Technical Field]
[0001]
The present invention relates to a coating composition for an electrical steel
sheet, an electrical steel sheet, a laminated core and an electric motor. Priority is
claimed on Japanese Patent Application No. 2020-104234, filed June 17, 2020, the
10 content of which is incorporated herein by reference.
[Background Art]
[0002]
As a core (iron core) used in an electric motor, a laminated core in which a
plurality of electrical steel sheets are bonded to each other and laminated is known.
15 Fastening and welding are known as methods of bonding electrical steel sheets to each
other. However, in fastening and welding, a magnetic property (core iron loss) of
electrical steel sheets may deteriorate due to mechanical strain and thermal strain during
processmg.
20
[0003]
As a bonding method other than fastening and welding, for example, a method
of adhering electrical steel sheets having an insulation coating having an adhesive ability
formed on the surface to each other is known (Patent Document 1 ). Adhesion using the
insulation coating does not impart mechanical strain or thermal strain and therefore it has
better core iron loss than fastening and welding. The epoxy resin has little change in
25 volume, has excellent heat resistance, oil r esistance, and chemical resistance, and is
1
excellent as an adhesive for adhering electrical steel sheets to each other (Patent
Documents 2 and 3 ).
[0004]
In recent years, in response to a request for further improvement of motor
5 efficiency, further reduction of core iron loss has been required. Thinning the electrical
steel sheet is effective in reducing core iron loss. However, since the Young's modulus
of a steel sheet decreases as the sheet thickness decreases, it is required not to apply
stress strain to the steel sheet, which causes deterioration of iron loss. In addition, in a
drive motor of an electric automobile or the like, the temperature changes drastically
10 from room temperature when driving begins to a high temperature during driving.
15
Therefore, it is important to have excellent heat resistance with which sufficient adhesive
strength can be maintained even with exposure to a high temperature during driving
while reducing core iron loss.
[0005]
Resins having excellent heat resistance are hard at room temperature and tend to
apply large stress to the laminated core. On the other hand, resins having an appropriate
hardness near room temperature are soft and inferior in heat resistance at a high
temperature. Epoxy resins have excellent heat resistance, but are hard and have low
toughness. Therefore, stress strain is applied to the steel sheet due to curing during
20 adhesion, and thus iron loss deteriorates as the steel sheet is thinned. In addition, if the
toughness is low, there is a risk of adhesion being released due to vibration impact during
driving.
[Citation List]
[Patent Document]
25 [0006]
2
[Patent Document 1]
Japanese Unexamined Patent Application, First Publication No. 2017-011863
[Patent Document 2]
Japanese Unexamined Patent Application, First Publication No. 2000-173816
5 [Patent Document 3]
10
PCT International Publication No. WO 2004/070080
[Summary of the Invention]
[Problems to be Solved by the Invention]
[0007]
An object of the present invention is to provide a coating composition for an
electrical steel sheet that can achieve both the magnetic property of a laminated core and
heat resi stance with which an adhesive strength between electrical steel sheets can be
maintained even in a high temperature state during driving, an electrical steel sheet using
the same, a laminated core and an electric motor.
15 [Means for Solving the Problem]
[0008]
The present invention includes the following aspects.
[1] A coating composition for an electrical steel sheet, including an epoxy resin, an
epoxy resin by latent curing agent, and a thermoplastic elastomer, wherein the
20 thermoplastic elastomer has a melting point of 1 00°C or higher and 200°C or lower and a
bending elastic modulus of more than 5 MPa and 100 MPa or less, and wherein the
amount of the thermoplastic elastomer with respect to a total amount of 100 parts by
mass of the epoxy resin and the epoxy resin by latent curing agent is 10 parts by mass or
more and less than 40 parts by mass.
25 [2] The coating composition for an electrical steel sheet according to [1], wherein the
3
thermoplastic elastomer is at least one selected from among an olefin-based elastomer, a
urethane-based elastomer and a polyester-based elastomer.
[3] An electrical steel sheet having an insulation coating formed by applying the coating
composition for an electrical steel sheet according to [1] or [2] to the surface of a base
5 steel sheet.
[4] The electrical steel sheet according to [3], wherein the base steel sheet has an average
sheet thickness of 0.30 mm or less.
[5] A laminated core in which a plurality of electrical steel sheets according to [3] or [ 4]
are laminated and are adhered to each other.
10 [6] An electric motor comprising the laminated core according to [5].
[Effects of the Invention]
[0009]
According to the present invention, it is possible to provide a coating
composition for an electrical steel sheet that can achieve both the magnetic property of a
15 laminated core and heat resistance with which an adhesive strength between electrical
steel sheets can be maintained even in a high temperature state during driving, an
electrical steel sheet using the same, a laminated core and an electric motor.
