Insulating material for stator, stator, and method for manufacturing a stator

Abstract

The present invention provides a stator insulating material suitably applicable to a stator having a high-density coil, as well as a stator having a coil insulated by the stator insulating material and a method for manufacturing the same. [Solution] The stator insulating material contains epoxy resin, a curing agent, and spherical inorganic fillers, and is used for insulating between the coils of the stator.

Description

Technical Field

[0001] The present disclosure relates to an insulating material for a stator, a stator, and a method for manufacturing a stator.

Background Art

[0002] Conventionally, a method using varnish has been generally used to fix the coils of a stator in a motor. For example, Patent Document 1 describes a configuration of a stator in which insulating paper is provided between a coil and a tooth, and the insulating paper and the coil are impregnated with varnish and cured.

[0003] In addition, a method of molding between a coil and a core with resin has also been proposed. For example, Patent Document 2 discloses a stator manufactured by fitting a coil and a core together and integrally molding the coil and the core by resin-molding between the coil and the core and the end face of the coil side.

[0004] Patent Document 3 describes a method of constructing a stator by fixing a coil and a stator core with a resin molding part using a synthetic resin such as an epoxy resin.

[0005] Patent Document 4 discloses a stator composed of a cured product of a thermosetting resin composition. Further, it is disclosed that the thermosetting resin composition contains one or more thermosetting resins selected from the group consisting of a phenol resin, an epoxy resin, and an unsaturated polyester resin, and an inorganic filler.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

[0007] On the other hand, in recent years, motors for vehicles such as hybrid and electric vehicles have been increasingly pursued for higher performance, with the aim of increasing output and improving fuel efficiency. In addition, there is a growing demand for smaller motors to secure more interior space, reduce vehicle weight, and lower costs. Along with the increased performance and miniaturization of motors, the number of turns is increasing due to higher coil density, and the gap between coils is narrowing. However, with current technology, no insulating materials have been considered that can handle high coil density while ensuring excellent insulation.

[0008] This disclosure relates to an insulating material for stators suitably applicable to stators having high-density coils, and to a stator having coils insulated by the insulating material for stators and a method for manufacturing the same. [Means for solving the problem]

[0009] The means for solving the above problems include the following embodiments. <1> A stator insulating material containing epoxy resin, a hardening agent, and spherical inorganic fillers, used for insulating between coils of a stator. <2> The curing agent includes a phenol curing agent. <1> Stator insulating material as described above. <3> The inorganic filler comprises at least one selected from the group consisting of silica, alumina, and magnesium oxide. <1> or <2> Stator insulating material as described above. <4> The inorganic filler content is 50% by mass or more relative to the total mass of the stator insulating material. <1> ~ <3> Stator insulating material as described in any one of the items. <5> The inorganic filler content is 70% by mass or more relative to the total mass of the stator insulating material. <4> Stator insulating material as described above. <6> The inorganic filler content is 80% by mass or more relative to the total mass of the stator insulating material. <5> Stator insulating material as described above. <7> The maximum particle size of the inorganic filler is 100 μm or less. <1> ~ <6> Stator insulating material as described in any one of the items. <8> The inorganic filler has an average aspect ratio of 0.8 to 1.0 when observed with a scanning electron microscope. <1> ~ <7> Stator insulating material as described in any one of the items. <9> <1> ~ <8> A stator having coils insulated with the stator insulating material described in any one of the items. <10> <1> ~ <8> A method for manufacturing a stator, comprising insulating the coils with an insulating material for stators as described in any one of the items. <11> The insulation between the coils is performed by transfer molding. <10> A method for manufacturing a stator as described above. <12> A method for using an insulating material containing epoxy resin, a hardening agent, and spherical inorganic fillers for insulation between stator coils. [Effects of the Invention]

[0010] This disclosure provides an insulating material for stators suitably applicable to stators having high-density coils, as well as a stator having coils insulated by the insulating material for stators and a method for manufacturing the same. [Modes for carrying out the invention]

[0011] The embodiments for carrying out the present invention will be described in detail below. However, the present invention is not limited to the following embodiments. In the following embodiments, the components (including elemental steps, etc.) are not essential unless otherwise specified. The same applies to numerical values ​​and their ranges, and they do not limit the present invention.

[0012] In this disclosure, the term "process" includes not only processes that are independent of other processes, but also processes that cannot be clearly distinguished from other processes, provided that the purpose of such process is achieved. In this disclosure, the numerical range indicated using "~" includes the numbers before and after "~" as the minimum and maximum values, respectively. In numerical ranges described in stages within this disclosure, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range described in stages. Furthermore, in numerical ranges described within this disclosure, the upper or lower limit of that range may be replaced with the values ​​shown in the examples. In this disclosure, each component may contain multiple types of the corresponding substance. If multiple types of the substance corresponding to each component are present in the composition, the content or amount of each component means the total content or amount of the multiple types of substances present in the composition, unless otherwise specified. In this disclosure, each component may contain multiple types of particles. If multiple types of particles corresponding to each component are present in the composition, the particle size of each component refers to the value for a mixture of such multiple types of particles present in the composition, unless otherwise specified. In this disclosure, the term "layer" includes cases where, when observing the region in which the layer exists, it is formed not only over the entire region but also over only a portion of the region.

