JP2013109987A - Microwave heating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To heat an object to be heated efficiently and uniformly with a simple structure, without using a rotation mechanism such as a table, an antenna, or the like.SOLUTION: Since the microwave transmission line in a microwave radiation section 120 of a rectangular waveguide 100 for transmitting microwaves generated by microwave generation means 50 to a heating chamber 200 is provided with a region of different height in the transmission direction of microwave, microwaves are radiated into the heating chamber 200, in good balance, from a plurality of radiation openings 120h arranged in the transmission direction of microwave. Consequently, a microwave heating device capable of heating an object to be heated uniformly with a compact and simple microwave power supply configuration, without using a rotation mechanism, can be provided.

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 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 rotated, a structure for rotating an antenna for radiating microwaves while fixing the object to be heated, or A microwave heating apparatus having a structure in which the phase of the microwave generated by the microwave generating means is changed by a phase shifter has been 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 addition, microwave heating devices, particularly microwave ovens, have been developed for high-power 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 directly heating food using dielectric heating is a major feature of the product. The problem of non-uniform heating will become more apparent.

  The following two points can be cited as structural problems of the conventional microwave heating apparatus. The first point requires a mechanism for rotating the table or antenna in order to reduce the non-uniformity of heating. 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. That is, the miniaturization of the microwave oven was hindered. The second point is that in order to stably rotate the table or antenna, it is necessary to provide the rotating antenna above or below the heating chamber, and the structure is limited.

  Installing a rotating mechanism such as a table or an antenna in the microwave radiation chamber of the microwave heating apparatus makes it difficult to achieve downsizing and cost reduction and to ensure reliability. Therefore, there is a demand for a microwave heating apparatus that does not require these mechanisms.

  Also, circularly polarized light is introduced into the interior of the heating chamber as described in Patent Document 2, which reduces the nonuniformity of heating of the object to be heated by microwave heating and reduces the cost and space saving of the power feeding unit. The microwave heating device having a single microwave radiating part that radiates has the advantage of not having a rotating mechanism, but the problem is that sufficient uniform heating by microwave heating has not been realized. There is room for further improvement.

  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 where uniform heating is realized without using a mechanism, it is effective to directly apply a microwave to a heated object accommodated in the heating chamber in a wide range. In this case, the microwave is applied to the heating chamber. As the radiation openings to be supplied, it is necessary to arrange a plurality of radiation openings in a wide range of the heating chamber, not to provide a single one.

  However, peripheral parts such as a power source and a cooling fan for a microwave generator are arranged in a general microwave heating apparatus, and heat sources and functional parts for other heating such as steam heating and heaters as the functions become higher Since there are many space restrictions on the form and power supply configuration of the waveguide that transmits microwaves, there are problems in achieving uniform heating by effectively arranging multiple openings. It is.

  Furthermore, it is a problem to appropriately distribute the amount of microwave radiation from each of the arranged radiation openings together with the arrangement of the radiation openings. That is, in a microwave heating apparatus such as a microwave oven, generally, microwaves generated from a magnetron that is a microwave generation apparatus are transmitted to a heating chamber through a rectangular waveguide formed by a transmission path having a rectangular cross section. It is a configuration.

  In such a configuration, when a plurality of radiation openings for supplying microwaves by connecting the waveguide to the heating chamber are disposed, the direction is perpendicular to the microwave transmission direction (that is, the width direction of the transmission path). The microwaves transmitted from the microwave generation means are radiated all at once at the same transmission distance toward the heating chamber by arranging them side by side. In the case where a plurality of radiation openings are provided, the number and interval of arrangements are limited due to dimensional restrictions of the waveguide, and uniform heating cannot be realized.

In contrast, when a plurality of radiation openings are arranged in the microwave transmission direction, the number and interval of the radiation openings can be set according to the heating chamber. However, in this configuration, the microwave to be transmitted is radiated sequentially from the radiation opening close to the microwave generating means to the heating chamber, so the object to be heated accommodated in the heating chamber is close to the microwave generating means. The radiation aperture side was strongly heated, resulting in heating unevenness in the microwave transmission direction. Therefore, there is room for improvement in order to properly distribute the amount of microwave radiation from each radiation opening so that heating unevenness in the microwave transmission direction can be eliminated in the heating chamber.

