JPH02174295A - Manufacture of wave absorber - Google Patents

Abstract

PURPOSE:To manufacture speedily and at a low cost by forming a wave absorber in which a core made of high-strength resin and a cover made of a soft material like a foaming material or rubber are integrally formed. CONSTITUTION:A wave absorber 1 is of a regular quadrangular shape, i.e., a pyramid. This wave absorber 1 is structured from two layers of a core 21 and a cover 3. The core 2 is formed by polypropylene resin, the inside of which is hollow. The cover 3 covering the outer surface of this core 2 is formed by a soft material like a foaming material of foaming urethane or rubber. Carbon powders are added, as a wave absorber, to resin forming the core 2. Thus, the core 2 has the property of conducting electricity and wave absorbing characteristics. By adding carbon powders to the cover 3 without making the core 2 have wave absorbing characteristics, this may have the wave absorbing characteristics. The electric conduction value can be set any value by the amount of addition by adjusting the amount of carbon.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a radio wave absorber used in a radio anechoic chamber.

(Problems to be solved by the prior art and the invention) In order to measure electromagnetic noise generated from various electronic devices such as computers without being affected by external radio waves, anechoic chambers and semi-anechoic radio waves are used. A radio wave anechoic chamber, also called a radio wave no-reflection chamber, is used. Such a radio anechoic chamber is formed by a housing space covered with a metal shield wall to prevent the intrusion of external radio waves. A receiving source is installed to determine the state of electromagnetic noise generation with the intrusion of external radio waves removed.

In a normal radio anechoic chamber, a radio wave absorber is attached to the inner surface of the shield wall, and the radio wave absorber is used in "Electronic Technology" (Published by Kogyo Shimbun Publishing Co., Ltd.), September 1985 issue. There is a resistor-type radio wave absorber as described on pages 44 and 45 of .

This type of radio wave absorber has a pyramid shape, and by gradually increasing the cross-sectional area of the resistor as the electromagnetic waves advance into it, the electrical energy of the electromagnetic waves that hit it is converted into thermal energy. Therefore, reflection of electromagnetic waves can be avoided.

Conventional 1-U type radio wave absorbers are manufactured using foamed materials, and the spaces created by the foaming are impregnated with carbon. It is necessary to manufacture the radio wave absorber in such a way that a continuous space is formed, and a special foaming technique must be used, resulting in variations in radio wave absorption performance and low yield.

Furthermore, if a foamed material is used, it lacks strength, so if such a radio wave absorber is placed on the wall of a radio anechoic chamber, its tip may deform or sink due to its own weight. For this purpose, attempts have been made to use hard resin as the base material of the radio wave absorber. In that case, the tip is sharp and pointed, and if a radio wave absorber made of such a hard resin is used, a worker can measure noise etc. in the accommodation space formed in the radio anechoic chamber. When working, there is a possibility of coming into contact with the sharp tip of the radio wave absorber, and if the worker comes into contact with the sharp tip, he or she may be injured. For this purpose, in addition to measurement work, workers also
Great care had to be taken to avoid contact with radio wave absorbers.

The present invention has been made in view of the problems of the prior art described above, and includes a pyramid-shaped core portion such as a quadrangular pyramid shape made of a hard resin, and a cover made of a soft material such as a foam material or rubber to cover the core portion. An object of the present invention is to make it possible to rapidly manufacture a radio wave absorber having a two-layer structure at low cost.

(Means for Solving the Problems) To achieve the above object, the present invention includes a hollow resin core having a pyramidal shape such as a square pyramid or a conical shape and having a space inside, and a foamed material. and a cover part formed of a soft material such as rubber or the like and covering the outer surface of the core part, and a radio wave absorbing material made of carbon or the like is added to at least one of the core part and the cover part. A manufacturing method, comprising: forming the core portion whose inner and outer surfaces are conical; forming the cover portion having an inner surface corresponding to the outer surface of the core portion; and bonding the inner surface of the cover part to the outer surface of the radio wave absorber.

