JP2006125156A - Sound insulating wall material with electromagnetic wave absorbing function - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sound insulating wall material having excellent radio wave absorbing function and noise absorbing function without newly adding a radio wave absorbing layer and a radio wave reflecting layer or changing the thickness dimension. <P>SOLUTION: This sound insulating material with electromagnetic wave absorbing function 10 comprises a resin-made front panel 28 on a surface. Since a magnetic powder is mixed to the resin-made front panel 28 in a predetermined ratio or more, new addition of radio wave absorbing layer or radio wave reflecting layer is not needed for providing the electromagnetic wave absorbing function. Accordingly, the sound insulating wall material 10 can be provided with excellent radio wave absorbing function and noise absorbing function without changing the thickness dimension of the material 10. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a soundproof wall material with an electromagnetic wave absorption function having a function of absorbing electromagnetic waves and absorbing noise.

  For example, soundproof wall materials are known that are erected on the shoulders of expressways and toll roads, or are installed around toll booths and on ceiling walls. Since such a soundproof wall member merely has a function of absorbing noise, it becomes a reflector of radio waves, and there is a possibility that radio wave interference may occur depending on the installation location. For example, in places where an automatic area collection system (ETC) or intelligent road traffic system (ITS) using radio waves is adopted, radio waves are irregularly reflected from road structures and sound barriers, and road communication devices and in-vehicle communication There is a risk of device malfunction. In particular, at a toll booth where an automatic area collection system is installed, there is a problem in that there are a plurality of radio wave propagation paths from an antenna in a certain place to the vehicle, and double charging occurs.

On the other hand, a soundproof wall material having a function of absorbing electromagnetic waves and a function of absorbing noise has been proposed. For example, the radio wave absorption panel described in Patent Document 1 is that. According to this, a sound absorbing layer, a radio wave absorption layer, a radio wave reflection layer, and a bottom portion of the back case are sequentially provided on the back surface of the front cover having a plurality of through holes in the stacking direction, thereby forming a wall shape.
JP 2003-119726 A

  By the way, the soundproof wall material having the function of absorbing the electromagnetic wave and the function of absorbing noise is inevitable that the thickness of the wall material is increased by the addition of the radio wave absorption layer and the radio wave reflection layer. Since simple replacement with the existing soundproof wall material is impossible, it is necessary to replace the entire soundproof wall and the fixing device including the soundproof wall, and there is a disadvantage that the cost becomes high in practice. The radio wave absorption layer and the radio wave reflection layer can be formed without changing the thickness dimension. In this case, however, the thickness of the 某 son layer must be reduced, and the soundproofing performance is inevitably sacrificed.

  The present invention has been made against the background of the above circumstances, and its object is to add a radio wave absorption layer and a radio wave reflection layer without changing the thickness dimension, and to have an excellent radio wave absorption function. And providing a soundproof wall material having a noise absorbing function.

  The inventors of the present invention pay attention to the fact that the conventional soundproof wall is provided with a resin front cover having a plurality of through holes on the surface of the sound absorbing layer having a predetermined thickness. Further, it has been found that when magnetic powder such as soft magnetic metal powder is mixed, the thickness of the soundproof wall is not increased, the soundproof performance is not impaired, and a radio wave absorbing function can be provided. The present invention has been made based on such findings.

  That is, the gist of the invention according to claim 1 is a soundproof wall material with an electromagnetic wave absorbing function provided with a resin front panel on the surface, and the resin front panel is mixed with a magnetic powder in a predetermined ratio or more. It is characterized by being.

  According to a second aspect of the present invention, the resin front panel has a soft magnetic metal powder dispersed in the polycarbonate resin at a rate of 20 to 35 (volume)% as the magnetic powder. It is characterized by being.

  According to a third aspect of the present invention, the resin front panel has an electromagnetic wave absorbing function with respect to circular polarization.

Further, the gist of the invention according to claim 4 is that the resin front panel includes a plurality of through holes provided with a uniform surface density,
A sound absorbing material having a predetermined thickness and a metal back panel are sequentially disposed on the back surface of the resin panel in the thickness direction.

