JP2021195606A - Coating composition for electromagnetic steel sheet, electromagnetic steel sheet, laminate core, and rotary electrical machinery - Google Patents

Abstract

To provide a coating composition for electromagnetic steel sheet capable of compatibly having both magnetic characteristics of a laminate core and heat resistance capable of maintaining contact strength between electromagnetic steel sheets even in a high-temperature state during driving, an electromagnetic steel sheet using the same, a laminate core, and rotary electrical machinery.SOLUTION: An electromagnetic steel sheet used for a laminate core is an electromagnetic steel sheet which has a surface of a base material steel sheet 2 covered with an insulation coating 3 formed by applying a coating composition for electromagnetic steel sheet, wherein the coating composition for electromagnetic steel sheet has a urethane prepolymer mixed at a specific ratio with epoxy resin and an epoxy resin hardener, and the urethane prepolymer contains one or both of a reactant of diisocyanate and polyether polyol and a reactant of diisocyanate and polyester polyol, and has one of an isocyanate group and a hydroxy group at a terminal, the number average molecular weight being 2,000-50,000.SELECTED DRAWING: Figure 5

Description

The present invention relates to a coating composition for an electromagnetic steel sheet, an electromagnetic steel sheet, a laminated core, and a rotary electric machine.

As a core (iron core) used in a rotary electric machine, a laminated core in which a plurality of electromagnetic steel sheets are joined to each other and laminated is known. Caulking and welding are known as methods for joining electrical steel sheets to each other. However, in caulking and welding, the magnetic properties (core iron loss) of electrical steel sheets tend to deteriorate due to mechanical strain and thermal strain during processing.

As a joining method other than caulking and welding, for example, a method of bonding electromagnetic steel sheets having an insulating film having an adhesive ability on the surface to each other is known (Patent Document 1). Adhesion using the insulating film does not give mechanical strain or thermal strain, so it is superior in core iron loss as compared with caulking and welding. Epoxy resin has little volume change, is excellent in heat resistance, oil resistance, and chemical resistance, and is very excellent as an adhesive for adhering electromagnetic steel sheets to each other.

In recent years, in response to a request for further improvement of motor efficiency, further reduction of core iron loss is required. Thinning of electrical steel sheets is an effective way to reduce core iron loss. However, since the Young's modulus of a steel sheet decreases as the plate thickness decreases, it is required not to apply stress strain to the steel sheet, which causes deterioration of iron loss. Since epoxy resin is hard and has low toughness, stress strain is applied to the steel sheet by hardening during bonding, and thinning of the steel sheet causes iron loss deterioration. Further, if the toughness is low, the adhesive may be peeled off due to the vibration impact during driving. In particular, in applications such as motors for electric vehicles, it is important to have heat resistance that can maintain sufficient adhesive strength even when exposed to high temperatures during driving.

Japanese Unexamined Patent Publication No. 2000-173816

INDUSTRIAL APPLICABILITY The present invention relates to a coating composition for electrical steel sheets that can achieve both the magnetic properties of a laminated core and heat resistance that can maintain the adhesive strength between electromagnetic steel sheets even in a high temperature state during driving, an electromagnetic steel sheet using the same, a laminated core, and rotation. The purpose is to provide electrical equipment.

The present invention has the following configurations.
[1] An epoxy resin, an epoxy resin curing agent, and a urethane prepolymer are contained, and the urethane prepolymer is either a reaction product of a diisocyanate and a polyether polyol or a reaction product of a diisocyanate and a polyester polyol. A coating composition for an electromagnetic steel plate, which contains either or both, and the urethane prepolymer has either an isocyanate group or a hydroxyl group at the terminal and has a number average molecular weight of 2000 or more and 50,000 or less.
[2] The coating composition for electrical steel sheets according to [1], wherein the content of the urethane prepolymer is 5 parts by mass or more and 40 parts by mass or less with respect to 100 parts by mass of the epoxy resin.
[3] An electromagnetic steel sheet having an insulating film on the surface coated with the coating composition for electrical steel sheets according to [1] or [2].
[4] A laminated core in which a plurality of electrical steel sheets according to [3] are laminated and bonded to each other.
[5] A rotary electric machine provided with the laminated core according to [4].

According to the present invention, a coating composition for electrical steel sheets that can achieve both the magnetic properties of a laminated core and heat resistance that can maintain the adhesive strength between electromagnetic steel sheets even in a high temperature state during driving, an electromagnetic steel sheet using the same, and a laminated core. And rotary electric machines can be provided.

It is sectional drawing of the rotary electric machine provided with the laminated core which concerns on 1st Embodiment of this invention. It is a side view of the laminated core. FIG. 2 is a cross-sectional view taken along the line AA of FIG. It is a top view of the material which forms the laminated core. FIG. 4 is a cross-sectional view taken along the line BB of FIG. It is an enlarged view of the part C of FIG. It is a side view of the manufacturing apparatus used for manufacturing the laminated core.

