WO2013005420A1

WO2013005420A1 - Microwave heating device

Info

Publication number: WO2013005420A1
Application number: PCT/JP2012/004304
Authority: WO
Inventors: 大介細川; 吉野　浩二; 貞平　匡史; 信江　等隆; 大森　義治
Original assignee: パナソニック株式会社
Priority date: 2011-07-04
Filing date: 2012-07-03
Publication date: 2013-01-10
Also published as: CN103650637A; JPWO2013005420A1; CN103650637B

Abstract

Provided is a microwave heating device configured such that: a waveguide unit (103) is positioned such that a center point (O) of a heating space within a heating chamber (101) is not included upon a perpendicular of a center axis (P) which is parallel to a transmission direction (X) in the waveguide unit; and a composite wave of microwaves which are radiated from each microwave radiation unit (104) has a directivity which radiates many microwaves toward the center part of the heating space; and uniform microwave heating of a substance to be heated within a heating chamber is possible.

Description

Microwave heating device

The present invention relates to a microwave heating apparatus such as a microwave oven, and more particularly to a microwave heating apparatus characterized by a structure for radiating microwaves into a heating chamber.

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

Magnetron is used as a microwave generation means in a conventional microwave oven. Microwaves generated by the magnetron are radiated from the microwave radiating portion into the heating chamber through the waveguide. If the electromagnetic field distribution (microwave distribution) of the microwave in the heating chamber is not uniform, there is a problem that the object to be heated cannot be uniformly heated by microwaves.

As a means for uniformly heating the object to be heated inside the heating chamber, a structure for rotating the table to place the object to be heated to rotate the object to be heated inside the heating chamber, fixing the object to be heated, and applying microwaves There is a structure for rotating a radiating antenna or a structure for changing the phase of the microwave from the microwave generating means using a phase shifter. A microwave heating apparatus having such a structure is generally used.

For example, in a conventional microwave heating apparatus, a rotatable antenna, an antenna shaft, and the like are arranged inside a waveguide, and the microwave distribution in the heating chamber is driven by driving the magnetron while rotating the antenna by a motor. Some have a structure that reduces the non-uniformity of the film.

Further, Japanese Patent Application Laid-Open No. 62-64093 (Patent Document 1) describes a microwave heating apparatus having another configuration. In this Patent Document 1, a rotatable antenna is provided on the upper part of a magnetron, and the antenna is rotated by the wind force of the blower fan by applying the wind from the blower fan to the blades of the antenna. Microwave heating devices that change the distribution have been proposed.

As an example having a phase shifter, a microwave heating apparatus that reduces heating unevenness of an object to be heated by microwave heating, reduces cost, and saves space in a power feeding unit is disclosed in US Pat. No. 4,301,347 (patented) Document 2). Patent Document 2 proposes a microwave heating apparatus having a single microwave radiating section that radiates circularly polarized waves inside a heating chamber.

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

The microwave heating apparatus having the above-described conventional configuration is required to have a simple structure as much as possible, and to efficiently heat an object to be heated without unevenness. However, the conventional configurations proposed so far are not satisfactory and have various problems in terms of efficiency and uniformity in terms of structure.

Also, in microwave heating devices, especially in microwave ovens, technological development for higher output has progressed, and products with a rated high-frequency output of 1000 W have been commercialized in Japan. Microwave ovens are notable for heating food by heat conduction, but the convenience of being able to heat food directly using dielectric heating is a major feature of this product. However, in a microwave oven, increasing the output in a state where non-uniform heating has not been solved has a big problem that non-uniform heating becomes more obvious.

The following three points are given as structural problems of the conventional microwave heating apparatus.
The first point requires a drive mechanism for rotating the table or antenna to reduce non-uniform heating, so that a rotation space and a space for installing a drive source such as a motor for rotating the table or antenna are secured. This is a point that obstructs miniaturization of the microwave oven.

The second point is that in order to rotate the table or antenna stably, it is necessary to provide the antenna above or below the heating chamber, and the arrangement of specific parts is limited on the structure.

The third point is that 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 Because of the large amount of heat generation, it is necessary to secure a cooling air path to achieve sufficient cooling performance, the installation position of the waveguide and microwave radiation part is limited, and the microwave distribution in the heating chamber is uneven It is a point.

Various mechanisms such as a table or antenna rotation mechanism and a phaser are installed in a space (applicator) that is connected to the heating chamber of the microwave heating apparatus and is irradiated with microwaves. The installation of the mechanism has a problem that the reliability of the apparatus may be lowered. Therefore, there is a demand for a microwave heating apparatus that does not require the installation of these mechanisms.

Furthermore, in the microwave heating apparatus described in Patent Document 2 that reduces uneven heating (heating unevenness) of an object to be heated by microwave heating, reduces manufacturing costs, and saves space in a power feeding unit. Has the following problems. The microwave heating device having a single microwave radiating unit that radiates circularly polarized waves into the inside of the heating chamber disclosed in Patent Document 2 has an advantage that it does not have a rotating mechanism. There is a problem that sufficient uniform heating cannot be realized.

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

One aspect of the microwave heating apparatus according to the present invention is:
A heating chamber for storing an object to be heated;
A microwave generator for generating microwaves;
A waveguide for transmitting microwaves;
A plurality of microwave radiating sections that radiate circularly polarized waves in the heating chamber,
The waveguide section is arranged so that the center point of the heating space in the heating chamber is not included on the vertical line of the central axis parallel to the transmission direction in the waveguide section,
A combined wave of the microwaves radiated from each of the microwave radiating portions is configured to have a directivity for radiating many microwaves toward the center side of the heating space.
The microwave heating device of one embodiment according to the present invention configured as described above can uniformly heat an object to be heated without using a rotation mechanism.

According to the present invention, it is possible to provide a microwave heating apparatus that can uniformly perform microwave heating on an object to be heated arranged in a heating chamber without using a rotation mechanism.

