Coaxial cable

Abstract

A coaxial cable includes an inner conductor formed by twisting one center conductor and six outer peripheral conductors around the center conductor, an insulator covering the outer periphery of the inner conductor, and a shield conductor covering the outer periphery of the insulator. In a cross section of the coaxial cable perpendicular to a longitudinal direction, a ratio of a total of areas of first regions, which are gaps formed between the center conductor and two adjacent outer peripheral conductors, to an area of a circumscribed circle of the inner conductor is 0.5% or more and 2.0% or less, and a ratio of a total of areas of second regions, which are gaps formed by surfaces of two adjacent outer peripheral conductors and a surface of the insulator, to the area of the circumscribed circle of the inner conductor is 2.0% or more and 5.0% or less.

Description

Technical Field

[0001] This disclosure relates to a coaxial cable.

[0002] This application claims priority based on Japanese Application No. 2020-155643, filed on September 16, 2020, and incorporates all the contents of that Japanese application. Background Technology

[0003] Patent Document 1 discloses a shielded cable comprising: an inner conductor; an insulator disposed to cover the outer periphery of the inner conductor; and an outer conductor disposed to cover the outer periphery of the insulator, the outer conductor having: a first outer conductor comprising a transversely wound shielding member formed by spirally winding a first wire around the outer periphery of the insulator; and a second outer conductor comprising a braided shielding member formed by braiding a second wire and covering the outer periphery of the first outer conductor.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2019-175781 Summary of the Invention

[0007] The coaxial cable disclosed herein comprises: an inner conductor formed by twisting a central wire with six outer peripheral wires arranged around the central wire; an insulator covering the outer periphery of the inner conductor; and a shielding conductor covering the outer periphery of the insulator. In a cross-section of the coaxial cable perpendicular to its longitudinal direction, the total area of ​​a first region is 0.5% to 2.0% of the area of ​​the circumcircle of the inner conductor, the first region being a gap formed between the central wire and two adjacent outer peripheral wires; and the total area of ​​a second region is 2.0% to 5.0% of the area of ​​the circumcircle of the inner conductor, the second region being a gap formed by the surfaces of the two adjacent outer peripheral wires and the surface of the insulator. Attached Figure Description

[0008] Figure 1 This is a cross-sectional view of a coaxial cable according to one embodiment of the present disclosure, taken at a plane perpendicular to its length.

[0009] Figure 2 This is a cross-sectional view of the internal conductor of a coaxial cable according to one embodiment of the present disclosure, at a plane perpendicular to the longitudinal direction.

[0010] Figure 3 yes Figure 1 An enlarged view of region A in the image.

[0011] Figure 4 This is an explanatory diagram of the bending test.

[0012] Figure 5 This is a photograph of a section perpendicular to the longitudinal direction of the inner conductor used in Experiment Example 1.

[0013] Figure 6 This is a photograph of a section perpendicular to the longitudinal direction of the inner conductor used in Experiment Example 2.

[0014] Figure 7 This is a photograph of a section perpendicular to the longitudinal direction of the inner conductor used in Experiment Example 3. Detailed Implementation

[0015] [The problem this disclosure aims to solve]

[0016] As disclosed in Patent Document 1, a coaxial cable for transmitting high-speed signals has been previously studied. However, the data transmission speed between electronic devices is increasing rapidly. Consequently, the required transmission speed and bandwidth for coaxial cables connecting electronic devices are also gradually increasing in speed and frequency.

[0017] As a characteristic value for evaluating coaxial cables used in high-speed transmission, time delay (Skew) is known. Time delay is a value defined as the difference in delay time between two coaxial cables of the same length and type.

[0018] Thunderbolt 3 (registered trademark), a high-speed general-purpose data transmission technology that has already been put into practical use, requires a latency of less than 10 ps / m. Furthermore, in data transmission standards that are faster than Thunderbolt 3, there is a higher probability that latency values ​​smaller than 10 ps / m will be required.

[0019] To achieve this time delay, the unevenness of the time delay in the coaxial cable also needs to be smaller than the previous requirement.

[0020] In addition, coaxial cables are sometimes repeatedly bent depending on the installation location and usage plan, so excellent bending resistance is also required.

[0021] Therefore, the purpose of this disclosure is to provide a coaxial cable with excellent bending resistance and suppression of time lag unevenness.

[0022] [The Effects of This Disclosure]

[0023] According to this disclosure, a coaxial cable with excellent bending resistance and suppressed time lag unevenness can be provided.

