WO2018229938A1

WO2018229938A1 - Microwave heating device

Info

Publication number: WO2018229938A1
Application number: PCT/JP2017/022145
Authority: WO
Inventors: 拓海杉谷; 政毅半谷; 山中　宏治
Original assignee: 三菱電機株式会社
Priority date: 2017-06-15
Filing date: 2017-06-15
Publication date: 2018-12-20

Abstract

According to the present invention, an antenna group (3) comprises n number of antennas which radiate microwaves in a heating chamber, wherein n is an integer of at least 2. The microwaves generated from a microwave oscillator (4) are amplified by a microwave amplifier (6). An irreversible circuit group (8) is provided with: n stages of irreversible circuits (8-1 to 8-3) corresponding to the n number of antennas (3-1 to 3-3) of the antenna group (3). Each of the irreversible circuits (8-1 to 8-3) has an input terminal, a first output terminal, and a second output terminal. In the case of the irreversible circuit (8-1) of a first stage, the input terminal is connected to an output terminal of the microwave amplifier (6), and the first output terminal is connected to the corresponding antenna (3-1 to 3-3) of the antenna group (3). In the case of the irreversible circuits (8-2, 8-3) of the second to n-th stages, the input terminal is connected to the second output terminal of the irreversible circuit (8-1, 8-2) of the previous stage and the first output terminal is connected to the corresponding antenna (3-1 to 3-3) of the antenna group (3).

Description

Microwave heating device

The present invention relates to a microwave heating apparatus that radiates microwaves to an object to be heated, and more particularly, to a microwave heating apparatus that includes a plurality of antennas that radiate microwaves in a heating chamber in which an object to be heated is accommodated.

A proposal for obtaining a microwave heating apparatus with excellent energy saving performance capable of consuming 100% of the microwave power output from the microwave generator ideally as the heating energy of the object to be heated has been republished Patent No. WO2009-157110 It is made by the gazette (patent document 1).
The microwave heating device disclosed in Patent Document 1 feeds the microwave generated by the microwave generation unit to the first heating chamber and circulates the reflected microwave returning from the first heating chamber to the microwave generation unit side. The non-reciprocal circuit is configured to transmit to the second heating chamber.

Republished patent WO2009-157110

Although the micro-heating device shown in Patent Document 1 uses two antennas, one antenna is disposed in each of the first heating chamber and the second heating chamber, and one heating chamber is provided. Therefore, there is no concept of efficiently using the output of the microwave generation unit by arranging a plurality of antennas.
As long as there is no idea of arranging a plurality of antennas in one heating chamber, in order to efficiently heat various objects to be heated in different shapes, sizes, and quantities accommodated in the heating chamber from a plurality of angles. There is also no idea of arranging a plurality of antennas for one heating chamber in order to irradiate microwaves.

This invention is made in view of the above-mentioned point, arranges a plurality of antennas in a heating chamber in which an object to be heated is accommodated, reuses the reflected microwaves returning to the antenna side, An object of the present invention is to obtain a microwave heating apparatus capable of efficiently using outputs from a microwave oscillator for a plurality of antennas for various objects to be heated having different sizes and amounts.

A microwave heating apparatus according to the present invention includes an antenna group consisting of n antennas that are integers of 2 or more that radiates microwaves into a heating chamber, a microwave oscillator that generates microwaves, and the microwave oscillator. A microwave amplifier that amplifies the generated microwave and an n-stage non-reciprocal circuit corresponding to n antennas of the antenna group, each non-reciprocal circuit having an input terminal, a first output terminal, and a second In the first stage non-reciprocal circuit, the input terminal is connected to the output terminal of the microwave amplifier, the first output terminal is connected to the corresponding antenna in the antenna group, and the second to nth stages. The non-reciprocal circuit includes a non-reciprocal circuit group whose input terminal is connected to the second output terminal of the preceding non-reciprocal circuit and whose first output terminal is connected to a corresponding antenna in the antenna group.

According to the present invention, since the microwaves are radiated from the plurality of antennas to the object to be heated accommodated in the heating chamber, the antenna side with respect to various objects to be heated having different shapes, sizes, and amounts is provided. The reflected microwave that returns can be reused, and the output from the microwave oscillator can be used efficiently.

BRIEF DESCRIPTION OF THE DRAWINGS Schematic which shows typically the microwave heating apparatus which concerns on Embodiment 1 of this invention. Schematic which shows typically the microwave heating device which concerns on Embodiment 2 of this invention. Schematic which shows typically the microwave heating device which concerns on Embodiment 3 of this invention.