It is a cross-sectional view which shows the microwave oven which is the microwave heating device of Embodiment 1 which concerns on this invention. It is a top view which shows the structure of the microwave radiation | emission part in the microwave oven of Embodiment 1 which concerns on this invention. It is a figure explaining the relationship between the microwave radiation | emission part and standing wave in the microwave heating apparatus of Embodiment 2 which concerns on this invention. It is a figure explaining the relationship among the standing wave of the microwave radiation | emission part in the microwave heating apparatus of Embodiment 2 which concerns on this invention, electric field distribution, magnetic field distribution, current distribution, etc. FIG. It is a figure explaining the relationship between the phase of the standing wave which arises in the waveguide part in the microwave heating device of Embodiment 2 which concerns on this invention, and directivity. It is explanatory drawing which shows the specific opening shape of the microwave radiation | emission part in the microwave heating apparatus of Embodiment 2 which concerns on this invention. It is a top view which shows the example of arrangement configuration of the microwave radiation | emission part provided in the waveguide part with respect to the heating chamber in the microwave heating apparatus of Embodiment 2 which concerns on this invention. The top view which shows the other structure of the microwave radiation | emission part which generate | occur | produces circularly polarized wave in the microwave heating apparatus of Embodiment 2 which concerns on this invention It is a top view which shows the example of a change of the structure of the microwave radiation | emission part in the microwave heating apparatus of Embodiment 2 which concerns on this invention.

The microwave heating apparatus according to the first aspect of the present invention is
A heating chamber for storing an object to be heated;
A microwave generator for generating microwaves;
A waveguide for transmitting microwaves;
A plurality of microwave radiating sections that radiate circularly polarized waves in the heating chamber,
The waveguide section is arranged so that the center point of the heating space in the heating chamber is not included on the vertical line of the central axis parallel to the transmission direction in the waveguide section,
A combined wave of the microwaves radiated from each of the microwave radiating portions is configured to have a directivity for radiating many microwaves toward the center side of the heating space.

The microwave heating apparatus according to the first aspect of the present invention configured as described above can adjust the number, shape, arrangement, and the like of the microwave radiating portions, and changes the microwave distribution in the heating chamber. A control factor increases and it becomes the structure which is easy to implement | achieve the target microwave distribution in heating space. Therefore, the microwave heating apparatus according to the first aspect of the present invention can uniformly heat the object to be heated without using a rotating mechanism.

Moreover, since the microwave heating apparatus according to the first aspect of the present invention has a microwave radiating unit that radiates circularly polarized waves, microwaves having a spread are radiated from the microwave radiating unit and heated. It is possible to make the microwave radiation uniform over a wider range. In particular, uniform heating in the circumferential direction of circular polarization can be expected.

In the microwave heating apparatus according to the second aspect of the present invention, the plurality of microwave radiating portions in the first aspect are non-axisymmetric with respect to a central axis parallel to the transmission direction in the waveguide. It is arranged to be. The microwave heating apparatus according to the second aspect of the present invention configured as described above can change the microwave distribution in the heating chamber, and can set the microwave distribution in the heating space to a desired state. It becomes.

In the microwave heating apparatus according to the third aspect of the present invention, at least one microwave radiating part in the plurality of microwave radiating parts in the first or second aspect is more than the other microwave radiating parts. Thus, it is configured to emit many microwaves in a specific direction. In the microwave heating apparatus according to the third aspect of the present invention configured as described above, the microwave radiating unit has a directivity structure, the microwave distribution in the heating chamber can be changed, and the rotation mechanism can be changed. Without using it, it becomes possible to uniformly heat the object to be heated.

In the microwave heating apparatus according to the fourth aspect of the present invention, in any one of the first to third aspects, transmission in the waveguide section is performed on the surface of the waveguide section facing the heating chamber. With the central axis parallel to the direction as a boundary, the microwave radiating portions provided in the respective regions on both sides of the boundary are configured such that the distances from the central axis to the center of the microwave radiating portion are different. The microwave heating device according to the fourth aspect of the present invention configured as described above has a configuration having directivity by a plurality of microwave radiating units, and can change the microwave distribution in the heating chamber.

In the microwave heating apparatus according to the fifth aspect of the present invention, in any one of the first to fourth aspects, the transmission in the waveguide section is performed on the surface of the waveguide section facing the heating chamber. With a central axis parallel to the direction as a boundary, the number of the microwave radiating portions provided on both sides of the boundary is closer to the center point of the heating space, and the number of the microwave radiating portions is closer to the far side. More than the number of radiation parts. The microwave heating apparatus according to the fifth aspect of the present invention configured as described above has a configuration having directivity by a plurality of microwave radiating units, and can change the microwave distribution in the heating chamber.

In the microwave heating apparatus according to a sixth aspect of the present invention, in any one of the first to fifth aspects, the transmission in the waveguide section is performed on the surface of the waveguide section facing the heating chamber. With the central axis parallel to the direction as a boundary, the microwave radiating portions on the side close to the center point of the heating space in the plurality of microwave radiating portions provided on both sides of the boundary are defined in the waveguide portion. It is formed at the position of the standing wave belly. In the microwave heating apparatus according to the sixth aspect of the present invention configured as described above, it is possible to radiate in the width direction of the waveguide from the microwave radiating unit on the side close to the center point of the heating space, The microwave distribution in the heating chamber can be changed.

A microwave heating apparatus according to a seventh aspect of the present invention is the microwave heating apparatus according to any one of the first to sixth aspects, wherein at least one microwave radiating portion is configured by a combination of two or more slits. The longitudinal direction of at least one slit in the microwave radiating portion is inclined with respect to the transmission direction in the waveguide portion, and the combined wave of the microwaves radiated from all the microwave radiating portions is in a specific direction. Are configured to have a directivity for radiating a large number of microwaves. In the microwave heating apparatus according to the seventh aspect of the present invention configured as described above, a circularly polarized microwave having a spread from the microwave radiating unit is reliably radiated, and the microwave is applied to the object to be heated. Can be made uniform over a wider range.

Further, the microwave heating apparatus according to the seventh aspect of the present invention has a configuration in which the microwave radiating portion is formed by two or more slits to reliably radiate circularly polarized waves. A mechanism for rotating the table or the antenna for reducing unevenness is not required, and the reliability of the apparatus can be improved and the power feeding unit can be downsized.

According to an eighth aspect of the present invention, there is provided the microwave heating apparatus according to the seventh aspect, wherein the length of the slit of the microwave radiating portion configured by the slit is the length of the transmission in the waveguide portion. It is comprised so that it may differ with the position in the direction orthogonal to an electric field direction. The microwave heating apparatus according to the eighth aspect of the present invention configured as described above is configured to have directivity by a plurality of microwave radiating units, and can change the microwave distribution in the heating chamber, It becomes possible to make the microwave distribution in the space a desired state.

