Coating composition for electromagnetic steel sheet, electromagnetic steel sheet, laminated core, and rotary electric machine

Abstract

The electromagnetic steel plate used for laminated iron cores is an electromagnetic steel plate having an insulating film (3) formed by coating an electromagnetic steel plate coating composition on the surface of the base steel plate (2). The electromagnetic steel plate coating composition contains epoxy resin, epoxy resin curing agent, and elastomer-modified phenolic resin. The content of the elastomer-modified phenolic resin is more than 10 parts by weight and less than 100 parts by weight relative to 100 parts by weight of the epoxy resin.

Description

Technical Field

[0001] This invention relates to a coating composition for an electromagnetic steel sheet, an electromagnetic steel sheet, a laminated iron core, and a rotary electric motor. This application claims priority based on Japanese Patent Application No. 2020-104254, filed on June 17, 2020, the contents of which are incorporated herein by reference. Background Technology

[0002] As a core used in rotating electric machines, a laminated core is known, which is formed by joining and stacking multiple electromagnetic steel sheets together. Riveting or welding are known methods for joining the electromagnetic steel sheets. However, in riveting or welding, the magnetic properties (core loss) of the electromagnetic steel sheets are easily degraded due to mechanical or thermal strain during processing.

[0003] As a joining method other than riveting and welding, for example, a method for bonding electromagnetic steel sheets to each other is known, wherein an insulating film with adhesive properties is formed on the surface of the electromagnetic steel sheets (Patent Document 1). Because bonding using the insulating film does not impart mechanical or thermal strain, the core loss is superior compared to riveting and welding. Epoxy resin exhibits less volume change and excellent heat resistance, oil resistance, and chemical resistance, making it an excellent adhesive for bonding electromagnetic steel sheets to each other (Patent Documents 2, 3).

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2017-011863

[0007] Patent Document 2: Japanese Patent Application Publication No. 2000-173816

[0008] Patent Document 3: International Publication No. 2004 / 070080 Summary of the Invention

[0009] The technical problem that the invention aims to solve

[0010] In recent years, the need for further improvements in motor efficiency has necessitated a reduction in core iron losses. Thinning of the electromagnetic steel sheet is a significant factor in reducing core iron losses. However, as the sheet thickness decreases, the Young's modulus of the steel sheet also decreases. Therefore, it is crucial that stress and strain, which contribute to iron loss degradation, are not imparted to the steel sheet. While epoxy resin exhibits excellent heat resistance, it is relatively hard and has low toughness. Consequently, stress and strain are imparted to the steel sheet during the curing process after bonding. Thus, as the steel sheet becomes thinner, it contributes to iron loss degradation.

[0011] Furthermore, in electric vehicle drive motors and other components, temperatures can rise during operation, thus requiring additional heat resistance.

[0012] One method to improve heat resistance is to incorporate phenolic resin. However, resins with excellent heat resistance are relatively hard at room temperature and impose significant stress on the laminated iron core, thus degrading magnetic properties. On the other hand, resins with appropriate hardness near room temperature become soft at high temperatures, resulting in poor heat resistance. For these reasons, it is difficult to simultaneously achieve excellent magnetic properties and excellent heat resistance, which refers to maintaining sufficient bond strength even when exposed to high temperatures during operation.

[0013] The purpose of this invention is to provide a coating composition for an electromagnetic steel sheet that can balance the magnetic properties of the laminated iron core with the heat resistance that maintains the bonding strength between the electromagnetic steel sheets under high temperature conditions during operation, an electromagnetic steel sheet using the coating composition for an electromagnetic steel sheet, a laminated iron core, and a rotary motor.

[0014] Technical means for solving technical problems

[0015] The present invention has the following solution.

[0016] [1] One aspect of the present invention provides a coating composition for an electromagnetic steel sheet containing an epoxy resin, an epoxy resin curing agent, and an elastomer-modified phenolic resin, wherein the content of the elastomer-modified phenolic resin is 10 parts by weight or more and 100 parts by weight or less relative to 100 parts by weight of the epoxy resin.

[0017] [2] Alternatively, in the coating composition for electromagnetic steel plates described above [1], the weight average molecular weight of the elastomer portion of the elastomer-modified phenolic resin is 2,000 or more and 200,000 or less.

[0018] [3] Alternatively, the curing shrinkage rate of the coating composition for electromagnetic steel sheet as described in [1] or [2] above may be less than 15%.

[0019] [4] In one aspect of the present invention, the electromagnetic steel sheet has an insulating film on its surface, the insulating film comprising a coating composition for electromagnetic steel sheets as described in any one of [1] to [3] above.

[0020] [5] In one embodiment of the present invention, multiple electromagnetic steel plates described above [4] are stacked and bonded to each other in a stacked iron core.

[0021] [6] One embodiment of the rotary motor of the present invention includes a stacked iron core as described above [5].

[0022] Invention Effects

[0023] According to the above-described solution of the present invention, it is possible to provide a coating composition for an electromagnetic steel sheet that can take into account both the magnetic properties of the laminated iron core and the heat resistance that can maintain the bonding strength between the electromagnetic steel sheets even at high temperatures during operation, an electromagnetic steel sheet using the coating composition for an electromagnetic steel sheet, a laminated iron core, and a rotary motor. Attached Figure Description

[0024] Figure 1 This is a cross-sectional view of a rotary electric motor with a stacked iron core according to the first embodiment of the present invention.

[0025] Figure 2 yes Figure 1 The side view of the stacked iron core shown.

[0026] Figure 3 yes Figure 2 A-A sectional view.

[0027] Figure 4 It is used to form Figure 1 A top view of the raw materials for the stacked iron core shown.

[0028] Figure 5 yes Figure 4 B-B sectional view.

[0029] Figure 6 yes Figure 5 Enlarged view of part C.

