JPH05329442A - Ultrasonic generator - Google Patents

Abstract

PURPOSE:To maintain the conjugate matching of a piezoelectric vibrator to be driven at a resonance frequency by the driving power of a driving circuit with the driving circuit in spite of a change in the resonance frequency of the piezoelectric vibrator of the ultrasonic generator which attains the conjugate matching by compensating the self-capacitance of the piezoelectric vibrator with an inductance. CONSTITUTION:The indutance is formed by the primary coil of an indictor 7 and a conjugate matching means 12 for energizing a DC current variable in a current value is connected to a secondary coil 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic wave generator for driving a piezoelectric vibrator of an ultrasonic wave application device such as an ultrasonic welder or an ultrasonic processing machine at a resonance frequency.

[0002]

2. Description of the Related Art Generally, an ultrasonic wave generator for oscillating a vibrator of an ultrasonic wave application device by ultrasonic waves has a sharpness Q of resonance characteristics.
In order to increase the operating efficiency of the vibrator having a large value, the vibrator is driven at the resonance frequency. However, in such an ultrasonic generator, when the horn or tool connected to the vibrator is replaced, temperature changes, load fluctuations, etc. occur, the resonance frequency of the vibrator changes and it deviates from the drive frequency, resulting in operational efficiency. Therefore, the oscillation frequency of the driving power of the oscillator is generally set to the PLL (Phase Locked
The loop-type automatic tracking circuit controls tracking to the resonance frequency. The automatic tracking circuit of such an ultrasonic generator is, for example, a VC whose oscillation frequency is variable in a drive circuit.
It is formed of O (Voltage Controlled Oscillator) or the like, and one of the drive voltage and drive current of the oscillator and the detection signal proportional to the oscillation speed of the oscillator have a constant relative phase so that the oscillator has a constant relative phase. The oscillation frequency of the driving power source is tracked and controlled.

Here, a piezoelectric vibrator or the like has been put into practical use as the above-mentioned vibrator, but since it has a capacitive characteristic, if it is driven by a constant voltage power supply as it is, the power factor of the circuit becomes "1". ", And power is not effectively transmitted. Therefore, as has been widely used in the past and is well-known, the inductors are connected in series to compensate for the self-capacitance of the piezoelectric vibrator, thereby realizing mutual matching. By doing so, the phase of the voltage and the current of the driving power source of the piezoelectric vibrator match and the power factor is improved to "1". Therefore, driving is performed corresponding to the load of the vibration system that vibrates at the resonance frequency. Energy will be satisfactorily transferred to the piezoelectric vibrator.

[0004]

In the ultrasonic generator as described above, the efficiency is improved by driving the piezoelectric vibrator at the resonance frequency with the power factor of the drive circuit set to "1".

However, in an actual ultrasonic wave generator, when the horn or the tool connected to the piezoelectric vibrator is replaced as described above, if there is a large variation in the resonance frequency of the piezoelectric vibrator, the matching with the inductor is achieved. As a result, vibration energy cannot be effectively extracted from the horn or the tool. For example, when the resonance frequency of the vibration system of the ultrasonic wave generator in which the piezoelectric vibrator connected with the horn or the tool and the inductor are matched changes by 10%, the maximum output decreases to about 70%. In other words, in an ultrasonic generator with a resonance frequency of 40 (kHz) and an output of 100 (W) when the vibration system and the inductor are matched, the resonance frequency of the vibration system is 36 (kHz) due to the replacement of the horn or tool. ) Or 44 (kHz), the output will change to 70
It will be reduced to (W).

Incidentally, such a decrease in output is not due to only the mismatch between the piezoelectric vibrator and the inductor,
By modifying these matches, most of them can be recovered.

[0007]

The invention according to claim 1 is
A drive circuit is connected to the piezoelectric vibrator through an inductor for common matching, and the self-capacitance of the piezoelectric vibrator driven at the resonance frequency by the drive power output by the drive circuit is compensated by the inductance of the inductor. In an ultrasonic wave generator that realizes mutual matching, the inductor is formed by a primary coil located on a core,
The secondary coil sharing the core with this inductor is provided with common matching means for supplying a direct current having a variable current value to vary the inductance of the inductor.

