Electromechanical converter element

Abstract

An electromechanical converter element (1) has a first electrode layer (4) and a second electrode layer (6) of an electrically conductive material, the second electrode layer being spaced apart from the first electrode layer. The first and the second electrode layer (4, 6) each have an electrically conductive electrode layer contact (7, 8), which can be connected to one another via a first measuring device (9). An electret structure (2) of an electrically insulating electret material is arranged between the first and second electrode layer (4, 6) such that in the event of a deformation of the electret structure (2) and / or of the first electrode layer (4) or in the event of a displacement of the electret structure (2) and at least one electrode layer (4, 6) relative to one another, the ratio of charge amounts in the first to the second electrode layer (4, 6) changes. The electromechanical converter element (1) has at least one conductor layer (10) of an electrically conductive material with a first electrically conductive conductor layer contact (11) and a second electrically conductive conductor layer contact (12), wherein a deformation of the first conductor layer (10) causes a change to the electric conductivity between the first electric conductor layer contact (11) and the second electric conductor contact (12) of the first conductor layer (10).

Description

[0001] Electromechanical transducer element

[0002] The invention relates to an electromechanical transducer element having a first electrode layer made of an electrically conductive material, with a second electrode layer made of an electrically conductive material arranged at a distance therefrom, wherein the first and second electrode layers each have an electrically conductive electrode layer contact which can be connected to one another via a first measuring device.

[0003] Electromechanical transducers can be used advantageously in many different application areas. Electromechanical transducers can be used as force or displacement sensors and, depending on the materials used and the design, can acquire measured values ​​with varying degrees of sensitivity. Electromechanical transducers can also be used as actuators and, depending on their design, can generate forces or movements with high dynamics.

[0004] Numerous different converter principles are known from practice. Electromechanical converter elements can be adapted to the specific application with regard to many properties, depending on the specific requirements, and are therefore used in a wide variety of different applications.

[0005] One application example for electromechanical transducer elements is pressure sensors. Pressure sensors with high sensitivity and a wide measuring range can be used advantageously for condition monitoring in process and plant engineering. Portable and flexible pressure sensors can be used to monitor human activity and health. Numerous different pressure sensors are known from practice. They differ in terms of their respective design, but also in the sensitivity and measuring range of the respective pressure sensor, thus covering a very wide variety of applications.

[0006] Conventional pressure sensors are usually based on a single transducer principle, which presents considerable design and metrological challenges and often entails major limitations when static pressures and dynamic pressure changes are to be measured simultaneously. Strain gauges, which are suitably applied to a deforming body, can be used to measure forces or pressures acting on the deforming body. Strain gauges are therefore suitable for measuring static pressures. A capacitive sensor can easily measure the displacement or deformation of two spaced-apart electrodes relative to one another. Capacitive sensors are therefore also suitable for measuring dynamic pressure changes.Various electromechanical transducer elements are also known from practice with which both static pressure and dynamic pressure changes can be recorded. For example, a suitable composite material which contains a sufficient number of electrical particles embedded in a polymer material and has been made electrically conductive can be contacted at two regions arranged at a distance from one another. The application of force changes the structure of the composite material, causing a change in conductivity of the composite material, which in turn causes a change in electrical resistance. The deformation of the piezoelectric particles within the composite material simultaneously causes a change in voltage. However, the simultaneous measurement of these two quantities is not easily possible.

[0007] In other electromechanical transducer elements, different layers of a piezoresistive material and a piezoelectric material are each arranged between electrode layers. When the piezoresistive layer is deformed or displaced relative to the associated electrode layers, the electrical resistance of the piezoresistive layer changes, which can be used to detect a static pressure causing this deformation or relative displacement. Pressure changes, however, can be detected using the piezoelectric layer.

[0008] However, the production of piezoresistive or piezoelectric materials, and especially the production of suitable composite materials for pressure sensors, is associated with considerable effort and is cost-intensive. Due to the properties of piezoresistive or piezoelectric materials, economically viable applications for pressure sensors containing these materials are comparatively limited.

[0009] It is therefore considered an object of the present invention to design an electromechanical transducer element in such a way that the electromechanical transducer element can be manufactured and used in a simple and cost-effective manner and enables simultaneous detection of static pressures and dynamic pressure changes.

