WO2005021298A1

WO2005021298A1 - Elastic assembly joint and use thereof for the measurement of a movement or force

Info

Publication number: WO2005021298A1
Application number: PCT/FR2004/001888
Authority: WO
Inventors: Valéry Poulbot; Franck Honneur
Original assignee: Societe De Technologie Michelin; Michelin Recherche Et Technique Sa
Priority date: 2003-08-07
Filing date: 2004-07-16
Publication date: 2005-03-10
Also published as: FR2858673A1; FR2858673B1

Abstract

The invention relates to an elastic joint (1) comprising two rigid reinforcements (2, 3) which are connected to one another by means of an elastomer body (4) which is disposed therebetween, such that said two reinforcements cannot slide. Moreover, the elastomer body is elastically deformable such as to enable the relative displacement of the reinforcements. The invention is characterised in that it comprises at least one magnetic measuring assembly consisting of: at least one sensor (C1) which has a zone that is sensitive to the magnetic field along at least one sensitivity axis of the sensor and which is fixed to a first (3) of the reinforcements; and at least one magnetic source (S1) which is fixed to a second (2) of the reinforcements in order to position the aforementioned at least one sensor of the magnetic measuring assembly in the magnetic field with a pre-determined spatial distribution. According to the invention, each sensor of the magnetic measuring assembly produces a measurement signal at a signal output (11), said signal being representative of an intensity of the magnetic field.

