FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
ROTOR, ELECTRIC MOTOR, COMPRESSOR, AND AIR CONDITIONER;
MITSUBISHI ELECTRIC CORPORATION, A CORPORATION ORGANISED AND
EXISTING UNDER THE LAWS OF JAPAN, WHOSE ADDRESS IS 7-3, MARUNOUCHI
2-CHOME, CHIYODA-KU, TOKYO 1008310, JAPAN
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE
INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED

2
DESCRIPTION
TECHNICAL FIELD
[0001]
5 The present invention relates to a rotor for use in an
electric motor.
BACKGROUND ART
[0002]
10 Rotors having magnet insertion holes provided with flux
barrier parts (also referred to as “flux barriers”), which are
space, have been used. In such a rotor, leakage flux can be
reduced, and thus motor efficiency can be enhanced. However,
because of the presence of thin portions between the outer
15 peripheral surface of the rotor and the flux barrier parts,
stress tends to be concentrated on these thin portions during
rotation of the rotor. As the rotation speed of the rotor
increases, this stress increases, and as a result, the rotor,
especially the thin portions, is easily deformed. In view of
20 this, a rotor having a center rib (also simply referred to as a
“rib”) between two magnet insertion holes is proposed (see, for
example, Patent Reference 1). In the rotor having the center
rib, a part of stress occurring in the rotor is dispersed to
the center rib, and thus stress generated on the thin portions
25 is reduced. Accordingly, deformation of the rotor can be
prevented.
PRIOR ART REFERENCE
PATENT REFERENCE
30 [0003]
Patent Reference 1: Japanese Patent Application
Publication No. 2017-192211

3
SUMMARY OF THE INVENTION
PROBLEM TO BE SOLVED BY THE INVENTION
[0004]
With a conventional technique, however, in the case where
5 the center rib is present between two magnet insertion holes,
the strength of the rotor to a centrifugal force increases, but
magnetic flux passing through the center rib, that is, leakage
flux, increases, and power of an electric motor decreases,
disadvantageously.
10 [0005]
An object of the present invention is to enhance power of
an electric motor.
MEANS OF SOLVING THE PROBLEM
15 [0006]
A rotor according to an aspect of the present invention
includes: a rotor core including a first magnet insertion hole,
a second magnet insertion hole, and a center lib between the
first magnet insertion hole and the second magnet insertion
20 hole;
a first permanent magnet disposed in the first magnet
insertion hole, the first permanent magnet being W1 mm long in
a longitudinal direction in a plane perpendicular to an axial
direction; and
25 a second permanent magnet disposed in the second magnet
insertion hole, the second permanent magnet being W1 mm long in
a longitudinal direction in the plane, wherein
the first magnet insertion hole includes
a first magnet disposition part in which the first
30 permanent magnet is disposed,
a first flux barrier part communicating with the first
magnet disposition part,
a first outside opening part located on an outer side
with respect to the first magnet disposition part in a radial

4
direction of the rotor core, the first outside opening part
having a radius of curvature of R1 mm in the plane, and
a first inside opening part located on an inner side with
respect to the first magnet disposition part in the radial
5 direction, the first inside opening part having a radius of
curvature of R2 mm in the plane, and
the second magnet insertion hole includes
a second magnet disposition part in which the second
permanent magnet is disposed,
10 a second flux barrier part communicating with the second
magnet disposition part,
a second outside opening part located on an outer side
with respect to the second magnet disposition part in the
radial direction, the second outside opening part having a
15 radius of curvature of R1 mm in the plane, and
a second inside opening part located on an inner side
with respect to the second magnet disposition part in the
radial direction, the second inside opening part having a
radius of curvature of R2 mm in the plane, and
20 the rotor satisfies R1 > R2 and 0 < (R1 + R2)/W1 < 0.082.
An electric motor according to another aspect of the
present invention includes:
a stator; and
the rotor disposed inside the stator.
25 A compressor according to yet another aspect of the
present invention includes:
a closed container;
a compression device disposed inside the closed
container; and
30 the electric motor to drive the compression device.
An air conditioner according to still another aspect
includes:
the compressor; and
a heat exchanger.

5
EFFECTS OF THE INVENTION
[0007]
According to the present invention, power of the electric
5 motor can be enhanced.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008]
FIG. 1 is a plan view schematically illustrating a
10 structure of an electric motor according to a first embodiment
of the present invention.
FIG. 2 is a plan view schematically illustrating a
structure of a rotor.
FIG. 3 is an enlarged view illustrating a region
15 constituting one magnetic pole of the rotor.
FIG. 4 is an enlarged view illustrating a peripheral
structure of a center lib.
FIG. 5 is an enlarged view illustrating the peripheral
structure of the center lib.
20 FIG. 6 is a graph showing a relationship between a
centrifugal force [p.u.] generated during rotation of the rotor
and a ratio of radii of curvature.
FIG. 7 is a graph showing a relationship between
demagnetization resistance [p.u.] and a ratio of radii of
25 curvature.
FIG. 8 is a graph showing a relationship between
demagnetization resistance [p.u.] and a ratio of radii of
curvature.
FIG. 9 is an enlarged view illustrating a peripheral
30 structure of an outside opening part.
FIG. 10 is a graph showing a relationship between a
centrifugal force [p.u.] and a ratio of radii of curvature.
FIG. 11 is a graph showing a relationship between a
demagnetization resistance [p.u.] and a ratio of radii of

