JP5877304B2 - Microwave heating device - Google Patents

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

  As a means for uniformly heating the object to be heated, a structure for rotating the object to be heated by rotating a table on which the object to be heated is 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 a phase of a microwave generated from a microwave generator 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 cooling air from the blower fan is applied to the blades of the rotary antenna so that the antenna is rotated by the wind force of the blower fan. A microwave heating apparatus that changes the microwave distribution in the heating chamber has been proposed.

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

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 heating devices are notable for heating food by heat conduction, but the convenience of being able to heat food directly using dielectric heating is a major feature of the product. Will make the subject of heating unevenness more obvious.

  The following three 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 heating unevenness. For this reason, it is necessary to secure a rotation space and an installation space such as a motor for rotating the table or antenna. It was that the miniaturization of the heating device was hindered.

  Secondly, in order to stably rotate the table or antenna, it is necessary to provide the rotating antenna at the upper or lower portion of the heating chamber, and the structure is limited.

  Third, with the advent of microwave ovens with various heating functions such as steam heating and hot air heating, many components are required inside the microwave oven casing, and control components inside the casing, etc. Because of the large amount of heat generation, it is necessary to secure an air path to achieve sufficient cooling performance, and the installation position of the waveguide means and the microwave radiation part is limited, so the microwave distribution in the heating chamber is non-uniform It becomes that.

  Installing a rotating mechanism of a table or a phaser in an applicator that is a microwave irradiation chamber in a microwave heating device lowers reliability. Therefore, there is a demand for a microwave heating apparatus that does not require these mechanisms.

  In addition, while reducing the heating unevenness of the object to be heated by microwave heating, as well as reducing the cost and saving the space of the power feeding unit, a single unit that radiates circularly polarized waves into the heating chamber is disclosed. The microwave heating apparatus having one microwave radiating portion has an advantage that it does not have a rotating mechanism, but it is a problem that sufficient uniform heating by microwaves is not realized.

  The present invention solves the above-described conventional problems, and an object of the present invention is to provide a microwave heating apparatus that can uniformly heat an object to be heated without using a rotating mechanism. In addition, even if the installation position is limited by the components inside the housing and the waveguide means is installed asymmetrically with respect to the center of the inner wall of the heating chamber, the microwave can uniformly heat the object to be heated. An object is to provide a wave heating device.

In order to solve the above-described conventional problems, the microwave heating apparatus of the present invention includes a heating chamber for storing an object to be heated, a microwave generating means for generating microwaves, a waveguide means for transmitting microwaves, The heating chamber has a microwave radiating portion for radiating microwaves, and the waveguide means is installed asymmetrically with respect to the center of the inner wall of the heating chamber, and the waveguide where the microwave radiating portion is located. The directivity of the microwave radiated into the heating chamber is adjusted by the phase of the microwave in the wave means so as to become stronger in parallel with the direction in which the waveguide means is biased .

  As a result, there are many control factors that change the microwave distribution in the heating chamber, the installation position is limited by the components inside the housing, and the waveguide means is installed asymmetrically with respect to the center of the inner wall of the heating chamber However, uniform microwave heating can be easily realized.

  Furthermore, it has several microwave radiation | emission parts. Since the microwave radiated from one microwave radiating part has a microwave radiating angle, there is a limit to the range that can be heated strongly by a single microwave radiating part.

  Therefore, by adjusting the number of the microwave radiation portions, it is possible to adjust the microwave distribution in a wide range of the heating chamber and realize more uniform heating.

  In addition, by adjusting the phase of the microwave in the waveguide means where each microwave radiating portion is located, a single microwave can be obtained by utilizing the mutual interference of the microwaves radiated from each microwave radiating portion. It is possible to obtain a microwave distribution that cannot be achieved by the wave radiation unit, and to achieve uniform heating.

  In addition, it has a microwave radiating part that radiates circularly polarized waves. Thereby, a microwave having a spread is emitted from the microwave radiating portion, and the microwave radiation to the object to be heated can be made uniform in a wider range. In particular, uniform heating in the circumferential direction of circular polarization can be expected.

  Moreover, the microwave radiation | emission part which radiates | emits a circularly polarized wave is made into the shape comprised by two or more slits. This eliminates the need for a mechanism for rotating the table or antenna for reducing the unevenness of heating of the object to be heated, thereby improving reliability and reducing the size of the power feeding unit.

  The microwave heating apparatus of the present invention adjusts the number and shape of the microwave radiating portions that radiate circularly polarized waves installed in the heating chamber, and the arrangement with respect to the phase of the microwaves in the waveguide means, thereby adjusting the inside of the casing. Even when the installation position is limited by the components and the waveguide means is installed asymmetrically with respect to the center of the inner wall of the heating chamber, uniform microwave heating of the object to be heated can be realized. In addition, by forming the microwave radiating portion into a shape that radiates circularly polarized waves composed of two or more slits, the antenna can be rotated without providing a mechanism for rotating the antenna, a mechanism for rotating the table, a phase shifter, or the like. The heated object can be uniformly heated by microwaves, and the power feeding unit can be reduced in size, improved in reliability, and reduced in cost.