Description

The present invention relates to the field of elastic assembly joints comprising two rigid frames linked together without possible sliding by an elastomer body arranged between said frames, said body elastomers being elastically deformable to allow relative movement of said frames relative to a rest position. Such joints are used for the suspension of motor vehicles, in particular for connecting the suspension arms to the wheel carriers and for connecting the suspension arms to the chassis or to the body of the vehicle. Fundamentally, the movement of a wheeled vehicle, and therefore the stability and maneuverability of the vehicle, is always governed by the forces that are transmitted between the wheels and the ground on which they roll. On-board electronic devices are known, for example of the ABS anti-lock regulation system, ASD anti-skid regulation system or ESP trajectory regulation system, serving to reinforce the road holding of a motor vehicle. For this, these systems try to automatically adapt the parameters of the maneuver, such as the braking force or the engine speed, so that the required longitudinal and / or lateral acceleration does not exceed the amount of effort that the road or the surface on which the vehicle is traveling can actually transmit to the vehicle through the tires. However, in known systems, the fundamental limit constituted by this amount of transmissible force is not determined and the regulation is based on parameters which are indirectly linked to it, with as a consequence regulation having a non-optimal result. For example, in known ABS systems, the regulation of the braking force of each wheel is based on the measurement of the sliding speed of the wheel. In ESP systems, the regulation of the braking force or the driving force applied to each wheel is based in particular on the measurement of the yaw speed of the vehicle, the transverse acceleration of the vehicle, and the angular position or the torque that the driver imposes at the wheel. The present invention aims to characterize more precisely the physical phenomenon in question, in particular to improve the regulation of the handling of a vehicle. The present invention starts from the observation that it is the bodies of the ground connection which transmit the force exerted by the ground on the wheels up to the suspended mass of the vehicle, which constitutes the predominant mass. The present invention also starts from the observation that the transmission of this force deforms the elastic joints and that the transmitted force is linked in a deterministic manner to the deformation of the body in elastomers by means of its stiffness. For this, the invention provides an elastic articulation comprising two rigid frames linked together without possible sliding by an elastomer body arranged between said frames, said elastomer body being elastically deformable to allow relative movement of said frames, characterized by at least one set magnetic measurement consisting of at least one sensor having a zone sensitive to the magnetic field in at least one direction of sensitivity of said sensor, which is fixed on a first of said frames, and of at least one magnetic source which is fixed on a second said armatures for immersing said at least one sensor of said magnetic measurement assembly in a magnetic field of predetermined spatial distribution, said or each sensor of said magnetic measurement assembly producing, at a signal output, a measurement signal representing an intensity of said magnetic field at level d e said sensitive zone in said at least one direction of sensitivity of said sensor. Such an articulation makes it possible to precisely measure the displacements between the reinforcements using the measurement signal produced by the sensor or each of the sensors, and therefore the deformation of the body in elastomers. Depending on the sensitivity of the sensor and the geometry of the field produced by the magnetic source, a single sensor can measure the relative displacement of the armatures in one direction or several directions. The use of several sensors and / or of several sources makes it possible to improve the precision of the displacement measurements as regards their amplitudes and / or directions. A magnetic source is used whose spatial distribution of the field is determined, for example a source magnetostatic or a stable oscillating source. The magnetostatic source can be of any type, for example a permanent magnet or an electromagnet. Preferably, in at least one said magnetic measurement assembly, for example in each magnetic measurement assembly, said at least one magnetic source has a main magnetization axis which is substantially parallel to the direction of sensitivity of said at least one sensor of said magnetic measurement assembly when said articulation is in a predetermined reference position. The reference position is the state of the articulation with respect to which it is desired to determine the relative displacements of the reinforcements with the best precision. This can be the rest position of the joint or a position taken by the joint under a predetermined static preload. The main axis of magnetization is the axis on which the magnetic field emitted by the magnetic source is of constant direction and parallel to this axis. The main magnetization axis is for example the polar axis when the magnetic source is constituted by a bipolar magnet or the winding axis when the magnetic source is constituted by an induction coil crossed by a current. Advantageously, at least one said magnetic measurement assembly, for example each magnetic measurement assembly, comprises at least two sensors having respective respective directions of sensitivity, said at least two sensors being mutually offset in a direction substantially perpendicular to a direction of spacing between said sensors and said at least one magnetic source of said magnetic measurement assembly. Such an arrangement of the measuring assembly makes it possible to precisely measure a relative movement of the armatures in the direction of separation of the two sensors. According to a particular embodiment of the invention, in at least one said magnetic measurement assembly, for example in each magnetic measurement assembly, said at least one magnetic source and said at least one sensor are mutually spaced in a direction of spacing substantially parallel to said main axis of magnetization of said at least one magnetic source when said articulation is in a predetermined reference position. Preferably in this case, in said at least one magnetic measurement assembly, for example in each magnetic measurement assembly, said at least one magnetic source has a main magnetization axis which is substantially secant to the sensitive zone of at least a said sensor of said magnetic measurement assembly. In particular, the main axis of magnetization of the magnetic source can advantageously be collinear with the axis of sensitivity of the sensor, that is to say the axis which crosses the center of the sensitive zone of the sensor while being oriented according to the sensitivity direction of the sensor. When the main magnetization axis is thus pointed towards the sensor, that is to say exactly on the sensitive zone of the sensor or else near the sensitive zone of the sensor, and the direction of sensitivity of the sensor is oriented parallel to this axis, the field component measured by the sensor has a maximum gradient along the main magnetization axis, which makes it possible to obtain an optimal measurement sensitivity for the relative displacements of the armatures in this direction. Thanks to this orientation of the magnetic source, the gradient of the field component measured by the sensor around the sensor is also sensitive in the directions transverse to the main magnetization axis, which also makes it possible to measure the displacements in these directions. . For example in this case, the main axis of magnetization of said magnetic source can point to a pair of adjacent sensors fixed on the first armature, the sensors of said pair being mutually offset along a direction transverse to said main axis d magnetization. Thanks to this arrangement, it is possible to precisely determine the amplitude and the direction of the relative displacements of the armatures in this first direction transverse to the principal axis of magnetization, in addition to the displacement measurements along the principal axis of radiation. To increase the possibilities of measurement, this configuration of the magnetic measurement assembly can be reproduced several times in the joint with sources having different magnetization axes and / or, for each magnetization axis, sensors offset according to different transverse directions. According to a particular embodiment of the invention, the first armature can also carry a second pair of adjacent sensors mutually offset along a second direction transverse to said main axis of magnetization. Thanks to this arrangement, it is possible to precisely determine the amplitude and the direction of the relative displacements of the armatures in this second direction transverse to the principal axis of magnetization, in addition to the displacement measurements along the principal axis of radiation and the first transverse direction. One thus obtains a measurement of the relative displacements of the reinforcements in three non-coplanar directions, which makes it possible to know all the relative translations of the reinforcements. The two pairs of sensors can be immersed in a magnetic field created by the same bipolar source, in which case the second pair of sensors is placed close to the first pair within the same magnetic measurement assembly. The two pairs can then have a sensor in common. As a variant, the second pair of adjacent sensors may be at a distance from the first pair, in another magnetic measurement assembly, and immersed in a field created by a second bipolar magnetic source having a main axis of magnetization substantially parallel to that of the first magnetic source. According to another embodiment of the invention, in at least one said magnetic measurement assembly, for example in each magnetic measurement assembly, said at least one magnetic source and said at least one sensor are mutually spaced in a direction of spacing substantially perpendicular to said main axis of magnetization of said at least one magnetic source when said articulation is in a predetermined reference position. Preferably, the elastic articulation according to the invention comprises several magnetic measurement assemblies arranged so that, in each of said magnetic measurement assemblies, said at least one sensor is immersed in a magnetic field created essentially by said at least one magnetic source. of said magnetic measuring assembly. For example, it can be provided for this that the overall spacing between two magnetic measurement sets is greater than the mutual spacing between source (s) and sensor (s) within each set and / or that the orientation of the sensitivity direction of the sensor (s) of one set is chosen so as not to capture the field created by the source (s) of another set. In this arrangement of the sensors and the magnetic sources, each sensor is under the preponderant influence of the magnetic source belonging to the same measurement set, so that the measurements are not complicated by the superposition of the magnetic fields created by the sources belonging to the different measuring sets. Advantageously, said frames are curved or folded around a longitudinal axis, in particular open or closed around said longitudinal axis, and arranged one around the other and, in at least one said magnetic measurement assembly, for example in each assembly. magnetic measurement, said at least one magnetic source and said at least one sensor are mutually spaced along a spacing direction substantially transverse to said longitudinal axis when said articulation is in a predetermined reference position. Advantageously, at least two magnetic measurement assemblies are provided having respective directions of sensor / magnetic source spacing substantially perpendicular to each other. Thanks to this arrangement, the translations of the armatures in two transverse and perpendicular directions l to one another, and therefore all the translations of the reinforcements in the plane transverse to the longitudinal axis can be measured. Preferably, at least two magnetic measurement assemblies are located in opposition on either side of said longitudinal axis of curvature of the reinforcements, said at least two magnetic measurement assemblies having respective sensor / magnetic source spacing directions substantially parallel or substantially collinear. For example in this case, the two assemblies are located along an axis transverse to said longitudinal axis, which cuts two zones of said first reinforcement and two zones of said second reinforcement, at least one respective sensor of each of the two measuring assemblies magnetic being fixed on a respective one of said zones of the first armature, a respective magnetic source of each of the two measuring assemblies being fixed on a respective one of said zones of the second armature. Thanks to this arrangement, the translational relative displacements of the reinforcements along the