Insulating sheet and manufacturing method therefor, insulating treatment method, and method for manufacturing rotary electrical machine

Abstract

This insulating sheet comprises: a substrate (3); and an insulation resin layer that is formed from a thermosetting resin composition in an uncured or semi-cured state and that is formed in a sheet shape on one surface or both surfaces of the substrate (3). The thermosetting resin composition is composed of: a thermosetting resin component (21) that is formed from a first thermosetting resin, which is a solid at 25°C, a second thermosetting resin, which is a liquid at 25°C, and a latent curing agent, which is reactively inactive at 60°C or less, where the first thermosetting resin content is 10 mass% to 90 mass% with respect to 100 parts by mass in total of the first thermosetting resin and the second thermosetting resin; and a thermally-expandable microcapsules (22), in which, when Gp is a value in the range of 0.5 times to 0.91 times the film thickness (t2), the maximum particle size is smaller than the Gp, the average particle diameter (φ22) is smaller than 0.5 times the Gp, and the foaming start temperature is 60°C or more.

Description

Insulating sheet and manufacturing method thereof, insulation treatment method and manufacturing method of rotating electric machine

[0001] The present application relates to an insulating sheet, a manufacturing method thereof, an insulation treatment method, and a manufacturing method of a rotating electrical machine.

[0002] Rotating electric machines, including electric motors, generators, compressors, etc., include a rotor and a stator having a stator core and a stator coil. In this field, with the trend toward smaller size and higher output, there is an increasing demand for insulation and heat dissipation, and insulating members disposed in the gaps between the components that make up these machines are required to have excellent insulation properties, heat resistance, and heat dissipation capabilities.

[0003] Here, for example, when an insulating member is placed in the gap between the stator core and the stator coil, if an air layer remains partially in the gap, it will cause a decrease in insulation, heat dissipation, and vibration resistance. Therefore, when the stator coil is placed in the slot of the stator core, insulating paper is inserted into the gap between the inner wall of the slot and the stator coil, and the stator coil is impregnated with liquid insulating varnish.

[0004] On the other hand, as the space factor of stator coils increases, the gaps between the slot inner wall, stator coil, and insulating paper, as well as the gaps within the stator coil, become narrower. This results in the problem of insufficient penetration of insulating varnish into the stator coil, resulting in partial adhesion. On the other hand, when a low-viscosity insulating varnish is used to increase penetration, much of the varnish dripped onto the coil end leaks onto the end face of the core, resulting in insufficient adhesion inside the stator coil. As a result, if the adhesion performance of the stator coil deteriorates, it will adversely affect the long-term insulation reliability of rotating electrical machines. In particular, in the case of rotating electrical machines for automobiles, a deterioration in the adhesion performance of the stator coil can worsen NVH (Noise, Vibration, Harshness), which is one of the criteria for estimating vehicle comfort.

[0005] In response to this, a method has been disclosed in which the stator coil is fixed to the stator core while being insulated from it by using an uncured or semi-cured insulating varnish in a sheet form, without impregnating the stator coil with insulating varnish (see, for example, Patent Document 1).Also disclosed is a method in which an adhesive sheet with an expandable adhesive layer that foams and cures in a short time is used to fill the gap between the stator coil and the stator core (see, for example, Patent Document 2).

[0006] JP 2021-70748 A (paragraphs 0023-0024, 0091-0093, FIG. 7) International Publication No. WO 2016 / 163514 (paragraphs 0011, 00210113, FIG. 1)

[0007] However, the surfaces of the iron core and coil, which are made of laminated electromagnetic steel plates, are uneven. When the unevenness is large or the varnish layer has high thermal fluidity, partial voids form, resulting in reduced cooling and insulating properties. On the other hand, expandable adhesives expand when heated, but do not flow into the gaps in the coil, making them unable to adhere. Furthermore, foaming can create large voids within the sheet, potentially causing partial discharges when voltage is applied or making the sheet brittle enough to crack due to vibration. This means that in addition to reduced insulation and heat dissipation, mechanical strength is also reduced.

[0008] The present application discloses technology for solving the above-mentioned problems, and aims to provide an insulating sheet that can penetrate into the fine gaps between components and reliably fill those gaps, or to use the insulating sheet to obtain electrical equipment that has excellent insulation reliability, heat dissipation properties, and vibration resistance.

[0009] The insulating sheet disclosed in the present application comprises a substrate made of at least one of insulating paper, insulating film, nonwoven fabric, and mesh cloth, and an uncured or semi-cured thermosetting resin composition, and an insulating resin layer formed in sheet form on one or both sides of the substrate, the thermosetting resin composition comprising a first thermosetting resin that is solid at 25°C, a second thermosetting resin that is liquid at 25°C, and a latent curing agent that is inactive at 60°C or less, the thermosetting resin portion containing 10 to 90 parts by mass of the first thermosetting resin relative to 100 parts by mass of the total of the first thermosetting resin and the second thermosetting resin, and thermally expandable microcapsules having a maximum particle size smaller than Gp, an average particle size smaller than 0.5 times Gp, and a foaming initiation temperature of 60°C or higher, where Gp is ​​a value in the range of 0.5 to 0.91 times the total thickness of the insulating resin layer.

[0010] According to the insulating sheet disclosed in the present application, the varnish layer flows during the curing process, penetrates into the fine spaces between components, and then thickens due to the expansion of the thermally expandable microcapsules, thereby reliably filling the gaps between the components to be insulated and insulating and bonding them together.

[0011] In particular, when the insulating sheet is used for insulation treatment, the insulation reliability, heat dissipation performance, and vibration resistance of electrical equipment, particularly rotating electrical machines, can be improved, and miniaturization and high output can be realized.

[0012] 1A to 1D are schematic cross-sectional views showing the configuration of an insulating sheet according to the first embodiment and insulating sheets according to first to third modified examples, respectively. FIGS. 2A to 2D are schematic cross-sectional views showing the configuration of insulating sheets according to fourth to seventh modified examples of the first embodiment, respectively. A schematic cross-sectional view showing a process of insulating between a stator coil and a stator core using the insulating sheet according to the first embodiment. A flowchart showing a method for manufacturing an insulating sheet according to a second embodiment. A schematic cross-sectional view showing the configuration of a rotating electric machine manufactured using an insulation treatment method according to a third embodiment. A perspective view of a stator of a rotating electric machine that is an object of insulation treatment in the insulation treatment method according to the third embodiment. A plan view of a stator of a rotating electric machine that is an object of insulation treatment in the insulation treatment method according to the third embodiment. A partial cross-sectional view showing an insulating state between a stator core and a stator coil in a stator of a rotating electric machine that has been subjected to the insulation treatment method according to the third embodiment. A flowchart showing an insulation treatment method according to the third embodiment. A flowchart showing a method for manufacturing a rotating electric machine according to the third embodiment.

[0013] First Embodiment. An insulating sheet according to a first embodiment will be described below with reference to the drawings. FIGS. 1A to 3 are used to explain the insulating sheet according to the first embodiment. FIG. 1A is a schematic cross-sectional view taken along the thickness direction to illustrate the configuration of an insulating sheet according to a first example. FIGS. 1B to 1D are schematic cross-sectional views corresponding to FIG. 1A of insulating sheets according to first to third modified examples, respectively. FIGS. 2A to 2D are schematic cross-sectional views corresponding to FIG. 1A of insulating sheets according to fourth to seventh modified examples, which are examples in which a filler is added to the first example and the first to third modified examples, respectively. FIG. 3 is a schematic cross-sectional view illustrating a process of insulating between a stator coil and a stator core that constitute a rotating electric machine using the insulating sheet described above.

[0014] 1A, 1B, 2A, and 2B, the insulating sheet 1 has an insulating resin layer 2 made of an uncured or semi-cured thermosetting resin composition formed on one or both sides of a substrate 3. The thermosetting resin composition has thermally expandable microcapsules 22 dispersed in a thermosetting resin portion 21, and is applied to the substrate 3 to form the insulating resin layer 2.

[0015] As shown in Figure 3, the insulating sheet 1 is placed in the gap between components to be insulated and then heated and cured in a curing process to firmly insulate the components. Specifically, the insulating sheet 1 is placed in advance on one of the components (stator coil 51, stator core 52, etc.) and then pressed and fixed to the other component (same as above). At this time, if the insulating sheet 1 does not have a surface adhesiveness described below, it may be attached with double-sided tape or the like to prevent it from falling off. In the figure, the thermally expandable resin portion hardened by the curing process described below is called "thermally expandable resin portion 21C," and the thermally expandable microcapsules after expansion are called "thermally expandable microcapsules 22E," distinguished by adding a "C" or "E" to the end of the reference numeral.

[0016] As will be described later, the composition of the insulating resin layer 2 is adjusted so that it is efficiently compressed to a predetermined thickness when pressurized at room temperature, flows when heated during curing, and penetrates into the fine spaces between components, after which the varnish layer thickens due to the expansion of the thermally expandable microcapsules 22. This eliminates air gaps and reliably fills the gaps between the components to be insulated, thereby insulating and bonding them together.

[0017] Therefore, in the insulation process, it is necessary to carry out the flow of the varnish, the foaming of the thermally expandable microcapsules 22, and the curing of the thermosetting resin portion 21 in the correct order and successively. Therefore, in the insulation process, the heating temperature may be set not to a constant temperature, but to be increased in stages from the flow temperature, to the foaming temperature, and to the curing temperature. It is assumed that the flow temperature is set to a temperature below the foaming start temperature of the thermally expandable microcapsules 22, the foaming temperature is set to a temperature above the foaming start temperature of the thermally expandable microcapsules 22 and below the reaction start temperature of the latent curing agent + 20°C, and the curing temperature is set to a temperature above the reaction start temperature of the latent curing agent.

[0018] Next, details of the components of the insulating sheet 1 having the above-described properties will be described. The substrate 3 is made of any of insulating paper, thermoplastic insulating film, nonwoven fabric, and mesh cloth. For example, in the first example shown in FIG. 1A and the fourth modified example shown in FIG. 2A, an insulating resin layer 2 formed by applying a thermosetting resin composition is formed on one side of the substrate 3. In the first modified example shown in FIG. 1B and the fifth modified example shown in FIG. 2B, insulating resin layers 2 are formed on both sides of the substrate 3.

[0019] 1A, 1B, 2A, and 2B, the base material 3 is not necessarily formed by a single base material sheet 31 (in the figures, the base material 3 is formed by a single sheet, and therefore the reference numeral "31" for the base material sheet is omitted). For example, as shown in FIGS. 1C, 1D, 2C, and 2D, a plurality of base material sheets 31a, 31b, and 31c (collectively referred to as base material sheets 31 when not distinguished from one another) may be laminated via adhesives 32a and 32b (similarly collectively referred to as adhesives 32). In this case, an insulating resin layer 2 may be formed on the base material sheet 31 at one end or both ends in the thickness direction of the base material 3.

[0020] For example, in the second modified example shown in Fig. 1C and the sixth modified example shown in Fig. 2C, an insulating resin layer 2 is formed on the base sheet 31a at one end. Furthermore, in the third modified example shown in Fig. 1D and the seventh modified example shown in Fig. 2D, a front insulating resin layer 2f and a back insulating resin layer 2r are formed on the base sheets 31a and 31c at both ends, respectively. The portion labeled adhesive 32 in Figs. 1C, 1D, 2C, and 2D may be composed of an insulating resin layer. Because the insulating resin layer is flexible and has a high adhesive strength to the base sheet 31, the base sheets 31 can be bonded together by heat and pressure bonding.

