Bearings – Rotary bearing – Antifriction bearing
Reexamination Certificate
2002-04-01
2004-01-06
Bucci, David A. (Department: 3682)
Bearings
Rotary bearing
Antifriction bearing
C301S108100
Reexamination Certificate
active
06672770
ABSTRACT:
FIELD OF THE INVENTION
The present invention is related to a rolling bearing unit for vehicle wheel support, specifically for rotatably supporting a vehicle wheel of an automobile with reference to a suspension apparatus.
BACKGROUND OF THE INVENTION
The vehicle wheel of the automobile is supported by a rolling bearing unit for vehicle wheel support as shown in
FIG. 17
where an example of the conventionally widely used rolling bearing units is illustrated.
This rolling bearing unit
1
for vehicle wheel support comprises a hub
2
, an inner ring
3
, an outer ring
4
and a plurality of rolling elements
5
. The hub
2
has an outer peripheral surface the axially outer end portion of which is formed with a first flange
6
to support the vehicle wheel.
The term “axially outer” means the widthwise outer side when installed in the automobile; the left side in the Figures in this application except for
FIGS. 4
to
6
, while the term “axially inner” means the widthwise central side when installed in the automobile; the right side in the Figures in this application except for
FIGS. 4
to
6
.
The intermediate portion of the outer peripheral surface of the hub
2
is formed with a first inner ring raceway
7
while the axially inner end portion of the outer peripheral surface is formed with a step portion
8
with a smaller diameter.
The inner ring
3
is fitted onto the step portion
8
and formed with a second inner ring raceway
9
on its outer peripheral surface.
The hub
2
has an axially inner end portion formed with a male thread portion
10
thereon, the tip end portion of which is projected axially inwards than the axially inner end face of the inner ring
3
.
A nut
11
is screwed on the male threaded portion
10
. The inner ring
3
is supported between the nut
11
and the step face
12
of the step portion
8
, and thereby fixed at a determined position of the hub
2
.
The male threaded portion
10
is formed with an engagement recess portion
14
in the outer peripheral surface of its tip end portion. After the nut
11
is clamped with a predetermined torque, a portion of the nut
11
in alignment with the engagement recess portion
14
is crimped radially inwards to prevent the nut
11
from being loosened.
Formed on the inner peripheral surface of the outer ring
4
are a first outer ring raceway
15
which is opposed to the first inner ring raceway
7
and a second outer ring raceway
16
which is opposed to the second inner ring raceway
9
. A plurality of rolling elements
5
are provided between the first outer ring raceway
15
and the first inner ring raceway
7
and between the second outer ring raceway
16
and the second inner ring raceway
9
, respectively.
Although balls are used for the rolling elements in the figure, tapered rollers may be used for the rolling elements in the case of the rolling bearing unit for the heavy automobiles.
In order to install the rolling bearing unit
1
as mentioned above into the automobile, a second flange
17
is formed on the outer peripheral surface of the outer ring
4
, and used to fix the outer ring
4
to a suspension apparatus, thereby fixing the vehicle wheel to the first flange
6
. Thus, the vehicle wheel can be rotatably supported by the suspension apparatus.
Disclosed in the specification of U.S. Pat. No. 5,490,732 is a rolling bearing unit
1
for vehicle wheel support, which is illustrated as a second conventional example in FIG.
18
.
This bearing unit
1
comprises a hub
18
having an peripheral surface on which a first flange
6
is provided and an inner ring
41
and a second inner ring
3
are fitted. The hub
18
has an axially inner end portion which is projected axially inwards than the axially inner end face of the second inner ring
3
and bent radially outwards to form a crimped portion
19
. This crimped portion
19
cooperates with the step face
12
provided on the base portion of the first flange
6
on the outer peripheral surface at the intermediate portion of the hub
18
to support the first inner ring
41
and second inner ring
3
therebetween. Specifically, the axially inner end portion of the hub
18
which is projected axially inwards than the second inner ring
3
is formed with a cylindrical portion which is crimped radially outwards to form the crimped portion
19
, which retains the first inner ring
41
and second inner ring
3
onto the step face
12
.
In the case of the first conventional example illustrated in
FIG. 17
, the processes for forming the engagement recess portion
14
on the tip end of the male thread portion
10
and crimping a portion of the nut
11
radially inwards are required. This leads to the cost up due to inconvenient parts production and assembling processes of the bearing unit
1
for vehicle wheel support.
In the case of the second conventional example in
FIG. 18
, the crimped portion
19
must be formed on the hub
18
to fix the first inner ring
41
and second inner ring
3
to the hub
18
. Accordingly, the hub
18
must be made of a material which can be formed with the crimped potion
19
. Specifically, in the case of the second conventional example in
FIG. 18
, since the hub
18
itself is formed with no inner ring raceway, that is since the first and second inner ring raceways
7
,
9
are formed on the outer peripheral surface of the first and second inner rings
41
,
3
fitted onto the hub
18
, the hub
18
can be made of a carbon steel containing less than 0.45 weight % carbon which is easily processed to form the crimped portion
19
. However, as the crimped portion
19
is formed, a large load is applied to the second inner ring
3
fitted onto the hub
18
, resulting in that the second inner ring
3
is deformed and that the inner clearance (plus or minus) of the rolling bearing unit may be displaced from the required value. When the inner clearance of the rolling bearing unit is displaced from the proper value, the rolling fatigue life of the second inner ring raceway
9
formed on the outer peripheral surface of the second inner ring
3
may be reduced.
Such inconvenience may be produced in the structure where the structure of FIG.
17
and the structure of
FIG. 18
are combined to provide the hub
2
with the first flange
6
and the first inner ring raceway
7
and where the inner ring
3
is securely affixed to the hub
2
by way of the crimped portion
19
.
In addition, in such a construction, when the hub
18
is made of a carbon steel containing less than 0.45 weight % carbon as in the conventional structure of
FIG. 18
, it is impossible to make the hardness in the portion of the first inner ring raceway
7
sufficiently large, and to secure the sufficient durability of the portion of the first inner ring raceway
7
.
SUMMARY OF THE INVENTION
An objective of the present invention is to provide a rolling bearing unit for vehicle wheel support with sufficient durability and lower cost.
Another objective of the present invention is to provide a bearing unit for vehicle wheel support comprising a shaft having a mounting flange for vehicle wheel or suspension apparatus, a step portion formed on one end portion thereof, a first inner ring raceway directly formed thereon, and a crimped portion formed on the end side of the step portion, and an inner ring fitted onto the step portion and having a second inner ring raceway thereon, the shaft being quench hardened at least at the first inner ring raceway with the crimped portion kept as formed and without quench hardened, and the inner ring being fixed to the shaft by the crimped portion of the shaft.
REFERENCES:
patent: 3583511 (1971-06-01), Asberg
patent: 3589747 (1971-06-01), Asberg
patent: 3713905 (1973-01-01), Philip et al.
patent: 4241957 (1980-12-01), Peck
patent: 4537270 (1985-08-01), Brandenstein et al.
patent: 4651140 (1987-03-01), Duggan
patent: 4880281 (1989-11-01), Merkelbach
patent: 4958944 (1990-09-01), Hofmann et al.
patent: 5030017 (1991-07-01), Murakami et al.
patent: 5131145 (1992-07-01), Badoureaux
patent: 5182079 (1993-01-01), Nelson
patent: 5226738 (1993
Kuwano Takafumi
Miyazaki Hiroya
Ohnuki Yoshihisa
Ouchi Hideo
Sawai Hiroyuki
Bucci David A.
Hansen Colby
NSK Ltd.
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