EP1039975A1 - Piezoelectric transducer with a temperature-sensitive component - Google Patents

Piezoelectric transducer with a temperature-sensitive component

Info

Publication number
EP1039975A1
EP1039975A1 EP98962248A EP98962248A EP1039975A1 EP 1039975 A1 EP1039975 A1 EP 1039975A1 EP 98962248 A EP98962248 A EP 98962248A EP 98962248 A EP98962248 A EP 98962248A EP 1039975 A1 EP1039975 A1 EP 1039975A1
Authority
EP
European Patent Office
Prior art keywords
component
electrode
temperature
piezoelectric
piezoelectric vibrator
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Withdrawn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
EP98962248A
Other languages
German (de)
French (fr)
Inventor
Thomas Hahn
Hans-Joachim Welsch
Martin Staut
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 Forderung der Angewandten Forschung eV
Original Assignee
Fraunhofer Gesellschaft zur Forderung 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 Forderung der Angewandten Forschung eV filed Critical Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
Publication of EP1039975A1 publication Critical patent/EP1039975A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/15—Constructional features of resonators consisting of piezoelectric or electrostrictive material
    • H03H9/17—Constructional features of resonators consisting of piezoelectric or electrostrictive material having a single resonator
    • H03H9/176—Constructional features of resonators consisting of piezoelectric or electrostrictive material having a single resonator consisting of ceramic material
    • 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
    • B06B1/0651—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 of circular shape
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/66—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by measuring frequency, phase shift or propagation time of electromagnetic or other waves, e.g. using ultrasonic flowmeters
    • G01F1/662—Constructional details
    • 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
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N30/00—Piezoelectric or electrostrictive devices
    • H10N30/80—Constructional details
    • H10N30/802—Drive or control circuitry or methods for piezoelectric or electrostrictive devices not otherwise provided for
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N30/00—Piezoelectric or electrostrictive devices
    • H10N30/80—Constructional details
    • H10N30/87—Electrodes or interconnections, e.g. leads or terminals
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F15/00—Details of, or accessories for, apparatus of groups G01F1/00 - G01F13/00 insofar as such details or appliances are not adapted to particular types of such apparatus
    • G01F15/02—Compensating or correcting for variations in pressure, density or temperature
    • G01F15/022—Compensating or correcting for variations in pressure, density or temperature using electrical means

Definitions

  • the present invention relates to a piezoelectric vibrator that can be used as an ultrasonic transducer.
  • a temperature measurement is therefore generally required before or during operation.
  • the temperature is realized in many cases by an external temperature sensor.
  • the external temperature sensor for recording the temperature must be led to the measuring point directly at the acoustic measuring point next to the ultrasonic transducer. This requires additional wiring and complicates the whole arrangement.
  • the piezoelectric vibrator consists of a piezoelectric substrate, preferably a piezoceramic, which has a first electrode on a first surface and a second electrode on a second surface opposite the first surface.
  • the first electrode does not completely cover the first surface of the vibrator, so that there is an electrode-free edge surface.
  • this can be achieved by selecting the diameter of the preferably circular electrode to be smaller than the diameter of the circular substrate surface.
  • the diameter of the piezoelectric substrate used is larger than the necessary radiating area (aperture) of the piezoelectric vibrator. This aperture is approximately determined by the overlap of the two opposite electrodes.
  • a component with temperature-dependent behavior is attached or integrated on the electrode-free edge surface.
  • a connection of this component is conductively connected to at least one of the two electrodes.
  • This design of the piezoelectric vibrator allows the temperature to be measured directly at the acoustic measuring point via the temperature-dependent component. Due to the integration of the component on the surface of the piezoelectric substrate, an uncomplicated Ornate temperature detection guaranteed. By connecting the component in parallel or in series with the capacitor formed by the two electrodes, the temperature can be measured directly via the two-pole lead for the electrodes. An additional supply line for the temperature sensor or the temperature-dependent component is therefore not necessary, so that complex cabling is avoided.
  • connection pads which are formed by the first and / or second electrode on a surface of the piezoelectric substrate
  • the integration of the temperature-dependent component can be implemented using a simple connection technology. Claims 3 and 4 ⁇ . There is no additional wiring between the or the electrodes and the component is required.
  • the piezoelectric vibrator according to the invention can therefore be produced with little effort.
