Rubber vibration isolator for muffler

A rubber vibration isolator is used as a muffler hanger or muffler mount between a car body and a muffler to hang the latter from the former. The isolator includes a body made of rubber-like elastic material whose damping factor is high, two holes, upper and lower, formed in the center of the body of rubber-like elastic material, and a weight provided between the two holes and supported at opposite sides thereof by rubber-like elastic members. The rubber vibration isolator is advantageous in that coefficients of transfer of vibrations of both high and low frequencies, respectively, are lowered.

BACKGROUND OF THE INVENTION 
The present invention relates to a rubber vibration isolator for a muffler, 
intended for use between the body of a car and the muffler. 
The conventional rubber vibration isolators of this type are called 
"muffler hanger" or "muffler mount" and are used to reduce the vibration 
transferred from the exhaust pipe located on the bottom of the body of a 
car when the car is running. For example, the conventional muffler hanger 
100 serves to hang the muffler 1 from the car body 2 as shown in FIG. 6. 
For this purpose, a muffler hanger shown in FIG. 7 or FIG. 8 has been 
used. The muffler hangers 100 shown in FIGS. 7 and 8 are made entirely of 
a rubber-like elastic material. 
The conventional muffler hanger 100 made entirely of rubber suppresses 
vibration of low frequency (10 to 20 Hz) but transfers vibrations of high 
frequency (50 to 150 Hz) at a high coefficient. If a rubber housing a low 
vibration damping factor is used to lower the coefficient of vibration 
transfer in the high-frequency band, it will transfer a vibration of low 
frequency with a high coefficient. 
SUMMARY OF THE INVENTION 
An object of the present invention is to overcome the above-mentioned 
drawbacks of the prior art by lowering both the coefficients of transfer 
of vibrations of high and low frequencies, respectively. 
The above object can be attained by providing a rubber vibration isolator 
for a muffler for use between the body of a car and the muffler, the 
isolator including a body made of a rubber having a high vibration damping 
factor for suspending the muffler from the car body, two holes, upper and 
lower, formed in the center of the body of rubber-like elastic material, 
and a weight provided between the two holes and supported at opposite 
sides thereof by means of rubber-like elastic members. 
According to the present invention, the coefficient of transfer of 
high-frequency vibration can be lowered since the weight supported by the 
rubber-like elastic members works as a dynamic damper. Also, because the 
body is made of a rubber-like elastic material whose vibration damping 
factor is high, the vibration level in the lower-frequency band can be 
made as low as that of the conventional vibration isolator. Furthermore, 
the vibration isolator of the present invention can be installed in a 
known manner. It does not need a wider space for installation and also 
meets the requirements for vibration damping in both the low-and 
high-frequency bands with a minimum increase of costs. 
These and other objects and advantages of the present invention will be 
better understood from the ensuing description of an embodiment of the 
rubber vibration isolator according to the present invention in 
conjunction with the drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The rubber vibration isolator according to the embodiment shown in FIG. 1, 
generally indicated as 10, is constructed as a muffler hanger as in 
conventional vibration isolators. The rubber vibration isolator 10 has a 
body 3 made of a rubber-like elastic material whose vibration damping 
factor is high and which is used to suspend a muffler 1 from the body of a 
car. Two holes 4 and 5, upper and lower, are formed in the center of the 
body 3, and there is provided between these two holes 4 and 5 a weight 6 
having opposite sides each supported by a rubber-like elastic member. A 
part of each rubber-like elastic member supporting the weight 6 forms the 
support members 7 and 8. It is well known that installation of a dynamic 
damper to a vibrating object can effectively minimize the transfer of 
vibration, but there has never been proposed use of such a dynamic damper 
as a rubber vibration isolator for a muffler, for example, a muffler 
hanger or muffler mount. As it is necessary to provide a rubber vibration 
isolator which occupies only a limited space and also costs as little as 
possible, it is difficult or disadvantageous from the standpoint of space 
and cost to use any rubber vibration isolator of a complicated 
construction. Therefore, the present invention was worked out for the 
purposes that such a rubber vibration isolator can be installed in a known 
manner in an extremely narrow space at a minimum cost. 
The above-mentioned weight 6 is made of a mass of metal which may be bonded 
by vulcanization to the support members 7 and 8 made of rubber-like 
elastic material. The portion indicated with an arrow A in FIG. 1 
functions as a dynamic damper. 
As described in the foregoing, with the arrangements of the embodiment of 
the present invention, it is possible to considerably reduce the 
coefficient of vibration transfer in a high-frequency band as compared 
with conventional vibration isolators, which will be apparent from FIG. 2. 
Also, the damping factor of the inventive rubber vibration isolator in a 
low-frequency band is nearly the same as in conventional vibration 
isolators, as shown in FIG. 3. 
The embodiments shown in FIGS. 4 and 5 are the inventive rubber vibration 
isolators, respectively, constructed in the form of muffler mounts. As 
shown, a rubber-like elastic member is interposed between metal pieces 11 
and 12 or 11 and 13. The rubber-like elastic member comprises a body 3, 
holes 4 and 5, weight 6, and supports 7 and 8 as in the first embodiment.