Bearings – Rotary bearing – Antifriction bearing
Reexamination Certificate
2001-08-23
2004-03-09
Graham, Matthew C. (Department: 3683)
Bearings
Rotary bearing
Antifriction bearing
C384S544000
Reexamination Certificate
active
06702472
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a wheel bearing device for rotatably supporting wheels with respect to suspensions for automobiles, and a method of crimping for the wheel bearing device which is performed in order to apply a preload to the rolling elements of the wheel bearing device.
As to wheel bearing devices for rotatably supporting wheels with respect to the suspension of an automobile, there are those which are disclosed, for example, in Japanese Patent Kokai Hei 10-95203, Japanese Patent Kokai Hei 10-196661, Japanese Patent Kokai Hei 10-272903, and Japanese Patent Kokai Hei 11-129703. Typical of these is Japanese Patent Kokai Hei 10-272903, and the wheel bearing device disclosed therein is shown in FIG.
8
.
This wheel bearing device comprises a hub ring
1
, an inner ring
2
, two rows of rolling elements
3
, and an outer ring
4
.
The hub ring
1
is formed on its outer peripheral surface with a raceway surface
5
on the outboard side and is provided with a flange
6
for attaching a wheel (not show). Hub bolts
7
for fixing a wheel disk are circumferentially equidistantly attached in the flange
6
. Further, the inner ring
2
is fitted in a small-diameter stepped portion
8
formed on the inboard side of the hub ring
1
, and is formed at its outer peripheral surface with a raceway surface
9
on the inboard side. The inner ring
2
is press-fitted with a suitable amount of interference in order to prevent creep. The raceway surfaces
5
and
9
positioned on the outboard and inboard sides of a vehicle, respectively, cooperate with each other to constitute two rows of raceway surfaces.
The outer ring
4
is formed at its inner peripheral surface with two rows of raceway surfaces
10
and
11
opposed to the raceway surfaces
5
and
9
of the hub ring
1
and inner ring
2
and is provided with a flange
12
for attachment to the vehicle. Rolling elements
3
are installed between the raceway surfaces
5
,
9
of the hub ring
1
and inner ring
2
and two rows of raceway surfaces
10
and
11
of the outer ring
4
. Seals
13
and
14
are installed in the openings in the opposite ends of the wheel bearing, that is, between the outer peripheral surfaces of the hub ring
1
and inner ring
2
and the inner peripheral surface of the outer ring
4
, so as to prevent leakage of the grease filled therein and intrusion of water or foreign matter from outside.
In the case where this wheel bearing device is used for driven wheels, in order to prevent falling of the inner ring
2
press-fitted in the small-diameter stepped portion
8
of the hub ring
1
, the cylindrical end of the hub ring
1
is diametrically outwardly crimped by a swing type crimping punch
m
, as shown in
FIG. 9
, and the inner ring
2
is fixed on the hub ring
1
by the thus-formed crimped portion
15
. Crimping the end of the hub ring
1
sets the bearing clearance at a predetermined value and applies a proper preload.
As to this crimping method, there is one as known from Germany Patent DE19613441A1, which comprises the steps of finding a load-displacement curve for the end of the hub ring
1
in cold-working the crimped portion, and controlling the punch
m
such that the terminal point of this displacement curve corresponds to a predetermined load value proportional to the required amount of preload. Besides this, there is a common method for crimping, with the lower dead point of the punch
m
kept constant.
In this connection, with the conventional wheel bearing device described above, when the crimped portion
15
is formed by plastically deforming the end of the hub ring
1
in order to fix the inner ring
2
on the hub ring
1
, the outer diameter surface of the inner rig
2
bulges diametrically outward, resulting in causing nonnegligible deformation in the raceway surface
9
formed on the outer diameter surface of the inner ring
2
, and excessive circumferential stresses in the positions where the rolling elements
3
contact the inner ring
2
, sometimes shortening the rolling fatigue life. Thus, in order to inhibit the increase of circumferential stresses at contact positions caused by crimping, it is necessary that the dimension from the contact position to the crimped portion
15
be greater than the predetermined value; thus, the inner ring
2
has inevitably increased axially on the inboard side.
On the other hand, while the bearing clearance is set at a predetermined value by crimping the end of the hub ring
1
, as described above, if such crimping deforms the inner ring
2
, the bearing clearance would deviate from the predetermined value, making it difficult to obtain the intended bearing characteristics.
Further, since expensive bearing steels, for example, high carbon steels such as SUJ2 defined by JIS G 4805 as high carbon chromium steels for bearings have been used for inner rings
2
, there has been a problem that this leads to increasing the costs of products.
Further, in the case of the crimping method which finds a load-displacement curve for the end of the hub ring
1
and controls the punch
m
such that the load is of a predetermined value, variations in load during actual machining with respect to the predetermined load value or variations in hardness and dimension of raw material directly appear as variations in the amount of preload, making it difficult to control the amount of preload so as to keep the latter in a suitable range. Further, since the greater the lowering speed of the punch
m
, the greater the gradient of load and the lower the accuracy of load control, actual machining is performed with the lower speed of the punch
m
set at a value on the conservative side, making it difficult to increase the machining efficiency.
Further, in the case of the common crimping method with the lower dead point of the punch kept constant, the machining efficiency can be increased by increasing the lowering speed of the punch, decreasing the variations in preload due to variations in the hardness of the raw material. However, there is still a problem that variations in dimension of the raw material inevitably increase variations in the amount of preload.
SUMMARY OF THE INVENTION
An object of the invention is to provide an inexpensive wheel bearing device which inhibits the deformation of an inner ring and is superior in durability.
A wheel bearing device according to the invention comprises an outer member having a car body-attached flange attached to a car body and two rows of raceway surfaces in the inner periphery, an inner member composed of a hub ring having a wheel-attaching flange for attaching a wheel and formed with one raceway surface in the outer periphery and an inner ring fitted on a small-diameter stepped portion of said hub ring and formed with the other raceway surface in the outer periphery, and two rows of rolling elements installed between the respective raceway surfaces of said inner and outer members, the end extending from the small-diameter stepped portion of said hub ring being crimped for their inseparable integration, and said wheel bearing device is characterized by the following points;
{circle around (1)} The end of said hub ring before being crimped is in the form of a hollow cylindrical portion whose wall-thickness gradually increases toward the front end. {circle around (2)} The outer end surface of said crimp portion is formed of a first taper surface whose wall thickness gradually increases from a deformation start point side in the direction of the outer diameter and the angle formed between said first taper surface and a radial plane is set within the range of 0-30°.
This makes it possible to reduce the deformation of the inner ring to a negligible extent, so that the distance from the crimp portion to the position where the rolling elements and the inner ring contact each other can be reduced provided that the rolling fatigue life is secured, and the inner ring and hub ring are designed compactly in the direction of the axle. Therefore, reduction of product weight can be attained and application of
Nishio Katsuhiko
Sera Akira
Suzuki Syougo
Arent Fox Kintner & Plotkin & Kahn, PLLC
Graham Matthew C.
NTN Corporation
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