Insulated wire, winding, coil, and method for manufacturing insulated wire

Abstract

This insulated wire comprises: a conductor including a metal mainly composed of aluminum; and an insulating layer provided on the outer periphery of the conductor. The insulating layer is formed from a fluororesin, and in an adhesion test conforming to JIS C3216-3:2011-5.5, the width of a cut provided in the insulating layer is substantially the same before and after elongation of the test piece, wherein the condition of the adhesion test is that the length of the test piece is 100 mm, the tensile speed is 5 ± 1 mm per second, and the elongation rate is 20%.

Description

Insulated wire, winding, coil, and method for manufacturing insulated wire

[0001] This disclosure relates to an insulated wire, a winding, a coil, and a method for manufacturing an insulated wire. This application claims priority to Japanese Patent Application No. 2023-174762 filed on October 6, 2023, and incorporates by reference all of the contents of said Japanese application.

[0002] Patent Document 1 discloses a magnet wire including a conductor and an insulating coating formed on the outer periphery of the conductor. The insulating coating is made of a fluororesin, which is a copolymer containing tetrafluoroethylene units and fluoroalkyl vinyl ether units. The conductor is made of a metal such as copper, a copper alloy, aluminum, or an aluminum alloy.

[0003] Japanese Patent Application Laid-Open No. 2020-183516

[0004] The insulated wire of the present disclosure includes a conductor made of a metal primarily composed of aluminum and an insulating layer disposed around the conductor. The insulating layer is made of a fluororesin. In an adhesion test conforming to JIS C 3216-3:2011, 5.5, the width of a slit in the insulating layer is substantially the same before and after elongation of the test specimen. The adhesion test is performed under the following conditions: the length of the test specimen is 100 mm, the tensile speed is 5±1 mm per second, and the elongation rate is 20%.

[0005] FIG. 1 is a schematic cross-sectional view showing an insulated wire according to a first embodiment. FIG. 2 is a schematic cross-sectional view showing another example of the insulated wire according to the first embodiment. FIG. 3 is a schematic cross-sectional view showing an insulated wire according to a second embodiment. FIG. 4 is a schematic view illustrating a method for an adhesion test. FIG. 5 is a schematic perspective view showing an example of a coil according to an embodiment. FIG. 6 is a graph showing an example of the loss tangent of a tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin. FIG. 7 is a graph showing an example of the loss tangent of a tetrafluoroethylene-hexafluoropropylene copolymer resin. FIG. 8 is a graph showing an example of the loss tangent of polyether ether ketone.

[0006] [Problem to be Solved by the Present Disclosure] Fluororesins have poor adhesion to metals. In particular, fluororesins have poor adhesion to aluminum or aluminum alloys. Therefore, insulated wires in which an insulating layer made of fluororesin is formed on a metal conductor have poor adhesion of the insulating layer to the conductor, and the insulating layer is prone to peeling off from the conductor.

[0007] An object of the present disclosure is to provide an insulated wire that includes an insulating layer made of a fluororesin and has high adhesion between the insulating layer and the conductor.

[0008] [Advantages of the Present Disclosure] The insulated wire of the present disclosure includes an insulating layer made of a fluororesin, and the insulating layer has high adhesion to the conductor.

[0009] [Description of Embodiments of the Present Disclosure] First, embodiments of the present disclosure will be listed and described.

[0010] (1) The insulated wire of the present disclosure includes a conductor made of a metal primarily composed of aluminum and an insulating layer disposed around the conductor. The insulating layer is made of a fluororesin. In an adhesion test conforming to JIS C 3216-3:2011, 5.5, the width of a slit in the insulating layer is substantially the same before and after elongation of the test specimen. The adhesion test is performed under the following conditions: the length of the test specimen is 100 mm, the tensile speed is 5±1 mm per second, and the elongation rate is 20%.

[0011] The insulated wire of (1) above has an insulating layer that adheres well to the conductor. This insulated wire is lightweight because the conductor is made of a metal primarily composed of aluminum. This insulated wire has an insulating layer made of a fluororesin, so it has excellent electrical insulation and partial discharge characteristics. "Excellent partial discharge characteristics" means that partial discharge is unlikely to occur.

[0012] (2) The insulated wire of (1) may further include a hard layer provided on the outer periphery of the insulating layer. The hard layer is made of a hard resin having a tensile modulus of elasticity of 1 GPa or more or a pencil hardness of F or more.

[0013] The insulated wire of (2) above can mechanically protect the insulating layer by providing the hard layer.

[0014] (3) In the insulated wire of (1) or (2), the fluororesin may be tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin (PFA) or tetrafluoroethylene-hexafluoropropylene copolymer resin (FEP). The tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin (PFA) has a loss tangent (tanδ) of 0.5 or more and 10 or less in dynamic viscoelasticity measurement at 282°C to 380°C. The tetrafluoroethylene-hexafluoropropylene copolymer resin (FEP) has a loss tangent (tanδ) of 0.5 or more and 20 or less in dynamic viscoelasticity measurement at 239°C to 380°C.

[0015] The insulated wire of (3) above is excellent in heat resistance, electrical insulation, and partial discharge characteristics.

[0016] (4) In the insulated wire according to any one of (1) to (3) above, the conductor may have a round or rectangular shape.

[0017] Insulated wires with round conductors are easy to bend. When used for windings, these insulated wires are easy to manufacture into coils. When used for windings, insulated wires with rectangular conductors can increase the space factor of the coil.

[0018] (5) In the insulated wire according to any one of (1) to (4) above, the insulating layer may have a thickness of 5 μm or more and 300 μm or less.

[0019] When the thickness of the insulating layer is 5 μm or more, the electrical insulation and partial discharge characteristics are improved. When the thickness of the insulating layer is 300 μm or less, the adhesion to the conductor is improved. Furthermore, when the thickness of the insulating layer is 300 μm or less, the diameter of the insulated wire can be reduced.

