Ultraschallsensor

Abstract

The present invention relates to an ultrasonic sensor comprising: a piezoelectric element (10), a membrane (20), a coupling element (30) and an electrical circuit (40), wherein the piezoelectric element (10) and the membrane (20) are planar elements which are mechanically connected to each other in respective edge regions of their surfaces via the coupling element (30), such that a cavity (50) is present between the respective central regions of the surfaces of the piezoelectric element (10) and the membrane (20), the piezoelectric element (10) and the membrane (20) are arranged, based on the cavity (50), to oscillate substantially independently of each other at their respective natural frequencies, wherein the piezoelectric element (10) has a natural frequency which differs from the natural frequency of the membrane (20) and wherein the electrical circuit (40) is arrangedto subject the piezoelectric element (10) to a first alternating electrical signal (S1) having a frequency that essentially corresponds to the natural frequency of the piezoelectric element (10) in order to set the piezoelectric element (10) into a resonant vibration and to subject it to a second alternating electrical signal (S2) having a frequency that essentially corresponds to the natural frequency of the membrane (20) in order to set the membrane (20) into a resonant vibration.

Description

State of the art

[0001] The present invention relates to an ultrasonic sensor and in particular an ultrasonic sensor for a vehicle.

[0002] The measuring principle of ultrasonic sensors is based on acoustic waves that are emitted in an inaudible frequency range into the environment of the ultrasonic sensors (which are used, for example, as sensors in a vehicle's parking assistance system).

[0003] The acoustic waves can be reflected by objects in the vicinity of the ultrasonic sensors, so that the reflected acoustic waves are received again by the ultrasonic sensors and an electronics is able to determine distances to objects in the vicinity of the ultrasonic sensors based on an evaluation of the travel times of the received acoustic waves.

[0004] In this process, the ultrasonic sensors typically use a piezoelectric element to convert electrical energy, which is used to control the ultrasonic sensors, into acoustic energy (i.e., sound energy).

[0005] Ultrasonic sensors known from the prior art are usually designed for only one transmission frequency, which advantageously corresponds to a resonance frequency of the entire system of ultrasonic sensors consisting of all mechanical and electrical components, in order to achieve the highest possible efficiency in sound conversion.

[0006] When determining such a resonant frequency, it is therefore necessary to find a compromise between a desired range (based on lower transmission frequencies) and a desired spatial resolution (based on higher transmission frequencies), since both quantities cannot be optimized based on a single transmission frequency of the ultrasonic sensors.

[0007] To optimize ultrasonic sensors with respect to both parameters, prior art concepts are known that additionally utilize a second, higher resonant frequency. This involves using a higher vibration mode.

[0008] For example, a circular membrane can be excited in the fundamental mode or (0,0) mode for the first resonance and in the (1,0) mode for the next higher resonance frequency. Due to the acoustic short circuits that occur in this process, the transmission power of an ultrasonic transducer based on this concept is correspondingly limited.

[0009] The aforementioned multi-mode concept is discussed, among other things, in the following publications: LK a. SD Andrew Feeney, “High-Frequency Measurement of Ultrasound Using Flexural Ultrasonic Transducers,” IEEE Sensors Journal, 2018. AF a. SD Lei Kang, “The High Frequency Flexural Ultrasonic Transducer for Transmitting and Receiving Ultrasound in Air,” IEEE Sensors Journal, 2020. SD a. SRTJR Eriksson, “Flexural Mode Metal Cap Transducer Design for Specific Frequency Air Coupled Ultrasound,” in Joint UFFC, EFTF and PFM Symposium, 2013. Disclosure of the invention

[0010] The ultrasonic sensor according to the invention comprises at least one piezoelectric element, a membrane, a coupling element, and an electrical circuit. It is understood that the ultrasonic sensor may advantageously include further components such as a housing, electrical connections for external contacting, etc.

