Sensor device for transmitting and / or receiving ultrasonic signals

Abstract

The invention relates to a sensor device (10) for transmitting and / or receiving an ultrasound signal (12, 13), wherein the sensor device (10) comprises a membrane (20) and a piezoelectric actuator element (30), wherein the actuator element (30) is mechanically fixed to the membrane (30) via at least one spacer element (40), wherein the spacer element (40) is designed and arranged such that the membrane (20) can be excited to transmit an ultrasound signal (12) by means of the actuator element (30) and the spacer element (40), and that the membrane (20) can be set into vibration in a partial region (22) of the membrane (20) by means of a received ultrasound signal (13), wherein the membrane (20) comprises a sensor element (50) by means of which the received ultrasound signal (13) can be detected. The invention also relates to a sensor unit with several sensor devices according to the invention (10).

Description

State of the art

[0001] Sensor devices for transmitting and / or receiving ultrasonic signals can be used, for example, in parking assist systems. These are typically installed in the bumper and / or adjacent body panels of a vehicle and have an active surface facing the outside, which is often membrane-like. The operating principle is usually based on measuring the time of flight of an acoustic signal in the ultrasonic range: at the beginning of a measurement, an ultrasonic signal is emitted from an active surface of the sensor device. When this ultrasonic signal encounters an obstacle, it is reflected. The reflected signal can then be detected by the sensor device via the active surface facing the outside. From the time interval between transmitting and receiving the signal, the distance to the obstacle can be calculated using the known speed of sound.

[0002] In prior art sensor devices, the active surface is typically designed as a piezoelectric membrane. This piezoelectric membrane is used to both transmit and receive the ultrasound signal. However, this means the sensor device can only operate resonantly within the range of the membrane's natural frequency; that is, the frequency of the transmitted and received ultrasound signals is fixed.

[0003] The invention aims to solve the aforementioned problem in the prior art. Disclosure of the invention

[0004] The invention relates to a sensor device for transmitting and / or receiving ultrasonic signals, wherein the sensor device comprises a membrane and a piezoelectric actuator element, wherein the actuator element is mechanically fixed to the membrane via at least one spacer element, wherein the spacer element is designed and arranged such that the membrane can be excited to transmit an ultrasonic signal by means of the actuator element and the spacer element and that the membrane can be set into vibration in a partial area of ​​the membrane by means of a received ultrasonic signal, wherein the membrane has a sensor element by means of which the received ultrasonic signal can be detected.

[0005] The advantage here is that, compared to a prior art sensor device, variable, non-resonant excitation of the diaphragm is possible over a wide frequency range and with different amplitudes. This allows the frequency and emission power of the sensor device to be adjusted accordingly. Furthermore, a reduction in frequency caused by additional mass on the diaphragm, e.g., by dirt, insects, water, or ice, can be compensated for by adjusting the drive frequency or amplitude. In addition, a closed-loop control system for the drive is achievable, as a comparison between target and actual states is possible.

[0006] The membrane is designed, for example, as a bending beam clamped at both ends or as a full-surface layer that can be deflected perpendicular to its main extension plane by the actuator element, above a recess, with the movement of the actuator element being transmitted to the membrane via the spacer element. An ultrasound signal is then typically emitted in its main outward transmission direction perpendicular to the main extension plane of the membrane.

[0007] The piezoelectric actuator element can convert an electrical voltage into a mechanical voltage, thereby achieving a corresponding expansion or compression. Applying an alternating voltage can, in turn, generate an oscillation.

[0008] The spacer element is positioned between the membrane and the actuator element and also serves as a distance holder, allowing the membrane to vibrate freely and / or resonantly, at least partially, when receiving ultrasound signals. The sensor device is designed such that a larger membrane area is effective when generating an ultrasound signal than when receiving one. The spacer element can also, for example, include cable glands for electrical cables running from the sensor element to the actuator element or to a corresponding control unit of the sensor device.

[0009] The sensor element can, for example, be designed as a piezoelectric sensor, which can convert the vibrations of the membrane into an electrical signal.

[0010] The sensor device can, for example, be arranged on a vehicle in order to collect information in the vehicle's environment for a higher-level parking monitoring system of the vehicle.

[0011] One embodiment of the invention provides that the piezoelectric actuator element is macroscopically designed.

[0012] An advantage of this design is that, in the case of a stacked actuator, even a low voltage applied to the piezoelectric actuator element is sufficient to deflect the membrane enough to generate the ultrasonic signals. The stacked actuator is designed in a layered structure, enabling good d33 coupling (deformation parallel to the electric field), which results in a higher electric field strength due to the smaller electrode spacing. This, in turn, leads to more effective electromechanical coupling. Furthermore, the macroscopic design of the actuator element results in greater rigidity of the sensor device, making it more robust, particularly against damage from negative external influences such as high-pressure cleaners.

