JP7769331B2 - Reflective member for antenna, manufacturing method of reflective member for antenna, and terahertz observation antenna - Google Patents

Description

The present invention relates to a reflecting member for an antenna, a method for manufacturing a reflecting member for an antenna, and an antenna for terahertz observation.

In some reflector antennas, an aluminum layer is formed on the radio wave reflection layer. For example, a structure has been disclosed in which an anchor coating agent layer is provided on the surface of a resin structural substrate preformed into a parabolic shape, and an aluminum layer is then formed by vacuum deposition (see, for example, Patent Document 1).
Also disclosed is a structure in which a reflective layer is formed by cold spraying on the surface of an anchor layer formed by plasma spraying on the surface of a substrate layer (for example, Patent Document 2).

Japanese Utility Model Application Laid-Open Publication No. 05-002429 Japanese Patent Application Laid-Open No. 2020-007573

As disclosed in Patent Document 1, when aluminum is deposited as a reflective surface layer by vacuum deposition, the metal reflective film of the reflective surface layer becomes thin, which results in low long-term durability in the space environment.
As shown in Patent Document 2, when a reflecting mirror surface is formed by plasma spraying, a fine void layer remains, which increases the mirror surface roughness. As a result, it is not possible to manufacture a mirror surface with high mirror shape precision.

For these reasons, the above-mentioned conventional structure cannot be used as a reflecting member for the terahertz wave band, which requires high mirror surface shape precision. Furthermore, when a reflecting member is mounted on an artificial satellite and used in space, a reflecting member that is lightweight and has excellent long-term durability in the space environment is required.

The present invention was made in consideration of the above-mentioned circumstances, and aims to provide a reflective member that is lightweight, highly accurate, and has excellent long-term environmental resistance.

In order to solve the above problems, the present invention proposes the following means.
The reflecting member for an antenna according to the present invention comprises a curved core material, a first skin provided along the inner surface of the core material, a second skin provided along the outer surface of the core material, and a reflective mirror surface coating provided on the side of the first skin that does not face the core material, wherein the core material, the first skin, and the second skin are formed from carbon fiber reinforced resin, the core material is formed from a plurality of pillars arranged such that the height direction faces the thickness direction, and the reflective mirror surface coating is formed from metal without having an internal void layer.

According to this invention, the core material, the first skin, and the second skin are made of carbon fiber reinforced resin, and the reflecting mirror surface coating is made of metal and has no void layer inside.
By providing the first and second skins on both sides of the core material in the thickness direction, a sandwich panel structure that is symmetrical in the thickness direction can be achieved, making it less likely to deform even when subjected to inputs perpendicular to the thickness direction of the core material.

By forming the core material, first skin, and second skin from carbon fiber reinforced resin, the overall weight of the reflective member can be reduced. Furthermore, carbon fiber reinforced resin has high thermal stability and is less affected by thermal expansion. This means that deformation due to thermal expansion caused by ambient temperature or direct sunlight can be minimized. This prevents the overall size of the reflective member from changing significantly due to thermal expansion. It also improves the durability of the reflective member.

Furthermore, if there is a void layer inside the metal, the void layer will cause unevenness on the surface when the surface of the reflective mirror coating is machined to a mirror finish. By forming the reflective mirror coating from metal without an internal void layer, the roughness of the reflective mirror surface of the reflective member after processing can be smoothed. Furthermore, compared to when the structure used for the reflective member is made entirely from metal, the amount of metal used can be minimized. By minimizing the amount of metal, deformation caused by thermal expansion of the metal due to factors such as ambient temperature or direct sunlight can be minimized.

These features prevent thermal strain from occurring in the first skin and the reflective mirror surface coating, thereby improving the durability of the reflective mirror surface coating and maintaining high accuracy in the reflective mirror surface coating for a long period of time.
From the above, it is possible to obtain a reflective member that is lightweight, highly accurate, and has excellent long-term environmental resistance. A reflective member having such properties brings about remarkable effects when applied to, for example, lightweight, highly accurate reflector antennas for space use or onboard artificial satellites.

The reflective mirror coating may also be made of aluminum.

According to this invention, the reflective mirror surface coating is made of aluminum, which contributes to further reducing the weight of the reflective member.

