Manufacturing method of hollow waveguide

Abstract

To provide a manufacturing method of a hollow waveguide capable of forming a metal layer with high adhesion strength to an outer peripheral surface of an insulation pipe, and provide the hollow waveguide in which the metal layer is formed in the high adhesion strength to the outer peripheral surface of the insulation pipe.SOLUTION: A hollow waveguide 1 is manufactured by an insulation pipe formation step of forming an insulation pipe 11 formed by an insulation body to an outer periphery of a shaft-like core material 4; a surface roughness step of making an outer peripheral surface 11a of the insulation pipe 11 roughened; a metal layer formation step of forming a metal layer 12 to the outer peripheral surface 11a of the roughened insulation pipe 11; and a cavity formation step of forming a cavity 110 at a center part of the insulation pipe 11 by removing the core material 4. The hollow waveguide 1 comprises: the insulation pipe 11 formed by the insulation body in which the cavity 110 is formed in the center part; and the metal layer 12 formed in the outer peripheral surface 11a of the insulation pipe 11, and the surface roughness of the outer peripheral surface 11a is larger than that of an inner peripheral surface 11b of the insulation pipe 11.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a hollow waveguide. By law Regarding. [Background technology]

[0002] Conventionally, hollow waveguides with a cavity formed in the center have been used as transmission paths for electromagnetic waves such as microwaves. Patent Document 1 describes a method for manufacturing a waveguide, in which a cylindrical transmission path member is made of a resin material, and a conductive layer is formed by plating the outer surface of this transmission path member with a conductive metal such as copper or aluminum. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-232740 Summary of the Invention [Problem to be solved by the invention]

[0004] When a hollow waveguide having a metal layer formed on the outer peripheral surface of a cylindrical insulating tube made of an insulator such as resin is used while being bent partially in the longitudinal direction, the metal layer needs to be adhered to the insulator with high adhesion strength to prevent the metal layer from peeling off. Therefore, an object of the present invention is to provide a method for manufacturing a hollow waveguide that can form a metal layer with high adhesion strength on the outer peripheral surface of an insulating tube, and a hollow waveguide in which a metal layer is formed with high adhesion strength on the outer peripheral surface of an insulating tube and peeling of the metal layer is suppressed. [Means for solving the problem]

[0005] In order to solve the above-mentioned problems, the present invention provides a method for manufacturing a hollow waveguide, including an insulating tube forming step of forming an insulating tube made of an insulator around the outer periphery of a axial core material, a roughening step of roughening the outer periphery of the insulating tube, a metal layer forming step of forming a metal layer on the outer periphery of the roughened insulating tube, and a cavity forming step of removing the core material to form a cavity in the center of the insulating tube.

[0006] Furthermore, in order to solve the above-mentioned problems, the present invention provides a hollow waveguide including an insulating tube made of an insulator with a cavity formed in the center, and a metal layer formed on the outer peripheral surface of the insulating tube, wherein the outer peripheral surface of the insulating tube has a greater surface roughness than the inner peripheral surface thereof. [Effects of the Invention]

[0007] The method for manufacturing a hollow waveguide according to the present invention makes it possible to form a metal layer with high adhesive strength on the outer peripheral surface of an insulating tube. Also, with the hollow waveguide according to the present invention, the metal layer is formed with high adhesive strength on the outer peripheral surface of an insulating tube, and peeling of the metal layer can be suppressed even when the waveguide is bent, for example. [Brief explanation of the drawings]

[0008] [Figure 1] 1(a) is an explanatory diagram showing an example of a state in which a hollow waveguide according to an embodiment of the present invention is used, and FIG. 1(b) is a cross-sectional view of the hollow waveguide taken along line AA in FIG. [Figure 2] 1(a) to 1(d) are perspective views showing the manufacturing process of a hollow waveguide. [Figure 3] FIG. 10 is a schematic view showing a state in which a core material is being pulled out in a cavity forming step. [Figure 4] 10(a) to 10(c) are perspective views showing hollow waveguides according to modified examples. DETAILED DESCRIPTION OF THE INVENTION

[0009] [Embodiment Mode] Fig. 1(a) is an explanatory diagram showing an example of a state in which a hollow waveguide 1 according to an embodiment of the present invention is used. Fig. 1(b) is a cross-sectional view of the hollow waveguide 1 taken along line AA in Fig. 1(a).

