JP7257558B1 - Insulated wires, coils, rotating electrical machines, and electric/electronic equipment - Google Patents

Abstract

An insulated wire capable of effectively increasing a partial discharge inception voltage under dry conditions, and a coil, rotating electric machine, and electric/electronic device using the insulated wire are provided. An insulated wire having a rectangular conductor and an insulating film covering the outer circumference of the rectangular conductor, wherein the insulating film has the following (a) to (c) on at least one surface of the insulated wire. Fulfillment: (a) the minimum thickness is 75 μm or more and 350 μm or less, (b) the difference between the maximum and minimum thickness is 10 μm or less, (c) the value obtained by dividing the minimum thickness by the maximum value is 0 .900 or more and 1.000 or less, and an insulated wire having a size of a gap of 20 μm or less generated when the surfaces satisfying the above (a) to (c) are overlapped with each other. [Selection figure] None

Description

The present invention relates to insulated wires, coils, rotating electric machines, and electrical/electronic equipment.

2. Description of the Related Art An insulated wire having a resin insulating film on the outer peripheral surface of a linear metal conductor is used as a magnet wire in coils for electric and electronic equipment such as high-speed switching elements, inverter motors, and transformers. The insulation film of the insulated wire is formed by applying and baking a thermosetting resin, extruding and coating a thermoplastic resin, or combining these.
In particular, in recent years, due to the depletion of energy resources and environmental problems, vehicles and transport machines powered by electric motors, such as hybrid cars and electric cars, are rapidly spreading. From the viewpoint of power performance and fuel efficiency improvement, there is a demand for high output and miniaturization of electric motors to be mounted.

Many reports have been made on techniques for improving the performance and usability of insulated wires from the viewpoint of insulating films covering conductors. For example, Patent Document 1 discloses an insulated wire having, as coating layers, at least one thermosetting resin layer and at least one thermoplastic resin layer in this order on a conductor with a rectangular cross section, wherein the thickness of the coating layer is However, the difference between the maximum value and the minimum value on each side formed on the four sides of the rectangular cross-section conductor is 20 μm or less, and the thickness of the coating layer on all sides An insulated wire is disclosed in which the value obtained by dividing the largest value by the smallest value is 1.3 or more. According to the technique described in Patent Document 1, the ratio (space factor) of the cross-sectional area of the conductor to the cross-sectional area of the slot of the stator can be increased, and the film shape changes even when the coil is molded under high pressure. It is said that it can provide insulated wires that are resistant to corrosion.

Further, Patent Document 2 discloses a flat conductor wire having a flat cross-sectional shape, and a resin insulation layer having a thickness of 1.5 μm or more and 5 μm or less made of a polyamide-imide resin covering the outer peripheral surface of the flat conductor wire. In the insulated wire, the exposure rate of the flat conductor in a portion with a predetermined width of 4 mm from the breaking point in side view after the rapid elongation test of the insulated wire based on JISC3216-3:2011 is 7%. and the Young's modulus of the resin insulation layer determined by a micro hardness tester is 9.0×10 ³ N/mm ² or more, and the thickness of the resin insulation layer is: An insulated wire is disclosed in which the thickness difference between the end corresponding portion, the corner corresponding portion and the short side corresponding portion is 3 μm or less. According to the technique described in Patent Document 2, it is possible to provide an insulated wire that has excellent adhesion of the resin insulation layer to the rectangular conductor, high uniformity of the thickness of the resin insulation layer, and excellent resistance to external damage.

WO2017/142036 JP 2020-155421 A

Electric motors mounted in automobiles and the like are usually mounted in the engine room and exposed to a severe high-temperature environment. In addition, increasing the output and miniaturization of electric motors also contributes to the increase in temperature of electric motors. The inventors of the present invention focused on the fact that the air becomes dry in such a high-temperature environment, and the insulation film also becomes dry. We came up with the idea that we could contribute to the further improvement of the performance of electric motors.

An object of the present invention is to provide an insulated wire capable of effectively increasing the partial discharge inception voltage under dry conditions, and a coil, rotating electric machine, and electric/electronic device using the insulated wire.

The present inventors have made extensive studies to solve the above problems. As a result, in an insulated wire using a rectangular conductor, after controlling the thickness of the insulating film to a thick film within a predetermined range, the size of the gap between the insulating films generated when the insulated wires are overlapped is The present inventors have found that the partial discharge inception voltage under dry conditions can be effectively increased by significantly suppressing the voltage as compared with the prior art.
The present invention has been completed through further studies based on these findings.

