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

Abstract

To provide a coating composition for an electromagnetic steel sheet capable of reducing application of stress strain caused by an adhesive component, even if a sheet thickness of the electromagnetic steel sheet is thin, and obtaining heat resistance capable of securing adhesive strength, even when a motor heats up; and to provide an electromagnetic steel sheet using the same, a laminated core and a rotating electrical machinery.SOLUTION: In a coating composition for an electromagnetic steel sheet, the electromagnetic steel sheet used for a laminated core is an electromagnetic steel sheet in which the surface of a base steel sheet 2 is coated with an insulation coating 3 formed by applying the coating composition for the electromagnetic steel sheet. The coating composition for the electromagnetic steel sheet contains a cross-linked hot-melt adhesive comprising a polyester urethane resin and aromatic amine having a melting point of 50°C or higher and 200°C or lower which is a hardener, and a room temperature solidified resin having a softening temperature of 100°C or higher and 200°C or lower, and the content of the room temperature solidified resin is 50 pts. mass or more and 300 pts. mass or less to 100 pts. mass of the cross-linked hot-melt adhesive.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a coating composition for an electromagnetic steel sheet, an electromagnetic steel sheet, a laminated core, and a rotating electric machine. [Background technology]

[0002] Laminated cores in which multiple electromagnetic steel sheets are joined together and laminated are known as cores (iron cores) used in rotating electric machines. Crimping and welding are known methods for joining electromagnetic steel sheets together. Joining methods such as crimping and welding tend to deteriorate core iron loss because they impart mechanical and thermal strain to the steel sheets. Adhesive bonding is known as a joining method other than crimping and welding. Adhesive bonding is superior in terms of core iron loss compared to crimping and welding because it does not impart mechanical or thermal strain to the steel sheets.

[0003] On the other hand, when joining magnetic steel sheets by adhesive bonding, the adhesive hardens and causes stress strain in the steel sheets. In recent years, there has been a demand for further improvements in motor efficiency, and so there is a need to further reduce core iron loss. Although thinning the magnetic steel sheets is an effective way to reduce core iron loss, the Young's modulus of the steel sheets decreases as the sheet thickness decreases. Therefore, there is a need to further reduce the stress strain that causes iron loss degradation.

[0004] Epoxy resins have little volume change and are excellent in heat resistance, oil resistance, and chemical resistance, making them excellent as adhesives for bonding electromagnetic steel sheets together. However, epoxy resins require a relatively high temperature to harden, which may cause stress to be applied to the steel sheets during bonding, resulting in deterioration of iron loss. Adhesives that can bond at lower temperatures than epoxy resins are known, for example, that use urethane resins (for example, Patent Documents 1 to 6). It is also known to form a polymer adhesive layer made of baked enamel such as polyvinyl butyral or polyamide on the surface of the steel sheets, and to further dispose a binder layer made of polyvinyl alcohol, amine, or the like between the polymer adhesive layers that bond the steel sheets together (Patent Document 7). However, it is difficult for these adhesives and binders to obtain sufficient heat resistance to be applicable to applications exposed to high temperatures during use, such as electric vehicle motors. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2017-179233 A [Patent Document 2] JP 2017-186542 A [Patent Document 3] Japanese Patent Application Publication No. 6-182929 [Patent Document 4] Japanese Patent Application Publication No. 6-271834 [Patent Document 5] Japanese Patent Application Publication No. 7-268051 [Patent Document 6] JP 2002-293864 A [Patent Document 7] Patent No. 6548081 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a coating composition for electromagnetic steel sheets that can reduce the stress strain caused by adhesive components even when the electromagnetic steel sheets are thin, and that can provide heat resistance that ensures adhesive strength even when a motor generates heat, and to provide an electromagnetic steel sheet, a laminated core, and a rotating electric machine that use the same. [Means for solving the problem]

[0007] The present invention has the following configuration. [1] A coating composition for electrical steel sheets comprising: a cross-linkable hot melt adhesive comprising a polyester-based urethane resin, which is a reaction product of a polyester polyol and a polyisocyanate, and a curing agent; and a room-temperature solidifying resin, wherein the softening point of the room-temperature solidifying resin is from 100°C to 200°C, and the content of the room-temperature solidifying resin is from 50 parts by mass to 300 parts by mass per 100 parts by mass of the cross-linkable hot melt adhesive. [2] The coating composition for electrical steel sheets according to [1], wherein the curing agent is an aromatic amine having a melting point of 50°C or more and 200°C or less. [3] An electrical steel sheet having an insulating coating on its surface, the insulating coating being formed by applying the coating composition for electrical steel sheet according to [1] or [2]. [4] The electrical steel sheet according to [3], having a sheet thickness of 0.50 mm or less. [5] A laminated core in which a plurality of the electromagnetic steel sheets according to [3] or [4] are laminated and bonded to each other. [6] A rotating electric machine comprising the laminated core described in [5]. Effect of the Invention

[0008] Effects of the Invention The present invention can provide a coating composition for electromagnetic steel sheets that can reduce the stress strain caused by adhesive components even when the electromagnetic steel sheets are thin, and can provide heat resistance that ensures adhesive strength even when a motor generates heat, as well as electromagnetic steel sheets, laminated cores, and rotating electric machines that use the same. [Brief description of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view of a rotating electrical machine including a laminated core according to a first embodiment of the present invention. [Diagram 2] FIG. [Diagram 3] 3 is a cross-sectional view taken along line AA in FIG. 2. [Figure 4] FIG. 2 is a plan view of a material forming the laminated core. [Diagram 5] 5 is a cross-sectional view of FIG. 4 taken along line B-B. [Figure 6] FIG. 6 is an enlarged view of part C in FIG. 5. [Figure 7] FIG. 2 is a side view of a manufacturing apparatus used to manufacture the laminated core. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, with reference to the drawings, a laminated core according to one embodiment of the present invention, a rotating electric machine including the laminated core, and a material forming the laminated core will be described. Note that in this embodiment, the rotating electric machine will be described as an electric motor, specifically an AC motor, more specifically a synchronous motor, and even more specifically a permanent magnet field type electric motor. This type of electric motor is preferably used in, for example, electric vehicles.

