JP2004063309A - High frequency heating equipment - Google Patents

Abstract

An object of the present invention is to provide a device for efficiently supplying a high frequency to a heating electrode arranged so as to sandwich an object to be heated placed on a placing portion of a nonmetallic material.
A mounting portion made of a non-metallic material, a heating electrode (comprising a bottom surface 11 of a heating chamber and a movable heating electrode 18) provided so as to sandwich an object to be heated mounted on the mounting portion. , A high-frequency generating means 25, a fixed impedance element 29 movable integrally with the heating electrode 18, a variable impedance element 28 connected in series, and a fixed impedance element 32 arranged in parallel. By changing only the value, the high frequency generated by the high frequency generation means 25 is supplied to the heating electrode with high efficiency to dielectrically heat the object to be heated.
[Selection diagram] Fig. 1

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a high-frequency heating device that performs dielectric heating by sandwiching an object to be heated between electrodes.
[0002]
[Prior art]
2. Description of the Related Art A microwave oven, which is a typical example of a high-frequency heating device, has become an indispensable device in daily life because it can directly heat an object to be heated, so that it is not necessary to prepare a pot. Further, the feature of the heating of the microwave oven is that heating energy can be supplied to the inside of the food, and the frozen food has been distributed in large quantities by utilizing this feature for thawing the frozen food.
[0003]
2. Description of the Related Art In a microwave oven, a heating chamber for storing an object to be heated generally has a size of about 30 to 40 cm in width and depth, and about 20 cm in height. On the other hand, the wavelength of the frequency used is about 12 cm, a strong and weak electric field distribution always occurs in the heating chamber, and the local heating may occur due to the synergistic effect of the shape of the object to be heated and its physical characteristics. is there. In the thawing of frozen foods, the heating energy is concentrated in the area where the ice has melted and turned into water, so that a local heating phenomenon appears remarkably, and there is a problem that partially boiled and unthawed coexist.
[0004]
A method of dielectrically heating an object to be heated by using a heating electrode by using a high frequency having a long wavelength has a long history, and even now, a batch system or a belt conveyor system is used for industrial use. These are large-sized apparatus configurations for processing large-sized frozen products and large-scale processing of frozen products, and the operation of the apparatus is also performed by skilled personnel.
[0005]
On the other hand, the application of the device using the heating electrode to a home device has been studied for a long time, but the value of convenience in life or convenience in use has not yet been provided to the user. As a conventional technique for providing practical value as a household device, there is, for example, Japanese Patent Application Laid-Open No. 9-92455. This publication discloses a configuration of a heating electrode that is used in combination with a microwave oven.
[0006]
[Problems to be solved by the invention]
The practical value of a household device is comparable to that of a microwave oven even if it is large in size, and the simple operation and the short processing time are the main issues to be solved like a microwave oven.
[0007]
Regarding the compactness of the shape, a major challenge is to reduce the size of various impedance matching elements for matching the impedance between the heating electrode and the high-frequency generator. In addition, the simple operation is to minimize the variable control target, and the short-time processing is to concentrate the heating energy between the heating electrodes.
[0008]
In Japanese Patent Application Laid-Open No. 9-92455, a rotating mounting table is used as one of the heating electrodes. However, when a frozen product as an object to be heated is directly placed on the heating electrode, heat generated in the contact portion is generated. There is a risk of causing uneven heating due to heat generation. In addition, when heating with a microwave generated by a magnetron, there is also a danger that the microwave will not easily propagate to the center of the object to be heated, and the center will be weakly heated.
[0009]
The present invention solves the above-mentioned problems, and places an object to be heated on a mounting portion of a non-metallic material, efficiently supplies a high frequency to a heating electrode arranged so as to sandwich the object to be heated, and It is an object of the present invention to provide a device for high-frequency heating.