[0021] Furthermore, each of sheets 32a, 32b, and 32c may be any of the above-mentioned insulating paper, insulating film, nonwoven fabric, and mesh cloth, and may be the same or different. Furthermore, the number of base sheets 31 included in insulating sheet 1 is not particularly limited. However, since the total thickness of insulating sheet 1 increases as the number of sheets increases, about three sheets is preferable.

[0022] The insulating paper, insulating film, nonwoven fabric, and mesh cloth forming the base sheet 31 are made of insulating materials, and may be selected appropriately from known materials depending on the desired characteristics, such as flexibility, or a combination of multiple materials may be used. The base sheet 31 may be made of, for example, an insulating resin material made of engineering plastic or super engineering plastic, an inorganic insulating material made of silica, alumina, or glass, or a fibrous insulating resin material or a material containing a fibrous inorganic insulating material. Insulating resin materials are flexible and therefore advantageous for molding, while inorganic insulating materials have high thermal conductivity, which allows for increased heat dissipation from the heated stator coil 51 to the stator core 52.

[0023] Specific examples include aramid paper, kraft paper, crepe paper, polyacetal, polyamide, polycarbonate, modified polyphenylene ether, polybutylene terephthalate, polyethylene naphthalate, polysulfone, polyethersulfone, polyphenylene sulfide, polyetheretherketone, polyimide, polyetherimide, polytetrafluoroethylene, tetrafluoroethylene-ethylene copolymer, polyvinylidene fluoride, polyester, polyethylene, polypropylene, nylon, nylon 6,6, vinylon, ethylene vinyl acetate, polyacrylonitrile, polyolefin, rayon, fluororesins such as Teflon (registered trademark) or polyvinylidene fluoride, liquid crystal polymers, cellulose, vinylon, glass, silica, and alumina. The nonwoven fabric may be a general-purpose nonwoven fabric, a microfiber nonwoven fabric, or a nanofiber nonwoven fabric.

[0024] Furthermore, when the substrate 3 is formed from a laminated sheet of multiple substrate sheets 31, it is desirable to form it by laminating, for example, either insulating paper or insulating film, or both. By forming the substrate 3 by lamination, the thickness can be freely selected. Furthermore, by laminating a combination of insulating paper and insulating film, it is possible to form a substrate 3 that makes use of the advantages of each. When the substrate 3 is formed from multiple insulating papers, the substrate 3 is a composite insulating paper. When the substrate 3 is formed from multiple insulating films, the substrate 3 is a composite insulating film.

[0025] Furthermore, laminating the substrate 3 via an insulating resin layer or adhesive 32 can increase the strength of the substrate 3. Furthermore, if an inorganic filler is added to the adhesive 32, the thermal conductivity of the adhesive 32 can be increased, thereby increasing the heat dissipation effect of the substrate 3.

[0026] When multiple base sheets 31 are bonded together via adhesive 32, the adhesive 32 used is, for example, a general-purpose acrylic or epoxy adhesive, or a highly thermally conductive adhesive containing filler 23. In the case of an insulating sheet 1 for a rotating electric machine 80 ( FIG. 5 ), which requires high heat resistance and insulation, a base material 3 formed by laminating highly heat-resistant materials such as aramid paper, polyethersulfone, polyphenylene sulfide, polyetheretherketone, polyethylene naphthalate, and polyimide is preferred. Furthermore, when the thermal conductivity of the base material 3 is low, through holes may be formed in the base material 3 and filled with insulating resin to enhance heat dissipation from the object to be insulated, such as the stator coil 51 to the stator core 52.

[0027] <Insulating Resin Layer> Next, we will explain the thermosetting resin composition that constitutes the insulating resin layer 2 and the insulating resin layer for laminating the above-mentioned multiple base sheets 31. The thermosetting resin composition has thermally expandable microcapsules 22 dispersed in a thermosetting resin portion 21, and is applied to the above-mentioned base material 3 to form the insulating resin layer 2.

[0028] The thermosetting resin portion 21 is composed of a thermosetting resin A (first curing resin) that is solid at 25°C, a thermosetting resin B (second thermosetting resin) that is liquid at 25°C, and a latent curing agent that is inactive at 60°C or below. Meanwhile, the thermally expandable microcapsules 22 have a foaming initiation temperature of 60°C or above. Here, the substrate 3 is flexible but incompressible with respect to thickness t3. In other words, since the substrate 3 functions as a spacer having thickness t3 within the gap, the actual dimension of the gap to be filled by the insulating resin layer 2 is the dimension of gap G5 minus the thickness t3 of the substrate 3 (referred to as actual gap Gp).

[0029] Therefore, the thermally expandable microcapsules 22 are particles whose maximum particle size is smaller than the actual gap Gp and whose average particle size φ22 is smaller than 0.5 times the actual gap Gp. Furthermore, from the viewpoint of improving the smoothness of the insulating resin layer 2, it is preferable that the maximum particle size is smaller than the film thickness of the insulating resin layer (2 in the case of one side, 2f and 2r in the case of both sides) formed on each surface of the substrate 3.

[0030] Furthermore, the thickness t2 of the insulating resin layer 2 is adjusted to a value between 1.1 and 2.0 times the actual gap Gp, as described below, and by back-calculation, the actual gap Gp is ​​in the range between 0.5 and 0.91 times the thickness t2. Therefore, the maximum particle diameter of the thermally expandable microcapsules 22 is smaller than 0.5 and 0.91 times the thickness t2, and the average particle diameter φ22 is smaller than the range between 0.25 and 0.45 (strictly, (1 / 1.1) / 2) times the thickness t2.

[0031] The thermosetting resin composition contains 10 parts by mass or more and 90 parts by mass or less of the first thermosetting resin relative to 100 parts by mass of the total of the first thermosetting resin and the second thermosetting resin, and optionally contains an inorganic or resin-based filler 23, a curing accelerator, a thermoplastic resin, a film-forming agent, a tackifier, an adhesion promoter, etc. In the following description, when referring to both the first thermosetting resin and the second thermosetting resin without making a distinction between them, or when referring to a mixed resin of these, the term "thermosetting resin" will be used. Furthermore, room temperature refers to approximately 25°C.

[0032] The insulating resin layer 2 formed on the substrate 3 using a thermosetting resin composition composed of a thermosetting resin portion 21 made from a combination of the above-mentioned raw materials and thermally expandable microcapsules 22 has the flexibility to be compressed to a predetermined thickness when pressurized at room temperature. Furthermore, the resin flows when heated during curing, penetrates into the fine spaces between components, and then expands to form a layer called a varnish layer, which increases in thickness due to the expansion of the thermally expandable microcapsules 22. Therefore, the insulating resin layer 2 constituting the insulating sheet 1 according to the first embodiment is suitable for reliably filling gaps between components to be insulated, insulating and bonding them together.

[0033] The thermosetting resin may be any of known resins such as epoxy resin, phenol resin, unsaturated polyester resin, polyurethane resin, diallyl phthalate resin, and silicone resin. In particular, it is preferable to use at least one of epoxy resin, phenol resin, and unsaturated polyester resin such as vinyl ester resin, which are commonly used as insulating varnishes.

[0034] Specific examples of thermosetting resins include bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol AD ​​type epoxy resins, brominated bisphenol A type epoxy resins, brominated bisphenol F type epoxy resins, brominated bisphenol AD ​​type epoxy resins, alicyclic epoxy resins, brominated alicyclic epoxy resins, phenol novolac type epoxy resins, cresol novolac type epoxy resins, brominated phenol novolac type epoxy resins, brominated cresol novolac type epoxy resins, hydrogenated bisphenol A type epoxy resins, triglycidyl isocyanate, hydantoin type epoxy resins, heterocyclic epoxy resins, biphenyl skeleton-containing aralkyl type epoxy resins, dicyclopentadiene type epoxy resins, novolac type phenolic resins, resol type phenolic resins, epoxy (meth)acrylate resins (vinyl ester resins), urethane (meth)acrylate resins, polyether (meth)acrylate resins, polyester (meth)acrylate resins, and the like. These resins may be used alone or in combination of two or more.

[0035] The first thermosetting resin is solid at room temperature, and has a melting point or a softening temperature of glass transition point of 160° C. or less, more preferably 125° C. or less. If the softening temperature exceeds 160° C., the polymerization reaction with the second thermosetting resin does not proceed easily when heated, and the heating temperature in the curing treatment step must be higher than 200° C., which is undesirable because it may induce deterioration of the components to be insulated.

[0036] Furthermore, the first thermosetting resin must be soluble in at least one of the liquid second thermosetting resin and the organic solvent for dilution (hereinafter referred to as the diluent). If the first thermosetting resin is not soluble, the resin components will not be uniformly dissolved when the slurry is prepared, and a homogeneous insulating sheet will not be formed.

[0037] Furthermore, when the first thermosetting resin is an epoxy resin, from the viewpoint of enhancing adhesive strength with the component to be insulated, an epoxy resin having an epoxy equivalent of 200 or more and a softening temperature in the range of 50° C. or more and 160° C. or less is more preferable. Also, when the first thermosetting resin is an unsaturated polyester resin such as a vinyl ester resin, one having a softening temperature of 50° C. or more and 160° C. or less is preferable. These resins have excellent workability when premixed with other raw materials at room temperature and are easily melted by heating, improving uniform mixing with other raw materials.

[0038] When the first thermosetting resin is an epoxy resin, an epoxy resin that is liquid at room temperature is suitable for the second thermosetting resin in order to enhance adhesive strength with the component to be insulated. Furthermore, to enhance the dissolving power of the first thermosetting resin, bisphenol A epoxy resin or bisphenol F epoxy resin is more preferably used as the second thermosetting resin. Furthermore, when the first thermosetting resin is an unsaturated polyester resin, a low-viscosity, low-molecular-weight unsaturated polyester resin oligomer or monomer is suitable for the second thermosetting resin in order to enhance the dissolving power of the first thermosetting resin.

[0039] In this way, by using two thermosetting resins (first thermosetting resin and second thermosetting resin) that are different in state at room temperature and adjusting the blending ratio by mass, it is possible to control the surface tackiness (tackiness), mechanical strength (toughness), adhesiveness, fluidity during heating, etc. at room temperature of the insulating resin layer 2. In this case, the first thermosetting resin is preferably 10 parts by mass or more and 90 parts by mass or less, and more preferably 15 parts by mass or more and 85 parts by mass or less, relative to 100 parts by mass of the total of the first thermosetting resin and the second thermosetting resin.

[0040] If the first thermosetting resin is less than 10 parts by mass, the liquid resin becomes excessive, and a stable insulating resin layer 2 cannot be obtained after drying, making it impossible to peel it off from the release substrate. On the other hand, if the first thermosetting resin exceeds 90 parts by mass, the solid resin becomes excessive, reducing the toughness (tensile strength of the material) of the insulating resin layer 2. As a result, cracks and chips are likely to occur during drying or peeling from the release substrate, making it difficult to work with.

[0041] In terms of the preferred range in terms of properties, the first thermosetting resin is preferably in the range of 15 parts by mass or more and 85 parts by mass or less to produce a highly tough and stable insulating resin layer 2. Furthermore, to ensure adhesion that allows easy attachment to the component to be insulated, a range of 15 parts by mass or more and 50 parts by mass or less is preferred. On the other hand, when adhesion on the surface of the insulating resin layer 2 is not required (for example, when adhesion deteriorates workability), a range of 50 parts by mass or more and 85 parts by mass or less is preferred to reduce surface adhesion, and the composition can be adjusted depending on the application.

[0042] The thermosetting resin portion 21 may contain a curing agent that hardens the thermosetting resin. The curing agent is not particularly limited, and a known curing agent may be appropriately selected depending on the type of thermosetting resin. Examples of the curing agent include amines, phenols, acid anhydrides, imidazoles, polymercaptan curing agents, and polyamide resins.

