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 100-8310, JAPAN
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE
INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.

2
DESCRIPTION
5 TECHNICAL FIELD
[0001]
The present invention relates to a rotor for use in an
electric motor.
10 BACKGROUND ART
[0002]
In general, a rotor having a plurality of slots provided
between a permanent magnet insertion hole of a rotor core and
the outer peripheral surface of the rotor core has been
15 proposed as a rotor for use in an electric motor. In this
rotor, a harmonic component of a magnetic flux density waveform
in an inter-pole part of the rotor is reduced, and thus cogging
torque is reduced (see, for example, Patent Reference 1).
20 PRIOR ART REFERENCE
PATENT REFERENCE
[0003]
Patent Reference 1: Japanese Patent Application
Publication No. 2011-101595
25
SUMMARY OF THE INVENTION
PROBLEM TO BE SOLVED BY THE INVENTION
[0004]
In a conventional technique, however, a plurality of
30 slits provided between a permanent magnet insertion hole and
the outer peripheral surface of a rotor core increase a
magnetic resistance and reduce an inductance. Consequently, a
harmonic component of an induced voltage in a stator winding
increases, and thus vibrations and noise in an electric motor
3
increase.
[0005]
An object of the present invention is to reduce
vibrations and noise in an electric motor.
5
MEANS OF SOLVING THE PROBLEM
[0006]
A rotor according to an aspect of the present invention
is a rotor including a magnetic pole center part and includes:
10 a rotor core including a permanent magnet insertion hole; and a
permanent magnet disposed in the permanent magnet insertion
hole, wherein the rotor core includes an outside slit provided
between the permanent magnet insertion hole and an outer
peripheral surface of the rotor core and extending in a
15 circumferential direction of the rotor core, and a plurality of
inside slits provided between the magnetic pole center part and
the outside slit and arranged in the circumferential direction,
the plurality of inside slits include a first inside slit
adjacent to the magnetic pole center part, and a minimum
20 distance from the first inside slit to the outer peripheral
surface of the rotor core is longer than a minimum distance
from any other inside slit except the first inside slit of the
plurality of inside slits to the outer peripheral surface of
the rotor core.
25 An electric motor according to another aspect of the
present invention includes: a stator; and the rotor disposed
inside the stator.
A compressor according to still another aspect of the
present invention includes: a closed container; a compression
30 device disposed inside the closed container; and the electric
motor to drive the compression device.
An air conditioner according to yet another aspect of the
present invention includes: the compressor; and a heat
exchanger.
4
EFFECTS OF THE INVENTION
[0007]
According to the present invention, vibrations and noise
5 in the electric motor can be reduced.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008]
FIG. 1 is a cross-sectional view schematically
10 illustrating a structure of an electric motor according to a
first embodiment of the present invention.
FIG. 2 is a cross-sectional view schematically
illustrating a structure of a rotor.
FIG. 3 is an enlarged view schematically illustrating a
15 structure of a part of the rotor illustrated in FIG. 2.
FIG. 4 is a diagram showing a relationship between a
ratio Lo1/Lo_min and a q-axis inductance.
FIG. 5 is a diagram showing a relationship between the
ratio Lo1/Lo_min and a d-axis inductance.
20 FIG. 6 is an enlarged view schematically illustrating a
structure of a part of the rotor illustrated in FIG. 2.
FIG. 7 is a diagram showing a relationship between a
ratio Li1/Li_min and a q-axis inductance.
FIG. 8 is a diagram showing a relationship between the
25 the ratio Li1/Li_min and a d-axis inductance.
FIG. 9 is an enlarged view schematically illustrating a
structure of a part of the rotor illustrated in FIG. 2.
FIG. 10 is a diagram showing a relationship between a
ratio Ws1/Ws2_total and a q-axis inductance.
30 FIG. 11 is a diagram illustrating a relationship between
a ratio Ws1/Ws2_total and a d-axis inductance.
FIG. 12 is a diagram illustrating a relationship between
a ratio Ws1_total/Wr and a q-axis inductance.
FIG. 13 is a diagram illustrating a relationship between
5
a ratio Ws1_total/Wr and a d-axis inductance.
FIG. 14 is a diagram showing a waveform of a carrier wave
in an electric motor.
FIG. 15 is a cross-sectional view schematically
5 illustrating a structure of a compressor according to a second
embodiment of the present invention.
FIG. 16 is a diagram schematically illustrating a
configuration of a refrigerating and air conditioning apparatus
according to a third embodiment of the present invention.
10
MODE FOR CARRYING OUT THE INVENTION
[0009]
FIRST EMBODIMENT
In xyz orthogonal coordinate systems illustrated in the
15 drawings, a z-axis direction (z axis) represents a direction
parallel to an axis line Ax of an electric motor 1, an x-axis
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
20 and the x-axis direction. An axis line Ax is a rotation center
of a rotor 2. A direction parallel to the axis line Ax will be
referred to as an “axial direction of the rotor 2” or simply as
an “axial direction.” A radial direction refers to a direction
of a radius of the rotor 2 or a stator 3, and a direction
25 orthogonal to the axis line Ax. An xy plane is a plane
orthogonal to the axial direction. An arrow D1 represents a
circumferential direction about the axis line Ax. The
circumferential direction of the rotor 2 or the stator 3 will
be referred to simply as a “circumferential direction.”
