Method for manufacturing heat-resistant insulated wire

Abstract

A heat-resistant insulated wire is provided, which is used for wiring and winding in equipment. The wire has a high partial discharge starting voltage, can achieve heat resistance, and can suppress oxidation of the conductor surface. The heat-resistant insulated wire solves the above-mentioned problem by being constructed as follows: the heat-resistant insulated wire is a heat-resistant insulated wire (10) having a conductor (1), a baking coating layer (2) provided on the outer periphery of the conductor (1), and an insulating coating (3) provided on the baking coating layer (2), wherein the baking coating layer (2) is a thermosetting resin layer, and the insulating coating (3) is a fluororesin layer that is extruded and coated. Preferably, the baking coating layer (2) is a polyurethane resin layer, and its thickness is in the range of 5μm to 30μm. Preferably, the diameter of the conductor (2) is in the range of 0.08mm to 0.30mm, and the thickness of the insulating coating (3) is in the range of 0.05mm to 0.10mm.

Description

Technical Field

[0001] The present invention relates to a method for producing a heat-resistant insulated electric wire used for wiring and winding in equipment. Background Art

[0002] Insulated wires are used in a variety of products. When used as coil windings for rotating electrical equipment such as motors, they are operated under high voltage. During this process, severe partial discharge (corona discharge) can occur on the surface of the insulation coating. This partial discharge is caused by a localized temperature rise or the generation of ozone and ions, which accelerates the degradation of the insulation coating. The occurrence of partial discharge can shorten the life of the equipment in which the components are used.

[0003] In recent years, with the increasing demand for small, high-output electric motors, there has been a demand for coils capable of increasing the applied voltage. However, increasing the applied voltage increases the electric field strength, making partial discharge more likely to occur. To address this issue, it is desirable to increase the voltage at which partial discharge occurs (called the partial discharge inception voltage). To increase the partial discharge inception voltage, efforts have been made to thicken the insulation coating of enameled wire, thicken the insulation coating through resin extrusion, and reduce the dielectric constant of the insulation coating through foaming.

[0004] For example, Patent Document 1 proposes an insulated wire having an insulating film with a low dielectric constant and a high partial discharge inception voltage. This insulated wire comprises a conductor and an insulating film covering the conductor. The insulating film is formed by coating and baking a mixed resin comprising (A) one or more resins selected from polyamide-imide resins, polyimide resins, polyester-imide resins, and three types of polyester resins, and (B) one or more resins selected from fluororesins and polysulfone resins.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2010-67521 Summary of the Invention

[0008] Problems to be solved by the invention

[0009] The insulated wires used for wiring and windings within equipment require heat resistance. However, when a fluororesin layer is provided as the insulating coating layer constituting such heat-resistant insulated wires, the melting point of the fluororesin is relatively high, and the temperature during extrusion molding must be raised to around 400°C, which easily causes the surface of the conductor to oxidize. In addition, when the fluororesin burns, hydrofluoric acid (hydrogen fluoride) is sometimes produced, which can promote oxidation of the conductor surface. Furthermore, there is the problem of difficulty in removing the oxide layer formed on the conductor surface. To address this problem, measures such as plating the conductor surface with metals such as tin and nickel are generally taken to prevent oxidation, but this is costly.

[0010] The present invention has been made to solve the above-mentioned problems, and its object is to provide a heat-resistant insulated wire used for wiring and winding in equipment, wherein the heat-resistant insulated wire has a high partial discharge inception voltage, is heat-resistant, and can suppress oxidation of the conductor surface.

[0011] Solutions for solving problems

[0012] The heat-resistant insulated wire of the present invention comprises a conductor, a baked coating layer provided on the outer periphery of the conductor, and an insulating coating provided on the baked coating layer. The baked coating layer is characterized in that the baked coating layer is a thermosetting resin layer, and the insulating coating is an extruded and coated fluororesin layer.

