FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
MOTOR, COMPRESSOR, REFRIGERATION CYCLE APPARATUS, AND MANUFACTURING
METHOD OF MOTOR;
MITSUBISHI ELECTRIC CORPORATION, A CORPORATION ORGANISED AND EXISTING
UNDER THE LAWS OF JAPAN, WHOSE ADDRESS IS 7-3, MARUNOUCHI 2-CHOME,
CHIYODA-KU, TOKYO 100-8310, JAPAN
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND
THE MANNER IN WHICH IT IS TO BE PERFORMED
2
5 DESCRIPTION
TECHNICAL FIELD
[0001]
The present disclosure relates to a motor, a compressor, a
refrigeration cycle apparatus, and a manufacturing method of the
10 motor.
BACKGROUND ART
[0002]
In a permanent magnet-embedded motor, permanent magnets are
inserted in magnet insertion holes formed in a rotor core. A
15 bridge portion is formed between each magnet insertion hole and the
outer circumference of the rotor core.
[0003]
When a magnetic flux flows through the bridge portion, the
magnetic flux is short circuited between adjacent permanent magnets.
20 For this reason, the width of the bridge portion is desired to be
narrow. Thus, Patent Reference 1 discloses a method of forming a
narrow bridge portion by etching an electromagnetic steel sheet.
PRIOR ART REFERENCE
PATENT REFERENCE
25 [0004]
Patent Reference 1: Japanese Patent Application Publication
No. 2011-114927 (see paragraphs 0026 and 0027)
SUMMARY OF THE INVENTION
PROBLEM TO BE SOLVED BY THE INVENTION
30 [0005]
However, the method by etching the electromagnetic steel
sheet is costly to manufacture and not appropriate for mass
production of motors.
[0006]
35 The present disclosure is intended to solve the abovedescribed problem, and an object of the present disclosure is to
suppress a short circuit of magnetic flux via a bridge portion
while suppressing an increase in manufacturing cost.
3
5 MEANS OF SOLVING THE PROBLEM
[0007]
A motor according to the present disclosure includes a rotor
having a rotor core having an annular shape about an axis and
formed of a first core sheet subjected to press processing, and a
10 permanent magnet embedded in the rotor core, and a stator
surrounding the rotor from outside in a radial direction about the
axis. The stator has a stator core formed of a second core sheet
subjected to press processing. A thickness of the first core sheet
is thicker than a thickness of the second core sheet. The rotor
15 core has an outer circumference, a magnet insertion hole in which
the permanent magnet is inserted, and a bridge portion between the
outer circumference and the magnet insertion hole. A minimum width
of the bridge portion in the radial direction is smaller than the
thickness of the first core sheet.
20 EFFECTS OF THE INVENTION
[0008]
With the above-described configuration, the minimum width of
the bridge portion is smaller than the thickness of the first core
sheet, and thus it is possible to suppress a short circuit of
25 magnetic flux via the bridge portion. Since the thickness of the
first core sheet is thicker than the thickness of the second core
sheet, deformation of the bridge portion can be suppressed during
press processing. Since the press processing can be used, an
increase in manufacturing cost can be suppressed.
30 BRIEF DESCRIPTION OF THE DRAWINGS
[0009]
FIG. 1 is a cross-sectional view illustrating a motor of a
first embodiment.
FIG. 2 is a longitudinal-sectional view illustrating the
35 motor of the first embodiment.
FIG. 3 is an enlarged view illustrating a part of the motor
of the first embodiment.
FIG. 4 is a diagram illustrating facing portions of a
4
5 magnetic pole of a rotor and a tooth of a stator of the first
embodiment.
FIG. 5 is an enlarged view illustrating the facing portions
of the magnetic pole of the rotor and the tooth of the stator
illustrated in FIG. 4.
10 FIG. 6 is a diagram for explaining a short circuit of
magnetic flux in a bridge portion of the first embodiment.
FIG. 7(A) is a flowchart illustrating a press processing
process for forming a first core sheet of the first embodiment, and
FIG. 7(B) is a flowchart illustrating a press processing process
15 for forming a second core sheet.
FIG. 8 is a plan view illustrating an electromagnetic steel
sheet from which the first core sheets are formed.
FIG. 9 is a plan view illustrating an electromagnetic steel
sheet from which the second core sheets are formed.
20 FIG. 10 is a flowchart illustrating a manufacturing process
of the motor in the first embodiment.
FIG. 11 is a plan view illustrating another example of an
electromagnetic steel sheet from which the second core sheets are
formed.
25 FIG. 12(A) is a schematic diagram for explaining the press
processing of the electromagnetic steel sheet, and FIG. 12(B) is a
schematic diagram illustrating a press die.
FIG. 13 is a schematic diagram illustrating a processed end
surface of the electromagnetic steel sheet.
30 FIG. 14(A) is a diagram illustrating a state in which magnet
insertion holes are formed in the first core sheet, and FIG. 14(B)
is a diagram illustrating a state in which bridge portions are
formed in the first core sheet.
FIG. 15(A) is a diagram illustrating a forming step of the
35 bridge portion, and FIG. 15 is a diagram illustrating a forming
step of a bridge portion in a reference example.
FIG. 16 is a longitudinal-sectional view illustrating a motor
of the comparative example.
5
5 FIG. 17 is an enlarged diagram illustrating a part of the
motor of the comparative example.
FIG. 18 is a diagram illustrating the relationship between a
magnetic pole of a rotor and a tooth of a stator of the comparative
example.
10 FIG. 19 is an enlarged diagram illustrating a bridge portion
of the rotor and its surroundings of the comparative example.
FIG. 20 is a diagram for explaining a short circuit of
magnetic flux in the bridge portion of the comparative example.
FIG. 21 is a flowchart illustrating a press processing
15 process for forming a first core sheet and a second core sheet of
the comparative example.
FIG. 22 is a plan view illustrating an electromagnetic steel
sheet from which the first core sheets and the second core sheets
of the comparative example are formed.
20 FIG. 23 is a longitudinal-sectional view illustrating a motor
of a second embodiment.
FIG. 24 is a longitudinal-sectional view illustrating a
compressor to which the motor of each embodiment is applicable.
FIG. 25 is a diagram illustrating a refrigeration cycle
25 apparatus to which the motor of each embodiment is applicable.
MODE FOR CARRYING OUT THE INVENTION
[0010]
First Embodiment
(Configuration of Motor)
30 FIG. 1 is a cross-sectional view illustrating a motor 100 of
a first embodiment. The motor 100 illustrated in FIG. 1 is a
permanent magnet-embedded motor and is used in, for example, a
compressor 300 (FIG. 24). The motor 100 is driven by an inverter.
[0011]
35 The motor 100 includes a rotor 1 having a shaft 25, which is
a rotary shaft, and a stator 5 provided so as to surround the rotor
1. An air gap of, for example, 0.3 to 1.0 mm, is formed between
the stator 5 and the rotor 1. The stator 5 is incorporated in a
6
5 cylindrical shell 6 of the compressor 300 (FIG. 24) to be described
later.
[0012]
Hereinafter, the direction of an axis Ax, which is a rotation
center axis of the rotor 1, is referred to as an “axial direction”.
10 The radial direction about the axis Ax is referred to as a “radial
direction”. The circumferential direction about the axis Ax is
referred to as a "circumferential direction" and indicated by the
arrow R1 in FIG. 1 and other figures. A sectional view in a plane
parallel to the axis Ax is referred to as a “longitudinal-sectional
15 view”. A sectional view in a plane orthogonal to the axis Ax is
referred to as a “cross-sectional view”.
[0013]
The rotor 1 includes a rotor core 10 having an annular shape
about the axis Ax and permanent magnets 20 embedded in the rotor
20 core 10. The rotor core 10 is composed of first core sheets 101
(FIG. 2) which are stacked in the axial direction and fixed
together by crimping portions 105.
[0014]
A center hole 15 is formed at the center of the rotor core 10
25 in the radial direction. The above-described shaft 25 is fixed to
the center hole 15 of the rotor core 10 by shrink-fitting, pressfitting, or the like. The rotor core 10 has an outer circumference
10a having a circular shape.
[0015]
30 A plurality of magnet insertion holes 11 are formed along the
outer circumference 10a of the rotor core 10. One permanent magnet
20 is inserted in each magnet insertion hole 11. Each magnet
insertion hole 11 corresponds to one magnetic pole. The rotor core
10 has six magnet insertion holes 11, and thus the number of poles
35 of the rotor 1 is six. Incidentally, the number of poles of the
rotor 1 is not limited to six and only needs to be two or more.
[0016]
The permanent magnet 20 is a flat-plate shaped member that is
7
5 elongated in the axial direction of the rotor core 10. The
permanent magnet 20 has a width in the circumferential direction,
and a thickness in the radial direction. The thickness of the
permanent magnet 20 is constant in the width direction and is, for
example, 2.0 mm. The permanent magnet 20 is composed of a rare
10 earth magnet that contains, for example, neodymium (Nd), iron (Fe),
and boron (B).
[0017]
Each permanent magnet 20 is magnetized in its thickness
direction. The permanent magnets 20 inserted in adjacent magnet
15 insertion holes 11 have opposite magnetic pole surfaces on the
outer side in the radial direction. Incidentally, two or more
permanent magnets 20 may be inserted in each magnet insertion hole
11.
[0018]
20 The stator 5 has a stator core 50 surrounding the rotor core
10 from outside in the radial direction and a coil 55 wound on the
stator core 50. The stator core 50 is composed of second core
sheets 501 (FIG. 2) which are stacked in the axial direction and
fixed together by crimping portions 58a and 58b.
