JP2014089942A - Microwave heating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a microwave heating device capable of uniformly heating an object to be heated with a simple structure using no driving part for stirring microwave.SOLUTION: The microwave heating device includes: plural first microwave emitting sections 220 which are disposed in a waveguide unit 201; plural second microwave emitting sections 221 which are disposed in a region where progressive wave closest to a microwave generating unit 202 is dominant, in which a single second microwave emitting section 221 is disposed or three or more odd-numbered second microwave emitting sections 221 are disposed in a direction orthogonal to a transmission direction and electric field direction. Even numbered microwave emitting sections which are disposed in a direction orthogonal to the transmission direction and the electric field direction in a progressive wave region can reduce and control the generation of a strong electric field area which is generated due to an interference of microwave radiation from a microwave emitting section; and thus, the object to be heated can be uniformly heated.

Description

  The present invention relates to a microwave heating apparatus such as a microwave oven that radiates microwaves to an object to be heated and dielectrically heats it, and more particularly to a microwave heating apparatus characterized by the arrangement position of a microwave radiation portion.

  A typical microwave heating apparatus that heats an object using a microwave is a microwave oven. In a microwave oven, microwaves generated in a microwave generator such as a magnetron are radiated into a metal heating chamber, and an object to be heated in the heating chamber is dielectrically heated by the radiated microwave.

  A magnetron is used as a microwave generator in a conventional microwave oven. Microwaves generated by the magnetron are radiated into the heating chamber through the waveguide. If the electromagnetic field distribution of the microwave in the heating chamber is not uniform, the object to be heated cannot be heated by microwaves uniformly.

  As a means for uniformly heating the object to be heated, a structure for rotating the object to be heated by rotating a table on which the object to be heated is mounted, a structure for rotating an antenna for radiating microwaves while fixing the object to be heated, or There is a method to make uniform by heating while changing the direction of the microwave radiated to the object to be heated using some kind of drive unit, such as a configuration that changes the phase of the microwave generated from the microwave generator by the phase shifter It was general.

  On the other hand, in order to simplify the configuration, a method of uniformly heating without a driving unit is expected, and a method using circularly polarized waves in which the polarization plane of an electric field rotates with time is proposed. Originally, since dielectric heating is based on the principle of heating an object to be heated having dielectric loss with a microwave electric field, rotation of the electric field is considered to have an effect on uniformity.

  For example, as a specific method of generating circularly polarized waves, Patent Document 1 discloses a method using X-shaped circularly polarized apertures 2 that intersect on the waveguide 1 as shown in FIG. FIG. 2 shows a method of disposing two elongated holes 1301 that are orthogonal to each other on the waveguide 1 as shown in FIG. 13 while facing each other, and Patent Document 3 introduces a method as shown in FIG. A method is described in which a notch 1402 is provided in the planar shape of a patch antenna 1401 coupled to the wave tube 1.

  For example, in a conventional microwave heating apparatus, a rotating antenna, an antenna shaft, and the like are arranged inside a waveguide. By driving a magnetron while rotating the rotating antenna by an antenna motor, the microwave distribution in the heating chamber is increased. Non-uniformity is reduced.

  Further, as described in Patent Document 1, a rotatable antenna is provided on the upper part of the magnetron, and the antenna is rotated by the wind of the blower fan by applying cooling air from the blower fan to the blades of the rotary antenna. There has been proposed a microwave heating apparatus that changes the microwave distribution in the heating chamber.

  On the other hand, as an example having a phase shifter, as described in Patent Document 2 in which heating unevenness of an object to be heated by microwave heating is reduced and cost reduction and space saving of a power feeding unit are achieved, a circular shape is provided inside the heating chamber. A microwave heating apparatus having a single microwave radiating unit that radiates polarized waves has been proposed.

U.S. Pat. No. 4,301,347 Japanese Patent No. 3510523 Japanese Patent Laying-Open No. 2005-235772

  However, in the microwave heating apparatus such as the microwave oven having the above-described conventional configuration, it is required to efficiently heat an object to be heated with a simple structure as much as possible, and has been proposed so far. The configuration had the following problems.

  Microwave heating devices, especially microwave ovens, have been developed for high-power technology, and products with a rated high-frequency output of 1000 W have been commercialized in Japan. Instead of heating food by heat conduction, dielectric heating Since the food is directly heated using, the increase in output while the uneven heating is unsolved will make the problem of uneven heating more obvious.

  The following three points are given as structural problems of the microwave heating apparatus having the conventional driving unit. The first point requires a mechanism for rotating the table or antenna in order to reduce heating unevenness. For this reason, it is necessary to secure a rotation space and an installation space such as a motor for rotating the table or antenna. It was that the miniaturization of the heating device was hindered. Secondly, in order to stably rotate the table or antenna, it is necessary to provide the rotating antenna at the upper part or the lower part of the heating chamber, and the structure is limited. Third, with the advent of microwave ovens with various heating functions such as steam heating and hot air heating, many components are required inside the microwave oven casing, and control components inside the casing, etc. Because of the large amount of heat generation, it is necessary to secure a cooling air path in order to achieve sufficient cooling performance, and the installation position of the waveguide means and the microwave radiating unit is limited, so the microwave distribution in the heating chamber is It becomes non-uniform.

  Furthermore, installing a table or a phaser rotation mechanism in an applicator, which is a microwave irradiation chamber in a microwave heating apparatus, causes a discharge phenomenon due to microwaves and lowers reliability. Therefore, there is a demand for a microwave heating apparatus that does not require these mechanisms.

  Next, the conventional microwave heating device using circularly polarized waves has a problem that in any case of Patent Documents 1 to 3, there is no uniform effect that can eliminate the drive unit. Both patent documents only describe that the synergistic effect of the circularly polarized wave and the drive unit is more uniform than the conventional drive unit alone.

  Specifically, Patent Document 1 has a rotating body called a phase shifter 1201 at the end of the waveguide 1 as shown in FIG. 12, and Patent Document 2 has a turntable (not shown) for rotating an object to be heated. Patent Document 3 describes a configuration in which a patch antenna 1401 is also rotated and used as an agitator in addition to the turntable 1403 as shown in FIG. It is not described that any drive unit can be used if circularly polarized waves are used. This is because if the drive unit is eliminated by circular polarization, the uniform heating performance is inferior to a configuration having a general drive unit (for example, a configuration in which a table is rotated, an antenna is rotated, etc.). .

