JP2013171648A - Microwave heating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a microwave heating device that can accelerate equalization of heating of a heated body with a simple configuration in which a movable member is not interposed in a heating chamber for housing and processing the heated body, and is superior in reliability and durability.SOLUTION: An opening 300 for radiating a microwave generated by microwave generation means 50 to a heating chamber 200 is constituted while deformation prevention means 400 is provided at a periphery of the opening. Consequently, a plurality of openings can be arranged at narrower intervals in a limited region connected to a waveguide, and a microwave can be dispersed and radiated in the heating chamber 200 in a well-balanced state. A microwave heating device is therefore provided which can uniformly heat a heated body with a simple microwave supply configuration in which no movable member is interposed.

Description

  The present invention relates to a microwave heating apparatus such as a microwave oven, and more particularly to a microwave heating apparatus characterized by the structure of a microwave power feeding unit.

  A typical microwave heating apparatus that heats an object to be heated with a microwave is a microwave oven. In the microwave oven, the microwave generated by the microwave generating means is radiated into the metal heating chamber, and the object to be heated in the heating chamber is heated by the radiated microwave.

  A magnetron is used as a microwave generating means 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 means for uniformly heating an 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 rotated, and a structure for rotating an antenna for radiating microwaves while fixing the object to be heated are provided. A microwave heating device was common.

  For example, in a conventional microwave heating apparatus, a rotating mechanism such as a rotating antenna and an antenna shaft is arranged inside a waveguide. By driving the magnetron while rotating the rotating antenna by an antenna motor, The non-uniformity of wave distribution 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 described in Patent Document 2 which reduces the uneven heating of the object to be heated by microwave heating and reduces the cost and saves the space of the power feeding unit, it simply radiates circularly polarized waves into the heating chamber. A microwave heating apparatus having a single microwave radiating portion has been proposed.

JP-A-62-64093 U.S. Pat. No. 4,301,347

  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. There were various problems with the structure.

In particular, microwave ovens have been developed with high output technology, and a rated high frequency output of 1000 W has been commercialized in Japan. Microwave ovens are notable for heating food by heat conduction, but the convenience of being able to heat food directly using microwaves is a major feature of the product. The problem of non-uniform heating will become more apparent.

  A structural problem with conventional microwave heating devices is that a mechanism that rotates the table or antenna is required to reduce the non-uniformity of heating, and therefore the table, antenna, and motor for rotating them are required. It was necessary to secure an installation space such as a microwave oven, which had hindered restrictions on the structure and miniaturization of the microwave oven, making it difficult to reduce costs and ensure reliability and durability. It was.

  Further, as described in Patent Document 2, the microwave heating apparatus having a single microwave radiating unit that radiates circularly polarized light into the heating chamber has an advantage of not having a rotation mechanism. However, sufficient uniform heating by microwave heating has not been realized, and there is room for further improvement. Due to the background of the above problems, there is a demand for a microwave heating apparatus that reduces the unevenness of heating of an object to be heated by microwave heating and eliminates these mechanisms.

  Rotate instead of the conventional method of placing the object to be heated on the table and rotating it against the microwave radiation opening provided at one place on the wall surface of the heating chamber, or the method of rotating the antenna to stir the microwave in the heating chamber In the case of realizing uniform heating without using a mechanism, it is necessary to disperse and radiate microwaves widely in a heating chamber that accommodates an object to be heated. In this case, microwaves are radiated to the heating chamber. It is effective to arrange a plurality of openings so that the amount of radiation is dispersed as much as possible. Furthermore, it is effective to appropriately distribute the amount of microwave radiation from each of the arranged openings together with the arrangement of the radiation openings. Desirably, a configuration in which the numerical aperture is increased and the electric power radiated from each aperture is limited to be small is important for promoting uniform heating of the object to be heated. Conversely, when the numerical aperture is decreased and the power radiated from one aperture is increased, there is a limit to uniform heating. In particular, when heating a plurality of objects to be heated in a heating chamber, even if the objects to be heated are of the same type, it is difficult to uniformly heat them depending on how they are arranged.

