[Technical Field]
[0001]
The present invention relates to a coating composition for an electrical steel
sheet, an electrical steel sheet, a laminated core and a rotary electric machine. Priority
is claimed on Japanese Patent Application No. 2020-104248, filed June 17, 2020, the
10 content of which is incorporated herein by reference.
[Background Art]
[0002]
As cores (cores) that are used for rotary electric machines, laminated cores in
which a plurality of electrical steel sheets are joined and laminated together are known.
15 As a method for joining electrical steel sheets, swaging or welding is known. However,
during swaging or welding, the magnetic characteristics (core iron losses) of electrical
steel sheets are likely to deteriorate due to mechanical strain or thermal strain during
processing.
20
[0003]
As joining methods other than swaging and welding, for example, a method in
which electrical steel sheets each having an insulating coating with an adhesive
capability formed on a surface are caused to adhere together is known (Patent Document
1). Since adhesion using the insulating coating does not impart mechanical strain or
thermal strain, the core iron loss is excellent compared with that in swaging or welding.
25 Epoxy resins change in volume only to a small extent, are excellent in terms of heat
1
resistance or oil resistance and chemical resistance and are excellent adhesives that cause
electrical steel sheets to adhere together (Patent Documents 2 and 3).
[Citation List]
[Patent Document]
5 [0004]
[Patent Document 1]
Japanese Unexamined Patent Application, First Publication No. 2017-011863
[Patent Document 2]
Japanese Unexamined Patent Application, First Publication No. 2000-173816
10 [Patent Document 3]
15
PTC International Publication No. WO 2004/070080
[Summary of the Invention]
[Problems to be Solved by the Invention]
[0005]
In recent years, in response to a request for additional improvement in motor
efficiency, additional reduction in core iron loss has been required. 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 steel sheet, it is necessary to prevent stress strain, which is a
20 cause for iron loss deterioration, from being imparted to the steel sheet. Epoxy resins
are excellent in terms of heat resistance, but are hard and have poor toughness and thus
impart stress strain to steel sheets when cured during adhesion. Therefore, a decrease in
the thickness of a steel sheet causes iron loss deterioration.
In addition, driving motors and the like of electric vehicles become hot while in
25 operation and are thus required to have additional heat resistance.
2
[0006]
As means for improving heat resistance, there is a method in which a phenolic
resin is blended. However, resins having excellent heat resistance are hard at normal
temperature and impart large stress to laminated cores, which degrades magnetic
5 characteristics. On the other hand, resins having appropriate hardness at near normal
temperature become soft at high temperatures and are thus poor in heat resistance.
These facts show that it is difficult to satisfy both excellent magnetic characteristics and
excellent heat resistance that is high enough to hold a sufficient adhesion strength even in
a state where resins are exposed to high temperatures while driving motors and the like
10 are in operation.
[0007]
An objective of the present invention is to provide a coating composition for an
electrical steel sheet capable of satisfying both the magnetic characteristics of laminated
cores and heat resistance that is high enough to hold an adhesion strength between
15 electrical steel sheets even in a high-temperature state while the laminated cores are in
operation, an electrical steel sheet, a laminated core and a rotary electric machine for all
of which the coating composition for an electrical steel sheet is used.
20
[Means for Solving the Problem]
[0008]
The present invention has the following aspects.
[ 1] A coating composition for an electrical steel sheet according to an aspect of
the present invention contains an epoxy resin, a first curing agent composed of a phenolic
resin including a phenol skeleton having any one or both of an alkyl group and an alkoxy
group and a second curing agent of one or more selected from the group consisting of a
25 phenolic resole resin and a phenolic novolac resin, and the amount of the first curing
3
agent is 5 parts by mass or more and 150 parts by mass or less with respect to 100 parts
by mass of the epoxy resin.
[2] The coating composition for an electrical steel sheet according to [ 1], in
which the first curing agent may be composed of a phenolic resin including a phenol
5 skeleton having any one or both of an alkyl group having two or more carbon atoms and
an alkoxy group having two or more carbon atoms.
