Multicore cable

Abstract

To provide a multicore cable in which generation of sack-out is suppressed.SOLUTION: A multicore cable has: a core in which four coated electric wires are stranded; a shield layer arranged outside the core; and an outer jacket arranged outside the shield layer, where the four coated electric wires consist of two first electric wires and two second electric wires, and the outer diameter of the first electric wire is larger than the outer diameter of the second electric wire. On a cross section perpendicular to the longitudinal side of the core, the centers of the two first electric wires are positioned on a first diagonal line of a square formed by connecting the centers of the four coated electric wires, the centers of the two second electric wires are positioned on a second diagonal line of the square, the two first electric wires contact each other, and the first electric wire contacts the second electric wire arranged adjacent along the outer periphery of the core.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] Patent Document 1 discloses a signal transmission cable including a cut structure wire formed by bundling a center conductor having four insulating coatings so as to form a cut structure.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a multi-core cable having four coated electric wires, a phenomenon called suck-out may occur in a predetermined frequency range, where rapid attenuation occurs.

[0005] An object of the present disclosure is to provide a multi-core cable in which the occurrence of suck-out is suppressed.

Means for Solving the Problems

[0006] The multi-core cable of the present disclosure includes a core formed by twisting four coated electric wires, a shielding layer disposed outside the core, and an outer covering disposed outside the shielding layer, and the four coated 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 perpendicular to the longitudinal direction of the core, the centers of the two first electric wires are located on the first diagonal of a quadrilateral formed by connecting the centers of the four covered electric wires, and the centers of the two second electric wires are located on the second diagonal of the quadrilateral. The two first electric wires are in contact with each other, and the first electric wire is in contact with the second electric wire arranged adjacent to each other along the outer circumference of the core.

Advantages of the Invention

[0007] According to the present disclosure, a multi-core cable capable of suppressing the occurrence of suck-out can be provided.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0009] The modes for carrying out the invention will be described below.

[0010] [Description of 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 are denoted by the same reference numerals, and the same description thereof will not be repeated.

[0011] (1) A multi-core cable according to an aspect of the present disclosure includes a core formed by twisting four covered electric wires, a shielding layer disposed outside the core, and an outer sheath disposed outside the shielding layer. The four covered electric wires are composed of two first electric wires and two second electric wires, and the outer diameter of the first electric wire is larger than the outer diameter of the second electric wire. The outer diameter of the first electric wire is larger than the outer diameter of the second electric wire. In a cross-section perpendicular to the longitudinal direction of the core, the centers of the two first electric wires are located on the first diagonal line of the quadrilateral connecting the centers of the four coated electric wires, the centers of the two second electric wires are located on the second diagonal line of the quadrilateral, the two first electric wires are in contact with each other, and the first electric wire is in contact with the second electric wire arranged adjacent along the outer periphery of the core.

[0012] The four coated electric wires are composed of two first electric wires and two second electric wires. By making the outer diameter of the first electric wire larger than the outer diameter of the second electric wire and arranging the two first electric wires to be in contact with each other in a cross-section perpendicular to the longitudinal direction of the core, the occurrence of sack out can be suppressed.

[0013] (2) In (1), the ratio of the outer diameter of the second electric wire to the outer diameter of the first electric wire may be 0.2 or more and 0.7 or less.

[0014] 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 perpendicular to the longitudinal direction of the multi-core cable, the shape of the shielding layer and the outer sheath can be made closer to a perfect circle. For this reason, the handleability of the multi-core cable can be improved. Also, the variation in the distance between the second electric wires at positions along the longitudinal direction of the multi-core cable can be suppressed, and the transmission characteristics of the signal propagated through the second electric wire can be made particularly stable.

[0015] (3) In (1) or (2), the ratio of the minimum value to the maximum value of the outer diameter in a cross-section perpendicular to the longitudinal direction may be 0.9 or more and 1.0 or less.

[0016] By setting the ratio of the minimum value to the maximum value of the outer diameter in a cross-section perpendicular to the longitudinal direction to be 0.9 or more and 1.0 or less, the cross-section of the multi-core cable according to one aspect of the present disclosure can be made closer to a perfect circle, and the handleability of the multi-core cable can be improved.