  On the other hand, in a microwave heating apparatus such as a microwave oven, generally, a microwave generated from a magnetron, which is a microwave generation apparatus, is transmitted through a waveguide having a rectangular cross section and supplied to a heating chamber. It is. In such a configuration, the arrangement of the openings for supplying the microwaves to the heating chamber is limited to the range where the waveguide and the heating chamber are connected. In the case where a plurality of openings are arranged at a narrow interval in a limited region, it is a problem to achieve uniform heating to prevent deformation around the openings and to ensure sufficient strength of the wall surface of the heating chamber. By solving this problem, for example, a plurality of waveguides can be arranged side by side at right angles to the microwave transmission direction of the connected waveguide (that is, in the width direction of the waveguide). These openings can be arranged close to each other, so that a large number of openings can be provided in a limited area, and the heating of the object to be heated stored in the heating chamber can be made uniform. It can be promoted stably.

  The present invention solves the above-mentioned problems, and after sufficiently securing the strength of the wall surface, a plurality of radiation openings are provided on the wall surface of the heating chamber, and microwaves are radiated in a balanced manner from the microwave radiation openings provided in the heating chamber. Thus, an object of the present invention is to provide a microwave heating apparatus that is excellent in terms of reliability and durability, in which an object to be heated can be uniformly microwave-heated with a simple configuration with no movable member interposed.

In order to solve the above-described conventional problems, a microwave heating apparatus according to the present invention includes a heating chamber that houses an object to be heated, a microwave generation unit that generates a microwave to be supplied to the heating chamber, and the microwave generation unit. A waveguide for transmitting generated microwaves to the heating chamber, a plurality of openings for radiating microwaves from the waveguide to the heating chamber, and a deformation preventing means are provided around the openings. .

  As a result, a plurality of openings for radiating microwaves can be placed close to each other in the heating chamber, so that the microwaves are distributed in a balanced manner and distributed in a plurality of openings provided in a limited area connected to the waveguide. Therefore, it is possible to stably and uniformly heat an object to be heated having various types, shapes, and amounts stored in the heating chamber.

  The microwave heating apparatus of the present invention has a configuration in which a plurality of openings for supplying microwaves to the heating chamber are provided, and a deformation preventing means is provided around the opening, whereby the plurality of openings are arranged close to each other. Since the microwaves can be distributed and distributed in a balanced manner in a limited area connected to the waveguide, various types, shapes, and quantities stored in the heating chamber The object to be heated can be stably and uniformly heated. Therefore, in the heating chamber for storing the object to be heated, the object to be heated is not involved with a movable member such as a rotating antenna for stirring the emitted microwave or a turntable for rotating the object to be heated. It is possible to provide a microwave heating device that is economical, reliable, and durable with a small and simple configuration, without the need for a rotating mechanism and power for stirring. it can.

Cross-sectional schematic diagram of the main part of the microwave heating apparatus according to Embodiment 1 of the present invention Configuration diagram of the opening and its peripheral portion of the microwave heating apparatus in the first embodiment of the present invention Sectional schematic diagram showing another configuration example of the deformation preventing means and the opening of the present invention The principal part cross-sectional schematic diagram of the microwave heating apparatus which shows the other structural example of the deformation | transformation prevention means and opening of this invention The block diagram of the opening part of the microwave heating apparatus which shows the other structural example of a deformation | transformation prevention means and opening of this invention, and its periphery part The principal part cross-sectional schematic diagram of the microwave heating apparatus which shows the other structural example of the deformation | transformation prevention means and opening of this invention The principal part cross-sectional schematic diagram of the microwave heating apparatus which shows the other structural example of the deformation | transformation prevention means and opening of this invention The block diagram of the opening part of the microwave heating device in Embodiment 2 of this invention, and its periphery part Cross-sectional schematic diagram of relevant parts of a microwave heating apparatus according to Embodiment 2 of the present invention

  1st invention transmits the microwave which the heating chamber which accommodates a to-be-heated material, the microwave generation means which generates the microwave supplied to the heating chamber, and the microwave generation means generates to the heating chamber A waveguide and a plurality of openings for radiating microwaves from the waveguide to the heating chamber are provided, and deformation preventing means are provided around the openings, thereby radiating microwaves into the heating chamber. Since multiple openings can be arranged close to each other, they can be dispersed in multiple openings provided in a limited area connected to the waveguide and radiate microwaves in a balanced manner. It is possible to stably and uniformly heat an object to be heated of various types, shapes and amounts.

