JP2010045420A - Electromagnetic shielding system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reliably shield electromagnetic waves radiated from an electronic apparatus even when a metal panel with corners is used in a simplified electromagnetic shielding system using an electromagnetic shielding tape or an electromagnetic shielding gasket for closing a gap in the metal panel. <P>SOLUTION: In a simplified electromagnetic shielding method for closing a gap in a metal panel 1 by using an electromagnetic shielding tape 2, fluctuation in electromagnetic shielding performance relative to an electromagnetic wave frequency to be shielded is reduced, even when the metal panel 1 with corners is used, by adjusting a distance (d) between a joint portion 3 and a corner which is parallel with and closest to the joint portion 3. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electromagnetic shielding device that constructs an electromagnetic shielding surface around an information technology device such as a computer or a communication device and shields electromagnetic waves radiated from the information technology device.

  As the internal circuits of information technology devices such as computers and communication devices are digitized, electromagnetic waves are unintentionally radiated with the operation of the devices. In order to prevent the unintentional electromagnetic waves from affecting television, radio broadcasting, wireless communication, and the like, it is required by laws and international standards to keep the electromagnetic wave level below the standard.

  On the other hand, due to high integration of digital circuits and the like, the operating voltage decreases, and the normal operation of the device may be hindered by electromagnetic waves, voltage, and current that enter from the outside of the device. In order to prevent this, it is important that the resistance of the device to external electromagnetic waves is higher than the standard defined in international standards.

  Furthermore, recently, there is a danger that display screen information and key input information will be stolen from electromagnetic waves radiated unintentionally from the device, and destruction and operation of the device by intentionally radiating strong electromagnetic waves from the outside. The danger of the act which induces the defect is pointed out.

  As a general means for dealing with the above problems, there is a method of surrounding the apparatus with an electromagnetic shield surface. For example, this corresponds to a case where all surfaces of a wall surface, a floor, and a ceiling of a room where the apparatus is installed are made of a metal electromagnetic shield material.

  The method of configuring the electromagnetic shield surface is broadly divided into a case of using a single metal plate having no joints and a case of forming a plurality of metal plates (panels) by joining. Recently, the latter construction method is often used from the viewpoint of materials, assembly cost, and workability.

  If there is a gap in the joint surface of the metal panel, it becomes a cause of deterioration of the electromagnetic shield performance. Therefore, different methods are used for joining the metal panels depending on the required electromagnetic shield performance. When high electromagnetic shielding performance (for example, 100 dB or more) is required, welding or fine screwing or riveting is used. When a moderate electromagnetic shielding performance (for example, about 50 to 60 dB) is required, a method of closing the gap with an electromagnetic shielding tape or an electromagnetic shielding gasket is used for the purpose of reducing the number of processes and costs.

  When electromagnetic shielding tape or electromagnetic shielding gasket is used, the worst electromagnetic shielding performance value for the frequency of the electromagnetic wave to be shielded is conventionally required based on the electromagnetic shielding performance of the electromagnetic shielding tape or electromagnetic shielding gasket alone. Designed to meet the requirements.

  The prior art document information related to this application includes the following.

"Latest absorption and shielding of electromagnetic waves" p321-p325, Nikkei Technical Books, 1999 "Introduction to EMC" p671-p674, Mimatsu Data System, 1996 “Examination of shielding effect of lossy material filled in gap”, IEICE Vol.J83-B, No.1, pp.128-130,

  However, the electromagnetic shielding tape or electromagnetic shielding gasket alone has sufficient electromagnetic shielding performance (for example, 80 dB or more), and the tape is attached and the gasket and the panel are electrically connected properly. However, there may be a problem that the constructed electromagnetic shield surface does not satisfy the requirements for electromagnetic shield performance.

  This is considered to be one of the causes that electromagnetic waves leaking from the coupling portion flow as current on the metal panel surface and re-radiate as electromagnetic waves on a discontinuous surface such as a corner. At this time, there is a resonance frequency due to the structure of the panel, and as shown in FIG. 6, particularly at the resonance frequency (p1 and p2), the re-radiation of the electromagnetic wave becomes large (as a result, the electromagnetic shielding performance deteriorates), At the resonance frequency (p3 and p4), the re-radiation of the electromagnetic wave is reduced (resulting in improved electromagnetic shielding performance). Since electromagnetic shielding performance is generally evaluated by whether the worst value for the frequency of the electromagnetic wave to be shielded satisfies the required conditions, the electromagnetic shielding performance value varies with the frequency of the electromagnetic wave to be shielded due to the influence of resonance, etc. The larger the value is, the more likely the average value will not satisfy the required condition, even if the average value satisfies the required condition of the electromagnetic shielding performance.