[0011] The piezoelectric element and the membrane (which is made of, for example, aluminum and / or a plastic and / or is designed differently) are planar elements which are mechanically connected to each other in the respective edge areas of their surfaces via the coupling element, so that a cavity is formed between the respective central areas of the surfaces of the piezoelectric element and the membrane.

[0012] The piezoelectric element and the membrane are set up on the basis of the cavity to oscillate essentially independently of each other at their respective natural frequencies, with the piezoelectric element having a natural frequency which differs from the natural frequency of the membrane.

[0013] It should be noted that the cavity may, for example, be partially or completely filled with air and / or another gas and / or another material, as long as the desired vibration behavior of the piezoelectric element and the membrane is not impaired to such an extent that the effect described below, which is to be achieved according to the invention, can no longer be provided to a sufficient degree.

[0014] It should be noted that the shape and / or surface area of ​​the piezoelectric element and the membrane can be identical or different. For example, the piezoelectric element and / or the membrane can be round, oval, rectangular, square, or other shapes.

[0015] In summary, the piezoelectric element and the membrane in the configuration according to the invention can be considered as parallel-connected bending beams or resonators, which have a weak mechanical coupling via the coupling element.

[0016] The respective natural frequency here represents in particular a frequency that results in a fully assembled state of the ultrasound transducer for the piezoelectric element and the membrane, and thus are resulting quantities which can usually be influenced by other components of the ultrasound transducer.

[0017] Preferably, the natural frequencies are determined depending on the respective required different transmission frequencies of ultrasonic signals (i.e., acoustic waves emitted by the ultrasonic sensor), which are intended for detecting an environment of the ultrasonic sensor.

[0018] The electrical circuit is set up to apply a first alternating electrical signal to the piezoelectric element, which has a frequency that essentially corresponds to the natural frequency of the piezoelectric element, in order to set the piezoelectric element into a resonant oscillation.

[0019] The electrical circuit is further set up to apply a second alternating electrical signal to the piezoelectric element, which has a frequency that essentially corresponds to the natural frequency of the membrane, in order to set the membrane into a resonant vibration.

[0020] Because both the piezoelectric element and the membrane can be operated in resonance (in their respective fundamental modes) depending on the excitation by the first alternating signal and / or the second alternating signal, the ultrasound sensor according to the invention offers the particular advantage that ultrasound signals with different transmission frequencies can be provided, while a high efficiency in the mechanical-acoustic conversion can be maintained regardless of the respective transmission frequency. This allows for a particularly flexible and reliable detection of the environment surrounding the ultrasound sensor.

[0021] In other words, the ultrasonic sensor according to the invention, which can also be referred to as a multi-resonance ultrasonic transducer, is configured to provide at least two different operating points in which the ultrasonic sensor can be operated as required. Additionally, the ultrasonic sensor has different directional characteristics in these operating points.

[0022] When the lower frequency of the two alternating signals is provided, the lower resonance frequency of the ultrasound transducer dominates, causing the acoustic waves (sound waves) to be emitted relatively broadly in relation to the higher resonance frequency, whereas when the higher frequency of the alternating signal is provided, the higher resonance frequency of the ultrasound transducer dominates and the acoustic waves are emitted relatively narrowly, i.e., with a stronger focus.

[0023] This effect can be used to advantage, for example, to classify the height of objects in the vicinity of the ultrasonic sensor. The object is first irradiated with both transmission frequencies. If the object is relatively short, reflections of the acoustic waves arriving at the ultrasonic sensor are primarily expected only from the wider radiation pattern in the lower frequency range, whereas objects of a relatively greater height generate reflections in both frequency ranges, thus allowing them to be distinguished from one another.

[0024] Based on the configuration described above, the ultrasound sensor according to the invention is also designed to convert reflected components of the emitted ultrasound signals in the respective different frequency ranges into corresponding electrical received signals on the receiving side with high efficiency.