In the second invention, in particular, the deformation preventing means of the first invention is constructed so as to protrude toward the inside of the heating chamber so as to surround the opening, thereby preventing deformation of the heating chamber wall surface around the opening. However, a plurality of openings for emitting microwaves can be arranged close to each other. Further, since it can be realized to prevent water generated in the heating chamber from entering the inside of the waveguide from the opening, a device excellent in reliability and durability can be provided.

  In the third invention, in particular, the heating chamber of the first or second invention is constituted by a wall surface of a metal plate, and the deformation preventing means is formed by pressing integrally with the wall surface constituting the opening. Therefore, it is possible to prevent deformation without fail by integrating the metal plate constituting the wall surface without increasing the thickness of the metal plate constituting the wall surface of the heating chamber or the waveguide, and without requiring a special reinforcing member. it can.

  In the fourth aspect of the invention, the end face of the metal plate that constitutes the opening of the first aspect of the invention is particularly directed to the inside of the heating chamber by providing a deformation preventing means, whereby the end face of the metal plate that constitutes the opening. Can be configured so as not to be directed to the inside of the waveguide having a strong electric field strength, and therefore, it is possible to prevent the occurrence of sparks due to electric field concentration regardless of the shape of the opening.

  In the fifth invention, in particular, the deformation preventing means of the first invention is an impedance matching element provided on the inner wall of the waveguide for adjusting the reflected power of the microwave transmission line, and thereby the matching provided around the opening. Deformation can also be prevented by serving as an element.

  In the sixth aspect of the invention, the deformation preventing means of the first aspect of the invention is a irregular reflector that is convex toward the heating chamber that diffusely reflects the microwave radiated to the heating chamber, and thereby the diffuse reflector provided around the opening. Therefore, deformation can be prevented.

  In the seventh invention, in particular, the aperture of any one of the first to sixth inventions includes an aperture shape that radiates circularly polarized waves, whereby a microwave of a rotating electric field is radiated from the cross aperture. Accordingly, the microwave distribution in the heating chamber can be temporally changed in a configuration having no movable part, and the microwave of the rotating electric field can be directly incident on the object to be heated to promote uniform heating.

  In the invention of the younger brother 8, in particular, the amount of microwave radiation that can be radiated from each opening in any one of the first to seventh inventions is determined in relation to the maximum amount of radiation emitted from all the apertures. As a result, the maximum amount of radiation from one opening is determined while ensuring the amount of microwave radiation to the heating chamber. Therefore, it is possible to stably and uniformly heat an object to be heated of various types, shapes, and amounts stored in the heating chamber. In addition, even in a configuration in which a plurality of openings are arranged side by side in the transmission direction of the waveguide and microwaves are sequentially emitted from the radiation openings into the heating chamber along with the transmission of the microwaves, it is possible to prevent an uneven transmission amount in the arrangement. .

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 is a schematic cross-sectional view of an essential part of a microwave heating apparatus according to Embodiment 1 of the present invention. FIG. 2 is a configuration diagram of the opening of the microwave heating apparatus and its periphery in the first embodiment of the present invention.

  1 and 2, the microwave heating apparatus according to the present invention includes a heating chamber 200 constituted by a space closed with a metal material that houses an object to be heated, and a microwave generation means for generating microwaves to be supplied to the heating chamber 200. 50. A waveguide 100 for transmitting the microwave generated by the microwave generating means 50 is provided. A microwave generation means 50 is attached to one end side of the waveguide 100.