[0010] This object is achieved according to the invention in that an electret structure made of an electrically insulating electret material is arranged between the first and second electrode layers, so that upon deformation of the electret structure and / or the first electrode layer or upon displacement of the electret structure and at least one electrode layer relative to one another, the ratio of the charge quantities located in the first and second electrode layers to one another changes, and wherein the electromechanical transducer element has a first conductor layer made of an electrically conductive material with a first electrically conductive conductor layer contact and with a second electrically conductive conductor layer contact, wherein the first conductor layer is designed in such a way thatthat a deformation of the first conductor layer causes a change in the electrical conductivity between the first electrical conductor layer contact and the second electrical conductor layer contact of the first conductor layer. By arranging an electret structure between the first and second electrode layers, a quantity of charge predetermined by the electret structure is arranged between the first and second electrode layers and, due to the properties of the electret structure, a quasi-permanent electric field is generated in its surroundings. Each deformation of the electret structure leads to a change in the electric field acting on the first and second electrode layers, whereby the respective charges held on the first electrode layer and on the second electrode layer,or accumulating charge quantities change this change in the charge quantities or a change in the ratio of the charge quantities located in the first and second electrode layers to one another can be detected with a suitable measuring device in such a way that, based on the detected change in the charge quantities or the ratio of the charge quantities on the first and second electrode layers, conclusions can be drawn about the deformation of the electret structure that caused the detected change. In the same way, a displacement of the electret structure relative to at least one electrode layer also leads to a change in the charge quantity held or accumulating on the respective electrode layer, which can be detected with the measuring device and also allows conclusions to be drawn about the relative displacement of the at least one electrode layer to one another. It is also conceivablethat an electrical capacitance of the electromechanical transducer element or between two components of the electromechanical transducer element can be detected and used, for example, to determine a deformation that changes the electrical capacitance and a force that causes this deformation. Furthermore, an electrical potential difference between two components, such as between the first and second electrode layers, can also be detected and used to determine a deformation or a state of the electromechanical transducer element.

[0011] The electret structure is made of an electret material, which is an electrically insulating material containing quasi-permanently stored electrical charges or quasi-permanently aligned electrical dipoles, thus generating a quasi-permanent electrical field in its surroundings or within its interior. The use of the electret structure generates the electrical field required to detect dynamic pressure changes, which is responsible for the change in the amount of charge when the electret structure and the two electrode layers are deformed or displaced relative to one another. An external energy supply or the external generation of an electrical potential difference or an electrical field is not necessary, so the electromechanical transducer element can be used very energy-efficiently to detect dynamic pressure changes.

[0012] It has been shown that with the electromechanical transducer element according to the invention, dynamically changing forces can be detected with significantly shorter response times and thus far more quickly than with conventional resistive sensors. One example of this is the detection of an intention to move with an electret structure, which cannot be measured with resistive sensors due to the typically slower response time. Furthermore, conventional resistive sensors are hardly or not at all suitable for dynamic changes in forces with a frequency above 100 Hz.

[0013] The change in the charge quantities on the first or second electrode layer caused by a deformation or displacement of the electret structure can be detected, for example, with a suitable charge amplifier and converted into a processable and analyzable voltage signal. Depending on the expected dynamics of the deformation or displacement of the electret structure and taking into account the structural design of the electromechanical transducer element, the measuring device can also be designed as a voltage measuring device and contacted in a suitable manner with the first electrode layer and the second electrode layer.

[0014] The electromechanical transducer element can optionally be designed such that either the electret structure and / or at least one electrode layer can be deformed by a force acting thereon and this deformation can be detected by the measuring device. It is also conceivable for the electret structure and / or at least one electrode layer to be rigid and to be able to be displaced relative to one another by the action of a force. In this case, for example, the electret structure and at least one electrode layer can be connected to one another via a suitable spring device, wherein the spring device generates a restoring force upon a relative deflection of the electret structure with the associated electrode layer, which restoring force tends to displace the electret structure and the electrode layer back into an initial position.It is also conceivable for the electret structure and / or at least one electrode layer to be connected and mounted to a housing or a frame of the electromechanical transducer element via a suitably designed spring device. The electret structure or an electrode layer are considered rigid if, when a force is applied to the electret structure or the electrode layer as intended, no deformation of the electret structure or an electrode layer is caused that would affect the measured values ​​recorded by the measuring device.

