Note: Descriptions are shown in the official language in which they were submitted.
METHOD O~ PRODUCING WHEELS OF LI~HT AILOY
TECHNICAL FIE~D
This invention relates to a method of producing
automobile wheels of such a light alloy as aluminum
alloy or magnesium alloy, and more particularly it
relates to a method of producing one-piece forged type
wheels of light alloy, wherein on the outer periphery
of the wheel disc formed with a predetermined pattern
defined by ribs~ the inner and outer rims projecting
in opposite directions axially of the wheel are integral
with the disc.
BACKGROUND ART
A method of producing automobile wheels of such.a
light alloy as aluminum alloy or magnesium alloy, partic-
ls ularly a method of producing one-piece wheels of light
alloy wherein on the outer periphery of the wheel disc,
the inner and outer rims projecting in opposite directions
axially of the wheel are integral with the disc.~ is
disclosed in Japanese Patent Application Disclosure Mo.
26648/1981.
A conventional method commonly used in producing such
one-piece forged type wheels of light alloy having ri~s
integral with the disk will now be described with reference
to the accompanying drawings.
I
~ t ~
To enable the prior art to be described with the aid
of diagrams, the fig~res of the drawings will first be
listed.
Fig. 1 is a sectional view showing how an outer
S rim is formed by die forging;
Fig. 2 is a front view showing an upper-die
exchanging device installed in a press;
Fig. 3 is a front view showing a portion of a
reticulate pattern formed on a disc;
Fig. 4 is a front view showing a disc having
a spoke pattern;
Fig. 5 is a front view showing a disc having
a simple pattern;
Fig. 6 is a sectional view of a light alloy
blank die-forged to form a disc of less undulating
pattern and an outer rim;
Fig. 7 is a sectional view of a light alloy blank
die-forged to form a disc of more undulating pattern
with ribs curved axially of the wheel and to form an
outer rim;
Fig. 8 is a sectional view showing how to spin
an inner flange disposed around the outer periphery
of a disc having more undulating pattern;
Fig. 9 is a sectional view showing how to flare
the inner flange spinned as shown in Fig. 8;
Fig. 10 is a sectional view showing how to re-spin
the inner flange flared as shown in Fig. 9;
Fig. 11 is a front view of a device for opening
unnecessary thin-walled portions between ribs on a
disc;
Fig. 12 is an enlarged flagmentar~ sectional
view showing how to open thin-walled portions by
the device of Fig. 11;
Fig. 13 is a sectional view of a wheel with a
disc having a less undulating pattern;
Fig. 14 is a sectional view of a wheel with a
disc having a more undulating pattern;
Fig. 15 is a ~ectional view of a light allo~
blank forged into a substantially H-shaped cross-section
wherein the disc has a less undulating pattern;
Fig. 16 is a sectional view showing how to spin
the outer flange disposed around the light alloy blank
of Fig. 15 into an outer rim of required shape;
Fig. 17 is a sectional view showing how to spin
an inner flange into an inner rim of required shape
after forming an outer rim around the outer periphery
of a disc having a less undulating pattern; and
~o Fig. 18 is an enlarged fragmentary front view
showing how a more undulating pattern on a disc deforms.
Conventionally, in producing such a wheel, a light
-- 3
~ t~
alloy blank 1 obtained b~ cutting into required
( lengths a cylindrical material produced b~ continuous
casting is used and said light allo~ blank 1 is
formed by forging, a~ shown in Fig. 15, into a
substantially H-shaped cross-section having flanges
2 and 3 on the outer peripher~ of a disc 11, said
flanges proaecting in opposite directions axially of
the wheel, said disc being formed with a required
pattern defined b~ thick-walled ribs 14 and thin-walled
portions 15 between said ribs 14. Subsequentl~, the
thus formed flange 2 outwardly projecting around the
outer periphery of the disc 11 is formed into an outer
rim 12 of suitable shape as shown in phantom lines in
~ig. 15. To this end, as shown in Fig. 16~ a mandrel
2G is disposed on the inner side of the disc 11 and a
center thrust rod 21 is disposed on the outer side of
the disc 11, said mandrel 20 and said center thrust
rod 21 cooperating with each other to clamp said disc
11 therebetween so that the light allo~ blank 1 ma~
be rotated with the rotation of the mandrel 20, while
a pair of stepped rollers 22 and 23 are disposed in
opposed relation to each other on the outer and inner
sides of said flange 2, respectivel~, so as to clamp
the flange 2 between said rollers 22 and 23, the ar-
rangement being such that while rotating the light
-- 4
- alloy blank 1 at a speed usually of 300-400 rpm by
said mandrel 20, said rollers 22 and 23 are moved
to deform the outer flange 2 into the outer rim 12
of required shape.