6
curvature.
FIG. 12 is a cross-sectional view schematically
illustrating a structure of a compressor according to a second
embodiment of the present invention.
5 FIG. 13 is a diagram schematically illustrating a
configuration of a refrigerating and air conditioning apparatus
according to a third embodiment of the present invention.
MODE FOR CARRYING OUT THE INVENTION
10 [0009]
FIRST EMBODIMENT
In an xyz orthogonal coordinate system shown in each
drawing, a z-axis direction (z axis) represents a direction
parallel to an axis Ax of an electric motor 1, an x-axis
15 direction (x axis) represents a direction orthogonal to the zaxis direction (z axis), and a y-axis direction (y axis)
represents a direction orthogonal to both the z-axis direction
and the x-axis direction. The axis Ax is a center of a stator
3, and is also a rotation center of a rotor 2. A direction
20 parallel to the axis Ax is also referred to as an “axial
direction of the electric motor 1,” an “axial direction of the
rotor 2,” or simply as an “axial direction.” The “radial
direction” is a radial direction of the rotor 2 or the stator 3,
and is a direction orthogonal to the axis Ax. An xy plane is a
25 plane perpendicular to the axial direction. An arrow D1
represents a circumferential direction about the axis Ax. The
circumferential direction of the rotor 2 or the stator 3 will
be also simply referred to as a “circumferential direction.”
[0010]
30
FIG. 1 is a plan view schematically illustrating a
structure of the electric motor 1 according to a first
embodiment of the present invention.
The electric motor 1 includes the rotor 2 and the stator

7
3.
[0011]
In this embodiment, the electric motor 1 is, for example,
a three-phase synchronous motor. Specifically, the electric
5 motor 1 is a permanent magnet synchronous motor (also called a
brushless DC motor) such as a permanent magnet-embedded motor.
[0012]
The rotor 2 is rotatably disposed inside the stator 3.
An air gap is formed between the rotor 2 and the stator 3. The
10 air gap is, for example, from 0.3 mm to 1 mm. The rotor 2
rotates about an axis Ax. The rotor 2 includes a rotor core 21,
at least one permanent magnet 22, and a shaft 24.
[0013]
The stator 3 is disposed outside the rotor 2. The stator
15 3 includes, for example, an annular stator core 31 and a stator
winding wound around the stator core 31. In the example
illustrated in FIG. 1, the stator 3 includes a yoke 35
extending in the circumferential direction of the stator 3, and
a plurality of teeth 34 extending radially from the yoke 35.
20 In the example illustrated in FIG. 1, the stator core 31
includes 18 teeth 34. Space between the teeth 34 is at least
one slot 33 in which the stator winding is disposed.
[0014]
The stator winding used for the stator 3 is, for example,
25 a winding in which an insulation film is formed around a
conductor such as copper or aluminium. The stator winding
forms a coil for generating a rotation magnetic field. When a
current flows in the stator winding, a rotation magnetic field
occurs. The number of windings and the diameter of the stator
30 winding are set in accordance with, for example, a voltage
applied to the stator winding, the rotation speed of the
electric motor 1, or the cross-sectional area of the slot.
[0015]
The stator core 31 of the stator 3 is constituted by, for

8
example, annular electromagnetic steel sheets stacked in the
axial direction. Each of the electromagnetic steel sheets is
punched in a predetermined shape beforehand. The thickness of
each electromagnetic steel sheet of the stator 3 is, for
5 example 0.1 mm to 0.7 mm. In this embodiment, the thickness of
each electromagnetic steel sheet of the stator 3 is 0.35 mm.
The electromagnetic steel sheets are fixed together by swaging.
[0016]
A structure of the rotor 2 will be described specifically.
10 FIG. 2 is a plan view schematically illustrating the
structure of the rotor 2.
FIG. 3 is an enlarged view illustrating a region
constituting one magnetic pole of the rotor 2.
[0017]
15 In the example illustrated in FIG. 2, the rotor 2
includes the rotor core 21, a plurality of permanent magnets 22
embedded in the rotor core 21, and the shaft 24 fitted in a
shaft hole 215 of the rotor core 21. The rotor 2 includes two
or more magnetic poles. Two or more permanent magnets 22
20 constitute one magnetic pole of the rotor 2. In this
embodiment, the electric motor 2 is a permanent magnet-embedded
electric rotor.
[0018]
The rotor core 21 is an annular rotor core. The rotor
25 core 21 is formed of, for example, a plurality of
electromagnetic steel sheets. The rotor core 21 includes at
least one pair of magnet insertion holes 210, at least one
center rib 213, and at least one thin portion 214.
[0019]
30 The rotor core 21 of the rotor 2 is constituted by, for
example, annular electromagnetic steel sheets stacked in the
axial direction. Each of the electromagnetic steel sheets is
punched in a predetermined shape beforehand. The thickness of
each electromagnetic steel sheet of the rotor 2 is, for example

