FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
ROTOR, MOTOR, FAN, 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
TECHNICAL FIELD
5 [0001]
The present invention relates to a rotor, a motor, a fan,
and an air conditioner.
BACKGROUND ART
[0002]
10 Conventionally, in order to reduce the number of permanent
magnets attached to a rotor of a motor, a consequent pole type
rotor having a magnet magnetic pole and a pseudo-magnetic pole
is developed. Further, in order to reduce noise, formation of a
slit in the consequent pole type rotor is proposed (see, for
15 example, Patent Reference 1).
PRIOR ART REFERENCE
PATENT REFERENCE
[0003]
Patent Reference 1: Japanese Patent Application
20 Publication No. 2012-244783 (see FIG. 14)
SUMMARY OF THE INVENTION
PROBLEM TO BE SOLVED BY THE INVENTION
[0004]
However, when a slit is formed in the rotor, there is a
25 problem that a magnetic flux of the permanent magnet is blocked
by the slit, and an output of the motor is reduced.
[0005]
The present invention is intended to solve the abovedescribed
problem, and an object of the present invention is to
30 suppress the reduction in the output of the motor while reducing
noise of the motor.
MEANS OF SOLVING THE PROBLEM
[0006]
A rotor of the present invention includes a rotor core
3
having an outer circumference of an annular shape surrounding a
center axis and a magnet insertion hole formed along the outer
circumference, and a permanent magnet disposed in the magnet
insertion hole. The permanent magnet constitutes a first
magnetic pole, and a part of the rotor core constitutes 5 a second
magnetic pole. The rotor core has a plurality of slits in the
second magnetic pole. The plurality of slits are symmetrically
formed with respect to a magnetic pole center line connecting a
pole center of the second magnetic pole and the center axis. On
10 one side of the magnetic pole center line in a circumferential
direction about the center axis, the plurality of slits have a
first slit closest to the magnetic pole center line and a second
slit adjacent to the first slit in the circumferential direction.
A minimum distance L1 from the first slit to the outer
15 circumference of the rotor core and a minimum distance L2 from
the second slit to the outer circumference of the rotor core
satisfy L1 < L2.
EFFECTS OF THE INVENTION
[0007]
20 According to the present invention, the magnetic flux of
the rotor can be concentrated on the pole center of the second
magnetic pole by the first slit and the second slit. Thus, it
is possible to reduce noise of the motor by suppressing torque
ripple and to suppress reduction in the output of the motor.
25 BRIEF DESCRIPTION OF THE DRAWINGS
[0008]
FIG. 1 is a cross-sectional view illustrating a motor of a
first embodiment.
FIG. 2 is a cross-sectional view illustrating a rotor core
30 and permanent magnets of the first embodiment.
FIG. 3 is an enlarged cross-sectional view illustrating a
part of a rotor of the first embodiment.
FIG. 4 is a schematic diagram illustrating the flow of a
magnetic flux in the motor of the first embodiment.
4
FIG. 5 is a graph illustrating a surface magnetic flux
distribution of the rotor of the motor.
FIG. 6 is a graph illustrating the relationship between
the surface magnetic flux of the rotor of the motor and W3/W2.
FIG. 7 is a graph illustrating the relationship 5 between
the surface magnetic flux of the rotor of the motor and W3/W1.
FIG. 8 is an enlarged cross-sectional view illustrating a
part of the rotor of the first embodiment.
FIG. 9 is a schematic diagram illustrating the flow of a
10 magnetic flux in a pseudo-magnetic pole of the rotor of the
first embodiment.
FIG. 10 is a cross-sectional view illustrating the rotor
core and the permanent magnets of the first embodiment.
FIG. 11 is a longitudinal sectional view illustrating a
15 mold motor to which the motor of the first embodiment is applied.
FIG. 12 is a cross-sectional view illustrating a rotor of
a second embodiment.
FIG. 13 is an enlarged cross-sectional view illustrating a
part of the rotor of the second embodiment.
20 FIG. 14(A) is a front view illustrating an air conditioner
to which the motor of each embodiment is applicable, and FIG.
14(B) is a cross-sectional view illustrating an outdoor unit of
the air conditioner.
FIG. 15 is a schematic diagram illustrating a refrigerant
25 circuit of the air conditioner illustrated in FIG. 14(A).
MODE FOR CARRYING OUT THE INVENTION
[0009]
FIRST EMBODIMENT
(Configuration of Motor)
30 FIG. 1 is a cross-sectional view illustrating a motor 1 of
a first embodiment. The motor 1 is an inner-rotor type motor
that includes a rotatable rotor 2 and an annular stator 5
provided so as to surround the rotor 2. The motor 1 is also a
permanent magnet embedded motor in which permanent magnets 25
5
are embedded in the rotor 2. An air gap (i.e., a gap) 10 of,
for example, 0.4 mm is provided between the stator 5 and the
rotor 2.
[0010]
Hereinafter, an axis serving as a center 5 of rotation of
the rotor 2 is referred to as a center axis C1, and a direction
of the center axis C1 is referred to as an “axial direction”. A
circumferential direction about the center axis C1 (indicated by
the arrow R1 in FIG. 1) is referred to as a “circumferential
10 direction”, and a radial direction about the center axis C1 is
referred to as a “radial direction”. FIG. 1 is a crosssectional
view at a plane perpendicular to the center axis C1 of
the rotor 2.
[0011]
15 (Configuration of Stator)
The stator 5 includes a stator core 50 and coils 55 wound
on the stator core 50. The stator core 50 is obtained by
stacking stack elements each having a thickness of, for example,
0.2 mm to 0.5 mm in the axial direction and fixing the stack
20 elements together by crimping or the like. In this example, the
stack element is an electromagnetic steel sheet that contains
iron (Fe) as a main component.
[0012]
The stator core 50 has a yoke 52 having an annular shape
25 about the center axis C1 and a plurality of teeth 51 extending
inward in the radial direction (i.e., toward the center axis C1)
from the yoke 52. The teeth 51 are arranged at equal intervals
in the circumferential direction. The number of teeth 51 is 12
in this example, but is not limited to 12. A slot 53, which is
30 a space for accommodating the coil 55, is formed between
adjacent teeth 51.
[0013]
A tip end of the tooth 51 on an inner side in the radial
direction has a width in the circumferential direction wider
6
than other portions of the tooth 51. The tip end of the tooth
51 faces an outer circumference of the rotor 2 via the abovedescribed
air gap 10. Each of an outer circumference 50a of the
stator core 50 (i.e., an outer circumference of the yoke 52) and
an inner circumference 50b of the stator core 5 50 (i.e., the tip
end of the tooth 51) has a circular annular shape.
[0014]
Crimping portions for integrally fixing the stack elements
of the stator core 50 are formed in the yoke 52 and the teeth 51
10 of the stator core 50, as indicated by reference characters 56
and 57. The crimping portions may be formed in any other
positions as long as the stack elements are integrally fixed by
the crimping portions.
[0015]
15 An insulator 54 serving as an insulating portion is
attached to the stator core 50. The insulator 54 is interposed
between the stator core 50 and the coil 55 and insulates the
stator core 50 from the coil 55. The insulator 54 is formed by
integrally molding a resin with the stator core 50 or assembling
20 a resin molded body, which is molded as a separate component, to
the stator core 50.
[0016]
The insulator 54 is formed of an insulating resin such as
polybutylene terephthalate (PBT), polyphenylene sulfide (PPS),
25 liquid crystal polymer (LCP), polyethylene terephthalate (PET)
or the like. The insulator 54 can also be formed of an
insulating resin film having a thickness of 0.035 to 0.4 mm.
[0017]
The coil 55 is wound around the tooth 51 via the insulator
30 54. The coil 55 is formed of a material that contains copper or
aluminum as a main component. The coil 55 may be wound around
each tooth 51 (concentrated winding) or may be wound across a
plurality of teeth 51 (distributed winding).
[0018]
7
(Configuration of Rotor)
FIG. 2 is a cross-sectional view illustrating a rotor core
20 and the permanent magnets 25. In FIG. 2, the resin portion 4
and the rotation shaft 11 are omitted. The rotor 2 has the
cylindrical rotor core 20 about the center axis 5 C1. The rotor
core 20 is formed of magnetic stack elements each having a
thickness of, example, 0.2 to 0.5 mm which are stacked in the
axial direction and fixed together by crimping or the like. The
stack element in this example is an electromagnetic steel sheet
10 that contains iron as a main component. The rotor core 20 may
be formed of a resin core that contains a combination of a soft
magnetic material and a resin. A diameter of the rotor 2 is 50
mm in this example.
