JP2000223260A - High-frequency heating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To arbitrarily and variably control the direction of a microwave emitted into a heating chamber and accelerate the equalization of the heating of a heated object. SOLUTION: This device is provided with a heating chamber 11 for receiving a heated object 10, a high-frequency wave generation means 17, an opening part 20 formed in the vicinity of a power feeding hole 19, a slot part 21 connected to the opening part 20, and an impedance varying means 22 formed in the slot part 21 for varying the impedance of the opening part 20. The impedance of the opening part 20 is varied by changing the position of the impedance varying means 22, and the radiation direction of the microwave radiated from the power feeding hole 19 is varied, so that the incident position of the microwave on the heated object 10, and the equalization of the heating of the heated object 10 is thereby furthered.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-frequency heating apparatus for dielectrically heating an object to be heated.

[0002]

2. Description of the Related Art A conventional high-frequency heating apparatus employs a radio wave stirring method, a rotating method for a heated object, a plurality of power feeding methods, or a method in which the wall surface of a heated chamber is uneven, as means for uniformizing the heating of the heated object housed in a heating chamber. Making it into a shape has been put to practical use.

[0003] The radio wave stirring system has a configuration in which a metallic plate-like blade provided in a heating chamber is rotationally driven. In this method, a microwave propagating while being repeatedly reflected on a metal boundary surface forming a heating chamber or on a surface of an object to be heated is also reflected by a metallic plate-like blade. The reflection of the microwaves from the metallic plate-like blades increases the propagation path of the microwaves in the heating chamber as compared with the case without the plate-like blades, and irregularly reflects the microwaves on the entire object to be heated. This promotes uniform heating of the object to be heated.

[0004] The heating object rotating system has a configuration in which a mounting plate on which an object to be heated is mounted is rotated. In this scheme,
With respect to the microwave propagation distribution generated in the heating chamber, which is determined by the type and shape of the heating chamber and the type of heating target housed in the heating chamber, move the heating target and apply microwaves to the entire heating target. The heat is propagated to promote uniform heating of the object to be heated.

[0005] The multiple power supply system has a configuration in which microwaves are supplied from a plurality of locations on a metal boundary surface forming a heating chamber. The most significant feature of this method as compared with a single power supply is that a plurality of microwaves having different phases are supplied to the heating chamber. By transmitting microwaves having different phases into the heating chamber, a diffused reflection state of the microwave is generated in the heating chamber as in the radio wave stirring method.

[0006] The method of forming an irregular shape on the wall surface of the heating chamber has a structure in which irregularities are provided on a metal boundary surface forming the heating chamber. In this method, microwaves are irregularly reflected by a metal interface having irregularities.

[0007]

However, there is a physical limit in the conventional radio frequency stirring type high frequency heating apparatus in that the microwave reflected by the metallic plate-like blade is uniformly and irregularly reflected in the heating chamber. This is because the rotation speed of the metallic plate-like blade is too slow relative to the microwave propagation speed. It is very difficult to propagate waves. Therefore, there is a problem that it is difficult to suppress occurrence of unexpected and uneven heating distribution depending on the type and amount of the object to be heated.

In the rotating method of the heated object, the microwave distribution generated in the heating chamber depends on the kind and amount of the heated object. Even if it is unsuitable for heating an object to be heated uniformly, there is a problem that its electromagnetic wave distribution cannot be changed.

Although the multiple power feeding method has the ideal behavior as described above, the behavior of the microwave radiated from one power feeding unit is affected by the microwave radiated from the other power feeding unit. For this reason, even if there are a plurality of power supply units, specific microwave propagation determined by the plurality of power supply configurations occurs in the heating chamber, and depending on the type and amount of the object to be heated, an unexpected uneven heating distribution may occur. There is a problem that it is difficult to suppress the occurrence of the problem.

Further, in order to generate irregular reflection in the heating chamber which can promote uniform heating of an object to be heated, the uneven structure on the wall of the heating chamber is provided with irregularities such as so-called dimples of a golf ball on the entire wall. In addition, it is necessary to make the depth dimension or protrusion dimension of the dimple a dimension that cannot be ignored with respect to the wavelength of the microwave to be used, for example, 1/10 wavelength dimension or more. As a result, there has been a problem that the configuration of the heating chamber becomes complicated and a configuration that is difficult for practical use is forced.