[0011] (Rotary Electric Machine 10) 1, the rotating electric machine 10 includes a stator 20, a rotor 30, a case 50, and a rotating shaft 60. The stator 20 and the rotor 30 are housed in the case 50. The stator 20 is fixed within the case 50. In this embodiment, an inner rotor type rotating electric machine 10 is used in which the rotor 30 is located radially inside the stator 20. However, an outer rotor type rotating electric machine 10 in which the rotor 30 is located outside the stator 20 may also be used. Also, in this embodiment, the rotating electric machine 10 is a three-phase AC motor with 12 poles and 18 slots. However, the number of poles, the number of slots, the number of phases, etc. can be changed as appropriate. The rotating electric machine 10 can rotate at a rotation speed of 1000 rpm by applying an excitation current with an effective value of 10 A and a frequency of 100 Hz to each phase, for example.

[0012] The stator 20 includes a stator adhesive laminated core (hereinafter, stator core) 21 and a winding (not shown). The stator core 21 includes an annular core back portion 22 and a plurality of teeth portions 23. Hereinafter, the direction of the central axis O of the stator core 21 (or the core back portion 22) will be referred to as the axial direction, the radial direction of the stator core 21 (or the core back portion 22) (the direction perpendicular to the central axis O) will be referred to as the radial direction, and the circumferential direction of the stator core 21 (or the core back portion 22) (the direction going around the central axis O) will be referred to as the circumferential direction.

[0013] The core back portion 22 is formed in an annular shape when viewed in a plan view of the stator 20 in the axial direction. The multiple teeth portions 23 protrude radially inward from the inner circumference of the core back portion 22 (toward the central axis O of the core back portion 22 along the radial direction). The multiple teeth portions 23 are arranged at equal angular intervals in the circumferential direction. In this embodiment, 18 teeth portions 23 are provided at central angle intervals of 20 degrees centered on the central axis O. The multiple teeth portions 23 are formed to have the same shape and size as one another. Therefore, the multiple teeth portions 23 have the same thickness dimension as one another. The winding is wound around the teeth portion 23. The winding may be a concentrated winding or a distributed winding.

[0014] The rotor 30 is disposed radially inside the stator 20 (the stator core 21). The rotor 30 includes a rotor core 31 and a plurality of permanent magnets 32. The rotor core 31 is formed in an annular (circular) shape and is disposed coaxially with the stator 20. The rotating shaft 60 is disposed within the rotor core 31. The rotating shaft 60 is fixed to the rotor core 31. The multiple permanent magnets 32 are fixed to the rotor core 31. In this embodiment, a pair of the permanent magnets 32 forms one magnetic pole. The multiple pairs of permanent magnets 32 are arranged at equal angular intervals in the circumferential direction. In this embodiment, 12 pairs (24 in total) of permanent magnets 32 are provided at central angle intervals of 30 degrees around the central axis O.

[0015] In this embodiment, an embedded magnet type motor is used as the permanent magnet field type motor. A rotor core 31 is formed with a plurality of through holes 33 that pass through 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 while being arranged in the corresponding through hole 33. Each permanent magnet 32 ​​can be fixed to the rotor core 31 by, for example, bonding the outer surface of the permanent magnet 32 ​​to the inner surface of the through hole 33 with an adhesive. Note that a surface magnet type motor may be used as the permanent magnet field type motor instead of the embedded magnet type.

[0016] Both the stator core 21 and the rotor core 31 are laminated cores. For example, the stator core 21 is formed by laminating a plurality of electromagnetic steel sheets 40 in a lamination direction, as shown in FIG. The lamination thickness (total 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 merely examples, and the lamination thickness, outer diameter, and inner diameter of the stator core 21 and the lamination 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 tip end of the teeth portion 23 of the stator core 21. In other words, the inner diameter of the stator core 21 is the diameter of an imaginary circle inscribed in the tip end of all the teeth portion 23.

[0017] Each of the electromagnetic steel sheets 40 forming the stator core 21 and the rotor core 31 is formed, for example, by punching a material 1 as shown in Fig. 4 to Fig. 6. The material 1 is a steel sheet (electromagnetic steel sheet) that serves as a base material for the electromagnetic steel sheets 40. Examples of the material 1 include a strip-shaped steel sheet and a cut sheet. Although we are still in the middle of explaining the laminated core, we will now explain this material 1. In this specification, the strip-shaped steel sheet that is the base material of the electromagnetic steel sheet 40 may be referred to as material 1. The steel sheet that is punched out from material 1 to have a shape used for the laminated core may be referred to as electromagnetic steel sheet 40.

