JP2013105690A - Microwave heating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To heat a heated object efficiently and uniformly by a simple structure not using a table, an antenna, a rotating mechanism of a phase shifter, or the like.SOLUTION: A waveguide 106 is provided with an annular part 106c configuring an annular microwave transmission line, and a microwave radiation part 108 having a plurality of openings for supplying microwaves, being transmitted to the annular part 106c, into a heating chamber 103. A heated object 102 can be heated uniformly without using a rotating mechanism by radiating microwaves having a changing radiation amount, being transmitted to the microwave radiation part 108 in the state of a traveling wave 301 with low standing wave, into the heating chamber 103 from the openings scattered to a plurality of positions.

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 radiation portion.

  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 in the microwave supply 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 supply 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 from the microwave supply means is changed by a phase shifter has been common.

  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 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 non-uniform heating. Therefore, it is necessary to secure a rotation space and an installation space such as a motor for rotating the table or antenna. That was hindering the miniaturization of the range. 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 table or a phaser rotation mechanism in the microwave irradiation chamber of the microwave heating apparatus lowers the reliability. Therefore, there is a demand for a microwave heating apparatus that does not require these mechanisms.

  Further, circularly polarized light is radiated into the heating chamber 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. The microwave heating apparatus having a single microwave radiating portion has an advantage that it does not have a rotating mechanism, but the problem is that sufficient uniform heating by microwave heating has not been realized.

  The present invention solves the above-described problems, and an object thereof is to provide a microwave heating apparatus capable of uniformly heating an object to be heated without using a rotating mechanism.

  In order to solve the above-described conventional problems, the microwave heating apparatus of the present invention generates a heating chamber for storing an object to be heated, a mounting portion for mounting the object to be heated, and a microwave supplied to the heating chamber. A microwave generating means, a waveguide for transmitting the microwave generated by the microwave generating means to the heating chamber, a waveguide having a start end connecting the microwave generating means, and an annular microwave transmission Consists of an annular part constituting the path and a branch part joined to the starting end part in the annular part, and the annular part is provided with a microwave radiation part in which a plurality of openings for supplying the transmitted microwave to the heating chamber are arranged It is. In other words, the waveguide for transmitting the microwave generated by the microwave generation means to the heating chamber prevents the reflected wave generated at the end of the conventional waveguide by configuring the microwave transmission path in an annular shape. By doing so, the microwave generated by the microwave generating means becomes a stable traveling wave with little interference, and can be supplied from the microwave radiating portion into the heating chamber to effectively heat the object to be heated.

  Furthermore, since microwaves with varying radiation amounts can be emitted from openings dispersed in a plurality of locations facing the object to be heated, microwaves can be radiated without bias to the entire object to be heated. A microwave heating apparatus that can uniformly heat an object to be heated without using a rotating mechanism can be provided.

According to the present invention, the waveguide for transmitting the microwave generated by the microwave generating means to the heating chamber is formed at the end portion in the conventional waveguide by configuring the microwave transmission path in an annular shape. The reflected wave can be prevented, and the microwave generated by the microwave generation means is transmitted as a stable traveling wave with little interference, and is supplied from the microwave radiating section into the heating chamber to effectively heat the object to be heated. be able to. In other words, since the conventional general waveguide has a terminal end, the traveling wave supplied from the microwave generating means interferes with the reflected wave from the terminal end and stays at the microwave radiating unit. However, according to the configuration of the present invention, the microwave radiation unit passes through the microwave radiation part. Since the microwaves are traveling waves whose phase and amplitude change, microwaves whose radiation amount changes are radiated from openings dispersed in multiple locations, and the object to be heated is evenly distributed without using a rotating mechanism. A microwave heating apparatus capable of performing microwave heating can be provided.

