RU2801189C1 - Electrical steel sheet coating composition, electrical steel sheet, laminated core and electric motor - Google Patents

Abstract

FIELD: electrical machines.

SUBSTANCE: invention relates to a coating composition for an electrical steel sheet, to an electrical steel sheet, a laminated core and a electric motor. The coating composition comprises an epoxy resin, an epoxy resin latent hardener, and a thermoplastic elastomer, the thermoplastic elastomer having a melting point of 100°C or higher and 200°C or lower and a flexural modulus of more than 5 MPa and 100 MPa or less, and wherein the amount of thermoplastic elastomer per 100 mass parts of the total amount of epoxy resin and the epoxy latent hardener is 10 mass parts or more and less than 40 mass parts.

EFFECT: invention provides for obtaining a coating composition for an electrical steel sheet, which makes it possible to achieve both the magnetic properties of a laminated core and heat resistance, in which the adhesive strength between electrical steel sheets can be maintained even in a high-temperature state during movement, which is important for use in an electric motor.

6 cl, 7 dwg, 2 tbl

Description

FIELD OF TECHNOLOGY

[0001] The present invention relates to a coating composition for electrical steel sheet, electrical steel sheet, laminated core and electric motor. Priority is claimed in accordance with Japanese Patent Application No. 2020-104234, filed June 17, 2020, the contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

[0002] As a core (iron core) used in a motor, a laminated core in which a plurality of electrical steel sheets are laminated and bonded to each other is known. Attachment and welding are known as methods for joining electrical steel sheets to each other. However, when attaching and welding, the magnetic properties (magnetic core loss) of electrical steel sheets may deteriorate due to mechanical deformation and thermal deformation during processing.

[0003] As a joining method other than affixing and welding, for example, a method of bonding electrical steel sheets with surface-formed insulating coating having adhesiveness to each other is known (Patent Document 1). Bonding using an insulating coating does not cause mechanical deformation and thermal deformation, and therefore the magnetic loss in the core is better than when attaching and welding. The epoxy resin has a small volume change, is excellent in heat resistance, oil resistance, and chemical resistance, and is excellent as an adhesive for bonding electrical steel sheets to each other (Patent Documents 2 and 3).

[0004] In recent years, in response to the need for further improvement in motor efficiency, further reduction in core magnetic loss has been required. Thinning the sheet of electrical steel is effective in reducing magnetic losses in the core. However, since the Young's modulus of the steel sheet decreases as the thickness of the sheet decreases, it is required not to apply a stress strain to the steel sheet, which causes deterioration of the magnetic loss. In addition, in the driving motor of an electric vehicle or the like, the temperature abruptly changes from room temperature at the start of travel to a high temperature during travel. Therefore, it is important to have excellent heat resistance in which sufficient adhesive strength can be maintained even under the influence of high temperature during movement while reducing the magnetic loss in the core.

[0005] Resins having excellent heat resistance are solid at room temperature and tend to apply a large stress to the laminated core. On the other hand, resins having suitable hardness near room temperature are soft and inferior in heat resistance at high temperature. Epoxy resins have excellent heat resistance, but are hard and have low fracture toughness. Therefore, a stress strain is applied to the steel sheet due to curing during adhesion, which means that as the steel sheet becomes thinner, the magnetic loss deteriorates. In addition, if the fracture toughness is low, then there is a risk of weakening the adhesion due to vibration during movement.

[List of cited documents]

[Patent documentation]

[0006] Patent Document 1: Unexamined Japanese Patent Application First Publication No. 2017-011863

Patent Document 2: Unexamined Japanese Patent Application First Publication No. 2000-173816

Patent Document 3: PCT International Publication No. WO 2004/070080

Brief description of the invention

Problems solved by the invention

[0007] It is an object of the present invention to provide a coating composition for an electrical steel sheet that achieves both the magnetic properties of the laminated core and the heat resistance in which the adhesive strength between the electrical steel sheets can be maintained even in a high temperature state during movement, a sheet of electrical steel with its use, a laminated core and an electric motor.

Solutions to the Problem

[0008] The present invention includes the following aspects.

[1] A coating composition for electrical steel sheet, comprising an epoxy resin, an epoxy latent curing agent, and a thermoplastic elastomer, wherein the thermoplastic elastomer has a melting point of 100°C or more and 200°C or less and a flexural modulus of more than 5 MPa and 100 MPa or less, and moreover, the amount of thermoplastic elastomer per 100 mass parts of the total amount of epoxy resin and the latent epoxy resin hardener is 10 mass parts or more and less than 40 mass parts.

[2] The coating composition for electrical steel sheet according to [1], wherein the thermoplastic elastomer is at least one selected from an olefin-based elastomer, a urethane-based elastomer, and a polyester-based elastomer.

[3] An electrical steel sheet with an insulating coating formed by applying an electrical steel sheet coating composition according to [1] or [2] to a surface of a base steel sheet.

[4] The electrical steel sheet of [3], wherein the base steel sheet has an average sheet thickness of 0.30 mm or less.

[5] A laminated core in which a plurality of electrical steel sheets according to [3] or [4] are laminated and bonded to each other.

[6] An electric motor comprising a laminated core according to [5].

Invention Effects

[0009] According to the present invention, it is possible to provide a coating composition for an electrical steel sheet that achieves both the magnetic properties of the laminated core and the heat resistance in which the adhesive strength between the electrical steel sheets can be maintained even in a high temperature state during movement, the electrical steel sheet steel with its use, laminated core and electric motor.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] FIG. 1 is a sectional view of an electric motor including a laminated core according to the first embodiment of the present invention.

Fig. 2 is a side view of a laminated core.

Fig. 3 is a sectional view taken along line A-A in FIG. 2.

Fig. 4 is a plan view of the material forming the laminated core.

Fig. 5 is a sectional view taken along line B-B in FIG. 4.

