Two-core cable, manufacturing method of two-core cable

Abstract

To provide a double-core cable in which a mode conversion amount from a differential mode to a common mode is suppressed.SOLUTION: A double-core cable 10 has two covered electric wires 11 having conductors 111 and insulation layers 112 covering the outer surfaces of the conductors, and a metal tape 12 for collectively covering the outer surfaces of the two covered electric wires. The metal tape 12 has a structure that a resin layer and a metal layer are stacked.EFFECT: The resin layer is arranged so as to be positioned on the side of the two covered electric wires, which can suppress a mode conversion amount from a differential mode to a common mode of the double-core cable.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to twin-core cables. [Background technology]

[0002] Patent Document 1 describes a pair of conductors arranged in parallel; a pair of coating layers each including a round pipe-shaped coating layer main body that is formed by extrusion molding on the outer peripheral surfaces of the pair of conductors and that is made of insulating resin and that covers the conductors, and a spiral pleat that is integrally formed on the outer peripheral surface of the coating layer main body; a pair of round pipe-shaped core outer layers each made of an insulating material and provided so as to cover the pair of coating layers; a drain wire provided between the pair of core outer layers; a pair of shielding members for shielding the core outer layer and the drain wire; A twin-ax cable is disclosed, which comprises: [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-259660 Summary of the Invention [Problem to be solved by the invention]

[0004] Two-core cables, also known as twin-ax cables, have been conventionally used for signal transmission and the like, and as disclosed in Patent Document 1, for example, various studies have been conducted to improve performance.

[0005] In recent years, there has been a demand for two-core cables capable of high-speed communication, i.e., capable of transmitting high-frequency signals. To achieve this, there has been a demand for two-core cables that can suppress the amount of mode conversion from differential mode to common mode.

[0006] Therefore, an object of the present disclosure is to provide a two-core cable that suppresses the amount of mode conversion from differential mode to common mode. [Means for solving the problem]

[0007] The two-core cable of the present disclosure comprises two coated wires each having a conductor and an insulating layer covering the outer surface of the conductor; a metal tape that collectively covers the outer surfaces of the two coated electric wires; The metal tape has a structure in which a resin layer and a metal layer are laminated, and is disposed so that the resin layer is located on the side of the two coated electric wires. [Effects of the Invention]

[0008] According to the present disclosure, it is possible to provide a two-core cable in which the amount of mode conversion from differential mode to common mode is suppressed. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a cross-sectional view of a dual-core cable according to one embodiment of the present disclosure taken along a plane perpendicular to the longitudinal direction. [Figure 2] FIG. 2 is a cross-sectional view of a surface of the metal tape along the lamination direction of the resin layer and the metal layer. [Figure 3] FIG. 3 is a cross-sectional view of a dual-core cable according to one embodiment of the present disclosure taken along a plane perpendicular to the longitudinal direction. [Figure 4] FIG. 4 is an explanatory diagram of another example of the structure of the coated electric wire. [Figure 5] FIG. 5 shows the measurement results of Scd21 of the cable produced in Experimental Example 4. DETAILED DESCRIPTION OF THE INVENTION

[0010] The embodiments for carrying out the invention are described below.

[0011] [Description of the embodiments of the present disclosure] First, embodiments of the present disclosure will be listed and described. In the following description, the same or corresponding elements will be denoted by the same reference numerals, and the same description will not be repeated.

[0012] (1) A two-core cable according to one embodiment of the present disclosure includes two covered electric wires each having a conductor and an insulating layer covering the outer surface of the conductor; a metal tape that collectively covers the outer surfaces of the two coated electric wires; The metal tape has a structure in which a resin layer and a metal layer are laminated, and is disposed so that the resin layer is located on the side of the two coated electric wires.

[0013] By arranging the metal tape so that the resin layer is located on the side of the two coated wires, a two-core cable can be created that suppresses the amount of mode conversion from differential mode to common mode.

[0014] (2) In a cross section perpendicular to the longitudinal direction of the two-core cable, the metal tapes are partially overlapped with each other, In the cross section, both ends of the metal tape may be positioned outside in the width direction of the two-core cable relative to the contact points between the outer circumferences of the two insulated electric wires and the common tangent of the outer circumferences of the two insulated electric wires.

[0015] By arranging the ends of the metal tape in the above-described manner, the shape of the two-core cable is stabilized, and the electrical characteristics of the two-core cable can also be stabilized.

