JPS58209089A - Radio wave leakage preventing 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 (Technical field) The present invention provides
Regarding radio wave leakage prevention 11. Improvement of equipment.

(Background) Techniques) Conventionally, means for preventing radio waves from leaking from the gap between the main body of a microwave heating device (for example, a microwave oven) and a JJ are as follows: 1. A metal contact method using a rolled spring; There are 1 out of 18 proposals for the choke coupling method or those using radio wave absorbing materials such as rubber ferrite and carbon rubber.4) 3゜Figure 1 is a cross-sectional view of a conventional radio wave leakage prevention device, and 1 shows the main body of a microwave heating device. wall, 2 is the ml opening 1 of the main body 1
3 indicates the inside of the refrigerator. ) J [2 has a metal finish on the periphery of the surface facing the front opening of the main body 1. A radio wave attenuation groove (hereinafter referred to as choke Furthermore, a radio wave absorbing member 7 made of rubber ferrite, carbon rubber, etc. is arranged on the outside of this choke groove to prevent dust from accumulating in the choke groove 6Vc. The chop cover that combines the holding force of 7] is kicked. This choke force...-8 is %3' of choke groove 6, 1lJ
It is composed of a low Rg 'jtq' material such as polypropylene, and a rate (・'+1). 9 is a plastic decorative horn bar, and 10 is a plastic decorative horn bar. Glass plate, 1] is wire mesh, 12 is mount 7.1
(The shield spring held in body 1 connects body 1 and sin 2 with metal contact, and prevents wave leakage.
1. do. The elasticity of the shield spring has deteriorated (・ indicates that the metal contact I・ is not redundant due to the formation of a film of metallic acid, or when insulating material such as dust has entered between the main body and the screen. When this happens, radio waves will leak through this gap.The leaked radio waves will be leaked to the outside by the choke groove 6. To prevent (・
Ru.

However, it is clear from experience that the conventional radio wave leakage prevention device does not have sufficient performance because the choke groove occupies a large amount of the volume. Due to the large number of parts, its workability is poor, so improvements have been made recently from the viewpoints of construction, cost, and mass production. For example, the choke force...- can be converted into a radio wave absorber...
It is said that Noh was organized by month.
- 4) Method 1jl of arranging a radio wave absorbing function inside the groove
A plan is being made. For example, “Tokukosho”, ++1-IQ2)
(Beef L Buns) Showa 51-31982, Jikko Showa 56-160
68(:l'1'-Example of the previous technology-r;l;,ru3,
These methods reduce the choke machine rff'', significantly lower -1.
The inside of the choke groove is
'r'J (11 degrees or strong ∆-me'N wave absorbing part will be burned out) I'm afraid 3 (...I) Not available for practical use, #rt.

(Invention θ), i', li :l'Q) This statement relates to the improvement of radio wave leakage ljJ and city equipment β, and has been made to improve the drawbacks of 1/C as mentioned above (7,). , tick()
) The structure of the Nayoke coupling can be changed to a small one (
By making it 11 and 112 wide, and reducing the number of parts, we have a device that is inexpensive and highly effective in suppressing radio wave leakage.
! r 6 o Tomachi ゛, the t time of the device by the light can be opened and closed. -1! : construction)
A box with a main body and a radio wave leakage passage between the main body and the fan; a box with a device to prevent wave leakage; /、c At least a choke groove is provided in one direction, and the person in the choke groove 21 is covered with a choke cover j < 1! The choke cover is a mixture of a magnetic material and an insulator, and the real number term ε' of the complex dielectric constant is less than 15, and the loss term is 11. The electromagnetic wave leakage prevention device has a wave absorbing portion formed integrally with the choke cover and made of the same material as the choke cover.

(Wlr structure and operation of the invention) The drawings relate to the present invention, and FIG. This creates a narrow radio wave leakage between the main body and the screen of the microwave heating device.
3 is a sectional view of a measuring device using step transducers 2; 3 for artificially structuring the path; FIG. CI is radio wave leakage', i
The camp of the passage 24 corresponding to the ff road is thick and 22'
indicates chalk grooving [1]. Also, a variable shorting plate 25 is installed inside so that the length of the choke groove can be adjusted.

FIG. 3 shows a portion (g' 2(i
0) I(S, indicates the open state l~, tabular γ′1ILI
Material 2+'+ (1!7 み2.Fimm, Length+5+
++m, ) is in the passage 24 (le)-') person 112Σ-
'Nagudo Jl, :l;, slightly elongated in the direction of leakage radio waves, radio wave absorption r? The role of +X4g is also similar.