According to a ninth aspect of the present invention, in the microwave heating apparatus according to the seventh aspect, the length in the width direction of the slit of the microwave radiating unit configured by the slit is the transmission in the waveguide unit. It is comprised so that it may differ with the position of the direction orthogonal to an electric field direction. The microwave heating apparatus according to the ninth aspect of the present invention configured as described above has a configuration having directivity by a plurality of microwave radiating units, and can change the microwave distribution in the heating chamber, It becomes possible to make the microwave distribution in the space a desired state.

In the microwave heating apparatus according to a tenth aspect of the present invention, in the seventh aspect described above, an R chamfering process or a C chamfering process is performed at the intersection of the slits of the microwave radiating unit configured by the slits. Has been. The microwave heating apparatus according to the tenth aspect of the present invention thus configured can alleviate electric field concentration, suppress energy loss, and increase the reliability of the apparatus.

In the microwave heating apparatus of the eleventh aspect according to the present invention, in the seventh aspect, an R chamfering process or a C chamfering process is performed on a slit end portion of the microwave radiating portion configured by a slit. ing. The microwave heating apparatus according to the tenth aspect of the present invention thus configured can alleviate electric field concentration, suppress energy loss, and increase the reliability of the apparatus.

Hereinafter, preferred embodiments of a microwave heating apparatus according to the present 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 includes appropriately combining arbitrary configurations described in the respective embodiments described below, and the combined configurations exhibit their respective effects. Furthermore, the present invention is not limited to the specific microwave oven configuration described in the following embodiments, and includes a configuration based on the same technical idea.

(Embodiment 1)
FIG. 1 is a cross-sectional view showing a microwave oven that is a microwave heating apparatus according to a first embodiment of the present invention. FIG. 2 is a plan view of the microwave radiating unit in the microwave oven according to the first embodiment of the present invention, and shows a positional relationship among the heating chamber 101, the waveguide unit 103, and the microwave radiating unit 104.

In FIG. 1, a microwave oven that is a microwave heating apparatus according to Embodiment 1 is supplied from a heating chamber 101 that stores an object to be heated 107, a microwave generation unit 102 that generates a microwave, and a microwave generation unit 102. Waveguide part 103 for transmitting the microwave to be heated to heating chamber 101, and microwave radiation that is provided on the tube wall surface of waveguide part 103 that faces heating chamber 101, and radiates circularly polarized waves in heating chamber 101 Part 104.

Note that the configuration in the microwave oven of the first embodiment is obtained by using a magnetron as the microwave generation unit 102, a rectangular waveguide as the waveguide unit 103, and an opening provided in the waveguide unit 103 as the microwave radiation unit 104. It can be easily realized.

As shown in FIG. 2, the waveguide unit 103 has a plurality of microwave radiation units 104 that radiate circularly polarized waves in the heating chamber 101. The positional relationship between the waveguide section 103 and the heating chamber 101 is such that, when the heating chamber 101 is viewed from above, the central axis P parallel to the transmission direction in the waveguide section 103 (the right direction in FIG. 2) is The center point O of the inner wall surface (bottom wall) of the heating chamber 101 provided with 103 is not included. Here, it is assumed that the center point O of the heating space in the heating chamber is on the vertical line (on the vertical line) of the center point O of the bottom wall (the wall surface of the heating chamber 101) facing the waveguide unit 103. In the description of the first embodiment, as described above, the central axis P parallel to the transmission direction in the waveguide section 103 does not include the center point O of the inner wall surface of the heating chamber 101 where the waveguide section 103 is installed. The related configuration is called off-center.

The operation and action of the microwave oven according to Embodiment 1 configured as described above will be described below.
First, the schematic operation of the microwave heating apparatus will be described. When the object to be heated 107 is arranged in the heating chamber 101 by the user and a heating start instruction is performed, the microwave heating apparatus transmits a microwave from the magnetron serving as the microwave generation unit 102 into the waveguide unit 103. Is supplied, and microwaves are radiated into the heating chamber 101 through the microwave radiating unit 104 that connects the heating chamber 101 and the waveguide unit 103. In this manner, the microwave is radiated into the heating chamber 101, so that the microwave heating apparatus performs a heat treatment on the object to be heated 107.

Next, the non-uniformity of the microwave distribution in the heating chamber 101 due to the shape of the inner wall surface of the heating chamber 101 will be described with reference to FIG.
The shape (heating space shape) in the heating chamber 101 is often asymmetric, and a large number of components having different dielectric constants are attached to the wall surface constituting the heating chamber 101. As specific examples, there are mainly the following three points.

1st point is that the door 108 and the door glass 109 for taking out the to-be-heated material 107 are attached. The second point is that the heater 110 is attached to the upper surface or the bottom surface to radiately heat the article to be heated 107. The third point is that since the heater 110 and the convection fan 111 are attached to the back side of the back surface to convectionly heat the object to be heated 107, the back side wall surface has a complicated shape.

As described above, the shape of the heating space in the heating chamber 101 is asymmetrical and / or components having different dielectric constants are attached to the wall surface of the heating chamber 101, so that microwaves are reflected on the inner wall surface of the heating chamber 101. Thus, the heating of the object to be heated 107 becomes uneven due to the reflected wave. Note that in the description of Embodiment Mode 1, microwaves radiated from the microwave radiating unit 104 and directly irradiating the object to be heated 107 are referred to as direct waves and reflected on the wall surface in the heating chamber 101 to be heated. The microwave that irradiates 107 is a reflected wave.

Next, the non-uniformity of the microwave distribution in the heating chamber 101 due to the positional relationship between the waveguide unit 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, the waveguide section is often configured to be off-center with respect to the heating chamber.

For this reason, even if the microwave radiating portion is symmetrically arranged with the central axis of the waveguide portion in the tube axis direction (see the central axis P in FIG. 2) as the symmetry axis, the heating chamber has a uniform microwave distribution. It is difficult.

Hereinafter, a specific example of a configuration in which the waveguide unit is off-center with respect to the heating chamber will be described with reference to the configuration illustrated in FIG. The following two points are mainly given as examples of the configuration that is off-center. The first point is in the case of a microwave heating device having a water vapor heating function. In order to realize the water vapor heating function, the water tank 112, the pump 113, the heater 110, and the spout 114 for ejecting water vapor into the heating chamber 101 are used. Etc. must be installed inside and outside of the heating chamber 101, and the waveguide 103 is off-centered with respect to the heating chamber 101.

