JP2010251607A - Electromagnetic wave shielding gasket - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electromagnetic wave shielding gasket mounted in a space between the chassis of electronic instruments, or between the chassis and a cover or the like, for securing both electromagnetic shielding performance and sealing performance. <P>SOLUTION: In the electromagnetic wave shielding gasket, a thin wall part is formed on both surface of a part in the direction of width of a conductive nonwoven fabric or woven cloth sheet body impregnated with rubber or resin, and a rubber or resin lip part is formed as one body with the thin wall part on both surfaces of the thin wall part. The electromagnetic wave shielding gasket is a gasket having both electromagnetic shielding performance and sealing performance, and can be applied to a chassis which is not subjected to groove processing. The use of the gasket having a narrow width and requiring no groove processing for the chassis side contributes, therefore, greatly to the miniaturization, weight saving and cost cutting of the chassis. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to an electromagnetic shielding gasket. More specifically, the present invention relates to an electromagnetic wave shielding gasket that is preferably used for a case without a groove.

  For electronic devices used in environments where water, oil, dust, etc., such as automobiles, construction machinery, and equipment installed in factories, or electronic devices for outdoor installation exposed to wind and rain, Sealing parts such as gaskets and packings that prevent entry of water and dust from the outside are required in the gaps between them, the gaps between wiring parts such as traffic lights and power lines, and the joints between the casings.

  On the other hand, in recent years, EMC (electromagnetic compatibility) regulations for electronic devices have become stricter in various industrial fields, and comprehensive EMC countermeasures for circuits, cases, and systems are required.

  Here, as a countermeasure against the casing, an electromagnetic wave shield that prevents the radiation and intrusion of electromagnetic waves is considered as one of the effective countermeasures. The present applicant has previously proposed a gasket in which a conductive woven or non-woven fabric is impregnated with rubber or resin (see Patent Document 1).

  In this proposal, from the viewpoint of sealing performance, a lip structure that can concentrate the surface pressure, increase the seal limit pressure, and further improve the seal reliability is preferably used. However, the seal itself is possible without adopting the lip structure, but the use conditions are limited. However, when adopting a lip structure, it is necessary to perform groove processing on the housing side where this member is inserted in order to position the lip and limit the amount of crushing of the lip. An appropriate flange width is required for securing, and it cannot be avoided that it becomes an obstacle to downsizing the housing.

  In particular, when the seal portion and the shield portion are separated from each other, the gasket width becomes wide, and the width of the casing portion where the gasket is disposed cannot be reduced. Further, if such a lip structure gasket is used in a housing that has not been grooved, the tightening amount cannot be controlled and there is a possibility of excessive compression.

  As a result, there is a possibility that the deterioration of the sealing performance in the long-term use due to the structural destruction of the lip portion or the compression set may increase. In addition, the lip part has a thickness (height) compared to its surroundings, and it has the possibility of being held horizontally, i.e. it cannot be erected, and may be crushed obliquely, without a grooved casing. Therefore, when unexpected stress is applied, such a problem may be accelerated.

  More recently, there has been a demand for a gasket that does not require grooving and can reduce the size of the housing in order to reduce the size and weight of electronic devices.

WO 2006/066442 JP 2004-288296 A

  An object of the present invention is to provide an electromagnetic shielding gasket that is mounted in a gap such as between a casing and a casing of an electronic device or between the casing and a lid, and enables simultaneous securing of an electromagnetic shielding property and a sealing property. There is.

  An object of the present invention is to form thin portions on both sides of a part of the conductive nonwoven fabric or woven fabric sheet impregnated with rubber or resin in the width direction, and to make a rubber or resin lip on both sides of the thin portion. This is achieved by an electromagnetic shielding gasket in which the part is formed integrally with the thin part.

  The gasket for electromagnetic wave shielding according to the present invention is a gasket having both electromagnetic wave shielding performance and sealing performance, and is applicable to a casing that is not subjected to groove processing. For this reason, the use of the gasket of the present invention having a narrow width and no need for groove processing on the housing side greatly contributes to reduction in size, weight, and cost of the housing.

  That is, the gasket for electromagnetic wave shielding of the present invention has high electromagnetic wave sealability due to high conductivity derived from the conductive nonwoven fabric or woven fabric, and is formed in a thin part of a rubber or resin nonwoven fabric or woven fabric. Control and management of the crushing amount of the rubber or resin lip portion is easy, and high reliability can be obtained in terms of sealing performance.

1 is a plan view of an embodiment of an electromagnetic wave shielding gasket according to the present invention and a cross-sectional view taken along the line II. It is sectional drawing which showed the formation process of the gasket for electromagnetic wave shields of this invention sequentially. It is sectional drawing which showed sequentially the compression process at the time of mounting | wearing the housing | casing and a cover body with the gasket for electromagnetic wave shields of this invention.

  As the conductive non-woven fabric or woven fabric impregnated with rubber or resin, non-woven fabric or woven fabric such as carbon fiber, brass fiber, stainless steel fiber or aluminum fiber is used, preferably with carbon fiber or electromagnetic shielding gasket. The fiber made of the same metal as the casing of the manufactured product is used.