[0018] (Material 1) The material 1 is handled in a state in which it is wound around a coil 1A shown in FIG. 7, for example. In this embodiment, a non-oriented electromagnetic steel sheet is used as the material 1. As the non-oriented electromagnetic steel sheet, a non-oriented electromagnetic steel strip according to JIS C 2552:2014 can be used. However, as the material 1, a directional electromagnetic steel sheet may be used instead of the non-oriented electromagnetic steel sheet. As the directional electromagnetic steel sheet in this case, a directional electromagnetic steel strip according to JIS C 2553:2019 can be used. In addition, a non-oriented thin electromagnetic steel strip or a directional thin electromagnetic steel strip according to JIS C 2558:2015 can be used.

[0019] The upper and lower limits of the average sheet thickness t0 of the raw material 1 are set, for example, as follows, taking into consideration the case where the raw material 1 is used as the electromagnetic steel sheet 40. The thinner the material 1, the higher the manufacturing cost of the material 1. Therefore, taking the manufacturing cost into consideration, the lower limit of the average plate thickness t0 of the material 1 is 0.10 mm, preferably 0.15 mm, and more preferably 0.18 mm. On the other hand, if the material 1 is too thick, the manufacturing cost will be favorable, but when the material 1 is used as an electromagnetic steel sheet 40, eddy current loss will increase and core iron loss will deteriorate. In addition, since the insulating coating according to this embodiment suppresses the occurrence of stress strain due to hardening, the adverse effect of the stress strain (increased iron loss) can be effectively suppressed, particularly when the material 1 is thin. Therefore, taking into account the core iron loss and manufacturing cost, the upper limit of the average sheet thickness t0 of the material 1 is 0.65 mm, preferably 0.35 mm. Furthermore, in order to obtain a sufficient stress strain suppression effect, the upper limit is preferably 0.30 mm, more preferably 0.26 mm. An example of the average sheet thickness t0 of the raw material 1 that satisfies the above range is 0.20 mm.

[0020] The average 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 coating 3. The average thickness t0 of the raw material 1 is measured, for example, by the following measurement method. For example, when the raw material 1 is wound in the shape of a coil 1A, at least a part of the raw material 1 is unwound into a flat plate shape. In the raw material 1 unwound into a flat plate shape, a predetermined position in the longitudinal direction of the raw material 1 (for example, a position away from an edge of the raw material 1 in the longitudinal direction by a length of 10% of the total length of the raw material 1) is selected. At this selected position, the raw material 1 is divided into five regions along its width direction. The thickness of the raw material 1 is measured at four locations that are the boundaries between these five regions. The average value of the thicknesses at the four locations can be set as the average thickness t0 of the raw material 1.

[0021] The upper and lower limits for the average sheet thickness t0 of the material 1 can naturally be adopted as the upper and lower limits for the average sheet thickness t0 of the electromagnetic steel sheets 40. The average sheet thickness t0 of the electromagnetic steel sheets 40 can be measured, for example, by the following measurement method. For example, the lamination thickness of the laminated core is measured at four locations equally spaced apart in the circumferential direction (i.e., at 90° intervals around the central axis O). Each of the measured lamination thicknesses at the four locations is divided by the number of laminated electromagnetic steel sheets 40 to calculate the sheet thickness per sheet. The average value of the sheet thicknesses at the four locations can be taken as the average sheet thickness t0 of the electromagnetic steel sheets 40.

[0022] 5 and 6, the material 1 includes a base steel plate 2 and an insulating coating 3. The material 1 is formed by covering both sides of a strip-shaped base steel plate 2 with the insulating coating 3. In this embodiment, most of the material 1 is formed of the base steel plate 2, and an insulating coating 3 that is thinner than the base steel plate 2 is laminated on the surface of the base steel plate 2.

[0023] The chemical composition of the base steel sheet 2 is shown below in mass %, and contains 2.5% to 4.5% Si by mass. By setting the chemical composition within this range, the yield strength of the material 1 (electromagnetic steel sheet 40) can be set to, for example, 380 MPa or more and 540 MPa or less.

[0024] Silicon: 2.5% to 4.5% Al: 0.001% to 3.0% Mn: 0.05% to 5.0%

[0025] When the material 1 is used as the electromagnetic steel sheet 40, the insulating coating 3 exerts insulating performance between adjacent electromagnetic steel sheets 40 in the stacking direction. In this embodiment, the insulating coating 3 has adhesive properties and bonds adjacent electromagnetic steel sheets 40 in the stacking direction. The insulating coating 3 may have a single layer configuration or a multi-layer configuration. More specifically, for example, the insulating coating 3 may have a single layer configuration that combines insulating properties and adhesive properties, or may have a multi-layer configuration including a base insulating coating with excellent insulating properties and a top insulating coating with excellent adhesive properties.

[0026] In this embodiment, the insulating coating 3 covers both sides of the base steel sheet 2 without any gaps over the entire surface. However, as long as the above-mentioned insulating performance and adhesive performance are ensured, some layers of the insulating coating 3 do not need to cover both sides of the base steel sheet 2 without any gaps. In other words, some layers of the insulating coating 3 may be provided intermittently on the surface of the base steel sheet 2. However, to ensure insulating performance, both sides of the base steel sheet 2 need to be covered with the insulating coating 3 so that the entire surface is not exposed. Specifically, when the insulating coating 3 does not have an underlying insulating coating with excellent insulating performance and has a single-layer configuration combining insulating performance and adhesive performance, the insulating coating 3 needs to be formed over the entire surface of the base steel sheet 2 without any gaps. In contrast, when the insulating coating 3 has a multi-layer structure including a base insulating coating with excellent insulating performance and a top insulating coating with excellent adhesion, it is possible to achieve both insulating performance and adhesion by forming both the base insulating coating and the top insulating coating without gaps over the entire surface of the base steel sheet 2, or by forming the base insulating coating without gaps over the entire surface of the base steel sheet and providing the top insulating coating intermittently.