[0043] Specific examples of the curing agent include alicyclic acid anhydrides such as methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, and himic anhydride; aliphatic acid anhydrides such as dodecenylsuccinic anhydride; aromatic acid anhydrides such as phthalic anhydride and trimellitic anhydride; aromatic diamines such as dicyandiamide and 4,4'-diaminodiphenyl sulfone; organic dihydrazides such as adipic acid dihydrazide; boron halide amine complexes such as boron trifluoride, boron trichloride, and boron tribromide; tris(dimethylamine) Examples of the phenol include 1,8-diazabicyclo(5,4,0)undecene and its derivatives, imidazoles such as 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, and 1-cyanoethyl-2-methylimidazole, polyhydric phenol compounds such as bisphenol A, bisphenol F, bisphenol S, phenol novolac resin, cresol novolac resin, and p-hydroxystyrene resin, and organic peroxides.

[0044] Representative examples of the boron halide amine complexes listed above include boron trifluoride monoethylamine complex, boron trifluoride diethylamine complex, boron trifluoride isopropylamine complex, boron trifluoride chlorophenylamine complex, boron trifluoride-triallylamine complex, boron trifluoride benzylamine complex, boron trifluoride aniline complex, boron trichloride monoethylamine complex, boron trichloride phenol complex, boron trichloride piperidine complex, boron trichloride dimethyl sulfide complex, boron trichloride N,N-dimethyloctylamine complex, boron trichloride N,N-dimethyldodecylamine complex, boron trichloride N,N-diethyldioctylamine complex, etc. These curing agents may be used alone or in combination of two or more.

[0045] The amount of curing agent to be added may be adjusted as appropriate depending on the type of thermosetting resin and curing agent to be used, and is usually preferably 0.1 parts by mass or more and 200 parts by mass or less per 100 parts by mass of the thermosetting resin.

[0046] Furthermore, when an epoxy resin is used as the thermosetting resin, a latent curing agent that is reactively inactive at 60°C or less is preferred from the viewpoints of the storage stability, curing ability, and physical properties of the cured resin of the insulating resin layer 2. Specific examples of latent curing agents include boron halide amine complexes such as boron trifluoride-amine complexes, dicyandiamide, organic acid hydrazides, and aromatic diamines such as 4,4'-diaminodiphenyl sulfone. These latent curing agents may be used alone or in combination of two or more. The amount of latent curing agent to be added is such that the equivalent ratio of the thermosetting resin to the epoxy resin is 0.3 or more and 2.0 or less, and more preferably 0.5 or more and 1.5 or less from the viewpoint of the stability of the properties of the cured product.

[0047] Furthermore, when an unsaturated polyester resin is used as the thermosetting resin, the organic peroxides listed above are used as a reaction initiator to start the polymerization reaction. The organic peroxide is not particularly limited as long as it has a 10-hour half-life temperature of 40°C or higher, and any organic peroxide known in the art can be used. Specific examples of organic peroxides include ketone peroxides, peroxyketals, hydroperoxides, dialkyl peroxides, diacyl peroxides, peroxyesters, and peroxydicarbonates. These organic peroxides may be used alone or in combination of two or more.

[0048] By selecting an organic peroxide with a high activation temperature, the usable life of the insulating resin layer 2 (i.e., the usable life of the insulating sheet) can be improved. From the viewpoint of ensuring a usable life of the insulating resin layer 2 suitable for the impregnation treatment of the stator coil 51 constituting the rotating electric machine 80, it is preferable that the 10-hour half-life temperature of the organic peroxide be 80°C or higher. Furthermore, in order to efficiently proceed with the curing of the insulating resin layer 2, it is preferable that the 10-hour half-life temperature of the organic peroxide be equal to or lower than the set temperature of the curing oven used to cure the insulating resin layer 2.

[0049] Specific examples of organic peroxides having such a 10-hour half-life temperature include 1,1-di(t-butylperoxy)cyclohexane, 1,1-di(t-hexylperoxy)cyclohexane, 1,1-di(t-hexylperoxy)-3,3,5-trimethylcyclohexane, 1,1-di(t-butylperoxy)-2-methylcyclohexane, 2,2-di(4,4-di-(butylperoxy)cyclohexyl)propane, n-butyl 4,4-di-(t-butylperoxy)valerate, 2,2-di-(t-butylperoxy)butane, t-hexylperoxyisopropyl monocarbonate, t-butylperoxymaleic acid, t-butylperoxy-3,5,5-trimethylhexanoic acid, t-butylperoxylauric acid, t-butylperoxyisopropyl monocarbonate, t-butylperoxybenzoate, t-butylperoxyacetate, t-butylperoxyisopropyl monocarbonate, t-butylperoxybenzoate, t-butylperoxyacetate, t-butylperoxyisopropyl monocarbonate, t-butylperoxybenzoate, t-butylperoxyacetate, t-butylperoxyisopropyl monocarbonate, t-butylperoxybenzoate, t-butylperoxyacetate, t-butylperoxybenzo ... Examples of the peroxybenzoate include xyl peroxybenzoate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, t-butylperoxy 2-ethylhexyl monocarbonate, di(2-t-butylperoxyisopropyl)benzene, dicumyl peroxide, di-t-hexyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, di-t-hexyl peroxide, t-butylcumyl peroxide, di-t-butyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3, p-menthane hydroperoxide, t-butylperoxyallyl monocarbonate, methyl ethyl ketone peroxide, 1,1,3,3-tetramethylbutyl hydroperoxide, t-butyl hydroperoxide, cumin hydroperoxide, and diisopropylbenzene hydroperoxide. These may be used alone or in combination of two or more.

[0050] The amount of organic peroxide is not particularly limited, but is usually 0.1 to 10 parts by mass, more preferably 0.5 to 5 parts by mass, per 100 parts by mass of the polyester resin (thermosetting resin). If the amount of organic peroxide is less than 0.1 part by mass, the crosslink density may be low and curing may be insufficient. On the other hand, if the amount of organic peroxide is more than 10 parts by mass, the usable life of the insulating resin layer 2 tends to be significantly shortened.

[0051] Furthermore, the thermosetting resin portion 21 may contain a curing accelerator as needed. The curing accelerator is not particularly limited, and a known accelerator can be appropriately selected depending on the type of thermosetting resin. Specific examples of curing accelerators include tertiary amines, imidazoles, and amine adducts. From the viewpoints of the storage stability, curability, and physical properties of the cured resin of the insulating resin layer 2, a curing accelerator that is inactive at 60°C or below is more preferable.

[0052] The amount of the curing accelerator is usually 0.01 to 10 parts by mass, more preferably 0.02 to 5.0 parts by mass, per 100 parts by mass of the total thermosetting resin. If the amount of the curing accelerator is less than 0.01 part by mass, the effect of accelerating the curing reaction is poor, and if it exceeds 10 parts by mass, the usable time tends to be shortened.

[0053] Furthermore, the thermosetting resin portion 21 may contain a film-forming agent as needed to improve film-forming properties such as film thickness uniformity and surface smoothness. The film-forming agent is a thermoplastic resin having a weight-average molecular weight of 10,000 or more and 100,000 or less. The amount of the thermoplastic resin is 1 part by mass or more and 50 parts by mass or less per 100 parts by mass of the first thermosetting resin and the second thermosetting resin combined. The thermoplastic resin is not particularly limited, and a known thermoplastic resin can be appropriately selected depending on the type of thermosetting resin. Specific examples of thermoplastic resins include phenoxy resin and saturated polyester resin. These film-forming agents may be used alone or in combination of two or more.

[0054] If the weight-average molecular weight of the thermoplastic resin is less than 10,000, the film-formability is not improved, and if it exceeds 100,000, the solubility and dispersibility in the liquid second thermosetting resin are poor, making it impossible to prepare a slurry. The amount of the film-formability imparting agent is usually 1 part by mass or more and 50 parts by mass or less, more preferably 5 parts by mass or more and 45 parts by mass or less, per 100 parts by mass of the thermosetting resin in total, from the viewpoints of curing acceleration and cured resin properties. If the film-formability imparting agent is less than 1 part by mass, the effect of improving film-formability is poor, and if it exceeds 50 parts by mass, the solubility and dispersibility in the liquid second thermosetting resin are poor, making it impossible to prepare a slurry.

[0055] Furthermore, the thermosetting resin portion 21 may contain a tackifier as needed to improve the surface adhesion of the insulating resin layer 2. The tackifier is not particularly limited as long as it has a weight-average molecular weight of 10,000 or more and 200,000 or less, and any known tackifier may be appropriately selected depending on the type of thermosetting resin. Specific examples of tackifiers include terpene-based resins, rosin-based resins, natural rubber, styrene-based elastomers, polyvinyl acetal-based resins, polyvinyl formal-based resins, and polyvinyl butyral-based resins. These tackifiers may be used alone or in combination of two or more.

[0056] If the weight-average molecular weight of the tackifier is less than 10,000, the adhesion is not improved, and if it exceeds 200,000, the solubility and dispersibility in the liquid second thermosetting resin are poor, making it impossible to prepare a slurry. From the viewpoint of curing acceleration and cured resin properties, the amount of tackifier to be added is usually 1 part by mass or more and 20 parts by mass or less, more preferably 2 parts by mass or more and 10 parts by mass or less, per 100 parts by mass of the thermosetting resin in total. If the amount of tackifier is less than 1 part by mass, the effect of improving surface adhesion is poor, and if it exceeds 20 parts by mass, the solubility and dispersibility in the liquid second thermosetting resin are poor, making it impossible to prepare a slurry.

[0057] The thermosetting resin portion 21 may contain an adhesion promoter from the viewpoint of improving the adhesive strength at the interface between the thermosetting resin and the inorganic filler (filler 23) or at the interface between the insulating resin layer 2 and the member to be insulated. The adhesion promoter is not particularly limited, and any known adhesion promoter may be appropriately selected depending on the type of thermosetting resin or inorganic filler.

[0058] Specific examples of adhesion promoters include silane coupling agents such as γ-glycidoxypropyltrimethoxysilane, N-β(aminoethyl)γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, and γ-mercaptopropyltrimethoxysilane. These adhesion promoters may be used alone or in combination of two or more. The amount of adhesion promoter may be appropriately determined depending on the type of thermosetting resin or adhesion promoter, and is typically preferably 0.01 to 5 parts by mass per 100 parts by mass of thermosetting resin.

[0059] Furthermore, if the insulating resin layer 2 is made up solely of the thermosetting resin portion 21, the gaps between the components to be insulated may not be filled and partial voids may occur if the surface of the component to be insulated is highly uneven or if the insulating resin layer 2, which is a varnish layer, has high thermal fluidity. However, because the thermosetting resin composition contains thermally expandable microcapsules 22 dispersed within it, the thermally expandable microcapsules 22 expand upon heating, thickening the varnish layer and eliminating the voids, thereby reliably filling the gaps between the components.

[0060] Furthermore, when the object to be insulated is the stator coil 51, the varnish layer is pressed against the material, so that the varnish flows when heated and penetrates into the stator coil 51 by capillary action, thereby bonding the stator coils 51 together. By bonding (adhering) the material and eliminating voids, it is possible to provide an electronic device or a rotating electrical machine 80 with high mechanical strength, cooling performance, and insulation performance.

[0061] The thermally expandable microcapsules 22 have preferred ranges for particle size, foaming initiation temperature, and expanded size, as described below, but the material is not particularly limited. For example, they may have a structure in which a thermal expansion agent, such as a low-boiling-point hydrocarbon, is encapsulated in a thermoplastic polymer shell made of a thermoplastic resin with gas barrier properties, such as vinylidene chloride resin or acrylic resin. This allows the thermoplastic resin of the shell to soften upon heating, increasing the volume of the thermal expansion agent and causing the capsules to expand.