[0016] (3) In the cross section, both ends of the metal tape may be located within a region between the contact point and an intersection of the metal tape and a line passing through the centers of the two covered electric wires.

[0017] By arranging the end of the metal tape within the above-mentioned region, the shape of the two-core cable is stabilized, and the electrical characteristics of the two-core cable can also be stabilized.

[0018] (4) The metal tape may be wound around the two insulated electric wires in a longitudinal direction.

[0019] By wrapping the metal tape vertically, the metal tape can be arranged more easily than when it is arranged horizontally.

[0020] (5) The thickness of the resin layer may be 5 μm or more and 25 μm or less.

[0021] By making the resin layer 5 μm or thicker, the thickness of the resin-containing layer placed around the conductor in the two-core cable can be made sufficiently thick, particularly suppressing the amount of mode conversion.Furthermore, by making the resin layer 25 μm or thicker, it becomes easier to wrap a metal tape around the two covered electric wires, and the shape of the two-core cable can be stabilized.

[0022] (6) The resin layer may have a larger dielectric loss tangent than the insulating layer.

[0023] By making the dielectric loss tangent of the resin layer larger than the dielectric loss tangent of the insulating layer, it is possible to suppress common mode signals in particular and reduce the amount of mode conversion.

[0024] (7) The insulating layer may include a foamed layer.

[0025] The relative dielectric constant of air is about 1, which is lower than that of the resin used in the insulation layer, so the relative dielectric constant of the foam layer is lower than that of the solid layer that is not a foam layer. Therefore, by including a foam layer in the insulation layer, the relative dielectric constant of the insulation layer can be reduced, and the thickness of the insulation layer required for a specified characteristic impedance of the insulated electric wire can also be reduced. As a result, the size of the insulated electric wire and the two-core cable can be reduced.

[0026] (8) The foam layer may have an expansion ratio of more than 0 and not more than 70%.

[0027] By setting the foaming ratio of the foam layer to 70% or less, the strength of the foam layer and the insulating layer containing the foam layer can be increased, and the conductor can be protected. Furthermore, by setting the foaming ratio of the foam layer to 70% or less, the shape of the covered electric wire and the two-core cable including the covered electric wire can be stabilized.

[0028] By making the foaming rate of the foam layer greater than 0, the relative dielectric constant of the insulating layer can be reduced, and the size of the coated wire or two-core cable can be reduced.

[0029] [Details of the embodiments of the present disclosure] Specific examples of a two-core cable according to one embodiment of the present disclosure (hereinafter referred to as "the present embodiment") will be described below with reference to the drawings. Note that the present invention is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope of the claims. [Two-core cable] Fig. 1 shows a cross-sectional view of a plane perpendicular to the longitudinal direction of a twin-core cable 10 according to this embodiment. In Fig. 1, the X-axis direction is the width direction of the twin-core cable 10, the Y-axis direction is the thickness direction of the twin-core cable 10, and the Z-axis direction perpendicular to the paper surface is the longitudinal direction of the twin-core cable 10. Furthermore, the outer surface side of the twin-core cable 10 in the width direction (X-axis direction) of the twin-core cable 10 may be referred to as the outside.

[0030] As shown in Fig. 1, a two-core cable 10 of this embodiment has two covered electric wires 11 and a metal tape 12 that collectively covers the outer surfaces of the two covered electric wires 11. Each member of the two-core cable of this embodiment will be described below. (1) Insulated wire 1, the two coated electric wires 11 each include a conductor 111 and an insulating layer 112 that covers the outer surface of the conductor 111. The two coated electric wires 11 can be arranged in parallel without being twisted together. (1-1) Conductor The material of the conductor 111 is not particularly limited, and may be one or more conductor materials selected from, for example, copper, annealed copper, silver, nickel-plated annealed copper, tin-plated annealed copper, etc. For example, the conductor 111 may be subjected to an annealing treatment in order to adjust the elongation, etc.

[0031] The conductor 111 may be a solid wire or a twisted wire, but is preferably a solid wire from the viewpoint of particularly improving the electrical properties of the coated electric wire 11. (1-2) Insulating layer The material of insulating layer 112 is not particularly limited, and can be selected depending on the characteristics required of twin-core cable 10, etc.

[0032] The insulating layer 112 may contain, for example, a resin, and the resin is not particularly limited, but may be one or more types of resin selected from fluororesins such as polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and ethylene-tetrafluoroethylene copolymer (ETFE), polyester resins such as polyethylene terephthalate (PET), and polyolefin resins such as polyethylene and polypropylene. The resin of the insulating layer 112 may or may not be crosslinked.

