JP3064875B2 - High frequency heating equipment - Google Patents

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 device for heating food.

[0002]

2. Description of the Related Art Conventionally, a heating method using a surface wave has been proposed as a method for heating food at a high frequency (for example, Japanese Patent Publication No. 49-16944). A conventional heating apparatus using surface wave heating will be described with reference to FIG. 11. A heating chamber 1, a magnetron 2 for oscillating a high frequency, a power supply circuit 3 for driving the magnetron 2, a waveguide for transmitting a high frequency, and a rectangular section. A waveguide 4 is provided. The waveguide 4 is provided with a ladder-shaped surface acoustic wave line 6 having a plurality of rectangular openings 5. A dielectric plate 7 made of a material having a small dielectric loss;
7 ', and foods 8, 8' are placed on the dielectric plates 7, 7 '. The foods 8, 8 'placed on the surface acoustic wave line 6 in the heating chamber 1 are dielectrically heated by high frequency.

[0003] The food 8 on the dielectric plate 7 placed on the surface acoustic wave line 6 can be scorched because the electric field concentrated near the surface acoustic wave line 6 strongly heats the portion of the food 8 near the line.

If it is desired to heat the entire body without the need for scorching, another dielectric plate 7 ′ is installed at a location distant from the surface acoustic wave line 6, a food 8 ′ is placed thereon, and separated from the surface acoustic wave line 6. The microwave on the surface wave line 6 does not act on the food 8 ′, and microwaves are radiated into the heating chamber 1 from the opening 9 at the tip of the surface wave line 6 and heated by the standing wave in the heating chamber 1. Was doing.

The electric field distribution on the surface acoustic wave line 6 as shown in FIG. 12C is concentrated near the surface acoustic wave line 6 as shown in FIG. 12A, and attenuates exponentially in the height direction (coordinate axis z direction). I do. By using the high-frequency energy concentrated in the vicinity of the surface acoustic wave line 6 for heating as described above, it is possible to impart a strongly heated burn near the surface acoustic wave line 6. The electric field is distributed in the opening of the ladder. Therefore, the electric field distribution in the microwave traveling direction (coordinate axis x direction) is as shown in FIG.
The strength of the microwave appears at the pitch of the surface wave line 6 having the ladder-like periodic structure as shown in a in b, and the ladder-like heating pattern appears in the food 7. At this time, since the pitch of the surface acoustic wave line 6 is designed to be shorter than the pitch of the standing wave in the heating chamber 1, heating unevenness is extremely small.

However, when heating is performed with a standing wave (a in FIG. 12B) in the heating chamber 1, the strength of the microwave appears at the pitch of the standing wave, and the transmission frequency of the magnetron is 2.45 GHz.
In this case, the intensity is generated at a pitch of about 6 cm of a half wavelength. Therefore, the food is affected by the intensity of the microwaves, causing large uneven heating.

[0007]

When the standing wave is used to heat the food, the food is affected by the strength of the microwave standing wave, causing large uneven heating.

An object of the present invention is to solve the above problems and to provide a high-frequency heating apparatus free from uneven heating.

[0009]

In order to solve the above-mentioned problems, a high-frequency heating apparatus according to the present invention has the following configuration.

That is, a heating chamber for accommodating an object to be heated, a microwave oscillator for oscillating microwaves, a waveguide for transmitting microwaves oscillated from the microwave oscillator to the heating chamber, And a single or a plurality of openings provided at a boundary of the waveguide, and a waveguide wave of the waveguide.
When the length is λg and n is a natural number, the microwave oscillator
The length from the antenna to the end face of the waveguide on the heating chamber side is L = (λg / 4) · (2n) ± (λg / 8), and the length of the waveguide is at least λg from the end face.
And variable means that can be changed in the range of / 4 .

The variable means has a moving body made of a conductive member and driving means for driving the moving body, wherein the moving body is located between the end face of the waveguide and a position of λg / 4 from the end face. in was <br/> reciprocating constitutes.

[0012] The variable unit includes a rotating body made of a conductive member, and driving means for rotationally driving the rotation body,
The rotator has a center of rotation of λg / 4 from the end face of the waveguide.
Configured in position .