[0062] The surfaces of the thermally expandable microcapsules 22 may be coated with an inert inorganic powder such as calcium carbonate, talc, or titanium oxide. For example, commercially available microspheres may be used as long as they are fine particles that expand when heated. These thermally expandable microcapsules 22 may be used alone or in combination of two or more types.

[0063] As described above, the insulating sheet 1 is used as interphase insulation by being placed, for example, by pasting or inserting into the gap between components to be insulated, such as the stator coil 51 and the stator core 52. Therefore, the maximum particle size of the thermally expandable microcapsules 22 is smaller than the thickness of the insulating resin layer (2 for one side, 2f and 2r for both sides) formed on each side of the substrate 3, and is smaller than 0.5 to 0.91 times the total thickness (film thickness t2). Furthermore, the average particle size φ22 is preferably smaller than 0.5 times the thickness of the insulating resin layer (2 for one side, 2f and 2r for both sides) formed on each side of the substrate 3, and is smaller than 0.25 to 0.45 times the total thickness (film thickness t2).

[0064] For example, if the dimension (effective gap Gp) obtained by subtracting the thickness t3 of the base material 3 of the insulating sheet 1 from the actual dimension of the gap G5 is 10 μm or more and 100 μm or less, including tolerances, thermally expandable microcapsules 22 having a maximum particle size of 10 μm or less and an average particle size φ22 of 5 μm or less are selected. Furthermore, from the viewpoint of improving the surface smoothness of the insulating resin layer 2, it is preferable to select thermally expandable microcapsules 22 whose maximum particle size is smaller than the film thickness of the insulating resin layer 2 that they form.

[0065] Because the insulating resin layer 2 is semi-cured or uncured, it flows when heated and functions as a varnish that penetrates into recesses on the surfaces of components to be insulated and into gaps between components to be insulated. To ensure efficient penetration and minimize hardening during flow, a latent curing agent that is inactive at temperatures below 60°C is used. On the other hand, if the thermally expandable microcapsules 22 foam when flowing as a varnish, this will hinder penetration into recesses or gaps, so the foaming start temperature of the thermally expandable microcapsules 22 is set to 60°C or higher.

[0066] To suppress an increase in viscosity during varnish flow, promote foaming of the thermally expandable microcapsules 22, and prevent excessively large foam size after curing, the foaming initiation temperature is preferably set to a temperature equal to or lower than the reaction initiation temperature of the latent curing agent plus 20°C. If the reaction initiation temperature of the latent curing agent is lowered by the use of a curing accelerator, the foaming initiation temperature is preferably set to a temperature equal to or lower than the reaction initiation temperature plus 20°C. To bond the insulating resin layer 2 between the components to be insulated, eliminate remaining voids, and reliably fill the gaps between the components, it is necessary to synchronize the flow, foaming, and hardening by heating. In other words, it is desirable to determine the heating conditions such that the thermally expandable microcapsules 22 do not foam during flow, foam after flow is completed, and hardening begins after foaming, by increasing the temperature or increasing it in stages.

[0067] There are no particular limitations on the amount of thermally expandable microcapsules 22 added, but if the expansion ratio is too high, it will result in a significant decrease in the strength and heat resistance of the cured insulating resin layer 2C (referred to as "insulating resin layer 2C" when distinguished from the insulating resin layer 2 before curing). Therefore, it is desirable to adjust the amount so that it can reliably fill the irregularities on the surface of the component to be insulated and the gaps between the components, but because the expansion ratio of the thermally expandable microcapsules 22 varies depending on the type and heating temperature, it is difficult to uniformly specify the amount to be added.

[0068] However, from the viewpoint of uniform dispersion within the thermosetting resin composition, the amount is usually 1 part by mass or more and 100 parts by mass or less per 100 parts by mass of the thermosetting resin, and from the viewpoint of ensuring the thermal fluidity of the varnish, it is more preferably 90 parts by mass or less. If it is less than 1 part by mass, the increase in thickness of the insulating resin layer 2 due to the expansion of the thermally expandable microcapsules 22 will be insufficient, and the gaps between the components will not be filled reliably, and if it exceeds 100 parts by mass, the thermal fluidity of the varnish will be poor and the stator coil 51 will not be able to be fixed.

[0069] Furthermore, inorganic blowing agents such as ammonium carbonate, ammonium borohydride, ammonium hydrogen carbonate, ammonium nitrite, and azides, or organic blowing agents such as azo compounds such as azobisisobutyronitrile, fluorinated alkanes such as trichloromonofluoromethane, semicarbazide compounds such as p-toluenesulfonylsemicarbazide, hydrazine compounds such as paratoluenesulfonylhydrazide, triazole compounds such as 5-morpholyl-1,2,3,4-thiatriazole, and N-nitroso compounds such as N,N'-dinitrosoterephthalamide may be used in combination as needed.

[0070] The thermosetting resin composition may contain a filler 23 from the viewpoints of improving thermal conductivity and mechanical strength, and thickening the insulating resin layer 2. The filler 23 is not particularly limited, and a known filler may be appropriately selected depending on the purpose. The filler 23 may be surface-treated with a silane coupling agent, a titanate coupling agent, or the like, or may not be surface-treated.

[0071] Specific examples of inorganic fillers among the fillers 23 include crystalline silica, fused silica, alumina, talc, clay, calcium carbonate, calcium silicate, titanium dioxide, silicon nitride, aluminum hydroxide, aluminum nitride, boron nitride, glass, barium sulfate, magnesia, beryllium oxide, mica, magnesium oxide, etc. The shape of the filler 23 is preferably crushed or spherical, but may also be sub-spherical, flaky, fibrous, milled fiber, whisker, etc. These fillers 23 may be used alone or in combination of two or more.

[0072] Furthermore, resin-based fillers such as thermoplastic resins, rubber components, and various oligomers may be added to improve the crack resistance and impact resistance of the cured insulating resin layer 2C. Specific examples of thermoplastic resins include butyral resins, polyvinyl acetal resins, polyamide resins, aromatic polyester resins, phenoxy resins, MBS resins (methyl methacrylate-butadiene-styrene copolymers), ABS resins (acrylonitrile-butadiene-styrene copolymers), and acrylic resins, which can be modified with silicone oils, silicone resins, silicone rubbers, fluororubbers, and the like. Various plastic powders, various engineering plastic powders, and the like may also be added.

[0073] The amount of filler 23 to be added may be any amount that allows for uniform mixing within the thermosetting resin composition. It is typically 70% by volume or less of the total amount of the thermosetting resin composition, and considering the ease of mixing, it is preferably 65% ​​by volume or less. If the amount of filler 23 added exceeds 70% by volume, it will not be possible to mix it uniformly with the resin composition, and the characteristics of the insulating resin layer 2 will tend to be difficult to reproduce. Furthermore, when the insulating sheet 1 is used while being folded, it is necessary to increase its flexibility, so an amount of 50% by volume or less is more preferable. Furthermore, if there is no need to increase the thermal conductivity of the insulating sheet 1 or to form a thick varnish layer, it is possible to not add filler 23 to the thermosetting resin composition.

[0074] As described above, the insulating sheet 1 is used as interphase insulation by being attached to or inserted into the gap between components to be insulated. Therefore, it is preferable that the maximum particle size of the filler 23 is also smaller than the actual gap Gp, and that the average particle size is smaller than 0.5 times the actual gap Gp. In other words, it is preferable that the maximum particle size of the filler 23 is smaller than the range of 0.5 to 0.91 times the total thickness (film thickness t2), and that the average particle size is smaller than the range of 0.25 to 0.45 times the total thickness (film thickness t2).

[0075] For example, when the actual dimension obtained by subtracting the thickness t3 of the base material 3 from the gap dimension G5 is 10 μm or more and 100 μm or less, including tolerance, a filler 23 having a maximum particle size of 10 μm or less and an average particle size of 5 μm or less is selected. Furthermore, when it is necessary to improve the surface smoothness of the insulating resin layer 2, it is preferable to select a filler 23 whose maximum particle size is smaller than the film thickness t2 of the insulating resin layer 2 to be formed.

[0076] Furthermore, the thermosetting resin portion 21 may also be blended with an anti-settling agent or dispersant that suppresses the settling of solid powder such as the filler 23 in the resin, an anti-foaming agent that prevents the generation of voids, an anti-blocking agent or slippage improver such as polymer beads that prevent the insulating resin layers 2 from blocking each other, a paint fixing agent, an antioxidant, a flame retardant, a colorant, a thickener, a viscosity reducer, a surfactant, etc.

[0077] Next, the characteristics of the insulating resin layer 2 and the insulating sheet 1 will be described. It is preferable that the insulating resin layer 2 has high surface smoothness and flexibility. To ensure good adhesion to the component to be insulated and to prevent an air gap from forming between the cured insulating resin layer 2C and the component to be insulated, the in-plane distribution of the film thickness t2 of the insulating resin layer 2 is set to within ±30% of the average value.

[0078] The insulating resin layer 2 must also have sufficient flexibility to prevent cracks from occurring even when bent 180 degrees at 25°C. If excessive heating causes drying, the diluent volatilizes and the resin hardening reaction progresses, resulting in a loss of flexibility. In this case, the insulating resin layer 2 lacks flexibility to conform to the surface shape of the components, which can lead to cracks when placed between components, or the insulating resin layer 2 may not adhere or bond to the components even after being heated and hardened.

[0079] Furthermore, if the thickness t2 of the insulating resin layer 2 is too thick, the internal stress will be high, and cracks may occur when the insulating resin layer 2 is bent 180 degrees. The thickness t2 of the insulating resin layer 2 is preferably 1 μm or more and 500 μm or less, and more preferably 5 μm or more and 300 μm or less in order to completely fill the gaps between the components to be insulated. If the thickness t2 is less than 1 μm, it is difficult to form an insulating resin layer 2 without pinholes, and if the thickness t2 exceeds 500 μm, there is a high possibility that cracks will occur during the 180-degree bending test.

[0080] Furthermore, in order to place the insulating sheet 1 between the stator coil 51 and the stator core 52 and allow the insulating resin layer 2 to flow into and completely fill the narrow gaps between the stator coils 51, it is preferable to place the insulating sheet 1 so that no gaps are formed between the stator coil 51 and the stator core 52. To ensure penetration into minute gaps, the film thickness t2 of the insulating resin layer 2 is 1.1 times or more the dimension obtained by subtracting the thickness t3 of the base material 3 from the gap dimension G5 between the members to be insulated, and is usually set to be 1.1 times or more and 2.0 times or less, and more preferably 1.3 times or more and 1.7 times or less.

[0081] Specifically, when the dimension obtained by subtracting the thickness t3 of the base material 3 from the dimension of the gap is 100 μm, the film thickness t2 of the insulating resin layer 2 is preferably 110 μm or more and 200 μm or less, and more preferably 130 μm or more and 170 μm or less. If the film thickness t2 is less than 110 μm, the heated insulating resin layer 2 will not sufficiently fill the fine gaps, and if it exceeds 200 μm, gaps will occur between the slots 52s when the stator 5 of the rotating electric machine 80 is molded, making it impossible to mold it into a circular shape, and this may result in poor assembly.

