Abstract
An ultrasonic sensor includes a housing encompassing a circumferential side wall. The ultrasonic sensor includes a transducer element to convert an incoming ultrasonic signal into a detectable electrical signal, or conversely, to convert an electrical signal into an ultrasonic signal to be emitted. The ultrasonic sensor includes an oscillatable diaphragm connected to the housing. A multitude of mass elements are situated on a surface of the diaphragm. Alternatively or in addition, a multitude of mass elements are situated within the diaphragm. The mass elements form an acoustic meta material, which is a stop band material, band gap material or phononic crystal and which has a resonant behavior within a frequency band. A resonance frequency of the diaphragm including the multitude of mass elements situated on and/or within the diaphragm is within the frequency band at which the mass elements exhibit a resonant behavior.
Claims
1-9. (canceled)
10. An ultrasonic sensor, comprising: a housing including a circumferential side wall; a transducer element to generate or to detect ultrasonic oscillations; a diaphragm connected to the housing; and a multitude of mass elements situated on a surface of the diaphragm and/or within the diaphragm; wherein the mass elements form an acoustic meta material including a frequency band, wherein the mass elements have a resonant behavior within the frequency band, and wherein a resonance frequency of the diaphragm includes the multitude of mass elements situated on and/or within the diaphragm is within the frequency band of the mass elements.
11. The ultrasonic sensor of claim 10, wherein the mass elements are embedded into the diaphragm.
12. The ultrasonic sensor of claim 10, wherein the mass elements are connected to an outer surface of the diaphragm.
13. The ultrasonic sensor of claim 11, wherein the mass elements represent ball resonators.
14. The ultrasonic sensor of claim 12, wherein the mass elements represent rod resonators.
15. The ultrasonic sensor of claim 10, wherein the transducer element represents an electrostatic transducer element, a first electrode of the electrostatic transducer element being situated on an inner side of the diaphragm, and a second electrode of the electrostatic transducer element being situated on a carrier element.
16. The ultrasonic sensor of claim 10, wherein the transducer element represents a piezoelectric element and is connected to an inner side of the diaphragm.
17. The ultrasonic sensor of claim 10, wherein the resonance frequency of the diaphragm includes the multitude of mass elements situated on and/or within the diaphragm corresponds to a frequency at which an oscillation mode having a nodal circle or a nodal ellipse of the diaphragm including the multitude of mass elements situated on and/or within the diaphragm forms.
18. The ultrasonic sensor of claim 10, wherein the ultrasonic sensor is a distance sensor.
19. The ultrasonic sensor of claim 10, wherein the ultrasonic sensor is a distance sensor for use in a driver assistance system of a motor vehicle.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1a shows a first specific embodiment of the ultrasonic sensor during the excitation of the diaphragm with the aid of a resonance frequency including an oscillation mode without nodal circles and nodal lines.
[0014] FIG. 1b shows the first specific embodiment of the ultrasonic sensor during the excitation of the diaphragm with the aid of a resonance frequency including an oscillation mode encompassing a nodal circle/ellipse.
[0015] FIG. 2a shows a second specific embodiment of the ultrasonic transducer.
[0016] FIG. 2b shows a third specific embodiment of the ultrasonic transducer.
[0017] FIG. 3a shows a first option of the arrangement of rod resonators on the diaphragm.
[0018] FIG. 3b shows a second option of the arrangement of rod resonators on the diaphragm.
[0019] FIG. 3c shows a first option of the arrangement of ball resonators on the diaphragm; and
[0020] FIG. 3d shows a second option of the arrangement of ball resonators on the diaphragm.
DETAILED DESCRIPTION
[0021] The first specific embodiment of the ultrasonic sensor in FIG. 1a shows housing 5 of the ultrasonic sensor, which includes a circumferential side wall 10. The bottom of housing 5 is formed with the aid of diaphragm 20, which is configured in such a way that it is excitable to carry out oscillations. On inner side 20a of diaphragm 20, a piezoelectric element 30 is situated in its center 36, and a multitude of rod resonators are situated on outer diaphragm area 35 as mass elements 40. In the situation shown in FIG. 1a, the overall system, made up of housing 5 including diaphragm 20 and the multitude of mass elements 40 situated on the inner side of diaphragm 20, is excited with the aid of a first resonance frequency to carry out an oscillation having an oscillation mode having no nodal circles and having no nodal lines on diaphragm 20. The rod resonators situated on outer diaphragm area 35 as mass elements 40 do not show any resonant behavior at this operating point.