[0020] (6) In the insulated wire of (2) above, the hard layer may have a thickness of 5 μm or more and 150 μm or less.

[0021] When the thickness of the hard layer is 5 μm or more, the insulating layer is easily protected, and when the thickness of the hard layer is 150 μm or less, the diameter of the insulated wire can be reduced.

[0022] (7) In the insulated wire according to any one of (1) to (6), the metal mainly containing aluminum may be a 1000 series aluminum or a 6000 series or 8000 series aluminum alloy specified in JIS H 4000:2014.

[0023] When the metal forming the conductor is 1000 series aluminum, the conductor has high conductivity. When the metal forming the conductor is 6000 series or 8000 series aluminum, the conductor has high strength.

[0024] (8) The winding of the present disclosure is made of any of the insulated wires described above in (1) to (7).

[0025] The winding (8) is made of the insulated wire of the present disclosure, and therefore has high reliability, because the insulating layer has high adhesion to the conductor and is less likely to peel off.

[0026] (9) The coil of the present disclosure is made up of the winding described above in (8).

[0027] The coil (9) above is highly reliable because it is made of the winding of the present disclosure, since the insulating layer has high adhesion to the conductor and is less likely to peel off.

[0028] (10) A method for manufacturing an insulated wire according to the present disclosure includes the steps of: coating an outer periphery of an aluminum-based metal conductor with a fluororesin; and subjecting the fluororesin coating to a heat treatment or radiation treatment to form an insulating layer of the fluororesin on the outer periphery of the conductor. The fluororesin is tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA) or tetrafluoroethylene-hexafluoropropylene copolymer (FEP). The heat treatment is performed at a heating temperature of 282°C or higher and 400°C or lower when the fluororesin is tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA), and at a heating temperature of 239°C or higher and 400°C or lower when the fluororesin is tetrafluoroethylene-hexafluoropropylene copolymer (FEP). The conditions for the irradiation treatment are, when the fluororesin is the tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin (PFA), an irradiation temperature of 250°C or higher and 400°C or lower and an irradiation dose of 20 kGy or higher and 300 kGy or lower; and, when the fluororesin is the tetrafluoroethylene-hexafluoropropylene copolymer resin (FEP), an irradiation temperature of 180°C or higher and 380°C or lower and an irradiation dose of 20 kGy or higher and 300 kGy or lower.

[0029] In the method for producing an insulated wire according to (10) above, the insulating layer made of fluororesin can be adhered to the conductor by the heat treatment or irradiation treatment satisfying specific conditions.

[0030] [Details of Embodiments of the Present Disclosure] Specific examples of insulated wires according to the present disclosure will be described below. The same reference numerals in the drawings indicate the same or corresponding parts. For ease of explanation, some components may be exaggerated or simplified in the drawings. The dimensional ratios of the various parts in the drawings may also differ from the actual ratios.

[0031] [Embodiment 1] <Insulated Wire> An insulated wire 1 of embodiment 1 will be described with reference to FIG. 1 . The insulated wire 1 is used, for example, as a winding for a coil. The coil is used in electrical equipment such as a motor, a generator, a transformer, or a reactor. As shown in FIG. 1 , the insulated wire 1 of embodiment 1 includes a conductor 10 and an insulating layer 11. The insulating layer 11 is provided on the outer periphery of the conductor 10. The conductor 10 is a portion through which current flows. The insulating layer 11 serves to electrically insulate the conductor 10. One of the features of the insulated wire 1 of embodiment 1 is that, in an adhesion test in accordance with "5.5 Adhesion Test" of JIS C 3216-3:2011, the width of a slit provided in the insulating layer is substantially the same before and after elongation of the test specimen. The configuration of the insulated wire 1 will be described in detail below.

[0032] (Conductor) The conductor 10 is made of a metal primarily composed of aluminum (Al). A metal primarily composed of Al is aluminum or an aluminum alloy containing 90% or more by mass of Al. "Aluminum" here refers to pure aluminum containing 99% or more by mass of Al. Pure aluminum has superior conductivity compared to aluminum alloys. Additive elements contained in aluminum alloys include, for example, copper (Cu), manganese (Mn), silicon (Si), magnesium (Mg), zinc (Zn), iron (Fe), and lithium (Li). Aluminum alloys have superior mechanical strength compared to pure aluminum. Hereinafter, "metal primarily composed of Al" will be referred to as "aluminum material."

[0033] Aluminum has a lower specific gravity than copper or copper alloys. Using aluminum for the conductor 10 allows for a lighter insulated wire 1. The aluminum material for the conductor 10 can be, for example, one with an alloy number specified in JIS H 4000:2014. Examples of the aluminum material include 1000-series aluminum, or 6000-series or 8000-series aluminum alloys. 1000-series aluminum is pure aluminum. 1000-series aluminum has high conductivity. 6000-series or 8000-series aluminum alloys have high strength. 8000-series aluminum alloys include Al-Fe-Si alloys such as 8011A, 8021, and 8079, and Al-Li alloys such as 8090. The composition of the conductor 10 can be identified by inductively coupled plasma atomic emission spectroscopy (ICP-AES).

[0034] The conductivity of the conductor 10, i.e., the conductivity of the aluminum material, is, for example, 40% IACS or more. The conductivity of the conductor 10 may further be 50% IACS or more, 55% IACS or more, or 60% IACS or more. The conductivity of the conductor 10 is, for example, 65% IACS or less. The conductivity of the conductor 10 can be measured by a four-terminal method. The conductivity of the conductor 10 is calculated from the resistance value measured by measuring the resistance value of the conductor 10 having a length of 1 m.

