Ultrasonic cleaning machine

Abstract

To provide an ultrasonic washing machine which can suppress generation of excessive voltage when switching a frequency.SOLUTION: An ultrasonic washing machine 10 includes: a rectification section 23; a high frequency generation section 26; an oscillation control section 28; and a power source voltage detection section 27. The rectification section 23 full-wave rectifies a commercial AC power source 21 and generates a pulsating flow 40. The high frequency generation section 26 inputs the pulsating flow 40 as a driving power source, oscillates a high frequency and outputs a driving signal V to an ultrasonic vibrator 13. The oscillation control section 28 drives and controls the driving signal V. The power source voltage detection section 27 detects voltage of the commercial AC power source 21 and outputs the voltage to the oscillation control section 28. The high frequency generation section 26 performs amplitude modulation synchronizing with a voltage change of the commercial AC power source 21 on the basis of the pulsating flow 40. The oscillation control section 28 controls the high frequency generation section 26 so as to perform frequency modulation of switching a frequency of the driving signal V when voltage of the commercial AC power source 21 is half of maximum voltage or less.SELECTED DRAWING: Figure 1

Description

Technical Field

[0004] , ,

[0005] , , ,

[0001] The present invention relates to an ultrasonic cleaner that irradiates ultrasonic waves to clean an object to be cleaned.

Background Art

[0002] Conventionally, an ultrasonic cleaner (for example, see Patent Document 1) that performs cleaning (ultrasonic cleaning) of an object to be cleaned by irradiating ultrasonic waves into a cleaning liquid has been put into practical use. Ultrasonic cleaning can act on the details of an object to be cleaned having a complex shape and can be efficiently cleaned by a combination of the physical action of ultrasonic waves and the chemical action of the cleaning liquid. Therefore, it has become essential for the manufacture of precision mechanical parts, optical parts, liquid crystal displays, semiconductors, and the like.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, the ultrasonic waves irradiated from the ultrasonic vibrator are reflected on the liquid surface of the cleaning liquid, generating standing waves in the cleaning liquid. This standing wave is a pattern in which portions where the sound pressure (acoustic radiation pressure) is maximum (antinodes) and portions where the sound pressure is minimum (nodes) are arranged alternately along the depth direction of the cleaning liquid. Therefore, when cleaning an object to be cleaned, while the portion of the surface of the object to be cleaned corresponding to the antinode of the standing wave is efficiently cleaned, the portion corresponding to the node of the standing wave is hardly cleaned. Thus, there is a problem that the surface of the object to be cleaned cannot be uniformly cleaned. ​​Therefore, in conventional ultrasonic cleaning machines, it has been proposed to apply amplitude modulation (AM modulation) and frequency modulation (FM modulation) to the drive signal that drives the ultrasonic transducer, thereby switching the frequency of the drive signal. In this way, the position of the antinodes of the standing wave moves as the frequency is switched, so the surface of the object being cleaned can be cleaned uniformly. However, when the frequency is switched, an excessive voltage due to stray inductance is applied to the switching element, which can easily cause circuit malfunction or damage.

[0006] The present invention has been made in view of the above-mentioned problems, and its objective is to provide an ultrasonic cleaning machine that can suppress the generation of excessive voltage when switching frequencies. [Means for solving the problem]

[0007] To solve the above problems, the invention described in claim 1 comprises: a rectifier unit that full-wave rectifies a commercial AC power supply to generate a pulsating current; a high-frequency generator unit that takes the pulsating current generated by the rectifier unit as a drive power supply, oscillates a high frequency, and outputs a high-frequency drive signal to an ultrasonic transducer; an oscillation control unit that drives and controls the drive signal output from the high-frequency generator unit; and a power supply voltage detection unit that monitors the commercial AC power supply or the pulsating current which is the drive power supply, detects the voltage of the commercial AC power supply, and outputs the result to the oscillation control unit, wherein the high-frequency generator unit performs amplitude modulation synchronized with the voltage change of the commercial AC power supply based on the input pulsating current, The power supply voltage detection unit detects the zero-crossing point of the commercial AC power supply voltage and outputs the result to the oscillation control unit. The oscillation control unit controls the high-frequency generation unit to perform frequency modulation, switching the frequency of the drive signal to a different frequency at regular intervals when the commercial AC power supply voltage reaches the zero-crossing point. The gist of this invention is an ultrasonic cleaning machine characterized by the following features.

