FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
ROTOR, ELECTRIC MOTOR, AIR BLOWER, AIR CONDITIONER, AND METHOD
FOR FABRICATING ROTOR
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
ROTOR, ELECTRIC MOTOR, AIR BLOWER, AIR CONDITIONER, AND METHOD
5 FOR FABRICATING ROTOR
TECHNICAL FIELD
[0001]
The present invention relates to a rotor for use in an
electric motor.
10 BACKGROUND ART
[0002]
A rotor having two types of magnets is generally used as
a rotor for use in an electric motor (see, for example, Patent
Reference 1). In Patent Reference 1, permanent magnets having
15 high magnetic force (also referred to as first permanent
magnets) form the entire outer peripheral surface of the rotor,
and permanent magnets having lower magnetic force than that of
the first permanent magnets (also referred to as second
permanent magnets) are disposed at the inner side of the first
20 permanent magnets. In this rotor, since the first permanent
magnets form the entire outer peripheral surface of the rotor,
magnetic force of the rotor can be effectively enhanced.
PRIOR ART REFERENCE
PATENT REFERENCE
25 [0003]
Patent Reference 1: Japanese Patent Application
Publication No. 2005-151757
SUMMARY OF THE INVENTION
PROBLEM TO BE SOLVED BY THE INVENTION
30 [0004]
In the case where the first permanent magnet having high
magnetic force form the entire outer peripheral surface of the
rotor, however, sufficient magnetic force of the rotor can be
obtained, but there is a problem in that the cost of the rotor
3
increases because of high price of a magnet having high
magnetic force.
[0005]
It is therefore an object of the present invention to
5 obtain sufficient magnetic force of a rotor even with reduction
of the amount of first permanent magnet having high magnetic
force.
MEANS OF SOLVING THE PROBLEM
[0006]
10 A rotor according to an aspect of the present invention
is a rotor having 2n (n is a natural number) magnetic poles and
including: at least one first permanent magnet forming part of
an outer peripheral surface of the rotor and magnetized to have
polar anisotropy; and at least one second permanent magnet that
15 is a different type from the at least one first permanent
magnet, is adjacent to the at least one first permanent magnet
in a circumferential direction of the rotor, has lower magnetic
force than magnetic force of the at least one first permanent
magnet, and is magnetized to have polar anisotropy.
20 A rotor according to another aspect of the present
invention is a rotor having 2n (n is a natural number) magnetic
poles and including a plurality of layered magnets composed of
two to m (m is a natural number and a divisor for n) layers
that are stacked in an axial direction, wherein each layered
25 magnet of the plurality of layered magnets includes at least
one first permanent magnet forming part of an outer peripheral
surface of the rotor and magnetized to have polar anisotropy,
and at least one second permanent magnet that is a different
type from the at least one first permanent magnet, is adjacent
30 to the at least one first permanent magnet in a circumferential
direction of the rotor, has lower magnetic force than magnetic
force of the at least one first permanent magnet, and is
magnetized to have polar anisotropy, and in each first
permanent magnet of the plurality of layered magnets, supposing
4
one cycle is an angle formed by adjacent north poles in a plane
orthogonal to the axial direction of the rotor, positions of
north poles of two first permanent magnets adjacent to each
other in the axial direction are shifted from each other by n/m
5 cycles in the circumferential direction.
EFFECTS OF THE INVENTION
[0007]
According to the present invention, even when the amount
of first permanent magnet having high magnetic force is reduced,
10 sufficient magnetic force of the rotor can be obtained.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008]
FIG. 1 is a side view schematically illustrating a
structure of a rotor according to a first embodiment of the
15 present invention.
FIG. 2 is a plan view schematically illustrating the
structure of the rotor.
FIG. 3 is a cross-sectional view schematically
illustrating the structure of the rotor.
20 FIG. 4 is a cross-sectional view schematically
illustrating the structure of the rotor.
FIG. 5 is a diagram showing a length of a first permanent
magnet in an axial direction of the rotor.
FIG. 6 is a flowchart depicting an example of a process
25 for fabricating the rotor.
FIG. 7 is a diagram illustrating an example of a molding
process of a second permanent magnet.
FIG. 8 is a diagram illustrating an example of the
molding process of the second permanent magnet.
30 FIG. 9 is a cross-sectional view schematically
illustrating a structure of a rotor according to a comparative
example.
FIG. 10 is a diagram showing a magnetic flux density
distribution on an outer peripheral surface of the rotor and
5
corresponding to a vicinity of a cross section of the rotor
illustrated in FIG. 2.
FIG. 11 is a diagram showing a magnetic flux density
distribution on the outer peripheral surface of the rotor and
5 corresponding to a vicinity of the cross section of the rotor
illustrated in FIG. 3.
FIG. 12 is a diagram showing a magnetic flux density
distribution on the outer peripheral surface of the rotor and
corresponding to a vicinity of the cross section of the rotor
10 illustrated in FIG. 4.
FIG. 13 is a diagram showing a magnetic flux density
distribution on the outer peripheral surface of the entire
rotor.
FIG. 14 illustrates a position at which a magnetic flux
15 density distribution on the outer peripheral surface of the
rotor according to the first embodiment is detected.
FIG. 15 is a diagram illustrating a position at which a
magnetic flux density distribution on the outer peripheral
surface of a rotor according to a comparative example is
20 detected.
FIG. 16 is a side view schematically illustrating a
structure of a rotor according to a first variation.
FIG. 17 is a plan view schematically illustrating the
structure of the rotor according to the first variation.
25 FIG. 18 is a cross-sectional view schematically
illustrating the structure of the rotor according to the first
variation.
FIG. 19 is a cross-sectional view schematically
illustrating the structure of the rotor according to the first
30 variation.
FIG. 20 is a diagram illustrating an example of a process
for fabricating the rotor according to the first variation.
FIG. 21 is a diagram illustrating an example of the
process for fabricating the rotor according to the first
6
variation.
FIG. 22 is a cross-sectional view schematically
illustrating a structure of a rotor according to a second
variation.
5 FIG. 23 is a plan view schematically illustrating a
structure of a rotor according to a third variation.
FIG. 24 is a side view schematically illustrating the
structure of the rotor according to the third variation.
FIG. 25 is a cross-sectional view schematically
10 illustrating the structure of the rotor according to the third
variation.
FIG. 26 is a plan view schematically illustrating a
structure of a rotor according to a fourth variation.
FIG. 27 is a side view schematically illustrating the
15 structure of the rotor according to the fourth variation.
FIG. 28 is a cross-sectional view schematically
illustrating the structure of the rotor according to the fourth
variation.
FIG. 29 is a plan view schematically illustrating a
20 structure of a rotor according to a fifth variation.
FIG. 30 is a side view schematically illustrating the
structure of the rotor according to the fifth variation.
FIG. 31 is a cross-sectional view schematically
illustrating a structure of a rotor according to a sixth
25 variation.
FIG. 32 is a side view schematically illustrating the
structure of the rotor according to the sixth variation.
FIG. 33 is a cross-sectional view schematically
illustrating a structure of a rotor according to a seventh
30 variation.
FIG. 34 is a side view schematically illustrating the
structure of the rotor according to the seventh variation.
FIG. 35 is a plan view schematically illustrating a
structure of a rotor according to an eighth variation.
7
FIG. 36 is a side view schematically illustrating the
structure of the rotor according to the eighth variation.
FIG. 37 is a plan view schematically illustrating a
structure of a rotor according to a ninth variation.
5 FIG. 38 is a side view schematically illustrating the
structure of the rotor according to the ninth variation.
FIG. 39 is a plan view schematically illustrating a
structure of a rotor according to a tenth variation.
FIG. 40 is a side view schematically illustrating the
10 structure of the rotor according to the tenth variation.
FIG. 41 is a partial cross-sectional view schematically
illustrating a structure of an electric motor according to a
second embodiment of the present invention.
FIG. 42 is a diagram schematically illustrating a
15 structure of a fan according to a third embodiment of the
present invention.
FIG. 43 is a diagram schematically illustrating a
configuration of an air conditioner according to a fourth
embodiment of the present invention.
