Process for spin forming a vehicle wheel

Details Process for spin forming a vehicle wheel Process for spin forming a vehicle wheel

1997-07-23

2003-03-25

Echols, P. W. (Department: 3726)

Metal working

Method of mechanical manufacture

Wheel making

C029S894350, C164S302000, C164S340000, C301S063106, C301S065000

Reexamination Certificate

active

06536111

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates in general to the manufacture of vehicle wheels and in particular to a process for spin forming a portion of a vehicle wheel rim.
It is known in the art to manufacture a one piece vehicle wheel. Referring to the drawings, there is shown in
FIG. 1
a fragmentary sectional view of a typical prior art one piece wheel
10
. The wheel
10
has a circular wheel disc
11
which extends across an annular wheel rim
12
.
The wheel disc
11
includes a wheel hub
15
having a central pilot hole
16
and a plurality of wheel lug holes
17
(one shown) formed therethrough. The hub
15
is supported by a plurality of wheel spokes
18
(one shown) within an annular sidewall
20
which forms the outboard end of the wheel rim
12
.
The wheel rim
12
includes an outboard tire bead retaining flange
21
which extends in a radial outward direction from the sidewall
20
. The rim
12
further includes an outboard tire bead seat
22
which is formed in the sidewall
20
adjacent to the retaining flange
21
. The rim
12
also includes an outboard tire safety bead
23
formed in the sidewall
20
between the tire bead seat
22
and a deep well
24
. A leg portion
25
extends axially across the rim
12
from the deep well
24
to an inboard tire safety bead
26
. An inboard tire bead seat
27
is formed adjacent to the safety bead
26
. The inboard end of the wheel rim
12
terminates in a conventional inboard tire bead retaining flange
28
.
Referring to
FIG. 2
, there is shown a flow chart for a known manufacturing process for fabricating the one piece wheel
10
illustrated in FIG.
1
. In functional block
30
, a wheel blank is formed from a light weight metal or light weight metal alloy by a conventional process, such as gravity, low pressure or die casting, or forging. The wheel blank includes a wheel rim formed integrally with a wheel disc and is formed oversize having the approximate shape of the wheel.
Finishing the wheel blank typically includes multiple machining operations. If the wheel blank is cast, sawing machines remove any casting gates and risers from the wheel blank in functional block
31
. In functional block
32
, a drilling machine drills the central pilot hole
16
and the wheel lug holes
17
through the wheel hub
15
. In functional block
33
, the wheel blank is mounted upon a wheel lathe for machining to its final shape. During the machining operations, the inboard surface of the wheel hub is usually faced to provide a flat mounting surface. Similarly, the outboard wheel hub surface is faced and both the inner and outer surfaces of the wheel rim are turned to their final shapes. During the turning of the wheel rim outer surface, the tire bead seats are turned to their final diameter. Alternately, the wheel blank can be mounted upon a wheel spinning machine (not shown), and the outer surface of the rim portion of the blank spun into its final shape.
Typically, the machined wheel is heat treated to assure that the wheel has desired mechanical properties, as shown in functional block
34
. However, the heat treatment can cause irregularities in the circularity of the wheel rim which affect the concentricity of the tire bead seats, causing undesired vibrations when the wheel is mounted upon a vehicle and the vehicle operated. Accordingly, the wheel is usually machined following heat treatment, as shown in functional block
35
to true the concentricity of the tire bead seats. Finally, in functional block
36
, portions of the wheel can be painted or covered with a clear coating to protect the wheel from corrosion and/or enhance its appearance.
It also is known in the art to fabricate a two piece vehicle wheel by attaching a wheel disc to a separately formed wheel rim. Typically, the wheel disc is cast or forged while the rim is rolled from strip stock. Such two piece wheels are less expensive to manufacture than a cast one piece wheel while permitting use of stylistic designs for the wheel disc. Both the wheel disc and rim can be formed from alloys of the same light weight metal, such as aluminum, magnesium or titanium, or, as a further cost reduction, a wheel disc formed from an alloy of a light weight metal can be attached to a rim rolled from steel. When different metals are used to form the wheel disc and wheel rim, the wheel is usually called a bimetal wheel.
To further improve the appearance of the wheel, the wheel disc can be formed to include the outboard tire bead retaining flange. The resulting wheel disc, which is called a full face wheel disc, is attached to the outboard end of a partial wheel rim. The attachment can occur at the outboard tire bead seat, the dropwell, or another location. The assembled wheel is often referred to as a full face wheel. When a tire is mounted upon a full face wheel, the joint between the wheel disc and wheel rim is completely hidden and only the wheel disc is visible. A decorative finish is often applied to the face of the wheel disc to further enhance the appearance of the wheel. Examples of typical decorative finishes include metal plating, such as chromium plating, clear coatings and paint.
Referring to
FIG. 3
, there is shown a flow chart for a known manufacturing process for fabricating a two piece wheel. In functional block
40
full face wheel disc is formed by a conventional process, such as casting or forging. The wheel disc is heat treated in functional block
41
and then machined to final shape in functional block
42
.
While the wheel disc is being formed, a flat strip of metal is rolled into a circular hoop and the ends butt welded together in functional block
45
. The hoop is formed into a partial wheel rim in functional block
46
by a conventional spinning process. The hoop is mounted upon a mandrel and the hoop and mandrel are spun while rollers are pressed against the outer surface of the hoop. The rollers and mandrel cooperate to form the hoop into a partial wheel rim.
In functional block
47
, the partial wheel rim is attached to the wheel disc formed in functional blocks
40
through
42
by a conventional welding process, such as electron beam or arc welding. Alternately, a conventional friction or inertial welding process can be used to form the weld. An air-tight continuous circumferential weld is formed between the outboard end of the wheel rim and the inboard surface of the wheel disc collar.
Typically, it is difficult to weld the partial wheel rim coaxially upon the wheel disc. If the outboard and inboard tire bead seats of the assembled wheel are outside the required tolerance limits for maintaining the a coaxial relationship between the tire bead seats, undesirable vibrations may occur when the wheel is mounted upon a vehicle and the vehicle operated. Thus, it is necessary to machine the tire bead seats of the assembled wheel in functional block
48
to assure that the required amount of coaxilality is achieved.
SUMMARY
This invention relates to a process for spin forming a portion of a vehicle wheel rim.
As described above, forming a one piece vehicle wheel involves machining a rough blank to a final shape. The sidewall formed on the outboard end of the wheel rim is typically solid due to the limitations of the casting and forging processes. While it is known to form lightener pockets in the wheel sidewall to reduce the wheel weight, the known methods typically involve complex mold or die mechanisms having retractable cores for forming the lightener pockets. The retractable cores permit removal of the casting from the mold or die. Accordingly, it would be desirable to simplify the formation of lightener pockets in the wheel sidewall to reduce the weight of the wheel.
As also described above, a two piece wheel is typically fabricated by welding a preformed wheel rim to a finished wheel disc. While forming the rim, it is difficult to achieve true circularity. Furthermore, it also is difficult to weld the rim coaxially onto the disc. Accordingly, machining is needed to true the coaxiality of the tire bead seats. Such machining is time consuming and

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