Leaky cable and manufacturing method for leaky cable

Abstract

To provide a leakage cable in which a slot through which an electromagnetic wave is leaked is formed in a metal layer formed in an outer periphery of a linear insulator, the leakage cable being capable of suppressing occurrence of positional displacement of the slot with respect to the insulator, and a manufacturing method thereof.SOLUTION: A leakage waveguide 1 comprises a linear insulator 2 and a metal layer 3 which is formed on an outer peripheral surface 2b of the insulator 2, and a plurality of slots 30 through which electromagnetic waves are leaked is formed while penetrating between an inner peripheral surface 3a and an outer peripheral surface 3b in the metal layer 3. Ruggedness which suppresses positional displacement of the slots 30 with respect to the insulator 2 is formed on the outer peripheral surface 2b of the insulator 2. A manufacturing method of the leakage waveguide 1 includes: an insulator forming step of forming the insulator 2; a surface roughening step of roughening the outer peripheral surface 2b of the insulator 2; a metal layer forming step of forming the metal layer 3 on the outer peripheral surface 2b of the insulator 2; and a slot forming step of forming the plurality of slots 30, which penetrates between the inner peripheral surface 3a and the outer peripheral surface 3b of the metal layer 3, in the metal layer 3.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a leaky cable having slots formed therein that allow electromagnetic waves to leak, and a method for manufacturing the same. [Background technology]

[0002] Conventionally, leaky cables, which transmit electromagnetic waves for communication and have slots (leakage holes) formed at multiple locations along their length that allow the electromagnetic waves to leak, have been laid in places such as tunnels and large rooms. Examples of such leaky cables include leaky waveguides, which are hollow corrugated tubes made of conductive metal such as copper or aluminum, and leaky coaxial cables, which have a central conductor disposed at the center of a linear insulator and a cylindrical conductive metal outer conductor disposed around the insulator. Such leaky cables are laid with their directivity adjusted so that the slots formed in the conductive metal open in the desired direction of the electromagnetic waves (see, for example, Patent Documents 1 to 3). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-99887 [Patent Document 2] Japanese Patent Application Laid-Open No. 2003-168330 [Patent Document 3] Japanese Patent Application Laid-Open No. 2011-199760 Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-mentioned leaky cables, it is desirable to make the conductive metal in which the slots are formed thin in order to improve flexibility and reduce costs and weight. For this reason, the inventors have devised a leaky waveguide and a leaky coaxial cable in which a thin metal layer is formed on the outer periphery of a linear insulator and a slot is formed in this metal layer. However, such a configuration has a problem in that, for example, during installation, the metal layer slides on the outer periphery of the insulator, easily causing the position of the slot to become misaligned.

[0005] Therefore, the present invention aims to provide a leakage cable having a slot formed in a metal layer formed on the outer periphery of a linear insulator to allow electromagnetic waves to leak, which is capable of suppressing the occurrence of misalignment of the slot relative to the insulator, and a method for manufacturing the same. [Means for solving the problem]

[0006] In order to solve the above problems, the present invention provides a leakage cable comprising a linear insulator and a metal layer formed on an outer peripheral surface of the insulator, wherein slots for leaking electromagnetic waves into the metal layer are formed by penetrating between the inner and outer peripheral surfaces of the metal layer, a protrusion formed by a portion of the insulator protruding from the inner peripheral surface of the metal layer at the peripheral portion of the slot toward the outer peripheral surface thereof, the protrusion being in close contact with at least a portion of the end surface of the metal layer at the peripheral portion of the slot and engaging with the slot; Provide a leaky cable.

[0007] In order to solve the above-mentioned problems, the present invention provides a method for manufacturing a cylindrical insulator, comprising: an insulator forming step of forming a tubular insulator made of a thermoplastic resin; a roughening step of roughening an outer peripheral surface of the insulator; a metal layer forming step of forming a metal layer on the outer peripheral surface of the insulator; and a slot forming step of forming a slot penetrating between an inner peripheral surface and an outer peripheral surface of the metal layer, the slot allowing electromagnetic waves to leak to the outside of the metal layer. The slot forming process is a process of applying laser light to the outer peripheral surface of the metal layer to open the slot and melt a part of the insulator, and a part of the re-solidified resin portion formed by solidifying the molten resin protrudes from the inner peripheral surface side of the metal layer toward the outer peripheral surface side at the peripheral portion of the slot to form a protrusion, and the protrusion is in close contact with at least a part of the end surface of the metal layer at the peripheral portion of the slot and engages with the slot. A method for manufacturing a leakage cable is provided. [Effects of the Invention]