Hereinafter, with reference to the drawings, a laminated core according to an embodiment of the present invention, a rotary electric machine provided with the laminated core, and a material forming the laminated core will be described. In this embodiment, an electric motor as a rotary electric machine, specifically an AC electric motor, more specifically a synchronous electric motor, and more specifically, a permanent magnet field type electric motor will be described as an example. This type of motor is suitably adopted for, for example, an electric vehicle.

(Rotating machine 10)
As shown in FIG. 1, the rotary electric machine 10 includes a stator 20, a rotor 30, a case 50, and a rotary shaft 60. The stator 20 and the rotor 30 are housed in the case 50. The stator 20 is fixed in the case 50.
In the present embodiment, the rotary electric machine 10 adopts an inner rotor type in which the rotor 30 is located inside the stator 20 in the radial direction. However, as the rotary electric machine 10, an outer rotor type in which the rotor 30 is located outside the stator 20 may be adopted. Further, in the present embodiment, the rotary electric machine 10 is a 12-pole 18-slot three-phase AC motor. However, the number of poles, the number of slots, the number of phases, and the like can be changed as appropriate.
The rotary electric machine 10 can rotate at a rotation speed of 1000 rpm, for example, by applying an exciting current having an effective value of 10 A and a frequency of 100 Hz to each phase.

The stator 20 includes an adhesive laminated core for a stator (hereinafter referred to as a stator core) 21 and a winding not shown.
The stator core 21 includes an annular core back portion 22 and a plurality of teeth portions 23. In the following, the central axis O direction of the stator core 21 (or core back portion 22) is referred to as an axial direction, and the radial direction of the stator core 21 (or core back portion 22) (direction orthogonal to the central axis O) is referred to as a radial direction. The circumferential direction of the stator core 21 (or core back portion 22) (direction that orbits around the central axis O) is referred to as a circumferential direction.

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

The rotor 30 is arranged radially inside the stator 20 (stator core 21). The rotor 30 includes a rotor core 31 and a plurality of permanent magnets 32.
The rotor core 31 is formed in an annular shape (annular ring) arranged coaxially with the stator 20. The rotating shaft 60 is arranged in 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 set of two permanent magnets 32 form one magnetic pole. The plurality of sets of permanent magnets 32 are arranged at equal angular intervals in the circumferential direction. In this embodiment, 12 sets (24 in total) of permanent magnets 32 are provided at every 30 degrees of the central angle centered on the central axis O.

In this embodiment, an embedded magnet type motor is adopted as a permanent magnet field type motor. The rotor core 31 is formed with 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 in a state of being arranged in the corresponding through hole 33. The fixing of each permanent magnet 32 to the rotor core 31 can be realized, for example, by adhering the outer surface of the permanent magnet 32 and the inner surface of the through hole 33 with an adhesive. As the permanent magnet field type motor, a surface magnet type motor may be adopted instead of the embedded magnet type.

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 sheets 40 in the laminating direction.
The product 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 examples, and the product thickness, outer diameter and inner diameter of the stator core 21, and the product thickness, outer diameter and inner diameter of the rotor core 31 are not limited to these values. Here, the inner diameter of the stator core 21 is based on the tip end portion of the teeth 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 tips of all the teeth portions 23.

Each of the electromagnetic steel sheets 40 forming the stator core 21 and the rotor core 31 is formed, for example, by punching the material 1 as shown in FIGS. 4 to 6. Material 1 is a steel sheet (electrical steel sheet) that is a base material of the electromagnetic steel sheet 40. Examples of the material 1 include strip-shaped steel plates and cut plates.
Although the explanation of the laminated core is in the middle, the material 1 will be described below. In the present specification, the strip-shaped steel sheet that is the base material of the electromagnetic steel sheet 40 may be referred to as material 1. A steel sheet having a shape used for a laminated core by punching the material 1 may be referred to as an electromagnetic steel sheet 40.

(Material 1)
The material 1 is handled, for example, in a state of being wound around the coil 1A shown in FIG. 7. In this embodiment, non-oriented electrical steel sheets are used as the material 1. As the non-oriented electrical steel sheet, JIS C 2552: 2014 non-oriented electrical steel sheet can be adopted. However, as the material 1, a grain-oriented electrical steel sheet may be used instead of the non-oriented electrical steel sheet. As the grain-oriented electrical steel sheet in this case, JIS C 2553: 2019 grain-oriented electrical steel sheet can be adopted. Further, a non-oriented thin electromagnetic steel strip or a directional thin electromagnetic steel strip of JIS C 2558: 2015 can be adopted.

The upper and lower limit values of the average plate thickness t0 of the material 1 are set as follows, for example, in consideration of the case where the material 1 is used as the electromagnetic steel sheet 40.
As the material 1 becomes thinner, the manufacturing cost of the material 1 increases. Therefore, in consideration of the manufacturing cost, 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 becomes good, but when the material 1 is used as the electromagnetic steel sheet 40, the eddy current loss increases and the core iron loss deteriorates. Therefore, considering the core iron loss and the manufacturing cost, the upper limit of the average plate thickness t0 of the material 1 is 0.65 mm, preferably 0.35 mm, and more preferably 0.30 mm.
0.20 mm can be exemplified as a material that satisfies the above range of the average plate thickness t0 of the material 1.