  • Fig. 1 shows an example of a piezoceramic transducer according to the invention before attaching the component in rear view (a), front view (b) and side view (O;
  • FIG. 2 shows the rear view of the vibrator from FIG. 1 with an integrated component (here: temperature-dependent resistance);
  • 3 shows the oscillator from FIG. 2 in a housing; and 4 shows a basic circuit diagram of the connection of the component with the capacitor formed by the two electrodes, as a parallel connection (a) or a series connection (b).
  • FIG. 1 shows an example of a piezo-ceramic transducer according to the invention in side, rear and front views before it is provided with a temperature-dependent component.
  • a circular, disk-shaped piezoceramic is used as the substrate (1).
  • On the back of the ceramic is also a circular electrode (2) (except for the foothills (4,5)), the diameter of which is smaller than the diameter of the piezoelectric ceramic.
  • the radiating surface of the vibrator is determined by the size of the electrode, a piezoceramic is therefore used in the present case, the diameter of which is larger than the radiating surface (aperture) of the vibrator required for the intended application.
  • an electrode-free edge surface (3) is available on the rear surface of the ceramic.
  • the rear electrode also has two extensions (4, 5) which extend into the electrode-free edge surface. These extensions form connection pads for the subsequent contacting of the electrode with a supply line (extension 4) and with the component with temperature-dependent behavior (extension 5).
  • the front electrode (6) over the entire front surface of the piezoceramic extends.
  • this front electrode also has two extensions (7, 8) which are guided around the edge of the disk-shaped piezoceramic in order to form two connection pads (7, 8) in the electrode-free edge region (3) on the back.
  • these two connection pads are provided for contacting the front electrode with a supply line (extension 7) and with the component (extension 8).
  • a sectional view through the line A-A 'in partial image (a) shows partial image (c).
  • the piezoelectric ceramic (1), the rear electrode (2) and the front electrode (6) with the extension (8) guided around the edge of the piezoceramic can be seen to form a connection pad on the opposite surface.
  • the electrodes are shown at a distance from the piezoceramic. In fact, however, they are in contact with the piezoceramic.
  • PZT lead zirconium titanate
  • Silver, gold or nickel are preferably used as electrode materials.
  • Typical dimensions of the piezoceramic are a thickness of 1 to 4 mm with a diameter of approx. 10 - 30 mm.
  • Fig. 2 shows the embodiment of Fig. 1 with integrated temperature-dependent resistor (9) and attached supply lines (10) to the electrodes.
  • the connection of the temperature-dependent resistor with the capacitor formed by the two electrodes corresponds in the present example to a parallel connection as shown schematically in FIG. 4 (a).
  • the feed approximately lines can be soldered to the connection pads (4, 7), for example.
  • the piezoelectric ceramic is advantageously used simultaneously as a circuit board.
  • the connection pads which are formed by the electrodes themselves, enable a very simple connection technique to be implemented with little wiring effort.
  • Such a vibrator can be used, for example, for external measurement of the filling level of gas cylinders.
  • the temperature-dependent resistor can be a PTC or an NTC, for example.
  • Another type of temperature sensor which should preferably be of SMD design, is also possible.
  • FIG. 3 shows a side view of a vibrator according to the invention, which is built into a housing (11) with a coupling layer (12) and has an integrated temperature-dependent resistor (for example SMD-NTC (9)).
  • the connecting cables (10) can also be seen.
  • FIG. 4 shows the two circuit variants when the component is integrated.
  • a high-resistance NTC should be used in conjunction with a low-resistance ceramic.
  • a 1.5 MHz oscillator which has an impedance of approximately 50 ⁇ (preferably the minimum of impedance at this frequency)
  • a low-resistance PTC should be used in series connection with a high-resistance piezoceramic.
  • the parallel connection or series connection shown makes it possible to transmit the temperature information with its low-frequency signal behavior via the same two-pole feed line (10) which is also used for the high-frequency ultrasound information. It is therefore not necessary to provide additional supply lines.
  • This simplified arrangement in particular allows the structure when using the vibrator to be significantly simplified.
  • the arrangement of the electrodes according to the invention in connection with the provision of a piezoceramic, the diameter of which is larger than the necessary radiating surface, offers the possibility of a very simple connection technique of the component with the electrodes via integrated connection pads.