[0013] Also, a plurality of openings is configured to form a surface-wave transmission line. The pitch of the opening portion is configured that Do and lambda] g / 4 or less.

[0014]

[0015]

[0016]

[0017] Also, to a single opening, a structure having a surface-wave transmission line having a pleated conductive plate in the waveguide.

Further , a dielectric plate is provided on the surface acoustic wave line.
Heating and waveguiding by surface wave by switching the presence or absence of the dielectric plate
And configured to Ru switching the heating by the standing wave in the tube.

[0019] Further, it has a plurality of dielectrics, and is provided on a surface acoustic wave line.
Heating by surface wave and waveguide by switching the dielectric plate
It was switched Ru constituting the heating by standing waves in the.

Further, the dielectric plate can be detached from the surface wave line.
It has a configuration that be installed to function.

[0021]

[0022]

[0023]

According to the present invention, the antenna is derived from a microwave oscillator antenna.
The length L of the waveguide to the end face on the heating chamber side is L = (λg / 4) · (2n) ± (λg / 8), and the length of the waveguide is at least λg from the end face.
Variable means that can be changed in the range of / 4
You. With this configuration, first, the variable means
The length of the waveguide up to the end face on the heating chamber side in the range of λg / 4
Because the standing wave distribution in the waveguide is strong because it can be changed
(Belly) and weak spots (knots) are completely reversed, causing uneven heating
Can complement each other. Also from the antenna at this time
The length of the waveguide to the end face on the heating chamber side is L = (λg / 4) · (2n) ± (λg / 8) L−λg / 4 = (λg / 4) · (2n) ± (Λg / 8)
−λg / 4 = (λg / 4) · (2n) + (− 2 ± 1) · λg / 8 , and the first term of the two equations is common and the second term is different.
The relationship of the second term is the phase from the antinode (or node) of the standing wave.
From the viewpoint of deviation, they are symmetrical and mean the same thing.
It is. So when you look at the waveguide from each antenna
The alignment can be similar. In addition, a moving body made of a metal plate is arranged in the waveguide, and the position of λg / 4 is switched from the end face of the waveguide to the end of the waveguide to heat the food. from rotated placed in a position of lambda] g / 4 Ri by the heating the food, easily
The position of the antinode and node of the standing wave in the waveguide can be shifted by shifting the reflection position of the microwave oscillating from the magnetron.

Also, a dielectric plate is detachably provided on the surface acoustic wave line, and a desired heating method can be properly used by using or not using a dielectric plate, or by properly using one of a plurality of dielectric plates. it can.

The distance from the magnetron antenna to the end face of the waveguide is defined as (λg / 4) · (2n) <L <(λg / 4) · (2n +
According to 1), even if the moving body made of the metal plate moves or the rotating body rotates, the microwave matching at both positions becomes almost equal.

Further, the pitch of the plurality of ladder-like openings of the surface acoustic wave line is set to λg / 4 or less so that the waveguide 14
When the standing wave in the inside is moved by λg / 4, a heating pattern appears at a position shifted by λg / 4 without being blocked by the metal part of the surface acoustic wave line.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

The same parts as those in the conventional example are denoted by the same reference numerals, and description thereof will be omitted. The microwave oscillated from the magnetron 2 is transmitted through the waveguide 14, and the surface of the ladder-shaped surface wave line 16 having at least three or more openings provided at the boundary of the waveguide 14 on the heating chamber 1 side is formed. The food 8 is heated at a high frequency by appropriately switching between the wave and the standing wave. Switching between the surface wave and the standing wave is performed by a single dielectric plate 17 detachably mounted on the surface wave line 16 or a plurality of dielectric plates 17 having different magnitudes of dielectric loss. Here, when heating using the surface wave, heating is performed on the surface wave line 16 without the dielectric plate 17, and when heating using the standing wave, the surface wave line 1 is used.
A dielectric plate 17 is placed on 6 and heated. In addition, the plurality of dielectric plates 17 may be selectively used. In this case, surface wave heating is performed using the smaller one of the plurality of dielectric plates 17 to reduce the dielectric loss of the plurality of dielectric plates 17. Use the larger one to heat with standing waves.

