EP1232023B1 - Ultrasonic transducer - Google Patents

Ultrasonic transducer Download PDF

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Publication number
EP1232023B1
EP1232023B1 EP00989772A EP00989772A EP1232023B1 EP 1232023 B1 EP1232023 B1 EP 1232023B1 EP 00989772 A EP00989772 A EP 00989772A EP 00989772 A EP00989772 A EP 00989772A EP 1232023 B1 EP1232023 B1 EP 1232023B1
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EP
European Patent Office
Prior art keywords
layer
ultrasound
layers
foam
converter
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EP00989772A
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German (de)
French (fr)
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EP1232023A1 (en
Inventor
Rudolf Thurn
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Siemens AG
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Siemens AG
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    • 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
    • G10K11/002—Devices for damping, suppressing, obstructing or conducting sound in acoustic devices
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B06—GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
    • B06B—METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
    • B06B1/00—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency
    • B06B1/02—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy
    • B06B1/06—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction
    • B06B1/0644—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction using a single piezoelectric element
    • B06B1/0662—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction using a single piezoelectric element with an electrode on the sensitive surface
    • B06B1/067—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction using a single piezoelectric element with an electrode on the sensitive surface which is used as, or combined with, an impedance matching layer

Definitions

  • the invention relates to an ultrasonic transducer, especially for use in proximity switches.
  • Ultrasonic proximity switches are used in automation technology mainly for contactless detection of presence or the distance of objects.
  • the barrier or the echo delay method are used for the measurement task Use.
  • An ultrasound transmitter transmits the barrier method Signals from the direct path to an ultrasound receiver reach.
  • the object to be detected interrupts the sound path and is thus detected.
  • the echo delay method on the other hand, that of the object to be captured reflected ultrasonic echo received and from the signal propagation time the distance between sending and receiving of the item determined.
  • the key components for both processes are the ultrasonic transducers. They are used to implement electrical Signals in sound waves and when received for implementation used by sound waves in electrical signals. at Devices based on the echo delay method are often one and the same Transducers used alternately for sending and receiving. This reduces the technical outlay on equipment, but also set a minimum distance below that because of the inevitable Transducer decay after the transmission cycle no measurements are possible.
  • Ultrasonic transducers are available in different technical versions Configurations. For industrial use their robustness mostly used solid-state transducers. They exist basically made of a piezoceramic as a conversion element between electrical and acoustic signals and a resonant Adaptation layer with which the sound transfer to the air is optimized. Typical examples of such arrangements show, inter alia, DE 25 41 492 B2 and DE 196 30 350 C2. For practical use, the ultrasonic transducer must be in be held in a suitable manner, without thereby its Function is impaired. Usually plastic molded parts are used for this and polymer foams are used, see e.g. DE 198 09 206 A1. The polymer foams also have an effect a desired mechanical damping of the ultrasonic transducer. Furthermore, can also be introduced into the arrangement Metal pots made an electrical shield become.
  • Ultrasonic transducers of the type described are used in industrial Proximity switches used in large numbers and have proven in operation.
  • there are increasing problems due to the coupling from structure-borne noise to the ultrasound transducer since the Layer thickness of the enveloping polymer foam layers and thus their damping ability against an undesirable radial Sound flow decreases.
  • the devices become sensitive for noise in the area of their working frequency, those from surrounding machine parts with fixed assembly mechanically can be coupled into the proximity switch. There is also a risk that part of the transmission sound escapes laterally into the surrounding machine parts and there leads to undefined echoes, which in turn lead to the proximity switch can be fed back.
  • the fourth layer can be a housing of the ultrasound transducer represent.
  • the mismatches in the wave resistance in the Layers one to three are in with the structure according to the invention usually so effective that conventional layers are also used for this layer Plastics with a wave resistance that is lower than that of metals is sufficient for structure-borne noise insulation are.
  • the third layer of the ultrasound transducer consists of a plastic with a density of less than 0.2 kg / dm 3 , since a particularly good structure-borne noise decoupling is achieved for this.
  • this increased structure-borne noise decoupling may be necessary.
  • lacquer-insulated high-frequency wire with a total cross section of less than 0.05 mm 2 is used.
  • the conductor or the stranded wire and / or the insulation which is generally made of plastics such as, for. B. PVC, PUR, Teflon or the like, transmitted to a disturbing extent structure-borne noise.
  • FIG. 1 shows the sectional view of an ultrasonic transducer 1 according to the invention, which is located at the end at the end of a metal sleeve 2 serving as a device housing, for example the metal sleeve may be an M18 threaded sleeve with an inner diameter of approximately 16 mm.
  • the active part of the ultrasound transducer 1 is, in a known manner, the composite called a ultrasound oscillator, made of a piezoceramic 3 and an adaptation layer 4, which are connected to one another, for example, by an adhesive bond 5.
  • the electrodes of the piezoceramic 3 are connected via lines 6, 7 to an electronic circuit (not shown further) for processing the transmit and receive signals.
  • the lines 6, 7 consist of enamel-insulated HF strands with a total cross section of 0.02 mm 2 each.
  • the upper part of the ultrasonic oscillator made of piezoceramic 3 and matching layer 4 is surrounded by a casting compound 8, which is advantageously designed as a driven or syntactic foam with low acoustic wave resistance.
  • the ultrasonic oscillator made of piezoceramic 3 and matching layer 4 is surrounded by a foam ring 9, which likewise has a low acoustic wave resistance and at the same time can have a centering function according to DE 198 09 206 A1.
  • the casting compound 8 or the foam ring 9 represent the first layer of at least four layers which surround the ultrasonic vibrator according to the teaching of the invention.
  • the metal pot 10 around the first layer also serves in a known manner for the electrical shielding of the ultrasonic oscillator made of piezoceramic 3 and matching layer 4, but within the layer construction according to the invention has the described additional function of structure-borne noise insulation due to mismatch.
  • it consists of 0.5 mm thick steel sheet and, due to the material data of the metal, has a high acoustic wave resistance and forms the second layer.
  • the openings in the pot 10 necessary for the passage of the lines 6, 7 and for the pouring in of the elastic damping mass 8 are to be made as small as possible to avoid structure-borne noise coupling and, if necessary, at least partially closed by suitable measures, for example gluing or soldering on a reverberant cover.
  • the metal pot 10 is surrounded in the radial direction by a tubular foam ring 11, which in turn has a very low acoustic wave resistance with a density of, for example, 50 kg / m 3 , has a thickness of, for example, 0.5 mm in the radial direction and the third layer of forms at least four layers according to the teaching of the invention.
  • the fourth layer is represented by the plastic ring 12, which has a high acoustic wave resistance in comparison to the third layer and is held in the metal sleeve 2 with a force fit.
  • the arrangement described is positively held by the undercut 13 of the plastic ring 12, the foam ring 14 having a low acoustic wave resistance with a density of, for example, 180 kg / m 3 and in the axial direction between the metal pot and the undercut 13 of the plastic ring 12 likewise forms the third layer of the at least four layers according to the teaching of the invention.
  • a foam with a closed-cell structure is advantageously used for the elements 11 and 14, so that moisture cannot penetrate from the outside and form structure-borne sound bridges.
  • Suitable materials for the acoustically soft third layer are, for example, PE foams, PVC foams, PUR foams, silicone foams, cellular rubbers, etc., for example as a foamed foam or as syntactic foam assembled as molded parts and / or introduced as a casting compound.
  • foams can be produced in different hardnesses and in densities of up to less than 20 kg / m 3 with correspondingly extremely low wave resistances, so that extraordinarily good structure-borne noise insulation values can be achieved with them.
  • FIG 2 differs from Embodiment according to FIG 1 only in that here the third in the rear area of the ultrasonic transducer Layer is formed by a foam part 17.
  • a foam part 17 can be used as a prefabricated molded part be formed and can have an even lower wave resistance as e.g. have the foam-like casting compound 15, whereby the structure-borne noise decoupling can be improved again can. Otherwise, both embodiments are the same.
  • the foam ring covers 11 only the upper part of the lateral surface in the axial direction the tin pot 10 and it is below of which an annular air gap 18, which is still essential has lower wave resistance than foam. Thereby will mismatch the wave resistance and thus the structure-borne sound insulation measure compared to the embodiment FIG 1 additionally increased.
  • the third layer after the Teaching of the invention is based in the radial direction Foam ring 11 and the air gap 18 together.
  • the foam ring 11 can also consist of two or more sub-elements, between which to increase the mismatch Air gaps can be located.
  • As an additional measure is one for pouring the casting compound 8 necessary opening in Tin pot 10 closed with a reverberant lid 19 been to a possible structure-borne noise coupling through this Avoid opening into the casting compound 15.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Multimedia (AREA)
  • Mechanical Engineering (AREA)
  • Measurement Of Velocity Or Position Using Acoustic Or Ultrasonic Waves (AREA)
  • Lubricants (AREA)