30 [0010]
FIG. 1 is a cross-sectional 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
6
3. The electric motor 1 is, for example, a permanent magnet
synchronous motor (also referred to as a brushless DC motor)
such as an interior permanent magnet electric motor. The
electric motor 1 may also include a motor frame 4 (which will
5 be referred to simply as a “frame”) covering the stator 3.
[0011]
The rotor 2 is rotatably disposed inside the stator 3.
An air gap is present between the rotor 2 and the stator 3.
The rotor 2 rotates about the axis line Ax.
10 [0012]
The stator 3 includes a stator core 31 and at least one
winding 32.
[0013]
The stator core 31 is made of, for example, a plurality
15 of electromagnetic steel sheets. In this case, the plurality
of electromagnetic steel sheets are stacked in the axial
direction. The plurality of electromagnetic steel sheets are
fixed by swaging. Each electromagnetic steel sheet is
processed to have a predetermined shape by press work such as
20 punching.
[0014]
The stator core 31 includes a ring-shaped yoke 311 and a
plurality of teeth 312. The yoke 311 extends in the
circumferential direction. Each of the teeth 312 extends in
25 the radial direction. Specifically, each of the teeth 312
projects from the yoke 311 toward the axis line Ax. The
plurality of teeth 312 are arranged at regular intervals in the
circumferential direction and extend radially.
[0015]
30 The winding 32 is wound around the stator core 31,
specifically, around each of the teeth 312. An insulator may
be disposed between the stator core 31 and the winding 32.
[0016]
FIG. 2 is a cross-sectional view schematically
7
illustrating a structure of the rotor 2.
The rotor 2 includes a plurality of magnetic pole center
parts C1 and a plurality of inter-pole parts C2. In the
example illustrated in FIG. 2, the magnetic pole center parts
5 C1 and the inter-pole parts C2 are indicated by broken lines.
[0017]
Each of the magnetic pole center parts C1 is located at a
center of each magnetic pole of the rotor 2 (i.e., a north pole
or a south pole of the rotor 2). Each magnetic pole (which
10 will also be referred to simply as “each magnetic pole” or
“magnetic pole”) of the rotor 2 means a region of the rotor 2
serving as a north pole or a south pole.
[0018]
Each of the inter-pole parts C2 is a boundary between two
15 magnetic poles adjacent to each other in the circumferential
direction (i.e., a north pole and a south pole of the rotor 2).
[0019]
The rotor 2 includes a rotor core 21, at least one
permanent magnet 22 provided in the rotor core 21, and a shaft
20 24 fixed to the rotor core 21.
[0020]
The rotor core 21 includes at least one permanent magnet
insertion hole 211 and a shaft hole 212.
[0021]
25 The rotor core 21 is made of, for example, a plurality of
electromagnetic steel sheets. In this case, the plurality of
electromagnetic steel sheets are stacked in the axial direction.
The plurality of electromagnetic steel sheets are fixed by
swaging. Each electromagnetic steel sheet is processed to have
30 a predetermined shape by press work such as punching.
[0022]
In this embodiment, the rotor core 21 has a plurality of
permanent magnet insertion holes 211 (specifically six
permanent magnet insertion holes 211). In the xy plane, the
8
plurality of permanent magnet insertion holes 211 are arranged
in the circumferential direction. The number of magnetic poles
of the rotor 2 is two or more. Each permanent magnet insertion
hole 211 corresponds to a magnetic pole of the rotor 2. Thus,
5 in this embodiment, the number of magnetic poles of the rotor 2
is six. At least one permanent magnet 22 is disposed in each
permanent magnet insertion hole 211.
[0023]
In the xy plane, a center portion of each permanent
10 magnet insertion hole 211 projects toward the axis line Ax.
That is, in the xy plane, each permanent magnet insertion hole
211 has a V shape. The shape of each permanent magnet
insertion hole 211 is not limited to the V shape, and may be a
straight shape, for example.
15 [0024]
In this embodiment, two permanent magnets 22 are disposed
in one permanent magnet insertion hole 211. That is, two
permanent magnets 22 are disposed for one magnetic pole. Thus,
in the xy plane, one pair of permanent magnets 22 is disposed
20 in one permanent magnet insertion hole 211 to have a V shape.
In this embodiment, the rotor 2 includes 12 permanent magnets
22.
[0025]
The shaft 24 is fixed to the shaft hole 212 by, for
25 example, shrink fitting or press fitting.
[0026]
Each of the permanent magnets 22 is a flat magnet
elongated in the axial direction. Each permanent magnet 22 is
a rare earth magnet containing, for example, neodymium (Nd),
30 iron (Fe), and boron (B). Two permanent magnets 22 disposed in
one permanent magnet insertion hole 211 serve as one magnetic
pole of the rotor 2.