25 [0019]
The stator core 50 includes a yoke 51 having an annular shape
about the axis Ax and a plurality of teeth 52 extending inward in
the radial direction from the yoke 51. The teeth 52 are arranged
at equal intervals in the circumferential direction. The number of
30 teeth 52 is nine in this example. Incidentally, the number of
teeth 52 is not limited to nine but only needs to be two or more.
[0020]
A slot 53, which is a space to house the coil 55, is formed
between teeth 52 adjacent to each other in the circumferential
35 direction. The number of slots 53 is the same as the number of
teeth 52, which is nine in this example. That is, the ratio of the
number of poles in the rotor 1 to the number of slots in the stator
5 is 2:3. However, the ratio is not limited to 2:3.
8
5 [0021]
The second core sheets 501 constituting the stator core 50
are fixed together by the crimping portions 58a and 58b. The
crimping portions 58a are formed in the yoke 51, while the crimping
portions 58b are formed in the teeth 52. Incidentally, the
10 positions of the crimping portions 58a and 58b are not limited to
these positions.
[0022]
The stator core 50 is composed of a plurality of split cores
50A which are combined in the circumferential direction. Each
15 split core 50A is a block including one tooth 52. The split cores
50A are joined together by welding at split surfaces 54 formed in
the yoke 51. Incidentally, the split cores 50A may be combined to
each other at thin-walled portions formed at outer circumferential
portions of the split surfaces 54.
20 [0023]
The coil 55 is formed of a magnet wire wound around each
tooth 52 in a concentrated winding. The wire diameter of the
magnet wire is, for example, 0.8 mm. The number of turns of the
coil 55 around one tooth 52 is, for example, 70 turns.
25 [0024]
The number of turns and the wire diameter of the coil 55 are
determined depending on the required specifications of the motor
100, such as a rotational speed and a torque, the applied voltage,
and the cross-sectional area of the slot 53. The coil 55 includes
30 winding portions of three phases, namely, U-phase, V-phase and Wphase winding portions, which are connected in Y-connection.
[0025]
An insulating film 56 having a thickness of 0.1 to 0.2 mm and
formed of a resin such as polyethylene terephthalate (PET) is
35 attached to the inner surface of each slot 53. An insulator 57
(FIG. 2) formed of a resin such as polybutylene terephthalate (PBT)
is attached to each end of the stator core 50 in the axial
direction. The insulating film 56 and the insulator 57 constitute
9
5 an insulating portion that insulates the stator core 50 from the
coil 55.
[0026]
FIG. 2 is a longitudinal-sectional view illustrating the
motor 100. A length H1 of the rotor core 10 in the axial direction
10 is longer than a length H2 of the stator core 50 in the axial
direction. The rotor core 10 protrudes from the stator core 50 on
both sides thereof in the axial direction.
[0027]
For example, the length H1 of the rotor core 10 is 50 mm,
15 while the length H2 of the stator core 50 is 45 mm. The length in
the axial direction is also referred to as a height in the stacking
direction. A balance weight may be provided at each end of the
rotor core 10 in the axial direction so as to increase inertia.
[0028]
20 The rotor core 10 is a stacked body in which the first core
sheets 101 are stacked in the axial direction. The first core
sheets 101 are formed by press processing on an electromagnetic
steel sheet.
[0029]
25 A thickness T1 of the first core sheet 101 is 0.50 mm. A Si
content of the first core sheet 101 is 3.3%. The Si content is a
content (wt%) of silicon (Si) in the first core sheet 101.
[0030]
A Vickers hardness Hv of the first core sheet 101 is 180. An
30 iron loss density of the first core sheet 101 is 1.18 W/kg. The
iron loss density is a measurement result obtained by a test in
conformity with JIS_C2550 in which a magnetic flux density of 1.0 T
is induced at a frequency of 50Hz.
[0031]
35 The stator core 50 is a stacked body in which the second core
sheets 501 are stacked in the axial direction. The second core
sheets 501 are formed by press processing on an electromagnetic
steel sheet.
10
5 [0032]
A thickness T2 of the second core sheet 501 is 0.35 mm. The
Si content of the second core sheet 501 is 3.5%. A Vickers
hardness Hv of the second core sheet 501 is 205. An iron loss
density of the second core sheet 501 is 0.98 W/kg.
10 [0033]
When the first core sheet 101 and the second core sheet 501
are compared, the thickness T1 of the first core sheet 101 is
thicker than the thickness T2 of the second core sheet 501. The Si
content of the first core sheet 101 is smaller than the Si content
15 of the second core sheet 501. The Vickers hardness Hv of the first
core sheet 101 is lower than the Vickers hardness Hv of the second
core sheet 501. The iron loss density of the first core sheet 101
is higher than the iron loss density of the second core sheet 501.
[0034]
20 That is, the first core sheet 101 can be easily subjected to
press processing, i.e., has good processability, as compared to the
second core sheet 501. Such a first core sheet 101 and a second
core sheet 501 can be obtained by changing the type and grade of
the electromagnetic steel sheets. The functions and effects of the
25 core sheets 101 and 501 depending on differences in their
properties will be described later.
[0035]
In this regard, the above-described values of the thickness,
the Si content, the Vickers hardness, and the iron loss density of
30 the core sheets 101 and 501 are merely examples.
[0036]
FIG. 3 is an enlarged diagram illustrating facing portions of
the rotor 1 and the stator 5. The permanent magnet 20 is inserted
in each magnet insertion hole 11 of the rotor 1 as described above.
35 The center of the magnet insertion hole 11 in the circumferential
direction is a pole center. An inter-pole portion M is formed
between adjacent magnet insertion holes 11.
[0037]
11
5 The magnet insertion hole 11 extends linearly in a direction
orthogonal to a straight line in the radial direction that passes
through the pole center, i.e., a magnetic pole center line C1.
Incidentally, the magnet insertion hole 11 may extend in a V shape
that is convex toward the axis Ax side.
10 [0038]
A plurality of slits 13 are formed on the outer side of each
magnet insertion hole 11 in the radial direction in the rotor core
10. Each of the slits 13 extends in the radial direction and has a
width of, for example, 1 mm in the circumferential direction. The
15 slits 13 are formed to make the magnetic flux distribution of the
permanent magnet 20 closer to a sine wave. In this example, seven
slits 13 are formed symmetrically with respect to the magnetic pole
center line C1. However, the number and arrangement of the slits
13 are not limited.
20 [0039]
In the rotor core 10, through holes 102 and 103 and slits 104
are formed on the inner side of the magnet insertion holes 11 in
the radial direction. The through holes 102 and 103 and the slits
104 are used as refrigerant flow paths through which the
25 refrigerant passes or as holes into which jigs are inserted.
[0040]
The through hole 102 is formed on the magnetic pole center
line C1. The through hole 103 is formed on the inner side of the
inter-pole portion M in the radial direction. The slit 104 is
30 formed on the inner side of the through hole 102 in the radial
direction and extends in an arc shape in the circumferential
direction. Incidentally, the through holes 102 and 103 and the
slits 104 are not necessarily provided.
[0041]
35 The crimping portions 105 for fixing the first core sheets
101 of the rotor core 10 are formed on the inner side of the interpole portions M in the radial direction. However, each crimping
portion 105 is not necessarily formed at such a position, but only
12
5 needs to be formed at any position at which the crimping portion
105 interferes as least as possible with the magnetic path in the
rotor core 10.
[0042]
The magnet insertion hole 11 has flux barriers 12 at both
10 ends thereof in the circumferential direction. The flux barrier 12
is an opening formed at each end of the magnet insertion hole 11 in
the circumferential direction and located on the outer side of the
permanent magnet 20 in the circumferential direction.
[0043]
15 A bridge portion 14 is formed between the flux barrier 12 and
an outer circumference 10a of the rotor core 10. The bridge
portion 14 is a thin-walled portion extending in the
circumferential direction along the outer circumference 10a.
[0044]
20 The tooth 52 of the stator 5 has a tooth tip portion 52a
facing the outer circumference 10a of the rotor core 10. The width
of the tooth tip portion 52a in the circumferential direction is
wider than other portions of the tooth 52. A straight line in the
radial direction that passes through the center of the tooth 52 in
25 the circumferential direction is referred to as a tooth center line
C5.
[0045]
The magnetic flux emanating from the permanent magnet 20 is
distributed in a sine wave shape that has its peak on the magnetic
30 pole center line C1. Therefore, as illustrated in FIG. 3, when the
center of the permanent magnet 20 faces the tooth 52 of the stator
5, that is, when the magnetic pole center line C1 coincides with
the tooth center line C5, the magnetic flux emanating from the
permanent magnet 20 flows the most into the tooth 52 and interlinks
35 with the coil 55.
[0046]
FIG. 4 is a diagram illustrating facing portions of the
magnetic pole of the rotor 1 and the tooth 52. End surfaces 52b
13
5 are formed at both ends of the tooth tip portion 52a of the tooth
52 in the circumferential direction. A slot opening A is formed
between the end surfaces 52b of the adjacent teeth 52. The slot
opening A serves as an entrance of the slot 53 facing the rotor 1.
[0047]
10 The magnet insertion hole 11 faces two slot openings A on
both sides of the tooth 52 in a state where the center of the
permanent magnet 20 faces the tooth 52. In this state, two bridge
portions 14 at both ends of the magnet insertion hole 11 face the
respective tooth tip portions 52a of the tooth 52 on both sides of
15 the tooth 52 that faces the permanent magnet 20.
