coil

Abstract

To provide a coil of a carbon nanotube-covered wire that is excellent in electric resistance reduction characteristics when the carbon nanotube-covered wire is wound.SOLUTION: In a coil formed by winding a carbon nanotube covered wire including a carbon nanotube wire obtained by twisting together a plurality of carbon nanotube strands each composed of one or a plurality of carbon nanotube aggregates composed of a plurality of carbon nanotubes, and a resin coating layer covering the carbon nanotube wire, when the Young's modulus of the resin of the resin coating layer is 0.40 GPa or more and 3.0 GPa or less, the hardness of the resin of the resin coating layer is 50 or more and 100 or less, and the equivalent circle diameter of a CNT wire is D (mm), the winding tension is 3000×D2 gf or more and 30000×D2 gf or less.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a coil formed by winding a carbon nanotube-coated wire, and more particularly to a coil of carbon nanotube-coated wire whose electrical resistance decreases when wound around the circumferential surface of a member. [Background technology]

[0002] Coils are used in various electric devices, such as motors, that carry high-output electric power. Coils are manufactured by spirally winding a winding having a conductor wire, such as a metal wire. To improve the output and reduce the weight of electric devices, coils are sometimes required to have improved conductivity and be lightweight. Furthermore, to maintain the output and other characteristics of electric devices constant throughout their lifespan, coils are sometimes required to maintain a high conductivity for a long period of time.

[0003] Furthermore, in order to reduce the size and increase the output of electric devices, coils are sometimes required to be wound with a narrow gap between adjacent turns. However, if the wound conductor wires are arranged closely to each other, eddy currents are generated in the conductor wire, increasing the amount of eddy currents. As a result, current loss due to the eddy currents generated in the conductor wire increases, resulting in increased current loss in the coil. Therefore, it has been proposed to reduce eddy currents and suppress current loss by using a coil wire that includes a conductor wire and a magnetic layer formed of a magnetic material on the outer periphery of the conductor wire (Patent Document 1).

[0004] On the other hand, carbon nanotubes are a material with various properties and are expected to be applied in many fields. For example, carbon nanotubes are three-dimensional network structures consisting of a single layer of cylindrical bodies with a hexagonal lattice network structure or multiple layers arranged approximately coaxially. They are lightweight and have excellent properties such as electrical conductivity, thermal conductivity, and mechanical strength. Therefore, the use of carbon nanotubes as a substitute for metals is being considered. When using carbon nanotubes as a substitute for metals, it is also required to further improve the electrical conductivity of carbon nanotubes.

[0005] In order to further improve the conductivity of carbon nanotubes, a carbon nanotube material has been proposed in which electrical resistance is reduced by forming conductive deposits made of metal or the like at the electrical junctions of adjacent carbon nanotube wires, and it has been disclosed that such carbon nanotube materials can be used in a wide range of applications (Patent Document 2).

[0006] However, while improved electrical conductivity is sometimes required for coils, Patent Document 2 is an invention that reduces the electrical resistance of carbon nanotube material to accommodate a wide range of applications, but when carbon nanotube material is formed into a coil, there is a problem that the electrical resistance is not sufficiently reduced. Therefore, in Patent Document 2, for example, when a winding of carbon nanotube material is used as a motor coil, the motor output may not be sufficiently improved. In particular, with conventional carbon nanotube wire, even when used in coils for in-wheel motors and the like that are wound with a small radius of curvature, the electrical resistance of the carbon nanotube wire is not sufficiently reduced, and there was a need for improvement. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-37896 [Patent Document 2] Special Publication No. 2015-523944 Summary of the Invention [Problem to be solved by the invention]

[0008] In view of the above circumstances, an object of the present invention is to provide a coil of carbon nanotube-coated wire that is excellent in reducing electrical resistance by winding the carbon nanotube-coated wire. [Means for solving the problem]

[0009] The gist of the configuration of the present invention is as follows. [1] A coil formed by winding a carbon nanotube-coated wire including a carbon nanotube wire formed by twisting together a plurality of carbon nanotube wires each made of a single or a plurality of carbon nanotube aggregates each made of a plurality of carbon nanotubes, and a resin coating layer that coats the carbon nanotube wire, the Young's modulus of the resin of the resin coating layer is 0.40 GPa or more and 3.0 GPa or less; the hardness of the resin of the resin coating layer is 50 or more and 100 or less; The winding tension is 3000 x D, where D (mm) is the equivalent diameter of the CNT wire. 2 gf more than 30000×D 2 gf or less, coil. [2] A coil formed by winding a carbon nanotube-coated wire including a carbon nanotube wire formed by twisting together a plurality of carbon nanotube wires each made of a single or a plurality of carbon nanotube aggregates each made of a plurality of carbon nanotubes, and a resin coating layer that coats the carbon nanotube wire, the Young's modulus of the resin of the resin coating layer is 0.40 GPa or more and 3.0 GPa or less; the hardness of the resin of the resin coating layer is 50 or more and 100 or less; The coil has an aspect ratio, calculated by dividing the major axis by the minor axis in a radial cross section of the carbon nanotube-covered wire, of greater than 1.15 and smaller than 1.50. [3] The coil according to [1], wherein the aspect ratio of the carbon nanotube-coated wire in a radial cross section, calculated by dividing the major axis by the minor axis, is greater than 1.15 and smaller than 1.50. [4] The coil according to any one of [1] to [3], wherein the ratio of the average thickness of the resin coating layer to the circle-equivalent diameter of the carbon nanotube wire is 0.10% or more and 10% or less. [5] The coil according to any one of [1] to [4], wherein the diameter of the member around which the carbon nanotube-coated wire is wound is 5.0 mm or more and 35 mm or less. [6] The coil according to any one of [1] to [5], wherein the number of twists of the carbon nanotube wire is 50 T / m or more and 600 T / m or less. [7] The coil according to any one of [1] to [6], wherein the number of twists of the carbon nanotube wire is 50 T / m or more and 500 T / m or less. [8] A coil according to any one of [1] to [7], wherein the ratio of the average thickness of the resin coating layer to the circle-equivalent diameter of the carbon nanotube wire is 0.10% or more and 8.0% or less. [9] The coil according to any one of [1] to [8], wherein the hardness of the resin of the resin coating layer is 50 or more and 80 or less.