The moving body 2 made of a metal plate is placed in the waveguide 14.
The motor 21 reciprocates in the microwave traveling direction (x direction in the figure) in the waveguide 14 by the motor 21. The moving body 20 moves by a distance D of λg / 4 when the guide wavelength is λg, and in this example, moves between the waveguide end face A and the position B of λg / 4. In this case, the end face A refers to the end face on the side coupled to the heating chamber 1 when viewed from the magnetron antenna 22. The moving body 20 moves between the position A and the position B at regular intervals or according to a control signal, and oscillates microwaves only when the moving body 20 is at the position A or B, or keeps oscillating the microwaves. Reciprocates continuously at a fixed cycle. The distance L of the waveguide 14 from the magnetron antenna 22 to the end face A is determined so as to be within the range determined by the following equation. (N is a natural number) (λg / 4) · (2n) <L <(λg / 4) · (2n + 1) (1) In this embodiment, the following values are used in order to obtain a greater effect.

L = (λg / 4) · (2n) + (λg / 4) (2) When heating with a surface wave in the above configuration, in this example, the pitch p of the opening 15 of the surface wave line 16 is 24 mm, which is sufficiently smaller than the half-wavelength 126 mm of the standing wave of the waveguide 14 having a width of 70 mm used here.
The heating unevenness of No. 8 can be kept small. However, in the case where the food 18 is heated by the standing wave, the food 18 is uniformly heated by the action of the moving body 20. However, in practicing the present invention, dimensions such as the pitch p are not limited to the above values. Further, in this example, the openings 15 are all located on the magnetron 2 side from the position B, but a part of the opening 15 may be provided between the position B and the position A using the short waveguide 14.

When the moving body 20 is located at the end face A of the waveguide 14 (FIG. 3A), the standing wave in the waveguide 14 becomes as shown in FIG. Since the electric field at the position of the node of the standing wave in 14 is strongly excited, the hatched portion of the food 18 is well heated.
Is about a half wavelength of the in-tube wavelength. When the moving body 20 moves to the position B in the waveguide 14, the standing wave in the waveguide 14 becomes as shown by c ′, and the heated portion is shifted by a quarter wavelength as shown in FIG. 3c. The part is heated well. Therefore, by heating the moving body 18 by switching between the position A and the position B, it is possible to compensate for the uneven heating of the antinodes and nodes of the wave in the waveguide 14 and uniformly heat the whole food 18 as shown in FIG. 3D. it can.

At this time, the standing wave in the waveguide 14 was moved by λg / 4 by setting the pitch of the openings of the surface acoustic wave line 16 having a plurality of ladder-shaped openings to λg / 4 or less. At this time, a heating pattern appears at a position shifted by λg / 4 without being blocked by the metal part of the surface acoustic wave line 16.

Further, by setting the length of the waveguide 14 as in the equation (2), the case where the moving body 20 is at the end face A and the case where the moving body 20 is at the position B
, The matching of the microwaves with the food 8 becomes almost equal, so that the heating can be performed with almost the same time distribution as when the moving body 20 is at the end face A and when it is at the position B. This will be described with reference to FIG. 4. The microwave oscillated from the magnetron 2 is transmitted through the waveguide 14 and reflected at the end of the waveguide 14 to generate a standing wave. At this time, since the magnetron antenna 22 emits a radio wave, the electric field becomes strong, and the electric field becomes zero on the metal surface at the reflection end.
, The antinode of the standing wave by the magnetron antenna 22, the waveguide 1
(3) (n is a natural number) L = (λg / 4) · (2n) The position of α that satisfies L = (λg / 4) · (2n) is the matching with the magnetron 2 so that it becomes a node of the standing wave at the four ends. Good. Conversely, it can be said that it is difficult to achieve alignment at the position β that is λg / 4 away from the position α. Now, for uniform heating, the end of the waveguide 14 is moved by λg / 4 by a moving body made of a metal plate. At this time, if the alignment of both positions is not the same, a time difference occurs between both heating times. Since the heating is performed in substantially the same time, the positions of the ends of the waveguide 14 are α and β.
In particular, by setting the position .gamma. To be .gamma.g / 8 away from .alpha., Almost the same alignment state is obtained even at the position .delta.