The second point is a case of a microwave heating apparatus having a radiant heating function, and it is necessary to install a heater 110 on the upper surface side or the bottom surface side of the heating chamber 101. It becomes an off-center configuration. In the microwave heating apparatus shown in FIG. 1, an example is shown in which a heater 110 is installed on the upper surface side of the heating chamber 101.

Also, in the microwave heating apparatus, parts with a large amount of heat generation such as an inverter, a magnetron, and a control board are installed in the casing. Such heat generating parts such as inverters, magnetrons and control bases must be sufficiently cooled, and a cooling air passage (cooling space) 115 (see FIG. 1) is secured in the housing for these heat generating parts. There is a need. If these heat generating parts are not sufficiently cooled, parts that do not operate normally or parts that burn out are generated, and the reliability of the apparatus is greatly impaired. Therefore, in order to ensure a sufficient cooling performance, there are many cases where the waveguide portion has to be configured to be an off-center position with respect to the heating chamber.

Considering the above points, in the microwave radiated from the microwave radiating unit, the object to be heated in the heating chamber is made uniform unless it has a desired directivity corresponding to the heating space in the heating chamber. It is difficult to heat by microwave.

Next, the advantage of the microwave heating apparatus having a plurality of microwave radiating portions will be described.
In the microwave heating apparatus having one microwave radiating portion, since the number of factors for adjusting the directivity of the microwave is small, it is difficult to obtain the uniformity of the microwave distribution with respect to the heating region in the target heating chamber. It is.

Further, in such a microwave heating apparatus, since microwaves are radiated from one point into the heating chamber, sufficient spreading of the microwaves cannot be expected, and the direct wave and the reflected wave have a heating area in a specific area. In many cases, the heat is concentrated, resulting in non-uniform microwave heating on the object to be heated.

In particular, when microwaves are radiated from the bottom of the heating chamber, the object to be heated is often placed at a short distance from the microwave radiation part, and the microwave does not spread sufficiently, and the microwave is near the object to be heated. The heating unevenness of the object to be heated becomes remarkable.

Therefore, by providing a plurality of microwave radiating portions in the waveguide portion and radiating microwaves to the heating chamber, not only the shape of the microwave radiating portions but also the directivity such as quantity and arrangement are adjusted. It is possible to increase the number of factors. Thus, by providing a plurality of microwave radiating portions, the number of adjustment factors can be significantly increased compared to the case of one microwave radiating portion. For this reason, it is possible to make the microwave distribution in the heating space uniform, and it becomes easy to obtain uniform microwave heating for the target object to be heated.

Next, features of circularly polarized waves and advantages of microwave heating using circularly polarized waves will be described.
Circular polarization is a technique widely used in the fields of mobile communication and satellite communication. Familiar use examples include ETC (Electronic Toll Collection System) “non-stop automatic toll collection system”. Circular polarization is a microwave in which the polarization plane of the electric field rotates with respect to the traveling direction of the radio wave, and when the circular polarization is formed, the direction of the electric field continues to change with time. The radiation angle of the emitted microwave continues to change, and the electric field strength does not change with time.

Due to the characteristics of the above circularly polarized waves, the microwave radiating part that radiates circularly polarized waves disperses microwaves over a wide range compared to microwave heating by linearly polarized waves used in conventional microwave heating devices. By being emitted, it becomes possible to heat the object to be heated more uniformly. 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: counter clockwise) from the direction of rotation, but there is no difference in heating performance.

Therefore, the standing wave in the heating chamber caused by interference between the direct wave and the reflected wave, which has been a problem in microwave heating by the conventional microwave heating apparatus using linearly polarized waves, is converted into circularly polarized radiation. It can be mitigated by use, and it is considered that more uniform microwave heating can be realized.

Microwaves transmitted through the waveguide are linearly polarized waves whose electric field and magnetic field oscillation directions are constant. As described above, in the conventional microwave heating apparatus that radiates linearly polarized waves into the heating chamber, in order to reduce the non-uniformity of the microwave distribution, a structure for rotating the table on which the object to be heated is placed, It has been necessary to provide a structure for rotating an antenna that radiates microwaves from the waveguide to the heating chamber, or a structure for changing the phase of the microwave by installing a phase shifter in the waveguide.

However, even if a mechanism for rotating the table or antenna or a mechanism for installing a phaser in the waveguide section is provided, it is difficult to achieve sufficiently uniform microwave heating for the object to be heated in the heating chamber. It was. Further, providing the microwave heating device with a configuration that installs a rotation mechanism or a phaser as described above causes a complicated structure, causes a structural limitation, and reduces the reliability of the device. It had the problem that.

As described above, in order to achieve uniform heating of the object to be heated in the configuration in which the heating space shape in the heating chamber is asymmetric and the waveguide with respect to the heating chamber is off-center, radiation is performed by a plurality of microwave radiation units. It is necessary to adjust the directivity of the synthesized wave of microwaves. Furthermore, it is necessary to improve the uniformity of the microwave distribution in the heating space by installing a microwave radiating unit that radiates circularly polarized waves.
Therefore, the inventor proposes, as one aspect, the configuration of the microwave heating apparatus according to the first embodiment of the present invention that solves the above-described problems.

A method for adjusting the directivity of the combined wave of the microwaves radiated by the plurality of microwave radiating units 104 configured in the microwave heating apparatus according to the first embodiment of the present invention will be described using a specific example.

As shown in FIG. 2, the waveguide section 103 is provided with a plurality of microwave radiating sections 104, and the waveguide section 103 is configured to be in an off-center position with respect to the heating chamber 101. In the first embodiment shown in FIG. 2, the waveguide section 103 is arranged so as to be on the back side (upper side in FIG. 2) from the center point O of the heating space of the heating chamber 101 when the heating chamber 101 is viewed from above. Has been.

If a plurality of microwave radiating portions are symmetrically arranged with the central axis (P) parallel to the transmission direction of the waveguide as a symmetric axis, the fundamental is increased as the distance from the microwave generating portion increases. The amount of microwave radiation decreases. In such a configuration, it is difficult to uniformly heat the object to be heated arranged in the center of the heating chamber.