[10] The coil according to any one of [1] to [9], wherein the number of the carbon nanotube strands constituting the carbon nanotube wire is 5 or more and 1000 or less.

[11] A coil for an electric motor using the coil according to any one of [1] to

[10] .

[0010] In this specification, the term "hardness of resin" refers to Rockwell hardness (R scale: RHR). [Effects of the Invention]

[0011] According to an embodiment of the coil of the present invention, the Young's modulus of the resin of the resin coating layer is 0.40 GPa or more and 3.0 GPa or less, the hardness of the resin of the resin coating layer is 50 or more and 100 or less, and the winding tension is 3000 × D (mm) where D is the circle equivalent diameter of the CNT wire. 2 gf more than 30000×D 2 When the wire has a thickness of gf or less, a coil of the carbon nanotube-covered wire can be obtained that has excellent characteristics of reducing electrical resistance when the carbon nanotube-covered wire is wound.

[0012] According to another aspect of the coil of the present invention, the Young's modulus of the resin in the resin coating layer is 0.40 GPa or more and 3.0 GPa or less, the hardness of the resin in the resin coating layer is 50 or more and 100 or less, and the carbon nanotube is When the aspect ratio of the carbon nanotube-coated wire, calculated by dividing the major axis by the minor axis in the radial cross section, is greater than 1.15 and less than 1.50, a coil of carbon nanotube-coated wire can be obtained that has excellent electrical resistance reduction properties due to the winding of the carbon nanotube-coated wire.

[0013] According to the coil embodiment of the present invention, the diameter of the member around which the carbon nanotube-coated wire is wound is 5.0 mm or more and 35 mm or less, so that the electrical resistance of the carbon nanotube-coated wire is further reliably reduced by winding the carbon nanotube-coated wire.

[0014] According to the coil embodiment of the present invention, the twist number of the carbon nanotube wire is 50 T / m or more and 600 T / m or less, so that the electrical resistance of the carbon nanotube-coated wire is further reliably reduced by winding the carbon nanotube-coated wire.

[0015] According to the coil embodiment of the present invention, the twist number of the carbon nanotube wire is 50 T / m or more and 500 T / m or less, so that the reduction in electrical resistance due to the winding of the carbon nanotube-coated wire is further improved.

[0016] According to an embodiment of the coil of the present invention, the ratio of the average thickness of the resin coating layer to the equivalent circle diameter of the carbon nanotube wire is 0.10% or more and 8.0% or less, thereby further improving the reduction in electrical resistance due to the winding of the carbon nanotube coated wire.

[0017] According to the coil embodiment of the present invention, the hardness of the resin in the resin coating layer is 50 or more and 80 or less, so that the reduction in electrical resistance due to the winding of the carbon nanotube coated wire is further improved.

[0018] According to the coil embodiment of the present invention, the number of carbon nanotube wires constituting the carbon nanotube wire is 5 or more and 1000 or less, and by winding the carbon nanotube-coated wire, the electrical resistance of the carbon nanotube-coated wire is further reliably reduced. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a radial cross-sectional view illustrating a state before being wound of a carbon nanotube-coated wire used as a coil of the present invention. [Figure 2] 1 is a radial cross-sectional view illustrating a coil of the present invention formed by winding a carbon nanotube-coated wire. DETAILED DESCRIPTION OF THE INVENTION

[0020] A coil formed by winding a carbon nanotube-coated wire according to an embodiment of the present invention will be described below with reference to the drawings. Fig. 1 is a radial cross-sectional view illustrating the state of a carbon nanotube-coated wire used in the coil of the present invention before winding. Fig. 2 is a radial cross-sectional view illustrating the coil of the present invention formed by winding a carbon nanotube-coated wire.

[0021] As shown in FIGS. 1 and 2, a carbon nanotube coated electric wire (hereinafter sometimes referred to as a "CNT coated electric wire") 1 according to an embodiment of the present invention has a configuration in which a resin coating layer 21 is coated on the outer surface of a carbon nanotube wire (hereinafter sometimes referred to as a "CNT wire") 10. That is, the resin coating layer 21 is coated along the longitudinal direction of the CNT wire 10. In the CNT coated electric wire 1, the entire outer surface of the CNT wire 10 is coated with the resin coating layer 21. Furthermore, the CNT wire 10 is a stranded wire in which a plurality of carbon nanotube strands (hereinafter sometimes referred to as "CNT strands") 12 are twisted together.

[0022] In the CNT wire 10 in the form of a twisted wire, the CNT wires 12 constituting the twisted wire exhibit high conductivity in the longitudinal direction, and the conductivity between the CNT wires 12 is lower than the conductivity in the longitudinal direction of the CNT wires 12. In the CNT wire 10, the CNT wires 12 are in contact with adjacent CNT wires 12 without a resin coating layer 21 therebetween. By twisting the CNT wire 10 into a twisted wire, the CNT wire 10 is made thicker.