[0019]
15 A plurality of magnet insertion holes 21 are formed along
an outer circumference of the rotor core 20. The magnet
insertion holes 21 are arranged at equal intervals in the
circumferential direction. Each magnet insertion hole 21 has an
elongated shape in the circumferential direction and passes
20 through the rotor core 20 in the axial direction. More
specifically, each magnet insertion hole 21 extends linearly in
a direction perpendicular to a straight line (hereinafter
referred to as a magnet pole center line) that passes through
the center axis C1 and a pole center to be described later. The
25 number of magnet insertion holes 21 is five in this example.
[0020]
The permanent magnet 25 is disposed in each magnet
insertion hole 21. The permanent magnet 25 is a member in the
form of a flat plate, and has a thickness T1 in a direction in
30 which the permanent magnet 25 faces the stator 5 (more
specifically, in the radial direction of the rotor core 20).
The permanent magnet 25 is magnetized in the thickness direction.
The permanent magnet 25 is constituted by, for example, a rare
earth magnet that contains neodymium (Nd) or samarium (Sm) as a
8
main component, or a ferrite magnet that contains iron as a main
component.
[0021]
The permanent magnet 25 disposed in each magnet insertion
hole 21 constitutes a magnet magnetic pole 5 P1. The permanent
magnets 25 are arranged so that pole-faces of the same polarity
(for example, N pole) face the outer circumferential side of the
rotor core 20. Thus, a portion through which a magnetic flux
flows in the radial direction is formed between adjacent
10 permanent magnets 25 in the rotor core 20. That is, a pseudomagnetic
pole P2 having an opposite polarity to that of the
permanent magnet 25 is formed.
[0022]
That is, the rotor 2 has five magnet magnetic poles P1 and
15 five pseudo-magnetic poles P2 which are alternately arranged in
the circumferential direction. Thus, the number of poles of the
rotor 2 is ten. Such a rotor configuration is referred to as a
consequent pole type. The number of poles of the rotor 2 is not
limited to ten.
20 [0023]
A center of the magnet magnetic pole P1 in the
circumferential direction (i.e., a center of the magnet
insertion hole 21 in the circumferential direction) is a pole
center of the magnet magnetic pole P1. A center of the pseudo25
magnetic pole P2 in the circumferential direction is a pole
center of the pseudo-magnetic pole P2. A straight line that
passes through the pole center and the center axis C1 is
referred to as a magnetic pole center line. An inter-pole
portion M is a portion between the magnet magnetic pole P1 and
30 the pseudo-magnetic pole P2.
[0024]
Although one permanent magnet 25 is disposed in one magnet
insertion hole 21 in this example, a plurality of permanent
magnets 25 may be disposed in one magnet insertion hole 21 side
9
by side in the circumferential direction. In this case, the
magnet insertion hole 21 may be formed in a V shape such that
its center in the circumferential direction protrudes inward in
the radial direction. An air hole may be formed on the inner
side in the radial direction with respect 5 to the magnet
insertion hole 21 in the rotor core 20.
[0025]
The rotor 2 has a rotation shaft 11 and a resin portion 4
on the inner side of the rotor core 20 in the radial direction.
10 The rotation shaft 11 is rotatably supported by bearings 12 and
13 (FIG. 11). The above-described center axis C1 is a center
axis of the rotation shaft 11. The rotation shaft 11 is formed
of, for example, a metal such as iron (Fe), nickel (Ni), or
chromium (Cr).
15 [0026]
The resin portion (supporting portion) 4 supports the
rotor core 20 with respect to the rotation shaft 11 and is
formed of a non-magnetic material, more specifically, a
thermoplastic resin such as polybutylene terephthalate (PBT) or
20 the like. The resin portion 4 can be formed by molding the
rotor core 20 and the rotation shaft 11 with resin.
[0027]
The resin portion 4 includes an inner cylindrical portion
41 fixed to an outer circumference of the rotation shaft 11, an
25 annular outer cylindrical portion 43 fixed to an inner
circumference 23 of the rotor core 20, and a plurality of ribs
(connecting portions) 42 connecting the inner cylindrical
portion 41 and the outer cylindrical portion 43.
[0028]
30 The rotation shaft 11 passes through the inner cylindrical
portion 41 of the resin portion 4. The ribs 42 are arranged at
equal intervals in the circumferential direction and radially
extend outward in the radial direction from the inner
cylindrical portion 41. The position where each rib 42 is
10
formed corresponds to the center of the permanent magnet 25 in
the circumferential direction (i.e., the pole center of the
magnet magnetic pole P1). A hollow portion 44 is formed between
ribs 42 adjacent to each other in the circumferential direction.
The outer cylindrical portion 43 is continuous 5 to outer ends of
the ribs 42 in the radial direction.
[0029]
Since the consequent pole type rotor 2 has no actual
permanent magnet in the pseudo-magnetic pole P2, the magnetic
10 flux passing through the pseudo-magnetic pole P2 tends to flow
toward the rotation shaft 11. By providing the resin portion 4
between the rotor core 20 and the rotation shaft 11, leakage
magnetic flux to the rotation shaft 11 can be suppressed
effectively.
15 [0030]
The outer circumference of the rotor core 20 has a flower
shape such that its outer diameter is maximum at the pole center
and is minimum at the inter-pole portion. More specifically,
the outer circumference of the rotor core 20 has outer
20 circumferential portions 20a whose centers are located at the
pole centers of the magnetic poles (the magnet poles P1 and the
pseudo-magnetic poles P2), and outer circumferential portions
20b whose centers are located at the inter-pole portions M.
Both of the outer circumferential portions 20a and 20b are arc25
shaped portions and have centers of curvature on the center axis
C1 side, but the outer circumferential portions 20a and 20b have
different radii of curvature.
[0031]
The outer circumferential portion 20a whose center is
30 located at the pole center of the magnet magnetic pole P1 may be
referred to as a first outer circumferential portion. The outer
circumferential portion 20a whose center is located at the pole
center of the pseudo-magnetic pole P2 may be referred to as a
second outer circumference. The outer circumferential portion
11
20b whose center is located at the inter-pole portion M may be
referred to as a third outer circumferential portion.
[0032]
A flux barrier 22, which is an opening, is formed on each
of both ends of the magnet insertion 5 hole 21 in the
circumferential direction. The flux barrier 22 is provided for
suppressing the leakage magnetic flux between the magnetic pole
P1 and the pseudo-magnetic pole P2.
[0033]
10 A core portion between the flux barrier 22 and the outer
circumference of the rotor core 20 is a thin-wall portion (also
referred to as a bridge portion). A thickness of the thin-wall
portion is desirably the same as a thickness of each of the
stack elements forming the rotor core 20. Thus, the leakage
15 magnetic flux between the adjacent magnetic poles can be
suppressed. The flux barrier 22 in this example is disposed on
each of both ends of the magnet insertion hole 21 in the
circumferential direction, but may be disposed only on one end
of the magnet insertion hole 21 in the circumferential direction.
20 [0034]
The outer circumference of the rotor core 20 has the
flower shape as described above, but the inner circumference 50b
of the stator core 50 has a circular annular shape. Thus, a
width of the air gap 10 between the stator 5 and the rotor 2 is
25 minimum at the pole center of each magnet pole (each of the
magnet magnetic pole P1 and the pseudo-magnetic pole P2), and is
maximum at the inter-pole portion M.
[0035]
FIG. 3 is an enlarged diagram illustrating a portion
30 including the pseudo-magnetic pole P2 of the rotor 2. The rotor
core 20 has a slit group 8 including a plurality of slits 81 and
82 in each pseudo-magnetic pole P2. In the first embodiment,
the slit group 8 has two first slits 81 closest to the magnetic
pole center line (indicated by the mark CL in FIG. 3) of the
12
pseudo-magnetic pole P2 and two second slits 82 formed on both
sides of these two first slits 81 in the circumferential
direction.
[0036]
The first slits 81 are formed symmetrically 5 with respect
to the magnetic pole center line CL of the pseudo-magnetic pole
P2. The second slits 82 are formed symmetrically with respect
to the magnetic pole center line CL of the pseudo-magnetic pole
P2. More specifically, the two first slits 81 are formed at
10 symmetrical positions and have symmetrical shapes with respect
to the magnetic pole center line CL. The two second slits 82
are formed at symmetrical positions and have symmetrical shapes
with respect to the magnetic pole center line CL.
[0037]
15 Instead of providing the two first slits 81, one first
slit 81 may be provided on the magnetic pole center line CL.
This configuration will be described in a second embodiment
(FIGS. 12 and 13).
[0038]
20 The first slit 81 has a shape elongated in the radial
direction. More specifically, the first slit 81 has an end
portion 81a on an outer side in the radial direction, an end
portion 81b on an inner side in the radial direction, an end
portion 81c on an outer side in the circumferential direction
25 (i.e., on a side far from the magnetic pole center line CL), and
an end portion 81d on an inner side in the circumferential
direction (i.e., on a side close to the magnetic pole center
line CL).
