EP0478611B1 - Wide-range ultrasonic transducer - Google Patents
Wide-range ultrasonic transducer Download PDFInfo
- Publication number
- EP0478611B1 EP0478611B1 EP90909133A EP90909133A EP0478611B1 EP 0478611 B1 EP0478611 B1 EP 0478611B1 EP 90909133 A EP90909133 A EP 90909133A EP 90909133 A EP90909133 A EP 90909133A EP 0478611 B1 EP0478611 B1 EP 0478611B1
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- European Patent Office
- Prior art keywords
- transducer
- sound
- plates
- synthetic
- lamellae
- 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.)
- Expired - Lifetime
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- 239000000463 material Substances 0.000 claims description 29
- 241000446313 Lamella Species 0.000 claims description 6
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- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
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- JRPBQTZRNDNNOP-UHFFFAOYSA-N barium titanate Chemical compound [Ba+2].[Ba+2].[O-][Ti]([O-])([O-])[O-] JRPBQTZRNDNNOP-UHFFFAOYSA-N 0.000 description 1
- 229910002113 barium titanate Inorganic materials 0.000 description 1
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- NKZSPGSOXYXWQA-UHFFFAOYSA-N dioxido(oxo)titanium;lead(2+) Chemical compound [Pb+2].[O-][Ti]([O-])=O NKZSPGSOXYXWQA-UHFFFAOYSA-N 0.000 description 1
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- 229910052500 inorganic mineral Inorganic materials 0.000 description 1
- WPBNNNQJVZRUHP-UHFFFAOYSA-L manganese(2+);methyl n-[[2-(methoxycarbonylcarbamothioylamino)phenyl]carbamothioyl]carbamate;n-[2-(sulfidocarbothioylamino)ethyl]carbamodithioate Chemical compound [Mn+2].[S-]C(=S)NCCNC([S-])=S.COC(=O)NC(=S)NC1=CC=CC=C1NC(=S)NC(=O)OC WPBNNNQJVZRUHP-UHFFFAOYSA-L 0.000 description 1
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- QEFYFXOXNSNQGX-UHFFFAOYSA-N neodymium atom Chemical compound [Nd] QEFYFXOXNSNQGX-UHFFFAOYSA-N 0.000 description 1
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Images
Classifications
-
- 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
Definitions
- the present invention relates to a wide-beam ultrasound transducer as specified in the preamble of claim 1.
- the ultrasonic transducer of the cited document has a sound characteristic impedance that comes relatively much closer to that of air. This is achieved by means of a sandwich structure consisting of individual piezoelectric lamellae arranged at intervals from one another, in planes parallel to one another, the interspaces between these lamellae corresponding to the intervals being filled with a dimensionally stable material which has a small value for the acoustic characteristic impedance .
- the material filling the gaps forms at least one closed surface of this electroacoustic transducer including the piezoelectric lamellae, namely a surface for the radiation and / or for the reception of acoustic radiation. In this case, for example, this material filling the gaps can extend beyond at least one of the edge surfaces of the individual slats, so that these edge surfaces of the slats are covered by this material filling the gaps with respect to the external environment.
- Such a known transducer can be designed in such a way that this surface of the same intended for radiation and / or reception has a relatively large dimension relative to the air wavelength of the emitted or received acoustic radiation. If the individual piezoelectric lamellae are excited to produce a convex oscillation, a sound wave with a largely flat phase front is emitted from this surface of the transducer.
- Piezoelectric ceramic is used as the material for the lamellae, e.g. Lead zirconate, lead titanate, barium titanate and the like, these materials to improve their respective properties doping and / or substitution of i.a. May contain manganese, niobium, neodymium, etc.
- the material for filling the spaces between the lamellae in this known converter is e.g. a thermoplastic. E.g. the whole body made of this material and the piezoelectric lamellae is hot glued together. The gaps can also be filled with a silicone rubber potting.
- the object of the present invention is to provide an electroacoustic transducer with a favorable adaptation of the acoustic characteristic impedance to the medium air, which as the acoustic radiation lobe has one which has a relatively small width in one coordinate direction x perpendicular to the direction z of the axis of the acoustic radiation , ie has a small opening angle, and which has a wide beam in the coordinate direction y perpendicular to this direction x and to the axis direction z, ie has a large opening angle in this direction.
- the structural design of the transducer to be specified should be such that, starting from a basic type, the choice of individual dimensions means that individual types with different opening angles that can be predefined from one another can be obtained in the y direction.
- the wide opening angle should be selectable in the range from 50 ° to 100 ° (-6 dB) for the individual type of converter.
- Sharp converters such as the converters known from DE-A-2 537 788 and GB-A-1 530 347 also have an opening angle of 5 ° to 10 ° (-6 dB).
