Coating composition for electromagnetic steel sheet, electromagnetic steel sheet, laminated iron core, and rotating electrical machine

Abstract

The electromagnetic steel sheet used in the laminated core is an electromagnetic steel sheet having an insulating coating (3) formed by applying a coating composition for an electromagnetic steel sheet on the surface of a base steel sheet (2), wherein the coating composition for the electromagnetic steel sheet is mixed with an epoxy resin, a first curing agent composed of an alkylphenol, and a second curing agent composed of either or both of a phenol resol resin and a phenol novolac resin in a specific ratio.

Description

Technical Field

[0001] The present invention relates to a coating composition for an electromagnetic steel sheet, an electromagnetic steel sheet, a laminated iron core, and a rotating electric machine. This application claims priority based on Japanese Patent Application No. 2020-104235 filed in Japan on June 17, 2020, and the contents are incorporated herein by reference. Background Art

[0002] As a core used in a rotating electric machine, a laminated core is known in which a plurality of electromagnetic steel sheets are joined and stacked. As a method for joining the electromagnetic steel sheets, riveting or welding is known. However, in riveting or welding, the magnetic properties (core iron loss) of the electromagnetic steel sheets are easily deteriorated due to mechanical strain or thermal strain during processing.

[0003] As a joining method other than riveting and welding, for example, a method of bonding electromagnetic steel sheets to each other is known, wherein an insulating film having bonding ability is formed on the surface of the electromagnetic steel sheets (Patent Document 1). Since bonding using the insulating film does not impart mechanical strain or thermal strain, the core iron loss is better than riveting and welding. Epoxy resin has little volume change, excellent heat resistance, oil resistance, and chemical resistance, and is excellent as an adhesive for bonding electromagnetic steel sheets to each other (Patent Documents 2 and 3).

[0004] Prior art literature

[0005] Patent Literature

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

[0007] Patent Document 2: Japanese Patent Application Publication No. 2000-173816

[0008] Patent Document 3: International Publication No. 2004 / 070080 Summary of the invention

[0009] Technical problem to be solved by the invention

[0010] In recent years, the demand for further improvement of motor efficiency has required further reduction of core iron loss. Thinning of electromagnetic steel sheets is effective in reducing core iron loss. However, as the thickness of the sheet decreases, the Young's modulus of the steel sheet decreases, so it is required that stress and strain, which are the cause of iron loss degradation, are not imparted to the steel sheet. Although epoxy resin has excellent heat resistance, it is relatively hard and has low toughness, so stress and strain are imparted to the steel sheet due to curing during bonding, so when the steel sheet becomes thinner, it will become the cause of iron loss degradation.

[0011] Furthermore, in a driving motor of an electric vehicle or the like, the temperature becomes high during driving, and thus further heat resistance is required.

[0012] As a method for improving heat resistance, there is a method of combining phenolic resin. However, resins with excellent heat resistance are harder at room temperature and will impart greater stress to the laminated core, thereby deteriorating the magnetic properties. On the other hand, resins with appropriate hardness near room temperature will become soft at high temperatures, so they have poor heat resistance. For these reasons, it is difficult to balance excellent magnetic properties with excellent heat resistance, which refers to the ability to maintain sufficient bonding strength even when exposed to high temperatures during driving.

[0013] An object of the present invention is to provide a coating composition for an electromagnetic steel sheet that can achieve both magnetic properties of a laminated core and heat resistance that can maintain the bonding strength between electromagnetic steel sheets even under high temperature conditions during driving, and an electromagnetic steel sheet, a laminated core, and a rotating electrical machine using the coating composition for an electromagnetic steel sheet.

[0014] Technical means for solving technical problems

[0015] The present invention has the following aspects.

[0016] [1] A coating composition for an electromagnetic steel sheet according to one embodiment of the present invention comprises an epoxy resin, a first curing agent composed of an alkylphenol, and a second curing agent composed of either or both of a phenol resol resin and a phenol novolac resin, wherein the content of the first curing agent is 1.0 part by mass or more and 20.0 parts by mass or less relative to 100 parts by mass of the epoxy resin.

[0017] [2] In the coating composition for an electromagnetic steel sheet according to [1] above, the alkylphenol may contain either or both of a monoalkylphenol having an alkyl group with 2 to 20 carbon atoms and a dialkylphenol having an alkyl group with 2 to 20 carbon atoms.

[0018] [3] In the coating composition for an electrical steel sheet according to [1] or [2] above, the content of the second curing agent may be 5.0 parts by mass or more and 150.0 parts by mass or less relative to 100 parts by mass of the epoxy resin.

[0019] [4] The coating composition for an electrical steel sheet according to any one of [1] to [3] above may have a cure shrinkage ratio of 15% or less.

[0020] [5] In the coating composition for an electrical steel sheet according to any one of [1] to [4] above, a mass ratio represented by [the content of the first curing agent (A)] / [the content of the second curing agent (B)] may be 0.01 to 4.0.

[0021] [6] An electrical steel sheet according to one embodiment of the present invention has an insulating coating film comprising the coating composition for an electrical steel sheet according to any one of [1] to [5] above on its surface.

[0022] [7] A laminated iron core according to one aspect of the present invention is formed by laminating a plurality of electromagnetic steel sheets as described in [6] above and bonding them to each other.

[0023] [8] A rotating electrical machine according to one aspect of the present invention includes the laminated core described in [7].

[0024] Effects of the Invention

[0025] According to the above aspects of the present invention, it is possible to provide a coating composition for electromagnetic steel sheets that can achieve both the magnetic properties of a laminated iron core and heat resistance that can maintain the bonding strength between the electromagnetic steel sheets even under high temperature conditions during driving, and an electromagnetic steel sheet, a laminated iron core, and a rotating electrical machine using the coating composition for electromagnetic steel sheets. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a cross-sectional view of a rotating electrical machine including a laminated iron core according to a first embodiment of the present invention.

[0027] Figure 2 yes Figure 1 Side view of the laminated core shown.

[0028] Figure 3 yes Figure 2 A-A section view.

