U.S. patent application number 11/647169 was filed with the patent office on 2007-05-31 for race member in hub unit and method of producing the same.
This patent application is currently assigned to NSK LTD.. Invention is credited to Kazuto Kobayashi, Kouhei Mori, Kiyoshi Ootsuka, Isao Shintou.
Application Number | 20070119054 11/647169 |
Document ID | / |
Family ID | 34709139 |
Filed Date | 2007-05-31 |
United States Patent
Application |
20070119054 |
Kind Code |
A1 |
Kobayashi; Kazuto ; et
al. |
May 31, 2007 |
Race member in hub unit and method of producing the same
Abstract
A race member in a hub unit for supporting a wheel. The race
member includes a cylinder portion, a flange portion bend radially
outward from the cylinder portion, and a continuous portion that
integrally connects the cylinder portion with the flange portion.
The race member is integrally formed by subjecting a metal plate to
punching and cold plastic working. The continuous portion is larger
in thickness than the metal plate.
Inventors: |
Kobayashi; Kazuto;
(Kanagawa, JP) ; Shintou; Isao; (Kanagawa, JP)
; Ootsuka; Kiyoshi; (Kanagawa, JP) ; Mori;
Kouhei; (Kanagawa, JP) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W.
SUITE 800
WASHINGTON
DC
20037
US
|
Assignee: |
NSK LTD.
|
Family ID: |
34709139 |
Appl. No.: |
11/647169 |
Filed: |
December 29, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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11037042 |
Jan 19, 2005 |
|
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11647169 |
Dec 29, 2006 |
|
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Current U.S.
Class: |
29/894 ;
29/894.36; 29/898.066 |
Current CPC
Class: |
B60B 27/0094 20130101;
Y10T 29/49481 20150115; Y10T 29/49533 20150115; F16C 2220/46
20130101; F16C 2326/02 20130101; Y10T 29/49689 20150115; B21K 23/04
20130101; F16C 19/186 20130101; B21K 21/00 20130101; B21K 1/40
20130101; B60B 27/0005 20130101; B60B 27/0084 20130101; B21K 1/02
20130101; F16C 33/64 20130101; B60B 27/00 20130101 |
Class at
Publication: |
029/894 ;
029/894.36; 029/898.066 |
International
Class: |
B21D 53/26 20060101
B21D053/26 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 20, 2004 |
JP |
P.2004-044237 |
Claims
1. A method of producing a race member in a hub unit for supporting
a wheel,: which comprises a cylinder portion; a flange portion
extended radially outward from the cylinder portion; and a
continuous portion that integrally connects the cylinder portion
with the flange portion, the method comprising: subjecting a metal
plate to punching and clod plastic working to form the cylinder
portion, the flange portion and the continuous portion integrally,
wherein the continuous portion is larger in thickness than the
metal plate.
2. A method of producing a race member in a hub unit for supporting
a wheel, which comprises a cylinder portion; a flange portion
extended radially outward from the cylinder portion; and a
continuous portion that integrally connects the cylinder portion
with the flange portion; and a second cylinder portion extending
from a radial inner end of the flange portion so as to be integral
with the race member, wherein the second cylinder portion extends
in an axial direction opposite to the cylinder portion, the method
comprising: making a portion of the continuous portion plastically
flow in a direction opposite to the cylinder portion in the axial
direction to form the second cylinder portion.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a hub unit for supporting a
wheel used for supporting a wheel of an automobile rotatably by a
suspension, as well as a race member (hub, outer race) forming the
hub unit for supporting the wheel and a method of producing the
same.
[0003] 2. Background Art
[0004] A wheel of an automobile is supported by a suspension by
means of a hub unit for supporting the wheel. FIG. 4 shows a first
example of a hub unit for supporting a wheel which has been known
in a background art for a driven wheel (rear wheel of FF vehicle,
front wheel of FR vehicle and RR vehicle). The hub unit for
supporting the wheel includes a hub 1 constituting a race member,
an inner race 2, an outer race 3 similarly constituting a race
member, and a plurality of pieces of rolling members 4, 4.