[0027] The coating composition for forming the insulating undercoat is not particularly limited, and for example, a general treatment agent such as a chromate-containing treatment agent or a phosphate-containing treatment agent can be used.

[0028] The insulating coating having adhesive properties is formed by applying a coating composition for electromagnetic steel sheets, which will be described below, onto a base steel sheet. The insulating coating made of the coating composition for electromagnetic steel sheets is in an uncured or semi-cured state (B stage) before thermocompression bonding during the manufacture of a laminated core, and the heat applied during thermocompression bonding causes a curing reaction to proceed, thereby developing adhesive properties.

[0029] The coating composition for electrical steel sheets contains a cross-linking hot melt adhesive made of a polyester-based urethane resin and a curing agent, and a room temperature setting resin.

[0030] Polyester-based urethane resin is a reaction product (urethane resin) obtained by reacting polyester polyol with polyisocyanate. In general, the viscoelastic properties of urethane resin can be adjusted by the length of the carbon chain of the polyol, and a wide range of products are available on the market, from hard glass-like to rubber-elastic.

[0031] Polyester polyols have superior mechanical strength compared to polyether polyols. The polyester polyols are not particularly limited, and examples thereof include polyester-polyether type copolymers (such as copolymers of butylene terephthalate and tetramethylene oxide glycol), polyester-polyester type copolymers (such as copolymers of butylene terephthalate and butylene adipate), etc. The polyester polyols may be used alone or in combination of two or more.

[0032] The polyisocyanate is not particularly limited, and examples thereof include tolylene diisocyanate (TDI), 4,4'-diphenylmethane diisocyanate, 3,3'-dimethyl-4,4'-biphenylene diisocyanate, 1,4-phenylene diisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate, naphthylene diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, crude TDI, polymethylene polyphenylisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, hydrogenated xylylene diisocyanate, their isocyanurates, carbodiimides, biuret compounds, etc. As the polyisocyanate, one type may be used alone, or two or more types may be used in combination.

[0033] In order to heat-harden the insulating coating during the manufacture of the laminated core, the hardener must have latency. Here, "the hardener has latency" means that the hardening reaction is inhibited from progressing until hardening is started by heating. In this embodiment, an aromatic amine having a melting point (MP) of 50°C or more and 200°C or less is used as the hardener having latency. If the MP of the aromatic amine is within the above range, both latency and an appropriate bonding temperature range can be achieved, and the adhesive strength between the magnetic steel sheets is increased. The MP of the aromatic amine is preferably 60°C or more and 180°C or less. The "melting point" is a value measured visually at a temperature rise rate of 1°C / min in accordance with JIS K0064 (1992).

[0034] Specific examples of aromatic amines include metaphenylenediamine (MP: 62° C.), diaminodiethyldimethyldiphenylmethane (MP: 76° C.), diaminodiphenylmethane (MP: 89° C.), dichlorodiaminodiphenylmethane (MP: 98° C.), trimethylenebis(4-aminobenzoate) (MP: 122 to 128° C.), etc. As the aromatic amines, one type may be used alone, or two or more types may be used in combination.

[0035] The content of the curing agent is preferably 3 parts by mass or more and 100 parts by mass or less, more preferably 5 parts by mass or more and 20 parts by mass or less, relative to 100 parts by mass of the polyester-based urethane resin. If the content of the curing agent is equal to or more than the lower limit of the above range, the adhesive strength between the magnetic steel sheets is increased. If the content of the curing agent is equal to or less than the upper limit of the above range, the pot life is extended.

[0036] Room temperature solidifying resins have a softening point of 100°C or higher and 200°C or lower, and can be solidified by cooling to room temperature (e.g., 25°C). Note that the "softening point" refers to the melting point if the resin is a crystalline polymer, and the glass transition temperature if the resin is an amorphous polymer, and is a value measured at a heating rate of 5°C / min using a differential scanning calorimeter (DSC) in accordance with JIS K6863 (1994).

[0037] Specific examples of room temperature solidifying resins include rosin, rosin derivatives (hydrogenated rosin, polymerized rosin, hydrogenated polymerized rosin, rosin glycerin ester, hydrogenated rosin glycerin ester, rosin pentaerythritol ester, hydrogenated rosin pentaerythritol ester, disproportionated rosin glycerin ester, water-proportionated rosin pentaerythritol ester, etc.), terpene phenol resin, hydrogenated terpene phenol resin, ketone resin, petroleum resin (aliphatic, aromatic, copolymers thereof, alicyclic, and hydrogenated petroleum resins thereof), terpene resin, hydrogenated terpene resin, coumarone-indene resin, phenol resin, xylene resin, etc. One type of room temperature solidifying resin may be used alone, or two or more types may be used in combination.