Fig. 6 is an enlarged view of part C in FIG. 5.

Fig. 7 is a side view of a manufacturing apparatus used to manufacture a laminated core.

Embodiment(s) of the invention

[0011] Next, with reference to the drawings, a laminated core according to one embodiment of the present invention, a motor including such a laminated core, and a material constituting such a laminated core will be described. Here, in the present embodiment, a motor, specifically an alternating current (AC) motor, more specifically a synchronous motor, and still more specifically, a permanent magnet excited motor, will be described as an example motor. This type of electric motor is suitable for use in an electric vehicle, for example.

(Electric motor 10)

[0012] As shown in FIG. 1, the motor 10 includes a stator 20, a rotor 30, a housing 50, and a rotating shaft 60. The stator 20 and the rotor 30 are housed in the housing 50. The stator 20 is fixed in the housing 50. In the present embodiment, an internal rotor machine is used as the motor 10. , in which the rotor 30 is located in the stator 20 in the radial direction. However, an external rotor machine in which the rotor 30 is located outside the stator 20 can be used as the motor 10. Also, in the present embodiment, the motor 10 is a 12-pole, 18-slot three-phase AC motor. However, the number of poles, the number of slots, the number of phases, and the like can be appropriately changed. The electric motor 10 can be rotated at 1000 rpm, for example, by applying in each phase a drive current having an effective value of 10 A and a frequency of 100 Hz.

[0013] The stator 20 includes a bonded-laminated stator core (hereinafter referred to as a stator core) 21 and a winding (not shown). The stator core 21 includes a circular (annular) back 22 of the core and a plurality of toothed parts (teeth) 23. In the following, the direction of the central axis O of the stator core 21 (or back 22 of the core) will be called the axial direction, the radial direction (the direction orthogonal to the central axis O) of the stator core 21 (or core back 22) will be called the radial direction, and the circumferential direction (direction around the central axis O) of the stator core 21 (or core back 22) will be called the circumferential direction.

[0014] The back 22 of the core is formed in an annular shape in a plan view of the stator 20 as viewed from the axial direction. A plurality of teeth 23 protrude from the inner periphery of the core back 22 in a radially inward direction (towards the central axis O of the core back 22 in the radial direction). A plurality of teeth 23 are arranged at equal angular intervals in the circumferential direction. In the present embodiment, 18 teeth 23 are provided every 20 degrees of the central angle centered on the central axis O. A plurality of teeth 23 are formed to have the same shape and the same size. Therefore, the plurality of teeth 23 have the same thickness dimension. The winding is wound around the teeth 23. The winding may be a concentrated winding or a distributed winding.

[0015] The rotor 30 is located inside the stator 20 (stator core 21) in the radial direction. The rotor 30 includes a rotor core 31 and a plurality of permanent magnets 32. The rotor core 31 is formed with a circular (annular) shape and is located coaxially with the stator 20. A rotating shaft 60 is located in the rotor core 31. The rotating shaft 60 is attached to the core 31 of the rotor. A plurality of permanent magnets 32 are attached to the rotor core 31. In the present embodiment, the pair of permanent magnets 32 forms one magnetic pole. A plurality of sets of permanent magnets 32 are arranged at equal angular intervals in the circumferential direction. In the present embodiment, 12 sets of permanent magnets 32 (a total of 24 magnets) are provided every 30 degrees of the central angle centered on the central axis O.

[0016] In the present embodiment, an embedded magnet motor is used as the permanent magnet motor. The rotor core 31 is formed with a plurality of through holes 33 that penetrate the rotor core 31 in the axial direction. The plurality of through holes 33 are provided corresponding to the location of the plurality of permanent magnets 32. The permanent magnets 32, which are located in the respective through holes 33, are attached to the rotor core 31. The attachment of each permanent magnet 32 to the rotor core 31 can be realized, for example, by gluing the outer surface of the permanent magnet 32 and the inner surface of the through hole 33 with an adhesive. Here, as a permanent magnet motor, a surface magnet motor can be used instead of an embedded magnet motor.

[0017] Both the stator core 21 and the rotor core 31 are laminated cores. For example, as shown in FIG. 2, the stator core 21 is formed by laminating (laminating) a plurality of electrical steel sheets 40 in the lamination direction. Here, the thickness of the layered structure (full length along the central axis O) of each of the stator core 21 and the rotor core 31 is, for example, 50.0 mm. The outer diameter of the stator core 21 is, for example, 250.0 mm. The inner diameter of the stator core 21 is, for example, 165.0 mm. The outer diameter of the rotor core 31 is, for example, 163.0 mm. The inner diameter of the rotor core 31 is, for example, 30.0 mm. However, these values are exemplary, and the layer structure thickness, outer diameter and inner diameter of the stator core 21 and the layer structure thickness, outer diameter and inner diameter of the rotor core 31 are not limited to these values. Here, the inner diameter of the stator core 21 is based on the end portion of the tooth 23 in the stator core 21. That is, the inner diameter of the stator core 21 is the diameter of an imaginary circle inscribed in the end portions of all teeth 23.

[0018] Each electrical steel sheet 40 constituting the stator core 21 and the rotor core 31 is formed by, for example, punching (punching) the material 1 as shown in FIG. 4-6. The material 1 is an electrical steel sheet which is the base of the electrical steel sheet 40 . As an example of the material 1, for example, a strip-shaped steel sheet and a cut sheet can be given. Although the laminated core is described, the material 1 will be described below. Here, in this specification, the strip-shaped steel sheet which is the base of the electrical steel sheet 40 may be referred to as material 1. The electrical steel sheet 40 may be referred to as a steel sheet having a used for the laminated core. shape obtained by punching material 1.

