Multiconductor cable

Abstract

To provide a multiconductor cable with bending resistance and oil resistance.SOLUTION: The multiconductor cable includes an oil-absorbing interposition and a core arranged so as to surround the oil-absorbing interposition and formed by twisting together a plurality of electric wires. In the cross section perpendicular to the longitudinal direction of the core, the core has a plurality of layers in which the plurality of electric wires are arranged on the circumference, and the innermost layer is closest to the oil-absorbing interposition. The twist pitch of the wires in the innermost layer is not less than 0.45 times and less than 0.8 times that of the wires in the outermost layer.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to multi-conductor cables. [Background technology]

[0002] Patent Document 1 describes a conductor made of multiple strands twisted together, a first insulating film covering an outer periphery of the conductor and including a polyethylene resin; The present invention discloses a core wire for a multi-core cable, which has a second insulating film provided in contact with the outer periphery of the first insulating film and containing a copolymer of ethylene and an α-olefin having a carbonyl group. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2022-040960 Summary of the Invention [Problem to be solved by the invention]

[0004] Multi-core cables used in factories and the like are sometimes arranged in drive units and the like. In addition, oil and the like may adhere to the multi-core cables in the factory. For this reason, multi-core cables used in factories and the like are required to have bending resistance and oil resistance.

[0005] Therefore, an object of the present disclosure is to provide a multi-core cable that is resistant to bending and oil resistance. [Means for solving the problem]

[0006] The multi-core cable of the present disclosure comprises an oil-absorbing filler and A core is disposed so as to surround the oil-absorbing intermediate layer, and is formed by twisting together a plurality of electric wires. In a cross section perpendicular to the longitudinal direction of the core, the core has a plurality of layers in which the plurality of electric wires are arranged circumferentially, and an innermost layer of the layers is closest to the oil-absorbing intermediate layer, The twist pitch of the electric wires in the innermost layer is 0.45 times or more and less than 0.8 times the twist pitch of the electric wires in the outermost layer of the layers. Effect of the Invention

[0007] According to the present disclosure, a multi-core cable having bending resistance and oil resistance can be provided. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a cross-sectional view of a multi-core cable according to one embodiment of the present disclosure taken along a plane perpendicular to the longitudinal direction. [Diagram 2] FIG. 2 is a cross-sectional view of a multi-core cable according to another embodiment of the present disclosure taken along a plane perpendicular to the longitudinal direction. [Diagram 3] FIG. 3 is a cross-sectional view of a multi-core cable according to another embodiment of the present disclosure taken along a plane perpendicular to the longitudinal direction. [Figure 4] FIG. 4 is an explanatory diagram of a method for evaluating bending resistance. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The embodiments for carrying out the invention are described below.

[0010] [Description of the embodiments of the present disclosure] First, the embodiments of the present disclosure will be 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 one embodiment of the present disclosure includes an oil-absorbing filler and A core is disposed so as to surround the oil-absorbing intermediate layer, and is formed by twisting together a plurality of electric wires. In a cross section perpendicular to the longitudinal direction of the core, the core has a plurality of layers in which the plurality of electric wires are arranged circumferentially, and an innermost layer of the layers is closest to the oil-absorbing intermediate layer, The twist pitch of the electric wires in the innermost layer is 0.45 times or more and less than 0.8 times the twist pitch of the electric wires in the outermost layer of the layers.

[0012] The multi-core cable according to one embodiment of the present disclosure has an oil-absorbent filler, which can absorb oil that adheres to the multi-core cable and penetrates into the inside of the multi-core cable. Therefore, even if oil penetrates into the inside of the multi-core cable, a decrease in the insulation resistance of the electric wires in the multi-core cable can be suppressed, and oil resistance can be improved.

[0013] By making the twist pitch of the electric wires in the innermost layer 0.45 times or more that of the electric wires in the outermost layer, it is possible to form a sufficient gap between the electric wires in the innermost layer for oil to easily penetrate. As a result, the oil that reaches the innermost layer can be easily absorbed by the oil-absorbing filler, thereby improving the oil resistance of the multi-core cable.