[0015] By arranging the electret structure between the first and second electrode layers, it is possible in particular to detect dynamic changes in a force acting on the electromechanical transducer element. The first conductor layer, the deformation of which brings about a change in the electrical conductivity of this first conductor layer, which can be detected via the contact between the first and second conductor layers arranged spaced apart from one another, makes it particularly advantageous to detect a static force acting on the first conductor layer and thus on the electromechanical transducer element. By combining the two action and measuring principles, it is possible with the electromechanical transducer element according to the invention to precisely detect both static and highly dynamic force effects, or pressures and pressure changes, and to subject them to suitable analysis.For the production of an electrode layer or a first conductor layer, numerous suitable materials and production methods are known which enable a cost-effective production of an electromechanical transducer element according to the invention in large quantities.

[0016] Numerous electret materials are known from practice with which a suitable electret structure can be produced in a simple and cost-effective manner. It is fundamentally possible for the electret structure to be a layer made of such a suitable electret material. The individual layers of the electromechanical transducer element can then be arranged one above the other and, if appropriate, formed in planar contact with one another with adjacent layers of the electromechanical transducer element. Such an electromechanical transducer element can, for example, be printed with the aid of suitable printing devices onto a surface of a component or a product in which static and dynamic forces acting on the component or product are to be recorded. The electrically conductive electrode layer contacts and conductor layer contacts can also be printed on.Using suitable printing devices, electromechanical transducer elements according to the invention can be printed particularly cost-effectively onto almost any surface of a component or product. The electret structure arranged between the first and second electrode layer forms an electrically insulating layer which is required to prevent an electrical short circuit between the two electrode layers. The electrode layers and / or the first conductor layer can each be of full-surface construction and can each partially or completely cover the electret structure. In particular, the first conductor layer can also be of flat, layered conductor structure. The layered conductor structure can, for example, have a linear profile in a layer plane that is optionally curved three-dimensionally.The layered conductor structure can also have a curved or meandering course in a planar or three-dimensionally curved layer plane. Each electrode layer or conductor layer can be designed as a planar layered structure and completely fill or cover an area within a peripheral edge delimiting the planar layered structure. Each electrode layer or conductor layer can also have a two-dimensional or three-dimensional structure, wherein the three-dimensional structure is either formed on only one side and opposite a planar outer side, or else is formed on both sides. The three-dimensional structure can be produced by a thickness of the electrode layer or conductor layer that changes in some areas, or, with a constant thickness, by a curvature of the electrode layer or conductor layer extending parallel to the electret structure.

[0017] According to a particularly advantageous embodiment of the inventive concept, the first electrode layer is designed as a first conductor layer. In this way, a particularly simple and compact design of the electromechanical transducer element can be achieved. A corresponding variant of the electromechanical transducer element has a first electrode layer designed as a conductor layer and a second electrode layer arranged at a distance therefrom, between which the electret structure is arranged, which is also designed as a further layer made of an electret material. When the first electrode layer designed as a conductor layer is deformed, this changes the electrical conductivity of this first conductor layer, which can be detected, for example, via a change in a voltage drop between the first conductor layer contact and the second conductor layer contact.At the same time, deformation of the first electrode layer, designed as a conductor layer, causes a change in the electric field generated by the electret material on the first electrode layer, which can be detected with the aid of the first measuring device, which is connected to the first and second electrode layers via the electrode layer contact. If both the first and second electrode layers and the electret structure are designed as layers arranged one above the other and optionally printed on top of one another, an external force usually deforms not only the first electrode layer, but all of the layers.When pressure is applied to the electromechanical transducer element, for example, the electret structure can be deformed and compressed, which also changes the distance between the electrode layers surrounding the electret structure on both sides and thus the amount of charge held or accumulated on the two electrode layers. In many cases, this can also result in increased sensitivity of the electromechanical transducer element.

[0018] It may be expedient, and is optionally provided, for the electromechanical transducer element to have a second conductor layer made of an electrically conductive material with a first electrically conductive conductor layer contact and with a second electrically conductive conductor layer contact, the second conductor layer being designed such that deformation of the second conductor layer brings about a change in the electrical conductivity between the first electrical conductor layer contact and the second electrical conductor layer contact of the second conductor layer. The second conductor layer can either be an additional, separately produced second conductor layer arranged in addition to the second electrode layer, or it can be a corresponding design of the second electrode layer.With the second conductor layer, a force acting on the second conductor layer can be detected independently of the first conductor layer and, in particular, a static force acting on the second conductor layer can be advantageously measured with an associated measuring device.

