Abstract:
A method of forming a one piece vehicle wheel is disclosed which method includes the steps of initially forging a rough vehicle wheel shape which is then subjected to a series of spinning operations to contour the rim portion thereof. Part of the final contouring of the rim portion of the wheel is performed without mandrel backing. The entire final contouring is performed after a solution heat treatment that imparts a T4 material condition thereto in order to assure accurate formation thereof. Additionally, if desired, final machining and/or trimming operations may be performed without removing the wheel from the final contouring apparatus.

Description:
This is a division of application Ser. No. 396,306, filed July 8, 1982, now U.S. Pat. No. 4,528,734. 
    
    
     The present invention relates generally to the formation of vehicle wheels and more particularly to an improved method for forming a one piece vehicle wheel by a spin forging process. 
     Numerous attempts have been made to provide a method to form a one piece vehicle wheel from a lightweight alloy which is both economical and efficient. Such one piece wheels offer many advantages over conventional welded steel wheels or the like particularly with regard to the present day efforts toward improved fuel efficiency. Not only do these wheels facilitate the use of lighter weight alloys such as aluminum but they also facilitate the structuring of the wheel itself to minimize cross sectional material area in areas of low stress and increase same in the higher areas of stress thereby providing a strong wheel while minimizing the overall weight thereof. 
     The method of the present invention begins with a cast log from which a billet is severed which is then subjected to a series of hot forging operations to form the wheel center and a pair of rim flange legs. Thereafter, the forging is subjected to a trimming operation. The forged and trimmed wheel blank is then rough formed by means of a pair of spinning rollers which operate to axially elongate one of the rim flange legs and to selectively vary the cross sectional thickness thereof. This rough formed wheel is then subjected to a first solution heat treatment after which final contouring and shaping is performed by additional spinning rollers. A portion of this final contouring is performed without a backing mandrel or chuck which substantially reduces the attendant tooling complexity and costs as well as facilitating mounting on and removal of the finally formed wheel from the chuck. Additionally, suitable cutters may be associated with the final spinning apparatus to face the mounting surface portion of the wheel center prior to removal of the wheel from the final spinning apparatus. Performing this machining operation on the same apparatus as the final spinning assures concentricity of the rim and wheel center. Upon final contouring of the wheel, final machining of valve and bolt holes may be done followed by suitable appearance finishing and heat treating to thereby provide a finished one piece vehicle wheel. 
     Additional advantages and features of the present invention will become apparent from the subsequent description and the appended claims taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIGS. 1 through 4 are sectioned views showing successively the initial steps of forming a one piece vehicle wheel in accordance with the present invention beginning with the severing of a billet from a cast log through a series of sequential hot forging operations, the sections being taken along a radial plane extending along the axis of rotation of the wheel; 
     FIGS. 5a and 5b are fragmentary sectioned views of the forging shown in FIG. 4 and illustrating an initial rough forming thereof by first and second spinning rollers respectively, the sections being taken along a radial plane extending along the axis of rotation of the vehicle wheel; 
     FIGS. 6a and 6b are fragmentary sectioned views of the rough formed wheel similar to those of FIGS. 5a and 5b but showing subsequent contouring thereof by additional spinning rollers; 
     FIG. 7 is a fragmentary sectioned view of the wheel similar to that of FIGS. 6a and b showing the sequential movement of the final spinning roller; and 
     FIG. 8 is a fragmentary sectioned view of the one piece vehicle wheel fully formed in accordance with the present method, the section also being taken along a radial plane extending along the axis of rotation. 
     FIG. 9 is a block diagram showing the basic method. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings and in particular to FIGS. 1 through 4, the initial forming steps of the present invention are shown and comprise severing a suitably sized generally cylindrical billet 10 from a cast log of a suitable forgeable and spinnable material such as for example an aluminum or other suitable alloy. The thus severed billet 10 is then heated to a suitable temperature to render it suitable for a series of hot forging operations such as for example approximately 850° to 900° F. for an aluminum alloy billet. The billet 10 is then progressively moved though a series of forging operations and transformed thereby first to an enlarged diameter biscuit 12 as shown in FIG. 2 to a partially formed blank 14 and ultimately to a fully forged wheel blank 16 of the general shape shown in FIG. 4 which includes in cross section a wheel center 18 and a rim portion 20 having a relatively long axial leg 22 and a relatively short radial leg 24 with wheel center 18 joining the rim portion 20 in the vicinity of the juncture 26 of axial and radial legs 22 and 24. 
     Once the forging of the billet has been completed, the outside diameter of the radially extending leg may be trimmed and any flashing surrounding the central opening 25 in the wheel center 18 of the forged wheel blank 16 removed. Additionally it should be noted that should it be desired, any openings 27 or the like may also be partially or even fully formed on the wheel center. The number, size and arrangement of any such openings 27, as well as the desirability of forming same at this stage, will depend on the design and/or the need for anchors for subsequent operations. It shold be noted that preferably the forming of these openings will be deferred to avoid the possibility that subsequent forming of the forging may result in collapsing or other deformation thereof. 
