JP3087521B2 - Magnetron abnormality detection method and high-frequency heating device using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high frequency heating apparatus for heating a dielectric material such as food by utilizing microwave dielectric heating, and more particularly to a power supply for generating microwaves.

[0002]

2. Description of the Related Art Conventionally, this type of high-frequency heating apparatus is configured such that a magnetron 3 is driven by an inverter power supply 2 as shown in FIG. The inverter power supply 2 receives supply of power from the commercial power supply 1 and obtains a main semiconductor switching element for converting into high-frequency AC, a resonance circuit including a capacitor and an inductor, and a high voltage necessary for driving a magnetron. And a step-up transformer. When energized by the inverter power supply 2, the magnetron 3 oscillates at about 2.4 GHz and generates microwaves. The magnetron 3 is provided with a temperature switch 20. The temperature switch 20 serves to cut off the power supply to the inverter power supply to prevent danger when the temperature of the magnetron 3 rises abnormally for some reason.

FIG. 8 is a perspective view of the appearance of a high-frequency heating device, showing the arrangement of an inverter power supply 2, a magnetron 3, and a temperature switch 20. After the object to be heated is placed in the cavity 21 and the door is closed, the object is irradiated with microwaves generated from the magnetron 3 and subjected to dielectric heating. The rate at which microwaves are absorbed changes depending on the shape or dielectric constant of the object to be heated, which is a load of the magnetron. Therefore, depending on the load, microwaves are hardly absorbed. Such loads may increase magnetron losses and may cause abnormal temperature rise of the magnetron. In addition, the magnetron may cause abnormal oscillation called moding due to the end of life or some other cause. Even in such a case, an abnormal temperature rise of the magnetron is caused. Further, when the temperature of the cavity rises abnormally due to excessive heating of the object to be heated placed in the cavity 21, the magnetron receives the heat and may cause an abnormal rise in temperature. Such an abnormal increase in the temperature of the magnetron may cause the magnetron to become cheaper to cause moding and may cause a temperature runaway. A temperature switch is provided to ensure safety against such an abnormal temperature rise of the magnetron.

[0004]

However, in the above-described configuration, when the moding occurs at a light load of a hop cone or the like, and the temperature of the magnetron rises abnormally, the temperature switch is turned off and cooking cannot be performed. There were challenges. In addition, there is a problem that deterioration of the magnetron due to moding under light load progresses and its life is shortened. Further, there is a problem that even if the temperature switch is turned off and cooking cannot be performed, the user of the high-frequency heating device cannot recognize the state. Furthermore, at the end of the life of the magnetron, moding is likely to occur and the temperature of the magnetron may rise abnormally.However, the temperature switch attached to the magnetron operates only when the magnetron temperature rises due to the modding. Or an increase in magnetron temperature due to overheating of the load,
Due to causes such as an increase in the ambient temperature around the high-frequency heating device, even if the temperature switch is turned off, it cannot be determined that moding has occurred in the magnetron, so it can be determined that the life of the magnetron has reached the end of life. However, there was a problem that it was not possible to know exactly when to replace the magnetron.

[0005]

In order to solve the above-mentioned problems, the present invention has the following method and a configuration using the same.

First, an input current detecting means for detecting an input current to the inverter power supply, and information on the input current obtained by the input current detecting means is compared with a predetermined reference value to detect abnormal oscillation of the magnetron. Was detected.

Secondly, in the above method, the abnormal oscillation detecting means comprises a first judging means for detecting the presence / absence of abnormal oscillation of the magnetron and a second judging means for judging the frequency of abnormal oscillation.

Third, in the above method, the first judging means comprises a reference level adjusted by setting the magnitude of the microwave output, and comparing means for comparing the reference level with information on the input current. And

Fourthly, an inverter power supply, a magnetron energized by the inverter power supply, an abnormal oscillation detecting means for detecting abnormal oscillation of the magnetron, and an output of the inverter power supply controlled by information from the abnormal oscillation detecting means. And control means.

Fifth, an inverter power supply, a magnetron energized by the inverter power supply, an abnormal oscillation detecting means for detecting abnormal oscillation of the magnetron, and an output of the inverter power supply controlled by information from the abnormal oscillation detecting means. It comprises control means and means for displaying or storing control information of the control means.

[0011]

According to the present invention, first, the input current to the inverter power supply is detected and compared with a predetermined reference value , so that the occurrence of moding, which is an abnormal operation of the magnetron, can be detected.

