阅读说明：本技术 带有压电陶瓷的超声换能器和用于制造这种超声换能器的方法 (Ultrasound transducer with a piezoceramic and method for producing such an ultrasound transducer ) 是由 彼得·迪塔斯 本杰明·森费尔德 于 2018-12-13 设计创作，主要内容包括：本发明涉及一种带有压电陶瓷的超声换能器和一种用于制造这种超声换能器的方法。为了提供一种超声换能器,其有出色的介质耐抗性并且通过减少零件数量有更为简单的结构,因而能以全自动化的生产方式制造该超声换能器。为此,本发明公开了一种根据权利要求1所述的特别是用于测量流体量的超声换能器,该超声换能器包括壳体,在该壳体内布置着接触元件和压电陶瓷,其中,压电陶瓷包括极性不同的两个电极,电极安装在压电陶瓷的不同的侧面上,其中,用于电接触两个电极的接触面布置在压电陶瓷的同一侧面上,并且接触元件具有至少两个极性不同的接触区段,接触区段与相应极性的两个电极的接触面处于导电的接触。(The invention relates to an ultrasonic transducer with a piezoceramic and a method for producing such an ultrasonic transducer. To provide an ultrasonic transducer which has excellent dielectric resistance and a simpler structure by reducing the number of parts, and thus can be manufactured in a fully automated production manner. To this end, the invention discloses an ultrasonic transducer, in particular for measuring a fluid quantity, according to claim 1, comprising a housing in which a contact element and a piezoelectric ceramic are arranged, wherein the piezoelectric ceramic comprises two electrodes of different polarity, which are mounted on different sides of the piezoelectric ceramic, wherein contact surfaces for electrically contacting the two electrodes are arranged on the same side of the piezoelectric ceramic, and the contact element has at least two contact sections of different polarity, which are in electrically conductive contact with the contact surfaces of the two electrodes of the respective polarity.)

1. An ultrasonic transducer (1), in particular for measuring a fluid quantity, comprising: a housing (2) in which a contact element (2c) and a piezoceramic (3) are arranged, wherein the piezoceramic (3) comprises two electrodes (4, 5) of different polarity which are mounted on different sides (A, B) of the piezoceramic (3), wherein contact surfaces (6, 7) for electrically contacting the two electrodes (4, 5) are arranged on the same side (A) of the piezoceramic (3), and the contact element (2c) comprises at least two contact sections (8, 9) of different polarity which are in electrically conductive contact with the contact surfaces (6, 7) of the two electrodes (4, 5) of the respective polarity.

2. The ultrasonic transducer (1) according to claim 1, characterized in that the respective contact section (8, 9) of the contact element (2c) is in planar contact with the respective contact face (6, 7) of the electrode (4, 5).

3. The ultrasonic transducer (1) according to claim 1 or 2, wherein a side of said first electrode (4) facing away from said piezoceramic (3) forms said contact face (6) of said first electrode (4).

4. The ultrasonic transducer (1) according to any of the preceding claims, wherein said first electrode (4) partially covers and/or contacts the first side (a) of said piezoelectric ceramic (3), wherein said first electrode (4) is preferably arranged centrally on the first side (a) of said piezoelectric ceramic (3), preferably such that an annular surface remains on the first side (a) of said piezoelectric ceramic (3) and is not covered by said first electrode (4).

5. The ultrasonic transducer (1) according to any of the preceding claims, characterized in that said second electrode (5) covers and/or contacts the second side (B) of said piezoelectric ceramic (3), preferably over the entire surface, wherein preferably at least one contact face (7) of said second electrode (5) is arranged on the first side (a) of said piezoelectric ceramic (3) and is electrically conductively connected to said second electrode (5) by a deflection contact (5a), wherein said deflection contact (5a) preferably extends through the third side (C) of said piezoelectric ceramic (3).

6. The ultrasonic transducer (1) according to any of the preceding claims, characterized in that said second electrode (5) has two, three, four or more contact faces (7), which are preferably uniformly configured and/or symmetrically and/or equidistantly arranged around said first electrode (4), preferably arranged on the edge side on said first side (a) of said piezoceramic (3).

7. Ultrasonic transducer (1) according to any of the preceding claims, characterized in that the piezoelectric ceramic (3) is configured as a piezoelectric ceramic disk or plate (3) and/or extends in one plane.