  Here, the waveguide 100 includes a transmission path having a rectangular cross section surrounded by a pair of width surfaces and a pair of height surfaces corresponding to the frequency and output of the microwave used in the microwave heating apparatus. In a general rectangular waveguide, the width dimension a and the height dimension b of the transmission line are selected by selecting the shape in the range of λ / 2 <a <λ and b <λ / 2 from the wavelength λ to be transmitted. It is transmitted in a form called TE10 mode. When the microwave generating means 50 oscillates at a frequency of 2450 MHz, since the wavelength λ is about 120 mm, the width dimension a is selected from 70 to 110 mm, the height dimension b is selected from 15 to 40 mm, and the like. Specifically, in this embodiment, the width is set to 100 mm and the height is set to 30 mm.

  Further, a plurality of openings 300 are formed in the bottom wall of the heating chamber 200 to which the waveguide 100 is joined, and the microwaves generated by the microwave generating means 50 are directly radiated into the heating chamber 200 from the plurality of openings 300. Further, a mounting plate 500 made of a glass plate of a low dielectric loss material on which an object to be heated is mounted is provided above the bottom wall where the plurality of openings 300 are arranged in the heating chamber 200. The mounting plate 500 and the bottom wall on which the opening 300 is disposed are arranged with a gap of 20 mm to 30 mm, and an inclined surface that extends from the bottom wall surface toward the outer shape of the mounting plate 500 is provided.

  The opening 300 is arranged based on the guide wavelength λg in the waveguide 100 at the center frequency (for example, 2460 MHz) of the microwave frequency band generated by the microwave generation means 50 and transmitted through the waveguide 100. Yes. The plurality of openings 300 are openings that radiate circularly polarized waves.

  Circular polarization is a technique widely used in the field 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 rotates with respect to the traveling direction of the radio wave according to time, and when the circular polarization is formed, the direction of the electric field continues to change with time. The characteristic is that the microwave radiation angle continues to change.

  Thereby, compared with the microwave heating by the linearly polarized wave used in the conventional microwave heating apparatus, the microwave is dispersed and radiated over a wide range so that the object to be heated can be microwave 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.

  Specifically, as shown in FIG. 2, a cross opening shape is formed by combining openings at predetermined angles (for example, approximately 45 degrees and approximately 135 degrees) with respect to the microwave transmission direction in the waveguide 100. As a result, when the microwave is transmitted through the waveguide 100 toward the end, the microwave radiated from the cross opening provided eccentrically with respect to the center of the width of the waveguide is a circular polarization whose electric field direction changes every moment. Since waves are radiated, microwaves of a rotating electric field can be directly incident on an object to be heated to further promote uniform heating.

  The length of the opening (the length in the longitudinal direction of the opening opened at a predetermined angle with respect to the microwave transmission direction in the waveguide) is free of the center frequency (for example, 2460 MHz) of the frequency band transmitting the waveguide. It is set to 1/4 or more of the propagation wavelength λ in space, for example, 45 mm.

The maximum energy that can be radiated from one opening can be adjusted by the geometry of the opening, but the total energy that can be radiated to the heating chamber is preferably the maximum energy that can be radiated for each opening. Therefore, it is possible to reliably suppress the energy from being biased toward a specific opening. In the present embodiment, a total of ten openings 300 are arranged in the waveguide 100, ie, five in the microwave transmission direction and two in the width direction of the waveguide 100 (perpendicular to the transmission direction). The amount of microwave radiation that can be radiated from the aperture is determined in relation to the maximum amount of radiation radiated from all the apertures, and the energy radiated from one aperture is transmitted from the microwave generation means 50. The opening size is set so as to radiate about 10 to 20% of the energy of the microwave radiated into the heating chamber 200.

  For example, in the case where 10 openings are arranged in a device with a maximum output of 1000 W, there is no problem in uniformly limiting the maximum output from one opening to 100 W. In this case, when heating at the maximum output of the apparatus, the energy radiated from each opening becomes equal. Even when this device is heated at an output of 500 W, the energy radiated from one opening is limited, so that it does not exceed 100 W, and the object to be heated is arranged with a bias with respect to the opening arrangement. Even in this case, uneven heating can be suppressed. Furthermore, it is effective to promote uniform heating by increasing the number of openings to be arranged and limiting the energy radiated from one opening to be small. In addition, the arrangement interval of the openings is set to approximately ¼ of the above-mentioned guide wavelength λg, thereby preventing mutual interference due to a phase difference of radiation from adjacent openings.

