Electrical steel sheets and laminated cores

Abstract

To provide an electromagnetic steel sheet capable of achieving both sufficient adhesive strength for forming a laminated core, high powdering resistance, and slit resistance, and a laminated core formed by laminating a plurality of these electromagnetic steel sheets.SOLUTION: An electromagnetic steel sheet includes a base steel plate 2, a first insulating coating 3A formed on a first surface 2a of the base steel plate 2 and having adhesive ability, and a second insulating coating 3B formed on a second surface 2b which is a back surface of the first surface 2a of the base steel sheet 2, and having adhesive ability, and the first insulating film 3A is composed of an organic resin phase containing at least one of an epoxy resin, a phenol resin and a urethane prepolymer, and the second insulating film 3B includes an organic resin phase including at least an epoxy resin, a phenol resin, and a urethane prepolymer, and a curing agent.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to an electromagnetic steel sheet and a laminated core.

Background Art

[0002] In rotating electrical machines, a laminated core formed by laminating a plurality of electromagnetic steel sheets is used. These electromagnetic steel sheets are integrated in a laminated state by means such as caulking, welding, and adhesion. However, when laminated by caulking or welding, the magnetic properties of each electromagnetic steel sheet may deteriorate due to mechanical stress, thermal stress applied during processing, and further interlayer short circuit, and the performance of the laminated core may not be fully exhibited. Lamination by adhesion is extremely effective in solving this problem.

[0003] For example, the non-oriented electromagnetic steel sheet product disclosed in Patent Document 1 below includes a plurality of non-oriented electromagnetic steel sheets and an adhesive coating layer located between the plurality of non-oriented electromagnetic steel sheets, and the adhesive coating layer includes a first component containing an organic-inorganic composite and a second component containing a composite metal phosphate. With respect to 100% by weight of the total amount of the adhesive coating layer, 70 to 99% by weight of the first component is contained, and 1 to 30% by weight of the second component is contained. The organic-inorganic composite is one in which inorganic nanoparticles are chemically substituted for some functional groups in an organic resin, and the organic resin is one or more selected from epoxy resins, ester resins, acrylic resins, styrene resins, urethane resins, and ethylene resins, and the inorganic nanoparticles are one or more selected from SiO2, Al2O3, TiO2, MgO, ZnO, and ZrO2. According to this configuration, it is explained that even if the thickness of the adhesive coating layer is formed thin, while exhibiting excellent adhesiveness and insulating properties, properties such as weldability, heat resistance, adhesion before and after SRA, and stacking factor can be improved.

[0004] Furthermore, the electromagnetic steel sheet disclosed in Patent Document 2 is an insulating coated electromagnetic steel sheet having a heat-resistant adhesive insulating coating on one or both sides thereof, wherein the heat-resistant adhesive insulating coating employs a configuration that contains 70% by mass or more of polyether urethane resin and 30 parts by mass or less of a silane compound per 100 parts by mass of the polyether urethane resin. This configuration is described as being suitable for manufacturing laminated electrical steel sheets used in applications requiring high-temperature adhesion, such as automotive motors. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Special Publication No. 2019-508573 [Patent Document 2] Japanese Patent Publication No. 2017-186542 [Overview of the project] [Problems that the invention aims to solve]

[0006] Electrical steel sheets are required to possess both adhesive properties and resistance to slitting and scratching. However, while the adhesive properties after lamination are examined in the above-mentioned Patent Documents 1 and 2, slitting resistance and scratch resistance are not examined at all. Here, adhesive ability refers to the ability of the insulating coating to melt and exhibit adhesive properties when at least one of heating and / or pressurizing is applied. This adhesive ability increases as the insulating coating becomes softer. On the other hand, slit resistance refers to the resistance of the insulating coating to damage and peeling when the front and back surfaces of the electrical steel sheet are rubbed against by pads used to hold the sheet in place for slitting. Furthermore, scratch resistance refers to the resistance to scratches that occur when the back surface of the base steel sheet is rubbed against during transfer between multiple molds. Both slit resistance and scratch resistance increase as the insulating coating becomes harder. Thus, adhesive strength, slit resistance, and scratch resistance are inversely related in terms of the hardness of the insulating coating that achieves them. In other words, increasing the hardness of the insulating coating sacrifices adhesive strength, while decreasing the hardness of the insulating coating impairs slit resistance and scratch resistance.

[0007] The present invention has been made in view of the above circumstances, and aims to provide an electrical steel sheet that can achieve both high adhesive strength, high slit resistance, and scratch resistance, and a laminated core constructed by laminating multiple sheets of this electrical steel sheet. [Means for solving the problem]

[0008] In order to solve the above problems and achieve the above objectives, the present invention employs the following embodiments. (1) An electromagnetic steel sheet according to one aspect of the present invention comprises a base steel sheet, a first insulating coating formed on a first surface of the base steel sheet and having adhesive properties, and a second insulating coating formed on a second surface which is the back surface of the first surface of the base steel sheet and having adhesive properties, wherein the first insulating coating consists of an organic resin phase containing at least one of epoxy resin, phenolic resin, and urethane prepolymer, and the second insulating coating contains an organic resin phase containing at least one of epoxy resin, phenolic resin, and urethane prepolymer and a curing agent. Furthermore, the average pencil hardness of the first insulating film is H or higher, and the average pencil hardness of the second insulating film is higher than the average pencil hardness of the first insulating film. . According to the electrical steel sheet described in (1) above, the second surface is covered with a relatively hard second insulating film containing a hardening agent, thus exhibiting high slit resistance and scratch resistance. On the other hand, the first surface is covered with a relatively soft first insulating film that does not contain a hardening agent, thus ensuring relatively high adhesive strength. Therefore, it is possible to achieve both adhesive ability for forming a laminated core and high slit resistance and scratch resistance. In this context, "having adhesive properties" means that it melts and exhibits adhesive characteristics when at least one of heating and / or pressurizing is applied.

