Electromagnetic steel sheet, laminated core, rotating electric machine, and method for manufacturing electromagnetic steel sheet

Abstract

To provide an electromagnetic steel sheet capable of striking balance between reduction of a scrap generation amount during punching, and adhesive strength between each electromagnetic steel sheet; and to provide a laminated core, rotating electrical machinery, and a manufacturing method of the electromagnetic steel sheet.SOLUTION: An 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 having adhesion ability. In the insulation coating 3, a spin-spin relaxation time T2(25) measured by Solid Echo method at 25°C by using pulse NMR is 50 μs or less, and a spin-spin relaxation time T2(180) measured by pulse NMR at 180°C is 50 μs or more and 100 μs or less.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to an electromagnetic steel sheet, a laminated core, a rotating electric machine, and a method for manufacturing the electromagnetic steel sheet. [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 electrical machines. Methods for joining electromagnetic steel sheets together include crimping and welding. However, crimping and welding can cause mechanical stress and thermal stress during processing, as well as interlayer short circuits, which can degrade the magnetic properties of the electromagnetic steel sheets and reduce the performance of the laminated core.

[0003] Adhesion is known as a joining method other than caulking and welding. For example, it has been proposed to laminate electromagnetic steel sheets having an adhesive insulating coating on the surface and adhere them to each other (for example, Patent Document 1). However, conventional adhesive insulating coatings generate a lot of peeled off chips (hereinafter referred to as "scrap") from the ends of the insulating coating when punching out a specific shape, which requires cleaning and affects productivity. In addition, when stacking electromagnetic steel sheets and hot pressing them, the insulating coating is likely to protrude from the sides, which may cause the electromagnetic steel sheets to tilt slightly and reduce the lamination accuracy of the laminated core. In addition, it is required to ensure sufficient adhesive strength for the insulating coating. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2000-173816 A Summary of the Invention [Problem to be solved by the invention]

[0005] In electrical steel sheets having an adhesive insulating coating on the surface, it is required to suppress the generation of scum, ensure lamination accuracy, and provide sufficient adhesive strength, but it has been thought that it is difficult to achieve all of these. The reason for this is that while a hard insulating coating is considered to be preferable for suppressing the generation of scum, a soft insulating coating is considered to be preferable for obtaining sufficient adhesive strength. In addition, with regard to lamination accuracy, if the insulating coating is too soft, the insulating coating from the side of the laminated core becomes large, while if it is too hard, the steel sheets do not fit well together during hot pressing, which not only reduces the lamination accuracy but also hinders contact between the steel sheets, adversely affecting the adhesive strength. An object of the present invention is to provide an electromagnetic steel sheet, a laminated core, a rotating electric machine, and a method for manufacturing an electromagnetic steel sheet, which are capable of reducing the amount of waste generated during punching, improving lamination accuracy during hot pressing, and further improving the adhesive strength between the electromagnetic steel sheets. [Means for solving the problem]