Embodiment 1 FIG.
A microwave heating apparatus according to Embodiment 1 of the present invention will be described with reference to FIG.
The object to be heated 2 is accommodated in the heating chamber 1 and supplied with microwaves. In the heating chamber 1, a door (not shown) for taking in and out the article to be heated 2 is provided on one side wall surface. Three side wall surfaces other than the side wall surface provided with the door of the heating chamber 1, the ceiling wall surface and the bottom wall surface are made of a shielding plate made of a metal material, and microwaves supplied into the heating chamber 1 are introduced into the heating chamber 1. Constructed to contain.

Each of the n antennas 3-1 to 3 -n radiates microwaves into the heating chamber 1, and receives microwaves reflected and returned from the object to be heated 2 and the wall surfaces constituting the heating chamber 1. These n antennas 3-1 to 3-n constitute an antenna group 3. In the first embodiment, all the n antennas 3-1 to 3-n are arranged on one side wall surface of three side wall surfaces other than the side wall surface provided with the door of the heating chamber 1.
n is an integer of 2 or more, and is 3 in the first embodiment. Considering the size of the heating chamber 1 and the shape, size, and amount of the object to be heated accommodated in the heating chamber 1, three antennas 3-1 to 3-n are preferable, but two antennas may be used. Four or more may be sufficient.

The microwave oscillator 4 that generates a microwave includes an oscillation circuit that includes a semiconductor element that generates a microwave on one main surface of a dielectric substrate that is formed of a low dielectric loss material. The microwave oscillator 4 has an oscillation frequency of 2400 MHz in an initial state, and is variably controlled based on 2400 MHz by a frequency control signal from the control means 5. In the first embodiment, the oscillation frequency of the microwave oscillator 4 is variably controlled by the control means 5, but the microwave oscillator 4 may output a constant frequency, that is, 2400 MHz. The control means 5 is formed on one main surface of the dielectric substrate on which the microwave oscillator 4 is formed. The control means 5 may be formed on the other main surface of the dielectric substrate, or may be formed on a dielectric substrate different from the dielectric substrate on which the microwave oscillator 4 is formed.

The microwave amplifier 6 amplifies the microwave output from the output terminal 4 a of the microwave oscillator 4. The microwave amplifier 6 includes an amplifier circuit constituted by a conductor pattern using a semiconductor element on a dielectric substrate made of a low dielectric loss material. The microwave amplifier 6 further includes matching circuits each formed of a conductor pattern on the same dielectric substrate as the amplifier circuit on the input side and the output side, respectively, in order to operate the amplifier circuit satisfactorily. In the first embodiment, the microwave oscillator 4 is formed on one main surface of the dielectric substrate, and the microwave amplifier 6 is formed on the other main surface of the same dielectric substrate, so that the circuit board is miniaturized. Note that the microwave oscillator 4 and the microwave amplifier 6 may be formed on separate dielectric substrates.
The microwave amplifier 6 receives the output control signal from the control means 5, and the output power level of the microwave amplifier 6 is variably controlled by this output control signal. In the first embodiment, the output power level of the microwave amplifier 6 is variably controlled by the control means 5, but the output of the microwave amplifier 6 may be rated power.

The connection between the output end 4a of the microwave oscillator 4 and the input end 6a of the microwave amplifier 6 is performed by a first microwave transmission line 7 serving as a transmission circuit constituted by a conductor pattern on a dielectric substrate. In the first embodiment, the first microwave transmission line 7 is formed by a conductor pattern on one main surface of a dielectric substrate on which the microwave oscillator 4 is formed, and has a characteristic impedance of 50Ω as a transmission circuit.

The nonreciprocal circuit group 8 includes n stages of nonreciprocal circuits 8-1 to 8-n corresponding to the n antennas 3-1 to 3-n of the antenna group 3. The n-stage nonreciprocal circuits 8-1 to 8-n have input terminals 8-1-a to 8-na, first output terminals 8-1-b to 8-nb, and second outputs, respectively. It has ends 8-1-c to 8-nc.
The first stage non-reciprocal circuit 8-1 has an input terminal 8-1-a connected to the output terminal 6b of the microwave amplifier 6 and a first output terminal 8-1-b corresponding to the corresponding antenna 3-in the antenna group 3. 1 is connected.

The non-reciprocal circuits 8-2 to 8-n from the second stage to the n-th stage are connected to the non-reciprocal circuits 8-1 to 8-n-1 of the preceding stage by the input terminals 8-2-a to 8-na. Are connected to the output terminals 8-1-c to 8-n-1-c of the second antenna, and the first output terminals 8-2-b to 8-nb are connected to the corresponding antennas 3-2 to 3-3 in the antenna group 3. -Connected to n. The n-stage nonreciprocal circuits 8-1 to 8-n in the nonreciprocal circuit group 8 are so-called cascade-connected.
n is an integer of 2 or more, and in the first embodiment, the number is three as in the antennas 3-1 to 3-3 of the antenna group 3. The number is the same as the number of antennas 3-1 to 3 -n. If there are two antennas, the number is two, and four or more is four or more.
Each of the n-stage non-reciprocal circuits 8-1 to 8-n is a circulation type, specifically a circulator.