[0017] [Details of Embodiments of the Present Disclosure] A specific example of a multi-core cable according to an embodiment of the present disclosure (hereinafter referred to as "this 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 of the patent, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0018] In this specification, when describing members such as the first electric wire, the second electric wire, the first conductor, the second conductor, the first insulator, and the second insulator, the names of the members may be appended with first, second, etc. The first, second, etc. are merely described to identify each member and prevent confusion during the explanation, and do not represent arrangement, priority, etc. Therefore, when there is no particular risk of confusion or when explaining collectively, it can be simply expressed as an electric wire, a conductor, an insulator, etc. [Multi-core cable] FIG. 1 shows a configuration example of a cross-section perpendicular to the longitudinal direction of the multi-core cable 10 of this embodiment. The Z-axis perpendicular to the paper surface in FIG. 1 corresponds to the axis along the longitudinal direction of the multi-core cable 10 and the core 100. The XY plane is a plane perpendicular to the longitudinal direction of the multi-core cable 10 and the core 100.

[0019] As shown in FIG. 1, the multi-core cable 10 of this embodiment includes a core 100 formed by twisting four covered electric wires 11, a shielding layer 12 disposed outside the core 100, and an outer sheath 13 disposed outside the shielding layer 12. (1) Regarding the members included in the multi-core cable Each member included in the multi-core cable of this embodiment will be described. (1-1) Core The core 100 has four covered electric wires 11. The covered electric wires 11 can be used, for example, for signal transmission. (1-1-1) Regarding the configuration of the covered electric wire The core 100 of the multi-core cable 10 shown in FIG. 1 is composed of two first electric wires 11A and two second electric wires 11B. The two first electric wires 11A can have the same configuration. The two second electric wires 11B can have the same configuration. Therefore, the four covered electric wires 11 can also be said to have two sets of covered electric wires. The two first electric wires 11A and the two second electric wires 11B are twisted together to form the core 100.

[0020] The covered electric wire 11 can have a conductor 111 and an insulator 112 that covers the outer surface of the conductor 111.

[0021] The first electric wire 11A, which is a covered electric wire 11, can have a first conductor 111A and a first insulator 112A that covers the outer surface of the first conductor 111A.

[0022] Similarly, the second electric wire 11B, which is a covered electric wire 11, can have a second conductor 111B and a second insulator 112B that covers the outer surface of the second conductor 111B.

[0023] An example of the configuration of each member of the covered electric wire 11 will be described. (Conductor) The conductor 111 can have a single-strand conductor element or a plurality of conductor elements. When the conductor has a plurality of conductor elements, the plurality of conductor elements can be twisted together. That is, when the conductor 111 has a plurality of conductor elements, the conductor can also be a stranded wire of a plurality of conductor elements.

[0024] The material of the conductor 111 is not particularly limited. For example, one or more conductor materials selected from copper, silver-plated soft copper, and tin-plated soft copper can be used. As the copper, soft copper can also be used.

[0025] 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 are not particularly limited, but can be, for example, 0.20 mm or more and 1.0 mm or less.

[0026] The outer diameter of the conductor 111 is obtained by measuring two perpendicular diameters in any cross-section perpendicular to the longitudinal direction of the conductor 111 and averaging the two measured diameters. (Insulator) The material constituting the insulator 112 is not particularly limited, but may include a resin material.

[0027] As the resin material, for example, one or more selected from 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), and polyolefin resins such as polyethylene, polypropylene, and polymethylpentene can be used. The resin material contained in the insulator may or may not be cross-linked. When the resin material is a polyolefin resin such as polyethylene or polypropylene, it is suitable for the transmission of high-speed signals and the cost can be particularly reduced.

[0028] The insulator 112 can also be composed only of the above resin material, but the insulator 112 can also contain one or more additives selected from flame retardants, flame retardant aids, antioxidants, lubricants, colorants, reflection imparting agents, concealing agents, processing stabilizers, plasticizers, etc. in addition to the resin material. (1-1-2) Regarding the outer diameters of the first electric wire and the second electric wire The outer diameter D11A of the first electric wire 11A of the multi-core cable 10 can be larger than the outer diameter D11B of the second electric wire 11B.

[0029] The outer diameter D111A of the first conductor 111A of the first electric wire 11A and the outer diameter D111B of the second conductor 111B of the second electric wire 11B may be the same. Therefore, for example, the thickness of the first insulator 112A of the first electric wire 11A can be made thicker than the thickness of the second insulator 112B of the second electric wire 11B.

[0030] 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 0.2 or more and 0.7 or less.

[0031] 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 be 0.2 or more and 0.7 or less, in a cross-section perpendicular to the longitudinal direction of the multi-core cable, the shapes of the shielding layer and the outer covering can be made closer to a perfect circle. Therefore, the handleability of the multi-core cable 10 can be improved. In addition, the variation in the distance between the second electric wires 11B at positions along the longitudinal direction of the multi-core cable 10 can be suppressed, and the transmission characteristics of the signals transmitted through the second electric wires 11B can be made particularly stable.