[0029] Figure 4 It is used to form Figure 1 A top view of the raw material of the laminated core is shown.

[0030] Figure 5 yes Figure 4 B-B section view.

[0031] Figure 6 yes Figure 5 An enlarged view of part C.

[0032] Figure 7 It is used to manufacture Figure 1 A side view of a manufacturing apparatus for a laminated core is shown. DETAILED DESCRIPTION

[0033] Hereinafter, a laminated iron core according to an embodiment of the present invention, a rotating electric machine having the laminated iron core, and a raw material for forming the laminated iron core will be described with reference to the accompanying drawings. In addition, in this embodiment, as a rotating electric machine, an electric motor, specifically an AC motor, more specifically a synchronous motor, and more specifically a permanent magnet excitation type motor will be described as an example. Such an electric motor is preferably used in, for example, electric vehicles, etc.

[0034] In addition, below, for the numerical range described between "to", the lower limit and the upper limit are included in the range. For the numerical value expressed as "less than" or "exceeding", the value is not included in the numerical range.

[0035] (Rotating electric machine 10)

[0036] like Figure 1 As shown, the rotary electric machine 10 includes a stator 20, a rotor 30, a housing 50, and a rotating shaft 60. The stator 20 and the rotor 30 are accommodated in the housing 50.

[0037] The stator 20 is fixed in the housing 50 .

[0038] In the present embodiment, an inner rotor type in which the rotor 30 is located radially inside the stator 20 is adopted as the rotating electrical machine 10. However, an outer rotor type in which the rotor 30 is located outside the stator 20 may be adopted as the rotating electrical machine 10. In addition, in the present embodiment, the rotating electrical machine 10 is a 12-pole 18-slot three-phase AC motor. However, the number of poles, the number of slots, the number of phases, etc. may be changed as appropriate.

[0039] The rotating electric machine 10 can be rotated at a rotation speed of 1000 rpm by applying an exciting current having an effective value of 10 A and a frequency of 100 Hz to each phase, for example.

[0040] The stator 20 includes a stator bonded laminated core (hereinafter referred to as a stator core) 21 and a winding (not shown).

[0041] The stator core 21 includes an annular core back 22 and a plurality of teeth 23. Hereinafter, the direction of the central axis O of the stator core 21 (or the core back 22) is referred to as the axial direction, the radial direction (the direction orthogonal to the central axis O) of the stator core 21 (or the core back 22) is referred to as the radial direction, and the circumferential direction (the direction surrounding the central axis O) of the stator core 21 (or the core back 22) is referred to as the circumferential direction.

[0042] The core back 22 is formed in an annular shape in a plan view of the stator 20 viewed from the axial direction.

[0043] A plurality of teeth 23 protrude radially inward from the inner circumference of the core back 22 (radially toward the center axis O of the core back 22). The plurality of teeth 23 are arranged at equal angular intervals in the circumferential direction. In the present embodiment, 18 teeth 23 are provided at a center angle of 20 degrees centered on the center axis O. The plurality of teeth 23 are formed into shapes and sizes that are equal to each other. Therefore, the plurality of teeth 23 have the same thickness dimensions as each other.

[0044] The winding is wound around the teeth 23. The winding may be concentratedly wound or distributedly wound.

[0045] The rotor 30 is arranged radially inward of the stator 20 (stator core 21 ) and includes a rotor core 31 and a plurality of permanent magnets 32 .

[0046] The rotor core 31 is formed in an annular shape (ring shape) arranged coaxially with the stator 20. The rotating shaft 60 is arranged in the rotor core 31. The rotating shaft 60 is fixed to the rotor core 31.

[0047] A plurality of permanent magnets 32 are fixed to the rotor core 31. In the present embodiment, a set of two permanent magnets 32 forms one magnetic pole. The plurality of sets of permanent magnets 32 are arranged at equal angular intervals in the circumferential direction. In the present embodiment, 12 sets (24 in total) of permanent magnets 32 are arranged at every central angle of 30 degrees about the central axis O.

[0048] In the present embodiment, an embedded magnet type motor is used as a permanent magnet excitation type motor.

[0049] The rotor core 31 is provided with a plurality of through holes 33 which penetrate the rotor core 31 in the axial direction. The plurality of through holes 33 are provided corresponding to the arrangement of the plurality of permanent magnets 32. Each permanent magnet 32 ​​is fixed to the rotor core 31 in a state arranged in the corresponding through hole 33. The fixing of each permanent magnet 32 ​​to the rotor core 31 can be achieved, for example, by bonding the outer surface of the permanent magnet 32 ​​to the inner surface of the through hole 33 using an adhesive. In addition, as a permanent magnet excitation type motor, a surface magnet type motor may be used instead of an embedded magnet type.

[0050] The stator core 21 and the rotor core 31 are both laminated cores. Figure 2 As shown, it is formed by laminating a plurality of electromagnetic steel sheets 40 in a laminating direction.

[0051] In addition, the stacking thickness (total length along the center axis O) of each of the stator core 21 and the rotor core 31 is set to 50.0 mm, for example. The outer diameter of the stator core 21 is set to 250.0 mm, for example. The inner diameter of the stator core 21 is set to 165.0 mm, for example. The outer diameter of the rotor core 31 is set to 163.0 mm, for example. The inner diameter of the rotor core 31 is set to 30.0 mm, for example. However, these values ​​are only examples, and the stacking thickness, outer diameter or inner diameter of the stator core 21, and the stacking thickness, outer diameter or 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 front end of the tooth portion 23 in the stator core 21. That is, the inner diameter of the stator core 21 is the diameter of a virtual circle inscribed in the front end of all the teeth 23.

[0052] The electromagnetic steel sheets 40 forming the stator core 21 and the rotor core 31 are formed by, for example, Figures 4 to 6 The raw material 1 shown is formed by punching or the like. The raw material 1 is an electromagnetic steel sheet that is a base material of the electromagnetic steel sheet 40. As the raw material 1, for example, a strip-shaped steel sheet or a cut sheet can be cited.

