DE102019102243A1 - Transducer element, ultrasonic sensor assembly and ultrasonic sensor - Google Patents

Abstract

The invention relates to a transducer element for generating and / or receiving ultrasonic vibrations for use in an ultrasonic sensor, in particular for a motor vehicle, in particular for distance measurement and / or for use in a driver assistance system, the transducer element having:
at least a first electrode on a first side of the transducer element and a second electrode on a second side of the transducer element, the second side of the transducer element being opposite the first side of the transducer element,
at least a first electrode on a first side of the transducer element and a second electrode on a second side of the transducer element, the second side of the transducer element being opposite the first side of the transducer element,
wherein the transducer element has an electrically conductive changeover contact, which extends from the second electrode to the first side of the transducer element, so that the first electrode and the second electrode can be electrically contacted from the first side of the transducer element,
wherein the first electrode has an electrode geometry that:
a) is at least substantially symmetrical with respect to at least two transducer element axes of symmetry, or
b) is at least essentially point-symmetrical with respect to a transducer element symmetry point.

Description

The invention relates to a transducer element and an ultrasound sensor assembly, in particular for a motor vehicle, in particular for distance measurement and / or for use in a driver assistance system. The invention also relates to an ultrasonic sensor with a transducer element or an ultrasonic sensor assembly.

Ultrasound sensors and corresponding transducer elements and ultrasound sensor assemblies are known in principle from the prior art. In the case of already known ultrasonic sensors, a transducer element, in particular a piezoelectrically active element, is typically glued to a rigid membrane. The piezo element can be made from a ceramic material that is coated with a metallization on the flat sides. This metallization then serves as electrodes of the piezo element. One of the electrodes faces the membrane, the membrane being able to be integrated in a housing part of the ultrasonic sensor or being part of the housing.

The electrodes are electrically connected to control and evaluation electronics. The contacting of the electrodes in the prior art is sometimes problematic. One of the electrodes (hereinafter also referred to as the “upper electrode”) is generally accessible inside the housing. Their electrical contacting is generally not problematic. However, problems can arise when contacting the other electrode that faces the membrane (hereinafter also referred to as the “lower electrode”) because it is less easily accessible.

In the prior art there is, among other things, an approach for contacting the lower electrode, which uses a so-called re-contact. Such a changeover contact generally has an electrically conductive connection between the lower electrode and the upper side of the transducer element (that is to say the side of the transducer element on which the upper electrode is also arranged). On the upper side of the converter element, the changeover contact is designed as a contact surface. Thus, both electrodes can be contacted on the upper side of the transducer element: the upper electrode by contacting this electrode itself, and the lower electrode by contacting the contact area of the changeover contact.

A transducer element with contact change is for example from the DE 10 2006 011 155 A1 known.

1 shows schematically the top view of a transducer element 100 with contact change 103 according to the state of the art. The converter element 100 is designed, for example, as a disk or relatively flat cylinder, with in 1 only the top is shown. The upper electrode is located on this 101 . The lower electrode (not visible) is located on the opposite side of the disc. From the contact change 103 you can see the area that is on top of the transducer element 100 located. A further partial area of the changeover contact is applied to the lateral surface of the transducer element and extends from the lower electrode to the partial area of the changeover contact 103 that is on the top of the transducer element 100 is arranged. Thus, the lower electrode can be contacted by contacting the via 103 on the top of the transducer element 100 be contacted. Around the top electrode 101 , also between the top electrode 101 and the contact change 103 , runs a non-electrically conductive area 104 by the ceramic material of the transducer element 100 can be formed. The top electrode is on this ceramic material 101 , the lower electrode and the contact change 103 applied as a coating, the in 1 area marked with 104 is not coated.

2nd shows a section through an ultrasonic sensor 110 with a transducer element 100 according to 1 . The converter element 100 is with its underside, on which the lower electrode 102 located on a membrane 105 of the ultrasonic sensor 102 arranged, for example glued to this. The membrane 105 is in a first housing part 111 attached or represents an integral part of this first housing part 111 The first housing part 111 is partly in a second housing part 112 added with a seal 113 is made of silicone or the like between the two housing parts. This seal 113 also serves as (mechanical) decoupling between the two housing parts 111 , 112 . The housing parts 111 , 112 can for example be pot-shaped or cup-shaped.

3rd shows a top view of the transducer element 100 of the 1 on the membrane 105 . In this example the membrane is 105 elliptical, the transducer element 100 concentric on the membrane 105 is arranged.

The inventor has recognized that ultrasonic sensors according to the prior art, as exemplified in the 3rd illustrates, can have disadvantages. These disadvantages relate to the vibration behavior or decay behavior of the membrane. In the case of ultrasound sensors according to the prior art, the pulse-echo method is used for distance measurement using the bending transducer principle in resonance mode. The piezoelectrically active serves Transducer element on the rigid membrane 105 is mounted, the electromechanical energy conversion.

If the same membrane is used as both a transmitter and a receiver, the vibration system should have a high damping. Generally this is done by applying a damping material to the membrane 105 realized, for example felts, foams or other materials with high intrinsic damping.

In order to achieve high sound conversion efficiency and directivity, which is dominated by a central main lobe, the basic mode of the membrane is generally used 105 selected as the operating mode, ie the excitation frequency selected accordingly. The inventor has recognized that in addition to this basic mode, there are an infinite number of other higher modes, of which, however, only the first harmonics are of greater interest in realistic systems. Since these harmonics have a plurality of antinodes, they produce directional characteristics with a plurality of lobes, which, according to the inventor's knowledge, is disadvantageous in the detection of the surroundings. Since these antinodes of the higher modes vibrate out of phase in some cases, according to the inventor's knowledge, these modes are significantly more difficult to dampen with the method described above, since a mechanical short circuit occurs. The more strongly these parasitic modes are excited, the longer the blind area of the ultrasound sensor, that is, the time range in which the ultrasound transducer is in the transmission or decay phase.