[0030] Figure 7 It is used for manufacturing Figure 1 A side view of the apparatus for manufacturing stacked iron cores. Detailed Implementation

[0031] Hereinafter, with reference to the accompanying drawings, a laminated iron core, a rotary electric motor having the laminated iron core, and the raw materials for forming the laminated iron core according to one embodiment of the present invention will be described. Furthermore, in this embodiment, an electric motor, specifically an AC motor, more specifically a synchronous motor, and even more specifically a permanent magnet excitation type motor will be described as an example of a rotary electric motor. Such a motor is preferably used, for example, in electric vehicles.

[0032] Furthermore, for numerical ranges enclosed in “~”, both the lower and upper limits are included within that range. Values ​​expressed as “less than” or “more than” are not included in the numerical range.

[0033] (Rotary motor 10)

[0034] like Figure 1 As shown, the rotary motor 10 includes a stator 20, a rotor 30, a housing 50, and a rotating shaft 60. The stator 20 and the rotor 30 are housed within the housing 50.

[0035] The stator 20 is fixed inside the housing 50.

[0036] In this embodiment, the rotary motor 10 is an inner rotor type with the rotor 30 located radially inside the stator 20. However, the rotary motor 10 can also be an outer rotor type with the rotor 30 located outside the stator 20. Furthermore, in this embodiment, the rotary motor 10 is a 12-pole, 18-slot three-phase AC motor. However, the number of poles, slots, and phases can be appropriately changed.

[0037] The rotary motor 10, for example, can rotate at a speed of 1000 rpm by applying an excitation current of 10 A effective value and 100 Hz to each phase.

[0038] The stator 20 includes a stator adhesive laminated iron core (hereinafter referred to as stator core) 21 and windings not shown.

[0039] The stator core 21 includes an annular core back 22 and a plurality of teeth 23. Hereinafter, the direction of the central axis O of the stator core 21 (or core back 22) is referred to as the axial direction, the radial direction (the direction orthogonal to the central axis O) of the stator core 21 (or core back 22) is referred to as the radial direction, and the circumferential direction (the direction around the central axis O) of the stator core 21 (or core back 22) is referred to as the circumferential direction.

[0040] When viewed from above along the axial direction, the back of the core 22 is formed into a ring shape.

[0041] Multiple teeth 23 protrude radially inward from the inner circumference of the back of the core 22 (along the radial direction towards the central axis O of the back of the core 22). The teeth 23 are arranged at equal angular intervals circumferentially. In this embodiment, 18 teeth 23 are provided at a central angle of 20 degrees centered on the central axis O. The teeth 23 are formed to be identical in shape and size. Therefore, the teeth 23 have the same thickness dimension.

[0042] The winding is wound around the tooth portion 23. The winding can be either concentrated or distributed.

[0043] 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.

[0044] The rotor core 31 is formed into an annular shape, coaxially arranged with the stator 20. The rotating shaft 60 is disposed within the rotor core 31. The rotating shaft 60 is fixed to the rotor core 31.

[0045] Multiple permanent magnets 32 are fixed to the rotor core 31. In this embodiment, two permanent magnets 32 form one magnetic pole. Multiple sets of permanent magnets 32 are arranged at equal angular intervals along the circumference. In this embodiment, 12 sets (24 in total) of permanent magnets 32 are arranged at a central angle of 30 degrees centered on the central axis O.

[0046] In this embodiment, an embedded magnet type motor is used as the permanent magnet excitation type motor.

[0047] Multiple through holes 33 are formed in the rotor core 31, extending axially through the rotor core 31. The multiple through holes 33 are arranged corresponding to the configuration of multiple permanent magnets 32. Each permanent magnet 32 ​​is fixed to the rotor core 31 in a state where it is disposed within its corresponding through hole 33. The fixing of 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 using an adhesive. Alternatively, as a permanent magnet excitation type motor, a surface magnet type motor may be used instead of an embedded magnet type.

[0048] Both the stator core 21 and the rotor core 31 are laminated cores. For example, the stator core 21 is as follows: Figure 2 As shown, it is formed by stacking multiple electromagnetic steel plates 40 along the stacking direction.

[0049] Furthermore, the stacking thickness (along the entire length of the central axis O) of both the stator core 21 and the rotor core 31 is, for example, set to 50.0 mm. The outer diameter of the stator core 21 is, for example, set to 250.0 mm. The inner diameter of the stator core 21 is, for example, set to 165.0 mm. The outer diameter of the rotor core 31 is, for example, set to 163.0 mm. The inner diameter of the rotor core 31 is, for example, set to 30.0 mm. However, these values ​​are merely examples, and the stacking thickness, outer diameter, or inner diameter of the stator core 21, and the stacking thickness, outer diameter, or 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 front end of the teeth 23 in the stator core 21. That is, the inner diameter of the stator core 21 is the diameter of the virtual circle inscribed in the front ends of all the teeth 23.

[0050] The electromagnetic steel plates 40 that form the stator core 21 and the rotor core 31 are, for example, formed by... Figures 4-6 The raw material 1 shown is formed by punching or other processing. The raw material 1 is an electromagnetic steel sheet that serves as the base material for the electromagnetic steel sheet 40. Examples of raw material 1 include strip steel sheets or cut plates.

[0051] In the description of the laminated iron core, the following description will focus on raw material 1. Additionally, in this specification, the strip-shaped steel sheet that serves as the base material for the electromagnetic steel sheet 40 is sometimes referred to as raw material 1. Sometimes, the steel sheet formed by punching raw material 1 into a shape used in the laminated iron core is referred to as electromagnetic steel sheet 40.