[0009] (2) In the electrical steel sheet described in (1) above, the equivalent ratio of the curing agent to the organic resin phase in the second insulating film may be 0.8 to 1.5. According to the electrical steel sheet described in (2) above, high slit resistance and scratch resistance can be more reliably obtained.

[0010] (3) A laminated core according to one aspect of the present invention is made by laminating two or more electromagnetic steel sheets as described in (1) or (2) above. According to the laminated core described in (3) above, it is manufactured using electrical steel sheets that achieve both high adhesive strength and high slit resistance and scratch resistance, resulting in high rigidity and good yield. [Effects of the Invention]

[0011] According to each of the above embodiments of the present invention, it is possible to provide an electrical steel sheet that can achieve both adhesive strength for forming a laminated core and high slit resistance and scratch resistance, and a laminated core constructed by laminating multiple sheets of this electrical steel sheet. [Brief explanation of the drawing]

[0012] [Figure 1] This is a cross-sectional view of a rotating electric machine equipped with a laminated core according to one embodiment of the present invention. [Figure 2] This is a side view of the same stacked core. [Figure 3] This is a plan view of the electrical steel sheets that make up the laminated core. [Figure 4] This is a plan view of the strip-shaped steel sheet, which is the material used for the electrical steel sheet. [Figure 5] This is a diagram showing the same material, and is a cross-sectional view of section B, part AA, in Figure 4. [Figure 6] This is a side view showing an example of a manufacturing apparatus for producing laminated cores by obtaining electrical steel sheets from the same material. [Modes for carrying out the invention]

[0013] Hereinafter, with reference to the drawings, a laminated core according to an embodiment of the present invention, a rotating electrical machine including this laminated core, and a material (electromagnetic steel sheet) forming this laminated core will be described. In this embodiment, as the rotating electrical machine, a motor, specifically an alternating current motor, more specifically a synchronous motor, and even more specifically a permanent magnet field excitation type motor will be described as an example. This type of motor is suitably employed, for example, in electric vehicles and the like.

[0014] (Rotating Electrical Machine 10) As shown in FIG. 1, the rotating electrical 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 inside the case 50. The stator 20 is fixed inside the case 50. In this embodiment, as the rotating electrical machine 10, an inner rotor type in which the rotor 30 is located radially inside the stator 20 is adopted. However, as the rotating electrical machine 10, an outer rotor type in which the rotor 30 is located outside the stator 20 may be adopted. Also, in this embodiment, the rotating electrical machine 10 is a three-phase alternating current 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 1000 rpm, for example, by applying an exciting current with an effective value of 10 A and a frequency of 100 Hz to each phase.

[0015] The stator 20 includes a stator laminated core (hereinafter, stator core) 21 and a winding (not shown). Each of the plurality of electromagnetic steel sheets 40 constituting 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 orthogonal 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 that circulates around the central axis O) will be referred to as the circumferential direction.

[0016] The core back portion 22 is formed in an annular shape in a plan view when the stator 20 is viewed from the axial direction. Multiple teeth portions 23 protrude radially inward from the inner circumference of the core back portion 22 (towards the central axis O of the core back portion 22 along the radial direction). The multiple teeth portions 23 are arranged at equal angular intervals in the circumferential direction. In this embodiment, 18 teeth portions 23 are provided at central angle intervals of 20 degrees around the central axis O. The multiple teeth portions 23 are formed to be of the same shape and size as each other. Therefore, the multiple teeth portions 23 have the same thickness dimension as each other. The windings are wound around each tooth portion 23. The windings may be concentrated windings or distributed windings.

[0017] The rotor 30 is positioned radially inward relative to the stator 20 (stator core 21). The rotor 30 comprises a rotor core 31 and a plurality of permanent magnets 32. The rotor core 31 is formed in an annular (ring-shaped) form and is arranged coaxially with the stator 20. The rotating shaft 60 is located inside the rotor core 31. The rotating shaft 60 is fixed to the rotor core 31. Multiple permanent magnets 32 are fixed to the rotor core 31. In this embodiment, pairs of permanent magnets 32 form one magnetic pole. Multiple pairs of permanent magnets 32 are arranged at equal angular intervals in the circumferential direction. In this embodiment, 12 pairs (24 in total) of permanent magnets 32 are provided at 30-degree intervals around the central axis O.

[0018] In this embodiment, an embedded magnet type motor is used as the permanent magnet field motor. The rotor core 31 has a plurality of through holes 33 that penetrate the rotor core 31 in the axial direction. The plurality of through holes 33 are provided corresponding to the arrangement of the plurality of permanent magnets 32. Each permanent magnet 32 ​​is fixed to the rotor core 31 while positioned within the corresponding through hole 33. Fixing each permanent magnet 32 ​​to the rotor core 31 can be achieved, for example, by bonding the outer surface of the permanent magnet 32 ​​to the inner surface of the through hole 33 with an adhesive. Note that a surface magnet type motor may be used instead of the embedded magnet type as the permanent magnet field motor.

[0019] Both the stator core 21 and the rotor core 31 are laminated cores. For example, as shown in Figure 2, the stator core 21 is formed by laminating multiple electromagnetic steel sheets 40 in the lamination direction. The lamination direction is the axial direction.

[0020] The stacking thickness (total length along the central axis O) of the stator core 21 and 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 just examples, and the stacking thickness, outer diameter, and inner diameter of the stator core 21, and the stacking 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 of the tooth portion 23 in the stator core 21. That is, the inner diameter of the stator core 21 is the diameter of a virtual circle inscribed in the tip of all the tooth portions 23.

