JP2012243614A - Insulated wire, and electric coil and motor using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an insulated wire which is superior in heat resistance and processing resistance, specially superior in heat resistance after processing, and to provide an electric coil and a motor using the insulated wire.SOLUTION: An insulated wire includes a conductor, and an insulating layer having two or more layers for coating the conductor. An outermost layer of the insulating layer is a single polyimide layer formed by once applying and baking a polyimide resin varnish containing a polyimide precursor resin as a main ingredient. A resin constituting the insulating layer except the outermost layer is preferable to be selected from the group consisting of polyamide-imide, polyesterimide, polyetherimide and an H-class polyester resin.

Description

  The present invention relates to an insulated wire and an electric coil and a motor using the insulated wire, and more particularly to an insulated wire excellent in heat resistance and workability.

  In an insulated wire used as a coil winding for a motor or the like, an insulating layer (insulating film) covering a conductor is required to have excellent insulation, adhesion to the conductor, heat resistance, mechanical strength, and the like. Examples of the resin forming the insulating layer include polyimide resin, polyamideimide resin, and polyesterimide resin.

  In addition, in an electric device having a high applied voltage, for example, a motor used at a high voltage, a high voltage is applied to an insulated wire constituting the electric device, and partial discharge (corona discharge) is likely to occur on the surface of the insulating film. The generation of corona discharge tends to cause a local temperature rise and the generation of ozone and ions. As a result, the insulation coating of the insulated wire is deteriorated, resulting in early dielectric breakdown and shortening the life of the electrical equipment. Insulated wires used at high voltages are also required to improve the corona discharge starting voltage for the above reasons, and it is known that reducing the dielectric constant of the insulating layer is effective for this purpose.

  Polyimide resin is particularly excellent in heat resistance among resins widely used as insulating layers for insulated wires. Moreover, since it has a low dielectric constant and excellent mechanical properties, it is used as an insulating layer for insulated wires with high required properties. For example, Patent Document 1 discloses an enameled wire in which a polyimide resin enamel film layer is applied and baked directly on a conductor as an enameled wire having a heat resistance class C (class of 180 ° C. or higher). Patent Document 2 discloses a polyamide-imide overcoat polyimide insulation in which a polyimide varnish is applied and baked on the outer peripheral surface of a copper wire, and then a polyamide-imide varnish is applied and baked at least once to form an enamel film. An electric wire is disclosed.

JP-A-9-198932 Japanese Patent Laid-Open No. 5-130759

  As described above, a polyimide resin is a material having excellent heat resistance, mechanical properties, and electrical properties, but has a problem of poor work resistance, particularly wear resistance. When using an insulated wire as a coil, the insulated wire is greatly deformed to increase the space factor of the coil. For example, after forming the coil by winding the insulated wire, the coil is inserted into the slot, or the insulated wire deformed in advance is welded to form the coil. If the abrasion resistance of the insulating layer is poor, the insulating layer is easily damaged during processing, and the insulating film may be cracked or pinholes may occur, resulting in poor electrical characteristics.

  In particular, it is known that the workability is lowered in an insulated wire having a polyimide film as the outermost layer. Therefore, when using polyimide as an insulating layer, a layer made of a resin other than polyimide is often provided as the outermost layer. In Patent Document 1, a film layer made of polybenzimidazole resin is provided on a polyimide film layer to achieve both heat resistance and wear resistance. Moreover, in patent document 2, the polyamide imide which is excellent in friction resistance is provided in the outer side of the polyimide membrane | film | coat. Thus, the insulated wire which provided the polyimide membrane | film | coat in the outermost layer was not used in the use where work resistance is required.

  On the other hand, high heat resistance is required for insulated wires used for applications such as in-vehicle motors. In particular, in order to increase the space factor of the coil, it is used in a high-temperature atmosphere after being subjected to processing that greatly deforms the insulated wire, so that it is required that the insulating film does not deteriorate even under such conditions.