Abstract

The invention relates to a piezoelectric transducer of the type used for ultrasound propagation, for example in acoustic flow rate measuring devices or level detecting devices. The inventive piezoelectric transducer preferably consists of a piezoelectric ceramic (1) which has a first electrode (2) on a first surface and a second electrode (6) on a second surface opposite the first. An electrode-free edge area (3) on which a temperature-sensitive component (9) is mounted is provided on the first surface of the piezoelectric ceramic. Said component is conductively connected to at least one of the electrodes (2, 6). The inventive piezoelectric transducer enables temperature to be measured directly at the acoustic measuring point without any additional cabling.

Description

PIEZOELEKTRISCHER SCHWINGER MIT TEMPERATURABHÄNGIGEM BAUELEMENTPIEZOELECTRIC SWINGARM WITH TEMPERATURE-DEPENDENT COMPONENT
Die vorl iegende Erf indung betri f f t einen piezoe lektri schen Schwinger , wie er als Ultraschal lwandler zum Einsatz kommen kann .The present invention relates to a piezoelectric vibrator that can be used as an ultrasonic transducer.
Die Effekte der Ultraschallausbreitung, insbesondere die Schallgeschwindigkeit und die Schalldämpfung sind temperaturabhängig. Weiterhin ist bei den sehr häufig in Ultraschallwandlern als Materialien zur elektromechanischen Energiekonversion eingesetzten Piezokeramiken eine deutliche Temperaturabhängigkeit der piezoelektrischen Konstanten vorhanden. Dadurch ergibt sich bei piezokerami- schen Ultraschallwandlern oder Schwingern ein temperaturabhängiges akustisches Übertragungsverhalten.The effects of ultrasound propagation, in particular the speed of sound and sound attenuation, are temperature-dependent. Furthermore, there is a clear temperature dependency of the piezoelectric constants in the piezoceramics used very frequently in ultrasonic transducers as materials for electromechanical energy conversion. This results in temperature-dependent acoustic transmission behavior in the case of piezoceramic ultrasonic transducers or oscillators.
Bei akustischen Durchflußmeßgeräten und Füllstandsdetektoren, die unter Verwendung von Ultraschallwandlern arbeiten, ist daher in der Regel vor oder während des Betriebes eine Temperaturmessung erforderlich. Im Stand der Technik wird die Temperatur hierbei in vielen Fällen durch einen externen Temperatursensor realisiert. Allerdings muß in einem solchen Fall der externe Temperatursensor zur Erfassung der Temperatur direkt an der akustischen Meßstelle neben dem Ultraschallwandler an die Meßstelle geführt werden. Dies erfordert eine zusätzliche Verkabelung und verkompliziert die gesamte Anordnung .In the case of acoustic flow meters and fill level detectors which operate using ultrasonic transducers, a temperature measurement is therefore generally required before or during operation. In the prior art, the temperature is realized in many cases by an external temperature sensor. In such a case, however, the external temperature sensor for recording the temperature must be led to the measuring point directly at the acoustic measuring point next to the ultrasonic transducer. This requires additional wiring and complicates the whole arrangement.
Es ist eine Aufgabe der vorliegenden Erfindung, einen piezoelektrischen Schwinger bereitzustellen, der auf ein- fache Weise eine Erfassung der Temperatur direkt an der akustischen Meßstelle ermöglicht.It is an object of the present invention to provide a piezoelectric vibrator that is responsive to allows the temperature to be recorded directly at the acoustic measuring point.
Die Aufgabe wird mit den Merkmalen des piezoelektrischen Schwingers nach Anspruch 1 gelöst. Vorteilhafte Ausfüh- rungsformen der Erfindung sind Gegenstand der Unteransprüche .The object is achieved with the features of the piezoelectric vibrator according to claim 1. Advantageous embodiments of the invention are the subject of the dependent claims.