[0005] A portion proximate to a side of an outer end (`outer` in an
axial direction designates an outer side in a width direction of a
vehicle in a state of being integrated to an automobile which is a
left side in FIGS. 1, 4 through 7. Conversely, `inner` in the axial
direction designates a side of a center in the width direction of
the vehicle which is a right side of FIGS. 1, 4 through 7. The same
goes with a total of the specification) of an outer end of an outer
peripheral face of the hub 1 there among is formed with an
attaching flange constituting a flange portion, a middle portion
thereof is formed with a first inner race track 6a, a portion
thereof proximate to aside of an inner end is formed with a small
diameter stepped portion 7 having an outer diameter dimension
smaller than that of the portion formed with the first inner race
track 6a, and an inner end portion thereof is formed with a male
screw portion 8, respectively. Further, there are a case in which
the first inner race track 6a is formed directly at the outer
peripheral face of the middle portion of the hub 1a illustrated as
well as a case in which the inner race track 6a is formed at an
outer peripheral face of an inner race constituting a separate
member outwardly fitted to the middle portion of the hub.
[0006] Further, the inner race 2 is fitted to the small diameter
stepped portion 7. Such an inner race 2 is screwed to the male
screw portion, and is pressed to a stepped difference face 10
present at a base end portion of the small diameter stepped portion
7 by a fastened nut 9. An outer peripheral face of such an inner
race 2 is formed with a second inner race track 6b.
[0007] Further, a total of the outer race 4 is constituted in a
cylindrical shape and a portion proximate to a side of an inner end
of an outer peripheral face thereof is provided with a coupling
flange 11 constituting a flange portion. Further, a first, a second
outer race track 13a, 13b are formed at an inner peripheral face of
a main body 12 in a cylindrical shape constituting a cylinder
portion present on an outer side in an axial direction of the
coupling flange 11 as well as an inner face of a portion thereof
provided with the coupling flange 11. Further, respective
pluralities of pieces of the rolling members 4, 4 are provided
between the first and the second respective outer race tracks 13a,
13b and the first and second respective inner race tracks 6a, 6b.
Further, although in the illustrated example, balls are used as the
respective rolling members 4, 4, in a case of a hub unit for
supporting a wheel for an automobile which is heavily weighted,
there is also a case of using tapered rollers as the rolling
members. Further, a cover 15 is inwardly fitted to fix to a
cylinder portion 14 for fitting in a cylindrical shape constituting
a second cylinder portion present at a portion of the outer race 4
on an inner side in the axial direction of the coupling flange
11.
[0008] When the hub unit for the wheel of the first example
constituted as described above is integrated to an automobile, the
coupling flange 11 provided at the outer peripheral face of the
outer race 4 is coupled to fix to a knuckle constituting a
suspension. Along therewith, rotating members for braking of a
wheel, a brake rotor and the like constituting the wheel are
coupled to fix to the attaching flange 5 provided at the outer
peripheral face of the portion of the hub 1 proximate to the side
of the outer end in a state of being outwardly fitted to a guide
cylinder portion 16 in a cylindrical shape constituting a second
cylinder portion formed at an outer end portion of the hub 1.
[0009] Next, FIG. 5 shows a second example of a hub unit for
supporting a wheel which has been known in a background art
similarly for a driven wheel. The hub unit for supporting the wheel
of the second example is constituted with a hub 1a having the
attaching flange 5 at a portion proximate to a side of an outer end
of an outer peripheral face thereof in a cylindrical shape. Along
therewith, the outer race tracks 13a, 13b in double rows are formed
at an inner peripheral face of a main body 17 in a cylindrical
shape constituting a cylinder portion present at a portion of the
hub 1a on an inner side in an axial direction of the attaching
flange 5. Further, a pair of inner races 2a, 2 are provided on an
inner side in a diameter direction of the hub 1a. Further,
respective pluralities of pieces of the rolling members 4, 4 are
provided between the respective inner race tracks 6a, 6b formed at
outer peripheral faces of the respective inner races 2a, 2 and the
respective outer race tracks 13a, 13b.
[0010] When the hub unit for supporting the wheel of the second
example constituted as described above is integrated to an
automobile, the respective inner races 2a, 2 are outwardly fitted
to fix to a supporting shaft which is not rotated even when used
constituting a suspension. Along therewith, a wheel and a rotating
member for braking constituting the wheel is coupled to fix to the
attaching flange 5 provided at an outer peripheral face of a
portion of the hub 1a proximate to an outer end thereof in a state
of being outwardly fitted to the guide cylinder portion 16
constituting the second cylinder portion provided at the outer end
portion of the hub 1a.
