METHOD OF MANUFACTURING AN ALUMINUM ALLOY WHEEL RIM

Abstract

A method of manufacturing a wheel rim for a motor vehicle comprises the steps of a strip of aluminum alloy sheet material having a predetermined cross-section suitable for forming into a wheel rim by extrusion molding, pressing the strip step-by-step lengthwise by an upper mold and a lower mold having complimentary profiles for causing the strip to have predetermined profiles as a hoop with a formed gap between the both ends, welding the gap to form an unfinished wheel rim, and annealing, shaping, heat treating, and polishing the unfinished wheel rim to form a finished wheel rim.

Description

FIELD OF THE INVENTION

[0001] The present invention relates to the field of wheel rim manufacturing and more particularly to an improved method of manufacturing an aluminum alloy wheel rim.

BACKGROUND OF THE INVENTION

[0002] Methods for making wheel rims are well known. For example, U.S. Pat. No. 4,589,177 to Secolo et al. and U.S. Pat. No. 4,185,370 to Evens both disclosed such methods. The method of Evans's Patent is illustrated in FIGS. 1 to 3. In FIG. 1, a strip 1 of aluminum sheet material used to form a wheel rim is shown. In FIG. 2, such strip 1 is formed into a hoop 3 and the opposing ends flash butt welded forming weld line 2. The thus formed hoop is subsequently passed through multiple forming operations (e.g., press and roll forming operations) resulting in a finished wheel rim 4 having desired sectional profiles shown in FIG. 3.

[0003] But this is unsatisfactory for the purpose for which the invention is concerned for the following reasons: Firstly, a variety of expensive rollers are employed in the roll forming operations in order to manufacture a wheel rim having desired sectional profiles. Further, such manufacturing processes are complex, time consuming, labor intensive, and excessive energy consumption. This results in an increase of manufacturing cost. Secondly, as stated above a series of forming operations (e.g., press and roll forming operations) are performed on the hoop to form a wheel rim having desired sectional profiles. But the formed wheel rim may be deformed or too thin due to non-uniform pressing in these manufacturing processes. As a result, the formed wheel rim is unbalanced in weight or unacceptable low in hardness, thus adversely shortening the useful life of wheel rim. Thus improvement exists.

SUMMARY OF THE INVENTION

[0004] It is therefore an object of the present invention to provide a method of manufacturing a wheel rim for a motor vehicle comprising the steps of (a) forming a strip of aluminum alloy sheet material having a predetermined cross-section suitable for forming into a wheel rim by extrusion molding; (b) pressing the strip step-by-step lengthwise by an upper mold and a lower mold having complimentary profiles for causing the strip to have predetermined profiles as a hoop with a formed gap between the both ends; (c) welding the gap to form an unfinished wheel rim; and (d) annealing, shaping, heat treating, and polishing the unfinished wheel rim to form a finished wheel rim.

[0005] The above and other objects, features and advantages of the present invention will become apparent from the following detailed description taken with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] FIG. 1 is a perspective view showing a strip of sheet material used to form a wheel rim by a conventional manufacturing method;

[0007] FIG. 2 is a perspective view showing the strip of FIG. 1 formed into a hoop;

[0008] FIG. 3 is a perspective view showing the wheel rim of FIG. 1 in its final configuration;

[0009] FIG. 4 is a perspective view showing an unfinished wheel rim of aluminum according to a first preferred embodiment of the method of the invention;

[0010] FIG. 5 is a perspective view showing molds and rollers used to form the wheel rim according to the method of the invention;

[0011] FIG. 6 is a perspective view showing an unfinished wheel rim of aluminum according to a second preferred embodiment of the method of the invention;

[0012] FIG. 7 is a fragmentary enlarged view of FIG. 6;

[0013] FIG. 8 is a side view of FIG. 6;

[0014] FIG. 9 is a perspective view showing the wheel rim of FIG. 6 formed into a hoop;

[0015] FIG. 10 is a sectional view taken along line X-X of FIG. 9 showing a soldering of the hoop for forming a wheel rim;

[0016] FIG. 11 is a sectional view showing the deformed hoop of FIG. 9 after undergoing the step of molding; and

[0017] FIG. 12 is a sectional view showing the assembly of wheel rim of the invention with a disk.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Referring to FIGS. 4 to 6, there is shown a method of manufacturing an aluminum alloy wheel rim in accordance with the invention comprising the steps of forming a strip 10 of aluminum alloy sheet material having a predetermined cross-section suitable for forming into a wheel rim by extrusion molding, pressing the strip 10 by an upper mold 20 and a lower mold 30 respectively, and bending both ends of strip 10 to forming a bent end having a predetermined curvature &thgr;.