20
25
[Brief Description of Drawings]
[0010]
Fig. 1 is a cross-sectional view of an electric motor including a laminated core
according to a first embodiment of the present invention.
Fig. 2 is a side view of the laminated core.
Fig. 3 is a cross-sectional view taken along the line A-A in Fig. 2.
Fig. 4 is a plan view of a material forming the laminated core.
Fig. 5 is a cross-sectional view taken along the B-B in Fig. 4.
4
Fig. 6 is an enlarged view of a part C in Fig. 5.
Fig. 7 is a side view of a production device used for producing the laminated
core.
[Embodiment(s) for implementing the Invention]
5 [0011]
Hereinafter, a laminated core according to one embodiment of the present
invention, an electric motor including the laminated core, and a material forming the
laminated core will be described with reference to the drawings. Here, in the present
embodiment, as an electric motor, an electric motor, specifically, an AC electric motor,
10 more specifically, a synchronous electric motor, and still more specifically, a permanent
magnet field type electric motor will be described as an example. This type of electric
motor is suitably used for, for example, an electric automobile.
15
[0012]
(Electric motor 10)
As shown in Fig. 1, an electric motor 10 includes a stator 20, a rotor 30, a case
50, and a rotating shaft 60. The stator 20 and the rotor 30 are accommodated in the case
50. The stator 20 is fixed into the case 50.
In the present embodiment, as the electric motor 10, an inner rotor type machine
in which the rotor 30 is positioned inside the stator 20 in the radial direction is used.
20 However, as the electric motor 10, an outer rotor type machine in which the rotor 30 is
25
positioned outside the stator 20 may be used. In addition, in the present embodiment,
the electric motor 10 is a 12-pole and 18-slot three-phase AC motor. However, the
number of poles, the number of slots, the number of phases, and the like can be
appropriately changed.
The electric motor 10 can rotate at a rotational speed of 1,000 rpm by applying,
5
for example, an excitation current having an effective value of 10 A and a frequency of
1 00 Hz to each phase.
[0013]
The stator 20 includes an adhesive laminated core for a stator (hereinafter
5 referred to as a stator core) 21 and a winding (not shown).
The stator core 21 includes a circular core back part 22 and a plurality of teeth
parts 23. In the following, the center axis 0 direction of the stator core 21 (or the core
back part 22) will be referred to as an axial direction, the radial direction (direction
orthogonal to the center axis 0) of the stator core 21 (or the core back part 22) will be
10 referred to as a radial direction, and the circumferential direction (direction around the
center axis 0) of the stator core 21 (or the core back part 22) will be referred to as a
circumferential direction.
[0014]
The core back part 22 is formed in an annular shape in a plan view of the stator
15 20 when viewed from the axial direction.
The plurality of teeth parts 23 protrude from the inner peripheral of the core
back part 22 in a radially inward direction (toward the center axis 0 of the core back part
22 in the radial direction). The plurality of teeth parts 23 are arranged at equal angular
intervals in the circumferential direction. In the present embodiment, 18 teeth parts 23
20 are provided at every 20 degrees in central angles centered on the center axis 0. The
plurality of teeth parts 23 are formed so that they have the same shape and the same size.
Therefore, the plurality of teeth parts 23 have the same thickness size.
The winding is wound around the teeth parts 23. The winding may be
concentrated winding or distributed winding.
25 [0015]
6
The rotor 30 is arranged inside the stator 20 (the stator core 21) in the radial
direction. The rotor 30 includes a rotor core 31 and a plurality of permanent magnets
32.
The rotor core 31 is formed in a circular (annular) shape and arranged coaxially
5 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 the
present embodiment, a pair of permanent magnets 32 form one magnetic pole. The
plurality of sets of permanent magnets 32 are arranged at equal angular intervals in the
10 circumferential direction. In the present embodiment, 12 sets (24 in total) of permanent
magnets 32 are provided at every 30 degrees in central angles centered on the center axis
0 .
[0016]
In the present embodiment, an embedded magnet type motor is used as the
15 permanent magnet field type electric motor. In the rotor core 31, a plurality of throughholes
33 that penetrate the rotor core 31 in the axial direction are formed. The plurality
of through-holes 33 are provided to correspond to the arrangement of the plurality of
permanent magnets 32. The permanent magnets 32 that are arranged in the
corresponding through-holes 33 are fixed to the rotor core 31. Fixing of each
20 permanent magnet 32 to the rotor core 31 can be realized by, for example, adhering the
outer surface of the permanent magnet 32 and the inner surface of the through-hole 33
with an adhesive. Here, as the permanent magnet field type electric motor, a surface
magnet type motor may be used in place of the embedded magnet type.
[0017]
25 Both the stator core 21 and the rotor core 31 are laminated cores. For example,
7
as shown in Fig. 2, the stator core 21 is formed by laminating a plurality of electrical
steel sheets 40 in the lamination direction.