After the flange 2 has been formed into the outer
rim 12 in this manner, the flange 3 inwardly proaecting
around the outer peripher~ of the disc 11 is formed
into an inner rim 13 as shown in phantom lines in ~ig.
15. To this end, as shown in Fig. 17, a mandrel 31
having an outer peripheral shape corresponding to the
shape of the inner rim 13 is disposed on the inner side
of the disc 11 and a holder mandrel 32 is disposed on
the outer side of the disc 11, said mandrels 31 and 32
cooperating with each other to clamp the disc 11
therebetween; thus, the light alloy blank 1 is rotated
with the rotation of the mandrels 31 and 32 while, as
shown in Fig. 17, a roller 33 for rolling operation
disposed on the outer periphery of the inner flange 3
is moved along the inner mandrel 31 while being pressed
against the flange 3, thereby forming the flange 3 into
the inner rim 13 of required shape.
~hereafter, unnecessary thin-walled portions 15
between the ribs 14 on the disc 11 are removed as by
punching on a press, cutting on a lathe, or end milling
on a milling machine, thereby producing a one-piece wheel
of light alloy wherein on the outer peripher~ of the
disc 11 having a required disc pattern, the rims 12
and 13 projecting in opposite directions axiall~ of
the wheel are integral with the disc 11.
In such wheel, however, the rise angle ~ of the
outer rim 12 at which it rises from the outer periphery
of the disc 11 is generally 65-80 degrees. In the
case of conventional forming, if the traveling speed of
said rollers 22 and 23 clamping the outer flange 2
}O therebetween is increased to shorten the forming time,
excessive forces will act on said rollers 22 and 23
and the flange 2, thus offering a problem that they are
damaged or the outer rim 12 is warped to a great extent.
On the other hand, if the traveling speed of the rollers
22 and 23 is reduced, there arises a problem that much
time is involved in forming the outer rim 12. Additionally,
when the flange 2 on the light alloy blank 1 which is
rotated as described above is deformed while being clamped
between the rollers 22 and 23, strains are produced in
the outer rim 12 owing to a rotational sway, degrading
the circularity of the outer rim 12; for example, in the
case of a wheel having a diameter of 15 inches, an error
of as much as 2.5-3 mm occurs in the diameter. ~hus,
there has been a problem that the outer rim 12 cannot be
accurately formed.
8~
he conventional mandrels 31 and 32 for clar,lping the
inner rim 13 therebetween are substantially flat at
their end surfaces~ offering no particular problem in
producing a wheel having a less undulating disc 11 as
shown in Fig. 13. ~oday, however, wheels with discs
11 having various patterns are demanded; thus, in
producing a wheel having a greatel~ undulating disc
11 as shown in Fig. 14 in which ribs 14 forming a pattern
on the disc 11 are greately curved axially of the wheel,
if the inner rim 13 is formed using a roller 33 for
rolling operation by clamping the undulating disc 11
between the mandrels 31 and 32 whose end surfaces are
flat and rotating the light alloy blank 1, as in the
conventional manner, then the torque on the light alloy
blank 1 cooperates with the pressing force~afthe rolling
roller 33 to warp or di~tort the ribs 14, as shown in
phantom lines in Fig. 18, thus disfiguring the pattern
on the disc 11. Additionally, where the rolling roller
33 is pressed against the flange 3 to roll the latter
along the inner mandrel 31, when the rolled flange 3
reaches the rise portion 31a of the mandrel 31, it
becomes difficult for the roller to perform any further
rolling, thus leaving the rise portion.of the rim 13
incomplete.