That is, the above problems of the present invention have been solved by the following means.
[1]
An insulated wire having a rectangular conductor and an insulating coating covering the outer periphery of the rectangular conductor,
On at least one surface of the insulated wire, the insulating coating satisfies the following (a) to (c):
(a) the minimum thickness is 75 μm or more and 350 μm or less;
(b) the difference between the maximum and minimum thickness is 10 μm or less;
(c) the value obtained by dividing the minimum thickness by the maximum thickness is greater than 0.900 and less than or equal to 1.000;
An insulated wire, wherein a gap of 20 μm or less is generated when the surfaces satisfying the above (a) to (c) are overlapped with each other.
[2]
The insulated wire according to [1], wherein the insulating coating includes an enamel layer.
[3]
The insulated wire according to [2], wherein the enamel layer is a thermosetting resin layer containing polyamideimide and/or polyimide.
[4]
The insulated wire according to any one of [1] to [3], wherein the insulating coating includes an extruded layer.
[5]
The insulated wire according to [4], wherein the extruded layer is a thermoplastic resin layer containing polyphenylene sulfide and/or polyetheretherketone.
[6]
The insulated wire according to [1], wherein the insulating coating has an enamel layer covering the conductor and an extruded layer covering the enamel layer.
[7]
The insulated wire according to [6], wherein the enamel layer is a thermosetting resin layer containing polyamideimide and/or polyimide, and the extruded layer is a thermoplastic resin layer containing polyphenylene sulfide and/or polyetheretherketone. .
[8]
A coil using the insulated wire according to any one of [1] to [7].
[9]
The coil according to [8], wherein the insulated wires are arranged so that the surfaces satisfying the above (a) to (c) are overlapped.
[10]
[8] or [9] rotating electrical machine, electrical and electronic equipment having the coil.

In the present invention or the specification, a numerical range represented by "-" means a range including the numerical values described before and after it as lower and upper limits.

In the insulated wire, coil, rotating electric machine, and electric/electronic device of the present invention, the insulated wire has the above structural characteristics, and the partial discharge inception voltage under dry conditions is effectively increased.

FIG. 1 is a schematic cross-sectional view showing one embodiment of the insulated wire of the present invention. FIG. 2 is a schematic cross-sectional view showing another embodiment of the insulated wire of the present invention. FIG. 3 is a schematic layout diagram of two insulated wires in measuring the partial discharge inception voltage (PDIV) and air gap evaluated in the examples. FIG. 4 is a schematic perspective view showing a preferred form of the stator used in the electric/electronic device of the present invention. FIG. 5 is a schematic exploded perspective view showing a preferred form of the stator used in the electrical/electronic equipment of the present invention.

[Insulated wire]
The insulated wire of the present invention has a rectangular conductor and an insulating coating covering the outer periphery of the conductor.

FIG. 1 shows a cross-sectional view of an embodiment of the insulated wire of the present invention. The insulated wire 1 has a rectangular conductor 11 and a thermosetting resin layer (enamel layer) 12 formed on the outer peripheral surface of the rectangular conductor 11 .
Moreover, FIG. 2 shows a cross-sectional view of another embodiment of the insulated wire of the present invention. This insulated wire 2 includes a rectangular conductor 21, a thermosetting resin layer (enamel layer) 22 formed on the outer peripheral surface of the rectangular conductor 21, and a thermoplastic resin layer formed on the outer peripheral surface of the thermosetting resin layer. (extruded layer) 23; As shown in FIGS. 1 and 2, the cross-sectional shape of the insulated wire of the present invention is substantially similar to the cross-sectional shape of the rectangular conductor.

In the present invention and this specification, the cross-sectional shape of the insulated wire including the conductor and the insulating film, which is perpendicular to the longitudinal direction of the insulated wire, may be simply referred to as the cross-sectional shape. The description of the cross-sectional shape in the present invention does not simply mean that only the cut surface has a specific shape, but that the cross-sectional shape is continuously connected in the longitudinal direction of the entire insulated wire. Unless otherwise specified, it means that the cross-sectional shape perpendicular to this direction is substantially the same for any portion of the insulated wire in its longitudinal direction.

(Gap size)
The insulated wire of the present invention has a gap of 20 μm or less in size when the surfaces of the insulated wire that satisfy (a) to (c) described later are overlapped with each other. By setting the size of the voids to 20 μm or less, partial discharge caused by the voids can be sufficiently suppressed in a dry environment, and the partial discharge inception voltage can be improved. From the same viewpoint as above, the size of the voids is preferably 15 μm or less, more preferably 10 μm or less, still more preferably 7 μm or less, and even more preferably 6 μm or less. Also, although the voids may be omitted, they are usually 0.1 μm or more, and more practically 0.2 μm or more. The size of the void means the maximum length of the void in the direction perpendicular to the plane when observing the cross section of the insulated wire with the planes superimposed. The size of this gap is substantially the same along the longitudinal direction of the insulated wire in which the surfaces are overlapped. The size of the voids is determined by the method described in the section [Examples] below.
In the present invention or in this specification, the term "surface of an insulated wire" means a surface formed by connecting the long sides or short sides of the cross-sectional shape of the insulated wire continuously in the longitudinal direction of the insulated wire. Therefore, the insulated wire of the present invention has four faces. In addition, "overlapping the surfaces" means that the surfaces are horizontally or substantially horizontally overlapped and brought into contact with each other. As a form of "overlapping faces", the faces corresponding to the long sides in the cross-sectional shape of the insulated wire may be overlapped, the faces corresponding to the short sides may be overlapped, and the faces corresponding to the long sides may be overlapped. The face and the face corresponding to the short side may be superimposed. At least two surfaces corresponding to two long sides satisfy (a) to (c) described later, and the size of the gap generated when these two surfaces are overlapped is 20 μm or less. is preferred.

<Conductor>
As the rectangular conductor used in the present invention, those conventionally used for insulated wires can be used, and examples thereof include metal conductors such as copper wires and aluminum wires. In the present invention, copper rectangular conductors are preferred. This copper is preferably low-oxygen copper with an oxygen content of 30 ppm or less, more preferably low-oxygen copper or oxygen-free copper with an oxygen content of 20 ppm or less, from the viewpoint of preventing the generation of voids during welding.
When the conductor is aluminum, various aluminum alloys can be used depending on the application, taking into account the required mechanical strength. For applications such as rotating electric machines, for example, pure aluminum with a purity of 99.00% or more is preferable because it provides a high current value.