[0039]
30 The end portions 81a and 81b of the first slit 81 extend
perpendicularly to the magnetic pole center line CL. The end
portions 81c and 81d extend in parallel to the magnetic pole
center line CL. A length A1 of the first slit 81 (i.e., an
interval between the end portions 81a and 81b) is longer than a
13
width H1 of the first slit 81 (i.e., an interval between the end
portions 81c and 81d).
[0040]
The second slit 82 has a shape elongated in the radial
direction. More specifically, the second 5 slit 82 has an end
portion 82a on an outer side in the radial direction, an end
portion 82b on an inner side in the radial direction, an end
portion 82c on an outer side in the circumferential direction
(i.e., on a side far from the magnetic pole center line CL), and
10 an end portion 82d on an inner side in the circumferential
direction (i.e., on a side close to the magnetic pole center
line CL).
[0041]
The end portion 82a of the second slit 82 extends along
15 the outer circumferential portion 20a. The end portion 82b
extends perpendicularly to the magnetic pole center line CL.
The end portions 82c and 82d extend in parallel to the magnetic
pole center line CL. A length A2 of the second slit 82 (i.e.,
an interval between the end portions 82a and 82b) is longer than
20 a width H2 of the second slit 82 (i.e., an interval between the
end portions 82c and 82d).
[0042]
The length A1 of the first slit 81 is shorter than the
length A2 of the second slit 82, and the width H1 of the first
25 slit 81 is narrower than the width H2 of the second slit 82.
That is, a cross-sectional area of the first slit 81 is smaller
than a cross-sectional area of the second slit 82.
[0043]
A thin-wall portion 83 is formed between the two first
30 slits 81. The thin-wall portion 83 has a width W1 which is the
minimum width in the circumferential direction (i.e., the
minimum interval between the end portions 81d of the two first
slits 81). The width of the thin-wall portion 83 is constant
along the radial direction in FIG. 3, but is not necessarily
14
constant. The thin-wall portion 83 is also referred to as a
pole-center thin-wall portion because it is located on the
magnetic pole center line CL.
[0044]
A thin-wall portion 84 is formed between 5 the first slit 81
and the second slit 82. The thin-wall portion 84 has a width W2
which is the minimum width in the circumferential direction
(i.e., the minimum interval between the end portion 81c of the
first slit 81 and the side end portion 82d of the second slit
10 82). The width of the thin-wall portion 84 is constant along
the radial direction in FIG. 3, but is not necessarily constant.
The thin-wall portion 84 is also referred to as an inter-slit
thin-wall portion.
[0045]
15 A core region 85 is formed between the second slit 82 and
the flux barrier 22. The core region 85 has a width W3 between
the second slit 82 and an end 22a of the flux barrier 22 closest
to the magnetic pole center line CL. The width W3 is the
minimum width of the core region 85 in the circumferential
20 direction.
[0046]
A distance L1 is defined as the minimum distance between
the first slit 81 and the outer circumferential portion 20a
(i.e., the minimum distance between the end portion 81a of the
25 first slit 81 and the outer circumferential portion 20a). A
distance L2 is defined as the minimum distance between the
second slit 82 and the outer circumferential portion 20a (i.e.,
the minimum distance between the end portion 82a of the second
slit 82 and the outer circumferential portion 20a). The
30 distances L1 and L2 satisfy the relationship of L1 < L2.
[0047]
(Action)
Next, the action of the first embodiment will be described.
In order to cause the magnetic flux distribution on the surface
15
(i.e., outer circumferential surface) of the rotor 2 to approach
a sinusoidal wave, it is effective to vary in the
circumferential direction the gap between the rotor 2 and the
stator 5. With a configuration in which the gap between the
rotor 2 and the stator 5 is minimum at the pole 5 center of each
of the magnetic poles (the magnet magnetic poles P1 and the
pseudo-magnetic poles P2) and increases as a distance from the
pole center increases, the magnetic flux is concentrated on the
pole center. Thus, the surface magnetic flux distribution of
10 the rotor 2 approaches the sinusoidal wave.
[0048]
In the consequent pole type rotor 2, a degree of freedom
of the magnetic flux flowing through the pseudo-magnetic pole P2
is high, and thus the surface magnetic flux of the rotor 2
15 significantly changes depending on the rotational positions of
the rotor 2 relative to the stator 5. Thus, by providing the
slits 81 and 82 in the pseudo-magnetic pole P2 to restrict the
degree of freedom of the magnetic flux, the effect of causing
the surface magnetic flux distribution of the rotor 2 to
20 approach the sinusoidal wave can be enhanced.
[0049]
FIG. 4 is a schematic diagram illustrating a result of
simulation of the magnetic flux flowing through the pseudomagnetic
pole P2 in a case where neither the slit 81 nor the
25 slit 82 is provided in the pseudo-magnetic pole P2. The
magnetic flux emitted from the permanent magnet 25 of the magnet
magnetic pole P1 flows through the pseudo-magnetic pole P2 and
then flows into the tooth 51 via the air gap 10. The magnetic
flux flowing into the tooth 51 flows into the yoke 52 located on
30 the outer side of the tooth 51 in the radial direction, further
flows through an adjacent tooth 51 inward in the radial
direction, and then returns to the permanent magnet 25.
[0050]
The magnetic flux passes through portions in which
16
magnetic resistance is low. The magnetic resistance decreases
as a magnetic path is shortened. Thus, in the pseudo-magnetic
pole P2, the magnetic flux is more likely to be concentrated on
a region close to the magnet magnetic pole P1 (i.e., a region
close to the inter-pole portion M), and 5 thus the amount of
magnetic flux flowing through the pole center of the pseudomagnetic
pole P2 is relatively small.
[0051]
FIG. 5 is a schematic diagram illustrating a result of
10 simulation of the magnetic flux flowing through the pseudomagnetic
pole P2 in a case where the slits 81 and 82 are
provided in the pseudo-magnetic pole P2. When the slits 81 and
82 are provided in the pseudo-pole P2, the magnetic resistance
can be adjusted by utilizing magnetic saturation in a core
15 portion, and thus it is possible to control the distribution of
the magnetic flux flowing through the pseudo-magnetic pole P2.
By arranging the plurality of slits 81 and 82 in a symmetrical
manner with respect to the magnetic pole center line CL, the
magnetic flux distribution can be caused to approach a
20 symmetrical distribution with respect to the magnetic pole
center line CL.
[0052]
In particular, when the distance L2 (FIG. 3) from the
second slit 82 to the outer circumferential portion 20a is made
25 longer than the distance L1 (FIG. 3) from the first slit 81 to
the outer circumferential portion 20a, the magnetic flux
decreases as compared to the case where none of these slits are
provided, but a magnetic flux flowing from a region close to the
inter-pole portion M toward the pole center of the pseudo30
magnetic pole P2 can be generated as indicated by the arrow F in
FIG. 5.
[0053]
Thus, it is possible to achieve a sinusoidal magnetic flux
distribution in which the magnetic flux is concentrated on the
17
pole center of the pseudo-magnetic pole P2 and decreases toward
the inter-pole portion M. That is, a spatial harmonic of the
surface magnetic flux of the rotor 2 is suppressed, so that
torque ripple can be suppressed. Thus, noise of the motor 1 can
5 be reduced.
[0054]
The distance L2 (FIG. 3) from the second slit 82 to the
outer circumferential portion 20a is longer than the distance L1
(FIG. 3) from the first slit 81 to the outer circumferential
10 portion 20a, and the second slit 82 is on the inter-pole portion
side where the magnetic flux is more likely to be concentrated.
Thus, the magnetic flux concentratedly flowing through a region
close to the inter-pole portion M is blocked as little as
possible. Thus, a decrease in the magnetic flux interlinking
15 with the coil 55 (FIG. 1) of the stator 5 can be suppressed, and
thus the reduction in the output of the motor 1 is suppressed.
[0055]
The results of simulation illustrated in FIGS. 4 and 5 are
obtained in the case where the air hole is provided on the inner
20 side of the magnet insertion hole 21 in the radial direction,
but the influence of the presence or absence of the air hole is
negligible with regard to the effect of the slits 81 and 82 on
the surface magnetic flux of the rotor 2.
[0056]
25 FIG. 6 is a graph illustrating the distribution of the
magnetic flux of the rotor 2 (hereinafter simply referred to as
a rotor magnetic flux) interlinking with the coil 55 in the
motor 1 of the first embodiment and that in a motor of a
comparative example in comparison with each other. In FIG. 6,
30 the vertical axis represents the surface magnetic flux of the
rotor 2 and the horizontal axis represents an angle about the
pole center of the pseudo-magnetic pole P2. The motor of the
comparative example is configured in a similar manner to the
motor 1 of the first embodiment except that the distances L1 and
18
L2 from the slits 81 and 82 to the outer circumferential portion
20a satisfy L1 > L2.