[0053] In the description of the laminated core, the following description will focus on the raw material 1. In addition, in this specification, a strip-shaped steel plate that is a base material of the electromagnetic steel plate 40 may be referred to as the raw material 1. A steel plate that is punched out of the raw material 1 and formed into a shape used for the laminated core may be referred to as the electromagnetic steel plate 40.

[0054] (raw material 1)

[0055] The raw material 1 is wound, for example, Figure 7 The steel coil 1A shown is processed in the state of being processed. In the present embodiment, a non-oriented electromagnetic steel sheet is used as the raw material 1. As the non-oriented electromagnetic steel sheet, a non-oriented electromagnetic steel sheet of JIS C 2552:2014 can be used. However, as the raw material 1, a oriented electromagnetic steel sheet may be used instead of a non-oriented electromagnetic steel sheet. As the oriented electromagnetic steel sheet in this case, a oriented electromagnetic steel sheet of JIS C 2553:2019 can be used. In addition, a non-oriented thin electromagnetic steel strip or a oriented thin electromagnetic steel strip of JIS C 2558:2015 can be used.

[0056] The upper and lower limits of the average plate thickness t0 of the material 1 are set, for example, as follows, also in consideration of the case where the material 1 is used as the electromagnetic steel sheet 40 .

[0057] As the raw material 1 becomes thinner, the manufacturing cost of the raw material 1 increases. Therefore, in consideration of the manufacturing cost, the lower limit of the average plate thickness t0 of the raw material 1 is 0.10 mm, preferably 0.15 mm, and more preferably 0.18 mm.

[0058] On the other hand, when the raw material 1 is too thick, the manufacturing cost becomes good, but when the raw material 1 is used as the electromagnetic steel sheet 40, the eddy current loss increases and the core iron loss deteriorates. Therefore, considering the core iron loss and the manufacturing cost, the upper limit of the average plate thickness t0 of the raw material 1 is 0.65 mm, preferably 0.35 mm, and more preferably 0.30 mm.

[0059] As a case where the average plate thickness t0 of the material 1 satisfies the above range, 0.20 mm can be exemplified.

[0060] In addition, the average plate thickness t0 of the raw material 1 includes not only the thickness of the base steel plate 2 described later, but also the thickness of the insulating film 3. In addition, the method for measuring the average plate thickness t0 of the raw material 1 is, for example, based on the following measurement method. For example, when the raw material 1 is wound into the shape of a steel coil 1A, at least a portion of the raw material 1 is disassembled into a flat plate shape. In the raw material 1 disassembled into a flat plate shape, a predetermined position in the length direction of the raw material 1 is selected (for example, a position that is 10% of the length of the total length of the raw material 1 away from the end edge in the length direction of the raw material 1). At the selected position, the raw material 1 is divided into 5 areas along its width direction. The plate thickness of the raw material 1 is measured at 4 locations that serve as the boundaries of these 5 areas. The average value of the plate thickness at the 4 locations can be used as the average plate thickness t0 of the raw material 1.

[0061] The upper and lower limits of the average thickness t0 of the raw material 1 can be used as the upper and lower limits of the average thickness t0 of the electromagnetic steel sheet 40. The average thickness t0 of the electromagnetic steel sheet 40 can be measured by, for example, the following measurement method. For example, the laminated thickness of the laminated core is measured at four locations (i.e., every 90 degrees around the central axis O) at equal intervals in the circumferential direction.

[0062] The stacking thickness at the four locations measured is divided by the number of stacked electromagnetic steel sheets 40 to calculate the sheet thickness per sheet. The average of the sheet thicknesses at the four locations can be taken as the average sheet thickness t0 of the electromagnetic steel sheets 40 .

[0063] like Figure 5 and Figure 6 As shown, the material 1 includes a base steel plate 2 and an insulating film 3 .

[0064] In the raw material 1, both surfaces of the strip-shaped base steel plate 2 are covered with an insulating film 3. In this embodiment, most of the raw material 1 is formed by the base steel plate 2, and the insulating film 3 is stacked on the surface of the base steel plate 2, and the insulating film 3 is thinner than the base steel plate 2.

[0065] The chemical composition of the base steel plate 2 contains 2.5% to 4.5% Si by mass % as shown below. By setting the chemical composition within this range, the yield strength of the material 1 (electromagnetic steel plate 40) can be set to, for example, 380 MPa to 540 MPa.

[0066] Si: 2.5% to 4.5%

[0067] Al: 0.001%~3.0%

[0068] Mn: 0.05%~5.0%

[0069] The rest: Fe and impurities

[0070] When the raw material 1 is used as the electromagnetic steel sheet 40, the insulating film 3 will exert the insulating performance between the electromagnetic steel sheets 40 adjacent in the stacking direction. In addition, in the present embodiment, the insulating film 3 has an adhesive ability to bond the electromagnetic steel sheets 40 adjacent in the stacking direction. The insulating film 3 can be a single-layer structure or a multi-layer structure. More specifically, for example, the insulating film 3 can be a single-layer structure having both insulating performance and adhesive performance, or a multi-layer structure including a lower insulating film with excellent insulating performance and an upper insulating film with excellent adhesive performance. In addition, the so-called "adhesive ability of the insulating film 3" in the present embodiment means the ability to exhibit an adhesive strength greater than a predetermined value under predetermined temperature conditions in a stack composed of a plurality of electromagnetic steel sheets 40 stacked with the insulating film 3 sandwiched therebetween.

[0071] In the present embodiment, the insulating film 3 covers both surfaces of the base steel plate 2 without gaps over the entire surface. However, it is also possible that a part of the insulating film 3 does not cover both surfaces of the base steel plate 2 without gaps within a range that can ensure the aforementioned insulating performance or bonding ability. In other words, it is also possible that a part of the insulating film 3 is intermittently provided on the surface of the base steel plate 2. However, in order to ensure the insulating performance, both surfaces of the base steel plate 2 need to be covered by the insulating film 3 so that the entire surface is not exposed. Specifically, in the case where the insulating film 3 does not have a lower insulating film with excellent insulating performance, but is a single-layer structure having both insulating performance and bonding ability, the insulating film 3 needs to be formed without gaps over the entire surface of the base steel plate 2. On the other hand, in the case where the insulating film 3 is a multi-layer structure including a lower insulating film with excellent insulating performance and an upper insulating film with excellent bonding ability, in addition to forming both the lower insulating film and the upper insulating film without gaps over the entire surface of the base steel plate 2, it is also possible to achieve both insulating performance and bonding ability by forming the lower insulating film without gaps over the entire surface of the base steel plate and intermittently providing the upper insulating film.