[0008] According to the leaky cable and the manufacturing method thereof of the present invention, it is possible to suppress the occurrence of misalignment of the slot with respect to the insulator, and it becomes easier to direct electromagnetic waves in a desired direction. [Brief explanation of the drawings]

[0009] [Figure 1] 1A is a perspective cross-sectional view showing an example of the configuration of a leaky waveguide according to a first embodiment of the present invention, and FIG. 1B is a cross-sectional view of the leaky waveguide taken along line AA in FIG. [Figure 2] 1(a) to 1(d) are perspective views showing the manufacturing process of the leaky waveguide. [Figure 3] FIG. 10 is a cross-sectional view showing a state in which the core material is being pulled out from the insulator. [Figure 4] (a) is a cross-sectional photograph of a leaky waveguide showing the periphery of a slot. (b) is an enlarged photograph of part B in (a). (c) is a schematic diagram showing the boundary line of the member in (b). [Figure 5] 10(a) to 10(c) are perspective views showing leaky waveguides according to modified examples. [Figure 6] 10(a) is a perspective cross-sectional view showing an example of the configuration of a leaky coaxial cable according to a second embodiment, and FIG. 10(b) is a cross-sectional view of the leaky coaxial cable in the CC line of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present invention will be described. In the first embodiment, the leaky cable of the present invention is implemented as a leaky waveguide, and in the second embodiment, the leaky cable of the present invention is implemented as a leaky coaxial cable.

[0011] [First embodiment] Fig. 1(a) is a perspective cross-sectional view showing an example of the configuration of a leaky waveguide 1 according to a first embodiment of the present invention, and Fig. 1(b) is a cross-sectional view of the leaky waveguide 1 taken along line AA in Fig. 1(a).

[0012] The leaky waveguide 1 transmits electromagnetic waves in the microwave band with wavelengths of, for example, 300 MHz to 3 THz, and also leaks the electromagnetic waves to the outside of the leaky waveguide 1 .

[0013] The leaky waveguide 1 includes a linear insulator 2 and a metal layer 3 formed on the outer periphery of the insulator 2. The insulator 2 is made of a thermoplastic resin that is flexible and electrically insulating. It is desirable to use a resin material for the insulator 2 that has a low dielectric constant in order to suppress dielectric loss. In this embodiment, the insulator 2 is made of polyethylene. However, the resin material for the insulator 2 is not limited to polyethylene, and other resins such as polypropylene and fluorine-based resins may also be used.

[0014] The insulator 2 is formed in a hollow cylindrical shape, and a cavity 20 is formed in the center thereof over the entire leaky waveguide 1. In this embodiment, the insulator 2 is cylindrical, and an inner circumferential surface 2a and an outer circumferential surface 2b of the insulator 2 in a cross section perpendicular to the longitudinal direction of the leaky waveguide 1 are each circular.

[0015] Slots 30 for leaking electromagnetic waves are formed in the metal layer 3 in a row at multiple locations along the longitudinal direction of the leaky waveguide 1. Each slot 30 penetrates between the inner peripheral surface 3a and the outer peripheral surface 3b of the metal layer 3. The electromagnetic waves are sent (leaked) from the portions where the slots 30 are formed toward the outside of the metal layer 3 with a predetermined directivity.

[0016] The metal layer 3 is made of, for example, copper, silver, aluminum, or iron, and is formed on the outer peripheral surface 2b of the insulator 2 by electroless plating. Electroless plating is a method of depositing a metal by a chemical reaction using a solution containing the metal ions to be deposited as plating, without electrolysis. When performing electroless plating, palladium, which serves as deposition nuclei, is adsorbed onto the outer peripheral surface 2b of the insulator 2.

