Technical Field
[0001] The present invention relates to a microwave heating apparatus.
Background Art
[0002] For example, a microwave processing apparatus using a vacuum tube called a magnetron
is known as a microwave heating apparatus (see, e.g., Patent Literature 1).
[0003] Patent Literature 1 discloses a microwave processing apparatus including a heating
chamber housing an object to be heated, an oscillation source oscillating a microwave,
a placing table for placing the object, a waveguide guiding the microwave to the placing
table, and a periodic structure disposed in association with the waveguide. In the
microwave processing apparatus of Patent Literature 1, a magnetron is used as the
oscillation source.
Citation List
Patent Literature
Summary of Invention
Technical Problem
[0005] However, the microwave processing apparatus of Patent Literature 1 still has room
for improvement in controlling a heating region for heating an object to be heated.
[0006] Therefore, an object of the present invention is to solve the problem and to provide
a microwave heating apparatus capable of easily controlling a heating region for heating
an object to be heated.
Solution to Problem
[0007] To achieve the object, a microwave heating apparatus according to an aspect of the
present invention comprises:
a heating chamber housing an object to be heated;
a microwave generator including a semiconductor element and generating one or more
microwaves;
a waveguide guiding the one or more microwaves to the heating chamber;
a periodic structure including a plurality of projection parts periodically arranged
in a first direction in the waveguide to allow the one or more microwaves to propagate
in a surface wave mode;
one or more power feeding parts connected to the microwave generator and supplying
the one or more microwaves to the waveguide; and
a controller controlling a frequency of the one or more microwaves to control a heating
region for heating the object.
[0008] A microwave heating apparatus according to an aspect of the present invention comprises:
a heating chamber housing an object to be heated;
a microwave generator including a semiconductor element and generating a plurality
of microwaves;
a waveguide guiding the plurality of microwaves to the heating chamber;
a periodic structure including a plurality of projection parts periodically arranged
in a first direction in the waveguide to allow the plurality of microwaves to propagate
in a surface wave mode;
a plurality of power feeding parts connected to the microwave generator and supplying
the plurality of microwaves to the waveguide; and
a controller controlling a phase difference of the plurality of microwaves to control
a heating region for heating the object, and
the plurality of power feeding parts includes at least two power feeding parts arranged
in the first direction at a distance from each other.
Advantageous Effects of Invention
[0009] The microwave heating apparatus according to the present invention can easily control
the heating region for heating the object to be heated.
Brief Description of Drawings
[0010]
Fig. 1 is a schematic cross-sectional configuration diagram of an example of a microwave
heating apparatus according to a first embodiment of the present invention.
Fig. 2 is a diagram showing a creepage distance between a plurality of projection
parts of a periodic structure.
Fig. 3 is a control block diagram of an example of the microwave heating apparatus
according to the first embodiment of the present invention.
Fig. 4A is a view showing an analysis model used for electric field distribution analysis.
Fig. 4B is a view showing the analysis model used for the electric field distribution
analysis.
Fig. 5 is a cross-sectional view of a plane immediately under loads of the analysis
model, showing an example of a result of the electric field distribution analysis
in the case of changing an oscillation frequency of a microwave when the analysis
model shown in Figs. 4A and 4B is used.
Fig. 6A is a diagram showing a periodic structure of a modification.
Fig. 6B is a diagram showing a periodic structure of another modification.
Fig. 7 is a schematic cross-sectional configuration diagram of an example of a microwave
heating apparatus according to a second embodiment of the present invention.
Fig. 8 is a control block diagram of an example of the microwave heating apparatus
according to the second embodiment of the present invention.
Fig. 9A is a view showing an analysis model used for electric field distribution analysis.
Fig. 9B is a view showing the analysis model used for the electric field distribution
analysis.
Fig. 10 is a cross-sectional view of a plane immediately under loads of the analysis
model, showing an example of a result of the electric field distribution analysis
in the case of changing oscillation frequencies of two microwaves when the analysis
model shown in Figs. 9A and 9B is used.
Fig. 11 is a cross-sectional view of a plane immediately under loads of the analysis
model, showing an example of a result of the electric field distribution analysis
in the case of changing a phase difference of two microwaves when the analysis model
shown in Figs. 9A and 9B is used.
Fig. 12 is a schematic cross-sectional configuration diagram when an example of a
microwave heating apparatus according to a third embodiment of the present invention
is viewed in a depth direction.
Fig. 13 is a schematic cross-sectional configuration diagram when an example of the
microwave heating apparatus according to the third embodiment of the present invention
is viewed in a width direction.
Fig. 14 is a diagram showing an example of a positional relationship of four power
feeding parts of the microwave heating apparatus according to the third embodiment
of the present invention.
Fig. 15 is a control block diagram of an example of the microwave heating apparatus
according to the third embodiment of the present invention.
Fig. 16A is a view showing an analysis model used for electric field distribution
analysis.
Fig. 16B is a view showing the analysis model used for the electric field distribution
analysis.
Fig. 17 is a cross-sectional view of a plane immediately under loads of the analysis
model, showing an example of a result of the electric field distribution analysis
in the case of changing oscillation frequencies and phase differences of four microwaves
when the analysis model shown in Figs. 16A and 16B is used.
Fig. 18 is a schematic cross-sectional configuration diagram of a microwave heating
apparatus according to a modification.
Fig. 19 is a schematic configuration diagram of a periodic structure according to
a modification.
Fig. 20 is a schematic cross-sectional view of the periodic structure of Fig. 19 taken
along a line A-A.
Fig. 21 is a schematic configuration diagram of a periodic structure according to
another modification.
Fig. 22 is a schematic configuration diagram of a periodic structure according to
another modification.
Description of Embodiments
(Knowledge Underlying the Present Disclosure)
[0011] In a microwave heating apparatus, it is required to control a heating region for
heating an object to be heated. Specifically, it is required to target and heat a
desired region in a heating chamber, or to uniformly heat the entire heating chamber,
depending on an object to be heated.
[0012] For example, when two different objects to be heated are housed and heated in a heating
chamber, it is required to control a heating region so as to heat one object to be
heated without heating the other object to be heated.
[0013] However, for example, in a microwave heating apparatus as disclosed in Patent Literature
1, use of a magnetron makes it difficult to control the heating region.
[0014] A turntable system or a rotating antenna system is often employed in a microwave
heating apparatus using a magnetron. In the turntable system, a heated portion moves,
and therefore, the selective heating is difficult. Even in the case of the rotating
antenna system, the selective heating can be performed in a narrow range limited by
a shape, or particularly, a diameter of an antenna, and it is difficult to achieve
sufficient selective heating performance even within the range. Moreover, no current
power feeding system can satisfy both the selective heating performance and the uniform
heating performance that is an essential function of a microwave oven.
[0015] The present inventors found that a heating region can easily be controlled by using
a microwave generator including a semiconductor element and a periodic structure to
control frequency and/or phase difference of one or more microwaves oscillated from
the microwave generator and conceived the following invention.
[0016] A microwave heating apparatus of a first aspect of the present invention comprises:
a heating chamber housing an object to be heated;
a microwave generator including a semiconductor element and generating one or more
microwaves;
a waveguide guiding the one or more microwaves to the heating chamber;
a periodic structure including a plurality of projection parts periodically arranged
in a first direction in the waveguide to allow the one or more microwaves to propagate
in a surface wave mode;
one or more power feeding parts connected to the microwave generator and supplying
the one or more microwaves to the waveguide; and
a controller controlling a frequency of the one or more microwaves to control a heating
region for heating the object.
[0017] In a microwave heating apparatus of a second aspect of the present invention, the
one or more power feeding parts may be disposed in the periodic structure.
[0018] In a microwave heating apparatus of a third aspect of the present invention,
the microwave generator may generate a plurality of microwaves having the same frequency,
and
the plurality of power feeding parts may include at least two power feeding parts
arranged in the first direction at a distance from each other.
[0019] A microwave heating apparatus of a fourth aspect comprises:
a heating chamber housing an object to be heated;
a microwave generator including a semiconductor element and generating a plurality
of microwaves;
a waveguide guiding the plurality of microwaves to the heating chamber;
a periodic structure including a plurality of projection parts periodically arranged
in a first direction in the waveguide to allow the plurality of microwaves to propagate
in a surface wave mode;
a plurality of power feeding parts connected to the microwave generator and supplying
the plurality of microwaves to the waveguide; and
a controller controlling a phase difference of the plurality of microwaves to control
a heating region for heating the object, and
the plurality of power feeding parts includes at least two power feeding parts arranged
in the first direction at a distance from each other.
