EP1738837A2 - Method and circuit arrangement for driving an ultrasonic vibrator - Google Patents

Method and circuit arrangement for driving an ultrasonic vibrator Download PDF

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Publication number
EP1738837A2
EP1738837A2 EP06013099A EP06013099A EP1738837A2 EP 1738837 A2 EP1738837 A2 EP 1738837A2 EP 06013099 A EP06013099 A EP 06013099A EP 06013099 A EP06013099 A EP 06013099A EP 1738837 A2 EP1738837 A2 EP 1738837A2
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Prior art keywords
input
current
ultrasonic
frequency
output
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German (de)
French (fr)
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EP1738837A3 (en
Inventor
Dieter Dipl.-Ing. Schief
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Martin Walter Ultraschalltechnik AG
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Martin Walter Ultraschalltechnik AG
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    • BPERFORMING OPERATIONS; TRANSPORTING
    • B06GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
    • B06BMETHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
    • B06B1/00Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency
    • B06B1/02Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy
    • B06B1/0207Driving circuits
    • B06B1/0223Driving circuits for generating signals continuous in time
    • B06B1/0238Driving circuits for generating signals continuous in time of a single frequency, e.g. a sine-wave
    • B06B1/0246Driving circuits for generating signals continuous in time of a single frequency, e.g. a sine-wave with a feedback signal
    • B06B1/0253Driving circuits for generating signals continuous in time of a single frequency, e.g. a sine-wave with a feedback signal taken directly from the generator circuit