[0072] The coating composition constituting the lower insulating film is not particularly limited, and for example, a general treatment agent such as a chromic acid treatment agent or a phosphate treatment agent can be used.

[0073] The insulating film 3 having adhesiveness is formed by applying a coating composition for an electromagnetic steel sheet containing an epoxy resin, a first curing agent (A), and a second curing agent (B).

[0074] The insulating film composed of the coating composition for an electromagnetic steel sheet is in an uncured state or a semi-cured state (B stage) before heat-pressing during the manufacture of a laminated core, and exhibits adhesiveness due to the curing reaction that proceeds due to the heating during heat-pressing. The coating composition for an electromagnetic steel sheet can be used to form an insulating film of a single layer or to form an upper insulating film provided on a lower insulating film.

[0075] As epoxy resin, general epoxy resin can be used, specifically, as long as it is an epoxy resin with more than 2 epoxy groups in one molecule, it can be used without particular restriction. As this epoxy resin, for example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, triphenylmethane type epoxy resin, alicyclic epoxy resin, glycidyl ester type epoxy resin, glycidylamine type epoxy resin, hydantoin type epoxy resin, isocyanurate type epoxy resin, acrylic modified epoxy resin (epoxy acrylate), phosphorus-containing epoxy resin, and their halides (brominated epoxy resin, etc.) or hydrides, etc. can be cited. As epoxy resin, one kind can be used alone, or two or more kinds can be used in combination.

[0076] The content of the epoxy resin is preferably 30 to 90 mass %, more preferably 40 to 80 mass %, and even more preferably 50 to 70 mass % relative to the total mass of the coating composition for the electromagnetic steel sheet. When the content of the epoxy resin is greater than or equal to the lower limit, the bonding strength of the electromagnetic steel sheet 40 can be further improved. When the content of the epoxy resin is less than or equal to the upper limit, the stress strain of the electromagnetic steel sheet 40 can be further suppressed.

[0077] The first curing agent is composed of alkylphenol.

[0078] The alkylphenol is not particularly limited, and examples thereof include cresol (o-cresol, etc.), ethylphenol (o-ethylphenol, etc.), propylphenol (p-propylphenol, p-isopropylphenol, etc.), butylphenol (p-butylphenol, p-sec-butylphenol, etc.), nonylphenol (p-nonylphenol, etc.), dodecylphenol (p-dodecylphenol, etc.), dimethylphenol (2,3-dimethylphenol, etc.), diethylphenol (2,3-diethylphenol, etc.), dibutylphenol (2,6-di-sec-butylphenol, etc.), trimethylphenol (2,3,4-trimethylphenol, etc.), etc. As the alkylphenol, one type may be used alone, or two or more types may be used in combination.

[0079] From the viewpoint of easily achieving both magnetic properties and heat resistance, the alkylphenol preferably contains either or both of a monoalkylphenol having an alkyl group with 2 to 20 carbon atoms and a dialkylphenol having an alkyl group with 2 to 20 carbon atoms.

[0080] The alkyl group of the monoalkylphenol more preferably has 3 to 16 carbon atoms, and still more preferably has 4 to 12 carbon atoms.

[0081] The number of carbon atoms of the two alkyl groups of the monoalkylphenol is independently preferably 3 to 20, and further preferably 4 to 12.

[0082] The content of the first curing agent (A) in the coating composition for electromagnetic steel sheets is 1.0 parts by mass or more and 20.0 parts by mass or less relative to 100 parts by mass of the epoxy resin. If the content of the first curing agent (A) is above the lower limit, a laminated iron core having excellent heat resistance is obtained. If the content of the first curing agent is below the upper limit, a laminated iron core having excellent magnetic properties is obtained.

[0083] The lower limit of the content of the first curing agent (A) is preferably 2.0 parts by mass or more, more preferably 3.0 parts by mass or more. The upper limit of the content of the first curing agent (A) is preferably 18.0, more preferably 16.0 parts by mass or less, and further preferably 15.0 parts by mass or less.

[0084] The second curing agent (B) is one or more selected from phenol resol resins and phenol novolac resins. Neither the phenol resol resins nor the phenol novolac resins as the second curing agent have an alkyl group or an alkoxy group in the phenol skeleton.

[0085] As the second curing agent (B), a phenol resol resin may be used alone, a phenol novolac resin may be used alone, or a phenol resol resin and a phenol novolac resin may be used in combination.

[0086] The total content of the second curing agent (B) in the coating composition for electromagnetic steel sheet is preferably 5.0 parts by mass or more and 150.0 parts by mass or less relative to 100 parts by mass of epoxy resin. If the content of the second curing agent (B) is above the lower limit, heat resistance can be ensured. If the content of the second curing agent (B) is below the upper limit, deterioration of magnetic properties can be suppressed.

[0087] The lower limit of the content of the second curing agent (B) is preferably 5.0 parts by mass or more, more preferably 10.0 parts by mass or more, and further preferably 20.0 parts by mass or more. The upper limit of the content of the second curing agent (B) is preferably 150.0 parts by mass or less, more preferably 100.0 parts by mass or less, and further preferably 70.0 parts by mass or less.

[0088] The mass ratio represented by [the content of the first curing agent (A)] / [the content of the second curing agent (B)] (hereinafter also referred to as [A / B ratio]) is preferably 0.01 to 4.0. The A / B ratio is more preferably 0.1 or more, and further preferably 0.25 or more. In addition, the A / B ratio is more preferably 3.8 or less, and further preferably 3.5 or less. If the A / B ratio is within the range of the above upper limit and lower limit, it is possible to better achieve both stress strain suppression and heat resistance.