The average plate thickness t0 of the material 1 includes not only the thickness of the base steel plate 2 described later but also the thickness of the insulating coating 3. Further, the method for measuring the average plate thickness t0 of the material 1 is, for example, the following measuring method. For example, when the material 1 is wound into the shape of the coil 1A, at least a part of the material 1 is unwound into a flat plate shape. In the material 1 unraveled into a flat plate shape, a predetermined position in the longitudinal direction of the material 1 (for example, a position 10% of the total length of the material 1 away from the longitudinal edge of the material 1) is selected. do. At this selected position, the material 1 is divided into five regions along the width direction thereof. The plate thickness of the material 1 is measured at four locations that are boundaries of these five regions. The average value of the plate thicknesses at the four locations can be set to the average plate thickness t0 of the material 1.

The upper and lower limit values of the average plate thickness t0 of the material 1 can be naturally adopted as the upper and lower limit values of 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 measuring method. For example, the thickness of the laminated core is measured at four locations (that is, every 90 degrees around the central axis O) at equal intervals in the circumferential direction. Each of the measured product thicknesses at the four locations is divided by the number of laminated electromagnetic steel sheets 40 to calculate the plate thickness per sheet. The average value of the plate thicknesses at the four locations can be set to the average plate thickness t0 of the electromagnetic steel sheet 40.

As shown in FIGS. 5 and 6, the material 1 includes a base steel plate 2 and an insulating coating 3. The material 1 is formed by covering both sides of a strip-shaped base steel plate 2 with an insulating coating 3. In the present embodiment, most of the material 1 is formed of the base steel plate 2, and the insulating film 3 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 contains 2.5% to 4.5% Si in mass%, as shown below in units of mass%. By setting the chemical composition within this range, the yield strength of the material 1 (electrical steel sheet 40) can be set to, for example, 380 MPa or more and 540 MPa or less.

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

When the material 1 is used as the electrical steel sheet 40, the insulating film 3 exhibits insulation performance between the electrical steel sheets 40 adjacent to each other in the stacking direction. Further, in the present embodiment, the insulating coating 3 has an adhesive ability and adheres the electromagnetic steel sheets 40 adjacent to each other in the laminating 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 having both insulating performance and adhesive ability, and may include a base insulating coating having excellent insulating performance and a ground insulating coating having excellent adhesive performance. It may have a multi-layer structure including.

In the present embodiment, the insulating coating 3 covers both sides of the base steel plate 2 without gaps over the entire surface. However, as long as the above-mentioned insulating performance and adhesive ability are ensured, a part of the layers of the insulating coating 3 may not cover both sides of the base steel plate 2 without gaps. In other words, a part of the layer of the insulating film 3 may be intermittently provided on the surface of the base steel sheet 2. However, in order to ensure the insulating performance, both sides of the base steel plate 2 need to be covered with the insulating film 3 so that the entire surface is not exposed. Specifically, when the insulating coating 3 does not have a base insulating coating having excellent insulating performance and has a single-layer structure having both insulating performance and adhesive ability, the insulating coating 3 has no gap over the entire surface of the base steel plate 2. Must be formed. On the other hand, when the insulating film 3 has a multi-layer structure including a base insulating film having excellent insulating performance and a ground insulating film having excellent adhesiveness, both the base insulating film and the ground insulating film are used as a base steel sheet. In addition to forming the base insulating film without gaps over the entire surface of No. 2, even if the base insulating film is formed without gaps over the entire surface of the base steel sheet and the upper ground insulating film is intermittently provided, both the insulating performance and the adhesive ability can be achieved.

The coating composition for forming the base insulating film is not particularly limited, and for example, a known base treatment agent can be used without limitation. As a specific example, a general treatment agent such as a chromic acid-containing treatment agent or a phosphate-containing treatment agent can be used.

The insulating coating 3 having an adhesive ability is formed by applying a coating composition for an electromagnetic steel sheet described below on a base steel sheet.
The insulating film made of the coating composition for electrical steel sheets is in an uncured or semi-cured state (B stage) before heat crimping at the time of manufacturing a laminated core, and the curing reaction proceeds by heating during heat crimping to adhere. Noh develops.

The coating composition for an electromagnetic steel plate contains an epoxy resin, an epoxy resin curing agent, and a urethane prepolymer.

As the epoxy resin, a 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 limitation. 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, and glycidyl amine type epoxy. Examples thereof include resins, hydride-in type epoxy resins, isocyanurate type epoxy resins, acrylic acid-modified epoxy resins (epoxy acrylates), phosphorus-containing epoxy resins, halides thereof (bromination epoxy resins and the like), hydrogen additives and the like. As the epoxy resin, one type may be used alone, or two or more types may be used in combination.

