ELASTIC BEARING ELEMENT

Description

[0001] US3623360 and FR2878998 disclose elastic bearing elements with force sensors.

[0002] The present invention relates to an elastic bearing element according to claim 1.

[0003] The installation of load cells and force transducers for measuring forces at the location of the elastic mounting is common. These sensors are arranged in addition to the elastic mounting, for example, parallel or in series with the force flow to be measured. Such sensors commonly available on the market are based on strain gauge sensors (strain gauges) or piezo sensors, sometimes with integrated amplifiers. For example, bending beams can be used to which strain gauge sensor elements are glued. Alternatively, in the case of air springs, air pressure measurements can be taken within the air spring.

[0004] The disadvantage here is that an additional component is required for each installation. This can lead to additional costs and require additional installation space. Furthermore, the sensor may need to be protected from external influences.

[0005] A further disadvantage of using strain gauge sensors is that they can only detect stresses or bending in a single spatial direction. This can lead to inaccurate measurements if force components occur in other directions. Overcoming this limitation by using multiple strain gauge sensors can increase the complexity and cost of both the sensors themselves and the electronics for evaluating and converting the stress values, thus driving up the overall price.

[0006] A disadvantage of measuring air pressure in air springs can be that air is compressible, and therefore the measured pressure value may be lower than the actual force exerted.

[0007] A general disadvantage of fluid pressure measurements is the removal of air present in the system. Venting the system is often difficult, especially when the air needs to be removed as completely as possible. The air that is unintentionally present in the system can reduce the accuracy of the measurement due to its compressibility.

[0008] An object of the present invention is to enable force measurement at the location of an elastic bearing element of the type described above to be carried out more simply, more cost-effectively, and more accurately than previously known. In particular, additional components such as load cells should be eliminated.

[0009] The problem is solved according to the invention by an elastic bearing element with the features according to claim 1. Advantageous embodiments are described in the dependent claims.

[0010] The present invention thus relates to an elastic bearing element comprising at least one first body, at least one second body, and at least one elastomeric element, which is arranged in the direction of force flow between the first body and the second body. The elastomeric element is elastically designed, i.e., it can change its shape under the influence of force and return to its original shape when the acting force is removed. Preferably, the elastomeric element comprises or is formed from a vulcanized rubber compound.

[0011] The elastic bearing element further comprises at least one sensor, which is designed and arranged to detect a force in the force flow between the first body and the second body, either directly or indirectly. For direct force detection, the sensor can be arranged directly in the force flow between the two bodies. For indirect force detection, the sensor can be arranged outside the force flow, whereby, for example, forces can be transmitted to the sensor via a fluid arranged in the force flow. The two bodies are designed to be rigidly connected to another body, so that force transmission can occur via the elastomeric element, whereby dynamic force transmission can be dampened by the elastic properties of the elastomeric element. The two bodies are preferably rigid, in particular made of metal.The two bodies can also be called stop elements.

[0012] The elastic bearing element is characterized in that the sensor comprises at least one elastic layer, at least one first electrode, and at least one second electrode, wherein the elastic layer is arranged at least partially between the first and second electrodes. The elastic layer preferably comprises or is formed from an elastomeric material. The elastic layer is non-electrically conductive, i.e., electrically insulating or dielectric, in order to electrically isolate the two electrodes from each other. The elastomeric material of the elastic layer preferably comprises or is formed from a vulcanized rubber compound, whereby, for example, polyurethanes can also be used.An electrode is an electron conductor that interacts with a second (counter) electrode and a medium located between the two electrodes, such as the elastic layer in this case. Electrodes can have or consist of electrical conductors such as metal or graphite. The electrodes can be flat or linear. Using such a sensor, the distance between the two electrodes can be measured, for example, capacitively.

