JP4523243B2 - Radio wave absorption panel - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a radio wave absorption panel.
[0002]
[Prior art]
In recent years, an automatic toll collection (ETC) system for toll roads, which is a field of highway traffic systems, has been adopted nationwide. According to this ETC system, it is possible to eliminate traffic congestion due to non-stop of cars at a toll gate, cope with cashless, unmanned at a toll gate, and the like.
[0003]
This ETC system transmits radio waves toward a road from a roadside antenna installed on the upper side of an arched gate (gantry) of a toll gate, and between the vehicle-mounted device and the roadside antenna that travels on this road. Two-way communication is performed. At that time, there will be no problem if the radio wave only reaches the vehicle-mounted device directly from the roadside antenna, but the radio wave transmitted from the roadside antenna is reflected once on the road surface etc. Re-reflecting on the ceiling or structures near the toll booth (such as the underside of an elevated road) will cause radio waves to reach the on-board device again, resulting in incorrect operation such as collecting charges twice regardless of whether the vehicle passes once. There was a fear.
Therefore, it is necessary to attach a radio wave absorption panel for reducing or eliminating radio wave reflection at the toll gate and its vicinity.
[0004]
In addition, the following radio wave absorbing sheets having conventionally known radio wave absorption characteristics include the following. (1) Magnetic powder (ferrite powder, carbonyl reduced iron powder, etc.) and conductive carbon are blended with polymer materials (resin materials such as chlorinated polyethylene, EVA, polyethylene, and rubber materials such as silicon rubber and ethylene propylene rubber). Ferrite and conductive carbon are blended into a material obtained by rolling or press-molding the resulting composition into a sheet (for example, see Patent Document 1 and Patent Document 2), and (2) Inorganic materials such as volcanic ejecta and calcium carbonate (3) A composition in which a magnetic powder is blended with a polymer material, and a radio wave incident surface is uneven. And the corresponding frequency is processed so as to have radio wave absorption characteristics in the high frequency range “GHz band” (for example, see Patent Document 5 and Patent Document 6).
[0005]
And these sheet-like electromagnetic wave absorbing sheets have been frequently used in recent years, and the opportunity to be used outdoors has increased. The sheet-like electromagnetic wave absorbing sheet is flexible and suitable for construction on a curved surface portion, and has an advantage that construction can be performed by utilizing its thinness even in a place where space is not available depending on the construction place.
In addition, a radio wave reflection layer is adhered to the back surface of the radio wave absorbing sheet in a laminated form with an adhesive or the like.
[0006]
[Patent Document 1]
JP 2000-151177 A [Patent Document 2]
JP 2000-151183 A [Patent Document 3]
JP 2001-326491 A [Patent Document 4]
JP-A-11-349720 [Patent Document 5]
JP-A-7-106785 [Patent Document 6]
Japanese Patent Laid-Open No. 2001-339190
[Problems to be solved by the invention]
However, it is difficult to construct a sheet-shaped electromagnetic wave absorbing sheet on an expanded metal surface or a complex part of the mounting surface, and since the electromagnetic wave absorbing sheet is exposed outdoors, the electromagnetic wave absorbing sheet and the reflective layer There is a risk that rainwater or the like may enter between the layers and the strength of the adhesive interface may be reduced, and may be peeled off to deteriorate the radio wave absorption characteristics.
[0008]
Therefore, the present invention makes use of the thinness of the radio wave absorbing sheet as it is, and can be easily installed even in a place where the radio wave absorbing sheet is thin and cannot be directly provided. Further, the radio wave absorbing panel having excellent environmental resistance is provided. The purpose is to provide.
[0009]
[Means for Solving the Problems]
In order to achieve the above-mentioned object, the radio wave absorption panel according to the present invention has a radio wave absorption sheet that faces downward and is an exposed radio wave incident surface, and is bonded in a laminated manner to the back surface of the radio wave absorption sheet. An inverted shallow dish having a sheet-like wave absorber comprising a reflective layer, a bottom wall portion to which a back surface of the sheet-like wave absorber is bonded, and a peripheral wall portion surrounding a peripheral edge of the sheet-like wave absorber And a depth dimension D of the casing and a thickness dimension T of the sheet-shaped wave absorber set to D> T.
