JPH05301078A - Oscillating circuit for ultrasonic washer - Google Patents

Abstract

PURPOSE:To unnecessitate the fine adjustment by variable resistance in an oscillating circuit of an ultrasonic washer and to precisely track the change in resonance frequency of an ultrasonic oscillator with the oscillating frequency of the ultrasonic oscillator. CONSTITUTION:The oscillating frequency of an ultrasonic oscillator is swept over the prescribed area (201) and the output of the ultrasonic oscillator at each frequency swept is captured (202). The frequency at which the output captured of the ultrasonic oscillator is maximum is selected as the oscillating frequency of the ultrasonic oscillator (203). Thereby the ultrasonic oscillator is excited at the selected frequency for a constant time. After this time has elapsed, the frequency is swept again to newly select the resonance frequency of the ultrasonic oscillator and the ultrasonic oscillator is excited by this frequency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oscillating circuit of an ultrasonic cleaning machine, and more particularly to an ultrasonic cleaning machine for automatically tracking the oscillation frequency of the ultrasonic vibrator with the fluctuation of the resonance frequency of the ultrasonic vibrator. The present invention relates to an oscillator circuit.

[0002]

2. Description of the Related Art Generally, an ultrasonic cleaning machine for cleaning an object to be cleaned in a cleaning tank is widely used by utilizing ultrasonic waves in a liquid generated by high frequency vibration of an ultrasonic vibrator. Conventionally, as a method of controlling the resonance frequency of the ultrasonic vibrator of the ultrasonic cleaner, the current or amplitude flowing in the ultrasonic vibrator is detected and the value is fed back, and the resonance frequency of the ultrasonic vibrator is analogized. Was in control.

[0003]

However, in this method, since the output is fed back in an analog manner, variations in circuit constants (eg, resistance and transistor characteristics) of components of the oscillation circuit that drives the ultrasonic transducer. It is necessary to provide a variable resistor or the like for absorbing the above in the circuit and adjust the resistance value or the like of these variable resistors, and it takes time and effort to manufacture them. Further, the resonance frequency of the ultrasonic transducer changes depending on the temperature including the ambient temperature, and in addition to the change of the resonance frequency, the variation of the resonance frequency due to the change of the load of the ultrasonic transducer (the ultrasonic cleaning machine It is necessary to change the flow rate of the cleaning liquid in the cleaning tank depending on the object to be cleaned, which causes the resonance frequency to change drastically). Could not be completely tracked.

The present invention has been made to solve the above problems, and an object of the present invention is to eliminate the need for fine adjustment by a variable resistor or the like for absorbing variations in the components of an oscillation circuit. It is to make it possible to easily manufacture a sonic cleaning machine. A further object of the present invention is to make it possible to more accurately track the oscillation frequency of the ultrasonic oscillator with respect to changes in the resonance frequency of the ultrasonic oscillator due to changes in temperature and load.

[0005]

In order to solve the above problems, the oscillation circuit of the ultrasonic cleaning machine of the present invention comprises an ultrasonic vibrator,
A control device for controlling the oscillation frequency of the ultrasonic transducer,
A drive circuit that drives the ultrasonic transducer by the output of the control device, and a detection circuit that detects a value proportional to the output of the ultrasonic transducer and outputs the value to the control device, the control device,
Frequency sweeping means for sweeping the oscillation frequency of the ultrasonic transducer over a certain range, output capturing means for capturing the output of the ultrasonic transducer based on the output of the detection circuit, and the output within the swept frequency range And an oscillation frequency selecting means for selecting the frequency at which the output captured by the capturing means is maximum as the oscillation frequency of the ultrasonic transducer.

