Abstract:
The invention relates to a functional hydro-elastic element to be lodged in a hydro-elastic joint for damping load vibrations between two structural parts, in particular a wheel suspension and a vehicle body, the functional hydro-elastic element having a longitudinal axis and a circumferential direction around this longitudinal axis. The functional hydro-elastic element has at least one row of hydraulic chambers, extending circumferentially and comprising at least three hydraulic chambers and at least one throttling duct that enables a communication of liquid between each pair of respective circumferentially adjacent hydraulic chambers so that a variation of at least one working volume of the hydraulic chambers due to load vibrations can be balanced by enabling a flow of liquid into at least one of the other hydraulic chambers.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. application Ser. No. 13/517,475, filed on Jun. 20, 2012, entitled “ FUNCTIONAL HYDRO-ELASTIC ELEMENT AND HYDRO-ELASTIC JOINT”, the contents of which is hereby incorporated by reference herein in its entirety ,which was filed under the provisions of 35 U.S.C. §371 and claims the benefit of International Patent Application No. PCT/EP2010/007578, filed on Dec. 13, 2010, entitled “HYDROELASTIC FUNCTIONAL ELEMENT AND HYDROELASTIC JOINT”, which claims the benefit of priority of French Application No. 0959423, filed on Dec. 22, 2009, the contents of both of which are hereby incorporated by reference herein in their entirety. 
     
    
     BACKGROUND 
       [0002]    The invention relates to a functional hydro-elastic element to be lodged in a hydro-elastic joint for damping load vibrations between two structural parts, in particular a wheel suspension and a vehicle body, the functional hydro-elastic element having a longitudinal axis and a circumferential direction around this longitudinal axis. Besides, the invention relates to a hydro-elastic joint for assembling two structural parts, in particular to connect a wheel suspension to a vehicle body, the joint comprising a longitudinal axis, a rigid external frame, a rigid internal frame, and a functional hydro-elastic element linking the internal frame to the external frame in a vibration-damping manner. 
         [0003]    In particular, the invention relates to hydro-elastic joints for automobiles or heavy vehicles. In the present case, it more particularly concerns joints, in particular multi-layer joints, for ground connection of wheeled vehicles, wherein the joint has to provide an acoustic filter for structure-borne vibrations. Typically, these joints must have a significant radial stiffness in view of the occurring stresses and of the joints&#39; guiding function; thus, these high stiffnesses facilitate the transmission of noise. 
         [0004]    Hydro-elastic mountings or joints are known for many years. These consist generally of at least two cylindrical, concentric frames, the annular space between which is filled with elastomer material in which hydraulic chambers are arranged and linked by channels. The liquid contained in these chambers can circulate from one chamber into the other for low excitation frequencies whereas from a certain frequency onwards an occurring resonance blocks passing of the liquid, which causes a phase shift associated with a dynamic stiffening used for filtering certain vibrations. This technique is explained in various patents such as U.S. Pat. No. 6,273,406. 
         [0005]    There are numerous variants of shapes for hydro-elastic joints that can be classified into two families. 
         [0006]    The first family comprises hydro-elastic joints having two hydraulic chambers opposite to each other at 180° according to a preferential radial direction corresponding to the principal excitation direction, or four hydraulic chambers opposing each other pairwise according to two radial directions that are orthogonal to each other. This is for example the case for the patent applications EP 1 348 885 and FR 2817007. 
         [0007]    The second family comprises hydro-elastic joints designed with a peripheral hydraulic chamber that is continuous but that can locally present throttling areas in the hydraulic circuit. This is for example particularly the case for the patent application FR2 910 577 and the application EP 0 410 455. 
         [0008]    The variations in these two families originate either from the two connection principles, one or double layer, or from the way the hydraulic chambers and channels are built, that is with or without an incorporated plastic piece. Finally, there are joints for filtering radial excitations and others for filtering axial excitations with hydraulic effect, wherein the axis is the axis of the cylindrical frames of the joint. Some rare applications provide the ability of filtering with hydraulic effect at the same time in axial and in radial direction. This is the case for the patent application FR 2 659 713 and in certain embodiments of the application FR 2 910 577. 
         [0009]    The patent application FR&#39;713 claims to provide hydraulic filtering in all radial directions with four hydraulic chambers. However, the breakdown of stresses it describes does not compensate for the fact that a hydraulic chamber exposed to a load that essentially differs from a radial direction will not be able to eject the hydraulic liquid in the same way as if the load was purely radial, that is perpendicular to the external surface of the hydraulic chamber. Additionally, despite the fact that the four peripheral chambers of the joint disclosed in FR&#39;713 provide filtering in all directions, the level of filtering will not be constant depending on the radial direction, which prohibits mounting such a joint without specific angular orientation. 
         [0010]    The patent application FR&#39;577 discloses a continuous and peripheral hydraulic chamber that a priori seems ideal to assure homogenous hydraulic filtering in all radial directions. However, the fluid transfer from an area subjected to an excitation towards a diametrically opposed area is only really controllable if a debit restriction is present at a specific location, as it is also disclosed in the application FR&#39;577. Thus, if during mounting the joint is angularly oriented such that this restricted area is directly above the radial axis of excitation, the flow of liquid will be strongly inhibited and the fluid will have a tendency to be repelled towards the two half-chambers at each side of the restricted area. This generates the risk of creating a phase shift already for low frequencies through blockage of the hydraulic fluid. In order to avoid localised peripheral restrictions, a solution with a hydraulic chamber in the shape of a very thin layer could be considered, as in the application FR&#39;577, but this arrangement is industrially problematic in view of the inevitable tolerances of manufacturing. 
         [0011]    Thus, the prior concepts of hydro-elastic joints require a specific orientation for the assembly, that is either angularly because they do not hydraulically filter in an essentially constant manner over all radial directions, or axially because they cannot be mounted head to head, or in both directions because they can only filter either radially or axially. 
