JP2998521B2 - 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 apparatus for heating an object to be heated such as food by applying an electromagnetic wave.

[0002]

2. Description of the Related Art A microwave oven as a typical high-frequency heating device will be described with reference to FIG.

An electromagnetic wave emitted from a magnetron 1 which is an electromagnetic wave radiating portion of a high-frequency heating device is transmitted through a waveguide 2, and is fixed in the heating chamber 4 by a shape of the heating chamber 4 and a position of an opening 25. The food 5 generates heat according to the electric field component of the standing wave and the dielectric loss of the food 5. The power P [W / m ³ ] absorbed per unit volume of the food is determined by the strength of the applied electric field E [V / m], the frequency f [Hz], and the relative permittivity ε _r and the dielectric loss tangent tan δ of the food. It is expressed as (Equation 1). Since the heating distribution of the food 5 is determined by the standing wave distribution of the electromagnetic wave, in order to suppress the unevenness of the heating distribution, the turntable 6 of the table on which the food is placed is rotated to make the heating distribution on the concentric circle uniform. . In many of the turntable types, a feeding point (where the electromagnetic wave enters the heating chamber, which is the opening 25 in the conventional example) is fixed on the top surface or the side surface, and is fixed. Although the distribution of the standing wave seems to be always constant, the distribution of the standing wave is liable to be disturbed as the distance from the power supply point increases due to the influence of the shape of the object to be heated and the degree of absorption of the electromagnetic wave depending on the dielectric constant.

[0004]

(Equation 1)

As another means for uniformity, a heating chamber 4
Among them, there is a stirrer that stirs an electromagnetic wave by a metal plate or a so-called rotating waveguide that rotates a metal part of an exit of the waveguide itself, but a turntable type is most widely used.

Further, as shown in FIG. 7, there is an apparatus having an electromagnetic wave detecting unit 8 for extracting a part of an electromagnetic wave in order to know the state of food for the purpose of automating the cooking of a microwave oven. This is to detect a part of the electromagnetic wave leaking from the opening 26 with the antenna 27 and to estimate the state of the food based on the magnitude and the amount of change of the voltage detected by the detection circuit 28. (For example,
JP-A-4-75293, etc.)

[0007]

However, in the above-described conventional configuration, the heating chamber 4 depends on the shape, material and weight of the food.
And the magnetron 1 change the matching state,
It has not always been possible to efficiently supply radio waves. In particular, since the output power of a microwave oven is regulated by 2 liters of water as a load replacing food, it is designed to supply the maximum output power with the best matching in this state, and is often used on a daily basis. Done 100c
The output of c to 200 cc (for example, a bowl of rice, a glass of milk, etc.) fell to about 40 to 70% due to misalignment compared to the output at 2 liters of water. For this reason, there is a problem that the heating time becomes extra and the waiting time of the user becomes longer, and the electromagnetic wave that has not entered the food 5 causes a loss in the magnetron 1 itself, the temperature rises, and the thermal stress increases, thereby lowering the reliability. Had issues.

An object of the present invention is to solve the above-described problems and to realize a highly reliable high-frequency heating apparatus which efficiently and quickly heats an object to be heated such as food regardless of its shape, material and weight. And

[0009]

In order to achieve the above object, the high frequency heating apparatus of the present invention has the following configuration.

That is, a heating chamber for taking in and out an object to be heated, an electromagnetic wave radiating section for radiating an electromagnetic wave, a waveguide for guiding the electromagnetic wave radiated from the electromagnetic wave radiating section into the heating chamber, An opening provided at a connection portion with the wave tube, an electromagnetic wave detection unit for extracting a part of an electromagnetic wave within a distance of 波長 wavelength or less from the opening, and a matching state between the electromagnetic wave radiating unit and the heating chamber And a control unit that receives a signal from the electromagnetic wave detecting unit, adjusts the matching state adjusting unit, and controls the emission of electromagnetic waves from the electromagnetic wave emitting unit.

[0011]

[0012]

The present invention has the following effects by the above-mentioned structure.

That is, since a part of the most stable standing wave electromagnetic wave at a distance within a half wavelength from the opening is taken out by the electromagnetic wave detecting unit, the electromagnetic wave radiating unit and the heating chamber are separated depending on the detection level. In addition, the matching state can be known, and the matching state adjusting section that can adjust the matching state between the electromagnetic wave radiating section and the heating chamber has an operation of changing the matching state.