The present invention also provides a method for fitting the core portion inside a mold having an inner surface larger than the outer surface of the core portion with a gap formed between the outer surface of the core portion and the inner surface of the mold. The method for manufacturing a radio wave absorber is characterized in that a material for a cover part is poured into the gap, and forming the cover part and joining the cover part and the core part are performed at the same time. The cover part is fitted onto the outside of a mold having an outer surface smaller than the inner surface of the part, with a gap formed between the inner back surface of the cover part and the outer surface of the mold, and the core is inserted into the gap. In this method of manufacturing a radio wave absorber, a material for the part is poured, and the formation of the core part and the joining of the cover part and the core part are performed at the same time.

Furthermore, the present invention provides an inner mold having a conical outer surface such as a square pyramid shape or a conical shape, and an outer mold having a conical inner surface.
When the outer surface of the inner mold and the inner surface of the outer mold are fitted together with a predetermined gap between them, the material for the core part or the material for the cover part is inserted into the gap. A method for manufacturing a radio wave absorber, in which the core part or the cover part are integrally molded, and further, by joining a plurality of triangular plate materials to each other at their side end surfaces, This is a method of manufacturing a radio wave absorber in which the core portion or the cover portion is formed.

(Function) In the above-mentioned present invention, the core part and the cover part, each manufactured in a predetermined shape, are integrated, so that the outer surface of the radio wave is covered with a cover made of a soft material such as rubber or foam. The absorbent body can be manufactured simply and easily. The core part and the cover part are manufactured by cutting out a plate material, or by using a mold. Moreover, by manufacturing the cover part using the core part as a mold, or manufacturing the core part using the cover part as a mold, it becomes possible to integrate or join these parts at the same time.

(Example) Hereinafter, the present invention will be described in detail based on the illustrated example of the present invention.

FIG. 1(A) is a diagram showing the entire radio wave absorber manufactured by the manufacturing method of the present invention, and FIG. 1(B) is a sectional view thereof.

As shown in FIG. 1(A), this radio wave absorber 1 has a regular square pyramid shape, that is, a pyramid shape. As shown in FIG. 1(B), this radio wave absorber 1 has a two-layer structure consisting of a core part 2 and a cover part 3. The core part 2 is made of polypropylene resin and is hollow inside. ing. However, the core portion 2 is not limited to the above-mentioned resin, but may be made of various resin materials such as vinyl chloride, as long as it is made of a hard material that has a predetermined strength. Further, the cover portion 3 covering the outer surface of the core portion 2 is formed of a foam material such as foamed urethane or a soft material such as rubber. In the illustrated case, carbon powder is added to the resin constituting the core portion 2 as a radio wave absorbing material. As a result, the core portion 2 has electrical conductivity and radio wave absorption characteristics.

However, without giving the core part 2 radio wave absorption characteristics,
By adding carbon powder to the cover part 3, it may be made to have radio wave absorption properties, or even both may be made to have radio wave absorption properties. Depending on the amount of carbon added, the radio wave absorber 1 is set to have a predetermined conductivity of, for example, several Ω to several MΩ, but this conductivity value can be arbitrarily set by adjusting the amount of carbon. However, the radio wave absorbing material is not limited to the above-mentioned carbon, and various materials such as copper oxide can be used, for example.

A square reinforcing plate 4 is attached inside the core part 2. This reinforcing plate 4 is unnecessary if the thickness of the plate material constituting the core part 2 is large and the core part 2 itself has a predetermined strength. As shown in FIG. 1(B), the illustrated radio wave absorber 1 has an open bottom, but a plate may also be attached to this portion.

FIG. 1(C) is a diagram showing the state in which the radio wave absorber 1 is attached to the inner surface of the shield wall of the radio anechoic chamber, and an accommodation space 7 is formed that is shielded from the outside by the front, rear, left, right, and upper and lower shield walls 6. In this space 7, a radio wave transmitting source 8 such as an electronic device and a receiving source 9 for receiving the transmitted radio waves are installed. In the radio anechoic chamber formed in this way, in order to reduce the amount of reflection of the radio waves that have reached the shield wall 6 from the transmission source 8 when detecting the state of the transmitted radio waves, the inner surface of the shield wall 6 is , the above-described radio wave absorber 1 of the present invention is attached. However, FIG. 1(C) shows a state in which the radio wave absorber 1 is attached to a part of the shield wall 6.