The connection between the output terminal of the microwave amplifier 6 and the input terminal 8-1 -a of the first stage irreversible circuit 8-1 in the irreversible circuit group 8 is a transmission circuit constituted by a conductor pattern on a dielectric substrate. This is performed by the second microwave transmission line 9. In the first embodiment, the second microwave transmission line 9 is formed by a conductor pattern on the other main surface of the dielectric substrate on which the microwave amplifier 6 is formed, and has a characteristic impedance of 50Ω as a transmission circuit.
The termination resistor 10 is connected between the second output terminal 8-nc of the final stage non-reciprocal circuit 8-n in the non-reciprocal circuit group 8 and the ground terminal GND. The terminating resistor 10 is a resistive element formed by a conductor pattern on the other main surface of the dielectric substrate on which the microwave amplifier 6 is formed and terminated at 50Ω.

Next, the operation of the microwave heating apparatus configured as described above will be described. For the sake of simplicity, description will be made assuming that n is 3 in the antennas 3-1 to 3-n of the antenna group 3 and the non-reciprocal circuits 8-1 to 8-n of the non-reciprocal circuit group 8. In the case of 4 or more, the microwaves reflected in the heating chamber 1 are sequentially processed in the same manner in the next stage.
The microwave oscillator 4 driven by a control signal from the control means 5 generates a microwave. The microwave generated by the microwave oscillator 4 is output at a frequency set from the output terminal 4 a and is guided to the input terminal 6 a of the microwave amplifier 6 through the first microwave transmission line 7. The microwave amplifier 6 amplifies the microwave guided by the first microwave transmission line 7 so that the output power level set by the control signal from the control means 5 is output to the output terminal 6b.

The microwave amplified by the microwave amplifier 6 and output from the output terminal 6 b is guided to the irreversible circuit group 8 through the second microwave transmission line 9.
The first stage irreversible circuit 8-1 in the irreversible circuit group 8 transmits the microwave guided to the input terminal 8-1-a via the second microwave transmission line 9 to the first output terminal 8-1-. b is transmitted to the corresponding antenna 3-1 in the antenna group 3. The microwave transmitted to the antenna 3-1 is radiated toward the heated object 2 in the heating chamber 1.
Thus, the antenna 3-1 irradiates the object to be heated 2 accommodated in the heating chamber 1 with microwaves. The object to be heated 2 that has been irradiated with the microwave is heated.

On the other hand, the microwave irradiated from the antenna 3-1 into the heating chamber 1 is not absorbed by the heated object 2, is reflected by the heated object 2 and the wall surface of the heating chamber 1, and returns to the antenna 3-1. come. Then, the returned microwave (hereinafter referred to as a reflected microwave) is input to the nonreciprocal circuit 8-1 from the first output terminal 8-1-b. The nonreciprocal circuit 8-1 converts the reflected microwave input from the first output terminal 8-1-b from the second output terminal 8-1-c to the input terminal of the second stage irreversible circuit 8-2. Output to 8-2-a. The non-reciprocal circuit 8-2 in the second stage transmits the reflected microwave input to the input terminal 8-2-a from the first output terminal 8--2-b to the corresponding antenna 3-2 in the antenna group 3. . The reflected microwave transmitted to the antenna 3-2 is radiated toward the object to be heated 2 in the heating chamber 1.

Since the antenna 3-2 is arranged at a position different from that of the antenna 3-1, the microwave irradiation angle from the antenna 3-2 to the object to be heated 2 accommodated in the heating chamber 1 is heated from the antenna 3-1. This is different from the microwave irradiation angle to the object to be heated 2 accommodated in the chamber 1. As a result, the microwave from the microwave oscillator 4 to the object to be heated 2 is effectively used, and the uniformity of irradiation to the object to be heated 2 is improved.

On the other hand, the microwave irradiated from the antenna 3-2 into the heating chamber 1 is not absorbed by the heated object 2, is reflected by the heated object 2 and the wall surface of the heating chamber 1, and returns to the antenna 3-2. come. Then, the returned reflected microwave is input to the nonreciprocal circuit 8-2 from the first output terminal 8-2-b. The non-reciprocal circuit 8-2 receives the reflected microwave input from the first output terminal 8-2-2b in the third stage from the second output terminal 8-2-2c, which is the final stage in the first embodiment. Output to the input terminal 8-3-a of the nonreciprocal circuit 8-3. The final stage irreversible circuit 8-3 transmits the reflected microwave input to the input terminal 8-3-a from the first output terminal 8-3-b to the corresponding antenna 3-3 in the antenna group 3. The reflected microwave transmitted to the antenna 3-3 is radiated toward the heated object 2 in the heating chamber 1.