[0033] In addition to the above resins, the insulating layer 112 may also contain additives such as flame retardants, flame retardant assistants, antioxidants, lubricants, colorants, reflectivity imparting agents, opacifying agents, processing stabilizers, and plasticizers.

[0034] For example, as in the coated electric wire 100 shown in Fig. 4, the insulating layer 112 may have a multilayer structure including multiple layers. Fig. 4 shows an example in which the insulating layer 112 has, in order from the conductor 111 side, a first insulating layer 1121, a second insulating layer 1122, and a third insulating layer 1123, but is not limited to this form, and the insulating layer 112 may also include two layers or four or more layers. When the insulating layer 112 has multiple layers, some or all of the multiple layers may have different compositions, such as materials.

[0035] The insulating layer 112 may include a foamed layer. For example, the second insulating layer 1122 in the coated electric wire 100 shown in Fig. 4 may be a foamed layer. A foamed layer refers to a layer containing air bubbles.

[0036] The relative dielectric constant of air is about 1, which is lower than that of the resin used in the insulating layer 112, and therefore the relative dielectric constant of the foamed layer is lower than that of a solid layer that is not a foamed layer. Therefore, by including a foamed layer in the insulating layer 112, the relative dielectric constant of the insulating layer 112 can be reduced, and the thickness of the insulating layer 112 required to achieve a predetermined characteristic impedance for the covered electric wire 100 can also be reduced. As a result, the size of the covered electric wire 11 and the two-core cable 10 can be reduced.

[0037] Although the degree of foaming in the foam layer is not particularly limited, it is preferable that the insulating layer 112 has a suitable strength because the insulating layer 112 including the foam layer also has the function of protecting the conductor 111. For this reason, the foaming ratio of the foam layer is preferably 70% or less, and more preferably 65% ​​or less.

[0038] By setting the foaming rate of the foam layer to 70% or less, it is possible to increase the strength of the foam layer and the insulating layer 112 containing the foam layer, and to protect the conductor 111. Furthermore, by setting the foaming rate of the foam layer to 70% or less, it is possible to stabilize the shape of the covered electric wire 11 and the two-core cable 10 including the covered electric wire 11.

[0039] Although the lower limit of the foaming rate of the foam layer is not particularly limited, the foaming rate of the foam layer is preferably greater than 0, and more preferably 5% or greater.

[0040] By making the foaming rate of the foam layer larger than 0, the relative dielectric constant of the insulating layer 112 can be reduced, and the size of the coated electric wire 11 and the two-core cable 10 can be reduced.

[0041] When the insulating layer 112 has a foamed layer, it is preferable that it also has a solid layer, which is a layer that is not foamed. The foaming rate of the solid layer is 0. The solid layer makes it easier to maintain the shape of the coated electric wire 11 and also protects the conductor 111. For example, as shown in Figure 4, the insulating layer 112 can have a three-layer structure, with the first insulating layer 1121 and the third insulating layer 1123 being solid layers and the second insulating layer 1122 being a foamed layer.

[0042] The foaming ratio can be calculated from the ratio of specific gravity before and after foaming. Specifically, for example, it can be calculated by dividing the specific gravity measured after foaming by the specific gravity measured before foaming. The specific gravity before foaming can be measured, for example, by cutting out a portion of the foam layer that does not contain bubbles. (2) Metal tape The two-core cable 10 of this embodiment can have a metal tape 12 that collectively covers the two covered electric wires.

[0043] The inventors of the present invention have studied a two-core cable that suppresses the amount of mode conversion from differential mode to common mode, i.e., reduces the common mode. As a result, they have found that in a metal tape that covers two insulated electric wires and has a resin layer and a metal layer, while the metal layer has conventionally been placed on the side of the two insulated electric wires, the amount of mode conversion can be suppressed by placing the resin layer on the side of the two insulated electric wires, and have completed the invention.

[0044] 2 shows a cross-sectional view of the metal tape 12 taken along the lamination direction of the resin layer and the metal layer. As shown in FIG. 2, the metal tape 12 has a structure in which a resin layer 121 and a metal layer 122 are laminated together. That is, the metal tape 12 has a structure in which the resin layer 121 is disposed on one side of the resin layer 121, and the metal layer 122 is disposed on one side of the resin layer 121. In the twin-core cable 10 of this embodiment, the resin layer 121 of the metal tape 12 can be disposed so as to face the two coated electric wires 11. That is, the first surface 21 of the resin layer 121 of the metal tape 12 in FIG. 2 can be disposed on the coated electric wire 11 side, and the second surface 22 of the metal layer 122 can be disposed on the outer surface side of the twin-core cable 10.