Sectional drawing of the microwave heating apparatus in Embodiment 1 of this invention (A) Top view of microwave radiation unit and object to be heated in microwave heating apparatus in embodiment 1 of the present invention (b) Microwave radiation section and standing of microwave heating apparatus in embodiment 1 of the present invention Wave relationship diagram Explanatory drawing of the relationship between the electric field of the waveguide means of the microwave heating apparatus in Embodiment 1 of this invention, a magnetic field, and an electric current FIG. 3 is an explanatory diagram of the relationship between the phase of the standing wave generated in the waveguide means of the microwave heating apparatus and the directivity according to the first embodiment of the present invention. (A) Top view of microwave radiating portion and microwave heating weak region of microwave heating apparatus in embodiment 1 of the present invention (b) Relationship between microwave radiating portion and standing wave in embodiment 1 of the present invention Illustration (A) Top view of microwave radiation part and object to be heated in microwave heating apparatus in embodiment 2 of the present invention (b) Microwave radiation part and standing of microwave heating apparatus in embodiment 2 of the present invention Wave relationship diagram The top view of the microwave radiation | emission part and microwave heating weak area | region of the microwave heating apparatus in Embodiment 2 of this invention, and the relationship explanatory drawing of a microwave radiation | emission part and a standing wave The top view of the microwave radiation | emission part and to-be-heated material of the microwave heating apparatus in Embodiment 3 of this invention, and relationship explanatory drawing of a microwave radiation | emission part and a standing wave Distribution diagram of effective radiated power of microwave heating apparatus in embodiment 3 of the present invention The top view of the microwave radiation | emission part and to-be-heated material of the microwave heating apparatus in Embodiment 4 of this invention, and relationship explanatory drawing of a microwave radiation | emission part and a standing wave Distribution diagram of effective radiated power of microwave heating apparatus in embodiment 4 of the present invention The top view of the microwave radiation | emission part and to-be-heated material of the microwave heating apparatus in Embodiment 5 of this invention, and relationship explanatory drawing of a microwave radiation | emission part and a standing wave Distribution diagram of effective radiated power of microwave heating apparatus in embodiment 5 of the present invention Explanatory drawing of the shape of the microwave radiation | emission part of the microwave heating apparatus in Embodiment 5 of this invention

A first invention is a heating chamber for storing an object to be heated, a microwave generating means for generating microwaves, a waveguide means for transmitting microwaves, and a microwave radiating section for radiating microwaves into the heating chamber. The waveguide means is installed asymmetrically with respect to the center of the inner wall of the heating chamber, and the microwave chamber in the waveguide means in which the microwave radiating portion is located, The directivity of the microwaves radiated to is adjusted so as to be strong in parallel with the direction in which the waveguide means is biased .

  As a result, there are many control factors that change the microwave distribution in the heating chamber, the installation position is limited by the components inside the housing, and the waveguide means is installed asymmetrically with respect to the center of the inner wall of the heating chamber However, uniform microwave heating can be easily realized.

The second aspect of the invention is particularly a microwave radiating unit in the first aspect of the invention, in which the waveguide means is off-center in a direction perpendicular to the transmission and electric field direction with respect to the center of the inner wall of the heating chamber. By setting the phase of the microwave in the waveguide means in which the position of the microwave is located to be an approximate position, the directivity of the microwave radiated into the heating chamber is changed in the direction in which the waveguide means is biased, that is, in the transmission and electric field directions. On the other hand, the adjustment is made so as to be strong in the perpendicular direction .

  Thereby, uniform and highly efficient microwave heating can be realized by increasing the amount of microwave radiated in a direction perpendicular to the transmission and electric field directions.

In a third aspect of the invention, in particular, in the first aspect of the invention, the waveguide means is located at the center of the inner wall of the heating chamber.
On the other hand, when it is biased in the transmission direction, the directivity of the microwave radiated into the heating chamber is set by setting the phase of the microwave in the waveguide means in which the microwave radiating portion is located to the approximate position. Adjustment is made so that the waveguide means becomes stronger in the biased direction, that is, in the transmission direction .

  Thereby, uniform and highly efficient microwave heating can be realized by increasing the amount of microwave radiated in the transmission direction.

  In a fourth aspect of the invention, in particular, in any one of the first to third aspects of the invention, a plurality of the microwave radiation portions are provided.

  Thereby, if the microwave distribution in the heating chamber is adjusted, more uniform heating can be realized in a wide range.

  According to a fifth aspect of the invention, in particular, in the fourth aspect of the invention, at least two of the microwave radiating portions are respectively positioned at substantially the same phase of the microwave in the waveguide means.

  This makes it possible to achieve more uniform heating.

  In a sixth aspect of the invention, in particular, in the fourth aspect of the invention, at least two of the microwave radiating portions are respectively located at different phases of the microwave in the waveguide means.

  This makes it possible to achieve more uniform heating.

In a seventh aspect of the invention, in particular, in any one of the first to sixth aspects of the invention, the microwave radiating portion is shaped to radiate circularly polarized waves.
This makes it possible to achieve more uniform heating.

In an eighth aspect based on the seventh aspect, the microwave radiating section is configured to radiate circularly polarized waves by arranging two slits at the center of each to be arranged in the same phase. There is .
This makes it possible to alleviate standing waves in the heating chamber caused by interference between the direct wave and the reflected wave, which has been a problem in microwave heating by a conventional microwave heating apparatus using linearly polarized waves. Uniform microwave heating can be realized .

  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 cross-sectional view of the microwave heating apparatus according to Embodiment 1 of the present invention. 2A is a top view of the microwave radiating unit and the object to be heated in the microwave heating apparatus according to the first embodiment of the present invention, and FIG. 2B is a micro view of the microwave heating apparatus in the first embodiment of the present invention. It is a relation explanatory drawing of a wave radiation part and a standing wave.

