Multi-core cable

Abstract

The present invention provides a multi-core cable that can reduce wire kinking even when bent while heated to high temperatures. [Solution] A multi-core cable comprising a plurality of insulated wires and a sheath disposed outside the plurality of insulated wires, wherein the resin of the sheath is cross-linked and the 5% modulus of the sheath is 1.0 MPa or less.

Description

[Technical Field]

[0001] This disclosure relates to multi-core cables. [Background technology]

[0002] Patent Document 1 discloses an electric wire / cable having an outermost coating layer, wherein the outermost coating layer is formed from a composition obtained by blending 0.1 to 1.1 parts by weight of a crosslinking agent with 100 parts by weight of a blend polymer consisting of 40 to 95 parts by weight of a polyolefin having crystals with a thermal softening point of 150°C or higher and 60 to 5 parts by weight of a soft polyolefin having a Shore D hardness of 65 or less, and further characterized in that either or both of the polyolefin having crystals with a thermal softening point of 150°C or higher and the soft polyolefin having a Shore D hardness of 65 or less are modified with maleic anhydride. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2000-030537 [Overview of the project] [Problems that the invention aims to solve]

[0004] As automobiles become increasingly electrified, many multi-core cables are installed inside vehicles to connect electronic devices. Various studies have been conducted on these multi-core cables, as disclosed in Patent Document 1, among others.

[0005] The purpose of this disclosure is to provide a multi-core cable that can reduce wire kinks even when bent while heated at high temperatures. [Means for solving the problem]

[0006] The cable of this disclosure comprises a plurality of insulated wires and a sheath disposed outside the plurality of insulated wires, wherein the resin of the sheath is crosslinked and the 5% modulus of the sheath is 1.0 MPa or less. [Effects of the Invention]

[0007] According to this disclosure, it is possible to provide a multi-core cable that can reduce wire kinks even when the cable is bent while heated at high temperatures. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a cross-sectional view of a multi-core cable according to one aspect of the present disclosure, in a plane perpendicular to the longitudinal side. [Figure 2] Figure 2 is an explanatory diagram of the method for measuring bending stiffness. [Figure 3A] Figure 3A is an explanatory diagram of the method for measuring the amount of line displacement. [Figure 3B] Figure 3B is an explanatory diagram of the method for measuring the amount of linear displacement. [Figure 3C] Figure 3C is an explanatory diagram of the method for measuring the amount of line displacement. [Figure 4] Figure 4 is an explanatory diagram of the flexibility test. [Figure 5] Figure 5 is a table summarizing the configuration of the multi-core cable in the experimental example and the evaluation results. [Figure 6] Figure 6 is an explanatory diagram illustrating the relationship between the amount of wire deformation displacement and the 5% modulus of the multi-core cables fabricated in Experimental Examples 1 to 5. [Figure 7] Figure 7 is an explanatory diagram illustrating the relationship between the amount of wire deformation displacement and bending stiffness of the multi-core cables fabricated in Experimental Examples 1 to 5. [Modes for carrying out the invention]

[0009] The implementation methods are described below.

[0010] [Description of Embodiments in this 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 plurality of coated electric wires and a sheath disposed outside the plurality of coated electric wires. The resin of the sheath is crosslinked, and the 5% modulus of the sheath is 1.0 MPa or less.

[0012] By having a sheath, the multi-core cable protects the coated electric wires disposed inside and can enhance durability.

[0013] By crosslinking the resin of the sheath, the heat resistance, oil resistance, liquid resistance, etc. (hereinafter also referred to as environmental resistance) of the sheath and the multi-core cable can be enhanced. By setting the 5% modulus of the sheath to 1.0 MPa or less, the wire kink displacement amount can be set to 170 mm or less. Thereby, the wire kink generated when the bending of the multi-core cable is maintained in a state heated at a high temperature can be sufficiently reduced. The wire kink means the degree of kink or bend remaining in the multi-core cable when the multi-core cable is bent, the bent state is maintained at a high temperature, and then the bending is released. Here, the high temperature is, for example, 80°C or higher. [[ID=​​​​​​​​​​​​​By including a first sheath and a second sheath, the material can be selected according to the function of the layer, and the properties of the sheath can be easily controlled.

[0018] (4) In the above (3), the first sheath may contain a polyolefin resin.

[0019] Because polyolefin resin is easily crosslinked, the properties of the first sheath can be easily controlled by including polyolefin resin in the first sheath. Furthermore, since polyolefin resin is less expensive than polyurethane resin and other materials, the cost of multi-core cables can be reduced.

[0020] (5) In (3) or (4) above, the room temperature modulus of the first sheath may be 40 MPa or less.