(Material 1)

[0019] For example, the material 1 which is wound into the roll 1A shown in FIG. 7. In the present embodiment, an isotropic electrical steel sheet is used as the material 1. As the isotropic electrical steel sheet, the isotropic electrical steel sheet of JIS C 2552:2014 can be used. However, as the material 1, an anisotropic electrical steel sheet may be used instead of the isotropic electrical steel sheet. As the anisotropic electrical steel sheet in this case, an anisotropic electrical steel sheet according to JIS C 2553:2019 can be used. In addition, thin strip of isotropic electrical steel or thin strip of anisotropic electrical steel according to JIS C 2558:2015 can be used.

[0020] The upper and lower limit values of the average thickness t0 of the material sheet 1 are set, for example, as follows, considering the case in which the material 1 is used for the electrical steel sheet 40. As the material 1 becomes thinner, the cost of manufacturing the material 1 increases. Therefore, considering the manufacturing costs, the lower limit value of the average thickness t0 of the material sheet 1 is 0.10 mm, preferably 0.15 mm, and more preferably 0.18 mm. On the other hand, when the material 1 is too thick, the manufacturing cost is favorable, but when the material 1 is used for the electrical steel sheet 40, the eddy current loss increases and the core magnetic loss deteriorates. Therefore, considering the magnetic core loss and manufacturing cost, the upper limit value of the average thickness t0 of the material sheet 1 is 0.65 mm, preferably 0.35 mm, and more preferably 0.30 mm. The value of 0.20 mm can be exemplified as a value that satisfies the above range of the average thickness t0 of the material sheet 1.

[0021] Here, the average thickness t0 of the material sheet 1 includes not only the thickness of the base steel sheet 2 described below, but also the thickness of the insulation coating 3. In addition, the method for measuring the average thickness t0 of the material sheet 1 is, for example, the following measurement method . For example, when the material 1 is wound in the form of a roll 1A, at least a portion of the material 1 is unwound in the form of a flat sheet. In the material 1 unwound in the form of a flat sheet, a predetermined position is selected on the material 1 in the longitudinal direction (for example, a position remote from the edge of the material 1 in the longitudinal direction by 10% of the total length of the material 1). In the selected position, the material 1 is divided into five regions in its width direction. At four locations that are the boundaries of these five regions, the thickness of the sheet of material 1 is measured. The average of the sheet thicknesses at the four locations can be taken as the average thickness t0 of the sheet of material 1.

[0022] The upper and lower limit values of the average thickness t0 of the material sheet 1 can, of course, be used as the upper and lower limit values of the average thickness t0 of the electrical steel sheet 40. Here, the method for measuring the average thickness t0 of the electrical steel sheet 40 is, for example, the following measurement method. For example, the thickness of the laminated core structure is measured at four locations (ie, every 90 degrees about the central axis O) at equal intervals in the circumferential direction. Each of the measured thicknesses of the laminar structure at four locations is divided by the number of laminated electrical steel sheets 40 to calculate the thickness per sheet. The average value of the sheet thicknesses at the four locations can be taken as the average thickness t0 of the electrical steel sheet 40 .

[0023] As shown in FIG. 5 and FIG. 6, the material 1 includes a base steel sheet 2 and an insulating coating 3. In the material 1, both surfaces of the base steel sheet 2 in the form of a strip are covered with an insulating coating 3. In the present embodiment, most of the material 1 is formed by the main steel sheet 2, and the insulating coating 3 thinner than the base steel sheet 2 is applied to the surface of the base steel sheet 2.

[0024] The chemical composition of the base steel sheet 2 includes 2.5% to 4.5% Si in mass%, as shown below in units of mass%. Here, when the chemical composition is in the above range, the yield strength of the material 1 (electrical steel sheet 40) can be set to 380 MPa or more and 540 MPa or less, for example.

[0025] Si: 2.5% to 4.5%

Al: 0.001% to 3.0%

Mn: 0.05% to 5.0%

The rest: Fe and impurities

[0026] When the material 1 is used for the electrical steel sheet 40, the insulating coating 3 exhibits an insulating characteristic between the electrical steel sheets 40 adjacent to each other in the lamination direction. In addition, in the present embodiment, the insulating coating 3 has adhesiveness and adheres the electrical steel sheets 40 adjacent to each other in the lamination direction. The insulation cover 3 may have a single layer structure or a multilayer structure. More specifically, for example, the insulating coating 3 may have a single layer structure with both insulating performance and adhesiveness, or may have a multi-layered structure including an underlying insulating coating with excellent insulating performance and an upper insulating coating with excellent adhesiveness. Here, the presence of adhesion means the manifestation of adhesive strength of a given or greater value under given temperature conditions.

[0027] In the present embodiment, the insulating coating 3 completely covers both surfaces of the base steel sheet 2 without gaps. However, as long as the above-mentioned insulating performance and adhesiveness are maintained, a portion of the insulating coating layer 3 should not cover both surfaces of the base steel sheet 2 without gaps. In other words, part of the insulating coating layer 3 may be provided discontinuously on the surface of the base steel sheet 2. However, in order to ensure the insulating performance, both surfaces of the base steel sheet 2 must be covered with the insulating coating 3 so that neither surface is exposed. Specifically, when the insulation coating 3 does not have an underlying insulation coating with excellent insulation performance, but has a single layer structure with both insulation performance and adhesiveness, the insulation coating 3 should be formed on the entire surface of the base steel sheet 2 without gaps. On the other hand, when the insulation coating 3 has a sandwich structure having an underlying insulation coating with excellent insulation performance and an upper insulation coating with excellent adhesiveness, even if the underlying insulation coating is formed on the entire surface of the base steel sheet without gaps, and the upper insulation coating is provided intermittently. in addition to forming both the underlying insulation coating and the upper insulation coating on the entire surface of the base steel sheet 2 without gaps, both insulation performance and adhesiveness can be ensured.

[0028] The coating composition for forming the underlying insulation coating is not particularly limited, and, for example, a conventional treatment agent such as a chromic acid-containing treatment agent or a phosphate-containing treatment agent can be used.