Here, the lamination thickness (total length along the center axis 0) of each of
the stator core 21 and the rotor core 31 is, for example, 50.0 mm. The outer diameter of
5 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 lamination thickness, the outer diameter and
the inner diameter of the stator core 21, and the lamination thickness, the outer diameter
10 and the 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 part of the teeth part 23 in the
stator core 21. That is, the inner diameter of the stator core 21 is the diameter of an
imaginary circle inscribed in the tip parts of all the teeth parts 23.
15
20
[0018]
Each electrical steel sheet 40 forming the stator core 21 and the rotor core 31 is
formed, for example, by punching a material 1 as shown in Fig. 4 to Fig. 6. The
material 1 is an electrical steel sheet that is a base of the electrical steel sheet 40. As the
material 1, for example, a strip-shaped steel sheet and a cut sheet is an exemplary
example.
Although description of the laminated core is in progress, the material 1 will be
described below. Here, in this specification, the strip-shaped steel sheet that is a base of
the electrical steel sheet 40 may be referred to as the material 1. A steel sheet having a
shape used for a laminated core obtained by punching the material 1 may be referred to
as the electrical steel sheet 40.
25 [0019]
8
(Material 1)
For example, the material 1 that is wound around a coil lA shown in Fig. 7 is
handled. In the present embodiment, a non-oriented electrical steel sheet is used as the
material 1. As the non-oriented electrical steel sheet, a non-oriented electrical steel
5 sheet according to JIS C 2552: 2014 can be used. However, as the material I, a grainoriented
electrical steel sheet may be used in place of the non-oriented electrical steel
sheet. As the grain-oriented electrical steel sheet in this case, a grain-oriented electrical
steel sheet according to JIS C 2553: 2019 can be used. In addition, a non-oriented thin
electrical steel strip or a grain-oriented thin electrical steel strip according to JIS C 2558:
10 2015 can be used.
15
[0020]
The upper and lower limit values of an average sheet thickness tO of the material
1 are set, for example, as follows, in consideration of a case in which the material 1 is
used for the electrical steel sheet 40.
As the material 1 becomes thinner, the production cost of the material 1
mcreases. Therefore, in consideration of the production cost, the lower limit value of
the average sheet thickness tO of the material 1 is 0.10 mm, preferably 0.15 mm, and
more preferably 0.18 mm.
On the other hand, when the material 1 is too thick, the production cost is
20 favorable, but when the material 1 is used for the electrical steel sheet 40, the eddy
25
current loss increases and the core iron loss deteriorates. Therefore, in consideration of
the core iron loss and the production cost, the upper limit value of the average sheet
thickness tO of the material 1 is 0.65 mm, preferably 0.35 mm, and more preferably 0.30
mm.
0.20 mm may be exemplified as a value that satisfies the above range of the
9
average sheet thickness tO of the material 1.
[0021]
Here, the average sheet thickness tO of the material! includes not only the
thickness of a base steel sheet 2 to be described below but also the thickness of an
5 insulation coating 3. In addition, a method of measuring the average sheet thickness tO
of the material 1 is, for example, the following measurement method. For example,
when the material 1 is wound in the shape of the coil lA, at least a part of the material 1
is unwound into a flat sheet shape. In the material 1 unwound into a flat sheet shape, a
predetermined position (for example, a position separated from the edge of the material 1
10 in the longitudinal direction by 10% of the total length ofthe material I) on the material
1 in the longitudinal direction is selected. At the selected position, the material 1 is
divided into five areas in the width direction thereof. At four locations that are
boundaries of these five areas, the sheet thickness of the material I is measured. The
average value of the sheet thicknesses at four locations can be set as the average sheet
15 thickness tO of the material 1.
[0022]
The upper and lower limit values of the average sheet thickness tO of the
material I can be naturally used as the upper and lower limit values of the average sheet
thickness tO of the electrical steel sheet 40. Here, a method of measuring the average
20 sheet thickness tO of the electrical steel sheet 40 is, for example, the following
measurement method. For example, the lamination thickness of the laminated core is
measured at four locations (that is, every 90 degrees around the center axis 0) at equal
intervals in the circumferential direction. Each of the measured lamination thicknesses
at four locations is divided by the number of laminated electrical steel sheets 40 to
25 calculate the sheet thickness per sheet. The average value of the sheet thicknesses at
10
four locations can be set as the average sheet thickness tO of the electrical steel sheet 40.
[0023]
As shown in Fig. 5 and Fig. 6, the material 1 includes the base steel sheet 2 and
the insulation coating 3. In the material 1, both surfaces of the strip-shaped base steel
5 sheet 2 are covered with the insulation coating 3. In the present embodiment, most of
the material! is formed with the base steel sheet 2, and the insulation coating 3 thinner
than the base steel sheet 2 is laminated on the surface of the base steel sheet 2.