[0021] By setting the room-temperature modulus of the first sheath to 40 MPa or less, the amount of wire deformation can be easily reduced to 170 mm or less. Therefore, the wire deformation that occurs when a multi-core cable is bent while heated at high temperatures can be sufficiently reduced.

[0022] (6) In any of (3) to (5) above, the second sheath may contain polyurethane resin.

[0023] The inclusion of polyurethane resin in the second sheath enhances the damage resistance and abrasion resistance of the multi-core cable 10.

[0024] (7) In any of (3) to (6) above, the room temperature modulus of the second sheath may be 40 MPa or less.

[0025] By setting the room-temperature modulus of the second sheath to 40 MPa or less, the amount of wire deformation can be easily reduced to 170 mm or less. Therefore, the wire deformation that occurs when a multi-core cable is bent while heated at high temperatures can be sufficiently reduced.

[0026] (8) In any of (3) to (7) above, the ratio of the cross-sectional area of ​​the first sheath to the total sheath may be 40% or more and 75% or less.

[0027] The first sheath, for example, has the function of making the sheath and multi-core cable more easily deformable. Therefore, by making the cross-sectional area of ​​the first sheath account for 40% or more of the total sheath area, a multi-core cable that is easily deformable can be made.

[0028] The second sheath has the function of protecting the multi-core cable. Therefore, by keeping the proportion of the cross-sectional area of ​​the first sheath to 75% or less of the total sheath, damage to the multi-core cable can be prevented.

[0029] (9) In any of the above (1) to (8), the bending stiffness is 780 N·mm 2 The following is also acceptable.

[0030] The bending rigidity of the multi-core cable is 780 N·mm. 2 By doing the following, the amount of wire deformation can be easily reduced to 170 mm or less, and the wire deformation that occurs when a multi-core cable is kept bent under high-temperature conditions can be sufficiently reduced.

[0031] [Details of the embodiments of this disclosure] A specific example of a multi-core cable according to one embodiment of this disclosure (hereinafter referred to as "this embodiment") will be described below with reference to the drawings. However, the present invention is not limited to these examples and is intended to be shown in the claims, with all modifications within the meaning and scope equivalent to the claims being included. [Multi-core cable] Figure 1 shows a schematic diagram of a cross-section perpendicular to the longitudinal side of the multi-core cable of this embodiment.

[0032] As shown in Figure 1, the multi-core cable 10 of this embodiment may have a plurality of insulated wires 11 and a sheath 12 arranged outside the plurality of insulated wires 11. (1) Regarding each component contained in the multi-core cable The individual components contained in the multi-core cable of this embodiment will now be described. (1-1) Insulated wire, core (1-1-1) Insulated wire The insulated wire 11 may have a conductor 111 and an insulator 112 disposed outside the conductor 111. (conductor) The conductor 111 can be a single wire or multiple wires. If the conductor 111 has multiple wires, these multiple wires can be twisted together. That is, if the conductor 111 has multiple wires, the conductor 111 can also be a stranded wire of multiple wires.

[0033] As the material for the conductor 111, one or more conductive materials selected from, for example, copper alloy, copper, aluminum, aluminum alloy, silver-plated soft copper, and tin-plated soft copper can be used. Soft copper may be used as the copper.

[0034] The cross-sectional area of ​​conductor 111 is 0.05 mm². 2 More than 3mm 2 The following is also acceptable. (Insulator) As shown in Figure 1, the insulator 112 can cover the outer surface of the conductor 111, specifically the outer surface along the longitudinal direction of the electric wire 11.

[0035] The insulator 112 may contain, for example, one or more resins selected from fluororesins, polyester resins, and polyolefin resins.

[0036] Examples of fluororesins include polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and ethylene-tetrafluoroethylene copolymer (ETFE).

[0037] Examples of polyester resins include polyethylene terephthalate (PET).

[0038] Examples of polyolefin resins include polyethylene (PE), polypropylene (PP), ethylene-vinyl acetate copolymer (EVA), ethylene-ethyl acrylate copolymer (EEA), ethylene α-olefin copolymer, ethylene methyl acrylate copolymer, ethylene butyl acrylate copolymer, ethylene methyl methacrylate copolymer, ethylene acrylic acid copolymer, partially saponified EVA, maleic anhydride-modified polyolefin, ethylene acrylic acid ester maleic anhydride copolymer, and the like.

[0039] As for polyethylene, LLDPE (linear low-density polyethylene) and VLDPE (very low-density polyethylene) can also be used.

[0040] The resin of the insulator 112 may or may not be crosslinked.