Figures 2 (A) to (E) show the radio wave absorber 1 shown in Figure 1.
FIG. 3 is a diagram showing a manufacturing process for manufacturing the core part 2 of FIG.

FIG. 2(A) shows a polypropylene resin plate 11 to which carbon powder has been added, and a triangular hard plate piece 2a is first cut out using a cutting means such as a cutter. FIG. 2(B) is a diagram showing a formwork 12 for manufacturing the core part 2 using the four hard plate pieces 2a described above.
The formwork 12 has a quadrangular pyramid-shaped inner surface 13, and four triangular hard plate pieces 2a are pressed onto each inner surface 13 as shown. In this state, as shown in FIG. 2(C), adhesive S is applied to the side edges of the adjacent hard plate pieces 2a to join the four plate pieces 2a to each other. In this way, the core portion 2 is formed. In order to increase the strength of the core portion 2, a square reinforcing plate 4 is used as shown in FIG. 2(D).
is bonded to the inside of the core part 2 using adhesive S.

A hot melt adhesive is used as the adhesive for these connections. Once the adhesive S has dried and solidified, as shown in FIG.
Manufacturing of the core part 2 is completed.

In the case shown in the figure, the hard plate pieces 2a are bonded to each other and the plate pieces 2a and the reinforcing plate 4 are bonded using the adhesive S as described above, but instead of this, adhesive tape is used. You may also use it. The formwork 12 is made up of four plate pieces 2.
Since a is for guiding to maintain a regular square, when each plate piece 2a is set,
The tip portion 14 may be cut out so that the tip portion protrudes.

FIG. 3 is a diagram showing another formwork 12a for manufacturing the core part 2, and this formwork 12a has guides that are perpendicular to each other in order to join two hard plate pieces 2a together. Surface 13a
, 13a. In this case, the illustrated formwork 1
After bonding the two plate pieces 2a together using the adhesive S, the core portion 2 is manufactured by using two sets of the plate pieces 2a and bonding each other.

FIGS. 4A and 4B are diagrams showing the manufacturing process of the cover part 3, in which the cover part 3 is formed using a first mold 21 and a second mold 22. First mold 21
is an outer mold, and has an inner surface in the shape of a regular square pyramid corresponding to the outer surface of the cover portion 3 shown in FIG.

This inner surface is larger than the outer surface of the core part 2 by an amount corresponding to the thickness of the cover part 3. Furthermore, the second mold 22 is an inner mold and has an outer surface corresponding to the inner surface of the cover part 3. The dimensions of this outer surface match those of the outer surface of the core portion 2.

With the first mold 21 installed on a base (not shown), a holder (not shown) holds the second mold 21 so that a predetermined gap 23 is formed with respect to the inner surface of the first mold 21. Fit 22. In this state, the gap 23
Pour the foam material Q inside. As the foam material Q, various materials such as urethane foam can be used. still,
Before pouring the foam material Q, a mold release agent P is applied to the inner surface of the first mold 21 and the outer surface of the second mold 22 in advance to prevent mold release after molding the cover part 3. Make it easy. After the foaming is completed, as shown in Fig. 4 (B
), the manufacturing of the cover portion 3 is completed by separating the first molding die 21 and the second molding die 22 from each other. The above-mentioned mold release agent P is shown with a dot in the figure. The cover portion 3 can be manufactured in the same manner when rubber is used as the soft material instead of the foam material.

Through each of the above-mentioned steps, a hollow hard core part 2 in the shape of a square pyramid and a cover part 3 made of a soft material are formed, and finally, as shown in FIG. The cover part 3 is placed on the outside of the part 2, and the outer surface of the core part and the inner surface of the cover part 3 are joined. These connections are performed by applying the adhesive to a portion between them.