[0017] The required thickness of the metal layer 3 varies depending on the frequency of the electromagnetic waves propagating through the leaky waveguide 1, but for example, it is about 0.4 μm when the frequency is 28 GHz, and about 5 μm when the frequency is several hundred MHz. Furthermore, when the electromagnetic waves propagating through the leaky waveguide 1 include a low frequency band of, for example, about 50 MHz, the thickness of the metal layer 3 may be 10 μm or more.

[0018] 1(b), when the radial thickness of the insulator 2 is T2 and the thickness of the metal layer 3 is T3, the ratio of T3 to T2 is, for example, 0.2% to 40%. By setting the ratio of T3 to T2 in this way, peeling of the metal layer 3 can be suppressed even when the leaky waveguide 1 is bent, and the leaky waveguide 1 can be installed in a bent state.

[0019] The outer diameter D of the leaky waveguide 1 is, for example, 0.16 mm or more and 42 mm or less. The outer diameter D suitable for the manufacturing method described below is preferably in the range of 1 mm or more and 8 mm or less. The leaky waveguide 1 can be bent at a bending radius of 2.5 times the outer diameter D by 90° without causing cracks or peeling in the metal layer 3.

[0020] The outer peripheral surface 2b of the insulator 2 is formed with irregularities that suppress misalignment of the slot 30 relative to the insulator 2, and the surface roughness of the outer peripheral surface 2b of the insulator 2 is greater than the surface roughness of the inner peripheral surface 2a of the insulator 2. The outer peripheral surface 2b of the insulator 2 is roughened by a roughening process described later, and this roughening increases the adhesive strength with the metal layer 3.

[0021] The surface roughness (arithmetic mean height Sa value defined in ISO25178) of the outer peripheral surface 2b of the insulator 2 in the portion covered with the metal layer 3 is 0.8 μm or more and 6.0 μm or less. If the surface roughness of the outer peripheral surface 2b of the insulator 2 is less than 0.8 μm, the adhesive strength with the metal layer 3 is insufficient, and if the surface roughness of the outer peripheral surface 2b of the insulator 2 is more than 6.0 μm, electromagnetic waves are diffusely reflected by the inner peripheral surface 3a of the metal layer 3.

[0022] The slots 30 are formed by forming the metal layer 3 on the outer periphery of the insulator 2 and then irradiating the metal layer 3 with laser light from the outer peripheral surface 3b toward the insulator 2. During this laser irradiation, a portion of the insulator 2 is heated by the heat of the laser light and melts into a liquid molten resin, which then solidifies. The solidified portion of the insulator 2 protrudes from the inner peripheral surface 3a toward the outer peripheral surface 3b of the metal layer 3 at the periphery of the slot 30. FIG. 1(b) shows the protrusions 21 formed in this manner. The protrusions 21 are in close contact with at least a portion of the end face 3c of the metal layer 3 at the periphery of the slot 30.

[0023] The protrusions 21, in combination with the roughened outer peripheral surface 2b of the insulator 2 in the portion covered with the metal layer 3, suppress misalignment of the slot 30 with respect to the insulator 2. More specifically, the roughened outer peripheral surface 2b of the insulator 2 in the portion covered with the metal layer 3 increases the adhesive strength between the outer peripheral surface 2b of the insulator 2 and the inner peripheral surface 3a of the metal layer 3 due to an anchor effect when the metal layer 3 is formed by electroless plating, and the engagement of the protrusions 21 with the slot 30 mechanically suppresses misalignment of the slot 30 with respect to the insulator 2.

[0024] In other words, in this embodiment, the unevenness that suppresses misalignment of the slot 30 relative to the insulator 2 is formed by roughening the outer surface 2b of the insulator 2 in the portion covered by the metal layer 3, and by the protrusion 21, which is part of the insulator 2 formed by solidifying the molten resin that was melted by the heat of the laser light when forming the slot 30 in the metal layer 3, protruding from the inner surface 3a side of the metal layer 3 at the periphery of the slot 30 toward the outer surface 3b side.

[0025] 2(a) to 2(d), a method for manufacturing the leaky waveguide 1 will be described. The method for manufacturing the leaky waveguide 1 includes an insulator forming step of forming a cylindrical insulator 2 on the outer periphery of an axial core material 4, a roughening step of roughening the outer peripheral surface 2b of the insulator 2, a metal layer forming step of forming a metal layer 3 on the roughened outer peripheral surface 2b of the insulator 2, a slot forming step of forming a plurality of slots 30 penetrating between the inner peripheral surface 3a and the outer peripheral surface 3b of the metal layer 3, and a cavity forming step of removing the core material 4 to form a cavity 20 in the center of the insulator 2 after the metal layer forming step or the slot forming step.