[0041] In addition to the resin mentioned above, the insulator 112 may also contain additives such as flame retardants, flame retardant enhancers, antioxidants, lubricants, colorants, reflective agents, opacifiers, processing stabilizers, and plasticizers. (1-1-2) Core The insulated wires 11 of the multi-core cable 10 can be twisted together spirally along their length to form a core 110.

[0042] The number of insulated wires 11 in the multi-core cable 10 can be any number of two or more.

[0043] Figure 1 shows an example where two insulated wires 11 of the same shape and size are twisted together to form a core 110, but the configuration is not limited to this. The multi-core cable 10 and the core 110 may include any number of insulated wires 11 with different cross-sectional areas of the conductors 111 or different wall thicknesses T112 of the insulators 112.

[0044] Furthermore, the multiple insulated wires 11 of the multi-core cable 10 may be twisted together in multiple stages to form a core 110. For example, some of the insulated wires 11 of the multi-core cable 10 may be twisted together in pairs to form a twisted-pair wire, and then further twisted together with other insulated wires 11 to form a core 110.

[0045] By twisting two insulated wires 11 together to form a twisted-pair wire, the signal transmitted by the insulated wires 11 can be made less susceptible to noise. (1-2) Sheath As shown in Figure 1, the multi-core cable 10 of this embodiment has a sheath 12 arranged outside of the multiple insulated wires 11.

[0046] The multi-core cable 10 has a sheath 12, which protects the insulated wires 11 placed inside and increases its durability.

[0047] The inventors of this invention investigated the reason why, in the case of multi-core cables, when a multi-core cable is heated to a high temperature and its bend is maintained, it develops a kink, and even when it returns to room temperature, it does not return to its original shape before the external force was applied.

[0048] In some cases, the resin in the sheath 12 is cross-linked to improve environmental resistance. However, when the resin in the sheath 12 is cross-linked, the flexibility of the sheath 12 decreases, making it more prone to coiling. Therefore, by making the sheath 12 of the multi-core cable 10 have predetermined characteristics, it was found that coiling can be reduced even when the bend of the multi-core cable is maintained under high-temperature heating conditions, thus completing the invention. (1-2-1) Regarding the structure of the sheath The sheath 12 may be formed from one layer, but it may also be formed from two or more layers.

[0049] For example, as shown in Figure 1, the sheath 12 may also include a first sheath 121 and a second sheath 122, starting from the position closest to the multiple insulated wires 11.

[0050] Since the sheath 12 includes a first sheath 121 and a second sheath 122, the material can be selected according to the function of the layer, and the properties of the sheath 12 can be easily controlled.

[0051] If the sheath 12 includes a first sheath 121 and a second sheath 122, the proportion of the first sheath 121 and the second sheath 122 in the sheath 12 can be selected according to the characteristics required of the multi-core cable 10 and the sheath 12. The proportion of the cross-sectional area of ​​the first sheath in the sheath 12 may be, for example, 40% to 75%, or 50% to 65%.

[0052] The first sheath 121 has the function of making the sheath 12 and the multi-core cable 10 more easily deformable. Therefore, by making the proportion of the cross-sectional area of ​​the first sheath 40% or more of the sheath 12, a multi-core cable 10 that is easily deformable can be made.

[0053] The second sheath 122 has the function of protecting the multi-core cable 10. Therefore, by making the ratio of the cross-sectional area of ​​the first sheath to that of the sheath 12 75% or less, damage to the multi-core cable 10 can be prevented. (1-2-2) Materials contained in the sheath The sheath 12 may contain resin.

[0054] The sheath 12 may contain one or more resins selected from polyolefin resin, polyurethane resin, polyvinyl chloride resin, and polyester resin.

[0055] The resin of the sheath 12 may be cross-linked. Cross-linking the resin of the sheath 12 can improve the environmental resistance of the sheath 12 and the multi-core cable 10. The cross-linking of the sheath 12 can be confirmed, for example, by a compression test such as the following.

[0056] A compression test involves clamping the sheath 12 with a force of 10N or more using a jig, heating it at 250°C for 3 seconds, and observing the state of the sheath 12 after heating. In a compression test, if the sheath 12 is not melted, i.e., not deformed, after heating while clamped in the jig, and visually observed, it can be determined that the sheath 12 is cross-linked. In a compression test, if the sheath 12 is melted, i.e., deformed, after heating while clamped in the jig, and visually observed, it can be determined that the sheath 12 is not cross-linked.