[0038] The softening point of the room-temperature-solidifying resin is preferably 80° C. or higher and 230° C. or lower, and more preferably 100° C. or higher and 200° C. or lower. When the softening point of the room-temperature-solidifying resin is equal to or higher than the lower limit of the above range, the coating composition for magnetic steel sheets has excellent coating properties, and heat resistance is obtained that can ensure adhesive strength even when the motor heats up. When the softening point of the room-temperature-solidifying resin is equal to or lower than the upper limit of the above range, a laminated core with excellent magnetic properties can be formed.

[0039] The content of the room-temperature-solidifying resin is 50 parts by mass or more and 300 parts by mass or less, and preferably 100 parts by mass or more and 180 parts by mass or less, per 100 parts by mass of the crosslinking hot melt adhesive. If the content of the room-temperature-solidifying resin is equal to or more than the lower limit, a laminated core with excellent magnetic properties can be formed. If the content of the room-temperature-solidifying resin is equal to or less than the upper limit, heat resistance that can ensure adhesive strength even when the motor heats up can be obtained.

[0040] Hot melt adhesives are bonded by heating and melting, and can be made solvent-free, which has the advantage of significantly reducing the amount of volatilized components during bonding. Furthermore, various properties can be expressed by molecular design and mixing with various resins. In the crosslinked hot melt adhesive used in this embodiment, the polyester-based urethane resin, which is characterized by its high mechanical strength, is crosslinked, so that heat resistance is obtained even after bonding and high-temperature strength can be secured, making it usable for motors. Furthermore, by mixing with a room-temperature solidifying resin, core iron loss and heat resistance can be achieved at the same time. In addition, by combining an aromatic amine with latent properties as a curing agent, sufficient coating properties can be secured, and low-temperature baking and low-temperature bonding are possible.

[0041] The insulating coating 3 can be formed, for example, by applying a coating composition for electrical steel sheets to the surface of the base steel sheet, drying it, and baking it. The lower limit of the temperature to be reached during baking is preferably 90° C., more preferably 110° C. The upper limit of the temperature to be reached during baking is preferably 180° C., more preferably 160° C. The lower limit of the baking time is preferably 5 seconds, more preferably 10 seconds, and the upper limit of the baking time is preferably 60 seconds, more preferably 45 seconds.

[0042] Taking into consideration the case where the material 1 is used as an electromagnetic steel sheet 40, the upper and lower limits of the average thickness t1 of the insulating coating 3 are set, for example, as follows. When the material 1 is used as the electromagnetic steel sheet 40, the average thickness t1 of the insulating coating 3 (the thickness per one side of the electromagnetic steel sheet 40 (material 1)) is adjusted so as to ensure the insulating performance and adhesive ability between the electromagnetic steel sheets 40 that are stacked on top of each other.

[0043] In the case of a single-layer insulating coating 3, the lower limit of the average thickness t1 of the insulating coating 3 is preferably 2.0 μm, more preferably 2.5 μm. On the other hand, as the insulating coating 3 becomes thicker, the insulating effect saturates. Also, as the insulating coating 3 becomes thicker, the proportion of the base steel sheet 2 in the laminated core decreases, and the performance of the laminated core decreases. Therefore, the upper limit of the average thickness t1 of the insulating coating 3 is preferably 8.0 μm, more preferably 6.0 μm. In the case of the insulating coating 3 having a multilayer structure, the average thickness of the base insulating coating may be, for example, from 0.3 μm to 2.5 μm, and preferably from 0.5 μm to 1.5 μm. The lower limit of the average thickness of the top insulating coating may be 2.0 μm, and preferably 2.5 μm. The upper limit of the average thickness of the top insulating coating may be 6.0 μm, and preferably 4.5 μm. The average thickness t1 of the insulating coating 3 on the base material 1 can be measured in the same manner as the average plate thickness t0 of the base material 1, by measuring the thicknesses of the insulating coating 3 at multiple locations and averaging these thicknesses.

[0044] The upper and lower limits for the average thickness t1 of the insulating coating 3 of the material 1 can naturally be adopted as the upper and lower limits for the average thickness t1 of the insulating coating 3 of the electromagnetic steel sheet 40. The average thickness t1 of the insulating coating 3 of the electromagnetic steel sheet 40 can be measured, for example, by the following measurement method. For example, among the multiple electromagnetic steel sheets forming the laminated core, the electromagnetic steel sheet 40 located at the outermost position in the lamination direction (the electromagnetic steel sheet 40 whose surface is exposed in the lamination direction) is selected. On the surface of the selected electromagnetic steel sheet 40, a predetermined position in the radial direction (for example, a position exactly halfway (center) between the inner peripheral edge and the outer peripheral edge of the electromagnetic steel sheet 40) is selected. At the selected position, the thickness of the insulating coating 3 of the electromagnetic steel sheet 40 is measured at four positions equally spaced apart in the circumferential direction (i.e., at 90° intervals around the central axis O). The average value of the thicknesses measured at the four positions can be set as the average thickness t1 of the insulating coating 3. The reason why the average thickness t1 of the insulating coating 3 was measured in this manner for the electromagnetic steel sheet 40 located at the outermost side in the stacking direction is that the insulating coating 3 is fabricated so that the thickness of the insulating coating 3 hardly changes depending on the stacking position along the stacking direction of the electromagnetic steel sheet 40.

[0045] The blank 1 as described above is punched to produce electromagnetic steel sheets 40, and bonded cores (the stator core 21 and the rotor core 31) are manufactured from the electromagnetic steel sheets 40.

