JPS6347240B2 - - 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 an improvement of a door with a periodic structure for preventing radio wave leakage.

Conventionally, in order to increase the radio wave leakage prevention effect of the chiyoke groove provided on the periphery of the door, a periodic structure was attached inside the chiyoke groove, or the peripheral wall of the chiyoke groove itself was formed with a periodic structure made of a large number of metal pieces. Although many proposals have been made, few have been put into practical use. The few that have been put into practical use are heating frequency
At 2450 MHz, the fundamental wave groove with a depth of approximately 1/4 of the free space wavelength λo (122 mm) is provided perpendicular to the heating chamber opening periphery (front flange surface), so the door It was thick, the space required for the radio wave seal was large, and the entire device was also large. Since radio wave sealing is performed only for fundamental waves, some products add radio wave absorbing material to seal against high frequencies. Furthermore, since the electromagnetic field is concentrated in the vicinity of the periodic structure, it has the disadvantage that it tends to promote abnormal heating and spark generation at the contact area between the door and the periphery of the opening of the heating chamber during dry firing.

SUMMARY OF THE INVENTION In view of the above points, it is an object of the present invention to provide a high-frequency heating device equipped with a door equipped with a periodic structure whose external dimensions can be reduced and where the abnormality described above is less likely to generate heat or sparks.

Next, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view of essential parts of the high-frequency heating device of the present invention. 1 is a heating chamber to which high frequency energy is supplied. A door 3 is arranged to face the opening periphery 2 of the heating chamber 1, and a door rear plate 3b made of a metal plate that makes plane contact with the opening periphery 2, and this door rear plate 3.
b and a door front plate 3a made of a metal plate to be attached with screws (not shown) or the like. Groove 5 in the fundamental wave chiyoke at the periphery of door 3
A radio wave attenuation cavity 4 having one inlet 7 is formed by opposing the channel a and the second harmonic groove 6a. In the fundamental wave channel groove 5a, the radio wave propagation path 5 shown by the arrow from the inlet 7 to the short-circuit surface 5b is approximately λo/4 with respect to the free space wavelength λo of the heating frequency. The fundamental wave channel groove 5a is arranged on the side closer to the heating chamber 1, and the door rear plate 3b, which is one wall surface of this groove 5a, is brought into planar contact with the opening periphery 2 (the first
In the figure, a gap is intentionally left open for clarity). In the second harmonic channel groove 6a, the radio wave propagation path 6 shown by the arrow from the inlet 7 to the shorting surface 6b is about λo/8. The edge 10 of the inlet 7 is a trapezoid whose width at the edge 10W'' is larger than the width at the edge 10W' of the inlet 7.
A plurality of corrugated plates 10 each having a trapezoidal shape larger than the width of W′
It is divided into W parts and placed at intervals.
This corrugated plate 10W prevents the radio waves that have passed from the heating chamber 1 through the gap between the opening periphery 2 and the door rear plate 3b from leaking to the outside, and prevents the radio waves from leaking to the outside. It is intended to act as a matching element that can be efficiently guided into the second harmonic chiyoke groove 6a, and the length from the peripheral edge 10W'' to the edge 10W' of the inlet 7 is preferably about λo/12 according to experiments.

A protruding surface 8 bent toward the inside of the radio wave attenuation cavity 4 is provided at the tip 10W' of the corrugated plate 10W, and a protruding surface 9 is also provided at the end of the door rear plate 3b substantially parallel to this protruding surface 8. By making the gap between both protruding surfaces 8 and 9 a radio wave propagation path perpendicular to the opening periphery 2, both the fundamental wave chiyok groove 5a and the second harmonic chiyok groove 6a are connected to the aperture periphery 2. The radio wave propagation paths 5 and 6 are L-shaped, consisting of a perpendicular direction and a parallel direction.

As mentioned above, the radio wave propagation paths 5 and 6 of both the yoke grooves 5a and 6a are approximately λo/4 and approximately λo/8, respectively, and are bent in a direction perpendicular to and parallel to the opening periphery 2. ing. Therefore, dimensions A and B corresponding to the thickness of the door 3 in the direction perpendicular to the opening periphery 2 and the opening periphery 2 of the radio wave attenuation cavity 4.
The dimension C in the direction parallel to can be reduced.