8. Ultrasound transducer (1) according to any of the preceding claims, characterized in that the housing (2) is made of a ceramic such as alumina or a plastic such as PPS, preferably in a die casting process or an injection molding process.

9. The ultrasonic transducer (1) according to any of the preceding claims, characterized in that said contact sections (8, 9) are on the same surface and/or in the same plane of said contact element (2 c).

10. The ultrasonic transducer (1) according to any of the preceding claims, characterized in that said contact element (2c) is configured pot-shaped, wherein said contact sections (8, 9) are arranged at the bottom of said contact element (2c) and are electrically contactable by edge sections (8a, 9a) of said contact element (2c) protruding therefrom.

11. Ultrasound transducer (1) according to one of the preceding claims, characterized in that the contact element (2c) forms part of the housing (2) and/or is constructed as a membrane through which the acoustic coupling of the piezoceramic (3) is accomplished, wherein the piezoceramic (3) is bonded to the contact element (2c) preferably over the entire surface.

12. The ultrasonic transducer (1) according to any of the preceding claims, characterized in that said contact segments (8, 9) are applied as a coating or metallization onto said contact elements (2c) or are incorporated into said contact elements (2c) by interposing an electrically conductive material, preferably in the form of particles.

13. Ultrasonic transducer (1) according to any of the preceding claims, characterized in that the housing (2) has a cover (2b) with electrodes (12, 13) of different polarity, wherein the electrodes (12, 13) are in electrically conductive connection with the contact sections (8, 9) of the respective polarity when the cover (2b) is closed, so that the piezoceramic (3) can be acted on with an alternating voltage by the electrodes of the cover (2 b).

14. Ultrasonic transducer (1) according to claim 12, characterized in that the electrodes (12, 13) are arranged at the outer side of the cover (2b) when the cover (2b) is closed and are in an electrically conductive connection, preferably by means of through holes, with contacts (10, 11) of the respective polarity at the inner side (E) of the cover (2b), wherein the contacts (10, 11) at the inner side (E) of the cover (2b) are in an electrically conductive connection and/or contact with the contact sections (8, 9) of the respective polarity when the cover (2b) is closed.

15. Method for manufacturing an ultrasound transducer (1) according to claim 13, comprising the steps of:

a. arranging the piezoceramic (3) in the housing (2) such that the contact surfaces (6, 7) of the piezoceramic (3) are in electrically conductive contact with the contact sections (8, 9) of the respective polarity of the contact element (2);

b. closing the housing (2) with the cover (2 b).

Technical Field

The invention relates to an ultrasonic transducer with a piezoceramic and a method for producing such an ultrasonic transducer.

Background

Ultrasonic transducers now used in a variety of water or heat meters and increasingly replacing conventional mechanical flow meters are often based on a simple combination of an active piezoelectric ceramic component with an acoustically transparent coupling layer, such as a stainless steel membrane.

Different solutions exist for the electrical contacting of piezoelectric components. One possibility is to use spring contacts, which, in view of the service life, of course, may represent a risk in terms of corrosion of the contacts. The contacts and contact points are subjected to dynamic stresses during operation, which in the long run can lead to changes in the transition resistance. The design and manufacturing requirements of such contacts are extremely high. A constant mass (contact pressure) is imperatively necessary for the functioning of the transducer in order to ensure a low-maintenance operation over a long service life. In many ultrasonic transducers, the contacting is also achieved by means of soldering of metal wires. The soldered connections on the piezoceramic represent an additional mass which has an effect on the vibration dynamics of the transducer. Manual soldering processes are subject to objective influences and lead to high production costs.

DE 10158015 a1 discloses such an ultrasonic transducer, in particular for use in a flowmeter for liquid or gaseous media.

A flow measuring device is known from EP 2267416 a 1.

DE 19820208 a1 discloses a piezoelectric vibrator in which the piezoelectric element is contacted by bipolar power supply lines. As explained above, the structural design required here for electrically connecting the electrodes of the piezoelectric ceramic to the soldering points of the supply lines has an adverse effect on the vibration dynamics of the ultrasonic transducer. The soldering points can be designed individually for each pole of the power supply line, which leads to high production costs.

The market for ultrasonic transducers in smart metering applications is under tremendous price pressure.

Disclosure of Invention

Starting from the prior art described above, the object of the present invention is to provide an ultrasonic transducer which has excellent dielectric resistance, improved vibration dynamics and a simpler construction by reducing the number of parts, and which can therefore be produced in a fully automated production manner.