[0027]
The rotor core 21 further includes a plurality of outside
9
slits 213 and a plurality of inside slits 214.
[0028]
Each of the outside slits 213 is disposed between the
permanent magnet insertion hole 211 and an outer peripheral
5 surface 21a of the rotor core 21. Each of the outside slits
213 extends in the circumferential direction of the rotor core
21. As illustrated in FIG. 3, two outside slits 213 for one
magnetic pole are disposed between the permanent magnet
insertion hole 211 and the outer peripheral surface 21a of the
10 rotor core 21. In this embodiment, however, the rotor core 21
includes 12 outside slits 213.
[0029]
In each magnetic pole, one of the two outside slits 213
is located at one end of the permanent magnet insertion hole
15 211 and the other outside slit 213 is located at the other end
of the permanent magnet insertion hole 211. In other words, at
each magnetic pole, one of the two outside slits 213 is opposed
to one end of the permanent magnet insertion hole 211, and the
other outside slit 213 is opposed to the other end of the
20 permanent magnet insertion hole 211. Accordingly, each of the
outside slits 213 reduces leakage of magnetic flux in the rotor
2. That is, each outside slit 213 serves as a flux barrier.
[0030]
Each inside slit 214 is provided between the permanent
25 magnet insertion hole 211 and the outer peripheral surface 21a
of the rotor core 21. Specifically, in each magnetic pole, the
plurality of inside slits 214 are provided between two outside
slits 213. The plurality of inside slits 214 are arranged in
the circumferential direction of the rotor core 21. More
30 specifically, the plurality of inside slits 214 are arranged in
a direction orthogonal to imaginary lines passing through the
magnetic pole center parts C1 in the xy plane. In the example
illustrated in FIGS. 2 and 3, each of the imaginary lines
passing through the magnetic pole center parts C1 passes
10
through two permanent magnets 22. The imaginary lines passing
through the magnetic pole center parts C1 are represented as
broken lines in FIGS. 2 and 3. In each magnetic pole, the
inside slits 214 extend in parallel with the imaginary line
5 passing through the magnetic pole center part C1.
[0031]
The plurality of inside slits 214 include at least one
first inside slit 214a, at least one second inside slit 214b,
and at least one third inside slit 214c.
10 [0032]
Each first inside slit 214a is adjacent to the magnetic
pole center part C1. That is, each first inside slit 214a is
closest to the magnetic pole center part C1 in the inside slits
214.
15 [0033]
Each second inside slit 214b is adjacent to the first
inside slit 214a, and is located between the first inside slit
214a and the third inside slit 214c.
[0034]
20 Each third inside slit 214c is adjacent to the second
inside slit 214b.
[0035]
In the xy plane, the first inside slit 214a, the second
inside slit 214b, and the third inside slit 214c are arranged
25 in this order in a direction away from the magnetic pole center
part C1. That is, one set of inside slits 214 (specifically,
one first inside slit 214a, one second inside slit 214b, and
one third inside slit 214c) is provided between the magnetic
pole center part C1 and one outside slit 213 (e.g., the right
30 outside slit 213 in FIG. 3). Similarly, another set of inside
slits 214 (specifically, another first inside slit 214a,
another second inside slit 214b, and another third inside slit
214c) is provided between the magnetic pole center part C1 and
another outside slit 213 (e.g., the left outside slit 213 in
11
FIG. 3).
[0036]
That is, in each magnetic pole of the rotor 2, the rotor
core 21 includes one set of inside slits 214 between the
5 magnetic pole center part C1 and one outside slit 213, and also
includes another set of inside slits 214 between the magnetic
pole center part C1 and yet another outside slit 213.
[0037]
In this embodiment, in each magnetic pole of the rotor 2,
10 the plurality of inside slits 214 (e.g., the right set of
inside slits 214 and the left set of inside slits 214 in FIG.
3) are symmetric with respect to the magnetic pole center part
C1. In other words, in each magnetic pole of the rotor 2, the
plurality of inside slits 214 are symmetrically disposed with
15 respect to the magnetic pole center part C1.
[0038]
In each magnetic pole of the rotor 2, two first inside
slits 214a, two second inside slits 214b, and two third inside
slits 214c are provided between two outside slits 213. That is,
20 in this embodiment, in each magnetic pole, six inside slits 214
are provided between two outside slits 213. However, the
number of inside slits 214 in each magnetic pole is not limited
to six.
[0039]
25 Since the plurality of inside slits 214 are provided
between the permanent magnet insertion hole 211 and the outer
peripheral surface 21a of the rotor core 21, a harmonic
component of a magnetic flux density waveform from the rotor 2
can be reduced. Accordingly, a harmonic component of an
30 induced voltage in the winding 32 and cogging torque can be
reduced.
[0040]
In general, however, a hole between a permanent magnet
insertion hole and the outer peripheral surface of a rotor core
12
increases a magnetic resistance and reduces an inductance.