  That is, the positional relationship among the heating chamber 101, the waveguide unit 103, the microwave radiating unit 104, and the object to be heated 105 and the relationship between the microwave radiating unit 104 and the standing wave 206 generated in the waveguide unit 103 are described. FIG.

  FIG. 3 is an explanatory diagram of the relationship between the electric field, magnetic field, and current of the waveguide means of the microwave heating apparatus according to Embodiment 1 of the present invention, and the relationship between the electric field 301, magnetic field 302, and current 303 generated in the waveguide means 103. It is a figure for demonstrating.

  FIG. 4 is a diagram for explaining that the directivity of the radiated microwave changes according to the phase of the microwave in the waveguide means 103 where the microwave radiating unit 104 is located. Obtained by field analysis. FIG. 5A is a top view of the microwave radiating portion and the microwave heating weak region of the microwave heating apparatus in the first embodiment of the present invention. FIG. 5B is a top view of the microwave radiating portion in the first embodiment of the present invention. It is a related explanatory view of standing waves.

  That is, the positional relationship among the heating chamber 101, the waveguide unit 103, the microwave radiating unit 104, and the microwave heating weak region 501 and the relationship between the microwave radiating unit 104 and the standing wave 206 generated in the waveguide unit 103 will be described. FIG.

  As shown in FIG. 1, a microwave oven that is a microwave heating apparatus of the present embodiment is supplied from a heating chamber 101 that stores an object to be heated 105, a microwave generation unit 102, and a microwave generation unit 102. Waveguide means 103 for transmitting microwaves to the heating chamber 101 and a microwave radiating section 104 for radiating microwaves into the heating chamber 101 are provided.

  This configuration can be easily realized by using a magnetron for the microwave generation means 102, a rectangular waveguide for the waveguide means 103, and an opening provided in the waveguide means 103 for the microwave radiation section 104.

  As shown in FIG. 2, the heating chamber 101 has a plurality of microwave radiating portions 104 that radiate microwaves. Further, the description will be made assuming that the central axis 203 in the transmission direction of the waveguide means is in a positional relationship that does not pass through the center 201 of the inner wall of the heating chamber in which the waveguide means 103 is installed.

  In the present invention, a configuration in which the central axis 203 in the transmission direction of the waveguide means is in a positional relationship that does not pass through the center 201 of the inner wall of the heating chamber in which the waveguide means 103 is installed is called off-center.

  About the microwave heating apparatus comprised as mentioned above, the operation | movement and an effect | action are demonstrated below.

  First, the general operation of the microwave heating apparatus will be described. When the object to be heated 105 is placed in the heating chamber 101 by the user and an instruction to start heating is given, the microwave heating apparatus supplies the microwave from the magnetron, which is the microwave generating means 102, into the waveguide means 103. The microwave heating apparatus heats the object to be heated 105 by radiating microwaves into the heating chamber 101 through the microwave radiating portion 104 connecting the heating chamber 101 and the waveguide means 103.

  Next, the non-uniformity of the microwave distribution in the heating chamber 101 due to the inner wall shape 502 of the heating chamber 101 will be described.

  The inner wall shape 502 in the heating chamber 101 is often asymmetric, and a large number of parts having different dielectric constants are attached. As specific examples, there are mainly the following three points. The first point is that a door 106 and a door glass 107 for taking out the object 105 to be heated are attached. The second point is that a heater 108 is attached to the upper surface or the bottom surface to radiately heat the article 105 to be heated. The third point is that the inner wall shape 502 is complicated because the heater 108 and the convection fan 109 are attached to the back side of the back surface in order to convectively heat the article 105 to be heated.

  As described above, when the inner wall shape 502 of the heating chamber 101 is asymmetrical or a component having a different dielectric constant is attached, heating by the reflected wave that reflects the inner wall of the heating chamber 101 and heats the object to be heated 105 is uneven. It becomes.

Note that in the present invention, microwaves radiated from the microwave radiating unit 104 and directly heating an object to be heated are called direct waves, and microwaves reflected by the inner wall of the heating chamber 101 are called reflected waves.

  Next, the non-uniformity of the microwave distribution in the heating chamber 101 due to the positional relationship between the waveguide means 103 and the heating chamber 101 will be described.

  In recent years, microwave heating apparatuses having not only a microwave heating function but also other heating methods (water vapor heating, radiation heating, hot air heating, etc.) have appeared. For this reason, in order to ensure the performance of other heating functions, it is often off-center.

  For this reason, it is difficult to obtain a uniform microwave distribution in the heating chamber 101 even if the microwave radiating section 104 is arranged with the central axis 203 in the transmission direction of the waveguide means as the axis of symmetry.

  As specific examples, there are mainly the following two points. The first point is a case of having a water vapor heating function, and in order to realize the water vapor heating function, a water tank 110, a pump 111, a heater 108, a spout 112 for jetting water vapor into the heating chamber 101, and the like inside and outside the heating chamber 101 It is necessary to install in.

The second point is a case where a radiation heating function is provided, and it is necessary to install the heater 108 on the upper surface or the bottom surface.

  Further, the amount of heat generated from the inverter, magnetron, control board, etc. installed in the casing of the microwave heating device is large, and there are parts that cannot operate normally or are burnt out unless they are sufficiently cooled. Therefore, in order to ensure sufficient cooling performance, the installation position of the cooling air passage 113 is prioritized and is often off-center.

  From the above, it is difficult to uniformly heat the object 105 to be heated unless the microwave radiated from the microwave radiating unit 104 has directivity.