[0013] <<Insulating material for stator>> The stator insulating material disclosed herein contains an epoxy resin, a curing agent, and spherical inorganic fillers, and is used for insulating between coils of a stator. The inventors attempted to develop an insulating material capable of obtaining excellent insulation between coils, and found that an insulating material containing an epoxy resin, a curing agent, and spherical inorganic fillers has excellent performance in terms of filling properties and dimensional stability, and is therefore suitable for insulating between coils of a stator. In this disclosure, insulation means electrical insulation.

[0014] The insulating material for the stator of the present disclosure may contain a resin material other than an epoxy resin and a curing agent (i.e., a curing agent for the epoxy resin). However, from the viewpoint of particularly well exhibiting effects such as dimensional stability, the total content ratio of the epoxy resin and the curing agent (i.e., a curing agent for the epoxy resin) in the components excluding the inorganic filler in the insulating material for the stator is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more. For example, when a phenolic curing agent is used as the curing agent, the total content ratio of the epoxy resin and the phenolic curing agent in the components excluding the inorganic filler in the insulating material for the stator is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more. Hereinafter, the components excluding the inorganic filler in the insulating material for the stator may be referred to as "resin components" for convenience. Hereinafter, each component of the insulating material for the stator of the present disclosure will be described in detail.

[0015] <Epoxy resin> The insulating material for the stator of the present disclosure contains an epoxy resin. The type of the epoxy resin is not particularly limited as long as it has an epoxy group in the molecule. The epoxy resin may be solid or liquid at normal temperature and normal pressure (for example, 25 °C, atmospheric pressure), and is preferably solid. Specifically, the epoxy resins include: novolac-type epoxy resins (phenol novolac-type epoxy resins, orthocresol novolac-type epoxy resins, etc.) obtained by condensing or co-condensing a novolac resin (phenol novolac-type epoxy resins, orthocresol novolac-type epoxy resins, etc.) obtained by condensing or co-condensing a novolac resin (phenol novolac-type epoxy resins, orthocresol novolac-type epoxy resins, etc.) obtained by condensing or co-condensing the above phenolic compound with an aromatic aldehyde compound (benzaldehyde, salicylaldehyde, etc.) under an acidic catalyst; triphenylmethane-type epoxy resins obtained by condensing or co-condensing a triphenylmethane-type phenolic resin (phenol novolac-type epoxy resins, orthocresol novolac-type epoxy resins, etc.) obtained by condensing or co-condensing the above phenolic compound with an aromatic aldehyde compound (benzaldehyde, salicylaldehyde, etc.) under an acidic catalyst; and novolac resins obtained by co-condensing the above phenolic compound and naphthol compound with an aldehyde compound under an acidic catalyst. Copolymer epoxy resins that are epoxidized fats; diphenylmethane type epoxy resins that are diglycidyl ethers of bisphenol A, bisphenol F, etc.; biphenyl type epoxy resins that are diglycidyl ethers of alkyl-substituted or unsubstituted biphenols; stilbene type epoxy resins that are diglycidyl ethers of stilbene-based phenol compounds; sulfur atom-containing epoxy resins that are diglycidyl ethers of bisphenol S, etc.; epoxy resins that are glycidyl ethers of alcohols such as butanediol, polyethylene glycol, and polypropylene glycol; glycidyl ester type epoxy resins that are glycidyl esters of polycarboxylic acid compounds such as phthalic acid, isophthalic acid, and tetrahydrophthalic acid; glycidylamine type epoxy resins in which the active hydrogen bonded to the nitrogen atom of aniline, diaminodiphenylmethane, isocyanuric acid, etc. is replaced with a glycidyl group; dicyclopentadiene type epoxy resins that are epoxidized from a copolymer resin of dicyclopentadiene and a phenol compound;Vinylcyclohexene diepoxide obtained by epoxidizing the olefin bond in the molecule, alicyclic epoxy resins such as 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, 2-(3,4-epoxy)cyclohexyl-5,5-spiro(3,4-epoxy)cyclohexane-m-dioxane; Paraxylylene-modified epoxy resin which is a glycidyl ether of paraxylylene-modified phenolic resin; Metaaxylylene-modified epoxy resin which is a glycidyl ether of metaaxylylene-modified phenolic resin; Terpene-modified epoxy resin which is a glycidyl ether of terpene-modified phenolic resin; Dicyclopentadiene-modified epoxy resin which is a glycidyl ether of dicyclopentadiene-modified phenolic resin; Cyclopentadiene-modified epoxy resin which is a glycidyl ether of cyclopentadiene-modified phenolic resin; Polycyclic aromatic ring-modified epoxy resin which is a glycidyl ether of polycyclic aromatic ring-modified phenolic resin; Naphthalene-type epoxy resin which is a glycidyl ether of naphthalene ring-containing phenolic resin; Halogenated phenolic novolak-type epoxy resin; Hydroquinone-type epoxy resin; Trimethylolpropane-type epoxy resin; Linear aliphatic epoxy resin obtained by oxidizing the olefin bond with a peracid such as peracetic acid; Aralkyl-type epoxy resin obtained by epoxidizing aralkyl-type phenolic resins such as phenol aralkyl resin and naphthol aralkyl resin; etc. are mentioned. Furthermore, epoxy compounds of silicone resins, epoxy compounds of acrylic resins, etc. are also mentioned as epoxy resins. The epoxy resin may be used alone or in combination of two or more.; Among them, preferred epoxy resins from the viewpoint of mechanical strength include polyfunctional epoxy resins such as triphenylmethane-type epoxy resins.;

