Multi-core cable

Abstract

The multi-core cable (1) according to an embodiment of the present disclosure comprises: a core wire (4) produced by twisting a pair of first core electric wires (2) and a wire rod (3) together; and a sheath layer (5) disposed around the core wire. The first core electric wire (2) comprises a conductor (2b) and an insulating layer (2a) covering the outer periphery of the conductor, wherein ratio d2 / d1 of average outer diameter d2 of the wire rod (3) to average outer diameter d1 of the first core electric wire (2) is greater than 0.5 but less than 2.0.

Description

[Technical Field]

[0001] The present disclosure relates to multi-conductor cables. This application claims priority to Japanese Application No. 2021-077349, filed on April 30, 2021, and incorporates by reference all of the contents of the above-mentioned Japanese application. [Background technology]

[0002] Patent Document 1 describes a core electric wire used in an in-vehicle multi-core cable for an electric parking brake (EPB) or a wheel speed sensor, which has a conductor and two insulating layers made of resin covering the conductor, one of which contains a copolymer of ethylene and an α-olefin having a carbonyl group, and the other of which contains a polyolefin or a fluororesin. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-032515 Summary of the Invention

[0004] A multi-core cable according to one embodiment of the present disclosure is a multi-core cable comprising a core wire formed by twisting together a pair of first core wires and one wire rod, and a sheath layer arranged around the core wire, wherein the first core wire comprises a conductor and an insulating layer that covers the outer periphery of the conductor, and the ratio d2 / d1 of the average outer diameter d2 of the wire rod to the average outer diameter d1 of the first core wire is greater than 0.5 and less than 2.0. [Brief explanation of the drawings]

[0005] [Figure 1] FIG. 1 is a schematic cross-sectional view showing a multi-core cable according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a schematic cross-sectional view showing a multi-core cable according to one embodiment of the present disclosure. [Figure 3] FIG. 3 is a schematic cross-sectional view showing a multi-core cable according to an embodiment of the present disclosure. [Figure 4] FIG. 4 is a schematic diagram illustrating a multi-core cable manufacturing apparatus according to an embodiment of the present disclosure. [Figure 5] FIG. 5 is a schematic diagram for explaining the bending test in the examples. DETAILED DESCRIPTION OF THE INVENTION

[0006] [Problem to be solved by this disclosure] Multi-core cables for automotive applications such as electric parking brakes and wheel speed sensors are required to have high bending resistance, as they are bent in complex ways when routed around the vehicle and used to drive actuators, etc. In addition, to improve workability, the sheath layer must be easily removable at the end of the multi-core cable (hereinafter also referred to as "excellent terminal processability").

[0007] The present disclosure has been made in light of the above circumstances, and an object of the present disclosure is to provide a multi-core cable that is excellent in bending resistance and terminal processability.

[0008] [Effects of this disclosure] A multi-core cable according to one aspect of the present disclosure has excellent bending resistance and terminal processability.

[0009] [Description of the embodiments of the present disclosure] First, embodiments of the present disclosure will be listed and described.

[0010] A multi-core cable according to one embodiment of the present disclosure is a multi-core cable comprising a core wire formed by twisting together a pair of first core wires and one wire rod, and a sheath layer arranged around the core wire, wherein the first core wire comprises a conductor and an insulating layer that covers the outer periphery of the conductor, and the ratio d2 / d1 of the average outer diameter d2 of the wire rod to the average outer diameter d1 of the first core wire is greater than 0.5 and less than 2.0.

[0011] The multi-core cable has excellent bending resistance and terminal processability due to the ratio d2 / d1 of the average outer diameter d2 of the wire rod to the average outer diameter d1 of the first core wire being greater than 0.5 and less than 2.0. "Bending resistance" refers to the ability of the conductor to withstand repeated bending of the wire or cable without breaking. The multi-core cable also has excellent bending resistance at low temperatures. "Low temperature" refers to a temperature range of 0°C or below.