To solve this object, the invention discloses an ultrasonic transducer, in particular for measuring a fluid quantity, according to claim 1. The ultrasonic transducer according to the invention comprises a housing in which a contact element and a piezoceramic are arranged, wherein the piezoceramic comprises two electrodes of different polarity, which are mounted on different sides of the piezoceramic, wherein contact surfaces for electrical contacting of the two electrodes are arranged on the same side of the piezoceramic, and the contact element has at least two contact sections of different polarity, which are in electrically conductive contact with the contact surfaces of the two electrodes of the respective polarity. This enables the two electrodes to be electrically contacted via the same side of the piezoceramic, so that the connection effort is significantly reduced by reducing the number of components that need to be connected by cables. The contact surfaces of the piezoelectric ceramic can be particularly advantageously acted upon by an alternating voltage via the two contact sections of the contact element. In particular, a direct interface with the electrode of the piezoceramic can be provided by using a contact element having two contact sections, which reduces the production effort when contacting the electrode of the piezoceramic.

It may be expedient for the respective contact section of the contact element to be in planar contact with the respective contact surface of the electrode. Reliable contacting of the electrodes can be achieved by means of the planar contact without the addition of additional mass.

It may be advantageous if the side of the first electrode facing away from the piezoceramic forms the contact surface of the first electrode. The first electrode can thus be electrically contacted through its back side.

However, it may also prove advantageous if the first electrode partially covers and/or contacts the first side of the piezoceramic, wherein the first electrode is preferably arranged centrally on the first side of the piezoceramic, preferably such that the annular surface remains on the first side of the piezoceramic and is not covered by the first electrode. This embodiment facilitates symmetrical excitation of the piezoelectric ceramic when an alternating voltage is applied to the electrodes.

However, it is also possible to envisage that the second electrode preferably completely covers and/or contacts the second side of the piezoceramic, wherein preferably at least one contact surface of both electrodes is arranged on the first side of the piezoceramic and is connected to the second electrode in an electrically conductive manner via a deflection contact (Umkontakt), wherein the deflection contact preferably extends over the third side of the piezoceramic. The deflection contact offers an excellent possibility of separating the contact surface of the second electrode from the electrically effective region of the second electrode.

It may also prove useful if the second electrode has two, three, four or more contact surfaces, which are preferably of uniform design and/or are arranged symmetrically and/or equidistantly around the first electrode, preferably on the edge side on the first side of the piezoceramic. This embodiment is advantageous for generating particularly symmetrical vibrations of the piezoelectric ceramic.

It may be advantageous for the piezoceramic to be configured as a piezoceramic disk or piezoceramic plate and/or to extend in one plane. This embodiment is particularly compact and can be produced cost-effectively from piezoelectric or piezoceramic materials.

It may also be expedient for the housing to be produced from a ceramic, such as aluminum oxide, or a plastic, such as PPS, preferably in a die-casting or injection molding process.

It may furthermore prove practical for the contact sections to lie on the same surface and/or in the same plane of the contact element. A particularly simple contacting of the contact surfaces of the two electrodes of the piezoceramic is thus achieved.

However, it may also be advantageous for the contact element to be pot-shaped, wherein the contact section is arranged at the bottom of the contact element and can be electrically contacted via an edge section of the contact element projecting from the bottom. This embodiment of the contact element is particularly stable and provides a bearing surface for the cover by means of the edge section of the contact element protruding from the base. The cover can on the one hand close the housing containing the piezoceramic and on the other hand can bring about the contacting of the edge sections of the contact elements.

It may be advantageous if the contact element forms part of the housing and/or is designed as a membrane, via which the piezo ceramic is acoustically coupled, wherein the piezo ceramic is preferably bonded to the contact element over the entire surface. In this embodiment, the number of components may be minimized.

However, it is also possible to apply the contact portions as a coating or metallization to the contact element or to process them into the contact element by inserting an electrically conductive material, preferably in the form of particles. The contact element can in particular be made of an electrically insulating material, wherein the respective contact section is subsequently formed by the technique. In this way, a plurality of different embodiments of the contact element can be produced without difficulty.

