Ultrasonic sensor, parking aid and motor vehicles

Abstract

Ultrasonic sensor (10) for generating and / or receiving ultrasonic pulses. The ultrasonic sensor (10) has a plurality of openings (14) for the ultrasonic pulses. Each opening (14) has a shape that cannot be mapped onto itself by rotation about its center of gravity (16) with a rotation angle φ that satisfies the condition 0° < φ ≤ 90°.

Description

Prior ArtThe invention relates to an ultrasonic sensor, a parking aid and a motor vehicle.Motor vehicles frequently have parking aids which facilitate parking, for example in a confined space. A parking aid typically has at least one ultrasonic sensor for ascertaining a distance between the motor vehicle and an object.Disclosure of the InventionThe invention is based on the object of providing an ultrasonic sensor which enables reliable detection of an object by means of ultrasonic pulses having high sound pressure levels. It is a further object of the present invention to provide a parking aid and a motor vehicle, each of which has an ultrasonic sensor of this type.The object underlying the invention is achieved by an ultrasonic sensor having the features of claim 1, a parking aid having the features of claim 11 and a motor vehicle having the features of claim 12. Advantageous refinements of the invention are mentioned in the dependent claims.An ultrasonic sensor according to the invention is configured for generating and / or receiving ultrasonic pulses. The ultrasonic sensor has a plurality, for example 2, 4, 6 or 8, of openings for the ultrasonic pulses.Each opening has a shape that is not imageable on itself by rotating about its center of gravity at a rotation angle φ that satisfies the condition 0°<φ≤90°.Advantageously, it can be achieved in this way that parasitic radiation of sound in undesired directions is reduced, for which reason ultrasonic pulses with high sound pressure levels can be generated. Due to the reduction of parasitic radiation of sound in unwanted directions, a sensitivity of the ultrasonic sensor can be advantageously improved, for which reason an object is reliably detectable. Therefore, for example, each opening for increasing the sound pressure level and the sensitivity can be made larger without degrading a relationship between a main lobe of the ultrasonic pulses and a side lobe of the ultrasonic pulses so as to prevent reliable detection of an object by the side lobe.The openings can be provided to emit and / or receive the ultrasonic pulses. Ultrasonic pulses can exit the ultrasonic sensor through the openings and ultrasonic pulses can enter the ultrasonic sensor. For example, the ultrasonic sensor can generate ultrasonic pulses that leave the ultrasonic sensor by exiting the openings. For example, the ultrasonic sensor may receive ultrasonic pulses by entering the ultrasonic pulses into the apertures.Each opening may form an acoustic aperture and / or an acoustically effective area.The shape may be a shape of a clear surface of the opening. The center of gravity may be a centroid of the clear surface of the opening.The shape may be a shape of a cross section of the opening. The center of gravity may be a centroid of the cross section of the opening.The shapes of the openings can be identical.In a development of the ultrasonic sensor, the shape of each opening can be mapped onto itself by rotation about its center of gravity with a rotation angle φ of 180° or 120°. Alternatively, the shape of each opening does not have rotational symmetry with respect to its center of gravity. In particular, the shape of each opening cannot be designed to be rotationally symmetrical, point-symmetrical and / or mirror-symmetrical.In a development of the ultrasonic sensor, each opening is rectangular. Advantageously, the rectangular shape has proven to be particularly suitable for the detection of an object by means of ultrasonic pulses. Opposite sides of each opening may be of equal length and parallel to each other. Each opening may be formed not as a square.In a development of the ultrasonic sensor, a length of each opening is greater than a width of the opening.In a development of the ultrasonic sensor, at least one corner of each opening is rounded. Advantageously, the rounded corner may facilitate establishing an adhesive connection. In particular, the rounded corner can produce the adhesive connection on a larger surface. As a result, an applicability of the ultrasonic sensor can be advantageously increased.In a development of the ultrasonic sensor, a radius of the rounded corner is at least half the width of the opening. For example, an amount of the radius of the rounded corner may be equal to an amount of the width of the opening.In a development of the ultrasonic sensor, the ultrasonic sensor has a plurality, for example 2, 4, 6 or 8, of elements. One element each is arranged in an opening. Each element is capable of being excited to oscillate for the purpose of generating and / or receiving the ultrasonic pulses. Each element can be formed as a membrane. An electroacoustic transducer, for example a piezoelectric element, of the ultrasonic sensor can be arranged on each membrane. The electroacoustic transducer can be connected to the diaphragm in terms of vibration.For example, the ultrasonic sensor can generate ultrasonic pulses by applying an electrical signal to an electroacoustic transducer, which oscillates the membrane, which propagates as an ultrasonic pulse, depending on the electrical signal.For example, the ultrasonic sensor can receive an ultrasonic pulse by the ultrasonic pulse to be received causing the diaphragm to oscillate and the electroacoustic transducer converting the oscillation of the diaphragm into an electrical