[0006] The present invention has the following configuration. [1] An electrical steel sheet in which at least a portion of one or both surfaces of a base steel sheet is covered with an insulating coating having adhesive properties, wherein the insulating coating has a spin-spin relaxation time T2(25) of 50.0 μs or less as measured by the Solid Echo method at 25°C using pulse NMR, and a spin-spin relaxation time T2(180) of 50.0 μs or more and 100.0 μs or less as measured by pulse NMR at 180°C. [2] The electrical steel sheet according to [1], wherein the difference between the spin-spin relaxation time T2(180) and the spin-spin relaxation time T2(25), T2(180) - T2(25), is 40.0 μs or more. [3] A laminated core, in which a plurality of the electromagnetic steel sheets according to [1] or [2] are laminated and bonded to each other. [4] A rotating electric machine comprising the laminated core described in [3]. [5] A method for producing an electrical steel sheet as set forth in [1] or [2], comprising the steps of applying a coating composition for electrical steel sheet to at least a part of a surface of one or both of a base steel sheet and drying it, and baking the coating composition for electrical steel sheet and then cooling to room temperature to form an insulating coating, wherein in the baking step, when the glass transition temperature of the insulating coating is Tg [°C] and the temperature Th reached during baking is higher than Tg+15°C and lower than 200°C, and when the average cooling rate in the temperature range from Th°C to (Tg+15)°C during the cooling process from the reached temperature Th to room temperature is CR1 [°C / s], the average cooling rate CR1 is 20°C / s or more and 30°C / s or less. [6] The method for producing an electrical steel sheet according to [5], characterized in that in the baking step, when the average cooling rate in the temperature range from (Tg+15)°C to Tg°C during the cooling process from the reached temperature to room temperature is CR2 [°C / s] and the average cooling rate from Tg°C to (Tg-15)°C is CR3 [°C / s], the following (Equations 1) and (Equations 2) are satisfied. |CR1-CR2|≦5℃ / s...Formula 1 CR1-CR3≧10℃ / s...Formula 2 Effect of the Invention

[0007] The present invention can provide an electromagnetic steel sheet, a laminated core, a rotating electric machine, and a method for manufacturing an electromagnetic steel sheet, which can reduce the amount of waste generated during punching, improve lamination accuracy during hot pressing, and also improve the adhesive strength between the electromagnetic steel sheets. [Brief description of the drawings]

[0008] [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

[0009] 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.

[0010] (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.

[0011] 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.

[0012] 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.

[0013] 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.

[0014] 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.

[0015] 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.

[0016] 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.

[0017] (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.

[0018] 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 the eddy current loss will increase and the core iron loss will deteriorate when the material 1 is used as the electromagnetic steel sheet 40. Therefore, taking into consideration the core iron loss and the manufacturing cost, the upper limit of the average sheet thickness t0 of the material 1 is 0.65 mm, preferably 0.35 mm, and more preferably 0.30 mm. An example of the average sheet thickness t0 of the raw material 1 that satisfies the above range is 0.20 mm.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] Silicon: 2.5% to 4.5% Al: 0.001% to 3.0% Mn: 0.05% to 5.0% Remainder: Fe and impurities

[0024] When the material 1 is used as the electromagnetic steel sheet 40, the insulating coating 3 exerts insulating performance between the electromagnetic steel sheets 40 adjacent to each other in the stacking direction. In this embodiment, the insulating coating 3 has adhesive properties and bonds the electromagnetic steel sheets 40 adjacent to each other 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 that includes a base insulating coating that has excellent insulating properties and a top insulating coating that has excellent adhesive properties.

[0025] 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.

[0026] 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.

[0027] The adhesive insulating coating is formed by applying a coating composition for electrical steel sheet, which will be described later, onto a base steel sheet. The adhesive insulating coating is, for example, a single-layer insulating coating having both insulating properties and adhesive properties, or a top insulating coating provided on a base insulating coating. The adhesive insulating coating is in an uncured or semi-cured state (B stage) before thermocompression bonding during laminated core production, and a curing reaction proceeds due to heating during thermocompression bonding, thereby developing adhesive properties.

[0028] An insulating coating having adhesive properties has a spin-spin relaxation time T2(25) of 50.0 μs or less as measured by the Solid Echo method at 25° C. using pulsed NMR, and a spin-spin relaxation time T2(180) of 50 μs or more and 100.0 μs or less as measured by pulsed NMR at 180° C. However, in the present invention, transverse relaxation observed in pulsed NMR measurement, i.e., relaxation in a plane perpendicular to the static magnetic field, is regarded as spin-spin relaxation. Measurement conditions for pulsed NMR include, for example, the conditions shown in the Examples.