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

The acrylic resin may have a structural unit derived from a monomer other than the acrylic monomer. Examples of other monomers include ethylene, propylene, styrene and the like. As the other monomer, one type may be used alone, or two or more types may be used in combination.

When an acrylic resin is used, it may be used as an acrylic modified epoxy resin obtained by grafting an acrylic resin onto an epoxy resin. In the coating composition for electrical steel sheets, it may be contained as a monomer forming an acrylic resin.

As the epoxy resin curing agent, a heat-curing type having potential can be used. For example, aromatic polyamines, acid anhydrides, phenolic curing agents, dicyandiamides, boron trifluoride-amine complexes, and organic acid hydrazides can be used. And so on. Examples of the aromatic polyamine include meta-phenylenediamine, diaminodiphenylmethane, diaminodiphenyl sulfone and the like. Examples of the phenol-based curing agent include phenol novolac resin, cresol novolak resin, bisphenol novolak resin, triazine-modified phenol novolac resin, phenol resol resin and the like.

From the viewpoint of pot life, the epoxy resin curing agent is preferably a phenolic curing agent, an aromatic polyamine, or a dicyandiamide, and more preferably a phenol resol resin or an aromatic polyamine. As the epoxy resin curing agent, one type may be used alone, or two or more types may be used in combination.

The lower limit of the content of the epoxy resin curing agent in the coating composition for electrical steel sheets is preferably 1 part by mass, more preferably 3 parts by mass with respect to 100 parts by mass of the epoxy resin. The upper limit of the content of the epoxy resin curing agent is preferably 20 parts by mass, more preferably 15 parts by mass.

The urethane prepolymer is a urethane resin composed of a reaction product of diisocyanate and a polyol and having only one of an isocyanate group and a hydroxyl group at the end of a molecular chain. That is, in the urethane prepolymer, it is preferable that all the terminal groups are either isocyanate groups or hydroxyl groups, and the terminals are hydroxyl groups.

The diisocyanate is not particularly limited, and examples thereof include hexamethylene diisocyanate, diphenylmethane diisocyanate, and tolylene diisocyanate. Of these, 4,4'-diphenylmethane diisocyanate is preferable from the viewpoint of workability. As the diisocyanate, one type may be used alone, or two or more types may be used in combination.

As the polyol forming the urethane prepolymer, polyether-based, polyester-based, polycarbonate-based, aliphatic-based and the like are commercially available, but in the present invention, a polyether polyol or a polyester polyol is used. That is, the coating composition for an electromagnetic steel plate is, as a urethane prepolymer, either a reaction product of a polyether polyol and a diisocyanate (prepolymer), a reaction product of a polyester polyol and a diisocyanate (prepolymer), or both of them. Contains both.

Examples of the polyether polyol include those obtained by polymerizing ethylene oxide or propylene oxide with a polyhydric alcohol, and a straight chain having a relatively high molecular weight is preferable. Examples of the polyether polyol include polyethylene glycol, polypropylene glycol, polyethylene propylene glycol, polytetramethylene glycol and the like. Of these, polytetramethylene glycol is preferable from the viewpoint of hydrolysis resistance. As the polyether polyol, one kind may be used alone, or two or more kinds may be used in combination.

Examples of the polyester polyol include those obtained by polycondensing a carboxylic acid or a derivative thereof (acid anhydride, acid halide, etc.) and a diol.
The carboxylic acid and its derivative are not particularly limited, and are, for example, succinic acid, adipic acid, azelaic acid, sebacic acid, dodecandicarboxylic 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, polycaprolactone and the like can be mentioned. Of these, polycaprolactone is preferable from the viewpoint of heat resistance. As the dicarboxylic acid and its derivative, one kind may be used alone, or two or more kinds may be used in combination.

The diol is not particularly limited, and for example, 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 -Propylene diol, 2-methyl-1,3-propanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol and the like can be mentioned. Of these, 1,4-butanediol is preferable because it is easy to control the molecular weight. As the diol, one type may be used alone, or two or more types may be used in combination.
As the polyester polyol, one kind may be used alone, or two or more kinds may be used in combination.

When containing both the prepolymer coating composition for electrical steel sheet using a prepolymer and a polyester polyol with the polyether polyol as the urethane prepolymer, the content of the polyether polyol to the content W _S of the polyester polyol W _H the weight ratio _W H / _{W S,} is preferably 0.1 to 10. If the weight ratio W _{H /} W _S is said lower limit value or more, excellent corrosion resistance. If the weight ratio W _{H /} W _S is less than or equal to the upper limit, excellent heat resistance.
The lower limit of the weight ratio _W H / _{W S} is preferably 1, more preferably 3. The upper limit of the mass ratio _W H / _{W S} is preferably 9, more preferably 8.

