JPH0446870Y2 - - Google Patents

Description

[Detailed description of the invention] (Field of industrial application) This invention relates to the improvement of the setting of the oscillation frequency, which is related to the electro-mechanical conversion efficiency and life of an ultrasonic vibrator (hereinafter simply referred to as a vibrator) of an ultrasonic cleaning machine. .

(Prior Art) Conventionally, as an oscillator for driving a vibrator of an ultrasonic cleaner, a current feedback self-excited oscillator as shown in FIG. 4 has been used. This oscillator returns the secondary current of the output transformer 4 via the current feedback transformer 1 to the bases of the transistors 2 and 2' forming the output amplification section, so that the phase difference between the input and output of the output amplification section is zero. The method was to oscillate at a frequency of .

(Problems to be solved by the invention) However, in this method, the frequency characteristic of the admittance of the electrostrictive vibrator 6 has the characteristic as shown in the vibrator admittance characteristic curve 12 in FIG. 6, and the oscillation conditions are Since this is a case where the matching inductance 5 and the electrostrictive vibrator 6 satisfy the conjugate condition, if the frequency characteristic of the admittance of the matching inductance 5 is shown by the matching inductance admittance characteristic curve 13 in FIG. , point B, and point C are the points that satisfy the condition, and point A, point B,
It will oscillate at one of the C's. Note that Fo and Fr in FIG. 6 are the resonant frequency and anti-resonant frequency of the electrostrictive vibrator, respectively.

On the other hand, a self-excited oscillator has a property of operating so that the loop gain is maximized, and in this case, a large gain means a large output.

As shown in FIG. 5, the output-load resistance characteristic of the output amplifying section shows that the smaller the load resistance, that is, the larger the admittance, the larger the output.

However, the frequency characteristic of the admittance seen on the secondary side of the output transformer 4 is as shown in the output transformer secondary side admittance characteristic curve 14 in Fig. 6, so
A corresponds to point D where the admittance is the largest
It will oscillate at a point. For this reason, point B is the resonant point for the vibrator, and even though the matching inductance 5 is set so that it oscillates at point B, it will oscillate at a frequency that deviates from point B. . As described above, if the electrostrictive vibrator 6 is driven at a frequency that deviates from the resonance point, the electro-mechanical conversion efficiency of the electrostrictive vibrator 6 will be poor, which will not only shorten the life of the electrostrictive vibrator 6 but also reduce the cleaning effect. It's causing things to get worse.

The purpose of the present invention is to solve the problems of the prior art described above by suppressing the output current of the output stage transistor to a predetermined value, thereby matching the resonance frequency unique to the electrostrictive vibrator with the oscillation frequency. The present invention aims to improve the electromechanical conversion efficiency of the vibrator, extend the life of the vibrator, and provide an ultrasonic cleaner with good cleaning effects.

(Means for solving the problems) The present invention has the following means configuration to achieve the above object. That is, the ultrasonic cleaning machine of the present invention includes: a transistor as an output stage; a matching inductance and an electrostrictive vibrator as a load; a current feedback circuit that returns the load current to the base of the output stage transistor; means for detecting an output current of a transistor; a load resistance value that corresponds to a resonant frequency and an anti-resonant frequency of a three-frequency internal electrostrictive resonator such that an admittance of the matching inductance and an admittance of the electrostrictive resonator are in a conjugate relationship; current control that controls the base current of the output stage transistor by the detected current so that the output stage transistor has a load resistance vs. output characteristic in which the output of the output stage transistor becomes maximum when the load resistance value becomes the same as the load resistance value at a frequency between An ultrasonic cleaning machine characterized by comprising a current feedback self-excited oscillator having a transistor circuit for use in the present invention.

(Function) Hereinafter, the function of the ultrasonic cleaning machine of the present invention having the above-described configuration will be described.

Whatever the means, when this device is connected to a power source and starts oscillating upon receiving some kind of transient signal, the oscillation frequency will settle down to point A as described above, and the output current will increase, but the output current will not be detected. The signal obtained by the means is applied to a current control transistor that controls the base current of the output transistor, and when the output current reaches a predetermined value, the current control transistor controls the current supplied to the base of the output stage transistor. decreases, and the output of the output stage transistor does not increase any further.

In other words, the output stage transistor output-load characteristic is the third
As shown in the figure, it does not increase beyond the predetermined value F point.

