JP2013033601A - Microwave processing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to prevent a semiconductor element from being damaged by heat generated by reflection power even if very large reflection power is generated when the frequency of a microwave is swept.SOLUTION: A microwave processing device makes microwave generation means radiate a microwave of a chirp signal to an object before processing of the object, and determines a frequency at which detected reflection power becomes minimum or local minimum as a processing frequency. By generating a microwave with the determined processing frequency at the time of processing the object, reflection power generated at the time of processing the object is reduced. Even if the microwave generation means generates heat due to the reduced reflection power, the microwave generation means is prevented from being damaged and broken down as a result of the reduced heat quantity. In addition, using the chirp signal allows the processing frequency to be determined with one sweep, which allows quality of the object to be less deteriorated than the prior art, and allows a processing time to be shortened.

Description

  The present invention relates to a microwave processing apparatus that processes an object with microwaves.

  Conventionally, microwave generators using semiconductor elements have been proposed in place of magnetrons generally used as microwave generators. According to the microwave generator using the semiconductor element, the frequency of the microwave can be easily adjusted with a small and inexpensive configuration. As described above, Patent Document 1 discloses a high-frequency heating device including a microwave generator using a semiconductor element.

  In the high-frequency heating device of Patent Document 1, the microwave frequency is swept in a predetermined frequency band, and the microwave frequency when the reflected power shows the minimum value is stored. And the microwave of the memorize | stored frequency is radiated | emitted from the antenna in a heating chamber, and a target object is heated. Thereby, power conversion efficiency improves.

JP-A-56-96486

  The semiconductor element is used in a state where the heat dissipation member is in contact. When the semiconductor element generates heat due to the reflected power, heat dissipation is performed by the heat dissipation member. However, when a very large reflected power is generated when the microwave frequency is swept, the heat generated by the reflected power may exceed the heat dissipation capability of the heat dissipation member. In this case, the semiconductor element may be damaged. In addition, when the microwave frequency is swept, the object to be heated such as food is irradiated with the microwave for a long time, so that the quality of the object may be deteriorated, and there is a problem that the processing time becomes longer. An object of the present invention is to provide a microwave processing apparatus that improves power conversion efficiency, prevents damage to a microwave generation apparatus due to reflected power, and operates at high speed.

  A microwave processing apparatus according to the present invention is a microwave processing apparatus that processes an object using microwaves, and includes microwave generation means for generating microwaves, and microwaves generated by the microwave generation means. A radiation unit that radiates to the object; a detection unit that detects reflected power from the radiation unit; and a control unit that controls the microwave generation unit. The control unit includes a microwave generation unit before processing the object. The microwave of the chirp signal is radiated from the radiating unit to the object, and the microwave frequency for processing the object is determined as the processing frequency based on the frequency at which the reflected power detected by the detection means is minimized or minimized. Then, at the time of processing the object, the microwave having the determined processing frequency is generated by the microwave generating means.

  As described above, since the microwave having the processing frequency determined based on the frequency at which the reflected power from the radiating unit is minimized or minimized is used for processing the object, the reflected power generated when the object is processed is reduced. The Thereby, the power conversion efficiency of the microwave processing apparatus is improved. Further, even when the microwave generating means generates heat due to the reflected power, the amount of generated heat is reduced.

As a result, breakage and failure of the microwave generation means due to the reflected power are prevented. The control means sets the power of the microwave radiated from the radiating unit to the target before processing the target to a value smaller than the power of the microwave radiated from the radiating unit to the target during processing of the target. Also good.

  In this case, the power of the microwave radiated from the radiating unit to the target object with the microwave of the chirp signal before the processing of the target part is smaller than the power of the microwave radiated when the target part is processed. It is possible to prevent the object from being processed by the microwave having a large electric power before the processing.

  Thereby, power consumption before the processing of the object is reduced, and the object is processed under undesired conditions and the quality of the object is prevented from being deteriorated. The treatment of the object may be a heat treatment, and the microwave processing apparatus may further include a heating chamber that accommodates the object for heating. In this case, the object can be heat-treated by accommodating the object in the heating chamber.