[0020] In a microwave heating apparatus of a fifth aspect of the present invention,
the controller may control frequencies of the plurality of microwaves, and
the plurality of microwaves may have the same frequency.
[0021] In a microwave heating apparatus of a sixth aspect of the present invention, the
plurality of power feeding parts may be disposed in the periodic structure.
[0022] In a microwave heating apparatus of a seventh aspect of the present invention, the
plurality of projection parts of the periodic structure may be periodically arranged
in the first direction and a second direction different from the first direction.
[0023] In a microwave heating apparatus of an eighth aspect of the present invention,
a first creepage distance between the projection parts arranged in the first direction
may be different from a second creepage distance between the projection parts arranged
in the second direction,
the first creepage distance may be a minimum distance along a surface of the periodic
structure between the adjacent projection parts arranged in the first direction, and
the second creepage distance may be a minimum distance along a surface of the periodic
structure between the adjacent projection parts arranged in the second direction.
[0024] In a microwave heating apparatus of a ninth aspect of the present invention, the
periodic structure may be disposed in at least one of bottom, upper, and side portions
of the heating chamber.
[0025] Embodiments of the present disclosure will now be described with reference to the
accompanying drawings. In the figures, elements are shown in an exaggerated manner
for ease of explanation.
(First Embodiment)
[Overall Configuration]
[0026] An example of a microwave heating apparatus according to a first embodiment of the
present invention will be described. Fig. 1 is a schematic cross-sectional configuration
diagram of an example of a microwave heating apparatus 1A according to the first embodiment
of the present invention. X, Y, and Z directions in Fig. 1 indicate a width direction,
a depth direction, and a height direction, respectively, of the microwave heating
apparatus 1A.
[0027] As shown in Fig. 1, the microwave heating apparatus 1A includes a heating chamber
10, a waveguide 11, a periodic structure 20, a microwave generator 30, a power feeding
part 40, and a controller 50. In the first embodiment, the microwave heating apparatus
1A includes the one power feeding part 40. In the microwave heating apparatus 1A,
the controller 50 controls a frequency of one microwave generated from the microwave
generator 30.
<Heating Chamber>
[0028] The heating chamber 10 has a substantially rectangular parallelepiped structure housing
an object 12 to be heated. The heating chamber 10 includes multiple wall surfaces
made of a metal material and an opening/closing door opened and closed for housing
the object 12. A placing table 13 for placing the object 12 is disposed inside the
heating chamber 10. The placing table 13 is disposed in a bottom portion of the heating
chamber 10.
<Waveguide>
[0029] The waveguide 11 is a microwave transmission path guiding the microwave into the
heating chamber 10. The waveguide 11 is disposed in the bottom portion of the heating
chamber 10. The periodic structure 20 is disposed inside the waveguide 11. In the
configuration described in the first embodiment, the microwave is supplied through
the waveguide 11 to the periodic structure 20; however, the present invention is not
limited thereto, and the microwave may be supplied in a configuration using an antenna
such that an electric field is generated between a plurality of projection parts.
<Periodic Structure>
[0030] The periodic structure 20 has a plurality of projection parts 21 periodically arranged
in a first direction (the X direction) in the waveguide 11 and propagates the microwave
in a surface wave mode. Specifically, the microwave supplied to the periodic structure
20 forms a slow wave and propagates in the surface wave mode. The microwave propagating
through the periodic structure 20 in the surface wave mode is then supplied into the
heating chamber 10.
[0031] In the first embodiment, the plurality of projection parts 21 are made up of multiple
metal plate-shaped structures arranged perpendicular to a microwave propagation direction.
The plurality of projection parts 21 are arranged in the first direction at a distance
from each other. The plurality of projection parts 21 are made up of the same plate-shaped
structures.
[0032] Specifically, the periodic structure 20 is made up of the plurality of metal plates
(the plurality of projection parts 21) extending from the waveguide 11 toward the
heating chamber 10. The periodic structure 20 is formed in the entire inside of the
waveguide 11.
[0033] A creepage distance between the plurality of projection parts 21 of the periodic
structure 20 is preferably an integral multiple of 1/4 of the wavelength of the microwave
generated from the microwave generating part 30. The creepage distance is the minimum
distance along the surface of the periodic structure 20 between the plurality of projection
parts 21.
[0034] The microwave has an antinode (maximum electric field value) and a node (minimum
electric field value/zero electric field) repeated for each quarter of the wavelength.
By setting the creepage distance between the plurality of projection parts 21 to an
integral multiple of 1/4 of the wavelength of the microwave, the same electric field
distributions can be achieved when the distributions are compared in any projections
and recesses. This is because the microwave is transmitted to adjacent projection
parts without causing a phase shift. Therefore, one food item defined as an object
to be heated can uniformly be heated. Particularly, when the creepage distance between
the plurality of projection parts 21 of the periodic structure 20 is set to an odd
multiple of 1/4 of the wavelength, bottom surfaces of recesses made of metal serve
as nodes of an electric field, and therefore, upper surfaces of the projection parts
21 serve as antinodes of the electric field, which enables highly efficient heating
in addition to uniform heating.
[0035] Fig. 2 is a diagram showing a creeping distance L1 between the plurality of projection
parts 21 of the periodic structure 20. In Fig. 2, the creepage distance L1 is highlighted
by hatching for easy understanding. As shown in Fig. 2, the creepage distance L1 is
a minimum distance along the surface of the periodic structure 20 between a first
projection part 21a and a second projection part 21b adjacent to each other. Specifically,
the creepage distance is the minimum distance from a start point that is a top of
the first projection part 21a, through a recess formed between the first projection
part 21a and the second projection part 21b, to an end point that is a top of the
second projection part 21b.
<Microwave Generator>
[0036] The microwave generator 30 is a semiconductor oscillator including a semiconductor
element and generating a microwave. The microwave generator 30 is connected to the
power feeding part 40. Specifically, the microwave output from the microwave generator
30 is supplied from the power feeding part 40 to the periodic structure 20 inside
the waveguide 11. The microwave is then propagated through the periodic structure
20 in the surface wave mode and supplied into the heating chamber 10. The microwave
generator 30 is controlled by the controller 50.
[0037] Fig. 3 shows a control block diagram of an example of the microwave heating apparatus
1A. As shown in Fig. 3, the microwave generator 30 has a frequency controller 31 and
an amplifier 32.
[0038] The frequency controller 31 oscillates the microwave from electric power supplied
from a power source 51 and controls the oscillation frequency thereof. For example,
the frequency controller 31 is a semiconductor oscillation circuit having a feedback
circuit including electronic components such as a capacitor, an inductor, and a resistor,
and a transistor. The semiconductor oscillation circuit can easily change the oscillation
frequency thereof by changing a resonance frequency of a resonance circuit included
in the feedback circuit.
[0039] The amplifier 32 amplifies the microwave output from the frequency controller 31.
For example, the amplifier 32 is an amplification circuit including a transistor etc.
[0040] The frequency controller 31, the amplifier 32, and the power source 51 are controlled
by the controller 50.
<Power feeding part>
[0041] The power feeding part 40 is connected to the microwave generator 30 to supply the
microwave output from the microwave generator 30 to the waveguide 11. The power feeding
part 40 is disposed on the waveguide 11 disposed in the bottom portion of the heating
chamber 10. In the first embodiment, the power feeding part 40 is a power feeding
port (opening) disposed in the bottom portion of the waveguide 11. The power feeding
part 40 is also disposed in the periodic structure 20. Specifically, the power feeding
part 40 is disposed between the two adjacent projection parts 21 of the periodic structure
20.
[0042] For example, the power feeding part 40 is made up of a rectangular power feeding
port as viewed from the upper side.
< Controller
[0043] The controller 50 controls the frequency of the microwave to control a heating region
for heating the object 12 to be heated. Specifically, the controller 50 controls the
frequency of the microwave by controlling the frequency controller 31 of the microwave
generator 30.
[0044] The controller 50 can control an amount of delay of the microwave propagating through
the periodic structure 20 by controlling the frequency of the microwave. As a result,
the directivity of the microwave supplied from the waveguide 11 into the heating chamber
10 can be controlled.