Furthermore, the thickness of the reflective mirror coating may be 20 μm or more and 40 μm or less.

According to this invention, the thickness of the reflective mirror coating is between 20 μm and 40 μm. This ensures a sufficient thickness of the reflective mirror coating, contributing to improved long-term durability in the space environment.

Furthermore, the reflecting member for an antenna according to the present invention may be used in outer space.

According to this invention, the reflective member is used in outer space, thereby significantly achieving the above-mentioned effects.

The method for manufacturing a reflecting member for an antenna according to the present invention is a method for manufacturing the reflecting member for an antenna, and comprises a spraying process for spraying metal onto the first skin, a shot peening process for removing void layers inside the metal sprayed onto the first skin, and a cutting process for cutting the surface of the metal after the shot peening process.

This invention includes a spraying process in which metal is sprayed onto the first skin, a shot peening process in which voids inside the metal sprayed onto the first skin are removed, and a cutting process in which the surface of the metal is cut after the shot peening process. In other words, after the shot peening process is performed on the metal sprayed onto the first skin, the surface is smoothed by the cutting process to form a reflective mirror coating.

The shot peening process can remove the void layer inside the metal after thermal spraying. By cutting the metal surface in the cutting process, the metal surface after the shot peening process can be modified. The void layer inside the metal is removed by the above-mentioned shot peening process. This eliminates the unevenness that occurs on the metal surface after the cutting process due to the void layer. This makes it possible to further smooth the surface roughness of the reflective mirror coating. This allows for a reflective member with high mirror shape precision.

Furthermore, in the thermal spraying process, the metal may be sprayed to a thickness of 250 μm or more.

According to this invention, the metal is sprayed to a thickness of 250 μm or more. This ensures that the thickness of the reflective mirror coating remains sufficient even after the subsequent shot peening and cutting processes.

The terahertz observation antenna according to the present invention also includes a reflecting member for the antenna.

According to this invention, a terahertz observation antenna is equipped with a reflector for an antenna according to the present invention. By using carbon fiber reinforced resin in its construction, the antenna can be lightweight and has stable performance. Furthermore, the reflector surface coating according to the present invention makes it possible to accommodate applications in the terahertz wave band. Therefore, a lightweight, high-precision reflector antenna can be created that is compatible with the terahertz wave band for space use and onboard artificial satellites, and is highly reliable.

The present invention makes it possible to provide a reflective member that is lightweight, highly accurate, and has excellent long-term environmental resistance.

1 is a perspective view showing an example of a terahertz observation antenna provided with a reflecting member according to the present invention. 2 is a schematic diagram showing the structure of each layer of a reflective member in the portion II shown in FIG. 1 . FIG. FIG. 1 is a first diagram showing a lamination process of a reflective member according to the present invention. FIG. 2 is a second diagram showing the lamination process of the reflective member according to the present invention. FIG. 2 is an enlarged view of a reflective mirror surface coating in the reflective member according to the present invention.

Hereinafter, a reflecting member for an antenna according to one embodiment of the present invention will be described with reference to the drawings.
1 is a so-called parabolic antenna that includes a reflecting member 10, a radiator 20, a support portion 30, and a base portion 40. Antenna 100 according to this embodiment is suitable for use in space or on an artificial satellite, for example, as an antenna for terahertz observation.

The reflecting member 10 reflects radio waves to be observed, including those in the terahertz wave band, toward the radiator 20 .
The radiator 20 observes the radio waves reflected by the reflecting member 10 and transmits them to a receiver (not shown). The radiator 20 is provided at the focal point of the reflecting member 10.
The support portion 30 serves to connect and support the reflecting member 10 and the base portion 40 .
Base portion 40 is a portion that supports reflecting member 10, radiator 20, and support portion 30. Base portion 40 is a portion that is connected to an artificial satellite when antenna 100 is mounted on the artificial satellite, for example. Alternatively, base portion 40 may be provided on the ground when antenna 100 is installed on the ground.