axis transverse to the longitudinal axis can be precisely measured in terms of their direction and amplitude because, in one of the two magnetic measurement systems, a sensor approaches the associated magnetic source when, in the other magnetic measurement system, the sensor moves away from it . The relative tilting of the reinforcements around an axis defined by the vector product between the longitudinal direction and said direction transverse to the longitudinal axis can also be measured. For each magnetic measurement set, the first frame can be the inner frame or the outer frame and, conversely, the second frame can be the outer frame or the inner frame. According to a particular embodiment, said reinforcements are closed around said longitudinal axis, for example with a circular section, and two other magnetic measurement assemblies are provided along another axis transverse to said longitudinal axis, preferably perpendicular to the first axis transverse to the longitudinal axis, which cuts two other zones of said first armature and two other zones of said second armature, a respective sensor of each of the two other magnetic measurement assemblies being fixed on a respective one of said other zones of the first armature, a respective magnetic source of each of the two other magnetic measurement assemblies being fixed on a respective one of said other zones of the second armature. Thanks to this arrangement, all the translations of the reinforcements in the plane transverse to the longitudinal axis can be precisely measured, as to their direction and their amplitude. The relative tilting around the two directions transverse to the longitudinal axis can also be determined. According to a preferred embodiment, said frames are closed around said longitudinal axis, said articulation having three magnetic measurement assemblies, in particular identical, arranged at an angle of 90 ° one after the other around said longitudinal axis . By means of non-linear processing of the measurement signals from the sensors, such an arrangement makes it possible to measure all the displacements in the transverse plane, in the absence of conical or axial displacements. Advantageously, said frames are closed around said longitudinal axis, said articulation having at least four magnetic measurement assemblies, in particular identical, arranged so as to have a symmetry of order 4 around said longitudinal axis. Such an arrangement also makes it possible to measure all the displacements in the transverse plane with a simpler processing of the measurement signals. Advantageously, said frames are made of diamagnetic or paramagnetic material. Such a material, in particular aluminum, has little or no magnetic susceptibility, so that the reinforcements thus produced allow the field of magnetic sources to pass without annoying disturbance. Preferably, in at least one said magnetic measurement assembly, for example in each magnetic measurement assembly, said at least one magnetic source is a bipolar permanent magnet. For example, Samarium-Cobalt magnets have proven to be advantageous because of their high remanent magnetization and the good heat resistance thereof. Other magnets which can validly be used are for example ferrite magnets (composed of iron oxide with a divalent metal, for example Barium or Strontium), magnets of ferrous alloy, for example Alnico, or other magnets made of rare earth alloys, for example Fer Bore Neodymium. Advantageously, in at least one said magnetic measurement assembly, for example in each magnetic measurement assembly, said at least one magnetic source is housed in a respective blind bore formed in said second frame. Such an arrangement allows secure attachment of the magnetic source, for example by punching the second frame, and protection of the magnetic source against mechanical stresses. Preferably, a ferromagnetic yoke, for example of iron, is placed in the or each blind bore on the side of the magnetic source opposite to said first frame. Such an arrangement makes it possible to increase, at best to double if we consider the perfect breech, the magnetic field of the source in the direction of the first armature and of the sensor or sensors that the latter carries. For example, the blind bore has an opening facing the first frame and the ferromagnetic yoke is disposed at the bottom of the bore behind the permanent magnet. Advantageously, in at least one said magnetic measurement assembly, for example in each magnetic measurement assembly, said at least one sensor sensitive to the magnetic field is substantially linear. Preferably, in at least one said magnetic measurement assembly, for example in each magnetic measurement assembly, said at least one sensor sensitive to the magnetic field is fixed in a groove formed in the first frame on a surface opposite to said elastomer body. Such an arrangement makes it possible to fix the magnetic sensor or sensors after the assembly of the elastomer body between the reinforcements, which can be produced by casting, injection or transfer for example. The sensors in the grooves are protected against mechanical stress during assembly of the joint and its operation. For example, the sensors can be attached by gluing. There are many types of sensors which are suitable for implementing the invention. According to a particular embodiment of the invention, in at least one said magnetic measurement assembly, for example in each magnetic measurement assembly, the sensitive area of said at least one sensor is plane, said direction of sensitivity being perpendicular to said sensitive area. For this, one can use for example a Hall effect sensor producing an electrical voltage signal proportional to a component of the magnetic field perpendicular to the plane sensitive area of the sensor. According to another particular embodiment of the invention, in at least one said magnetic measurement assembly, for example in each magnetic measurement assembly, the sensitive area of said at least one sensor is planar, said direction of sensitivity being parallel to said sensitive area . For this, it is possible, for example, to use a sensor of the MRA (anisotropic magnetoresistance) or GMR (giant magnetoresistance) or GMI (giant magneto-impedance) type. Other magnetic field sensors are still the flow gate sensors and the micro-coil sensors. For each application, the choice of sensor must take into account the risks of drift of the measurement signal with the temperature and the bandwidth of the sensor. In particular, for dynamic measurements, the high cut-off frequency of the sensor must be higher than the frequency of the displacement to be measured. Hall or MRA type sensors have the advantage of being suitable for both static and dynamic measurements. The invention also provides a use of the above-mentioned elastic articulation joint, characterized in that a relative displacement is measured between two rigid parts respectively attached to the two armatures from the magnetic field measurement signal produced by the or each sensor. For this, knowledge of the geometry of the magnetic field created by the or each magnetic source is used to determine a displacement from a variation of the measured field. The relation between variation of the measured field and displacement can be acquired experimentally or by calculation. Advantageously, the difference between the measurement signals of two sensors belonging respectively to the two magnetic measurement assemblies situated in opposition with respect to said longitudinal axis is calculated to determine a relative displacement parallel to the transverse direction joining the two assemblies. Preferably, said relative displacement measurements between the two rigid parts are converted into force measurements using stiffness characteristics of said body into elastomers. Thus, from the magnetic field measurement signal produced by the or each sensor, the forces transmitted between the two parts assembled by the joint are measured. For this, we use the dynamic stiffness of the elastomer body, which has for example been measured experimentally. In this case, the intermediate result constituted by the displacement measurements is not necessarily explained, in particular if one is interested only in the measurement of effort. Advantageously, the temperature of said elastomer body is measured and said effort measurements are adjusted as a function of said temperature. This makes it possible to take account of the variations in the stiffness characteristics of the elastomer body with its temperature. According to a particular embodiment of the invention, one of said parts is a transverse suspension arm connected to a wheel of a vehicle and the other of said parts is secured to a body of said vehicle. The force transmitted between a transverse suspension arm and the The vehicle body can be used to calculate the forces transmitted at the point of contact between the wheel and the ground. To carry out such a calculation, one can refer to the methods described in the French patent application FR 2 843 194 registered under the number 0209718 on 07.31.02. Another advantage of determining the forces transmitted by the joints, by applying it to each wheel, is the possibility of measuring the torsor of the forces which apply to the body. From this measurement, we can deduce the accelerations and in particular provide the same type of data as that from a yaw speed sensor. It is thus possible to implement a trajectory regulation system, of the ESP type, without using this expensive sensor. The invention will be better understood, and other objects, details, characteristics and advantages thereof will appear more clearly during the following description of several particular embodiments of the invention, given solely by way of illustration and without limitation. , with reference to the accompanying drawings. In these drawings: - Figure 1 is a perspective view of an elastic joint assembly according to a first embodiment of the invention, before installation of the sensors, - Figure 2 is a view similar to Figure 1 showing the finished joint, - Figure 3 is a view of the joint of Figure 2 in axial section along line III-III of Figure 4, - Figure 4 is a view of the joint of Figure 2 in section along line IV-IV of Figure 3, - Figure 5 is a cutaway perspective view of a front axle of a vehicle in which the joint of Figure 2 connects a suspension arm to the body, - Figure 6 schematically represents the field diagram of a bipolar permanent magnet used in the joint of FIG. 2, - Figures 7a and 7b show signatures that can be measured with a sensor sensitive to the magnetic field that is moved respectively along the R axis and the Q axis of Figure 6, - Figures 8 and 9 show the measurement signals produced by the four sensors of the joint of FIG. 2 for a relative transverse displacement of the armatures, - FIGS. 10 and 11 represent functional modules of a computer on board the vehicle of FIG. 5, - the FIGS. 12 to 14 represent an elastic articulation joint according to a second embodiment of the invention, - FIG. 15 represents the measurement signals produced by a pair of adjacent sensors in the articulation of FIG. 12 for a relative transverse displacement reinforcements, - Figure 16 is a partial cross-sectional view in the median plane of an elastic joint according to a third embodiment of the invention. With reference to FIGS. 1 to 4, according to the first embodiment, the elastic articulation 1 comprises an internal reinforcement 2 and an external reinforcement 3 having generally tubular shapes of revolution arranged coaxially and linked by a block of elastomeric material 4 disposed between they. The Z axis is the common longitudinal axis of the armatures 2 and 3 at rest. The inner frame 2 and the outer frame 3 are made of aluminum. Block 4 is made from any suitable mixture of elastomers, optionally with fillers, and can be obtained by injection or transfer (for example with rubber) or casting (for example with polyurethane) according to conventional techniques. The inner frame 2 has a central axial bore 5 intended to receive a fixing bolt. The axial end portions of the frame 2 protrude from the outer frame 3. On its surface lateral lateral, halfway in the axial direction, the armature 2 has a toroidal peripheral bulge 6 which makes it possible to reduce the stiffness of the articulation 1 compared to the so-called “conical” stresses, which tend to tilt the armatures mutually of a transverse axis. In the peripheral bulge 6, at the level of the median transverse plane of the frame 2, four blind radial bores 8 are formed opening out onto the outer surface of the frame 2. The four bores 8 are opposed two by two along two axes transversely mutually perpendicular X and Y, in the manner of the four cardinal points. In each bore 8 are arranged a bipolar permanent magnet S _i5 i = l to 4 and an iron yoke 9 which concentrates the magnetic field of the magnet Sj radially outwards. The magnets S _is i = l to 4, each have a disc shape with a main magnetization axis Pj or polar axis oriented radially respectively in the direction + X, + Y, -X and -Y. The presence of the bulge 6 on the frame 2 constitutes a possible but not compulsory embodiment. The magnets Sj can also be fixed on a straight cylindrical frame devoid of such a bulge. The magnets Sj are for example chosen in Samarium-