[0013] According to the present invention, an insulating coating composed of a fluororesin layer is provided on a baked coating layer, thereby preventing oxidation of the conductor surface due to heat generated during extrusion molding of the fluororesin, hydrofluoric acid generated, and the like. This results in a heat-resistant insulated wire in which oxidation of the conductor surface is suppressed. Furthermore, since the fluororesin layer is heat-resistant, the insulated wire itself also has heat resistance. Furthermore, since a magnetic wire with a baked coating layer formed on the conductor can be used, manufacturing costs can be reduced compared to using metal plating to prevent oxidation, and the adhesion between the conductor and the baked coating layer is improved.

[0014] In the heat-resistant insulated wire of the present invention, the baked coating layer is a polyurethane resin layer having a thickness in the range of 5 μm to 30 μm. This allows the use of enameled polyurethane wire, thereby reducing manufacturing costs.

[0015] In the heat-resistant insulated wire of the present invention, the diameter of the conductor is within a range of 0.08 mm to 0.30 mm, and the thickness of the insulation coating is within a range of 0.05 mm to 0.10 mm.

[0016] In the heat-resistant insulated wire of the present invention, the dielectric withstand voltage is 4.0 kV or higher.

[0017] In the heat-resistant insulated wire of the present invention, it is preferred that when the baked coating layer is formed of general-purpose polyurethane, the fluororesin layer is an ETFE resin layer, when the baked coating layer is formed of modified polyurethane, the fluororesin layer is an FEP resin layer, and when the baked coating layer is formed of polyesterimide, the fluororesin layer is a PFA resin layer.

[0018] Effects of the Invention

[0019] According to the present invention, a heat-resistant insulated wire can be provided, which is used for wiring and winding in equipment and has a high partial discharge inception voltage, can achieve heat resistance, and can suppress oxidation of the conductor surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is an explanatory diagram showing an example of the heat-resistant insulated wire of the present invention.

[0021] Figure 2 yes Figure 1 A cross-sectional view of a heat-resistant insulated wire is shown. DETAILED DESCRIPTION

[0022] The heat-resistant insulated wire of the present invention will be described with reference to the accompanying drawings. The present invention can be modified in various ways as long as it has its technical features, and is not limited to the following description and drawings.

[0023] [Heat-resistant insulated wire]

[0024] like Figure 1 and Figure 2 As shown, the heat-resistant insulated wire 10 of the present invention comprises a conductor 1, a baked coating layer 2 provided on the outer periphery of the conductor 1, and an insulating coating 3 provided on the baked coating layer 2. The characteristic structure is that the baked coating layer 2 is a thermosetting resin layer, and the insulating coating 3 is an extruded and coated fluororesin layer.

[0025] In this heat-resistant insulated wire 10, the insulating coating 3, composed of a fluororesin layer, is provided on the baked coating layer 2. This prevents oxidation of the conductor surface due to heat generated during extrusion molding of the fluororesin, hydrofluoric acid, and the like. As a result, the heat-resistant insulated wire 10 suppresses oxidation of the conductor surface. Furthermore, since the fluororesin layer is heat-resistant, the insulated wire itself also has heat resistance. Furthermore, since a magnetic wire having the baked coating layer 2 formed on the conductor 1 can be used, manufacturing costs can be reduced compared to using metal plating to prevent oxidation, and the adhesion between the conductor 1 and the baked coating layer 2 is improved.

[0026] Hereinafter, each structure will be described.

[0027] (conductor)

[0028] The conductor 1 is not particularly limited as long as it is suitable for use as the center conductor of the heat-resistant insulated wire 10, especially the heat-resistant insulated wire 10 used for wiring or winding within equipment, and can be any type of conductor, regardless of the material or twisting structure. For example, it can be a conductor composed of a single wire extending in the longitudinal direction, a conductor composed of multiple wires twisted together, or a conductor constructed as a Litz wire. As long as the wire is a metal with good conductivity, its type is not particularly limited, but preferably, metal conductors with good conductivity such as copper wire, copper alloy wire, aluminum wire, aluminum alloy wire, and copper-aluminum composite wire can be mentioned. From the perspective of coil use, copper wire and copper alloy wire are particularly preferred.