[0052] (raw material 1)

[0053] Raw material 1, for example, is wound in Figure 7 The steel coil 1A shown is processed in its original state. In this embodiment, non-oriented electromagnetic steel sheet is used as raw material 1. JIS C 2552:2014 non-oriented electromagnetic steel sheet can be used as the non-oriented electromagnetic steel sheet. However, oriented electromagnetic steel sheet can also be used instead of non-oriented electromagnetic steel sheet as raw material 1. In this case, JIS C 2553:2019 oriented electromagnetic steel sheet can be used. Furthermore, JIS C 2558:2015 non-oriented thin electromagnetic steel strip or oriented thin electromagnetic steel strip can be used.

[0054] The upper and lower limits of the average plate thickness t0 of raw material 1 are also taken into account when raw material 1 is used as electromagnetic steel plate 40, and are set as follows, for example.

[0055] As the thickness of raw material 1 decreases, its manufacturing cost increases. Therefore, considering the manufacturing cost, the lower limit of the average plate thickness t0 of raw material 1 is 0.10 mm, preferably 0.15 mm, and more preferably 0.18 mm.

[0056] On the other hand, while manufacturing costs improve when raw material 1 is too thick, eddy current losses increase and core losses deteriorate when raw material 1 is used as electromagnetic steel plate 40. Therefore, considering core losses and manufacturing costs, the upper limit of the average plate thickness t0 of raw material 1 is 0.65 mm, preferably 0.35 mm, and more preferably 0.30 mm.

[0057] For example, 0.20 mm can be used to satisfy the above-mentioned range of average plate thickness t0 of raw material 1.

[0058] Furthermore, the average plate thickness t0 of raw material 1 includes not only the thickness of the base steel plate 2 (described later) but also the thickness of the insulating film 3. Moreover, the method for measuring the average plate thickness t0 of raw material 1 is, for example, according to the following method. For example, when raw material 1 is wound into a steel coil 1A, at least a portion of raw material 1 is unwound into a flat plate shape. In the unwound flat raw material 1, a predetermined position in the length direction of raw material 1 is selected (e.g., a position 10% of the total length of raw material 1 from its end edge in the length direction). At this selected position, raw material 1 is divided into 5 regions along its width direction. The plate thickness of raw material 1 is measured at 4 points that serve as the boundaries of these 5 regions. The average plate thickness at these 4 points can be taken as the average plate thickness t0 of raw material 1.

[0059] The upper and lower limits of the average plate thickness t0 of the raw material 1 can also be used as the upper and lower limits of the average plate thickness t0 of the electromagnetic steel plate 40. Furthermore, the method for measuring the average plate thickness t0 of the electromagnetic steel plate 40 is, for example, the following method: The lamination thickness of the laminated core is measured at four locations (i.e., every 90 degrees centered on the central axis O) at equal intervals along the circumference.

[0060] Divide the measured thickness at the four locations by the number of electromagnetic steel sheets 40 being stacked to calculate the thickness of each sheet. The average thickness of the four locations can be taken as the average thickness t0 of the electromagnetic steel sheet 40.

[0061] like Figure 5 and Figure 6 As shown, raw material 1 includes base material steel plate 2 and insulating film 3.

[0062] In raw material 1, both sides of the strip-shaped base steel plate 2 are covered with an insulating film 3. In this embodiment, most of the raw material 1 is formed from the base steel plate 2, and an insulating film 3 is laminated on the surface of the base steel plate 2. The insulating film 3 is thinner than the base steel plate 2.

[0063] Regarding the chemical composition of the base steel plate 2, as shown below, it contains 2.5% to 4.5% Si by mass. Furthermore, by setting the chemical composition within this range, the yield strength of the raw material 1 (electromagnetic steel plate 40) can be set, for example, to be 380 MPa or more and 540 MPa or less.

[0064] Si: 2.5%–4.5%

[0065] Al: 0.001%–3.0%

[0066] Mn: 0.05%~5.0%

[0067] Remaining components: Fe and impurities

[0068] When raw material 1 is used as the electromagnetic steel sheet 40, the insulating film 3 provides insulation between adjacent electromagnetic steel sheets 40 in the stacking direction. Furthermore, in this embodiment, the insulating film 3 has adhesive properties, bonding adjacent electromagnetic steel sheets 40 in the stacking direction. The insulating film 3 can be a single layer or a multilayer structure. More specifically, for example, the insulating film 3 can be a single layer possessing both insulation and adhesive properties, or a multilayer structure comprising a lower insulating film with excellent insulation properties and an upper insulating film with excellent adhesive properties. Additionally, the term "adhesive properties of the insulating film 3" in this embodiment refers to the ability to exhibit an adhesive strength exceeding a predetermined value under predetermined temperature conditions in a laminate composed of multiple electromagnetic steel sheets 40 stacked with the insulating film 3 sandwiched between them.

[0069] In this embodiment, the insulating film 3 covers both sides of the base steel plate 2 without gaps, covering the entire surface. However, it is also possible that, within the range that ensures the aforementioned insulation performance or adhesion, a portion of the insulating film 3 does not cover both sides of the base steel plate 2 without gaps. In other words, a portion of the insulating film 3 may be intermittently disposed on the surface of the base steel plate 2. However, to ensure insulation performance, both sides of the base steel plate 2 need to be covered by the insulating film 3 so that the entire surface is not exposed. Specifically, when the insulating film 3 does not have a lower insulating film with excellent insulation performance, but is a single-layer structure that combines insulation performance and adhesion, the insulating film 3 needs to be formed without gaps, covering the entire surface of the base steel plate 2. In contrast, when the insulating film 3 is composed of multiple layers including a lower insulating film with excellent insulation performance and an upper insulating film with excellent adhesion, in addition to forming both the lower and upper insulating films across the entire surface of the base steel plate 2 without gaps, forming the lower insulating film across the entire surface of the base steel plate without gaps and intermittently setting the upper insulating film can also take into account both insulation performance and adhesion.

[0070] The coating composition constituting the lower insulating film is not particularly limited, and for example, general treatment agents such as chromic acid treatment agents and phosphate treatment agents can be used.