Erfindungsgemäß besteht der piezoelektrische Schwinger aus einem piezoelektrischen Substrat, vorzugsweise einer Piezokeramik, das auf einer ersten Oberfläche eine erste Elektrode und auf einer der ersten Oberfläche gegenüberliegenden zweiten Oberfläche eine zweite Elektrode aufweist. Die erste Elektrode bedeckt die erste Oberfläche des Schwingers nicht vollständig, so daß eine elektrodenfreie Randfläche vorhanden ist. Dies kann bei einem scheibenförmigen Substrat dadurch realisiert werden, daß der Durchmesser der vorzugsweise kreisförmigen Elektrode kleiner als der Durchmesser der kreisförmigen Substrato- berflache gewählt wird. Dadurch ist der Durchmesser des verwendeten piezoelektrischen Substrates größer als die notwendige abstrahlende Fläche (Apertur) des piezoelektrischen Schwingers. Diese Apertur wird näherungsweise durch den Überlapp der beiden gegenüberliegenden Elektro- den bestimmt.According to the invention, the piezoelectric vibrator consists of a piezoelectric substrate, preferably a piezoceramic, which has a first electrode on a first surface and a second electrode on a second surface opposite the first surface. The first electrode does not completely cover the first surface of the vibrator, so that there is an electrode-free edge surface. In the case of a disk-shaped substrate, this can be achieved by selecting the diameter of the preferably circular electrode to be smaller than the diameter of the circular substrate surface. As a result, the diameter of the piezoelectric substrate used is larger than the necessary radiating area (aperture) of the piezoelectric vibrator. This aperture is approximately determined by the overlap of the two opposite electrodes.
Auf der elektrodenfreien Randfläche ist ein Bauelement mit temperaturabhängigem Verhalten angebracht bzw. integriert. Ein Anschluß dieses Bauelementes ist mit zumin- dest einer der beiden Elektroden leitend verbunden.A component with temperature-dependent behavior is attached or integrated on the electrode-free edge surface. A connection of this component is conductively connected to at least one of the two electrodes.
Durch diese Bauweise des piezoelektrischen Schwingers kann über das temperaturabhängige Bauelement die Temperatur direkt an der akustischen Meßstelle erfaßt werden. Aufgrund der Integration des Bauelements auf die Oberfläche des piezoelektrischen Substrates wird eine unkompli- zierte Temperaturerfassung gewährleistet. Durch Parallelschaltung oder Serienschaltung des Bauelementes zu dem durch die beiden Elektroden gebildeten Kondensator kann die Temperaturmessung direkt über die zweipolige Zulei- tung für die Elektroden erfolgen. Eine zusätzliche Zuleitung für den Temperatursensor bzw. das temperaturabhängige Bauelement ist daher nicht erforderlich, so daß eine aufwendige Verkabelung vermieden wird.This design of the piezoelectric vibrator allows the temperature to be measured directly at the acoustic measuring point via the temperature-dependent component. Due to the integration of the component on the surface of the piezoelectric substrate, an uncomplicated Ornate temperature detection guaranteed. By connecting the component in parallel or in series with the capacitor formed by the two electrodes, the temperature can be measured directly via the two-pole lead for the electrodes. An additional supply line for the temperature sensor or the temperature-dependent component is therefore not necessary, so that complex cabling is avoided.
Durch das Vorsehen von Verbindungspads, die durch die erste und/oder zweite Elektrode auf einer Oberfläche des piezoelektrischen Substrates gebildet werden, kann die Integration des temperaturabhängigen Bauelementes über eine einfache Verbindungstechnik realisiert werden (Ansprüche 3 und 4} . Es ist keine zusätzliche Verdrahtung zwischen der oder den Elektroden und dem Bauelement erforderlich. Der erfindungsgemäße piezoelektrische Schwinger kann daher mit geringem Aufwand hergestellt werden.By providing connection pads, which are formed by the first and / or second electrode on a surface of the piezoelectric substrate, the integration of the temperature-dependent component can be implemented using a simple connection technology. Claims 3 and 4}. There is no additional wiring between the or the electrodes and the component is required. The piezoelectric vibrator according to the invention can therefore be produced with little effort.
Die vorliegende Erfindung soll im folgenden anhand eines Ausführungsbeispiels in Verbindung mit den Zeichnungen näher erläutert werden. Hierbei zeigenThe present invention will be explained in the following using an exemplary embodiment in conjunction with the drawings. Show here
Fig. 1 ein Beispiel für einen erfindungsgemäßen piezokeramischen Schwinger vor dem Anbringen des Bauelementes in Rückansicht (a) , Vorderansicht (b) und Seitenansicht (O ;Fig. 1 shows an example of a piezoceramic transducer according to the invention before attaching the component in rear view (a), front view (b) and side view (O;
Fig. 2 die Rückansicht des Schwingers aus Fig. 1 mit integriertem Bauelement (hier: temperaturabhängiger Widerstand) ;FIG. 2 shows the rear view of the vibrator from FIG. 1 with an integrated component (here: temperature-dependent resistance);
Fig. 3 den Schwinger aus Fig. 2 in einem Gehäu- se; und Fig. 4 ein Prinzipschaltbild der Verschaltung des Bauelementes mit dem durch die beiden Elektroden gebildeten Kondensator, als Parallelschaltung (a) oder Serienschal- tung (b) .3 shows the oscillator from FIG. 2 in a housing; and 4 shows a basic circuit diagram of the connection of the component with the capacitor formed by the two electrodes, as a parallel connection (a) or a series connection (b).
