Wire, coil and method for producing a wire

Abstract

According to one embodiment, there is provided a conductive wire including a conductive flat wire and an insulating film covering the flat wire. A portion of the insulating film covering an end portion of the flat electric wire in the width direction is thicker than a portion thereof covering a center of the flat electric wire in the width direction.

Description

Cross-reference to related applications

[0001] This application is based on and claims priority to Japanese Patent Application No. 2023-154184, filed on September 21, 2023, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This disclosure relates to wires, coils, and methods for manufacturing wires. Background Technology

[0003] For example, coils obtained by winding wires are used in drive components of electric motors. For instance, coils using superconducting wires are used as superconducting coils to generate strong magnetic fields in nuclear magnetic resonance (NMR) devices, magnetic resonance imaging (MRI) devices, etc. In such coils as described above, insulating members, such as insulating tape, are inserted between the wires to prevent short circuits between the turns of the wound coil; however, short circuits may still occur between turns due to winding deviations or interlayer pressures in the wires and insulating members.

[0004] Reference List Patent documents PTL 1: Japanese Patent Application Publication No. 2020-167039 PTL 2: Japanese Patent Application Publication No. 2013-254563 PTL 3: Japanese Patent Application Publication No. 2019-39024 PTL 4: International Publication No. 2013 / 129568 Attached Figure Description

[0005] Figure 1 This is a perspective view schematically showing an example of a coil.

[0006] Figure 2 It shows Figure 1 A schematic cross-sectional view of an example of part A in the diagram.

[0007] Figure 3 It shows Figure 1 A schematic cross-sectional view of another example of part A in the diagram.

[0008] Figure 4 This is a schematic cross-sectional view showing an example of a wire according to an embodiment.

[0009] Figure 5 This is a schematic cross-sectional view showing another example of a wire according to an embodiment.

[0010] Figure 6 This is a schematic cross-sectional view showing yet another example of a conductor according to an embodiment.

[0011] Figure 7 It is shown Figure 4 Enlarged cross-sectional view of section B.

[0012] Figure 8 This is a schematic diagram illustrating an example of the manufacture of a wire according to an embodiment. Detailed Implementation

[0013] According to one embodiment, a conductor is provided, comprising a conductive flat wire and an insulating film covering the flat wire. The portion of the insulating film covering the ends of the flat wire in the width direction is thicker than the portion covering the center of the flat wire in the width direction.

[0014] According to another embodiment, a conductor is provided, comprising a flat wire and an insulating film covering the flat wire. The insulating film includes resin beads and voids disposed within the insulating film.

[0015] According to yet another embodiment, a coil is provided, the coil comprising a wound wire and resin disposed on the wound wire. The wound wire comprises a conductor according to the above embodiment. A portion of the resin is impregnated into an insulating film.

[0016] According to another embodiment, a method for manufacturing a conductor is provided, comprising forming an insulating film on a flat wire. The insulating film is formed by depositing a charged raw material solution onto the flat wire. The formed insulating film is thicker at the ends of the flat wire in the width direction than at the center.

[0017] Based on the above construction, a wire capable of suppressing short circuits in a coil and having high durability, a coil including the wire, and a method for manufacturing the wire are provided.

[0018] One known method for reducing defects (such as short circuits in coils) and improving reliability is to form an insulating film on the surface of the conductor. On one hand, for example, from the perspective of increasing coil density, a thin insulating film is ideal to avoid increasing coil size, etc. On the other hand, durable properties, including resistance to degradation and peeling, are also desirable, preventing conductor deterioration. Furthermore, high thermal conductivity is preferred. Of course, low-cost insulating film formation techniques are preferred.

[0019] The conductor according to an embodiment includes a conductive flat wire and an insulating film covering the flat wire. That is, the conductor is a conductor having an insulating film. According to one aspect, in the conductor, the portion of the insulating film covering the ends of the flat wire in the width direction is thicker than the portion covering the center of the flat wire in the width direction. According to another aspect, the insulating film of the conductor contains resin beads. The conductor has voids disposed within the insulating film. The conductor can have both of these characteristics simultaneously. That is, in the conductor, the insulating film containing resin beads and having voids can cover the ends thicker than the center of the flat wire in the width direction.

