Superconducting coil and manufacturing method

Abstract

To reduce frictional heat generated in a superconducting wire in a winding portion formed by winding the superconducting wire, thereby suppressing thermal damage to a superconducting coil due to quenching.SOLUTION: A tape-shaped superconducting wire 1 having a superconducting layer laminated together with other layers on a metal substrate includes a winding portion 11 formed by overlapping and winding tape wide surfaces 1A and 1B, and heat transfer members 12 and 13 bonded via a resin layer 16 to end surfaces 11A and 11B of the winding portion that are perpendicular to the direction of the winding axis O, and the superconducting wire 1 is configured such that an insulating layer 14 is provided on the outer surface including at least one of the two tape wide surfaces 1A and 1B.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] SUMMARY OF THE INVENTION Embodiments of the present invention relate to a superconducting coil and a method for manufacturing a superconducting coil. [Background technology]

[0002] With the advancement of superconductivity technology, superconducting devices such as magnetic resonance imaging (MRI), superconducting magnetic energy storage (SMES), and single crystal pulling devices have been put into practical use. These superconducting devices contain superconducting coils made by winding superconducting wires.

[0003] In recent years, superconducting coils have been developed using high-temperature superconducting wires that have excellent critical current characteristics at high temperatures and in strong magnetic fields. Examples of such high-temperature superconducting wires include thin-film superconducting wires (hereinafter simply referred to as superconducting wires) with a multilayer structure that includes a tape-shaped metal substrate such as Hastelloy (registered trademark), an intermediate layer such as cerium oxide, an oxide superconducting layer such as YBa2Cu3O7, and a protective metal layer such as silver.

[0004] Superconducting coils that are impregnated with thermosetting synthetic resins such as epoxy resins are known to maintain the wound shape and improve heat transfer characteristics in a vacuum. However, multilayered superconducting wires are vulnerable to peeling force, which is a tensile stress perpendicular to the wide surface of the tape. Thermal stress caused by the difference in thermal contraction rate between the thermosetting synthetic resin and the superconducting wires can cause delamination, which can degrade the superconducting characteristics. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-103587 [Patent Document 2] Japanese Patent Application Publication No. 2022-108794 [Patent Document 3] Japanese Patent Application Publication No. 2020-167039 [Patent Document 4] Japanese Patent Application Laid-Open No. 2012-59403 Summary of the Invention [Problem to be solved by the invention]

[0006] In response to this, Patent Document 1 proposes a configuration in which a heat transfer member is bonded to the end face of a winding formed by co-winding a superconducting wire and an insulating wire. The heat transfer member is bonded only to the end face of the winding using resin, without impregnating the wire with resin, and the superconducting wires are spaced apart, thereby reducing the peeling force acting on the superconducting wires. Furthermore, by bonding the end face of the winding and the heat transfer member with resin, a heat transfer path from the superconducting wire to the refrigerator is secured, and heat generated by the superconducting wires is removed.

[0007] However, in the configuration described in Patent Document 1, in which only the end faces of the windings are bonded, the superconducting wire and the insulating wire are not bonded at the center in the tape width direction, so they are configured to be able to slide slightly. Therefore, there is a risk that the superconducting wire and the insulating wire will slide due to vibrations acting on the superconducting coil and electromagnetic forces acting on the superconducting wire during operation, and frictional heat will be generated at their interface. Furthermore, as described in Patent Document 2, the temperature of the superconducting wire will rise due to the above-mentioned frictional heat, and if this heat is not removed, a quench may occur, causing thermal damage to the superconducting coil.

[0008] The superconducting coil described in Patent Document 1 will be described in further detail with reference to Figures 8 and 9. In superconducting coil 100 described in Patent Document 1, superconducting wire 101 and insulating wire 102 are wound together to form winding portion 103. Winding portion 103 has two end faces 103A and 103B that are perpendicular to the direction of winding axis P. Heat transfer members 105 and 106 are bonded to winding portion 103 by resin layers 104 formed on end faces 103A and 103B, respectively.

[0009] Resin layer 104 is not disposed between turns of winding portion 103, and therefore superconducting wire 101 is not bonded to insulated wire 102 of adjacent turns, resulting in a configuration in which peeling force does not act on superconducting wire 101. In such superconducting coil 100, when vibration acts inside winding portion 103 during operation, superconducting wire 101 and insulated wire 102 that are not bonded between turns in winding portion 103 slide against each other at the center of the width direction of the wide tape surfaces, generating frictional heat at interfaces 108 and 109 between the two members (superconducting wire 101, insulated wire 102). As described above, there are two interfaces between superconducting wire 101 and insulated wire 102 where frictional heat is generated per turn of winding portion 103: interface 108 and interface 109.