It may also be useful, however, for the housing to have a cover with electrodes of different polarities, wherein, when the cover is closed, the electrodes are in electrically conductive connection with the contact sections of the respective polarity, so that an alternating voltage can be applied to the piezoelectric ceramic via the electrodes of the cover. In this embodiment, the piezo ceramic and the contact element are protected inside the closed housing. Furthermore, the establishment of contact between the piezoceramic and the contact element is linked to the closed state of the cover, so that the establishment of contact between the piezoceramic and the contact element can also be verified optically, i.e. by checking the closed state of the cover.

However, it has also proven to be advantageous if the electrodes are arranged on the outside of the cover when the cover is closed and are preferably in electrically conductive connection with the contacts of the respective polarity on the inside of the cover via the through-holes, wherein the contacts on the inside of the cover are in electrically conductive connection and/or contact with the contact regions of the respective polarity when the cover is closed. In this embodiment, the piezoelectric ceramic can be applied with an alternating voltage in a particularly simple and comfortable manner, while the piezoelectric ceramic and the contact element are protected inside the closed housing.

Another aspect of the invention relates to a method for manufacturing an ultrasound transducer according to the previous embodiment, the method comprising the steps of:

a. arranging the piezo ceramic in the housing such that the contact surfaces of the piezo ceramic are in electrically conductive contact with the contact sections of the contact element of the respective polarity;

b. the case is closed with a lid.

The aforementioned advantages for the previous embodiments of the ultrasound transducer apply correspondingly also to the method of manufacturing the ultrasound transducer.

Important terms and definitions are explained next in connection with the claimed invention:

terms and definitions

The term "fluid" refers to a liquid or a gas.

The term "piezoceramic" refers to a piezoelectric element which is in particular designed in the form of a disk and preferably extends in one plane.

The piezoelectric ceramic may have the following characteristics:

the piezoceramic material consists of a piezoceramic material.

The piezoceramic is configured as a disk or plate.

The piezoceramic comprises a first side and a second side facing away from the first side, wherein the first side and the second side are preferably arranged exactly or substantially parallel to one another.

The piezoceramic has a disc shape or a flat cylindrical shape, the axial end sides of which form the first side and the second side of the piezoceramic, wherein the side surfaces form the third side of the piezoceramic.

The first electrode may have the following characteristics:

the first electrode has a disc shape.

The first electrode is arranged centrally on the first side of the piezoceramic.

The first electrode is preferably applied with its entire surface to the first side of the piezoelectric ceramic by means of a sputtering process.

The first electrode partially covers the first side of the piezoceramic, so that a preferably annular edge remains outside the first electrode on the first side of the piezoceramic, which edge is not covered by the first electrode.

The first electrode has a contact surface on its side facing away from the piezoceramic for electrically contacting the first electrode.

The second electrode may have the following characteristics:

the second electrode has a disc shape.

The second electrode is arranged on the second side of the piezoceramic.

The second electrode covers the second side of the piezoelectric ceramic over the entire surface.

The second electrode is preferably applied with its entire surface to the second side of the piezoelectric ceramic by means of a sputtering process

The second electrode comprises at least one contact surface, which is arranged on the same side of the piezoceramic as the contact surface of the first electrode, wherein the contact surface is connected via the deflection contact to a portion of the second electrode arranged on the second side of the piezoceramic. The deflection contact is preferably designed as a strip-shaped flat conductor and extends at least through the third side of the piezoceramic.

The second electrode comprises two, three, four or more contact surfaces, which are preferably arranged symmetrically and/or equidistantly on the same side of the piezoceramic as the contact surfaces of the first electrode. The contact surfaces are preferably arranged on the edge side on the respective side of the piezoceramic. The shape of each contact surface may correspond exactly or substantially to a semi-circle. The second electrode preferably has four identically formed, preferably semicircular contact surfaces which are arranged symmetrically and equidistantly at an angular distance of approximately 90 ° on the first side of the piezoceramic.

The contact element may have the following features:

the contact element is configured in the shape of a disc.

The contact element has a first contact section which extends in a strip-like manner in the radial direction over the first side of the contact element, wherein a preferably substantially circular section is formed in the center of the first side of the contact element, which section corresponds to the shape and size of the contact surface of the first electrode of the piezoceramic in order to contact the contact surface of the first electrode of the piezoceramic over the entire surface in the connected state.

The contact element has two second contact sections, which are arranged on the first side of the contact element on both sides of and insulated from the first contact section, in order to contact the contact surface of the second electrode of the piezoceramic in the connected state.