[0071] An insulating film 3 with adhesive properties is coated with a coating composition for electromagnetic steel sheets, which contains epoxy resin, epoxy resin curing agent, and elastomer-modified phenolic resin.

[0072] Before the heating and pressing during the manufacturing of laminated iron cores, the insulating film composed of the coating composition for electromagnetic steel sheets is in an uncured or semi-cured state (stage B). Due to the heating during the heating and pressing process, a curing reaction occurs, resulting in adhesive ability. The coating composition for electromagnetic steel sheets can be used to form a single-layer insulating film or to form an upper insulating film disposed on a lower insulating film.

[0073] As the epoxy resin, any general epoxy resin can be used; specifically, any epoxy resin having two or more epoxy groups per molecule can be used without particular restrictions. Examples of such epoxy resins include bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenolic resin, cresol-phenolic resin, triphenylmethane type epoxy resin, alicyclic epoxy resin, glycidyl ester type epoxy resin, glycidylamine type epoxy resin, hydantoin type epoxy resin, isocyanurate type epoxy resin, acrylic modified epoxy resin (epoxy acrylate), phosphorus-containing epoxy resin, and their halides (brominated epoxy resins, etc.) or hydrides. One type of epoxy resin can be used alone, or two or more types can be used in combination.

[0074] Relative to the total mass of the coating composition for the electromagnetic steel sheet, the epoxy resin content is preferably 30-90% by mass, more preferably 40-80% by mass, and even more preferably 50-70% by mass. When the epoxy resin content is above the lower limit mentioned above, the adhesive strength of the electromagnetic steel sheet 40 can be further improved. When the epoxy resin content is below the upper limit mentioned above, the stress and strain of the electromagnetic steel sheet 40 can be further suppressed.

[0075] As an epoxy resin curing agent, a latent curing agent is used to cure epoxy resin, which is a type of latent curing agent that initiates the curing reaction by heating to a predetermined temperature. Examples of epoxy resin curing agents include aromatic polyamines, acid anhydrides, phenolic curing agents, dicyandiamide, boron trifluoride-amine complexes, and organic hydrazides.

[0076] Examples of aromatic polyamines include m-phenylenediamine, diaminodiphenylmethane, diaminodiphenylethane, and diaminodiphenyl sulfone.

[0077] Examples of acid anhydrides include phthalic anhydride, hexahydrophthalic anhydride, tetrahydrophthalic anhydride, pyromellitic anhydride, and metapyrophthalic anhydride.

[0078] Examples of phenolic curing agents include phenolic resin, cresol resin, bisphenol resin, triazine-modified phenolic resin, and phenol-formaldehyde resin.

[0079] From the perspective of easily balancing magnetic properties and heat resistance, aromatic polyamines, phenolic curing agents, and dicyandiamide are preferred as epoxy resin curing agents. Phenolic curing agents are more preferred, and phenolic resins and phenolic resins are even more preferred. As epoxy resin curing agents, one type can be used alone, or two or more types can be used in combination.

[0080] The lower limit of the content of epoxy resin curing agent in the coating composition for electromagnetic steel sheets relative to 100 parts by weight of epoxy resin is preferably 1 part by weight or more, more preferably 3 parts by weight or more. The upper limit of the content of epoxy resin curing agent is preferably 50 parts by weight or less, more preferably 35 parts by weight or less.

[0081] Elastomer-modified phenolic resin is a phenolic resin obtained by grafting a thermoplastic elastomer with soft and hard segments. For example, an elastomer-modified phenolic resin can be obtained by combining an elastomer with a phenolic resin during polycondensation. Furthermore, an elastomer-modified phenolic resin can also be obtained by reacting an elastomer with a phenolic resin.

[0082] The phenolic resin in elastomer-modified phenolic resin can be either phenolic resin or phenolic methyl resin.

[0083] As phenols, they are not particularly limited; examples include phenol, o-cresol, cashew phenol, alkylphenols (isopropylphenol, p-isobutylphenol, etc.), bisphenols (bisphenol A, bisphenol F, etc.), and polyphenols (resorcinol, etc.). As phenols, one type can be used alone, or two or more types can be used in combination.

[0084] As aldehydes, they are not particularly limited; examples include formaldehyde, paraformaldehyde, acetaldehyde, and benzaldehyde. Aldehydes can be used alone or in combination with two or more.

[0085] Examples of thermoplastic elastomers include acrylic rubber, ethylene-propylene rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber, isoprene rubber, and silicone rubber. As thermoplastic elastomers, one type can be used alone, or two or more types can be used in combination.

[0086] The lower limit of the weight average molecular weight (Mw) of the elastomer portion of the elastomer-modified phenolic resin is 2,000 to 200,000. When the Mw of the elastomer portion is above the lower limit, it is easy to suppress the iron loss degradation of the laminated iron core. When the Mw of the elastomer portion is below the upper limit, it is possible to suppress the thickening of the coating composition for electromagnetic steel sheets coated on steel sheets.

[0087] The lower limit of Mw for the elastomer portion is preferably 3,000 or more, and more preferably 4,000 or more. The upper limit of Mw for the elastomer portion is preferably 180,000 or less, and more preferably 160,000 or less.

[0088] In addition, regarding the Mw of the elastomer portion, the elastomer and phenolic resin were decomposed by hydrolysis, separated by HPLC (high-performance liquid chromatography), and determined as a polystyrene conversion value by GPC (gel permeation chromatography).

[0089] The lower limit of the content of the elastomer portion in the elastomer-modified phenolic resin is preferably 5% by mass or more, and more preferably 10% by mass or more. When the content of the elastomer portion is at or above the lower limit, the iron core loss is good.

[0090] The upper limit of the content of the elastomer portion is preferably 40% by mass or less, more preferably 35% by mass or less. When the content of the elastomer portion is below the said upper limit value, it can be cured rapidly.