[0057]
In FIG. 6, the solid line represents the distribution of
the rotor magnetic flux in the motor 1 of the 5 first embodiment
when L1 = 1 mm, L2 = 1.35 (therefore, L2/L1 = 1.35). The dashed
line represents the distribution of the rotor magnetic flux in
the motor of the comparative example when L1 = 1 mm, L2 = 0.75
(therefore, L1/L2 = 1.33). These values of L1 and L2 are
10 selected so that substantially the same value is obtained when a
longer distance of L1 and L2 is divided by a shorter distance of
L1 and L2.
[0058]
From FIG. 6, it is understood that the surface magnetic
15 flux of the rotor 2 in the motor 1 of the first embodiment is
higher than that in the motor of the comparative example. It is
understood that, particularly in the pole center of the pseudomagnetic
pole P2, the surface magnetic flux of the rotor 2 in
the motor 1 of the first embodiment is higher than that in the
20 motor of the comparative example.
[0059]
Next, the dimensions of the thin-wall portions 83 and 84
and the core region 85 will be described. As described above,
the thin-wall portion 83 between the two first slits 81 has the
25 width W1. The thin-wall portion 84 between the first slit 81
and the second slit 82 has the width W2. The core region 85
between the second slit 82 and the flux barrier 22 has the width
W3.
[0060]
30 FIG. 7 is a graph illustrating the relationship between
the ratio W3/W2 of the width W3 of the core region 85 to the
width W2 of the thin-wall portion 84 and the surface magnetic
flux of the rotor 2. From FIG. 7, it is understood that the
value of the surface magnetic flux of the rotor 2 is high
19
particularly when W3/W2 is in a range of 1 ≤ W3/W2 ≤ 2.2.
[0061]
This is because of the following reasons. Since the width
W3 of the core region 85 is greater than or equal to the width
W2 of the thin-wall portion 84 (i.e., 1 ≤ W3/5 W2), the magnetic
flux concentratedly flowing through the region close to the
inter-pole portion M is blocked as little as possible. Further,
since the width W2 of the thin-wall portion 84 is not extremely
narrow (i.e., W3/W2 ≤ 2.2), an increase in the magnetic
10 resistance of the thin-wall portion 84 can be suppressed.
[0062]
By suppressing a significant decrease in the surface
magnetic flux of the rotor 2 as above, the magnetic flux
interlinking with the coil 55 of the stator 5 is increased. As
15 a result, the reduction in the output of the motor 1 can be
suppressed.
[0063]
FIG. 8 is a graph illustrating the relationship between
the ratio W3/W1 of the width W3 of the core region 85 to the
20 width W1 of the thin-wall portion 83 and the surface magnetic
flux of the rotor 2. From FIG. 8, it is understood that the
surface magnetic flux of the rotor 2 is particularly high when
W3/W1 is in a range of 1 ≤ W3/W1 ≤ 2.1.
[0064]
25 This is because of the following reasons. Since the width
W3 of the core region 85 is greater than or equal to the width
W1 of the thin-wall portion 84 (i.e., 1 ≤ W3/W1), the magnetic
flux concentratedly flowing through the region close to the
inter-pole portion M is blocked as little as possible. Further,
30 since the width W1 of the thin-wall portion 83 is not extremely
narrow (i.e., W3/W1 ≤ 2.1), an increase in the magnetic
resistance of the thin-wall portion 83 can be suppressed.
[0065]
By suppressing a significant decrease in the surface magnetic
20
flux of the rotor 2 as above, the magnetic flux interlinking
with the coil 55 of the stator 5 is increased. As a result, the
reduction in the output of the motor 1 can be suppressed.
[0066]
In FIG. 3, the sum (W1+W2) of the width 5 W1 of the thinwall
portion 83 and the width W2 of the thin-wall portion 84 and
the width W3 of the core region 85 desirably satisfy W1 + W2 ≤
W3.
[0067]
10 By making the width W3 of the core region 85 greater than
or equal to the sum (W1 + W2) of the widths W1 and W2 of the
thin-wall portions 83 and 84, the magnetic flux flowing through
the region close to the inter-pole portion M is more likely to
flow toward the pole center of the pseudo-magnetic pole P2
15 through the core region 85. Thus, it is possible to enhance the
effect of causing the surface magnetic flux distribution of the
rotor 2 to approach the sinusoidal wave. Furthermore, the
magnetic flux interlinking with the coil 55 of the stator 5 is
increased by suppressing a significant decrease in the surface
20 magnetic flux of the rotor 2. As a result, the reduction in the
output of the motor 1 can be suppressed.
[0068]
In addition, the distance L2 between the second slit 82
and the outer circumferential portion 20a of the rotor 2 is
25 desirably greater than or equal to the sum (W1 + W2) of the
widths W1 and W2 of the thin-wall portions 83 and 83. In other
words, W1 + W2 ≤ L2 is desirably satisfied.
[0069]
With this configuration, a magnetic path from the core
30 region 85 toward the pole center of the pseudo-magnetic pole P2
via a magnetic path (indicated by the sign S in FIG. 3) on the
outer circumferential side of the second slit 82 is wider, and
the magnetic resistance therein is reduced, as compared with
magnetic paths toward the pole center of the pseudo-magnetic
21
pole P2 via the thin-wall portions 83 and 84. Thus, it is
possible to enhance the effect of causing the surface magnetic
flux distribution of the rotor 2 to approach the sinusoidal wave.
Furthermore, the magnetic flux interlinking with the coil 55 of
the stator 5 is increased by suppressing a significant 5 decrease
in the amount of the surface magnetic flux of the rotor 2. As a
result, the reduction in the output of the motor 1 can be
suppressed.
[0070]
10 FIG. 9 is an enlarged diagram illustrating a portion
including the pseudo-magnetic pole P2 of the rotor 2. In FIG. 8,
a length T1 is defined as the length of the thin-wall portion 84
between the first slit 81 and the second slit 82 in the
circumferential direction. The length T1 is desirably greater
15 than or equal to the width H2 of the second slit 82 in the
circumferential direction (i.e., T1  H2 is satisfied).
[0071]
The width H2 of the second slit 82 is equal to the length
of the magnetic path S on the outer side of the second slit 82
20 in the radial direction. When both of the thin-wall portion 84
and the magnetic path S on the outer side of the second slit 82
in the radial direction reach a magnetic saturation state at
which the magnetic flux density is, for example, 1.6 T, the
magnetic flux flows through the shorter one of the magnetic
25 paths in which the magnetic saturation occurs. Thus, when the
length T1 of the thin-wall portion 84 is longer than the width
H2 of the second slit 82, the magnetic flux flows more through
the magnetic path S on the outer side of the second slit 82 in
the radial direction than through the thin-wall portion 84.
30 [0072]
Therefore, the magnetic flux flowing through the region
close to the inter-pole portion M can be guided toward the pole
center of the pseudo-magnetic pole P2 through the magnetic path
S on the outer side of the second slit 82 in the radial
22
direction. As a result, the effect of causing the surface
magnetic flux distribution of the rotor 2 to approach the
sinusoidal wave can be enhanced, and the reduction in the output
of the motor 1 can be suppressed.
5 [0073]
FIG. 10 is a diagram for explaining the positions of the
slits 81 and 82 in the radial direction in the rotor 2. A
minimum distance D1 from the center axis C1 of the rotor 2 to
the magnet insertion hole 21 is desirably longer than a minimum
10 distance D2 from the center axis C1 to the second slit 82 (i.e.,
D1 > D2 is satisfied).
[0074]
The magnetic flux from the permanent magnet 25 flows
through an end portion of the magnet insertion hole 21 on the
15 inner side in the radial direction toward the pseudo-magnetic
pole P2. When the minimum distance D1 from the center axis C1
to the magnet insertion hole 21 is shorter than the minimum
distance D2 from the center axis C1 to the second slit 82 (i.e.,
D1 < D2 is satisfied), most of the magnetic flux emitted from
20 the permanent magnet 25 flows into the thin-wall portion 84.
This is because the first slit 81 is not present on a magnetic
path connecting the permanent magnet 25 and the thin-wall
portion 84 by the shortest distance.
[0075]
25 In contrast, as illustrated in FIG. 10, when the minimum
distance D1 from the center axis C1 to the magnet insertion hole
21 is longer than the minimum distance D2 from the center axis
C1 to the second slit 82, the magnetic flux emitted from the
permanent magnet 25 and flowing into the thin-wall portion 84 is
30 reduced. This is because the second slit 82 is present on the
magnetic path connecting the permanent magnet 25 and the thinwall
portion 84 by the shortest distance and the second slit 82
serves as a magnetic barrier.