[0045] Regarding the elements constituting the controller 50, for example, a memory (not
shown) storing a program causing these elements to function and a processing circuit
(not shown) corresponding to a processor such as a CPU (central processing unit) may
be included so that the processor executes the program to function as these elements.
[Example of Analysis Result of Heating Control in First Embodiment]
[0046] An example of an analysis result of heating control of the microwave heating apparatus
1A will be described. For analysis of the heating control, electric field distribution
analysis was performed by using an analysis model of the microwave heating apparatus
1A. The electric field distribution analysis was performed by using COMSOL Multiphysics
(manufactured by COMSOL AB).
[0047] Figs. 4A and 4B both show an analysis model 60A used for the electric field distribution
analysis. Fig. 4A shows a view of the analysis model 60A as viewed from above. Fig.
4B shows a view of the analysis model 60A as viewed from the front. In Figs. 4A and
4B, a region on the left side of the heating chamber 10 is referred to as a first
region R1, and a region on the right side of the heating chamber 10 is referred to
as a second region R2.
[0048] As shown in Figs. 4A and 4B, the analysis model 60A includes the constituent elements
of the microwave heating apparatus 1A, and two objects 61 to be heated are placed
on the placing table 13 in the heating chamber 10. In the analysis model 60A, the
power feeding part 40 is disposed in the first region R1 on the left side of the heating
chamber 10.
[0049] The two objects 61 are respectively disposed in the left and right regions in the
heating chamber 10 at a distance from each other. Specifically, when the analysis
model 60A is viewed from above, one of the objects 61 is disposed in the first region
R1 on the left side relative to the center of the heating chamber 10, and the other
object 61 is disposed in the second region R2 on the right side relative to the center
of the heating chamber 10.
[0050] In the analysis model 60A, the heating chamber 10 is a metal conductor, and the placing
table 13 is a glass plate. For the objects (loads) 61, water and ice are used.
[0051] In the electric field distribution analysis using the analysis model 60A, the electric
field distribution in the heating chamber 10 viewed from above is examined by using
an oscillation frequency of a microwave as a parameter.
[0052] The conditions of the electric field distribution analysis using the analysis model
60A are as shown in Table 1.
[Table 1]
number of power feeding ports |
1 |
frequency |
2400-2500 MHz |
port input |
Port 1: 100 W |
boundary condition |
whole surface: Impedance Boundary (εr=µr=1, |
|
σ=1e6 [S/m]) |
physical property (relative permittivity) |
water |
ice |
glass plate |
78-j*11.7 |
8.4-j*2.1 |
4.1-j*4.51e-3 |
[0053] Port 1 in Table 1 denotes the power feeding part 40.
[0054] Fig. 5 shows a cross-sectional view of a plane immediately under the loads 61 of
the analysis model 60A as an example of a result of the electric field distribution
analysis in the case of changing the oscillation frequency of the microwave when the
analysis model 60A is used. Fig. 5 shows the analysis result when the objects 61 are
water. As shown in Fig. 5, the electric field distribution can be changed in the heating
chamber 10 by changing the oscillation frequency of the microwave.
[0055] When the oscillation frequency is 2400 MHz, the electric field is intensively formed
in a central region of the heating chamber 10. No electric field is formed near side
walls of the heating chamber 10. In other words, the microwave is intensively supplied
to the central region of the heating chamber 10. Therefore, when the oscillation frequency
is set to 2400 MHz, the heating region can intensively be formed in the center of
the heating chamber 10.
[0056] When the oscillation frequency is 2420 MHz, the electric field is intensively formed
in a left-of-center region of the heating chamber 10. No electric field is formed
in the region (the second region R2) on the right side relative to the center of the
heating chamber 10. In other words, the microwave is intensively supplied to the left-of-center
region of the heating chamber 10. Therefore, when the oscillation frequency is set
to 2420 MHz, the heating region can intensively be formed in the left-of-center region
of the heating chamber 10.
[0057] When the oscillation frequency is 2440 MHz, the electric field is intensively formed
in the left-of-center region of the heating chamber 10. The electric field is also
formed in the entire right region (the second region R2) of the heating chamber 10.
In other words, the microwave is intensively supplied to the left-of-center region
of the heating chamber 10 and is supplied in the entire right region of the heating
chamber 10. Therefore, when the oscillation frequency is set to 2440 MHz, the heating
region can intensively be formed in the left-of-center region of the heating chamber
10, and the heating region can be formed in the entire right region of the heating
chamber 10. Additionally, the heating in the left-of-center region of the heating
chamber 10 can be made stronger than the heating in the other regions.
[0058] When the oscillation frequency is 2460 MHz, the electric field is formed in the entire
heating chamber 10. In other words, the microwave is supplied to the entire heating
chamber 10. Therefore, when the oscillation frequency is set to 2440 MHz, the heating
region can be formed in the entire heating chamber 10.
[0059] When the oscillation frequency is 2480 MHz, the electric field is formed in the entire
heating chamber 10. The electric field distribution in the right region of the heating
chamber 10 is wider than the electric field distribution in the left region (the first
region R1). In other words, the microwave is supplied to the entire heating chamber
10 and is supplied to the right region more intensively than the left region. Therefore,
when the oscillation frequency is set to 2480 MHz, the heating region can be formed
wider in the right region than the left region of the heating chamber 10 while the
heating region is formed in the entire heating chamber 10.
[0060] When the oscillation frequency is 2500 MHz, the electric field is formed in the entire
heating chamber 10. The electric field is formed more intensively in the left region
than the right region of the heating chamber 10. In other words, the microwave is
supplied to the entire heating chamber 10 and is supplied more intensively to the
left region than the right region of the heating chamber 10. Therefore, when the oscillation
frequency is set to 2500 MHz, the heating in the left region of the heating chamber
10 can be made stronger than the heating in the right region while the heating region
is formed in the entire heating chamber 10.
[0061] As described above, by adjusting the oscillation frequency of the microwave supplied
into the heating chamber 10, the heating region formed in the heating chamber 10 can
be changed. A heating power, i.e., a heating intensity, in the heating region can
be adjusted. Although the analysis result shown in Fig. 5 represents an example in
which the objects 61 are water, the same analysis result is obtained in an example
in which the objects 61 are ice.
[0062] The analysis result of the heating control of the microwave heating apparatus 1A
described above is an example, and the frequency band is not limited to 2400 MHz or
more and 2500 MHz or less. The heating control of the microwave heating apparatus
1A is applicable to different frequency bands. For example, the frequency band may
be set in a range of 10 MHz or more to 10 GHz or less. Even when the frequency band
is set in this way, the microwave heating apparatus 1A can control the heating region.
[Effects]
[0063] According to the microwave heating apparatus 1A of the first embodiment, the following
effects can be produced.
[0064] The microwave heating apparatus 1A supplies one microwave generated from the microwave
generator 30 to the periodic structure 20 in the waveguide 11 from the one power feeding
part 40. Since the microwave generator 30 includes a semiconductor element, the controller
50 can easily control the frequency of the microwave. With such a configuration, the
directivity of the microwave supplied from the waveguide 11 into the heating chamber
10 can be controlled. As a result, the heating region for heating the object 12 to
be heated can easily be controlled.
[0065] According to the microwave heating apparatus 1A, a desired region can be targeted
and heated by controlling the frequency of the microwave. For example, the left region
of the heating chamber 10 can be targeted and heated, or the central region can be
targeted and heated. The microwave heating apparatus 1A can also uniformly heat the
entire heating chamber 10 by controlling the frequency of the microwave. The microwave
heating apparatus 1A can also control the heating intensity (heating power) in the
heating region by controlling the frequency of the microwave.
[0066] According to the microwave heating apparatus 1A, the heating of the object 12 to
be heated can be adjusted depending on a state of the object 12. For example, when
the microwave heating apparatus 1A includes a temperature detector detecting the temperature
of the object 12, the controller 50 controls the frequency of the microwave oscillated
from the microwave generator 30 based on the temperature detected by the temperature
detector. As a result, the heating region and/or the heating intensity in the heating
region can be controlled depending on the temperature of the object 12. Consequently,
the heating of the object 12 can be adjusted.