[0021] Figure 3 shows one of the multiple electromagnetic steel sheets 40 that make up the stator core 21. This electromagnetic steel sheet 40 comprises a base steel sheet 2, a first insulating coating 3A formed on the first surface 2a, which is the surface of the base steel sheet 2, and having adhesive properties, and a second insulating coating 3B formed on the second surface 2b, which is the back surface of the base steel sheet 2, and having adhesive properties. The arrangement of the first insulating coating 3A, the base steel sheet 2, and the second insulating coating 3B is the same as that of material 1 described later, and specifically the same arrangement as shown in Figure 5, which will be described later. Furthermore, the phrase "having adhesive properties" as described above means that when pressure and / or heat are applied, the first insulating film 3A and the second insulating film 3B melt and exhibit adhesive properties.

[0022] The average pencil hardness of the second insulating coating 3B is higher than that of the first insulating coating 3A. The average pencil hardness of the first insulating coating 3A is between HB and 3H. The average pencil hardness of the second insulating coating 3B should be higher than that of the first insulating coating 3A, but preferably between 4H and 9H. The average pencil hardness can be determined by the scratch hardness (pencil method) described in JIS K5400 5-4. The first insulating coating 3A is formed on the upper surface of the core back portion 22 and on the upper surface of each tooth portion 23. The second insulating coating 3B is formed on the lower surface of the core back portion 22 and on the lower surface of each tooth portion 23. At least a portion of the side surface of the core back portion 22 may be covered by at least one of the first insulating coating 3A and the second insulating coating 3B. Similarly, at least a portion of the side surface of each tooth portion 23 may be covered by at least one of the first insulating coating 3A and the second insulating coating 3B. The side surface referred to here, in the case where the electromagnetic steel sheet 40 is formed by punching out material 1 described later, is the cut surface formed after punching, and includes the outer peripheral side surface that forms the outer shape of the core back portion 22, and the side surface that forms the outer shape of the tooth portion 23 and the inner shape of the core back portion 22.

[0023] Each electrical steel sheet 40 is formed by punching out material 1 as shown in Figures 4 and 5. Material 1 is a steel sheet (electrical steel sheet) that serves as the base material for the electrical steel sheet 40. As material 1, a strip of steel sheet or a cut sheet can be used. Although the explanation of the stator core 21 is still in progress, the following will describe 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 has been punched out from material 1 to form the shape used for the laminated core may be referred to as electromagnetic steel sheet 40.

[0024] (Material 1) If material 1 is a strip of steel, it is handled, for example, in a state wound onto coil 1A (see Figure 6). In this embodiment, non-oriented electrical steel sheet is used as material 1. As non-oriented electrical steel sheet, non-oriented electrical steel strip according to JIS C 2552:2014 can be used. However, grain-oriented electrical steel sheet may be used as material 1 instead of non-oriented electrical steel sheet. In this case, grain-oriented electrical steel strip according to JIS C 2553:2019 can be used as grain-oriented electrical steel sheet. Also, as material 1, non-oriented thin electrical steel strip or grain-oriented thin electrical steel strip according to JIS C 2558:2015 can be used.

[0025] The upper and lower limits of the average plate thickness t0 of material 1 are set, for example, as follows: As material 1 becomes thinner, the manufacturing cost of material 1 increases. Therefore, considering the manufacturing cost, the lower limit of the average plate thickness t0 of material 1 is 0.10 mm, preferably 0.15 mm, and more preferably 0.18 mm. On the other hand, if material 1 is too thick, the manufacturing cost will be good, but when material 1 is used as electrical steel sheet 40, eddy current loss will increase and core iron loss will deteriorate. Therefore, considering core iron loss and manufacturing cost, the upper limit of the average sheet thickness t0 of material 1 is 0.65 mm, preferably 0.35 mm, and more preferably 0.30 mm. As an example of an average plate thickness t0 of material 1 that satisfies the above range, 0.20 mm can be used.

[0026] The average plate thickness t0 of material 1 includes not only the thickness of the base steel plate 2 described later, but also the thickness of the first insulating coating 3A and the second insulating coating 3B. The method for measuring the average plate thickness t0 of material 1 is, for example, the following method. For example, if material 1 is a strip of steel sheet wound into the shape of a coil 1A (see Figure 6), at least a portion of material 1 is unwound into a flat plate shape. A predetermined position in the longitudinal direction of material 1 (for example, a position 10% of the total length of material 1 from the longitudinal edge of material 1) is selected. At this selected position, material 1 is divided into five regions along its width. The plate thickness of material 1 is measured at four locations that form the boundaries of these five regions. The average value of the plate thicknesses at these four locations can be taken as the average plate thickness t0 of material 1.

[0027] The upper and lower limits for the average plate thickness t0 of material 1 can also be used as the upper and lower limits for the average plate thickness t0 of the electrical steel sheet 40. The method for measuring the average plate thickness t0 of the electrical steel sheet 40 is, for example, the following method: For example, the stacked thickness of the laminated core is measured at four locations with equal spacing in the circumferential direction (i.e., at 90-degree intervals around the central axis O). The thickness per sheet is calculated by dividing each of the four measured stacked thicknesses by the number of laminated electrical steel sheets 40. The average value of the four thicknesses can be taken as the average plate thickness t0 of the electrical steel sheet 40. The average plate thickness t0 measured in this electrical steel sheet 40 state is equal to the average plate thickness t0 measured in the material 1 state.

[0028] As shown in Figures 4 and 5, the material 1 comprises a base steel sheet 2, a first insulating coating 3A formed on the first surface 2a of the base steel sheet 2 and having adhesive properties, and a second insulating coating 3B formed on the second surface 2b of the base steel sheet 2 and having adhesive properties. The average pencil hardness of the second insulating coating 3B is higher than the average pencil hardness of the first insulating coating 3A. The average pencil hardness of the first insulating coating 3A is HB or higher and 3H. The average pencil hardness of the second insulating coating 3B should be higher than the average pencil hardness of the first insulating coating 3A, but 4H or higher and 9H or lower is preferable. The average pencil hardness of the first insulating coating 3A can also be determined by the scratch hardness (pencil method) described in JIS K5400 5-4, similar to the second insulating coating 3B.