[0014] In addition, by making the twist pitch of the electric wires in the innermost layer less than 0.8 times the twist pitch of the electric wires in the outermost layer, the bending resistance of the multi-core cable can be improved.

[0015] (2) In the above (1), the electric wire has a conductor and an insulator covering the conductor, The insulator may contain a resin material containing polyvinyl chloride or polyolefin as a main component.

[0016] By making the insulator contain polyvinyl chloride or polyolefin as a main component of the resin material, the flexibility of the electric wire or the multi-core cable including the electric wire can be increased, and the cost can be reduced compared to the case where a fluororesin or the like is used as the resin material. By increasing the flexibility of the electric wire or the multi-core cable, the bending resistance of the multi-core cable can also be increased.

[0017] (3) In the above (1) or (2), the core has three or more layers of the electric wire, The twist pitch of the electric wires in an intermediate layer that is adjacent to the outermost layer and is located closer to the oil-absorbing interlayer than the outermost layer may be 0.7 times or more and less than 0.95 times the twist pitch of the electric wires in the outermost layer.

[0018] By making the twist pitch of the electric wires in the intermediate layer 0.7 times or more the twist pitch of the electric wires in the outermost layer, it is possible to form sufficient gaps between the electric wires in the intermediate layer for oil to easily penetrate. As a result, oil that has reached the intermediate layer can penetrate further into the core and be easily absorbed by the oil-absorbing filler, thereby improving the oil resistance of the multi-core cable.

[0019] Moreover, by making the twist pitch of the electric wires in the intermediate layer less than 0.95 times the twist pitch of the electric wires in the outermost layer, the bending resistance of the multi-core cable can be improved.

[0020] (4) In any one of the above (1) to (3), the rotor further has an outer jacket covering the core, The jacket may contain a resin material containing polyvinyl chloride or polyolefin as a main component.

[0021] By providing a sheath to a multi-core cable, the electric wires contained in the cores disposed inside the sheath can be protected, thereby increasing durability.

[0022] By making the outer sheath contain polyvinyl chloride or polyolefin as the main component of the resin material, the flexibility of the multi-core cable is increased, and the cost can be reduced compared to when a fluororesin or the like is used as the resin material. By increasing the flexibility of the multi-core cable, the bending resistance of the multi-core cable can also be increased.

[0023] (5) In the above (4), a pressure winding layer is provided between the core and the jacket, The backing layer may include an oil-absorbent tape.

[0024] By disposing the pressure winding layer between the core and the sheath, it is possible to prevent the core and the sheath from coming into direct contact with each other, which makes it easy to peel off the sheath when taking out the electric wires at the longitudinal end of the multi-core cable.

[0025] By including the oil-absorbing tape in the pressure winding layer, it is possible to prevent oil that has penetrated into the multi-core cable from penetrating further into the interior and coming into contact with the electric wires, thereby preventing a decrease in the insulation resistance of the electric wires in the multi-core cable and improving the oil resistance.

[0026] (6) In the above (5), a metal shielding layer may be further provided between the outer sheath and the pressure winding layer.

[0027] By having a metal shielding layer in the multi-core cable, it is possible to suppress signal leakage to the outside and radio wave intrusion from the outside while increasing the bending resistance of the multi-core cable. In addition, by having a metal shielding layer in the multi-core cable, it is possible to block heat from the outside and protect the core from the outside heat. Furthermore, by having a metal shielding layer in the multi-core cable, it is possible to mechanically protect the core even if the jacket is damaged.

[0028] [Details of the embodiment of the present disclosure] Specific examples of a multi-core cable according to an embodiment of the present disclosure (hereinafter, referred to as the present embodiment) will be described below with reference to the drawings. Note that the present invention is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope of the claims. [Multi-core cable] Fig. 1 shows a schematic diagram of a cross section perpendicular to the longitudinal direction of the multi-core cable of this embodiment. Fig. 2 and Fig. 3 show schematic diagrams of cross sections perpendicular to the longitudinal direction of a multi-core cable according to another configuration example of this embodiment. In Fig. 1, Fig. 2, and Fig. 3, the longitudinal direction of the multi-core cable means the direction along the Z axis, that is, the axis perpendicular to the paper surface. Fig. 1, Fig. 2, and Fig. 3 show a cross section on the XY plane perpendicular to the Z axis.