Second, the abnormal oscillation detecting means is constituted by first judging means for detecting the presence or absence of abnormal oscillation of the magnetron and second judging means for judging the frequency of abnormal oscillation. The modulating frequency can be determined.

Third, the first judging means comprises a reference level adjusted by setting the magnitude of the microwave output, and comparing means for comparing the reference level with information on the input current. Even if the magnitude of the microwave output is set variously, it is possible to accurately detect the magnetron moding.

Fourth, by comprising the control means for controlling the output of the inverter power supply based on the information from the abnormal oscillation detection means, it is possible to reduce the output of the inverter power supply when the magnetron moding occurs.
As a result, even if the object to be heated is lightly loaded, the microwave output can be reduced and heating can be performed while suppressing the moding. Degradation can be prevented.

Fifth, by comprising control means for displaying or storing the control information of the control means, the user of the high-frequency heating device recognizes that the output of the inverter power supply has been reduced due to the occurrence of moding of the magnetron. Depending on the type of object to be heated by the high-frequency heating device, it can be determined whether moding is occurring due to light load or modulating due to the end of the life of the magnetron. Has the effect of being able to. That is, it is possible to accurately know the magnetron replacement time.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, reference numeral 1 denotes a commercial power supply for supplying power to a second inverter power supply. The magnetron 3 is energized by the output of the inverter power supply 2 to generate microwaves. 4 is an input current detecting means. The inverter power supply 2 is composed of component parts such as a main semiconductor switching element 5 and a transformer 6, and converts a commercial power supply into a high-frequency AC, boosts the voltage with a transformer, and generates a high voltage necessary for energizing the magnetron. The transformer 6 not only boosts the voltage but also matches the impedance between the primary side (the side to which the commercial power supply is connected) and the secondary side (the side to which the magnetron 3 is connected) of the transformer 6. It also has a role to take.

The magnetron 3 is a so-called bipolar vacuum tube, having a cathode and an anode, and is composed of a magnet for creating a magnetic field, oscillates at a frequency of 2.4 GHz, and outputs microwaves. The cathode uses tungsten, from which electrons are emitted. If the cathode deteriorates or the cathode temperature rises or falls abnormally due to the use of a high-frequency heating device with no load, stable emission of electrons will not be performed. Cause abnormal oscillation. If this modulating occurs continuously, the temperature of the magnetron itself rises abnormally, causing the destruction of the magnet and the melting of the cooling aluminum fins that constitute a part of the magnetron, resulting in a dangerous state. When the moding occurs, a change occurs in the input current of the second inverter power supply. Therefore, by detecting the input current using the input current detecting means 4 and transmitting the information to the abnormal oscillation detecting means 7, the occurrence of the moding can be detected. Specifically, FIG.
The waveform I1 shown in (C) is the input current waveform, and when the moding occurs, a sudden change in the current occurs as shown in FIG. This is caused by a sudden impedance change of the magnetron due to the moding. Therefore, by detecting the sudden change in the input current by the abnormal oscillation detecting means 7, it is possible to detect the magnetron moding.

Returning to FIG. 1, the abnormal oscillation detecting means 7 comprises a first judging means 8 and a second judging means 9. The first judging means 8 rectifies and divides the output voltage of the input current detecting means 4 and divides the voltages V2 and 17 by the reference voltage V2.
3, a comparing means 11 for comparing a voltage V5 obtained by rectifying and dividing the voltage of the commercial power supply 1 with a reference voltage V6, an output voltage V4 of the comparing means 10 and a comparing means It comprises a logical operation means 12 for performing a logical operation with the output voltage V7.

FIG. 2A shows a voltage waveform V1 of a commercial power supply, and FIG. 2B shows an input current waveform I1 in the same phase. (C) shows the input current waveform I1 when moding occurs. (D) shows the voltage V2 obtained by rectifying and dividing the output voltage detected by the input current detection means 4 of the input current of (C). FIG. 3A shows the voltage V2 and the reference voltage V3, and FIG. 3B shows the output voltage V4 of the comparing means 10. An output voltage is generated when V2 becomes lower than V3. Since the output voltage V4 is output when moding occurs and in the vicinity of the valley of the envelope, it is impossible to detect only the moding as it is. Therefore, as shown in FIG. 3C, the voltage V5 obtained by rectifying and dividing the voltage of the commercial power supply is compared with the reference voltage V6 by the comparison means 11 to obtain the output voltage V7 shown in FIG. When the product of the output voltage V7 and the output voltage V4 is performed by the logic operation means 12, an output voltage V8 as shown in (E) is obtained. This output voltage V8 is a voltage that is output only when moding occurs.

