JPS6322440B2 - - 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.

Compact, multifunctional electronic components such as ICs and microcomputers are being actively incorporated into the control circuits of high-frequency heating equipment, and operation panels are becoming smaller and thinner. There is a demand for thin doors. Furthermore, there is a growing tendency to automate complex operations, and as electronic circuits become more expensive, there is a demand for lower costs for mechanical parts, especially door mechanisms.

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 was made in the United States to increase the attenuation effect of the chiyoke groove as a radio wave propagation direction regulating device by periodically arranging conductor pieces of λ/4 length, so-called slits, on one side of the chiyoke groove, which has a depth of 1/4 of the used wavelength λ. Patent 2772402
(1956.11.27 patent) and 2850706 (1958.9.2 patent).

3767884 has a radio wave leakage prevention structure similar to the above patent.
(Japanese Patent Application Publication No. 48-81146, Japanese Patent 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 slot is opposite to the slit. This method forcibly maintains the distance between the metal surface and the metal surface 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, and its function as a radio wave propagation direction regulating device (electromagnetic energy mode sustaining structure) decreases. be. With this method, a large number of radio waves enter the gap between the door and the periphery of the heating chamber opening, and to prevent leakage of fundamental waves and high frequencies, it is necessary to add conductive rubber or to complicate the propagation path of the leaked radio waves, resulting in large attenuation. It is necessary to produce an effect, and it is not suitable for making doors thinner and lowering costs.

In addition, many proposals have been made, such as British Patent No. 1392498 and Japanese Patent Publication No. 51-22663, 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 to the fundamental wave and harmonics by dividing the wall surface of the chiyoke groove into multiple corrugated plates and giving specific relationships to the shapes and dimensions of the 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, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is an external view showing an example of a 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. The fundamental wave groove 19a for preventing radio wave leakage at a heating frequency of, for example, 2450 MHz, and the second high frequency wave groove 19b for preventing radio wave leakage at the second harmonic of the above frequency of 4900 MHz are arranged in opposite directions to each other. , forming one radio wave attenuation cavity 19 having one inlet 23. 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 one wall surface 16a of this groove 19a is used as a contact surface with the heating chamber opening periphery 18. In the second harmonic channel groove 19b, the L-shaped radio wave propagation path from the inlet 23 to the shorting surface 15b is approximately λo/8. The wall surface 15c of the second harmonic channel groove 19b is divided into a plurality of tapered corrugated plates 15w as shown in FIG.
The tips w have their tips at the entrance 23 of the radio wave attenuation cavity 19, and are arranged in the longitudinal direction with a gap dimension B larger than the entrance dimension A. The gap size B between adjacent corrugated plates 15w is larger than the entrance size A of the radio wave attenuation cavity 19 near the tip 15w' of the corrugated plate 15w.
The electric field tends to concentrate on w′. This is entrance 23
Although the electric field is discontinuous in the vicinity, this means that the corrugated plate 15w has the effect of increasing the electric field component that propagates into the radio wave attenuation cavity 19 and reducing the electric field component that cannot propagate into the radio wave attenuation cavity 19. 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 reduces the radio waves leaking to the outside. let 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. ing. The heating chamber opening periphery 18 and one wall surface 16a of the fundamental wave cheese yoke groove 19a come into plane contact when the door 2 is closed.
Since the gap between them is substantially small, the amount of leakage radio waves entering this contact portion is also small. 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. By the action of the matching posts of the corrugated plate 15w, these minute radio waves are efficiently guided into the radio wave attenuation cavity 19 and held as accumulated energy in the space inside the cavity 19, and some of it is consumed as power loss on the wall surface. Ru.