[0076]
23
The magnetic flux flowing through the core region 85
increases with a decrease in the magnetic flux flowing into the
thin-wall portion 84. This results in an increase in the
magnetic flux flowing toward the pole center of the pseudomagnetic
pole P2 through the magnetic path S 5 on the outer side
of the second slit 82 in the radial direction. Thus, it is
possible to enhance the effect of causing the surface magnetic
flux distribution of the rotor 2 to approach the sinusoidal wave,
and to suppress the reduction in the output of the motor 1.
10 [0077]
(Configuration of Mold Motor)
FIG. 11 is a longitudinal sectional view illustrating a
mold motor to which the motor 1 of the first embodiment is
applied. The stator 5 is covered with a mold resin portion 60
15 to constitute a mold stator 6.
[0078]
The mold resin portion 60 is formed of, for example, a
thermosetting resin such as a bulk molding compound (BMC) or the
like. The mold resin portion 60 has an opening 62 on the left
20 side (a load side described later) in FIG. 11 and a bearing
supporting portion 61 on the opposite side to the opening 62 (a
counter-load side described later). The rotor 3 is inserted
through the opening 62 into a hollow portion inside the stator 5.
[0079]
25 A metal bracket 15 is mounted to the opening 62 of the
mold resin portion 60. One bearing 12 that supports the
rotation shaft 11 is held by the bracket 15. A cap 14 for
preventing water or the like from entering the bearing 12 is
mounted outside the bracket 15. The other bearing 13 that
30 supports the rotation shaft 11 is held by the bearing supporting
portion 61.
[0080]
The rotation shaft 11 protrudes from the stator 5 to the
left side in FIG. 11. For example, an impeller of a fan is
24
attached to a tip end 11a of the rotation shaft 11. Thus, the
protruding side (the left side in FIG. 11) of the rotation shaft
11 is referred to as the “load side”, and the opposite side
thereto (the right side in FIG. 11) is referred to as the
“5 counter-load side”.
[0081]
A board 7 is disposed on the counter-load side of the
stator 5. A magnetic sensor 71 and a drive circuit 72 for
driving the motor 1 are mounted on the board 7. The magnetic
10 sensor 71 is disposed so as to face a sensor magnet 26 attached
to the rotor 2. It is also possible to provide the drive
circuit 72 outside the motor 1 instead of on the board 7.
[0082]
Lead wires 73 are wired on the board 7. The lead wires 73
15 include power source lead wires for supplying power to the coil
55 of the stator 5 and sensor lead wires for transmitting a
signal from the magnetic sensor 71 to the outside. A lead wire
outlet part 74 for drawing out the lead wire 73 to the outside
is attached to an outer circumferential portion of the mold
20 resin portion 60.
[0083]
The resin portion 4 described above is provided on the
inner circumferential side of the rotor core 20, but covers both
end surfaces of the rotor core 20 in the axial direction. A
25 part of the resin portion 4 is desirably inserted into the
magnet insertion hole 31. Thus, the permanent magnet 25 can be
prevented from falling out of the magnet insertion hole 21.
[0084]
The sensor magnet (i.e., position detecting magnets) 36
30 having an annular shape is attached to the rotor core 20. The
sensor magnet 26 is disposed on the side of the rotor core 20
that faces the board 7 in the axial direction, and is held so
that the sensor magnet 26 is surrounded by the resin portion 4.
The sensor magnets 26 has magnetic poles the number of which is
25
the same as the number of poles of the rotor 2, and the magnetic
poles are arranged at equal intervals in the circumferential
direction. The magnetization direction of the sensor magnet 26
is the axial direction, but is not limited thereto.
5 [0085]
The magnetic sensor 71 is constituted by, for example, a
Hall IC and disposed so as to face the sensor magnet 26 of the
rotor 2. The magnetic sensor 71 detects a position (i.e., a
rotational position) of the rotor 2 in the circumferential
10 direction based on a change in the magnetic flux (N/S) from the
sensor magnet 26 and outputs a detection signal. The magnetic
sensor 71 is not limited to the Hall IC and may be a Magneto-
Resistive (MR) element, a Giant-Magneto-Resistive (GMR) element,
or a magnetic impedance element.
15 [0086]
The detection signal of the magnetic sensor 71 is output
to the drive circuit 72. In the case where the drive circuit 72
is disposed outside the motor 1, the detection signal of the
magnetic sensor 71 is output to the drive circuit 72 via the
20 sensor lead wire. The drive circuit 72 controls the current
applied to the coil 55 according to the rotational position of
the rotor 2 relative to the stator 5, based on the detection
signal from the magnetic sensor 71.
[0087]
25 An example in which the rotational position of the rotor 2
is detected using the sensor magnet 26 and the magnetic sensor
71 has been described, but it is also possible to perform
sensorless control in which the rotational position of the rotor
2 is estimated based on the current flowing through the coil 55
30 or the like.
[0088]
Moreover, a configuration in which the stator 5 is covered
with the mold resin portion 60 has been described, but it is
also possible to employ a configuration in which the stator 5 is
26
fixed by shrink-fitting into the inside of a shell.
[0089]
(Effects of Embodiment)
As described above, the rotor 2 of the first embodiment
includes the magnet magnetic pole P1 (i.e., 5 the first magnetic
pole) constituted by the permanent magnet 25 and the pseudomagnetic
pole P2 (i.e., the second magnetic pole) constituted by
the rotor core 20. The rotor 2 has the plurality of slits 81
and 82 in the pseudo-magnetic pole P2. The slits 81 and 82 are
10 symmetrically formed with respect to the magnetic pole center
line CL of the pseudo-magnetic pole P2. The distance L1 from
the first slit 81 to the outer circumferential portion 20a of
the rotor core 20 and the distance L2 from the second slit 82 to
the outer circumferential portion 20a of the rotor core 20
15 satisfy L1 < L2. With this configuration, the magnetic flux
flowing from the region close to the inter-pole portion M toward
the pole center of the pseudo-magnetic pole P2 can be increased.
[0090]
As a result, it is possible to cause the surface magnetic
20 flux distribution of the rotor 2 to approach the sinusoidal wave
in which the magnetic flux is concentrated on the pole center
and decreases toward the inter-pole portion M. Thus, a spatial
harmonic of the surface magnetic flux of the rotor 2 is
suppressed, and the torque ripple can be reduced. In other
25 words, noise of the motor 1 can be reduced. Since the magnetic
flux interlinking with the coil 55 of the stator 5 increases,
the reduction in the output of the motor 1 due to the provision
of the slits 81 and 82 can be suppressed.
[0091]
30 Since the two first slits 81 are provided on both sides of
the magnetic pole center line CL, the magnetic flux can be
guided toward the pole center of the pseudo-magnetic pole P2 via
the thin-wall portion 83 between the two first slits 81.
[0092]
27
The interval W1 between the two first slits 81 in the
circumferential direction (i.e., the width of the thin-wall
portion 83) and the interval W3 between the second slit 82 and
the magnet insertion hole 21 in the circumferential direction
(i.e., the width of the core region 85) satisfy 5 1 ≤ W3/W1 ≤ 2.
Thus, the magnetic flux flowing through the region close to the
inter-pole portion M is blocked as little as possible, and thus
the reduction in the output of the motor 1 can be suppressed.
[0093]
10 The interval W1 between the two first slits 81 in the
circumferential direction (i.e., the width of the thin-wall
portion 83), the interval W2 between the slits 81 and 82 in the
circumferential direction (i.e., the width of the thin-wall
portion 84), and the interval W3 between the second slit 82 and
15 the magnet insertion hole 21 in the circumferential direction
(i.e., the width of the core region 85) satisfy W1 + W2 < W3.
Thus, the magnetic flux is more likely to flow to the pole
center of the pseudo-magnetic pole P2 through the core region 85.
Thus, it is possible to enhance the effect of causing the
20 surface magnetic flux distribution of the rotor 2 to approach
the sinusoidal wave, and to suppress the reduction in the output
of the motor 1.
[0094]
The interval W1 between the two first slits 81 in the
25 circumferential direction (i.e., the width of the thin-wall
portion 83), the interval W2 between the slits 81 and 82 in the
circumferential direction (i.e., the width of the thin-wall
portion 84), and the distance L2 from the second slit 82 to the
outer circumferential portion 20a of the rotor core 20 satisfy
30 W1 + W2 < L2. Thus, the magnetic path reaching the pole center
of the pseudo-magnetic pole P2 through the core region 85 and
through the magnetic path S of the second slit 82 on the outer
circumferential side of the second slit 82 is widened, and the
magnetic resistance thereof is reduced. Thus, it is possible to
28
enhance the effect of causing the surface magnetic flux
distribution of the rotor 2 to approach the sinusoidal wave, and
to suppress the reduction in the output of the motor 1.