Cobalt (Sm ₂ Cθπ), for their advantageous properties in terms of remanent magnetization and heat resistance. Thanks to their good resistance to temperature, they are put in place before molding the block 4 by punching the armature 2 to permanently immobilize the magnets Sj in the bores 8. The external armature 3 has end flanges 7 which are folded transversely inward to improve the resistance of the joint 1 to axial stresses along the axis Z. In the outer lateral surface of the frame 3 are machined four axial grooves 10, opening at a axial face of the frame 3 and extending slightly beyond the mid-height of the frame 3. The grooves 10 are also opposite in pairs along the two transverse axes X and Y. Each groove 10 is located opposite one of the magnets S _i5 i = l to 4, separated from it by the thickness of the block of elastomers 4 in the radial direction and by a portion of the thickness of the armature 3. Four sensors Hall effect, i = l to 4, are fixed by gluing in l throats 10 of so as to present their sensitive zone halfway up the armature 3, that is to say at the same axial level as the magnets Sj. Thus, the main magnetization axis P _; of each magnet Sj points directly and perpendicularly to the sensitive area 29 of the sensor Q (i = l to 4). The sensitive zone 29 is only indicated for the sensor C ₃ in FIG. 3 because all the sensors are identical. The grooves 10 are machined after molding the block 4 with a depth greater than the thickness of the sensors, so that the joint 1 retains a cylindrical external geometry in the end. The sensors Ci are fixed by gluing, for example with a cyanoacrylate resin. The grooves 10 are also dimensioned so that the wires 11 of the sensors Ci can come out easily. Resin is therefore applied to the sensors and the wires 11 to protect them during mounting on a vehicle and to avoid any movement of the sensors Ci or the wires 11 which could disturb the measurements. The sensors Ci are for example Hall effect sensors, for example chosen from the SS490 series offered by Honeywell®. For example, for the SS495A1 model, the response is linear with a sensitivity of 3.125 mV / Gauss for a field range of +/- 670 Gauss. The supply voltage range is 4.5 to 10 Vdc for a maximum current of 8.5A. The sensors can also be chosen from another type, for example MRA, while retaining an orientation making it possible to measure the radial component of the magnetic field. Thus, in this first embodiment, the joint 1 has four identical magnetic measurement assemblies, each consisting of a magnet and a Hall effect sensor, and distributed around the Z axis with symmetry d 'order 4. In Figure 5, there is shown a motor vehicle 12 in which the joint 1 is used for the ground connection. The front axle of the vehicle 12 is more particularly represented, the other parts of the vehicle 12 being sketched in broken lines. As the axle is symmetrical, the description of half an axle is sufficient. The front wheel 13 is rotatably mounted on a hub carrier 14 which is movably assembled to the body 15 of the vehicle 12 by a suspension arm 16 and by a strut 17. The body 15 designates the suspended mass of the vehicle 1. A steering link 18 connects the hub carrier 14 to a steering column 19 of the vehicle 12 to modify the orientation of the wheel 3. The turning pivot of the wheel 13 and of the hub carrier 14 takes place around one end 16a of the arm of suspension 16. In FIG. 1, the wheels are oriented so as to roll in a straight line. The connection between the suspension arm 16 and the body 15 is carried out at two connection points A and B by means of two anti-vibration joints, for example joints of the elastic or hydroelastic type. The anti-vibration joint at point A is joint 1 described above. In this layout, the axes X, Y and Z of the articulation 1 respectively coincide with the longitudinal, transverse and vertical direction of the vehicle 12. The external frame 3 is rigidly fixed in a housing located substantially at the midpoint of the suspension arm 16, and the inner frame 2 is fixed to the body 15 using a bolt (not shown) which is engaged in its axial bore 5. To avoid degrading the sensors Ci during the fitting of the articulation 1, a guide tool is used which is provided with a bore with a slightly conical profile which is placed in alignment with the straight housing bored in the suspension arm 16 and which allows a sufficiently gentle positioning of articulation 1 in the suspension arm 16. For point A, the stiffness characteristics of articulation 1 can be chosen as follows: - dynamic transverse stiffness Kx = Ky = 20 kN / mm at a frequency of 150 Hz for u no vibration amplitude of around 50 μm; - static transverse stiffness Kx = Ky = 10 kN / mm for a static load of 9kN, i.e. a deformation amplitude of around 1 mm, and - static longitudinal stiffness Kz = 2850N / mm for a static load 2.5 kN, that is to say a deformation amplitude of about 1.5 mm. In joint 1, the sensors Ci and the magnets Si, i = l to 4, are used to measure the displacements between the reinforcements 2 and 3, that is to say the deformations of the block of elastomers 4, and the transmitted forces. For this, the bundle 20 formed of the sensor wires 1 1 emerging from the articulation 1 is connected to an on-board computer 21 which supplies the sensors with electricity and uses the measurement signals which they produce, as will be explained below. For an explanation of the principle of the displacement and force measurement method, there is shown diagrammatically in FIG. 6 the magnetic induction lines 22 created in the non-magnetic surrounding space, for example in air, by a bipolar magnet S such as those used as magnets Si in the joint 1. By definition, the magnetic induction vector is tangent along each of the lines 22 and of constant amplitude along a given line 22. The strongest field is observed on the main magnetization axis Q, while it is increasingly weak along the lines 22 which are further from this axis. The magnetization of the magnet S is represented by the vector 23, which is therefore collinear with the main axis of magnetization Q of the magnet S. FIG. 7A schematically represents the variation along the axis R of the magnetic field component parallel to the vector 23. Figure 7B schematically represents the variation along the Q axis of the magnetic field component parallel to the vector 23. It should be noted that the gradient of this magnetic field component is stronger the along the Q axis than along the R axis. For each sensor Cj, the field of the associated magnet Si is very largely preponderant because of its greater proximity and its orientation. Thus, the field of the other magnets can be neglected vis-à-vis the sensor. FIGS. 7A and 7B therefore represent qualitatively the shape of the variation of the magnetic field which is measured by each of the sensors Ci when it is displaced respectively transversely to the main axis of magnetization of the magnet Si and along the main axis of magnetization of the magnet Sj. Therefore, when the articulation 1 is subjected to a force which transversely shifts the armatures 2 and 3, for example when the vehicle brakes or accelerates or the wheel 13 moves back in contact with an obstacle, the measurement signals produced by the sensors account for this movement in the form of a determined signature. With reference to FIGS. 8 and 9, which correspond to enlarged views of zones VIII and IX in FIGS. 7B and 7A, there is described the example of a displacement of the external reinforcement 3 in the direction + X relative to the internal reinforcement 2. In FIG. 8, a curve representing the field measured by the sensor C ₃ has been added in broken line function of the displacement along the X axis. In these figures, X ₀ i represents the position of the sensor when the joint 1 is at rest. In this case, the sensors Q, i = l to 4, measure variations in the magnetic field δj which are represented diagrammatically by arrows in FIGS. 8 and 9. For a fairly small amplitude of movement, the variation in field measured can be considered as linearly related to displacement as a first approximation. We obtain for example: δι = -M; δ ₃ = + M and δ ₂ = δ ₄ = -m, with M »m, for example M / m≈lO. For a greater amplitude of displacement, it is necessary to take account of the convexity of the curves of figure 8 using a nonlinear model, so that the measurement signal of a sensor which approaches the magnet associated has a greater variation than the measurement signal from the opposite sensor which moves away from the associated magnet. Indeed, the magnetic field evolves as the distance to the power -3. However by forming the difference between these two measurement signals, that is to say by observing the variation (δ ₃ -δι) in this example, the range of linearity between the variation of measured signal and the displacement is increased, by example up to +/- 1 mm, which covers the most common operating range of the joint 1. Appropriate processing of the measurement signals from the four sensors Ci therefore makes it possible to determine the direction and the amplitude of all the translational displacements in the XY plane. Table 1 in the explicit appendix, for two canonical translations of the external reinforcement 3 with respect to the internal reinforcement 2 in the XY plane, the variations of magnetic field δj measured by the sensors Q which constitute discriminating signatures of each movement. This processing is carried out by a displacement measurement module 24 integrated in the on-board computer 21 and shown diagrammatically in FIG. 10. The module 24 receives as input the four measurement signals V _; (t) of sensors Ci, in the form of electrical voltages. In a simple model, the translations and rotations between the reinforcements along the Z axis are assumed to be negligible. Module 24 calculates the instantaneous positive or negative displacements x (t) along the X axis and y (t) along the axis Y by the relations: x (t) = a ₁ [V ₃ (t) -V ₁ (t)] + b ₁ (El) y (t) = a ₂ [V ₄ (t) -V ₂ (t) ] + b ₂ (E2) aj, a ₂ , bi and b ₂ being of experimentally predetermined constant coefficients. The displacements are measured both for static stress and for dynamic stress on joint 1, for example up to 100 Hz and more, with an accuracy of the order of 10 μm. As mentioned, the displacement measurement could also be carried out with a single sensor for the X direction and a single sensor for the Y direction, provided that a non-linear relationship between the measurement signal and the displacement is used. It is also possible to characterize the displacements in the XY plane in polar coordinates. The on-board computer 21 also includes a force calculation module 25 shown diagrammatically in FIG. 11. The module 25 receives as input the displacement signals x (t) and y (t) and produces as an output an estimation signal of the force transmitted by the articulation 1. The module 25 comprises a first module 26 which calculates an effort estimation signal at a reference temperature T _ref , ie F _Tr ef ( _> ^{and a} second module 27 which calculates a signal for estimating the force at the actual temperature T of the block of elastomers 4, ie F _τ (t), by applying a temperature-dependent correction T to the signal F _Tréf (t), for example, T _ref = 40 ° C. The signals F _Tréf and F _τ comprise two scalar signals representing respectively the component of effort according to X and the component of effort according to Y, which can be calculated separately in a scalar form or together in a vector form. Module 26 calculates the signal F _Tréf (t) in a pplicating a modeling of the stiffness characteristics of the elastomer block 4 at the reference temperature. Given the well-known properties of elastomers (hysteresis, non-linearity), this is a non-linear modeling with delay. The modeling is constructed and validated from corresponding force and displacement measurements carried out on an experimental measurement bench. The module 26 is for example produced in the form of two similar neural networks with a time loop on the inputs and outputs, which respectively calculate the force component according to X from the displacement x (t) and the force component according to Y from the displacement y (t). The loopback is at least two memories on the input and the output, or a state network of order 3. The complexity is at least four hidden neurons. The training sequence used is a pseudo-random sequence of frequency 30Hz filtered at 30Hz and of amplitude +/- 0.8mm. After studying different models of neural networks, the most suitable has turned out to be a network with a hidden layer of four neurons with hyperbolic tangent type activation function, a linear output layer linked linearly to the inputs, two memories on the output and two memories on the input. The calculations carried out by the modules 24 and 26 can be combined to be carried out by a single module, that is to say that the estimate of the force can be calculated directly from the measurement signals of the sensors without measuring explicitly displacement. In fact, the displacement is implicitly contained in the measurement signals V ₍ (t). The stiffness characteristics of the elastomer block 4 change when its temperature changes. A heating is produced in particular during the operation of the joint 1. For take the temperature into account in the modeling of the relationship between force and displacement x (t), y (t) or between force and measurement signal V _; (t), a thermocouple 28 is placed inside the rubber , shown in FIG. 3, and connected to the module 27. The module 27 applies to the signal F _Tréf (t) a correction depending on the temperature T measured by the thermocouple 28. The range of variation of temperature considered is between -20 ° C. and + 50 ° C. Module 27 applies a semi-physical model which takes into account the stiffening of elastomers when the temperature decreases and the properties observed by spectral analysis of rigidity. We define the spectral function of transfer displacement-effort G (f) = F (ι) / x (f) of joint 1 as the ratio between the force F (f) exerted on an armature at a frequency f and the amplitude x (f) of the displacement of this armature at the frequency f, the other armature being fixed. For articulation 1, this transfer function is isotropic in the XY plane, but depends on the temperature T. The experimental observation of the modulus of the spectral functions of transfer-effort transfer | G (f, T) | for each temperature T shows that these functions are proportional, except possibly at very low frequencies. We therefore define a temperature correction coefficient c (T) independent of the frequency: c (T) = [| G (f, T) | - | G (0, T) | j7 [| G (f, T _ref ) | - | G (0, T _ref ) |] (E3). At a temperature T, we finally calculate the estimate of the force transmitted by joint 1 with the linear relationship:

