FR2828541A1 - Hydraulic anti-vibration support comprises two frames connected by elastomer body delimiting work chamber which communicates through throttled passage with compensation chamber - Google Patents

Abstract

The anti-vibration support comprises two frames (2,3) connected together by an elastomer body (7) partially delimiting a work chamber (A) filled with fluid. The work chamber communicates through a throttled passage (C) with a compensation chamber (B) separated from the work chamber by a rigid partition (11). The throttled passage comprises two stages (C1,C2) delimited by two metal sheets (12,13) forming the partition.

Description

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Hydraulic antivibration support.

 The present invention relates to hydraulic antivibration mounts, intended for example for mounting motor vehicle engines on the bodies of these vehicles.

une chambre de compensation remplie de liquide, délimitée partiellement par une paroi souple en élastomère, une cloison rigide qui sépare la chambre de travail et la chambre de compensation, cette cloison rigide comportant une première pièce de tôle qui est en contact étanche avec la base annulaire du corps en élastomère et une deuxième pièce rigide qui est en contact étanche avec ladite première pièce de tôle et qui délimite la chambre de compensation avec la paroi souple, la première pièce de tôle comportant une première grille centrale qui communique avec la chambre de travail et la deuxième pièce rigide comportant une deuxième grille centrale qui communique avec la chambre de compensation en délimitant avec la première grille un logement de clapet, un clapet de découplage disposé dans le logement de clapet de façon à être déplaçable avec un More particularly, the invention relates to a hydraulic antivibration support for connecting together first and second rigid elements for damping and filtering vibrations between these elements, this support comprising: first and second rigid armatures intended to be fixed respectively to the first and second second rigid element to be joined, an elastomer body which has substantially a bell shape extending along a central axis between a vertex integral with the first armature and an annular base integral with the second armature, a working chamber filled with liquid, at least partially delimited by the elastomer body,

a liquid-filled compensation chamber, partially delimited by a flexible elastomer wall, a rigid partition which separates the working chamber and the compensation chamber, this rigid partition comprising a first piece of sheet metal which is in sealing contact with the annular base of the elastomeric body and a second rigid part which is in sealing contact with said first sheet metal part and which delimits the compensation chamber with the flexible wall, the first sheet metal part comprising a first central grid which communicates with the working chamber and the second rigid part comprising a second central grid which communicates with the compensation chamber by delimiting with the first gate a valve housing, a decoupling valve disposed in the valve housing so as to be movable with a

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 low clearance parallel to the central axis by closing the first and second grids, and a throttled passage filled with liquid, which communicates the working chamber with the compensation chamber, the constricted passage being partially delimited by the first piece of sheet metal and the second rigid part of the rigid partition, said throttled passage extending angularly around the decoupling valve on a linear length greater than the perimeter of the rigid partition, and this constricted passage comprising first and second stages, the first stage of the constricted passage being adjacent to the working chamber and extending between a first end which communicates with the working chamber and a second end which communicates with the second stage, while the second stage of the constricted passage is adjacent to the clearing chamber and extends between a first end that communicates with the second ext end of the first stage and a second end which communicates with the compensation chamber.

 A hydraulic antivibration support of this type is disclosed for example in document FR-A-2 751 042, in which the second rigid part of the rigid partition is a casting part.

 This known antivibration support is satisfactory in terms of its technical operation. In particular, it is known that the resonant frequency of the throttled passage, which is also the frequency at which the antivibration support has its best performance with respect to large amplitude vibrations, depends on the ratio in length and the equivalent diameter of the throttled passage. : thanks to the realization of the throttled passage on two floors, one can obtain a large length of this passage and therefore a relatively low resonance frequency of said throttled passage, which may be necessary in some applications.

 But the aforementioned known antivibration support

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 However, the disadvantage is that the casting of its rigid partition is relatively expensive to achieve and also relatively massive, which tends to increase both the cost and the weight of the antivibration support.

 The present invention is intended to overcome these disadvantages.