The polyol used for the urethane prepolymer includes, in addition to the polyether polyol or the polyester polyol, other polyols such as those exemplified as the polycarbonate polyol and the diol constituting the polyester polyol, as long as the effect of the present invention is not impaired. But it may be. From the viewpoint that the effects of the present invention can be easily obtained, the polyol used for the urethane prepolymer is preferably either a polyether polyol or a polyester polyol, or a combination thereof with 1,4-butanediol.

The number average molecular weight (Mn) of the urethane prepolymer is preferably 2000 or more and 50,000 or less. When the Mn of the urethane prepolymer is at least the above lower limit value, the adhesive strength between the electromagnetic steel sheets is high. When the Mn of the urethane prepolymer is not more than the above upper limit value, it is possible to achieve both heat resistance and magnetic characteristics that can secure the adhesive strength between the electromagnetic steel sheets even at a high temperature.
The lower limit of Mn of the urethane prepolymer is preferably 5000, more preferably 8000. The upper limit of Mn of the urethane prepolymer is preferably 45,000, more preferably 40,000.

The terminal group of the urethane prepolymer can be controlled by the molar ratio NCO / OH of the isocyanate group and the hydroxyl group when the diisocyanate and the polyol are reacted. For example, by setting the molar ratio NCO / OH to 1.00 or more and 3.00 or less, preferably 1.03 or more and 2.00 or less, a urethane prepolymer having an isocyanate group as a terminal group can be obtained. Further, by setting the molar ratio NCO / OH to 0.50 or more and 0.80 or less, preferably 0.60 or more and 0.80 or less, a urethane prepolymer having a hydroxyl group as a terminal group can be obtained.

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

The coating composition for an electromagnetic steel plate may contain components other than the epoxy resin, the epoxy resin curing agent and the urethane prepolymer as long as the effects of the present invention are not impaired. Examples of other components include a curing accelerator (curing catalyst), an emulsifier, an antifoaming agent, a mineral and the like.
The upper limit of the content of other components in the coating composition for electrical steel sheets is preferably 30% by mass, more preferably 20% by mass, based on the total mass of the coating composition for electrical steel sheets.

The insulating film 3 can be formed, for example, by applying a coating composition for an electromagnetic steel sheet to the surface of a base steel sheet, drying it, and baking it.
The lower limit of the temperature reached during baking is preferably 120 ° C, more preferably 150 ° C. The upper limit of the temperature reached during baking is preferably 250 ° C, more preferably 230 ° C.
The lower limit of the baking time is preferably 5 seconds, more preferably 8 seconds. The upper limit of the baking time is preferably 60 seconds, more preferably 30 seconds.

In general, an epoxy resin adhesive having high heat resistance has a Young's modulus that becomes too large near room temperature if the adhesive strength at a high temperature is guaranteed, so that stress is applied to the steel sheet and the core iron loss tends to deteriorate. On the other hand, a resin composition having an appropriate strength near room temperature tends to have insufficient heat resistance.
On the other hand, in the present invention, the urethane prepolymer compatible with the epoxy resin is blended with the epoxy resin in a specific ratio. As a result, the cured urethane resin functions as an elastic body, and stress application at around room temperature can be alleviated, so that deterioration of core iron loss is suppressed. In addition, the cured urethane resins are not connected to each other, and the flow of the resin is suppressed even at a high temperature, so that the adhesive strength at a high temperature is guaranteed. As described above, by using a specific amount of a specific urethane prepolymer, both magnetic properties (core iron loss) and heat resistance can be achieved.

The upper and lower limit values of the average thickness t1 of the insulating film 3 are set as follows, for example, in consideration of the case where the material 1 is used as the electromagnetic steel sheet 40.
When the material 1 is used as the electrical steel sheet 40, the average thickness t1 of the insulating film 3 (thickness per one side of the electrical steel sheet 40 (material 1)) is the insulation performance and adhesive ability between the electrical steel sheets 40 laminated with each other. Adjust so that can be secured.

In the case of the single-layer insulating coating 3, the average thickness t1 (thickness per one side of the electromagnetic steel sheet 40 (material 1)) of the insulating coating 3 can be, for example, 1.5 μm or more and 8.0 μm or less.
In the case of the insulating coating 3 having a multi-layer structure, the average thickness of the underlying insulating coating can be, for example, 0.3 μm or more and 2.5 μm or less, preferably 0.5 μm or more and 1.5 μm or less. The average thickness of the upper insulating coating can be, for example, 1.5 μm or more and 8.0 μm or less.
The method of measuring the average thickness t1 of the insulating coating 3 in the material 1 is the same as that of the average plate thickness t0 of the material 1, and the thicknesses of the insulating coatings 3 at a plurality of locations can be obtained and obtained as the average of those thicknesses. can.