[0082] Furthermore, in order to place the insulating sheet 1 between the stator coil 51 and the stator core 52 and allow the insulating resin layer 2 to flow into and completely fill the narrow gaps between the stator coils 51, the insulating resin layer 2 must be compressed by 10% or more in thickness (total thickness) at 25°C under a pressure of 25 MPa. Considering the dimensional tolerance of the gaps between components, it is more preferable that the insulating resin layer 2 be compressed by 20% or more in thickness under a pressure of 25 MPa at 25°C. Because the insulating resin layer 2 has a nonvolatile content of 97% by mass or more, it experiences a volumetric shrinkage of 3% to 10% upon complete curing. Furthermore, depending on the type, the base material 3 of the insulating sheet 1 is barely compressed at a pressure of 25 MPa. Therefore, the thickness t2 of the insulating resin layer 2 must be 10% or more larger than the gap dimension G5 minus the thickness t3 of the base material 3. If the film thickness t2 of the insulating resin layer 2 is compressed by less than 10% at a pressure of 25 MPa at 25°C, even if the gaps are filled when the insulating sheet 1 is placed, tiny gaps may occur due to hardening shrinkage.

[0083] Furthermore, when the insulating sheet 1 is to be attached to a component before use, it is preferable that it has surface tackiness (tackiness) at 25°C. On the other hand, if attaching it to a component beforehand would result in poor workability, the surface tackiness can be eliminated while maintaining flexibility and film thickness compressibility by adjusting the blending ratio and drying conditions described above. An indicator of no surface tackiness is that the sheet does not stick even when pressed against the component to be insulated at a pressure of 2 MPa at 40°C. If the sheet is attached under these conditions, the surface tackiness may increase depending on the working environment temperature (25 to 35°C), potentially resulting in poor workability.

[0084] The insulating resin layer 2 of the insulating sheet 1 must have flexibility that allows it to be compressed at 25°C, and must be able to flow when heated and penetrate into the fine details between components (such as the uneven shapes of the stator coil 51 and the stator core 52). To achieve these characteristics, the dry state of the insulating resin layer 2 is important. Flexibility can be easily determined by whether or not cracks occur when the insulating resin layer 2 is bent at 180°C. A method for more quantitatively determining these flexibility and fluidity characteristics may be to use elastic modulus evaluation by viscoelasticity measurement, as disclosed in Patent Document 1.

[0085] The flexibility and fluidity characteristics of the insulating resin layer 2 can also be evaluated by complex viscosity. The complex viscosity at 25°C must be 6.0×102 Pa s or more and 1.0×104 Pa s or less. The condition is that the viscosity decreases with increasing temperature, and its minimum value must be 5.0×102 Pa s or less in the range of 80°C to 150°C.

[0086] An insulating resin layer 2 that does not satisfy these values ​​will not achieve the required compression ratio when pressurized, and will not be able to penetrate into the fine details between components. Furthermore, from the viewpoint of maintaining the shape of the insulating resin layer 2 and exhibiting fluidity at heating temperatures, the complex viscosity at 25°C is 1.0 x 103 Pa s or more and 5.0 x 103 Pa s or less. Furthermore, the minimum value of the complex viscosity at 80°C or more and 150°C or less is 1 Pa s or more and 5.0 x 102 Pa s or less, more preferably one-tenth or less of the value at 25°C. The complex viscosity at 180°C or more saturates at 1.0 x 104 Pa s or more due to the effects of curing.

[0087] After curing, the thermally expandable microcapsules 22 in the insulating resin layer 2 foam, forming voids inside. Because voids reduce the insulating properties and mechanical strength of the cured product, the void size is set to an average of 30 μm or less to maintain insulating properties, and an average of 20 μm or less is more preferable to obtain uniform insulating properties and stable mechanical strength. If the void size exceeds an average of 30 μm, the insulating properties will be degraded, such as a decrease in breakdown voltage or the occurrence of partial discharge, after the varnish has cured, and the mechanical strength will be reduced, resulting in a deterioration in the vibration resistance of the product.

[0088] The thermally expandable microcapsules 22 can obtain hollow microparticles by controlling the heating temperature and heating time to change the internal gas pressure and adjust the increase in volume (expansion). The heating temperature and heating time must be set so that the average pore size of the hollow microparticles is 30 μm or less. The heating temperature (foaming temperature) is preferably 60° C. or higher and 200° C. or lower, but it must be below 20° C. above the reaction initiation temperature of the latent curing agent.

[0089] When the reaction initiation temperature of the latent curing agent is lowered by the use of a curing accelerator, the temperature is preferably set to a temperature equal to or lower than the reaction initiation temperature plus 20°C. In order to suppress foaming variation, a temperature of 80°C or higher and 180°C or lower is more preferable. A temperature lower than 60°C hinders the flow of the varnish, and a temperature higher than 200°C causes the varnish to cure first, resulting in foaming failure or making it impossible to control the pore size. The heating time (foaming time) is not particularly limited as long as it is a time that can control the pore size to an average of 30 μm or less, and from the viewpoint of suppressing foaming variation, a temperature of 30 seconds or higher and 1 hour or lower is preferable.

[0090] The thickness increase of the insulating resin layer 2 after curing is not particularly limited as long as the hollow microparticles of the thermally expandable microcapsules 22 have an average pore size of 30 μm or less and can reliably fill the gaps between the components to be insulated, but it is preferable that the film thickness after curing increase by 10% or more compared to the initial film thickness. If the increase is less than 10%, the gaps cannot be filled in detail and air spaces remain. In other words, it is desirable to set the expansion coefficient of the thermally expandable microcapsules 22 and their content in the insulating resin layer 2 so that the expansion of the thermally expandable microcapsules 22 during the curing process can be expected to increase the volume of the insulating resin layer 2 by 10% or more.

[0091] After being placed in the gap between the components to be insulated, the insulating sheet 1 is heated and cured in a curing process. The heating temperature in the curing process varies depending on the type of curing agent and curing accelerator, but the heating temperature and time are set so as not to deteriorate the components to be insulated. Specifically, the heating temperature is preferably 100°C or higher and 200°C or lower, and more preferably 130°C or higher and 190°C or lower. The heating time is preferably 1 minute or higher and 6 hours or lower, and more preferably 3 minutes or higher and 2 hours or lower.

[0092] If the heating temperature is less than 100°C or the heating time is less than 1 minute, curing will be insufficient, making it difficult to bond and fix to components. At relatively low temperatures of 100°C or higher and 170°C or lower, heating for more than 6 hours will not cause deterioration of the components, but heating for more than 6 hours at 170°C or higher, or heating at high temperatures of 200°C or higher, may cause deterioration of the components. Furthermore, because the insulating sheet 1 contains almost no solvent, it can be cured by induction heating or electric heating, which can simplify the curing process.

[0093] Furthermore, in order to integrate the components to be insulated and improve vibration resistance, the insulating sheet 1 preferably has an adhesive strength to the components after curing of 10 N / m or more, and more preferably 20 N / m or more in order to suppress variations in vibration resistance characteristics. If the adhesive strength is less than 10 N / m, sufficient vibration resistance cannot be obtained, and the long-term reliability of the device will decrease.

[0094] If the insulating sheet 1 is constructed to have the above-mentioned properties, the insulating resin layer 2 is efficiently compressed to a predetermined thickness when pressurized at room temperature, and flows when heated during curing, penetrating into the fine spaces between components. The thermally expandable microcapsules 22 then foam to thicken the varnish layer, eliminating air pockets and reliably filling the gaps between the components to be insulated, thereby insulating and bonding them together.

[0095] Second Embodiment In the first embodiment, the configuration and uses of the insulating sheet, as well as the characteristics suitable for the uses, have been described. In the second embodiment, a method for manufacturing the insulating sheet will be described. Figure 4 is a flowchart for explaining the method for manufacturing the insulating sheet according to the second embodiment.

[0096] 4, the manufacturing process of the insulating sheet 1 includes a first step (step S110) of preparing a slurry of a thermosetting resin composition, and a second step (steps S210 to S220) of applying the slurry prepared in the first step to a substrate 3 or the like and drying it. In the first step, a diluent is added to the thermosetting resin composition to achieve a predetermined mixture viscosity, and the mixture is stirred and mixed with a stirrer until the thermally expandable microcapsules 22 and the filler 23 are uniformly dispersed without settling, to prepare a slurry (step S110).

[0097] The slurry contains at least a first thermosetting resin that is solid at 25°C, a second thermosetting resin that is liquid at 25°C, a latent curing agent, thermally expandable microcapsules 22 that have a foaming initiation temperature of 60°C or higher, an inorganic filler as filler 23, and a diluent. When the gap dimension G5 between the components to be insulated is known in advance, thermally expandable microcapsules 22 are selected that have a maximum particle size smaller than the actual gap Gp and an average particle size φ22 that is less than 0.5 times the actual gap Gp. The filler 23 is selected to have a maximum particle size smaller than the actual gap Gp and an average particle size less than 0.5 times the actual gap Gp.

[0098] In addition, the first thermosetting resin is contained in an amount of 10 parts by mass or more and 90 parts by mass or less per 100 parts by mass of the thermosetting resin in total, and the thermally expandable microcapsules 22 are blended in an amount of 1 part by mass or more and 100 parts by mass or less per 100 parts by mass of the thermosetting resin in total.

[0099] The diluent that dissolves the thermosetting resin volatilizes or evaporates and disappears almost completely after the coating. The diluent is not particularly limited, and a known diluent can be appropriately selected depending on the type of thermosetting resin and inorganic filler used. Specific examples of diluents include toluene and methyl ethyl ketone. These solvents may be used alone or in combination of two or more. The amount of solvent to be added is not particularly limited as long as it provides a mixture viscosity that allows kneading, and is usually 20 parts by mass or more and 200 parts by mass or less per 100 parts by mass of the total of the thermosetting resin and inorganic filler.

[0100] In the second step, the slurry is applied to a substrate 3 or release paper or release film that constitutes the insulating sheet 1 by a sheet coater to a predetermined thickness (step S210).Then, the slurry is dried in a drying oven at a temperature of 80°C or higher and 160°C or lower to volatilize the diluent and form the insulating resin layer 2 (step S220).

[0101] The coating method is not particularly limited, and may be performed using a coating machine known in the art. When the slurry is applied to a release paper or release film and dried in the second step, a third step (step S310) is performed in which the thermosetting resin composition dried in the second step is transferred to one or both sides of the substrate 3 by heating and pressing. A laminator or other device known in the art may be used in the third step.

[0102] As another manufacturing method, the insulating film or insulating paper serving as the substrate 3 may be impregnated with the slurry prepared in the first step, and while being pulled up, the diluent may be volatilized in a drying furnace at a temperature of 80° C. or higher and 160° C. or lower to form the insulating resin layer 2. In this case, the film thickness t2 of the insulating resin layer 2 is adjusted by the viscosity of the slurry.

[0103] The nonvolatile content after drying is 97 parts by mass or more, more preferably 99 parts by mass or more, per 100 parts by mass of the total mass of the insulating resin layer 2. If the content is less than 97 parts by mass, the remaining diluent makes it difficult to release the insulating resin layer 2 from the release paper or the like. The insulating resin layer 2 may be in an uncured state (A-stage state) in which only the diluent has been evaporated, or may be in a semi-cured state (B-stage state) by further heating to promote the curing reaction after the diluent has evaporated. Because the insulating resin layers 2 of the manufactured insulating sheet 1 will bond (block) if they are in contact with each other, the surfaces of the insulating resin layers 2 are covered with a release film or release paper (step S410). This completes the insulating sheet 1, which can be used by peeling off the release film when in use.

[0104] Embodiment 3 In this embodiment 3, an insulation processing method for insulating an electrical device using the insulating sheet described in embodiment 1 will be described, more specifically, a method for manufacturing a rotating electrical machine in which the stator coil and the stator core are insulated using an insulating sheet.