[0029] Furthermore, the present invention uses an enameled wire having a baked coating layer 2 on the conductor 1. This eliminates the need for plating on the conductor surface, reducing manufacturing costs compared to plating. The cross-sectional shape of the wire is not particularly limited, but may be circular or substantially circular, or rectangular.

[0030] The cross-sectional shape of the conductor 1 is not particularly limited, and may be circular (including elliptical) or rectangular. The outer diameter of the conductor 1 is also not particularly limited, but for example, a circular wire is preferably approximately 0.08 mm to 0.30 mm.

[0031] (Baking coating layer)

[0032] like Figure 1 and Figure 2 As shown, the baked coating layer 2 is a thermosetting resin layer provided on the outer periphery of the conductor 1. In the present invention, since a magnetic wire having the baked coating layer 2 formed on the conductor 1 can be used, compared with the case of using metal plating to prevent oxidation, the manufacturing cost can be reduced and the adhesion between the conductor 1 and the baked coating layer 2 can be improved.

[0033] The baked coating layer 2 is not particularly limited as long as it is a thermosetting resin layer, but various enamel coatings can be used. For example, a baked coating layer 2 formed by applying and baking a solderable enamel coating such as general-purpose polyurethane, modified polyurethane, or polyesterimide is preferred. A polyurethane resin layer formed from general-purpose polyurethane or modified polyurethane is particularly preferred. The thickness of the baked coating layer 2 is within the range of 5 μm to 30 μm. This allows the use of enameled polyurethane wire, reducing manufacturing costs.

[0034] (Insulation coating)

[0035] like Figure 1 and Figure 2As shown, the insulating coating 3 is a fluororesin layer extruded and coated on the baking coating layer 2. The fluororesin constituting the fluororesin layer is not particularly limited, but examples thereof include PFA, ETFE, and FEP. These fluororesins have excellent heat resistance, thereby enabling the heat-resistant insulated wire 10 to have high heat resistance. Furthermore, fluororesins have a low dielectric constant, which is also advantageous in terms of increasing the partial discharge inception voltage. Thus, in the present invention, the insulating coating 3 composed of a fluororesin layer is provided on the baking coating layer 2, thereby preventing the conductor surface from being oxidized by heat, hydrofluoric acid, and the like generated during extrusion molding of the fluororesin. As a result, a heat-resistant insulated wire is obtained in which oxidation of the conductor surface is suppressed.

[0036] The thickness of the insulating coating 3 is preferably within the range of 0.05 mm to 0.10 mm, which enables the insulation withstand voltage (insulation breakdown voltage) of the heat-resistant insulated wire 10 to be 4.0 kV or higher, preferably 10.0 kV or higher. The insulation withstand voltage can be obtained by twisting two insulated wires and measuring them using a withstand voltage tester.

[0037] Since the baked coating layer 2 is provided under the insulating coating 3, even if the fluororesin is extruded at a high temperature, the conductor surface is not easily oxidized by the heat during extrusion. In addition, an insulating sheath (not shown) may be further provided on the outermost periphery of the heat-resistant insulated wire 10 as needed.

[0038] (Combination of baking coating layer and insulation coating)