In the embodiment described above, the core part 2 and the cover part 3 are manufactured separately and then joined together. However, the core part 2 and the cover part 3 are joined to the core part 2 at the same time as the cover part 3 is formed. It is also possible. Figure 6 (A) (B)
4 is a diagram showing a manufacturing process in which molding and bonding are performed simultaneously in this way, using a mold 21a having the same shape as the first mold 21 shown in FIG.
The core part 2 manufactured by the process shown in the figure is
Instead of the mold 22, it is fitted into a mold 21a. In this case, in the gap 23a formed between the outer surface of the core part 2 and the inner surface of the mold 21a,
By pouring the foam material Q, the cover part 3 is formed and at the same time, the cover part 3 is integrally joined to the core part 2. In this case, the mold release agent P is applied only to the inner surface of the mold 21a, and each bonding can be achieved without using an adhesive. Figure 6 (B
), when the core part 2 with the integrated cover part 3 is extracted from the mold 21a, the production of the radio wave absorber 1 with the integrated core part 2 and cover part 3 is completed. Become.

In the embodiment described above, the core part 2 is manufactured by cutting it using a board cutter 11 as shown in FIG. It may also be manufactured using a mold. Figure 7 (A)
(B) is a diagram showing a first mold 31 and a second mold 32 for molding the core part. The second mold 32 has an outer surface corresponding to the inner surface of the core portion 2 . The core portion 2 is manufactured by pouring the molten resin material R into the gap 33 formed by these molds. FIG. 7(B) shows a state in which molding of the core portion 2 is completed by separating the respective molds. Incidentally, the molding molds 31 and 32 are also coated with a mold release agent P in advance so that the core portion 2 can be easily peeled off.

8(A) and 8(B) are diagrams showing a modification of FIG. 6.

In FIG. 6, the core part 2 is used as a mold to form the cover part 3, but in this case, the cover part 3 is used as a mold to mold the core part 2. The manufacturing and the joining of the cover part 3 thereto are performed.

As shown in the figure, the cover part 3 is supported using a mold 41 having an inner surface corresponding to the outer surface of the cover part 3 manufactured in advance. A mold 42 having an outer surface with a smaller circumference is fitted. As a result, a gap 43 is formed between the inner surface of the cover part 3 and the mold 42, and the molten resin material R is poured into the gap 43. Thereby, the core part 2 integrated with the cover part 3 is manufactured. If a mold is used to manufacture the core part 2, or if the cover part 3 is used as the other mold, the reinforcing plate 4 is not necessary because the strength is stronger than when the plate pieces 2a are joined. .

Alternatively, the cover portion 3 may be manufactured by cutting out plate pieces 2a and joining them together as shown in FIG. Furthermore, if we do not take into account the amount of foam material used to make up the cover part 3, the outer surface shape of the cover part 3 will not be shaped like a regular square pyramid, as shown by the imaginary line in FIG. 1(B). The surface may be shaped into a cube. However, in that case, carbon powder is not added into the cover part 3,
Add only to the core part.

[In the embodiment described in U, the outer surface shape of the core portion 2 is entirely in the shape of a regular quadrangular pyramid, but it may be set in a polygonal pyramid shape other than this, or even in a conical shape. However, in the case of a conical shape, it is desirable to manufacture both the core part 2 and the cover part 3 using a mold.

FIG. 9 is a diagram showing another specific example for manufacturing the core portion 2, in which the resin plate 11 for the core portion 2 shown in FIG. 2(A) is formed by a single plate. In contrast, in this case, the plate 11a is formed from two wall plates 51 and 52 and a number of connecting plates 53 for connecting them. These plates 51 to 53 have a thickness of 11!1I1
It is set to about 1 to about several fflff1, which suppresses an increase in overall weight while providing a lightweight structure with a space 54 inside. However, when such a plate material 11a is used, the core portion 3 will be manufactured by the method shown in FIGS. 2(A) to 3(E) or FIG. 3.