  Conventionally, the microwave radiating unit 104 is arranged so that the central axis 203 in the transmission direction of the single or waveguide means is a symmetric axis. Therefore, when the waveguide means 103 is off-center, the inside of the heating chamber 101 The microwave distribution was asymmetric with respect to the center 201 of the inner wall of the heating chamber, and the object to be heated 105 could not be heated uniformly.

  Next, a configuration for adjusting the directivity of the microwave radiated from the microwave radiating unit 104 will be described.

  As shown in FIG. 2B, when a rectangular waveguide is used as the waveguide means 103, the traveling wave generated from the microwave generation means 102 and the reflected wave reflected at the end 202 of the waveguide are mutually connected. Interfering creates a standing wave 206 in the waveguide. The directivity of the microwave radiating unit 104 varies depending on the phase of the standing wave 206 where the microwave radiating unit 104 is located. The principle of changing directivity will be described below.

  The relationship among the electric field 301, magnetic field 302, and current 303 in the standing wave 206 will be described with reference to FIG. In the traveling wave, the directions of the electric field 301 and the magnetic field 302 are shifted by 90 °, and the phase is the same. On the other hand, in the standing wave 206, the directions of the electric field 301 and the magnetic field 302 are shifted by 90 °, and the phase is shifted by π / 2. Therefore, the relationship between the electric field 301 and the magnetic field 302 in the rectangular waveguide in which the standing wave 206 is generated is as shown in FIG. In the case of the standing wave 206, this is mainly due to the fact that the phase of the electric field 301 is shifted by 180 ° when the traveling wave is reflected at the end 202 of the waveguide. The current 303 flows on the surface of the waveguide means 103 in a direction perpendicular to the magnetic field 302.

  The principle of microwave directivity when the microwave radiating unit 104 is installed on a plane perpendicular to the electric field direction 207 in the rectangular waveguide where the standing wave 206 is generated will be described.

  As shown in FIG. 3, consider a case where the microwave radiating portion 104 is placed at the approximate antinode position 208 and the approximate node position 209 for the standing wave 206 in the waveguide. When considering the transmission direction 205 component of the current 303 in the microwave radiating unit 104 and the direction 204 component perpendicular to the transmission and electric field direction, the current 303 in the microwave radiating unit 104 placed at the approximate abdominal position includes the transmission and electric field. There are many 204 components perpendicular to the direction.

  Since the direction in which the current 303 flows and the direction in which the electric field 301 spreads are the same, the radiated microwave has directivity in the direction 204 perpendicular to the transmission and electric field direction.

  In addition, the current 303 in the microwave radiation unit 104 placed at the approximate node position has many components in the transmission direction 205. For this reason, the emitted microwave has directivity in the transmission direction 205.

  Next, FIG. 4 shows the relationship between the phase of the standing wave 206 immediately below the microwave radiating unit 104 and the directivity of the emitted microwave.

  FIG. 4 is an explanatory diagram of the relationship between the phase and directivity of the standing wave generated in the waveguide means of the microwave heating apparatus according to Embodiment 1 of the present invention, and is obtained by electromagnetic field analysis. FIG. 4A is a diagram in which the phase of the standing wave in the waveguide directly under the microwave radiating portion 104 is changed by changing the distance of the microwave radiating portion 104 from the end of the waveguide, and FIG. In the case where the phase is about 0 ° (generally abdominal position), it is a diagram showing that the transmission direction 205 has microwave directivity as in the above description of the principle.

  The position of the antinode of the standing wave 206 is set to 0 °, the node position is set to 180 °, and the distribution of the microwave radiated from the microwave radiating unit 104 is electromagnetic in steps of about 45 ° from the phase of about 0 ° to about 180 °. Obtained by field analysis.

  As shown in FIG. 4A, in this analysis, the standing wave in the waveguide where the microwave radiating unit 104 is located is changed by changing the distance from the end 202 of the waveguide to the microwave radiating unit 104. The phase of 206 is changed.

  As shown in FIG. 4A, when the phase is about 0 ° (generally antinode position 208), the directivity in the direction perpendicular to the direction of transmission and electric field 204 is obtained as in the above description of the principle.

  By shifting the phase by about 45 °, the directivity of the microwave changes counterclockwise, and when the phase is about 180 ° (general node position 209), the directivity of the microwave in the transmission direction 205 Have This is also consistent with the above explanation of the principle.

  By applying the above technique, the microwave radiating unit 104 having directivity in the target direction can be installed, and the non-uniform microwave distribution in the heating chamber 101 can be improved.

  Next, analysis conditions for the analysis results shown in FIG. 4 are described below.

  In this analysis, a microwave generated from a magnetron, which is a microwave generator, is transmitted using a rectangular waveguide, and only the magnetic field 302 component exists in the transmission direction 205 of the waveguide, and there is no electric field 301 component. A case is assumed in which microwaves are transmitted in a transmission mode called a TE10 mode in an H wave (TE wave; Transverse Electric Wave) which is a transmission mode.

  Note that transmission modes other than the TE10 mode are rarely applied to the waveguide means 103 of the microwave heating apparatus. Note that the upper and lower limits of the dimension in the direction perpendicular to the transmission and electric field direction of the waveguide are determined by the frequency of the microwave and the dimension in the electric field direction 207 of the waveguide.

  The rectangular waveguide in this analysis is 30 mm in the electric field direction 207 and 100 mm in the direction 204 perpendicular to the transmission and electric field directions, and the microwave frequency used in the analysis is 2.46 GHz. .