[0010] When superconducting wire 101 and insulated wire 102 are actually wound, as described in Patent Document 3 and shown in Figure 9, superconducting wire 101 and insulated wire 102 may be misaligned in the direction of winding axis P and wound off to one end face (e.g., end face 103A). Furthermore, due to differences in the shapes of the two components (superconducting wire 101 and insulated wire 102), such as warpage, a gap D may occur between superconducting wire 101 and insulated wire 102. Figure 9 shows, as an example, a case where part of superconducting wire 101 and insulated wire 102 is off to the end face 103A.

[0011] When superconducting wire 101 and insulating wire 102 are misaligned in the direction of winding axis P, unevenness occurs on end faces 103A and 103B of winding portion 103. Resin layer 104 is heated and compressed by its thickness, allowing its shape (thickness) to be changed to match the uneven shape of end faces 103A and 103B of winding portion 103. However, increasing the thickness of resin layer 104 not only increases thermal resistance in the direction of winding axis P, but also makes it more likely for the resin to penetrate between superconducting wire 101 and insulating wire 102 as the amount of resin increases. For this reason, there is a limit to how thick resin layer 104 can be. If the distance (difference in size) between the recesses and protrusions of end faces 103A and 103B of winding portion 103 is equal to or greater than the thickness of resin layer 104, there is a risk that end faces 103B of winding portion 103 and resin layer 104 will not come into contact, as shown in an example of FIG. 9 . Therefore, the tape width direction end portion of superconducting wire 101 on end face 103B side does not contact resin layer 104, and furthermore, the tape width direction end portion of insulating wire 102 on end face 103B side does not contact resin layer 104, and there is a risk that both will not adhere to heat transfer member 106.

[0012] Furthermore, from the viewpoint of improving current density, a thin wire having a thickness of several tens of micrometers is often used as the insulated wire 102. Therefore, the rigidity of the insulated wire 102 is often low, and in particular, the deformation and displacement due to external forces applied during winding are significant. Therefore, the superconducting wire 101 and the insulated wire 102 may bend like a cantilever beam if one end in the tape width direction is not bonded to the resin layer 104. Therefore, when vibration acts on the superconducting coil 100, the superconducting wire 101 and the insulated wire 102 slide violently on, for example, the end surface 103B side of the winding portion 103, and frictional heat may increase compared to when both ends in the tape width direction are bonded to the resin layer 104.

[0013] In addition, when the superconducting wire 101 and the resin layer 104 are not in contact, a heat transfer path between the superconducting wire 101 and the heat transfer member 106, i.e., a heat transfer path in the axial direction of the superconducting coil 100, cannot be secured, and as the heat transfer path is limited, there is a risk that the heat generated by the superconducting wire 101 cannot be sufficiently removed.

[0014] In FIG. 8, the superconducting wire 101 and the insulated wire 102 have the same rectangular shape. However, in reality, they are components with different wire widths, cross-sectional shapes, and warpage. When components with such different shapes are wound, a wide gap D is likely to occur between the two components (the superconducting wire 101 and the insulated wire 102), as shown in FIG. 9. Patent Document 1 also discloses a technology for preventing the resin from penetrating into the gap D by using a highly viscous material for the resin layer 104. Preventing this resin penetration makes it possible to leave the gap D in the center of the wide tape surface of the superconducting wire 101 and the insulated wire 102, as shown in FIG. 9. This reduces the risk of the turns of the winding portion 103 adhering to each other and applying a peeling force to the superconducting wire 101. However, if the gap D between the superconducting wire 101 and the insulated wire 102 is wide, the sliding range between the two components becomes wider, which may increase the sliding distance due to vibration.

[0015] Furthermore, as described in Patent Document 2, when superconducting wire 101 moves in the direction of winding axis P in winding portion 103, a change in inductance occurs in superconducting coil 100, which may cause a quench detection mechanism (not shown) to erroneously detect a quench.

[0016] The embodiments of the present invention have been made in consideration of the above-mentioned circumstances, and have an object to provide a superconducting coil and a method for manufacturing a superconducting coil that can reduce frictional heat generated in the superconducting wire in the winding portion formed by winding the superconducting wire, and suppress thermal damage to the superconducting coil due to quenching. [Means for solving the problem]

[0017] A superconducting coil in an embodiment of the present invention comprises a winding section formed by overlapping and winding a tape-shaped superconducting wire having a superconducting layer laminated together with other layers on a metal substrate, and a heat transfer member bonded via a resin layer to an end face of the winding section perpendicular to the winding axis direction, and the superconducting wire is characterized in that an insulating layer is provided on an outer surface including at least one of the two tape wide faces.