[0012] The wire is preferably a second core wire including a conductor and an insulating layer covering the conductor, which allows the cable to have a symmetrical cross section and further improves the bending resistance of the multi-core cable.

[0013] Preferably, the wire is a twisted-core electric wire including a core wire formed by twisting together a plurality of third core electric wires and a sheath layer disposed around the core wire, and the third core electric wire includes a conductor and an insulating layer covering the conductor, which further improves the bending resistance of the multi-core cable.

[0014] It is preferable that the ratio D / d1 of the average outer diameter D of the multi-core cable to the average outer diameter d1 of the first core wires is greater than 2.7 and less than 4.0, thereby enhancing the effects of improving the bending resistance and terminal processability of the multi-core cable.

[0015] The multi-core cable is suitable for use as an in-vehicle cable.

[0016] [Details of the embodiments of the present disclosure] A multi-core cable according to an embodiment of the present disclosure will be described in detail below with reference to the drawings.

[0017] <Multi-core cable> The multi-core cable 1 shown in Fig. 1 is a multi-core cable including a core wire 4 formed by twisting together a pair of core wires 2 and one wire rod 3, and a sheath layer 5 disposed around the core wire 4. The multi-core cable 1 can be suitably used as an in-vehicle cable. Specific applications include, for example, electric parking brakes (EPBs), wheel speed sensors, and in-wheel motors.

[0018] The cross-sectional shape of the multi-core cable 1 is not particularly limited and may be, for example, circular. The average outer diameter D of the multi-core cable 1 can be designed appropriately depending on the application, with a lower limit of, for example, 6 mm, preferably 8 mm, and an upper limit of, for example, 16 mm, preferably 12 mm. The "average outer diameter" refers to the average value of the outer diameters of 10 arbitrary cross sections. Note that, for example, if the cross section is flat and the measured value varies depending on how the diameter is measured, the average of the maximum and minimum outer diameters is considered to be the outer diameter.

[0019] In the multi-core cable 1, the ratio d2 / d1 of the average outer diameter d2 of the wires 3 to the average outer diameter d1 of the core wires 2 is greater than 0.5 and less than 2.0. By setting the ratio d2 / d1 within the above range, the cable has excellent bending resistance and terminal processability. While the reason for this is not entirely clear, it is presumed that, for example, by setting the ratio d2 / d1 within the above range, the cross-sectional shapes of the core wires 4 are uniformly arranged, which can suppress disturbance of the bunched twist structure of the core wires 4 when bent, thereby improving bending resistance. Furthermore, it is presumed that the uniform arrangement of the cross-sectional shapes of the core wires 4 makes the thickness of the sheath layer 5 constant in the circumferential direction, which allows for uniform penetration of the blade when removing the sheath layer 5, thereby improving terminal processability.

[0020] The lower limit of the ratio d2 / d1 is preferably 0.7, more preferably 0.8, and even more preferably 1.0. The upper limit of the ratio d2 / d1 is preferably 1.7, more preferably 1.5, and even more preferably 1.3. When the ratio d2 / d1 is within the above range, bending resistance and terminal processability can be further improved. Furthermore, the internal space of the sheath layer 5 can be reduced, thereby improving cross-sectional shape stability.

[0021] In the multi-core cable 1, the ratio D / d1 of the average outer diameter D of the multi-core cable 1 to the average outer diameter d1 of the core wires 2 is preferably greater than 2.7 and less than 4.0. When the ratio D / d1 is within the above range, the bending resistance and terminal processability can be further improved. The lower limit of the ratio D / d1 is more preferably 2.8, and even more preferably 3.0. When the ratio D / d1 is equal to or greater than the above lower limit, the bending resistance can be further improved. The upper limit of the ratio D / d1 is more preferably 3.7, and even more preferably 3.5. When the ratio D / d1 is equal to or less than the above upper limit, the terminal processability can be further improved.

