[Technical Field]
[0001]
The present invention relates to a coating composition for an electrical steel
sheet, an adhesive surface-coated electrical steel sheet and a laminated core. Priority is
claimed on Japanese Patent Application No. 2020-104233, filed June 17,2020, the
10 content of which is incorporated herein by reference.
[Background Art]
[0002]
Ordinarily, in the case of assembling a laminated core such as a motor or a
transformer using electrical steel sheets, unit iron cores are produced by shearing or
15 blanking, and then the unit iron cores are laminated and firmly fixed by bolting, swaging,
welding or adhesion, thereby obtaining a laminated core. In a firm fixing method such
as swaging or welding, mechanical strain or thermal strain is imparted to the laminated
core, and thus there are cases where the core iron loss deteriorates.
20
[0003]
Regarding such a problem, for example, Patent Documents 1 to 3 have proposed
adhesion methods in which an insulating coating exhibiting an adhesive capability by
either or both of heating and pressurization (a coating composition for an electrical steel
sheet) is used.
[Citation List]
25 [Patent Document]
1
5
[0004]
[Patent Document 1]
Japanese Unexamined Patent Application, First Publication No. 2000-173816
[Patent Document 2]
PTC International Publication No. WO 2004/070080
[Patent Document 3]
Japanese Unexamined Patent Application, First Publication No. 2017-11863
[Summary of the Invention]
[Problems to be Solved by the Invention]
10 [0005]
Laminated cores in which unit iron cores are caused to adhere together with the
insulating coatings are not imparted with mechanical strain or thermal strain and are thus
excellent in terms of core iron loss. However, in recent years, there has been a request
for additional improvement in motor efficiency, and additional reduction in core iron loss
15 has been required.
[0006]
A decrease in the thickness of an electrical steel sheet has been effective for
reducing core iron loss. However, since a decrease in the sheet thickness is
accompanied by a decrease in the Young's modulus of the electrical steel sheet, it is
20 necessary to prevent stress strain, which is a cause of deterioration of core iron loss, from
being imparted to the electrical steel sheet.
Furthermore, in uses such as electrical vehicle motors, high heat resistance is
required, but insulating coatings that impart no stress strain to electrical steel sheets are
ordinarii y soft and have poor heat resistance.
25 [0007]
2
The present invention has been made in consideration of the above-described
circumstances, and an objective of the present invention is to provide a coating
composition for an electrical steel sheet, an adhesive surface-coated electrical steel sheet
and a laminated core that are capable of further suppressing stress strain that is imparted
5 to electrical steel sheets and have heat resistance high enough to maintain the adhesion
strength even during the generation of heat from motors.
[Means for Solving the Problem]
[0008]
In order to solve the above-described problems, the present invention proposes
10 the following means.
15
[ 1] A coating composition for an electrical steel sheet according to an aspect of
the present invention contains an epoxy resin, a phenolic curing agent (A) and one or
more amine-based curing agents (B) selected from an aromatic amine and
dicyandiamide,
in which the amount of the phenolic curing agent (A) is 1 to 40 parts by mass
with respect to 100 parts by mass of the epoxy resin, and the amount of the amine-based
curing agents (B) is 0.5 to 5 parts by mass with respect to 100 parts by mass of the epoxy
resin.
[2] The coating composition for an electrical steel sheet according to [ 1], in
20 which a mass ratio represented by [the amount of the phenolic curing agent (A)]/[ the
amount of the amine-based curing agents (B)] may be 1 to 20.
[3] An adhesive surface-coated electrical steel sheet according to an aspect of
the present invention has an insulating coating containing the coating composition for an
electrical steel sheet according to [1] or [2] on a surface, in which the thickness is 0.65
25 mm or less.
3
5
[ 4] A laminated core according to an aspect of the present invention is formed by
laminating two or more adhesive surface-coated electrical steel sheets according to [3].