Definitions

  • the invention relates to a method according to the preamble of claim 1, for operating an ultrasonic vibrator with a constant oscillation amplitude, in which an excitation voltage is applied to an ultrasonic oscillation system for generating an exciter current comprising a component consisting of the ultrasonic oscillator and this resonant circuit whose frequency is outside a resonant frequency of the oscillating system, wherein the size of the exciting current is adjusted by changing the frequency.
  • the invention relates to a circuit arrangement according to the preamble of claim 3, for operating an ultrasonic vibrator according to the aforementioned method, with an amplifier having an input and an output, which output supplies the excitation voltage and the exciting current for the ultrasonic vibration system, and an oscillator whose frequency is adjustable at a control input and whose output is connected to the input of the amplifier, and a current sensor for detecting the excitation current.
  • the oscillation amplitude of the ultrasonic vibrator is constant.
  • the oscillation amplitude of the ultrasonic oscillator depends on the excitation current of the ultrasonic oscillator consisting of the ultrasonic oscillator and components that complement it, the oscillation amplitude of the ultrasonic oscillator is kept constant by keeping the exciting current of the ultrasonic oscillating system constant.
  • the ultrasonic vibration system In order to control the excitation current, the ultrasonic vibration system is not operated in its series resonance but regularly with a frequency that is between the series resonance and the parallel resonance of the ultrasonic vibration system. Since changing the frequency with which the ultrasonic vibration system is operated, the impedance of the ultrasonic vibrator changes, by changing the operating frequency of the ultrasonic vibration system, the current through the ultrasonic vibration system can be changed.
  • the frequency of the exciter voltage applied to the ultrasound oscillation system is changed until the exciter current of the ultrasound oscillation system has again reached its previous value.
  • a method for operating an ultrasonic vibrator having a constant oscillation amplitude wherein at which from the ultrasonic oscillator and this to a resonant complementary components existing ultrasonic oscillating system for generating an excitation current, an excitation voltage is applied, whose frequency is outside a resonant frequency of the Ultrasonic vibration system is, wherein the size of the excitation current is adjusted by changing the frequency of the excitation voltage to a predetermined value, characterized in that the size of the excitation voltage is detected and the predetermined value of the size of the excitation current in dependence of the size of the excitation voltage is set.
  • a circuit arrangement for operating an ultrasonic vibrator according to the above method with an amplifier having an input and an output, which output provides the excitation voltage and the excitation current for the ultrasonic vibration system, and an oscillator whose frequency at a Control input is adjustable and whose output is connected to the input of the amplifier, and a current sensor, for detecting the excitation current, characterized in that a voltage sensor is present, for detecting the excitation voltage.
  • the predetermined value to which the excitation current is to be set can be determined as a function of the size of the excitation voltage. As a result, a correction which is dependent on a change in the exciter voltage can be carried out during the excitation current.
  • an exciting current deviating from the previous excitation current and adjusted to the changed excitation voltage can be set, in which the oscillation amplitude of the ultrasonic oscillator has the same value as it had at the preceding values of the excitation voltage and the exciter current. It can thus be taken into account the fact that the dependence of the oscillation amplitude of the ultrasonic vibrator is frequency-dependent on the exciting current. Because it has been shown that the oscillation amplitude of the ultrasonic vibrator changes when the operating frequency changes, although the excitation current is kept constant.
  • the excitation current can thus be kept constant by changing the frequency to a predetermined value. That is, even when using the inventive method, the exciting current can be controlled by changing the frequency.
  • One way to carry out the method according to the invention is to detect the deviation of the excitation voltage from its desired value and to determine in an empirically derived table such a change in the operating frequency, which would be required to flow the same exciting current through the ultrasonic vibration system, as he flowed before the change of excitation voltage through the ultrasonic vibration system.
  • Another empirically derived table can then be found the value of the excitation current, which is required so that the oscillation amplitude of the ultrasonic vibrator at the changed operating frequency has the same value as it was before changing the excitation voltage or before changing the original operating frequency.
  • This new value of the excitation current thus obtained can then form the setpoint to which the excitation current is regulated at the changed excitation voltage.
  • the new desired value of the exciter current can also be determined by means of a calculation algorithm. It should be noted, however, that the calculation algorithm must always be adapted to the actual existing ultrasonic oscillator.
  • the single figure shows a schematic representation of a circuit arrangement according to the invention.
  • an ultrasonic oscillation system 1 of an ultrasonic welding apparatus consisting of the ultrasonic oscillator and components which complement it to form a resonant circuit is connected to the output 2b of an amplifier 2.
  • the amplifier 2 has a mains input 2c, by means of which the amplifier 2 is connected to a power supply network.
  • the input 2a of the amplifier 2 is connected to the output 3b of an oscillator 3.
  • the frequency of the oscillator 3 can be adjusted at a control input 3a.
  • the adjustable frequency range extends from about 15 kilohertz to 70 kilohertz.
  • the control input 3a of the oscillator 3 is connected to the output 7c of a second comparison element 7, which has a first input 7a and a second input 7b.
  • the second input 7b of the second comparison element 7 is connected to the output of a current sensor 4, which detects the output current I of the amplifier 2 and thus the excitation current I of the ultrasonic vibration system 1.
  • the first input 7a of the second comparison element 7 is with the output 6c of a firstticianselements 6, which has a first input 6a and a second input 6b connected.
  • the second input 6b of the first comparison element 6 is connected to the output 5b "of a second signal generator 5" designed as a memory 5.
  • the input 5a “of the second signal generator 5" is connected to the output 5b 'of a first signal generator 5' designed as a memory
  • the input 5a 'of the first signal generator 5' is connected to the output of a voltage sensor 5, which detects the output voltage U of the amplifier 2 and thus the excitation voltage U of the ultrasonic vibration system 1.
  • the first input 6a of the first comparison element 6 is connected to a setpoint generator 8.
  • the setpoint generator 8 supplies a signal for setting the desired value of the frequency of the oscillator 3.
  • the excitation voltage U of the ultrasonic vibration system 1 Decreases, for example due to a fluctuation of the power supply system, the excitation voltage U of the ultrasonic vibration system 1, the excitation current I of the ultrasonic vibration system 1 decreases. This has the consequence that the output voltage of the secondticianselements 7 decreases, with the result that reduces the frequency of the oscillator 3. Since the ultrasonic vibration system 1 has a lower impedance at the reduced frequency, the exciting current I of the ultrasonic vibration system 1 increases again. The excitation current I of the ultrasonic vibration system 1 increases until it has reached its previous value except for one control deviation.
  • the voltage sensor 5 detects the reduced excitation voltage and outputs this value to the input 5a 'of the first signal generator 5'.
  • the first signal generator 5 'outputs at its output 5b' a signal FK which corresponds to the value by which the frequency of the oscillator 3 would have to be reduced so that the exciting current returns to its previous one Value achieved.
  • the value of the output signal FK essentially corresponds to the frequency change described above. However, it is free of influences which could result from other disturbances and would result in an additional frequency change.
  • the output signal FK of the first signal generator 5 ' is applied to the input 5a "of the second signal generator 5", in which correction values are stored, by means of which the additional dependence of the oscillation amplitude of the ultrasonic oscillator 1 on the frequency can be compensated. That is, the second signal generator 5 "outputs at its output 5b" a signal whose magnitude corresponds to the value by which the excitation current I must be changed so that the oscillation amplitude of the ultrasonic vibrator 1 at the new operating frequency has the same value as at the previous frequency, ie at the frequency that had the excitation voltage U before their change. To this value, the output signal of the setpoint generator 8 is changed in the first predicate 6, whereby the subordinate current control receives a new setpoint. As a result, an excitation current sets in with the changed excitation voltage, which produces the same oscillation amplitude in the case of the ultrasonic oscillator 1 as it was present before the excitation voltage U was changed.

Abstract

The method involves using a resonant circuit in supplying energizing current and excitation voltage (U) to the ultrasonic oscillator (1) included in an existing ultrasonic oscillation system. The frequency of the resonant circuit is set outside of the resonant frequency of the ultrasonic oscillation system, and can be set and adjusted by changing size of the energizing current and changing the frequency of the excitation voltage to predetermined value. The size of the energizing current depends on the size of the excitation voltage. An independent claim is included for the switching configuration used in operating an ultrasonic oscillator.

