JP3498756B2 - Membrane material for metal space frame radome - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film material used for a metal space frame radome.

[0002]

2. Description of the Related Art A radome is used to protect a radar antenna from wind, rain, snow, etc., and its performance is evaluated by radio wave transmission, radio wave deviation, durability, etc., and its characteristics are the constituent materials and structure of the radome. Determined by

A metal space frame radome was developed for the purpose of improving the performance of the radome, which is made as small as possible by using a metal frame having a high elastic modulus as a strength member for the entire radome. By providing a film material with good radio wave transmission between metal frames, it is used for a radome to prevent wind and rain.

Compared with the conventional FRP radome, the metal space frame radome uses a metal having a high elastic modulus as a strength member, so that the block area for radio waves can be reduced. Therefore, the radio wave transmission loss and the radio wave deviation are significantly improved as compared with the FRP radome. On the other hand, however, the radio wave transmission performance of the radome as a whole is greatly influenced by the performance of the film material stretched between the frames. Therefore, the film material for the metal space frame radome must have excellent weather resistance in order to protect the radar from wind and rain, and also have excellent radio wave permeability.

In order to meet such demands, some film materials having excellent radio wave transparency and weather resistance have been proposed. For example, JP-B-58-3406 has a structure in which a woven fabric of organic fiber is coated with ethylene propylene rubber such as EPM or EPDM, and this ethylene propylene rubber is coated with titanium white for improving weather resistance. Blending techniques are described. In addition, Japanese Patent Publication No. 60-28402 proposes a film material having a similar structure, in which carbon black is mixed with ethylene propylene rubber.

[0006]

The frequency of the radio wave used in the radar has hitherto been mainly in the S band (several GHz), but recently, in order to increase the information density and improve the resolution of the radar, the frequency is increased. The high Ka band (several tens GHz) is becoming the mainstream, and in the future, there is a tendency to shift to the high frequency band capable of further increasing the information density.

However, when the radio wave used by the radar is in a high frequency band such as the Ka band, the radio wave transmission performance of the metal space frame radome film material deteriorates, and the radio wave transmission performance of the above conventional film material is insufficient. It has become to.
In order to improve the radio wave transmission performance of the film material, it is conceivable to reduce the content of the filler such as carbon black or titanium white compounded in the rubber, but with that, the weather resistance deteriorates, and it takes 10 to 15 years. The radar cannot be protected from wind and rain for a long time.

In view of such conventional circumstances, the present invention is based on Ka
It is an object of the present invention to provide a film material for a metal space frame radome which has excellent radio wave transmission performance even in a higher frequency band such as a band and has excellent weather resistance.

[0009]

In order to achieve the above object, a metal space frame radome membrane material provided by the present invention is a metal space frame radome membrane material in which both sides of an organic fiber woven fabric are covered with rubber layers. In the above, the filler contained in the outer rubber layer facing the outer side of the radome is larger than the filler contained in the inner rubber layer facing the inner side of the radome.

The membrane material of the present invention has a reinforcing organic fiber woven fabric at the center, and rubber layers are coated on both sides of the woven fabric. It is desirable that the organic fiber woven fabric has good radio wave transmission, excellent tensile strength, and low elongation.
Most preferred is a fabric of aramid fibers represented by Kevlar manufactured by (DuPont).

The rubber layer is preferably ethylene propylene rubber which is excellent in weather resistance and radio wave transmission,
Of these, a three-component copolymer (EPDM) of ethylene and propylene and a diene compound as the third component is most preferable.
The filler to be added to the rubber for improving the weather resistance may be carbon black, white carbon (silica white), titanium white or the like which has been conventionally added for reinforcing the rubber. Among them, titanium white is preferable as the filler for changing the content because titanium white has the greatest effect on radio wave transmission.

Although the outer rubber layer and the inner rubber layer may be one layer or a plurality of rubber layers, the inner rubber layer is the outer rubber layer facing the outside of the radome and exposed to wind and rain. It is necessary that more filler be included.
Further, it is preferable that the filler contained in both the outer rubber layer and the inner rubber layer gradually increases toward the outer surface, and in that case, the content of the filler can be linearly increased at a constant rate. However, by constituting the outer and inner rubber layers by a plurality of layers and changing the filler content for each layer,
From the viewpoint of production, it is preferable to gradually increase the content. Further, the inner rubber layer which is on the inner side and is not exposed to the weather does not need to contain a reinforcing filler.

The method for coating both sides of the organic fiber woven fabric with the rubber layer is generally carried out by a calendering machine used for producing a rubberized cloth, or by a rubber melted in a solvent such as toluene and a gluing machine such as a spreader. There is a method of coating with. Alternatively, a rubber sheet may be manufactured in advance and integrated with an organic fiber woven fabric by a laminating machine or the like.

