Air-coupled ultrasonic array sensor for detecting distances between a vehicle and objects in the surroundings of the vehicle, parking assistance system and vehicle

Abstract

The invention relates to an ultrasonic array sensor (100) for detecting distances between a vehicle and objects in the surroundings of the vehicle, comprising at least one diaphragm component (110) having a vibrating diaphragm (111) and a cavity (113) in the interior of the diaphragm component (110); and at least two transducer elements (130), wherein each transducer element (130) is mechanically coupled to a diaphragm region (112), wherein the ultrasonic array sensor (100) has a support structure (120) which is arranged in the cavity (113) of the diaphragm component (110) and contacts a contact region of the diaphragm (111) on the inner side (118), as a result of which the diaphragm (111) is divided into at least two separate vibrating diaphragm regions (112), wherein the support structure (120) creates a natural frequency distance Δf eig between the different vibration modes of the diaphragm (111) of the ultrasonic array sensor (100) of less than or equal to 10% with respect to the operating frequency op of the ultrasonic array sensor (100).

Description

[0001] R. 418448

[0002] - 1 -

[0003] Description

[0004] title

[0005] Air-coupled ultrasonic array sensor for detecting distances between a vehicle and objects in the vehicle's vicinity, parking assistance system and vehicle

[0006] The present invention relates to an air-coupled ultrasonic array sensor for detecting distances between a vehicle and objects in the vehicle's vicinity. The invention also relates to a parking assistance system comprising at least the ultrasonic array sensor according to the invention. Furthermore, the invention relates to a vehicle comprising either the parking assistance system or the ultrasonic array sensor according to the invention.

[0007] State of the art

[0008] State-of-the-art ultrasonic sensors are actively electrically controlled sensors that preferably operate on the pulse-echo principle to detect and advantageously display distances between a vehicle and objects in the immediate vicinity, for example, between 10 centimeters and 6 meters. This can, for instance, facilitate parking maneuvers for the driver. In such an ultrasonic sensor, an electrical current or voltage signal is used to excite vibrations in an electromechanical transducer element, such as a piezoelectric transducer, where the transducer element is mechanically coupled to a vibrating diaphragm. The mechanical vibration of the transducer element generates a diaphragm vibration, which is coupled out or emitted as ultrasound. The sound propagates through the air.The surface of an object in the vicinity of the vehicle, for example another vehicle, a curb, or a person, reflects the emitted ultrasonic wave back. R. 418448.

[0009] - 2 - to the ultrasonic sensor. The diaphragm of the ultrasonic sensor, which has meanwhile come to a standstill, is excited to vibration by the incoming ultrasonic wave. This vibration can be detected as an electrical signal at the transducer element. The distance between the ultrasonic sensor and the object is determined based on the known propagation speed of ultrasound in air, depending on the transit time between the emission of the ultrasonic wave and the reception of the reflected signal. Air-coupled ultrasonic sensors are usually operated at a frequency corresponding to the diaphragm's natural resonance, resulting in the largest possible vibration amplitude with low power consumption. Typically, the operating frequency is selected to be in the range of approximately 40 to 60 kHz, and the diaphragm is designed accordingly, for example, with regard to its thickness.The wavelength of ultrasound waves, according to the formula = c / f, where X is the wavelength, c is the speed of sound in air and f is the frequency, is therefore between approximately 5 and 9 mm.

[0010] An ultrasonic array sensor comprises several array elements, or transducer elements, and diaphragm sections that are intended to operate as independently as possible in both transmit and receive modes. An ultrasonic array sensor therefore includes at least two transducer elements. Due to the spatial proximity of the different diaphragm sections and the different transducer elements, and also due to the use of a common, continuous diaphragm encompassing the different diaphragm sections, a vibrational coupling occurs between the individual array elements, diaphragms, or transducer elements. This vibrational coupling leads to crosstalk effects, in which the individual array elements influence each other during operation and vibrations are transmitted to adjacent diaphragm sections.However, the coupling of an ultrasonic wave is only desired at the membrane area deflected by the corresponding transducer element. Crosstalk, also known as transducer interference, is therefore primarily caused by the vibrational characteristics of the continuous membrane. The membrane can be considered, from a vibrational dynamics perspective, as a clamped, for example circular, plate element. A circular plate possesses several vibration modes. A vibration mode, also called a natural frequency or eigenmode, describes a specific type and R. 418448.