[0014]

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of a high-frequency heating apparatus according to one embodiment of the present invention. An electromagnetic wave emitted from the magnetron 1 as an electromagnetic wave radiating portion heats the food 5 in the heating chamber 4 via the waveguide 2 and the first opening 3. The food 5 is placed on a turntable 6 as a forced uniforming means for uniforming the heating distribution, and its rotation is controlled by the control unit 7.
The configuration of the electromagnetic wave detection unit 8 is the same as the configuration described in JP-A-4-75293, and the state of the food 5 is estimated by extracting a part of the electromagnetic wave in the heating chamber 4 from the second opening 9,
The optimum heating time is determined and applied to cooking automation such as warming and thawing. However, according to the present invention, the distance L10 between the first opening 3 and the second opening 9 is λ / 2 or less, where λ is the wavelength of the electromagnetic wave, and the electromagnetic wave detecting unit 8 detects the distance between the heating chamber 4 and the magnetron 1. The matching state can also be detected. The matching state adjusting unit 11 moves the position of the dielectric 13 within a certain range through the third opening 12 of the waveguide 2 by the control unit 7. Can be changed.

The flow of control by the control unit 7 immediately after the start of heating is such that the magnetron 1 emits electromagnetic waves to start heating the food 5 in the heating chamber 4 and the matching state adjusting unit 1
The electromagnetic wave detector 8 detects a part of the electromagnetic wave in the heating chamber 4 while moving the position of the dielectric 13. Dielectric 13
Is completed, the position of the dielectric 13 that gives the maximum level of the detection signal (the state in which the electromagnetic wave enters the heating chamber 4 most efficiently) is determined, and the matching state adjustment unit 11 again moves the dielectric 13 to that position. It is moved and fixed, and rotation of the turntable 6 is started.

In this embodiment, the turntable 6 is not rotated until the optimum position of the dielectric 13 is determined. Originally,
If the position of the food 5 changes, the matching state changes, so that the optimal position of the dielectric 13 changes every moment as the position of the food 5 moves due to the rotation of the turntable 6. Therefore, every time the turntable 6 is slightly moved, the optimum position of the dielectric 13 can be determined. However, this requires an enormous amount of time just to determine the optimum position, and there is a high risk of eventually causing loss. Therefore, in the present embodiment, the optimum position of the dielectric 13 is quickly determined in a state in which the food 5 is put and the turntable 6 is stopped, and then the turntable 6 is rotated. However, there is an effect of improving the matching state in a short time.

FIG. 2 is a sectional view of a main part of a matching portion between the waveguide and the heating chamber. The direction of the electric field generated by the electromagnetic wave changes, for example, as indicated by an arrow in the drawing at a certain moment. In the waveguide 2, an electromagnetic wave is transmitted and an electric field perpendicular to the wall surface is generated, and an electric field 14 is applied immediately before the first opening 3. However, when trying to enter the heating chamber 4 from the first opening, the direction of the electric field is bent to become the electric field 15, and since the heating chamber 4 is considered to be a cavity resonator, the electromagnetic wave is distributed as a standing wave. One opening 3
, Electric fields 16 and 17 in opposite directions are generated.

The hatched portion 18 in FIG. 2 indicates a region where the electric field is stronger than a certain level among the electric fields generated on the wall surface of the heating chamber 4, and four strong electric fields are generated in the vertical direction of the heating chamber. I have. This is the antinode of the electric field caused by the electromagnetic wave being distributed as a standing wave in the heating chamber 4 due to the resonance, and the number of antinodes is called a mode. Usually heating room 4
When the shape is represented in three dimensions and the dimensions in each direction are x, y, and z, if the antinodes of the electric field are only m, n, and p in each direction, the mode is (mnp). For reference, when the food is not in the heating chamber 4 and the heating chamber 4 is a rectangular parallelepiped, depending on the dimensions of the heating chamber 4 and the position of the first opening 3,
A mode that can stand can be obtained. The dimensions of the heating chamber 4 are x, y, and z, and the number of modes standing in each direction is a combination of m, n, and p that satisfies (Equation 2) (x, y, and z are in mm units, and m, n, and p are Integer, λ is wavelength).

[0021]

(Equation 2)

On the other hand, when there is a food, deviation from (Equation 2) occurs due to the influence of wavelength compression due to the dielectric constant of the food.
However, even if there is food, a mode that satisfies (Equation 2) is about to be established near the first opening 3, and the mode is disturbed at a position away from the first opening 3. I understand. Therefore, knowing the magnitude of the stable strong electric fields 16 and 17 closest to the first opening 3 and knowing how much electromagnetic waves enter the heating chamber 4, that is, the matching state between the heating chamber 4 and the magnetron 1 You can know. Therefore, in the present invention, λ /
The second opening 9 is provided within a distance of 2 or less, and a part of the electromagnetic wave corresponding to the strong electric field 17 is detected by the electromagnetic wave detector 8. It is determined that the larger the amount detected by the electromagnetic wave detector 8, the better the matching state, and the smaller the amount detected, the worse the matching state.