The present invention provides a high-frequency heating apparatus which intentionally variably controls the direction of microwaves radiated to a heating chamber to promote uniform heating of an object to be heated.

[0012]

In order to solve the above-mentioned problems, a high-frequency heating apparatus according to the present invention includes a heating chamber for accommodating an object to be heated, a high-frequency generating means for generating microwaves, and a high-frequency generating means for generating the microwaves. Radiating means for radiating the microwaves to the heating chamber, an opening provided in a wall forming the heating chamber in the vicinity of the radiating means, a groove connected to the opening and a closed end, Impedance changing means provided in the groove to change impedance at the opening.

According to the invention, the impedance formed by the impedance varying means is variably controlled from an extremely small value (ideally zero) to an extremely large value (ideally infinity). On the other hand, the microwave radiated into the heating chamber from the radiating means is affected by the impedance value formed in the opening. When the impedance value is extremely small, microwaves are radiated in a predetermined direction by regarding the opening as a metal wall surface. On the other hand, when the impedance value is extremely large, the high-frequency current flowing through the wall of the heating chamber is cut off by the opening. This allows
The wall of the heating chamber on the side of the opening cannot be coupled to the radiated microwave by an electromagnetic field, and the microwave radiated from the radiating means is radiated in a direction avoiding the opening. That is, by changing the impedance value of the opening, the radiation direction of the microwave from the radiation means changes. This allows
The location where microwaves are incident on the object to be heated can be changed, and uniform heating of the object to be heated can be promoted.

[0014]

DETAILED DESCRIPTION OF THE INVENTION A high-frequency heating apparatus according to claim 1 of the present invention comprises a heating chamber for accommodating an object to be heated, a high-frequency generating means for generating microwaves, and a microwave generated by the high-frequency generating means. A radiating unit that radiates to the heating chamber, an opening provided in a wall forming the heating chamber in the vicinity of the radiating unit, a groove connected to the opening and having a closed end, and provided in the groove. Impedance changing means for changing the impedance at the opening.

The impedance formed by the opening by the impedance varying means is changed from a very small value (ideally zero) to a very large value (ideally infinite).
Is variably controlled. On the other hand, the microwave radiated into the heating chamber from the radiating means is affected by the impedance value formed in the opening. When the impedance value is extremely small, microwaves are radiated in a predetermined direction by regarding the opening as a metal wall surface. On the other hand, when the impedance value is extremely large, the high-frequency current flowing through the wall of the heating chamber is cut off by the opening. As a result, the wall of the heating chamber on the side of the opening cannot be coupled to the radiated microwave by the electromagnetic field, and the microwave radiated from the radiating means is radiated in a direction avoiding the opening. That is, by changing the impedance value of the opening, the radiation direction of the microwave from the radiation means changes. This makes it possible to change the position where microwaves are incident on the object to be heated, and to promote uniform heating of the object to be heated.

Further, in the high frequency heating apparatus according to a second aspect, the radiating means is configured such that a power supply hole provided on a wall surface forming the heating chamber and an opening is provided adjacent to the power supply hole.

The radiation direction of the microwave radiated from the power supply hole is determined by the shape of the metal wall surface at the power supply outlet. The microwave can be radiated in a direction avoiding the opening by changing the impedance of the opening provided near the power supply hole. As a result, it is possible to change the incident position of the microwave to the object to be heated and promote uniform heating of the object to be heated.

Further, the high-frequency heating device according to the third aspect has a configuration in which an opening is provided with the power supply hole interposed therebetween. By changing the impedance of each opening, the radiation direction of the microwave from the power supply hole can be changed over a wider range. This makes it possible to selectively control the radiation direction according to the object to be heated having various shapes, and to promote uniform heating of the object to be heated.