[0035] The conductor 10 is a solid wire. The cross-sectional shape of the conductor 10 may be any shape. The shape of the conductor 10 may be, for example, a round wire or a rectangular wire. "Round wire" means that the cross-sectional shape of the conductor 10 is circular, as shown in FIG. 1. "Rectangular wire" means that the cross-sectional shape of the conductor 10 is rectangular, as shown in FIG. 2. "Cross-section" refers to a cross section perpendicular to the length of the conductor 10. "Circle" includes not only perfect circles but also ellipses and ovals. "Rectangle" includes squares. "Rectangle" is not limited to geometric rectangles but also includes rectangles with minor modifications, such as a shape in which at least one of the four corners is rounded. An insulated electric wire 1 having a round conductor 10 is easy to bend. Therefore, using an insulated electric wire 1 having a round conductor 10 for winding facilitates coil manufacturing. Using an insulated electric wire 1 having a rectangular conductor 10 for winding can increase the space factor of the coil. The cross-sectional area of ​​the conductor 10 can be appropriately selected depending on the application of the insulated wire 1. For example, the cross-sectional area of ​​the conductor 10 is 0.004 mm ２ More than 100 mm ２ Below that, another 0.1 mm ２ 30mm or more ２ The following is the result.

[0036] (Insulating Layer) The insulating layer 11 covers the entire periphery of the conductor 10. The insulating layer 11 is in contact with the conductor 10. The insulating layer 11 is made of a fluororesin. The fluororesin is a thermoplastic resin. The fluororesin may contain other components such as additives as necessary. Examples of additives include crosslinking agents, antistatic agents, heat stabilizers, foaming agents, foam nucleating agents, antioxidants, surfactants, anti-wear agents, surface modifiers, and colorants. The content of the additives in the fluororesin is, for example, less than 1% by mass. The content of the additives may be 0.5% by mass or less, or 0.1% by mass or less. The fluororesin may not contain any additives. The content of the additives is, for example, 0% by mass or more, 1% by mass or less, or 0.5% by mass or less. The content of the fluororesin in the insulating layer 11 is, for example, more than 99% by mass and 100% by mass or less, when the entire insulating layer 11 is 100% by mass. The content of the fluororesin may further be 99.5% by mass or more and 100% by mass or less, or 99.9% by mass or more and 100% by mass or less.

[0037] The fluororesin may be any fluororesin that can be extruded to coat the conductor 10 when producing the insulated wire 1. The melt flow rate of the fluororesin is, for example, 1 g / 10 min or more and 60 g / 10 min or less. The melt flow rate of the fluororesin may further be 20 g / 10 min or more and 50 g / 10 min or less.

[0038] Fluororesin has a low dielectric constant and excellent electrical insulation. The insulating layer 11 made of fluororesin has a low relative dielectric constant, so partial discharge is less likely to occur. The lower the relative dielectric constant of the insulating layer 11, the more partial discharge can be reduced. The relative dielectric constant of the fluororesin forming the insulating layer 11 is, for example, 1.5 or more and 2.5 or less. From the viewpoint of partial discharge characteristics, the relative dielectric constant of the fluororesin may be 2.1 or less. The relative dielectric constant of the fluororesin may be 1.6 or more.

[0039] The higher the melting point of the fluororesin forming the insulating layer 11, the more excellent the heat resistance. The melting point of the fluororesin is, for example, 240°C or higher and 320°C or lower. From the viewpoint of heat resistance, the melting point of the fluororesin may be 250°C or higher, 260°C or higher, or 280°C or higher. The melting point of the fluororesin may be 315°C or lower, or 310°C or lower. The melting point of the fluororesin can be measured by differential scanning calorimetry (DSC).

[0040] An insulated wire 1 having an insulating layer 11 made of fluororesin has excellent heat resistance, electrical insulation, and partial discharge characteristics. The thickness of the insulating layer 11 is, for example, 5 μm to 300 μm. The thicker the insulating layer 11, the better the electrical insulation and partial discharge characteristics. The thinner the insulating layer 11, the better the adhesion to the conductor 10. Furthermore, the thinner the insulating layer 11, the thinner the insulated wire 1 can be. In an insulated wire 1 having a thin insulating layer 11, the insulating layer 11 occupies a smaller area ratio in the cross section of the insulated wire 1. Therefore, using an insulated wire 1 having a thin insulating layer 11 for winding can improve the space factor of the coil and reduce the size of the electrical device. The thickness of the insulating layer 11 may further be 10 μm to 250 μm, 20 μm to 200 μm, or 30 μm to 150 μm.

[0041] The thickness of the insulating layer 11 is measured as follows: A cross section of the insulated wire 1 is observed using a microscope. The microscope may be an optical microscope or a scanning electron microscope (SEM). Multiple measurement points are set on the outer periphery of the conductor 10 in one cross section. The measurement points are spaced at equal intervals. A straight line is drawn from one measurement point in the normal direction to the surface of the conductor 10, and the intersection point on the outer periphery of the insulating layer 11 where this line intersects is determined. For each measurement point, the length from the measurement point to each intersection point on the outer periphery of the insulating layer 11 is measured, and the average value is taken as the thickness of the insulating layer 11. The number of measurement points on one cross section is 8 if the conductor 10 is a round wire and 16 if the conductor 10 is a rectangular wire.

[0042] The fluororesin forming the insulating layer 11 is, for example, tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin or tetrafluoroethylene-hexafluoropropylene copolymer resin. Tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin is also called perfluoroalkoxyalkane (PFA). Tetrafluoroethylene-hexafluoropropylene copolymer resin is also called perfluoroethylenepropene copolymer (FEP). Hereinafter, "tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin" will be referred to as "PFA." "Tetrafluoroethylene-hexafluoropropylene copolymer resin" will be referred to as "FEP." The insulating layer 11 made of PFA or FEP has excellent heat resistance, electrical insulation, and partial discharge characteristics. The type of fluororesin can be identified by infrared spectroscopy (IR).

[0043] The melting point of PFA is, for example, 300° C. or higher and 320° C. or lower, and the melting point of FEP is, for example, 250° C. or higher and 270° C. or lower.

