JPH0456197A - Cable introduction port electromagnetic shield device - Google Patents

Abstract

PURPOSE:To enable periphery of a cable to be blocked without any gap and obtain a high shielding performance by surrounding the cable with a conductive cloth in a cable introduction port of an enclosure, by fixing one edge to the peripheral part, and by clamping the other at a wide clamping part. CONSTITUTION:A lower edge of a conductive cloth 9 is sealed to a cable introduction port 4 and then a cable 3 is introduced into an enclosure. At this time, an upper edge of the conductive cloth 9 is in open state having opening dimensions which are equal to or more than those of the lower edge. Thus, sealing of the conductive cloth 9 does not prevent introduction of the cable. After introducing the cable, the conductive cloth is adhered to widely, thus forming a shielding structure by clamping a fastener 12 so that an upper edge of the conductive cloth 9 surrounds the cable 3 without any gap.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a cable inlet electromagnetic shielding device for a cable inlet of an electronic device housing.

Background of the Invention In recent years, computers, communication devices, etc. have become digital and faster, and as these have become widespread,
Electromagnetic interference emitted from equipment into the surrounding space has become a problem.

For this reason, the Japan Information Processing Equipment Self-Regulatory Council (
VCCI) has been established and is working to prevent interference with other equipment by setting regulatory values. On the other hand, due to a decrease in the operating level of the electronic components that make up the device, the device itself is also affected by external electromagnetic fields, making it more likely to cause malfunctions.

For this reason, electronic devices are generally electromagnetically shielded by housing them in metal casings. The casing includes
Openings are provided for cable introduction and cooling, but to obtain good shielding performance, these openings must be made as small as possible.

FIG. 3 shows a schematic structure of a conventional general electronic device housing.

The panel, which is a component of the housing, is provided with a cable introduction port for introducing the cable 3 into the housing. The cable 3 is a signal cable between devices, a power cable, etc. The cable 3 is connected to the electronic circuit unit B via a connector. Normally, the connector j is attached to the cable 3 in advance, so the cable inlet is made considerably wider than the outer circumference of the cable 3 so that the cable can be introduced smoothly.

In addition, due to the addition of electronic circuit unit O, cable 3
In consideration of the case where the number of cables increases, the cable inlet ≠ is made to have a sufficient width.

As a result, a large gap is created around the cable 30 at the cable inlet ≠, resulting in very low shielding performance.

FIGS. 4(a) and 4(b) show a conventional example of a shielding device for reducing the gap created in such a cable introduction log. In the structure of (a), a flat metal closing plate 7a is fixed using screws g to close the gap created in the cable introduction log. Although this structure can reduce the gap between the cable inlet μ to some extent,
It cannot be completely blocked. Also, as shown in (b), a closing plate 7b is provided with a notch that matches the outer circumference of the cable 3.
When using a cable inlet, the gap between the cable entry port and the cable entry port is reduced, but it cannot be completely closed.

In such a planar gap formed at the cable entry port, good shielding performance cannot be obtained unless the dimension of the negative side is reduced to a few percent or less of the wavelength of the electromagnetic interference wave.
The conventional structure shown in FIGS. 4(a) and 4(b) is insufficient.

Furthermore, there is a risk that the cable 3 may be damaged by the closing plates 7a and 7b coming into contact with the cable 3;
In Figure (b), it is necessary to prepare and replace a blocking plate with a different shape for each different amount of cables, which also impairs economic efficiency.

That is, since the conventional structure used a simple plate-shaped closing plate, there were problems in that sufficient shielding performance could not be obtained, and that the cable could be damaged and become uneconomical.

Problems to be Solved by the Invention An object of the present invention is to provide an economical cable inlet electromagnetic shielding device that has high shielding performance and does not damage the cable.

Means for Solving the Problems The present invention provides a cable inlet electromagnetic shielding device in which one end of a cylindrical conductive cloth is fixed to the periphery of the cable inlet of an electronic device housing, and the other end of the conductive cloth is provided with: The cable bundle is configured to include a wide tightening portion whose length is equal to or greater than the outer diameter of the cable bundle.

Function The present invention fixes one end of the cylindrical conductive cloth to the peripheral edge of the cable inlet of the electronic device housing, and provides the other end with a tightening part with a width equal to or larger than the outer diameter of the cable bundle. This allows for high shielding performance and high reliability as there is no damage to the cable.No screws are required for the tightening part, reducing work time. Therefore, the same structure can be used, which improves economic efficiency.

Embodiment FIG. 1 shows a perspective view of an embodiment of the cable inlet electromagnetic shielding device of the present invention.

In the figure, the same reference numerals as in FIGS. 3 and 4 indicate the same parts and parts.

/l is screw, /2 is fastener, /3 is 7 fastener support,
It is.

Conductive fabrics are commercially available conductive fabrics such as those woven from thin metal wires, those woven from metal-plated fibers, and those made by laminating soft metal plates such as aluminum foil onto cloth. The members are sewn together into a cylindrical shape.

The lower end of the conductive cloth is fixed to the periphery of the cable inlet by the metal frame 10 using screws. The fixing means may be either a means of directly sandwiching the conductive cloth between the frame 10 and the panel, or a means of fixing the conductive cloth to which the frame 10 has been attached in advance to the panel.