Further, in the high-frequency heating apparatus according to the fourth aspect, the radiating means is an antenna made of a metal plate, and an opening is provided on a wall surface of the heating chamber facing the antenna. Then, the electric field generated between the antenna and the metal wall surface of the heating chamber causes the electric field to be coupled or broken by changing the impedance of the opening. When the coupling is broken, the microwave does not propagate to the antenna in that region, and the radiation of the microwave is suppressed. This allows
By changing the impedance value of the aperture, the radiation distribution of the antenna can be changed. By changing the radiation distribution, the microwave propagation in the heating chamber changes, the incident position of the microwave on the object to be heated can be changed, and uniform heating of the object to be heated can be promoted.

The high-frequency heating device according to the fifth aspect is configured such that the antenna is driven to rotate. This makes it possible to change the microwave radiation distribution from the antenna and change the microwave propagation even when the microwave radiated from the antenna propagates through the heating chamber and enters the opening. Microwave propagation can be made more random. As a result, uniform heating of the object to be heated can be further promoted.

According to a sixth aspect of the present invention, in the high-frequency heating device, in the rotary drive antenna, a plurality of apertures are provided, and at least one set of the high-frequency heating device has at least one opening about 180 degrees around the rotation axis of the antenna.
It is configured to be arranged at an interval of °. As a result, the microwave radiation distribution from the antenna can be made symmetric or asymmetric. As a result, uniform heating can be further promoted according to the shape and amount of the object to be heated.

[0022]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIGS. 1 and 2 are diagrams showing the configuration of a high-frequency heating apparatus according to Embodiment 1 of the present invention, and FIG. 3 is a characteristic diagram showing the behavior of microwaves in a groove by the impedance variable means of the present invention. It is.

In FIGS. 1 and 2, a heating chamber 11 for accommodating an object to be heated 10 is a right side wall 12, a left side wall 13, a back wall 14, an upper wall 15, a bottom wall, which are metal boundaries formed of a metal material. 16 and a front opening / closing wall (not shown), which is an opening / closing wall through which an object to be heated is put in and out of the heating chamber 11, is formed in a substantially rectangular parallelepiped shape. 17
Is a magnetron which is a high-frequency generating means for generating a microwave. The microwave generated by the magnetron 17 propagates through the waveguide 18 and passes through a power supply hole 19 provided on the right wall surface 12 of the heating chamber 11 so as to generate a microwave. Is radiated. An opening 20 is provided near the power supply hole 19. Reference numeral 21 denotes a groove having a shape with the opening 20 at one end and the other end closed, and a rotatable impedance variable means 22 supported on the wall surface of the groove 21 is disposed inside the groove.

The impedance varying means 22 is made of a flat plate made of a low dielectric loss material, and its relative permittivity is about 5 or more, preferably 15 or less. The plate thickness can be reduced by increasing the relative permittivity. 5 to ensure mechanical strength
mm. Available materials are alumina or mullite ceramics, polyphenylene sulfide (PPS), polyethylene (PE)
This is a heat-resistant resin material which is a composite material of a polystyrene (PS) type or a polystyrene (PS) type.

Reference numeral 23 denotes a plate on which the object to be heated 10 is placed. The mounting plate may be configured to be rotationally driven by a motor.

Next, the principle of changing the impedance value of the opening by the impedance variable means will be described with reference to FIG. First, the configuration will be described.

The groove 21 having the opening 20 as one end is formed in a spatially continuous manner with the opening 20 and is formed of a wall surface made of a metal material covering the opening 20. The end of the groove 21 is closed by a groove plate 24. In the groove 21, an impedance varying means 22 is provided.

The impedance varying means 22 has a plate-like structure made of a material having a low dielectric loss, and has a support portion at both ends thereof for penetrating a hole provided in the wall surface of the groove. The impedance varying means 22 is supported by the groove wall surface by the support. In order to rotationally drive the impedance variable means 20, a motor (not shown) having an output shaft connected to a support of one of the impedance variable means is provided.

As means for judging the rotation angle of the impedance variable means, a support angle judging means integrally formed with the output shaft of the motor may be provided, or a stepping motor may be used as the motor.