[0046] (Lamination method of laminated core) Returning to the description of the laminated core, a plurality of electromagnetic steel sheets 40 forming the stator core 21 are laminated with insulating coatings 3 interposed therebetween, as shown in FIG. The electromagnetic steel sheets 40 adjacent to each other in the stacking direction are bonded over their entire surfaces by the insulating coating 3. In other words, the surface of the electromagnetic steel sheet 40 facing the stacking direction (hereinafter referred to as the first surface) is the bonding region 41a over its entire surface. However, the electromagnetic steel sheets 40 adjacent to each other in the stacking direction do not have to be bonded over their entire surfaces. In other words, the first surface of the electromagnetic steel sheet 40 may include a mixture of bonding regions 41a and non-bonding regions (not shown).

[0047] In this embodiment, the multiple electromagnetic steel sheets forming rotor core 31 are fixed to one another by crimps 42 (dowels) shown in Fig. 1. However, the multiple electromagnetic steel sheets forming rotor core 31 may also have a laminated structure fixed by insulating coating 3, similar to stator core 21. Furthermore, laminated cores such as the stator core 21 and the rotor core 31 may be formed by so-called rotational lamination.

[0048] (Laminated core manufacturing method) The stator core 21 is manufactured, for example, by using a manufacturing apparatus 100 shown in Fig. 7. In the following, before describing the manufacturing method, the manufacturing apparatus 100 for laminated cores (hereinafter simply referred to as the manufacturing apparatus 100) will first be described. In the manufacturing apparatus 100, the raw material 1 is fed from the coil 1A (hoop) in the direction of the arrow F, while being punched multiple times using dies arranged at each stage, gradually forming it into the shape of the electromagnetic steel sheet 40. The punched electromagnetic steel sheets 40 are then stacked and pressurized while being heated. As a result, adjacent electromagnetic steel sheets 40 in the stacking direction are bonded by the insulating coating 3 (i.e., the portion of the insulating coating 3 located in the bonding region 41a is allowed to exert its adhesive ability), completing the bonding.

[0049] 7, the manufacturing apparatus 100 includes a plurality of punching stations 110. The punching stations 110 may include two or more punching stations. Each punching station 110 includes a female die 111 disposed below the material 1 and a male die 112 disposed above the material 1.

[0050] The manufacturing apparatus 100 further includes a lamination station 140 located downstream of the most downstream punching station 110. The lamination station 140 includes a heating device 141, a peripheral punching female die 142, a heat insulating member 143, a peripheral punching male die 144, and a spring 145. The heating device 141, the outer periphery punching female die 142, and the heat insulating member 143 are disposed below the material 1. On the other hand, the outer periphery punching male die 144 and the spring 145 are disposed above the material 1. The reference numeral 21 denotes a stator core.

[0051] In the manufacturing apparatus 100 having the configuration described above, first, the material 1 is sequentially sent out from the coil 1A in the direction of the arrow F in Fig. 7. Then, the material 1 is subjected to a punching process in a plurality of stages of punching stations 110 in sequence. Through these punching processes, the material 1 is given the shape of the electromagnetic steel sheet 40 having the core back portion 22 and the plurality of teeth portions 23 shown in Fig. 3. However, since the material is not completely punched out at this point, it proceeds to the next process along the direction of the arrow F.

[0052] Finally, the blank 1 is sent to a lamination station 140, where it is punched out by a peripheral punching male die 144 and laminated with high precision. During this lamination, the electromagnetic steel sheets 40 receive a constant pressure from a spring 145. By sequentially repeating the punching and lamination processes as described above, 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 manner is heated by a heating device 141 to a temperature of, for example, 200°C. This heating bonds the insulating coatings 3 of adjacent electromagnetic steel sheets 40 together. It should be noted that the heating device 141 does not have to be disposed in the outer periphery punching female die 142. In other words, the electromagnetic steel sheets 40 stacked in the outer periphery punching female die 142 may be removed from the outer periphery punching female die 142 before bonding. In this case, the outer periphery punching female die 142 may not have the heat insulating member 143. Furthermore, in this case, the stacked electromagnetic steel sheets 40 before bonding may be held by clamping them from both sides in the stacking direction with a jig (not shown), and then transported or heated. Through the above steps, the stator core 21 is completed.

[0053] As described above, in the present invention, a specific cross-linking hot melt adhesive and a room temperature solidifying resin are combined in a specific ratio as a coating composition for an electromagnetic steel sheet that forms an insulating coating on the electromagnetic steel sheet. This makes it possible to suppress the application of stress distortion due to the adhesive components even if the electromagnetic steel sheet is thin, so that a laminated core with excellent magnetic properties (core iron loss) can be formed. In addition, since the adhesive strength between the electromagnetic steel sheets is high and has excellent heat resistance, a laminated core that can ensure adhesive strength even when the motor heats up can be formed.

[0054] 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 spirit of the present invention. The shape of the stator core is not limited to the form shown in the above embodiment. Specifically, the outer diameter and inner diameter of the stator core, the lamination thickness, the number of slots, the circumferential and radial dimensional ratio of the teeth portion, and the radial dimensional ratio of the teeth portion and the core back portion can be designed as desired according to the characteristics of the rotating electric machine.

[0055] In the rotor in the above embodiment, a pair of permanent magnets 32 form 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.