  The present invention solves the above-described problem, and radiates microwaves in a well-balanced manner from a plurality of microwave radiation openings into a heating chamber, thereby uniformly heating an object to be heated without using a rotating mechanism. An object of the present invention is to provide a microwave heating apparatus that can be used.

  In order to solve the above-described conventional problems, the microwave heating apparatus of the present invention includes a heating chamber that stores a heated object, a microwave generation unit that generates a microwave to be supplied to the heating chamber, and a microwave generation unit. A rectangular waveguide including an input portion connected to the microwave generating means so as to transmit the microwave to be heated to the heating chamber and a microwave radiating portion provided with a plurality of radiation openings connected to the heating chamber. In the microwave radiating portion of the wave tube, a plurality of radiation openings are arranged at least in the transmission direction, and the microwave transmission path has regions having different heights in the transmission direction. As a result, microwaves can be radiated in a well-balanced manner from the radiation openings widely arranged at a plurality of locations with respect to the object to be heated stored in the heating chamber. Good heating can be realized.

  According to the present invention, the rectangular waveguide for transmitting the microwave generated by the microwave generating means to the heating chamber heats the microwave radiating section provided with a plurality of radiation openings in at least the microwave transmission direction in the transmission path. Further, the microwave transmission path of the rectangular waveguide connected to the chamber has a region having a different height in the transmission direction. By setting the height of the transmission path according to the arrangement of the radiation openings in the microwave radiation section, microwaves can be radiated in a well-balanced manner in the heating chamber, so that uneven heating due to the position of the radiation openings in the microwave transmission direction can be achieved. Thus, it is possible to provide a microwave heating apparatus capable of uniformly heating an object to be heated with a simple microwave power feeding configuration without using a rotation mechanism.

  That is, by arranging a plurality of radiation openings for radiating microwaves at least in the microwave transmission direction in the microwave radiation portion, the microwaves can be directly incident on a wide range of the object to be heated accommodated in the heating chamber. Furthermore, according to the setting of the shape and dimensions of each radiation aperture, appropriate radiation characteristics and radiation amount can be obtained by providing different areas in the transmission path of the rectangular waveguide in the microwave transmission direction. Therefore, the object to be heated can be effectively heated uniformly.

  In other words, in a configuration in which a plurality of radiation openings are provided in the microwave radiation portion of the rectangular waveguide, if the radiation openings are arranged in the width direction of the transmission path of the rectangular waveguide, the number and arrangement interval of the radiation openings depends on the width of the transmission path. Therefore, it is difficult to arrange the radiation opening in a wide range of the heating chamber.

  On the other hand, when a plurality of radiation openings are arranged in the microwave transmission direction, the microwave radiation part is connected to a wide range of the heating chamber by setting the length of the transmission path according to the dimensions of the heating chamber. On the other hand, since microwaves are radiated into the heating chamber sequentially from the radiation opening on the side close to the microwave generating means and absorbed by the object to be heated, the radiation from the radiation opening is passed through the radiation opening. The amount of radiation will decrease, and this tends to increase the heating rate on the side close to the microwave generating means even in the heating chamber containing the non-heated material from which microwaves are radiated.

  In other words, when correcting to obtain appropriate microwave radiation, it is possible to adjust by changing the aperture size as long as the radiation amount alone, but in this case, characteristics such as the radiation range and radiation direction also change. Will do.

  In the present invention, the shape of the radiating aperture is maintained so as to obtain the desired characteristics, and heating is performed by appropriately changing the characteristic impedance of the rectangular waveguide in the region where the radiating aperture is provided by changing the height of the transmission line. There is an effect that a suitable microwave radiation can be obtained by changing the radiation efficiency according to the relationship with the spatial impedance in the room. In other words, in the range where the radiation aperture is provided, changing the height of the characteristic impedance of the transmission line will approach the spatial impedance of the heating chamber, and microwaves from the radiation aperture are likely to be emitted, reducing loss from the radiation aperture. And high radiation efficiency.

