JPS6262435B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high-frequency heating device that heats an object to be heated such as food using high-frequency energy.
In particular, the present invention relates to a door equipped with a chiyoke groove for preventing radio wave leakage.

Conventionally, small, multifunctional electronic components such as ICs and microcomputers have been actively incorporated into the control circuits of high-frequency heating equipment, and operation panels have become smaller and thinner, making it difficult to balance these types of operation panels. A thin door with a flat profile is requested. In addition, there is a growing tendency to automate complex operations, which increases the cost of electronic circuits, so there is a demand for lower costs for mechanical parts, especially door structures.

Conventional doors often use a combination of chiyolk grooves and ferrite, which is a radio wave absorbing material, but this is disadvantageous in terms of cost because ferrite is attached to the entire circumference of the door. Furthermore, proposals have been made to increase the damping effect of the chiyoke groove itself and to remove ferrite. This proposal is as follows.

A proposal has been made to increase the attenuation effect of the chiyoke groove by periodically arranging λ/4 length conductor pieces, so-called slits, on one side of the chiyoke groove, which has a depth of 1/4 of the used wavelength λ, as a radio wave propagation direction regulating device. US Patent 2772402
(1956/11/27 patent) and 2850706 (1958/9/2 patent)
patent). In addition, the radio wave leakage prevention structure similar to the above patent is patented in 3767884 (Japanese Unexamined Patent Publication No. 3767884).
48-81146, Japan Patent Publication Publication No. 53-4660), but in this proposal, the slit is one side of the radio wave propagation path before entering the chiyoke groove, and the slit and the opposing metal surface are This is a method in which the spacing is forcibly maintained by filling it with dielectric material. This is because when the slit partially contacts the opposing metal surface, the length of the slit becomes substantially shorter than λ/4, which reduces its function as a radio wave propagation direction regulating device (electromagnetic energy mode maintenance structure). be. With this method, a large number of radio waves enter the gap between the door and the heating chamber opening, and to prevent leakage of fundamental waves and harmonics, it is necessary to add conductive rubber or to complicate the propagation path of leaked radio waves. It is necessary to produce a damping effect, and it is not suitable for making doors thinner and lower in cost.

In addition, many proposals have been made, such as British Patent No. 1392498 and Japanese Patent Publication No. 1983-22663, to increase the damping effect by dividing the choke groove into two with a metal wall having a slit of approximately λ/4, but this method does not However, the yoke groove becomes large, making it unsuitable for making doors thinner and lower in cost.

Furthermore, a structure in which a periodic structure other than the above-mentioned slits is inserted into the chiyoke groove has been proposed in Japan Patent Publication No. 54-21574 and Japanese Patent Publication Publication No. 52-40461, but the surface forming the chiyoke groove itself Moreover, since harmonics are not taken into account, it is also necessary to add ferrite etc. for practical use, which is disadvantageous in terms of cost.

As mentioned above, conventional doors are not suitable for thinning and cost reduction.

Therefore, in the present invention, one radio wave attenuation cavity with one entrance is provided at the periphery of the door by arranging the fundamental wave groove and the second harmonic wave groove in opposite directions, A simple radio wave leakage prevention structure that minimizes radio wave leakage of fundamental waves and harmonics by dividing the wall surface of the chiyoke groove itself into multiple corrugated plates and giving specific relationships to the shapes and dimensions of these corrugated plates. An object of the present invention is to provide a high-frequency heating device equipped with a door that can be made thinner and lower in cost.

Next, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is an external view showing an example of the high frequency heating device of the present invention. 1 is an outer box, 2 is a door, and 3 is an operation panel whose thickness is balanced with the thickness of the door 2. Although the operation panel 3 can be changed in various ways depending on the application, the case of automatic heating will be explained as an example.
4 is a display device that shows high frequency output, residual heating time, etc., 5 is a menu selection button that determines the optimal heating pattern for each menu, 6 is a finish adjustment knob that allows you to select the degree of finish according to your preference, and 7 is when to start heating. 8 is the heating button to press, and 8 is the door open button to open the door.