  The present invention has been made in view of the above circumstances, and in a simple electromagnetic shield system that closes a gap between metal panels using an electromagnetic shield tape, an electromagnetic shield gasket, or the like, a metal panel having corners is used. It is another object of the present invention to provide an electromagnetic shield device that can shield electromagnetic waves radiated from electronic devices.

  In order to achieve the above object, according to the present invention, a plurality of metal panels are joined using an electromagnetic shielding tape or an electromagnetic shielding gasket to form an electromagnetic shielding surface, thereby shielding electromagnetic waves radiated from an electronic device. An electromagnetic shielding device, wherein a part of the plurality of metal panels includes at least one or more corners arranged in parallel along a joint portion between the metal panels, and a frequency range of electromagnetic waves to be shielded Assuming that the distribution of the electromagnetic shielding performance value in the inside is a normal distribution, when the joint is the first end of the metal panel and the second end that is the end opposite to the joint is the corner The width of ± 2σ (σ is a standard deviation) with respect to the average value of the normal distribution is set to 0 dB, and the width of ± 2σ is exponentially based on 10 as the corner on the second end side approaches the joint. To increase Based on the relationship between the distance from the joint to the corner and the width of ± 2σ obtained by calculation, the distance from the joint is such that the width of ± 2σ becomes a desired value. The corners closest to the joint are arranged.

  The present invention according to claim 2 is an electromagnetic shielding device that shields electromagnetic waves radiated from an electronic device by joining a plurality of metal panels using an electromagnetic shielding tape or an electromagnetic shielding gasket to constitute an electromagnetic shielding surface. A part of the plurality of metal panels includes at least one or more corners arranged in parallel along the joint between the metal panels, and the electromagnetic shielding performance value within the frequency range of the electromagnetic wave to be shielded Assuming that the distribution is a normal distribution, the width of ± 2σ (σ is a standard deviation) with respect to the average value of the normal distribution when the metal panel does not have the corner is a reference (0 dB), and the width of ± 2σ is Based on the relationship between the number of corners obtained by calculation and the width of ± 2σ, assuming that the number increases in proportion to the square root of the number of corners, a number such that the width of ± 2σ becomes a desired value The corner of And characterized in that location.

  According to the present invention, even if a metal panel with corners is used in a simple electromagnetic shield system that closes a gap between metal panels using an electromagnetic shield tape, an electromagnetic shield gasket, or the like, the structure of the metal panel around the joint is used. By controlling this, it becomes possible to reduce the fluctuation of the electromagnetic shielding performance value with respect to the electromagnetic wave frequency to be shielded, so that the electromagnetic wave radiated from the electronic device can be reliably shielded.

In the electromagnetic shielding design method according to the first embodiment of the present invention, this is a specific example showing the relationship between the distance between the joint and the corner and the width of ± 2σ. It is a block diagram of an electromagnetic shielding apparatus. It is a figure explaining how to count the corner in a metal panel. It is a figure which compares the image of the fluctuation | variation with respect to the electromagnetic wave frequency which electromagnetic shielding performance value shields with the past and this invention. In the electromagnetic shielding design method which concerns on the 2nd Embodiment of this invention, it is an example which shows the relationship between the number of corners, and the width | variety of +/- 2 (sigma). It is an image of the fluctuation | variation with respect to the electromagnetic wave frequency which the electromagnetic shielding performance value shields.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<First Embodiment>
Before describing the electromagnetic shield design method according to the first embodiment of the present invention, the electromagnetic shield device 10 used in the present embodiment will be described. The electromagnetic shield device 10 shown in FIG. 2 has a plurality of metal panels 1 (two in FIG. 2) arranged with a predetermined gap (it is optimal that there is no gap, but in actuality the joining work) In this case, a slight gap is generated), and the gap is joined by the electromagnetic shield tape 2 to form an electromagnetic shield surface. As shown in FIG. 2, the metal panel 1 is configured not to be a flat plane but to have corners 4 in order to increase the strength. That is, in the present embodiment, an electromagnetic shield design method for shielding an electromagnetic wave radiated from an electronic device by forming an electromagnetic shield surface by joining a plurality of metal panels using an electromagnetic shield tape or an electromagnetic shield gasket. Is applied when the metal panel 1 has corners 4.