where x (t) denotes the value of the displacement vector at time t and d (T) = [| G (0, T) | -c (T) | G (0, T _ref ) |] (E5). The functions c (T) and d (T) are determined from experimental measurements, and are obtained for example in the form of exponential functions cιexp (-c ₂ T) and dιexp (-d ₂ T), by a process d 'adjustment of the parameters Ci, c ₂ , di and d ₂ , or in the form of polynomial functions. The measuring device described above made it possible to determine the force transmitted between the two armatures of the joint 1 with a margin of error of approximately 100N over an operating range of +/- 10kN. The module 27 is not necessarily physically separated from the module 26. The calculations made by the module 27 can be combined with the calculations made by the neuron networks of the module 26. The correction of the force estimate as a function of the temperature however, is not always essential. In the examples of displacement described above, the relative displacement of the reinforcements is supposed to be a translation in the XY plane. However, the presence of a conical deformation of the joint 1, that is to say of a relative inclination of the longitudinal axes of the reinforcements with an angle θ, influences the slope and the ordinate at the origin. of the relationship between the field measured by the sensors Ci and the displacement. To take this into account, we can correct the equations (El) and (E2) above by making the coefficients depend on the value of the angle θ. The coefficients thus modified aι (θ), bj (θ), a ₂ (θ), b ₂ (θ) can be estimated by optimization. Insofar as the angle θ is known, one can thus take account of the conical deformation to improve the precision of the measurement of displacements. Table 1 in the appendix shows that the conical deformation by rotation around the X axis or the Y axis can also be detected using the sensors. Indeed, it will be easily verified that the field-displacement transfer matrix represented by table 1 is invertible. In particular, at small angles, the field measured by the sensors depends linearly on the tilt angle. With reference to FIGS. 12 to 14, a second embodiment of the elastic joint will now be described. Elements identical or analogous to those of the first embodiment are designated by the same reference number increased by 100. The general structure of the articulation 101 is identical to that of the articulation 1. Only the number and the position of the magnets and sensors. The internal frame 102 carries only three magnets Ai, A ₂ and A ₃ designed, arranged and fixed in the same way as three magnets S; of the first embodiment. In an area located opposite each of the magnets Ai, A ₂ and A ₃ , the external armature 103 each carries two grooves 110, partially shown as similar to the grooves 10 of the first embodiment, which are mutually offset along from the periphery of the outer frame 103 to be on either side of the main magnetization axis of the magnet Ai, A ₂ or A ₃ which faces them. Sensors, i = ll to 16, designed and fixed in the same way as the sensors of the first embodiment are placed in the six grooves of the frame 103. The sensors Cn and Cι ₂ which face the magnet Ai are placed in two adjacent grooves, therefore placed on either side of the main magnetization axis of the magnet Ai in the direction Y, and are placed at different levels in the direction Z, so as to be also placed on either side of the main magnetization axis of the magnet Ai in the direction Z. The sensors Cι ₃ and Cj which face the magnet A ₂ are likewise placed on either side other of the main magnetization axis of magnet A ₂ in the direction X and in the direction Z. The sensors Cι ₅ and Cι ₆ which face the magnet A ₃ are placed on either side of the main magnetization axis of the magnet A ₃ in the direction X, and are placed at the same level in the direction Z. Thus, in this second embodiment, the articulation