[0010]
[Means for Solving the Problems]
In order to solve the above-described problems, the high-frequency heating device of the present invention has a heating chamber having a mounting portion of a non-metallic material for storing and mounting an object to be heated, and the other electrode having the heating chamber wall surface as one electrode. And a heating electrode arranged so as to sandwich the object to be heated.
[0011]
According to the invention described above, a non-metallic material is used for the mounting portion of the object to be heated, so that a sense of security can be provided, and local heating of the object to be heated can be prevented by insulating the object to be heated from the heating electrode. it can.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
The invention according to claim 1 is a heating chamber having a mounting portion of a non-metallic material for storing and mounting an object to be heated, wherein the wall of the heating chamber is one electrode and the other electrode sandwiches the object to be heated. With the heating electrode arranged in the above, it is possible to provide a sense of security and to insulate the heating object from the heating electrode by using a non-metallic material for the mounting part of the heating object. Thereby, local heating of the object to be heated can be prevented.
[0013]
According to a second aspect of the present invention, in particular, the high frequency heating device according to the first aspect generates a high frequency to be supplied to a heating electrode, and a high frequency generating unit between the high frequency generating unit and the heating electrode. A fixed impedance element and a variable impedance element connected in series are provided, and one of the heating electrodes is configured to be movable, and the fixed impedance element is integrally disposed on the heating electrode, thereby providing a high impedance. By dividing the voltage and shortening the connection between the heating electrode and the fixed impedance element, heat generation at the connection portion can be suppressed.
[0014]
According to a third aspect of the present invention, in the high frequency heating apparatus according to the second aspect, the impedance value of the fixed impedance element is twice or more the maximum impedance value of the variable impedance element. Is concentrated on the heating electrode and the fixed impedance element, so that heat generation at the connection between the fixed impedance element and the variable impedance element can be suppressed, and a highly flexible conductor can be used for this connection.
[0015]
According to a fourth aspect of the present invention, in particular, the high-frequency heating device according to the second aspect further includes a fixed impedance element in parallel between the variable impedance element and the high-frequency generation means. The adjustment of the impedance matching between the electrode and the heating electrode is integrated into a variable impedance element connected in series, whereby the variable control can be simplified and the operability can be simplified.
[0016]
In the invention according to claim 5, the variable impedance element connected in series of the high-frequency heating device according to claim 2 has a coil configuration, a plurality of taps are provided, and the impedance is changed by tap switching. Therefore, the optimum impedance matching can be selected by a simple control of the switching operation.
[0017]
According to a sixth aspect of the present invention, in particular, the fixed impedance element in the parallel arrangement of the high-frequency heating device according to the fourth aspect is constituted by a capacitor having a multilayer structure of a dielectric and an electrode. Thus, a small-sized fixed impedance element can be formed, and mounting on a device can be easily performed.
[0018]
In the invention according to claim 7, the variable impedance element connected in series of the high-frequency heating device according to claim 2 is constituted by a capacitor having a multilayer structure of a dielectric and an electrode, and one of the electrodes is rotated. By doing so, the opposing area is changed, whereby a flat and small-sized fixed impedance element can be formed, and mounting to the device can be easily performed.
[0019]
According to an eighth aspect of the present invention, in particular, the high-frequency heating device according to the second aspect includes a fixed impedance element and a variable impedance element in parallel between the variable impedance element and the high-frequency generation means connected in series. Therefore, the range of impedance matching between the high-frequency generator and the heating electrode can be expanded, the high-frequency of the high-frequency generator can be efficiently supplied to the object to be heated, and heating can be performed in a short time.
[0020]
According to a ninth aspect of the present invention, in particular, the variable impedance element of the high-frequency heating device according to the eighth aspect is constituted by a capacitor having a multilayer structure of a dielectric and an electrode, and is rotated by rotating one of the electrodes. This is a configuration in which the area is changed, so that a flat and small-sized variable impedance element can be formed, and mounting to a device together with fixed impedance can be easily performed.