Further, in removing unnecessary thin-walled portions
15 between the ribs 14 on the di~c 11, the use of
conventional punching on a press makes it necessary
to prepare a number of dies according to a pattern
to be formed on the disc 11, resulting in a high cost
for such dies. Moreover, in the case of a disc 11
having a complicate pattern or a disc 11 having heavy
undulations, it is very difficult to punch out such
thin-walled portions 15. Further, cutting on a lathe
or milling on a milling machine is low in efficiency
of operation, and particularly milling on a milling
machine takes-much time in making many holes. A further
problem is that these machining operations involve much
loss of material.
DISCIOSURE OF INVEN~IO~
~his invention has been accomplished with a view
to solving the aforesaid problems encountered in producing
one-piece forged type automobile wheels of light alloy
using a light allo~ blank such as aluminum alloy or
magnesium alloy, wherein the disc and the rims on the
outer periphery thereof are integral.
In a production method according to this invention,
an outer rim which rises at a sharp angle on the outer
periphery of the disc of the wheel on the axially outer
side of the wheel is formed by die forging simultaneously
with a pattern on the disc; thus, the formation of an
1~3~
outer rim can be effected in a simple manner and in a
( short time together with the formation of a pattern on
the disc, while ensuring high degrees of circularit~
and dimensional accuracy of the outer rim. Further,
in performing such die forging using some types of upper
and bottom dies, the invention provides an arrangement
comprising a guide rail disposed in the upper region
of a press, and an attaching block adapted to travel
along said guide rail and having some types of upper
dies attached to the lower surface thereof for successi~e
exchange of upper dies so as to effect exchange of upper
dies simply and in a short time.
~urther, in this invention, after the outer rim
has been formed by die forging together with the pattern
on the disc, as described aboYe,the disc is clamped
between a pair of mandrels and a flange projecting inwardly
arou~d the outer periphery of the disc is formed by spinn-
ing into an inner rim of re~uired shape. In this connection,
in the case where the ribs which form the pattern on the
disc are curved axially of the wheel and have an undulat~ng
pattern, at least one of the mandrels clamping the disc
therebetween iB 80 shaped that part or the whole of the end
surface thereof for clamping the disc has a shape correspond-
ing to the undulating pattern on the disc surface. The end
surface of such mandrel is fitted to the undulating pattern
g _
on the disc so that the disc is clamped between the
pair of mandrels, thereb~ preventing deformation of
the disc during forming the inner rim by spinning.
Further, in this invention, in clamping the disc
between a pair of mandrels and rolling the inwardly
projecting flange on the outer periphery of the disc
by a rolling roll along the outer peripheral surface
of the inner mandrel so as to form an inner rim, as
described above, the end portion of the rolled flange
is outwardl~ flared as by a press according to the
need, the thus flared fl~nge being pressed against the
mandrel by the rolling roller again, thereby facilitat-
ing the formation of inner rim whose end edge is raised.
Further, in spinni~g the inner rim in this manner, a
rolling roller having a central circumferential groove
formed on the roll surface is used, so that simultaneously
with the formation of the inner rim, tire fixing ridges
are formed at required positions adjacent said outer and
inner rims by said rolling roller having said groove.
2Q Additionally, in this invention, unnecessary thin-
walled portions present between ribs formed on the disc
b~ said die forging are opened b~ plasma cutting; thus,
even if the disc has a complicate pattern or is heavil~
undulating, such thin-walled portions can be easily opened.
BEST MODE OF CARRyING OUT THE INVENTION
An embodiment of this invention wherein a blank of
light alloy such as aluminum alloy or magnesium alloy is
forged to produce a one-piece forged type
-- 10 --
automobile wheel of light alloy in which the disc
and rims are integral with each other, will now be
described with reference to the accompanying drawings.