  According to the first aspect of the present invention, in the soundproof wall material with an electromagnetic wave absorbing function provided with a resin front panel on the surface, the resin front panel is mixed with a magnetic powder in a predetermined ratio or more. Since a new absorption layer and radio wave reflection layer are not added, the thickness of the soundproof wall material is not changed, and a soundproof wall material having an excellent radio wave absorption function and noise absorption function is obtained.

According to a second aspect of the present invention, the resin front panel is obtained by dispersing soft magnetic metal powder in the polycarbonate resin at a rate of 20 to 35 (volume)% as the magnetic powder. Thus, the complex relative permeability μ _r ″ and the complex relative permittivity ε _r ″ of the resin front panel are preferably increased to obtain high radio wave absorption performance. For example, when the incident angle of the electromagnetic wave to the resin front panel is 70 °, the return loss S21 is ensured to be at least −10 dB, and the communication interference problem is preferably solved. If the soft magnetic metal powder is lower than 20 (volume)%, sufficiently large complex relative permeability μ _r ″ and complex relative permittivity ε _r ″ cannot be obtained, and radio wave absorption performance cannot be obtained. On the contrary, when the soft magnetic metal powder is higher than 35 (volume)%, the mechanical strength of the resin front panel, for example, the bending elastic modulus cannot be obtained.

  According to the invention of claim 3, since the resin front panel has an electromagnetic wave absorbing function with respect to circularly polarized waves, suitable absorption performance for circularly polarized waves can be obtained. .

  According to the invention of claim 4, since the resin front panel is provided with a large number of through holes provided with a uniform surface density, sound transmission is obtained, and the resin front panel is provided. Reflection of sound at is suitably suppressed. In addition, since a sound absorbing material having a predetermined thickness and a metal back panel are sequentially arranged in the thickness direction on the back surface of the resin front panel, there is no radio wave between the resin front panel and the metal back panel. The absorption layer and the radio wave reflection layer are not newly provided, and the thickness dimension of the soundproof wall material is not changed. In addition, since the radio wave that has passed through the resin front panel is reflected by the back metal panel and is allowed to pass through the resin front panel again, the radio wave is more preferably absorbed.

Here, the soft magnetic metal powder mixed in the resin front panel is more preferably 25 to 30 (volume)%. In this way, the complex relative permeability μ _r ″ and the complex relative permittivity ε _r ″, which can obtain a radio wave absorption characteristic of dispersion in a higher polycarbonate resin, are suitably increased to obtain high radio wave absorption performance, The mechanical strength of the resin front panel is increased.

  In the resin front panel, the magnetic powder may be mixed in the entire thickness direction, but may be mixed in a part of the thickness direction, for example, only in the surface layer. Or you may comprise by laminating | stacking the surface resin panel in which magnetic powder was mixed uniformly, and the main resin panel in which magnetic powder was not mixed.

  In addition, the resin front panel has high mechanical strength, excellent weather resistance, and needs to withstand long-term use. Therefore, polycarbonate resin, polypropylene resin, vinyl chloride, and those resins are fiber reinforced. Are used.

  The magnetic powder may be ferrite or the like, but Fe, 13Cr—Fe, carbonyl iron, Fe—Si alloy, iron nickel alloy (permalloy, Fe—Ni alloy), Fe—Co alloy, Fe—Cr alloy, A powder of soft magnetic metal such as Fe—Cr—Al alloy, Fe—Cr—Si alloy, iron aluminum silicon alloy (Sendust, Fe—Al—Si alloy), amorphous alloy or the like is preferably used.