[0019] Depending on the design of the electromechanical transducer element, it can be provided that when an external force is applied, an essentially identical force acts on the first conductor layer and on the second conductor layer. In this case, the respectively detected changes in the electrical conductivity of the detected conductor layer and the second conductor layer should match, so that, based on the two measured values, a particularly precise evaluation of the force acting on the electromechanical transducer element is possible. Optionally, it can also be provided that the first conductor layer and the second conductor layer either have different deformabilities or are mounted differently relative to the electret structure and / or the respective other conductor layer in order to advantageously influence the accuracy and, if appropriate, a measuring range of the electromechanical transducer element.The first conductor layer and the second conductor layer can also be made of different materials.

[0020] Instead, it can also be provided by a different structural design of the electromechanical transducer element that an external force should have a different effect on the first conductor layer and on the second conductor layer and that this different effect on the first conductor layer and on the second conductor layer can be detected separately.

[0021] According to one embodiment of the inventive concept, it can be provided that the first electrode layer is arranged on a first surface of the electret structure, and that when a predetermined force is applied, a deformation of the electret structure with the first electrode layer arranged on the first surface is brought about. It is also conceivable that instead or in addition thereto, the second electrode layer is arranged on a second surface of the electret structure opposite the first surface of the electret structure, and that when a predetermined force is applied, a deformation of the electret structure with the second electrode layer arranged on the second surface is brought about.The respective deformability of the electret structure and of a first and / or second electrode layer arranged directly on a surface of the electret structure can be influenced and predetermined by a suitable choice of material and appropriate dimensioning, for example, of the layer thickness of the individual layers. Such a design of the electromechanical transducer element particularly advantageously enables such an electromechanical transducer element to be cost-effectively applied to a surface of a component or a product or to be printed directly onto it.

[0022] According to a further embodiment of the inventive concept, it is optionally provided that the first electrode layer and / or the second electrode layer is arranged at a distance from the electret structure, so that when a force is applied as intended, a displacement of the first and / or second electrode layer arranged at a distance from the electret structure is effected relative to the electret structure. Such a configuration makes it possible to design the electret structure and / or one or both electrode layers as rigid layers or rigid structures. Such a structural configuration can be advantageous in various fields of application.

[0023] Advantageously, particularly with such a design of the individual layers, it is optionally provided that the first and / or second electrode layer arranged at a distance from the electret structure is mounted so as to be displaceable relative to the electret structure against a spring force. For this purpose, it can furthermore be optionally provided that the first and / or second electrode layer arranged at a distance from the electret structure is operatively connected to the electret structure via a spring device. By means of a suitable design of the spring device and a resulting specification of the spring force, a measuring range for the electromechanical transducer element can be specified in a simple manner, within which the electromechanical transducer element can detect the forces acting on the electromechanical transducer element with a sensitivity sufficient for the application in question.As a result, the measuring range and sensitivity of the electromechanical transducer element are less dependent on the material and dimensions of the electret structure and the individual electrode layers or conductor layers, but can be specified within a wide range by a suitable design of the spring device and the spring forces or restoring forces generated thereby. If necessary, the spring device can be designed to be manually or automatically adjustable, so that the restoring forces generated by the spring device can change and the electromechanical transducer element can be adapted to different applications or to different measuring ranges and sensitivities.

[0024] It can optionally be provided that the first and / or second electrode layer arranged at a distance from the electret structure and / or the electret structure is connected to a support structure of the electromechanical transducer element via a spring device. The support structure can be a housing or a frame, for example. A support structure makes it possible to equip the electromechanical transducer element with a spring device without the spring device having to be supported on an external component or on an external object, which usually has to be done separately or during assembly of the electromechanical transducer element at the intended location. The support structure, on the other hand, allows the spring device to be arranged and set up during manufacture of the electromechanical transducer element, independently of the later use of the electromechanical transducer element.

[0025] Depending on the intended use of the electromechanical transducer element, the first conductor layer and / or optionally the second conductor layer may be made of a piezoresistive material. In piezoresistive materials, which are often manufactured as semiconductor materials, deformation typically leads to a significantly greater change in resistance than in metals, which is why piezoresistive materials can achieve high sensitivity and an advantageously high signal-to-noise ratio.