[0021]
The invention according to claim 10 is that, in a heating chamber for storing an object to be heated, one of the heating electrodes arranged so as to sandwich the object to be heated is a wall surface of the heating chamber, and the wall surface of the heating chamber is connected to the heating chamber. To supply microwaves to the device, thereby providing a device that enables both high-frequency heating using electrodes and high-frequency heating using microwaves.
[0022]
According to an eleventh aspect of the present invention, in particular, the high-frequency heating apparatus according to the tenth aspect is configured such that the non-metallic material for mounting the object to be heated is placed between the wall of the heating chamber for supplying the microwave and the object to be heated. The high-frequency heating using the electrodes and the high-frequency heating using the microwave can be continuously performed without moving the object to be heated.
[0023]
According to a twelfth aspect of the present invention, in particular, the high-frequency heating apparatus according to the tenth aspect is provided with a stirring means for stirring the supplied microwave, and thereby the microwave can be moved without moving the object to be heated. The uniformity of the heating under the supply can be promoted.
[0024]
According to a thirteenth aspect of the present invention, in particular, the stirring means of the high-frequency heating device according to the twelfth aspect has a plate-like configuration, and a plate surface is disposed substantially parallel to a wall of a heating chamber for supplying microwaves. Thus, in the high-frequency heating using the electrodes, the high-frequency heating can be performed without disturbing the electric field distribution between the electrodes.
[0025]
【Example】
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0026]
(Example 1)
FIG. 1 is a front cross-sectional configuration diagram of a high-frequency heating apparatus according to a first embodiment of the present invention, FIG. 2 is a front cross-sectional configuration diagram when a heating electrode is moved in FIG. 1, and FIG. FIG. 4 is a cross-sectional view taken along the line AA ′ of FIG. 1, and FIG. 5 is a circuit configuration diagram of FIG. 1.
[0027]
1 and 2, reference numeral 10 denotes a heating chamber for storing an object to be heated, and a bottom surface 11 of the heating chamber 10 also serves as a heating electrode. On the bottom surface 11 of the heating chamber, there is provided a radiating section 13 for supplying the microwave (2450 MHz band) generated by the microwave generating means 12 into the heating chamber 10. Reference numeral 14 denotes a waveguide for transmitting microwaves to the radiation section 13. The configuration around the radiation section 13 will be described later.
[0028]
Reference numeral 15 denotes a stirring means having a plate-like structure made of a metal material (a non-magnetic metal material, for example, aluminum), which is rotationally driven by a motor 16. A mounting portion 17 made of a non-metallic material (for example, heat-resistant glass, ceramics, or heat-resistant resin) on which the object to be heated is placed is placed so as to cover the stirring means 15. By using a non-metallic material for the mounting portion of the object to be heated, a sense of security can be provided, and since the object to be heated is insulated from the heating electrode 11, local heating of the object to be heated can be prevented.
[0029]
On the other hand, reference numeral 18 denotes another heating electrode (a non-magnetic metal material, for example, aluminum or SUS304), which is supported by arms 19 and 20 made of an insulating material (PPS or PS). The other ends of the arms 19 and 20 are fixedly connected to racks 21 and 22, respectively. Reference numeral 23 denotes a motor, and a pinion 24 made of a resin material is arranged on an output shaft of the motor. By driving the motor 23, a rack meshed with a gear of the pinion 24 moves left and right in the drawing. The motor 23 is a synchronous motor whose rotation direction is not restricted. Incidentally, the motor 23 may use a stepping motor.
[0030]
25 is a high-frequency generating means for generating a high frequency (for example, 13.56 MHz, 27.12 MHz) supplied between the bottom surface 11 of the heating chamber and the heating electrode 18, and 26 is an output power provided on the output side of the high-frequency generating means 25. And a power detector (such as a CM type SWR circuit) for detecting reflected power, and 27 is a power supply line. The power supply line 27 is formed of a coaxial cable, and the outer conductor 27a is connected to the wall surface 11 of the heating chamber 10 so as to be electrically conductive. The central conductor 27b of the power supply line 27 formed of a coaxial cable is connected to a coil 28 having a tap switching terminal, which is a variable impedance element.