[0067] According to the microwave heating apparatus 1A, the object 12 can be recognized
by an image sensor, and the frequency of the microwave can be controlled depending
on the object 12 which is recognized by the image sensor.
[0068] According to the microwave heating apparatus 1A, the power feeding part 40 is disposed
in the periodic structure 20. With such a configuration, the microwave supplied from
the power feeding part 40 can easily propagate through the periodic structure 20,
and the heating region can more easily be controlled. In other words, the direction
of the microwave can more easily be controlled.
[0069] In the example described in the first embodiment, the plurality of projection parts
21 constituting the periodic structure 20 are arranged in the first direction (X direction);
however, the present invention is not limited thereto. For example, the plurality
of projection parts 21 may be arranged in the Y direction.
[0070] Alternatively, the plurality of projection parts 21 may be arranged in the first
direction (X direction) and a second direction (the Y direction) different from the
first direction. In this case, the plurality of projection parts 21 may be made up
of multiple columnar members, multiple square members, or a combination thereof.
[0071] Although the periodic structure 20 has a configuration in which the multiple metal
plate-shaped structures (the plurality of projection parts 21) are arranged in the
described example, the present invention is not limited thereto. Figs. 6A and 6B respectively
show periodic structures 20a, 20b of modifications. As shown in Fig. 6A, for example,
a periodic structure 20a may be made up of a corrugated plate obtained by processing
a single plate. Specifically, a single plate may be processed into a wavy shape to
form the plurality of projection parts 21. Alternatively, as shown in Fig. 6B, for
example, a periodic structure 20b may be made up of a convex-concave plate (press
plate). Specifically, the plurality of projection parts 21 may be formed by pressing
a single plate. With such a configuration, a reduction in manufacturing cost, a reduction
of material, and an improvement in assemblability of the periodic structure can be
expected.
[0072] By changing the shape of the periodic structure 20 as described above, the direction
of the microwave can finely be controlled. As a result, the directivity of the microwave
can be improved. Consequently, the control of the heating region is further facilitated,
and heating patterns can be increased.
[0073] In the example described in the first embodiment, the periodic structure 20 is disposed
in the bottom portion of the heating chamber 10; however, the present invention is
not limited thereto. For example, the periodic structure 20 may be disposed in at
least one of bottom, upper, and side portions of the heating chamber 10. In this case,
the waveguide 11 is also disposed in at least one of bottom, upper, and side portions
of the heating chamber 10.
[0074] In the example described in the first embodiment, the microwave heating apparatus
1A includes the microwave generator 30 generating one microwave and the one power
feeding part 40; however, the present invention is not limited thereto. For example,
the microwave generator 30 may have a configuration generating a plurality of microwaves.
Additionally, a plurality of microwaves may be supplied into the waveguide 11 by multiple
power feeding parts 40.
[0075] In this case, the plurality of microwaves generated from the microwave generator
30 may have the same frequency. For example, the microwave generator 30 may have a
distributor distributing the output from the frequency controller 31. As a result,
the microwave output from the frequency controller 31 can be distributed in the microwave
generator 30 to generate a plurality of microwaves. Consequently, the number of components
can be reduced to achieve cost reduction and space saving.
[0076] At least two power feeding parts of the multiple power feeding parts 40 may be arranged
side by side at a distance from each other in the first direction (X direction) in
which the plurality of projection parts 21 of the periodic structure 20 are arranged.
With such a configuration, the microwave supplied from the power feeding part 40 propagates
through the periodic structure 20 in a direction crossing the direction of arrangement
of the plurality of projection parts 21. As a result, the microwave output from the
power feeding part 40 easily propagates through the periodic structure 20 in the surface
wave mode.
[0077] In the example described in the first embodiment, the power feeding part 40 is disposed
in the periodic structure 20; however, the present invention is not limited thereto.
The power feeding part 40 may not be disposed in the periodic structure 20. The power
feeding part 40 may be arranged at a position where the microwave output from the
power feeding part 40 can propagate through the periodic structure 20.
[0078] In the example described in the first embodiment, the power feeding part 40 is made
up of a rectangular power feeding port when viewed from above, for example; however,
the present invention is not limited thereto. For example, the shape of the power
feeding part 40 may be circular, elliptic, or polygonal.
(Second Embodiment)
[0079] A microwave heating apparatus according to a second embodiment of the present invention
will be described. In the second embodiment, differences from the first embodiment
will mainly be described. In the second embodiment, the same or equivalent constituent
elements as the first embodiment are denoted by the same reference numerals. In the
second embodiment, description overlapping with the first embodiment will not be made.
[0080] Fig. 7 shows a schematic cross-sectional configuration diagram of an example of a
microwave heating apparatus 1B according to the second embodiment of the present invention.
Fig. 8 shows a control block diagram of an example of the microwave heating apparatus
1B. As shown in Figs. 7 and 8, the second embodiment is different from the first embodiment
in that two power feeding parts 40a, 40b are included, that a microwave generator
30a generates two microwaves, and that the controller 50 controls a phase difference
of two microwaves.
<Power feeding part>
[0081] The microwave heating apparatus 1B has the two power feeding parts 40a, 40b as multiple
power feeding parts. The two power feeding parts 40a, 40b are arranged at a distance
from each other in a direction in which the plurality of projection parts 21 of the
periodic structure 20 are arranged. In the second embodiment, the power feeding parts
are arranged in the first direction (X direction) at a distance from each other with
the central region of the heating chamber 10 interposed therebetween.
[0082] In this description, when the microwave heating apparatus 1B is viewed in the depth
direction (Y direction), the power feeding part 40a disposed in a region on the left
side relative to the center of the heating chamber 10 is referred to as the first
power feeding part 40a, and the power feeding part 40b disposed in a region on the
right side is referred to as the second power feeding part 40b.
[0083] The first power feeding part 40a and the second power feeding part 40b are disposed
in the bottom portion of the waveguide 11. Specifically, the first power feeding part
40a and the second power feeding part 40b are disposed in the periodic structure 20
disposed inside the waveguide 11. The first power feeding part 40a and the second
power feeding part 40b are connected to the microwave generator 30a. In the second
embodiment, the first power feeding part 40a and the second power feeding part 40b
have the same shape as the power feeding part 40 of the first embodiment.
<Microwave generator>
[0084] The microwave generator 30a is a semiconductor oscillator including a semiconductor
element and generating two microwaves. The microwave generator 30a supplies a microwave
to each of the first power feeding part 40a and the second power feeding part 40b.
[0085] In this description, the microwave supplied to the first power feeding part 40a is
referred to as a first microwave, and the microwave supplied to the second power feeding
part 40b is referred to as a second microwave.
[0086] As shown in Fig. 8, the microwave generator 30a includes the frequency controller
31, a distributor 33, a first phase controller 34a, a first amplifier 32a, a second
phase controller 34b, and a second amplifier 32b. In the second embodiment, the first
amplifier 32a and the second amplifier 32b have the same configuration as the amplifier
32 of the first embodiment. These elements constituting the microwave generator 30a
are controlled by the controller 50.
[0087] The microwave generated by the frequency controller 31 is distributed by the distributor
33 into the first microwave and the second microwave. The first microwave is supplied
to the first phase controller 34a, and the second microwave is supplied to the second
phase controller 34b. Since the microwave generated by the frequency controller 31
is distributed into the first microwave and the second microwave by the distributor
33, the frequency of the first microwave and the frequency of the second microwave
are the same. In other words, the microwave generator 30a generates the plurality
of microwaves having the same frequency.
[0088] The first phase controller 34a controls the phase of the first microwave. The second
phase controller 34b controls the phase of the second microwave. Specifically, the
first phase controller 34a and the second phase controller 34b are controlled by the
controller 50. The controller 50 controls the first phase controller 34a and the second
phase controller 34b to set a phase difference between the first microwave and the
second microwave.
[0089] The first microwave having the phase set by the first phase controller 34a is supplied
to the first amplifier 32a. The first microwave is amplified by the first amplifier
32a and then supplied from the first power feeding part 40a to the periodic structure
20 inside the waveguide 11.
[0090] The second microwave having the phase set by the second phase controller 34b is supplied
to the second amplifier 32b. The second microwave is amplified by the second amplifier
32b and then supplied from the second power feeding part 40b to the periodic structure
20 inside the waveguide 11.
