Multi-core cable

Abstract

The present disclosure provides a multi-core cable in which the occurrence of a band gap is suppressed. A multi-core cable is provided with: a core formed by twisting four coated wires; a shield layer disposed outside the core; and a sheath disposed outside the shielding layer, the four covered wires are composed of two first wires and two second wires, the outer diameter of the first wires is larger than that of the second wires, and the outer diameter of the first wires is larger than that of the second wires in a cross section perpendicular to the longitudinal direction of the core. The centers of the two first electric wires are located on a first diagonal line of a quadrangle formed by connecting the centers of the four covered electric wires, the centers of the two second electric wires are located on a second diagonal line of the quadrangle, and the two first electric wires are in contact with each other. The first electric wire is in contact with the second electric wire disposed adjacent to the outer periphery of the core.

Description

Technical Field

[0001] The present disclosure relates to a multi-core cable. Background Art

[0002] Patent Document 1 discloses a signal transmission cable having a four-core (quad) structure wire, wherein the four-core structure wire is formed by bundling four center conductors having insulating coatings into a four-core structure.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2003-132743

[0006] In a multi-core cable having four coated wires, a phenomenon called "suck-out" may occur in a prescribed frequency range, where there is a sharp attenuation. Summary of the Invention

[0007] An object of the present disclosure is to provide a multi-core cable in which the occurrence of suck-out is suppressed.

[0008] The multi-core cable of the present disclosure includes: a core formed by stranding four coated wires; a shielding layer disposed outside the core; and an outer sheath disposed outside the shielding layer. The four coated wires are composed of two first wires and two second wires. The outer diameter of the first wire is larger than the outer diameter of the second wire. In a cross-section of the core perpendicular to the length direction, the centers of the two first wires are located on a first diagonal of a quadrilateral formed by connecting the centers of the four coated wires, the centers of the two second wires are located on a second diagonal of the quadrilateral, the two first wires are in contact with each other, and the first wire is in contact with the second wire disposed adjacent to the outer periphery of the core.

[0009] Advantages of the Invention

[0010] According to the present disclosure, a multi-core cable in which the occurrence of suck-out is suppressed can be provided. Brief Description of the Drawings

[0011] Figure 1 is a cross-sectional view of a multi-core cable according to an aspect of the present disclosure taken in a plane perpendicular to the length direction.

[0012] Figure 2 is a cross-sectional view of a multi-core cable produced in Experimental Example 2 taken in a plane perpendicular to the length direction.

[0013] Figure 3 is an evaluation result of the attenuation amount of the multi-core cable produced in Experimental Example 1 and Experimental Example 2.

[0014] Description of Reference Numerals

[0015] 10: Multi-core cable

[0016] D10: Outer diameter

[0017] 20: Multi-core cable

[0018] D20: Outer diameter

[0019] 100: Core

[0020] D100: Outer diameter of the core

[0021] 200: Core

[0022] D200: Outer diameter of the core

[0023] 11: Covered wire

[0024] D11: Outer diameter of the covered wire

[0025] 111: Conductor

[0026] D111: Outer diameter of the conductor

[0027] 112: Insulator

[0028] 11A: First wire

[0029] D11A: Outer diameter of the first wire

[0030] 111A: First conductor

[0031] D111A: Outer diameter of the first conductor

[0032] 112A: First insulator

[0033] 11B: Second wire

[0034] D11B: Outer diameter of the second wire

[0035] 111B: Second conductor

[0036] D111B: Outer diameter of the second conductor

[0037] 112B: Second insulator

[0038] C11: Center

[0039] C12: Center

[0040] C21: Center

[0041] C22: Center

[0042] S1: Quadrilateral

[0043] L1: First diagonal line

[0044] L2: Second diagonal line

[0045] P10: Contact portion

[0046] P11: Contact portion

[0047] P12: Contact portion

[0048] P13: Contact portion

[0049] P14: Contact portion

[0050] P21: Contact portion

[0051] P22: Contact portion

[0052] P23: Contact portion

[0053] P24: Contact portion

[0054] 12: Shielding layer

[0055] 121: First shielding layer

[0056] 122: Second shielding layer

[0057] 13: Outer sheath. Detailed implementation manners

[0058] Hereinafter, the detailed implementation manners will be described.