[0089] The coating composition for electromagnetic steel sheet may also contain other ingredients besides epoxy resin, the first curing agent (A) and the second curing agent (B). As other ingredients, for example, other curing agents besides acrylic resin, the first curing agent (A) and the second curing agent (B), curing accelerators (curing catalysts), emulsifiers, defoaming agents, etc. may be cited. In addition, from the viewpoint of ensuring bonding strength, the coating composition for electromagnetic steel sheet does not contain inorganic fillers such as silica, alumina, and glass. As other ingredients, only one may be used, or two or more may be used in combination.

[0090] As acrylic resin, it is not particularly limited. As monomers for acrylic resin, for example, unsaturated carboxylic acids such as acrylic acid and methacrylic acid, methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, n-butyl iso (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, and (meth) acrylate hydroxypropyl esters such as (meth) acrylate can be exemplified. In addition, so-called (meth) acrylate means acrylate or methacrylate. As acrylic resin, one kind can be used alone, or two or more kinds can be used in combination.

[0091] The acrylic resin may also have constituent units derived from other monomers other than the acrylic acid monomer. As other monomers, for example, ethylene, propylene, styrene, etc. may be mentioned. As other monomers, either one kind may be used alone or two or more kinds may be used in combination.

[0092] The glass transition point (Tg point) of the acrylic resin is not particularly limited, but the lower limit is preferably -40°C, more preferably -20°C. The upper limit of the Tg point of the acrylic resin is preferably 80°C, more preferably 50°C.

[0093] When the coating composition for an electrical steel sheet contains an acrylic resin, the content of the acrylic resin is not particularly limited, and can be, for example, 1% by mass or more and 50% by mass or less relative to the total amount of the epoxy resin and the acrylic resin. The same applies to the content when the acrylic resin is contained as an acrylic modified epoxy resin or an acrylic monomer.

[0094] When an acrylic resin is used, it may be used as an acrylic-modified epoxy resin obtained by grafting an acrylic resin to an epoxy resin. It may be contained in the coating composition for an electrical steel sheet as a monomer forming an acrylic resin.

[0095] As other curing agents, latent epoxy resin curing agents that start curing reaction by heating can be cited. Specifically, aromatic polyamines, acid anhydrides, dicyandiamide, boron trifluoride-amine complexes, organic acid hydrazines, etc. can be cited. As other curing agents, one type can be used alone, or two or more types can be used in combination.

[0096] The content of the other curing agent in the coating composition for an electrical steel sheet is preferably 20 parts by mass or less, more preferably 10 parts by mass or less, based on 100 parts by mass of the epoxy resin.

[0097] Generally, if the epoxy resin adhesive with excellent heat resistance ensures the bonding strength at high temperature, the Young's modulus is large near room temperature, which applies stress to the steel plate and deteriorates the magnetic properties (core iron loss). On the other hand, if the resin composition has moderate strength near room temperature, the heat resistance is reduced.

[0098] In this embodiment, by using the alkylphenol of the first curing agent (A) in combination with the second curing agent (B), the cured product has a structure having an alkyl group as a side chain. Therefore, the elastic modulus of the cured product is moderately reduced, the stress imparted to the steel plate is reduced, and a laminated iron core with excellent magnetic properties is obtained. In addition, since phenolic resin has excellent heat resistance, the heat resistance is also improved by using the first curing agent (A) and the second curing agent (B) in combination. Thus, it is possible to take both magnetic properties and heat resistance into account.

[0099] The curing shrinkage of the coating composition for an electromagnetic steel sheet is preferably 15% or less, more preferably 12% or less, further preferably 10% or less, and particularly preferably 8% or less. If the curing shrinkage is below the upper limit, it is easy to reduce the stress imparted to the steel sheet, and it is easy to obtain a laminated core with excellent magnetic properties.

[0100] In addition, the cure shrinkage ratio was measured by the method based on JIS K6941.

[0101] The insulating film 3 can be formed, for example, by applying a coating composition for an electromagnetic steel sheet to the surface of a base steel sheet, followed by drying and sintering.

[0102] The lower limit of the temperature reached during sintering is preferably 120°C or more, more preferably 140°C or more. The upper limit of the temperature reached during sintering is preferably 200°C or less, more preferably 180°C or less. When the reaching temperature is above the lower limit, the coating composition for the electromagnetic steel sheet will be fully bonded to the electromagnetic steel sheet, and peeling will be suppressed. When the reaching temperature is below the upper limit, curing of the epoxy resin can be suppressed, and the bonding ability of the coating composition for the electromagnetic steel sheet can be maintained.

[0103] The lower limit of the sintering time is preferably 5 seconds or more, more preferably 10 seconds or more. The upper limit of the sintering time is preferably 40 seconds or less, more preferably 30 seconds or less. When the sintering time is above the lower limit, the coating composition for the electromagnetic steel sheet will be fully bonded to the electromagnetic steel sheet, and peeling will be suppressed. When the sintering time is below the upper limit, the curing of the epoxy resin can be suppressed, and the bonding ability of the coating composition for the electromagnetic steel sheet can be maintained.

[0104] Taking into consideration the case where the material 1 is used as the electromagnetic steel sheet 40 , the upper and lower limits of the average thickness t1 of the insulating film 3 may be set, for example, as follows.

[0105] When the material 1 is used as the electromagnetic steel sheet 40 , the average thickness t1 of the insulating film 3 (thickness per single side of the electromagnetic steel sheet 40 (material 1 )) is adjusted so as to ensure insulation performance and adhesion between the stacked electromagnetic steel sheets 40 .

[0106] In the case of the insulating film 3 having a single-layer structure, the average thickness t1 of the entire insulating film 3 (the thickness of the electromagnetic steel sheet 40 (material 1 )) can be set to, for example, 1.5 μm or more and 8.0 μm or less.

