Sensor structure

Abstract

The invention relates to a sensor structure (1) for arrangement on a body (2), the sensor structure comprising a support (3), in which there are integrated at least one transmitter (4) and at least one receiver (5), the transmitter (4) being designed to generate mechanical waves in the body (2) and the receiver (5) being designed to detect the mechanical waves in the body (2).

Description

[0001] Description

[0002] Sensor structure

[0003] This patent application claims priority from German patent application DE 102022109302.6, the disclosure of which is hereby incorporated by reference.

[0004] A sensor structure is specified.

[0005] Sensor structures are used, for example, for ultrasonic testing and / or structural monitoring of materials. In particular, ultrasonic testing or structural monitoring can detect material defects in materials or homogeneous and inhomogeneous bodies. In ultrasonic testing, for example, mechanical waves with frequencies in the ultrasonic range are excited in the body to be tested. Material defects lead, for example, to scattering, diffraction, and / or reflections of the mechanical waves. By detecting the scattered, diffracted, and / or reflected mechanical waves, the structural condition and / or structural integrity of the body can be determined.

[0006] The paper V. Giurgiutiu, "Structural health monitoring with piezoelectric wafer active sensors", Academic Press, 2014, describes piezoelectric sensors for structural integrity monitoring.

[0007] The paper XP Qing et al., "Effect of adhesive on the performance of piezoelectric elements used to monitor structural health", Int. Journal of adhesion & adhesives, 2006, describes the effect of adhesives on piezoelectric elements used to monitor structural integrity.

[0008] The paper by V. Giurgiutiu and C. Soutis, "Enhanced composite integrity through structural health monitoring", Appl. Compos. Mater., Springer 2012, describes how the integrity of safety-critical composite materials can be improved through the use of structural integrity monitoring techniques.

[0009] The document US 8966997 B2 describes a pressure-sensitive mat.

[0010] The publication US 2014 / 0090489 Al describes a pressure-sensitive mat with several sensor types.

[0011] The document EP 1944095 A2 describes a device, a system and a method for structural integrity monitoring.

[0012] The publication ES 2555683 T3 describes a sensor infrastructure with integrated electronics.

[0013] The document CN 101365928 A describes a sensor and a system for structural integrity monitoring.

[0014] The document EP 2548473 Bl describes a humidity measurement system for use in a hospital bed.

[0015] The publication US 2011 / 0190761 A1 describes a neutral electrode with temperature measurement. In order to excite mechanical waves in a body, for example, a piezo element is arranged on a surface of the body. In order to transfer the excitation energy of the piezo element to the body as efficiently as possible, the piezo element is in particular firmly attached to the body. The piezo element consists, for example, of a ceramic material and can therefore be brittle. In particular, the piezo element can be damaged and / or break when applied to a mechanically stressed body, for example a fiber composite material or a lithium ion cell in an electric car. Electrical contacts of the piezo element can also be damaged and / or break due to mechanical stress in the body. Furthermore, the function of the piezo element can be impaired by environmental influences.Environmental influences include, for example, external mechanical forces, dust, moisture, temperature fluctuations and / or ultraviolet light.

[0016] At least one object of certain embodiments is to provide an improved sensor structure that is particularly robust and / or particularly easy to mount on a mechanically braced body. This object is achieved by an object having the features of patent claim 1.

[0017] Advantageous embodiments and further developments of the sensor structure are specified in the dependent claims.

[0018] The sensor structure for arrangement on a body comprises a carrier into which at least one transmitter and at least one receiver are integrated such that the carrier at least partially encloses the transmitter and the receiver and only an emission surface of the transmitter and only a detection surface of the receiver are free from the carrier. In particular, all surfaces of the transmitter and the receiver with the exception of the emission surface of the transmitter and with the exception of the detection surface of the receiver are at least partially covered by the carrier. For example, the carrier at least partially covers a rear surface and side surfaces of the receiver and / or the transmitter, wherein the rear surface is opposite the emission surface or the detection surface and the side surfaces connect the rear surface to the emission surface or the detection surface.

[0019] The transmitter and receiver are preferably spatially separated elements. In other words, the sensor structure does not, for example, have an element that performs both a transmitter and a receiver function. Thus, the transmitter and receiver can be adapted and / or optimized for their respective functions. For example, the transmitter and receiver are designed differently.

[0020] The sensor structure, for example, has exactly one transmitter and exactly one receiver. Alternatively, the sensor structure can also comprise multiple transmitters and / or multiple receivers. The number of transmitters and / or receivers can be adapted to the body.

[0021] Alternatively or additionally, the transmitter and receiver can be designed as a single, common element. The common element thus assumes, in particular, the functions of the transmitter and receiver described below. Furthermore, the transmitter and receiver can be interchangeable or interchangeable in their functions.

[0022] For example, the transmitter can be configured as a receiver, and vice versa. For example, the functions of the transmitter and receiver can be swapped during operation of the sensor structure.

[0023] The carrier is particularly designed to mechanically stabilize the sensor structure. The carrier is preferably flexible. In other words, the carrier comprises a soft material that can be bent with little force. For example, the elastic modulus of the carrier is at most 5 GPa. For example, the carrier comprises a silicone, a soft polymer such as polyurethane, or a foam-based material, or consists of one of these materials.

