JPS6361755B2 - - 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 operation and effects of the present invention will be explained with reference to FIG. 2 and FIG. 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 ) will increase,
The electric field component generated between the metal pieces 10 (leaking radio waves cannot enter the radio wave maze 7) is reduced. 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 input/4, the fundamental wave and second harmonic that enter the radio maze 7 are cut off, and radio waves passing through the gap B and leaking to the outside are prevented. I'm here. Since the overhang dimension H is smaller than I/8, there is no series resonance for the fundamental wave and the second harmonic, so a large amount of high-frequency current does not flow through the metal piece 10, and the cited practical application As stated in 130642/1982, the serious drawback that the slit portion of the conventional slit yoke generates heat 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 line formed between the two 3a and 10 can be Since only the transmission mode TEM waves of each microstrip line can be transmitted independently from each other, a significant reduction in leakage radio waves can be achieved.

According to experiments, the distance D between the metal plate 3a and the metal piece 10 is 3.5 mm, and the width W of the metal piece 10 is
10mm, overhang dimension H is 10mm, gap dimension B is 10
mm, entrance dimension A is 6 mm, door rear plate 5 and flange 2
The gap between the two is 1mm, the high frequency output is 500W,
The maximum leakage power at a distance of 5 cm from the aircraft is 0.03 m under the conditions of wavelength input of 122 mm and water load of 275 ml.
It was found that the power consumption was as low as W/cm ² (approximately 0.2 mW/cm ² in the conventional example, 130642/1983, with a radio wave absorbing material), and was 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, and the gap size and width of the metal pieces are made larger than the distance between the two, making it possible to significantly reduce leakage radio waves, eliminating the need for radio wave absorbing materials, and furthermore Since a part of the front panel itself is a periodic structure and no additional parts are required, it is possible to provide a high-frequency heating device with a small number of parts, a simple structure, easy assembly, small door dimensions, and a good space factor. , the effects of implementation are significant.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a 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 a 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 edge is made up of a plurality of metal pieces 10 that are radio wave independent of each other, and a sash 3a is placed opposite the metal pieces 10 to periodically form a narrow microstrip line. , and between the metal pieces 10 = Dimension B, width W is the distance D between the sash 3a and the metal piece 10
A high-frequency heating device characterized by being larger than.