JP4079672B2 - Sound absorbing panel with radio wave absorption performance - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a structure of a sound absorbing panel used for a soundproof wall installed on a side wall of an expressway or the like, and more specifically, a radio wave for preventing radio wave interference due to reflection of unnecessary electromagnetic waves generated during road-to-vehicle communication or vehicle-to-vehicle communication. The present invention relates to a structure of a sound absorbing panel having an absorbing performance.
[0002]
[Prior art]
Development of a driving support system for automobiles that travel as part of an intelligent transportation system (ITS), which is a next-generation road transportation system, is in progress.
[0003]
In this automobile driving support system, road-to-vehicle communication and vehicle-to-vehicle communication are performed using electromagnetic waves, but it is assumed that soundproof walls installed on the side walls of highways and the like become unnecessary electromagnetic wave reflection sources and cause radio interference. The
[0004]
For example, as shown in FIG. 3, a soundproof wall 1 is installed on a side wall of an expressway or the like so as not to dissipate noise around the vehicle, and a number of sound absorbing panels 2 are incorporated in the soundproof wall 1. It is configured to absorb noise from the traveling vehicle.
[0005]
The conventional sound absorbing panel 2 has a glass wall or the like with an air layer 4 interposed on the surface side of the sound insulating plate 3 made of metal or the like forming the back surface of the soundproof wall 1 as shown in FIG. The sound-absorbing layer 5 is arranged, and the outer surface thereof is covered with a protective layer 6 made of a metal plate (punching metal) having a large number of through holes.
[0006]
As a result, the noise that has passed through the through-hole of the protective layer 6 is attenuated as it passes through the sound absorbing layer 5, and the remaining noise is reflected and canceled by the sound insulating plate 3 in the air layer 4, and a part of the remaining noise is also generated. Re-radiating to the outside has been prevented by utilizing the sound absorption by the sound absorbing layer 5 again.
[0007]
However, the sound absorbing panel 2 itself does not have a function of absorbing electromagnetic waves, but the surface of the protective layer 6 made of a metal plate becomes a reflector of electromagnetic waves, which causes radio interference, In addition to the sound absorbing function, the sound barrier 1 under the next generation intelligent transportation system (ITS) is required to have a new function of absorbing radio waves.
[0008]
[Problems to be solved by the invention]
An object of the present invention is to provide a sound absorbing panel having excellent radio wave absorption performance without impairing sound absorption performance.
[0009]
[Means for Solving the Problems]
The sound absorbing panel having the radio wave absorbing performance of the present invention that achieves the above object is obtained by laminating a radio wave absorbing layer on the surface of the sound insulating plate and disposing the sound absorbing layer with an air layer interposed on the surface side of the radio wave absorbing layer, A sound- absorbing panel in which an outer surface of the sound-absorbing layer is covered with a net-like protective layer made of resin, and the radio wave absorbing layer is composed of 20 to 60 parts by weight of conductive titanium oxide and 1 to 10 parts per 100 parts by weight of the resin material. The gist of the invention is that it is composed of a resin composition blended with parts by weight of conductive carbon black so that the complex relative dielectric constant of the resin composition is 15 ± 5-j5 ± 3 .
[0011]
As a result, the noise gradually attenuates while being absorbed as it passes through the sound absorbing layer, and the remaining noise cancels each other while being reflected by the sound insulating plate in the air layer, and a part of the remaining noise is again absorbed by the sound absorbing layer. Is not released to the outside.
[0012]
On the other hand, the electromagnetic wave passes through the sound absorption layer and the air layer as it is, enters the radio wave absorption layer, attenuates while being absorbed inside the radio wave absorption layer, and the residual electromagnetic wave is reflected by the surface of the sound insulation board and passes through the radio wave absorption layer again. To do.
[0013]
Here, by adjusting the configuration (thickness, etc.) of the radio wave absorption layer so that the phase of the incident radio wave to the radio wave absorption layer is opposite to the phase of the reflected radio wave, the incident radio wave and the reflected radio wave are synthesized. By canceling each other, the electromagnetic waves radiated from the sound absorbing panel are finally reduced efficiently.