  For example, stainless steel fibers are used for a stainless steel housing, and aluminum fibers are used for an aluminum housing as a sheet of conductive nonwoven fabric or woven fabric. When conductive non-woven fabric or woven fabric fiber is made of a metal made of a metal that is different from the casing of the product to which the gasket is attached, the contact moisture between the different metals for a long period of time or in a moisture-rich atmosphere However, the use of carbon fibers that are not ionized or fibers made of the same metal as the casing of the product to which the gasket is attached as a sheet-like material makes it possible to cause electric corrosion due to contact via Eating can be avoided.

  The thickness and width of the conductive nonwoven fabric or woven fabric can take various dimensions depending on the application to the extent that the electromagnetic wave is reflected and the shielding action is ensured. In addition, the gasket body can be formed of resin, but generally rubber is used. As the rubber used in such applications, liquid rubbers such as liquid silicone rubber, liquid fluororubber, liquid acrylic rubber, and liquid EPDM are preferably used, but thermoplastic elastomers and solid rubbers can also be used. Examples of the thermoplastic elastomer include olefin-based and styrene-based ones, and examples thereof include a polystyrene-based thermoplastic elastomer or a blended material thereof with a partially thermoplastic crosslinked polyolefin-based thermoplastic elastomer. The impregnation with these liquid rubbers is performed by a compression molding method, a screen printing method, or the like (see Patent Document 2).

  Since the electromagnetic shielding gasket is mainly used for a housing without a groove, it is generally manufactured as an annular gasket. A plan view of one embodiment is shown in FIG. 1 (a), and a sectional view taken along the line II is shown in FIG. 1 (b). It is. In this quadrangular annular gasket 1, reference numerals 2 and 2 ′ are rubber- or resin-impregnated sheet-like bodies made of conductive nonwoven fabric or woven cloth, and reference numeral 3 is a part of the sheet-like body in the width direction, preferably in the width direction. Reference numeral 4 denotes a rubber or resin lip portion formed integrally with the sheet-like body on both surfaces of the thin portion 3. As the sheet-like body 2, one having a thickness of about 3 to 10 mm is generally used.

  As shown in the cross-sectional view of FIG. 2, the annular gasket having such a structure is manufactured by placing a conductive sheet 13 on a lower mold 11 having a molding surface having a predetermined shape (a), and further forming a molding surface having a predetermined shape. The upper mold 12 having the above is placed above the conductive sheet 13 (b), and the thin mold 14 is formed by closing these molds (c), and then the lip portion forming space Rubber or resin is injected into 15 to form the lip portion 16. Here, the sheet-like body at a position corresponding to the lip portion forming space 15 is not compressed by the mold, but is compressed in the form dragged by the surrounding compression to form a thin portion.

  At this time, the impregnation of the conductive sheet-like material with rubber or resin may use a rubber or resin-impregnated conductive sheet-like material at the stage (a), or the lip portion 4 at the stage (d). The impregnation of the completely compressed conductive sheet-like material with rubber or resin is performed in advance so that the conductive nonwoven fabric or woven fabric on the sheet-like surface is not completely covered. It is carried out by compressing to about 80 to 90% of the original thickness, that is, by impregnating the gap at that time with 100% in a state of 20 to 10% as the compression rate during molding. At this time, the compression is physically performed as in a mold, and the mold used for the compression is brought into contact with the conductive nonwoven fabric or woven fabric. Nonwoven fabric or woven fabric remains, and surface conductivity can be ensured.

  In addition, partial thinning of a sheet-like body made of a conductive nonwoven fabric or woven fabric can be compression-molded without problems if a mold having a desired shape is used in the case of compression molding. The thickness of the thin part is determined by the volume of the part, the volume of the gasket, the state of assembly in the housing, etc. In the state of assembly in FIG. It is necessary to form a sufficiently large space from the thickness and width of the thin portion. However, the amount of compression is limited to a compression rate comparable to the porosity of the nonwoven fabric or woven fabric in the initial state. In addition, if two or more conductive nonwoven fabrics or woven fabrics are superposed on a portion other than the thin-walled portion and impregnated with rubber or resin, two or more conductive nonwoven fabrics or woven fabrics are integrated and desired. The structure can be realized.

  A rubber- or resin-made lip portion 4 is provided on both surfaces of a thin portion 3 formed in a part in the width direction of the conductive nonwoven fabric or woven sheet-like body impregnated with rubber or resin, preferably in the center in the width direction. 4 'is formed integrally with the thin portion. As the lip portion forming material, the same material as the rubber material or resin material generally used for impregnating the sheet-like body is used. When a rubber material is used, it is generally heated and vulcanized at about 130 to 180 ° C for about 2 to 10 minutes after impregnation into the sheet and injection molding for lip formation. Thus, the lip rubber portion is firmly integrated with the sheet-like body.

