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EP1080345A2 - Ultrasonic transducer - Google Patents

Ultrasonic transducer

Info

Publication number
EP1080345A2
EP1080345A2 EP99932668A EP99932668A EP1080345A2 EP 1080345 A2 EP1080345 A2 EP 1080345A2 EP 99932668 A EP99932668 A EP 99932668A EP 99932668 A EP99932668 A EP 99932668A EP 1080345 A2 EP1080345 A2 EP 1080345A2
Authority
EP
European Patent Office
Prior art keywords
ultrasonic transducer
coupling layer
transducer according
coupling
measurement object
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP99932668A
Other languages
German (de)
French (fr)
Inventor
Thomas Hahn
Matthias Molitor
Thomas Trautmann
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Fraunhofer Gesellschaft zur Foerderung der Angewandten Forschung eV
Original Assignee
Fraunhofer Gesellschaft zur Foerderung der Angewandten Forschung eV
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Fraunhofer Gesellschaft zur Foerderung der Angewandten Forschung eV filed Critical Fraunhofer Gesellschaft zur Foerderung der Angewandten Forschung eV
Publication of EP1080345A2 publication Critical patent/EP1080345A2/en
Withdrawn legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F23/00—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
    • G01F23/22—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water
    • G01F23/28—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring the variations of parameters of electromagnetic or acoustic waves applied directly to the liquid or fluent solid material
    • G01F23/296—Acoustic waves
    • G01F23/2968—Transducers specially adapted for acoustic level indicators
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/02—Mechanical acoustic impedances; Impedance matching, e.g. by horns; Acoustic resonators