- a converter according to the invention with e.g. An opening angle of 70 ° in the direction labeled y above and with a sharp directivity in the x direction is an extremely wide-beam ultrasound transducer.
- the cross-section of the sound lobe of such a transducer according to the invention is relatively flat in the x-direction, but broad in the y-direction and overall represents an at least approximately elliptical-like surface. With increasing distance (z - z0 ) from the surface Zo of the transducer, this cross-sectional area becomes ever larger, without, however, losing its characteristic shape of a transducer radiating wide in a transverse direction y.
- this transducer 1 shows the principle of a transducer 1 designed according to the invention and selected in terms of its relative dimensions according to the invention.
- this transducer 1 consists of a piezoelectric ceramic lamella 2 provided with electrodes (not shown in the figure) and of layers or plates 3, 13 from one Plastic material.
- the length of the rectangular composite body of the transducer 1 shown is designated by L. Its width is labeled B. Its total thickness is denoted by D, which is the sum of the thickness dimensions d p of the plates 3, 13 and the thickness dimension d k of the lamella 2.
- the area of the transducer 1 designated by 5 is the radiation or sound receiving area provided or selected according to the invention.
- the arrows 6 refer to the radiation provided according to the invention.
- the ceramic lamella 2 and the layers or plates 3, 13 are firmly connected to one another, as shown.
- the connecting means adheresive
- the connecting means can be the material of the layers or plates 3, 13 themselves.
- a converter according to the invention can also consist of several ceramic lamellae and a corresponding number of layers or plates.
- the material of the plates 3, 13 on both sides of the piezoelectric lamella 2 is selected with regard to the low acoustic impedance Z and with the smallest possible Poisson number u less than 0.3 and with regard to the highest possible vibration quality Q greater than 20.
- Low acoustic impedance serves as good an adaptation as possible to the sound transmission medium air.
- a small Poisson number helps to avoid transverse modes if possible. This is because these can occur when the thickness D is even smaller than the width B of the transducer 1.
- High quality Q of this material enables vibration deflection in the material of the plates 3, 13 to be achieved, which is close to, preferably exceeds, the vibration deflection of the ceramic lamella 2.
- Such a material is that material which is described in DE-C-25 37 788 and in GB-A-1 530 347 and which is an epoxy resin filled with hollow glass or silicon dioxide balls, also under the Scotch trademark. Ply is known. Another material is polystyrene, a "glass foam", a sintered glass, etc. As far as the material of Plates / layers 3, 13 ... is referred to as plastic, the mineral "glass" is also included in the forms specified in the sense of the invention.
- a vibration mode of the transducer 1 is guaranteed according to the invention, in which the surface 5 vibrates approximately in the same phase, i.e. executes a "piston oscillation" with a high coupling factor.
- FIG 2 shows an embodiment according to the invention with two ceramic fins 2 and with 3 plates 3, 13, 23.
- Fig. 3 shows an embodiment of the invention also with two ceramic fins 2, a plate 3 and 2 compared to the thickness of the plate 3 considerably thinner coatings 31 and 32, which are located on the outwardly facing surfaces of the ceramic fins 2.
- An embodiment according to FIG. 1 is preferably selected if the quality Q p of the material of the plates 3, 13... Is less than the quality Q k of the piezoceramic of the lamellae 2. If Q p is approximately equal to Q k , the choice of a converter according to FIG. 1 is recommended. If Q p is greater than Q k , an embodiment according to FIG. 3 is expediently chosen, namely with 1/2 d p greater than d p 'greater than 1 / 5 d p .
- the objective is decisive, in the case of a vibration behavior of the radiation surface 5 that is as phase-symmetrical as possible (transverse to the lamellae), to ensure an amplitude that decreases towards the edge regions, which results in a directional behavior that is poor in side lobes.
- the plastic material can also cover the entire surface 5, as shown in FIG. 4 with the layer region 51.
- Optimal sound effectiveness for a vibration mode results for a transducer according to the invention if the thickness ratio d p : d k is optimally selected.
- Other disturbing modes are avoided by observing the above rule, namely that the plastic is selected or is present in such a (eg foamed) form that its Poisson number is less than 0.3.
- the optimal d p : d k ratio is when the transducer dimensioned in this way has a vibration amplitude or sound velocity when excited by resonance, which is half the size of a transducer (with the same external dimensions), but which is made purely of the piezoelectric material exists or is not such a composite converter. The vibration energy is then divided in half between the two material parts of the individual transducer.