[0091] The content of elastomer-modified phenolic resin in the coating composition for electromagnetic steel sheets is 10 parts by weight to 100 parts by weight, relative to 100 parts by weight of epoxy resin. When the content of elastomer-modified phenolic resin is above the lower limit, a laminated iron core with excellent magnetic properties can be obtained. When the content of elastomer-modified phenolic resin is below the upper limit, a laminated iron core with excellent heat resistance can be obtained.

[0092] The lower limit of the content of elastomer-modified phenolic resin is preferably 10 parts by weight or more, and more preferably 20 parts by weight or more. The upper limit of the content of elastomer-modified phenolic resin is preferably 80 parts by weight or less, and more preferably 70 parts by weight or less.

[0093] The coating composition for electromagnetic steel sheets may also contain components other than epoxy resin, epoxy resin curing agent, and elastomer-modified phenolic resin. Examples of such components include acrylic resin, curing accelerator (curing catalyst), emulsifier, and defoamer. Furthermore, from the viewpoint of ensuring adhesive strength, the coating composition for electromagnetic steel sheets does not contain inorganic fillers such as silica, alumina, or glass. As other components, only one type may be used, or two or more may be used in combination.

[0094] The term "acrylic resin" is not particularly limited. Examples of monomers used in acrylic resins include, for instance, unsaturated carboxylic acids such as acrylic acid and methacrylic acid, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, n-butyl isobutyl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl methacrylate, 2-hydroxyethyl methacrylate, and hydroxypropyl methacrylate. Furthermore, the term "methacrylate" refers to either acrylate or methacrylate. One type of acrylic resin can be used alone, or two or more types can be used in combination.

[0095] Acrylic resins can also contain constituent units derived from monomers other than acrylic acid monomers. Examples of such monomers include ethylene, propylene, and styrene. These monomers can be used individually or in combination of two or more.

[0096] The glass transition point (Tg point) of acrylic resin is not particularly limited, but the lower limit is preferably -40°C, more preferably -20°C. The upper limit of the Tg point of acrylic resin is preferably 80°C, more preferably 50°C.

[0097] When the coating composition for electromagnetic steel sheets contains acrylic resin, the content of acrylic resin is not particularly limited; for example, it can be set to 5% by mass or more and 60% by mass or less relative to the total amount of epoxy resin and acrylic resin. The same applies when it contains acrylic-modified epoxy resin or acrylic monomer.

[0098] When using acrylic resin, it can also be used as an acrylic-modified epoxy resin obtained by grafting acrylic resin onto epoxy resin. Alternatively, it can be included as a monomer forming acrylic resin in a coating composition for electromagnetic steel sheets.

[0099] Generally, when ensuring bond strength at high temperatures, epoxy resin adhesives with excellent heat resistance have a large Young's modulus near room temperature, which can impose stress on the steel plate and degrade magnetic properties (core loss). On the other hand, when the resin composition is set to have moderate strength near room temperature, the heat resistance will decrease.

[0100] In this embodiment, by using an elastomer-modified phenolic resin obtained by grafting a thermoplastic elastomer with soft and hard segments and a large elastic modulus, the stress imparted to the steel plate near room temperature is suppressed, thereby suppressing the deterioration of magnetic properties (core iron loss).

[0101] Furthermore, because the elastomer is bonded to the phenolic resin, it does not flow even when exposed to high temperatures, thus ensuring adhesive strength at high temperatures. Therefore, by using a specific amount of elastomer-modified phenolic resin, both magnetic properties and heat resistance can be achieved. Additionally, the effects of this invention are difficult to obtain if the thermoplastic elastomer is simply included in the composition without grafting it. That is, by using an elastomer-modified phenolic resin obtained by grafting the thermoplastic elastomer, superior magnetic properties can be obtained. When using an ungrafted thermoplastic elastomer, there are risks that the adhesive strength at high temperatures may decrease, or that only the thermoplastic elastomer component may flow when pressure is applied to the steel sheet, thereby altering the lamination state.

[0102] The curing shrinkage rate of the coating composition for electromagnetic steel sheets is preferably 15% or less, more preferably 12% or less, even more preferably 10% or less, and particularly preferably 8% or less. When the curing shrinkage rate is below the aforementioned upper limit, it is easy to reduce the stress imposed on the steel sheet and to obtain a laminated iron core with excellent magnetic properties.

[0103] In addition, the curing shrinkage rate was determined according to the method of JIS K6941.

[0104] The insulating film 3 can be formed, for example, by coating an electromagnetic steel sheet with a coating composition onto the surface of a base steel sheet and then drying and sintering it.

[0105] The lower limit of the sintering temperature is preferably 120°C or higher, more preferably 140°C or higher. The upper limit of the sintering temperature is preferably 200°C or lower, more preferably 180°C or lower. When the temperature is above the lower limit, the coating composition for the electromagnetic steel sheet will adhere sufficiently to the electromagnetic steel sheet, and peeling will be suppressed. When the temperature is below the upper limit, over-curing of the epoxy resin can be suppressed, and the adhesive ability of the coating composition for the electromagnetic steel sheet can be maintained.

[0106] The lower limit of the sintering time is preferably 5 seconds or more, more preferably 10 seconds or more. The upper limit of the sintering time is preferably 40 seconds or less, more preferably 30 seconds or less. When the sintering time is above the lower limit, the coating composition for the electromagnetic steel sheet will adhere sufficiently to the electromagnetic steel sheet, and peeling will be suppressed. When the sintering time is below the upper limit, over-curing of the epoxy resin can be suppressed, and the adhesive ability of the coating composition for the electromagnetic steel sheet can be maintained.

[0107] Considering that raw material 1 is used as electromagnetic steel plate 40, the upper and lower limits of the average thickness t1 of insulating film 3 can also be set as follows, for example.

