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

Abstract

To provide an electromagnetic steel sheet, a laminated core and a rotary electric machine that make it possible to reduce the amount of debris during punching of an electromagnetic steel sheet.SOLUTION: An electromagnetic steel sheet is used in a laminated core and has a base steel sheet 2 coated with an adhesive insulation coating 3. The insulation coating 3 is subjected to two-components separation analysis for a transition curve measured by Solid Echo method at 25°C with pulse NMR, so that an SS component with a fast transition has a spin-spin transition time T2S of 15 μs or less and an SL component with a slow transition has a spin-spin transition time T2L of 30 μs or less, and the proportion of the SS component to the total of the SS component and the SL component is 50 mass% or more and 80 mass% 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, which are made by joining multiple electromagnetic steel sheets together and laminating them, are known as cores (iron cores) used in rotating electrical machines. Crimping and welding are known methods for joining electromagnetic steel sheets together. 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 a known joining method other than caulking and welding. For example, it has been proposed to stack and adhere electrical steel sheets with adhesive insulating coatings on their surfaces (see, for example, Patent Document 1). However, with conventional adhesive insulating coatings, it is necessary to clean up the peeled off edges of the insulating coating (hereinafter referred to as "waste") that are generated when punching out the sheet into a predetermined shape, which affects productivity. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-173816 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide an electromagnetic steel sheet, a laminated core, and a rotating electrical machine that can reduce the amount of waste generated during punching of the electromagnetic steel sheet. [Means for solving the problem]

[0006] The present invention has the following configuration. [1] An electromagnetic steel sheet in which at least a part of one or both surfaces of a base steel sheet is coated with an insulating film having adhesiveness. When a relaxation curve measured by the Solid Echo method at 25 °C using pulsed NMR is subjected to two-component separation analysis for the insulating film, the spin-spin relaxation time T 2S of the SS component with fast relaxation is 15.0 μs or less, and the spin-spin relaxation time T 2L of the SL component with slow relaxation is 30.0 μs or less, and the ratio of the SS component to the total amount of the SS component and the SL component is 50.0 mass% or more and 80.0 mass% or less. An electromagnetic steel sheet. [2] The electromagnetic steel sheet according to [1], wherein the spin-spin relaxation time T2(25) measured by pulsed NMR at 25 °C is 50.0 μs or less. [3] A laminated core in which a plurality of the electromagnetic steel sheets according to [1] or [2] are laminated and adhered to each other. [4] A rotating electric machine including the laminated core according to [3]. [5] A method for manufacturing the electromagnetic steel sheet according to [1] or [2], including a step of applying an electromagnetic steel sheet coating composition to at least a part of one or both surfaces of a base steel sheet and drying it, and a baking step of baking the electromagnetic steel sheet coating composition and then cooling it to room temperature to form an insulating film. In the baking step, the glass transition temperature of the insulating film is Tg [°C], the reaching temperature during baking is Tg + 15 °C or more and less than 200 °C, and when the average cooling rate in the temperature range from Tg °C to (Tg - 15) °C in the cooling process from the reaching temperature to room temperature is CR3, the average cooling rate CR3 is 10 °C / s or less. A method for manufacturing an electromagnetic steel sheet. [6] The method for manufacturing an electromagnetic steel sheet according to [5], wherein in the baking step, when the average cooling rate in the temperature range from (Tg + 15) °C to Tg °C in the cooling process from the reaching temperature to room temperature is CR2, CR3 < CR2.

Advantages of the Invention

[0007] According to the present invention, it is possible to provide an electromagnetic steel sheet, a laminated core, and a rotating electrical machine that can reduce the amount of waste generated during punching of the electromagnetic steel sheet. [Brief explanation 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. [Figure 2] FIG. [Figure 3] 3 is a cross-sectional view taken along the line AA in FIG. 2. [Figure 4] FIG. 2 is a plan view of a material forming the laminated core. [Figure 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 device used to manufacture the laminated core. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, with reference to the drawings, a laminated core according to one embodiment of the present invention, a rotating electric machine including this laminated core, and materials forming this laminated core will be described. Note that in this embodiment, the rotating electric machine will be described as an electric motor, specifically an AC electric motor, more specifically a synchronous electric motor, and even more specifically a permanent magnet field electric motor. This type of electric motor is suitable for use in, for example, electric vehicles.

[0010] (Rotating 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, the rotating electric machine 10 is an inner rotor type in which the rotor 30 is located radially inside the stator 20. However, the rotating electric machine 10 may also be an outer rotor type in which the rotor 30 is located outside the stator 20. 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 electrical machine 10 can rotate at a rotation speed of 1000 rpm by applying an excitation current of, for example, an effective value of 10 A and a frequency of 100 Hz to each phase.

[0011] The stator 20 includes a stator adhesive laminated core (hereinafter referred to as a 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 23 protrude radially inward from the inner periphery of the core back portion 22 (toward the central axis O of the core back portion 22 along the radial direction). The multiple teeth 23 are arranged at equal angular intervals in the circumferential direction. In this embodiment, 18 teeth 23 are provided at central angle intervals of 20 degrees around the central axis O. The multiple teeth 23 are formed to have the same shape and size as one another. Therefore, the multiple teeth 23 have the same thickness dimension as one another. The winding is wound around the teeth 23. The winding may be a concentrated winding or a distributed winding.

[0013] The rotor 30 is disposed radially inside the stator 20 (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 ring) shape and is arranged coaxially with the stator 20. The rotating shaft 60 is arranged inside the rotor core 31. The rotating shaft 60 is fixed to the rotor core 31. The permanent magnets 32 are fixed to the rotor core 31. In this embodiment, a pair of permanent magnets 32 forms one magnetic pole. The pairs of permanent magnets 32 are arranged at equal angular intervals in the circumferential direction. In this embodiment, 12 pairs of permanent magnets 32 (24 in total) are provided at central angle intervals of 30 degrees around the central axis O.

[0014] In this embodiment, an interior permanent magnet motor is used as the permanent magnet field 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 a plurality of permanent magnets 32. Each permanent magnet 32 is fixed to the rotor core 31 while being disposed in the corresponding through hole 33. Each permanent magnet 32 can be fixed to the rotor core 31, for example, by 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 permanent magnet motor may be used as the permanent magnet field motor instead of the interior permanent magnet type.

[0015] Both the stator core 21 and the rotor core 31 are laminated cores. For example, as shown in Fig. 2, the stator core 21 is formed by laminating a plurality of electromagnetic steel plates 40 in a lamination direction. 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 ends of the teeth 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 ends of all of the teeth 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 Figs. 4 to 6. The material 1 is a steel sheet (electromagnetic steel sheet) that serves as the base material of 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 serves as the base material for the electromagnetic steel sheet 40 may be referred to as material 1. The steel sheet that is punched from material 1 into 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 where it is wound around a coil 1A shown in FIG. 7, for example. In this embodiment, a non-oriented electrical steel sheet is used as the material 1. As the non-oriented electrical steel sheet, a non-oriented electrical steel strip according to JIS C 2552:2014 can be used. However, a grain-oriented electrical steel sheet may be used as the material 1 instead of the non-oriented electrical steel sheet. In this case, as the grain-oriented electrical steel sheet, a grain-oriented electrical steel strip according to JIS C 2553:2019 can be used. Furthermore, a non-oriented thin-film electrical steel strip or a grain-oriented thin-film electrical 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 when the material 1 is used as the electromagnetic steel sheet 40, the eddy current loss will increase and the core iron loss will deteriorate. Therefore, taking the core iron loss and manufacturing cost into consideration, 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 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 into the shape of a coil 1A, at least a portion of the raw material 1 is unwound into a flat plate. In the unwound raw material 1, 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 that is 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 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 also be used 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-degree 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 used as the average sheet thickness t0 of the electromagnetic steel sheets 40.

[0021] 5 and 6, the raw material 1 includes a base steel plate 2 and an insulating coating 3. The raw material 1 is formed by coating both surfaces of a strip-shaped base steel plate 2 with the insulating coating 3. In this embodiment, the majority of the raw material 1 is formed by the base steel plate 2, and the insulating coating 3, which 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% by mass of Si. By setting the chemical composition within this range, the yield strength of the material 1 (electrical steel sheet 40) can be set to, for example, 380 MPa or more and 540 MPa or less.

[0023] Si: 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 an electrical steel sheet 40, the insulating coating 3 provides insulation between adjacent electrical steel sheets 40 in the stacking direction. In this embodiment, the insulating coating 3 also has adhesive properties and bonds adjacent electrical steel sheets 40 in the stacking direction. The insulating coating 3 may have a single-layer structure or a multi-layer structure. More specifically, for example, the insulating coating 3 may have a single-layer structure that combines insulating properties and adhesive properties, or a multi-layer structure 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 completely covers both surfaces of the base steel sheet 2 without any gaps. However, as long as the above-mentioned insulating performance and adhesive performance are ensured, some layers of the insulating coating 3 do not have to completely cover both surfaces of the base steel sheet 2. 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 surfaces of the base steel sheet 2 need to be covered with the insulating coating 3 so that the entire surface is not exposed. Specifically, if the insulating coating 3 does not have an underlying insulating coating with excellent insulating performance and has a single-layer configuration that combines insulating performance and adhesive performance, the insulating coating 3 needs to be formed completely 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 adhesive performance, it is possible to achieve both insulating performance and adhesive performance 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 base coating is not particularly limited, and for example, a general treatment agent such as a chromic acid-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 (described later) to a base steel sheet. Examples of adhesive insulating coatings include a single-layer insulating coating that combines insulating properties and adhesive properties, and a top insulating coating that is provided on a base insulating coating. Before thermocompression bonding during laminated core production, the adhesive insulating coating is in an uncured or semi-cured state (B stage). Heating during thermocompression bonding causes a curing reaction, resulting in the development of adhesive properties.

[0028] When the relaxation curve of the insulating coating with adhesive properties measured by the Solid Echo method at 25°C was analyzed by pulse NMR, the spin-spin relaxation time T 2S is 15.0 μs or less, and the spin-spin relaxation time T 2Lis 30.0 μs or less.

[0029] In the present invention, transverse relaxation observed in pulsed NMR measurements, i.e., relaxation in a plane perpendicular to the static magnetic field, is considered to be spin-spin relaxation. The SS component is the component with fast relaxation and low molecular mobility, which corresponds to the separation curve with the shorter relaxation time of the two separation curves obtained by separating the relaxation curve obtained by pulsed NMR measurements. The SL component is the component with slow relaxation and high molecular mobility, which corresponds to the separation curve with the longer relaxation time of the two separation curves obtained by separating the relaxation curve obtained by pulsed NMR measurements. Measurement conditions for pulsed NMR include, for example, the conditions shown in the Examples.

[0030] T at 25°C 2S is 15.0 μs or less, T 2L By controlling the time to 30.0 μs or less, the insulating coating 3 has very low molecular mobility and is hard during punching, thereby reducing the amount of waste generated. T 2S is preferably 13.0 μs or less, and more preferably 10.0 μs or less. T 2L is preferably 28.0 μs or less, and more preferably 27.0 μs or less.

[0031] The proportion of the SS component relative to the total amount (100% by mass) of the SS component and the SL component at 25° C. is 50.0% by mass or more and 80.0% by mass or less, and preferably 70.0% by mass or more and 80.0% by mass or less. If the proportion of the SS component is within this range, the effect of reducing the amount of waste generated during punching processing is further enhanced. The ratio of the SS component to the SL component can be determined by analyzing the results of pulsed NMR measurements.

[0032] The adhesive insulating coating 3 preferably has a spin-spin relaxation time T2(25) of 55.0 μs or less as measured by pulsed NMR at 25° C. This allows the insulating coating 3 to have even lower molecular mobility and become harder during punching, further reducing the amount of waste generated during punching.

[0033] T2(25) is more preferably 40.0 μs or less, and even more preferably 30.0 μs or less, from the viewpoint of reducing the amount of waste generated during punching. There is no particular restriction on the lower limit of T2(25), but it may be 5.0 μs or more. T 2S , T 2L and T2(25) can be adjusted, for example, by adjusting the type and content of the curing agent and the degree of crosslinking.

[0034] 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 a composition 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.

[0035] 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 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 (such as brominated epoxy resins) and hydrogenated products. As the epoxy resin, one type may be used alone, or two or more types may be used in combination.

[0036] The coating composition for an electrical steel sheet 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. Note that (meth)acrylate means acrylate or methacrylate. One type of acrylic resin may be used alone, or two or more types may be used in combination.

[0037] 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.

[0038] 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 contained in the coating composition for an electrical steel sheet as a monomer that forms the acrylic resin.

[0039] As the epoxy resin curing agent, a latent heat-curing type can be used, and examples thereof include aromatic polyamines, acid anhydrides, phenolic curing agents, dicyandiamide, boron trifluoride-amine complexes, and organic acid hydrazides. Examples of aromatic polyamines include metaphenylenediamine, diaminodiphenylmethane, and diaminodiphenyl sulfone. Examples of phenolic curing agents include phenol novolac resins, cresol novolac resins, bisphenol novolac resins, triazine-modified phenol novolac resins, and phenol resole resins. Among these, phenolic curing agents are preferred as epoxy resin curing agents, and phenol resole 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.

[0040] The content of the epoxy resin curing agent in the coating composition for electrical steel sheets is preferably 5 to 35 parts by mass, more preferably 10 to 30 parts by mass, per 100 parts by mass of the epoxy resin.

[0041] The coating composition for electrical steel sheets may contain additives such as a curing accelerator (curing catalyst), an emulsifier, an antifoaming agent, etc. Only one type of additive may be used, or two or more types may be used in combination.

[0042] 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 it, and a baking step of baking the coating composition for electrical steel sheets and then cooling it to room temperature to form the insulating coating 3. The baking step will be described in detail below.

[0043] The insulating coating 3 can be formed, for example, by applying a coating composition for an electromagnetic steel sheet 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, more preferably 130°C or higher. The temperature reached during baking is preferably less than 200°C, more preferably 190°C or lower. The "temperature reached" here refers to the maximum temperature reached by the electrical steel sheet during the baking process. Measurement can be performed using a general method, such as a radiation thermometer or a Thermo Label (registered trademark) (a thermometer sticker attached to the steel sheet) to measure the surface temperature of the steel sheet. When the effects of the present invention are achieved by controlling the cooling rate during the baking step (described later), the temperature history is controlled in relation to the glass transition temperature Tg [°C] of the insulating coating 3 (coating composition for electrical steel sheets), and therefore the ultimate temperature is limited by Tg. In this case, the lower limit of the ultimate temperature is set to Tg + 15 [°C]. This ensures that the molecular chains of the insulating coating are sufficiently separated when held at the ultimate temperature, allowing for effective control of the molecular chain alignment during the subsequent cooling step. The ultimate temperature is preferably (Tg + 30) [°C] or higher, and more preferably (Tg + 45) [°C] or higher. However, when the effects of the present invention are achieved by controlling the cooling rate, if the ultimate temperature is too high, satisfactory adhesive strength may not be obtained. Therefore, the ultimate temperature is preferably kept below 200°C, and even more 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.

[0044] In the manufacturing of the electromagnetic steel sheet 40 of this embodiment, the cooling process to room temperature in the baking step is performed in accordance with the T defined in this embodiment. 2S , T 2L This can be effectively utilized for controlling T2(25). One embodiment of the method for manufacturing the electrical steel sheet 40 of this embodiment will be described below. In this embodiment, the glass transition temperature of the insulating coating 3 (coating composition) is Tg [°C], and the average cooling rate in the temperature range from Tg°C to (Tg-15)°C during the cooling process from the maximum temperature reached in the baking step of the insulating coating 3 to room temperature is CR3. By cooling this temperature range at a relatively slow rate of 10°C / s or less, the average cooling rate CR3 is set to 10°C / s or less. 2S and T 2L can be controlled in a desirable manner, and the proportion of SS components can be controlled within an appropriate range. 2S and T 2LBy controlling it within a preferable range, the insulating film 3 becomes moderately hard. Therefore, afterwards, the amount of burrs generated when punching the electromagnetic steel sheet 40 can be reduced. On the other hand, when the average cooling rate CR3 exceeds 10°C / s, especially when T 2S and T 2L become longer and the insulating film 3 softens, and the generation of burrs during punching cannot be suppressed. The lower limit value of the average cooling rate CR3 does not particularly need to be limited, but considering the productivity of the baking process, it is preferably 1°C / s or more.

[0045] Furthermore, when the average cooling rate from (Tg + Temperature range from the maximum temperature reached to room temperature, when the average cooling rate from (Tg + 15)°C to Tg°C is defined as CR2, it is preferable that CR3 < CR2. Thereby, since T2(25) is controlled within a more preferable range, in addition to a high burr generation suppressing effect, it becomes possible to achieve both high adhesive strength.

[0046] Although the mechanism by which high burr generation suppressing effect and high adhesive strength can be achieved simultaneously by controlling the average cooling rate CR3 in the temperature range immediately below the glass transition temperature Tg as described above is not clear, it is considered to be achieved by avoiding the molecular mobility of the insulating film 3 from becoming too low due to the appropriate arrangement of the molecular chains.

[0047] As described above, the manufacturing method of the electromagnetic steel sheet 40 of the present embodiment has been explained. However, each of the above conditions is an example for obtaining the electromagnetic steel sheet 40 of the present embodiment, and the electromagnetic steel sheet 40 of the present embodiment is not limited by each of these conditions.

[0048] The upper and lower limit values of the average thickness t of the insulating film 3 are set as follows, for example, considering the case where the material 1 is used as the electromagnetic steel sheet 40. When the material 1 is used as the electromagnetic steel sheet 40, the average thickness t1 of the insulating film 3 (the thickness per one side of the electromagnetic steel sheet 40 (material 1)) is adjusted so as to ensure the insulation performance and adhesion ability between the electromagnetic steel sheets 40 laminated on each other.

[0049] In the case of a single-layer insulating coating 3, the average thickness t1 of the insulating coating 3 (thickness per side of the electromagnetic steel sheet 40 (material 1)) can be, for example, 1.5 μm or more and 8.0 μm or less. In the case of a multi-layer insulating coating 3, the average thickness of the base insulating coating can 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 can 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 way 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.

[0050] The upper and lower limits for the average thickness t1 of the insulating coating 3 of the material 1 can naturally also be used 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, of the multiple electromagnetic steel sheets that form the laminated core, the outermost electromagnetic steel sheet 40 in the stacking direction (the electromagnetic steel sheet 40 whose surface is exposed in the stacking direction) is selected. On the surface of the selected electromagnetic steel sheet 40, a predetermined radial position (for example, a position exactly midway (center) between the inner and outer circumferential edges 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 locations equally spaced apart in the circumferential direction (i.e., at 90-degree intervals around the central axis O). The average value of the thicknesses measured at the four locations can be used as the average thickness t1 of the insulating coating 3. The reason why the average thickness t1 of the insulating coating 3 was measured on the magnetic 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 remains almost constant at any stacking position along the stacking direction of the magnetic steel sheet 40.

[0051] The blank 1 as described above is punched to produce electromagnetic steel sheets 40, and the electromagnetic steel sheets 40 are used to produce bonded cores (the stator core 21 and the rotor core 31).

[0052] (Lamination method for laminated core) Returning to the description of the laminated core, the stator core 21 is made up of a plurality of electromagnetic steel sheets 40, which are laminated with insulating coatings 3 interposed therebetween, as shown in FIG. Adjacent electromagnetic steel sheets 40 in the stacking direction are bonded over their entire surfaces by the insulating coating 3. In other words, the surfaces of the electromagnetic steel sheets 40 facing the stacking direction (hereinafter referred to as the first surfaces) are bonded over their entire surfaces as bonding regions 41a. However, adjacent electromagnetic steel sheets 40 in the stacking direction do not have to be bonded over their entire surfaces. In other words, the first surfaces of the electromagnetic steel sheets 40 may include a mixture of bonding regions 41a and non-bonding regions (not shown).

[0053] In this embodiment, the multiple electromagnetic steel sheets that form rotor core 31 are fixed to one another by crimps 42 (dowels) as shown in Fig. 1. However, the multiple electromagnetic steel sheets that form 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.

[0054] (Laminated core manufacturing method) The stator core 21 is manufactured, for example, 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 arrow F, and is gradually formed into the shape of the electromagnetic steel sheets 40 by punching multiple times using dies arranged at each stage. 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 portions of the insulating coating 3 located in the bonding regions 41a are allowed to exhibit adhesive properties), and bonding is completed.

[0055] 7, the manufacturing apparatus 100 includes a multi-stage punching station 110. The punching station 110 may include two stages, or three or more stages. Each stage of the punching station 110 includes a female die 111 arranged below the blank 1 and a male die 112 arranged above the blank 1.

[0056] 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 female outer peripheral punching die 142, a heat insulating member 143, a male outer peripheral punching die 144, and a spring 145. The heating device 141, the outer periphery punching female die 142, and the heat insulating member 143 are arranged below the material 1. On the other hand, the outer periphery punching male die 144 and the spring 145 are arranged above the material 1. The reference numeral 21 denotes a stator core.

[0057] In the manufacturing apparatus 100 having the configuration described above, first, the material 1 is sequentially fed from the coil 1A in the direction of arrow F in FIG. 7. Then, this material 1 is sequentially punched by multiple stages of punching stations 110. Through these punching processes, the material 1 is given the shape of the electromagnetic steel sheet 40 having the core back portion 22 and multiple 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 in the direction of arrow F.

[0058] Finally, the blank 1 is sent to the 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 are subjected to a constant pressure by 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 arranged 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 being bonded. 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 being bonded 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.

[0059] As described above, in this embodiment, the T 2S and T 2L is controlled to a specific value or less, thereby reducing the amount of scrap generated during punching of the electromagnetic steel sheet. Furthermore, T2(25) at 25°C is controlled within a specific range, which not only achieves a higher effect of suppressing residue generation but also makes it possible to achieve higher adhesive strength. By controlling the average cooling rate CR3 in a specific temperature range during the cooling process to room temperature in the baking process of the insulating coating, the above T 2S , T 2L and T2(25) can be controlled within an appropriate range.

[0060] 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 and inner diameters of the stator core, the lamination thickness, the number of slots, the circumferential and radial dimensional ratio of the teeth, and the radial dimensional ratio of the teeth and core back can be designed as desired according to the characteristics of the rotating electric machine.

[0061] In the rotor of the above embodiment, a pair of permanent magnets 32 forms one magnetic pole, but the present invention is not limited to this. For example, one permanent magnet 32 may form one magnetic pole, or three or more permanent magnets 32 may form one magnetic pole.

[0062] In the above embodiment, a permanent magnet field type electric motor has been used as an example of a rotating electric machine, but the structure of the rotating electric machine 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 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 motor or an electromagnetic field motor (wound field 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.

[0063] 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 can also be used in a transformer instead of a rotating electrical machine. In this case, it is preferable to use grain-oriented electromagnetic steel sheets as the electromagnetic steel sheets instead of non-oriented electromagnetic steel sheets.

[0064] In addition, within the scope of the spirit of the present invention, the components in the above-described embodiments may be replaced with well-known components as appropriate, and the above-described modifications may be combined as appropriate. [Example]

[0065] The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following descriptions. [Pulse NMR measurement] The insulating coating of the electromagnetic steel strip manufactured in each example was scraped off with a chisel to obtain a powdered sample. Pulse NMR measurement of the powdered sample was carried out using a JNM-MU25 (25 MHz) manufactured by JEOL under the following conditions. The relaxation curve obtained in the measurement at 25°C was subjected to two-component separation analysis to obtain T 2S and T 2L The T2(25) was also calculated from the relaxation curve obtained by pulsed NMR measurement at 25°C. The proportion of SS components was calculated by analyzing the results of pulsed NMR measurement using the analysis software attached to the JNM-MU25. (Measurement conditions) Measurement method: Solid Echo method Pulse width: 90°pulse, 2.5μs Repeat time: 4 seconds Accumulation count: 16 times Measurement temperature: 25℃

[0066] [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 swarf generation amount (g) of 10.0 g or less was judged to be acceptable.

[0067] [Adhesive strength] Two rectangular electromagnetic steel sheets measuring 30 mm wide and 60 mm long were cut from the electromagnetic steel strip manufactured in each example. The 30 mm wide and 10 mm long ends of the sheets were overlapped and bonded together at a steel sheet temperature of 180°C, a pressure of 10 MPa, and a pressing time of 1 hour to produce a sample. The shear tensile strength of the obtained samples was measured at an ambient temperature of 25°C and a pulling speed of 3 mm / min, and the value obtained by dividing the value by the adhesive area was taken as the adhesive strength (MPa). In this example, adhesive strengths of 4.5 MPa or more were considered acceptable. In particular, adhesive strengths of 5.0 MPa or more were evaluated as "excellent," and adhesive strengths of 4.5 MPa or more but less than 5.0 MPa were evaluated as "good."

[0068] [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 curing agent 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 curing agent 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 curing agent are mixed. The base steel sheet used was a strip-shaped non-oriented electrical steel sheet with a thickness of 0.25 mm and a width of 300 mm, which consisted of, by mass%, 3.0% Si, 0.2% Mn, 0.5% Al, and the remainder being Fe and impurities. 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 that the thickness was as follows: and baked under each condition to form an insulating coating having an average thickness t1 of 3.0 μm, thereby obtaining an electrical steel strip.

[0069] T at 180°C of the insulating coating formed from the coating composition for electrical steel sheets 2S , T 2L The measurement results of T2(25) and the evaluation results are shown in Table 1.

[0070] [Table 1]

[0071] As shown in Table 1, proper cooling is performed during the baking process, and the T 2S , T 2L In the invention example where the ratio of the SS component is in an appropriate range, T 2S and T 2L、Compared with the comparative examples where any of the ratios of the SS components was out of the range, the amount of chips during punching was less. Also, the adhesive strength between electromagnetic steel sheets was high. Furthermore, under the condition that CR3 < CR2 is satisfied, T2(25) was controlled within a more preferable range, and the coexistence of a low chip generation amount and a high adhesive strength was achieved at an even better level.

Industrial Applicability

[0072] According to the present invention, the amount of chips generated during punching of electromagnetic steel sheets in the manufacture of laminated cores can be reduced. Therefore, the industrial applicability is great.

Explanation of Signs

[0073] 1... Material, 2... Base steel sheet, 3... Insulating coating, 10... Rotating electrical machine, 20... Stator, 21... Stator core, 40... Electromagnetic steel sheet.

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, When the relaxation curve of the insulating coating is measured by the solid echo method at 25°C using pulse NMR, the spin-spin relaxation time T ２Ｓ is 15.0 μs or less, and the spin-spin relaxation time T ２Ｌ is 30.0 μs or less, An electrical steel sheet, wherein a ratio of the SS component to the total amount of the SS component and the SL component is 50.0 mass % or more and 80.0 mass % or less.

2. Spin-spin relaxation time T measured by pulsed NMR at 25°C ２ The electrical steel sheet according to claim 1, characterized in that (25) is 55.0 μs or less.

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. The method for producing an electrical steel sheet according to claim 1 or 2, applying a coating composition for an electrical steel sheet to at least a portion of one or both surfaces of a base steel sheet, and drying the coating composition; a baking step of baking the coating composition for an electrical steel sheet 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 reached during baking is Tg+15°C or higher and lower than 200°C, wherein, in the cooling process from the ultimate temperature to room temperature, the average cooling rate CR3 in the temperature range from Tg ° C to (Tg-15) ° C is 10 ° 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 ultimate temperature to room temperature is defined as CR2, CR3<CR2.

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