Definitions

  • the invention relates to an ultrasonic transducer as it can be used, for example, in level measuring devices for measuring the level of a liquid in open or closed containers.
  • This coupling method also fails when there are strong mechanical tensions between the ultrasonic sensor and the test object, for example due to temperature differences, or with undefined test object surfaces.
  • the clamping in connection with the additional application of fat or gel as a coupling agent is very cumbersome.
  • This device for monitoring the liquid level in a container comprises a carrier element, an ultrasonic transducer and a pressing mechanism which is provided in the carrier element and presses the ultrasonic transducer against the container when the carrier element is fastened to the latter.
  • the carrier element is provided with an all-round elastic seal that clings to the surface of the container.
  • a coupling layer made of an auxiliary (silicone gel) must be placed between the membrane of the ultrasonic transducer and the container wall in order to improve the acoustic coupling. As already explained above, this procedure is very cumbersome.
  • US 5 477 729 describes a further ultrasonic transducer arrangement and a coupling technique for coupling the ultrasonic transducer to a measurement object.
  • the arrangement includes a housing, a piezoelectric measuring element and a coupling layer firmly connected thereto, which is connected to a circumferential membrane.
  • the coupling layer is printed against the surface of the measurement object by the restoring force of the membrane.
  • the membrane acts as a pressure element. This ensures defined and constant contact conditions, which are essential for a reliable coupling or measurement.
  • the invention is achieved with the ultrasonic transducer according to claim 1.
  • Advantageous embodiments of the sensor are the subject of the dependent claims.
  • the ultrasonic transducer comprises a piezoelectric disk in a holder.
  • a coupling layer for ultrasound is firmly applied, for example cast on, to the front (radiating) surface of the piezoelectric disk.
  • This coupling layer consists of an elastic material, the elasticity of which allows the coupling layer to nestle against a measurement object surface when the ultrasound transducer is printed against the measurement object surface.
  • the material of the coupling layer should form as smooth a surface as possible. Furthermore, the acoustic impedance of the material must be sufficiently low to still allow measurement at a given thickness. The elasticity must allow the coupling pad to nestle against the surface of the measurement object when a corresponding pressure force is exerted, so that the ultrasonic waves onne large losses or reflections m can be coupled into the measurement object.
  • the coupling layer is preferably made of an elastic polymer (e.g. PU or silicone) with low acoustic impedance, i.e. an acoustic impedance below 4 * 10 ° kg / (m's) (corresponds to 4 MRayl).
  • an elastic polymer e.g. PU or silicone
  • low acoustic impedance i.e. an acoustic impedance below 4 * 10 ° kg / (m's) (corresponds to 4 MRayl).
  • the ultrasound transducer consists, for example, of a piezoceramic disk, which is vaporized on the back by a sound-absorbing potting compound and is provided on the front with the coupling layer (also referred to below as a coupling pad).
  • Unevenness (drops of paint, rust, scratches) on the surface of the measurement object can be compensated for by the elastic properties of the coupling pad m connection with a defined contact pressure of the transducer on the surface.
  • Measuring object surface or a curved shape of the measuring object surface itself This leads to a position-independent coupling possibility.
  • the ultrasonic transducer according to the invention enables an acoustic connection of the transducer to the measurement object wall (dry coupling) that can be released as often as required, without additives or auxiliary substances.
  • dry coupling we also achieve a high abrasion resistance of the transducer surface and thus wear resistance of the transducer.
  • the coupling cushion provides mechanical decoupling against impacts when the transducer is attached to the surface of the measurement object, for example when the container is placed on the transducer, and thus improves its mechanical protection by the shock-absorbing behavior of the elastomer. Since there is no rigid connection between the transducer surface and the measurement object surface, the transducer is suitable for large temperature ranges or high temperature differences between the transducer and measurement object. In a preferred embodiment, the
  • the encapsulation encapsulator fulfills the requirements for explosion protection (possible spark formation inside does not come into contact with the outside atmosphere) and also offers good dust and moisture protection.
  • Figure 1 shows schematically an example of the construction of the converter. The essential feature of the
  • Ultrasonic transducer consists of the permanently elastic coupling layer 1 (coupling cushion) on the radiating surface of the piezoceramic disk 2.
  • the piezoceramic disk 2 is held in a housing 3 which is filled with a sound-absorbing material 4.
  • the electrodes applied to the piezoceramic disk are just as little shown in the figure as the electrical contacting of the transducer. These can be designed in accordance with the prior art and have no influence on the teaching according to the invention.
  • the coupling layer is convex in the figure, the thickness of which in this example is approximately 3 mm in the middle and approximately 2 mm at the edge.
  • ALBIPOL F-1515/3 from Haus Chemie can be used as the material for the coupling layer, which fulfills the material requirements mentioned above.
  • others can also be used as the material for the coupling layer, which fulfills the material requirements mentioned above.
  • PU foam can be used as the full material 4 for the rear vapor deposition.
  • PU with fillers especially made of aluminum oxide, as used in the potting of electronic components, also shows good properties.
  • Converter is the design of the coupling pillow geometry.
  • additional structuring of the surface of the coupling cushion in conjunction with a corresponding contact pressure, a reduction in disturbing surface waves can be achieved.
  • These surface waves preferably arise in thin-walled container walls and prevent accurate echo detection in areas close to the wall.
  • a convex coupling pad surface with concentric, matrix-shaped and / or radial grooves or with individual elevations can be used.
  • the depth of these grooves or elevations is preferably a maximum of about half the maximum thickness of the coupling layer.
  • the thickness of the coupling layer is limited on the one hand by the formation of surface waves, which occur with increasing thickness of the layer, on the other hand by the thickness of the ripple, the surface shape or the unevenness on the surface of the measurement object, which must be compensated for by the coupling layer.
  • the ultrasonic transducer according to the invention advantageously allows an auxiliary material-free, freely exchangeable, acoustic coupling to test objects.

Landscapes

  • Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Electromagnetism (AREA)
  • Thermal Sciences (AREA)
  • Fluid Mechanics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Measurement Of Levels Of Liquids Or Fluent Solid Materials (AREA)

Abstract

The invention relates to an ultrasonic transducer which can, for example, be used in level measuring devices for measuring the level of a liquid in open or closed receptacles. The inventive ultrasonic transducer comprises a piezoelectric wafer (2) which is situated in a retaining device (3). A coupling layer (1) for ultrasound is applied, e.g. cast, in a fixed manner to the fore-side (radiating ) surface of the piezoelectric wafer (2). This coupling layer (1) is comprised of an elastic material whose elasticity enables the coupling layer to adapt to a surface of an object to be measured when the ultrasonic transducer is pressed against the surface of said object to be measured. In an advantageous manner, the inventive ultrasonic transducer permits an acoustic coupling to objects to be measured which does not require the use of auxiliary materials and which can be changed in any manner.