Description

Die Erfindung bezieht sich auf einen Ultraschall-Wandler, insbesondere für die Anwendung in Näherungsschaltern.The invention relates to an ultrasonic transducer, especially for use in proximity switches.

Ultraschall-Näherungsschalter werden in der Automatisierungstechnik hauptsächlich zur berührungslosen Erfassung der Anwesenheit oder des Abstandes von Objekten eingesetzt. Je nach Meßaufgabe finden das Schranken- oder das Echolaufzeitverfahren Verwendung. Beim Schrankenverfahren sendet ein Ultraschallsender Signale aus, die auf direktem Weg zu einem Ultraschallempfänger gelangen. Der zu erfassende Gegenstand unterbricht den Schallweg und wird damit detektiert. Beim Echolaufzeitverfahren wird dagegen das vom zu erfassenden Gegenstand reflektierte Ultraschallecho empfangen und aus der Signallaufzeit zwischen Aussendung und Empfang die Entfernung des Gegenstandes ermittelt.Ultrasonic proximity switches are used in automation technology mainly for contactless detection of presence or the distance of objects. Depending on The barrier or the echo delay method are used for the measurement task Use. An ultrasound transmitter transmits the barrier method Signals from the direct path to an ultrasound receiver reach. The object to be detected interrupts the sound path and is thus detected. With the echo delay method on the other hand, that of the object to be captured reflected ultrasonic echo received and from the signal propagation time the distance between sending and receiving of the item determined.