[0013] Macroscopic refers to a size of the actuator element in the upper micrometer range or in the millimeter range.

[0014] One embodiment of the invention provides that the spacer element at least partially rests against the membrane at the edge of the partial area of ​​the membrane.

[0015] The advantage here is that the design and arrangement of the spacer element allows the surface area of ​​the membrane to be adjusted, which is capable of vibrating when receiving an ultrasound signal.

[0016] The portion of the membrane that vibrates upon receiving an ultrasound signal is primarily defined by the spacer element, in that the membrane is mechanically connected to the spacer element at least at certain points in the lateral direction. Where the membrane is not connected to the spacer element, it can be set into vibration by an ultrasound signal.

[0017] Another embodiment of the invention provides that the spacer element is designed in a ring shape.

[0018] The advantage here is that this design enables good force transmission from the actuator element to the membrane, while still allowing the membrane to vibrate freely, at least in that partial area.

[0019] The diaphragm essentially rests on the ring-shaped spacer, whose axis is oriented perpendicular to the main plane of extension of the diaphragm. The vibrating portion of the diaphragm is typically located above the inner area of ​​the spacer, since the outer area of ​​the diaphragm is fixed, for example, to the housing.

[0020] According to a further embodiment of the invention, it is provided that the sensor element is arranged at least on or in the partial area of ​​the membrane or forms the membrane itself.

[0021] The advantage here is that this is a simple way to detect a received ultrasound signal.

[0022] The sensor element can be integrated into the membrane or positioned on its underside or top surface. Alternatively, the entire membrane can be designed as a sensor component, for example as a piezoelectric bending transducer.

[0023] According to a further embodiment of the invention, the sensor element is designed as a piezoelectric bending transducer. An advantage of this is that such a bending transducer can be manufactured quickly and cost-effectively. Furthermore, this allows the movement of the membrane to be converted into electrical signals, which can be used to evaluate the received ultrasound signals and to control the drive frequency of the actuator element.

[0024] According to a further embodiment of the invention, the sensor device comprises a housing, wherein the actuator element is arranged within the housing and wherein the housing encompasses the membrane. An advantage here is that the housing protects the actuator element, and in particular also other elements such as the spacer element or a sensor element arranged on the underside of the membrane, from negative external influences such as impacts, contamination, or water.

[0025] The housing accordingly comprises a base, side walls, and a lid. The entire lid, or at least a part of it, is designed to be correspondingly thin, forming the membrane of the sensor device.

[0026] According to a further embodiment of the invention, the piezoelectric actuator element and the spacer element and / or the membrane and the spacer element and / or the sensor element and the spacer element are formed in one piece. The advantage here is that this enables faster and therefore more cost-effective manufacturing of the sensor device. In addition, the stability of the corresponding components can be increased.

[0027] The term "one-piece" refers in particular to combination components, e.g., a silicon-based MEMS chip, which combines the functions of two or more components.

[0028] The invention also relates to a sensor unit with several sensor devices according to the invention.

[0029] This allows for the simultaneous measurement of elevation and azimuth angles when receiving an echo, as well as the option to choose between spherical and focused directional characteristics.

[0030] In particular, the sensor devices are arranged side by side, forming a sensor array. This allows, among other things, the direction of the emitted ultrasound waves to be influenced. Drawings Fig. Figure 1 shows an embodiment of a sensor device according to the invention in a side sectional view. Fig. Figure 2 shows the embodiment of the sensor device according to the invention in a sectional view from above. Fig. 3a to Fig. Figures 3c each show a section of the sensor device according to the invention in different states. Description of exemplary implementations

[0031] Fig. Figure 1 shows an embodiment of a sensor device according to the invention in a side sectional view.

[0032] Shown is a sensor device 10 for emitting and / or receiving ultrasonic signals 12, 13. The section in the illustration is made along the section plane A, which is in Fig. Figure 2 shows the sensor device 10, which comprises a membrane 20 and a piezoelectric actuator element 30. The piezoelectric actuator element 30 is macroscopically designed.

[0033] Furthermore, the sensor device 10 has a housing 60, wherein the actuator element 30 is arranged inside the housing 60 and wherein the housing 60 includes the membrane 20 as a cover element.