[0026] 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). The cross section of the core material 4 is circular, and its outer peripheral surface 4a is a smooth surface without any irregularities.

[0027] 2(b) is a perspective view showing the state in which the outer peripheral surface 2b of the insulator 2 formed in the insulator forming process is roughened. In the insulator forming process, the resin material that will become the insulator 2 is heated and melted, and then extruded into a tubular shape around the core material 4 to form the insulator 2 by extrusion molding. At this time, to prevent the core material 4 and the insulator 2 from melting and becoming one, it is desirable that the melting point of the core material 4 be higher than that of the resin material of the insulator 2.

[0028] In this embodiment, as shown in Fig. 2(b), the roughening process is performed by dry ice blasting, in which fine granular dry ice 50 is sprayed from a spray nozzle 5 together with a spray gas. The portions hit by the dry ice 50 become fine recesses 22. This dry ice blasting forms fine irregularities on the outer peripheral surface 2b of the insulator 2.

[0029] 2(c) is a perspective view showing a state in which slots 30 are formed by laser processing in the metal layer 3 formed in the metal layer forming step. In the metal layer forming step, the metal layer 3 is formed by electroless plating as described above. By forming the metal layer 3 by electroless plating, the metal layer 3 is formed so as to bite into the minute recesses 22 formed in the outer peripheral surface 2b of the insulator 2.

[0030] The slot forming process is a process in which a laser beam 60 is applied to the outer peripheral surface 3b of the metal layer 3 to open the slot 30, and a portion of the insulator 2 is melted by the heat of the laser beam 60. Specifically, the laser beam 60 is applied from the laser processing head 6 so as to surround the portion that will become the slot 30, cutting the metal layer 3, and removing the metal piece 300 inside the cut portion, thereby forming the slot 30. Depending on the size of the slot 30, the slot 30 may be formed in the metal layer 3 by applying laser beam having a shape corresponding to the shape of the slot 30.

[0031] The heat of the laser light 60 also acts on the insulator 2, melting part of the insulator 2, and the molten resin flows and solidifies, forming the protrusion 21. In other words, a part of the re-solidified resin portion, which is formed by solidifying the molten resin that has been melted by the heat of the laser light 60, protrudes from the inner circumferential surface 3a of the metal layer 3 at the periphery of the slot 30 toward the outer circumferential surface 3b, and becomes the protrusion 21.

[0032] FIG. 2(d) is a perspective view showing the leaky waveguide 1 in which the core material 4 has been removed in the cavity forming step, forming a cavity 20 in the center of the insulator 2. In the cavity forming step, the core material 4 is removed by pulling it out from the insulator 2. The dynamic friction coefficient between the insulator 2 and the metal layer 3 during the cavity forming step is greater than the dynamic friction coefficient between the insulator 2 and the core material 4. This makes it possible to pull out the core material 4 while suppressing peeling of the metal layer 3 in the cavity forming step. In this embodiment, the dynamic friction coefficient between the insulator 2 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 insulator 2 and the core material 4 is increased by roughening the outer peripheral surface 2b of the insulator 2.

[0033] 2(c) and 2(d) show the case where the cavity forming step is performed after the slot forming step, but the cavity forming step may be performed after the metal layer forming step and before the slot forming step. However, it is more preferable to perform the cavity forming step after the slot forming step so that the position of the slot 30 relative to the insulator 2 does not shift when the core material 4 is pulled out.

[0034] 3 is a cross-sectional view showing the state in which the core material 4 is being pulled out from the insulator 2 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 2a of the insulator 2 are in close contact with each other, but when the core material 4 is pulled out, the core material 4 is peeled off from the inner peripheral surface 2a of the insulator 2. The portion of the core material 4 that has peeled off from the inner peripheral surface 2a of the insulator 2 is stretched in the axial direction and becomes thinner, thereby suppressing friction with the inner peripheral surface 2a of the insulator 2. That is, in this embodiment, the core material 4 is pulled out while being stretched in the axial direction in the cavity forming step.