  Furthermore, since the electric field strength is high on the side closer to the microwave generation means in the transmission of microwaves, the height of the transmission line should be reduced from the viewpoint of preventing the occurrence of sparks in order to reduce the characteristic impedance by reducing the height of the transmission line. Although there are restrictions, the microwave is radiated sequentially from the radiation opening into the heating chamber as the microwave is transmitted, and the electric field strength is reduced, so that the height of the transmission path can be set low, and a spark is generated. The transmission path of the rectangular waveguide can be made thin while suppressing the above. Furthermore, by making the rectangular waveguide thin, it is possible to effectively use the space, and it is effective in ensuring the reliability such as the expansion of the heating chamber and the downsizing of the apparatus.

  Therefore, it is possible to efficiently radiate microwaves to a wide range of the heating chamber and uniformly and efficiently heat the object to be heated accommodated therein. It is not a method of stirring using a special rotation mechanism, but a configuration that always radiates and radiates microwaves widely is realized, and since it does not require a rotation mechanism or electric power for stirring, it is economical with a small and simple configuration. And a highly reliable microwave heating apparatus can be provided.

1 is an external perspective view of a main part of a microwave heating apparatus according to Embodiment 1 of the present invention. The perspective view of the waveguide of the microwave heating device in Embodiment 1 of this invention Cross-sectional schematic diagram of relevant parts of the microwave heating apparatus according to Embodiment 1 of the present invention. FIG. 3 is a schematic cross-sectional view of an essential part taken along line KK in FIG. 3 showing the shape of the radiation opening of the microwave heating apparatus according to Embodiment 1 of the present invention.

  According to a first aspect of the present invention, there is provided a heating chamber for storing a heated object, a microwave generating means for generating a microwave to be supplied to the heating chamber, and a microwave generated by the microwave generating means to be transmitted to the heating chamber. A rectangular waveguide including an input section connected to the microwave generation means and a microwave radiation section provided with a plurality of radiation openings connected to the heating chamber, and the microwave radiation of the rectangular waveguide In the section, a plurality of the radiation apertures are arranged at least in the transmission direction, and the microwave transmission path has regions having different heights in the transmission direction. As a result, microwaves can be directly incident on a wide range of the object to be heated accommodated in the heating chamber. Further, in the microwave radiating section, the arrangement of the radiation openings in the transmission direction and the height of the transmission path in the transmission direction By providing different areas, it is possible to suppress the occurrence of a difference in the amount of radiation from each radiation opening in the transmission direction and to obtain a desired radiation characteristic, so that the object to be heated can be effectively heated uniformly. . In other words, it is possible to effectively radiate microwaves over a wide area of the heating chamber and uniformly and efficiently heat the object to be heated contained therein, so that it does not depend on a special stirring method using a rotating mechanism. In both cases, a configuration that always radiates and radiates microwaves is realized, so there is no need for a rotating mechanism or electric power for stirring, so it is possible to provide a microwave heating device that is economical and easy to use with a small and simple configuration. it can.

  In a second aspect of the invention, the rectangular waveguide according to the first aspect of the present invention is provided with a changing portion between regions having different heights in the transmission direction of the microwave transmission path in the microwave radiating portion, It is composed of a plane or a curved surface inclined in the transmission direction so as to connect regions having different heights without a step. As a result, even if regions having different heights are provided in the microwave transmission direction, the regions are connected to each other without a step in a tapered shape, so that the microwave can be efficiently transmitted while suppressing reflection of the microwaves on the transmission path. Is. Therefore, microwaves can be radiated effectively over a wide area of the heating chamber, and the object to be heated contained can be heated uniformly and efficiently. Therefore, it is possible to provide an economical and reliable microwave heating device with a small and simple configuration because a configuration for radiating and radiating microwaves is realized. .