[0105] 5 to 10 are diagrams illustrating an insulation treatment method and a manufacturing method for a rotating electric machine according to a third embodiment, with Fig. 5 being a cross-sectional view along the rotation axis showing the configuration of a rotating electric machine manufactured using the insulation treatment method. Fig. 6 is a perspective view of a stator to be insulated, illustrating a manufacturing method for a rotating electric machine using the insulation treatment method, Fig. 7 is a plan view of the stator, and Fig. 8 is a partial cross-sectional view showing the state of insulation between the stator core and the stator coil in the stator of a rotating electric machine that has been subjected to the insulation treatment method. Fig. 9 is a flowchart illustrating the insulation treatment method, and Fig. 10 is a flowchart illustrating a manufacturing method for a rotating electric machine.

[0106] Before describing the insulation treatment method according to the third embodiment and the method for manufacturing a rotating electric machine using the same, the configuration of the rotating electric machine to be insulated will be described. A rotating electric machine 80 such as an electric motor, a generator, or a compressor includes a stator 5 including a stator coil 51 and an annular stator core 52, as shown in Figures 5 to 7. A predetermined number of slots 52s are provided in the circumferential direction between the teeth 52t of the stator core 52, and the stator coil 51 is housed in each of the slots 52s.

[0107] As shown in FIG. 8 , the gap between the stator core 52 (strictly speaking, the inner wall of the slot 52s) and the stator coil 51 is insulated by a cured insulating sheet 1C (insulator). This insulating sheet 1 may have an insulating resin layer 2 disposed on one or both sides of a substrate 3. That is, in the case of a rotating electric machine 80, the gap between the components to be insulated is the gap between the stator core 52 and the stator coil 51, the gap between the substrate 3 and the stator coil 51, or the gap between the stator core 52 and the substrate 3. Note that insulating tape may be attached to the stator coil 51. The insulating sheet 1C, in which the thermosetting resin composition forming the insulating resin layer 2 is cured, is disposed between the inner wall of the slot 52s and the stator coil 51, and insulates and fixes the stator core 52 and the stator coil 51.

[0108] When the insulating sheet 1 is attached to the stator coil 51 or the stator core 52 in advance, the insulating resin layer 2 is selected to have surface tackiness at 25° C. Furthermore, if attaching the insulating sheet 1 in advance reduces the ease of inserting the stator coil 51, an insulating sheet 1 that does not have surface tackiness at 25° C. is selected.

[0109] The insulating sheet 1 may have the insulating resin layer 2 formed on both sides of the base material 3, or may have the insulating resin layer 2 formed on one side of the base material 3. When the insulating resin layer 2 is on only one side, or when the insulating resin layer 2 does not have surface adhesiveness, the insulating sheet 1 may be attached to the stator core 52 using double-sided tape or the like. Furthermore, when the insulating resin layer 2 is on only one side, for example, when the insulating sheet 1 is installed between the stator coil 51 and the stator core 52, the insulating resin layer 2 is placed facing the stator coil 51 in order to fix the stator coil 51 to the stator core 52.

[0110] Assuming the above-described configuration, the insulation method will be described with reference to the flowchart in Fig. 9, and the manufacturing method for the rotating electric machine will be described with reference to the flowchart in Fig. 10. In assembling the stator 5 in the manufacturing process (insulation process: step S810), the insulating sheet 1 is inserted or attached to the gap between the stator core 52 and the stator coil 51 (step S710). Then, the stator core 52 is formed into an annular shape, whereby the insulating sheet 1 is compressed and fixed (crimped) between the stator core 52 and the stator coil 51, which are the areas to be insulated (step S720).

[0111] As described above, the film thickness t2 of the insulating resin layer 2 is set to 1.1 to 2.0 times, and more preferably 1.3 to 1.7 times, the dimension obtained by subtracting the thickness t3 of the substrate 3 from the dimension (gap dimension G5) of the gap between the stator core 52 (the inner wall of the slot 52s) and the stator coil 51. Therefore, the film thickness is reduced by the pressure applied when the stator core 52 is formed into an annular shape. That is, the film thickness is set to be compressed by 10% or more, and more preferably 20% or more, at a pressure of 25 MPa at 25°C. Therefore, the thickness of the insulating sheet 1 inside the slot 52s is thinner than the thickness t1 of the insulating sheet 1 outside the slot 52s.

[0112] Next, a curing process (step S730) is performed. The insulating resin layer 2 penetrates the gaps between the stator core 52 and the stator coil 51 and into the fine gaps in the stator coil 51 due to the heat applied during the curing process. The thermally expandable microcapsules 22 are then expanded by heating, increasing the thickness of the insulating resin layer 2, eliminating the voids and reliably filling the gaps between the components. Furthermore, because the thickness of the insulating resin layer 2 increases where the insulating sheet 1 is folded, even if there is variation in the gap dimensions between the corners of the stator core 52 and the stator coil 51, the gaps can be easily filled. In other words, the gaps at the corners of the stator core 52 and the stator coil 51 that existed before curing are filled by the insulating sheet 1C after the curing process. The cured insulating resin layer 2C has an adhesive strength of 20 N / m or more between the stator core 52 and the stator coil 51.

[0113] The stator 5, which has been insulated and assembled in this manner, is attached to, for example, the inner peripheral surface of the housing 7 (step S820). Then, the rotor 6 (FIG. 5) is rotatably attached to the housing 7 via a bearing (not shown) so that the outer peripheral surface faces the inner peripheral surface of the stator 5 via a magnetic gap (step S830). This completes the rotating electric machine 80 shown in FIG. 5.

[0114] For these reasons, the rotating electric machine 80 insulated using the insulating sheet 1 has high insulation performance for the stator coil 51 and is less susceptible to insulation degradation. Furthermore, heat generated by the windings of the stator coil 51 can be efficiently dissipated to the stator core 52. Furthermore, since the stator coil 51 is reliably fixed, mechanical strength is maintained and NVH characteristics are improved. Furthermore, since the insulating sheet 1 contains almost no solvent, it can be cured not only in a general-purpose heating furnace but also by induction heating and current heating. Furthermore, since energy loss during the curing process is minimal, the curing time is short, simplifying the manufacturing process of the rotating electric machine 80. Therefore, the rotating electric machine 80 insulated using the insulating sheet 1 has improved insulation reliability, heat dissipation, and vibration resistance, and is capable of being made smaller and with higher output.

[0115] The present application will be described in detail below with reference to examples and comparative examples, but the present application is not limited thereto. In the examples and comparative examples, the following materials were mixed in the formulations shown in Tables 1 and 2 to prepare thermosetting resin compositions. A diluent was added to these thermosetting resin compositions to prepare slurries, which were then applied to a substrate. The diluent was then evaporated and dried to prepare insulating resin layers 2. In the "(x-y)" notation shown in the following explanations and tables, the type of material within the thermosetting resin composition is indicated by "x." For example, the first thermosetting resin is indicated by "1," the second thermosetting resin is indicated by "2," and the thermally expandable microcapsules are indicated by "6." Differences in composition within a type are indicated by "y." When there is no distinction between examples and comparative examples, or when the subject is a comparative example, the reference numeral is omitted, as in "insulating resin layer," for example.

[0116] <1: Solid Thermosetting Resin: First Thermosetting Resin> (1-1) Bisphenol A type epoxy resin (epoxy equivalent 1800, softening point 120°C) (1-2) Bisphenol A type vinyl ester resin (weight average molecular weight 2800, softening point 85°C)

[0117] <2: Liquid thermosetting resin: second thermosetting resin> (2-1) Bisphenol A type epoxy resin (epoxy equivalent: 195) (2-2) Neopentyl glycol dimethacrylate (weight average molecular weight: 240)

[0118] <3: Curing agent> (3-1) Dicyandiamide (reaction initiation temperature 160°C) (3-2) 2,5-dimethyl-2,5-di(t-butylperoxy)hexane (10-hour half-life temperature 117.9°C) (3-3) Xylylenediamine (reactive at room temperature)

[0119] <4: Curing accelerator> (4-1) 1-cyanoethyl-2-methylimidazole (reaction initiation temperature 100°C) (4-2) 1,8-diazabicyclo[5.4.0]undecene-7 (reaction initiation temperature 100°C)

[0120] <5: Thermoplastic resin> (5-1) Phenoxy resin (polymerization average molecular weight: 180,000) (5-2) Polyester resin (polymerization average molecular weight: 100,000)

[0121] <6: Thermally expandable microcapsules> (6-1) Maximum particle size 13 μm, average particle size 10 μm, foaming start temperature 63°C (6-2) Maximum particle size 35 μm, average particle size 22 μm, foaming start temperature 125°C (6-3) Maximum particle size 100 μm, average particle size 53 μm, foaming start temperature 178°C (6-4) Maximum particle size 40 μm, average particle size 28 μm, foaming start temperature 125°C (6-5) Maximum particle size 55 μm, average particle size 40 μm, foaming start temperature 185°C (6-6) Maximum particle size 100 μm, average particle size 50 μm, foaming start temperature 45°C (6-7) Maximum particle size 125 μm, average particle size 60 μm , foaming start temperature 120℃

[0122] <7: Inorganic Fillers> (7-1) Fused Silica (Maximum Particle Size 8 μm, Average Particle Size 3 μm) (7-2) Alumina (Maximum Particle Size 20 μm, Average Particle Size 8 μm) (7-3) Crystalline Silica (Maximum Particle Size 130 μm, Average Particle Size 65 μm)

[0123] <8: Base material> (8-1) Aramid paper (thickness 0.2 mm) (8-2) Polyethylene terephthalate (thickness 0.12 mm) (8-3) Composite insulating film: Polyphenylene sulfide / Polyethylene terephthalate / Polyphenylene sulfide (thickness 0.18 mm, with interlayer adhesive) (8-4) Mesh cloth: Alumina (thickness: 0.24 mm, opening size 80 μm, opening ratio 50%)

[0124]

[0125]

[0126] As shown in Table 1, the insulating resin layers 2 shown in Examples 1 to 6 were produced in accordance with the raw materials and their compositions described in Embodiment 1. On the other hand, as shown in Table 2, the insulating resin layers according to Comparative Examples 1 to 7 did not follow the raw materials and their compositions described in Embodiment 1, and are therefore not compatible with the insulating sheet 1 of the present application.

[0127] The insulating resin layers shown in Examples 1 to 6 and Comparative Examples 1 to 7 were evaluated for surface smoothness, flexibility, compressibility, adhesion, releasability, gelation time, storage shear modulus, loss modulus, loss tangent, and complex viscosity. The cured insulating resin layers were also evaluated for adhesive strength, dielectric strength, film thickness increase rate, and pore size of the thermally expandable microcapsules. Furthermore, stators were fabricated, and the gap state between the stator coil and the stator core and the coil adhesion state were observed.

[0128] The details of each evaluation are explained below. Surface smoothness was determined by whether the in-plane thickness distribution of an insulating resin layer formed to a thickness of approximately 120 μm was within ±30% of the average value (◯: within ±30%, ×: more than ±30%). Flexibility and compressibility were measured twice to confirm the usable life of the insulating resin layer: immediately after the insulating sheet was produced and after 30 days of storage at 40°C. Flexibility was determined by the presence or absence of cracks or chips when the insulating sheet was bent 180 degrees at 25°C (◯: no cracks or chips, ×: cracks). The compressibility of the insulating resin layer was calculated from the reduction in thickness of the insulating sheet when the insulating sheet was placed on a rolled steel plate and a pressure of 25 MPa was applied at 25°C. The compressibility was evaluated by whether the compressibility was 10% or more (◯: 10% or more, ×: less than 10%).

[0129] The adhesiveness was evaluated by placing the insulating sheet on a rolled steel plate and pressing it with a pressure of 2 MPa at 40°C to see whether it adhered, immediately after production and after 30 days of storage at 40°C. It should be noted that adhesiveness is sometimes preferable depending on the application of the insulating sheet, and sometimes not, so it is difficult to say which is better. However, since it is undesirable for adhesiveness to change between immediately after production and after 30 days, this point was evaluated.