[0020] According to the former aspect, since the thickness of the insulating film at its ends is greater than that at its center, high coil density can be achieved by making the insulating film thinner overall. Simultaneously, reliability is improved by increasing the film thickness at the ends to prevent short circuits. The average film thickness of the insulating film is preferably 10 μm or less. More preferably, the film thickness of the insulating film is 10 μm or less in any part. Therefore, using a wire including a thin insulating film, a high coil density can be achieved. The thickness of the portion of the insulating film covering the ends of the flat wire is preferably more than one and less than two times the thickness of the portion covering the center of the flat wire. By maintaining a ratio in the thickness relationship of the insulating film, improvements in preventing short circuits can be effectively obtained, while keeping the thickness at the ends within a range suitable for configuring high-density coils.

[0021] According to the latter, the porous insulating film is formed from resin beads. When constructing a coil, resin is typically impregnated into a wound wire consisting of wound conductors to form a heat transfer path for each turn of conductor and to improve the mechanical strength of the coil. In coils using conductors, the resin enters the voids in the insulating film, making them integral, thereby improving the coil's vibration resistance and thermal conductivity.

[0022] Flat wires (and therefore conductors) included in the conductor can also be superconducting wires. Furthermore, flat wires and conductors can be high-temperature superconducting wires with a critical temperature of 25 K (Kelvin) or higher, exhibiting superconductivity even at 25 K or higher. Coils using conductors as superconducting wires can be superconducting coils.

[0023] Examples of coils in Figures 1 to 3 As shown in the image. Figure 2 and Figure 3 By magnification Figure 1 A schematic cross-section obtained from part A in the diagram, and Figure 2 and Figure 3 Each of the examples shows a different coil. Figure 2 yes Figure 1 The coil 30 shown is an enlarged cross-sectional view of section A in the case of a conventional coil. Figure 3 Is Figure 1 The coil 30 shown is an enlarged cross-sectional view of section A in the case of an example coil according to an embodiment.

[0024] The conventional coil 30 includes a wire 31, an insulating tape 32, and a resin 33. Figure 2 Specifically, the outer periphery of the coil, where the wires 31 and insulating tape 32 overlap and are wound, is secured by resin 33 through layers of the wound stacked wires 31 and insulating tape 32. The coil 30 may have a flat coil shape, as shown in the example. Although not shown, the coil 30 may also include a winding frame around which the wires 31 and insulating tape 32 are wound. Ideally, the insulating tape 32 is arranged between adjacent turns of the wires 31, and the gaps between the layers are impregnated with resin 33, thereby preventing short circuits due to contact between the wires 31. However, when the wires 31 and insulating tape 32 are wound, winding deviations or interlayer pressures may occur, resulting in, for example, the ends of the wires 31 in the width direction possibly contacting each other. Since the wires 31 included in a conventional coil 30 are not covered with insulating material, short circuits may occur between the turns.

[0025] In the example of the coil according to the embodiment, the coil 30 includes a conductor as an electrical wire, the conductor including a flat wire 10 and an insulating film 2 covering the flat wire 10. Figure 3 Instead of bare wires 31, resin 33 is disposed on the wound wire including the conductor, and a portion of the resin is impregnated into the insulating film 2. Apart from these points, the coil has the same structure as an example of a conventional coil. Since the conductor formed by covering the flat wire 10 with the insulating film 2 is used as the wire, no inter-turn short circuit occurs in the coil 30 even if the wires come into contact with each other due to winding deviation or interlayer pressure. Furthermore, since the resin 33 partially penetrates into the insulating film 2, the conductor exhibits high durability.

[0026] Note that the aforementioned width direction of wire 31 and the width direction of the conductor including flat wire 10 and insulating film 2 refer to the direction along the thickness direction of the flat coil shape of coil 30. Figures 1 to 3 The z-direction is represented in the middle.