[0022] [Core wire] The core wire 4 is a bunched stranded wire in which a pair of core wires 2 and one wire rod 3 are twisted together.

[0023] (Core wire) The core electric wire 2 includes a conductor 2b and an insulating layer 2a covering the outer periphery of the conductor 2b. The pair of core electric wires 2 have the same average outer diameter. Here, "same" means that the difference between the average outer diameters of the pair of core electric wires 2 is 5% or less of the outer diameter of the smaller core electric wire 2.

[0024] The lower limit of the average outer diameter d1 of the core wire 2 is, for example, 1.3 mm, and preferably 2.0 mm, and the upper limit is, for example, 5.0 mm, and preferably 4.5 mm.

[0025] Conductor 2b is a conductor made of multiple strands of wire twisted together at a fixed pitch. The strands are not particularly limited, and examples include copper wire, copper alloy wire, aluminum wire, and aluminum alloy wire. Conductor 2b may be a stranded wire made of multiple strands of wire twisted together, and may be a twisted wire made by further twisting multiple stranded wires. It is preferable that the stranded wires be made of the same number of strands of wire.

[0026] The lower limit of the average diameter of the wire is preferably 40 μm, more preferably 50 μm, and even more preferably 60 μm. On the other hand, the upper limit of the average diameter of the wire is preferably 100 μm, more preferably 90 μm. The average diameter of the wire refers to the average value when the average diameter of any three points on the wire is measured using a micrometer with cylindrical ends.

[0027] The number of wires is appropriately designed depending on the application of the multi-core cable 1, the diameter of the wires, etc., and the lower limit is preferably 196, more preferably 294. On the other hand, the upper limit of the number of wires is preferably 2450, more preferably 2000. Examples of twisted wires include a twisted wire having 196 wires, which is made by twisting 28 wires together to form 7 twisted wires, which are further twisted together; a twisted wire having 294 wires, which is made by twisting 42 wires together to form 7 twisted wires, which are further twisted together; a twisted wire having 380 wires, which is made by twisting 20 wires together to form 19 twisted wires, which are further twisted together; a twisted wire having 1568 wires, which is made by twisting 32 wires together to form 7 twisted wires, which are further twisted together to form 224 wires; and a twisted wire having 2450 wires, which is made by twisting 50 wires together to form 7 twisted wires, which are further twisted together to form 350 wires.

[0028] The lower limit of the average area (including the gaps between the wires) in the cross section of the conductor 2b is 1.0 mm 2 is preferable, 1.5 mm 2 is more preferable, and 1.8 mm 2 is more preferable, and 2.0 mm 2 On the other hand, the upper limit of the average area of ​​the cross section of the conductor 2b is 3.0 mm 2 is preferable, 2.8 mm 2 The average area in the cross section of the conductor 2b is calculated by measuring the outer diameter of any three points of the conductor 2b with a vernier caliper while being careful not to crush the stranded structure of the conductor, and then calculating the average value as the average outer diameter.

[0029] The insulating layer 2a is formed from an insulating layer-forming composition whose main component is synthetic resin, and is laminated around the outer periphery of the conductor 2b to cover the conductor 2b. The "main component" refers to the substance that has the highest content among the substances that make up the insulating layer 2a. The average thickness of the insulating layer 2a is not particularly limited, and is, for example, 0.1 mm or more and 5 mm or less. The "average thickness" refers to the average value of thicknesses measured at any 10 points.

[0030] The synthetic resin that is the main component of the insulating layer 2a may be crosslinked by electron beam irradiation or the like. When the main component of the insulating layer 2a is a crosslinked synthetic resin, deformation of the insulating layer 2a due to heat can be suppressed, for example, when forming the sheath layer 5 by extrusion molding in the manufacture of the multi-core cable 1. The crosslinking can be performed by irradiating the insulating layer-forming composition with ionizing radiation. Examples of ionizing radiation that can be used include gamma rays, electron beams, X-rays, neutron beams, and high-energy ion beams. The lower limit of the exposure dose of ionizing radiation is preferably 10 kGy, more preferably 30 kGy. The upper limit of the exposure dose of ionizing radiation is preferably 300 kGy, more preferably 240 kGy.