[0023] The CNT wire 12 is formed from a single carbon nanotube aggregate (hereinafter sometimes referred to as a "CNT aggregate") composed of multiple carbon nanotubes (hereinafter sometimes referred to as "CNTs") having a single-layer or two or more multi-layer structure, or by bundling multiple CNT aggregates. Here, CNT wire means a CNT wire with a CNT ratio of 90 mass % or more. Note that the calculation of the CNT ratio in the CNT wire excludes plating and dopants. The CNT aggregate is linear, and the longitudinal direction of the CNT aggregate forms the longitudinal direction of the CNT wire 10 and the CNT wire 12. The multiple CNT wires 12, 12, 12... in the CNT wire 10 are twisted together with a predetermined twist number along the central axis in the longitudinal direction of the CNT wire 10. Therefore, the multiple CNT wires 12, 12, 12... in the CNT wire 10 are aligned.

[0024] The CNT strand 12 is a bundle of long CNTs having a single-layer or multi-layer structure of two or more layers. The longitudinal direction of the CNTs forms the longitudinal direction of the CNT wire 10 and the CNT strand 12. The CNTs in the CNT strand 12 are arranged with their major axes aligned. Therefore, the CNTs in the CNT strand 12 are aligned. The CNT strand 12 has an equivalent circle diameter of, for example, 10 μm to 1000 μm, and the CNT aggregate has an equivalent circle diameter of, for example, 20 nm to 200 nm. The width of the outermost layer of the CNT is, for example, 1.0 nm to 5.0 nm.

[0025] In the CNT-coated wire 1 used as the coil 100, the CNTs constituting the CNT strand 12 are cylindrical bodies having a single-layer structure or a multi-layer structure, and are called SWNTs (single-walled nanotubes) or MWNTs (multi-walled nanotubes), respectively. To impart excellent electrical conductivity to the CNT strand 12, the CNTs constituting the CNT strand 12 preferably have a two-layer structure. This is because a two-layer CNT has a highly graphitic structure and therefore has high electrical conductivity. On the other hand, the CNT strand 12 may also include CNTs having a three-layer or more layer structure or a single-layer structure, and the CNT strand 12 may be formed from CNTs having a three-layer or more layer structure or a single-layer structure.

[0026] Among the CNTs that make up the CNT strand 12, those with a double-walled structure have a three-dimensional network structure in which two cylindrical bodies with a hexagonal lattice network structure are arranged approximately coaxially, and are called DWNTs (double-walled nanotubes). The hexagonal lattice, which is the structural unit, is a six-membered ring with carbon atoms at its vertices, and these are adjacent to other six-membered rings and are continuously bonded.

[0027] The properties of the CNTs constituting the CNT strand 12 depend on the chirality of the cylindrical body. Chirality is broadly classified into armchair, zigzag, and chiral types, with the armchair type exhibiting metallic behavior, the zigzag type exhibiting semiconducting and semimetallic behavior, and the chiral type exhibiting semiconducting and semimetallic behavior. Therefore, the conductivity of the CNTs varies significantly depending on the chirality of the cylindrical body. In the CNT strand 12 constituting the CNT-coated wire 1 used in the coil 100, it is preferable to increase the proportion of armchair CNTs exhibiting metallic behavior in order to further improve conductivity.

[0028] Next, the orientation of the CNTs and CNT strands 12 in the CNT wire 10 will be described. Analysis of the X-ray scattering image of the CNT wire 10 using small-angle X-ray scattering (SAXS) reveals that the CNTs and CNT strands 12, 12, 12... in the CNT wire 10 have good orientation. For example, the half-width Δθ of the azimuth angle in the azimuth plot obtained by small-angle X-ray scattering, which shows the orientation of the CNTs and CNT strands 12, 12, 12..., is preferably 60° or less, and particularly preferably 50° or less. Because the CNTs and CNT strands 12, 12, 12... have good orientation, the CNT wire 10 has excellent conductivity along the longitudinal direction of the CNTs and CNT strands 12. In other words, because the CNT strands 12 have longitudinal orientation, the CNT strands 12 have superior longitudinal conductivity compared to radial conductivity. Therefore, the CNT wire 10 in which multiple CNT wires 12, 12, 12... are twisted together has excellent conductivity in the longitudinal direction of the CNT wire 10, but the conductivity between the twisted CNT wires 12 is lower than the conductivity in the longitudinal direction. From the above, in the CNT coated wire 1 used as the coil 100, in order to improve the conductivity of the CNT wire 10 in the form of the coil 100, it is necessary that the wound CNT coated wire 1 has improved conductivity not only in the longitudinal direction of the CNT wire 10 but also between the twisted CNT wires 12.

[0029] Note that the CNT wire 10 of the CNT coated wire 1 used as the coil 100 exhibits better electrical conductivity in the longitudinal direction than in the radial direction, so there is no need to coat each of the CNT strands 12 with an insulating coating layer. Therefore, in the CNT wire 10, the CNT strands 12 can be twisted together in a state where they are in direct contact with other adjacent CNT strands 12. Furthermore, since there is no need to form an insulating coating layer on each of the CNT strands 12 in the CNT wire 10, the manufacturing cost can be reduced.

[0030] As shown in Fig. 1, in the present invention, a CNT-coated wire 1 used as a coil 100 includes a CNT wire 10 formed by twisting together a plurality of CNT strands 12, each of which has superior longitudinal conductivity compared to radial conductivity, and a resin coating layer 21 that coats the CNT wire 10. The CNT-coated wire 1 has a substantially circular cross-sectional shape in the radial direction before being wound. As shown in Fig. 2, the coil 100 is formed by winding the CNT-coated wire 1 around a member 200. The CNT-coated wire 1 is subjected to stress when being wound around the outer peripheral surface of the member 200, and is deformed from a substantially circular shape to an elliptical shape, for example.