[0024] The carrier is specifically designed to protect the transmitter and receiver from environmental influences. For example, the carrier protects the transmitter and receiver from dust, moisture, UV light, temperature fluctuations, and / or external mechanical forces.

[0025] The transmitter is configured to generate mechanical waves in the body, and the receiver is configured to detect the mechanical waves in the body. The transmitter is preferably configured to excite Lamb waves in the body. Lamb waves, for example, comprise a combination of transverse and longitudinal waves in the body, wherein the body is deformed both longitudinally and transversely to a propagation direction of the mechanical wave. Lamb waves, for example, have an approximately uniform distribution across the thickness of the body. The thickness here refers to a spatial extent of the body in a direction perpendicular to the propagation direction, wherein the mechanical waves propagate in particular from the transmitter to the receiver. The structural state of the body can thus advantageously be determined across the entire thickness of the body.

[0026] The transmitter and / or receiver are preferably sound transducers. For example, the transmitter converts an electrical input signal into a mechanical wave, while the receiver converts a mechanical wave into an electrical output signal.

[0027] The mechanical waves preferably have a frequency in an ultrasonic range. The ultrasonic range includes, in particular, frequencies above the human hearing frequency range. For example, the ultrasonic range includes frequencies between 20 kHz and 1 GHz. The mechanical waves can also have frequencies within the human hearing frequency range. For example, the mechanical waves have a frequency of less than 20 kHz. The frequency of the mechanical waves can advantageously be adapted to the properties of the body.

[0028] According to a further embodiment of the sensor structure, the transmitter is arranged on a first side of the carrier and the receiver is arranged on a second side of the carrier, which is opposite the first side. The transmitter and the receiver can in particular be arranged on the same side of the carrier or on different sides of the carrier. For example, the emission surface of the transmitter and the detection surface of the receiver are aligned the same or differently. In other words, a surface normal of the emission surface and a surface normal of the detection surface can point in the same or different directions. For example, an angle between the surface normals of the emission surface and the detection surface is approximately 0°, approximately 90°, or approximately 180°, wherein the angle can be changed within a certain range by the flexible design of the carrier.

[0029] For example, the emission surface is arranged on an underside of the carrier, while the detection surface is arranged on an upper side of the carrier, or vice versa. The upper side and the underside denote opposite main surfaces of the carrier. In a plan view of the main surface of the carrier, the transmitter and the receiver can, for example, be arranged one above the other or offset from one another.

[0030] A plurality of transmitters and / or a plurality of receivers can also be arranged on any side of the carrier. For example, transmitters and / or receivers are arranged on both the underside and the top side of the carrier.

[0031] According to a further embodiment of the sensor structure, the transmitter and the receiver are laterally spaced from each other. Here and in the following, "lateral" refers to a main extension direction of the carrier.

[0032] In particular, the carrier extends in lateral directions and has a thickness in a vertical direction, wherein the vertical direction is perpendicular to the lateral directions. The thickness of the carrier is preferably smaller than the lateral extent of the carrier. For example, a lateral distance between the transmitter and the receiver is greater than a lateral extent of the transmitter and / or a lateral extent of the receiver.

[0033] According to a further embodiment of the sensor structure, the transmitter is configured only for generating mechanical waves, and the receiver is configured only for detecting mechanical waves. In other words, the transmitter is configured exclusively for generating mechanical waves and not for detecting mechanical waves, while the receiver is configured exclusively for detecting mechanical waves and not for generating mechanical waves.

[0034] According to a further embodiment of the sensor structure, an elastic modulus of the carrier is smaller than an elastic modulus of the body. In other words, the carrier is softer than the body. In particular, the mechanical waves between the transmitter and the receiver propagate preferentially through the body. A transmission of the mechanical waves from the transmitter to the receiver through the carrier is hindered or suppressed, for example, by the small elastic modulus of the body. For example, the elastic modulus of the body is at least a factor of 10 greater than the elastic modulus of the carrier.

[0035] If the elastic modulus of the body is at least a factor of 10 greater than the elastic modulus of the carrier, then, for example, only a negligible proportion of the mechanical waves generated by the transmitter propagates via the carrier to the receiver. In particular, the mechanical waves are essentially transmitted via the body from the transmitter to the receiver. Ultrasonic waves that propagate from the transmitter via the carrier to the receiver cannot contribute to testing the structural integrity of the body and represent, for example, an interference signal. Therefore, the carrier is preferably designed to suppress and / or at least strongly dampen such waves.

[0036] According to a further embodiment of the sensor structure, the carrier has a damping element which is arranged between the transmitter and the receiver and has a lower modulus of elasticity than the carrier. The damping element is designed in particular to hinder or reduce a direct transmission of mechanical waves between the transmitter and the receiver through the carrier. For example, the damping element is designed as a section of the carrier which has a softer material than the carrier. The modulus of elasticity of the carrier is, for example, at least a factor of 2 greater than the modulus of elasticity of the damping element.