[0108] When raw material 1 is used as electromagnetic steel plate 40, the average thickness t1 (thickness of each single electromagnetic steel plate 40 (raw material 1)) of insulating film 3 is adjusted to ensure the insulation performance and adhesion between the electromagnetic steel plates 40 that are stacked together.

[0109] In the case of a single-layer insulating film 3, the average thickness t1 of the insulating film 3 as a whole (the thickness of the electromagnetic steel plate 40 (raw material 1)) can be set to, for example, 1.5 μm or more and 8.0 μm or less.

[0110] In the case of a multilayer insulating film 3, the average thickness of the lower insulating film can be set to, 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 film can be set to, for example, 1.5 μm or more and 8.0 μm or less.

[0111] Furthermore, regarding the method for measuring the average thickness t1 of the insulating film 3 in raw material 1, the thickness of the insulating film 3 at multiple locations can be calculated using the same consideration method as the average thickness t0 of raw material 1, and then obtained as the average of their thicknesses.

[0112] The upper and lower limits of the average thickness t1 of the insulating film 3 in the raw material 1 can also be used as the upper and lower limits of the average thickness t1 of the insulating film 3 in the electromagnetic steel plate 40.

[0113] Furthermore, the method for measuring the average thickness t1 of the insulating film 3 in the electromagnetic steel plate 40 is, for example, according to the following measurement method. For example, the electromagnetic steel plate 40 located on the outermost side in the stacking direction (the electromagnetic steel plate 40 whose surface is exposed in the stacking direction) among a plurality of electromagnetic steel plates forming a laminated core is selected. On the surface of the selected electromagnetic steel plate 40, a predetermined radial position is selected (for example, the exact midpoint between the inner and outer peripheries of the electromagnetic steel plate 40). At the selected position, the thickness of the insulating film 3 of the electromagnetic steel plate 40 is measured at four locations (i.e., every 90 degrees centered on the central axis O) spaced equally along the circumferential direction. The average value of the measured thicknesses at the four locations can be used as the average thickness t1 of the insulating film 3.

[0114] Furthermore, the reason for measuring the average thickness t1 of the insulating film 3 in the outermost electromagnetic steel plate 40 located in the stacking direction is that the insulating film 3 is made in such a way that the thickness of the insulating film 3 hardly changes at the stacking position of the electromagnetic steel plate 40 along the stacking direction.

[0115] Electromagnetic steel plate 40 is manufactured by punching the raw material 1 described above, and the electromagnetic steel plate 40 is used to manufacture the laminated iron core (stator iron core 21 or rotor iron core 31).

[0116] (Layering method for laminated iron cores)

[0117] Now, let's return to the explanation of laminated iron cores.

[0118] Multiple electromagnetic steel plates 40 forming the stator core 21 Figure 3 As shown, it is laminated by an insulating film 3.

[0119] Adjacent electromagnetic steel plates 40 in the stacking direction are bonded together by an insulating film 3 covering their entire surface. In other words, the surface of the electromagnetic steel plate 40 facing the stacking direction (hereinafter referred to as the first surface) forms the bonding region 41a covering its entire surface. However, adjacent electromagnetic steel plates 40 in the stacking direction may not be bonded together covering their entire surface. In other words, the bonding region 41a and the non-bonded region (not shown) may coexist on the first surface of the electromagnetic steel plate 40.

[0120] In this embodiment, the plurality of electromagnetic steel plates forming the rotor core 31 are made of Figure 1 The riveted parts 42 (pins) shown are fixed to each other. However, the multiple electromagnetic steel plates forming the rotor core 31 can also have a laminated structure fixed by the insulating film 3, just like the stator core 21.

[0121] Alternatively, the stator core 21 and rotor core 31, etc., can be formed by so-called rotary stacking.

[0122] (Manufacturing method of laminated iron core)

[0123] The stator core 21 is, for example, used as... Figure 7 The manufacturing apparatus 100 shown is used to manufacture the core. Hereinafter, when describing the manufacturing method, the manufacturing apparatus 100 (hereinafter referred to as manufacturing apparatus 100) will be described first.

[0124] In the manufacturing apparatus 100, raw material 1 is fed from steel coil 1A (coil) in the direction of arrow F and is punched multiple times by dies arranged on each worktable, gradually forming the shape of an electromagnetic steel sheet 40. Then, the punched electromagnetic steel sheets 40 are stacked and heated while being pressurized. As a result, adjacent electromagnetic steel sheets 40 in the stacking direction are bonded together by the insulating film 3 (that is, the portion of the insulating film 3 located in the bonding area 41a exerts its adhesive ability), and the bonding is completed.

[0125] like Figure 7 As shown, the manufacturing apparatus 100 includes a multi-stage punching station 110. The punching station 110 can be two-stage or three-stage or more. Each punching station 110 includes: a die 111 disposed below the raw material 1; and a punch 112 disposed above the raw material 1.

[0126] The manufacturing apparatus 100 also includes a stacking station 140 located downstream of the downstream blanking station 110. The stacking station 140 includes a heating device 141, an outer peripheral blanking die 142, a heat insulation component 143, an outer peripheral blanking punch 144, and a spring 145.

[0127] The heating device 141, the outer peripheral blanking die 142, and the heat insulation member 143 are arranged below the raw material 1. On the other hand, the outer peripheral blanking punch 144 and the spring 145 are arranged above the raw material 1. In addition, reference numeral 21 indicates the stator core.

[0128] In the manufacturing apparatus 100 having the configuration described above, firstly, from the steel coil 1A along... Figure 7 The raw material 1 is sequentially fed out in the direction of arrow F. Then, for this raw material 1, it undergoes sequential punching processing at multi-stage punching stations 110. Through these punching processes, for raw material 1, a product is obtained. Figure 3 The shape of the electromagnetic steel plate 40 shown is that it has an iron core back 22 and multiple teeth 23. However, at this point in time, it has not been punched at all, so it proceeds to the next process in the direction of arrow F.