[0029] 2 and 3 are explanatory diagrams of other configuration examples of the multi-core cable of this embodiment, so the description will be given mainly with reference to FIG. 1, and with reference to FIGS. 2 and 3 as necessary.

[0030] As shown in FIG. 1, a multi-core cable 10 of this embodiment can have an oil-absorbent interposer 11 and a core 13 that is arranged to surround the oil-absorbent interposer 11 and has a plurality of electric wires 12 twisted together. (1) Regarding the components contained in multi-core cables Each member contained in the multi-core cable of this embodiment will be described. (1-1) Oil-absorbing intervention The multi-core cable 10 of the present embodiment can have an oil-absorbing filler 11. The oil-absorbing filler 11 is a filler that can absorb oil, and means a filler that can absorb 10 times or more its own weight in oil when immersed in oil.

[0031] The material of the oil-absorbent media 11 is not particularly limited, but the oil-absorbent media 11 may contain one or more types of fibers selected from staple fiber, cotton, kapok fiber, and the like.

[0032] The oil-absorbent intermediate layer 11 can be arranged so as to be surrounded by the core 13, and can be arranged in the gaps 134 of the core 13. The gaps 134 in which the oil-absorbent intermediate layer 11 is arranged may be arranged inside the core 13 in which a plurality of electric wires 12 are twisted together, and can be arranged in a central region including the center of the core 13 in a cross section perpendicular to the longitudinal direction of the core 13 as shown in FIG. 1, for example. The multi-core cable of the present embodiment has oil-absorbent interposer 11, which can absorb oil that adheres to multi-core cable 10 and penetrates into the inside. Therefore, even if oil penetrates into multi-core cable 10, the insulation resistance of electric wires 12 in multi-core cable 10 can be prevented from decreasing, and oil resistance can be improved.

[0033] In this specification, oil resistance refers to a property that can suppress a decrease in insulation resistance when multi-core cable 10 is immersed in oil. (1-2) Core Core 13 has a configuration in which a plurality of electric wires 12 are twisted together. In a cross section perpendicular to the longitudinal direction of core 13, core 13 has a configuration in which electric wires 12 are arranged and twisted together so as to have a plurality of layers in which a plurality of electric wires 12 are arranged circumferentially. Core 13 can have two or more layers of electric wires 12, including innermost layer 131 closest to oil-absorbent intervening layer 11 and outermost layer 133 furthest from oil-absorbent intervening layer 11 and including the outer surface of core 13.

[0034] The term "arranged to have a plurality of layers in which a plurality of electric wires 12 are arranged circumferentially" means that, in a cross section perpendicular to the longitudinal direction of the core 13 as shown in Fig. 1, the electric wires 12 are arranged along the circumference of a circle, and each layer is arranged along the diameter of the circle to form a plurality of layers. The core 13 of the multi-core cable 10 shown in Fig. 1 has three layers, an innermost layer 131, an intermediate layer 132, and an outermost layer 133. The innermost layer 131 has a structure in which the electric wires 12 are arranged along the circumference between the circle C1 and the circle C2. The intermediate layer 132 has a structure in which the electric wires 12 are arranged along the circumference between the circle C2 and the circle C3. The outermost layer 133 has a structure in which the electric wires 12 are arranged along the circumference between the circle C3 and the circle C4.

[0035] The twist pitch PI of the electric wires 12 in the innermost layer 131 is preferably 0.45 to less than 0.8 times the twist pitch PO of the electric wires 12 in the outermost layer 133. In other words, PI÷PO is preferably 0.45 to less than 0.8.

[0036] The twist pitch means the length of one twist of the electric wires 12 constituting the core 13, which is a twisted wire. The length means the length along the central axis of the twisted wire. The twist pitch can be measured in accordance with JIS C 3005 (2014).

