Insulated wire

Abstract

To provide an insulated wire with high adhesion between the layers constituting the insulating coating. [Solution] The insulated wire comprises a conductor and an insulating film covering the conductor. The insulating film contains polyimide and an inorganic filler. The polyimide contains a biphenyl structure. The dielectric loss tangent of the insulating film at 280°C is 0.03 or more and 0.1 or less. For example, among the layers constituting the insulating film, the layer in contact with the conductor contains the polyimide but does not contain the inorganic filler. For example, the layer in contact with the conductor contains a polyimide containing a biphenyl structure. For example, among the layers constituting the insulating film, at least a portion of the layer not in contact with the conductor contains the polyimide but does not contain the inorganic filler.

Description

Technical Field

[0001] This disclosure relates to insulated wires.

Background Art

[0002] Patent Document 1 discloses an insulated wire. The insulated wire includes a conductor and an insulating film. The insulating film covers the conductor. Examples of the insulated wire include enameled wires. The insulated wire is used for coils of electrical equipment such as motors and transformers. The electrical equipment is incorporated into hybrid vehicles, electric vehicles, and the like.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The insulating film is formed by laminating a plurality of layers. In order to enhance the surge resistance, an inorganic filler may be blended into the insulating film. In this case, the polymer component present at the interface between the layers constituting the insulating film decreases. When the polymer component present at the interface between the layers decreases, the entanglement of the polymer components' molecules between the layers decreases. As a result, the adhesion between the layers constituting the insulating film deteriorates. In one aspect of this disclosure, it is preferable to provide an insulated wire with high adhesion between the layers constituting the insulating film.

Means for Solving the Problems

[0005] One aspect of this disclosure includes a conductor and an insulating film that covers the conductor. The insulating film contains polyimide and an inorganic filler. The polyimide includes a biphenyl structure. The dielectric tangent of the insulating film at 280°C is 0.03 or more and 0.1 or less. In the insulated wire which is one aspect of this disclosure, the adhesion between the layers constituting the insulating film is high. [Brief explanation of the drawing]

[0006] [Figure 1] This is an explanatory diagram showing the configuration of a manufacturing apparatus for rectangular enameled copper wire. [Figure 2] This is a cross-sectional view showing the cross-sectional shape of a rectangular copper wire. [Figure 3] This is a cross-sectional view showing the cross-sectional shape of a rectangular copper wire. [Figure 4] This is a cross-sectional view showing the cross-section of a rectangular enameled copper wire. [Figure 5] This is an explanatory diagram illustrating the method of the cut lengthening test. [Modes for carrying out the invention]

[0007] Exemplary embodiments of this disclosure will be described with reference to the drawings. <First Embodiment> 1. Manufacturing method of flat rectangular enameled copper wire 25 The manufacturing method for the rectangular enameled copper wire 25 will be explained based on Figures 1 to 4. The rectangular enameled copper wire 25 corresponds to an insulated electric wire. The manufacturing apparatus 1 shown in Figure 1 is used for manufacturing the rectangular enameled copper wire 25. The manufacturing apparatus 1 comprises a spindle or bobbin 3, a round wire drawing machine 5, a rectangular rolling mill 7, an annealing furnace 9, a rectangular wire drawing machine 11, an annealing furnace 13, a paint coating machine 15, a baking furnace 17, and a winding machine 19.

[0008] A linear conductor 23 is wound around a spindle or bobbin 3. The conductor 23 is drawn out from the spindle or bobbin 3 and travels along a path that passes through the round wire drawing machine 5, the flat wire rolling mill 7, the annealing furnace 9, the flat wire drawing machine 11, the annealing furnace 13, the paint application machine 15, and the baking furnace 17 in that order, before being wound onto a winding machine 19. However, the processed conductor 23, which is the flat copper wire rod 23B described later, passes through the section including the paint application machine 15 and the baking furnace 17 multiple times.