Also, a radio wave absorbing sheet that faces downward and is an exposed radio wave incident surface, a bottom wall portion to which the back surface of the radio wave absorbing sheet is bonded, and a peripheral wall that surrounds the peripheral edge of the radio wave absorbing sheet And an inverted shallow dish-shaped metal casing having a portion, wherein the depth dimension D of the casing and the thickness dimension t of the radio wave absorbing sheet satisfy D> t . It is set.
[0010]
Further, a reinforcing member is provided on the back surface of the casing. The surface of the radio wave absorbing sheet may have an uneven shape.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail based on the illustrated embodiment.
[0012]
FIG. 1 and FIG. 2 are perspective views showing an embodiment of a radio wave absorption panel P according to the present invention. FIG. 1 is a diagram showing the radio wave absorption panel P as seen from the surface side, and FIG. It is the figure seen from the side.
In the present invention, the expression surface refers to the surface side on which radio waves (electromagnetic waves) are incident, and the back surface is the opposite surface and the mounting surface. Therefore, as shown in the cross-sectional view of the radio wave absorption panel P in the installed state of FIG. 5, the arrow A is the traveling direction of the radio wave (reflected by a road or the like), and the radio wave absorption panel P is the ceiling 9 When installed, the surface of the radio wave absorption panel P faces downward and the back surface faces upward.
[0013]
FIG. 3 is a cross-sectional view of the radio wave absorption panel P of the present invention. The radio wave absorption panel P includes a sheet-like wave absorber 1 and a shallow dish-like housing 4 that houses the sheet-like wave absorber 1. Are provided. The sheet-shaped radio wave absorber 1 is composed of a radio wave absorption sheet 2 whose surface 2a is on the radio wave incident surface side, and a reflective layer 3 provided on the back surface 2b of the radio wave absorption sheet 2 in a laminated manner.
[0014]
The radio wave absorbing sheet 2 is also called an electromagnetic wave absorbing sheet, and conventionally known ones can be applied. Specifically, the radio wave absorbing sheet 2 is, for example, a radio wave loss in a binder (polymer material such as resin or rubber). In some cases, a composition obtained by blending an agent (conductive carbon, magnetic powder) and kneading is stretched by press working or roll rolling and formed into a sheet having a thickness of about 1 mm to 10 mm.
[0015]
As the binder, a resin material or a rubber material can be used, and the resin material is preferably chlorinated polyethylene, ethylene-vinyl acetate copolymer (EVA), polyethylene, or the like, and can improve radio wave absorption characteristics. The rubber material is preferably silicon rubber, ethylene propylene rubber, or the like, and can contain a large amount of a radio wave loss agent to improve radio wave absorption characteristics.
Magnetic powder used as a radio wave loss agent is ferrite powder, carbonyl reduced iron powder, or the like.
[0016]
The blending ratio will be described. For example, with respect to 100 parts by weight of the binder, the blending of the radio wave loss agent may be 10 parts by weight to 1000 parts by weight (although it varies slightly depending on the type of the binder and the radio wave absorber). If it is less than the lower limit, it is difficult to obtain sufficient radio wave absorption characteristics, and if it exceeds the upper limit, it tends to be difficult to process into a sheet shape.
[0017]
Another specific example of the radio wave absorbing sheet 2 is a composition in which an inorganic material such as volcanic ejecta (shirasu) or calcium carbonate is blended with ferrite powder, carbonyl reduced iron powder or conductive carbon. Is formed into a thin sheet.
The radio wave absorbing sheet 2 may be appropriately blended with a filler, a plasticizer, a colorant and the like as long as the radio wave absorption characteristics are not affected.