The contact element is pot-shaped, wherein the preferably circumferential edge projects from the first side or the base of the contact element on the edge side, wherein the edge section is formed at the upper edge of the contact element for the purpose of electrically contacting the contact section. The height of the edge section above the base of the contact element is preferably greater than the height of the piezoceramic. The inner diameter or inner circumference of the edge protruding from the bottom of the contact element is preferably in the range of 120% to 200% of the outer diameter or outer circumference of the piezoelectric ceramic.

The contact element is designed as a membrane for the acoustic coupling of the piezoceramic.

The contact element is firmly connected, preferably adhesively bonded, to the piezoceramic.

The contact element is made of an electrically insulating material, wherein the first and second contact sections made of an electrically conductive material are subsequently applied to the contact element, for example as a metallization or as a coating, or wherein the first and second contact sections made of an electrically conductive material in the form of embedded electrically conductive particles are machined into the contact element.

The housing may have the following features:

the housing comprises a pot-shaped housing lower part and a cover.

The cover of the housing comprises a printed circuit board or is configured as a printed circuit board. The printed circuit board may comprise electrodes of different polarity for applying an alternating voltage to the piezoelectric ceramic. The electrodes of the printed circuit board are preferably located on the outer side of the printed circuit board or of the housing when the housing is closed. The electrodes of the printed circuit board are preferably connected to contacts of the respective polarity on the inner side of the printed circuit board, for example, by means of through holes. The printed circuit board can preferably be mounted in the lower housing part only in certain rotational positions, so that the terminal is in electrically conductive contact with the edge section for electrical contact with the contact section of the contact element when the cover is closed. The contact pressure between the terminal and the edge section for electrical contact with the contact section of the contact element can be increased as desired, for example, by pressing the cover. The shape and size of the joint preferably correspond to the position of the edge section for electrical contact with the contact section of the contact element.

The housing is made of an electrically insulating material.

The housing is made of a structural ceramic, preferably of alumina.

The housing is made of plastic, preferably PPS. At least the pot-shaped lower housing part is preferably produced from plastic in an injection molding process.

The housing comprises a flat cylindrical and preferably rotationally symmetrical shape.

The housing comprises a diameter in the range of 150% to 300% of the diameter of the piezoelectric ceramic.

The housing comprises a height or axial length in the range of 150% to 500% of the height or axial length of the piezoceramic.

The piezoceramic and/or contact element is arranged centrally in the housing or concentrically with the axis of the housing.

Further advantageous embodiments of the entire invention result from the combination of the features disclosed in the description, the claims and the drawings.

Drawings

Fig. 1 is a perspective view of a piezoceramic of an ultrasound transducer according to the invention, having a first side (bottom side) view, wherein the piezoceramic is in the form of a flat cylindrical piezoceramic disk and the first electrode (+) is in the form of a circle and is applied centrally over the entire surface to the first side (bottom side) of the piezoceramic by means of a sputtering process, so that an annular edge remains on the first side of the piezoceramic, which edge is not covered by the first electrode and in which a total of four semicircular contact surfaces of the second electrode (-) are arranged symmetrically to the edge side and equidistantly spaced apart from one another;

FIG. 2 is a perspective view of the piezoceramic according to FIG. 1, with a second side (upper side) covered by a circular second electrode (-) applied by a sputtering process over the entire surface, wherein the deflection contact leads from the second electrode via the side surface of the piezoceramic to the contact surface of the second electrode on the first side of the piezoceramic;

fig. 3 is a perspective exploded view of a device comprising the piezoceramic of fig. 2 and a contact element having contact sections of different polarity which can be brought into contact with a contact surface of the piezoceramic for producing an electrically conductive connection, wherein the contact element is of disc-shaped design and a first contact section (+) runs in the form of a strip in the radial direction over the center of the contact element in order to form a circular central section, and wherein two second contact sections (-) are arranged on both sides of the first contact section and are of substantially semicircular design;

fig. 4 is a perspective view of the device according to fig. 3 in a state in which the piezoceramic is arranged on the contact element as intended, so that the contact surface of the piezoceramic is in electrically conductive contact with the contact section of the contact element of the respective polarity;

FIG. 5 is a bottom view of the device according to FIG. 4, wherein the contact element is shown partially transparent;