If this moding occurs continuously, the temperature of the magnetron itself rises abnormally, causing destruction of the magnet and melting of the cooling aluminum fins that constitute a part of the magnetron, resulting in a dangerous state. Since the intermoding does not cause an abnormal rise in the temperature of the magnetron, it is necessary to know the degree of occurrence of the moding. The second judging means 9 shown in FIG. 1 judges the degree of occurrence of the moding. The second judging means 9 is composed of a capacitor and a resistor.
The capacitor is charged with the output voltage V8 of 2 and
It is configured to be discharged through a resistor. Accordingly, the time constant can be set by the capacitor and the resistor so that the output voltage of a certain level can be obtained from the second judging means 9 when the magnetron is in such a state that the magnetron is in a dangerous state.

FIG. 4 shows a configuration in which the reference voltage V3 applied to the comparison means 10 constituting the first judgment means 8 is applied from the microcomputer 13. The microcomputer 13 transmits a signal to control means 16 for driving the main semiconductor switching element of the inverter power supply 2 based on information provided from the operation unit 14, and the control means 16 controls the output of the inverter power supply to the main semiconductor switching element based on the signal. It is configured to be variable by doing so. When the output of the inverter power supply is varied, the input current also changes in proportion thereto. Therefore, the voltage V2 obtained by rectifying and dividing the output voltage of the input current detecting means 4 also changes. FIG. 5 shows this state, where the waveform V2 shows the case where the input current is large, and the waveform V2 'shows the case where the input current is small. If the reference voltage V3 applied to the comparing means 10 is a waveform V2 corresponding to a large input current, the moding can be detected. However, if the reference voltage V3 is a waveform V2 corresponding to a small input current, the reference voltage V3 has a waveform. Since it is larger than V2, it becomes impossible to detect the moding. For this reason, when the input current is small, it is necessary to reduce the voltage of the reference voltage V3 accordingly to V3 '. That is, when the output of the inverter power supply changes, the input current also changes in proportion thereto, so that the reference voltage V3 applied to the comparison means 10 must also change with the change of the output of the inverter power supply. In the embodiment shown in FIG. 4, the signal from the microcomputer 13 causes the inverter power supply to set the magnitude of the output. The microcomputer 13 sets the drive time and output of the inverter power supply according to a signal from an operation unit provided in the high-frequency heating device,
The signal is transmitted to the inverter power supply 2. Therefore, the reference voltage V3 supplied to the comparing means 10 is supplied from the microcomputer 13 so that the reference voltage V3 corresponding to the output setting of the inverter power supply is supplied to the comparing means 10.

In one embodiment of the present invention shown in FIG. 6, the signal obtained by the input current detecting means 4 is transmitted to an abnormal oscillation detecting means 7 comprising a first judging means 8 and a second judging means 9. The output of the abnormal oscillation detecting means 7 is transmitted to the control means 16 for driving the main semiconductor switching element 5 of the inverter power supply 2. More specifically, the modulating occurs in the magnetron, the abnormal oscillation is detected by the abnormal oscillation detecting means 7, and a signal corresponding to the frequency of the modulating is transmitted to the controlling means 16. The output of the inverter power supply 2 is adjusted by changing the drive frequency of the main semiconductor switching element 5 according to That is, if moding occurs, the output of the inverter power supply 2 is reduced according to the level.

FIG. 6 shows that the control means 16 transmits a signal indicating the driving state of the main semiconductor switching element 5 to the microcomputer 13. This signal is a signal indicating that the output of the inverter power supply 2 is being adjusted by changing the drive frequency of the main semiconductor switching element 5 according to the output level of the abnormal oscillation detecting means 7. That is, in order to notify the user of the high-frequency heating device of the state in which the moding has occurred and the output of the inverter power supply 2 has been reduced or stopped,
A signal is transmitted from the control means 16 to the microcomputer 13, and in accordance with the signal, the microcomputer 13 transmits a signal to the display unit 15, and the display unit 15 outputs the magnitude of the output of the inverter power supply 2 or a state such as stop of operation. Is displayed.

As described above, in the present invention, the magnetron abnormality can be detected by a method of comparing the input current information to the inverter power supply with the reference value of the abnormality detection means. Further, by adjusting the output of the magnetron by the control means based on the output from the abnormality occurrence detection means, the reliability of the high-frequency heating device can be improved.