[0057] As shown in Figure 1, when the sheath 12 has a first sheath 121 and a second sheath 122, the first sheath 121 may contain polyolefin resin. Since polyolefin resin is easily crosslinked, the properties of the first sheath 121 can be easily controlled by including polyolefin resin in the first sheath 121. In addition, since polyolefin resin is less expensive than polyurethane resin and the like, the cost of the multi-core cable 10 can be reduced.

[0058] As the polyolefin resin, for example, the materials listed in the description of insulator 112 can be used.

[0059] When using copolymers such as ethylene-vinyl acetate copolymer (EVA) or ethylene-ethyl acrylate copolymer (EEA) as the polyolefin resin, the deformability of the first sheath 121 can be selected by selecting the content ratio of the monomers constituting the copolymer. Furthermore, the deformability of the first sheath 121 can also be selected by using multiple types of polyolefin resins and selecting their mixing ratio. By selecting the deformability of the first sheath 121, the 5% modulus and other properties described later can be controlled within a predetermined range.

[0060] The second sheath 122 may contain polyurethane resin. By including polyurethane resin in the second sheath 122, the resistance to trauma and abrasion of the multi-core cable 10 can be improved.

[0061] Sheath 12 may also contain additives other than resin, such as flame retardants, flame retardant enhancers, antioxidants, lubricants, colorants, reflective agents, opacifiers, processing stabilizers, plasticizers, and crosslinking aids. (1-2-3) Characteristics of the sheath (5% modulus) The 5% modulus is the magnitude of the tensile stress that occurs when sheath 12 is pulled so that its elongation is 5%. A smaller modulus means that it is more easily deformed.

[0062] Furthermore, according to the inventors' considerations of the present invention, the 5% modulus of the sheath 12 may be 1.0 MPa or less, 0.9 MPa or less, 0.6 MPa or less, or 0.5 MPa or less.

[0063] By setting the 5% modulus of sheath 12 to 1.0 MPa or less, the amount of wire deformation can be reduced to 170 mm or less. This effectively reduces the wire deformation that occurs when a multi-core cable is kept bent under high-temperature conditions.

[0064] In this specification, "wire kinks" refers to the condition where, when the first end of a multi-core cable is fixed and the second end is left hanging, the cable does not become straight but instead develops a bend or kink. Furthermore, "reducing wire kinks" means that the amount of wire kink displacement can be reduced to 170 mm or less. The amount of wire kink displacement is explained in "1. Evaluation Method" of the experimental example.

[0065] By setting the 5% modulus of sheath 12 to 0.9 MPa or less, the amount of wire deformation can be reduced to 160 mm or less. By setting the 5% modulus of sheath 12 to 0.6 MPa or less, the amount of wire deformation can be reduced to 140 mm or less. By setting the 5% modulus of sheath 12 to 0.5 MPa or less, the amount of wire deformation can be reduced to less than 125 mm. Therefore, by setting the 5% modulus of sheath 12 within the above range, the wire deformation that occurs when a multi-core cable is bent while heated at high temperatures can be sufficiently reduced.

[0066] The lower limit of the 5% modulus of sheath 12 is greater than 0. Therefore, the 5% modulus of sheath 12 may be greater than 0 and 1.0 MPa or less, greater than 0 and 0.9 MPa or less, greater than 0 and 0.6 MPa or less, or greater than 0 and 0.5 MPa or less.

[0067] Note that the 5% modulus of sheath 12 mentioned above refers to the value for the entire sheath 12, even if sheath 12 has multiple layers, such as the first sheath 121 and the second sheath 122. (Room temperature modulus of elasticity) If the sheath 12 has a first sheath 121 and a second sheath 122, the room temperature modulus of the first sheath 121 may be 40 MPa or less, or 35 MPa or less.

[0068] By setting the room-temperature modulus of the first sheath 121 to 40 MPa or less or 35 MPa or less, the amount of wire deformation can be easily reduced to 170 mm or less. Therefore, by setting the room-temperature modulus of the first sheath 121 within the above range, the wire deformation that occurs when the bending of a multi-core cable is maintained while heated at high temperatures can be sufficiently reduced.

[0069] The lower limit of the room temperature modulus of the first sheath 121 may be 2 MPa or higher, or 5 MPa or higher.

[0070] Therefore, the room temperature modulus of the first sheath 121 may be 2 MPa or more and 40 MPa or less, or 5 MPa or more and 35 MPa or less.

[0071] In this specification, room temperature modulus refers to the storage modulus at room temperature (25°C).

[0072] Furthermore, the room temperature modulus of the second sheath 122 may be 40 MPa or less, or 35 MPa or less.