         [0012]    Furthermore, the frequencies or frequency ranges to be absorbed for a hybrid or electric vehicle are different from the frequency ranges for a vehicle solely driven by a combustion engine. Hybrid vehicles can be driven in parallel or sequentially by an electric motor and a combustion engine. For example, if the hybrid vehicle is driven solely by an electric motor, a driver can hear noises that are normally masked by the noise or the vibration of the combustion engine. For example the noise of a gearbox or of a transmission can be disturbing for a passenger. 
       SUMMARY 
       [0013]    Embodiments disclosed herein may provide a functional hydro-elastic element and a joint that overcomes the inconveniences of the known joints, and in particular may provide a joint that is simple and easy to manufacture and also to mount in an automated way. 
         [0014]    To this end the invention provides a functional hydro-elastic element of the above-mentioned type that is characterised by at least one row of hydraulic chambers, extending circumferentially and comprising at least three hydraulic chambers and at least one throttling duct that enables communication of liquid respectively between each pair of circumferentially adjacent hydraulic chambers so that a variation of at least one working volume of the hydraulic chambers caused by working-load vibrations can be balanced by enabling a flow of liquid into at least one of the other hydraulic chambers. 
         [0015]    In an embodiment of the invention the joint and/or the functional hydro-elastic element can be realised completely symmetrical and/or can be mounted in any direction in its housing, for instance in a sleeve of a suspension arm, without a specific orientation of the longitudinal axis of the joint before the assembly and without a particular angular orientation in a plane perpendicular to the longitudinal axis. Thus, the productivity during the—if possible, automated—assembly of the joint to a car-to-ground connecting element is improved. 
         [0016]    Besides, the joint of one embodiment can ensure hydraulic filtering along any of its radial axes in a plane that is perpendicular to the longitudinal axis. In the case of joints for car-to-ground connection this hydraulic filtering can be essentially equal in all the radial directions if assembly of the joint without a particular angular orientation is desired. 
         [0017]    For example, the hydro-elastic joint and/or functional element with several elastomer layers, separated by one or several intermedial frames combines at the same time the possibility of assembling the joint in its receiving housing without specific angular orientation and in any direction along the axis of the receiving housing, hydraulic filtering being essentially radially constant for any radial excitation direction, a reduced ejection path for the hydraulic fluid, and finally the optional possibility, in one embodiment, to provide hydraulic filtering axially. 
         [0018]    In one embodiment the external, intermedial and/or internal frame are stiffer than the elastic bodies of the elastic unit of the functional hydro-elastic element. For example, the external and/or internal frame can be made from metal. 
         [0019]    For example, in one embodiment at least one of the rows of hydraulic chambers comprises more than three, four, five, six, seven, eight, twelve, 16 or 24 hydraulic chambers, in particular exactly four, five, six, seven, eight, twelve, sixteen or 24 hydraulic chambers. 
         [0020]    According to one embodiment at least two hydraulic chambers can be necessary for at most every 90° of angular sector, that is at least  8  peripheral hydraulic chambers. In another embodiment 10 to 12 hydraulic chambers and/or partial chambers are arranged side by side in a circumferential row in the functional hydro-elastic element, for example in the case of two circumferential rows  20  to  24  hydraulic chambers and/or partial chambers, or even more if the perimeter of the joint allows. 
         [0021]    In one embodiment the functional hydro-elastic element is limited to less than 48 hydraulic chambers, in particular less than 30 hydraulic chambers, which are in particular arranged in a circumferential row. 
         [0022]    In one embodiment each hydraulic chamber of a row of hydraulic chambers has a circumferential width of less than or equal to about 45 degrees, for example less than about 30 degrees, in particular between 10 and 30 degrees. 
         [0023]    In another embodiment the hydraulic chambers of the at least one row of hydraulic chambers cover at least 50%, in particular at least 70% of a circumferential surface of the functional hydroelastic element between its two axial ends. 
         [0024]    For example, in one embodiment the hydraulic chambers have a mean radial extension between 2 and 10 mm, in particular between 3 and 5 mm. 
         [0025]    The joint can be characterised in that the hydraulic chambers of the at least one row of hydraulic chambers have a mean radial extension between 10 and 60 percent of the maximum radial extension of the functional hydro-elastic element, in particular between 20 and 50 percent. 
         [0026]    The smaller the hydraulic chambers are the easier the liquid contained in them can be ejected via an orifice or a calibrated opening, the ejection path being reduced, and the larger becomes the number of hydraulic chambers side by side, forming a peripheral layer of significant surface area without suffering from the inconveniences of solutions providing only one or two thin peripheral layers. 
         [0027]    In another embodiment the hydraulic chambers of the at least one row of hydraulic chambers are essentially identical. 
         [0028]    In one embodiment the hydraulic chambers are essentially rectangular from a radial side view, and have, in particular, an essentially identical radial extension and circumferential extension. 
         [0029]    In another embodiment the functional hydro-elastic element can be characterised in that the hydraulic chambers are circumferentially delimited by axial walls extending in axial direction, and/or are delimited in axial direction by circumferential walls extending in circumferential direction, wherein the axial and/or circumferential walls are formed by the functional hydro-elastic element. 
         [0030]    In one embodiment the axial walls have a circumferential width of between 1/20 and ⅕, in particular about a tenth, of the circumferential extension of a hydraulic chamber of a row of hydraulic chambers. 
         [0031]    In one embodiment the relationship between the axial extension of the hydraulic chambers and the axial extension of the throttling ducts is at least 5, in particular at least 10, in order to achieve a throttling effect. For example, the relationship of the axial extension of the at least one hydraulic chamber towards the axial extension of the at least one throttling duct is at least 15. 
         [0032]    In one embodiment the at least one throttling duct is permanently open under load vibrations. 
         [0033]    For example, in one embodiment at least one throttling duct leads into at least one of the axial walls, in particular at at least one of the transitions between an axial wall and a circumferential wall. 
         [0034]    In another embodiment the throttling ducts lead into the two axial walls of each hydraulic chamber of the same row of hydraulic chambers, in particular respectively at a transition between the respective axial wall and the same circumferential wall, or in each hydraulic chamber of the same row of hydraulic chambers a first throttling duct leads into the first axial wall at a transition between the first axial wall and a first circumferential wall and a second throttling duct leads into the second axial wall at a transition between the second axial wall and a second circumferential wall. 