9
0.1 mm to 0.7 mm. In this embodiment, the thickness of each
electromagnetic steel sheet of the rotor 2 is 0.35 mm. The
electromagnetic steel sheets are fixed together by swaging.
[0020]
5 The pair of magnet insertion holes 210 includes a first
magnet insertion hole 211 and a second magnet insertion hole
212. In the xy plane, the center of one pair of magnet
insertion holes 210 projects toward the center (i.e., the axis
Ax) of the rotor core 21. That is, one pair of magnet
10 insertion holes 210 (i.e., the first magnet insertion hole 211
and the second magnet insertion hole 212) is disposed in a V
shape in the xy plane.
[0021]
The center lib 213 is a part of the rotor core 21, and
15 extends in the radial direction. The center lib 213 is
disposed between the first magnet insertion hole 211 and the
second magnet insertion hole 212. Thus, the center lib 213 is
located at a magnetic pole center part of the rotor 2.
[0022]
20 As long as the rotor core 21 includes the center lib 213,
arrangement of the pair of magnet insertion holes 210 (i.e.,
the first magnet insertion hole 211 and the second magnet
insertion hole 212) is not limited to a V shape.
[0023]
25 The first magnet insertion hole 211 includes a magnet
disposition part 211a (also referred to as a first magnet
disposition part) in which the permanent magnet 22 as a first
permanent magnet is disposed, a flux barrier part 211b (also
referred to as a first flux barrier part) that is space
30 communicating with the magnet disposition part 211a, an outside
opening part 211c (also referred to as a first outside opening
part), and an inside opening part 211d (also referred to as a
first inside opening part).
[0024]

10
The second magnet insertion hole 212 includes a magnet
disposition part 212a (also referred to as a second magnet
disposition part) in which the permanent magnet 22 as a second
permanent magnet is disposed, a flux barrier part 212b (also
5 referred to as a second flux barrier part) that is space
communicating with the magnet disposition part 212a, an outside
opening part 212c (also referred to as a second outside opening
part), and an inside opening part 212d (also referred to as a
second inside opening part).
10 [0025]
The flux barrier part 211b is located at an inter-pole
part of the rotor 2 or near the inter-pole part. Similarly,
the flux barrier part 212b is located at an inter-pole part of
the rotor 2 or near the inter-pole part.
15 [0026]
The thin portion 214 between the outer peripheral surface
of the rotor core 21 and the first magnet insertion hole 211
will be also referred to as a “first thin portion.” The thin
portion 214 between the outer peripheral surface of the rotor
20 core 21 and the second magnet insertion hole 212 will be also
referred to as a “second thin portion.” In this case, the
first thin portion is a region between the flux barrier part
211b and the outer peripheral surface of the rotor core 21, and
the second thin portion is a region between the flux barrier
25 part 212b and the outer peripheral surface of the rotor core 21.
[0027]
A minimum width of each thinner portion 214 in the radial
direction is, for example, greater than or equal to the
thickness of one electromagnetic steel sheet of the rotor core
30 21. The minimum width of each thinner portion 214 in the
radial direction is preferably substantially equal to the
thickness of one electromagnetic steel sheet of the rotor core
21. In this case, an increase of leakage flux in each thin
portion 214 can be effectively suppressed.

11
[0028]
In the example illustrated in FIG. 2, the rotor core 21
includes six magnet insertion holes 210, six center ribs 213,
and twelve thin portions 214, and the shaft hole 215. The six
5 magnet insertion holes 210 are arranged in the circumferential
direction of the rotor 2. Each first magnet insertion hole 211
and each second magnet insertion hole 212 extend in the axial
direction.
[0029]
10 The permanent magnet 22 as the first permanent magnet is
placed in each first magnet insertion hole 211. The permanent
magnet 22 as the second permanent magnet is placed in each
second magnet insertion hole 212.
[0030]
15 The shaft 24 is fixed to the shaft hole 215 by a
technique such as shrink fitting or press fitting. When a
current flows in the stator winding of the stator 3, the rotor
2 (specifically, the rotor core 21) rotates, and rotation
energy of the rotor core 21 is transferred to the shaft 24.
20 [0031]
Each permanent magnet 22 is, for example, a flat-plate
permanent magnet. Each permanent magnet 22 is, for example, a
rare earth magnet containing neodymium (Nd) and dysprosium (Dy).
The rare earth magnet has a high residual flux density and a
25 high coercive force. Thus, in the case of using rare earth
magnets as the permanent magnets 22, efficiency of the electric
motor 1 can be enhanced. As the permanent magnets 22, magnets
except for rare earth magnets, such as ferrite sintered magnets,
may be used.
30 [0032]
Each permanent magnet 22 is magnetized in a direction
perpendicular to the longitudinal direction of the permanent
magnet 22 in the xy plane. That is, each permanent magnet 22
is magnetized in the lateral direction of the permanent magnet