20 MODE FOR CARRYING OUT THE INVENTION
[0009]
FIRST EMBODIMENT
In an xyz orthogonal coordinate system shown in each
drawing, a z-axis direction (z axis) represents a direction
25 parallel to an axis Ax of a rotor 2, an x-axis direction (x
axis) represents a direction orthogonal to the z-axis direction
(z axis), and a y-axis direction (y axis) represents a
direction orthogonal to both the z-axis direction and the xaxis direction. The axis Ax is a rotation center of the rotor
30 2. The axis Ax also represents an axis of an electric motor 1
described later. A direction parallel to the axis Ax is also
referred to as an “axial direction of the rotor 2” or simply as
an “axial direction.” The “radial direction” is a radial
direction of the rotor 2 or a stator 3, and a direction
8
orthogonal to the axis Ax. An xy plane is a plane orthogonal
to the axial direction. An arrow D1 represents a
circumferential direction about the axis Ax.
[0010]
5 In some drawings, “N” and “S” respectively represent a
north pole and a south pole in the rotor 2 (including
variations).
[0011]
FIG. 1 is a side view schematically illustrating a
10 structure of the rotor 2 according to a first embodiment of the
present invention. In FIG. 1, broken lines represent positions
of magnetic poles (north poles or south poles) of the rotor 2.
FIG. 2 is a plan view schematically illustrating the
structure of the rotor 2.
15 FIGS. 3 and 4 are cross-sectional views schematically
illustrating the structure of the rotor 2.
FIG. 2 is a plan view taken along line C2-C2 in FIG. 1.
FIG. 3 is a cross-sectional view taken along line C3-C3 in FIG.
1. FIG. 4 is a cross-sectional view taken along line C4-C4 in
20 FIG. 1.
In FIGS. 2 through 4, arrows on the rotor 2 represent
directions of main magnetic flux.
[0012]
The rotor 2 is used for an electric motor (e.g., the
25 electric motor 1 described later).
[0013]
The rotor 2 includes at least one first permanent magnet
21 and at least one second permanent magnet 22 that is a
different type from the first permanent magnet 21.
30 [0014]
The “at least one first permanent magnet 21” includes two
or more first permanent magnets 21. The “at least one second
permanent magnet 22” includes two or more second permanent
magnets 22.
9
[0015]
The rotor 2 has 2n (n is a natural number) magnetic poles.
In this embodiment, n is 4, and the rotor 2 has eight magnetic
poles. In this embodiment, the rotor 2 includes eight first
5 permanent magnets 21 and one second permanent magnet 22. For
example, as illustrated in FIG. 1, the north poles of the first
permanent magnets 21 and the south poles of the first permanent
magnets 21 are alternately arranged on the outer peripheral
surface of the rotor 2. It should be noted that the plurality
10 of first permanent magnets 21 may be coupled to each other by,
for example, ring-shaped coupling parts, and the second
permanent magnet 22 may be divided into a plurality of parts.
[0016]
Each first permanent magnet 21 forms part of the outer
15 peripheral surface of the rotor 2. Each first permanent magnet
21 is magnetized to have polar anisotropy. In other words,
each first permanent magnet 21 is magnetized so that the rotor
2 has polar anisotropy. Each first permanent magnet 21 is a
rare earth magnet. For example, each first permanent magnet 21
20 is a bonded magnet as a mixture of a rare earth magnet and a
resin, that is, a rare earth bonded magnet. Each first
permanent magnet 21 has higher magnetic force than that of the
second permanent magnet 22.
[0017]
25 The rare earth magnet is, for example, a magnet
containing neodymium (Nd)- iron (Fe)- boron (B) or a magnet
containing samarium (Sm)- iron (Fe)- nitrogen (N). The resin
is, for example, a nylon resin, a polyphenylene sulfide (PPS)
resin, or an epoxy resin.
30 [0018]
The second permanent magnet 22 is adjacent to the first
permanent magnets 21 in the circumferential direction of the
rotor 2, and forms part of the outer peripheral surface of the
rotor 2. Specifically, part of the second permanent magnet 22
10
is adjacent to the first permanent magnets 21 in the
circumferential direction of the rotor 2, and another part of
the second permanent magnet 22 is located on the inner side
with respect to the first permanent magnets 21 in the radial
5 direction of the rotor 2. Thus, the second permanent magnet 22
is a ring-shaped magnet.
[0019]
In the examples illustrated in FIGS. 1 and 2, on the
outer peripheral surface of the rotor 2, the plurality of first
10 permanent magnets 21 and a plurality of parts of the second
permanent magnet 22 are alternately arranged in the
circumferential direction of the rotor 2.
[0020]
The second permanent magnet 22 is magnetized to have
15 polar anisotropy. In other words, the second permanent magnet
22 is magnetized so that the rotor 2 has polar anisotropy. In
this embodiment, the second permanent magnet 22 is a single
integral magnet. The second permanent magnet 22 constitutes
magnetic poles in the rotor 2 together with the first permanent
20 magnets 21.
[0021]
The second permanent magnet 22 is a magnet that is a
different type from the first permanent magnets 21. The second
permanent magnet 22 is a ferrite magnet. For example, the
25 second permanent magnet 22 is a bonded magnet as a mixture of a
ferrite magnet and a resin, that is, a ferrite bonded magnet.
The resin is, for example, a nylon resin, a polyphenylene
sulfide (PPS) resin, or an epoxy resin.
The second permanent magnet 22 has lower magnetic force
30 than that of each first permanent magnet.
[0022]
In the xy plane, the inner peripheral surfaces and the
outer peripheral surfaces of the first permanent magnets 21 are
concentrically formed. That is, the thickness of the first
11
permanent magnets 21 in the xy plane is uniform in the
circumferential direction.
[0023]
FIG. 5 is a diagram showing a length of the first
5 permanent magnets 21 in the axial direction of the rotor 2.
The length of the first permanent magnets 21 in the axial
direction of the rotor 2 is longest at a center P1 of the first
permanent magnets 21 in the circumferential direction of the
rotor 2. The center P1 of the first permanent magnets 21 in
10 the circumferential direction of the rotor 2 is located on the
magnetic pole center of the rotor 2 in the xy plane. That is,
as illustrated in FIG. 5, a length L1 at the center P1 is
longest in the first permanent magnets 21.
[0024]
15 As illustrated in FIG. 5, the length of the first
permanent magnets 21 in the axial direction of the rotor 2
gradually decreases with being away from the center P1 along
the circumferential direction. For example, as illustrated in
FIG. 1, a length L2 at a position P2 away from the center P1 in
20 the circumferential direction is smaller than the length L1.
In other words, the length of the first permanent magnets 21 in
the axial direction gradually decreases toward an inter-pole
part from a magnetic pole center part (i.e., the center P1).
The inter-pole part is located at the center of two magnetic
25 poles (i.e., a north pole and a south pole) adjacent to each
other in the circumferential direction.
[0025]
An example of a method for fabricating the rotor 2 will
be described.
30 FIG. 6 is a flowchart depicting an example of a process
for fabricating the rotor 2.
FIGS. 7 and 8 are diagrams illustrating an example of a
molding process of the second permanent magnet 22.
[0026]
12
In a first step S1, a magnetic field having polar
anisotropy is generated inside a mold M11 for the second
permanent magnet 22 by using a magnet for magnetization.
[0027]
5 In a second step S2, the second permanent magnet 22 is
molded. Specifically, in the mold M11, the second permanent
magnet 22 is molded by injection molding (FIG. 7). In this
manner, the second permanent magnet 22 magnetized to have polar
anisotropy is molded. In addition, as illustrated in FIG. 8,
10 the mold M11 is pulled out and consequently the second
permanent magnet 22 magnetized to have polar anisotropy is
obtained.
[0028]
Since a mold corresponding to the shape of each first
15 permanent magnet 21 is formed in the mold M11, the shape of the
first permanent magnets 21 is molded on the outer peripheral
surface of the second permanent magnet 22 concurrently with
obtainment of the second permanent magnet 22.
[0029]
20 In a third step S3, a magnetic field having polar
anisotropy is generated inside the mold for the first permanent
magnets 21 by using a magnet for magnetization.
[0030]
In a fourth step S4, one or more first permanent magnets
25 21 are molded. Specifically, one or more first permanent
magnets 21 are molded by injection molding on the outer
peripheral surface of the second permanent magnet 22 so that
the one or more first permanent magnets 21 form part of the
outer peripheral surface of the rotor 2, in the state where the
30 second permanent magnet 22 is disposed inside the mold for the
first permanent magnets 21. In this manner, one or more first
permanent magnets 21 magnetized to have polar anisotropy are
molded and thus the rotor 2 is obtained.
