Hydraulic antivibration support

The hydraulic antivibration support has two rigid strength members interconnected by a bell-shaped elastomer body, a flexible elastomer wall connected to the second strength member, and a rigid partition secured to the second strength member and defining both a working chamber on its elastomer body side and a compensation chamber on its flexible wall side. These two chambers are filled with liquid and are connected to each other via a narrow channel, via a central nozzle fitted with an axially movable shutter, and via an annular flap disposed around the central nozzle between two grids. One of the grids is axially slidable and is connected to the shutter so as to block the flap when the shutter is open.

FIELD OF THE INVENTION 
The present invention relates to hydraulic antivibration supports, intended 
in particular for supporting the engines of motor vehicles. 
More particularly, the invention relates to a hydraulic antivibration 
support designed to be interposed between two rigid elements in order to 
damp and attenuate vibratory motion between said two elements along a 
central axis and to support an axial load exerted by one of said two 
elements, the support comprising: 
first and second rigid strength members designed to be secured to 
respective ones of the two rigid elements to be united; 
an elastomer body connecting the two strength members together, said 
elastomer body supporting the axial load and having a bell-shaped side 
wall which extends axially, flaring downwards from a top secured to the 
first strength member to an annular base secured to the second strength 
member; 
a flexible and easily deformable wall of elastomer having a peripheral edge 
connected in sealed manner to the second strength member, and co-operating 
therewith and with the elastomer body to define a sealed housing filled 
with liquid; 
a rigid partition which is secured to the second strength member and which 
extends perpendicularly to the central axis, thereby subdividing said 
sealed housing into two liquid-filled chambers, namely a working chamber 
defined in part by the elastomer body, and a compensation chamber defined 
in part by the flexible elastomer wall; 
a narrow passage interconnecting the working and compensation chambers, 
said channel having a certain length L and a certain equivalent diameter D 
such that the ratio L/D is greater than 10; 
a central nozzle formed through the rigid partition to put the working and 
compensation chambers into communication with each other, said central 
nozzle having an axial length l and an equivalent diameter d such that the 
ratio l/d is less than 10; 
a shutter secured to a central portion of the flexible elastomer wall and 
displaceable axially between a closed position in which it closes the 
nozzle and an open position in which it opens said nozzle; 
a control device for selectively placing the shutter either in its open 
position or in its closed position, said control device including an 
actuator member which is secured to the shutter member; and 
at least one passage formed through the rigid partition between the working 
and compensation chambers, at a position that is situated radially outside 
the nozzle, said passage being closed by a flap which extends 
perpendicularly to the central axis and which has two opposite faces 
respectively in communication with the working chamber and with the 
compensation chamber, said flap having at least a portion that is 
displaceable parallel to the central axis between first and second 
abutments with clearance of less than 1 mm, the first abutment being 
secured to the rigid partition. 
BACKGROUND OF THE INVENTION 
Such a hydraulic antivibration support is disclosed, for example, in 
document EP-A-0 547 287. 
The antivibration support disclosed in that document nevertheless suffers 
from the drawback that the flap is always free to vibrate between its two 
abutments, even when the central nozzle is open. 
Unfortunately, experience shows that that phenomenon spoils the operating 
efficiency of the central nozzle: in other words, when the central nozzle 
is opened essentially for the purpose of reducing the elastic stiffness of 
the antivibration support, in particular when the engine is idling, the 
fact that the flap remains free to vibrate in this situation prevents the 
elastic stiffness of the support from decreasing as much as it could if 
the flap were prevented from moving. 
Also, document EP-A-0 297 974 describes a hydraulic antivibration support 
in which provision is made to lock the decoupling flap at the same time as 
a nozzle is opened between the working chamber and the compensation 
chamber. 
That hydraulic antivibration support operates in entirely satisfactory 
manner, but suffers from the drawback of using relatively complex control 
means. 
Also, the control means in question are mounted on the side of the 
hydraulic antivibration support, thereby increasing the size of the 
support and making it considerably more complicated to assembly and to 
fill. 
OBJECTS AND SUMMARY OF THE INVENTION 
An object of the present invention is to mitigate the various 
above-mentioned drawbacks. 