12
22 in the xy plane.
[0033]
In the xy plane, each permanent magnet 22 is W1 mm long
in the longitudinal direction. The length of W1 is a maximum
5 length of each permanent magnet 22 in the longitudinal
direction. It should be noted that the length of each
permanent magnet 22 in the longitudinal direction in the first
magnet insertion hole 211 may be different from the length of
each permanent magnet 22 in the longitudinal direction in the
10 second magnet insertion hole 212.
[0034]
One pair of magnet insertion holes 210 is associated with
one magnetic pole of the rotor 2. Specifically, two permanent
magnets 22 (i.e., the first permanent magnet and the second
15 permanent magnet) placed in one pair of magnet insertion holes
210 constitute one magnetic pole (i.e., a north pole or a south
pole) of the rotor 2. The number of magnetic poles of the
rotor 2 only needs to two or more. In this embodiment, the
rotor 2 has six magnetic poles.
20 [0035]
Each of the magnetic poles (“each magnetic pole” or
“magnetic pole”) refers to a region serving as a north pole or
a south pole of the rotor 2.
[0036]
25 In general, while a rotor rotates, a centrifugal force is
exerted on a rotor core. Thus, if the rotor core does not
include a center lib, large stress is applied to thin portions
between the outer peripheral surface of the rotor core and
magnet insertion holes (specifically, flux barrier parts). If
30 this stress is large, the rotor core (especially, the thin
portions) is easily deformed. On the other hand, in this
embodiment, since the rotor core 21 includes the center ribs
213, part of the stress generated in the rotor 2 is dispersed
to the center ribs 213, and thus stress applied to the thin

13
portions 214 is alleviated. Accordingly, deformation of the
rotor core 21, especially the thin portions 214, can be
prevented. As a result, the electric motor 1 can rotate at
high speed and consequently power of the electric motor 1 can
5 be enhanced.
[0037]
FIGS. 4 and 5 are enlarged views each illustrating a
peripheral structure of the center lib 213.
As illustrated in FIG. 4, the first magnet insertion hole
10 211 includes the magnet disposition part 211a, the flux barrier
part 211b (FIG. 3), the outside opening part 211c, and the
inside opening part 211d. The second magnet insertion hole 212,
includes the magnet disposition part 212a, the flux barrier
part 212b (FIG. 3), the outside opening part 212c, and the
15 inside opening part 2121d.
[0038]
The outside opening part 211c is located on an outer side
of the magnet disposition part 211a in the radial direction of
the rotor core 21, and adjacent to the center lib 213. The
20 outside opening part 211c has a radius of curvature of R1 in
the xy plane. Thus, the outside opening part 211c projects
from the magnet disposition part 211a outward in the radial
direction.
[0039]
25 The inside opening part 211d is located on an inner side
of the magnet disposition part 211a in the radial direction of
the rotor core 21, and adjacent to the center lib 213. The
inside opening part 211d has a radius of curvature of R2 in the
xy plane. Thus, the inside opening part 211d projects from the
30 magnet disposition part 211a inward in the radial direction.
[0040]
Since the rotor core 21 includes the outside opening part
211c and the inside opening part 211d, demagnetization of the
permanent magnets 22 (especially, the permanent magnets 22 in

14
the first magnet insertion holes 211) generated by a magnetic
field from the stator winding of the stator 3 can be reduced.
As a result, power of the electric motor 1 can be enhanced.
[0041]
5 The outside opening part 212c is located on an outer side
of the magnet disposition part 212a in the radial direction of
the rotor core 21, and adjacent to the center lib 213. The
outside opening part 212c has a radius of curvature of R1 in
the xy plane. Thus, the outside opening part 212c projects
10 from the magnet disposition part 212a outward in the radial
direction.
[0042]
The inside opening part 212d is located on an inner side
of the magnet disposition part 212a in the radial direction of
15 the rotor core 21, and adjacent to the center lib 213. The
inside opening part 212d has a radius of curvature of R2 in the
xy plane. Thus, the inside opening part 212d projects from the
magnet disposition part 212a inward in the radial direction.
[0043]
20 Since the rotor core 21 includes the outside opening part
212c and the inside opening part 212d, demagnetization of the
permanent magnets 22 (especially, the permanent magnets 22 in
the second magnet insertion holes 212) generated by a magnetic
field from the stator winding of the stator 3 can be reduced.
25 As a result, power of the electric motor 1 can be enhanced.
[0044]
In this embodiment, the radius of curvature of R1 is 0.5
mm, the radius of curvature of R2 is 0.3 mm, and the length of
W1 of each permanent magnet 22 is 21.5 mm. It should be noted
30 that the radius of curvature of R1, the radius of curvature of
R2, and the length of W1 of each permanent magnet 22 are not
limited to these examples. The shape of the first magnet
insertion hole 211 may be different from the shape of the
second magnet insertion hole 212.

15
[0045]
As illustrated in FIG. 4, the rotor core 21 includes, at
each magnetic pole, an outside curved part 216a (also referred
to as a first outside curved part), an outside curved part 216b
5 (also referred to as a second outside curved part), an inside
curved part 217a (also referred to as a first inside curved
part), an inside curved part 217b (also referred to as a second
inside curved part), an outside support part 218a (also
referred to as a first outside support part), an outside
10 support part 218b (also referred to as a second outside support
part), an inside support part 219a (also referred to as a first
inside support part), an inside support part 219b (also
referred to as a second inside support part), an outside
connection part 220a (also referred to as a first outside
15 connection part), an outside connection part 220b (also
referred to as a second outside connection part), an inside
connection part 221a (also referred to as a first inside
connection part), and an inside connection part 221b (also
referred to as a second inside connection part).
20 [0046]
The outside curved part 216a defines the outside opening
part 211c. The outside curved part 216a has a curvature of
1/R1 in the xy plane. Accordingly, the outside opening part
211c has a radius of curvature of R1 in the xy plane.
25 [0047]
The outside curved part 216b defines the outside opening
part 212c. The outside curved part 216b has a curvature of
1/R1 in the xy plane. Accordingly, the outside opening part
212c has a radius of curvature of R1 in the xy plane.
30 [0048]
The inside curved part 217a defines the inside opening
part 211d. The inside curved part 217a has a curvature of 1/R2
in the xy plane. Accordingly, the inside opening part 211d has
a radius of curvature of R2 in the xy plane.