The rectangular conductor used in the present invention has a rectangular (including square) cross-sectional shape perpendicular to the longitudinal direction. By using rectangular conductors, it is possible to increase the space factor with respect to the slots of the stator core during winding.
The size of the rectangular conductor may be set according to the application and is not particularly limited. For example, the width (long side in cross-sectional shape) can be 1.0 to 5.0 mm, and may be 1.4 to 4.0 mm, and the thickness (short side in cross-sectional shape) is 0.4 to 3.0 mm. It can be 0 mm, and may be 0.5 to 2.5 mm. Further, the rectangular conductor generally has a rectangular cross section rather than a square cross section. When the application is a rotating electric machine, the chamfering (curvature radius r) of the four corners of the cross section is preferably as small as possible from the viewpoint of increasing the conductor space factor in the slots of the stator. On the other hand, from the viewpoint of suppressing the partial discharge phenomenon due to the electric field concentration at the four corners, the radius of curvature r is preferably large. For example, the curvature radius r can be 0.6 mm or less, more preferably 0.2 to 0.4 mm.
Also, a rectangular conductor may be formed by twisting or combining a plurality of conductors.

<Insulating film>
An insulating film is formed around the conductor. This insulating coating may be a single layer or may have a multi-layer structure of two or more layers. The insulating coating in the insulated wire of the present invention preferably contains an enamel layer formed by baking varnish. It is also preferred to include an extruded layer that is extrusion coated with a thermoplastic resin.
When the insulating film has a multilayer structure, the inner layer (innermost layer) in contact with the conductor is an enamel layer (preferably a thermosetting resin layer), and an extruded layer of thermoplastic resin is provided on the outer periphery of the enamel layer. is preferred. In particular, when the innermost layer contains a thermosetting resin having an imide bond, the adhesion to the conductor and the interlayer adhesion can be further improved.

In the insulated wire of the present invention, at least one of the four faces (preferably on each of the two faces, more preferably on the two faces corresponding to the long sides or the two faces corresponding to the short sides, more preferably three faces) The insulating coating satisfies the following (a) to (c) on each side (more preferably on each of the four sides).
(a) The minimum thickness is 75 μm or more and 350 μm or less.
(b) The difference between the maximum thickness and the minimum thickness is 10 μm or less.
(c) The value obtained by dividing the minimum thickness by the maximum thickness is more than 0.900 and less than or equal to 1.000.

The thickness of the insulating coating can be determined by analyzing a cross-sectional image of the surface perpendicular to the longitudinal direction of the insulated wire using a microscope. In the measurement of the thickness of the insulating film, the straight lines along the four straight sides are used as the reference, without considering the chamfered parts (curved parts) at the four corners of the rectangular conductor cross section. Measure the thickness of the insulating film in the vertical direction.

The minimum value of the thickness of the insulating coating in (a) above is preferably 80 to 330 μm, more preferably 100 to 320 μm, more preferably 120 μm, from the viewpoint of further increasing the partial discharge inception voltage under dry conditions and improving the space factor. ~310 µm is more preferred, and 140 to 300 µm is even more preferred.
The difference between the maximum value and the minimum value of the thickness of the insulating film in (b) above is preferably 9 μm or less, more preferably 8 μm or less, more preferably 7 μm, from the viewpoint of further increasing the partial discharge inception voltage under dry conditions. The following is more preferable, 6 μm or less is more preferable, 5 μm or less is still more preferable, 4 μm or less is still more preferable, and 3 μm or less is even more preferable.
In the above (c), the value obtained by dividing the minimum value of the thickness of the insulating film by the maximum value is preferably 0.920 or more and 1.000 or less, from the viewpoint of further increasing the partial discharge inception voltage under dry conditions. 930 or more and 1.000 or less are more preferable, 0.940 or more and 1.000 or less are more preferable, 0.950 or more and 1.000 or less are still more preferable, 0.960 or more and 1.000 or less are more preferable, 0.970 or more 1.000 or less is more preferable, 0.980 or more and 1.000 or less is still more preferable, 0.985 or more and 0.999 or less is still more preferable, and 0.985 or more and 0.998 or less is still more preferable.

In the insulated wire of the present invention, the cross-sectional shape perpendicular to the longitudinal direction is a dogbone shape (a shape generated in the formation of an enamel layer, and a shape in which the insulating film at the four corners is thickened, see FIG. 3). It is also preferable to have
In addition, the value obtained by dividing the maximum thickness by the minimum thickness of the entire insulating coating is preferably less than 1.3, more preferably 1.2 or less. The maximum and minimum thicknesses of the entire insulating coating are not limited to the maximum and minimum thicknesses on the same surface, but may be the maximum and minimum thicknesses on different surfaces. may In addition, the maximum and minimum values of the thickness of the entire insulation film are the thickness of the insulation film on the flat portion excluding the corner portion (for example, in the case of a dog bone shape, the flat portion excluding the raised portion of the corner portion). is the value obtained by dividing the maximum value of by the minimum value of the thickness of the insulating film on the flat portions excluding the corner portions.