[0095]
The interval W2 between the slits 5 81 and 82 in the
circumferential direction (i.e., the width of the thin-wall
portion 84) and the interval W3 between the second slit 82 and
the magnet insertion hole 21 in the circumferential direction
(i.e., the width of the core region 85) satisfy 1 ≤ W3/W2 ≤ 2.2.
10 Thus, the magnetic flux flowing through the region close to the
inter-pole portion M is blocked as little as possible, and thus
the reduction in the output of the motor 1 can be suppressed.
[0096]
Since the length T1 of the thin-wall portion 84 between
15 the slits 81 and 82 in the radial direction and the width H2 of
the second slit 82 in the circumferential direction satisfy T1 >
H2, the magnetic flux flows more through the magnetic path S on
the outer side of the second slit 82 in the radial direction
than through the thin-wall portion 84. Thus, it is possible to
20 enhance the effect of causing the surface magnetic flux
distribution of the rotor 2 to approach the sinusoidal wave, and
to suppress the reduction in the output of the motor 1.
[0097]
Since the minimum distance D1 from the center axis C1 to
25 the magnet insertion hole 21 is longer than the minimum distance
D2 from the center axis C1 to the second slit 82, the magnetic
flux flowing through the core region 85 can be increased. Thus,
the magnetic flux flowing from the magnetic path S on the outer
side of the second slit 82 in the radial direction to the pole
30 center of the pseudo-magnetic pole P2 increases. As a result,
it is possible to enhance the effect of causing the surface
magnetic flux distribution of the rotor 2 to approach the
sinusoidal wave, and to suppress the reduction in the output of
the motor 1.
29
[0098]
Since the resin portion 4 formed of non-magnetic material
is provided between the rotation shaft 11 and the rotor core 20,
it is possible to suppress the leakage of the magnetic flux from
the rotor core 20 to the rotation shaft 11. Although 5 the resin
portion 4 is provided between the rotor core 20 and the rotation
shaft 11 in this example, it is also possible to fix the
rotation shaft 11 to a center hole of the rotor core 20 without
providing the resin portion 4.
10 [0099]
Second Embodiment
Next, a second embodiment of the present invention will be
described. A motor of the second embodiment differs from the
motor 1 of the first embodiment in the configuration of a rotor
15 2A. A stator of the motor of the second embodiment has a
configuration similar to that of the stator 5 of the motor 1 of
the first embodiment.
[0100]
(Configuration of Rotor)
20 FIG. 12 is a cross-sectional view illustrating the rotor
2A of the second embodiment. The rotor 2A has a rotor core 200
having a cylindrical shape about the center axis C1. The rotor
core 200 is formed of magnetic stack elements each having a
thickness of for example, 0.2 to 0.5 mm which are stacked in the
25 axial direction and fixed together by crimping or the like. The
stack element in this example is an electromagnetic steel sheet
that contains iron as a main component. The rotor core 200 may
be formed of a resin core that contains a combination of a soft
magnetic material and a resin. The diameter of the rotor 2A is
30 50 mm in this example.
[0101]
A plurality of magnet insertion holes 21 are formed along
an outer circumference of the rotor core 200. The number of
magnet insertion holes 21 is five in this example. A permanent
30
magnet 25 is disposed in each magnet insertion hole 21. The
shape and arrangement of the magnet insertion hole 21 are as
described in the first embodiment. The material and shape of
the permanent magnet 25 are as described in the first embodiment.
5 [0102]
A magnet magnetic pole P1 is formed by the permanent
magnet 25 disposed in each magnet insertion hole 21. A pseudomagnetic
pole P2 having an opposite polarity to that of the
permanent magnet 25 is formed between adjacent permanent magnets
10 25 in the rotor core 200. That is, the rotor 2A has five magnet
magnetic poles P1 and five pseudo-magnetic poles P2 which are
alternately arranged in the circumferential direction. Thus,
the number of poles of the rotor 2A is ten. The number of poles
of the rotor 2A is not limited to ten.
15 [0103]
The rotor core 200 has a center hole 28 at a center
thereof in the radial direction, and the rotation shaft 11 is
fixed to the center hole 28. That is, the rotor 2A of the
second embodiment does not have the resin portion 4 (FIG. 1)
20 described in the first embodiment. The material and shape of
the rotation shaft 11 are as described in the first embodiment.
An air hole 27 is provided on the inner side in the radial
direction with respect to the magnet insertion hole 21 in the
rotor core 200 as illustrated in FIG. 12, but it is also
25 possible to provide no air hole 27.
[0104]
The outer circumference of the rotor core 200 has a flower
shape as described in the first embodiment. That is, the outer
circumference of the rotor core 200 has outer circumferential
30 portions 20a whose centers are located at the pole centers of
the magnetic poles (the magnet poles P1 or pseudo-magnetic poles
P2), and outer circumferential portions 20b whose centers are
located at the inter-pole portions M. Both of the outer
circumferential portions 20a and 20b are arc-shaped portions,
31
and have the centers of curvature on the center axis C1 side,
but the outer circumferential portions 20a and 20b have
different radii of curvature.
[0105]
The flux barrier 22 described in the first 5 embodiment is
provided on each of both sides of the magnet insertion hole 21
in the circumferential direction. The flux barrier 22 in this
example is disposed on each of both ends of the magnet insertion
hole 21 in the circumferential direction, but may be disposed
10 only on one end of the magnet insertion hole 21 in the
circumferential direction.
[0106]
FIG. 13 is an enlarged diagram illustrating a portion
including the pseudo-magnetic pole P2 of the rotor 2A. The
15 rotor core 200 has a slit group 8 including a plurality of slits
81 and 82 in each pseudo-magnetic pole P2. In the second
embodiment, the slit group 8 has one first slit 81 located on
the magnetic pole center line CL of the pseudo-magnetic pole P2
and two second slits 82 formed on both sides of the first slit
20 81 in the circumferential direction.
[0107]
The first slit 81 is formed symmetrically with respect to
the magnetic pole center line CL of the pseudo-magnetic pole P2,
and the second slits 82 are formed symmetrically with respect to
25 the magnetic pole center line CL of the pseudo-magnetic pole P2.
More specifically, the first slit 81 is formed such that its
center in the circumferential direction is located on the
magnetic pole center line CL, and the first slit 81 has a
symmetric shape with respect to the magnetic pole center line CL.
30 The two second slits 82 are formed at symmetrical positions and
have symmetrical shapes with respect to the magnetic pole center
line CL.
[0108]
The first slit 81 has a shape elongated in the radial
32
direction. More specifically, the first slit 81 has an end
portion 81a on an outer side in the radial direction, an end
portion 81b on an inner side in the radial direction, and end
portions 81c and 81d on both sides in the circumferential
5 direction.
[0109]
The end portions 81a and 81b of the first slit 81 extend
perpendicularly to the magnetic pole center line CL. The end
portions 81c and 81d extend in parallel to the magnetic pole
10 center line CL. A length S1 of the first slit 81 (i.e., an
interval between the end portions 81a and 81b) is longer than a
width H1 of the first slit 81 (i.e., an interval between the end
portions 81c and 81d).
[0110]
15 The second slit 82 has a shape elongated in the radial
direction. More specifically, the second slit 82 has an end
portion 82a on an outer side in the radial direction, an end
portion 82b on an inner side in the radial direction, an end
portion 82c on an outer side in the circumferential direction
20 (i.e., on a side far from the magnetic pole center line CL), and
an end portion 82d on an inner side in the circumferential
direction (i.e., on a side close to the magnetic pole center
line CL).
[0111]
25 The end portion 82a of the second slit 82 extends along
the outer circumferential portion 20a, and the end portion 82b
extends perpendicularly to the magnetic pole center line CL.
The end portions 82c and 82d extend in parallel to the magnetic
pole center line CL. A length A2 of the second slit 82 (i.e.,
30 an interval between the end portions 82a and 82b) is longer than
a width H2 of the second slit 82 (i.e., an interval between the
end portions 82c and 82d).
[0112]
The length A1 of the first slit 81 is shorter than the
33
length A2 of the second slit 82. The width H1 of the first slit
81 is shorter than the width H2 of the second slit 82. That is,
a cross-sectional area of the first slit 81 is smaller than a
cross-sectional area of the second slit 82.