According to a second aspect of the present invention, in the first aspect of the present invention, a direct current is applied to the secondary coil of the inductor so that the relative phase between the drive voltage and the drive current output from the drive circuit becomes "0". A common matching means for setting the power factor of the output of the drive circuit to “1” by providing the PLL control of the current is provided.

[0009]

According to the invention described in claim 1, since the power factor can be set to "1" by coherently matching the piezoelectric oscillator and the drive circuit even if the resonance frequency of the piezoelectric oscillator changes, the piezoelectric vibration is generated. It is possible to prevent the output of the child from decreasing and contribute to power saving and efficiency improvement.

According to the second aspect of the present invention, even if the resonance frequency of the piezoelectric vibrator changes, the piezoelectric vibrator and the drive circuit can automatically and coherently match each other, and the power factor can be set to "1". It is possible to prevent a decrease in output of the piezoelectric vibrator and contribute to power saving and efficiency improvement.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the invention described in claim 1 will be described with reference to FIG. First, in this ultrasonic generator 1, the PLL
The drive circuit 5 is formed by connecting the VCO 3 to which the circuit 2 is connected to the power amplifier 4.
Is connected to the piezoelectric vibrator 8 via the output transformer 6 and the inductor 7. Further, in this ultrasonic generator 1, the inductor 7 is formed of a primary coil,
The secondary coil 11 sharing the core 10 with the inductor 7, which is the primary coil, is connected with the common matching means 12 in which the current value of the output DC current is variable. here,
The common matching means 12 has a structure in which an inductor 15 is connected in series to a DC constant current power source 14 in which a capacitor 13 is connected in parallel. The inductor 15 is formed by a coil located on one core 16. Has been done.

In this ultrasonic generator 1, the capacitor 13 is provided so that the high frequency current does not flow into the DC constant current power source 14, and the capacitor 13 is provided.
Functions as a bypass capacitor. In the ultrasonic generator 1, the inductor 15 includes the secondary coil 1 that shares the core 10 with the inductor 7.
Since the voltage generated at 1 is not short-circuited in the DC constant current power source 14, the inductance of the inductor 15 has a sufficiently large value as compared with the inductance of the secondary coil 11.

In the ultrasonic generator 1 having such a structure, for example, an ultrasonic welder or an ultrasonic processing machine in which a plurality of types of horns and tools (neither are shown) are exchangeably connected to the piezoelectric vibrator 8 is used. It has come to be used for. Then, in such an ultrasonic generator 1, when the resonance frequency of the piezoelectric vibrator 8 changes due to replacement of the horn or temperature change, the generation frequency of the drive circuit 5 of the piezoelectric vibrator 8 is tracked to the resonance frequency. It is designed to be controlled.

More specifically, in this ultrasonic wave generator 1, for example, a vibration sensor (not shown) detects the vibration speed of the piezoelectric vibrator 8. The PLL circuit 2 controls the oscillation frequency of the VCO 3 so that the relative phase with the drive current of the vibrator 8 becomes “0”, so that the frequency of the drive power output by the power amplifier 4 is the resonance frequency of the piezoelectric vibrator 8. The tracking is controlled by.

Therefore, the driving power output from the power amplifier 4 is transformed by the output transformer 6 in this way to perform impedance matching with the piezoelectric vibrator 8, and the piezoelectric vibrator 8 is jointly matched by the inductor 7. Will be energized. At this time, in the ultrasonic generator 1, the secondary coil 11 of the inductor 7 is connected to the DC constant current power supply 14 via the inductor 15, and the inductor 7 is DC magnetized by the DC current of the DC constant current power supply 14. Since the inductor 7 superposed with the DC magnetic bias in this way has a stable decrease in inductance.