  The present invention has been made in view of the above problems, and it is an object to provide an insulated wire excellent in heat resistance and workability, particularly excellent in heat resistance after processing, and an electric coil and a motor using the insulated wire. And

  The present invention relates to an insulated wire having a conductor and two or more insulating layers covering the conductor, and the outermost layer of the insulating layer is coated and baked once with a polyimide resin varnish mainly composed of a polyimide precursor. The insulated wire is a single-layer polyimide layer formed as described above (claim 1).

  One factor that lowers the wear resistance of polyimide is that the solubility of the polyimide film in the solvent is poor. The polyimide film is formed by applying and baking a varnish (polyimide resin varnish) obtained by dissolving a polyimide precursor resin in a solvent on a conductor. The polyamic acid, which is a polyimide precursor, is imidized by heat during baking to become polyimide. Since only a thin film of about several μm can be formed by a single coating and baking process, a normal coating and baking process is repeated a plurality of times to form a polyimide film having a predetermined thickness (several tens of μm). Therefore, in the second and subsequent steps, a polyimide resin varnish is applied on the polyimide layer formed in the previous step. At this time, the solvent contained in the polyimide varnish dissolves the lower layer (polyimide layer formed in the previous step) slightly, so that the compatibility between the layers is improved and the adhesion between the layers is obtained. However, polyimides baked and imidized have lower solubility in solvents than other resins such as polyamideimide, and the lower layer hardly dissolves when varnish is applied. Accordingly, the adhesion force (adhesive force) between the layers is reduced, and if the processing causes a large deformation in the film, the film is destroyed due to the peeling between the layers.

  In a single-layer polyimide layer formed by applying and baking processes only once, such a problem due to delamination does not occur. An insulating layer made of a resin other than polyimide is formed below the polyimide layer. Since resins other than polyimide have better solubility in solvents than polyimide, the adhesion between the polyimide layer and the insulating layer, which is the lower layer of the polyimide layer, and the interlayer adhesion in the lower layer are also good.

  Furthermore, heat resistance and heat resistance after processing become good by providing a polyimide layer as the outermost layer. Polyimide has the highest heat resistance among resins widely used as insulating layers for insulated wires, and has high tensile elongation at break and tensile strength at break and excellent toughness. When processing to greatly deform an insulated wire, the insulation film is greatly deformed as it goes to the outside. Therefore, by providing a polyimide layer with high toughness as the outermost layer, the workability (deformation resistance) of the entire insulating layer is good. Become.

  The resin constituting the insulating layer other than the outermost layer is preferably at least one selected from the group consisting of polyamideimide, polyesterimide, polyetherimide and H-type polyester. Since these resins are excellent in heat resistance and toughness after polyimide, the heat resistance of the entire insulated wire can be improved. These resins are selected according to the required heat resistance of the insulated wire. These resins may be used alone or in a plurality of types. The insulating layer made of each resin may be a single layer formed by one coating and baking process, or may be a plurality of layers formed by repeating the coating and baking processes a plurality of times. Of these, polyamide imide is particularly excellent in heat resistance, and therefore it is preferable to use polyamide imide for all insulating layers other than the outermost layer in applications where high heat resistance is required. Since polyimide is more expensive than other resins, the insulated wire having such a configuration also has an advantage that the cost is lower than an insulated wire in which the entire insulating layer is made of polyimide.

  The invention described in claim 4 is an electric coil formed by winding the insulated wire. A fifth aspect of the present invention is a motor having the electric coil according to the fourth aspect. Since an insulated wire excellent in workability and heat resistance is used, a coil with a high space factor can be obtained, and the coil and motor can be miniaturized and used in a high-temperature atmosphere.

  According to the present invention, it is possible to obtain an insulated wire excellent in heat resistance and workability, and particularly excellent in heat resistance after processing, and an electric coil and a motor using the insulated wire.