[0045] By arranging the metal tape 12 in the above-described manner, i.e., by arranging the resin layer 121 on the side of the two coated electric wires 11, it is possible to obtain a two-core cable 10 in which the amount of mode conversion from differential mode to common mode is suppressed, as described above.

[0046] The distribution of the electromagnetic field formed around the insulated electric wire 11 differs between the differential mode and the common mode.

[0047] In the differential mode, an electromagnetic field is distributed between the conductors 111 and between the conductors 111 and the metal tape 12, and the strength of the electromagnetic field distributed between the conductors 111 is high. In contrast, in the common mode, the electromagnetic field is hardly distributed between the conductors 111, but is distributed mainly between the conductors 111 and the metal tape 12. For this reason, in the common mode, it is thought that the influence of the environment between the conductors 111 and the metal tape 12 is strong. Specifically, it is thought that by arranging the resin layer 121 of the metal tape 12 on the side of the two coated electric wires 11 and increasing the thickness of the layer containing resin, which is made up of the insulating layer 112 and the resin layer 121, it is possible to attenuate the common mode signal and suppress the amount of mode conversion.

[0048] An adhesive layer can also be disposed on the surface of resin layer 121 of metal tape 12, i.e., on first surface 21. By disposing the adhesive layer, metal tape 12 can be adhered to two coated electric wires 11, and the shape of twin-core cable 10 can be stabilized.

[0049] The metal tape 12 can be arranged so as to collectively cover the outer surfaces of the two covered electric wires 11 as shown in Fig. 1. In Fig. 1, the metal tape 12 is linear between the two covered electric wires 11, but is not limited to this form, and may be recessed toward the covered electric wires 11 between the two covered electric wires 11, for example.

[0050] The metal tape 12 is preferably wrapped longitudinally around the two coated electric wires 11. By wrapping the metal tape 12 longitudinally, the arrangement of the metal tape 12 can be simplified compared to when the metal tape 12 is wrapped horizontally.

[0051] In a cross section perpendicular to the longitudinal direction of the twin-core cable 10, the metal tapes 12 are preferably arranged so that they partially overlap each other. In this case, in a cross section perpendicular to the longitudinal direction of the twin-core cable 10, the metal tape 12 has an end 12A and an end 12B that is located on the outer periphery of the end 12A. As shown in FIG. 1, the end 12A located on the inner periphery of the metal tape 12 is covered by the metal tape 12. As shown in FIG. 1, the metal tape 12 can overlap between the end 12A and the end 12B to form two layers.

[0052] In this case, in the cross section, it is preferable that end 12A, which is both end portions of metal tape 12, and end 12B, which is closer to the outer periphery than end 12A, are respectively arranged outside, in the width direction of twin-core cable 10, contact points P1 and P2 between the outer peripheries of two covered electric wires 11 and a common tangent line L1 to the outer peripheries of two covered electric wires 11. As described above, the width direction of twin-core cable 10 is the X-axis direction in Fig. 1, and can also be said to be the direction in which the two covered electric wires are arranged.

[0053] Arranging end 12A and end 12B of metal tape 12 as described above stabilizes the shape of twin-core cable 10 and also stabilizes the electrical characteristics of twin-core cable 10. End 12A and end 12B of metal tape 12 are preferably arranged at positions along the outer surface of coated wire 11 as shown in FIG.

[0054] The length of the overlapping area of ​​the metal tapes 12 in a cross section perpendicular to the longitudinal direction of the two-core cable 10 is not particularly limited, but it is preferable that it be less than half the sum of the length of the area where the metal tapes 12 do not overlap and the length of the overlapping area.

[0055] It is more preferable that the end 12A of the metal tape 12 is disposed within a region R1 between the contact point P1 and point P3, which is the intersection of the line L2 passing through the centers O1 and O2 of the two covered electric wires 11 with the metal tape 12. It is also more preferable that the end 12B of the metal tape 12 is disposed within a region R2 between point P4, which is the intersection of the line L2 passing through the centers O1 and O2 of the two covered electric wires 11 with the metal tape 12, and point P2.