[0031]
13
Advantages of the rotor 2 according to the first
embodiment will be described.
FIG. 9 is a cross-sectional view schematically
illustrating a structure of a rotor 200 according to a
5 comparative example. In the rotor 200 according to the
comparative example illustrated in the FIG. 9, a ring-shaped
rare earth bonded magnet 201 having higher magnetic force than
that of a cylindrical ferrite bonded magnet 202 is disposed on
the outer peripheral surface of the ferrite bonded magnet 202.
10 The ring-shaped rare earth bonded magnet 201 extends in the
circumferential direction of the rotor 200, and the thickness
of the rare earth bonded magnet 201 in the xy plane is uniform
in the axial direction of the rotor 200. That is, the ringshaped rare earth bonded magnet 201 forms the entire outer
15 peripheral surface of the rotor 200.
[0032]
On the other hand, the rotor 2 according to the first
embodiment includes a plurality of first permanent magnets 21.
The first permanent magnets 21 form part of the outer
20 peripheral surface of the rotor 2, and do not form the entire
outer peripheral surface of the rotor 2. Accordingly, the
amount of the first permanent magnets 21 having high magnetic
force can be reduced, as compared to the rotor 200 according to
the comparative example. In the case where the first permanent
25 magnets 21 are expensive rare earth bonded magnets, the amount
of rare earth bonded magnets can be reduced as compared to the
rotor 200 according to the comparative example, and thus, the
cost of the rotor 2 can be reduced.
[0033]
30 FIG. 10 is a diagram showing a magnetic flux density
distribution on the outer peripheral surface of the rotor 2 and
corresponding to a vicinity of the cross section of the rotor 2
illustrated in FIG. 2. Specifically, FIG. 10 is a diagram
showing a magnetic flux density distribution at a position E1
14
illustrated in FIGS. 14 and 15.
FIG. 11 is a diagram showing a magnetic flux density
distribution on the outer peripheral surface of the rotor 2 and
corresponding to a vicinity of the cross section of the rotor 2
5 illustrated in FIG. 3. Specifically, FIG. 11 is a diagram
showing a magnetic flux density distribution at a position E2
illustrated in FIGS. 14 and 15.
FIG. 12 is a diagram showing a magnetic flux density
distribution on the outer peripheral surface of the rotor 2 and
10 corresponding to a vicinity of the cross section of the rotor 2
illustrated in FIG. 4. Specifically, FIG. 12 is a diagram
showing a magnetic flux density distribution at a position E3
illustrated in FIGS. 14 and 15.
FIG. 13 is a diagram showing a magnetic flux density
15 distribution on the outer peripheral surface of the entire
rotor 2.
In FIGS. 10 through 13, the horizontal axis represents a
relative position [degrees] in the circumferential direction of
the rotor 2, and the vertical axis represents a magnetic flux
20 density. In FIGS. 10 through 13, the continuous line
represents a magnetic flux density distribution of the rotor 2
according to the first embodiment, and the broken line
represents a magnetic flux density distribution of the rotor
200 according to the comparative example.
25 [0034]
FIG. 14 is a diagram illustrating a position at which a
magnetic flux density distribution on the outer peripheral
surface of the rotor 2 according to the first embodiment is
detected. In FIG. 14, the broken line indicates a position of
30 a magnetic pole center part (a north pole or a south pole) of
the rotor 2, “N” represents a north pole, and “S” represents a
south pole.
FIG. 15 is a diagram illustrating a position at which a
magnetic flux density distribution on the outer peripheral
15
surface of the rotor 200 according to the comparative example
is detected. In FIG. 15, the broken line indicates a position
of a magnetic pole center part (a north pole or a south pole)
of the rotor 200, “N” represents a north pole, and “S”
5 represents a south pole.
[0035]
As illustrated in FIGS. 10 through 12, in the rotor 200
according to the comparative example, a sine wave that is
uniform in the circumferential direction is formed. On the
10 other hand, in a vicinity of each cross section of the rotor 2
according to the first embodiment, a nonuniform sine wave is
formed. However, a magnetic flux density distribution obtained
in the entire rotor 2 forms a relatively uniform sine wave as
illustrated in FIG. 13. That is, in the entire rotor 2
15 according to the first embodiment, an abrupt change of the
magnetic flux density in the circumferential direction is
suppressed. Accordingly, an induced voltage substantially
equal to that of the rotor 200 according to the comparative
example can be obtained.
20 [0036]
As described above, in the rotor 2 according to the first
embodiment, the amount of the first permanent magnets 21 having
high magnetic force can be reduced, as compared to the rotor
200 according to the comparative example. Specifically, in the
25 rotor 2 according to the first embodiment, since the first
permanent magnets 21 form part of the outer peripheral surface
of the rotor 2, the amount of the first permanent magnets 21
can be reduced by about 20%, as compared to the rotor 200
according to the comparative example. In general, a material
30 unit price of rare earth magnets is greater than or equal to 10
times that of ferrite magnets. Thus, in the case where a
magnet including a rare earth magnet (e.g., a rare earth bonded
magnet) is used as the first permanent magnet 21 and a magnet
including a ferrite magnet (e.g., a ferrite bonded magnet) is
16
used as the second permanent magnet 22, even when the amount of
the second permanent magnet 22 is large, the costs of the first
permanent magnets 21 can be significantly reduced. As a result,
the cost of the rotor 2 can be significantly reduced.
5 [0037]
In addition, as described above, in the rotor 2 according
to the first embodiment, even when the amount of the first
permanent magnets 21 having high magnetic force is reduced, a
sufficient magnetic force of the rotor 2 can be obtained. As a
10 result, an induced voltage substantially equal to that of the
rotor 2 according to the comparative example can be obtained,
and thus, an accuracy of rotation control substantially equal
to that of the rotor 2 of the comparative example can be
obtained.
15 [0038]
In addition, with the method for fabricating the rotor 2,
the rotor 2 having the advantages described above can be
fabricated.
[0039]
20 First Variation
FIG. 16 is a side view schematically illustrating a
structure of a rotor 2a according to a first variation.
FIG. 17 is a plan view schematically illustrating the
structure of the rotor 2a according to the first variation.
25 FIGS. 18 and 19 are cross-sectional views schematically
illustrating the structure of the rotor 2a according to the
first variation.
FIG. 17 is a plan view taken along line C17-C17 in FIG.
16. FIG. 18 is a cross-sectional view taken along line C18-C18
30 in FIG. 16. FIG. 19 is a cross-sectional view taken along line
C19-C19 in FIG. 16.
[0040]
In the rotor 2a according to the first variation, the
width of each first permanent magnet 21 in the circumferential
17
direction of the rotor 2a varies in the axial direction of the
rotor 2a. Specifically, in each first permanent magnet 21, the
width of the first permanent magnet 21 in the circumferential
direction of the rotor 2a is largest at the center in the axial
5 direction of the rotor 2a. This largest width is indicated by
d2 in FIG. 16. In each first permanent magnet 21, the width in
the circumferential direction is smallest at an end portion in
the axial direction. This smallest width is indicated by d3 in
FIG. 16. That is, a relationship between the width d2 and the
10 width d3 satisfies d2 > d3 in each first permanent magnet 21.
[0041]
In this case, the width of the outer peripheral surface
of a second permanent magnet 22 in the circumferential
direction varies in the axial direction. Specifically, the
15 width of the outer peripheral surface of the second permanent
magnet 22 in the circumferential direction is largest in an end
portion in the axial direction. This largest width is
indicated by d4 in FIG. 16. The width of the outer peripheral
surface of the second permanent magnet 22 in the
20 circumferential direction is smallest at the center in the
axial direction. This smallest width is indicated by d5 in FIG.
16. That is, a relationship between the width d4 and the width
d5 satisfies d4 > d5 in the second permanent magnet 22.
[0042]
25 A method for fabricating the rotor 2a according to the
first variation will be described.
FIGS. 20 and 21 are diagrams illustrating an example of a
process for fabricating the rotor 2a according to the first
variation. Specifically, FIGS. 20 and 21 are diagrams
30 illustrating a molding process of the second permanent magnet
22.
[0043]
In the molding process of the second permanent magnet 22,
the second permanent magnet 22 is molded by using molds divided
18
into two, that is, a mold M21 and a mold M22.