[0009] The material of the conductor 23 is copper or a copper alloy. The cross-sectional shape of the conductor 23 is circular until the flat rolling process described later is performed. The cross-section of the conductor 23 is the cross-section perpendicular to the longitudinal direction of the conductor 23.

[0010] The round wire drawing machine 5 draws the conductor 23, which has a circular cross-section. The rectangular rolling mill 7 performs rectangular rolling on the moving conductor 23. The conductor 23 that has undergone rectangular rolling is made into rectangular copper wire 23A. As shown in Figure 2, the cross-sectional shape of the rectangular copper wire 23A is composed of two parallel sides 24A and 24B and two arc-shaped outer edges 26A and 26B. In the cross-section, the shapes of sides 24A and 24B are straight lines. In the cross-section, the lengths of sides 24A and 24B are greater than the lengths of the outer edges 26A and 26B. The annealing furnace 9 anneals the rectangular copper wire 23A.

[0011] The flat-angle wire drawing machine 11 performs flat-angle wire drawing on the moving flat-angle copper wire 23A. Flat-angle wire drawing is a process in which the flat-angle copper wire 23A is continuously cold-drawn using a flat-angle wire drawing die. The conductor 23 that has undergone flat-angle wire drawing is called flat-angle copper wire material 23B.

[0012] The cross-sectional shape of the rectangular copper wire 23B is a rounded rectangle, as shown in Figure 3. The longer sides of the rounded rectangle are sides 24A and 24B. The shorter sides 22A and 22B of the rounded rectangle are sides that originate from the outer edges 26A and 26B of the rectangular copper wire 23A.

[0013] As shown in Figure 1, in the flat wire drawing machine 11, the direction in which the conductor 23 travels is defined as the travel direction TR. The direction opposite to the travel direction TR is defined as the upstream direction US. The annealing furnace 13 anneals the flat copper wire 23B. The paint application machine 15 applies enamel paint to the surface of the flat copper wire 23B, thereby forming an enamel paint film of a predetermined thickness on the surface of the flat copper wire 23B.

[0014] The baking furnace 17 applies heat to the running flat rectangular copper wire 23B, which has been coated with enamel paint of a predetermined thickness by the paint applicator 15, and bakes it to form the insulating coating 28 shown in Figure 4. As shown in Figure 1, the application of enamel paint by the paint applicator 15 and the baking by the baking furnace 17 are repeated. The flat rectangular enamel copper wire 25 is then wound onto the winding machine 19.

[0015] The method for forming the insulating film 28 is as follows: Enamel paint is applied to the surface of the flat copper wire 23B using a paint applicator 15. The enamel paint is a paint containing a resin, a solvent, and an inorganic filler. The resin contains polyamic acid. Polyamic acid is a compound synthesized from raw materials containing an acid anhydride and a diamine.

[0016] Examples of acid anhydrides include PMDA (pyromellitic anhydride), BPDA (3,3',4,4'-biphenyltetracarboxylic anhydride), and TMA (trimellitic anhydride). Examples of diamines include ODA (4,4'-diaminodiphenyl ether) and BODA (4,4'-bis(4-aminophenoxy)biphenyl).

[0017] For example, acid anhydrides contain a biphenyl structure. Examples of acid anhydrides containing a biphenyl structure include BPDA and BODA. If an acid anhydride contains a biphenyl structure, then polyamic acids also contain a biphenyl structure. If a diamine contains a biphenyl structure, then polyamic acids also contain a biphenyl structure. If a polyamic acid contains a biphenyl structure, then the polyimides produced from polyamic acids also contain a biphenyl structure.

[0018] The mass ratio of the solid content in the enamel paint is, for example, 15% by mass or more and 30% by mass or less. Examples of the inorganic filler contained in the enamel paint include silica, alumina, titanium oxide, and the like. For example, the surface of the inorganic filler is surface-treated with an organic substance. In this case, the inorganic filler has good dispersibility in polyimide. When the enamel paint is applied and baked, the polyamic acid changes into polyimide. Therefore, the insulating film 28 contains polyimide.