The upper and lower limit values of the average thickness t1 of the insulating coating 3 in the material 1 can be naturally adopted as the upper and lower limit values of the average thickness t1 of the insulating coating 3 in the electrical steel sheet 40. The method for measuring the average thickness t1 of the insulating coating 3 on the electrical steel sheet 40 is, for example, the following measuring method. For example, among a plurality of electrical steel sheets forming a laminated core, the electrical steel sheet 40 located on the outermost side in the laminated direction (the electrical steel sheet 40 whose surface is exposed in the laminated direction) is selected. On the surface of the selected electrical steel sheet 40, a predetermined position in the radial direction (for example, a position just intermediate (center) between the inner peripheral edge and the outer peripheral edge of the electrical steel sheet 40) is selected. At the selected positions, the thickness of the insulating coating 3 of the electrical steel sheet 40 is measured at four locations (that is, every 90 degrees around the central axis O) at equal intervals in the circumferential direction. The average value of the measured thicknesses at the four locations can be taken 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 outermost electromagnetic steel sheet 40 in the laminating direction is that the thickness of the insulating coating 3 is the laminating position along the laminating direction of the electromagnetic steel sheet 40. This is because the insulating film 3 is built so that it hardly changes.

The electromagnetic steel sheet 40 is manufactured by punching the material 1 as described above, and the laminated core (stator core 21 and rotor core 31) is manufactured by the electromagnetic steel sheet 40.

(Laminating method of laminated core)
Hereinafter, the description of the laminated core will be returned. As shown in FIG. 3, the plurality of electrical steel sheets 40 forming the stator core 21 are laminated via the insulating coating 3.
The electromagnetic steel sheets 40 adjacent to each other in the stacking direction are adhered over the entire surface by the insulating coating 3. In other words, the surface of the electromagnetic steel sheet 40 facing the stacking direction (hereinafter referred to as the first surface) is the bonding region 41a over the entire surface. However, the electromagnetic steel sheets 40 adjacent to each other in the stacking direction may not be adhered over the entire surface. In other words, the adhesive region 41a and the non-adhesive region (not shown) may coexist on the first surface of the electrical steel sheet 40.

In the present embodiment, the plurality of electrical steel sheets forming the rotor core 31 are fixed to each other by the caulking 42 (dowel) shown in FIG. However, the plurality of electrical steel sheets forming the rotor core 31 may also have a laminated structure fixed by the insulating coating 3 as in the stator core 21.
Further, the laminated core such as the stator core 21 and the rotor core 31 may be formed by so-called rotating stacking.

(Manufacturing method of laminated core)
The stator core 21 is manufactured, for example, by using the manufacturing apparatus 100 shown in FIG. 7. In the following, in explaining the manufacturing method, first, the laminated core manufacturing apparatus 100 (hereinafter, simply referred to as the manufacturing apparatus 100) will be described.
In the manufacturing apparatus 100, while the material 1 is sent out from the coil 1A (hoop) in the direction of the arrow F, the material 1 is punched a plurality of times by the dies arranged on each stage to gradually form the shape of the electromagnetic steel sheet 40. go. Then, the punched electrical steel sheets 40 are laminated and pressurized while raising the temperature. As a result, the electromagnetic steel sheets 40 adjacent to each other in the laminating direction are adhered by the insulating coating 3 (that is, the portion of the insulating coating 3 located in the adhesive region 41a exerts an adhesive ability), and the adhesion is completed.

As shown in FIG. 7, the manufacturing apparatus 100 includes a plurality of stages of punching stations 110. The punching station 110 may have two stages or three or more stages. The punching station 110 of each stage includes 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 stacking station 140 at a position downstream of the most downstream punching station 110. The laminating station 140 includes a heating device 141, an outer peripheral punching female die 142, a heat insulating member 143, an outer peripheral punching male die 144, and a spring 145.
The heating device 141, the outer peripheral punched female die 142, and the heat insulating member 143 are arranged below the material 1. On the other hand, the outer peripheral punching die 144 and the spring 145 are arranged above the material 1. Reference numeral 21 indicates a stator core.

In the manufacturing apparatus 100 having the above-described configuration, first, the material 1 is sequentially fed from the coil 1A in the direction of the arrow F in FIG. Then, the material 1 is sequentially punched by a plurality of punching stations 110. By these punching processes, the shape of the electromagnetic steel sheet 40 having the core back portion 22 and the plurality of tooth portions 23 shown in FIG. 3 is obtained on the material 1. However, since it is not completely punched at this point, the process proceeds to the next step along the arrow F direction.

Finally, the material 1 is sent out to the laminating station 140, punched out by the outer peripheral punching die 144, and laminated with high accuracy. At the time of this laminating, the electromagnetic steel sheet 40 receives a constant pressing force by the spring 145. By sequentially repeating the punching process and the laminating process as described above, a predetermined number of electrical steel sheets 40 can be stacked. Further, the laminated core formed by stacking the electromagnetic steel sheets 40 in this way is heated to, for example, a temperature of 200 ° C. by the heating device 141. By this heating, the insulating coatings 3 of the adjacent electromagnetic steel sheets 40 are adhered to each other.
The heating device 141 may not be arranged on the outer peripheral punched female die 142. That is, before the electromagnetic steel sheets 40 laminated by the outer peripheral punched female die 142 are adhered, they may be taken out of the outer peripheral punched female die 142. In this case, the outer peripheral punched female die 142 may not have the heat insulating member 143. Further, in this case, the stacked electromagnetic steel sheets 40 before bonding may be sandwiched and held from both sides in the stacking direction by a jig (not shown), and then transported or heated.
The stator core 21 is completed by each of the above steps.