The interest rates shown in Table 1 with different values of ε' were used as ΔI/plate-like capital.

As shown in Table 1, samples Nn1 to 3 are rubber ferrites made of a mixture of Ni-M, -Zo-based ferrite powder and chloroprene rubber, which have relatively low dielectric constants and large magnetic losses. 'A;) Sample 1'! '14 to 7 are from a mixture of Mn-Zn ferrite with high dielectric constant and large magnetic loss and powdered chloroprene rubber.7':Cl
) Kono2 ferrite k) b).

Table 1 shows the transparency when the chalk cover consisting of NIL I to NIL7 is grasped into the chalk person 1-12:'. Compare and evaluate. The measurement force method sweeps the frequency range of 2200 to 2fifi (l M I I z, converts the output level into l ng,
After the comparison, the waveform was observed with an oscilloscope, and its characteristics were evaluated based on the wave color: 16 value.

(7) Figure 4 shows the characteristics (curves) when the choke inlet is closed with a metal plate, that is, when there is no choke and when there is a choke. Characteristics (in the curve) ) % 0 ・ Shown in Figure 2 - 1 - As (, Samples 1 to 7 Material 2 (i (', fig shape is IIF 2.5
v11n Dimensions in the direction of radio wave propagation, that is, length l! 'im+
++ ) θ) ゛Old friend j The shadow-shaped chalk cover shows the !+, !l characteristics (curves ■ to ■) when I is blocked. Previously, the dielectric constant ε' was set to 4
5 to 11.・There is -C' in 1. Without choke, song #j (('+N like ~
, 1li41t (t, , is almost constant and O (output standard). In case of only choke, 2450 as shown in curve ■
MIIZ outputs 411 θ) Toru 1 Naotane roaring leaked radio waves are
At this number of cycles θ, the fire part decreases [7, transmission loss without choke] / I 0O (only 10 power exceeds J'14 (ρ
111 leak) (・1, -Jmi, -rihito 11 is blocked with radio wave absorbing 7111H material sample %1~7) 4!1l
From l1 curves (1) to (7), ε' is relatively small15
According to positive 1 to negative 1 below, the characteristic 5 has a peak value, and only choke θ)! Broadband and 15[ro] compared to l','r characteristics. However, the value of minimum 1ffQ over 111゛ becomes slightly larger, and the frequency at that time becomes 2450MI.
It can be seen that there is a transition from IZ to low (8) at 1~(・low). Also, when ε' is large and 20 or more, lNn, 5~Nα7, the characteristic hardly shows a peak value (choke). Although there is some attenuation due to the influence, the attenuation is mostly flat.

In particular, in the material of [Material] East7ε' = 41.4, the influence of the choke is characterized only by the transmission attenuation of 7<magnetic material 1 East7. This is thought to be because when ε' is large, the reflection from the sample itself is thick (and the radio waves do not enter the inside of the choke).

Next, as shown in Figure 4, the point of minimum transmission is shifted toward lower frequencies depending on the material, but if the length of the choke is shortened (if this is done, the frequency characteristics due to the choke will change significantly in that state as well). It is estimated that the minimum transmission amount can be obtained at 2450 MTfz, and by adjusting the choke size (by reducing the choke size by 1-) using the variable frequency filter 25 shown in Fig. 2, the minimum transmission amount can be obtained at the center frequency of 2450 MTfz. We measured the characteristics when the magnetic material was placed at the choke inlet by moving the permeation point (from 0.5 mm to 1 mm).As a result, the characteristics shown in Figure 5 were obtained.Figure 5 As can be seen, ε' is about 15JJ, and the samples Nn1 to 4 below have 1d and Q1-
It has been found that the new function of the choke is utilized, and that it is possible to obtain a broadband characteristic compared to the choke only. In addition, for samples NC, 5 to 7, where ε′ is 20 or more,
After all, the reflection is large inside the chalk (sufficient city 1 for flIS)
Because the waves were small, the choke characteristics were not utilized, and a sufficiently small amount of transmission could not be obtained (1°). ' value, minimum transmission amount, transmission ij1-J'2 (bll, J, less area (in the band), and transmission attenuation of gain 1.1)11111'l are summarized in Table 2. Also, The relationship between ε′ and characteristic values is shown in Figures 6 and 7.
As shown in the figure. Figure 6 shows the relationship between ε' and the minimum attenuation [11 value], and Figure 87 shows the relationship between ε' and the relationship between ε' and the band j. From this, it can be seen that when ε' is approximately 15" or lower, it is slightly worse than the minimum transmission amount of only a choke (2.5 dB"), which is a practically sufficient characteristic (712). , and the band [1] is also 240 MITz.
l! It can be seen from Figures 6 and 7 that ε' shows a rapid deterioration of !14' as it approaches 15 degrees.