[0019] Since the enamel paint contains an inorganic filler, the insulating film 28 contains the inorganic filler. Since the insulating film 28 contains the inorganic filler, the surge resistance of the insulating film 28 is improved. The compounding amount of the inorganic filler in the enamel paint and the insulating film 28 is preferably 1 phr or more and 100 phr or less, more preferably 5 phr or more and 80 phr or less, and particularly preferably 10 phr or more and 50 phr or less. Note that phr (per hundred resin) is the part by mass of an additive (for example, an inorganic filler) blended when the resin mass is 100.

[0020] Next, the solvent in the enamel paint applied to the surface of the flat copper drawn wire 23B is evaporated and baked in the baking furnace 17. By performing the application of the enamel paint by the paint applicator 15 and the baking by the baking furnace 17 once, one layer constituting the insulating film 28 is formed. By repeating the application of the enamel paint by the paint applicator 15 and the baking by the baking furnace 17, the insulating film 28 in which a plurality of layers are laminated is formed.

[0021] The baking furnace 17 includes an evaporation zone and a curing zone. The running flat copper drawn wire 23B first passes through the evaporation zone and then passes through the curing zone. The lower the temperatures of the evaporation zone and the curing zone are, the larger the value of 280°C tanδ described later is. The faster the linear velocity of the flat copper drawn wire 23B in the evaporation zone and the curing zone is, the larger the value of the 280°C tanδ is.

[0022] Through the above process, an insulating film 28 is formed, and a rectangular enamel copper wire 25 is formed. The insulating film 28 contains polyimide derived from polyamic acid contained in the enamel paint. Therefore, the insulating film 28 contains polyimide and an inorganic filler.

[0023] 2. Composition of the flat rectangular enamel copper wire 25 The structure of the rectangular enameled copper wire 25 will be explained based on Figure 4. The rectangular enameled copper wire 25 comprises a rectangular drawn copper wire 23B and an insulating coating 28. The rectangular drawn copper wire 23B corresponds to the conductor. The insulating coating 28 covers the rectangular drawn copper wire 23B. The thickness of the insulating coating 28 is, for example, 30 μm or more and 200 μm or less.

[0024] The insulating film 28 contains polyimide and an inorganic filler. The polyimide contains a biphenyl structure. The dielectric loss tangent of the insulating film 28 at 280°C (hereinafter referred to as 280°C tanδ) is 0.03 or more and 0.1 or less. Preferably, 280°C tanδ is 0.032 or more and 0.099 or less.

[0025] 3. Effects of using 25mm flat enameled copper wire (1A) In the case of the flat enameled copper wire 25, the adhesion between the layers constituting the insulating film 28 is high because the tanδ at 280°C of the insulating film 28 is between 0.03 and 0.1. Furthermore, when the tanδ at 280°C of the insulating film 28 is between 0.03 and 0.1, it is presumed that the firing of the insulating film 28 is progressing appropriately, resulting in high adhesion between the layers constituting the insulating film 28. (1B) In the case of the flat rectangular enameled copper wire 25, the adhesion between the insulating coating 28 and the flat rectangular drawn copper wire 23B is high.

[0026] <Examples> 1. Manufacturing of enameled copper wire Enameled copper wires of Examples 1-4 and Comparative Examples 1-9 were manufactured using the method described in the first embodiment. However, in each example and comparative example, the enameled copper wire was round wire, not flat wire. Also, in each example and comparative example, the diameter of the conductor 23 in the paint application machine 15 and the baking furnace 17 was 0.8 mm. Also, in each example and comparative example, the thickness of the insulating coating 28 was 35 μm.