[0107] In the case of a multilayer insulating film 3 , the average thickness of the lower insulating film can be, for example, 0.3 μm to 2.5 μm, preferably 0.5 μm to 1.5 μm. The average thickness of the upper insulating film can be, for example, 1.5 μm to 8.0 μm.

[0108] The average thickness t1 of the insulating film 3 in the material 1 can be determined by the same method as the average thickness t0 of the material 1 , by obtaining the thickness of the insulating film 3 at a plurality of locations and averaging the thicknesses.

[0109] It is a matter of course that the upper and lower limits of the average thickness t1 of the insulating film 3 in the material 1 can also be adopted as the upper and lower limits of the average thickness t1 of the insulating film 3 in the electromagnetic steel sheet 40 .

[0110] In addition, the method for measuring the average thickness t1 of the insulating film 3 in the electromagnetic steel sheet 40 is, for example, based on the following measurement method. For example, the electromagnetic steel sheet 40 located on the outermost side in the stacking direction (the electromagnetic steel sheet 40 whose surface is exposed in the stacking direction) among the multiple electromagnetic steel sheets forming the laminated iron core is selected. On the surface of the selected electromagnetic steel sheet 40, a predetermined radial position is selected (for example, the position exactly in the middle (center) between the inner periphery and the outer periphery in the electromagnetic steel sheet 40). At the selected position, the thickness of the insulating film 3 of the electromagnetic steel sheet 40 is measured at four locations (that is, every 90 degrees centered on the central axis O) at equal intervals in the circumferential direction. The average value of the thicknesses measured at the four locations can be used as the average thickness t1 of the insulating film 3.

[0111] The reason why the average thickness t1 of the insulating film 3 is measured in the outermost electromagnetic steel sheet 40 in the stacking direction is that the insulating film 3 is manufactured so that the thickness of the insulating film 3 hardly changes at stacking positions of the electromagnetic steel sheets 40 along the stacking direction.

[0112] The electromagnetic steel sheet 40 is manufactured by punching the material 1 as described above, and a laminated core (the stator core 21 or the rotor core 31 ) is manufactured using the electromagnetic steel sheet 40 .

[0113] (Laminate method of laminated core)

[0114] Next, we return to the description of the laminated core.

[0115] The plurality of electromagnetic steel sheets 40 forming the stator core 21 are as follows. Figure 3 As shown, they are stacked with an insulating film 3 interposed therebetween.

[0116] The electromagnetic steel sheets 40 adjacent to each other in the stacking direction are bonded over the entire surface by the insulating film 3. In other words, in the electromagnetic steel sheet 40, the surface facing the stacking direction (hereinafter referred to as the first surface) becomes the bonding area 41a over the entire surface. However, the electromagnetic steel sheets 40 adjacent to each other in the stacking direction may not be bonded over the entire surface. In other words, the bonding area 41a and the non-bonding area (not shown) may be mixed in the first surface of the electromagnetic steel sheet 40.

[0117] In this embodiment, the plurality of electromagnetic steel sheets forming the rotor core 31 are composed of Figure 1 The caulking portions 42 (pins) shown are fixed to each other. However, the plurality of electromagnetic steel sheets forming the rotor core 31 may have a stacked structure fixed by the insulating film 3 similarly to the stator core 21 .

[0118] Furthermore, the stator core 21 and the rotor core 31 and other laminated cores may be formed by so-called rotational lamination.

[0119] (Method for manufacturing laminated core)

[0120] The stator core 21 is, for example, Figure 7 The laminated core is manufactured by the manufacturing apparatus 100 shown in the figure. When the manufacturing method is described below, first, a manufacturing apparatus 100 for the laminated core (hereinafter simply referred to as the manufacturing apparatus 100) will be described.

[0121] In the manufacturing device 100, the raw material 1 is fed from the steel coil 1A (coil) in the direction of the arrow F, and is punched multiple times by the die arranged on each worktable, and gradually formed into the shape of the electromagnetic steel sheet 40. Then, the punched electromagnetic steel sheets 40 are stacked, and pressurized while heating them. As a result, the electromagnetic steel sheets 40 adjacent to each other in the stacking direction are bonded by the insulating film 3 (that is, the portion of the insulating film 3 located in the bonding area 41a exerts its bonding ability), and the bonding is completed.

[0122] like Figure 7 As shown, the manufacturing device 100 includes a multi-stage punching station 110. The punching station 110 can be two-stage or three-stage or more. Each stage of the punching station 110 includes: a die 111, which is arranged below the raw material 1; and a punch 112, which is arranged above the raw material 1.

[0123] The manufacturing apparatus 100 further includes a stacking station 140 at a downstream position of the most downstream punching station 110. The stacking station 140 includes a heating device 141, an outer peripheral punching die 142, a heat insulating member 143, an outer peripheral punching punch 144, and a spring 145.

[0124] The heating device 141, the outer peripheral punching die 142, and the heat insulating member 143 are arranged below the raw material 1. On the other hand, the outer peripheral punching die 144 and the spring 145 are arranged above the raw material 1. In addition, reference numeral 21 denotes a stator core.

[0125] In the manufacturing device 100 having the above-described configuration, first, a steel coil 1A is formed along the Figure 7 The raw material 1 is fed out in the direction of arrow F. Then, the raw material 1 is subjected to punching processing in the multi-stage punching station 110 in sequence. Through these punching processing, the raw material 1 is obtained. Figure 3 The shape of the electromagnetic steel sheet 40 having the core back 22 and the plurality of teeth 23 is shown. However, at this point in time, it has not been punched out at all, so it proceeds to the next step in the direction of arrow F.

[0126] Then, finally, the raw material 1 is sent to the stacking station 140, punched by the outer peripheral punching punch 144, and stacked with high precision. During the stacking, the electromagnetic steel sheet 40 is subjected to a certain pressure due to the spring 145. By repeating the punching process and the stacking process described above in sequence, a predetermined number of electromagnetic steel sheets 40 can be stacked. Furthermore, the laminated core formed by stacking the electromagnetic steel sheets 40 in this way is heated by the heating device 141, for example, to a temperature of 200°C. By this heating, the insulating films 3 of the adjacent electromagnetic steel sheets 40 are bonded to each other (bonding process).