As a means for improving the uniform heating property, a plurality of microwave radiation portions may be arranged in a direction orthogonal to the transmission direction of the waveguide means, the transmission direction, and the electric field direction. As described above, by arranging a plurality of microwave radiation portions, the microwave radiation range can be expanded in each of the transmission direction into the heating chamber, the transmission direction, and the direction orthogonal to the electric field direction. Uniform microwave radiation.

  However, in the region where the traveling wave of the microwave transmitted from the microwave generating means is dominant in the microwave radiating part in the waveguide means, the microwave radiation is performed in the direction orthogonal to the transmission direction of the waveguide means and the electric field direction. When multiple parts are arranged, the radiated microwaves have a strong directivity. Especially when an even number of microwave radiating parts are arranged, the microwaves radiated from the respective microwave radiating parts are strengthened by interference. In the meantime, a region having a strong electric field is formed in the direction opposite to the transmission direction near the center between the microwave radiation portions. Due to this strong electric field region, the heating unevenness becomes remarkable, for example, the heated object is locally overheated, and the cooking performance deteriorates, for example, the bottom surface of the heated object is burnt.

  This invention solves the said subject, and it aims at providing the microwave heating apparatus which can heat a to-be-heated material uniformly. In particular, when circularly polarized light is radiated from the opening of the waveguide 1 as shown in FIGS. 12 and 13, in the region where the traveling wave of the microwave transmitted from the microwave generating means is dominant, the waveguide 1 In order to suppress interference generated by microwave radiation from the second microwave radiation section when an even number of microwave transmission directions and directions perpendicular to the electric field direction are arranged, the number of second microwave radiation sections Is a single or an odd number of microwave radiation portions of 3 or more. When the microwave radiating unit is arranged in a single unit, the shape of the microwave radiating unit is changed in order to further enhance the microwave radiation in the direction orthogonal to the microwave transmission direction and the electric field direction in the waveguide. There is also a method. An object of the present invention is to make the microwave distribution in the heating chamber uniform and to uniformly heat the object to be heated.

  In order to solve the above-described conventional problems, a microwave heating apparatus of the present invention includes a heating chamber that houses an object to be heated, a microwave generating unit that generates a microwave, a waveguide unit that transmits the microwave, A microwave radiating part that radiates microwaves into the heating chamber, and a first microwave in which a plurality of microwave radiating parts are arranged in each of the transmission direction of the waveguide means and the direction orthogonal to the transmission and electric field direction A radiation unit, a second microwave radiation unit disposed in a region closer to the microwave generation means than the first microwave radiation unit, and a microwave in which the second microwave radiation unit is disposed in a single unit It is configured to be a microwave radiating portion or a microwave radiating portion arranged in an odd number of 3 or more in a direction orthogonal to the transmission and electric field direction of the waveguide means.

  With the above configuration, in the region where the traveling wave of the microwave is dominant, the interference of the microwave due to the microwave radiated from each of the microwave radiating means arranged so as to be orthogonal to the transmission of the waveguide means and the electric field direction. It is possible to suppress the strong electric field region generated in the direction opposite to the transmission direction.

  Even when the second microwave radiating unit is single, the microwave radiated from the microwave radiating unit becomes stronger as it is arranged closest to the microwave generating means. It is possible to eliminate a strong electric field region due to the interference of microwaves generated in the case where they are arranged, and at the same time to ensure uniform heating.

  Further, when the second microwave radiating portions are arranged in an odd number of 3 or more, the microwave radiating portion located in the center is arranged on the tube axis of the waveguide means, thereby causing interference of microwaves. Generation of a strong electric field region is suppressed, and the overheated region is reduced, so that heating of the object to be heated can be made uniform.

Further, at least one of the microwave radiating portions is constituted by at least one long hole, and in the microwave radiating portion having the long holes, the longitudinal direction of the long holes intersects the tube axis of the waveguide means. The spreading direction of the microwave radiated from the microwave radiating unit into the heating chamber varies depending on the angle.

  In the present invention, the crossing angle between the longitudinal direction of the long hole and the tube axis of the waveguide means is the smallest angle among the angles formed by the longitudinal direction of the long hole and the tube axis of the waveguide means. Means that.

  In particular, when the crossing angle between the longitudinal direction of the long hole and the tube axis of the waveguide means is smaller than 45 °, microwaves having directivity are radiated in the direction orthogonal to the transmission of the waveguide means and the electric field direction. When the crossing angle between the longitudinal direction of the hole and the tube axis of the waveguide means is larger than 45 °, microwaves having directivity are radiated in the transmission direction of the waveguide means and in the direction opposite to the transmission direction.

  By utilizing this, microwave transmission in the direction orthogonal to the direction of the electric field and transmission of the microwave is stronger with respect to the waveguide means from the microwave radiating section, and the heating can be made more uniform.

  Further, in the microwave radiating section having at least one long hole arranged so as to be orthogonal to the transmission of the waveguide means and the electric field direction in a region where the traveling wave of the microwave is dominant, at least one long By making the length of the longitudinal direction of the hole longer than the length of the first microwave radiation portion, the length of the second microwave radiation portion is opposite to the transmission direction due to interference from the microwave radiation portion. In addition to suppressing the strong electric field region generated at the same time, the transmission from the second microwave radiating part and the microwave radiation in the direction perpendicular to the electric field direction can be strengthened, and the heated object can be heated more uniformly. A microwave heating apparatus can be realized.

  In addition, by arranging a microwave radiating part that radiates circularly polarized waves, microwaves with a spread characteristic of circularly polarized waves are radiated from the microwave radiating parts, and microwave radiation to the object to be heated is radiated. It is possible to make uniform in a wider range. In particular, microwave heating by circular polarization can be expected to be uniform in the circumferential direction.

  Furthermore, the microwave radiation part that radiates circularly polarized waves has a simple shape composed of two or more long holes, so that not only uniform heating of the object to be heated, but also a simple structure without a drive part is reliable. The improvement in performance and the miniaturization of the power feeding unit can be realized.

  The present invention makes it possible to reduce the strong electric field region generated in the direction opposite to the transmission direction of the waveguide means due to the interference of the microwaves radiated from each microwave radiating portion, and to realize a microwave heating apparatus capable of uniform heating. .

  Further, in the microwave radiating portion having at least one long hole, the crossing angle between the longitudinal direction of the long hole and the tube axis of the waveguide means is smaller than 45 °, so that the transmission of the waveguide means is performed. In addition to the direction, it becomes possible to radiate more microwaves, particularly in the direction orthogonal to the transmission and electric field directions, and the uniform heating property of the object to be heated can be improved.

