JPS6361759B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in the radio wave leakage prevention structure of a door provided at the entrance of a heating chamber of a high-frequency heating device so as to be openable and closable.

A radio maze is installed around the door of the high-frequency heating device,
There is a proposal in Utility Model Application Publication No. 54-130642 to provide slits in the partition plates that make up this radio maze (width 2 mm ± 0.5 mm,
Since it cannot be said that the radio wave sealing effect is sufficient only with a pitch of 10 mm or less, radio wave absorbing material is added to the outer wall of the partition plate. As a result, the number of parts increases, the structure becomes complicated, assembly is difficult, and the outer dimensions of the door become large, resulting in a high-frequency heating device with a poor space factor.

Therefore, rather than providing a slit (slit) in the peripheral wall of the radio maze as in the conventional example, the present invention constructs a part of the peripheral wall of the radio maze from a plurality of metal pieces spaced sufficiently apart. By applying specific conditions to the metal pieces, they are made to act as mutually independent matching elements in terms of radio waves that efficiently guide leakage current into the radio maze.
The purpose is to obtain a high-frequency heating device that has a simple structure, is easy to assemble, has a small door external dimension, and has a good space factor.

Next, the structure and operation of the high frequency heating device of the present invention will be explained with reference to the drawings.

FIG. 1 is a sectional view of essential parts of an embodiment of the high-frequency heating device of the present invention. 1 is a heating chamber into which an object to be heated is placed; 2 is a flange surrounding the entire opening of the heating chamber 1; 3 is an outer box that stores heating chamber 1;
The front periphery of the outer box 3 also serves as a sash 3a that extends the metal plate constituting the outer box 3 and surrounds the door 4. 5 is a door rear plate that makes plane contact with the flange 2;
This door rear plate 5 and the door front plate 6 forming the exterior form a radio wave maze 7. heating chamber 1, flange 2,
The sash 3a, the door rear plate 5 and the door front plate 6 are each made of a metal plate. A maze cover 7b made of a radio wave transparent dielectric material is press-fitted into the entrance 7a of the radio wave maze 7, and a door cover 8 made of a radio wave transparent dielectric material is press-fitted onto the outer periphery of the door front plate 6. Reference numeral 9 denotes a transparent outer window cover provided on the outside of the viewing window 11 consisting of a large number of small holes, and 12 represents a transparent inner window cover provided on the heating chamber 1 side of the viewing window 11. Reference numeral 10 denotes a plurality of metal pieces periodically extending from the outermost edge of the door front plate 6, which periodically form narrow microstrip lines facing the sash 3a.

FIG. 2 is an explanatory diagram showing the action of the metal piece 10. The configuration, operation, and effects of the present invention will be explained with reference to this FIG. 2 and the above-mentioned FIG. 1. The gap dimension B between adjacent metal pieces 10 is set to be equal to or larger than the entrance dimension A of the radio wave maze 7, and smaller than 1/4 of the input wavelength used. The overhang dimension H is smaller than the input/8. Therefore, for leakage radio waves including higher-order modes and second harmonics, an electric field component (leaking radio waves entering the radio maze 7 can)
increases, and an electric field component occurs between the metal pieces 10 (leakage radio waves cannot enter the radio maze 7).
becomes less. That is, the metal piece 10 functions as a kind of matching element that efficiently guides leaked radio waves into the radio wave maze 7 and is independent of each other in terms of radio waves.

In addition, since the gap dimension B is smaller than I/4, it is cut off for the fundamental wave and second harmonic that enter the radio maze 7, and prevents radio waves from leaking to the outside through the gap B. There is. Overhang dimension H
Since it is smaller than input/8, there is no series resonance for the fundamental wave and second harmonic, so
A large amount of high-frequency current does not flow through the metal piece 10, and the serious drawback that the slit portion of the conventional slit yoke generates heat as described in the cited Japanese Utility Model Application No. 54-130642 is eliminated. Furthermore, by making the gap size B and width W larger than the distance D between the metal plates between the sash 3a and the metal piece 10,
The periodic microstrip lines formed between a and 10 are radio wave independent of each other, and only the transmission mode TEM waves of each microstrip line can be transmitted, resulting in a significant reduction in leakage radio waves. can.

According to experiments, the distance D between the metal plate 3a and the metal piece 10 was 3.5 mm, and the width W of the metal piece 10 was 10 mm.
mm, overhang dimension H is 10 mm, gap dimension B is 10 mm,
The maximum amount of leakage power at a distance of 5 cm from the fuselage is under the conditions that the entrance dimension A is 6 mm, the gap between the door rear plate 5 and the flange 2 is 1 mm, the high frequency output is 500 W, the input wavelength used is 122 mm, and the water load is 275 ml. 0.03mW/
cm ² (conventional example, 130642/1983, using a radio wave absorbing material) was as low as about 0.2 mW/cm ² and was found to be sufficiently practical.

As described above, according to the present invention, the outermost edge of the door front plate that forms the wall of the radio maze is composed of a plurality of metal pieces that are independent from each other in terms of radio waves, and the sash is placed opposite to the metal pieces to create a narrow micro Strip lines are formed periodically to significantly reduce leakage radio waves, eliminating the need for radio wave absorbing material and requiring the addition of special parts by making part of the door front plate itself a periodic structure. Therefore, it is possible to provide a high-frequency heating device with a small number of parts, a simple structure, good assemblability, a small door external dimension, and a good space factor, and the effects of implementation are great.

Furthermore, since the overhanging dimension of the metal piece is made smaller than I/8, the disadvantage of heat generation near the metal piece can be solved without adding any special parts or materials.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of the main part of the high-frequency heating device of the present invention, and FIG. 2 is a perspective view of the main part for explaining the action of the metal piece 10. 1...Heating chamber, 2...Flange, 3a...Sash, 4...Door, 5...Door rear plate, 6...Door front plate, 7...Radio wave maze, 10...Metal piece.

Claims (1)

[Claims] 1 Flange 2 surrounding the entire opening of heating chamber 1
A radio labyrinth 7 is formed around the periphery of the door 4 which opens and closes the opening, and the labyrinth 7 includes a door rear plate 5 which is in plane contact with the flange 2. and a door front plate 6 whose outermost periphery is made up of a plurality of metal pieces 10 that are radio wave independent of each other, and a sash 3a is opposed to the metal pieces 10 to periodically form a narrow microstrip line. , and the overhang dimension H of the metal piece 10 is made smaller than 1/8 of the wavelength used.