Hydraulic two-chamber engine mount with rigid oscillating diaphragm and seal therefor

A hydraulically damping two-chamber engine mount includes chambers being bordered with rubber-elastic material and an intermediate plate with an overflow conduit and a central diaphragm. For force-free motion of the diaphragm in the vertical direction, the diaphragm is constructed as a rolling diaphragm, in such a way that a conduit of reduced width at the top and bottom is provided between the diaphragm of rigid material and the intermediate plate surrounding it annularly. In the conduit, on the opposed conduit walls, rolling elements with a circular cross section are inserted for rolling support of the diaphragm.

The invention relates to a hydraulically damping two-chamber engine mount, 
including two chambers being rubber-elastically bordered, and a rigid 
intermediate plate between the chambers having an overflow conduit and a 
central, rigid diaphragm with a predetermined vertical clearance, for 
decoupling high-frequency, low-amplitude vibration. 
With such a mount, low-frequency vibration, in particular, is intended to 
be damped, while high-frequency vibration and in particular acoustic 
vibration is intended to be isolated. Among others, the demands made on 
such a mount in terms of its damping and isolation properties are that the 
attained damping action and the attained isolating action can be optimized 
independently of one another, and that the damping and isolation action 
depend on the amplitude of the vibration being induced. 
In terms of its basic principle, such a requisite action is achieved by the 
parallel connection of a conduit that is tuned to low frequency, as a 
connecting opening between the working chamber and the compensating 
chamber, and by closing the connecting opening which is tuned to high 
frequency by a diaphragm having a limited clearance or play, so that the 
exchange of fluid through the connecting opening is limited to a certain 
volume, which can be as low as zero. 
In the prior art, the problem of creating a diaphragm with limited 
clearance has been solved in various ways, such as those described in 
Published European Application No. 0040290 B1, German Patent DE 3024089 
C2, or German Patent DE 3246587 C2, corresponding to U.S. Pat. No. 
4,697,794. Essentially two solutions have developed, which can be 
summarized as follows. In the first solution, diaphragms are strained for 
flexion and have a geometry that provides a progressive behavior in terms 
of their spring characteristic, or are limited in their clearance by 
stops, such as a diaphragm cage. Such devices also include rigid diaphragm 
plates that are suspended by a highly flexible joint. With that type of 
diaphragm, the amplitude separation between high and low-frequency 
vibration is often inadequate, since at greater amplitudes, or in other 
words higher differential pressures between the fluid chambers, the 
flexing of the diaphragm increases as well. Moreover, in clearance 
limitation, close production tolerances are necessary, which are in the 
range of tenths of millimeters. Additionally, limiting clearance by means 
of stops can lead to noise production. 
Another option for constructing the diaphragm includes translationally 
moved diaphragm plates that are fastened free-floatingly between two 
stops. With such diaphragms the production tolerances are even more 
critical, because in addition to the clearance tolerance, the diameter 
tolerance of the diaphragm and of the diaphragm cage must also be adhered 
to precisely. In addition, a kind of loosening effect can be observed 
because of friction, and that is a force that must be overcome before the 
diaphragm can move freely in its cage. 
A further translationally movable but rigid diaphragm is known from U.S. 
Pat. No. 4,756,513. However, in that case the rigid diaphragm is sheathed 
on the outer periphery by a rubber ring, which is displaceably retained in 
a corresponding recess of the rigid intermediate plate surrounding the 
diaphragm. With that kind of diaphragm structure, although rattling noises 
upon impact at the upper and lower boundary are avoided, nevertheless with 
suitably tight guidance, considerable frictional forces must be overcome 
in such a case as well, so that such a diaphragm has inadequate ease of 
motion. 
It is accordingly an object of the invention to provide a hydraulically 
damping two-chamber engine mount, which overcomes the 
hereinafore-mentioned disadvantages of the heretofore-known devices of 
this general type and which creates a diaphragm with limited clearance, 
which is simple in structure and in which a virtually force-free motion is 
possible, in other words a motion that can freely follow the induced 
vibration with only extremely slight external influences. 
With the foregoing and other objects in view there is provided, in 
accordance with the invention, a hydraulically damping two-chamber engine 
mount, comprising two chambers with rubber-elastically borders or 
boundaries, a rigid intermediate plate being disposed between the chambers 
and having an overflow conduit, a central, rigid diaphragm being annularly 
surrounded by the rigid intermediate plate and having a predetermined 
vertical clearance or play for decoupling high-frequency, low-amplitude 
vibration, the rigid diaphragm and the rigid intermediate plate having 
opposed conduit walls defining an annular conduit between the conduit 
walls being open toward the chambers and having a top and a bottom with 
reduced cross sections forming stops for clearance limitation, and at 
least one element with a circular cross section disposed on at least one 
of the conduit walls in the annular conduit for rolling support of the 
rigid diaphragm. 
This rolling support of the diaphragm creates free mobility of the 
diaphragm, subject to only very small frictional forces. The structure 
itself is quite simple, and the various components may be manufactured by 
favorable production methods, since the necessary tolerances are within 
the usual limits. 
In accordance with another feature of the invention, the at least one 
rolling element is an elastic ring that is inserted into the conduit. The 
diaphragm can then easily roll on the ring and the clearance of the 
diaphragm is limited by the reduced width of the conduit at the top and 
bottom. 
In accordance with a further feature of the invention, the at least one 
rolling element is a plurality of elastic ring segments, cylindrical 
rollers or balls. 
In accordance with an added feature of the invention, the the conduit walls 
are parallel and conically converge at the top and bottom. 
In accordance with an additional feature of the invention, the conduit 
walls converge in curved fashion. 
In accordance with yet another feature of the invention, the radius of 
curvature at the conduit walls is at least twice as great as the radius of 
the inserted elements. 
In accordance with a concomitant feature of the invention, the intermediate 
plate is horizontally split. This is done in particular to facilitate 
assembly. 
Other features which are considered as characteristic for the invention are 
set forth in the appended claims. 
Although the invention is illustrated and described herein as embodied in a 
hydraulically damping two-chamber engine mount, it is nevertheless not 
intended to be limited to the details shown, since various modifications 
and structural changes may be made therein without departing from the 
spirit of the invention and within the scope and range of equivalents of 
the claims. 
The construction and method of operation of the invention, however, 
together with additional objects and advantages thereof will be best 
understood from the following description of specific embodiments when 
read in connection with the accompanying drawings.