  According to the present invention, the microwave having the processing frequency determined based on the frequency at which the reflected power from the radiating unit is minimized or minimized is used for the processing of the object. Therefore, the reflected power generated during the processing of the object is reduced. Reduced. Thereby, the power conversion efficiency of the microwave processing apparatus is improved, and damage and failure of the microwave generating means due to heat caused by the reflected power are prevented. In addition, since the microwave frequency is swept in a short time, it is possible to provide a microwave processing apparatus that can prevent deterioration of food and the like and can process at high speed.

1 is a block diagram illustrating a configuration of a microwave generator according to a first embodiment. Explanation of chirp signal The figure which shows the example of a FFT process result The flowchart which shows the control procedure of the microwave generator of FIG.

(Embodiment 1)
The microwave processing apparatus according to the present invention will be described below.

(1-1) Description of Configuration FIG. 1 is a block diagram illustrating a configuration of a microwave processing apparatus. As shown in FIG. 1, the microwave processing apparatus according to the present embodiment includes a chirp signal generator 1, an amplifier 2, a circulator 3, a heating chamber 9, and a microcomputer 11. The heating chamber 9 includes an antenna 4 and an object. The microcomputer 11 includes a frequency determination process 5, an FFT process 6, an A / D converter 7, and a control unit 10. The chirp signal generator 1 outputs a signal continuously variable with the frequencies f0, f1, f2,... Fn as shown in FIG. 2 by the linear frequency modulation method (details of the linear frequency modulation method and the chirp signal generator). Is changed at any set step in the entire frequency band from 2400 MHz to 2500 MHz when the frequency band ISM (Industrial Scientific and Medical) band is used. For example, in the case of 10 MHz steps, f0 = 2400 MHz, f1 = 2410 MHz, f2 = 2420 MHz... Fn = 2500 MHz. Further, the chirp signal generator 1 can output a continuous wave having an arbitrary constant frequency according to a command from the microcomputer 11. The amplifier 2 amplifies the signal output from the chirp signal generator 1 to a desired power value. The circulator 3 functions to transmit the reflected wave from the antenna 4 to the A / D converter 7 while operating the amplifier 2 stably. The antenna 4 is installed in a heating chamber 9 made of metal or a material that reflects electromagnetic waves, and functions to radiate a chirp signal amplified by the amplifier 2, and propagates, reflects or directly passes through the heating chamber 9. 8 is irradiated with a chirp signal. Here, in the heating chamber 9, the natural frequency is determined by the eigenvalue depending on the structure and the position, size, composition, and the like of the object 8, and frequencies other than the natural frequency are reflected outside the heating chamber 9. For example, when the natural frequency is 2420 MHz and the chirp signal is output at 10 MHz step and f0 = 2400 MHz, f1 = 2410 MHz, f2 = 2420 MHz ·· fn = 2500 MHz, the power of f2 is absorbed in the heating chamber 9. The power of other frequencies is reflected and received by the antenna 4 and then transmitted to the microcomputer 11 via the circulator 3. In the microcomputer 11, when converted to a digital signal by the A / D converter 7 and then converted from the time axis to the frequency axis by the FFT processing 6, the power value of the reflected signal in frequency units can be obtained. In the above example, as shown in FIG. 3, only the natural frequency f2 = 2420 MHz in the heating chamber 9 results in the reflected power value being lower than the other f0, f1, f3... Fn. In the frequency determination process 5, the frequency at which the power value is minimum and minimum is examined based on the result of the FFT process 6. In the case of the above example, it is determined that the optimum frequency for heating the object 8 is f2 = 2420 MHz, and the control unit 10 sets the chirp signal generator 1 to emit a continuous wave with a frequency of 2420 MHz. At the same time, the amplifier 2 is adjusted to be larger than the power value when the chirp signal is output, and the object 8 is heated.

(1-2) Description of Operation Flow FIG. 4 is a flowchart showing a control procedure of the microcomputer 11 of FIG. The microcomputer 11 in FIG. 1 performs the following microwave processing when the heating of the object is commanded by the user's operation. As shown in FIG. 4, the microcomputer 11 controls the amplifier 2 by the control unit 10 to set a predetermined first output power. The first output power is smaller than the second output power described later.

  For example, when the microwave processing apparatus according to the present embodiment is applied to a microwave oven with a rating of 1000 W, the second output power is 1000 W, and the first output power may be a value smaller than this, It may be set to 1/5, 200 W, or 1/10, 100 W. Further, when the output power of the chirp signal generator 1 is 0.1 W and the first output power is 100 W, the amplifier 2 is set so that it can amplify 1000 times.