[0037] According to a further embodiment of the sensor structure, the damping element extends completely over a cross-sectional area of ​​the carrier. The damping element can also extend only partially over the cross-sectional area of ​​the carrier. In this case, the cross-sectional area refers in particular to an area that extends through the carrier, wherein the transmitter is arranged on one side of the cross-sectional area, while the receiver is arranged on another side of the cross-sectional area. In other words, the cross-sectional area separates the carrier into two separate regions, wherein the transmitter is arranged in one of the two regions and the receiver in another of the two regions. A damping element extending completely over the cross-sectional area of ​​the carrier thus separates the carrier into two separate parts that are connected to one another via the damping element.This allows the direct transmission of mechanical waves between the transmitter and the receiver via the carrier to be significantly reduced.

[0038] According to a further embodiment of the sensor structure, the transmitter and / or the receiver comprises a piezoelectric element. The piezoelectric element of the transmitter deforms, in particular, when an electrical voltage is applied. The piezoelectric element of the receiver generates an electrical voltage, for example, when the piezoelectric element is mechanically deformed by an external mechanical force.

[0039] The piezoelectric element comprises, for example, a piezoelectric crystal, a polycrystalline piezoelectric ceramic, or a piezoelectric polymer, such as polyvinylidene fluoride (PVDF). In particular, the piezoelectric element is designed as a sound transducer that converts an electrical signal into a mechanical wave, or vice versa.

[0040] The piezo element has, for example, a platelet shape or a wedge shape, with a lateral dimension being particularly larger than a vertical dimension of the piezo element. In a lateral plane, the piezo element has, for example, a circular, oval, square, rectangular, or polygonal cross-sectional area.

[0041] The piezoelectric element is made, for example, from a single piece of piezoelectric crystal or piezoelectric ceramic. Alternatively or additionally, the piezoelectric element can comprise a plurality of piezoelectric subelements embedded in a matrix material. The matrix material is, for example, a plastic, in particular an epoxy.

[0042] According to a further embodiment of the sensor structure, a thickness of the transmitter and / or a thickness of the receiver is at most 1 mm and / or a thickness of the sensor structure is at most 3 mm. Here and below, the thickness refers to a spatial extension in the vertical direction. Due to a low thickness, the sensor structure advantageously exhibits a high degree of flexibility.

[0043] According to a further embodiment of the sensor structure, flexible electrical lines for electrically contacting the transmitter and / or the receiver are integrated into the carrier. The flexible electrical lines comprise, for example, metallic conductor tracks or a coaxial cable. In particular, the flexible electrical lines are designed such that they are not damaged or broken when the carrier is bent. Preferably, the flexible electrical lines are at least partially enclosed by the carrier. For example, the carrier is designed to electrically insulate the flexible electrical lines.

[0044] The flexible electrical cables are electrically connected to the transmitter and / or the receiver, for example via a solder connection or with an electrically conductive adhesive.

[0045] According to a further embodiment, the sensor structure additionally comprises at least one sensor integrated into the carrier. The sensor is configured to measure at least one operating parameter. For example, the sensor is a humidity sensor, a temperature sensor, and / or a pressure sensor.

[0046] Here and in the following, "integrated" means that the sensor is at least partially enclosed by the carrier. In particular, at least two different surfaces or sides of the sensor are at least partially covered by the carrier. Several sensors can also be integrated into the carrier. The carrier is particularly designed to protect sensors integrated into the carrier from environmental influences.

[0047] Together with the transmitter and receiver, the humidity sensor, the temperature sensor, and / or the pressure sensor are configured, for example, to monitor a body condition. For example, the transmitter, the receiver, the humidity sensor, the temperature sensor, and / or the pressure sensor are connected to evaluation electronics. The evaluation electronics are configured, for example, to generate a warning and / or change operating parameters when predefined threshold values ​​are reached.

[0048] According to a further embodiment of the sensor structure, the carrier encloses the transmitter and the receiver in such a way that only an emission surface of the transmitter and only a detection surface of the receiver are free of the carrier. In particular, all surfaces of the transmitter and all surfaces of the receiver, with the exception of the emission surface of the transmitter and the detection surface of the receiver, are covered by the material of the carrier. The mechanical waves are preferably coupled out of the transmitter via the emission surface. Furthermore, the mechanical waves are preferably coupled into the receiver via the detection surface. During operation of the sensor structure, the emission surface of the transmitter and the detection surface of the receiver are preferably reversibly or irreversibly connected to the body directly or via a connecting means. Thus, the transmitter and the receiver are in particular covered on all sides either by the carrier or by the body.During operation of the sensor structure, the transmitter and the receiver are therefore advantageously protected from environmental influences.

[0049] For example, the emission surface of the transmitter and / or the detection surface of the receiver is flush with the carrier. In other words, the side surfaces of the transmitter and / or the receiver are completely covered by the carrier, so that the emission surface and / or the detection surface forms a plane with a surface of the carrier. This advantageously allows direct contact to be established between the body and the transmitter and / or the receiver, while protecting the transmitter and / or the receiver from environmental influences.