[0018] A method for manufacturing a superconducting coil in an embodiment of the present invention is characterized in that a tape-shaped superconducting wire having a superconducting layer laminated together with other layers on a metal substrate is prepared, an insulating layer is then provided on the outer surface of the superconducting wire, including at least one of the two wide tape surfaces, to form an insulating coated superconducting wire, the insulating coated superconducting wire is then wound so that the wide tape surfaces are overlapped to form a winding section, and then a heat transfer member is adhered using a resin layer to the end surface of the winding section that is perpendicular to the winding axis direction, thereby manufacturing a superconducting coil. [Effects of the Invention]

[0019] According to an embodiment of the present invention, frictional heat generated in the superconducting wire in the winding portion formed by winding the superconducting wire can be reduced, and thermal damage to the superconducting coil due to quenching can be suppressed. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a perspective view showing a superconducting coil according to a first embodiment, cut in a diameter direction along a winding axis. [Figure 2] FIG. 2 is an enlarged cross-sectional view of cross section S in FIG. 1. [Figure 3] FIG. 3 is a cutaway perspective view of the insulating-coated superconducting wire of FIG. 2. [Figure 4] 4 is a cross-sectional view corresponding to FIG. 2 and showing a superconducting coil according to a second embodiment. [Figure 5] FIG. 10 is a cross-sectional view corresponding to FIG. 2, showing a modified example of the second embodiment. [Figure 6] 10 is a cross-sectional view corresponding to FIG. 2 and showing a superconducting coil according to a third embodiment. [Figure 7] FIG. 10 is a cross-sectional view corresponding to FIG. 2, showing a modified example of the third embodiment. [Figure 8] 3 is a cross-sectional view corresponding to FIG. 2, showing a conventional superconducting coil cut in the diameter direction along the winding axis. [Figure 9] 9 is a cross-sectional view corresponding to FIG. 8, showing a state in which the superconducting wire and the insulating wire are misaligned in the winding portion of a conventional superconducting coil. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. [A] First embodiment (Figs. 1 to 3) Fig. 1 is a perspective view showing a superconducting coil according to a first embodiment cut in the diameter direction along the winding axis. Fig. 2 is an enlarged cross-sectional view of cross section S in Fig. 1. Superconducting coil 10 shown in Figs. 1 and 2 includes winding section 11 formed by winding insulation-coated superconducting wire 15 having insulating material layer 14 on the outer surface of superconducting wire 1 around winding axis O, and heat transfer members 12 and 13 bonded to both end faces 11A and 11B of winding section 11 in the direction of winding axis O using resin layer 16.

[0022] As shown in Fig. 3, the superconducting wire 1 is a tape-shaped wire formed by laminating a plurality of thin film layers. The superconducting wire 1 has at least a metal substrate 2, an intermediate layer 3, and a superconducting layer 4, which are covered with a stabilization layer 5. If necessary, an orientation layer 6 is provided between the metal substrate 2 and the intermediate layer 3. Furthermore, a protective layer 7 is provided between the superconducting layer 4 and the stabilization layer 5.

[0023] The metal substrate 2 is made of a high-strength metal material, such as stainless steel or a nickel alloy such as Hastelloy (registered trademark). The intermediate layer 3 is made of a material such as cerium oxide, magnesium oxide, yttrium oxide, or ytterbium oxide. The intermediate layer 3 functions as a buffer layer between the superconducting layer 4 and the metal substrate 2.

[0024] The superconducting layer 4 is made of a Re123-based high-temperature superconductor such as YBCO, DyBCO, or GdBCO. The stabilizing layer 5 is made of a conductive material such as copper or silver. The stabilizing layer 5 functions as a bypass for commutating current to the stabilizing layer 5 when excessive current flows through the superconducting layer 4.

[0025] The orientation layer 6 is provided for the purpose of orienting the intermediate layer 3. The orientation layer 6 is made of a material such as magnesium oxide. The protective layer 7 is provided for the purpose of preventing the superconducting layer 4 from being deteriorated due to contact with moisture in the air. The protective layer 7 is made of a material such as silver. The protective layer 7 also functions as a bypass for diverting current when excessive electricity flows through the superconducting layer 4.

[0026] Each of the layers 2 to 7 of the superconducting wire 1 has an asymmetric structure with respect to the stacking direction, and is divided into a tape wide surface 1A that is closer to the superconducting layer 4 and a tape wide surface 1B that is closer to the metal substrate 2. The asymmetric structure with respect to the stacking direction means that the types of the stacked layers are different.