As described above, the reflecting member 10 reflects radio waves from an observation target. As shown in Fig. 2, the reflecting member 10 includes a core material 11, a first skin 12, a second skin 13, an adhesive layer 14, and a reflective mirror surface coating 15.
The core material 11 is a member having a circular outer periphery and a curved surface. The curved surface of the core material 11 is formed so that any cross-sectional curve passing through the center of the core material 11 is, for example, a parabola. This allows the core material 11 to have a focal point for incoming radio waves and forms the basis of the reflecting member 10 in the antenna 100. Alternatively, the cross-sectional curve may not be parabolic, but may be determined as appropriate based on the electrical design of the antenna 100 and the optical system.
The core material 11 is preferably made of carbon fiber reinforced plastic (CFRP). The core material 11 is formed by arranging a plurality of pillars whose height direction faces the thickness direction. For example, as shown in FIG. 2, the core material 11 preferably has a so-called honeycomb structure in which the pillars are hexagonal pillars. This suppresses deformation of the core material 11 in the thickness direction. The pillars may be triangular pillars, square pillars, or may be formed by arranging a plurality of circular pillars. The pillars may be hollow or solid.

The first skin 12 is a sheet-like member provided along the curved inner surface of the core material 11. In other words, the first skin 12 is a curved member similar to the core material 11. A reflective mirror surface deposition film 15 (described later) is formed on the side of the first skin 12 that does not face the core material 11.
The second skin 13 is a sheet-like member provided along the curved outer surface of the core material 11. In other words, the second skin 13 is a curved member similar to the core material 11. Alternatively, depending on the design of each component, the second skin 13 does not have to be curved. For example, it may be flat. In this embodiment, for example, a support part 30 is attached to the side of the second skin 13 that does not face the core material 11.

The first skin 12 and the second skin 13 are preferably formed from carbon fiber reinforced resin. Specifically, it is preferable to laminate sheets of carbon fiber reinforced resin and autoclave mold them using a molding die D, as shown in Figure 3. At this time, it is preferable to place a mold release agent P between the first skin 12 or second skin 13 and the molding die D.

The adhesive layer 14 fixes the core material 11 to the first skin 12 and the core material 11 to the second skin 13. For example, an epoxy resin is preferably used for the adhesive layer 14.
In this way, the first skin 12 and the second skin 13 formed from carbon fiber reinforced resin are arranged to sandwich both side surfaces of the core material 11, thereby forming a sandwich panel structure in the reflecting member 10.

As described above, the core material 11, the first skin 12, and the second skin 13 are preferably all formed of carbon fiber reinforced resin. Specifically, they preferably have a quasi-isotropic laminate structure using unidirectional fiber material of pitch-based high-elasticity carbon fiber. Furthermore, the high-elasticity carbon fiber preferably has an elastic modulus of, for example, 60t. This reduces thermal deformation of each of the above-mentioned components. Furthermore, it is preferable to have a structure that does not have an in-plane structure direction.
Furthermore, the matrix resin in the carbon fiber reinforced resin is preferably a polycyanate resin, which reduces moisture absorption and thus reduces moisture decomposition deformation of the panel in a vacuum state.
It is more preferable to set the carbon fiber content of the carbon fiber reinforced resin to 60% to further reduce thermal deformation.

The reflective mirror coating 15 is provided on the side of the first skin 12 that does not face the core material 11. The reflective mirror coating 15 reflects radio waves (particularly those in the terahertz wave band) that are incident toward the reflecting member 10. As described above, the first skin 12 is provided along the curved surface of the core material 11, and the curved surface has a focal point. Therefore, the radio waves reflected by the reflective mirror coating 15 are concentrated at the focal point.
The reflective mirror surface coating 15 is preferably formed of a metal such as aluminum without an internal void layer. In this embodiment, "without an internal void layer" refers to a state in which the internal void layer of the metal forming the reflective mirror surface coating 15 is less than 5%. Below, a method for manufacturing the reflective member 10 and a method for forming the reflective mirror surface coating 15 will be described.

(Method for manufacturing the reflecting member 10)
The reflecting member 10 is formed by bonding a core material 11, a first skin 12, and a second skin 13 together with an adhesive layer 14, and providing a reflective mirror surface coating 15 on the first skin 12. Specifically, the reflecting member 10 is manufactured as follows.
4, the adhesive layer 14 is placed on the first skin 12 or the second skin 13 that has been autoclave-molded using the mold D as described above, and the core material 11 is then placed on top of that. Thereafter, the adhesive layer 14 is placed on the core material 11, and the second skin 13 or the first skin 12 is placed on top of that. This completes the basic structure of the reflective member 10.
Next, the reflective mirror coating 15 is formed on the first skin 12 of the structure formed as described above. The procedure for forming the reflective mirror coating 15 includes a thermal spraying process, a shot peening process, and a cutting process.

