JPH0142584B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to improving the heating distribution performance of a high frequency heating device such as a microwave oven.

Conventional structure and problems High-frequency heating devices such as microwave ovens that use microwaves to heat dielectric materials such as food generally have a problem with the interaction between the unique wavelength of the microwave and the size and shape of the heating chamber and the object to be heated. This relationship causes a problem in that standing waves are generated in the heating chamber, resulting in uneven heating of the object to be heated. To improve this heating unevenness, a turntable method in which the object to be heated is rotated and a stirrer method in which the electric field within the heating chamber is disturbed are used. FIG. 1 shows a conventional high-frequency heating device using this stirrer method, in which a microwave excitation port is provided at the bottom of the heating chamber. In the figure, 1 is an oscillator that generates microwaves, 2 is a waveguide that transmits the microwaves generated by the oscillator 1, and 3 is a heating chamber that heats the object to be heated.
4 is an excitation port that excites the heating chamber 3 with the microwave transmitted by the waveguide 2; 5 is an antenna; and 6 is an excitation port that excites the microwave supplied from the excitation port 4 within the heating chamber 3. a rotating waveguide having an opening 6-a at its end for emitting radiation from the direction; 7 a table provided in the heating chamber 3 for placing the object to be heated; 8 a rotating waveguide; This is a motor for rotating the wave tube 6. The rotating waveguide 6 is box-shaped so as to cover the excitation port 4, has a gap between it and the bottom wall surface of the heating chamber 3, and has an opening 6-a toward the heating chamber at its end. The reason for this configuration for radio wave stirring is that when heating an object, the microwaves from the excitation port 4 directly reach the center of the bottom of the object, strongly heating that part. This is to prevent this from happening. That is, the excitation port 4
Most of the microwaves from the heating chamber 3 pass through the opening 6-a of the waveguide 6 and are radiated into the heating chamber 3 via the table 7 made of a dielectric material. However, such a configuration has the disadvantage that the heating of the central part of the bottom surface of the object to be heated becomes too weak, and the heating becomes too strong when an opening is formed in the wall surface of the rotating waveguide.

OBJECTS OF THE INVENTION The present invention solves the above-mentioned conventional drawbacks, and an object of the present invention is to provide a high-frequency heating device with excellent heating distribution performance.

Structure of the Invention In order to achieve the above object, the high frequency heating device of the present invention includes a heating chamber that heats an object to be heated, an oscillator that generates microwaves, and an output of the oscillator that is installed on the wall of the heating chamber and sends the output of the oscillator to the heating chamber. an excitation port for supplying;
a rotating waveguide that covers the excitation port, rotates parallel to the heating chamber wall surface around the excitation port, and has an opening at an end, and the rotating waveguide is provided with an excitation port on the heating chamber wall surface. has a flat part substantially parallel to the wall surface, and has a recess in a part of the flat part, and allows microwaves to pass through the wall surface forming the recess on the same side as the opening at the end of the rotating waveguide. The microwave supplied from the excitation port into the rotating waveguide propagates through the rotating waveguide, is partially reflected by a vertical portion of the heating chamber wall, etc., and is directed toward the excitation port. A part of the reflected waves that return to the heating chamber are radiated through the opening to the heated object placed in the heating chamber, so the strength of the microwave is moderately weakened and the heating distribution of the heated object is improved. It has the following.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is a perspective view of a high-frequency heating device according to an embodiment of the present invention, with the table 7 partially cut away. In the figure, 3 is a heating chamber that heats the object to be heated;
6 is a rotating waveguide that rotates the direction of supply of microwaves; 7 is a table on which the object to be heated is placed; 9 is a door for putting in and taking out the object to be heated; 10 is a heating time;
This is an operation panel for setting heating output, etc. FIG. 3 is a cross-sectional view taken along the line A-A' in FIG.
4 is an excitation port that excites the heating chamber 3 with the microwave transmitted by the waveguide 2; 5 is an antenna; and 6 is an excitation port that excites the microwave supplied from the excitation port 4 within the heating chamber 3. 7 is a rotating waveguide having an opening 6-a at its end for emitting radiation from the direction; 7 is a dielectric table provided in the heating chamber 3 for placing the object to be heated; 8 is a table made of a dielectric material; This is a motor for rotating the rotating waveguide 6. The rotating waveguide 6 is made of a metal body, has a box shape that covers the excitation port 4, has a gap between it and the bottom wall surface of the heating chamber 3, and has an opening A6-a toward the heating chamber at the end. are doing. As shown in FIG. 4, the rotating waveguide has a flat part 6-b that is substantially parallel to the wall surface of the heating chamber where the excitation port is provided, and a depression 6- is formed in a part of the flat part 6-b. c, and has an opening B6-d through which microwaves can pass on the same side as the opening 6-a at the end of the rotating waveguide 6 on the wall surface forming the recess 6-c. The rotating waveguide 6 is rotated by the motor 8 about the excitation port 4 in parallel to the bottom wall surface of the heating chamber 3 . Figure 5 is B- in Figure 3.
In the sectional view B', the opening B6-d is the recess 6-d.
A slit-like shape is provided on the inclined part of the wall surface forming c, and the length of the long side is about 1/4 or more of the wavelength of the microwave.