[0039] The insulating coating 3, composed of a fluororesin layer made of a thermoplastic resin, is not applied to the conductor 1 but is extruded directly onto the baked coating layer 2 made of a thermosetting resin applied to the conductor 1. In the baked coating layer 2 described above, general-purpose polyurethane and modified polyurethane differ in the following respects: The polymer structure of general-purpose polyurethane is flexible, while that of modified polyurethane is rigid, depending on the type of diisocyanate used as the polyurethane raw material. This difference manifests itself in differences in thermal decomposition temperature and soldering temperature. Polyesterimide has a higher thermal decomposition temperature (TGI: 140°C to 150°C) than general-purpose and modified polyurethanes, and also has a higher soldering temperature (420°C to 460°C). In the present invention, the baked coating layer 2, formed of a thermosetting resin, functions to prevent oxidation of the conductor surface at the extrusion temperature of the fluororesin layer, described later. Therefore, it is desirable to have "thermal stability," meaning it does not decompose even at the extrusion temperature of the fluororesin layer, and to be stable. Furthermore, it is desirable to easily decompose at the soldering temperature corresponding to the type of baked coating layer 2, thereby providing good "solderability." The optimal choice of baked coating layer 2, among general-purpose polyurethane (TGI: 120°C to 130°C, soldering temperature: 320°C to 360°C), modified polyurethane (TGI: 130°C to 140°C, soldering temperature: 360°C to 420°C), or polyesterimide (TGI: 140°C to 150°C, soldering temperature: 420°C to 460°C), is crucial in relation to the extrusion temperature of the fluororesin layer.

[0040] Because the baked coating layer 2 is applied and baked on the conductor 1 directly beneath the fluororesin layer, it prevents the conductor surface from being oxidized by the heat generated during extrusion of the fluororesin layer, which has a relatively high extrusion temperature. The extrusion temperature of the fluororesin layer varies depending on the type of fluororesin. For example, PFA is approximately 330°C to 420°C, ETFE is approximately 260°C to 350°C, and FEP is approximately 280°C to 380°C. The extrusion temperatures, from highest to lowest, are PFA, FEP, and ETFE, with ETFE having the lowest extrusion temperature. Furthermore, the ease with which hydrofluoric acid is generated during extrusion also depends on the extrusion temperature. Fluororesins with higher extrusion temperatures are more likely to generate hydrofluoric acid. At the aforementioned extrusion temperatures, PFA is most likely to generate hydrofluoric acid, followed by FEP, and ETFE is least likely to generate hydrofluoric acid.

[0041] Regarding the specific combination of the baking film layer 2 and the insulating film 3, it is important that the baking film layer 2 is not easily decomposed even when the insulating film 3 is extruded, even if the heat during the extrusion molding is applied. As a result, by providing a baking film layer 2 with thermal stability, it is possible to prevent oxidation of the conductor surface caused by heat, hydrofluoric acid, etc. during the extrusion molding of the insulating film 3. Furthermore, after the extrusion molding of the insulating film 3, it is important to have good solderability at the soldering temperature. As shown in Experiment 1 described below, as a specific combination of the baking film layer 2 and the insulating film 3, it is preferred that the insulating film 3 be an ETFE resin layer when the baking film layer 2 is a general-purpose polyurethane, a FEP resin layer when the baking film layer 2 is a modified polyurethane, and a PFA resin layer when the baking film layer 2 is a polyesterimide.

[0042] Specifically, general-purpose polyurethane can decompose at temperatures above 260°C. Therefore, when extruding a fluororesin layer onto this general-purpose polyurethane, it is preferable to extrude ETFE, which has the lowest extrusion temperature, into the insulation coating 3, in order to achieve a balance between thermal stability and solderability. Modified polyurethane can decompose at temperatures above 280°C. Therefore, when extruding a fluororesin layer onto this modified polyurethane, it is preferable to extrude FEP, which has a higher extrusion temperature, into the insulation coating 3, in order to achieve a balance between thermal stability and solderability. Polyesterimide can decompose at temperatures above 310°C. Therefore, when extruding a fluororesin layer onto this polyesterimide, it is preferable to extrude PFA, which has the highest extrusion temperature, into the insulation coating 3, in order to achieve a balance between thermal stability and solderability. Combining these combinations of heat-resistant insulated wires effectively prevents the conductor surface from being oxidized by the heat generated during fluororesin extrusion, hydrofluoric acid, and the like.

[0043] Example

[0044] The present invention will be described in more detail with reference to the following examples. The present invention is not limited to the following examples, and those skilled in the art can make various changes, modifications, and variations within the scope of the present invention.