Therefore, if this point F is set to the impedance corresponding to point B in Fig. 6, the optimum frequency of the electrostrictive vibrator (resonant frequency Fo and anti-resonant frequency Fr) will always be maintained.
The electrostrictive vibrator oscillates at a frequency between 1 and 2, thereby increasing the electromechanical conversion efficiency of the electrostrictive vibrator, operating as an efficient ultrasonic cleaner, and extending the life of the electrostrictive vibrator.

(Example) Hereinafter, an example of the present invention will be described based on the drawings. FIG. 1 is a diagram showing the configuration of an embodiment of the present invention. The output oscillation current is fed back to the output stage transistors 2 and 2' via the current feedback transformer 1.

The output currents of the output stage transistors 2 and 2' are detected by emitter resistors 3 and 3', and are applied to the bases of current control transistors 7 and 7'.

Bias resistors 8 and 8' are selected to set the operating point of the current control transistors 7 and 7'. 11 is a capacitor that serves as a power source when the output stage transistor 2' is on, and 4 is an output transformer that converts and supplies the voltage required to the electrostrictive vibrator 6 while at the same time insulating it from the load.

The oscillation frequency works to maximize the output for the reasons mentioned above, and the output current increases as it tries to settle down at point A. However, as the output current increases, the voltage across emitter resistors 3 and 3' increases. , when a predetermined value is exceeded, the current control transistors 7 and 7' become conductive, and the base current of the output stage transistors 2 and 2' decreases, so that the output current cannot increase any further. Figure 3 shows this situation.

The F point is a predetermined value, and the F point is B shown in FIG.
If you set it so that the output corresponds to the point,
Oscillation will occur at the frequency of point B.

FIG. 2 shows another embodiment of the present invention. In this embodiment, the output current is generated by the pick-up transformer 10, and in this detection means, when the output stage transistor 2, 2'' is on, the output stage transistor 2,
The output stage transistors 2 and 2 are reverse biased, and conversely, when the output stage transistors 2' and 2 are on, the output stage transistors 2 and 2'' are reverse biased, so the output stage transistors 2 and 2'' and the output stage transistor 2' ,
The spike waveform at the switching point between on and off can be removed. 9, 9' are transistors 7,
This is a diode for preventing backflow from the base to the collector when the circuit 7' is saturated.

(Effects of the invention) As explained above, in the ultrasonic cleaning machine of the invention, the current feedback self-excited oscillator can be driven by oscillating at the resonant frequency of the vibrator.
It has the advantage of increasing electro-mechanical conversion efficiency, operating as an efficient ultrasonic cleaner, and prolonging the life of the electrostrictive vibrator.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of the first embodiment of the present invention;
FIG. 2 is a circuit configuration diagram of a second embodiment of the present invention, FIG. 3 is an output-load resistance characteristic diagram of the output stage transistor of the present invention, and FIG. 4 is a circuit configuration diagram of a conventional device example.
FIG. 5 is an output-load resistance characteristic diagram of a conventional output amplifying section, and FIG. 6 is a frequency characteristic diagram of load admittance. 1... Current feedback transformer, 2, 2', 2'', 2
... Output stage transistor, 3, 3' ... Emitter resistance, 4 ... Output transformer, 5 ... Matching inductance, 6 ... Electrostrictive vibrator, 7, 7' ... Current control transistor, 8, 8 '...Bias resistor, 9,9'...Reverse current prevention diode, 10...
...Pickup transformer, 11...Capacitor,
12... Admittance characteristic curve of the vibrator, 13...
...Admittance characteristics of matching inductance, 1
4... Admittance characteristics of the secondary side of the output transformer,
15...Power terminal.

Claims (1)

[Scope of utility model registration request] a transistor as an output stage; a matching inductance and an electrostrictive resonator as a load; a current feedback circuit that feeds back a load current to the base of the output stage transistor; means for detecting the output current of the output stage transistor; The load resistance value is the same as the load resistance value at a frequency between the resonant frequency and anti-resonance frequency of the three-frequency internal electrostrictive resonator where the admittance of the matching inductance and the admittance of the electrostrictive resonator have a conjugate relationship. a current feedback transistor circuit, comprising: a current control transistor circuit that controls the base current of the output stage transistor by the detected current so that the output of the output stage transistor becomes a maximum when the load resistance vs. output characteristic reaches a maximum; An ultrasonic cleaning machine characterized by being equipped with a self-excited oscillator.