[0032] 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 can be, for example, 0.6 mm or more and 2.6 mm or less.

[0033] The outer diameter of the coated electric wire 11, the outer diameter of the multi-core cable 10 described later, and the strand diameter of the metal strand are obtained by the same procedure as in the case of the conductor 111, except that the measurement target is the first electric wire 11A, the second electric wire 11B, the multi-core cable 10, or the metal strand, and thus the description is omitted. (1-1-3) Arrangement of the first electric wire and the second electric wire In a cross-section perpendicular to the longitudinal direction of the core 100, the four coated electric wires 11 can be arranged so as to form a single layer along the outer circumference of the core 100, and the first electric wire 11A and the second electric wire 11B are arranged alternately along the outer circumference of the core 100.

[0034] Therefore, in a cross-section perpendicular to the longitudinal direction of the core 100, the centers C11 and C12 of the two first electric wires 11A are located on the first diagonal line L1 of the quadrilateral S1 connecting the centers of the four coated electric wires. Also, 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 connecting the centers C11, C12, C21, and C22 in order 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.

[0035] 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 covered wire 11, and do not constitute the multi-core cable 10.

[0036] The two first electric wires 11A are in contact with each other at the contact portion P10. Note that the two second electric wires 11B can be configured not to contact each other.

[0037] And the first electric wire 11A can contact the second electric wire 11B arranged adjacent along the outer periphery of the core 100. Specifically, as shown in FIG. 1, at the contact portions P11, P12, P13, and P14, the first electric wire 11A is in contact with the second electric wire 11B adjacent along the outer periphery of the core 100. That is, the four covered wires 11 are in contact with the covered wires 11 adjacent along the outer periphery of the core 100, respectively.

[0038] Conventionally, when a multi-core cable is formed by twisting four covered wires, as in the multi-core cable 20 shown in FIG. 2, it has been configured by twisting four covered wires 11 having the same configuration such as the outer diameter D11. In the multi-core cable 20, in a cross section perpendicular to the longitudinal direction of the core 200, the covered wires 11 adjacent along the outer periphery of the core 200 are in contact with each other at the contact portions P21, P22, P23, and P24. However, the covered wires 11 located on the diagonal line of the quadrilateral connecting the centers of the covered wires 11 were not in contact with each other.

[0039] In contrast, as described above, the multi-core cable 10 of the present embodiment is composed of two first electric wires 11A and two second electric wires 11B for the four coated electric wires 11, 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 the cross section perpendicular to the longitudinal direction of the core 100, the two first electric wires 11A are arranged to be in contact with each other. According to the study of the inventor of the present invention, by arranging the two first electric wires 11A to be in contact with each other in the cross section perpendicular to the longitudinal direction of the core 100 like the multi-core cable 10, the occurrence of crosstalk can be suppressed for the signal propagating through the first electric wire. (1-2) Shielding layer The shielding layer 12 can be arranged outside the core 100.

[0040] Since the multi-core cable 10 has the shielding layer 12, it is possible to suppress noise from being added to the signal propagated by the coated electric wire 11. Also, the influence of noise on external devices can be suppressed.

[0041] The shielding layer 12 can contain a conductive material.

[0042] For example, the shielding layer 12 can be formed by spirally winding a conductive tape including a conductive layer along the longitudinal direction of the core 100.

[0043] The conductive tape can have a base material and a conductive layer disposed on at least one of the upper and lower surfaces of the base material. The conductive tape may have conductive layers on both the upper and lower surfaces of the base material. The conductive tape may not have a base material and may be composed of only a conductive layer.

[0044] The material of the conductive layer is not particularly limited, but it can contain a metal and can be, for example, a metal foil. When the conductive layer contains a metal, the metal material is not particularly limited, and for example, copper, copper alloy, aluminum, aluminum alloy, etc. can be used.

[0045] The material of the base material is not particularly limited, and for example, an insulating material such as an organic polymer material or a non-woven fabric may be used. Examples of the organic polymer material include polyester resins such as polyethylene terephthalate (PET), polyolefin resins such as polypropylene, and vinyl resins such as polyvinyl chloride. The base material can be a base material containing an insulating material, or can be a base material consisting only of an insulating material.

[0046] Therefore, as the conductive tape, for example, one or more selected from copper-coated polyester tape, aluminum-coated polyester tape, etc. can be used.