[0044] PFA and FEP have specific dynamic viscoelasticity. Specifically, PFA and FEP have a loss tangent of 0.5 or more in dynamic viscoelasticity measurement within a specific temperature range. For example, PFA has a loss tangent of 0.5 or more and 10 or less at 282°C or more and 380°C or less. For example, FEP has a loss tangent of 0.5 or more and 20 or less at 239°C or more and 380°C or less.

[0045] The "loss tangent" is the ratio of the storage modulus to the loss modulus, and is expressed as "tan δ." The loss tangent (tan δ) is the value obtained by dividing the loss modulus by the storage modulus. In other words, tan δ = loss modulus / storage modulus. The loss tangent is also called the loss factor. The loss tangent, storage modulus, and loss modulus are parameters that represent dynamic viscoelasticity. The storage modulus indicates the elastic component, and the loss modulus indicates the viscous component. The loss tangent (tan δ) represents the degree of stickiness of a material. The smaller the tan δ, the higher the elastic component and the closer it is to an elastic body. The larger the tan δ, the higher the viscous component and the closer it is to a viscous body. In particular, when tan δ is 0.5 or more, it is in a state of high viscosity and exhibits high adhesive strength. Tan δ can be measured by dynamic viscoelasticity measurement. Viscoelasticity measurement can be performed, for example, using an Anton Paar rheometer MCR102. The viscoelasticity is measured under conditions of a shear strain of 0.5% and a frequency of 1 Hz, while the temperature is lowered from 390° C. to 200° C. The reason why tan δ is within the above-mentioned specific range will be explained in detail in the section on the manufacturing method of an insulated electric wire to be described later.

[0046] Known or commercially available PFA and FEP can be used. For example, the copolymer of tetrafluoroethylene and fluoroalkyl vinyl ether described in Patent Document 1 may be used as PFA. Commercially available PFA includes, for example, Fluon (registered trademark) PFA, a product of AGC Inc. Specific product numbers for Fluon PFA are P-61XP, P-62XP, P-63P, P-65P, and P-66P. Commercially available FEP includes, for example, Teflon (registered trademark) FEP, a product of Mitsui-Chemours Fluoroproducts Co., Ltd. Specific product numbers for Teflon FEP are 9494X, 100X, 130-J, and 140-J.

[0047] <Adhesion> The insulating layer 11 has high adhesion. In an adhesion test based on 5.5 of JIS C 3216-3:2011, the width of a slit in the insulating layer 11 of the insulated wire 1 is substantially the same before and after elongation of the test specimen. The adhesion test was performed under the following conditions: the length of the test specimen was 100 mm, the tensile speed was 5±1 mm per second, and the elongation rate was 20%.

[0048] The adhesion test method will be described with reference to FIG. 4 . A linear test piece 1s is prepared. The test piece 1s is cut from an insulated wire 1. The length L of the test piece 1s is 100 mm. The length L of the test piece 1s excludes both ends gripped by chucks (not shown). The length of each end gripped by the chuck is, for example, 25 mm. If the length of each gripping portion is 25 mm, the total length of the test piece 1s, including the gripping portions, is 150 mm. The distance between the chucks pulling the test piece 1s is set to 100 mm. A slit c is made in the insulating layer 11 at approximately the center of the length of the test piece 1s, reaching the conductor 10, along the entire circumference. The slit c is continuous around the entire circumference of the insulating layer 11. Using an elongation tester or tensile tester (not shown), the test piece 1s is stretched to a predetermined elongation rate at a rate of 5±1 mm per second. The elongation rate is 20%. That is, the test piece 1s is stretched until its length reaches 120 mm. After stretching, the insulating layer 11 of the test piece 1s is examined for lifting. The lifting of the insulating layer 11 is examined by examining the change in the width of the gap c before and after stretching. The entire circumference of the insulating layer 11 is observed to determine whether the width of the gap c is substantially the same before and after stretching. In other words, it is examined whether there is any exposed portion of the conductor 10 except for the gap c. If the width of the gap c is substantially the same before and after stretching, that is, if the change in the width of the gap c before and after stretching is substantially zero, it can be said that the insulating layer 11 has high adhesion to the conductor 10. The width of the gap c is approximately 1 mm. The width of the gap c can be measured, for example, using a ruler. In other words, "the width of the gap is substantially the same before and after stretching of the test piece" means that no difference is observed in the width of the gap before and after stretching of the test piece when measured using a ruler.

[0049] [Embodiment 2] An insulated wire 1 of embodiment 2 will be described with reference to Fig. 3. The insulated wire 1 of embodiment 2 shown in Fig. 3 differs from the insulated wire 1 of embodiment 1 shown in Fig. 1 in that it includes a hard layer 12. The following description will focus on the differences from embodiment 1 described above, and a description of similar points will be omitted.

[0050] (Hard Layer) The hard layer 12 is provided on the outer periphery of the insulating layer 11. The hard layer 12 covers the entire periphery of the insulating layer 11. The hard layer 12 is in contact with the insulating layer 11. The hard layer 12 serves to mechanically protect the insulating layer 11. Because the fluororesin that forms the insulating layer 11 is soft, the insulating layer 11 is easily damaged. For example, when the insulated wire 1 is bent, the insulating layer 11 may be crushed. The insulated wire 1 that includes the hard layer 12 can prevent the insulating layer 11 from being damaged or crushed.

[0051] The hard layer 12 has superior mechanical strength compared to the insulating layer 11. The hard layer 12 is made of, for example, a hard resin having a tensile modulus of elasticity of 1 GPa or more or a pencil hardness of F or more. A hard resin having such mechanical properties is harder than a fluororesin and can therefore protect the insulating layer 11. The higher the tensile modulus of elasticity or pencil hardness of the hard layer 12, the less susceptible the hard layer 12 is to scratches or deformation. The tensile modulus of elasticity of the hard layer 12 may be 2 GPa or more or 3 GPa or more. The tensile modulus of elasticity of the hard layer 12 is, for example, 5 GPa or less. The pencil hardness of the hard layer 12 may be 2H or more or 3H or more. The pencil hardness of the hard layer 12 is, for example, 6H or less.