[0024]
The chemical composition of the base steel sheet 2 includes 2.5% to 4.5% of Si
10 in mass%, as shown below in units of mass%. Here, when the chemical composition is
within the above range, the yield strength of the material 1 (the electrical steel sheet 40)
can be set to, for example, 380 MPa or more and 540 MPa or less.
[0025]
Si: 2.5% to 4.5%
15 Al: 0.001% to 3.0%
Mn: 0.05% to 5.0%
The remainder: Fe and impurities
[0026]
When the material 1 is used for the electrical steel sheet 40, the insulation
20 coating 3 exhibits insulation performance between the electrical steel sheets 40 adjacent
to each other in the lamination direction. In addition, in the present embodiment, the
insulation coating 3 has an adhesive ability, and adheres the electrical steel sheets 40
adjacent to each other in the lamination direction. The insulation coating 3 may have a
single-layer structure or a multi-layer structure. More specifically, for example, the
25 insulation coating 3 may have a single-layer structure having both insulation performance
11
and an adhesive ability or may have a multi-layer structure including an underlying
insulation coating having excellent insulation performance and a top insulation coating
having an excellent adhesive ability. Here, having an adhesive ability means exhibiting
an adhesive strength of a predetermined value or more under a predetermined
5 temperature condition.
[0027]
In the present embodiment, the insulation coating 3 entirely covers both the
surfaces of the base steel sheet 2 without gaps. However, as long as the above
insulation performance and adhesive ability are secured, a part of the layer of the
10 insulation coating 3 does not have to cover both surfaces of the base steel sheet 2 without
gaps. In other words, a part of the layer of the insulation coating 3 may be provided
intermittently on the surface of the base steel sheet 2. However, in order to secure the
insulation performance, both surfaces of the base steel sheet 2 need to be covered with
the insulation coating 3 so that none of surface is exposed. Specifically, when the
15 insulation coating 3 does not have an underlying insulation coating having excellent
insulation performance and has a single-layer structure having both insulation
performance and an adhesive ability, the insulation coating 3 needs to be formed over the
entire surface of the base steel sheet 2 without gaps. On the other hand, when the
insulation coating 3 has a multi-layer structure having an underlying insulation coating
20 having excellent insulation performance and a top insulation coating having an excellent
adhesive ability, even if the underlying insulation coating is formed over the entire
surface of the base steel sheet without gaps and the top insulation coating is provided
intermittently in addition to forming both the underlying insulation coating and the top
insulation coating over the entire surface of the base steel sheet 2 without gaps, it is
25 possible to achieve both the insulation performance and the adhesive ability.
12
[0028]
The coating composition for forming an underlying insulation coating is not
particularly limited, and for example, a general treatment agent such as a chromic acidcontaining
treatment agent or a phosphate-containing treatment can be used.
5 [0029]
The insulation coating having an adhesive ability is coated with a coating
composition for an electrical steel sheet including an epoxy resin, an epoxy resin by
latent curing agent, and a thermoplastic elastomer.
The insulation coating composed of the coating composition for an electrical
10 steel sheet is in an uncured state or a semi-cured state (B stage) before heating and
pressurizing when a laminated core is produced, a curing reaction proceeds by heating
during heating and pressurizing, and an adhesive ability is exhibited. The coating
composition for an electrical steel sheet may be used for forming an insulation coating
having a single-layer structure or may be used for forming a top insulation coating
15 provided on an underlying insulation coating.
[0030]
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
20 resins, bisphenol F type epoxy resins, phenol novolak type epoxy resins, cresol novolak
type epoxy resins, alicyclic epoxy resins, glycidyl ester type epoxy resins, glycidylamine
type epoxy resins, hydantoin type epoxy resins, isocyanurate type epoxy resins, acrylic
acid-modified epoxy resins (epoxy acrylate), phosphorus-containing epoxy resins, and
halides thereof (brominated epoxy resins, etc.), hydrogen additives and the like. The
25 epoxy resins may be used alone or two or more thereof may be used in combination.
13
[0031]
The coating composition for an electrical steel sheet may contain an acrylic
resm.
The acrylic resin is not particularly limited. Examples of monomers used for
5 acrylic resins include unsaturated carboxylic acids such as acrylic acid and methacrylic
acid, and (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl
(meth)acrylate, isobutyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl
(meth)acrylate, 2-hydroxyethyl (meth)acrylate, and hydroxypropyl (meth)acrylate.
Here, the (meth)acrylate is acrylate or methacrylate. The acrylic resins may be used
10 alone or two or more thereof may be used in combination.
[0032]
The acrylic resin may have a structural unit derived from a monomer other than
an acrylic monomer. Examples of other monomers include ethylene, propylene, and
styrene. The other monomers may be used alone or two or more thereof may be used in
15 combination.