[0018]
The thus obtained radio wave absorption sheet 2 and the reflection layer (radio wave reflection layer) 3 provided in a laminated form are the opposite surface (rear surface 2b) to the radio wave incident surface (represented surface 2a) of the radio wave absorption sheet 2. The reflective layer 3 is made of a conductive material, for example, a metal plate, a metal sheet, a metal foil, or a conductive paint applied to the back surface 2 b of the radio wave absorbing sheet 2.
The reflection layer 3 is provided to reflect the incident radio wave and subsequently cancel out the newly incident radio wave. The reflection layer 3 has conductivity and has a terminal impedance of 0 (zero). ) Can be used without particular limitation.
[0019]
As a specific material of the reflective layer 3, a metal foil such as aluminum, copper, or iron is preferable, and an aluminum foil is particularly preferable. Such a reflective layer 3 is preferably arranged in a laminated manner with the radio wave absorbing sheet 2 and the reflective layer 3 adjacent to each other without a gap in order to provide the radio wave absorber 1 with excellent radio wave absorption characteristics.
The radio wave absorbing sheet 2 and the reflective layer 3 can be bonded by means such as thermocompression bonding or using an adhesive.
[0020]
Next, the housing 4 will be described. As shown in FIGS. 1, 2, and 3, the housing 4 includes a bottom wall portion 5 that covers the back surface 1 b of the sheet-like wave absorber 1, and a sheet-like wave absorber. 1 and a peripheral wall portion 7 surrounding the entire periphery of the peripheral edge 6, and has a shallow dish shape.
Since the casing 4 is formed with a peripheral wall portion 7 that stands upright at the periphery of the bottom wall portion 5 having a large area, the peripheral wall portion 7 acts as a reinforcing rib. Can be increased.
[0021]
And the sheet-like electromagnetic wave absorber 1 and the housing 4 may be bonded to each other using an adhesive, or may be connected by a connecting member such as a small screw (drilling screw) or a screw, Or it is set as the integral panel shape (panel body) by bonding with an adhesive agent and connecting by a connection member. In the case of bonding with an adhesive, it is preferable to apply an adhesive so that an adhesive interface is formed over the entire back surface 1b of the sheet-shaped radio wave absorber 1, and when fixing with a connecting member, a sheet-like What is necessary is just to provide a through-hole in the several places of the electromagnetic wave absorber 1, and fix it so that a slack may not arise in the whole by making a connection member into insertion shape.
[0022]
The casing 4 can be made of metal, resin, etc. In the case of metal, the side wall of the thin plate may be bent to form the peripheral wall portion 7. For example, the four sides of a rectangular metal plate may be formed. What is necessary is just to make it the shallow box-shaped dish-shaped container which bends by the dimension more than the thickness dimension T of the sheet-like electromagnetic wave absorber 1, and one side opens. Specific materials include steel, stainless steel, aluminum, aluminum alloy and the like.
Further, when the housing 4 is made of resin, it may be molded by a mold. For example, the bottom wall portion 5 and the peripheral wall portion 7 can be simultaneously manufactured in one step by injection molding. As the material, polycarbonate resin and acrylic resin are preferable, and in particular, FRP made of a composite material of these resins and inorganic fibers is preferable.
[0023]
In addition, when the housing 4 is made of metal, the housing 4 itself has the role of the reflective layer 3 having the above-described function. Therefore, as shown in a cross-sectional view showing another embodiment of FIG. The wave absorbing sheet 2 may be provided directly on the metal housing 4 (omitting the reflective layer 3 in FIG. 3). In this case, the housing 4 and the radio wave absorbing sheet 2 may be formed into an integral panel by connecting with an adhesive and / or a connecting member, as in the case of FIG.
[0024]
That is, as shown in FIG. 6, the radio wave absorption panel P includes a radio wave absorption sheet 2 whose surface 2 a is the radio wave incident surface side, a bottom wall portion 5 that covers the back surface 2 b of the radio wave absorption sheet 2, and the radio wave absorption sheet 2. A shallow dish-shaped metal housing 4 having a peripheral wall portion 7 surrounding the peripheral edge 11 of the metal plate.