In the door of the above example, A is 13mm, B is 16mm, and C
Experiments have confirmed that a diameter of about 40 mm is sufficient for practical use, and the empty space around the periphery of the door 3 required to prevent radio wave leakage can be kept small. Therefore, the external dimensions of the door 3 can be made smaller and thinner, and the heating chamber 1 can be made smaller and thinner than the external dimensions of the entire device.
It is possible to provide a high-frequency heating device with a good volume ratio (space factor) of . This is convenient for built-in types and other cases where space is limited, and is also suitable for thin electronic control panels, which is advantageous in terms of design. Of course, since less material is required, it is also advantageous in terms of cost.

Further, as shown in FIG. 2, a protruding surface 8 is provided by bending the tip 10W' of the corrugated plate 10W, and the protruding surface 8 and the protruding surface 9 at the end of the door rear plate 3b are made substantially parallel to each other so that their planes are mutually connected. Because they are facing each other,
The electric field becomes like the arrow and is not locally strong. Therefore, the door 3 with the periodic structure of this embodiment is free from abnormalities due to high-frequency electromagnetic fields that are likely to occur during dry firing at the contact area between the door rear plate 3b and the opening periphery 2, especially near the curved area of the protruding surface 9. Inconveniences such as heating and sparks can be reduced.

Furthermore, for the corrugated plate 10W, the width of the peripheral edge 10W'' is
Because it has a trapezoidal shape larger than the width of 0W',
The strength of the corrugated plate 10W is strong and prevents deterioration of radio wave leakage prevention effect due to deformation.

As described above, the present invention has the following effects.

1. The radio wave attenuation cavity volume of the door becomes compact, the door can be made smaller and thinner, and a high-frequency heating device with a good space factor can be provided.

2. Fewer materials are required for door component parts, which is advantageous for cost reduction.

3. Since the corrugated plate and the end of the door rear plate face each other on a plane basis, it is possible to reduce abnormal heating and generation of sparks at the contact area between the door and the periphery of the opening of the heating chamber during dry firing.

4. Since the corrugated plate has a trapezoidal shape in which the width of the periphery is larger than the width of the edge, the strength of the corrugated plate is strong, and the deterioration of the radio wave leakage prevention effect due to deformation can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a main part of a high-frequency heating device according to an embodiment of the present invention, and FIG. 2 is a perspective view of a main part corresponding to FIG. 1... Heating chamber, 2... Opening periphery of heating chamber 1, 3...
Door, 3a...Door front plate, 3b...Door rear plate, 4...Radio wave attenuation cavity, 5...Radio wave propagation path of fundamental wave chock groove 5a, 6...Radio wave propagation path of second harmonic wave chock groove 6a, 7 ... Entrance of the radio wave attenuation cavity 4, 8... Protruding surface, 9... Protruding surface, 10... One wall surface of the second harmonic chiyoke groove 6a, 10W... Corrugated plate, 10W'... Edge of corrugated plate 10W, 10W''... Periphery of corrugated plate 10W.

Claims (1)

[Claims] 1 In a high-frequency heating device in which a periodic structure for preventing radio wave leakage is provided on the periphery of the door 3 facing the opening periphery 2 of the heating chamber 1, one inlet 7 facing the opening periphery 2 and then the heating chamber Fundamental wave chiyoke groove 5a having a radio wave propagation path 5 of approximately λo/4 (λo: free space wavelength) parallel to the opening periphery 2 in one direction.
, and has a radio wave propagation path 6 of about λo/8 from the entrance 7 to the peripheral edge of the door 3, and the dimension of the peripheral edge 10W'' of the surface 10 facing the opening peripheral edge 2 is the edge 10W' of the entrance 7. A larger trapezoidal corrugated plate 10W is used, and a second harmonic wave groove 6a is arranged at intervals, and a groove 5a, 6a side is formed parallel to each other from both edges 9', 10W' of the inlet 7. It consists of protruding surfaces 9 and 8 that protrude to each chiyoke groove 5.
The respective radio wave propagation paths 5 and 6 of a and 6a are connected to the opening periphery 2.
A high-frequency heating device characterized in that a periodic structure for preventing leakage of radio waves is provided which is bent in a direction perpendicular to and in a direction parallel to the direction.