Description

Die Erfindung betrifft ein Verfahren nach dem Oberbegriff des Anspruchs 1, zum Betreiben eines Ultraschall-Schwingers mit konstanter Schwingungsamplitude, bei welchem an ein aus dem Ultraschall-Schwinger und diesen zu einem Schwingkreis ergänzenden Komponenten bestehenden Ultraschall-Schwingsystem zur Erzeugung eines Erregerstroms eine Erregerspannung angelegt wird, deren Frequenz außerhalb einer Resonanzfrequenz des Schwingsystems liegt, wobei die Größe des Erregerstroms durch Verändern der Frequenz eingestellt wird.The invention relates to a method according to the preamble of claim 1, for operating an ultrasonic vibrator with a constant oscillation amplitude, in which an excitation voltage is applied to an ultrasonic oscillation system for generating an exciter current comprising a component consisting of the ultrasonic oscillator and this resonant circuit whose frequency is outside a resonant frequency of the oscillating system, wherein the size of the exciting current is adjusted by changing the frequency.

Des Weiteren betrifft die Erfindung eine Schaltungsanordnung nach dem Oberbegriff des Anspruchs 3, zum Betreiben eines Ultraschall-Schwingers nach dem zuvor genannten Verfahren, mit einem Verstärker mit einem Eingang und einem Ausgang, welcher Ausgang die Erregerspannung sowie den Erregerstrom für das Ultraschall-Schwingsystem liefert, und einem Oszillator, dessen Frequenz an einem Steuereingang einstellbar ist und dessen Ausgang mit dem Eingang des Verstärkers verbunden ist, sowie einem Stromsensor, zur Erfassung des Erregerstroms.Furthermore, the invention relates to a circuit arrangement according to the preamble of claim 3, for operating an ultrasonic vibrator according to the aforementioned method, with an amplifier having an input and an output, which output supplies the excitation voltage and the exciting current for the ultrasonic vibration system, and an oscillator whose frequency is adjustable at a control input and whose output is connected to the input of the amplifier, and a current sensor for detecting the excitation current.

Ein derartiges Verfahren sowie eine derartige Schaltungsanordnung sind im Stand der Technik hinlänglich bekannt und werden beispielsweise bei von der Patentanmelderin hergestellten und vertriebenen Ultraschallschweißgeräten angewandt beziehungsweise verwendet.Such a method and such a circuit arrangement are well known in the art and are used or used, for example, in ultrasonic welding machines manufactured and sold by the patent applicant.

Bei Ultraschallschweißgeräten ist es erforderlich, dass der Energieeintrag in ein betreffendes Werkstück konstant ist. Es ist somit insbesondere bei Ultraschallschweißgeräten erforderlich, dass die Schwingungsamplitude des Ultraschall-Schwingers konstant ist. Denn der Energieeintrag in ein betreffendes Werkstück hängt von der Schwingungsamplitude ab, die der Schweißkopf ausführt, was heißt, der Energieeintrag in ein betreffendes Werkstück hängt von der Schwingungsamplitude ab, die der Ultraschall-Schwinger ausführt. Da die Schwingungsamplitude des Ultraschall-Schwingers vom Erregerstrom des aus dem Ultraschall-Schwinger und diesen zu einem Schwingkreis ergänzenden Komponenten bestehenden Ultraschall-Schwingsystems abhängt, wird die Schwingungsamplitude des Ultraschall-Schwingers dadurch konstant gehalten, dass der Erregerstrom des Ultraschall-Schwingsystems konstant gehalten wird.In ultrasonic welders, it is necessary that the energy input to a respective workpiece is constant. It is thus necessary in particular for ultrasonic welding equipment, that the oscillation amplitude of the ultrasonic vibrator is constant. For the energy input into a respective workpiece depends on the oscillation amplitude which the welding head carries out, which means that the energy input into a respective workpiece depends on the oscillation amplitude from which the ultrasonic vibrator performs. Since the oscillation amplitude of the ultrasonic oscillator depends on the excitation current of the ultrasonic oscillator consisting of the ultrasonic oscillator and components that complement it, the oscillation amplitude of the ultrasonic oscillator is kept constant by keeping the exciting current of the ultrasonic oscillating system constant.

Um den Erregerstrom steuem zu können, wird das Ultraschall-Schwingsystem nicht in seiner Serienresonanz betrieben sondem regelmäßig mit einer Frequenz, die zwischen der Serienresonanz und der Parallelresonanz des Ultraschall-Schwingsystems liegt. Da sich durch Verändern der Frequenz, mit der das Ultraschall-Schwingsystem betrieben wird, die Impedanz des Ultraschall-Schwingers ändert, lässt sich durch Verändern der Betriebsfrequenz des Ultraschall-Schwingsystems der Strom durch das Ultraschall-Schwingsystem verändem.In order to control the excitation current, the ultrasonic vibration system is not operated in its series resonance but regularly with a frequency that is between the series resonance and the parallel resonance of the ultrasonic vibration system. Since changing the frequency with which the ultrasonic vibration system is operated, the impedance of the ultrasonic vibrator changes, by changing the operating frequency of the ultrasonic vibration system, the current through the ultrasonic vibration system can be changed.