In this embodiment, use i9 made of a light alloy
blank 1 obtained by cutting into required length~ a
long cylindrical form of light alloy such as aluminum
allo~ or magnesium alloy usually produced by continuous
casting for use as blanks for wheels. This light alloy
blank 1, as shown in ~ig, 1, is pressed between upper
and bottom dies 41 and 42 of required shape, whereby
a disc 11 is formed with a required disc pattern defined
by thick-walled ribs 14 and thin-walled portions 15
disposed between said ribs 14 and the formation of an
outer rim 12 outwardly projecting axially of the wheel
and around the ou~er periphery of the disc 11 is effected
simultaneously with the formation of said pattern on said
disc 11.
~he angle at which the outer rim 12 rises from the
outer periphery of the disc 11 is 65-80 degrees, as
pre~iously described, which means that it is necessary
to deform the light alloy blank 1 to a great extent.
~or this reason, the die forging operation using the upper
and bottom dies 41 and 42 is generally performed ho-~ by
heating the light allo~ blank 1. In this die forging,
usually, some types of upper and bottom dies 41 and 42
-11-
are used and these upper and bottom dies 41 and 42 are
successively exchanged to progressively deform the
light alloy blank 1 so as to form the outer rim 12.
In performing such die forging, in this embodiment,
an arrangement is provided, as shown in ~ig. 2,
comprising a guide rail 43 horizontall~ installed in
the upper region of a press 40, an attaching block 45
having traveling rollers 45 for travel along said guide
rail 43, with some t~pes (two types, in this embodiment)
of upper dies 41 attached to the lower side of said
attaching block 45, and a hydraulic cylinder 46
installed on the guide rail 43 for moving said attaching
block 45 to exchange the upper dies 41. At a position
where a positioning pin 47 fixed to the press 40 fits in
a first engaging recess 48a formed in the attaching block
45, a first die 41 lies above a bottom die 42 fixed on a
bed 49, while at a position where the attaching block 45
is locked by the positioning pin 47 fitting in a second
engaging recess 48b formed in:.the attaching block 45, a
second upper die 41 lies above the bottom die 42.
In this manner, the upper dies 41 are exchanged to hot-
forge the light allo~ blank 1 by the first and second
upper dies 41 and 42. ~hus, with this arrangement, the
upper dies 41 c.an be exchanged in a short time and the
light alloy blank 1 ca~ be die-forged continuously without
_12-
l~J~
having to re-heat the light alloy blank 1 each time
the die is exchanged.
The pattern to be formed on the disc 11 of the wheel
is determined by the shapes engraved in the upper
and bottom dies 41 and 42 to be used at the final
forging step. Thus, any desired pattern may be
formed; for example, a reticulate pattern shown in
Fig. 3, a spoke pattern shown in Fig. 4, and a simple
pattern shown in Fig. 5 may be formed. Further, such
pattern on the disc 11 is not limited to a less
undulating one shown in ~ig. 6; a heavily undulating
pattern, as shown in Fig. 7, may be formed wherein
ribs 14 forming the pattern are greately curved axially
of the wheel.
After the pattern on the disc 11 and the outer
rim have been formed in this manner, the flange 3
projecting axially inwardly of the wheel is formed by
spinning into an outer rim 13 of desired shape.
As shown in Fig. 6, in the ca~e where an inner
rim 13 is formed around thé outer periphery of the
disc 11 having a less undulating pattern with ribs 14
on the disc 11 curving to a small extent, as in the
prior art as shown in Fig. 17 a mandrel 31 having an
outer peripheral shape corresponding to the shape of
the outer rim 13 to be formed is disposed on the inner
-13-
side of the disc 11 and a holder mandrel 32 is disposed
on the outer side of the disc 11 and the latter is
clamped between said pair of mandrels 31 and 32 whose
end surfaces are substnatially flat~ the mandrels 31
and 32 together with the disc 11 being rotated at a
speed usually of 300-400 rpm by an electric motor through
a speed change device. A rolling roller 33 disposed on
the outer peripher~ of the inner flange 3 is controlled
as by a hydroelectric servo or hydraulic servo 80 that
the inner flange 3 on the rotating light alloy blank 1
is squeezed by the rolling roller 33, the flange 3 being
rolled along the inner mandrel 31.