[0027] The insulation-coated superconducting wire 15 is a tape-shaped wire in which an insulating layer 14 is provided to cover an outer surface including at least one of the two tape wide surfaces 1A and 1B of the superconducting wire 1, for example, the tape wide surfaces 1A and 1B and the tape end surfaces 1C and 1D. As shown in Figures 2 and 3 , the insulation-coated superconducting wire 15 is wound around a winding axis O by overlapping tape wide surfaces 15A and 15B corresponding to the tape wide surfaces 1A and 1B of the superconducting wire 1.

[0028] In the conventional technology shown in Fig. 8, frictional heat is generated per turn in winding portion 103 of superconducting coil 100 on two surfaces, namely, interfaces 108 and 109 between superconducting wire 101 and insulated wire 102. In contrast, in superconducting coil 10, as shown in Fig. 2, frictional heat is generated per turn in winding portion 11 on only one surface, namely, interface 17, where insulating-coated superconducting wires 15 come into contact with each other.

[0029] Insulating layer 14 insulates at least one of tape wide surfaces 1A, 1B of superconducting wire 1, thereby preventing direct contact between stabilizing layers 5 of superconducting wire 1 between adjacent turns in winding portion 11 and providing insulation between turns in winding portion 11. This insulating layer 14 is not particularly limited as long as it is a paintable material, and examples thereof include phenolic resin, epoxy resin, polyamide resin, polyimide resin, polyamideimide resin, and acrylic resin.

[0030] In other words, if insulating layer 14 is made of at least one material selected from the group consisting of fluorine-based resin, paraffin, grease, and silicone oil, which also function as a release agent, there is a risk that resin layer 16 and insulating layer 14 will be separated from each other, making it impossible to ensure a heat transfer path. For this reason, insulating layer 14 is preferably made of at least one material selected from the group consisting of phenolic resin, epoxy resin, unsaturated polyester resin, polyamide resin, polyimide resin, polyamideimide resin, acrylic resin, polyurethane resin, polyethylene resin, and polypropylene resin.

[0031] Furthermore, in order to prevent a decrease in the critical current value of superconducting wire 1, it is preferable that insulating material layer 14 can be formed by a process that does not require heating at 200° C. or higher. In addition, from the viewpoint of achieving a high current density, it is preferable that insulating material layer 14 is thin.

[0032] Heat transfer members 12 and 13 assist in the radial heat transfer of superconducting coil 10 and thermally connect superconducting coil 10 to a refrigerator (not shown). Heat transfer members 12 and 13 are made of insulating oxygen-free copper, high-purity aluminum, or other high-thermal conductivity materials, glass fiber reinforced plastic, etc. Heat transfer members 12 and 13 may be made of different materials.

[0033] Resin layer 16 bonds heat transfer members 12, 13 to end faces 11A, 11B of winding portion 11, and preferably has a glass transition temperature lower than that of insulating material layer 14. By heating winding portion 11 at a temperature lower than the glass transition temperature of insulating material layer 14 and higher than the glass transition temperature of resin layer 16, it becomes possible to soften only resin layer 16 without softening insulating material layer 14, thereby bonding insulation-coated superconducting wire 15 and heat transfer members 12, 13. Resin layer 16 may be made of any material that can be softened in a later process to bond to insulation-coated superconducting wire 15, such as a thermoplastic resin or a thermosetting resin (particularly, a sheet obtained by prepreg-processing semi-cured thermosetting resin).

[0034] If insulating layer 14 is softened, insulating layers 14 of insulating coated superconducting wire 15 may adhere to each other at interface 17 of insulating coated superconducting wire 15 between adjacent turns of winding portion 11, exerting a peeling force on superconducting wire 1 and possibly deteriorating its superconducting properties. Furthermore, there is a risk that the critical current value of superconducting wire 1 may decrease if heated to 200°C or higher. For these reasons, resin layer 16, which needs to be softened by heating to a temperature above its glass transition temperature, preferably has a glass transition temperature of 200°C or lower.

[0035] The thermoplastic resin is made of at least one material selected from a group of resins such as polyethylene, acrylonitrile-butadiene-styrene, polypropylene, polystyrene, polyvinylidene chloride, methyl methacrylate, polyethylene terephthalate, polyvinyl chloride, polyamide, polycarbonate, polyacetal, modified polyphenylene ether, polybutylene terephthalate, polysulfone, glass fiber reinforced polyethylene terephthalate, polyethersulfone, polyphenylene sulfide, polyarylate, polyether ether ketone, polyamide imide, liquid crystal polymer, polyetherimide, polyimide, and polyhydroxy polyether.