  Further, the moving distance of the microwave radiating unit 104 necessary for changing the radiation direction by 90 ° is about a half wavelength of the standing wave 206 in the tube, and the frequency of the microwave used for the analysis is 2.46 GHz. The moving distance of the microwave radiating unit 104 necessary for changing the radiation direction by 90 ° is about 60 mm.

As shown in FIG. 2, the microwave radiating unit 104 has a configuration in which two slits are orthogonal to each other at the center of each slit and the slit is inclined by 45 ° with respect to the transmission direction 205.

  Further, the number of the microwave radiating portions 104 is one, the length of each slit is 55 mm, and the directional display data in FIG. 4B is the effective radiated power.

  The microwave distribution in the heating chamber 101 is non-uniform due to the non-uniformity of the direct wave / reflected wave due to the off-center and the non-uniformity of the reflected wave due to the inner wall shape 502 of the heating chamber 101, the door glass 107, and the like. In this case, an example of a method for improving the microwave distribution in the heating chamber 101 by adjusting the directivity of the microwave to be radiated by the phase of the microwave in the waveguide unit 103 where the microwave radiating unit 104 is located. Will be explained.

  First, consider the case where the waveguide means 103 is off-center in the direction 204 perpendicular to the transmission and electric field direction with respect to the center 201 of the inner wall of the heating chamber as shown in FIG.

  When the conventional microwave heating is used, the heating of the article 105 to be heated tends to be weakened as the distance from the microwave radiating portion 104 becomes longer. Therefore, in the to-be-heated object 105 placed at a position as shown in FIG. 2, microwave heating is weak and low-efficiency heating occurs.

  Therefore, by utilizing the relation between the phase and directivity of the microwave in the waveguide means 103 where the microwave radiating unit 104 is located, the microwave radiating unit 104 is installed at the approximate abdominal position 208, so that transmission and transmission can be performed. By increasing the amount of microwaves radiated in the direction 204 perpendicular to the electric field direction, uniform and highly efficient microwave heating can be realized.

  Further, as shown in FIG. 5, due to the non-uniformity of the reflected wave due to the influence of the inner wall shape 502 of the heating chamber 101, the door glass 107, etc., the transmission of the waveguide means 103 and Consider a case where a weak region 501 of microwave heating occurs in a direction 204 perpendicular to the electric field direction.

  Also in this case, as in the case of the off-center described above, by installing the microwave radiating unit 104 at the approximate abdominal position 208, the amount of microwaves radiated in the direction 204 perpendicular to the transmission and electric field direction is increased. Uniform and highly efficient microwave heating can be realized.

(Embodiment 2)
FIG. 6A is a top view of the microwave radiating unit and the object to be heated of the microwave heating apparatus according to the second embodiment of the present invention. FIG. 6B is a microwave diagram of the microwave heating apparatus according to the second embodiment of the present invention. It is explanatory drawing of the relationship between the microwave radiation | emission part of a heating apparatus, and a standing wave.

  That is, it is a diagram showing the positional relationship between the heating chamber 101, the waveguide means 103, the microwave radiating portion 104, and the article to be heated 105, and shows that the waveguide means 103 is off-center. FIG. 6B is a diagram showing the relationship between the position of the microwave radiating unit 104 and the phase of the standing wave 206 in the waveguide unit 103.

  FIG. 7A is a diagram showing the positional relationship among the heating chamber 101, the waveguide means 103, the microwave radiating unit 104, and the article to be heated 105 in the present embodiment. This shows that the microwave heating weak region 501 is generated due to the non-uniformity of the reflected wave by the door glass 107 or the like. FIG. 7B shows the relationship between the position of the microwave radiating unit 104 and the phase of the standing wave 206 in the waveguide unit 103.

  In the drawings, the same reference numerals are given to the portions showing the same operations as those in (Embodiment 1). Further, assuming that the basic operation in (Embodiment 2) is the same as in (Embodiment 1), the operation and action will be described below.

  6 and 7 as in the first embodiment, the non-uniformity of the direct wave / reflected wave due to off-center and the non-uniformity of the reflected wave due to the inner wall shape 502 of the heating chamber 101, the door glass 107, etc. When the microwave distribution in the heating chamber 101 is non-uniform due to the characteristics, the directivity of the microwave to be radiated by the phase of the microwave in the waveguide unit 103 where the microwave radiating unit 104 is located is described. An example of a method for improving the microwave distribution in the heating chamber 101 will be described.

  First, consider a case in which the waveguide means 103 is arranged in the transmission direction 205 with respect to the center 201 of the inner wall of the heating chamber as shown in FIG.

  When the conventional microwave heating is used, the heating of the article 105 to be heated tends to be weakened as the distance from the microwave radiating portion 104 becomes longer. Therefore, in the to-be-heated object 105 placed at a position as shown in FIG. 6, microwave heating is weak and low-efficiency heating occurs.

  Therefore, by utilizing the relationship between the phase and directivity of the microwave in the waveguide means 103 where the microwave radiating unit 104 is located, the microwave radiating unit 104 is installed at the approximate node position 209, thereby transmitting the transmission direction. By increasing the amount of microwave radiated to 205, uniform and highly efficient microwave heating can be realized.