Referring now to the figures of the drawing in detail and first, 
particularly, to FIG. 1 thereof, there is seen a longitudinal section 
through a two-chamber engine mount, in which a working chamber 1 is 
bordered or bounded in the conventional manner by a frustoconical support 
spring 2. The top of the support spring 2 carries a bearing plate 3 with a 
bolt 4 for supporting an engine. Below an intermediate plate 5 is a 
compensating chamber 6, which is defined at the bottom by a flexible wall 
7. The support spring 2, the intermediate plate 5 and the flexible wall 7, 
together with a lower, cup-shaped closure plate 8, which is fixed to a 
vehicle body by a bolt 9, are held together by an annular flange 10 
serving as an outer wall. 
An outer peripheral region of the intermediate plate 5 has an overflow 
conduit 11, which forms a connection between the working chamber 1 and the 
compensating chamber 6 through non-illustrated overflow openings and which 
is tuned for damping low-frequency vibrations of high amplitude. 
A rolling diaphragm 12 is also supported centrally in the intermediate 
plate 5. The structure and disposition of the rolling diaphragm 12 are 
visible in detail and on a larger scale in FIG. 2. 
A conduit 15 is left open between the rigid diaphragm 12 and the 
intermediate plate 5. The conduit 15 has conduit walls 16 and 17 that 
extend parallel to one another in a middle region and narrow conically by 
a given angle alpha at upper and lower ends. An elastic ring 18 which is 
inserted into this conduit 15 has a diameter which corresponds to the 
width of the conduit 15, or it may be constructed in such a way as to be 
slightly larger. 
When vibration is induced, the diaphragm plate 12 can be deflected freely 
up and down and the ring 18 rolls upward or downward along the conduit 
walls 16 and 17, so that the approximate result may be a lower terminal 
position of the diaphragm 12 as shown in FIG. 2a. 
As can be seen from the drawing, the rolling path, that is the conduit 
walls 16 and 17, is constructed in terms of geometry in such a way that 
the rolling travel and therefore the clearance of the diaphragm 12 is 
limited. The ring 18 therefore takes on a rolling function and it seals 
off the diaphragm 12 from the intermediate plate 5, it can compensate for 
production tolerances and it assures a softer impact of the diaphragm 12 
in its terminal positions. 
It is also practical to split the intermediate plate 5 in two so that it 
includes a lower ring part 20 and an upper ring part 21. This horizontal 
split need not necessarily be in the center, as can be seen from FIG. 2. 
This split also substantially facilitates assembly, because the ring 18 is 
first slipped onto the diaphragm 12, and subsequently the parts 20 and 21 
of the intermediate plate 5 are mounted on the outsides. 
Another optional embodiment of the conduit 15 is shown in FIG. 3. In this 
case, conduit walls 23 and 24 are constructed in such a way as to be 
curved relative to one another, suitably with a radius R, which is at 
least twice as great as the radius of the ring 18. Through the use of such 
a structure, the rolling behavior of the ring 18 and the impact behavior 
of the diaphragm 12 can be even further varied. 
The result of using the embodiment described above is accordingly a 
two-chamber engine mount having a diaphragm for isolating high-frequency, 
low-amplitude vibrations. The diaphragm can follow the induced vibration 
virtually without force and thus effects optimal damping. 
FIG. 4A shows elastic ring segments 18' which may be used instead of the 
ring 18. Similarly, cylindrical rollers 18" some of which are shown in 
FIG. 4B or balls 18'" one of which is shown in FIG. 4C, may be substituted 
for the ring 18.