[0036] By using a thermoplastic resin for resin layer 16, it becomes possible to repair the manufactured superconducting coil 10 when deterioration of the superconducting properties is observed. A specific method is to reheat the manufactured superconducting coil 10 to melt the thermoplastic resin, remove heat transfer members 12, 13 and resin layer 16, and rewind the superconducting wire 1. The rewound superconducting wire 1 is inspected, and the deteriorated portions are removed and reconnected, making it possible to remanufacture the superconducting coil 10. This method can also be implemented when resin layer 16 is made of a thermosetting resin, but because there is a risk of deteriorating the superconducting properties of the superconducting wire 1 when the thermosetting resin is melted and removed, a thermoplastic resin that can be easily removed is preferred.

[0037] In addition, it is preferable that resin layer 16 be made of a highly viscous material to prevent resin from entering the gaps between the turns of insulation-coated superconducting wire 15 in winding portion 11 and causing a peeling force to act on superconducting wire 1.

[0038] Next, a method for manufacturing the above-mentioned superconducting coil 10 will be described. A tape-shaped superconducting wire 1 is prepared, and an insulating layer 14 is provided on the outer surface including at least one of the two tape wide surfaces 1A and 1B of the superconducting wire 1, for example, on the tape wide surfaces 1A and 1B and tape end surfaces 1C and 1D of the superconducting wire 1, to coat the superconducting wire 1 with the insulating layer 14, thereby forming a tape-shaped insulating-coated superconducting wire 15.

[0039] Next, the insulation-coated superconducting wire 15 is wound around the winding axis O so that the tape wide surfaces 15A and 15B are overlapped to form the winding portion 11. After that, the heat transfer members 12 and 13 are bonded to both end surfaces 11A and 11B of the winding portion 11 using the resin layer 16 to manufacture the superconducting coil 10.

[0040] Heat transfer members 12, 13 can be bonded to end faces 11A, 11B of winding portion 11 in one method, where heat transfer members 12, 13 having resin layer 16 formed on their surfaces are attached to end faces 11A, 11B of winding portion 11 and heated while being compressed to soften the resin of resin layer 16, thereby bonding heat transfer members 12, 13 to winding portion 11. Another method involves sandwiching a resin film made of the material of resin layer 16 between heat transfer members 12, 13 and winding portion 11, and then heating and compressing it.

[0041] As configured as above, the first embodiment provides the following advantages (1) to (3). (1) The member wound to form the winding portion 11 is a single insulation-coated superconducting wire 15, which is a superconducting wire 1 provided with an insulating layer 14. Therefore, friction occurs only on one surface, the interface 17, between the insulation-coated superconducting wires 15 per turn of the winding portion 11. This reduces frictional heat generated by sliding of the insulation-coated superconducting wires 15 in the direction of the winding axis O. Furthermore, since a single insulation-coated superconducting wire 15 is wound in the winding portion 11, it is possible to prevent gaps from being generated between the wound insulation-coated superconducting wires 15. This limits the sliding distance of the wound insulation-coated superconducting wire 15 in the direction of the winding axis O, which also reduces frictional heat generated by sliding of the insulation-coated superconducting wires 15. For these reasons, the superconducting coil 10 can suppress thermal damage due to quenching.

[0042] (2) The only member wound to form the winding portion 11 is a single insulation-coated superconducting wire 15, and no insulated wire 102 (FIG. 8) is required. This prevents gaps from forming in the wound insulation-coated superconducting wire 15 in the winding portion 11, and also prevents misalignment in the direction of the winding axis O. This prevents unevenness from forming on the end faces 11A and 11B of the winding portion 11, allowing the heat transfer members 12 and 13 to be reliably bonded to the end faces 11A and 11B using the resin layer 16. As a result, a heat transfer path for the superconducting coil 10 using the heat transfer members 12 and 13 can be secured, thereby ensuring the removal of heat generated by the superconducting wire 1 in the superconducting coil 10 and preventing thermal damage to the superconducting coil 10.

[0043] (3) In the winding section 11 formed by winding a single insulating-coated superconducting wire 15, sliding of the insulating-coated superconducting wire 15 in the direction of the winding axis O is suppressed, so that changes in inductance are less likely to occur in the superconducting coil 10, and quenching of the superconducting coil 10 can be detected with high accuracy by a quench detection mechanism not shown.

[0044] [B] Second embodiment (Figs. 4 and 5) Fig. 4 is a cross-sectional view corresponding to Fig. 2 showing a superconducting coil according to a second embodiment. Fig. 5 is a cross-sectional view corresponding to Fig. 2 showing a modified form of the second embodiment. In this second embodiment and its modified form, parts similar to those in the first embodiment are given the same reference numerals as in the first embodiment, and explanations thereof will be simplified or omitted.

[0045] The superconducting coil 20 of the second embodiment and the superconducting coil 25 of the modified form of the second embodiment differ from the first embodiment in that a lubricating layer 22 having a surface friction coefficient smaller than that of the insulating material layer 14 is provided on the outer surface of the insulation-coated superconducting wire 15 (FIG. 4) or is provided to replace part of the insulating material layer 14 in the insulation-coated superconducting wire 15 (FIG. 5).

