JPH053268Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to an automatic frequency tracking type ultrasonic oscillator used in ultrasonic cleaning machines, ultrasonic processing machines, and the like.

(Prior Art) Ultrasonic oscillators used in cleaning machines, processing machines, etc. are generally excited at the resonant frequency of a vibrated system including a vibrator in order to increase the work efficiency. As is well known, the resonant frequency of an ultrasonic transducer fluctuates with changes in mechanical load conditions, drive level, temperature, etc., so it is possible to follow the fluctuations in the resonant frequency without fixing the frequency of the driving oscillator. It is desirable to adopt a method that allows driving at the resonance point at all times. For this reason, conventionally, so-called vibration feedback type oscillators that feed back vibration signals from a vibrator have been widely used. However, this method has the disadvantage that oscillation stops if the mechanical load is too large.Recently, however, a built-in voltage-controlled oscillator that does not have this disadvantage, and the voltage and current of the excitation signal that excites the resonator, has been developed. A so-called PLL that automatically tracks the resonant frequency of the vibrator by controlling the oscillation frequency based on the phase difference between the
(Phase Locked Loop) type oscillators have come into use.

FIG. 2 shows a block diagram of a recently used PLL type oscillator. In the figure, a signal output from a voltage controlled oscillator 1 is amplified by a power amplifier circuit 2 and supplied to an ultrasonic transducer 5 as an excitation signal. The voltage phase of this excitation signal is detected by the output voltage detection circuit 3, the current phase is detected by the output current detection circuit 4, and each of these detection signals is applied to the phase comparison circuit 6. There is. The phase comparison circuit 6 compares the phases of the voltage phase and the current phase, outputs a control signal proportional to the phase difference, and controls the oscillation frequency of the voltage-controlled oscillator 1 so that the phase difference becomes zero.

By controlling this oscillation frequency, it becomes possible to make the frequency of the excitation signal track the resonance frequency of the vibrated system.

(Problems to be solved by the invention) However, the conventional PLL type oscillator is
For example, when used in an ultrasonic cleaning machine, it is susceptible to the effects of waves caused by the cleaning liquid, especially when the depth of the cleaning liquid is inappropriate (especially when the distance between the vibration radiation surface and the liquid level is 1 /4 If the wavelength is an odd multiple)
etc., several resonant frequencies appear. As a result, there are several frequencies at which the phase difference between the output current and output voltage becomes 0, and in the PLL type oscillator described above,
In principle, it is impossible to always oscillate at the optimal frequency because the oscillation frequency is not determined or the output is not at the maximum and oscillates at an inappropriate frequency. As a result, there is a problem that the cleaning effect deteriorates and sufficient cleaning performance cannot be exhibited.

This invention was made to solve the above-mentioned conventional problems, and its purpose is to find the optimal resonant frequency when multiple resonant frequencies occur due to the above-mentioned standing waves or other causes. An object of the present invention is to provide an ultrasonic oscillator that can excite a vibrator more stably.

(Means for solving the problems) In order to achieve the above object, the present invention is configured as follows. That is, the present invention provides a voltage controlled oscillator and a phase control system that compares the voltage phase and current phase of an excitation signal that excites a vibrator and controls the frequency of the voltage controlled oscillator so that the phase difference becomes zero. an oscillation frequency controller that can manually adjust the frequency of the voltage-controlled oscillator; and a detection signal that detects a signal proportional to the power of the excitation signal or the displacement amplitude of the vibrator. a comparison switching circuit that compares the detected value of the detection signal with a reference setting value and outputs a switching signal when the detected value becomes smaller than the reference setting value; a first switching contact for interrupting a frequency control signal from the circuit to the voltage controlled oscillator; and a second switching contact for connecting the oscillation frequency controller to the voltage controlled oscillator according to the switching signal.
The ultrasonic oscillator has a switching contact and an indicator that notifies the output of the switching signal.

(Function) In the present invention having the above configuration, the vibrator is normally excited by controlling the frequency of the voltage-controlled oscillator using the control signal of the phase comparison circuit, as in the conventional example. In the present invention, a signal proportional to the power of the excitation signal or the displacement amplitude of the vibrator is constantly detected by the detection circuit, and this detected value is compared with a predetermined reference setting value by the comparison switching circuit. It will be done.

Therefore, for example, in a washing machine, multiple resonance frequencies appear due to the influence of standing waves caused by changes in liquid depth, etc., and tracking of the oscillation frequency becomes unstable.
If the output starts to oscillate at an inappropriate frequency that is not at its maximum, the comparison and switching circuit determines that this output has decreased, and the comparison and switching circuit outputs a switching signal.
This switching signal causes a desired display to be displayed on the display, and the first switching contact is automatically or manually opened to cut off the control signal applied from the phase comparison circuit to the voltage-controlled oscillator. Then, the second switching contact is automatically or manually closed to establish a connection between the voltage controlled oscillator and the oscillation frequency controller. Therefore, by manually adjusting the oscillation frequency controller in this state, the oscillation frequency of the voltage-controlled oscillator can be set to the optimal value, which allows the vibrator to be stably excited at a high-output resonance frequency. It is possible.