Description

Ultraschallwandler Ultrasonic transducer

Die Erfindung betrifft einen Ultraschallwandler, wie er beispielsweise in Füllstands eßgeraten zur Messung des Füllstandes einer Fl ssigkeit in offenen oder geschlossenen Behaltnissen eingesetzt werden kann.The invention relates to an ultrasonic transducer as it can be used, for example, in level measuring devices for measuring the level of a liquid in open or closed containers.

Bei der Anwendung von Ultraschall ist es erforderlich, den m einem elektromechanischen Wandler erzeugten Ultraschall in das Ausbreitungsmedium emzukoppeln. Für viele technische Applikationen, insbesondere die Durchflußmessung oder die Fullstandmessung muß der Schall durch eine Behalterwand in dessen gefüllten Innenraum geleitet werden.When using ultrasound, it is necessary to couple the ultrasound generated in an electromechanical transducer into the propagation medium. For many technical applications, in particular flow measurement or full level measurement, the sound has to be conducted through a container wall into its filled interior.

Im Stand der Technik erfolgt dies durch kraftschlussiges Ankleben des Ultraschallsensors an die Behalterwand oder durch eine Klemmverbindung unterstützt durch Koppelmittel wie Fett oder Gel.In the prior art, this is done by non-positively adhering the ultrasonic sensor to the container wall or by a clamp connection supported by coupling agents such as grease or gel.

Insbesondere bei Meßeinrichtungen mit häufigem Wechsel des Meßobjektes ist das Ankleben des Sensors jedoch nicht möglich. Auch bei starken mechanischen Spannungen zwischen Ultraschallsensor und Meßobjekt , beispielsweise aufgrund von Temperaturunterschieden, oder bei Undefinierten Meßobjektoberflachen versagt diese Ankoppelmethode. Das Anklemmen in Verbindung mit dem zusatzlichen Aufbringen von Fett oder Gel als Koppelmittel ist sehr umständlich. Eine derartige Vorrichtung ist beispielsweise in der DE 195 38 696 AI beschrieben. Diese Vorrichtung zur Überwachung des Flussigkeitspegels in einem Behalter umfaßt ein Tragerelement, einen Ultraschallwandler und einen Anpreßmechanismus, der im Tragerelement vorgesehen ist und den Ultraschallwandler bei einer Befestigung des Tragerelementes am Behalter gegen diesen druckt. Das Tragerelement ist mit einer umlaufenden elastischen Dichtung versehen, die sich an die Oberflache des Behalters anschmiegt. Vor derIn particular in the case of measuring devices with frequent changing of the measurement object, the sensor cannot be glued on. This coupling method also fails when there are strong mechanical tensions between the ultrasonic sensor and the test object, for example due to temperature differences, or with undefined test object surfaces. The clamping in connection with the additional application of fat or gel as a coupling agent is very cumbersome. Such a device is described for example in DE 195 38 696 AI. This device for monitoring the liquid level in a container comprises a carrier element, an ultrasonic transducer and a pressing mechanism which is provided in the carrier element and presses the ultrasonic transducer against the container when the carrier element is fastened to the latter. The carrier element is provided with an all-round elastic seal that clings to the surface of the container. Before the

Messung muß eine Kopplungsschicht aus einem Hilfsstoff (Silicon-Gel) zwischen die Membran des Ultraschallwandlers und die Behalterwand gebracht werden, um die akustische Ankopplung zu verbessern. Wie bereits oben dargelegt ist diese Vorgehensweise jedoch sehr umständlich.Measurement, a coupling layer made of an auxiliary (silicone gel) must be placed between the membrane of the ultrasonic transducer and the container wall in order to improve the acoustic coupling. As already explained above, this procedure is very cumbersome.