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Transducers For Ultrasonic Waves (AREA)
Abstract
Description
Die vorliegende Erfindung bezieht sich auf einen breitstrahlenden Ultraschallwandler wie er im Oberbegriff des Anspruches 1 angegeben ist.The present invention relates to a wide-beam ultrasound transducer as specified in the preamble of
Aus der US-A-4 677 337 ist ein piezoelektrischer Wandler bekannt, der als Sendewandler oder als Empfangswandler für Luftultraschall zu verwenden ist. Mit dem aus dieser Druckschrift bekannten Wandler sind wesentliche Probleme gelöst worden, die im Zusammenhang stehen mit dem extremen Unterschied zwischen dem akustischen Wellenwiderstand des schallübertragenden Mediums Luft und dem akustischen Wellenwiderstand eines den Ultraschall aussendenden bzw. empfangenden festen Körpers. Dieser akustische Wellenwiderstand wird auch als Schallkenn-Impedanz bezeichnet.From US-A-4 677 337 a piezoelectric transducer is known which is to be used as a transmitter transducer or as a receiver transducer for air ultrasound. With the transducer known from this publication, essential problems have been solved which are related to the extreme difference between the acoustic wave resistance of the sound-transmitting medium air and the acoustic wave resistance of a solid body emitting or receiving the ultrasound. This acoustic wave resistance is also referred to as acoustic characteristic impedance.
Der Ultraschallwandler der genannten Druckschrift hat eine Schallkenn-Impedanz, die dem Wert derjenigen von Luft relativ wesentlich näher kommt. Erreicht ist dies durch einen Sandwich-Aufbau, der aus einzelnen in Abständen voneinander, in Ebenen parallel zueinander angeordneten piezoelektrischen Lamellen besteht, wobei die den Abständen entsprechenden Zwischenräume zwischen diesen Lamellen mit einem formstabilen Material gefullt sind, das einen kleinen Wert der Schallkenn-Impedanz hat. Das die Zwischenräume ausfüllende Material bildet wenigstens eine geschlossene Fläche dieses die piezoelektrischen Lamellen einschließenden elektroakustischen Wandlers, nämlich eine Fläche für die Abstrahlung und/oder für den Empfang akustischer Strahlung. Dabei kann z.B. dieses die Zwischenräume ausfüllende Material über wenigstens jeweils eine der Kantenflächen der einzelnen Lamellen hinausreichen, so daß diese Kantenflächen der Lamellen durch dieses die Zwischenräume ausfüllende Material gegenüber der äußeren Umgebung abgedeckt sind.The ultrasonic transducer of the cited document has a sound characteristic impedance that comes relatively much closer to that of air. This is achieved by means of a sandwich structure consisting of individual piezoelectric lamellae arranged at intervals from one another, in planes parallel to one another, the interspaces between these lamellae corresponding to the intervals being filled with a dimensionally stable material which has a small value for the acoustic characteristic impedance . The material filling the gaps forms at least one closed surface of this electroacoustic transducer including the piezoelectric lamellae, namely a surface for the radiation and / or for the reception of acoustic radiation. In this case, for example, this material filling the gaps can extend beyond at least one of the edge surfaces of the individual slats, so that these edge surfaces of the slats are covered by this material filling the gaps with respect to the external environment.
Ein solcher bekannter Wandler kann so ausgeführt sein, daß diese für Abstrahlung und/oder Empfang vorgesehene Fläche desselben gegenüber der Luftwellenlänge der ausgesandten bzw. empfangenenen akustischen Strahlung relative große Abmessung hat. Werden die einzelnen piezoelektrischen Lamellen zu konphaser Schwingung angeregt, so wird von dieser Fläche des Wandlers ausgehend eine Schallwelle mit weitgehend ebener Phasenfront ausgesandt.Such a known transducer can be designed in such a way that this surface of the same intended for radiation and / or reception has a relatively large dimension relative to the air wavelength of the emitted or received acoustic radiation. If the individual piezoelectric lamellae are excited to produce a convex oscillation, a sound wave with a largely flat phase front is emitted from this surface of the transducer.
Als Material für die Lamellen wird piezoelektrische Keramik verwendet, z.B. Bleizirkonattitannat, Bleititanat, Bariumtitanat und dergleichen, wobei diese Materialien zur Verbesserung ihrer jeweiligen Eigenschaften Dotierungen und/oder Substitionen von u.a. Mangan, Niob, Neodym usw. enthalten können. Das Material zum Ausfüllen der Zwischenräume zwischen den Lamellen ist bei diesem bekannten Wandler z.B. ein thermoplastischer Kunststoff. Z.B. ist der ganze aus diesem Material und den piezoelektrischen Lamellen bestehende Körper heiß miteinander verklebt. Die Zwischenräume können dort aber auch mit einem Verguß aus Silikongummi gefüllt sein.Piezoelectric ceramic is used as the material for the lamellae, e.g. Lead zirconate, lead titanate, barium titanate and the like, these materials to improve their respective properties doping and / or substitution of i.a. May contain manganese, niobium, neodymium, etc. The material for filling the spaces between the lamellae in this known converter is e.g. a thermoplastic. E.g. the whole body made of this material and the piezoelectric lamellae is hot glued together. The gaps can also be filled with a silicone rubber potting.