In the ultrasonic wave generator 1, when the resonance frequency of the piezoelectric vibrator 8 is changed due to the replacement of the horn or the temperature change, the common matching with the drive circuit 5 is hindered.
The inductance of the inductor 7 is adjusted by changing the current value of the DC current output from the DC constant current power supply 14. By doing so, in the ultrasonic generator 1, even if the resonance frequency of the piezoelectric vibrator 8 changes, the inductance of the inductor 7 is changed so that the piezoelectric vibrator 8 and the drive circuit 5 are consistently matched. Since the power factor can be returned to "1", it is possible to prevent a decrease in the output of the piezoelectric vibrator 8 and contribute to power saving and efficiency improvement.

Next, an embodiment of the invention described in claim 2 will be described with reference to FIG. In the ultrasonic wave generator 17 illustrated in this embodiment, the parts other than the common matching means 18 are the same as the ultrasonic wave generator 1 described above as the embodiment of the invention of claim 1, and thus the same parts are used. The same names and reference numerals are used for the parts, and the description is omitted. First, in the common matching means 18 of the ultrasonic generator 17, a phase comparator 20 serving as a phase difference change detecting means is connected to both ends of a secondary coil of the output transformer 6 having a current detecting resistor 19 connected to one end. This phase comparator 20 is integrated with an integrating capacitor 22 and a DC (Direct Current) via an integrating resistor 21.
It is connected to the amplifier 23. The DC amplifier 23 is connected to the offset resistor 24 and the negative terminal of the offset amplifier 25 via a resistor, and the output terminal of the offset amplifier 25 whose input and output are shunted by a feedback resistor is , Constant current amplifier 2
6 is connected to the positive terminal. Further, the output terminal of the constant current amplifier 26 is connected to the base of the power transistor 27, and the emitter of the power transistor 27 is connected to the current detection resistor 28 and is fed back to the negative terminal of the constant current amplifier 26. It is connected. Further, the collector of the power transistor 27 is connected to the capacitor 13 and the inductor 15, and the DC coil 29 is connected to the other end of the secondary coil 11 of the inductor 7 to which the inductor 15 is connected to one end. There is.

In this ultrasonic generator 17, the output value of the DC amplifier 23 is inverted and amplified by the offset amplifier 25 before being input to the constant current amplifier 26. Since the power transistor 27 and the current detection resistor 28 form a constant current control circuit, the current value of the exciting current supplied from the DC power supply 29 to the secondary coil 11 and the inductor 15 of the inductor 7 is The output of the DC amplifier 23 is controlled by the power transistor 27 and the like. Further, in this ultrasonic generator 17, an offset resistor 24 having one end connected to a negative power source (not shown)
By driving the constant current amplifier 26 with the offset voltage generated in the offset amplifier 25, the operation reference point of the DC excitation of the inductor 7 is set.

In such a structure, the ultrasonic wave generator 17 drives the piezoelectric vibrator 8 at the resonance frequency like the ultrasonic wave generator 1 described above, and the resonance of the piezoelectric vibrator 8 occurs. When the frequency changes due to replacement of the horn or temperature change, the generated frequency of the drive circuit 5 is tracked to the resonance frequency, and the drive power output from the drive circuit 5 is controlled by the inductor 7 to automatically control the power factor. The piezoelectric vibrators 8 are energized after they are jointly matched so as to be "1".

Here, in the ultrasonic generator 17, the direct-current exciting current set by the resistance value of the offset resistor 24 as described above is applied to the secondary coil 11 of the inductor 7 to share the core 10 with the inductor 7. If both are matched, the phases of the drive power voltage and the current output from the secondary coil of the output transformer 6 are in phase.

In such a state, the output of the phase comparator 20 is inevitably "0" and the output of the DC amplifier 23 is also "0". Therefore, the current value of the exciting current of the inductor 15 is changed to the power transistor 27. There is no influence on the operation controlled by etc.