[0027] Next, we will refer to Figures 4 to 7 The wires according to the embodiments are described in more detail. Figure 4 This is a schematic cross-sectional view showing an example of a conductor. Figure 5 and Figure 6 Each is a schematic cross-sectional view showing another example of a conductor. Figures 4 to 6 The cross-section intersecting the longitudinal direction of the conductor is shown. Figure 7 yes Figure 4 An enlarged cross-sectional view of part B shown. Although Figure 5 and Figure 6 Enlarged cross-sectional views have been omitted, but comparisons with... Figure 7 China regarding Figure 4 The structure is similar to the structure.

[0028] The conductor 1 includes a flat wire 10 and an insulating film 2 covering its outer periphery. For example, the flat wire 10 may include a substrate 11 and a stabilizing layer 12 disposed on the substrate 11. Although not shown, the substrate 11 includes, for example, a metal substrate and a superconducting layer disposed thereon. That is, the conductor 1 may be a superconducting wire. A coil using such a conductor 1 may be a superconducting coil.

[0029] For example, the ribbon-like superconducting layer can be disposed on one surface of the ribbon substrate 11, or it can be disposed on each of the two surfaces of the ribbon substrate 11. Note that the metal substrate typically has a thickness on the order of tens of micrometers, and the superconducting layer is typically a thin film on the order of a few micrometers. The substrate 11 may also include an intermediate layer disposed between the metal substrate and the superconducting layer. For example, the intermediate layer is a thin film such as magnesium oxide (MgO) with a thickness on the order of 1 / 10 micrometer, and is sometimes referred to as a buffer layer. The substrate 11 may also include a protective layer made of, for example, silver. For example, the protective layer is disposed on the superconducting layer. Furthermore, in the substrate 11 where the superconducting layer is disposed on only one surface of the metal substrate, the protective layer can be disposed not only on the superconducting layer but also on the surface of the opposite side of the metal substrate, where no superconducting layer is disposed. The protective layer typically has a thickness on the order of a few micrometers.

[0030] For example, the stabilizing layer 12 is formed of copper and typically has a thickness on the order of several micrometers to tens of micrometers. The stabilizing layer 12 can be omitted.

[0031] An insulating film 2 covers the outer perimeter of the flat wire 10. Along the width direction of the flat wire 10, the thickness of the insulating film 2 at both ends is greater than its thickness at the center. Figures 4 to 6 The thickness of the insulating film 2 in this document refers to the thickness in the thickness direction of the flat wire 10, for example, the thickness along the vertical direction of each figure. The thickness of the insulating film 2 at each end may refer to the thickness along the width direction of the flat wire 10, for example, the thickness along the horizontal direction of each figure.

[0032] exist Figure 4 In the example shown, the thickness of the insulating film 2 on the main surfaces at both ends of the flat wire 10 is greater in the thickness direction than the thickness of the insulating film 2 at the center. Figure 5In the example shown, the thickness of the insulating film 2 in the width direction on the side surfaces (end faces) at both ends of the flat wire 10 is thicker than the thickness (thickness in the thickness direction) of the insulating film 2 at the center. Figure 6 In the example shown, the insulation film 2 covering both ends of the flat wire 10 in both the thickness and width directions is thicker than the thickness of the insulation film 2 at the center (thickness in the thickness direction).

[0033] Regarding the thickness in the thickness direction, the thickness of the insulating film at each portion on one main surface side can differ from the thickness of the insulating film at each corresponding portion on the other main surface side. Furthermore, by satisfying the relationship between each surface of the conductor 1, the relationship that the thickness of the portion of the insulating film 2 located at each of the two ends is greater than the thickness of the portion located at the center in the width direction of the flat wire 10 will be sufficiently satisfied. For example, the portion of the insulating film 2 covering the center of one surface of the flat wire 10 can be thicker than the portions covering one or both ends of the other surface (reverse side) of the flat wire 10. Furthermore, within the insulating film 2 on the same surface side, the thickness of the portions at each end can differ from each other.

[0034] Similarly, the thickness of the insulating film covering the side surfaces of the flat wire 10 at one end and the thickness of the insulating film covering its side surfaces at the other end can be different from each other, relative to the thickness at both ends in the width direction. By satisfying the relationship of each side surface (end face) in the width direction of the flat wire 10, the thickness of the portion at both ends will be greater than the thickness of the central portion of the insulating film 2.