FIG. 2 is a schematic sectional view of a main part of the high-frequency heating device of the present invention corresponding to FIG. 1. 9 is a high frequency oscillator that generates high frequency energy, and 10 is a waveguide for transmitting the high frequency energy from the high frequency oscillator 9 to the heating chamber 11. 12 is a turntable for uniform heating, on which the object to be heated is placed. A turntable 12 is used as a uniform heating device.
In addition, there are stirrers, rotating antennas, fixed antennas, etc., and any of them may be used. Reference numeral 13 denotes a transparent plate attached to the front surface of the door 2, and the transparent plate 13 is fixed to the door front plate 15 by a door cover 14. The door front plate 15 is attached to the door rear plate 16 with screw 1.
It is attached by 7. Both the door front plate 15 and the door rear plate 16 are made of metal plates, and form a radio wave attenuation cavity 19 facing the heating chamber opening periphery 18. 20 is a transparent plate facing the heating chamber 11;
is wire mesh (or perforated metal plate). The inside of the heating chamber 11 can be seen through the transparent plate 13, the wire mesh 21, and the transparent plate 20. 22 is door 2
It is Satsushi that surrounds.

FIG. 3 is an enlarged view of the vicinity of the radio wave attenuation cavity 19 shown in FIG. A fundamental wave groove 19a for preventing radio wave leakage at a heating frequency of, for example, 2450 MHz, and a second harmonic of the above frequency of 4900 MHz.
One radio wave attenuation cavity 1 having one inlet 23 has second harmonic channel grooves 19b facing each other in opposite directions to prevent radio wave leakage.
9 is formed. In the fundamental wave channel groove 19a, the L-shaped radio wave propagation path from the inlet 23 to the short-circuit surface 15a is approximately λo/4 with respect to the free space wavelength λo of the heating frequency. The fundamental wave chiyoke groove 19a is arranged on the side closer to the heating chamber 11, and this groove 1
One wall surface 16a of the heating chamber opening 16a is used as a contact surface with the heating chamber opening periphery 18. Chiyoke groove 19 for second harmonic
In b, the L-shaped radio wave propagation path from the inlet 23 to the short-circuit surface 15b is approximately λo/8. The wall surface 15 of the second harmonic channel groove 19b is divided into a plurality of tapered corrugated plates 15w as shown in FIG. They are arranged in the longitudinal direction with a gap size B larger than the entrance size A. The gap size B between adjacent corrugated plates 15w is the tip 15 of the corrugated plates 15w.
Since the entrance dimension A of the radio wave attenuation cavity 19 is larger near w', the electric field tends to concentrate at the tip 15w' of the corrugated plate 15w. Although the electric field is in a discontinuous state near the entrance 23, this has the effect of increasing the electric field component in the direction that propagates into the radio wave attenuation cavity 19 and reducing the electric field component in the direction that cannot propagate into the radio wave attenuation cavity 19. This means that the plate 15w has it. In other words, the corrugated plate 15w has the function of a matching post that efficiently introduces all high-order mode radio waves leaking between the heating chamber opening periphery 18 and the door 2 into the radio wave attenuation cavity 19, and the radio waves leaking to the outside. decrease. Furthermore, as shown in FIG. 3, the radio wave propagation path lengths in the two directions within the radio wave attenuation cavity 19 are set to approximately λo/4 and approximately λo/8 to provide high impedance for the fundamental wave and the second harmonic, respectively. I have to. The peripheral edge 18 of the opening of the heating chamber and the wall surface 16a of the fundamental wave channel 19a come into plane contact when the door 2 is closed, and since there is substantially little gap between them, this contact portion There are also fewer leakage radio waves entering. Further, since the contact portion has a low impedance (characteristic impedance as a transmission line) and is largely reflected from the high impedance of the inlet 23, the radio waves reaching the corrugated plate 15w are also very small. This minute radio wave is efficiently introduced into the radio wave attenuation cavity 19 by the action of the matching post of the corrugated plate 15w, and is retained as energy stored in the space inside this cavity 19, and a part of it is consumed as power loss on the wall surface. be done.