  Incidentally, the corner 4 in the present embodiment means a portion bent at the outside or the inside at a right angle or a near right angle with respect to the plane. Moreover, the corner | angular 4 of this Embodiment means what was arrange | positioned in parallel along the junction part 3 between metal panels, and a perpendicular | vertical corner is not included in the junction part 3 between metal panels. Accordingly, the single metal panel 1 shown in FIG. 2 has four corners. FIG. 3 shows a specific example of the shape of the metal panel 1 when the number of corners n is n = 2, 4, 6 (top view).

  1 assumes that the distribution of electromagnetic shielding performance values within a predetermined frequency range is a normal distribution in the electromagnetic shielding apparatus 10 shown in FIG. 2, and ± 2σ (σ is the standard value) with respect to the average value of the normal distribution. It is a figure which shows the relationship between the width | variety of deviation), and the distance d of the corner | angular 4 which is the nearest from the junction part 3 and this junction part 3. FIG.

  Here, the solid line indicates that the width of the average value ± 2σ is 0 dB when the corner 4 is on the end (the other end) opposite to the joint portion 3 (one end) of the panel on one metal panel 1, and the corner 4 Is a calculated value that assumes that the width of the average value ± 2σ increases exponentially with 10 as the base as it approaches the joint 3. Also, ◆ measures the electromagnetic shielding performance value using two iron metal panels 1 with a height of 655 mm, a width of 425 mm, and a thickness of 0.6 mm. From this measurement result, the width of the average value ± 2σ is actually obtained. It is a thing. In the normal distribution, since the ratio included in the range of ± 2σ with the average as the center is 95.44% of the whole, almost all of the measurement objects are included.

  According to FIG. 1, the width of the average value ± 2σ can be reduced by adjusting the distance d between the joint 3 and the corner 4 that is parallel to the joint 3 and closest to the joint 3. Therefore, the fluctuation | variation with respect to the electromagnetic wave frequency which electromagnetic shielding performance shields can be made small.

  Therefore, according to this embodiment, even if the metal panel 1 having the corner 4 is used in a simple electromagnetic shielding method for closing the gap between the metal panels 1 using the electromagnetic shielding tape 2 or the like, By adjusting the distance d with the corner 4 that is parallel to the joint 3 and closest to the joint 3, it is possible to reduce the fluctuation of the electromagnetic shielding performance value with respect to the electromagnetic wave frequency to be shielded. Electromagnetic waves radiated from electronic devices can be shielded.

  In the conventional electromagnetic shielding system, as shown in FIG. 4A, when the electromagnetic shielding performance is worse than the required condition (shielding performance value Q1 indicated by the dotted line), for example, the electromagnetic shielding tape 2 is pasted twice. As a result, the entire shield performance value is raised as shown by the shield performance value Q2 indicated by the solid line, and the electromagnetic shield performance is improved. However, in the present embodiment, as shown in FIG. 4B, when the electromagnetic shielding performance is worse than the required condition (shielding performance value Q1 indicated by the dotted line), the shielding performance value Q3 indicated by the solid line is obtained. Since the electromagnetic shield performance is improved by bringing the maximum value and minimum value of the resonance point and antiresonance point close to the average value, the present invention has a completely different action from the conventional electromagnetic shield system.

  As described above, in the present embodiment, the electromagnetic shielding tape 2 is used to increase the average value of the electromagnetic shielding performance value, and the fluctuation of the electromagnetic shielding performance value with respect to the electromagnetic wave frequency to be shielded is reduced by adjusting the distance d. Even if it is an electromagnetic shielding system, a favorable electromagnetic shielding performance value can be shown.

  According to the results of FIG. 1, generally, the distance d between the joint 3 and the corner 4 contributes to the improvement of the electromagnetic shielding performance. The optimal distance d is determined in consideration of other various conditions such as the gap interval is not uniform and the size of the metal panel 1 to be used is not necessarily the same.

  <Second Embodiment> An electromagnetic shield designing method according to the second embodiment of the present invention will be described. In the present embodiment, only the configuration and functions different from those of the first embodiment will be described, and the other components and functions will be denoted by the same reference numerals and the description thereof will be omitted.