[0016] The epoxy equivalent (molecular weight / number of epoxy groups) of the epoxy resin is not particularly limited. From the viewpoint of mechanical strength, the epoxy equivalent of the epoxy resin is preferably 100 g / eq to 1000 g / eq, and more preferably 150 g / eq to 500 g / eq.;

[0017] The epoxy equivalent of the epoxy resin shall be the value measured according to the method conforming to JIS K 7236:2009.

[0018] When the epoxy resin is solid, its softening point or melting point is not particularly limited. From the viewpoint of moldability, the softening point or melting point of the epoxy resin is preferably 40°C to 180°C, and from the viewpoint of ease of handling when preparing the insulating material for the stator, it is more preferably 50°C to 130°C.

[0019] The melting point of the epoxy resin shall be the value measured by differential scanning calorimetry (DSC), and the softening point of the epoxy resin shall be the value measured by the method (ring-ball method) in accordance with JIS K 7234:1986.

[0020] The epoxy resin content is not particularly limited. From the viewpoint of fluidity, fillability, etc., the epoxy resin content is preferably 5% by mass or more, and preferably 8% by mass or more, based on the total mass of the stator insulating material. Furthermore, from the viewpoint of mechanical strength, etc., the epoxy resin content is preferably 20% by mass or less, and more preferably 15% by mass or less, based on the total mass of the stator insulating material. From this viewpoint, the epoxy resin content is preferably 5% to 20% by mass, more preferably 8% to 15% by mass, and may also be 8% to 12% by mass, or 10% to 15% by mass, based on the total mass of the stator insulating material.

[0021] <Hardening agent> The stator insulating material contains a curing agent. The curing agent is not particularly limited as long as it can react with the epoxy groups of the epoxy resin to cure the epoxy resin. Examples of curing agents include phenol curing agents (compounds having phenolic hydroxyl groups in their molecules), amine curing agents, acid anhydride curing agents, polymer captan curing agents, polyaminoamide curing agents, isocyanate curing agents, and blocked isocyanate curing agents. From the viewpoint of heat resistance, high strength, and filling properties, a phenol curing agent is preferred. The curing agent may be solid or liquid at 25°C and atmospheric pressure, but it is preferably solid.

[0022] Specifically, the phenol curing agents include polyhydric phenol compounds such as resorcinol, catechol, bisphenol A, bisphenol F, and substituted or unsubstituted biphenols; novolac-type phenolic resins obtained by condensing or co-condensing at least one phenolic compound selected from the group consisting of phenol compounds such as phenol, cresol, xylenol, resorcinol, catechol, bisphenol A, bisphenol F, phenylphenol, aminophenol, and naphthol compounds such as α-naphthol, β-naphthol, and dihydroxynaphthalene, with aldehyde compounds such as formaldehyde, acetaldehyde, and propionaldehyde under an acidic catalyst; and compounding the above phenolic compounds with dimethoxyp-xylene, bis(methoxymethyl)biphenyl, etc. Examples include aralkyl-type phenolic resins such as phenol aralkyl resins and naphthol aralkyl resins; paraxylylene and / or metaxylylene-modified phenolic resins; melamine-modified phenolic resins; terpene-modified phenolic resins; dicyclopentadiene-type phenolic resins and dicyclopentadiene-type naphthol resins synthesized by copolymerization of the above phenolic compound and dicyclopentadiene; cyclopentadiene-modified phenolic resins; polycyclic aromatic ring-modified phenolic resins; biphenyl-type phenolic resins; triphenylmethane-type phenolic resins obtained by condensation or co-condensation of the above phenolic compound and aromatic aldehyde compounds such as benzaldehyde and salicylaldehyde under an acidic catalyst; and phenolic resins obtained by copolymerizing two or more of these. The phenolic curing agent may be used alone or in combination of two or more. A preferred phenolic resin from the viewpoint of curability and mechanical strength is novolac-type phenolic resin.

[0023] The functional group equivalent of the curing agent (hydroxyl group equivalent in the case of a phenol curing agent, and active hydrogen equivalent in the case of an amine curing agent) is not particularly limited. From the viewpoint of mechanical strength, the functional group equivalent of the curing agent is preferably 70 g / eq to 1000 g / eq, and more preferably 80 g / eq to 500 g / eq.

[0024] In the case of phenolic curing agents, the hydroxyl group equivalent refers to the value calculated based on the hydroxyl value measured in accordance with JIS K0070:1992. In the case of amine-based curing agents, the active hydrogen equivalent refers to the value calculated based on the amine value measured in accordance with JIS K7237:1995.

[0025] If the curing agent is solid, its softening point or melting point is not particularly limited. From the viewpoint of moldability, the softening point or melting point of the curing agent is preferably 40°C to 180°C, and from the viewpoint of handlingability of the stator insulating material, it is more preferably 50°C to 130°C.