[0052] The tensile modulus of elasticity of the hard layer 12 is measured as follows: Only the hard layer 12 is peeled off from the insulated wire 1. The peeled hard layer 12 is used as a test piece. A tensile test is performed on the test piece in accordance with JIS K 7161-1:2014 to measure the tensile modulus of elasticity.

[0053] The pencil hardness of the hard layer 12 is measured by a test method conforming to the scratch hardness (pencil method) specified in JIS K 5600-5-4: 1999. The pencil hardness is measured by pressing the lead of a pencil against the surface of the hard layer 12 covering the insulated wire 1.

[0054] Examples of hard resins that form the hard layer 12 include polyether ether ketone (PEEK), PES (polyethersulfone), PI (polyimide), PAI (polyamideimide), and PPS (polyphenylene sulfide). The tensile modulus and pencil hardness of each of the above-mentioned resins and fluororesins are approximately as shown in Table 1.

[0055]

[0056] The thickness of the hard layer 12 is, for example, 5 μm or more and 150 μm or less. If the thickness of the hard layer 12 is 5 μm or more, the insulating layer 11 is easily protected. If the thickness of the hard layer 12 is 150 μm or less, the diameter of the insulated wire 1 can be reduced. Therefore, by using an insulated wire 1 with a thin hard layer 12 for winding, the space factor of the coil can be improved and the electrical device can be made smaller. The thickness of the hard layer 12 may further be 10 μm or more and 150 μm or less, 20 μm or more and 130 μm or less, or 30 μm or more and 100 μm or less.

[0057] The thickness of the hard layer 12 is measured in the same manner as the thickness of the insulating layer 11. A cross section of the insulated wire 1 is observed under a microscope. Multiple measurement points are set on the outer periphery of the insulating layer 11 in one cross section. The measurement points are arranged at equal intervals. A straight line is drawn from one measurement point in the normal direction to the surface of the insulating layer 11, and the intersection point on the outer periphery of the hard layer 12 where this line intersects is found. For each measurement point, the length from the measurement point to the intersection point on the outer periphery of the hard layer 12 is measured, and the average value is taken as the thickness of the hard layer 12. The number of measurement points on one cross section is 8 if the conductor 10 is a round wire and 16 if the conductor 10 is a rectangular wire.

[0058] <Winding / Coil> The winding 2 and coil 3 according to this embodiment will be described with reference to FIG. 5 . The insulated wire 1 of the first and second embodiments described above can be used for the winding 2 of the coil 3. The winding 2 is made of the insulated wire 1. The coil 3 is made of the winding 2. The coil 3 shown in FIG. 5 is formed by winding the winding 2 in a cylindrical shape. The diameter of the coil 3 and the number of turns of the winding 2 can be selected as appropriate. The coil 3 may be formed by winding the winding 2 in a rectangular tube shape, for example. The winding 2, i.e., the insulated wire 1 shown in FIG. 5, is a round wire, but it may also be a rectangular wire. When the winding 2 is a rectangular wire, the coil 3 may be an edgewise coil or a flatwise coil.

[0059] <Method for Manufacturing Insulated Wire> The method for manufacturing an insulated wire according to the embodiment includes a first step and a second step.

[0060] The first step is a step of coating the outer periphery of the conductor 10 made of a metal mainly containing Al with a fluororesin. The second step is a step of subjecting the fluororesin coating on the conductor 10 to a heat treatment or radiation treatment to form an insulating layer 11 made of fluororesin on the outer periphery of the conductor 10. Each step will be described in detail below.

[0061] (First Step) The fluororesin coating is performed, for example, by extruding the fluororesin onto the outer periphery of the conductor 10. Known conditions can be used for the extrusion molding. Another method for coating the fluororesin is, for example, inserting the conductor 10 into a tube made of fluororesin and then thermally shrinking the tube. The fluororesin tube is, for example, obtained by extruding the fluororesin into a tubular shape. The fluororesin is PFA or FEP.

[0062] (Second Step) In the second step, the fluororesin is subjected to a heat treatment or radiation irradiation treatment to adhere the fluororesin to the conductor 10. The heat treatment makes the fluororesin highly viscous, allowing the insulating layer 11 to adhere to the conductor 10. The radiation irradiation treatment crosslinks the fluororesin, allowing the insulating layer 11 to adhere to the conductor 10.

[0063] <Heat Treatment> The conditions for the heat treatment vary depending on the type of fluororesin. The heating temperature is, for example, a temperature at which the loss tangent (tan δ) of the fluororesin is 0.5 or more. When the fluororesin is heated to a temperature at which tan δ is 0.5 or more, the fluororesin has high viscosity and can be adhered to the conductor 10. In the case of PFA, the heating temperature is 282°C or more and 400°C or less. In the case of FEP, the heating temperature is 239°C or more and 400°C or less. The heating temperature is preferably a temperature at which the tan δ of the fluororesin is 1.0 or more.

[0064] Figure 6 is a graph showing the temperature dependence of the loss tangent (tan δ) of PFA. The PFA used in the measurement was P-61XP manufactured by AGC Inc. The melting point of this PFA is 300°C. The horizontal axis of the graph shown in Figure 6 represents temperature, and the right vertical axis represents tan δ. Viscoelasticity measurements were performed using an Anton Paar MCR102 rheometer to measure tan δ. Parallel plates with a diameter of 12 mm were used for the viscoelasticity measurements. The viscoelasticity measurements were performed under conditions of a shear strain of 0.5% and a frequency of 1 Hz, with the temperature being lowered from 390°C to 200°C.

[0065] Figure 7 is a graph showing the temperature dependence of the loss tangent (tan δ) of FEP. The FEP used in the measurement was 9494X manufactured by Mitsui-Chemours Fluoroproducts Co., Ltd. The melting point of this FEP is 255°C. The horizontal axis of the graph shown in Figure 7 represents temperature, and the right vertical axis represents tan δ. The tan δ of FEP was measured in the same manner as the tan δ of PFA.