signal.In a development of the ultrasonic sensor, each element has a structuring, in particular facing the opening. The structuring can be, for example, an elevation or a depression. The structuring can define, for example, an oscillation shape of the ultrasonic pulses.In a development of the ultrasonic sensor, at least one distance between the centroids of two adjacent openings is half of a wavelength of the ultrasonic pulses. As a result, it is advantageously possible to reduce or completely avoid radiation of sound in an undesired direction.Each opening may have a longitudinal axis. The longitudinal axes of the openings can be oriented parallel to one another. The longitudinal axes of two adjacent openings oriented parallel to one another can be spaced apart from one another by half a wavelength of the ultrasonic pulses.For example, the openings may be arranged to form a first row of openings and a second row of openings. A distance between the centroids of two adjacent openings of the first opening row may be half a wavelength of the ultrasonic pulses. A distance between the centroids of two adjacent openings of the second opening row may be half a wavelength of the ultrasonic pulses. A distance between the centroids of the openings of the first opening row and the centroids of the openings of the second opening row may be greater than a length of an opening.In a development of the ultrasonic sensor, the ultrasonic sensor has a membrane pot. The membrane pot has the plurality of openings for the ultrasonic pulses. The membrane pot can serve as an interface between the element, in particular the membrane, of the ultrasonic sensor and a free field.The diaphragm pot can be designed for carrying the element, in particular the diaphragm, and the electroacoustic transducer. In particular, the membrane can be fastened to the electroacoustic transducer and the electroacoustic transducer can be fastened to the membrane pot.A parking aid according to the invention for a motor vehicle has at least one ultrasonic sensor described above. The ultrasonic sensor can emit individual ultrasonic pulses and receive them after reflection on an object. The parking aid may be configured to ascertain and output a distance between the ultrasonic sensor and the object based on the received ultrasonic pulses. For example, the parking aid can output the distance by means of an acoustic signal.A motor vehicle according to the invention has a parking aid described above. The motor vehicle may be a partially electrically or fully electrically operated vehicle.Possible exemplary embodiments of the invention are explained below with reference to the attached drawings. The following are shown: FIG. 1 shows a schematic illustration of an ultrasonic sensor, FIG. 2 shows a schematic illustration of a membrane pot of the ultrasonic sensor from FIG. 1, FIG. 3 is a graph of an exemplary sound pressure level versus angle, FIG. 4 shows a graph of an exemplary maximum sound pressure level over a pivot angle, FIG. 5 shows a graph of an exemplary direction max over a pivot angle, FIG. 6 is a graph of an example HPBW -3dB versus swing angle, FIG. 7 shows a graph of an exemplary side lobe level over a pivot angle, FIG. 8 shows a schematic illustration of a further exemplary embodiment of an ultrasonic sensor, and FIG. 9 shows a schematic illustration of a further exemplary embodiment of an ultrasonic sensor.FIG. 1 shows an ultrasonic sensor 10.The ultrasonic sensor 10 has a diaphragm pot 12.FIG. 2 shows that the membrane pot 12 has a plurality of openings 14 for the ultrasonic pulses. The openings 14 can also be referred to as acoustic aperture and / or as acoustically effective area. In the exemplary embodiment shown, the diaphragm pot 12 has four openings 14.Each opening 14 has a shape that cannot be mapped onto itself by rotation about its center of gravity 16 with a rotation angle φ that satisfies the condition 0°<φ≤90°. The shape of each opening 14 is mapped onto itself by rotation about its center of gravity 16 with a rotation angle φ of 180°. Thus, each opening 14 is rotationally symmetrical with respect to its center of gravity 16.Each opening 14 is rectangular. Two opposite sides of each opening 14 are of equal length and are oriented parallel to one another. Each opening 14 is not square. A length 18 of each opening 14 is greater than a width 20 of the opening 14.Each opening 14 has a longitudinal axis 22, and the openings 14 are arranged relative to each other such that the longitudinal axes 22 of the openings 14 are oriented parallel to each other. A pivot direction 23 of the ultrasonic sensor 10 runs perpendicular to the longitudinal axes 22 of the openings 14.The openings 14 are arranged in a 2x2 grid. The apertures 14 are arranged relative to each other to form a first aperture row 24 and a second aperture row 26. The first opening row 24 and the second opening row 26 are arranged parallel to each other.A distance 28 between the centroids 16 of two adjacent openings 14 of each opening row 24, 26 is half a wavelength of the ultrasonic pulses which can be generated and / or received by means of the ultrasonic sensor 10. In other words, the longitudinal axes 22 of two adjacent openings 14 of each opening row 24, 26 are spaced apart from one another by half a wavelength of the ultrasonic pulses. A distance 30 between the centroids 16 of the apertures 14 of the first aperture row 24 and the centroids 16 of the apertures 14 of the second aperture row 26 is greater than the width 18 of each aperture 14.FIG. 1 shows that the ultrasonic sensor 10 has four elements in the form of a membrane 32. Each membrane 32 has a structuring 34 in the form of an elevation. The structuring 34 defines an oscillation shape