[0130] Additionally, to investigate the effect on the coating of the enameled wire that forms the wire strand of the coil, the occurrence of crazing was confirmed. Enameled wire (φ1.0 mm) with a polyesterimide / polyamideimide coating was stretched 5% and then bent into a U-shape to prepare test specimens. An insulating sheet was attached to the surface of the coating at room temperature and then peeled off after 5 minutes. If the insulating sheet lacked tackiness and could not be attached, it was fixed with a clip to allow contact. After peeling, the presence or absence of crazing was evaluated by optical microscope observation and pinhole testing.

[0131] The pinhole test was conducted in accordance with JIS C3003. A test piece of a specified length (approximately 5 m) was immersed in saline solution, and the solution was used as the positive electrode and the test piece as the negative electrode. A direct current voltage of 12 V was applied for 1 minute to check the number of pinholes that occurred. Furthermore, test pieces that had been cured at 150°C for 1 hour after application were also examined using an optical microscope for the presence or absence of cracks or pinholes on the coating surface. If no cracks or pinholes were found and no decrease in breakdown voltage was observed, it was judged that no crazing had occurred. If cracks or pinholes were found and the breakdown voltage was reduced, it was judged that crazing had occurred (○: no crazing, ×: crazing).

[0132] The gel time was measured by taking a sample of the thermosetting resin composition of the insulating sheet and measuring the gel time at 150°C using a hot plate method. The softening point was measured by taking a sheet made of the thermosetting resin composition and measuring it in accordance with JIS C2161 "Test Methods for Electrical Insulation Powder Coatings." The storage shear modulus, loss modulus, loss tangent, complex viscosity, and minimum complex viscosity were measured by dynamic viscoelasticity evaluation using an insulating resin layer with a film thickness of 100 μm or more and 300 μm or less, when the temperature was raised from room temperature at a heating rate of 5°C / min using a parallel plate jig.

[0133] Test pieces for measuring the cured product properties of the insulating resin layer were prepared by heating the test pieces in a heating furnace from room temperature to 150°C over 10 minutes and curing them at 150°C for 1 hour, in order to sequentially proceed with the flow, foaming, and curing of the varnish.

[0134] The adhesive strength was evaluated by preparing adhesive test specimens and using a tensile tester. The adhesive strength was evaluated by preparing adhesive test specimens and using a tensile tester. The adhesive test specimens were prepared by pressing an insulating sheet against an electromagnetic steel sheet whose surface had been treated with acetone degreasing and then curing the sheet. The tensile test was performed at 25°C with a peel angle of 180° and a pulling rate of 10 mm / min, and evaluated according to the following criteria (◯: adhesive strength of 10 N / m or more, ×: adhesive strength of less than 10 N / m).

[0135] The dielectric strength voltage was measured by applying a voltage at a constant rate of 0.5 kV / sec to a test specimen in oil using a dielectric breakdown tester, in which an insulating sheet was attached to one side of a steel plate, the temperature was raised from room temperature to 150°C over 10 minutes, and the specimen was cured at 150°C for 1 hour. The dielectric breakdown voltage was then measured and evaluated according to the following criteria (◯: dielectric breakdown voltage 8 kV or more, ×: dielectric breakdown voltage 8 kV or less).

[0136] The film thickness increase rate was calculated by dividing the film thickness after curing by the film thickness before curing to confirm whether or not the film thickness increased after curing. In addition, the pore size of the cured thermally expandable microcapsules was measured by cross-sectional observation and judged (◯: average particle size 30 μm or less, ×: more than 30 μm).

[0137] To verify the use of the insulating sheet in a rotating electric machine, a stator was fabricated by changing the cross-sectional shape of the wires of the stator coil 51 in Figure 8 from rectangular to round with a diameter of 1.5 mm to increase the gap between the stator coil and the stator core. An insulating sheet with a total thickness of 120 μm formed on one or both sides of the insulating resin layer was inserted and crimped into the 100 μm gap (gap dimension G5) between the stator coil and the stator core. The temperature was then raised from room temperature to 150 °C in 10 minutes and cured at 150 °C for 1 hour. After curing, the cross section was observed to determine whether there was an air gap between the stator core and the stator coil (◯: no air gap, ×: air gap). The stator coil was then removed to check the adhesion between the stator coils (◯: completely adhered, ×: not adhered).

[0138] The evaluation results of the insulating sheets shown in Examples 1 to 6 are shown in Table 3, and the evaluation results of the insulating sheets shown in Comparative Examples 1 to 7 are shown in Table 4.

[0139]

[0140]

[0141] All of the insulating sheets shown in Examples 1 to 5 have excellent flexibility and releasability immediately after production and after 30 days, and a compression rate of 20% or more. They do not cause crazing on enameled wire. Furthermore, their storage shear modulus at 25°C is in the range of 1.0 x 10 Pa or more to 5.0 x 10 Pa or less, with a minimum value of 10 Pa or more to 2.0 x 10 Pa or less at temperatures between 80°C and 150°C. Furthermore, their loss modulus at 25°C is in the range of 1.0 x 10 Pa or more to 5.0 x 10 Pa or less, with a minimum value of 10 Pa or more to 2.0 x 10 Pa or less at temperatures between 80°C and 150°C.

[0142] The maximum value of the loss tangent is in the range of 1.0 to 3.5 at temperatures between 80°C and 150°C. Furthermore, the complex viscosity at 25°C is in the range of 6.0 x 102 Pa s to 1.0 x 104 Pa s, and its minimum value is in the range of 80°C to 150°C and 500 Pa s or less. From the above evaluation results, it is clear that the insulating resin layers according to Examples 1 to 6 can be compressed to a predetermined thickness by applying pressure at room temperature, and can be permeated into the fine details between components by heating during curing.

[0143] Furthermore, the insulating resin layers 2 of Examples 1 to 6 all have an adhesive strength of 20 MPa or more at 25°C, allowing them to firmly bond and fix components to be insulated. Furthermore, they have a high dielectric strength after curing, providing excellent insulation reliability. Furthermore, since there was no change in flexibility or compressibility after 30 days of storage at 40°C, the reaction progresses slowly at room temperature, providing a long usable life. The thermally expandable microcapsules 22 foam after curing, with pore sizes of 30 μm or less and an increased varnish film thickness. Furthermore, in tests using a stator, there was no gap between the stator coil and the stator core, and the stator coil was completely fixed, resulting in high adhesive strength and dielectric strength in all cases.

[0144] In contrast, Comparative Example 1, although similar in composition to Example 1, does not contain thermally expandable microcapsules, so the varnish layer does not increase in thickness after hardening, and the gap between the stator coil and the stator core is not filled, leaving an air layer.

[0145] Comparative Example 2 has a similar formulation to Example 2, but contains 105 parts by mass of thermally expandable microcapsules (6-1) per 100 parts by mass of thermosetting resin. As a result, an insulating resin layer with a smooth surface cannot be obtained, and the varnish layer has high viscosity when heated, so it does not flow into the gaps between the stator coils, making it impossible to fix the stator coils.

[0146] Comparative Example 3, while similar to the formulation of Example 3, contains a curing agent (3-3) that is reactive at room temperature, and the foaming initiation temperature of the thermally expandable microcapsules (6-3) is 178°C, significantly higher than the reaction initiation temperature of the curing agent. Therefore, the reaction proceeds when left standing at room temperature, causing physical properties to change over time, resulting in poor usable life. After 30 days, flexibility and adhesion are lost, and the compression ratio reaches 0%. Furthermore, due to low fluidity during heat curing, penetration into small gaps is not achieved, resulting in poor adhesion to components. Furthermore, because curing proceeds at room temperature, the varnish layer does not flow, the thermally expandable microcapsules do not foam, and the insulating resin layer does not increase in thickness at all. Therefore, the gap between the stator coil and the iron core is not filled, and the stator coil cannot be fixed. Furthermore, cracking and peeling occur when the product is bent during use, resulting in poor workability.

[0147] Comparative Example 4 is similar to the formulation of Example 4, but contains thermally expandable microcapsules (6-4) with an average particle size of 28 μm and a foaming initiation temperature of 125°C. Because the constituent raw materials of the composition are satisfactory, the characteristics of the insulating resin layer and the stator test were also satisfactory. However, the pore size of the thermally expandable microcapsules that foamed after curing was large, averaging 34 μm. This resulted in a decrease in insulation and a decrease in the adhesion of the stator coil due to insufficient strength of the cured product. It should be noted that these problems can sometimes be improved by reducing the pore size and reviewing curing conditions such as the heating rate or curing temperature.

[0148] Comparative Example 5, while similar in formulation to Example 5, uses thermally expandable microcapsules (6-5) with a foaming initiation temperature 25°C higher than the reaction initiation temperature of the latent curing agent (3-1) and crystalline silica (7-3) with a maximum particle size of 130 μm and an average particle size of 65 μm as an inorganic filler. Due to the inclusion of the large particle size inorganic filler, surface smoothness deteriorated when an insulating resin layer with a thickness of 120 μm was fabricated. Upon heating, the varnish flows into the gaps in the stator coil, securing the stator coil. However, because the curing reaction proceeds first, the thermally expandable microcapsules do not foam, and the insulating resin layer does not increase in thickness at all. As a result, the air gap between the stator coil and the stator core could not be filled. Furthermore, in testing a stator with a 100 μm gap between the stator coil and the stator core, the maximum particle size (130 μm) of the inorganic filler was larger than the gap (100 μm), creating a gap between the teeth, making it impossible to fabricate a stator.

[0149] Comparative Example 6 is similar to the formulation of Example 5, but contains thermally expandable microcapsules (6-6) with an average particle size of 50 μm and a foaming initiation temperature of 45°C, and 73 volume% of fused silica (7-1) as an inorganic filler. Because it contains a large amount of inorganic filler, the insulating resin layer has poor smoothness, low toughness, no flexibility or adhesiveness, and a compressibility of 0%. Furthermore, because it contains thermally expandable microcapsules with a low foaming initiation temperature (45°C), foaming progresses when heating begins, inhibiting the fluidity of the varnish and making it impossible to fix the stator coil.

[0150] Comparative Example 7 was similar to the formulation of Example 2, but used thermally expandable microcapsules (6-7) with a maximum particle size of 125 μm, an average particle size of 60 μm, and a foaming initiation temperature of 120°C. Because it contained thermally expandable microcapsules with a large maximum particle size, the surface smoothness decreased when an insulating resin layer with a film thickness of 120 μm was produced. Because the particle size of the thermally expandable microcapsules was large, the pore size increased to an average of 50 μm during foaming after curing. This not only reduced the insulation properties, but also reduced the adhesion of the stator coil due to the insufficient strength of the cured product.

[0151] Furthermore, verification with the stator showed that the thermally expandable microcapsules contained microcapsules whose maximum particle size was larger than the gap size (100 μm) and whose average particle size was larger than 0.5 times the gap size (50 μm). Therefore, when the microcapsules were inserted into the gap between the stator coil and the iron core and pressed together, they did not foam sufficiently and were unable to fill the air layer that existed in the gap between the stator coil and the iron core when they hardened.

[0152] As described above, all evaluation items were good in Examples 1 to 6. On the other hand, in Comparative Examples 1 to 7, some were poor in one or more evaluation items.

[0153] Although various exemplary embodiments and examples are described in this application, the various features, aspects, and functions described in one or more embodiments are not limited to the application of a particular embodiment, but may be applied to the embodiments alone or in various combinations. Therefore, countless variations not illustrated are contemplated within the scope of the technology disclosed in this specification. For example, this includes cases where at least one component is modified, added, or omitted, or where at least one component is extracted and combined with components of another embodiment.