  5 assumes that the distribution of electromagnetic shielding performance values within a predetermined frequency range is a normal distribution in the electromagnetic shielding apparatus 10 shown in FIG. 2, and ± 2σ (σ is the standard value) with respect to the average value of the normal distribution. It is a figure which shows the relationship between the width | variety of (deviation), and the number n of the corner | angular 4 which exists in one metal panel containing the junction part 3. FIG.

  Here, the solid line is a calculated value on the assumption that the width of the average value ± 2σ increases in proportion to the square root of the number n of corners 4 with reference to the case where there is no corner 4. Also, ◆ indicates the electromagnetic shielding performance value using two steel metal panels 1 of 655mm height x 425mm width x 0.6mm thickness, and the average value is obtained from the measurement result as ± 2σ width. It is a thing.

  According to FIG. 5, the width of the average value ± 2σ can be reduced by adjusting the joint portion 3 and the number n of corners 4 existing in one metal panel 1 including the joint portion 3. Therefore, the fluctuation | variation with respect to the electromagnetic wave frequency which electromagnetic shielding performance shields can be made small.

  Therefore, according to the present embodiment, the same effect as in the first embodiment can be obtained by adjusting the number n of corners 4 instead of the distance d from the joint 3 to the corners 4. That is, in the simple electromagnetic shielding method of closing the gap between the metal panels 1 using the electromagnetic shielding tape 2, even if the metal panel 1 having the corner 4 is used, the joining portion 3 and one piece including the joining portion 3 are used. By adjusting the number n of the corners 4 existing in the metal panel, it is possible to reduce the fluctuation of the electromagnetic shielding performance value with respect to the electromagnetic wave frequency to be shielded, so that the electromagnetic wave radiated from the electronic device is surely shielded. be able to.

  While the embodiments of the present invention have been described above, various modifications and changes can be made to the embodiments of the present invention without departing from the spirit of the present invention. For example, by adopting an electromagnetic shield design method considering the requirements of both the electromagnetic shield design method according to the first embodiment and the electromagnetic shield design method according to the second embodiment, the electromagnetic shield performance value Of course, the variation with respect to the electromagnetic wave frequency to be shielded may be reduced.

DESCRIPTION OF SYMBOLS 1 ... Metal panel 2 ... Electromagnetic shielding tape 3 ... Joint part 4 ... Corner 10 ... Electromagnetic shielding apparatus

Claims (2)

A plurality of metal panels are joined using an electromagnetic shielding tape or an electromagnetic shielding gasket to constitute an electromagnetic shielding surface, which is an electromagnetic shielding device that shields electromagnetic waves radiated from electronic equipment,
A portion of the plurality of metal panels comprises at least one corner disposed in parallel along a joint between the metal panels,
Assuming that the distribution of electromagnetic shielding performance values within the range of the frequency of the electromagnetic wave to be shielded is a normal distribution, the joint that is the first end of the metal panel and the second end that is opposite to the joint are the second end. The width of ± 2σ (σ is a standard deviation) with respect to the average value of the normal distribution when the corner is at the end is set to 0 dB, and as the corner on the second end side approaches the joint, the ± 2σ Based on the relationship between the distance from the joint to the corner and the width of the ± 2σ obtained by calculation on the assumption that the width exponentially increases from the base of 10, the width of the ± 2σ is a desired value. The electromagnetic shield device according to claim 1, wherein the corner closest to the joint is disposed at a distance from the joint. A plurality of metal panels are joined using an electromagnetic shielding tape or an electromagnetic shielding gasket to constitute an electromagnetic shielding surface, which is an electromagnetic shielding device that shields electromagnetic waves radiated from electronic equipment,
A portion of the plurality of metal panels comprising at least one or more corners disposed in parallel along a joint between the metal panels;
Assuming that the distribution of electromagnetic shielding performance values within the frequency range of the electromagnetic wave to be shielded is a normal distribution, ± 2σ (σ is a standard deviation) with respect to the average value of the normal distribution when the metal panel has no corner ) Based on the relationship between the number of corners obtained by calculation and the width of ± 2σ, assuming that the width of ± 2σ increases in proportion to the square root of the number of corners. Thus, an electromagnetic shield device having the number of the corners such that the width of ± 2σ becomes a desired value.

Images