 For this purpose, according to the invention, an antivibration support of the kind in question is characterized: in that the second rigid part of the rigid shell is constituted by a second piece of sheet metal, cut and stamped, in that the flexible wall of elastomer is secured to a rigid base which is itself secured to the second frame and which has at least one side wall extending along the central axis from the second frame to an inner annular support edge, in that that the second sheet metal part comprises an outer annular support edge which is in sealing contact with the inner annular bearing edge of the base, the second sheet metal part further comprising a projection which extends along the axis central from said outer annular support edge to a solid annular zone which is in sealing contact with the first sheet metal part, the second stage of the constricted passage being delimited between the first sheet metal part, the side wall of the base, the inner annular support edge of the base, the outer annular support edge of the second sheet metal part and the projection of said second sheet metal part, and in that that the first stage of the constricted passage is defined between the annular base of the elastomeric body and the first piece of sheet metal.

 Thanks to these arrangements, we obtain a strangulated passage of great length, extending over two floors, using a partition simply made of two parts

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 sheet metal, so particularly light and inexpensive.

 In preferred embodiments of the antivibration support according to the invention, one or more of the following arrangements may also be used: the second reinforcement comprises an annular inner part which belongs to the base; of the elastomer body and which forms an open groove towards the first piece of sheet metal, this groove delimiting the first stage of the passage constricted with said first piece of sheet metal, the first and second ends of the first stage of the constricted passage being separated from each other; the other by an elastomeric plug belonging to the elastomer body; the first sheet metal part comprises an outer annular flange which extends along the central axis towards the second reinforcement, to a free annular edge applied axially in leaktight contact against an outer part of the second reinforcement, the inner part of the second armature having an inner skirt which extends parallel to the central axis beyond said free annular edge, to the contact of a radial annular portion belonging to the first piece of sheet metal, the first stage of the constricted passage being defined partially by said inner skirt and said outer rim of the first sheet metal part; the first sheet metal part comprises a solid annular part which is in tight axial contact with the second sheet metal part and which extends inwards by an annular projection itself extended by the first grid, the valve housing being delimited laterally by said annular projection of the first piece of sheet metal; the first stage of the throttled passage communicates with the second stage of the throttled passage via an opening cut in the first sheet metal part, and the second stage of the throttled passage communicates with the compensation chamber by

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 via an opening cut in the second piece of sheet metal; - The opening cut in the second sheet metal part is made at least in the outer annular bearing edge and in the projection of said second sheet metal part, the first and second ends of the second stage of the throttled passage being separated from one another. on the other by an elastomeric plug molded in one piece with the flexible elastomer wall against an inner face of the inner bearing edge and the side wall of the base, said elastomer plug of the a base penetrating partially into the opening of the second piece of sheet metal, and the second gate having a solid annular portion which is applied axially in sealing contact against said elastomer plug of the base; the elastomer plug of the base comprises a slit open axially towards the elastomer body and laterally towards the first end of the second stage of the throttled passage, the projection of the second sheet metal part comprising a slice which laterally delimits the opening; cut into said second piece of sheet metal and which penetrates into said slot; the flexible elastomer wall is overmolded on the base forming an extra thickness in the vicinity of the elastomer plug of the base on the inner bearing edge of the base, the opening cut in the second sheet metal part forming two slices; in the outer annular support edge of said second sheet metal part, these two wafers being disposed on either side of the elastomer plug of the base and said excess thickness; the elastomer plug of the base comprises a pin which protrudes axially towards the elastomer body and the first piece of sheet metal has a portion which bears in axial tight engagement against the elastomer plug of the base and which comprises a hole in

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 which is engaged the pawn.

 Other features and advantages of the invention will become apparent from the following description of one of its embodiments, given by way of non-limiting example, with reference to the accompanying drawings.

 In the drawings: - Figure 1 is a vertical sectional view of an antivibration support according to one embodiment of the invention, Figures 2 and 3 are perspective views of the two faces of a decoupling valve belonging to the antivibration support of FIG. 1, - FIG. 4 is a graph representing the dynamic stiffness of the antivibration support of FIG. 1 as a function of the frequency, compared to the dynamic stiffness of the same antivibration support provided with a decoupling valve without pins and 5 and 6 are exploded views in perspective of the antivibration support of FIG. 1, FIGS. 7 and 8 are detailed perspective views of two parts of the antivibration support of FIG. 1. comprising one, a compression-resistant elastomeric body and the other an elastomeric bellows.

 In the different figures, the same references designate identical or similar elements.

 FIG. 1 represents a hydraulic antivibration support 1 comprising first and second frames 2, 3 which are for example intended to be fixed respectively to the power unit and to the body of a vehicle.