Here, in such an ultrasonic generator 17, for example, when the resonance frequency of the piezoelectric vibrator 8 rises due to the replacement of the horn or the temperature change, the drive voltage is changed to the drive voltage at the frequency tracking the resonance frequency. On the other hand, since the drive current is delayed, the voltage generated by the current detection resistor 19 directly connected to the secondary coil of the output transformer 6 and the drive voltage of the secondary coil of the output transformer 6 are relative to each other. A phase difference is generated and detected by the phase comparator 20. Then, the negative output of the phase comparator 20 is integrated by an integrating circuit composed of an integrating resistor 21 and an integrating capacitor 22, and then DC
It is amplified by the amplifier 23. Then, this DC amplifier 23
Since the output voltage of the offset amplifier 25 to which the output value of is input is displaced more positively than the voltage at the operation reference point, the current value supplied to the secondary coil 11 of the inductor 7 increases and the inductance of the inductor 7 decreases. Therefore, in this ultrasonic generator 17, the power factor of the output of the drive circuit 5 is "1".
Returning to, the coherence will be maintained. Further, when the resonance frequency of the piezoelectric vibrator 8 is lowered due to replacement of the horn, temperature change, or the like, the inductance of the inductor 7 increases and the power factor of the drive circuit 5 increases by the operation opposite to that described above. It is designed to return to 1 ".

That is, in the ultrasonic generator 17, when the resonance frequency of the piezoelectric vibrator 8 changes and the power factor of the drive circuit 5 is about to decrease, the direct current flowing through the secondary coil 11 of the inductor 7 is PLL controlled. As a result, the power factor of the output of the drive circuit 5 becomes "1" and the common matching is maintained.

[0024]

According to the first aspect of the present invention, a drive circuit is connected to the piezoelectric vibrator through an inductor for common matching, and the piezoelectric vibration driven by the drive power output from the drive circuit at the resonance frequency. In an ultrasonic generator in which the self-capacitance of a child is compensated by the inductance of the inductor to realize common matching, the inductor is formed by a primary coil located on the core, and the inductor and the core are shared. Since the secondary coil is provided with a common matching means for supplying a direct current having a variable current value to vary the inductance of the inductor, even if the resonance frequency of the piezoelectric vibrator changes, the piezoelectric vibrator and the drive circuit. Since the power factor can be made "1" by coordinating and, it is possible to prevent the output reduction of the piezoelectric vibrator and contribute to power saving and efficiency improvement. Those having an effect equal.

According to a second aspect of the present invention, in the first aspect of the present invention, a direct current is applied to the secondary coil of the inductor so that the relative phase between the drive voltage and the drive current output from the drive circuit becomes "0". By providing the common matching means for setting the power factor of the output of the drive circuit to "1" by controlling the current by the PLL, even if the resonance frequency of the piezoelectric vibrator changes, the piezoelectric vibrator and the drive circuit Automatically adjusts the power factor to "1", which can prevent the output of the piezoelectric vibrator from decreasing and contribute to power saving and efficiency improvement. Is.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the invention described in claim 1.

FIG. 2 is a block diagram showing an embodiment of the invention described in claim 2.

[Explanation of symbols]

 1,17 Ultrasonic wave generator 5 Drive circuit 7 Inductor 8 Piezoelectric vibrator 10 Core 11 Secondary coil 12,18 Shared matching means

Claims (2)

[Claims] 1. A drive circuit is connected to a piezoelectric vibrator through an inductor for common matching, and a self-capacitance of the piezoelectric vibrator driven at a resonance frequency by drive power output from the drive circuit is set to the inductor. In an ultrasonic generator that compensates with an inductance to achieve joint matching, the primary coil located on the core forms the inductor, and the secondary coil sharing the core with the inductor has a variable current value. An ultrasonic wave generator comprising a common matching means for applying a free direct current to vary the inductance of the inductor. 2. The output of the drive circuit is controlled by PLL control of the direct current supplied to the secondary coil of the inductor so that the relative phase between the drive voltage and the drive current output by the drive circuit becomes “0”. The ultrasonic generator according to claim 1, further comprising a common matching means for setting the power factor to "1".