[0029] An adhesive insulating coating is applied with an electrical steel sheet coating composition comprising an epoxy resin, an epoxy resin latent hardener, and a thermoplastic elastomer. An insulating coating composed of a coating composition for electrical steel sheet is in an uncured state or a semi-cured state (Step B) before being heated and pressurized to make a laminated core, a curing reaction proceeds by heating during heating and pressurizing, and adhesiveness is exhibited. The coating composition for electrical steel sheet may be used to form an insulating coating with a single layer structure, or may be used to form an upper insulating coating provided on an underlying insulating coating.

[0030] As the epoxy resin, an ordinary epoxy resin can be used, and specifically, any epoxy resin having two or more epoxy groups in one molecule can be used without particular limitation. Examples of such epoxy resins include bisphenol A type epoxy resins, bisphenol F type epoxy resins, phenolic novolac type epoxy resins, cresol novolac type epoxy resins, alicyclic epoxy resins, glycidyl ester type epoxy resins, glycidyl amine type epoxy resins, epoxy oxide glycolyl urea-type resins, isocyanurate-type epoxy resins, acrylic acid-modified epoxy resins (epoxyacrylate), phosphorus-containing epoxy resins and their halides (brominated epoxy resins, etc.), hydrogen additives, and the like. Epoxy resins may be used alone, or two or more of them may be used in combination.

[0031] The coating composition for electrical steel sheet may contain an acrylic resin. Acrylic resin is not particularly limited. Examples of monomers used for acrylic resins include unsaturated carboxylic acids such as acrylic acid and methacrylic acid, and (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, cyclohexyl(meth)acrylate, 2-ethylhexyl(meth)acrylate, 2-hydroxyethyl(meth)acrylate and hydroxypropyl(meth)acrylate. Here (meth)acrylate is acrylate or methacrylate. Acrylic resins may be used alone, or two or more of them may be used in combination.

[0032] The acrylic resin may have a structural unit derived from a different monomer than the acrylic monomer. Examples of other monomers include ethylene, propylene and styrene. The other monomers may be used alone, or two or more of them may be used in combination.

[0033] When acrylic resin is used, it can be used as an acrylic-modified epoxy resin obtained by copolymerization grafting of acrylic resin to epoxy resin. In a coating composition for an electrical steel sheet, it may be present as an acrylic resin-forming monomer.

[0034] An epoxy latent hardener is a type of hardener that cures an epoxy resin and initiates a curing reaction when heated to a predetermined temperature. Examples of latent epoxy hardeners include aromatic polyamines, acid anhydrides, phenolic hardeners, dicyandiamides, amine-boron trifluoride complexes, and organic acid hydrazides.

[0035] Examples of aromatic polyamines include m-phenylenediamine, diaminodiphenylmethane, diaminodiphenylethane, and diaminodiphenyl sulfone. Examples of the acid anhydrides include phthalic anhydride, hexahydrophthalic anhydride, tetrahydrophthalic anhydride, pyromellitic dianhydride and pyromellitic acid anhydride, and among them, an acid anhydride which has a melting point of 160°C or higher and is solid at room temperature is preferable, and trimellitic anhydride and benzophenone are particularly preferable. -tetracarboxylic anhydride. Examples of phenolic hardeners include phenol novolac resins, cresol novolac resins, bisphenol novolac resins, triazine modified phenol novolac resins, and phenol resole resins.

[0036] Considering the heat resistance of the cured product, aromatic polyamines, phenolic curing agents, and dicyandiamides are preferred as the latent epoxy resin curing agent, and phenol-resol resins, diaminodiphenylmethane, and dicyandiamides are more preferred. Epoxy latent hardeners may be used alone, or two or more of them may be used in combination.

[0037] The lower limit value of the amount of latent epoxy hardener in the coating composition for electrical steel sheet per 100 mass parts of epoxy resin is preferably 1 mass part, and more preferably 2 mass parts. The upper limit value of the amount of epoxy latent hardener is preferably 20 mass parts, and more preferably 15 mass parts.

[0038] A thermoplastic elastomer is a compound consisting of a soft segment and a hard segment that retains the elasticity of rubber, and preferably one that can be finely dispersed in an epoxy resin.

[0039] The melting point of the thermoplastic elastomer is 100°C or higher and 200°C or lower. When the melting point of the thermoplastic elastomer is equal to or greater than the lower limit value, the high temperature adhesive strength is maintained. When the melting point of the thermoplastic elastomer is equal to or less than the upper limit value, the magnetic loss in the core is favorable. The lower limit value of the melting point of the thermoplastic elastomer is preferably 90°C, more preferably 110°C, and even more preferably 130°C or higher. The upper limit value of the melting point of the thermoplastic elastomer is preferably 180°C, and more preferably 160°C. Here, "melting point" is a value measured at a temperature rise rate of 10°C/min according to JIS K7121 (1987) using a differential scanning calorimeter (DSC).

[0040] The flexural modulus of the thermoplastic elastomer is more than 5 MPa and 100 MPa or less. When the flexural modulus of the thermoplastic elastomer exceeds the lower limit value, it is possible to prevent the thermoplastic elastomer from protruding from the end due to pressure during bonding. When the flexural modulus of the thermoplastic elastomer is equal to or less than the upper limit value, the magnetic loss in the core is favorable. The lower limit value of the flexural modulus of the thermoplastic elastomer is preferably 6 MPa, and more preferably 7 MPa. The upper limit value of the flexural modulus of the thermoplastic elastomer is preferably 80 MPa, and more preferably 60 MPa. Here, the flexural modulus is measured under the condition of a test speed of 10 mm/min (1 mm/min when the test specimen has a size of 3.5 mm or less) according to JIS K 7171 (2008).