If foreign matter such as metal powder adhered to the surface of the insulated wire, fibers, resin, voids (those that swell like balloons and exist in a convex shape on the surface of the coating), the above (a) to (c) If the surfaces satisfying ) are superimposed on each other, foreign matter may cause gaps between the insulating films, which may be a factor in lowering the partial discharge inception voltage under dry conditions. Therefore, it is preferable that the surface of the insulated wire of the present invention does not substantially contain foreign substances having a height of 20 μm or more over the entire range, and more preferably substantially does not contain foreign substances having a height of 10 μm or more over the entire range. preferable.

(Enamel layer)
When the insulating coating has an enamel layer, the enamel layer may be a thermoplastic resin layer or a thermosetting resin layer, preferably a thermosetting resin layer. The resin used for forming the enamel layer is not particularly limited. For example, thermosetting resins having imide bonds such as polyimide (PI), polyamideimide (PAI), polyetherimide (PEI), and polyesterimide (PEsI), polyurethane (PU), thermosetting polyester (PEst), Type H polyester (HPE), polyimide hydantoin-modified polyester, polyhydantoin, polybenzimidazole, melamine resin, epoxy resin and the like can be mentioned, and one or more of these can be used. The enamel layer more preferably contains at least one of polyimide, polyamideimide, and polyetherimide, and is more preferably a thermosetting resin layer containing polyamideimide and/or polyimide.

The type of polyimide (PI) is not particularly limited, and ordinary polyimide such as wholly aromatic polyimide or thermosetting aromatic polyimide can be used. In addition, by a conventional method, a polyamic acid solution obtained by reacting an aromatic tetracarboxylic dianhydride and an aromatic diamine compound in a polar solvent is used, and the polyamic acid solution is imidized by heat treatment during baking. can be used.
Examples of commercially available polyimides (PI) include U-imide (trade name, manufactured by Unitika Ltd.), U-varnish (trade name, manufactured by Ube Industries, Ltd.), and the like.

The polyamideimide (PAI) has a lower thermal conductivity and a higher dielectric breakdown voltage than other resins, and can be cured by baking. The type of polyamideimide that can be used in the present invention is not particularly limited, for example, those obtained by directly reacting a tricarboxylic anhydride and a diisocyanate compound in a polar solvent, or a diamine compound to a tricarboxylic anhydride in a polar solvent. Examples include those obtained by first reacting to introduce an imide bond and then amidating with a diisocyanate compound.
Commercially available polyamideimides (PAI) include, for example, HI-406 and HCI series (both are trade names, manufactured by Hitachi Chemical Co., Ltd.).

The type of polyetherimide (PEI) is not particularly limited as long as it is a polymer having an ether bond and an imide bond in the molecule.
In addition, polyetherimide, for example, uses a polyamic acid solution obtained by reacting an aromatic tetracarboxylic dianhydride and an aromatic diamine having an ether bond in the molecule in a polar solvent, and baking during coating It is also possible to use those obtained by imidization by heat treatment.
Examples of commercially available polyetherimide (PEI) include ULTEM (trade name, manufactured by SABIC).

(extrusion layer)
It is also preferred that the insulating coating has an extruded layer. The extruded layer is an insulating layer formed by extruding and coating a thermoplastic resin. The thermoplastic resin used for the extruded layer is not particularly limited, and may be crystalline or amorphous. For example, polyamide (PA) (nylon), polyetherimide (PEI), polyacetal (POM), polycarbonate (PC), polyphenylene ether (including modified polyphenylene ether), polybutylene terephthalate (PBT), polyethylene terephthalate (PET), In addition to general-purpose engineering plastics such as polyethylene naphthalate (PEN) and ultra-high molecular weight polyethylene, polysulfone (PSF), polyethersulfone (PES), polyphenylene sulfide (PPS), polyarylate (U polymer), polyamideimide, polyetherketone (PEK), polyaryletherketone (PAEK), tetrafluoroethylene/ethylene copolymer (ETFE), polyetheretherketone (PEEK) (including modified polyetheretherketone (modified PEEK)), tetrafluoroethylene per Super engineering plastics such as fluoroalkyl vinyl ether copolymers (PFA), polytetrafluoroethylene (PTFE), thermoplastic polyimide resins (TPI), and liquid crystal polyesters can be mentioned, and one or more of these can be used. . The extruded layer is preferably a thermoplastic layer comprising polyphenylene sulfide and/or polyetheretherketone.
Examples of commercially available polyphenylene sulfide (PPS) include FZ-2100 (trade name, manufactured by DIC). Examples of commercially available polyetheretherketone (PEEK) include KetaSpire KT-820 (trade name, manufactured by Solvay Specialty Polymers).

In addition to the resins described above, the insulating film may optionally contain a foaming nucleating agent, an antioxidant, an antistatic agent, an ultraviolet inhibitor, a light stabilizer, a fluorescent whitening agent, a pigment, a dye, and a compatibilizer. , lubricants, reinforcing agents, flame retardants, cross-linking agents, cross-linking aids, plasticizers, thickeners, thinning agents and elastomers.

[Manufacturing method of insulated wire]
The insulated wire of the present invention is manufactured through a step of forming an insulating film on the outer peripheral surface of a rectangular conductor. For the formation of the insulation film, basically, any method commonly used in the formation of the insulation film of the insulated wire can be appropriately applied. For example, the enamel layer can be formed by applying and baking a varnish containing a thermosetting resin or a thermoplastic resin. The extruded layer can also be formed by extrusion coating a thermoplastic resin. At that time, as will be described later, the desired insulated wire can be obtained by controlling the insulation film on the desired surface so as to satisfy the above (a) to (c).