[0014]

[Function] In order to reduce the radio wave transmission loss of the film material for the radome, the relative permittivity (ε _r ) and the dielectric loss tangent (tan δ) of the film material are used.
Needs to be small. However, the rubber constituting a part of the film material is mixed with a filler such as titanium white in order to ensure weather resistance, and this filler (particularly titanium white) has a large relative dielectric constant. Therefore, when rubber is mixed with a large amount of filler, weather resistance can be secured, but sufficient radio wave transmission cannot be obtained particularly in a high frequency region.

In the film material for a radome of the present invention, the outer rubber layer facing the outside of the radome and exposed to the weather and the like contains a sufficient amount of filler to ensure excellent weather resistance, and the inside thereof The inner rubber layer that does not need to ensure weather resistance because it faces the surface does not contain a filler or contains a smaller amount of a filler than the outer rubber layer, so it has excellent weather resistance and radio waves. Combines transparency.

In particular, by increasing the amount of the filler contained in the outer rubber layer linearly or stepwise from the organic fiber fabric side to the outer surface side, the outermost rubber layer is exposed to the weather. While the amount of filler in the outer layer is relatively increased to ensure sufficient weather resistance, the amount of filler in the entire outer rubber layer can be reduced as compared to the conventional one, resulting in even better weather resistance and radio wave transmission. Can be achieved at the same time.

[0017]

EXAMPLE 1 As shown in FIG. 1, an inner rubber layer 2 having a thickness of 0.2 mm was calendered on both sides of an organic fiber woven fabric 1 made of a Kevlar fiber woven fabric having a thickness of 0.2 mm. The outer rubber layer 3 was formed. The inner rubber layer 2 and the outer rubber layer 3 in this membrane material of the present invention are EPDM manufactured by Sumitomo Chemical Co., Ltd.
The main component is rubber (trade name "Esprene"), and the rubber composition is shown in Table 1 below with the parts by weight of the filler (titanium white and white carbon), plasticizer, colorant, and vulcanizing agent relative to 100 parts by weight of EPDM rubber. As shown.

[0018]

[Table 1]

On the other hand, for comparison, a film material having the same structure as that shown in FIG. 1 was manufactured in the same manner as in Example 1 except that the content of titanium white in the inner rubber layer was 30 parts by weight.
The film material of this comparative example has been practically used as an S-band radar film material in the past, and has an excellent weather resistance of 10 years or more in actual use, and has an S-band (for example, 3 GHz).
The radio wave transmission loss in z) is also excellent at 10.7%.

However, the film material of this comparative example has a radio wave transmission loss of 22.9 in the Ka band (for example, 40 GHz).
%, Which causes the performance of the radar system to deteriorate. On the other hand, the film material of the present invention has the same weather resistance as the conventional one because the outer rubber layer 3 contains the same amount of filler such as titanium white as the film material of the comparative example. Is a rubber compound that does not substantially contain titanium white, and therefore has excellent radio wave transmission as a whole. For example, 40 GHz
The radio wave transmission loss was 17.6%.

In the film material of the present invention, the inner rubber layer is deteriorated particularly by ultraviolet rays when it is used in a portion which is directly exposed to light, so that the function of protecting the radar from wind and rain cannot be achieved. Since the portion directly exposed to the light is only the outer rubber layer having the same weather resistance as the conventional one, it is possible to maintain sufficient durability as a radome.

Embodiment 2 As shown in FIG. 2, the outer surface rubber layer 3 is formed from the inside in order of the same thickness of 0.067 mm as the first layer 3a, the second layer 3b, and the third layer.
It is composed of layers 3c, and the content of titanium white contained in each layer is 15 phr for the first layer 3a and 30 ph for the second layer 3b.
A film material similar to that of Example 1 was manufactured except that r and the third layer 3c were 45 phr. However, although the inner rubber layer 2 was provided by calendering, each layer 3a of the outer rubber layer 3,
Since 3b and 3c are thin, they were formed by a spread process in which the rubber was dissolved in toluene and coated.

The radio wave transmission loss of the obtained film material was equal to that of the film material of Example 1, but the content of titanium white contained in the third layer 3c which is the outermost layer of the outer rubber layer 3 was 45 phr. Since the amount was large, it showed better weather resistance than the film material of Example 1.

The influence of the titanium white content on the weather resistance of EPDM rubber is shown in FIG. 4, which shows the relationship between weather meter exposure time and elongation at break for each titanium white content. As the amount increases, the weather resistance also improves. Therefore, up to 100 parts by weight of titanium white can be added to 100 parts by weight of EPDM rubber, but it has been found that the range of 30 to 80 parts by weight is preferable in the outer rubber layer in order to achieve both weather resistance and radio wave transparency. .