  According to a third aspect of the invention, the height of the microwave transmission path in the microwave radiating portion of the rectangular waveguide according to the first or second aspect of the invention is reduced stepwise as the distance from the input portion increases. It has been done. Each time it passes through the radiation opening, microwaves are radiated into the heating chamber and the electric field strength is lowered. By setting the height of the transmission path to be lower step by step, the characteristic impedance of the microwave radiating section is set to the heating chamber. Since the difference from the impedance decreases step by step each time it passes through the radiation aperture, the microwave transmitted to the radiation aperture is easily radiated into the heating chamber. Therefore, the microwave radiation from the plurality of radiation openings arranged in the transmission direction can be appropriately radiated in a well-balanced manner by suppressing the decrease in the radiation amount as compared with the case where the height of the transmission path in the microwave radiation portion is constant. . Therefore, it is possible to provide a microwave heating apparatus capable of uniformly heating an object to be heated with a simple microwave power feeding configuration without using a rotation mechanism.

  In the fourth invention, the height of the microwave transmission path in the microwave radiating portion of the rectangular waveguide according to the third invention is particularly the height of the radiation opening provided on the side far from the input portion of the rectangular waveguide. The region is set lower than the region of the radiation aperture provided on the side closer to the input unit. That is, in the first invention, the regions having different heights of the microwave transmission path are provided with a plurality of different regions corresponding to the plurality of arrangements of the radiation openings in the microwave radiation portion in the microwave transmission direction. . As a result, by setting the height of the transmission path of the radiation opening on the side far from the input part in the microwave radiation part, the difference between the characteristic impedance and the impedance of the heating chamber becomes small, so that the microwave is emitted from the radiation opening on the far side. There is an effect that makes it easy to radiate, and the microwaves from each of the radiation openings arranged in the transmission direction can be radiated appropriately in a balanced manner. Therefore, it is possible to provide a microwave heating apparatus capable of uniformly heating an object to be heated with a simple microwave power feeding configuration without using a rotation mechanism.

  According to a fifth aspect of the present invention, in the microwave waveguide of the rectangular waveguide according to any one of the first to fourth aspects, a surface connected to the heating chamber in the microwave radiating portion is configured in the same plane. As a result, even if the transmission path of the rectangular waveguide is set to a different height, the surface provided with the radiation opening in the microwave radiating portion of the rectangular waveguide has no step and can be easily connected to the wall surface of the heating chamber. it can. With this configuration, there is no difference in distance due to the difference in height of the transmission path from a plurality of radiation openings arranged in the microwave transmission direction with respect to the object to be heated accommodated in the heating chamber. An object to be heated can be efficiently heated. It is not a method of stirring using a special rotating mechanism, but a structure that always radiates and spreads microwaves is realized. It does not require a rotating mechanism or power for stirring, so it is economical and reliable with a small and simple structure. A microwave heating apparatus with good quality can be provided.

Furthermore, as a special effect of the first to fifth aspects of the present invention, since the microwave is radiated sequentially from the radiation opening into the heating chamber along with the transmission of the microwave, the electric field strength is lowered. The height of the transmission line can be set low while reliably preventing the occurrence of sparks. Thus, by making the rectangular waveguide thin, it is possible to effectively use the space, and it is possible to ensure the reliability and enlarge the heating chamber and reduce the size of the product.

  Therefore, it is possible to efficiently radiate microwaves over a wide area of the heating chamber and uniformly and efficiently heat the object to be heated, which is not a method of stirring using a special rotation mechanism. Realizes a configuration that radiates widely and does not require a rotating mechanism or electric power for stirring, so it can further save space in combination with the configuration, and it is economical and reliable with a small and simple configuration A microwave heating apparatus with good quality can be provided.

  A sixth invention is a microwave heating apparatus including a plurality of radiation openings in the microwave radiation portion of the rectangular waveguide according to any one of the first to fifth inventions, wherein the plurality of radiation openings radiate circularly polarized waves. is there. As a result, microwaves whose electric field direction rotates and radiates from the openings that radiate circularly polarized waves and are radiated to the object to be heated, and it is possible to more effectively heat the object to be heated in combination with multiple openings. A microwave heating apparatus can be provided.