 In the example considered, the first armature 2 is in the form of a metal stud, made for example of light alloy, which is centered on a vertical axis Z and which is integral with a threaded stud 4 allowing

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 for example the fixing of the stud to the power unit.

 The second armature 3, for its part, is formed by a cut and pressed sheet metal crown, also centered on the Z axis. In the example shown, the second armature 3 comprises an outer part 5 which extends in a plane radial with respect to the Z axis and which is intended to be fixed for example to the vehicle body, and an inner portion 6 hollow, substantially U-shaped section inverted, forming an annular groove 33 open axially opposite of the first frame 2.

The inner portion 6 further forms an axial inner skirt 6a, which extends downwardly beyond the outer portion 5.

 The two armatures 2,3 are interconnected by a relatively thick elastomeric body 7, which has sufficient compressive strength to take up the static forces due to the weight of the power unit. This elastomer body 7 has a bell-shaped lateral wall which extends between an apex 8 molded on the first armature 2, and an annular base 9 which is overmolded on the inner part 6 of the second armature.

 Furthermore, the second armature 3 is secured to a limiter cap 10 made of sheet metal, which has an annular shape and covers playfully the elastomer body 7, leaving the passage to the stud 4. The cap 10 thus limits the relative deflections between the first and second frames 2,3.

 The second armature 3 is also integral with a rigid partition 11 which defines with the elastomer body 5 a first chamber A filled with liquid, called working chamber.

 In the example under consideration, the rigid partition 11 consists of first and second superimposed shaped sheet metal parts 12, 13, which form, in their central portions, first and second

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 second flat grids 14,15 which have holes 16 and which extend perpendicularly to the central axis Z.

 The first sheet metal part 12 comprises for example: an annular flange 17 which extends parallel to the axis Z, this annular flange having an upper free annular edge 18 in sealing engagement against an elastomer layer 19, which layer 19 belongs to to the elastomer body 7 and is overmolded under the outer portion 5 of the second armature, an annular portion 20 which extends radially inwardly from the lower end of the flange 17, the inner skirt 6a of the second armature being in sealing engagement against this annular portion 20, a projection 21 which extends towards the working chamber A from the radially inner edge of the annular portion 12, and said first gate 14, which extends the projection 21 radially towards the inside.

 Moreover, the second sheet metal part 13 comprises, in the example under consideration: an annular outer bearing edge 22 which extends radially with respect to the central axis Z, an annular projection 23 which extends axially parallel to the Z axis to the first sheet metal part 12, and said second grid 15, which has an outer periphery bearing under the annular part 20 of the first sheet metal part 12.

 The antivibration support 1 further comprises a base 24 made of cut sheet metal and stamped, which comprises: an annular support edge 25 which is fixed to the outer part 5 of the second reinforcement, for example by crimping, and which is supported sealing against said elastomer layer 19 under the outer portion 5 of the second armature, an axial annular side wall 26 which

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 extends from the inner periphery of the bearing edge 25, parallel to the Z axis and away from the second frame 3, a lower bearing edge 27, which extends radially inwards the lower end of the side wall 26, and an axial rib 28 which extends axially opposite the elastomeric body 7 from the radially inner portion of the bearing edge 27.

 The bearing edge 27 and the rib 28 of the base 24 are overmolded by a flexible bellows 29 made of elastomer, which also forms an elastomer layer 30 covering the support edge 27 of the base and against which the edge support 22 of the second piece of sheet 13 comes into sealing support.

 Thus, the bellows 29 defines with the partition 11 a second chamber B, said compensation chamber, which is filled with liquid.

 This compensation chamber B communicates with the working chamber A via an annular narrow passage C, which extends over substantially two towers and on two floors around the chambers A and B, namely: a first stage C1 which communicates with the working chamber A via an opening 31 obtained by a cutout 32 of the inner skirt 6a of the second armature and by a corresponding recess of the base 9 of the elastomer body, the first stage Cl of the passage constricted being defined between on the one hand, the first sheet metal part 12 and secondly, the annular groove 33 formed in the base 9 of the elastomer body inside the hollow inner part 6, and a second stage C2 which is delimited by the first and second pieces of sheet metal 12, 13 and by the side wall 26 of the base, this second stage C2 communicating with the first stage C1 via a

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 opening 34 formed in the first piece of sheet metal 12 (see Figure 5), and said second stage C2 further communicating with the compensation chamber B through an opening 35 formed in the second sheet metal part 13 (see Figure 6).