In order to electrically connect the conductive cloth to the panel λ with low impedance, the surfaces of the frame 10 and the panel 2 in contact with the conductive cloth are made conductive by metal plating, conductive coating, etc. .

At the top end of the conductive cloth there is a fastener / 2 and 7 fastener supports /
A belt consisting of 3 is attached. 12 fasteners, etc.
Commercially available parts may be used. When using Velcro, it can be sewn onto conductive fabric in advance.
Fastener support /3 can be omitted.

In this embodiment, two or more fasteners are used.

By tightening with two or more fasteners, the shape of the portion at the upper end of the conductive cloth where the cable is tightened without any gaps becomes a cylindrical shape with a length L.

In this structure, first, the lower end of the conductive cloth is ≠ the cable entry port.
The cable 3 is then introduced into the housing.

At this time, the upper end of the conductive cloth is still open and has an opening size equal to or larger than the lower end. Therefore, the installation of the cable is not hindered by fixing the conductive cloth.

After the cable is introduced, the fastener 2 is tightened until the upper end of the conductive cloth surrounds the cable 3 without any gaps, thereby forming the conductive cloth into a purse-string shape and forming a shield structure.

When increasing or decreasing the number of cables due to the addition or removal of electronic circuit units, first remove the fastener 2 to open the upper end of the conductive cloth, increase or decrease the number of cables, and then repeat the same procedure as above.

With such a structure, it is possible to completely eliminate the gap between the cable inlets and obtain good shielding performance. Furthermore, the cylindrical cable clamping portion acts as a waveguide, ie a high-pass filter, and exhibits a significant damping effect at frequencies below the cut-off frequency.

Since the cross section of the cylindrical cable tightening portion is approximately circular, the cutoff frequency Fc and attenuation Att are expressed by the following equations based on the characteristics of the circular waveguide.

F c = 16.3X10'/D (Hz), A
tt=2c+, 7XL/D (dB).

Here, D is the inner diameter of the cylinder (σ), L is the length of the cylinder (6n
), Att is an approximate expression when the frequency is about 10% or less of Fc. From this, for example, the inner diameter D1 of the cylinder and the length L
When both are 5 crn, approximately 30 dB of attenuation is obtained in the frequency range up to several 100 MHz. Therefore, very high shielding performance can be obtained by selecting the mounting interval of the fasteners so that the length L of the cable tightening portion is equal to or more than the pre-estimated outer diameter of the cable bundle at the maximum cable amount.

The effect of such a cylindrical cable tightening part is when a large amount of optical fiber cable is introduced into the housing and even if it is covered with the above-mentioned drawstring-like conductive cloth, a transparent part remains for electromagnetic interference waves. This is even more noticeable.

Furthermore, since only the soft conductive cloth comes into contact with the cable, the cable will not be damaged even if the fastener is tightened. Further, since screws or the like are not used to tighten the fasteners, the working time can be shortened.

Furthermore, since it can be tightened freely regardless of the amount of cable, there is no need to prepare several types of conductive cloths and bands of different sizes, which is economical.

FIG. 2 is a diagram illustrating a second embodiment of the present invention.

3 is a cable, ri is a cylindrical conductive cloth, IO is a frame, //
is a screw, /≠ is a fastener, and /j is a fastener support. In this embodiment, one wide fastener is used to fasten the upper end of the conductive cloth. The structure and assembly procedure except for this point are completely the same as the first embodiment.

The width of the fastener/≠ is approximately the same as the length of the cable tightening part, so this one fastener/≠
By simply tightening ≠, the same effect as in the first embodiment can be obtained, and high shielding performance can be obtained.

In addition, although the above embodiments all show the case where the cable inlet is provided on the bottom surface of the case, it is not possible to have exactly the same effect even if it is provided on the top and side surfaces of the case due to the same structure. Needless to say.

Further, in all of the above embodiments, the conductive cloth is attached to the inside of the casing, but the same structure can also be used to attach the conductive cloth to the outside of the casing.

The effect in this case is exactly the same.

As described in detail, according to the present invention, the cable is surrounded by a conductive cloth at the cable inlet of the housing, and
One end is fixed to the periphery, and the other end is tightened with a wide tightening part, so it closes the cable without any gaps, providing high shielding performance, and has the advantage of not damaging the cable, resulting in high reliability. . Further, since no screws or the like are used in the tightening part, the working time can be shortened, and the same structure can be used regardless of the amount of cable, which has the effect of greatly contributing to improving economic efficiency.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a first embodiment of a cable inlet electromagnetic shielding device of the present invention, FIG. 2 is a perspective view of a second embodiment of the present invention, and FIG. 3 is a schematic structure of an electronic device housing. FIG. 4 is a perspective view for explaining a conventional example. l: housing, 2=panel, 3: cable, ≠: cable inlet, j: connector, B: electronic circuit unit,
7a17b=closing plate, r, ii', screw, ta: conductive cloth, 10 two frames, lj: /2, /hiro: fastener, fastener support.

Claims (1)

[Claims] One end of a cylindrical conductive cloth is fixed to the periphery of the cable inlet of the electronic device housing, and the length of the tightening part of the cable bundle is at least equal to the outer diameter of the cable bundle at the other end of the conductive cloth. A cable inlet electromagnetic shielding device characterized by comprising a wide tightening part.