[0031] Examples of the synthetic resin include polyvinyl chloride, polyolefin resin, and polyurethane resin. Examples of the polyolefin resin include polypropylene (homopolymer, block polymer, random polymer, etc.), polypropylene thermoplastic elastomer, reactor-type polypropylene thermoplastic elastomer, dynamically crosslinked polypropylene thermoplastic elastomer, polyethylene (high-density polyethylene, linear low-density polyethylene, low-density polyethylene, very low-density polyethylene, etc.), polyethylene resins such as ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ethylene-methyl methacrylate copolymer, ethylene-methyl acrylate copolymer, ethylene-methyl methacrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene-butyl acrylate copolymer, ethylene-propylene rubber, ethylene-acrylic rubber, ethylene-glycidyl methacrylate copolymer, and ethylene-methacrylic acid copolymer. Examples of the polyolefin resin include ionomer resins in which the molecules of copolymers such as ethylene-methacrylic acid copolymer and ethylene-acrylic acid copolymer are intermolecularly bonded by metal ions such as sodium or zinc. Furthermore, these resins may be modified with maleic anhydride or the like. Furthermore, these resins may have an epoxy group, an amino group, an imide group, or the like.

[0032] The lower limit of the product C×E of the coefficient of linear expansion C of the insulating layer 2a from -35°C to 25°C and the modulus of elasticity E at -35°C is 0.01 MPaK. -1 On the other hand, the upper limit of the product C×E is preferably 0.9 MPaK. -1 The product C×E can be adjusted by the type of synthetic resin, the content ratio, the presence or absence of additives, etc.

[0033] The lower limit of the linear expansion coefficient C of the insulating layer 2a from -35°C to 25°C is 1.0 × 10 - 5 K -1 is preferred, and 1.0 × 10 -4 K -1 On the other hand, the upper limit of the linear expansion coefficient C of the insulating layer 2a is 2.5×10-4 K -1 is preferred, and 2.0 × 10 -4 K -1 The "coefficient of linear expansion" is a value calculated from the dimensional change of a thin plate relative to a temperature change using a viscoelasticity measuring device ("DVA-220" manufactured by IT Measurement & Control Co., Ltd.) in a tensile mode in a temperature range of -100°C to 200°C, at a heating rate of 5°C / min, a frequency of 10 Hz, and a strain of 0.05%, in accordance with the test method for dynamic mechanical properties described in JIS-K7244-4 (1999).

[0034] The lower limit of the elastic modulus E of the insulating layer 2a at -35°C is preferably 1,000 MPa, more preferably 2,000 MPa. On the other hand, the upper limit of the elastic modulus E of the insulating layer 2a is preferably 3,500 MPa, more preferably 3,000 MPa. The "elastic modulus" refers to the value of the storage elastic modulus measured in tension mode using the above-mentioned viscoelasticity measuring device in the temperature range of -100°C to 200°C, at a heating rate of 5°C / min, a frequency of 10 Hz, and a strain of 0.05%, in accordance with the dynamic mechanical property testing method described in JIS-K7244-4 (1999).

[0035] The insulating layer 2a may contain additives such as flame retardants, flame retardant auxiliaries, antioxidants, lubricants, colorants, reflectivity-imparting agents, opacifying agents, processing stabilizers, and plasticizers, as necessary. Examples of flame retardants include halogen-based flame retardants such as bromine-based flame retardants and chlorine-based flame retardants, and non-halogen-based flame retardants such as metal hydroxides, nitrogen-based flame retardants, and phosphorus-based flame retardants. The flame retardants may be used alone or in combination of two or more.