[0031] In the coil 100 according to the first embodiment of the present invention, the Young's modulus of the resin of the resin coating layer 21 is 0.40 GPa or more and 3.0 GPa or less, the hardness of the resin of the resin coating layer 21 is 50 or more and 100 or less, and the winding tension is 3000×D where D (mm) is the circle equivalent diameter of the CNT wire 10. 2 gf more than 30000×D 2 gf or less. By having the coil 100 of the CNT-coated wire 1 have the above-mentioned configurations, the radial deformation of the CNT-coated wire 1 caused by winding the CNT-coated wire 1 is controlled within an appropriate range, compressing the twisted CNT wires 12 and resulting in improved contact between the CNT wires 12. By winding the CNT-coated wire 1, the contact between the twisted CNT wires 12 is improved, which reduces the electrical resistance between the CNT wires 12 and the CNT wires 12, and therefore a coil 100 with excellent electrical resistance reduction properties can be obtained.

[0032] In this way, the electrical resistance between the CNT wires 12 is reduced, and the conductivity between the twisted CNT wires 12 is also improved, so that the conductivity of the CNT wire 10 in the form of the coil 100 is improved.

[0033] In the coil 100 of the first embodiment of the present invention, as described above, the Young's modulus of the resin of the resin coating layer 21 is 0.40 GPa or more and 3.0 GPa or less. If the Young's modulus of the resin of the resin coating layer 21 is less than 0.40 GPa, the wound CNT wire 10 cannot be gripped, and the CNT wires 12 may come apart within the resin coating layer 21. If the Young's modulus of the resin of the resin coating layer 21 is greater than 3.0 GPa, the wound CNT wire 10 cannot be adequately crushed, and the contact between the CNT wires 12 cannot be improved. On the other hand, since the Young's modulus of the resin of the resin coating layer 21 is 0.40 GPa or more and 3.0 GPa or less, winding the CNT-coated wire 1 compresses the twisted CNT wires 12, contributing to improving the contact between the CNT wires 12.

[0034] The Young's modulus of the resin of the resin coating layer 21 is not particularly limited as long as it is in the range of 0.40 GPa to 3.0 GPa, but the lower limit is preferably 0.50 GPa, and particularly preferably 0.60 GPa, from the viewpoint of appropriately suppressing radial deformation of the CNT-coated wire 1 caused by winding the CNT-coated wire 1 and reliably maintaining excellent contact between the twisted CNT wires 12. On the other hand, the upper limit of the Young's modulus of the resin of the resin coating layer 21 is preferably 2.5 GPa, more preferably 2.0 GPa, and particularly preferably 1.5 GPa, from the viewpoint of appropriately smoothing radial deformation of the CNT-coated wire 1 caused by winding the CNT-coated wire 1 and reliably improving contact between the twisted CNT wires 12.

[0035] In the coil 100 of the first embodiment of the present invention, as described above, the hardness of the resin of the resin coating layer 21 is 50 or more and 100 or less. If the hardness of the resin of the resin coating layer 21 is less than 50, the wound CNT wire 10 cannot be gripped, and the CNT wires 12 may come apart within the resin coating layer 21. Also, if the hardness of the resin of the resin coating layer 21 is greater than 100, the wound CNT wire 10 cannot be adequately crushed, and the contact between the CNT wires 12 cannot be improved. On the other hand, since the hardness of the resin of the resin coating layer 21 is 50 or more and 100 or less, winding the CNT-coated wire 1 compresses the twisted CNT wires 12, which contributes to improving the contact between the CNT wires 12.

[0036] The hardness of the resin of the resin coating layer 21 is not particularly limited as long as it is in the range of 50 or more and 100 or less, but the lower limit is preferably 55, and particularly preferably 60, from the viewpoint of appropriately suppressing radial deformation of the CNT-coated wire 1 caused by winding the CNT-coated wire 1 and reliably maintaining excellent contact between the twisted CNT wires 12. On the other hand, the upper limit of the hardness of the resin of the resin coating layer 21 is preferably 90, and particularly preferably 80, from the viewpoint of appropriately smoothing radial deformation of the CNT-coated wire 1 caused by winding the CNT-coated wire 1 and reliably improving contact between the twisted CNT wires 12, thereby further improving the electrical resistance reduction characteristics of the coil 100.

[0037] Examples of resins having a Young's modulus of 0.40 GPa or more and 3.0 GPa or less and a hardness of 50 or more and 100 or less include thermoplastic resins such as polytetrafluoroethylene (PTFE), polyethylene, polypropylene, polyacetal, polystyrene, polycarbonate, polyamide, polyvinyl chloride, polymethyl methacrylate, polyurethane, polyether ketone, and styrene-butadiene-acrylonitrile polymers, and thermosetting resins such as polyimide and phenolic resins. These may be used alone or in combination of two or more.

[0038] The resin coating layer 21 may be a single layer, or alternatively, may have a multi-layer structure of two or more layers.

[0039] In the coil 100 according to the first embodiment of the present invention, as described above, when the circle-equivalent diameter of the CNT wire 10 is D (mm), the winding tension is 3000×D 2 gf more than 30000×D 2 The winding tension is 3000 × D, where D (mm) is the equivalent diameter of the CNT wire 10. 2 gf more than 30000×D 2 Since the CNT coated wire 1 is wound around the wire 1 at a pressure of not more than gf, the twisted CNT strands 12 are compressed, which contributes to improving the contact between the CNT strands 12.