[0026] The melting point or softening point of the curing agent shall be a value measured in the same manner as the melting point or softening point of the epoxy resin.

[0027] The equivalent ratio of epoxy resin to curing agent, i.e., the ratio of the number of functional groups in the curing agent to the number of epoxy groups in the epoxy resin (number of functional groups in curing agent / number of epoxy groups in epoxy resin), is not particularly limited. From the viewpoint of minimizing unreacted components, the equivalent ratio of epoxy resin to curing agent is preferably set in the range of 0.5 to 2.0, and more preferably in the range of 0.6 to 1.3. From the viewpoint of moldability, it is even more preferable that the equivalent ratio of epoxy resin to curing agent is set in the range of 0.8 to 1.2.

[0028] <Inorganic filler> The stator insulating material contains spherical inorganic fillers. In the inorganic fillers of this disclosure, "spherical" includes not only perfectly spherical particles but also ellipsoidal or nearly spherical particles, and the surface may have irregularities, and there may be voids within the particles. In the case of ellipsoidal or nearly spherical particles, the spherical inorganic fillers shall include particles with a circularity of 0.8 to 1.0 as observed by a scanning electron microscope (SEM). In this disclosure, the "circularity" of an inorganic filler is a value calculated using the following formula. The closer the circularity is to 1, the closer the particle shape is to a perfect circle. Roundness = 4π × (area) ÷ (perimeter)2 Area: Area of ​​the particle determined by SEM observation. Perimeter: The perimeter of the particle determined by SEM observation.

[0029] The average circularity of the spherical inorganic filler observed by SEM is preferably 0.8 to 1.0, and more preferably 0.9 to 1.0. The average circularity is the arithmetic mean of the circularity of 100 particles arbitrarily selected from the SEM image. The circularity of the inorganic filler can be calculated using known image analysis methods as needed.

[0030] The stator insulating material of this disclosure may contain inorganic fillers having shapes other than spherical (plate-shaped, needle-shaped, fibrous, polygonal, etc.), but from the viewpoint of further improving filling properties and mechanical strength, the content of spherical inorganic fillers in the total inorganic filler is preferably 50% or more, more preferably 70% or more, and preferably 90% or more. The above-mentioned ratio of spherical inorganic fillers based on the number of particles is the ratio of spherical particles in 1000 particles randomly selected from an SEM image of the inorganic filler.

[0031] The average aspect ratio of the above-mentioned spherical inorganic filler in SEM observation is preferably 0.8 to 1.0, and more preferably 0.9 to 1.0. In this disclosure, the "aspect ratio" of the inorganic filler refers to the value obtained by dividing the length of the short axis of the particle by the length of the long axis (short axis / long axis). Furthermore, the average aspect ratio of the inorganic filler is the arithmetic mean of the aspect ratios of 100 particles randomly selected from the SEM image of the inorganic filler. The aspect ratio of the inorganic filler can be calculated from the image of the inorganic filler using known image analysis means as necessary.

[0032] The type of inorganic filler is not particularly limited. For example, examples of inorganic fillers include silica such as fused silica and crystalline silica, glass, alumina, calcium carbonate, zirconium silicate, calcium silicate, silicon nitride, aluminum nitride, boron nitride, magnesium oxide, beryllia, zirconia, zircon, fossilite, steatite, spinel, mullite, titania, talc, clay, mica, and other fine powders, or beads made by shaping these into spheres. Inorganic fillers with flame retardant properties may also be used. Examples of inorganic fillers with flame retardant properties include aluminum hydroxide, magnesium hydroxide, composite metal hydroxides such as magnesium and zinc hydroxide, and zinc borate.

[0033] In particular, from the viewpoint of moldability, it is preferable that the inorganic filler includes at least one selected from the group consisting of silica, alumina, and magnesium oxide. When the inorganic filler includes at least one selected from the group consisting of silica, alumina, and magnesium oxide, the total amount of the at least one selected from the group consisting of silica, alumina, and magnesium oxide is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more, based on the total mass of the inorganic filler.

[0034] The content of the inorganic filler is not particularly limited, but is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, and may be 80% by mass or more, relative to the total mass of the stator insulating material. When the content of the inorganic filler is 50% by mass or more relative to the total mass of the stator insulating material, the insulation between coils tends to be further improved. It also tends to reduce water absorption and improve chemical resistance. From the viewpoint of ensuring fluidity during molding and improving the ability to fill voids, the content of the inorganic filler is preferably 95% by mass or less, more preferably 90% by mass or less, even more preferably 85% by mass or less, and may be 80% by mass or less, relative to the total mass of the stator insulating material. From the above perspective, the content of the inorganic filler is preferably 50% to 95% by mass, more preferably 60% to 90% by mass, even more preferably 70% to 90% by mass, particularly preferably 70% to 85% by mass, and may also be 70% to 80% by mass or 80% to 90% by mass, based on the total mass of the insulating material for the stator.

[0035] When the insulating material for the stator is cured, the inorganic filler content in the cured material can be measured as follows: First, the total mass of the cured material is measured. The thermosetting material is then fired at 400°C for 2 hours, and then at 700°C for 3 hours to evaporate the resin components, and the mass of the remaining inorganic filler is measured. The ratio of the mass of the inorganic filler to the total mass of the cured material is obtained and defined as the inorganic filler content.