It is a cross-sectional schematic diagram which shows an example of the insulated wire of this invention. It is a schematic diagram which shows an example of the coil of this invention. It is a schematic diagram which shows an example of the motor of this invention.

  The insulated wire of the present invention has two or more insulating layers on a conductor, and the outermost layer of the insulating layer is a single layer (one-time coating) polyimide layer. Any resin other than polyimide can be used for the insulating layer other than the outermost layer. Polyamideimide, polyesterimide, polyetherimide H type polyester, polyesterimide, polyurethane and the like are exemplified as the resin constituting the insulating layer other than the outermost layer.

  The insulating layer is formed by applying and baking a resin varnish obtained by dissolving the above resin in a solvent directly on the conductor or through another layer. The total thickness of the insulating layer is about 10 μm to 150 μm. Since only a coating of about several μm can be formed in one application and baking process, the insulating layer is usually formed by repeating the application and baking processes of resin varnish several times. As described above, since the outermost layer is a layer obtained by applying and baking the polyimide resin varnish once, the thickness of the outermost layer is as thin as about 1 μm to 5 μm. Therefore, the insulating layer other than the outermost layer is repeatedly applied and baked multiple times. Form.

  Application and baking can be performed in the same manner as in the production of a normal insulated wire. For example, after applying a resin varnish to a conductor coated with a conductor or an insulating layer, the process of baking by passing the inside of a furnace with a set temperature of 350 to 500 ° C. for 5 to 10 seconds per pass is repeated several times. Form.

  When an insulating layer other than the outermost layer is used as a single resin, the same resin varnish is applied and baked several times. When an insulating layer other than the outermost layer is formed of a plurality of resins, the first resin varnish is applied once or several times and baked to form an insulating layer made of the first resin, and then the second resin. A varnish is applied once or several times and baked to form an insulating layer made of the second resin. This process is repeated, and finally the polyimide resin varnish is applied and baked once to form the outermost layer.

  As the conductor, copper, copper alloy, aluminum or the like can be used. The size of the conductor and the cross-sectional shape thereof are not particularly limited, but in the case of a round wire, a conductor diameter of 100 μm to 5 mm is generally used, and in the case of a flat wire, one having a side length of 500 μm to 5 mm is generally used.

  The polyimide resin varnish that forms the outermost layer is mainly composed of a polyimide precursor (polyamic acid) obtained by reacting an aromatic diamine and an aromatic tetracarboxylic dianhydride. A polyimide precursor is synthesized by a condensation polymerization reaction between an aromatic diamine and an aromatic tetracarboxylic dianhydride.

  As aromatic tetracarboxylic dianhydrides, pyromellitic dianhydride (PMDA), 4,4′-oxydiphthalic dianhydride (ODPA), 3,4,3 ′, 4′-biphenyltetracarboxylic dianhydride Anhydride (BPDA), 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride (BTDA), 3,3 ′, 4,4′-diphenylsulfone tetracarboxylic dianhydride, bicyclo (2, 2,2) -Oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 2,2-bis (3 Examples include 4-dicarboxyxyphenyl) hexafluoropropane dianhydride, 5- (2,5-dioxotetrahydrofuryl) -3-methyl-3-cyclohexene-1,2-dicarboxylic dianhydride, and the like. Among these, pyromellitic dianhydride (PMDA) is preferable because it has a low molecular weight and a rigid structure and can improve the heat resistance of the polyimide resin.

  Aromatic diamines include 4,4′-diaminodiphenyl ether (ODA), 4,4′-methylenedianiline (MDA), 2,2-bis [4- (aminophenoxy) phenyl] propane (BAPP), 1, 4-bis (4-aminophenoxy) benzene (TPE-Q), 1,3-bis (4-aminophenoxy) benzene (TPE-R), 1,1-bis [4- (4-aminophenoxy) phenyl] Examples include cyclohexane (4-APBZ), 1,3-bis (3-aminophenoxy) benzene (3-APB), 1,5-bis (3-aminophenoxy) naphthalene (1,5-BAPN), and the like.