[0027] The manufacturing methods for each example and comparative example differed in the temperature of the baking furnace 17 and the linear velocity of the conductor in the baking furnace 17, but were otherwise identical. The raw materials and manufacturing methods for the enamel paint were the same for each example and comparative example. The types, names, chemical names, and molar ratios of the raw materials for the enamel paint are shown in Table 1. The solvent used in the enamel paint was DMAc (N,N-dimethylacetamide). When manufacturing the enamel paint, the mass ratio of raw materials to solvent was 25:75.

[0028] [Table 1]

[0029] The enamel paint was manufactured as follows: ODA, BODA, and DMAc were placed in a flask. Next, ODA and BODA were mixed while stirring with a stirrer until completely dissolved to obtain a reaction solution. Then, PMDA and BPDA were added to the reaction solution while stirring. After the PMDA and BPDA were dissolved, TMA was added and the mixture was stirred further.

[0030] Next, silica sol was added to a filler amount of 25 phr, and the mixture was stirred. Then, it was diluted with DMAc. Enamel paint was obtained through the above steps.

[0031] The temperature of the firing furnace 17 and the linear velocity of the conductor in the firing furnace 17 for each example and each comparative example are shown in Table 2. In Table 2, the temperature of the evaporation zone and the temperature of the hardening zone are shown as the temperature of the firing furnace 17, respectively.

[0032] [Table 2]

[0033] 2.280℃ tanδ measurement For each example and comparative example, the tanδ at 280°C was measured. The measurement method was as follows.

[0034] A Totoku Paint LCR meter 4263B was used to measure tanδ at 280°C. A 40mm long enameled copper wire was prepared. The insulating coating 28 was stripped from the 10mm portion of the enameled copper wire from the end. The enameled copper wire after the insulating coating 28 was stripped was used as the measurement sample. Next, the measurement sample was placed in a metal bath, and the detached end of the measurement sample was connected to an electrode clip. The detached end is the portion from which the insulating coating 28 was stripped. In this state, the dielectric loss tangent at a measurement frequency of 1kHz was measured while the metal bath was heated, and the dielectric loss tangent (i.e., tanδ at 280°C) was measured when the temperature of the metal bath was 280°C. The measurement results are shown in Table 2.

[0035] 3. Cut lengthening test A cut-and-stretch test was performed on each example and each comparative example. The cut-and-stretch test is a test to evaluate the adhesion between the layers constituting the insulating coating 28. First, a measurement sample 101 was prepared as shown in S1 of Figure 5. The measurement sample 101 was made by cutting an enameled copper wire to a length of 200 mm. The cut surface was the cross-section of the enameled copper wire.

[0036] Next, as shown in S2 of Figure 5, a notch 103 was formed in the measurement sample 101. The position of the notch 103 was in the center of the longitudinal direction of the measurement sample 101. The notch 103 was formed along the circumferential direction of the measurement sample 101, extending all the way around. The notch 103 reached from the surface of the insulating film 28 to the surface of the conductor 23. Next, as shown in S3, the measurement sample 101 was stretched by 20% in its longitudinal direction.

[0037] After the formation of the cut 103, a delamination region 105 was created around the cut 103, as shown in S4 of Figure 5. The delamination region 105 is the part where the inner layer 28A of the insulating film 28 and the outer layer 28B of the insulating film 28 have separated, or where the conductor 23 and the inner layer 28A of the insulating film 28 have separated. The delamination region 105 is visible from outside the measurement sample 101. The length L of the delamination region 105 was measured. The length L was the length in the longitudinal direction of the measurement sample 101. The measurement results for length L are shown in Table 2.

[0038] The length L was short in Examples 1-4 and long in Comparative Examples 1-9. The shorter the length L, the higher the adhesion between the layers constituting the insulating film 28. Therefore, the adhesion between the layers constituting the insulating film 28 was high in Examples 1-4 and low in Comparative Examples 1-9.

[0039] <Other Embodiments> Although embodiments of the present disclosure have been described above, the present disclosure is not limited to the embodiments described above and can be implemented in various modified forms.