(Thermal spraying process)
In the thermal spraying process, aluminum (metal) is sprayed onto the first skin 12 (skin). Specifically, atmospheric plasma spraying is preferably used. When spraying aluminum onto the first skin 12, an undercoat layer UC is preferably provided on the surface of the first skin 12, as shown in FIG. 5. The undercoat layer UC is preferably made of an inorganic material containing silica, for example. Here, a void layer is generated inside the aluminum sprayed by atmospheric plasma spraying. The void layer is removed by the shot peening process described below.

(Shot peening process)
As described above, this is a process for removing the void layer inside the aluminum sprayed onto the first skin 12. Specifically, countless shots are collided with the surface of the aluminum. For example, carbon steel beads with a diameter of approximately 70 μm are preferably used as the shots. The impact speed of the shots is preferably approximately 40 m/s. This process removes the void layer that has formed inside the aluminum and modifies and hardens the surface of the aluminum.

(Cutting process)
This is a process of cutting the aluminum surface after the shot peening process. Specifically, the aluminum layer formed as described above is cut by CNC machine cutting so as to form a designed curved surface. By correcting the aluminum layer by machine cutting, a highly accurate mirror surface shape is formed. Alternatively, accuracy errors are reduced. This results in a highly accurate aluminum reflecting surface shape (for example, a surface roughness of 1 μm or less).

The above-mentioned processes, particularly the thermal spraying process and shot peening process, can be performed as follows. That is, for example, a single thermal spraying process can form a relatively thick aluminum layer (e.g., about 40 μm) that does not expose the first skin 12 even in the subsequent shot peening and cutting processes. Alternatively, the thermal spraying process and shot peening process can be alternately repeated to form a thin aluminum layer (e.g., about 20 μm) in a single thermal spraying process.

When forming the aluminum layer, it is preferable to form a layer having a thickness of at least 250 μm in order to ensure a cutting allowance during cutting work.
Through these steps, a reflective mirror coating 15 is formed, as shown in the cross section of FIG. 5, which does not have a void layer inside the aluminum layer and has a smooth aluminum surface.

As described above, in the reflective member 10 according to this embodiment, the core material 11, the first skin 12, and the second skin 13 are formed from carbon fiber reinforced resin, and the reflective mirror surface coating 15 is formed from metal without having an internal void layer.
The first skin 12 and the second skin 13 are provided on both thickness-wise sides of the core material 11, resulting in a sandwich panel structure that is symmetrical in the thickness direction. This makes it possible to create a structure that is less likely to deform even when subjected to input from a direction perpendicular to the thickness direction of the core material 11.

By forming the core material 11, first skin 12, and second skin 13 from carbon fiber reinforced resin, the overall weight of the reflective member 10 can be reduced. Furthermore, carbon fiber reinforced resin has high thermal stability and is less affected by thermal expansion. This means that deformation due to thermal expansion caused by ambient temperature or direct sunlight can be minimized. This prevents the overall size of the reflective member 10 from changing significantly due to thermal expansion. Furthermore, the durability of the reflective member 10 can be improved.

Furthermore, if there is a void layer inside the metal, the void layer will cause unevenness on the surface when the surface of the reflective mirror coating 15 is mirror-finished by cutting. By forming the reflective mirror coating 15 from metal without a void layer inside, the roughness of the reflective mirror surface of the reflective member 10 after processing can be smoothed. Furthermore, compared to when the structure used in the reflective member 10 is made entirely of metal, the amount of metal used can be minimized. By minimizing the amount of metal, deformation due to thermal expansion of the metal caused by ambient temperature or direct sunlight can be minimized.

These features make it possible to prevent thermal strain from occurring in the first skin 12 and the reflective mirror surface coating 15. This improves the durability of the reflective mirror surface coating 15, and allows the precision of the reflective mirror surface coating 15 to be maintained at a high level for a long period of time.
From the above, it is possible to obtain a lightweight, highly accurate, and long-term environmentally resistant reflector 10. The reflector 10 having such properties brings about remarkable effects when applied to, for example, a lightweight, highly accurate reflector antenna for space use or for use on an artificial satellite.