[0050] Alternatively or additionally, the transmitter and / or receiver can also protrude from the carrier. Thus, the side surfaces of the receiver and / or the transmitter are, in particular, only partially covered by the carrier. This allows, for example, better contact to be established between the body and the emission surface of the transmitter and / or the detection surface of the receiver.

[0051] Furthermore, the carrier can be compressed, for example, by mechanically bracing the sensor structure to the body. This deforms the carrier applied to the body, for example, such that the side surfaces of the transmitter and / or receiver are completely covered by the carrier. Thus, the transmitter and / or receiver are advantageously completely enclosed by the carrier and the body due to the mechanical bracing.

[0052] According to a further embodiment of the sensor structure, a carrier film is applied to the emission surface of the transmitter and / or the detection surface of the receiver. The carrier film is designed, for example, to protect the emission surface and / or the detection surface. In particular, the carrier film protects the transmitter and / or the receiver, for example, from moisture, dust, mechanical forces, and / or ultraviolet light. For example, the carrier film comprises glass, a metal, or a polymer, or is made of one of these materials.

[0053] According to a further embodiment of the sensor structure, the carrier film is configured to change a resonant frequency of the transmitter and / or the receiver. For example, the carrier film increases an inertial mass of the transmitter and / or the receiver. Thus, in particular, a resonant frequency of the transmitter and / or the receiver can be lowered. For example, a resonant frequency of the transmitter and / or the receiver can thereby be adapted to structural properties of the body.

[0054] According to a further embodiment of the sensor structure, the thickness of the carrier film is at most 500 μm. The thickness here refers to a spatial extent of the carrier film in a direction perpendicular to the emission surface of the transmitter or perpendicular to the detection surface of the receiver. In particular, a thin carrier film with a thickness of, for example, at most 500 μm is advantageous for good mechanical coupling between the body and the transmitter and / or the receiver. For example, the attenuation of the mechanical waves by the thin carrier film is advantageously small, whereby the attenuation can also depend on the material of the carrier film.

[0055] According to a further embodiment of the sensor structure, the transmitter and / or the receiver comprises an electrical shielding element. The electrical shielding element is particularly designed to shield and / or protect the transmitter and / or the receiver from electromagnetic interference. For example, the shielding covers all surfaces of the transmitter and / or the receiver with the exception of the emission surface and / or the detection surface.

[0056] In particular, the shielding element is arranged between the carrier and the receiver and / or between the carrier and the transmitter.

[0057] Alternatively or additionally, the shielding element can also cover the emission surface of the transmitter and / or the detection surface of the receiver. Thus, the shielding element also assumes the function of the carrier foil, for example. In this case, all surfaces of the transmitter and / or the receiver are covered and / or enclosed by the shielding element, with the flexible electrical lines for electrically contacting the transmitter and / or the receiver being routed, in particular, through the shielding element.

[0058] The shielding element comprises an electrically conductive material or consists of an electrically conductive material. The electrically conductive material is, for example, a metal, in particular copper. The shielding element is, for example, a metal foil, a metallic mesh, or comprises metallic wires or a metallic foam. In particular, an electrically insulating structure is arranged between the shielding element and the flexible electrical lines as well as the electrodes of the transmitter and the receiver. The shielding element can also be designed to provide mechanical protection for the receiver and / or the transmitter.

[0059] According to a further embodiment, the sensor structure comprises evaluation electronics that are electrically connected to the transmitter and the receiver and configured to determine a structural state of the body from the detected mechanical waves. The evaluation electronics can also be electronically connected to one or more additional sensors that are integrated into the support of the sensor structure. In particular, the additional sensor is configured to determine a state of the body. For example, the additional sensor is a humidity sensor, a temperature sensor, and / or a pressure sensor.

[0060] The evaluation electronics can be mounted on the carrier, integrated into the carrier, or spatially separated from the carrier. Spatial separation of the evaluation electronics from the carrier is particularly advantageous when only a small installation space is available in which the carrier is to be positioned on the body. For example, the evaluation electronics are connected to the transmitter and receiver via flexible electrical cables.

[0061] Furthermore, an arrangement is specified. The arrangement comprises, in particular, a sensor structure described here and a body on which the sensor structure is applied. All features of the sensor structure are also disclosed for the arrangement, and vice versa.

[0062] According to one embodiment, the arrangement comprises a sensor structure described here and a body, wherein the sensor structure is permanently or reversibly connected to the body. For example, the sensor structure is permanently, i.e., irreversibly, bonded to the body. In particular, an adhesive layer is arranged between a surface of the body and the emission surface of the transmitter and the detection surface.

[0063] The adhesive layer is as thin and as hard as possible. In particular, the adhesive layer is designed to provide good mechanical coupling and thus efficient transmission of mechanical waves between the sensor structure and the body. For example, the adhesive layer has a maximum thickness of 10 pm.

[0064] Alternatively, the sensor structure can also be reversibly connected to the body. For example, a coupling gel is arranged between the sensor structure and the body. The coupling gel can be easily removed. Furthermore, the sensor structure can be mechanically clamped to the body. The clamping is particularly reversible, and the sensor structure can be removed from the body, for example, after a measurement process.