[0024] The following describes the implementation method.

[0025] [Description of embodiments of this disclosure]

[0026] First, embodiments of this disclosure are listed for illustration. In the following description, the same or corresponding elements are labeled with the same reference numerals, and they are not described in the same way repeatedly.

[0027] (1) A coaxial cable according to one embodiment of the present disclosure comprises: an inner conductor formed by twisting a central wire with six outer peripheral wires arranged around the central wire; an insulator covering the outer periphery of the inner conductor; and a shielding conductor covering the outer periphery of the insulator. In a cross-section of the coaxial cable perpendicular to the longitudinal direction, the total area of ​​a first region is 0.5% or more and 2.0% or less relative to the area of ​​the circumcircle of the inner conductor. The first region is a gap formed between the central wire and two adjacent outer peripheral wires. The total area of ​​a second region is 2.0% or more and 5.0% or less relative to the area of ​​the circumcircle of the inner conductor. The second region is a gap formed by the surfaces of the two adjacent outer peripheral wires and the surface of the insulator.

[0028] The area ratio of the total area of ​​the first region to the area of ​​the outer circle of the inner conductor is defined as the area ratio of the first region, which is the gap formed between the center wire and the two adjacent outer peripheral wires.

[0029] In this case, by setting the area ratio of the first region to 2.0% or less, the inner conductor is sufficiently compressed, suppressing any unevenness on the outer surface of the inner conductor. Therefore, when the insulator is placed around the outer periphery of the inner conductor, the generation of gaps between the inner conductor and the insulator can be suppressed, and the unevenness in the amount of gaps can be suppressed. As a result, the unevenness of the electrostatic capacitance of the coaxial cable can be suppressed, thereby suppressing the unevenness of the time delay.

[0030] However, excessive compression of the internal conductor would require multiple processes, potentially reducing productivity. Therefore, the area ratio of the first region is preferably 0.5% or more. Setting the area ratio of the first region to 0.5% or more improves productivity.

[0031] The area ratio of the total area of ​​the second region relative to the area of ​​the outer circle of the inner conductor is set as the area ratio of the second region, which is the gap formed by the surfaces of the two adjacent outer wires and the surface of the insulator.

[0032] The area ratio of the second region indicates the degree to which the surface irregularities of the inner conductor fill the insulator. Therefore, by setting the area ratio of the second region to 5.0% or less, the amount of voids between the inner conductor and the insulator is sufficiently suppressed. As a result, the unevenness of the electrostatic capacitance inherent in the coaxial cable can be suppressed, thereby suppressing the unevenness of the time delay.

[0033] However, it is difficult to completely fill the insulator with the unevenness of the inner conductor's surface. Therefore, the area ratio of the second region is preferably 2.0% or more. By setting the area ratio of the second region to 2.0% or more, productivity can be improved.

[0034] (2) Alternatively, the total length of the contact portion where the circumference of the outer circle of the inner conductor meets the length of the inner conductor is more than 40% and less than 70% of the circumference of the outer circle.

[0035] The ratio of the total length of the contact portion between the circumference of the inner conductor and the inner conductor to the circumference of the circumference of the inner conductor is defined as the contact portion ratio.

[0036] If the inner conductor is completely compressed, the cross-section of the inner conductor perpendicular to its longitudinal direction becomes circular, completely overlapping with the circumscribed circle. That is, the proportion of the aforementioned contact portion becomes 100%.

[0037] However, excessive compression of the internal conductor would increase the number of processes and potentially decrease productivity. Therefore, the proportion of the contact portion is preferably 70% or less. Setting the proportion of the contact portion to 70% or less improves productivity.

[0038] Furthermore, by setting the contact portion to over 40%, the inner conductor is sufficiently compressed. Therefore, when the insulator is positioned around the outer periphery of the inner conductor, the amount of void between the inner conductor and the insulator can be sufficiently suppressed. As a result, the uneven electrostatic capacitance inherent in coaxial cables can be suppressed, thereby suppressing uneven time delays.

[0039] (3) Alternatively, the outer diameter of the circumscribed circle of the inner conductor may be 0.1 mm or more and 0.4 mm or less.

[0040] By setting the outer diameter of the inner conductor's outer circle to 0.4 mm or less, the outer diameter of the coaxial cable can be controlled, thereby enabling the manufacture of a coaxial cable with excellent usability. Furthermore, by setting the outer diameter of the inner conductor's outer circle to 0.1 mm or more, a coaxial cable with high reliability can be manufactured.