[0073] By setting the room-temperature modulus of the second sheath 122 to 40 MPa or less or 35 MPa or less, the amount of wire deformation can be easily reduced to 170 mm or less. Therefore, by setting the room-temperature modulus of the second sheath 122 within the above range, the wire deformation that occurs when the bending of a multi-core cable is maintained while heated at high temperatures can be sufficiently reduced.

[0074] The lower limit of the room temperature modulus of the second sheath 122 may be 2 MPa or higher, or 5 MPa or higher.

[0075] Therefore, the room temperature modulus of the second sheath 122 may be between 2 MPa and 40 MPa, or between 5 MPa and 35 MPa. (1-3) Lubricants The multi-core cable 10 of this embodiment may further include a lubricant 13. Specifically, the multi-core cable 10 of this embodiment may have the lubricant 13 placed between the insulated wire 11 and the sheath 12, i.e., on the surface of the insulated wire 11.

[0076] By placing a lubricant 13 between the insulated wire 11 and the sheath 12, the adhesion force of the sheath 12 to the insulated wire 11 can be adjusted. The placement of the lubricant 13 improves the peelability of the sheath 12 from the insulated wire 11, thereby improving workability when connecting connectors or the like to the end of the multi-core cable 10.

[0077] For example, talc can be used as the material for the lubricant 13. (2) Characteristics of multi-core cables (bending stiffness) The multi-core cable 10 has a bending rigidity of 780 N·mm 2 The following may also be true: 470 N·mm 2 The following values ​​are also acceptable. A smaller bending stiffness value indicates that the material is more easily deformed.

[0078] The bending rigidity of the multi-core cable 10 is 780 N·mm 2By setting the following, the kink displacement amount can be easily made 170 mm or less, and the kink generated when the bending of the multi-core cable is maintained in a state heated at a high temperature can be sufficiently reduced.

[0079] The bending rigidity of the multi-core cable 10 is 470 N·mm 2 By setting the following, the kink displacement amount can be made less than 125 mm, and the kink generated when the bending of the multi-core cable is maintained in a state heated at a high temperature can be sufficiently reduced.

[0080] The lower limit value of the bending rigidity of the multi-core cable 10 may be greater than 0. For this reason, the bending rigidity of the multi-core cable 10 may be greater than 0 and 780 N·mm 2 It may be below, or may be greater than 0 and 470 N·mm 2 It may be below. (Kink displacement amount) The multi-core cable 10 of the present embodiment may have a kink displacement amount of 170 mm or less, 160 mm or less, 140 mm or less, or less than 125 mm.

[0081] The multi-core cable mounted on an automobile may bend when an external force such as torsion is applied during the operation of the automobile depending on the device to be connected. In addition, the multi-core cable mounted on an automobile may be heated directly or indirectly by exhaust heat from an internal combustion engine or the like, direct sunlight, etc., and heated to a high temperature. In the conventionally used multi-core cable, if it is held at a high temperature while being bent by an external force, a kink will occur, and even when it returns to room temperature after the operation ends, etc., it will not return to the shape before the external force is applied and may interfere with other members.

[0082] By making the kink displacement amount 170 mm or less, the kink generated when held at a high temperature in a bent state can be sufficiently reduced.

[0083] The lower limit of the wire deformation displacement is 0 mm or more, and may also be 50 mm or more. Therefore, the wire deformation displacement of the multi-core cable 10 may be 0 mm or more and 170 mm or less, 0 mm or more and 160 mm or less, 50 mm or more and 140 mm or less, or 50 mm or more and less than 125 mm.

[0084] The amount of wire deformation displacement is the displacement of the length of the multi-core cable 10 from before heating, measured vertically while the multi-core cable 10 is hanging down after being bent into a U-shape and heated at 80°C for 24 hours. The specific measurement method is explained in "1. Evaluation Method" of the experimental example. [Examples]

[0085] The present invention will be described with specific examples below, but it is not limited to these examples. 1. Evaluation Method First, we will explain the evaluation method for the wires fabricated in the following experimental example. (1) Wire diameter, outer diameter The outer diameter of the conductor strands used in conductor 111 was determined by measuring the lengths of two perpendicular diameters in an arbitrary cross-section perpendicular to the longitudinal side of the conductor strand, and taking the average of the two diameters.

[0086] The outer diameters D111 of the conductor 111, D112 of the insulator 112, D110 of the core 110, D121 of the first sheath 121, and D122 of the second sheath 122 were measured and calculated at any cross section perpendicular to the longitudinal direction of the multi-core cable 10.