[0044]
In a first step, a magnetic field having polar anisotropy
is generated inside the mold M21 and the mold M22 for the
5 second permanent magnet 22 by using a magnet for magnetization.
[0045]
In a second step, the second permanent magnet 22 is
molded. Specifically, in the mold M21 and the mold M22, the
second permanent magnet 22 is injection-molded (FIG. 20). In
10 this manner, the second permanent magnet 22 magnetized to have
polar anisotropy is molded. In addition, as illustrated in FIG.
21, the mold M21 and the mold M22 are pulled out in opposite
directions and consequently the second permanent magnet 22
magnetized to have polar anisotropy is obtained.
15 [0046]
Since molds corresponding to the shape of each first
permanent magnet 21 is formed in the mold M21 and the mold M22,
the shape of the first permanent magnet 21 is molded on the
outer peripheral surface of the second permanent magnet 22
20 concurrently with obtainment of the second permanent magnet 22.
[0047]
In a third step, a magnetic field having polar anisotropy
is generated inside the molds for the first permanent magnet 21
by using a magnet for magnetization.
25 [0048]
In a fourth step, one or more first permanent magnets 21
are molded. Specifically, with the second permanent magnet 22
being disposed inside the molds for the first permanent magnets
21, one or more first permanent magnets 21 are injection-molded
30 on the outer peripheral surface of the second permanent magnet
22 to form part of the outer peripheral surface of the rotor 2a.
In this manner, one or more first permanent magnets 21
magnetized to have polar anisotropy are molded and thus the
rotor 2 is obtained.
19
[0049]
The other part of the structure of the rotor 2a is the
same as that of the rotor 2 according to the first embodiment.
The rotor 2a according to the first variation has the same
5 advantages as the advantages of the rotor 2 according to the
first embodiment described above.
[0050]
In addition, in the rotor 2a according to the first
variation, a magnetic flux density distribution obtained in the
10 entire rotor 2a can be made as a more uniform sine wave.
Accordingly, a proportion of a harmonic component in the
induced voltage can be reduced and thus distortion of the
induced voltage decreases. As a result, during driving of an
electric motor, pulsations of a torque of the electric motor
15 decreases and thus vibrations and noise in the electric motor
can be reduced.
[0051]
In the method for fabricating the rotor 2a according to
the first variation, the rotor 2a having the advantages
20 described above can be fabricated. In addition, in the method
for fabricating the rotor 2a, the use of the divided molds M21
and M22 can increase flexibility in the shape of each first
permanent magnet 21. Furthermore, according to the method for
fabricating the rotor 2a, since the divided molds M21 and M22
25 are used, the mold M21 and the mold M22 can be easily pulled
out from the second permanent magnet 22.
[0052]
Second Variation
FIG. 22 is a cross-sectional view schematically
30 illustrating a structure of a rotor 2b according to a second
variation.
In the xy plane, an angle A1 formed by two lines T11
passing through a rotation center (i.e., an axis Ax) of the
rotor 2b and both ends P11 of the inner peripheral surface of a
20
first permanent magnet 21 is larger than an angle A2 formed by
two lines T12 passing through the rotation center of the rotor
2b and both ends P12 of the outer peripheral surface of the
first permanent magnet 21. The inner peripheral surface of the
5 first permanent magnet 21 is the surface facing inward in the
radial direction, of the first permanent magnet 21. The outer
peripheral surface of the first permanent magnet 21 is the
surface facing outward in the radial direction, of the first
permanent magnet 21.
10 [0053]
Accordingly, a centrifugal force generated during
rotation of the rotor 2b can prevent detachment of the first
permanent magnet 21 from the second permanent magnet 22.
[0054]
15 In the xy plane, an angle A3 is smaller than an angle A4.
Accordingly, a centrifugal force generated during rotation of
the rotor 2b can prevent detachment of the first permanent
magnet 21 from the second permanent magnet 22. In the xy plane,
the angle A3 is an angle formed by two lines T22 passing
20 through adjacent end portions P13 of the inner peripheral
surfaces of two first permanent magnets 21, and these end
portions P13 are adjacent to each other in the circumferential
direction of the rotor 2. In other words, the two end portions
P13 face each other in the circumferential direction of the
25 rotor 2. In the xy plane, the angle A4 is an angle formed by
two lines T21 passing through both ends P21 of the outer
peripheral surface of the second permanent magnet 22 between
two first permanent magnets 21. The outer peripheral surface
of the second permanent magnet 22 is the surface of the second
30 permanent magnet 22 facing outward in the radial direction.
[0055]
Third Variation
FIG. 23 is a plan view schematically illustrating a
structure of a rotor 2c according to a third variation.
21
FIG. 24 is a side view schematically illustrating the
structure of the rotor 2c according to the third variation.
FIG. 25 is a cross-sectional view schematically
illustrating the structure of the rotor 2c according to the
5 third variation. Specifically, FIG. 25 is a cross-sectional
view taken along line C25-C25 in FIG. 23.
[0056]
In the rotor 2c according to the third variation, a first
permanent magnet 21 is integral. The first permanent magnet 21
10 includes a plurality of bodies 21a and at least one ring-shaped
portion 21b. The plurality of bodies 21a correspond to the
first permanent magnets 21 in the first embodiment (the first
permanent magnets 21 illustrated in FIG. 1). Thus, each of the
bodies 21a forms part of the outer peripheral surface of the
15 rotor 2c and is magnetized to have polar anisotropy. Part of a
second permanent magnet 22 is present between two bodies 21a
adjacent to each other in the circumferential direction.
[0057]
The ring-shaped portion 21b is integrated with the
20 plurality of bodies 21a. Thus, in the third variation, the
rotor 2c includes one first permanent magnet 21 and one second
permanent magnet 22. In the example illustrated in FIG. 24,
the ring-shaped portion 21b is formed at each end of the first
permanent magnet 21 in the axial direction. It should be noted
25 that the ring-shaped portion 21b may be formed at one end of
the first permanent magnet 21 in the axial direction. Each
ring-shaped portion 21b covers an end portion of the second
permanent magnet 22 in the axial direction of the rotor 2c.
[0058]
30 As illustrated in FIG. 25, each ring-shaped portion 21b
may include at least one projection 21c or at least one recess
21d. Each ring-shaped portion 21b may include both at least
one projection 21c and at least one recess 21d. The projection
21c projects toward the second permanent magnet 22. For
22
example, the projection 21c is engaged with a recess formed in
the second permanent magnet 22. For example, the recess 21d is
engaged with a projection formed on the second permanent magnet
22.
5 [0059]
In general, when the temperature of a rotor changes,
magnets deform in some cases. In such cases, one of two types
of magnets might be detached from the rotor because of a
difference in thermal shrinkage. In the third variation, since
10 the rotor 2c has the ring-shaped portion 21b, when the
temperature of the rotor 2c changes, even in the case where the
first permanent magnet 21 or the second permanent magnet 22
deforms because of a difference in thermal shrinkage, it is
possible to prevent detachment of the first permanent magnet 21
15 (especially the bodies 21a) from the second permanent magnet 22.
In addition, a centrifugal force generated during rotation of
the rotor 2c can prevent detachment of the first permanent
magnet 21 (especially the bodies 21a) from the second permanent
magnet 22.
20 [0060]
Furthermore, since each ring-shaped portion 21b has at
least one projection 21c to be engaged with the second
permanent magnet 22, the first permanent magnet 21 can be
firmly fixed to the second permanent magnet 22. Accordingly,
25 detachment of the first permanent magnet 21 (especially the
bodies 21a) from the second permanent magnet 22 can be
effectively prevented.
[0061]
Moreover, since each ring-shaped portion 21b has at least
30 one recess 21d to be engaged with the second permanent magnet
22, the first permanent magnet 21 can be firmly fixed to the
second permanent magnet 22. Accordingly, detachment of the
first permanent magnet 21 (especially the bodies 21a) from the
second permanent magnet 22 can be effectively prevented.
23
[0062]
Fourth Variation
FIG. 26 is a plan view schematically illustrating a
structure of a rotor 2d according to a fourth variation.
5 FIG. 27 is a side view schematically illustrating the
structure of the rotor 2d according to the fourth variation.
FIG. 28 is a cross-sectional view schematically
illustrating the structure of the rotor 2d according to the
fourth variation. Specifically, FIG. 28 is a cross-sectional
10 view taken along line C28-C28 in FIG. 26.