[0036] The average particle size of the inorganic filler is not particularly limited. From the viewpoint of filling into narrow gaps, the average particle size of the inorganic filler is preferably 50 μm or less, more preferably 30 μm or less, and even more preferably 20 μm or less. Furthermore, from the viewpoint of the mechanical strength of the cured product, the average particle size of the inorganic filler is preferably 5 μm or more, more preferably 10 μm or more, and even more preferably 15 μm or more. From this viewpoint, the average particle size of the inorganic filler is preferably 5 μm to 50 μm, more preferably 10 μm to 30 μm, even more preferably 10 μm to 20 μm, and particularly preferably 15 μm to 20 μm. The average particle size of the inorganic filler can be measured as the particle size (D50) when the cumulative amount from the small diameter side reaches 50% in the volume-based particle size distribution measured by a laser scattering diffraction particle size distribution analyzer.

[0037] From the viewpoint of filling narrow gaps and the resulting mechanical strength of the cured product, the maximum particle size of the inorganic filler is preferably 100 μm or less, more preferably 80 μm or less, even more preferably 60 μm or less, and may also be 50 μm or less. The maximum particle diameter can be measured as the particle diameter (D99) at which the cumulative total from the smaller diameter side reaches 99% in the volume-based particle size distribution measured by a laser scattering diffraction particle size distribution analyzer.

[0038] <Other ingredients> The stator insulating material may contain epoxy resin, a curing agent, and an inorganic filler, as well as various additives. Examples of additives include curing accelerators, coupling agents, ion exchangers, mold release agents, flame retardants, colorants, stress relievers, and adhesion promoters.

[0039] (Curing accelerator) The stator insulating material may contain a curing accelerator. The type of curing accelerator is not particularly limited and includes imidazoles such as 2-ethyl-4-methylimidazole and 2-phenylimidazole; tertiary amines such as 1,8-diazabicyclo[5.4.0]-7-undecene; phosphonium salts such as tetra-n-butylphosphonium tetraphenylborate; and triphenylphosphine. The curing accelerator may be used alone or in combination of two or more types.

[0040] If the stator insulating material contains a curing accelerator, the amount of curing accelerator is preferably 0.1 to 30 parts by mass, and more preferably 1 to 15 parts by mass, per 100 parts by mass of the resin component.

[0041] (Coupling agent) The stator insulating material may contain a coupling agent from the viewpoint of improving the compatibility between the resin component and the inorganic filler, and improving adhesion to the substrate. Examples of coupling agents include silane compounds such as epoxysilane, phenylsilane, mercaptosilane, aminosilane, phenylaminosilane, alkylsilane, ureidosilane, and vinylsilane, as well as titanium compounds, aluminum chelate compounds, and aluminum / zirconium compounds. The coupling agent may be used alone or in combination of two or more types.

[0042] If the stator insulating material contains a coupling agent, the amount of the coupling agent is preferably 0.05 to 5 parts by mass, and more preferably 0.1 to 2.5 parts by mass, per 100 parts by mass of the inorganic filler.

[0043] (Ion exchanger) The stator insulating material may contain an ion exchanger to improve moisture resistance, heat resistance, and other properties. The type of ion exchanger is not particularly limited and includes hydrotalcite compounds and hydrated oxides of at least one element selected from the group consisting of magnesium, aluminum, titanium, zirconium, and bismuth. One type of ion exchanger may be used alone, or two or more types may be used in combination.

[0044] If the stator insulating material contains an ion exchanger, the amount is not particularly limited. For example, the amount of ion exchanger is preferably 0.1 to 30 parts by mass, and more preferably 1 to 15 parts by mass, per 100 parts by mass of the resin component.

[0045] (Release agent) The insulating material for the stator may contain a release agent to obtain good release properties from the mold during molding. The type of release agent is not particularly limited and includes carnauba wax, higher fatty acids such as montanic acid and stearic acid, higher fatty acid metal salts, ester waxes such as montanic acid esters, and polyolefin waxes such as oxidized polyethylene and non-oxidized polyethylene. The release agent may be used alone or in combination of two or more types.

[0046] If the insulating material for the stator contains a release agent, its content is not particularly limited. For example, the release agent content is preferably 0.01 to 15 parts by mass, more preferably 0.1 to 10 parts by mass, and may be 0.1 to 5 parts by mass, or 0.1 to 3 parts by mass, per 100 parts by mass of the resin component. When the amount of release agent is 0.01 parts by mass or more per 100 parts by mass of the resin component, sufficient release properties tend to be obtained. When the amount of release agent is 15 parts by mass or less per 100 parts by mass of the resin component, better adhesion tends to be obtained.

[0047] (Flame retardant) The stator insulating material may contain a flame retardant. The type of flame retardant is not particularly limited and includes organic or inorganic compounds containing halogen atoms, antimony atoms, nitrogen atoms, or phosphorus atoms, metal hydroxides, etc. One type of flame retardant may be used alone, or two or more types may be used in combination.