[0026] According to an advantageous embodiment of the inventive concept for various fields of application, the electromechanical transducer element can comprise a first electret structure and a second electret structure arranged at a distance therefrom, both of which are arranged between the first electrode layer and the second electrode layer. Air or another electrically conductive or non-conductive spacer structure can be arranged between the two electret structures. The spacer structure can be deformable or compressible, so that the distance between the two electret structures is changed by the application of pressure.

[0027] However, it can also be provided that a conductor layer with a first electrical conductor layer contact and with a second conductor layer contact is arranged between the two electret structures. However, it can also preferably be provided that two conductor layers are arranged between the first electret structure and the second electret structure, electrically insulated from one another. The two conductor layers are expediently arranged electrically insulated from one another. For this purpose, air or another electrically non-conductive spacer structure can be arranged between the two conductor layers.The two conductor layers can also be arranged on mutually facing outer sides of the two electret structures in such a way that when the two electret structures come into contact, the two conductor layers run laterally next to one another and, when the electromechanical transducer element is used as intended, no electrically conductive connection can arise between the two conductor layers. The two electret structures are expediently made from a deformable electret material so that when a force is applied to the electromechanical transducer element as intended, at least one electret structure and, with it, the conductor layer arranged on the relevant electret structure is deformed, so that this deformation can be detected via the resulting change in resistance in the conductor layer.

[0028] The various possibilities and aspects of the electromechanical transducer element according to the invention have been described primarily with reference to its intended use as a force or pressure sensor. However, the electromechanical transducer element can also be used as an actuator or for heat generation, for example, by applying a variable electrical voltage between the two electrode layers or by generating a current flow through at least one conductor layer, which causes heating of the conductor layer depending on the respective electrical resistance of the conductor layer.

[0029] The invention therefore also relates to an actuator or a sensor, each of which has an electromechanical transducer element with the features or combinations of features described above.

[0030] Below, various embodiments are explained, which are illustrated schematically in the drawings. It shows:

[0031] Figure 1 shows a first embodiment of an electromechanical transducer element with an electret structure, with a first electrode layer and with a second electrode layer which is designed and contacted as a conductor layer,

[0032] Figure 2 shows a different embodiment of the electromechanical transducer element, in which both electrode layers are each designed and contacted as a conductor layer,

[0033] Figure 3 shows a modified embodiment of the electromechanical transducer element, wherein the electrode layer formed as a conductor layer is arranged at a distance from the electret structure via a spring device,

[0034] Figure 4 shows a further modified embodiment of the electromechanical transducer element, wherein in addition to the first electrode layer and a conductor layer, which are arranged on opposite outer sides of the electret structure, a second electrode layer is mounted at a distance therefrom via a spring device,

[0035] Figure 5 shows a further modified embodiment of the electromechanical transducer element, wherein, in contrast to the variant shown in Figure 4, it is not the second electrode layer but the electret structure with the first electrode layer and the conductor layer arranged thereon that is arranged displaceably relative to the second electrode layer via a spring device,

[0036] Figure 6 shows a further modified embodiment of the electromechanical transducer element, wherein two electret structures are arranged at a distance from one another and an electrode layer and a conductor layer are arranged on each electret structure, and wherein one electret structure is displaceable relative to the other electret structure via a spring device, Figure 7 shows a further modified embodiment of the electromechanical transducer element similar to the variant shown in Figure 6, wherein both electret structures are each mounted displaceably relative to one another via a spring device,

[0037] Figure 8 shows a modified embodiment of the electromechanical converter element similar to the variant shown in Figure 1, wherein a voltage measuring device is used instead of a charge measuring device,

[0038] Figure 9 shows a modified embodiment of the electromechanical converter element similar to the variant shown in Figure 5, wherein a voltage measuring device is used instead of a charge measuring device, and

[0039] Figure 10 shows a further modified embodiment of the electromechanical transducer element similar to the variant shown in Figure 7, wherein a voltage measuring device is used instead of a charge measuring device.

[0040] Figure 1 schematically illustrates a first exemplary embodiment of an electromechanical transducer element 1 designed according to the invention. The electromechanical transducer element 1 comprises a layered electret structure 2 made of an electrically insulating electret material, which contains quasi-permanent electrical charges and thereby generates a quasi-permanent electric field in the vicinity of the electret structure 2. When the electromechanical transducer element 1 is used as intended, the electret structure 2 is deformable and can be both bent and compressed.