[0065] For example, the body exhibits a mechanical prestress. Mechanical prestress is, in particular, a mechanical tension within the body that exists with or without the application of an external force. In other words, tensile forces and / or compressive forces act within the body, with or without the application of an external force. For example, mechanical prestress can be used to adjust the behavior of the body under the application of an external force.

[0066] In lithium-ion cells in electric cars, for example, mechanical prestressing serves to increase the service life of the cells. The sensor structure described here can be mechanically prestressed together with the cells and monitor cell function during operation. Advantageously, the sensor structure remains functional despite the stress caused by the mechanical stress.

[0067] According to a further embodiment of the arrangement, the body comprises a plurality of battery cells and / or a fiber composite material. For example, the body is a battery of an electrically powered vehicle, wherein the battery comprises a plurality of battery cells in a housing. The sensor structure can in particular be arranged between the battery cells and the housing. For example, the sensor structure is designed to determine a structural state of the battery cells. Furthermore, the sensor structure can be designed as a spacer between the battery cells and the housing. The battery cells are thus protected from direct contact with the housing.

[0068] The fiber composite material comprises, for example, a plurality of fabric mats comprising glass fibers and / or carbon fibers. The fabric mats are bonded to one another, in particular with a synthetic resin. The glass fibers or carbon fibers can also be randomly distributed in a matrix material, for example a plastic. For example, the fiber composite material is a glass fiber reinforced plastic (GRP for short). The sensor structure can, for example, be permanently arranged between fabric mats of the fiber composite material. Alternatively or additionally, the sensor structure can also be laminated onto the fiber composite material.

[0069] Furthermore, the sensor structure can be designed to protect the body from environmental influences, for example from mechanical forces, dust, moisture, UV light, and / or rapid temperature fluctuations.

[0070] Furthermore, a method for operating a sensor structure is specified. The method is particularly designed for operating a sensor structure described here. All features of the sensor structure are also disclosed for the method for operating a sensor structure, and vice versa.

[0071] According to one embodiment of the method for operating a sensor structure, a sensor structure as described here is arranged on the body in such a way that the emission surface of the transmitter and the detection surface of the receiver are in contact with the body. For example, the sensor structure is clamped onto the body in such a way that the detection surface of the receiver and the emission surface of the transmitter are in direct contact with a surface of the body. A coupling gel, a wax or an adhesive can also be arranged, for example, between the emission surface of the transmitter and the body and between the detection surface of the receiver and the body. The coupling gel, the wax or the adhesive are designed in particular to produce good mechanical contact between the sensor structure and the body for the transmission of mechanical waves.

[0072] Alternatively or additionally, the sensor structure can be glued to the body or permanently bonded in another way. In particular, the emitting surface of the transmitter and the detecting surface of the receiver can be permanently bonded to a surface of the body.

[0073] According to a further embodiment of the method, the transmitter excites mechanical waves in the body during operation, and the receiver detects the mechanical waves in the body. For example, the transmitter converts the electrical input signal into mechanical waves that propagate in the body. The receiver detects the mechanical waves propagating in the body and converts them, for example, into the electrical output signal.

[0074] The transmitter and / or the receiver can also be configured to excite and detect the mechanical waves.

[0075] According to a further embodiment of the method, a structural condition of the body is determined from the detected mechanical waves. For example, evaluation electronics can determine the propagation times of various scattered components of the mechanical wave between a time of emission at the transmitter and a time of detection at the receiver. This allows, in particular, material defects in the body to be detected and thus the structural integrity of the body to be determined.

[0076] According to a further embodiment of the method, the transmitter generates lateral, vertical and / or radial oscillation modes during operation. For example, an electrical input signal from the transmitter is converted into a lateral, vertical and / or radial deformation of the transmitter. A radial deformation is, for example, a uniform deformation in all lateral directions. Depending on the type of deformation of the transmitter, different mechanical waves can be excited in the body, for example. Lamb waves that are distributed evenly over the thickness of the body are preferably excited in the body.

[0077] Further advantageous embodiments and developments of the sensor structure as well as the arrangement and method for operating a sensor structure emerge from the exemplary embodiments described below in conjunction with the figures.

[0078] Figure 1 shows a schematic sectional view of a sensor structure according to an embodiment.

[0079] Figures 2 and 3 show schematic perspective representations of a sensor structure according to various embodiments.

[0080] Figure 4 shows a schematic sectional view of a sensor structure according to a further embodiment.

[0081] Figures 5, 6 and 7 show schematic perspective representations of an arrangement according to an embodiment.

[0082] Figures 8 and 9 show schematic representations of a flexible electrical cable according to various examples. Figures 10 and 11 show schematic

[0083] Sectional views of an arrangement according to various embodiments.

[0084] Figure 12 shows measurement results of an impedance of a transmitter or a receiver as a function of a frequency.

[0085] Figures 13 and 14 show schematic sectional views of a sensor structure according to further embodiments.

[0086] Figure 15 shows a schematic sectional view of an arrangement according to a further embodiment.

