Land vehicles: wheels and axles – Wheel – Hub
Reexamination Certificate
2001-02-22
2004-01-06
Stormer, Russell D. (Department: 3617)
Land vehicles: wheels and axles
Wheel
Hub
C301S006100, C029S898090, C188S01800A, C188S2180XL, C384S544000
Reexamination Certificate
active
06672679
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an improvement of a bearing unit for wheel for supporting a wheel of an automobile as well as a rotary body for braking such as a rotor or a drum, and to an improvement of a method of manufacturing such a bearing unit for wheel.
2. Description of the Related Art
A wheel
1
constituting a traveling wheel of an automobile and a rotor
2
constituting a disc brake as a braking apparatus are rotatably supported by a knuckle
3
which constitutes a suspending apparatus with a structure, for example, as shown in FIG.
8
. To be specific, a circular supporting hole
4
is formed in the knuckle
3
. An outer ring
6
being a stationary ring constituting a bearing unit
5
for the wheel, to which the present invention is applied, is fixed to within the supporting hole
4
by use of a plurality of bolts
7
. On the other hand, the wheel
1
and the rotor
2
are fixedly connected to a hub
8
as a component of the wheel bearing unit
5
through a plurality of studs
9
and a plurality of nuts
10
.
Outer ring double raceways
11
a,
11
b
each serving as a stationary-side raceway surface are formed in an inner circumference of the outer ring
6
, and a joint flange
12
is provided on an outer circumference thereof. The thus configured outer ring
6
is fixed to the knuckle
3
by connecting the joint flange
12
to the knuckle
3
by the bolts
7
.
On the other hand, a mounting flange
13
is formed at a portion projecting from an outer end opening of the outer ring
6
, and the flange
13
is formed at a part of the outer circumference of the hub
8
. (Herein, the term “outer” implies an outside portion in the width direction in a state of being assembled to the automobile, that is, the left side in
FIGS. 1 through 4
,
6
and
8
. In contrast, the term “inner” implies a central portion in the width direction in the state of being assembled to the automobile, that is, the right side in
FIGS. 1 through 4
,
6
and
8
). The wheel
1
and the rotor
2
are fixedly connected in combination to one side surface of the flange
13
(in general, the outer side as illustrated) through the studs
9
and nuts
10
. Further, an inner ring raceway
14
a
is formed in a portion, facing to the more external raceway
11
a
of the outer ring double raceways
11
a,
11
b,
of the outer peripheral face of an intermediate portion of the hub
8
. Moreover, an inner ring is fixedly connected onto a small-diameter stepped portion
15
formed at the inner end of the hub
8
. An inner ring raceway
14
b
formed at the outer peripheral of the inner ring
16
is disposed opposite to the more internal raceway
11
b
of the outer ring double raceways
11
a,
11
b.
Balls
17
,
17
each defined as a rolling member are provided in a rollable manner by pluralities between the outer ring raceways
11
a
and
11
b
and the inner ring raceways
14
a
and
14
b,
in a state of being held by retainers
18
,
18
. With this structure being provided, a double-row angular ball bearing with a back face combination is structured, the hub
8
is rotatably supported in the inner side of the outer ring
6
so as to support radial and thrust loads. Between the inner peripheries of both ends of the outer ring
6
, the outer periphery of the intermediate portion of the hub
8
, and the outer periphery of the inner end of the inner ring
16
, seal rings
19
a,
19
b
are provided respectively to intercept a space holding the balls
17
,
17
from an outside space. Further, since the illustrated embodiment is the wheel bearing unit
5
for a drive wheel (a rear wheel of FR car and RR car, a front wheel of FF car and all wheels of 4WD car), the hub
8
has a spline hole
20
formed at the center thereof. Then, a spline shaft
22
of a constant speed joint
21
is inserted into the spline hole
20
.
When the rolling bearing unit
5
for the wheel is used, the outer ring
6
is fixedly connected to the knuckle
3
and at the same time the wheel
1
combined with a tire (not shown) and the rotor
2
are fixedly connected to the fitting flange
13
of the hub
8
, as shown in FIG.
8
. The rotor
2
of these components is combined with a support and a caliper (both not shown) which are fixed to the knuckle
3
, thus constituting a disc brake for braking. When braking operation, a pair of pads sandwiching the rotor
2
are pressed against both side surfaces of the rotor
2
.
It is known that vibrations called as a judder followed by unpleasant noises often occur when braking the automobile. As one of various causes of these vibrations, known is an ununiform state of frictions between the side surface of the rotor
2
and the lining of the pad, however, deflections of the rotor
2
are also known as other causes. Deflection of the rotor
2
is also a big cause. That is, the side surface of the rotor
2
must be substantially normal to the rotation center of the rotor
2
. It is, however, difficult to obtain a perfect perpendicularity due to an unavoidable manufacturing error. As a result, while the car is running, the side surface of the rotor
2
will inevitably deflect in the direction of the rotation axis (left and right directions in
FIG. 8
) though being more or less. When the deflection is increased (displacing amount in the left and right directions in the same), and the linings of the pair of pads are pressed against both sides of the rotor
2
for braking, the judder is produced.
For restraining the judder generated by such causes, it is important to suppress (improve) the deflection (axial deflection) in the axial directions of the side surfaces of the rotor
2
. And for preventing this deflection, it is necessary to improve a perpendicularity of the mounting surface (one side surface of the mounting flange
13
) of the mounting flange
13
with respect to the rotational center of the hub
8
as well as the surface precision of the mounting surface itself. There respectively exist a plurality of factors giving influences to the perpendicularity and the surface precision. As remarkably influencing factors, they are, as to the perpendicularity, a parallelism between the mounting surface and the raceway surface (the outer ring raceways
11
a,
11
b
and the inner ring raceways
14
a,
14
b
), and as to the surface precision, a heat treatment deformation, and elastic deformation or plastic deformations accompanied with press-fitting of the studs
9
into the mounting holes. Further, for heightening the parallelism of these factors, among the constructive elements of the hub
8
, there must be a necessity for setting highly accurately a positional relationship between the mounting surface of the mounting flange
13
, the inner ring raceway
14
a
formed in the outer periphery of the intermediate portion thereof and the stepped part
15
of small diameter formed at the inner end of the same, and configurations and dimensions of these components. If the precision of shapes and dimensions of the inner ring raceway
14
a
and the small-diameter stepped portion
15
are enhanced in connection to the mounting surface, the perpendicularity of the mounting surface with respect to the rotational center of the hub
8
may be increased. Further, if removing the heat treatment deformation, elastic or plastic deformation of the mounting surface, the surface precision of the mounting surface may be enhanced.
A technology for preventing the deflection of the flange
13
which conduces to the deflection of the rotor
2
is disclosed, for example, in JP-A-10-217001. However, since the prior art disclosed in this publication precisely finishes a surface which is not originally needed as a reference surface, not only a cost increases, but also no consideration is taken for applying a heat treatment to the respective components. On the other hand, since the inner ring raceway
14
a
and the small-diameter stepped portion
15
are hardened over the surfaces thereof, a heat treatment such as a high frequency hardening is required. Since the configurations and dimens
NSK Ltd.
Stormer Russell D.
Sughrue & Mion, PLLC
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