[0036] (wire rod) The wire material 3 is different from the pair of core wires 2 that constitute the core wire 4, and examples thereof include a core wire different from the core wires 2, a twisted core wire formed by twisting together multiple core wires, and a dummy wire such as a resin rod.

[0037] The lower limit of the average outer diameter d2 of the wire 3 is not particularly limited as long as the ratio d2 / d1 in relation to the average outer diameter d1 of the core wire 2 satisfies the above range, and is, for example, 1.3 mm, preferably 2.0 mm, and the upper limit is, for example, 5.0 mm, preferably 4.5 mm.

[0038] When the wire 3 is a core electric wire different from the core electric wire 2, the core electric wire preferably includes a conductor 3b and an insulating layer 3a that covers the outer periphery of the conductor, as shown in Fig. 2. The conductor 3b may be the same as the conductor 2b, for example. The insulating layer 3a may be the same as the insulating layer 2a, for example.

[0039] When the wire 3 is a stranded core electric wire formed by stranding a plurality of electric core wires, the stranded core electric wire is, for example, as shown in FIG. 3, a stranded core electric wire including a core wire 7 formed by stranding a plurality of electric core wires 6 and a sheath layer 8 disposed around the core wire, and the electric core wire 6 preferably includes a conductor 6b and an insulating layer 6a covering the outer periphery of the conductor. The conductor 6b may be, for example, the same as the conductor 2b. The insulating layer 6a may be, for example, the same as the insulating layer 2a. The sheath layer 8 may be, for example, the same as the outer sheath layer 5b described below.

[0040] When the wire 3 is a dummy wire such as a resin rod, the resin rod may be made of, for example, polyethylene or polypropylene.

[0041] [Sheath layer] The sheath layer 5 has a two-layer structure including an inner sheath layer 5a laminated on the outside of the core wire 4 and an outer sheath layer 5b laminated on the outer periphery of the inner sheath layer 5a.

[0042] The main component of the inner sheath layer 5a is not particularly limited as long as it is a flexible synthetic resin, and examples thereof include polyolefins such as polyethylene and ethylene-vinyl acetate copolymer (EVA), polyurethane elastomers, polyester elastomers, etc. Two or more of these may be mixed together.

[0043] The minimum thickness of the inner sheath layer 5a (the minimum distance between the core wire 4 and the outer periphery of the inner sheath layer 5a) is preferably 0.3 mm, more preferably 0.4 mm, and more preferably 0.9 mm, more preferably 0.8 mm.

[0044] The main component of the outer sheath layer 5b is not particularly limited as long as it is a synthetic resin having excellent flame retardancy and abrasion resistance, and examples thereof include polyurethane.

[0045] The average thickness of the outer sheath layer 5b is preferably 0.3 mm or more and 0.7 mm or less.

[0046] The resin components of the inner sheath layer 5a and the outer sheath layer 5b are preferably cross-linked. The cross-linking method for the inner sheath layer 5a and the outer sheath layer 5b can be the same as the cross-linking method for the insulating layer 2a.

[0047] The inner sheath layer 5a and the outer sheath layer 5b may also contain the additives exemplified for the insulating layer 2a.

[0048] A tape member such as paper or nonwoven fabric may be wound between the core wire 4 and the sheath layer 5 as a restraining member.

[0049] <Manufacturing method of multi-core cable> The multi-core cable 1 can be obtained by a manufacturing method including a step of twisting a pair of core wires 2 and one wire 3 together (twisting step), and a step of covering the outside of the core wire 4, which is made by twisting a pair of core wires 2 and one wire 3 together, with a sheath layer 5 (sheath layer covering step).

[0050] The method for manufacturing the multi-core cable can be performed using, for example, a multi-core cable manufacturing apparatus shown in Fig. 4. The multi-core cable manufacturing apparatus mainly includes a plurality of supply reels 102, a twisting unit 103, an inner sheath layer covering unit 104, an outer sheath layer covering unit 105, a cooling unit 106, and a cable winding reel 107.