[0031]
The other end of the coil 28 with the tap switching terminal, which is a variable impedance element, and one end of the fixed impedance element 29 are connected by a flexible plate-shaped conductor 30 having an insulator attached to the surface.
[0032]
The fixed impedance element 29 has a coil configuration and is formed by winding a conductive wire several times around a body 31 made of an insulating material fixed to the heating electrode 18. The other end of the fixed impedance element 29 is connected to the heating electrode 18. The body 31 is fixedly assembled to the heating electrode 18. With this configuration, the heating electrode 18 and the fixed impedance element 29 have an integral structure, and the fixed impedance element 29 is integrally formed with the movement of the heating electrode 18. Go up and down.
[0033]
Further, according to this configuration, the fixed impedance element 29 and the variable impedance element 28 are configured to be connected in series between the high frequency generation means 25 and the heating electrode 18. Further, a fixed impedance element 32 arranged in parallel between the variable impedance element 28 and the high frequency generation means 25 is provided.
[0034]
This fixed impedance element 32 is a capacitor. FIG. 3 shows the detailed configuration of this capacitor. In FIG. 3, reference numerals 321 and 322 denote one electrode, 323 denotes the other electrode, and 324 and 325 denote a dielectric (a material having a high relative permittivity, for example, alumina) laminated between the electrodes.
[0035]
Each electrode and the dielectric are provided with a hole having a predetermined size in the center, and after laminating them in order, a metal is inserted into the hole in the center to make the electrodes 321 and 322 conductive. To form a capacitor. The holes 326 and 327 provided on the electrodes 321 and 322 are holes for connecting one electrode, and the holes 328 provided on the electrode 323 are holes for connecting the other electrode. In FIGS. 1 and 2, a metal screw passed through the center is assembled with a metal surface that is electrically connected to the bottom surface 11 of the heating chamber.
[0036]
Next, the radiation section 13 will be described with reference to FIG.
The radiating portion 13 has a waveguide end face 33 on the side of the waveguide 14 far from the side on which the microwave generating means is mounted, and a distance of approximately の of the transmission wavelength of the frequency transmitting the waveguide 14 from the end face 33. It is arranged on the wall surface (H-plane of the waveguide) between the distant positions. The radiating portion 13 is constituted by L-shaped openings 13a and 13b, respectively, and is arranged point-symmetrically. The point-symmetric position is on the tube axis of the waveguide 14 and is the center of the hole 34 in FIG. Each of the openings 13a and 13b of the radiation section 13 has a portion parallel to and perpendicular to the tube axis of the waveguide 14, and each opening is arranged so as not to cross the tube axis.
[0037]
The output shaft (made of an insulating material) of the motor 16 that connects to the stirring means 15 and rotates the stirring means 15 passes through the hole 34. The stirring means 15 has a plate-like configuration made of a metal material as described above, and its plate surface is disposed substantially parallel to the bottom surface 11 of the heating chamber. Further, the stirring means 15 is arranged so as to be insulated from the wall surface 11 of the heating chamber 10. With such a configuration of the stirring means 15, the disturbance of the distribution of the high-frequency electric field generated between the heating electrodes is minimized. In addition, 35 is a hole for inserting and assembling the output antenna of the microwave generation means 12, and 36 is an opening provided on the wall surface of the heating chamber.
[0038]
The microwave transmitted through the waveguide 14 radiates into the heating chamber 10 while generating a rotating electric field from the radiation section 13. This radiation is disturbed by the stirring means 15, and microwaves are uniformly radiated to the entire inside of the heating chamber 10 to promote uniform heating of the object to be heated. In addition, as the stirring means 15, for example, a plate having a width of 20 mm and a length of 90 mm or more, or a configuration in which a plurality of predetermined openings are provided inside a disk having a diameter of 90 mm or more can be used.
