JPH11204985A - Radio wave/sound wave absorber utilizing used tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the cost of a radio wave/sound wave absorber required for preventing troubles, by utilizing rich recycled resources, considering the absorber hardly comes into wide use due to its high price. SOLUTION: A radio wave/sound wave absorber is formed by integrally molding a main material composed of a rubber piece recycled from a used tire and a foamed plastic, an adhesive, paint, etc., added to the main material. A base section 1 of the absorber is composed of a 1/8 cut piece recycled from the tread section of the tire and an intermediate layer section 2 of the absorber is composed of rubber chips, rubber particles, and a foamed plastic. A rough surface section 3 of the absorber is composed of rough rubber particles, and a perforated board 4 is used for absorbing sound waves. When the absorber is arranged in parallel with another absorber along the side of a highway or railroad for preventing electromagnetic troubles and noise, ghost troubles in TV by near field reflection, mobile radio systems, and milliwave radar and running vehicle noise troubles can be relieved simultaneously.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio wave absorber for preventing reflection and transmission of radio waves radiated from an electronic device, and belongs to a technical field of radio wave propagation and electrophysics. Next, since the material of the radio wave absorber is mainly composed of rubber, it also has an absorption / attenuation ability for sound waves, so that acoustic physics is used to realize the sound wave absorber.

[0002]

2. Description of the Related Art Most of conventional radio wave absorbers are formed by mixing a sintered ferrite plate or a ferrite powder or carbon black with a foamed plastic to form a rectangular, conical or pyramid shape.

[0003] There is no prior art relating to radio wave absorbers made from waste tire rubber pieces. As in the present invention, by using an irregularly shaped rubber piece, not only the heat loss, but also the scattering loss, the skin loss is increased, and the method of improving the broadband property and the transmission loss as a radio wave absorber is: Not in the prior art.

Further, with respect to claim 4 and the embodiment (FIG. 3) of the present invention, the proposal of a radio wave absorber having a lattice structure having an inverted pyramid-shaped air gap (8) as viewed from the base portion suggests not only absorption loss. Predicts the weighting effect of diffraction loss, and there is no precedent in principle.

[0005]

With the development of the electronics industry, the deterioration of the electromagnetic environment has become a social problem. For example,
Ghost obstruction due to reflection of TV radio waves in buildings, interference of mobile phones on medical equipment and aircraft control systems, false image obstruction of radars and navigators due to reflection of nearby buildings, and errors in disturbance measurement systems due to reflections on floors and nearby objects And so on.

[0006] One of the measures to prevent or reduce electromagnetic interference is the outer wall, road surface, inner wall,
There is a method of attaching a radio wave absorber to the floor or ceiling. For that purpose, it is desired that the performance of the radio wave absorber be good and be as inexpensive as possible.

The problem to be solved by the present invention is that the surface reflection is small for any incident radio wave, the passage loss is large for an invading wave, physicochemically stable, good weatherability, To provide a radio wave absorber that is inexpensive and easily available, as lightweight as possible, and easy to install. In addition, it is to enhance the function as a sound wave absorbing or shielding body.

[Means for Solving the Problems]

[0008] The material of the radio wave absorber according to the present invention is mainly composed of "rubber pieces of waste tires (rubber cut pieces, rubber chips, rubber powder, recycled rubber, etc.)", and the remainder is "foamed plastic, paint, adhesive, auxiliary material". Absorbent material, holding material, etc. "

According to the Tire Recycling Handbook issued by the Japan Automobile Tire Association, the amount of waste tires generated in 1995 was 99 million, 940,000 tons, and the recycling rate was 93%. %, 40% for original or processed. Of the latter, rubber powder (rubber particles) is 6% (5
6000 tons). The rubber cut pieces are obtained by dividing the tread of the waste tire (tread) by 4 to 32 parts. A rubber chip is a crushed rubber piece obtained by crushing a waste tire, and is recycled into recycled rubber or further divided into rubber powder. Recycled rubber powder products include mats, elastic pavements, blocks, and asphalt modifiers. Research on expanding the application fields is underway, but radio wave absorbers have not been targeted in the past. Waste tire rubber pieces as the material of the radio wave absorber have the advantage of being cheap, abundant, and easily available.