Next, the operation and operation of each unit will be described.
The opening 20 is formed in a substantially rectangular shape that is long in a direction in which a flow of a high-frequency current flowing through each metal wall forming the heating chamber generated by the microwave propagating in the heating chamber 11 is cut off. When the impedance of the opening 20 is reduced to zero, the flow of the high-frequency current is not interrupted. Therefore, the propagation of the microwave does not change at all regardless of the existence of the aperture 20. On the other hand, by setting the impedance of the opening 20 to infinity, the high-frequency current stops flowing, so that the microwave propagation changes from the expected characteristics. Further, the phase difference between the incident wave and the reflected wave of the microwave at the aperture 20 is 180 degrees when the impedance of the aperture is zero, and is 0 degrees when the impedance of the aperture is infinite. Therefore, by changing the impedance of the aperture, the microwave generated in the heating chamber is multiply propagated, and various microwave distributions can be formed, and the heating of the object to be heated placed in the heating chamber 11 is made uniform. Can be promoted.

Next, the groove 21 including the impedance varying means 22 will be described. The shape of the groove 21 in this embodiment is such that the groove depth L1 is 40 mm, L2 is 20 mm,
The groove height (height of the opening) H is 30 mm, and the width of the opening is 8
0 mm. Further, the impedance variable means 22 includes:
The dielectric constant is 12.3, the plate thickness is 6.2 mm, and it is disposed substantially at the center of the groove 21.

FIG. 3 shows a microwave distribution generated in the groove 21 including the impedance varying means 22 having such a configuration. In FIG. 3, a solid line 25 indicates a microwave distribution when the wide surface 22 a of the impedance varying unit 22 is provided perpendicular to the depth direction of the groove 21.
The impedance generated at zero is an extremely small value (ideally zero). In addition, the wide surface 22a is
The broken line 26 indicates the microwave distribution in the case where the microwave distribution is provided in parallel with the depth direction. In this case, the impedance generated in the opening 20 has an extremely large value (ideally infinite).

Next, the operation and operation of the high-frequency heating apparatus of the present invention having the above-described structure will be described with reference to FIGS. FIG. 1 shows that the impedance variable means 22 is
FIG. 2 shows the microwave propagation behavior when the impedance varying means 22 is arranged parallel to the depth direction of the groove 21. FIG.

In FIG. 1, the impedance value of the aperture 20 is extremely small, and the radiation direction of the microwave radiated from the power supply hole 19 into the heating chamber 11 depends on the direction of the aperture 20.
Irradiates in the direction determined by the structure around the power supply hole 19 without being affected by the above. On the other hand, in FIG. 2, since the impedance value of the opening 20 is set to an extremely large value, the microwave radiated from the feed hole 19 is disconnected from the metal wall surface of the heating chamber on the opening 20 side. , And is radiated in the direction shown in the figure, with the offset being offset to the side opposite to the position where the opening 20 is provided.

As described above, by changing the radiation direction of the microwave from the feed hole 19, the position of the microwave incident on the object to be heated 10 can be changed. By changing the microwave incident position on the object to be heated 10, uniform heating of the object to be heated 10 can be promoted.

The position control of the impedance variable means can be put to practical use by classifying in advance according to the type, shape or amount of the object to be heated, and arranging a dedicated heating menu switch on the operation section of the apparatus main body. .

The rotation position of the impedance variable means 22 is set at a predetermined position (for example, the opening 20) after the heating is completed.
It is preferable to add a control for resetting the impedance to a value at which the impedance becomes extremely small.

(Embodiment 2) Next, Embodiment 2 of the present invention will be described with reference to FIG. The configuration of the second embodiment differs from that of the first embodiment in that an opening 27 is additionally provided and an opening is provided with the power supply hole 19 interposed therebetween. Reference numeral 28 denotes a groove having the opening 27 as one end, and reference numeral 29 denotes a groove provided in the groove 28.
This is an impedance varying means for changing the impedance of.

By variably controlling the impedances of the two openings, the radiation direction of the microwave from the feed hole 19 can be changed over a wider range. For example, as illustrated, the impedance value of the aperture 27 is set to an extremely large value, and the impedance value of the aperture 20 is set to an extremely small value. It can be controlled downward. As a result, even in the case of a flat object to be heated, the microwave can be incident on the entire surface of the object to be heated, and uniform heating of the object to be heated can be promoted.

