Reexamination Certificate
2002-02-27
2003-03-25
Graham, Matthew C. (Department: 3613)
C267S141000, C267S153000, C248S632000
Reexamination Certificate
active
06536594
ABSTRACT:
This application claims the benefit of Japanese Patent Application No. 2001-081452, filed on Mar. 21, 2001, the entirety of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates in general to a vibration damping bushing and an assembly including the bushing, and more particularly to a mechanism for assembling the bushing and a mounting bracket together so as to improve the durability of the bushing.
2. Discussion of Related Art
A vibration damping bushing having a generally cylindrical shape has been employed for various applications, such that the bushing is interposed between two members, for connecting these members in a vibration damping manner. For example, such a generally cylindrical vibration damping bushing includes an elastic body formed of a rubber or elastic material and having a bore through which there is inserted a shaft member connected to one of the two members indicated above. The elastic body has an outer flat mounting surface extending in its axial direction (in which the bore extends). The bushing is connected to the other of the two members through a mounting bracket such that the elastic body is fixed to the mounting bracket at the above-indicated outer flat mounting surface. For instance, the generally cylindrical vibration damping bushing is used in an automotive vehicle, as a stabilizer bushing for elastically connecting a stabilizer bar to a body of the vehicle in a vibration damping fashion.
In the case of the stabilizer bushing, the bushing is fixed to a frame of the vehicle body through the mounting bracket, such that the bushing and the mounting bracket are fixed together as a unit. To this end, the bushing is provided with an integrally formed projection for insertion through a mounting hole formed through the mounting bracket, so that the bushing and the mounting bracket constitute an assembly.
Described in detail by reference to
FIG. 9
showing a vibration damping bushing in the form of a stabilizer bushing
2
, the bushing
2
consists of an elastic body
3
formed of a rubber material and having a generally cylindrical shape in transverse cross section, with a center bore
2
a
formed therethrough so as to extend in its axial direction, so that a stabilizer bar extends through the center bore
2
a.
Described more precisely, the outer profile of the elastic body
3
in the transverse cross section consists of an upper semicircle and a lower rectangle, which cooperate to take the form of a tunnel or a barrel-roof or Nissen hut, as shown in FIG.
9
. The elastic body
3
has a lower flat mounting surface
2
b
extending in the axial direction, and an internal slit
2
c
which permits the stabilizer bar to be inserted into the center bore
2
a
in the radial direction of the center bore
2
a.
The elastic body
3
of the stabilizer bushing
2
has an integrally formed mounting projection
4
extending downwards from an intermediate portion of the lower flat mounting surface
2
b.
The mounting projection
4
has a frusto-conical head for insertion through a mounting hole
8
formed through an intermediate part of a top wall of a U-shaped portion of a mounting bracket
6
. The top wall of the mounting bracket
6
has an upper bearing surface
6
a
for contact with the mounting surface
2
b
of the stabilizer bushing
2
(elastic body
3
), when the stabilizer bushing
2
is fixed to the mounting bracket
6
, with the mounting projection
4
being inserted through the mounting hole
8
with elastic deformation of the frusto-conical head of the projection
4
, such that the shoulder surface of the mounting projection
4
which is adjacent to the frusto-conical head is held in contact with the edge of the lower open end of the mounting hole
8
, as indicated in FIG.
10
. Thus, the stabilizer bushing
2
and the mounting bracket
6
are fixed together as a unit or assembly, which is subsequently fixed to the vehicle body.
While the stabilizer bushing
2
is installed on the vehicle body, with the assembly of the stabilizer bushing
2
and the mounting bracket
6
being fixed at the mounting bracket
6
to a suitable member of the vehicle body, however, the elastic body
3
suffers from insufficient durability due to stress concentration on a portion of the mounting surface
2
b
around the fixed end of the mounting projection
4
inserted through the mounting hole
8
formed through the upper bearing surface
6
a
of the mounting bracket
6
, when a load acts on the stabilizer bushing
2
in a direction toward the bearing surface
6
a
due to a relative displacement between the stabilizer bar inserted through the center bore
2
a
of the stabilizer bushing
2
and the member of the vehicle body to which the mounting bracket
6
is fixed. The stress is concentrated on the portion of the mounting surface
2
b
around the fixed end of the projection
4
, in the presence of the mounting hole
8
, since the above-indicated portion of the mounting surface
2
b
is located adjacent to the edge of the upper open end of the hole
8
and is forced into the upper end portion of the hole
8
upon application of the load on the elastic body
3
in the direction toward the bearing surface
6
a.
Accordingly, the elastic body
3
tends to suffer from cracking at the portion of the mounting surface
2
b
around the fixed end of the mounting projection
4
, leading to a risk of fracture of the projection
4
during the use of the stabilizer bushing
2
for a long time.
SUMMARY OF THE INVENTION
It is therefore a first object of the present invention to provide a vibration damping bushing having improved durability, without a risk of cracking or other damages due to a load acting on the bushing in a direction toward a mounting bracket. A second object of this invention is to provide an assembly of a vibration damping bushing and a mounting bracket, which assembly is improved in its durability without a risk of such damages of the bushing as described above.
The first object indicated above may be achieved according to a first aspect of this invention, which provides a vibration damping bushing including an elastic body of generally cylindrical shape formed of an elastic material and having a bore through which there is inserted a shaft member whose vibration is to be damped, and an outer mounting surface which extends in an axial direction of the elastic body and at which the elastic body is fixed to a mounting bracket, the vibration damping bushing comprising a plurality of engaging jaws formed integrally with the elastic body, on respective peripheral portions of the outer flat mounting surface of the elastic body, such that the engaging jaws extend from the mounting surface and are elastically engageable with respective engaging portions of the mounting bracket, so that the elastic body is fixed to the mounting bracket.
In the vibration damping bushing constructed as described above according to the first aspect of the present invention, the engaging jaws of the elastic body are not formed on a central portion of the outer flat mounting surface, but are formed on respective peripheral portions of the mounting surface, for engagement with the respective engaging portions of the mounting bracket. Accordingly, a bearing surface of the mounting bracket for contact with the mounting surface of the elastic body of the present bushing does not have a mounting hole which would cause a stress concentration on the mounting surface of the elastic body, due to a compressive load acting on the bushing fixed to the mounting bracket, upon application of a vibrational load between the shaft member inserted through the bushing and the mounting bracket. The engaging jaws are held in engagement with the respective engaging portions of the mounting bracket, under elastic forces of the engaging jaws owing to the elasticity of their elastic material, which elastic forces act on the surfaces of the engaging portions in a lateral direction parallel to the bearing surface, such that the engaging jaws are freely mov
Burr & Brown
Graham Matthew C.
Tokai Rubber Industries Ltd.
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