(Formation of enamel layer)
When part or all of the insulating coating is an enamel layer, the enamel layer can be formed by preparing a varnish (insulating varnish) of a desired resin, applying the varnish, and baking the varnish. At that time, there is a method of using a varnish coating die having a cross-sectional shape not similar to that of the rectangular conductor. By forming a non-similar shape, it is possible to create a surface that satisfies the above (b) and (c) so as to offset the resin flow and the like on the target surface.
Baking after application of the varnish can be performed by a conventional method, for example, baking can be performed in a baking furnace. The specific baking conditions depend on the shape of the furnace used, etc., and cannot be determined unambiguously. A condition in which the passing time is 10 to 90 seconds can be mentioned. In addition, the production speed (line speed) is set high from the viewpoint of more reliably suppressing the difference in the thickness of the enamel layer by suppressing the flow of the varnish after the varnish is applied (the varnish flowing and unevenly distributed). It is also preferable to

The number of repetitions of coating and baking for forming the insulating film is preferably 35 times or less, more preferably 16 times or more and 35 times or less, and further preferably 15 times or more and 30 times or less. It is preferable that the number is 18 times or more and 27 times or less. By setting the number of repetitions of coating and baking within the above range, an appropriate baking state can be achieved and the mechanical properties of each insulating layer can be improved, which is thought to improve the flexibility of the insulated wire.

(resin varnish)
The resin varnish is preferably a high-viscosity resin varnish. By using such a high-viscosity resin varnish, it is possible to suppress the flow of the varnish after application, and it is possible to form an enamel layer with a smaller thickness difference in each plane.
Further, the resin varnish contains an organic solvent (organic solvent) or the like to turn the resin into a varnish. Examples of organic solvents include amide solvents such as N,N-dimethylacetamide (DMAc), N-methyl-2-pyrrolidone (NMP), N,N-dimethylformamide (DMF), N,N-dimethylethylene urea, Urea solvents such as N,N-dimethylpropylene urea and tetramethylurea, lactone solvents such as γ-butyrolactone and γ-caprolactone, carbonate solvents such as propylene carbonate, ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone. , Ester solvents such as ethyl acetate, n-butyl acetate, butyl cellosolve acetate, butyl carbitol acetate, ethyl cellosolve acetate, ethyl carbitol acetate; glyme solvents such as diglyme, triglyme and tetraglyme; Examples include hydrocarbon solvents, phenolic solvents such as cresol, phenol, and halogenated phenols, sulfone solvents such as sulfolane, and dimethylsulfoxide (DMSO).

Among these, it is preferable that the resin varnish is mixed with an organic solvent having a low boiling point (organic solvent) from the viewpoint of promoting evaporation during baking and curing the varnish quickly.
Among these, from the viewpoint of preventing inhibition of the cross-linking reaction by heating, an aprotic solvent such as DMAc, NMP, DMF, N,N-dimethylethylene urea, N,N-dimethylpropylene urea, tetramethylurea, and DMSO is preferred.
One of the above organic solvents and the like may be used alone, or two or more thereof may be used in combination.

If necessary, the resin varnish may contain an adhesion aid, a foaming agent for foam formation, an antioxidant, an antistatic agent, an ultraviolet inhibitor, a light stabilizer, a fluorescent whitening agent, a pigment, a dye, a compatibilizer, a lubricant, and a reinforcing agent. It may contain various additives such as agents, flame retardants, cross-linking agents, co-agents, plasticizers, thickeners, thinning agents and elastomers.

(Formation of extruded layer)
A rectangular conductor or an insulated wire consisting of a rectangular conductor and an enamel layer covering its periphery is used as a core wire, and a thermoplastic resin is extrusion-coated using an extrusion die and an extruder screw similar to these to form an extruded layer. can be formed. The extrusion coating temperature can be, for example, 200-450°C. When an insulated wire composed of a rectangular conductor and an enamel layer covering the periphery thereof is used as the core wire, it is preferable that the difference between the maximum value and the minimum value of the enamel layer is suppressed to a desired small difference in the enamel layer.
The shape of the inside of the die used for extrusion coating can be determined in consideration of resin flow during extrusion coating in order to suppress the formation of weld lines and dog bones.

[Characteristics of insulated wire]
The insulated wire of the present invention is resistant to partial discharge even under dry conditions, and has a sufficiently high partial discharge inception voltage under dry conditions. In the insulated wire of the present invention, the partial discharge inception voltage under dry conditions is preferably 1,000 to 3,000 Vp, more preferably 1,200 to 3,000 Vp, still more preferably 1,250 to 3,000 Vp, and particularly preferably 1,300 to 3,000 Vp. The partial discharge inception voltage can be measured, for example, by the method described in Examples, and the drying conditions described in Examples can be used.

[Coils, Rotating Electric Machines, and Electric/Electronic Devices]
INDUSTRIAL APPLICABILITY The insulated wire of the present invention can be used as a coil in fields that require electrical properties (withstanding voltage) and heat resistance, such as rotary electric machines and various electric/electronic devices. For example, the insulated wire of the present invention can be used in motors, transformers, and the like, and can constitute high-performance rotary electric machines and electric/electronic devices. In particular, it is suitably used as windings for driving motors such as hybrid vehicles (HV) and electric vehicles (EV).