[0029] By controlling T2(25) to 50.0 μs or less, the insulating coating 3 has very low molecular mobility and is hard during punching, reducing the amount of waste generated. Furthermore, by controlling T2(180) within the above range, the molecular mobility of the insulating coating 3 is appropriately increased when the electromagnetic steel sheets 40 are thermocompression-bonded together, preventing the insulating coating from protruding from the sides of the laminated core during thermocompression bonding, and providing favorable contact conditions between the laminated electromagnetic steel sheets, improving lamination accuracy. Furthermore, the curing reactivity is improved, resulting in high adhesive strength.

[0030] T2(25) is preferably 40.0 μs or less, and more preferably 30.0 μs or less, in order to reduce the amount of waste generated during punching. From the viewpoints of ensuring the adhesive strength between the electromagnetic steel sheets 40 and improving lamination precision, T2(180) is preferably 60.0 μs or more and 100.0 μs or less, and more preferably 70.0 μs or more and 100.0 μs or less. T2(25) and T2(180) can be adjusted, for example, by adjusting the type and content of the curing agent and the degree of crosslinking.

[0031] Furthermore, it is preferable that the difference between the spin-spin relaxation time T2(180) and the spin-spin relaxation time T2(25), {T2(180)-T2(25)}, is 40.0 μs or greater. This minimizes the molecular mobility of the insulating coating 3 when the electromagnetic steel sheets 40 are punched, while at the same time appropriately increasing the molecular mobility of the insulating coating 3 when the electromagnetic steel sheets 40 are laminated and bonded together. As a result, it is possible to reduce the amount of waste generated during punching, improve the lamination accuracy during hot pressing, and maintain a high level of adhesive strength between the electromagnetic steel sheets.

[0032] By controlling {T2(180)-T2(25)} to 50.0 μs or more, it is possible to reduce the amount of waste generated during punching, improve lamination accuracy during hot pressing, and achieve an even higher level of adhesive strength between the electromagnetic steel sheets. It is more preferable that {T2(180)-T2(25)} is 65.0 μs or more. Since the maximum value of T2(180) is 100 μs and the minimum value of T2(25) is 0 μs to more efficiently obtain the effects of the present invention, the upper limit of {T2(180)-T2(25)} is automatically determined to be 100.0 μs.

[0033] The components of the coating composition for electrical steel sheets are not particularly limited as long as they satisfy the above-mentioned conditions, and examples thereof include compositions containing an epoxy resin and an epoxy resin curing agent. That is, an example of an insulating coating film having adhesive properties is a film containing an epoxy resin and an epoxy resin curing agent.

[0034] As the epoxy resin, a general epoxy resin can be used, specifically, any epoxy resin having two or more epoxy groups in one molecule can be used without any particular limitation. Examples of such epoxy resins include bisphenol A type epoxy resins, bisphenol F type epoxy resins, phenol novolac type epoxy resins, cresol novolac type epoxy resins, alicyclic epoxy resins, glycidyl ester type epoxy resins, glycidyl amine type epoxy resins, hydantoin type epoxy resins, isocyanurate type epoxy resins, acrylic acid modified epoxy resins (epoxy acrylates), phosphorus-containing epoxy resins, and their halides (brominated epoxy resins, etc.) and hydrogenated products. As the epoxy resin, one type may be used alone, or two or more types may be used in combination.

[0035] The coating composition for electrical steel sheets may contain an acrylic resin. The acrylic resin is not particularly limited. Examples of monomers used for the acrylic resin include unsaturated carboxylic acids such as acrylic acid and methacrylic acid, and (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, and hydroxypropyl (meth)acrylate. The (meth)acrylate means acrylate or methacrylate. The acrylic resin may be used alone or in combination of two or more.

[0036] The acrylic resin may have a structural unit derived from a monomer other than the acrylic monomer. Examples of the other monomer include ethylene, propylene, and styrene. The other monomer may be used alone or in combination of two or more.