Hinsichtlich weiterer Einzelheiten bezüglich des konstruktiven Aufbaus und der Herstellung eines solchen bekannten Wandlers sei auf die obengenannte Druckschrift hingewiesen.With regard to further details regarding the construction and manufacture of such a known converter, reference is made to the above-mentioned publication.
Aufgabe der vorliegenden Erfindung ist es, einen elektroakustischen Wandler mit günstiger Anpassung der Schallkenn-Impedanz an das Medium Luft anzugeben, der als Schallstrahlungs-Keule eine solche hat, die in der einen Koordinatenrichtung x senkrecht zur Richtung z der Achse der Schallstrahlung eine relativ geringe Breite, d.h. einen kleinen Öffnungswinkel, hat, und der in der zu dieser Richtung x und zur Achsenrichtung z jeweils senkrechten Koordinatenrichtung y breitstrahlend ist, d.h. in dieser Richtung großen Öffnungswinkel besitzt. Der konstruktive Aufbau des anzugebenden Wandlers soll derart sein, daß, ausgehend von einem Grundtyp, durch die Wahl einzelner Bemessungen einzelne Typen mit vorgebbar voneinander unterschiedlichen Öffnungswinkeln in in y-Richtung zu erhalten sind. Insbesondere soll der breite Öffnungswinkel im Bereich von 50° bis 100° (-6 dB) für den Einzeltyp des Wandlers wählbar sein.The object of the present invention is to provide an electroacoustic transducer with a favorable adaptation of the acoustic characteristic impedance to the medium air, which as the acoustic radiation lobe has one which has a relatively small width in one coordinate direction x perpendicular to the direction z of the axis of the acoustic radiation , ie has a small opening angle, and which has a wide beam in the coordinate direction y perpendicular to this direction x and to the axis direction z, ie has a large opening angle in this direction. The structural design of the transducer to be specified should be such that, starting from a basic type, the choice of individual dimensions means that individual types with different opening angles that can be predefined from one another can be obtained in the y direction. In particular, the wide opening angle should be selectable in the range from 50 ° to 100 ° (-6 dB) for the individual type of converter.
Diese Aufgabe wird mit einem Wandler mit den Merkmalen des Anspruches 1 gelöst und weitere Ausgestaltungen der Erfindung gehen aus den Unteransprüchen hervor.This object is achieved with a converter having the features of
Richtscharfe Wandler wie z.B. auch die aus der DE-A-2 537 788 und der GB-A-1 530 347 bekannten Wandler haben einen Öffnungswinkel von 5° bis 10° (- 6 dB). Ein erfindungsgemäßer Wandler mit z.B. 70° Öffnungswinkel in der oben mit y bezeichneten Richtung und mit scharfer Richtwirkung in der x-Richtung ist ein ausgesprochen breitstrahlender Ultraschallwandler. In einer zur axialen Richtung z jeweils senkrechten Ebene ist der Querschnitt der Schallkeule eines solchen erfindungsgemäßen Wandlers in der x-Richtung relativ flach, in der y-Richtung dagegen breit und stellt insgesamt eine wenigstens angenahert ellipsenähnliche Fläche dar. Mit zunehmendem Abstand (z - z₀) von der Oberfläche Zo des Wandlers wird diese Querschnittsfläche immer größer, ohne jedoch ihre charakteristische Form eines in einer Querrichtung y breitstrahlenden Wandlers zu verlieren.Sharp converters such as the converters known from DE-A-2 537 788 and GB-A-1 530 347 also have an opening angle of 5 ° to 10 ° (-6 dB). A converter according to the invention with e.g. An opening angle of 70 ° in the direction labeled y above and with a sharp directivity in the x direction is an extremely wide-beam ultrasound transducer. In a plane perpendicular to the axial direction z, the cross-section of the sound lobe of such a transducer according to the invention is relatively flat in the x-direction, but broad in the y-direction and overall represents an at least approximately elliptical-like surface. With increasing distance (z - z₀ ) from the surface Zo of the transducer, this cross-sectional area becomes ever larger, without, however, losing its characteristic shape of a transducer radiating wide in a transverse direction y.