[0056] In the above embodiment, a permanent magnet field type electric motor has been used as an example of a rotating electric motor, but the structure of the rotating electric motor is not limited to this, as exemplified below, and various known structures not exemplified below can also be adopted. In the above embodiment, a permanent magnet field type motor is used as an example of a rotating electric machine, but the present invention is not limited to this. For example, the rotating electric machine may be a reluctance type motor or an electromagnetic field type motor (wound field type motor). In the above embodiment, a synchronous motor is used as an example of an AC motor, but the present invention is not limited to this. For example, the rotating electric machine may be an induction motor. In the above embodiment, an AC motor is used as an example of the electric motor, but the present invention is not limited to this. For example, the rotating electric machine may be a DC motor. In the above embodiment, an electric motor is used as an example of a rotating electric machine, but the present invention is not limited to this. For example, the rotating electric machine may be a generator.

[0057] In the above embodiment, the laminated core according to the present invention is applied to a stator core, but it can also be applied to a rotor core. The laminated core may be used in a transformer instead of a rotating electric machine. In this case, it is preferable to use grain-oriented magnetic steel sheets as the magnetic steel sheets instead of non-oriented magnetic steel sheets.

[0058] In addition, within the scope of the invention, the components in the above-described embodiments may be replaced with well-known components, and the above-described modified examples may be combined as appropriate. EXAMPLES

[0059] The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following description.

[0060] [Raw materials] The raw materials used are shown below. (Polyester-based urethane resin) PE1: Polyester-based urethane prepolymer (weight average molecular weight (Mw): 5000) A reaction vessel equipped with a stirrer, thermometer, reflux condenser, dropping device, and nitrogen inlet tube was charged with 500 parts by mass of a polyester polyol obtained from terephthalic acid, adipic acid, and 3-methyl-1,5-pentanediol ("Kuraray Polyol P-2011" manufactured by Kuraray Co., Ltd., Mn=2040), 15 parts by mass of dimethylolbutanoic acid, 100 parts by mass of isophorone diisocyanate, and 80 parts by mass of toluene, and reacted for 4 hours at 90°C under a nitrogen atmosphere. 350 parts by mass of toluene was added to this to obtain a solution of a polyester-based urethane prepolymer containing isocyanate groups (Mw=5000, molar ratio (NCO / OH)=1:1).

[0061] PE2: Polyester-based urethane prepolymer (Mw: 12000) A solution of a polyester-based urethane prepolymer (Mw=12000, molar ratio (NCO / OH)=1:1) containing an isocyanate group was obtained in the same manner as in PE1, except that the reaction time was changed.

[0062] PE3: Polyester-based urethane prepolymer (Mw: 35000) A solution of a polyester-based urethane prepolymer (Mw=35,000, molar ratio (NCO / OH)=1:1) containing an isocyanate group was obtained in the same manner as in PE1, except that the reaction time was changed.

[0063] (Polyether-based urethane resin) PO1: Polyether-based urethane prepolymer (Mw: 5000) 100 parts by mass of an isocyanate mixture of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate in a mass ratio of 8:2 was reacted with 600 parts by mass of polypropylene glycol at 80°C for 2 hours and then at 100°C for 3 hours to obtain a solution of a polyether-based urethane prepolymer (Mw=5000, molar ratio (NCO / OH)=3:1) containing an isocyanate group.

[0064] PO2: Polyether-based urethane prepolymer (Mw: 35,000) A solution of a polyether-based urethane prepolymer (Mw=35,000, molar ratio (NCO / OH)=3:1) containing an isocyanate group was obtained in the same manner as PE1, except that the molecular weight of the polypropylene glycol was changed.

[0065] (hardening agent) H1: Polytetramethylene oxide-di-p-aminobenzoate (MP: 60°C) H2: 3,3'-dichloro-4,4'-diaminophenylmethane (MP: 98°C) H3: Trimethylene-bis(4-aminobenzoate) (MP: 125°C) G1: Xylylenediamine trimer (viscous liquid, MP: below 0°C) G2: Polytetramethylene oxide-di-p-aminobenzoate (MP: 15°C) G3: Blocked isocyanate (MP: 105℃) G4: Dicyandiamide (MP: 210℃)

[0066] (Room temperature hardening resin) R1: Rosin derivative resin (softening point: 110℃) R2: Aromatic hydrocarbon resin (softening point: 140°C) R3: Terpene phenol resin (softening point: 160°C) R4: Novolac phenolic resin (softening point: 180°C)

[0067] (Comparative resin) S1: Terpene resin (softening point: 65°C) S2: Rosin resin (softening point: 82°C) S3: Novolac phenolic resin (softening point: 230°C)

[0068] [Magnetic properties] A non-oriented electrical steel sheet having a thickness of 0.25 mm and a width of 100 mm and consisting of, by mass%, 3.0% Si, 0.2% Mn, 0.5% Al, and the remainder being Fe and impurities was manufactured as an electrical steel strip. The coating composition for electrical steel sheet of each example was applied to both sides of the electrical steel strip and baked under the conditions shown in Table 1 to form an insulating coating with an average sheet thickness t1 of 3 μm. A rectangular magnetic steel sheet measuring 55 mm x 55 mm was cut from the magnetic steel strip, and 10 magnetic steel sheets were laminated and bonded together at a steel sheet temperature of 180°C, a pressure of 10 MPa, and a pressure time of 1 hour to produce a laminated core. The magnetic properties of the single sheet obtained were measured in the rolling direction and perpendicular to the rolling direction using the single sheet magnetic measurement method in accordance with JIS C2556 (2015), and the average of these values ​​was calculated as the magnetic properties.