  When ODA or MDA is selected as the aromatic diamine, the heat resistance of the polyimide resin can be improved. Also, 2,2-bis [4- (aminophenoxy) phenyl] propane (BAPP), 1,3-bis (4-aminophenoxy) benzene (TPE-R), 1,4-bis (4-amino) having a large molecular weight When phenoxy) benzene (TPE-Q) is selected, the dielectric constant of the polyimide resin can be lowered. When an aromatic diamine having a high molecular weight and an aromatic diamine having a low molecular weight such as ODA or MDA are used in combination, a polyimide having a balanced property can be obtained.

  The above aromatic tetracarboxylic dianhydride and aromatic diamine are mixed and reacted. When the total amount (equivalent) of aromatic diamine and the total amount (equivalent) of aromatic tetracarboxylic dianhydride is about 1: 1, the reaction proceeds favorably, which is preferable. Each material is mixed and heated to react in an organic solvent to obtain a polyimide precursor resin.

  As the organic solvent, an aprotic polar organic solvent such as N-methyl-2-pyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide, and γ-butyrolactone can be used. These organic solvents may be used alone or in combination of two or more.

  The amount of the organic solvent is not particularly limited as long as it is an amount capable of uniformly dispersing the aromatic tetracarboxylic dianhydride and the aromatic diamine, but usually 100 parts by mass per 100 parts by mass of the total amount of these components. ˜1000 parts by mass (so that the resin concentration is about 10% to 50%). If the amount of the organic solvent is reduced, the amount of the solid content of the polyimide resin varnish obtained is increased, which is effective for cost reduction.

  Various additives such as pigments, dyes, inorganic or organic fillers, lubricants, adhesion improvers, reactive low molecules, compatibilizers, and the like may be added to the polyimide resin varnish. When melamine is added as an adhesion improver, adhesion with the conductor can be improved. Furthermore, other resins can be mixed and used within a range not impairing the gist of the present invention.

  For the insulating layer other than the outermost layer, a resin varnish mainly composed of polyamideimide, polyesterimide, polyetherimide, H-type polyester, polyesterimide, polyurethane or the like is used. In order to improve heat resistance, polyamideimide, polyesterimide, polyetherimide, and H-type polyester are preferable, and polyamideimide is particularly preferable.

  Polyamideimide is a resin having an amide bond and an imide bond in the molecule, and is obtained by polymerizing a diisocyanate component containing an aromatic diisocyanate component and an acid component containing trimellitic anhydride. Examples of the diisocyanate component include diphenylmethane-4,4′-diisocyanate (MDI), diphenylmethane-3,3′-diisocyanate, diphenylmethane-3,4′-diisocyanate, diphenylether-4,4′-diisocyanate, benzophenone-4,4′-. Aromatic diisocyanates such as diisocyanate and diphenylsulfone-4,4′-diisocyanate can be used.

  Acid components include trimellitic anhydride (TMA), 1,2,5-trimellitic acid (1,2,5-ETM), biphenyltetracarboxylic dianhydride, benzophenonetetracarboxylic dianhydride, diphenyl Sulfonetetracarboxylic dianhydride, oxydiphthalic dianhydride (OPDA), pyromellitic dianhydride (PMDA), 4,4 ′-(2,2′-hexafluoroisopropylidene) diphthalic dianhydride, etc. Can be used. The isocyanate component and the acid component may be used one by one or a plurality of types may be combined.

  An acid component and a diisocyanate component are mixed in an approximately equivalent amount, and heated and reacted in an organic solvent to obtain a polyamideimide resin varnish. A caprolactam compound may be added to the reaction system. As the organic solvent, N-methyl-2-pyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide, tetramethylurea, hexaethylphosphoric triamide, γ-butyrolactam and the like can be used. Various additives such as pigments, dyes, inorganic or organic fillers, lubricants, adhesion improvers, reactive low molecules, compatibilizers, and the like may be added to the polyamideimide resin varnish.

