plurality of grooves (102) in said annular flange section, said web joining said annular flange section at the axial center thereof, and a bearing rest (108) integrally formed with said web section by bending, said bearing rest having an axially extending first section for setting a bearing (110) and a radially extending section inwardly extending from said first section for restricting axial displacement of said bearing, said bearing rest being formed along an inner peripheral edge of said web section.

Inventors: MATSUOKA, KEN, YAMAZAKI, MASANOBU
Applicants: FUJI KIKO COMPANY, LIMITED
Application year: 1984
Main classification: B21H1
IPC codes: F16H7, B21D53, B21H1