         [0035]    In one embodiment a system of throttling ducts is formed such that the throttling ducts hydraulically connect in series the hydraulic chambers of a row of hydraulic chambers. 
         [0036]    In one embodiment a system of throttling ducts, comprising at least one throttling duct, is formed such that a liquid ejected from a hydraulic chamber can be introduced into any hydraulic chamber without passing via another intermediate chamber in particular of the same row of hydraulic chambers. Hydraulic filtering of a load in radial direction of the joint can thus be achieved. 
         [0037]    In one embodiment, with respect to radial loads, complementary lateral orifices are provided for the expulsion of hydraulic liquid, and these orifices are disposed in an aligned manner either at least at an extremity of each hydraulic chamber, or at the middle of the chamber walls, or in an unaligned way, the orifices being disposed in a staggered pattern. 
         [0038]    In another embodiment the functional hydro-elastic element comprises or consists of an elastic body. 
         [0039]    For example, the joint can be characterised in that the functional hydro-elastic element comprises at least two rows of hydraulic chambers superimposed in axial direction, in particular a first row and a second row. 
         [0040]    In one embodiment a throttling duct is formed between the two rows of hydraulic chambers and is separated from the hydraulic chambers of the first row by a first circumferential wall and/or from the hydraulic chambers of the second row by a second circumferential wall. 
         [0041]    In another embodiment the hydraulic chambers of the first row and the second row are in liquid communication between each other in order to allow hydraulic filtering in direction of the longitudinal axis. 
         [0042]    For example, in one embodiment the first circumferential walls and/or the second circumferential walls have at least one axial opening, wherein in particular the at least one axial opening in a first circumferential wall is facing the at least one axial opening in a second circumferential wall, axially adjacent to the first circumferential wall. 
         [0043]    In one embodiment the hydraulic chambers of the first row and of the second row are symmetrical with respect to a plane orthogonal to the longitudinal axis and disposed between the first and the second row. 
         [0044]    In another embodiment the axial openings have a circumferential width corresponding to the calibrated opening necessary for the hydraulic filtering along the longitudinal axis. 
         [0045]    For example, in one embodiment the openings themselves are bordered by small opening wall sections, aligned with the axial direction. For example, the opening wall sections can be formed in the elastic body of the functional hydro-elastic element. 
         [0046]    In another embodiment each hydraulic chamber has a radial profile having a circumferential reference plane defined by a peripheral cylindrical surface of the functional hydro-elastic element, wherein the radial profile comprises an abutment area having a first depth with respect to the reference plane and at least one cavity, in particular in the shape of a groove, between the abutment area and at least one of the axial and/or circumferential walls of the hydraulic chamber, wherein the cavity has a greater depth than the abutment area. 
         [0047]    In one embodiment each hydraulic chamber comprises an abutment area forming a radial abutment and/or a drainage piston. For example, within each hydraulic chamber or each partial chamber a radial abutment made of elastomer is disposed in order to force and facilitate the flow of the liquid contained in said chambers. 
         [0048]    In another embodiment the abutment area is bordered at each side by a cavity. 
         [0049]    In one embodiment a part of one of at least one cavity or groove extends circumferentially, extending from the throttling ducts. In one embodiment the part of the cavity or groove extending from the lateral openings is disposed along the edges or circumferential walls that respectively delimit the area covered by the chambers. 
         [0050]    For example, in one embodiment the abutment area is bordered at each side by a radial cavity. 
         [0051]    Furthermore, a cavity, groove or neck is arranged at at least one of the sides of each chamber to increase the volume of the hydraulic liquid, facilitate its expulsion, and increase the effect of the bottom piston or of the abutment area of each chamber. 
         [0052]    In another embodiment the abutment area and/or the at least one radial cavity is/are arranged in the elastic body and/or the functional hydro-elastic element. 
         [0053]    In one embodiment the functional hydro-elastic element is characterised by at least two groups of rows of hydraulic chambers, wherein each group of rows of hydraulic chambers comprises at least one row of hydraulic chambers, and by a system of throttling ducts formed such that the hydraulic chambers of a first group of rows of hydraulic chambers are hydraulically separated from the hydraulic chambers of a second group of rows of hydraulic chambers. 
         [0054]    For example, in one embodiment the volume of each hydraulic chamber of a first row of hydraulic chambers, in particular of the first group of rows of hydraulic chambers, is larger than the volume of the respective hydraulic chambers of a second row of hydraulic chambers, in particular of the second group of rows of hydraulic chambers. 
         [0055]    For example, the volume of each hydraulic chamber of a first row of hydraulic chambers is at least 1.5 times larger, in particular at least two times larger than the volume of the respective hydraulic chambers of a second row of hydraulic chambers. 
         [0056]    In one embodiment the transverse cross-sectional area, in particular in radial direction in the axial walls, of the throttling ducts of a first row of hydraulic chambers, in particular of the first group of rows of hydraulic chambers, is larger than the transverse cross-sectional area, in particular in radial direction in the axial walls, of the throttling ducts of a second row of hydraulic chambers, in particular of the second group of rows of hydraulic chambers. Typically, a transverse cross-section is orthogonal to the direction of flow of a liquid in the throttling duct. 
         [0057]    For example, the cross-sectional area in radial direction of the throttling ducts of a first row of hydraulic chambers is at least two times larger, in particular at least three times larger than the cross-sectional area of the throttling ducts of a second row of hydraulic chambers. 
         [0058]    For example, the axial dimension of the throttling ducts in the axial walls of a first row of hydraulic chambers is larger than the axial dimension of the throttling ducts in the axial walls of a second row of hydraulic chambers. 
         [0059]    For example, in one embodiment the damping frequency for the load vibrations in radial direction of a first row of hydraulic chambers, in particular of the first group of rows of hydraulic chambers is lower than the damping frequency for the load vibrations in radial direction of a second row of hydraulic chambers, in particular of the second group of rows of hydraulic chambers. 