If the loads at the end face A and the position B do not match each other, uniform heating can be obtained by appropriately distributing the time between the end face A and the position B depending on the state of the mismatch. To

FIG. 5 shows another embodiment in which a similar effect can be obtained by rotating a motor 31 in which a rotating body 30 of a metal plate is installed in the waveguide 14. This rotating body 3
0 rotates around the y-axis. The rotating body 30 is installed at λg / 4 from the end face of the waveguide, where the guide wavelength is λg. The rotating body 30 rotates according to the control signal, and oscillates microwaves only when the rotating body 30 made of a metal plate is parallel to the yz plane or parallel to the xy plane. It rotates continuously while oscillating.

In the above configuration, when the rotating body 30 made of a metal plate is parallel to the zy plane, the microwave passes through the rotating body 30 and is reflected at the end face A of the waveguide 14, and the microwaves are used. The heating pattern is the same as when the moving body is on the end face A. When the rotating body 30 is parallel to the zy plane, the microwaves are reflected by the rotating body 30 and have the same heating pattern as when the moving body is at the position B. Therefore, the case parallel to the xy plane and the case
By switching and heating the case parallel to the y-plane, uneven heating of the antinode of the standing wave and the nodes can be compensated to achieve uniform heating.

FIG. 6 shows still another embodiment, in which a waveguide 1 is provided.
The same effect as described above is obtained by appropriately switching between the upright state and the state in which the metal plate 40 is in close contact with the waveguide surface by a driving means (not shown) provided with a metal plate 40 in 4.

At this time, it was confirmed by experiments that the size of the metal plate forming the moving body and the rotating body was as effective as shown in the table of FIG. 86% of the width of the tube The height of the metal plate is 88% of the height of the waveguide.
%.

FIG. 8 shows another embodiment. The microwave oscillated from the magnetron 2 is transmitted through the waveguide 1
4 is transmitted, and the food 8 is heated by the surface acoustic wave line 16 provided in the waveguide 14. A metal moving body 20 is installed in the waveguide 14, and the waveguide 14 has an end face A2 and an end face A2.
To the position B of λg / 4. The food 8 is placed on a turntable 23 made of a low-loss dielectric material provided in 1 and heated to further reduce uneven heating.

As another embodiment, a waveguide 24 having a cross-finger type surface wave line 26 having a single bent opening 25 in a waveguide 24 as shown in FIG. Tube 3
A surface wave line 36 having a single opening 35 in FIG. 4 and having a pleated conductor plate in the waveguide 34 is also conceivable.

[0041]

As described above, according to the high frequency heating apparatus of the present invention, the following effects can be obtained.

(1) By providing a variable means in the waveguide, it is possible to eliminate uneven heating due to antinodes and nodes of the radio wave when heating with a standing wave.

(2) The heating by the surface wave and the heating by the standing wave can be easily switched only by detaching or replacing the dielectric plate.

(3) The variable means disposed in the waveguide is set at a position of λg / 4 from the end of the waveguide, or the variable means is moved between the end of the waveguide and the position of λg / 4 from the end of the waveguide. By switching, it is possible to compensate for uneven heating of the belly and nodes when heating with standing waves.

(4) By setting the length of the waveguide as in the present invention, there is no difference in matching at the time of switching by the variable means in the waveguide, and the variable means is switched at substantially the same time, thereby making the waveguide uniform. Can be heated.

(5) By setting the pitch of the surface acoustic wave line to λg / 4 or less, a heating pattern appears at a position where the standing wave in the waveguide moves λg / 4 without being interrupted by the metal part of the surface acoustic wave line. Uniform heating becomes possible.

[Brief description of the drawings]

FIG. 1 is a side sectional view of a high-frequency heating device according to an embodiment of the present invention.

FIG. 2 is a cutaway perspective view of a main part of the high-frequency heating device.

3A is a plan view of an object to be heated by the high-frequency heating device; FIG. 3B is a waveform diagram of a standing wave in a waveguide of the high-frequency heating device; (D) A diagram showing how the object to be heated is heated by the high-frequency heating device.