  The sound absorbing material may be a single layer or multiple layer porous sound absorbing material such as foamed glass, porous ceramics in which inorganic particles are bound by an inorganic binder (glass), rock wool, glass fiber, polyester fiber or the like. Preferably used.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 and FIG. 2 are diagrams for explaining a use state of a soundproof wall member 10 according to an embodiment of the present invention. In FIG. 1, a soundproofing device 10 provided on the shoulder of an expressway or a toll road becomes a soundproofing wall 12 having a predetermined shape as a whole by assembling a plurality of soundproofing wall materials 10 using a fixing frame (not shown). It is configured as follows. In FIG. 2, there is an example in which a plurality of soundproof wall members 10 are covered by a wall surface 14 of a ceiling of a toll road where an automatic area collection system (ETC) using radio waves is applied. It is shown. In this case, for the propagation of radio waves between the transceiver 18 mounted on the vehicle 16 and the antenna 20 of the automatic area collection system, for example, there are a path indicated by a solid line and a shortest path indicated by a two-dot chain line. Although there is a possibility that heavy charging may occur, the electromagnetic wave absorbing function of the soundproof wall member 10 of this embodiment attenuates the radio wave along the path indicated by the solid line due to absorption, thereby greatly reducing the possibility of double charging. .

  In FIG. 1, a soundproof wall material 10 according to an embodiment of the present invention has a flat plate shape as a whole. For example, a frame member 22 made of metal such as steel and a frame member 22 for closing the back surface thereof. A sound-absorbing material 26 and a resin-made front panel 28, which are sequentially fitted in a rectangular parallelepiped box composed of the frame member 22 and the back panel 24, for example, a metal back panel 24 fixed to In order to fix the resin front panel 28, it is mainly composed of a fixing member 30 fixed to the frame member 22.

  The sound absorbing material 26 has a rectangular parallelepiped shape that is slightly smaller in the thickness direction than the space in the rectangular parallelepiped box composed of the frame member 22 and the back panel 24, and is made of inorganic particles by foamed glass or an inorganic binder (glass). Is composed of a porous sound absorbing material such as porous ceramics, rock wool, glass fiber, polyester fiber, etc., having a single layer or multiple layer structure.

  The resin front panel 28 is a resin plate having a thickness of, for example, about 1.5 to 5 mm in which a large number of through holes 28a provided with a uniform surface density are formed, and has a high mechanical strength. It is composed of a resin excellent in weather resistance and capable of withstanding use for a long period of time, such as polycarbonate resin, polypropylene resin, vinyl chloride, and those in which those resins are fiber reinforced. In addition, magnetic powder is uniformly mixed in the resin front panel 28 at a rate of 20 to 35 (volume)%. Such a resin front panel 28 is heated at a temperature sufficiently higher than the glass transition point of the polycarbonate resin, for example, after a powdery polycarbonate resin and magnetic powder are uniformly mixed at a predetermined ratio. After being made into a fluidized state, it is cured in a state of being put in a mold, and formed into a panel shape having a uniform thickness.

  The magnetic powder mixed in the resin front panel 28 may be ferrite or the like, but Fe, Fe-13Cr alloy, carbonyl iron, Fe—Si alloy, iron nickel alloy (permalloy, Fe—Ni alloy), Fe— Co-alloy, Fe-Cr alloy, Fe-Cr-Al alloy, Fe-Cr-Si alloy, iron-aluminum-silicon alloy (Sendust, Fe-Al-Si alloy), soft magnetic metal having excellent magnetism such as amorphous alloy Powder is used.

As described above, since the magnetic powder is mixed in the resin front panel 28, the complex relative permeability μ _r ″ and the complex relative permittivity ε _r ″ of the front panel 28 are preferably increased. High electromagnetic wave absorption performance is provided. 4, 5, and 6 show the results of tests conducted by the present inventors under the following experimental condition 1. FIG. FIG. 7 shows the results of tests conducted by the present inventors under the following experimental condition 2.

(Experimental condition 1)
(a) An Fe-13Cr alloy powder having an average particle diameter of 8 μm φ is mixed in a polycarbonate resin, mixed and formed into a plate having a predetermined size, whereby a mixing ratio (0, Four types of test pieces (longitudinal and transverse dimensions of the waveguide cross section of the measuring instrument × thickness of 3 mm) having different 10), 20 and 30% by volume) were prepared.
(b) For each of the above-mentioned multiple types of test pieces, the complex relative permittivity (real part) ε _r ′ and the complex relative permittivity (imaginary part) using a network analyzer (HP 8510C type measuring instrument manufactured by Agilent Technologies) ε _r ″ was measured at a frequency of 5.8 GHz.
(c) For each of the above-mentioned multiple types of test pieces, using a network analyzer (HP 8510C type measuring instrument manufactured by Agilent Technologies), complex relative permeability (real part) μ _r ′ and complex relative permeability (imaginary part) the μ _r "were measured at a frequency of 5.8GHz.
(d) With respect to each of the above-mentioned plural types of test pieces, the flexural modulus (MPa) was measured by a three-point bending measurement method based on JIS standards.