However, as shown in ~ig. 7, in the case where ribs
14 forming a pattern on the disc 11 are greately curved
axially of the wheel and an inner rim 13 iæ to be formed
around the outer periphery of a disc having a heavily
undulating pattern, if the disc 11 is clamped by a pair
of mandrelæ 31 and 32 who~e end surfaces are
subatantially flat so ast~spin the in~er flange 3, as
2Q described above, the disc 11 would deform as in the prior
art. ~hus, in a~ embodiment shown in ~ig. 8~ a pair of
mandrels 31 and 32 whose end surfaces are shaped to
correæpond to the undulating pattern on the disc 11;~e
used, and the undulating end surfaces of these mandrels
31 and 32 are fitted to the undulating pattern on the
_14-
disc 11 to clamp the disc 11 between ~he mandrels 31
and 32. In this state, the light allo~ blank 1 i5
rotated together with these mandrels 31 and 32, as
described above, and the inner flange 3 ia rolled b~
the rolling roller 33. In this case, even if a torsional
force resulting from a combination of the torque on the
light alloy blank 1 and the pressing force of the rolling
roller 33 acts on the disc 11, deformation of the pattern
on the disc 11 is prevented by the mandrel~ 31 and 32
lQ whose end surfaces fit to the undulating pattern on the
disc 11. In addition, in this embodiment, where the
inner flange 3 is to be spinned around the outer periphery
of the di c 11 having a heavily undulating pattern, only
an example has been shown using a pair of mandrels whose
end surface are shaped to correspond to the undulating
pattern on the disc 11. ~owever, in the case where the
disc 11 has a heavily undulating pattern when the outer
rim 12 is to be spinned around the outer periphery of the
disc 11, as in the prior art, it is, of course, possible
to use such mandrels 31 and 32 to clamp the disc therebetween
so as to prevent deformation of the pattern on the disc 11.
~urther, in the case of forming the inner rim 13 by
clamping the disc 11 between the mandrels 31 and 32,
rotating the light alloy blank 1 together with the mandrels
31 and 32, and rolling the inner flange 3 along the inner
-15-
mandrel 31 by the rolling roller 33, as described above,
it may occur that the rolled flange 3 abuts against the
rise portion 31a of the inner mandrel and is thereby
prevented from being rolled an~ further and hense the
end edge of the inner rim 13 cannot be raised. In
such case, in this embodiment, after the flange 3 has
been rolled to some extent b~ the rolling roller 33, the
end of the rolled flange 3 is outwardly flared b~ upper
and bottom mandrels 51 and 52, as shown in Fig. 9, until
the end of the flange 3 passes over the rise portion 31a
of the mandrel 31. After the end of the flange 3 has
thus been flared, the disc 11 is clamped again between
mandrels 31 and 32, as shown in ~ig. 10, and is thereb~
rotated, while a rolling roller 33 presses the flared
flange 3 against the inner mandrel 31 to form the inner
rim 13 whose end is raised. In the example shown in
~ig. 10, the rolling roller 33 for forming the inner rim
13 has a central circumferential groove 33b to circum-
ferentially form tire fixing ridges 12a and 13a at required
positions adjacent the outer and inner rims 12 and 13.
After the inner rim 13 has been formed as described
above, un~ecessary thin-walled portions 15 present
between the ribs 14 on the disc 11 are opened, whereby,
as shown in ~igs. 13 and 14, a one-piece wheel of light
alloy in which the disc 11 is integral with the rims 12
-16-
and 13 is produced.