[0019] FIGS. 4 and 5 show a first preferred embodiment of the invention. Upper mold 20 and lower mold 30 are activated by a lever and a seat of a hydraulic press (not shown) respectively. The pressing sides 21 and 32 of molds 20 and 30 are of the cross-sections met with the predetermined cross-section of the stripe 10 allowing the strip 10 being placed between molds 20 and 30. Both ends of strip 10 are bent to form a predetermined curvature &thgr;. Once the hydraulic press is activated molds 20 and 30 will press on strip 10 from opposite directions, thus forming a predetermined curvature e thereon. The degree of curvature &thgr; is depending on manufacturing process. Preferably, curvature &thgr; is in the range between 15 to 60 degrees. Further, the radius of curvature &thgr; is substantially the same as that of formed wheel rim. In the embodiment, a roller 40 is provided in either side of upper mold 20. The wheel mounts 41 of roller 40 are coupled to lever of the hydraulic press. Rollers 40 are activated in synchronous with the activation of upper mold 20. Hence, the unchanged section of strip 10 adjacent to the deformed section thereof will be deformed continuously along the curvature &thgr;. This can prevent an undesired discontinuous deformation of strip 10 between the formed section of strip 10 and the adjacent unchanged section thereof from occurring.

[0020] As shown in FIG. 7, a lengthwise non-uniform deformation is occurred in both ends of strip 10 each having a predetermined curvature &thgr; due to molecular compression of the metal strip 10. It is found that the deformation &Dgr;Lc in the center of the lengthwise direction of strip 10 is larger than &Dgr;Ls in either side thereof. For ensuring strip 10 to be formed as a hoop and a gap formed between two ends of the hoop after performing subsequent forming processes, a non-uniform deformation &Dgr;L on either end of strip 10 will be cut out by a bench saw as shown in FIG. 8. Hence, only a desired length L of strip 10 will be preserved. Moreover, a milling machine is used to form a guide angle on either end of strip 10. As such, both ends of strip 10 may be proximate after strip 10 is formed as a hoop. As an end, a V-shaped gap is formed between both ends of strip 10 (FIG. 10). Then strip 10 is again placed between molds 20 and 30. The unchanged section of strip 10 is pressed step-by-step by molds 20 and 30 lengthwise. Further, bend the strip 10 to form a hoop 50 (FIG. 9). A V-shaped gap 51 is formed between both ends of hoop 50. A point soldering 60 is performed on the gap 51 for partially connecting the both ends of hoop 50 together. Then a welding is performed on V-shaped gap 51 to melt the aluminum alloy solder 61 so as to unite the both ends of strip 10 together (FIG. 10). An unfinished wheel rim 50 is thus formed. The invention then anneal the unfinished wheel rim 50 to eliminate stress concentration in the gap 51 portion by rearrange the molecular structure of the unfinished wheel rim 50. After annealed, such unfinished wheel rim 50 is placed between an upper mold 81 and a lower mold 82 of another hydraulic press (not shown) as shown in FIG. 11. Upper mold 81 and lower mold 82 are activated by a lever and a seat of the another hydraulic press respectively. A wheel rim to be formed has the same profiles as the junction of molds 81 and 82 since molds 81 and 82 have complimentary profiles. Also, any irregularity formed on the unfinished wheel rim 50 will be eliminated after molds 81 and 82 pressing on the inner face of unfinished wheel rim 50. This substantially forms an unfinished wheel rim 50 having a desired size. In addition, a series of heat treatment processes are performed on the unfinished wheel rim 50 so as to cure the metal material and increase the strength. Moreover, a polishing is performed on uneven portion of the unfinished wheel rim 50 to form a finished wheel rim having a smooth surface.