[0041] (4) Alternatively, the outer diameter of the insulator may be 0.25 mm or more and 1.5 mm or less.

[0042] By setting the outer diameter of the insulator to 0.25 mm or more, the bending resistance can be significantly improved. Furthermore, by setting the outer diameter of the insulator to 1.5 mm or less, fine-diameter coaxial cables can be manufactured, thereby improving usability.

[0043] (5) Alternatively, the center wire and the outer peripheral wire may be silver-plated soft copper wire.

[0044] By using silver-plated soft copper wire as the material for the inner conductor's center wire and the outer wire, coaxial cables with high reliability and excellent high-frequency characteristics can be manufactured.

[0045] (6) Alternatively, the shielding conductor may be wound laterally.

[0046] By making the shielding conductor laterally wound, a coaxial cable that is more flexible than one with a braided construction can be made, thereby improving its bending resistance.

[0047] (7) Alternatively, the total area of ​​the third region may be more than 7% and less than 14% of the area of ​​the outer circle of the inner conductor, and the third region may be the area enclosed by the outer circle of the inner conductor and the surfaces of the two adjacent outer peripheral wires.

[0048] The area ratio of the total area of ​​the third region relative to the area of ​​the outer circle of the inner conductor is set as the area ratio of the third region, which is the area enclosed by the outer circle of the inner conductor and the surfaces of the two adjacent outer wires.

[0049] The area ratio of the aforementioned third region serves as an indicator of the degree of unevenness of the outer surface of the inner conductor. Furthermore, the area ratio of the third region also serves as an indicator of the degree of compression of the inner conductor; the higher the degree of compression, the smaller the area ratio of the third region.

[0050] By setting the area ratio of the third region to 14% or less, the inner conductor is sufficiently compressed, suppressing any unevenness on the outer surface of the inner conductor. Therefore, when the insulator is placed around the outer periphery of the inner conductor, the generation of gaps between the inner conductor and the insulator can be suppressed, as can the unevenness in the amount of gaps. As a result, the unevenness of the electrostatic capacitance inherent in the coaxial cable can be suppressed, thereby suppressing the unevenness of the time delay.

[0051] However, excessive compression of the internal conductor would increase the number of processes, potentially decreasing productivity. Therefore, the area ratio of the third region is preferably 7% or more. Setting the area ratio of the third region to 7% or more improves productivity.

[0052] Furthermore, by setting the area ratio of the third region to 7% or more, a suitable unevenness can be left on the surface of the inner conductor, thus improving the fit between the inner conductor and the insulator when the insulator is placed on the outer periphery of the inner conductor.

[0053] (8) Alternatively, the insulator may contain a fluoropolymer.

[0054] By using fluoropolymer resin as the insulation material, coaxial cables can be heat-resistant, oil-resistant, and easily bent.

[0055] [Details of the embodiments of this disclosure]

[0056] Hereinafter, a specific example of a coaxial cable according to one embodiment of the present disclosure (hereinafter referred to as "this embodiment") will be described with reference to the accompanying drawings. It should be noted that the present invention is not limited to these examples, but is shown in the claims and is intended to include all modifications with the same meaning and scope as the claims.

[0057] (coaxial cable)

[0058] exist Figure 1 The diagram shows an example of a cross-section of the coaxial cable of this embodiment that is perpendicular to its longitudinal direction. Figure 2 The diagram shows an enlarged view of the internal conductor 11. Furthermore, in... Figure 3 shown in the Figure 1 The enlarged image of region A.

[0059] like Figure 1 As shown, the coaxial cable 10 of this embodiment may include: an inner conductor 11; an insulator 14 covering the outer periphery of the inner conductor 11; and a shielding conductor 15 covering the outer periphery of the insulator 14.

[0060] The inner conductor 11 has a center wire 12 and six outer peripheral wires 13 arranged around the center wire 12. The inner conductor 11 may be configured as a stranded wire formed by twisting the center wire 12 and the six outer peripheral wires 13 together.

[0061] The following is a description of each component.

[0062] (1) Internal conductor

[0063] (1-1) Regarding materials

[0064] The materials of the center wire 12 and the outer peripheral wire 13 constituting the inner conductor 11 are not particularly limited, and silver-plated soft copper wire can be preferred.

[0065] By using silver-plated soft copper wire as the material for the center wire 12 and the outer peripheral wire 13 of the inner conductor 11, a coaxial cable with high reliability and excellent high-frequency characteristics can be manufactured.