[0025] Furthermore, when using the alternating signal from the first alternating signal and the second alternating signal which has the higher frequency, it is advantageously possible to reduce the settling time of the ultrasonic sensor according to the invention (e.g. by up to 30%).

[0026] The dependent claims describe preferred embodiments of the invention.

[0027] Preferably, the electrical circuit is configured to apply the first and second alternating signals to the piezoelectric element with a time delay and / or simultaneously. For simultaneous output of the first and second alternating signals, the electrical circuit is configured, for example, to perform frequency and / or amplitude modulation and / or a different modulation, and to provide the first and second signals simultaneously as a resulting combined signal.

[0028] Furthermore, the coupling element can be configured as a separate element and / or as a component of the piezoelectric element and / or as a component of the membrane. If the coupling element is configured as a separate element, it can, for example, be a frame-shaped (especially rectangular) element, a ring-shaped element, etc., and in particular conform to the shape of the edge region of the piezoelectric element and / or the membrane. The coupling element configured in this way can be connected to the piezoelectric element and the membrane, for example, by means of an adhesive and / or a weld and / or a different type of connection. It is also conceivable that the coupling element is configured solely by means of an adhesive applied to the entire circumference of the piezoelectric element and the membrane.In a case where the coupling element is designed as part of the piezoelectric element and / or the membrane, a depression can be formed in the middle areas of the piezoelectric element and / or the membrane (which can be formed, for example, by milling and / or injection molding, etc.), resulting in a correspondingly raised edge area which acts as a coupling element.

[0029] In an advantageous embodiment of the present invention, the electrical circuit is configured to generate, for the greatest possible range during a measurement using the ultrasonic sensor, the alternating signal with the lower frequency from the first and second alternating signals, and, for the greatest possible spatial resolution during a measurement using the ultrasonic sensor, to generate, the alternating signal with the higher frequency from the first and second alternating signals. Advantageously, the electrical circuit is configured to receive an external signal (for example, from a higher-level component) that determines whether the current measurement using the ultrasonic sensor according to the invention should achieve the greatest possible range or the highest possible spatial resolution.This can therefore be dynamically adjusted, particularly depending on current boundary conditions. In an exemplary case where the ultrasonic sensor according to the invention is intended for detecting the surroundings of a vehicle, such dynamic adjustment can be set, for example, depending on the current speed of the vehicle and / or current weather conditions and / or current traffic conditions and / or current visibility conditions, etc.

[0030] Furthermore, the coupling element is, for example, a single, continuous element (e.g., a ring-shaped or a rectangular frame-shaped element) or it is formed from a plurality of individual coupling elements (e.g., individual struts), which are arranged, in particular, at intervals from one another. The specific design of the coupling element can preferably be determined depending on a required mechanical load-bearing capacity and / or a desired degree of mechanical coupling between the piezoelectric element and the membrane, etc.

[0031] In a further advantageous embodiment of the present invention, the ultrasonic sensor comprises a plurality of piezoelectric elements and a plurality of coupling elements, each of the plurality of piezoelectric elements having a natural frequency that differs from the natural frequency of the membrane and the natural frequency of the other piezoelectric elements. The piezoelectric elements are each stacked on top of one another based on one of the plurality of coupling elements, while the electrical circuit is configured to supply each piezoelectric element with a corresponding alternating electrical signal, each of which has a frequency that essentially corresponds to the respective natural frequency of the respective piezoelectric element.In this way, ultrasound signals with additional transmission frequencies can be advantageously generated, thereby further increasing the flexibility and / or reliability of a measurement based on the ultrasound sensor according to the invention. It should be noted that the respective coupling elements can be identical or at least partially different from one another.