[0048] If the stator insulating material contains a flame retardant, the amount is not particularly limited. For example, the amount of flame retardant is preferably 1 to 300 parts by mass, and more preferably 2 to 150 parts by mass, per 100 parts by mass of the resin component.

[0049] (Coloring agent) The stator insulating material may contain a coloring agent. The type of coloring agent is not particularly limited and examples include carbon black, organic dyes, organic pigments, titanium dioxide, red lead, and red iron oxide. One coloring agent may be used alone, or two or more may be used in combination. The amount of coloring agent may be appropriately selected depending on the purpose.

[0050] (Stress reliever) The stator insulating material may contain a stress-relieving agent. The type of stress-relieving agent is not particularly limited and includes thermoplastic elastomers such as silicone-based, styrene-based, olefin-based, urethane-based, polyester-based, polyether-based, polyamide-based, and polybutadiene-based; rubber particles such as NR (natural rubber), NBR (acrylonitrile-butadiene rubber), acrylic rubber, urethane rubber, and silicone powder; and rubber particles having a core-shell structure such as methyl methacrylate-styrene-butadiene copolymer (MBS), methyl methacrylate-silicone copolymer, and methyl methacrylate-butyl acrylate copolymer. One type of stress-relieving agent may be used alone, or two or more types may be used in combination. The content of the stress-relieving agent may be appropriately selected depending on the purpose.

[0051] (Adhesion-enhancing agent) The stator insulating material may contain an adhesion promoter to improve adhesion to the metal and improve insulation properties. The type of adhesion promoter is not particularly limited, and examples include compounds having carboxyl groups, hydroxyl groups, amino groups, etc. The adhesion promoter may be used alone or in combination of two or more types.

[0052] If the stator insulating material contains an adhesion promoter, the amount is not particularly limited, but is preferably 0.01 to 20.0 parts by mass, and more preferably 5.0 to 10.0 parts by mass, per 100 parts by mass of the resin component.

[0053] [Method for preparing insulating material for stator] The method for preparing the insulating material for the stator is not particularly limited. For example, one method is to thoroughly mix each component using a mixer, then melt-knead it using a mixing roll, extruder, etc., cool it, and pulverize it. More specifically, one method is to mix and stir each component, knead it using a preheated kneader, roll, extruder, etc., cool it, and pulverize it.

[0054] [Characteristics of stator insulating materials] (Properties) The stator insulating material may be solid or liquid at 25°C and atmospheric pressure, but it is preferable to be solid from the viewpoint of the mechanical strength of the cured product. When the stator insulating material is solid, there are no particular restrictions on its shape, and examples include powder, granules, and tablets. When the stator insulating material is in tablet form, it is preferable from the viewpoint of handling that its dimensions and mass are such that they are suitable for the molding conditions.

[0055] (viscosity) The viscosity of the stator insulating material is not particularly limited. From the viewpoint of filling narrow gaps, the viscosity of the stator insulating material is preferably 1000 Pa·s or less at 175°C, more preferably 500 Pa·s or less, and even more preferably 200 Pa·s or less. The lower limit of the viscosity of the stator insulating material is not particularly limited and may be, for example, 100 Pa·s or more at 175°C. The viscosity of the stator insulating material can be measured by a high-efficiency flow tester (for example, manufactured by Shimadzu Corporation).

[0056] (Molding shrinkage rate) The molding shrinkage rate of the cured stator insulating material obtained by the following method is preferably 0.30% or less, more preferably 0.25% or less, even more preferably 0.20% or less, and particularly preferably 0.15% or less. A lower molding shrinkage rate is preferable. The cured stator insulating material was treated at 175°C for 5 hours, and the molding shrinkage rate was determined using the following formula. Molding shrinkage rate (%) = {(Length of cured material before treatment - Length of cured material after treatment) / (Length of cured material before treatment)} × 100 The length of the cured material is the length of any one side of the rectangular cured material. In one embodiment, the above molding shrinkage rate is the molding shrinkage rate of a cured product obtained by molding the stator insulating material using a transfer molding machine under the conditions of a mold temperature of 175°C, a molding pressure of 6.9 MPa, and a curing time of 90 seconds.

[0057] (Glass transition temperature) The glass transition temperature (Tg) of the cured stator insulating material is preferably 130°C or higher, more preferably 150°C or higher, and even more preferably 170°C or higher, from the viewpoint of heat resistance and mechanical strength. In one embodiment, the glass transition temperature is, for example, the glass transition temperature of a cured product obtained by molding a stator insulating material in a transfer molding machine under the conditions of a mold temperature of 175°C, a molding pressure of 6.9 MPa, and 90 seconds, and then further curing it under the conditions of 175°C and 5 hours. The glass transition temperature can be measured, for example, as follows: A test specimen is prepared by cutting the cured material into strips, and the temperature is calculated by performing dynamic viscoelasticity measurements in tensile mode. The measurement conditions are a frequency of 10 Hz, a heating rate of 5 °C / min, and a strain of 0.1%. The temperature at which tanδ is maximum in the resulting temperature-tanδ relationship diagram is considered to be the glass transition temperature. As an evaluation device, for example, RSA-G2 (T.A. Instruments Corporation) can be used.