Schlüsselbauelemente für beide Verfahren sind die Ultraschall-Wandler. Sie werden im Sendefall zur Umsetzung elektrischer Signale in Schallwellen und im Empfangsfall zur Umsetzung von Schallwellen in elektrische Signale benutzt. Bei Geräten nach dem Echolaufzeitverfahren wird oft ein und derselbe Wandler abwechselnd für Sendung und Empfang verwendet. Damit wird der gerätetechnische Aufwand verringert, aber auch ein Mindestabstand festgelegt, unterhalb dem wegen der unvermeidlichen Ausschwingvorgänge des Wandlers nach dem Sendezyklus keine Messungen möglich sind.The key components for both processes are the ultrasonic transducers. They are used to implement electrical Signals in sound waves and when received for implementation used by sound waves in electrical signals. at Devices based on the echo delay method are often one and the same Transducers used alternately for sending and receiving. This reduces the technical outlay on equipment, but also set a minimum distance below that because of the inevitable Transducer decay after the transmission cycle no measurements are possible.

Ultraschall-Wandler gibt es in unterschiedlichen technischen Ausgestaltungen. Für den industriellen Einsatz werden wegen ihrer Robustheit meist Festkörperwandler eingesetzt. Sie bestehen grundsätzlich aus einer Piezokeramik als Umsetzelement zwischen elektrischen und akustischen Signalen und einer resonanten Anpaßschicht, mit der der Schallübergang zur Luft optimiert wird. Typische Beispiele für derartige Anordnungen zeigen unter anderem DE 25 41 492 B2 und DE 196 30 350 C2. Für die praktische Anwendung muß der Ultraschall-Wandler in geeigneter Weise gehaltert werden, ohne daß dadurch seine Funktion beeinträchtigt wird. Hierzu werden meist Kunststoffformteile und Polymer-Schaumstoffe verwendet, siehe z.B. DE 198 09 206 A1. Die Polymer-Schaumstoffe bewirken außerdem eine gewünschte mechanische Dämpfung des Ultraschall-Wandlers. Weiterhin kann mit zusätzlich in die Anordnung eingebrachten Metalltöpfen eine elektrische Abschirmung vorgenommen werden.Ultrasonic transducers are available in different technical versions Configurations. For industrial use their robustness mostly used solid-state transducers. They exist basically made of a piezoceramic as a conversion element between electrical and acoustic signals and a resonant Adaptation layer with which the sound transfer to the air is optimized. Typical examples of such arrangements show, inter alia, DE 25 41 492 B2 and DE 196 30 350 C2. For practical use, the ultrasonic transducer must be in be held in a suitable manner, without thereby its Function is impaired. Mostly plastic molded parts are used for this and polymer foams are used, see e.g. DE 198 09 206 A1. The polymer foams also have an effect a desired mechanical damping of the ultrasonic transducer. Furthermore, can also be introduced into the arrangement Metal pots made an electrical shield become.

Ultraschall-Wandler der beschriebenen Art werden in industriellen Näherungsschaltern in großer Zahl eingesetzt und haben sich im Betrieb bewährt. Im Zuge der Miniaturisierung der Geräte stellen sich aber zunehmend Probleme durch die Überkopplung von Körperschall auf den Ultraschall-Wandler ein, da die Schichtdicke der umhüllenden Polymer-Schaumschichten und damit ihre Dämpfungsfähigkeit gegenüber einer unerwünschten radialen Schallströmung abnimmt. Die Geräte werden damit empfindlich für Störgeräusche im Bereich ihrer Arbeitsfrequenz, die aus umgebenden Maschinenteilen bei fester Montage mechanisch in die Näherungsschalter eingekoppelt werden können. Außerdem besteht die Gefahr, daß ein Teil des Sendeschalls seitlich in die umgebenden Maschinenteile entweicht und dort zu undefinierten Echos führt, die wiederum zum Näherungsschalter zurückgekoppelt werden können.Ultrasonic transducers of the type described are used in industrial Proximity switches used in large numbers and have proven in operation. In the course of miniaturization of the devices however, there are increasing problems due to the coupling from structure-borne noise to the ultrasound transducer, since the Layer thickness of the enveloping polymer foam layers and thus their damping ability against an undesirable radial Sound flow decreases. The devices become sensitive for noise in the area of their working frequency, those from surrounding machine parts with fixed assembly mechanically can be coupled into the proximity switch. There is also a risk that part of the transmission sound escapes laterally into the surrounding machine parts and there leads to undefined echoes, which in turn lead to the proximity switch can be fed back.