[0011] Next, FIG. 6 shows a third example of a'structure of a
background art of a hub unit for supporting a wheel for a drive
wheel (front wheel of FF vehicle, rear wheel of FR vehicle and RR
vehicle, all wheels for 4WD vehicle)--The hub unit for supporting
the wheel is for the drive wheel and therefore, a center portion of
the hub 1b is provided with a spline hole 16 for engaging a spline
shaft constituting the drive shaft. Further, in the case of the
illustrated example, a calking portion 20 is formed by plastically
deforming an inner end portion of the shaft portion 19 in a
cylindrical shape constituting a cylinder portion present on an
inner side in an axial direction of the attaching flange 5 to an
outer side in a diameter direction. Further, an inner end face of
the inner race 2 is pressed by the calking portion 20. A structure
and operation of other portion are substantially similar to those
of the case of the first example shown in FIG. 4, mentioned
above.
[0012] Further, in the above-described cases of the hub unit for
supporting the wheel of the first through the third examples, the
hubs 1, 1a, 1b and the outer race 3 having the flange portions
(attaching flange 5, coupling flange 11) at the outer peripheral
faces are frequently constituted by products formed by hot forging.
However, in forming the products by hot forging in this way, not
only cost of energy required for working is increased but also a
margin for turning after working a material by hot forging is
increased and therefore, yield of the material is deteriorated and
as a result, there poses a problem that fabricating st is
increased.
[0013] Next, FIG. 7 shows a fourth example of a structure of a
background art of a hub unit for supporting a wheel described in
JP-A-2003-159904. In the case of a hub unit for supporting a wheel
of the fourth example, a hub 1c is constituted by a product formed
by deep drawing which is a kind of cold plastic working. That is,
the hub 1c is constituted by combining a first and a second hub
element 21, 22 by subjecting metal plates respectively constituting
materials to deep drawing to each other. The first hub element 21
in the two elements is constituted substantially by an L-like shape
in a section thereof and in a shape of a circular cylinder for a
total thereof, and includes a shaft portion 19a in a cylindrical
shape constituting a cylinder portion and an attaching flange 5a in
a shape of a circular ring constituting a flange portion on the
other hand, the second hub element 22 is constituted by a crank
shape in a section thereof and in a shape of a circular ring for a
total thereof and a cylinder portion on a large diameter side is
constituted by a guide cylinder portion 16a constituting a second
cylinder portion. Further, the hub 1c is constituted by coupling to
fix (fix by press-fit, fix by calking, fix by welding or the like)
the first and the second hub elements 21, 22 as illustrated.
Further, in the illustrated example, the pair of inner race tracks
6a, 6b are formed at outer peripheral faces of a pair of inner
races 2b, 2b made by sheet drawing outwardly fitted to the shaft
portion 19a. A structure and operation of other portion are
substantially similar to those of the above-described case of the
first example shown in FIG. 4.
[0014] In the above-described case of the fourth example of the
structure of the background art, in subjecting the metal plate
constituting the material to deep drawing in order to produce the
above-described first hub element 21, walls of the shaft portion
19a constituting the first hub element 21 and a portion 23
continuous to the shaft portion 19a and the attaching flange 5a are
thinned. That is, wall thicknesses of the shaft portion 19a and the
continuous portion 23 become smaller than a wall thickness of the
metal plate constituting the material. In contrast thereto,
the-continuous portion 23 is a portion applied with a large load
when used. Therefore, in order to sufficiently ensure a strength
(wall thickness) of the continuous portion 23, it is necessary to
use the metal plate constituting the material having a sufficiently
large wall thickness. Therefore, there is brought about a drawback
that a weight of the hub 1c becomes heavy.
[0015] Further, the guide cylinder portion 16a constituting the hub
1c is a portion extended in a direction opposed to the shaft
portion 19a in an axial direction from an inner end portion in a
diameter direction of the attaching flange 5a. Such a guide
cylinder portion 16a is not integrally formed with the attaching
flange 5a and the shaft portion 19a by only subjecting the metal
plate to deep drawing. Therefore, when the hub 1c is going to be
formed by subjecting the metal plates constituting the materials to
deep drawing as in the above-described fourth example of the
structure of the background art, in order to form the cylinder
portion 16a, it is necessary to produce the second hub element 22
which is a member separate from the first hub element 21.