[0022] In contrast to FIG. 1a, FIG. 1b shows a situation in which the overall system, made up of diaphragm 20 and the rod resonators situated on inner side 20a as mass elements 40, is excited with the aid of a resonance frequency to carry out an oscillation having an oscillation mode having a nodal circle/ellipse on the diaphragm. Mass elements 40 are configured in such a way that, in this case, the resonance frequency of diaphragm 20 and the frequency band in which mass elements 40 situated on diaphragm 20 show a resonant behavior coincide. In this case, mass elements 40 thus also resonantly co-oscillate during the oscillation of diaphragm 20 and deprive diaphragm 20 of oscillation energy for their own oscillating movements. In this way, a free wave propagation and a deflection of diaphragm 20 are prevented on outer diaphragm area 35. In this way, an oscillation mode which has no nodal lines and a nodal circle is achieved. This results in an oscillation mode which has a deflection at the diaphragm center, but little or no deflection in the boundary areas, outside the area enclosed by the nodal circle. In the area of the diaphragm deflection, the oscillation mode is thus adapted, taking a different oscillation amplitude of the oscillation mode from FIG. 1a into consideration, to the effect that only one antinode results, or 3 antinodes, of which the 2 outer ones have only a very small deflection.
[0023] Both FIG. 1a and FIG. 1b do not show a representation true to scale, but the deflection of diaphragm 20 is shown highly exaggerated.
[0024] FIG. 2a shows a second specific embodiment of the ultrasonic sensor including a portion of circumferential side wall 10 of the housing. Ball resonators may be embedded into diaphragm 20 as mass elements 50 in the process. The ball resonators may, for example, include silicone-coated steel balls in an epoxy resin matrix. The lead balls within the matrix also co-oscillate as a function of an excitation of the overall system, made up of diaphragm 20 and ball resonators, with the aid of a resonance frequency which is within the frequency band of the resonant behavior of the sphere resonators. In this way, diaphragm 20 is deprived of oscillation energy for its own oscillating movements, and a deflection of diaphragm 20 into outer diaphragm areas 37 in which the ball resonators are embedded is at least mitigated or even entirely prevented. In this second exemplary embodiment, transducer element 30 is configured as a piezoelectric element, which is connected in center 38 of the diaphragm to inner side 20a of diaphragm 20.
[0025] In a third specific embodiment of the ultrasonic sensor in FIG. 2b, the ultrasonic sensor, in contrast to FIG. 2a, includes a transducer element 60a and 60b, which is implemented as an electrostatic transducer. A first electrode 20a is situated on inner side 20a of diaphragm 20, and a second electrode 60b is situated on a side 80 of carrier element 70 situated opposite inner side 20a of diaphragm 20.
[0026] FIG. 3a, in the top view, shows a first possible arrangement of rod resonators as mass elements 40 on inner side 20a of the diaphragm. The rod resonators are situated in the outer area of the diaphragm in such a way that the wave propagation is mitigated both perpendicular to and in parallel to the diaphragm main axis.
[0027] A piezoelectric element 30 is situated centrically on inner side 20a of the diaphragm.
[0028] FIG. 3b, in the top view, shows a second possible arrangement of rod resonators as mass elements 40 on inner side 20a of the diaphragm. The rod resonators are situated in the outer area of the diaphragm in such a way that the wave propagation is mitigated more strongly perpendicular to the diaphragm main axis, and thus the formation of an oscillation mode having a nodal ellipse is supported. Piezoelectric element 30 is also situated centrically on inner side 20a of the diaphragm.
[0029] FIG. 3c, in the top view, shows a first possible arrangement of ball resonators as mass elements 50 within diaphragm 20. The ball resonators are situated in the outer area of the diaphragm in such a way that an elliptical area free of mass elements results in the center of the diaphragm. In this way, the wave propagation is mitigated more strongly perpendicular to the diaphragm main axis, and thus the formation of an oscillation mode having a nodal ellipse is supported.
[0030] FIG. 3d, in the top view, shows a second possible arrangement of ball resonators as mass elements 50 within diaphragm 20. The ball resonators are situated in the outer area of the diaphragm in such a way that a circular area free of mass elements results in the center of the diaphragm. In this way, the wave propagation is mitigated both perpendicularly to and in parallel to the diaphragm main axis.