[0029] The chemical composition of the base steel sheet 2 contains 2.5% to 4.5% Si by mass, as shown below in mass percent. By setting the chemical composition within this range, the yield strength of material 1 (electrical steel sheet 40) can be set to, for example, 380 MPa to 540 MPa.

[0030] Si: 2.5%~4.5% Al: 0.001%~3.0% Mn: 0.05%~5.0% Remainder: Fe and impurities

[0031] When material 1 is used as an electrical steel sheet 40, both the first insulating film 3A and the second insulating film 3B exhibit insulating performance between adjacent electrical steel sheets 40 in the lamination direction. Furthermore, both the first insulating film 3A and the second insulating film 3B have adhesive properties (self-fusing function) and bond adjacent electrical steel sheets 40 in the lamination direction. More specifically, both the first insulating film 3A and the second insulating film 3B fuse together by being subjected to at least one of pressurization and / or heating.

[0032] On the other hand, the first insulating coating 3A and the second insulating coating 3B have different functions. In other words, the average pencil hardness of the second insulating coating 3B is set high in order to ensure slit resistance and scratch resistance. "Slit resistance" refers to the resistance of the first insulating coating 3A and the second insulating coating 3B to scratches and peeling when the front and back surfaces of the electromagnetic steel sheet 40 are rubbed by a pad (not shown) that holds the electromagnetic steel sheet 40 in place for slitting. "Scratch resistance" refers to the resistance of the second insulating coating 3B, which forms the back (bottom) surface of the material 1, to scratches when the material 1 is transferred between molds. These slit resistance and scratch resistance capabilities increase as the second insulating coating 3B becomes harder. The degree of damage to the second insulating coating 3B can be evaluated by pressing the material 1 against a steel sheet support roll on the factory line and rubbing them together, and visually determining the degree of damage the second insulating coating 3B receives at that time. The slit resistance and scratch prevention capabilities of the second insulating coating 3B are already required properties even before the electrical steel sheets 40 are laminated. On the other hand, the softness required for the first insulating coating 3A is a property required during bonding by pressurizing and heating after the electrical steel sheets 40 have been laminated.

[0033] If the average pencil hardness is increased, insufficient adhesive strength occurs when the electrical steel sheets 40 are laminated to manufacture a laminated core. Therefore, to compensate for this insufficient adhesive strength, the average pencil hardness of the first insulating coating 3A is lowered to make it softer. Specifically, the average pencil hardness of the first insulating coating 3A is between HB and 3H. On the other hand, the average pencil hardness of the second insulating coating 3B should be higher than that of the first insulating coating 3A, but preferably between 4H and 9H. Between the first insulating coating 3A and the second insulating coating 3B, in any combination of average pencil hardness, the second insulating coating 3B is relatively harder than the first insulating coating 3A. Conversely, the first insulating coating 3A is relatively softer than the second insulating coating 3B. This difference in average pencil hardness is determined by the presence or absence of a hardening agent. In other words, the first insulating coating 3A consists only of an organic resin phase and does not contain a curing agent, so it has a low average pencil hardness and is soft. On the other hand, the second insulating coating 3B contains a curing agent in addition to the organic resin phase, so it has a high average pencil hardness and is hard.

[0034] The first insulating film 3A and the second insulating film 3B may each be a single-layer or multi-layer structure. More specifically, the first insulating film 3A and the second insulating film 3B may each be a single-layer structure possessing both insulating and adhesive properties. Alternatively, the first insulating film 3A and the second insulating film 3B may each be a multi-layer structure including a base insulating film with excellent insulating properties and a top insulating film with excellent adhesive properties. In this case, the base insulating film is formed to cover the surface of the base steel sheet 2 without gaps, and the top insulating film is formed on top of the surface of the base insulating film. In this multi-layer structure, the top insulating film formed on the outermost surface (uppermost surface) of the electromagnetic steel sheet 40 will have the average pencil hardness required for the first insulating film 3A. Similarly, the top insulating film formed on the innermost surface (lowest surface) of the electromagnetic steel sheet 40 will have the average pencil hardness required for the second insulating film 3B. In other words, the average pencil hardness of the top insulating coating formed on the outermost surface (topmost surface) of the electrical steel sheet 40 is between HB and 3H. Furthermore, the average pencil hardness of the top insulating coating formed on the innermost surface (bottommost surface) of the electrical steel sheet 40 is higher than the average pencil hardness of the top insulating coating formed on the outermost surface (topmost surface) of the electrical steel sheet 40.

[0035] Within the limits of ensuring insulation and adhesive properties, the undercoat insulation coating does not need to completely cover both sides of the base steel plate 2 without any gaps. In other words, a portion of the undercoat insulation coating may be intermittently provided on the surface of the base steel plate 2. However, to ensure insulation performance, it is preferable that both sides of the base steel plate 2 are covered by the undercoat insulation coating so that their entire surfaces are not exposed. The coating composition for forming the underlying insulating film is not particularly limited, and general treatment agents such as chromic acid-containing treatment agents and phosphate-containing treatment agents can be used.

[0036] The first insulating film 3A and the second insulating film 3B are formed by applying a coating composition for electrical steel sheets onto the base steel sheet 2. Before heating and pressing during the manufacturing of the laminated core, the first insulating film 3A and the second insulating film 3B are in an uncured or semi-cured state (stage B), and the curing reaction proceeds due to heating during heating and pressing, resulting in the development of adhesive properties.