Schematic diagram of essential parts of the microwave heating apparatus according to Embodiment 1 of the present invention. The top view which shows the structure of the waveguide of the microwave heating apparatus in Embodiment 1 of this invention The principal part side view and principal part top view which show the microwave radiation | emission part of the microwave heating apparatus in Embodiment 1 of this invention The principal part schematic diagram and the partial cross section figure of the microwave heating apparatus which were the structure which the microwave radiation | emission part in Embodiment 2 of this invention radiates | emits circularly polarized wave The principal part schematic diagram of the microwave heating apparatus which comprised the circulator in the branch part of the waveguide in Embodiment 3 of this invention, and its partial sectional view Explanatory drawing of the length of the transmission line of the waveguide of the microwave heating device in Embodiment 4 of this invention Schematic view of a main part of a microwave heating apparatus in which a matching portion is provided in a waveguide according to a fifth embodiment of the present invention, and a partial cross-sectional view thereof The perspective view of the waveguide which is another Example in Embodiment 1-5 of this invention, and has a bending part and comprised three-dimensionally The perspective view of the microwave heating apparatus which is another Example in Embodiment 1-5 of this invention, and connected the waveguide which has the bending part and was comprised three-dimensionally.

  1st invention is the heating chamber which accommodates to-be-heated material, the mounting part which mounts the said to-be-heated material, the microwave generation means to generate | occur | produce the microwave supplied to the said heating chamber, and the said microwave generation A waveguide for transmitting the microwave generated by the means to the heating chamber, the waveguide includes a start end for connecting the microwave generating means, and an annular portion constituting an annular microwave transmission path; Microwave heating comprising a branching portion joined to the start end portion in the annular portion, wherein the annular portion is provided with a microwave radiating portion in which a plurality of openings for supplying transmitted microwaves to the heating chamber are arranged. Device. The present invention prevents the generation of the reflected wave in the waveguide, so that the microwave generated by the microwave generating means is transmitted as a stable traveling wave with less interference, and the object to be heated can be effectively heated. it can. Furthermore, by using a microwave heating apparatus in which a plurality of the microwave radiation portions are arranged, microwaves can be dispersed and radiated over a wide range of the object to be heated in the heating chamber, so a rotating mechanism is used. A microwave heating apparatus that can uniformly heat an object to be heated without microwave can be provided.

  According to a second aspect of the invention, in particular, the microwave radiating portion of the first aspect of the invention has an opening shape that communicates from the waveguide into the heating chamber and radiates circularly polarized waves. The microwaves that are supplied from the microwave radiating unit to the heating chamber by the traveling wave transmitted from the radiated wave form a circularly polarized wave whose electric field direction changes with time, and thus is heated without using a rotating mechanism. It is possible to provide a microwave heating apparatus that can uniformly heat the substrate.

According to a third aspect of the invention, in particular, the branching portion of the waveguide according to the first or second aspect of the invention comprises a circulator (irreversible branching means) for regulating the branching direction of the microwave to be transmitted. The microwave generated by the microwave generation means is transmitted in a stable state with little interference, and is supplied to the heating chamber from the microwave radiating unit to effectively heat the object to be heated. A microwave heating apparatus that can uniformly heat an object to be heated without microwave can be provided.

  In the fourth invention, in particular, the effective length of the microwave transmission path of the annular portion in the waveguide of any one of the first to third inventions is the wavelength of the microwave in the waveguide to be transmitted. By making the integer multiple, the microwave generated by the microwave generating means by matching the phase at the branching portion is transmitted in a stable state with little interference, and is supplied from the microwave radiating portion to the heating chamber to be heated. Therefore, it is possible to provide a microwave heating apparatus capable of uniformly heating an object to be heated without using a rotating mechanism.

  In the fifth invention, in particular, the waveguide according to any one of the first to fourth inventions includes a plurality of impedance adjustment matching portions sandwiching both sides of the microwave radiation portion provided in the annular portion. By providing the above, it is possible to suitably adjust the alignment from the microwave generating means to the waveguide, the microwave radiating portion, and the heating chamber for storing the object to be heated. A microwave heating apparatus capable of uniformly heating a heated object with a microwave 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 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)
FIG. 1 is a schematic diagram of a main part of a microwave heating apparatus according to Embodiment 1 of the present invention. In FIG. 1, 102 is an object to be heated, 103 is a heating chamber, 104 is a placement section, 105 is a microwave generation means, 106 is a waveguide, and 108 is a microwave radiation section. A glass plate is used for the mounting portion 104, a magnetron is used for the microwave generation means 105, a rectangular waveguide is used for the waveguide 106, and an opening provided in the waveguide 106 is used for the microwave radiating portion 108. This configuration can be easily realized.