[0008] Accordingly, according to the invention described in claim 1, the oscillation control unit controls the high-frequency generator so as to perform frequency modulation, switching the frequency of the drive signal to a different frequency when the voltage of the commercial AC power supply is less than half of the maximum voltage. That is, since the control is performed to switch the frequency of the drive signal at a timing when the voltage is less than half of the maximum voltage and not much current is flowing, the generation of excessive voltage caused by stray inductance can be suppressed. Therefore, protection circuits such as snubber circuits for absorbing excessive voltage can be miniaturized, and the cost of the ultrasonic cleaning machine can be reduced. In addition, by suppressing the generation of excessive voltage, malfunctions and damage to the high-frequency generator and other components can be prevented. Furthermore, by switching the frequency of the drive signal at a timing when the voltage is less than half of the maximum voltage, the kickback that occurs when switching frequencies is reduced, and high-frequency noise caused by kickback can be reduced. In addition, the high-frequency generator performs amplitude modulation and frequency modulation using the frequency of the commercial AC power supply. Therefore, amplitude modulation and frequency modulation can be easily performed even without a program to operate the oscillation control unit.

[0011] In the above section, The power supply voltage detection unit detects the zero-crossing point of the commercial AC power supply voltage and outputs the result to the oscillation control unit. The oscillation control unit controls the high-frequency generation unit to perform frequency modulation, switching the frequency of the drive signal to a different frequency at regular intervals when the commercial AC power supply voltage reaches the zero-crossing point. 。

[0012] in this case By switching the drive signal frequency at the moment when the commercial AC power supply voltage is at its minimum and no current is flowing, the generation of excessive voltage caused by stray inductance can be more reliably suppressed. In addition, by switching the drive signal frequency at the moment the voltage crosses zero, the kickback that occurs during frequency switching is further reduced, thus more reliably reducing high-frequency noise caused by kickback. [Effects of the Invention]

[0019] As detailed above, 1 According to the invention described herein, it is possible to provide an ultrasonic cleaning machine that can suppress the generation of excessive voltage when switching frequencies. [Brief explanation of the drawing]

[0020] [Figure 1] A schematic diagram showing an ultrasonic cleaning machine in the first embodiment. [Figure 2] A graph showing the voltage waveform of the alternating current from an AC power supply. [Figure 3] A graph showing the waveform of pulsating flow. [Figure 4] A graph showing the waveform of the drive signal output to the ultrasonic transducer. [Figure 5] A graph schematically showing the waveform of an amplitude-modulated drive signal. [Figure 6] A graph schematically showing the waveforms of amplitude-modulated and frequency-modulated drive signals. [Figure 7] A schematic diagram showing an ultrasonic cleaning machine in the second embodiment. [Figure 8] A graph showing the voltage waveform of an amplitude-modulated signal. [Modes for carrying out the invention]

[0021] [First Embodiment] A first embodiment of the present invention will be described in detail below with reference to the drawings.

[0022] As shown in Figure 1, the ultrasonic cleaning machine 10 of this embodiment includes a cleaning tank 11 for storing cleaning liquid W1, an ultrasonic transducer 13 mounted on the bottom plate 12 of the cleaning tank 11, and an ultrasonic oscillator 20 for driving and controlling the output of the ultrasonic transducer 13. The object to be cleaned 14 is immersed in the cleaning liquid W1 stored in the cleaning tank 11.

[0023] The bottom plate 12 of the cleaning tank 11 is made of a metal plate such as stainless steel and functions as a diaphragm for emitting ultrasonic waves S1. Further, the ultrasonic vibrator 13 is joined to the bottom plate 12 of the cleaning tank 11 with its vibration surface facing upward. The ultrasonic vibrator 13 is electrically connected to the ultrasonic oscillator 20 and mechanically vibrates based on a drive signal V (see FIG. 4) output from the ultrasonic oscillator 20. Due to this mechanical vibration of the ultrasonic vibrator 13, ultrasonic waves S1 are output from the bottom plate 12 into the cleaning tank 11.