[0041] On a first surface 3 of the electret structure 2, a first electrode layer 4 is arranged in direct contact, which covers the electret structure 2 over its entire surface but does not completely overlap laterally. The first electrode layer 4 can be essentially planar or can have a two-dimensional or three-dimensional structure. On an opposite second surface 5 of the electret structure 2, a second electrode layer 6 is arranged, likewise in direct contact, which also covers the electret structure 2 over its entire surface but does not completely overlap laterally.The first electrode layer 4 and the second electrode layer 6 are each made of an electrically conductive material, wherein the electret structure 2 forms an electrical insulation between the two electrode layers 4, 6 and prevents a direct electrically conductive contact between the two electrode layers 4, 6.

[0042] The first electrode layer 4 has a first electrically conductive electrode layer contact 7, and the second electrode layer 6 has a second electrically conductive electrode layer contact 8. The first and second electrically conductive electrode layer contacts 7, 8 are connected to one another via a first measuring device 9. The first measuring device 9 has, for example, a suitable charge amplifier with which any change in the charges on the first electrode layer 4 and the second electrode layer 6 can be detected and converted into an analyzable voltage signal.A change in the charges can be caused by a deformation of the electret structure 2 or at least one of the two electrode layers 4, 6, or by a relative displacement of the electret structure 2 and at least one of the two electrode layers 4, 6, so that the electromechanical transducer element 1 can be used to detect forces that act on the electromechanical transducer element 1 and cause the respective deformations or displacements. In this way, the first measuring device 9 can be used particularly advantageously to detect dynamic forces or pressure changes that act on the electromechanical transducer element 1.

[0043] The first electrode layer 4 is formed as a first conductor layer 10 made of an electrically conductive material and has a first electrically conductive conductor layer contact 11 and a second electrically conductive conductor layer contact 12, which contact the first conductor layer 10 at a distance from one another. The first conductor layer 10 is formed such that a deformation of the first conductor layer 10 causes a change in the electrical conductivity between the first electrical conductor layer contact 11 and the second electrical conductor layer contact 12 of the first conductor layer 10.The first electrical conductor layer contact 11 and the second electrical conductor layer contact 12 are connected to a second measuring device 13, with which, for example, an electrical resistance between the first and second electrical conductor layer contacts 11, 12 can be detected and converted into an electrical measurement signal. In this way, the second measuring device 13 can particularly advantageously detect a deformation of the first conductor layer 10 and thus static force or pressure effects on the electromechanical transducer element 1.

[0044] The simultaneous use of the first electrode layer 4 as the first conductor layer 10 enables a particularly simple, space-saving, and cost-effective construction of the electromechanical transducer element 1. In addition, the first electrode layer 4, the electret structure 2, and the second electrode layer 6 can be applied as a layer sequence to a surface of an object on which forces or pressures acting on the object and on the electromechanical transducer element 1 arranged on the surface of the object are to be recorded. The individual layers can be printed on inexpensively with a suitable choice of material, thus enabling economically viable use of the electromechanical transducer element 1 according to the invention in large quantities and in numerous areas of application.

[0045] The following figures illustrate various variants of the electromechanical transducer element 1 according to the invention by way of example and schematically. The following explanations of the individual figures describe, in particular, the different aspects and features, while consistent aspects and features are not mentioned separately for each variant.

[0046] Figure 2 shows another example of the electromechanical transducer element 1. The second electrode layer 6 is also designed as a second conductor layer 14 and has a first electrical conductor layer contact 15 and, spaced therefrom, a second electrical conductor layer contact 16. The first and second electrical conductor layer contacts 15, 16 are also connected to one another via a third measuring device 17, with which an electrical resistance between the first and second electrical conductor layer contacts 15, 16 of the second conductor layer 14 can be detected.

[0047] Depending on the structural design of the electromechanical transducer element 1, the first conductor layer 10 and the second conductor layer 14 or the second and third measuring devices 13, 17 can be evaluated in such a way that either both measuring devices 13, 17 should generate a matching measurement signal and the precision of the measurement can be improved by simultaneously detecting the deformation of the first and second conductor layers 10, 14, which is assumed to be of the same type, or different deformations of the first and second conductor layers 10, 14 are expected and a difference in the measurement signals of the second and third measuring devices 13, 17 can be detected and evaluated, whereby the sensitivity of the electromechanical transducer element 1 can be increased.