[0066] (1-2) Regarding the structure

[0067] The inner conductor 11 can be configured as a compressed conductor formed by compression from the outer periphery. Figure 1 , Figure 2 In the diagram, each wire is schematically shown as a circle, but due to the compression as described above, each wire is not a perfect circle but has a compressed and deformed shape.

[0068] The time delay of a coaxial cable is generally determined by three parameters: the outer diameter of the inner conductor, the outer diameter of the insulator, and the electrostatic capacitance of the coaxial cable. Furthermore, to suppress the unevenness of the time delay, it is necessary to suppress the unevenness of the coaxial cable's time delay. However, the outer diameters of the inner conductor and the insulator are subject to limited adjustment due to constraints such as coaxial cable standards. Therefore, to reduce the unevenness of the time delay, it is also necessary to consider suppressing the unevenness of the electrostatic capacitance of the coaxial cable.

[0069] When stranded wire is used as the inner conductor 11, the unevenness of the electrostatic capacitance of the coaxial cable is caused by the random generation of gaps between the inner conductor 11 and the insulator 14 due to the unevenness of the surface of the stranded wire. Therefore, by suppressing the generation of these gaps and suppressing the unevenness of the amount of the generated gaps, the unevenness of the electrostatic capacitance of the coaxial cable can be suppressed.

[0070] Furthermore, by using a stranded compressed conductor as the inner conductor 11, unevenness generated on the outer surface of the inner conductor can be suppressed. Therefore, the generation of gaps between the inner conductor 11 and the insulator 14 can be suppressed, and the unevenness in the amount of gaps generated can be suppressed. Moreover, by using stranded wire as the inner conductor 11 as described above, a coaxial cable with excellent bending resistance can be manufactured.

[0071] The outer diameter D11 of the circumcircle C11 of the inner conductor 11 is not particularly limited, but is preferably 0.1 mm or more and 0.4 mm or less, more preferably 0.15 mm or more and 0.3 mm or less. By setting the outer diameter D11 of the circumcircle C11 of the inner conductor 11 to 0.4 mm or less, the outer diameter of the coaxial cable can be suppressed, thereby enabling the manufacture of a coaxial cable with excellent usability. Furthermore, by setting the outer diameter D11 of the circumcircle C11 of the inner conductor 11 to 0.1 mm or more, a coaxial cable with high reliability can be manufactured.

[0072] It should be noted that the outer diameter D11 of the circumcircle C11 of the inner conductor 11 is equivalent to the outer diameter of the inner conductor 11.

[0073] (1-2-1) Area proportion of the first region

[0074] Here, in the cross-section of the coaxial cable 10 perpendicular to its longitudinal direction, the first region 21 (refer to...) Figure 2 The area ratio of the total area of ​​the inner conductor 11 to the area of ​​the outer circle C11 is defined as the area ratio of the first region 21, which is the gap formed between the center wire 12 and the two adjacent outer peripheral wires 13. It should be noted that, as described above, the area of ​​the first region 21 and the area of ​​the outer circle C11 are calculated from the area of ​​a cross-section of the coaxial cable 10 perpendicular to its longitudinal direction. Furthermore, the area of ​​the outer circle C11 is the area of ​​a circle calculated based on its outer diameter D11. In the coaxial cable of this embodiment, the area ratio of the first region is preferably 0.5% or more and 2.0% or less, more preferably 0.6% or more and 1.9% or less.

[0075] like Figure 2 As shown, the gap formed between the central wire 12 and the two adjacent outer peripheral wires 131 and 132 is designated as the first region 21. The inner conductor 11 has six such first regions 21 along the circumference of the central wire 12, and the total area of ​​the six first regions 21 is the total area of ​​the aforementioned first regions 21.

[0076] Furthermore, the area ratio of the first region can be calculated using the following formula (1).

[0077] (Area ratio of the first region) = (Total area of ​​the first region) ÷ (Area of ​​circumcircle C11) × 100……(1)

[0078] By setting the area ratio of the first region to 2.0% or less, the inner conductor 11 is sufficiently compressed, suppressing any unevenness on the outer surface of the inner conductor 11. Therefore, when the insulator 14 is disposed around the outer periphery of the inner conductor 11, the generation of gaps between the inner conductor 11 and the insulator 14 can be suppressed, and the unevenness in the amount of gaps can be suppressed. As a result, the unevenness of the electrostatic capacitance of the coaxial cable can be suppressed, thereby suppressing the unevenness of the time delay.