[0032] A particularly advantageous feature is that the cavity formed by the piezoelectric element and the membrane is connected to the environment of the ultrasonic sensor via at least one opening. This offers the benefit that any air pressure fluctuations in the vicinity of the ultrasonic sensor and / or temperature fluctuations do not lead to unwanted deformation and / or prestressing of the piezoelectric element and / or the membrane, which can occur with a hermetically sealed cavity. In addition to providing pressure equalization, such an opening can also be used for heat dissipation from the cavity to prevent exceeding a predetermined operating temperature range. In a case where the coupling element, as described above, is formed from individual spaced elements (e.g., struts), such an opening can be implicitly provided by these elements.Accordingly, it can be advantageous to provide a large number of openings to improve air exchange between the cavity and its surroundings.

[0033] In a further advantageous embodiment of the present invention, a vibration bandwidth of the piezoelectric element and / or the membrane is defined based on an elastic modulus and / or a width of the coupling element. A correspondingly adapted vibration bandwidth can be relevant, for example, when the ultrasonic sensor uses not only electrical excitation signals with a fixed frequency, but also so-called "chirps," in which the electrical excitation frequency changes over time, for example, to reduce interference such as noise during measurements by the ultrasonic transducer. In such a case, the frequency of the first alternating signal and the frequency of the second alternating signal are traversed or reached within each "chirp."

[0034] Preferably, the ultrasonic sensor is configured to convert ultrasonic signals received (i.e., reflected) from its surroundings into an electrical receiving signal via the piezoelectric element and to process the receiving signal in a frequency range corresponding to both the natural frequency of the piezoelectric element and the natural frequency of the membrane. Advantageously, the ultrasonic sensor is configured to process additional frequency ranges and / or a correspondingly wide frequency band containing both the natural frequency of the piezoelectric element and the natural frequency of the membrane, so that the aforementioned "chirp" signals can also be used.

[0035] The ultrasonic sensor is advantageously designed as an environmental sensing sensor for a vehicle and, in particular, as a parking sensor for a parking assistance system of such a vehicle. For this purpose, the ultrasonic sensor according to the invention has, for example, suitable mounting elements for attachment to a vehicle and / or robustness adapted to environmental conditions and / or a power supply adapted to a vehicle electrical system, etc. A vehicle on which the ultrasonic sensor according to the invention can be arranged is, for example, a road vehicle such as a car, truck, bus, van, motorcycle, etc., or a rail vehicle. Brief description of the drawings

[0036] Exemplary embodiments of the invention are described in detail below with reference to the accompanying drawings. The drawing shows: Fig. 1 a schematic cross-sectional view of a part of an embodiment of an ultrasonic sensor according to the invention; Fig. 2 a schematic cross-sectional view of a part of a further embodiment of an ultrasonic sensor according to the invention; Fig. 3 a schematic cross-sectional view of a part of a further embodiment of an ultrasonic sensor according to the invention; Fig. 4 a schematic top view of an embodiment of a membrane and a coupling element of an ultrasonic sensor according to the invention; Fig. 5 a schematic top view of a further embodiment of a membrane and a coupling element of an ultrasonic sensor according to the invention; Fig. 6 a comparison of an exemplary frequency response of an ultrasonic transducer according to the invention and an exemplary frequency response of a conventional ultrasonic transducer; and Fig. 7 an exemplary overview of different directional characteristics of an ultrasound transducer according to the invention. Embodiments of the invention

[0037] Fig. Figure 1 shows a schematic cross-sectional view of a part of an embodiment of an ultrasonic sensor according to the invention, wherein the ultrasonic sensor is designed, for example, as an ultrasonic sensor for a parking assistance system of a vehicle designed as a passenger car and is used as such.

[0038] The ultrasonic sensor according to the invention comprises a piezoelectric element 10, a membrane 20, a coupling element 30 and an electrical circuit 40, wherein further components of the ultrasonic sensor such as a housing, connections for electrical contacting of the ultrasonic sensor to the outside, etc., have been omitted here for the sake of simplicity.

