JP2005325640A - Soundproof radio wave absorbing panel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a soundproof radio wave absorbing panel having excellently both sound wave absorbing performance and radio wave absorbing performance. <P>SOLUTION: This soundproof radio wave absorbing panel is constituted so as to absorb a sound wave by a sound absorbing material 15 by passing the sound wave while protecting the inside sound absorbing material 15 from a flying object from an external part, by absorbing a radio wave by a mesh structure 1 constituted by installing a linear body 5 in a mesh shape by covering the surface of a reinforced cord 3 composed of an Aramid fiber with an epoxy resin blended with a particle having a radio wave absorbing capacity. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a soundproof type radio wave absorption panel, and more particularly to a soundproof type radio wave absorption panel having both soundproof performance and radio wave absorption performance.

In recent years, in the field of road traffic, efforts on intelligent traffic systems (ITS) have been activated, and for example, development of driving support systems for traveling vehicles is progressing. In this driving support system for automobiles, it is planned to control the distance between vehicles by radio wave communication between the road surface and the automobile or between the automobile and the automobile. On the other hand, on highways, as a measure against road noise against the local environment, a soundproof panel having sound insulation and sound absorption functions is generally installed on the road shoulder.

  For example, as shown in FIG. 5, a conventional general soundproof panel has a structure in which a metal plate (punching metal) 31 having a large number of through holes is attached to a frame 33 for surface protection. A sound absorbing material 35 made of glass wool or the like is provided inside. However, since the metal surface protection plate 31 reflects radio waves, it is assumed that when the metal surface protection plate 31 is used on an expressway such as the above-described intelligent traffic system (ITS), the radio wave interference occurs and the system does not function well.

  As a soundproof wall that does not cause radio interference even when used in an intelligent system as described above, the surface protection plate is, for example, a protection plate with a resin louver structure, and the sound absorber inside is made of carbon fiber or the like. The thing which mixed what has an electromagnetic wave absorption capability is mentioned (patent document 1). However, the protective plate made of resin has a restriction that an opening area such as a gap of a louver cannot be increased so as to sufficiently secure the protective function. For this reason, the amount of sound absorption by the sound absorbing material is restricted, and there is a problem that the sound absorbing effect must be sacrificed to some extent.

In addition, a sound absorbing layer is laminated on the surface of the sound insulation board, and a sound absorbing layer is disposed on the surface side with an air layer interposed between them. The outer surface of the sound absorbing layer is covered with a net-like protective layer, and sound absorbing performance and wave absorbing performance Has been proposed (Patent Document 2). However, this net-like protective layer is made of a resin or the like, and has not been considered for impact resistance and flame retardancy, and further improvements have been desired.
JP-A-9-41328 Japanese Patent Laid-Open No. 2003-301422

  An object of the present invention is to provide a soundproof type radio wave absorption panel that is well equipped with both sound wave absorption performance and radio wave absorption performance.

  The soundproof type radio wave absorption panel of the present invention that achieves the above object has a mesh structure in which a sound absorbing material is housed in a case-like frame having an opening on one side, and the opening of the frame faces the sound absorbing material. The wire structure is formed by assembling a linear body in which the surface of the reinforcing cord is coated with a resin mixed with particles having radio wave absorption capability.

  According to the present invention, since the network structure serving as the surface protection plate is composed of a linear resin body blended with particles having radio wave absorption capability reinforced with a reinforcing cord, the network structure itself has good radio wave absorption. In addition to exhibiting performance, since a large opening area can be easily secured on the surface, the sound absorbing performance of the inner sound absorbing material can be increased, and good sound absorbing performance can be exhibited.

Hereinafter, a specific description will be given based on the embodiment of the present invention shown in the drawings.
In the soundproof type radio wave absorption panel shown in FIG. 1, the sound absorbing material 15 is housed in a case-like frame body 10, and the mesh structure 1 is attached to the opening side of the frame body 10 so as to cover the front surface of the sound absorbing material 15. Yes. A radio wave absorbing layer 9 is laminated on the surface of the back plate 13 of the frame 10 facing the sound absorbing material 15.

  The frame 10 is made of a material having excellent sound insulation such as a resin plate or a metal plate, and the sound absorbing material 15 is made of a mat-like material in which long fibers or short fibers are accumulated, or a resin foam. . The radio wave absorption layer 9 is made of a resin composition in which conductive titanium oxide and conductive carbon black are blended with an epoxy resin.

  The network structure 1 is configured by braiding a linear body 5 that is reinforced by covering a reinforcing cord 3 with a resin blended with particles having radio wave absorption capability. Although the network structure by the linear body 5 of the network structure 1 is not specifically limited, For example, what is necessary is just to make it a structure like Fig.3 (a)-(c).