[0091] As described above, in the second embodiment, the controller 50 causes the microwave
generator 30a to generate two microwaves and controls the phase difference in addition
to the frequency of the two microwaves.
[Example of Analysis Result of Heating Control in Second Embodiment]
[0092] An example of an analysis result of heating control of the microwave heating apparatus
1B will be described. For analysis of the heating control, electric field distribution
analysis was performed by using an analysis model of the microwave heating apparatus
1B. The electric field distribution analysis was performed by using COMSOL Multiphysics
(manufactured by COMSOL AB).
[0093] Figs. 9A and 9B both show an analysis model 60B used for the electric field distribution
analysis. Fig. 9A shows a view of the analysis model 60B as viewed from above. Fig.
9B shows a view of the analysis model 60B as viewed from the front. In Figs. 9A and
9B, the left region of the heating chamber 10 is referred to as the first region R1,
and the right region of the heating chamber 10 is referred to as the second region
R2.
[0094] As shown in Figs. 9A and 9B, the analysis model 60B includes the constituent elements
of the microwave heating apparatus 1B, and the two objects 61 are placed on the placing
table 13 in the heating chamber 10. The analysis model 60B is different from the analysis
model 60A of the first embodiment (see Figs. 4A and 4B) in that the two power feeding
parts 40a, 40b are included. Specifically, the analysis model 60B has the first power
feeding part 40a disposed in the first region R1 on the left side of the heating chamber
10 and the second power feeding part 40b disposed in the second region R2 on the right
side of the heating chamber 10. In the second embodiment, when the analysis model
60B is viewed from above, the first power feeding part 40a and the second power feeding
part 40b are arranged at positions symmetrical to each other about the center in a
left-right direction of the heating chamber 10.
[0095] The other configurations of the analysis model 60B are the same as those of the analysis
model 60A.
[0096] In the electric field distribution analysis using the analysis model 60B, the electric
field distribution in the heating chamber 10 viewed from above is examined by using
the oscillation frequency and the phase difference of the first microwave and the
second microwave as parameters.
[0097] The conditions of the electric field distribution analysis using the analysis model
60B are as shown in Table 2.
[Table 2]
number of power feeding ports |
2 |
frequency |
2400-2500 MHz |
port input |
Port 1: 100 W, Port 2: 100 W |
phase difference (from Port 1) |
0-180 deg. (90 deg. step) |
boundary condition |
whole surface: Impedance Boundary (εr=µr=1, σ=1e6 [S/m]) |
physical property (relative permittivity) |
water |
ice |
glass plate |
78-j*11.7 |
8.4-j*2.1 |
4.1-j*4.51e-3 |
[0098] In Table 2, Port 1 denotes the first power feeding part 40a, and Port 2 denotes the
second power feeding part 40b.
[0099] Fig. 10 shows a cross section of a plane immediately under the loads 61 of the analysis
model 60B as an example of a result of the electric field distribution analysis in
the case of changing the oscillation frequencies of the two microwaves when the analysis
model 60B is used. Fig. 10 shows the analysis result when the objects 61 are water.
[0100] As shown in Fig. 10, the electric field distribution can be changed in the heating
chamber 10 by changing the oscillation frequencies of the first microwave and the
second microwave supplied respectively from the first power feeding part 40a and the
second power feeding part 40b. The first microwave and the second microwave have the
same oscillation frequency.
[0101] When the oscillation frequency is 2400 MHz, the electric field is intensively formed
in the center of the heating chamber 10. No electric field is formed near the side
walls of the heating chamber 10. In other words, the microwaves are intensively supplied
to the center of the heating chamber 10. Therefore, when the oscillation frequency
is set to 2400 MHz, the heating region can intensively be formed in the center of
the heating chamber 10.
[0102] When the oscillation frequency is 2440 MHz, the electric field is intensively formed
in the center of the heating chamber 10, and the electric field is also formed in
the left region and the right region. In other words, the microwaves are supplied
to the almost entire heating chamber 10 and are intensively supplied to the central
region of the heating chamber. Therefore, when the oscillation frequency is set to
2440 MHz, the heating in the central region of the heating chamber 10 can be made
stronger than the heating in the other regions while the heating region is formed
in the entire heating chamber 10.
[0103] When the oscillation frequency is 2500 MHz, the electric field is uniformly formed
in the entire heating chamber 10. In other words, the microwaves are uniformly supplied
to the entire heating chamber 10. In other words, the microwaves are uniformly supplied
to the entire heating chamber 10. Therefore, when the oscillation frequency is set
to 2500 MHz, the heating region can be formed in the entire heating chamber 10 to
uniformly heat the entire heating chamber 10.
[0104] As described above, in the second embodiment, the heating region formed in the heating
chamber 10 can be changed by controlling the oscillation frequencies of the two microwaves
supplied into the heating chamber 10, as in the first embodiment.
[0105] Fig. 11 shows a cross section of a plane immediately under the loads of the analysis
model 60B as an example of a result of the electric field distribution analysis in
the case of changing the phase difference of the two microwaves when the analysis
model 60B is used. Fig. 11 shows the analysis result when the objects 61 are water.
[0106] In the electric field distribution analysis shown in Fig. 11, the phase difference
between the first microwave wave and the second microwave is set by adjusting the
phase of the second microwave output from the second power feeding part 40b with respect
to the first microwave output from the first power feeding part 40a.
[0107] As shown in Fig. 11, the electric field distribution can be changed in the heating
chamber 10 by changing the phase difference between the first microwave and the second
microwave supplied respectively from the first power feeding part 40a and the second
power feeding part 40b. The oscillation frequencies of the first microwave and the
second microwave were set to 2500 MHz.
[0108] When the phase difference is 0 degree, the electric field is uniformly formed in
the entire heating chamber 10. In other words, the microwaves are uniformly supplied
to the entire heating chamber 10. In other words, the microwaves are uniformly supplied
to the entire heating chamber 10. Therefore, when the phase difference is set to 0
degree, the heating region can be formed in the entire heating chamber 10 to uniformly
heat the entire heating chamber 10.
[0109] When the phase difference is 90 degree, the electric field is formed more intensively
in the left region than the right region of the heating chamber 10. In other words,
the microwaves are supplied more intensively to the left region than the right region
of the heating chamber 10. Therefore, when the phase difference is set to 90 degree,
the heating region can intensively be formed on the left region as compared to the
right region of the heating chamber 10.
[0110] When the phase difference is 180 degree, the electric field is uniformly formed in
the entire heating chamber 10. In other words, the microwaves are uniformly supplied
to the entire heating chamber 10. Therefore, when the phase difference is set to 180
degree, the heating region can be formed in the entire heating chamber 10 to uniformly
heat the entire heating chamber 10.
[0111] In the second embodiment, the first power feeding part 40a and the second power feeding
part 40b are arranged at positions left-right-symmetrical to each other when the analysis
model 60B is viewed from above. Therefore, although not shown in Fig. 11, when the
phase difference is 270 degree, the electric field distribution is left and right
reversed as compared to when the phase difference is 90 degree. Specifically, when
the phase difference is 270 degree, the electric field is formed more intensively
in the right region than the left region of the heating chamber 10. In other words,
the microwaves are supplied more intensively to the right region than the left region
of the heating chamber 10. Therefore, when the phase difference is set to 270 degree,
the heating region can intensively be formed on the right region as compared to the
left region of the heating chamber 10.
[0112] As described above, the heating region formed in the heating chamber 10 can be changed
by controlling the phase difference of the two microwaves supplied into the heating
chamber 10.
[0113] Although the analysis result shown in Figs. 10 and 11 represents an example in which
the objects to be heated 61 are water, the same analysis result is obtained in an
example in which the objects 61 are ice.
[0114] The analysis result of the heating control of the microwave heating apparatus 1B
described above is an example, and the frequency band is not limited to 2400 MHz or
more and 2500 MHz or less. The heating control of the microwave heating apparatus
1B is applicable to different frequency bands. For example, the frequency band may
be set in a range of 10 MHz or more to 10 GHz or less. The phase difference is not
limited to 90 degree, 180 degree, and 270 degree. For example, the phase difference
may be set in a range of 0 degree to 360 degree. Even when the frequency band and/or
the phase difference are set in this way, the microwave heating apparatus 1B can control
the heating region.
[Effects]
[0115] According to the microwave heating apparatus 1B of the second embodiment, the following
effects can be produced.