[0048]
FIG. 5 is an enlarged diagram illustrating the bridge
portions 14 and their surroundings. The bridge portion 14 extends
in the circumferential direction along the outer circumference 10a
20 of the rotor core 10. The width of the bridge portion 14 in the
radial direction is uniform along the extending direction of the
bridge portion 14 in this example. However, the width of the
bridge portion 14 in the radial direction may vary.
[0049]
25 A minimum width of the bridge portion 14 in the radial
direction is denoted by Hb. A length of the bridge portion 14 in
the circumferential direction is denoted by Wb. The minimum width
Hb of the bridge portion 14 is set to a width so that the bridge
portion 14 can suppress a short circuit of magnetic flux between
30 adjacent permanent magnets 20.
[0050]
Specifically, the minimum width Hb of the bridge portion 14
is set smaller than the thickness T1 of the first core sheet 101
(FIG. 2) (Hb < T1). For example, when the thickness T1 of the
35 first core sheet 101 is 0.50 mm, the minimum width Hb of the bridge
portion 14 is 0.30 mm. The length Wb of the bridge portion 14 is
longer than the minimum width Hb.
[0051]
14
5 With reference to FIG. 4 again, the minimum interval between
two bridge portions 14 at both ends of the magnet insertion hole 11
is denoted by Lb. The minimum interval Lb is an interval between
two end points Pb closest to each other in the two bridge portions
14 located at both ends of the magnet insertion hole 11.
10 [0052]
The maximum interval between two slot openings A facing the
magnet insertion hole 11 is denoted by Ls. The maximum interval Ls
is an interval between two end points Ps far from each other at
inner circumferential side ends of the two slot openings A facing
15 the magnet insertion hole 11.
[0053]
In the first embodiment, the minimum interval Lb between the
two bridge portions 14 at both ends of the magnet insertion hole 11
is narrower than the maximum interval Ls between the two slot
20 openings A facing the magnet insertion hole 11 (Lb < Ls).
[0054]
FIG. 6 is a diagram for explaining a short circuit of
magnetic flux between adjacent permanent magnets 20. The magnetic
flux between the adjacent permanent magnets 20 flows through the
25 bridge portions 14, as indicated by the arrow F1. By making the
minimum width Hb of the bridge portion 14 narrower, a short circuit
of the magnetic flux between the adjacent permanent magnets 20 can
be reduced. A forming method of the bridge portion 14 with the
narrow minimum width Hb will be described later.
30 [0055]
Further, when magnetic saturation occurs in the bridge
portions 14, it causes a short circuit of magnetic flux from the
bridge portions 14 through the tooth tip portions 52a as indicated
by the arrow F2. For this reason, the minimum interval Lb between
35 the two bridge portions 14 at both ends of the magnet insertion
hole 11 is made narrower than the maximum interval Ls between the
two slot openings A facing the magnet insertion hole 11 (Lb < Ls).
[0056]
15
5 As described above, in a state where the center of the
permanent magnet 20 faces the tooth 52, the magnetic flux emanating
from the permanent magnet 20 flows the most into the tooth 52. At
this time, when Lb < Ls is satisfied, the end point Pb of the
bridge portion 14 is located closer to the pole center than the end
10 point Ps of the tooth tip portion 52a of the tooth 52.
[0057]
Consequently, as indicated by the arrow F2 in FIG. 6, the
magnetic flux between the permanent magnet 20 and the tooth tip
portion 52a flows around to the pole center side (left side in the
15 figure), and thus a short circuit of magnetic flux via the tooth
tip 52a is less likely to occur. The case where Lb > Ls is
satisfied will be described in the comparative example (FIG. 20).
[0058]
(Manufacturing Method of Motor)
20 Next, a manufacturing method of the motor 100 of the first
embodiment will be described. The first core sheet 101
constituting the rotor core 10 and the second core sheet 501
constituting the stator core 50 are formed of different
electromagnetic steel sheets subjected to press processing.
25 [0059]
FIG. 7(A) is a flowchart illustrating a press processing
process for forming the first core sheets 101. FIG. 8 is a plan
view illustrating an electromagnetic steel sheet 10S from which the
first core sheets 101 are punched.
30 [0060]
As illustrated in FIG. 8, the electromagnetic steel sheet 10S
is a strip-shaped steel sheet that is elongated in one direction
and is also referred to as a first electromagnetic steel sheet.
The electromagnetic steel sheet 10S has a thickness of 0.50 mm, a
35 Si content of 3.3%, a Vickers hardness Hv of 180, and an iron loss
density of 1.18 W/kg.
[0061]
The electromagnetic steel sheet 10S is conveyed in the
16
5 longitudinal direction (step S11), and then punched using a press
die in multiple stages to form the first core sheets 101 (step S12).
In this example, the electromagnetic steel sheet 10S is punched
into the respective shapes of the center hole 15, the through holes
102 and 103, the slits 104, the slits 13, the magnet insertion
10 holes 11 (including the flux barriers 12) and the outer
circumference 10a.
[0062]
A die clearance of the press die at this time is 5% of the
thickness T1 of the electromagnetic steel sheet 10S, specifically
15 0.025 mm. These will be described later with reference to FIGS.
12(A) and 12(B).
[0063]
FIG. 7(B) is a flowchart illustrating a press processing
process for forming the second core sheets 501. FIG. 9 is a plan
20 view illustrating an electromagnetic steel sheet 50S from which the
second core sheets 501 are punched.
[0064]
As illustrated in FIG. 9, the electromagnetic steel sheet 50S
is a strip-shaped steel sheet that is elongated in one direction
25 and is also referred to as a second electromagnetic steel sheet.
The electromagnetic steel sheet 50S has a thickness of 0.35 mm, a
Si content of 3.5%, a Vickers hardness Hv of 205, and an iron loss
density of 0.98 W/kg.
[0065]
30 The electromagnetic steel sheet 50S is conveyed in the
longitudinal direction (step S21), and then punched using a press
die to form the second core sheets 501 (step S22). In this example,
the electromagnetic steel sheet 50S is punched into a shape in
which the split cores 50A are linearly arranged.
35 [0066]
A die clearance of the press die at this time is 8% of the
thickness T2 of the electromagnetic steel sheet 50S, specifically
0.028 mm.
17
5 [0067]
FIG. 10 is a flowchart illustrating an assembly process of
the motor 100. First, the first core sheets 101 obtained by the
process of FIG. 7(A) are stacked in the axial direction to form the
rotor core 10 (step S101). Thereafter, the permanent magnets 20
10 are embedded in the rotor core 10. That is, the permanent magnets
20 are inserted into the magnet insertion holes 11 of the rotor
core 10 (step S102). Balance weights are fixed to the rotor core
10 as necessary. Thus, the rotor 1 is completed.
[0068]
15 Further, the second core sheets 501 obtained by the process
of FIG. 7(B) are stacked in the axial direction to form the split
cores 50A (step S201). Then, the split cores 50A are combined in
an annular shape and joined together by welding or the like to form
the stator core 50 (step S202). Then, the insulating portion is
20 attached to the stator core 50 (step S203), and the coil 55 is
wound on the stator core 50 (step S204). Thus, the stator 5 is
completed.
[0069]
The rotor 1 is incorporated inside the stator 5 formed in
25 this way (step S110). Therefore, the motor 100 is completed.
[0070]
Although the coil 55 is wound after forming the annular
stator core 50 in this example, the coil 55 may be wound on the
split cores 50A, and thereafter the split cores 50A may be combined
30 in an annular shape.
[0071]
Incidentally, the stator core 50 is not necessarily limited
to a structure in which the split cores 50A are combined, but may
have an annular integrated structure. In this case, as illustrated
35 in FIG. 11, when the electromagnetic steel sheet 50S is punched
into annular shapes to form the second core sheets 501, inner parts
of the respective second core sheets 501 of the electromagnetic
steel sheet 50S (denoted by reference character D) are not used,
18
5 and thus these parts are wasted. That is, the electromagnetic
steel sheet 50S cannot be utilized efficiently.
[0072]
In contrast, as illustrated in FIG. 9, when the
electromagnetic steel sheet 50S is punched into the shapes of the
10 split cores 50A, the waste of the electromagnetic steel sheet 50S
can be reduced, for example, by punching the electromagnetic steel
sheet 50S so that the split cores 50 are arranged side by side
linearly. That is, the material of the electromagnetic steel sheet
50S can be utilized efficiently.
15 [0073]
Next, the press processing of the first core sheet 101
described with reference to FIG. 7(A) will be further described.
FIG. 12(A) is a schematic diagram illustrating a state in which the
electromagnetic steel sheet 10S is punched to form the first core
20 sheet 101. For convenience of illustration, the first core sheet
101 is shown in a disc shape. FIG. 12(B) is a schematic diagram
illustrating a press die 8.
[0074]
As illustrated in FIG. 12(A), the electromagnetic steel sheet
25 10S is punched by being pressed in its thickness direction to form
the first core sheet 101 by shearing. As illustrated in FIG. 12(B),
the press die 8 has a die 81 supporting the electromagnetic steel
sheet 10S from below and a punch 82 to apply the pressure P to the
electromagnetic steel sheet 10S from above.
30 [0075]
The inner dimension of the die 81 is denoted by Dd, and the
outer dimension of the punch 82 is denoted by Dp. Shearing force
is applied to the electromagnetic steel sheet 10S between a tooth
surface 81a of the die 81 and a tooth surface 82a of the punch 82.
35 A clearance is set between the tooth surface 81a of the die 81 and
the tooth surface 82a of the punch 82. This clearance is referred
to as a die clearance C.