[0056] That is, in the cross section described above, it is more preferable that end 12A and end 12B, which are both ends of metal tape 12, are respectively positioned within region R1 and region R2 between points P3 and P4, which are the intersections of the line passing through the centers of the two coated electric wires 11 and metal tape 12, and the aforementioned contact points P1 and P2.

[0057] By arranging end 12A and end 12B of metal tape 12 within the above-mentioned region, the shape of twin-core cable 10 is stabilized, and the electrical characteristics of twin-core cable 10 can also be stabilized.

[0058] The centers O1 and O2 of the insulated electric wires 11 when drawing the line L2 can be the centers of the circumscribing circles of the insulated electric wires 11.

[0059] The resin layer 121 of the metal tape 12 may be made of any material as long as it contains a resin. The resin may be the same as or different from the resin contained in the insulating layer 112 of the coated electric wire 11.

[0060] The resin layer 121 can also have a dielectric loss tangent (tan δ) greater than that of the insulating layer 112 of the coated electric wire 11. By making the dielectric loss tangent of the resin layer 121 greater than that of the insulating layer 112, it is possible to suppress signals, particularly common mode signals, and to suppress the amount of mode conversion.

[0061] Examples of the resin contained in the resin layer 121 include polyethylene terephthalate (PET) and polyethylene naphthalate (PEN).

[0062] For example, a metal foil can be used as the metal layer 122. There are no particular limitations on the material of the metal foil, but copper or aluminum can be used.

[0063] Although thickness T121 of resin layer 121 is not particularly limited, it is preferably 5 μm or more and 25 μm or less, and more preferably 9 μm or more and 15 μm or less. By setting thickness T121 of resin layer 121 to 5 μm or more, the thickness of the resin-containing layer arranged around conductor 111 in twin-core cable 10 can be made sufficiently thick, and the amount of mode conversion can be particularly suppressed. Furthermore, by setting thickness T121 of resin layer 121 to 25 μm or less, it becomes easier to wrap metal tape 12 around two coated electric wires 11, and the shape of twin-core cable 10 can be stabilized. (3) Retaining wrap In the twin-core cable 10 of this embodiment, a pressure winding 13 can also be arranged so as to cover the outer surface of the metal tape 12. The pressure winding 13 can be formed by winding a tape body spirally around the outer periphery of the metal tape 12 along the longitudinal direction of the twin-core cable 10.

[0064] The presence of the pressure winding 13 in the two-core cable 10 stabilizes the shape of the metal tape 12 and the shape and electrical characteristics of the two-core cable 10. Furthermore, by adjusting the tension applied to the pressure winding 13 when winding the pressure winding 13 around the outer periphery of the metal tape 12, the positions of the ends 12A and 12B of the metal tape 12 can also be adjusted.

[0065] The material of the pressure retainer 13 is not particularly limited, and may be one or more insulating materials selected from, for example, paper, nonwoven fabric, resin such as polyester, and the like.

[0066] The pressure winding 13 may be one layer or two or more layers.

[0067] An adhesive layer can also be disposed on the surface of the pressure winding 13 facing the metal tape 12. By disposing an adhesive layer, the pressure winding 13 can be adhered to the metal tape 12, and the shape of the two-core cable 10 can be stabilized. (4) Drain wire As shown in Fig. 3, the twin-core cable 30 of this embodiment may also have a drain wire 31. The twin-core cable 30 shown in Fig. 3 can be configured in the same manner as the twin-core cable 10 shown in Fig. 1, except for having the drain wire 31. The twin-core cable 30 having the drain wire 31 makes it easier to connect the metal layer 122 of the metal tape 12 to a terminal or the like via the drain wire 31.

[0068] Therefore, the drain wire 31 can be arranged so as to be in contact with the metal layer 122, and for example, as shown in Figure 3, it can be arranged between the metal tape 12 and the pressure winding 13, and the drain wire 31 can be fixed by the pressure winding 13.

[0069] The drain wire 31 may be disposed so as to be in contact with the metal layer 122, and its location is not particularly limited. However, since the allowable range for the thickness of the twin-core cable 30, i.e., the length in the Y-axis direction in Fig. 3, is often narrow, it is preferable that the drain wire 31 be disposed on the side of the twin-core cable 30 so as not to affect the thickness direction of the twin-core cable 30. For example, it is preferable that the drain wire 31 be disposed outside in the width direction, i.e., in the X-axis direction, of a line A that passes through the center O1 of the coated electric wire 11 shown in Fig. 3 and runs along the thickness direction.