Table 2 The radio wave absorption characteristics are also utilized in this case, and as shown in Table 1, the transmission attenuation is 2 dB/m. The effect is fully utilized and the band is widened.

Further, even if the choke function deteriorates due to the increase in the dimension d in FIG. 2, the radio wave leakage prevention effect is still exhibited due to the attenuation characteristics of the material. l of sample tooth 3 and grout 4 in Table 1; ma2. The transmission attenuation amount is 7.27+llt/Cm, which is 0.70, and there is a large difference in transmission attenuation. , -('f,c, the transmission attenuation varies greatly depending on the ferrite quality, but it greatly contributes to the J optical overattenuation meter'f 7;)l;ma,, (7+"/μ
') is (l(sample 1 east of 1) tan δ1 is 0118
Throat transmission attenuation 111α (C output/cm ) is 2.37d
B/m, so to obtain 3rllll, which attenuates at least half of the radio waves, requires at least 05"2. The shape of the choke horn bar is such that the surface facing the radio wave leakage path is flat and protrudes toward the choke l'J rfB, thereby preventing radio waves from entering the choke due to the antenna effect of 14→]i. It can be said that the characteristics can be improved without impairing the choke function.

Using sample 1-3, as shown in T4'l, Figure 8 (Ij-naka) C→, the installation that closes the entrance 1-122/ of Geetbitty 22 in Figure 2 shows the characteristics when changing the condition. As shown in the figure. Figure 8 (a) is a flat plate, Figure 8 (b) is a convex shape, and
In Figure e), the convexity is even thicker (it has a shape that protrudes into the choke gap).In both cases, the choke characteristics are not significantly impaired (11), and a wide band is obtained.

As described above (according to the present invention), the structure of the choke can be made compact without significantly impairing the function of the choke, and it also has a function of absorbing radio waves while preventing dust from entering the inside of the choke. It is possible to further increase the leakage prevention effect.Also, by reducing the number of parts, an inexpensive device can be provided.

Examples of the present invention are shown below.

(Example 1) FIG. 10 shows a cross-sectional view of the radio wave leakage prevention device of Example 1. Since the symbols -J'-o are the same as those in FIG. 1, explanation of the parts with the same symbols will be omitted. Reference numeral 14 denotes a chalk cover, which consists of a mixture sample tooth 3 of ferrite powder and an insulating material such as rubber or plastic, and one end L4a of which is connected to a metal partition plate 2.
5, and the other end 14b extends outward to close the entrance of the choke groove, and is fixed at the end of the decorative cover 9. In other words, the choke cover The surface is made almost parallel to the main wall 10 and the opposite wall 1', and the yoke groove 1'-'l is set so as to close the entrance part of i6 and the adjacent chamber 6'. (Example 2) Figure 11 (A+ and (11) shows a cross-sectional view of the radio wave leakage prevention device of Example 2. III is a choke cover, which is made of ferrite powder and an insulator such as rubber or plastic One end is formed into a cylindrical shape to fit with the metal partition plate 5, and the other end is formed with a chalk groove.
It closes and extends outward, and is fixed at the end of the decorative cover 9. The surface of the choke cover is the opposite wall 1' of the main body 1.
It is considered to be a nearly parallel plane with l ~, and there is a chalk on the back side 7)
A protrusion 141 that protrudes inward at /f6 is integrally formed. As shown in Figure 11 (Bl), a plurality of protrusions should be provided around the door at appropriate intervals.These protrusions act as antennas and emit radio waves into the choke groove, improving the radio wave absorption characteristics. .

(Example 3) Figure 12 is a cross-sectional view of the radio wave leakage prevention device of Example 3. Reference numerals 1 and 14 are chief covers, and 1 c is made from a mixture of ferrite powder and an insulator such as gono or plastic. ,
The front surface of the choke horn bar is a plane parallel to the opposing wall 1' of the main body 1, and the back surface is inserted into a narrow cavity surrounded by metal partition plates 4 and 15, which is located outside the choke groove 6. A radio wave absorber 142 is integrally formed. This radio wave absorber 142 is provided almost all around the door as shown in FIG. 12(B).