[0039] The piezoelectric element 10 and the membrane 20 are here planar, circular elements which are mechanically connected to each other in respective edge regions of their surfaces via the coupling element 30, so that a cavity 50 exists between respective central regions of the surfaces of the piezoelectric element 10 and the membrane 20.

[0040] In this embodiment, the coupling element 30 is formed as a component of the membrane 20 by manufacturing the membrane 20 in such a way that it has a ring-shaped circumferential elevation in its edge region, which forms the coupling element 30.

[0041] A vibration bandwidth of the ultrasound transducer according to the invention, which is to be achieved in accordance with the requirements for the ultrasound transducer according to the invention, is determined on the basis of an elastic modulus and a width of the coupling element 30.

[0042] The piezoelectric element 10 and the membrane 20 are arranged on the basis of the cavity 50 to oscillate largely independently of each other at their respective natural frequencies, with the piezoelectric element 10 having a natural frequency of 60 kHz, which differs from the natural frequency of the membrane 20, which here corresponds to 40 kHz.

[0043] The electrical circuit 40, which is at least partially designed as an analog circuit, is configured to subject the piezoelectric element 10 to a first alternating electrical signal which has a frequency of 60 kHz and thus corresponds to the natural frequency of the piezoelectric element 10 in order to set the piezoelectric element 10 into a resonant oscillation.

[0044] Furthermore, the electrical circuit 40 is set up to apply a second alternating electrical signal to the piezoelectric element 10, which has a frequency of 40 kHz, corresponding to the natural frequency of the membrane 20, in order to set the membrane 20 into a resonant vibration.

[0045] Furthermore, the electrical circuit 40 is designed to simultaneously excite the piezoelectric element 10 and the membrane 20 with their respective natural frequencies, if required, on the basis of frequency modulation.

[0046] Based on the configuration described above, the ultrasound transducer according to the invention is configured to emit ultrasound signals (i.e., sound waves) with different oscillation frequencies with high efficiency, i.e., high sound pressure, into an environment 70 of the ultrasound sensor and to receive reflections of the ultrasound signals received from the environment 70 also with high efficiency and to convert them into electrical reception signals, thereby providing, among other things, a particularly high signal-to-noise ratio in the received signals.

[0047] This enables particularly reliable and flexible detection of objects or obstacles in the vicinity of the ultrasonic sensor by alternating or simultaneous use of the two transmission frequencies.

[0048] Fig. Figure 2 shows a schematic cross-sectional view of a part of another embodiment of an ultrasonic sensor according to the invention. Due to numerous similarities between the one in Fig. 1 and the one in Fig. To avoid repetition, only the differences between the two ultrasound transducers according to the invention shown below will be discussed. Fig. 1 and Fig. 2 described and otherwise refers to the description to Fig. 1 referred.

[0049] In Fig. 2 the coupling element 30 is designed as a separate element, which is preferably ring-shaped in the case of a circular design of the piezoelectric element 10 and the membrane 20.

[0050] In the course of manufacturing the ultrasound transducer according to the invention, the coupling element 30 is inserted here between the piezoelectric element 10 and the membrane 20 by means of an adhesive, so that a mechanical coupling is produced between the respective edge regions of the piezoelectric element 10 and the membrane 20.

[0051] Fig. Figure 3 shows a schematic cross-sectional view of a part of another embodiment of an ultrasonic sensor according to the invention. Due to numerous similarities between the one in Fig. 2 and the one in Fig. To avoid repetition, only the differences between the 3 ultrasound transducers according to the invention shown below will be discussed. Fig. 2 and Fig. 3 described and otherwise refers to the description to Fig. 2 referred.

[0052] In Fig. 3 The ultrasonic sensor according to the invention comprises a first piezoelectric element 10 and a second piezoelectric element 60, which are mechanically connected to each other via a second coupling element 32, while the first piezoelectric element 10 and the membrane 20 are as shown in Fig. 2 shown are mechanically coupled to each other via a first coupling element 30.