(Example) Hereinafter, an example of the present invention will be described based on the drawings. In the description of this embodiment, the same parts as those of the conventional example are denoted by the same reference numerals, and the description thereof will be omitted.

FIG. 1 shows a block configuration of an embodiment of the present invention. This embodiment has the same configuration as the conventional example, but includes an oscillation frequency controller 7, a detection circuit 8, a comparison switching circuit 9, a display 10, and a first switching contact 11.
and a second switching contact 12 are newly added. The oscillation frequency controller 7 is used to manually adjust the oscillation frequency of the voltage controlled oscillator 1. The detection circuit 8 detects a signal compared with the power of the excitation signal or the displacement amplitude of the vibrator 5, and applies the detected value to the comparison switching circuit 9 as a detection signal. The comparison switching circuit 9 compares the detected value with a reference set value of power corresponding to the detected value of the detection signal given in advance or a reference set value for a signal proportional to the displacement amplitude of the vibrator 5, and determines the detected value. When the value becomes smaller than a reference set value, a switching signal is applied to the indicator 10 and the first switching contact 11 and the second switching contact 12, each consisting of a relay contact. In response to the switching signal, the display 10 notifies that the switching signal has been output from the comparison switching circuit 9, that is, that the output of the excitation signal has fallen below the reference setting value, by a desired means such as flashing, lighting, or an alarm. do. On the other hand, the first switching contact 11 connects the phase comparison circuit 6 and the voltage controlled oscillator 1.
In response to the switching signal, the switch opens and automatically cuts off the control signal applied from the phase comparator circuit 6 to the voltage controlled oscillator 1.
Further, the second switching contact 12 is connected to the voltage controlled oscillator 1.
and the oscillation frequency controller 7,
Upon receiving the switching signal, the switch is closed;
The controlled oscillator 1 and the oscillation frequency controller 7 are connected. In this connection state, the oscillation frequency controller 7
By manually operating
In other words, the resonance frequency is adjusted to the maximum output. According to this embodiment configured as described above, the output of the excitation signal, that is, the power of the excitation signal or the amplitude of the vibrator 5 (actually a signal value proportional to the amplitude of the vibrator 5) is set as the reference. When the value is greater than or equal to the value,
As in the conventional example, the control signal from the phase comparison circuit 6 causes the vibrator 5 to be excited by automatic tracking of the so-called resonance frequency. If the output of the excitation signal decreases due to multiple resonance frequencies appearing due to standing waves or other causes, this abnormal condition is detected by the comparison switching circuit, and the switching signal is used to switch the switching contact. Automatic tracking is stopped by the required contact switching operations 11 and 12, and the abnormality is notified on the display 10.
Therefore, the operator manually operates the oscillation frequency controller 7 based on the notification on the display 10 to adjust the oscillation frequency (frequency of the excitation signal) of the voltage-controlled oscillator 1.
can be set to an optimal value, it is possible to stably maintain extremely efficient excitation of the vibrator 5.

In the above embodiment, the first switching contact 11 and the second switching contact 12 are configured as relay contacts, and each contact is automatically switched by a switching signal. Contact 11
And 12 is a manual switching contact (switching switch)
Alternatively, the operator may manually switch the contacts based on the notification from the display 10.

(Effects of the invention) Since the invention has the configuration and operation described above, when the ultrasonic oscillator tracks the resonant frequency of the vibrated system and performs the oscillation operation, even if the Even if the output of the excitation signal drops due to the appearance of multiple resonance frequencies, this abnormality can be detected immediately and the oscillation frequency of the voltage controlled oscillator can be manually set to the optimal value.
It is possible to always excite the vibrator using a stable resonant frequency with high output.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.
FIG. 2 is a block diagram showing the configuration of a conventional device. DESCRIPTION OF SYMBOLS 1... Voltage controlled oscillator, 2... Power amplifier circuit, 3... Output voltage detection circuit, 4... Output current detection circuit, 5... Vibrator, 6... Phase comparison circuit, 7
...Oscillation frequency controller, 8...Detection circuit, 9...
Comparison switching circuit, 10... Indicator, 11... First switching contact, 12... Second switching contact.

Claims (1)

[Scope of utility model registration request] Comprising a voltage-controlled oscillator and a phase comparison circuit that compares the voltage phase and current phase of an excitation signal that excites the vibrator and controls the frequency of the voltage-controlled oscillator so that the phase difference becomes zero. The ultrasonic oscillator comprises: an oscillation frequency controller capable of manually adjusting the frequency of the voltage-controlled oscillator; and a detection circuit that detects a signal proportional to the power of the excitation signal or the displacement amplitude of the vibrator and outputs a detection signal. , a comparison switching circuit that compares the detected value of the detection signal with a reference setting value and outputs a switching signal when the detected value becomes smaller than the reference setting value; and a voltage controlled oscillator from the phase comparison circuit by this switching signal. a first switching contact that cuts off a control signal to the switching signal; a second switching contact that connects the oscillation frequency controller to the voltage-controlled oscillator according to the switching signal; and an indicator that notifies the output of the switching signal. An ultrasonic oscillator characterized by: