JP2012234996A - Method for suppressing electromagnetic wave leakage - Google Patents
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Abstract
Description
本発明は、電子機器の金属製筐体で金属板と金属板が重なった部分のすき間から漏洩する電磁波を抑制する、電磁波漏洩の抑制方法に関するものである。 The present invention relates to a method for suppressing electromagnetic wave leakage, which suppresses electromagnetic waves leaking from a gap where a metal plate and a metal plate overlap in a metal casing of an electronic device.
ＯＡ・電機製品には、製品内部に組み込まれた電子回路からの漏洩電磁波をシールドすることが求められている。これは、漏洩電磁波が他のＯＡ・電機製品を誤作動させる可能性があるだけでなく、心臓ペースメーカなどの電子機器を誤作動させて、使用している人へ影響を及ぼす可能性があるためである。 OA / electrical products are required to shield leakage electromagnetic waves from electronic circuits incorporated in the product. This is because leaked electromagnetic waves may not only cause other OA / electrical products to malfunction, but also may cause electronic devices such as cardiac pacemakers to malfunction and affect people using them. It is.
ＯＡ・電機製品の筐体は、鋼板やアルミ板等の金属で作製されている場合が多い。そして、金属製の筐体内部に電磁波の発信源がある場合に、金属板が重なった部分を溶接など連続的な接合を施さない限り、隙間ができてしまい、ここから電磁波が漏洩することが問題となる。 The casing of OA / electrical products is often made of a metal such as a steel plate or an aluminum plate. If there is an electromagnetic wave source inside the metal housing, a gap will be created unless the metal plate overlaps the welded part, and electromagnetic waves may leak from here. It becomes a problem.
このため、電磁波シールド用ガスケットを、金属板と金属板の間に挟んで、電磁波の漏洩を抑制することが広く行われている。例えば、特許文献１には、電磁波シールド用ガスケットとして、スポンジ状の芯材の周囲にシート状の導電性シートを覆設したもの、また特許文献２には、導電性の布で弾性体を被覆したものがそれぞれ開示されている。 For this reason, it is widely practiced to suppress leakage of electromagnetic waves by sandwiching an electromagnetic shielding gasket between metal plates. For example, Patent Document 1 discloses an electromagnetic wave shielding gasket in which a sheet-like conductive sheet is covered around a sponge-like core material, and Patent Document 2 covers an elastic body with a conductive cloth. Each of which has been disclosed.
このように、柔軟な材料の周囲を導電体で被覆するもの、つまり、隙間を導電体で塞ぐ方法が主流となっている。しかし、電磁波シールド用のガスケットは製造方法が複雑で価格が高いという問題がある。 As described above, a method of covering the periphery of a flexible material with a conductor, that is, a method of closing a gap with a conductor has become the mainstream. However, the electromagnetic shielding gasket has a problem that the manufacturing method is complicated and the price is high.
これに対して、本発明者らは特許文献３において、簡便かつ高精度に漏洩電磁波の強度を評価する電磁波漏洩の評価方法および装置を開示し、金属板と金属板が重なった部分の隙間を、導電体ではなく、絶縁体で塞いでも電磁波漏洩を抑制する効果があることを見出した。 On the other hand, the present inventors disclosed an electromagnetic wave leakage evaluation method and apparatus for evaluating the intensity of leaked electromagnetic waves in a simple and highly accurate manner in Patent Document 3, and the gap between the overlapping portions of the metal plate and the metal plate is disclosed. It has been found that there is an effect of suppressing electromagnetic wave leakage even if it is covered with an insulator instead of a conductor.
しかしながら、特許文献３に開示した技術では、絶縁体の厚さや絶縁体同士の位置関係が電磁波の減衰にどのように影響するかについては明らかにされておらず、具体的な電磁波漏洩の抑制方法となっていなかった。 However, in the technique disclosed in Patent Document 3, it has not been clarified how the thickness of the insulator and the positional relationship between the insulators affect the attenuation of the electromagnetic wave, and a specific method for suppressing electromagnetic wave leakage. It was not.