[0059] [Description of the embodiments of the present disclosure]

[0060] First, the embodiments of the present disclosure will be listed for description. In the following description, the same or corresponding elements are denoted by the same reference numerals, and the same description thereof will not be repeated.

[0061] (1) A multi-core cable according to one aspect of the present disclosure includes: a core formed by stranding four coated wires; a shielding layer disposed outside the core; and an outer sheath disposed outside the shielding layer. The four coated wires are composed of two first wires and two second wires. The outer diameter of the first wire is larger than that of the second wire. In a cross-section of the core perpendicular to the length direction, the centers of the two first wires are located on the first diagonal line of a quadrilateral formed by connecting the centers of the four coated wires, the centers of the two second wires are located on the second diagonal line of the quadrilateral, the two first wires are in contact with each other, and the first wire is in contact with the second wire disposed adjacent to the outer periphery of the core.

[0062] Regarding four covered electric wires, which are composed of two first electric wires and two second electric wires, with the outer diameter of the first electric wire being larger than that of the second electric wire, in a cross-section of the core perpendicular to the length direction, the two first electric wires are arranged in contact with each other, thereby being able to suppress the occurrence of band gaps.

[0063] (2) In (1), it may also be that the ratio of the outer diameter of the second electric wire to the outer diameter of the first electric wire is 0.2 or more and 0.7 or less.

[0064] By setting the ratio of the outer diameter of the second electric wire to the outer diameter of the first electric wire to be 0.2 or more and 0.7 or less, in a cross-section of the multi-core cable perpendicular to the length direction, the shapes of the shielding layer and the outer skin can be made close to a perfect circle. Therefore, the processability of the multi-core cable can be improved. In addition, the unevenness of the distance between the second electric wires in the position along the length direction of the multi-core cable can be suppressed, and the transmission characteristics of the signals propagated in the second electric wires can be made particularly stable.

[0065] (3) In (1) or (2), it may also be that the ratio of the minimum value of the outer diameter of the multi-core cable in a cross-section perpendicular to the length direction to the maximum value of the outer diameter of the multi-core cable is 0.9 or more and 1.0 or less.

[0066] By setting the ratio of the minimum value of the outer diameter of the multi-core cable in a cross-section perpendicular to the length direction to the maximum value of the outer diameter of the multi-core cable to be 0.9 or more and 1.0 or less, the cross-section of the multi-core cable of one aspect of the present disclosure can be made close to a perfect circle, and the processability of the multi-core cable can be improved.

[0067] [Details of the Embodiment of the Present Disclosure]

[0068] Hereinafter, a specific example of a multi-core cable of 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 by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0069] In this specification, sometimes, for the names of components, such as the first electric wire, the second electric wire, the first conductor, the second conductor, the first insulator, and the second insulator, the first, second, etc. are added for explanation. The first, second, etc. are only recorded for distinguishing each component and preventing confusion during the explanation, and do not represent the configuration, priority order, etc. Therefore, in cases where there is no particular concern about confusion and when explaining in a summary manner, it may be simply recorded as an electric wire, a conductor, or an insulator.

[0070] [Multi-core Cable]

[0071] Figure 1 shows a configuration example of a cross-section of the multi-core cable 10 of this embodiment perpendicular to the length direction. Figure 1The Z-axis perpendicular to the paper surface is equivalent to the axis along the length direction of the multi-core cable 10 and the core 100. The XY plane becomes a plane perpendicular to the length direction of the multi-core cable 10 and the core 100.