[0070] There is no particular limitation on the configuration of the drain wire 31. The drain wire 31 may be a solid wire or a twisted wire.

[0071] The material of the drain wire 31 is not particularly limited, and one or more conductive materials selected from copper, annealed copper, silver, nickel-plated annealed copper, tin-plated annealed copper, etc. For example, the drain wire 31 may be subjected to an annealing treatment in order to adjust the elongation, etc. [Example]

[0072] The present invention will be explained below by giving specific examples, but the present invention is not limited to these examples. (1) Evaluation method The Scd21 was measured for the two-core cables produced in the following experimental examples.

[0073] Scd21 is the amount of mode conversion from differential mode to common mode from port 1 to port 2, and is one of the mixed-mode S-parameters.

[0074] The length of the two-core cable to be measured for Scd21 was 3 m, and it was measured using a network analyzer. Three samples of the same two-core cable were evaluated under the same conditions for the same experimental example. For example, the evaluation results for the two-core cable produced in Experimental Example 4 were as shown in the graph in Figure 5. Note that the evaluation results for the two-core cables produced in the other experimental examples also had similar shapes. Since a smaller maximum Scd21 indicates better suppression of mode conversion, the intensity of the first peak 50 from the lowest frequency side, where the value is greatest, was determined, and the average value for the three samples was used as the Scd21 for that sample. (2) Manufacturing conditions for two-core cable The conditions and results of each experiment are explained below: Experiments 1 to 3 are working examples, and Experiments 4 to 6 are comparative examples. [Experimental Example 1] A two-core cable 30 having the cross-sectional structure shown in FIG. 3 was produced. (1) Insulated wire Each of the two coated electric wires 11 includes a conductor 111 and an insulating layer 112 covering the outer surface of the conductor 111, which will be described below. (conductor) The conductor 111 of the coated electric wire 11 was a single copper wire having an outer diameter of 0.5 mm as shown in Table 1 and having been subjected to an annealing treatment.

[0075] The outer diameter of the conductor 111 was evaluated by the following procedure. In an arbitrary cross section perpendicular to the longitudinal direction of the conductor 111, the outer diameter was measured with a micrometer along two perpendicular diameters of the conductor 111. The average of the measurements at these two points was then taken as the outer diameter of the conductor 111. (insulating layer) The insulating layer 112 of the coated electric wire 11 is an insulating layer made up of three layers, namely, a first insulating layer 1121, a second insulating layer 1122, and a third insulating layer 1123, as shown in FIG.

[0076] The thickness of each layer is as shown in Table 1, with the first layer representing the first insulating layer 1121, the second layer representing the second insulating layer 1122, and the third layer representing the third insulating layer 1123. The thickness of each insulating layer was calculated by measuring the outer diameter of each insulating layer in the same manner as for the conductor 111, subtracting the outer diameter of the layer located inside the insulating layer being evaluated, and then dividing the result by 2. For example, in the case of the first insulating layer 1121, the thickness of the first insulating layer 1121 was calculated by subtracting the outer diameter of the conductor 111 from the outer diameter of the first insulating layer 1121 and dividing the result by 2.

[0077] Polyethylene was used as the resin for all insulating layers 112. Second insulating layer 1122 was a foamed layer with an expansion rate of 50%. First insulating layer 1121 and third insulating layer 1123 were solid layers with no expansion rate, i.e., no expansion rate.

[0078] The foaming ratio of the foam layer was calculated from the ratio of specific gravity before and after foaming. Specifically, it was calculated by dividing the specific gravity measured after foaming by the specific gravity measured before foaming. The specific gravity before foaming was measured by cutting out a portion of the foam layer that did not contain bubbles. The specific gravity was measured in accordance with JIS Z 8807 (2012). (2) Metal tape 2, the metal tape 12 had a structure in which a resin layer 121 and a metal layer 122 were laminated, and had an overall thickness of 0.021 mm, with the thickness T121 of the resin layer 121 being 12 μm and the thickness of the metal layer 122 being 9 μm. The resin layer 121 was made of polyethylene terephthalate, and the metal layer 122 was copper foil. The dielectric loss tangent of the resin layer 121 was larger than the dielectric loss tangent of the insulating layer 112.