[0035] The insulating film 2 comprises resin beads 21, and ideally is an assembly of resin beads 21. Gaps 22 are formed between the resin beads 21 joined together to form the insulating film 2. The gaps 22 are ideally continuous holes, rather than isolated spaces. When the gaps 22 are continuous, they are easily impregnated with resin when constructing a coil, and a coil with resin penetrating into the interior of the insulating film 2 can be obtained.

[0036] In addition to resin beads 21, the insulating film 2 may also contain organic fibers (e.g., fibers made of resin). The ratio of resin beads to organic fibers in the insulating film 2 can be selectively set, but resin beads 21 ideally account for 50% by volume or more. That is, the insulating film 2 preferably contains resin beads 21 as the main component. Although the membrane whose main component is organic fibers includes many through-pores, voids 22 can be formed in the insulating film 2 whose main component is resin beads 21.

[0037] The resin beads 21 are ideally microparticles. Specifically, one side of the circumscribed quadrilateral of the resin bead is ideally 10 μm or smaller. The insulating film 2 formed from the resin beads 21 in microparticle form can be made very thin while still including voids 22.

[0038] For example, insulating film 2 can be observed as follows: The wire to be observed is embedded in the resin and polished to expose a cross-section that intersects the wire longitudinally and along the width and thickness directions. The cross-section of the obtained sample is observed using an optical microscope.

[0039] The observed cross-section can be similar to Figures 4 to 6 The example shown. On the front and back of the flat wire 10 ( Figures 4 to 6 On each of the upper and lower surfaces of the flat wire 10, along the width direction ( Figures 4 to 6 The thickness of the insulating film 2 covering both ends and the center (in the horizontal direction) is measured. Here, the flat wire 10 is divided into 15 equal parts in the width direction, and the central part is defined as the center of the flat wire 10. The thickness T of the insulating film 2 at the center is measured. C Of these 15 sections, the portion located at each of the two ends is defined as the end of the flat wire 10. The thickness T of the insulating film 2 at the end is measured. E .exist Figure 4 The image shows only the thickness T at the upper center. C And the thickness T at the upper left and lower right surfaces E However, the measurement includes the thickness (T) at the lower center. C Thickness (T) at the lower left and upper right surfaces E ) and the thickness at the end side surface (e.g., corresponding to Figure 5 The thickness T shown in the figure E The thickness at a total of eight points (these thicknesses are not shown). Similarly, in Figure 5 and Figure 6 Some thickness diagrams have been omitted.

[0040] The metal substrate of a flat wire included in a conductor can have, for example, a strip shape, or more specifically, a flat wire shape. For example, the metal substrate is formed of a high-strength metallic material, such as a nickel-based alloy, stainless steel, or copper.

[0041] The superconducting layer of the flat wire is made of a superconducting material and includes, for example, Nb-Ti alloys, niobium compounds (such as Nb3Sn), magnesium diboride (MgB2), iron-based superconductors, bismuth-based oxide superconductors, and rare-earth-based oxide superconductors. It may include at least one rare-earth element from the group consisting of yttrium (Y), lanthanum (La), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu).

[0042] Examples of resins that are wound on a wire including conductors in a coil and partially impregnated in an insulating film may include thermosetting resins, such as epoxy resins and thermoplastic resins.

[0043] The conductor may also include a release layer on top of the insulating film. By providing a release layer, the bond between the conductor and the resin used to hold the wound wire within the coil can be weakened. For example, a superconducting coil is cooled to a critical temperature or lower during operation to exhibit superconductivity. Thermal stress generated by cooling or electromagnetic stress generated by excitation applies a peel stress to the conductor. For a conductor with a weakened bond to the resin due to the release layer, the conductor can peel off from the resin when peel stress is applied, thus reducing the peel stress applied to the conductor. As a result, degradation of the conductor and the performance of the coil can be suppressed. The release layer is formed of, for example, at least one selected from fluoropolymers (such as Teflon, a registered trademark), paraffin wax, grease, and silicone oil.