[0069] [Adhesive strength] Two rectangular electromagnetic steel sheets, 30 mm wide x 60 mm long, were cut out from the electromagnetic steel strip manufactured in the above test for [Magnetic properties], and the 30 mm wide x 10 mm long tips of each sheet were overlapped and bonded together at a steel sheet temperature of 180°C, a pressure of 10 MPa, and a pressure time of 1 hour to produce a sample. The shear tensile strength was measured at an atmospheric temperature of 25°C or 150°C and a tensile speed of 2 mm / min, and the value divided by the adhesive area was taken as the adhesive strength (MPa).

[0070] [judgement] Each example was judged according to the following criteria. ◯ (Excellent): Adhesive strength at 25°C is 5 MPa or more, adhesive strength at 180°C is 0.5 MPa or more, and magnetic properties are less than 12 W / kg. △ (Acceptable): The adhesive strength at 25°C is 4 MPa or more and less than 5 MPa, the adhesive strength at 180°C is 0.5 MPa or more, and the magnetic properties are less than 12 W / kg. × (Fail): Does not satisfy one or more of the following: adhesive strength at 25°C is 4 MPa or more, adhesive strength at 180°C is 0.5 MPa or more, and magnetic properties are less than 12 W / kg.

[0071] [Examples 1 to 10, Comparative Examples 1 to 11] The components shown in Table 1 were mixed together to prepare a coating composition for electrical steel sheets.

[0072] The composition of the coating composition for electrical steel sheets and the baking conditions for each example are shown in Table 1. The evaluation results for each example are shown in Table 2.

[0073] [Table 1]

[0074] [Table 2]

[0075] As shown in Table 2, in Examples 1 to 10, in which a specific cross-linking hot melt adhesive and a room temperature solidifying resin were combined in a specific ratio, the adhesive strength between the magnetic steel sheets was high at both room temperature (25°C) and 150°C, and the magnetic properties of the laminated core were also excellent. In Comparative Examples 1 to 11, which did not satisfy the conditions such as the type of urethane resin and the softening point and content of the room-temperature solidifying resin, it was not possible to achieve both adhesive strength and magnetic properties at room temperature and 150°C.

[0076] [Examples 21 to 26, Comparative Examples 21 to 26] Next, an example will be shown regarding the influence of the insulating coating when the average sheet thickness t0 of the raw material (electromagnetic steel sheet) is changed. The average thickness t1 of the insulating coating was fixed at "3 μm," and the average sheet thickness t0 of the raw material was changed by changing the sheet thickness of the base steel sheet. The raw materials of the insulating coating used were the same as those in Example 2 or Comparative Example 3. The base steel sheet used was a non-oriented electromagnetic steel sheet with a width of 100 mm, consisting of, by mass%, 2.95% Si, 0.2% Mn, 0.4% Al, with the balance being Fe and impurities. The various evaluation methods were the same as those for [Magnetic properties], [Adhesive strength], and [Evaluation] described above, and only the thickness of the non-oriented electrical steel sheet used as the base steel sheet was changed. The coating composition and baking conditions for Examples 21 to 25 were the same as those for Example 2 in Tables 1 and 2, and for Comparative Examples 21 to 25, they were the same as those for Comparative Example 3 in Tables 1 and 2. The evaluation results for each example are shown in Table 3. Note that "base sheet thickness t0" in Table 3 includes the average thickness t1 (3 μm) of the insulating coating.

[0077] As shown in Table 3, both the steel sheets of the Examples and the Comparative Examples have reduced iron loss as the base sheet thickness t0 becomes thinner, but the electrical steel sheet having an insulating coating according to the present invention is able to keep iron loss lower than that of the electrical steel sheet of the Comparative Examples, particularly when the base sheet thickness t0 is thin. This is thought to be because, as mentioned above, the insulating coating of the present invention suppresses the occurrence of stress strain associated with hardening.

[0078] [Table 3] [Industrial Applicability]

[0079] According to the present invention, it is possible to achieve both magnetic properties and heat resistance, and thus the industrial applicability is great. [Explanation of symbols]

[0080] 1...material, 2...base steel plate, 3...insulating coating, 10...rotating electric machine, 20...stator, 21...stator core, 40...electromagnetic steel plate.

Claims

1. The adhesive contains a crosslinkable hot melt adhesive made of a polyester-based urethane resin, which is a reaction product of a polyester polyol and a polyisocyanate, and a curing agent, and a room temperature solidifying resin. The softening point of the room temperature solidifying resin is 100° C. or more and 200° C. or less, A coating composition for electrical steel sheets, wherein the content of the room-temperature-solidifying resin is 50 parts by mass or more and 300 parts by mass or less relative to 100 parts by mass of the crosslinkable hot melt adhesive.

2. 2. The coating composition for electrical steel sheets according to claim 1, wherein the curing agent is an aromatic amine having a melting point of 50° C. or more and 200° C. or less.

3. 3. An electrical steel sheet having an insulating coating on a surface thereof, the insulating coating being formed by applying the coating composition for electrical steel sheet according to claim 1 or 2.

4. The electrical steel sheet according to claim 3, having a sheet thickness of 0.50 mm or less.

5. A laminated core, comprising a plurality of the electromagnetic steel sheets according to claim 3 or 4 laminated and bonded to each other.

6. A rotating electrical machine comprising the laminated core according to claim 5 .

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