[0035] FIG. 4(a) is a cross-sectional photograph of the leaky waveguide 1 showing the peripheral portion of the slot 30. FIG. 4(b) is an enlarged photograph showing part B in FIG. 4(a). FIG. 4(c) is a schematic diagram showing the boundary of the members in FIG. 4(b). The cross-sectional photograph of FIG. 4(a) shows a state in which a coating layer 7 made of resin is formed on the outer periphery of the metal layer 3, and the insulator 2 and the metal layer 3 are cut together with the coating layer 7.

[0036] 4(c), the protrusions 21 protrude from the inner peripheral surface 3a of the metal layer 3 at the periphery of the slot 30 toward the outer peripheral surface 3b, and are in close contact with the end face 3c of the metal layer 3 cut by the laser light 60. By forming the protrusions 21 in this manner, it is possible to suppress misalignment of the slot 30 with respect to the insulator 2. It is also possible to suppress peeling of the metal layer 3 starting from the end face 3c of the metal layer 3.

[0037] As shown in Figure 4(c), it is desirable that the protrusion 21 covers the entire end face 3c of the metal layer 3 from the inner surface 3a to the outer surface 3b at least in part of the periphery of the slot 30. However, if the protrusion 21 covers at least a part of the end face 3c of the metal layer 3, it is possible to suppress misalignment of the slot 30 and peeling of the metal layer 3.

[0038] (Effects of the embodiment) According to the embodiment described above, the unevenness formed on the outer peripheral surface 2b of the insulator 2 makes it possible to suppress misalignment of the slot 30 relative to the insulator 2, making it easier to direct electromagnetic waves in the desired direction. Furthermore, by forming the metal layer 3 on the outer periphery of the insulator 2 after the insulator 2 has been formed on the outer periphery of the core material 4, the shape of the insulator 2 in the solution in the metal layer formation process can be properly maintained, and even if the insulator 2 is made thin, the metal layer 3 can be formed with a uniform thickness on the outer peripheral surface 2b. In addition, by forming the insulator 2 thin, it is possible to reduce dielectric loss.

[0039] [Manufacturing method variation 1] In the above embodiment, the leaky waveguide 1 is manufactured through an insulator forming process, a roughening process, a metal layer forming process, a slot forming process, and a cavity forming process. However, a temperature change process may be further provided after the metal layer forming process and before the cavity forming process, in which the thermal expansion coefficient of the core material 4 and the thermal expansion coefficient of the insulator 2 are made different from each other, and the temperatures of the core material 4 and the insulator 2 are changed to reduce the adhesion between the core material 4 and the insulator 2.

[0040] For example, if the thermal expansion coefficient of the insulator 2 is higher than that of the core material 4, heating the core material 4 and the insulator 2 causes the insulator 2 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 insulator 2. Also, if the thermal expansion coefficient of the core material 4 is higher than that of the insulator 2, cooling the core material 4 and the insulator 2 causes the insulator 2 to contract at a rate higher than that of the core material 4, thereby reducing the adhesive strength between the core material 4 and the insulator 2.

[0041] Furthermore, when the core material 4 and the insulator 2 are heated together with the metal layer 3 and then cooled, or when the core material 4, the insulator 2, and the metal layer 3 are cooled from room temperature, the thermal expansion coefficient of the resin is generally about 10 times higher than that of the metal, so a peeling force acts between the insulator 2 and the metal layer 3 due to the difference in their contraction rates.However, since the outer surface 2b of the insulator 2 is roughened by the roughening process and the adhesion to the metal layer 3 is increased, the insulator 2 is prevented from peeling off from the metal layer 3.

[0042] In this way, by performing a temperature change process before the cavity formation process, the adhesion between the core material 4 and the insulator 2 is reduced, making it easier to remove the core material 4 during the cavity formation process without causing damage to the insulator 2 or the metal layer 3.