[0079] However, excessive compression of the internal conductor 11 would require multiple processes, potentially reducing productivity. Therefore, the area ratio of the first region is preferably 0.5% or more. Setting the area ratio of the first region to 0.5% or more improves productivity.

[0080] (1-2-2) Area proportion of the second region

[0081] Refer to the second region 31 Figure 3The area ratio of the total area of ​​the inner conductor 11 to the area of ​​the outer circle C11 is defined as the area ratio of the second region 31, which is the gap formed by the surfaces of the two adjacent outer wires 131 and 132 and the surface of the insulator 14. It should be noted that the area of ​​the second region 31 is the area calculated in a cross-section of the coaxial cable 10 perpendicular to its longitudinal direction. In the coaxial cable of this embodiment, the area ratio of the second region is preferably 2.0% or more and 5.0% or less, more preferably 2.5% or more and 4.5% or less.

[0082] As a result Figure 1 The enlarged image of region A Figure 3 As shown, the gap formed by the surfaces of the two adjacent outer peripheral wires 131 and 132 and the surface of the insulator 14 is defined as the second region 31. The inner conductor 11 has six such second regions along its circumference, and the total area of ​​the six second regions 31 is the total area of ​​the aforementioned second regions 31.

[0083] Furthermore, the area ratio of the second region mentioned above can be calculated using the following formula (2).

[0084] (Area ratio of the second region) = (Total area of ​​the second region) ÷ (Area of ​​circumcircle C11) × 100……(2)

[0085] The area ratio of the second region indicates the degree to which the surface of the inner conductor 11 is filled with the insulator 14. Therefore, by setting the area ratio of the second region to 5.0% or less, the amount of voids between the inner conductor 11 and the insulator 14 is sufficiently suppressed. As a result, the unevenness of the electrostatic capacitance of the coaxial cable can be suppressed, thereby suppressing the unevenness of the time delay.

[0086] However, it is difficult to completely fill the insulator 14 with the unevenness of the surface of the inner conductor 11. Therefore, the area ratio of the second region is preferably 2.0% or more. By setting the area ratio of the second region to 2.0% or more, productivity can be improved.

[0087] (1-2-3) Area proportion of the third region

[0088] The third region 22 (refer to) Figure 2The area ratio of the total area of ​​the inner conductor 11 to the area of ​​the outer circle C11 is defined as the area ratio of the third region. This third region is the area enclosed by the outer circle C11 of the inner conductor 11 and the surfaces of the two adjacent outer peripheral wires 13. It should be noted that the area of ​​the third region 22 is calculated from the cross-section of the coaxial cable 10 perpendicular to its longitudinal direction. In the coaxial cable of this embodiment, the area ratio of the third region is preferably 7% or more and 14% or less, more preferably 9% or more and 13.5% or less.

[0089] like Figure 2 As shown, the area enclosed by the outer circle C11 of the inner conductor 11 and the surfaces of the two adjacent outer peripheral wires 131 and 132 is designated as the third region 22. The inner conductor 11 has six such third regions along its circumference, and the total area of ​​the six third regions 22 is the total area of ​​the aforementioned third region 22.

[0090] Furthermore, the area ratio of the aforementioned third region can be calculated using the following formula (3).

[0091] (Area ratio of the third region) = (Total area of ​​the third region) ÷ (Area of ​​circumcircle C11) × 100……(3)

[0092] The area ratio of the third region 22 serves as an indicator of the degree of unevenness of the outer surface of the inner conductor 11. Furthermore, the area ratio of the third region 22 also serves as an indicator of the degree of compression of the inner conductor 11; the higher the degree of compression, the smaller the area ratio of the third region 22.

[0093] By setting the area ratio of the third region to 14% or less, the inner conductor 11 is sufficiently compressed, suppressing any unevenness on the outer surface of the inner conductor 11. Therefore, when the insulator 14 is positioned around the outer periphery of the inner conductor 11, the generation of gaps between the inner conductor 11 and the insulator 14 can be suppressed, as can the unevenness in the amount of gaps. As a result, the unevenness of the electrostatic capacitance inherent in the coaxial cable can be suppressed, thereby suppressing the unevenness of the time delay.

[0094] However, excessive compression of the internal conductor 11 would increase the number of processes and potentially decrease productivity. Therefore, the area ratio of the third region is preferably 7% or more. Setting the area ratio of the third region to 7% or more improves productivity.