[0033]
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 an electrical steel sheet, it may be contained as a monomer forming an acrylic resin.
20 [0034]
The epoxy resin by latent curing agent is a type of curing agent that cures an
epoxy resin and starts a curing reaction when heated to a predetermined temperature.
Examples of epoxy resin by latent curing agents include aromatic polyamines, acid
anhydrides, phenolic curing agents, dicyandiamides, boron trifluoride-amine complexes,
25 and organic acid hydrazides.
14
[0035]
Examples of aromatic polyamines include m-phenylenediamine,
diaminodiphenyl methane, diaminodiphenylethane, and diaminodiphenyl sulfone.
Examples of acid anhydrides include phthalic anhydride, hexahydrophthalic
5 anhydride, tetrahydrophthalic anhydride, pyromellitic dianhydride, and pyromellitic acid
anhydride, and among these, an acid anhydride which has a melting point of 160oc or
higher and is solid at room temperature is preferable, and trimellitic anhydride, and
benzophenone tetracarboxylic anhydride are particularly preferable.
Examples of phenolic curing agents include phenol novolak resins, cresol
10 novolak resins, bisphenol novolak resins, triazine-modified phenol novolak resins, and
phenol resol resins.
[0036]
In consideration of the heat resistance of the cured product, as the epoxy resin by
latent curing agent, aromatic polyamines, phenolic curing agents, and dicyandiamides are
15 preferable, and phenol resol resins, diaminodiphenyl methane, and dicyandiamides are
more preferable. The epoxy resin by latent curing agents may be used alone or two or
more thereof may be used in combination.
[0037]
The lower limit value of the amount of the epoxy resin by latent curing agent in
20 the coating composition for an electrical steel sheet with respect to 100 parts by mass of
the epoxy resin is preferably 1 part by mass, and more preferably 2 parts by mass. The
upper limit value of the amount of the epoxy resin by latent curing agent is preferably 20
parts by mass, and more preferably 15 parts by mass .
[0038]
25 The thermoplastic elastomer i s a compound composed of a soft segment and a
15
hard segment that retains rubber elasticity, and one that can be finely dispersed in an
epoxy resin is preferable.
[0039]
The melting point of the thermoplastic elastomer is 1 00°C or higher and 200°C
5 or lower. When the melting point of the thermoplastic elastomer is equal to or larger
than the lower limit value, the adhesive strength at a high temperature is maintained.
When the melting point of the thermoplastic elastomer is equal to or less than the upper
limit value, the core iron loss is favorable.
The lower limit value of the melting point of the thermoplastic elastomer is
10 preferably 90°C, more preferably ll0°C, and still more preferably 130°C or higher.
The upper limit value of the melting point of the thermoplastic elastomer is preferably
180°C, and more preferably 160oc.
Here, "melting point" is a value measured at a temperature rise rate of 10°C/min
according to JIS K7121 (1987) using a differential scanning calorimeter (DSC).
15 [0040]
The bending elastic modulus of the thermoplastic elastomer is more than 5 MPa
and 100 MPa or less. When the bending elastic modulus of the thermoplastic elastomer
exceeds the lower limit value, it is possible to prevent the thermoplastic elastomer from
protruding from the end due to pressurization during adhesion. When the bending
20 elastic modulus of the thermoplastic elastomer is equal to or less than the upper limit
value, the core iron loss is favorable.
The lower limit value of the bending elastic modulus of the thermoplastic
elastomer is preferably 6 MPa, and more preferably 7 MPa. The upper limit value of
the bending elastic modulus of the thermoplastic elastomer is preferably 80 MPa, and
25 more preferably 60 MPa.
16
5
Here, the bending elastic modulus is measured under the condition of a test
speed of 10 mm/min (1 mm/min when the test piece has a size of 3.5 mm or less)
according to JIS K 7171 (2008).
[0041]
As the thermoplastic elastomer, at least one selected from among an olefin-based
elastomer, a urethane-based elastomer and a polyester-based elastomer is preferable
because it is easy to achieve both the magnetic property and heat resistance. The
thermoplastic elastomers may be used alone or two or more thereof may be used in
combination.
10 [0042]
Examples of olefin-based elastomers include those obtained by combining or
mixing an ethylene-propylene copolymer with polypropylene.
[0043]
Examples of urethane-based elastomers include compounds having a urethane
15 bond in which diisocyanate and a diol are reacted. The viscoelastic properties of the
urethane-based elastomer can be adjusted by the length of the carbon chain of the dioL
[0044]
Examples of diisocyanates include hexamethylene diisocyanate,
dicyclohexylmethane diisocyanate, diphenyl-methane diisocyanate, tolylene
20 diisocyanate, and urethane prepolymers having an isocyanate type at both ends.