16
[0049]
The inside curved part 217b defines the inside opening
part 212d. The inside curved part 217b has a curvature of 1/R2
in the xy plane. Accordingly, the inside opening part 212d has
5 a radius of curvature of R2 in the xy plane.
[0050]
The outside support part 218a supports the permanent
magnet 22 in the first magnet insertion hole 211. The outside
support part 218a defines the magnet disposition part 211a.
10 [0051]
The outside support part 218b supports the permanent
magnet 22 in the second magnet insertion hole 212. The outside
support part 218b defines the magnet disposition part 212a.
[0052]
15 The inside support part 219a supports the permanent
magnet 22 in the first magnet insertion hole 211. The inside
support part 219a defines the magnet disposition part 211a.
[0053]
The inside support part 219b supports the permanent
20 magnet 22 in the second magnet insertion hole 212. The inside
support part 219b defines the magnet disposition part 212a.
[0054]
The outside connection part 220a is located between the
outside curved part 216a and the outside support part 218a, and
25 connects the outside curved part 216a and the outside support
part 218a. The outside connection part 220a has a radius of
curvature of R3 in the xy plane. In other words, the outside
connection part 220a has a curvature of 1/R3 in the xy plane.
[0055]
30 The outside connection part 220b is located between the
outside curved part 216b and the outside support part 218b, and
connects the outside curved part 216b and the outside support
part 218b. The outside connection part 220b has a radius of
curvature of R3 in the xy plane. In other words, the outside

17
connection part 220b has a curvature of 1/R3 in the xy plane.
[0056]
The inside connection part 221a is located between the
inside curved part 217a and the inside support part 219a, and
5 connects the inside curved part 217a and the inside support
part 219a. The inside connection part 221a has a radius of
curvature of R4 in the xy plane. In other words, the inside
connection part 221a has a curvature of 1/R4 in the xy plane.
[0057]
10 The inside connection part 221b is located between the
inside curved part 217b and the inside support part 219b, and
connects the inside curved part 217b and the inside support
part 219b. The inside connection part 221b has a radius of
curvature of R4 in the xy plane. In other words, the inside
15 connection part 221b has a curvature of 1/R4 in the xy plane.
[0058]
The relationship between the radii of curvature of R1 and
R2 satisfies R1 > R2. Accordingly, stress concentrated on the
center libs 213 is dispersed, and thus, mechanical strength of
20 the rotor core 21 to a centrifugal force generated in the rotor
2 can be increased, and deformation of the rotor core 21,
especially the thin portions 214, and be prevented.
Consequently, the electric motor 1 can rotate at high speed,
and thus power of the electric motor 1 can be enhanced. In
25 addition, a magnetic resistance becomes large in the outside
opening part 211c and the outside opening part 212c, and thus,
demagnetization in each permanent magnet 22 can be reduced. On
the other hand, magnetic resistance in the inside opening part
211d and the inside opening part 212d is smaller than that in
30 the outside opening part 211c and the outside opening part 212c,
and thus a magnetic force of each permanent magnet 22 can be
effectively used. That is, if the rotor 2 satisfies R1 > R2,
demagnetization of the permanent magnets 22 can be reduced, and
power of the electric motor 1 can be enhanced.

18
[0059]
The relationship between the radii of curvature of R3 and
R4 satisfies R3 > R4. Accordingly, it is possible to achieve
both reduction of demagnetization of the permanent magnets 22
5 and increase in power of the electric motor 1. Specifically,
as the radius of curvature of R3 increases, the lengths of the
outside support part 218a and the outside support part 218b
decrease. Accordingly, the outside opening part 211c and the
outside opening part 212c become larger, and magnetic
10 resistance increases. As a result, demagnetization in each
permanent magnet 22 can be reduced. On the other hand, as the
radius of curvature of R4 decreases, the lengths of the inside
support part 219a and the inside support part 219b increase.
Accordingly, the inside opening part 211d and the inside
15 opening part 212d become smaller, and thus a magnetic force of
each permanent magnet 22 can be effectively used. As a result,
it is possible to achieve both reduction of demagnetization of
the permanent magnets 22 and increase in power of the electric
motor 1.
20 [0060]
FIG. 6 is a graph showing a relationship between a
centrifugal force [p.u.] generated during rotation of the rotor
2 and a ratio between radii of curvature (specifically, a ratio
of radius of curvature of R1 + R2 to the length of W1 of each
25 permanent magnet).
As shown in FIG. 6, the rotor 2 preferably satisfies 0 <
(R1 + R2)/W1 < 0.082. Accordingly, a centrifugal force
generated during rotation of the rotor 2 can be reduced, and
deformation of the rotor core 21, especially the thin portions
30 214, can be prevented. The rotor 2 more preferably satisfies
0.02 < (R1 + R2)/W1 < 0.082. Accordingly, a centrifugal force
generated during rotation of the rotor 2 can be effectively
reduced, and deformation of the rotor core 21, especially the
thin portions 214, can be effectively prevented.