4th shows schematically a harmonic of the membrane just described 105 with two phase-shifted antinodes 120 , 121 . The phase offset of the antinodes 120 , 121 is indicated by a plus sign or a minus sign, ie while the membrane 105 in the area of the left antinode 120 swings into the plane of the drawing, for example, it swings in the area of the right antinode 121 out of the drawing plane, and vice versa.

In addition, according to the inventor's knowledge, an amplitude modulation of the signal occurs when the total vibration energy is distributed over several modes, each with a significant proportion. This amplitude modulation can still be misinterpreted by the evaluation electronics as a reflected echo signal if the signal energy of the parasitic modes is reduced by filters.

5 shows an example of such an amplitude modulation. The horizontal axis shows the time (in any units) and the vertical axis shows the deflection of the membrane at a certain point (any units). The inventor has recognized that the in 5 shown vibration decays only relatively slowly.

Due to the time-limited excitation in pulse mode, each excitation signal also contains frequency components outside the working frequency, that is, the frequency of the basic mode. Consequently, the higher, parasitic modes of the membrane are always excited in the pulse mode.

The inventor has recognized that the relatively strong excitation of the parasitic modes of the membrane (as in 4th shown) is particularly due to the geometry of the transducer element. So he realized that the in 3rd Shown geometry of the transducer element 100 with the top electrode 101 that are on the surface of the transducer element 100 covers a larger area in the right half than in the left half, which leads to undesired vibration behavior.

Against this background, it is an object of the invention to provide an alternative transducer element, in particular an improved transducer element, an alternative, in particular improved, ultrasonic sensor assembly and an alternative, in particular improved, ultrasonic sensor.

According to the invention, this object is achieved by a transducer element, an ultrasound sensor assembly and an ultrasound sensor with the features according to the respective independent patent claims. Advantageous embodiments of the invention are the subject of the dependent claims, the description and the figures.

In the present case, the term “transducer element” is understood to mean a sensor element which can generate and transmit ultrasonic waves as a function of a signal and / or which can generate a signal from received ultrasonic waves as a function of the received ultrasonic waves.

A transducer element in the sense of the invention has in particular at least one piezo element with a polycrystalline piezo ceramic. With the aid of a signal pulse, this transducer element can excite at least one ultrasound membrane to defined vibrations, which can be transmitted to the environment by means of the ultrasound membrane. In particular, ultrasound waves from the environment can also excite the ultrasound membrane and cause the piezo-ceramic to vibrate, and as a result a defined signal pulse can be generated.

• wenigstens eine erste Elektrode an einer ersten Seite des Wandlerelements und eine zweite Elektrode an einer zweiten Seite des Wandlerelements, wobei die zweite Seite des Wandlerelements der ersten Seite des Wandlerelements gegenüberliegt,
• wobei das Wandlerelement eine elektrisch leitfähige Umkontaktierung aufweist, die sich von der zweiten Elektrode bis zur ersten Seite des Wandlerelements erstreckt, so dass die erste Elektrode und die zweite Elektrode von der ersten Seite des Wandlerelements elektrisch kontaktierbar sind,
• wobei die erste Elektrode eine Elektroden-Geometrie aufweist, die:
  1. a) wenigstens im Wesentlichen symmetrisch bezüglich mindestens zwei Wandlerelement-Symmetrieachsen ist, oder
  2. b) wenigstens im Wesentlichen punktsymmetrisch bezüglich eines Wandlerelement-Symmetriepunktes ist.

A first aspect of the invention relates to a transducer element for generating and / or receiving ultrasonic vibrations for use in an ultrasonic sensor, in particular for a motor vehicle, in particular for distance measurement and / or for use in a driver assistance system, the transducer element having:

• at least a first electrode on a first side of the transducer element and a second electrode on a second side of the transducer element, the second side of the transducer element being opposite the first side of the transducer element,
• wherein the transducer element has an electrically conductive changeover contact, which extends from the second electrode to the first side of the transducer element, so that the first electrode and the second electrode can be electrically contacted from the first side of the transducer element,
• wherein the first electrode has an electrode geometry that:
  1. a) is at least substantially symmetrical with respect to at least two transducer element axes of symmetry, or
  2. b) is at least essentially point-symmetrical with respect to a transducer element symmetry point.

If the transducer element according to the first aspect with a membrane and an ultrasonic sensor housing according to 2nd the first electrode would be an upper electrode and the second electrode would be a lower electrode.

In the present application, the terms “transducer element symmetry axis”, “transducer element symmetry point”, “membrane symmetry axis” and “membrane symmetry point” are used. These terms are only used to distinguish, i. H. each is an axis of symmetry or a point of symmetry of the geometry of the first electrode of the transducer element or the membrane.

The inventor has found that a transducer element with a first electrode, which has an electrode geometry according to variant a) or b) of the first aspect, can lead to less parasitic oscillation behavior than when using a transducer element that does not meet these conditions.

• ein Wandlerelement gemäß dem ersten Aspekt, und
• eine Membran, die eine Membran-Geometrie aufweist, die im Wesentlichen punktsymmetrisch bezüglich eines Membran-Symmetriepunktes ist, und/oder:
  1. a) wenigstens im Wesentlichen symmetrisch bezüglich genau einer Membran-Symmetrieachse ist, oder
  2. b) wenigstens im Wesentlichen symmetrisch bezüglich genau zwei Membran-Symmetrieachsen ist, oder
  3. c) wenigstens im Wesentlichen symmetrisch bezüglich mehr als zwei, insbesondere unendlich vieler Membran-Symmetrieachsen ist.