[0066] As shown in Figures 6 and 7, the tan δ of PFA and FEP increases with increasing temperature. In other words, the viscosity increases with increasing temperature. At temperatures above the melting point, tan δ remains nearly constant. In the case of PFA, as shown in Figure 6, tan δ rises sharply between 270°C and 290°C, reaching 0.5 or greater at 282°C or higher. tan δ is 1.0 or greater at 283°C or higher. In the case of PFA, tan δ is 0.5 or greater at heating temperatures of 282°C or higher, and 1.0 or greater at heating temperatures of 283°C or higher, resulting in improved adhesion of the insulating layer 11. In the case of FEP, as shown in Figure 7, tan δ rises sharply between 230°C and 250°C, reaching 0.5 at approximately 238.1°C and 1.0 at approximately 238.8°C. In the case of FEP, if the heating temperature is 239° C. or higher, tan δ is 0.5 or higher, and particularly if the heating temperature is 240° C. or higher, tan δ is 1.0 or higher, so that the adhesiveness of the insulating layer 11 is high.

[0067] The heating temperature may be lower than the melting point of the fluororesin, provided that it is equal to or higher than the temperature at which the loss tangent (tan δ) of the fluororesin is 0.5 or higher. In the case of PFA, the heating temperature may be 282°C or higher and lower than 300°C. In the case of FEP, the heating temperature may be 239°C or higher and lower than 255°C. If the heating temperature is lower than the melting point of the fluororesin, the heat resistance of the insulating layer 11 is less likely to deteriorate. In other words, this is effective in improving the long-term heat resistance of the insulating layer 11. Furthermore, if the heating temperature is lower than the melting point of the fluororesin, the dimensions of the insulating layer 11 are easily maintained.

[0068] The higher the heating temperature and the longer the heating time, the better the adhesion of the insulating layer 11. The heating time is, for example, 3 minutes or more. The heating time may be longer as the heating temperature is lower. The heating time may even be 10 minutes or more.

[0069] <Irradiation Treatment> The conditions for the irradiation treatment vary depending on the type of fluororesin. In the case of PFA, the irradiation temperature is 250°C or higher and 400°C or lower, and the irradiation dose is 20 kGy or higher and 300 kGy or lower. In the case of FEP, the irradiation temperature is 180°C or higher and 380°C or lower, and the irradiation dose is 20 kGy or higher and 300 kGy or lower. By performing the irradiation treatment under these conditions, the fluororesin is crosslinked, thereby increasing the adhesion of the insulating layer 11. The radiation may be, for example, an electron beam, ultraviolet light, gamma rays, X-rays, neutron rays, or high-energy ions.

[0070] The higher the irradiation temperature and the larger the irradiation dose, the better the adhesion of the insulating layer 11. In the case of PFA, the irradiation temperature may be 280°C or higher, 285°C or higher, or 290°C or higher. In the case of FEP, the irradiation temperature may be 200°C or higher, or 240°C or higher. In both the case of PFA and FEP, the irradiation dose may be 60 kGy or higher, or 100 kGy or higher.

[0071] The irradiation temperature may be lower than the melting point of the fluororesin. In the case of PFA, the irradiation temperature may be 250°C or higher and lower than 300°C. In the case of FEP, the irradiation temperature may be 180°C or higher and lower than 255°C. If the irradiation temperature is lower than the melting point of the fluororesin, the heat resistance of the insulating layer 11 is less likely to deteriorate. In other words, this is effective in improving the long-term heat resistance of the insulating layer 11. Furthermore, if the irradiation temperature is lower than the melting point of the fluororesin, the dimensions of the insulating layer 11 are easily maintained.

[0072] (Third Step) When manufacturing an insulated wire 1 having a hard layer 12 as in the second embodiment shown in Fig. 3 , the method for manufacturing an insulated wire further includes a third step in which the hard layer 12 is formed by coating the insulated wire with a hard resin having a tensile modulus of elasticity of 1 GPa or more or a pencil hardness of F or more.

[0073] The hard resin coating is performed, for example, by extrusion molding the hard resin. The third step may be performed between the first step and the second step, or after the second step. When the third step is performed between the first step and the second step, the hard resin is coated on the outer periphery of the fluororesin layer coated on the conductor 10 in the first step. After the third step, a heat treatment or radiation irradiation treatment is performed in the second step. In this case, the hard layer 12 is also subjected to a heat treatment or radiation irradiation treatment in conjunction with the heat treatment or radiation irradiation treatment of the insulating layer 11. When the third step is performed between the first step and the second step, the heat treatment or radiation irradiation treatment in the second step after the third step can improve the adhesion between the insulating layer 11 and the hard layer 12. When the third step is performed after the second step, the hard resin is coated on the outer periphery of the insulating layer 11 formed in the first second step to form the hard layer 12. Furthermore, the hard layer 12 may be subjected to a second heat treatment or radiation irradiation treatment as the second step.

[0074] Figure 8 is a graph showing the temperature dependence of the loss tangent (tan δ) of PEEK. The PEEK used in the measurement was PEEK 150P manufactured by Victrex. The melting point of this PEEK is 343°C. The horizontal axis of the graph shown in Figure 8 represents temperature, and the right vertical axis represents tan δ. The tan δ of PEEK was measured in the same manner as the measurement method for tan δ of PFA.

[0075] As shown in Figure 8, the tan δ of PEEK decreases slightly with increasing heating temperature up to approximately 300°C. On the other hand, tan δ increases rapidly when the heating temperature exceeds approximately 300°C. In the case of PEEK, tan δ increases sharply between 300°C and 320°C. At a heating temperature of approximately 306°C, tan δ becomes 0.5, and at a heating temperature of approximately 313°C or higher, tan δ becomes 1.0 or higher. When extruding the insulating layer 11 and then extruding the PEEK hard layer 12 and subsequently subjecting the insulating layer 11 and hard layer 12 to a heat treatment together, it is recommended to perform the heat treatment at the PEEK temperature at which the tan δ of the resin forming the insulating layer 11 and hard layer 12 reaches 0.5 or higher. This effectively improves the adhesion between the conductor 10 and the insulating layer 11 and between the insulating layer 11 and the hard layer 12.