Das beschriebene Problem ist bislang nicht befriedigend gelöst. Behelfsmäßige Ansätze nutzen eine verringerte Empfindlichkeit des Näherungsschalters, die aber für den normalen Betrieb nachteilig ist. Ein weiterer Lösungsansatz besteht darin, den Utraschall-Wandler gegenüber der Front der Gehäusehülse vorstehen zu lassen, so daß der Übertragungsweg zwischen dem akustisch aktiven Teil des Wandlers und den umgebenden Konstruktionsteilen verlängert wird, über den der Körperschall übertragen werden könnte. Eine spezielle Ausgestaltung dieses Prinzips ist in DE 38 32 947 C2 angegeben, bei der die Anpaßschicht über die Rückseite der Piezokeramik hinaus dünnwandig und rohrförmig verlängert ist, wobei diese Verlängerung etwa ein Viertel der Schallwellenlänge beträgt. In diesem Bereich wird der Wandler über einen elastischen Einspannring gehalten, wodurch die Körperschallübertragung deutlich verringert wird. Nachteilig ist bei Lösungen dieser Art, daß der aus der Gerätekontur hervorstehende Wandler empfindlich gegen Beschädigungen ist und häufig auch die Baulänge des Näherungsschalters vergrößert.The problem described has not yet been satisfactorily solved. Makeshift approaches take advantage of reduced sensitivity of the proximity switch, but for normal Operation is disadvantageous. Another solution exists in it, the ultrasonic transducer opposite the front of the housing sleeve protrude so that the transmission path between the acoustically active part of the transducer and the surrounding Construction parts is extended over which the Structure-borne noise could be transmitted. A special design this principle is specified in DE 38 32 947 C2, where the matching layer over the back of the piezoceramic is also thin-walled and elongated tubular, this Extension is about a quarter of the sound wavelength. In this area the transducer is elastic Clamping ring held by the structure-borne noise transmission is significantly reduced. This is disadvantageous in the case of solutions Kind that the transducer protruding from the device contour is sensitive is against damage and often also the overall length of the proximity switch enlarged.

Es ist daher Aufgabe der vorliegenden Erfindung, eine Einrichtung zum Senden und Empfangen von Ultraschall vorzugsweise für Ultraschall-Näherungsschalter anzugeben, die unempfindlich gegenüber einer Übertragung von Körperschall ist und dabei die Nachteile der beschriebenen bekannten Lösungsansätze vermeidet.It is therefore an object of the present invention to provide a device for sending and receiving ultrasound preferably Specify for ultrasonic proximity switches that are insensitive against a transmission of structure-borne noise and the disadvantages of the known approaches described avoids.

Die Aufgabe wird erfindungsgemäß mit den folgenden Merkmalen nach Anspruch 1 gelöst:

  • a) mit einem Gehäuse, in dem ein aus einer Piezokeramik und einer Anpaßschicht gebildeter Ultraschallschwinger kraftund/oder formschlüssig gehaltert ist,
  • b) der Kraft- und/oder Formschluß erfolgt über mindestens vier Schichten mit abwechselnd stark unterschiedlichen akustischen Wellenwiderständen,
  • c) die Schichten sind von dem Ultraschallschwinger aus betrachtet in folgender Reihenfolge angeordnet,
  • d) der Ultraschallschwinger ist in eine erste schallweiche Schicht mit mindestens einem elastischem Dämpfungsmaterial als Bestandteil eingebettet,
  • e) die erste Schicht ist von einer zweiten Schicht umgeben, die aus mindestens einem schallharten Material, vorzugsweise Metall, besteht,
  • f) um die zweite, schallharte Schicht liegt eine dritte, schallweiche Schicht, die die zweite Schicht mindestens in der vom Ultraschallschwinger radial nach außen zum Gehäuse hin gerichteten Richtung umgibt und die einen oder mehrere schaumförmige Kunststoffe umfaßt, deren Dichte stets kleiner als 0,6 kg/dm3 ist, und
  • g) die dritte Schicht ist mindestens teilweise von einer vierten Schicht mit hohem akustischen Wellenwiderstand umgeben.
    • The object is achieved according to the invention with the following features according to claim 1:
  • a) with a housing in which an ultrasonic oscillator formed from a piezoceramic and an adaptation layer is held in a force-locking and / or form-fitting manner,
  • b) the force and / or positive locking takes place over at least four layers with alternating strongly different acoustic wave resistances,
  • c) the layers are arranged from the ultrasonic vibrator in the following order,
  • d) the ultrasonic oscillator is embedded in a first sound-soft layer with at least one elastic damping material as a component,
  • e) the first layer is surrounded by a second layer, which consists of at least one reverberant material, preferably metal,
  • f) around the second, reverberant layer there is a third, reverberant layer which surrounds the second layer at least in the direction radially outward from the ultrasonic oscillator towards the housing and which comprises one or more foam-shaped plastics, the density of which is always less than 0.6 kg / dm 3 , and
  • g) the third layer is at least partially surrounded by a fourth layer with high acoustic wave resistance.

    • Unter schallweichen bzw. schallharten Materialien werden solche Materialien verstanden, deren Wellenwiderstand, definiert als das Produkt aus Materialdichte und Materialwellengeschwindigkeit, sehr niedrig bzw. sehr hoch liegt. Durch die erfindungsgemäße Aufeinanderfolge von Schichten mit abwechselnd schallweichen und schallharten Materialien findet der vom Ultraschallschwinger nach außen ins Gehäuse überkoppelnde Körperschall sowie auch der zum Ultraschallschwinger zurück gerichtete Körperschallstrom eine starke Fehlanpassung vor, an den unterschiedlich schallharten Schichten findet stets jeweils annähernde Totalreflexion statt, so daß die Gesamt-Transmission auf ein Minimum reduziert wird. Die Körperschalldämmung ist dabei um so besser, je größer die Unterschiede der Wellenwiderstände an den einzelnen Schichten sind.These are known as soft or hard materials Understand materials whose wave resistance is defined as the product of material density and material wave speed, is very low or very high. Through the Sequence of layers according to the invention with alternating sound-soft and reverberant materials find the coupling from the ultrasonic transducer to the outside into the housing Structure-borne noise as well as that to the ultrasonic transducer directional structure-borne sound current a strong mismatch, always takes place on the different reverberant layers approximate total reflection instead, so that the total transmission is reduced to a minimum. Structure-borne noise insulation the bigger the differences, the better the wave resistances at the individual layers are.