Um die oben angegebene Aufgabenstellung zu lösen, war versucht worden, den aus der US-A-4 677 337 bekannten Wandler weiterzuentwickeln. Es zeigte sich aber, daß die spezielle Aufgabe der vorliegenden Erfindung auf diese Weise nicht zu lösen war. Schwierigkeiten entstanden z.B., wenn die Dicke des die Zwischenräume ausfüllenden Kunststoffs wesentlich größer ist, als die Dicke der piezoelektrischen Lamellen. Bei Impulsbetrieb führte die Anregung der Lamellen aufgrund der geringen Schallwellengeschwindigkeit in Richtung y nicht mehr zu konphaser Oberflächenverformung, sondern ließ störende Oberflächenwelligkeit auftreten. Bei Resonanzanregung eines impulsbetriebenen Wandlers mit damit notwendigerweise verbundenen Einschwingen zeigte sich der Gewinn an Wirkungsgrad als relativ begrenzt. Bei einer Konstruktion und Bemessung mit der Zielrichtung hoher mechanischer Verluste, d.h. geringer Schwinggüte, war die Belastbarkeit des Wandlers der Wärmeentwicklung wegen relativ stark begrenzt. Die Verwendung des schon erwähnten Silikongummis oder eines diesem vergleichbaren Materials, derartige Materialien haben relativ große Querkontraktion, ergab zu starke Modenkopplung mit Dickenresonanzen des in Sandwich-Bauweise aufgebauten Schichtwandlers, namlich sobald die Stapelhöhe einen bestimmten Wert überschreitet. Für Impulswandler ist dies an sich von Vorteil, da ein Multimode-Impulswandler notwendigerweise breitbandig ist. Für einen monofrequenten Wandler ist jedoch eine Modenkopplung meist mit einer Beeinträchtigung des elektromechanischen Kopplungsfaktors und damit des elektroakustischen Wirkungsgrades verbunden. Für monofrequent betriebene Wandler, wie sie für die Erfindung vorgesehen, bzw. erforderlich sind, ist eine weitestgehende Kontrolle des Auftretens von Eigenmoden der im Wandler enthaltenen piezoelektrischen Lamellen hinsichtlich der Frequenz, der Form der Schwingung und des elektromechanischen Kopplungsfaktors k unerläßlich, nämlich um definierte Richtungscharakteristik und besten Wirkungsgrad zu erzielen. Zur Lösung der erfindungsgemäßen Aufgabe müßte also ein prinzipiell neuer Weg beschritten werden, auch wenn ein erfindungsgemäßer Wandler generell wiederum aus rechteckigen piezoelektrischen Lamellen und Verbundmaterial besteht.
- Fig. 1
- zeigt das Prinzip eines erfindungsgemäßen Wandlers,
- Fig. 2 und 3
- zeigen spezielle Ausführungsformen,
- Fig. 4
- zeigt eine Ausführungsform mit ganzflächiger Kunststoffüberdeckung.
- Fig. 1
- shows the principle of a converter according to the invention,
- 2 and 3
- show special embodiments,
- Fig. 4
- shows an embodiment with full-surface plastic covering.
Fig. 1 zeigt das Prinzip eines erfindungsgemäßen gestalteten und in seinen relativen Abmessungen erfindungsgemäß gewählten Wandlers 1. In der in der Fig. 1 gezeigten Ausgestaltung besteht dieser Wandler 1 aus einer mit (in der Figur nicht dargestellten) Elektroden versehnen piezoelektrischen Keramiklamelle 2 und aus Schichten oder Platten 3, 13 aus einem Kunststoffmaterial. Die Länge des dargestellten rechteckigen Verbundkörpers des Wandlers 1 ist mit L bezeichnet. Seine Breite ist mit B bezeichnet. Seine Gesamtdicke ist mit D bezeichnet, die die Summe der Dickenabmessungen dp der Platten 3, 13 und der Dickenabmessung dk der Lamelle 2 ist.1 shows the principle of a
Die mit 5 bezeichnete Fläche des Wandlers 1 ist die entsprechend der Erfindung vorgesehene bzw. ausgewählte Abstrahl- bzw. Schallempfangsfläche. Mit den Pfeilen 6 ist auf die erfindungsgemäß vorgesehene Abstrahlung hingewiesen.The area of the
Die Keramiklamelle 2 und die Schichten bzw. Platten 3, 13 sind flächig, wie dargestellt, fest miteinander verbunden. Bei thermoplastischem Material kann das Verbindungsmittel (Klebstoff) das Material der Schichten bzw. Platten 3, 13 selbst sein.The
Ein erfindungsgemäßer Wandler kann auch aus mehreren Keramiklamellen und entsprechend vielen Schichten bzw. Platten bestehen.A converter according to the invention can also consist of several ceramic lamellae and a corresponding number of layers or plates.