Die US 5 477 729 beschreibt eine weitere Ultraschallwandler-Anordnung und eine Ankopplungs- technik zum Ankoppein des Ultraschallwandlers an ein Meßobjekt. Die Anordnung umfaßt u.a. ein Gehäuse, ein piezoelektrisches Meßelement und eine damit fest verbundene Ankoppelschicht, die mit einer umlaufenden Membran verbunden ist. Bei der Ankopplung wird die Ankoppelschicht durch die Ruckstellkraft der Membran gegen die Oberflache des Meßobjektes gedruckt. Die Membran fungiert hierbei als Anpreße1ement . Dies gewahrleistet definierte und konstante Anpreßverhält- nisse, die für eine zuverlässige Ankopplung bzw. Messung wesentlich sind.US 5 477 729 describes a further ultrasonic transducer arrangement and a coupling technique for coupling the ultrasonic transducer to a measurement object. The arrangement includes a housing, a piezoelectric measuring element and a coupling layer firmly connected thereto, which is connected to a circumferential membrane. During the coupling, the coupling layer is printed against the surface of the measurement object by the restoring force of the membrane. The membrane acts as a pressure element. This ensures defined and constant contact conditions, which are essential for a reliable coupling or measurement.

Es ist eine Aufgabe der vorliegenden Erfindung, einen Ultraschallwandler bereitzustellen, der die obigen Probleme vermeidet, so daß ohne zusatzlich bereitzustellende Hilfsstoffe eine zuverlässige Ankopplung an unterschiedlich geformte Meßobiekt- oberflachen ermöglicht und ein schneller Wechsel der Meßobjekte realisiert werden kann.It is an object of the present invention to provide an ultrasonic transducer that can Avoids the above problems, so that without additional auxiliary materials to be provided, a reliable coupling to differently shaped measuring object surfaces is made possible and a quick change of the measuring objects can be realized.

Die Erfindung wird mit dem Ultraschallwandler gemäß Anspruch 1 gelost. Vorteilhafte Ausgestaltungen des Sensors sind Gegenstand der Unteranspruche .The invention is achieved with the ultrasonic transducer according to claim 1. Advantageous embodiments of the sensor are the subject of the dependent claims.

Der erfindungsgemaße Ultraschallwandler umfaßt eine piezoelektrische Scheibe in einer Halterung. Auf der vorderseitigen (abstrahlenden) Oberflache der piezoelektrischen Scheibe ist eine Ankoppelschicht für Ultraschall fest aufgebracht, beispielsweise aufgegossen. Diese Ankoppelschicht besteht aus einem elastischen Material, dessen Elastizität ein Anschmiegen der Ankoppelschicht an eine Meßobjektoberflache ermöglicht, wenn der Ultraschallwandler gegen die Meßobjektoberflache gedruckt wird.The ultrasonic transducer according to the invention comprises a piezoelectric disk in a holder. A coupling layer for ultrasound is firmly applied, for example cast on, to the front (radiating) surface of the piezoelectric disk. This coupling layer consists of an elastic material, the elasticity of which allows the coupling layer to nestle against a measurement object surface when the ultrasound transducer is printed against the measurement object surface.

Für die Wahl des Materials ist wichtig, daß dieses fest an der Oberflache der piezokeramischen Scheibe haftet, jedoch nicht an der Meßobjektoberflache, die in der Regel aus Metall besteht. Das Material der Ankoppelschicht sollte eine möglichst glatte Oberflache bilden. Weiterhin muß die akustische Impedanz des Materials ausreichend niedrig sein, um bei gegebener Dicke die Messung noch zu ermöglichen. Die Elastizität muß das Anschmiegen des Koppelkissens an die Meßobjektoberflache bei Ausübung einer entsprechenden Andruckkraft ermöglichen, so daß die Ultraschallwellen onne große Verluste oder Reflexionen m das Meßobjekt eingekoppelt werden können.For the selection of the material it is important that it adheres firmly to the surface of the piezoceramic disk, but not to the surface of the measurement object, which is usually made of metal. The material of the coupling layer should form as smooth a surface as possible. Furthermore, the acoustic impedance of the material must be sufficiently low to still allow measurement at a given thickness. The elasticity must allow the coupling pad to nestle against the surface of the measurement object when a corresponding pressure force is exerted, so that the ultrasonic waves onne large losses or reflections m can be coupled into the measurement object.