  As shown in FIG. 2, the linear body 5 constituting the mesh structure 1 is formed by coating a resin in which particles 7 having radio wave absorption capability are mixed around an organic or inorganic reinforcing cord 3 as a core material. Yes.

  Examples of the organic reinforcing cord 3 include an aramid fiber, a polyparaphenylene benzoxazole fiber, and a nylon fiber. Examples of the inorganic reinforcing cord 3 include carbon fiber and glass fiber. Among these, aramid fiber and carbon fiber having high strength and high elastic modulus are particularly preferable. By using an aramid fiber or carbon fiber, the mesh structure 1 can be provided with sufficient structural strength and impact resistance strength, and thereby the mesh opening area can be further increased. The sound absorption volume by the sound absorbing material 15 can be increased. Moreover, the sound absorbing material 15 can be appropriately protected from flying objects such as flying stones.

  The particles 7 having radio wave absorbing ability are not particularly limited as long as they have radio wave absorbing ability, and examples thereof include carbon black, metal powder, and carbon fiber cut powder. These particles 7 can be attenuated by absorbing radio waves in a state of being dispersed in the resin and converting them into thermal energy.

  As the resin, either a thermoplastic resin or a thermosetting resin may be used, but it is preferable to use an epoxy resin of a thermosetting resin from the viewpoint of ease of impregnation into the reinforcing cord 3 and application. Moreover, it is preferable to mix | blend flame retardants, such as a halide, with resin.

  In the present invention, the mesh structure 1 is characterized by having a radio wave absorption capability simultaneously with the role of the protective plate of the internal sound absorbing material 15. If the mesh size is too large, the sound-absorbing material 15 cannot be protected from flying objects such as stones flying from the road surface. If the mesh size is too small, the soundproofing performance is impaired. A corner of 10 mm or more is preferable.

  The mesh shape may be any shape as illustrated in FIGS. 3A to 3C, for example, but is not particularly limited, and may be, for example, a horizontally long slit shape. Furthermore, the mesh can be triangular, for example, one side can be 5 mm or more and 10 mm or less.

  The ratio of the total area of the network (opening portion) to the total area of the network structure 1 (hereinafter referred to as the “opening ratio”) is preferably 20% or more. This is because the soundproofing performance is impaired if the hole area ratio is less than 20%.

  When an epoxy resin is used, the network structure 1 can be manufactured by thermosetting a reinforcing cord impregnated with an epoxy resin solution in which particles having radio wave absorption ability are mixed and dispersed.

  In the present invention, the sound absorbing material 15 may be a foamed resin such as urethane foam in addition to a mat-like material that is an aggregate of fibers. In the case of a fiber mat, for example, glass wool or the like is used as the fiber. In the frame 10, it is preferable to provide an air layer 17 between the sound absorbing material 15 and the back plate 13, and the installation of the air layer 17 can improve the soundproofing effect and the radio wave absorption effect.

  In the present invention, the radio wave absorption layer 9 includes a resin composition in which conductive titanium oxide and conductive carbon black are mixed in an epoxy resin, and at least one of conductive titanium oxide and conductive carbon black in an epoxy resin. It may be a resin composition. The radio wave absorption performance can be further improved by laminating the radio wave absorption layer 9 on the surface of the back plate 13.

  The operation of the soundproof type radio wave absorption panel of the present invention will be described. The soundproofing effect is attenuated and absorbed by the noise that has passed through the mesh of the mesh structure 1 on the front surface entering the sound absorbing material 15.

  The radio wave incident on the soundproof type radio wave absorption panel is first absorbed through the resin constituting the linear body 5 of the mesh structure 1 into the particles 7 having radio wave absorption ability dispersed in the resin, and changed into heat. It attenuates. The radio wave that has passed through the mesh structure 1 as it is is absorbed by the radio wave absorption layer 9, and the remaining radio wave is reflected by the back plate 13 when the frame 10 is made of a metal plate, and again by the radio wave absorption layer 9. The radio waves that are absorbed and remain there interfere with the incident radio waves in the air layer 17 and cancel out. Further, the remaining part of the radio wave is again absorbed by the mesh structure 1.

  Since the mesh structure 1 is reinforced by the reinforcing cord 3, it has sufficient impact resistance even when a flying object such as a stone hits the road surface, and protects the internal sound absorbing material 15 without being easily destroyed. can do.

  Further, by replacing the surface protection plate (punching metal) 31 that reflects the radio waves of the existing soundproof panel as shown in FIG. Soundproof panel.