[0011] - 3 - The way a system can oscillate when displaced from its equilibrium position and then released. Every complex system capable of oscillation has multiple modes of vibration, each defined by a specific natural frequency and a characteristic waveform. Based on the physical properties (e.g., mass, stiffness, length) of the oscillating system, each mode of vibration has a specific natural frequency at which it oscillates. The waveform describes a spatial distribution of the vibration, for example, of a particular mode. A system can oscillate in multiple modes simultaneously. The resulting vibration is then a superposition of the individual modes.

[0012] The document EP 3 807632 B1 discloses a 1D ultrasonic transducer unit for detecting objects, contours or distances.

[0013] Document DE 10 2022 206 262 A1 discloses an ultrasonic array sensor with at least two ultrasonic membrane elements for emitting and receiving ultrasonic signals and a housing with a cover plate.

[0014] Document EP 1 202 249 A1 discloses an ultrasonic array sensor.

[0015] The object of the present invention is to improve an ultrasonic array sensor.

[0016] Disclosure of the invention

[0017] The above problem is solved according to the invention in accordance with independent claims 1, 14 and 15.

[0018] The invention relates to an ultrasonic array sensor for detecting distances between a vehicle and objects in the vehicle's vicinity. The ultrasonic array sensor advantageously couples or emits ultrasonic waves into the air and advantageously receives reflected ultrasonic waves from the air. The ultrasonic array sensor comprises at least one membrane component, having a vibrating membrane and a cavity inside the membrane component. For example, the membrane component is a cylindrical membrane pot, particularly one made of aluminum, in R. 418448

[0019] - 4 -a cylindrical cavity is arranged inside the membrane housing. Preferably, the bottom of the membrane housing comprises the membrane. The membrane is configured to vibrate, preferably with a direction of vibration normal to the membrane surface. According to the invention, the ultrasonic array sensor also has a mechanical support structure, wherein the support structure is arranged in the cavity of the membrane component. The support structure contacts the membrane on the inside, in particular with a contact area, thereby dividing the membrane into at least two separately vibrating membrane areas. Advantageously, the support structure and the membrane are bonded or welded together in the contact area of ​​the support structure and the membrane, respectively; that is, the support structure and the membrane are in particular directly connected to or fixed to each other.Furthermore, the ultrasonic array sensor comprises at least two transducer elements, in particular piezoceramic oscillators or vibrating elements, which can be separately driven to vibrate by electrical control. Each transducer element is mechanically coupled to one of the membrane regions, in particular by bonding. The distance between two adjacent transducer elements is advantageously less than or equal to half the emitted and / or received ultrasonic wavelength. Advantageously, each transducer element is configured to generate a mechanical vibration by electrical control to emit an ultrasonic wave into the environment via the coupled membrane region and / or to electrically detect a vibration of the coupled membrane region as a mechanical vibration, wherein the detected mechanical vibration advantageously represents an ultrasonic wave received from the environment in the coupled membrane region.The membrane regions are preferably symmetrical to each other. In particular, the membrane regions preferably each have a resonant frequency that corresponds to the operating frequency of the ultrasonic sensor when emitting an ultrasonic wave and / or when receiving the reflected ultrasonic wave. According to the invention, the support structure generates a natural frequency difference Afeig between the different vibration modes of the membrane of the ultrasonic array sensor with respect to the operating frequency f. op of the ultrasonic array sensor of less than or equal to 10% (Afeilfop < 10%). Preferably, the natural frequency spacing Afeig between the different vibration modes of the diaphragm of the ultrasonic array sensor with respect to the operating frequency f is op of the ultrasonic array sensor smaller or R. 418448