To this end, according to the invention, in a hydraulic antivibration 
support of the kind in question, the second abutment for the flap is 
itself mounted with axial clearance of less than 1 mm between the flap and 
a counter-abutment secured to the rigid partition, said second abutment 
being mechanically linked with the shutter, the second abutment being 
pressed against the flap by the shutter when it is in its open position, 
then preventing substantially all axial movement of the flap, and said 
second abutment being pressed against the counter-abutment by the shutter 
when it is in its closed position. 
In preferred embodiments, use may optionally be made of one or more of the 
following dispositions: 
the first abutment is in contact with the face of the flap that is in 
communication with the compensation chamber, while the second abutment is 
in contact with the face of the flap that is in communication with the 
working chamber, the outside of the nozzle being defined by a tube which 
extends along the central axis from a first end secured to the second 
abutment towards the flexible elastomer wall to a second end having at 
least an outwardly-directed flange, the shutter being pressed axially 
against said second end towards the elastomer body when said shutter is in 
its closed position, thereby axially pressing the second abutment against 
the counter-abutment, and the shutter being secured to a set of catches 
surrounding the tube and sliding axially along the tube, said catches 
being designed to engage with the flange at the second end of the tube, 
thereby pulling said tube and the second abutment towards the flexible 
elastomer wall when the shutter is in its open position, such that the 
second abutment is then pressed against the flap; 
the catches are constituted by resilient metal tabs which are cut out from 
a piece of sheet metal fixed to the shutter and which are snapped against 
the tube defining the nozzle; 
the piece of sheet metal from which the resilient tabs are cut out has a 
central portion which is interposed between the shutter and the flexible 
elastomer wall, each resilient tab extending at an angle axially towards 
the rigid partition and radially inwards from said central portion to a 
free end which has an axial lip bearing resiliently against the tube and 
directed towards the outwardly-directed flange of said tube; 
there are two catches which are disposed on opposite sides of the tube 
which defines the nozzle; 
the control device consists in a suction capsule disposed in the vicinity 
of the flexile elastomer wall outside the sealed housing, said suction 
capsule having a hollow inside volume in communication, via an 
electrically controlled valve, either with the atmosphere or else with a 
suction source, said hollow inside volume being defined in part by a 
moving wall which constitutes the member for actuating the shutter and 
which is axially displaceable towards the inside of the suction capsule, 
entraining the shutter to its open position and pressing the second 
abutment against the flap when the suction capsule is in communication 
with the suction source, and the inside volume of the suction capsule also 
including a spring urging the moving wall towards the liquid-filled sealed 
housing, thereby placing the shutter in its closed position and pressing 
the second abutment against the corresponding counter-abutment when the 
suction capsule is in communication with the atmosphere; 
the suction capsule has a fixed rigid wall which is secured to the second 
strength member, the moving wall of said capsule having a rigid central 
portion which is connected in sealed manner to the fixed wall via an 
annular bellows of elastomer; 
the flap is annular in shape, surrounding the central nozzle, the first and 
second abutments for the flap being constituted by annular grids; and 
the shutter is constituted by a rigid washer having elastomer overmolded 
thereon, the central portion of the flexible elastomer wall itself having 
a rigid washer with elastomer overmolded thereon, these two washers and 
the actuator member of the shutter being connected together by means of a 
rivet which passes through them axially.

MORE DETAILED DESCRIPTION 
In the description below, terms such as "up", "down", "top", "bottom", etc. 
are used solely to clarify the description, and they are not limiting in 
any way. 
The hydraulic antivibration support considered herein is designed to be 
interposed vertically between a vehicle power unit and the structure of 
the vehicle, in order to support the weight of the power unit and to damp 
and attenuate vibratory motion between those two elements along a vertical 
axis Z. 