[0043] [Manufacturing method variation 2] In the above embodiment, the slots 30 are formed by removing the metal pieces 300 by laser processing in the slot forming step. However, in this modified example, the slots 30 are formed by not depositing metal in the portions that will become the slots 30 in the metal layer forming step. As described above, when performing electroless plating, palladium, which serves as precipitation nuclei, is adsorbed onto the outer peripheral surface 2 b of the insulator 2. In this modified example, the palladium adsorbed onto the outer peripheral surface 2 b of the insulator 2 in the portions that will become the slots 30 is removed, for example, with laser light, before electroless plating is performed. As a result, metal does not deposit in the portions from which the palladium has been removed, and the slots 30 are formed. In other words, in this modified example, the slot forming step is the process of removing the palladium adsorbed onto the outer peripheral surface 2 b of the insulator 2 in the portions that will become the slots 30.

[0044] [Modifications of the leaky waveguide shape] In the above embodiment, the case where the leaky waveguide 1 has a circular shape in the cross section perpendicular to the axial direction has been described. However, for example, by changing the shape of the core material used in the insulating tube forming process, leaky waveguides of various shapes can be formed depending on the application, etc.

[0045] 5(a) to 5(c) are perspective views showing leaky waveguides 1A to 1C according to first to third modified examples, which have shapes different from those of the above embodiment. The leaky waveguides 1A to 1C have an insulator 2 and a metal layer 3, as in the above embodiment, and a cavity 20 is formed in the center of the insulator 2, but have shapes different from those of the leaky waveguide 1 according to the above embodiment.

[0046] A leaky waveguide 1A according to a first modification shown in Fig. 5(a) has an elliptical shape in a cross section perpendicular to the axial direction. A leaky waveguide 1B according to a second modification shown in Fig. 5(b) has a rectangular shape in a cross section perpendicular to the axial direction. A leaky waveguide 1C according to a third modification shown in Fig. 5(c) has a triangular shape in a cross section perpendicular to the axial direction.

[0047] The leaky 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 leaky waveguide 1A according to the first modification, a core material having an elliptical cross section is used to manufacture the leaky waveguide 1B according to the second modification, and a core material having a triangular cross section is used to manufacture the leaky waveguide 1C according to the third modification. The shape and size of the cavity 20 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 leaky waveguides of various shapes depending on the shape of the core material.

[0048] [Second embodiment] Fig. 6(a) is a perspective cross-sectional view showing an example of the configuration of a leaky coaxial cable 10 according to a second embodiment of the present invention. Fig. 6(b) is a cross-sectional view of the leaky coaxial cable 10 taken along the CC line of Fig. 6(a).

[0049] Like the leaky waveguide 1 according to the first embodiment, the leaky coaxial cable 10 includes an insulator 2 made of linear resin and a metal layer 3 formed on the outer periphery of the insulator 2. A plurality of slots 30 are formed penetrating between the inner circumferential surface 3a and the outer circumferential surface 3b of the metal layer 3. However, the leaky coaxial cable 10 differs from the leaky waveguide 1 in that a central conductor 11 is disposed at the center of the insulator 2. The insulator 2 is cylindrical, and the inner circumferential surface 2a of the insulator 2 is in close contact with the outer circumferential surface 11a of the central conductor 11. The materials and thicknesses of the insulator 2 and the metal layer 3 are the same as those of the first embodiment. The central conductor 11 is made of, for example, copper or aluminum. The metal layer 3 functions as an outer conductor.

[0050] In the leaky coaxial cable 10, similarly to the leaky waveguide 1 according to the first embodiment, the outer peripheral surface 2b of the insulator 2 is roughened so that the surface roughness of the outer peripheral surface 2b is greater than the surface roughness of the inner peripheral surface 2a, and protrusions 21 are formed on the periphery of the slot 30. Misalignment of the slot 30 with respect to the insulator 2 is suppressed by the irregularities formed on the outer peripheral surface 2b of the insulator 2.

[0051] The manufacturing method of the leaky coaxial cable 10 includes an insulator forming step of forming a tubular insulator 2 around the central conductor 11, a roughening step of roughening the outer peripheral surface 2b of the insulator 2, a metal layer forming step of forming a metal layer 3 on the roughened outer peripheral surface 2b of the insulator 2, and a slot forming step of forming a plurality of slots 30 penetrating between the inner peripheral surface 3a and the outer peripheral surface 3b of the metal layer 3. Each of these steps is the same as the insulator forming step, roughening step, metal layer forming step, and slot forming step of the first embodiment.