    Die vierte Schicht kann ein Gehäuse des Ultraschall-Wandlers darstellen. Die Fehlanpassungen des Wellenwiderstands in den Schichten eins bis drei sind bei erfindungsgemäßem Aufbau in der Regel schon so effektiv, daß für diese Schicht auch herkömmliche Kunststoffe mit einem Wellenwiderstand, der niedriger als der von Metallen ist, zur Körperschalldämmung ausreichend sind.The fourth layer can be a housing of the ultrasound transducer represent. The mismatches in the wave resistance in the Layers one to three are in with the structure according to the invention usually so effective that conventional layers are also used for this layer Plastics with a wave resistance that is lower than that of metals is sufficient for structure-borne noise insulation are.

    Vorteilhafte Weiterbildungen der Erfindung sind den Unteransprüchen 2, 3 und 4 zu entnehmen.Advantageous developments of the invention are the subclaims 2, 3 and 4.

    Besonders vorteilhaft ist es, wenn die dritte Schicht des Ultraschall-Wandlers aus einem Kunststoff mit einer Dichte kleiner 0,2 kg/dm3 besteht, da hierfür eine besonders gute Körperschallentkopplung erreicht wird. Bei körperschallmäßig sehr ungünstigen Einbaubedingungen des Wandlers und/oder bei sehr hoher Signalverstärkung der Sensorelektronik kann diese erhöhte Körperschallentkopplung notwendig sein.It is particularly advantageous if the third layer of the ultrasound transducer consists of a plastic with a density of less than 0.2 kg / dm 3 , since a particularly good structure-borne noise decoupling is achieved for this. In the case of installation conditions of the transducer that are very unfavorable in terms of structure-borne noise and / or in the case of very high signal amplification of the sensor electronics, this increased structure-borne noise decoupling may be necessary.

    Bei der Herstellung der Wandler sind Schichten mit derartig kleinen Dichten nur mit Aufwand als Gießmasse einzubringen, besonders wenn die Schichtstärke bei kleinen Bauformen sehr dünn ist. Daher ist es vorteilhaft, für die dritte Schicht vorgefertigte Schaumstoff-Formteile zu verwenden.Layers with such are used in the manufacture of the transducers to apply small densities as casting compound only with great effort, especially if the layer thickness is very small for small designs is thin. Therefore, it is advantageous for the third layer use prefabricated foam molded parts.

    Weiterhin ist es besonders vorteilhaft, wenn zum elektrischen Anschluß des Ultraschall-Wandlers lackisolierte Hochfrequenzlitze mit einem Gesamtquerschnitt von weniger als 0,05 mm2 verwendet wird. Bei herkömmlichen Anschlußleitungen wird über den Leiter bzw. die Litze und/oder über die Isolierung, die in der Regel aus Kunststoffen wie z. B. PVC, PUR, Teflon oder ähnlichem besteht, in störendem Ausmaß Körperschall übertragen.Furthermore, it is particularly advantageous if, for the electrical connection of the ultrasound transducer, lacquer-insulated high-frequency wire with a total cross section of less than 0.05 mm 2 is used. In the case of conventional connecting lines, the conductor or the stranded wire and / or the insulation, which is generally made of plastics such as, for. B. PVC, PUR, Teflon or the like, transmitted to a disturbing extent structure-borne noise.

    Ein Ausführungsbeispiel der Erfindung wird im folgenden anhand einer Zeichnung näher erläutert. Es zeigen:

    FIG 1
    eine Schnittdarstellung des erfindungsgemäßen Ultraschall-Wandlers in einer ersten Ausführungsform,
    FIG 2
    eine Schnittdarstellung einer weiteren Ausführungsform mit zusätzlichem Schaumstoffelement und
    FIG 3
    eine Schnittdarstellung einer weiteren Ausführungsform mit zusätzlichem ringförmigen Luftspalt und mit einer mit einem Deckel verschlossenen Öffnung.
    An embodiment of the invention is explained below with reference to a drawing. Show it:
    FIG. 1
    2 shows a sectional illustration of the ultrasound transducer according to the invention in a first embodiment,
    FIG 2
    a sectional view of a further embodiment with an additional foam element and
    FIG 3
    a sectional view of a further embodiment with an additional annular air gap and with an opening closed with a lid.