[0063]
The rotor 2d according to the fourth variation further
includes at least one resin 25. For example, the resin 25 can
be molded integrally with a rib for fixing a shaft in the rotor
15 2d.
[0064]
In the example illustrated in FIG. 27, the resin 25 is
fixed to both ends of each first permanent magnet 21 in the
axial direction of the rotor 2d. It should be noted that the
20 resin 25 may be formed at one end of the first permanent magnet
21 in the axial direction of the rotor 2d. In the example
illustrated in FIG. 26, each resin 25 is a ring-shaped resin in
the xy plane. The resin 25 covers end portions of the first
permanent magnet 21 in the axial direction of the rotor 2d.
25 [0065]
As illustrated in FIG. 28, each resin 25 may include at
least one projection 25a or at least one recess 25b. Each
resin 25 may include both at least one projection 25a and at
least one recess 25b. The projection 25a projects toward the
30 second permanent magnet 22. For example, the projection 25a is
engaged with a recess formed in the first permanent magnet 21
or the second permanent magnet 22. For example, the recess 25b
is engaged with a projection formed on the first permanent
magnet 21 or the second permanent magnet 22.
24
[0066]
In general, when the temperature of a rotor changes,
magnets deform in some cases. In such cases, one of two types
of magnets might be detached from the rotor because of a
5 difference in thermal shrinkage. In the fourth variation,
since the rotor 2d includes the resin 25, when the temperature
of the rotor 2d changes, even in the case where the first
permanent magnet 21 or the second permanent magnet 22 deforms
because of a difference in thermal shrinkage, it is possible to
10 prevent detachment of the first permanent magnet 21 from the
second permanent magnet 22. In addition, a centrifugal force
generated during rotation of the rotor 2d can prevent
detachment of the first permanent magnet 21 from the second
permanent magnet 22.
15 [0067]
Furthermore, since each resin 25 includes at least one
projection 25a to be engaged with the first permanent magnet 21
or the second permanent magnet 22, each resin 25 can be firmly
fixed to the first permanent magnet 21 or the second permanent
20 magnet 22 with the resin 25 covering each first permanent
magnet 21. Accordingly, detachment of the first permanent
magnet 21 from the second permanent magnet 22 can be
effectively prevented.
[0068]
25 Furthermore, since each resin 25 includes at least one
recess 25b to be engaged with the first permanent magnet 21 or
the second permanent magnet 22, the resin 25 can be firmly
fixed to the first permanent magnet 21 or the second permanent
magnet 22 with the resin 25 covering each first permanent
30 magnet 21. Accordingly, detachment of the first permanent
magnet 21 from the second permanent magnet 22 can be
effectively prevented.
[0069]
Moreover, since the rotor 2d according to the fourth
25
variation includes at least one resin 25, the amount of the
first permanent magnet 21 can be reduced, as compared to the
rotor 2c according to the third variation.
[0070]
5 Fifth Variation
FIG. 29 is a plan view schematically illustrating a
structure of a rotor 2e according to a fifth variation.
FIG. 30 is a side view schematically illustrating the
structure of the rotor 2e according to the fifth variation.
10 [0071]
The rotor 2e according to the fifth variation includes at
least one first permanent magnet 21, one second permanent
magnet 22, at least one third permanent magnet 23, and at least
one fourth permanent magnet 24. In the example illustrated in
15 FIG. 29, the structure of each third permanent magnet 23 is the
same as the structure of the first permanent magnet 21, and the
structure of each fourth permanent magnet 24 is the same as the
structure of the second permanent magnet 22.
[0072]
20 As illustrated in FIG. 30, the third permanent magnet 23
and the fourth permanent magnet 24 are stacked on the first
permanent magnet 21 and the second permanent magnet 22 in the
axial direction of the rotor 2e.
[0073]
25 That is, each third permanent magnet 23 forms part of the
outer peripheral surface of the rotor 2e, and is magnetized to
have polar anisotropy. Each third permanent magnet 23 is, for
example, a bonded magnet as a mixture of a rare earth magnet
and a resin, that is, a rare earth bonded magnet. Each third
30 permanent magnet 23 has higher magnetic force than that of the
fourth permanent magnet 24. The rare earth magnet is, for
example, a magnet containing neodymium (Nd)- iron (Fe)- boron
(B) or a magnet containing samarium (Sm)- iron (Fe)- nitrogen
(N). The resin is, for example, a nylon resin, a polyphenylene
26
sulfide (PPS) resin, or an epoxy resin.
[0074]
The fourth permanent magnet 24 is adjacent to the third
permanent magnet 23 in the circumferential direction of the
5 rotor 2e, and forms part of the outer peripheral surface of the
rotor 2e. Specifically, part of the fourth permanent magnet 24
is adjacent to the third permanent magnet 23 in the
circumferential direction of the rotor 2e, and another part of
the fourth permanent magnet 24 is located on the inner side
10 with respect to the third permanent magnet 23 in the radial
direction of the rotor 2e. Thus, the fourth permanent magnet
24 is a ring-shaped magnet.
[0075]
The fourth permanent magnet 24 is magnetized to have
15 polar anisotropy. The fourth permanent magnet 24 is a magnet
that is a different type from the third permanent magnet 23.
Specifically, the fourth permanent magnet 24 is, for example, a
bonded magnet as a mixture of a ferrite magnet and a resin,
that is, a ferrite bonded magnet. The resin is, for example, a
20 nylon resin, a polyphenylene sulfide (PPS) resin, or an epoxy
resin. The fourth permanent magnet 24 has lower magnetic force
than that of each third permanent magnet.
[0076]
In the fifth variation, the rotor 2e includes two layers
25 of magnets. In other words, the rotor 2e is divided into two
layers. Specifically, the rotor 2e includes a first-layer
layered magnet 20 constituted by the first permanent magnet 21
and the second permanent magnet 22, and a second-layer layered
magnet 20 constituted by the third permanent magnet 23 and the
30 fourth permanent magnet 24. Thus, since the rotor 2e includes
the plurality of layers, an eddy-current loss in the rotor 2e
can be reduced.
[0077]
In the xy plane, a magnetic pole center position (e.g., a
27
position of a north pole) of the first permanent magnet 21
preferably coincides with a magnetic pole center position (e.g.,
a position of a north pole) of the third permanent magnet 23.
Accordingly, a magnetic flux density at each magnetic pole
5 center position of the rotor 2e can be increased, and thus, the
amount of magnetic flux flowing from the rotor 2e into the
stator increases in an electric motor, and an output of the
electric motor can be enhanced. Each magnetic pole center
position of the first permanent magnet 21 and each magnetic
10 pole center position of the third permanent magnet 23 are a
position indicated by the broken line in FIG. 30.
[0078]
The rotor 2e has 2n (n is a natural number) magnetic
poles. In addition, the rotor 2e includes a plurality of
15 layered magnets 20 from two to m (m is a natural number and a
divisor for n) layers stacked in the axial direction. In the
example illustrated in FIG. 30, n = 4 and m = 2. In each first
permanent magnet 21 of the plurality of layered magnets 20,
supposing one cycle is an angle between adjacent north poles in
20 the xy plane, positions of north poles of two first permanent
magnets 21 adjacent to each other in the axial direction may be
shifted from each other by n/m cycles in the circumferential
direction with respect to positions in orientation. In this
case, positions of south poles of two first permanent magnets
25 21 adjacent to each other in the axial direction are also
shifted from each other by n/m cycles in the circumferential
direction. Accordingly, even in the case where the layered
magnets 20 have variations in orientation, variations of
magnetic flux density are reduced in the circumferential
30 direction in the entire rotor 2e, and distortion of an induced
voltage is reduced and consequently vibrations and noise in the
electric motor can be thereby reduced.
[0079]
Sixth Variation
28
FIG. 31 is a cross-sectional view schematically
illustrating a structure of a rotor 2f according to a sixth
variation. Specifically, FIG. 31 is a cross-sectional view
taken along line C31-C31 in FIG. 32.
5 FIG. 32 is a side view schematically illustrating the
structure of the rotor 2f according to the sixth variation.
[0080]
The rotor 2f according to the sixth variation includes at
least one first permanent magnet 21, one second permanent
10 magnet 22, at least one third permanent magnet 23, and at least
one fourth permanent magnet 24. In the example illustrated in
FIG. 32, the structure of each third permanent magnet 23 is the
same as the structure of the first permanent magnet 21, and the
structure of each fourth permanent magnet 24 is the same as the
15 structure of the second permanent magnet 22.