Fig. 1 zeigt ein Beispiel eines erfindungsgemäßen piezo- keramischen Schwingers in Seiten-, Rück- und Vorderansicht, bevor dieser mit einem temperaturabhängigen Bau- element versehen wird. Bei der gezeigten Ausführungsform wird eine kreisrunde, scheibenförmige Piezokeramik als Substrat (1) eingesetzt. Auf der Rückseite der Keramik (siehe Fig.l(a)) ist eine ebenfalls (bis auf die Ausläufer (4,5)) kreisrunde Elektrode (2) aufgebracht, deren Durchmesser kleiner als der Durchmesser der piezoelektrischen Keramik ist.1 shows an example of a piezo-ceramic transducer according to the invention in side, rear and front views before it is provided with a temperature-dependent component. In the embodiment shown, a circular, disk-shaped piezoceramic is used as the substrate (1). On the back of the ceramic (see Fig.l (a)) is also a circular electrode (2) (except for the foothills (4,5)), the diameter of which is smaller than the diameter of the piezoelectric ceramic.
Da die abstrahlende Fläche des Schwingers durch die Größe der Elektrode bestimmt ist, wird im vorliegenden Fall demnach eine Piezokeramik eingesetzt, deren Durchmesser größer ist als die für die vorgesehene Anwendung notwendige abstrahlende Fläche (Apertur) des Schwingers.Since the radiating surface of the vibrator is determined by the size of the electrode, a piezoceramic is therefore used in the present case, the diameter of which is larger than the radiating surface (aperture) of the vibrator required for the intended application.
Aufgrund der unterschiedlichen Durchmesser der Piezokera- mik und der rückwärtigen Elektrode steht auf der rückseitigen Oberfläche der Keramik eine elektrodenfreie Randfläche (3) zur Verfügung. Die rückwärtige Elektrode weist weiterhin zwei Ausläufer (4, 5) auf, die sich in die elektrodenfreie Randfläche hinein erstrecken. Diese Aus- läufer bilden Verbindungspads für die spätere Kontaktie- rung der Elektrode mit einer Zuführungsleitung (Ausläufer 4) und mit dem Bauelement mit temperaturabhängigem Verhalten (Ausläufer 5) .Due to the different diameters of the piezoceramic and the rear electrode, an electrode-free edge surface (3) is available on the rear surface of the ceramic. The rear electrode also has two extensions (4, 5) which extend into the electrode-free edge surface. These extensions form connection pads for the subsequent contacting of the electrode with a supply line (extension 4) and with the component with temperature-dependent behavior (extension 5).
In der Frontansicht (b) der Fig. 1 ist zu erkennen, daß sich im vorliegenden Beispiel die Frontelektrode (6) über die gesamte vorderseitige Oberfläche der Piezokeramik erstreckt. Diese Frontelektrode weist in diesem Beispiel ebenfalls zwei Ausläufer (7, 8) auf, die um den Rand der scheibenförmigen Piezokeramik herumgeführt werden, um auf der Rückseite zwei Verbindungspads (7, 8) im elektrodenfreien Randbereich (3) zu bilden. Diese beiden Verbindungspads sind, wie bei der rückseitigen Elektrode (2) , zur Kontaktierung der Frontelektrode mit einer Zuführungsleitung (Ausläufer 7) und mit dem Bauelement (Ausläufer 8) vorgesehen.In the front view (b) of Fig. 1 it can be seen that in the present example, the front electrode (6) over the entire front surface of the piezoceramic extends. In this example, this front electrode also has two extensions (7, 8) which are guided around the edge of the disk-shaped piezoceramic in order to form two connection pads (7, 8) in the electrode-free edge region (3) on the back. As with the rear electrode (2), these two connection pads are provided for contacting the front electrode with a supply line (extension 7) and with the component (extension 8).