Die Ankoppelschicht besteht vorzugsweise aus einem elastischen Polymer (z.B. PU oder Silikon) mit geringer akustischer Impedanz, d.h. einer akustischen Impedanz unterhalb von 4*10° kg/(m's) (entspricht 4 MRayl) .The coupling layer is preferably made of an elastic polymer (e.g. PU or silicone) with low acoustic impedance, i.e. an acoustic impedance below 4 * 10 ° kg / (m's) (corresponds to 4 MRayl).

Der Ultraschallwandler besteht beipielsweise aus einer piezokeramischen Scheibe, die r ckwärtig durch einen Schallschwachenden Verguß bedampft, und frontseitig mit der Ankoppelschicht (im folgenden auch als Koppelkissen bezeichnet) versehen ist.The ultrasound transducer consists, for example, of a piezoceramic disk, which is vaporized on the back by a sound-absorbing potting compound and is provided on the front with the coupling layer (also referred to below as a coupling pad).

Durch den Einsatz des erfmdungsgemäßen Wandlers m Verbindung mit einer federnden Anpressung des Wandlers an die Meßobjektoberflache werden folgende Vorteile erreicht:By using the transducer according to the invention in connection with a resilient pressing of the transducer on the surface of the measurement object, the following advantages are achieved:

Unebenheiten (Farbtropfen, Rost, Kratzer) auf der Oberflache des Meßobjektes können durch die elastischen Eigenschaften des Koppelkissens m Verbindung mit einem definierten Anpreßdruck des Wandlers an die Oberflache ausgeglichen werden. Entsprechendes gilt für Welligkelten (konkave, konvexe Form) auf derUnevenness (drops of paint, rust, scratches) on the surface of the measurement object can be compensated for by the elastic properties of the coupling pad m connection with a defined contact pressure of the transducer on the surface. The same applies to Wavy Celts (concave, convex shape) on the

Meßobjektoberflache oder eine gekrümmte Form der Meßob ektoberflache selbst. Dies fuhrt zu einer lageunabhangigen Ankopplungsmoglichkeit .Measuring object surface or a curved shape of the measuring object surface itself. This leads to a position-independent coupling possibility.

Der erfmdungsgemäße Ultraschallwandler ermöglicht ohne Zusatz- bzw. Hilfsstoffe eine beliebig häufig losbare akustische Verbindung des Wandlers mit der Meßobjektwand (Trockenankopplung) . Durch das Koppelkissen wir zudem eine hohe Abriebfestigkeit der Wandleroberflache und damit Verschleißfestigkeit des Wandlers erreicht.The ultrasonic transducer according to the invention enables an acoustic connection of the transducer to the measurement object wall (dry coupling) that can be released as often as required, without additives or auxiliary substances. With the coupling cushion, we also achieve a high abrasion resistance of the transducer surface and thus wear resistance of the transducer.

Das Koppelkissen bewirkt eine mechanische Entkopplung gegen Stoße beim Ansetzen des Wandlers an d e Meßobjektoberflache, beispielsweise beim Aufsetzen des Behalters auf den Wandler, und verbessert damit dessen mechanischen Schutz durch stoßdampfendes Verhalten des Elastomeres. Da keine starre Verbindung zwischen der Wandleroberflache und der Meßobjektoberflache hergestellt wird, eignet sich der Wandler für große Temperaturbereiche oder hohe Temperaturdifferenzen zwischen Wandler und Meßob ektwand. In einer bevorzugten Ausfuhrungsform kann derThe coupling cushion provides mechanical decoupling against impacts when the transducer is attached to the surface of the measurement object, for example when the container is placed on the transducer, and thus improves its mechanical protection by the shock-absorbing behavior of the elastomer. Since there is no rigid connection between the transducer surface and the measurement object surface, the transducer is suitable for large temperature ranges or high temperature differences between the transducer and measurement object. In a preferred embodiment, the

Wandler durch eine Vergußkapselung die Anforderungen an Exlosions-Schutzfahigkeit erfüllen (mögliche Funkenbildung im Innern kommt nicht Kontakt mit der Außenatmosphare) und bietet weiterhin einen guten Staub- sowie Feuchtigkeitsschutz .The encapsulation encapsulator fulfills the requirements for explosion protection (possible spark formation inside does not come into contact with the outside atmosphere) and also offers good dust and moisture protection.