[0039]
FIG. 5 shows a circuit diagram of the above configuration. In FIG. 5, 25 is a high-frequency generation means, 26 is a power detection unit, 32 is a fixed impedance element arranged in parallel, 28 is a series-connected variable impedance element composed of a variable coil with tap switching, and 29 is a series-connected fixed impedance element. An impedance element, 18 is a movable heating electrode, 11 is a bottom surface of a heating chamber, 17 is a mounting portion, and 37 is an object to be heated.
[0040]
Next, the movable operation of the heating electrode 18 will be described.
When the motor 23 is operated in the state shown in FIG. 1, the rotation direction of the motor 23 is regulated in a direction in which the racks 21 and 22 can move freely, whereby the motor 23 rotates in a direction in which the heating electrode 18 moves down. The lowering of the heating electrode 18 continues as shown in FIG. 2 until the arms 19 and 20 become substantially vertical. In this state, one ends of the racks 21 and 22 hit the wall surfaces 38 and 39 of the heating chamber. Then, the driving torque of the motor 23 in the current rotation direction increases, and the motor 23 starts rotating in the opposite direction to eliminate the increase. Thereby, the heating electrode 18 starts to rise and returns to the highest position as shown in FIG.
[0041]
At the highest position shown in FIG. 1, the heating electrode 18 is restricted from rising by the metal plates 40 and 41. The arrival of this position is detected by a limit switch (not shown), and the operation of the motor 23 is stopped.
[0042]
A method of controlling the heating electrode 18 when the object to be heated is stored will be described below with respect to the elevating operation of the heating electrode 18. When the motor 23 is operated after the object to be heated is mounted, the heating electrode 18 starts to descend, and when the heating electrode 18 comes into contact with the object to be heated or the container for the object to be heated, the descending operation stops. At this time, a driving torque is generated in the motor 23, and the driving current of the motor increases accordingly. The driving current is monitored, and after detecting an increase in the driving current, the operation of the motor is stopped after a predetermined time has elapsed, so that the heating electrode 18 is stopped and fixed in the heating chamber 10.
[0043]
Thereafter, the high-frequency generator 25 is operated, and based on the detection signal of the power detector 26, the tap switching position of the variable impedance element 28 is selected so that the reflected power is minimized. In this way, the high-frequency heating is continued, and the heating is stopped for a predetermined time or based on a temporal change of the reflected power.
[0044]
Next, the effectiveness of high-frequency heating using the electrode having the above configuration will be described with reference to FIG. FIG. 6 shows a point P1 in FIG. 5 when the gap between the heating electrode 18 and the object to be heated is set to 10 mm and the value of the variable impedance element is selected so that the reflected power is minimized. Is a plot of the impedance value, as viewed from the side of the heating electrode side, on the Smith chart. The measurement frequency is 13.56 MHz, the fixed impedance elements 32 arranged in parallel are 690 pF capacitors, the fixed impedance elements 29 connected in series are 2 μH coils, and the variable impedance elements 28 are 0.7 μH, 0.8 μH, 0.9 μH. Was used. The shape of the heating electrode 18 is 250 mm x 200 mm, and the objects to be heated are 100 g, 300 g of beef sliced meat (marked with □ in the figure), minced meat (marked with △ in the figure), and tuna block (marked with ● in the figure). 500 g were used.
[0045]
The broken line circle 42 in the figure indicates that the value of the voltage standing wave ratio is 2, which is about 11% in terms of power reflectance. Although impedance matching adjustment is performed only by selecting the value of the variable impedance element 28 for the object to be used, the reflected power can be made sufficiently small, and the output power of the high-frequency generator 25 can be efficiently applied to the object to be heated. It was confirmed that the material could be supplied well, and the object to be heated could be well thawed in a short time.