FIG. 4 is a sectional view of a waveguide of the high-frequency heating device.

FIG. 5 is a cutaway perspective view of a main part of a high-frequency heating device according to a second embodiment of the present invention.

FIG. 6 is a cutaway perspective view of a main part of a high-frequency heating device according to a third embodiment of the present invention.

FIG. 7 is a diagram showing an effect in the embodiment of the present invention.

FIG. 8 is a perspective view of a high-frequency heating device according to a fourth embodiment of the present invention.

FIG. 9 is a perspective sectional view of a main part of a high-frequency heating device according to a fifth embodiment of the present invention.

FIG. 10 is a perspective sectional view of a main part of a high-frequency heating device according to a sixth embodiment of the present invention.

FIG. 11 is a side sectional view of a conventional high-frequency heating device.

FIG. 12 (a) Electric field intensity distribution diagram in z direction of high frequency heating device (b) Electric field intensity distribution diagram in x direction of high frequency heating device (c) Perspective view of main part of high frequency heating device

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heating room 2 Magnetron (microwave oscillator) 14 Waveguide 15 Opening 16 Surface acoustic wave line 17 Dielectric plate 18 Heated object 20 Moving body 30 Rotating body

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akira Abane 1006 Kazuma Kadoma, Kadoma-shi, Osaka Matsushita Electric Industrial Co., Ltd. (56) References JP-A-52-155444 (JP, A) JP-A-58- 161290 (JP, A) Japanese Utility Model Showa 53-153245 (JP, U) Japanese Patent Publication No. 58-32757 (JP, B2) Japanese Patent Publication No. 2-16518 (JP, B2) (58) Fields surveyed (Int. Cl. ⁷ , DB name) H05B 6/70-6/74

Claims (10)

(57) [Claims] A heating chamber for accommodating an object to be heated; a microwave oscillator for oscillating microwaves; a waveguide for transmitting microwaves oscillated from the microwave oscillator to the heating chamber; And a single or a plurality of openings provided at the boundary of the waveguide, and the guide wavelength of the waveguide λg,
When n is a natural number, is it a microwave oscillator antenna?
The length from the end face to the heating chamber side end of the waveguide is L = (λg / 4) · (2n) ± (λg / 8), and the length of the waveguide is at least λg from the end face.
A high-frequency heating device having a variable means that can be changed in the range of / 4 . 2. The variable means has a moving body made of a conductive member and a driving means for driving the moving body, wherein the moving body is located between an end face of the waveguide and a position λg / 4 from the end face. in construction and claims 1 high frequency heating apparatus according to reciprocate. Wherein the variable means includes a rotating body made of a conductive member, and driving means for rotationally driving the rotating body, the rotating body is lambda] g / 4 rotation center from the end face of the waveguide Position of
The high-frequency heating device according to claim 1, wherein 4. The device according to claim 1, wherein the plurality of openings form a surface acoustic wave line.
4. The high-frequency heating device according to any one of items 3 to 3 . 5. A structure in which the pitch of the openings is λg / 4 or less.
The high-frequency heating device according to claim 4, wherein 6. A cross-finger surface wave line having a single opening.
The structure according to any one of claims 1 to 3, wherein
The high-frequency heating device as described . 7. A single opening and a pleated guide in a waveguide.
No claim 1 having a configuration having a surface wave line having a body plate
The high-frequency heating device according to any one of Items 3 to 3 . 8. A dielectric plate having a dielectric plate on a surface acoustic wave line.
By switching the presence or absence of the body plate, heating by the surface wave and the inside of the waveguide
No claim 4 wherein the heating by the standing wave is switched.
The high-frequency heating device according to any one of claims 7 to 10 . 9. A semiconductor device comprising : a plurality of dielectrics;
Heating by surface wave by switching dielectric plate and constant in waveguide
Claim 4 or Claim 4 wherein the heating by the standing wave is switched.
The high-frequency heating device according to any one of items 7 to 7 . 10. A dielectric plate is detachably mounted on a surface acoustic wave line.
High-frequency heating apparatus according to claim 8 or 9, wherein the location.