  FIG. 2 shows the configuration of the waveguide 106 with the heating chamber 103 of the microwave heating apparatus according to the first embodiment removed, from the direction of arrow A in FIG. 1 (that is, the surface on which the microwave radiating portion 108 is provided). FIG. In FIG. 2, 106 a is a start end portion for connecting the microwave generation means 105 in the waveguide 106, 106 b is an annular portion constituting an annular microwave transmission path in the waveguide 106, and 106 c is a waveguide 106. It is a branching part joined to the starting end part in the annular part.

  FIG. 3A is a side view of the main part of the waveguide 106, and FIG. 3B is a plan view of the main part of the microwave radiation part on the upper surface of the waveguide. Here, the microwave radiating portion 108 is described as an opening provided in the upper portion of the waveguide 106, and the microwave existing in the waveguide 106 is emitted to the heating chamber 103.

  Hereinafter, the operation of the microwave heating apparatus will be described. When the object to be heated 102 is placed on the mounting portion 104 in the heating chamber 103 and a heating start instruction is given by the user, the microwave heating apparatus moves from the magnetron, which is the microwave generation means 105, into the waveguide 106. To supply microwaves. Here, since the waveguide 106 is provided with the annular portion 106b constituting the annular microwave transmission path, it is possible to prevent the generation of the reflected wave generated at the end portion of the waveguide.

  With this configuration, the microwave is transmitted into the waveguide 106 in a state where the microwave radiating unit 108 is connected to the heating chamber 103, so that the microwave passing through the waveguide 106 can be converted into a micro wave as shown in FIG. It can be a traveling wave 301 traveling in the wave transmission direction 302. When the traveling wave 301 is transmitted through the waveguide 106, the traveling wave 301 travels while changing the amplitude in the microwave radiating unit 108 as indicated by a dotted line in FIG.

  Therefore, the microwave radiated from the microwave radiating unit 108 to the heating chamber 103 and heating the object to be heated 102 is radiated to the heating chamber while changing the amount of radiation according to the change in the amplitude (phase) of the traveling wave 301 serving as the radiation source. Will be.

  As described above, in the present embodiment, the waveguide 106 is provided with the annular portion 106b that constitutes the annular microwave transmission path, so that the reflected wave generated due to the presence of the termination in the conventional general waveguide is provided. Therefore, the microwave generated by the microwave generation means 105 becomes a stable traveling wave with little interference, and is supplied from the microwave radiating unit 108 into the heating chamber 103 to effectively heat the object to be heated 102. be able to. Further, by configuring the microwave radiating portion 108 to have a plurality of openings, it is possible to disperse and radiate microwaves over a wide range of the object to be heated 102 in the heating chamber 103. According to this configuration, since the traveling wave 301 whose amplitude changes passes through the microwave radiating unit 108, the rotating mechanism is radiated from the openings in which the microwaves whose amount of radiation changes is dispersed at a plurality of locations. It is possible to provide a microwave heating apparatus that can uniformly heat an object to be heated without using a microwave.

  In the present embodiment, the plurality of microwave radiating portions 108 have an opening area set in accordance with the radiation amount of each opening. Specifically, the opening area on the side close to the microwave generating means 105 is reduced in accordance with the microwave transmission direction 302, and the opening on the far side is increased so that the amount of microwave radiation from each opening becomes substantially the same. doing. Further, the arrangement of the openings includes an arrangement of intervals that do not coincide with the in-tube wavelength of the microwave transmitted through the waveguide 106, so that the amount of microwave radiation from each opening can be alternately changed, and the heating chamber 103 Since the electromagnetic field intensity distribution of the microwave changes every moment, the heating of the article to be heated 102 can be more reliably made uniform. In the present embodiment, the shape of the opening of the microwave radiating portion 108 has been described with reference to the shape of FIG. 3, but the shape is not limited to this shape.

(Embodiment 2)
FIG. 4 is an explanatory view of the arrangement of the microwave radiating unit 108 having a shape for radiating circularly polarized waves in the second embodiment of the present invention. Fig.4 (a) is BB sectional drawing in FIG.4 (b) which is principal part sectional drawing of a microwave heating apparatus. The operation and action will be described below. 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).