Examples of the coil of the present invention include those formed by coiling the insulated wire of the present invention, and those formed by electrically connecting predetermined portions after bending the insulated wire of the present invention.
The coil formed by coiling the insulated wire of the present invention is not particularly limited, and examples thereof include those obtained by spirally winding a long insulated wire. In such a coil, the number of turns of the insulated wire is not particularly limited. Normally, an iron core or the like is used when winding an insulated wire.
In the coil of the present invention, it is preferable that the insulated wires of the present invention are arranged so that the surfaces satisfying the above (a) to (c) are overlapped with each other. The faces are preferably faces corresponding to long sides or faces corresponding to short sides.

A coil used for a stator of a rotary electric machine or the like is exemplified as a product obtained by electrically connecting predetermined portions after bending the insulated wire of the present invention. Such a coil, for example, as shown in FIG. A coil 33 (see FIGS. 4 and 5) is made by alternately connecting two open ends (terminals) 34a such as U-shaped segments 34 .

Electric/electronic equipment using this coil is not particularly limited. A preferred embodiment of such an electric/electronic device is a transformer. Further, for example, a rotating electrical machine (particularly, a drive motor for HV and EV) having a stator 30 shown in FIGS. 4 and 5 can be used. This rotating electrical machine can have the same configuration as a conventional rotating electrical machine, except that the stator 30 is provided.
The stator 30 may be constructed similarly to conventional stators, except that the wire segments 34 are formed from the insulated wire of the present invention. That is, the stator 30 includes a stator core 31 and a wire segment 34 made of an insulated wire of the present invention as shown in FIG. A coil 33 is provided. The coil 33 is in a fixed state in which the adjacent fusion layers or the fusion layer and the slot 32 are fixed together. Here, the wire segments 34 may be installed singly in the slots 32, but are preferably installed in pairs as shown in FIG. In this stator 30 , coils 33 formed by alternately connecting open ends 34 a of wire segments 34 bent as described above are housed in slots 32 of a stator core 31 . At this time, the open ends 34a of the wire segments 34 may be connected before being housed in the slots 32, or after the insulating segments 34 are housed in the slots 32, the open ends 34a of the wire segments 34 may be bent. may be connected.

EXAMPLES The present invention will be described in more detail below based on examples, but the present invention is not limited to these embodiments.

Each insulated wire composed of a conductor and an insulating film was produced by the following method. The "average thickness" of the insulation coating described below is based on the maximum and minimum thicknesses of the insulation coatings on the overlapping surfaces [maximum thickness + minimum thickness]/2 The value calculated by

[Example 1]
As the conductor, a rectangular conductor (copper with an oxygen content of 15 ppm) having a rectangular cross section (long side 3.5 mm×short side 2.0 mm, radius of curvature of chamfered corners r=0.3 mm) was used.
Polyamideimide (PAI) varnish (model number: HI-406, manufactured by Hitachi Chemical Co., Ltd.) is applied to the surface of the conductor using a die with a cross-sectional shape that is not similar to the conductor, and the furnace temperature is set to 600 ° C. A thermosetting resin layer (first layer) with an average thickness of 80 μm was formed by passing through an 8 m long natural convection baking furnace at a speed that gave a passing time of 25 seconds, and repeating this several times. Thus, an insulated wire having an insulating coating made of an enamel layer was obtained. Of the four faces of this insulated wire, one face corresponding to the long side of the cross section was in the state of the insulation film shown in the table below (state satisfying (a) to (c) above).

[Example 2]
Insulation consisting of an enamel layer in the same manner as in Example 1 except that the resin varnish was polyimide (PI) varnish (model number: U-imide, manufactured by Unitika) and the average thickness of the resulting thermosetting resin layer was 100 μm. An insulated wire with a coating was produced. Of the four faces of this insulated wire, one face corresponding to the long side of the cross section was in the state of the insulation film shown in the table below (state satisfying (a) to (c) above).

[Example 3]
The polyimide (PI) varnish coating and baking were repeated multiple times in the same manner as in Example 2 to form a thermosetting resin layer (first layer) with an average thickness of 130 μm on the outer periphery of the conductor.
Next, on the outer periphery of the first layer, polyamideimide (PAI) varnish (model number: HI-406, manufactured by Hitachi Chemical Co., Ltd.) is applied using a die whose cross-sectional shape is not similar to the conductor, and in the furnace A thermosetting resin layer with an average thickness of 20 μm (second layer) was formed. Thus, an insulated wire having an enamel layer with an average thickness of 150 μm was obtained. Of the four faces of this insulated wire, one face corresponding to the long side of the cross section was in the state of the insulation film shown in the table below (state satisfying (a) to (c) above).

[Example 4]
As the conductor, a rectangular conductor (copper with an oxygen content of 15 ppm) having a rectangular cross section (long side 3.5 mm×short side 2.0 mm, radius of curvature of chamfered corners r=0.3 mm) was used.
Using the rectangular conductor as a core wire, using an extruder equipped with a 30 mm full-flight screw (screw L/D = 25, screw compression ratio = 3), the temperature of the extrusion die was set to 400 ° C., and the average thickness was applied to the outside of the core wire. A thermoplastic resin layer (first layer) having a thickness of 200 μm was formed. Polyetheretherketone (trade name: KetaSpire KT-820, manufactured by Solvay Specialty Polymers) was used as the thermoplastic resin. In this way, an insulated wire having an insulating coating made of an extruded layer was obtained. Of the four faces of this insulated wire, one face corresponding to the long side of the cross section was in the state of the insulation film shown in the table below (state satisfying (a) to (c) above).