[0058] (Bending strength) The flexural strength of the cured product, as measured by the following method, is preferably 80 MPa or higher, more preferably 100 MPa or higher, and even more preferably 120 MPa or higher. There is no particular upper limit to the flexural strength. A rectangular parallelepiped measuring 2.0 mm × 5.0 mm × 40 mm is cut from the cured insulating material to prepare a test specimen for evaluating bending strength. Using this specimen, a bending test is performed on a Tensilon universal material testing machine (e.g., Instron 5948, Instron Corporation) under the conditions of a support distance of 32 mm and a crosshead speed of 1 mm / min. Using the measured results, a bending stress-displacement curve is created from equation (A), and the maximum stress is defined as the bending strength.

[0059] σ = 3FL / 2bh 2 ··· Formula (A)

[0060] σ: Bending stress (MPa) F: Bending load (N) L: Distance between fulcrums (mm) b: Test specimen width (mm) h: Test specimen thickness (mm)

[0061] In one embodiment, the above bending strength is the bending strength of a cured product obtained by molding the stator insulating material in a transfer molding machine under the conditions of a mold temperature of 175°C, a molding pressure of 6.9 MPa, and a curing time of 90 seconds, and then post-curing it under the conditions of 175°C for 5 hours.

[0062] [Insulation Method] The method for insulating the coils using stator insulating material is not particularly limited, and methods for sealing the coils include transfer molding, injection molding, and compression molding. In particular, by sealing the coils under pressurized and heated conditions using transfer molding, it is possible to achieve a tight seal while suppressing the entrapment of voids, and thus tend to improve insulation performance. The stator insulating material of this disclosure contains spherical inorganic fillers and has superior fluidity compared to materials containing non-spherical inorganic fillers, making suitable molding by transfer molding possible. The temperature and time of transfer molding can be appropriately selected depending on the type of stator insulating material. For example, molding may be performed under conditions of a mold temperature of 170°C to 180°C, a molding pressure of 5 MPa to 150 MPa, and a molding time of 1 to 3 minutes.

[0063] In one embodiment, the entire stator, including the coil portion, may be sealed together with the stator insulating material of this disclosure by transfer molding. Conventionally, sealing a stator by transfer molding has been difficult, mainly due to size constraints. However, by performing transfer molding using the stator insulating material of this disclosure, insulation between coils can be easily achieved. Alternatively, each component of the stator may be sealed individually.

[0064] [Applications of stator insulating materials] As described above, the stator insulating material of this disclosure can be used for insulating between coils of a stator.

[0065] ≪Stata≫ The stator of this disclosure has a coil insulated with the aforementioned stator insulating material. The stator insulating material of this disclosure can be applied to any winding method of the coil, such as distributed winding or concentrated winding.

[0066] The material of the coil is not particularly limited. For example, conductors such as copper, aluminum, silver, and alloys thereof can be used as coil materials. A coil in which the conductor is covered with an insulating layer such as resin may also be used.

[0067] The stator of this disclosure can be applied to various motors, such as motors for hybrid vehicles, electric vehicles, hybrid diesel locomotives, electric motorcycles, elevators, and construction machinery. In particular, because the stator of this disclosure has excellent insulation properties between coils, it can be suitably applied even to motors for vehicles that have been made more powerful or smaller.

[0068] ≪Method of manufacturing a stator≫ The method for manufacturing a stator according to this disclosure includes insulating the coils with a stator insulating material. Details of the stator insulating material, the insulating method, and the stator are as described above. <<Insulating material used>> The disclosure further includes the use of an insulating material comprising an epoxy resin, a curing agent, and spherical inorganic fillers for insulating between coils of a stator. Details of the insulating material, stator, and insulating method are as described above. [Examples]

[0069] The following are test data for stator insulating materials. The present invention is not limited in any way to the following test data.

[0070] <Fabrication of insulating materials> First, we prepared the following components. • Epoxy resin: Polyfunctional epoxy resin with epoxy equivalent weight of 163g / eq to 175g / eq and a softening point of 57°C to 63°C. • Hardener: Phenolic novolac resin with a hydroxyl group equivalent of 106 g / eq and a softening point of 68°C to 74°C. • Inorganic filler 1: D50 is 19.9 μm (catalog value), fused silica particles with a maximum particle diameter of 55 μm or less (average circularity is in the range of 0.8 to 1.0, and average aspect ratio is in the range of 0.9 to 1.0).

[0071] For comparison, the following ingredients were prepared. • Phenolic resin: Resol type • Inorganic filler 2: Glass (fibrous inorganic filler)

[0072] Each component shown in Table 1 was blended in the amounts shown in the table and thoroughly mixed in a mixer. Then, the mixture was melt-kneaded at a temperature of 70°C to 100°C using a twin-screw kneader. Next, after the molten material was cooled, the resulting solid was pulverized into a powder to prepare the desired powdered insulating material.

[0073] <Rating> The fabricated insulating materials were evaluated by the following tests. Unless otherwise specified, the insulating materials were molded using a transfer molding machine under the following conditions: mold temperature 175°C, molding pressure 6.9 MPa, and curing time 90 seconds. Post-curing was also performed at 175°C for 5 hours as needed.