  The network structure 1 according to the present invention shown in Table 1 and three types of wire meshes were prepared as comparative examples to evaluate the radio wave absorption performance. As shown in FIG. 1, the same frame 10 in which the radio wave absorption layer 9 is laminated on the surface of the back plate 13 as shown in FIG. 1 is used, and the mesh structure 1 is attached to the opening (C1). There were five states, an attached state (C2 to C4) and a state where nothing was attached to the opening (C5). As the sound absorbing material 15, a mat-like material (with a poly film bag) having a thickness of 50 mm in which glass wool is accumulated is used.

  The network structure 1 according to the present invention includes a urethane-modified epoxy resin (Alps Chemical Industries, Ltd .: Albon EX-320 (a mixture of a bisphenol-type epoxy resin and a urethane resin)) and an amine curing agent (Sanwa). Chemical Industry Co., Ltd .: Sanmide X-963 (modified aliphatic polyamine)) Into 100 parts by mass of a flexible epoxy resin composed of a mixture of 50 parts by mass, a liquid flame retardant (Asahi Denka Kogyo Co., Ltd .: ADK STAB PFR ( 1,3 dihydroxybenzene / trichlorophosphine oxide polycondensate)), 30 parts by mass, powder flame retardant (manufactured by Nippon Chemical Industry Co., Ltd .: Hishigart N-3C (nitrilotristyrenephosphonate calcium)), 50 parts by mass, radio wave Carbon chopped fiber (manufactured by Donac Co., Ltd .: Donna carbon chop S-33) ) 6.2 parts by mass of the resin composition was impregnated into an aramid fiber (Toray Dupont Co., Ltd .: Kevlar K-129) having a wire diameter of 0.7 mm, and the cured wire diameter was φ4. A linear body of 5 mm has a mesh structure. The wire mesh is a general one, and a wire mesh made by welding steel wire rods.

  The radio wave absorbing layer 9 is composed of 50 parts by mass of conductive titanium oxide (Ishihara Sangyo Co., Ltd .: FT2000) and conductive carbon black (Nippon EC Co., Ltd .: Ketjen Black) with respect to 100 parts by mass of commercially available epoxy resin. It was a composition containing 3 parts by mass, and the thickness was laminated to 3 mm.

  As the evaluation method, the vector network analyzer HP8722C was used to measure the radio wave absorption performance at 5.8 GHz (circular polarization) by the free space method, and the incident angle dependence of the absorption performance is shown in FIG.

  As shown in FIG. 4, the state (C1) with the mesh structure 1 according to the present invention is superior to the state (C2 to C4) with the wire mesh attached at all incident angles of 10 to 70 °, and the radio wave of 20 dB or more. Absorption performance was obtained. Further, compared with a state where nothing is attached to the opening (C5), there is a difference at an incident angle of 50 °, but almost the same performance was confirmed, and a better performance was obtained at an incident angle of 30 °.

It is a thickness direction longitudinal cross-sectional view which shows the structure of the soundproof type electromagnetic wave absorption panel of this invention. It is a cross-sectional enlarged view of the linear body which comprises a mesh structure. It is a top view which shows the general | schematic form of the mesh structure of the soundproof type electromagnetic wave absorption panel of this invention. It is a graph which shows the incident angle dependence of the electromagnetic wave absorption performance of the soundproof type electromagnetic wave absorption panel of the Example of this invention. It is a thickness direction longitudinal cross-sectional view which shows an example of the structure of the conventional soundproof panel.

Explanation of symbols

1 Mesh structure 3 Reinforcement cord 5 Linear body
7 Particles having radio wave absorption capability 9 Radio wave absorption layer 10 Frame body 13 Back plate 15 Sound absorbing material 17 Air layer 31 Surface protection plate (punching metal) 33 Frame body 35 Sound absorbing material

Claims (6)

  A sound absorbing material is stored in a case-like frame having an opening on one side, a mesh structure is attached to the opening of the frame so as to face the sound absorbing material, and the mesh structure is a particle having radio wave absorption capability. A soundproof type radio wave absorption panel constructed by assembling a linear body in which a resin blended with a resin is coated on the surface of a reinforcing cord in a mesh shape.   The soundproof type radio wave absorption panel according to claim 1, wherein the particles having radio wave absorption capability are at least one of carbon black, metal powder, and carbon fiber powder.   The soundproof type radio wave absorption panel according to claim 1 or 2, wherein the reinforcing cord is made of at least one of aramid fiber, glass fiber, and carbon fiber.   The soundproof type radio wave absorption panel according to any one of claims 1 to 3, wherein the mesh of the mesh structure has a size of 5 mm square or more and 10 mm square or less.   The soundproof type radio wave absorption panel according to any one of claims 1 to 4, wherein the sound absorbing material is a mat-like material in which fibers are accumulated. The soundproof type radio wave absorption panel according to any one of claims 1 to 5, wherein a radio wave absorption layer is laminated on a surface of a back plate of the frame body facing the sound absorbing material.

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