Since the antenna 3-3 is arranged at a different position from the antennas 3-1 and 3-2, the irradiation angle of the microwave from the antenna 3-3 to the heated object 2 accommodated in the heating chamber 1 is the antenna 3 -1 and 3-2 are different from the irradiation angle of the microwave to the object to be heated 2 accommodated in the heating chamber 1. As a result, the microwave from the microwave oscillator 4 to the object to be heated 2 is further effectively used, and the uniformity of irradiation to the object to be heated 2 is further improved.

On the other hand, the microwave irradiated into the heating chamber 1 from the antenna 3-3 is not absorbed by the heated object 2, is reflected by the heated object 2 and the wall surface of the heating chamber 1, and returns to the antenna 3-3. come. Then, the returned reflected microwave is input to the nonreciprocal circuit 8-3 from the first output terminal 8-3-b. The nonreciprocal circuit 8-3 outputs the reflected microwave input from the first output terminal 8-3-b to the termination resistor 10 from the second output terminal 8-3-c. The terminating resistor 10 consumes the reflected microwave power from the antenna 3-3.

In the microwave heating apparatus configured as described above, the microwave from the microwave oscillator 4 is irradiated from the antenna 3-1 to the object to be heated 2 accommodated in the heating chamber 1, and the object to be heated 2 and the heating object are heated. The microwave reflected by the wall surface of the chamber 1 is irradiated from the antenna 3-1 to the heated object 2 from the antennas 3-2 and 3-3 in the second and subsequent stages, so that the heated object 2 can be efficiently heated. Used.
Further, since the antennas 3-1 to 3-3 are arranged at different positions, the uniformity of irradiation of the object to be heated 2 with respect to various objects to be heated having different shapes, types, sizes, and amounts. Is improved, and uneven heating of the article to be heated 2 is suppressed.

Embodiment 2. FIG.
A microwave heating apparatus according to Embodiment 2 of the present invention will be described below with reference to FIG.
In the microwave heating apparatus according to the second embodiment, the microwave heating apparatus according to the first embodiment is configured such that all n antennas 3-1 to 3-n of the antenna group 3 are arranged on the same wall surface of the heating chamber 1. In contrast, the n antennas 3-1 to 3-n are divided into a plurality of pieces, and the divided antennas are arranged on the wall surface of the heating chamber 1.
Specifically, the second embodiment shows a case where n is 3, in which the first antenna 3-1 is placed on the side wall surface adjacent to the side wall surface on which the door is formed, and the second antenna 3-2 is placed on the ceiling. The third antenna 3-3 is disposed on the side wall surface opposite to the side wall surface on which the first antenna 3-1 is disposed on the wall surface.
In other respects, the second embodiment is the same as the first embodiment. In addition, in each figure, the same code | symbol shows the same or an equivalent part.

Even the microwave heating apparatus according to the second embodiment configured as described above operates in the same manner as the microwave heating apparatus according to the first embodiment.
In the microwave heating apparatus according to the second embodiment, the microwave from the microwave oscillator 4 is efficiently used for heating the object to be heated 2, and the antennas 3-1 to 3-3 are large. Since they are arranged at different positions, the uniformity of irradiation to the object to be heated 2 is further improved with respect to various objects to be heated of different shapes, types, sizes, and quantities, and the object to be heated 2 is heated. Unevenness is suppressed.

Embodiment 3 FIG.
Next, a microwave heating apparatus according to Embodiment 3 of the present invention will be described with reference to FIG.
The microwave heating apparatus according to the third embodiment is largely different from the microwave heating apparatus according to the first embodiment in the following four points, and the other points are the same as those in the first embodiment. In addition, in each figure, the same code | symbol shows the same or an equivalent part.
First, the arrangement of the n antennas 3-1 to 3-n in the antenna group 3 is different.
Second, the microwave heating apparatus according to Embodiment 1 has one non-reciprocal circuit 8-1 in the first stage in the non-reciprocal circuit group 8, whereas the microwave heating apparatus according to Embodiment 3 The difference is that a plurality of non-reciprocal circuits connected in cascade are provided.
Third, the microwave heating apparatus according to the first embodiment is terminated between the second output terminal 8-nc of the final stage non-reciprocal circuit 8-n in the non-reciprocal circuit group 8 and the ground terminal GND. Whereas the resistor 10 is connected, the microwave heating apparatus according to the third embodiment has a second output terminal 8-nc of the non-reciprocal circuit 8-n in the final stage in the non-reciprocal circuit group 8. The non-reciprocal circuit group 8 is different in that it is connected to the input terminal 8-11-a of the first stage non-reciprocal circuit 8-11.
Fourth, the microwave heating apparatus according to the third embodiment includes the second output terminal 8-nc of the last stage nonreciprocal circuit 8-n in the nonreciprocal circuit group 8 and the first stage in the nonreciprocal circuit group 8. The power detection unit 11 is connected to the input terminal 8-11-a of the nonreciprocal circuit 8-11, and the second output terminal 8-nc of the final stage nonreciprocal circuit 8-n and the first stage nonreciprocal circuit are connected. The difference is that the power appearing at the input terminal 8-11-a of 8-11 is detected.