[0010] The rubber of the waste tire contains an average of 25% of carbon black. This is a heat loss type (resistance type)
It has a sufficient carbon content as a radio wave absorber. It has a specific gravity of about 1.2, is light, is much harder than raw rubber, but has elasticity, and is easy to cut, drill, accumulate, mold, bond, etc. Rubber chips and rubber powder are indefinite, rubber chips are several cm to 20 cm or more, and rubber powder is 1 mm or less to 20
mm (Standard products are about 5, 3, 2, 0.7 mm or less)
Is the size of Since there is a wide range of dimensions, the size of the rubber piece as the material can be freely selected according to the wavelength of the radio wave and the configuration type of the radio wave absorber. The rubber piece remains in an irregular shape,
Mold into the required shape according to the purpose of use.

Under the electrical conditions required for a radio wave absorber, it is necessary to match the wave impedance of the incident surface to the value of free space in order to achieve non-reflection. For this purpose, it is substantially effective to make the refractive index of the radio wave near the surface layer of the radio wave absorber close to 1, and to make the surface layer rough and scatter the incident wave. The reflection reduction effect by rough surface scattering requires a step of the rough surface of about 1/10 wavelength or more in practical use, and it is known that the larger the step, the more remarkable the effect. The value of 1/10 wavelength corresponds to 10 cm at 300 MHz, 3 cm at 1 GHz, 3 mm at 10 GHz, and 0.5 mm at 60 GHz for radio waves. For sound waves in air,
The equivalent value of 10 wavelengths is 11cm at 300Hz, 1000H
If it is 3.3 cm at 10000 Hz, it will be 3.3 mm. That is, the wavelength of the radio wave in MHz and the wavelength of the sound wave in Hz are substantially equal. Since the rubber piece itself is indefinite, the rough surface condition in a short wavelength band can be naturally obtained, and the stepping process is easy. (Electromagnetic wave is a transverse wave, sound wave is a longitudinal wave, and both are qualitatively different, but the wavelengths in the target range are almost the same, and the rough surface effect is similar.) In the present invention, for example,
By adjusting the mixing ratio of rubber pieces and foamed plastic near the front surface layer of the absorber (decreasing the ratio of rubber pieces) to make the refractive index of the radio waves as close to 1 as possible, and by providing unevenness on the surface, Increases the scattering effect. For the high frequency band, the required roughness may be obtained simply by arranging the rubber particles on the surface layer, and there are also methods of providing a large number of protrusions or holes in the surface layer.

The radio wave absorber has a small thickness and allows passage (absorption,
It is desirable that scattering (loss) is large. To do so, it is necessary to increase the mixing ratio of the rubber pieces except for the vicinity of the front surface layer. The absorption loss is proportional to the carbon content. Scattering loss is an additional effect due to the irregular shape of the rubber piece. In addition, the fact that the rubber piece is indefinite shape has a large surface area, and can be expected to have an effect of increasing loss with respect to skin current. In the present invention, for example,
From the front surface layer of the radio wave absorber toward the inside, the ratio of the rubber pieces to the mixing ratio of the rubber pieces and the foamed plastic is gradually increased (when the limit ratio is 1, the carbon content is 25%).
%) Either adopt a design method or prepare several types of mats from the same viewpoint, and stack them to form an integrated radio wave absorber.