[0079] As shown in Fig. 3, the metal tape 12 was longitudinally wrapped around the outer surfaces of the two covered electric wires 11 so as to cover them together, and its width was set to 9 mm so that they partially overlapped in a plane perpendicular to the longitudinal direction of the two-core cable 30. The metal tape 12 was arranged so that the resin layer 121 was located on the side of the two covered electric wires 11. For this reason, the first surface 21 of the resin layer 121 of the metal tape 12 in Fig. 2 was located on the side of the covered electric wires 11, and the second surface 22 of the metal layer 122 was located on the outer surface side of the two-core cable 30.

[0080] In a plane perpendicular to the longitudinal direction of the twin-core cable 30, the ends 12A and 12B of the metal tape 12 were located outside the contact points P1 and P2 between the outer peripheries of the two covered electric wires 11 and a common tangent line L1 to the outer peripheries of the two covered electric wires 11 in the width direction of the twin-core cable (see FIG. 1 ). More specifically, the end 12A of the metal tape 12 was located within a region R1 between a point P3, which is the intersection of a line L2 passing through the centers O1 and O2 of the two covered electric wires 11 with the metal tape 12, and the contact point P1. The end 12B of the metal tape 12 was located within a region R2 between a point P4, which is the intersection of a line L2 passing through the centers O1 and O2 of the two covered electric wires 11 with the metal tape 12, and the contact point P2. In the other experimental examples described below, the ends 12A and 12B of the metal tape 12 were also located within the regions R1 and R2, respectively. (3) Drain wire As the drain wire 31, a single wire having an outer diameter of 0.2 mm and tin-plated copper wire that had been annealed as shown in Table 1 was used.

[0081] As shown in FIG. 3, the drain wire 31 is arranged on the side of the two-core cable 30, specifically, passing through the center O1 of the coated electric wire 11, and on the outside in the width direction, i.e., in the X-axis direction, of a straight line A along the thickness direction. (4) Retaining wrap A polyethylene terephthalate resin tape was used as the pressure winding 13, and the thickness and width were as shown in Table 1. The pressure winding 13 was formed by winding the resin tape in a spiral shape along the longitudinal direction of the two-core cable 30 so that the twist pitch was the value shown in Table 1.

[0082] When the resin tape was wound, a tension of 1.96 N (200 gf) was applied along the longitudinal direction of the resin tape.

[0083] The obtained two-core cable was evaluated for Scd21 as described above. The evaluation results are shown in Table 2. [Experimental Example 2] A two-core cable was produced in the same manner as in Experimental Example 1, except that when winding the resin tape of the pressure winding 13, a tension of 3.43 N (350 gf) was applied along the longitudinal direction of the resin tape.

[0084] The obtained two-core cable was evaluated for Scd21 as described above. The evaluation results are shown in Table 2. [Experimental Example 3] A two-core cable was produced in the same manner as in Experimental Example 1, except that when winding the resin tape of the pressure winding 13, a tension of 3.92 N (400 gf) was applied along the longitudinal direction of the resin tape.

[0085] The obtained two-core cable was evaluated for Scd21 as described above. The evaluation results are shown in Table 2. [Experimental Example 4] The metal tape 12 was arranged so that the metal layer 122 was located on the two coated electric wires 11 side, opposite to that in Experimental Example 1. Except for the above points, a two-core cable was produced in the same manner as in Experimental Example 1. When winding the resin tape of the pressure winding 13, a force was applied so that the tension was 1.96 N (200 gf) along the longitudinal direction of the resin tape. [Experimental Example 5] A two-core cable was produced in the same manner as in Experimental Example 4, except that when winding the resin tape of the pressure winding 13, a tension of 3.43 N (350 gf) was applied along the longitudinal direction of the resin tape.

[0086] The obtained two-core cable was evaluated for Scd21 as described above. The evaluation results are shown in Table 2. [Experimental Example 6] A two-core cable was produced in the same manner as in Experimental Example 4, except that when winding the resin tape of the pressure winding 13, a tension of 3.92 N (400 gf) was applied along the longitudinal direction of the resin tape.

[0087] The obtained two-core cable was evaluated for Scd21 as described above. The evaluation results are shown in Table 2.

[0088] [Table 1]

[0089] [Table 2] As mentioned above, Scd21 was measured for three samples prepared under the same conditions in each experimental example, and the intensity of the first peak 50 from the low frequency side (see Figure 5), which has the largest value, was determined and the average value was calculated. Table 2 shows the average values ​​calculated for each experimental example.