A second aspect of the invention relates to an ultrasonic sensor assembly, comprising:

• a transducer element according to the first aspect, and
• a membrane which has a membrane geometry which is essentially point-symmetrical with respect to a membrane symmetry point, and / or:
  1. a) is at least substantially symmetrical with respect to exactly one membrane axis of symmetry, or
  2. b) is at least substantially symmetrical with respect to exactly two membrane axes of symmetry, or
  3. c) is at least substantially symmetrical with respect to more than two, in particular an infinite number of membrane symmetry axes.

The interaction of the membrane geometry defined according to the second aspect and the electrode geometry defined according to the first aspect can lead to a particularly advantageous oscillation behavior of the membrane, in particular an oscillation behavior in which parasitic modes are not excited or only to a comparatively small extent which the excitation of the membrane fades away relatively quickly, especially faster than it does according to the 5 the case is.

1. a) wenigstens eine Wandlerelement-Symmetrieachse im Wesentlichen parallel zu wenigstens einer Membran-Symmetrieachse verläuft, und/oder
2. b) wenigstens eine Wandlerelement-Symmetrieachse im Wesentlichen mit wenigstens einer Membran-Symmetrieachse zusammenfällt, und/oder
3. c) wenigstens eine Wandlerelement-Symmetrieachse im Wesentlichen senkrecht auf wenigstens einer Membran-Symmetrieachse steht, und/oder
4. d) wenigstens eine Wandlerelement-Symmetrieachse im Wesentlichen einen Winkel von 45 Grad mit wenigstens einer Membran-Symmetrieachse einschließt, und/oder
5. e) wenigstens zwei Wandlerelement-Symmetrieachsen im Wesentlichen mit wenigstens zwei Membran-Symmetrieachsen zusammenfallen, und/oder
6. f) wenigstens zwei Wandlerelement-Symmetrieachsen im Wesentlichen einen Winkel von 45 Grad paarweise mit wenigstens zwei Membran-Symmetrieachsen einschließen, und/oder
7. g) der Wandlerelement-Symmetriepunkt im Wesentlichen mit dem Membran-Symmetriepunkt zusammenfällt, und/oder
8. h) der Wandlerelement-Symmetriepunkt im Wesentlichen auf einer Membran-Symmetrieachse liegt, und/oder
9. i) der Wandlerelement-Symmetriepunkt im Wesentlichen auf zwei Membran-Symmetrieachsen liegt, und/oder
10. j) der Membran-Symmetriepunkt im Wesentlichen auf einer Wandlerelement-Symmetrieachse liegt, und/oder
11. k) der Membran-Symmetriepunkt im Wesentlichen auf zwei Wandlerelement-Symmetrieachsen liegt.

After execution, an ultrasonic sensor assembly is defined so that, when projected onto one level:

1. a) at least one transducer element axis of symmetry runs essentially parallel to at least one membrane axis of symmetry, and / or
2. b) at least one transducer element axis of symmetry essentially coincides with at least one membrane axis of symmetry, and / or
3. c) at least one transducer element axis of symmetry is substantially perpendicular to at least one membrane axis of symmetry, and / or
4. d) at least one transducer element axis of symmetry essentially encloses an angle of 45 degrees with at least one membrane axis of symmetry, and / or
5. e) at least two transducer element axes of symmetry essentially coincide with at least two membrane axes of symmetry, and / or
6. f) include at least two transducer element axes of symmetry essentially an angle of 45 degrees in pairs with at least two membrane axes of symmetry, and / or
7. g) the transducer element symmetry point essentially coincides with the membrane symmetry point, and / or
8. h) the transducer element symmetry point lies essentially on a membrane axis of symmetry, and / or
9. i) the transducer element symmetry point lies essentially on two membrane symmetry axes, and / or
10. j) the membrane symmetry point lies essentially on a transducer element axis of symmetry, and / or
11. k) the membrane symmetry point lies essentially on two transducer element axes of symmetry.

According to this embodiment, different constellations, that is to say different combinations of electrode geometries and membrane geometries, are considered advantageous, in particular with regard to their vibration behavior. There are differences between the different combinations when it comes to suppressing parasitic modes. For example, variants e) and f) can be regarded as particularly advantageous.

According to one embodiment, the transducer element is connected to the membrane such that the first side of the transducer element is oriented away from the membrane and the second side of the transducer element is oriented toward the membrane.

• ein Wandlerelement zur Erzeugung und/oder zum Empfangen von Ultraschallschwingungen, wobei das Wandlerelement wenigstens eine erste Elektrode an einer ersten Seite des Wandlerelements und eine zweite Elektrode an einer zweiten Seite des Wandlerelements aufweist, wobei die zweite Seite des Wandlerelements der ersten Seite des Wandlerelements gegenüberliegt,
• eine Membran, die eine Membran-Geometrie aufweist, die
  1. a) wenigstens im Wesentlichen symmetrisch bezüglich genau einer Membran-Symmetrieachse ist, oder
  2. b) im Wesentlichen punktsymmetrisch bezüglich eines Membran-Symmetriepunktes ist, aber nicht achsensymmetrisch ist,

wobei das Wandlerelement so mit der Membran verbunden ist, dass die erste Seite des Wandlerelements von der Membran weg orientiert ist und die zweite Seite des Wandlerelements zur Membran hin orientiert ist, wobei das Wandlerelement eine elektrisch leitfähige Umkontaktierung aufweist, die sich von der zweiten Elektrode bis zur ersten Seite des Wandlerelements erstreckt, so dass die erste Elektrode und die zweite Elektrode von der ersten Seite des Wandlerelements elektrisch kontaktierbar sind, wobei die erste Elektrode eine Elektroden-Geometrie aufweist, die im Wesentlichen punktsymmetrisch bezüglich eines Wandlerelement-Symmetriepunktes ist, und/oder:

1. a) wenigstens im Wesentlichen symmetrisch bezüglich genau einer Wandlerelement-Symmetrieachse ist, oder
2. b) wenigstens im Wesentlichen symmetrisch bezüglich genau zwei Wandlerelement-Symmetrieachsen ist, oder
3. c) wenigstens im Wesentlichen symmetrisch bezüglich mehr als zwei, insbesondere unendlich vieler Wandlerelement-Symmetrieachsen ist.