Der Vollständigkeit halber sei auf die Druckschrift IEEE, Transactions on Sonics and Ultrasonics, Vol. SU 15 (1968) S. 97/105 verwiesen, wofür eine rechteckige piezoelektrische Platte, jedoch nur für allein eine einzelne aktive Platte, zahlreiche Resonanzschwingungsformen angegeben sind.For the sake of completeness, reference is made to the publication IEEE, Transactions on Sonics and Ultrasonics, Vol. SU 15 (1968) pp. 97/105, for which a rectangular piezoelectric plate, but only for a single active plate alone, numerous forms of resonance oscillations are specified.
Das Material der Flatten 3,13 beiderseits der piezoelektrischen Lamelle 2 ist hinsichtlich niedriger Schallkenn-Impedanz Z und hinsichtlich einer möglichst kleinen Poissonzahl u kleiner als 0,3 und hinsichtlich möglichst hoher Schwinggüte Q größer als 20 ausgewählt. Niedrige Schallkenn-Impedanz dient möglichst guter Anpassung an das Schallübertragungsmedium Luft. Kleiner Poissonzahl trägt dazu bei, möglichst keine Quermoden anzuregen. Diese können nämlich schon dann auftreten, wenn die Dicke D noch kleiner als die Breite B des Wandlers 1 ist. Hohe Güte Q dieses Materials ermöglicht Schwingungsauslenkung im Material der Platten 3, 13 zu erreichen, die der Schwingungsauslenkung der Keramiklamelle 2 nahekommt, vorzugsweise übertrifft. Ein Beispiel für derartiges Material ist das jenige Material, was in der DE-C-25 37 788 und in der GB-A-1 530 347 beschrieben und das ein mit Glas- oder Siliziumdioxid-Hohlkugeln gefülltes Epoxydharz, auch unter dem Warenzeichen Scotch-Ply bekannt, ist. Ein ananderes Material ist Polystyrol ein "Glasschaum", ein Sinterglas ccer dergl.. Soweit hier das Material der Platten/Schichten 3, 13 ... als Kunststoff bezeichnet ist, ist auch der Mineralstoff "Glas" in wie angegebenen Formen im Sinne der Erfindung eingeschlossen.The material of the
Erfindungsgemäß ist das Verhältnis der beiden in der Fig. 1 angebenen Abmessungen B und L bemessen zu:
B:L wenigstens angenähert = 0,42.According to the invention, the ratio of the two dimensions B and L shown in FIG. 1 is dimensioned to:
B: L at least approximately = 0.42.
Mit dieser Bemessungsvorschrift ist gemäß der Erfindung ein Schwingungsmode des Wandlers 1 gewährleistet, bei dem die Fläche 5 weitestgehend angenähert konphas schwingt, d.h. eine "Kolbenschwingung" ausführt, und zwar bei gleichzeitig hohem Kopplungsfaktor.With this dimensioning regulation, a vibration mode of the
Fig. 2 zeigt eine erfindungsgemäße Ausführungsform mit zwei Keramiklamellen 2 und mit 3 Platten, 3, 13, 23.2 shows an embodiment according to the invention with two
Die Fig. 3 zeigt eine ebenfalls erfindungsgemäße Ausführungsform mit zwei Keramiklamellen 2, einer Platte 3 und mit 2 vergleichsweise zur Dicke der Platte 3 erheblich dünneren Beschichtungen 3₁ und 3₂, die sich auf den nach außen weisenden Oberflächen der Keramiklamellen 2 befinden.Fig. 3 shows an embodiment of the invention also with two
Bevorzugt wird eine Ausführungsform nach Fig. 1 gewählt, wenn die Güte Qp des Materials der Platten 3, 13 ... kleiner als die Güte Qk der Piezokeramik der Lamellen 2 ist. Gilt Qp ungefähr gleich Qk empfiehlt sich die Wahl eines Wandlers nach Fig. 1. Ist Qp größer als Qk wird zweckmäßigerweise eine Ausführungsform nach Fig. 3 gewählt, und zwar mit 1/2 dp größer dp' größer 1/5 dp. Für die jeweilige Wahl ist die Zielsetzung maßgebend, bei möglichst (quer zu den Lamellen) konphasem Schwingungsverhalten der Abstrahlfläche 5 eine zu den Randbereichen abnehmende Amplitude zu gewährleisten, was ein Richtverhalten bewirkt, das arm an Nebenzipfeln ist.An embodiment according to FIG. 1 is preferably selected if the quality Q p of the material of the
Für alle Ausführungsformen gilt, daß das Kunststoffmaterial auch die ganze Fläche 5 überdecken kann, wie dies die Figur 4 mit dem Schichtbereich 51 zeigt.It applies to all embodiments that the plastic material can also cover the