Below, it demonstrates centering on the above-mentioned difference.
The n antennas 3-1 to 3-n of the antenna group 3 are divided into a plurality of pieces, and the divided antennas are arranged on the wall surface of the heating chamber 1.
Specifically, in Embodiment 3, the case where n is 3 is shown, the first antenna 3-1 is formed on the ceiling wall surface, and the second antenna 3-2 and the third antenna 3-3 are formed by the door. It is arrange | positioned on the side wall surface which is not made.

The first-stage nonreciprocal circuit 8-1 in the nonreciprocal circuit group 8 includes a plurality of nonreciprocal circuits 8-11 and 8-12 connected in cascade, that is, connected in series. In the third embodiment, two cases are shown, but the number is not limited to two, and may be three or more.
In the nonreciprocal circuit 8-11 located on the output side, the first output end 8-11-b is connected to the corresponding antenna 3-1 of the antenna group 3, and the input end 8-11-a is the non-return circuit of the final stage. The second output terminal 8-11-c is connected to the second output terminal 8-3-c of the reversible circuit 8-3, and the second output terminal 8-11-c is connected to the input terminal 8--2-a of the second stage non-reciprocal circuit 8-2. Connected. The input terminal 8-11-a of the non-reciprocal circuit 8-11 and the second output terminal 8--3-c of the final stage non-reciprocal circuit 8-3 are connected by a third microwave transmission line 12.

In the nonreciprocal circuit 8-12 located on the input side, the input end 8-12-a is connected to the output end 6b of the microwave amplifier 6, and the first output end 8-12-b is located on the output side. The reversible circuit 8-11 is connected to the input terminal 8-11-a, and the second output terminal 8-12-c is connected to the ground terminal GND through the termination resistor 10a. The terminating resistor 10a is a resistive element formed by a conductor pattern on the other main surface of the dielectric substrate on which the microwave amplifier 6 is formed and terminated at 50Ω.

The power detector 11 is a non-reciprocal circuit located on the output side of the second output terminal 8-3-c of the final stage non-reciprocal circuit 8-3 and the first stage non-reciprocal circuit 8-1 in the non-reciprocal circuit group 8. It is connected to the input terminal 8-11-a of 8-11. The power detection unit 11 includes a non-reciprocal circuit 8 located on the output side of the second output terminal 8-3-c of the final stage non-reciprocal circuit 8-3 and the first stage non-reciprocal circuit 8-1 in the non-reciprocal circuit group 8. The power appearing at the input terminal 8-11-a of -11 is detected and output to the control means 5a as the amount of power. The power detection unit 11 and the input terminal 8-11-a of the nonreciprocal circuit 8-11 located on the output side of the first stage nonreciprocal circuit 8-1 are connected by a fourth microwave transmission line 13.
Although not shown, the power detector 11 is a directional coupler having a coupling degree of about 40 dB, a detector diode that rectifies the amount of power detected by the directional coupler, and rectified by the detector diode. A smoothing capacitor that smoothes the processed signal and outputs it to the control means 5a is provided.

The directional coupler in the power detector 11 detects an amount of power that is about 1/10000 of the transmitted and reflected power. In the third embodiment, the amount of microwave power transmitted to the input terminal 8-11-a of the non-reciprocal circuit 8-11 located on the output side of the first-stage non-reciprocal circuit 8-1 and the antenna group 3 Detecting the amount of reflected microwave power returned by the final stage antenna 3 and output from the second output terminal 8-3-c of the final stage nonreciprocal circuit 8-3 in the nonreciprocal circuit group 8. An electric signal corresponding to the amount of electric power is output. Note that the amount of microwave power transmitted to the input terminal 8-11-a of the nonreciprocal circuit 8-11 located on the output side in the first stage nonreciprocal circuit 8-1 is the microwave output from the microwave amplifier 6. It corresponds to the amount of power. Hereinafter, this electric energy is referred to as the electric energy of the transmission microwave.
Similar to the control means 5a, the power detector 11 is formed on one main surface of the dielectric substrate on which the microwave oscillator 4 is formed, one formed on the other main surface of the dielectric substrate, Any one formed on a dielectric substrate different from the dielectric substrate on which the wave oscillator 4 is formed may be used.