Further, as shown in FIG. 7, due to the non-uniformity of the reflected wave due to the influence of the inner wall shape 502 of the heating chamber 101, the door glass 107, etc., the microwave heating in the direction 204 perpendicular to the transmission of the waveguide means 103 and the electric field direction is performed. Consider a case where a weak region 501 occurs.
In this case as well, as in the case of the off-center described above, by installing the microwave radiating unit 104 at the approximate node position 209, the amount of microwave radiated in the transmission direction 205 is increased, so that a uniform and highly efficient micro wave is obtained. Wave heating can be realized.

(Embodiment 3)
FIG. 8A is a diagram showing a positional relationship among the heating chamber 101, the waveguide means 103, the microwave radiating unit 104, and the article to be heated 105 in the third embodiment of the present invention. FIG. 8B is a diagram illustrating the relationship between the position of the microwave radiating unit 104 and the phase of the standing wave 206 in the waveguide unit 103.

  FIG. 9 shows the distribution of direct waves radiated from the microwave radiating unit 104 in the present embodiment by electromagnetic field analysis, and the directional display data is effective radiated power. The analysis conditions in (Embodiment 1) are the same as those in (Embodiment 1), except that the number of microwave radiation units 104 is two.

  In the drawing, the same reference numerals are given to portions showing the same operations as those in (Embodiment 1) or (Embodiment 2). Further, assuming that the basic operation in (Embodiment 3) is the same as that in (Embodiment 1) and (Embodiment 2), the operation and action will be described below.

  First, the advantage of the microwave heating apparatus having the plurality of microwave radiating units 104 will be described.

Since the microwave radiated from the single microwave radiating unit 104 has a radiation angle, there is a limit to the range in which the single microwave radiating unit 104 can be heated strongly, and the microwave radiating unit 104 is heated strongly. This often results in non-uniform microwave heating.

  In particular, in the case where the microwave radiating unit 104 is installed on the bottom surface of the heating chamber 101, the object to be heated 105 is often placed at a short distance from the microwave radiating unit 104, and the microwave is sufficiently expanded. The microwave concentration becomes remarkable.

  Therefore, by adjusting the microwave distribution in the heating chamber 101 by increasing the number of the microwave radiating units 104, more uniform heating can be realized in a wide range.

  In addition, by adjusting the phase of the microwave in the waveguide means 103 where each microwave radiating unit 104 is located, the directivity of the microwave radiated from each microwave radiating unit 104 is adjusted, By utilizing the mutual interference of the microwaves radiated from each of the microwave radiating units 104, it is possible to obtain a microwave distribution that cannot be achieved by the single microwave radiating unit 104, and to achieve uniform heating. It becomes.

  Next, as shown in FIG. 8, in the heating chamber 101 when two microwave radiating portions 104 are arranged side by side in the transmission direction 205 at the approximate abdominal position 208 in the phase of the standing wave 206 in the waveguide means 103. The reason why the distribution of the effective radiant power of the direct wave to the waveform is as shown in FIG.

  As described with reference to FIG. 4 of (Embodiment 1), a microwave having directivity in the direction 204 perpendicular to the transmission and electric field direction is transmitted from the microwave radiating unit 104 installed at the approximate abdominal position 208. Radiated.

  In the present embodiment, two microwave radiating portions 104 are installed at the approximate abdominal position 208, and each microwave radiating portion 104 has directivity in the direction 204 perpendicular to the transmission and electric field directions. Microwaves are emitted and interfere with each other in the heating chamber 101.

  The mutual interference of the microwaves at an arbitrary point is determined by the distance from each microwave radiation unit 104. When the radiated microwave has no directivity, the difference in distance from each microwave radiating unit 104 to an arbitrary point is an even multiple of half the wavelength in the microwave heating chamber 101 (including 0). ), The microwaves strengthen each other, and when odd times, they weaken each other.

  Note that in the case of a microwave frequency of 2.45 GHz used in a general microwave heating apparatus, the wavelength in the air such as in the heating chamber 101 is about 120 mm.

  However, since the microwave radiation unit 104 installed at the approximate abdominal position 208 has the above-described directivity, the two microwaves at the approximate abdominal position 208 as shown in FIG. In the positional relationship in which the radiating units 104 are arranged side by side in the transmission direction 205, the mutual interference of the microwaves does not clearly affect the direct wave distribution. As shown in FIG. The distribution of effective radiated power has directivity in the direction 204 perpendicular to the transmission and electric field directions.

  In the case of the distribution of effective radiated power as shown in FIG. 9, as shown in FIG. 8A, the object to be heated 105 is placed at the four corners where the effective radiated power is strong with the microwave radiating portion 104 as the center. , Uniform heating becomes possible.

(Embodiment 4)
FIG. 10A is a diagram showing the positional relationship among the heating chamber 101, the waveguide means 103, the microwave radiating unit 104, and the article to be heated 105 in the fourth embodiment of the present invention. FIG. 10B is a diagram illustrating the relationship between the position of the microwave radiating unit 104 and the phase of the standing wave 206 in the waveguide unit 103.

  FIG. 11 shows the distribution of direct waves radiated from the microwave radiating unit 104 according to the present embodiment by electromagnetic field analysis, and the microwave distribution is displayed as effective radiated power.

  In the drawing, the same reference numerals are given to portions showing the same operations as those in (Embodiment 1) to (Embodiment 3). Further, assuming that the basic operation and electromagnetic field analysis conditions in (Embodiment 4) are the same as those in (Embodiment 1) to (Embodiment 3), the operation and action will be described below.

  First, as shown in FIG. 10, two microwave radiating portions 104 are arranged at an approximate node position 209 in the phase of the standing wave 206 in the waveguide means 103, and perpendicular to the transmission direction 205 and the transmission and electric field directions. The reason why the distribution of the effective radiated power of the direct wave into the heating chamber 101 when installed so as to have a distance at 204 is as shown in FIG. 11 will be described.