 Furthermore, the antivibration support 1 also comprises a decoupling valve 37, visible in Figures 1 to 3, which is mounted with a small clearance (for example, of the order of 0.5 to 1 mm) between the first and second grids 14,15.

 This decoupling valve is in the form of an elastomer plate which is adapted to vibrate between the first and second grids 14, 15 by alternately applying against these two grids and by closing them when the first and second frames 2 , 3 undergo relative vibratory movements.

 The decoupling valve 37 has, on its first and second faces 38, 39, protruding spikes 40 of elastomer which are arranged to bear on the first and second grids 14, 15, so that in the absence of relative vibrations. between the first and second reinforcement 2,3, the valve 37 has an average plane P disposed obliquely with respect to the first and second grids 14,15.

 When the decoupling valve is subjected to vibrations, the pins 40 are adapted to collapse under the effect of the pressure of the liquid in the chambers A, B which communicate respectively with the first and second faces 38,39 of the valve. decoupling via the first and second grids 14,15. Thus, the peripheral flange 41 of the valve may then bear against sealing solid annular portions 14a, 15a surrounding the holes 16 of the grids 14, 15.

 In addition, the valve 37 advantageously comprises first and second centering studs 42, 43 which cooperate by mutual engagement with the grids 14, 15 to center

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 the decoupling valve 37. In the example shown, the first centering pin 42 has a hemispherical shape and penetrates into a hole 14b of the first grid 14, while the second centering pin 43 is clipped into a hole 15b of the second grid 15, the second centering pin 43 having an enlarged head 43a which enters the compensation chamber B.

 As shown in more detail in Figures 2 and 3, the pins 40 which induce the inclined position of the decoupling valve are preferably disposed near the outer periphery of the decoupling valve and will be hereinafter external pins.

 The external pins 40 of the decoupling valve are preferably distributed in first and second groups of external pins 40: the external pins 40 of the first group are arranged only on the first face 38, on one side of an imaginary line crossing the decoupling valve parallel to the average plane P of said decoupling valve, while the outer pins 40 of the second group are arranged only on the second face 39 of the decoupling valve, on the other side of said imaginary line.

 In the example considered, the decoupling valve 37 has the shape of a disk and the imaginary line in question is a diametrical axis Y substantially perpendicular to the central axis Z and passing through the center 0 of the valve.

 In the example shown, the first group of external pins comprises three external pins 40, one of which is arranged in alignment with an axis X passing through the center 0 of the valve and perpendicular to the Y axis (the X, Y axes define the aforementioned mean plane P of the decoupling valve), while the two other external pins 40 of the first group are disposed substantially at 60 of the X axis relative to the center 0 of the decoupling valve.

 In addition, again in the example shown, the

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 second group of outer pins also includes three outer pins 40 which are arranged substantially symmetric outer pins 40 of the first group, relative to the Y axis: thus, the outer pins 40 of the second group also include an outer pin aligned with the X axis and two outer pins disposed substantially at 600 of the X axis relative to the center 0 of the decoupling valve. The external pins 40 of the first and second groups are arranged in the vicinity of the above-mentioned outer rim 41 of the decoupling valve, which outer rim 41 protrudes towards the gates 14,15 from the two faces 38,39 of the decoupling valve. The outer pins 40 however extend beyond the outer edge 41 to the grids 14,15.

 Thanks to these arrangements, and in particular thanks to the inclined position of the valve imposed by the external pins 40, significantly reduces the phenomena of flapper clappers against the grids and reduces the dynamic stiffness of the antivibration support at high frequencies.

peut également avoir recours aux dispositions suivantes : on peut réaliser sur la première face 38 du clapet de découplage deux picots intérieurs 44 disposés au voisinage du téton de centrage 42 et présentant par exemple la même taille que les picots extérieurs 40, ces picots intérieurs 44 étant par exemple disposés en alignement avec le centre 0 du clapet selon l'axe X, on peut réaliser sur la deuxième face 39 du clapet de découplage, deux picots intérieurs 45 situés au voisinage du téton de centrage 43 et disposés par exemple à l'opposé des picots extérieurs 40 du deuxième groupe par rapport à l'axe Y, les picots intérieurs 45 étant par exemple disposés symétriquement par rapport à l'axe X en Advantageously, to further contribute to improving the acoustic performance of the antivibration support, it is