Ändert sich während des Betriebs des Ultraschall-Schwingsystems beispielsweise aufgrund äußerer Einflüsse der Strom durch das Ultraschall-Schwingsystem, wird die Frequenz der an das Ultraschall-Schwingsystem angelegten Erregerspannung solange verändert, bis der Erregerstrom des Ultraschall-Schwingsystems wieder seinen vorhergehenden Wert erreicht hat.If, during operation of the ultrasound oscillation system, the current through the ultrasound oscillation system changes, for example because of external influences, the frequency of the exciter voltage applied to the ultrasound oscillation system is changed until the exciter current of the ultrasound oscillation system has again reached its previous value.

Es hat sich jedoch herausgestellt, dass trotz einer qualitativ hochwertigen Regelung des Erregerstroms auf einen konstanten Wert die Schwingungsamplitude des Ultraschall-Schwingers Abweichungen aufweist.However, it has been found that, despite a high-quality control of the exciter current to a constant value, the oscillation amplitude of the ultrasonic oscillator has deviations.

Es ist Aufgabe der Erfindung, ein eingangs genanntes Verfahren beziehungsweise eine eingangs genannte Schaltungsanordnung derart auszubilden, dass die Konstanz der Schwingungsamplitude verbessert ist.It is an object of the invention to form an initially mentioned method or a circuit arrangement mentioned in such a way that the constancy of the oscillation amplitude is improved.

Die Lösung dieser Aufgabe ergibt sich aus den Merkmalen des kennzeichnenden Teils des Anspruchs 1 beziehungsweise 3. Vorteilhafte Weiterbildungen der Erfindung ergeben sich aus den Unteransprüchen.The solution of this problem arises from the features of the characterizing part of claim 1 and 3. Advantageous developments of the invention will become apparent from the dependent claims.

Gemäß der Erfindung ist ein Verfahren zum Betreiben eines Ultraschall-Schwingers mit konstanter Schwingungsamplitude, bei welchem an aus dem Ultraschall-Schwinger und diesen zu einem Schwingkreis ergänzenden Komponenten bestehenden Ultraschall-Schwingsystem zur Erzeugung eines Erregerstroms eine Erregerspannung angelegt wird, deren Frequenz außerhalb einer Resonanzfrequenz des Ultraschall-Schwingsystems liegt, wobei die Größe des Erregerstroms durch Verändern der Frequenz der Erregerspannung auf einen vorbestimmten Wert eingestellt wird, dadurch gekennzeichnet, dass die Größe der Erregerspannung erfasst wird und der vorbestimmte Wert der Größe des Erregerstromes in Abhängigkeit der Größe der Erregerspannung festgelegt wird.According to the invention, a method for operating an ultrasonic vibrator having a constant oscillation amplitude, wherein at which from the ultrasonic oscillator and this to a resonant complementary components existing ultrasonic oscillating system for generating an excitation current, an excitation voltage is applied, whose frequency is outside a resonant frequency of the Ultrasonic vibration system is, wherein the size of the excitation current is adjusted by changing the frequency of the excitation voltage to a predetermined value, characterized in that the size of the excitation voltage is detected and the predetermined value of the size of the excitation current in dependence of the size of the excitation voltage is set.

Des Weiteren ist gemäß der Erfindung eine Schaltungsanordnung zum Betreiben eines Ultraschall-Schwingers nach dem vorstehenden Verfahren mit einem Verstärker mit einem Eingang und einem Ausgang, welcher Ausgang die Erregerspannung sowie den Erregerstrom für das Ultraschall-Schwingsystem liefert, und einem Oszillator, dessen Frequenz an einem Steuereingang einstellbar ist und dessen Ausgang mit dem Eingang des Verstärkers verbunden ist, sowie einem Stromsensor, zur Erfassung des Erregerstroms, dadurch gekennzeichnet, dass ein Spannungssensor vorhanden ist, zur Erfassung der Erregerspannung.Furthermore, according to the invention, a circuit arrangement for operating an ultrasonic vibrator according to the above method with an amplifier having an input and an output, which output provides the excitation voltage and the excitation current for the ultrasonic vibration system, and an oscillator whose frequency at a Control input is adjustable and whose output is connected to the input of the amplifier, and a current sensor, for detecting the excitation current, characterized in that a voltage sensor is present, for detecting the excitation voltage.

Dadurch, dass die Größe der Erregerspannung erfasst werden kann, lässt sich der vorbestimmte Wert, auf den der Erregerstrom eingestellt werden soll, in Abhängigkeit der Größe der Erregerspannung festlegen. Hierdurch lässt sich beim Erregerstrom eine von einer Änderung der Erregerspannung abhängige Korrektur vornehmen.Because the size of the excitation voltage can be detected, the predetermined value to which the excitation current is to be set can be determined as a function of the size of the excitation voltage. As a result, a correction which is dependent on a change in the exciter voltage can be carried out during the excitation current.