[0037] When measuring the twist pitch of the electric wire 12 in the innermost layer 131 or the intermediate layer 132, the measurement can be performed after removing the electric wire 12 in other covering layers so as to expose the layer to be measured.

[0038] By setting the twist pitch PI of the electric wires 12 in the innermost layer 131 to be 0.45 times or more the twist pitch PO of the electric wires 12 in the outermost layer 133, it is possible to form a sufficient gap through which oil can easily permeate between the electric wires 12 in the innermost layer 131. Therefore, the oil that reaches the innermost layer 131 can be easily absorbed by the oil-absorbing intervening layer 11, and the oil resistance of the multi-core cable 10 can be improved.

[0039] Moreover, by setting the twist pitch PI of the electric wires 12 in the innermost layer 131 to less than 0.8 times the twist pitch PO of the electric wires 12 in the outermost layer 133, the bending resistance of the multi-core cable 10 can be improved.

[0040] 1, the core 13 may further have an intermediate layer 132 in addition to the innermost layer 131 and the outermost layer 133, and may have three or more layers of the electric wire 12. The core 13 may also have a plurality of layers as the intermediate layer 132.

[0041] In the core 13, the twist pitch PM of the electric wire 12 in the intermediate layer 132 arranged adjacent to the outermost layer 133 and closer to the oil-absorbing interlayer 11 than the outermost layer 133 is preferably 0.7 times or more and less than 0.95 times the twist pitch PO of the electric wire 12 in the outermost layer 133. In other words, PM÷PO is preferably 0.7 or more and less than 0.95.

[0042] By setting the twist pitch PM of the electric wires 12 in the intermediate layer 132 to be 0.7 times or more the twist pitch PO of the electric wires 12 in the outermost layer 133, it is possible to form a sufficient gap into which oil can easily penetrate between the electric wires 12 in the intermediate layer 132. As a result, the oil that has reached the intermediate layer 132 can penetrate further into the core 13 and be easily absorbed by the oil-absorbing filler 11, thereby improving the oil resistance of the multi-core cable 10.

[0043] Moreover, by setting the twist pitch PM of the electric wires 12 in the intermediate layer 132 to less than 0.95 times the twist pitch PO of the electric wires 12 in the outermost layer 133, the bending resistance of the multi-core cable 10 can be improved. (1-2-1) Electric wire Electric wire 12 included in core 13 of the multi-core cable of this embodiment can have conductor 121 and insulator 122 that covers conductor 121. Therefore, conductor 121 and insulator 122 will be described. (A) Conductor The conductor 121 can be a single conductor wire or multiple conductor wires. When the conductor 121 has multiple conductor wires, the multiple conductor wires can be twisted together. In other words, when the conductor 121 has multiple conductor wires, the conductor 121 can be a twisted wire of multiple conductor wires.

[0044] The material of the conductor 121 is not particularly limited, but may be one or more conductor materials selected from, for example, copper alloy, copper, silver-plated soft copper, and tin-plated soft copper. Soft copper is preferably used as the copper.

[0045] The cross-sectional area of ​​the conductor 121 is not particularly limited. For example, 2 More than 3mm 2 It is preferable that: (B) Insulator 1, the insulator 122 can cover the outer surface of the conductor 121, specifically, the outer surface along the longitudinal direction of the electric wire 12. The insulator 122 can include a resin material described below.

[0046] (Resin material) The insulator 122 may contain a resin material. The resin material is not particularly limited, but it is preferable that the resin material contains, for example, polyvinyl chloride or polyolefin as a main component. The main component means that the resin material contains the largest amount of the resin material in terms of mass percentage.

[0047] By making the insulator 122 contain polyvinyl chloride or polyolefin as a main component of the resin material, the flexibility of the electric wire 12 and the multi-core cable 10 including the electric wire 12 can be increased, and the cost can be reduced compared to the case where a fluororesin or the like is used as the resin material. By increasing the flexibility of the electric wire 12 and the multi-core cable 10, the bending resistance of the multi-core cable 10 can also be increased.