[Example 5]
The application and baking of polyamide-imide (PAI) varnish were repeated multiple times in the same manner as in Example 1 to form a thermosetting resin layer (first layer) having an average thickness of 50 μm on the outer periphery of the conductor.
Next, on the outer periphery of the first layer, polyphenylene sulfide (trade name: FZ-2100, manufactured by DIC) was extrusion-coated in the same manner as the extrusion layer formation in Example 4, and a thermoplastic resin having an average thickness of 150 μm was formed. A resin layer (second layer) was formed. Thus, an insulated wire having an insulating coating (thermosetting resin layer and thermoplastic resin layer) with an average thickness of 200 μm was obtained. Of the four faces of this insulated wire, one face corresponding to the long side of the cross section was in the state of the insulation film shown in the table below (state satisfying (a) to (c) above).

[Example 6]
Enamel was performed in the same manner as in Example 1 except that polyetherimide (PEI) varnish (model number: ULTEM, manufactured by SABIC) was used as the resin varnish and the average thickness of the resulting thermoplastic resin layer (enamel layer) was 5 μm. A layer (first layer) was formed.
Then, on the outer periphery of the first layer, polyether ether ketone (trade name: KetaSpire KT-820, manufactured by Solvay Specialty Polymers) was extrusion-coated in the same manner as the formation of the extrusion layer in Example 4, and the average A thermoplastic resin layer (second layer) having a thickness of 295 μm was formed. Thus, an insulated wire having an insulating film (a thermoplastic resin layer and a thermoplastic resin layer) with an average thickness of 300 μm was obtained. Of the four faces of this insulated wire, one face corresponding to the long side of the cross section was in the state of the insulation film shown in the table below (state satisfying (a) to (c) above).

[Example 7]
Enamel was prepared in the same manner as in Example 6, except that polyimide (PI) varnish (model number: U-imide, manufactured by Unitika) was used as the resin varnish, and the resulting thermosetting resin layer (enamel layer) had an average thickness of 50 µm. A layer (first layer) was formed.
Then, on the outer periphery of the first layer, polyether ether ketone (trade name: KetaSpire KT-820, manufactured by Solvay Specialty Polymers) was extrusion-coated in the same manner as the formation of the extrusion layer in Example 4, and the average A thermoplastic resin layer (second layer) having a thickness of 250 μm was formed. Thus, an insulated wire having an insulating coating (thermosetting resin layer and thermoplastic resin layer) with an average thickness of 300 μm was obtained. Of the four faces of this insulated wire, one face corresponding to the long side of the cross section was in the state of the insulation film shown in the table below (state satisfying (a) to (c) above).

[Comparative Example 1]
An enamel layer was formed in the same manner as in Example 1, except that a die with a cross-sectional shape similar to that of the conductor was used, and the maximum, minimum, and average thicknesses of the enamel layer were as shown in Table 1. An insulated wire having an insulating film consisting of was obtained. This insulated wire was in the state of the insulating film shown in the table below on the two sides corresponding to the long sides.

[Comparative Example 2]
An insulated wire having an insulating coating made of an enamel layer was obtained in the same manner as in Example 1 except that the maximum value, minimum value and average thickness of the enamel layer were set as shown in Table 1. This insulated wire was in the state of the insulating film shown in the table below on all of the two sides corresponding to the long sides.

Evaluation of partial discharge inception voltage (PDIV) and measurement of voids were performed as follows for each of the insulated wires produced above. The obtained results are summarized in Table 1 below.
In the insulated wires of Examples 1 to 7 produced above, the values obtained by dividing the maximum value of the thickness of the entire insulating coating by the minimum value were all 1.2 or less.

<Measurement of void size>
Two insulated wires each of Examples 1 to 7 and Comparative Examples 1 and 2 were prepared (one insulated wire was cut into two wires), and when stretched by 1%, the cross-sectional shape was measured in the longitudinal direction. The surfaces corresponding to the long sides of (in each example, the surfaces that satisfy the above (a) to (c)) are superimposed in parallel, and two clips (product name: double clip, product number: Cree-34, manufactured by Kokuyo Co., Ltd. ) were used to hold the insulated wires at a position where the distance between the clips was 25 mm, and the superimposed insulated wires were fixed. The space between the clips is embedded in epoxy resin, and the short side of the cross-sectional shape of the insulated wire is rotated using a rotating polishing machine (LaboPol-30 (polishing machine), LaboForce-100 (sample rotating device), both manufactured by Struers). The corresponding face side was ground parallel to that face to expose a cross-section of the two insulated wires located between the clips. Using a microscope (product name: DVM5000HD, manufactured by Leica), this cross section was observed at a magnification of 400 to measure the distance between the insulated wires. Polishing and measurement of the distance between the insulated wires were repeated, and the distance when the distance between the insulated wires reached its maximum was taken as the size of the gap.
The gripping force of the clip used for the above measurement was approximately 2 kg.

