JPS62145686A - Radio frequency heater - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a high-frequency heating device, and more particularly to a radio wave leakage prevention structure for an openable and closable door provided at the entrance of a heating chamber of a high-frequency heating device.

A conventional high-frequency heating device heats or cooks food, which is an object to be heated, placed in a heating chamber using high-frequency energy supplied from a magnetron, which is a source of high-frequency radio waves. This high-frequency heating device is equipped with a door that can be opened and closed, but there is a slight gap between the main body of the heating chamber and the door, and radio waves leak to the outside through this gap, so there is no risk of harm to two people, etc. Taking into account the negative effects, it is necessary to suppress the amount of leakage below the legally permissible value, and for this purpose, a leakage prevention mechanism is provided mainly on the door surface.

As a mechanism for preventing radio wave leakage in general doors.

In the choke method, a choke structure with radio wave attenuation grooves is placed around the circumference and edge of the door, and the dimension from the entrance of the radio wave passage formed by the heating chamber and the door to the groove and the width of the groove are determined respectively by the wavelength of the radio waves used. There is a means to make it 1/4 of . This means has the advantage that it is equivalent to short-circuiting the entrance of the radio wave path in terms of impedance, and prevents leakage of radio waves.

On the other hand, since the width of the groove is regulated, it is difficult to make the door more compact and, by extension, the entire high-frequency heating device more compact. In addition, as another radio wave leakage prevention mechanism, for example,
As shown in Japanese Patent Publication No. 52-7586, an extended portion of a sealing plate is positioned at the opening of a choke groove, a part of this extended portion is bent inward toward the choke groove, and a plurality of holes are inserted into this bent portion. A method of providing a slit has been proposed, but this method also requires a choke groove with a width lfi (1/4 of the radio wavelength), so it was not possible to reduce the size of the door. In various radio wave sealing means that seal leakage radio waves by arranging plates, the sealing effect is exhibited when periodic structures having slits are arranged in close contact with the flanged portion of the door.

However, in reality, in order to prevent the surface of the periodic structure from becoming dirty and to prevent fragments of the heated object from entering the radio wave seal part,
It is necessary to cover the radio wave cool part with a dielectric cover of a certain thickness. Furthermore, even if a dielectric cover is not used and a film coating is applied instead to maintain close contact, the coating may be damaged due to impact and abrasion due to opening and closing of the door (lζ) and the opening between the periodic structure and the heating chamber. Metallic contact occurs between the peripheral edges and sparks are generated between the two.Therefore, in this case as well, it is necessary to interpose a dielectric cover to electrically insulate the two.These dielectric covers also cover the door. This impedes downsizing.

The problem to be solved by the invention is that the size of the choke groove, dielectric cover, etc. makes it impossible to downsize the door.

Means for Solving the Problems The present invention provides the above-mentioned device by providing a groove (hereinafter referred to as groove) surrounded by metal having a substantially U-shaped cross section on one peripheral edge of the door body. At the same time, the #4 opening is opened facing the opening peripheral wall of the heating chamber (opening 7 flange part or sash plate part), and this opening has a horizontal part that covers more than half the width of the groove. , Abbreviation-shaped periodic structures having vertical portions with a length equal to or shorter than this horizontal portion are provided periodically in the longitudinal direction of the groove.2 The width of the periodic structure, arrangement pinch, etc. By selecting the optimum conditions, a door with less radio wave leakage and a small size can be constructed, thereby making the high-frequency heating device more compact.

Function The function of the present invention is that by changing the length, width, arrangement pitch, etc. of each part of the L-shaped periodic structure that constitutes the transmission line for leakage radio waves, the impedance when looking inside from the opening of the groove becomes open. The leakage radio waves are reduced by repeating multiple reflections.

Example An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view showing the appearance of the high-frequency heating device of the present invention. In the figure, 1 is a heating chamber that stores objects to be heated, and 2 is a cabinet that surrounds the heating chamber 1.

The front edge of the cabinet 2 is an extension of the metal plate forming the cabinet 2 and surrounds the door 3.

A sash plate 4 is formed as a part of the opening peripheral wall of the heating chamber 1. Reference numeral 5 denotes a flange portion surrounding the entire circumference of the opening of the heating chamber 1, and constitutes another part of the peripheral wall of the opening of the heating chamber. Reference numeral 6 denotes an operation section and display section for operating the high-frequency heating device, 7 a door handle, and 8 a viewing window. Fig. 2 is a sectional view showing one embodiment of the high frequency heating device of the present invention;
The figure is an enlarged perspective view of the main part of FIG. 2. The same parts as in Figure 1 are indicated by the same numbers. As shown in the figure, a part of the side wall 9 of the heating chamber 1 is bent to form a flange.

There is an upright sash plate 4 in its extension, and this sash plate 4 and the flange portion constitute a heating chamber opening peripheral wall 5 that supports the door.

In front of the flange portion, radio wave seal portions disposed on the peripheral edge of the door body B are placed facing each other, and the two are partially in contact with each other. The radio wave seal mechanism includes a groove formed of metal and a plurality of periodic structures that cover the opening surface of the groove. That is, on the periphery of the door body 3, there is a metal groove 10 having a substantially U-shaped cross section, forming a groove space 11. The width L1 of the groove 10 is approximately /4 of the radio wave wavelength used.
The wavelength is narrower, 1/6. The depth of the groove is also 1/6 wavelength. Further, the openings 12 of the grooves 10 are arranged one opening aJ across the wall 5.