101 presents three magnetic measurement assemblies arranged around the Z axis at an angle of 90 ° one after the other and each consisting of a magnet and two offset Hall effect sensors. For the displacement measurement, the response of the sensors Q, i = l 1 to 16, to displacements parallel to the main axis of magnetization of the associated magnet is substantially identical to the response obtained in the arrangement of the first mode of production. However, the doubling of the sensors for each magnet, and their arrangement in pairs of sensors placed on either side of the main magnetization axis in a direction peφendicular to the main magnetization axis makes it possible to improve detection movements of the sensors in this direction. At these positions, the gradient of the magnetic field is higher and more uniform and, for such a displacement, the measurement signal from one sensor increases while the measurement signal from the other decreases. Figure 15 illustrates this principle. FIG. 15 represents the variation parallel to the X axis of the magnetic field component produced by the magnet A ₂ along the Y axis. X ₀ 'and X ₀ "indicate the respective positions of the sensors Cι ₃ and Cι ₄ at Thus, when the outer frame 103 is translated in the + X direction relative to the inner frame 102, the measurement signals from the sensors Cπ and C _H show opposite variations δι ₃ = + m and δι ₄ = - m which are represented diagrammatically by arrows in FIG. 15. Thus, the difference between these two signals makes it possible to detect this type of displacement with increased sensitivity. Thanks to the six sensors C „i = l 1 to 16, of the joint 101, it is possible to determine the translations along the three axes X, Y, and Z and the rotations around these three axes Table 2 in the appendix explains the variations in magnetic field δj measured by the sensors Q which constitute discriminating signatures of each type We can easily see that this transfer matrix is invertible. With reference to FIG. 16, a third embodiment of the elastic joint will now be described. Elements identical or analogous to those of the first embodiment are designated by the same reference number. The general structure of the joint 201 is similar to that of the joint 1. Only the orientation of the magnets and sensors change, the symmetry of order 4 of the joint being preserved. For this reason, only one quadrant of the joint 201 has been shown in FIG. 16. In the joint 201, the sensor Ci has an axis of sensitivity, represented by an arrow, which is oriented in the direction tangent peripheral of the external armature 3. For example, the sensor Ci is a Hall effect sensor whose sensitive surface is peφendicular to the tangential peripheral direction of the armature 3 or an MRA type sensor whose sensitive surface is peφendicular to the radial direction X. On the other side of the elastic coφs 4 in the radial direction X, the internal armature 2 carries a magnet Sj whose main magnetization axis, represented by an arrow, is also oriented in the peripheral direction tangent of the inner armature 2. This magnet magnet Si / sensor Ci forms a magnetic measurement assembly whose response to the relative displacements of the armatures 2 and 3 is similar, at least qualitatively, to the response of the measurement systems of the first embodiment. Figures 6 and 7a-b explain this similarity. When the joints 2 and 3 are mutually displaced in the direction X, the displacement of the sensor Ci in the field created by the magnet Si is equivalent, with respect to the magnet S of FIG. 6, to a displacement along the axis T for a sensor whose direction of sensitivity is parallel to the axis Q. In this case, the field variation measured by the sensor is represented qualitatively by FIG. 7b, that is to say that it is identical in shape to the variation measured by the sensor Ci in FIG. 4 for this same movement of the armatures. When the joints 2 and 3 are mutually displaced in the direction Y, the displacement of the sensor Ci in the field created by the magnet Si is equivalent, with respect to the magnet S of FIG. 6, to a displacement along the the N axis for a sensor whose sensitivity direction is parallel to the Q axis. In this case, the field variation measured by the sensor is represented qualitatively by FIG. 7a, that is to say, it is of identical shape to the variation measured by the sensor Ci of FIG. 4 for this same movement of the armatures. Table 1 in the appendix therefore also applies to the third embodiment described in FIG. 16. The amplitude of the variations may however be different in the two embodiments. Magnets and sensors whose respective axes of magnetization and sensitivity are tangential instead of radials, as in the third embodiment, can also be used in the second embodiment above. As a variant, in all the embodiments described, it is also possible to use magnets and sensors whose respective magnetization and sensitivity axes are oriented along the Z axis. The articulation 101 or 201, in conjunction with an on-board computer can be used to measure, qualitatively or quantitatively, the displacements and / or the forces at the point A of the connection to the ground of a vehicle, in a similar manner to the articulation 1 of the first embodiment. Such joints can also be used to measure displacements, for example vibrations, and / or forces in any mechanical structure. In the articulations 1 and 101 or 201, the sensors could also be fixed in the bore of the internal reinforcement 2 or 102 and the magnets on the internal surface of the external reinforcement 3 or 103. The elastomer block 4 or 104 can also be loaded with soft ferrite, to promote magnetic permeability between the magnets and the associated sensors in a magnetic measurement assembly. For this, the loading of soft ferrite is advantageously located between the magnet / sensor pairs associated with the magnetic measurement assemblies and / or the ferrite particles are oriented so as to promote magnetic permeability in the magnet / sensor direction associated, for example the radial direction of the joints 1 and 101, with respect to the other directions. In an alternative embodiment, suitable for a joint intended to work under a predetermined static preload, magnet-sensor pairs of one or more magnetic measurement assemblies can be positioned in an offset manner when the joint is at rest, to be facing one another once the static preload is applied to the joint. The number and position of the magnets, the number and position of the sensors, and the shape of the armatures can vary within wide limits depending on the application. For example, the reinforcements can have substantially planar shapes or shapes curved around an axis with a semi-circular or polygonal cross section, open or closed. The invention also applies to hydroelastic joints, that is to say a particular type of elastic joints in which the coφs of elastomers is shaped so as to define, between the two reinforcements, a volume containing a liquid of damping and comprising at least two opposite chambers in a predefined damping direction, and possibly at least one channel connecting said chambers. Although the invention has been described in connection with several particular embodiments, it is obvious that it is in no way limited thereto and that it includes all the technical equivalents of the means described as well as their combinations if these fall within the scope of the invention.

