Spring devices – Vehicle – Torsion
Reexamination Certificate
2001-03-16
2002-11-05
Rodriguez, Ram (Department: 3613)
Spring devices
Vehicle
Torsion
C267S033000, C267S140300, C267S141000, C267S153000
Reexamination Certificate
active
06474631
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a vehicle stabilizer bushing entirely made of rubber having a sliding surface on the inner side thereof particularly suitable for mounting a stabilizer bar in automobile suspension on the vehicle body or suspension. The present invention can be applied also to a rubber laminate having a sliding rubber portion other than stabilizer bushing.
The present application is based on Japanese Patent Applications No. 2000-73651 and No. 2000-215001, which are incorporated herein by reference.
2. Description of the Related Art
A conventional vehicle stabilizer bushing
112
has a structure as shown in
FIG. 10
(see JP-A-60-180619 (The term “JP-A” as used herein means an “unexamined published Japanese patent application”)).
A rubber elastic member
10
constituting the stabilizer bushing
112
is essentially a cylindrical material surrounded by an inner surface
114
and an outer surface
16
(formed by a U-shaped surface
16
a
and a flat surface
16
b
closing the upper opening thereof). The cylindrical material is provided with a flange portion
101
at the both axial ends of the U-shaped surface
16
a
and a cut
120
for allowing a stabilizer bar S to be inserted thereinto. The vehicle stabilizer bar S is inserted into and retained by the thick cylindrical rubber elastic member
10
.
In order to mount the bushing
112
on the vehicle body, the bushing
112
is fitted on the stabilizer bar S through the cut
120
, and then mounted on the vehicle body with a bracket
20
. In some detail, the both mounting seats
20
b
of the U-shaped retaining portion are screwed to the vehicle body (not shown) through a hole
201
with the U-shaped surface of the bushing
112
being retained by the bracket
20
at its U-shaped retaining portion
20
a.
The radially protruding flange
101
provided at both axial ends of the rubber elastic member
10
prevents the rubber elastic member
10
from coming off from the bracket
20
.
It has been found that when the torsional torque developed upon the reception of torsion of the stabilizer bar S retained by the bushing
12
is reduced, it has an effect on the riding comfort. A known technique for reducing torsional torque of the stabilizer bar S is a bushing having an inner surface formed by a resin layer having high sliding properties (low friction coefficient) (JP-A-63-57310, JP-A-63-57311, etc.).
However, the bushing having an inner surface formed by a resin layer is disadvantageous in that the elastic modulus (spring constant) of the entire bushing can hardly be lowered than a predetermined value since the resin material has a high elastic modulus (spring constant) than the rubber material. On the other hand, in the case a soft rubber material is used as the rubber portion of the bushing so as to derive an elastic modulus (spring constant) of the entire bushing lower than a predetermined value, the resulting bushing has a deteriorated durability.
In order to cope with the foregoing problems, JP-A-10-82441 proposes a bushing
112
a
arranged such that a sliding rubber portion (rubber with high sliding properties)
10
a
which comes in contact with the stabilizer bar S is formed on the inner surface of a main body rubber portion (base rubber)
10
b
constituting the outer surface as shown in FIG.
12
.
Further, a stabilizer bushing comprising a rubber elastic member
10
consisting of two layers, namely, inner layer rubber
10
a
made of a rubber material having high sliding properties and outer layer rubber
10
b
as shown in
FIG. 11
has recently been studied. The structure of stabilizer bushing shown in
FIG. 10
is disadvantageous in that the desired stability in operation and riding comfort can hardly be attained at the same time, that is, when the rigidity of the rubber elastic member
10
is raised to enhance the stability in operation, the riding comfort is deteriorated while when the rubber elastic member
10
is made of a softer material, the stability in operation is deteriorated. Meanwhile, the structure of
FIG. 11
is advantageous in that the riding comfort is raised since the sliding resistance of the inner layer rubber
10
a
is low, as well as in that the stability in operation is improved since the outer layer rubber
10
b
can be made of a rubber material having a higher rigidity than that of the inner layer rubber
10
a
to enhance the rigidity of the rubber elastic member
10
. Further, the generation of abnormal noise due to rapid relative displacement between the inner layer rubber
10
a
and the stabilizer bar S can be prevented.
However, the most modern design of vehicles requires that components be received in as small area as possible. Thus, there is no sufficient space between the components. Therefore, when the stabilizer bar S makes an axial relative movement with respect to the rubber elastic member
10
to show a horizontal shift, the stabilizer bar S can interfere with its surrounding components. In order to cope with this problem, a horizontal shift stopper
2
made of metal ring is provided around the stabilizer bar S as shown in
FIG. 11
to control the relative movement. However, a new problem has arisen that the horizontal shift stopper
2
and the rubber elastic member
10
generate abnormal noise by an interference with each other.
Besides, the bushing
112
a
having the foregoing structure is normally prepared by using an injection mold as shown in FIG.
13
.
In some detail, the main body rubber portion
10
b
is prepared by injection-molding a rubber material for main body rubber portion (first rubber compound) which has been injected through a first material injection passage
34
in a cavity for main body rubber portion
32
formed by a first top force
28
and a bottom force
30
. When the vulcanization of the main body rubber portion
10
b
has proceeded to a certain extent, the first top force
28
is then replaced by a second top force
36
. A rubber material for sliding rubber portion (second rubber compound) is then injected into a cavity for sliding rubber portion
38
formed inside the main body rubber portion
10
b
through a second material injection passage
40
so that it is injection-molded. When the vulcanization of the main body rubber portion
10
b
as well as the sliding rubber portion
10
a
has been completed, the mold is then opened to release the bushing (molded product)
It was found that if the vulcanization of the main body rubber portion
10
b
proceeds too much (e.g., 90% vulcanization) at the time the second rubber compound is injected, there cannot be made a sufficient vulcanized bonding (co-crosslinking: by simultaneous vulcanization) between the main body rubber portion
10
b
and the sliding rubber portion
10
a
. The term “co-crosslinking (co-vulcanization)” as used herein is meant to indicate crosslinking between different rubber phases. The term “co-crosslinking agent” as used herein is meant to indicate a vulcanizing agent to be added for the purpose of improving the foregoing “co-crosslinkability”.
If the time of injection of the second rubber compound is predetermined to be sooner from that of the first rubber compound (50% vulcanization), a sufficient vulcanized bonding strength can be attained. However, the main body rubber portion
10
b
is insufficiently vulcanized, reducing stability in shape of the main body rubber portion
10
b
. Thus, this approach is not practical. In other words, the injection pressure of the material for sliding rubber portion may cause the main body rubber portion
10
b
to be compressed or the raw material for sliding rubber portion to penetrate into interfaces between the main body rubber portion
10
b
and the forces
30
,
36
, generating defects in shape of the molded product.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a stabilizer bushing having a horizontal shift stopper provided thereon which can prevent the generation of abnormal noise due to the interference with the horizontal shift stopper without impairing the stabil
Ando Takaaki
Hadano Katsuya
Imai Hideyuki
Yokoi Hiroshi
Pillsbury & Winthrop LLP
Rodriguez Ram
Toyo Tire & Rubber Co., Ltd.
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