    FIG 1 zeigt die Schnittdarstellung eines erfindungsgemäßen Ultraschall-Wandlers 1, der sich als stirnseitiger Abschluß am Ende einer als Gerätegehäuse dienenden Metallhülse 2 befindet, beispielsweise kann die Metallhülse eine M18-Gewindehülse sein mit einem Innendurchmesser von ca. 16 mm. Der aktive Teil des Ultraschall-Wandlers 1 ist in bekannter Weise der als Ultraschallschwinger bezeichnete Verbund aus einer Piezokeramik 3 und einer Anpaßschicht 4, die z.B. durch eine Verklebung 5 miteinander verbunden sind. Die Elektroden der Piezokeramik 3 sind über Leitungen 6,7 mit einer nicht weiter dargestellten elektronischen Schaltung zur Aufbereitung der Sende- und Empfangssignale verbunden. Die Leitungen 6,7 bestehen aus lackisolierten HF-Litzen mit einem Gesamtquerschnitt von jeweils 0,02 mm2. Der Ultraschallschwinger aus Piezokeramik 3 und Anpaßschicht 4 ist in seinem oberen Teil von einer Gießmasse 8 umgeben, die vorteilhaft als getriebener oder syntaktischer Schaum mit niedrigem akustischem Wellenwiderstand ausgeführt ist. Im unteren Teil ist der Ultraschallschwinger aus Piezokeramik 3 und Anpaßschicht 4 von einem Schaumstoffring 9 umgeben, der ebenfalls einen niedrigen akustischen Wellenwiderstand aufweist und gleichzeitig eine Zentrierfunktion gemäß DE 198 09 206 A1 haben kann. Die Gießmasse 8 bzw. der Schaumstoffring 9 stellen die erste Schicht von mindestens vier Schichten dar, die den Ultraschallschwinger nach der Lehre der Erfindung umgeben. Der Metalltopf 10 um die erste Schicht dient in bekannter Weise auch zur elektrischen Abschirmung des Ultraschallschwingers aus Piezokeramik 3 und Anpaßschicht 4, hat aber innerhalb der erfindungsgemäßen Schichtbauweise die beschriebene zusätzliche Funktion der Körperschalldämmung durch Fehlanpassung. Er besteht beispielsweise aus 0,5 mm dickem Stahlblech und hat, bedingt durch die Materialdaten des Metalls, einen hohen akustischen Wellenwiderstand und bildet die zweite Schicht. Die für die Durchführung der Leitungen 6,7 und für das Eingießen der elastischen Dämpfungsmasse 8 notwendigen Öffnungen im Topf 10 sind zur Vermeidung von Körperschallüberkopplung möglichst klein auszubilden und erforderlichenfalls durch geeignete Maßnahmen z.B. Aufkleben oder Anlöten eines schallharten Deckels mindestens teilweise zu verschließen. Der Metalltopf 10 ist in radialer Richtung von einem rohrförmigen Schaumstoffring 11 umgeben, der wiederum einen sehr niedrigen akustischen Wellenwiderstand mit einer Dichte von beispielsweise 50 kg/m3 aufweist, in radialer Richtung eine Dicke von beispielsweise 0,5 mm hat und die dritte Schicht der mindestens vier Schichten nach der Lehre der Erfindung bildet. Die vierte Schicht wird durch den Kunststoffring 12 dargestellt, der einen im Vergleich zur dritten Schicht hohen akustischen Wellenwiderstand aufweist und in der Metallhülse 2 kraftschlüssig gehalten wird. In axialer Richtung wird die beschriebene Anordnung durch den Hinterschnitt 13 des Kunststoffrings 12 formschlüssig gehalten, wobei der Schaumstoffring 14 einen niedrigen akustischen Wellenwiderstand mit einer Dichte von beispielsweise 180 kg/m3 hat und in axialer Richtung zwischen dem Metalltopf und dem Hinterschnitt 13 des Kunststoffrings 12 ebenfalls die dritte Schicht der mindestens vier Schichten nach der Lehre der Erfindung bildet. Für die Elemente 11 und 14 nimmt man vorteilhafterweise einen Schaum mit geschlossenzelliger Struktur, damit Feuchtigkeit von außen nicht eindringen und Körperschallbrücken bilden kann. Geeignete Materialien für die schallweiche dritte Schicht sind beispielsweise PE-Schäume, PVC-Schäume, PUR-Schäume, Silikonschäume, Zellkautschuke usw. z.B. als getriebener Schaum oder als syntaktischer Schaum montiert als Formteile und/oder eingebracht als Gießmasse. Derartige Schaumstoffe können in verschiedenen Härten und in Dichten von bis zu unter 20 kg/m3 hergestellt werden mit entsprechend extrem niedrigen Wellenwiderständen, so daß hiermit außerordentlich gute Körperschalldämmwerte erreicht werden können.1 shows the sectional view of an ultrasonic transducer 1 according to the invention, which is located at the end at the end of a metal sleeve 2 serving as a device housing, for example the metal sleeve may be an M18 threaded sleeve with an inner diameter of approximately 16 mm. The active part of the ultrasound transducer 1 is, in a known manner, the composite called a ultrasound oscillator, made of a piezoceramic 3 and an adaptation layer 4, which are connected to one another, for example, by an adhesive bond 5. The electrodes of the piezoceramic 3 are connected via lines 6, 7 to an electronic circuit (not shown further) for processing the transmit and receive signals. The lines 6, 7 consist of enamel-insulated HF strands with a total cross section of 0.02 mm 2 each. The upper part of the ultrasonic oscillator made of piezoceramic 3 and matching layer 4 is surrounded by a casting compound 8, which is advantageously designed as a driven or syntactic foam with low acoustic wave resistance. In the lower part, the ultrasonic oscillator made of piezoceramic 3 and matching layer 4 is surrounded by a foam ring 9, which likewise has a low acoustic wave resistance and at the same time can have a centering function according to DE 198 09 206 A1. The casting compound 8 or the foam ring 9 represent the first layer of at least four layers which surround the ultrasonic vibrator according to the teaching of the invention. The metal pot 10 around the first layer also serves in a known manner for the electrical shielding of the ultrasonic oscillator made of piezoceramic 3 and matching layer 4, but within the layer construction according to the invention has the described additional function of structure-borne noise insulation due to mismatch. For example, it consists of 0.5 mm thick steel sheet and, due to the material data of the metal, has a high acoustic wave resistance and forms the second layer. The openings in the pot 10 necessary for the passage of the lines 6, 7 and for the pouring in of the elastic damping mass 8 are to be made as small as possible to avoid structure-borne noise coupling and, if necessary, at least partially closed by suitable measures, for example gluing or soldering on a reverberant cover. The metal pot 10 is surrounded in the radial direction by a tubular foam ring 11, which in turn has a very low acoustic wave resistance with a density of, for example, 50 kg / m 3 , has a thickness of, for example, 0.5 mm in the radial direction and the third layer of forms at least four layers according to the teaching of the invention. The fourth layer is represented by the plastic ring 12, which has a high acoustic wave resistance in comparison to the third layer and is held in the metal sleeve 2 with a force fit. In the axial direction, the arrangement described is positively held by the undercut 13 of the plastic ring 12, the foam ring 14 having a low acoustic wave resistance with a density of, for example, 180 kg / m 3 and in the axial direction between the metal pot and the undercut 13 of the plastic ring 12 likewise forms the third layer of the at least four layers according to the teaching of the invention. A foam with a closed-cell structure is advantageously used for the elements 11 and 14, so that moisture cannot penetrate from the outside and form structure-borne sound bridges. Suitable materials for the acoustically soft third layer are, for example, PE foams, PVC foams, PUR foams, silicone foams, cellular rubbers, etc., for example as a foamed foam or as syntactic foam assembled as molded parts and / or introduced as a casting compound. Such foams can be produced in different hardnesses and in densities of up to less than 20 kg / m 3 with correspondingly extremely low wave resistances, so that extraordinarily good structure-borne noise insulation values can be achieved with them.