A third aspect of the invention relates to an ultrasound sensor assembly, in particular for a motor vehicle, in particular for distance measurement and / or for use in a driver assistance system, comprising:

• a transducer element for generating and / or receiving ultrasonic vibrations, the transducer element having at least a first electrode on a first side of the transducer element and a second electrode on a second side of the transducer element, the second side of the transducer element being opposite the first side of the transducer element,
• a membrane that has a membrane geometry that
  1. a) is at least substantially symmetrical with respect to exactly one membrane axis of symmetry, or
  2. b) is essentially point-symmetrical with respect to a membrane symmetry point, but is not axisymmetric,

wherein the transducer element is connected to the membrane such that the first side of the transducer element is oriented away from the membrane and the second side of the transducer element is oriented toward the membrane, the transducer element having an electrically conductive changeover contact that extends from the second electrode to extends to the first side of the transducer element so that the first electrode and the second electrode can be electrically contacted from the first side of the transducer element, the first electrode having an electrode geometry that is essentially point-symmetrical with respect to a transducer element symmetry point, and / or :

1. a) is at least substantially symmetrical with respect to exactly one transducer element axis of symmetry, or
2. b) is at least substantially symmetrical with respect to exactly two transducer element axes of symmetry, or
3. c) is at least substantially symmetrical with respect to more than two, in particular an infinite number of transducer element axes of symmetry.

Although the geometries according to the third aspect differ in part from the geometries according to the second aspect, the basic idea on which the second and third aspects are based is the same, i. H. the geometries / symmetries and their combinations are selected according to the invention such that the vibration behavior can be improved and in particular that parasitic modes are excited as little as possible, in particular suppressed.

1. a) wenigstens eine Wandlerelement-Symmetrieachse im Wesentlichen parallel zu der Membran-Symmetrieachse verläuft, oder
2. b) wenigstens eine Wandlerelement-Symmetrieachse im Wesentlichen mit der Membran-Symmetrieachse zusammenfällt, oder
3. c) wenigstens eine Wandlerelement-Symmetrieachse im Wesentlichen senkrecht auf der Membran-Symmetrieachse steht, oder
4. d) wenigstens eine Wandlerelement-Symmetrieachse im Wesentlichen einen Winkel von 45 Grad mit der Membran-Symmetrieachse einschließt, oder
5. e) der Wandlerelement-Symmetriepunkt im Wesentlichen mit dem Membran-Symmetriepunkt zusammenfällt, oder
6. f) der Wandlerelement-Symmetriepunkt im Wesentlichen auf der Membran-Symmetrieachse liegt, oder
7. g) der Membran-Symmetriepunkt im Wesentlichen auf einer Wandlerelement-Symmetrieachse liegt, oder
8. h) der Membran-Symmetriepunkt im Wesentlichen auf zwei Wandlerelement-Symmetrieachsen liegt.

After execution, the geometries of the ultrasonic sensor assembly are defined such that, when projected onto one level:

1. a) at least one transducer element axis of symmetry runs essentially parallel to the membrane axis of symmetry, or
2. b) at least one transducer element axis of symmetry essentially coincides with the membrane axis of symmetry, or
3. c) at least one transducer element axis of symmetry is substantially perpendicular to the membrane axis of symmetry, or
4. d) at least one transducer element axis of symmetry essentially forms an angle of 45 degrees with the membrane axis of symmetry, or
5. e) the transducer element symmetry point essentially coincides with the membrane symmetry point, or
6. f) the transducer element point of symmetry lies essentially on the membrane axis of symmetry, or
7. g) the membrane symmetry point lies essentially on a transducer element axis of symmetry, or
8. h) the membrane symmetry point lies essentially on two transducer element symmetry axes.

According to one embodiment, the plane is parallel to the first side of the transducer element and / or to the second side of the transducer element and / or to a side of the membrane facing the transducer element.

Typically, the first side of the transducer element, the second side of the transducer element and the side of the membrane that faces the transducer element run parallel, so that the respective projections correspond.

According to an embodiment of the above-described transducer element or the above-described ultrasonic sensor assembly, the changeover contact has a first section and a second section made of a conductive material, the first section forming a contact area on the first side of the transducer element and the second section extends on the outer periphery of the transducer element between the first side and the second side of the transducer element.

The first section of the changeover contact can thus serve to contact the second electrode, because the contact area formed by the first section is electrically connected to the second electrode by the second section of the changeover contact.

According to one embodiment, the changeover contact is designed as a coating, in particular with or made of silver.

A fourth aspect relates to an ultrasonic sensor, comprising a transducer element as described above or an ultrasonic sensor assembly as described above.

The advantageous refinements and embodiments presented with reference to the transducer element and their advantages also apply correspondingly to the ultrasonic sensor assembly according to the invention and the ultrasonic sensor according to the invention and vice versa.

Further features of the invention result from the claims, the figures and the description of the figures. All of the features and combinations of features mentioned above in the description and the features and combinations of features mentioned below in the description of the figures and / or shown alone in the figures can be used not only in the combination indicated in each case, but also in other combinations or on their own, provided that these combinations are executable and are particularly technically sensible.

The invention will now be explained in more detail with the aid of some preferred exemplary embodiments and with reference to the accompanying drawings, in which functionally identical or functionally similar components are provided with the same reference numerals.