[0081]
The third permanent magnet 23 may be integral, or may be
divided into a plurality of parts. The fourth permanent magnet
24 may be integral, or may be divided into a plurality of parts.
20 [0082]
As illustrated in FIG. 32, the third permanent magnet 23
and the fourth permanent magnet 24 are stacked on the first
permanent magnet 21 and the second permanent magnet 22 in the
axial direction of the rotor 2f.
25 [0083]
That is, each third permanent magnet 23 forms part of the
outer peripheral surface of the rotor 2f, and is magnetized to
have polar anisotropy. Each third permanent magnet 23 is, for
example, a bonded magnet as a mixture of a rare earth magnet
30 and a resin, that is, a rare earth bonded magnet. Each third
permanent magnet 23 has higher magnetic force than that of the
fourth permanent magnet 24. The rare earth magnet is, for
example, a magnet containing neodymium (Nd)- iron (Fe)- boron
(B) or a magnet containing samarium (Sm)- iron (Fe)- nitrogen
29
(N). The resin is, for example, a nylon resin, a polyphenylene
sulfide (PPS) resin, or an epoxy resin.
[0084]
The fourth permanent magnet 24 is adjacent to the third
5 permanent magnet 23 in the circumferential direction of the
rotor 2f, and forms part of the outer peripheral surface of the
rotor 2f. Specifically, part of the fourth permanent magnet 24
is adjacent to the third permanent magnet 23 in the
circumferential direction of the rotor 2f, and another part of
10 the fourth permanent magnet 24 is located on the inner side
with respect to the third permanent magnet 23 in the radial
direction of the rotor 2f. Thus, the fourth permanent magnet
24 is a ring-shaped magnet.
[0085]
15 The fourth permanent magnet 24 is magnetized to have
polar anisotropy. The fourth permanent magnet 24 is a magnet
that is a different type from the third permanent magnet 23.
Specifically, the fourth permanent magnet 24 is, for example, a
bonded magnet as a mixture of a ferrite magnet and a resin,
20 that is, a ferrite bonded magnet. The resin is, for example, a
nylon resin, a polyphenylene sulfide (PPS) resin, or an epoxy
resin. The fourth permanent magnet 24 has lower magnetic force
than that of each third permanent magnet.
[0086]
25 In the rotor 2f according to the sixth variation, the
first permanent magnet 21 is integral. The first permanent
magnet 21 includes a plurality of bodies 21a and at least one
ring-shaped portion 21b (also referred to as a first ringshaped portion in the sixth variation). The plurality of
30 bodies 21a correspond to the first permanent magnets 21 in the
first embodiment (the first permanent magnets 21 illustrated in
FIG. 1). Thus, each of the bodies 21a forms part of the outer
peripheral surface of the rotor 2f and is magnetized to have
polar anisotropy. Part of the second permanent magnet 22 is
30
present between two bodies 21a adjacent to each other in the
circumferential direction.
[0087]
The ring-shaped portion 21b is integrated with the
5 plurality of bodies 21a. Thus, in the sixth variation, the
rotor 2f includes one first permanent magnet 21 and one second
permanent magnet 22. In the example illustrated in FIG. 32,
the ring-shaped portion 21b is formed at an end portion of the
first permanent magnet 21 in the axial direction. The ring10 shaped portion 21b covers an end portion of the second
permanent magnet 22 in the axial direction of the rotor 2f.
[0088]
In the rotor 2f according to the sixth variation, the
third permanent magnet 23 is integral. The third permanent
15 magnet 23 includes a plurality of bodies 23a, at least one
ring-shaped portion 23b (also referred to as a second ringshaped portion in the sixth variation). The plurality of
bodies 23a correspond to the first permanent magnets 21 in the
first embodiment (the first permanent magnets 21 illustrated in
20 FIG. 1). Thus, each of the bodies 23a forms part of the outer
peripheral surface of the rotor 2f and is magnetized to have
polar anisotropy. Part of the fourth permanent magnet 24 is
present between two bodies 23a adjacent to each other in the
circumferential direction.
25 [0089]
The ring-shaped portion 23b is integrated with the
plurality of bodies 23a. Thus, in the sixth variation, the
rotor 2f includes one third permanent magnet 23 and one fourth
permanent magnet 24. In the example illustrated in FIG. 32,
30 the ring-shaped portion 23b is formed at an end portion of the
third permanent magnet 23 in the axial direction. The ringshaped portion 23b covers an end portion of the fourth
permanent magnet 24 in the axial direction of the rotor 2f.
[0090]
31
In the axial direction of the rotor 2f, the ring-shaped
portion 21b faces the ring-shaped portion 23b. Accordingly,
the proportion of the first permanent magnet 21 and the third
permanent magnet 23 can be increased in a center portion of the
5 rotor 2f in the axial direction. As a result, in an electric
motor, the amount of magnetic flux flowing from the rotor 2f
into a stator increases and thus an output of the electric
motor can be thereby increased.
[0091]
10 In the electric motor, the length of the rotor 2f in the
axial direction is preferably larger than the length of the
stator in the axial direction. Accordingly, leakage of
magnetic flux from the rotor 2f can be reduced. Specifically,
in an electric motor, the amount of magnetic flux flowing from
15 the rotor 2f into a stator increases and thus an output of the
electric motor can be increased.
[0092]
In the sixth variation, the rotor 2f includes two layers
of magnets. In other words, the rotor 2f is divided into two
20 layers. Specifically, the rotor 2f includes a first layer
constituted by the first permanent magnet 21 and the second
permanent magnet 22, and a second layer constituted by the
third permanent magnet 23 and the fourth permanent magnet 24.
Thus, since the rotor 2f includes the plurality of layers, an
25 eddy-current loss in the rotor 2f can be reduced.
[0093]
In the xy plane, a magnetic pole center position (e.g., a
position of a north pole) of the first permanent magnet 21
preferably coincides with a magnetic pole center position (e.g.,
30 a position of a north pole) of the third permanent magnet 23.
Accordingly, a magnetic flux density at each magnetic pole
center position of the rotor 2f can be increased, and thus, the
amount of magnetic flux flowing from the rotor 2f into the
stator in the electric motor increases, and an output of the
32
electric motor can be enhanced. Each magnetic pole center
position of the first permanent magnet 21 and each magnetic
pole center position of the third permanent magnet 23 are a
position indicated by the broken line in FIG. 32.
5 [0094]
Seventh Variation
FIG. 33 is a cross-sectional view schematically
illustrating a structure of a rotor 2g according to a seventh
variation. FIG. 33 is a cross-sectional view taken along line
10 C33-C33 in FIG. 34.
FIG. 34 is a side view schematically illustrating the
structure of the rotor 2g according to the seventh variation.
[0095]
The rotor 2g according to the seventh variation has 2n (n
15 is a natural number) magnetic poles, as in the first embodiment
and the variations thereof described above. In addition, the
rotor 2g includes a plurality of layered magnets 20 from two to
m (m is a natural number and a divisor for n) layers stacked in
the axial direction. In the example illustrated in FIG. 34, n
20 = 4 and m = 2. That is, in the example illustrated in FIG. 34,
the rotor 2g includes two layers of layered magnets 20.
[0096]
Each layered magnet 20 of the plurality of layered
magnets 20 includes at least one first permanent magnet 21 and
25 one second permanent magnet 22.
[0097]
As illustrated in FIG. 34, the plurality of layered
magnets 20 are stacked in the axial direction of the rotor 2g.
As described above, the rotor 2g includes two layers of magnets.
30 In other words, the rotor 2g is divided into two layers. Thus,
since the rotor 2g includes the plurality of layers, an eddycurrent loss in the rotor 2g can be reduced.
[0098]
In the axial direction of the rotor 2g, a ring-shaped
33
portion 21b of each first permanent magnet 21 faces a ringshaped portion 21b of another first permanent magnet 21.
Accordingly, a proportion of the first permanent magnets 21 can
be increased in a center portion of the rotor 2g in the axial
5 direction. As a result, in an electric motor, the amount of
magnetic flux flowing from the rotor 2g into a stator increases
and thus an output of the electric motor can be increased.