[0041] As a thermoplastic elastomer, at least one selected from an olefin-based elastomer, a urethane-based elastomer, and a polyester-based elastomer is preferable because both magnetic property and heat resistance are easy to achieve. The thermoplastic elastomers may be used alone, or two or more of them may be used in combination.

[0042] Examples of olefin-based elastomers include elastomers obtained by combining or blending an ethylene-propylene copolymer with polypropylene.

[0043] Examples of urethane-based elastomers include urethane bonded compounds in which a diisocyanate and a diol have reacted. The viscoelastic properties of the urethane elastomer can be controlled by the length of the carbon chain of the diol.

[0044] Examples of diisocyanates include hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, diphenylmethane diisocyanate, tolylene diisocyanate, and urethane prepolymers with isocyanate-type groups at both ends. Examples of diols include ethylene glycol, dipropylene glycol, tetraethylene glycol, 1,4-butanediol, 1,4-cyclohexanediol, dihydroxynaphthalene, and bisphenol A.

[0045] Examples of the polyester elastomer include polyester-polyether type copolymers (polybutylene terephthalate and tetrahydrofuranglicol copolymers, etc.) and polyester-polyester type copolymers (polybutylene terephthalate and polybutylene adipate copolymers, etc.).

[0046] The amount of thermoplastic elastomer in the coating composition for electrical steel sheet per 100 mass parts of the total amount of epoxy resin and epoxy latent hardener is 10 mass parts or more and less than 40 mass parts. When the amount of thermoplastic elastomer is equal to or greater than the lower limit value, the magnetic loss in the core is favorable. When the amount of thermoplastic elastomer is equal to or less than the upper limit value, high temperature adhesive strength is maintained.

[0047] In general, when the adhesive strength at high temperature is ensured, the high temperature resistant epoxy resin adhesive has too high a Young's modulus near room temperature, a voltage is applied to the steel sheet, and the magnetic loss in the core deteriorates. On the other hand, heat resistance deteriorates when the resin is formulated with a suitable strength near room temperature. In the present invention, a thermoplastic elastomer which has a soft segment and a hard segment and has a large flexural modulus is finely dispersed in an epoxy resin. Accordingly, the voltage applied near room temperature is minimized and the deterioration of the magnetic loss in the core is minimized. In addition, since thermoplastic elastomers are not bonded to each other, epoxy resin flow is minimized at high temperature, and adhesive strength is maintained. When a specific amount of such special thermoplastic elastomer is used, both core magnetic loss and heat resistance near room temperature are achieved.

[0048] Since, in the present invention, an insulating coating can be formed with such a coating composition for an electrical steel sheet and the voltage applied to the electrical steel sheet can be reduced, it can be suitably applied to a thin electrical steel sheet that is effective for reducing magnetic losses. More specifically, the coating composition for electrical steel sheet of the present invention is particularly effective as a coating composition for forming an insulating coating on the surface of a base steel sheet having an average sheet thickness of 0.30 mm or less.

[0049] The insulating coating 3 can be formed, for example, by applying a coating liquid in which a coating composition for an electrical steel sheet is dissolved in a solvent to the surface of a base steel sheet, drying it, and firing it. The solvent used for the coating liquid is not particularly limited as long as it can dissolve the coating composition for the electrical steel sheet, and it is preferable to use an aqueous solution to prevent emission of the organic solvent. The lower limit value of the final temperature during firing is preferably 120°C, and more preferably 150°C. The upper limit value of the final temperature during firing is preferably 250°C, and more preferably 230°C. The lower limit value of the firing time is preferably 5 seconds, and more preferably 8 seconds. The upper limit value of the firing time is preferably 60 seconds, and more preferably 30 seconds.

[0050] The upper and lower limit values of the average thickness t1 of the insulating coating 3 are set, for example, as follows, considering the case in which the material 1 is used for the electrical steel sheet 40. When the material 1 is used for the electrical steel sheet 40, the average thickness t1 of the insulating coating 3 (thickness per surface of the electrical steel sheet 40 (material 1)) is controlled so that the insulating performance and adhesiveness between the sheets laminated to each other can be secured. 40 electrical steel. In the case of the insulating coating 3 having a single layer structure, the average thickness t1 of the insulating coating 3 (thickness per surface of the electrical steel sheet 40 (material 1)) may be, for example, 1.5 µm or more and 8.0 µm or less . In the case of the insulation cover 3 having a multi-layer structure, the average thickness of the underlying insulation cover may be, for example, 0.3 µm or more and 2.5 µm or less, and preferably 0.5 µm or more and 1.5 µm or less. . The average thickness of the upper insulation coating may be, for example, 1.5 µm or more and 8.0 µm or less. Here, the method for measuring the average thickness t1 of the insulation coating 3 in the material 1 is the same as for the average thickness t0 of the sheet of material 1, and the average thickness can be determined by obtaining the thickness of the insulation coating 3 at a plurality of locations and averaging these thicknesses.

[0051] The upper and lower limit values of the average thickness t1 of the insulating coating 3 in the material 1 can naturally be used as the upper and lower limit values of the average thickness t1 of the insulating coating 3 in the electrical steel sheet 40. Here, the method for measuring the average thickness t1 of the insulating coating 3 in the electrical steel sheet 40 is, for example, the following measurement method. For example, among the plurality of electrical steel sheets constituting the laminated core, the electrical steel sheet 40 located on the outermost side in the lamination direction (the electrical steel sheet 40 whose surface is exposed in the lamination direction) is selected. On the surface of the selected electrical steel sheet 40, a predetermined position in the radial direction (eg, a position exactly in the middle (center) between the inner peripheral edge and the outer peripheral edge of the electrical steel sheet 40) is selected. At the selected position, the thickness of the insulating coating 3 of the electrical steel sheet 40 is measured at four locations (that is, every 90 degrees around the central axis O) at equal intervals in the circumferential direction. The average of the measured thicknesses at the four locations can be taken as the average thickness t1 of the insulating coating 3. Here, the reason why the average thickness t1 of the insulating coating 3 is measured in this way on the electrical steel sheet 40 located at the outermost side in the lamination direction is, that the insulating coating 3 is formed such that the thickness of the insulating coating 3 barely changes at the lamination position in the lamination direction of the electrical steel sheet 40 .