[0024] As shown in FIG. 1, the ultrasonic oscillator 20 includes an AC power supply 21, a protection circuit 22, a rectification circuit 23 (rectification unit), a first power supply circuit 24, a second power supply circuit 25, a high-frequency generation circuit 26 (high-frequency generation unit), a power supply voltage detection circuit 27 (power supply voltage detection unit), an oscillation control circuit 28 (oscillation control unit), and a matching circuit 29. Further, the ultrasonic oscillator 20 includes a control unit (not shown) for overall control of the entire device. The control unit is composed of a well-known computer including a CPU, a ROM, a RAM, etc. The CPU is electrically connected to the above-mentioned power supply voltage detection circuit 27 and oscillation control circuit 28 and controls them with various drive signals.

[0025] Also, the AC power supply 21 is a commercial AC power supply for supplying 100V AC power to each circuit 22 - 29. As shown in of FIG. 1 and FIG. 2, the voltage waveform of the AC current of the AC power supply 21 is a sine wave output with a period T0. Further, the protection circuit 22 is a circuit for protecting each circuit 23 - 29 from overvoltage.

[0026] As shown in FIG. 1, the rectification circuit 23 is a circuit that rectifies the alternating current supplied from the AC power supply 21 to generate a pulsating current 40 (see of FIG. 1 and FIG. 3). More specifically, the rectification circuit 23 performs full-wave rectification that converts and rectifies the negative pulse 41 (see FIG. 2), which is the negative voltage part of the alternating voltage, into the positive pulse 42 (see FIG. 3), which is the positive voltage part, to generate a pulsating current 40 (direct current) in which a plurality of positive pulses 42 are continuous.

[0027] The first power supply circuit 24 is a circuit that smooths the pulsating current 40 supplied from the rectifier circuit 23 and converts it into 12V DC for output. The converted 12V DC is output to the second power supply circuit 25 and also to the high-frequency generation circuit 26 as a power supply for transistor drive control. The second power supply circuit 25 is a circuit that converts the 12V DC supplied from the first power supply circuit 24 into 5V DC and outputs it to the oscillation control circuit 28, etc.

[0028] The high-frequency generation circuit 26 is a circuit that receives the pulsating current 40 generated by the rectifier circuit 23 as a driving power supply, oscillates a high frequency, and outputs a high-frequency drive signal V to the ultrasonic transducer 13 via the matching circuit 29. In this embodiment, the high-frequency generation circuit 26 is formed by an inverter circuit composed of multiple transistors such as IGBTs (Insulated Gate Bipolar Transistors) and MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors). Specifically, the high-frequency generation circuit 26 converts the pulsating current 40 supplied from the rectifier circuit 23 into a high-frequency drive signal V by amplifying and switching the transistor drive control signal output from the oscillation control circuit 28. As shown in Figure 4, the waveform of the drive signal V is a sine wave output with a period T2. The high-frequency generation circuit 26 is driven by a transistor drive control power supply output from the first power supply circuit 24.

[0029] As shown in Figure 1, the power supply voltage detection circuit 27 is a circuit that detects the voltage of the AC power supply 21 by monitoring the pulsating current 40, which is the driving power supply, and outputs the result to the oscillation control circuit 28. Specifically, the power supply voltage detection circuit 27 detects the zero-crossing point Z1 (see <C> in Figure 1 and Figure 3), which is the point where the AC voltage of the pulsating current 40 becomes 0V, and outputs the result to the oscillation control circuit 28 as a trigger signal for when the voltage is 0V.

[0030] The oscillation control circuit 28 is a circuit that drives and controls the drive signal V output from the high-frequency generation circuit 26. Specifically, the oscillation control circuit 28 controls the switching waveform pattern of the high-frequency generation circuit 26 by switching the oscillation (transistor drive control signal) on and off at the timing when a trigger signal is input. The oscillation control circuit 28 is driven by 5V DC output from the second power supply circuit 25.

[0031] As shown in Figure 1, the matching circuit 29 is a circuit that performs impedance conversion using elements such as transformers to make the impedance value of the drive signal on the sending side (oscillation control circuit 28 side) the same as (match) the impedance value of the drive signal on the receiving side (ultrasonic transducer 13 side). The matching circuit 29 then supplies the impedance-matched high-frequency drive signal V to the ultrasonic transducer 13.

[0032] Next, a method for cleaning the object to be cleaned 14 using the ultrasonic cleaner 10 will be described.