[0129] Then, finally, the raw material 1 is fed to the stacking station 140, punched by the outer peripheral punching punch 144, and stacked with high precision. During this stacking, the electromagnetic steel sheet 40 is subjected to a certain pressure due to the spring 145. By repeating the punching process and the stacking process as described above in sequence, a predetermined number of electromagnetic steel sheets 40 can be stacked. Furthermore, the stacked iron core formed by stacking the electromagnetic steel sheets 40 in this way is heated to a temperature of 200°C, for example, by the heating device 141. Through this heating, the insulating film 3 of adjacent electromagnetic steel sheets 40 is bonded to each other (bonding process).

[0130] The conditions for the bonding process are not particularly limited. For example, the heating temperature in the bonding process is preferably 120 to 250°C. The heating time in the bonding process is affected by the size of the laminated core or the heating method, but is preferably, for example, 30 seconds to 120 minutes. Alternatively, the insulating films 3 can be bonded together by applying pressure to the laminate. The pressure and time for applying pressure to the laminate are preferably, for example, 2 to 300 MPa and 30 seconds to 120 minutes.

[0131] Alternatively, the heating device 141 may not be disposed in the outer peripheral blanking die 142. That is, the electromagnetic steel plates 40 stacked in the outer peripheral blanking die 142 may be removed from the outer peripheral blanking die 142 before bonding. In this case, the heat insulation member 143 may not be present in the outer peripheral blanking die 142. Furthermore, in this case, the electromagnetic steel plates 40 to be bonded may be clamped and held from both sides in the stacking direction using a clamp (not shown) before being conveyed or heated.

[0132] Through the above processes, the stator core 21 is completed.

[0133] As explained above, in this invention, an insulating film is formed on the surface of an electromagnetic steel sheet using a coating composition for electromagnetic steel sheets. This coating composition is obtained by combining an elastomer-modified phenolic resin with an epoxy resin and an epoxy resin curing agent in a specific ratio. This allows for the simultaneous achievement of excellent magnetic properties (core iron loss) of the laminated core and excellent heat resistance, maintaining the bonding strength between the electromagnetic steel sheets even at high temperatures during operation.

[0134] Furthermore, the technical scope of the present invention is not limited to the described embodiments, and various modifications can be made without departing from the spirit of the present invention.

[0135] The shape of the stator core is not limited to the form shown in the embodiment. Specifically, it can be designed arbitrarily according to the desired characteristics of the rotating motor, such as the outer and inner diameters of the stator core, the stack thickness, the number of slots, the circumferential and radial dimensional ratio of the teeth, and the radial dimensional ratio of the teeth to the back of the core.

[0136] In the rotor of the described embodiment, two permanent magnets 32 in a group form one magnetic pole, but the present invention is not limited thereto. For example, one permanent magnet 32 ​​may form one magnetic pole, or three or more permanent magnets 32 may form one magnetic pole.

[0137] In the above embodiments, a permanent magnet excitation type motor is used as an example of the rotary motor 10. However, the structure of the rotary motor 10 is not limited to the example shown below. Furthermore, various known structures not shown below can also be adopted.

[0138] In the above embodiments, a permanent magnet excitation type motor was described as an example of the rotary motor 10, but the present invention is not limited thereto. For example, the rotary motor 10 may also be a reluctance type motor or an electromagnet excitation type motor (winding excitation type motor).

[0139] In the above embodiments, a synchronous motor was described as an example of an AC motor, but the present invention is not limited thereto. For example, the rotary motor 10 may also be an induction motor.

[0140] In the above embodiment, an AC motor was used as an example of a rotary motor 10, but the present invention is not limited thereto. For example, the rotary motor 10 may also be a DC generator.

[0141] In the above embodiment, an electric motor was described as an example of a rotary motor 10, but the present invention is not limited thereto. For example, the rotary motor 10 may also be a generator.

[0142] Furthermore, the constituent elements in the embodiments can be appropriately replaced with well-known constituent elements without departing from the spirit of the invention. In addition, the modified examples can be appropriately combined.

[0143] Example

[0144] Hereinafter, the effects of one aspect of the present invention will be specifically described according to an embodiment. However, the conditions in the embodiment are merely examples of conditions adopted to confirm the feasibility and effects of the present invention, and the present invention is not limited to the following description. Various conditions can be adopted by the present invention as long as they do not depart from the spirit of the present invention and achieve the purpose of the present invention.

[0145] [raw material]

[0146] The raw materials used in the examples are shown below.

[0147] (Epoxy resin)

[0148] E1: Bisphenol A type epoxy resin

[0149] E2: Bisphenol F type epoxy resin

[0150] E3: Cresol-phenolic epoxy resin

[0151] (Elastomer-modified phenolic resin)

[0152] A1: Acrylic rubber modified phenolic resin (phenolic type, mass ratio of phenolic resin part to elastomer part = 70:30, Mw of elastomer part: 35000)

[0153] A2: Styrene-butadiene rubber modified phenolic resin (phenolic type, mass ratio of phenolic resin part to elastomer part = 65:35, Mw of elastomer part: 20000)

[0154] A3: Ethylene-propylene rubber modified phenolic resin (phenolic type, mass ratio of phenolic resin part to elastomer part = 85:15, Mw of elastomer part: 160000)

[0155] A4: Silicone rubber modified with phenolic resin (phenolic type, mass ratio of phenolic resin part to elastomer part = 90:10, Mw of elastomer part: 3000)

[0156] (Epoxy resin curing agent)

[0157] H1: Phenolic resin (formaldehyde resin)

[0158] H2: Phenolic resin

[0159] H3: Diaminodiphenylmethane

[0160] H4: Dicyandiamide

[0161] H5: 4-Methylhexahydrophthalic anhydride

[0162] (Combining agents)

[0163] M1: Acrylic resin (Methyl methacrylate: Styrene: 2-ethylhexyl acrylate (molar ratio = 60:30:10, glass transition temperature: 40℃)