         [0060]    Additionally, the invention provides a hydro-elastic joint for assembling two structural parts, in particular to connect a wheel suspension to a vehicle body, comprising a longitudinal axis, a rigid external frame, a rigid internal frame, and a functional hydro-elastic element linking the internal frame to the external frame in a vibration-damping manner according to one of the embodiments described in the present disclosure. 
         [0061]    In one embodiment the hydraulic chambers are delimited by one of the internal, intermedial and external frame, and the functional hydro-elastic element. 
         [0062]    In one embodiment where the hydraulic chambers are limited by the external or internal frame, the joint is simple and easy to manufacture and the chambers and hydraulic ducts can be disposed at the periphery of the elastomeric body of the hydro-elastic spring unit, just below the external frame, without employment of an additional plastic clip to keep the price low, and without difficulty for the introduction of the hydraulic liquid in order to avoid the presence of air bubbles in the fluid. 
         [0063]    In one embodiment at least one of the frames, in particular all of the frames is or are a sleeve, in particular a cylindrical sleeve. 
         [0064]    In one embodiment the internal, external and intermedial frames are essentially concentric in a relaxed state of the joint. 
         [0065]    In one embodiment the multi-layer joints feature at least  3  concentric frames that thus delimit two or more annular areas of elastomer. These joints can be very stiff radially (commonly between 8000 and 30000 N/mm), but relatively flexible in torsional direction about their longitudinal axis Z. 
         [0066]    The following description allows to add a certain number of further details and variants to the principal characteristics explained above, and to present some examples of devices corresponding to the present invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0067]      FIG. 1  is a perspective view of a joint according to an embodiment just before the body of the joint is inserted into its outer sleeve; 
           [0068]      FIG. 2  is a cross-sectional view of  FIG. 1  according to AA, the body of the joint being inserted in its outer sleeve; 
           [0069]      FIG. 3  is a partial view of the joint in longitudinal cross-section according to BB of  FIG. 2 ; 
           [0070]      FIG. 4  is a partial side view, taken radially, of the embodiment of  FIG. 1 ; 
           [0071]      FIG. 5  is a partial view of another embodiment of the joint in longitudinal cross-section according to BB of  FIG. 2 ; 
           [0072]      FIG. 6  is a partial side view, taken radially, of the embodiment of  FIG. 5 ; 
           [0073]      FIG. 7  is a partial side view, taken radially, of another embodiment of a joint; 
           [0074]      FIG. 8  is a perspective view of a joint according to another embodiment; 
           [0075]      FIG. 9  is a partial side view, taken radially, of the embodiment of  FIG. 8 ; 
           [0076]      FIG. 10  is a perspective view of a joint according to another embodiment; 
           [0077]      FIG. 11  is a partial side view, taken radially, of the embodiment of  FIG. 10 ; and 
           [0078]      FIG. 12  is a partial side view, taken radially, of another embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0079]      FIG. 1  is a perspective view of a joint  1  according to an embodiment of the present invention. The joint comprises a hydro-elastic spring or a functional hydro-elastic element  3  and a cylindrical external frame  5 . The figure shows the joint just before the functional hydro-elastic element  3  is slipped into the cylindrical external frame  5 . The hydro-elastic spring  3  has an internal frame  7  and an intermedial frame  9 . The internal, intermedial and external frames have the shape of a sleeve or of a socket and are all three essentially cylindrical and coaxial with respect to a longitudinal axis Z. The sleeves or external  5  and internal  7  frames are designed to be fixed respectively at two parts of a structure (not represented) in order to assemble these parts and damp the transmission of vibrations between them. For example, one of these two parts can be fixed in a bore formed in the internal frame. The bore is essentially coaxial with the longitudinal axis Z. The external or internal frame can, for example, be fixed to a suspension arm of a car-to-ground connection of a vehicle. 
         [0080]    In the description, “upper” and “lower” are defined with respect to the axis Z that represents a direction. Nonetheless, the joint can be essentially symmetrical with respect to a plane orthogonal to the longitudinal axis. 
         [0081]    The functional hydro-elastic element  3  is disposed between the external  5  and the internal  7  sleeve. The functional hydro-elastic element  3  comprises an elastic body  12 . The elastic body  12  comprises an intermedial frame  9 . In one embodiment the elastic body  12  can comprise several intermedial frames  9  in order to adjust the torsional stiffness and the axial stiffness of such joints. The elastic body  12  can be an elastomeric or rubber body. The elastic body  12  extends axially between two ends, each of which has a circular rim  14 ,  16 , in particular an upper rim  14  and a lower rim  16 . Additionally, at each of its ends in axial direction the joint has fitting areas  18 ,  20 . 
         [0082]      FIG. 1  shows hydraulic chambers  24 ,  26 , disposed in two circumferential rows  28  and  30  superimposed in axial direction, in particular one upper circumferential row  28  and a lower circumferential row  30 . The upper row comprises upper hydraulic chambers  24  and the lower row comprises lower hydraulic chambers  26 . The circumferential upper and lower rows  28 ,  30  have an essentially identical design and are symmetrical with respect to a plane between the two rows, the plane being orthogonal to the longitudinal axis Z. This plane can correspond to a plane of symmetry of the joint. The hydraulic chambers  24 ,  26  of the two circumferential rows  28 ,  30  form a mesh and, in one embodiment, together cover 70% of the periphery of the joint between the two axial ends of the elastic body  12  and/or between the circular upper rim  14  and the circular lower rim  16 . The circumferential rows  28 ,  30  of hydraulic chambers  24 ,  26  are disposed annularly in the elastic body  12  in the form of a ring that is concentric with the internal  7 , external  5  and intermedial  9  frame in a relaxed state of the joint  1 . Typically, the hydraulic chambers are arranged in the elastic body  12 . 
         [0083]    The hydraulic chambers  24 ,  26  of each circumferential row  28 ,  30  are disposed circumferentially and adjacent to each other. Two consecutive hydraulic chambers  24 ,  26  on the circumference of a same circumferential row are separated by an axial wall  32 . In one embodiment the axial wall  32  can be perforated by lateral or circumferential holes  38 , thereby forming throttling ducts  40 . The hydraulic chambers of the upper circumferential row of hydraulic chambers are limited in the axial direction by upper circumferential walls  41  and lower circumferential walls  42 . The hydrualic chambers of the lower circumferential row of hydraulic chambers are limited in the axial direction by upper circumferential walls  44  and lower circumferential walls  43 . 