[0090] According to the results shown in Table 2, it was confirmed that the two-core cables of Experimental Examples 1 to 3, in which the resin layer 121 of the metal tape 12 is positioned on the side of the two coated electric wires 11, i.e., on the inside, can suppress Scd21 compared to the two-core cables of Experimental Examples 4 to 6.

[0091] Therefore, it was confirmed that by positioning a metal tape having a laminated structure of a resin layer and a metal layer so that the resin layer is located on the side of the two coated wires, a two-core cable can be created in which the amount of mode conversion from differential mode to common mode is suppressed. [Explanation of symbols]

[0092] 10, 30 two-core cable 11, 100 coated wire 111 Conductor 112 Insulating layer 1121 First insulating layer 1122 Second insulating layer 1123 Third insulating layer 12 Metal Tape 121 Resin layer 122 Metal layer 21 Page 1 22 Side 2 T121 Resin layer thickness 12A end 12B End 13 Retainer L1 tangent L2 straight line P1 contact P2 contact P3 point P4 points R1 area R2 area O1 center O2 center 31 Drain wire A straight line 50 Peak

Claims

1. A two-core cable, Two coated wires each having a conductor and an insulating layer covering the outer surface of the conductor; a metal tape that collectively covers the outer surfaces of the two coated electric wires; a pressure winding formed by winding a tape body spirally along the longitudinal direction of the two-core cable so as to cover an outer surface of the metal tape, the insulating layer includes a first insulating layer, a second insulating layer, and a third insulating layer in this order from a position closest to the conductor, the first insulating layer and the third insulating layer being solid layers, and the second insulating layer being a foamed layer; the metal tape has a structure in which a resin layer and a metal layer are laminated, and is arranged so that the resin layer is located on the two coated electric wires side; The metal tape is wound around the two insulated electric wires longitudinally, In a cross section perpendicular to the longitudinal direction of the two-core cable, the metal tapes are partially overlapped with each other, In the cross section, both end portions of the metal tape are respectively arranged on the outer side in the width direction of the two-core cable relative to points of contact between the outer peripheries of the two covered electric wires and a common tangent to the outer peripheries of the two covered electric wires, In the cross section, both ends of the metal tape are respectively disposed within a region between an intersection of the metal tape and a line passing through the centers of the two covered electric wires, and the contact point; The two-core cable has an Scd21 value of −24.9 dB or less at the first peak from the low frequency side, which is the largest value between 0 GHz and 40 GHz.

2. A two-core cable as described in Claim 1, wherein tension is applied to the tape body along the longitudinal direction of the tape body.

3. Further having a drain wire, 3. The twin-core cable according to claim 1, wherein the drain wire is disposed outside the metal tape so as to be in contact with the metal layer.

4. 4. The twin-core cable according to claim 1, wherein the resin layer has a thickness of 5 μm or more and 25 μm or less.

5. 5. The two-core cable according to claim 1, wherein the resin layer has a larger dielectric loss tangent than the insulating layer.

6. 6. The twin-core cable according to claim 1, wherein the foam layer has an expansion rate of more than 0% but not more than 70%.

7. A method for manufacturing a two-core cable, comprising: The two-core cable is Two coated wires each having a conductor and an insulating layer covering the outer surface of the conductor; a metal tape that collectively covers the outer surfaces of the two coated electric wires; a pressure winding formed by winding a tape body spirally along the longitudinal direction of the two-core cable so as to cover an outer surface of the metal tape, the insulating layer includes a first insulating layer, a second insulating layer, and a third insulating layer in this order from a position closest to the conductor, the first insulating layer and the third insulating layer being solid layers, and the second insulating layer being a foamed layer; the metal tape has a structure in which a resin layer and a metal layer are laminated, and is arranged so that the resin layer is located on the two coated electric wires side; The metal tape is wound around the two insulated electric wires longitudinally, In a cross section perpendicular to the longitudinal direction of the two-core cable, the metal tapes are partially overlapped with each other, In the cross section, both end portions of the metal tape are respectively arranged on the outer side in the width direction of the two-core cable relative to points of contact between the outer peripheries of the two covered electric wires and a common tangent to the outer peripheries of the two covered electric wires, In the cross section, both ends of the metal tape are respectively disposed within a region between an intersection of the metal tape and a line passing through the centers of the two covered electric wires, and the contact point; When winding the tape body, a tension of 1.96 N or more is applied along the longitudinal direction of the tape body while winding the tape body.

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