[0006]

In the oscillator circuit of the ultrasonic cleaning machine of the present invention, the frequency of the ultrasonic oscillator is controlled by the control device. This control device sweeps the oscillation frequency of the ultrasonic transducer over a certain range by the frequency sweeping means, and captures the output of the ultrasonic transducer at each frequency in the range swept by the output capturing means,
Then, a frequency that maximizes the captured output is selected within the range swept by the oscillation frequency selection means, and this is set as the oscillation frequency of the ultrasonic transducer.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a block diagram of an oscillator circuit of an ultrasonic cleaning machine according to an embodiment of the present invention. CPU as control device
Reference numeral 10 controls the oscillation frequency of the ultrasonic transducer 30, and the drive circuit 20 drives the ultrasonic transducer 30 based on the output from the output terminal 12 of the CPU 10. The drive circuit 20 includes a gate drive circuit 22, a half bridge circuit 24, and a matching circuit 26. The ultrasonic transducer 30 driven by the drive circuit 20 generates ultrasonic waves in the cleaning liquid and cleans the object to be cleaned in the cleaning tank. The voltage detection circuit 40 includes a voltage transformer 42 that converts the voltage applied to the ultrasonic transducer 30 for detecting the output of the ultrasonic transducer 30, and a rectifier 44 that rectifies the voltage converted by the voltage transformer 42. ing. The current detection circuit 50 includes a current transformer 52 for detecting a current flowing through the ultrasonic transducer 30, and a current transformer 5 for detecting the current.
2 and a rectifier 54 that rectifies the electric current detected by 2. The outputs of the voltage detection circuit 40 and the current detection circuit 50 are applied to the detection voltage input terminal 14 and the detection current input terminal 16 of the CPU 10, respectively.
Is used to select the frequency of the ultrasonic transducer 30 by converting these input values into numerical information (A / D conversion).

Next, the function of the CPU 10 will be described with reference to FIG. The CPU 10 changes the pulse cycle applied to the ultrasonic transducer 30 from 24.6 μs (frequency 40.6 KHz) to 2
0.125 up to 6.7 μs (frequency 37.4 KHz)
a frequency sweep function 201 that changes (sweeps) every μs,
The value of the current flowing through the ultrasonic transducer 30 and the value of the voltage applied thereto are A / D converted, and the product of these values is obtained to obtain the ultrasonic transducer 3 in each pulse cycle.
An output capturing function 202 that captures an output of 0, and an oscillation frequency selection function 203 that selects a pulse cycle (oscillation frequency) applied to the ultrasonic transducer 30 based on the value captured by the output capturing function 202.
And have. Each function of the CPU 10 will be described in more detail below with reference to the flowchart of FIG. 3 and the block diagram of FIG.

As shown in FIG. 4, the CPU 10 of this embodiment keeps the pulse width t constant at 10 μs and sets the pulse period T to C.
5 [24.6 μs (frequency 40.6 kHz)] to D5
0.1 up to [26.7 μs (frequency 37.4 kHz)]
It is changed every 25 μs. Here, C5 and D5 represent the frequencies in hexadecimal notation, and will be described in more detail later.

In the flowchart of FIG. 3, first, CP
U10 determines the initial value of the pulse period T (T
0) C5 [24.6 μs] is set, and step 3
The drive circuit 20 is controlled by 02 to oscillate the ultrasonic transducer 30 in this cycle. The voltage applied to the ultrasonic transducer 30 is detected by the voltage detection circuit 40 and input to the detection voltage input terminal 14 of the CPU 10. Similarly, the ultrasonic transducer 30
The current flowing in the CPU is detected by the current detection circuit 50 and is detected by the CPU.
The detected current is input to the detection current input terminal 16 of 10. These input values are A / D converted in step 303 and used as data for oscillation frequency selection. Since about 50 μs is required for this A / D conversion, the CPU 10 continues to drive the ultrasonic transducer 30 with the pulse cycle C5 [24.6 μs] for 20 ms.

During the above 20 ms, the determination at step 304 is NO, and the processing from step 305 onward is performed. In step 305, the product P0 of the current value I0 and the voltage value V0 detected in the pulse period T0 is obtained, and in step 306, the product P0 obtained this time and the previously detected current and voltage held in the CPU 10 are obtained. The maximum product value Pm is compared. If the product P0 is larger than the past maximum value Pm (Yes in step 306), the maximum value Pm is replaced with P0 in step 307, and the pulse period T0 at this time indicates that the output of the ultrasonic transducer 30 is the maximum. Is held as the pulse period Tm.

When this process continues for 20 ms described above (Yes in step 304), 1 is added to the value of T0 in the next step 308. This makes the pulse period 0.125 μs longer (frequency lower) than the pulse period T0 [24.6 μs], and the pulse period T1 [24.725 μs].
Means to That is, Tn + in step 308
1 indicates that the pulse cycle is lengthened by 0.125 μs, and Tn is 0.125 when the initial pulse cycle T0 is 0.125 μs.
It means a pulse cycle lengthened n times by μs, and similarly, In, Vn and Pn in step 305 described above respectively mean a current value, a voltage value and a product thereof in the pulse cycle Tn.