[0048] The polyolefin is not particularly limited. Examples of the polyolefin include polyethylene (PE), ethylene-vinyl acetate copolymer (EVA), ethylene-ethyl acrylate copolymer (EEA), and other ethylene acrylate ester copolymers, ethylene α-olefin copolymers, ethylene methyl acrylate copolymers, ethylene butyl acrylate copolymers, ethylene methyl methacrylate copolymers, ethylene acrylic acid copolymers, partially saponified EVA, maleic anhydride modified polyolefins, and ethylene acrylate ester maleic anhydride copolymers. One of these resins may be used alone, or two or more may be used in combination.

[0049] The resin material may or may not be crosslinked.

[0050] However, if the resin material is cross-linked, it is possible to improve the heat resistance, strength, and corrosion resistance of the electric wire 12. For this reason, when the electric wire 12 is used for an application requiring heat resistance, strength, and corrosion resistance, it is preferable that the resin material is cross-linked. (Additives) In addition to the above-mentioned resin materials, the insulator 122 may contain additives such as flame retardants, flame retardant assistants, antioxidants, lubricants, colorants, reflectivity imparting agents, opacifying agents, processing stabilizers, and plasticizers. (1-2-2) Wire composition The configuration of the electric wires 12 in the core 13 of the multi-core cable of the present embodiment is not particularly limited. For example, the core 13 may be configured of a plurality of electric wires 12 having the same configuration such as size, as in the multi-core cable 10 and the multi-core cable 20 shown in Figs.

[0051] Also, like a multi-core cable 30 shown in FIG. 3, a core 33 may be formed by a first electric wire 12A, a second electric wire 12B, and a third electric wire 12C having different configurations such as sizes.

[0052] In the multi-core cable 30 shown in Fig. 3, the first electric wire 12A has a first conductor 121A and a first insulator 122A, the second electric wire 12B has a second conductor 121B and a second insulator 122B, and the third electric wire 12C has a third conductor 121C and a third insulator 122C. The preferred configurations of the conductors and insulators have already been described, and therefore will not be described here.

[0053] As in the multi-core cable 30 shown in Fig. 3, two first electric wires 12A may be twisted together to form a twisted pair electric wire 32, and then twisted with another electric wire 12 to form a core 33. Although Fig. 3 shows an example in which the first electric wire 12A is used to form the twisted pair electric wire 32, the second electric wire 12B and the third electric wire 12C may also be twisted together to form a twisted pair electric wire. (1-3) Outer covering As shown in FIG. 1, the multi-core cable 10 may further include an outer jacket 15 that covers the cores 13 .

[0054] By having the outer sheath 15, the multi-core cable 10 can protect the electric wires 12 contained in the cores 13 arranged inside, and can increase durability. (Resin material) The jacket 15 may contain a resin material. The resin material is not particularly limited, but preferably contains, for example, polyvinyl chloride or polyolefin as a main component, and more preferably contains polyolefin as a main component. The definition of the main component and suitable polyolefins have already been explained in the insulator 122 of the electric wire 12, and therefore will not be explained here.

[0055] By making the outer jacket 15 contain polyvinyl chloride or polyolefin as a main component of the resin material, the flexibility of the multi-core cable 10 is increased, and the cost can be reduced compared to the case where a fluororesin or the like is used as the resin material. By increasing the flexibility of the multi-core cable 10, the bending resistance of the multi-core cable 10 can also be increased.

[0056] The resin material may or may not be crosslinked.

[0057] However, if the resin material is cross-linked, it is possible to improve the heat resistance, strength, and corrosion resistance of multi-core cable 10. For this reason, when multi-core cable 10 is used for applications requiring heat resistance, strength, and corrosion resistance, it is preferable that the resin material is cross-linked. (Additives) In addition to the above-mentioned resin materials, the jacket 15 may contain additives such as flame retardants, flame retardant assistants, antioxidants, lubricants, colorants, reflectivity imparting agents, opacifying agents, processing stabilizers, and plasticizers. (1-4) Retaining winding layer The multi-core cable 10 of the present embodiment may also have a pressure winding layer 14 between the core 13 and the jacket 15. The pressure winding layer 14 may be, for example, a tape made of an insulating material such as paper, nonwoven fabric, or polyester resin wound spirally around the outer periphery of the core 13 along the longitudinal direction of the core 13.