[Effects of the Invention]
[0009]
According to the above-described aspects of the present invention, it is possible
to provide a coating composition for an electrical steel sheet, an adhesive surface-coated
electrical steel sheet and a laminated core that are capable of further suppressing stress
strain that is imparted to electrical steel sheets and have heat resistance high enough to
maintain the adhesion strength even during the generation of heat from motors.
10 [Brief Description of Drawings]
15
20
[0010]
Fig. 1 is a cross-sectional view of a rotary electric machine including a
laminated core according to an embodiment of the present invention.
1.
Fig. 2 is a side view of the laminated core shown in Fig. 1.
Fig. 3 is a cross-sectional view inn a direction of a line A-A in Fig. 2.
Fig. 4 is a plan view of a material for forming the laminated core shown in Fig.
Fig. 5 is a cross-sectional view in a direction of a line B-B in Fig. 4.
Fig. 6 is an enlarged view of a C part of Fig. 5.
Fig. 7 is a side view of a manufacturing device that is used for manufacturing
the laminated core shown in Fig. 1.
[Embodiment for implementing the Invention]
[0011]
Hereinafter, a laminated core (laminated core) according to an embodiment of
25 the present invention, a rotary electric machine including this laminated core and a
4
material that forms this laminated core will be described. In the present embodiment, as
the rotary electric machine, an electric motor, specifically, an alternating-current electric
motor, 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
5 of electric motor is preferably employed in, for example, electric vehicles.
[0012]
In addition, numerical limiting ranges expressed below using "to" include the
lower limit value and the upper limit value in the ranges. Numerical values expressed
with "less than" or "more than" are not included in numerical ranges.
10 [0013]
As shown in Fig. 1, a rotary electric machine 10 includes a stator 20, a rotor 30,
a case 50 and a rotary shaft 60. The stator 20 and rotor 30 are accommodated in the
case 50. The stator 20 is fixed in the case 50.
In the present embodiment, as the rotary electric machine 10, an inner rotor type
15 in which the rotor 30 is positioned radially inside the stator 20 is employed. However,
as the rotary electric machine 10, an outer rotor type in which the rotor 30 is positioned
outside the stator 20 may also be employed. In addition, in the present embodiment, the
rotary electric machine 10 is a three-phase alternating-current motor having 12 poles and
18 slots. However, the number of poles, the number of slots, the number of phases, and
20 the like can be changed as appropriate.
25
The rotary electric machine 10 can be rotated at a rotation speed of 1000 rpm by,
for example, applying an excitation current of an effective value of 10 A and a frequency
of 100 Hz to each phase.
[0014]
The stator 20 includes an adhesive laminated core for the stator (hereinafter,
5
stator core) 21 and a winding, not shown.
The stator core 21 includes a ring-shaped core back portion 22 and a plurality of
tooth portions 23. Hereinafter, a direction along the central axis 0 of the stator core 21
(or the core back portion 22) will be referred to as the axial direction, the radial direction
5 of the stator core 21 (or the core back portion 22) (a direction orthogonal to the central
axis 0) will be referred to as the radial direction, and the circumferential direction (a
direction around the central axis 0) of the stator core 21 (or the core back portion 22)
will be referred to as the circumferential direction.
10
[0015]
The core back portion 22 is formed in an annular shape in a plan view of the
stator 20 seen in the axial direction.
The plurality of tooth portions 23 protrude radially inward (toward the central
axis 0 of the core back portion 22 along the radial direction) from the inner
circumference of the core back portion 22. The plurality of tooth portions 23 are
15 disposed at equal angular intervals in the circumferential direction. In the present
20
25
embodiment, 18 tooth portions 23 are provided every center angle of 20 degrees around
the central axis 0. The plurality of tooth portions 23 are formed in mutually equivalent
shapes and mutually equivalent sizes. This makes the plurality of tooth portions 23
have mutually the same thickness dimensions.
The winding is wound around the tooth portions 23. The winding may be a
concentrated winding or a distributed winding.