So kann bei einer beispielsweise aufgrund einer Netzspannungsschwankung veränderten Erregerspannung ein an die veränderte Erregerspannung angepasster vom bisherigen Erregerstrom abweichender Erregerstrom eingestellt werden, bei welchem die Schwingungsamplitude des Ultraschall-Schwingers denselben Wert hat, den sie bei den vorhergehenden Werten der Erregerspannung und des Erregerstroms gehabt hat. Es kann somit dem Umstand Rechnung getragen werden, dass die Abhängigkeit der Schwingungsamplitude des Ultraschall-Schwingers vom Erregerstrom frequenzabhängig ist. Denn es hat sich gezeigt, dass sich die Schwingungsamplitude des Ultraschall-Schwingers bei Änderung der Betriebsfrequenz ändert, obwohl der Erregerstrom konstant gehalten wird.Thus, in the case of an excitation voltage changed, for example, due to a mains voltage fluctuation, an exciting current deviating from the previous excitation current and adjusted to the changed excitation voltage can be set, in which the oscillation amplitude of the ultrasonic oscillator has the same value as it had at the preceding values of the excitation voltage and the exciter current. It can thus be taken into account the fact that the dependence of the oscillation amplitude of the ultrasonic vibrator is frequency-dependent on the exciting current. Because it has been shown that the oscillation amplitude of the ultrasonic vibrator changes when the operating frequency changes, although the excitation current is kept constant.

Durch die Abhängigkeit des Sollwerts des Erregerstroms von der Größe der Erregerspannung lassen sich diese Abweichungen auch bei einem auf einen Konstantwert geregelten Erregerstrom korrigieren. In vorteilhafter Weise kann der Erregerstrom somit durch Verändern der Frequenz auf einem vorbestimmten Wert konstant gehalten werden. Das heißt, auch bei Anwendung des erfindungsgemä-ßen Verfahrens lässt sich der Erregerstrom durch Verändern der Frequenz regeln.As a result of the dependence of the setpoint value of the excitation current on the size of the excitation voltage, these deviations can also be corrected in the case of an excitation current regulated to a constant value. Advantageously, the excitation current can thus be kept constant by changing the frequency to a predetermined value. That is, even when using the inventive method, the exciting current can be controlled by changing the frequency.

Eine Möglichkeit zur Durchführung des erfindungsgemäßen Verfahrens besteht darin, die Abweichung der Erregerspannung von ihrem Sollwert zu erfassen und in einer empirisch gewonnenen Tabelle eine solche Änderung der Betriebsfrequenz zu ermitteln, die erforderlich wäre, denselben Erregerstrom durch das Ultraschall-Schwingsystem fließen zu lassen, wie er vor der Veränderung der Erregerspannung durch das Ultraschall-Schwingsystem geflossen ist. Einer weiteren empirisch gewonnenen Tabelle lässt sich dann der Wert des Erregerstroms entnehmen, der erforderlich ist, damit die Schwingungsamplitude des Ultraschall-Schwingers bei der geänderten Betriebsfrequenz denselben Wert hat, wie er vor Veränderung der Erregerspannung beziehungsweise vor Änderung der ursprünglichen Betriebsfrequenz vorhanden war. Dieser so gewonnene neue Wert des Erregerstroms kann dann den Sollwert bilden, auf den der Erregerstrom bei der veränderten Erregerspannung geregelt wird.One way to carry out the method according to the invention is to detect the deviation of the excitation voltage from its desired value and to determine in an empirically derived table such a change in the operating frequency, which would be required to flow the same exciting current through the ultrasonic vibration system, as he flowed before the change of excitation voltage through the ultrasonic vibration system. Another empirically derived table can then be found the value of the excitation current, which is required so that the oscillation amplitude of the ultrasonic vibrator at the changed operating frequency has the same value as it was before changing the excitation voltage or before changing the original operating frequency. This new value of the excitation current thus obtained can then form the setpoint to which the excitation current is regulated at the changed excitation voltage.

Selbstverständlich lässt sich der neue Sollwert des Erregerstroms auch mittels eines Rechenalgorithmus bestimmen. Es ist jedoch zu beachten, dass der Rechenalgorithmus jeweils an den tatsächlich vorhandenen Ultraschall-Schwinger angepasst werden muss.Of course, the new desired value of the exciter current can also be determined by means of a calculation algorithm. It should be noted, however, that the calculation algorithm must always be adapted to the actual existing ultrasonic oscillator.

Nachfolgend sind Ausführungsbeispiele der Erfindung anhand der Zeichnung näher erläutert.Embodiments of the invention are explained in more detail with reference to the drawing.

Es zeigt die einzige Figur eine schematische Darstellung einer erfindungsgemäßen Schaltungsanordnung.The single figure shows a schematic representation of a circuit arrangement according to the invention.