[0045] [Example 1]

[0046] A heat-resistant insulated wire 10 with a total outer diameter of 0.374 mm was manufactured using a 0.270 mm diameter magnet wire with a 10 μm thick baked coating layer 2 made of polyurethane resin applied to an unplated 0.250 mm diameter copper wire. A 52 μm thick insulating coating 3 made of ETFE was applied to the outer circumference of the magnet wire. The conductor resistance of the resulting heat-resistant insulated wire 10, measured using an ohmmeter, was 0.358 Ω / m. Furthermore, the dielectric breakdown voltage of the resulting heat-resistant insulated wire 10, measured by twisting two strands of the heat-resistant insulated wire 10 using a withstand voltage tester, was 22.28 kV.

[0047] [Example 2]

[0048] A heat-resistant insulated wire 10 with a total outer diameter of 0.238 mm was manufactured using a 0.134 mm diameter magnet wire having a 7 μm thick baked coating layer 2 made of polyurethane resin applied to an unplated 0.120 mm diameter copper wire. A 52 μm thick insulation coating 3 made of PFA was then applied to the outer circumference of the magnet wire. The resulting heat-resistant insulated wire 10 had a conductor resistance of 1.556 Ω / m and a dielectric breakdown voltage of 21.50 kV.

[0049] [Example 3]

[0050] A heat-resistant insulated wire 10 with an overall outer diameter of 0.302 mm was manufactured using a 0.200 mm diameter magnet wire having a 10 μm thick baked coating layer 2 made of polyurethane resin applied to an unplated 0.180 mm diameter copper wire. A 51 μm thick insulating coating 3 made of FEP was then applied to the outer circumference of the magnet wire. The resulting heat-resistant insulated wire 10 had a conductor resistance of 0.691 Ω / m and a dielectric breakdown voltage of 20.12 kV.

[0051] [Comparative Example 1]

[0052] A heat-resistant insulated wire with a total outer diameter of 0.370 mm was produced by applying a 60 μm thick ETFE insulation coating to an unplated copper wire with a diameter of 0.250 mm without a baked coating layer. The resulting heat-resistant insulated wire had a conductor resistance of 0.383 Ω / m and a dielectric breakdown voltage of 17.08 kV.

[0053] [Experiment 1]

[0054] Next, an experiment was conducted on the preferred combination of the baked coating layer 2 and the insulating coating 3. The basic structure is the same as that of Example 1, using a magnetic wire with a diameter of 0.270 mm, in which a baked coating layer 2 formed of a single layer (not a laminated layer, the same in this application) with a thickness of 10 μm and made of a single resin material (not a composite resin material, the same in this application) is provided on an unplated copper wire with a diameter of 0.250 mm. An insulating coating 3 formed of a single layer with a thickness of 52 μm and made of a single resin material is provided on the periphery of the magnetic wire to produce a heat-resistant insulated wire 10 with a total outer diameter of 0.374 mm. In addition, the general-purpose polyurethane used in this embodiment column, including the above-mentioned Examples 1 to 3, is a general-purpose polyurethane obtained by baking an enamel paint with the trade name: TPU-5100 manufactured by Toto Paint Co., Ltd. (TGI: 125°C, soldering temperature: 360°C). The following modified polyurethane was obtained by baking an enamel coating named TSF-400N (TGI: 130°C, soldering temperature: 380°C) manufactured by Totoku Paint Co., Ltd. The following polyester imide was obtained by baking an enamel coating named TSF-500 (TGI: 140°C, soldering temperature: 460°C) manufactured by Totoku Paint Co., Ltd.

[0055] The combination of the baked coating layer 2 and the insulating coating 3 used in the experiment is as follows.