[0016]
The rotor 30 is disposed radially inside the stator 20 (stator core 21). The rotor
30 includes a rotor core 31 and a plurality of permanent magnets 32.
The rotor core 31 is formed in a ring shape (annular shape) that is concentrically
6
disposed with respect to the stator 20. The rotary shaft 60 is disposed in the rotor core
31. The rotary 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, one set of two permanent magnets 32 forms one magnetic pole.
5 The plurality of permanent magnets 32 are disposed at equal angular intervals in the
circumferential direction. In the present embodiment, 12 sets of permanent magnets 32
(24 permanent magnets in total) are provided every center angle of 30 degrees around the
central axis 0.
10
[0017]
In the present embodiment, as the permanent magnet field-type electric motor,
an embedded magnet-type motor is employed. In the rotor core 31, a plurality of
through holes 33 penetrating the rotor core 31 in the axial direction are formed. The
plurality of through holes 33 are provided so as to correspond to the disposition of the
plurality of permanent magnets 32. Each permanent magnet 32 is fixed to the rotor core
15 31 in a state of being disposed in the corresponding through hole 33. Each permanent
magnet 32 can be fixed to the rotor core 31 by, for example, causing the outer surface of
the permanent magnet 32 and the inner surface of the through hole 33 to adhere to each
other with an adhesive. As the permanent magnet field-type electric motor, a surface
permanent magnet-type motor may be employed instead of the embedded magnet-type
20 motor
25
[0018]
The stator core 21 and the rotor core 31 are both laminated cores. For example,
the stator core 21 is formed by laminating a plurality of electrical steel sheets (adhesive
surface-coated electrical steel sheets) 40 in the lamination direction as shown in Fig. 2.
The lamination thickness (total length along the central axis 0) of each of the
7
stator core 21 and the rotor core 31 is set to, for example, 50.0 mm. The outer diameter
of the stator core 21 is set to, for example, 250.0 mm. The inner diameter of the stator
core 21 is set to, for example, 165.0 mm. The outer diameter of the rotor core 31 is set
to, for example, 163.0 mm. The inner diameter of the rotor core 31 is set to, for
5 example, 30.0 mm. These values are simply examples, and the lamination thickness,
outer diameter and inner diameter of the stator core 21 and the lamination thickness,
outer diameter and inner diameter of the rotor core 31 are not limited to these values.
Here, the inner diameter of the stator core 21 is based on the tip portions of the tooth
portions 23 in the stator core 21. That is, the inner diameter of the stator core 21 is the
10 diameter of a virtual circle that inscribes the tip portions of all of the tooth portions 23.
[0019]
Each of the electrical steel sheets 40 that form the stator core 21 and the rotor
core 31 is formed by, for example, blanking a material 1 as shown in Fig. 4 to Fig. 6 or
the like. The material 1 is a steel sheet (electrical steel sheet) that serves as the base
15 material of the electrical steel sheet 40. Examples of the material 1 include a stripshaped
steel sheet (electrical steel strip), a cut-to-length sheet and the like.
[0020]
While the topic of the current description is the laminated core, this material 1
will be described below. In the present specification, there is a case where a strip-
20 shaped steel sheet that serves as the base material of the electrical steel sheet 40 is
referred to as the material 1. There is a case where a steel sheet formed into a shape that
is used in the laminated core by blanking the material 1 is referred to as the electrical
steel sheet 40.
[0021]
25 The material 1 is handled in a state of, for example, being wound around a coil
8
lA. In the present embodiment, a non-oriented electrical steel sheet is employed as the
material 1. As the non-oriented electrical steel sheet, a non-oriented electrical steel strip
of JIS C 2552: 2014 can be employed. However, instead of the non-oriented electrical
steel sheet, an oriented electrical steel sheet may be employed as the material 1. As the
5 oriented electrical steel sheet in this case, an oriented electrical steel strip of JIS C 2553:
2019 can be employed. In addition, a non-oriented thin electrical steel strip or oriented
thin electrical steel strip of JIS C 2558: 2015 can be employed.
