A hydraulic vibration-damping support comprising two strength members interconnected by an elastomer body that defines a hydraulic working chamber filled with liquid, which chamber communicates via two passageways with two hydraulic chambers surrounding each other and defined by two juxtaposed pouches formed in a common flexible wall. One of the pouches is surrounded by a pneumatic chamber that can be subjected to suction, and one of the constricted passageways is defined by a tube that projects into said pouch.

FIELD OF THE INVENTION

The present invention relates to pneumatically-controlled hydraulic vibration-damping supports.

More particularly, the invention relates to a hydraulic vibration-damping support designed to be interposed for vibration-damping purposes between first and second rigid elements, said vibration-damping support comprising:first and second strength members serving to be fastened to the two rigid elements;a rigid partition comprising at least one plate;an elastomer body which connects the two strength members together and which co-operates with the partition to define a working chamber filled with liquid;first and second flexible pouches which co-operate with said rigid partition to define respectively a compensation chamber and an additional hydraulic chamber, which chambers are adjacent and liquid-filled, the compensation chamber being connected to the working chamber via a first constricted passageway filled with liquid and that has a first resonant frequency of less than 20 hertz (Hz), and the additional hydraulic chamber being connected to the working chamber via a second constricted passageway that has a second resonant frequency lying in the range 20 Hz to 80 Hz; anda cup co-operating with said partition to define a pneumatic chamber formed around the second pouch.

BACKGROUND OF THE INVENTION

Document EP-A-0 984 193 describes an example of such a hydraulic support, in which the second constricted passageway is formed in the thickness of the above-mentioned plate. When it is desired to obtain said second resonant frequency, that results in said plate having large thickness, and hence large weight, and in the vibration-damping support having relatively large axial size.

OBJECTS AND SUMMARY OF THE INVENTION

A particular object of the invention is to mitigate those drawbacks.

To this end, according to the invention, in a vibration-damping support of the type in question, said plate is secured to a tube that extends inside the second flexible pouch and defines the second constricted passageway.

By means of these provisions, it is not necessary to use a thick plate in order to obtain a second constricted passageway having the desired resonant frequency. This results in a saving in weight and in overall size in the axial direction (i.e. perpendicularly to the above-mentioned plate). In addition, advantageous use is made of the volume of the additional hydraulic chamber by making provision for it to receive the tube that defines the second constricted passageway, thereby further improving the compactness of the support in the axial direction, said tube being surrounded radially by the side wall of the cup, a portion of the second pouch lying between the tube and said side wall.

In preferred embodiments of the invention, it is optionally possible to use one or more of the following provisions:the partition further comprises an annular shell that has a groove defining the first constricted passageway and closed by said plate towards the working chamber, the first constricted passageway being disposed radially outside the cup;the compensation chamber is disposed, at least in part, radially between the cup and the annular shell;the first and second flexible pouches are formed in the same flexible wall, the cup having a side wall that bears against the flexible wall and that locally presses said flexible wall against the rigid partition, thereby separating the compensation chamber from the additional hydraulic chamber;the cup presses the flexible wall against the plate around the tube;the tube is formed integrally with the plate;the tube and the plate are made of plastics material;the tube is extended inside the working chamber;the tube is extended inside the working chamber by forming a collar in said working chamber, said collar having an axial length that is less than one tenth of the total axial length of the tube;the second constricted passageway is mainly disposed inside the cup;said plate is plane;the cup is formed integrally with a rigid cover that covers said flexible wall;the second constricted passageway extends substantially parallel to a central axis that is perpendicular to the plate; andthe pneumatic chamber is connected to the outside via a vent passageway.

MORE DETAILED DESCRIPTION

In the various figures, like references designate elements that are identical or similar.

FIG. 1shows a motor vehicle V whose body C supports an engine M by means of at least one hydraulic vibration-damping support S such as, for example, the support shown inFIG. 2for a first embodiment of the invention.

The vibration-damping support S comprises:a first rigid strength member1in the form of a metal base which is secured to a pin2that extends upwards along a vertical central axis Z and that serves to be fastened, for example, to the engine M of the vehicle;a second rigid strength member3, e.g. made of metal, that serves to be fastened, for example, to the body C of the vehicle, and that has, in particular, a ring4; andan elastomer body5capable of withstanding, in particular, the static forces due to the weight of the engine M, it being possible for said elastomer body to be bell-shaped, for example, the bell shape extending between a top5aovermolded on and bonded to the base1, and an annular base5bovermolded on and bonded to the ring4.

In addition, the support S further comprises a bottom protective cover6which is, for example, made of metal or optionally of a plastics material.

In the example shown inFIG. 2, the cover6has a bottom7that is substantially horizontal, that can have a pneumatic connection piece8, e.g. situated in its center, and that is extended upwards by a side wall9terminated by an optionally-annular outwardly-extending flange10.

In correspondence with the pneumatic connection piece8, the cover6forms a cup11which has an annular side wall12extending upwards from the bottom7and internally defining a pneumatic chamber P communicating with the above-mentioned pneumatic connection piece8.