[0087] Identical, similar, or functionally identical elements are provided with the same reference symbols in the figures. The figures and the relative sizes of the elements depicted in the figures are not to scale. Rather, individual elements may be exaggeratedly large or small for clarity and / or clarity.

[0088] The exemplary embodiment of the sensor structure 1 in Figure 1 has a carrier 3, a transmitter 4 and a receiver 5. The carrier 3 has a soft polymer, for example polyurethane, in which the transmitter 4 and the receiver 5 are integrated. In particular, the carrier 3 at least partially encloses surfaces of the transmitter 4 and the receiver 5, with only an emission surface 11 of the transmitter 4 and a detection surface 12 of the receiver 5 remaining free from the carrier. A thickness D of the transmitter 4 and the receiver 5 is at most 1 mm, while the thickness D of the sensor structure 1 is at most 3 mm. The transmitter 4 and the receiver 5 comprise a piezo element. The piezo element of the transmitter 4 is designed to convert an electrical input signal into mechanical waves. The piezo element of the receiver 5 is designed to convert mechanical waves into an electrical output signal.The transmitter 4 and the receiver 5 are spaced apart from each other in the lateral direction L.

[0089] Flexible electrical lines 7 are integrated into the carrier 3. The flexible electrical lines 7 are designed to electrically contact the transmitter 4 and the receiver 5. Preferably, the flexible electrical lines 7 have an elastic modulus that is the same as or smaller than that of the carrier 3. Thus, the flexible electrical lines 7 are advantageously not damaged, for example, in the event of a bending load on the sensor structure 1.

[0090] The sensor structure 1 is applied in particular to a body 2 (not shown here, see e.g. Fig. 5) whose structural condition is to be determined. During operation of the sensor structure 1, the transmitter 4 generates mechanical waves which propagate through the body 2 and are detected by the receiver 5. By evaluating the mechanical waves detected by the receiver, the structural integrity of the body 2 can be checked in particular.

[0091] The exemplary embodiment of the sensor structure 1 in Figure 2 comprises, in addition to the sensor structure 1 described in connection with Figure 1, a damping element 6. The damping element 6 is arranged between the transmitter 4 and the receiver 5 and has a smaller modulus of elasticity than the carrier 3. Thus, the damping element 6 hinders and / or reduces a direct transmission of the mechanical waves from the transmitter 4 to the receiver 5 through the carrier 3.

[0092] Furthermore, the sensor structure 1 has carrier films 13, which are applied to the emission surface 11 of the transmitter 4 and to the detection surface 12 of the receiver 5. The carrier films 13 comprise, for example, a hard polymer and protect the receiver 4 and the transmitter 5 from environmental influences, such as dust, moisture, or mechanical forces. The carrier films 13 are also designed to set a resonance frequency of the transmitter 4 and the receiver 5. A thickness D of the carrier film 13 is, in particular, at most 500 micrometers.

[0093] Flexible electrical lines 7 comprise conductor tracks 19 that are integrated into the carrier 3 and extend through the carrier 3 in a lateral direction L. Alternatively or additionally, the flexible electrical lines 7 can also extend in a vertical direction V.

[0094] The sensor structure 1 has two integrated sensors 8, such as a humidity sensor, a temperature sensor, and / or a pressure sensor. The sensor structure 1 can also have one or more than two integrated sensors 8. Electrical lines for electrically contacting the additional sensors 8 are not shown for clarity.

[0095] In contrast to the sensor structure 1 in Figure 2, the sensor structure 1 in Figure 3 has flexible electrical lines 7, which are designed as coaxial cables and extend in the vertical direction V through the carrier 3. Alternatively or additionally, the coaxial cables can also be guided in the lateral direction L.

[0096] In comparison to the sensor structure 1 described in connection with Figure 2, the exemplary embodiment of the sensor structure 1 in Figure 4 additionally has an electrical shielding element 14. The electrical shielding element 14 is arranged between the carrier 3 and the transmitter 4 and / or the receiver 5. The electrical shielding element 14 is designed to protect the transmitter 4 and / or the receiver 5 from electromagnetic interference and has a metallic foil, for example made of copper. In addition, the electrical shielding element 14 can protect the transmitter 4 and / or the receiver 5 from mechanical forces.

[0097] An electrical insulation 16 is arranged between the electrical shielding element 14 and the transmitter 4 and / or the receiver 5. The electrical insulation protects the transmitter 4 and / or the receiver 5, in particular, from electrical short circuits by means of the electrically conductive electrical shielding element 14.

[0098] The exemplary embodiment in Figure 5 shows an arrangement comprising a body 2 with a sensor structure 1 arranged thereon. The sensor structure 1 is configured, in particular, to determine a structural state of the body 2. For example, the body 2 is a battery of an electrically powered vehicle or a fiber composite material.

[0099] A lateral extension of the sensor structure 1 is particularly adapted to a lateral extension of the body 2. The sensor structure 1 comprises a carrier 3 with an integrated transmitter 4 and an integrated receiver 5. An emission surface 11 of the transmitter 4 and a detection surface 12 of the receiver 5 are arranged on a surface of the body 2. For example, the sensor structure 1 is glued or clamped to the body 2.