(Effects of the Invention) As described above, according to the present invention, a radio wave absorber is provided in which a core made of a resin with high strength and a cover made of a soft material such as foam or rubber are integrated. has become,
As the outside of the radio wave absorber is covered with a soft material with relatively low strength, workers in a radio anechoic chamber using this radio wave absorber can work without considering the presence of the radio wave absorber. be able to. In other words, even if the worker comes into contact with the radio wave absorber, it is only a part of the soft material.
Measurement work can be carried out safely without injury to the operator. Moreover, such a radio wave absorber can be manufactured by a simple manufacturing method, and it has become possible to manufacture the radio wave absorber at low cost.

[Brief explanation of the drawing]

FIG. 1(A) is a partially cutaway perspective view showing a radio wave absorber manufactured according to the present invention, FIG. 1(B) is a sectional view of FIG. 1(A), and FIG. A schematic perspective view showing a radio wave anechoic chamber to which a radio wave absorber manufactured by the manufacturing method is pasted, and FIGS. 2(A) to (E) are steps showing the manufacturing process for manufacturing the core part using plate material. Figures 3 and 3 are perspective views showing other methods for manufacturing the core part, and Figures 4 (A) and (B).
) is a sectional view showing a mold forming the manufacturing process for manufacturing the cover part, FIG. 5 is a partially cutaway perspective view showing the joining process of the core part and the cover part, and FIGS. ) is a process diagram showing the case in which the cover part is molded and integrated with the core part at the same time, and Figures 7 (A) and (B) are the manufacturing process in the case where a part of the core is manufactured using a mold. A process diagram showing
Figures 8(A) and 8(B) are process diagrams showing the case in which the core part is formed and the core part is integrated with the cover part at the same time, and Figure 9 is another example of the plate material for manufacturing the core. It is a sectional view showing an example. DESCRIPTION OF SYMBOLS 1...Radio wave absorber, 2...Core part, 3...Cover part, Q...Material for cover part, R...Element H0 for core part Diagram (C) (D) Ward size 5 Correction procedure amendment dust March 17, 1999

Claims (5)

[Claims] (1) A hollow resin core part having a conical shape such as a square pyramid or a cone and having a space inside, and a cover part made of a soft material such as foam material or rubber and covering the outer surface of the core part. A method for manufacturing a radio wave absorber in which a radio wave absorbing material made of carbon or the like is added to at least one of the core portion and the cover portion, the core having the inner and outer surfaces having the conical shape. manufacturing a radio wave absorber comprising the steps of: forming a section, forming the cover section having an inner surface corresponding to the outer surface of the core section, and joining the inner surface of the cover section to the outer surface of the core section. Method. (2) Fitting the core part inside a mold having an inner surface larger than the outer surface of the core part with a gap formed between the outer surface and the inner surface of the mold, and 2. The method of manufacturing a radio wave absorber according to claim 1, wherein a material for the cover part is poured into the gap, and formation of the cover part and joining of the cover part and the core part are performed at the same time. (3) fitting the cover part to the outside of a mold having an outer surface smaller than the inner surface of the cover part with a gap formed between the inner surface of the cover part and the outer surface of the mold;
2. The method of manufacturing a radio wave absorber according to claim 1, wherein a material for the core portion is poured into the gap, and formation of the core portion and bonding of the cover portion and the core portion are performed simultaneously. (4) An inner mold having a conical outer surface such as a square pyramid or a cone, and an outer mold having a conical inner surface, the outer surface of the inner mold and the inner surface of the outer mold. Pour the material for the core part or the material for the cover part into the gap while they are fitted into each other so that a predetermined gap is formed between them, and then the core part or the cover part is The method for manufacturing a radio wave absorber according to any one of claims 1 to 3, wherein each of the radio wave absorbers is molded integrally. (5) The radio wave absorber according to any one of claims 1 to 3, wherein the core portion or the cover portion is formed by joining a plurality of triangular plate materials to each other at their side end surfaces. Production method.