5 [0113]
A thin-wall portion 84 is formed between the first slit 81
and the second slit 82. The thin-wall portion 84 has a minimum
width W2 in the circumferential direction (i.e., a minimum
interval between the end portion 81c of the first slit 81 and
10 the side end portion 82d of the second slit 82). The width W2
of the thin-wall portion 84 is constant along the radial
direction in FIG. 13, but is not necessarily constant.
[0114]
A core region 85 is formed between the second slit 82 and
15 the flux barrier 22. The core region 85 has a width W3 between
the second slit 82 and an end of the flux barrier 22 closest to
the magnetic pole center line CL. The width W3 is the minimum
width of the core region 85 in the circumferential direction.
[0115]
20 A distance L1 is defined as the minimum distance between
the first slit 81 and the outer circumferential portion 20a
(i.e., the minimum distance between the end portion 81a of the
first slit 81 and the outer circumferential portion). A
distance L2 is defined as the minimum distance between the
25 second slit 82 and the outer circumferential portion 20a (i.e.,
the minimum distance between the end portion 82a of the second
slit 82 and the outer circumferential portion 20a). The
distances L1 and L2 satisfy the relationship of L1 < L2.
[0116]
30 (Action)
Next, the action of the second embodiment will be
described. With a configuration in which the gap between the
rotor 2A and the stator 5 is minimum at the pole center of each
of the magnetic poles (the magnet magnetic poles P1 and the
34
pseudo-magnetic poles P2) and increases as a distance from the
pole center increase as described in the first embodiment, the
magnetic flux is concentrated on the pole center. Thus, the
surface magnetic flux distribution of the rotor 2A approaches
the 5 sinusoidal wave.
[0117]
In the rotor 2A, a degree of freedom of the magnetic flux
flowing through the pseudo-magnetic pole P2 is high, and thus
the surface magnetic flux of the rotor 2A significantly changes
10 depending on the rotational position of the rotor 2A relative to
the stator 5. Thus, by providing the slits 81 and 82 in the
rotor 2A to restrict the degree of freedom of the magnetic flux,
the effect of causing the surface magnetic flux distribution of
the rotor 2A to approach the sinusoidal wave can be enhanced.
15 [0118]
In particular, since the distance L2 from the second slit
82 to the outer circumferential portion 20a is longer than the
distance L1 from the first slit 81 to the outer circumferential
portion 20a, the magnetic flux flowing from the region close to
20 the inter-pole portion M toward the pole center of the pseudomagnetic
pole P2 can be increased. Thus, the surface magnetic
flux distribution of the rotor 2A approaches the sinusoidal wave,
and a spatial harmonic can be suppressed. Thus, the torque
ripple can be suppressed, and noise of the motor 1 is reduced.
25 [0119]
Since the magnetic flux flowing from the region close to
the inter-pole portion M toward the pole center of the pseudomagnetic
pole P2 increases, the magnetic flux interlinking with
the coil 55 (FIG. 1) of the stator 5 increases, and thus the
30 reduction in the output of the motor 1 can be suppressed. That
is, noise of the motor 1 can be reduced and the reduction in the
output of the motor can be suppressed.
[0120]
Next, the dimensions of the thin-wall portion 84 and the
35
core region 85 will be described. As described above, the thinwall
portion 84 between the first slit 81 and the second slit 82
has the width W2. The core region 85 between the second slit 82
and the flux barrier 22 has the width W3.
5 [0121]
As described in the first embodiment, when W3/W2 is in the
range of 1 ≤ W3/W2 ≤ 2.2, the surface magnetic flux of the rotor
2A becomes especially high. That is, since the width W3 of the
core region 85 is greater than or equal to the width W2 of the
10 thin-wall portion 84, the magnetic flux flowing through the
region close to the inter-pole portion M is blocked as little as
possible. Further, since the width W2 of the thin-wall portion
84 is not extremely narrow, an increase in the magnetic
resistance of the thin-wall portion 84 can be suppressed.
15 [0122]
In addition, the distance L2 between the second slit 82
and the outer circumferential portion 20a of the rotor 2A is
desirably greater than or equal to the width W2 of the thin-wall
portion 84 (i.e., W2 ≤ L2 is satisfied). With this
20 configuration, the magnetic path from the core region 85 toward
the pole center of the pseudo-magnetic pole P2 via the magnetic
path S on the outer circumferential side of the second slit 82
is wider than the magnetic path toward the pole center of the
pseudo-magnetic pole P2 via the thin-wall portion 84, and thus
25 the magnetic resistance is reduced. Thus, it is possible to
enhance the effect of causing the surface magnetic flux
distribution of the rotor 2A to approach the sinusoidal wave,
and to suppress the reduction in the magnetic force.
[0123]
30 A length T1 is defined as the length of the thin-wall
portion 84 between the first slit 81 and the second slit 82 in
the circumferential direction. The length T1 is desirably
greater than or equal to the width H2 of the second slit 82 in
the circumferential direction (i.e., T1  H2 is satisfied).
36
[0124]
As described in the first embodiment, when both the thinwall
portion 84 and the magnetic path S on the outer side of the
second slit 82 in the radial direction reach the magnetic
saturation state, the magnetic flux flows through 5 the shorter
one of the magnetic paths in which the magnetic saturation
occurs. Thus, when the length T1 of the thin-wall portion 84 is
longer than the width H2 of the second slit 82, the magnetic
flux flows more through the magnetic path S on the outer side of
10 the second slit 82 in the radial direction than through the
thin-wall portion 84. Therefore, the magnetic flux flowing
through the region close to the inter-pole portion M can be
guided toward the pole center of the pseudo-magnetic pole P2
through the magnetic path S on the outer side of the second slit
15 82 in the radial direction. As a result, the effect of causing
the surface magnetic flux distribution of the rotor 2A to
approach the sinusoidal wave can be enhanced, and the reduction
in the magnetic force can be suppressed.
[0125]
20 The minimum distance D1 from the center axis C1 of the
rotor 2A to the magnet insertion hole 21 is desirably longer
than the minimum distance D2 from the center axis C1 to the
second slit 82 (i.e., D1 > D2 is satisfied). The magnetic flux
emitted from the permanent magnet 25 and flowing into the thin25
wall portion 84 is reduced. This is because the second slit 82
is present on the magnetic path connecting the permanent magnet
25 and the thin-wall portion 84 by the shortest distance, and
the second slit 82 serves as a magnetic barrier.
[0126]
30 The magnetic flux flowing through the core region 85
increases as the magnetic flux flowing into the thin-wall
portion 84 decreases. This results in an increase in the
magnetic flux flowing toward the pole center of the pseudomagnetic
pole P2 through the magnetic path S on the outer side
37
of the second slit 82 in the radial direction. Thus, it is
possible to enhance the effect of causing the surface magnetic
flux distribution of the rotor 2A to approach the sinusoidal
wave, and to suppress the reduction in the magnetic force.
5 [0127]
(Effects of Embodiment)
As described above, in the second embodiment, there are
three slits 81 and 82 in the rotor 2A, and the first slit 81 is
located on the magnetic pole center line CL. As in the first
10 embodiment, the distance L1 from the first slit 81 to the outer
circumferential portion 20a of the rotor core 200 and the
distance L2 from the second slit 82 to the outer circumferential
portion 20a of the rotor core 200 satisfy L1 < L2. Thus, the
magnetic flux flowing toward the pole center of the pseudo15
magnetic pole P2 from the region close to the inter-pole portion
M can be increased.
[0128]
Thus, it is possible to cause the surface magnetic flux
distribution of the rotor 2A to approach the sinusoidal wave.
20 Consequently, a spatial harmonic of the surface magnetic flux of
the rotor 2A is suppressed, so that the torque ripple can be
reduced. In other words, noise of the motor 1 can be reduced.
Since the magnetic flux interlinking with the coil 55 of the
stator 5 increases, the reduction in the magnetic force due to
25 the provision of the slits 81 and 82 can be suppressed.
[0129]
A configuration in which the rotation shaft 11 is fixed to
the center hole 28 of the rotor core 200 of the rotor 2A has
been described, but the resin portion 4 (FIG. 1) may be provided
30 between the rotor core 200 and the rotation shaft 11 as
described in the first embodiment.
[0130]
Although the pseudo-magnetic pole P2 is provided with the
four slits in the first embodiment and the three slits in the
38
second embodiment, the pseudo-magnetic pole P2 may be provided
with five or more slits.
[0131]
(Air Conditioner)
Next, an air conditioner to which the motor 5 of each of the
above-described embodiments is applicable will be described.
FIG. 14(A) is a diagram illustrating a configuration of an air
conditioner 500 to which the motor of each embodiment is
applicable. The air conditioner 500 includes an outdoor unit
10 501, an indoor unit 502, and a refrigerant pipe 503 connecting
these units. The outdoor unit 501 has a fan (an outdoor fan)
510.