• 1 eine Draufsicht auf ein Wandlerelement gemäß dem Stand der Technik,
• 2 einen Schnitt durch einen Ultraschallsensor mit einem Wandlerelement gemäß dem Stand der Technik,
• 3 eine Draufsicht einer Ultraschallsensor-Baugruppe mit einem Wandlerelement und einer Membran gemäß dem Stand der Technik,
• 4 eine Membran mit Schwingungsbäuchen gemäß dem Stand der Technik,
• 5 das Schwingungsverhalten eines Ultraschallsensors gemäß dem Stand der Technik,
• 6 eine Draufsicht eines Wandlerelements nach einem Ausführungsbeispiel der Erfindung,
• 7 einen Schnitt durch einen Ultraschallsensor mit einem Wandlerelement nach einem Ausführungsbeispiel der Erfindung,
• 8 eine Draufsicht eines Wandlerelements nach einem Ausführungsbeispiel der Erfindung,
• 9 eine Draufsicht eines Wandlerelements nach einem Ausführungsbeispiel der Erfindung,
• 10 eine Draufsicht eines Wandlerelements nach einem Ausführungsbeispiel der Erfindung,
• 11 eine Draufsicht eines Wandlerelements nach einem Ausführungsbeispiel der Erfindung,
• 12 eine Draufsicht eines Wandlerelements nach einem Ausführungsbeispiel der Erfindung,
• 13 eine Draufsicht eines Wandlerelements nach einem Ausführungsbeispiel der Erfindung,
• 14 eine Draufsicht eines Wandlerelements nach einem Ausführungsbeispiel der Erfindung,
• 15 eine Draufsicht einer Membran mit einem Schwingungsbauch nach einem Ausführungsbeispiel der Erfindung, und
• 16 das Schwingungsverhalten einer Ultraschallsensor-Baugruppe nach einem Ausführungsbeispiel der Erfindung.

In a schematic representation:

• 1 3 shows a plan view of a converter element according to the prior art,
• 2nd 3 shows a section through an ultrasonic sensor with a transducer element according to the prior art,
• 3rd 1 shows a top view of an ultrasonic sensor assembly with a transducer element and a membrane according to the prior art,
• 4th a membrane with antinodes according to the prior art,
• 5 the vibration behavior of an ultrasonic sensor according to the prior art,
• 6 2 shows a top view of a transducer element according to an embodiment of the invention,
• 7 3 shows a section through an ultrasonic sensor with a transducer element according to an exemplary embodiment of the invention,
• 8th 2 shows a top view of a transducer element according to an embodiment of the invention,
• 9 2 shows a top view of a transducer element according to an embodiment of the invention,
• 10th 2 shows a top view of a transducer element according to an embodiment of the invention,
• 11 2 shows a top view of a transducer element according to an embodiment of the invention,
• 12th 2 shows a top view of a transducer element according to an embodiment of the invention,
• 13 2 shows a top view of a transducer element according to an embodiment of the invention,
• 14 2 shows a top view of a transducer element according to an embodiment of the invention,
• 15 a plan view of a membrane with an antinode according to an embodiment of the invention, and
• 16 the vibration behavior of an ultrasonic sensor assembly according to an embodiment of the invention.

6 shows a plan view of a transducer element according to an embodiment of the invention. Similar to 1 is on the upper side of the transducer element 20 a first electrode 1 arranged. In contrast to the electrode 101 of the 1 but is the electrode 1 of the 6 circular, so it has an infinite number of symmetry axes. The electrode 1 is concentric on the piezo ceramic 4th applied as a coating so that the piezo ceramic material 4th is only visible as a ring on the surface. In addition, the transducer element 20 a contact change 3rd on, this on the surface of the transducer element 20 consists of two opposing separate areas, which are designed as segments in the example shown. In the example shown, the segments are essentially of the same size and are both due to the section of the contact change that is on the lateral surface of the cylindrical converter element 20 is applied, electrically connected to the second electrode on the second side (underside, not shown) of the transducer element.

Unlike the one in 1 shown, already known transducer element, in which the upper electrode 101 on the left side is "cut off" to provide enough space for the contact change 103 To create, are in the embodiment of the invention 6 the first electrode 1 and the via areas 3rd dimensioned and arranged so that the shape of the first electrode 1 not through the contact areas 3rd is affected.

Because of the circular shape of the first electrode 1 of in 6 The embodiment shown results when the transducer element is assembled 20 on a membrane 5 a vibration behavior that reduces parasitic modes or essentially suppresses them.

The converter element 20 can in principle be analogous to the 2nd and 3rd on a membrane 5 be assembled, ie as centrally / concentrically as possible. This is also in 7 shown the the 2nd very similar. In contrast to 2nd are the two contacting areas 103 on opposite sides of the transducer element 20 visible.

When considering the 3rd and 4th you might get the impression that the harmonics that are in 4th through the antiphase antinodes 120 and 121 are illustrated (mainly) because the membrane is excited 105 is not circular, but elliptical. According to the inventor's knowledge, however, this is not the case. Rather, the excitation of these antiphase harmonics is due to the fact that the coupling between the membrane 105 and the top electrode 101 is more pronounced in the right half than in the left half. The vibration behavior would be corresponding or similar (again with two antiphase antinodes) if the transducer element 100 of the 3rd would be mounted on a circular membrane. Furthermore, the inventor has found that when using the transducer element 20 of the 6 with its circular first electrode 1 the antiphase antinodes of the 4th (largely) avoided, even if the transducer element 20 on an elliptical membrane similar to that 3rd is assembled. The resulting and in 15 illustrated membrane vibration 5 has a single, centered antinode 21 on.

The 8th to 14 show exemplary converter elements 20 with different geometries in plan view, each of these figures a first electrode 1 on the first side of a transducer element 20 shows. In addition, these figures either show two mutually opposite contacting areas 3rd ( 8th , 9 and 14 ), four contact change areas rotated by 90 degrees 3rd ( 10th ) or a single circumferential contacting area 3rd ( 11 , 12th and 13 ). Also in these figures is the piezo ceramic material 4th shown as far as it is not through the first electrode 1 or the contact areas 3rd is covered.