  FIG. 1 is a schematic cross-sectional view showing an example of the insulated wire of the present invention. There are a first insulating layer 1 covering the conductor 3 and a second insulating layer 2 (outermost layer) covering the first insulating layer outside the conductor 3 having a rectangular cross section. The first insulating layer 1 is made of an arbitrary resin such as polyamideimide, and the second insulating layer 2 is made of polyimide. The insulated wire of the present invention is not limited to this shape.

  FIG. 2A is a schematic view showing an example of the electric coil of the present invention, and FIG. 2B is a cross-sectional view taken along the line A-A ′ of FIG. The electric wire 12 is formed by winding the insulated wire 11 outside the core 13 made of a magnetic material. A member composed of a core and an electric coil is used as a rotor or a stator of a motor. For example, as shown in FIG. 3, a stator 15 in which a plurality of divided stators 14 including a core 13 and an electric coil 12 are combined and arranged in an annular shape is used as a constituent member of a motor.

  Next, the present invention will be described in more detail based on examples. The scope of the present invention is not limited to this example.

(Preparation of polyamideimide resin varnish)
TMA (trimellitic anhydride, Mitsubishi Gas Chemical Co., Ltd.) was passed through a flask equipped with a thermometer, cooling pipe, calcium chloride filled pipe, stirrer, and nitrogen blowing pipe while flowing 150 ml of nitrogen gas from the nitrogen blowing pipe per minute. 108.6 g of MDI (methylene diisocyanate, manufactured by Mitsui Takeda Chemical Co., Ltd., trade name Cosmonate PH) was added. Next, 637 g of N-methylpyrrolidone was added and heated at 80 ° C. for 3 hours while stirring with a stirrer. Further, the temperature of the reaction system was raised to 140 ° C. over about 3 hours and then heated at 140 ° C. for 1 hour. When one hour had passed, heating was stopped and the product was allowed to cool to obtain a polyamideimide resin varnish having a nonvolatile content of 25%.

(Preparation of polyimide resin varnish)
After dissolving 94.3 g of 4,4′-diaminodiphenyl ether (ODA), which is an aromatic diamine, in 803 g of N-methylpyrrolidone, pyromellitic dianhydride (PMDA), which is an aromatic tetracarboxylic dianhydride 102.7 g was added and stirred for 1 hour at room temperature under a nitrogen atmosphere. Thereafter, the mixture was stirred at 60 ° C. for 20 hours to finish the reaction and cooled to room temperature to obtain a polyimide resin varnish having a nonvolatile content of 18%.

(Production of insulated wires)
Example 1
After forming a polyamideimide insulating layer having a thickness of about 33 μm by repeating the process of applying and baking a polyamideimide resin varnish on the surface of a flat conductor (copper wire) having a thickness of 1.5 mm and a width of 3.0 mm, a polyimide resin is formed. The varnish was applied once and baked to form a polyimide layer having a thickness of about 3 μm. In the obtained insulated wire, the outermost layer is a polyimide single layer, and the insulating layers other than the outermost layer are made of polyamideimide.

(Comparative Example 1)
The process of applying and baking a polyimide resin varnish on the surface of a flat rectangular conductor (copper wire) having a thickness of 1.5 mm and a width of 3.0 mm was repeated 12 times to form a polyimide insulating layer having a thickness of about 36 μm. The insulating layer of the obtained insulated wire is entirely made of polyimide including the outermost layer.

(Comparative Example 2)
The process of applying and baking a polyamideimide resin varnish on the surface of a flat rectangular conductor (copper wire) having a thickness of 1.5 mm and a width of 3.0 mm was repeated 12 times to form a polyamideimide insulating layer having a thickness of about 36 μm. The insulating layers of the obtained insulated wires are all made of polyamideimide including the outermost layer.