[0013] The sensor is positioned in the force path between the first and second bodies in such a way that the force changes the distance between the two electrodes, allowing the force to be at least partially detected. In other words, the sensor is designed to infer the magnitude of the force between the two bodies, which changes this distance, from the distance between the electrodes. Due to the elastic properties of the elastomer element, the distance between the two electrodes can decrease as the force increases. Conversely, as the force decreases, the distance between the two electrodes can increase again, returning to the distance of the unloaded state.

[0014] The elastic layer comprises a rubber mixture containing at least one silicone rubber as the sole rubber component and hollow microspheres. Any silicone rubber known to a person skilled in the art can be used. Silicone rubbers, which can also be referred to as poly(organo)siloxanes, can preferably be used. These contain groups susceptible to crosslinking reactions, predominantly, but not exclusively, hydrogen atoms, hydroxyl groups, and vinyl groups, which can each be located in the chain or at the chain ends.

[0015] Both cold-curing (RTV = room temperature curing) and hot-curing (HTV = high-temperature curing) silicone rubbers can be used. RTV silicone rubbers are available in one-component and two-component systems. The silicone rubber can also be used as a premix of polymer, filler, and oil, as is common practice on the market.

[0016] In particular, to adjust the viscosity, the rubber compound can additionally contain at least one plasticizer. Any plasticizer known to a person skilled in the art that is compatible with the respective silicone rubber can be used. The use of silicone oil has proven particularly advantageous in this regard, as it is highly compatible with the silicone rubber. Crosslinking silicone oils, which participate in the crosslinking of the rubber compound and are often referred to as crosslinkable silicone oils, have proven particularly suitable. These lead to a further significant reduction in the potential for plasticizer exudation, as can sometimes be observed with prior art insulating hoses.

[0017] To increase the elasticity and compressibility of the rubber compound, the rubber compound has a porous structure. This can simultaneously improve the thermal and acoustic insulation properties of the rubber compound. This porous structure is achieved through the use of hollow microspheres mixed into the rubber compound. Hollow microspheres, often simply referred to as microspheres, are hollow spheres (microspheres) with a diameter in the µm range made of glass, phenolic resin, carbon, or thermoplastic material. They are available in expandable form, where they are filled with a blowing agent and expand upon heating, or in pre-expanded form, where the expansion is already complete.Preferably, the rubber mixture contains 2 to 200 phr microspheres, particularly preferably 2 to 30 phr, most preferably 2 to 15 phr already expanded microspheres made of thermoplastic material, so that the rubber mixture already has a pore structure before the formation of the elastic layer or before crosslinking.

[0018] In addition to the increased elasticity and compressibility of the rubber compound, microspheres offer the further advantage of forming a closed-pore structure, which is better suited for insulation purposes due to reduced convection within the pores. The higher the quantity of expanded microspheres, the better the insulation effect due to the increased pore size. However, excessively large quantities of microspheres can lead to processing problems during compound production or application.

[0019] Alternatively, the rubber compound can contain 10 to 200 phr glass microspheres. This variant yields a rubber compound with higher stability but lower elasticity and compressibility, since glass microspheres, unlike thermoplastic microspheres, cannot be compressed. This reduced elasticity and compressibility, which may still be greater than that of known sensors of this type, can be accepted in favor of the increased stability and lifespan of the elastic layer, depending on the application.

[0020] The present invention is based on the finding that by means of such a sensor, an exceptionally sensitive sensor can be created due to the comparatively high elasticity or compressibility of the elastic layer of the sensor, which can deliver correspondingly precise measured values. At the same time, such a sensor can be easily and robustly integrated into such an elastic bearing element. In this way, a comparatively accurate measurement of the force in the force flow of such an elastic bearing element can be created without the use of external components that may require protection. At the same time, such a sensor or such an elastic bearing arrangement can be implemented easily and / or inexpensively. Such a sensor or such an elastic bearing arrangement can also be robust against environmental influences such as water, moisture, dust, mud, stones and the like.

[0021] The sensor can be positioned within the elastomer element or between the elastomer element and one of the two bodies. Depending on the application, this allows for an arrangement that enables the most effective and accurate measurement of the force flow.

