JPS6363119B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" 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.

``Conventional technology'' A radio maze is installed around the door of the high-frequency heating device.
There is a proposal in Utility Model Application No. 130642/1983 to provide slits in the partition plates that make up this radio maze, but the conventional slits (width 2 mm ± 0.5 mm, pitch 10 mm or less) alone are not sufficient for radio wave sealing. However, radio wave absorbing material has been added to the outer wall of the partition plate.

``Problems to be Solved by the Invention'' 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.

``Means for Solving the Problems'' Rather than providing a slit (slit) in the peripheral wall of the radio maze as in the conventional example, the present invention provides a method in which a portion of the peripheral wall of the radio maze is formed by forming a plurality of slits at sufficient intervals. It consists of metal pieces, and specific conditions are given to these metal pieces.

``Function'' Metal pieces are made to act as mutually independent matching elements in terms of radio waves so as to efficiently guide leaked radio waves into the radio maze.

"Embodiment" An embodiment of the high-frequency heating device of the present invention will be described with reference to the drawings.

1 is a heating chamber in which the object to be heated is placed, 2 is heating chamber 1
It is a flange that surrounds the entire circumference of the opening. Reference numeral 3 denotes an outer box that houses the heating chamber 1, and 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. Reference numeral 5 denotes a door rear plate that is in plane contact with the flange 2, and the door rear plate 5 and the door front plate 6 forming the exterior form a radio wave maze 7. The heating chamber 1, flange 2, sash 3a, door rear plate 5, and 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. 9 is a transparent window cover provided on the outside of the viewing window 11 consisting of many small holes;
2 is a transparent 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;
Narrow microstrip lines are periodically formed opposite to a.

FIG. 2 is an explanatory diagram showing the action of the metal piece 10. 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 labyrinth 7, and the facing length x between the sash 3a and the metal piece 10 is set to be 1/2 or more of the protruding size H of the metal piece 10.
Therefore, for leakage radio waves including higher-order modes and second harmonics, an electric field component (leaking radio waves entering the radio maze 7 The electric field component generated between the metal pieces 10 (which prevents leakage radio waves from entering 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 from each other in terms of radio waves (more precisely, in terms of electric field distribution). Further, it is cut off against the fundamental wave and second harmonics that enter the radio wave maze 7, and prevents radio waves from leaking to the outside.

According to the experiment, the width W of the metal piece 10 is 10 mm, the overhang dimension H is 10 mm, the distance between the metal plates between the sash 3a and the metal piece 10 is 3.5 mm, the gap dimension B is 10 mm, the entrance dimension A is 6 mm, and the door rear plate. 5 from the aircraft under the conditions that the gap between 5 and flange 2 is 1 mm, the high frequency output is 500 W, the wavelength used is 122 mm, and the water load is 275 ml.
The maximum leakage power at a distance of cm is 0.03mW/cm ²
(The conventional example, 130642 (1973-130642), was equipped with a radio wave absorbing material and was approximately
It was found that the power consumption was as low as 0.2 mW/cm ² ), which is sufficient for practical use. Incidentally, FIG. 3 shows the amount of leakage radio waves (mW/cm ² ) when the opposing length x is changed in accordance with the change in the overhang dimension H.

"Effects of the Invention" 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. Narrow microstrip lines are periodically formed using the maze, and the gap size between the metal pieces is equal to or larger than the entrance size of the maze, and the facing length between the sash and the metal piece is set to the overhang size of the metal piece. Since it is possible to significantly reduce leakage radio waves by more than half of 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 implementation effect is great.

[Brief explanation of drawings]

FIG. 1 is a sectional view of the main part of the high-frequency heating device of the present invention, FIG. 2 is a perspective view of the main part for explaining the action of the metal piece 10, and FIG. It is a characteristic diagram showing the amount of leakage radio waves. 1...Heating chamber, 2...Flange, 3a...Sash, 4...Door, 5...Door rear plate, 6...Door front plate, 7...Radio maze, 10...Metal piece, A...
Entrance dimension of the radio maze 7, B...Gap dimension between the metal pieces 10, H...Protrusion dimension of the metal pieces 10,
x...The opposing length between the sash 3a and the metal piece 10.

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. , between adjacent metal pieces 10 = dimension B is equal to or larger than the entrance dimension A of the same maze 7, and between the sash 3a and the metal pieces 10
The opposing length x is 1/ of the overhang dimension H of the metal piece 10.
A high frequency heating device characterized in that the heating frequency is 2 or more.