[0051] (Twisting process) In the twisting process, pairs of core wires 2 and wire rods 3 wound around a plurality of supply reels 102 are supplied to a twisting section 103, where they are twisted together to form a core wire 4.

[0052] (Sheath layer coating process) In the sheath layer covering step, the inner sheath layer covering unit 104 extrudes the resin composition for forming the inner sheath layer stored in the storage unit 104a onto the outside of the core wire 4 formed in the twisting unit 103. In this way, the outside of the core wire 4 is covered with the inner sheath layer 5a.

[0053] After the inner sheath layer 5a is coated, the resin composition for forming the outer sheath layer stored in the reservoir 105a is extruded onto the outer periphery of the inner sheath layer 5a by the outer sheath layer coating unit 105. As a result, the outer periphery of the inner sheath layer 5a is coated with the outer sheath layer 5b.

[0054] After being covered with outer sheath layer 5b, core wire 4 is cooled in cooling section 106 to harden sheath layer 5, thereby obtaining multi-core cable 1. Multi-core cable 1 is wound and collected by cable winding reel 107.

[0055] The method for manufacturing the multi-core cable may further include a step (crosslinking step) of crosslinking the resin component of the sheath layer 5. The crosslinking step may be performed before or after covering the core wire 4 with the composition that forms the sheath layer 5 (after the sheath layer 5 is formed).

[0056] The crosslinking can be carried out by irradiating the same insulating layer-forming composition as that for the insulating layer 2a of the multi-core cable 1 with ionizing radiation.

[0057] [Other embodiments] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present disclosure is not limited to the configurations of the above-described embodiments, but is defined by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0058] The sheath layer 5 of the multi-core cable 1 may be a single layer or may have a multi-layer structure of two or more layers.

[0059] The multi-core cable 1 may have other layers between the core wires 4 and the sheath layer 5 or around the sheath layer 5. Examples of other layers disposed between the core wires 4 and the sheath layer 5 include a restraining material layer such as a paper tape layer or a nonwoven fabric layer. Examples of other layers disposed around the sheath layer 5 include a shielding layer. [Example]

[0060] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0061] [Making core wire] An insulating layer-forming composition was prepared by blending 100 parts by weight of ethylene-ethyl acrylate copolymer, 70 parts by weight of flame retardant, and 2 parts by weight of antioxidant. The insulating layer-forming composition was extruded onto the outer periphery of a conductor (average diameter 2.4 mm) consisting of 72 stranded annealed copper strands, each with an average diameter of 80 μm, to form an insulating layer. This resulted in a core wire with an average outer diameter d1 of 3.0 mm. The insulating layer was irradiated with an electron beam at 60 kGy to crosslink the resin components. The ethylene-ethyl acrylate copolymer used in the preparation of the insulating layer-forming composition was ENEOS NUC Corporation's "DPDJ-6182" (ethyl acrylate content 15% by weight), the flame retardant was aluminum hydroxide (Showa Denko K.K.'s "Higilite® H-31"), and the antioxidant was BASF's "Irganox® 1010".

[0062] [Wire rod production] An insulating layer was formed by extruding cross-linked polyurethane onto the outer periphery of a conductor (average diameter 0.72 mm) made by twisting 60 copper alloy wires with an average diameter of 80 μm, to obtain wires with an average outer diameter d2 shown in Table 1 below.

[0063] [Making multi-core cables] A pair of the core wires prepared above was twisted together with the wire material prepared above to form a core wire, and a sheath layer was extruded around the core wire to obtain multi-core cables Nos. 1 to 14 with average outer diameters D shown in Table 1 below. The sheath layer was formed from a flame-retardant cross-linked polyurethane as its main component. The resin component of the sheath layer was cross-linked by electron beam irradiation at 180 kGy.