1. 1. Das Schwingungsverhalten ist besonders gut, wenn die Geometrie der ersten Elektrode 1 unendlich viele Symmetrieachsen hat.
2. 2. Bei Verwendung einer ersten Elektrode mit mindestens zwei Symmetrieachsen ist das Schwingungsverhalten besonders gut, wenn mindestens eine dieser Wandlerelement-Symmetrieachsen parallel zu mindestens einer Symmetrieachse der Membran verläuft. Dies wäre beispielsweise der Fall, wenn eines der Wandlerelemente der 6 oder 8 bis 14 in der gezeigten Orientierung auf der Membran 5 der 15 in der gezeigten Orientierung montiert wird. Dabei muss das Wandlerelement nicht notwendigerweise zentral auf der Membran 5 angeordnet werden.
3. 3. Als Sonderfall der im vorigen Absatz beschriebenen Konstellationen werden noch bessere Ergebnisse erzielt, wenn mindestens eine der Wandlerelement-Symmetrieachsen mit mindestens einer Membran-Symmetrieachse zusammenfällt, noch besser, wenn mindestens zwei Wandlerelement-Symmetrieachsen mit mindestens zwei Membran-Symmetrieachsen zusammenfallen. Letzteres wäre beispielsweise der Fall, wenn eines der Wandlerelemente 20 der 6 oder 8 bis 14 in der gezeigten Orientierung zentral auf der Membran 5 der 15 angeordnet wird.
4. 4. Gleichwohl kann das Schwingungsverhalten gegenüber dem Stand der Technik verbessert werden, wenn keine Wandlerelement-Symmetrieachse parallel zu einer Membran-Symmetrieachse verläuft oder mit einer solchen zusammenfällt, wobei dann aber vorzugsweise mindestens eine Wandlerelement-Symmetrieachse mit mindestens einer Membran-Symmetrieachse einen Winkel von 90 oder 45 Grad einschließt. Hier ist wiederum eine zentrale Positionierung des Wandlerelements 20 auf der Membran 5 bevorzugt, aber nicht zwingend. Ein solcher Fall könnte sich ergeben, wenn eine Membran verwendet wird, die beispielsweise nur eine Symmetrieachse hat (beispielsweise eine annäherungsweise trapezförmige Membran) und wenn ein Wandlerelement 20 der 6, 8, 9 oder 14 so auf dieser Membran montiert wird, dass sich beispielsweise ein Winkel von 45 Grad ergibt. Bei Benutzung eines Wandlerelements mit genau einer Symmetrieachse lässt sich auch ein Winkel von 90 Grad zwischen der Wandlerelement-Symmetrieachse und der Membran-Symmetrieachse erzeugen.
5. 5. Auch bei der Verwendung eines Wandlerelements oder einer Membran ohne Symmetrieachse lässt sich eine Verbesserung gegenüber dem Stand der Technik erreichen, wenn entweder das Wandlerelement oder die Membran eine Punktsymmetrie aufweist und das andere Bauteil entweder auch punktsymmetrisch ist und/oder mindestens eine Symmetrieachse, vorzugsweise zwei Symmetrieachsen, und vorzugsweise mehr als zwei Symmetrieachsen, insbesondere unendlich viele Symmetrieachsen, aufweist. Hier könnte für eines der Bauteile (Membran; erste Elektrode) beispielsweise die Geometrie eines Parallelogramms verwendet werden und für das andere Bauteil ein Kreis, eine Ellipse, ein Rechteck, Quadrat, Trapez, Parallelogramm usw.
6. 6. Bei den im vorangegangenen Absatz beschriebenen Konstellationen fällt die Verbesserung gegenüber dem Stand der Technik wiederum größer aus, wenn die Symmetriepunkte der Bauelemente zusammenfallen oder wenn der Symmetriepunkt des einen Bauelements auf einer Symmetrieachse des anderen Bauelements liegt, insbesondere mit dem Schnittpunkt von zwei oder mehr Symmetrieachsen zusammenfällt.
7. 7. Auch die Verwendung eines Bauteils (Membran; erste Elektrode), das mehr als zwei Symmetrieachsen hat, aber nicht punktsymmetrisch ist, kann eine Verbesserung gegenüber dem Stand der Technik darstellen. Eine entsprechende Geometrie könnte beispielsweise als regelmäßiges Fünf-, Sieben- oder Neun-Eck ausgebildet sein.
8. 8. Die Geometrie des mindestens einen Umkontaktierungsbereichs hat zwar auch einen Einfluss auf das Schwingungsverhalten, in den meisten Fällen aber einen kleineren Einfluss als die Geometrie der Membran bzw. der ersten Elektrode und die Relativposition und Orientierung dieser Bauelemente zueinander. Insofern wäre es als Variante beispielsweise der 6 möglich, nur einen Umkontaktierungsbereich 3 auf dem Wandlerelement 20 anzuordnen, solange die erste Elektrode ihre Symmetrie beibehält. Andere Varianten basierend auf den 6 bzw. 8 bis 14 sind auch denkbar, beispielsweise Umkontaktierungsbereiche, die nicht um 180 Grad versetzt sind, sondern um einen beliebigen anderen Winkel; Umkontaktierungsbereiche 3, die nicht die gleiche Form haben; ein Umkontaktierungsbereich 3, der, anders als in den 11, 12 und 13, nicht geschlossen um die erste Elektrode 1 umläuft, sondern eine Unterbrechung hat.