[0076] [Test Example 1] Samples of insulated wires shown in Table 2 were manufactured. Round or rectangular wires made of aluminum were used as conductors. The type of aluminum material forming the conductors and the shape of the conductors are shown in Table 2. The diameter φ of the round wires was 2 mm. The dimensions of the rectangular wires were 1 mm thick and 2 mm wide.

[0077] Fluororesin, PI, or PAI was used as the resin forming the insulating layer. Sample No. 1-101 used PI as the resin forming the insulating layer. Sample No. 1-102 used PAI as the resin forming the insulating layer. All other samples used fluororesin as the resin forming the insulating layer. The type of fluororesin was PFA or FEP. The type of resin forming the insulating layer and the thickness of the insulating layer are shown in Table 2. The PFA was P-61XP manufactured by AGC Inc. The FEP was 9494X manufactured by Mitsui-Chemours Fluoroproducts Co., Ltd.

[0078] The insulated wire samples, except for No. 1-101 and No. 1-102, were manufactured by covering the outer periphery of a conductor with PFA or FEP by extrusion molding, followed by a heat treatment or radiation irradiation treatment. The conditions for the heat treatment or radiation treatment are shown in Table 2. The radiation used in the irradiation treatment was an electron beam. Table 2 also shows the tan δ of the fluororesin. The tan δ of the fluororesin represents the tan δ of PFA or FEP at the heating temperature or radiation temperature. No. 1-101 and No. 1-102 were manufactured by covering the outer periphery of a conductor with PI or PAI by extrusion molding. After covering with PI or PAI, no heat treatment or radiation irradiation treatment was performed.

[0079] The manufactured insulated wire samples were subjected to an adhesion test in accordance with 5.5 of JIS C 3216-3:2011 to evaluate the adhesion of the insulating layer to the conductor. The conditions for the adhesion test were as described above. The adhesion evaluation in the adhesion test was rated as A if the width of the slit provided in the insulating layer 11 was substantially the same before and after elongation of the test piece, and B otherwise. The adhesion evaluation for each sample is shown in Table 2.

[0080]

[0081] In all of No. 1-1 to No. 1-15, the adhesion rating was A, indicating high adhesion of the insulating layer. In contrast, in all of No. 1-101 to No. 1-107, the adhesion rating was B, indicating low adhesion of the insulating layer. It is believed that in No. 1-101 and No. 1-102, the resin forming the insulating layer was PI or PAI, and therefore the insulating layer did not adhere sufficiently.

[0082] In samples No. 1-1 to No. 1-5, No. 1-13, and No. 1-104 to No. 1-106, the resin forming the insulating layer was PFA, and the insulating layer was formed by irradiation with radiation. The irradiation conditions for samples No. 1-1 to No. 1-5 and No. 1-13 were an irradiation temperature of 250°C or higher and an irradiation dose of 20 kGy or higher. It is believed that the insulating layers of these samples were sufficiently adhered because the irradiation conditions met the specific conditions. In contrast, the irradiation temperature for samples No. 1-104 to No. 1-106 was 245°C or lower, and therefore the insulating layers were not sufficiently adhered.

[0083] In Nos. 1-8 to 1-10 and 1-14, the resin forming the insulating layer is FEP, and the insulating layer is formed by irradiation with radiation. The irradiation conditions for Nos. 1-8 to 1-10 and 1-14 are an irradiation temperature of 180°C or higher and an irradiation dose of 20 kGy or higher. It is believed that the insulating layer of these samples is sufficiently adhered because the irradiation treatment met the specific conditions.

[0084] In No. 1-6, No. 1-7, No. 1-15, and No. 1-103, the resin forming the insulating layer is PFA, and the insulating layer was formed by heat treatment. The heat treatment conditions for No. 1-6, No. 1-7, and No. 1-15 were a heating temperature of 285°C or higher. It is believed that the insulating layers of these samples were sufficiently adhered because the heat treatment satisfied the specific conditions. In contrast, the heating temperature for No. 1-103 was 280°C, which is believed to be why the insulating layer did not adhere sufficiently.

[0085] In No. 1-11, No. 1-12, and No. 1-107, the resin forming the insulating layer is FEP, and the insulating layer was formed by heat treatment. The heat treatment conditions for No. 1-11 and No. 1-12 were a heating temperature of 240°C or higher. It is believed that the insulating layer of these samples was sufficiently adhered because the heat treatment satisfied the specific conditions. In contrast, the heating temperature for No. 1-108 was 200°C, which is believed to be why the insulating layer did not adhere sufficiently.

[0086] [Test Example 2] The insulated wire samples shown in Table 3 were manufactured. Test Example 2 differs from Test Example 1 in that a hard layer was formed around the outer periphery of the insulating layer. However, No. 2-101 and No. 2-102 did not have a hard layer. No. 2-103 and No. 2-104 had only a hard layer formed around the outer periphery of the conductor. As in Test Example 1, the type of aluminum material forming the conductor, the shape of the conductor, the type of fluororesin forming the insulating layer, and the thickness of the insulating layer are shown in Table 3. Table 3 also shows the tan δ of the fluororesin, along with the conditions for the heat treatment or irradiation treatment.

[0087] The resin used to form the hard layer was PEEK. The types of resins used to form the hard layer and the thicknesses of the hard layers are shown in Table 3.

