JPS611096A - Radio wave sealing device - 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 Industrial Application The present invention relates to a radio wave seal for a high frequency heater, mainly against harmonic components of a fundamental wave leaking from a gap between the heater body and a door or the like.

Purchase of conventional examples and their problems There are many prior arts related to radio wave seal devices, but most of them are related to fundamental wave seals. With the recent diversification of the use of radio waves due to advanced information technology, the harmonic region, which previously had few problems for high-frequency heaters, has begun to be used for communication purposes.

For example, 12.25 of the fifth harmonic of 2,45 GHz
Radio waves around GHz have begun to be used as carrier waves for SHF broadcasting, and this trend will continue to increase in the future.

Therefore, while conventional radio wave sealing technology for high-frequency heaters focuses on fundamental waves, it is necessary to develop a technology that can prevent harmonic leakage and seal over a wide band to prevent interference from entering SHF broadcasts. become.

Figure 1 shows a conventional example, where 1 is a heating chamber of a high-frequency heater;
A top mark 2 is provided on the front surface, and a door 3 covers the opening so as to be openable and closable. A composite ferrite 5 (a mixture of ferrite powder and dielectric material) held by a U-shaped metal plate 4 is fixed with screws 6 to the surface of the top mark 2 facing the end surface of the door 3. Although this groove or radio wave absorber is effective as a radio wave sealing technique, the frequency band is narrow, and although it seals against fundamental waves, harmonics tend to leak.

In addition, the sealing means using a mixture of foam and carbon powder used in anechoic chambers has a wide band, but only a few centimeters.
- Requires a thickness of several tens of centimeters, hinders miniaturization, and is unsuitable for household microwave ovens.

Purpose of the Invention The present invention prevents not only fundamental waves but also harmonic components from leaking from a high frequency heater.

Structure of the Invention In order to achieve the above object, the present invention is such that two or more layers of composite ferrite having different resonant frequencies are bonded together with a metal plate and provided in a gap where radio waves are likely to leak in a high frequency heater.

Description of examples An embodiment of the present invention will be described below using a diagram.

In FIG. 2, the same parts as in FIG. 1 are given the same numbers and will be explained.

As shown in FIG. 2, instead of the conventional single-layer composite ferrite 5, dog marks 2 having mutually different resonance frequencies are used.
It is fixed at . The composite ferrite 7 and the metal plate 4 are fixed to each other with an adhesive. Figure 3 shows the details. 9 is an adhesive. The volume resistance of composite ferrite 1-7 is smaller than that of composite ferrite 8, improving radio wave absorption efficiency.

Figure 4 shows the frequency characteristics of the amount of radio wave absorption. f□ represents the fundamental frequency, curve A represents a conventional example, and curve opening represents an embodiment of the present invention.

By setting the lowest resonant frequency of the composite ferrite 1-7.8 higher than the frequency of the fundamental wave, leakage of harmonic radio waves can be prevented. The twisted metal plate 4 was fixed by cutting and raising a piece 10 and sandwiching the top mark 2 without using screws or the like.

Also, bend the end of the metal plate 4 and attach it to the heating chamber 1 with the screw 11.
It was fixed to the structural body to make the installation strong. Furthermore, it is effective to protect the surface of the composite ferrite 7.8 with bluffing or the like to stabilize the sealing performance over the long term.

It goes without saying that a configuration in which paint-like composite ferrite is applied to a metal plate in the order of volume resistance as a radio wave absorber or a configuration in which the metal plate is adhesively fixed to the main body may also be used.

Effects of the Invention According to the present invention, in addition to being able to configure a harmonic radio wave shield compactly, there are the following effects. - (1) The absorber and metal plate are fixed with adhesive (adhesive thickness approx. 200μ
m), the performance of the harmonic seal, which requires stricter clearance control than the fundamental wave, is stabilized.

(2) Highly efficient sealing is possible because the structure is such that the volume resistivity is stacked in ascending order from the metal plate side.

(3) Radio waves can be converted into thermal energy at the part closest to the metal plate, which has good heat dissipation characteristics, so it is possible to prevent the lifespan of adhesives and the like from being shortened at high temperatures.

(4) In order to fix the absorber to the main body, a metal plate, which is an elemental member for absorbing radio waves, can be used.

(5) Since the metal plate is bonded to the absorber, there is no need to make it into a U-shape as in the conventional case, and the radio wave absorption area can be substantially widened, so that efficient radio wave absorption can be achieved.

(6) Since the bending part is provided along the direction of the radio wave absorbing part, the mechanical strength of the radio wave absorbing part is increased, and the sealing performance can be stabilized over a long period of time.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a main part of a conventional high-frequency heater, Fig. 2 is a sectional view of a main part of a high-frequency heater according to an embodiment of the present invention, Fig. 3 is a sectional view of a radio wave absorber, and Fig. 4 is a characteristic diagram of a radio wave absorber. 2...Top mark (body part), 3-door,
4... Metal plate, 7a, 7b... Multiple composite ferrites. Name of agent: Patent attorney Toshio Nakao and 1 other person
1 Figure 2 Figure 3 Figure 4 River Shikiban ζ

Claims (2)

[Claims] (1) A plurality of composite ferrites having resonant frequencies higher than the fundamental wave and different from each other are layered on a metal plate, and the part where the area of the metal plate is larger than the bonding area with the composite ferrite is used as the fixed part. Radio wave seal device. (2) The radio wave sealing device according to claim 1, wherein the plurality of composite ferrites are laminated on the metal plate in order of volume resistance starting from the one with the lowest specific resistance.