[0033] First, the object to be cleaned 14 is placed in the cleaning tank 11 along with the cleaning solution W1, and then the AC power supply 21 of the ultrasonic cleaner 10 is turned on. At this time, the oscillation control circuit 28 (CPU) of the ultrasonic oscillator 20 controls the ultrasonic transducer 13 to output a drive signal V, thereby driving the ultrasonic transducer 13. Specifically, the oscillation control circuit 28 first outputs a transistor drive control signal to the high-frequency generation circuit 26. As a result, the oscillation of the high-frequency generation circuit 26 is started (switched on), and the drive signal V (see Figure 4) is generated. Since the high-frequency generation circuit 26 is burst-driven, the drive signal V in this embodiment is formed by a single-frequency burst wave.

[0034] Next, the oscillation control circuit 28 (CPU) of the ultrasonic oscillator 20 controls the high-frequency generation circuit 26 to apply amplitude modulation (AM modulation) and frequency modulation (FM modulation) to the drive signal V for driving the ultrasonic transducer 13 in order to improve the cleaning efficiency of the object to be cleaned 14. Specifically, first, the oscillation control circuit 28 controls the high-frequency generation circuit 26 to perform amplitude modulation on the drive signal V in synchronization with the voltage change of the AC power supply 21 (pulsating current 40) based on the input pulsating current 40. More specifically, the high-frequency generation circuit 26 performs amplitude modulation (100% modulation) with a modulation degree of 100%, modulating the amplitude of the drive signal V within a range of 0% to 100% of the maximum amplitude Hmax (see Figures 4 and 5). Furthermore, in the amplitude-modulated drive signal V, the period T3 (see Figure 5) during which the amplitude is continuously modulated in the order of 0% of the maximum amplitude Hmax → 100% of the maximum amplitude Hmax → 0% of the maximum amplitude Hmax is equal to the voltage period T1 (see Figure 3) of the pulsating current 40.

[0035] Furthermore, the oscillation control circuit 28 drives and controls the high-frequency generation circuit 26 to frequency modulate the drive signal V at the timing when the voltage of the AC power supply 21 (in this embodiment, the voltage of the pulsating current 40) reaches the zero-crossing point Z1 (see Figure 3), based on the detection result (trigger signal) of the power supply voltage detection circuit 27. In other words, the high-frequency generation circuit 26 switches the frequency when the voltage of the AC power supply 21 (and the pulsating current 40) is 0% of the maximum voltage V1max (see Figures 2 and 3). Then, in frequency modulation, the high-frequency generation circuit 26 controls the frequency of the drive signal V to switch to a different frequency every certain time interval T4 (see Figure 6). The certain time interval T4 is equal to the period T3 during which the amplitude of the drive signal V is modulated in the order of 0% → 100% → 0% of the maximum amplitude Hmax. In more detail, first, the high-frequency generation circuit 26 sets five frequencies (in this embodiment, 38kHz, 39kHz, 40kHz, 41kHz, and 42kHz). The high-frequency generation circuit 26 then controls the frequency of the drive signal V in a stepwise manner by switching the frequency to a different frequency every certain period of time T4. As shown in Figure 6, the high-frequency generation circuit 26 controls the frequency of the drive signal V in a stepwise manner in the order of 40kHz→41kHz→42kHz→41kHz→40kHz→39kHz→38kHz→39kHz→40kHz→…

[0036] Then, when the amplitude-modulated and frequency-modulated drive signal V is input to the ultrasonic transducer 13, the ultrasonic transducer 13 vibrates continuously, and ultrasonic waves S1 are irradiated into the cleaning liquid W1 from the bottom plate 12 of the cleaning tank 11. The ultrasonic waves S1 propagate through the cleaning liquid W1 and act on the object to be cleaned 14. As a result, the surface of the object to be cleaned 14 is cleaned. After that, when the operator turns off the AC power supply 21, the CPU stops the ultrasonic oscillator 20, and the cleaning of the object to be cleaned 14 is completed.

[0037] Therefore, according to this embodiment, the following effects can be obtained.