[0164] M2: Acrylic resin (methyl methacrylate units: n-butyl acrylate units (molar ratio) = 70:30, glass transition temperature: 15℃)

[0165] [Magnetic properties]

[0166] Rectangular electromagnetic steel sheets (single sheets) with dimensions of 55mm × 55mm were cut from the electromagnetic steel strips in each example. Ten electromagnetic steel sheets were stacked and bonded together under the conditions of steel sheet temperature of 200℃, pressure of 10MPa, and pressing time of 1 hour to produce a laminated iron core. For the obtained laminated iron core, the magnetic properties of the single sheet in the rolling direction and in the direction perpendicular to the rolling direction were measured according to the single sheet magnetic measurement method of JIS C2556 (2015), and the average value of their values ​​was used as the magnetic property. In addition, as a magnetic property (magnetism) and as an iron loss, "W10 / 400 (W / kg)" was evaluated. "W10 / 400" is the iron loss at a frequency of 400Hz and a maximum magnetic flux density of 1.0T.

[0167] [Adhesion strength]

[0168] Two rectangular electromagnetic steel sheets (single sheets) with a width of 30 mm and a length of 60 mm were cut from the electromagnetic steel strips in each example. Next, an electromagnetic steel sheet coating composition was applied to the surface, and the front ends (30 mm wide x 10 mm long) were overlapped and pressurized to produce a sample for testing. The pressurization conditions were set as follows: steel sheet temperature 200°C, pressure 10 MPa, and pressurization time 1 hour.

[0169] For the obtained samples, the tensile speed was set to 2 mm / min under an atmosphere temperature of 25℃ or 150℃. The maximum load (N) until peeling was measured, and the value obtained by dividing the maximum load (N) by the bonded area was taken as the bond strength (MPa).

[0170] [Curing shrinkage rate]

[0171] Electromagnetic steel sheet coating compositions were applied to the surface of each example of electromagnetic steel strip, and the curing shrinkage rate was measured. The curing shrinkage rate was measured according to JIS K 6941, based on changes in film thickness.

[0172] [determination]

[0173] For each case, the following criteria were used for evaluation. Furthermore, lower iron loss indicates that the stress and strain imparted to the electromagnetic steel sheet are more suppressed. The measurement and evaluation results are shown in Table 2. Values ​​outside the scope of the invention are underlined in the table.

[0174] [Benchmark]

[0175] "Good": The bond strength at 25℃ is above 5.0MPa, the bond strength at 150℃ is above 1.0MPa, and the magnetic properties are less than 12.0W / kg.

[0176] "Poor": The bonding strength at 25℃ is less than 5.0MPa, the bonding strength at 150℃ is less than 1.0MPa, or the magnetic properties are above 12.0W / kg.

[0177] [Example 1]

[0178] The base steel sheet used was a non-oriented electromagnetic steel sheet with a thickness of 0.25 mm and a width of 100 mm, containing Si: 3.0%, Mn: 0.2%, Al: 0.5% by mass, with the remainder consisting of Fe and impurities.

[0179] The components shown in Table 1 were mixed to prepare a coating composition for electromagnetic steel sheets. The obtained coating composition for electromagnetic steel sheets was coated onto the surface of a base steel sheet and sintered at 200°C for 5 seconds, thereby obtaining an electromagnetic steel strip with an insulating film having an average thickness of 3 μm.

[0180] [Examples 2-10, Comparative Examples 1-6]

[0181] Except for changes to the composition and sintering conditions of the coating composition for the electromagnetic steel sheet, as shown in Table 1, electromagnetic steel strips were obtained in the same manner as in Example 1.

[0182] The composition and sintering conditions of the coating compositions for each example of electromagnetic steel sheet are shown in Table 1. The evaluation results of the magnetic properties (magnetism) and bond strength for each example are shown in Table 2.

[0183] [Table 1]

[0184]

[0185] [Table 2]

[0186]

[0187] As shown in Table 2, in Examples 1 to 10, in which elastomer-modified phenolic resin is combined with epoxy resin and epoxy resin curing agent in a specific ratio, sufficient bonding strength is ensured even at 150°C, and the magnetic properties are also excellent in addition to excellent heat resistance.

[0188] On the other hand, in Comparative Examples 1 to 4, where the content of elastomer-modified phenolic resin is outside the scope of the present invention, Comparative Example 5, which does not contain elastomer-modified phenolic resin, and Comparative Example 6, which does not contain epoxy resin curing agent, it is impossible to simultaneously achieve both heat resistance and magnetic properties.

[0189] Industrial availability

[0190] According to the present invention, both the heat resistance and magnetic properties of the laminated iron core can be achieved. Therefore, it has great industrial applicability.

[0191] Explanation of reference numerals in the attached figures

[0192] 1…Raw materials, 2…Base steel plate, 3…Insulating film, 10…Rotating motor, 20…Stator, 21…Stator core, 40…Electromagnetic steel plate.

Claims

1. A coating composition for electromagnetic steel sheets, comprising epoxy resin, epoxy resin curing agent, and elastomer-modified phenolic resin; The content of the elastomer-modified phenolic resin is between 10 and 100 parts by weight relative to 100 parts by weight of the epoxy resin. The weight average molecular weight of the elastomer portion of the elastomer-modified phenolic resin is between 2,000 and 200,000.

2. The coating composition for electromagnetic steel sheets as described in claim 1, wherein, The curing shrinkage rate is less than 15%.

3. An electromagnetic steel sheet having an insulating film on its surface, the insulating film comprising the coating composition for electromagnetic steel sheets as described in claim 1 or 2.

4. A laminated iron core, wherein, Multiple electromagnetic steel plates as described in claim 3 are stacked and bonded together.

5. A rotary electric motor comprising the laminated iron core as described in claim 4.

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