The radio wave absorber must function effectively even when the direction of incidence of the radio wave is other than the front direction. In order to prevent transmission of oblique incident waves in arbitrary directions, a method of arranging radio screens in a grid is effective. In FIG.
The cross section of the radio screen is made triangular because the attenuation increases toward the inside. The shielding effect of the radio screen array is based on the long wavelength VHF band (30 MHz to 30 MHz).
It is also effective for the 0 MHz band and has the advantage that the thickness of the radio wave absorber can be reduced.

In the present invention, any material may be added as long as it is useful as a radio wave absorber, except that the tire rubber piece is a main component. For example, if carbon black is added to the surface of the rubber piece or the mixture, the resistance attenuation ability can be enhanced, and if ferrite powder is added, a magnetic attenuation effect can be expected. The same applies to the case where a ferrite plate or a recycled rubber plate is attached to the base.

Since the radio wave absorber of the present invention is mainly composed of rubber, it also has the ability to absorb mechanical vibration and sound, and can be said to be a radio wave acoustic wave absorber. If a perforated board is attached to the front, the sound absorption can be improved and the sound range can be adjusted.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described based on embodiments with reference to the drawings. FIG. 1 is an explanatory view of an embodiment having a three-layer structure, in which the structure of each layer is exposed for easy understanding. Reference numeral (1) denotes a base portion on which 1/8 cut pieces of the waste tire tread are laid, and (2) denotes a middle layer portion made of a rubber chip, rubber powder, or foamed plastic. (3)
Is a rough wavy surface formed by using coarse particles of rubber powder formed on the surface layer or by shaping. (4) Perforated board for sound absorption. (5) is a void. (2) may have a multiplex structure of different types of mats. FIG. 2 is an explanatory diagram of an embodiment having a two-layer structure. (1) is the same base as before. (6)
Is a front portion made of a rubber piece provided with alternating protrusions and holes, and has both radio wave and sound wave absorbability.

The application range of the electromagnetic wave absorber of the type based on these two embodiments is wide, and it can be applied to electromagnetic and acoustic countermeasures in theaters, public halls, and conference rooms, to make shield rooms and semi-anechoic rooms completely anechoic, and to use open sites. Suitable for free space. Furthermore, if they are installed side by side on expressways and railway tracks, T
V, mobile radio, near-wave reflection of millimeter wave radar, prevention of false image obstruction, and prevention of running noise can be achieved at the same time. In addition, since it is strong and flexible, the anti-reflection guardrails also help traffic safety.

FIG. 3 shows a form which can be applied to a wide frequency band up to VHF having a long wavelength, and uses, in principle, a synergistic effect of shielding by a plurality of radio screens (radio wave barriers) and diffraction loss. The overall shape is a box with a grid-like frame with an open top, assembled by pressing rubber pieces or making members. 3A is a plan view, and FIG. 3B is an XY cross-sectional view of FIG. The symbol (7) is a radio screen having a triangular cross section. (8) is a void portion, which is three-dimensionally a “truncated inverted pyramid”. (In the three-dimensional form opposite to that of a commercially available pyramid-shaped radio wave absorber, based on the idea of reversal)

If the forms of the embodiments shown in FIGS. 1 to 3 are properly combined, an application system of a radio wave absorber covering all of VHF, UHF and SHF can be constructed at low cost.

[0020]

(1) The present invention contributes to the reuse of valuable resources through the recycling of waste tires, as well as the prevention of radio interference in electronic science and industrial equipment, medical systems, and information systems, the radiated interference measurement system, Construction of a dark room can be realized at low cost.

(2) By providing the “panel for preventing radio interference noise” according to the present invention as a side wall of a road or a track, it is possible to prevent a reflection obstacle of a vehicle radar, a navigator, a mobile phone, etc. Bell, P
Prevention of radio interference against HS and the like and prevention of noise from automobiles and trains can be achieved at the same time.