(Embodiment 3) Next, Embodiment 3 will be described with reference to FIG.
This will be described with reference to FIG. Embodiment 3 is different from the above-described embodiment in that an antenna 30 made of a metal plate is used as a means for radiating microwaves. Magnetron 17
The generated microwave propagates through the waveguide 31 and couples to the metal column 32 disposed near the other end. An antenna 30 made of a metal plate is disposed at the tip of the metal support 32. The other end of the metal column 32 is connected to an output shaft of a motor 33 that drives the metal column 32 to rotate. An opening 34 for penetrating the metal column 32 is provided in the metal wall surface of the heating chamber 11, and the opening 34 is configured to rotatably support the metal column 32 and shield the opening 34. (Not shown) are provided.

An opening 35 is provided on the wall surface of the heating chamber facing the antenna 30 made of a metal plate. A groove 36 having one end of the opening 35 is provided, and an impedance changing means 37 for changing the impedance of the opening 35 is provided in the groove 36.

In the above configuration, the metal plate antenna 3
In the presence of microwaves radiated from the antenna 30 by propagating 0, a high-frequency electric field is generated between the antenna 30 made of a metal plate and the metal wall surface of the heating chamber. Antenna 30
When the impedance value of the opening 35 becomes extremely large, the high-frequency electric field generated between the heating chamber and the metal wall surface is broken. When the coupling is broken, the microwave is not propagated to the antenna 30 in that area, and the radiation of the microwave is suppressed. FIG. 5 schematically shows microwave radiation (radiation distributions 38 and 39) from the antenna 30 when the impedance of the aperture 35 is extremely small. From this state, when the impedance variable means 37 is rotationally controlled to increase the impedance value of the aperture 35, the microwave propagation energy in the radiation distribution 38 decreases and the microwave propagation energy in the radiation distribution 39 increases. . As a result, in the figure, heating of the object to be heated 10 by the radiation distribution 39 is promoted.

As described above, the antenna 30 made of a metal plate
By changing the radiation distribution, the microwave propagation in the heating chamber 11 can be changed, and the incident position of the microwave on the object to be heated can be changed. As a result, uniform heating of the object to be heated can be promoted.

Fourth Embodiment Next, a fourth embodiment of the present invention will be described with reference to FIG. Example 4 differs from Example 3 in that a plurality of apertures are provided.

That is, in FIG. 6, reference numeral 40 denotes an antenna made of a metal plate, which has a substantially cross shape. Reference numeral 41 denotes a rotation axis of the antenna 40, and reference numerals 42 and 43 denote openings provided at intervals of approximately 180 ° with respect to the rotation axis 41 of the antenna 40. The apertures 42 and 43 are provided at positions facing the antenna 40 made of a metal plate. The openings 42, 43 are provided with grooves 44, 45, impedance varying means 46, 47, and motors 48, 49 for rotating the impedance varying means 46, 47, respectively. 50 is a waveguide for transmitting the microwave generated by the magnetron.

The microwave propagated through the waveguide is applied to the antenna 4
The light is coupled to the rotation axis of 0, propagates along the rotation axis, and is radiated from the antenna 40 into the heating chamber 51. The rotation of the antenna 40 is controlled by a motor (not shown). The metal blades of the antenna 40 whose rotational drive is controlled are formed by the apertures 42, 4
When passing through the position facing 3, the radiation distribution is changed under the influence of the impedance values formed in the apertures 42 and 43.

As described above, by rotating the antenna, even when the microwave radiated from the antenna propagates in the heating chamber 51 and enters the apertures 42 and 43 again, the propagation of the microwave is changed. Can be. Therefore, a more random microwave propagation can be formed in the heating chamber by a synergistic effect of a change in the radiation distribution from the antenna and a change in the propagation of the microwave incident on the aperture. As a result, uniform heating of the object to be heated can be further promoted.

Further, the opening is formed in the rotating shaft 41 of the antenna 40.
By arranging them at an interval of about 180 °, it is possible to easily make the radiation distribution from the antenna 40 have symmetry or break the symmetry. Thereby, it is possible to further promote uniform heating according to the shape and amount of the object to be heated.

[0050]

As described above, the present invention has the following effects.