  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 addition, although the microwave oven is demonstrated in the microwave heating apparatus of the following embodiment. 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)
FIG. 1 is a schematic external view of a main part of a microwave heating apparatus according to Embodiment 1 of the present invention. In FIG. 1, 10 is an object to be heated, 200 is a heating chamber, 50 is a magnetron as a microwave generating means, and 100 is a rectangular waveguide. The heating chamber 200 is configured in a substantially rectangular parallelepiped shape with a wall surface made of a metal material that reflects microwaves and an opening / closing door 200d for taking in and out the object to be heated 10, and is configured to confine the supplied microwaves inside.

  FIG. 2 is a perspective view showing a configuration of rectangular waveguide 100 in a state where magnetron 50 and heating chamber 200 are not connected in the first embodiment. In FIG. 2, 110 h is a connection port of the magnetron 50 provided at the input unit 110 of the rectangular waveguide 100. Reference numeral 120 denotes a microwave radiating unit connected to the heating chamber 200 of the rectangular waveguide 100, and 120 h denotes a plurality of radiation openings for radiating the microwaves provided in the microwave radiating unit 120 to the heating chamber 200.

  Hereinafter, the operation of the microwave heating apparatus will be described. The article to be heated 10 is put in from an opening / closing door 200d provided on a part of the wall surface constituting the heating chamber 200 and placed on the mounting portion 201 in the heating chamber 200. The placement unit 201 is provided with a glass plate of a low dielectric loss material facing the wall surface to which the microwave radiation unit 120 is connected. When a heating start instruction is given by the user, the microwave heating apparatus operates the magnetron 50 as a microwave generating means to generate a microwave in the rectangular waveguide 100 and transmit it to the microwave radiating unit 120. The heated object 10 is heated by being supplied to the heating chamber 200 from the radiation opening 120h.

  Here, the rectangular waveguide 100 is configured by 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 magnetron 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.

As shown in FIG. 2, the rectangular waveguide 100 of the present embodiment is configured such that the second width 102 in the microwave radiating unit 120 is larger than the first width 101 in the input unit 110 to which the magnetron 50 is connected. . Specifically, in the present embodiment, the dimension of the first width 101 is set to 75 mm, whereas the second width 102 is set to 105 mm wider than the first width 101.

  In the microwave radiating unit 120, a plurality of radiation openings 120 h that radiate microwaves to the heating chamber 200 can be dispersed over a wide range of the second width 102. In the present embodiment, the microwave radiating portion 120 in the rectangular waveguide 100 is arranged in wide contact with the bottom surface of the heating chamber 200, bent upward from the microwave radiating portion, and input to the side surface adjacent to the bottom surface of the heating chamber 200. The unit 110 is arranged. In the heating chamber 200, a plurality of radiation openings 120h that radiate microwaves are arranged at least in the microwave transmission direction.

  As shown in FIG. 2, three radiation openings 120h are arranged in the microwave transmission direction, and a total of six radiation openings 120h are arranged in two rows in the direction of the second width 102 in the microwave radiation portion. Yes.

  FIG. 3 is a schematic cross-sectional view of an essential part of the microwave heating apparatus according to Embodiment 1 of the present invention. As shown in FIG. 3, the transmission path in the microwave radiating unit 120 has a transmission line height 121 (1B) on the side close to the input unit 110 and an intermediate transmission line height 122 (2B). A region having a three-stage height difference with the height 123 (3B) of the transmission line on the end side is provided. The height of the transmission path is set so that the area of the radiation opening provided on the side far from the input unit 110 is set lower than the area of the radiation opening provided on the side close to the input part.

  Further, the height of the transmission path in the microwave radiating unit is configured so as to decrease stepwise as the distance from the input unit increases such that 1B> 2B> 3B. Specifically, in the present embodiment, the height 121 of the transmission line closer to the input unit is set to 25 mm, and the height 123 of the transmission line closer to the end is set to 15 mm. The height 122 of the transmission path in the meantime (center portion) is set to an intermediate 20 mm.