[0056] (Sample 1) General-purpose polyurethane and PFA (extrusion temperature: 330°C to 420°C)

[0057] (Sample 2) General-purpose polyurethane and ETFE (extrusion temperature: 260°C to 350°C)

[0058] (Sample 3) General-purpose polyurethane and FEP (extrusion temperature: 280°C to 380°C)

[0059] (Sample 4) Modified polyurethane and PFA (extrusion temperature: 330°C to 420°C)

[0060] (Sample 5) Modified polyurethane and ETFE (extrusion temperature: 260°C to 350°C)

[0061] (Sample 6) Modified polyurethane and FEP (extrusion temperature: 280°C to 380°C)

[0062] (Sample 7) Polyester imide and ETFE (Extrusion temperature: 260°C to 350°C)

[0063] (Sample 8) Polyesterimide and PFA (Extrusion temperature: 330°C to 420°C)

[0064] (Sample 9) Polyester imide and ETFE (Extrusion temperature: 260°C to 350°C)

[0065] (evaluate)

[0066] Samples 1 to 9 were evaluated for thermal stability, solderability, and conductor surface oxidation. Regarding thermal stability, the breakdown voltage of the resulting heat-resistant insulated wires was evaluated using the same method as in Examples 1 to 3. A breakdown voltage of 10 kV or higher was rated as "○," while a breakdown voltage of less than 10 kV was rated as "△." Regarding solderability, the resulting heat-resistant insulated wires were immersed in 96.5% Sn solder at 360°C, 380°C, and 460°C. The solderability was visually verified, with a rating of "○" indicating good solderability and "△" indicating poor solderability. Regarding conductor surface oxidation, the insulation coating 3 and baked coating layer 2 of the resulting heat-resistant insulated wires were peeled off, and the conductor surface was visually observed under a microscope to evaluate the presence of surface oxidation. A rating of "○" indicated no oxidation on the conductor surface, while a rating of "△" indicated oxidation was observed.

[0067] [Table 1]

[0068] Table 1

[0069] Thermal stability Solderability Oxidation state of the conductor surface Sample 1 ○ ○ ○ Sample 2 ○ ○ ○ Sample 3 ○ ○ ○ Sample 4 ○ △ ○ Sample 5 ○ △ ○ Sample 6 ○ △ ○ Sample 7 ○ △ ○ Sample 8 ○ △ ○ Sample 9 ○ △ ○

[0070] Description of Reference Numerals

[0071] 1. Conductor; 2. Baking coating layer; 3. Extrusion coating layer; 10. Heat-resistant insulated wire.

Claims

1. A method for producing a heat-resistant insulated wire, comprising providing a baked coating layer on the outer periphery of a conductor, and extruding and coating an insulating coating composed of a fluororesin layer on the baked coating layer, wherein: The baked coating layer and the insulating coating are composed of any one of the following combinations, which have a high partial discharge inception voltage and are used to achieve heat resistance and suppress oxidation of the conductor surface. The baking coating layer is a general polyurethane baking coating layer with a TGI of 120°C to 130°C, and the insulating coating is an ETFE resin layer with an extrusion temperature of 260°C to 350°C; The baking coating layer is a modified polyurethane baking coating layer with a TGI of 130°C to 140°C, and the insulating coating is an FEP resin layer with an extrusion temperature of 280°C to 380°C; The baking coating layer is a polyester imide baking coating layer with a TGI of 140° C. to 150° C., and the insulating coating is a PFA resin layer with an extrusion temperature of 330° C. to 420° C.

2. The method for producing a heat-resistant insulated wire according to claim 1, wherein: The thickness of the baked coating layer is in the range of 5 μm to 30 μm.

3. The method for producing a heat-resistant insulated wire according to claim 1 or 2, wherein: The thickness of the insulating film is in the range of 0.05 mm to 0.10 mm.

4. The method for producing a heat-resistant insulated wire according to claim 1 or 2, wherein: The diameter of the conductor is in the range of 0.08 mm to 0.30 mm.

5. The method for producing a heat-resistant insulated wire according to claim 1 or 2, wherein: The insulation withstand voltage is 4.0kV or above.

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