[0100] Compared to the arrangement described in connection with Figure 5, the exemplary embodiment of the arrangement in Figure 6 additionally has flexible electrical lines 7, which are designed to electrically contact the transmitter 4 and the receiver 5. The flexible electrical lines 7 are integrated into the carrier 3 of the sensor structure 1 and extend in the lateral direction L.

[0101] Compared to the arrangement described in connection with Figure 6, the exemplary embodiment of the arrangement in Figure 7 additionally comprises carrier foils 13 arranged on the emission surface 11 of the transmitter 4 and on the detection surface 12 of the receiver 5. Furthermore, the arrangement comprises a damping element arranged in the carrier 3 between the transmitter 4 and the receiver 5.

[0102] Figure 8 shows an example of a flexible electrical line 7 which comprises metallic conductor tracks 19. The flexible electrical line 7 has a first connection region 17 for electrically contacting the transmitter 4 (not shown) or the receiver 5 (not shown). Furthermore, the flexible electrical line 7 has a second connection region 18 which is designed, for example, for electrically contacting an evaluation electronics 15 (not shown). The flexible electrical line has, for example, a thickness of at most 200 pm.

[0103] Figure 9 shows a further example of a flexible electrical line 7. In addition to the example described in connection with Figure 8, the flexible electrical line 7 has one or more shielding layers 20 designed to protect the flexible electrical line 7 from electromagnetic interference.

[0104] The exemplary embodiment of the arrangement in Figure 10 has a body 2 which comprises at least two layers, between which an adhesive layer 21 is arranged. For example, the body 2 is a fiber composite material. A sensor structure 1 is applied to each opposite surface of the body 2, which is each permanently bonded to the body 2 via an adhesive layer 21. Each sensor structure 1 has a transmitter 4 and a receiver 5. The sensor structures 1 are in particular also designed to protect the body 2, for example against moisture or mechanical forces. Alternatively, the sensor structures 1 can also be applied reversibly to the body 2, for example with a coupling gel being arranged between the body 2 and the sensor structures 1.

[0105] Figure 11 shows an arrangement according to an exemplary embodiment, comprising a sensor structure 1, a body 2, and evaluation electronics 15. The sensor structure 1, together with the evaluation electronics 15, is configured to determine a structural state of the body 2 and is connected to the evaluation electronics 15 via a flexible electrical line 7. The evaluation electronics 15 is spatially separated from the sensor structure 1.

[0106] The evaluation electronics 15, for example, provides an electrical input signal for the sensor structure 1, which is converted by the sensor structure 1 into mechanical waves. Mechanical waves detected by the sensor structure 1 are converted into an electrical output signal, which is analyzed by the evaluation electronics 15.

[0107] Figure 12 shows measurement results of an impedance Z of a transmitter 4 comprising a piezoelectric element. In particular, the impedance Z of the piezoelectric element is shown as a function of a frequency f of an electrical input signal applied to the piezoelectric element. The impedance Z exhibits a resonance at which the impedance Z changes, for example, by an order of magnitude, within a small frequency interval. The frequency f at which the resonance occurs depends in particular on a geometric structure and a mass of the piezoelectric element.

[0108] The first curve 31 shows the impedance Z of a piezoelectric element without a carrier 3, without a flexible electrical line 7 applied thereto, and without a carrier foil 13. In this case, the resonance occurs at a frequency f of approximately 95 kHz.

[0109] The second curve 32 shows the impedance Z of the same piezo element with a flexible electrical line 7 applied thereto, which is integrated into a carrier 3. In particular, this does not change the resonance frequency significantly. The third curve 33 shows the impedance Z of the same piezo element with a flexible electrical line 7 applied thereto and with a carrier foil 13 applied thereto, wherein the piezo element is integrated into a carrier 3. The carrier foil 13 increases in particular an inertial mass of the piezo element. This lowers the resonance frequency, which in this case occurs at approximately 75 kHz. Thus, the carrier foil shifts the resonance frequency in this example by approximately 20 kHz.

[0110] In comparison to the sensor structure 1 described in connection with Figure 1, the exemplary embodiment of the sensor structure 1 in Figure 13 has a transmitter 4 and a receiver 5 arranged on opposite sides of the carrier 3. The sensor structure 1 is designed, for example, for arrangement within a body 2 (see, for example, Figure 15).

[0111] Compared to the sensor structure 1 described in connection with Figure 13, the exemplary embodiment of the sensor structure 1 in Figure 14 has a second transmitter 4 arranged on the same side of the carrier 3 as the receiver 5, while the first transmitter 4 is arranged on an opposite side of the carrier 3. Instead of the second transmitter 4, a second receiver 5 can also be arranged in the carrier 3, for example.

[0112] The sensor structure 1 can also have a plurality of transmitters 4 and / or a plurality of receivers 5. For example, the sensor structure 1 has a receiver array. For example, the transmitters 4 can be arranged on one side and the receivers 5 on the opposite side of the carrier 3, or both the transmitters 4 and the receivers 5 can be arranged on both opposite sides of the carrier 3.