Examples of diols include ethylene glycol, dipropylene glycol, tetraethylene
glycol, 1,4-butanediol, 1,4-cyclohexanediol, dihydroxynaphthalene, and bisphenolA.
[0045]
Examples of polyester-based elastomers include polyester-polyether type
25 copolymers (copolymers of polybutylene terephthalate and tetramethylene oxide glycol,
17
etc.) and polyester-polyester type copolymers (copolymers of polybutylene terephthalate
and polybutylene adipate, etc.).
[0046]
The amount of the thermoplastic elastomer in the coating composition for an
5 electrical steel sheet with respect to a total amount of 100 parts by mass of the epoxy
resin and the epoxy resin by latent curing agent is 10 parts by mass or more and less than
40 parts by mass. When the amount of the thermoplastic elastomer is equal to or larger
than the lower limit value, core iron loss is favorable. When the amount of the
thermoplastic elastomer is equal to or less than the upper limit value, the adhesive
10 strength at a high temperature is maintained.
[0047]
In general, when the adhesive strength at a high temperature is secured, an
epoxy resin adhesive having high heat resistance has too large a Young's modulus near
room temperature, stress is applied to the steel sheet, and core iron loss deteriorates. On
15 the other hand, the heat resistance deteriorates with a resin composition having an
appropriate strength near room temperature. In the present invention, a thermoplastic
elastomer that has a soft segment and a hard segment and has a large bending elastic
modulus is finely dispersed in an epoxy resin. Accordingly, stress applied near room
temperature is minimized and deterioration of core iron loss is minimized. In addition,
20 since the thermoplastic elastomers are not connected to each other, flowing of the epoxy
resin at a high temperature is minimized and the adhesive strength is secured. When a
specific amount of such a specific thermoplastic elastomer is used, both core iron loss
and heat resistance near room temperature are achieved.
[0048]
25 In the present invention, since an insulation coating can be formed with such a
18
coating composition for an electrical steel sheet, and stress applied to the electrical steel
sheet can be reduced, it can be suitably applied to a thin electrical steel sheet which is
effective in reducing iron loss. More specifically, the coating composition for an
electrical steel sheet of the present invention is particularly effective as a coating
5 composition for forming an insulation coating on the surface of a base steel sheet having
an average sheet thickness of 0.30 mm or less.
[0049]
The insulation coating 3 can be formed, for example, by applying a coating
liquid in which a coating composition for an electrical steel sheet is dissolved in a solvent
10 onto the surface of the base steel sheet, drying and baking it. The solvent used for a
coating liquid is not particularly limited as long as it can dissolve a coating composition
for an electrical steel sheet, and it is preferable to use an aqueous solution in order to
prevent the organic solvent from being emitted. The lower limit value of the end-point
temperature during baking is preferably l20°C, and more preferably 150°C. The upper
15 limit value of the end-point temperature during baking is preferably 250°C, and more
preferably 230°C.
The lower limit value of the baking time is preferably 5 seconds, and more
preferably 8 seconds. The upper limit value of the baking time is preferably 60 seconds,
and more preferably 30 seconds.
20 [0050]
The upper and lower limit values of an average thickness t 1 of the insulation
coating 3 are set, for example, as follows, in consideration of a case in which the material
1 is used for the electrical steel sheet 40.
When the material 1 is used for the electrical steel sheet 40, the average
25 thickness t1 of the insulation coating 3 (the thickness per one surface of the electrical
19
steel sheet 40 (the material 1)) is adjusted so that the insulation performance and
adhesive ability between the electrical steel sheets 40 laminated with each other can be
secured.
In the case of the insulation coating 3 having a single-layer structure, the
5 average thickness tl of the insulation coating 3 (the thickness per one surface of the
electrical steel sheet 40 (the material 1)) may be, for example, 1.5 11m or more and 8.0
11m or less.
In the case of the insulation coating 3 having a multi-layer structure, the average
thickness of the underlying insulation coating may be, for example, 0.3 11m or more and
10 2.5 11m or less, and is preferably 0.5 11m or more and 1.5 11m or less. The average
thickness of the top insulation coating may be, for example, 1.5 11m or more and 8.0 11m
or less.
Here, a method of measuring the average thickness tl of the insulation coating 3
in the material 1 is the same as that of the average sheet thickness tO of the material 1,
15 and the average thickness can be determined by obtaining the thickness of the insulation
coating 3 at a plurality of locations and averaging these thicknesses.
[0051]
The upper and lower limit values of the average thickness tl of the insulation
coating 3 in the material 1 can be naturally used as the upper and lower limit values of
20 the average thickness tl of the insulation coating 3 in the electrical steel sheet 40. Here,
a method of measuring the average thickness tl of the insulation coating 3 in the
electrical steel sheet 40 is, for example, the following measurement method. For
example, among the plurality of electrical steel sheets forming the laminated core, the
electrical steel sheet 40 positioned on the outmost side in the lamination direction (the
25 electrical steel sheet 40 whose surface is exposed in the lamination direction) is selected.