  A deformation preventing means 400 is provided around the opening 300 to prevent the opening shape from being held and its peripheral deformation in a configuration in which a plurality of openings 300 are arranged on the wall surface of the heating chamber 200 in the region where the waveguide 100 is connected. It has a configuration. In this embodiment, the amount of radiation from the opening 300 is equally distributed due to the symmetry of the heating chamber 200. For example, in a heating chamber having an asymmetrical shape in the front / rear and left / right directions, the corresponding opening is provided. The amount of radiation may be distributed by changing the size.

  Hereinafter, operation | movement and an effect | action of a microwave heating apparatus are demonstrated. When an object to be heated is placed on the placing plate 500 and a heating start instruction is given by the user, the microwave heating unit 50, which is a microwave generating unit, operates in the microwave heating apparatus, and the microwave 100 is placed in the waveguide 100. Waves are generated and transmitted, and directly radiated from the plurality of openings 300 to the heating chamber 200 to heat the object to be heated. The object to be heated placed on the placement plate 500 is heated by the microwaves radiated from the plurality of openings 300. However, the amount of radiation from one of the provided openings is suppressed, and the plurality of openings are used. Can be radiated. In other words, in order to promote uniform heating of the object to be heated at a high level corresponding to the type and size arrangement of the object to be heated without interposing a rotating antenna or the like, microwave radiation can be performed for each opening as much as possible. It is effective to disperse.

  On the other hand, in a microwave oven or the like, the metal wall surface constituting the heating chamber is generally formed of a thin plate having a thickness of about 0.5 mm from the viewpoints of strength, workability, and product weight. In a configuration in which microwaves are derived coaxially or in a configuration with a single aperture, such as the conventional method in which the antenna shaft to be rotationally driven is inserted into the waveguide aperture, the strength of the aperture arrangement has multiple apertures. It was small compared to the case of providing. On the other hand, if an attempt is made to arrange a plurality of openings in the heating chamber, the shape and arrangement of the openings will be limited because the strength of the walls constituting the openings will be reduced and the shape of the openings will be deformed. It was difficult to promote. Further, as a problem in the configuration in which a plurality of openings are arranged close to each other, there is thermal stress in addition to mechanical stress. This is due to the high-frequency current flowing through the metal wall between the openings by microwaves, but the narrow gap between the openings concentrates the high-frequency current around the openings and causes thermal deformation. Since the circular distance between the openings becomes longer by providing, there is an effect of preventing thermal deformation due to high-frequency current concentration.

In the microwave heating apparatus of the present invention, an opening may be arranged close to a limited region in order to ensure the amount of radiation necessary for heating by the effect of the deformation preventing means 400 while realizing the dispersion radiation of the microwave. Is possible. Furthermore, a plurality of openings are not disposed to reduce the strength of the heating chamber wall surface.

  As shown in FIGS. 1 and 2, the deformation preventing means 400 is provided in a convex shape toward the inside of the heating chamber 200 so as to surround the opening 300 along the periphery of the cross opening shape of the opening 300. This has the effect of preventing water generated in the heating chamber from entering the inside of the waveguide from the opening. Further, the deformation preventing means 400 can be formed by pressing integrally with the metal plate constituting the opening 300. In this embodiment, the deformation preventing means 400 is formed by burring so that the end surface of the metal plate faces the heating chamber 200. . As a result, the metal plate constituting the wall of the heating chamber and the waveguide does not need to be thickened, and there is no need to provide a special reinforcing member. Can do. Further, the structure in which the end face of the metal plate is not suitable for the transmission path of the waveguide having a high electric field strength has an effect of preventing sparks generated by the concentration of the electric field on the protrusion on the end face of the metal.

  Note that the shape of the deformation preventing means is not limited to the present embodiment, and may be configured as shown in FIGS. The deformation preventing means 420 shown in FIG. 3A is obtained by curling a metal plate. The deformation preventing means 430 shown in FIG. 3B is obtained by hemming a metal plate. The deformation preventing means 440 shown in FIG. The deformation preventing means 450 shown in (D) is a bead-processed one, and an opening is provided on the drawn (or stepped) surface, and the same effect can be obtained.