  Further, the length in the longitudinal direction of the at least one long hole when the second microwave radiating portion is single is the length of the at least one long hole of the microwave radiating portion constituting the first microwave radiating portion. Being longer than the length of the direction can eliminate the interference caused by microwave radiation and suppress the strong electric field region, and at the same time, enhance the microwave transmission and the microwave radiation in the direction perpendicular to the electric field direction. Therefore, it is possible to realize a microwave heating apparatus that can more uniformly heat an object to be heated.

  In addition, by arranging a microwave radiating section that radiates circularly polarized waves, microwaves with a spread characteristic of circularly polarized waves are radiated from the microwave radiating section, and microwave radiation to the object to be heated is radiated. Can be made uniform in a wider range. In particular, microwave heating by circular polarization can be expected to be uniform in the circumferential direction.

  Furthermore, the microwave radiation part that radiates circularly polarized waves has a simple shape composed of two or more long holes, so that not only uniform heating of the object to be heated, but also a simple structure without a drive part is reliable. The improvement in performance and the miniaturization of the power feeding unit can be realized.

The perspective view of the microwave heating apparatus in Embodiment 1 of this invention The top view of the microwave radiation | emission part of the microwave heating apparatus in Embodiment 1 of this invention The perspective view explaining the waveguide means of the microwave heating device in Embodiment 1 of this invention Explanatory drawing of the relationship between the electric field, magnetic field, and current in the waveguide means of the microwave heating apparatus in the first embodiment of the present invention. Explanatory drawing of the strong electric field area | region by interference with the microwave radiation | emission part of the microwave heating device in Embodiment 1 of this invention Explanatory drawing regarding the single shape and arrangement | positioning of the 2nd microwave radiation | emission part of the microwave heating device in Embodiment 1 of this invention The top view in the case of arrangement | positioning 3 or more odd number of the 2nd microwave radiation | emission part of the microwave heating apparatus in Embodiment 2 of this invention The top view of the microwave radiation | emission part which changed the crossing angle of the longitudinal direction of two long holes and the pipe axis of the microwave heating device in Embodiment 3 of this invention Explanatory drawing of the relationship between the directivity of the microwaves radiated from the microwave radiation part of the microwave heating apparatus according to the third embodiment of the present invention. Explanatory drawing of the microwave radiation | emission part shape of the microwave heating apparatus in Embodiment 3 of this invention Explanatory drawing of the shape according to the microwave radiation | emission part of the microwave heating apparatus in Embodiment 3 of this invention Configuration diagram of a microwave heating device that generates circularly polarized waves with a conventional X-shaped opening Configuration diagram of a conventional microwave heating device that generates circularly polarized waves with two orthogonal long holes Configuration diagram of a microwave heating device that generates circularly polarized waves with a conventional patch antenna

  A microwave heating apparatus according to a first aspect of the present invention is a heating chamber for storing an object to be heated, a microwave generating means for generating microwaves, a waveguide means for transmitting microwaves, and radiating microwaves into the heating chamber. A plurality of microwave radiating portions, a plurality of the microwave radiating portions disposed in each of a transmission direction of the waveguide means and a direction orthogonal to the transmission and electric field directions, and the first microwave radiating portion, A second microwave radiating section disposed in a region closer to the microwave generating means than the microwave radiating section; and a microwave radiating section in which the second microwave radiating section is disposed in a single unit, or the waveguide. Since the microwave radiating unit is arranged in an odd number of 3 or more in a direction orthogonal to the transmission and electric field direction, an even number of microwave radiating means is arranged in a region where the traveling wave of the microwave is dominant. In this case, the microwaves radiated from the microwave radiating portions interfere with each other, and the generation of a strong electric field region generated in the direction opposite to the microwave transmission direction can be suppressed, and the overheating region of the object to be heated is reduced. And uniform heating is possible.

In the second invention, the waveguide means for transmitting the microwave of the first invention is a rectangular waveguide for transmitting the TE10 mode, and a plurality of the waveguide means are arranged in the width direction and the longitudinal direction of the rectangular waveguide. In the heating chamber, the microwave radiating section can spread the microwave radiation in the width direction and the longitudinal direction of the rectangular waveguide, and the object to be heated can be uniformly heated.

  In the third invention, in particular, the microwave radiating unit disposed in a single portion of the second microwave radiating unit of the first or second invention is configured to radiate circularly polarized waves. In addition to suppressing the generation of a strong electric field region due to interference, the microwave is radiated from the center of the circularly polarized radiation section so as to vortex, so that it can be heated uniformly in the circumferential direction, It becomes possible to heat more uniformly.

  In the fourth aspect of the invention, in particular, the microwave radiating unit disposed in a single part of the second microwave radiating unit in the first or second aspect of the invention is configured to radiate linearly polarized waves. In addition to suppressing the generation of a strong electric field region due to interference, it is possible to provide directivity in the direction of heating more, so that the heating can be made uniform and the uniform heating property of the object to be heated can be improved. Become.

  In the fifth aspect of the invention, in particular, among the microwave radiating portions arranged in an odd number of three or more of the second microwave radiating portions in the first or second invention, the microwave radiating portion located in the center is By adopting a configuration that is arranged on the tube axis of the waveguide means, the microwave radiation from the central microwave radiation portion suppresses the generation of a strong electric field region due to the interference of the microwave and reduces the overheating region. Thus, it is possible to achieve uniform heating of the object to be heated.

  In the sixth aspect of the invention, in particular, at least one of the microwave radiating portions in any one of the first to fourth aspects of the invention is configured by at least one long hole, and the microwave radiating portion has at least one long hole. By making the crossing angle between the longitudinal direction and the tube axis of the waveguide means smaller than 45 °, microwave transmission from the microwave radiating section and microwave radiation in the direction perpendicular to the electric field direction become stronger. Since it is possible to heat in a wider region, it is possible to suppress a strong electric field region due to microwave interference and to further improve the uniform heating property of the object to be heated.

  In the seventh aspect of the invention, in particular, the second microwave radiation in which at least one of the microwave radiation portions in any one of the first to fourth aspects of the invention is composed of at least one long hole and is disposed in a single unit. The length of the longitudinal direction of the at least one long hole of the portion is longer than the length of the longitudinal direction of the at least one long hole of the first microwave radiation portion, thereby suppressing interference of microwave radiation. In addition, the strong electric field region generated in the direction opposite to the transmission direction of the waveguide means is suppressed, and at the same time, microwave radiation can be radiated in a wide range in the direction perpendicular to the transmission direction and the transmission and electric field direction. The uniform heating property can be improved.