[0040] The winding tension is 3000 × D, where D (mm) is the equivalent diameter of the CNT wire 10. 2 gf more than 30000×D 2 There are no particular limitations as long as it is in the range of gf or less, but the lower limit is set to 6000×D where D (mm) is the equivalent circle diameter of the CNT wire 10, in order to more appropriately adjust the amount of radial deformation of the CNT coated wire 1 caused by winding the CNT coated wire 1 and reliably improve the contact between the twisted CNT strands 12. 2 gf is preferable, and when the circle equivalent diameter of the CNT wire 10 is D (mm), it is 7000 × D 2 On the other hand, the upper limit of the winding tension is 27000×D (mm), where D is the equivalent circle diameter of the CNT wire 10, in order to prevent breakage during the coil winding process. 2 gf is preferable, and when the circle equivalent diameter of the CNT wire 10 is D (mm), it is 25000 × D 2 gf is more preferable, and when the circle equivalent diameter of the CNT wire 10 is D (mm), 20000×D 2 gf is particularly preferred.

[0041] Next, a coil 100 according to a second embodiment of the present invention will be described with reference to Figures 1 and 2. In the coil 100 according to the second embodiment of the present invention, the Young's modulus of the resin of the resin coating layer 21 is 0.40 GPa or more and 3.0 GPa or less, the hardness of the resin of the resin coating layer 21 is 50 or more and 100 or less, and the aspect ratio (L1 / L2) obtained by dividing the major axis L1 by the minor axis L2 in the radial cross section of the CNT coated wire 1 is greater than 1.15 and smaller than 1.50. That is, in the coil 100 according to the second embodiment, the winding tension of the coil 100 according to the first embodiment is 3000 x D (mm), where D is the equivalent circle diameter of the CNT wire 10. 2 gf more than 30000×D 2 gf or less, the aspect ratio in the radial cross section of the CNT-coated wire 1 is greater than 1.15 and smaller than 1.50. The aspect ratio in the radial cross section of the CNT-coated wire 1 is an index that indicates the degree of deformation when the CNT-coated wire 1 is wound around the member 200 and deforms from a substantially circular shape to an elliptical shape, etc.

[0042] In the coil 100 of the second embodiment, too, since the coil 100 of the CNT-coated wire 1 has the above-mentioned configurations, the radial deformation of the CNT-coated wire 1 caused by winding the CNT-coated wire 1 is controlled within an appropriate range, compressing the stranded CNT wires 12 and resulting in improved contact between the CNT wires 12. The improved contact between the stranded CNT wires 12 caused by winding the CNT-coated wire 1 reduces the electrical resistance between the CNT wires 12, thereby providing a coil 100 with excellent electrical resistance reduction properties.

[0043] In the coil 100 of the second embodiment of the present invention, as described above, the aspect ratio of the radial cross section of the CNT-coated wire 1 is greater than 1.15 and smaller than 1.50, so that when the CNT-coated wire 1 is wound, the twisted CNT strands 12 are compressed, contributing to improved contact between the CNT strands 12.

[0044] The aspect ratio of the CNT-coated wire 1 in its radial cross section is not particularly limited as long as it is greater than 1.15 and less than 1.50, but the lower limit is preferably 1.17, more preferably 1.20, and particularly preferably 1.22, in order to ensure improved contact between the twisted CNT wires 12. On the other hand, the upper limit of the aspect ratio of the CNT-coated wire 1 in its radial cross section is preferably 1.45, and particularly preferably 1.40, in order to ensure that radial deformation of the CNT-coated wire 1 is appropriately suppressed and excellent contact between the twisted CNT wires 12 is maintained.

[0045] Furthermore, in the coil 100 of the first embodiment, as in the coil 100 of the second embodiment, the aspect ratio of the CNT-coated wire 1 in the radial cross section may be greater than 1.15 and smaller than 1.50. In the coil 100 of the first embodiment, the aspect ratio of the CNT-coated wire 1 in the radial cross section is greater than 1.15 and smaller than 1.50, so that when the CNT-coated wire 1 is wound, the twisted CNT strands 12 are compressed, which contributes to improving the contact between the CNT strands 12.

[0046] In the coil 100 of each of the above embodiments, by setting the average thickness of the resin coating layer 21, the Young's modulus of the resin of the resin coating layer 21, the hardness of the resin of the resin coating layer 21, the winding tension, or the average thickness of the resin coating layer 21, the Young's modulus of the resin of the resin coating layer 21, the hardness of the resin of the resin coating layer 21, and the aspect ratio of the radial cross section of the CNT-coated wire 1 within the above-mentioned specified ranges, there is an effect of preventing the elastic CNT wires 12 from exerting a restoring force (referring to a gradual decrease in the contact area between the CNT wires 12 and the cross section of the coil 100 returning to an approximately perfect circle). Therefore, the present invention can maintain contact between the CNT wires 12 for a long period of time, making it possible to provide a coil 100 with excellent conductivity.

[0047] In the coil 100 of the first embodiment and the coil 100 of the second embodiment of the present invention, the ratio of the average thickness of the resin coating layer 21 to the circle-equivalent diameter of the CNT wire 10 is adjusted appropriately according to the Young's modulus and hardness of the resin coating layer 21, but is preferably 0.10% or more and 10% or less. By setting the ratio of the average thickness of the resin coating layer 21 to the circle-equivalent diameter of the CNT wire 10 to 0.10% or more and 10% or less, winding the CNT-coated wire 1 compresses the twisted CNT strands 12, which contributes to improving contact between the CNT strands 12.

[0048] As shown in FIG. 1, the CNT coated wire 1 used as the coil 100 has a substantially circular radial cross-sectional shape before being wound, and the "equivalent circle diameter of the CNT wire 10" in the "ratio of the average thickness of the resin coating layer 21 to the equivalent circle diameter of the CNT wire 10" in the coil 100 corresponds to the equivalent circle diameter of the CNT wire 10 before being wound.