[0095] Furthermore, by setting the area ratio of the third region to 7% or more, a suitable unevenness can be left on the surface of the inner conductor. Therefore, when the insulator 14 is disposed on the outer periphery of the inner conductor 11, the tightness between the inner conductor 11 and the insulator 14 can be improved.

[0096] (1-2-4) The ratio of the total length of the circumference of the inner conductor to the length of the contact portion where the inner conductor meets the circumference of the circumference of the inner conductor.

[0097] The total length of the circumference of the circumcircle C11 of the inner conductor 11 and the contact portion 23 that connects to the inner conductor 11 is preferably 40% or more and 70% or less of the circumference of the circumcircle C11. It should be noted that the length of the contact portion 23 is the length obtained from the cross-section of the coaxial cable 10 perpendicular to the longitudinal direction.

[0098] For example, Figure 2 As shown, contact portion 23 refers to the portion where the circumference of the outer circle C11 of the inner conductor 11 connects with the inner conductor 11. The inner conductor 11 has six such contact portions along the circumference of the outer circle C11. Therefore, the total length of these six contact portions 23 is the total length of the contact portions 23 where the circumference of the outer circle C11 connects with the inner conductor 11 (hereinafter also referred to as "the total length of the contact portions").

[0099] The ratio of the total length of the circumference of the outer circle of the inner conductor to the length of the contact portion where the inner conductor connects (hereinafter also referred to as the "proportion of the contact portion") can be calculated by the following formula (4).

[0100] (Proportion of the contact area) = (Total length of the contact area) ÷ (Circumference of the circumference of the circumcircle C11) × 100……(4)

[0101] If the inner conductor 11 is completely compressed, the cross-section of the inner conductor 11 perpendicular to its longitudinal direction becomes circular, completely overlapping with the circumscribed circle C11. That is, the proportion of the aforementioned contact portion becomes 100%.

[0102] However, as already described, excessive compression of the internal conductor 11 would increase the number of processes and likely decrease productivity. Therefore, the proportion of the contact portion is preferably 70% or less. By setting the proportion of the contact portion to 70% or less, productivity can be improved.

[0103] Furthermore, by setting the proportion of the contact portion to 40% or more, the inner conductor is sufficiently compressed. Therefore, when the insulator 14 is positioned on the outer periphery of the inner conductor 11, the amount of void between the inner conductor 11 and the insulator 14 can be sufficiently suppressed. As a result, the unevenness of the electrostatic capacitance inherent in the coaxial cable can be suppressed, thereby suppressing the unevenness of the time delay.

[0104] (2) Insulator

[0105] (2-1) About the materials

[0106] The material of insulator 14 is not particularly limited; for example, fluoropolymer can be used. That is, insulator 14 may contain fluoropolymer.

[0107] By using fluororesin as the material for insulator 14, it can be heat-resistant, oil-resistant, and easily bent.

[0108] As a fluoropolymer, one or more of the following can be used, for example: ethylene-tetrafluoroethylene copolymer (ETFE), polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), vinylidene fluoride resin (PVDF), etc.

[0109] The insulator 14 can be coated onto the inner conductor 11, for example, by stretch forming.

[0110] (2-2) Regarding the outer diameter

[0111] The outer diameter D14 of the insulator 14 is not particularly limited, but is preferably 0.25 mm or more and 1.5 mm or less, and more preferably 0.4 mm or more and 1.2 mm or less.

[0112] By setting the outer diameter D14 of the insulator 14 to 0.25 mm or more, the bending resistance can be significantly improved. Furthermore, by setting the outer diameter D14 of the insulator 14 to 1.5 mm or less, a small-diameter coaxial cable can be manufactured, thereby improving usability.

[0113] (3) Shielding conductor

[0114] The shielding conductor 15 has a structure in which the shielding wire 151 is arranged on the outer periphery of the insulator 14 by transverse winding (wrapping) or braiding. The shielding conductor 15 is preferably transversely wound. By making the shielding conductor 15 transversely wound, a coaxial cable that is more flexible than one with a braided structure can be made, thereby improving its bending resistance.

[0115] The material for the shielding wire 151 of the shielding conductor 15 can be copper, aluminum, copper alloy, etc. Therefore, hard copper wire, etc., can also be used as the material for the shielding wire 151. The surface of the shielding wire 151 can also be plated with silver or tin. Therefore, the material for the metal wire of the shielding conductor can, for example, be silver-plated copper alloy, tin-plated copper alloy, etc.