Therefore, as shown in FIG. 2, the plurality of microwave radiating portions 104 are arranged so as not to be axially symmetric with respect to the central axis P parallel to the transmission direction X of the waveguide portion 103 (non-axisymmetric arrangement). . In the configuration shown in FIG. 2, two waveguide portions 103 are provided in the region on the back side from the central axis P of the waveguide portion 103, and three in the region on the front side from the central axis P of the waveguide portion 103. The waveguide section 103 is provided. When configured in this manner, with the central axis P as a boundary, the total opening area of the microwave radiating portions 104 in the region where the number of the microwave radiating portions 104 is large (front region) is the opposite region (rear region). ) And the total microwave radiation in the regions on both sides is biased.

As a result, in the configuration of the first embodiment shown in FIG. 2, the microwaves radiated from the front-side microwave radiating units 104 to the front side of the heating chamber 101 are microwave radiations on the back side. More than the microwaves radiated from each of the sections 104 to the back side of the heating chamber 101. As a result, the synthesized wave from the waveguide unit 103 is configured to have directivity on the side with the large numerical aperture (front side) of the microwave radiating unit 104.

Therefore, when the waveguide 103 is off-center with respect to the heating chamber 101, the surface of the waveguide 103 facing the heating chamber 101 is closer to the center O of the heating space of the heating chamber 101. By increasing the numerical aperture of the microwave radiating unit 104 in the region (for example, the front side region or the back side region), uniform heating of the article to be heated 107 can be achieved.

In the configuration of the first embodiment, even if the center axis P parallel to the transmission direction of the waveguide 103 is used as a boundary, the distance from the center axis P to the center of the microwave radiating unit 104 may be adjusted to be different. good. For example, in FIG. 2, the distance L1 from the central axis P to the center of the microwave radiating unit 104 on the front side is from the central axis P as shown in the microwave radiating unit 104 closest to the terminal end 201 of the waveguide unit 103. It is set longer than the distance L2 to the microwave radiation part 104 on the back side (L1> L2). That is, by providing each microwave radiating portion 104 closer to the center point O of the heating space of the heating chamber 101, in the microwave radiation from the microwave radiating portion 104 provided in the waveguide portion 103, the heating chamber More microwaves are radiated in the direction toward the center of 101, and directivity is obtained in the radiation direction of the combined wave (total amount) of the microwaves.

As described above, in the configuration of the first embodiment, the heating chamber is adjusted by adjusting the position of the microwave radiating unit 104 in the direction Y (the width direction of the waveguide unit 103) orthogonal to the transmission and electric field directions. More microwaves can be radiated to the center side of 101, and the configuration has directivity.

As described above, for the specific configuration in which the number of the microwave radiating units arranged in the transmission direction X is changed, or the specific configuration in which the distance to the central axis P is changed, the waveguide unit 103 has the heating chamber 101. However, the present invention can be applied not only to the case where the heating chamber 101 is arranged off-center, but also to the case where the bias of the microwave distribution that occurs when the heating space shape of the heating chamber 101 is asymmetrical becomes a problem.
In addition, the two specific configurations described above can be configured to achieve more uniform heating of the object to be heated by combining these configurations.

(Embodiment 2)
Hereinafter, the microwave heating apparatus according to the second embodiment of the present invention will be described. The microwave heating apparatus of the second embodiment is different from the microwave heating apparatus of the first embodiment described above in that the directivity of the microwave radiating unit is specified in relation to the standing wave in the waveguide. Yes, the other configurations are the same.

In the description of the microwave heating apparatus of the second embodiment below, the same reference numerals are given to the components having the same functions and configurations as those in the microwave heating apparatus of the first embodiment, and the detailed description thereof is carried out. The description of Form 1 is applied. In addition, since the basic operation in the second embodiment is the same as the operation in the first embodiment described above, in the following description, operations and actions different from the operation in the first embodiment will be described.

FIG. 3 is a diagram for explaining the relationship between the microwave radiating unit 104 and the standing wave 301 in the microwave heating apparatus according to the second embodiment of the present invention. FIG. 3 illustrates the positional relationship between the standing wave 301 and the microwave radiating unit 104 generated in the waveguide unit 103.

First, it will be described that the waveguide 103 has at least one microwave radiating unit 104 at a specific position, so that the microwave radiated from the microwave radiating unit 104 has directivity.

As shown in FIG. 3, when a rectangular waveguide is used as the waveguide unit 103, the traveling wave generated in the microwave generation unit 102 (see FIG. 1) and supplied to the waveguide unit 103, and the waveguide The reflected waves reflected at the terminal end 201 of the section 103 interfere with each other, and a standing wave 301 is generated inside the waveguide section 103. The present inventor confirmed by experiments that the directivity of the microwave radiated from the microwave radiating unit 104 changes due to the difference in the phase of the standing wave 301 immediately below the microwave radiating unit 104. Yes. The principle that the directivity of the microwave radiated from the microwave radiating unit 104 changes according to the phase of the standing wave 301 will be described below.

The relationship among the electric field, magnetic field, and current in the waveguide 103 by the standing wave 301 will be described with reference to FIG. FIG. 4 is a diagram for explaining a relationship among an electric field, a magnetic field, and a current with respect to the microwave radiating unit 104 in the microwave heating apparatus of the second embodiment. FIG. 4 shows the principle that the directivity changes depending on the installation position of the microwave radiating unit 104, and explains the relationship between the electric field, magnetic field, and current in the waveguide unit 103 where the standing wave 301 is generated. Yes. In FIG. 4, reference numeral 402 indicates a curve of electric field distribution, reference numeral 403 indicates a curve indicating magnetic field distribution, and reference numeral 404 indicates a current flow.

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

Hereinafter, in the waveguide section (rectangular waveguide) 103 in which the microwave radiation section 104 is provided on the surface orthogonal to the electric field direction Z (see FIG. 3), the radiation is generated when the standing wave 301 is generated therein. The principle of microwave directivity will be described.

As shown in FIG. 4, the case where the microwave radiation part 104 is arrange | positioned in the position of the "antinode" and the position of the "node" in the standing wave 301 in the waveguide part 103 is demonstrated. In the microwave radiating unit 104, when considering a component in the current transmission direction X (X direction component) and a component in the width direction Y (Y direction component) orthogonal to the transmission and electric field directions, The current in the microwave radiating unit 104 arranged at the position of “antinode” increases the current in the Y direction component in the width direction Y perpendicular to the transmission and electric field direction.