[0058] By disposing the pressure winding layer 14 between the core 13 and the outer sheath 15, it is possible to prevent the core 13 from coming into direct contact with the outer sheath 15. Therefore, the outer sheath 15 can be easily peeled off at the end of the multi-core cable 10 in the longitudinal direction when the electric wire 12 is taken out.

[0059] The pressure winding layer 14 may also contain an oil-absorbent tape. When the pressure winding layer 14 contains an oil-absorbent tape, it is possible to prevent oil that has penetrated into the multi-core cable 10 from penetrating further inside and coming into contact with the electric wires 12. This makes it possible to prevent a decrease in the insulation resistance of the electric wires 12 of the multi-core cable 10 and to increase the oil resistance.

[0060] An oil-absorbent tape is a tape that can absorb 10 times its own weight in oil when immersed in oil.

[0061] As described above, when a tape body is wound around the outer periphery of the core 13 to form the pressure winding layer 14, the winding direction of the tape body can be selected arbitrarily, and for example, it may be the same direction as the twist direction of the core 13 described above, or it may be a different direction. (1-5) Metal shielding layer Like the multi-core cable 20 shown in FIG. 2 and the multi-core cable 30 shown in FIG. 3, the multi-core cable of this embodiment may further have a metal shielding layer 16 between the outer sheath 15 and the pressure winding layer 14.

[0062] The metallic shielding layer 16 may include an electrically conductive material.

[0063] For example, the metal shielding layer 16 can be formed by spirally winding a conductive tape including a conductive layer along the longitudinal direction of the core 13 .

[0064] In this case, the conductive tape may be composed of only a conductive layer, or may have a conductive layer disposed on one or more surfaces selected from the upper and lower surfaces of a substrate.

[0065] The material of the conductive layer is not particularly limited, but preferably contains a metal, and may be, for example, a metal foil. When the conductive layer contains a metal, the metal material is not particularly limited, but may be, for example, copper, a copper alloy, aluminum, an aluminum alloy, or the like.

[0066] The material of the substrate is not particularly limited, but it is preferable that the substrate is made of an insulating material such as an organic polymer material or a nonwoven fabric. 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 substrate may contain an insulating material, or may be made of only an insulating material.

[0067] As described above, when forming the metal shielding layer 16 by winding a conductive tape, the winding direction of the conductive tape can be selected arbitrarily, for example, it may be the same direction as the twisting direction of the core 13, or it may be a different direction.

[0068] The metal shielding layer 16 can also be formed of metal wires. In this case, the metal shielding layer 16 can be formed by arranging the metal wires in a braided structure or a spiral wound structure.

[0069] The material of the metal wire may be copper, aluminum, a copper alloy, etc. The surface of the metal wire may be plated with silver or tin. Therefore, the metal wire may be made of, for example, a silver-plated copper alloy or a tin-plated copper alloy.

[0070] The multi-core cable has the metal shielding layer 16, which can increase the bending resistance of the multi-core cable while suppressing signal leakage to the outside and radio wave intrusion from the outside. In addition, the multi-core cable has the metal shielding layer 16, which can block heat from the outside and protect the core 13 from the outside heat. Furthermore, the multi-core cable has the metal shielding layer 16, which can mechanically protect the core 13 even if the jacket 15 is damaged. EXAMPLES

[0071] The present invention will be described below with reference to specific examples, but is not limited to these examples. (Evaluation method) First, the method for evaluating the electric wires produced in the following experimental examples will be described. (1) Wire diameter, outer diameter, thickness of each layer The wire diameter of the conductor and the outer diameter of each part were determined by measuring the lengths of two perpendicular diameters at each part in any cross section perpendicular to the longitudinal direction of the wire or multi-core cable, and taking the average value.