(Example 4) FIG. 13 is a cross-sectional view of the radio wave leakage prevention device of Example 4. 14 is a choke cover, Ferai]
- The surface of the choke cover made of a mixture of powder and an insulator such as rubber or plastic is a plane parallel to the opposing wall 1' of the main body 1, and the back surface has a protrusion 141 that protrudes inward of the choke groove 6. and a radio wave absorbing member 142 inserted into a narrow cavity surrounded by the metal partition plates 4 and 15 outside the choke groove 6 are integrally formed (FIG. 13(B)). In all of Examples 1 to 4, it may be attached to the periphery of the door in a frame-like manner, or it may be attached so as to surround the periphery of the door using several rod-shaped objects.

”-Variations of the Kiriya example are also 1. (1) and (1) in Fig. 11 are examples of the fixing structure of the choke cover 14, and (21) is an example of the fixing structure of the choke cover 14. It's erotic. At this time, in embodiments in which the radio wave absorbing parts 1 and 12 are located on the right side, this member may be supported by holding it against the wall of the empty room.

Figure 14 (bl shows a structure in which a snap-action pin 5a is set up on the dividing plate 5, a corresponding hole is made in the choke horn bar 1, and the choke cover 14 is fixed with the pin.The pin is attached to the choke cover It may also be fixed in a hole made in the dividing plate using a V-resnap operation. Figures 1 and 1 (C) have a structure in which the empty space has been removed. It is okay to remove the empty room l～.Figure 14(d) 4:r,
(River and Figure 13 Prisoner.

(In Bl, the protrusion 11 has three shapes (trapezoid, cylinder, and square pyramid).The material of the choke horn bar is a mixture of ferrite and rubber, as well as a mixture of ferrite and synthetic resin. It is possible (a) and (4). The chalk cover is shaped like a rectangular picture frame and consists of four long and narrow sides.
It is also possible for the sides to be of integral construction, or for the four sides to be constructed separately and fixed to the wall of the choke groove.

(Effects of the Invention) As explained above, according to the present invention, by constructing the choke cover with a magnetic material, a radio wave leakage prevention device with a wide band, simple structure, and excellent absorption characteristics can be obtained.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of a conventional radio wave leakage prevention device, Fig. 2 is a cross-sectional view of the main part of the measuring device, Fig. 3 is a state diagram with a choke cover attached, and Figs. 4 and 5 are choke cover sample N. [l
Figures 6 and 7 show the transmission amount and band 11] characteristic diagram depending on the difference in ε', and Figure 8 (a) ( B)
Fig. 9 is a frequency characteristic diagram when using sample Nn3 with the shape shown in Fig. 8 (a), (b), and e). Figure, 11th
Figures (A) and (Bl), Figures 12 (A) and (Bl), and Figures 13 (A) and (Bl) are structural examples according to the present invention, and Figures 1 and 1 (a) to (dj are structural examples according to the present invention). (17) A11 (9-1-Explanation of the bow, clear; Ri-12 (A)) 6; Choke groove 14; Choke horn bar 1112; 'III wave absorption j%B patent Applicant Tokyo Denki Kagaku Kogyo Co., Ltd. Patent Application Attorney ± 111 Megumi Moto - (18) Trap 6 Figure 57 Dielectric rod and ' Early, 8 Figure (A) (Ron (C) Breast 70 Figure 1 ( A) Trap//Figure (B bottom 13 figure (A> Bō 13 figure (8) 與 14 close ((L) bottom 74 figure ζb) 襄 14 (2
) (Rishi

Claims (1)

[Claims] In a device for preventing radio wave leakage from a radio wave leakage path between the main body and the device, the device has a body having a closed structure including a fan that can be opened and closed by 5 f, on the side facing the radio wave leakage path, It has a structure in which a choke groove is provided in at least one of the main body or the fan, and the choke groove is closed by a choke cover, and the choke cover is a mixture of a magnetic material and an insulator, and the real number term ε' of the complex dielectric constant is 15 or less. A radio wave leakage prevention device comprising a magnetic material which is a loss component, and having a radio wave absorbing portion integrally formed of the same material as the choke cover on the outside of the choke groove.