[0037] When an acrylic resin is used, it may be used as an acrylic-modified epoxy resin obtained by grafting an acrylic resin onto an epoxy resin, or may be included as a monomer forming an acrylic resin in a coating composition for an electrical steel sheet.

[0038] As the epoxy resin curing agent, a latent heat-curing type can be used, and examples thereof include aromatic polyamines, acid anhydrides, phenol-based curing agents, dicyandiamide, boron trifluoride-amine complexes, and organic acid hydrazides. As the aromatic polyamines, examples thereof include metaphenylenediamine, diaminodiphenylmethane, and diaminodiphenylsulfone. As the phenol-based curing agents, examples thereof include phenol novolac resins, cresol novolac resins, bisphenol novolac resins, triazine-modified phenol novolac resins, and phenol resol resins. Among them, as the epoxy resin curing agent, phenol-based curing agents are preferred, and phenol resol resins are more preferred. As the epoxy resin curing agent, one type may be used alone, or two or more types may be used in combination.

[0039] The content of the epoxy resin curing agent in the coating composition for electrical steel sheets is preferably 5 to 35 parts by mass, and more preferably 10 to 30 parts by mass, per 100 parts by mass of the epoxy resin.

[0040] The coating composition for electrical steel sheets may contain additives such as a curing accelerator (curing catalyst), an emulsifier, an antifoaming agent, etc. As the additives, only one type may be used, or two or more types may be used in combination.

[0041] Next, a method for manufacturing the electromagnetic steel sheet 40 of this embodiment will be described. The production of the electrical steel sheet 40 includes a step of applying a coating composition for electrical steel sheets to at least a portion of one or both surfaces of the base steel sheet 2 and drying the composition, and a baking step of baking the coating composition for electrical steel sheets and then cooling to room temperature to form an insulating coating 3. The baking process will be described in detail below.

[0042] 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 2, drying it, and baking it. The lower limit of the temperature reached during baking is preferably 120°C or higher, and more preferably 130°C or higher. The temperature reached during baking is preferably less than 200°C, and more preferably the upper limit is 190°C or lower. The "temperature reached" here refers to the maximum temperature reached by the electromagnetic steel sheet in the baking process. Measurement can be performed by applying a general method, and the surface temperature of the steel sheet is measured using a radiation thermometer or a Thermo Label (registered trademark) (a thermometer in the form of a sticker attached to the steel sheet). In addition, when the effect of the present invention is obtained by controlling the cooling rate in the cooling process of the baking step described later, the temperature history is controlled in relation to the glass transition temperature Tg [°C] of the insulating coating 3 (electromagnetic steel sheet coating composition), so that the reached temperature is restricted in relation to Tg. In this case, the lower limit of the reached temperature is set to be higher than Tg+15 [°C]. This allows the molecular chains of the insulating coating to be sufficiently separated at the time of holding at the reached temperature, and the control of the molecular chain arrangement in the subsequent cooling process becomes effective. The temperature is preferably Tg+20 [°C] or higher, more preferably Tg+30 [°C] or higher, and even more preferably Tg+45 [°C] or higher. However, when the effect of the present invention is obtained by controlling the cooling rate, if the reached temperature is too high, there is a risk that good lamination accuracy and adhesive strength cannot be obtained. Therefore, it is preferable to keep the reached temperature below 200°C, and further preferably below 190°C. The lower limit of the baking time is preferably 20 seconds, more preferably 30 seconds, and the upper limit of the baking time is preferably 70 seconds, more preferably 60 seconds.