         [0084]    Each hydraulic chamber  24 ,  26  has a height in axial direction  24   h ,  26   h  and a circumferential width  24   a ,  26   a . The angular or circumferential width of a hydraulic chamber of an upper or lower circumferential row  24 ,  26  corresponding to the circumferential, curvilinear width  24   a ,  26   a  is less or equal to 45°. In an other embodiment the angular width is about 10° to 30°. In this case it is possible to multiply the number of hydraulic chambers. In the case of  FIGS. 1 and 2  the joint comprises  24  chambers divided into two circumferential rows  28 ,  30  of 12 hydraulic chambers  24 ,  26  each, superimposed according to the longitudinal axis Z. 
         [0085]      FIGS. 1 to 4  show a circumferential channel or a throttling duct  40  that is disposed between the two circumferential rows  28  and  30  of hydraulic chambers  24 ,  26  for the circumferential flow of a hydraulic liquid. Segments of the circumferential throttling duct  40  and the adjacent hydraulic chambers  24  of the upper row  28  are respectively separated by the lower circumferential wall  42 , and the segments of the circumferential channel  40  and the adjacent hydraulic chambers  26  of the lower circumferential row  30  are separated by the upper circumferential wall  44  of the respective hydraulic chambers  26 . Consequently, the circumferential throttling duct  40  passes via the intermediate circumferential openings  38  in the axial walls  32  and between the circumferential walls  42 ,  44 . The relationship between an axial dimension  38   h  of the intermediate circumferential openings  38  and an axial dimension  24   h ,  26   h  of the hydraulic chambers  24 ,  26  is between 1/10 and 1/30, for example between 1/15 and 1/25. Thus, the axial dimension  38   h  of the intermediate circumferential openings or a width in axial direction of the circumferential throttling duct  40  corresponds to the calibrated orifice necessary for the hydraulic filtering in circumferential direction. The circumferential throttling duct  40  typically has a radial extension  40   r  that is larger than the radial extension of a hydraulic chamber  24   r ,  26   r.    
         [0086]    An axial opening  46 ,  48  is formed in the middle of the upper circumferential wall  44  of the chambers  26  of the lower circumferential row of hydraulic chambers  30 , and in the middle of the lower circumferential wall  42  of the chambers  24  of the upper circumferential row of hydraulic chambers  28 , which walls respectively separate a hydraulic chamber  24 ,  26  from the circumferential throttling duct  40 , wherein the axial opening  46 ,  48  has a circumferential width  46   a ,  48   a.    
         [0087]    Between the axial openings  46 ,  48  of two circumferentially adjacent hydraulic chambers the respective section of the circumferential throttling duct has a length  40   a  in circumferential direction. Furthermore, the axial openings  46 ,  48  of axially adjacent hydraulic chambers  24 ,  26  are facing each other. The circumferential width  46   a ,  48   a  corresponds to the calibrated orifice necessary for the hydraulic filtering along the longitudinal axis Z between two superimposed or axially adjacent hydraulic chambers  24 ,  26 . For example, in one embodiment the width  46   a ,  48   a  can be 1/10 to ⅓ of the circumferential length of the upper or lower wall  42 ,  44  of the respective hydraulic chamber. 
         [0088]    The hydraulic chambers  24 ,  26  are delimited in axial direction by the upper or lower circumferential walls  41 ,  42 ,  43 ,  44 , and circumferentially by the axial walls  32 . The external frame  5  closes the periphery of the hydraulic chambers  24 ,  26  and keeps the hydraulic liquid in the hydraulic chambers. Hence the hydraulic chambers  24 ,  26  are delimited in radial direction by the external frame  5  and a bottom  50  formed by the elastic body  12 . Thus, the joint has hydraulic chambers  24 ,  26  under its periphery, just underneath the external frame. In one embodiment the bottom  50  has a depth in radial direction between 3 and 5 mm with respect to the radial end of a part of the elastic body  12  between the circumferential rows  28 ,  30  of hydraulic chambers and the upper and lower circular rims  14 ,  16 , or to the internal surface of the external frame  5 . 
         [0089]    Each hydraulic chamber has a radial profile. The radial profile has a circumferential reference plane  51  defined by a peripheral cylindrical surface of the functional hydro-elastic element  3 . The radial end portion of the elastic body  12  between the circumferential rows  28 ,  30  and the upper and lower circular rims can be in this reference plane. The reference plane  51  can correspond to the internal surface of the external frame. The bottom  50  of each hydraulic chamber  24 ,  26 , in particular with respect to the external frame  5 , comprises at least at one of its four sides a border area or a cavity  52  that is deeper with respect to a central part or an abutment area  54  of the bottom  50  of the respective hydraulic chamber  24 ,  26 . Thus, the cavity  52  has a greater depth than the abutment area  54  with respect to the reference plane. In one embodiment this cavity is disposed at four sides of the hydraulic chamber  24 ,  26  in the case of an essentially rectangular chamber. In another embodiment each hydraulic chamber comprises a cavity in form of a circumferential groove at one of its axial ends, in particular at the axial end of the hydraulic chamber  24 ,  26 . 
         [0090]      FIG. 2  is a cross-sectional view of  FIG. 1  according to AA, wherein this line symbolises the trace left by a plane perpendicular to Z passing through the middle of the row  28  of hydraulic chambers  24 . This sectional view is directed towards the middle of the articulation  1 , which enables to show in the background the circumferential length  40   a  of the sections of the circumferential throttling duct  40  between two axial openings as well as the circumferential width  46   a ,  48   a  of the axial openings in the lower and upper walls  46 ,  48  or the distance between two sections of the circumferential throttling duct  40  in circumferential succession. In  FIG. 2  the circumferential width  24   a ,  26   a  of a hydraulic chamber  24 ,  26  can also be found. 