    Es ist vorteilhaft, in axialer Richtung der Anordnung unmittelbar hinter dem Metalltopf 10 eine weitere schaumstofförmige Gießmasse 15 mit niedrigem akustischem Wellenwiderstand aufzubringen, die entsprechend der Lehre der Erfindung gegenüber dem folgenden Geräteverguß 16 mit relativ hohem akustischem Wellenwiderstand die dritte Schicht der mindestens vier Schichten darstellt. It is advantageous to immediately in the axial direction of the arrangement behind the metal pot 10 another foam Casting compound 15 with low acoustic wave resistance to apply, according to the teaching of the invention the following device encapsulation 16 with a relatively high acoustic Wave resistance the third layer of at least four Represents layers.

    Bei der Wahl der Schichtdicken ist zu beachten, daß keine vielfache der halben Schallwellenlänge in der jeweiligen Schicht auftreten. Zur Vermeidung einer Körperschallübertragung durch die Anschlußleitungen 6,7 ist es vorteilhaft, diese aus lackisolierter Hochfrequenzlitze mit einem Gesamtquerschnitt von weniger als 0,05 mm2 zu realisieren.When choosing the layer thickness, it should be noted that no multiples of half the sound wavelength occur in the respective layer. To avoid structure-borne noise transmission through the connecting lines 6, 7, it is advantageous to implement them from lacquer-insulated high-frequency strands with a total cross section of less than 0.05 mm 2 .

    Das Ausführungsbeispiel gemäß FIG 2 unterscheidet sich vom Ausführungsbeispiel gemäß FIG 1 lediglich dadurch, daß hier im rückwärtigen Bereich des Ultraschallschwingers die dritte Schicht durch ein Schaumstoffteil 17 gebildet ist. Eine derartige Schaumstoffschicht 17 kann als vorgefertigtes Formteil ausgebildet sein und kann einen noch niedrigeren Wellenwiderstand als z.B. die schaumförmige Gießmasse 15 aufweisen, wodurch die Körperschallentkopplung nochmals verbessert werden kann. Ansonsten stimmen beide Ausführungsformen überein.The embodiment of FIG 2 differs from Embodiment according to FIG 1 only in that here the third in the rear area of the ultrasonic transducer Layer is formed by a foam part 17. Such one Foam layer 17 can be used as a prefabricated molded part be formed and can have an even lower wave resistance as e.g. have the foam-like casting compound 15, whereby the structure-borne noise decoupling can be improved again can. Otherwise, both embodiments are the same.