20
On the surface of the selected electrical steel sheet 40, a predetermined position in the
radial direction (for example, a position exactly at the middle (center) between the inner
peripheral edge and the outer peripheral edge of the electrical steel sheet 40) is selected.
At the selected position, the thickness of the insulation coating 3 of the electrical steel
5 sheet 40 is measured at four locations (that is, every 90 degrees around the center axis 0)
at equal intervals in the circumferential direction. The average value of the measured
thicknesses at four locations can be set as the average thickness t1 of the insulation
coating 3.
Here, the reason why the average thickness t1 of the insulation coating 3 is
10 measured on the electrical steel sheet 40 positioned on the outmost side in the lamination
direction in this manner is that the insulation coating 3 is formed so that the thickness of
the insulation coating 3 hardly changes at the lamination position in the lamination
direction of the electrical steel sheet 40.
15
20
[0052]
The electrical steel sheet 40 is produced by punching the material 1 as described
above, and the laminated core (the stator core 21 and the rotor core 31) is produced using
the electrical steel sheet 40.
[0053]
(Method of laminating laminated core)
Hereinafter, description will return to the laminated core. As shown in Fig. 3,
the plurality of electrical steel sheets 40 forming the stator core 21 are laminated via the
insulation coating 3.
The electrical steel sheets 40 adjacent to each other in the lamination direction
are adhered over the entire surface with the insulation coating 3. In other words, a
25 surface of the electrical steel sheet 40 (hereinafter referred to as a first surface) facing the
21
lamination direction is an adhesive area or region 4la over the entire surface. However,
the electrical steel sheets 40 adjacent to each other in the lamination direction may not be
adhered over the entire surface. In other words, on the first surface of the electrical
steel sheet 40, the adhesive area or region 4la and the non-adhesive area or region (not
5 shown) may be mixed.
[0054]
In the present embodiment, the plurality of electrical steel sheets forming the
rotor core 31 are fixed to each other by a fastening 42 Goggle) shown in Fig. 1.
However, the plurality of electrical steel sheets forming the rotor core 31 may also have a
10 laminate structure fixed by the insulation coating 3 as in the stator core 21.
15
In addition, the laminated core such as the stator core 21 and the rotor core 31
may be formed by so-called rotating stacking.
[0055]
(Method of producing laminated core)
The stator core 21 is produced, for example, using a production device 100
shown in Fig. 7. Hereinafter, in description of the production method, first, the
laminated core production device 100 (hereinafter simply referred to as the production
device 1 00) will be described.
In the production device 100, while the material 1 is sent out from the coil lA
20 (hoop) in the arrow F direction, it is punched a plurality of times using molds arranged
on stages, and gradually formed into the shape of the electrical steel sheet 40. Then, the
punched electrical steel sheets 40 are laminated and pressurized while raising the
temperature. As a result, the electrical steel sheets 40 adjacent to each other in the
lamination direction are adhered to each other with the insulation coating 3 (that i s, a part
25 of the insulation coating 3 positioned in the adhesive area or region 4la is caused to
22
exhibit an adhesive ability), and the adhesion is completed.
[0056]
As shown in Fig. 7, the production device 100 includes a plurality of stages of
punching stations 110. The punching station 110 may have two stages or three or more
5 stages. The punching station 110 of each stage includes a female mold 111 arranged
below the material 1 and a male mold 112 arranged above the material 1.
[0057]
The production device 100 further includes a lamination station 140 at a position
downstream from the most downstream punching station 110. The lamination station
10 140 includes a heating device 141, an outer peripheral punching female mold 142, a heat
insulation member 143, an outer peripheral punching male mold 144, and a spring 145.
The heating device 141, the outer peripheral punching female mold 142, and the
heat insulation member 143 are arranged below the material 1. On the other hand, the
outer peripheral punching male mold 144 and the spring 145 are arranged above the
15 material I. Here, reference numeral21 indicates a stator core.
[0058]
In the production device 100 having the configuration described above, first, the
material I is sequentially sent out from the coil lAin the arrow F direction in Fig. 7.
Then, the material I is sequentially punched on the plurality of stages of punching
20 stations 110. According to these punching procedures, in the material I, the shape of
the electrical steel sheet 40 having the core back part 22 and the plurality of teeth parts 23
shown in Fig. 3 is obtained. However, since the material is not completely punched at
this time, it proceeds to the next process in the arrow F direction.
[0059]
25 Then, finally, the material 1 is sent out to the lamination station 140, punched
23
out by the outer peripheral punching male mold 144, and laminated with high accuracy.