[0049] The ratio of the average thickness of the resin coating layer 21 to the circle-equivalent diameter of the CNT wire 10 is preferably in the range of 0.10% to 10% inclusive, with the lower limit being more preferably 0.5%, even more preferably 1.0%, and particularly preferably 2.0%, in order to appropriately suppress radial deformation of the CNT-coated wire 1 caused by winding the CNT-coated wire 1 and reliably maintain excellent contact between the twisted CNT wires 12. On the other hand, the upper limit of the ratio of the average thickness of the resin coating layer 21 to the circle-equivalent diameter of the CNT wire 10 is more preferably 8.0%, and particularly preferably 7.0%, in order to appropriately smooth radial deformation of the CNT-coated wire 1 caused by winding the CNT-coated wire 1 and reliably improve contact between the twisted CNT wires 12, thereby further improving the electrical resistance reduction characteristics of the coil 100.

[0050] Furthermore, the ratio of the average thickness of the resin coating layer 21 to the circle-equivalent diameter of the CNT wire 10 can be adjusted to a preferred range depending on the Young's modulus and hardness of the resin coating layer 21. For example, if the resin coating layer 21 has a low Young's modulus and hardness, even if the average thickness of the resin coating layer 21 is large, sufficient contact with the CNT wire 12 can be maintained. Furthermore, if the resin coating layer 21 has a high Young's modulus and hardness, reducing the average thickness of the resin coating layer 21 will provide a heat dissipation effect to the CNT coated wire 1.

[0051] In the coil 100 of each of the above embodiments, the diameter of the member 200 around which the CNT-coated wire 1 is wound is not particularly limited, but since winding the CNT-coated wire 1 around the member 200 improves the contact between the CNT strands 12 and further reliably reduces the electrical resistance of the CNT-coated wire 1, the diameter is preferably 5.0 mm or more and 35 mm or less, more preferably 5.0 mm or more and 30 mm or less, and particularly preferably 5.0 mm or more and 25 mm or less.

[0052] When the coil 100 is used as a coil for an electric motor, the member 200 can be, for example, a slot in an iron core through which the rotating shaft of a rotor passes. When the coil 100 formed by winding the CNT-coated wire 1 is used as a coil for a motor, the weight of the coil is reduced and the electrical resistance between the CNT strands 12 is reduced, thereby improving the output of the motor. In particular, when the coil 100 formed by winding the CNT-coated wire 1 is used as a coil for an in-wheel motor that is wound with a small radius of curvature, the electrical resistance of the CNT-coated wire 1 is sufficiently reduced, improving the output of the in-wheel motor.

[0053] In the coil 100 of each of the above embodiments, the twist number (T / m) of the CNT wire 10 is not particularly limited, but the lower limit is preferably 50 T / m, and particularly preferably 70 T / m, from the viewpoint of reliably contributing to improved contact between the CNT bare wires 12. On the other hand, the upper limit of the twist number (T / m) of the CNT wire 10 is preferably 600 T / m, more preferably 500 T / m, and particularly preferably 400 T / m, from the viewpoint of appropriately smoothing radial deformation of the CNT coated wire 1 caused by winding the CNT coated wire 1 and reliably improving contact between the twisted CNT bare wires 12. That is, by setting the twist number of the CNT wire 10 to 50 T / m or more and 600 T / m or less, the electrical resistance of the CNT coated wire 1 is further reliably reduced by winding the CNT coated wire 1, and by setting the twist number of the CNT wire 10 to 50 T / m or more and 500 T / m or less, the electrical resistance reduction characteristics by winding the CNT coated wire 1 are further improved.

[0054] Furthermore, by setting the twist number (T / m) of the CNT wire 10 to 50 T / m or more and 600 T / m or less, it is possible to easily form and wind the twisted wire.

[0055] In the coil 100 of each of the above embodiments, the number of CNT wires 12 constituting the CNT wire 10 is not particularly limited as long as it is plural, but from the viewpoint of further reliably reducing the electrical resistance of the CNT coated wire 1 by winding the CNT coated wire 1 while also obtaining ease of forming the CNT wire 10, which is a twisted wire, the number is preferably 5 to 1000, more preferably 10 to 800, and particularly preferably 300 to 600.

[0056] In the coil 100 of each of the above embodiments, the circle-equivalent diameter of the twisted CNT wire 10 is not particularly limited, but from the viewpoint of large current conduction due to thicker wire and ease of winding, it is preferably 0.01 mm or more and 5.0 mm or less, more preferably 0.05 mm or more and 3.5 mm or less, and particularly preferably 0.30 mm or more and 2.0 mm or less.

[0057] In the coil 100 of each of the above embodiments, the density of the CNT wire 10 is not particularly limited. For example, it is set to 0.50 g / cm because it is easy to form a twisted wire while improving the contact between the CNT strands 12. 3 More than 2.5g / cm 3 Less than 1.2 g / cm is preferred 3 More than 1.8g / cm 3 The density of the CNT wire 12 is not particularly limited, and is, for example, 1.0 g / cm 3 in terms of improving the electrical conductivity in the longitudinal direction and providing excellent productivity for the CNT wire 12. 3 More than 3.0g / cm 3 Less than 1.2 g / cm is preferred 3 More than 1.8g / cm 3 The following are particularly preferred:

[0058] Next, an example of a manufacturing method for the CNT-coated wire 1 used as the coil 100 according to the embodiment of the present invention will be described. The CNT-coated wire 1 is manufactured by first manufacturing CNTs, manufacturing a CNT aggregate from a plurality of the obtained CNTs, and manufacturing a CNT wire 12 from the CNT aggregate. Next, the plurality of CNT wires 12 are twisted together to manufacture the CNT wire 10. Next, the outer peripheral surface of the CNT wire 10 is coated with a resin coating layer 21, thereby manufacturing the CNT-coated wire 1 used as the coil 100.