[0037] The first insulating film 3A consists of an organic resin phase containing at least one of epoxy resin, phenolic resin, and urethane prepolymer. On the other hand, the second insulating film 3B contains an organic resin phase containing at least one of epoxy resin, phenolic resin, and urethane prepolymer, and a curing agent. The coating composition for electrical steel sheets is not particularly limited, and examples include compositions containing an epoxy resin and an epoxy resin curing agent. That is, an example of an insulating film with adhesive properties is a film containing an epoxy resin and an epoxy resin curing agent.

[0038] As the epoxy resin (epoxy resin), any general epoxy resin can be used, and specifically, any epoxy resin having two or more epoxy groups in one molecule can be used without particular restriction. Examples of such epoxy resins include bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, alicyclic epoxy resin, glycidyl ester type epoxy resin, glycidylamine type epoxy resin, hydantoin type epoxy resin, isocyanurate type epoxy resin, acrylic acid modified epoxy resin (epoxy acrylate), phosphorus-containing epoxy resin, and halogens thereof (brominated epoxy resin, etc.) and hydrogenated products. As the epoxy resin, one type may be used alone, or two or more types may be used in combination.

[0039] The coating composition for electrical steel sheets may also contain acrylic resin. The acrylic resin is not particularly limited. Examples of monomers used in 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. The acrylic resin may be used alone or in combination of two or more types.

[0040] Acrylic resins may have constituent units derived from monomers other than acrylic monomers. Examples of other monomers include ethylene, propylene, and styrene. These other monomers may be used individually or in combination of two or more.

[0041] When using acrylic resin, it may be used as an acrylic-modified epoxy resin obtained by grafting acrylic resin onto an epoxy resin. In coating compositions for electrical steel sheets, it may be included as a monomer that forms the acrylic resin.

[0042] As the epoxy resin curing agent included in the second insulating coating 3B, latent heat-curing type agents can be used, such as aromatic polyamines, acid anhydrides, phenolic curing agents, dicyandiamides, boron trifluoride-amine complexes, and organic acid hydrazides. Examples of aromatic polyamines include metaphenylenediamine, diaminodiphenylmethane, and diaminodiphenylsulfone. Examples of phenolic curing agents include phenol novolac resins, cresol novolac resins, bisphenol novolac resins, triazine-modified phenol novolac resins, and phenol resol resins. Among these, phenolic curing agents are preferred as epoxy resin curing agents, and phenol resol resins are more preferred. One type of epoxy resin curing agent may be used alone, or two or more types may be used in combination.

[0043] The amount of epoxy resin curing agent in the coating composition for electromagnetic steel sheets that forms the second insulating film 3B 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.

[0044] A urethane prepolymer is a urethane resin composed of a reaction product of diisocyanate and polyol, and having only one of either an isocyanate group or a hydroxyl group at the end of its molecular chain. In other words, in a urethane prepolymer, all terminal groups are either isocyanate groups or hydroxyl groups, and it is preferable that the terminal groups are hydroxyl groups.

[0045] The diisocyanate is not particularly limited, and examples include hexamethylene diisocyanate, diphenylmethane diisocyanate, and tolylene diisocyanate. Among these, 4,4'-diphenylmethane diisocyanate is preferred from the viewpoint of workability. One type of diisocyanate may be used alone, or two or more types may be used in combination.

[0046] Polyols used to form urethane prepolymers include polyether-based, polyester-based, polycarbonate-based, and aliphatic-based polyols, which are commercially available. However, in this invention, polyether polyol or polyester polyol is used. Specifically, the coating composition for electrical steel sheets contains either a reaction product (prepolymer) of polyether polyol and diisocyanate, or a reaction product (prepolymer) of polyester polyol and diisocyanate, or both, as the urethane prepolymer.

[0047] Polyether polyols are obtained by polymerizing polyhydric alcohols with ethylene oxide or propylene oxide, and relatively high molecular weight linear polyols are preferred. Examples of polyether polyols include polyethylene glycol, polypropylene glycol, polyethylene propylene glycol, and polytetramethylene glycol. Among these, polytetramethylene glycol is preferred from the viewpoint of hydrolysis resistance. Polyether polyols may be used individually or in combination of two or more.

[0048] Examples of polyester polyols include those obtained by condensation polymerization of a carboxylic acid or its derivative (such as an acid anhydride or acid halide) with a diol. The carboxylic acids and their derivatives are not particularly limited and include, for example, succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, maleic anhydride, fumaric acid, 1,3-cyclopentanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, terephthalic acid, isophthalic acid, phthalic anhydride, orthophthalic acid, naphthalenedicarboxylic acid, biphenyldicarboxylic acid, and polycaprolactone. Among these, polycaprolactone is preferred from the viewpoint of heat resistance. Dicarboxylic acids and their derivatives may be used individually or in combination of two or more.

[0049] The diol is not particularly limited and examples include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, 3-methyl-1,5-pentanediol, 2-butyl-2-ethyl-1,3-propanediol, 2-methyl-1,3-propanediol, 1,4-cyclohexanediol, and 1,4-cyclohexanedimethanol. Among these, 1,4-butanediol is preferred because its molecular weight is easy to control. The diol may be used alone or in combination of two or more types. Polyester polyols may be used individually or in combination of two or more types.

[0050] The polyol used in the urethane prepolymer may include, in addition to polyether polyol or polyester polyol, other polyols such as polycarbonate polyol or those exemplified as diols constituting polyester polyol, as long as the effects of the present invention are not impaired. In terms of easily obtaining the effects of the present invention, the polyol used in the urethane prepolymer is preferably either polyether polyol or polyester polyol, or a combination of either of them with 1,4-butanediol.

[0051] The urethane prepolymer content in the coating composition for electrical steel sheets is 5 parts by mass or more and 40 parts by mass or less per 100 parts by mass of epoxy resin. If the urethane prepolymer content is within the above range, a laminated core with excellent magnetic properties can be obtained. The lower limit of the urethane prepolymer content is preferably 10 parts by mass, more preferably 20 parts by mass, per 100 parts by mass of epoxy resin. The upper limit of the urethane prepolymer content is preferably 39 parts by mass, more preferably 38 parts by mass, per 100 parts by mass of epoxy resin.