Therefore, there poses a problem that the weight of the hub 1c
similarly becomes heavy and the fabrication cost is increased by
increasing a number of parts.
[0016] Further, although illustration is omitted, Japanese Patent
No. 3352226 describes a hub unit for supporting a wheel
constituting an outer race having a flange portion at an outer
peripheral face by a product formed by deep drawing. Also in the
case of the hub unit for supporting the wheel, the outer race is
produced by deep drawing and therefore, there is brought about a
drawback similar to that of the above-described case of the hub 1c
with regard to the outer race.
SUMMARY OF THE INVENTION
[0017] In view of the above-described situation, a race member in a
hub unit for supporting a wheel, a method of producing the same and
a hub unit for supporting a wheel according to the invention has
been invented so that a race member which is sufficiently
light-weighted with a high strength can be produced
inexpensively.
[0018] The invention provides a race member in a hub unit for
supporting a wheel, including: a cylinder portion; a flange portion
bend radially outward from the cylinder portion; and a continuous
portion that integrally connects the cylinder portion with the
flange portion; wherein the race member is integrally formed by
subjecting a metal plate to punching and cold plastic working; and
the continuous portion is larger in thickness than the metal
plate.
[0019] Preferably, the race member, further includes: a second
cylinder portion; wherein the second cylinder portion extends from
a radial inner end portion of the flange portion; and the second
cylinder portion extends in an axial direction opposite to the
cylinder portion.
[0020] The invention provides a hub unit for supporting a wheel,
including: a race member; wherein the race member includes: a
cylinder portion, a flange portion bend radially outward from the
cylinder portion, and a continuous portion that integrally connects
the cylinder portion with the flange portion; the race member is
integrally formed by subjecting a metal plate to punching and cold
plastic working; and the continuous portion is larger in thickness
than the metal plate.
[0021] Preferably, the race member includes a second cylinder
portion; the second cylinder portion extends from an inner end
portion in the diameter direction of the flange portion; and the
second cylinder portion extends in an axial direction opposite to
the cylinder portion.
[0022] The invention provides a method of producing a race member
in a hub unit for supporting a wheel, wherein the race member
includes a cylinder portion, a flange portion bend outward from the
cylinder portion in a diameter direction thereof, and a continuous
portion that integrally connects the cylinder portion with the
flange portion; the method including: subjecting a metal plate to
punching and cold plastic working to form the cylinder portion, the
flange portion, and the continuous portion; contracting the
cylinder portion diametrally to increase a wall thickness of the
cylinder portion; and making a portion of a wall of the cylinder
portion plastically flow to the continuous portion to make the
continuous portion larger in thickness than the metal plate.
[0023] Preferably, the method further including: making a portion
of the continuous portion plastically flow in a direction opposite
to the cylinder portion in the axial direction to form a second
cylinder portion that extends from a radial inner end portion of
the flange portion.
[0024] As described above, in the case of the race member in the
hub unit for supporting a wheel, the method of producing the same
and the hub unit for supporting a wheel according to the invention,
the race member is produced by subjecting the metal plate to cold
plastic working. When the metal plate is subjected to cold plastic
working in this way, dimension accuracy after the working can be
improved and therefore, working for ensuring accuracy to be
performed thereafter can be reduced or omitted. Further, in the
case of the invention, the race member is produced as an integrally
formed product. Therefore, yield of the material can be improved.
Further, it is not necessary to couple a plurality of members by
welding or the like and therefore, a reduction in fabricating cost
can be achieved. Further, in the case of the invention, the portion
continuous to the cylinder portion and the flange portion forming
the race member is made larger in thickness than the metal plate to
be used as a material. Therefore, without using a metal plate
having a large wall thickness more than necessary, a strength (wall
thickness) of the continuous portion can sufficiently be ensured.
Therefore, a reduction in fabricating cost and light-weighted
formation can be achieved also in this regard.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] The present invention may be more readily described with
reference to the accompanying drawings:
[0026] FIG. 1 is a sectional view showing an embodiment of the
invention.
[0027] FIGS. 2A-2L are sectional views and a plan view showing
steps of fabricating a hub.