[0044] A method for manufacturing a conductor according to an embodiment includes depositing a charged raw material solution onto a flat wire to form an insulating film on the flat wire, wherein the insulating film is thicker at the ends than at the center in the width direction of the flat wire. That is, the conductor can be manufactured by electrostatic coating. By using electrostatic coating, an insulating film with a thicker portion at the ends can be formed. Furthermore, by using electrostatic coating, an insulating film with voids can also be obtained, unlike the dense film formed by electrodeposition methods. Moreover, by using electrostatic coating, manufacturing costs can be reduced compared to using electrodeposition methods.

[0045] When forming an insulating film by electrostatic coating, it is desirable to use a raw material solution as the manufacturing condition for droplet deposition on flat wires. Upon drying, the deposited droplets transform into resin beads, and an assembled film of resin beads can be obtained. It is preferable to appropriately control the concentration and viscosity of the raw material solution, as well as the molecular weight of the organic materials contained in the raw material solution, to achieve the condition for the raw material solution to deposit as droplets on flat wires. Low-concentration raw material solutions tend to more easily form droplets and deposit as resin beads on flat wires. Conversely, high-concentration raw material solutions tend to deposit into fibers to form a fiber membrane. Low-viscosity raw material solutions tend to more easily form droplets and deposit as resin beads, while high-viscosity raw material solutions tend to form fiber membranes. Solutions containing low-molecular-weight raw materials tend to more easily form droplets and deposit as resin beads. Conversely, solutions containing high-molecular-weight raw materials tend to more easily form fiber membranes. Low pressure within the pipe tends to more easily form droplets and deposit resin beads, while high pressure within the pipe tends to more easily form fiber membranes.

[0046] After the insulating film is formed, no pressing process is performed. When the wire is pressed, the internal structure of the wire is damaged, which may impair its performance.

[0047] Figure 8 An example of manufacturing wires is shown. Figure 8 This is a schematic diagram illustrating an example of a wire manufacturing apparatus. As shown, the manufacturing apparatus 100 includes an unwinding machine 120, a coating mechanism 130, a dryer 150, and a winding machine 160. Furthermore, a conveyor line 180 is formed in the manufacturing apparatus 100. In the manufacturing apparatus 100, flat wires 10 are conveyed from the unwinding machine 120, through the coating mechanism 130, and the dryer 150, to the winding machine 160 via the conveyor line 180.

[0048] The unwinding machine 120 includes a spool 121. Flat wires 10 are wound in coils on the spool 121. In the unwinding machine 120, the spool 121 is rotated in the direction indicated by arrow R1 by driving a drive member (not shown), such as an electric motor. As a result, the flat wires 10 wound on the spool 121 are unwound. The unwound flat wires 10 are then conveyed to a conveyor line 180.

[0049] The winding machine 160 includes a spool 161. In the winding machine 160, the spool 161 is rotated in the direction of arrow R2 by driving a drive member (not shown), such as an electric motor. Thus, the flat wire 10 conveyed by the conveyor line 180 is wound into a coil by the spool 161.

[0050] In the manufacturing apparatus 100, the flat wire 10 is conveyed from the unwinder 120 to the winding machine 160 via the conveyor line 180 by rotating the spool 121 in the direction indicated by arrow R1 and simultaneously rotating the spool 161 in the direction indicated by arrow R2. Note that one or more guide rollers (not shown) guiding the flat wire 10 from the unwinder 120 to the winding machine 160 may be provided on the conveyor line 180. In this case, the guide rollers are provided on the conveyor line 180 at least in any of the following locations: between the unwinder 120 and the coating mechanism 130, between the coating mechanism 130 and the dryer 150, and between the dryer 150 and the winding machine 160. The guide rollers may also be provided in the coating mechanism 130 or the dryer 150.

[0051] Furthermore, the layout of the conveyor line 180 from the unwinder 120 to the winding machine 160 is not particularly limited. In one example, the conveyor line 180 extends horizontally, and in another example, it extends vertically. Additionally, one or more bends, folds, etc., of the conveyor line 180 can be provided between the unwinder 120 and the winding machine 160, and the extension direction of the conveyor line 180 can be changed at the bends, folds, etc. In one example, the fold-back portion of the conveyor line 180 is provided between the coating mechanism 130 and the dryer 150; in another example, the fold-back portion of the conveyor line 180 is provided in either the coating mechanism 130 or the dryer 150.