Leaked radio waves that do not enter the radio wave attenuation cavity 19 but pass through the inlet 23 and enter the gap between the heating chamber opening periphery 18 and the corrugated plate 15w and head to the outside are reflected to the heating chamber 11 side. By returning it, the effect of preventing radio wave leakage of the door 2 can be further improved. To do this, as is well known, the reflection at the connection point of two lines with different impedances increases as the difference in impedance between the two lines increases. For high impedance, the impedance (more precisely, the characteristic impedance) of the approximate parallel plate line formed between the conductors of the heating chamber opening periphery 18 and the corrugated plate 15w may be made small. Furthermore, it is known that the impedance of parallel plate lines decreases as the width of the line increases.

Therefore, by maintaining the dimensional relationship of gap size B>inlet size A at the tip 15w' of the corrugated plate 15w, and tapering the corrugated plate 15w so that the width becomes wider toward the base 15w', the heating chamber opening periphery 18 and the corrugated plate 15
The impedance of the line formed by w is reduced. That is, by increasing the reflection between the low impedance between the heating chamber opening periphery 18 and the conductors of the corrugated plate and the high impedance of the upper entrance 23, leakage radio waves passing through the entrance 23 and heading outside are further suppressed. . Therefore, ferrite, conductive rubber, etc. are not required, and costs can be reduced.

Furthermore, when opening the door 2, assuming that the black circle in FIG. 3 is the rotation axis 24 on the hinge side, the door cover end 14a and the corrugated plate 15w move as shown by arc-shaped arrows centered on this rotation axis 24. The base 15w'' and the tip 15w' rotate. When the door 2 opens,
The door cover end 14a on the hinge side and the root 15w'' of the corrugated plate 15w approach the heating chamber opening periphery 18, but the tip 15w' of the corrugated plate 15w moves away. On the side, the gap between the corrugated plate 15w and the heating chamber opening periphery 18 may be made smaller from the base 15w'' of the corrugated plate 15w toward the tip 15w'. In this way, when the door 2 is opened and closed, the corrugated plate 15w does not collide with the heating chamber opening periphery 18, and deformation of the corrugated plate 15w can be prevented. Furthermore, since the average distance between the conductor surfaces between the corrugated plate 15w and the heating chamber opening periphery 18 can be reduced, the impedance between the conductors can be reduced. Therefore, the effect of preventing radio wave leakage of the door 2 can be fully exhibited.

Furthermore, the required 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 chock groove 19b in the direction parallel to the heating chamber opening periphery 18. Since the thickness of 2 may be thin, it is possible to achieve a desired appearance in terms of design that is in balance with a thin electronic operation panel.

As described above, according to the present invention, it is possible to provide a high-frequency heating device including a door 2 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.
This figure is an enlarged sectional view of the vicinity of the radio wave attenuation cavity 19 in FIG. 2, and FIG. 4 is a perspective view for explaining the action of the corrugated plate 15w in the vicinity of the entrance 23 of the radio wave attenuation cavity 19. 2...Door, 11...Heating chamber, 15c...Wall surface of second harmonic chiyoke groove 19b, 15w...Corrugated plate, 15
w'... Tip of the corrugated plate 15w, 15w''... Root of the corrugated plate 15w, 16a... One wall surface of the fundamental wave chyo yoke groove 19a, 18... Heating chamber opening periphery, 19... Radio wave attenuation cavity, 19a... For the fundamental wave Chiyoke groove, 19b...2nd
Harmonic channel 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 and the fundamental wave groove 19a is connected to the heating chamber 1.
1, one wall surface 16a of this groove 19a is brought into planar contact with the heating chamber opening periphery 18, and the wall surface 15c itself facing the heating chamber opening periphery 18 of the second harmonic chiyoke groove 19b is placed in planar contact with the heating chamber opening periphery 18. It is divided into a plurality of tapered corrugated plates 15w equivalent to alignment posts that efficiently introduce leakage radio waves into the radio wave attenuation cavity 19, and the gap between the corrugated plates 15w and the heating chamber opening periphery 18 is set at the door 2. A high-frequency heating device characterized in that the corrugated plate 15w becomes smaller from the root to the tip on the hinge side where the rotating shaft 24 is located.