In each of the 8th to 14 (and also 6 ) is the geometry of the first electrode 1 axisymmetric with respect to at least two axes of symmetry, at least two of which are perpendicular to one another. In addition, the first electrodes have 1 of these exemplary embodiments exhibits point symmetry with respect to a point of symmetry. Particularly due to these symmetries, there is the advantageous vibration behavior, which reduces or largely suppresses parasitic modes. The inventor has ascertained the following (wherein the symmetry axes and symmetry points are each viewed in a projection onto a plane, for example onto the plane of the membrane 5 ):

1. 1. The vibration behavior is particularly good when the geometry of the first electrode 1 has an infinite number of axes of symmetry.
2. 2. When using a first electrode with at least two axes of symmetry, the vibration behavior is particularly good if at least one of these transducer element axes of symmetry is parallel to at least one The axis of symmetry of the membrane runs. This would be the case, for example, if one of the transducer elements 6 or 8th to 14 in the orientation shown on the membrane 5 of the 15 is mounted in the orientation shown. The transducer element does not necessarily have to be central on the membrane 5 to be ordered.
3. 3. As a special case of the constellations described in the previous paragraph, even better results are achieved if at least one of the transducer element symmetry axes coincides with at least one membrane symmetry axis, even better if at least two transducer element symmetry axes coincide with at least two membrane symmetry axes. The latter would be the case, for example, if one of the transducer elements 20 of the 6 or 8th to 14 in the orientation shown, centrally on the membrane 5 of the 15 is arranged.
4. 4. Nevertheless, the vibration behavior can be improved compared to the prior art if no transducer element axis of symmetry runs parallel to or coincides with a membrane symmetry axis, but then preferably at least one transducer element axis of symmetry with at least one membrane symmetry axis has an angle of Includes 90 or 45 degrees. Here again is a central positioning of the transducer element 20 on the membrane 5 preferred but not mandatory. Such a case could arise if a membrane is used which, for example, has only one axis of symmetry (for example an approximately trapezoidal membrane) and if a transducer element 20 of the 6 , 8th , 9 or 14 is mounted on this membrane so that, for example, there is an angle of 45 degrees. When using a transducer element with exactly one axis of symmetry, an angle of 90 degrees can also be generated between the transducer element axis of symmetry and the membrane axis of symmetry.
5. 5. Even when using a transducer element or a membrane without an axis of symmetry, an improvement over the prior art can be achieved if either the transducer element or the membrane has point symmetry and the other component is also point symmetrical and / or at least one axis of symmetry, preferably has two axes of symmetry, and preferably more than two axes of symmetry, in particular an infinite number of axes of symmetry. Here, for example, the geometry of a parallelogram could be used for one of the components (membrane; first electrode) and a circle, an ellipse, a rectangle, square, trapezoid, parallelogram, etc. for the other component.
6. 6. In the constellations described in the previous paragraph, the improvement over the prior art is again greater if the symmetry points of the components coincide or if the symmetry point of one component lies on an axis of symmetry of the other component, in particular with the intersection of two or more Axes of symmetry coincide.
7. 7. The use of a component (membrane; first electrode) that has more than two axes of symmetry but is not point-symmetrical can represent an improvement over the prior art. A corresponding geometry could be designed, for example, as a regular pentagon, heptagon, or nine corner.
8. 8. The geometry of the at least one contact-change region also has an influence on the vibration behavior, but in most cases has a smaller influence than the geometry of the membrane or the first electrode and the relative position and orientation of these components to one another. In this respect it would be a variant, for example, of 6 possible, only one contacting area 3rd on the transducer element 20 to be arranged as long as the first electrode maintains its symmetry. Other variants based on the 6 or. 8th to 14 are also conceivable, for example, through-contact regions that are not offset by 180 degrees, but by any other angle; Rerouting areas 3rd that are not the same shape; a via area 3rd who, unlike in the 11 , 12th and 13 , not closed around the first electrode 1 circulates, but has an interruption.

In the exemplary embodiments illustrated, described or indicated above, it should be noted with respect to the axes of symmetry or points of symmetry of the first electrode or the membrane that the improvement in the oscillation behavior (in particular the avoidance of parasitic modes) is more pronounced the more exactly one point of symmetry coincides with another point of symmetry or lies on an axis of symmetry, or the more precisely an axis of symmetry is parallel to another axis of symmetry, which coincides with it, is rotated by an angle of 45 or 90 degrees, or the more exactly the transducer element 20 or the first electrode 1 concentric on the membrane 5 is arranged. Nevertheless, improvements over the state of the art can be identified if the desired shape of the components or their desired relative position or orientation to one another is not exactly achieved, but deviations can be determined. In this respect, it will be clear to the person skilled in the art that combinations (membrane; first electrode) which have such deviations also fall within the scope of protection, in particular if an improvement (if only a slight one) is possible compared to the prior art.

16 shows an example of the vibration behavior of a membrane when using a combination of a transducer element and a membrane according to the invention. As can clearly be seen, the vibration decays comparatively quickly, especially faster than in the in 5 shown example from the prior art.

In the present application, the terms “electrical contact”, “conductive” or the like are used. used. These relate in particular to materials with an electrical conductivity of more than 10 ⁴ S / cm.