[0010] The hollow waveguide 1 is used to transmit electromagnetic waves in the microwave band with wavelengths of, for example, 300 MHz to 3 THz. In the example shown in Fig. 1(a), the hollow waveguide 1 is disposed between an antenna 2 and a transceiver 3, and is bent at a bending portion 10. The hollow waveguide 1 transmits electromagnetic waves as received waves from the antenna 2 to the transceiver 3, and also transmits electromagnetic waves as transmitted waves from the transceiver 3 to the antenna 2.

[0011] As shown in FIG. 1(b), the hollow waveguide 1 includes an insulating tube 11 having a cavity 110 formed in the center and a metal layer 12 formed on the outer circumferential surface 11a of the insulating tube 11. The insulating tube 11 is made of an insulator that is flexible and electrically insulating. To suppress dielectric loss, it is desirable to use a resin with a low dielectric constant for this insulator. In this embodiment, the insulating tube 11 is made of polyethylene. However, the insulator that constitutes the insulating tube 11 is not limited to polyethylene, and resins such as polypropylene and fluorine-based resins may also be used.

[0012] The metal layer 12 is made of, for example, copper, silver, aluminum, or iron, and is formed on the outer peripheral surface 11a of the insulating tube 11 by electroless plating. Electroless plating is a method of depositing a metal by a chemical reaction using a solution containing ions of the metal to be deposited as plating, without electrolysis. The required thickness of the metal layer 12 varies depending on the frequency of the electromagnetic waves propagating through the cavity 110. For example, the required thickness is approximately 0.4 μm if the frequency is 28 GHz, and approximately 5 μm if the frequency is several hundred MHz. Furthermore, if the electromagnetic waves propagating through the hollow waveguide 1 include a low frequency band, for example, approximately 50 MHz, the thickness of the metal layer 12 may be 10 μm or more.

[0013] The outer peripheral surface 11a of the insulating tube 11 is roughened to increase the adhesive strength with the metal layer 12. The surface roughness of the outer peripheral surface 11a of the insulating tube 11 is greater than the surface roughness of the inner peripheral surface 11b of the insulating tube 11. The surface roughness (arithmetic mean height Sa value defined in ISO 25178) of the outer peripheral surface 11a of the insulating tube 11 is 0.8 μm or more and 6.0 μm or less. If the surface roughness of the outer peripheral surface 11a of the insulating tube 11 is less than 0.8 μm, the adhesive strength with the metal layer 12 will be insufficient, and if the surface roughness of the outer peripheral surface 11a of the insulating tube 11 is more than 6.0 μm, electromagnetic waves will be diffused by the inner surface of the metal layer 12.

[0014] 1(b), when the thickness of the insulating tube 11 is T1 and the thickness of the metal layer 12 is T2, the ratio of T2 to T1 is 0.2% or more and 40% or less. By setting the ratio of T2 to T1 in this way, it is possible to increase the flexibility of the hollow waveguide 1 while suppressing peeling of the metal layer 12.

[0015] The outer diameter D of the metal layer 12 is, for example, 0.16 mm or more and 42 mm or less. Furthermore, a desirable range for the outer diameter D suitable for the manufacturing method described below is 1 mm or more and 8 mm or less. As shown in FIG. 1(a), when the bending radius of the hollow waveguide 1 is R, the hollow waveguide 1 can be bent by 90° with a bending radius R that is 2.5 times the outer diameter D of the metal layer 12 without causing cracks or peeling in the metal layer 12.

[0016] 2(a) to 2(d), a method for manufacturing the hollow waveguide 1 will be described. The method for manufacturing the hollow waveguide 1 includes an insulating tube forming step of forming an insulating tube 11 made of an insulator around the outer periphery of an axial core member 4, a roughening step of roughening the outer circumferential surface 11a of the insulating tube 11, a metal layer forming step of forming a metal layer 12 on the roughened outer circumferential surface 11a of the insulating tube 11, and a cavity forming step of removing the core member 4 to form a cavity 110 in the center of the insulating tube 11.