Next, in step 309, the pulse period Tn + 1
Is the final (longest) pulse period D5 [26.7 μs (3
7.4 kHz)] is exceeded. Here, since the pulse period is 24.725 μs, step 30
The determination result of 9 is No, and the processing from step 302 is repeated. The CPU 10 repeats this process by increasing the pulse period by 0.125 μs until the pulse period becomes D5, thereby changing the frequency from 40.6 KHz (pulse period 24.6 μs) to 37.4 KHz (pulse period 26,7 μs). To sweep. After this frequency sweep (Yes in step 309), the process proceeds to step 310.

In step 310, it is determined whether the processing from step 301 to step 309 (frequency sweep) is repeated twice. When these processes are performed only once (No in step 310), the maximum value P of the product of the current and the voltage held in step 311 is set.
m and the pulse period Tm that maximizes the output of the vibrator are the first
The values are held as the data of the second sweep and these values are cleared, and the process returns to step 301 to start the second process (frequency sweep). The processing from step 301 to step 309 is repeated again, and the maximum value Pm ′ and the pulse period Tm ′ when this value is obtained are obtained as the data of the second frequency sweep. When the frequency is swept twice (Yes in step 310),
At step 312, the average value of the pulse period Tm at the first sweep and the pulse period Tm 'at the second sweep is obtained, and all the processes are completed. The CPU 10 uses the average value of the pulse periods Tm and Tm ′ obtained by the above processing as the oscillation frequency of the ultrasonic transducer 30. As described above, in this embodiment, the sweep is performed twice, and the oscillation frequency is more accurately selected by taking the average value of the values thus obtained.

Next, the control of the oscillation frequency by the CPU 10 will be described with reference to FIG. CPU10 is 20
The ultrasonic transducer 30 is oscillated at the pulse cycle selected by the above process for one second, and then the frequency is swept twice to select a new resonance frequency, and the ultrasonic transducer 30 is oscillated for 20 seconds at this new resonance frequency. Let By repeating the oscillation for 20 seconds and the selection of the resonance frequency by sweeping,
The CPU 10 follows the fluctuation of the resonance frequency of the ultrasonic transducer 30 due to the change of the load and drives the ultrasonic transducer 30.

FIG. 6 shows the relationship between the oscillation frequency and the output of the ultrasonic transducer 30 according to this embodiment. The polygonal line a shows the relationship between the oscillation frequency and the output of the ultrasonic transducer 30 when the flow rate of the cleaning liquid (water) in the cleaning tank is 18 l / min.
Similarly, the broken line b has a flow rate of 23 l / min, the broken line c has a flow rate of 29 l / min, and the broken line d has a flow rate of 39 l / min.
Shows the relationship in the case of. In this figure, the frequency is 1
Hexadecimal display. For example, in CA, A is 10, B is 11, C is 12, D is 13, E is 14, and F is 15.
Note that it means. As shown in FIG. 6, the frequency at which the output of the vibrator is maximized (resonance frequency) changes depending on the flow rate of the cleaning liquid, but the oscillation circuit of the ultrasonic cleaning machine according to the present embodiment causes ultrasonic vibration at each flow rate. Figure 3 shows the oscillation frequency (pulse period) that maximizes the output of the child.
As described with reference to the flowchart of FIG. 2, the ultrasonic transducer 30 is selected by sweeping the frequency, and the variation of the resonance frequency due to the change of the flow rate is tracked. Oscillate.

In the embodiment described above, the resonance frequency is obtained by sweeping the frequency twice and obtaining the average value thereof, but the sweep may be performed once, or may be performed three times or more. Further, in the present embodiment, the sweep is performed from the high frequency to the low frequency twice, but the first sweep is performed from the high frequency to the low frequency, and the second sweep is performed from the low frequency to the high frequency. It is also suitable to change the way. In the above description, various numerical values have been described as examples, but these numerical values can be appropriately changed.