[0020] - 5 - equal to 3% (A feig / fop < 3%). The natural frequency difference A feig between the different vibration modes of the membrane of the ultrasonic array sensor with respect to the operating frequency f is particularly preferred. op of the ultrasonic array sensor less than or equal to 1% (Afeig / f op < 1%). Due to the small natural frequency difference A f eis During operation, when an ultrasonic wave is emitted or when a transducer element is excited to vibrate at the operating frequency f, the different vibration modes of the membrane of the ultrasonic array sensor are compared. opThis generates superimposed vibration modes of the diaphragm, resulting in destructive interference at the inactive transducer elements or unexcited diaphragm areas. This reduces crosstalk from the activated diaphragm area to unactivated areas, thereby increasing the accuracy of distance detection. Furthermore, at near-natural frequencies of the vibration modes, the vibration at the activated transducer element or excited diaphragm area is advantageously amplified, increasing the amplitude of the emitted ultrasonic wave. This, in turn, increases the maximum detectable distances between the ultrasonic sensor and an object in its vicinity.The ultrasound array sensor according to the invention therefore has the advantage that the transmission of unwanted vibrations, crosstalk, or interference between the separate membrane areas is reduced. In other words, the support structure advantageously results in a reduced transmission of vibrations between the membrane areas or vibrating sub-areas of the membrane; that is, for example, a vibration of one membrane area is not transmitted, or is transmitted less, to the other membrane area. In particular, the support structure adapts or adjusts the physical properties of the vibrating membrane so that the natural frequencies of the vibration modes and waveforms of the membrane areas are defined. The natural frequencies of the vibration modes are advantageously set by shaping the support structure on the back side of the membrane.The natural frequencies of the vibration modes are adapted in particular by the wall thickness between two adjacent recesses of the support structure and the height of the support structure. The support structure is advantageously dimensioned, designed, or shaped such that different vibration modes of the membrane of the ultrasonic array sensor have a small natural frequency separation, R. 418448.

[0021] - 6 - thereby achieving an advantageous superposition of the vibration modes and reducing crosstalk by eliminating destructive interference. A particularly advantageous superposition is achieved when the natural frequencies of the vibration modes to be superimposed have a natural frequency separation Afeig with respect to the operating frequency f. opAfei / fop < 3%, preferably Afei / fop < 1%, are achieved. In other words, the superposition of the vibration modes during operation preferably leads to a superposition, thereby reducing crosstalk or the transmission of vibrations between the array elements. The ultrasonic array sensor according to the invention unifies the sound-emitting surfaces of the transducer elements or individual elements of the array into a common, continuous outer surface, resulting in high robustness against external influences. For example, robustness against mechanical impact and against environmental influences, such as moisture and soiling, is increased. Additionally, the common outer surface allows for simple and homogeneous painting. This enables the ultrasonic array sensor to be used analogously to the established single ultrasonic sensor in vehicles.

[0022] Advantageously, the height of the support structure perpendicular to the membrane is greater than the membrane thickness; particularly preferably, the height of the support structure perpendicular to the membrane is five to fifty times greater than the membrane thickness. This design achieves a particularly advantageous reduction in crosstalk.

[0023] In one embodiment, the wall thickness in the direction parallel to the membrane path and between the recesses of the support structure at the narrowest point has an amount of at least the membrane thickness, wherein the wall thickness is preferably up to five times the membrane thickness.

[0024] In an advantageous embodiment, the support structure comprises at least two recesses, in particular feedthroughs, each of which is arranged on one of the membrane regions. This embodiment advantageously allows, for example, the arrangement of the transducer element on the respective membrane region and the electrical contacting of the transducer element, in particular a piezoceramic transducer, through the recess, in particular feedthrough. R. 418448

[0025] - 7 -

[0026] In a further development of this design, the recesses of the support structure have a substantially semicircular, circular, elliptical, and / or polygonal cross-section in a plane parallel to the diaphragm or diaphragm regions. This recess shape influences the vibration mode and the reduction of unwanted crosstalk. In a possible embodiment, different recesses of the support structure have different cross-sections, for example, one recess with a semicircular cross-section and another with a rectangular cross-section, thereby influencing the vibration mode and the vibration shape in such a way as to further reduce unwanted crosstalk. Preferably, the recesses of the support structure have identical cross-sections and are particularly symmetrical, which improves the accuracy of the measurement capability and / or signal processing.

[0027] In a further embodiment, the support structure and the membrane are connected to each other by material and / or force-fit, in particular by welding or bonding. This embodiment advantageously allows the support structure and the membrane component to be made of different materials, thus simplifying the manufacturing of the ultrasonic array sensor.

[0028] Preferably, the support structure has a cylindrical outer contour and is designed to be inserted into the membrane component, in particular the membrane pot, and advantageously pressed or fixed to the membrane in the direction perpendicular to the membrane.