[0014]
Conductive titanium oxide and / or conductive carbon black plays a role in promoting the efficient absorption of electromagnetic waves by adjusting the complex relative dielectric constant of the resin composition constituting the radio wave absorption layer, and also outside the sound absorption layer. The net-like protective layer covering the surface plays a role of protecting the surface of the sound absorbing layer from the outside without being an obstacle for noise and electromagnetic waves to enter the inside of the sound absorbing panel.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In each figure, the same components are denoted by the same reference numerals, and redundant description is omitted.
[0016]
FIG. 1 is a partial sectional view in a vertical direction according to an embodiment for explaining a laminated structure of a sound absorbing panel according to the present invention. The sound absorbing panel 2 has a radio wave absorbing layer 7 laminated on the surface of a sound insulating plate 3 made of metal or the like. The sound absorbing layer 5 made of glass wool or the like is disposed on the surface side with the air layer 4 interposed.
[0017]
In the figure, reference numeral 6 denotes a net-like protective layer made of resin or the like, which serves to protect the sound-absorbing layer 5 by covering the outer surface of the sound-absorbing layer 5 and guides noise and electromagnetic waves into the sound-absorbing panel 2. It is formed in a plate shape having through holes. The protective layer 6 can be omitted depending on the configuration of the sound absorbing layer 5.
[0018]
Here, the noise entering from the outside is gradually attenuated while being absorbed as it passes through the sound absorbing layer 5, and the residual noise is reflected on the surface of the radio wave absorbing layer 7 through the air layer 4, but is incident on the air layer 4. The noise and the reflected noise cancel each other, and a part of the residual reflected noise that has not been canceled is absorbed from the air layer 4 through the sound absorbing layer 5 again, so that it is not finally diffused to the outside.
[0019]
On the other hand, the electromagnetic wave passes through the sound absorbing layer 5 and the air layer 4 as it is, enters the radio wave absorbing layer 7, is reflected on the surface of the sound insulating plate 3 while being gradually absorbed inside the radio wave absorbing layer 7, and again passes through the radio wave absorbing layer 7. pass.
[0020]
Here, the radio wave absorption layer 7 sets the dielectric constant and thickness of the radio wave absorption layer 7 in accordance with the wavelength of the electromagnetic wave to be absorbed, thereby improving the radio wave absorption performance and the phase of the incident radio wave to the radio wave absorption layer 7. By adjusting the reflected radio wave so that the phase of the reflected radio wave is opposite and the incident radio wave and the reflected radio wave are combined and cancel each other, the radiated electromagnetic wave from the sound absorbing panel 2 is efficiently reduced.
[0021]
The radio wave absorption layer 7 is made of a resin composition in which conductive titanium oxide and / or conductive carbon black is blended, and the complex of the radio wave absorption layer 7 is adjusted by adjusting the blending amount of the conductive titanium oxide and / or conductive carbon black. Increase the electromagnetic wave absorption performance by changing the relative permittivity.
[0022]
As the resin material, a material selected from thermoplastic resins, thermosetting resins, various rubbers, elastomers and the like is used.
[0023]
Examples of the thermoplastic resin include polyolefin resins such as polyethylene and polypropylene, polyamide resins such as nylon 6 and nylon 66, polyester resins such as polyethylene terephthalate and polybutylene terephthalate, or a mixture thereof.
[0024]
The thermosetting resin is appropriately selected from, for example, an epoxy resin, a polyurethane resin, a polyester resin, a phenol resin, and the like.
[0025]
In the sound absorbing panel of the present invention, the blending amount of the conductive titanium oxide and the conductive carbon black for obtaining the radio wave absorption performance is 20 to 60 parts by weight of the conductive titanium oxide and 100 parts by weight of the resin material. Ca - and the carbon black 10 parts by weight, thereby adjusting so complex relative permittivity of the radio wave absorbing layer is 15 ± 5-j5 ± 3 in.