  Next, the control unit 10 sets the frequency of the microwave generated by the chirp signal generator 1 over the entire frequency band of, for example, 2400 MHz to 2500 MHz (this frequency band is called an ISM: Industrial Scientific and Medical band). In addition, in the case of 10 MHz steps, settings such as f0 = 2400 MHz, f1 = 2410 MHz, f2 = 2420 MHz... Fn = 2500 MHz are performed, and the chirp signal generator 1 is turned on.

  For example, in the high-frequency heating device disclosed in Patent Document 1, the microwave frequency is swept in a predetermined frequency band, and the microwave frequency when the reflected power shows the minimum value is stored. When time is required, the entire ISM band requires 100 ms. However, when the microwave processing apparatus according to the present embodiment is applied, one sweep is sufficient and the time can be reduced to 10 ms.

  Next, the A / D converter 7 in FIG. 1 is turned on, the detected signal is subjected to FFT processing, the relationship between the reflected power and the frequency is calculated, and the result is stored.

Note that the microcomputer 11 may store only the relationship between the reflected power and the frequency when the reflected power shows a minimum value, instead of storing the relationship between the reflected power and the frequency in the entire frequency band of the microwave frequency. Good. In this case, the use area of the storage device in the microcomputer 11 can be reduced. Subsequently, the frequency determination process 5 performs a frequency determination process for extracting a specific frequency from the ISM band. In this frequency determination process 5, for example, a specific reflected power (for example, a minimum value) is identified from the stored reflected power, and the frequency when the reflected power is obtained is extracted as the main heating frequency.

  In the example of FIG. 3, 2420 MHz is set as the main heating frequency. Next, the control unit 10 sets a predetermined second output power. This 2nd output electric power is electric power for heating the target object arrange | positioned in the heating chamber 9 of FIG.

  Then, the control unit 10 sets the chirp signal generator 1 to a continuous wave of the main heating frequency, and then sets the amplifier 2 so as to have the second output power. For example, when the output power of the chirp signal generator 1 is 0.1 W and the second output power is 1000 W, the amplifier 2 is set so that it can be amplified 10,000 times. Next, the chirp signal generator 1 is turned on to radiate microwaves of the main heating frequency from the antenna 4 into the heating chamber 9. Thereby, the target object arrange | positioned in the heating chamber 9 is heated (main heating).

(1-3) Correspondence between Each Component of Claim and Each Part of Embodiment The following describes an example of correspondence between each component of the claim and each part of the embodiment, but the present invention is not limited to the following example. .

  In the present embodiment, the microwave generation means corresponds to the chirp signal generation device 1, the amplifier 2, and the circulator 3, the radiation section corresponds to the antenna 4, and the detection means includes frequency determination processing included in the microcomputer 11. 5, the FFT processing 6 and the A / D converter 7, and the control means corresponds to the control unit 10 included in the microcomputer 11.

  INDUSTRIAL APPLICABILITY The present invention can be used for a processing apparatus that generates reflected power, such as a microwave oven, a plasma generator, a drying apparatus, and an apparatus that promotes an enzyme reaction.

DESCRIPTION OF SYMBOLS 1 Chirp signal generator 2 Amplifier 3 Circulator 4 Antenna 5 Frequency determination process 6 FFT process 7 A / D converter 8 Target object 9 Heating chamber 10 Control part 11 Microcomputer

Claims (3)

A microwave processing apparatus for processing an object using a microwave, a microwave generation means for generating a microwave, and a radiation unit for radiating a microwave generated by the microwave generation means to the object, Detection means for detecting the reflected power from the radiating section and control means for controlling the microwave generation means, the control means, before processing the object, by the microwave generation means by the microwave of the chirp signal A wave is radiated from the radiating unit to the object, and the frequency of the microwave for processing the object is determined as a processing frequency based on the frequency at which the reflected power detected by the detection unit is minimized or minimized. A microwave processing apparatus, wherein a microwave having the determined processing frequency is generated by the microwave generating means when an object is processed. The control means sets the microwave power radiated from the radiating unit to the target before processing the target to a value smaller than the microwave power radiated from the radiating unit to the target during processing of the target. The microwave processing device according to claim 1, wherein the microwave processing device is set. The microwave processing apparatus according to claim 1, wherein the processing of the object is a heat treatment, and further includes a heating chamber that accommodates the object for heating.

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