[0076]
19
5 When the electromagnetic steel sheet 10S for the rotor core
10 is punched, the die clearance C of the press die 8 is set to 5%
of the thickness T1 of the electromagnetic steel sheet 10S. As
described later, the die clearance C when the electromagnetic steel
sheet 10S is punched to form portions other than the bridge portion
10 14 is not necessarily 5% of the thickness T1, but may be, for
example, 8% of the thickness T1.
[0077]
On the other hand, when the electromagnetic steel sheet 50S
for the stator core 50 is punched, the die clearance C between the
15 die 81 and the punch 82 is set to 8% of the thickness of the
electromagnetic steel sheet 50S.
[0078]
FIG. 13 is a diagram illustrating a state of a processed
surface of a general electromagnetic steel sheet (referred to as an
20 electromagnetic steel sheet S). The cut surface (denoted by
reference character E in FIG. 12(A)) formed by punching the
electromagnetic steel sheet S is referred to as the processed
surface. On the processed surface, a sag, a shear surface, a
fracture surface and a burr are formed in the shearing direction.
25 [0079]
The sag is a warped surface formed by the surface of the
electromagnetic steel sheet S which is deformed by being pressed
down by the punch 82. The shear surface is a flat surface formed
by rubbing against the punch 82, and scratches are generated in the
30 shearing direction. The fracture surface is a surface that is
broken by cracking and is rougher than the shear surface. The burr
is a protrusion formed when the electromagnetic steel sheet S is
pressed down by the punch 82.
[0080]
35 When the sag, the fracture surface, and the burr are large,
it may cause the reduction in dimensional accuracy. Thus, it is
desirable that the sag, the fracture surface, and the burr are
small.
20
5 [0081]
As the die clearance C increases, the sag, the fracture
surface and the burr tend to increase, and the shear surface tends
to decrease, which results in lower processing accuracy. As the
die clearance C decreases, the sag, the fracture surface and the
10 burr tend to decrease, and the shear surface tends to increase,
which results in higher processing accuracy.
[0082]
In order to make the minimum width Hb of the bridge portion
14 narrower, it is desirable that the die clearance C is small.
15 However, when the die clearance C is small, wear of the press die 8
may occur, that is, die wear may occur. As the die wear progresses,
it develops into abnormal wear called die galling.
[0083]
In this example, the Si content of the first core sheet 101
20 is reduced to thereby reduce the hardness of the first core sheet
101, so as to suppress die wear and die galling when the die
clearance C is made small.
[0084]
FIG. 14(A) is a diagram illustrating a state immediately
25 before the bridge portion 14 is formed by punching the
electromagnetic steel sheet 10S. As illustrated in FIG. 14(A), the
magnet insertion holes 11 including the flux barriers 12 are formed.
[0085]
FIG. 14(B) is a diagram illustrating a state where the bridge
30 portions 14 are formed by punching the electromagnetic steel sheet
10S. As illustrated in FIG. 14(B), the outer circumference 10a of
the rotor core 10 is formed by punching the electromagnetic steel
sheet 10S. By the formation of the outer circumference 10a of the
rotor core 10, the bridge portions 14 are formed between the outer
35 circumference 10a and the flux barriers 12.
[0086]
FIG. 15(A) is a diagram illustrating a forming step of the
bridge portion 14 illustrated in FIG. 14(B). In forming the bridge
21
5 portion 14, the electromagnetic steel sheet 10S is cut at the outer
circumference 10a of the rotor core 10. The die clearance C of the
press die 8 for forming the bridge portion 14 is 5% of the
thickness T1 of the electromagnetic steel sheet 10S.
[0087]
10 At this time, it is desirable to hold the bridge portion 14
by a plate holder 83 so that the bridge portion 14 does not float
up from the die 81.
[0088]
If the bridge portion 14 is not held by the plate holder 83,
15 as illustrated in FIG. 15(B), warping of the electromagnetic steel
sheet 10S pressed by the punch 82 may cause deformation, such as
warping (curling), of the bridge portion 14. As the width of the
bridge portion 14 decreases, deformation of the bridge portion 14
is more likely to occur.
20 [0089]
By holding the bridge portions 14 using the plate holder 83,
the deformation of the bridge portion 14 can be suppressed even
when the width of the bridge portion 14 is made narrower.
[0090]
25 Incidentally, in the rotor core 10, the bridge portion 14 has
the narrowest width and therefore requires high processing accuracy.
In contrast, the magnet insertion hole 11, the slit 13, the center
hole 15, and the like of the rotor core 10 do not require high
processing accuracy, as compared to that required for the bridge
30 portion 14.
[0091]
For this reason, in punching the electromagnetic steel sheet
10S to form the magnet insertion holes 11, the slits 13, the center
hole 15, and the like, the die clearance C in the press die 8 does
35 not need to be set to 5% of the thickness T1 of the electromagnetic
steel sheet 10S and may be set to, for example, 8% of the thickness
T1.
[0092]
22
5 (Comparative Example)
Next, a comparative example to be compared to the first
embodiment will be described. FIG. 16 is a longitudinal-sectional
view illustrating a motor 100D of the comparative example.
[0093]
10 In the comparative example, the first core sheets 101
constituting the rotor core 10 and the second core sheets 501
constituting the stator core 50 are formed of the same
electromagnetic steel sheet. The electromagnetic steel sheet has a
thickness T of 3.5 mm, a Si content of 3.5%, a Vickers hardness Hv
15 of 205, and an iron loss density of 0.98 W/kg.
[0094]
The length H1 of the rotor core 10 in the axial direction is
50 mm, while the length H2 of the stator core 50 in the axial
direction is 45 mm.
20 [0095]
FIG. 17 is an enlarged diagram illustrating facing portions
of the rotor 1 and the stator 5 in the comparative example. The
rotor 1 of the comparative example is configured in the same manner
as the rotor 1 of the first embodiment except for the bridge
25 portion 14. The stator 5 of the comparative example is configured
in the same manner as the stator 5 of the first embodiment.
[0096]
FIG. 18 is a diagram illustrating facing portions of the
magnetic pole of the rotor 1 and the tooth 52. The minimum
30 interval between two bridge portions 14 at both ends of the magnet
insertion hole 11 is denoted by Lb. The minimum interval Lb is an
interval between two end points Pb closest to each other in the two
bridge portions 14 at both ends of the magnet insertion hole 11.
[0097]
35 The maximum interval between two slot openings A facing the
magnet insertion hole 11 is denoted by Ls. The maximum interval Ls
is an interval between two end points Ps far from each other at
inner circumferential side ends of the two slot openings A facing
23
5 the magnet insertion hole 11.
[0098]
In the comparative example, the minimum interval Lb between
the two bridge portions 14 at both ends of the magnet insertion
hole 11 is wider than the maximum interval Ls between the two slot
10 openings A facing the magnet insertion hole 11 (Lb > Ls).
[0099]
FIG. 19 is an enlarged diagram illustrating the bridge
portions 14 and their surroundings. Since the thickness T of the
first core sheet 101 is 0.35 mm, the minimum width Hb of the bridge
15 portion 14 is set to 0.40 mm so as to suppress the bridge portion
14 from being deformed during press processing.
[0100]
FIG. 20 is a diagram for explaining a short circuit of
magnetic flux between adjacent permanent magnets 20. The minimum
20 width Hb of the bridge portion 14 in the comparative example is
0.40 mm, and is wider than the minimum width Hb (0.30 mm) of the
bridge portion 14 of the first embodiment. Thus, the magnetic flux
flowing through the bridge portion 14 as indicated by the arrow F1
increases, as compared to in the first embodiment. That is, the
25 short-circuit magnetic flux between adjacent permanent magnets 20
increases.
[0101]
In the comparative example, the minimum interval Lb between
the two bridge portions 14 at both ends of the magnet insertion
30 hole 11 is wider than the maximum interval Ls between the two slot
openings A facing the magnet insertion hole 11 (Lb > Ls). Thus, as
illustrated in FIG. 20, the end point Ps of the tooth tip portion
52a of the tooth 52 is located closer to the pole center than the
end point Pb of the bridge portion 14 in a state where the center
35 of the permanent magnet 20 faces the tooth 52.
[0102]
As a result, the magnetic flux can flow easily in the radial
direction between the permanent magnet 20 and the tooth tip portion
24
5 52a as indicated by the arrow F2 in FIG. 20. That is, a short
circuit of magnetic flux is more likely to occur between the
permanent magnets 20 via the tooth tip portion 52a.
[0103]
Next, a manufacturing method of a motor of the comparative
10 example will be described. The first core sheets 101 and the
second core sheets 501 are formed by punching the same
electromagnetic steel sheet.
[0104]
FIG. 21 is a flowchart illustrating a forming process of the
15 first core sheets 101 and the second core sheets 501 by punching
the electromagnetic steel sheet 100S. FIG. 22 is a plan view
illustrating the electromagnetic steel sheet 100S from which the
core sheets 101 and 501 are punched.
[0105]
20 The electromagnetic steel sheet 100S has a thickness of 0.35
mm, a Si content of 3.5%, a Vickers hardness Hv of 205, and an iron
loss density of 0.98 W/kg. The electromagnetic steel sheet 100S is
a strip-shaped steel sheet that is elongated in one direction.
[0106]
25 The electromagnetic steel sheet 100S is conveyed in the
longitudinal direction (step S301), and then punched using a press
die into the shapes of the rotor cores 10 to form the first core
sheets 101 (step S302). A die clearance at this time is 8% of the
thickness of the electromagnetic steel sheet 100S.
30 [0107]
Next, the electromagnetic steel sheet 100S is punched into
the shapes of the stator cores 50 to form the second core sheets
501 (step S303). A die clearance at this time is also 8% of the
thickness of the electromagnetic steel sheet 100S.