  As described with reference to FIG. 4 of (Embodiment 1), microwaves having directivity in the transmission direction 205 are radiated from the microwave radiation unit 104 installed at the approximate node position 209.

  In the present embodiment, two microwave radiating units 104 are installed at the approximate node position 209, and microwaves having directivity in the transmission direction 205 are radiated from the respective microwave radiating units 104, and heating is performed. Interference occurs in the chamber 101.

  As described in (Embodiment 3), the mutual interference of microwaves at an arbitrary point is determined by the directivity of the microwave radiating unit 104, the distance from each microwave radiating unit 104, and the microwaves. Determined by wavelength.

  As described above, when the two microwave radiating units 104 are installed at the approximate node position 209, both microwave radiating units 104 have directivity in the transmission direction 205.

  As shown in FIG. 10A, a positional relationship in which two microwave radiating portions 104 at the approximate node position 209 are installed so as to have a distance in the direction 204 perpendicular to the transmission direction 205 and the transmission and electric field direction. Then, as shown in FIG. 11, the microwaves strengthen each other at the center between the microwave radiating portions 104, and the effective radiated power becomes stronger, resulting in a distribution of the effective radiated power having directivity in the transmission direction 205.

  In the case of the distribution of effective radiated power as shown in FIG. 11, uniform heating is possible by placing a plurality of heated objects 105 in the transmission direction 205 where the effective radiated power is strong, as shown in FIG. It becomes.

(Embodiment 5)
FIG. 12A is a diagram showing a positional relationship among the heating chamber 101, the waveguide means 103, the microwave radiating unit 104, and the article to be heated 105 in the fifth embodiment of the present invention. FIG. 12B is a diagram showing the relationship between the position of the microwave radiating unit 104 and the phase of the standing wave 206 in the waveguide unit 103.

  FIG. 13 shows the distribution of direct waves radiated from the microwave radiating unit 104 in the present embodiment by electromagnetic field analysis, and the microwave distribution is displayed as effective radiated power.

  FIG. 14 is a diagram showing an example of the shape of the microwave radiation unit 104 that radiates circularly polarized waves.

  In the drawing, the same reference numerals are given to portions showing the same operations as those in (Embodiment 1) to (Embodiment 4). Further, assuming that the basic operation and electromagnetic field analysis conditions in (Embodiment 5) are the same as those in (Embodiment 1) to (Embodiment 4), the operation and action will be described below.

  First, the characteristics of circular polarization and the micro using circular polarization will explain the advantages of heating.

  Circular polarization is a technique widely used in the fields of mobile communication and satellite communication. Examples of familiar use include an ETC (Electronic Toll Collection System) “non-stop automatic toll collection system” and the like. Circular polarization is a microwave in which the polarization plane of the electric field 301 rotates with respect to the traveling direction of the radio wave, and when the circular polarization is formed, the direction of the electric field 301 continues to change with time. The radiation angle of the microwave radiated into the chamber 101 continues to change, and the electric field strength does not change with time.

  Due to the above-described characteristics, compared to microwave heating by linear polarization used in a conventional microwave heating apparatus, microwaves are dispersed and radiated over a wide range, and the object to be heated 105 can be heated uniformly. It becomes like this. 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.

  Therefore, it becomes possible to relieve the standing wave in the heating chamber 101 caused by the interference between the direct wave and the reflected wave, which has been a problem in the microwave heating by the microwave heating apparatus using the conventional linearly polarized wave, More uniform microwave heating can be realized.

  With respect to the circularly polarized wave, the microwave in the waveguide means 103 is a linearly polarized wave whose electric field and magnetic field oscillation directions are constant. In the conventional microwave heating apparatus that radiates the linearly polarized wave into the heating chamber 101, in order to reduce the non-uniformity of the microwave distribution, a structure for rotating the table on which the object 105 is to be heated is introduced. A structure in which an antenna that radiates microwaves from the wave unit 103 to the heating chamber 101 is rotated, or a phase shifter has to be installed in the waveguide unit 103.

  However, even if a table, a mechanism for rotating the antenna, and a phaser are installed, it is not sufficient to realize sufficiently uniform microwave heating in the heating chamber 101. Furthermore, by installing the rotation mechanism and the phaser, the structure of the microwave heating device is complicated, the structure is limited, or the reliability is lowered.

  Next, the shape of the microwave radiation unit 104 that generates circularly polarized waves will be described. In particular, here, the microwave radiation unit 104 constituted by at least two or more slits will be described.

14 (a) to 14 (f) showing examples of the shape, it is configured by two or more slits, and the long side 601 of at least one of these slits is arranged in the microwave transmission direction 205. It is sufficient that the shape is inclined with respect to it. Therefore, a shape that does not intersect as shown in FIGS. 14E and 14F, or a shape that includes three slits as shown in FIG. 8D may be used.

  In addition, as shown in FIG. 14, the following three points are mentioned as the conditions of the best shape of the microwave radiation | emission part 104 which radiates | emits the circularly polarized wave comprised by two slits.

  The first point is that the length of the long side 601 of each slit is ¼ or more of the in-tube wavelength of the microwave transmitted through the waveguide means 103.

  The second point is that the two slits are orthogonal to each other and the long side of each slit is inclined 45 ° with respect to the transmission direction 205.