[0043] In the manufacture of the electrical steel sheet 40 of this embodiment, the cooling process to room temperature in the baking step can be effectively utilized for controlling T2(25) and T2(180) defined in this embodiment. One embodiment of a method for manufacturing the electrical steel sheet 40 of this embodiment will be described below. In this embodiment, when the glass transition temperature of the insulating coating 3 (coating composition) is Tg [°C] and the average cooling rate in the temperature range from Th°C to (Tg+15)°C during the cooling process from the ultimate temperature Th to room temperature is CR1 [°C / s], the cooling rate CR1 is set to 20°C / s or more and 30°C / s or less. By cooling at a relatively high rate in this temperature range, the molecular chains of the coating composition constituting the insulating coating 3 are preferably controlled, and the generation of waste in the subsequent punching process of the electromagnetic steel sheet 40 is suppressed. Furthermore, even when the electromagnetic steel sheets 40 are laminated and heated and pressed, the insulating coating 3 is unlikely to soften excessively, and the electromagnetic steel sheets 40 can be laminated with high precision, and at the same time, high adhesive strength can be obtained because the sheets are moderately softened.

[0044] If the average cooling rate CR1 in this temperature range exceeds 30°C / s, it becomes difficult to align the molecular chains of the coating material, making it difficult to suppress the amount of waste generated during punching, and the insulating coating 3 becomes excessively softened during thermocompression bonding, making it impossible to maintain appropriate lamination accuracy. On the other hand, if the average cooling rate CR1 in this temperature range is less than 20°C / s, the molecular chains of the coating material become excessively aligned during cooling in this temperature range, causing the contact state of adjacent magnetic steel sheets 40 in contact in the lamination direction during thermocompression bonding to become poor, making it impossible to maintain appropriate lamination accuracy and making it difficult to sufficiently increase the adhesive strength.

[0045] In addition, when the average cooling rate from (Tg+15)°C to Tg°C during the cooling process from the reached temperature Th to room temperature in the baking step is CR2 [°C / s] and the average cooling rate from Tg°C to (Tg-15)°C is CR3 [°C / s], it is preferable to satisfy the following (Equation 1) and (Equation 2).

[0046] |CR1-CR2|≦5℃ / s...Formula 1 CR1-CR3≧10℃ / s...Formula 2

[0047] By satisfying these two formulas, it is possible to reduce the amount of waste generated during punching, improve lamination accuracy during hot pressing, and achieve an even higher level of adhesive strength between the electromagnetic steel sheets. The mechanism by which the effects of the present invention are so pronounced in relation to the average cooling rates CR2 and CR3 in the temperature ranges around the glass transition temperature Tg is not clear, but is thought to be as follows: Even in the cooling process in a low-temperature range below (Tg+15)°C after the average cooling rate CR1 is applied in a higher temperature range, the arrangement of the molecular chains in the insulating coating 3 changes depending on the temperature history associated with cooling. It is thought that the arrangement of the molecular chains in the insulating coating 3, which is appropriately arranged in the temperature range where CR1 is applied, is reliably fixed into an even more preferable arrangement by appropriately controlling the subsequent cooling process.

[0048] The above has described the manufacturing method of the electromagnetic steel sheet 40 of this embodiment, but the above conditions are only an example for obtaining the electromagnetic steel sheet 40 of this embodiment, and the electromagnetic steel sheet 40 of this embodiment is not limited by these conditions.

[0049] 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.

[0050] In the case of the insulating coating 3 having a single layer configuration, the average thickness t1 of the insulating coating 3 (the thickness per one side of the electromagnetic steel sheet 40 (material 1)) can be, for example, not less than 1.5 μm and not more than 8.0 μm. In the case of the insulating coating 3 having a multi-layer structure, the average thickness of the base insulating coating may be, for example, from 0.3 μm to 1.2 μm, and preferably from 0.7 μm to 0.9 μm. The average thickness of the top insulating coating may be, for example, from 1.5 μm to 8.0 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.

[0051] 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 position 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.

[0052] 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.

[0053] (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).

[0054] 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.