[0116] The microwave heating apparatus 1B supplies two microwaves generated from the microwave
generator 30 to the periodic structure 20 in the waveguide 11 from the two power feeding
parts 40. In the microwave heating apparatus 1B, the controller 50 controls the frequencies
and the phase difference of the two microwaves generated from the microwave generator
30. With such a configuration, the directivity of the two microwaves supplied into
the heating chamber 10 can be controlled. As a result, the microwave heating apparatus
1B can more finely control the heating region for heating the object 12.
[0117] The controller 50 can control various heating patterns by combining the frequencies
and the phase difference of the two microwaves. For example, the controller 50 can
easily create multiple heating patterns for targeting and heating desired regions
such as the left side, the right side, the center, and the whole of the heating chamber
10. The intensity of the heating power for heating the heating region can also easily
be adjusted.
[0118] In the example described in the second embodiment, the controller 50 controls the
frequencies and the phase difference of the two microwaves; however, the present invention
is not limited thereto. For example, the controller 50 may control the phase difference
without controlling the frequencies of the two microwaves. Even in this case, the
directivity of the microwaves supplied into the heating chamber 10 can be controlled,
and the heating region can be controlled.
[0119] In the example described in the second embodiment, the microwave heating apparatus
1B includes the microwave generator 30a generating two microwaves and the two power
feeding parts 40a, 40b; however, the present invention is not limited thereto. For
example, the microwave generator 30a may have a configuration generating two or more
microwaves. Additionally, two or more microwaves may be supplied into the heating
chamber 10 by two or more power feeding parts.
[0120] In the example described in the second embodiment, the first power feeding part 40a
and the second power feeding part 40b are arranged in the first direction (X direction);
however, the present invention is not limited thereto. For example, the power feeding
parts may be arranged in the second direction (Y direction) different from the first
direction. In this case, the plurality of projection parts 21 of the periodic structure
20 may periodically be arranged in the second direction. Even in such a configuration,
the heating region can be controlled.
[0121] In the example described in the second embodiment, the microwave generator 30a includes
the one frequency controller 31; however, the present invention is not limited thereto.
For example, the microwave generator 30a may include multiple frequency controllers
31. With such a configuration, the respective oscillation frequencies of the plurality
of microwaves can be controlled.
(Third Embodiment)
[0122] A microwave heating apparatus according to a second embodiment of the present invention
will be described. In the second embodiment, differences from the first embodiment
will mainly be described. In the third embodiment, the same or equivalent constituent
elements as the first and second embodiments are denoted by the same reference numerals.
In the third embodiment, description overlapping with the first and second embodiments
will not be made.
[0123] Fig. 12 is a schematic cross-sectional configuration diagram when an example of the
microwave heating apparatus 1C according to the third embodiment of the present invention
is viewed in the depth direction. Fig. 13 is a schematic cross-sectional configuration
diagram when an example of the microwave heating apparatus 1C is viewed in the width
direction. Fig. 14 is a diagram showing a positional relationship of four power feeding
parts 40a, 40b, 40c, 40d of the microwave heating apparatus 1C. Fig. 15 shows a control
block diagram of an example of the microwave heating apparatus 1C.
[0124] As shown in Figs. 12 to 15, the third embodiment is different from the first and
second embodiments in that the four power feeding parts 40a, 40b, 40c, 40d are included,
that a microwave generator 30b generates four microwaves, that a periodic structure
20c is made up of a plurality of projection parts 21c periodically arranged in the
first direction (X direction) and the second direction (Y direction), and that the
controller 50 controls frequencies and phase differences of four microwaves.
<Power feeding part>
[0125] As shown in Figs. 12 to 15, the microwave heating apparatus 1C has the four power
feeding parts 40a, 40b, 40c, 40d as multiple power feeding parts. As shown in Fig.
14, the two power feeding parts 40a, 40b are arranged in the first direction (X direction)
at a distance from each other. The remaining two power feeding parts 40c, 40d are
arranged in the second direction (Y direction) different from the first direction
at a distance from each other.
[0126] In this description, when the microwave heating apparatus 1C is viewed in the height
direction (Z direction), the power feeding part 40a disposed on the left side in the
first direction (X direction) is referred to as the first power feeding part 40a,
and the power feeding part 40b disposed on the right side is referred to as the second
power feeding part 40b. The power feeding part 40c disposed on the lower side (front
side) in the second direction (Y direction) is referred to as the third power feeding
part 40c, and the power feeding part 40d disposed on the upper side (rear side) is
referred to as the fourth power feeding part 40d.
[0127] The four power feeding parts 40a, 40b, 40c, 40d are disposed in the bottom portion
of the heating chamber 10. Specifically, the four power feeding parts 40a, 40b, 40c,
40d are disposed in the periodic structure 20c disposed in the bottom portion of the
heating chamber 10. The four power feeding parts 40a, 40b, 40c, 40 are connected to
the microwave generator 30b. In the third embodiment, the four power feeding parts
40a, 40b, 40c, 40d have the same shape.
<Periodic Structure>
[0128] The periodic structure 20c is made up of the plurality of projection parts 21c periodically
arranged in the first direction (X direction) and the second direction (Y direction)
different from the first direction. Specifically, the plurality of projection parts
21c are multiple columnar projection members extending in the height direction (Z
direction) and periodically arranged in the first and second directions. The four
power feeding parts 40a, 40b, 40c, 40d are arranged between the plurality of projection
parts 21c.
<Microwave generator>
[0129] The microwave generator 30b is a semiconductor oscillator including a semiconductor
element and generating four microwaves. The microwave generator 30b supplies a microwave
to each of the four power feeding parts 40a, 40b, 40c, 40d.
[0130] In this description, the microwaves respectively supplied to the first power feeding
part 40a, the second power feeding part 40b, the third power feeding part 40c, and
the fourth power feeding part 40d are referred to as a first microwave, a second microwave,
a third microwave, and a fourth microwave.
[0131] As shown in Fig. 15, the microwave generator 30b includes the frequency controller
31, three distribution parts 33a, 33b, 33c, four phase controllers 34a, 34b, 34c,
34d, and four amplifiers 32a, 32b, 32c, 32d. In the second embodiment, the distribution
parts 33a, 33b, 33c each have the same configuration as the distribution part 33 of
the second embodiment. The four amplifiers 32a, 32b, 32c, 32d each have the same configuration
as the amplifier 32 of the first embodiment. These elements constituting the microwave
generator 30b are controlled by the controller 50.
[0132] In this description, the three distributors 33a, 33b, 33c are respectively referred
to as the first distributor 33a, the second distributor 33b, and the third distributor
33c. The four phase controllers 34a, 34b, 34c, 34d are respectively referred to as
the first phase controller 34a, the second phase controller 34b, the third phase controller
34c, and the fourth phase controller 34d. The four amplifiers 32a, 32b, 32c, 32d are
respectively referred to as the first amplifier 32a, the second amplifier 32b, the
third amplifier 32c, and the fourth amplifier 32d.
[0133] The microwave oscillated by the frequency controller 31 is distributed by the three
distributors 33a, 33b, 33c into four microwaves. Specifically, the microwave oscillated
by the frequency controller 31 is distributed by the first distributor 33a into two
microwaves.
[0134] One of the microwaves distributed by the first distributor 33a is supplied to the
second distributor 33b and is distributed by the second distributor 33b into the first
microwave and the second microwave. The other microwave distributed by the first distributor
33a is supplied to the third distributor 33c and is distributed by the third distributor
33c into the third microwave and the fourth microwave.
[0135] The first microwave, the second microwave, the third microwave, and the fourth microwave
are supplied to the first phase controller 34a, the second phase controller 34b, the
third phase controller 34c, and the fourth phase controller 34d, respectively. Since
the microwave generated by the frequency controller 31 is distributed by the three
distributors 33a, 33b, 33c into the four microwaves, the four microwaves have the
same frequency.
[0136] The four phase controllers 34a, 34b, 34c, 34d each control the phase of the supplied
microwave. Specifically, the four phase controllers 34a, 34b, 34c, 34d are controlled
by the controller 50. The controller 50 controls the four phase controllers 34a, 34b,
34c, 34d to set the phase differences of the four microwaves.