In opening thin-walled portion~ 15, in this
embodiment, a required number of light allo~ blanks
with their inner rims 13 formed in the manner described
above are indexably positioned on a turntable 63
rotatably supported b~ rollers 62 installed on the upper
ends of support legs 61, while an operating range is
stored in the memory unit of a working robot 66 having
an operating arm 64 with a plasma arc blow nozzle 65
attached therets. ~he operating arm 64 of the working
robot 66 IS actuated on instructions from the memory
unit to move the blowing nozzle 64, which blows off
plasma arcs b~ which the unnecessary thin-walled portions
15 are cut and opened, as shown in Fig. 12_~herefore,
even if the disc 11 has a complicate pattern or is curved,
the unnecessary thin-walled portions 15 can be easily
opened without deforming the pattern. In performing
cutting by plasma arcs~ a cutting current of 148 A
(29-3O A during pilot arcing) is usually used, the cutting
speed is 2 m/min, and compressed air at 6 kgf/cm2 is used
as cutting gas.
In addition, it is not absolutely necessary that the
opening of such thin-walled portions 15 succeed the
formation of the inner rim 13; it ma~ precede the forma-
tion of the inner rim 13.
-17-
INDUS~RIAL~APP~ICABILI~Y
As has been described so far in detail, according
to the present method of producing light alloy wheels,
in producing one-piece forged type light alloy wheels
using aluminum alloy or maænesium alloy wherein the
disc is integral with the inner and outer rims project-
ing in opposite directions axially of the wheel, the
formation of the outer rim rising at a sharp angle from
the outer periphery of the disc i5 effected by die
forging simultaneously with the formation of a pattern
on the disc; thus, the outer rim can be formed in a short
time and in a simple manner while ensuring high degrees
of circular~ and accuracy. In such die forging, in
the case where a light alloy blank is heated and some
types of upper and bottom dies are used to successively
deform said light alloy blank, an arrangement is provided
which comprises a guide rail installed in the upper region
of a press, and an attaching block adapted to travel
along said guide rail and having some types of upper
dies attached to the lower side thereof, the attaching
block being moved along the guide rail for successive
exchange of upper dies, so that the exchange of upper
dies can be made in a short time and in a simple manner
without having to re-heat the light alloy blank each the
die is exchanged, thereb~ ensuring continuous die forging.
-18-
Further, according to this invention, after the
pattern on the disc and the outer rim have been formed
by die forging as described above, the disc is clamped
between a pair of mandrels and the light alloy blank is
rotated together with the mandrels, while a flange
projecting inwardly arotmd the outer peripher~ of the
disc is rolled along the outer peripheral surface o~
the inner mandrel by a rolling roller, wherepy said
flange i5 formed by spinning into an inner rim of required
shape. In this case, if the ribs forming a pattern on
the disc are curved axially of the wheel and have an
undulating pattern, at least one of the mandrels clamping
the disc therebetween has a part or the whole of its end
surface clamping the disc shaped to correspond to the
undulating pattern on the disc, the end surface of such
mandrel being fitted to the undulating pattern on the
disc so as to clamp the di~c between the pair of mandrels~
thereby ensuring that the undulating pattern on the disc
does not deform even in the case of forming by spinning
an inner rim around the outer peripher~ of the disc
having an undulating pattern.
In the case where the inner flange around the outer
periphery of the disc is to be raised along the rise
portion of the mandrel in forming said inner flange into
an inner rim of required shape by the rolling roller as
_19-
described above, in this invention, the inner flange
is rolled to a certain extent and then the end of the
thus rolled flange is flared as by a press until it
passes over the rise portion of the mandrel, whereupon
the flared flange is pressed again b~ the rolling roller
against the mandrel; in this manner, the inner rim whose
end edge is raised can be easily formed. ~urther, in
forming the inner rim b~ spinning in this manner, if
a rolling roller having a central circumferential
groove on its roll surface is used, the wheel can be
circumferentiall~ formed with tire fixing ridges at
required positions adjacent the outer and inner rims
b~ the groove of said rolling roller simultaneously
with the formation of the inner rim.
Additionall~, in this invention, thin-walled
portions present between ribs formed on the disc b~
said die forging are opened by plasma cutting. ~hus,
even if the pattern on the disc is complicate or
curved, such thin-walled portions can be easil~ opened
without deforming the pattern on the disc.
-20-