[0072] As Figure 1 shown, the multi-core cable 10 of the present embodiment has: a core 100 formed by stranding four coated wires 11; a shielding layer 12 disposed outside the core 100; and an outer sheath 13 disposed outside the shielding layer 12.

[0073] (1) Regarding the components of the multi-core cable

[0074] Each component included in the multi-core cable of the present embodiment will be described.

[0075] (1-1) Core

[0076] The core 100 has four coated wires 11. The coated wires 11 can be used for signal transmission, for example.

[0077] (1-1-1) Regarding the constitution of the coated wire

[0078] Figure 1 The core 100 of the multi-core cable 10 shown is composed of two first wires 11A and two second wires 11B. The two first wires 11A can have the same constitution. The two second wires 11B can have the same constitution. Therefore, it can also be said that the four coated wires 11 have two sets of coated wires. The two first wires 11A and the two second wires 11B are stranded to form the core 100.

[0079] The coated wire 11 can have a conductor 111 and an insulator 112 covering the outer surface of the conductor 111.

[0080] The first wire 11A as the coated wire 11 can have a first conductor 111A and a first insulator 112A covering the outer surface of the first conductor 111A.

[0081] Regarding the second wire 11B as the coated wire 11, it can also have a second conductor 111B and a second insulator 112B covering the outer surface of the second conductor 111B.

[0082] The constitution example of each component included in the coated wire 11 will be described.

[0083] (Conductor)

[0084] The conductor 111 can have a single-wire conductor wire or multiple conductor wires. When the conductor 111 has multiple conductor wires, the multiple conductor wires can be stranded in advance. That is, when the conductor 111 has multiple conductor wires, the conductor 111 can also adopt a stranded wire of multiple conductor wires.

[0085] The material of the conductor 111 is not particularly limited, but for example, one or more conductor materials selected from copper, silver-plated soft copper, and tin-plated soft copper can be used. Soft copper can also be used as copper.

[0086] The outer diameter of the conductor 111, that is, the outer diameter D111A of the first conductor 111A and the outer diameter D111B of the second conductor 111B, is not particularly limited, but for example, it can be set to 0.20 mm or more and 1.0 mm or less.

[0087] The outer diameter of the conductor 111 is obtained by measuring two orthogonal diameters in any cross-section perpendicular to the length direction of the conductor 111 and averaging the two measured diameters.

[0088] (Insulator)

[0089] The material constituting the insulator 112 is not particularly limited, but may include a resin material.

[0090] For example, one or more of fluororesins such as polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), ethylene-tetrafluoroethylene copolymer (ETFE), polyester resins such as polyethylene terephthalate (PET), polyolefin resins such as polyethylene, polypropylene, and polymethylpentene can be used as the resin material. The resin material contained in the insulator 112 may or may not be crosslinked. When the resin material is a polyolefin resin such as polyethylene or polypropylene, it is suitable for the transmission of high-speed signals and can particularly reduce costs.

[0091] The insulator 112 may also be composed only of the above resin material, but in addition to containing the resin material, the insulator 112 may also contain one or more additives selected from flame retardants, flame retardant aids, antioxidants, lubricants, colorants, reflection imparting agents, masking agents, processing stabilizers, plasticizers, etc.

[0092] (1-1-2) Regarding the outer diameters of the first wire and the second wire

[0093] The outer diameter D11A of the first wire 11A of the multi-core cable 10 may be larger than the outer diameter D11B of the second wire 11B.

[0094] The outer diameter D111A of the first conductor 111A of the first wire 11A and the outer diameter D111B of the second conductor 111B of the second wire 11B may be the same. Therefore, for example, the thickness of the first insulator 112A of the first wire 11A may be thicker than the thickness of the second insulator 112B of the second wire 11B.

[0095] For example, the ratio of the outer diameter D11B of the second electric wire 11B to the outer diameter D11A of the first electric wire 11A, that is, D11B÷D11A, may be set to 0.2 or more and 0.7 or less.