         [0091]      FIG. 2  shows 12 hydraulic chambers side by side, separated from each other by the respective axial wall  32  of elastomer. The 12 hydraulic chambers  24  form the upper circumferential row  28  of hydraulic chambers  24  of  FIG. 1 . In another embodiment the joint can also have a different number of hydraulic chambers. For example, in one embodiment the joint can have at least eight hydraulic chambers of essentially identical shape in one circumferential row. 
         [0092]      FIG. 3  is a longitudinal sectional view according to BB of  FIG. 2 , and  FIG. 4  is a partial side view, taken radially, of an embodiment of the joint without its external frame  5 . 
         [0093]    On the right hand side of  FIG. 3  the section line crosses the circumferential throttling duct  40  for peripheral communication between the hydraulic chambers while on the left hand side of that figure the section line passes the axial communication openings  46 ,  48  in the respective upper and lower circumferential walls  42 ,  44  (visible in  FIGS. 2 and 4 ) between two superimposed or axially adjacent hydraulic chambers, wherein the openings have a width  46   a ,  48   a . The axial openings result, in one embodiment, in a continuous bottom surface  50  for two superimposed hydraulic chambers  24 ,  26 . Each section of the circumferential throttling duct  40  is delimited and surrounded by the parallel upper circumferential walls  44  of the chambers of a lower circumferential row and the lower circumferential walls  42  of the chambers of an upper circumferential row, which walls create between them a space corresponding to the calibrated orifice necessary for the radial hydraulic filtering (peripheral flow). 
         [0094]    In  FIG. 4  it can also be seen that each chamber is bordered at at least one side, in particular at all sides, by a cavity  52  that is deeper compared to the abutment area  54  and located between this abutment area  54  and the axial walls  32  of the hydraulic chamber  26 . The upper and lower walls  42  and  44  that define the sections of the circumferential throttling duct  40  for circumferential communication of the hydraulic liquid have such a length that the distance between two consecutive sections of the circumferential throttling duct leave a clearance  46   a ,  48   a  which corresponds to the necessary calibration of the orifice allowing the hydraulic liquid to pass in direction of the longitudinal axis Z. 
         [0095]    In one embodiment, owing to its outer surface in radial direction, the abutment area  54  of each hydraulic chamber serves as an abutment during a significant transverse or radial deformation of the joint. Furthermore, the abutment area serves as a small piston to facilitate the ejection of hydraulic liquid via the circumferential throttling ducts  40 , which would be difficult to do with a thin hydraulic chamber of large dimension. 
         [0096]    Collars or pieces of external frame  56  are embedded in the periphery of the elastic body  12  between the rows  28 ,  30  of upper and lower hydraulic chambers  24 ,  26  and the respective rims  14 ,  16  of the elastic body  12  of the hydro-elastic spring. Thus, a part of the periphery of the elastic body  12  that delimits the hydraulic chambers  24 ,  26  is disposed between these collars  56  or pieces of external frame  5 . The collars  56  have a cylindrical shape concentric with respect to the external frame or sleeve and are located at two ends of the joint just before the conical end sections. The collars  56  can reinforce the radial strength of the joints. The collars are respectively aligned with the edge of the circular rims  14  and  16 . In another embodiment the collars  56  can be arranged such that they abut against the external frame. In  FIG. 3  they are shown as embedded in the elastic or rubber body  12 , and thus there is a fine layer of rubber or elastomer between the external surface of these collars  56  and the bore or internal surface of the external frame  5 . 
         [0097]      FIG. 5  is a longitudinal sectional view according to BB of  FIG. 2  of another embodiment. The same reference numerals denominate the same elements of the joint with an addition of 100. The fitting areas, for example those of  FIG. 1 , are not represented in this longitudinal cut, which is limited to the cylindrical part of the joint between the upper and lower rims. Here the cavity  152 , which is deeper than the abutment area, lines the four sides of the periphery of each hydraulic chamber  124 ,  126 . This variant enables to reinforce the piston effect of the bottom  150  of each hydraulic chamber  124 ,  126  and increases the possible hydraulic debit. 
         [0098]      FIG. 6  is a partial side view, taken radially, of one embodiment of a joint without its external frame  105 . The axial walls  132  do not completely close each hydraulic chamber in circumferential direction. The axial walls  132  have orifices  134 ,  136 , in particular at a transition between the axial walls  132  and the upper circumferential walls  141  in the hydraulic chambers  124  of the upper circumferential row  128  and at a transition between the axial walls  132  and the lower circumferential walls  143  in the hydraulic chambers  126  of the lower circumferential row  130 . The upper and lower lateral orifices or openings  134 ,  136 , that form throttling ducts, increase the possibilities of peripheral hydraulic debit during a radial excitation. A relationship between an axial dimension  134   h ,  136   h  of the upper and lower lateral openings  134 ,  136  and an axial dimension  124   h ,  126   h  of the hydraulic chambers  124 ,  126  is between ⅕ and 1/25, for example between 1/10 and 1/20. Thus, the axial dimension  134   h ,  136   h  of the intermediate, upper and lower openings corresponds to the calibrated orifice necessary for the hydraulic filtering in circumferential direction. The cavities  152  located beside the upper circumferential wall  141  of the hydraulic chambers  124  of the upper circumferential row  128  or located beside the lower circumferential wall  143  of the hydraulic chambers  126  of the lower circumferential row  130  of hydraulic chambers can be continuous, passing from one hydraulic chamber to another circumferentially adjacent hydraulic chamber. Thus, these cavities  152  at the lower end of the hydraulic chambers of the lower row and at the upper end of the hydraulic chambers of the upper row respectively form a circumferential channel that is supplementary to the circumferential throttling duct  140 . 
         [0099]    In one embodiment each hydraulic chamber  124 ,  126  of width  124   a ,  126   a  and height  124   h ,  126   h  comprises an abutment area  154  surrounded at its four sides by a cavity  152  that is somewhat deeper than the central part  154  with respect to the reference plane. 