Optimale Schall-Effektivität für einen Schwingungsmode ergibt sich für einen erfindungsgemäßen Wandler, wenn das Dicken-verhältnis dp:dk optimal gewählt ist. Störende andere Moden werden dadurch vermieden, daß die obige Vorschrift eingehalten ist, nämlich daß der Kunststoff so ausgewählt ist bzw. in einer solchen (z.B. geschäumten) Form vorliegt, daß dessen Poissonzahl kleiner als 0,3 ist. Optimales dp:dk-Verhältnis liegt vor, wenn der so bemessene Wandler bei Resonanzanregung eine Schwingungsamplitude bzw. Schallschnelle hat, die halb so groß ist, wie sie bei einem Wandler (mit gleichen Außenabmessungen) vorliegt, der jedoch rein aus dem piezoelektrischen Material besteht bzw. kein solcher Verbundwandler ist. Die Schwingungsenergie ist dann hälftig auf die beiden Material-Anteile des einzelnen Wandlers verteilt.Optimal sound effectiveness for a vibration mode results for a transducer according to the invention if the thickness ratio d p : d k is optimally selected. Other disturbing modes are avoided by observing the above rule, namely that the plastic is selected or is present in such a (eg foamed) form that its Poisson number is less than 0.3. The optimal d p : d k ratio is when the transducer dimensioned in this way has a vibration amplitude or sound velocity when excited by resonance, which is half the size of a transducer (with the same external dimensions), but which is made purely of the piezoelectric material exists or is not such a composite converter. The vibration energy is then divided in half between the two material parts of the individual transducer.
Claims (5)
- Electroacoustic laminated transducer (1) having a transducer body in the form of a parallelepiped having the length (L), the width (B) and the thickness (D) and a face of the transducer body as sound-radiating and/or sound-receiving face (5), this transducer body comprising, on the one hand, at least one lamella (2) provided with electrodes and composed of piezoelectric material and, on the other hand, at least two plates/layers (3, 13, 23 ...; 3₁, 3₂ ...) composed of a synthetic and these lamellae and plates/layers being joined together alternately and consecutively in the direction of the thickness (D), characterized- in that the ratio of the width (B) to the length (L) of the block has at least approximately the value 0.42,- in that the long lateral face (D x L) of the block is the sound-radiating and/or sound-receiving face (5) and- the synthetic being a material having a mechanical vibrational (Q) in the order of magnitude of that of the piezoelectric material of the lamellae (2), this synthetic material having a lower characteristic acoustic impedance (Z) than the piezoelectric material of the lamellae (2) and the Poisson number of the synthetic material being less than/equal to 0.3.
- Transducer according to Claim 1, characterized in that the thickness ratio dp:dk, with dp for the components (3, 13, 23...; 3₁, 3₂, ...) composed of the synthetic and with dk for the components (2) composed of the piezoelectric material is chosen in such a way that the sound particle velocity of the transducer (1) designed in this way is at least approximately half as great as that of the piezoelectric material for equal excitation conditions, preferably equal voltage, in each case at resonance.
- Transducer according to Claim 1 or 2, characterized in that the synthetic material of the plates/ layers (3, 13, 23...; 3₁ 3₂...) is a foamed glass.
- Transducer according to Claim 1 or 2, characterized in that the synthetic material of the plates/ layers (3, 13, 23...; 3₁, 3₂...) is a coarse-pored sintered glass.
- Transducer according to one of Claims 1 to 4, characterized in that the sound-radiating or sound-receiving face (5) of the transducer body is the surface of a closed layer region (51) comprising the synthetic material.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE3920663 | 1989-06-23 | ||
| DE3920663A DE3920663A1 (en) | 1989-06-23 | 1989-06-23 | WIDE-RADIATION ULTRASONIC transducer |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| EP0478611A1 EP0478611A1 (en) | 1992-04-08 |
| EP0478611B1 true EP0478611B1 (en) | 1994-01-19 |
Family
ID=6383453
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP90909133A Expired - Lifetime EP0478611B1 (en) | 1989-06-23 | 1990-06-22 | Wide-range ultrasonic transducer |
Country Status (5)
| Country | Link |
|---|---|
| US (1) | US5254900A (en) |
| EP (1) | EP0478611B1 (en) |