35 [0108]
In the comparative example, since the first core sheets 101
and the second core sheets 501 are formed of the same
electromagnetic steel sheet 100S, as illustrated in FIG. 22, the
25
5 electromagnetic steel sheet 100S can be punched to form the first
core sheets 101, and then their surroundings can be punched to form
the annular second core sheets 501, which results in good material
yield.
[0109]
10 Using the first core sheets 101 and the second core sheets
501 formed in this way, the rotor 1 and the stator 5 are assembled
as described with reference to FIG. 10 to manufacture the motor 100.
[0110]
(Functions)
15 Next, the functions of the first embodiment will be described
in comparison with the comparative example. In the rotor 1, a
short circuit of magnetic flux may occur between adjacent permanent
magnets 20 via the bridge portions 14 located between the outer
circumference 10a of the rotor core 10 and the magnet insertion
20 holes 11.
[0111]
For this reason, the minimum width Hb of the bridge portion
14 is desired to be narrow. However, making the minimum width Hb
of the bridge portion 14 narrower may cause deformation of the
25 bridge portion 14 during press processing. Thus, the minimum width
Hb of the bridge portion 14 is generally set to be larger than or
equal to the thickness of the electromagnetic steel sheet, for
example, 0.40 mm.
[0112]
30 In order to make the minimum width Hb of the bridge portion
14 narrower, it is desirable that the die clearance C is small.
However, when the die clearance C is small, die wear or die galling
may occur. The die wear or die galling is more likely to occur as
the die clearance C decreases, and more likely to occur as the
35 hardness of the electromagnetic steel sheet increases. Thus, the
die clearance C is generally set to 5 to 15% of the thickness of
the electromagnetic steel sheet.
[0113]
26
5 Here, the iron loss generated in a core such as the rotor
core 10 and stator core 50 includes hysteresis loss and eddy
current loss. Hysteresis loss is the loss that occurs when the
magnetic domain of the core changes the direction of its magnetic
field due to an alternating magnetic field. Hysteresis loss Ph is
10 expressed by Steinmetz's experimental equation (1) as follows:
Ph = khfBm
1.6
(1)
where kh is a proportionality constant, f is the frequency, and Bm
is the maximum magnetic flux density.
[0114]
15 Eddy current loss is caused by an eddy current generated
inside the core. As the frequency of the alternating magnetic
field increases, the ratio of eddy current loss increases. Eddy
current loss Pe is expressed by equation (2) as follows:
Pe = ke(tfBm)
2/ρ (2)
20 where ke is a proportionality constant, t is the thickness of the
electromagnetic steel sheet, f is the frequency, Bm is the maximum
magnetic flux density, and ρ is the electrical resistivity of the
electromagnetic steel sheet.
[0115]
25 As the electrical resistivity ρ of the electromagnetic steel
sheet increases, the eddy current loss decreases. Thus, by using
the electromagnetic steel sheet containing iron (Fe) with silicon
(Si) added, the electrical resistivity ρ is increased, and thus the
eddy current loss can be reduced. However, the electromagnetic
30 steel sheet is made harder and brittler as the Si content increases.
If the hardness of the electromagnetic steel sheet is extremely
high, the electromagnetic steel sheet is more likely to be broken,
and it is difficult to perform press processing.
[0116]
35 For this reason, the rotor core 10 and the stator core 50 are
generally formed of electromagnetic steel sheets that contain 3 to
4% of silicon. If the Si content exceeds 4%, the press processing
is made difficult. Thus, the upper limit of the Si content is 4%.
27
5 [0117]
As is clear from the equation (2), eddy current loss is
proportional to the square of the thickness T of the
electromagnetic steel sheet. Thus, as the thickness T of the
electromagnetic steel sheet decreases, the eddy current loss
10 decreases, and the iron loss density decreases. The rotor core 10
and the stator core 50 are both generally composed of
electromagnetic steel sheets, each having a thickness of 0.2 to 1.0
mm. If the thickness of the electromagnetic steel sheet is less
than 0.2 mm, a rolling process is made difficult to perform, and
15 the manufacturing cost of the electromagnetic steel sheet increases.
Thus, the lower limit of the thickness of the electromagnetic steel
sheet is 0.2 mm.
[0118]
On the other hand, as the thickness of the electromagnetic
20 steel sheet decreases, the volume of the bridge portion 14 of the
rotor core 10 decreases. As a result, the bridge portion 14 is
more likely to be deformed during press processing. The
deformation of the bridge portion 14 refers to warping of the
bridge portion 14 as illustrated in FIG. 15(B). In addition, the
25 bridge portion 14 is more likely to be broken due to a centrifugal
force during rotation of the rotor 1.
[0119]
In order to make the bridge portion 14 narrower by the
processing, it is necessary to reduce a sag, a fracture surface and
30 a burr at a processed surface (FIG. 13) of the bridge portion 14,
and also to increase a shear surface. For this reason, the die
clearance C of the press die 8 needs to be decreased. However, if
the hardness of the electromagnetic steel sheet is high, it is
difficult to reduce the die clearance.
35 [0120]
In general, the first core sheets 101 of the rotor core 10
and the second core sheets 501 of the stator core 50 are formed by
punching the same electromagnetic steel sheet as described in the
28
5 comparative example (FIG. 22). In this case, in order to reduce
iron loss in the stator core 50, the electromagnetic steel sheet
having a thickness of 0.35 mm and a Si content of 3.5% is often
used. The die clearance C of the press die is set to 8% of the
thickness of the electromagnetic steel sheet.
10 [0121]
In contrast, in the first embodiment, the first core sheets
101 of the rotor core 10 and the second core sheets 501 of the
stator core 50 are formed of different electromagnetic steel sheets.
The first core sheet 101 has the thickness of 0.50 mm, the Si
15 content of 3.3%, and the Vickers hardness Hv of 180, while the
second core sheet 501 has the thickness of 0.35 mm, the Si content
of 3.5%, and the Vickers hardness Hv of 205.
[0122]
In the first embodiment, the die clearance C when the first
20 core sheet 101 is formed by punching the electromagnetic steel
sheet 10S is different from the die clearance C when the second
core sheet 501 is formed by punching the electromagnetic steel
sheet 50S.
[0123]
25 The die clearance C when the first core sheet 101 is formed
by punching the electromagnetic steel sheet 10S is set to 5% of the
thickness T1 of the first core sheet 101. Meanwhile, the die
clearance C when the second core sheet 501 is formed by punching
the electromagnetic steel sheet 50S is set to 8% of the thickness
30 T2 of the second core sheet 501.
[0124]
By decreasing the Si content of the first core sheet 101, the
hardness of the first core sheet 101 is lowered, so that die wear
and die galling are less likely to occur even when the die
35 clearance C is made small. Thus, die wear and die galling are less
likely to occur even when the ratio of the die clearance C to the
thickness T1 of the first core sheet 101 is decreased to 5%, for
example.
29
5 [0125]
In addition, by setting the thickness T1 of the first core
sheet 101 to 0.50 mm, the volume of the bridge portion 14 increases,
and the bridge portion 14 is less likely to be deformed during
press processing. As a result, the minimum width Hb of the bridge
10 portion 14 can be made narrower to 0.30 mm, which is smaller than
the thickness T1 of the first core sheet 101.
[0126]
Because the minimum width Hb of the bridge portion 14 can be
made narrower by the press processing in this way, a short circuit
15 of magnetic flux between adjacent permanent magnets 20 can be
suppressed. That is, a short circuit of magnetic flux between the
permanent magnets 20 via the bridge portions 14 can be suppressed
while suppressing an increase in manufacturing cost.
[0127]
20 Here, the thickness of the first core sheet 101 of the first
embodiment is, for example, 0.50 mm, which is thicker than that in
the comparative example, namely 0.35 mm. The Si content of the
first core sheet 101 of the first embodiment is, for example, 3.3%,
which is smaller than that in the comparative example, namely 3.5%.
25 Therefore, the iron loss density of the first core sheet 101 of the
first embodiment is higher than the iron loss density of the first
core sheet 101 of the comparative example.
[0128]
When an iron loss density is measured by inducing the
30 magnetic flux density of 1.0 T at a frequency of 50 Hz, the iron
loss density of the first core sheet 101 of the first embodiment is
1.18 W/kg, while that of the comparative example is 0.98 W/kg. The
iron loss density of the second core sheet 501 is 0.98 W/kg in both
the comparative example and the first embodiment.
35 [0129]
An iron loss during driving of the motor 100 is generated
more in the stator core 50 than in the rotor core 10. The ratio of
the iron loss generated in the rotor core 10 to that in the stator
30
5 core 50 is 2:8.
[0130]
The reason for this is as follows. That is, in the rotor
core 10, the permanent magnets 20 are fixed and thus continuously
generate constant magnetic flux, and thus a small change occurs in
10 the magnetic flux inside the rotor core 10 due to rotation of the
rotor 1. In contrast, in the stator core 50, magnetic flux flowing
therein from the rotor 1 changes depending on the rotational
position of the rotor 1, and thus the magnetic flux largely changes.
Thus, the iron loss generated in the rotor core 10 is smaller than
15 the iron loss generated in the stator core 50.
[0131]
That is, even when the iron loss density of the first core
sheet 101 of the rotor core 10 is high, an increase in the iron
loss in the entire motor 100 is small.