[0046] 4, the lubricating layer 22 is provided on the entire outer surface of the insulating layer 14 of the insulation-coated superconducting wire 15 that forms the winding portion 21, in a region including a portion corresponding to at least one of the two tape wide surfaces 1A and 1B of the superconducting wire 1, for example, the region corresponding to the tape wide surfaces 1A and 1B and the tape end surfaces 1C and 1D of the superconducting wire 1. As a result, the lubricating layer 22 is disposed at the interface 17 where the insulation-coated superconducting wires 15 come into contact with each other, where friction occurs during one turn of the winding portion 21. The winding portion 21 has end surfaces 21A and 21B at both ends in the direction of the winding axis O.

[0047] 5, the insulation-coated superconducting wire 15 forming the winding portion 26 has a portion of the insulating layer 14 replaced with a lubricating layer 22 to form the insulation-coated superconducting wire 27. In the insulation-coated superconducting wire 27, the lubricating layer 22 is provided on a portion including one of the two tape wide surfaces 1A and 1B of the superconducting wire 1, for example, on the tape wide surface 1B of the superconducting wire 1 and on portions of the tape end surfaces 1C and 1D that are continuous with the tape wide surface 1B. As a result, the lubricating layer 22 is disposed at the interface 17 where the insulation-coated superconducting wires 27 come into contact with each other, where friction occurs in one turn of the winding portion 26. The winding portion 26 has end surfaces 26A and 26B at both ends in the direction of the winding axis O.

[0048] Here, the material of the lubricating layer 22 is not limited as long as the coefficient of friction of the surface is smaller than the coefficient of friction of the surface of the insulating material layer 14. That is, the lubricating layer 22 may be formed using a material and process different from that of the insulating material layer 14, or may be formed using the same material as the insulating material layer 14 and then subjected to a surface treatment to form the lubricating layer 22. From the viewpoint of improving current density, it is desirable that the lubricating layer 22 is thin. The other material may be, for example, at least one material selected from the group consisting of fluororesin, paraffin, grease, and silicone.

[0049] 5 may be produced by forming an insulating material layer 14 on a superconducting wire 1, and then polishing a part of the surface of the insulating material layer 14 to make the surface roughness smaller than that of the insulating material layer 14, thereby forming a lubricating layer 22. Alternatively, the insulating material layer 14 may be formed in a state where a part of the surface of the superconducting wire 1 is masked, and then another material may be applied to the masked area to form a lubricating layer 22.

[0050] As configured as described above, the second embodiment and its modified form have the same advantages as the advantages (1) to (3) of the first embodiment, and also have the following advantage (4).

[0051] (4) In the superconducting coil 20 shown in Fig. 4, a lubricating layer 22 is disposed at an interface 17 where the insulation-coated superconducting wires 15 come into contact with each other, where friction occurs within one turn of the winding portion 21. In the superconducting coil 25 shown in Fig. 5, a lubricating layer 22 is disposed at an interface 17 where the insulation-coated superconducting wires 27 come into contact with each other, where friction occurs within one turn of the winding portion 26. The lubricating layer 22 has a smaller friction coefficient on its surface than the friction coefficient on the surface of the insulating layer 14, and therefore can reduce frictional heat generated by the sliding of the insulation-coated superconducting wires 15, 27 at the interface 17 in the direction of the winding axis O. As a result, thermal damage to the superconducting coils 20 and 25 due to quenching can be suppressed more effectively than in the first embodiment.

[0052] [C] Third embodiment (Figs. 6 and 7) Fig. 6 is a cross-sectional view corresponding to Fig. 2 showing a superconducting coil according to a third embodiment. Fig. 7 is a cross-sectional view corresponding to Fig. 2 showing a modified form of the third embodiment. In this third embodiment and its modified form, parts similar to those in the first embodiment are designated by the same reference numerals as in the first embodiment, and description thereof will be simplified or omitted.

[0053] The superconducting coil 30 of the third embodiment and the superconducting coil 35 of the modified third embodiment differ from the first embodiment in that the lubricating layer 32, whose surface friction coefficient is smaller than that of the insulating material layer 14, also functions as a release agent, and that the lubricating layer 32 is provided on the outer surface of the insulating material layer 14 excluding the tape end faces 15C and 15D of the insulation-coated superconducting wire 15 (FIG. 6), or is provided to replace part of the insulating material layer 14 excluding the tape end faces 15C and 15D of the insulation-coated superconducting wire 15 (FIG. 7). Here, the lubricating layer 32 is composed of at least one material selected from the group consisting of fluororesin, paraffin, grease, and silicone, which functions as a release agent.