    In dem Ausführungsbeispiel gemäß FIG 3 bedeckt der Schaumstoffring 11 in axialer Richtung nur den oberen Teil der Mantelfläche des Blechtopfs 10 und es befindet sich unterhalb davon ein ringförmiger Luftspalt 18, der einen noch wesentlich niedrigeren Wellenwiderstand als Schaumstoff hat. Dadurch wird die Fehlanpassung des Wellenwiderstands und damit das Körperschalldämmmaß gegenüber dem Ausführungsbeispiel gemäß FIG 1 zusätzlich gesteigert. Die dritte Schicht nach der Lehre der Erfindung setzt sich in radialer Richtung aus dem Schaumstoffring 11 und dem Luftspalt 18 zusammen. Der Schaumstoffring 11 kann auch aus zwei oder mehr Teilelementen bestehen, zwischen denen sich zur Steigerung der Fehlanpassung Luftspalte befinden können. Als zusätzliche Maßnahme ist eine für das Eingießen der Gießmasse 8 notwendige Öffnung im Blechtopf 10 mit einem schallharten Deckel 19 verschlossen worden, um eine mögliche Körperschallkopplung durch diese Öffnung in die Gießmasse 15 zu vermeiden.In the exemplary embodiment according to FIG. 3, the foam ring covers 11 only the upper part of the lateral surface in the axial direction the tin pot 10 and it is below of which an annular air gap 18, which is still essential has lower wave resistance than foam. Thereby will mismatch the wave resistance and thus the structure-borne sound insulation measure compared to the embodiment FIG 1 additionally increased. The third layer after the Teaching of the invention is based in the radial direction Foam ring 11 and the air gap 18 together. The foam ring 11 can also consist of two or more sub-elements, between which to increase the mismatch Air gaps can be located. As an additional measure is one for pouring the casting compound 8 necessary opening in Tin pot 10 closed with a reverberant lid 19 been to a possible structure-borne noise coupling through this Avoid opening into the casting compound 15.

    Wenn auch die beschriebenen Ausführungsbeispiele aus FIG 1 bis FIG 3 von rotationssymmetrischen Wandleranordnungen ausgehen, so sind die beschriebenen erfindungsgemäßen Maßnahmen zur Körperschallreduzierung nicht darauf beschränkt, sondern haben auch bei beliebigen Wandleranordnungen Gültigkeit.Although the described exemplary embodiments from FIG. 1 to FIG. 3 assume rotationally symmetrical converter arrangements, this is the described measures according to the invention to reduce structure-borne noise not limited to this, but are also valid for any converter arrangement.

    Claims (4)

    1. Ultrasound converter (1), especially for use in approximation switches, with the following features:
      a) with a housing (2), in which an ultrasound vibrator formed from a piezoceramic (3) and an adapter layer (4) is held by a key or interference fit,
      b) the key and/or interference fit is made via at least four layers (8,9,10,11,12,2) with alternating strengths of acoustic surge impedances,
      c) the layers,(8,9,10,11,12,2) viewed from the ultrasound vibrator, are arranged in the following order,
      d) the ultrasound vibrator is embedded into a first soft level (8,9) with at least one elastic damping material as a component,
      e) the first layer (8,9) is surrounded by a second layer (10) which consists of at least one hard material, preferably metal,
      f) around the second hard layer (10) lies a third, soft layer (11), which surrounds the second layer (10) at least in the direction pointing radially outwards from the ultrasound vibrator radial to the housing (2) and which comprises one or more foam plastics, with a density always less than 0.6 kg/ cu m3, and
      g) the third layer (11) is at least partly surrounded by a fourth layer (12,2) with high acoustic surge impedance.
    2. Ultrasound converter in accordance with Claim 1,
      characterized in that the third layer (11) comprises foam plastic with a density of less than 0.2 kg/cu m3.
    3. Ultrasound converter in accordance with Claims 1 or 2,
      characterized in that the third layer (11) consists of at least one prefabricated plastic part.
    4. Ultrasound converter in accordance with Claim 1,2 or 3,
      characterized in that for electrical connection (6,7) of the ultrasound converter enameled high-frequency leads with an overall cross section of less than 0.05mm are used.
    EP00989772A 1999-11-26 2000-11-14 Ultrasonic transducer Expired - Lifetime EP1232023B1 (en)

    Applications Claiming Priority (3)

    Application Number Priority Date Filing Date Title
    DE19957125 1999-11-26
    DE19957125A DE19957125A1 (en) 1999-11-26 1999-11-26 Ultrasound transducer
    PCT/DE2000/004001 WO2001038011A1 (en) 1999-11-26 2000-11-14 Ultrasonic transducer

    Publications (2)

    Publication Number Publication Date
    EP1232023A1 EP1232023A1 (en) 2002-08-21
    EP1232023B1 true EP1232023B1 (en) 2004-05-26

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    EP00989772A Expired - Lifetime EP1232023B1 (en) 1999-11-26 2000-11-14 Ultrasonic transducer

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    US (1) US6825594B1 (en)
    EP (1) EP1232023B1 (en)
    DE (2) DE19957125A1 (en)
    WO (1) WO2001038011A1 (en)

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    Also Published As

    Publication number Publication date
    US6825594B1 (en) 2004-11-30
    EP1232023A1 (en) 2002-08-21
    DE50006628D1 (en) 2004-07-01
    DE19957125A1 (en) 2001-06-21
    WO2001038011A1 (en) 2001-05-31

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