<Evaluation of partial discharge inception voltage (PDIV)>
A partial discharge measuring device "DAC-PD-3" (manufactured by Soken Denki Co., Ltd., trade name) was used to measure the partial discharge inception voltage of each of the manufactured insulated wires. Prepare two insulated wires each of Examples 1 to 7 and Comparative Examples 1 and 2 (one insulated wire is cut into two wires), and correspond to the long side of the cross-sectional shape in the longitudinal direction. A sample was prepared by overlapping surfaces (surfaces satisfying the above (a) to (c) in each example) over a length of 150 mm. An electrode was connected between the two conductors, and a 1 kHz sinusoidal AC voltage was applied for measurement. The voltage peak value (peak voltage, Vp) at the time when partial discharges of 100 pC or more occurred 1000 times or more per second was recorded as the partial discharge inception voltage.
The temperature and humidity of the measurement environment were dry conditions (25° C., 20% RH (relative humidity)). Here, since the partial discharge inception voltage also depends on the thickness of the insulating film and the dielectric constant of the film material, the partial discharge inception voltage under wet conditions (25 ° C., 65% RH) was also measured in the same manner, and under dry conditions, was divided by the partial discharge inception voltage under wet conditions, the rate of increase in the partial discharge inception voltage due to the dry environment was calculated. The increase rate of the obtained partial discharge inception voltage was evaluated based on the following evaluation criteria. In the following evaluation criteria, "X" is the partial discharge inception voltage measured under the conditions of 25 ° C. and 20% RH (dry conditions), and "Y" is the condition of 25 ° C. and 65% RH (wet conditions). bottom), and "X/Y" indicates the increase rate of the partial discharge inception voltage due to the dry environment. Under any of the above measurement conditions, each insulated wire used for measurement was allowed to stand for 60 minutes in a constant temperature bath held at 110 ° C immediately before measurement to dry the insulating film (moisture in the insulating film removed), and the partial discharge inception voltage was measured immediately after the insulated wire cooled to about room temperature.
The partial discharge inception voltages of Examples 1 to 7 under dry conditions were all sufficiently high values.

-Evaluation criteria-
A+: The value of X/Y is 1.1 or more A: The value of X/Y is 1.06 or more and less than 1.1 B: The value of X/Y is 1.03 or more and less than 1.06 C: X/ Y value less than 1.03

As shown in Table 1 above, it was found that the insulated wires (Examples 1-7) satisfying all the requirements of the present invention exhibited a higher partial discharge inception voltage under dry conditions than under wet conditions.

1, 2 Insulated wires 11, 21 Rectangular conductors 12, 22 Thermosetting resin layer (enamel layer)
23 Thermoplastic resin layer (extrusion layer)
14 Maximum value of film thickness 15 Minimum value of film thickness 16 Size of gap (gap distance)
30 stator 31 stator core 32 slot 33 coil 34 wire segment 34a open end

Claims (11)

An insulated wire having a rectangular conductor and an insulating coating covering the outer periphery of the rectangular conductor,
A radius of curvature of four corners of a cross section of the rectangular conductor is 0.2 to 0.4 mm,
the insulating coating comprises an extruded layer;
On at least one surface of the insulated wire, the insulating coating satisfies the following (a) to (c):
(a) the minimum thickness is 299 μm or more and 350 μm or less;
(b) the difference between the maximum and minimum thickness is 10 μm or less;
(c) the value obtained by dividing the minimum thickness by the maximum thickness is greater than 0.900 and less than or equal to 1.000;
An insulated wire, wherein a gap of 20 μm or less is generated when the surfaces satisfying the above (a) to (c) are overlapped with each other. An insulated wire having a rectangular conductor and an insulating coating covering the outer periphery of the rectangular conductor,
When the flat conductor is a copper wire, the copper wire is made of oxygen-free copper, and the radius of curvature of the four corners of the cross section of the flat conductor is 0.2 to 0.4 mm,
On at least one surface of the insulated wire, the insulating coating satisfies the following (a) to (c):
(a) the minimum thickness is 299 μm or more and 350 μm or less;
(b) the difference between the maximum and minimum thickness is 10 μm or less;
(c) the value obtained by dividing the minimum thickness by the maximum thickness is greater than 0.900 and less than or equal to 1.000;
An insulated wire, wherein a gap of 20 μm or less is generated when the surfaces satisfying the above (a) to (c) are overlapped with each other. 3. The insulated wire of claim 2, wherein said insulation coating comprises an extruded layer. The insulated wire according to claim 1 or 3, wherein the extruded layer is a thermoplastic resin layer containing polyphenylene sulfide and/or polyetheretherketone. The insulated wire according to any one of claims 1 to 4 , wherein said insulating coating includes an enamel layer. The insulated wire according to claim 5 , wherein the enamel layer is a thermosetting resin layer containing polyamideimide and/or polyimide. The insulated wire according to claim 1 or 2 , wherein the insulating coating has an enamel layer covering the conductor and an extruded layer covering the enamel layer. The insulated wire according to claim 7 , wherein the enamel layer is a thermosetting resin layer containing polyamideimide and/or polyimide, and the extruded layer is a thermoplastic resin layer containing polyphenylene sulfide and/or polyetheretherketone. A coil using the insulated wire according to any one of claims 1 to 8 . 10. The coil according to claim 9 , wherein the insulated wires are arranged so that the surfaces satisfying the conditions (a) to (c) are overlapped. A rotary electric machine, electric/electronic equipment, comprising the coil according to claim 9 or 10 .

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