  In the eighth aspect of the invention, in particular, the microwave radiating portion that radiates circularly polarized waves according to any one of the first to seventh aspects of the invention has a substantially X-shaped configuration in which two long holes intersect. Thereby, it is possible to reliably radiate circularly polarized waves with a simple configuration.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, a preferred embodiment of a microwave heating apparatus according to the invention will be described with reference to the accompanying drawings. In the microwave heating apparatus of the following embodiment, a microwave oven will be described. However, the microwave oven is an example, and the microwave heating apparatus of the present invention is not limited to the microwave oven, and uses dielectric heating. And a microwave heating device such as a garbage processing machine or a semiconductor manufacturing device. Further, the present invention is not limited to the specific configurations of the following embodiments, and configurations based on similar technical ideas are included in the present invention.

(Embodiment 1)
1-6 is explanatory drawing of the microwave heating apparatus in Embodiment 1 of this invention.

  FIG. 1 is a perspective view showing the overall configuration of the microwave heating apparatus. In FIG. 1, a microwave heating device 101 is configured by a microwave radiation unit 102, a heating chamber 103, a mounting table 104, and a door 105. FIG. 2 is an explanatory diagram of an arrangement position of the microwave radiation unit 102 that radiates circularly polarized waves. In FIG. 2, the microwave is generated by the microwave generation means 202 and is radiated from the microwave radiation section 102 that is transmitted through the waveguide means 201 and radiates circularly polarized waves. Further, a standing wave is formed in the waveguide unit 201 by being reflected by the terminal portion 203. The long hole of the microwave radiating part 102 is opposite to the long hole longitudinal direction 204, the crossing angle 205 of the long hole long direction 204 and the tube axis 211 of the waveguide means, the microwave transmission direction 207, and the microwave transmission direction. Direction 208, transmission and electric field. FIG. 3 is a schematic view of a rectangular waveguide 301 that is one of the waveguide means 201. FIG. 4 is a diagram for explaining the transmission mode of the waveguide means 201, the electric field, the magnetic field, the current, and the standing wave. FIG. 5 is an explanatory diagram of the strong electric field region 501 generated by the interference of the microwaves radiated from the respective microwave radiating units 102 arranged in the region where the traveling wave of the microwave is dominant in the waveguide unit 201. FIG. 5A shows a time variation of the electric field intensity around the microwave radiating portion in a contour diagram, and FIG. 5B shows a plan view of the microwave heating device 101 along the tube axis 211 of the waveguide means. In the vertical cross section, the electric field strength is represented by a contour diagram. These results are the results of electromagnetic field analysis. As an analysis condition, the boundary condition of the heating chamber wall surface is an absorption boundary, and the number of microwave radiation portions is eight. FIG. 6 is a schematic diagram of the arrangement and shape in the case where the second microwave radiating portion 221 is single.

  A microwave oven, which is a typical microwave heating apparatus, is radiated from a heating chamber 103 in which an object to be heated (not shown) can be stored, a microwave generation unit 202 that generates a microwave, and a microwave generation unit 202. A waveguide unit 201 that guides the microwave to the heating chamber 103, and a microwave radiation unit 102 that radiates the microwave in the waveguide unit 201 provided on the H surface 302 of the waveguide unit 201 into the heating chamber 103. ing.

  As shown in FIG. 1, the microwave oven includes a mounting table 104 on which an object to be heated is placed while covering the upper part of the microwave radiating unit 102, and a door 105 for taking in and out the object to be heated. Here, the mounting table 104 is made of a material that easily transmits microwaves, such as glass or ceramic.

  The above configuration can be easily realized by using a magnetron for the microwave generation means 202, a rectangular waveguide 301 for the waveguide means 201, and an opening provided in the waveguide means 201 for the microwave radiation section 102. it can.

  First, the schematic operation of the microwave heating apparatus will be described. When an object to be heated is placed in the heating chamber 103 by the user and a heating start instruction is given, the microwave heating apparatus supplies microwaves from the magnetron, which is the microwave generating means 202, into the waveguide means 201, The microwave heating apparatus heats an object to be heated by radiating microwaves into the heating chamber 103 through the microwave radiating unit 102 connecting the heating chamber 103 and the waveguide unit 201.

  Note that in the present invention, microwaves radiated from the microwave radiating unit 102 and directly heating an object to be heated are called direct waves, and microwaves reflected by the inner wall of the heating chamber 103 are called reflected waves.

Next, a rectangular waveguide 301 which is a typical waveguide unit 201 mounted on a microwave oven will be described with reference to FIG. The simplest and general waveguide means 201 is a rectangular parallelepiped having a certain rectangular cross section (width a × height b) extending in the transmission direction 207 as shown in FIG. 3, and the wavelength of the microwave is λ. And a waveguide width a (microwave wavelength λ>a> λ / 2) and height b (<
It is known to transmit microwaves in the TE10 mode by selecting in the range of λ / 2).

  The TE10 mode is an H wave (TE wave; Electrical Transverse Electric Wave) in which the magnetic field 402 component exists only in the waveguide transmission direction 207 in the rectangular waveguide 301 and has no electric field 401 component. Refers to the transmission mode. Note that transmission modes other than the TE10 mode are rarely applied to the waveguide means 201 of the microwave heating apparatus 101.

  In a microwave oven, the wavelength λ is about 120 mm, and in general, the width a is often selected to be 80 to 100 mm and the height b is selected to be about 15 to 40 mm.

  At this time, the upper and lower surfaces in FIG. 3 are referred to as the H surface 302 in the sense that the magnetic field 402 spirals in parallel, and the left and right surfaces are referred to as the E surface 303 in the meaning parallel to the electric field 401. The wavelength when the microwave is transmitted through the waveguide is expressed as an in-tube wavelength λg, which is λg = λ / √ (1- (λ / (2 × a)) ^ 2), depending on the width a dimension. Although it varies, it is determined regardless of the height b dimension.

  In the TE10 mode, the electric field 401 is 0 at both ends (E plane 303) in the width direction of the waveguide unit 201, and the electric field 401 is maximum at the center in the width direction. Therefore, the magnetron is configured to be coupled to the center in the width direction of the waveguide unit 201 where the electric field 401 is maximum.

  As described above, in a microwave oven that is a microwave heating device using a frequency around 2.45 GHz, when transmitting microwaves in the TE10 mode, the width a of the waveguide is often set to 80 to 100 mm.

  However, since the dimension of the heating chamber 103 in the direction 209 orthogonal to the transmission and electric field direction of the waveguide means 201 is often larger than the width a dimension of the waveguide, the microwave radiated from the microwave radiating unit 102 is reduced. It is difficult to achieve uniform heating without spreading in the direction 209 orthogonal to the transmission and electric field directions.