[0052] The coating composition for electrical steel sheets may contain other components besides epoxy resin, epoxy resin curing agent, and urethane prepolymer, as long as they do not impair the effects of the present invention. Examples of other components include curing accelerators (curing catalysts), emulsifiers, defoamers, minerals, and the like.

[0053] Since the second insulating coating 3B of this embodiment contains a curing agent, its average pencil hardness is relatively higher than that of the first insulating coating 3A, which does not contain a curing agent. Furthermore, the following configuration A or B can be adopted as a means to finely adjust the average pencil hardness of the second insulating coating 3B.

[0054] [Configuration A] In this configuration A, the average pencil hardness of the second insulating coating 3B is adjusted by changing the combination of the main agent and the hardener contained in the second insulating coating 3B, or by changing the mixing ratio of the hardener contained in the second insulating coating 3B. [Configuration B] In this configuration B, the combination of the main component and the hardener contained in the second insulating coating 3B is fixed, and the equivalent ratio of the hardener to the main component contained in the second insulating coating 3B is constant. Under these conditions, the combination of the curing temperature and curing time of the second insulating coating 3B is changed. In other words, even at the same curing temperature, increasing the curing time increases the average pencil hardness (hardness). Similarly, even at the same curing time, increasing the curing temperature increases the average pencil hardness (hardness). In this configuration B, under the condition that the combination of main agent and hardener contained in the second insulating coating 3B and the equivalent ratio of the hardener are constant, the average pencil hardness of the second insulating coating 3B is adjusted by changing the combination of curing temperature and curing time of the second insulating coating 3B.

[0055] In either configuration A or B described above, the second surface 2b of the base steel plate 2 can be covered with a relatively hard second insulating coating 3B, thereby exhibiting high slit resistance and scratch resistance. On the other hand, the first surface 2a is covered with a relatively soft first insulating coating 3A, ensuring sufficient adhesive strength. Therefore, it is possible to achieve both adhesive strength for forming a laminated core and high slit resistance and scratch resistance.

[0056] The upper and lower limits of the average thickness t1 of the first insulating film 3A and the second insulating film 3B are set, for example, as follows. Note that the average thickness t1 may be the same for the first insulating film 3A and the second insulating film 3B. Alternatively, the average thickness t1 may be different for the first insulating film 3A and the second insulating film 3B, as long as the difference in average pencil hardness between them is maintained. When material 1 is used as an electrical steel sheet 40, the average thickness t1 (thickness per side of the electrical steel sheet 40 (material 1)) of the first insulating coating 3A and the second insulating coating 3B is adjusted to ensure insulation performance and adhesive performance between the electrical steel sheets 40 that are laminated together. When the first insulating film 3A and the second insulating film 3B are single-layer structures, their average thickness t1 (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. On the other hand, when the first insulating film 3A and the second insulating film 3B have a multi-layer structure, the average thickness of the base insulating film can be, for example, 0.3 μm or more and 1.2 μm or less. The average thickness of the base insulating film 3b is preferably 0.7 μm or more and 0.9 μm or less. The average thickness of the top insulating film can be, for example, 1.5 μm or more and 8.0 μm or less. Furthermore, the method for measuring the average thickness t1 of the first insulating coating 3A and the second insulating coating 3B in material 1 is the same as for the average plate thickness t0 of material 1; for example, the thickness can be determined at 10 points and then the average of those thicknesses can be used to determine the average thickness t1.

[0057] The upper and lower limits for the average thickness t1 of the first insulating film 3A and the second insulating film 3B in this material 1 can also be used as the upper and lower limits for the average thickness t1 of the first insulating film 3A and the second insulating film 3B in the electromagnetic steel sheet 40. The method for measuring the average thickness t1 of the first insulating film 3A and the second insulating film 3B in the electromagnetic steel sheet 40 is, for example, the following measurement method. For example, among the multiple electromagnetic steel sheets 40 that form the laminated core, select the electromagnetic steel sheet 40 located on the outermost side in the lamination direction (the electromagnetic steel sheet 40 whose surface is exposed in the lamination direction). On the surface of the selected electromagnetic steel sheet 40, select a predetermined position in the radial direction (for example, the position exactly midway (center) between the inner edge and the outer edge of the electromagnetic steel sheet 40). At the selected position, determine the thickness at, for example, 10 points. Measure these at four locations in the circumferential direction of the electromagnetic steel sheet 40 at equal intervals (i.e., every 90 degrees around the central axis O). The average of the thicknesses measured at four locations can be taken as the average thickness t1 of the first insulating coating 3A and the second insulating coating 3B. The reason why the average thickness t1 of the first insulating film 3A and the second insulating film 3B was measured on the outermost electrical steel sheet 40 in the lamination direction is that the first insulating film 3A and the second insulating film 3B are manufactured in such a way that their thicknesses hardly change at the lamination position along the lamination direction of the electrical steel sheet 40.

[0058] Multiple sheets of electromagnetic steel 40 are produced by punching material 1 as described above multiple times, and laminated cores (stator core 21 and rotor core 31) are produced by laminating these electromagnetic steel sheets 40. This laminated core is manufactured using electromagnetic steel 40 that can achieve both sufficient adhesive strength and high resistance to powdering and slitting, resulting in high rigidity and good yield.

[0059] (Layer stacking method for stacked cores) The following is a description of the laminated core. The multiple electromagnetic steel sheets 40 forming the stator core 21 are laminated via a first insulating coating 3A and a second insulating coating 3B, as shown in Figure 2. Adjacent electrical steel sheets 40 in the lamination direction are bonded together over their entire surface, mainly by the adhesive properties of the first insulating coating 3A. In other words, the surface of the electrical steel sheet 40 facing the lamination direction (hereinafter referred to as the first surface) is an adhesive region over its entire surface. However, adjacent electrical steel sheets 40 in the lamination direction do not necessarily have to be bonded together over their entire surface. In other words, the first surface of the electrical steel sheet 40 may contain a mixture of adhesive and non-adhesive regions.