[0137] The four microwaves having the phase set by the four phase controllers 34a, 34b,
34c, 34d are supplied to the four amplifiers 32a, 32b, 32c, 32d, respectively. The
four microwaves are respectively amplified by the four amplifiers 32a, 32b, 32c, 32d
and then supplied from the four power feeding parts 40a, 40b, 40c, 40d to the periodic
structure 20c.
[0138] As described above, in the third embodiment, the microwave generator 30b oscillates
the four microwaves and controls the frequencies and the phase differences of the
four microwaves.
[Example of Analysis Result of Heating Control in Third Embodiment]
[0139] An example of an analysis result of heating control of the microwave heating apparatus
1C will be described. For analysis of the heating control, electric field distribution
analysis was performed by using an analysis model of the microwave heating apparatus
1C. The electric field distribution analysis was performed by using COMSOL Multiphysics
(manufactured by COMSOL AB).
[0140] Figs. 16A and 16B both show an analysis model 60C used for the electric field distribution
analysis. Fig. 16A shows a view of the analysis model 60C as viewed from above. Fig.
16B shows a view of the analysis model 60C as viewed from the front. In Figs. 16A
and 16B, when the heating chamber 10 is viewed from above, the left region, the right
region, the lower (front) region, and the upper (rear) region of the heating chamber
10 are referred to as a first region R1, a second region R2, a third region R3, and
a fourth region R4, respectively.
[0141] As shown in Figs. 16A and 16B, the analysis model 60C includes the constituent elements
of the microwave heating apparatus 1C, and the two objects61 are placed on the placing
table 13 in the heating chamber 10. The analysis model 60C is different from the analysis
model 60A of the first embodiment (see Figs. 4A and 4B) and the analysis model 60B
of the second embodiment (see Figs. 9A and 9B) in that the four power feeding parts
40a, 40b, 40c, 40d are included. Specifically, the analysis model 60C has the first
power feeding part 40a, the second power feeding part 40b, the third power feeding
part 40c, and the fourth power feeding part 40d disposed in the first region R1, the
second region R2, the third region R3, and the fourth region R4, respectively, of
the heating chamber 10. In the third embodiment, when the analysis model 60C is viewed
from above, the first power feeding part 40a and the second power feeding part 40b
are arranged at positions symmetrical to each other about the center in the left-right
direction of the heating chamber 10. When the analysis model 60C is viewed from above,
the third power feeding part 40c and the fourth power feeding part 40d are arranged
at positions symmetrical to each other about the center in the depth direction of
the heating chamber 10.
[0142] The analysis model 60C is different from the analysis model 60A and the analysis
model 60B in that the periodic structure 20c is made up of the plurality of projection
parts 21c periodically arranged in the first direction (X direction) and the second
direction (Y direction).
[0143] The other configurations of the analysis model 60C are the same as those of the analysis
model 60A and the analysis model 60B.
[0144] In the electric field distribution analysis using the analysis model 60C, the electric
field distribution in the heating chamber 10 viewed from above is examined by using
the oscillation frequencies and the phase differences of the four microwaves as parameters.
[0145] The conditions of the electric field distribution analysis using the analysis model
60C are as shown in Table 3.
[Table 3]
number of power feeding ports |
4 |
frequency |
2400-2500 MHz |
port input |
Port 1: 100 W, Port 2: 100 W, Port 3: 100 W, Port 4: 100 W |
phase difference (from Port 1) |
0-180 deg. (90 deg. step) |
boundary condition |
whole surface: Impedance Boundary (εr=µr=1, σ=1e6 [S/m]) |
physical property (relative permittivity) |
water |
ice |
glass plate |
78-j*11.7 |
8.4-j*2.1 |
4.1-j*4.51e-3 |
[0146] Port1, Port2, Port3, and Port4 in Table 3 denote the first power feeding part 40a,
the second power feeding part 40b, the third power feeding part 40c, and the fourth
power feeding part 40d, respectively.
[0147] Fig. 17 shows a cross section of a plane immediately under the loads 61 of the analysis
model 60C as an example of a result of the electric field distribution analysis in
the case of changing the oscillation frequencies and the phase differences of the
four microwaves when the analysis model 60C is used. Fig. 17 shows the analysis result
when the objects 61 are water.
[0148] In the electric field distribution analysis shown in Fig. 17, the phase differences
are set by adjusting the phases of the second microwave, the third microwave, the
fourth microwave output from the second power feeding part 40b, the third power feeding
part 40c, and the fourth power feeding part 40d, respectively, with respect to the
first microwave output from the first power feeding part 40a.
[0149] In an example of setting of the phase differences used in the electric field distribution
analysis shown in Fig. 17, the phase difference between the first microwave and the
second microwave was set to 90 degree, the phase difference between the first microwave
and the third microwave was set to 0 degree, and the phase difference between the
first microwave and the fourth microwave was set to 90 degree. This setting condition
is referred to as a phase difference condition 1. In another example of setting of
the phase differences used in the electric field distribution analysis shown in Fig.
17, the phase difference between the first microwave and the second microwave was
set to 180 degree, the phase difference between the first microwave and the third
microwave was set to 0 degree, and the phase difference between the first microwave
and the fourth microwave was set to 180 degree. This setting condition is referred
to as a phase difference condition 2.
[0150] In the electric field distribution analysis shown in Fig. 17, the electric field
distribution in the heating chamber 10 is analyzed by changing the oscillation frequencies
of the four microwaves under the phase difference conditions 1 and 2. The first microwave,
the second microwave, the third microwave, and the fourth microwave have the same
oscillation frequency.
[0151] As shown in Fig. 17, the electric field distribution can be changed in the heating
chamber 10 by changing the oscillation frequency and the phase differences of the
first microwave, the second microwave, the third microwave, and the fourth microwave
supplied respectively from the four power feeding parts 40a, 40b, 40c, 40d.
[0152] When the oscillation frequency is 2480 MHz and 2490 MHz under the phase difference
condition 1, the electric field is intensively formed on the left region as compared
to the right region of the heating chamber 10. In other words, the microwaves are
intensively supplied to the left region of the heating chamber 10. Therefore, when
the oscillation frequency is set to 2480 MHz and 2490 MHz under the phase difference
condition 1, the heating region can intensively be formed on the left region of the
heating chamber 10. Additionally, the heating of the left region of the heating chamber
10 can be made stronger than the heating of the right region.
[0153] In the phase difference condition 2, when the oscillation frequency is 2400 MHz,
2410 MHz, and 2420 MHz, the electric field is uniformly formed in the entire heating
chamber 10. In other words, the microwaves are uniformly supplied to the entire heating
chamber 10. Therefore, when the oscillation frequency is set to 2400 MHz, 2410 MHz,
and 2420 MHz under the phase difference condition 2, the heating region can be formed
in the entire heating chamber 10 to uniformly heat the entire heating chamber 10.
[0154] When the oscillation frequency is 2440 MHz under the phase difference condition 2,
the electric field is intensively formed in the central region of the heating chamber
10. In other words, the microwaves are intensively supplied to the center of the heating
chamber 10. Therefore, when the oscillation frequency is set to 2440 MHz under the
phase difference condition 2, the heating region can intensively be formed in the
center of the heating chamber 10. The heating in the central region of the heating
chamber 10 can be made stronger than the heating in the other regions.
[0155] In the third embodiment, when the analysis model 60C is viewed from above, the first
power feeding part 40a and the second power feeding part 40b are arranged at positions
symmetrical to each other about the center in a left-right direction of the heating
chamber 10. The third power feeding part 40c and the fourth power feeding part 40d
are arranged at positions symmetrical to each other about the center in the depth
direction of the heating chamber 10 when the analysis model 60C is viewed from above.
Therefore, although not shown in Fig. 17, when the phase differences are set to 270
degree between the first microwave and the second microwave, to 0 degree between the
first microwave and the third microwave, and to 270 degree between the first microwave
and the fourth microwave for a phase difference condition 3, the electric field distribution
under the phase difference condition 3 is the distribution inverse to the electric
field distribution under the phase difference condition 1. Specifically, when the
oscillation frequency is 2480 MHz and 2490 MHz under the phase difference condition
3, the electric field is intensively formed on the right region as compared to the
left region of the heating chamber 10. In other words, the microwaves are intensively
supplied to the right region of the heating chamber 10. Therefore, when the oscillation
frequency is set to 2480 MHz and 2490 MHz under the phase difference condition 3,
the heating region can intensively be formed on the right region of the heating chamber
10. Additionally, the heating of the right region of the heating chamber 10 can be
made stronger than the heating of the left region.