  Therefore, a technique for spreading the microwave radiated from the microwave radiation unit 102 in the direction 209 orthogonal to the transmission and electric field direction is important.

  Next, as a conventional technique for spreading and radiating the microwave radiated from the microwave radiating unit 102 in the direction 209 orthogonal to the transmission and electric field direction, the microwave is placed at the approximate belly position 405 of the electric field 401 distribution in the waveguide unit 201. A method for arranging the radiation unit 102 will be described.

  When the rectangular waveguide 301 as shown in FIG. 3 is used as the waveguide unit 201, the traveling wave generated from the microwave generation unit 202 interferes with the reflected wave reflected by the terminal portion 203 of the waveguide unit 201. As shown in FIG. 4, a standing wave 404 is generated in the waveguide.

  Note that the spread of the microwave radiated from the waveguide unit 201 to the heating chamber 103 changes depending on the phase of the electric field 401 of the standing wave 404 in the waveguide unit 201 where the microwave radiation unit 102 is located. The principle of changing the spread of the microwave will be described below.

First, the relationship between the electric field 401, the magnetic field 402, and the current 403 in the standing wave 404 will be described with reference to FIG. In the traveling wave, the directions of the electric field 401 and the magnetic field 402 are shifted by 90 °, and the phase is the same. On the other hand, in the standing wave 404, the directions of the electric field 401 and the magnetic field 402 are shifted by 90 °, and the phase is shifted by π / 2. Therefore, the rectangular waveguide 301 in which the standing wave 404 is generated.
The relationship between the electric field 401 and the magnetic field 402 is as shown in FIG. In the case of the standing wave 404, this is mainly due to the phase of the electric field 401 being shifted by π / 2 when the traveling wave is reflected by the terminal portion 203 of the waveguide unit 201. The current 403 flows on the surface of the waveguide unit 201 in a direction perpendicular to the magnetic field 402.

  The principle of microwave directivity when the microwave radiating portion 102 is arranged on the H surface 302 of the rectangular waveguide 301 where the standing wave 404 is generated will be described.

  As shown in FIG. 4, consider a case where the microwave radiating unit 102 is disposed at the approximate belly position 405 and the approximate node position 406 for the standing wave 404 in the waveguide unit 201. The antinodes and nodes in the present invention indicate the strength of the electric field 401 in the transmission direction 207 of the waveguide means 201, and do not mean the strength of the electric field 401 in the direction 209 orthogonal to the transmission and electric field direction.

  Considering the transmission direction 207 component of the current 403 in the microwave radiating unit 102 and the direction 209 component orthogonal to the transmission and electric field direction, the current 403 in the microwave radiating unit 102 placed at the approximate position 405 includes the transmission and electric field. There are many direction 209 components orthogonal to a direction.

  Since the direction in which the current 403 flows and the direction in which the electric field 401 spreads are the same, the microwave radiated from the waveguide unit 201 to the heating chamber 103 mainly spreads in the direction 209 orthogonal to the transmission and electric field direction.

  In addition, the current 403 in the microwave radiation unit 102 placed at the approximate node position 406 has many components in the transmission direction 207. For this reason, the microwave radiated from the waveguide unit 201 to the heating chamber 103 mainly spreads in the transmission direction 207 of the waveguide unit 201.

  Next, the node position of the electric field 401 in the waveguide unit 201 will be described. When microwaves are transmitted through the waveguide unit 201 having the termination portion 203 as shown in FIG. 4, a standing wave 404 is formed in the microwave transmission direction 207. Since the waveguide unit 201 is closed by the terminal end 203, the amplitude at the terminal end 203 is zero. Further, the supply side of the microwave generation means 202 is a free end indicating the maximum amplitude value.

  Here, the standing wave 404 existing in the waveguide unit 201 is a wave based on the oscillation frequency supplied by the microwave generation unit 202. Therefore, the wavelength of the standing wave 404 existing in the waveguide unit 201 is about ½ of the in-tube wavelength λg generated by the oscillation frequency of the microwave generation unit 202.

  Therefore, in the waveguide means 201, the node position of the standing wave 404 is generated at every half of the guide wavelength λg with the terminal end 203 as a base point. Further, the antinode position of the standing wave 404 exists substantially in the middle of the adjacent node positions.

  However, in the waveguide that is the actual waveguide unit 201, the electric field 401 in the waveguide unit 201 around the microwave generation unit 202 is often not stable, and the state of the terminal portion 203 is not ideal. In some cases, an in-tube wavelength λg around the theoretical value is generated. Therefore, it is certain to actually measure the amplitude of the standing wave 404 in the actual waveguide in the waveguide means 201.

  Next, features of circularly polarized waves and advantages of microwave heating using circularly polarized waves will be described.

Circular polarization is a technique widely used in the fields of mobile communication and satellite communication. Examples of familiar use include an ETC (Electronic Toll Collection System) “non-stop automatic toll collection system” and the like. Circular polarization is a microwave in which the polarization plane of the electric field 401 rotates with respect to the traveling direction of the radio wave, and when the circular polarization is formed, the direction of the electric field 401 continues to change with time. The radiation angle of the microwave radiated into the chamber 103 continues to change, and the intensity of the electric field 401 does not change with time.

  Due to the above characteristics, compared to microwave heating by linear polarization used in conventional microwave heating devices, microwaves are dispersed and radiated over a wide range so that the object to be heated can be heated uniformly. become. In particular, there is a strong tendency for uniform heating in the circumferential direction of circular polarization.

  Note that circularly polarized waves are classified into two types, that is, right-handed polarization (CW: clockwise) and left-handed polarization (CCW: counterclockwise) from the direction of rotation, but there is no difference in heating performance.

  Note that the direction of vibration of the microwave electric field and the magnetic field in the waveguide unit 201 is constant with respect to the circularly polarized wave, which is a linearly polarized wave. In the conventional microwave heating apparatus that radiates linearly polarized waves into the heating chamber 103, in order to reduce the non-uniformity of the microwave distribution, a structure for rotating the table on which the object to be heated is placed, or waveguide means It is necessary to install a structure for rotating an antenna that radiates microwaves from 201 to the heating chamber 103.

  Therefore, the standing wave 404 generated in the heating chamber 103 due to the interference between the direct wave and the reflected wave, which has been a problem in the microwave heating by the microwave heating device using the conventional linearly polarized wave, can be relaxed. Uniform microwave heating can be realized.

  The circularly polarized wave in the present invention does not mean only when the microwave spread from the microwave radiating unit 102 is an exact circle, but the microwave spread is an ellipse. It also includes cases such as That is, as the direction of the electric field 401 continues to change according to time, the radiation angle of the microwave radiated into the heating chamber 103 also continues to change, and the intensity of the electric field 401 does not change with time. What it has is also called circular polarization.