[0087] In the case of conductor 111 with an outer diameter D111, the lengths of two orthogonal diameters of conductor 111 were measured in the cross-section of the multi-core cable 10 being measured, and the average of the two diameters was taken. The outer diameters of each part were measured and calculated using the same procedure, except that the object of measurement was changed from conductor 111 to insulator 112, core 110, first sheath 121, and second sheath 122. (2) Thick The thickness T112 of the insulator 112 was calculated by subtracting the outer diameter D111 of the conductor 111 from the outer diameter D112 of the insulator 112.

[0088] The wall thickness T121 of the first sheath 121 was calculated by subtracting the outer diameter D110 of the core 110 from the outer diameter D121 of the first sheath 121.

[0089] The wall thickness T122 of the second sheath 122 was calculated by subtracting the outer diameter D121 of the first sheath 121 from the outer diameter D122 of the second sheath 122. (3) Cross-sectional area of ​​the first sheath and the second sheath The cross-sectional area of ​​the first sheath 121 was calculated by considering the cross-sectional shape of the first sheath 121 and the insulated wire 11 as circles, and using the outer diameter D121 of the first sheath 121 and the outer diameter D112 of the insulator 112 which corresponds to the outer diameter of the insulated wire 11, and then calculating the cross-sectional area of ​​each part. Specifically, it was calculated using the following formula (A).

[0090] (Cross-sectional area of ​​the first sheath) = [(D121 / 2) 2 ×π]-[(D112 / 2) 2 ×π]×2···(A) The cross-sectional area of ​​the second sheath 122 was calculated by considering the cross-sectional shapes of the first sheath 121 and the second sheath 122 as circles, and using the outer diameters D121 of the first sheath 121 and D122 of the second sheath 122 to determine the cross-sectional areas of each part. Specifically, it was calculated using the following formula (B).

[0091] (Cross-sectional area of ​​the second sheath) = [(D122 / 2) 2 ×π]-[(D121 / 2) 2 ×π]···(B) From the obtained cross-sectional areas of the first and second sheaths, the proportion of the cross-sectional area of ​​the first sheath to the total area of ​​the sheath was calculated. (4) Room temperature modulus The first or second sheath to be evaluated was cut to a size of 5 mm x 42 mm to be used as a sample for measurement. The prepared sample was measured using a dynamic viscoelasticity analyzer (product name: Rheogel-E4000F, manufactured by UBM Co., Ltd.) within a measurement temperature range of 0°C to 100°C, under conditions of a heating rate of 5°C / min and a frequency of 1 Hz. The elastic modulus value at 25°C was then determined. (5) 5% modulus The 5% modulus was measured in accordance with JIS K 7161 (2014). (6) Bending stiffness As shown in Figure 2, both ends of the multi-core cable 10 along its longitudinal direction were supported by the support 21, and an external force F was applied perpendicular to the longitudinal direction of the multi-core cable 10 at its center, as indicated by the block arrow 22. In other words, a three-point bending test was performed. The displacement A when the external force was applied to the multi-core cable 10 was measured, and Young's modulus E was determined.

[0092] Furthermore, the bending stiffness of the multi-core cable 10 was calculated by determining the second moment of area I from the cross-sectional shape of the multi-core cable 10 and then calculating the product EI of Young's modulus E and the second moment of area I. (7) Weight per unit length The weight of a multi-core cable 10 with a length of 1m along its longitudinal axis was measured, and the weight per unit length of the multi-core cable 10 was calculated. (8) Line displacement The amount of line displacement was measured using the following procedure.

[0093] First, as shown in Figure 3A, the first end 10A of the multi-core cable 10 was fixed to the first clip 31 installed on the beam 30, while the second end 10B, located opposite the first end 10A, was left hanging without being fixed. The length L100 of the multi-core cable 10 was set to 400 mm.

[0094] As shown in Figure 3A, the multi-core cable 10 was heated at 80°C for 1 hour and then cooled to room temperature to remove any kinks or distortions it had.

[0095] Next, as shown in Figure 3B, the second end 10B of the multi-core cable 10 was also fixed to the beam 30 using a second clip 32. As a result, the multi-core cable 10 was U-shaped, as shown in Figure 3B.

[0096] The mixture, as shown in Figure 3B, was heated at 80°C for 24 hours and then cooled to room temperature.

[0097] Next, as shown in Figure 3C, the second end 10B of the multi-core cable 10 was released from the second clip 32 and left to hang. The amount of wire deformation L30, which is the difference between the length L101 of the multi-core cable after heat treatment and the length L100 of the multi-core cable before heat treatment, was measured and calculated along the vertical direction. In Figure 3C, the multi-core cable 10 before heat treatment is shown by a dotted line, and its length L100 is also shown.