[0099]
In each first permanent magnet 21 of the plurality of
10 layered magnets 20, supposing one cycle is an angle between
adjacent north poles in the xy plane, positions of north poles
of two first permanent magnets 21 adjacent to each other in the
axial direction are shifted from each other by n/m cycles in
the circumferential direction. Positions of south poles of two
15 first permanent magnets 21 adjacent to each other in the axial
direction are also shifted from each other by n/m cycles in the
circumferential direction. Accordingly, even in the case where
the layered magnets 20 have variations in orientation, a
uniform orientation in the rotor 2g can be obtained. As a
20 result, in a manner similar to the example illustrated in FIG.
13, in the entire rotor 2g, an abrupt change of the flux
density in the circumferential direction can be suppressed, and
vibrations and noise in an electric motor can be reduced.
[0100]
25 Eighth Variation
FIG. 35 is a plan view schematically illustrating a
structure of a rotor 2h according to an eighth variation.
FIG. 36 is a side view schematically illustrating the
structure of the rotor 2h according to the eighth variation.
30 [0101]
In the rotor 2h according to the eighth variation, a
structure of first permanent magnets 21 of the rotor 2h is
different from the structure of the first permanent magnets 21
of the rotor 2 according to the first embodiment. Specifically,
34
as illustrated in FIGS. 35 and 36, both ends of the first
permanent magnets 21 in the axial direction overlap each other
by an angle w1 [degrees] in an xy plane. In this case, the
angle w1 satisfies 0 < w1 < 0.2 × 2n/360. In a manner similar
5 to the first embodiment, the rotor 2h has 2n (n is a natural
number) magnetic poles. In the eighth variation, n is 4.
[0102]
Accordingly, the volume of the first permanent magnet 21
near a magnetic pole center part of the rotor 2h can be
10 increased. In other words, a proportion of the first permanent
magnets 21 near the magnetic pole center part of the rotor 2h
can be increased. As a result, magnetic force of the rotor 2h
can be increased and thus efficiency of an electric motor
including the rotor 2h can be enhanced.
15 [0103]
Ninth Variation
FIG. 37 is a plan view schematically illustrating a
structure of a rotor 2i according to a ninth variation.
FIG. 38 is a side view schematically illustrating the
20 structure of the rotor 2i according to the ninth variation.
[0104]
In the rotor 2i according to the ninth variation, a
structure of first permanent magnets 21 of the rotor 2i is
different from the structure of the first permanent magnets 21
25 of the rotor 2 according to the first embodiment. Specifically,
as illustrated in FIGS. 37 and 38, both ends of the first
permanent magnets 21 in the axial direction overlap each other
by an angle w1 [degrees] in an xy plane. In this case, the
angle w1 satisfies 0 < w1 < 0.2 × 2n/360. In a manner similar
30 to the first embodiment, the rotor 2i has 2n (n is a natural
number) magnetic poles. In the ninth variation, n is 4.
[0105]
Accordingly, the volume of the first permanent magnets 21
near a magnetic pole center part of the rotor 2i can be
35
increased. In other words, a proportion of the first permanent
magnets 21 near the magnetic pole center part of the rotor 2h
can be increased. As a result, magnetic force of the rotor 2i
can be increased and thus efficiency of an electric motor
5 including the rotor 2i can be enhanced.
[0106]
The rotor 2i includes a plurality of layered magnets 20
from two to m (m is a natural number and a divisor for n)
layers stacked in the axial direction. In the example
10 illustrated in FIG. 38, n = 4 and m = 2. That is, in the
example illustrated in FIG. 38, the rotor 2i includes two
layers of layered magnets 20.
[0107]
Each layered magnet 20 of the plurality of layered
15 magnets 20 includes at least one first permanent magnet 21 and
one second permanent magnet 22.
[0108]
As illustrated in FIG. 38, the plurality of layered
magnets 20 are stacked in the axial direction of the rotor 2i.
20 As described above, the rotor 2i includes two layers of magnets.
In other words, the rotor 2i is divided into two layers. Thus,
since the rotor 2i includes the plurality of layers, an eddycurrent loss in the rotor 2i can be reduced.
[0109]
25 In the axial direction of the rotor 2i, a ring-shaped
portion 21b of each first permanent magnet 21 faces a ringshaped portion 21b of another first permanent magnet 21.
Accordingly, a proportion of the first permanent magnets 21 can
be increased in a center portion of the rotor 2i in the axial
30 direction. As a result, in an electric motor, the amount of
magnetic flux flowing from the rotor 2i into the stator can be
increased.
[0110]
In each first permanent magnet 21 of the plurality of
36
layered magnets 20, supposing one cycle is an angle between
adjacent north poles in an xy plane, positions of north poles
of two first permanent magnets 21 adjacent to each other in the
axial direction are shifted from each other by n/m cycles in
5 the circumferential direction. Positions of south poles of two
first permanent magnets 21 adjacent to each other in the axial
direction are also shifted from each other by n/m cycles in the
circumferential direction. Accordingly, even in the case where
the layered magnets 20 have variations in orientation, a
10 uniform orientation in the rotor 2i can be obtained. As a
result, in a manner similar to the example illustrated in FIG.
13, in the entire rotor 2i, an abrupt change of the flux
density in the circumferential direction can be suppressed, and
vibrations and noise in an electric motor can be reduced.
15 [0111]
Tenth Variation
FIG. 39 is a plan view schematically illustrating a
structure of a rotor 2j according to a tenth variation.
FIG. 40 is a side view schematically illustrating the
20 structure of the rotor 2j according to the tenth variation.
[0112]
In the rotor 2j according to the tenth variation, a
structure of first permanent magnets 21 of the rotor 2j is
different from the structure of the first permanent magnets 21
25 of the rotor 2 according to the first embodiment. Specifically,
as illustrated in FIGS. 39 and 40, in an xy plane, both ends of
the first permanent magnets 21 in the axial direction overlap
each other by an angle w2 [degrees] in an inter-pole part of
the rotor 2j. In this case, the angle w2 satisfies 0 < w2 <
30 0.2 × 2n/360. In a manner similar to the first embodiment, the
rotor 2i has 2n (n is a natural number) magnetic poles. In the
tenth variation, n is 4.
[0113]
Accordingly, a magnetic flux density distribution
obtained in the entire rotor 2j can be made as a more uniform
sine wave. Accordingly, a proportion of a harmonic component
in the induced voltage can be reduced and thus distortion of
the induced voltage thereby decreases. As a result, during
5 driving of an electric motor, pulsations of a torque of the
electric motor decreases and consequently vibrations and noise
in the electric motor can be reduced.
[0114]
The rotor 2j includes a plurality of layered magnets 20
10 from two to m (m is a natural number and a divisor for n)
layers stacked in the axial direction. In the example
illustrated in FIG. 40, n = 4 and m = 2. That is, in the
example illustrated in FIG. 40, the rotor 2j includes two
layers of layered magnets 20.
15 [0115]
Each layered magnet 20 of the plurality of layered
magnets 20 includes at least one first permanent magnet 21 and
one second permanent magnet 22.
[0116]
20 As illustrated in FIG. 40, the plurality of layered
magnets 20 are stacked in the axial direction of the rotor 2j.
As described above, the rotor 2j includes two layers of magnets.
In other words, the rotor 2j is divided into two layers. Thus,
since the rotor 2j includes the plurality of layers, an eddy25 current loss in the rotor 2j can be reduced.
[0117]
In each first permanent magnet 21 of the plurality of
layered magnets 20, supposing one cycle is an angle between
adjacent north poles in an xy plane, positions of north poles
30 of two first permanent magnets 21 adjacent to each other in the
axial direction are shifted from each other by n/m cycles in
the circumferential direction. Positions of south poles of two
first permanent magnets 21 adjacent to each other in the axial
direction are also shifted from each other by n/m cycles in the
38
circumferential direction. Accordingly, even in the case where
the layered magnets 20 have variations in orientation, a
uniform orientation can be obtained in the rotor 2j. As a
result, in a manner similar to the example illustrated in FIG.
5 13, an abrupt change of the flux density in the circumferential
direction can be suppressed in the entire rotor 2j, and
vibrations and noise in an electric motor can be reduced.
[0118]
The rotors 2a through 2j according to the variations
10 described above also have the advantages of the rotor 2
according to the first embodiment.
[0119]
SECOND EMBODIMENT
FIG. 41 is a partial cross-sectional view schematically
15 illustrating a structure of an electric motor 1 according to a
second embodiment of the present invention.