[0038] (1) In the ultrasonic cleaning machine 10 of this embodiment, the oscillation control circuit 28 controls the high-frequency generation circuit 26 so as to perform frequency modulation, switching the frequency of the drive signal V to a different frequency at the timing when the voltage of the pulsating current 40 reaches the zero-crossing point Z1. That is, since the control is performed to switch the frequency of the drive signal V at the timing when the voltage is at its minimum value V1min (see Figures 2 and 3) and no current is flowing, the generation of excessive voltage caused by stray inductance can be suppressed. Therefore, the size of protection circuits such as snubber circuits for absorbing excessive voltage can be reduced, thus reducing the cost of the ultrasonic cleaning machine 10. In addition, by suppressing the generation of excessive voltage, malfunctions and damage to the ultrasonic oscillator 20 can be prevented. Furthermore, by switching the frequency of the drive signal V at the timing when the voltage reaches the zero-crossing point Z1, the kickback that occurs when switching frequencies is reduced, and thus high-frequency noise caused by kickback can be reduced.

[0039] (2) In this embodiment, the high-frequency generation circuit 26 performs amplitude modulation and frequency modulation using the frequency (50Hz or 60Hz) of the AC power supply 21, which is a commercial AC power supply. Therefore, amplitude modulation and frequency modulation can be easily performed without a program to make the CPU function (a program for amplitude modulation and a program for frequency modulation).

[0040] (3) In this embodiment, five frequencies (38kHz, 39kHz, 40kHz, 41kHz, 42kHz) are set as the frequency of the drive signal V. The high-frequency generation circuit 26 performs frequency modulation by stepwise switching between the five set frequencies, so that acoustic mismatch (disturbance) occurs in the cleaning solution W1 during the very short time when the frequency is switched. As a result, the way in which the ultrasonic waves S1 act on the surface of the object to be cleaned 14 becomes more complex compared to the case of simple frequency modulation in which the frequency is changed continuously without steps, and thus the cleaning efficiency is improved. Therefore, a different cleaning effect can be obtained compared to conventional frequency modulation in which the frequency is changed continuously.

[0041] (4) For example, it is possible to switch frequencies in the same way as in this embodiment by using multiple ultrasonic transducers with different frequencies or by using a multi-frequency ultrasonic transducer. However, in this embodiment, frequency switching can be achieved simply by adjusting the drive signal V, which makes it easier to miniaturize and simplify the ultrasonic cleaning machine 10.

[0042] [Second Embodiment] A second embodiment of the present invention will be described below with reference to the drawings. Here, the differences from the first embodiment will be the main focus of the description, and the common parts will be given the same part numbers and detailed descriptions will be omitted.

[0043] As shown in Figure 7, the control method of the ultrasonic cleaning machine 50 of the second embodiment differs from that of the ultrasonic cleaning machine 10 of the first embodiment. Specifically, while the ultrasonic cleaning machine 10 of the first embodiment performed amplitude modulation (AM modulation) and frequency modulation (FM modulation) using the frequency of the AC power supply 21, the ultrasonic cleaning machine 50 of this embodiment performs amplitude modulation and frequency modulation using a processor 52 (CPU) instead of the frequency of the AC power supply 21.

[0044] Specifically, the ultrasonic oscillator 51 of the ultrasonic cleaning machine 50 includes a first power supply circuit 24 (drive power supply generation unit), a high-frequency generation circuit 26 (high-frequency generation unit), and a processor 52 (oscillation control unit). The first power supply circuit 24 is a circuit that smooths the pulsating current 40 supplied from the rectifier circuit 23 and converts it into a 12V DC drive power supply for output. The converted 12V drive power supply is output to the second power supply circuit 25 and also to the high-frequency generation circuit 26 as a power supply for transistor drive control. The high-frequency generation circuit 26 is a circuit that takes the DC drive power supply generated (converted) by the first power supply circuit 24 as input, oscillates a high frequency, and outputs a high-frequency drive signal V to the ultrasonic transducer 13.

[0045] As shown in Figure 7, the processor 52 is composed of a well-known computer consisting of a CPU, ROM, RAM, etc. The processor 52 drives and controls the drive signal V output from the high-frequency generation circuit 26 by generating an amplitude modulation signal V2 for controlling amplitude modulation and outputting it to the high-frequency generation circuit 26. As shown in Figure 8, the voltage waveform of the amplitude modulation signal V2 is a pulsating current output with a voltage period T5. Furthermore, the amplitude modulation signal V2 is generated independently of the period T0 of the voltage waveform of the commercial AC power supply (AC power supply 21). The high-frequency generation circuit 26 then performs amplitude modulation synchronized with the voltage change of the input amplitude modulation signal V2. More specifically, the high-frequency generation circuit 26 performs amplitude modulation (100% modulation) that modulates the amplitude of the drive signal V within the range of 0% to 100% of the maximum amplitude Hmax (see Figure 5).