Eine Schnittansicht durch die Linie A-A' in Teilbild (a) zeigt Teilbild (c) . Dort sind die piezoelektrische Keramik (1) , die rückwärtige Elektrode (2) und die Frontelek- trode (6) mit dem um den Rand der Piezokeramik herum geführten Ausläufer (8) zur Bildung eines Verbindungspads auf der gegenüberliegenden Oberfläche zu erkennen. In der Abbildung (c) der Fig. 1 sind der Übersichtlichkeit halber die Elektroden in einem Abstand zur Piezokeramik ein- gezeichnet. Tatsächlich stehen sie jedoch in Kontakt mit der Piezokeramik.A sectional view through the line A-A 'in partial image (a) shows partial image (c). There, the piezoelectric ceramic (1), the rear electrode (2) and the front electrode (6) with the extension (8) guided around the edge of the piezoceramic can be seen to form a connection pad on the opposite surface. 1, for the sake of clarity, the electrodes are shown at a distance from the piezoceramic. In fact, however, they are in contact with the piezoceramic.
Als Materialien für das piezokeramische Material kommen übliche Materialien wie Bleizirkontitanat (PZT) in Frage. Als Elektrodenmaterialien werden vorzugsweise Silber, Gold oder Nickel eingesetzt. Typische Abmessungen der Piezokeramik sind eine Dicke von 1 bis 4 mm bei einem Durchmesser von ca. 10 - 30 mm.Common materials such as lead zirconium titanate (PZT) are suitable as materials for the piezoceramic material. Silver, gold or nickel are preferably used as electrode materials. Typical dimensions of the piezoceramic are a thickness of 1 to 4 mm with a diameter of approx. 10 - 30 mm.
Fig. 2 zeigt die Ausführungsform der Fig. 1 mit integriertem temperaturabhängigen Widerstand (9) und angebrachten Zuführungsleitungen (10) zu den Elektroden. Die Verschaltung des temperaturabhängigen Widerstandes mit dem durch die beiden Elektroden gebildeten Kondensator entspricht im vorliegenden Beispiel einer Parallelschaltung wie in Fig. 4 (a) εchematisch dargestellt. Die Zufüh- rungsleitungen können beispielsweise an die Verbindungspads (4, 7) angelötet werden.Fig. 2 shows the embodiment of Fig. 1 with integrated temperature-dependent resistor (9) and attached supply lines (10) to the electrodes. The connection of the temperature-dependent resistor with the capacitor formed by the two electrodes corresponds in the present example to a parallel connection as shown schematically in FIG. 4 (a). The feed approximately lines can be soldered to the connection pads (4, 7), for example.
Bei der erfindungsgemäßen Ausführung des piezokeramischen Schwingers wird die piezoelektrische Keramik in vorteilhafter Weise gleichzeitig als Platine eingesetzt. Durch die Verbindungspads, die durch die Elektroden selbst gebildet werden, läßt sich eine sehr einfache Verbindungstechnik mit einem geringen Aufwand an Verkabelung reali- sieren.In the embodiment of the piezoceramic vibrator according to the invention, the piezoelectric ceramic is advantageously used simultaneously as a circuit board. The connection pads, which are formed by the electrodes themselves, enable a very simple connection technique to be implemented with little wiring effort.
Ein derartiger Schwinger kann beispielsweise zur externen Messung des Füllstands von Gasflaschen eingesetzt werden.Such a vibrator can be used, for example, for external measurement of the filling level of gas cylinders.
Der temperaturabhängige Widerstand kann beispielsweise ein PTC oder ein NTC sein. Auch eine andere Art von Temperatursensor, der vorzugsweise in SMD-Bauweise ausgeführt sein sollte, ist möglich.The temperature-dependent resistor can be a PTC or an NTC, for example. Another type of temperature sensor, which should preferably be of SMD design, is also possible.
In Fig. 3 ist ein in ein Gehäuse (11) mit einer Ankoppelschicht (12) eingebauter erfindungsgemäßer Schwinger mit integriertem temperaturabhängigem Widerstand (beispielsweise SMD-NTC (9)) in Seitenansicht dargestellt. Ebenso sind die Verbindungskabel (10) zu erkennen.3 shows a side view of a vibrator according to the invention, which is built into a housing (11) with a coupling layer (12) and has an integrated temperature-dependent resistor (for example SMD-NTC (9)). The connecting cables (10) can also be seen.