[0046]
That is, it is possible to realize a sufficiently practical high-frequency heating device by using only one variable impedance element. In this case, in the two impedance elements (fixed impedance element and variable impedance element) connected in series, the impedance value of the fixed impedance element provided on the heating electrode side is set to be at least twice the maximum impedance value of the variable impedance element. This divides the high voltage between the heating electrodes and the two impedance elements connected in series. Since the fixed impedance element shares a high voltage, the connection between the fixed impedance element and the heating electrode is basically thick and short, and the fixed impedance element is integrally assembled with the heating electrode. Thereby, heat generation of the connection portion can be suppressed.
[0047]
In addition, since the high voltage is concentrated on the heating electrode and the fixed impedance element, heat generation at the connection between the fixed impedance element and the variable impedance element can be suppressed, and a highly flexible conductive wire can be used for this connection. .
[0048]
The larger the ratio of the impedance value is, the more effective it is. However, in consideration of securing the variable range of the variable impedance, it can be practically used up to about 4 to 5 times.
[0049]
As described above, each of the fixed impedance elements connected in series, the fixed impedance elements connected in series, and the variable impedance elements connected in series are used to optimize the impedance ratio of each impedance element connected in series. An apparatus can be realized in which the impedance element can be made compact and adjustment of impedance matching can be realized by simple control.
[0050]
(Example 2)
Next, a second embodiment of the present invention will be described with reference to FIG. The second embodiment differs from the first embodiment in that the variable impedance element is constituted by a capacitor.
[0051]
FIG. 7 shows the configuration of a capacitor-type variable impedance element 50 that changes the capacitance by changing the facing area. In the figure, reference numerals 501 and 502 denote one electrode to be rotated, 503 denotes the other electrode, and 504 and 505 denote a dielectric (a material having a high relative permittivity, for example, alumina) laminated between the electrodes. Each electrode has a substantially semicircular opening 501a, 502a, 503a.
[0052]
In the center of the rotating electrodes 501 and 502, holes 501b and 502b each having a D-cut portion are provided. In the center of the electrode 503, a semicircular hole 503b is provided. In each of the dielectrics 504 and 505, the center is provided. Round holes 504a and 505a are provided. Then, after laminating these in order on a metallic rotating shaft that becomes one electrode, the electrode 501 and the electrode 502 are conductively fixed to the rotating shaft. The electrode 503 is fixed in a non-rotational state with respect to the metallic rotation shaft via an insulating material, and the electrodes 501 and 502 are rotated to change the facing area between the electrodes. Reference numeral 503c provided on the electrode 503 is a connection hole. As a specific configuration, when alumina having a diameter of 50 mm and a thickness of 1 mm is used as a dielectric, a variable capacitance element of about 15 pF to 100 pF can be realized.
[0053]
Since the variable impedance element having such a configuration has a flat configuration as compared with a general-purpose air variable condenser, the degree of freedom of mounting on a high-frequency heating device can be secured.
[0054]
FIG. 8 shows an example of a specific circuit diagram. FIG. 8 shows a capacitor type variable impedance element arranged in series and in parallel. That is, by replacing the coil-type variable impedance element with tap switching with the capacitor-type variable impedance element 51, the impedance can be continuously varied, and the impedance matching can be adjusted while supplying a high frequency. In addition, since the impedance matching range can be expanded by arranging the capacitor-type variable impedance element 52 in parallel with the fixed impedance 32 elements arranged in parallel, it is possible to provide an apparatus that efficiently heats a wider range of objects to be heated at high frequency. .
[0055]
【The invention's effect】
As described above, according to the present invention, the placement of the object to be heated is made of a non-metallic material, so that a sense of security can be provided, and the object to be heated can be insulated from the heating electrode by insulating the object to be heated. Local heating can be prevented.
[0056]
In addition, the distribution of the impedance values of the variable impedance elements, the selection of the impedance values, the flat configuration, and the like increase the degree of freedom in mounting on the apparatus and can perform the heating with simple control.