There is a flat end face 16 on the heating chamber side of the two ends of the groove 10, and on this end face 16 there is a viewing window 8 made of punched metal and a glass cover (not shown). Reference numeral 14 denotes a door back plate, which is supported on the end face 13 together with the peripheral edge of the viewing window 80 by means of screws jt at a support portion 15.This door back plate 14 also connects the base portion of the periodic structure j7 and the periodic structure 17 It constitutes the main body part.

That is, the door back plate 14 has a flat portion 1 without a notch.
6 and 1 periodic structure 17 (the boundary between the two coincides with the end face of the opening of the groove), and the tip part 1 of the periodic structure 17
8 is bent to form a generally rectangular cross section.

This tip portion 18 is designed to protrude into the groove space 11, but it must be arranged so that there is always a gap between its end surface 19 and the bottom surface 20 of the groove 10. 21 is dielectric cover 1
It covers the groove opening 12 containing the periodic structure (the outer periphery of the groove 10 is also covered with a dielectric cover, but this is omitted).

FIG. 6 shows the structural conditions of the periodic structure for exhibiting excellent radio wave sealing performance.

However, the value t2 of the first JD periodic structure 17 is set to be smaller than approximately 1/4 of the wavelength of the radio waves used. The second is the horizontal length 13 of the periodic structure 17.

This t3 is groove/fuku 1. Although it changes depending on the
0172 or more, that is, under the condition of t3≧1/2 t+, the radio wave effect is large. 6th is the bent tip 1
8, but as a condition to suppress the leakage amount to a low level, as shown in Fig. 4, if t3 is a dog, then t4
needs to be small, and if t3 is small, then t
You need to listen to 4. This is the area of t3-44 where the radio wave/-sill effect is high. The fourth is the length of the arrangement interval t5 of the periodic structures.Although the optimum condition for this t5 changes slightly depending on the width t2 of the periodic structure, it is approximately the same as the set width of t2, that is, the approximate radio wave wavelength used. The radio wave sealing effect will be high if you provide a distance of about 10 to 10 minutes. Also 42
The arrangement period P of the periodic structure represented by +t5 is suitably a length of about 4 of the radio wave wavelength used. FIG. 5 is a characteristic diagram showing the amount of radio wave leakage in the embodiment of the present invention. t2 = 20mm + at the opening of the groove narrower than 4 of the radio wave wavelength used
Periodic structures between l-3=14 are arranged at regular intervals and +t
4, the leakage amount could be reduced to 0.05 mW/crd, and it was confirmed that this is a highly safe radio wave leakage prevention means.

The amount of leakage can be reduced by a transmission line for leaky radio waves constructed from such a periodic structure shape because the impedance of the transmission line can be freely changed by changing the shape of the line as described above. This is thought to be due to the fact that, as an optimum condition, the impedance seen from the inside of the groove is open, and the leakage radio waves are reduced through repeated multiple reflections.

Effects of the Invention As described above, according to the present invention, as a door component in a high-frequency heating device, a groove whose groove width is narrower than /4 of the wave wavelength used is installed, and a groove is installed so as to cover the opening of the groove. A periodic structure with a cross section is provided.

By making the tip protrude into the internal space of the groove, a transmission line for leakage radio waves is formed, and the transmission line is arranged in the longitudinal direction of the groove with an arrangement interval of approximately 1/6 to 1/1 of the wavelength of the radio wave used.
//12. Since they are arranged periodically so that the arrangement period is also negative, the radio waves leaking from the flange part of the opening peripheral wall of the heating chamber and the gap between the Sanon plate and the door can be suppressed to an extremely low level, and safe high-frequency waves can be suppressed. It has the advantage of being able to provide a heating device. Furthermore, in this radio wave sealing means, the leakage prevention effect can be achieved even if the depth and width of the groove are each smaller than 1/4 of the radio wave wavelength used, so the door can be made smaller and the high frequency heating device can be made more compact. has advantages.

Note that a similar radio wave sealing effect can be obtained even when the radio wave leakage prevention means of the present invention is provided on the wall surface of the heating chamber.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing the external appearance of a high-frequency heating device according to an embodiment of the present invention, FIG. 2 is a cross-sectional view of the high-frequency heating device according to an embodiment of the present invention, and FIG. 2 is an enlarged view of the main part of FIG. A cross-sectional view, FIG. 4 is a relationship diagram of t3+t4 dimensions for explaining FIG. 6, and FIG. 5 is a characteristic diagram for explaining the present invention in detail. 1. Heating chamber, 6. Door. 5... Opening peripheral wall, 10... Groove. 12... Groove opening, 17... Periodic structure. 18... Periodic structure bending part. t5...Sequence interval, P...Sequence period.

Claims (1)

[Claims] In a heating chamber that stores an object to be heated and a door that can be opened and closed at the opening of the heating chamber, it is used over the entire circumference of the periphery of the door (3) or at least one side of the heating chamber wall facing the door (3). A groove (10) having a width narrower than approximately 1/4 of the radio wavelength is installed, and the opening (12) of this groove (10) has an array interval (l_5) of approximately 1/6 to 1/6 of the radio wavelength used.
A periodic structure (17) whose arrangement period (P) is approximately 1/12 and approximately 1/4, whose cross section is approximately L-shaped, and whose tip protrudes into the internal space of the groove (10). , the groove (1
0) A high-frequency heating device characterized in that it is installed periodically in the longitudinal direction to prevent radio wave leakage.