[0052] Like the first embodiment, the leaky coaxial cable 10 according to the second embodiment also makes it possible to suppress misalignment of the slot 30 with respect to the insulator 2, making it easier to direct electromagnetic waves in a desired direction.

[0053] (Summary of the embodiment) Next, the technical ideas grasped from the above-described embodiments will be described by using the reference numerals and the like in the embodiments. 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 embodiments.

[0054] [1] A leaky cable (leaky waveguide 1, 1A to 1C, leaky coaxial cable 10) comprising a linear insulator (2) and a metal layer (3) formed on the outer peripheral surface (2b) of the insulator (2), in which a slot (30) for leaking electromagnetic waves into the metal layer (3) is formed by penetrating between the inner peripheral surface (3a) and the outer peripheral surface (3b) of the metal layer (3), and in which irregularities are formed on the outer peripheral surface (2b) of the insulator (2) to suppress misalignment of the slot (30) relative to the insulator (2).

[0055] [2] The leakage cable (1, 1A to 1C, 10) described in [1] above, wherein a part of the insulator (2) protrudes from the inner surface (3a) of the metal layer (3) toward the outer surface (3b) at the peripheral portion of the slot (30).

[0056] [3] The leakage cable (1, 1A to 1C, 10) described in [2] above, wherein the insulator (2) is made of a thermoplastic resin, and the portion of the insulator (2) is a solidified portion of the molten resin that melted the insulator (2) due to the heat of the laser light (60) when forming the slot (30) in the metal layer (3).

[0057] [4] The leakage cable (1, 1A to 1C, 10) according to the above [1], wherein the insulator (2) is formed in a cylindrical shape, and the surface roughness of the outer peripheral surface (2b) of the insulator (2) is greater than the surface roughness of the inner peripheral surface (2a) of the insulator (2).

[0058] [5] The leakage cable (1, 1A to 1C, 10) according to the above [4], wherein the surface roughness (Sa) of the outer surface (2b) of the insulator (2) in the portion covered with the metal layer (3) is 0.8 μm or more and 6.0 μm or less.

[0059] [6] The leakage cable (1, 1A to 1C) according to any one of [1] to [5] above, wherein the insulator (2) is hollow.

[0060] [7] The leakage cable (10) according to any one of [1] to [5] above, wherein a central conductor (11) is disposed at the center of the insulator (2).

[0061] [8] A method for manufacturing a leakage cable (1, 1A to 1C, 10), comprising: an insulator forming step of forming a tubular insulator (2) made of a thermoplastic resin; a roughening step of roughening the outer surface (2b) of the insulator (2); a metal layer forming step of forming a metal layer (3) on the outer surface (2b) of the insulator (2); and a slot forming step of forming a slot (30) penetrating between the inner surface (3a) and the outer surface (3b) of the metal layer (3) to leak electromagnetic waves to the outside of the metal layer (3).

[0062] [9] The method for manufacturing the leakage cable (1, 1A to 1C, 10) described in [8] above, wherein the slot forming process is a process of applying a laser beam (60) to the outer peripheral surface (3b) of the metal layer (3) to open the slot (30) and melt a part of the insulator (2), and a part of the re-solidified resin portion formed by solidifying the molten resin protrudes from the inner peripheral surface (3a) side of the metal layer (3) toward the outer peripheral surface (3b) side at the periphery of the slot (30).

[0063]

[10] The method for manufacturing the leakage cable (1, 1A to 1C) described in [8] above, wherein the insulator forming process is a process for forming the insulator (2) on the outer periphery of an axial core material (4), and includes a cavity forming process for removing the core material (4) and forming a cavity (20) in the center of the insulator (2) after the metal layer forming process or the slot forming process.

[0064]

[11] A method for manufacturing a leaky cable (1, 1A to 1C) according to the above

[10] , wherein the core material (4) is made of resin, and the cavity forming process is a process of pulling out the core material (4) while stretching it in the axial direction.

[0065]

[12] A method for manufacturing a leaky cable (1, 1A to 1C) described in

[10] or

[11] above, wherein the core material (4) and the insulator (2) have different thermal expansion coefficients, and further includes a temperature change process before the cavity formation process, in which the temperatures of the core material (4) and the insulator (2) are changed to reduce the adhesion between the core material (4) and the insulator (2).

