JPS62145688A - 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.

Prior Art A 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 outside through this gap, causing negative effects on the human body. It is necessary to take precautions to suppress the amount of leakage below the legally permissible value, and for this purpose, a leakage prevention mechanism is mainly provided on the door surface.

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

In the choke method, a choke structure with a radio wave attenuation groove is placed around the periphery of the door, and the dimension from the entrance of the radio wave path formed by the heating chamber and the door to the groove and the width of the groove are set to 1/1/2 of the radio wave wavelength used. There is a way to make it 4. This method has the advantage of preventing leakage of radio waves because it is equivalent to short-circuiting the entrance of the radio wave passage in terms of impedance, but on the other hand, because the width of the groove is specified, it is possible to reduce the size of the door and prevent high-frequency This caused problems in making the entire heating device more compact. In addition, as another radio wave leakage prevention mechanism, 2, for example, as shown in Japanese Patent Publication No. 52-7585, there is a method in which a groove sealing plate is extended from the opening of the choke groove, and a plurality of slits are formed in this extension. has been proposed, but even in this method, the width of the choke groove must be 1/4 of the radio wave wavelength used.

It was not possible to respond to the miniaturization of the door. In addition, in various radio wave sealing means that seal leakage radio waves by arranging metal plates having slits, periodic structures having slits are arranged in close contact with the 7272 part of the door, but in reality, the surface of the periodic structure is It gets dirty.

In order to prevent flying objects from the object to be heated from entering the radio wave seal part, it is necessary to cover the radio wave seal part with a dielectric cover of a certain thickness. Furthermore, even if a film coating is applied instead of a dielectric cover to maintain close contact, the coating may be damaged due to impact or abrasion caused by opening and closing the door, and the periphery of the opening of the heating chamber and the periodic structure may be damaged. A metal contact occurs between the two parts, and a spark is generated between the two parts. Therefore, in order to prevent this problem, it is necessary to interpose a dielectric cover that electrically insulates both. These dielectric covers also hinder the compactness of the door.

The problem to be solved by the invention is that the dimensions of the choke groove, dielectric cover, etc. 1 make it impossible to make the door more compact.

Means for Solving the Problems The present invention provides the above-mentioned device by providing a groove (hereinafter referred to as a groove) surrounded by metal having a substantially U-shaped cross section at the periphery of the door body so as to extend the periphery of the door body. At the same time, the opening of the groove is opened facing the opening peripheral wall (opening flange part or sash plate part) of the heating chamber, and a flat periodic plate covering more than half of the width of the groove is placed in this opening. structure,
The grooves are arranged periodically in the longitudinal direction of the grooves, and the width, arrangement pitch, etc. of the two-periodic structures are selected to optimal conditions.

The power source inside the heating chamber enters the gap between the heating chamber body and the door, but the grooves and periodic structure prevent radio waves from leaking to the outside. If the above gap is about one cabinet, the amount of radio wave leakage should be 0.1 m.
Reduce to below W/c-. Namely.

By optimally selecting the length, width, arrangement pinch, etc. of the planar periodic structure that constitutes the leakage radio wave transmission line, the impedance when looking inside from the opening of the groove becomes open. The leakage radio waves decrease through repeated 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 cross-sectional view showing one embodiment of the high-frequency heating device of the present invention, and FIG.
The figure is an enlarged partially cutaway 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 two parts of 7 runs,
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 3 are placed facing each other, and the two are partially in contact with each other. The radio wave seal mechanism is composed of 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 B, there is a metal I'#1 with a substantially U-shaped cross section.
0, forming a groove space 11. Width of groove 101.
is 1/6 narrower than 1/4 (approximately 30 degrees) of the radio wave wavelength used.
wavelength. The depth of the grooves should also be the same. Further, the opening 12 of the groove 10 is open toward the opening peripheral wall 5. There is a flat end face 13 on the heating chamber side of the upper end of the groove 10, and on this end face 13 there is a viewing window 8 made of punched metal and a glass cover (not shown). Reference numeral 14 denotes a door rear plate, which is supported on the end surface 13 together with the peripheral edge of the viewing window 8 by screws at a support portion 15 . This door back plate 14 also constitutes the basic part of the periodic structure 17 and the main part of one periodic structure 17. In other words, the door back plate 14
has a flat portion 16 without a notch and a portion constituting a one-periodic structure 17. The boundary surface 18 between the two is made to coincide with the end surface of the opening of the groove 10, and a step is provided on this boundary surface 18, and a dielectric material is placed on the lower side, that is, on the periodic structure 17. There is a cover 19 and a groove opening 12
is covered. (The outer periphery of the groove 10 is also covered with a dielectric force), but is omitted. ) 20 is the bottom surface of the groove.