  Next, in the use of circularly polarized waves, there are some differences between the communication field in the open space and the heating field in the closed space. In the communications field, it is necessary to send and receive only the necessary information while avoiding mixing with other microwaves, so the transmitting side transmits only to right-handed polarized waves or left-handed polarized waves, and the receiving side also sends The optimum receiving antenna is selected accordingly.

  On the other hand, in the field of heating, instead of a receiving antenna having directivity, an object to be heated such as food with no directivity receives microwaves, so that it is only important that the microwaves are evenly applied to the whole.

  Therefore, in the heating field, there is no problem even if right-handed polarized waves and left-handed polarized waves are mixed, but it is necessary to prevent uneven distribution depending on the position and shape of the object to be heated. For example, in the case of a single circularly polarized aperture, it is better to place the object to be heated directly above the circularly polarized aperture, but if it is shifted back and forth or left and right, the part close to the circularly polarized aperture is likely to be heated, Distant parts are difficult to be heated, resulting in uneven heating. Therefore, it is desirable to arrange a plurality of circularly polarized apertures.

In the case where microwaves are transmitted in the TE10 mode as in the present embodiment, the direction of circularly polarized light radiated from the circularly polarized aperture with the tube axis 211 of the waveguide means in the waveguide means 201 as a boundary Is reversed (right-handed polarized wave and left-handed polarized wave), but such an arrangement is unthinkable in the communication field, and is an arrangement unique to the heating field realized for the first time in the present invention.

  In the present embodiment, the microwave radiating portion 102 that radiates circularly polarized waves has a substantially X-shaped configuration in which two long holes intersect. Thereby, it is possible to reliably radiate circularly polarized waves with a simple configuration.

  Next, interference of microwaves radiated from the waveguide unit 201 to the heating chamber 103 through the microwave radiation unit 102 will be described.

  The mutual interference of the microwaves at an arbitrary point is determined by the difference between the spreading direction of the microwaves from each microwave radiation unit 102 and the distance to the arbitrary point and the wavelength of the microwaves in the heating chamber 103. In addition, it is strengthened when it is an even multiple (including 0) of ½ of the wavelength in the heating chamber 103 and weakened when it is an odd multiple. In the case of a microwave frequency of 2.45 GHz used in a general microwave heating apparatus, the wavelength in air such as in the heating chamber 103 is about 120 mm.

  For example, the crossing angle 205 of the major axis direction of the long hole and the tube axis of the waveguide means intersects the microwave radiating portion 102 where the long axis direction 204 of the long hole and the tube axis 211 of the waveguide means are parallel. Consider a case where the microwave radiating portions 102 having an angle 205 of 45 ° are arranged one by one.

  When the crossing angle 205 between the major axis direction of the long hole and the tube axis of the waveguide means is 0 °, the microwave radiated from the waveguide means 201 to the heating chamber 103 is mainly orthogonal to the transmission and electric field directions. When the crossing angle 205 between the long axis direction of the long hole and the tube axis of the waveguide means is 45 °, the light is emitted almost evenly in the transmission direction 207 and the direction 209 orthogonal to the transmission and electric field directions. Interfering with each other in the heating chamber 103.

  Although the microwaves locally generate in the heating chamber 103 due to the mutual interference of the microwaves radiated from each of the microwave radiating units 102, the spread of the microwaves included in each microwave radiating unit 102 is remarkable. Will not change.

  Therefore, the microwave distribution in the heating chamber 103 is close to a distribution obtained by adding the spread of the microwaves radiated from the microwave radiating units 102.

  In particular, in the microwave radiating unit 102 disposed at a position closest to the microwave generating means 202, the microwave transmitted in the waveguide means 201 is in a traveling wave state at a position close to the microwave generating means 202. Radiated from the wave radiation unit 102. Further, the region close to the terminal end 203 of the waveguide means 201 is in a standing wave state. On the contrary, the microwave exists as a standing wave in a region near the terminal end portion 203 of the waveguide means away from the microwave generating means 202. When microwaves are radiated from the microwave radiating unit 102 in a region where the microwave is a traveling wave, a strong electric field region is formed near the center between the microwave radiating units 102 in the direction opposite to the transmission direction of the waveguide unit 201. Occur.

FIG. 5 shows the result of obtaining the generation of the strong electric field region 501 by electromagnetic field analysis. In FIG. 5A, the intensity of the electric field generated from the microwave radiating portion is represented by a contour diagram. A microwave is transmitted from the right side to the left side of the figure, and a strong electric field region 501 is generated in the direction opposite to the transmission direction from the center between the two microwave radiating portions 102 close to the microwave generating means 202 at the time step T3. doing. This is because interference occurs when microwaves are radiated from the two microwave radiating portions 102 arranged in the traveling wave region, and the strength of the microwaves is opposite to the transmission direction in the vicinity of the center between the microwave radiating portions. Arising from what happens. In the traveling wave region, the directivity of microwave radiation is stronger than in the standing wave region, and the strengthening of the microwave becomes significant. In FIG. 5 (b), the analysis result of the electric field strength by the electromagnetic field analysis is represented by a contour diagram in a cross section in which the microwave heating device 101 is cut in the vertical direction on the plane along the tube axis 211 of the waveguide means. In the figure, the result of generation of the strong electric field region 501 was obtained. The analysis condition here is that the heating chamber wall boundary is an absorption boundary.

  In FIG. 6, in order not to generate the strong electric field region 501 generated from the interference of the microwave radiation as described above, the second microwave radiation portion 221 is configured as a single microwave radiation portion. In such a configuration, interference of microwaves can be eliminated, the strong electric field region 501 is not generated, and overheating of the object to be heated can be prevented and the uniform heating property can be improved.

  FIG. 6A shows a case where the second microwave radiating portion 221 is a microwave radiating portion that generates circularly polarized waves, and the shape is a substantially X shape combining two long holes. ing. FIG. 6B shows a configuration in which the second microwave radiating portion 221 has the substantially X shape and is disposed on the tube axis 211 of the waveguide means 201. FIG. 6C illustrates a configuration in which the second microwave radiating unit 221 is disposed on the tube axis 211 of the waveguide unit 201 and has a slit shape parallel to the transmission direction 207. (D) represents that the slit is formed in a shape parallel to the direction orthogonal to the transmission and electric field direction.

  Hereinafter, specific configurations, operations, and effects in the present embodiment will be described.