[0048] In the embodiment of the electromechanical transducer element 1 shown as an example in Figure 3, the first electrode layer 4 is arranged at a distance from the electret structure 2 and is mounted displaceably on a support device 19 (not shown in detail) via a spring device 18. The first electrode layer 4 is simultaneously designed as a first conductor layer 10 and is electrically contacted or connected to a first measuring device 9 and to a second measuring device 13. In the two embodiments according to Figures 1 and 2, the mechanical properties of the electromechanical transducer element 1 are essentially predetermined by the mechanical properties of the electret structure 2 and the first and second electrode layers 4, 6 or of an object on which the electromechanical transducer element 1 is arranged during its use.In contrast, a displacement of the first electrode layer 4 relative to the electret structure 2 in the embodiment shown in Figure 3 can be influenced or predetermined via the spring properties of the spring device 18 and the support device 19. In this way, both the sensitivity and the measuring range of the electromechanical transducer element 1 can be influenced and predetermined via the spring device 18 and the support device 19, in addition to the respective material selection and structural design of the electret structure 2 and the two electrode layers 4, 6.

[0049] In the embodiment of the electromechanical transducer element 1 shown schematically and by way of example in Figure 4, the first conductor layer 10 is designed as an additional layer in addition to the first electrode layer 4 and the second electrode layer 6. The first conductor layer 10 is arranged on the first surface 3 of the electret structure 2. The second electrode layer 6 is arranged on the second surface 5 of the electret structure 2. At a distance from the first conductor layer 10, the electrode layer 4 is mounted via the spring device 18 and the support device 19 (not shown in detail) so that it can be displaced relative to the first conductor layer 10 and the electret structure 2. The first measuring device 9 is connected to the first electrode layer 4 and to the second electrode layer 6. The second measuring device 13 is connected to the two electrically conductive conductor layer contacts 11, 12.

[0050] Figure 5 shows a further modified variant of the electromechanical transducer element 1, which is designed similarly to the variant shown in Figure 4. In contrast to the variant shown in Figure 4, the electret structure 2 with the first conductor layer 10 and the second electrode layer 6 arranged thereon is not fixed in a stationary manner to an object or to the support device 19, but is mounted via the spring device 18 and the support device 19 so as to be displaceable relative to the first electrode layer 4 which is fixed in a stationary manner to an object or to the support device 19.

[0051] The two embodiments shown in Figure 6 and Figure 7 each show the electromechanical transducer element 1 with two electret structures 2 arranged at a distance from one another. In each electret structure 2, the first electrode layer 4 is arranged on the first surface 3, which simultaneously serves as the first conductor layer 10 and has electrically conductive conductor layer contacts 11, 12 arranged at a distance from one another. In each electret structure 2, the second electrode layer 6 is arranged on the opposite second surface 5. The two electret structures 2 are arranged and aligned relative to one another such that the two conductor layers 10 face one another and are arranged at a distance from one another.

[0052] In the embodiment shown in Figure 6, one of the two electret structures 2 is fixed in place on an object or on a support device 19 (not shown in detail), while the other electret structure 2 is mounted via the spring device 18 and the support device 19 so as to be displaceable relative to the first-mentioned electret structure 2. In contrast, in the embodiment shown in Figure 7, both electret structures 2 are mounted so as to be displaceable relative to one another via a spring device 18 and the support device 19.

[0053] Figures 8 and 10 each show variants which differ from the embodiments of Figures 1 and 7. The variants shown in Figures 8 and 10 differ essentially in a different design of the first measuring device 9, which does not have a charge amplifier but rather has a voltage measuring device with which a change in the electrical potential difference caused by a deformation or displacement of the electromechanical transducer element 1 can be detected.

[0054] The embodiment of the electromechanical transducer element 1 shown in Figure 9 is similar to the embodiment shown in Figure 5. However, an additional electret structure 2 is fixed to the first electrode layer 4, which is arranged at a distance from the second electret structure 2 and the conductor layer 10 arranged thereon. As in the embodiment variants shown in Figures 8 and 10, the first measuring device 9 does not have a charge amplifier, but rather a voltage measuring device. If, instead of the first measuring device 9, a voltage source is connected to the first and second electrically conductive electrode layer contacts 7, 8, the electromechanical transducer element 1 can be operated as an actuator and a displacement or deformation of the two electrode layers 4, 6 relative to one another can be forced.If a current source is used instead of the second or third measuring device 13, 17 and is connected to the first and second electrically conductive conductor layer contacts 11, 12, the conductor layers 10 connected to a current source in this way can be used to generate heat.