[0029] In another embodiment, the support structure and the membrane are manufactured or produced as a single piece. This embodiment advantageously eliminates an assembly step in the production of the ultrasonic array sensor.

[0030] The ultrasonic array sensor may additionally comprise at least one filling material, in particular a foam, which is arranged on the inside of the membrane component at least in each of the recesses of the support structure, wherein the filling material contacts the membrane area on the inside of the membrane. The filling material may also be arranged in a common cavity and / or engage in several recesses. R. 418448

[0031] - 8 - During the decay of the emitting membrane area, a reflected ultrasonic wave cannot yet be detected, which affects the minimum resolvable or detectable distance between the ultrasonic array sensor or the vehicle and an object in the vehicle's vicinity. The filling material, through its contact with the membrane area, is advantageously designed to dampen or shorten the decay of the emitting membrane area.

[0032] In another embodiment of the ultrasonic array sensor, the center-to-center distance between two adjacent transducer elements is greater than half the emitted and / or received ultrasonic wavelength. This simplifies the use of piezoceramic transducers as transducer elements.

[0033] In another iteration of the above design, the center-to-center distance between two adjacent transducer elements is smaller than the emitted and / or received ultrasonic wavelength. This configuration results in a still sufficient measurement capability of the ultrasonic array sensor.

[0034] In another embodiment, the support structure comprises a metal, in particular aluminum or steel, a plastic, in particular a fiber-reinforced plastic, and / or a ceramic. The support structure advantageously comprises a material that has a lower or higher stiffness than the membrane component.

[0035] The invention also relates to a parking assistance system comprising at least one ultrasonic array sensor according to the invention.

[0036] The invention also relates to a vehicle with the parking assistance system according to the invention or at least comprising an ultrasonic array sensor according to the invention.

[0037] Further advantages will become apparent from the following description of exemplary embodiments with reference to the figures.

[0038] Figure 1: Ultrasonic array sensor with support structure R. 418448

[0039] - 9 - Examples of Implementation

[0040] Figure 1 schematically shows an exploded view of an ultrasonic array sensor 100, which is configured for measuring the distance between a vehicle and objects in the vehicle's vicinity. In other words, for clarity, an exploded view is shown, which spatially separates the individual parts or components depicted, which may be connected to each other within the ultrasonic array sensor. The ultrasonic array sensor 100 comprises a cylindrical diaphragm housing as a diaphragm component 110 with a vibrating diaphragm 111 in the base 115 of the diaphragm housing, wherein a cylindrical cavity 113 is located inside the diaphragm housing. The diaphragm housing as a diaphragm component 110 comprises, or is made of, aluminum or a plastic.A mechanical support structure 120 with a cylindrical outer contour 121 is arranged in the cavity 113 of the membrane component 110 of the ultrasonic array sensor 100. The support structure 120 is inserted into the cavity 113 in contact with the vibrating membrane 111 and is, in particular, fixed to the membrane 111. This support structure 120 also comprises, for example, aluminum or, advantageously, a stiffer material than the membrane component 110, such as steel or ceramic. The support structure 120 contacts the membrane 111 with a contact area 124 of the support structure 120. The support structure 120 and the membrane 111 are, in particular, bonded or welded together. In other words, the connection between the support structure 120 and the membrane 111 is material- or force-fit, for example, by welding or bonding. Alternatively, the support structure 120 and the membrane component 110, or the membrane housing, are manufactured as a single piece or together.The support structure 120 divides the membrane 111 into at least two separately or independently oscillating membrane regions 112. The support structure 120 generates a natural frequency difference A feig between the different vibration modes of the membrane 111 of the ultrasonic array sensor 100 with respect to the operating frequency f. op of the ultrasonic array sensor 100 of less than or equal to 10%, in particular of less than or equal to 3% and preferably of less than or equal to 1%.

[0041] The support structure 120 has at least two recesses 122 with substantially semicircular, circular, elliptical or polygonal transverse grooves. 418448

[0042] - 10 -cut, with each recess 122 being assigned to one of the membrane areas 112. These recesses 122 allow the attachment of at least two transducer elements 130 - for example, piezoceramic transducers - which are each arranged in a recess 122 and mechanically coupled to one of the membrane areas 112, usually by bonding. Optionally, a filling material, in particular a foam, at least partially fills the recesses 122 and provides additional contact with the membrane area 112. The filling material reduces the vibration behavior of the respective membrane area 112.