[0025]
The shape of the housing 4 (the radio wave absorption panel P) may have a notch in addition to the rectangular shape in plan view. Further, in addition to the flat plate-like panel body, The surface (surface 1a of the sheet-shaped electromagnetic wave absorber 1) may have a stepped structure having a plurality of steps, or a curved structure in which the entire surface or a part thereof has a curved surface. If 2) is flexible, such a configuration is also possible.
[0026]
Furthermore, as shown in FIGS. 1 and 2, a reinforcing member 8 may be provided on the back surface 4 b of the housing 4. As the reinforcing member 8, there are long reinforcing beam members such as a steel plate (groove steel, an angle material, a ductor, etc.), a square pipe, a shaft member, and the like, and one or a plurality are provided. In FIG. Are arranged along the longitudinal direction of the panel P. Alternatively, although not shown, they may be arranged in a cross beam shape.
[0027]
FIG. 4 is a cross-sectional view showing another embodiment of the radio wave absorption panel P of the present invention. In the sheet-like radio wave absorber 1 provided in the panel P, the surface 2a of the radio wave absorption sheet 2 is formed in an uneven shape. . In FIG. 4, the triangular cross-sectional concavo-convex shape is used. However, the shape is not limited to this, but the cross-sectional concavo-convex shape may be used, and the concave portion may form a plurality of slits. Although not shown, the surface 2a of the radio wave absorption sheet 2 of the radio wave absorption panel P shown in FIG.
[0028]
3 and 4, the depth dimension D of the housing 4 is set to be larger than the thickness dimension T of the sheet-like wave absorber 1 (D> T) . In the embodiment of FIG. 6, the depth dimension D of the housing 4 is set to be larger than the thickness dimension t of the radio wave absorbing sheet 2 (D> t) . In other words, the front surface 2 a of the radio wave absorbing sheet 2 does not protrude from the end surface 10 of the peripheral wall portion 7 of the housing 4, and the front surface 2 a is kept inward from the end surface 10 of the peripheral wall portion 7. It becomes. Specifically, the depth dimension D may be 1.1 times to 10 times the dimension of the thickness T (t) is, in terms of radio wave absorbing characteristic, and, preferably from the standpoint of weather resistance, rainwater draining .
[0029]
The radio wave absorption panel P described above has a mounting portion 9 such as the ceiling of the toll gate on the toll road or the underside of the elevated road near the toll gate as shown in the cross-sectional view of the radio wave absorption panel P in the installed state shown in FIG. The radio wave absorption panel P has a mounting surface 9 on the mounting portion 9 using a connecting member such as a bolt and nut (not shown). It is fixed so that it faces downward (lower surface).
[0030]
【The invention's effect】
The present invention has the following effects by the above-described configuration.
[0031]
(According to claim 1) A thin wave absorbing panel P can be formed, and a sheet can be formed by forming a panel even in a place that cannot be directly provided only by the wave absorbing sheet 2 or in a small space. The shaped wave absorber 1 can be easily disposed.
Since the joint surface between the radio wave absorbing sheet 2 and the reflective layer 3 is housed in the housing 4, even if the panel P is installed outdoors and exposed to wind and rain, rainwater does not enter the joint surface. There is no risk of a decrease in strength of the joint surface. That is, the peripheral wall 7 is drained, water can be prevented from entering from the joint surface, the radio wave absorbing sheet 2 and the reflective layer 3 can be prevented from being peeled off, and can be installed in a place where environmental resistance is required. .
Moreover, the sheet-like radio wave absorber 1 can be fixed to the bottom wall portion 5 of the housing 4 so that the whole is not loosened by bonding with an adhesive on the wide surface of the back surface 1 b of the sheet-like radio wave absorber 1.
In addition, it is possible to prevent water from entering the side peripheral surface of the sheet-shaped wave absorber 1, and it is not exposed to direct sunlight and has excellent environmental resistance.