[0047] As described above, when forming the shielding layer 12 by winding the conductive tape, the winding direction of the conductive tape can be arbitrarily selected. For example, it may be the same direction as the twisting direction of the four covered electric wires 11 of the core 100, or a different direction.

[0048] The shielding layer 12 can also include metal strands. In this case, the shielding layer 12 can have a configuration in which the metal strands are wound horizontally or braided. When the shielding layer 12 includes metal strands, by braiding the metal strands, the mechanical strength of the shielding layer can be increased, and the durability of the multi-core cable can be increased.

[0049] As the material of the metal strand, copper, aluminum, copper alloy, etc. can be used. As the copper, soft copper wire can also be used. The metal strand may be subjected to a silver or tin plating treatment on the surface. Therefore, the metal strand may be a silver-plated soft copper wire or a tin-plated soft copper wire.

[0050] By using, for example, one or more selected from soft copper wire, tin-plated soft copper wire, etc. as the metal strand, the cost can be particularly reduced.

[0051] The shielding layer 12 can be composed of not only one layer but also a plurality of layers. As shown in FIG. 1, the shielding layer 12 can also have a first shielding layer 121 and a second shielding layer 122 in order from a position close to the core 100. In this case, for example, the first shielding layer 121 can be a layer formed by spirally winding a conductive tape along the longitudinal direction of the core 100. For example, the second shielding layer 122 can also be a layer formed by winding a metal strand horizontally or braiding. The multi-core cable 10 of the present embodiment can also have two layers of the second shielding layer 122 formed by winding a metal strand horizontally or braiding. In this case, the shielding layer 12 can include three layers including the first shielding layer 121. (1-3) Outer sheath The outer sheath 13 can be disposed outside the shielding layer 12.

[0052] By having the outer sheath 13, the multi-core cable 10 protects the coated electric wires 11 included in the core 100, prevents an electrical short circuit of the shielding layer 12, and can enhance the durability of the multi-core cable 10. (Resin material) The outer sheath 13 can include a resin material. The resin material is not particularly limited. For example, a polyolefin resin such as polyethylene or ethylene-vinyl acetate copolymer (EVA), polyvinyl chloride, polyurethane elastomer (polyurethane resin), or a composition formed by mixing one type selected from polyester elastomers or at least two of these can be used. When the resin material is one or more selected from polyolefin resins and polyvinyl chloride, the cost can be particularly reduced.

[0053] The resin material of the outer sheath 13 may or may not be crosslinked. (1-4) Retaining wrap The multi-core cable 10 can also have a retaining wrap (not shown) that covers the outer surface of the core 100. The retaining wrap can be disposed, for example, between the core 100 and the shielding layer 12.

[0054] By having the retaining wrap, the multi-core cable 10 can stabilize and bundle the arrangement of the four coated electric wires 11 included in the multi-core cable 10.

[0055] As the restraining tape, for example, a resin tape such as polyethylene terephthalate (PET) can be used.

[0056] The winding direction of the restraining tape may be the same as or different from the twisting direction of the four covered electric wires 11 of the core 100. (2) Regarding the shape of the multi-core cable The multi-core cable 10 can have a circular shape in a cross-section perpendicular to the longitudinal direction, for example, as shown in FIG. 1. In the cross-section perpendicular to the longitudinal direction of the multi-core cable 10, the ratio of the minimum value to the maximum value of the outer diameter, that is, minimum value ÷ maximum value, is not particularly limited, but can be, for example, 0.9 or more and 1.0 or less.

[0057] By setting the ratio of the minimum value to the maximum value of the outer diameter in the cross-section perpendicular to the longitudinal direction to 0.9 or more and 1.0 or less, the cross-section of the multi-core cable 10 can be made closer to a perfect circle, and the handleability of the multi-core cable 10 can be improved.

[0058] The outer diameter D10 of the multi-core cable 10 is not particularly limited either, but can be, for example, 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, sufficient thickness of the outer sheath 13 etc. can be 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 handleability can be improved.

Examples

[0059] Specific examples will be given below for explanation, but the present invention is not limited to these examples. (Evaluation method) First, the evaluation method of the multi-core cable manufactured in the following experimental examples will be described. (1) Outer diameters of the conductor, covered electric wire, core, and multi-core cable The outer diameters of the conductor, covered electric wire, core, and multi-core cable were measured in accordance with JIS C 3005 (2014).

[0060] Specifically, for example, in any cross-section perpendicular (right-angled) to the longitudinal direction of the coated wire 11, the outer diameter of the conductor 111 was measured along two perpendicular diameters, and the average value was taken as the outer diameter D111 of the conductor 111.