[0098] A measured value of the linear displacement was rated as C if it was greater than 170 mm, B if it was between 125 mm and 170 mm, and A if it was less than 125 mm.

[0099] A rating of A for wire deformation displacement indicates that the wire deformation caused by high-temperature heating is minimized, with B and C being the next lowest ratings. A rating of A or B for wire deformation displacement indicates that the wire deformation that occurs when a multi-core cable is bent while heated at high temperatures is sufficiently reduced. (9) Flexibility test Flexibility was evaluated using the following procedure.

[0100] As shown in Figure 4, the first bracket 411 gripped and fixed the first end 10A of the multi-core cable 10 to be evaluated. The first bracket 411 was fixed in place so as not to move during the flexibility test.

[0101] Furthermore, the second bracket 412 gripped the second end 10B of the multi-core cable 10. When installing the first bracket 411 and the second bracket 412, the length of the portion of the multi-core cable 10 sandwiched between the first bracket 411 and the second bracket 412 was set to 170 mm. The second end 10B of the multi-core cable 10, gripped by the second bracket 412, was made movable vertically.

[0102] Then, the second bracket 412 was moved vertically up and down from the reference position 42A along the arrows 431 and 432 in Figure 4, repeatedly bending the cable 10. The reference position 42A is the position where the height of the second bracket 412 and the height of the first bracket 411 are the same. When the first bracket 411 and the second bracket 412 are at the reference position 42A, the distance L40 between them is set to 100 mm.

[0103] The bending motion was performed 2 million times in a -35°C environment, with the second bracket 412 moving sequentially from the reference position 42A to the upper end 42B, back to the reference position 42A, to the lower end 42C, and back to the reference position 42A, with a period of 2.5 Hz.

[0104] Furthermore, the distance L431 between the reference position 42A and the upper end 42B, and the distance L432 between the reference position 42A and the lower end 42C, were set to be equal and constant even when repeatedly bent. Specifically, the distance L431 from the reference position 42A to the upper end 42B, and the distance L432 from the reference position 42A to the lower end 42C were both set to 65 mm.

[0105] After the flexibility test, the current flow was measured for all the insulated wires 11 conductors 111 in the multi-core cable 10. If no current flowed through an insulated wire 11, it was determined to be broken. Conversely, if current flowed through any of the insulated wires 11 conductors 111 in the multi-core cable 10 after the flexibility test, it was determined that the wire was not broken.

[0106] Furthermore, the appearance of the multi-core cable 10 after the bending test was visually inspected to check for the presence or absence of cracks.

[0107] If none of the conductors 111 of any of the insulated wires 11 in the multi-core cable 10 were broken after the bending test and no cracks were observed in appearance, it was evaluated as A. If any of the conductors 111 of any of the insulated wires 11 in the multi-core cable 10 were found to be broken after the bending test, or if cracks were observed in appearance, it was evaluated as B.

[0108] If the evaluation after the bending test is A, it can be said that the multi-core cable has excellent flexibility, and if the evaluation after the bending test is B, it can be said that the multi-core cable has poor flexibility. The evaluation results are shown in the "Flexibility" column of Figure 5. 2. Cable manufacturing conditions The cables used in each experimental example are described below.

[0109] Experimental Examples 1 and 2 are comparative examples, while Experimental Examples 3 through 5 are examples of actual cases. (Experimental Example 1) A multi-core cable 10 having the cross-sectional structure shown in Figure 1 and the configuration shown in the "Multi-core cable configuration" section of Figure 5 was fabricated and evaluated.

[0110] The "Material / Composition" column for the conductor 111 of the insulated wire 11 of the multi-core cable 10, which states "copper alloy 48 / 0.08", means that 48 strands of copper alloy conductor wire with an outer diameter of 0.08 mm are twisted together. The "Material" column for the insulator, which states "EVA", means ethylene-vinyl acetate copolymer. The "Material" column for the second sheath, which states "TPU", means a polyurethane resin, or thermoplastic polyurethane elastomer. In this experimental example, the sheath was not divided into a first sheath and a second sheath, but formed from a single component, so it is only entered in the column for the second sheath.

[0111] In Experimental Example 1, the resin used for the sheath was non-crosslinked.

[0112] The evaluation results are shown in Figure 5. (Experimental Example 2) A multi-core cable 10 having the cross-sectional structure shown in Figure 1 and the configuration shown in the "Multi-core cable configuration" section of Figure 5 was fabricated and evaluated.

[0113] The "Material / Composition" section for the conductor 111 of the insulated wire 11 of the multi-core cable 10 states "copper alloy 3 / 16 / 0.08," which means that three strands of strands, each made by twisting together 16 strands of copper alloy conductor wire with a strand diameter of 0.08 mm, are further twisted together.