Consequently, in a pulse width modulation control method (also
referred to as a PWM control method), for example, a harmonic
component of a carrier wave for generating a PWM control signal
5 increases, and vibrations and noise in an electric motor
increase.
[0041]
FIG. 3 is an enlarged view schematically illustrating a
structure of a part of the rotor 2 illustrated in FIG. 2.
10 A distance Lo1 is a minimum distance from the first
inside slit 214a to the outer peripheral surface 21a of the
rotor core 21. A distance Lo2 is a minimum distance from the
second inside slit 214b to the outer peripheral surface 21a of
the rotor core 21. A distance Lo3 is a minimum distance from
15 the third inside slit 214c to the outer peripheral surface 21a
of the rotor core 21.
[0042]
In this embodiment, the distance Lo1 as the minimum
distance from the first inside slit 214a to the outer
20 peripheral surface 21a of the rotor core 21 is longer than the
minimum distance from any other inside slit 214 except the
first inside slit 214a to the outer peripheral surface 21a of
the rotor core 21. In other words, the distance Lo1 is the
longest of the distances from the plurality of inside slits 214
25 to the outer peripheral surface 21a of the rotor core 21. In
the example illustrated in FIG. 3, the distance Lo1 is longer
than the distance Lo2 and longer than the distance Lo3.
[0043]
A relationship between the distance Lo1 and a minimum
30 value Lo_min satisfies 3 < Lo1/Lo_min, where Lo_min is a
minimum value of minimum distances from the inside slits 214
except the first inside slit 214a of the plurality of inside
slits 214 between the magnetic pole center part C1 and one
outside slit 213, to the outer peripheral surface 21a of the
13
rotor core 21.
[0044]
In the example illustrated in FIG. 3, Lo1 > Lo3 > Lo2.
In the example illustrated in FIG. 3, a minimum value of the
5 minimum distance from each inside slit 214 to the outer
peripheral surface 21a of the rotor core 21 is Lo2. That is,
in the example illustrated in FIG. 3, Lo_min = Lo2. In this
case, the relationship between the distance Lo1 and the minimum
value Lo2 satisfies 3 < Lo1/Lo2.
10 [0045]
FIG. 4 is a diagram showing a relationship between a
ratio Lo1/Lo_min and a q-axis inductance.
In the range Lo1/Lo_min ≤ 3, since a magnetic resistance
in the q-axis direction increases near the outer peripheral
15 surface 21a of the rotor core 21, the q-axis inductance rapidly
decreases, as shown in FIG. 4.
[0046]
As described above, in this embodiment, the relationship
between the distance Lo1 and the minimum value Lo_min satisfies
20 3 < Lo1/Lo_min. Accordingly, the magnetic resistance in the qaxis direction decreases near the outer peripheral surface 21a
of the rotor core 21, and a decrease in the q-axis inductance
can be suppressed. That is, if Lo1/Lo_min is larger than three,
a sufficient q-axis inductance is obtained. Consequently, in a
25 PWM control method, a harmonic component of a carrier wave for
generating a PWM control signal decreases, and thus vibrations
and noise in an electric motor can be reduced.
[0047]
FIG. 5 is a diagram showing a relationship between the
30 ratio Lo1/Lo_min and a d-axis inductance.
As shown in FIG. 5, if 3 < Lo1/Lo_min, the d-axis
inductance increases. Thus, the relationship between the
distance Lo1 and the minimum value Lo_min preferably satisfies
3 < Lo1/Lo_min. Accordingly, a magnetic resistance in a d-axis
14
direction decreases near the outer peripheral surface 21a of
the rotor core 21. Consequently, in a PWM control method, a
harmonic component of a carrier wave for generating a PWM
control signal decreases, and thus vibrations and noise in an
5 electric motor can be reduced.
[0048]
FIG. 6 is an enlarged view schematically illustrating a
structure of a part of the rotor 2 illustrated in FIG. 2.
A distance Li1 is a minimum distance from the first
10 inside slit 214a to the permanent magnet insertion hole 211. A
distance Li2 is a minimum distance from the second inside slit
214b to the permanent magnet insertion hole 211. A distance
Li3 is a minimum distance from the third inside slit 214c to
the permanent magnet insertion hole 211.
15 [0049]
In this embodiment, the minimum distance from the first
inside slit 214a to the permanent magnet insertion hole 211 is
longer than the minimum distance from any other inside slit 214
except the first inside slit 214a of the plurality of inside
20 slits 214 between the magnetic pole center part C1 and one
outside slit 213, to the permanent magnet insertion hole 211.
In other words, the distance Li1 is the smallest of the
distances from the plurality of inside slits 214 to the
permanent magnet insertion hole 211. In the example
25 illustrated in FIG. 6, the distance Li1 is shorter than the
distance Li2 and shorter than the distance Li3.
[0050]
A relationship between the distance Li1 and the minimum
value Li_min satisfies 1 < Li1/Li_min, where Li_min is a
30 minimum value of minimum distances from the inside slits 214
except the first inside slit 214a of the plurality of inside
slits 214 between the magnetic pole center part C1 and one
outside slit 213, to the permanent magnet insertion hole 211.