19
[0061]
FIG. 7 is a graph showing a relationship between a
demagnetization resistance [p.u.] and a ratio between radii of
curvature (specifically, a ratio of radii of curvature of R1 +
5 R2 to the length of W1 of each permanent magnet). In this
embodiment, the demagnetization resistance refers to the
magnitude of a current flowing in the stator winding of the
stator 3 when the amount of magnetic flux from the permanent
magnets 22 decreases by 1%. That is, in FIG. 7, as the
10 demagnetization resistance increases, the value of current
flowing in the stator winding of the stator 3 can be increased.
Accordingly, as the demagnetization resistance increases, power
of the electric motor 1 can be enhanced.
[0062]
15 As shown in FIG. 7, the rotor 2 preferably satisfies 0 <
(R1 + R2)/W1 < 0.082. As a result, demagnetization resistance
increases, and power of the electric motor 1 can be enhanced.
[0063]
As the proportion of the radii of curvature of R1 and R2
20 to the length of W1 of each permanent magnet 22 increases, the
area of the permanent magnet 22 facing the outside opening part
211c and the area of the permanent magnet 22 facing the outside
opening part 212c increase. Accordingly, an effective amount
of magnetic flux from each permanent magnet 22 decreases, and
25 power of the electric motor 1 decreases. On the other hand, as
the proportion of the radii of curvature of R1 and R2 to the
length of W1 of each permanent magnet 22 decreases, the
permanent magnets 22 are more easily demagnetized. Accordingly,
the rotor 2 more preferably satisfies 0.02 < (R1 + R2)/W1 <
30 0.06. As a result, demagnetization resistance further
increases, and power of the electric motor 1 can be enhanced.
[0064]
In addition, if the rotor 2 satisfies R1 > R2 and 0 < (R1
+ R2)/W1 < 0.082, demagnetization of the permanent magnets 22

20
can be further reduced, and power of the electric motor 1 can
be further enhanced.
[0065]
If the rotor 2 satisfies R1 > R2 and 0.02 < (R1 + R2)/W1
5 < 0.082, demagnetization of the permanent magnets 22 can be
further reduced, and power of the electric motor 1 can be
further enhanced.
[0066]
If the rotor 2 satisfies R1 > R2 and 0.02 < (R1 + R2)/W1
10 < 0.06, demagnetization of the permanent magnets 22 can be
further reduced, and power of the electric motor 1 can be
further enhanced.
[0067]
FIG. 8 is a graph showing a relationship between a
15 demagnetization resistance [p.u.] and a ratio R3/R4 of a radius
of curvature.
As shown in FIG. 8, the rotor 2 preferably satisfies 0 <
R3/R4 < 4.45. As a result, demagnetization resistance
increases, and power of the electric motor 1 can be enhanced.
20 The rotor 2 more preferably satisfies 0 < R3/R4 < 4. As a
result, demagnetization resistance further increases, and power
of the electric motor 1 can be enhanced.
[0068]
The radii of curvature of R3 and R4 may be the same. In
25 this case, the radii of curvature of R3 and R4 are, for example,
0.9 mm, and the rotor 2 satisfies R3/R4 = 1. As a result,
demagnetization resistance can be enhanced, as compared to a
conventional rotor (i.e., R3 = R4 = 0).
[0069]
30 FIG. 9 is an enlarged view illustrating a peripheral
structure of the outside opening part 211c.
As illustrated in FIG. 9, the radius of curvature of R3
may be larger than the radius of curvature of R1. As the
radius of curvature of R3 increases, the outside support part

21
218a and the outside support part 218b become shorter.
Accordingly, the outside opening part 211c and the outside
opening part 212c become larger, and magnetic resistance
increases. As a result, demagnetization in each permanent
5 magnet 22 decreases, and power of the electric motor 1 can be
further enhanced.
[0070]
FIG. 10 is a graph showing a relationship between a
centrifugal force [p.u.] and a ratio of R1/R3 of a radius of
10 curvature.
As shown in FIG. 10, the rotor 2 preferably satisfies 0 <
R1/R3 < 3. Accordingly, a centrifugal force generated during
rotation of the rotor 2 can be reduced, and deformation of the
rotor core 21, especially the thin portions 214, can be
15 prevented.
[0071]
FIG. 11 is a graph showing a relationship between a
demagnetization resistance [p.u.] and a ratio of R1/R3 of a
radius of curvature.
20 As shown in FIG. 11, the rotor 2 preferably satisfies 0 <
R1/R3 < 3. As a result, demagnetization resistance increases,
and power of the electric motor 1 can be enhanced.
[0072]
The rotor 2 more preferably satisfies 0.5 < R1/R3 < 3.
25 Accordingly, a centrifugal force generated during rotation of
the rotor 2 can be further reduced, and deformation of the
rotor core 21, especially the thin portions 214, can be further
prevented.
[0073]
30 In the examples shown in FIGS. 10 and 11, the radius of
curvature of R1 is, for example, 0.5 mm, and the radius of
curvature of R3 is, for example, 0.6 mm, and the rotor 2
satisfies 0 < R1/R3 < 3. As a result, demagnetization
resistance can be enhanced, as compared to a conventional rotor