[0096] By setting the ratio of the outer diameter D11B of the second electric wire 11B to the outer diameter D11A of the first electric wire 11A to 0.2 or more and 0.7 or less, in a cross-section of the multi-core cable perpendicular to the length direction, the shapes of the shielding layer and the outer skin can be made close to a perfect circle. Therefore, the processability of the multi-core cable 10 can be improved. In addition, the unevenness of the distance between the second electric wires 11B in the position along the length direction of the multi-core cable 10 can be suppressed, and the transmission characteristics of the signals propagated in the second electric wires 11B can be made particularly stable.

[0097] The outer diameter D11A of the first electric wire 11A and the outer diameter D11B of the second electric wire 11B are not particularly limited, but for example, they may be set to 0.6 mm or more and 2.6 mm or less.

[0098] Regarding the outer diameter of the coated electric wire 11, the outer diameter of the multi-core cable 10 described later, and the wire diameter of the metal wire, except for setting the measurement object to the first electric wire 11A, the second electric wire 11B, the multi-core cable 10, and the metal wire as the coated electric wire 11, they are also obtained by the same process as in the case of the conductor 111, so the description is omitted.

[0099] (1-1-3) Arrangement of the first electric wire and the second electric wire

[0100] In a cross-section of the core 100 perpendicular to the length direction, the four coated electric wires 11 may be arranged in a layer along the outer circumference of the core 100, and the first electric wire 11A and the second electric wire 11B may be arranged alternately along the outer circumference of the core 100.

[0101] Therefore, in a cross-section of the core 100 perpendicular to the length direction, the centers C11 and C12 of the two first electric wires 11A are located on the first diagonal line L1 of the quadrilateral S1 formed by connecting the centers of the four coated electric wires. In addition, the centers C21 and C22 of the two second electric wires 11B are located on the second diagonal line L2 of the quadrilateral S1. The quadrilateral S1 is a figure formed by connecting the centers C11, C12, C21, and C22 in sequence along the outer circumference of the core 100. The first diagonal line L1 and the second diagonal line L2 are different diagonal lines of the quadrilateral S1.

[0102] The quadrilateral S1, the first diagonal line L1, the second diagonal line L2, the centers C11, C12, C21, and C22 are auxiliary lines and points for explaining the arrangement of the coated electric wires 11, and are not components constituting the multi-core cable 10.

[0103] Two first electric wires 11A are in contact with each other at the contact portion P10. It should be noted that the two second electric wires 11B can be configured not to be in contact with each other.

[0104] Moreover, the first electric wire 11A can be in contact with the second electric wire 11B disposed adjacent to the outer periphery of the core 100. Specifically, as Figure 1 shown, at the contact portions P11, P12, P13, and P14, the first electric wire 11A is in contact with the second electric wire 11B disposed adjacent to the outer periphery of the core 100. That is, the four coated electric wires 11 are respectively in contact with the coated electric wires 11 disposed adjacent to the outer periphery of the core 100.

[0105] Conventionally, in the case of using a multi-core cable formed by stranding four coated electric wires, as Figure 2 the multi-core cable 20 shown, a configuration is adopted in which four coated electric wires 11 having the same outer diameter D11 and the like are stranded. In the multi-core cable 20, in a cross section perpendicular to the length direction of the core 200, the coated electric wires 11 disposed adjacent to the outer periphery of the core 200 are in contact with each other at the contact portions P21, P22, P23, and P24. However, the coated electric wires 11 located on the diagonal of the quadrilateral formed by connecting the centers of the coated electric wires 11 do not contact each other.

[0106] In contrast, as described above, in the multi-core cable 10 of the present embodiment, regarding the four coated electric wires 11, it is composed of two first electric wires 11A and two second electric wires 11B, and the outer diameter D11A of the first electric wire 11A is made larger than the outer diameter D11B of the second electric wire 11B. And, in a cross section perpendicular to the length direction of the core 100, the two first electric wires 11A are arranged to be in contact with each other. According to the research of the inventor of the present invention, as in the multi-core cable 10, in a cross section perpendicular to the length direction of the core 100, the two first electric wires 11A are arranged to be in contact with each other, whereby the occurrence of a frequency band gap can be suppressed for the signal propagating in the first electric wire.