of the ultrasonic pulses.Each membrane 32 is arranged in an opening 14. An electroacoustic transducer in the form of a piezoelectric element of the ultrasonic sensor 10 is arranged on each membrane 32. The electroacoustic transducer is arranged on a side of the membrane 32, which side is not illustrated in FIG. 1.The ultrasonic sensor 10 may generate an ultrasonic pulse by applying an electrical signal to the electroacoustic transducers. The electroacoustic transducer vibrates the diaphragm 32 in response to the electric signal. The oscillation propagates as an ultrasonic pulse. The ultrasonic pulse exits the ultrasonic sensor 10 from the opening 14.The ultrasonic sensor 10 may receive an ultrasonic pulse. The ultrasonic pulse to be received enters the ultrasonic sensor 10 through the opening 14 and impinges on the diaphragm 32. the ultrasonic pulse to be received vibrates the diaphragm 32 and the electroacoustic transducer converts the vibration of the diaphragm 32 into an electric signal.The membrane pot 12 thus serves as an interface between the membrane 32 and a free field.FIG. 3 shows a graph of a sound pressure level of an ultrasonic pulse generated by means of the ultrasonic sensor 10 over an angle for an opening 14. Due to the size of the opening 14, the side lobes 38 are formed, which may also be referred to as side lobe. A side lobe level 40 is defined as a measure of the strength of the side lobes 38. The side lobe level 40 is calculated from a difference between a maximum of the main lobe 36 and a maximum of the side lobes 38, see FIG. 3. A low side lobe level 40 represents a poor signal-to-noise distance, which increases the risk of an erroneous measurement of a distance between an object and the ultrasonic sensor 10.FIG. 4 shows a curve 42 of a maximum sound pressure level (sound pressure level max) over a pivot angle for the ultrasonic sensor 10 for an opening 14. In other words, the opening of the further ultrasonic sensor is square. The opening of the ultrasonic sensor 10 thus has a larger area compared to the opening of the further ultrasonic sensor. Due to the larger area of the opening of the ultrasonic sensor 10, a higher maximum sound pressure level is achieved with the ultrasonic sensor 10 than with the further ultrasonic sensor. The ultrasonic sensor 10 has a maximum sound pressure level higher by 5 dB (decibels) compared to the further ultrasonic sensor.FIG. 5 shows a course 46 of a direction of the main lobe 36 (direction max) of the ultrasonic sensor 10 over the pivot angle for an opening 14. The direction of the main lobe 36 of the ultrasonic sensor 10 differs insignificantly from the direction of the main lobe of the further underprint sensor.FIG. 6 shows a curve 50 of an HPBW -3dB( half power beam width) over a pivot angle of the ultrasonic sensor 10 for an opening 14. The course 50 differs insignificantly from the course 52.FIG. 7 shows a course 54 of the side lobe level 40 over a pivot angle of the ultrasonic sensor 10 for an opening 14. The curve 54 differs insignificantly from the curve 56.FIGS. 4 to 7 show that the ultrasonic sensor 10 can provide a higher sound pressure level due to the larger opening 14, wherein no increase of the side lobe level 40 occurs in the swivel direction 23. This increases the transmission and reception sensitivity of the ultrasonic sensor 10. Since the side lobe level 40 does not increase in the pivot direction 32, beamforming can be carried out in a direction orthogonal to the pivot direction 32 without influencing the side lobe level 40 in the pivot direction 32.Beamforming can be understood to mean that the ultrasonic pulses generated by means of the first opening row 24 are phase-shifted with respect to the ultrasonic pulses generated by means of the second opening row 26. The ultrasonic pulses generated by the first opening row 24 may be radiated in a first direction and the ultrasonic pulses generated by the second opening row 26 may be radiated in a second direction. The first direction and the second direction may be different from each other. Advantageously, this achieves an expansion of the working range of the ultrasonic sensor 10.FIG. 8 shows a variant of the ultrasonic sensor 10 of FIGS. 1 to 7, wherein the same reference numerals are used for identical and functionally equivalent elements and insofar reference can be made to the above explanations relating to the exemplary embodiment of FIGS. 1 to 7, so that substantially only the existing differences are discussed.Each opening 14 is formed larger than the diaphragm 32 disposed in the opening 14. A length of each diaphragm 32 is equal to a width of the diaphragm 32 In the illustrated embodiment, the width and the length of the diaphragm 32 are each 3 mm.FIG. 9 shows a further variant of the ultrasonic sensor 10 from FIGS. 1 to 7, wherein the same reference numerals are used for identical and functionally equivalent elements and in this respect reference can be made to the above explanations relating to the exemplary embodiment from FIGS. 1 to 7, so that substantially only the existing differences are discussed.A corner 58 of each opening 14 is rounded. An amount of a radius of the rounded corner 58 is equal to an amount of the width 20 of the opening 14.In an exemplary embodiment, which is not shown, a parking aid for a motor vehicle has at least one ultrasonic sensor 10 described above. For this purpose, the parking aid controls the ultrasonic sensor 10 in such a way that it emits ultrasonic pulses and receives the ultrasonic pulses reflected by an object. The parking aid is designed to ascertain and output the distance as a function of the received ultrasonic pulses.In an exemplary embodiment, not shown, a motor vehicle has the parking aid.