[0072] The thickness of each layer, for example the thickness of the outer jacket 15 shown in Table 2, is calculated by subtracting the outer diameter of the pressure winding layer 14, which is a layer that is in contact with the outer jacket 15 and is located more inside than the outer jacket 15, from the outer diameter of the outer jacket 15, and dividing the result by 2. Similarly, the thickness of the insulation of each electric wire is calculated by subtracting the outer diameter of the conductor, which is a layer that is in contact with the insulator and is located more inside than the insulator, from the outer diameter of the insulator, and dividing the result by 2. (2) Twist pitch When measuring the twist pitch, other covering materials were removed so that the layer to be measured was exposed. Next, the twist pitch of each layer was measured according to JIS C 3005 (2014), and the twist pitch ratio of each layer was calculated. The twist pitch ratio of each layer of the core is shown in the "Twist Pitch Ratio" column in Table 1. (3) Oil resistance The oil resistance test was carried out according to the following procedure.

[0073] The multi-core cables produced in each experimental example were immersed in oil for 20 hours. The multi-core cables were then removed from the oil, and the insulation resistance of the insulation of all the electric wires contained in the multi-core cables was measured according to JIS C 3005 (2014). For all the electric wires contained in the multi-core cables, if the insulation resistance was 10 MΩ·km or more, it was rated as A, and if all were 9 MΩ·km or more and less than 10 MΩ·km, it was rated as B. If the insulation resistance of at least some of the electric wires contained in the multi-core cable was less than 9 MΩ·km, it was rated as C.

[0074] A rating of A in the oil resistance test indicates that the multi-core cable has the best oil resistance, with ratings of B and C decreasing in order. A rating of A or B indicates that the multi-core cable has sufficient oil resistance. A rating of C indicates that the multi-core cable does not have sufficient oil resistance. (4) Flexibility The bending resistance test was carried out according to the following procedure.

[0075] As shown in FIG. 4, the multi-core cable 40 to be evaluated is placed vertically between two first mandrels 411 and 412, each having a diameter of 60 mm, which are arranged horizontally and parallel to each other. Then, the upper end of the multi-core cable 40 is bent horizontally by 90° so as to abut against the upper side of the first mandrel 411, and then bent horizontally by 90° so as to abut against the upper side of the second mandrel 412, repeatedly. This repetition was performed while measuring the resistance value of the conductors of all the electric wires in the multi-core cable, and the number of bendings when the resistance of any electric wire increased to 10 times or more the initial resistance value was used as the index value of the bending resistance test. The number of bendings evaluated in the bending resistance test was defined as one bending of the multi-core cable 40 from the left side in FIG. 4 to the right side, and then back to the left side. During the bending resistance test, a load of 5 N was applied downward to the multi-core cable 40 along the block arrow 42 in FIG. 4.

[0076] The index values ​​of the bending resistance test, that is, the number of bending times of 50,000 or more, were evaluated as A, the number of bending times of 40,000 or more but less than 50,000 was evaluated as B, and the number of bending times of less than 40,000 was evaluated as C.

[0077] A multi-core cable that is rated A in the bending resistance test can be said to have the best bending resistance, with bending resistance decreasing in the order of B, C, etc. A multi-core cable that is rated A or B in the bending resistance test can be evaluated as having sufficient bending resistance. A multi-core cable that is rated C in the bending resistance test can be evaluated as having insufficient bending resistance.

[0078] The multi-core cables in each experimental example are described below.

[0079] Experimental examples 1 to 5 are examples of the present invention, and experimental examples 6, 7, and 8 are comparative examples. (Experimental Example 1) As shown in the column for the configuration of the multi-core cable in Table 1, a multi-core cable A was produced that has the same structure as the multi-core cable 10 shown in FIG. 1 in a cross section perpendicular to the longitudinal direction.

[0080] The configuration of multi-core cable A is shown in Table 2, and the configuration of wire A in the core of multi-core cable A is shown in Table 3.

[0081] The evaluation results are shown in Table 1. (Experimental Example 2) A multi-core cable B was produced, which has the same structure as the multi-core cable 30 shown in FIG. 3 in a cross section perpendicular to the longitudinal direction.