22
(i.e., R1 = R3 = 0).
[0074]
SECOND EMBODIMENT
A compressor 300 according to a second embodiment of the
5 present invention will be described.
FIG. 12 is a cross-sectional view schematically
illustrating a structure of the compressor 300.
[0075]
The compressor 300 includes an electric motor 1 serving
10 as an electric element, a closed container 307 serving as a
housing, and a compression mechanism 305 serving as a
compression element (also referred to as a compression device).
In this embodiment, the compressor 300 is a scroll compressor.
It should be noted that the compressor 300 is not limited to a
15 scroll compressor. The compressor 300 may be a compressor
other than the scroll compressor, for example, may be a rotary
compressor.
[0076]
The electric motor 1 in the compressor 300 is the
20 electric motor 1 described in the first embodiment. The
electric motor 1 drives the compression mechanism 305.
[0077]
The compressor 300 also includes a subframe 308
supporting a lower end (i.e., an end opposite to the
25 compression mechanism 305) of the shaft 24.
[0078]
The compression mechanism 305 is disposed inside the
closed container 307. The compressor mechanism 305 includes a
fixed scroll 301 having a spiral portion, a swing scroll 302
30 having a spiral portion forming a compression chamber between
the spiral portion of the swing scroll 302 and the spiral
portion of the fixed scroll 301, a compliance frame 303 holding
the upper end of the shaft 24, and a guide frame 304 fixed to
the closed container 307 and holding the compliance frame 303.

23
[0079]
A suction pipe 310 penetrating the closed container 307
is press fitted in the fixed scroll 301. The closed container
307 is provided with a discharge pipe 306 that discharges a
5 high-pressure refrigerant gas discharged from the fixed scroll
301, to the outside. The discharge pipe 306 communicates with
an opening disposed between the compressor mechanism 305 of the
closed container 307 and the electric motor 1.
[0080]
10 The electric motor 1 is fixed to the closed container 307
by fitting the stator 3 in the closed container 307. A
configuration of the electric motor 1 has been described above.
To the closed container 307, a glass terminal 309 for supplying
electric power to the electric motor 1 is fixed by welding.
15 [0081]
When a current flows in a stator winding 32 of the
electric motor 1, the electric motor 1 is driven. When the
electric motor 2 rotates, this rotation is transferred to the
swing scroll 302, and the swing scroll 302 swings. When the
20 swing scroll 302 swings, the volume of the compression chamber
formed by the spiral portion of the swing scroll 302 and the
spiral portion of the fixed scroll 301 changes. Then, a
refrigerant gas is sucked from the suction pipe 310, compressed,
and then discharged from the discharge pipe 306.
25 [0082]
The compressor 300 includes the electric motor 1
described in the first embodiment, and thus, obtains advantages
described in the first embodiment.
[0083]
30 In addition, since the compressor 300 includes the
electric motor 1 described in the first embodiment, the
efficient compressor 300 can be provided.
[0084]
THIRD EMBODIMENT

24
A refrigerating and air conditioning apparatus 7 serving
as an air conditioner and including a compressor 300 according
to a third embodiment will be described.
FIG. 13 is a diagram schematically illustrating a
5 configuration of the refrigerating air conditioning device 7
according to the third embodiment.
[0085]
The refrigerating and air conditioning apparatus 7 is
capable of performing cooling and heating operations, for
10 example. A refrigerant circuit diagram illustrated in FIG. 31
is an example of a refrigerant circuit diagram of an air
conditioner capable of performing a cooling operation.
[0086]
The refrigerating and air conditioning apparatus 7
15 according to the third embodiment includes an outdoor unit 71,
an indoor unit 72, and a refrigerant pipe 73 connecting the
outdoor unit 71 and the indoor unit 72.
[0087]
The outdoor unit 71 includes a compressor 300, a
20 condenser 74 as a heat exchanger, a throttling device 75, and
an outdoor air blower 76 (first air blower). The condenser 74
condenses a refrigerant compressed by the compressor 300. The
throttling device 75 decompresses the refrigerant condensed by
the condenser 74 to thereby adjust a flow rate of the
25 refrigerant. The throttling device 75 will be also referred to
as a decompression device.
[0088]
The indoor unit 72 includes an evaporator 77 as a heat
exchanger, and an indoor air blower 78 (second air blower).
30 The evaporator 77 evaporates the refrigerant decompressed by
the throttling device 75 to thereby cool indoor air.
[0089]
A basic operation of a cooling operation in the
refrigerating and air conditioning apparatus 7 will now be

