FIELD OF INVENTION
This invention relates to rubber bushing with variable stiffness in automobile
suspension. The rubber bushing is particularly employed in lower control arms
of automobile suspension.
BACKGROUND/ PRIOR ART
Bushing placed at the .end of both lower control arms of automobile suspension
constitutes a cylindrical structure comprising a part made of resilient material
(1) interposed between inner and outer metallic sleeve (2 and 3) as illustrated
in figure 1.
Some bushings are known to be in existence in the prior art, which can be
discussed hereinbelow:
Solid type bushing, for which reference may be made to fig. 2 is ,a cylindrical
part having constant radial stiffness in all directions i.e. all around 360".
As can be observed from the figure 2, the thickness of the resilient part (P) is
constant at all sections in both directions (X-X and Y-Y). It involves ease of
manufacture with no need to control the orientation while press fitting in
assembly part. However, it may lead to compromise in maintaining balance
between RH and NVH performance.
In order to offer a solution to the above, void-type bushing was suggested in the
art as in fig. 3 having variable radial stiffness in different directions which is
achieved with the provision of void (V) in one direction in the resilient part.
However it is associated with the following drawbacks:
- Assembly to be ensured with orientation control of voids during press
fitting in assembly part.
- May lead to NVI-I problem.
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- Manufacturing complexity.
- Less durable owing to friction and provision of void.
There is also another technology proposed in the art for accom.plishment of
variable radial stiffness in different directions, according to which two different
grades of' resilient part are injected in two different directions of bushing.
However, it is expensive in manufacturing and complicated in design.
In the current circumstances, a novel design is required to be developed to
address the aforesaid issues of available technologies.
OBJECTS OF THE INVENTION
An object of this invention is to propose rubber bushing with variable stiffness
in automobile suspension which obviates shortcomings of prior arts.
Another object of this invention is to propose rubber bushing with variable
stiffness in automobile suspension which is cost effective comparatively.
Further object of this invention is to propose rubber bushing with variable
= stiffness in . automobile suspension which involves no complexity in
manufacturing .
Still further object of this invention is to propose rubber bushing with variable
stiffness in automobile suspension which is having longer life span.
Yet further ob~ecto f this invention ,is to 'propose rubber bushing with variable
stiffness in qutomobile suspension which involves improved ride, handling and
NVH Performance comparatively.
SUMMARY OF INVENTION
According to this invention there is provided a rubber bushing with variable ~
I stiffness in automobile suspension comprising a cylindrical structure having
i
I ' resilient material part interposed between inner and outer metallic sleeve,
' wherein the resilient part is provided with variable thickness in different
directions.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Further objects and advantages of this invention will be more apparent from
the ensuing description when read in conjunction with the accompanying
drawings of exemplary embodiments of invention and wherein:
Fig. 1 shows: Conventional bushing in automobile.
Fig. 2 shows: Solid type bushing in prior art.
Fig. 3 shows: Void type bushing in known art.
Fig. 4 shows: A rubber bushing with variable stiffness in automobile
suspension in accordance with present invention:
Fig. 5 shows: Cross-section of bush of present invention in assembled
condition.
Fig. 6 shows: Isometric view of present invention.
DETAIL DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE
ACCOMPANYING DRAWINGS
The present invention makes a disclosure in respect of rubber bushing with
variable stiffness in automobile suspension.
The rubber bushing in lower control arms of automobile suspension needs to
perform dllierently in various driving condilioris ulldel. the different load for a
particular vehicle. d his necessitates provision of bushing with variable radial
stiffness in different directions. The stiffness of said rubber bushing is defined
as follows:
I
Stiffness = Lond I
i
Deflection I
As load on the bush is constant, hence stiffness of bush relies on deflection of 1I
resilient material part of bush.
As a result variation in the deflection of the resilient material part leads to
variation in the stiffness of the bush in a'particular way.
According to the present invention, variation in the deflection of the resilient
material part is effected by varying thickness (t) of the m'aterial itself.
Now, reference may be made to fig. 4, wherein thickness of resilient part (R) is
less in one direction (X-X) and more in other direction (Y-Y). * .
The direction in which less stiffness is required, thickness of resilient part is
reduced in that particular direction so as to give rise high deflection of the .
resilient part.
Similarly, the direction in which high stiffness is needed, thickness of resilierit
part is devised to be more in that particular direction as compared to other
direction in order to have low deflection of the resilient part for serving the
purpose.
I . Thus, the variable radial stiffness in different directions is accomplished by
designing the resilient part in such away that, it is having more thickness (tl)
I
in one direction than in other direction (t2) i.e. tl>t2as in fig 4.
The difference in thickness is visible in the cross section of the resilient part,
for which reference may be made to fig 5 reflecting the assembled condition of
cross sections in both directions (X-X and Y-Y) with mating part.(M) to indicate
that tl>t2.
Further, reference may be made to fig. 6, wherein the reduction in thickness in
one direction (X-X) can be observed by means of a depression in that particular
zone. The depression includes a smooth curve.
The instant invention makes implementation of high grade resilient material for
resilient part of the bush.
The same is such as high durable Nli(natura1 rubber) base with less hardness
and low damping as compared to existing less durable NR base with more
hardness and high damping. The material of invention possesses improved
. durability characteristics as compared to conventional resilient material.
With the above provision, the vehicle can be tuned as per required ride and
handling parameters keeping NVH. performance requirement as per desired
range.
The stiffness/deflection of the resilient part varies from variant to variant of
automobile. Accordingly variation in thickness is devised so as to. cater to the
requirement.
Advantageous Features
- Maintains durability of bush.
1 . - Ease in manufacturing.
- Enhanced NVH, vehicle ride and handling pcrformanct..
- Cost effective and'longer life span.
- 'Makes it possible to tune vehicle as per required RH parameter keeping
I NVH performance in desired range
i It is to be noted that 'the present invention is susceptible to modifications,
~ I
adaptations and changes by those ,skilled in the art. Such variant embodiments
I
j employing the concepts and fcatures of this invention are intended to be within
i' the scope of the present invention, which is further set forth under the
following claims:-

WE CLAIM:
1. A rubber bushing with variable stiffness in automobile suspension
comprising a cylindrical structure having resilient material part
interposed between inner and outer metallic sleeve, wherein the resilient
part is prnvided with variablc thickness i11 different directions.
2. A rubber bushing with variable stiffness in automobile suspension as
claimed in claim 1 wherein the resilient part, thickness of which is less
in one direction and more in other direction. I
. .
3. A rubber bushing with variable stiffness in automobile suspension as
claimed in claim 1 or 2 wherein the direction in which less stiffness is I
required, thickness of the resilient part is reduced in that particular . , I
direction to obtain high deflection of the part and vice versa. I
4. A rubber bushing with variable stiffness in automobile suspension as
claimed in any of the proceeding claims wherein said different thickness I is accommodated in the different cross section of the resilient part.
5. A rubber bushing with variable stiffness in automobile suspension as
claimed in any of the proceeding claims wherein the reduction in
thickness constitutes a depression comprising a smooth curve in the I
claimed in any of the proceeding claims wherein the resilient part is I
made of high grade resilient material such as high dui-able NR base with
less hardness and low damping. I
7. A rubber bushing with variable stiffness in automobile suspension as
claimed in any of the preceding claims is associated with the
,advantageous features such as herein described.
8. A rubber bushing with variable stiffness in automobile suspension
substantially as herein described with reference to the accompanying
drawings.