         [0100]      FIG. 7  is a partial side view, taken radially, of another embodiment of a joint without its external frame. The embodiment of  FIG. 7  is a variant of the embodiment of the  FIGS. 5 and 6 . The same reference numerals denominate the same elements of the joint as in the embodiments of  FIG. 1  with an addition of  200 . In the embodiment of  FIG. 7  the axial openings  246 ,  248 , which form throttling ducts of the hydraulic chambers  224 ,  226  towards the circumferential throttling duct  240  that is in direction of the longitudinal axis Z, have at each side an opening wall  258  extending from the circumferential throttling duct  240  towards the centre of the respective hydraulic chambers. The opening walls  258  have a length in axial direction between a quarter and a third of the axial extension of a hydraulic chamber  224 ,  226 . The openings are designed to let the hydraulic fluid pass during an excitation along the Z-axis. 
         [0101]    In the figures, the axial walls  232 , the opening walls  258 , and the upper and lower circumferential walls  241 ,  242 ,  243  and  244  are drawn as thick lines in order to distinguish them from the cavities  252  that are arranged peripherally to each hydraulic chamber. 
         [0102]      FIG. 8  shows another embodiment of a joint  301  in a perspective view without the external frame, and  FIG. 9  shows a partial side view of the joint  301 , taken radially. The same reference numerals denominate the same elements of the joint as in the embodiments of  FIG. 1  with an addition of  300 . The joint  301  comprises a single circumferential row of hydraulic chambers  322 , and lateral openings  334 ,  336  for the communication between hydraulic chambers  322 , forming throttling ducts, are disposed in the axial walls  332 . The lateral or circumferential openings  334 ,  336  are arranged in a zigzag pattern. Upper and lower are defined with respect to the axial direction Z. The openings  334 ,  336  in the consecutive axial walls  332  are formed alternatingly at a transition between the axial wall  332  and the lower circumferential wall  343  and at a transition between the axial wall  332  and the upper circumferential wall  341 . Thus, once an opening  334  and once a closed piece of wall  332  is found at the upper side of the axial wall  332  of a hydraulic chamber. At the lower side along axial direction Z an alternation of openings  336  and of closed pieces of wall  332  is found. During a radial excitation the fluid must transit circumferentially and must perform zigzags through the openings  334  and  336 . 
         [0103]      FIG. 10  shows a perspective view of another embodiment of a joint  401  without the external frame, and  FIG. 11  shows a partial side view, taken radially, of the joint  401 . The same reference numerals denominate the same elements of the joint as in the embodiments of  FIG. 1  with an addition of  400 . The joint  401  comprises a single circumferential row of hydraulic chambers  422 , but the openings  434 ,  436  for communication between the hydraulic chambers form throttling ducts at two ends of the chambers or at two transitions between the axial wall  432  and the upper and lower circumferential walls  441 ,  443 . Each wall between two hydraulic chambers has a small opening at its two axial ends. The embodiment of the  FIGS. 10 and 11  is a variant of the embodiment of  FIGS. 8 and 9  but with a different arrangement of the throttling ducts for circulation of the hydraulic fluid. 
         [0104]      FIG. 12  is a partial side view, taken radially, of another embodiment of a joint without its external frame. The embodiment of  FIG. 12  is a variant of the embodiment of  FIGS. 5 and 6 . The same reference numerals denominate the same elements of the joint as in the embodiments of  FIG. 1  with an addition of  500 . The embodiment of  FIG. 12  comprises two rows of hydraulic chambers or circumferential rows, in particular a first row  528  of hydraulic chambers  524  and a second row  530  of hydraulic chambers  526  that extend in circumferential direction. In one embodiment the volume of each hydraulic chambers  524  of the first row  528  of hydraulic chambers is different from the volume of the respective hydraulic chambers  526  of the second row  530  of hydraulic chambers. For example, in a radial side view the surface of the hydraulic chambers  524  of the first row  528  of hydraulic chambers is larger than the surface of the hydraulic chambers  526  of the second row  530  of hydraulic chambers. In one embodiment the respective circumferential extension  524   a ,  526   a  of the hydraulic chambers  524 ,  526  of the first row  528  of hydraulic chambers and of the second row  530  of hydraulic chambers is essentially equal, but the axial extension  524   h  of the hydraulic chambers  524  of the first row  528  is larger than the axial extension  526   h  of the hydraulic chambers  526  of the second row  530 . In the embodiment of  FIG. 12  the number of hydraulic chambers of the first row  528  corresponds to the number of hydraulic chambers of the second row  530 . The hydraulic chambers of the upper circumferential row or first row  528  of hydraulic chambers are respectively limited in axial direction by upper circumferential walls  541  and by lower circumferential walls  542  in direction of the second row  530  of hydraulic chambers. The hydraulic chambers of the lower circumferential row or second row  530  of hydraulic chambers are respectively limited in axial direction by upper circumferential walls  544  in direction of the first row  528  of hydraulic chambers and by lower circumferential walls  543 . Two hydraulic chambers  524 ,  526 , consecutive along the circumference of a same circumferential row, are respectively separated by an axial wall  532 ,  533 . 
         [0105]    The axial walls  532 ,  533  have orifices  534 ,  536 , in particular in the middle in axial direction of the axial walls. The orifices or lateral openings  534 ,  536  of the first row  528  and of the second row  530  form throttling ducts and respectively have an axial dimension  534   h ,  536   h . The axial dimension  534   h  of the throttling ducts  534  of the first row  528  corresponds to the calibrated orifice necessary for the hydraulic filtering in circumferential direction of a first range of frequencies of a load vibration in radial direction, and the axial dimension  536   h  of the throttling ducts  536  of the second row  530  corresponds to the calibrated orifice necessary for the hydraulic filtering in circumferential direction of a second range of frequencies of a load vibration in radial direction. Additionally, the hydraulic chambers  524  of the first row of hydraulic chambers and the hydraulic chambers  526  of the second row of hydraulic chambers are axially without hydraulic connection between each other. Thus, in the embodiment of  FIG. 12  a system of throttling ducts  534 ,  536  is formed such that the hydraulic chambers  524  of the first row  528  of hydraulic chambers are hydraulically separated from the hydraulic chambers  526  of the second row  530  of hydraulic chambers. 