  In addition, in a mode in which two or more conductive non-woven fabrics or woven fabrics are superposed on portions other than the thin-walled portion and the rubber or resin is impregnated therewith, the sheet-like body is impregnated and the lip portion is simultaneously formed. be able to.

  As shown in the compression process of FIG. 3, the electromagnetic shielding gasket according to the present invention configured as described above is compressed in the state before compression (a) from above and below by, for example, the casing 21 and the lid 22. In the initial stage (b), when the lip portion 4 is first crushed, the crushed amount is increased, the lip height is lowered, and the lip portion is compressed to the same thickness as the portions 2 and 2 'impregnated with rubber or resin. (c) Since the impregnated portions 2 and 2 'are harder and have a larger area than the lip portions 4 and 4' made of only rubber or resin, the reaction force accompanying compression increases.

  At this time, the conductive nonwoven fabric or woven fabric comes into contact with the casing 21 and the lid body 22 on the surfaces of the impregnated portions 2 and 2 ′, and conduction between the casing and the lid body is ensured, and electromagnetic shielding properties can be realized. Moreover, excessive compression of the lip part 4 which is a rubber | gum or resin single-piece | unit can be suppressed by adjusting the tightening degree in the area | region where this reaction force increased. Thereby, the groove | channel is unnecessary and the gasket which has electromagnetic wave shielding property can be obtained.

  Furthermore, in the electromagnetic wave shielding gasket according to the present invention, only the inner lip portion of the entire thickness has a thick structure, and in this respect, it is the same as the conventional gasket structure having only the lip portion, The absolute amount is a structure that is only slightly thicker than the lip portion. The amount of crushing of the lip portion varies greatly depending on the size of the housing and the pressure required for sealing, but is about 0.2 to 1.0 mm. Therefore, the uprightness is higher than that of a conventional gasket having a structure with only a lip, and the ratio of oblique compression is extremely small, so that the reliability of the seal is improved.

  Next, the present invention will be described with reference to examples.

Example A rectangular gasket having an outer dimension of 239 × 149 mm and a width of 4 mm was manufactured as a rectangular annular gasket to be applied to a metal casing having a flange surface outer dimension of 240 × 150 mm and a width of 5 mm. (See Figure 1)

  That is, the center part in the width direction of the carbon fiber nonwoven fabric having a thickness of 0.6 mm was compressed to 0.28 mm using a mold as shown in FIG. 2, and liquid silicone rubber was impregnated into the nonwoven fabric. Although the force compressed by the mold does not act on the sheet-like body at the position corresponding to the lip portion forming space, it is compressed in a form dragged by the surrounding compression, and that portion also forms a thin portion. In this state, liquid silicone rubber was injected into the lip portion forming space to form a lip portion having a thickness of 0.9 mm and a height of 0.15 mm at a lip tip angle of 45 °. The impregnated liquid silicone rubber and the injected liquid silicone rubber are vulcanized at 130 ° C. for 2 minutes to be integrated with the sheet-like body. After the molding, the mold was opened and fixed in a cross-sectional shape as shown in FIG. 1 (b). The burr was punched out and processed into a gasket.

  The obtained gasket is attached between a metal case without a groove and a metal lid, the radiated electromagnetic field from the inside of the metal case is measured, and the radiated electromagnetic field strength when the non-conductive gasket is attached When the difference between the two is considered to be a shielding property, the shielding characteristic is 40 to 50 dB, and the electromagnetic shielding performance is confirmed.

DESCRIPTION OF SYMBOLS 1 Square annular gasket 2, 2 'Rubber or resin impregnation sheet-like body 3, 3' Sheet-like body thin part 4, 4 'Lip part 11 Lower mold 12 Upper mold 13 Conductive sheet-like body 21 Case 22 Lid body

Claims (7)

  A thin wall portion is formed on both sides of a part of the conductive nonwoven fabric or woven fabric sheet impregnated with rubber or resin in the width direction, and a rubber or resin lip portion is integrated with the thin wall portion on both sides of the thin wall portion. An electromagnetic shielding gasket formed.   The gasket for electromagnetic wave shielding according to claim 1, wherein the thin portion is formed at a central portion in the width direction of the sheet-like body.   The electromagnetic shielding gasket according to claim 1 or 2, which is attached to a gap between the casing and the casing of the electronic device or the casing and the lid.   The electromagnetic wave shielding gasket according to claim 3, which is applied to a housing without a groove and a housing or a housing and a lid.   The electromagnetic wave shield according to claim 3 or 4, wherein when compressed for use as a gasket, a thick conductive nonwoven fabric or woven fabric portion and a rubber or resin lip portion both contact the housing. Gasket.   Claims in which a thick portion of a nonwoven fabric or woven fabric impregnated with rubber or resin secures conductivity by securing electromagnetic shielding properties, and a sealing property is secured by a rubber or resin lip portion in which surface pressure is concentrated. The gasket for electromagnetic wave shielding according to 3, 4, or 5.   The electromagnetic wave shielding gasket according to any one of claims 1 to 6, wherein a conductive nonwoven fabric or woven fabric made of the same metal as that of a casing portion of a product to which the gasket is attached is used.

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