[0064] [Bending resistance] As shown in Figure 5, multi-core cables X Nos. 1 to 14 were passed vertically between two 60 mm diameter mandrels arranged horizontally and parallel to each other. The upper end of each cable was bent horizontally by 90° so that it abutted against the upper side of one mandrel A1, and then repeatedly bent by 90° in the opposite direction so that it abutted against the upper side of the other mandrel A2. The test conditions were as follows: a downward load of 2 kg was applied to the lower end of the multi-core cable X, the temperature was -30°C, and the bending rate was 60 times / min. In the test, the number of bendings until the multi-core cable broke (a state in which it could no longer conduct electricity) was measured. The results are shown in Table 1 below. The bending resistance was evaluated as "good" when the number of bending times was 30,000 or more, and "poor" when the number of bending times was less than 30,000.

[0065] [Terminal processability] The V-shaped blade was used to make a cut in the sheath layer of the multi-core cable, and the load required to tear off the sheath layer was measured using a load cell. The results are shown in Table 1 below. Terminal workability was evaluated as "good" when the load was 40N or less, and "poor" when the load was over 40N.

[0066] [comprehensive evaluation] The overall evaluation of multi-core cables was based on two items: bending resistance and terminal workability. If both items were "good," the cable was rated "A" (good). If one of the two items was "good" and the other "poor," the cable was rated "B" (fairly good). If both items were "poor," the cable was rated "C" (poor). Multi-core cables with an overall evaluation of "B" or higher were deemed to have passed the evaluation.

[0067] [Table 1]

[0068] As shown in Table 1, the multi-core cables No. 1 to No. 3, No. 5 to No. 7, and No. 9 to No. 14, in which the ratio d2 / d1 of the average outer diameter d2 of the wire rod to the average outer diameter d1 of the core wires was more than 0.5 and less than 2.0, received an overall rating of "B" or higher. Furthermore, the multi-core cables No. 1 to No. 3, No. 5 to No. 7, No. 9, No. 10, No. 12, and No. 13, in which the ratio D / d1 of the average outer diameter D of the multi-core cable to the average outer diameter d1 of the core wires was more than 2.7 and less than 4.0, received an overall rating of "A." [Explanation of symbols]

[0069] 1 multi-core cable 2-core wire 2a Insulating layer 2b conductor 3 wire rod 3a Insulating layer 3b conductor 4-core wire 5 Sheath layer 5a Inner sheath layer 5b outer sheath layer 6-core wire 6a Insulating layer 6b Conductor 7 core wire 8 Sheath layer d1 Average outer diameter of core wire 2 d2 Average outer diameter of wire 3 D Average outer diameter of multi-core cable 1 102 Supply Reel 103 Twisted section 104 Inner sheath layer covering 104a, 105a Reservoir 105 outer sheath layer covering 106 Cooling section 107 Cable winding reel A1, A2 mandrels X multi-core cable

Claims

1. A multi-core cable including a core wire formed by twisting together a pair of first core wires and one wire rod, and a sheath layer disposed around the core wire, The first core wire includes a conductor and an insulating layer covering an outer periphery of the conductor, a ratio d2 / d1 of the average outer diameter d2 of the wire to the average outer diameter d1 of the first core electric wire is greater than 0.5 and less than 2.0; A multi-core cable in which the ratio D / d1 of the average outer diameter D of the multi-core cable to the average outer diameter d1 of the first core wires is greater than 2.7 and less than 4.

0.

2. 2. The multi-core cable according to claim 1, wherein the wire is a second core wire having a conductor and an insulating layer covering the outer periphery of the conductor.

3. the wire is a stranded-core electric wire including a core wire formed by stranding a plurality of third core electric wires together and a sheath layer disposed around the core wire, The multi-core cable according to claim 1 , wherein the third core wire comprises a conductor and an insulating layer covering the outer periphery of the conductor.

4. The multi-core cable according to any one of claims 1 to 3, which is an in-vehicle cable.

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