Durch Wahl der abschallenden Flache ist die Beeinflussung des abgestrahlten Schallfeldes und damit die Ausblendung von Reflexionen an Meßobjekten möglich.By choosing the sounding surface, it is possible to influence the emitted sound field and thus to suppress reflections from the objects being measured.

Der erf dungsgemaße Ultraschallwandler wird im folgenden anhand eines Ausfuhrungsbeispiels Verbindung mit der Zeichnung nochmals erläutert.The ultrasonic transducer according to the invention is explained again below using an exemplary embodiment in conjunction with the drawing.

Figur 1 zeigt schematisch ein Beispiel f r den Aufbau des Wandlers. Das wesentliche Merkmal desFigure 1 shows schematically an example of the construction of the converter. The essential feature of the

Ultraschallwandlers besteht hierbei der dauerhaft elastischen Ankoppelschicht 1 (Koppelkissen) auf der abstrahlenden Oberflache der piezokeramischen Scheibe 2. Die piezokeramische Scheibe 2 ist einem Gehäuse 3 gehaltert, das mit einem schalldämpfenden Material 4 aufgefüllt ist. Die auf der piezokeramischen Scheibe aufgebrachten Elektroden sind in der Figur ebensowenig dargestellt wie die elektrische Kontaktierung des Wandlers. Diese können entsprechend dem Stand der Technik ausgeführt sein und haben keinen Einfluß auf die erfindungsgemaße Lehre.Ultrasonic transducer consists of the permanently elastic coupling layer 1 (coupling cushion) on the radiating surface of the piezoceramic disk 2. The piezoceramic disk 2 is held in a housing 3 which is filled with a sound-absorbing material 4. The electrodes applied to the piezoceramic disk are just as little shown in the figure as the electrical contacting of the transducer. These can be designed in accordance with the prior art and have no influence on the teaching according to the invention.

Die Ankoppelschicht ist in der Figur konvex ausgeführt, wobei deren Dicke in diesem Beispiel in der Mitte ca. 3mm und am Rand ca. 2mm betragt. Als Material für die Ankoppelschicht kann beipielsweise ALBIPOL F-1515/3 der Firma Hause Chemie eingesetzt werden, das die oben angeführten Materialanforderungen erfüllt. Selbstverständlich lassen sich auch andereThe coupling layer is convex in the figure, the thickness of which in this example is approximately 3 mm in the middle and approximately 2 mm at the edge. For example, ALBIPOL F-1515/3 from Haus Chemie can be used as the material for the coupling layer, which fulfills the material requirements mentioned above. Of course, others can also

Materialien finden, die die entsprechenden elastischen Eigenschaften bei geringer akustischer Impedanz aufweisen.Find materials that have the appropriate elastic properties with low acoustic impedance.

Als Fullmaterial 4 für die rückseitige Bedampfung kann beispielsweise PU-Schaum eingesetzt werden. Auch PU mit Füllstoffen (insbesondere aus Aluminiumoxid), wie es beim Verguß von Elektronikbauteilen verwendet wird, zeigt gute Eigenschaften.For example, PU foam can be used as the full material 4 for the rear vapor deposition. PU with fillers (especially made of aluminum oxide), as used in the potting of electronic components, also shows good properties.

Ein besonderer Faktor bei der Konstruktion desA special factor in the construction of the

Wandlers ist die Gestaltung der Koppelkissengeometrie. Insbesondere durch die zusätzliche Strukturierung der Oberfläche des Koppelkissens kann in Verbindung mit einem entsprechenden Anpreßdruck eine Verminderung von störenden Oberflachenwellen erreicht werden.Converter is the design of the coupling pillow geometry. In particular through the additional structuring of the surface of the coupling cushion, in conjunction with a corresponding contact pressure, a reduction in disturbing surface waves can be achieved.