During this lamination, the electrical steel sheet 40 receives a certain pressurizing force
from the spring 145. When the punching process and the lamination process as
described above are sequentially repeated, a predetermined number of electrical steel
5 sheets 40 can be stacked. In addition, the laminated core formed by stacking the
electrical steel sheets 40 in this manner is heated to for example, a temperature of 200°C,
by the heating device 141. According to this heating, the insulation coatings 3 of the
adjacent electrical steel sheets 40 are adhered to each other.
Here, the heating device 141 may not be arranged on the outer peripheral
10 punching female mold 142. That is, it may be taken out of the outer peripheral
punching female mold 142 before the electrical steel sheet 40 laminated with the outer
peripheral punching female mold 142 is adhered. In this case, the outer peripheral
punching female mold 142 may not have the heat insulation member 143. In addition,
in this case, the stacked electrical steel sheets 40 before adhesion may be sandwiched and
15 held from both sides in the lamination direction with a jig (not shown) and then
transported and heated.
According to the above processes, the stator core 21 is completed.
[0060]
As described above, in the present invention, an insulation coating is formed on
20 the surface of the electrical steel sheet u sing a coating composition for an electrical steel
sheet in which an epoxy resin, an epoxy resin by latent curing agent and a specific
thermoplastic elastomer are combined at a specific ratio. Accordingly, it is possible to
achieve both an excellent magnetic property (core iron loss) of the laminated core and
excellent heat resistance with which the adhesive strength between electrical steel sheets
25 can be maintained even in a high temperature state during driving.
24
5
[0061]
Here, the technical scope of the present invention is not limited to the above
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 sizes of the outer diameter and the inner diameter of the
stator core, the lamination thickness, the number of slots, the size ratio between the
circumferential direction and the radial direction of the teeth part, the size ratio between
the teeth part and the core back part in the radial direction, and the like can be arbitrarily
10 designed according to desired properties of the electric motor.
[0062]
In the rotor in the above embodiment, a pair of permanent magnets 32 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
15 32 may form one magnetic pole.
[0063]
One embodiment and examples of the present invention have been described
above. However, the technical scope of the present invention is not limited to the above
embodiments and examples, and various modifications can be made without departing
20 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 sizes of the outer diameter and the inner
diameter of the stator core 21, the lamination thickness, the number of slots, the size ratio
between the circumferential direction and the radial direction of the teeth part 23, the size
25 ratio between the teeth part 23 and the core back part 22 in the radial direction, and the
25
like can be arbitrarily designed according to desired properties of the electric motor.
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 form. For example,
one permanent magnet 32 may form one magnetic pole or three or more permanent
5 magnets 32 may form one magnetic pole.
[0064]
In the above embodiment, the permanent magnet field type electric motor has
been described as the electric motor 10 as an example, but the structure of the electric
motor 10 is not limited to this as exemplified below, and additionally various known
10 structures not provided as an exemplary example below can be used.
15
In the above embodiment, the permanent magnet field type electric motor has
been described as the electric motor 10 as an example, but the present invention is not
limited thereto. For example, the electric motor 10 may be a reluctance type electric
motor or an electromagnet field type electric motor (winding field type electric motor).
In the above embodiment, the synchronous electric motor has been described as
the AC electric motor as an example, but the present invention is not limited thereto.
For example, the electric motor 10 may be an induction electric motor
In the above embodiment, the AC electric motor has been described as the
electric motor 10 as an example, but the present invention is not limited thereto. For
20 example, the electric motor 10 may be a DC electric motor.
25
In the above embodiment, the electric motor has been described as the electric
motor 10 as an example, but the present invention is not limited thereto. For example,
the electric motor 10 may be a generator.

[CLAIMS]
What is claimed is:
1. A coating composition for an electrical steel sheet, comprising an epoxy resin, an
5 epoxy resin by latent curing agent, and a thermoplastic elastomer,
wherein the thermoplastic elastomer has a melting point of 1 ooac or higher and
200°C or lower and a bending elastic modulus of more than 5 MPa and 100 MPa or les s,
and
wherein the amount of the thermoplastic elastomer with respect to a total
10 amount of 100 parts by mass of the epoxy resin and the epoxy resin by latent curing
agent is 10 parts by mass or more and less than 40 parts by mass.
2. The coating composition for an electrical steel sheet according to claim 1,
wherein the thermoplastic elastomer is at least one selected from among an
15 olefin-based elastomer, a urethane-based elastomer and a polyester-based elastomer.
20
3. An electrical steel sheet having an insulation coating formed by applying the coating
composition for an electrical steel sheet according to claim 1 or 2 to the surface of a base
steel sheet.
4. The electrical steel sheet according to claim 3,
wherein the base steel sheet has an average sheet thickness of 0.30 mm or less.
5. A laminated core in which a plurality of electrical steel sheets according to claim 3
25 or 4 are laminated and are adhered to each other.