[0054] 6, the lubricating layer 32 is provided on the outer surface of the insulating layer 14 of the insulation-coated superconducting wire 15 forming the winding portion 31 in a portion corresponding to at least one of the two tape wide surfaces 1A and 1B of the superconducting wire 1, excluding portions corresponding to the tape end surfaces 1C and 1D of the superconducting wire 1, for example, on the tape wide surface 15B of the insulation-coated superconducting wire 15 excluding the tape end surfaces 15C and 15D, which is the portion corresponding to the tape wide surface 1B of the superconducting wire 1 excluding the tape end surfaces 1C and 1D. As a result, in the superconducting coil 30 as well, the lubricating layer 32 is provided at the interface 17 where the insulation-coated superconducting wires 15 come into contact with each other, where friction occurs in one turn of the winding portion 31, as in the second embodiment. The winding portion 31 has end surfaces 31A and 31B at both ends in the direction of the winding axis O.

[0055] 7, the insulation-coated superconducting wire 15 forming the winding portion 36 has a portion of the insulating layer 14 replaced with a lubricating layer 32 to form an insulation-coated superconducting wire 37. In the insulation-coated superconducting wire 37, the lubricating layer 32 is provided on one of two tape wide surfaces 1A and 1B of the superconducting wire 1 excluding tape end surfaces 1C and 1D of the superconducting wire 1, for example, on tape wide surface 1B excluding tape end surfaces 1C and 1B of the superconducting wire 1. As a result, in the superconducting coil 35 as well, as in the modified example of the second embodiment, the lubricating layer 32 is provided at an interface 17 where the insulation-coated superconducting wires 37 come into contact with each other and friction occurs in one turn of the winding portion 36. The winding portion 36 has end surfaces 36A and 36B at both ends in the direction of the winding axis O.

[0056] 6 and 7, when resin layer 16 has low viscosity and high fluidity, there is a risk that resin layer 16 may get into the gaps between insulation-coated superconducting wires 15, 37 between adjacent turns of winding portions 31, 36. If resin layer 16 gets into the gaps between the turns, insulation-coated superconducting wires 15, 37 of adjacent turns in winding portions 31, 36 will be adhered to each other, and a peeling force may be transmitted to superconducting wire 1 of superconducting coils 30, 35 during cooling, which may deteriorate the superconducting properties thereof.

[0057] By forming lubricating layer 32 from at least one selected from fluorine-based resin, paraffin, grease, and silicone oil, which also functions as a release agent, when a peeling force acts on insulation-coated superconducting wire 15, 37, peeling occurs between lubricating layer 32 and resin layer 16 before superconducting wire 1 is destroyed. This makes it possible to prevent peeling force from acting on superconducting wire 1 of insulation-coated superconducting wire 15, 37 between adjacent turns in winding portions 31, 36.

[0058] As configured as described above, the third embodiment and its modified forms achieve the same effects as the effects (1) to (4) of the first and second embodiments, as well as the following effects (5) and (6).

[0059] (5) Lubricating layer 32 is composed of at least one material selected from the group consisting of fluororesin, paraffin, grease, and silicone, which also functions as a release agent. Therefore, even if resin layer 16 flows into the spaces between insulation-coated superconducting wires 15 in winding portion 31 or between insulation-coated superconducting wires 37 in winding portion 36, when a peeling force acts on insulation-coated superconducting wires 15, 37, lubricating layer 32 separates from resin layer 16, thereby reducing the peeling force acting on superconducting wires 1 of insulation-coated superconducting wires 15, 37. As a result, deterioration of the superconducting properties of superconducting wire 1 in superconducting coils 30 and 35 can be reliably prevented.

[0060] (6) The area where the lubricating layer 32 is provided is at least one of the tape wide surfaces 15A and 15B excluding the tape end surfaces 15C and 15D in the insulation-coated superconducting wire 15 in the winding portion 31 of the superconducting coil 30, and is the tape wide surface 1A or 1B excluding the tape end surfaces 1C and 1D in the insulation-coated superconducting wire 37 in the winding portion 36 of the superconducting coil 35. In this way, the lubricating layer 32, which also functions as a release agent that inhibits adhesion of the resin layer 16, is not provided on the tape end surfaces 15C and 15D in the insulation-coated superconducting wire 15 in the winding portion 31, and on the tape end surfaces 1C and 1D of the superconducting wire 1 in the insulation-coated superconducting wire 37 in the winding portion 36. Therefore, it is possible to ensure adhesion between the winding portion 31 and the heat transfer members 12 and 13, and adhesion between the winding portion 36 and the heat transfer members 12 and 13, using the resin layer 16. As a result, the heat transfer path through the heat transfer members 12 and 13 in the superconducting coils 30 and 35 can be maintained more reliably than in the second embodiment, and thermal damage to the superconducting coils 30 and 35 due to quenching can be suitably suppressed.