[0046] Furthermore, the processor 52 drives and controls the high-frequency generation circuit 26 to frequency modulate the drive signal V at timing Z2 when the voltage of the amplitude-modulated signal V2 becomes zero. In other words, the high-frequency generation unit 26 switches the frequency when the voltage of the amplitude-modulated signal V2 is 0% of the maximum voltage V2max (see Figure 8). Then, in frequency modulation, the high-frequency generation circuit 26 controls the frequency of the drive signal V to switch to a different frequency every certain time interval T4 (see Figure 6).

[0047] When the amplitude-modulated and frequency-modulated drive signal V is input to the ultrasonic transducer 13, the ultrasonic waves S1 are emitted by the mechanical vibration of the ultrasonic transducer 13. The ultrasonic waves S1 then propagate through the cleaning solution W1 and act on the object to be cleaned 14, thereby cleaning the surface of the object to be cleaned 14.

[0048] Therefore, in the ultrasonic cleaning machine 50 of this embodiment, the processor 52 controls the high-frequency generation circuit 26 to perform frequency modulation by switching the frequency of the drive signal V to a different frequency at timing Z2 when the voltage of the amplitude modulation signal V2 becomes zero. That is, since the control is performed to switch the frequency of the drive signal V at timing Z2 when the voltage is at its minimum value V2min (see Figure 8) and no current is flowing, the generation of excessive voltage due to stray inductance can be suppressed. In addition, by switching the frequency of the drive signal V at timing Z2 when the voltage becomes zero, the kickback that occurs when the frequency is switched is reduced, and high-frequency noise caused by kickback can be reduced. Furthermore, since the processor 52 performs amplitude modulation using the amplitude modulation signal V2 generated by the processor 52 rather than using the frequency of the AC power supply 21, the degree of freedom in the start timing of amplitude modulation is increased. Also, the ultrasonic oscillator 51 of this embodiment is an existing device that does not have the power supply voltage detection circuit 27 of the first embodiment, but this can be accommodated by changing the program of the processor 52.

[0049] Furthermore, each of the above embodiments may be modified as follows.

[0050] In the first embodiment described above, the oscillation control circuit 28 controlled the high-frequency generation circuit 26 to perform frequency modulation, switching the frequency of the drive signal V, when the power supply voltage detection circuit 27 detected that the voltage of the AC power supply 21 (pulsating current 40) was at 0% of the maximum voltage V1max (zero crossing point Z1). However, the oscillation control circuit 28 may also control the high-frequency generation circuit 26 to perform frequency modulation even when the voltage of the AC power supply 21 is near the zero crossing point Z1. Specifically, the oscillation control circuit 28 may control the high-frequency generation circuit 26 to perform frequency modulation when the voltage of the AC power supply 21 is 50% (half) or less of the maximum voltage V1max. Furthermore, the oscillation control circuit 28 may also control the high-frequency generation circuit 26 to perform frequency modulation when the voltage of the AC power supply 21 is 20% or 30% or less of the maximum voltage V1max.

[0051] In the second embodiment described above, the processor 52, acting as the oscillation control unit, controlled the high-frequency generation circuit 26 to perform frequency modulation, switching the frequency of the drive signal V when the voltage of the amplitude modulation signal V2 was 0% (zero) of the maximum voltage V2max. However, the processor 52 may also control the high-frequency generation circuit 26 to perform frequency modulation even near the timing Z2 when the voltage of the amplitude modulation signal V2 becomes zero. Specifically, the processor 52 may control the high-frequency generation circuit 26 to perform frequency modulation when the voltage of the amplitude modulation signal V2 is 50% (half) or less of the maximum voltage V2max. Furthermore, the processor 52 may also control the high-frequency generation circuit 26 to perform frequency modulation when the voltage of the amplitude modulation signal V2 is 20% or less or 30% or less of the maximum voltage V2max.

[0052] In the above embodiments, five-frequency ultrasonic oscillators 20, 51 that switch between five frequencies were used, but two to four-frequency ultrasonic oscillators that switch between two to four frequencies may be used, or six or more-frequency ultrasonic oscillators that switch between six or more frequencies may be used. Note that the more frequencies that can be switched, the more complex the action of the ultrasonic waves S1 becomes, thus improving cleaning efficiency.