  Further, as shown in FIG. 3, the regions with different heights of the transmission line are provided with a tapered inclined surface to prevent the reflection of the microwave in the transmission line. In other words, the changing portion 124 configured by a plane or a curved surface inclined in the transmission direction is provided so as to connect regions having different heights without a step.

  In this way, by providing different areas of the transmission path in the microwave radiating section 120, the characteristic impedance is appropriately changed in the area where the radiation opening 120h is provided, and the radiation amount due to the change in the transmission amount of the microwave to the radiation opening is obtained. The occurrence of the difference can be suppressed, and the microwaves are radiated into the heating chamber 200 from the radiation openings 120h arranged in the microwave transmission direction in a well-balanced manner.

  Here, when the rectangular waveguide has only a transmission line having no radiation opening, the characteristic impedance of the transmission line is inversely proportional to the width of the waveguide, and the microwave radiation with the width of the transmission line wider than the region of the input unit 110 is used. The characteristic impedance is lower in the region of the portion 120 immediately before the radiation opening. In this embodiment, the characteristic impedance of the transmission line of the rectangular waveguide 100 is 652Ω at the input unit 110 and 464Ω at the microwave radiation unit.

On the other hand, the characteristic impedance of the microwave radiation unit 120 having a radiation opening provided in the transmission line is different from the characteristic impedance of the transmission line in different regions, and the characteristic impedance is lower as the transmission line is lower. Become. That is, the difference from the spatial impedance (about 377Ω) in the heating chamber is further reduced in the radiation opening 120h far from the input unit 110 to which the microwave generating means 50 is connected, so that the microwave is transmitted from the transmission path to the heating chamber 200. It becomes easy to derive.

  Furthermore, since the electric field tends to concentrate at the peripheral portion of the radiation opening 120h, it is necessary to secure a spatial distance according to the electric field strength that can prevent sparks. In this embodiment, the microwave with the high electric field strength remains. The transmission path in the region where the radiation opening 120h on the side close to the generation means 50 is arranged is made high, and the radiation opening 120h on the side far from the microwave generation means 50 where the electric field strength decreases as the microwave is emitted into the heating chamber. Since the transmission path is lowered in the provided area, it is possible to reliably prevent sparks and ensure safety and reliability. Further, by lowering the transmission path, the vacant space can be effectively used to increase the volume of the heating chamber and reduce the size of the apparatus.

  Further, in the present embodiment, the plurality of radiation openings 120 h in the microwave radiation unit 120 are connected to the bottom surface of the heating chamber 200 and provided on the same surface. That is, even in the configuration in which regions having different transmission line heights are provided in the microwave radiating unit 120, the surface of the microwave radiating unit provided with the radiation opening 120h has no step and can be easily connected to the bottom surface of the heating chamber. . Furthermore, since it can be configured so as not to cause a difference in distance from a plurality of radiation openings facing the placement unit 201 on which the article to be heated 10 accommodated in the heating chamber 200 is placed, the emitted microwaves are uniform. An object to be heated can be efficiently heated.

  FIG. 4 is a cross-sectional view taken along the line KK in FIG. 3 and is viewed from above (heating chamber) perpendicular to the radiation opening 120h.

Further, in the present embodiment, the plurality of radiation openings 120h in the microwave radiation unit 120 are configured to radiate circularly polarized waves. Circular polarization is a technology widely used in the field of mobile communications and satellite communications. As a familiar use example, 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, and when the circular polarization is formed, the direction of the electric field continues to change with time. The radiation angle of the emitted microwave has a feature that it keeps changing. 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.