Wie der Figur entnommen werden kann, ist ein aus dem Ultraschall-Schwinger und diesen zu einem Schwingkreis ergänzenden Komponenten bestehendes Ultraschall-Schwingsystem 1 eines Ultraschall-Schweißgeräts mit dem Ausgang 2b eines Verstärkers 2 verbunden. Zur Stromversorgung weist der Verstärker 2 einen Netzeingang 2c auf, mittels welchem der Verstärker 2 mit einem Stromversorgungsnetz verbunden ist. Der Eingang 2a des Verstärkers 2 ist mit dem Ausgang 3b eines Oszillators 3 verbunden. Die Frequenz des Oszillators 3 lässt sich an einem Steuereingang 3a einstellen. Der einstellbare Frequenzbereich erstreckt sich von etwa 15 Kilohertz bis 70 Kilohertz.As can be seen from the figure, an ultrasonic oscillation system 1 of an ultrasonic welding apparatus consisting of the ultrasonic oscillator and components which complement it to form a resonant circuit is connected to the output 2b of an amplifier 2. For the power supply, the amplifier 2 has a mains input 2c, by means of which the amplifier 2 is connected to a power supply network. The input 2a of the amplifier 2 is connected to the output 3b of an oscillator 3. The frequency of the oscillator 3 can be adjusted at a control input 3a. The adjustable frequency range extends from about 15 kilohertz to 70 kilohertz.

Der Steuereingang 3a des Oszillators 3 ist mit dem Ausgang 7c eines zweiten Vergleichselements 7, welches einen ersten Eingang 7a und einen zweiten Eingang 7b hat, verbunden. Der zweite Eingang 7b des zweiten Vergleichselements 7 ist mit dem Ausgang eines Stromsensors 4, welcher den Ausgangsstrom I des Verstärkers 2 und somit den Erregerstrom I des Ultraschall-Schwingsystems 1 erfasst, verbunden. Der erste Eingang 7a des zweiten Vergleichselements 7 ist mit dem Ausgang 6c eines ersten Vergleichselements 6, welches einen ersten Eingang 6a und einen zweiten Eingang 6b hat, verbunden.The control input 3a of the oscillator 3 is connected to the output 7c of a second comparison element 7, which has a first input 7a and a second input 7b. The second input 7b of the second comparison element 7 is connected to the output of a current sensor 4, which detects the output current I of the amplifier 2 and thus the excitation current I of the ultrasonic vibration system 1. The first input 7a of the second comparison element 7 is with the output 6c of a first Vergleichselements 6, which has a first input 6a and a second input 6b connected.

Der zweite Eingang 6b des ersten Vergleichselements 6 ist mit dem Ausgang 5b" eines als Speicher 5" ausgebildeten zweiten Signalbildners 5" verbunden. Der Eingang 5a" des zweiten Signalbildners 5" ist mit dem Ausgang 5b' eines als Speicher ausgebildeten ersten Signalbildners 5' verbunden. Der Eingang 5a' des ersten Signalbildners 5' ist mit dem Ausgang eines Spannungssensors 5 verbunden, welcher die Ausgangsspannung U des Verstärkers 2 und somit die Erregerspannung U des Ultraschall-Schwingsystems 1 erfasst.The second input 6b of the first comparison element 6 is connected to the output 5b "of a second signal generator 5" designed as a memory 5. The input 5a "of the second signal generator 5" is connected to the output 5b 'of a first signal generator 5' designed as a memory The input 5a 'of the first signal generator 5' is connected to the output of a voltage sensor 5, which detects the output voltage U of the amplifier 2 and thus the excitation voltage U of the ultrasonic vibration system 1.

Der erste Eingang 6a des ersten Vergleichselements 6 ist mit einem Sollwertgeber 8 verbunden. Der Sollwertgeber 8 liefert ein Signal zur Einstellung des Sollwerts der Frequenz des Oszillators 3.The first input 6a of the first comparison element 6 is connected to a setpoint generator 8. The setpoint generator 8 supplies a signal for setting the desired value of the frequency of the oscillator 3.

Verringert sich beispielsweise aufgrund einer Schwankung des Stromversorgungsnetzes die Erregerspannung U des Ultraschall-Schwingsystems 1, verringert sich der Erregerstrom I des Ultraschall-Schwingsystems 1. Dies hat zur Folge, dass sich die Ausgangsspannung des zweiten Vergleichselements 7 verringert, was zur Folge hat, dass sich die Frequenz des Oszillators 3 verringert. Da das Ultraschall-Schwingsystem 1 bei der verringerten Frequenz eine niedrigere Impedanz hat, steigt der Erregerstrom I des Ultraschall-Schwingsystems 1 wieder an. Der Erregerstrom I des Ultraschall-Schwingsystems 1 steigt solange an, bis er bis auf eine Regelabweichung wieder seinen vorhergehenden Wert erreicht hat.Decreases, for example due to a fluctuation of the power supply system, the excitation voltage U of the ultrasonic vibration system 1, the excitation current I of the ultrasonic vibration system 1 decreases. This has the consequence that the output voltage of the second Vergleichselements 7 decreases, with the result that reduces the frequency of the oscillator 3. Since the ultrasonic vibration system 1 has a lower impedance at the reduced frequency, the exciting current I of the ultrasonic vibration system 1 increases again. The excitation current I of the ultrasonic vibration system 1 increases until it has reached its previous value except for one control deviation.