As described above, in the present invention, an insulating film is formed on the surface of the electromagnetic steel plate by a coating composition for an electromagnetic steel plate in which an epoxy resin, an epoxy resin curing agent, and a specific urethane prepolymer are combined in a specific ratio. As a result, it is possible to achieve both the excellent magnetic properties (core iron loss) of the laminated core and the excellent heat resistance that can maintain the adhesive strength between the electromagnetic steel sheets even in a high temperature state during driving.

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 dimensions of the outer diameter and inner diameter of the stator core, the product thickness, the number of slots, the dimensional ratio in the circumferential direction and the radial direction of the teeth portion, the dimensional ratio in the radial direction between the teeth portion and the core back portion, etc. are desired. It can be arbitrarily designed according to the characteristics of the rotary electric machine.

In the rotor in the above embodiment, a set of two 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.

The embodiments and examples of the present invention have been described above. However, the technical scope of the present invention is not limited to the above-described embodiments and examples, and various modifications can be made without departing 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 diameter and inner diameter of the stator core 21, the stack thickness, the number of slots, the circumferential and radial dimensional ratios of the teeth portion 23, the radial dimensional ratios of the teeth portion 23 and the core back portion 22, etc. Can be arbitrarily designed according to the characteristics of the desired rotary electric machine.
In the rotor 30 in the above embodiment, a pair of permanent magnets 32 form one magnetic pole, but the present invention is not limited to this embodiment. 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, the permanent magnet field type electric machine has been described as an example of the rotary electric machine 10, but the structure of the rotary electric machine 10 is not limited to this as illustrated below, and is not further exemplified below. Various known structures can also be adopted.
In the above embodiment, the permanent magnet field type motor has been described as an example of the rotary electric machine 10, but the present invention is not limited to this. For example, the rotary electric machine 10 may be a reluctance type electric machine or an electromagnet field type electric machine (winding field type electric machine).
In the above embodiment, the synchronous motor has been described as an example of the AC motor, but the present invention is not limited to this. For example, the rotary electric machine 10 may be an induction motor.
In the above embodiment, the AC electric machine has been described as an example of the rotary electric machine 10, but the present invention is not limited to this. For example, the rotary electric machine 10 may be a DC motor.
In the above embodiment, the rotary electric machine 10 has been described by taking an electric machine as an example, but the present invention is not limited to this. For example, the rotary electric machine 10 may be a generator.

In addition, it is appropriately possible to replace the constituent elements in the above-described embodiment with well-known constituent elements without departing from the spirit of the present invention, and the above-mentioned modifications may be appropriately combined.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to the following description.

[material]
The raw materials used in the examples are shown below.
(Epoxy resin)
E1: Phenolic novolac type epoxy resin E2: Bisphenol A type epoxy resin

(Epoxy resin curing agent)
A1: Phenolic resol resin A2: Dicyanodiamide

(Urethane prepolymer)
B1: Urethane prepolymer (Mn: 6000)
In a reaction vessel equipped with a stirrer, a thermometer, a reflux cooler, a dropping device, and a nitrogen introduction tube, 100 parts by mass of polyester diol (“Kurare polyol P-2010” manufactured by Kuraray Co., Ltd., Mn = 2000), 4, 45 parts by mass of 4'-diphenylmethane diisocyanate (NCO / OH (molar ratio) = 1.05) and 0.01 part by mass of di-n-butyltin dilaurate were charged and reacted at 80 ° C. for 2 hours under a nitrogen atmosphere to make urethane. A prepolymer (Mn = 6000) solution was obtained.

B2: Urethane prepolymer (Mn: 11000)
B3: Urethane prepolymer (Mn: 26000)
B4: Urethane prepolymer (Mn: 46000)
B5: Urethane prepolymer (Mn: 3000)
B6: Urethane prepolymer (Mn: 7000)
The urethane prepolymers B2 to B6 were synthesized in the same manner as the urethane prepolymer B1 except that the preparation was changed as shown in Table 1.

(Urethane prepolymer (comparison target))
C1: Urethane prepolymer (Mn: 1600)
C2: Urethane prepolymer (Mn: 55000)
C3: Urethane prepolymer (Mn: 89000)
Urethane prepolymers C1 to C3 were synthesized by the same method as urethane prepolymer B1 except that the preparation was changed as shown in Table 1.