20 [0132]
The iron loss density of the first core sheet 101 is 0.98
W/kg in the comparative example, and 1.18 W/kg in the first
embodiment. In this case, the iron loss generated in the rotor
core 10 of the first embodiment is 1.2 (= 1.18/0.98) times higher
25 than that of the comparative example. However, the comparative
example and the first embodiment are the same in the iron loss
generated in the stator core 50, which occupies 80% of the entire
iron loss. As a result, the iron loss in the motor 100 of the
first embodiment is 1.04 (= 0.2 x 1.2 + 0.8 × 1.0) times higher
30 than the iron loss in the motor of the comparative example, which
means that an increase rate in the iron loss is 4%.
[0133]
Meanwhile, in the first embodiment, as illustrated in FIG. 4,
the minimum interval Lb between the two bridge portions 14 at both
35 ends of the magnet insertion hole 11 and the maximum interval Ls
between the two slot openings A facing the magnet insertion hole 11
satisfy Lb < Ls.
[0134]
31
5 In this case, the end point Pb of the bridge portion 14 is
located closer to the pole center than the end point Ps of the
tooth tip portion 52a in a state where the center of the permanent
magnet 20 faces the tooth 52. Thus, the magnetic flux between the
permanent magnet 20 and the tooth tip portion 52a flows around to
10 the pole center side (see FIG. 6), and thus a short circuit of
magnetic flux via the tooth tip 52a is less likely to occur.
[0135]
That is, a short circuit of magnetic flux between the
permanent magnets 20 can be effectively suppressed when the minimum
15 width Hb of the bridge portion 14 is smaller than the thickness T1
of the first core sheet 101 and Lb < Ls is satisfied. By
suppressing a short circuit of magnetic flux between the permanent
magnets 20, the amount of magnetic flux interlinked with the coil
55 of the stator 5 increases.
20 [0136]
For example, in the motor 100 of the first embodiment where
the minimum width Hb of the bridge portion 14 is 0.30 mm and Lb <
Ls is satisfied, the amount of magnetic flux interlinked with the
coil 55 of the stator 5 is improved by 4% through the reduction of
25 a short circuit of magnetic flux at the bridge portion 14, as
compared to the motor of the comparative example where the minimum
width Hb of the bridge portion 14 is 0.40 mm and Lb > Ls is
satisfied.
[0137]
30 The magnet torque of the rotor 1 is determined by the product
of the magnetic flux interlinked with the coil 55 of the stator 5
and the current flowing through the coil 55. Thus, by increasing
the amount of magnetic flux interlinked with the coil 55, the
current for generating the magnet torque can be reduced, and thus
35 copper loss that is generated in the coil 55 can be reduced.
[0138]
For example, when the amount of magnetic flux interlinked
with the coil 55 of the stator 5 is increased by 4%, the current
32
5 for generating the magnetic torque is reduced by 4%, in other words,
is 0.96 times of the original current. Because the copper loss of
the coil 55 is proportional to the square of the current, the
copper loss is 0.92 (= 0.962) times of the original copper loss and
therefore is reduced by 8%.
10 [0139]
That is, by forming the rotor core 10 using the first core
sheets 101, which have an iron loss density higher than that of the
second core sheets 501 of the stator core 50, and by setting the
minimum width Hb of the bridge portion 14 smaller than the
15 thickness T1 of the first core sheet 101, the copper loss can be
reduced, although the iron loss is increased.
[0140]
In the first embodiment, the copper loss of the rotor core 10
is reduced by 8%, and the iron loss of the motor 100 is increased
20 by 4%, as compared to the comparative example. That is, a decrease
in the copper loss is more than an increase in the iron loss.
Therefore, the motor efficiency can be improved.
[0141]
In general, as the thickness of the electromagnetic steel
25 sheet increases and the iron loss density thereof increases, the
price per unit weight of the electromagnetic steel sheet decreases.
In this embodiment, since the first core sheet 101 of the rotor
core 10 is thick and its iron loss density is high, an inexpensive
electromagnetic steel sheet can be used, and thus the manufacturing
30 cost of the motor 100 can be reduced.
[0142]
In the first embodiment, the thickness T1 of the first core
sheet 101 is thicker than in the comparative example, but the
length H1 of the rotor core 10 is the same as that of the
35 comparative example. Thus, the number of stacked first core sheets
101 in the rotor core 10 in the first embodiment is smaller than
that in the comparative example. As the number of stacked first
core sheets 101 decreases, the number of times of punching the
33
5 electromagnetic steel sheet 10S decreases, and thus the
manufacturing cost can be reduced.
[0143]
As the thickness T1 of the first core sheet 101 increases,
the length in the axial direction of the bridge portion 14 per
10 first core sheet 101 increases. Thus, even when the minimum width
Hb of the bridge portion 14 is made narrower, the volume of the
bridge portion 14 per first core sheet 101 is made larger. Thus,
the bridge portion 14 can be suppressed from being broken due to
the centrifugal force during rotation of the rotor 1.
15 [0144]
The suppression of a short circuit of magnetic flux between
the permanent magnets 20 leads to an increase in the amount of
magnetic flux from the permanent magnets 20 interlinked with the
coil 55, so that the size of each permanent magnet 20 can be
20 reduced by an amount of increase in magnetic flux. When the amount
of magnetic flux interlinked with the coil 55 of the stator 5 is
increased by 4% as compared to the comparative example, the same
level of torque as that in the comparative example can be generated
even when the length in the axial direction of each permanent
25 magnet 20 is decreased by 4%. As a result, the motor 100 can be
downsized, and the manufacturing cost thereof can be reduced.
[0145]
Further, in the motor 100 where the rotor core 10 protrudes
from the stator core 50 in the axial direction, portions of the
30 permanent magnets 20 disposed in protruding portions of the rotor
core 10 do not face the stator core 50. Thus, magnetic flux
emanating from the portions of the permanent magnet 20 disposed in
the protruding portions of the rotor core 10 is more likely to flow
to the adjacent permanent magnet 20. The above configuration that
35 suppresses a short circuit of magnetic flux via the bridge portion
14 is useful particularly in the motor 100 where the rotor core 10
protrudes from the stator core 50 in the axial direction.
[0146]
34
5 In forming the bridge portions 14, the electromagnetic steel
sheet 10S is punched to form the magnet insertion holes 11 as
illustrated in FIG. 14(A), and then the electromagnetic steel sheet
10S is punched to form the outer circumference 10a of the rotor
core 10 as illustrated in FIG. 14(B). At the time of forming the
10 outer circumference 10a of the rotor core 10, the bridge portions
14 can be held by the plate holder 83 as illustrated in FIG. 15(A)
to suppress the deformation of the bridge portions 14. That is,
the bridge portions 14 with the narrow minimum width Hb can be
formed easily.
15 [0147]
In the comparative example, the first core sheets 101 and the
second core sheets 501 are formed of the same electromagnetic steel
sheet 100S. Thus, the plate holder 83 for holding the bridge
portion 14 must be disposed in consideration of the position of the
20 press die for punching the electromagnetic steel sheet 100S into
the shape of the stator core 50, and thus it is difficult to
dispose the plate holder 83.
[0148]
However, in this embodiment, the first core sheet 101 and the
25 second core sheet 501 are formed of different electromagnetic steel
sheets 10S and 50S, and thus it is made easier to dispose the plate
holder 83 for holding the bridge portions 14.
[0149]
In the first embodiment, in order to suppress the deformation
30 of the bridge portion 14 with the narrow minimum width Hb during
press processing, the following requirements (1) to (4) are
satisfied.
(1) The thickness T1 of the first core sheet 101 of the rotor
core 10 is thicker than the thickness T2 of the second core sheet
35 501 of the stator core 50.
(2) The iron loss density of the first core sheet 101 is
higher than the iron loss density of the second core sheet 501.
(3) The Si content of the first core sheet 101 is smaller
35
5 than the Si content of the second core sheet 501.
(4) The hardness of the first core sheet 101 is lower than
the hardness of the second core sheet 501.
[0150]
However, the effect of improving the processability of the
10 bridge portion 14 can be obtained even when any one of these
requirements (1) to (4) is satisfied. Thus, the minimum width Hb
of the bridge portion 14 can be made narrower by the press
processing, and a short circuit of magnetic flux between adjacent
permanent magnets 20 can be suppressed.
15 [0151]
(Effects of Embodiment)
As described above, in the motor 100 of the first embodiment,
the rotor core 10 is formed of the first core sheets 101, and the
stator core 50 is formed of the second core sheets 501, wherein the
20 thickness T1 of the first core sheet 101 is thicker than the
thickness T2 of the second core sheet 501. The bridge portion 14
is formed between the outer circumference 10a of the rotor core 10
and the magnet insertion hole 11, and the minimum width Hb of the
bridge portion 14 in the radial direction is smaller than the
25 thickness T1 of the first core sheet 101.
[0152]
Since the minimum width Hb of the bridge portion 14 is
smaller than the thickness T1 of the first core sheet 101, a short
circuit of magnetic flux between adjacent permanent magnets 20 can
30 be suppressed. Since the thickness T1 of the first core sheet 101
is thicker than the thickness T2 of the second core sheet 501, the
volume of the bridge portion 14 per first core sheet 101 increases.
As a result, the deformation of the bridge portion 14 during press
processing can be suppressed even when the minimum width Hb of the
35 bridge portion 14 is made narrower. Thus, the bridge portion 14
can be suppressed from being broken due to the centrifugal force
during rotation of the rotor 1.
[0153]
36
5 The iron loss density of the first core sheet 101 is higher
than the iron loss density of the second core sheet 501. This is
because the thickness T1 of the first core sheet 101 is thicker
than the thickness T2 of the second core sheet 501, and the Si
content of the first core sheet 101 is smaller than the Si content
10 of the second core sheet 501. Thus, the deformation of the bridge
portion 14 during press processing can be suppressed, and the die
clearance C can be reduced without causing die wear and die galling.