In the present embodiment, the microwave radiating portion 108 is shaped to radiate circularly polarized waves as shown in FIG. 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, and when the circular polarization is formed, the direction of the electric field continues to change with time. The radiation angle of the microwaves radiated inside is also characterized by continuing 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. In addition,
Although circularly polarized waves are classified into two types, that is, right-handed polarization (CW: clockwise) and left-handed polarization (CCW: counterclockwise) from the rotation direction, there is no difference in heating performance.

  By utilizing the above feature and radiating circularly polarized microwaves through the microwave radiating unit 108, the heating distribution in the heating chamber 103 can be made more uniform. As shown in FIG. 4A, the opening shape for outputting the circularly polarized wave from the microwave radiating portion 108 provided in the waveguide 106 is a combination of the linearly polarized waves according to the electromagnetic field theory. Two slots (apertures) having a width so as to be polarized are crossed at the center and inclined at 45 degrees with respect to the microwave transmission direction, and the tube axis 401 of the waveguide 106 in the microwave transmission direction is It is placed in a position that does not pass.

  As described above, in the present embodiment, the microwave radiating unit 108 is configured to radiate circularly polarized waves, so that microwaves that have spread from the microwave radiating unit 108 are radiated into the heating chamber 103. Thus, the microwave radiation to the object to be heated 102 can be made uniform over a wider range. The microwave radiating section 108 includes five openings in the transmission path on the upper side of the paper surface in FIG. 4A of the annular portion 106b of the waveguide 106, and five openings in the transmission path on the lower side of the paper surface facing the microwave path 108b. And is arranged so as to be substantially symmetric with respect to the center of the heating chamber 103. More effectively, the micro-waves are effectively placed in the heating chamber by arranging them at an opening pitch based on the wavelength of the microwave in the waveguide so that the swirling direction of the circularly polarized wave from the adjacent opening is reversed left and right. Waves can be dispersed and emitted. In the present embodiment, the shape of the microwave radiating unit 108 that radiates circularly polarized waves has been described with reference to the shape shown in FIG. 4, but the shape is not limited to that shown in FIG. Anything is fine. Also, the present invention is not limited to the arrangement of the openings in this embodiment.

(Embodiment 3)
FIG. 5 is a schematic diagram of a main part of the microwave heating apparatus according to Embodiment 3 of the present invention. 4 is different from FIG. 4 of the second embodiment in that the branching portion 106c of the waveguide 106 constitutes a circulator (non-reciprocal branching means) 800 for regulating the branching direction of the microwave to be transmitted. The operation will be described. In addition, in the drawing, the same number is given to the part which shows the same operation as (Embodiments 1 and 2). The basic operation in (Embodiment 3) is the same as that in (Embodiment 2).

  In this embodiment, 800a is a cylindrical ferrite fixed to the central inner wall of the branching portion 106c of the waveguide 106, and 800b is arranged without contacting the outer walls on both sides of the central portion of the branching portion 106c of the waveguide 106. A pair of permanent magnets, one side S-type magnet and the other is an N-type magnet, and are provided to face each other so as to sandwich the ferrite 800a. As a result, the branching portion 106c of the waveguide 106 constitutes a transmission path of a three-branch type waveguide circulator where the annular portion 106b and the starting end portion 106a are joined, and therefore the action of the ferrite 800a magnetized by the permanent magnet 800b. The microwave transmitted through the waveguide 106 has its transmission direction defined by the branching portion 106c by electromagnetic induction (Faraday rotation) action. In the present embodiment, circulator 800 is configured such that the microwave branches rightward in FIG. That is, the microwave transmitted from the microwave generation means 105 goes straight through the branching portion 106c in FIG. 5A and is radiated sequentially into the heating chamber 103 while passing through the microwave radiating portion 108 toward the left side in the drawing. . Microwaves that circulate around the annular portion 106 b of the waveguide 106 and are not consumed in some of the heating chambers 103 are transmitted to the right in the branching portion 106 c and transmitted to the microwave generation means 105.

As described above, according to the present embodiment, the microwave transmission direction is reliably defined by the circulator 800 in addition to preventing the reflected wave generated at the end portion of the waveguide conventionally. The microwave generated in 105 becomes a stable traveling wave with less interference more effectively, and is supplied from the microwave radiating portion 108 into the heating chamber 103 to effectively heat the object to be heated 102.