FIG. 6 is a perspective view of the device according to FIGS. 4 and 5, with a second side (top side) of the piezoceramic, wherein the piezoceramic is partially shown in transparent form;

fig. 7 is a plan view of a device comprising a pot-shaped lower housing part and a pot-shaped contact element, wherein the contact element is constructed similarly to the contact element shown in fig. 3 and additionally rises from the bottom of the contact element on the edge side by a circumferential edge, wherein contact sections of different polarity at the bottom of the contact element can be contacted by corresponding edge sections at the upper end of the circumferential edge;

FIG. 8 is a perspective top view of the device according to FIG. 7;

fig. 9 is a perspective top view of the device according to fig. 7 in a state in which the piezoceramic according to fig. 2 is arranged in a defined manner on the contact element, so that the contact surface of the piezoceramic is in electrically conductive contact with the contact section of the contact element of the respective polarity;

FIG. 10 is a bottom view of the device according to FIG. 9, wherein the lower housing part and the contact element are shown partially transparent;

fig. 11 is a perspective top view of a printed circuit board with electrodes of different polarity, via which an alternating voltage can be applied to the electrodes of the piezoceramic, wherein the printed circuit board forms a cover for the housing lower part shown in fig. 7 to 10, respectively;

fig. 12 is a perspective bottom view of the printed circuit board according to fig. 11, wherein contacts of different polarity for contacting edge sections of the respective polarity of the contact elements shown in fig. 7 to 9 are arranged at the bottom side or at the inner side of the printed circuit board, wherein the contacts are electrically conductively connected to the electrodes at the outer side by means of through-holes;

fig. 13 is a perspective top view of an ultrasound transducer according to the invention, comprising the device shown in fig. 9 in combination with the piezoceramic shown in fig. 2, wherein the printed circuit board is enclosed in the lower housing part shown in fig. 7 to 10, so that the connections at the inner side of the cover are in electrically conductive contact with the edge sections of the respective polarity of the contact elements, wherein the printed circuit board is shown partially transparent;

fig. 14 is a further perspective top view of the ultrasound transducer according to fig. 13.

Detailed Description

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

The preferred embodiment of the invention comprises an ultrasonic transducer 1, which is designed as a dielectric-resistant ultrasonic transducer and is formed by a pot-shaped housing 2 made of a structural ceramic (for example aluminum oxide) with structured electrodes in the base, which are designed as contact elements 2c with contact sections 8, 9, to which a structured piezoceramic 3 of a specially adapted deflection contact design is bonded (see fig. 1 to 6). When a chemically resistant material is used as a film by means of an oxide ceramic and electrical conductivity is achieved by means of a structured metallization structure of the contact elements 2c shaped as contact sections 8, 9, the innovation is that the piezoelectric ceramic 3 is electrically contacted only by means of the pot. The piezoceramic 3 therefore does not have to be additionally contacted by spring pins or metal wires and is therefore loaded or damped. The sensor is closed in a locked manner by a printed circuit board 2d or a circuit board glued into the housing 2 and can be contacted in any desired manner via this.

The alternative principle of contacting by means of structured electrodes can of course be applied not only to cans, but also to films of different shapes or shapes.

It is also conceivable to manufacture the housing from plastic (PPS). In the injection molding technique, a stamped grid may be injected, for example, for electrical contact. Another alternative for producing special electrode structures in the housing is the metallization of plastics, which is also a technical solution in this field.

The ultrasound transducer 1 according to the invention comprises in particular the following components:

fig. 1 and 2 show an embodiment of a piezoelectric ceramic 3 for an ultrasonic transducer 1 according to the invention for measuring a fluid quantity. The piezoceramic 3 is in the form of a flat cylinder or disk and extends substantially in one plane, wherein two circular electrodes 4, 5 of different polarity are applied to different sides A, B of the piezoceramic 3. The thickness of the piezoceramic 3 or the distance between the two side faces A, B is approximately in the range from 10% to 25% of the diameter of the piezoceramic 3.

The first electrode 4 partially covers and contacts the first side a of the piezoceramic 3 and is applied in a planar manner centrally on the first side a of the piezoceramic 3 by means of a sputtering process. The annular surface remains around the entire first electrode 4 on the first side a of the piezoelectric ceramic 3 and is not covered by the first electrode 4. The side of the first electrode 4 facing away from the piezoceramic 3 forms the contact surface 6 of the first electrode 4.