[0022] Another advantage is that such a sensor can be positioned directly in the force flow between the two bodies for direct force measurement. This eliminates the need for force transmission, e.g., via a fluid.

[0023] Furthermore, it is advantageous that such a sensor can be integrated into or attached to the elastomer element before its vulcanization. This can simplify the manufacturing of the elastic bearing element as a whole, thus enabling the sensor function.

[0024] A further advantage is that such an elastic bearing element can also be created retroactively by integrating such a sensor into an existing elastic bearing element. Thus, the properties and advantages achievable according to the invention can be retrofitted and utilized in existing, suitable elastic bearing elements.

[0025] Multiple such sensors, which can be designed and arranged identically or differently, can also be used. This allows measurement values ​​to be recorded independently at multiple locations. These multiple measurement values ​​can be evaluated, for example, to detect tilting and / or twisting of the elastic bearing element, as well as to determine the extent of the tilting or twisting.

[0026] The sensor can be designed and arranged in all sorts of shapes. For example, it can be laid out in a straight line, curved, spiral, circular, as an inner and outer circle, in a cross shape, triangular, square, etc. This allows for the most representative force measurement possible, depending on the application.

[0027] According to one aspect of the present invention, the sensor is coaxial, wherein the first electrode is cylindrically surrounded at least in sections, preferably completely, by the elastic layer, and wherein the elastic layer is cylindrically surrounded at least in sections, preferably completely, by the second electrode. This enables a compact arrangement of the sensor elements to be achieved in order to obtain a space-saving sensor of this type. Furthermore, a sensor can be created which, due to its rotational symmetry, can be used as the axis of rotational symmetry regardless of its orientation about the longitudinal axis, since a radial change in distance in any orientation leads to the same change in the distance between the two electrodes. Thus, the same change in distance can always be detected regardless of the orientation about the longitudinal axis.

[0028] According to a further aspect of the present invention, the first electrode is designed as an electrically conductive wire made of solid material or as a stranded wire, wherein the wire preferably comprises or consists of copper, aluminum, silver, or gold. A wire made of solid material can be easily manufactured and processed. A stranded wire can have greater extensibility than a wire made of solid material, so that the sensor can withstand force loads for longer and thus have a longer service life. The materials copper, aluminum, silver, or gold can have high electrical conductivity, whereby, depending on the application, a balance must be struck between the degree of electrical conductivity, the material costs, and possibly other properties of the materials.

[0029] According to a further aspect of the present invention, the second electrode is configured as an electrically conductive layer in the form of a film or as a braid, knitted fabric, or woven fabric, wherein the layer preferably comprises or consists of copper, aluminum, silver, or gold. By using a layer, a second electrode with a maximum surface area can be created, so that a force flow can be detected over a correspondingly large area, provided the layer is at least substantially flat. When using the second electrode layer in a cylindrical shape in a coaxially configured sensor, the first electrode can be enclosed by the second electrode to create the coaxial arrangement. In any case, a layer in the form of a film can be produced simply and cost-effectively. The alternative configuration of the layer as a braid, knitted fabric, or woven fabric, similar to a stranded wire as the first electrode, can result in higher extensibility than with a film.A braid is a flat structure created by braiding, the regular interlacing of several strands of flexible material. A woven fabric is a textile structure made up of at least two thread systems crossed at right angles or nearly at right angles. The difference between a braid and a woven fabric lies in the fact that the threads are not introduced at right angles during braiding. A knitted fabric is a thread system produced by forming loops.

[0030] According to a further aspect of the present invention, the sensor also has at least one protective layer, which is preferably arranged directly on the side of at least one electrode, preferably the second electrode, facing the elastomer element. This protects the electrode on this side. This protective layer can serve to protect the electrode in its uninstalled state, but also to protect it from the elastomer element in its installed state.

[0031] According to a further aspect of the present invention, the protective layer is designed to be electrically insulating. This allows the electrode on this side to be electrically insulated, so that an electrical sensor function can be performed better compared to another electrode on the side facing away from the protective layer.