[0022]
The upper and lower limit values of the average sheet thickness tO of the
10 material 1 are set, for example, as described below in consideration of a case where the
material 1 is used as the electrical steel sheet 40.
As the material 1 becomes thinner, the manufacturing cost of the material 1
Increases. Therefore, when the manufacturing cost is taken into account, the lower limit
value of the average sheet thickness tO of the material I becomes 0.10 mm, preferably
15 becomes 0.15 mm and more preferably becomes 0.18 mm.
On the other hand, when the material 1 is too thick, the manufacturing cost
becomes favorable; however, in a case where the material l has been used as the
electrical steel sheet 40, the eddy-current loss increases, and the core iron loss
deteriorates. Therefore, when the core iron loss and the manufacturing cost are taken
20 into account, the upper limit value of the average sheet thickness tO of the material 1
becomes 0.65 mm, preferably becomes 0.35 mm and more preferably becomes 0.30 mm.
25
As the thickness that satisfies the above-described range of the average sheet
thickness tO of the material 1, 0.20 mm can be an example.
[0023]
The average sheet thickness tO of the material I includes not only the thickness
9
of a base material steel sheet 2 to be described below but also the thickness of an
insulating coating 3. In addition, as a method for measuring the average sheet thickness
tO of the material 1, for example, the following measurement method is followed. For
example, in a case where the material I is wound in the shape of the coil I A, at least a
5 part of the material 1 is unwound in a flat sheet shape. In the material 1 unwound in a
flat sheet shape, a predetermined position in the longitudinal direction of the material 1
(for example, a position apart from one end edge of the material 1 in the longitudinal
direction by 10% of the total length of the material 1) is selected. At this selected
position, the material 1 is divided into five regions along the width direction. At four
10 sites that become the boundaries of these five regions, the sheet thickness of the material
1 is measured. The average value of the sheet thicknesses at the four sites can be
defined as the average sheet thickness tO of the material 1.
[0024]
It is needless to say that the upper and lower limit values of the average sheet
15 thickness tO of this material 1 can also be employed as the upper and lower limit values
of the average sheet thickness tO of the electrical steel sheet 40. As a method for
measuring the average sheet thickness tO of the electrical steel sheet 40, for example, the
following measurement method is followed. For example, the lamination thickness of
the laminated core is measured at four sites at equal intervals in the circumferential
20 direction (that is, every 90 degrees around the central axis 0). Each of the measured
lamination thicknesses at the four sites is divided by the number of the electrical steel
sheets 40 laminated, thereby calculating the sheet thickness per sheet. The average
value of the sheet thicknesses at the four sites can be defined as the average sheet
thickness tO of the electrical steel sheet 40.
25

[CLAIMS]
What is claimed is:
1. A coating composition for an electrical steel sheet comprising:
an epoxy resin;
a phenolic curing agent (A); and
one or more amine-based curing agents (B) selected from an aromatic amine and
dicyandiamide,
wherein an amount of the phenolic curing agent (A) is 1 to 40 parts by mass
with respect to 100 parts by mass of the epoxy resin, and an amount of the amine-based
10 curing agents (B) is 0.5 to 5 parts by mass with respect to 100 parts by mass of the epoxy
resin.
2. The coating composition for an electrical steel sheet according to claim 1,
wherein a mass ratio represented by [the amount of the phenolic curing agent
15 (A)]/[the amount of the amine-based curing agents (B)] is 1 to 20.
3. An adhesive surface-coated electrical steel sheet comprising:
an insulating coating containing the coating composition for an electrical steel
sheet according to claim 1 or 2 on a surface,
20 wherein a thickness is 0.65 mm or less.
4. A laminated core formed by laminating two or more adhesive surface-coated
electrical steel sheets according to claim 3.