The second electrode 5, which is applied in a planar manner by means of a sputtering process, covers and contacts the second side B of the piezoelectric ceramic 3 over the entire surface. A total of four contact surfaces 7 of the second electrode 5 are arranged on the first side a of the piezoelectric ceramic 3 symmetrically on the edge side and equidistantly at an angular distance of approximately 90 ° from the center axis of the piezoelectric ceramic 3 and are each electrically conductively connected to the active part of the second electrode 5 via a deflection contact 5a extending over the side surface C of the piezoelectric ceramic 3. The contact surfaces 6, 7 for electrically contacting the two electrodes 4, 5 are therefore arranged on the same side a of the piezoceramic 3. The contact surface 7 of the second electrode 5 is substantially semicircular in shape.

In addition to the piezoceramic 3 shown in fig. 1 and 2, a contact element 2c is shown in fig. 3 to 6, which has at least two contact sections 8, 9 of different polarity, which can be brought into electrically conductive contact with the contact surfaces 6, 7 of the two electrodes 4, 5 of the respective polarity.

The contact element 2c is in the embodiment according to fig. 3 to 6 configured in a disc shape and extends in one plane. The diameter of the contact element 2c is approximately in the range of 150% to 300% of the diameter of the piezoelectric ceramic 3. The first contact section 8 for contacting the first electrode 4(+) of the piezoceramic 3 extends substantially in the form of a strip in the radial direction over the surface of the contact element 2c, in order to form a substantially disk-shaped section in the center of the surface of the contact element 2c, which section is intended for contacting the contact surface 6 of the first electrode 4 and is matched in its dimensions to the contact surface 6 of the first electrode 4. The first contact section 8 has insulating sections on both sides of the edge, which separate the first contact section 8 from the second contact section 9, which is arranged on both sides and is substantially semicircular in shape. The second contact portion 9 is provided and designed to be in electrically conductive contact with the contact surface 7 of the second electrode 5 when the piezoceramic 3 is arranged on the contact element 2c in a defined manner and is adhesively bonded to it in a planar manner. The first and second contact sections 8, 9 are in the same plane and on the same surface of the contact element 2 c. The contact element 2c can be designed as a membrane, through which the acoustic coupling of the piezoceramic 3 takes place. The contact sections 8, 9 are applied to the contact element 2c, for example, as a coating or metallization, or are machined into the contact element 2c by inserting an electrically conductive material, for example in the form of particles.

In an alternative embodiment according to fig. 7 to 10, the contact element 2c can be of pot-shaped design and inserted into the pot-shaped housing part 2a below or form part of the housing 2, wherein the first and second contact sections 8 and 9 are arranged substantially similarly to the embodiment according to fig. 3 to 6 at the bottom of the contact element 2c, while, in contrast to fig. 3 to 6, the edge sections 8a, 9a for electrical contact with the contact sections 8 and 9 project from the bottom of the contact element 2c on the edge side. The size of the receptacle formed by the lower pot-shaped housing part 2a exceeds the size of the piezoelectric ceramic 3, so that the piezoelectric ceramic 3 is completely enclosed in the receptacle.

Fig. 11 and 12 show a printed circuit board 2d which forms a cover 2b for closing the lower pot-shaped housing part 2a according to fig. 7 to 10.

Fig. 13 and 14 show an ultrasound transducer 1 according to the invention, which is designed in particular for measuring a fluid quantity. This ultrasonic transducer 1 comprises a housing 2, which is formed from a lower pot-shaped housing part 2a according to fig. 7 to 10 and a cover 2b, which is embodied as a printed circuit board 2d, according to fig. 11 and 12. The housing 2 can be made of a ceramic, such as aluminum oxide, or a plastic, such as PPS, wherein the housing made of plastic is preferably produced in a die-casting process or an injection molding process. The piezoceramic 3 and the contact element 2c according to fig. 1 and 2 are arranged in the housing such that the contact sections 8, 9 of the contact element 2c of different polarity are in electrically conductive contact with the contact surfaces 6, 7 of the two electrodes 4, 5 of the respective polarity.

At the first side D, the cover 2b has electrodes 12, 13 of different polarity, which are arranged when the cover 2b is closed on the outside of the cover 2b or of the housing 2 and are electrically conductively connected to the contact sections 8, 9 of the respective polarity via the edge sections 8a, 9a, so that the piezoelectric ceramic 3 can be acted upon by an alternating voltage via the electrodes of the cover 2 b. The electrodes 12, 13 are in electrically conductive connection with the contacts 10, 11 of the respective polarity on the inner side E of the cover 2b via the respective through-holes. The connections 10, 11 on the inner side E of the cover 2b establish an electrical contact ratio with the edge sections 8a and 9a of the contact element 2c when the cover 2b is closed and are in electrically conductive connection with the contact sections 8, 9 of the respective polarity.