[0060] In this embodiment, the multiple electromagnetic steel sheets forming the rotor core 31 are fixed to each other by the crimping 42 (dowels) shown in Figure 1. However, the multiple 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 rotor core 31 may be formed by a so-called spiral stacking method.

[0061] (Method of manufacturing a laminated core) Next, we will explain the manufacturing method (hereinafter also simply referred to as the manufacturing method) for the laminated core that produces the stator core 21 configured as described above. Figure 6 shows a side view of a laminated core manufacturing apparatus 100 (hereinafter simply referred to as manufacturing apparatus 100) that is preferably used in this manufacturing method. In the manufacturing apparatus 100, the material 1 is fed from the coil 1A (hoop) in the direction of arrow F, and multiple punching operations are performed by dies positioned at each stage to gradually form the shape of the electromagnetic steel sheet 40. Then, the punched electrical steel sheets 40 are stacked on top of several already stacked electrical steel sheets 40, and then pressurized while the temperature is increased. When stacking each electrical steel sheet 40, the top and bottom orientations of the first insulating coating 3A and the second insulating coating 3B are the same. That is, the first insulating coating 3A is placed on the upper surface of each electrical steel sheet 40, and the second insulating coating 3B is placed on the lower surface. Alternatively, the second insulating coating 3B is placed on the upper surface of each electrical steel sheet 40, and the first insulating coating 3A is placed on the lower surface.

[0062] Then, the first insulating film 3A or the second insulating film 3B on the upper surface of the electrical steel sheet 40 located relatively below it overlaps with the second insulating film 3B or the first insulating film 3A on the lower surface of the other electrical steel sheet 40 that is placed on top of this electrical steel sheet 40, and they bond (or fuse) together. At this time, the adhesive force of the second insulating film 3B is relatively weak because it is hard, but the first insulating film 3A is soft and can exhibit high adhesive force. Therefore, the adhesive force between each electrical steel sheet 40 is sufficiently maintained, so the rigidity of the laminated core can be increased. On the other hand, because the second insulating film 3B is hard, powder generation and slitting during punching and transport are less likely to occur. Therefore, the effort of removing powder can be saved, and productivity can be increased. As described above, adjacent electrical steel sheets 40 in the lamination direction are bonded (fused) together by the first insulating coating 3A and the second insulating coating 3B.

[0063] As shown in Figure 6, the manufacturing apparatus 100 has multiple punching stations. These punching stations may have two stages, or three or more stages. To illustrate with an example of a three-stage punching station, the manufacturing apparatus 100 includes a first-stage punching station 110 located closest to the coil 1A, a second-stage punching station 120 located adjacent to the first-stage punching station 110 downstream along the material 1 transport direction, and a third-stage punching station 130 located adjacent to the first-stage punching station 120 downstream along the material 1 transport direction. The punching station 110 includes a female die 111 positioned below the material 1 and a male die 112 positioned above the material 1. The punching station 120 includes a female die 121 positioned below the material 1 and a male die 122 positioned above the material 1. The punching station 130 includes a female die 131 positioned below the material 1 and a male die 132 positioned above the material 1. Furthermore, the punching station may be set up in three or more stages.

[0064] The manufacturing apparatus 100 further includes a stacking station 140 located downstream of the second-stage punching station 120. This stacking station 140 includes a heating device 141, an outer-circumferential female punching die 142, a heat insulating member 143, an outer-circumferential male punching die 144, and a spring 145. The heating device 141, the outer peripheral punching female die 142, and the heat insulating member 143 are located below the material 1. On the other hand, the outer peripheral punching male die 144 and the spring 145 are located above the material 1. Reference numeral 21 indicates the stator core.

[0065] In this example, in addition to lamination of the electromagnetic steel sheets 40, pressure and heating are also performed to bond them, but the present invention is not limited to the apparatus and method of this example. For example, the manufacturing apparatus 100 may perform the lamination of the electromagnetic steel sheets 40, and the bonding between each electromagnetic steel sheet 40 may be performed in a later process by a separate apparatus. In this case, the heating device 141 and the heat insulating member 143 are not required in the manufacturing apparatus 100 and will be equipped in the separate apparatus. In this case, before moving the stator core 21 in an unbonded state from the manufacturing apparatus 100 to the separate apparatus, it is preferable to fix the positions of each electromagnetic steel sheet 40 with a jig (not shown) to prevent misalignment between them.

[0066] In the manufacturing apparatus 100 having the configuration described above, first, material 1 is sequentially fed from coil 1A in the direction of arrow F in Figure 6. Then, punching is performed on this material 1 by punching station 110. Next, punching is performed on this material 1 by punching station 120. Furthermore, punching is performed on this material 1 by punching station 130. By sequentially performing these punching processes, the material 1 is given the shape of an electromagnetic steel sheet 40 having a core back portion 22 and multiple tooth portions 23 as shown in Figure 3. However, since it is not completely punched at this point, the process proceeds to the next step along the direction of arrow F.

[0067] Finally, material 1 is sent to the lamination station 140, where it is punched out by the outer peripheral punching die 144 and laminated with precision. During this lamination, the electromagnetic steel sheets 40 are subjected to a constant pressure by the spring 145. By sequentially repeating the punching process and the lamination process 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 to, for example, 200°C by the heating device 141. This heating hardens the first insulating film 3A and the second insulating film 3B, and the electromagnetic steel sheets 40 are bonded together. The stator core 21 is completed through the above steps. [Examples]

[0068] Using the manufacturing apparatus 100 shown in Figure 6, the above-mentioned stator core 21 (hereinafter referred to as "stator core") was manufactured using non-oriented electrical steel sheets with a thickness of 0.25 mm while varying various manufacturing conditions, and the adhesive strength and degree of coating damage of the stator core were evaluated. More specifically, the average pencil hardness was adjusted for each of the first insulating coating 3A (front surface) and the second insulating coating 3B (back surface) by changing the combination or equivalent ratio of the main agent and hardener. The results are summarized in Tables 1 and 2. The heating conditions for all stator cores were kept the same, with a heating temperature of 200°C and a heating time of 30 minutes.