[0059] CNTs can be produced by, for example, a floating catalyst method (Japanese Patent No. 5819888), a substrate method (Japanese Patent No. 5590603), etc. CNT strands 11 can be produced by, for example, dry spinning (Japanese Patent Nos. 5819888, 5990202, and 5350635), wet spinning (Japanese Patent Nos. 5135620, 5131571, and 5288359), liquid crystal spinning (Japanese Patent Publication No. 2014-530964), etc.

[0060] The resin coating layer 21 can be formed on the outer surface of the CNT wire 10 obtained as described above by a method similar to that used to coat an aluminum or copper core wire with an insulating coating layer. For example, the resin coating layer 21 can be formed by melting a resin, which is the raw material for the resin coating layer 21, and extruding it around the CNT wire 10 to coat the CNT wire 10. [Example]

[0061] Next, examples of the present invention will be described, but the present invention is not limited to the following examples as long as they do not depart from the spirit of the present invention.

[0062] Regarding Examples 1 to 13 and Comparative Examples 1 to 10 Regarding the manufacturing method of CNT wires in Examples 1 to 13 First, CNT strands were obtained by a dry spinning method (Patent No. 5819888) or a wet spinning method (Patent Nos. 5135620, 5131571, and 5288359), in which CNTs produced by the floating catalyst method were directly spun. Next, the CNT strands were twisted together with the number of twisted wires and twist count shown in Table 1 below to obtain CNT wires (twisted wires) with the circle-equivalent diameter shown in Table 1 below.

[0063] How to coat the outer surface of a CNT wire with a resin coating (insulating coating) The following polyethylene resins, which have the Young's modulus and hardness shown in Table 1 below, were extrusion coated around the CNT wire using a regular extrusion molding machine for electric wire production, to form a resin coating layer with the ratio of the average thickness of the resin coating layer to the circle-equivalent diameter of the CNT wire shown in Table 1 below, thereby producing CNT-coated wire. <Type of resin for resin coating layer> Examples 1 to 4, 8 to 13: Polyethylene A, manufactured by Tosoh Corporation, Nipolon Hard Example 5: Polyvinyl chloride A, manufactured by Mitsubishi Chemical Corporation, Vinica Example 6: Polyethylene B, Novatec HD, manufactured by Japan Polyethylene Co., Ltd. Example 7: Polyethylene C, manufactured by Asahi Kasei Corporation, Suntech-HD Comparative Example 1: Polyethylene A, manufactured by Tosoh Corporation, Nipolon Hard Comparative Example 2: Polyethylene D, manufactured by Tosoh Corporation, Petrothene Comparative Example 3: Polyvinyl chloride B, manufactured by YK Acros Co., Ltd., vinyl chloride resin compound Comparative Example 4: Polyethylene E, manufactured by Asahi Kasei Corporation, Suntech-LD Comparative Example 5: Styrene-butadiene-acrylonitrile copolymer, manufactured by Denka Co., Ltd., Denka ABS Comparative Examples 6 to 10: Polyethylene A, manufactured by Tosoh Corporation, Nipolon Hard

[0064] Coils formed by winding CNT-coated wires The CNT-coated wire produced as described above was wound around the outer circumferential surface of a cylindrical member having a diameter shown in Table 1 below with a winding tension shown in Table 1 below to obtain a coil.

[0065] Aspect ratio of the radial cross section of CNT coated wire The coil obtained as described above was filled with epoxy resin (manufactured by Struers), and then a cross section of one slot was taken on a surface parallel to the radial direction of the CNT wire. By observing this with a microscope, the major and minor axes of each cross section in the radial direction of the CNT-coated wire were measured, and the aspect ratio was calculated by dividing the major axis by the minor axis, and the average value was calculated.

[0066] Evaluation items Resistance change rate (%) The resistance of the CNT-coated wire before forming the coil (pre-winding resistance) R1 was determined by measuring the voltage value when a current of 100 mA was applied using a source meter (Keithley). The resistance of the CNT-coated wire after forming the coil (post-winding resistance) R2 was also determined by measuring the voltage value when a current of 100 mA was applied using a source meter (Keithley). The resistance change rate was calculated from R1 / R2. A resistance change rate of 95% or less was considered acceptable.

[0067] The evaluation results are shown in Table 1 below.

[0068] [Table 1]

[0069] As shown in Table 1 above, the Young's modulus of the resin in the resin coating layer is 0.40 GPa or more and 3.0 GPa or less, the hardness of the resin in the resin coating layer is 50 or more and 100 or less, and the winding tension is 3000 × D, where D (mm) is the equivalent circle diameter of the CNT wire. 2 gf more than 30000×D 2 In Examples 1 to 13, where the resistance change rate was 95% or less, coils with excellent electrical resistance reduction properties were obtained. Furthermore, in Examples 1 to 13, the aspect ratio of the radial cross section of the CNT-coated wire was greater than 1.15 and less than 1.50. This is thought to be because, in the CNT-coated wires of Examples 1 to 13, the radial deformation of the CNT-coated wire 1 due to winding was controlled within an appropriate range, compressing the twisted CNT strands, thereby improving the contact between the CNT strands. In the CNT-coated wires of Examples 1 to 13, the diameter of the winding member was in the range of 5.0 mm to 35 mm, resulting in coils with a small radius of curvature. Furthermore, in the CNT-coated wires of Examples 1 to 13, the twist rate was in the range of 100 T / m to 550 T / m.