[0107] (1 - 2) Shielding layer

[0108] The shielding layer 12 can be disposed outside the core 100.

[0109] By the multi-core cable 10 having the shielding layer 12, noise can be suppressed from being superimposed on the signal propagated by the coated electric wire 11. In addition, the influence of noise on external devices can be suppressed.

[0110] The shielding layer 12 can contain a conductive material.

[0111] For example, the shielding layer 12 can be formed by spirally winding a conductive tape including a conductive layer along the length direction of the core 100.

[0112] The conductive tape may have a base member and a conductive layer disposed on at least one of the upper and lower surfaces of the base member. The conductive tape may also have conductive layers on both the upper and lower surfaces of the base member. The conductive tape may also not have a base member and be composed only of a conductive layer.

[0113] The material of the conductive layer is not particularly limited, but may include a metal. For example, a metal foil may be used. When the conductive layer contains a metal, the material of the metal is not particularly limited, but for example, copper, copper alloy, aluminum, aluminum alloy, etc. may be used.

[0114] Regarding the material of the base member, it is also not particularly limited, but for example, insulating materials such as organic polymer materials and non-woven fabrics may be used. As the organic polymer material, for example, polyester resins such as polyethylene terephthalate (PET), polyolefin resins such as polypropylene, vinyl resins such as polyvinyl chloride, etc. may be cited. The base member may be a base member containing an insulating material or a base member composed only of an insulating material.

[0115] Therefore, for example, one or more selected from copper-clad polyester tapes, aluminum-clad polyester tapes, etc. may be used as the conductive tape.

[0116] When forming the shielding layer 12 by winding the conductive tape as described above, the winding direction of the conductive tape can be arbitrarily selected. For example, it can be the same direction as the stranding direction of the four covered wires 11 of the core 100 or a direction different from the stranding direction of the four covered wires 11.

[0117] The shielding layer 12 may also include metal wires. In this case, the shielding layer 12 may have a structure formed by laterally winding the metal wires or a structure formed by braiding the metal wires. When the shielding layer 12 includes metal wires, by forming the metal wires into a braid, the mechanical strength of the shielding layer can be improved and the durability of the multi-core cable can be improved.

[0118] Copper, aluminum, copper alloy, etc. can be used as the material of the metal wires. Soft copper wires can also be used as the metal wires. Silver or tin plating treatment can also be performed on the surface of the metal wires. Therefore, the metal wires can also be silver-plated soft copper wires or tin-plated soft copper wires.

[0119] By, for example, using one or more selected from soft copper wires, tin-plated soft copper wires, etc. as the metal wires, the cost can be particularly reduced.

[0120] The shielding layer 12 may be composed of not only one layer but also multiple layers. As Figure 1As shown, the shielding layer 12 may also have a first shielding layer 121 and a second shielding layer 122 in sequence starting from a position close to the core 100. In this case, for example, the first shielding layer 121 may be a layer formed by spirally winding a conductive tape along the length direction of the core 100. For example, the second shielding layer 122 may also be a layer formed by laterally winding a metal wire or a layer formed by braiding a metal wire. The multi-core cable 10 of the present embodiment may also have two second shielding layers 122 formed by laterally winding a metal wire or braiding a metal wire. In this case, the shielding layer 12 may also include the first shielding layer 121 and thus include three layers.

[0121] (1 - 3) Outer sheath

[0122] The outer sheath 13 may be disposed outside the shielding layer 12.

[0123] By having the outer sheath 13 in the multi-core cable 10, the coated wires 11 included in the core 100 can be protected, electrical short circuits of the shielding layer 12 can be prevented, and the durability of the multi-core cable 10 can be improved.