[0052] The coating mechanism 130 includes one or more nozzle heads 131, and... Figure 8 The example includes six nozzle heads 131. Each nozzle head 131 includes a head body 132 and a nozzle 133 protruding from the head body 132. Each nozzle head 131 may have only one nozzle 133 or multiple nozzles 133. In each nozzle head 131, a raw material solution in which the organic material is dissolved in a solvent may be stored within the head body 132.

[0053] In the coating mechanism 130, the flat wire 10 unwound from the spool 121 is conveyed toward the winding machine 160. Furthermore, the coating mechanism 130 is provided with a power source (not shown), and voltage can be applied between the unwound flat wire 10 and each nozzle 133 of the nozzle head 131. With the raw material solution stored inside the head body 132 of each nozzle head 131, the raw material solution in the nozzle head 131 is charged by applying voltage between the flat wire 10 and the nozzle head 131. The charged raw material solution is sprayed from the nozzle 133 toward the surface of the flat wire 10 unwound by the unwinding machine 120. The sprayed raw material solution deposits to form an insulating film 2 on the surface of the flat wire 10. Therefore, the coating mechanism 130 forms the insulating film 2 by electrostatic coating.

[0054] The organic materials used in the feed solution are, for example, any one or more of polyolefins, polyethers, polyimides, polyketides, polysulfones, cellulose, polyvinyl alcohol (PVA), polyamides, polyamide-imides, and polyvinylidene fluoride (PVdF). Examples of polyolefins include polypropylene (PP) and polyethylene (PE). The organic materials contained in the feed solution serve as raw materials for the insulating film and the resin beads that form the insulating film.

[0055] In each nozzle of nozzle head 131, the organic material is dissolved in a solvent. Solvents used to dissolve the organic material in the raw material solution include dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), N-methylpyrrolidone (NMP), acetone, dimethoxyethylene, toluene, tetrahydrofuran, water, alkanes, ketones, esters, alcohols, ethers, etc. For organic materials with low solubility, a single piece of organic material can be dissolved using a laser or similar method. Furthermore, multiple solvents can be mixed and used in the raw material solution. Here, one or more solvents used in the raw material solution are preferably organic solvents with a boiling point of 100°C or higher. Examples of organic solvents with a boiling point of 100°C or higher include dimethylacetamide, dimethyl sulfoxide, N,N-dimethylformamide, N-methylpyrrolidone, and toluene.

[0056] Based on the types of solvents and solutes in the raw material solution, the boiling point and vapor pressure profile of the solvent in the raw material solution, the concentration and temperature of the raw material solution, the shape of the nozzle 133, and the distance between the flat wire 10 and the nozzle 133, the voltage between the nozzle 133 and the flat wire 10 of each nozzle head 131 is appropriately determined. As described above, the shape of the raw material solution discharged from the nozzle 133 varies depending on the concentration and viscosity of the raw material solution, the molecular weight of the organic material contained in the raw material solution, and the pressure in the pipeline when the raw material solution is supplied to the nozzle head 131.

[0057] exist Figure 6 In the example, in the coating mechanism 130 between the unwinding machine 120 and the winding machine 160, as described above, an insulating film 2 is formed on the surface of the flat wire 10. Therefore, in the winding machine 160, the wire having the insulating film 2 is wound onto the spool 161.

[0058] A dryer 150 is disposed between a coating mechanism 130 and a winding machine 160 on a conveyor line 180. Furthermore, a flat wire 10 with an insulating film 2 formed on its surface is conveyed from the coating mechanism 130 to the dryer 150. The dryer 150 dries the insulating film 2 formed on the surface of the flat wire 10 before the wire with the insulating film 2 is wound onto the spool 161 of the winding machine 160.