Claims

Ultrasonic sensor (10) for generating and / or receiving ultrasonic pulses, comprising: - a plurality of openings (14) for the ultrasonic pulses, - wherein each opening (14) has a shape that cannot be mapped onto itself by rotation about its center of gravity (16) with a rotation angle φ that satisfies the condition 0° < φ ≤ 90°.Ultrasonic sensor (10) according to claim 1, - wherein the shape of each opening (14) can be mapped onto itself by rotation about its centre of gravity (16) with a rotation angle φ of 180° or 120°, or - wherein the shape of each opening (14) does not have any rotational symmetry with respect to its centre of gravity (16).Ultrasonic sensor (10) according to Claim 1 or 2, - wherein each opening (14) is of rectangular configuration.Ultrasonic sensor (10) according to one of the preceding claims, - wherein a length (18) of each opening (14) is greater than a width (20) of the opening (14).Ultrasonic sensor (10) according to one of the preceding claims, - wherein at least one corner (58) of each opening (14) is rounded.Ultrasonic sensor (10) according to claim 5, - wherein a radius of the rounded corner (58) is at least half the width (20) of the opening (14).Ultrasonic sensor (10) according to one of the preceding claims, - wherein the ultrasonic sensor (10) has a plurality of elements (32), - wherein one element (32) each is arranged in an opening (14), - wherein each element (32) can be excited to oscillate for the purpose of generating and / or receiving the ultrasonic pulses.Ultrasonic sensor (10) according to Claim 7, - wherein each element (32) has a structuring (34).Ultrasonic sensor (10) according to one of the preceding claims, - wherein at least one distance (28) between the centroids (16) of two adjacent openings (14) is half a wavelength of the ultrasonic pulses.Ultrasonic sensor (10) according to one of the preceding claims, - wherein the ultrasonic sensor (10) has a membrane pot (12), - wherein the membrane pot (12) has the plurality of openings (14) for the ultrasonic pulses.Parking aid for a motor vehicle, having - at least one ultrasonic sensor (10) according to one of the preceding claims.Motor vehicle, having - a parking aid according to Claim 11.

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