FIG. 3 is a characteristic diagram showing the relationship between the weight of the water load and the electromagnetic wave output. The horizontal axis shows the amount of water, and the vertical axis shows the ratio of each electromagnetic wave output normalized by the electromagnetic wave output at 2 liters of water. In the case of the conventional microwave oven, the characteristic is 19, and it can be seen that the electromagnetic wave output drops to about 1/2 at 100 cc. On the other hand, according to the present invention, if matching is achieved at all loads, the characteristic 20 approaches an ideal state.

FIG. 4 is a schematic diagram of a main part of an embodiment of the high-frequency heating apparatus according to the present invention. FIG. 4A is a perspective view, and FIG. 4B is a cross-sectional view taken along line AA ′ of FIG. 4A, in which the dielectric 13 moves through the third opening 12 of the waveguide 2. Is represented. To adjust the matching state, the dielectric 1
Reference numeral 3 denotes a drive in the vertical direction 21 or the horizontal direction 22. Of course, as is generally known, even if a metal is used instead of the dielectric 13, the matching state cannot be changed.

FIG. 5 is a sectional view showing the structure of a main part of another embodiment of the high frequency heating apparatus of the present invention. In order to change the matching state, a variable metal plate 23 is provided at the end of the waveguide 2, and the distance (so-called back flange) B24 between the magnetron 1 and the end is changed.

[0026]

As described above, the high-frequency heating device of the present invention has the following effects.

(1) Since a part of the electromagnetic wave within a half wavelength from the opening is taken out by the electromagnetic wave detecting unit, the matching state between the electromagnetic wave emitting unit and the heating chamber is most accurately obtained for any object to be heated. The electromagnetic wave corresponding to can be detected.

[0028]

Therefore, a good alignment state can be maintained at all times for any object to be heated, so that cooking can be speeded up by increasing the efficiency of heating, and the user can easily use the apparatus with less waiting time.

Further, since electromagnetic waves returning to the electromagnetic wave radiating portion without entering the heating chamber are reduced, loss in the electromagnetic wave radiating portion is reduced, heat stress due to temperature rise is reduced, and reliability is improved.

Further, the loss at the time of heating is small, which leads to energy saving.

[Brief description of the drawings]

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

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

FIG. 3 is a characteristic diagram of the high-frequency heating device.

FIG. 4 is a configuration diagram of a main part of the high-frequency heating device.

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

FIG. 6 is a configuration diagram of a conventional high-frequency heating device.

FIG. 7 is a configuration diagram of another conventional high-frequency heating device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magnetron 2 Waveguide 3 First opening 4 Heating chamber 5 Food 6 Turntable 7 Control part 8 Electromagnetic wave detecting part 9 Second opening 11 Matching state adjusting part

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-144564 (JP, A) JP-A-5-266976 (JP, A) JP-A-5-121158 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) H05B 6/68 320 F24C 7/02 511 H05B 6/70

Claims (3)

(57) [Claims] 1. A heating chamber for taking in and out an object to be heated, an electromagnetic wave radiating section for radiating electromagnetic waves, a waveguide for guiding electromagnetic waves radiated from the electromagnetic wave radiating section into the heating chamber, An opening provided at a connection portion with the wave tube, an electromagnetic wave detection unit for extracting a part of an electromagnetic wave within a distance of 波長 wavelength or less from the opening, and a matching state between the electromagnetic wave radiating unit and the heating chamber A high-frequency heating device having a configuration that includes a matching state adjusting unit that can adjust the temperature and a control unit that receives a signal from the electromagnetic wave detecting unit, adjusts the matching state adjusting unit, and controls emission of electromagnetic waves from the electromagnetic wave emitting unit. . 2. The method according to claim 1, further comprising: forcibly uniformizing means for rotating the food or stirring electromagnetic waves in order to equalize the heating distribution of the food, wherein the control unit determines the adjustment state giving the maximum signal, 2. The method according to claim 1, wherein the forcible uniforming means is operated.
Mounting the high-frequency heating apparatus. 3. The control section estimates a state of food in the heating chamber based on a signal from the electromagnetic wave detection section, determines an optimal heating time in accordance with the state, and applies the heating time or thawing to automation of cooking. The high-frequency heating device according to claim 1 .