Since the direction in which the current flows and the direction in which the electric field spreads are the same, the radiated microwave has directivity in the Y direction (width direction of the waveguide 103) perpendicular to the transmission and electric field direction.

On the other hand, the current in the microwave radiating unit 104 arranged at the position of the “node” of the standing wave has more components in the transmission direction X (X-direction component). For this reason, the emitted microwave has directivity in the X direction, which is the transmission direction X of the waveguide section 103.

Next, the relationship between the phase of the standing wave immediately below the microwave radiating unit 104 and the directivity of the emitted microwave will be described with reference to FIG. FIG. 5 is a diagram for explaining the relationship between the phase and directivity of the standing wave 301 generated in the waveguide section 103 in the microwave heating apparatus of the second embodiment. FIG. 5 illustrates the relationship between the phase of the standing wave 301 generated in the waveguide 103 where the microwave radiating unit 104 is located and the directivity of the microwave radiated into the heating chamber 101. The results shown in FIG. 5 are obtained by analysis.

FIG. 5A shows a change in the distance from the end 201 (see FIG. 4) of the waveguide 103 to the center of the microwave radiating unit 104, thereby changing the waveguide 103 immediately below the microwave radiating unit 104. It is the figure which changed the phase of the standing wave inside. In addition, the center of the microwave radiation | emission part 104 shows the gravity center position of the board | plate material, when it assumes that the opening shape was comprised with the board | plate material of the same thickness.

In the analysis shown in FIG. 5A, the position of the “antinode” of the standing wave is set to phase 0 °, the position of the “node” is set to phase 180 °, and the phase ranges from about 0 ° to about 180 °. The microwave distribution radiated from the microwave radiating unit 104 at an interval of about 45 ° in phase was obtained by analysis.

As shown in FIG. 5A, in this analysis, the microwave radiating unit 104 is changed by changing the distance from the end 201 of the waveguide unit (rectangular waveguide) 103 to the center of the microwave radiating unit 104. The phase of the standing wave in the waveguide 103 immediately below is changed. The end 201 of the waveguide 103 is a waveguide that is the end position in the transmission direction with the microwave output position of the magnetron serving as the microwave generator 102 as the start end in the transmission space in the waveguide 103. The inner wall surface of the closed part of the part 103 is said.

When the phase immediately below the microwave radiating unit 104 is about 180 ° (the position of almost “node” in the standing wave), the microwave radiating unit 104 radiates microwaves in the transmission direction X in the same manner as described above. Have directivity. Then, as shown in FIG. 5B, by shifting the phase by about 45 °, the directivity of the microwave shifts counterclockwise, and the phase is about 0 ° (standing wave). When the position is substantially “antinode”, the directivity is in the width direction (Y direction) orthogonal to the transmission and electric field directions. That is, when the phase directly below the microwave radiating unit 104 is about 0 ° (position of almost “antinode” in the standing wave), the microwave radiating unit 104 has a width direction orthogonal to the transmission and electric field directions ( (Y direction) has directivity of microwave radiation. This result is also consistent with the above explanation of the principle.

By applying the technology relating to the relationship between the phase of the standing wave and the directivity of the microwave radiating unit 104 described above, the microwave radiating unit 104 having directivity in the target direction can be provided, and heating is performed. The non-uniform microwave distribution in the chamber 101 can be improved.

Next, analysis conditions for the analysis results shown in FIG. 5 will be described.
In this analysis, a rectangular waveguide is used as the waveguide unit 103 to transmit a microwave generated from a magnetron as a microwave generation unit, and in the transmission direction of the rectangular waveguide (see arrow X in FIG. 4). Assumes a case where a microwave having a transmission mode called TE10 mode is transmitted in an H wave (TE wave; Transverse Electric Wave) which is a transmission mode having only a magnetic field component and no electric field component. ing.

Note that transmission modes other than the TE10 mode are rarely applied to the waveguide unit 103 of the microwave heating apparatus. Note that the upper and lower limits of the dimensions of the rectangular waveguide transmission and the direction orthogonal to the electric field direction (see arrow Y in FIG. 4) are the microwave frequency and the electric field direction of the rectangular waveguide (FIG. 3). (See arrow Z).
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 in the tube.

FIG. 6 is an explanatory diagram of a specific opening shape of the microwave radiating unit 104 in the microwave heating apparatus of the second embodiment. The microwave radiating unit 104 shown in FIG. 6 is configured so that two slits (openings) that are linear openings intersect each other, and the longitudinal direction of at least one slit (the length L in FIG. 6 is shown). (Direction) is a shape inclined with respect to the transmission direction X in the waveguide section 103. In FIG. 6, the length in the longitudinal direction of the slit constituting the microwave radiating portion 104 is L, and the width of the slit is S.

As shown in FIG. 6, the analysis condition for the above analysis results is that the opening shape of the microwave radiating unit 104 is orthogonal to the transmission direction X so that two slits intersect each other at the center of each slit. The longitudinal direction of the slit is inclined by 45 °.
Further, the number of the microwave radiating portions 104 is one, the length L of each slit is 55 mm, the thickness (height) of the rectangular waveguide is 30 mm, and the directivity display data is effective radiated power.

FIG. 7 shows an arrangement configuration example of the microwave radiating unit 104 provided in the waveguide unit 103 with respect to the heating chamber 101 in the microwave heating apparatus according to the second embodiment of the present invention configured based on the above analysis result. It is a top view. As shown in FIG. 7, the waveguide unit 103 includes a plurality of microwave radiation units 104 that radiate circularly polarized waves in the heating chamber 101. The positional relationship between the waveguide section 103 and the heating chamber 101 is a vertical line (vertical) of the central axis P parallel to the transmission direction (right direction in FIG. 7) in the waveguide section 103 when the heating chamber 101 is viewed from above. (On the line) is configured off-center so as not to include the center point O of the heating space of the heating chamber 101 in which the waveguide unit 103 is installed. In the above-described configuration, the regions on both sides of the waveguide 103 that are parallel to the transmission direction as a boundary, that is, the regions on both sides, that is, the back wall region and the front surface of the tube wall surface facing the heating chamber 101 with the center axis P as a boundary. A plurality of microwave radiating portions 104 are provided in each region. Two microwave radiating portions 104 are arranged in the position of the “node” of the standing wave in the waveguide section 103 in the back side region, and “standing wave“ of the standing wave in the waveguide portion 103 is arranged in the front side region. Three microwave radiating portions 104 are arranged at the position of “belly”.