[0043] The center-to-center distance 131 between the transducer elements 130 is advantageously less than half, or alternatively greater than half but less than the full wavelength of the emitted and / or received ultrasonic waves. The height H of the support structure 120 is advantageously 5 to 50 times greater than the membrane thickness 119, while the wall thickness 123 between the recesses is at least equal to the membrane thickness 119 and at most five times the membrane thickness 119. The support structure 120 influences the vibration shape and mode. The resulting design enables precise distance measurements in the vehicle environment using only one sensor.

Claims

R. 418448 - 11 - Claims 1. Ultrasonic array sensor (100) for detecting distances between a vehicle and objects in the vicinity of the vehicle, comprising at least • a membrane component (110) comprising a vibrating membrane (111) and a cavity (113) inside the membrane component (110), and • at least two transducer elements (130), wherein each transducer element (130) is mechanically coupled to a membrane area (112), characterized in that the ultrasonic array sensor (100) has the following component • a support structure (120), wherein the support structure (120) is arranged in the cavity (113) of the membrane component (110) and the membrane (111) contacts the inner side (118), wherein the support structure (120) divides the membrane (111) into at least two separate vibrating membrane areas (112), wherein the support structure (120) provides a natural frequency difference Afeig between the different vibration modes of the membrane (111) of the ultrasonic array sensor (100) with respect to the operating frequency f op of the ultrasonic array sensor (100) of less than or equal to 10% 2. Ultrasonic array sensor according to one of the preceding claims, wherein the height of the support structure (120) is greater than the membrane thickness (119), preferably the height (H) of the support structure (120) is five to fifty times greater than the membrane thickness (119).

3. Ultrasonic array sensor according to one of the preceding claims, wherein the wall thickness (123) between the recesses (122) of the support structure (120) at the narrowest point is at least the membrane thickness (119), wherein the wall thickness (123) is in particular up to five times the membrane thickness (119). R. 418448 - 12 - 4. Ultrasonic array sensor according to one of claims 1 to 3, wherein the support structure (120) comprises at least two recesses (122), in particular feedthroughs, wherein each of the recesses (122) is arranged on one of the membrane regions (112).

5. Ultrasonic array sensor according to claim 4, wherein the recesses (122) of the support structure (120) have a substantially semicircular, circular, elliptical and / or polygonal cross-section in a plane parallel to the membrane (111) or to the membrane regions (112).

6. Ultrasonic array sensor according to one of the preceding claims, wherein the support structure (120) and the membrane (111) are connected to each other by material and / or force-fit, in particular they are welded or bonded together.

7. Ultrasonic array sensor according to one of the preceding claims, wherein the support structure (120) has a cylindrical outer contour (121) and is configured to be inserted into the membrane component (110) and, in particular, to be fixed in the direction perpendicular to the membrane (111).

8. Ultrasonic array sensor according to one of claims 1 to 5, wherein the support structure (120) and the membrane component (110) are manufactured or constructed in one piece.

9. Ultrasonic array sensor according to one of the preceding claims, further comprising at least • a filler material (140) which is arranged on the inside (118) of the membrane component (110) in each of the recesses (122), wherein the filler material (140) contacts the membrane area (112).

10. Ultrasonic array sensor according to one of the preceding claims, wherein a center-to-center distance (131) between two adjacent transducer elements (130) is greater than half the emitted and / or received ultrasonic wavelength. R. 418448 - 13 - 11. Ultrasonic array sensor according to one of the preceding claims, wherein a center distance (131) between two adjacent transducer elements (130) is smaller than the emitted and / or received ultrasonic wavelength.

12. Ultrasonic array sensor according to one of the preceding claims, wherein the support structure (120) comprises a metal, a plastic and / or a ceramic.

13. Ultrasonic array sensor according to one of the preceding claims, wherein the support structure (120) comprises a material which has a lower or higher stiffness than the membrane component (110).

14. Parking assistance system comprising at least one ultrasonic array sensor (100) according to one of claims 1 to 13 15. Vehicle comprising at least one parking assistance system according to claim 14 or an ultrasonic array sensor (100) according to one of claims 1 to 13.

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