The control unit 5 a receives the output from the power detection unit 11 and performs variable control of the oscillation frequency of the microwave oscillator 4 and variable control of the output power level of the microwave amplifier 6.
The control means 5a drives the microwave oscillator 4 and the microwave amplifier 6 in the initial state. That is, the control means 5 a gives a frequency control signal to the microwave oscillator 4 so that the initial oscillation frequency of the microwave oscillator 4 is 2400 MHz which is an initial value, and outputs the rated value of the microwave amplifier 6. An output control signal is given to the microwave amplifier 6. The output control signal corresponds to a driving voltage for the microwave amplifier 6.

When the microwave oscillator 4 and the microwave amplifier 6 are operated in the initial state, and the control means 5a receives the output from the power detector 11, the ratio of the reflected microwave power amount to the transmitted microwave power amount is set. Then, it is determined whether or not the power amount ratio exceeds a set value. In the third embodiment, the set value is 10%. When the object to be heated 2 is heated, when the amount of reflected microwave power from the power detection unit 11 exceeds a set value with respect to the amount of transmitted microwave power, the control means 5a sets the oscillation frequency to the microwave oscillator 4. Provides a frequency control signal that switches to a different frequency. Further, an output control signal for adjusting the output power level is given to the microwave amplifier 6.
In addition, when the amount of reflected microwave power from the power detection unit 11 is equal to or lower than the set value with respect to the amount of transmitted microwave power, the control means 5a gives the microwave oscillator 4 a frequency control signal for maintaining the oscillation frequency. Then, an output control signal for reducing the output power level is given to the microwave amplifier 6. That is, the drive voltage for the microwave amplifier 6 is reduced.

In short, the control means 5a receives the output from the power detector 11, and (i) obtains the power amount ratio of the reflected microwave power amount to the transmission microwave power amount, and whether or not the power amount ratio exceeds the set value. (Ii) A frequency control signal is given to the microwave oscillator 4 and the oscillation frequency of the microwave oscillator 4 is variably controlled around a reference value. (Iii) An output control signal is given to the microwave amplifier 6 The output power level of the microwave amplifier 6 is variably controlled around the rated output.
As a result, the microwave heating apparatus according to the third embodiment suppresses the power consumption of the microwave amplifier 6 so that the amount of reflected microwave power is equal to or lower than the set value, and the microwave from the microwave oscillator 4 is efficiently generated. It is used for heating the article 2 to be heated.

In the above-described third embodiment, the control means 5a receives the output from the power detector 11, and performs both the variable control of the oscillation frequency of the microwave oscillator 4 and the control of the output power level of the microwave amplifier. However, any one of the controls may be used.

Next, the operation of the microwave heating apparatus configured as described above will be described. For the sake of simplicity, description will be made assuming that n is 3 in the antennas 3-1 to 3-n of the antenna group 3 and the non-reciprocal circuits 8-1 to 8-n of the non-reciprocal circuit group 8. In the case of 4 or more, the microwaves reflected in the heating chamber 1 are sequentially processed in the same manner in the next stage.
The microwave oscillator 4 is driven at the initial oscillation frequency by the frequency control signal from the control means 5a, and the microwave amplifier 6 is driven at the rated value by the output control signal from the control means 5a.

The microwave oscillator 4 generates a microwave at the oscillation frequency of the initial value, and the microwave amplifier 6 outputs the microwave from the output terminal 6b at the rated output power level. The microwave output in this way is guided to the nonreciprocal circuit group 8 via the second microwave transmission line 9.
The microwave guided to the nonreciprocal circuit group 8 is radiated from the antenna 3-1 toward the object to be heated 2 in the heating chamber 1 via the first stage nonreciprocal circuit 8-1.
The microwave reflected by the object to be heated 2 and the wall surface of the heating chamber 1 is heated from the antenna 3-1 → the nonreciprocal circuit 8-1 → the second stage nonreciprocal circuit 8-2 → the antenna 3-2 to the heating chamber 1. Radiated toward the object 2 to be heated.
Microwaves reflected by the object 2 and the wall of the heating chamber 1 are transmitted from the antenna 3-2 → the second stage nonreciprocal circuit 8-2 → the last stage nonreciprocal circuit 8-3 → the antenna 3-3. Radiated toward the object to be heated 2 in the heating chamber 1.
The microwave reflected by the object to be heated 2 and the wall surface of the heating chamber 1 returns from the antenna 3-3 to the final stage nonreciprocal circuit 8-3, and the second output of the final stage nonreciprocal circuit 8-3. Since the operation similar to that of the first embodiment is performed up to the point output from the terminal 8-3-c, detailed description thereof is omitted.