[0127] The heating temperature in the bonding step is, for example, preferably 120 to 250° C., more preferably 150 to 230° C., and even more preferably 200 to 220° C. If the heating temperature is above the lower limit, the insulating film 3 is sufficiently cured, and the bonding strength of the laminated core is further improved. If the heating temperature is below the upper limit, thermal degradation of the insulating film 3 can be suppressed, and the bonding strength of the laminated core can be further improved.

[0128] The heating time in the bonding process is affected by the size of the laminated core or the heating method, and is preferably 30 to 120 minutes, more preferably 45 to 100 minutes, and even more preferably 60 to 80 minutes. If the heating time is greater than the lower limit, the insulating film 3 is fully cured, and the bonding strength of the laminated core is further improved. If the heating time is less than the upper limit, thermal degradation of the insulating film 3 can be suppressed, and the bonding strength of the laminated core can be further improved.

[0129] The pressure when the laminate is pressurized is, for example, preferably 2 to 50 MPa, more preferably 3 to 30 MPa, and even more preferably 4 to 20 MPa. If the pressure when the laminate is pressurized is above the lower limit, the insulating film 3 is sufficiently adhered, and the bonding strength of the laminated core is further improved. If the pressure when the laminate is pressurized is below the upper limit, the insulating film 3 can be suppressed from being exposed from the end, and the stacking accuracy of the laminated core can be further improved.

[0130] In addition, the heating device 141 may not be disposed in the outer peripheral punching die 142. That is, the electromagnetic steel sheets 40 stacked in the outer peripheral punching die 142 may be taken out of the outer peripheral punching die 142 before bonding. In this case, the heat insulating member 143 may not be provided in the outer peripheral punching die 142. Furthermore, in this case, the stacked electromagnetic steel sheets 40 before bonding may be sandwiched and held from both sides in the stacking direction by a jig (not shown) and then transported or heated.

[0131] Through the above steps, the stator core 21 is completed.

[0132] As described above, in the present invention, an insulating film is formed on the surface of an electromagnetic steel sheet by combining an epoxy resin, a first curing agent (A) and a second curing agent (B) at a specific ratio. This makes it possible to achieve both excellent magnetic properties (core iron loss) of the laminated core and excellent heat resistance that can maintain the bonding strength between the electromagnetic steel sheets even at high temperatures during driving.

[0133] In addition, the technical scope of the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention.

[0134] The shape of the stator core is not limited to the form shown in the above embodiment. Specifically, it can be arbitrarily designed according to the desired characteristics of the rotating electrical machine, such as the outer diameter and inner diameter of the stator core, the stacking thickness, the number of slots, the circumferential and radial dimension ratio of the teeth, the radial dimension ratio of the teeth and the back of the core, etc.

[0135] In the rotor of the above embodiment, a set of two permanent magnets 32 forms one magnetic pole, but the present invention is not limited thereto. For example, one permanent magnet 32 ​​may form one magnetic pole, or three or more permanent magnets 32 may form one magnetic pole.

[0136] In the above embodiment, a permanent magnet excitation motor is described as an example of the rotating electrical machine 10 , but the structure of the rotating electrical machine 10 is not limited to the structure shown below, and various known structures not shown below can also be adopted.

[0137] In the above embodiment, a permanent magnet excitation motor is described as an example of the rotating electrical machine 10, but the present invention is not limited thereto. For example, the rotating electrical machine 10 may be a reluctance motor or an electromagnetic excitation motor (winding excitation motor).

[0138] In the above embodiment, a synchronous motor is described as an example of an AC motor, but the present invention is not limited thereto. For example, the rotating electric machine 10 may be an induction motor.

[0139] In the above embodiment, an AC motor is described as an example of the rotating electrical machine 10, but the present invention is not limited thereto. For example, the rotating electrical machine 10 may be a DC generator.

[0140] In the above embodiment, an electric motor is described as an example of the rotating electric machine 10, but the present invention is not limited thereto. For example, the rotating electric machine 10 may be a generator.

[0141] Furthermore, components in the above-described embodiments may be appropriately replaced with well-known components without departing from the gist of the present invention, and the above-described modifications may be appropriately combined.

[0142] Example

[0143] Hereinafter, the effect of one scheme of the present invention will be specifically described according to the embodiments, but the conditions in the embodiments are only a conditional example adopted to confirm the feasibility and effect of the present invention, and the present invention is not limited by the following description. As long as it does not deviate from the gist of the present invention and achieves the purpose of the present invention, the present invention can adopt various conditions.

[0144] [raw material]

[0145] The raw materials used in the examples are shown below.

[0146] (Epoxy resin)

[0147] E1: Bisphenol A epoxy resin

[0148] E2: Bisphenol F epoxy resin

[0149] E3: Triphenylmethane type epoxy resin

[0150] (First Curing Agent)

[0151] A1: 4-Sec-Butylphenol

[0152] A2: p-Nonylphenol

[0153] A3: p-Dodecylphenol

[0154] A4: 2,6-di-sec-butylphenol

[0155] A5: p-Propylphenol

[0156] (Second Curing Agent)

[0157] H1: Phenol resol resin

[0158] H2: Phenol novolac resin

[0159] (Curing agent (comparison object))

[0160] B1: diaminodiphenylmethane

[0161] B2: Dicyandiamide

[0162] B3: 4-Methylhexahydrophthalic anhydride

[0163] (Compounding agent)

[0164] M1: acrylic resin (methyl methacrylate unit: isopropyl acrylate unit: styrene unit: 2-ethylhexyl acrylate unit (molar ratio) = 40:30:20:10, glass transition temperature: 17°C)

[0165] M2: acrylic resin (methyl methacrylate unit: n-butyl acrylate unit (molar ratio) = 55:45, glass transition temperature: 10°C)

[0166] [Magnetic properties]

[0167] A rectangular electromagnetic steel plate (single plate) of 55 mm × 55 mm size was cut out from the electromagnetic steel strip of each example, and 10 electromagnetic steel plates were stacked and bonded under the conditions of a steel plate temperature of 200°C, a pressure of 10 MPa, and a pressing time of 1 hour to produce a laminated iron core. For the obtained laminated iron core, the magnetic properties of the single plate in the rolling direction and the direction perpendicular to the rolling direction were measured by the single plate magnetic measurement method specified in JIS C2556 (2015), and the average value of their values ​​was obtained as the magnetic property. In addition, as a magnetic property (magnetism), "W10 / 400 (W / kg)" was evaluated as the iron loss. "W10 / 400" is the iron loss at a frequency of 400 Hz and a maximum magnetic flux density of 1.0 T.