25
described. In the cooling operation, a refrigerant is
compressed by the compressor 300 and the compressed refrigerant
flows into the condenser 74. The condenser 74 condenses the
refrigerant, and the condensed refrigerant flows into the
5 throttling device 75. The throttling device 75 decompresses
the refrigerant, and the decompressed refrigerant flows into
the evaporator 77. In the evaporator 77, the refrigerant
evaporates, and the refrigerant (specifically a refrigerant
gas) flows into the compressor 300 of the outdoor unit 71 again.
10 When the air is sent to the condenser 74 by the outdoor air
blower 76, heat moves between the refrigerant and the air, and
similarly, when the air is sent to the evaporator 77 by the
indoor air blower 78, heat is moved between the refrigerant and
the air.
15 [0090]
The configuration and operation of the refrigerating and
air conditioning apparatus 7 described above are examples, and
the present invention is not limited to the examples described
above.
20 [0091]
The refrigerating and air conditioning apparatus 7
according to the third embodiment has the advantages described
in the first and second embodiments.
[0092]
25 In addition, since the refrigerating and air conditioning
apparatus 7 according to the third embodiment includes the
compressor 300 according to the second embodiment. Thus, the
refrigerating and air conditioning apparatus 7 has high
efficiency.
30 [0093]
Features of the embodiments and features of the
variations described above can be combined as appropriate.
DESCRIPTION OF REFERENCE CHARACTERS

26
[0094]
1 electric motor, 2 rotor, 3 stator, 7 refrigerating and air
conditioning apparatus, 21 rotor core, 22 permanent magnet, 71
outdoor unit, 72 indoor unit, 211 first magnet insertion hole,
5 211a magnet disposition part (first magnet disposition part),
211b flux barrier part (first flux barrier part), 211c outside
opening part (first outside opening part), 211d inside opening
part (first inside opening part), 212 second magnet insertion
hole, 212a magnet disposition part (second magnet disposition
10 part), 212b flux barrier part (second flux barrier part), 212c
outside opening part (second outside opening part), 212d inside
opening part (second inside opening part), 213 center lib, 300
compressor, 305 compression mechanism, 307 closed container, 74
condenser, 77 evaporator.
15

27
We Claim:
1. A rotor comprising:
5 a rotor core including a first magnet insertion hole, a
second magnet insertion hole, and a center lib between the
first magnet insertion hole and the second magnet insertion
hole;
a first permanent magnet disposed in the first magnet
10 insertion hole, the first permanent magnet being W1 mm long in
a longitudinal direction in a plane perpendicular to an axial
direction; and
a second permanent magnet disposed in the second magnet
insertion hole, the second permanent magnet being W1 mm long in
15 a longitudinal direction in the plane, wherein
the first magnet insertion hole includes
a first magnet disposition part in which the first
permanent magnet is disposed,
a first flux barrier part communicating with the first
20 magnet disposition part,
a first outside opening part located on an outer side
with respect to the first magnet disposition part in a radial
direction of the rotor core, the first outside opening part
having a radius of curvature of R1 mm in the plane, and
25 a first inside opening part located on an inner side with
respect to the first magnet disposition part in the radial
direction, the first inside opening part having a radius of
curvature of R2 mm in the plane, and
the second magnet insertion hole includes
30 a second magnet disposition part in which the second
permanent magnet is disposed,
a second flux barrier part communicating with the second
magnet disposition part,
a second outside opening part located on an outer side

28
with respect to the second magnet disposition part in the
radial direction, the second outside opening part having a
radius of curvature of R1 mm in the plane, and
a second inside opening part located on an inner side
5 with respect to the second magnet disposition part in the
radial direction, the second inside opening part having a
radius of curvature of R2 mm in the plane, and
the rotor satisfies R1 > R2 and 0 < (R1 + R2)/W1 < 0.082.
10 2. The rotor according to claim 1, wherein
the rotor core includes
a first outside curved part defining the first outside
opening part,
a first outside support part supporting the first
15 permanent magnet,
a first outside connection part connecting the first
outside curved part and the first outside support part, the
first outside connection part having a radius of curvature of
R3 in the plane,
20 a first inside curved part defining the first inside
opening part,
a first inside support part supporting the first
permanent magnet,
a first inside connection part connecting the first
25 inside curved part and the first inside support part, the first
inside connection part having a radius of curvature of R4 in
the plane,
a second outside curved part defining the second outside
opening part,
30 a second outside support part supporting the second
permanent magnet,
a second outside connection part connecting the second
outside curved part and the second outside support part, the
second outside connection part having a radius of curvature of

29
R3 in the plane,
a second inside curved part defining the second inside
opening part,
a second inside support part supporting the second
5 permanent magnet, and
a second inside connection part connecting the second
inside curved part and the second inside support part, the
second inside connection part having a radius of curvature of
R4 in the plane, and
10 the rotor satisfies 0 < R3/R4 < 4.45.
3. The rotor according to claim 2, wherein the rotor
satisfies 0 < R3/R4 < 4.
15 4. The rotor according to any one of claims 1 to 3, wherein
the rotor satisfies 0 < R1/R3 < 3.
5. The rotor according to any one of claims 1 to 4, wherein
the rotor satisfies R1 > R2 and 0.02 < (R1 + R2)/W1 < 0.082.
20
6. The rotor according to any one of claims 1 to 4, wherein
the rotor satisfies R1 > R2 and 0.02 < (R1 + R2)/W1 < 0.06.
7. An electric motor comprising:
25 a stator; and
the rotor according to any one of claims 1 to 6, the
rotor being disposed inside the stator.
8. A compressor comprising:
30 a closed container;
a compression device disposed inside the closed
container; and
the electric motor according to claim 7, to drive the
compression device.

9. An air conditioner comprising:
the compressor according to claim 8; and
a heat exchanger.