| JP (1) | JPH0787639B2 (en) |
| DE (2) | DE3920663A1 (en) |
| WO (1) | WO1991000153A1 (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE19512417C2 (en) * | 1995-04-03 | 1997-02-06 | Marco Systemanalyse Entw | Piezoelectric ultrasonic transducer |
| DE19527018C1 (en) * | 1995-07-24 | 1997-02-20 | Siemens Ag | Ultrasonic transducer |
| US6288477B1 (en) * | 1999-12-03 | 2001-09-11 | Atl Ultrasound | Composite ultrasonic transducer array operating in the K31 mode |
| DE102006013220B3 (en) * | 2006-03-22 | 2007-08-02 | Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. | Ultrasound converter with phased-array strip-form piezo-elements, has sound-radiating surface curved along given direction of curvature |
| GB2545004B (en) * | 2015-12-03 | 2019-04-03 | Rolls Royce Plc | Method and apparatus for machining objects |
| CN108433744B (en) * | 2018-04-23 | 2023-11-28 | 中国科学院苏州生物医学工程技术研究所 | Ultrasonic transducer, ultrasonic probe and ultrasonic hydrophone |
Family Cites Families (18)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2814575A (en) * | 1954-08-13 | 1957-11-26 | Hodes Lange Corp | Method and apparatus for cleaning ampoules with the aid of ultrasonic vibration |
| US2901644A (en) * | 1955-12-05 | 1959-08-25 | Tibbetts Lab Inc | Electromechanical device and method of making same |
| US3024701A (en) * | 1956-12-03 | 1962-03-13 | Alvin M Marks | Flake glass panel structures |
| BE637983A (en) * | 1961-05-02 | |||
| US3674945A (en) * | 1970-03-11 | 1972-07-04 | Raytheon Co | Acoustic impedance matching system |
| DE2537788C3 (en) * | 1975-08-25 | 1980-04-10 | Siemens Ag, 1000 Berlin Und 8000 Muenchen | Ultrasonic transducer |
| AT353506B (en) * | 1976-10-19 | 1979-11-26 | List Hans | PIEZOELECTRIC RESONATOR |
| DE2851745C2 (en) * | 1978-11-30 | 1985-01-10 | Elektrotechnik Ehmann Gmbh, 6953 Gundelsheim | Multi-layer membrane for an electroacoustic transducer |
| JPS612028Y2 (en) * | 1980-05-24 | 1986-01-23 | ||
| DE3101208C2 (en) * | 1981-01-16 | 1983-05-11 | W.C. Heraeus Gmbh, 6450 Hanau | Process for the production of a multilayer system |
| DE3478357D1 (en) * | 1983-03-17 | 1989-06-29 | Matsushita Electric Ind Co Ltd | Ultrasonic transducers having improved acoustic impedance matching layers |
| FR2551611B1 (en) * | 1983-08-31 | 1986-10-24 | Labo Electronique Physique | NOVEL ULTRASONIC TRANSDUCER STRUCTURE AND ULTRASONIC ECHOGRAPHY MEDIA EXAMINATION APPARATUS COMPRISING SUCH A STRUCTURE |
| DE8408180U1 (en) * | 1984-03-16 | 1986-07-17 | Siemens AG, 1000 Berlin und 8000 München | Piezoelectric air-ultrasonic transducer with broadband characteristics |
| DE3430186A1 (en) * | 1984-08-16 | 1986-02-27 | Siemens AG, 1000 Berlin und 8000 München | METHOD FOR PRODUCING A POROUS PIEZOELECTRIC MATERIAL AND MATERIAL PRODUCED BY THIS METHOD |
| US4656384A (en) * | 1984-10-25 | 1987-04-07 | Siemens Aktiengesellschaft | Ultrasonic detection sensor in hybrid structure with appertaining electronic circuit |
| US4756808A (en) * | 1985-05-31 | 1988-07-12 | Nec Corporation | Piezoelectric transducer and process for preparation thereof |
| US4810675A (en) * | 1986-01-24 | 1989-03-07 | Potters Industries, Inc. | Process for making lightweight body suitable for use as an additive in an article of manufacture |
| DE3731649A1 (en) * | 1987-09-19 | 1989-03-30 | Schott Glaswerke | METHOD FOR PRODUCING OPEN-POROUS SINTER BODIES |
-
1989
- 1989-06-23 DE DE3920663A patent/DE3920663A1/en not_active Withdrawn
-
1990
- 1990-06-22 WO PCT/DE1990/000478 patent/WO1991000153A1/en active IP Right Grant
- 1990-06-22 US US07/778,817 patent/US5254900A/en not_active Expired - Fee Related
- 1990-06-22 JP JP2508616A patent/JPH0787639B2/en not_active Expired - Fee Related
- 1990-06-22 DE DE90909133T patent/DE59004358D1/en not_active Expired - Fee Related
- 1990-06-22 EP EP90909133A patent/EP0478611B1/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| DE59004358D1 (en) | 1994-03-03 |
| US5254900A (en) | 1993-10-19 |
| WO1991000153A1 (en) | 1991-01-10 |
| JPH0787639B2 (en) | 1995-09-20 |
| DE3920663A1 (en) | 1991-01-10 |
| JPH04502543A (en) | 1992-05-07 |
| EP0478611A1 (en) | 1992-04-08 |
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