As described above, by arranging the plurality of microwave radiating portions 104, each of the microwave radiating portions 104 in the back side region of the waveguide portion 103 has directivity in the tube axis direction (left-right direction in FIG. 7). Perform microwave radiation. On the other hand, each of the microwave radiating portions 104 in the front side region of the waveguide portion 103 performs microwave radiation having directivity in a direction orthogonal to the tube axis direction (vertical direction in FIG. 7). Further, since the total amount of microwave radiation from the microwave radiation unit 104 in the front side region is larger than the total amount of microwave radiation from the microwave radiation unit 104 in the rear side region, A large amount of microwave radiation is performed from the microwave radiation unit 104 on the front side. As a result, in the microwave heating apparatus according to the second embodiment configured as described above, the object to be heated can be uniformly heated.

In addition, the following three points can be given as conditions for the best shape of the microwave radiating unit 104 that radiates circularly polarized waves constituted by the two linear slits shown in FIG.

The first point is that the length L in the longitudinal direction of each slit is ¼ or more of the in-tube wavelength (λg) of the microwave transmitted through the waveguide section 103.

The second point is that the two slits are orthogonal to each other at the center, and that the longitudinal direction of each slit is inclined 45 ° with respect to the transmission direction X.

The third point is a straight line parallel to the transmission direction X of the waveguide section 103, and the electric field distribution in the waveguide section 103 is not axisymmetric with respect to a straight line passing through the center of the microwave radiating section 104. It is. For example, as shown in Patent Document 2, in the case where microwaves are transmitted in the TE10 mode, the central axis (tube axis) parallel to the transmission direction in the waveguide is set as the symmetry axis in the waveguide. Has a distributed electric field. For this reason, it is a condition that the opening shape of the microwave radiating unit 104 is arranged (asymmetrically arranged) so as not to be axially symmetric with respect to the central axis P (tube axis) in the transmission direction X in the waveguide unit 103.

Next, another shape of the microwave radiating unit 104 that generates circularly polarized waves will be described. In particular, here, the configuration of the microwave radiation unit 104 configured by at least two slits will be described.

FIG. 8 is a diagram illustrating another configuration of the microwave radiating unit 104 that generates circularly polarized waves in the microwave heating apparatus according to the second embodiment of the present invention, and faces the heating chamber 101 in the waveguide unit 103. It is a top view which shows the state formed in the pipe wall surface. In FIG. 8, as another configuration of the microwave radiating unit 104, an example of a different shape of the microwave radiating unit 104 configured by two or more linear slits (openings) and radiating circularly polarized waves is shown. ing.

As shown in FIGS. 8A to 8F, the microwave radiating portion 104 is configured by two or more linearly opened slits, and the longitudinal direction of at least one of these slits is The shape may be inclined with respect to the microwave transmission direction X. Therefore, as shown in (e) and (f) of FIG. 8, a shape in which the slits do not intersect, or a shape constituted by three slits as shown in (d) of FIG. 8 may be used.

Next, in the microwave radiating unit 104 composed of two or more slits, the microwave radiated from the waveguide unit 103 to the heating chamber 101 through the microwave radiating unit 104 is increased or decreased by increasing or decreasing the opening area of the slit. A method for adjusting the amount of wave radiation will be described.

When the length in the longitudinal direction of the slit (length L in FIG. 6) is shortened or when the length in the width direction of the slit (length S in FIG. 6) is shortened, radiation from the microwave radiation unit 104 is performed. The amount of microwave radiation is reduced. Conversely, when each length is increased, the amount of microwave radiation emitted from the microwave radiation unit 104 increases.

Therefore, when the waveguide 103 is off-center with respect to the heating chamber 101 as described above, or when the shape of the heating space formed by the inner wall surface in the heating chamber 101 is asymmetric, the object to be heated is uniform. In order to realize the heating, it is necessary to adjust the directivity of the combined wave of the microwaves radiated from all the microwave radiation units 104 in the waveguide unit 103 in accordance with each configuration. As described above, the total amount of microwaves radiated from the microwave radiation unit 104 can be changed by increasing or decreasing the respective opening areas of the microwave radiation unit 104. Therefore, it is possible to adjust the directivity of the composite wave of the microwaves radiated from all the microwave radiation units 104 in the waveguide unit 103.

For example, two microwave radiating units 104 are symmetrically arranged in regions on both sides of the central axis P parallel to the transmission direction X of the waveguide unit 103 (front region and front region), and the heating space of the heating chamber 101 Let us consider a case where the waveguide 103 is disposed at an off-center position with respect to the center point O.

In this case, if the same number of microwave radiating parts 104 having the same opening area are arranged so as to be symmetric with respect to the central axis P parallel to the transmission direction X in the waveguide part 103, the distance from the microwave generating part (for example, magnetron). Since the intensity of the microwave basically decreases with increasing distance, it is difficult to uniformly heat the object to be heated placed in the center of the heating chamber 101.

Therefore, when the central axis P parallel to the transmission direction X in the waveguide 103 is considered as a boundary, the length of the slit of the microwave radiating unit 104 disposed on the front side of the heating chamber 101 (the center side of the heating space). By making the length L in the direction and / or the length S in the width direction of the slit longer than the microwave radiation portion 104 on the back side, which is the opposite side, microwave radiation on the front side (center side) of the heating chamber 101 The amount can be increased.

FIG. 9 is a plan view showing an example in which the configuration of the microwave radiating unit 104 in the microwave heating apparatus of the second embodiment is changed. In the configuration shown in FIG. 9, a plurality of microwave radiating portions 104 that radiate circularly polarized waves are formed in the waveguide 103 in the heating chamber 101, and the waveguide 103 is off-center with respect to the heating chamber 101. It has become. As shown in the left microwave radiating unit 104 in FIG. 9, for example, the length L in the longitudinal direction of the slit of the microwave radiating unit 104 arranged on the front surface side (center side) of the heating chamber 101 is set to the back side micro wave. By making it longer (thicker) than the wave radiating unit 104, the amount of microwave radiation on the front side (center side) of the heating chamber 101 can be increased from the microwave radiating unit 104 on the back side.

Further, as shown in the right-side microwave radiating unit 104 in FIG. 9, the length S in the width direction of the slit of the microwave radiating unit 104 arranged on the front side (center side) of the heating chamber 101 is set to the back side. By making it longer (thicker) than the microwave radiating unit 104, the amount of microwave radiation on the front side (center side) of the heating chamber 101 can be increased from the microwave radiating unit 104 on the back side.