[0124] (Resin material)

[0125] The outer sheath 13 may contain a resin material. The resin material is not particularly limited, but for example, a composition formed by mixing one selected from polyolefin resins such as polyethylene and ethylene-vinyl acetate copolymer (EVA), polyvinyl chloride, polyurethane elastomer (polyurethane resin), and polyester elastomer or at least two of them can be used. When the resin material is one or more selected from polyolefin resins and polyvinyl chloride, the cost can be particularly reduced.

[0126] The resin material of the outer sheath 13 may or may not be crosslinked.

[0127] (1 - 4) Press winding

[0128] The multi-core cable 10 may also have an unillustrated press winding covering the outer surface of the core 100. The press winding can be disposed, for example, between the core 100 and the shielding layer 12.

[0129] By having the press winding in the multi-core cable 10, the arrangement of the four coated wires 11 included in the multi-core cable 10 can be stabilized and bundled.

[0130] For example, a resin tape such as polyethylene terephthalate (PET) can be used as the press winding.

[0131] The winding direction of the press winding may be the same as the stranding direction of the four coated wires 11 included in the core 100 or may be different from the stranding direction of the four coated wires 11.

[0132] (2) Regarding the shape of the multi-core cable

[0133] For example, as Figure 1 shown, for the multi-core cable 10, the shape in the cross-section perpendicular to the length direction can be formed into a circle. In the cross-section of the multi-core cable 10 perpendicular to the length direction, the ratio of the minimum value of the outer diameter of the multi-core cable 10 to the maximum value of the outer diameter of the multi-core cable 10, that is, the minimum value ÷ the maximum value, is not particularly limited, but for example, it can be set to 0.9 or more and 1.0 or less.

[0134] By setting the ratio of the minimum value of the outer diameter to the maximum value of the outer diameter in the cross-section perpendicular to the length direction to 0.9 or more and 1.0 or less, the cross-section of the multi-core cable 10 can be made close to a perfect circle, and the processability of the multi-core cable 10 can be improved.

[0135] Regarding the outer diameter D10 of the multi-core cable 10, it is not particularly limited either, but for example, it can be set to 2.0 mm or more and 9.0 mm or less. By setting the outer diameter D10 of the multi-core cable 10 to 2.0 mm or more, the thickness of the outer sheath 13 etc. can be sufficiently ensured, and the durability of the multi-core cable 10 can be improved. By setting the outer diameter D10 of the multi-core cable 10 to 9.0 mm or less, the flexibility of the multi-core cable 10 can be improved, and the processability can be improved.

[0136] [Embodiment]

[0137] Hereinafter, specific embodiments will be given for illustration, but the present invention is not limited to these embodiments.

[0138] (Evaluation method)

[0139] First, the evaluation method for the multi-core cables produced in the following experimental examples will be described.

[0140] (1) Outer diameters of the conductor, the covered wire, the core, and the multi-core cable

[0141] The outer diameters of the conductor, the covered wire, the core, and the multi-core cable were measured in accordance with JIS C 3005 (2014).

[0142] Specifically, for example, in any cross-section of the covered wire 11 perpendicular (at a right angle) to the length direction, the outer diameter of the conductor 111 was measured along two orthogonal diameters, and the average value was set as the outer diameter D111 of the conductor 111.

[0143] Here, the conductor 111 was used as an example for illustration, but for the outer diameter D11 of the covered wire 11, the outer diameter D100 of the core 100, the outer diameter D10 of the multi-core cable 10, etc., except for setting the evaluation object to the covered wire 11, the core 100, and the multi-core cable 10, they were also obtained through the same process. It should be noted that in Figure 1In the case of the multi-core cable 10 shown, measurements were made on the first wire 11A and the second wire 11B, which are covered wires 11, respectively. In addition, in Figure 2 In the case of the multi-core cable 20 shown, the outer diameter D200 of the core 200 and the outer diameter D20 of the multi-core cable 20 were measured.