4 and 5 show that the complex relative permittivity (real part) ε _r ′ and the complex relative permittivity (imaginary part) ε _r ″ increase as the mixing ratio (volume%) of the Fe-13Cr alloy contained in the polycarbonate resin increases. , The complex relative permeability (real part) μ _r ′ and the complex relative permeability (imaginary part) μ _r ″ increase. FIG. 6 shows that even when the mixing ratio (volume%) of the Fe-13Cr alloy contained in the polycarbonate resin increases, the strength indicated by the flexural modulus (MPa) does not change so much. The increase in the complex relative dielectric constant (imaginary part) ε _r ″ and the complex relative magnetic permeability (imaginary part) μ _r ″ indicates high radio wave absorption performance. In general, the radio wave absorption energy E of a magnetic substance increases as the complex relative permittivity (imaginary part) ε _r ″ and the complex relative permeability (imaginary part) μ _r ″ increase as shown in the following equation (1). To do.

E = 1/2 (ω · ε _r ″ · | E |) +1/2 (ω · μ _r ″ · | H |) + σω
... (1)

(Experimental condition 2)
(a) An Fe-13Cr alloy powder having an average particle diameter of 8 μm φ is mixed in a polycarbonate resin, mixed, and formed into a plate having a predetermined size, thereby mixing the Fe-13Cr alloy (volume%). ) Were mixed and formed into a plate shape of a predetermined size to create a plurality of types of test pieces (longitudinal and transverse dimensions of the waveguide cross section of the measuring instrument × thickness 3 mm).
(b) For each of the above-mentioned multiple types of test pieces, the return loss S21 [dB] of a circularly polarized wave of 5.8 GHz is measured using a network analyzer (HP 8510C type measuring instrument manufactured by Agilent Technologies). did.

  FIG. 7 shows the measurement results obtained in accordance with the above experimental condition 2. As the mixing ratio of the Fe-13Cr alloy increases, the return loss S21 increases acceleratingly, but the mixing ratio is 28 to 29% by volume. A minimum is formed in the vicinity. In FIG. 7, the incident angle θ with respect to the resin front panel 28 is used as a parameter. As shown in FIG. 7, if the required return loss is -10 [dB], a polycarbonate resin plate (resin front panel 28) having a mixing ratio of Fe-13Cr alloy of 20 to 35% by volume is used. I just need it. That is, the return loss S21 is ensured to be −10 [dB] at an incident angle of 70 °. If the required return loss is -15 [dB], the polycarbonate resin plate (resin front panel 28) having a mixing ratio of Fe-13Cr alloy of 25 to 35% by volume may be used. Further, if the required return loss is −20 [dB], it is sufficient to use a polycarbonate resin plate (resin front panel 28) in which the mixing ratio of the Fe-13Cr alloy is 27 to 32% by volume. If the mixing ratio of the Fe-13Cr alloy exceeds 35% by volume, the formability is impaired and the mechanical strength of the resin front panel 28 cannot be obtained.

  As described above, according to the present embodiment, in the soundproof wall member 10 with the electromagnetic wave absorption function provided with the resin front panel 28 on the surface, the resin front panel 28 is mixed with a magnetic powder at a predetermined ratio or more. Therefore, it is not necessary to newly add a radio wave absorption layer or a radio wave reflection layer in order to provide an electromagnetic wave absorption function. Therefore, the thickness dimension of the soundproof wall material 10 is not changed, and an excellent radio wave absorption function and noise absorption function are provided. The soundproof wall material 10 provided with is obtained.