Fig. 4 zeigt die beiden Schaltungsvarianten bei Integration des Bauelements. Bei Verwirklichung der Parallelschaltung wie in Fig. 4a gezeigt (und in Fig. 2 realisiert) ist darauf zu achten, daß der elektrische Wider- stand des Bauelementes (hier temperaturabhängiger Widerstand) das hochfrequente Ultraschallnutzsignal zur An- steuerung der Elektroden nur geringfügig bedämpft. Hierbei sollte beispielsweise ein hochohmiger NTC in Verbindung mit einer niederohmigen Keramik eingesetzt werden. Beispielsweise kommt bei Verwirklichung eines 1,5 MHz- Schwingers, der eine Impedanz von ca. 50 Ω (vorzugsweise das Minimum der Impedanz bei dieser Frequenz) aufweist, der Einsatz eines NTC mit einem Widerstand von mindestens 10 bis 20 kΩ in Eetracht .4 shows the two circuit variants when the component is integrated. When implementing the parallel connection as shown in FIG. 4a (and implemented in FIG. 2), care must be taken that the electrical resistance of the component (here temperature-dependent resistance) only slightly damps the high-frequency useful ultrasonic signal for controlling the electrodes. For example, a high-resistance NTC should be used in conjunction with a low-resistance ceramic. For example, when a 1.5 MHz oscillator is implemented, which has an impedance of approximately 50 Ω (preferably the minimum of impedance at this frequency), the use of an NTC with a resistance of at least 10 to 20 kΩ in Eetracht.
Bei Verwirklichung einer Serienschaltung wie in Fig. 4b gezeigt, sollte ein niederohmiger PTC in Serienschaltung mit einer hochoh igen Piezokeramik eingesetzt werden.When realizing a series connection as shown in FIG. 4b, a low-resistance PTC should be used in series connection with a high-resistance piezoceramic.
Durch die dargestellte Parallelschaltung bzw. Serien- Schaltung ist es möglich, die Temperaturinformation mit ihrem niederfrequenten Signalverhalten über die gleiche zweipolige Zuleitung (10) zu übertragen, die auch für die hochfrequente Ultraschallinformation verwendet wird. Das Vorsehen weiterer Zuleitungen ist daher nicht notwendig. Gerade durch diese vereinfachte Anordnung kann der Aufbau beim Einsatz des Schwingers deutlich vereinfacht werden.The parallel connection or series connection shown makes it possible to transmit the temperature information with its low-frequency signal behavior via the same two-pole feed line (10) which is also used for the high-frequency ultrasound information. It is therefore not necessary to provide additional supply lines. This simplified arrangement in particular allows the structure when using the vibrator to be significantly simplified.
Die erfindungsgemäße Anordnung der Elektroden in Verbindung mit dem Vorsehen einer Piezokeramik, deren Durchmes- ser größer als die notwendige abstrahlende Fläche ist, bietet die Möglichkeit einer sehr einfachen Verbindungstechnik des Bauelementes mit den Elektroden über integrierte Verbindungspads .The arrangement of the electrodes according to the invention in connection with the provision of a piezoceramic, the diameter of which is larger than the necessary radiating surface, offers the possibility of a very simple connection technique of the component with the electrodes via integrated connection pads.
Es versteht sich von selbst, daß die Form und die genauen Abmessungen der Piezokeramik und der Elektroden von den jeweiligen Anwendungsfällen abhängen und durch die Lehre der vorliegenden Erfindung in keinster Weise eingeschränkt sind. Ebenso können statt temperaturabhängiger Widerstände andere integrierbare Bauelemente zur Erfassung der Temperatur eingesetzt werden. It goes without saying that the shape and the exact dimensions of the piezoceramic and the electrodes depend on the respective applications and are in no way restricted by the teaching of the present invention. Likewise, instead of temperature-dependent resistors, other integrable components can be used to record the temperature.

Claims

Patentansprüche : Claims:
1. Piezoelektrischer Schwinger mit einem Substrat (1) aus piezoelektrischem Material, das auf einer ersten Oberfläche eine erste Elektrode (2) und auf einer der ersten Oberfläche gegenüberliegenden zweiten Oberflä- ehe eine zweite Elektrode (6) aufweist, wobei auf der ersten Oberfläche eine elektrodenfreie Randfläche (3) vorhanden ist, auf der ein Bauelement (9) mit temperaturabhängigem Verhalten angebracht ist, das über einen Anschluß mit zumindest einer der Elektroden (2, 6) leitend verbunden ist.1. Piezoelectric oscillator with a substrate (1) made of piezoelectric material, which has a first electrode (2) on a first surface and a second electrode (6) on a second surface opposite the first surface, one on the first surface there is an electrode-free edge surface (3) on which a component (9) with temperature-dependent behavior is attached, which is conductively connected to at least one of the electrodes (2, 6) via a connection.