[0066] 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.

[0067] Furthermore, the present invention can be appropriately modified and implemented without departing from the spirit and scope of the present invention. For example, in the first and second embodiments, the outer peripheral surface 2b of the insulator 2 is roughened by dry ice blasting. However, the outer peripheral surface 2b of the insulator 2 may be roughened by other mechanical or chemical methods. In addition, in the first and second embodiments, the unevenness caused by the roughening process and the unevenness caused by the protrusions 21 formed in the slot forming process are used to prevent misalignment of the slots 30 relative to the insulator 2. However, the present invention is not limited to this. For example, the unevenness caused by the roughening process alone may prevent misalignment of the slots 30, or the unevenness caused by the protrusions 21 alone may prevent misalignment of the slots 30. In other words, the unevenness that prevents misalignment of the slots 30 relative to the insulator 2 may be formed in at least one of the roughening process and the slot forming process. [Explanation of symbols]

[0068] 1...Leaky waveguide (leaky cable) 1A~1C...Leaky waveguide (leaky cable) 10...Leaky coaxial cable (leaky cable) 11...Center conductor 2...insulator 2a...inner surface 2b…Outer surface 20…Cavity 21...Protrusion 3...Metal layer 3a…Inner peripheral surface 3b…Outer peripheral surface 30...Slot 4...Core 60...Laser light

Claims

1. A leakage cable comprising a linear insulator and a metal layer formed on an outer peripheral surface of the insulator, wherein slots for leaking electromagnetic waves into the metal layer are formed by penetrating between an inner peripheral surface and an outer peripheral surface of the metal layer, a protrusion formed by a portion of the insulator protruding from the inner peripheral surface of the metal layer at the peripheral portion of the slot toward the outer peripheral surface thereof, the protrusion being in close contact with at least a portion of the end surface of the metal layer at the peripheral portion of the slot and engaging with the slot; Leaky cable.

2. the insulator is made of a thermoplastic resin, the portion of the insulator is a portion where molten resin that has melted the insulator due to heat from the laser light when the slot is formed in the metal layer has solidified.

2. The leaky cable of claim 1.

3. The insulator is formed in a cylindrical shape, the surface roughness of the outer circumferential surface of the insulator is greater than the surface roughness of the inner circumferential surface of the insulator; 2. The leaky cable of claim 1.

4. The surface roughness (Sa) of the outer peripheral surface of the insulator in the portion covered with the metal layer is 0.8 μm or more and 6.0 μm or less.

4. The leaky cable of claim 3.

5. The insulator is hollow. A leaky cable according to any one of claims 1 to 4.

6. A central conductor is disposed in the center of the insulator. A leaky cable according to any one of claims 1 to 4.

7. an insulator forming step of forming a tubular insulator made of a thermoplastic resin; a roughening step of roughening the outer peripheral surface of the insulator; a metal layer forming step of forming a metal layer on the outer peripheral surface of the insulator; a slot forming step of forming slots that penetrate between the inner and outer peripheral surfaces of the metal layer and allow electromagnetic waves to leak to the outside of the metal layer, the slot forming step is a step of applying a laser beam to an outer peripheral surface of the metal layer to open the slot and melt a part of the insulator, a part of the resolidified resin portion formed by solidifying the molten resin protrudes from the inner peripheral surface side of the metal layer at the peripheral portion of the slot toward the outer peripheral surface side to form a protrusion, and the protrusion is in close contact with at least a part of the end face of the metal layer at the peripheral portion of the slot to engage with the slot; Leaky cable manufacturing method.

8. the insulator forming step is a step of forming the insulator on an outer periphery of a shaft-shaped core material, a cavity forming step of removing the core material to form a cavity in the center of the insulator after the metal layer forming step or the slot forming step; A method for manufacturing a leaky cable according to claim 7.

9. The core material is made of resin, The cavity forming step is a step of extracting the core material while stretching it in the axial direction. A method for manufacturing a leaky cable according to claim 8.

10. The core material and the insulator have different thermal expansion coefficients, The method further includes a temperature change step of changing temperatures of the core material and the insulator to reduce adhesion between the core material and the insulator before the cavity forming step.

10. A method for manufacturing a leaky cable according to claim 8 or 9.

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