[0028] FIG. 3A-O are sectional views and plan views showing steps
of fabricating an outer race.
[0029] FIG. 4 is a sectional view showing a first example of a hub
unit for supporting a wheel which has been known in a background
art.
[0030] FIG. 5 is a sectional view showing a second example of the
background art.
[0031] FIG. 6 is a sectional view showing a third example of the
background art.
[0032] FIG. 7 is a sectional view showing a fourth example of the
background art.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0033] FIGS. 1 through 30 show an embodiment of the invention. A
hub unit for supporting a wheel according to the embodiment is for
a driven wheel and a basic structure thereof is substantially
similar to that of the hub unit for supporting a wheel of the first
example of the above-described structure of the background art
shown in FIG. 4. However, in the case of the hub unit for
supporting a wheel of the embodiment, the inner race 2 is pressed
to the stepped difference face 10 by the calking portion 20 formed
by plastically deforming an inner end portion of a hub id to an
outer side in a diameter direction. Further, in the case of the hub
unit for supporting a wheel of the embodiment, the hub Id and an
outer race 3a respectively constituting race members are integrally
formed by subjecting metal plates respectively constituting
materials to punching and cold plastic working. Wall thicknesses
T.sub.24, T.sub.26 of portions 24, 25 continuous to cylinder
portions (shaft portion 19b, main body 12a) and flange portions
(attaching flange 5b, coupling flange 11a) are made to be larger
than wall thicknesses t.sub.1, t.sub.2 {refer to FIG. 2(A), FIG.
3(A)} of metal plates constituting materials therefor
(T.sub.2.sub.4>t.sub.1, T.sub.2.sub.5>t.sub.2). An
explanation will be given of steps of fabricating the hub 1d and
the outer race 3a of the embodiment as follows.
[0034] FIGS. 2A-L show steps of fabricating the hub 1d. Further,
all of respective steps shown in FIGS. 2B through 2D and 2F through
2J are steps of cold plastic working. In the case of fabricating
the hub 1d, first, by punching a metal plate constituting a
material (for example, a plate made of S55C through S48C which can
be quenched by high frequency after forming can be used. The plate
thickness t.sub.1 is determined in consideration of a size of the
hub 1d to be produced), a material plate 26 shown in FIG. 2A can be
provided. In the case of the embodiment, a planer shape (shape
viewed from upper side or lower side of the drawing) is constituted
by a circular shape. Successively, by drawing the material plate
26, there is constituted a first intermediate material 27 having a
section substantially in a V-like shape a center portion of which
is considerably recessed as shown in FIG. 2B.
[0035] Successively, a middle portion in an axial direction (up and
down direction of the drawing) of the first intermediate material
27 is necked (contract diameter) in two steps. That is, in necking
at a first step, a second intermediate material 28 as shown in FIG.
2C is formed and by necking in a second step, a third intermediate
material 29 as shown in FIG. 2D is formed. Further, by subjecting
material to respective necking, an attaching a flange element 30
functioning as a flange portion is formed at an outer peripheral
face of one end portion (upper end portion of the drawing) of the
third intermediate material 29. Successively, by punching
(piercing) a center portion of a bottom portion present at other
end portion (lower end portion of the drawing) of the third
intermediate material 29, a fourth intermediate material 31 as
shown in FIG. 2E is formed. By producing the fourth intermediate
material 31 in this way, a shaft portion element 32a functioning as
a cylinder portion is formed at a portion on an inner diameter side
of the fourth intermediate material 31.
[0036] Successively, the shaft portion element 32 constituting the
fourth intermediate material 31 is necked in two steps. That is, by
necking at a first step, a fifth intermediate material 33 as shown
in FIG. 2F is formed and by necking at a second step, a sixth
intermediate material 34 as shown in FIG. 2G is formed. Further, by
respectively necking in this way, wall thicknesses of respective
portions constituting the sixth intermediate material 34 (shaft
portion element 32c, a portion 24a continuous to the shaft portion
element 32c and attaching flange element 30) are increased.