[0069] As shown in Table 1, in No. 1 and 2, the presence or absence of curing agent was changed between the first insulating coating 3A and the second insulating coating 3B under the same baking conditions. Furthermore, for Nos. 3-12 and 14 and 15, not only were the formulations of the main agent and hardener changed, but the baking conditions were also modified. For No. 13, the formulations of the main agent and hardener were changed, and the baking condition pattern remained the same. This is an example of the invention. 2,3,5 ~12 And examples No. 1 and 4. In all cases, the equivalent ratio of the second insulating coating 3B to the organic resin phase (main component) is within the range of 0.8 to 1.5.

[0070] [Table 1]

[0071] Stator cores were manufactured with a first insulating coating 3A and a second insulating coating 3B having these combinations, and their adhesive strength and degree of coating damage were measured. The adhesive strength was measured by the maximum load at which the laminated surfaces separated and the iron core was separated by pressing a wedge into the center of the laminated surface. The wedge used had a tip angle of 7 degrees. This wedge was then pressed into the center of the stator core in the lamination direction. In Table 1, a higher adhesive strength value is preferable as it indicates higher stator core rigidity. In Table 1, the criteria for judging adhesive strength were as follows: less than 980N is "unacceptable," 980N to 1450N is "acceptable," and greater than 1450N is "good." The degree of coating damage was determined by pressing material 1 against a steel plate support roll on the factory line and rubbing it against the material, visually inspecting the degree of damage to the second insulating coating 3B. Based on the degree of damage, it was judged as "unacceptable," "acceptable," "good," or "excellent." Here, the degree of coating damage is used as an evaluation criterion for judging slit resistance and scratch resistance. The results for adhesive strength and the degree of damage to the back surface coating are shown in Table 2 below.

[0072] [Table 2]

[0073] Invention example No. 2,3,5 ~12 And examples No. 1 and 4. In this study, both the adhesive strength and the degree of film damage were evaluated as favorable. On the other hand, in comparative example No. 13, neither the first insulating coating 3A nor the second insulating coating 3B contained a curing agent, resulting in a high degree of coating damage and rendering it unsuitable. Furthermore, in comparative example No. 14, a curing agent was included in both the first insulating film 3A and the second insulating film 3B. As a result, the first insulating film 3A hardened, making it impossible to secure the required adhesive strength, thus rendering it unsuitable. In comparative example No. 15, the first insulating coating 3A contained a curing agent, while the second insulating coating 3B did not. As a result, the second insulating coating 3B was too soft, leading to a high degree of coating damage and rendering it unsuitable.

[0074] Although one embodiment of the present invention and its examples have been described in detail above with reference to the drawings, the specific configuration is not limited to these embodiments and examples, and may include modifications, combinations, deletions, etc. of the configuration that do not depart from the spirit of the present invention. For example, the shape of the stator core 21 is not limited to the form shown in the above embodiment. Specifically, the outer and inner diameters of the stator core 21, the stacking thickness, the number of slots, the circumferential and radial dimensional ratios of the teeth portion 23, and the radial dimensional ratio between the teeth portion 23 and the core back portion 22 can be arbitrarily designed according to the desired characteristics of the rotating electric machine. In the rotor 30 of the above embodiment, a pair of permanent magnets 32 form one magnetic pole, but the present invention is not limited to this form. For example, one permanent magnet 32 ​​may form one magnetic pole, or three or more permanent magnets 32 may form one magnetic pole.

[0075] In the above embodiment, a permanent magnet field type motor was used as an example to describe the rotating electric machine 10, but the present invention is not limited to this. For example, the rotating electric machine 10 may be a reluctance type motor or an electromagnet field type motor (wound field type motor). In the above embodiment, a synchronous motor was used as an example of an AC motor, but the present invention is not limited thereto. For example, the rotating electric machine 10 may be an induction motor. In the above embodiment, an AC motor was used as an example of the rotating electric machine 10, but the present invention is not limited thereto. For example, the rotating electric machine 10 may be a DC motor. In the above embodiment, an electric motor was used as an example of the rotating electric machine 10, but the present invention is not limited thereto. For example, the rotating electric machine 10 may be a generator. [Explanation of symbols]

[0076] 1 Material (electromagnetic steel sheet) 2 Base steel plate 3A First insulating coating 3B Second insulating coating 21 Stator core (stacked core) 40 Electrical steel sheet

Claims

1. Base material steel plate, A first insulating coating formed on the first surface of the base steel sheet and having adhesive properties, A second insulating coating having adhesive properties is formed on the second surface, which is the back surface of the first surface of the base steel sheet, Equipped with, The first insulating film consists of an organic resin phase containing at least one of epoxy resin, phenolic resin, and urethane prepolymer. The second insulating film contains an organic resin phase comprising at least one of epoxy resin, phenolic resin, and urethane prepolymer, and a curing agent. The average pencil hardness of the first insulating film is H or more and 3H or less. The average pencil hardness of the second insulating coating is higher than the average pencil hardness of the first insulating coating. An electrical steel sheet characterized by the following features.

2. The equivalent ratio of the curing agent to the organic resin phase in the second insulating film is 0.8 to 1.

5. The electrical steel sheet according to feature 1.

3. A laminated core characterized by being formed by laminating two or more electromagnetic steel sheets as described in claim 1 or 2.

Images