[0026]

The present invention has the following effects by the above-described configuration.

That is, first, by detecting the input current to the inverter power supply and comparing it with a predetermined reference value, it is possible to detect the occurrence of moding, which is an abnormal operation of the magnetron.

Second, the abnormal oscillation detecting means is constituted by first judging means for detecting the presence or absence of abnormal oscillation of the magnetron and second judging means for judging the frequency of abnormal oscillation, so that the magnetron is generated. The modulating frequency can be determined.

Third, the first judging means comprises a reference level adjusted by setting the magnitude of the microwave output, and a comparing means for comparing the reference level with information on the input current. Even if the magnitude of the microwave output is set variously, it is possible to accurately detect the magnetron moding.

Fourth, by comprising the control means for controlling the output of the inverter power supply in accordance with the information from the abnormal oscillation detection means, the output of the inverter power supply can be reduced when the magnetron moding occurs.

Fifthly, by comprising means for displaying or storing the control information of the control means, the user of the high-frequency heating device recognizes that the output of the inverter power supply has been reduced due to the occurrence of the magnetron moding. Depending on the type of object to be heated by the high-frequency heating device, it can be determined whether moding is occurring due to light load or modulating due to the end of the life of the magnetron. it can.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a circuit configuration of a high-frequency heating device according to an embodiment of the present invention.

FIG. 2 is a waveform chart for explaining the operation of the circuit of the high-frequency heating device.

FIG. 3 is a waveform chart for explaining the operation of the circuit of the high-frequency heating device.

FIG. 4 is a circuit diagram showing a circuit configuration of a high-frequency heating device according to another embodiment of the present invention.

FIG. 5 is a waveform chart for explaining the operation of the circuit of the high-frequency heating device.

FIG. 6 is a circuit diagram showing a circuit configuration of a high-frequency heating device according to another embodiment of the present invention.

FIG. 7 is a circuit diagram showing a circuit configuration of a conventional high-frequency heating device.

FIG. 8 is a partially cutaway perspective view of a high-frequency heating device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Commercial power supply 2 Inverter power supply 3 Magnetron 4 Input current detection means 7 Abnormal oscillation detection means 8 First judgment means 9 Second judgment means 10 Comparison means 16 Control means 17 Reference level 15 Display means

Continuing on the front page (72) Inventor Kazuho Sakamoto 1006 Kadoma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. Inventor Toyotsugu Matsukura 1006 Kazuma Kadoma, Osaka Pref.Matsushita Electric Industrial Co., Ltd. (72) Inventor Makoto Shibuya 1006 Kadoma Kadoma, Kadoma City Osaka Pref. 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) References JP-A-3-78995 (JP, A) JP-A 1-313887 (JP, A) JP-A 1-225090 (JP) , A) Japanese Utility Model Application Hei 4-111191 (JP, U) Japanese Utility Model Application Hei 4-105493 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) H05B 6/66-6/68

Claims (5)

(57) [Claims] 1. An inverter power supply for receiving input power, converting the input power into high-frequency AC power, boosting the voltage and energizing a magnetron, input current detection means for detecting an input current to the inverter power supply, and an abnormality of the magnetron. It consists abnormal oscillation detection means for detecting the oscillation, the abnormal oscillation detection hand
The stage includes a maximum input current detected by the input current detection means.
The reference value provided between the value and the minimum value, and the
Compare with the value caused by a sudden change that cannot occur under normal conditions.
A method for detecting magnetron abnormalities by detecting abnormal oscillation of magnetrons by comparing . Wherein abnormal oscillation detection means and the first determining means for detecting the presence or absence of abnormal oscillation of the magnetron, the magnet
2. The magnetron abnormality detection method according to claim 1, further comprising a second determination unit configured to determine the frequency of the abnormal oscillation of the magnetron. Wherein the first determination means and a reference level to be adjusted by setting the size of the microwave power, composed of a comparing means for comparing the information of the reference level and the input current claims 1 or magnetron abnormality detection method described in 2. 4. An inverter power supply for receiving input power, converting the input power into high-frequency AC power, boosting the voltage and energizing the magnetron, abnormal oscillation detection means for detecting abnormal oscillation of the magnetron, and detecting abnormal oscillation of the magnetron. wherein the information from the unit to any one of claims 1 to 3 comprising a control means for controlling an output of the inverter power supply
High-frequency heating device using the abnormality detection method . 5. The high-frequency heating apparatus according to claim 4, further comprising means for displaying or storing control information of the control means.