[0032]
(According to claim 2) A thin radio wave absorption panel P can be constructed, and even in places that cannot be directly provided only by the radio wave absorption sheet 2 or in small gaps in the space, It can be easily arranged.
Since the radio wave absorbing sheet 2 is housed in the housing 4, rainwater does not enter even if the panel P is installed outdoors and exposed to wind and rain. That is, the surrounding wall portion 7 is drained and can be installed in a place where environmental resistance is required.
Since the metal housing 4 has a function as a reflection layer for radio waves, the configuration can be simplified and the cost can be reduced.
Moreover, the radio wave absorbing sheet 2 can be fixed to the bottom wall portion 5 of the metal housing 4 so that the whole is not loosened by bonding with the adhesive on the wide surface of the radio wave absorbing sheet 2 back surface 2b.
In addition, it is possible to prevent water from entering the side peripheral surface of the radio wave absorbing sheet 2 and not to be exposed to direct sunlight and to have excellent environmental resistance.
[0033]
(According to claim 3) Even if the radio wave absorption panel P is thin and has a large area, the rigidity of the panel P can be increased, it is easy to handle at the time of construction, and it can be made stable and strong after installation.
(According to claim 4) It is possible to provide a radio wave absorption characteristic in which the frequency of the radio wave to be absorbed can correspond to the high frequency range “GHz band”.
[Brief description of the drawings]
FIG. 1 is a perspective view from the front surface side showing an embodiment of a radio wave absorption panel according to the present invention.
FIG. 2 is a perspective view of a radio wave absorption panel from the back side.
FIG. 3 is a cross-sectional view of a radio wave absorption panel.
FIG. 4 is a cross-sectional view showing another embodiment of the radio wave absorption panel.
FIG. 5 is a cross-sectional view of a radio wave absorption panel in an installed state.
FIG. 6 is a cross-sectional view showing another embodiment of the radio wave absorption panel.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Sheet-like electromagnetic wave absorber 1b Back surface 2 Radio wave absorption sheet 2a Front surface 2b Back surface 3 Reflective layer 4 Case 4b Back surface 5 Bottom wall part 6 Peripheral edge 7 Peripheral wall part 8 Reinforcement member
11 Perimeter edge D Depth dimension T Thickness dimension t Thickness dimension

Claims (4)

The wave absorbing sheet (2) whose surface (2a) faces downward and becomes an exposed radio wave incident surface, and the reflective layer (3) adhered in a laminated manner to the back surface (2b) of the radio wave absorbing sheet (2) A sheet-like wave absorber (1) comprising: a bottom wall (5) to which the back surface (1b) of the sheet-like wave absorber (1) is bonded; and a peripheral edge of the sheet-like wave absorber (1) edge peripheral wall portion surrounding the (6) (7) and an inverted shallow dish-shaped housing having a (4) and, a radio wave absorbing panel having a, the housing (4) of the depth (D) And the thickness dimension (T) of the said sheet-like electromagnetic wave absorber (1) was set to D> T , The electromagnetic wave absorption panel characterized by the above-mentioned. A radio wave absorbing sheet (2) whose front surface (2a) faces downward and becomes an exposed radio wave incident surface, and a bottom wall portion (5) to which the back surface (2b) of the radio wave absorbing sheet (2) is bonded. And an inverted shallow dish-shaped metal casing (4) having a peripheral wall (7) surrounding the peripheral edge (11) of the radio wave absorbing sheet (2), A radio wave absorption panel, wherein a depth dimension (D) of the casing (4) and a thickness dimension (t) of the radio wave absorption sheet (2) are set to D> t .   The radio wave absorption panel according to claim 1 or 2, wherein a reinforcing member (8) is provided on the back surface (4b) of the casing (4).   The radio wave absorption panel according to claim 1, 2, or 3, wherein the surface (2a) of the radio wave absorption sheet (2) has an uneven shape.

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