[0061] In the third embodiment, the lubricating layer 32 may be attached to at least one of the tape end faces 15C and 15D of the insulation-coated superconducting wire 15 of the winding portion 31, and to at least one of the tape end faces 1C and 1D of the superconducting wire 1 of the insulation-coated superconducting wire 37 of the winding portion 36. However, from the viewpoint of cooling the superconducting coils 30, 35 by heat transfer via the heat transfer members 12, 13, it is preferable that the lubricating layer 32 be provided only on the tape wide faces (at least one of the tape wide faces 15A and 15B of the insulation-coated superconducting wire 15, and the tape wide face 1A or 1B of the superconducting wire 1 of the insulation-coated superconducting wire 37).

[0062] Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, changes, and combinations can be made without departing from the spirit of the invention. Furthermore, such substitutions, changes, and combinations are included in the scope and spirit of the invention, and are also included in the inventions and their equivalents as set forth in the claims. [Explanation of symbols]

[0063] REFERENCE SIGNS LIST 1...superconducting wire, 1A, 1B...wide surface of tape, 1C, 1D...tape end surface, 10...superconducting coil, 11...winding portion, 11A, 11B...end surface, 12, 13...heat transfer member, 14...insulating material layer, 15...insulating-coated superconducting wire, 16...resin layer, 20...superconducting coil, 22...lubricating layer, 25...superconducting coil, 27...insulating-coated superconducting wire, 30...superconducting coil, 32...lubricating layer, 35...superconducting coil, 37...insulating-coated superconducting wire, O...winding axis

Claims

1. a winding portion formed by overlapping and winding a tape-shaped superconducting wire having a superconducting layer laminated together with other layers on a metal substrate, with the wide surface of the tape being wound; a heat transfer member bonded via a resin layer to an end face of the winding portion perpendicular to the winding axis, The superconducting coil is characterized in that the superconducting wire is configured such that an insulating layer is provided on an outer surface including at least one of the two wide surfaces of the tape.

2. a lubricating layer is provided on the outer surface of the insulating material layer in a region including a portion corresponding to at least one of the two tape wide surfaces of the superconducting wire; 2. The superconducting coil according to claim 1, wherein the lubricating layer has a surface friction coefficient smaller than that of the insulating layer.

3. a portion of the insulating material layer is replaced with a lubricating layer, the lubricating layer being provided on a portion of the superconducting wire including one of the two tape wide surfaces; 2. The superconducting coil according to claim 1, wherein the lubricating layer has a surface with a friction coefficient smaller than that of the insulating layer.

4. a lubricating layer is provided on the outer surface of the insulating layer in a portion corresponding to at least one of the two tape wide surfaces of the superconducting wire, excluding a portion corresponding to an end face of the superconducting wire; 2. The superconducting coil according to claim 1, wherein the lubricating layer has a surface friction coefficient smaller than that of the insulating layer.

5. a portion of the insulating material layer is replaced with a lubricating layer, and the lubricating layer is provided on one of two tape wide surfaces of the superconducting wire except for an end surface of the superconducting wire; 2. The superconducting coil according to claim 1, wherein the lubricating layer has a surface with a friction coefficient smaller than that of the insulating layer.

6. 6. The superconducting coil according to claim 1, wherein the insulating layer is made of at least one resin selected from the group consisting of phenolic resin, epoxy resin, unsaturated polyester resin, polyamide resin, polyimide resin, polyamideimide resin, acrylic resin, polyurethane resin, polyethylene resin, and polypropylene resin.

7. 6. The superconducting coil according to claim 2, wherein the lubricating layer contains at least one material selected from the group consisting of fluororesin, paraffin, grease, and silicone.

8. the resin layer is made of a thermoplastic resin or a thermosetting resin, 2. The superconducting coil according to claim 1, wherein the resin layer made of the thermosetting resin is formed by heating and curing a semi-cured thermosetting prepreg sheet.

9. preparing a tape-shaped superconducting wire having a superconducting layer laminated on a metal substrate together with other layers; Next, an insulating layer is provided on an outer surface of the superconducting wire, including at least one of the two tape wide surfaces, to form an insulating-coated superconducting wire; Next, the insulating coated superconducting wire is wound so that the wide tape surfaces overlap each other to form a winding portion; Then, a heat transfer member is bonded to an end face of the winding portion perpendicular to the winding axis direction using a resin layer, thereby manufacturing a superconducting coil.

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