Successively, the shaft portion element 32c constituting the sixth
intermediate material 34 is subjected to diameter contracting and
drawing with ironing. Thereby, a seventh intermediate material 35
as shown in FIG. 2H is formed by contracting a diameter of the
shaft portion element 32c and by making a portion of a wall of the
shaft portion element 32c plastically flow to the continuous
portion 24a. In the case of the embodiment, in a state of providing
the seventh intermediate material 35 in this way, a wall thickness
T.sub.24a of the continuous portion 24a constituting the seventh
intermediate material 35 is made to be sufficiently larger than the
wall thickness t.sub.1 of the material plate 26
(T.sub.24.sup.a>t.sub.1).
[0037] Successively, an eighth intermediate material 36 as shown in
FIG. 2I is formed by subjecting respective portions of the seventh
intermediate material 35 to predetermined plastic working.
Particularly, at this occasion, a guide cylinder portion element 37
in a cylindrical shape extended in a direction opposed to a shaft
portion element 32e in an axial direction is formed at an inner end
portion in a diameter direction of the attaching flange element 30
constituting the eighth intermediate element. Successively, a ninth
intermediate material 38 as shown in FIG. 2J is formed by
subjecting respective portions of the eighth intermediate material
36 to predetermined plastic working. Particularly, at this
occasion, by shaping outer shapes of the guide cylinder portion
element 37 and the shaft portion element 32e constituting the
eighth intermediate material 36, the guide cylinder portion 16b and
the shaft portion 19b are respectively constituted. Further, in the
case of the embodiment, the ninth intermediate material 38 is
constituted in a state of providing the ninth intermediate material
38 in this way. The wall thickness T.sub.24 of the portion 24
continuous to the attaching flange element 30 and the shaft portion
19b is made to be larger than the wall thickness t.sub.1 of the
material plate 26 (T.sub.24>t.sub.1). Successively, by
subjecting the attaching flange element 30 constituting the ninth
intermediate material 38 to working for shaping an outer shape of
the attaching flange element 30, a tenth intermediate material 39
as shown in FIGS. 2K and 2L is formed. That is, at this occasion,
by subjecting the attaching flange element 30 constituting the
ninth intermediate material 38 to chipping off (trimming) for
shaping a shape of an outer peripheral edge and punching (piercing)
for forming a hole 58 for press-fitting a stud 9 (FIG. 1), the
attaching flange element 30 is made to constitute the attaching
flange 5b.
[0038] When the above-described tenth intermediate material 39 is
provided, thereafter, by subjecting respective portions of the
tenth intermediate material 39 to turning and polishing for
constituting accuracy, there is provided the hub 1d as shown in
FIG. 1 (however, the calking portion 20 is not formed at the inner
end portion and the shape of the inner end portion is a cylindrical
shape). Further, when the metal plate is subjected to cold plastic
working to form as in the embodiment, working accuracy can be
improved. Therefore, when shape accuracy of a state of providing
the tenth intermediate material 39 is excellent, the
above-described working for constituting accuracy which is carried
out for the tenth intermediate material 39 can also be omitted.
[0039] Next, FIGS. 3A-0 show steps of fabricating the outer race
3a. Further, all of respective steps shown in FIGS. 3B through 3K,
and 3M and 3O are steps of cold plastic working. In fabricating the
outer race 3a, first, by punching a metal plate constituting a
material (for example, a plate made of S55C through S48C which can
be quenched by high frequency after forming can be used. The plate
thickness t.sub.2 is determined in consideration of a size of the
outer race 3a to be produced), a material plate 40 as shown in FIG.
3A is provided. In the case of the embodiment, a planer shape
(shape viewed from upper side or lower side of the drawing) of the
material plate 40 is constituted by a quadrangular shape. Thereby,
yield in providing the material plate 40 by punching the metal
plate (for example, strip plate or coil member) constituting the
material as described above is increased.
[0040] When the above-described material plate 40 is provided,
successively, by drawing the material plate 40, there is formed a
first intermediate material member 41 one end side (upper side of
the drawing) of which is opened, a section of which is in a U-like
shape and in a shape of a bottomed cylinder as shown in FIG. 3B.
Further, generally, in the case of drawing the material plate, when
a thickness of the material plate is increased, a radius of
curvature of a front end portion of a drawing die to be used is
also increased. As a result, particularly, when a planer shape of
the material plate is a circular shape, a sufficient cushion force
is difficult to be exerted and when the material plate is drawn, a
side thereof is liable to be shifted. In contrast thereto, when the
planer shape of the material plate 40 is formed by the quadrangular
shape as in the embodiment, the cushion force is operated to
concentrate on four portions of corner portions of the material
plate 40, further, the side can be made to be difficult to shift
when the material plate is drawn as described above since uniform
curl is present at the four portions of the material plate 40.