[0053] In each of the above embodiments, the high-frequency generation circuit 26 of the ultrasonic oscillators 20, 51 controlled the frequency of the drive signal V to switch in the order of 40kHz → 41kHz → 42kHz → 41kHz → 40kHz → 39kHz → 38kHz → 39kHz → 40kHz →… That is, the high-frequency generation circuit 26 set the amount of change when switching the frequency to a constant value (1kHz). However, the high-frequency generation circuit 26 may set the amount of change when switching the frequency to multiple values ​​of 1kHz or more and randomly select from those values. For example, the high-frequency generation circuit 26 may control the frequency to change in steps in the order of 38kHz → 41kHz (change amount 3kHz) → 39kHz (change amount 2kHz) → 42kHz (change amount 3kHz) → 40kHz (change amount 2kHz) → 38kHz (change amount 2kHz). In this way, since the frequency changes randomly, the sound pressure of the ultrasonic waves S1 irradiated onto the surface of the object to be cleaned 14 is constantly changing. As a result, the surface of the object to be cleaned 14 is cleaned evenly, further improving cleaning efficiency.

[0054] In each of the above embodiments, the oscillation control unit (oscillation control circuit 28, processor 52) controlled the high-frequency generation circuit 26 to perform frequency modulation, switching the frequency of the drive signal V to a different frequency. However, the oscillation control unit may also change the maximum amplitude Hmax of the drive signal V at the same time as switching the frequency, or change the length of the period T3 (see Figure 5) of the drive signal V at the same time as switching the frequency. In order to achieve these, it is preferable to adopt the second embodiment.

[0055] • In each of the above embodiments, the high-frequency generation circuit 26 performed amplitude modulation with a modulation degree of 100%, where the amplitude of the drive signal V was modulated within a range of 0% to 100% of the maximum amplitude Hmax. However, amplitude modulation with different modulation degrees may also be performed.

[0056] • In each of the above embodiments, the high-frequency generation circuit 26 performed frequency modulation by stepwise switching between multiple frequencies, but it may also perform frequency modulation that continuously changes the frequency without step. Specifically, the high-frequency generation circuit 26 may perform sweep modulation in which the frequency is gradually increased (or decreased) within each period T3 (see Figure 5) of the drive signal V.

[0057] In the first embodiment described above, the power supply voltage detection circuit 27 detects the voltage of the AC power supply 21 by monitoring the pulsating current 40, which is the driving power supply, and outputs the result to the oscillation control circuit 28. However, the power supply voltage detection circuit 27 may also detect the voltage of the AC power supply 21 by monitoring the AC power supply 21 and output the result to the oscillation control circuit 28. In this case, the power supply voltage detection circuit 27 detects the zero-crossing point Z0 (see in Figure 1 and Figure 2), which is the point where the AC voltage of the AC power supply 21 becomes 0V, by monitoring the AC current of the AC power supply 21 before full-wave rectification (before the pulsating current 40 is generated), and outputs the result to the oscillation control circuit 28 as a trigger signal at 0V.

[0058] The power supply voltage detection circuit 27 and the oscillation control circuit 28 in the first embodiment described above may be configured in hardware, but the CPU may be made to perform the same operations as the power supply voltage detection circuit 27 and the oscillation control circuit 28 by predetermined software.

[0059] • In the above embodiments, the ultrasonic oscillator 20 was used in ultrasonic cleaning machines 10 and 50, but it may also be used in other applications, such as ultrasonic dispersers, ultrasonic sterilizers, ultrasonic reactors that carry out chemical reactions using sonochemistry, etc.

[0060] Next, in addition to the technical ideas described in the claims, the technical ideas that can be grasped by the embodiments described above are listed below.

[0061] (1) An ultrasonic cleaning machine according to any one of claims 1 to 3, characterized in that the high-frequency generating unit performs amplitude modulation, which modulates the amplitude of the drive signal within a range of 0% to 100% of the maximum amplitude.

[0062] (2) The ultrasonic cleaning machine according to claim 1, characterized in that the oscillation control unit controls the high-frequency generating unit to perform frequency modulation, which switches the frequency of the drive signal to a different frequency at regular intervals when the power supply voltage unit detects that the voltage of the commercial AC power supply is 30% or less of the maximum voltage.