[0051]
15
In the example illustrated in FIG. 6, a minimum value of
the minimum distances from the inside slits 214 except the
first inside slit 214a to the permanent magnet insertion hole
211 is Li3. That is, in the example illustrated in FIG. 6,
5 Li_min = Li3. In the example illustrated in FIG. 6, Li1 < Li3
< Li2. In this case, a relationship between the distance Li1
and the minimum value Li3 satisfies 1 < Li1/Li3.
[0052]
FIG. 7 is a diagram showing a relationship between a
10 ratio Li1/Li_min and a q-axis inductance.
If Li1/Li_min ≤ 1, since the magnetic resistance in the
q-axis direction increases near the outer peripheral surface
21a of the rotor core 21, the q-axis inductance rapidly
decreases, as shown in FIG. 7.
15 [0053]
As described above, in this embodiment, the relationship
between the distance Li1 and the minimum value Li_min satisfies
1 < Li1/Li_min. Accordingly, the magnetic resistance in the qaxis direction decreases near the outer peripheral surface 21a
20 of the rotor core 21, and a decrease in the q-axis inductance
can be suppressed. That is, if Li1/Li_min is larger than one,
a sufficient q-axis inductance is obtained. Consequently, in a
PWM control method, a harmonic component of a carrier wave for
generating a PWM control signal decreases, and thus vibrations
25 and noise in an electric motor can be reduced.
[0054]
FIG. 8 is a diagram showing a relationship between the
ratio Li1/Li_min and the d-axis inductance.
As shown in FIG. 8, a change in d-axis inductance is
30 small, independently of the ratio Li1/Li_min. Thus, the
relationship between the distance Li1 and the minimum value
Li_min preferably satisfies 1 < Li1/Li_min. Accordingly, as
described above, vibrations and noise in the electric motor can
be reduced.
16
[0055]
FIG. 9 is an enlarged view schematically illustrating a
structure of a part of the rotor 2 illustrated in FIG. 2.
A width Ws1 is a maximum width of the first inside slit
5 214a in the lateral direction in the xy plane. The lateral
direction of the first inside slit 214a is a direction
orthogonal to an imaginary line passing through the magnetic
pole center part C1 in the xy plane. The width Ws2 is a
maximum width of the second inside slit 214b in the lateral
10 direction in the xy plane. The lateral direction of the second
inside slit 214b is a direction orthogonal to an imaginary line
passing through the magnetic pole center part C1 in the xy
plane. The width Ws3 is a maximum width of the third inside
slit 214c in the lateral direction in the xy plane. The
15 lateral direction of the third inside slit 214c is a direction
orthogonal to an imaginary line passing through the magnetic
pole center part C1 in the xy plane. That is, the “lateral
direction” is the x-axis direction in FIG. 9.
[0056]
20 Supposing the sum of widths of inside slits 214 except
the first inside slit 214 of the plurality of inside slits 214
between the magnetic pole center part C1 and one outside slit
213 in the lateral direction is Ws2_total, Ws1/Ws2_total > 0.85
is satisfied.
25 [0057]
In the example illustrated in FIG. 9, the sum of widths
of the inside slits 214 except the first inside slit 214
between the magnetic pole center part C1 and one outside slit
213 is the sum of the width Ws2 and the width Ws3. That is, in
30 the example illustrated in FIG. 9, Ws2_total = Ws2 + Ws3. In
this case, a relationship between the width Ws1 and the sum of
widths Ws2_total satisfies Ws1/(Ws2 + Ws3) > 0.85.
[0058]
FIG. 10 is a diagram showing a relationship between a
17
ratio Ws1/Ws2_total and the q-axis inductance.
In the range Ws1/Ws2_total ≤ 0.85, since a magnetic
resistance in the q-axis direction increases near the outer
peripheral surface 21a of the rotor core 21, the q-axis
5 inductance is low, as shown in FIG. 10.
[0059]
As described above, in this embodiment, the relationship
between the width Ws1 and the sum of widths Ws2_total satisfies
Ws1/(Ws2 + Ws3) > 0.85. Accordingly, the magnetic resistance
10 in the q-axis direction decreases near the outer peripheral
surface 21a of the rotor core 21, and the q-axis inductance
increases. That is, if Ws1/(Ws2 + Ws3) is larger than 0.85, a
sufficient q-axis inductance is obtained. Consequently, in a
PWM control method, a harmonic component of a carrier wave for
15 generating a PWM control signal decreases, and thus vibrations
and noise in an electric motor can be reduced.
[0060]
FIG. 11 is a diagram showing a relationship between the
ratio Ws1/Ws2_total and the d-axis inductance.
20 As shown in FIG. 11, a sufficient d-axis inductance is
maintained, independently of the ratio Ws1/Ws2_total. Thus,
the relationship between the width Ws1 and the sum of widths
Ws2_total preferably satisfies Ws1/(Ws2 + Ws3) > 0.85.