(Comparative Example 3)
After a polyamideimide insulating layer having a thickness of about 30 μm is formed by repeating the process of applying and baking a polyamideimide resin varnish on the surface of a flat conductor (copper wire) having a thickness of 1.5 mm and a width of 3.0 mm, a polyimide resin is formed. The process of applying and baking the varnish was repeated twice to form a polyimide layer having a thickness of about 6 μm. In the obtained insulated wire, the outermost layer is two polyimide layers, and the insulating layers other than the outermost layer are made of polyamideimide.

(Long-term heat resistance)
The obtained insulated wire was left in a thermostatic bath at 200 ° C. for 500 hours, and then the state of the insulating layer was observed. The case where cracks occurred in the film (insulating layer) was rated as x, and the case where no film cracks occurred was marked as o.

(Long-term heat resistance after processing)
The obtained insulated wire was left in a thermostatic bath at 200 ° C. for 500 hours in a state of being bent at an angle of 180 ° so as to have an inner diameter of 2 mm, and then the state of the insulating layer was observed. The case where cracks occurred in the film (insulating layer) was rated as x, and the case where no film cracks occurred was marked as o.

(Interlayer adhesion)
The insulation layer of the obtained insulated wire was cut into a 0.5 mm width partway through the insulation layer, and the interlayer adhesion was measured by a 180 ° peel test.

(Abrasion resistance)
JIS C3003 9. The wear resistance was evaluated according to the wear resistance test. A linear test piece (insulated wire) is subjected to a continuously increasing load on the needle, and the surface of the wire is rubbed with the needle. The load when conduction occurs between the needle and the conductor is the breaking load. The first measurement is performed by rotating 30 ° from the state where the sample is placed so that the long side of the test piece becomes the bottom side. Further, it is rotated 90 ° to measure the second point, further rotated 90 ° to the third point, and further rotated 90 ° to measure the fourth point. The average value of 4 points was calculated and used as a unidirectional wear fracture load. The results are shown in Table 1. In the table, polyimide is described as PI, and polyamideimide is described as PAI.

  It can be seen that the insulated wire of Example 1 has good heat resistance, heat resistance after processing, interlayer adhesion, and wear resistance, and is excellent in heat resistance and workability. The insulated wire of Comparative Example 1 in which the insulating layer is all polyimide has good heat resistance and heat resistance after processing, but has low interlayer adhesion and poor wear resistance. The insulated wire of Comparative Example 2 in which the insulating layer is all polyamideimide has good interlayer adhesion, wear resistance, and heat resistance, but has poor heat resistance after processing. The insulated wire of Comparative Example 3 has good heat resistance and heat resistance after processing, but has poor interlayer adhesion and wear resistance. The difference between Example 1 and Comparative Example 3 is only the number of times the outermost polyimide is applied, but a significant difference appears in the characteristics.

DESCRIPTION OF SYMBOLS 1 1st insulating layer 2 2nd insulating layer (outermost layer)
3 Conductor 11 Insulated Wire 12 Electric Coil 13 Core 14 Split Stator 15 Stator

Claims (5)

  An insulated wire having a conductor and two or more insulating layers covering the conductor, wherein the outermost layer of the insulating layer is formed by applying and baking a polyimide resin varnish mainly composed of a polyimide precursor. An insulated wire that is a single-layer polyimide layer.   The insulated wire according to claim 2, wherein the resin constituting the insulating layer other than the outermost layer is at least one selected from the group consisting of polyamideimide, polyesterimide, polyetherimide, and H-type polyester.   The insulated wire according to claim 2, wherein the resin constituting the insulating layer other than the outermost layer is polyamideimide.   An electric coil formed by winding the insulated wire according to any one of claims 1 to 3.   A motor having the electric coil according to claim 4.

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