[0070] In particular, comparing Examples 1, 6, and 7, the resistance change rate was further reduced when the hardness of the resin was 50 or more and less than 90. Also, comparing Examples 1, 11, and 12, it was found that the winding tension was 10000×D, where D (mm) is the equivalent circle diameter of the CNT wire. 2 gf more than 30000×D 2 The resistance change rate was further reduced when the aspect ratio in the radial cross section of the CNT-coated wire was greater than 1.22 and less than or equal to 1.50.

[0071] Furthermore, a comparison of Examples 1, 2, and 3 shows that the resistance change rate was further reduced at a twist number of 450 T / m, and the resistance change rate reduction characteristics were further improved at twist numbers of less than 450 T / m.

[0072] Furthermore, comparing Example 1 and Example 4, when the ratio of the average thickness of the resin coating layer to the circle-equivalent diameter of the CNT wire was 0.10% or more and less than 10%, the resistance change rate was further reduced, and a coil with further improved electrical resistance reduction characteristics was obtained.

[0073] On the other hand, in Comparative Example 1, the aspect ratio in the radial cross section of the CNT coated wire is 1.15, in Comparative Example 2, the Young's modulus of the resin of the resin coating layer is 0.2 GPa, in Comparative Example 3, the Young's modulus of the resin of the resin coating layer is 4.0 GPa, in Comparative Example 4, the hardness of the resin of the resin coating layer is 35, in Comparative Example 5, the hardness of the resin of the resin coating layer is 120, and in Comparative Example 6, the winding tension is 2000 gf, and when the circle equivalent diameter of the CNT wire is D (mm), the winding tension is 3000 × D 2 In Comparative Example 6, where the aspect ratio in the radial cross section of the CNT coated wire was 1.12, the resistance change rate was 96% or more, and a coil with excellent electrical resistance reduction properties could not be obtained. In addition, when the winding tension was 35,000 gf and the equivalent circle diameter of the CNT wire was D (mm), the winding tension was 30,000 × D 2 In Comparative Example 7, which was larger than gf, breakage occurred during winding, and the rate of resistance change could not be measured.

[0074] Furthermore, in Comparative Example 8, which had 1,200 CNT wires, wire breakage occurred during winding, making it impossible to measure the rate of resistance change. In Comparative Example 9, in which the twist rate was 15 T / m and the aspect ratio of the CNT-coated wire in the radial cross section was 1.52, and in Comparative Example 10, in which the twist rate was 1,000 T / m and the aspect ratio of the CNT-coated wire in the radial cross section was 1.13, the rate of resistance change exceeded 95%, and good coils could not be obtained. [Industrial Applicability]

[0075] The coil of the CNT-coated wire of the present invention has excellent properties in reducing electrical resistance due to the winding of the CNT-coated wire, and is therefore highly useful in the field of coils used in electric motors in particular. [Explanation of symbols]

[0076] 1. Carbon nanotube coated wire 10 Carbon nanotube wire 12 Carbon nanotube wire 21 Resin coating layer 100 coils

Claims

1. a carbon nanotube wire formed by twisting together a plurality of carbon nanotube wires each made of a single or a plurality of carbon nanotube aggregates each made of a plurality of carbon nanotubes, and a resin coating layer coating the carbon nanotube wire; and a coil formed by winding a carbon nanotube-coated wire. the Young's modulus of the resin of the resin coating layer is 0.40 GPa or more and 3.0 GPa or less; the hardness of the resin of the resin coating layer is 50 or more and 100 or less; The winding tension is 3000 x D, where D (mm) is the equivalent circle diameter of the carbon nanotube wire. ２ gf or more 30000×D ２ A coil that is less than gf.

2. a carbon nanotube wire formed by twisting together a plurality of carbon nanotube wires each made of a single or a plurality of carbon nanotube aggregates each made of a plurality of carbon nanotubes, and a resin coating layer coating the carbon nanotube wire; and a coil formed by winding a carbon nanotube-coated wire. the Young's modulus of the resin of the resin coating layer is 0.40 GPa or more and 3.0 GPa or less; the hardness of the resin of the resin coating layer is 50 or more and 100 or less; A coil, wherein the aspect ratio of the carbon nanotube-covered wire in a radial cross section, calculated by dividing the major axis by the minor axis, is greater than 1.15 and smaller than 1.

50.

3. 2. The coil according to claim 1, wherein the aspect ratio of the carbon nanotube-coated wire, calculated by dividing the major axis by the minor axis in a cross section in the radial direction, is greater than 1.15 and smaller than 1.

50.

4. 4. The coil according to claim 1, wherein the ratio of an average thickness of the resin coating layer to a circle-equivalent diameter of the carbon nanotube wire is 0.10% or more and 10% or less.

5. 5. The coil according to claim 1, wherein the diameter of a member around which the carbon nanotube-coated wire is wound is 5.0 mm or more and 35 mm or less.

6. The coil according to claim 1 , wherein the number of twists of the carbon nanotube wire is 50 T / m or more and 600 T / m or less.

7. 7. The coil according to claim 1, wherein the number of twists of the carbon nanotube wire is 50 T / m or more and 500 T / m or less.

8. 8. The coil according to claim 1, wherein the ratio of an average thickness of the resin coating layer to a circle-equivalent diameter of the carbon nanotube wire is 0.10% or more and 8.0% or less.

9. 9. The coil according to claim 1, wherein the hardness of the resin of the resin coating layer is 50 or more and 80 or less.

10. The coil according to claim 1 , wherein the number of the carbon nanotube strands constituting the carbon nanotube wire is 5 or more and 1000 or less.

11. A coil for an electric motor using the coil according to any one of claims 1 to 10.

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