本発明では、これら従来技術の問題点に鑑みなされたものであり、電磁波漏洩を抑制するための、金属板と金属板が重なった部分の隙間を塞ぐ絶縁体の厚さや絶縁体同士の位置を規定する、電磁波漏洩の抑制方法を提供することを課題とする。 The present invention has been made in view of these problems of the prior art, and in order to suppress electromagnetic wave leakage, the thickness of the insulator and the position of the insulators that block the gap between the overlapping portions of the metal plate and the metal plate are determined. It is an object of the present invention to provide a method for suppressing electromagnetic wave leakage.
［１］ 金属製筐体の金属板と金属板が重なった部分の金属板間に挟みこんだ絶縁体によって漏洩する電磁波を抑制する、電磁波漏洩の抑制方法であって、
前記電磁波の周波数をｆ（GHｚ）とした場合に、前記絶縁体の厚さｈ（ｍｍ）を次の（２）式を満足する厚さとすることを特徴とする電磁波漏洩の抑制方法。
[1] An electromagnetic wave leakage suppression method that suppresses electromagnetic waves leaking by an insulator sandwiched between metal plates of a metal casing and a portion where the metal plates overlap,
When the frequency of the electromagnetic wave is set to f (GHz), the thickness h (mm) of the insulator is set to a thickness that satisfies the following expression (2).
［２］ 上記［１］に記載の電磁波漏洩の抑制方法において、
前記絶縁体同士の距離ｗ（ｍｍ）を、電磁波の透過する方向に対して直角に、次の（３）式を満足する距離とすることを特徴とする電磁波漏洩の抑制方法。
[2] In the method for suppressing electromagnetic wave leakage according to [1] above,
A method for suppressing electromagnetic wave leakage, characterized in that a distance w (mm) between the insulators is set to a distance satisfying the following expression (3) at right angles to a direction through which electromagnetic waves are transmitted.
本発明は、電磁波の周波数に対応した、絶縁体の厚さならびに絶縁体同士の距離を規定するようにしたので、これに基づいた筐体設計ならびに製作を行えば十分な電磁波漏洩の抑制効果を得ることができる。 In the present invention, the thickness of the insulator and the distance between the insulators corresponding to the frequency of the electromagnetic wave are regulated, so that a sufficient electromagnetic wave leakage suppressing effect can be obtained if the housing design and production based on this is performed. Can be obtained.
図１は、本発明に係る電磁波漏洩の抑制方法を概説する図である。金属製の筐体内部に電磁波の発信源があり、筐体の金属板重ね合わせ部の隙間(電磁波の透過部)から電磁波が筐体の外に漏洩している様子を示している。 FIG. 1 is a diagram outlining an electromagnetic wave leakage suppression method according to the present invention. In the figure, there is an electromagnetic wave transmission source inside a metal casing, and electromagnetic waves are leaking out of the casing through a gap (electromagnetic wave transmitting portion) between metal plate overlapping portions of the casing.
電磁波を図１に示すように透過させて、電磁波の透過部の出口から出てきた電磁波の電界強度を測定し、電磁波の減衰量を次の（１）式で求める。 The electromagnetic wave is transmitted as shown in FIG. 1, the electric field strength of the electromagnetic wave emitted from the exit of the electromagnetic wave transmission part is measured, and the attenuation amount of the electromagnetic wave is obtained by the following equation (1).
（１）式における基準となる状態とは、金属板が重なった部分の電磁波の透過する方向に対する長さLは30ｍｍであり、電磁波の透過部の幅が200ｍｍ（図１における電極を設置しない場合）であり、電磁波の透過部における金属板間の隙間（h0）が1ｍｍ(導電部に挟み込む金属板の厚さで調節)である。この基準となる状態における、電磁波の透過部の出口から出てきた電磁波の強度(電磁波の電界強度)を基準とする。 The reference state in equation (1) is that the length L of the portion where the metal plates overlap with respect to the direction in which the electromagnetic wave is transmitted is 30 mm, and the width of the electromagnetic wave transmission portion is 200 mm (when the electrode in FIG. 1 is not installed) And the gap (h 0 ) between the metal plates in the electromagnetic wave transmission part is 1 mm (adjusted by the thickness of the metal plate sandwiched between the conductive parts). The intensity of the electromagnetic wave coming out from the exit of the electromagnetic wave transmitting portion (the electric field intensity of the electromagnetic wave) in this reference state is used as a reference.
図２は、本発明に用いる絶縁部を示す図である。図２（ａ）および（ｂ）は、上面図および側面図をそれぞれ示す。絶縁部は、金属板に厚さｈ、長さ３０ｍｍの絶縁体を挟み込んで形成されている（金属板の厚さの合計はh0-hとなる）。絶縁体の厚さｈならびに幅ｗ０を変化させて、絶縁部の形状を変えている。なお、絶縁体としては、固体の絶縁体（誘電体、樹脂、接着剤等）、気体、真空、気体あるいは真空と固体の絶縁体の混合物のいずれかを使用できる。以下では、絶縁体として紙を用いて、絶縁体の厚さｈ(紙の重ね合わせ枚数を調節)ならびに幅ｗ０を変化させている。 FIG. 2 is a diagram showing an insulating portion used in the present invention. 2A and 2B show a top view and a side view, respectively. The insulating portion is formed by sandwiching an insulator having a thickness h and a length of 30 mm between metal plates (the total thickness of the metal plates is h 0 -h). The shape of the insulating part is changed by changing the thickness h and the width w 0 of the insulator. As the insulator, a solid insulator (dielectric, resin, adhesive, etc.), gas, vacuum, gas, or a mixture of vacuum and solid insulator can be used. In the following, paper is used as the insulator, and the thickness h of the insulator (adjusting the number of stacked sheets of paper) and the width w 0 are changed.
図３は、h0を1ｍｍとして絶縁体の厚さを変化させた場合の電磁波の減衰特性例を示す図である。筐体内部から電磁波の周波数ｆを１〜８GHｚと変化させて電磁波を発信し、筐体外部に設置したアンテナを介して漏洩した電磁波を受信したものである。絶縁体の厚さｈを０〜１ｍｍと変化させて、前述の（１）式で求めた電磁波の減衰量をプロットしたものである。 FIG. 3 is a diagram showing an example of electromagnetic wave attenuation characteristics when h 0 is 1 mm and the thickness of the insulator is changed. The electromagnetic wave is transmitted from the inside of the case by changing the frequency f of the electromagnetic wave to 1 to 8 GHz, and the leaked electromagnetic wave is received through the antenna installed outside the case. The thickness h of the insulator is changed from 0 to 1 mm, and the attenuation amount of the electromagnetic wave obtained by the above equation (1) is plotted.
図中の破線で囲んだ部分は、減衰量−２０ｄB、すなわち基準となる状態の電磁波の電界強度の１／１０になることを示している。この減衰量を得るためには、電磁波の周波数ｆが小さくなるにしたがって、絶縁体の厚さｈを薄くしなければならない(比例する)ことが分る。 A portion surrounded by a broken line in the figure indicates that the attenuation is −20 dB, that is, 1/10 of the electric field strength of the electromagnetic wave in the reference state. It can be seen that in order to obtain this attenuation, the thickness h of the insulator must be reduced (proportional) as the frequency f of the electromagnetic wave decreases.
減衰量−２０ｄB以上の減衰を得るための、絶縁体の厚さｈ(ｍｍ)と電磁波の周波数ｆ(GHｚ)との関係を表したのが、次の（２）式である。 The following equation (2) expresses the relationship between the thickness h (mm) of the insulator and the frequency f (GHz) of the electromagnetic wave in order to obtain an attenuation of −20 dB or more.
すなわち、絶縁体の厚さｈが（２）式で計算される値未満となった場合に、減衰量が小さく(−２０ｄB)なり、電磁波の透過部での減衰が大きくなる。 That is, when the thickness h of the insulator becomes less than the value calculated by the equation (2), the attenuation amount becomes small (−20 dB), and the attenuation at the electromagnetic wave transmission portion increases.