[0113] The exemplary embodiment of the arrangement in Figure 15 has a body 2 comprising at least two layers, between which a sensor structure 1 is arranged. For example, the body 2 is a fiber composite material. The sensor structure 1 is, in particular, a sensor structure 1 according to one of the exemplary embodiments in Figures 13 and 14.

[0114] Thus, the sensor structure 1 can advantageously monitor both layers of the body 2. The sensor structure 1 can have at least one transmitter 4 and at least one receiver 5 on its top side and on its bottom side, respectively.

[0115] The arrangement shown in Figure 15 can also be combined with the arrangement shown in Figure 10, so that sensor structures 1 are arranged both within the body 2 and on surfaces of the body 2. For example, the sensor structure 1 within the body has a plurality of transmitters 4 on both opposite sides of the carrier 3, while the sensor structures 1 on the surfaces of the body 2 have a plurality of receivers 5, or vice versa.

[0116] The invention is not limited to the embodiments by the description thereof. Rather, the invention encompasses any novel feature and any combination of features, including in particular any combination of features in the patent claims, even if this feature or combination itself is not explicitly stated in the patent claims or embodiments. Reference sign

[0117] 1 Sensor structure

[0118] 2 bodies

[0119] 3 carriers

[0120] 4 channels

[0121] 5 recipients

[0122] 6 Damping element

[0123] 7 flexible electrical cables

[0124] 8 Sensor

[0125] 11 Emission area

[0126] 12 detection area

[0127] 13 Carrier film

[0128] 14 electrical shielding element

[0129] 15 Evaluation electronics

[0130] 16 electrical insulation

[0131] 17 first connection area

[0132] 18 second connection area

[0133] 19 Conductor track

[0134] 20 Shielding layer

[0135] 21 adhesive layer

[0136] 31 first curve

[0137] 32 second curve

[0138] 33 third curve

[0139] D Thickness

[0140] Z Impedance f Frequency

Claims

Patent claims:

1. Sensor structure (1) for arrangement on a body (2) comprising a carrier (3) in which at least one transmitter (4) and at least one receiver (5) are integrated such that the carrier (3) at least partially encloses the transmitter (4) and the receiver (5) and only one emission surface (11) of the transmitter (4) and only one detection surface (12) of the receiver (5) are free from the carrier (3), wherein the transmitter (4) is configured to generate mechanical waves in the body (2) and the receiver (5) is configured to detect the mechanical waves in the body (2).

2. Sensor structure (1) according to the previous claim, wherein the transmitter (4) is arranged on a first side of the carrier (3) and the receiver (5) is arranged on a second side of the carrier (3) opposite the first side.

3. Sensor structure (1) according to one of the preceding claims, wherein the transmitter (4) and the receiver (5) are laterally spaced apart from each other.

4. Sensor structure (1) according to one of the preceding claims, wherein the transmitter (4) is configured only for generating mechanical waves and the receiver (5) is configured only for detecting mechanical waves.

5. Sensor structure (1) according to one of the preceding claims, wherein an elastic modulus of the support (3) is smaller than an elastic modulus of the body (2) .

6. Sensor structure (1) according to one of the preceding claims, wherein the carrier (3) has a damping element (6) arranged between the transmitter (4) and the receiver (5), and the damping element (6) has a lower modulus of elasticity than the carrier (3).

7. Sensor structure (1) according to the previous claim, wherein the damping element (6) extends completely over a cross-sectional area of ​​the carrier (3).

8. Sensor structure (1) according to one of the preceding claims, wherein the transmitter (4) and / or the receiver (5) comprises a piezoelectric element.

9. Sensor structure (1) according to one of the preceding claims, wherein flexible electrical conductors (7) for electrical contacting the transmitter (4) and / or the receiver (5) are integrated into the carrier (3).

10. Sensor structure (1) according to one of the preceding claims, additionally comprising at least one sensor (8) integrated into the carrier (3).

11. Sensor structure (1) according to one of the preceding claims, wherein a carrier film (13) is applied to the emission surface (11) of the transmitter (4) and / or to the detection surface (12) of the receiver (5).

12. Sensor structure (1) according to the previous claim, wherein the carrier film (13) is configured to change a resonance frequency of the transmitter (4) and / or the receiver (5).

13. Sensor structure (1) according to one of the preceding claims, wherein the transmitter (4) and / or the receiver (5) has an electrical shielding element (14).

14. Arrangement comprising a sensor structure (1) according to any one of claims 1 to 13 and a body (2) wherein the sensor structure (1) is permanently or reversibly connected to the body (2).

15. Arrangement according to the preceding claim, wherein the body (2) comprises a plurality of battery cells and / or a fiber composite material.

16. Method for operating a sensor structure (1) according to any one of claims 1 to 13, wherein - the sensor structure (1) is arranged on the body such that an emission surface (11) of the transmitter (4) and a detection surface (12) of the receiver (5) are in contact with the body (2), - the transmitter (4) excites mechanical waves in the body (2) during operation, - the receiver (5) detects the mechanical waves in the body (2), and - a structural state of the body (2) is determined from the detected mechanical waves.

17. Method according to the preceding claim, wherein the transmitter (4) generates lateral, vertical and / or radial vibration modes during operation.