Next, in FIG. 6, the structural conditions of the periodic structure 17 for exhibiting excellent radio wave sealing performance are described. First of all
is the width t2 of the periodic structure 17, and this 12 is made smaller than approximately 4 of the radio wave wavelength used. The second is the length t3 of the periodic structure.

Although this t3 is electrified due to the groove width t1, it is approximately 5 of tl.
The radio wave seal effect is strong when the condition is 0 to 80%. 6th
is the length of the arrangement interval t4 of the periodic structures 17.

Although the optimum condition for this t4 changes slightly depending on @L2 of the periodic structure, the radio wave sealing effect is high if the length is set to the same length as the set L2, that is, approximately 1/6 to 1/6 of the radio wave wavelength used. . Furthermore, the arrangement period of the periodic structure 17 expressed as p=t2+t4 is approximately 1// of the radio wave wavelength used.
A length of 4 is appropriate. According to such structural conditions, even if there is a gap of about 1 m in the radio wave sealing surface, the amount of radio wave leakage from this part can be reduced to 0.1 mW/c or less.

Effects of the Invention As described above, according to the present invention, as a door component in a high-frequency heating device, the groove width is narrower than the radio wave wavelength used, and a flat plate is formed so as to cover five or more of the openings of the groove. A transmission line for leakage radio waves is formed by arranging periodic structures in the form of shapes.

In the longitudinal direction of the groove, the transmission lines are arranged at intervals of approximately 1/12' to 1/12' of the used radio wave wavelength, and the arrangement period is also 4.
I arranged them periodically so that

This has the advantage of being able to suppress radio waves leaking from the 7-lung portion, which is the opening peripheral wall of the heating chamber, and the gap between the sash plate and the door to an extremely low level, thereby providing a safe high-frequency heating device. In addition, in this radio wave sealing means, not only the depth of the groove but also the depth of the groove is 1.5 mm of the radio wave wavelength used. The leak prevention effect can be achieved even if the size is smaller than /4, so the door can be made smaller,
This has the advantage that the high-frequency heating device can be made more compact.

Note that the same 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 appearance of a high-frequency heating device according to an embodiment of the present invention, FIG. 2 is a sectional view of the high-frequency heating device according to an embodiment of the present invention, and FIG. 6 is an enlarged view of the main part of FIG. 2. It is a partially cutaway perspective view. 1...Heating chamber, 6...Door. 5... Opening peripheral wall, 10... Groove. 12... Groove opening, 17... Periodic structure. P...Sequence period + 64...Sequence interval. □Applicant Hitachi Thermal Appliances Co., Ltd. Figure 1 @ Figure 2

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) with a width narrower than approximately 1/4 of the radio wave wavelength is installed, and the arrangement interval (l_4) is approximately 1/6 to 1/4 of the radio wave wavelength used in the opening (12) of this groove (10).
12. A periodic structure (17) whose arrangement period (P) is approximately 1/4 and whose shape is approximately flat and covers more than 1/2 of the opening is inserted in the longitudinal direction of the groove (10). A high-frequency heating device characterized in that it is periodically installed toward.