Accordingly, as described above, vibrations and noise in the
25 electric motor can be reduced.
[0061]
As shown in FIG. 9, a relationship between a minimum
distance Wr and the sum of widths Ws1_total satisfies
Ws1_total/Wr < 0.62, where a minimum distance from the magnetic
30 pole center part C1 to one outside slit 213 is Wr, and the sum
of widths of the plurality of inside slits 214 in the lateral
direction between the magnetic pole center part C1 and one
outside slit 213 is Ws1_total.
[0062]
18
In the example illustrated in FIG. 9, the sum of widths
of the plurality of inside slits 214 in the lateral direction
between the magnetic pole center part C1 and one outside slit
213 is the sum of the width Ws1, the width Ws2, and the width
5 Ws3. That is, in the example illustrated in FIG. 9, Ws1_total
= Ws1 + Ws2 + Ws3. In this case, a relationship between the
minimum distance Wr and the sum of widths Ws1_total satisfies
(Ws1 + Ws2 + Ws3)/Wr < 0.62.
[0063]
10 FIG. 12 is a diagram illustrating a relationship between
a ratio Ws1_total/Wr and a q-axis inductance.
As shown in FIG. 12, if Ws1_total/Wr is smaller than 0.62,
a change in q-axis inductance is small. In addition, if
Ws1_total/Wr is smaller than 0.62, a sufficient q-axis
15 inductance is maintained, independently of the ratio
Ws1_total/Wr.
[0064]
FIG. 13 is a diagram illustrating a relationship between
the ratio Ws1_total/Wr and a d-axis inductance.
20 If 0.62 ≤ Ws1_total/Wr, since the magnetic resistance in
the d-axis direction increases near the outer peripheral
surface 21a of the rotor core 21, the q-axis inductance rapidly
decreases, as shown in FIG. 13.
[0065]
25 As described above, in this embodiment, the relationship
between the minimum distance Wr and the sum of widths Ws1_total
satisfies Ws1_total/Wr < 0.62. Accordingly, a magnetic
resistance in the d-axis direction decreases near the outer
peripheral surface 21a of the rotor core 21, and a decrease in
30 d-axis inductance can be thereby suppressed. That is, if
Ws1_total/Wr is smaller than 0.62, a sufficient d-axis
inductance is obtained. Consequently, in a PWM control method,
a harmonic component of a carrier wave for generating a PWM
control signal decreases, and thus vibrations and noise in an
19
electric motor can be reduced.
[0066]
The relationship between the minimum distance Wr and the
sum of widths Ws1_total more preferably satisfies Ws1_total/Wr
5 < 0.6. Accordingly, a magnetic resistance in the d-axis
direction further decreases near the outer peripheral surface
21a of the rotor core 21, and a decrease in d-axis inductance
can be effectively suppressed. That is, if Ws1_total/Wr is
smaller than 0.60, the d-axis inductance further increases.
10 Consequently, in a PWM control method, a harmonic component of
a carrier wave for generating a PWM control signal decreases,
and thus vibrations and noise in an electric motor can be
reduced.
[0067]
15 FIG. 14 is a diagram showing a waveform of a carrier wave
in the electric motor 1.
In FIG. 14, a bold line represents a carrier wave in the
electric motor 1, and a thin line represents a carrier wave in
an electric motor as a reference. In a rotor of the electric
20 motor as a reference, Lo1 = Lo2 = Lo3 and Li1 = Li2 = Li3.
[0068]
As described above, in the electric motor 1 including the
rotor 2, a magnetic resistance in the q-axis direction
decreases near the outer peripheral surface 21a of the rotor
25 core 21, and a decrease in q-axis inductance can be suppressed.
Thus, a sufficient q-axis inductance is obtained. Consequently,
as shown in FIG. 14, in a PWM control method, a harmonic
component of a carrier wave for generating a PWM control signal
decreases, and thus vibrations and noise in an electric motor
30 can be reduced.
[0069]
SECOND EMBODIMENT
A compressor 6 according to a second embodiment of the
present invention will be described.
20
FIG. 15 is a cross-sectional view schematically
illustrating a structure of the compressor 6 according to the
second embodiment.
[0070]
5 The compressor 6 includes an electric motor 1 as an
electric element, a closed container 61 as a housing, and a
compressor mechanism 62 as a compression element (also referred
to as a compression device). In this embodiment, the
compressor 6 is a rotary compressor. It should be noted that
10 the compressor 6 is not limited to the rotary compressor.
[0071]
The electric motor 1 in the compressor 6 is the electric
motor 1 described in the second embodiment. The electric motor
1 drives the compressor mechanism 62.
15 [0072]
The closed container 61 covers the electric motor 1 and
the compressor mechanism 62. The closed container 61 is a
cylindrical container. In a bottom portion of the closed
container 61, refrigerating machine oil for lubricating a
20 sliding portion of the compressor mechanism 62 is stored.
[0073]
The compressor 6 further includes a glass terminal 63
fixed to the closed container 61, an accumulator 64, a suction
pipe 65, and a discharge pipe 66.