[0032] According to a further aspect of the present invention, the protective layer is elastic, wherein the protective layer preferably comprises a silicone, particularly preferably made of a silicone. In this way, the force can be transmitted through the protective layer with as little or no interference as possible, while utilizing the advantageous properties of the protective layer. This can be achieved simply, robustly, and / or cost-effectively by using silicone.

[0033] According to a further aspect of the present invention, at least one electrode, preferably the second electrode, is in direct contact with the elastomer element, wherein the electrode preferably has, at least in sections, preferably completely, an adhesion promoter, preferably further an adhesive elastomer mixture, on the side facing the elastomer element, so that adhesion is established between the electrode and the elastomer element. This makes it possible to achieve the most direct and thus undisturbed force transmission possible. The use of an adhesion promoter and, if appropriate, an additional adhesive elastomer mixture can improve the connection between the electrode and the elastomer element, so that the direct force transmission can also be increased or ensured, which can improve the accuracy of the force measurement. The service life of the sensor can also be improved as a result.

[0034] According to the present invention, the sensor is elongated, wherein the sensor is arranged at least in sections in the direction of its elongated extent at least substantially transversely to the direction of the force flow.

[0035] An elongated sensor is defined as one that extends significantly further in one direction, namely its longitudinal direction, than in the other two Cartesian spatial directions, namely the transverse direction and the vertical direction. Viewed in cylindrical coordinates, the elongated sensor extends considerably further along its longitudinal axis than in the radial direction. This elongated extension allows for the detection of a large area within the elastomeric element without unduly interrupting the force transmission through the element. Positioning the elongated sensor at least substantially, and preferably precisely, perpendicular to the direction of force flow enables the use of a very short sensor. Furthermore, the force of the force flow acting perpendicular to the sensor can be directly detected.

[0036] According to a further aspect of the present invention, the sensor extends at least partially, preferably completely, in a straight line. This can simplify the subsequent introduction of such a sensor into an elastomer element, since a straight hole can be introduced from the outside as a blind hole or as a through-opening to accommodate the sensor. This can be achieved quickly and easily in terms of production, e.g., by drilling, due to the straightness of a bore. Furthermore, a region of the elastomer element that extends as far as possible can be detected by a sensor that extends in a straight line and is as short as possible, which can keep the costs required for this to a minimum.

[0037] According to a further aspect of the present invention, the sensor extends at least partially, preferably completely, in a ring shape. This allows for a comparatively large area over which the sensor can detect the force of the force flow. This can increase the accuracy of the detection.

[0038] According to a further aspect of the present invention, the sensor is designed in two parts, with the first electrode being continuous and the second electrode being interrupted. This allows two measurements to be acquired with one sensor, so that a force distribution can be detected, e.g., whether the load is concentrated on the left or right.

[0039] Simultaneously, the respective force values ​​can be used to sensorily detect the forces and calculate the difference in load. The total force can be determined by summing the two individual measurements.

[0040] According to a further aspect of the present invention, the sensor is designed such that the change in the distance between the two electrodes is proportional to the force of the force flow between the first body and the second body. This can be achieved by selecting the geometries of the electrodes and their distance from each other, depending on the application. A proportional relationship between distance or change in distance and force is understood to be a linear relationship, which can be evaluated accordingly simply and directly.

[0041] According to a further aspect of the present invention, the sensor is designed such that the capacitance between the two electrodes is proportional to the distance between the two electrodes. The linear relationship between the capacitance and the distance can be detected and evaluated in a correspondingly simple and direct manner.

[0042] According to a further aspect of the present invention, the elastic layer of the sensor exhibits at least substantially the same elasticity as the elastomer element. This allows the sensor to be positioned in the force flow in such a way that the force can be detected as representatively as possible, because, due to the identical elasticity of the elastomer element and the sensor, the same force can flow through the sensor as through the elastomer element. This can improve the quality of the detected sensor signal and simplify its evaluation.