Der Spannungssensor 5 erfasst aber gleichzeitig die verringerte Erregerspannung und gibt diesen Wert auf den Eingang 5a' des ersten Signalbildners 5'. Abhängig von diesem Wert gibt der erste Signalbildner 5' an seinem Ausgang 5b' ein Signal FK aus, welches dem Wert entspricht, um den die Frequenz des Oszillators 3 verringert werden müsste, damit der Erregerstrom wieder seinen vorhergehenden Wert erreicht. Der Wert des Ausgangssignals FK entspricht im Wesentlichen der zuvor beschriebenen Frequenzänderung. Jedoch ist er frei von Einflüssen, welche sich aufgrund anderer Störgrößen ergeben könnten und eine zusätzliche Frequenzänderung zur Folge haben würden.At the same time, the voltage sensor 5 detects the reduced excitation voltage and outputs this value to the input 5a 'of the first signal generator 5'. Depending on this value, the first signal generator 5 'outputs at its output 5b' a signal FK which corresponds to the value by which the frequency of the oscillator 3 would have to be reduced so that the exciting current returns to its previous one Value achieved. The value of the output signal FK essentially corresponds to the frequency change described above. However, it is free of influences which could result from other disturbances and would result in an additional frequency change.

Das Ausgangssignal FK des ersten Signalbildners 5' wird auf den Eingang 5a" des zweiten Signalbildners 5" gegeben, in welchem Korrekturwerte gespeichert sind, mittels welcher die zusätzliche Abhängigkeit der Schwingungsamplitude des Ultraschall-Schwingers 1 von der Frequenz ausgeglichen werden kann. Das heißt, der zweite Signalbildner 5" gibt an seinem Ausgang 5b" ein Signal aus, dessen Größe dem Wert entspricht, um den der Erregerstrom I geändert werden muss, damit die Schwingungsamplitude des Ultraschall-Schwingers 1 bei der neuen Betriebsfrequenz denselben Wert hat wie bei der vorhergehenden Frequenz, also bei der Frequenz, die die Erregerspannung U vor ihrer Veränderung hatte. Um diesen Wert wird das Ausgangssignal des Sollwertgebers 8 im ersten Vergleichselement 6 verändert, wodurch die unterlagerte Stromregelung einen neuen Sollwert erhält. Hierdurch stellt sich bei der veränderten Erregerspannung ein Erregerstrom ein, welcher beim Ultraschall-Schwinger 1 dieselbe Schwingungsamplitude erzeugt, wie sie vor Veränderung der Erregerspannung U vorhanden war.The output signal FK of the first signal generator 5 'is applied to the input 5a "of the second signal generator 5", in which correction values are stored, by means of which the additional dependence of the oscillation amplitude of the ultrasonic oscillator 1 on the frequency can be compensated. That is, the second signal generator 5 "outputs at its output 5b" a signal whose magnitude corresponds to the value by which the excitation current I must be changed so that the oscillation amplitude of the ultrasonic vibrator 1 at the new operating frequency has the same value as at the previous frequency, ie at the frequency that had the excitation voltage U before their change. To this value, the output signal of the setpoint generator 8 is changed in the first predicate 6, whereby the subordinate current control receives a new setpoint. As a result, an excitation current sets in with the changed excitation voltage, which produces the same oscillation amplitude in the case of the ultrasonic oscillator 1 as it was present before the excitation voltage U was changed.

Claims (7)