The following provisions may also be used: it is possible to make on the first face 38 of the decoupling valve two inner pins 44 arranged in the vicinity of the centering pin 42 and having, for example, the same size as the external pins 40, these inner pins 44 being for example arranged in alignment with the center 0 of the valve along the axis X, it is possible to realize on the second face 39 of the decoupling valve, two inner pins 45 situated in the vicinity of the centering stud 43 and arranged for example the opposite external pins 40 of the second group relative to the Y axis, the inner pins 45 being for example arranged symmetrically with respect to the X axis in

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 each forming with this axis an angle of the order of 600 relative to the center 0 of the valve, and can be made on both sides 38,39 of the decoupling valve rounded bosses 46 which project respectively to the first and second grids 14,15, preferably flush with the flange 41 and in any case without exceeding the pins 40,44,45.

 Note that the faces 38,39 of the valve 37 could be inverted, without departing from the scope of the invention.

 Advantageously, the antivibration support 1 further comprises a deflector 47 in the form of an annular ring centered on the Z axis, which extends inside the working chamber A by surrounding the first gate 14 and converging towards the top 8 of the elastomer body.

The opening 31, through which the constricted passage C opens into the working chamber A, is located radially outside the deflector 47.

 In the example shown, the deflector 47 comprises a bearing edge 48 which extends radially with respect to the Z axis and which is clamped axially between the base 9 of the elastomer body and the annular portion 20 of the first part This bearing edge 48 extends radially inwards and axially towards the apex 8 of the elastomer body by a lateral wall 49 which in the example shown has a frustoconical shape, forming an angle α understood by This lateral wall 49 is itself extended, at its upper end, by a flattened rim 50 which extends substantially radially inwards and which delimits a circular opening 51. width of the flange 50 is for example between 2 and 5% of the diameter of the opening 51.

 Thanks to the arrangements just described, the acoustic characteristics of the antivibration support 1, and in particular its

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 dynamic stiffness K at high frequencies.

 In particular, there is shown in FIG. 4, in solid lines, the curve 52 of the dynamic stiffness K of the antivibration support along the Z axis as a function of the frequency F, and the curve 53 of the stiffness is shown in dashed lines. dynamic of the same antivibration support 1 but provided with a conventional decoupling valve and without the deflector 47.

 It can be seen in FIG. 4 that the antivibration support according to the invention makes it possible to avoid a stiffness peak 54 characteristic of the antivibration mounts of the prior art, a peak of stiffness which corresponded to the transmission of acoustic vibrations between the engine and the engine. vehicle body.

 It will be noted that the decoupling valve 37 according to the invention and the deflector 47 according to the invention each have a beneficial effect on the acoustic characteristics of the antivibration support, and that, where appropriate, each of these elements could be used independently. one of the other.

 In other words, the deflector 47 can be effectively used with a decoupling valve other than the valve 37 described above, and the valve 37 described above could be used profitably in the absence of the deflector 47.

 However, the inventors of the present invention have found that the combination of the decoupling valve 37 according to the invention with the deflector 47 according to the invention produces beneficial effects still much greater than the effects that could have been expected taking into account the effects produced. by the valve 37 alone and effects produced by the deflector 47 in isolation.

 Furthermore, it will be noted that the embodiment described above of the throttled passage C is particularly economical, insofar as this embodiment makes it possible to obtain a long throttled passage C extending over two

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 without the use of a light alloy casting, as is usually the case.

 The way in which this throttled passage is made in the example considered is shown in more detail in FIGS. 5 to 8: as shown in FIGS. 5 and 7, the elastomer body 7 forms an elastomer plug 55 which closes the first stage Cl of the throttled passage between on the one hand, the opening 31 which communicates the throttled passage with the working chamber A and on the other hand, the opening 34 which is cut in the annular rim 17 and in the part annular 20 of the sheet metal part 12 to communicate with each other the first and second stages Cl, C2 of the throttled passage, and the elastomeric bellows 29 is molded in one piece with an elastomer plug 56, clearly visible on the FIGS. 6 and 8, which elastomeric plug closes the second stage C2, of the passageway between the above-mentioned opening 34 and the opening 35 which makes the second stage C2 of the constricted passage communicate with the compensating chamber B, the opening 35 being cut in the bearing edge 22, in the projection 23 and in the outer periphery of the full annular portion 15a of the second sheet metal part 13.