Successively, by coining a bottom portion of the first intermediate
material 41, there is formed a second intermediate material 42 a
wall thickness of a bottom portion of which is thin at a center
portion and thick at a peripheral edge portion, as shown in FIG.
3C. Successively, by punching (piercing) the center portion the
wall thickness of which is thinned in the bottom portion of the
second intermediate material 42, a third intermediate material 43
as shown in FIG. 3D is formed. Successively, by contracting a
diameter of a half portion on other end side (lower side of the
drawing) of the third intermediate material 43, a fourth
intermediate material 44 as shown in FIG. 3E is formed. Further, a
main body element 45a in a cylindrical shape constituting a
cylinder portion is constituted by the half portion on the lower
end side of the fourth intermediate material 44 a wall thickness of
which is increased by contracting the diameter in this way.
[0041] Successively, the half portion on one end side of the fourth
intermediate material 44 is pressed to open over an entire
periphery thereof in two steps. That is, by pressing to open the
half portion at a first step, there is constituted a fifth
intermediate material 46 a half portion on one end side of which is
pressed to open by 45 degrees relative to a center axis as shown in
FIG. 3F. Further, by pressing to open the half portion at a second
step, there is formed a sixth intermediate material 47 a half
portion on one end side of which is pressed to open by 90 degrees
relative to the center axis as shown in FIG. 3G. Further, the half
portion on the one end side pressed to open by 90 degrees relative
to the center axis in this way is made to constitute a coupling
flange element 48a constituting a flange portion. Further,
generally, in a case of forming a flange portion by pressing to
open an end portion of a cylindrical member horizontally, when the
end portion of the cylindrical member is continuous over an entire
periphery thereof, a large tensile stress in a circumferential
direction is applied when the end portion is pressed to open, a
material is liable to be ruptured. In contrast thereto, in the case
of the embodiment, since the planer shape of the material plate 40
is the quadrangular shape, the half portion on the one end side of
the fourth intermediate material 44 constituting the portion to be
pressed to open is not constituted by the shape continuous over the
entire periphery (shape in which four portions in a circumferential
direction are projected from an axial direction than other
portions). Therefore, operation of pressing to open the half
portion on the one end side of the fourth intermediate material 44
as described above becomes operation near to simple bending, a
large tensile stress in the circumferential direction is not
applied and the material is not liable to be ruptured.
[0042] At any rate, when the above-described sixth intermediate
material 47 is provided, successively, the main body element 45a
constituting the sixth intermediate material 47 is subjected to
drawing with ironing. Thereby, a seventh intermediate material 49
as shown in FIG. 3H is formed by making a portion of a wall of the
main body element 44a plastically flow to a portion 25a continuous
to the main body element 45a and the coupling flange element 48a.
In the case of the embodiment, by providing the seventh
intermediate material 49 in this way, a wall thickners T.sub.24a of
the continuous portion 25a constituting the seventh intermediate
material 49 is made to be sufficiently larger than the wall
thickness t.sub.2 of the material plate 40
(T.sub.24>t.sub.2)
[0043] Successively, by pressing other end face of a main body
element 45b in an axial direction {upper side of FIG. 3H} in a
state of fixing the coupling flange element 48a constituting the
seventh intermediate material 49, an eighth intermediate material
50 as shown in FIG. 3I is formed by making a portion of a wall of
the continuous portion 25a plastically flow in a direction opposed
to the main body element 44b in the axial direction. Successively,
by forming a wall raised at one end face of the continuous portion
25a constituting the eighth intermediate material 50, there is
formed a ninth intermediate material 52 including a fitting
cylinder portion element 51 in a cylindrical shape at one end face
of the continuous portion 25a. Successively, by subjecting
respective portions of the ninth intermediate material 52 to
predetermined plastic working, a tenth intermediate material 53 as
shown in FIG. 3K is formed. Particularly, at this occasion, a
fitting cylinder portion 14a is constituted by shaping an outer
shape of the fitting cylinder portion element 51 constituting the
ninth intermediate material 52. Further, in the case of the
embodiment, in a state of providing the tenth intermediate material
53 in this way, the wall thickness T.sub.2.sup.5 of the portion 25
continuous to a coupling flange element 48a and the main body
element 45c is made to be larger than the wall thickness t.sub.2 of
the material plate 40 (T.sub.25>t.sub.2).