[0074] [Fillability] Prepare a mold (L=100mm) with a 0.3mm gap, and perform transfer molding under the above conditions. Visually check whether or not there is any void in the 0.3mm gap. The filling properties are evaluated as follows: A: No unfilled areas B: Flow marks are observed, but there are no unfilled areas.

[0075] [Dimensional stability (molding shrinkage rate)] The molding shrinkage rate before and after post-curing is measured, and compositions with low shrinkage rates are considered good. The molding shrinkage rate is calculated using the following formula. Molding shrinkage rate (%) = {(Length of cured material before post-curing - Length of cured material after post-curing) / (Length of cured material before post-curing)} × 100 The length of the cured material is the length of any one side of the rectangular cured material.

[0076] [Glass transition temperature (Tg)] The glass transition temperature is measured using the following method, and compositions with a high Tg are considered good. After post-curing, the cured material is cut into strips to prepare test specimens, and the glass transition temperature is calculated by performing dynamic viscoelasticity measurements in tensile mode. The measurement conditions are a frequency of 10 Hz, a heating rate of 5 °C / min, and a strain of 0.1%. The temperature at which tanδ is maximum in the resulting temperature-tanδ relationship diagram is considered to be the glass transition temperature. The evaluation device used is RSA-G2 (T.A. Instruments).

[0077] [Bending strength] The bending strength is measured using the following method, and compositions exhibiting high bending strength are considered good. After the insulating material has hardened, a rectangular parallelepiped measuring 2.0 mm × 5.0 mm × 40 mm is cut out to prepare a test specimen for evaluating bending strength. Using this test specimen, a bending test is performed on a Tensilon universal material testing machine (Instron 5948, Instron Corporation) under the conditions of a support distance of 32 mm and a crosshead speed of 1 mm / min. Using the measured results, a bending stress-displacement curve is created from equation (A), and the maximum stress is defined as the bending strength.

[0078] σ = 3FL / 2bh 2 ··· Formula (A)

[0079] σ: Bending stress (MPa) F: Bending load (N) L: Distance between fulcrums (mm) b: Test specimen width (mm) h: Test specimen thickness (mm)

[0080] [Table 1]

[0081] In Examples 1 and 2, due to the excellent fluidity of the insulating material, excellent filling properties were obtained without any unfilled areas even when the inorganic filler content was increased to 85% by mass. Furthermore, in Examples 1 and 2, fluidity equivalent to or better than that of Comparative Example 1 was obtained. Furthermore, it was found that the insulating materials of Examples 1 and 2 have low molding shrinkage rates and can be suitably applied as insulating materials for stators, enabling high-precision sealing. On the other hand, Comparative Example 1 had a high molding shrinkage rate, and flow marks due to fiber orientation were observed, resulting in an uneven distribution of the filler material. Therefore, it was found that it is difficult to apply to insulating materials for stators that require high precision.

[0082] Measurement of the glass transition temperature (Tg) revealed that the Tg of the insulating materials in Example 1, Example 2, and Comparative Example 1 was 175°C, 175°C, and 300°C, respectively, indicating that all materials exhibited good heat resistance. The bending strength measurements revealed that the bending strengths of the insulating materials in Example 1, Example 2, and Comparative Example 1 were 100 MPa, 130 MPa, and 200 MPa, respectively, indicating that all materials exhibited good strength.

[0083] From these results, it can be seen that the stator insulating material of the example has superior filling properties and dimensional stability compared to the stator insulating material of the comparative example, and also exhibits good mechanical strength and heat resistance.

[0084] The disclosure of Japanese Patent Application No. 2020-134787 is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards described herein are incorporated by reference to the same extent as if each individual document, patent application, and technical standard were specifically and individually noted as being incorporated by reference.

Claims

1. A stator insulating material containing epoxy resin, a hardening agent, and spherical inorganic fillers, used for insulating between coils of a stator.

2. The stator insulating material according to claim 1, wherein the curing agent comprises a phenol curing agent.

3. The stator insulating material according to claim 1 or claim 2, wherein the inorganic filler comprises at least one selected from the group consisting of silica, alumina, and magnesium oxide.

4. The stator insulating material according to any one of claims 1 to 3, wherein the content of the inorganic filler is 50% by mass or more with respect to the total mass of the stator insulating material.

5. The stator insulating material according to claim 4, wherein the content of the inorganic filler is 70% by mass or more with respect to the total mass of the stator insulating material.

6. The stator insulating material according to claim 5, wherein the content of the inorganic filler is 80% by mass or more with respect to the total mass of the stator insulating material.

7. The stator insulating material according to any one of claims 1 to 6, wherein the maximum particle size of the inorganic filler is 100 μm or less.

8. The stator insulating material according to any one of claims 1 to 7, wherein the average aspect ratio of the inorganic filler observed with a scanning electron microscope is 0.8 to 1.

0.

9. A stator having coils insulated with the stator insulating material described in any one of claims 1 to 8.

10. A method for manufacturing a stator, comprising insulating the coils with an insulating material for stator as described in any one of claims 1 to 8.

11. The method for manufacturing a stator according to claim 10, wherein insulation between the coils is performed by transfer molding.

12. A method for using an insulating material containing epoxy resin, a hardening agent, and spherical inorganic fillers for insulation between stator coils.

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