Table 1: signatures allowing to recognize four canonical displacements of the external reinforcement 3 compared to the internal reinforcement 2 in the articulation 1

Table 2: signatures making it possible to recognize six canonical displacements of the external reinforcement 103 relative to the internal reinforcement 102 in the joint 101

Claims

CLAIMS 1. Elastic articulation (1; 101) comprising two rigid reinforcements (2, 3; 102, 103) linked together without possible sliding by a coφs in elastomers (4; 104) arranged between said reinforcements, said coφs in elastomers being elastically deformable to allow relative movement of said armatures, characterized by at least one magnetic measurement assembly consisting of at least one sensor (Ci; Cn, Cj ₂ ) having an area sensitive to the magnetic field in at least one direction of sensitivity of said sensor, which is fixed on a first (3; 103) of said plates, and at least one magnetic source (Si; Ai) which is fixed on a second (2; 102) of said plates to immerse said at least one sensor of said measuring assembly magnetic in a magnetic field of predetermined spatial distribution, said or each sensor of said magnetic measuring assembly producing, at a signal output (11; 111), a si general measurement (Vi) representing an intensity of said magnetic field at said sensitive area in said at least one direction of sensitivity of said sensor.

2. Elastic joint according to claim 1, characterized in that, in at least one said magnetic measurement assembly, said at least one magnetic source (Si; Ai) has a main magnetization axis (P); P ₁₀ ι) which is substantially parallel to the direction of sensitivity of said at least one sensor (Ci; Cn, ₂ ) of said magnetic measurement assembly when said articulation is in a predetermined reference position.