[0040] (1) Insulated wires may be insulated wires other than enameled wires. (2) Of the layers constituting the insulating film 28, one or more layers on the conductor 23 side may be an adhesion layer containing polyimide but not inorganic fillers. The polyimide contained in the adhesion layer may, for example, contain a biphenyl structure. The adhesion layer can be formed by applying an enamel paint that does not contain inorganic fillers.

[0041] The adhesion layer is the layer in contact with the conductor 23. The layer on the outer periphery of the adhesion layer is a surge-resistant layer containing polyimide and inorganic filler. In this case, the insulated wire of this disclosure can improve the adhesion between the adhesion layer and the surge-resistant layer. Furthermore, the insulated wire of this disclosure can improve the adhesion between the surge-resistant layers. Since the adhesion layer does not contain inorganic filler, the adhesion between the conductor 23 and the adhesion layer is high. For example, the insulating film 28 has 14 layers. Of these, 1 to 7 are adhesion layers and 7 to 13 are surge-resistant layers. Alternatively, the insulating film 28 has 40 layers. Of these, 1 to 20 are adhesion layers and 20 to 39 are surge-resistant layers. (3) Of the layers constituting the insulating film 28, at least a portion of the layer that does not come into contact with the conductor 23 may be a layer that contains polyimide but does not contain inorganic fillers. For example, among the layers constituting the insulating film 28, one or more layers on the conductor 23 side are surge-resistant layers containing polyimide and inorganic fillers. Layers on the outer periphery of the surge-resistant layer contain polyimide but do not contain inorganic fillers. For example, the insulating coating 28 has 14 layers. Of these, 1 to 7 are surge-resistant layers, and 7 to 13 are layers that contain polyimide but do not contain inorganic fillers. Alternatively, the insulating coating 28 has 40 layers. Of these, 1 to 20 are surge-resistant layers, and 20 to 39 are layers that contain polyimide but do not contain inorganic fillers.

[0042] (4) The function of one component in each of the above embodiments may be divided among multiple components, or the function of multiple components may be performed by one component. Also, some of the configurations of each of the above embodiments may be omitted. Also, at least some of the configurations of each of the above embodiments may be added to, replaced with, etc., the configurations of other embodiments.

[0043] (5) In addition to the insulated wire described above, this disclosure can also be realized in various forms, such as products that use the insulated wire as a component, and methods for manufacturing the insulated wire. [Explanation of Symbols]

[0044] 1...Manufacturing equipment, 3...Dance wheel or bobbin, 5...Round wire drawing machine, 7...Flat rolling mill, 9...Annealing furnace, 11...Flat wire drawing machine, 13...Annealing furnace, 15...Paint application machine, 17...Baking furnace, 19...Winding machine, 22A, 22B...Short side, 23...Conductor, 23A...Flat copper wire, 23B...Flat copper drawn wire material, 24A, 24B...Side, 25...Flat enameled copper wire, 26A, 26B...Outer edge, 28...Insulating coating, 28A...Inner layer, 28B...Outer layer, 101...Measurement sample, 103...Cut, 105...Peeling area

Claims

1. A conductor and An insulating film covering the conductor, Equipped with, The insulating film comprises polyimide and an inorganic filler. The polyimide contains a biphenyl structure, The dielectric loss tangent of the insulating film at 280°C is 0.03 or more and 0.1 or less. Insulated wire.

2. An insulated wire according to claim 1, Of the layers constituting the insulating film, the layer in contact with the conductor is a layer that contains polyimide but does not contain inorganic fillers. Insulated wire.

3. An insulated wire according to claim 1, Of the layers constituting the insulating film, at least a portion of the layer not in contact with the conductor is a layer that contains polyimide but does not contain inorganic fillers. Insulated wire.

4. An insulated wire according to claim 2, The layer in contact with the conductor is a layer containing polyimide with a biphenyl structure. Insulated wire.

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