Verfahren zum Betreiben eines Ultraschall-Schwingers (1) mit konstanter Schwingungsamplitude, bei welchem an aus dem Ultraschall-Schwinger und diesen zu einem Schwingkreis ergänzenden Komponenten bestehenden Ultraschall-Schwingsystem (1) zur Erzeugung eines Erregerstroms (I) eine Erregerspannung (U) angelegt wird, deren Frequenz außerhalb einer Resonanzfrequenz des Ultraschall-Schwingsystems liegt, wobei die Größe des Erregerstroms (I) durch Verändern der Frequenz der Erregerspannung (U) auf einen vorbestimmten Wert eingestellt wird,
dadurch gekennzeichnet,
dass die Größe der Erregerspannung (U) erfasst wird und der vorbestimmte Wert der Größe des Erregerstromes (I) in Abhängigkeit der Größe der Erregerspannung (U) festgelegt wird.
Method for operating an ultrasonic oscillator (1) having a constant oscillation amplitude, in which an excitation voltage (U) is applied to an ultrasonic oscillation system (1) for generating an exciter current (I) from the ultrasonic oscillator and components that complement it whose frequency is outside a resonance frequency of the ultrasonic vibration system, wherein the size of the exciting current (I) is adjusted to a predetermined value by changing the frequency of the exciting voltage (U),
characterized,
that the magnitude of the excitation voltage (U) is detected and the predetermined value of the magnitude of the excitation current (I) depending on the magnitude of the excitation voltage (U) is determined.
Verfahren nach Anspruch 1,
dadurch gekennzeichnet,
dass die Größe des Erregerstroms (I) durch Verändern der Frequenz auf dem vorbestimmten Wert konstant gehalten wird.
Method according to claim 1,
characterized,
that the size of the excitation current (I) is kept constant by changing the frequency at the predetermined value.
Schaltungsanordnung zum Betreiben eines Ultraschall-Schwingers (1) nach einem Verfahren gemäß einem der vorstehenden Ansprüche, mit einem Verstärker (2) mit einem Eingang (2a) und einem Ausgang (2b), welcher Ausgang (2b) die Erregerspannung sowie den Erregerstrom für das Ultraschall-Schwingsystem (1) liefert, und einem Oszillator (3), dessen Frequenz an einem Steuereingang (3a) einstellbar ist und dessen Ausgang (3b) mit dem Eingang (2a) des Verstärkers (2) verbunden ist, sowie einem Stromsensor (4), zur Erfassung des Erregerstroms (I),
dadurch gekennzeichnet,
dass ein Spannungssensor (5) vorhanden ist, zur Erfassung der Erregerspannung (U).
Circuit arrangement for operating an ultrasonic vibrator (1) according to a method according to one of the preceding claims, comprising an amplifier (2) having an input (2a) and an output (2b), which output (2b) the excitation voltage and the exciting current for the Ultrasonic vibration system (1) provides, and an oscillator (3) whose frequency at a control input (3a) is adjustable and whose output (3b) to the input (2a) of the amplifier (2) is connected, and a current sensor (4 ), for detecting the excitation current (I),
characterized,
that a voltage sensor (5) is provided for detecting the excitation voltage (U).
Schaltungsanordnung nach Anspruch 3,
dadurch gekennzeichnet,
dass ein erstes Vergleichselement (6) vorhanden ist, mit einem ersten Eingang (6a), welcher mit einem Sollwertgeber (8) verbunden ist, und einem zweiten Eingang (6b), welcher mit dem Spannungssensor (5) verbunden ist, sowie einem Ausgang (6c), welcher mit dem Steuereingang (3a) des Oszillators (3) verbunden ist.
Circuit arrangement according to Claim 3,
characterized,
in that a first comparison element (6) is present, having a first input (6a) which is connected to a nominal value transmitter (8) and a second input (6b) which is connected to the voltage sensor (5) and an output ( 6c) which is connected to the control input (3a) of the oscillator (3).
Schaltungsanordnung nach Anspruch 4,
dadurch gekennzeichnet,
dass ein erster Signalbildner (5') vorhanden ist, mittels welchem aus dem Ausgangssignal des Spannungssensors (5) ein erster Korrekturwert (FK) bildbar ist.
Circuit arrangement according to Claim 4,
characterized,
that a first signal conditioner (5 ') is present, by means of which from the output signal of the voltage sensor (5) a first correction value (FK) can be formed.
Schaltungsanordnung nach Anspruch 5,
dadurch gekennzeichnet,
dass ein zweiter Signalbildner (5") vorhanden ist, mittels welchem aus dem ersten Korrekturwert (FK) ein zweiter Korrekturwert (UK) bildbar ist.
Circuit arrangement according to Claim 5,
characterized,
that a second signal conditioner (5 ') is provided, by means of which from the first correction value (FK) a second correction value (UK) can be formed.
Schaltungsanordnung nach einem der Ansprüche 4 bis 6,
dadurch gekennzeichnet,
dass zweites Vergleichselement (7) vorhanden ist, mit einem ersten Eingang (7a), welcher mit dem Ausgang (6c) des ersten Vergleichselements (6) verbunden ist, und einem zweiten Eingang (7b), welcher mit dem Stromsensor (4) verbunden ist, sowie einem Ausgang (7c), welcher mit dem Steuereingang (3a) des Oszillators (3) verbunden ist.
Circuit arrangement according to one of Claims 4 to 6,
characterized,
in that second comparison element (7) is present, having a first input (7a) which is connected to the output (6c) of the first comparison element (6), and a second input (7b) which is connected to the current sensor (4) , and an output (7c) which is connected to the control input (3a) of the oscillator (3).
EP06013099A 2005-07-01 2006-06-26 Method and circuit arrangement for driving an ultrasonic vibrator Withdrawn EP1738837A3 (en)

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JP2007007649A (en) 2007-01-18
DE102005030777B4 (en) 2016-10-20
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US7345401B2 (en) 2008-03-18
EP1738837A3 (en) 2009-06-03

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