[0116] The shielding conductor 15 can be formed, for example, by overlapping and winding copper-plated polyester tape or the like around the outer surface of the insulator 14.

[0117] (4) Outer skin

[0118] The coaxial cable 10 may also have an outer sheath 16 around the outer periphery of the shielding conductor 15.

[0119] The material of the outer skin 16 is not particularly limited, and resins such as polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), ethylene-tetrafluoroethylene copolymer (ETFE) and polyester resins such as polyethylene terephthalate (PET) can be used.

[0120] For example, the outer sheath 16 can be formed by wrapping polyester tape or the like around the outer periphery of the shielding conductor 15.

[0121] The embodiments have been described in detail above, but are not limited to specific embodiments. Various modifications and alterations can be made within the scope of the claims.

[0122] [Example]

[0123] The following specific embodiments are provided for illustration, but the present invention is not limited to these embodiments.

[0124] (Evaluation Method)

[0125] First, the evaluation method for the coaxial cables produced in the following experimental examples will be explained.

[0126] (1) The outer diameter D11 of the circumcircle C11 of the inner conductor 11 and the outer diameter D14 of the insulator.

[0127] Observe any cross-section of the coaxial cable perpendicular to its length using a microscope, draw the circumcircle C11 of the inner conductor 11, and measure the diameter of the circumcircle C11. From this, calculate the outer diameter D11 of the circumcircle C11 of the inner conductor 11. It should be noted that the outer diameter D11 of the circumcircle C11 of the inner conductor 11 is equivalent to the outer diameter of the inner conductor 11.

[0128] The outer diameter D14 of insulator 14 is determined by observing the cross-section with a microscope, drawing the circumcircle of insulator 14, and measuring the diameter of the circumcircle.

[0129] The area ratios of the first region, the second region, the third region, and the contact area were also measured in the same cross section.

[0130] (2) Area proportions of the first region, the second region, the third region, and the contact area

[0131] Using a microscope, observe any cross-section of the coaxial cable fabricated in the following experimental example perpendicular to its length, and measure the areas of the first region, the second region, and the third region. Then, calculate the area ratios of the first region, the second region, and the third region relative to the area of ​​the circumcircle C11, respectively. The area of ​​the circumcircle C11 is determined based on the previously measured outer diameter D11 of the circumcircle C11 of the inner conductor 11.

[0132] In addition, the total length of the contact portion where the circumference of the inner conductor 11's outer circle C11 meets the length of the inner conductor 11 in the observed image is measured, and the proportion of the contact portion to the circumference of the outer circle C11 is calculated.

[0133] (3) Maximum value of time delay

[0134] For one sample, two coaxial cables fabricated in the following experimental example were prepared. Then, electrical pulses were sent to the two high-frequency coaxial cables of specified lengths using a digital serial analyzer, and the delay time per 1m was measured.

[0135] From the measurement results of the delay time of ten samples, the value obtained by subtracting the minimum delay time from the maximum delay time is calculated, and this value is shown in Table 1 as the "maximum value of time delay".

[0136] (4) Bending test

[0137] like Figure 4 As shown, the coaxial cable 10 to be evaluated is positioned and clamped between two horizontally arranged, parallel mandrels 411 and 412 with a diameter of 4 mm. A load of 200g is applied vertically downward to the coaxial cable 10. In this state, the following actions are repeatedly performed: after bending the upper end of the coaxial cable 10 90° horizontally so as to abut the upper side of one mandrel 411, the upper end of the coaxial cable 10 is bent 90° horizontally so as to abut the upper side of the other mandrel 412.

[0138] Then, the number of bends until the coaxial cable broke was counted. It should be noted that one bend is defined as the period from when the coaxial cable is bent to the left until it is bent to the right and then back to the left. A higher number of bends indicates better bending resistance.

[0139] The coaxial cables used in each experimental example will be described below. Experimental examples 1 and 2 are designated as exemplary cases, and experimental example 3 is designated as a comparative case.

[0140] (Experimental Example 1)

[0141] The coaxial cable is made by following these steps.

[0142] A stranded wire, consisting of seven silver-plated soft copper wires with a diameter of 0.102 mm, was prepared. Then, a compressed conductor, formed by compressing this stranded wire, was used as the inner conductor 11.

[0143] It should be noted that stranded wire has a configuration with one center wire and six outer wires. The center wire and the outer wires use the same wire.

[0144] An FEP insulator 14 is disposed around the outer periphery of the inner conductor 11. The thickness of the insulator 14 is adjusted such that the outer diameter of the insulator 14 is 0.79 mm.