[0043] Several embodiments of the present invention are explained below in connection with the following figures. These show: Fig. 1 shows a schematic longitudinal section of a sensor of an elastic bearing element according to the invention; Fig. 2 shows a schematic cross-section of the Fig. 1Fig. 3 shows a perspective view of an elastic bearing element according to a first embodiment according to the invention; Fig. 4 shows a perspective view of an elastic bearing element according to a second embodiment according to the invention; and Fig. 5 shows a perspective view of an elastic bearing element according to a third embodiment according to the invention.

[0044] Fig. 1 shows a schematic longitudinal section of a sensor 2 of an elastic bearing element 1 according to the invention. Fig. 2 shows a schematic cross-section of the Fig. 1The sensor 2 extends longitudinally along its longitudinal axis L, from which a radial direction R extends perpendicularly. Radially inside the sensor 2 is a first electrode 21, which can also be referred to as the inner electrode 21. Radially around the first electrode 21 is a cylindrical elastic layer 20, which surrounds the first electrode 21 in the circumferential direction U. The elastic layer 20 is surrounded radially outside by a second electrode 22 in the circumferential direction U.

[0045] The two electrodes 21, 22 are electrically conductive and are contacted externally along the longitudinal axis L (not shown). The intervening layer 20 is elastic and electrically insulating, allowing, for example, the detection of capacitance between the two electrodes 21, 22. If a force or pressure is applied externally to the second electrode 22, the radial distance between the two electrodes 21, 22 decreases at this point. This can be detected via a corresponding change in capacitance and converted into a force or pressure value, so that the sensor 2 can also be referred to as a force or pressure sensor 2.

[0046] The elastic layer 20 comprises a rubber compound containing at least one silicone rubber as its sole rubber component and microhollow spheres. This allows for the creation of an elastic, electrically insulating layer 20 between the two electrodes 21, 22, which is also highly compressible, enabling the sensor to detect even small forces with comparatively high accuracy.

[0047] Optional and in the Fig. 1 and 2 The second electrode 22 is shown enclosed by a ring-shaped protective layer 23 in the circumferential direction U to protect against external influences. The protective layer 23 is made of an elastic and electrically insulating silicone compound. The protective layer 23 can also be omitted.

[0048] Fig. 3shows a perspective view of an elastic bearing element 1 according to the invention according to a first exemplary embodiment. A sensor 2 is arranged linearly and perpendicular to the main deflection direction A of the elastic bearing element 1, integrated into the latter. The elastic bearing element 1 has an elastomer body 10 in the form of a rubber spring 11, which is arranged between a first body 11 as the lower stop element 11 and a second body 12 as the upper stop element 12. The sensor 2 is arranged within the elastomer body 10 in such a way that forces from the force flow in the main deflection direction A of the elastomer body 10 can be detected by sensors as described above.

[0049] Fig. 4shows a perspective view of an elastic bearing element 1 according to the invention according to a second exemplary embodiment. In this case, the sensor 2 is designed to be interrupted, with the first electrode 21 being designed to be continuous.

[0050] Fig. 5 shows a perspective view of an elastic bearing element 1 according to the invention according to a third exemplary embodiment. In this case, the sensor 2 is arranged in a ring shape to increase the sensor-effective area. Reference symbol list (part of the description)

[0051] AMain deflection direction of the elastic bearing element 1 LLongitudinal axis Rradial direction UCircumferential direction 1Elastic bearing element 10Elastomer element; rubber spring 11First body; lower stop element 12Second body; upper stop element 2 Sensor; pressure sensor; force sensor 20 Elastic layer; rubber compound 21 First electrode; inner electrode 22 Second electrode; outer electrode 23 Protective layer