[0063] (3) The ultrasonic cleaning machine according to claim 4, characterized in that the oscillation control unit controls the high-frequency generating unit to perform frequency modulation, which switches the frequency of the drive signal to a different frequency at regular intervals when the voltage of the amplitude modulation signal is 30% or less of the maximum voltage.

[0064] (4) An ultrasonic cleaning machine according to any one of claims 1 to 3, characterized in that the rectifier unit generates a pulsating flow in which a plurality of positive voltage units are successive by performing full-wave rectification which converts the negative voltage portion of the AC voltage of the commercial AC power supply into a positive voltage portion.

[0065] (5) An ultrasonic reactor comprising: a rectifier unit that full-wave rectifies a commercial AC power supply to generate a pulsating current; a high-frequency generator unit that takes the pulsating current generated by the rectifier unit as a drive power supply, oscillates a high frequency, and outputs a high-frequency drive signal to an ultrasonic transducer; an oscillation control unit that drives and controls the drive signal output from the high-frequency generator unit; and a power supply voltage detection unit that monitors the commercial AC power supply or the pulsating current which is the drive power supply, detects the voltage of the commercial AC power supply, and outputs the result to the oscillation control unit, wherein the high-frequency generator unit performs amplitude modulation synchronized with the voltage change of the commercial AC power supply based on the input pulsating current, and the oscillation control unit controls the high-frequency generator unit to perform frequency modulation such that it switches the frequency of the drive signal to another frequency when the power supply voltage detection unit detects that the voltage of the commercial AC power supply is less than or equal to half of the maximum voltage.

[0066] (6) An ultrasonic reactor comprising: a drive power generation unit that generates a DC drive power supply by full-wave rectifying a commercial AC power supply; a high-frequency generation unit that receives the DC drive power supply generated by the drive power generation unit, oscillates a high frequency, and outputs a high-frequency drive signal to an ultrasonic transducer; and a processor as an oscillation control unit that generates an amplitude modulation signal for controlling amplitude modulation and outputs it to the high-frequency generation unit, thereby controlling the drive signal output from the high-frequency generation unit, wherein the high-frequency generation unit performs amplitude modulation synchronized with the voltage change of the input amplitude modulation signal, and the processor as an oscillation control unit controls the high-frequency generation unit to perform frequency modulation, which switches the frequency of the drive signal to another frequency when the voltage of the amplitude modulation signal is less than or equal to half of the maximum voltage. [Explanation of symbols]

[0067] 10,50... Ultrasonic cleaning machine 13… Ultrasonic transducer 21…AC power supply as a commercial AC power source 23...Rectifier circuit as a rectifier section 24...First power supply circuit as a drive power supply generation unit 26...High-frequency generation circuit as a high-frequency generation unit 27...Power supply voltage detection circuit as a power supply voltage detection unit 28…Oscillator control as an oscillator control unit 40…pulsating current 52…Processor as an oscillator control unit T4…certain time V...Drive signal V1max, V2max... Maximum voltage V2… Amplitude Modulated Signal Z1... Zero Cross Point Z2... The timing of becoming zero

Claims

[Claim 1] A rectifier section that generates a pulsating current by full-wave rectifying the commercial AC power supply, A high-frequency generation unit receives the pulsating current generated by the rectifier as a driving power source, oscillates a high frequency, and outputs a high-frequency driving signal to an ultrasonic transducer. An oscillation control unit that drives and controls the drive signal output from the high-frequency generation unit, A power supply voltage detection unit monitors the pulsating current which is the commercial AC power supply or the drive power supply to detect the voltage of the commercial AC power supply and outputs the result to the oscillation control unit. In addition to being equipped, The high-frequency generation unit performs amplitude modulation synchronized with the voltage change of the commercial AC power supply based on the input pulsating current, The power supply voltage detection unit detects the zero-crossing point of the voltage of the commercial AC power supply and outputs the result to the oscillation control unit. The oscillation control unit controls the high-frequency generation unit to perform frequency modulation, which switches the frequency of the drive signal to a different frequency at regular intervals when the voltage of the commercial AC power supply reaches the zero-crossing point. An ultrasonic cleaning machine characterized by the following features.

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