 Thus, the liquid that passes from the working chamber A to the compensation chamber B follows the entire length of the constricted passage C, firstly following the first stage C1 in an angular direction, then the second stage C2, preferably in the same angular direction.

 It will be noted that the assembly of the first and second pieces of sheet metal 12, 13 in the antivibration support is facilitated, in the example in question, by virtue of the following provisions: the slices 22a of the bearing edge 22, which partially delimit the blank of the second piece of sheet metal 13, engage on both sides of the

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 elastomer plug 56 and an elastomer thickening 57 molded in one piece with said elastomer plug 56 (see FIGS. 6 and 8), the plug 56 having a bearing surface 56a oriented along a radial plane and on which a portion of the solid annular portion 15a of the grid 15 seals in the vicinity of one 23a of the slices of the projection 23 of the second piece of sheet metal 13, so that the elastomer plug 56 closes off a portion of the opening 35 thus separating said opening 35 from the opening 34 which communicates with the first stage Cl of the constricted passage, - the edge 23a of the projection 23, which partially delimits the opening 35 opposite the the unclosed portion of said opening is shifted inwardly of said opening 35 relative to the corresponding wafer 22a of the support edge 22, and this wafer 23a engages in a slot 58 in a circular arc, centered around the Z axis, said slot 58 being formed in the elastomer plug 56, opposite the portion of the opening 35 left free by the plug 56, the elastomer plug 56 advantageously comprises a centering pin 59 oriented axially towards the first sheet metal part 12 and engaging in a corresponding hole 60 of said first sheet metal part, so as to angularly position said first piece of sheet metal, - the bearing edge 25 of the base and the outer part 5 of the second armature have a non-symmetrical shape of revolution, so as to determine the relative angular position of these two parts relative to each other during assembly.

Claims (9)