[0088] For insulated wire samples No. 2-1 to No. 2-8, the conductor was coated with PFA or FEP by extrusion molding, and then the fluororesin layer was coated with a hard resin by extrusion molding. Then, a heat treatment or radiation irradiation treatment was performed. The conditions for the heat treatment or radiation treatment are shown in Table 3. The radiation used in the irradiation treatment was an electron beam. Table 3 also shows the tan δ of the fluororesin and the tan δ of PEEK. The tan δ of the fluororesin represents the tan δ of PFA or FEP at the heating temperature or irradiation temperature. The tan δ of PEEK represents the tan δ of PEEK at the heating temperature or irradiation temperature. For No. 2-101 and No. 2-102, the conductor was coated with PFA or FEP by extrusion molding, and then the heat treatment was performed without coating with a hard resin. For No. 2-101 and No. 2-102, the conductor was coated with PFA or FEP by extrusion molding, and then the hard resin was not coated. No. 2-102 has only an insulating layer made of PFA or FEP. No. 2-103 and No. 2-104 are made by covering the outer periphery of the conductor with PEEK by extrusion molding and then heat treating. No. 2-103 and No. 2-104 do not have an insulating layer made of PFA or FEP and have only a hard layer made of PEEK.

[0089] The adhesiveness of the insulating layer to the conductor of the manufactured insulated wire samples was evaluated in the same manner as in Test Example 1. The evaluation of adhesiveness for each sample is shown in Table 4. The pencil hardness of the hard layer was also measured. The results are shown in Table 4. However, for No. 2-101 and No. 2-102, the pencil hardness of the insulating layer arranged at the outermost periphery of the insulated wire was measured. For No. 2-103 and No. 2-103, the adhesiveness to the conductor of the hard layer arranged at the outermost periphery of the insulated wire was evaluated. Furthermore, the dielectric constant of the insulating layer and the hard layer combined was determined. The dielectric constant was measured in accordance with JIS K 6935-2:1999. The results are shown in Table 4. The dielectric constant of No. 2-101 and No. 2-102 is the dielectric constant of the insulating layer alone. For No. 2-103 and No. The relative dielectric constant of 2-104 is the relative dielectric constant of the hard layer alone.

[0090]

[0091]

[0092] All of Nos. 2-1 to 2-8, as well as Nos. 2-101 and 2-102, received an adhesion rating of A, indicating high adhesion of the insulating layer. Nos. 2-1 to 2-8 include a hard layer made of PEEK. The pencil hardness of these hard layers is H or higher, which is higher than the pencil hardness of the insulating layer made of PFA or FEP. In Nos. 2-1 to 2-8, the hard layer provides mechanical protection for the insulating layer.

[0093] For example, a comparison of No. 2-2 and No. 2-5 with No. 2-103, or a comparison of No. 2-6 with No. 2-104, shows that when an insulating layer made of PFA or FEP is provided, the dielectric constant of the insulating layer and hard layer combined can be made lower than the dielectric constant of the hard layer alone. Therefore, an insulated wire having an insulating layer and a hard layer can reduce partial discharge more than an insulated wire having only a hard layer.

[0094] It should be noted that the present invention is not limited to these examples, but is defined by the scope of the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0095] REFERENCE SIGNS LIST 1 insulated wire 10 conductor 11 insulating layer 12 hard layer 1s test piece 2 winding 3 coil L length of test piece c gap

Claims

1. An insulated wire comprising: a conductor made of a metal mainly composed of aluminum; and an insulating layer provided on the outer periphery of the conductor, wherein the insulating layer is made of fluororesin; and in an adhesion test conforming to JIS C 3216-3:2011, 5.5, the width of a slit provided in the insulating layer is substantially the same before and after elongation of a test specimen, and the adhesion test conditions are as follows: the length of the test specimen is 100 mm, the tensile speed is 5±1 mm per second, and the elongation rate is 20%.

2. The insulated wire according to claim 1, further comprising a hard layer provided on the outer periphery of the insulating layer, the hard layer being made of a hard resin having a tensile modulus of elasticity of 1 GPa or more or a pencil hardness of F or more.

3. The insulated electric wire according to claim 1 or 2, wherein the fluororesin is a tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin or a tetrafluoroethylene-hexafluoropropylene copolymer resin, the tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin has a loss tangent of 0.5 or more and 10 or less in dynamic viscoelasticity measurement at 282°C or more and 380°C or less, and the tetrafluoroethylene-hexafluoropropylene copolymer resin has a loss tangent of 0.5 or more and 20 or less in dynamic viscoelasticity measurement at 239°C or more and 380°C or less.

4. The insulated wire according to any one of claims 1 to 3, wherein the conductor has a round wire or a rectangular wire shape.

5. An insulated wire according to any one of claims 1 to 4, wherein the insulating layer has a thickness of 5 μm or more and 300 μm or less.

6. The insulated wire according to claim 2, wherein the hard layer has a thickness of 5 μm or more and 150 μm or less.

7. The insulated electric wire according to any one of claims 1 to 6, wherein the metal mainly containing aluminum is 1000 series aluminum or 6000 series or 8000 series aluminum alloy specified in JIS H 4000:2014.

8. A winding wire comprising the insulated wire according to any one of claims 1 to 7.

9. A coil comprising the winding according to claim 8.

10. A method for manufacturing a conductor, comprising the steps of: coating the conductor with a fluororesin; and applying a heat treatment or radiation irradiation treatment to the fluororesin coating the conductor to form an insulating layer made of the fluororesin on the conductor; wherein the fluororesin is tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin or tetrafluoroethylene-hexafluoropropylene copolymer resin; and the conditions for the heat treatment are: when the fluororesin is the tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin, the heating temperature is 282°C or higher and 400°C or lower; when the fluororesin is the tetrafluoroethylene-hexafluoropropylene copolymer resin, the heating temperature is 239°C or higher and 400°C or lower; and the conditions for the irradiation treatment are: when the fluororesin is the tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin, the irradiation temperature is 250°C or higher and 400°C or lower, and the irradiation dose is 20 kGy or higher and 300 kGy or lower; When the fluororesin is a tetrafluoroethylene-hexafluoropropylene copolymer resin, the irradiation temperature is 180° C. or higher and 380° C. or lower, and the irradiation amount is 20 kGy or higher and 300 kGy or lower.

Images