     In any event, the thus completely forged wheel blank 16 is then mounted on a chuck 28 having an externally contoured surface 30 generally as shown in FIGS. 5(a) and 5(b) which is positioned in adjacent radial alignment with the radially inner surface 32 of axially extending leg 22. This contoured surface 30 has an axial dimension substantially greater than that of axial leg 22. Chuck 28 also has a leading surface 33 contoured to engage the axially inner surface 34 of wheel center 18. A tail stock 36 is provided which engages the opposite surface 38 of the wheel center 18 so as to clamp the wheel forging 16 against surface 32 of chuck 28. The thus clamped wheel forging 16 and associated tail stock 36 and chuck 28 are then rotated about the axis of wheel forging 16 while the rounded peripheral edge 40 of metal spinning roller 42 is advanced into engagement with wheel forging 16 at approximately juncture 26 between the axial and radially extending legs 22 and 24. Metal spinning roller 42 is forced generally radially inwardly at juncture 26 and thence moved generally axially away from the radially outwardly extending leg 24 so as to deform and reduce the thickness of and to lengthen or extend axial leg 22 along contoured surface 30. 
     As shown in FIG. 5(b), a second metal spinning roller 44 also having a rounded peripheral edge 46 is advanced and forced into engagement with forged wheel 16 at approximately juncture 26 simultaneously or subsequent to engagement of roller 40 therewith. Roller 44 is then also advanced generally axially along leg 22 and away from radial leg 24 during which it is also simultaneously moved in a generally radial direction so as to roughly contour axial leg 22 thereby varying the radial thickness thereof. Preferably rollers 42 and 44 will be positioned on diametrically opposite sides of wheel 16 and will operate substantially simultaneously to move axially along axial leg 22 with roller 44 trailing slightly behind roller 42. As shown the peripheral edge 40 of metal spinning roller 42 has a substantially greater radius of curvature than the peripheral edge 46 of metal spinning roller 44. While the generally opposite positioning and simultaneous movement of rollers 42 and 44 offers the advantage of reduced processing time, should it be desirable these two forming steps may also be performed sequentially on the same or different spinning apparatus. 
     Once the wheel has been rough formed by forming rollers 42 and 44 it is then subjected to a solution heat treatment to impart a T4 material condition thereto. For a 6061 aluminum alloy, this heat treatment may comprise raising the temperature to the rough formed wheel structure to approximately 980° F. after which it may be liquid quenched. 
     Next the forged rough formed and heat treated wheel 16 is mounted and clamped between a second chuck 48 and tail stock 50. Chuck 48 also has an external contoured surface 52 generally as shown and which conforms substantially to the final shape of the inside surface of the finished rim portion of the wheel from the minimum inside diameter portion 54 of the drop center to the axially outer surface 56 of the tire bead retaining flange 58 disposed furthest from the wheel center 18. Contoured surface 52 also extends generally axially from the minimum inside diameter portion of the drop center 54 to and engages the inside axial surface 34 of the wheel center 18. Tail stock 50 will also have a contoured surface 60 conforming to the radially outside surface 38 of the wheel center 18 and the outside surface of the tire bead retaining flange 62 most adjacent thereto. Once clamped, forged rough formed wheel 16 and associated tail stock 50 and chuck 48 will then be rotated and another metal spinning roller 64 also having a rounded peripheral edge will be advanced and forced into engagement with wheel 16 approximately at or adjacent juncture 26 and thence moved in a generally radially outwardly direction and thence axially toward tailstock 50 so as to deform tire bead retaining flange 62 thereover. This sequence of movement is shown in FIG. 6a as including movement of roller 64 into position 1 and thence through positions 2 and 3. Roller 64 will then be moved out of engagement with the rotating wheel 16 and in a generally axially direction into position 4 as indicated in FIG. 6a whereupon it will once again be advanced and forced into engagement with axial leg 22 at a position axially spaced from the wheel center 18 so as to cause a generally radially inward deformation of a portion of axial leg 22 into engagement with contoured surface 52 of chuck 48 thereby forming a first portion of the drop center 54. Thereafter metal spinning roller 64 will be moved in a generally axial direction away from the wheel center 18 so as to cause the generally axially extending leg 22 of the forged rough formed wheel 16 to roughly conform to surface contour 52 of the chuck 48. This process is shown in FIG. 6(b) by the successive advancement of the metal spinning roller from the position indicated by reference number 5 through positions 6, 7, 8, and finally into position 9 wherein the bead retaining flange 58 is deformed. 
     It should be noted that while metal spinning roller 64 has been described and shown as initially moving through successive steps 1 through 3, and then from position 4 through 9, should it be desired, the movement of this roller from position 4 through 9 may be carried out prior to the sequence of movement from positions 1 through 3. It should also be noted that both the force and angle or direction of movement of roller 64 from position 4 to 5 wherein the axial leg is being radially deformed to initially form the drop center portion of the wheel 16 must be carefully controlled relative to the material being formed so as to prevent collapse or other deformation of the portion of axial leg 22 extending to bead retaining flange 62 which is not supported by chuck 48. 