[0168] [Adhesion strength]

[0169] From the electrical steel strip of each example, two rectangular electrical steel sheets (single sheets) with a width of 30 mm and a length of 60 mm were cut out. Next, the surface was coated with the coating composition for the electrical steel sheet, and the front ends with a width of 30 mm and a length of 10 mm were overlapped and pressed to prepare a sample for measurement. The pressing conditions were set to a steel sheet temperature of 200°C, a pressure of 10 MPa, and a pressing time of 1 hour.

[0170] The obtained samples were stretched at a tension rate of 2 mm / min in an atmosphere at an ambient temperature of 25°C or 150°C, and the maximum load (N) until peeling was measured. The value obtained by dividing the maximum load (N) by the bonding area was set as the bonding strength (MPa).

[0171] <Curing shrinkage>

[0172] The coating composition for an electrical steel sheet was applied to the surface of the electrical steel strip of each example, and the curing shrinkage was measured. The curing shrinkage was measured based on the change in film thickness in accordance with JIS K 6941.

[0173] [determination]

[0174] Each example was judged according to the following criteria. In addition, the smaller the iron loss, the more the stress strain applied to the electromagnetic steel sheet is suppressed. The measurement results and the judgment results are shown in Table 2. In the table, the values ​​outside the scope of the invention are underlined.

[0175] [Benchmark]

[0176] “Good”: The adhesive strength at 25° C. is 5.0 MPa or more, the adhesive strength at 150° C. is 1.0 MPa or more, and the magnetic property is less than 12.0 W / kg.

[0177] "Poor": The bonding strength at 25°C is less than 5.0 MPa, the bonding strength at 150°C is less than 1.0 MPa, or the magnetic property is 12.0 W / kg or more.

[0178] [Example 1]

[0179] As the base steel plate, a non-oriented electrical steel plate having a thickness of 0.25 mm and a width of 100 mm, wherein, by mass %, Si: 3.0%, Mn: 0.2%, Al: 0.5%, and the remainder being Fe and impurities, was used.

[0180] The components shown in Table 1 were mixed to prepare a coating composition for an electrical steel sheet. The obtained coating composition for an electrical steel sheet was applied to the surface of a base steel sheet and sintered at 160° C. for 15 seconds to obtain an electrical steel strip having an insulating film with an average thickness of 3 μm.

[0181] [Examples 2 to 10, Comparative Examples 1 to 9]

[0182] An electrical steel strip was obtained in the same manner as in Example 1 except that the composition of the coating composition for an electrical steel sheet and the sintering conditions were changed as shown in Table 1.

[0183] The composition of the coating composition for an electrical steel sheet and the sintering conditions of each example are shown in Table 1. Table 2 shows the evaluation results of the magnetic properties (magnetism) and the adhesive strength of each example.

[0184] [Table 1]

[0185]

[0186] [Table 2]

[0187]

[0188] As shown in Table 2, Examples 1 to 10 in which the epoxy resin, the first curing agent (A), and the second curing agent (B) were combined at a specific ratio ensured sufficient adhesive strength even at 150° C., had excellent heat resistance, and also had excellent magnetic properties.

[0189] On the other hand, in Comparative Examples 1 to 4 in which the content of the first curing agent was outside the range of the present invention, Comparative Examples 5 to 7 and 9 containing no first curing agent, and Comparative Example 8 containing no second curing agent, both heat resistance and magnetic properties could not be achieved.

[0190] Industrial Availability

[0191] According to the present invention, it is possible to achieve both heat resistance and magnetic properties of a laminated iron core, and therefore the industrial applicability is high.

[0192] Description of Reference Numerals

[0193] 1…Raw material, 2…Base steel plate, 3…Insulation coating, 10…Rotating electric machine, 20…Stator, 21…Stator core, 40…Magnetic steel plate.

Claims

1. A coating composition for an electromagnetic steel sheet, It contains an epoxy resin, a first curing agent A composed of an alkylphenol, and a second curing agent (B) composed of either or both of a phenol resol resin and a phenol novolac resin; The content of the first curing agent A is 1.0 parts by mass or more and 20.0 parts by mass or less relative to 100 parts by mass of the epoxy resin. The content of the second curing agent B is 5.0 parts by mass or more and 150.0 parts by mass or less based on 100 parts by mass of the epoxy resin.

2. The coating composition for an electromagnetic steel sheet according to claim 1, The alkylphenol includes either or both of a monoalkylphenol having an alkyl group with 2 to 20 carbon atoms and a dialkylphenol having an alkyl group with 2 to 20 carbon atoms.

3. The coating composition for an electromagnetic steel sheet according to claim 1 or 2, The curing shrinkage is less than 15%.

4. The coating composition for an electromagnetic steel sheet according to claim 1 or 2, The mass ratio represented by [the content of the first curing agent A] / [the content of the second curing agent B] is 0.01 to 4.

0.

5. The coating composition for an electromagnetic steel sheet according to claim 3, The mass ratio represented by [the content of the first curing agent A] / [the content of the second curing agent B] is 0.01 to 4.

0.

6. An electromagnetic steel plate, The coating composition has an insulating film formed of the coating composition for an electrical steel sheet according to any one of claims 1 to 5 on its surface.

7. A laminated core, The electromagnetic steel sheet according to claim 6 is stacked in plurality and bonded to each other.

8. A rotating electrical machine, It comprises the laminated iron core according to claim 7.

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