1. Hydraulic antivibration support for connecting together first and second rigid elements for damping and filtering vibrations between these elements, this support comprising: first and second rigid armatures (2, 3) intended to be fixed respectively to the first and second rigid elements to be joined, an elastomer body (7) which has substantially a bell shape extending along a central axis (Z) between a vertex (8) integral with the first armature (2) and an annular base (9) secured to the second armature (3), a working chamber (A) filled with liquid, at least partially delimited by the elastomer body (7), a compensation chamber (B) filled with liquid, partially delimited by a flexible wall elastomer (29), a rigid partition (11) separating the working chamber (A) and the compensation chamber (B), the rigid partition comprising a first piece of sheet metal (12) which is in con sealed contact with the annular base (9) of the elastomer body and a second rigid part (13) which is in sealing contact with said first sheet metal part (12) and which delimits the compensation chamber (B) with the flexible wall ( 29), the first sheet metal part (12) having a first central grid (14) which communicates with the working chamber (A) and the second rigid part (13) having a second central grid (15) which communicates with the chamber for compensating (B) by defining with the first gate (14) a valve housing, a decoupling valve (37) disposed in the valve housing so as to be movable with a <Desc / Clms Page number 18>  low clearance parallel to the central axis (Z) by closing the first and second grids (14,15), and a throttled passage (C) filled with liquid, which communicates the working chamber (A) with the compensation chamber (B), this constricted passage being partially delimited by the first piece of sheet metal (12) and the second rigid part (13) of the rigid partition, said throttled passage extending angularly around the decoupling valve (37) for a length linear greater than the perimeter of the rigid partition, and this constricted passage having first and second stages (C1, C2), the first stage (Cl) of the constricted passage being close to the working chamber (A) and extending between a first end which communicates with the working chamber and a second end (32) which communicates with the second stage (C2), while the second stage (C2) of the constricted passage is close to the compensation chamber (B) and extends between a first end which communicates with the second end of the first stage and a second end which communicates with the compensation chamber (B), characterized in that the second rigid piece (13) of the rigid shell is constituted by a second sheet metal part, cut and stamped, in that the flexible elastomer wall (29) is secured to a rigid base (24) which is itself secured to the second reinforcement (3) and which has at least one side wall (26) extending along the central axis (Z) from the second armature (3) to an inner annular support edge (27), in that the second sheet metal part (13) has an edge external annular support (22) which is in sealing contact with the inner annular bearing edge (27) of the base, the second sheet metal part further comprising a projection (23) which extends along the central axis (Z) from said outer annular support edge (22) to a ring area <Desc / Clms Page number 19>  solid (15a) which is in sealing contact with the first sheet metal part, the second stage (C2) of the constricted passage being delimited between the first sheet metal part (12), the side wall (26) of the base, the edge the inner annular bearing support (27) of the base, the outer annular bearing edge (22) of the second sheet metal part and the projection (23) of the said second sheet metal part, and in that the first stage ( Cl) of the constricted passage is delimited between the annular base (9) of the elastomeric body and the first sheet metal part (12).  2. Antivibration support according to claim 1, wherein the second armature (3) comprises an annular inner portion (6) which belongs to the base (9) of the elastomeric body and which forms a groove (33) open to the first piece of sheet metal (12), this groove delimiting the first stage (Cl) of the passage constricted with said first sheet metal part, the first and second ends of the first stage of the constricted passage being separated from each other by a plug of elastomer (55) belonging to the elastomeric body.  An antivibration support according to claim 1 or claim 2, wherein the first sheet metal part (12) has an outer annular flange (17) extending from the central axis (Z) to the second armature (3). to a free annular edge (18) applied axially in sealing engagement with an outer portion (5) of the second armature, the inner portion (6) of the second armature having an inner skirt (6a) extending parallel to the central axis (Z) beyond said free annular edge (18), to the contact of a radial annular portion (20) belonging to the first sheet metal part, the first stage (Cl) of the constricted passage being delimited partially by said inner skirt (6a) and said outer annular flange (17) of the first sheet metal part.  4. Antivibration support according to any one <Desc / Clms Page number 20>  of the preceding claims, wherein the first sheet metal part (12) has a solid annular part (20) which is in axial sealing contact with the second sheet metal part (13) and which is extended inwards by an annular projection ( 21) itself extended by the first grid (14), the valve housing being delimited laterally by said annular projection (21) of the first sheet metal part.  5. Antivibration support according to any one of the preceding claims, wherein the first stage (Cl) of the throttled passage communicates with the second stage (C2) of the throttled passage via an opening (32) cut in the first sheet metal part, and the second stage (C2) of the constricted passage communicates with the compensation chamber (B) through an opening (33) cut in the second sheet metal part.  6. antivibration support according to claim 5, wherein the opening (33) cut in the second sheet metal part is formed at least in the outer annular bearing edge (22) and in the projection (23) of said second piece of sheet metal, the first and second ends of the second stage (C2) of the constricted passage being separated from each other by an elastomeric plug (56) integrally molded with the flexible elastomeric wall (29) against an inner face of the inner bearing edge (27) and the side wall (26) of the base, said elastomer plug of the base (56) partially penetrating the opening (33) of the second sheet metal part, and the second gate (15) having a solid annular portion (15a) which is axially applied in sealing engagement against said elastomer plug of the base (56).  An antivibration mounts according to claim 6, wherein the elastomer plug of the base (56) has a slot (58) open axially to the elastomeric body (7) and laterally to the first end of the second stage of the passage. strangled, the projection (23) of <Desc / Clms Page number 21>  the second sheet metal part comprising a wafer (23a) which laterally delimits the opening (33) cut in said second sheet metal part and which penetrates into said slot (58).  8. antivibration support according to any one of the preceding claims, wherein the flexible elastomer wall (29) is overmolded on the base (24) forming an extra thickness (57) in the vicinity of the elastomer plug of the base (56) on the inner bearing edge (27) of the base, the opening (33) cut in the second sheet metal part forming two slices (22a) in the outer annular bearing edge (22) of said second piece of sheet metal, these two slices (22a) being disposed on either side of the elastomer plug of the base (56) and said thickening (57).  An antivibration mounts according to any one of claims 5 to 8, wherein the elastomer plug of the base (56) comprises a pin (59) which protrudes axially towards the elastomer body (7) and the first sheet metal part (12) comprises a part (20) which bears tightly against the elastomer plug of the base (56) and which comprises a hole in which the pin (59) is engaged.