[0154] For example, the insulating sheet 1 is used to insulate the stator core 52 and stator coil 51 of the stator 5, but the present invention is not limited to this. If a rotor is made up of a coil and an iron core, the coil and iron core of the rotor may be insulated using the insulating sheet 1. It goes without saying that the insulating sheet 1 can be used not only in rotating electrical machines but also in other electrical devices that require insulation.

[0155] As described above, the insulating sheet 1 according to the first embodiment includes the substrate 3 made of at least one of insulating paper, insulating film, nonwoven fabric, and mesh cloth, and the insulating resin layer 2 made of an uncured or semi-cured thermosetting resin composition and formed in a sheet shape on one or both sides of the substrate 3. The thermosetting resin composition includes a first thermosetting resin (thermosetting resin (A)) that is solid at 25°C, a second thermosetting resin (thermosetting resin (B)) that is liquid at 25°C, and a latent resin that is inactive at 60°C or below. The insulating resin layer 2 is composed of a thermosetting resin part 21 containing 10 to 90 parts by mass of the first thermosetting resin relative to a total of 100 parts by mass of the first thermosetting resin and the second thermosetting resin, and thermally expandable microcapsules 22 having a maximum particle size smaller than the actual gap Gp, an average particle size smaller than 0.5 times the actual gap Gp, and a foaming start temperature of 60° C., where the actual gap Gp is ​​a value in the range of 0.5 to 0.91 times the total thickness (film thickness t2 (= t2a + t2b)) of the insulating resin layer 2. As a result, the varnish layer (corresponding to film thickness t2) increases in thickness due to foaming of the thermally expandable microcapsules 22 after flowing and penetrating into the fine spaces between the components during a curing process, thereby reliably filling the gaps between the components to be insulated and insulating and bonding them together.

[0156] In particular, if the foaming initiation temperature is set to a value equal to or lower than the reaction initiation temperature of the latent curing agent plus 20°C, the thermosetting resin part 21 will flow and the thermally expandable microcapsules 22 will be able to expand before hardening, so that the gaps can be reliably filled with the varnish layer of the insulating resin layer 2.

[0157] A curing accelerator is added to the thermosetting resin part 21 to lower the reaction initiation temperature of the latent curing agent, and the foaming initiation temperature is set to be equal to or lower than the temperature lowered from the reaction initiation temperature by the curing accelerator plus 20°C. This allows the insulating resin layer 2 to flow even when a curing accelerator is used, and the thermally expandable microcapsules 22 to expand before hardening, so that the gaps can be reliably filled with a varnish layer made of the insulating resin layer 2.

[0158] If the amount of thermally expandable microcapsules 22 is 1% by mass or more and 100% by mass or less relative to 100 parts by mass of the total of the first thermosetting resin and the second thermosetting resin, they can be uniformly dispersed within the insulating resin layer 2, thereby filling gaps and reliably fixing the objects to be insulated (e.g., the stator coil 51 and the stator core 52).

[0159] Furthermore, if the base material 3 is constructed by laminating multiple sheets (base material sheets 31) made of at least one of insulating paper, insulating film, nonwoven fabric, and mesh cloth via a thermosetting resin or adhesive 32, the properties and thickness can be freely adjusted according to the object to be insulated.

[0160] If the first thermosetting resin is an epoxy resin having a softening point in the range of 50° C. or higher and 160° C. or lower, the timing of flow, hardening, and expansion can be more reliably adjusted.

[0161] If the thermosetting resin composition is composed of an inorganic or resin system and contains a filler 23 in an amount of 70 volume % or less relative to the total amount of the thermosetting resin composition, the properties of the insulating sheet 1, including its heat dissipation properties, can be further optimized.

[0162] Furthermore, the method for manufacturing the insulating sheet 1 described above includes a first step (step S110) of stirring and mixing the first thermosetting resin, the second thermosetting resin, the latent curing agent, the thermally expandable microcapsules 22, and the organic solvent for dilution to prepare a slurry of the thermosetting resin composition, and a second step (steps S210 to S220) of applying the slurry to a substrate 3 or a release paper or a release film and drying it to form the insulating resin layer 2. In the second step, if the drying state is determined so that the insulating resin layer 2 has a compressibility such that the film thickness t2 decreases by 10% or more when a pressure of 25 MPa is applied at 25°C, the manufactured insulating sheet 1 can be easily pressure-bonded when inserted between objects to be insulated by the insulation processing method described below.

[0163] If the second step (step S210) involves applying the slurry to release paper or a release film, then including a third step (step S310) of pressing the dried slurry onto one or both sides of the substrate 3 makes it easier to form the insulating resin layer 2 regardless of the properties of the substrate 3.

[0164] Furthermore, according to the insulation treatment method of the present application, by including the steps of inserting the above-mentioned insulating sheet 1 between a first component (e.g., stator coil 51) and a second component (e.g., stator core 52) that constitute an electrical device (step S710), crimping the inserted insulating sheet 1 between the first component and the second component (step S720), and heating the crimped insulating sheet 1 to harden the insulating resin layer 2 and form an insulator (insulating sheet 1C) interposed between the first component and the second component (step S730), the first component and the second component can be reliably insulated and fixed together, thereby making it possible to obtain an electrical device that is excellent in insulation reliability, heat dissipation performance, and vibration resistance.

[0165] In particular, in the step of forming the insulator, if the volume of the insulating resin layer 2 is increased by 10% or more by the expansion of the thermally expandable microcapsules 22, the gaps can be reliably filled.

[0166] Furthermore, in the process of forming the insulator, if the heating temperature and pressure are adjusted so that the average size of the voids formed inside the thermally expandable microcapsules 22 due to expansion is 30 μm or less, the occurrence of partial discharges caused by the voids can be suppressed and insulation reliability can be further improved.

[0167] Furthermore, the manufacturing method of the rotating electric machine 80 of the present application includes a process of assembling the stator 5 to form a ring shape (steps S810 to S820), a process of assembling the rotor 6 (step S830), and a process of supporting the rotor 6 so that the outer peripheral surface faces the inner peripheral surface of the stator 5 with a gap therebetween, and if, in at least one of the processes of assembling the stator 5 and assembling the rotor 6, insulation is performed between the iron core and the coil using the insulation processing method described above, a rotating electric machine 80 with excellent insulation reliability, heat dissipation performance, and vibration resistance can be obtained.

[0168] 1: Insulating sheet, 1C: (cured) insulating sheet (insulator), 2: Insulating resin layer, 21: Thermosetting resin portion, 22: Thermally expandable microcapsule, 22E: (foamed) thermally expandable microcapsule, 23: Filler, 3: Base material, 31: Base material sheet, 32: Adhesive, 5: Stator, 51: Stator coil, 52: Stator core, 52t: Teeth portion, 52s: Slot, 6: Rotor, 80: Rotating electric machine, G5: Gap dimension, Gp: Actual gap, t2: Film thickness, t3: Thickness,

Claims

1. A substrate made of at least one of insulating paper, insulating film, nonwoven fabric, and mesh cloth; and The insulating resin layer is made of an uncured or semi-cured thermosetting resin composition and is formed in a sheet shape on one or both sides of the base material. The thermosetting resin composition comprises: a thermosetting resin part including a first thermosetting resin that is solid at 25° C., a second thermosetting resin that is liquid at 25° C., and a latent curing agent that is inactive at 60° C. or less, the thermosetting resin part including 10 parts by mass or more and 90 parts by mass or less of the first thermosetting resin relative to 100 parts by mass of the total of the first thermosetting resin and the second thermosetting resin; An insulating sheet characterized in that it is composed of thermally expandable microcapsules having a maximum particle size smaller than Gp, an average particle size smaller than 0.5 times Gp, and a foaming initiation temperature of 60°C or higher, where Gp is ​​a value in the range of 0.5 to 0.91 times the total thickness of the insulating resin layer.

2. 2 . The insulating sheet according to claim 1 , wherein the foaming initiation temperature is equal to or lower than a value obtained by adding 20° C. to a reaction initiation temperature of the latent curing agent.

3. A curing accelerator that lowers the reaction initiation temperature of the latent curing agent is added to the thermosetting resin portion, 3. The insulating sheet according to claim 2, wherein the foaming initiation temperature is equal to or lower than a value obtained by adding 20° C. to a temperature drop from the reaction initiation temperature caused by the curing accelerator.

4. An insulating sheet according to any one of claims 1 to 3, characterized in that the amount of the thermally expandable microcapsules is 1 mass% or more and 100 mass% or less relative to a total of 100 mass parts of the first thermosetting resin and the second thermosetting resin.

5. 4. The insulating sheet according to claim 1, wherein the material of the substrate is an insulating resin material made of engineering plastic or super engineering plastic, an inorganic insulating material made of silica, alumina or glass, or a material containing the insulating resin material in fibrous form or the inorganic insulating material in fibrous form.

6. The insulating sheet according to any one of claims 1 to 3, characterized in that the substrate is formed by laminating multiple sheets made of at least one of insulating paper, insulating film, nonwoven fabric, and mesh cloth via a thermosetting resin or an adhesive.

7. 4. The insulating sheet according to claim 1, wherein the first thermosetting resin and the second thermosetting resin include at least one of an epoxy resin, a phenolic resin, and an unsaturated polyester resin.

8. 4. The insulating sheet according to claim 1, wherein the first thermosetting resin is an epoxy resin having a softening point in the range of 50° C. or more and 160° C. or less.

9. 4. The insulating sheet according to claim 1, wherein the latent curing agent is any one of a boron trifluoride-amine complex, dicyandiamide, and an organic acid hydrazide.

10. 4. The insulating sheet according to claim 1, wherein the thermosetting resin composition is composed of an inorganic or resin-based material and contains a filler whose content is 70 volume % or less with respect to the total amount of the thermosetting resin composition.

11. A method for producing the insulating sheet according to any one of claims 1 to 3, comprising the steps of: a first step of stirring and mixing the first thermosetting resin, the second thermosetting resin, the latent curing agent, the thermally expandable microcapsules, and an organic solvent for dilution to prepare a slurry of the thermosetting resin composition; and A second step of applying the slurry to the substrate, a release paper, or a release film and drying the slurry to form the insulating resin layer, A method for manufacturing an insulating sheet, characterized in that in the second step, a drying state is determined so that the insulating resin layer has a compression rate that reduces a film thickness of the insulating resin layer by 10% or more when a pressure of 25 MPa is applied to the insulating resin layer at 25°C.

12. In the second step, when the slurry is applied to the release paper or the release film, A third step of applying the dried slurry to one or both surfaces of the substrate by pressure bonding. The method for producing an insulating sheet according to claim 11, further comprising the steps of:

13. A step of inserting the insulating sheet according to any one of claims 1 to 3 between a first component and a second component that constitute an electrical device; crimping the inserted insulating sheet between the first component and the second component; and a step of heating the compressed insulating sheet to harden the insulating resin layer and form an insulator interposed between the first component and the second component; 1. An insulation treatment method comprising:

14. 14. The insulation treatment method according to claim 13, wherein in the step of forming the insulator, the volume of the insulating resin layer is increased by 10% or more by expansion of the thermally expandable microcapsules.

15. The insulation treatment method according to claim 13, characterized in that in the process of forming the insulator, the heating temperature and compression force are adjusted so that the average size of the voids formed inside the thermally expandable microcapsules by expansion is 30 μm or less.

16. Assembling the stator to form a ring shape; Assembling the rotor; and supporting the rotor so that an outer circumferential surface of the rotor faces an inner circumferential surface of the stator with a gap therebetween; 14. A method for manufacturing a rotating electric machine, comprising the steps of: insulating a space between an iron core and a coil by using the insulation method according to claim 13 in at least one of the steps of assembling the stator and assembling the rotor.