[0055] (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 laminated core manufacturing apparatus 100 (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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] As described above, in this embodiment, T2(25) and T2(180) of the insulating coating capable of adhering to electromagnetic steel sheets are each controlled within a specific range. This makes it possible to reduce the amount of waste generated during punching of the electromagnetic steel sheets, improve lamination accuracy during hot pressing, and further improve the adhesive strength between the electromagnetic steel sheets. Furthermore, the difference between T2(180) and T2(25) is controlled within a specific range, which makes it possible to suppress the generation of residue, achieve higher levels of lamination accuracy, and improve adhesive strength. Furthermore, by controlling the average cooling rate CR1 in a specific temperature range during the cooling process to room temperature in the baking process of the insulating coating, it is possible to control the above T2(25) and T2(180) within appropriate ranges.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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

[0066] The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following description. [Pulsed NMR measurements] The insulating coating of the electromagnetic steel strip produced in each example was scraped off with a carving knife to obtain a powdered sample. The powdered sample was subjected to pulsed NMR measurement under the following conditions using a JNM-MU25 (25 MHz) manufactured by JEOL Co., Ltd., and T2(25) and T2(180) were obtained from the obtained relaxation curve. (Measurement conditions) Measurement method: Solid Echo method Pulse width: 90°pulse, 2.5μs Repeat time: 4sec Number of times: 16 Measurement temperature: 25℃ or 180℃

[0067] [Punching processability] Using the electromagnetic steel strip manufactured in each example, ten electromagnetic steel sheets with an outer diameter of 250.0 mm and an inner diameter of 165.0 mm were punched out in the shape illustrated in Fig. 3, and the total amount of generated swarf was measured. In this example, a case in which the amount of generated swarf (g) was 10.0 g or less was judged as acceptable.

[0068] [Adhesive strength] Two rectangular electromagnetic steel sheets, each 30 mm wide x 60 mm long, were cut out from the electromagnetic steel strip manufactured in each example, and the tip portions of each sheet, each 30 mm wide x 10 mm long, were overlapped with each other, and bonded at a steel sheet temperature of 180°C, a pressure of 10 MPa, and a pressurizing time of 1 hour to prepare a sample. The shear tensile strength of the obtained sample was measured at an atmospheric temperature of 25°C and a tensile speed of 3 mm / min, and the value divided by the adhesive area was taken as the adhesive strength (MPa). In this example, an adhesive strength of 4.5 MPa or more was judged to be acceptable. In particular, an adhesive strength of 5.0 MPa or more was evaluated as "excellent", and an adhesive strength of 4.5 MPa or more but less than 5.0 MPa was evaluated as "good".

[0069] [Layer Accuracy] Using the electromagnetic steel strip manufactured in each example, ten electromagnetic steel sheets with an outer diameter of 250.0 mm and an inner diameter of 165.0 mm were punched out in the shape illustrated in FIG. 3, and samples (laminated cores) were produced by pressing them at a steel sheet temperature of 200° C., a pressure of 10 MPa, and a pressing time of 1 hour. The thickness of the laminate was measured at 10 points in the width direction of the sample, and the lamination precision was evaluated based on the average deviation. A laminate thickness average deviation of less than 1 / 2 of the thickness of one electromagnetic steel sheet was rated as "excellent," a deviation of 1 / 2 or more but less than 1 was rated as "fair," and a deviation of 1 or more was rated as "poor."

[0070] [Example 1] The following three types of coating compositions for electrical steel sheets were prepared. (A) 100 parts by mass of bisphenol F type epoxy resin and 25 parts by mass of phenol resol resin as an epoxy resin hardener are mixed. (B) 100 parts by mass of bisphenol F type epoxy resin and 25 parts by mass of diaminodiphenylmethane resin as an epoxy resin hardener are mixed. (C) 100 parts by mass of acrylic acid-modified epoxy resin and 25 parts by mass of phenol resol resin as an epoxy resin hardener are mixed. As the base steel sheet, a strip-shaped non-oriented electrical steel sheet having a thickness of 0.25 mm and a width of 300 mm and consisting of, by mass%, 3.0% Si, 0.2% Mn, 0.5% Al, and the balance being Fe and impurities, was used. The coating composition for electrical steel sheet of each example was applied to both sides of the base steel sheet at a rate of 4.5 g / m. 2 The coating was applied so as to obtain an insulating coating having an average thickness t1 of 3.0 μm, and the coating was baked under each condition to obtain an electrical steel strip.

[0071] Table 1 shows the measurement results of T2(25) and T2(180) and the evaluation results of the insulating coating formed from the above coating composition for electrical steel sheets.

[0072] [Table 1]

[0073] As shown in Table 1, in the examples of the invention in which appropriate cooling was performed in the baking process and the T2(25) and T2(180) of the insulating coating of the electromagnetic steel sheets were within appropriate ranges, the amount of swarf generated during punching was small, the lamination accuracy during hot pressing was good, and the adhesive strength between the electromagnetic steel sheets was high. On the other hand, in the comparative examples in which T2(25) and T2(180) were outside the ranges, the amount of swarf generated was large, the lamination accuracy was poor, or the adhesive strength between the electromagnetic steel sheets was insufficient. Furthermore, under conditions that satisfied (Equation 1) and (Equation 2), T2(25) and T2(180) were controlled to a more preferable range, and suppression of swarf generation, high lamination accuracy, and high adhesive strength were all achieved at a higher level. [Industrial Applicability]

[0074] According to the present invention, it is possible to reduce the amount of waste generated during punching of electromagnetic steel sheets, improve lamination accuracy during hot pressing, and further improve the adhesive strength between the electromagnetic steel sheets. Therefore, the present invention has great industrial applicability. [Explanation of symbols]

[0075] 1...material, 2...base steel plate, 3...insulating coating, 10...rotating electric machine, 20...stator, 21...stator core, 40...electromagnetic steel plate.

Claims

1. An electrical steel sheet in which at least a portion of one or both surfaces of a base steel sheet is covered with an insulating coating having adhesive properties, The spin-spin relaxation time T of the insulating film measured by the Solid Echo method at 25° C. using pulse NMR ２ (25) is 50.0 μs or less, and the spin-spin relaxation time T measured by pulsed NMR at 180 ° C. ２ (180) is 50.0 μs or more and 100.0 μs or less.

2. The spin-spin relaxation time T ２ (180) and the spin-spin relaxation time T ２ The difference between (25), T ２ (180)-T ２ The electrical steel sheet according to claim 1, characterized in that (25) is 40.0 μs or more.

3. A laminated core, comprising a plurality of the electromagnetic steel sheets according to claim 1 or 2 laminated and bonded to each other.

4. A rotating electrical machine comprising the laminated core according to claim 3.

5. A method for producing an electrical steel sheet according to claim 1 or 2, A step of applying a coating composition for an electrical steel sheet to at least a part of one or both surfaces of a base steel sheet and drying the composition; A baking step of baking the coating composition for electrical steel sheets and then cooling it to room temperature to form an insulating coating, In the baking step, The glass transition temperature of the insulating coating is Tg [°C], The temperature Th reached during baking is higher than Tg+15° C. and lower than 200° C., a manufacturing method of an electrical steel sheet, characterized in that, when an average cooling rate in a temperature range from Th°C to (Tg+15)°C during the cooling process from the reached temperature Th to room temperature is defined as CR1 [°C / s], the average cooling rate CR1 is 20°C / s or more and 30°C / s or less.

6. 6. The method for producing an electrical steel sheet according to claim 5, wherein, in the baking step, when an average cooling rate in a temperature range from (Tg+15) °C to Tg °C during the cooling process from the reached temperature to room temperature is CR2 [°C / s] and an average cooling rate from Tg °C to (Tg-15) °C is CR3 [°C / s], the following (Equation 1) and (Equation 2) are satisfied: |CR1-CR2|≦5℃ / s ・・・Formula 1 CR1-CR3≧10℃ / s...Formula 2

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