[0061] Here, the conductor 111 was used as an example for explanation. However, for the outer diameter D11 of the coated wire 11, the outer diameter D100 of the core 100, the outer diameter D10 of the multi-core cable 10, etc., they were obtained by the same procedure except that the evaluation objects were the coated wire 11, the core 100, and the multi-core cable 10. In the case of the multi-core cable 10 shown in FIG. 1, measurements were made for each of the first wire 11A and the second wire 11B as the coated wire 11. Also, in the case of the multi-core cable 20 shown in FIG. 2, the outer diameter D200 of the core 200 and the outer diameter D20 of the multi-core cable 20 were measured.

[0062] Also, 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. (2) Characteristic Impedance For the first wire 11A of the multi-core cable manufactured in the following experimental examples, the characteristic impedance was measured by the Time Domain Reflectometry (TDR method). In Experimental Example 2, measurements were made for the coated wire 11 instead of the first wire 11A. The same applies to the following Skew and attenuation amount. (3) Skew For the two first wires 11A of the multi-core cable manufactured in the following experimental examples, an electrical pulse was sent using a digital serial analyzer, and the delay time per meter was measured to obtain the Skew. (4) Attenuation Amount For the first wire 11A in the 5 - m long multi-core cable manufactured in each of the following experimental examples, measurements were made using a network analyzer. The measurement results are shown in FIG. 3. Table 2 lists the attenuation amount for a 2 - GHz signal. (Experimental Conditions, Results) The multi-core cables manufactured in each of the following experimental examples will be described below.

[0063] In Experimental Example 1 and Experimental Example 2 below, a multi-core cable was fabricated. Experimental Example 1 is the example, and Experimental Example 2 is the comparative example. [Experimental Example 1] A multi-core cable 10 having a structure of a cross-section perpendicular to the longitudinal direction shown in FIG. 1 was fabricated. The sizes of each part of the multi-core cable 10 are shown in Table 1. Also, the results of measuring the characteristic impedance, Skew, and attenuation of the obtained multi-core cable 10 are shown in Table 2 and FIG. 3. [Experimental Example 2] A multi-core cable 20 having a structure of a cross-section perpendicular to the longitudinal direction shown in FIG. 2 was fabricated. The multi-core cable 20 has the same configuration of four covered electric wires 11, and the outer diameter D11 of the four covered electric wires 11 is the same as shown in Table 2. The sizes of each part of the multi-core cable 20 are shown in Table 1. Also, the results of measuring the characteristic impedance, Skew, and attenuation of the obtained multi-core cable 20 are shown in Table 2 and FIG. 3.

[0064] As shown in FIG. 3, in the multi-core cable of Experimental Example 2, a sharp drop in the attenuation was confirmed near 2.5 GHz. As shown in Table 2, the attenuation at 2 GHz was improved by 13% in Experimental Example 1 compared to Experimental Example 2.

[0065]

Table 1

[0066]

Table 2

Explanation of Signs

[0067] 10 Multi-core cable D10 Outer diameter 20 Multi-core cable D20 Outer diameter 100 Core D100 Outer diameter of the core 200 Core D200 Outer diameter of the core 11 Covered electric wire D11 Outer diameter of the covered electric wire 111 Conductor Outer diameter of conductor D111 112 Insulator 11A First electric wire Outer diameter of first electric wire D11A 111A First conductor Outer diameter of first conductor D111A 112A First insulator 11B Second electric wire Outer diameter of second electric wire D11B 111B Second conductor Outer diameter of second conductor D111B 112B Second insulator C11 Center C12 Center C21 Center C22 Center S1 Quadrilateral L1 First diagonal line L2 Second diagonal line P10 Contact part P11 Contact part P12 Contact part P13 Contact part P14 Contact part P21 Contact part P22 Contact part P23 Contact part P24 Contact part 12 Shielding layer 121 First shielding layer 122 Second shielding layer 13 Outer sheath

Claims

1. A core formed by twisting four covered electric wires, A shielding layer disposed outside the core, An outer jacket disposed outside the shielding layer, and having, 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 perpendicular to the longitudinal direction of the core, the centers of the two first electric wires are located on the first diagonal line of the quadrilateral connecting the centers of the four covered electric wires, and the centers of the two second electric wires are located on the second diagonal line of the quadrilateral. The two first electric wires are in contact with each other, and the first electric wire is in contact with the second electric wire disposed adjacent along the outer periphery of the core., Multi-core cable.

2. The multi-core cable according to claim 1, wherein 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.

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

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