[0052] The electrical steel sheet 40 is manufactured by punching the material 1 as described above, and using the electrical steel sheet 40, a laminated core (stator core 21 and rotor core 31) is manufactured.

(Method of laminating a laminated core)

[0053] Next, the description will return to the laminated core. As shown in FIG. 3, a plurality of electrical steel sheets 40 constituting the stator core 21 are laminated through the insulating coating 3. The electrical steel sheets 40 adjacent to each other in the lamination direction are bonded over the entire surface with the insulating coating 3. In other words, the surface facing in the lamination direction of the electrical steel sheet 40 ( hereinafter referred to as the first surface) is the adhesive area or zone 41a on the entire surface. However, electrical steel sheets 40 adjacent to each other in the lamination direction may not be adhered over the entire surface. In other words, on the first surface of the electrical steel sheet 40, the adhesive area or area 41a and the non-adhesive area or area (not shown) can be mixed.

[0054] In the present embodiment, a plurality of electrical steel sheets constituting the rotor core 31 are fastened to each other by a fastening means (connecting protrusion) 42 shown in FIG. 1. However, the plurality of electrical steel sheets constituting the rotor core 31 may also have a sandwich structure bonded by the insulating coating 3, as in the stator core 21. In addition, a laminated core such as the stator core 21 and the rotor core 31 can be formed by a so-called rotary stack.

(Method of manufacturing laminated core)

[0055] The stator core 21 is manufactured, for example, using the manufacturing apparatus 100 shown in FIG. 7. In the following, when describing the manufacturing method, the laminated core manufacturing apparatus 100 (hereinafter, simply referred to as the manufacturing apparatus 100) will be described first. In the production apparatus 100, while the material 1 is fed from the roll 1A (reel) in the direction of the arrow F, it is repeatedly punched using the staging dies and gradually shaped into the electrical steel sheet 40 . Then, the punched electrical steel sheets 40 are layered and pressed while the temperature rises. As a result, the electrical steel sheets 40 adjacent to each other in the lamination direction are bonded to each other by the insulating coating 3 (that is, the part of the insulating coating 3 located in the adhesive region or zone 41a is caused to exhibit adhesiveness), and adhesion is achieved.

[0056] As shown in FIG. 7, manufacturing apparatus 100 includes a plurality of stages with punching stations 110. Punching station 110 may have two stages or three or more stages. The punching station 110 of each stage includes a die 111 located below the material 1 and a die 112 located above the material 1.

[0057] The manufacturing apparatus 100 further includes a blending station 140 at a position downstream of the last punching station 110 downstream. The batching station 140 includes a heating device 141, an outer shaping die 142, a heat insulating member 143, an outer shaping die 144, and a spring 145. The heating device 141, the outer shaping die 142, and the heat insulating member 143 material 1. On the other hand, the punch die 144 for giving the outer shape and the spring 145 are located above the material 1. Here, reference numeral 21 indicates the stator core.

[0058] In the production apparatus 100 having the above-described configuration, first, the material 1 is sequentially fed from the roll 1A in the direction of the arrow F in FIG. 7. The material 1 is then sequentially punched in a plurality of stages of punching stations 110. According to these punching procedures, the material 1 is shaped into an electrical steel sheet 40 having a core back 22 and a plurality of teeth 23 shown in FIG. 3. However, since the material is not completely pierced at this time, it is fed to the next process in the direction of arrow F.

[0059] Then, finally, the material 1 is fed into the blending station 140, punched out with a cutting die 144 to give an outer shape, and layered with high precision. During this lamination, the electrical steel sheet 40 receives a certain pressure force from the spring 145. When the piercing process and the lamination process as described above are sequentially repeated, a predetermined number of electrical steel sheets 40 can be stacked. In addition, the laminated core formed by stacking the electrical steel sheets 40 in this way is heated, for example, to a temperature of 200° C., by the heating device 141. According to this heating, the insulating coatings 3 of the adjacent electrical steel sheets 40 are bonded to each other. Here, the heating device 141 may not be located on the punching die 142 for external shaping. That is, it can be removed from the outer-shaping die 142 before the electrical steel sheet 40 laminated by the outer-shape die 142 is adhered. In this case, the outer shaping die 142 may not have the heat insulating member 143. In addition, in this case, the stacked electrical steel sheets 40 may be clamped and held on both sides in the lamination direction by a clamp (not shown) before gluing and then transported and heat. According to the processes described above, the manufacture of the stator core 21 is completed.

[0060] As described above, in the present invention, an insulating coating is formed on the surface of an electrical steel sheet using an electrical steel sheet coating composition in which an epoxy resin, an epoxy latent curing agent, and a special thermoplastic elastomer are combined in a specific ratio. Accordingly, both an excellent magnetic property of the laminated core (magnetic core loss) and an excellent heat resistance in which the adhesive strength between electrical steel sheets can be maintained even in a high-temperature state during movement can be achieved.

[0061] Here, the technical scope of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention. The shape of the stator core is not limited to the shape shown in the above embodiment. Specifically, the dimensions of the outer diameter and the inner diameter of the stator core, the thickness of the layer structure, the number of slots, the size ratio between the circumferential direction and the radial direction of the tooth, the size ratio between the tooth and the back of the core in the radial direction, and the like can be arbitrarily designed in accordance with the desired properties of the motor. .

[0062] In the rotor in the above embodiment, the pair of permanent magnets 32 forms one magnetic pole, but the present invention is not limited to this. For example, one permanent magnet 32 may form one magnetic pole, or three or more permanent magnets 32 may form one magnetic pole.