[0044] Successively, by subjecting the coupling flange element 48a
constituting the tenth intermediate material 53 to chipping off
(trimming) for shaping an outer shape of the coupling flange
element 48a, an eleventh intermediate material 54 as shown in FIGS.
3L and 3N is provided. Further, as shown in FIG. 3L, a planer shape
of an outer peripheral edge of the coupling flange element 48b
constituting the eleventh intermediate material 54 is substantially
a quadrangular shape. Meanwhile, in the case of the embodiment, the
planer shape of the material plate 40 is formed by the quadrangular
shape as described above and therefore, also a planer shape (not
illustrated) of the outer peripheral edge of the coupling flange
element 48a constituting the tenth intermediate material 53 becomes
substantially a quadrangular shape. Therefore, in the case of the
embodiment, an amount of chipping off the outer peripheral edge
portion of the coupling flange element 48a can be reduced.
Therefore, the yield of the material can be improved.
[0045] When the above-described eleventh intermediate material 54
is provided, successively, by respectively punching (piercing) four
portions in a circumferential direction of a coupling flange
element 48b constituting the eleventh intermediate material 54,
there is constituted a twelfth intermediate material 57 formed with
element holes 56, 56 for forming screw holes 55 (FIG. 1) for
screwing coupling bolts as shown in FIG. 3M and 3O.
[0046] When the above-described twelfth intermediate material 57 is
provided, thereafter, the outer ring 3a as shown in FIG. 1 is
provided by turning for forming the outer race tracks 13a, 13b
(FIG. 1) of double rows at an inner peripheral face of the twelfth
intermediate material 57, tapping inner peripheral faces of the
respective element holes 56, 56 for forming screw grooves, and
turning and polishing for constituting accuracy. Further, when the
invention is embodied, the outer race tracks 13a, 13b of double
rows can also be formed by the above-described cold plastic
forming. Further, similar to the above-described case of steps of
fabricating the hub 1d, when shape accuracy of a state of providing
the twelfth intermediate material 57 is excellent, the
above-described working for constituting accuracy which is carried
out for the twelfth intermediate material 57 can also be
omitted.
[0047] As described above, in the case of the embodiment, the hub
1d and the outer race 3a are produced by subjecting the metal
plates to cold plastic working and therefore, dimensional accuracy
after the cold plastic working can be improved. Therefore, working
for constituting accuracy which is carried out thereafter can be
reduced or can be omitted. Further, in the case of the embodiment,
the hub 1d and the outer race 3a are constituted by integrally
molded products. Therefore, yield of material can be improved,
further, since a plurality of members need not to couple by welding
or the like, fabricating cost can be reduced. Further, in the case
of the embodiment, wall thicknesses T.sub.24, T.sub.25 of the
portions 24, 25 continuous to the cylinder portions (shaft portion
19b, main body 12a) constituting the hub 1d and the outer race 3a
and the flange portions (attaching flange 5b, coupling flange 11a)
can be made to be larger than the wall thicknesses t.sub.1, t.sub.2
of the metal plates constituting the material plates
(T.sub.24>t.sub.1, T.sub.25>t.sub.2). Therefore, even when
metal plates having large wall thicknesses more than necessary are
not used, strength (wall thickness) of the respective continuous
portions 24, 25 are sufficiently be ensured. Therefore, a reduction
in fabricating cost and. light-weighted formation can be achieved
also in this regard.
[0048] Further, the invention is not limited to the structure of
the above-described embodiment but applicable also to, for example,
the hub 1a forming the hub unit for supporting the wheel for the
driven wheel as shown in FIG. 5, mentioned above, and the hub 1b
forming the hub unit for supporting the wheel for the drive wheel
as shown in FIG. 6, mentioned above.
[0049] Further, when the invention is embodied, the material of the
metal plate for producing the race member is not limited to the
material exemplified in the above-described embodiment but various
materials can be used therefor.
* * * * *