[0156] As described above, in the third embodiment, the heating region formed in the heating
chamber 10 can be controlled by controlling the oscillation frequencies and the phase
differences of the four microwaves supplied into the heating chamber 10, as in the
first and second embodiments. Although the analysis result shown in Fig. 17 represents
an example in which the objects to be heated 61 are water, the same analysis result
is obtained in an example in which the objects61 are ice.
[0157] The analysis result of the heating control of the microwave heating apparatus 1C
described above is an example, and the frequency band is not limited to 2400 MHz or
more and 2500 MHz or less. The heating control of the microwave heating apparatus
1C is applicable to different frequency bands. For example, the frequency band may
be set in a range of 10 MHz or more to 10 GHz or less. The phase difference is not
limited to 90 degree, 180 degree, and 270 degree. For example, the phase difference
may be set in a range of 0 degree to 360 degree. Even when the frequency band and/or
the phase difference are set in this way, the microwave heating apparatus 1C can control
the heating region.
[Effects]
[0158] According to the microwave heating apparatus 1C of the third embodiment, the following
effects can be produced.
[0159] The microwave heating apparatus 1C supplies four microwaves generated from the microwave
generator 30b to the periodic structure 20c from the four power feeding parts 40a,
40b, 40c, 40d. In the microwave heating apparatus 1C, the controller 50 controls the
frequencies and the phase differences of the four microwaves generated from the microwave
generator 30. With such a configuration, the directivity of the four microwaves supplied
into the heating chamber 10 can be controlled. As a result, the microwave heating
apparatus 1C can more finely control the heating region for heating the object 12.
[0160] The controller 50 can control various heating patterns by combining the frequencies
and the phase differences of the four microwaves. For example, the controller 50 can
easily create multiple heating patterns for heating the left side, the right side,
the center, the front side, the rear side, the whole, etc. of the heating chamber
10. The intensity of the heating power for heating the heating region can also easily
be adjusted.
[0161] The periodic structure 20c is made up of the plurality of projection parts 21c periodically
arranged in the first direction (X direction) and the second direction (Y direction)
different from the first direction (X direction). With such a configuration, the directivity
of the four microwaves supplied to the periodic structure 20c from the four power
feeding parts 40a, 40b, 40c, 40d can more easily be controlled.
[0162] The first power feeding part 40a and the second power feeding part 40b are arranged
in the first direction (X direction) at a distance from each other with the central
region of the heating chamber 10 interposed therebetween. The third power feeding
part 40c and the fourth power feeding part 40d are arranged in the second direction
(Y direction) at a distance from each other with the central region of the heating
chamber 10 interposed therebetween. With such a configuration, the microwaves output
from the first power feeding part 40a and the second power feeding part 40b easily
propagate in the first direction, and the microwaves output from the third power feeding
part 40c and the fourth power feeding part 40d easily propagate in the second direction.
As a result, the microwaves can easily be output in the first direction and the second
direction, and the heating region can easily be formed in the left-right direction
(first direction) and the depth direction (second direction) of the heating chamber
10.
[0163] In the example described in the third embodiment, the periodic structure 20c is disposed
in the bottom portion of the heating chamber 10; however, the present invention is
not limited thereto. For example, the periodic structure 20c may be disposed in the
bottom portion, the upper portion, and/or the side portions of the heating chamber
10.
[0164] Fig. 18 is a schematic cross-sectional configuration diagram of a microwave heating
apparatus 1D according to a modification. As shown in Fig. 18, a periodic structure
20d may be disposed in the bottom portion and both side portions of the heating chamber
10. Specifically, the waveguide 11 is disposed in the bottom portion and both side
portions of the heating chamber 10. The plurality of projection parts 21d constituting
the periodic structure 20d are arranged inside the waveguide 11 disposed in the bottom
portion and both side portions of the heating chamber 10.
[0165] In the microwave heating apparatus 1D shown in Fig. 18, a fifth power feeding part
40e and a sixth power feeding part 40f are disposed in the periodic structure 20d
disposed in the side portions of the heating chamber 10. With such a configuration,
microwaves can be supplied also from the side portions of the heating chamber 10 into
the heating chamber 10. As a result, the heating region can more easily be controlled.
Additionally, microwave radiation can be performed not only from below the heating
chamber 10 but also from the side or above, so that uniform heating performance can
be improved.
[0166] In the example described in the first to third embodiments, the periodic structures
20, 20c, 20d have the configuration in which the plurality of projection parts 21,
21c, 21d are periodically arranged; however, the present invention is not limited
thereto. Fig. 19 shows a schematic configuration of a periodic structure 20e according
to a modification. Fig. 20 is a schematic cross-sectional view of the periodic structure
20e of Fig. 19 taken along a line A-A.
[0167] As shown in Figs. 19 and 20, the periodic structure 20e may have a configuration
in which multiple resonance conductors 22 are periodically arranged in the first direction
(X direction) and the second direction (Y direction) different from the first direction.
In the periodic structure 20e shown in Fig. 19, the multiple resonance conductors
22 are arranged in three columns and three rows. A power feeding part 40g is disposed
in the resonance conductor 22 at the center of the periodic structure 20e.
[0168] Each of the multiple resonance conductors 22 has a rectangular flat plate and a
bar-shaped member disposed on a bottom surface of the flat plate. The multiple resonance
conductors 22 are made of a conductor such as metal, for example.
[0169] When an arrangement interval of the multiple resonance conductors 22 is 1/4 wavelength
of a microwave, the microwave propagates through the periodic structure 20e most easily.
When microwaves of the same frequency are oscillated from four power feeding parts,
the arrangement intervals of the multiple resonance conductors 22 can be differently
configured to change a frequency easily transmitted in each direction, so that the
controllability of the heating pattern is enhanced.
[0170] Figs. 21 and 22 respectively show schematic configurations of periodic structures
20f, 20g of other modifications. As shown in Figs. 21 and 22, in the periodic structures
20f, 20g, multiple resonance conductors 23 have a disk-shaped flat plate and a bar-shaped
member disposed on a bottom surface of the flat plate.
[0171] In the periodic structure 20f shown in Fig. 21, the four resonance conductors 23
are arranged in two columns and two rows. A power feeding part 40h is disposed at
the center of the periodic structure 20f, i.e., in a space formed by the four resonance
conductors 23.
[0172] In the periodic structure 20g shown in Fig. 22, the nine resonance conductors 23
are arranged in three columns and three rows. A power feeding part 40i is disposed
in the resonance conductor 23 at the center of the periodic structure 20g.
[0173] The other configurations of the periodic structures 20f, 20g shown in Figs. 21 and
22 are the same as those of the periodic structure 20e shown in Fig. 19.
[0174] Even in such a configuration, the heating region can easily be controlled. Furthermore,
the microwave heating apparatus can be reduced in height.
[0175] Although the present invention has been sufficiently described in terms of preferable
embodiments with reference to the accompanying drawings, various modifications and
corrections are apparent to those skilled in the art. It should be understood that
such modifications and corrections are included in the present invention without departing
from the scope of the present invention according to the accompanying claims.
Industrial Applicability
[0176] The microwave heating apparatus according to the present invention can easily control
the heating region for heating the object and is therefore useful for a cooking appliance
such as a microwave heater, for example. For example, the present invention is useful
for a heating cooker radiating microwaves to a food considered as an object for induction
heating, or particularly, a heating cooker used in combination with other heating
using an oven, a grill, heating steam, etc.
Reference Signs List
[0177]
1A, 1B, 1C, 1D microwave heating apparatus
10 heating chamber
11 waveguide
12 object to be heated
13 placing table
20, 20a, 20b, 20c, 20d, 20e, 20f, 20g periodic structure
21, 21a, 21b, 21c, 21d projection part
22 resonance conductor
23 resonance conductor
30, 30a, 30b microwave generator
31 frequency controller
32, 32a, 32b, 32c, 32d amplifier
33, 33a, 33b, 33c distributor
34a, 34b, 34c, 34d phase controller
40, 40a, 40b, 40c, 40d, 40e, 40f, 40g, 40h, 40i power feeding part
50 controller
60A, 60B, 60C analysis model
61 object to be heated
R1, R2, R3, R4 region