As a result, the bridge portion 14 with the narrow minimum width Hb
can be formed by press processing, and a short circuit of magnetic
15 flux between the permanent magnets 20 can be suppressed.
[0154]
Since the Si content of the first core sheet 101 is smaller
than the Si content of the second core sheet 501, the hardness of
the first core sheet 101 is higher than the hardness of the second
20 core sheet 501. Thus, the die clearance C can be reduced without
causing die wear and die galling during the press processing of the
first core sheets 101. As a result, the bridge portion 14 with the
narrow minimum width Hb can be formed by the press processing, and
a short circuit of magnetic flux between the permanent magnets 20
25 can be suppressed.
[0155]
Further, since the hardness of the first core sheet 101 is
lower than the hardness of the second core sheet 501, the die
clearance C can be reduced without causing die wear and die galling
30 during the press processing of the first core sheets 101. As a
result, the bridge portion 14 with the narrow minimum width Hb can
be formed by the press processing, and a short circuit of magnetic
flux between the permanent magnets 20 can be suppressed.
[0156]
35 In addition, since the minimum interval Lb between the two
bridge portions 14 at both ends of the magnet insertion hole 11 and
the maximum interval Ls between the two slot openings A facing the
magnet insertion hole 11 satisfy Lb < Ls, a short circuit of
37
5 magnetic flux between the permanent magnets 20 through the tooth
tip portion 52a of the tooth 52 can be suppressed in a state where
the center of the permanent magnet 20 faces the tooth 52.
[0157]
Since the minimum width Hb of the bridge portion 14 is
10 smaller than the thickness T2 of the second core sheet 501, the
magnetic flux is less likely to flow through the bridge portion 14,
so that a short circuit of magnetic flux between adjacent permanent
magnets 20 can be suppressed.
[0158]
15 The stator core 50 is composed of a plurality of split cores
50A which are combined in the circumferential direction, and thus
it is possible to punch the electromagnetic steel sheet 50S into
the shape in which the split cores 50A are arranged side by side
linearly. Accordingly, the electromagnetic steel sheet 50S can be
20 effectively utilized and the manufacturing cost of the motor 100
can be reduced.
[0159]
Since the thickness of the first core sheet 101 is more than
0.35 mm, and the thickness of the second core sheet 501 is 0.35 mm
25 or less, the deformation of the bridge portion 14 during press
processing can be suppressed, and an increase in the iron loss of
the stator core 50 can also be suppressed.
[0160]
Since the Si content of the first core sheet 101 is less than
30 3.5%, and the Si content of the second core sheet 501 is 3.5% or
more, die wear and die galling during the press processing of the
first core sheets 101 can be suppressed, and an increase in the
iron loss of the stator core 50 can also be suppressed.
[0161]
35 Furthermore, since the Vickers hardness of the first core
sheet 101 is less than 200, and the Vickers hardness of the core
sheet 500 is 200 or more, die wear and die galling during the press
processing of the first core sheets 101 can be suppressed, and the
38
5 rigidity of the stator core 50 can be enhanced.
[0162]
Second Embodiment
FIG. 23 is a longitudinal-sectional view illustrating a motor
100A of a second embodiment. In the second embodiment, the stator
10 core 50 of the stator 5 is subjected to an annealing process to
improve its magnetic properties. The motor 100A of the second
embodiment is configured in the same manner as the motor 100 of the
first embodiment except that the stator core 50 is subjected to the
annealing process.
15 [0163]
When the second core sheets 501 are formed by punching the
electromagnetic steel sheet 50S, a strain occurs on the processed
surface due to the shearing force and remains as the residual
strain. The residual strain may change the magnetic properties of
20 the second core sheet 501.
[0164]
In the second embodiment, the second core sheets 501 obtained
by punching the electromagnetic steel sheet 50S is subjected to the
annealing process. This eliminates the residual strain that has
25 occurred due to the punching and thus improves the magnetic
properties of the second core sheets 501. Thus, an iron loss in
the stator core 50 can be reduced and motor efficiency can be
improved.
[0165]
30 Meanwhile, in the rotor core 10, the change in the magnetic
flux is smaller, and thus the iron loss is smaller as compared to
the stator core 50. Further, when the residual strain remains in
the bridge portions 14 of the rotor core 10, the effect of
suppressing a short circuit of magnetic flux between the permanent
35 magnets 20 increases, which is desirable. Therefore, it is
desirable that the annealing process is performed on the stator
core 50, but not on the rotor core 10.
[0166]
39
5 As described above, the second embodiment can improve motor
efficiency by reducing iron loss in the stator core 50, in addition
to achieving the effect described in the first embodiment.
[0167]
(Compressor)
10 FIG. 24 is a longitudinal-sectional view illustrating the
compressor 300 to which the motor of each embodiment is applicable.
The compressor 300 is a rotary compressor, and is used, for example,
in a refrigeration cycle apparatus 400 (FIG. 25).
[0168]
15 The compressor 300 includes a compression mechanism 310, the
motor 100 that drives the compression mechanism 310, the shaft 25
that connects the compression mechanism 310 and the motor 100, and
a sealed container 301 that houses these components.
[0169]
20 The sealed container 301 is a container made of a steel sheet
and has a cylindrical shell and a container top that covers the top
of the shell. The stator 5 of the motor 100 is incorporated in the
shell of the sealed container 301 by shrink-fitting, press-fitting,
welding, or the like.
25 [0170]
The container top of the sealed container 301 is provided
with a discharge pipe 307 for discharging a refrigerant to the
outside and terminals 305 for supplying electric power to the motor
100. An accumulator 302 that stores a refrigerant gas is attached
30 to the outside of the sealed container 301. At the bottom of the
sealed container 301, refrigerant oil is retained to lubricate a
bearing of the compression mechanism 310.
[0171]
The compression mechanism 310 has a cylinder 311 with a
35 cylinder chamber 312, a rolling piston 314 fixed to the shaft 25, a
vane dividing the inside of the cylinder chamber 312 into a suction
side and a compression side, and an upper frame 316 and a lower
frame 317 which close both ends of the cylinder chamber 312 in the
40
5 axial direction.
[0172]
Both the upper frame 316 and lower frame 317 have bearings
that rotatably support the shaft 25. An upper discharge muffler
318 and a lower discharge muffler 319 are installed on the upper
10 frame 316 and the lower frame 317, respectively.
[0173]
The cylinder 311 is provided with the cylinder chamber 312
having a cylindrical shape about the axis Ax. An eccentric shaft
portion 25a of the shaft 25 is located inside the cylinder chamber
15 312. The eccentric shaft portion 25a has the center that is
eccentric relative to the axis Ax. The rolling piston 314 is
fitted to the outer circumference of the eccentric shaft portion
25a. When the motor 100 rotates, the eccentric shaft portion 25a
and the rolling piston 314 rotate eccentrically within the cylinder
20 chamber 312.
[0174]
A suction port 313 through which the refrigerant gas is
sucked into the cylinder chamber 312 is formed in the cylinder 311.
A suction pipe 303 that communicates with the suction port 313 is
25 attached to the sealed container 301, whereby the refrigerant gas
is supplied from the accumulator 302 to the cylinder chamber 312
via the suction pipe 303.
[0175]
The compressor 300 is supplied with a mixture of low-pressure
30 refrigerant gas and a liquid refrigerant from a refrigerant circuit
of the refrigeration cycle apparatus 400 (FIG. 25). If the liquid
refrigerant flows into and is compressed by the compression
mechanism 310, it may cause the failure of the compression
mechanism 310. Thus, the accumulator 302 separates the refrigerant
35 into the liquid refrigerant and the refrigerant gas and supplies
only the refrigerant gas to the compression mechanism 310.
[0176]
For example, R410A, R407C, or R22 may be used as the
41
5 refrigerant, but it is desirable to use a refrigerant with a low
global warming potential (GWP) from the viewpoint of preventing
global warming. Examples of the usable low-GWP refrigerant include
the following.
[0177]
10 (1) First, a halogenated hydrocarbon having a carbon-carbon
double bond in its composition, for example, HFO (Hydro-FluoroOlefin)-1234yf (CF3CF=CH2), can be used. The GWP of HFO-1234yf is
4.
(2) A hydrocarbon having a carbon-carbon double bond in its
15 composition, for example, R1270 (propylene), may be used. The GWP
of R1270 is 3, which is lower than that of HFO-1234yf, but R1270
has higher flammability than HFO-1234yf.
(3) A mixture containing at least one of a halogenated
hydrocarbon having a carbon-carbon double bond in its composition
20 and a hydrocarbon having a carbon-carbon double bond in its
composition may be used. For example, a mixture of HFO-1234yf and
R32 may be used. HFO-1234yf described above is a low-pressure
refrigerant and thus tends to increase a pressure loss, which may
lead to reduction in the performance of the refrigeration cycle
25 (particularly, an evaporator). For this reason, a mixture of the
HFO-1234yf with R32 or R41, which is a high-pressure refrigerant
compared to HFO-1234yf, is desirably used in practice.
[0178]
The operation of the compressor 300 is as follows. The
30 refrigerant gas supplied from the accumulator 302 is supplied
through the suction pipe 303 into the cylinder chamber 312 of the
cylinder 311. When the motor 100 is driven to rotate the rotor 1,
the shaft 25 rotates with the rotor 1. Then, the rolling piston
314 fitted to the shaft 25 eccentrically rotates inside the
35 cylinder chamber 312, thereby compressing the refrigerant in the
cylinder chamber 312. The compressed refrigerant passes through
the discharge mufflers 318 and 319, further rises inside the sealed
container 301 through the through holes 102 and 103, and the like
42
5 of the motor 100 (FIG. 1), and is then discharged through the
discharge pipe 307.