(Embodiment 4)
FIG. 6 shows the configuration of the waveguide 106 with the heating chamber 103 removed, similarly to FIG. 2 of the microwave heating apparatus according to the fourth embodiment of the present invention.

  In FIG. 6, the effective length of the microwave transmission path of the annular portion 106b is approximately an integral multiple of the wavelength λg of the microwave to be transmitted in the waveguide. Specifically, in the present embodiment, the circumferential length of the tube axis 401 corresponding to the effective length of the microwave transmission path in the annular portion 106b is set to 615 mm, which is substantially four times the wavelength λg.

  As a result, the microwaves generated by the microwave generating means are transmitted in a stable state with little interference by combining the phases at the branching portions of the microwaves, and the microwaves are supplied from the microwave radiating unit to the heating chamber to be heated. Can be effectively heated.

(Embodiment 5)
FIG. 7 is a layout explanatory diagram of the microwave radiation unit 108 according to the fifth embodiment of the present invention. Fig.7 (a) is BB sectional drawing in FIG.7 (b) which is principal part sectional drawing of a microwave heating apparatus. In addition, in the drawing, the same number is given to the part which shows the same operation as (Embodiments 1 to 4). The basic operation in (Embodiment 5) is the same as that in (Embodiment 2). (Embodiment 5) is different from the other embodiments in that the waveguide is provided with two impedance adjustment matching portions so as to sandwich both front and rear sides of the microwave radiating portion provided in the annular portion. Is a point.

  With the above configuration, impedance matching can be adjusted from the microwave generating means 105 to the waveguide 106 and the heating chamber 103 in which the object to be heated 102 is accommodated. That is, the impedance matching accuracy of the annular transmission line can be made suitable, and the object to be heated can be efficiently heated while suppressing reflection to the microwave generation means 105.

  In the above-described (Embodiments 1 to 5), the shape of the waveguide 106 is simply (schematic) configured in a plane, but the shape of the waveguide 106 is the same as that of the heating chamber 103. A compact microwave heating apparatus can be provided by configuring three-dimensionally along the shape.

  In FIG. 8, reference numeral 106 is a perspective view showing an example of a three-dimensionally configured waveguide, in which both sides of the microwave radiating portion facing the bottom surface of the heating chamber are bent along the side wall of the heating chamber. .

  FIG. 9 is a perspective view showing a state in which the waveguide 106 shown in FIG. 8 is connected to the heating chamber 103, and 103d is a heating chamber door for taking in and out the object to be heated. The waveguide 106 constitutes a permanent magnet 800b of the circulator.

  As described above, the microwave heating apparatus of the present invention can uniformly irradiate an object to be heated, and further eliminates the need to provide a special movable part for supplying microwaves, so that it has high reliability and durability. Is also excellent. It can be effectively used in a microwave heating apparatus that performs heating processing and sterilization of food.

DESCRIPTION OF SYMBOLS 102 Object to be heated 103 Heating chamber 104 Placement part 105 Microwave generation means 106 Waveguide 108 Microwave radiation part 301 Traveling wave 302 Microwave transmission direction 401 Tube axis

Claims (5)

A heating chamber for storing an object to be heated;
A placement section for placing the 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, and the waveguide constitutes an annular microwave transmission path, with a start end connecting the microwave generating means And a microwave radiating portion in which a plurality of openings for supplying microwaves to be transmitted to the heating chamber are arranged in the annular portion. Microwave heating device. The microwave heating device according to claim 1, wherein the microwave radiating unit has an opening shape that communicates from the waveguide into the heating chamber to radiate circularly polarized waves. The microwave heating device according to claim 1 or 2, wherein the branching portion of the waveguide constitutes a circulator (irreversible branching means) for regulating a branching direction of a microwave to be transmitted. 4. The effective length of the microwave transmission path of the annular portion in the waveguide is substantially an integral multiple of the wavelength of the microwave to be transmitted in the waveguide. 5. Microwave heating device. 5. The micro according to claim 1, wherein the waveguide is provided with a plurality of matching portions for impedance adjustment so as to sandwich both front and rear sides of the microwave radiating portion provided in the annular portion. Wave heating device.

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