25 [0074]
The compressor mechanism 62 includes a cylinder 62a, a
piston 62b, an upper frame 62c (also referred to as a first
frame), a lower frame 62d (also referred to as a second frame),
and a plurality of mufflers 62e attached to the upper frame 62c
30 and the lower frame 62d. The compressor mechanism 62 also
includes a vane partitioning the inside of the cylinder 62a
into a suction side and a compression side. The compressor
mechanism 62 is disposed in the closed container 61. The
compressor mechanism 62 is driven by the electric motor 1.
21
[0075]
The electric motor 1 is fixed in the closed container 61
by press fitting or shrink fitting. The electric motor 1 may
be directly attached to the closed container 61 by welding,
5 instead of press fitting or shrink fitting.
[0076]
Electric power is supplied to a coil (e.g., the winding
32 described in the first embodiment) of the electric motor 1
through the glass terminal 63.
10 [0077]
A rotor 2 (specifically one side of a shaft 24) of the
electric motor 1 is rotatably supported by bearings provided on
the upper frame 62c and the lower frame 62d.
[0078]
15 The shaft 24 is inserted in the piston 62b. The shaft 24
is rotatably inserted in the upper frame 62c and the lower
frame 62d. The upper frame 62c and the lower frame 62d close
an end face of the cylinder 62a. The accumulator 64 supplies a
refrigerant (e.g., refrigerant gas) to the cylinder 62a through
20 the suction pipe 65.
[0079]
Next, an operation of the compressor 6 will be described.
The refrigerant supplied from the accumulator 64 is sucked into
the cylinder 62a through the suction pipe 65 fixed to the
25 closed container 61. When the electric motor 1 rotates, the
piston 62b fitted in the shaft 24 thereby rotates in the
cylinder 62a. Accordingly, the refrigerant is compressed in
the cylinder 62a.
[0080]
30 The compressed refrigerant passes through the mufflers
62e and rises in the closed container 61. In this manner, the
compressed refrigeration cycle is supplied to a high-pressure
side of a refrigeration cycle through the discharge pipe 66.
[0081]
22
As a refrigerant used in the compressor 6, for example,
R410A, R407C, or R22 can be used. It should be noted that a
refrigerant for the compressor 6 is not limited to these types.
As a refrigerant used in the compressor 6, a refrigerant having
5 a small global warming potential (GWP), e.g., refrigerants
described below, can be used.
[0082]
(1) Halogenated hydrocarbon having a carbon double bond in a
composition, such as hydro-fluoro-orefin (HFO)-1234yf (CF3CF =
10 CH2), can be used. HFO-1234yf has a GWP of 4.
(2) Hydrocarbon having a carbon double bond in a composition,
such as R1270 (propylene), may be used. R1270 has a GWP of 3,
which is lower than that of HFO-1234yf, but has a flammability
higher than that of HFO-1234yf.
15 (3) A mixture including either halogenated hydrocarbon having a
carbon double bond in a composition or hydrocarbon having a
carbon double bond in a composition, such as a mixture of HFO1234yf and R32, may be used. HFO-1234yf described above is a
low-pressure refrigerant, and thus, has a tendency of having a
20 large pressure loss and consequently degradation of performance
of a refrigeration cycle (especially an evaporator) might occur.
Accordingly, it is practically preferable to use a mixture
including R32 or R41, which is a higher-pressure refrigerant
than HFO-1234yf.
25 [0083]
The compressor 6 according to the second embodiment has
the advantages described in the first embodiment.
[0084]
In addition, the compressor 6 according to the second
30 embodiment includes the electric motor 1 according to the
second embodiment, and thus, vibrations and noise in the
compressor 6 can be reduced.
[0085]
THIRD EMBODIMENT
23
A refrigerating and air conditioning apparatus 7
including the compressor 6 according to the second embodiment
and serving as an air conditioner will be described.
FIG. 16 is a diagram schematically illustrating a
5 configuration of the refrigerating and air conditioning
apparatus 7 according to a third embodiment of the present
invention.
[0086]
The refrigerating and air conditioning apparatus 7 is
10 capable of performing heating and operations, for example. A
refrigerant circuit diagram illustrated in FIG. 16 is an
example of a refrigerant circuit diagram of an air conditioner
capable of performing a cooling operation.
[0087]
15 The refrigerating and air conditioning apparatus 7
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.
[0088]
20 The outdoor unit 71 includes the compressor 6, a
condenser 74 as a heat exchanger, a throttling device 75, and
an outdoor fan 76 (first fan). The condenser 74 condenses a
refrigerant compressed by the compressor 6. The throttling
device 75 reduces the pressure of the refrigerant condensed by
25 the condenser 74 and adjusts a flow rate of the refrigerant.
The throttling device 75 is also referred to as a decompressor.
[0089]
The indoor unit 72 includes an evaporator 77 as a heat
exchanger and an indoor fan 78 (second fan). The evaporator 77
30 evaporates the refrigerant decompressed by the throttling
device 75 and cools indoor air.