[0132]
FIG. 14(B) is a cross-sectional view taken along the line
15 14B-14B illustrated in FIG. 14(A). The outdoor unit 501 has a
housing 508 and a frame 509 fixed in the housing 508. The motor
1 serving as a drive source of the fan 510 is fixed to the frame
509. An impeller (blade portion) 511 is attached to the
rotation shaft 11 of the motor 1 via a hub 512.
20 [0133]
FIG. 15 is a schematic diagram illustrating a refrigerant
circuit in the air conditioner 500. The air conditioner 500
includes a compressor 504, a condenser 505, a throttle device (a
decompression device) 506, and an evaporator 507. The
25 compressor 504, the condenser 505, the throttle device 506, and
the evaporator 507 are connected together by the refrigerant
pipe 503 to constitute a refrigeration cycle. That is,
refrigerant circulates through the compressor 504, the condenser
505, the throttle device 506, and the evaporator 507 in this
30 order.
[0134]
The compressor 504, the condenser 505, and the throttle
device 506 are provided in the outdoor unit 501. The evaporator
507 is provided in the indoor unit 502. A fan (an indoor fan)
39
520 that supplies indoor air to the evaporator 507 is provided
in the indoor unit 502.
[0135]
The operation of the air conditioner 500 is as follows.
The compressor 504 compresses sucked refrigerant 5 and sends out
the compressed refrigerant. The condenser 505 exchanges heat
between the refrigerant flowing in from the compressor 504 and
the outdoor air to condense and liquefy the refrigerant, and
sends out the liquefied refrigerant to the refrigerant pipe 503.
10 The fan 510 of the outdoor unit 501 releases the heat dissipated
when the refrigerant is condensed in the condenser 505, to the
outside of a room. The throttle device 506 adjusts the pressure
or the like of the refrigerant flowing through the refrigerant
pipe 503.
15 [0136]
The evaporator 507 exchanges heat between the refrigerant
brought into a low-pressure state by the throttle device 506 and
the indoor air to cause the refrigerant to take heat from the
indoor air and evaporate (vaporize), and then sends out the
20 evaporated refrigerant to the refrigerant pipe 503. The fan 520
of the indoor unit 502 supplies the indoor air to the evaporator
507. Thus, cooled air deprived of heat at the evaporator 507 is
supplied to the interior of the room.
[0137]
25 The motor 1 of each of the above-described embodiments is
configured to suppress demagnetization of the permanent magnets
25. Thus, by using the motor 1 as the power source of the fan
510, the operation efficiency of the air conditioner 500 can be
enhanced for a long time, and energy consumption can be reduced.
30 [0138]
Although the motor 1 of each embodiment is used as the
drive source of the fan 510 (i.e., the outdoor fan) in this
example, the motor 1 of each embodiment may be used as a drive
source of a fan 520 (i.e., the indoor fan). The motor 1 of each
40
embodiment is not limited to the drive source for the fan and
may be used as, for example, a drive source for the compressor
504.
[0139]
The motor 1 of each embodiment is not limited 5 to the motor
for the air conditioner 500 and may be used as motors for
ventilation fans, home appliances or machine tools, for example.
[0140]
Although the desirable embodiments of the present
10 invention have been described in detail, the present invention
is not limited to the above-described embodiments, and various
modifications or changes can be made without departing from the
scope of the present invention.
DESCRIPTION OF REFERENCE CHARACTERS
15 [0141]
1 motor; 2, 2A rotor; 4 resin portion (supporting
portion); 5 stator; 6 mold stator; 7 board; 8 slit group; 10
air gap; 11 rotation shaft; 20, 200 rotor core; 20a outer
circumferential portion (first outer circumferential portion);
20 20b outer circumferential portion (second outer circumferential
portion); 21 magnet insertion hole; 22 flux barrier; 23 inner
circumference; 25 permanent magnet; 26 sensor magnet (position
detecting magnet); 28 center hole; 41 inner cylindrical
portion; 42 connecting portion; 43 outer cylindrical portion;
25 50 stator core; 50a outer circumference; 50b inner
circumference; 51 tooth; 52 yoke; 53 slot; 54 insulator; 55
coil; 60 mold resin portion; 81 first slit; 82 second slit; 83
thin-wall portion (pole-center thin-wall portion); 84 thinwall
portion (inter-slit thin-wall portion); 85 core region;
30 101 drive device; 102 converter; 103 inverter; 105 controller;
106 CPU; 107 inverter drive circuit; 108 current detection
circuit; 500 air conditioner; 501 outdoor unit; 502 indoor
unit; 503 refrigerant pipe; 504 compressor; 505 condenser; 506
throttle device; 507 evaporator; 510 fan (outdoor fan); 511
41
impeller (blade portion); 520 fan (indoor fan).
42
We Claim :
1. A rotor comprising:
a rotor core having an outer circumference of an annular
shape surrounding a center axis and a magnet 5 insertion hole
formed along the outer circumference; and
a permanent magnet disposed in the magnet insertion hole,
wherein the permanent magnet constitutes a first magnetic
pole, and a part of the rotor core constitutes a second magnetic
10 pole;
wherein the rotor core has a plurality of slits in the
second magnetic pole;
wherein the plurality of slits are symmetrically formed
with respect to a magnetic pole center line connecting a pole
15 center of the second magnetic pole and the center axis;
wherein, on one side of the magnetic pole center line in a
circumferential direction about the center axis, the plurality
of slits have a first slit closest to the magnetic pole center
line and a second slit adjacent to the first slit in the
20 circumferential direction; and
wherein a minimum distance L1 from the first slit to the
outer circumference of the rotor core and a minimum distance L2
from the second slit to the outer circumference of the rotor
core satisfy L1 < L2.
25
2. The rotor according to claim 1, wherein the first slit is
formed on the magnetic pole center line.
3. The rotor according to claim 1, wherein the plurality of
30 slits have another first slit formed symmetrically to the first
slit with respect to the magnetic pole center line, on the other
side of the magnetic pole center line in the circumferential
direction.
43
4. The rotor according to claim 3, wherein an interval W1
between the first slit and the another first slit in the
circumferential direction and an interval W3 between the second
slit and the magnet insertion hole in the circumferential
direction satisfy 5 1 ≤ W3/W1 ≤ 2.1.
5. The rotor according to claim 3 or 4, wherein an interval
W1 between the first slit and the another first slit in the
circumferential direction, an interval W2 between the first slit
10 and the second slit in the circumferential direction, and an
interval W3 between the second slit and the magnet insertion
hole in the circumferential direction satisfy W1 + W2 < W3.
6. The rotor according to claim 4 or 5, wherein the interval
15 W1, the interval W2, and the minimum distance L2 satisfy W1 + W2
< L2.
7. The rotor according to any one of claims 1 to 6, wherein
an interval W2 between the first slit and the second slit in the
20 circumferential direction, and
wherein an interval W3 between the second slit and the
magnet insertion hole in the circumferential direction satisfy
1 ≤ W3/W2 ≤ 2.2.
25 8. The rotor according to any one of claims 1 to 7, wherein
the rotor core has a thin-wall portion between the first slit
and the second slit, and
wherein a length T1 of the thin-wall portion in a radial
direction about the center axis and a width H2 of the second
30 slit in the circumferential direction satisfy T1 > H2.
9. The rotor according to any one of claims 1 to 8, wherein a
minimum distance from the center axis to the magnet insertion
hole is longer than a minimum distance from the center axis to
44
the second slit.
10. The rotor according to any one of claims 1 to 9, wherein
an outer circumference of the rotor core has a first outer
circumferential portion extending through a 5 pole center of the
first magnetic pole, a second outer circumferential portion
extending through a pole center of the second magnetic pole, and
a third outer circumferential portion formed between the first
outer circumferential portion and the second outer
10 circumferential portion, and
wherein a maximum distance from the center axis to the
third outer circumferential portion is shorter than a maximum
distance from the center axis to the first outer circumferential
portion and shorter than a maximum distance from the center axis
15 to the second outer circumferential portion.
11. The rotor according to any one of claims 1 to 10, further
comprising:
a rotation shaft; and
20 a supporting portion provided between the rotation shaft
and the rotor core and formed of non-magnetic material.
12. A motor comprising:
the rotor according to any one of claims 1 to 11; and
25 a stator surrounding the rotor from an outer side in a
radial direction about the center axis.
13. A fan comprising:
the motor according to claim 12; and
30 a blade portion driven to rotate by the motor.
14. An air conditioner comprising an outdoor unit, an indoor
unit, and a refrigerant pipe connecting the outdoor unit and the
indoor unit,
45
at least one of the outdoor unit and the indoor unit
comprising the fan according to claim 13.