The antivibration support comprises: 
a first rigid metal strength member 1 which may be fixed to the power unit, 
for example, said first strength member being constituted by a central 
head 2 that is extended upwards by a pin 3 for fixing to an element that 
is secured to the power unit; 
a second rigid metal strength member 4 in the form of a ring centered on 
the axis Z, said second strength member forming a tray 5 locally 
presenting fixing tabs (not shown) pierced with holes for fixing the 
second strength member to the structure of the vehicle; 
an elastomer body 6 interconnecting the two strength members 1 and 4, said 
elastomer body being strong enough to support the axial load imposed on 
the support by the power unit, and said elastomer body having a 
bell-shaped side wall that may be circularly symmetrical about the axis Z 
and that flares downwards from a top secured to the first strength member 
down to an annular base secured to the second strength member; 
an easily deformable flexible wall 7 made of elastomer, having a peripheral 
edge connected in sealed manner to the second strength member 4 and 
co-operating therewith and with the elastomer body to define a sealed 
housing full of liquid; and 
a rigid partition 8 secured to the second strength member 4 by said second 
strength member being crimped thereover, the partition extending 
perpendicularly to the axis Z and separating the sealed housing into two 
chambers filled with liquid, namely a working chamber "A" partially 
defined by the elastomer body 6, and a compensation chamber "B" partially 
defined by the flexible elastomer wall 7. 
The partition 8 includes a bottom metal plate 9 having a thickened outside 
edge in which there is formed an upwardly-open groove 10. The groove is 
covered by a metal washer 11, with the plate 9 and the washer 11 being 
axially clamped together to form a stack by the crimping of the second 
strength member 4. 
The groove 10 co-operates with the washer 11 to define a narrow channel 12 
which extends angularly between two ends that are separated from each 
other by a solid piece of the thickened edge of the plate 9. 
The narrow channel opens out firstly in an axial direction to the working 
chamber "A" via an orifice 13 through the washer 11, and secondly it opens 
out radially inwards into the compensation chamber "B" via an orifice 14 
formed through the bottom plate 9. 
The narrow channel 12 has a certain length L and a certain equivalent 
diameter D (where D=2S/.pi.!.sup.1/2, where S is the mean right section 
of the channel 12) such that the ratio L/D is greater than 10, and 
generally lies in the range 10 to 100. 
The narrow channel 12 makes it possible to provide sufficient damping of 
relative vibratory motion at relatively low frequency (e.g. less than 20 
Hz) and of relatively large amplitude (e.g. greater than 1 mm) between the 
power unit and the vehicle structure, such vibratory motion being due, in 
particular, to the vehicle running over the ground. 
Also, the bottom plate 9 has a central orifice 15, and the plate also forms 
between its thickened edge and the orifice 15 a flap horizontal annular 
grid 16. 
The partition 8 also includes an annular metal part 17 that is generally 
circularly cylindrical about the axis Z and that includes a flat 
horizontal grid 18 whose radially inner edge is extended axially downwards 
by a tube 19. The tube 19 extends to a bottom end fitted with an outwardly 
projecting flange 20 which forms a shoulder facing upwards. 
The tube 19 is engaged with clearance in the central orifice 15 of the 
plate 9, said central orifice being large enough to pass the flange 20. 
Also, the grid 18 is disposed above the grid 16 and it is held in the 
vicinity of said grid 16 via the inside edge 11a of the washer 11 which 
overlies the periphery of said grid 18. 
In addition, a flap 21 is housed between the two grids 16 and 18, which 
flap is in the form of a thin flat elastomer washer whose outside and 
inside edges are in sealed radial contact respectively with the thick 
outside edge of the plate 9 and with the tube 19. 
Optionally, in order to make such sealed contact easier to achieve, the 
inside and outside edges of the flap 21 may be formed with thin sealing 
lips, for example, with the inside edge of the flap presenting a chamfered 
profile forming a single sealing lip while the outside edge of the flap 
presents an annular radial groove which defines two sealing lips. 
When the grid 18 is in abutment against the metal washer 11, the flap 21 is 
free to move axially between the grids 16 and 18 with a small amount of 
axial clearance, generally less than 1 mm, and for example of the order of 
0.5 mm. 
In this configuration, the flap 21 serves to absorb vibratory motion of the 
power unit at relatively high frequency (e.g. greater than 50 Hz) and of 
relatively small amplitude (e.g. less than 1 mm). 