     Another metal spinning roller 66 is also preferably moved into engagement with the rough formed wheel structure while it is being rotated between the contoured chuck 48 and tail stock 50 and as shown in FIG. 7, this second metal spinning roller 66 will be initially moved into engagement with juncture 26 of the axial and radially extending legs 22 and 24 and thence moved in a general radially outward direction and thereafter in an axial direction away from the axially extending leg so as to finish form bead retaining flange 62. This is represented by the successive movement of the metal spinning roller from position 1 through position 4 in FIG. 7. Thereafter metal spining roller 66 is moved out of engagement with rotating wheel 16 and then in a generally axial direction into position 4a whereupon it is moved in a generally radial direction back into engagement with juncture 26 between axial and radially extending legs 22 and 24. Thereafter, metal spinning roller 66 is moved in a generally axial direction so as to finally form axial flange portion 68 which defines a bead seat. This movement is shown by the advancement of roller 66 from position 5 in FIG. 7 through position 6. Thereafter, metal spinning roller 66 is moved in a generally radial inward direction so as to finally form a first wall portion 70 of the drop center section and thence in a general axial direction so as to finally form the drop center portion against contoured surface 52 of chuck 48. Continued generally axial and radially outward movement of metal spinning roller 66 will cause final deformation of the generally axially extending leg 22 into substantial conformance with the contour provided on the contoured surface 52 of chuck 48 which, as previously mentioned, conforms to the final desired inner contour of the vehicle wheel. 
     While the first final forming steps shown and described with reference to FIGS. 6a and 6b and second final forming steps shown in FIG. 7 may be performed separately in sequence on the same or different apparatus, it is preferred that they be performed simultaneously with rollers 64 and 66 positioned on diametric opposite sides of wheel 16 in order to reduce the overall time required for manufacturing of the wheel 16. In this respect the position sequence reference numbers of roller 64 and roller 66 correspond. That is, when roller 64 is in position 1, roller 66 will also be in position 1, as roller 64 moves to position 2, roller 66 will also move to position 2. It is noted that roller 64 performs the major forming and hence will be advanced slightly ahead of roller 66 which finishes the forming operation. Also, it is noted that the peripheral edge of roller 64 is provided with a substantially greater radius of curvature than the peripheral edge of roller 66. 
     It is noted that the final forming of bead seat 68 is performed without support from chuck 48. Thus, in order to avoid deflection of this seat 68 during the final forming pass of roller 66, roller 64 is advanced from position 4 to position 5 (as shown in FIG. 6(a)) and remains there while roller 66 is moved from position 4a to position 5 and thence through position 5(a) and to position 5(b). 
     While the above forming sequence has indicated that rollers 64 and 66 are moved sequentially from position 1 through 9, if desired, the forming steps represented by movement of rollers 64 and 66 from position 4 through 9 may be performed prior to the steps represented by movement of rollers 64 and 66 from position 1 though position 3. 
     Once rim portion 20 of wheel 16 has thus been final formed to the desired shape and preferably before it is removed from chuck 48, it is desirable to face mounting surface 72 of wheel center 18 and to machine center opening 25 to its finished size. Accordingly, a plurality of circumferentially spaced cutters 74 are provided and axially reciprocable with respect to wheel 16. As shown in FIG. 7, each of the cutters 74 will be substantially identical and will include a first cutting surface 76 operative to initially engage and machine the periphery of opening 25 to size as wheel 16 continues to rotate. A second cutting surface 78 is provided which will move into engagement and face mounting surface 72 of wheel center 18. 
     Performing this cutting operation while wheel 16 is still clamped on the final forming apparatus offers several advantages in that it insures that the center opening 25 and mounting surface 72 will be precisely concentric and true with respect to the tire supporting bead seats. 
     Thereafter the finally contoured wheel 16 may be removed from between the chuck 48 and tail stock 50 and final machining operations performed thereon such as to finally trim ends 80 and 82 of the bead retaining rim flanges, drill and counterbore the valve hole 84 and drill and chamfer bolt holes 86 as necessary. Upon completion of these machining operations the completed wheel may then be finished in any desired manner such as with a clear coat and/or painting. Additionally, it is also necessary to subject the finished wheel to a precipitation heat treatment in order to increase the hardness thereof and achieve a T6 material condition. For example, when a 6061 aluminum alloy is used this may be achieved by subjecting the finished wheel to a temperature of around 350° F. for a period of about eight hours. It should be noted, however, that this precipitation heat treat procedure may be varied slightly because the spinning operations heretofore described have been carried out with a material condition of T4. 
     While it will be apparent that the preferred embodiment of the invention disclosed is well calculated to provide the advantages and features above stated, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope or fair meaning of the subjoined claims.