In the embodiment described with reference to the block diagram of FIG. 1, the voltage detection circuit 40 and the current detection circuit 50 are used to detect the output of the ultrasonic transducer 30, and the voltage and current are detected. The maximum output of the ultrasonic transducer 30 was obtained from the product of As another example of this embodiment, it is also preferable to detect only the current and obtain the pulse period at which the ultrasonic transducer 30 has the maximum output based on the detected current. In this case the CPU
In the processing of 10, the step 305 is omitted in the flowchart of FIG. 3, and the product Pn of the current and the voltage in step 306 and the maximum value Pm of the detected current value In are respectively detected.
To the maximum value Im, and similarly, step 307
Pm and Pn of the current maximum value Im and current value I, respectively
This can be done by substituting n. Then, in the process, the current maximum value Im is compared with the detected current value In in step 306, and if In is larger than the past maximum value Im (Yes in step 306), step 3
At 07, the maximum value Im is replaced with In, and the pulse period Tm is replaced with the pulse period Tn from which In was obtained. The pulse cycle Tm selected in this way is used as the oscillation pulse cycle of the ultrasonic transducer 30. According to this another embodiment, there is an advantage that the voltage detection circuit is not required and the oscillation circuit can be simplified.

[0019]

As described above in detail, according to the present invention, fine adjustment by a variable resistor for accommodating the variation of the components of the oscillation circuit which is required in the conventional feedback type ultrasonic cleaning machine is unnecessary. It is possible to easily manufacture the ultrasonic cleaning machine and reduce the manufacturing cost. Further, it becomes possible to accurately track the oscillation frequency of the vibrator with the fluctuation of the resonance frequency of the ultrasonic vibrator due to changes in temperature and load.

[Brief description of drawings]

FIG. 1 is a block diagram of an oscillation circuit of an ultrasonic cleaning machine according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a function of a CPU of the oscillation circuit of FIG.

FIG. 3 is a flowchart of a process performed by a CPU of the oscillator circuit of FIG.

FIG. 4 is a waveform diagram of pulses applied to the ultrasonic transducer according to the embodiment of the present invention.

5 is a graph showing the relationship between time and output by the oscillator circuit of FIG.

FIG. 6 is a graph showing the relationship between the oscillation frequency and the output of the vibrator when the flow rate of the cleaning liquid changes.

[Explanation of symbols]

 10 CPU (Control Device) 20 Drive Circuit 30 Ultrasonic Transducer 40 Voltage Detection Circuit 50 Current Detection Circuit 201 Frequency Sweep Function 202 Output Capture Function 203 Oscillation Frequency Selection Function

Claims (4)

[Claims] 1. An ultrasonic transducer, a control device for controlling an oscillation frequency of the ultrasonic transducer, a drive circuit for driving the ultrasonic transducer by an output of the control device, and a control circuit for the ultrasonic transducer. A detection circuit that detects a value proportional to the output and outputs the detected value to the control device, wherein the control device sweeps the oscillation frequency of the ultrasonic transducer over a certain range, and the detection circuit. Output capturing means for capturing the output of the ultrasonic transducer based on the output of, and the frequency at which the output captured by the output capturing means becomes maximum within the frequency range to be swept is set as the oscillation frequency of the ultrasonic transducer. An oscillation circuit for an ultrasonic cleaning machine, comprising: an oscillation frequency selecting means for selecting. 2. The detection circuit detects the current flowing through the ultrasonic transducer as a value proportional to the output of the ultrasonic transducer, and the oscillation frequency selecting means of the control device determines the frequency at which the value of the current becomes maximum. The oscillation circuit of the ultrasonic cleaning machine according to claim 1, wherein the oscillation frequency is selected as the oscillation frequency of the ultrasonic oscillator. 3. The oscillation frequency selecting means of the control device detects the current flowing through the ultrasonic oscillator and the voltage of the ultrasonic oscillator as a value proportional to the output of the ultrasonic oscillator by the detection circuit. The oscillation circuit of the ultrasonic cleaning machine according to claim 1, wherein a frequency at which a product of a current value and the voltage value becomes maximum is selected as an oscillation frequency of the ultrasonic transducer. 4. The oscillation circuit of an ultrasonic cleaning machine according to claim 1, wherein the frequency sweeping means of the control device sweeps the oscillation frequency of the ultrasonic oscillator two or more times.