Further, according to this embodiment, the resin front panel is formed by dispersing soft magnetic metal powder as the magnetic powder in a proportion of 20 to 35 (volume)% in polycarbonate resin. The complex relative permeability μ _r ″ and the complex relative permittivity ε _r ″ of the front panel 28 are preferably increased to obtain high radio wave absorption performance. For example, when the soft magnetic metal powder has a ratio of 20 to 35 (volume)%, the return loss can be ensured to be −10 dB when the incident angle of the electromagnetic wave with respect to the resin front panel 28 is 70 °. The communication interference problem is preferably solved.

  In addition, according to the present embodiment, the resin front panel 28 has an electromagnetic wave absorbing function with respect to circularly polarized waves, so that suitable absorption performance for circularly polarized waves can be obtained.

  In addition, according to the present embodiment, the resin front panel 28 includes a large number of through holes 28a provided with a uniform surface density, so that sound transmission is obtained. The reflection of the sound is suitably suppressed. Further, since the sound absorbing material 26 and the metal back panel 24 having a predetermined thickness are sequentially arranged in the thickness direction on the back surface of the resin front panel 28, the resin front panel 28 and the back metal panel 24 are provided. A radio wave absorption layer and a radio wave reflection layer are not newly provided between them, and the thickness dimension of the soundproof wall member 10 is not changed. In addition, since the radio wave that has passed through the resin front panel 28 is reflected by the metal back panel 24 and is allowed to pass through the resin front panel 28 again, the radio wave is more preferably absorbed.

  As mentioned above, although the Example of this invention was described based on drawing, this invention is applied also in another aspect.

  For example, although the soundproof wall member 10 with the electromagnetic wave absorbing function of the above-described embodiment has a flat plate shape as a whole, it may have a curved shape such as a partial cylindrical shape or a partial spherical shape. .

  Further, a metal layer such as a metal foil or a metal vapor deposition layer may be fixed to the entire back surface of the resin front panel 28.

  The steel frame member 22 and the back panel 24 described above may be made of synthetic resin.

  In addition, although not illustrated one by one, the present invention is implemented with various modifications within a range not departing from the gist thereof.

It is a figure explaining the soundproof wall using the soundproof wall material with an electromagnetic wave absorption function of one Example of this invention. It is a figure which shows the state which utilized the soundproof wall material with an electromagnetic wave absorption function of one Example of this invention for the wall surface of the ceiling of a toll gate. It is sectional drawing explaining the structure of the soundproof wall material with an electromagnetic wave absorption function of one Example of this invention. It is a figure which shows the relationship between the dielectric constant of the resin-made front panel of the sound-insulating wall material of FIG. 3, and the quantity of the soft-magnetic metal powder contained in it. It is a figure which shows the relationship between the relative magnetic permeability of the resin-made front panel of the sound-insulating wall material of FIG. 3, and the quantity of the soft magnetic metal powder contained in it. It is a figure which shows the relationship between the bending elastic modulus of the resin-made front panel of the sound-insulating wall material of FIG. 3, and the quantity of the soft-magnetic metal powder contained in it. It is a figure which shows the relationship between return loss S21 of the resin-made front panel of the sound-insulating wall material of FIG. 3, and the quantity of the soft-magnetic metal powder contained in it.

10: Soundproof wall material with electromagnetic wave absorbing function 24: Back panel 26: Sound absorbing material 28: Resin front panel

Claims (4)

A soundproof wall material with an electromagnetic wave absorbing function of a predetermined thickness provided on the surface with a resin front panel,
The soundproof wall material with an electromagnetic wave absorbing function, wherein the resin front panel is mixed with a magnetic powder in a predetermined ratio or more. 2. The soundproof wall material with an electromagnetic wave absorbing function according to claim 1, wherein the resin front panel is made of a soft magnetic metal powder dispersed in a polycarbonate resin at a rate of 20 to 35 (volume)% as the magnetic powder. The soundproof wall material with an electromagnetic wave absorbing function according to claim 1, wherein the resin front panel has an electromagnetic wave absorbing function with respect to circularly polarized waves. The resin front panel is provided with a large number of through holes provided with a uniform surface density,
A soundproof wall material with an electromagnetic wave absorbing function, wherein a sound absorbing material having a predetermined thickness and a metal back panel are sequentially arranged in the thickness direction on the back surface of the resin front panel.

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