The symbols in Table 1 have the following meanings.
P-2010: Polyester diol ("Kuraray polyol P-2010" manufactured by Kuraray Co., Ltd., Mn = 2000)
P-1010: Polyester diol ("Kuraray polyol P-1010" manufactured by Kuraray Co., Ltd., Mn = 1000)
PTG (650): Polyetherdiol (“PTG” manufactured by Hodogaya Chemical Industry Co., Ltd., Mn = 650)
PTG (2000): Polyetherdiol ("PTG" manufactured by Hodogaya Chemical Industry Co., Ltd., Mn = 2000)
MDI: 4,4'-diphenylmethane diisocyanate TDI: toluene diisocyanate 1,4-BD: 1,4-butanediol

[Magnetic characteristics]
A rectangular electromagnetic steel sheet having a size of 55 mm × 55 mm was cut out from the electromagnetic steel strip of each example, and two electromagnetic steel sheets were laminated and bonded under the conditions of a steel sheet temperature of 180 ° C., a pressure of 10 MPa, and a pressurizing time of 1 hour to prepare a laminated core. With respect to the obtained laminated core, the single plate magnetic characteristics in the direction perpendicular to the rolling direction and the rolling direction are measured by the single plate magnetic measurement method specified in JIS C2556, and the average value of these values is obtained as the magnetic characteristics. rice field. As the magnetic property (magnetism), "W10 / 400 (W / kg)" was evaluated as the iron loss. "W10 / 400" is the iron loss when the frequency is 400 Hz and the maximum magnetic flux density is 1.0 T.

[Adhesive strength]
Two rectangular steel sheets having a width of 30 mm and a length of 60 mm are cut out from the electrical steel strips of each example, and the tip portions having a width of 30 mm and a length of 10 mm are overlapped with each other. A sample was prepared by adhering in 1 hour. The shear tensile strength was measured at an ambient temperature of 25 ° C. and a tensile speed of 2 mm / min, and the value divided by the adhesive area was taken as the adhesive strength (MPa).

[judgement]
For each example, the judgment was made according to the following criteria.
◯ (excellent): The adhesive strength at 25 ° C. is 5 MPa or more, the adhesive strength at 180 ° C. is 0.5 MPa or more, and the magnetic property is less than 12 W / kg.
Δ (possible): The adhesive strength at 25 ° C. is 4 MPa or more and less than 5 MPa, the adhesive strength at 180 ° C. is 0.5 MPa or more, and the magnetic property is less than 12 W / kg.
X (defective): Does not satisfy any one or more of the adhesive strength at 25 ° C. of 4 MPa or more, the adhesive strength at 180 ° C. of 0.5 MPa or more, and the magnetic property of less than 12 W / kg.

[Example 1]
As a base steel sheet, non-directional electromagnetic steel having a mass% of Si: 3.0%, Mn: 0.2%, Al: 0.5%, a plate thickness of 0.25 mm and a width of 100 mm, the balance of which is composed of Fe and impurities. A steel plate was used.
Each component shown in Table 2 was mixed to prepare a coating composition for electrical steel sheets. The obtained coating composition for an electromagnetic steel sheet was applied to the surface of a base steel sheet and baked at 200 ° C. for 10 seconds to form an insulating film having an average thickness of 3.0 μm to obtain an electromagnetic steel strip.

[Examples 2 to 6, Comparative Examples 1 to 8]
An electromagnetic steel strip was obtained in the same manner as in Example 1 except that the composition and baking conditions of the coating composition for electrical steel sheets were changed as shown in Table 2.

Table 3 shows the evaluation results of the magnetic properties (magnetism) and the adhesive strength of each example.

As shown in Table 3, in Examples 1 to 6 in which an epoxy resin, an epoxy resin curing agent, and a specific urethane prepolymer are combined in a specific ratio, sufficient adhesive strength at 150 ° C. is ensured and excellent heat resistance is obtained. Moreover, it was excellent in magnetic properties.
On the other hand, in Comparative Examples 1 to 7 in which the content of the urethane prepolymer and Mn were outside the range of the present invention, both heat resistance and magnetic properties could not be achieved at the same time. In Comparative Example 8 in which the urethane prepolymer was not blended, the magnetic properties were inferior.

According to the present invention, both the heat resistance and the magnetic characteristics of the laminated core can be achieved at the same time. Therefore, the industrial applicability is great.

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

Claims (5)

It contains an epoxy resin, an epoxy resin curing agent, and a urethane prepolymer, and the urethane prepolymer contains one or both of a reaction product of a diisocyanate and a polyether polyol and a reaction product of a diisocyanate and a polyester polyol. A coating composition for an electromagnetic steel plate, which contains the urethane prepolymer and has either an isocyanate group or a hydroxyl group at the terminal and has a number average molecular weight of 2000 or more and 50,000 or less. The coating composition for an electromagnetic steel plate according to claim 1, wherein the content of the urethane prepolymer is 5 parts by mass or more and 40 parts by mass or less with respect to 100 parts by mass of the epoxy resin. An electromagnetic steel sheet having an insulating film coated with the coating composition for electrical steel sheets according to claim 1 or 2 on the surface. A laminated core in which a plurality of electrical steel sheets according to claim 3 are laminated and bonded to each other. A rotary electric machine provided with the laminated core according to claim 4.

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