In order to excite piezoelectric ceramic 3 to vibrate, an alternating electric field must be generated in piezoelectric ceramic 3. This occurs by applying an alternating voltage to the surface-mounted electrodes 4, 5 of the piezoelectric ceramic 3.

Due to the deflection contact 5a extending over the side surface C of the piezoceramic 3, the contact surfaces 6, 7 of the two electrodes 4, 5 of the piezoceramic 3, that is to say the contact points for the positive and negative electrodes, can be mounted on one side of the piezoceramic 3.

The piezoceramic 3 has a symmetrical design to form an optimal acoustic beam (Schallkeule), wherein the centrally arranged first electrode 4 forms an active region for sound emission and additionally an inactive region with four deflection contacts 5a and a contact surface 7 is present.

The substrate forming the contact element 2c can be realized in a cost-effective manner, for example, by means of a sputtering process (physical vapor deposition or PVD).

The acoustic coupling of the piezoelectric ceramic 3 to the contact element 2c is achieved by adhesion over the entire surface. The electrical contact of the piezoceramic 3 with the contact element 2c is also achieved at the same time by means of adhesive bonding, so that no additional contacting, for example by means of soldering or spring contacts, is required. The electrical contact between the piezoceramic 3 and the contact element 2c is achieved by the surface roughness of the mating parts of the joint. An electrically conductive adhesive is therefore not absolutely necessary. The contact of the contact surface of the central electrode 4 (positive pole) of the piezoelectric ceramic 3 and the contact surface 7 of the negative pole 5 on the contact element 2c is achieved by a special electrode structure shaped as contact sections 8, 9 and a special positioning of the piezoelectric ceramic 3.

The contact of the two electrodes 4, 5 of the piezoceramic 3 with the contact element 2c is therefore of particularly simple design. The adhesive (acoustic coupling) and electrical contacting of the defined function can be realized in one mounting step.

The device can be mounted in a housing 2 with corresponding electrical contact sections 8, 9. Another possibility consists in implementing the above-described design in a pot-shaped housing 2 a.

The realization or integration of the contact element 2c into the housing 2 is possible, wherein the housing 2 can be made of structural ceramic or plastic. The continuation of the electrode lines of the contact sections 8, 9 is effected, for example, by metallization (for example by PVD) of the contact elements 2c and/or of the inner wall of the housing 2 at a contact surface in an easily accessible shoulder in the housing 2. The internal metallization of the housing 2 provides additional shielding.

The housing 2 is closed with a cover 2b shaped as a printed circuit board 2d (FR4), wherein the design of the printed circuit board 2d can also be carried out in hybrid technology (printed circuit on alumina ceramic).

The adhesion of the printed circuit board 2d to the remaining housing 2 can be achieved by means of a non-conductive adhesive, wherein the electrical contact between the contact surfaces of the housing 2 and the electrode surfaces of the PCB is achieved by means of a surface roughness.

The ultrasound transducer 1 according to the invention is thus composed of only three parts in integrated contact with the piezoelectric disc 3. This results in a defined interface (solder contact or plug connector) to the counter electronics and in a simple, automatable assembly and connection technology, in which the mounting can be carried out from one side.

List of reference numerals

1 ultrasonic transducer

2 casing

2a tank

2b cover

2c contact element

2d printed circuit board

3 piezoelectric ceramics

4 electrodes (+) (piezoelectric ceramics)

5 electrode (-) (piezoelectric ceramics)

5a deflection contact electrode (-)

Contact surface of 6 electrodes (+)

Contact surface of 7 electrodes (-)

8 contact section for electrode (+)

8a edge of a contact element for contacting the contact section (+)

9 contact section for electrodes (-)

9a edge of a contact element for contact with a contact section (-)

10 connector (+) (cover inner side)

11 connection (-) (cover inner side)

12 electrode (+) (cover)

13 electrode (-) (cover)

A first side (bottom side) of piezoelectric ceramics

B second side (upper side) of piezoelectric ceramics

C third side (side surface) of piezoelectric ceramic

Outside of D cover

Inside of E cover