[0017] FIG. 2(a) is a perspective view showing the core material 4. The core material 4 is made of resin. To facilitate the removal of the core material 4 in the cavity forming step, it is desirable for the resin material for the core material 4 to have a low coefficient of friction. In this embodiment, the core material 4 is made of a fluorine-based resin such as PTFE (polytetrafluoroethylene), PFA (perfluoroalkoxyalkane), or FEP (tetrafluoroethylene-hexafluoropropylene copolymer). In this embodiment, the cross section of the core material 4 is circular, and its outer peripheral surface 4a is a smooth surface without any irregularities.

[0018] 2(b) is a perspective view showing a state in which the outer circumferential surface 11a of the insulating tube 11 formed in the insulating tube forming process is roughened. In the insulating tube forming process, the resin material that will become the insulating tube 11 is heated and melted, and then extruded into a tubular shape around the outer periphery of the core material 4 to form the insulating tube 11 by extrusion molding. At this time, to prevent the core material 4 and the insulating tube 11 from melting and becoming one, it is desirable that the melting point of the core material 4 be higher than the melting point of the resin material of the insulating tube 11.

[0019] 2(b), in this embodiment, the roughening process is performed by dry ice blasting, in which fine granular dry ice 50 is sprayed together with spray gas from a spray nozzle 5. This dry ice blasting forms a large number of fine recesses 111 on the outer peripheral surface 11a of the insulating tube 11.

[0020] 2(c) is a perspective view showing the state in which the metal layer 12 has been formed on the roughened outer peripheral surface 11a of the insulating tube 11 by the metal layer forming step. In the metal layer forming step, the metal layer 12 is formed by electroless plating, as described above. By forming the metal layer 12 by electroless plating, the metal layer 12 is formed so as to bite into the minute recesses 111 formed on the outer peripheral surface 11a of the insulating tube 11, and the adhesive strength between the insulating tube 11 and the metal layer 12 is increased.

[0021] FIG. 2(d) is a perspective view showing the hollow waveguide 1 after the core material 4 has been removed in the cavity forming step, forming a cavity 110 in the center of the insulating tube 11. In the cavity forming step, the core material 4 is removed by pulling it out of the insulating tube 11. The dynamic friction coefficient between the insulating tube 11 and the metal layer 12 during the cavity forming step is greater than the dynamic friction coefficient between the insulating tube 11 and the core material 4. This makes it possible to pull out the core material 4 while suppressing peeling of the metal layer 12 in the cavity forming step. In this embodiment, the dynamic friction coefficient between the insulating tube 11 and the core material 4 is kept low by forming the core material 4 from a fluorine-based resin, and the dynamic friction coefficient between the insulating tube 11 and the core material 4 is increased by roughening the outer circumferential surface 11a of the insulating tube 11.

[0022] 3 is a cross-sectional view showing the state in which the core material 4 is being pulled out of the insulating tube 11 in the direction of the arrow in the cavity forming step. Before the cavity forming step, the outer peripheral surface 4a of the core material 4 and the inner peripheral surface 11b of the insulating tube 11 are in close contact with each other, but when the core material 4 is pulled out, the core material 4 peels off from the inner peripheral surface 11b of the insulating tube 11. The portion of the core material 4 that has peeled off from the inner peripheral surface 11b of the insulating tube 11 is stretched in the axial direction and becomes thinner, thereby reducing friction with the inner peripheral surface 11b of the insulating tube 11. That is, in the cavity forming step in this embodiment, the core material 4 is pulled out while being stretched in the axial direction.

[0023] (Effects of the embodiment) According to the embodiment described above, the metal layer 12 can be formed with high adhesion strength on the outer peripheral surface 11a of the insulating tube 11, and peeling of the metal layer 12 can be suppressed, for example, when the insulating tube 11 is bent. Furthermore, by forming the metal layer 12 on the outer periphery of the insulating tube 11 in a state where the insulating tube 11 is already formed on the outer periphery of the core material 4, the shape of the insulating tube 11 in the solution in the metal layer formation step can be properly maintained, and the metal layer 12 can be formed with a uniform thickness on the outer peripheral surface 11a even if the insulating tube 11 is made thin. In addition, forming the insulating tube 11 thin can reduce dielectric loss.