  Further, like the deformation preventing means 410 shown in FIGS. 4 and 5, it may be provided around the plurality of openings, may be provided along the shape of the opening, or the opening interval is narrow in addition to this. The structure which is partially provided in a certain range may be used.

  Further, as shown in FIGS. 6 and 7, the deformation preventing means 460 has a convex spherical shape toward the inside of the heating chamber 200 disposed around the opening 360 in order to diffusely reflect the microwave radiated into the heating chamber 200. This also serves as a diffuse reflector, thereby preventing deformation due to the diffusion effect of microwave radiation by the diffuse reflector provided around the opening. Further, the deformation preventing means 460 (diffuse reflector) is disposed around the opening 360 so that it effectively diffuses the microwave together with the deformation preventing action, and is disposed below the mounting plate 500 so that the object to be heated is disposed. Even when housed in the heating chamber 200, it does not get in the way or impair the appearance.

(Embodiment 2)
Next, a microwave heating apparatus according to another embodiment of the present invention will be described with reference to FIGS. FIG. 8 is a schematic cross-sectional view of the main part of the microwave heating apparatus according to the second embodiment of the present invention, and FIG. 9 is a configuration diagram of the opening of the microwave heating apparatus according to the second embodiment of the present invention and its surroundings. .

  8 and 9 differ from the first embodiment in the configuration of the deformation preventing means. The deformation preventing means 470 shown in FIG. 7 is provided so as to protrude into the transmission path of the waveguide 100. That is, as shown in FIG. 8, a waveguide that adjusts the reflected power toward the microwave generating means 50 in the microwave transmission path corresponding to the openings arranged in a plurality of rows in the microwave transmission direction in the waveguide 100. The deformation preventing means 470 is provided in combination with the impedance matching element provided on the inner wall of this. The deformation prevention means 470 can be provided in the region where the end of the cross opening is close to the four directions and the mechanical stress and the thermal stress increase, and the deformation can be prevented. Even if it arrange | positions, it becomes possible to distribute uniformly the energy of the microwave radiated | emitted from each opening. Thereby, the to-be-heated object which consists of various kinds, shapes, and quantity accommodated in the heating chamber can be stably and uniformly heated.

  As described above, the microwave heating apparatus of the present invention can realize uniform irradiation of microwaves to the object to be heated, and further, has no need to provide a special movable part for supplying microwaves, It is also excellent in terms of durability. It can be effectively used in a microwave heating apparatus that performs heating processing and sterilization of food.

50 Microwave generation means 100 Waveguide 200 Heating chamber 300 Opening 400 Deformation prevention means

Claims (8)

A heating chamber for storing an object to be heated;
Microwave generation means for generating a microwave to be supplied to the heating chamber;
A waveguide for transmitting the microwave generated by the microwave generating means to the heating chamber;
A plurality of openings for radiating microwaves from the waveguide to the heating chamber;
A microwave heating apparatus provided with deformation preventing means around the opening. The microwave heating apparatus according to claim 1, wherein the deformation preventing means is configured to be convex toward the inside of the heating chamber so as to surround the opening. The microwave heating apparatus according to claim 1 or 2, wherein the heating chamber is constituted by a wall surface of a metal plate, and the deformation preventing means is formed integrally with the wall surface constituting the opening by a press working method. The microwave heating apparatus according to claim 3, wherein the end face of the metal plate constituting the opening is provided with deformation preventing means toward the inside of the heating chamber. 2. The microwave heating apparatus according to claim 1, wherein the deformation preventing means is an impedance matching element provided on the inner wall of the waveguide for adjusting the reflected power of the microwave transmission path. 2. The microwave heating apparatus according to claim 1, wherein the deformation preventing means is a diffused reflector having a convex surface toward the heating chamber that reflects the microwave radiated to the heating chamber. The microwave heating device according to claim 1, wherein the opening includes an opening shape that radiates circularly polarized waves. The microwave heating device according to any one of claims 1 to 7, wherein the amount of microwave radiation that can be radiated from each opening is determined in relation to the maximum amount of radiation emitted from all the openings.