         [0106]    For example, in one embodiment the first frequency range can damp vibrations perceptible from a hybrid vehicle driving with a combustion engine, and the second frequency range can damp vibrations perceptible from a hybrid vehicle driving with an electric motor. For example, one of the frequency ranges can be from 500 to 1000 Hz while the other frequency range is from 50 to 500 Hz. The frequency ranges can intersect with each other. Thus, with a joint according to the embodiment of  FIG. 12  it is possible to generate two troughs of stiffness that enable a double radial filtering at two different frequencies. 
         [0107]    In the embodiment of  FIG. 12  the lateral openings  534 ,  536  form throttling ducts, having at each side an opening wall  558 ,  559  extending circumferentially from the axial wall  532 ,  533  towards the centre of the hydraulic chamber. The opening walls  558  of the lateral openings  534  of the first row  528  of hydraulic chambers have a smaller circumferential extension than the opening walls  559  of the lateral openings  536  of the second row of hydraulic chambers. 
         [0108]    In another embodiment at least two arrangements of hydraulic chambers shown in the embodiments of the figures can be axially superimposed. Thus, the joint can comprise at least four superimposed rows of hydraulic chambers. 
       LIST OF REFERENCE NUMERALS 
       [0000]    
       
           1  joint 
           3  functional hydro-elastic element 
           5  external frame 
           7  internal frame 
           9  intermedial frame 
           10  elastic body 
           12  elastic body 
           14  upper rim 
           16  lower rim 
           18  fitting areas 
           20  fitting areas 
           24  upper hydraulic chamber 
           24   a  circumferential width of a hydraulic chamber 
           24   h  height of a hydraulic chamber in axial direction 
           24   r  radial extension of a hydraulic chamber 
           26  lower hydraulic chamber 
           26   a  circumferential width of a hydraulic chamber 
           26   h  height of a hydraulic chamber in axial direction 
           26   r  radial extension of a hydraulic chamber 
           28  upper circumferential row 
           30  lower circumferential row 
           32  axial wall 
           38  circumferential hole 
           38  axial dimension of circumferential hole 
           40  circumferential throttling duct 
           40   a  circumferential length of a segment 
           40   r  radial extension of the circumferential throttling duct 
           41  upper circumferential walls 
           42  lower circumferential walls 
           43  lower circumferential walls 
           44  upper circumferential walls 
           46  axial opening 
           46   a  circumferential width of the axial opening 
           48  axial opening 
           48   a  circumferential width of the axial opening 
           50  bottom 
           52  cavity 
           54  abutment area 
           56  collars 
           101  joint 
           103  functional hydro-elastic element 
           105  external frame 
           107  internal frame 
           109  intermedial frame 
           110  elastic body 
           112  elastic body 
           124  upper hydraulic chamber 
           124   a  circumferential width of a hydraulic chamber 
           124   h  height of a hydraulic chamber in axial direction 
           126  lower hydraulic chamber 
           126   a  circumferential width of a hydraulic chamber 
           126   h  height of a hydraulic chamber in axial direction 
           128  upper circumferential row 
           130  lower circumferential row 
           132  axial wall 
           134  circumferential hole 
           134   h  axial dimension of circumferential hole 
           136  circumferential hole 
           136   h  axial dimension of circumferential hole 
           138  circumferential hole 
           138   h  axial dimension of circumferential hole 
           140  circumferential throttling duct 
           140   a  circumferential length of a segment 
           141  upper circumferential walls 
           142  lower circumferential walls 
           143  lower circumferential walls 
           144  upper circumferential walls 
           146  axial opening 
           146   a  circumferential width of the axial opening 
           148  axial opening 
           148   a  circumferential width of the axial opening 
           150  bottom 
           152  cavity 
           154  abutment area 
           156  collars 
           224  upper hydraulic chamber 
           224   a  circumferential width of a hydraulic chamber 
           224   h  height of a hydraulic chamber in axial direction 
           226  lower hydraulic chamber 
           226   a  circumferential width of a hydraulic chamber 
           226   h  height of a hydraulic chamber in axial direction 
           228  upper circumferential row 
           230  lower circumferential row 
           232  axial wall 
           234  circumferential hole 
           234   h  axial dimension of circumferential hole 
           236  circumferential hole 
           236   h  axial dimension of circumferential hole 
           238  circumferential hole 
           238  axial dimension of circumferential hole 
           240  circumferential throttling duct 
           240   a  circumferential length of a segment 
           241  upper circumferential walls 
           243  lower circumferential walls 
           244  upper circumferential walls 
           246  axial opening 
           246   a  circumferential width of the axial opening 
           248  axial opening 
           248   a  circumferential width of the axial opening 
           250  bottom 
           252  cavity 
           254  abutment area 
           258  opening wall 
           301  joint 
           303  functional hydro-elastic element 
           307  internal frame 
           309  intermedial frame 
           312  elastic body 
           314  upper rim 
           316  lower rim 
           318  fitting areas 
           320  fitting areas 
           322  hydraulic chambers 
           322   a  circumferential width of a hydraulic chamber 
           322   h  height of a hydraulic chamber in axial direction 
           332  axial wall 
           334  circumferential hole 
           334   h  axial dimension of circumferential hole 
           336  circumferential hole 
           336   h  axial dimension of circumferential hole 
           341  upper circumferential walls 
           343  lower circumferential walls 
           350  bottom 
           352  cavity 
           354  abutment area 
           401  joint 
           403  functional hydro-elastic element 
           407  internal frame 
           409  intermedial frame 
           412  elastic body 
           414  upper rim 
           416  lower rim 
           418  fitting areas 
           420  fitting areas 
           422  hydraulic chambers 
           422   a  circumferential width of a hydraulic chamber 
           422   h  height of a hydraulic chamber in axial direction 
           432  axial wall 
           434  circumferential hole 
           434  axial dimension of circumferential hole 
           436  axial dimension of circumferential hole 
           436  axial dimension of circumferential hole 
           441  upper circumferential walls 
           443  lower circumferential walls 
           450  bottom 
           452  cavity 
           454  abutment area 
         Z longitudinal axis