[0021] In another preferred embodiment of the method of the invention (FIG. 4), a strip 10 of aluminum alloy sheet material having a predetermined cross-section suitable for forming into a wheel rim by extrusion molding further comprises a lengthwise rib 11 thereon. In the second preferred embodiment of the method of the invention (FIG. 6), strip 10 is then placed between molds 20 and 30 facing a pressing side 21 and a pressing side 32 thereof respectively. Upper mold 20 and lower mold 30 are activated by a hydraulic press. A well 31 is provided on pressing side 32 sized to receive the rib 11. Then a series of forming operations (e.g., press and roll forming operations) are performed on strip 10 to form a hoop. Thereafter, welding, annealing, shaping, heat treatment, and polishing operations are performed to form a finished wheel rim 50 having a perimetric rib 11 along inner side. Also, a plurality of equally spaced holes 13 are formed along rib 11 (FIG. 12). A plurality of fasteners 90 are driven to fix a disk 70 onto the rib 11 of wheel rim 50 through the holes 13. The wheel rim 50 may then be installed to axle of a motor vehicle to secure them together via the disk 70. In brief, the advantages of the invention are the following: the equipment required is simple and inexpensive. The quality of formed aluminum alloy wheel rim is high. No welding operation is required for fastening wheel rim 50 and disk 70. The provision of rib 11 greatly enhances the strength of finished wheel rim 50.

[0022] While the invention has been described by means of specific embodiments, numerous modifications and variations could be made thereto by those skilled in the art without departing from the scope and spirit of the invention set forth in the claims.

Claims

1. A method of manufacturing a wheel rim for a motor vehicle comprising the steps of:

forming a strip of aluminum alloy sheet material having a predetermined cross-section suitable for forming into a wheel rim by extrusion molding;

pressing said strip step-by-step lengthwise by an upper mold and a lower mold having complimentary profiles for causing said strip to have predetermined profiles as a hoop with a formed gap between said both ends; and

welding said gap to form an unfinished wheel rim.

2. The method of claim 1, wherein said strip of aluminum alloy sheet material having a predetermined cross-section suitable for forming into a wheel rim by extrusion molding further comprises a lengthwise rib 11 thereon.

3. The method of claim 2, wherein said upper and lower molds are coupled to and activated by a lever and a seat of a hydraulic press respectively, pressing sides of said molds are of the cross-sections met with the predetermined cross-section of the stripe allowing the strip being placed between said molds and sandwiched by said molds having complimentary profiles, and being bent to form said predetermined curvature when said hydraulic press is activated and said molds press on said strip from opposite directions.

4. The method of claim 3, wherein a degree of said curvature is in the range between 15 to 60 degrees.

5. The method of claim 3, wherein a radius of said curvature is substantially the same as that of said wheel rim to be formed.

6. The method of claim 3, wherein on both sides of said upper mold further comprises a pair of rollers, each roller having a wheel mount coupled to said lever of said hydraulic press so that said rollers are capable of activating in synchronous with the activation of said upper mold and an unchanged section of said strip adjacent to a deformed section thereof is deformed continuously along said curvature.

7. The method of claim 6, wherein after forming said stripe, further comprises the step of pressing on both ends of said strip to form said curved sections by said upper and lower molds.

8. The method of claim 7, wherein after forming said curved sections on both ends of said strip, further comprises the step of cutting out a non-uniform deformation on either end of said strip by a saw.

9. The method of claim 8, wherein after cutting out said non-uniform deformation on either end of said strip, further comprises the step of forming a guide angle on either end of said strip by a milling machine so that both ends of said strip are proximate after said strip is formed as said hoop and a V-shaped gap is formed between both ends of said strip.

10. The method of claim 9, wherein after both ends of said strip are proximate and said V-shaped gap is formed, further comprises the step of performing a point soldering on said gap for partially connecting both ends of said hoop together.

11. The method of claim 10, wherein after both ends of said hoop are partially connected together, further comprises the step of performing a welding on said V-shaped gap to melt an aluminum alloy solder placed in said V-shaped gap so as to unite both ends of said strip together for forming said unfinished wheel rim.