(3) A "wave anechoic chamber" is required for conducting tests, adjustments, inspections, unnecessary radiation measurements, and electromagnetic immunity tests of electronic equipment, and demand is expected to increase rapidly in the future. However, at present, the spread of the radio wave absorber constituting the anechoic chamber is expensive, and it is difficult to disregard it. Since the electromagnetic wave absorber of the present invention uses recycled rubber mass-produced, it can contribute to the spread of low-cost anechoic chambers.

(4) Conventionally, extra-large anechoic chambers for radiated disturbance tests for large construction machines, large electronic control industrial equipment, aircraft, and the like have been too expensive to be constructed on a private basis. According to the present invention, since the price can be reduced to 1/3 to 1/5 or less, there is an increased possibility that construction requirements can be met regardless of the government or private sector.

(5) Since the current sintered ferrite plate-based radio wave absorber is rigid and has a large specific gravity (approximate to iron), special measures are required to hold the wall surface and the ceiling surface. The majority of existing anti-reflection TVs attached to the outer walls of high-rise buildings, extraneous radio waves installed on ceilings and walls of theaters, public halls, auditoriums, conference rooms, etc., and information leakage prevention It was designed before the Great Hanshin Earthquake, and does not meet the new seismic standard of seismic intensity 7. There are many problems, such as losing the flexible structure of a high-rise building and biasing the load. If it collapses, it becomes a weapon that attacks the public.

The radio wave acoustic wave absorber of the present invention is lightweight, flexible and resistant to earthquake disasters, so that it can be expected to be safely applied to the above public facilities. In addition, it is easy to install an anechoic chamber in an existing building or to convert a shielded room into an anechoic chamber.

(6) The open site (outdoor type) and the semi-anechoic chamber (indoor type) for radiated disturbance measurement and the semi-anechoic chamber (indoor type) recommended by the current CISPR (International Special Committee on Radio Interference) have strong reflected waves because the floor is metal. Exists. In recent years, a defect of this type has been pointed out, and for improvement, a need has arisen to provide a free space by suppressing a reflected wave on the floor surface by laying a screen for preventing reflected waves and a radio wave absorber. In other words, the conversion to "free space open site (open free site)" and "complete anechoic chamber" requires a huge amount of radio wave absorbers to be laid on the floor both domestically and internationally. By using the radio-acoustic absorber according to the present invention, the purpose of free space can be achieved in a short period of time at much lower cost, and the contribution to socio-economics is immense.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an embodiment of a three-layer structure.

FIG. 2 is an explanatory view of an embodiment having a two-layer structure.

FIG. 3 is an explanatory view of an embodiment of a radio screen lattice type.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Base part 2 Middle part 3 Surface rough surface part 4 Perforated board for sound wave absorption 5 Gap part 6 Perforated board for radio wave sound absorption 7 Radio wave screen 8 Inverted pyramid type space

Claims (8)

[Claims] 1. A radio wave absorber using a waste tire, which is formed by integrating a waste tire rubber piece with a fusion adhesive such as foamed plastic or paint. 2. The radio wave absorber according to claim 1, wherein the mat-like aggregates having different mixing ratios of waste tire rubber pieces and foamed plastic are overlapped. 3. The radio wave acoustic absorption using waste tires according to claim 1, wherein the depth of the envelope surface at the tip of the waste tire rubber piece at the front of the radio wave incidence is formed as a rough surface having irregularities of about 1/10 wavelength or more. body 4. A radio wave absorber according to claim 1, wherein a plurality of rows of radio screens having a triangular cross section are crossed to form a grid by integrating and molding waste tire rubber pieces. 5. The radio wave absorber according to claim 1, wherein an electric resistance material is attached to an outer periphery of the waste tire rubber piece. 6. The electromagnetic wave absorber according to claim 1, wherein a polyiron material such as ferrite powder is mixed. 7. The radio-wave and sound absorber using waste tires according to claim 1, wherein a magnetic wave-absorbing material such as a ferrite plate is provided on the base. 8. A radio wave absorber using waste tires according to claim 1, wherein a perforated board is provided on the front surface.