Light wheel disk with large space for brake

Process for producing a motorized land vehicle wheel, in general having a wheel disk and an essentially cylindrical rim, the wheel disk being obtained from a blank plate of specific thickness subjected to several shaping operations, and composed of an essentially flat central part having an opening that serves to center and attach the wheel to the vehicle's axle hub, an essentially conical interior riser, another inverted conical part that defines, with the interior riser, a curved tip that has a large radius of curvature, the inverted conical part terminating in a flanged edge used to join the disk to the rim, a process characterized in that during the forming operation of the flanged edge, the plate is laminated in such a way as to preserve or reduce the thickness of the base plate.

The process according to the invention concerns the production of a motorized land vehicle wheel 1 , in general having a wheel disk 2 and an essentially cylindrical rim 3 , the wheel disk 2 being obtained from a blank plate 4 of specific thickness subjected in particular to various shaping operations, and composed of an essentially flat central part 5 having an opening 6 used to center and attach the wheel 1 to the vehicle's axle hub, an essentially conical interior riser 7 , another inverted conical part 8 defining, with the interior riser 7 , a rounded tip 9 that has a large radius of curvature, the inverted conical part 8 terminating in a flanged edge 10 designed to join the disk 2 to the rim 3 . According to the invention, during the operation to form the flanged edge 10 , the blank plate 4 is laminated around the whole periphery of the disk 2 in order to preserve the thickness of the plate if it is optimized, or to reduce the thickness of the base plate in order to optimize the mechanical characteristics of said wheel 1 . The problem resolved in particular is that of providing just the right thickness for the flanged edge. A reduction of thickness in this area allows the inside diameter of the disk to be increased. An advantage of the proposed solution is the decrease in the thickness of the wheel disk in the area of the flanged edge. This decrease in thickness is accomplished during the flanged edge operation, included in the stamping as represented in FIGS. 2 a , 2 b , 2 c , 2 d . The operation consists in laminating the blank plate during the flanged edge operation. The first stamping operations, diagrammed in FIGS. 2 a , 2 b , 2 c , are standard. FIG. 2 a represents a first stamping operation to form the interior riser 7 , FIG. 2 b represents a second stamping operation to form the inverted conical part 8 , FIG. 2 c shows the operation of cutting the periphery of the wheel disk before stamping the flanged edge 10 , and FIG. 2 d shows the wheel disk after formation of the flanged edge 10 . At the end of the laminating operation of the flanged edge 10 , the periphery of the blank is cut off. The diameter of the cut can be reduced to accommodate the overlength caused by the laminating operation. FIG. 3 a shows an image of part of a vehicle wheel in axial cross section produced in the standard manner, and FIG. 3 b shows the same wheel part produced according to the invention. In the standard method of forming, the part 11 of the blank plate used to form the flanged edge is contracted, thus necessarily causing an increase in the thickness of the blank plate. According to the invention, the forming by lamination of the portion of the blank plate to be used to form the flanged edge 10 is subject to a forced drawing, generating an elongation of the formed part; the drawing can either preserve the thickness of the base blank plate, or if needed, reduce the thickness of the blank plate in a constant or progressive manner. In this same laminating operation, the final edge 12 of the periphery of the laminated part can be beveled instead of straight. The laminating of the part of the blank used for the flanged edge can be done with or without scalloping, depending on the diameter of cut chosen following the laminating operation of the flanged edge. The presence of scalloping is not prohibitive. It should be noted that this technique requires more press power than what is used for the standard flanged edge operation. According to the invention, the flanged edge laminating operation requires suitable tooling. As shown in FIG. 4 , the tool 15 of the stamping device for motorized land vehicle wheel disk 2 is composed of an essentially cylindrical die 16 having, in axial cross section, the profile of the disk, i.e., the profile of the essentially flat central part, of the essentially conical interior riser and of the conical part, a cylindrical blank holder 17 having, in axial cross section, the complementary shape of the die 16 and a header die 18 composed in particular of a ring 19 coaxial to the die 16 and to the blank holder 17 and the interior surface of which has a conical laminating part 20 . the conical part of the laminating tool has an aperture angle of between 10° and 40°, and preferably 30°, the conical part of the laminating tool has a die mouth radius of between 8 mm and 20 mm, and preferably 12 mm; the conical part of the laminating tool has an end-of-die radius of between 2 mm and 20 mm, and preferably 5 mm; the tool has on its surface a hardening lining selected from among TiN, CrN, IC carbon, non-crystalline carbon, or any other lining suited to improving the laminating conditions; the surface of the tool has an Ra roughness of between 0.2 &mgr;m and 0.5 &mgr;m, and preferably between 0.3 &mgr;m and 0.4 &mgr;m. The geometry of the tool 15 is suited for the laminating operation as well as for reducing to the desired thickness. The final thickness of the flanged edge is directly related to the gap between the header die 18 and the die 16 . In effect, the size of the tool 15 must be able to withstand heavy loads, and must also resist frictional forces. In one example of application the header die 18 has a female cone with an aperture angle 21 of 30°, a die mouth radius 22 of 15 mm and an end-of-die radius 23 , laminating radius, of 20 mm. The lining of the tool 15 is important. It determines the value of die header load, lateral loads, stripping, and whether or not wear and sticking phenomena occur. A lining of TiN, CrN, IC carbon or non-crystalline carbon is advised. The roughness is important to allow better trapping of the oil. An Ra on the order of 0.3 &mgr;m or 0.4 &mgr;m in the example seems optimal. According to the forming procedure used, an additional circular cutting operation may be necessary. This cut can also be used to scallop the flanged edge in the areas that will not be used to weld the disk to the rim. The final reduction in weight of the wheel according to the invention is about 0.3 kg for a 15-inch wheel disk. Variations of embodiment concern the position of the cut, in the process of producing the wheel, to cut the flanged edge to length. This cut can be made prior to the flanged edge operation or at the end using a cam cut if it is done on the press line, or by using a cut-off tool.