3. Elastic articulation according to claim 1 or 2, characterized in that at least one said magnetic measurement assembly, comprises at least two sensors (Cn, Cι ₂ ) having respective respective directions of sensitivity, said at least two sensors being mutually offset in a direction substantially peφendicular to a spacing direction (X) between said sensors and said at least one magnetic source (Ai) of said magnetic measurement assembly.

4. Elastic joint (1, 101) according to one of claims 1 to 3, characterized in that, in at least one said magnetic measurement assembly, said at least one magnetic source (Si; Ai) and said at least one sensor (Ci; Cn, C _{) 2} ) are mutually spaced along a spacing direction (X) substantially parallel to said main axis of magnetization (Pi; P _JOI ) of said at least a magnetic source when said articulation is in a predetermined reference position.

5. Elastic articulation according to claim 4, characterized in that, in said at least one magnetic measurement assembly, said at least one magnetic source (Si; Ai) has a main magnetization axis (Pj; P _JOI ) which is substantially secant to the sensitive zone of at least one said sensor (Ci; Cn, C _{) 2} ) of said magnetic measurement assembly.

6. Elastic articulation (201) according to one of claims 1 to 5, characterized in that, in at least one said magnetic measurement assembly, said at least one magnetic source (Si) and said at least one sensor (Ci ) are mutually spaced along a spacing direction (X) substantially peφendicular to said main axis of magnetization of said at least one magnetic source when said articulation is in a predetermined reference position.

7. elastic joint (1, 10, 201) according to one of claims 1 to 6, characterized in that it comprises several magnetic measurement assemblies arranged so that, in each of said magnetic measurement assemblies, said at least a sensor (Cj. ₄ ; Cn.ι ₆ ) is immersed in a magnetic field created essentially by said at least one magnetic source (Sι _-4 ; Aι _-4 ) of said magnetic measurement assembly.

8. Elastic articulation according to one of claims 1 to 7, characterized in that said reinforcements (2, 3; 102, 103) are curved around a longitudinal axis (Z) and arranged one around the other and that, in at least one said magnetic measurement assembly, said at least one magnetic source and said at least one sensor are mutually spaced along a spacing direction (X, Y) substantially transverse to said longitudinal axis when said articulation is in a predetermined reference position.

9. Elastic joint according to claim 8, characterized in that it comprises at least two sets of magnetic measurement having respective directions of sensor / magnetic source spacing (X, Y) substantially perpendicular to each other.

10. Elastic joint according to claim 8 or 9, characterized in that it comprises at least two magnetic measurement assemblies (C ₂ , S ₂ ; C ₄ , S ₄ ) located in opposition on either side of said axis longitudinal (Z) of curvature of the reinforcements, said at least two magnetic measurement assemblies having respective sensor / magnetic source spacing directions (Y) substantially parallel or substantially collinear.

11. Elastic articulation (101) according to one of claims 8 to 10, characterized in that the said armatures are closed around the said longitudinal axis (Z), the said articulation having three sets of magnetic measurement (A ₂ , C13.1 ₄ ; Ai, Cn_ι ₂ ; A ₃ , C _15. ₁₆ ) arranged at an angle of 90 ° one after the other around said longitudinal axis.

12. Elastic articulation according to one of claims 8 to 11, characterized in that the said reinforcements are closed around the said longitudinal axis (Z), the said articulation having at least four magnetic measurement assemblies (, Si; i = 1.2 , 3, 4), arranged so as to have a symmetry of order 4 around said longitudinal axis (Z).

13. Elastic joint according to one of claims 1 to 12, characterized in that said frames (2, 3; 102, 103) are made of diamagnetic or paramagnetic material.

14. Elastic articulation according to one of claims 1 to 13, characterized in that, in at least one said magnetic measurement assembly, said at least one magnetic source (S _1. ₄ ; A _1. ₃ ) is a magnet bipolar permanent.

15. Elastic joint according to one of claims 1 to 14, characterized in that, in at least one said magnetic measurement assembly, said at least one magnetic source (S ₁ - ₄ ; A ₁ .3) is housed in a respective blind bore (8) formed in said second frame (2, 102).

16. Elastic joint according to claim 15, characterized in that an iron cylinder head (9) is arranged in the or each blind bore (8) on the side of the magnetic source (S 1.4; Aι _-3 ) opposite to said first frame (3, 103).

17. Elastic articulation according to one of claims 1 to 16, characterized in that, in at least one said magnetic measurement assembly, said at least one sensor (Cι _-4 ; C .iô) sensitive to the magnetic field is fixed in a groove (10; 110) formed in the first frame (3; 103) on a surface opposite to said elastomer coφs (4; 104).

18. Elastic articulation according to one of claims 1 to 17, characterized in that, in at least one said magnetic measurement assembly, the sensitive area of said at least one sensor (Cι _-4 ; Cn-i _ό ) is plane , said direction of sensitivity being peφendicular to said sensitive area.

19. Elastic articulation according to one of claims 1 to 18, characterized in that, in at least one said magnetic measurement assembly, the sensitive area of said at least one sensor (Cι. ₄ ) is plane, said direction of sensitivity being parallel to said sensitive area.

20. Use of an elastic articulation (1; 101) according to one of claims 1 to 19, characterized in that a relative displacement is measured between two rigid parts (15, 16) respectively attached to the two frames ( 2, 3; 102, 103) from the magnetic field measurement signal produced by the or each sensor (C;

21. Use according to claim 20, said elastic articulation being according to claim 10, characterized in that the difference between the measurement signals of two sensors (C ₂ , C ₄ ; Cι _3- ι, Ci5-) is calculated ι ₆ ) belonging respectively to the two sets of magnetic measurement situated in opposition with respect to said longitudinal axis, to determine a relative displacement (y) parallel to the transverse direction (Y) joining the two sets.

22. Use according to claim 20 or 21, characterized in that one converts said relative displacement measurements (x, y) between the two rigid parts into measurements of a force (F _Tréf , F _τ ) at using stiffness characteristics of said elastomer co éls (4; 104).

23. Use according to claim 22, characterized in that the temperature (T) of said coφs in elastomers (4; 104) is measured and that said force measurements (F _τ ) are adjusted as a function of said temperature.

24. Use according to one of claims 20 to 23, characterized in that one of said parts is a transverse suspension arm (16) connected to a wheel (13) of a vehicle (12) and the other of said parts is integral with a body (15) of said vehicle.