[3] The coating composition for an electrical steel sheet according to [1] or [2],
in which the total amount of the first curing agent and the second curing agent may be 5
parts by mass or more and 155 parts by mass or less with respect to 100 parts by mass of
10 the epoxy resin.
[ 4] The coating composition for an electrical steel sheet according to any one of
[1] to [3], in which a cure shrinkage may be 15% or less.
[ 5] An electrical steel sheet according to an aspect of the present invention
having an insulating coating containing the coating composition for an electrical steel
15 sheet according to any one of [1] to [ 4] on a surface.
[6] A laminated core according to an aspect of the present invention, in which a
plurality of the electrical steel sheets according to [5] are laminated and caused to adhere
together.
[7] A rotary electric machine according to an aspect of the present invention
20 including the laminated core according to [6].
[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 capable of satisfying both
25 the magnetic characteristics of laminated cores and heat resistance that is high enough to
4
hold an adhesion strength between electrical steel sheets even in a high-temperature state
while the laminated cores are in operation, an electrical steel sheet, a laminated core and
a rotary electric machine for all of which the coating composition for an electrical steel
sheet is used.
5 [Brief Description of Drawings]
[0010]
10
15
Fig. 1 is a cross-sectional view of a rotary electric machine including a
laminated core according to a first 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 in 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 to manufacture the
laminated core shown in Fig. 1.
[Embodiment(s) for implementing the Invention]
[0011]
Hereinafter, a laminated core according to an embodiment of the present
20 invention, a rotary electric machine including this laminated core and a material that
forms this laminated core will be described with reference to the drawings. 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
25 an example. This type of electric motor is preferably employed in, for example, electric
5
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
5 with "less than" or "more than" are not included in numerical ranges.
[0013]
(Rotary electric machine 1 0)
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
10 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
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
15 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
the like can be changed as appropriate.
The rotary electric machine 10 can be rotated at a rotation speed of 1000 rpm by,
20 for example, applying an excitation current of an effective value of 10 A and a frequency
of 100 Hz to each phase.
25
[0014]
The stator 20 includes an adhesive laminated core for a stator (hereinafter, stator
core) 21 and a winding, not shown.
The stator core 21 includes a ring-shaped core back portion 22 and a plurality of
6
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
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
5 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
disposed at equal angular intervals in the circumferential direction. In the present
embodiment, 18 tooth portions 23 are provided every center angle of 20 degrees around
15 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.
20 [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
disposed with respect to the stator 20. The rotary shaft 60 is disposed in the rotor core
25 31. The rotary shaft 60 is fixed to the rotor core 31.
7
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.
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
5 (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 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
15 example, causing the outer surface of the permanent magnet 32 and the inner surface of
20
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 motor.

What is claimed is:
1. A coating composition for an electrical steel sheet comprising:
an epoxy res1n;
a first curing agent composed of a phenolic resin including a phenol skeleton
having any one or both of an alkyl group and an alkoxy group; and
a second curing agent of one or more selected from a phenolic resole resin and a
phenolic novolac resin,
wherein an amount of the first curing agent is 5 parts by mass or more and 150
10 parts by mass or less 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 the first curing agent is composed of a phenolic resin including a phenol
skeleton having any one or both of an alkyl group having two or more carbon atoms and
15 an alkoxy group having two or more carbon atoms.
3. The coating composition for an electrical steel sheet according to claim 1 or 2,
wherein a total amount of the first curing agent and the second curing agent is 10
parts by mass or more and 155 parts by mass or less with respect to 100 parts by mass of
20 the epoxy resin.
25
4. The coating composition for an electrical steel sheet according to any one of claims 1
to 3,
wherein a cure shrinkage is 15% or less.
44
5. An electrical steel sheet comprising:
an insulating coating containing the coating composition for an electrical steel
sheet according to any one of claims 1 to 4 on a surface.
5 6. A laminated core,
wherein a plurality of the electrical steel sheets according to claim 5 are
laminated and caused to adhere together.
7. A rotary electric machine comprising:
10 the laminated core according to claim 6.