[0024] [Modification of manufacturing method] In the above embodiment, a case has been described in which the hollow waveguide 1 is manufactured through an insulating tube forming process, a roughening process, a metal layer forming process, and a cavity forming process. However, it is also possible to provide a temperature change process in which the thermal expansion coefficient of the core material 4 and the thermal expansion coefficient of the insulating tube 11 are made different from each other and the temperatures of the core material 4 and the insulating tube 11 are changed after the metal layer forming process and before the cavity forming process to reduce the adhesion between the core material 4 and the insulating tube 11.

[0025] For example, if the thermal expansion coefficient of the insulating tube 11 is higher than that of the core material 4, heating the core material 4 and the insulating tube 11 causes the insulating tube 11 to expand at a rate higher than that of the core material 4, thereby reducing the adhesive strength between the core material 4 and the insulating tube 11. Furthermore, if the thermal expansion coefficient of the core material 4 is higher than that of the insulating tube 11, cooling the core material 4 and the insulating tube 11 causes the insulating tube 11 to shrink at a rate higher than that of the core material 4, thereby reducing the adhesive strength between the core material 4 and the insulating tube 11.

[0026] In addition, when the core material 4 and the insulating tube 11 are heated together with the metal layer 12 and then cooled, or when the core material 4, the insulating tube 11, and the metal layer 12 are cooled from room temperature, the thermal expansion coefficient of resin is generally about 10 times higher than that of metal, and therefore a peeling force acts between the insulating tube 11 and the metal layer 12 due to the difference in their contraction rates.However, the outer surface 11a of the insulating tube 11 is roughened in the roughening process, thereby increasing the adhesion to the metal layer 12, and therefore the insulating tube 11 is prevented from peeling off from the metal layer 12.

[0027] In this way, by performing a temperature change process before the cavity formation process, the adhesion between the core material 4 and the insulating tube 11 is reduced, making it easier to remove the core material 4 during the cavity formation process without causing damage to the insulating tube 11 or the metal layer 12.

[0028] [Modifications of the hollow waveguide shape] In the above embodiment, the case where the shape of the hollow waveguide 1 in the cross section perpendicular to the axial direction is circular has been described. However, for example, by changing the shape of the core material used in the insulating tube forming process, hollow waveguides of various shapes can be formed depending on the application, etc.

[0029] 4(a) to 4(c) are perspective views showing hollow waveguides 1A to 1C according to first to third modified examples, which have shapes different from those of the above embodiment. The hollow waveguides 1A to 1C have an insulating tube 11 and a metal layer 12, as in the above embodiment, and a cavity 110 is formed in the center of the insulating tube 11, but have shapes different from those of the hollow waveguide 1 according to the above embodiment.

[0030] A hollow waveguide 1A according to a first modified example shown in Fig. 4(a) has an elliptical shape in a cross section perpendicular to the axial direction. A hollow waveguide 1B according to a second modified example shown in Fig. 4(b) has a rectangular shape in a cross section perpendicular to the axial direction. A hollow waveguide 1C according to a third modified example shown in Fig. 4(c) has a triangular shape in a cross section perpendicular to the axial direction.

[0031] The hollow waveguides 1A to 1C according to the first to third modifications are manufactured by the same manufacturing method as that of the above-described embodiment or modifications, but a core material having an elliptical cross section is used to manufacture the hollow waveguide 1A according to the first modification, a core material having an elliptical cross section is used to manufacture the hollow waveguide 1B according to the second modification, and a core material having a triangular cross section is used to manufacture the hollow waveguide 1C according to the third modification. The shape and size of the cavity 110 correspond to the shape and size of the core material. In this way, the manufacturing method of the present invention makes it possible to form hollow waveguides of various shapes depending on the shape of the core material.

[0032] (Summary of the embodiment) Next, the technical ideas grasped from the above-described embodiment and modified examples will be described using the reference numerals and the like in the embodiment. However, the reference numerals in the following description do not limit the components in the claims to the members and the like specifically shown in the embodiment.

[0033] [1] A method for manufacturing a hollow waveguide (1, 1A to 1C), comprising: an insulating tube forming step of forming an insulating tube (11) made of an insulator around an outer periphery of a shaft-shaped core material (4); a roughening step of roughening the outer periphery (11a) of the insulating tube (11); a metal layer forming step of forming a metal layer (12) on the outer periphery (11a) of the roughened insulating tube (11); and a cavity forming step of removing the core material (4) to form a cavity (110) in the center of the insulating tube (11).