[0053] Furthermore, the electrical circuit 40 is configured in this case to excite the second piezoelectric element 60, which has a natural frequency different from that of the first piezoelectric element 10 and the membrane 20, by means of a third alternating signal S3 with the natural frequency of the second piezoelectric element 60.

[0054] In this way, the ultrasound transducer according to the invention is configured to emit three ultrasound signals with three different frequencies, each with high efficiency, into an environment 70 of the ultrasound transducer, resulting in particularly high flexibility in environmental detection based on the ultrasound transducer according to the invention.

[0055] It should be noted that, for example, one or more additional piezoelectric elements can be added to the ultrasonic sensor in a similar manner, resulting, among other things, in even greater flexibility.

[0056] Fig. Figure 4 shows a schematic top view of an embodiment of a membrane 20 and a coupling element 30 of an ultrasonic sensor according to the invention, in which the overlying piezoelectric element 10 is not shown for better visibility of the coupling element 30.

[0057] The circular membrane 20 is mechanically fixed in its edge region to an annular coupling element 30, wherein the coupling element 30 is not completely closed, so that an opening 52 is formed which forms the cavity 50 (see e.g. Fig. 2) between the piezoelectric element 10 (see e.g. Fig. 2) and connects the membrane 20 with an environment 70 of the ultrasound transducer according to the invention.

[0058] In this way, pressure equalization and / or temperature equalization between the cavity 50 and the environment 70 can be ensured, which can improve the reliability of the ultrasonic sensor according to the invention.

[0059] Fig. Figure 5 shows a schematic top view of a further embodiment of a membrane 20 and a coupling element 30 of an ultrasonic sensor according to the invention, wherein the coupling element 30 is composed of a plurality of spaced-apart webs which are arranged in a ring shape in the edge region of the membrane 20.

[0060] The advantageous opening 52 (here formed by a plurality of openings 52) between the cavity 50 (see Fig. 2) and an environment 70 of the ultrasonic sensor according to the invention is ensured by the distances between the individual struts which form the coupling element 30.

[0061] Fig. Figure 6 shows a comparison of an exemplary frequency response 80 of an ultrasound transducer according to the invention and an exemplary frequency response 90 of a conventional ultrasound transducer.

[0062] The transverse axis in Fig. 6 represents the frequency f, while the vertical axis in Fig. 6 represents the sound pressure level SPL.

[0063] The frequency responses 80, 90 are relevant, for example, in a "chirp"-based measurement using the ultrasonic sensors, in which the transmission frequency of the ultrasonic transducer varies accordingly over time.

[0064] The frequency response 90 of the conventional ultrasound transducer has only a single resonance frequency in the range of 40 kHz, whereas the frequency response 80 of the ultrasound transducer according to the invention has two resonance frequencies, which result from the natural frequency 12 of the piezoelectric element 10 (see e.g. Fig. 1) and the natural frequency 22 of the membrane 20 (see e.g. Fig. 1) result.

[0065] Fig.Figure 7 shows an exemplary overview of different directional characteristics 100, 110 of an ultrasound transducer according to the invention, which result from the different frequencies of the generated ultrasound signals (i.e., the generated sound waves). QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited non-patent literature

[0000] LK a. SD Andrew Feeney, “High-Frequency Measurement of Ultrasound Using Flexural Ultrasonic Transducers,” IEEE Sensors Journal, 2018

[0009] A. F. a. S. D. Lei Kang, „The High Frequency Flexural Ultrasonic Transducer for Transmitting and Receiving Ultrasound in Air“, IEEE Sensors Journal, 2020

[0009] S. D. a. S. R. T.J.R. Eriksson, „Flexural Mode Metal Cap Transducer Design for Specific Frequency Air Coupled Ultrasound“, in Joint UFFC, EFTF and PFM Symposium, 2013

[0009]