  As shown in FIGS. 2 and 6, the microwave oven that is the microwave heating apparatus 101 of the present embodiment includes a heating chamber 103 that stores an object to be heated, a microwave generation unit 202 that generates a microwave, and a microwave. A plurality of waveguide means 201 for transmitting waves and a first microwave radiation portion 220 for radiating microwaves into the heating chamber 103 are arranged in a direction 209 orthogonal to the transmission of the waveguide means 201 and the electric field direction. .

  In addition, a second microwave radiating portion 221 is disposed in a region closer to the microwave generating means 202 than the first microwave radiating portion 220. The second microwave radiating portion 221 arranged at a position closest to the microwave generating means 202, which is a region where traveling waves are dominant, is configured by at least one long hole, and a single microwave radiating portion. As described above, the strong electric field region 501 generated by microwave interference can be eliminated, and uniform heating of the object to be heated can be realized.

  This is because, when an even number of microwave radiating parts are arranged in a region where the traveling wave of the microwave is dominant, the microwaves radiated from each microwave radiating part interfere with each other and are opposite to the transmission direction of the microwaves. Generation of a strong electric field region generated in the direction can be suppressed, an overheating region of the object to be heated can be reduced, and heating can be made uniform.

  Note that even if the second microwave radiating unit 221 is a microwave radiating unit that generates circularly polarized waves as shown in FIG. 6A, FIGS. 6B, 6C, and 6D are used. Even in the microwave radiating unit that generates linearly polarized waves represented by (), the interference of microwaves can be eliminated and the strong electric field region 501 can be suppressed.

(Embodiment 2)
FIG. 7 is an explanatory diagram of the microwave heating apparatus according to Embodiment 2 of the present invention.

FIG. 7 shows the waveguide means 201, the first microwave radiating section 220, and the second microwave radiating section 2.
21 is a diagram for explaining the positional relationship between the microwave generation means 202, and in particular, the second microwave radiating section 221 is arranged in an odd number of 3 or more in the direction 209 orthogonal to the microwave transmission and electric field direction, A configuration in which the central microwave radiation portion is arranged on the tube axis 211 of the waveguide means 201 is shown. FIG. 7A shows a configuration in which the microwave radiation part on the tube axis 211 is on a slit in a direction parallel to the transmission direction 207, and FIG. 7B shows the microwave radiation on the tube axis 211. FIG. 7C shows a configuration in which the microwave radiating portion on the tube axis 211 is a combination of two long holes. FIG. 7C shows a configuration in which the portion has a slit shape parallel to the direction 209 orthogonal to the transmission and electric field direction. It represents a configuration having a letter shape.

  By arranging the second microwave radiating portion 221 on the tube axis 211 of the waveguide means 201 as shown in FIG. 7, microwave radiation is generated on the tube axis 211, so that the direction 208 is opposite to the transmission direction. Occurrence of a strong region due to generated microwave interference is suppressed.

  Therefore, strong electric field region 501 due to interference does not occur, and overheating of the object to be heated is suppressed, so that it is possible to improve the heating uniformity performance.

In the drawings, the same reference numerals are given to the portions showing the same operations as those in (Embodiment 1). The basic operation in (Embodiment 2) is the same as that in (Embodiment 1).
Moreover, the microwave radiation | emission part arrange | positioned on the tube axis | shaft 211 may have a slit shape or a substantially X shape as shown in the figure.

(Embodiment 3)
Hereinafter, specific configurations, operations, and effects in the present embodiment will be described.

  8-11 is explanatory drawing of the microwave heating apparatus 101 in Embodiment 3 of this invention.

  FIG. 8 is a diagram for explaining the positional relationship among the waveguide means 201, the second microwave radiating portion 221, and the microwave generating means 202, and in particular, at least one long hole of the second microwave radiating portion 221. The crossing angle 205 between the longitudinal direction of the waveguide and the tube axis of the waveguide means represents a configuration smaller than 45 °.

  FIG. 9 shows the crossing angle 205 between the direction of at least two long holes of the second microwave radiating portion 221 and the tube axis of the waveguide means, and the spread of the microwave radiated from the waveguide means 201 to the heating chamber 103. Is a diagram illustrating the electric field distribution obtained by electromagnetic field analysis.

  10 shows that the longitudinal length 216 of at least one long hole of the second microwave radiating portion 221 is longer than the length 215 of at least one long hole of the first microwave radiating portion 220 in the longitudinal direction. Represents a long configuration.

  FIG. 11 shows a shape in which the second microwave radiating portion 221 is formed by connecting two substantially X-shaped microwave radiating portions.

  Note that the basic operation in (Embodiment 3) is the same as that in (Embodiment 1) and (Embodiment 2), and the description is omitted unless it is a main point of the invention. explain.

  The principle of changing the direction in which the microwave radiated from the waveguide unit 201 to the heating chamber 103 changes depending on the crossing angle 205 between the longitudinal direction of the long hole and the tube axis of the waveguide unit will be described.

  When the microwave radiation means is a long hole, the distance between the long sides is shorter than the distance between the short sides, so that an electric field is likely to occur between the long sides.

  Therefore, since an electric field distribution is generated in a direction perpendicular to the longitudinal direction 204 of the long hole, changing the crossing angle 205 between the longitudinal direction of the long hole and the tube axis of the waveguide means also changes the direction in which the microwave spreads.

  From the above, when the crossing angle 205 between the longitudinal direction of the long hole and the tube axis of the waveguide means is smaller than 45 °, the microwave spreads mainly in the direction 209 orthogonal to the transmission and electric field direction.

  When the crossing angle 205 between the longitudinal direction of the long hole and the tube axis of the waveguide means is larger than 45 °, the microwave spreads mainly in the transmission direction 207.

  Next, in FIG. 9, from the microwave radiating unit 102 to the heating chamber when the crossing angle 205 between the longitudinal direction of the long hole and the tube axis of the waveguide means is changed in increments of 10 ° from 25 ° to 65 °. The distribution of the microwave radiated to 103 was obtained by electromagnetic field analysis.

  In this analysis, the longitudinal direction 204 of the long hole is rotated clockwise, but the same result can be obtained in the case of counterclockwise rotation.

  As shown in FIG. 9, when the crossing angle 205 between the longitudinal direction of the long hole and the tube axis of the waveguide means is 45 ° or less, the microwave radiation is transmitted in the direction 209 orthogonal to the transmission and electric field direction of the waveguide means. It can be seen that it has occurred remarkably. On the other hand, it can be seen that when the crossing angle 205 between the longitudinal direction of the long hole and the tube axis of the waveguide means is 45 ° or more, the microwave radiation spreads more in the transmission direction.