The operation of the above configuration will be explained below.
Microwaves generated by the oscillator 1 are transmitted by the waveguide 2 and radiated into the rotating waveguide 6 through a coupling portion formed by the excitation port 4 and the antenna 5. The microwave radiated into the rotating waveguide 6 travels through the rotating waveguide and reaches the opening A.
The light enters the heating chamber from 6-a. At this time, a part of the microwave is reflected on the wall surface of the heating chamber 3 facing the opening A6-a, and a reflected wave that returns toward the center of the rotating waveguide 6 is generated. A part of this reflected wave enters the heating chamber through an opening B6-d provided in an inclined portion of the recess 6-c that is not directly visible from the excitation port 4. Considering the state in which the object to be heated is placed in the heating chamber, the upper part and surroundings of the object to be heated are heated by the microwaves radiated from the opening A6-a of the rotating rotating waveguide 6. The center of the bottom of the object to be heated is heated by the microwave radiated from the opening B6-d.

As described above, according to this embodiment, there are the following two effects as the effect of the indirect opening, that is, the effect of the configuration in which the opening B6-d is provided in a part that is not directly visible from the excitation port 4. The first effect is that the intensity of the microwave to the center of the bottom of the object to be heated is moderately suppressed, and the heating state of the center of the bottom becomes appropriate with respect to the heating state of the entire object to be heated, thereby increasing uniformity. This is an opening B6-d in a part that cannot be seen directly from the excitation port.
This is because by providing a configuration in which a relatively weak microwave can be guided to the center of the bottom of the object to be heated by utilizing a portion of the microwave that returns to the oscillator side as a reflected wave, it is possible to guide the relatively weak microwave to the center of the bottom of the heated object. In other words, when an opening is provided in a part that can be seen directly from the excitation port, the microwave directly enters the heating chamber from the excitation port, and its intensity becomes extremely strong, extremely heating the center of the bottom of the object to be heated. Even if the size is reduced, if the size becomes about 1/4 of the wavelength of the microwave, the area around the opening will overheat and the loss will be large, making it impractical, so it is not possible to moderate the overheating state at the center of the bottom. The second effect is that the reflected waves to the oscillator become weaker, lowering the oscillator's temperature and increasing its durability. This is because the reflected wave returning to the oscillator 1 becomes weaker by guiding a part of the reflected wave to the heating chamber 3 through the opening B6-d as described above. Next, there are the following two effects as effects of providing the recessed portions. The first effect is that the distance from the bottom of the object to be heated to the top of the rotating waveguide, which is a metal body, increases, so the microwaves reach a wide area in the center of the bottom of the object, causing local overheating of the bottom of the object. It means preventing. This effect appears to be due to the height dimension of the rotating waveguide, that is, the fourth dimension, even if no depression is provided.
It is thought that this can be obtained by reducing the l dimension in the figure, but if this l dimension is made smaller, a gap between the lower surface of the rotating waveguide and the wall surface of the heating chamber, that is, the fourth
The ratio l/g to the g dimension in the figure becomes smaller. When the value of l/g becomes 3 or less, the leakage of microwaves from the gap increases and it no longer functions as a rotating waveguide.On the other hand, the g dimension cannot be reduced to prevent discharge, so the l dimension is reduced. It is not desirable to do so. The second effect is that the length of the antenna 5, which supports the rotating waveguide 6 and guides microwaves into the rotating waveguide 6, can be shortened and costs can be reduced.

Effects of the Invention As described above, according to the present invention, the following effects can be obtained.

(1) The strength of the microwave to the center of the bottom of the object to be heated is moderately suppressed, and the heating state of the center of the bottom becomes appropriate with respect to the heating state of the entire object to be heated, and the microwave spreads over a wide area at the center of the bottom of the object to be heated. It is possible to provide a high-frequency heating device that prevents local overheating of the heated bottom surface and has excellent heating distribution performance.

(2) The reflected waves to the oscillator become weaker, the temperature of the oscillator decreases, and the durability improves.

(3) The dimensions of the antenna supporting the rotating waveguide can be shortened, reducing costs.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of a conventional high-frequency heating device;
The figure is a perspective view of a high-frequency heating device that is an embodiment of the present invention, FIG. 3 is a sectional view taken along line A-A' in FIG. 2, and FIG. 4 is a partially enlarged view of FIG. 3.
Figure 5 shows B- in Figure 3 of the same high frequency heating device.
B′ cross-sectional view. 1... Oscillator, 2... Waveguide, 3... Heating chamber,
4...Excitation port, 5...Antenna, 6...Rotating waveguide, 6-a...Aperture A, 6-b...Plane part, 6-
c... recess, 6-d... opening B, 7... table, 8... motor, 9... door, 10... operation panel.

Claims (1)

[Claims] 1. A heating chamber that heats an object to be heated, an oscillator that generates microwaves, and an excitation port that is provided on a wall of the heating chamber and supplies the output of the oscillator to the heating chamber.
a rotating waveguide that covers the excitation port, rotates in parallel to the heating chamber wall surface around the excitation port, and has an opening at an end, and the rotating waveguide covers the excitation port on the heating chamber wall surface. a flat part substantially parallel to the provided wall surface, a recess in a part of the flat part, and a wall surface forming the recess on the same side as the opening at the end of the rotating waveguide for the passage of microwaves; A high-frequency heating device configured to have a possible opening.