In addition, the reflective mirror surface coating 15 is made of aluminum, which further contributes to reducing the weight of the reflective member 10.

In addition, the thickness of the reflective mirror surface coating 15 is between 20 μm and 40 μm. This ensures a sufficient thickness for the reflective mirror surface coating 15, contributing to improved long-term durability in the space environment.

The reflective member 10 can also be used in outer space, which can significantly enhance the effects described above.

The method also includes a spraying process in which metal is sprayed onto the first skin 12, a shot peening process in which voids within the metal sprayed onto the first skin 12 are removed, and a cutting process in which the surface of the metal is cut after the shot peening process. In other words, the metal sprayed onto the first skin 12 is subjected to the shot peening process, and then the surface is smoothed by the cutting process to form the reflective mirror coating 15.

The shot peening process can remove the void layer inside the metal after thermal spraying. By cutting the metal surface in the cutting process, the metal surface after the shot peening process can be modified. The void layer inside the metal is removed by the above-mentioned shot peening process. This eliminates the unevenness that occurs on the metal surface after the cutting process due to the void layer. This makes it possible to further smooth the surface roughness of the reflective mirror coating 15. This allows for a reflective member 10 with high mirror shape precision.

In addition, the metal is sprayed to a thickness of 250 μm or more. This ensures that the reflective mirror coating 15 remains sufficiently thick even after the subsequent shot peening and cutting processes.

The reflecting member 10 according to the present invention is also included in an antenna for terahertz observation. By using carbon fiber reinforced resin in its construction, the antenna 100 can be made lightweight and have stable performance. Furthermore, the reflecting mirror surface coating 15 according to the present invention makes it suitable for use in the terahertz wave band. This makes it possible to create a lightweight, high-precision reflector antenna that is highly reliable and can handle up to the terahertz wave band for use in space or onboard an artificial satellite.

The technical scope of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.
For example, the surface of the core material 11 on the side where the second skin 13 is provided, i.e., the side on which the reflective mirror surface coating 15 is not provided, does not need to be curved.
The reflecting mirror surface film 15 may be made of a metal other than aluminum.
Furthermore, the antenna 100 may not have the support portion 30 or the base portion 40, and the reflecting member 10 may be attached directly to the satellite.
Furthermore, by increasing the thickness of the above-described sandwich panel structure, i.e., the core material 11, it may be possible to further suppress deformation due to heat.

In addition, the components in the above embodiment may be replaced with well-known components as appropriate, and the above-mentioned modifications may be combined as appropriate, without departing from the spirit of the present invention.

10 Reflecting member 11 Core material 12 First skin 13 Second skin 15 Reflecting mirror surface coating 100 Antenna

Claims (7)

A curved core material,
a first skin provided along an inner surface of the core material;
a second skin provided along the outer surface of the core material;
a reflective mirror coating provided on the side of the first skin that does not face the core material;
Equipped with
The core material is formed by arranging a plurality of pillars ,
the plurality of pillars are arranged such that the height direction of the plurality of pillars is along the thickness direction of the core material,
The reflective mirror coating is formed of metal without an internal void layer.
Reflective material for antennas. The reflective mirror coating is made of aluminum.
The reflector for an antenna according to claim 1. The thickness of the reflective mirror coating is 20 μm or more and 40 μm or less.
The reflector for an antenna according to claim 1 or 2. A reflector for an antenna according to any one of claims 1 to 3, for use in outer space. A method for manufacturing a reflecting member for an antenna according to any one of claims 1 to 4, comprising the steps of:
a thermal spraying step of thermally spraying a metal onto the first skin;
a shot peening process for removing a void layer inside the metal sprayed on the first skin;
a cutting step of cutting the surface of the metal after the shot peening step;
Equipped with
A method for manufacturing a reflector for an antenna. In the thermal spraying step, the metal is sprayed to a thickness of 250 μm or more.
A method for manufacturing the reflector for an antenna according to claim 5. A reflector for an antenna according to any one of claims 1 to 4,
Antenna for terahertz observation.