[0145] Next, a shielding conductor is formed on the outer periphery of the insulator 14 by laterally winding tinned soft copper wire.

[0146] Furthermore, polyester tape is adhered to the outer periphery of the shielding conductor 15 to form the outer sheath 16, thereby manufacturing the coaxial cable of this experimental example.

[0147] The obtained coaxial cable underwent the evaluation described above. The evaluation results are shown in Table 1. Furthermore, photographs of the cross-section of the inner conductor perpendicular to the longitudinal direction are shown. Figure 5 .

[0148] (Experimental Example 2)

[0149] Except for changing the degree of compression of the stranded wire in the inner conductor 11, the coaxial cable was manufactured and evaluated in the same manner as in Experimental Example 1.

[0150] The results are shown in Table 1. Furthermore, photographs of the cross-section of the internal conductor perpendicular to its long dimension are shown. Figure 6 .

[0151] (Experimental Example 3)

[0152] Except for the use of uncompressed stranded wire for the inner conductor 11, the coaxial cable was fabricated and evaluated in the same manner as in Experimental Example 1.

[0153] The results are shown in Table 1. Furthermore, photographs of the cross-section of the internal conductor perpendicular to its long dimension are shown. Figure 7 .

[0154] [Table 1]

[0155]

[0156] Based on the results shown in Table 1, it was confirmed that the maximum time delay of the coaxial cables in Examples 1 and 2, where the area ratio of the first region is 0.5% or more and 2.0% or less, and the area ratio of the second region is 2.0% or more and 5.0% or less, is 7.5 ps / m or less. That is, compared to the coaxial cable in Example 3, which does not meet the area ratio requirement of the first region, it was confirmed that the time delay unevenness can be suppressed.

[0157] In addition, the bending test results of the coaxial cables in Experiments 1 and 2 were also more than 4,500 times, confirming that they have sufficient bending resistance.

[0158] Explanation of reference numerals in the attached figures

[0159] 10: Coaxial cable

[0160] 11: Internal conductor

[0161] 12: Center wire

[0162] 13, 131, 132: Outer circumference wire

[0163] 14: Insulator

[0164] 15: Shielding conductor

[0165] 151: Shielded Wire

[0166] 16: Outer skin

[0167] 21: Area 1

[0168] 22: Third Zone

[0169] 23: Contact Department

[0170] 31: Second Area

[0171] 411, 412: Mandrel

[0172] A: Area

[0173] C11: Circumcircle

[0174] D11: Outer diameter

[0175] D14: Outer diameter.

Claims

1. A coaxial cable, comprising: An inner conductor is formed by twisting a central wire with six outer peripheral wires arranged around the central wire; An insulator covering the outer periphery of the inner conductor; and The shielding conductor covers the outer periphery of the insulator. In the cross-section of the coaxial cable perpendicular to its longitudinal direction, The total area of ​​the first region is 0.5% to 2.0% of the area of ​​the outer circle of the inner conductor. This first region is the gap formed between the center wire and the two adjacent outer peripheral wires. The total area of ​​the second region is more than 2.0% and less than 5.0% of the area of ​​the outer circle of the inner conductor, and the second region is a gap formed by the surfaces of the two adjacent outer wires and the surface of the insulator.

2. The coaxial cable according to claim 1, wherein, The total length of the contact portion where the circumference of the circumference of the inner conductor meets the contact portion of the inner conductor accounts for more than 40% and less than 70% of the circumference of the circumference of the circumference.

3. The coaxial cable according to claim 1, wherein, The outer diameter of the circumscribed circle of the inner conductor is 0.1 mm or more and 0.4 mm or less.

4. The coaxial cable according to any one of claims 1 to 3, wherein, The outer diameter of the insulator is 0.25 mm or more and 1.5 mm or less.

5. The coaxial cable according to any one of claims 1 to 3, wherein, The center wire and the outer peripheral wire are silver-plated soft copper wires.

6. The coaxial cable according to any one of claims 1 to 3, wherein, The shielding conductor is wound laterally.

7. The coaxial cable according to any one of claims 1 to 3, wherein, The total area of ​​the third region is more than 7% and less than 14% of the area of ​​the circumcircle of the inner conductor. The third region is the area enclosed by the circumcircle of the inner conductor and the surfaces of the two adjacent outer peripheral wires.

8. The coaxial cable according to any one of claims 1 to 3, wherein, The insulator contains fluoropolymer.

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