[0034] [2] The method for manufacturing a hollow waveguide (1, 1A to 1C) according to [1] above, wherein the roughening step involves dry ice blasting the outer circumferential surface (11a) of the insulating tube (11).

[0035] [3] A method for manufacturing a hollow waveguide (1, 1A to 1C) according to [1] above, wherein the core material (4) is made of resin, and the cavity forming step is a step of pulling out the core material (4) while stretching it in the axial direction.

[0036] [4] The method for producing the hollow waveguide (1, 1A to 1C) according to the above [3], wherein the core material (4) is made of a fluorine-based resin.

[0037] [5] The method for manufacturing the hollow waveguide (1, 1A to 1C) according to [1] above, wherein the coefficient of dynamic friction between the insulating tube (11) and the metal layer (12) during the cavity forming step is greater than the coefficient of dynamic friction between the insulating tube (11) and the core material (4).

[0038] [6] A method for manufacturing a hollow waveguide (1, 1A to 1C) according to any one of [1] to [5] above, wherein the core material (4) and the insulating tube (11) have different thermal expansion coefficients, and further comprises a temperature change step, prior to the cavity formation step, of changing the temperatures of the core material (4) and the insulating tube (11) to reduce the adhesion between the core material (4) and the insulating tube (11).

[0039] [7] A hollow waveguide (1, 1A to 1C) comprising an insulating tube (11) made of an insulator with a cavity (110) formed in the center, and a metal layer (12) formed on an outer peripheral surface (11a) of the insulating tube (11), wherein the surface roughness of the outer peripheral surface (11a) of the insulating tube (11) is greater than the surface roughness of its inner peripheral surface (11b).

[0040] [8] The hollow waveguide (1, 1A to 1C) according to the above [7], wherein the surface roughness (Sa) of the outer circumferential surface (11a) of the insulating tube (11) is 0.8 μm or more and 6.0 μm or less.

[0041] [9] The hollow waveguide (1, 1A to 1C) according to [7] above, wherein the thickness (T2) of the metal layer (12) is 0.2% or more and 40% or less of the thickness (T1) of the insulating tube (11).

[0042]

[10] A hollow waveguide (1, 1A to 1C) according to any one of [7] to [9] above, which can be bent at a bending radius (R) of 2.5 times the outer diameter of the metal layer (12) by 90° without causing cracks or peeling in the metal layer (12).

[0043] Although the embodiments and modifications of the present invention have been described above, the above-described embodiments and modifications do not limit the scope of the invention as claimed. It should be noted that not all of the combinations of features described in the embodiments and modifications are necessarily essential to the means for solving the problems of the invention. [Explanation of symbols]

[0044] 1, 1A to 1C... Hollow waveguide 11... Insulating tube 11a…Outer peripheral surface 11b…Inner peripheral surface 110...Cavity 12...Metal layer 4...Core material

Claims

1. An insulating tube forming process in which an insulating material having a melting point lower than the melting point of a fluororesin core material is heated and melted around the outer periphery of the core material, and the melted material is extruded into a tubular shape to form an insulating tube; a roughening step of roughening an outer peripheral surface of the insulating tube; a metal layer forming step of forming a metal layer on the roughened outer peripheral surface of the insulating tube; a cavity forming step of removing the core material to form a cavity in the center of the insulating tube; A method for manufacturing a hollow waveguide having the above structure.

2. In the surface roughening step, the outer peripheral surface of the insulating tube is subjected to dry ice blasting. The method for manufacturing the hollow waveguide according to claim 1 .

3. The cavity forming step is a step of pulling out the core material while stretching it in the axial direction. The method for manufacturing the hollow waveguide according to claim 1 .

4. The insulator is made of polyethylene. The method for manufacturing the hollow waveguide according to claim 1 .

5. a coefficient of dynamic friction between the insulating tube and the metal layer during the cavity forming step is greater than a coefficient of dynamic friction between the insulating tube and the core material; The method for manufacturing the hollow waveguide according to claim 1 .

6. the core material and the insulating tube have different thermal expansion coefficients, The method further includes a temperature change step, which is performed before the cavity forming step, of changing the temperatures of the core material and the insulating tube to reduce the adhesive strength between the core material and the insulating tube. A method for manufacturing a hollow waveguide according to any one of claims 1 to 5.

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