[0059] In the example shown, the dryer 150 includes an infrared heater 151. The infrared heater 151 generates infrared radiation. The infrared heater 151 emits the generated infrared radiation toward an insulating film 2 formed on the surface of the flat wire 10. Functional groups contained in the organic material, solvent, etc., in the insulating film 2 absorb the infrared radiation emitted from the infrared heater 151, causing the insulating film 2 to be heated and the solvent contained in the insulating film 2 to evaporate. As a result, the amount of solvent contained in the insulating film 2 decreases, and the insulating film 2 is dried.

[0060] The drying of the insulating film 2 in the dryer 150 is not limited to drying using infrared rays emitted from the infrared heater 151. In one example, hot air can be used in the dryer 150 instead of infrared rays emitted from the infrared heater 151 to dry the insulating film 2.

[0061] Example Examples will be described below, but the embodiments are not limited to the examples below.

[0062] The following describes the fabrication of a wire with an insulating film. A flat, wire-like superconducting wire is fabricated, wherein an oxide-based high-temperature superconducting material layer is disposed on a metal substrate, and its outer periphery is covered with copper. Insulating resin beads are deposited on the superconducting wire by electrostatic coating to form an insulating film.

[0063] A raw material solution for forming an insulating film is prepared by dissolving polyamide-imide in dimethylacetamide. The raw material solution is prepared such that its solid content concentration is 22% by mass. A low molecular weight polyamide-imide is used.

[0064] Prepare a wire with an insulating film as described above.

[0065] The cross-section of the obtained conductor with an insulating film was observed using the method described above. Two cross-sections were obtained along the longitudinal direction of the conductor's width. In both cross-sections, it was confirmed that an insulating film was formed over the entire outer periphery, including the ends in the conductor's width direction. As shown in Table 1, in both cross-sections, the thickness of the insulating film formed on both the upper and lower surfaces of the flat wire (superconducting conductor) was greater at the ends than at the center. Furthermore, the thickness of the insulating film on the side surfaces (end surfaces in the width direction) of the flat wire was greater on the side surfaces than on the upper and lower surfaces.

[0066] [Table 1] Table 1 The thickness of the insulating film on one end side The thickness of the central insulating film The thickness of the insulating film on the other end side upper surface side of cross section 1 4.8μm 3.9μm 4.2μm Cross-section 1, lower surface side 5.4μm 4.4μm 5.3μm Cross-section 1 side surface side 8.7μm - 8.0μm upper surface side of cross section 2 6.4μm 5.1μm 5.5μm Cross-section 2, lower surface side 6.6μm 4.1μm 4.6μm Cross-section 2 side surface side 10.7μm - 8.7μm The insulating wires obtained were evaluated for five projects. The results are summarized in Table 2 below. As shown in Table 2, the insulating wires obtained showed good results for each evaluation project. Details are as follows.

[0067] Samples of wires with insulating films were immersed in resin liquid and ethanol, and the elution of the resin forming the insulating film was examined. As shown in Table 2, elution was not confirmed.

[0068] To check the mechanical strength of the insulating film, samples were transported using a roll-to-roll method, and the film was inspected for scratches, peeling, or other defects from the flat wire. As shown in Table 2, the insulating film did not peel off.

[0069] The thermal cycling strength of the insulating film was evaluated as follows. Thermal cycling tests were conducted, in which the samples were alternately exposed to a low-temperature environment of 77 K and a room-temperature environment. As shown in Table 2, no cracking or peeling of the insulating film was observed in the samples after the thermal cycling tests.

[0070] The insulation performance of the insulating film was evaluated. Specifically, the contact resistance was measured at room temperature and 77 K. As shown in Table 2, the samples exhibited a resistance of 1 Ω or greater at both measurement temperatures.

[0071] To evaluate the superconducting properties of the wire with the insulating film, the critical current (Ic) was measured at 77 K before and after the formation of the insulating film. As shown in Table 2, no decrease in the critical current value associated with film formation was confirmed. Furthermore, since the superconductivity was exhibited at 77 K, the obtained wire with the insulating film can be considered a high-temperature superconducting wire with a critical temperature of 25 K or higher.