  As described above, the transmission of microwaves is strong in the direction perpendicular to the longitudinal direction, and the crossing angle 205 between the longitudinal direction of the long hole and the tube axis of the waveguide means is less than 45 ° with respect to 45 °. In addition, the amount of microwave radiated in the direction 209 orthogonal to the electric field direction is larger than the amount of microwave radiated in the transmission direction 207.

  Therefore, at least one of the microwave radiating portions 102 is composed of at least one long hole, and the crossing angle 205 between the longitudinal direction of the at least one long hole and the tube axis of the waveguide means is smaller than 45 °. By doing so, the microwave can be spread outside the width of the waveguide means 201, and the strong electric field region 501 generated in the direction opposite to the transmission direction due to the interference of the microwave is reduced. It becomes possible to uniformly heat the object to be heated.

  The operation and action in this embodiment will be described below.

  A microwave oven that is the microwave heating apparatus 101 of the present embodiment includes a heating chamber 103 that stores an object to be heated, a microwave generation unit 202 that generates a microwave, a waveguide unit 201 that transmits a microwave, A plurality of microwave radiating portions 102 that radiate microwaves are arranged in the heating chamber 103 in a direction 209 orthogonal to the transmission direction of the waveguide means 201 and the transmission and electric field directions.

  As shown in FIG. 8, the second microwave radiating portion 221 disposed at a position closest to the microwave generating means 202 is configured with at least one long hole and also has at least one long length. The intersection angle 205 between the longitudinal direction of the hole and the tube axis of the waveguide means is configured to be smaller than 45 °.

  As described above, the heating uniformity can be improved by making the second microwave radiating portion 221 as single as in the first embodiment, and at least one of the microwave radiating portions 102 has at least one length. The crossing angle 205 between the longitudinal direction of the at least one long hole and the tube axis of the waveguide means is smaller than 45 °, and is formed in a direction 209 orthogonal to the transmission and electric field direction of the waveguide means 201. It becomes possible to spread the microwave.

  Further, as shown in FIG. 10, the longitudinal length 216 of at least one long hole of the second microwave radiating portion 221 is equal to the longitudinal length of at least one long hole of the first microwave radiating portion 220. When the configuration is longer than 215, it is possible to suppress microwave interference and simultaneously spread the microwave in the direction 209 perpendicular to the transmission of the waveguide means 201 and the electric field direction, thereby improving the heating uniformity. I can do it.

  The second microwave radiating portion 221 reduces the interference of the radiated microwave and reduces the strong electric field region 501 even when the plurality of X-shaped microwave radiating portions are connected as shown in FIG. As a result, the object to be heated can be uniformly heated.

  Further, the same effect is obtained even if the length in the short direction of at least one long hole of the second microwave radiating portion 221 is longer than the length in the short direction of at least one long hole of the first microwave radiating portion 220. Is obtained.

  Further, the microwave radiating portion 102 has a shape in which the length in the longitudinal direction is shortened and an X-shaped intersection is different from the longitudinal center of the long hole, or a corner is added to the end of the microwave radiating portion. The same effects as described above can be obtained also in

  From the above, in addition to arranging the second microwave radiating section as a single or an odd number of 3 or more, changing the shape of the microwave radiating section reduces the microwave interference in the traveling wave region and transmits at the same time. In addition, it is possible to improve the spread of the microwave in the electric field direction, and it is possible to provide the microwave heating apparatus 101 that makes the heating distribution of the object to be heated more uniform.

  In addition, when the number and position of the microwave radiation | emission parts 102 are symmetrical with respect to the center 210 of a heating chamber, when the microwave radiation | emission part 102 is shapes other than a long hole, all the microwave radiation | emission parts 102 are the same. The present invention includes a case where the shape is not used.

  As described above, since the microwave heating apparatus of the present invention can uniformly irradiate an object to be heated, it can be effectively used for a microwave heating apparatus that performs food heating or sterilization.

DESCRIPTION OF SYMBOLS 101 Microwave heating apparatus 102 Microwave radiation | radiation part 103 Heating chamber 104 Mounting stand 105 Door 201 Waveguide means 202 Microwave generation means 203 Termination part 204 Longitudinal direction of long hole 205 Crossing angle 207 Transmission direction 208 Direction opposite to transmission direction 209 Transmission And the direction orthogonal to the electric field direction 210 center of the heating chamber 211 tube axis 220 first microwave radiating portion 221 second microwave radiating portion 301 rectangular waveguide 302 H surface 303 E surface 401 electric field 402 magnetic field 403 current 404 constant Standing wave 405 Rough position 406 Rough position 407 Electric field direction 501 Strong electric field region

Claims (8)

A heating chamber for storing an object to be heated;
Microwave generation means for generating microwaves;
Waveguide means for transmitting microwaves;
A microwave radiating section for radiating microwaves into the heating chamber;
A plurality of the microwave radiating units disposed in each of the transmission direction of the waveguide means and the direction orthogonal to the transmission and electric field direction; and
A second microwave radiation portion disposed in a region closer to the microwave generation means than the first microwave radiation portion;
The second microwave radiating unit is a microwave radiating unit arranged in a single unit, or a microwave radiating unit arranged in an odd number of 3 or more in a direction orthogonal to the transmission and electric field direction of the waveguide means. Microwave heating device. The microwave heating apparatus according to claim 1, wherein the waveguide means for transmitting the microwave is a rectangular waveguide for transmitting the TE10 mode. The microwave heating device according to claim 1 or 2, wherein the single microwave radiating portion of the second microwave radiating portion radiates circularly polarized waves. The microwave heating device according to claim 1 or 2, wherein the single microwave radiating portion of the second microwave radiating portion radiates linearly polarized waves. The microwave radiating portion located at the center is arranged on the tube axis of the waveguide means among the microwave radiating portions arranged in an odd number of 3 or more of the second microwave radiating portions. 3. The microwave heating apparatus according to 1 or 2. 5. At least one of the microwave radiating portions is composed of at least one long hole, and the crossing angle between the longitudinal direction of the long hole and the tube axis of the waveguide means is smaller than 45 degrees. 2. The microwave heating apparatus according to item 1. At least one of the microwave radiating portions is composed of at least one long hole, and the longitudinal length of at least one long hole of the second microwave radiating portion arranged in a single unit is set to be the first microwave. The microwave heating device according to any one of claims 1 to 4, wherein the microwave heating device is longer than a length in a longitudinal direction of at least one long hole of the radiating portion. The microwave heating apparatus according to any one of claims 1 to 7, wherein the microwave radiating portion that radiates circularly polarized waves has a substantially X-shaped configuration in which two long holes intersect.