Claims

P A T E N T A N S P R Ü C H E 1. An electromechanical transducer element (1) comprising a first electrode layer (4) made of an electrically conductive material, with a second electrode layer (6) made of an electrically conductive material arranged at a distance therefrom, wherein the first and second electrode layers (4, 6) each have an electrically conductive electrode layer contact (7, 8) which can be connected to one another via a first measuring device (9), characterized in that an electret structure (2) made of an electrically insulating electret material is arranged between the first and second electrode layers (4, 6), so that upon deformation of the electret structure (2) and / or the first electrode layer (4) or upon displacement of the electret structure (2) and at least one electrode layer (4, 6) relative to one another, the ratio of the charge quantities located in the first and second electrode layers (4, 6) to one another changes,and wherein the electromechanical transducer element (1) has a first conductor layer (10) made of an electrically conductive material with a first electrically conductive conductor layer contact (11) and with a second electrically conductive conductor layer contact (12), wherein the first conductor layer (10) is designed such that a deformation of the first conductor layer (10) causes a change in the electrical conductivity between the first electrical conductor layer contact (11) and the, second electrical conductor layer contact (12) of the first conductor layer (10).

2. Electromechanical transducer element (1) according to claim 1, characterized in that the first electrode layer (4) is designed as a first conductor layer (10).

3. Electromechanical transducer element (1) according to claim 1 or claim 2, characterized in that the electromechanical transducer element (1) has a second conductor layer (14) made of an electrically conductive material with a first electrically conductive conductor layer contact (15) and with a second electrically conductive conductor layer contact (16), wherein the second conductor layer (14) is designed such that a deformation of the second conductor layer (14) causes a change in the electrical conductivity between the first electrical conductor layer contact (15) and the second electrical conductor layer contact (16) of the second conductor layer (14).

4. Electromechanical transducer element (1) according to one of the preceding claims, characterized in that the first electrode layer (4) is arranged on a first surface (3) of the electret structure (2), and that in the case of a force action predetermined as intended, a deformation of the electret structure (2) with the force applied on the first surface (3) arranged first electrode layer (4).

5. Electromechanical transducer element (1) according to one of the preceding claims, characterized in that the second electrode layer (6) is applied to one of the first surfaces (3) of the electret structure (2) opposite the second surface (5) of the electret structure (2), and that when a predetermined force is applied, a deformation of the electret structure (2) with the second electrode layer (6) arranged on the second surface (5) is brought about.

6. Electromechanical transducer element (1) according to one of the preceding claims, characterized in that the first electrode layer (4) and / or the second electrode layer (6) is arranged at a distance from the electret structure (2) and, when a force is applied as intended, a displacement of the first and / or second electrode layer (4, 6) arranged at a distance from the electret structure (2) is effected relative to the electret structure (2).

7. Electromechanical transducer element (1) according to claim 6, characterized in that the first and / or second electrode layer (4, 6) arranged at a distance from the electret structure (2) is mounted displaceably relative to the electret structure (2) against a spring force.

8. Electromechanical transducer element (1) according to claim 7, characterized in that the first and / or second electrode layer (4, 6) arranged at a distance from the electret structure (2) is in operative connection with the electret structure (2) via a spring device (18).

9. Electromechanical transducer element (1) according to claim 7, characterized in that the first and / or second Electrode layer (4, 6) and / or the electret structure (2) is connected to a support structure (19) of the electromechanical transducer element (1) via a spring device (18).

10. Electromechanical transducer element (1) according to one of the preceding claims, characterized in that the first conductor layer (10) and / or optionally the second conductor layer (14) consists of a piezoresistive material.

11. Electromechanical transducer element (1) according to one of the preceding claims, characterized in that the electromechanical transducer element (1) has a first electret structure (2) and a second electret structure (2) arranged at a distance therefrom, both of which are arranged between the first electrode layer (4) and the second electrode layer (6).

12. Electromechanical transducer element (1) according to claim 11, characterized in that two conductor layers (10) are arranged between the first electret structure (2) and the second electret structure (2) in an electrically insulated manner from one another.

13. Sensor, characterized in that the sensor comprises an electromechanical transducer element (1) according to one of claims 1 to 12.

14. Actuator, characterized in that the actuator comprises an electromechanical transducer element (1) according to one of claims 1 to 12.

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