Claims

1. Elastic bearing element (1) having at least one first body (11), having at least one second body (12), and having at least one elastomer element (10) arranged in the direction of a force flow between the first body (11) and the second body (12), furthermore having at least one sensor (2) configured and arranged to detect directly or indirectly a force in the force flow between the first body (11) and the second body (12), wherein the sensor (2) comprises at least one elastic layer (20), at least one first electrode (21) and at least one second electrode (22), , wherein the elastic layer (20) is arranged at least in sections between the first electrode (21) and the second electrode (22), wherein the sensor (2) is arranged in the force flow between the first body (11) and the second body (12) such that, by means of the force, the distance between the two electrodes (21, 22) can be altered and, by this means, the force can be at least partly detected, characterized in that the elastic layer (20) comprises a rubber mixture comprising at least one silicone rubber, as the sole rubber component, and hollow microspheres, wherein the sensor (2) is embodied in an elongate fashion, wherein the sensor (2), at least in sections in the direction of its elongate extent, is arranged at least substantially transversely with respect to the direction of the force flow.

2. Elastic bearing element (1) according to Claim 1, characterized in that the sensor (2) is embodied in a coaxial fashion, wherein the first electrode (21) is surrounded by the elastic layer (20) cylindrically at least in sections, preferably completely, and wherein the elastic layer (20) is surrounded by the second electrode (22) cylindrically at least in sections, preferably completely.

3. Elastic bearing element (1) according to Claim 1 or 2, characterized in that the first electrode (21) is embodied as an electrically conductive wire composed of solid material or as a multiple-stranded wire, wherein the wire preferably comprises or consists of copper, aluminium, silver or gold.

4. Elastic bearing element (1) according to any of the preceding claims, characterized in that the second electrode (22) is embodied as an electrically conductive layer as a film or as a braiding, a knitted fabric or a woven fabric, wherein the layer preferably comprises or consists of copper, aluminium, silver or gold.

5. Elastic bearing element (1) according to any of the preceding claims, characterized in that the sensor (2) furthermore comprises at least one protective layer (23) arranged, preferably directly, on that side of at least one electrode (21, 22), preferably of the second electrode (22), which faces the elastomer element (10).

6. Elastic bearing element (1) according to Claim 5, characterized in that the protective layer (23) is embodied in an electrically insulating fashion.

7. Elastic bearing element (1) according to Claim 5 or 6, characterized in that the protective layer (23) is embodied in an elastic fashion, wherein the protective layer (23) preferably comprises a silicone, particularly preferably consists of a silicone.

8. Elastic bearing element (1) according to any of Claims 1 to 4, characterized in that at least one electrode (21, 22), preferably the second electrode (22), is in direct contact with the elastomer element (10), wherein the electrode (21, 22) preferably comprises on the side facing the elastomer element (10), at least in sections, preferably completely, an adhesion promoter, preferably furthermore an adhesive elastomer mixture, thereby producing adhesion between the electrode (21, 22) and the elastomer element (10).

9. Elastic bearing element (1) according to any of the preceding claims, characterized in that the sensor (2) extends rectilinearly at least in sections, preferably completely.

10. Elastic bearing element (1) according to any of the preceding claims, characterized in that the sensor (2) extends in a ring-shaped fashion at least in sections, preferably completely.

11. Elastic bearing element (1) according to any of the preceding claims, characterized in that the sensor (2) is embodied in a divided fashion, wherein the first electrode (21) is embodied in a continuous fashion and the second electrode (22) is embodied in an interrupted fashion.

12. Elastic bearing element (1) according to any of the preceding claims, characterized in that the sensor (2) is embodied such that the alteration of the distance between the two electrodes (21, 22) is proportional to the force of the force flow between the first body (11) and the second body (12).

13. Elastic bearing element (1) according to any of the preceding claims, characterized in that the sensor (2) is embodied such that the capacitance between the two electrodes (21, 22) is proportional to the distance between the two electrodes (21, 22).

14. Elastic bearing element (1) according to any of the preceding claims, characterized in that the elastic layer (20) of the sensor (2) at least substantially has the same elasticity as the elastomer element (10).