  By utilizing the above feature and emitting circularly polarized microwaves through the radiation opening 120h, the heating distribution in the heating chamber 200 can be made more uniform. In addition, as an opening shape for outputting circularly polarized waves from the radiation opening 120h of the microwave radiating section 120 provided in the rectangular waveguide 100, as shown in FIG. The two slots (openings) having a width so as to be circularly polarized intersect with each other at the center, and are inclined by 45 degrees with respect to the microwave transmission direction. Further, in the microwave radiating unit 120 of the rectangular waveguide 100 A total of six radiation openings 120h are provided in two rows sandwiching the center 106 of the second width.

As described above, in the present embodiment, the radiation opening 120h of the microwave radiating unit 120 has a shape that radiates circularly polarized waves, so that the plurality of radiation openings 120h of the microwave radiating unit 120 are expanded. Microwaves are radiated into the heating chamber 200, and the microwave radiation to the object to be heated 10 can be made uniform over a wider range. Further, by making the second width 102 wide in the microwave radiating section 120, the shape and size of the opening can be set for each opening so that an appropriate radiation characteristic and radiation amount can be obtained. The object 10 can be heated uniformly.

  That is, by arranging the radiation opening 120h in accordance with the phase of the microwave transmitted in the microwave radiating unit 120, it is possible to make the radiation direction of the microwave appropriate, and the amount of radiation is controlled by the size of the radiation opening 120h. The microwave radiation characteristics can be made appropriate depending on the shape of the opening, the transmission direction of the microwave, and the arrangement angle of the radiation opening 120h. There is an effect that uniform heating can be realized.

  In the present embodiment, the change portion 124 provided between regions having different heights in the transmission direction of the transmission path is provided between the radiation opening 120h and the radiation opening 120h arranged in the transmission direction. As long as a desired radiation characteristic from a plurality of radiation apertures can be obtained, the change in the height of the transmission line may be changed within the range of the radiation apertures, or in a region where the plurality of radiation apertures 120h are arranged. A wide configuration may be used. Further, the transmission line height changing portion may be changed not only in a tapered shape but also in a curved shape as long as reflection on the wall surface of the transmission line can be prevented.

  Furthermore, in the present embodiment, the shape of the radiation opening 120h of the microwave radiating unit 120 that radiates circularly polarized waves has been described with reference to the shape shown in FIG. 4, but the shape is not limited to FIG. The shape of the radiation aperture is not limited as long as the desired radiation characteristics can be obtained by radiating the light, and the present invention is not limited to the arrangement of the radiation aperture in the present embodiment.

  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.

DESCRIPTION OF SYMBOLS 10 Object to be heated 50 Microwave generation means 100 Rectangular waveguide 110 Input part 120 Microwave radiation part 120h Radiation opening 200 Heating chamber

Claims (6)

A heating chamber for storing an object to be heated;
Microwave generation means for generating a microwave to be supplied to the heating chamber;
An input unit connected to the microwave generation unit to transmit the microwave generated by the microwave generation unit to the heating chamber, and a microwave radiation unit provided with a plurality of radiation openings connected to the heating chamber. A rectangular waveguide,
In the microwave radiating portion of the rectangular waveguide, a plurality of the radiation openings are arranged at least in the transmission direction, and the microwave transmission path has regions having different heights in the transmission direction. A changing portion is provided between regions having different heights in the transmission direction of the microwave transmission path in the microwave radiating portion, and the changing portion is inclined in the transmission direction so as to connect regions having different heights without a step. The microwave heating apparatus according to claim 1, wherein the microwave heating apparatus is configured by a flat surface or a curved surface. 3. The microwave heating apparatus according to claim 1, wherein a height of a microwave transmission path in the microwave radiating unit is configured to decrease stepwise as the distance from the input unit increases. The height of the microwave transmission path in the microwave radiating unit is set to be lower in the region of the radiation opening provided on the side farther from the input unit than the region of the radiation opening provided on the side closer to the input unit. Item 4. The microwave heating apparatus according to Item 3. 5. The microwave heating apparatus according to claim 1, wherein surfaces of the microwave radiating unit connected to the heating chamber are configured in the same plane. 6. The microwave heating apparatus according to claim 1, wherein the plurality of radiation openings connected to the heating chamber in the microwave radiation section include radiation openings that radiate circularly polarized waves.