[0114] The "Cross-linked PE" listed in the "Material" column for the insulator refers to cross-linked polyethylene resin.

[0115] The "EEA" indicated in the "Material" column of the first sheath refers to ethylene-ethyl acrylate copolymer.

[0116] In Experimental Example 2, both the first sheath 121 and the second sheath 122 were cross-linked.

[0117] The evaluation results are shown in Figure 5. (Experimental Examples 3 to 5) A multi-core cable 10 having the cross-sectional structure shown in Figure 1 and the configuration shown in the "Multi-core cable configuration" section of Figure 5 was fabricated and evaluated.

[0118] In Experimental Examples 3 to 5, both the first sheath 121 and the second sheath 122 were cross-linked.

[0119] The evaluation results are shown in Figure 5.

[0120] As shown in Figure 5, the multi-core cables in Experimental Examples 3, 4, and 5, where the 5% modulus of the sheath was 1.0 MPa or less, had measured wire deformation displacement of 170 mm or less, confirming that they received an evaluation of A or B. In other words, the multi-core cables in Experimental Examples 3, 4, and 5 demonstrated excellent environmental resistance and flexibility, and it was confirmed that wire deformation was sufficiently reduced even when the multi-core cable was maintained in a bent state under high-temperature heating conditions.

[0121] In Experimental Example 1, although the sheath's 5% modulus was 1.0 MPa or less and the measured value of the wire displacement was 170 mm or less, the sheath's environmental resistance was poor because the resin was not cross-linked.

[0122] Figure 6 shows the relationship between the amount of wire deformation and the 5% modulus for multi-core cables from Experimental Examples 1 to 5. As shown in Figure 6, a correlation was observed between the amount of wire deformation and the 5% modulus. When the amount of wire deformation is x and the 5% modulus is y, the approximate straight line 60 shown in Figure 6 becomes y = 0.0114x - 0.92.

[0123] Furthermore, according to the results shown in Figure 5, the bending rigidity of the sheath is 780 N·mm 2 In the following experimental examples 3, 4, and 5, the multi-core cables had measured wire displacement values ​​of 170 mm or less, and it was confirmed that they received an evaluation of A or B.

[0124] Figure 7 shows the relationship between the amount of wire deformation displacement and bending stiffness for multi-core cables from Experimental Examples 1 to 5. As shown in Figure 7, a correlation was observed between the amount of wire deformation displacement and bending stiffness. When the amount of wire deformation displacement is denoted as x and y as y, the approximate straight line 70 shown in Figure 7 becomes y = 6.9x - 395. [Explanation of Symbols]

[0125] 10-core multi-cable 10A 1st end 10B 2nd end 11 Insulated wires 111 Conductor 112 Insulator 12 sheaths 121 First Sheath 122 Second Sheath 13 Lubricant D111 Outer diameter D112 Outer diameter D110 outer diameter D121 Outer diameter D122 outer diameter T112 wall thickness T121 Thick T122 Thick 21 Support 22 Block Arrows A Displacement Amount 30 Beam 31 Clip 1 32. Clip 2 L100 Length L101 Length L30 Linear displacement 411 First bracket 412 Second bracket 42A Reference position 42B top end 42C bottom end 431 Arrow 432 Arrow L40 distance L431 distance L432 distance 60 Approximate straight line 70 Approximate straight line

Claims

1. Multiple insulated wires, It has a sheath arranged outside the plurality of insulated wires, A multi-core cable in which the resin of the sheath is cross-linked and the 5% modulus of the sheath is 1.0 MPa or less.

2. The multi-core cable according to claim 1, wherein the 5% modulus of the sheath is 0.5 MPa or less.

3. The multi-core cable according to claim 1, wherein the sheath includes a first sheath and a second sheath, in order from the position closest to the plurality of insulated wires.

4. The multi-core cable according to claim 3, wherein the first sheath comprises a polyolefin resin.

5. The multi-core cable according to claim 3 or claim 4, wherein the room temperature modulus of the first sheath is 40 MPa or less.

6. The multi-core cable according to claim 3 or claim 4, wherein the second sheath comprises a polyurethane resin.

7. The multi-core cable according to claim 3 or claim 4, wherein the room temperature modulus of the second sheath is 40 MPa or less.

8. The multi-core cable according to claim 3 or claim 4, wherein the proportion of the cross-sectional area of ​​the first sheath among the sheaths is 40% or more and 75% or less.

9. Bending rigidity of 780 N·mm ２ The multi-core cable according to any one of claims 1 to 4, as follows:

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