[0063] One embodiment and examples of the present invention have been described above. However, the technical scope of the present invention is not limited to the above-described embodiments and examples, and various modifications can be made without departing from the gist of the present invention. For example, the shape of the stator core 21 is not limited to the shape shown in the above embodiment. Specifically, the dimensions of the outer diameter and the inner diameter of the stator core 21, the thickness of the laminar structure, the number of slots, the size ratio between the circumferential direction and the radial direction of the tooth 23, the size ratio between the tooth 23 and the core back portion 22 in the radial direction, and the like can be arbitrarily designed in according to the desired motor properties. In the rotor 30 in the above embodiment, the pair of permanent magnets 32 forms one magnetic pole, but the present invention is not limited to this form. For example, one permanent magnet 32 may form one magnetic pole, or three or more permanent magnets 32 may form one magnetic pole.

[0064] In the above-described embodiment, a permanent magnet excitation motor has been described as an example of the motor 10, but the structure of the motor 10 is not limited to this as shown below, and various well-known structures not shown as examples below can also be additionally used. In the above-described embodiment, as the motor 10, a permanent magnet motor has been described as an example, but the present invention is not limited thereto. For example, the motor 10 may be a reluctance type motor or an electromagnetic excitation motor (field motor). In the above embodiment, the synchronous motor has been described as an AC motor as an example, but the present invention is not limited thereto. For example, motor 10 may be an induction motor. In the above embodiment, the AC motor has been described as the motor 10 as an example, but the present invention is not limited thereto. For example, motor 10 may be a DC motor. In the above embodiment, the motor has been described as the motor 10 as an example, but the present invention is not limited to this. For example, motor 10 may be a generator.

[0065] In addition, the constituent elements in the above embodiment can be suitably replaced by well-known constituent elements without deviating from the gist of the present invention, and the above-described modified elements can be appropriately combined.

Examples

[0066] Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to the following description.

[0067] [Source materials]

The starting materials used in the examples are as follows.

(Epoxy resin)

E1: cresol novolac type epoxy

E2: Phenol novolac type epoxy

E3: Bisphenol A type epoxy resin

[0068] (Latent epoxy hardener)

A1: phenol resole resin

A2: dicyandiamide

A3: diaminodiphenylethane

[0069] (Thermoplastic elastomer)

B1: olefin-based elastomer (melting point: 110°C, flexural modulus: 10 MPa)

B2: urethane based elastomer (melting point: 130°C, flexural modulus: 40 MPa)

B3: urethane based elastomer (melting point: 160°C, flexural modulus: 60 MPa)

B4: polyester based elastomer (melting point: 180°C, flexural modulus: 80 MPa)

[0070] (Thermoplastic elastomer (for comparison))

C1: polyester based elastomer (melting point: 210°C, flexural modulus: 90 MPa)

C2: olefin-based elastomer (melting point: 90°C, flexural modulus: 60 MPa)

C3: polyester based elastomer (melting point: 180°C, flexural modulus: 150 MPa)

C4: olefin-based elastomer (melting point: 105°C, flexural modulus: 5 MPa)

C5: polyamide based elastomer (melting point: 160°C, flexural modulus: 150 MPa)

C6: polyester based elastomer (melting point: 220°C, flexural modulus: 120 MPa)

C7: styrene-based elastomer (melting point: 105°C, flexural modulus: 5 MPa)

C8: urethane based elastomer (melting point: 130°C, flexural modulus: 80 MPa)

[0071] [Magnetic property]

From the electrical steel strip of each example, a square electrical steel sheet (single sheet) with a size of 55 mm × 55 mm was cut, and two electrical steel sheets were laminated and glued under the conditions of the steel sheet temperature of 200°C, pressure of 10 MPa, and pressure exposure time of 1 hour. to obtain a laminated core. For the obtained laminated core, according to the single sheet magnetic property measurement method defined in JIS C2556, the magnetic properties of the single sheet in the rolling direction and the direction perpendicular to the rolling direction were measured, and the average value of these values was taken as the magnetic property. Here, for the magnetic property (magnetism), "W10/400 (W/kg)" was evaluated as the magnetic loss. "W10/400" is the magnetic loss when the frequency is 400Hz and the maximum magnetic induction is 1.0T.

[0072] [Adhesion strength]

From the electrical steel strip of each example, two rectangular electrical steel sheets (single sheets) having a width of 30 mm and a length of 60 mm were cut, and the end portions of a width of 30 mm and a length of 10 mm were overlapped with each other and glued at a steel sheet temperature of 200°C. , a pressure of 10 MPa and a pressure exposure time of 1 hour to obtain a sample. Shear tensile strength was measured at an air temperature of 25° C. or 150° C. and a stretching speed of 2 mm/min, and the numerical value divided by the bonding (gluing) area was taken as adhesive strength (MPa).

[0073] [Definition]

The determination was performed for each of the examples according to the following criteria. Very good is considered satisfactory.

Very good: the adhesive strength at 25°C was more than 5 MPa, the adhesive strength at 150°C was more than 0.5 MPa, and the magnetic property was less than 12 W/kg.

Good: adhesive strength at 25°C was 5 MPa or less, or adhesive strength at 150°C was 0.5 MPa or less, but adhesive strength at 25°C was 3 MPa or more, adhesive strength at 150°C was 0 .2 MPa or more, and the magnetic property was less than 12 W/kg.

Poor: Any one or more of an adhesive strength of 3 MPa or more at 25°C, an adhesive strength of 0.2 MPa or more at 150°C, and a magnetic property of less than 12 W/kg were not satisfied.