次に、絶縁体の厚さｈを０．１ｍｍと固定し、図２に示す絶縁体の幅ｗ０を変化させて図１の電極間距離ｗを変えた場合における電磁波の減衰について説明する。図４は、電極間距離を変えた場合の電磁波の減衰特性例(１−２GHz)を示す図である。図５は、電極間距離を変えた場合の電磁波の減衰特性例(４−８GHz)を示す図である。 Next, the thickness h of the insulator was fixed with 0.1 mm, the electromagnetic wave attenuation is described in a case of changing the inter-electrode distance w in Figure 1 by changing the width w 0 of the insulator shown in FIG. FIG. 4 is a diagram showing an example of electromagnetic wave attenuation characteristics (1-2 GHz) when the distance between the electrodes is changed. FIG. 5 is a diagram showing an example of electromagnetic wave attenuation characteristics (4-8 GHz) when the distance between the electrodes is changed.
図３と同様に、図中の破線で囲んだ部分は、減衰量−２０ｄB、すなわち基準となる状態の電磁波の電界強度の１／１０になることを示している。この減衰量を得るためには、電磁波の周波数ｆが大きくなるにしたがって、電極間距離ｗを短くしなければならない(反比例する)ことが分る。 As in FIG. 3, the portion surrounded by the broken line in the figure indicates that the attenuation is −20 dB, that is, 1/10 of the electric field strength of the electromagnetic wave in the reference state. It can be seen that in order to obtain this attenuation, the inter-electrode distance w must be shortened (inversely proportional) as the frequency f of the electromagnetic wave increases.
減衰量−２０ｄB以上の減衰を得るための、電極間距離ｗ(ｍｍ)と電磁波の周波数ｆ(GHｚ)との関係を表したのが、次の（３）式である。 The following equation (3) expresses the relationship between the interelectrode distance w (mm) and the electromagnetic wave frequency f (GHz) in order to obtain an attenuation of -20 dB or more.
すなわち、電極間距離ｗが（３）式で計算される値未満となった場合に、減衰量が小さく(−２０ｄB)なり、電磁波の透過部での減衰が大きくなる。 That is, when the inter-electrode distance w is less than the value calculated by the expression (3), the attenuation amount becomes small (−20 dB), and the attenuation at the electromagnetic wave transmission portion becomes large.
以上説明を行ったように、本発明では、電磁波の周波数に対応した、絶縁体の厚さならびに絶縁体同士の距離を規定するようにしたので、これに基づいた筐体設計ならびに製作を行えば十分な電磁波漏洩の抑制効果を得ることができる。 As described above, in the present invention, the thickness of the insulator and the distance between the insulators corresponding to the frequency of the electromagnetic wave are regulated. A sufficient effect of suppressing electromagnetic wave leakage can be obtained.
Claims (2)
前記電磁波の周波数をｆ（GHｚ）とした場合に、前記絶縁体の厚さｈ（ｍｍ）を次の（２）式を満足する厚さとすることを特徴とする電磁波漏洩の抑制方法。
When the frequency of the electromagnetic wave is set to f (GHz), the thickness h (mm) of the insulator is set to a thickness that satisfies the following expression (2).
前記絶縁体同士の距離ｗ（ｍｍ）を、電磁波の透過する方向に対して直角に、次の（３）式を満足する距離とすることを特徴とする電磁波漏洩の抑制方法。
A method for suppressing electromagnetic wave leakage, characterized in that a distance w (mm) between the insulators is set to a distance satisfying the following expression (3) at right angles to a direction through which electromagnetic waves are transmitted.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JP2001284875A (en) * | 2000-03-31 | 2001-10-12 | Matsushita Electric Ind Co Ltd | Spurious electromagnetic radiation shield structure of enclosure and conductive enclosure constituent element |
| JP2010232473A (en) * | 2009-03-27 | 2010-10-14 | Nec Corp | Electronic device-mounted machine and method for reducing noise of electronic device-mounted machine |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JP2001284875A (en) * | 2000-03-31 | 2001-10-12 | Matsushita Electric Ind Co Ltd | Spurious electromagnetic radiation shield structure of enclosure and conductive enclosure constituent element |
| JP2010232473A (en) * | 2009-03-27 | 2010-10-14 | Nec Corp | Electronic device-mounted machine and method for reducing noise of electronic device-mounted machine |
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