[0090]
A basic operation in a cooling operation of the
refrigerating and air conditioning apparatus 7 will be
24
described below. In a cooling operation, a refrigerant is
compressed by the compressor 6 and flows into the condenser 74.
The refrigerant is condensed by the condenser 74, and the
condensed refrigerant flows into the throttling device 75. The
5 refrigerant is decompressed by the throttling device 75, and
the decompressed refrigerant flows into the evaporator 77. The
refrigerant evaporates in the evaporator 77, and the
refrigerant (specifically a refrigerant gas) flows into the
compressor 6 of the outdoor unit 71 again. When air is sent to
10 the condenser 74 by the outdoor fan 76, heat moves between the
refrigerant and air. Similarly, when air is sent to the
evaporator 77 by the indoor fan 78, heat moves between the
refrigerant and air.
[0091]
15 A configuration and an operation of the refrigerating and
air conditioning apparatus 7 described above is an example and
is not limited to the example described above.
[0092]
The refrigerating and air conditioning apparatus 7
20 according to the third embodiment has the advantages described
in the first and second embodiments.
[0093]
In addition, since the refrigerating and air conditioning
apparatus 7 according to the third embodiment includes the
25 compressor 6 according to the second embodiment, vibrations and
noise in the refrigerating and air conditioning apparatus 7 can
be reduced.
[0094]
As described above, although preferred embodiments have
30 been specifically described above, it is obvious that various
modifications can be made by those skilled in the art based on
a basic technical idea and teaching of the present invention.
[0095]
Features of the embodiments described above can be
25
combined as appropriate.
DESCRIPTION OF REFERENCE CHARACTERS
[0096]
5 1 electric motor, 2 rotor, 3 stator, 6 compressor, 7
refrigerating and air conditioning apparatus, 21 rotor core,
21a outer peripheral surface, 22 permanent magnet, 61 closed
container, 62 compressor mechanism, 211 permanent magnet
insertion hole, 213 outside slit, 214 inside slit, 214a first
10 inside slit, 214b second inside slit, 214c third inside slit.

26
We Claim :
1. A rotor including a magnetic pole center part, the rotor
comprising:
5 a rotor core including a permanent magnet insertion hole;
and
a permanent magnet disposed in the permanent magnet
insertion hole, wherein
the rotor core includes
10 an outside slit provided between the permanent magnet
insertion hole and an outer peripheral surface of the rotor
core and extending in a circumferential direction of the rotor
core, and
a plurality of inside slits provided between the magnetic
15 pole center part and the outside slit and arranged in the
circumferential direction,
the plurality of inside slits include a first inside slit
adjacent to the magnetic pole center part, and
a minimum distance from the first inside slit to the
20 outer peripheral surface of the rotor core is longer than a
minimum distance from any other inside slit except the first
inside slit of the plurality of inside slits to the outer
peripheral surface of the rotor core.
25 2. The rotor according to claim 1, wherein the rotor
satisfies 3 < Lo1/Lo_min
where Lo1 is the minimum distance from the first inside
slit to the outer peripheral surface of the rotor core and
Lo_min is a minimum value of minimum distances from inside
30 slits except the first inside slit of the plurality of inside
slits to the outer peripheral surface of the rotor core.
3. The rotor according to claim 1 or 2, wherein a minimum
distance from the first inside slit to the permanent magnet
27
insertion hole is shorter than a minimum distance from any
other inside slit except the first inside slit of the plurality
of inside slits to the permanent magnet insertion hole.
5 4. The rotor according to any one of claims 1 to 3, wherein
the rotor satisfies 1 < Li1/Li_min
where Li1 is a minimum distance from the first inside
slit to the permanent magnet insertion hole and Li_min is a
minimum value of minimum distances from inside slits except the
10 first inside slit of the plurality of inside slits to the
permanent magnet insertion hole.
5. The rotor according to any one of claims 1 to 4, wherein
the rotor satisfies Ws1/Ws2_total > 0.85
15 where Ws1 is a width of the first inside slit in a
lateral direction and Ws2_total is the sum of widths of inside
slits except the first inside slit of the plurality of inside
slits in the lateral direction, in a plane orthogonal to an
axial direction of the rotor.
20
6. The rotor according to any one of claims 1 to 5, wherein
the rotor satisfies Ws1_total/Wr < 0.62
where Wr is a minimum distance from the magnetic pole
center part to the outside slit and Ws1_total is the sum of
25 widths of the plurality of inside slits in a lateral direction.
7. The rotor according to any one of claims 1 to 6, wherein
the rotor core further includes a set of inside slits,
and
30 the plurality of inside slits and the set of inside slits
are symmetric with respect to the magnetic pole center part.
8. An electric motor comprising:
a stator; and
28
the rotor according to any one of claims 1 to 7 disposed
inside the stator.
9. A compressor comprising:
5 a closed container;
a compression device disposed inside the closed
container; and
the electric motor according to claim 8 to drive the
compression device.
10
10. An air conditioner, comprising:
the compressor according to claim 9; and
a heat exchanger.