Diese Oberflachenwellen entstehen vorzugsweise in dünnwandigen Behalterwanden und verhindern eine genaue Echodetektion in wandnahen Bereichen. Zur Vermeidung dieser Störungen kann beispielsweise eine konvexe Koppelkissenoberfläche mit konzentrischen, matrixformigen und/oder radialen Rillen oder mit einzelnen Erhebungen eingesetzt werden. Die Tiefe dieser Rillen oder Erhebungen betragt hierbei vorzugsweise maximal etwa die Hälfte der maximalen Dicke der Ankoppelschicht.These surface waves preferably arise in thin-walled container walls and prevent accurate echo detection in areas close to the wall. To avoid these disturbances, for example, a convex coupling pad surface with concentric, matrix-shaped and / or radial grooves or with individual elevations can be used. The depth of these grooves or elevations is preferably a maximum of about half the maximum thickness of the coupling layer.

Die Dicke der Ankoppelschicht ist einerseits nach oben durch das Entstehen von Oberflächenwellen begrenzt, die mit zunehmender Dicke der Schicht verstärkt auftreten, andererseits nach unten durch die Starke der Welligkeit, der Oberflachenform oder der Unebenheiten auf der Meßobjektoberflache, die durch die Ankoppelschicht ausgeglichen werden müssen.The thickness of the coupling layer is limited on the one hand by the formation of surface waves, which occur with increasing thickness of the layer, on the other hand by the thickness of the ripple, the surface shape or the unevenness on the surface of the measurement object, which must be compensated for by the coupling layer.

Der erfindungsgemäße Ultraschallwandler erlaubt in vorteilhafter Weise eine hilfsstoffreie, beliebig wechselbare, akustische Ankopplung an Meßobjekte. The ultrasonic transducer according to the invention advantageously allows an auxiliary material-free, freely exchangeable, acoustic coupling to test objects.