As described above, it is possible to improve the non-uniform microwave distribution in the heating chamber 101 by selecting the opening shape of the microwave radiating portion 104 to a desired shape as in the configuration shown in FIG. It becomes composition.

6 and FIG. 9 is a microwave having a shape in which the longitudinal direction of the slit is inclined by 45 ° with respect to the transmission direction X in the waveguide section 103, with the two slits shown in FIGS. The amount of microwave radiation radiated from the radiating unit 104 can be determined based on the following equation (Equation 1) for obtaining the coupling degree C of the cruciform directional coupler. Here, the degree of coupling C of the cruciform directional coupler means the microwave emissivity from the waveguide unit 103 to the heating chamber 101 through the microwave radiating unit 104.

Next, the R chamfering process and the C chamfering process performed on the microwave radiating unit 104 including two or more slits will be described with reference to FIG.

∙ Microwaves have the property of concentrating on corners and sharp points. Therefore, if there is a corner or pointed portion at the slit crossing portion A (see FIG. 6) or the slit end portion B (see FIG. 6), the electric field concentrates on that portion and heat is generated. When the electric field concentrates in this way, energy loss occurs, so that the heating efficiency of the object to be heated decreases, and ultimately the reliability of the microwave heating apparatus decreases.

Therefore, for example, as shown in FIG. 6 described above, an R chamfering process is performed at the slit intersecting portion A or the slit end portion B of the microwave radiating portion 104 configured by intersecting two linear slits. By applying the C chamfering process (the symbol T portion in FIG. 6) or the C chamfering process (the symbol T portion in FIG. 6), energy loss due to electric field concentration in the microwave radiation unit 104 can be reduced. As a result, the microwave heating apparatus having the microwave radiating unit 104 processed in this way can improve the heating efficiency for the object to be heated, and can improve the reliability of the microwave heating apparatus. It becomes.

The microwave heating apparatus according to the present invention adjusts the number, shape, and arrangement of a plurality of microwave radiating portions that radiate circularly polarized waves installed in a heating chamber, thereby adjusting an object to be heated arranged in the heating chamber. Uniform microwave heating can be realized. In addition, by forming the microwave radiating portion into a shape composed of two or more slits, the object to be heated can be uniformly micro-shaped without providing a mechanism for rotating the antenna, a mechanism for rotating the table, and a phase shifter. It becomes possible to perform wave heating, and it becomes possible to reduce the size of the power supply unit, improve the reliability, and reduce the manufacturing cost.

Since the microwave heating apparatus of the present invention can uniformly irradiate the object to be heated with microwaves, it can be effectively used for a microwave heating apparatus that performs heating processing or sterilization of food.

DESCRIPTION OF SYMBOLS 101 Heating chamber 102 Microwave generation part 103 Waveguide part 104 Microwave radiation part O The center point of the heating space in a heating chamber L The length of the slit of a microwave radiation part in the longitudinal direction S The width direction of the slit of a microwave radiation part Length (thickness)
P Central axis of transmission direction in waveguide section X Transmission direction of waveguide section Y Direction perpendicular to transmission direction and electric field direction in waveguide section (width direction)
Z Electric field direction in waveguide

Claims

A heating chamber for storing an object to be heated;
A microwave generator for generating microwaves;
A waveguide for transmitting microwaves;
A plurality of microwave radiating sections that radiate circularly polarized waves in the heating chamber,
The waveguide section is arranged so that the center point of the heating space in the heating chamber is not included on the vertical line of the central axis parallel to the transmission direction in the waveguide section,
A microwave heating apparatus configured such that a combined wave of microwaves radiated from each of the microwave radiating units has a directivity for radiating a large number of microwaves toward the center of the heating space.
The microwave heating device according to claim 1, wherein the plurality of microwave radiating portions are arranged so as to be non-axisymmetric with respect to a central axis parallel to a transmission direction in the waveguide portion.
3. The microwave according to claim 1, wherein at least one of the plurality of microwave radiating units is configured to radiate more microwaves in a specific direction than other microwave radiating units. Wave heating device.
On the surface facing the heating chamber in the waveguide section, with the central axis parallel to the transmission direction in the waveguide section as a boundary, the microwave radiating section provided in each region on both sides of the boundary is the central axis The microwave heating device according to any one of claims 1 to 3, wherein the distance from the center to the center of the microwave radiation unit is different.
A plurality of microwave radiating portions provided on both sides of the boundary, with a central axis parallel to the transmission direction in the waveguide portion, as a boundary, on the surface of the waveguide portion facing the heating chamber, is the center of the heating space. The microwave heating device according to any one of claims 1 to 4, wherein the number of the microwave radiating units closer to the point is larger than the number of the microwave radiating units on the far side.
The center point of the heating space in the plurality of microwave radiating portions provided on both sides of the boundary, with the central axis parallel to the transmission direction in the waveguide portion as a boundary, on the surface facing the heating chamber in the waveguide portion The microwave heating device according to any one of claims 1 to 5, wherein the microwave radiating portion on the side close to the surface is formed at a position of an antinode of a standing wave generated in the waveguide portion.
At least one microwave radiating portion is composed of a combination of two or more slits, and the longitudinal direction of at least one slit in the microwave radiating portion is inclined with respect to the transmission direction in the waveguide portion; The microwave according to any one of claims 1 to 6, wherein a combined wave of the microwaves radiated from all the microwave radiation units has a directivity for radiating many microwaves in a specific direction. Heating device.
8. The micro of claim 7, wherein the length of the microwave radiating portion formed of the slit in the longitudinal direction of the microwave varies depending on the transmission in the waveguide and the position in the direction orthogonal to the electric field direction. Wave heating device.
8. The micro of claim 7, wherein a length in a width direction of the microwave radiating portion configured by the slit is different depending on a position in a direction orthogonal to the transmission and electric field direction in the waveguide portion. Wave heating device.
The microwave heating apparatus according to claim 7, wherein an R chamfering process or a C chamfering process is performed on a crossing portion of the slit of the microwave radiating unit configured by a slit.
The microwave heating apparatus according to claim 7, wherein an R chamfering process or a C chamfering process is performed on a slit end portion of the microwave radiating unit configured by a slit.