Embodiment 3 As shown in FIG. 3, the outer surface rubber layer 3 is formed from the inside in order of the same thickness of 0.05 mm, that is, the first layer 3a, the second layer 3b, and the third layer 3
c and the fourth layer 3d, the content of titanium white contained in each layer is 10 phr for the first layer 3a and the second layer 3
A film material similar to that of Example 1 was manufactured except that b was 15 phr, the third layer 3c was 30, and the fourth layer 3d was 65 phr.

As shown in FIG. 5, the titanium white content of this film material has a steeper stepwise change in the outer rubber layer 3 than in the case of Example 2. That is, when the first layer 3a is compared, the white titanium content of Example 3 is lower than that of Example 2, but when the outermost layers are compared, the fourth layer 3d of Example 3 is better than that of Example 2. The titanium white content is higher than that of the third layer 3c. Therefore, the film material of Example 3 was equivalent to the film materials of Examples 1 and 2 in radio wave transmission, but could further improve weather resistance.

Example 4 As in Example 3, as shown in FIG. 3, the outer surface rubber layer 3 was formed from the inside in order of the first layer 3a having the same thickness of 0.05 mm and the second layer 3a.
The layer 3b, the third layer 3c, and the fourth layer 3d were formed. The content of titanium white contained in each layer was 0 phr for the first layer 3a, 10 phr for the second layer 3b, and 2 for the third layer 3c.
0, and the fourth layer 3d was 30 phr. Other configurations were the same as those of the film material of Example 1.

In this film material, the content of titanium white contained in the outermost fourth layer 3d is the same as that of the outer rubber layer of Example 1, so that the weather resistance is equivalent to that of the film material of Example 1. However, since the content of titanium white contained in the whole film material is low, the radio wave transmission loss is 1 at 40 GHz.
4%, which was superior to the film material of Example 1.

Example 5 In the same manner as in Example 1, both sides of the Kevlar fiber woven fabric 1 having a thickness of 0.2 mm were 0.2 mm on both sides.
A 2 mm inner rubber layer 2 and an outer rubber layer 3 were formed. The rubber composition of the inner rubber layer 2 and the outer rubber layer 3 is shown in Table 2 below.
The parts by weight of the filler (titanium white and white carbon), the plasticizer, the colorant, and the vulcanizing agent relative to 100 parts by weight of the M rubber are shown.

[0030]

[Table 2]

On the other hand, for comparison, the same structure
The same film material as in Example 1 was manufactured except that the content of white carbon in the inner rubber layer was 50 parts by weight. The film material of this comparative example has a Ka band (for example, 40 GH).
In z), the radio wave transmission loss decreased to 22.9%.

On the other hand, the film material of the present invention has the same weather resistance as the conventional one because the outer rubber layer 3 contains the same amount of filler such as titanium white as the film material of the comparative example. Rubber layer 2
Has substantially less than half the content of white carbon in the outer rubber layer 3, and therefore has excellent radio wave transmission properties as a whole. For example, the radio wave transmission loss at 40 GHz is 19.8.
%Met.

[0033]

According to the present invention, since the characteristics of the outer rubber layer and the inner rubber layer of the membrane material are changed depending on the content of the filler, compared to the case where the outer rubber layer and the inner rubber layer have the same characteristics. , If the radio wave transmission is equivalent, a film material with better weather resistance is obtained, and conversely, if the weather resistance is equal, a film material with better radio wave transmission is obtained. It is possible to provide a film material for a metal space frame radome having excellent radio wave transmission performance and excellent weather resistance.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing a specific example of a film material for metal space frame radome according to the present invention.

FIG. 2 is an external cross-sectional view showing a specific example of the film material of the present invention having a plurality of external rubber layers.

FIG. 3 is an external cross-sectional view showing another specific example of the film material of the present invention in which the external rubber layer is composed of a plurality of layers.

FIG. 4 is a graph showing the relationship between the weather resistance of EPDM rubber and the filler content.

FIG. 5 is a graph showing the filler content in the outer rubber layer of the membrane materials of Examples 2 and 3.

[Explanation of symbols]

1 organic fiber fabric 2 inner rubber layer 3 outer rubber layer 3a First layer 3b second layer 3c Third layer 3d 4th layer

─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Masatoshi Kuroda 1-3-1 Shimaya, Konohana-ku, Osaka Sumitomo Electric Industries, Ltd. (56) Reference JP-A-52-7656 (JP, A) Actual Kai 56-95106 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01Q 1/42 B32B 25/10

Claims (3)

(57) [Claims] 1. A metal space frame radome membrane material comprising both surfaces of an organic fiber woven fabric covered with rubber layers, wherein the filler contained in the outer rubber layer facing the outside of the radome is the inner rubber facing the inside of the radome. Membrane material for metal space frame radome, characterized in that it is more than the filler contained in the layer. 2. The film material for a metal space frame radome according to claim 1, wherein the filler contained in the outer rubber layer is gradually increased from the organic fiber fabric side toward the outer surface side. 3. The film material for metal space frame radome according to claim 1, wherein the inner rubber layer does not contain a filler.