Liquid sealed type bushing

Details Liquid sealed type bushing Liquid sealed type bushing

1998-08-11

2001-01-09

Graham, Matthew C. (Department: 3613)

Spring devices

Resilient shock or vibration absorber

Including energy absorbing means or feature

C267S219000

Reexamination Certificate

active

06170810

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a liquid sealed type bushing used for an automobile engine mount and the like.
2. Description of the Prior Art
Liquid sealed type bushings are known, which comprise a generally cylindrical shaped outer cylinder and a core member arranged therein, an elastic member interposed between the outer cylinder and the core member, wherein a plurality of recesses are provided as liquid chambers on an outer peripheral side of a middle portion of the elastic member. A partition member divides two adjoining liquid chambers and is formed by a part of the elastic member and a medium to high frequency device, which includes an umbrella shaped member projecting into a liquid chamber and supported by the core member side.
According to this construction, because the partition member is rather thick (almost as thick as a minimum thickness of a circular wall portion formed on both ends of the core and the outer cylinder in an axial direction) and the outer peripheral portions thereof are directly or indirectly secured by baking to the inside of the outer cylinder, as shown in a characteristic curve {circle around (
1
)} of
FIG. 6
, the dynamic spring characteristic curve possesses a minimum value B and a large peak C generated by a reaction thereof.
A reason why the minimum value B and the peak C are generated is described referring to
FIG. 7-A
to
FIG. 7-C
.
FIG. 7-A
is a view showing a change of a dynamic spring constant by a membrane resonance vs. frequency. The membrane resonance is generated in that the partition member conducts as an elastic membrane against an inside liquid flow, because the partition member is thinner than the peripheral circular wall portion or other portion. The axis of abscissa shows frequency and the axis of ordinate shows a dynamic spring constant.
In these figures, a characteristic curve {circle around (
4
)} shows a conventional plot. Here, since the partition member is rather thick and is secured on the outer cylinder side, the characteristic shows the relatively high dynamic spring constant, and possesses a peak p
1
and a minimum value b
1
changing abruptly around a border area of the medium frequency region and the high frequency region by membrane resonance.
FIG. 7-B
shows a change of a liquid column resonance vs. frequency by the medium to high frequency device. The axis of abscissa shows frequency and the axis of the ordinate shows a dynamic spring constant. In the drawing, a characteristic curve {circle around (
6
)} shows a conventional plot, the characteristic possesses a minimum value b
2
owing to a liquid column resonance on a medium frequency region close to the high frequency region, and the frequency of the minimum value b
2
is arranged to be almost the same as that of the peak p
1
.
When the characteristic curves {circle around (
4
)} and {circle around (
6
)} are overlapped, characteristic curve {circle around (
1
)} of
FIG. 7-C
results, namely, the peak p
1
generated by the membrane resonance is cancelled by the minimum value b
2
of the liquid column resonance, so the minimum value B is yielded.
Even if the minimum value of the dynamic spring constant is generated as above by using the medium to high frequency device, as shown in
FIG. 7B
, the peak p
2
, which results from the reaction of the resonance by the medium to high frequency device, remains as the peak C in the characteristic curve {circle around (
1
)}. Because of the extremely high dynamic spring constant in the higher frequency region, it cannot be realized to make the low dynamic spring characteristics in the wide frequency range across the medium to high frequency range.
On the other hand, in recent years, it is required for such a liquid sealed type bushing to actualize the low dynamic spring constant in the wide range of the medium frequency region (40 to 500 Hz), especially more than the 100 Hz region, and the high frequency region (500 to 1000 Hz).
SUMMARY OF THE INVENTION
In order to solve the problems described above, according to the first embodiment of the present invention, there is provided a liquid sealed type bushing comprising, an outer cylinder formed in a cylindrical shape, a core member arranged inside thereof, an elastic member interposed between the outer cylinder and the core member, a plurality of recesses formed as liquid chambers on an outer peripheral side of a middle portion of the elastic member, and a partition member made by a part of the elastic member provided between the chambers. The chambers are mutually communicated with an orifice passage and a medium to high frequency device projected into at least one liquid chamber and including an umbrella shaped member supported on the core member side. A thin wall portion is formed on a part of the partition member to yield a peak for a dynamic spring characteristic according to a vibration input in a medium to high frequency range by a membrane resonance, and an outer peripheral portion of the partition member is made to contact tightly but not to combine with the outer cylinder. The second embodiment includes a liquid sealed type bushing similar to the first embodiment wherein two peaks of a dynamic spring characteristic are made to occur in a medium frequency region and high frequency region owing to said membrane resonance and the peak of the high frequency region is made to be offset due to a minimum value generated by the medium to high frequency device.
The invention may include a liquid sealed type bushing of the first invention wherein said medium to high frequency device is constructed to yield minimum values of dynamic spring characteristic at two different resonance frequencies f
3
and f
4
, and these frequencies and a frequency f
1
at a peak of the dynamic spring characteristic by said membrane resonance have a following relation:
f
3
<f
1
<f
4
.
According to the first invention, when the partition member membrane resonates in the medium to high frequency region, because the partition member pocesses the thin wall portion, and the outer peripheral portion thereof are made not to combine but to be relatively movable with the outer cylinder, the peak of the dynamic spring characteristic is lowered. Moreover, in the medium to high frequency range, the minimum value is lowered owing to the medium to high frequency device. Therefore, when each frequency of the peak value and the minimum value of the dynamic spring characteristic is arranged to shift, the low dynamic spring constant can be realized in a wide frequency range.
The characteristic curve {circle around (
5
)} is
FIG. 7-A
is a view showing the membrane resonance of the partition member in the present invention. As shown in the drawing, the thin wall portion is provided on said partition member and the outer peripheral portion is made not to be combined with the outer cylinder, so the lower dynamic spring constant, as compared with the conventional example of the characteristic curve {circle around (
4
)}, is achieved in the medium frequency range. The minimum value b
3
generated by the membrane resonance occurs in a lower frequency of the medium frequency region than that of the peak p
1
of the characteristic curve {circle around (
4
)} and affects to the relatively wide frequency range and the peak value p
3
occurred at somewhat lower frequency is also lowered.
However, the peak value p
4
generated by the reaction owing to the minimum value b
3
in the higher frequency is almost as large as the peak value p
1
, and the curve shows the higher dynamic spring constant than the characteristic curve {circle around (
4
)} in a higher frequency than that of p
4
. Each frequency of the peak value p
3
and p
4
is assumed as f
5
and f
6
.
The characteristic curve {circle around (
7
)} of
FIG. 7-B
is a view showing the characteristics of the liquid column resonance caused by the medium to high frequency device. A position of the minimum value b
4
in the curve {circle around (
7
)} is shifted to higher frequency side from that of the character

Affiliated with

Also associated with

Rating

Liquid sealed type bushing does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Liquid sealed type bushing, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Liquid sealed type bushing will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2476636