[0082] The configuration of multi-core cable B is shown in Table 4, and the configuration of electric wire B in the core of multi-core cable B is shown in Table 5. As shown in Table 5, electric wire B has a first electric wire, a second electric wire, and a third electric wire with different configurations, and the first electric wire is made by twisting two wires together to form a twisted pair.

[0083] The evaluation results are shown in Table 1. (Experimental Example 3) A multi-core cable C was produced, which has the same structure as multi-core cable 10 shown in FIG. 1, except that the number of electric wires in core 13 is different in a cross section perpendicular to the longitudinal direction.

[0084] The configuration of the multi-core cable C is shown in Table 6, and the configuration of the electric wire C in the core of the multi-core cable C is shown in Table 7.

[0085] The evaluation results are shown in Table 1. (Experimental Example 4, Experimental Example 5, Experimental Example 7, Experimental Example 8) A multi-core cable was produced under the same conditions as in Experimental Example 1, except that the twist pitch of each layer of the core 13 was set to have the twist pitch ratio shown in Table 1, and an evaluation was performed.

[0086] The evaluation results are shown in Table 1. (Experimental Example 6) A multi-core cable was produced under the same conditions as in Experimental Example 1, except that a PP string (a string made of polypropylene) was used as the oil-absorbing filler material, and an evaluation was carried out.

[0087] PP strings have an oil absorption capacity of less than 10 times their own weight, and therefore do not have oil absorption properties. For this reason, they can be simply referred to as "intercalated" rather than "oil-absorbent".

[0088] The evaluation results are shown in Table 1.

[0089] [Table 1]

[0090] [Table 2]

[0091] [Table 3]

[0092] [Table 4]

[0093] [Table 5]

[0094] [Table 6]

[0095] [Table 7] [Explanation of symbols]

[0096] 10 Multi-core cable 20 Multi-core cable 30 Multi-core cable 11 Oil-absorbing intervention 12 Electric wire 12A first electric wire 12B Second electric wire 12C third wire 121 Conductor 121A First Conductor 121B Second Conductor 121C Third Conductor 122 Insulator 122A First Insulator 122B Second Insulator 122C Third Insulator 32 Twisted pair wire 13 cores 33 cores 131 Innermost layer (layer) 132 Middle Class (Class) 133 Outermost layer (layer) 134 Gap 14 Retaining layer 15 Outer cover 16 Metal shielding layer C1 Yen C2 Yen C3 Circle C4 Circle 40 Multi-core cable 411 First Mandrel 412 Second Mandrel 42 Block Arrow

Claims

1. An oil-absorbing interposition; A core is disposed so as to surround the oil-absorbing intermediate layer, and is formed by twisting together a plurality of electric wires. In a cross section perpendicular to the longitudinal direction of the core, the core has a plurality of layers in which the plurality of electric wires are arranged circumferentially, and an innermost layer of the layers is closest to the oil-absorbing intermediate layer, A multi-core cable, wherein the twist pitch of the electric wires in the innermost layer is 0.45 times or more and less than 0.8 times the twist pitch of the electric wires in the outermost layer of the layers.

2. The electric wire includes a conductor and an insulator covering the conductor, 2. The multi-core cable according to claim 1, wherein the insulator contains a resin material mainly composed of polyvinyl chloride or polyolefin.

3. The core has three or more layers of the electric wire, 3. The multi-core cable according to claim 1, wherein the twist pitch of the electric wires in an intermediate layer adjacent to the outermost layer and located closer to the oil-absorbing interlayer than the outermost layer is 0.7 times or more and less than 0.95 times the twist pitch of the electric wires in the outermost layer.

4. Further comprising an outer covering covering the core, 3. The multi-core cable according to claim 1, wherein the outer sheath contains a resin material mainly composed of polyvinyl chloride or polyolefin.

5. A pressure winding layer is provided between the core and the jacket, 5. The multi-conductor cable of claim 4, wherein the hold-down wrap comprises an oil-absorbent tape.

6. 6. The multi-conductor cable of claim 5, further comprising a metallic shield layer between said jacket and said holddown layer.

Images