On the other hand, in order to maintain the dimensional relationship of gap dimension B>inlet dimension A and to increase the conductor surface of the corrugated plate 18w facing the heating chamber opening periphery 18 to lower the impedance between both conductors, the corrugated plate 15w is root 1
5w'' has a wide width, and the tip 15w' has a narrow taper shape.The reflection between the low impedance between these two conductors and the high impedance of the inlet 23 is increased, and the conductor passes through the inlet 23 to the outside. This further reduces the amount of leaked radio waves.

FIG. 5 shows a corrugated plate 15 at the corner 2a of the door 2.
The dimensional relationship between w is shown. At the corner 2a, the gap size C between the bases 15w'' of adjacent corrugated plates 15w is set to λo/4 or less. This corresponds to 1/2 wavelength and becomes a shearing region, which is a necessary condition to prevent the second harmonic that once entered the groove 19b from exiting the groove 19b again. If the gap size B between the tips 15w' of the corrugated plates 15w is also set to λo/4 or less for the same reason as above, the damping effect of the second harmonic tooth yoke groove 19b will be improved. At the circumference, the gap size B is larger than the entrance size A and is less than λo/4.

The radio wave attenuation cavity 19 as described above is for the fundamental wave, the second
Since it has a sufficient attenuation effect against harmonics, it is practically unnecessary to use auxiliary means such as ferrite or conductive rubber, which is advantageous in terms of cost reduction.

Furthermore, the necessary dimensions of the radio wave attenuation cavity 19 can be obtained by appropriately selecting the depths of both the fundamental wave chock groove 19a and the second harmonic wave groove in the direction parallel to the heating chamber opening periphery 18. Since the thickness may be thin, it is possible to create a desirable appearance in terms of design that is in balance with the thin electronic operation panel.

As described above, according to the present invention, it is possible to provide a high-frequency heating device equipped with a door that can reduce radio wave leakage and is suitable for reduction in thickness and cost.

[Brief explanation of the drawing]

FIG. 1 is an external view showing an example of the high-frequency heating device of the present invention, FIG. 2 is a schematic cross-sectional view of essential parts showing an example of the high-frequency heating device of the present invention corresponding to FIG. 1, and FIG.
The figure is an enlarged sectional view of the radio wave attenuation cavity 19 in FIG. 2, and FIGS. 4 and 5 are perspective views for explaining the dimensional relationship and function of the corrugated plate 15w near the entrance 23 of the radio wave attenuation cavity 19. It is. 2...door, 2a...corner of door 2, 11...
...Heating chamber, 15c...Chiyoke groove 1 for second harmonic
Wall surface of 9b, 15w...corrugated plate, 15w'...tip of corrugated plate 15w, 15w''...root of corrugated plate 15w,
16a... One wall surface of the fundamental wave chiyoke groove 19a,
18...Heating chamber opening periphery, 19...Radio wave attenuation cavity, 19a...Fundamental wave chiyoke groove, 19b...
Second harmonic chiyoke groove, 23... Entrance of the radio wave attenuation cavity 19, 24... Rotating shaft on the hinge side of the door 2.

Claims (1)

[Claims] 1. Fundamental wave chiyoke groove 19a and second harmonic chiyoke groove 1 obtained by appropriately selecting the depth in the direction parallel to the heating chamber opening peripheral edge 18 at the periphery of the door 2.
9b, and these two grooves face each other in opposite directions to form one radio wave attenuation cavity 1 having one inlet 23.
9, the fundamental wave channel groove 19a is arranged on the side closer to the heating chamber 11, one wall surface 16a of this groove 19a is brought into plane contact with the heating chamber opening periphery 18, and the second harmonic channel channel 19b is arranged. A plurality of tapered corrugated plates 15w, which are equivalent to alignment posts that efficiently guide leaked radio waves into the radio wave attenuation cavity 19, are formed by a wall surface 15c facing the heating chamber opening periphery 18.
A high-frequency heating device characterized in that the corrugated plate 15w is divided into two parts, and the gap size C between the roots of the corrugated plate 15w is set to 1/4 or less of the free space wavelength of the heating frequency at the corner 2a of the door 2.