[0057]
Further, one of the heating electrodes arranged so as to sandwich the object to be heated is a wall surface of the heating chamber, and a microwave is supplied from the wall surface of the heating chamber into the heating chamber, so that high-frequency heating using the electrode is performed. Which can be used in combination with high-frequency heating using microwaves.
[Brief description of the drawings]
FIG. 1 is a front cross-sectional view of a high-frequency heating device according to a first embodiment of the present invention; FIG. 2 is a front cross-sectional view when a heating electrode of the high-frequency heating device is moved; FIG. FIG. 4 is a cross-sectional view taken along the line AA ′ of the high-frequency heating device. FIG. 5 is a circuit configuration diagram of the high-frequency heating device. FIG. 6 is a load impedance characteristic of the high-frequency heating device with respect to various objects to be heated. FIG. 7 is a component configuration diagram of a variable impedance element according to a second embodiment of the present invention. FIG. 8 is a circuit configuration diagram of the high-frequency heating device.
10 heating chamber 11 bottom of heating chamber (one heating electrode)
12 Microwave generation means 13 Microwave radiation part (supply part)
15 Stirring means 17 Mounting part 18 Heating electrode (movable heating electrode)
25 High-frequency generator 28 Variable impedance element 29 connected in series 29 Fixed impedance element 32 connected in series Fixed impedance element arranged in parallel (multilayer capacitor)
37 Object to be heated 50, 51, 52 Variable impedance element (multilayer capacitor)

Claims (13)

A heating chamber having a mounting portion of a non-metallic material for storing and mounting the object to be heated, and a heating electrode having the heating chamber wall surface as one electrode and the other electrode arranged so as to sandwich the object to be heated. High frequency heating equipment. A high-frequency generator for generating a high-frequency supplied to the heating electrode, a fixed impedance element and a variable impedance element connected in series between the high-frequency generator and the heating electrode, and one of the heating electrodes The high-frequency heating apparatus according to claim 1, wherein the heating impedance is movable, and the fixed impedance element is integrally disposed on the heating electrode. The high-frequency heating device according to claim 2, wherein the impedance value of the fixed impedance element is at least twice the maximum impedance value of the variable impedance element. 3. The high-frequency heating device according to claim 2, further comprising a fixed impedance element in parallel between the variable impedance element and the high-frequency generation means. The high-frequency heating device according to claim 2, wherein the variable impedance elements connected in series are provided with a plurality of taps, and change the impedance by switching taps. The high-frequency heating device according to claim 4, wherein the fixed impedance elements arranged in parallel are constituted by a capacitor having a multilayer structure of a dielectric and an electrode. 3. The high-frequency heating apparatus according to claim 2, wherein the variable impedance elements connected in series are formed of a capacitor having a multilayer structure of a dielectric and an electrode, and the facing area is changed by rotating one of the electrodes. The high-frequency heating device according to claim 2, further comprising a fixed impedance element and a variable impedance element in parallel between the variable impedance element and the high-frequency generation means connected in series. The high-frequency heating device according to claim 8, wherein the variable impedance element is configured by a capacitor having a multilayer structure of a dielectric and an electrode, and the facing area is changed by rotating one of the electrodes. A high-frequency heating device for supplying a microwave from the wall of the heating chamber into the heating chamber, wherein one of the heating electrodes arranged so as to sandwich the object to be heated in the heating chamber for storing the object to be heated is provided. . The high-frequency heating apparatus according to claim 10, further comprising a mounting portion of a nonmetallic material for mounting the object to be heated between the wall of the heating chamber that supplies the microwave and the object to be heated. The high-frequency heating apparatus according to claim 10, further comprising a stirring unit that stirs the supplied microwave. The high-frequency heating apparatus according to claim 12, wherein the stirring means has a plate-like configuration, and the plate surface is arranged substantially parallel to a wall surface of the heating chamber for supplying the microwave.

Images