[0027]
Since the sound absorbing panel 2 of the present invention is configured as described above, it exhibits excellent radio wave absorption performance without impairing the sound absorption performance.
[0028]
【Example】
A test piece of a sound-absorbing panel having the following characteristics was prepared, and the radio wave absorption performance at 5.8 GHz was measured by a free space method using a horn antenna and a circularly polarized antenna by a vector network analyzer HP8722C. FIG. 2 shows the incident angle dependence of the absorption performance. The measurement conditions were as follows.
[0029]
Here, 50 parts by weight of conductive titanium oxide (trade name “FT2000” manufactured by Ishihara Sangyo Co., Ltd.) and conductive carbon black (trade name manufactured by Nippon IC Co., Ltd.) with respect to 100 parts by weight of commercially available epoxy resin as a radio wave absorption layer. “Ketjen Black”) 3 parts by weight of material was used.
(Characteristic)
Sound absorbing layer: complex relative dielectric constant ε = 1.1−j0.01, thickness 50 mm
Air layer: complex dielectric constant ε = 1, thickness 35mm
Radio wave absorption layer: complex relative dielectric constant ε = 11.9-j4.6, thickness 3.8 mm
(Measurement condition)
Measurement frequency: 5.8 GHz
Incident angle: 10 °, 20 °, 30 °, 40 °, 50 °, 60 °
Polarization: Circularly polarized wave, TM wave, TE wave Test piece direction: vertical, horizontal As shown in FIG. 2, absorption performance of 20 dB or more was obtained at an incident angle of up to 60 ° for both circularly polarized wave, TM wave, and TE wave. In addition, in the TM wave and the TE wave, a tendency for the absorption performance to decrease at an incident angle of 50 ° or more was observed.
[0030]
【The invention's effect】
The sound absorbing panel of the present invention has a sound absorbing layer and an air layer that have sound absorbing performance on the front side, and a radio wave absorbing layer that has radio wave absorbing performance on the back side, so that the sound absorbing performance as a whole is not impaired. It has a structure that demonstrates excellent electromagnetic wave absorption performance.
[0031]
Particularly, the resin composition constituting the radio wave absorption layer is adjusted so that the complex dielectric constant is 15 ± 5-j5 ± 3 by changing the blending amount of conductive titanium oxide and / or conductive carbon black. Enables excellent radio wave absorption.
[0032]
In addition, the sound absorbing panel of the present invention employs many parts of the structure of the conventional sound absorbing panel, and by changing a part thereof, it is possible to provide radio wave absorbing performance without impairing soundproof performance. Therefore, it has the advantage that the construction required for manufacturing and construction is easy.
[Brief description of the drawings]
FIG. 1 is a partial sectional view in a vertical direction according to an embodiment for explaining a laminated structure of a sound absorbing panel according to the present invention.
FIG. 2 is a diagram showing the radio wave absorption performance of the sound absorbing panel according to the present invention, and shows the incident angle dependence of the radio wave absorption performance.
FIG. 3 is a diagram for explaining a usage pattern of a sound absorbing panel, and shows a situation where the sound absorbing panel is used on a soundproof wall installed on a side wall of a highway.
FIG. 4 is a cross-sectional view similar to FIG. 1 for explaining a laminated structure of a conventional sound absorbing panel.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Sound barrier 2 Sound absorption panel 3 Sound insulation board 4 Air layer 5 Sound absorption layer 6 Protective layer 7 Electric wave absorption layer

Claims (1)

A radio wave absorption layer is laminated on the surface of the sound insulating plate, and a sound absorbing layer is disposed with an air layer interposed on the surface side of the radio wave absorbing layer, and the outer surface of the sound absorbing layer is covered with a net-like protective layer made of resin. A sound absorbing panel, wherein the radio wave absorbing layer is composed of a resin composition in which 20 to 60 parts by weight of conductive titanium oxide and 1 to 10 parts by weight of conductive carbon black are blended with respect to 100 parts by weight of a resin material. A sound-absorbing panel having radio wave absorption performance in which the complex relative dielectric constant of the resin composition is 15 ± 5-j5 ± 3 .

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