JPS6361756B2 - - 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 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. 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 current maze by a plurality of metal pieces spaced sufficiently apart. By applying specific conditions to the metal pieces, they are made to act as radio-independent matching elements that efficiently guide leakage current into the radio maze.The purpose is to have a simple structure and ease of assembly. The goal is to obtain a high-frequency heating device with good space factor, small external dimensions of the door, and 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 peripheral edge 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. 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 used wavelength λ. The overhang dimension H is made smaller than λ/8. Therefore, the tip of the metal piece 10 and the peripheral edge 5a of the door rear plate 5 are prevented from leaking radio waves including high-order modes and second harmonics.
The electric field component generated between the
(can enter inward) increases, and metal pieces 10
The electric field component generated between the radio waves (leaked radio waves cannot enter the radio wave maze 7) is reduced. In other words, the metal piece 10 efficiently guides leaked radio waves into the radio maze 7 in a radio wave manner (more precisely, in terms of electric field distribution).
They function as a kind of matching element that is independent of each other.

In addition, since the gap dimension B is smaller than λ/4, the fundamental wave and second harmonics that enter the radio maze 7 are cut off, and current leaking to the outside through the gap B is prevented. There is. Overhang dimension H
Since it is smaller than λ/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, if the gap size B and width W between the sash 3a and the metal piece 10 are made larger than the distance D between the metal plates, the periodic microstrip lines formed between the two 3a and 10 will be mutually connected to each other in terms of radio waves. Since only the transmission mode TEM wave of each microstrip line can be transmitted independently, leakage radio waves are significantly reduced.

According to experiments, the width W of the metal piece 10 is 10 mm, the overhang dimension H is 10 mm, the distance D between the metal plates between the sash 3a and the metal piece 10 is 3.5 mm, and the gap size 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 wavelength used is 122 mm, and the water load is 275 ml. 0.03mW/
It was found that the power consumption was as low ^as 0.2 mW/cm ² (conventional example No. 54-130642 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, which forms the wall surface 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-stack. Rip lines are formed periodically to significantly reduce leakage radio waves, which eliminates the need for radio wave absorbing material and eliminates the need to add special parts by making part of the door front plate itself a periodic structure. Because there are no parts, the number of parts is small.
It is possible to provide a high-frequency heating device with a simple structure, good assemblability, a small outer diameter of the door, and a good space factor, and the effects of implementation are great.

[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 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. A high frequency heating device characterized by: