JPS6155754B2 - - 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 one that has been put into practical use has a heating frequency of 2450MHz.
The fundamental wave groove, which has a depth of about 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 is 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 harmonic waves. 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, an object of the present invention is to provide a high-frequency heating device equipped with a door equipped with a periodic structure that can have a small external size and is less likely to cause abnormal heating or sparks.

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

FIG. 1 is a perspective view of essential parts showing an embodiment of the high-frequency heating device of the present invention. 1 is a high frequency oscillator that generates high frequency energy; 2 is a waveguide that connects the high frequency oscillator 1 and the heating chamber 3; 4 is heating chamber 3
This flange is provided on the front side of the opening.
There are latch insertion openings 4a and 4b through which latches 5a and 5b provided on the door 5 pass. Latch 5
a and 5b control on/off of the high frequency oscillator 1 and keep the door 5 in a sealed state. Reference numeral 5c denotes a door rear plate that makes plane contact with the flange 4 when the door 5 is closed, and is made of a metal plate. 5d is a viewing window made of a transparent plate and a wire mesh or a perforated metal plate. 5
Reference character e denotes a dielectric cover that covers the entrance 7 of the radio wave attenuation cavity 6 and the periodic structure 8 provided at the peripheral edge of the door 5 as shown in FIG.

FIG. 2 is an enlarged cross-sectional view of the planar contact portion between the door 5 and the flange 4 in FIG. 1. At the periphery of the door 5, a fundamental wave groove 9 and a second harmonic wave groove 10 are opposed to form one radio wave attenuation cavity 6 having one entrance 7. In the fundamental wave channel groove 9, the radio wave propagation path 9a shown by the arrow from the inlet 7 to the short-circuit surface is connected to the free space wavelength λ of the heating frequency.
It is set to approximately λo/4 for o. The fundamental wave chiyoke groove 9 is arranged on the side closer to the heating chamber 3, and the door rear plate 5c, which is one wall surface of this groove 9, is in plane contact with the flange 4 (a gap is intentionally left in Fig. 2 for clarity). (Illustrated). Second
In the harmonic channel groove 10, the radio wave propagation path 10a shown by the arrow from the inlet 7 to the short-circuit surface is approximately λo/8. One wall surface of the second harmonic chiyoke groove 10 facing the flange 4 is divided into corrugated plates 8 (periodic structure) consisting of a plurality of metal pieces each having a trapezoidal shape in which the width of the base 8a is larger than the width of the tip 8b. (See Figure 3). This corrugated plate 8 prevents the radio waves that have passed from the heating chamber 3 through the gap between the flange 4 and the door rear plate 5c from leaking to the outside as shown by the dotted arrow 11. It is used as a matching element to efficiently guide the wave into the channel groove 9 or the channel groove 10 for the second harmonic, and according to experiments, the length from the root 8a to the tip 8b is preferably about λo/12. The tip 8b of the corrugated plate 8 has a protruding surface 12 bent toward the inside of the radio wave attenuation cavity 6.
is provided, and a door rear plate 5 is provided approximately parallel to this protruding surface 12.
A protruding surface 13 is also provided at the end of c, and both protruding surfaces 12,
By making the gap between 13 a radio wave propagation path perpendicular to the flange 4, both the fundamental wave channel groove 9 and the second harmonic channel groove 10 are connected to the flange 4.
The radio wave propagation paths 9a and 10a consist of a direction perpendicular to the direction and a direction parallel to the direction. As mentioned above, the radio wave propagation paths 9a and 10a of both the yoke grooves 9 and 10
and about λo/4 and about λo/8, respectively, and are bent in a direction perpendicular to and parallel to the flange 4. Therefore, dimensions A and B corresponding to the thickness of the door 5 in the direction perpendicular to the flange 4, and dimension C of the radio wave attenuation cavity 6 in the direction parallel to the flange 4.
can be made smaller. For example, heating frequency
In a 2450MHz (wavelength λo = 122mm) high-frequency heating device, it has been confirmed through experiments that A of 13mm, B of 16mm, and C of 40mm are sufficient for practical use. The empty space can be kept extremely small. Therefore, the external dimensions of the door 5 can be made smaller and thinner, and a high-frequency heating device with a good volume ratio (space factor) of the heating chamber 3 to the external dimensions of the entire device can be provided. This is a built-in expression,
In addition, it is convenient when the space is limited, and it 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.

As shown in FIG. 3, a protruding surface 12 is provided by bending the tip 8b of the corrugated plate 8, and the protruding surface 12 and the protruding surface 13 at the end of the door rear plate 5c are made substantially parallel and face each other. Therefore, both planes 1
The electric field between 2 and 13 does not become locally strong. Therefore, the door 5 with the periodic structure has the door rear plate 5
This has the effect of reducing inconveniences such as abnormal heating and sparks caused by high-frequency electromagnetic fields that are likely to occur during dry firing at the contact portion between c and the flange 4, particularly near the curved portion of the protruding surface 13. Further, since the corrugated plate 8 has a trapezoidal shape in which the width of the base 8a is larger than the width of the tip 8b, the strength of the corrugated plate 8 is strong, and the deterioration of the radio wave leakage prevention effect due to deformation can be prevented.

Furthermore, as shown in FIG. 3, a latch storage section 14 made of a metal plate with a U-shaped cross section is provided outside the radio wave attenuation cavity 6 to store the latches 5a, 5b and related parts (not shown). Entrance 1 of section 14
4a is opposed to the flange 4 and covered with a second corrugated plate 81 having the same shape as the corrugated plate 8 forming one wall surface of the second harmonic channel groove 10. The second corrugated plate 81 faces oppositely to the corrugated plate 8, and has a trapezoidal shape in which a base 81a is larger than a tip 81b, and a protruding surface 121 that is bent toward the inside of the latch storage portion 14 is provided at the tip 81b. , this protruding surface 121 is substantially parallel to the side wall 14b of the latch housing 14. In the second corrugated plate 81, only the protruding portions of the latches 5a and 5b are removed. Second corrugated plate 8 for the amount of radio wave leakage when only the corrugated plate 8 is provided around the entire periphery of the door 5
1 is added to the entrance 14a of the latch storage section 14, the ratio of the amount of radio wave leakage is as shown in FIG. It was confirmed that by adding , the amount of radio wave leakage can be kept relatively smaller than when not adding. The data in Figure 4 is latch 5.
This was obtained by short-circuiting door switches (not shown) related to a and 5b. Even if the flatness of the contact surface between the door 5 and the flange 4 is poor and there are irregular gaps in the contact surface, the amount of radio wave leakage can be reduced by adding the second corrugated plate 81 to the entrance 14a of the latch storage section 14. It can be kept small. In this way the second
Even if the second corrugated plate 81 is added, the external dimensions of the door 5 do not change compared to when the second corrugated plate 81 is not added, and the above-mentioned effects such as being able to provide a good high-frequency heating device for the space factor are also maintained. . Further, the tip 81b of the second corrugated plate 81 faces the outermost peripheral wall of the door 5 (the side wall 14b of the latch storage portion 14) in a plane-to-plane manner, and only minute radio waves that have passed through the radio wave attenuation cavity 6 reach it. Therefore, no sparks or abnormal heating will occur due to high frequency electromagnetic fields.

Further, the corrugated plate connecting surface 15 connecting the bases 81a of the second corrugated plate 81 is brought into planar contact with the inner wall 14c of the latch storage portion near the radio wave attenuation cavity 6, and is attached removably. The installation workability and serviceability of the latches 5a, 5b and related parts (not shown) are improved without reducing the radio wave attenuation effect. Reference numeral 16 denotes a mounting foot from which a part of the corrugated plate connecting surface 15 protrudes, as shown in FIG.
It is adapted to engage with a support piece 17 provided in the. Even if the corrugated plate connecting surface 15 and the inner wall 14c are screwed together (not shown), planar contact between the two 15 and 14c is maintained, allowing easy attachment and detachment.

As described above, the present invention has a simple configuration, has small external dimensions, is unlikely to cause abnormal heating or sparks, and can be used even when the flatness of the contact area between the door and the flange on the front surface of the heating chamber opening is poor. A high-frequency heating device including a door with a periodic structure that can withstand use can be provided. Furthermore, since the second corrugated plate is detachable, the installation workability and serviceability of the latch and related parts (not shown) are improved.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of essential parts showing an embodiment of the high-frequency heating device of the present invention, and FIG. 2 is a door 5 in FIG. 1.
Enlarged cross-sectional view of the planar contact portion between the flange 4 and the flange 4, 3rd
The figure is a perspective view of the inside of the door 5 seen diagonally from above with the dielectric cover 5e removed, and FIG. 4 shows the second corrugated plate 8 shown in FIG.
5 is a perspective view of the second corrugated plate 81. FIG. DESCRIPTION OF SYMBOLS 1... High frequency oscillator, 3... Heating chamber, 4... Flange, 5... Door, 5a, 5b... Latch, 6... Radio wave attenuation cavity, 7... Entrance of radio wave attenuation cavity 6, 8... Corrugated plate,
81...Second corrugated plate, 9...Chiyoke groove for fundamental wave, 1
0... Second harmonic choke, 14... Latch storage section, 14a... Entrance of latch storage section 14, 15... Corrugated plate connection surface.

Claims (1)

[Claims] 1. A radio wave attenuation cavity having one entrance is formed by arranging a fundamental wave groove and a second harmonic wave groove facing each other on the peripheral edge of the door that seals the opening of the heating chamber, and The wall surface facing the flange of the heating chamber opening of the second harmonic chiyoke groove is formed into a corrugated plate made of a trapezoidal metal piece with multiple bent ends, which controls the on/off of the high frequency oscillator and also controls the sealing state of the door. A latch accommodating section made of a metal plate having a U-shaped cross section for accommodating a latch, etc. that holds the wave is provided outside the radio wave attenuation cavity, and the entrance of the latch accommodating section is arranged to face the flange of the opening of the heating chamber. It is covered with a second corrugated plate having the same shape as the plate, and the corrugated plate connecting surface that connects the bases of this second corrugated plate is brought into planar contact with the inner wall of the latch housing near the radio wave attenuation cavity, and is attached removably. A high frequency heating device characterized by: