JP7723249B2 - Electromagnetic steel sheet, laminated core and rotating electric machine, and method for manufacturing electromagnetic steel sheet - Google Patents

Description

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.

Laminated cores, in which multiple electromagnetic steel sheets are joined together and layered, are known as cores (iron cores) used in rotating electrical machines. Crimping and welding are known methods for joining electromagnetic steel sheets. However, crimping and welding can cause deterioration in the magnetic properties of the electromagnetic steel sheets due to mechanical stress and thermal stress during processing, as well as interlayer short circuits, which can reduce the performance of the laminated core.

Apart from caulking and welding, adhesive bonding is a known joining method. For example, it has been proposed to stack and bond electrical steel sheets with adhesive insulating coatings on their surfaces (see, for example, Patent Document 1). However, with conventional adhesive insulating coatings, the scraps (hereinafter referred to as "waste") that peel off from the edges of the insulating coating when punching out the desired shape must be cleaned up, which affects productivity.

Japanese Patent Application Laid-Open No. 2000-173816

The present invention aims to provide an electromagnetic steel sheet, laminated core, and rotating electrical machine that can reduce the amount of scrap generated during punching of the electromagnetic steel sheet.

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, and when a relaxation curve of the insulating coating measured by a solid echo method at 25°C using pulse NMR is subjected to two-component separation analysis, the spin-spin relaxation time _T2S of an SS component which relaxes quickly is 15.0 μs or less, and the spin-spin relaxation time _T2L of an SL component which relaxes slowly is 30.0 μs or less, and the proportion 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] The electrical steel sheet according to [1], characterized in that the spin-spin relaxation time T ₂ (25) measured by pulse 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 bonded to each other.
[4] A rotating electrical machine comprising the laminated core according to [3].
[5] A method for producing an electrical steel sheet according to [1] or [2], comprising: a step of applying a coating composition for an electrical steel sheet to at least a part of the surface of one or both of a base steel sheet and drying the coating composition; and a baking step of baking the coating composition for an electrical steel sheet and then cooling to room temperature to form an insulating coating, wherein in the baking step, the glass transition temperature of the insulating coating is Tg [°C], the temperature achieved during baking is Tg + 15°C or higher and lower than 200°C, and when the average cooling rate in the temperature range from Tg°C to (Tg - 15)°C during the cooling process from the achieved temperature to room temperature is CR3, the average cooling rate CR3 is 10°C/s or lower.
[6] The method for producing an electrical 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 during the cooling process from the ultimate temperature to room temperature is defined as CR2, CR3 < CR2.

The present invention provides an electromagnetic steel sheet, laminated core, and rotating electrical machine that can reduce the amount of scrap generated during punching of the electromagnetic steel sheet.

1 is a cross-sectional view of a rotating electrical machine including a laminated core according to a first embodiment of the present invention. FIG. 3 is a cross-sectional view taken along line AA in FIG. 2. FIG. 2 is a plan view of a material forming the laminated core. 5 is a cross-sectional view taken along the line B-B of FIG. 4. FIG. 6 is an enlarged view of part C in FIG. 5 . FIG. 2 is a side view of a manufacturing device used to manufacture the laminated core.

The following describes, with reference to the drawings, a laminated core according to one embodiment of the present invention, a rotating electric machine equipped with this laminated core, and the material from which this laminated core is formed. In this embodiment, the rotating electric machine will be described using an electric motor, specifically an AC motor, more specifically a synchronous motor, and even more specifically a permanent magnet field motor, as an example. This type of electric motor is suitable for use in electric vehicles, for example.

(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 electric 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.

The stator 20 includes a stator adhesive laminated core (hereinafter referred to as a stator core) 21 and windings (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.

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 each other. Therefore, the multiple teeth 23 have the same thickness dimension as each other.
The winding is wound around the teeth 23. The winding may be a concentrated winding or a distributed winding.

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 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 plurality of permanent magnets 32 are fixed to the rotor core 31. In this embodiment, a pair of permanent magnets 32 forms one magnetic pole. The plurality of 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 magnets in total) are provided at 30-degree central angle intervals around the central axis O.

In this embodiment, an embedded permanent magnet motor is used as the permanent magnet field motor. The rotor core 31 has multiple through holes 33 that pass through it in the axial direction. The multiple through holes 33 are provided to correspond to the arrangement of the multiple permanent magnets 32. Each permanent magnet 32 is fixed to the rotor core 31 while positioned within 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 an embedded permanent magnet motor.

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.

Each of the electromagnetic steel sheets 40 forming the stator core 21 and the rotor core 31 is formed, for example, by punching a blank 1 as shown in Figures 4 to 6. The blank 1 is a steel sheet (electromagnetic steel sheet) that serves as the base material of the electromagnetic steel sheets 40. Examples of the blank 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.

(Material 1)
The material 1 is handled in a state where it is wound into 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.

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, in consideration of 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 plate thickness t0 of the raw material 1 that satisfies the above range is 0.20 mm.

The average thickness t0 of the raw material 1 includes not only the thickness of the base steel plate 2 (described below) but also the thickness of the insulating coating 3. The average thickness t0 of the raw material 1 can be measured, for example, by the following method. For example, if 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. A predetermined position in the longitudinal direction of the raw material 1 (for example, a position away from the longitudinal edge of the raw material 1 by a length equal to 10% of the total length of the raw material 1) is selected from the unwound raw material 1. At this selected position, the raw material 1 is divided into five regions along its width. The thickness of the raw material 1 is measured at four locations that form the boundaries between these five regions. The average of the thicknesses at the four locations can be used as the average thickness t0 of the raw material 1.

The upper and lower limits for the average sheet thickness t0 of this 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 stack thickness of the laminated core is measured at four locations equally spaced circumferentially (i.e., every 90 degrees around the central axis O). The stack thickness at each of the four measured locations is divided by the number of stacked 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.

As shown in Figures 5 and 6, the material 1 comprises a base steel plate 2 and an insulating coating 3. The material 1 is formed by coating both sides of a strip-shaped base steel plate 2 with an insulating coating 3. In this embodiment, the majority of the material 1 is formed from 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.

The chemical composition of the base steel sheet 2 is shown below in mass percent, and contains 2.5% to 4.5% Si by mass. By keeping 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.

Si: 2.5% to 4.5%
Al: 0.001% to 3.0%
Mn: 0.05% to 5.0%
Remainder: Fe and impurities

When the material 1 is used as an electromagnetic steel sheet 40, the insulating coating 3 provides insulation between adjacent electromagnetic steel sheets 40 in the stacking direction. In this embodiment, the insulating coating 3 also has adhesive properties, bonding adjacent electromagnetic 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 with excellent insulating properties and a top insulating coating with excellent adhesive properties.

In this embodiment, the insulating coating 3 completely covers both surfaces of the base steel plate 2 without any gaps. However, as long as the aforementioned insulating performance and adhesive properties are ensured, some layers of the insulating coating 3 do not have to completely cover both surfaces of the base steel plate 2. In other words, some layers of the insulating coating 3 may be provided intermittently on the surface of the base steel plate 2. However, to ensure insulating performance, both surfaces of the base steel plate 2 must 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 structure that combines insulating performance and adhesive properties, the insulating coating 3 must be formed completely over the entire surface of the base steel plate 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 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.

The coating composition used to form the base insulating coating is not particularly limited, and common treatments such as chromate-containing treatments and phosphate-containing treatments can be used.

An adhesive insulating coating is formed by applying the coating composition for electrical steel sheet described below to a base steel sheet. An adhesive insulating coating can be, for example, a single-layer insulating coating that combines insulating properties and adhesive properties, or a top insulating coating that is applied to a base insulating coating. Before the thermocompression bonding process during laminated core manufacturing, 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.

When a relaxation curve of the adhesive insulating coating is measured by a solid echo method at 25°C using pulse NMR and analyzed by two-component separation, the fast-relaxing SS component has a spin-spin relaxation time T _2S of 15.0 μs or less, and the slow-relaxing SL component has a spin-spin relaxation time T _2L of 30.0 μs or less.

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 a component with fast relaxation and low molecular mobility that corresponds to the separation curve with the shorter relaxation time of the two separation curves obtained by separating a relaxation curve obtained by pulsed NMR measurements into two components. The SL component is a component with slow relaxation and high molecular mobility that corresponds to the separation curve with the longer relaxation time of the two separation curves obtained by separating a relaxation curve obtained by pulsed NMR measurements into two components.
The measurement conditions for pulsed NMR may be, for example, those shown in the Examples.

By controlling T _2S at 25° C. to 15.0 μs or less and T _2L 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.
_T2S is preferably 13.0 μs or less, and more preferably 10.0 μs or less.
_T2L is preferably 28.0 μs or less, and more preferably 27.0 μs or less.

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 is further enhanced.
The ratio of the SS component to the SL component can be determined by analyzing the results of pulsed NMR measurements.

The adhesive insulating coating 3 preferably has a spin-spin relaxation time T ₂ (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 harder during punching, further reducing the amount of waste generated during punching.

_T2 (25) is more preferably 40.0 μs or less, and even more preferably 30.0 μs or less, from the viewpoint of easily reducing the amount of waste generated during punching. The lower limit of _T2 (25) is not particularly limited, but may be 5.0 μs or more.
T _2S , T _2L and T ₂ (25) can be adjusted by, for example, adjusting the type and content of the curing agent and the degree of crosslinking.

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 include compositions containing an epoxy resin and an epoxy resin curing agent. In other words, one example of an insulating coating with adhesive properties is a film containing an epoxy resin and an epoxy resin curing agent.

General epoxy resins can be used as the epoxy resin. Specifically, any epoxy resin containing two or more epoxy groups per molecule can be used without particular restrictions. Examples of such epoxy resins include bisphenol A epoxy resins, bisphenol F epoxy resins, phenol novolac epoxy resins, cresol novolac epoxy resins, alicyclic epoxy resins, glycidyl ester epoxy resins, glycidyl amine epoxy resins, hydantoin epoxy resins, isocyanurate epoxy resins, acrylic acid-modified epoxy resins (epoxy acrylates), phosphorus-containing epoxy resins, and their halides (e.g., brominated epoxy resins) and hydrogenated versions. One type of epoxy resin may be used alone, or two or more types may be used in combination.

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.

The acrylic resin may contain structural units derived from monomers other than acrylic monomers. Examples of such other monomers include ethylene, propylene, and styrene. One type of such other monomer may be used alone, or two or more types may be used in combination.

When using an acrylic resin, it may be used as an acrylic-modified epoxy resin in which the acrylic resin is grafted onto an epoxy resin. In coating compositions for electrical steel sheets, it may be included as a monomer that forms the acrylic resin.

Epoxy resin curing agents that can be used include latent heat-curing agents, such as 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 resin, cresol novolac resin, bisphenol novolac resin, triazine-modified phenol novolac resin, and phenol resole resin. Of these, phenolic curing agents are preferred as epoxy resin curing agents, and phenol resole resin is more preferred. Epoxy resin curing agents may be used alone or in combination.

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 epoxy resin.

The coating composition for electrical steel sheets may contain additives such as curing accelerators (curing catalysts), emulsifiers, and antifoaming agents. A single type of additive may be used, or two or more types may be used in combination.

Next, a method for manufacturing the electromagnetic steel sheet 40 of this embodiment will be described.
The production of the electromagnetic steel sheet 40 includes a step of applying a coating composition for an electromagnetic steel sheet 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 an electromagnetic steel sheet and then cooling it to room temperature to form the insulating coating 3.
The baking step will be described in detail below.

The insulating coating 3 can be formed, for example, by applying a coating composition for electromagnetic 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, 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, 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).
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.

In the manufacturing of the electromagnetic steel sheet 40 of this embodiment, the cooling process to room temperature in the baking step can be effectively utilized for controlling _T2S , _T2L , and _T2 (25) defined in this embodiment. One embodiment of the manufacturing method of the electromagnetic 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. The average cooling rate CR3 is set to 10°C/s or less. By cooling this temperature range at a relatively low rate of 10°C/s or less, _T2S and _T2L in particular can be favorably controlled, and the proportion of the SS component can be controlled within an appropriate range. Furthermore, by controlling _T2S and _T2L within the preferred range, the insulating coating 3 becomes appropriately hard. This reduces the amount of swarf generated when the electrical steel sheet 40 is subsequently punched. On the other hand, if the average cooling rate CR3 exceeds 10°C/s, the _T2S and _T2L in particular increase in time, the insulating coating 3 softens, and swarf generation during punching cannot be suppressed. There is no need to particularly limit the lower limit of the average cooling rate CR3, but in consideration of the productivity of the baking step, it is preferable to set it to 1° C./s or more.

Furthermore, when the average cooling rate from (Tg+15)°C to Tg°C during the cooling process from the maximum temperature to room temperature is defined as CR2, it is preferable that CR3 < CR2. This allows _T2 (25) to be controlled within a more preferable range, making it possible to achieve both a high effect of suppressing scum generation and high adhesive strength.

Although the mechanism by which control of the average cooling rate CR3 in the temperature range just below the glass transition temperature Tg as described above achieves both a high effect of suppressing scum generation and high adhesive strength is unclear, it is thought that this is achieved by preventing molecular mobility from becoming too low by appropriately arranging the molecular chains of the insulating coating 3.

The above describes the manufacturing method for 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.

The upper and lower limits of the average thickness t1 of the insulating coating 3 are set, for example, as follows, taking into consideration the case where the material 1 is used as an electromagnetic steel sheet 40.
When the material 1 is used as the electromagnetic steel sheet 40, the average thickness t1 of the insulating coating 3 (the thickness per 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 stacked on top of each other.

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 (base material 1)) can be, for example, 1.5 μm or more and 8.0 μm or less.
In the case of the multilayer insulating coating 3, 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 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.

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 sheets 40. The average thickness t1 of the insulating coating 3 of the electromagnetic steel sheets 40 can be measured, for example, by the following measurement method. For example, among the multiple electromagnetic steel sheets that form the laminated core, the electromagnetic steel sheets 40 that are located outermost in the stacking direction (the electromagnetic steel sheets 40 whose surfaces are exposed in the stacking direction) are selected. A predetermined radial position (for example, a position exactly midway (center) between the inner and outer circumferential edges of the electromagnetic steel sheets 40) is selected on the surface of the selected electromagnetic steel sheets 40. At the selected position, the thickness of the insulating coating 3 of the electromagnetic steel sheets 40 is measured at four equally spaced locations 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 electromagnetic steel sheet 40 located outermost 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 electromagnetic steel sheet 40.

Electromagnetic steel sheets 40 are manufactured by punching the above-described material 1, and bonded cores (stator core 21 and rotor core 31) are manufactured using the electromagnetic steel sheets 40.

(Lamination method of 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. 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 bonded areas 41a and non-bonded areas (not shown).

In this embodiment, the plurality of electromagnetic steel sheets forming the rotor core 31 are fixed to one another by crimps 42 (dowels) as shown in Fig. 1. However, the plurality of electromagnetic steel sheets forming the rotor core 31 may also have a laminated structure fixed by an insulating coating 3, similar to the 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.

(Manufacturing method of laminated core)
The stator core 21 is manufactured using, for example, 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 together by the insulating coating 3 (i.e., the portions of the insulating coating 3 located in the bonding regions 41a are allowed to exhibit their adhesive properties), completing the bonding process.

As shown in FIG. 7, the manufacturing apparatus 100 has multiple punching stations 110. The punching stations 110 may have two stages, or three or more stages. Each punching station 110 has a female die 111 arranged below the material 1 and a male die 112 arranged above the material 1.

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 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.

In the manufacturing apparatus 100 having the configuration described above, the raw material 1 is first sequentially fed from the coil 1A in the direction of arrow F in Figure 7. This raw material 1 is then sequentially punched by multiple stages of punching stations 110. Through these punching processes, the raw material 1 is given the shape of an electromagnetic steel sheet 40 having a core back portion 22 and multiple teeth portions 23 as shown in Figure 3. However, since it is not completely punched out at this point, it proceeds to the next process in the direction of arrow F.

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.
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.

As described above, in this embodiment, the _T2S and _T2L at 25°C of the insulating coating that has adhesive properties to the electrical steel sheets are controlled to be equal to or less than specific values, thereby reducing the amount of waste generated during punching of the electrical steel sheets.
Furthermore, T ₂ (25) at 25° C. is controlled within a specific range, which makes it possible to achieve both a higher effect of suppressing scum generation and a 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 step of the insulating coating, it becomes possible to control the above T _2S , T _2L and T ₂ (25) within appropriate ranges.

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.

In the rotor of 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.

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.

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.

In addition, the components in the above embodiments may be replaced with well-known components as appropriate, and the above-described modifications may be combined as appropriate, without departing from the spirit of the present invention.

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 produced in each example was scraped off with a chisel to prepare a powdered sample. Pulse NMR measurements of the powdered sample were carried out using a JNM-MU25 (25 MHz) manufactured by JEOL Ltd. under the following conditions. The relaxation curves obtained by the measurements at 25°C were subjected to two-component separation analysis to determine _T2S and _T2L . In addition, _T2 (25) was determined from the relaxation curves obtained by the pulse NMR measurements at 25°C. The proportion of the SS component was determined by analyzing the results of the pulse NMR measurements using the analysis software provided with the JNM-MU25.
(Measurement conditions)
Measurement method: Solid Echo method Pulse width: 90° pulse, 2.5 μs
Repeat time: 4 seconds
Number of measurements: 16 Measurement temperature: 25°C

[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 to be acceptable.

[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, and the 30 mm wide and 10 mm long tip portions of each sheet 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 prepare samples. 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."

[Example 1]
The following three types of coating compositions for electrical steel sheets were prepared.
(A) A mixture of 100 parts by mass of bisphenol F-type epoxy resin and 25 parts by mass of phenol resole resin as an epoxy resin curing agent; (B) A mixture of 100 parts by mass of bisphenol F-type epoxy resin and 25 parts by mass of diaminodiphenylmethane resin as an epoxy resin curing agent; (C) A mixture of 100 parts by mass of acrylic acid-modified epoxy resin and 25 parts by mass of phenol resole resin as an epoxy resin curing agent. A non-oriented electrical steel sheet strip with a thickness of 0.25 mm and a width of 300 mm was used as the base steel sheet, consisting of 3.0% Si, 0.2% Mn, 0.5% Al, and the remainder Fe and impurities. Each 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/ ^m² and baked under the respective conditions to form an insulating coating with an average thickness t1 of 3.0 µm, thereby obtaining an electrical steel strip.

Table 1 shows the measurement results of T _2S , T _2L , and T ₂ (25) at 180° C. and the evaluation results of the insulating coating formed from the above coating composition for electrical steel sheet.

As shown in Table 1, in the inventive examples in which appropriate cooling was performed in the baking process and the proportions of _T2S , _T2L , and SS components in the insulating coating of the electrical steel sheets were within appropriate ranges, the amount of swarf generated during punching was smaller than in the comparative examples in which the proportions of _T2S , _T2L , and SS components were outside the ranges. The adhesive strength between the electrical steel sheets was also high. Furthermore, under the condition that CR3 < CR2 was satisfied, _T2 (25) was controlled within a more preferable range, and both low swarf generation and high adhesive strength were achieved at an even better level.

This invention can reduce the amount of scrap generated during punching of electromagnetic steel sheets in the manufacture of laminated cores. Therefore, it has great industrial applicability.

1...Material, 2...Base steel plate, 3...Insulating coating, 10...Rotating electric machine, 20...Stator, 21...Stator core, 40...Electromagnetic steel plate.

Claims (6)

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 a relaxation curve of the insulating coating is measured by a solid echo method at 25°C using pulse NMR and analyzed by two-component separation, the spin-spin relaxation time T _2S of the SS component, which relaxes quickly, is 15.0 μs or less, and the spin-spin relaxation time T _2L of the SL component, which relaxes slowly, 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. The electrical steel sheet according to claim 1, wherein the spin-spin relaxation time T ₂ (25) measured by pulsed NMR at 25° C. is 55.0 μs or less. A laminated core in which multiple electromagnetic steel sheets according to claim 1 or 2 are stacked and bonded together. A rotating electric machine equipped with the laminated core according to claim 3. 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. The method for manufacturing an electrical steel sheet according to claim 5, characterized in that, in the baking process, when the average cooling rate in the temperature range from (Tg + 15)°C to Tg°C during the cooling process from the ultimate temperature to room temperature is CR2, CR3 < CR2.