  The third point is that the distribution of the electric field 301 is not an axis contrast with a straight line passing through the center of the microwave radiating unit 104 parallel to the transmission direction 205 of the waveguide means 103 as an axis. For example, as shown in Patent Document 2, when microwaves are transmitted in the TE10 mode, the electric field 301 is distributed with the central axis 203 in the transmission direction of the waveguide means as the symmetry axis. The condition is that the microwave radiating portion 104 is arranged so that the shape of the microwave radiating portion 104 does not become an axis contrast with respect to the central axis 203 in the transmission direction of the waveguide means.

  Next, as shown in FIG. 12, two microwave radiating portions 104 are arranged side by side in the transmission direction 205 at the approximate node position 209 in the phase of the standing wave 206 in the waveguide means 103, and the approximate node position is set. In the middle of the transmission direction 205 of the microwave radiating unit 104 of 209, when one microwave radiating unit 104 is installed at the abdominal position 208 so as to have a distance in the direction 204 perpendicular to the transmission and electric field direction. The reason why the distribution of the effective radiation power of the direct wave into the heating chamber 101 becomes as shown in FIG.

  As described with reference to FIG. 4 of (Embodiment 1), a microwave having directivity in the transmission direction 205 is radiated from the microwave radiation unit 104 installed at the approximate node position 209, and the approximate abdominal position 208. A microwave having directivity in a direction 204 perpendicular to the direction of transmission and electric field is radiated from the microwave radiating unit 104 installed in.

  In the present embodiment, two microwave radiating portions 104 are installed at the approximate node position 209 and one at the approximate abdominal position 208, and each microwave radiating portion 104 has a directivity. Microwaves having directivity in the direction 204 perpendicular to the wave, transmission and electric field directions are radiated and interfere with each other in the heating chamber 101.

  As described in (Embodiment 3), the mutual interference of microwaves at an arbitrary point is determined by the directivity of the microwave radiating unit 104, the distance from each microwave radiating unit 104, and the microwaves. Determined by wavelength.

  As shown in FIG. 12A, since the two microwave radiating portions 104 are installed at the approximate node position 209, it becomes possible to radiate microwaves in the transmission direction 205. Furthermore, since one microwave radiating unit 104 is installed at the approximate abdominal position 208, it is possible to radiate microwaves in a direction 204 perpendicular to the transmission and electric field directions.

  Since the directivity of the microwaves radiated from the microwave radiation unit 104 installed at the approximate node position 209 and the approximate abdominal position 208 is substantially perpendicular, the mutual interference of the microwaves has a clear influence on the direct wave distribution. There is no effect, and it becomes possible to radiate microwaves uniformly in the circumferential direction around the center of the three microwave radiating portions 104.

Note that the distribution of effective radiated power tends to become weaker as the center of the microwave radiating unit 104 is moved away from the center.

  Therefore, as shown in FIG. 13, the effective radiated power is strong in the center between the microwave radiating portions 104, and the effective radiated power having uniform directivity in the circumferential direction around the center of the three microwave radiating portions 104. Distribution.

  In the case of the distribution of effective radiated power as shown in FIG. 13, when each heated object 105 is compared by placing a plurality of heated objects 105 at the same distance from the center of the three microwave radiating portions 104, Uniform heating is possible.

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

DESCRIPTION OF SYMBOLS 101 Heating chamber 102 Microwave generation means 103 Waveguide means 104 Microwave radiation part 204 The direction perpendicular to the transmission and electric field direction 205 Transmission direction 208 General position 209 General position

Claims (8)

Includes a heating chamber for accommodating an object to be heated, a microwave generator for generating microwaves, a waveguide means for transmitting the microwave, the microwave radiating portion for radiating the microwave into the heating chamber, the guide The wave means is installed asymmetrically with respect to the center of the inner wall of the heating chamber, and the microwave radiated into the heating chamber is caused by the phase of the microwave in the waveguide means where the microwave radiating portion is located. A microwave heating apparatus that adjusts directivity so that the waveguide means becomes stronger in parallel with the direction in which the waveguide means is biased . When the waveguide means is off-center in the direction perpendicular to the transmission and electric field direction with respect to the center of the inner wall of the heating chamber, the phase of the microwave in the waveguide means where the microwave radiating unit is located is 2. The directivity of the microwave radiated into the heating chamber is adjusted by setting the position to be approximately abdomen so that the waveguide means becomes stronger in a direction in which the waveguide means is biased, that is, in a direction perpendicular to the transmission and electric field directions. The microwave heating apparatus as described. When the waveguide means is biased in the transmission direction with respect to the center of the inner wall of the heating chamber, the phase of the microwave in the waveguide means in which the microwave radiating portion is located is set to a general position. The microwave heating apparatus according to claim 1 , wherein the directivity of the microwave radiated into the heating chamber is adjusted so as to become stronger in a direction in which the waveguide means is biased, that is, in a transmission direction. The microwave heating device according to any one of claims 1 to 3, comprising a plurality of the microwave radiation portions. The microwave heating device according to claim 4, wherein at least two of the microwave radiating portions are respectively positioned in substantially the same phase of the microwave in the waveguide means. The microwave heating device according to claim 4, wherein at least two of the microwave radiating portions are respectively located in different phases of the microwave in the waveguide means. The microwave radiation portion has a shape that radiates circularly polarized waves.
The microwave heating device according to item. The microwave heating device according to claim 7, wherein the microwave radiating unit is configured to radiate circularly polarized waves by arranging two slits at the center of each to arrange them in the same phase.