Claims

Patentansprüche claims 1. Ultraschallwandler mit einer piezoelektrischen Scheibe (2), die einer Halterung (3) angeordnet ist, wobei eine erste, vorderseitige Oberflache der piezoelektrischen Scheibe (2) eine Ankoppelschicht (1) f r Ultraschall aufweist, die fest mit der ersten Oberflache verbunden ist, dadurch gekennzeichnet, daß die Ankoppelschicht (1) aus einem elastischen Material besteht, das sich beim Anpressen an eine Meßobjektoberflache an die Meßobjektoberflache anschmiegt.1. Ultrasonic transducer with a piezoelectric disk (2), which is arranged in a holder (3), a first, front surface of the piezoelectric disk (2) having a coupling layer (1) for ultrasound, which is firmly connected to the first surface, characterized in that the coupling layer (1) consists of an elastic material which, when pressed against a measurement object surface, conforms to the measurement object surface. 2. Ultraschallwandler nach Anspruch 1, dadurch gekennzeichnet, daß das elastische Material ein elastisches Polymer mit einer akustischen Impedanz unterhalb von 4*10° kg/ (πrs) ist.2. Ultrasonic transducer according to claim 1, characterized in that the elastic material is an elastic polymer with an acoustic impedance below 4 * 10 ° kg / (πrs). 3. Ultraschallwandler nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß die Ankoppelschicht (1) eine konvexe Oberflachenform aufweist.3. Ultrasonic transducer according to claim 1 or 2, characterized in that the coupling layer (1) has a convex surface shape. 4. Ultraschallwandler nach einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, daß die Ankoppelschicht (1) eine strukturierte Oberflache aufweist.4. Ultrasonic transducer according to one of claims 1 to 3, characterized in that the coupling layer (1) has a structured surface. 5. Ultraschallwandler nach Anspruch 4, dadurch gekennzeichnet, daß die Oberflache der Ankoppelschicht (1) konzentrische Ringe, matrixformige und/oder radiale Rillen oder einzelne Erhebungen aufweist. 5. Ultrasonic transducer according to claim 4, characterized in that the surface of the coupling layer (1) has concentric rings, matrix-shaped and / or radial grooves or individual elevations. 6. Ultraschallwandler nach einem der Anspr che 1 bis6. Ultrasonic transducer according to one of claims 1 to 1 5, dadurch gekennzeichnet, daß die Ankoppelschicht (1) auf die piezoelektrische Scheibe (2) aufgegossen ist.5, characterized in that the coupling layer (1) is cast onto the piezoelectric disc (2). 7. Ultraschallwandler nach einem der Ansprüche 1 bis7. Ultrasonic transducer according to one of claims 1 to 6, dadurch gekennzeichnet, daß die piezoelektrische Scheibe (2) eine Piezokera ik ist.6, characterized in that the piezoelectric disc (2) is a Piezokera ik. 8. Ultraschallwandler nach einem der Ansprüche 1 bis8. Ultrasonic transducer according to one of claims 1 to 7, dadurch gekennzeichnet, daß die Halterung (3) ein zylmderformiges Gehäuse aus einem Schallschwachenden Verguß ist, dessen vorderseitige Öffnung durch die piezoelektrische Scheibe (2) verschlossen wird, und in dessen rückseitige Öffnung ein schalldampfender Füllstoff (4) eingefüllt ist.7, characterized in that the holder (3) is a cylinder-shaped housing made of a sound-absorbing potting, the front opening of which is closed by the piezoelectric disc (2), and a sound-damping filler (4) is filled into the rear opening. 9. Anordnung, bei der die Ankoppelschicht (1) eines Ultraschallwandlers nach einem der Anspr che 1 bis 8 über ein Anpreßelement an die Oberflache eines Meßobjektes angepreßt wird. 9. Arrangement in which the coupling layer (1) of an ultrasonic transducer according to one of claims 1 to 8 is pressed via a pressing element onto the surface of a measurement object.
EP99932668A 1998-05-07 1999-05-06 Ultrasonic transducer Withdrawn EP1080345A2 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE19820419 1998-05-07
DE19820419A DE19820419A1 (en) 1998-05-07 1998-05-07 Ultrasonic transducer
PCT/DE1999/001402 WO1999057526A2 (en) 1998-05-07 1999-05-06 Ultrasonic transducer

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EP1080345A2 true EP1080345A2 (en) 2001-03-07

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EP (1) EP1080345A2 (en)
DE (1) DE19820419A1 (en)
WO (1) WO1999057526A2 (en)

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DE10344741A1 (en) 2003-09-25 2005-04-14 Endress + Hauser Gmbh + Co. Kg Sound or ultrasonic transducer
US8104341B2 (en) * 2009-03-25 2012-01-31 Schmitt Measurement Systems, Inc. Ultrasonic liquid level monitoring system
DE102012104227A1 (en) * 2012-05-15 2013-11-21 Endress + Hauser Gmbh + Co. Kg Ultrasonic transducer has attenuation capping portion that is interlaced with metal or metal oxide particles at room temperature, such that cross-linking encapsulation is conditioned with micro hollow spheres
DE102012209777A1 (en) * 2012-06-12 2013-12-12 Continental Automotive Gmbh Coupling device for coupling sound converter of acoustic measuring device with fluid conduit or fluid reservoir, comprises acoustic coupling layer firmly coupled with housing element of sound converter by injection molding
DE102018216624B4 (en) * 2018-09-27 2022-12-08 Vitesco Technologies Germany Gmbh Method and device for determining the filling level and/or the quality of a fluid in a fluid container
CN115568905B (en) * 2022-10-17 2024-11-19 深圳迈菲超声医疗器械有限公司 Ultrasonic cutting device

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CH642503A5 (en) * 1979-08-02 1984-04-13 Landis & Gyr Ag Ultrasound converter
US4570482A (en) * 1982-04-23 1986-02-18 Murata Manufacturing Co., Ltd. Load-sensitive level detecting device
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Publication number Publication date
DE19820419A1 (en) 1999-11-18
WO1999057526A2 (en) 1999-11-11
WO1999057526A3 (en) 2000-03-16

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