Claims

[1] Equipped with an ultrasonic sensor: - a piezoelectric element (10), - a membrane (20), - a coupling element (30), and - an electrical circuit (40), wherein - the piezoelectric element (10) and the membrane (20) are planar elements which are mechanically connected to each other in respective edge regions of their surfaces via the coupling element (30), so that a cavity (50) exists between the respective central regions of the surfaces of the piezoelectric element (10) and the membrane (20), - the piezoelectric element (10) and the membrane (20) are arranged on the basis of the cavity (50) to oscillate essentially independently of each other at their respective natural frequencies (12, 14), wherein the piezoelectric element (10) has a natural frequency (12) which differs from the natural frequency (24) of the membrane (20), and - the electrical circuit (40) is set up, the piezoelectric element (10) is connected to a - to apply the first alternating electrical signal (S1), which has a frequency that essentially corresponds to the natural frequency (12) of the piezoelectric element (10), in order to set the piezoelectric element (10) into a resonant oscillation, and - to apply a second alternating electrical signal (S2) which has a frequency that essentially corresponds to the natural frequency (24) of the membrane (20) in order to set the membrane (20) into a resonant vibration. [2] Ultrasonic sensor according to claim 1, wherein the electrical circuit (40) is configured to apply the first alternating signal (S1) and the second alternating signal (S2) to the piezoelectric element (10) in a time-shifted manner and / or simultaneously. [3] Ultrasonic sensor according to one of the preceding claims, wherein the coupling element (30) is configured as - separate element, and / or - a component of the piezoelectric element (10, and / or - is formed as a component of the membrane (20). [4] Ultrasonic sensor according to one of the preceding claims, wherein the electrical circuit (40) is set up, - to generate the alternating signal (S1, S2) with the lower frequency from the first alternating signal (S1) and the second alternating signal (S2) for the greatest possible range when measuring with the ultrasonic sensor, and - to generate the highest possible spatial resolution in a measurement using the ultrasonic sensor, the alternating signal (S1, S2) from the first alternating signal (S1) and the second alternating signal (S2) which has the higher frequency. [5] Ultrasonic sensor according to one of the preceding claims, wherein the coupling element (30) is a one-piece continuous element or is formed from a plurality of individual coupling elements (30), which are in particular spaced apart from each other. [6] Ultrasonic sensor according to one of the preceding claims, wherein - the ultrasonic sensor has a multitude of piezoelectric elements (10, 60) and a multitude of coupling elements (30, 32), - each of the multitude of piezoelectric elements (10, 60) has a natural frequency that differs from the natural frequency (24) of the membrane and the natural frequency of the other piezoelectric elements (10, 60), - the piezoelectric elements (10, 60) are each stacked on top of one of the multiple coupling elements (30, 32), and - the electrical circuit (40) is set up to apply a corresponding alternating electrical signal (S1, S3) to each piezoelectric element (10, 60), each of which has a frequency that essentially corresponds to the respective natural frequency of the respective piezoelectric element (10). [7] Ultrasound sensor according to one of the preceding claims, wherein the cavity (50) formed by the piezoelectric element (10) and the membrane (20) is connected to an environment (70) of the ultrasound sensor via at least one opening (52). [8] Ultrasound sensor according to one of the preceding claims, wherein a vibration bandwidth of the piezoelectric element (10) and / or the membrane (20) is determined on the basis of an elastic modulus and / or a width of the coupling element (30). [9] Ultrasonic sensor according to one of the preceding claims, wherein - the electrical circuit (40) is set up to convert ultrasonic vibrations received from an environment (70) of the ultrasonic sensor into an electrical receiving signal via the piezoelectric element (10), and - to process the received signal in a frequency range corresponding to the natural frequency (12) of the piezoelectric element (10) as well as in a frequency range corresponding to the natural frequency (24) of the membrane (20). [10] Ultrasonic sensor according to one of the preceding claims, wherein the ultrasonic sensor is designed as an environment detection sensor for a vehicle.

Images