The reflected microwave output from the second output terminal 8-3-c of the final stage nonreciprocal circuit 8-3 is input to the nonreciprocal circuit 8-11 on the output side of the first stage nonreciprocal circuit 8-1. 8-11-a. The microwave guided to the input terminal 8-11-a is transmitted from the first output terminal 8-11-b to the corresponding antenna 3-1 in the antenna group 3. The microwave transmitted to the antenna 3-1 is radiated toward the heated object 2 in the heating chamber 1.
As described above, the antenna 3-1 radiates the reflected microwave together with the transmission microwave to the object to be heated 2 accommodated in the heating chamber 1.
Therefore, the microwaves radiated from the antenna 3-3 at the final stage to the object to be heated 2 and reflected by the object to be heated 2 and the wall surface of the heating chamber 1, etc. It is guided to the input terminal 8-11-a of the nonreciprocal circuit 8-11 on the output side of the first stage nonreciprocal circuit 8-1 through the microwave transmission line 12, and is radiated from the antenna 3-1 to the heated object 2. Therefore, the microwave heating device according to the first embodiment also reuses the power consumed by the termination resistor 10.

Further, in the nonreciprocal circuit group 8, the second output terminal 8-3-c of the final stage nonreciprocal circuit 8-3 and the nonreciprocal circuit 8-11 positioned on the output side of the first stage nonreciprocal circuit 8-1. The power appearing at the input terminal 8-11-a is detected by the power detection unit 11. The power detection unit 11 converts the detected power into an electrical signal corresponding to the amount of power and outputs it to the control means 5a. In the non-reciprocal circuit group 8, an electric signal corresponding to the amount of power appearing at the second output terminal 8-3-c of the final stage non-reciprocal circuit 8-3 is used as the reflected power information and the first stage non-reciprocal circuit 8-1. An electric signal corresponding to the power appearing at the input terminal 8-11-a of the nonreciprocal circuit 8-11 located on the output side is hereinafter referred to as transmission power information.

The control means 5a receives the reflected power information and the transmission power information from the power detection unit 11, obtains the power amount ratio of the reflected microwave power amount to the transmission microwave power amount, and this power amount ratio exceeds the set value. It is determined whether or not.
When the object to be heated 2 is heated, when the power amount ratio exceeds the set value, the control means 5a gives the microwave oscillator 4 a frequency control signal for switching the oscillation frequency to a different frequency. Further, an output control signal for adjusting the output power level is given to the microwave amplifier 6.

The microwave oscillator 4 receives the frequency control signal and outputs a microwave whose frequency is changed with reference to the initial oscillation frequency from the output terminal 4a.
The microwave amplifier 6 receives the output control signal, and outputs the microwave whose output voltage level is changed based on the rated value from the output terminal 6b.
On the other hand, if the power amount ratio is equal to or lower than the set value, the control means 5a gives a frequency control signal for maintaining the oscillation frequency to the microwave oscillator 4 and gives an output control signal for reducing the output power level to the microwave amplifier 6.

Thus, in the microwave heating apparatus according to the third embodiment, the power detection unit 11 is connected to the second output terminal 8-3-c of the final stage nonreciprocal circuit 8-3 in the nonreciprocal circuit group 8 and the first stage. The power appearing at the input terminal 8-11-a of the irreversible circuit 8-11 located on the output side of the irreversible circuit 8-1 is detected, and the control means 5a reflects the reflected power information and the transmitted power information from the power detector 11. Based on the above, the oscillation frequency of the microwave oscillator 4 is variably controlled around the reference value, and the output power level of the microwave amplifier 6 is variably controlled around the rated output.
As a result, the power consumption of the microwave amplifier 6 is suppressed so that the amount of reflected microwave power is not more than a set value, and the microwave from the microwave oscillator 4 can be efficiently used for heating the article to be heated 2.

As described above, in the microwave heating apparatus according to the third embodiment, the microwave from the microwave oscillator 4 is irradiated from the antenna 3-1 to the object to be heated 2 accommodated in the heating chamber 1. The microwaves reflected by the heated object 2 and the wall surface of the heating chamber 1 are irradiated from the antenna 3-1 to the heated object 2 from the antennas 3-2 and 3-3 on the second and subsequent stages. Since the reflected microwave from is returned to the antenna 3-1 in the first stage, it is efficiently used for heating the article 2 to be heated.
Further, since the antennas 3-1 to 3-3 are arranged at different positions, the uniformity of irradiation to the heated object 2 with respect to various heated objects having different shapes, types, sizes, and amounts. Is improved, and uneven heating of the article to be heated 2 is suppressed.
Further, in the nonreciprocal circuit group 8, the nonreciprocal circuit 8-11 located on the output side of the second output terminal 8-3-c of the final stage nonreciprocal circuit 8-3 and the first stage nonreciprocal circuit 8-1. Since the oscillation frequency of the microwave oscillator 4 and the output power level of the microwave amplifier 6 are variably controlled according to the amount of power appearing at the input terminal 8-11-a, the power consumption of the microwave amplifier 6 can be suppressed. The electric energy of the reflected microwave is set to a set value or less, and the microwave from the microwave oscillator 4 can be efficiently used for heating the article 2 to be heated.

In the present invention, within the scope of the invention, any combination of each embodiment, any component of each embodiment can be modified, or any component can be omitted in each embodiment. .