2. Piezoelektrischer Schwinger nach Anspruch 1, dadurch gekennzeichnet, daß das Substrat (1) aus piezoelektrischem Material eine Piezokeramik ist.2. Piezoelectric vibrator according to claim 1, characterized in that the substrate (1) made of piezoelectric material is a piezoceramic.
3. Piezoelektrischer Schwinger nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß die erste Elektrode (2) eine Form mit einem Ausläufer (5) hat, der auf der ersten Oberfläche ein Verbindungspad bildet, über das der Anschluß des Bauelements (9) mit der ersten Elektrode (2) leitend verbunden ist.3. Piezoelectric vibrator according to claim 1 or 2, characterized in that the first electrode (2) has a shape with an extension (5) which forms a connection pad on the first surface, via which the connection of the component (9) with the first electrode (2) is conductively connected.
4. Piezoelektrischer Schwinger nach einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, daß die zweite Elek- trode (6) eine Form mit einem Ausläufer (8) hat, der um den Rand des Substrates (1) herumgeführt ist und auf der ersten Oberfläche ein Verbindungspad bildet, über das der oder ein weiterer Anschluß des Bauelements (9) mit der zweiten Elektrode (6) leitend ver- bunden ist. 4. Piezoelectric vibrator according to one of claims 1 to 3, characterized in that the second electrode (6) has a shape with an extension (8) which is guided around the edge of the substrate (1) and on the first surface forms a connection pad via which the or a further connection of the component (9) is conductively connected to the second electrode (6).
5. Piezoelektrischer Schwinger nach einem der Ansprüche 1 bis 4, dadurch gekennzeichnet, daß der durch die beiden Elektroden (2, 6) gebildete Kondensator in Reihe mit dem Bauelement (9) geschaltet ist, und das Bauelement im Vergleich zum Substrat einen niedrigen Widerstand aufweist.5. Piezoelectric vibrator according to one of claims 1 to 4, characterized in that the capacitor formed by the two electrodes (2, 6) is connected in series with the component (9), and the component has a low resistance compared to the substrate .
6. Piezoelektrischer Schwinger nach einem der Ansprüche 1 bis 4, dadurch gekennzeichnet, daß der durch die beiden Elektroden (2, 6) gebildete Kondensator parallel zum Bauelement (9) geschaltet ist, und das Bauelement im Vergleich zum Substrat einen hohen Widerstand aufweist.6. Piezoelectric vibrator according to one of claims 1 to 4, characterized in that the capacitor formed by the two electrodes (2, 6) is connected in parallel to the component (9), and the component has a high resistance compared to the substrate.
7. Piezoelektrischer Schwinger nach einem der Ansprüche 1 bis 6, dadurch gekennzeichnet, daß das Bauelement (9) ein PTC-Widerstand ist.7. Piezoelectric vibrator according to one of claims 1 to 6, characterized in that the component (9) is a PTC resistor.
8. Piezoelektrischer Schwinger nach einem der Ansprüche 1 bis 6, dadurch gekennzeichnet, daß das Bauelement8. Piezoelectric vibrator according to one of claims 1 to 6, characterized in that the component
(9) ein NTC-Widerstand ist.(9) is an NTC resistor.
9. Piezoelektrischer Schwinger nach einem der Ansprüche 1 bis 8, dadurch gekennzeichnet, daß das Bauelement (9) in SMD-Bauweise ausgeführt ist. 9. Piezoelectric vibrator according to one of claims 1 to 8, characterized in that the component (9) is designed in SMD construction.
EP98962248A 1997-12-18 1998-11-03 Piezoelectric transducer with a temperature-sensitive component Withdrawn EP1039975A1 (en)

Applications Claiming Priority (4)

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DE19756534 1997-12-18
DE19756534 1997-12-18
DE19820208A DE19820208C2 (en) 1997-12-18 1998-05-06 Piezoelectric oscillator
DE19820208 1998-05-06

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