[0179]
The motor described in each embodiment has a high motor
efficiency because a short circuit of magnetic flux between the
10 permanent magnets 20 is suppressed. Thus, the operating efficiency
of the compressor 300 can be improved.
[0180]
(Refrigeration Cycle Apparatus)
Next, the refrigeration cycle apparatus 400 to which the
15 motor of each embodiment is applicable will be described. FIG. 25
is a diagram illustrating the configuration of the refrigeration
cycle apparatus 400. The refrigeration cycle apparatus 400 is an
air conditioner in this example, but is not limited to thereto and
may be, for example, a refrigerator.
20 [0181]
The refrigeration cycle apparatus 400 includes a compressor
401, a condenser 402, a decompressor 403, and an evaporator 404.
The compressor 401, the condenser 402, the decompressor 403, and
the evaporator 404 are connected together by a refrigerant pipe 407
25 to configure the refrigeration cycle. That is, the refrigerant
circulates through the compressor 401, the condenser 402, the
decompressor 403, and the evaporator 404 in this order.
[0182]
The compressor 401, the condenser 402, and the decompressor
30 403 are provided in an outdoor unit 410. The compressor 401 is
constituted by of the compressor 300 described with reference to
FIG. 24. The outdoor unit 410 is provided with an outdoor fan 405.
The evaporator 404 is provided in an indoor unit 420. The indoor
unit 420 is provided with an indoor fan 406.
35 [0183]
The operation of the refrigeration cycle apparatus 400 is as
follows. The compressor 401 compresses the sucked refrigerant and
sends out the compressed refrigerant. The condenser 402 exchanges
43
5 heat between the refrigerant sent from the compressor 401 and the
outdoor air to condense the refrigerant and sends out the condensed
refrigerant as a liquid refrigerant. The decompressor 403 expands
the liquid refrigerant sent from the condenser 402 and then sends
out the expanded refrigerant as a low-temperature and low-pressure
10 liquid refrigerant.
[0184]
The evaporator 404 exchanges heat between indoor air and the
low-temperature and low-pressure liquid refrigerant sent from the
decompressor 403 to evaporate the refrigerant and then sends out
15 the evaporated refrigerant as a refrigerant gas. Thus, air from
which heat is removed in the evaporator 404 is supplied to the
interior of a room by the indoor fan 406.
[0185]
The refrigeration cycle apparatus 400 includes the compressor
20 300 with high operating efficiency as described above, and thus the
operating efficiency of the refrigeration cycle apparatus 400 can
be improved.
[0186]
Although the desirable embodiments have been specifically
25 described above, the present disclosure is not limited to the above
embodiments, and various modifications or changes can be made to
those embodiments.
DESCRIPTION OF REFERENCE CHARACTERS
[0187]
30 1: rotor; 5: stator; 8: press die; 10: rotor core; 10S:
electromagnetic steel sheet (first electromagnetic steel sheet);
10a: outer circumference; 11: magnet insertion hole; 12: flux
barrier; 14: bridge portion; 15: center hole; 20: permanent
magnet; 25: shaft; 50: stator core; 50A: split core; 50S:
35 electromagnetic steel sheet (second electromagnetic steel sheet);
51: yoke; 52: tooth; 52a: tooth tip portion; 52b: end surface;
53: slot; 54: split surface; 55: coil; 81: die; 82: punch; 83:
plate holder; 100, 100A: motor; 101: first core sheet; 300:
44
5 compressor; 301: sealed container; 310: compression mechanism;
400: refrigeration cycle apparatus; 401: four-way valve; 402:
condenser; 403: decompressor; 404: evaporator; 407: refrigerant
pipe; 501: second core sheet; A: slot opening; C: die clearance.

5 WE CLAIM:
1. A motor comprising:
a rotor having a rotor core having an annular shape about an
axis and formed of a first core sheet subjected to press processing,
10 and a permanent magnet embedded in the rotor core; and
a stator surrounding the rotor from outside in a radial
direction about the axis, the stator having a stator core formed of
a second core sheet subjected to press processing,
wherein a thickness of the first core sheet is thicker than a
15 thickness of the second core sheet,
wherein the rotor core has an outer circumference, a magnet
insertion hole in which the permanent magnet is inserted, and a
bridge portion between the outer circumference and the magnet
insertion hole, and
20 wherein a minimum width of the bridge portion in the radial
direction is smaller than the thickness of the first core sheet.
2. A motor comprising:
a rotor having a rotor core having an annular shape about an
25 axis and formed of a first core sheet subjected to press processing,
and a permanent magnet embedded in the rotor core; and
a stator surrounding the rotor from outside in a radial
direction about the axis, the stator having a stator core formed of
a second core sheet subjected to press processing,
30 wherein an iron loss density of the first core sheet is
higher than an iron loss density of the second core sheet,
wherein the rotor core has an outer circumference, a magnet
insertion hole in which the permanent magnet is inserted, and a
bridge portion between the outer circumference and the magnet
35 insertion hole, and
wherein a minimum width of the bridge portion in the radial
direction is smaller than the thickness of the first core sheet.
46
5 3. A motor comprising:
a rotor having a rotor core having an annular shape about an
axis and formed of a first core sheet subjected to press processing,
and a permanent magnet embedded in the rotor core; and
a stator surrounding the rotor from outside in a radial
10 direction about the axis, the stator having a stator core formed of
a second core sheet subjected to press processing,
wherein a Si content of the first core sheet is smaller than
a Si content of the second core sheet,
wherein the rotor core has an outer circumference, a magnet
15 insertion hole in which the permanent magnet is inserted, and a
bridge portion between the outer circumference and the magnet
insertion hole, and
wherein a minimum width of the bridge portion in the radial
direction is smaller than the thickness of the first core sheet.
20
4. A motor comprising:
a rotor having a rotor core having an annular shape about an
axis and formed of a first core sheet subjected to press processing,
and a permanent magnet embedded in the rotor core; and
25 a stator surrounding the rotor from outside in a radial
direction about the axis, the stator having a stator core formed of
a second core sheet subjected to press processing,
wherein a hardness of the first core sheet is lower than a
hardness of the second core sheet,
30 wherein the rotor core has an outer circumference, a magnet
insertion hole in which the permanent magnet is inserted, and a
bridge portion between the outer circumference and the magnet
insertion hole, and
wherein a minimum width of the bridge portion in the radial
35 direction is smaller than the thickness of the first core sheet.
5. The motor according to any one of claims 1 to 4, wherein the
rotor core has two bridges on both sides of the magnet insertion
47
5 hole in a circumferential direction about the axis,
wherein the stator has a yoke having an annular shape about
the axis, a tooth extending from the yoke toward the rotor, and two
slot openings formed on both sides of the tooth in the
circumferential direction, and
10 wherein a maximum interval Ls between the two slot openings
and a minimum interval Lb between the two bridges satisfy Lb < Ls.
6. The motor according to any one of claims 1 to 5, wherein a
minimum width of the bridge portion in the radial direction is
15 smaller than the thickness of the second core sheet.
7. The motor according to any one of claims 1 to 6, wherein the
stator core has a plurality of split cores 50A that are combined in
an annular shape.
20
8. The motor according to any one of claims 1 to 7, wherein the
stator core is subjected to an annealing process.
9. The motor according to any one of claims 1 to 8, wherein a
25 length of the rotor core in a direction of the axis is longer than
a length of the stator core in the direction of the axis.
10. The motor according to any one of claims 1 to 9,
wherein the first core sheet has a thickness of more than
30 0.35 mm, and
wherein the second core sheet has a thickness of 0.35 mm or
less.
11. The motor according to any one of claims 1 to 10, wherein the
35 first core sheet has a Si content of less than 3.5%, and
wherein the second core sheet has a Si content of 3.5% or
more.
48
5 12. The motor according to any one of claims 1 to 11, wherein the
first core sheet has a Vickers hardness of lower than 200, and
wherein the second core sheet has a Vickers hardness of 200
or higher.
10 13. A compressor comprising:
the motor according to any one of claims 1 to 12; and
a compression mechanism to be driven by the motor.
14. A refrigeration cycle apparatus comprising the compressor
15 according to claim 13, a condenser, a decompressor, and an
evaporator.
15. A manufacturing method of a motor, comprising the steps of:
punching a first electromagnetic steel sheet to form a first
20 core sheet;
punching a second electromagnetic steel sheet to form a
second core sheet;
forming an annular rotor core of the first core sheet;
embedding a permanent magnet in the rotor core to obtain a
25 rotor;
forming a stator core of the second core sheet; and
winding a coil on the stator core to form a stator,
wherein the rotor core has an outer circumference, a magnet
insertion hole, and a bridge portion between the outer
30 circumference and the magnet insertion hole, and
wherein in the punching step of the first electromagnetic
steel sheet, a die clearance at least when the bridge portion is
formed is narrower than a die clearance in the punching step of the
second electromagnetic steel sheet.
35
16. The manufacturing method of the motor according to claim 15,
wherein a minimum width of the bridge portion in a radial direction
of the rotor core is smaller than a thickness of the first core
49
5 sheet.
17. The manufacturing method of the motor according to claim 15
or 16,
wherein the stator core has a plurality of split cores that
10 are combined in an annular shape, and
wherein in the step of punching the first electromagnetic
steel sheet, the first electromagnetic steel sheet is punched so
that the plurality of split cores are arranged side by side
linearly.
15
18. The manufacturing method of the motor according to any one of
claims 15 to 17, further comprising the step of:
performing an annealing process on the stator core after the
step of forming the stator core.