(1) According to the high-frequency heating device of the first aspect, the microwave coupling between the aperture and the radiating means is changed by variably controlling the impedance variable means, thereby radiating the microwave from the radiating means. The direction can be changed. This makes it possible to change the incident position of the microwave on the object to be heated, thereby promoting uniform heating of the entire object to be heated.

(2) According to the high-frequency heating device of the second aspect, the microwave can be radiated in a direction avoiding the opening by changing the impedance of the opening provided near the power supply hole. As a result, it is possible to change the incident position of the microwave on the object to be heated and promote uniform heating of the entire object to be heated.

(3) According to the high-frequency heating device of the third aspect, the direction of microwave radiation from the feed hole can be changed over a wider range by changing the impedance of the two openings. As a result, it is possible to uniformly heat the object to be heated by forming microwave propagation in the microwave space in an optimal state for the type, amount, and shape of the object to be heated.

(4) According to the high-frequency heating device of the fourth aspect, the radiation distribution of the antenna made of a metal plate is changed by changing the impedance of the opening, thereby
By changing the propagation of microwaves in the heating chamber, uniform heating of the object to be heated can be promoted.

(5) According to the high-frequency heating device of the fifth aspect, in addition to changing the radiation distribution from the antenna, the microwave radiated from the antenna propagates in the heating chamber and enters the aperture again. By changing the propagation of the microwave even when the heating is performed, the propagation of the microwave in the heating chamber is made more random, so that uniform heating of the object to be heated can be further promoted.

(6) According to the high-frequency heating device of the sixth aspect, by providing a plurality of apertures for the rotationally driven antenna, the radiation distribution from the antenna can be made symmetrical or the radiation distribution can be reduced. By making it asymmetric, the uniformity of heating of the object to be heated can be promoted by selectively controlling the radiation distribution according to the shape and amount of the non-heated object.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a high-frequency heating device according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram showing another state of the high-frequency heating device.

FIG. 3 is a diagram showing a microwave distribution characteristic in a groove portion including an impedance varying unit of the high-frequency heating device.

FIG. 4 is a configuration diagram of a high-frequency heating device according to a second embodiment of the present invention.

FIG. 5 is a configuration diagram of a high-frequency heating device according to a third embodiment of the present invention.

FIG. 6 is a configuration diagram of a high-frequency heating device according to a fourth embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Heated object 11 Heating chamber 17 Magnetron (high frequency generation means) 19 Power supply hole (radiation means) 20, 27, 35, 42, 43 Openings 21, 28, 36, 44, 45 Grooves 22, 29, 37, 46 , 47 Impedance variable means 30 Antenna (radiating means) 33 Antenna rotation drive motor 41 Antenna rotation axis

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Akemi Fukumoto 1006 Kazuma Kadoma, Kadoma-shi, Osaka Matsushita Electric Industrial Co., Ltd. F-term (reference) 3K090 AA01 AB02 BA01 BB07 BB17 CA01 CA21 DA04 DA08 EA01 EB02 EB16 EB29

Claims (6)

[Claims] 1. A heating chamber for accommodating an object to be heated, high frequency generating means for generating microwaves, radiating means for radiating microwaves generated by the high frequency generating means to the heating chamber, and a vicinity of the radiating means. An opening provided on a wall surface forming the heating chamber, a groove connected to the opening and having a closed end, and impedance changing means provided in the groove and changing impedance at the opening. High frequency heating device. 2. The high-frequency heating apparatus according to claim 1, wherein the radiating means is a power supply hole provided in a wall surface forming the heating chamber, and an opening is provided adjacent to the power supply hole. 3. The high-frequency heating apparatus according to claim 2, wherein an opening is provided so as to sandwich the power supply hole. 4. The high-frequency heating apparatus according to claim 1, wherein the radiating means is an antenna made of a metal plate, and an aperture is provided on a wall surface of the heating chamber facing the antenna. 5. The high-frequency heating device according to claim 4, wherein the antenna is configured to be rotatable. 6. The high-frequency heating apparatus according to claim 5, wherein a plurality of apertures are provided, and at least one set is provided at an interval of about 180 ° about the rotation axis of the antenna.