[0072] [Table 2] Table 2 Evaluation Project result Chemical resistance of the film It was not eluted into the resin or ethanol. Mechanical strength of the film No peeling Thermal cycling intensity between low temperature (77 K) and room temperature No cracks or peeling Contact resistance value (room temperature 77 K) 1Ω or greater at any temperature Evaluation of superconducting properties The critical current (Ic) does not decrease. According to at least one embodiment and example described above, a conductor is provided. The conductor includes a conductive flat wire and an insulating film covering the flat wire. In the insulating film, the portion covering the ends of the flat wire in the width direction is thicker than the portion covering the center. Optionally, the insulating film includes resin beads and includes voids within it. This conductor has high durability and can provide a coil that suppresses short circuits.

[0073] While certain embodiments have been described, these embodiments are presented by way of example only and are not intended to limit the scope of the invention. In fact, the novel embodiments described herein can be embodied in various other forms; furthermore, various omissions, substitutions, and changes can be made to the forms of the embodiments described herein without departing from the spirit of the invention. The appended claims and their equivalents are intended to cover these forms or modifications that fall within the scope and spirit of the invention.

[0074] Several currently disclosed embodiments are listed below.

[0075] 1. A conductor, comprising: Conductive flat wires; and The insulating film covering the flat wire, The portion of the insulating film covering the ends of the flat wire in the width direction is thicker than the portion covering the center of the flat wire in the width direction.

[0076] 2. The conductor according to Clause 1, wherein the average film thickness of the insulating film is 10 μm or less, and the thickness of the portion of the insulating film covering the end is more than 1 to 2 times the thickness of the portion covering the center.

[0077] 3. A conductor, comprising: Flat wires; and The insulating film covering the flat wire, The insulating film includes resin beads and voids disposed inside the insulating film.

[0078] 4. The wire according to Clause 3, wherein one side of the circumscribed quadrilateral of the resin bead is 10 μm or smaller.

[0079] 5. The conductor according to any one of clauses 1 to 4, wherein the flat wire is a superconducting wire.

[0080] 6. The conductor according to any one of clauses 1 to 5 further includes a release layer on the insulating film.

[0081] 7. A coil, comprising: Winded wire, including conductors according to any one of clauses 1 to 6; and A portion of the resin disposed on the wound wire is impregnated into the insulating film.

[0082] 8. A method for manufacturing a conductor, comprising: depositing a charged raw material solution onto a flat wire to form an insulating film on the flat wire, the insulating film being thicker at the ends of the flat wire than at the center in the width direction.

[0083] List of reference numerals 1… Wire, 2… Insulating film, 10… Flat wire, 11… Substrate, 12… Stabilizing layer, 21… Resin bead, 22… Void, 30… Coil, 31… Wire, 32… Insulating tape, 33… Resin, 100… Manufacturing apparatus, 120… Unwinding machine, 130… Coating mechanism, 131… Nozzle head, 132… Nozzle body, 133… Nozzle, 150… Dryer, 151… Winding, 160… Winding machine.

Claims

1. A conductor, comprising: Conductive flat wire; as well as The insulating film covering the flat wire, The portion of the insulating film covering the ends of the flat wire in the width direction is thicker than the portion covering the center of the flat wire in the width direction.

2. The conductor according to claim 1, wherein the average film thickness of the insulating film is 10 μm or less, and the thickness of the portion of the insulating film covering the end is more than 1 and less than 2 times the thickness of the portion covering the center.

3. A conductor, comprising: Flat electrical wire; as well as The insulating film covering the flat wire, The insulating film includes resin beads and voids disposed inside the insulating film.

4. The wire according to claim 3, wherein one side of the circumscribed quadrilateral of the resin bead is 10 μm or smaller.

5. The conductor according to any one of claims 1 to 4, wherein the flat wire is a superconducting wire.

6. The conductor according to any one of claims 1 to 4, further comprising a release layer on the insulating film.

7. The conductor according to claim 5, further comprising a release layer on the insulating film.

8. A coil, comprising: A wound wire, comprising a conductor according to any one of claims 1 to 4; as well as A portion of the resin disposed on the wound wire is impregnated into the insulating film.

9. A method for manufacturing a wire, comprising: A charged raw material solution is deposited onto a flat wire to form an insulating film on the flat wire, the insulating film being thicker at the ends of the flat wire than at the center in the width direction.

Images