Also, the inside of the tube 19 defines a nozzle 22 putting the working 
chamber A directly into communication with the compensation chamber B, 
which nozzle is of length l and a diameter d (or an equivalent diameter d 
using the same definition as that given above for the diameter D), such 
that the ratio l/d is less than 10, e.g. lying in the range 0.5 to 10. 
The nozzle 22 can be selectively closed or opened by means of a shutter 23 
e.g. under the control of a suction capsule 24 situated beneath the 
flexible wall 7. 
By way of example, the shutter 23 is in the form of an elastomer washer 
overmolded on a metal washer 25, which metal washer is secured to another 
metal washer 26 also overmolded with elastomer, and constituting the 
central portion of the flexible wall 7. 
Between the two washers 25 and 26, there is interposed a central portion of 
a piece 27 cut out from sheet metal and extending radially outwards in the 
form of two diametrically opposite resilient tabs 28 which are folded 
upwards and inwards towards the tube 19, each of the tabs 28 being 
terminated by a downwardly-folded lip 29 that slides against the outside 
surface of the tube 19. 
Optionally there may be three tabs 28. 
In addition, the suction capsule 24 includes: 
a rigid sheet metal wall 30 in the form of a cup; 
a rigid metal ring 31 stacked on the periphery of the wall 30 and secured 
to said wall and also to the second strength member 4, the assembly 
constituted by the periphery of the flexible wall 7, the periphery of the 
ring 31, and the periphery of the wall 30 being axially clamped against 
the bottom of the metal plate 9 by the crimping of the second strength 
member 4; and 
a moving wall 32 which includes a central horizontal rigid metal plate 33 
connected to the ring 31 via an annular bellows 34 of elastomer overmolded 
on the inside and outside edges respectively of the ring 31 and the plate 
33. 
The plate 33 is secured to the central portion of the flexible wall 7 of 
elastomer by means of a rivet 35 that passes through and secures the stack 
constituted by the washer 25, the central portion of the sheet metal piece 
27, the washer 26, and the plate 33. 
Between the walls 30 and 32, the suction capsule 24 has an inside volume 36 
which communicates either with the atmosphere, or else with a suction 
source 37 (air admission circuit of the engine, or optionally a vacuum 
pump), via an electrically controlled valve 38 having three ports and 
itself under the control of a computer 39 or other control system. 
In addition, a compression spring 40 is disposed between the wall 30 and 
the plate 33 in such a manner as to urge the plate 33 upwards. 
It will also be observed that the wall 30 and the ring 31 are pierced by at 
least one orifice 41 above the moving wall 32 to cause the intermediate 
space between the wall 32 and the flexible wall 7 to communicate with the 
atmosphere in such a manner that these two walls can be deformed freely 
without generating an increase or a decrease of pressure in said 
intermediate space. 
During normal operation of the vehicle, the electrically controlled valve 
38 causes the inside volume 36 of the suction capsule to communicate with 
the atmosphere, thereby causing the shutter 23 to be pressed axially 
against the bottom end of the tube 19, thereby closing the nozzle 22. 
Consequently, the grid 18 which is secured to the tube 19 is also pressed 
in abutment against the inside edge of the washer 11, and as a result the 
flap 21 is free to move vertically between the two grids 16 and 18. 
In contrast, in certain modes of vehicle operation, and in particular when 
the engine is idling, it is desirable to lock the flap 21 in position and 
to open the nozzle 22. 
To this end, the computer 39 controls the valve 38 to cause the inside 
volume 36 of the depression capsule to communicate with the suction source 
37. 
Under such circumstances, and as shown in FIG. 2, the moving wall 32 of the 
suction capsule is displaced downwards against the resilient force of the 
spring 40, thereby opening the nozzle 22. 
In addition, the lips 29 of the tabs 28 then come into abutment against the 
outwardly directed flange 20 of the tube 19, thus pulling the grid 18 
downwards which in turn comes into abutment against the flap 21, thereby 
preventing it from moving. 
In this position, the antivibration support is caused to have very low 
elastic stiffness, and thus becomes an excellent absorber of the 
vibrations produced by the engine at frequencies in the vicinity of 30 Hz, 
for example.