[0144] In addition, in Experimental Example 1, the ratio (D11B / D11A) of the outer diameter D11B of the second wire 11B to the outer diameter D11A of the first wire 11A was calculated.

[0145] (2) Characteristic impedance

[0146] For the first wire 11A of the multi-core cable produced in the following experimental examples, the characteristic impedance was measured by the Time Domain Reflectometry (TDR method). It should be noted that in Experimental Example 2, instead of the first wire 11A, the covered wire 11 was measured. The same applies to the following time delay and attenuation.

[0147] (3) Time delay (Skew)

[0148] For the two first wires 11A of the multi-core cable produced in the following experimental examples, electrical pulses were sent through a digital serial analyzer, and the delay time per 1 m was measured to obtain the time delay.

[0149] (4) Attenuation

[0150] For the first wire 11A in the 5-m multi-core cable produced in each of the following experimental examples, measurements were made using a network analyzer. The measurement results are shown in Figure 3 . In Table 2, the attenuation is recorded for a 2-GHz signal.

[0151] (Experimental conditions, results)

[0152] Hereinafter, the multi-core cables manufactured in each experimental example will be described.

[0153] In the following Experimental Example 1 and Experimental Example 2, multi-core cables were produced. Experimental Example 1 is an example, and Experimental Example 2 is a comparative example.

[0154] [Experimental Example 1]

[0155] A multi-core cable 10 having a structure with a cross-section perpendicular to the length direction as shown in Figure 1 was produced. The dimensions of each part of the multi-core cable 10 are shown in Table 1. In addition, for the obtained multi-core cable 10, the results obtained by measuring the characteristic impedance, time delay, and attenuation are shown in Table 2, Figure 3 .

[0156] [Experimental Example 2]

[0157] Manufacture a multi-core cable 20 having a structure with a cross-section perpendicular to the length direction as Figure 2 shown. The four covered wires 11 of the multi-core cable 20 have the same constitution. As shown in Table 1, the outer diameters D11 of the four covered wires 11 are the same. The dimensions of each part of the multi-core cable 20 are shown in Table 1. In addition, regarding the obtained multi-core cable 20, the results obtained by measuring the characteristic impedance, time delay, and attenuation amount are shown in Table 2, Figure 3 .

[0158] As Figure 3 shown, in the multi-core cable of Experimental Example 2, a sharp decrease in the attenuation amount was confirmed near 2.5 GHz. As shown in Table 2, in Experimental Example 1, compared with Experimental Example 2, the attenuation amount at 2 GHz was improved by 13%.

[0159] [Table 1]

[0160]

[0161] [Table 2]

[0162] Characteristic impedance (Ω) Time delay (ps / m) Attenuation (@2 GHz) (dB / 5 m) Experimental Example 1 98.2 2.8 -8.2 Experimental Example 2 97.7 5.7 -9.4

Claims

1. A multi-core cable having: The core is made by twisting four covered wires; a shielding layer disposed outside the core; and An outer skin is arranged outside the shielding layer, The four covered electric wires are composed of two first electric wires and two second electric wires, The outer diameter of the first electric wire is larger than the outer diameter of the second electric wire, In a cross section of the core perpendicular to the length direction, centers of two of the first electric wires are located on a first diagonal of a quadrilateral formed by connecting the centers of the four covered electric wires, centers of two of the second electric wires are located on a second diagonal of the quadrilateral, the two first electric wires are in contact with each other, and the first electric wires are in contact with the second electric wires arranged adjacently along the outer periphery of the core.

2. The multi-core cable according to claim 1, wherein: A ratio of an outer diameter of the second electric wire to an outer diameter of the first electric wire is greater than or equal to 0.2 and less than or equal to 0.

7.

3. The multi-core cable according to claim 1 or 2, wherein: A ratio of a minimum value of an outer diameter of the multi-core cable to a maximum value of an outer diameter of the multi-core cable in a cross section perpendicular to a longitudinal direction is 0.9 or more and 1.0 or less.

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