[0034] The actuator element 30 is mechanically fixed to the membrane 30 via at least one spacer element 40. The spacer element 40 is designed and arranged such that the membrane 20 can be excited to transmit an ultrasound signal 12 by means of the actuator element 30 and the spacer element 40, and that the membrane 20 can be set into vibration in a partial region 22 of the membrane 20 by a received ultrasound signal 13. The spacer element 40 is arranged such that it rests at least partially against the membrane 20 at the edge of the partial region 22 of the membrane 20. The direction of deflection of the membrane 20 is indicated by the dashed arrow.

[0035] Furthermore, the membrane 20 has a sensor element 50 by means of which the received ultrasound signal 13 can be detected. The sensor element 50 is designed as a piezoelectric bending transducer and is arranged on the sub-area 22 of the membrane 20 within the housing 60.

[0036] In particular, the piezoelectric actuator element 30 and the spacer element 40, or the membrane 20 and the spacer element 40, or the sensor element 50 and the spacer element 40, can be formed in one piece.

[0037] Furthermore, in an embodiment not shown in the illustration, several sensor devices 10 can be combined to form a sensor unit.

[0038] Fig. Figure 2 shows the embodiment of the sensor device according to the invention in a sectional view from above.

[0039] The sensor device 10 is shown again. Fig. 1, where the cut in the representation now takes place along the cutting plane B, which is in Fig. 1 is shown accordingly.

[0040] The sensor device 10 comprises the housing 60, the piezoelectric actuator element 30, the spacer element 40, and the sensor element 50. The ring-shaped design of the spacer element 40 is clearly visible. Furthermore, it can be seen that the sensor element 50 is arranged centered on the spacer element 40.

[0041] Fig. 3a to Fig. Figures 3c each show a section of the sensor device according to the invention in different states.

[0042] The cutouts each show the membrane 20, the spacer element 40 and the sensor element 50 in a side sectional view as shown in the diagram. Fig. 1.

[0043] In Fig. 3a The sensor device 10 is at rest and no ultrasound signals 12, 13 are emitted or received. The membrane 20 is therefore not deflected.

[0044] Fig. Figure 3b shows the sensor device 10 at maximum and minimum deflection of the membrane 20, which is deflected via the spacer element 40 and the actuator element 30 to generate the ultrasound signal 12. The membrane 20 is deflected perpendicular to its main direction of extension, as indicated by the dashed arrow.

[0045] Fig. Figure 3c represents the maximum and minimum deflection of the membrane 20 when receiving an ultrasound signal 13. Only the portion 22 of the membrane 20 located above the inner area of ​​the spacer element 40 vibrates. The membrane 20 is deflected perpendicular to its main direction of extension, as indicated by the dashed arrow. The respective deflection of the membrane 20 is detected by the sensor element 50, which bends along with the membrane 20 at the corresponding deflection.

Claims

[1] Sensor device (10) for transmitting and / or receiving ultrasonic signals (12, 13), wherein the sensor device (10) comprises a membrane (20) and a piezoelectric actuator element (30), wherein the actuator element (30) is mechanically fixedly connected to the membrane (30) via at least one spacer element (40), wherein the spacer element (40) is designed and arranged such that the membrane (20) can be excited to transmit an ultrasonic signal (12) by means of the actuator element (30) and the spacer element (40), and that the membrane (20) can be set into vibration in a partial area (22) of the membrane (20) by means of a received ultrasonic signal (13), wherein the membrane (20) comprises a sensor element (50) by means of which the received ultrasonic signal (13) can be detected. [2] Sensor device (10) according to claim 1, characterized by , that the piezoelectric actuator element (30) is macroscopically formed. [3] Sensor device (10) according to one of the preceding claims, characterized by , that the spacer element (40) is at least partially in contact with the membrane (20) at the edge of the sub-area (22) of the membrane (20). [4] Sensor device (10) according to any one of the preceding claims, characterized by , that the spacer element (40) is designed in a ring shape. [5] Sensor device (10) according to any one of the preceding claims, characterized by that the sensor element (50) is arranged at least on or in the sub-area (22) of the membrane (20) or forms the membrane (20) itself. [6] Sensor device (10) according to any one of the preceding claims, characterized by , that the sensor element (50) is designed as a piezoelectric bending transducer. [7] Sensor device (10) according to any one of the preceding claims, characterized by, that the sensor device (10) has a housing (60), wherein the actuator element (30) is arranged inside the housing (60) and wherein the housing (60) comprises the membrane (20). [8] Sensor device (10) according to any one of the preceding claims, characterized by , that the piezoelectric actuator element (30) and the spacer element (40) and / or the membrane (20) and the spacer element (40) and / or the sensor element (50) and the spacer element (40) are formed in one piece. [9] Sensor unit with multiple sensor devices (10) according to one of the preceding claims.

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