Reference list

1

First / top electrode

2nd

Second / lower electrode

3rd

Rerouting / Rerouting area

4th

Piezo ceramic

5

membrane

10th

Ultrasonic sensor

11

First housing part

12th

Second housing part

13

poetry

20

Transducer element

21

Antinode

100

Transducer element

101

Upper electrode

102

Lower electrode

103

Reconnection

104

Piezo ceramic

105

membrane

110

Ultrasonic sensor

111

First housing part

112

Second housing part

113

poetry

120, 121

Antinodes

QUOTES INCLUDE IN THE DESCRIPTION

This list of documents listed by the applicant has been generated automatically and is only included for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 102006011155 A1 [0005]

Claims (10)

Transducer element (20) for generating and / or receiving ultrasonic vibrations for use in an ultrasonic sensor (10), in particular for a motor vehicle, in particular for distance measurement and / or for use in a driver assistance system, the transducer element (20) having: at least a first electrode (1) on a first side of the transducer element (20) and a second electrode (2) on a second side of the transducer element (20), the second side of the transducer element (20) being the first side of the transducer element (20) opposite, wherein the transducer element (20) has an electrically conductive changeover contact (3) which extends from the second electrode (2) to the first side of the transducer element (20), so that the first electrode (1) and the second electrode (2) are electrically contactable from the first side of the transducer element (20), the first electrode (1) having an electrode geometry which: a) is at least substantially symmetrical with respect to at least two transducer element axes of symmetry, or b) is at least essentially point-symmetrical with respect to a transducer element symmetry point. Ultrasonic sensor assembly (5, 20), comprising: a transducer element (20) Claim 1 , and a membrane (5) which has a membrane geometry which is essentially point-symmetrical with respect to a membrane symmetry point, and / or: a) is at least essentially symmetrical with respect to exactly one membrane axis of symmetry, or b) at least essentially is symmetrical with respect to exactly two membrane symmetry axes, or c) is at least substantially symmetrical with respect to more than two, in particular an infinite number of membrane symmetry axes. Ultrasonic sensor assembly (5, 20) after Claim 2 , wherein, when projected onto a plane: a) at least one transducer element symmetry axis runs essentially parallel to at least one membrane symmetry axis, and / or b) at least one transducer element symmetry axis essentially coincides with at least one membrane symmetry axis, and / or c) at least one transducer element axis of symmetry is substantially perpendicular to at least one membrane symmetry axis, and / or d) at least one transducer element axis of symmetry essentially encloses an angle of 45 degrees with at least one membrane symmetry axis, and / or e) at least two Transducer element symmetry axes essentially coincide with at least two diaphragm symmetry axes, and / or f) at least two transducer element symmetry axes essentially enclose an angle of 45 degrees in pairs with at least two diaphragm symmetry axes, and / or g) the transducer element symmetry point essentially coincides with the membrane symmetry point, and / or h) the transducer element symmetry point essentially lies on a membrane symmetry axis, and / or i) the transducer element symmetry point lies essentially on two membrane symmetry axes, and / or j) the membrane symmetry point essentially on a transducer element Axis of symmetry, and / or k) the membrane symmetry point lies essentially on two transducer element axes of symmetry. Ultrasonic sensor assembly (5, 20) after Claim 2 or 3rd , wherein the transducer element (20) is connected to the membrane (5) such that the first side of the transducer element (20) is oriented away from the membrane (5) and the second side of the transducer element (20) towards the membrane (5) is oriented. Ultrasonic sensor assembly (5, 20), in particular for a motor vehicle, in particular for distance measurement and / or for use in a driver assistance system, comprising: a transducer element (20) for generating and / or receiving ultrasonic vibrations, the transducer element (20) at least has a first electrode (1) on a first side of the transducer element (20) and a second electrode (2) on a second side of the transducer element (20), the second side of the transducer element (20) of the first side of the transducer element (20) opposite, a membrane (5) which has a membrane geometry which a) is at least substantially symmetrical with respect to exactly one membrane axis of symmetry, or b) is essentially point symmetrical with respect to a membrane symmetry point, but is not axisymmetric, wherein the Transducer element (20) is connected to the membrane (5) such that the first side of the transducer element (20) is oriented away from the membrane (5) and the second side of the transducer element (20) is oriented towards the membrane (5), the transducer element (20) having an electrically conductive changeover contact (3) which extends from the second electrode (2) to the first side of the transducer element (20) extends so that the first electrode (1) and the second electrode (2) from the first Side of the transducer element (20) are electrically contactable, the first electrode (1) having an electrode geometry that is essentially point-symmetrical with respect to a transducer element symmetry point, and / or: a) at least substantially symmetrical with respect to exactly one transducer element axis of symmetry is, or b) is at least substantially symmetrical with respect to exactly two transducer element symmetry axes, or c) is at least substantially symmetrical with more than two, in particular an infinite number of transducer element symmetry axes. Ultrasonic sensor assembly (5, 20) after Claim 5 , where, when projected onto a plane: a) at least one transducer element symmetry axis runs essentially parallel to the membrane symmetry axis, or b) at least one transducer element symmetry axis essentially coincides with the membrane symmetry axis, or c) at least one transducer element axis The axis of symmetry is substantially perpendicular to the membrane axis of symmetry, or d) at least one transducer element axis of symmetry essentially forms an angle of 45 degrees with the membrane axis of symmetry, or e) the transducer element symmetry point essentially coincides with the membrane symmetry point, or f) the transducer element symmetry point essentially lies on the membrane symmetry axis, or g) the membrane symmetry point essentially lies on a transducer element symmetry axis, or h) the membrane symmetry point essentially lies on two transducer element symmetry axes. Ultrasonic sensor assembly (5, 20) after Claim 3 or 6 , wherein the plane is parallel to the first side of the transducer element (20) and / or to the second side of the transducer element (20) and / or to a side of the membrane (5) facing the transducer element (20). Transducer element (20) after Claim 1 or ultrasonic sensor assembly (5, 20) according to one of the Claims 2 to 7 , wherein the changeover contact (3) has a first section and a second section made of a conductive material, the first section forming a contact area on the first side of the transducer element (20) and the second portion on the outer circumference of the transducer element (20) between the first side and the second side of the transducer element (20). Transducer element (20) or ultrasonic sensor assembly (5, 20) Claim 8 , wherein the changeover (3) is designed as a coating, in particular with or made of silver. Ultrasonic sensor (10), comprising a transducer element (20) according to one of the Claims 1 , 8th or 9 or an ultrasonic sensor assembly (5, 20) according to one of the Claims 2 to 9 .

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