In addition, the second strength member3is secured to a rigid partition13which extends perpendicularly to the axis Z and which is clamped between the base5bof elastomer body5and the flange10on the cover6.

This rigid partition co-operates with the elastomer body5to define a hydraulic working chamber A filled with liquid. In addition, on its side opposite from the working chamber A, the rigid partition13co-operates with a fine, flexible wall14which can, in particular, be made of elastomer, to define an annular hydraulic compensation chamber B and an additional hydraulic chamber E situated in the center of the compensation chamber B.

The periphery of the flexible wall14is secured to the rigid partition13, e.g. by being overmolded on and bonded to said rigid partition, and/or by being nipped between the rigid partition13and the top annular edge of the wall9of the cup.

The compensation chamber B is filled with liquid and communicates with the working chamber A via a first constricted passageway C which is itself filled with liquid, which is defined, for example, inside the partition13, and which is dimensioned to have a resonant frequency of less than 20 Hz, for example. The additional hydraulic chamber E is also filled with liquid and communicates with the working chamber A via a second constricted passageway D itself filled with liquid, which passageway can, for example, be a cylindrical passageway extending along the vertical axis Z, and can be dimensioned to have a resonant frequency lying in the range 20 Hz to 80 Hz, for example.

In the example shown inFIG. 2, the rigid partition13comprises:a recessed annular shell15made of a light alloy or of a plastics material, for example; anda thin plane plate16made of a plastics material or optionally of metal, of thickness lying, for example, in the range 4 millimeters (mm) to 6 mm, which plate covers the shell15towards the working chamber A and can be fastened to said shell by being crimped, by being pressed by the base5bof the elastomer body, or by some other means.

In this example, at its outside periphery, the annular shell15is provided with a groove17that is open upwards and that defines the first constricted passageway C. The first constricted passageway C communicates firstly with the working chamber A via a recess18provided in the plate16, and secondly with the compensation chamber B via a recess provided in the partition15(not shown).

At its center, the plate16defines a nozzle24advantageously extending along the central axis Z and that defines the above-mentioned second constricted passageway D. The nozzle24is formed inside a tube25that is secured to the plate16or is formed integrally therewith. The tube25extends axially inside the cup11while being surrounded by the central portion27of the flexible wall14, which flexible wall is pressed locally into leaktight contact with the bottom face of the plate16around the tube25. The flexible wall14thus forms first and second flexible pouches26,27constituted respectively by the peripheral portion26of the flexible wall, situated radially outside the cup11, and by the central portion27of the flexible wall14, situated radially inside said cup11.

The tube25can also optionally be extended inwards from the working chamber A via a collar25a. The collar25acan advantageously have an axial length that is considerably shorter than the total axial length of the tube25, e.g. less than one tenth of the total axial length of the tube25, so that the second constricted passageway D is mainly situated inside the cup11.

These provisions enable the vibration-damping support S to be very compact along the central axis Z and to be small in weight, without degrading the vibration-damping performance of the support.

Finally, the pneumatic connection piece8communicates with a three-port valve28that is adapted to put the pneumatic chamber P either into communication with a suction source29(DEP.) provided in the vehicle (vacuum pump, optionally the vacuum circuit used for assisting braking of the vehicle, or some other source), or else into communication with the atmosphere.

The three-port valve28can advantageously be constituted by a solenoid valve controlled by an electronic control circuit30(CALC.) such as, for example, the on-board computer of the vehicle, itself connected to a sensor31(RPM) indicating the speed of the engine.

Thus, when the engine of the vehicle is idling, i.e. when the sensor31indicates a speed lower than a predetermined limit corresponding, for example, to a vibration frequency lying in the range 20 Hz to 100 Hz, the control circuit30actuates the valve28so that it puts the pneumatic chamber P into communication with the atmosphere, as shown inFIG. 2.

In this mode of operation, the vibration from the engine M is transmitted to the working chamber A via the elastomer body5, thereby causing fluctuations in the volume of said working chamber that are absorbed by deformation in the additional hydraulic chamber E: in view of the resonant frequency of the second constricted passageway D, which frequency corresponds substantially to the frequency of the vibration emitted by the engine when it is idling, said constricted passageway D is then the subject of resonance phenomena that make it possible to filter out effectively the vibration from the engine.

At this engine speed, it is also possible to control the valve28so that it subjects the pneumatic chamber alternately to suction and to atmospheric pressure, so as to generate counter-vibration suitable for reducing the effect of the vibration from the motor.

Conversely, in predetermined conditions corresponding, for example, to the vehicle traveling, i.e. in particular at an engine speed grater than said predetermined limit, the control circuit30preferably actuates the valve28so that the pneumatic chamber P communicates continuously with the suction source29so that the flexible pouch27is then held pressed against the inside surface of the cup11.

In this mode of operation, it is as if the additional hydraulic chamber E no longer existed, and the vibration-damping support operates conventionally by damping vibration of low frequency (e.g. less than 20 Hz) and of large amplitude (e.g. greater than 1 mm) by liquid transfer between the compensation chambers A and B through the constricted passageway C.