[Example 1]

[0074] As the main steel sheet, an isotropic electrical steel sheet was used, containing, in mass%, Si: 3.0%, Mn: 0.2% and Al: 0.5%, the rest is Fe and impurities, and having sheet thickness 0.25 mm and width 100 mm. The components shown in Table 1 were mixed to prepare an aqueous solution containing a coating composition for electrical steel sheet with a solid content concentration of 25 mass%. When dissolution was difficult, 5% by weight or less of a dissolution aid such as alcohol or cellosolves was added. An aqueous solution containing the obtained electrical steel sheet coating composition was applied to the surface of a base steel sheet and fired at a temperature of 200°C for 10 seconds, and an insulating coating having an average thickness of 3 µm was formed to obtain an electrical steel strip.

[Examples 2-7 and Comparative Examples 1-11]

[0075] Electrical steel strips were prepared in the same manner as in Example 1, except that the composition and firing conditions of the electrical steel sheet coating composition were changed as shown in Table 1.

[0076] Table 1 shows compositions and firing conditions of coating compositions for electrical steel sheet by examples. Here, the "Q ratio" in Table 1 is the amount of thermoplastic elastomer when the total amount of epoxy resin and epoxy latent hardener is 100 parts.

[0077]

[Table 1] Epoxy
resin Latent Epoxy Hardener Thermoplastic elastomer Firing conditions Type Bulk parts Type Bulk parts Type Bulk parts Q ratio Final temperature [°C] Time [seconds] Example 1 E1 100 A1 3 B1 thirty 29.1 200 10 Example 2 E1 A1 3 B1 13 12.6 200 10 Example 3 E1 A1 3 B2 25 24.3 200 10 Example 4 E2 A3 2 B2 15 14.7 200 20 Example 5 E2 A3 2 B3 35 34.3 200 20 Example 6 E3 A2 14 B3 16 14.0 160 10 Example 7 E3 A2 14 B4 thirty 26.3 160 10 Comparative Example 1 E1 A1 1 B2 50 49.5 200 20 Comparative Example 2 E1 A1 4 B2 5 4.8 200 10 Comparative Example 3 E1 A1 4 C1 20 19.2 200 10 Comparative Example 4 E3 A2 14 C2 20 17.5 160 20 Comparative Example 5 E3 A2 14 C3 25 21.9 160 20 Comparative Example 6 E2 A3 1 C4 25 24.8 200 20 Comparative Example 7 E2 A2 4 C5 thirty 28.8 200 10 Comparative Example 8 E2 A2 4 C6 thirty 28.8 200 10 Comparative Example 9 E1 A1 3 C7 thirty 29.1 200 10 Comparative Example 10 E1 A1 3 C8 25 24.3 200 20 Comparative Example 11 E1 A1 3 - - - 200 10

[0078] Table 2 shows the results of the evaluation of the magnetic property (magnetism) and adhesive strength by examples.

[0079]

[Table 2] Adhesion strength [MPa] Magnetism [W/kg] Definition 25°C 150°C W10/400 Example 1 12.0 3.0 10.7 Very good Example 2 10.0 3.0 10.9 Very good Example 3 12.0 1.0 11.3 Very good Example 4 6.0 3.0 11.1 Very good Example 5 8.0 1.0 11.7 Very good Example 6 12.0 3.0 11.6 Very good Example 7 11.0 3.0 11.4 Very good Comparative Example 1 6.0 0.4 11.3 Fine Comparative Example 2 16.0 4.0 12.5 Badly Comparative Example 3 13.0 4.0 12.3 Badly Comparative Example 4 4.0 0.3 11.9 Fine Comparative Example 5 13.0 3.0 12.1 Badly Comparative Example 6 4.0 0.3 11.1 Fine Comparative Example 7 14.0 1.0 12.9 Badly Comparative Example 8 12.0 0.6 12.0 Badly Comparative Example 9 3.0 0.2 11.4 Fine Comparative Example 10 6.4 0.3 11.1 Fine Comparative Example 11 15.0 3.0 13.8 Badly

[0080] As shown in Table 2, in Examples 1 to 7, in which epoxy resin, latent epoxy resin hardener, and special thermoplastic elastomer are combined in a specific ratio, sufficient adhesive strength was provided even at 150°C, heat resistance was excellent, and magnetic property was excellent. On the other hand, in Comparative Examples 1 to 10, in which the amount, melting point, and flexural modulus of the thermoplastic elastomer were outside the scope of the present invention, both heat resistance and magnetic property could not be achieved. In Comparative Example 11, in which no thermoplastic elastomer was mixed in, the magnetic property was worse.

[Industrial applicability]

[0081] In accordance with the present invention, it is possible to provide both heat resistance and magnetic property of the laminated core. Therefore, its industrial applicability is great.

[Brief description of reference numerals]

[0082] 1 material, 2 base steel sheet, 3 insulation coating, 10 electric motor, 20 stator, 21 stator core, 40 electrical steel sheet.

Claims (8)

1. Coating composition for electrical steel sheet containing epoxy resin, latent epoxy resin hardener and thermoplastic elastomer, wherein the thermoplastic elastomer has a melting point of 100°C or more and 200°C or less and a flexural modulus of more than 5 MPa and 100 MPa or less, and moreover, the amount of thermoplastic elastomer per 100 mass parts of the total amount of epoxy resin and the latent epoxy resin hardener is 10 mass parts or more and less than 40 mass parts. 2. An electrical steel sheet coating composition according to claim 1, wherein the thermoplastic elastomer is at least one selected from an olefin-based elastomer, a urethane-based elastomer, and a polyester-based elastomer. 3. An electrical steel sheet with an insulating coating formed by applying an electrical steel sheet coating composition according to claim 1 or 2 to a surface of a base steel sheet. 4. The electrical steel sheet according to claim 3, wherein the base steel sheet has an average sheet thickness of 0.30 mm or less. 5. A laminated core in which a plurality of electrical steel sheets according to claim 3 or 4 are laminated and bonded to each other. 6. An electric motor containing a laminated core according to claim 5.