1 Heating chamber, 2 heated object, 3 antenna group, 3-1 to 3-3 antenna, 4 microwave oscillator, 5, 5a control means, 6 microwave amplifier, 8 non-reciprocal circuit group, 8-1 to 8- 3 Non-reciprocal circuit, 10, 10a termination resistor, 11 power detector.

Claims

A heating chamber in which an object to be heated is accommodated,
An antenna group consisting of n antennas, each of which is an integer of 2 or greater, that radiates microwaves into the heating chamber;
A microwave oscillator that generates microwaves,
A microwave amplifier that amplifies the microwave generated by this microwave oscillator,
An n-stage non-reciprocal circuit corresponding to n antennas of the antenna group is provided, each non-reciprocal circuit having an input terminal, a first output terminal, and a second output terminal. The input terminal is connected to the output terminal of the microwave amplifier, the first output terminal is connected to the corresponding antenna in the antenna group, and the non-reciprocal circuit from the second stage to the n-th stage has the input terminal at the front stage. A microwave heating device comprising: a nonreciprocal circuit group connected to a second output terminal of the nonreciprocal circuit, wherein the first output terminal is connected to a corresponding antenna in the antenna group.
The microwave oscillator includes an oscillation circuit configured using a semiconductor element that generates a microwave on a dielectric substrate formed of a low dielectric loss material,
The microwave amplifier includes an amplifier circuit configured using a semiconductor element on a dielectric substrate made of a low dielectric loss material,
The microwave heating apparatus according to claim 1, wherein each of the n-stage nonreciprocal circuits in the nonreciprocal circuit group is a circulator.
The microwave amplifier includes a matching circuit on each of an input side and an output side of an amplifier circuit,
3. The microwave heating apparatus according to claim 2, wherein the microwave oscillator is formed on one main surface of the dielectric substrate, and the microwave amplifier is formed on the other main surface of the dielectric substrate.
The connection between the output end of the microwave oscillator and the input end of the microwave amplifier is performed by a first microwave transmission line including a transmission circuit configured by a conductor pattern on the dielectric substrate,
The connection between the output terminal of the microwave amplifier and the first input terminal of the first stage non-reciprocal circuit in the non-reciprocal circuit group includes a second transmission circuit including a conductor pattern on the dielectric substrate. The microwave heating device according to claim 3, wherein the microwave heating device is a microwave transmission line.
5. The terminal resistor according to claim 1, wherein a termination resistor is connected between the second output terminal and the ground terminal of the final stage non-reciprocal circuit in the non-reciprocal circuit group. The microwave heating apparatus as described.
A power detection unit connected to the second output terminal of the final stage of the non-reciprocal circuit in the non-reciprocal circuit group;
2. A control means for receiving an output from the power detector and controlling at least one of control of an oscillation frequency of the microwave oscillator and control of an output power level of the microwave amplifier. The microwave heating device according to any one of claims 1 to 4.
The power detector includes a directional coupler, a detection diode that rectifies the amount of power detected by the directional coupler, and a smoothing process on a signal rectified by the detection diode, and the control means The microwave heating apparatus according to claim 6, further comprising a smoothing capacitor that outputs to the output.
The non-reciprocal circuit of the first stage in the non-reciprocal circuit group includes a plurality of non-reciprocal circuits connected in cascade, and the input terminal of the non-reciprocal circuit arranged on the output side of the non-reciprocal circuit of the first stage is the non-reciprocal circuit of the final stage. A nonreciprocal circuit connected to the second output terminal of the reversible circuit, the second output terminal connected to the input terminal of the second stage nonreciprocal circuit, and arranged on the input side of the first stage nonreciprocal circuit The microwave output device according to any one of claims 1 to 4, wherein the second output terminal of the first and second output terminals is connected to the ground terminal via a termination resistor.
A power detector for detecting power appearing at the second output terminal of the last stage nonreciprocal circuit and the input terminal of the nonreciprocal circuit located on the output side of the first stage nonreciprocal circuit in the nonreciprocal circuit group;
9. A control means for receiving an output from the power detection unit and performing control of at least one of control of an oscillation frequency of the microwave oscillator and control of an output power level of the microwave amplifier. A microwave heating apparatus according to 1.
The power detector includes a directional coupler, a detection diode that rectifies the amount of power detected by the directional coupler, and a smoothing process on a signal rectified by the detection diode, and the control means The microwave heating apparatus according to claim 9, further comprising a smoothing capacitor that outputs to the outside.
The microwave heating apparatus according to any one of claims 1 to 4, wherein all n antennas of the antenna group are arranged on the same wall surface of the heating chamber.
The n antennas of the antenna group are divided into a plurality of antennas, and each of the divided antennas is disposed on a wall surface of the heating chamber. The microwave heating apparatus as described.