The electric motor 1 includes the rotor 2 according to
the first embodiment, and a stator 3. Instead of the rotor 2,
the rotors 2a through 2j according to the variations of the
20 first embodiment are applicable to the electric motor 1.
[0120]
The electric motor 1 includes the rotor 2, the stator 3,
a circuit board 4, a magnetic sensor 5 for detecting a rotation
position of the rotor 2, a bracket 6, bearings 7a and 7b, a
25 sensor magnet 8 as a magnet for detecting a rotation position
of the rotor 2, and a shaft 37 fixed to the rotor 2. The
electric motor 1 is, for example, a permanent magnet
synchronous motor.
[0121]
30 The rotor 2 is rotatably disposed at the inner side of
the stator 3. An air gap is formed between the rotor 2 and the
stator 3. The rotor 2 rotates about an axis Ax.
[0122]
Since the electric motor 1 according to the second
39
embodiment includes the rotor 2 according to the first
embodiment (including the variations thereof), the same
advantages as those of the rotor 2 described in the first
embodiment (including advantages of the variations thereof).
5 [0123]
The electric motor 1 according to the second embodiment
includes the rotor 2 according to the first embodiment, and
thus, efficiency of the electric motor 1 can be increased.
[0124]
10 THIRD EMBODIMENT
FIG. 42 is a diagram schematically illustrating a
structure of a fan 60 according to a third embodiment of the
present invention.
The fan 60 includes a blade 61 and an electric motor 62.
15 The fan 60 is also called an air blower. The electric motor 62
is the electric motor 1 according to the second embodiment.
The blade 61 is fixed to a shaft of the electric motor 62. The
electric motor 62 drives the blade 61. When the electric motor
62 is driven, the blade 61 rotates to generate an airflow. In
20 this manner, the fan 60 is capable of supplying air.
[0125]
In the fan 60 according to the third embodiment, the
electric motor 1 described in the second embodiment is applied
to the electric motor 62, and thus, the same advantages as
25 those described in the second embodiment can be obtained. In
addition, efficiency of the fan 60 can be enhanced.
[0126]
FOURTH EMBODIMENT
An air conditioner 50 (also referred to as a
30 refrigeration air conditioning apparatus or a refrigeration
cycle apparatus) according to a fourth embodiment of the
present invention will be described.
FIG. 43 is a diagram schematically illustrating a
configuration of the air conditioner 50 according to the fourth
40
embodiment.
[0127]
The air conditioner 50 according to the fourth embodiment
includes an indoor unit 51 as an air blower (first air blower),
5 a refrigerant pipe 52, and an outdoor unit 53 as an air blower
(second air blower) connected to the indoor unit 51 through the
refrigerant pipe 52.
[0128]
The indoor unit 51 includes an electric motor 51a (e.g.,
10 the electric motor 1 according to the second embodiment), an
air blowing unit 51b that supplies air when being driven by the
electric motor 51a, and a housing 51c covering the electric
motor 51a and the air blowing unit 51b. The air blowing unit
51b includes, for example, a blade 51d that is driven by the
15 electric motor 51a. For example, the blade 51d is fixed to a
shaft of the electric motor 51a, and generates an airflow.
[0129]
The outdoor unit 53 includes an electric motor 53a (e.g.,
the electric motor 1 according to the second embodiment), an
20 air blowing unit 53b, a compressor 54, and a heat exchanger
(not shown). When the air blowing unit 53b is driven by the
electric motor 53a, the air blowing unit 53b supplies air. The
air blowing unit 53b includes, for example, a blade 53d that is
driven by the electric motor 53a. For example, the blade 53d
25 is fixed to a shaft of the electric motor 53a, and generates an
airflow. The compressor 54 includes an electric motor 54a
(e.g., the electric motor 1 according to the second embodiment),
a compression mechanism 54b (e.g., a refrigerant circuit) that
is driven by the electric motor 54a, and a housing 54c covering
30 the electric motor 54a and the compression mechanism 54b.
[0130]
In the air conditioner 50, at least one of the indoor
unit 51 or the outdoor unit 53 includes the electric motor 1
described in the second embodiment. Specifically, as a driving
41
source of an air blowing unit, the electric motor 1 described
in the second embodiment is applied to at least one of the
electric motors 51a or 53a. In addition, as the electric motor
54a of the compressor 54, the electric motor 1 described in the
5 second embodiment may be used.
[0131]
The air conditioner 50 is capable of performing a cooling
operation of sending cold air from the indoor unit 51, and a
heating operation of sending hot air, for example. In the
10 indoor unit 51, the electric motor 51a is a driving source for
driving the air blowing unit 51b. The air blowing unit 51b is
capable of supplying conditioned air.
[0132]
In the air conditioner 50 according to the fourth
15 embodiment, the electric motor 1 described in the second
embodiment is applied to at least one of the electric motors
51a or 53a, and thus, the same advantages as those described in
the second embodiment can be obtained. In addition, efficiency
of the air conditioner 50 can be enhanced.
20 [0133]
Furthermore, with the use of the electric motor 1
according to the second embodiment as a driving source of an
air blower (e.g., the indoor unit 51), the same advantages as
those described in the second embodiment can be obtained.
25 Accordingly, efficiency of the air blower can be enhanced. The
air blower including the electric motor 1 according to the
second embodiment and the blade (e.g., the blade 51d or 53d)
driven by the electric motor 1 can be used alone as a device
for supplying air. This air blower is also applicable to
30 equipment except for the air conditioner 50.
[0134]
In addition, the use of the electric motor 1 according to
the second embodiment as a driving source of the compressor 54
can obtain the same advantages as those described in the second
42
embodiment. Moreover, efficiency of the compressor 54 can be
enhanced.
[0135]
The electric motor 1 described in the second embodiment
5 can be mounted on equipment including a driving source, such as
a ventilator, a household electrical appliance, or a machine
tool, as well as the air conditioner 50.
[0136]
Features of the embodiments and features of the
10 variations described above can be combined as appropriate.
DESCRIPTION OF REFERENCE CHARACTERS
[0137]
1 electric motor, 2 rotor, 3 stator, 21 first permanent
magnet, 22 second permanent magnet, 23 third permanent magnet,
15 24 fourth permanent magnet, 50 air conditioner, 51 indoor unit,
51d, 61 blade, 53 outdoor unit, 60 fan (air blower).

43
We Claim :
1. A rotor having 2n (n is a natural number) magnetic poles,
comprising;
5 at least one first permanent magnet forming part of an
outer peripheral surface of the rotor and magnetized to have
polar anisotropy; and
at least one second permanent magnet that is a different
type from the at least one first permanent magnet, is adjacent
10 to the at least one first permanent magnet in a circumferential
direction of the rotor, has lower magnetic force than magnetic
force of the at least one first permanent magnet, and is
magnetized to have polar anisotropy.
15 2. The rotor according to claim 1, wherein a length of the
at least one first permanent magnet in an axial direction of
the rotor is longest at a center of the at least one first
permanent magnet in the circumferential direction of the rotor.
20 3. The rotor according to claim 2, wherein the length of the
at least one first permanent magnet in the axial direction of
the rotor gradually decreases with being away from the center
along the circumferential direction.
25 4. The rotor according to any one of claims 1 to 3, wherein
in a plane orthogonal to an axial direction of the rotor, an
angle formed by two lines passing through a rotation center of
the rotor and both ends of an inner peripheral surface of the
at least one first permanent magnet is larger than an angle
30 formed by two lines passing through the rotation center of the
rotor and both ends of the outer peripheral surface of the at
least one first permanent magnet.
5. The rotor according to any one of claims 1 to 4, wherein
44
the at least one first permanent magnet comprises two
first permanent magnets, and
in a plane orthogonal to an axial direction of the rotor,
an angle formed by two lines passing through adjacent ends of
5 inner peripheral surfaces of the two first permanent magnets is
smaller than an angle formed by two lines passing through both
ends of the outer peripheral surface of the second permanent
magnet between the two first permanent magnet, the adjacent
ends being adjacent to each other in the circumferential
10 direction.
6. The rotor according to any one of claims 1 to 3, wherein
the at least one first permanent magnet includes a ring-shaped
portion covering an end portion of the second permanent magnet
15 in an axial direction of the rotor.
7. The rotor according to any one of claims 1 to 5, further
comprising a resin covering an end portion of the at least one
first permanent magnet in an axial direction of the rotor.
20
8. The rotor according to any one of claims 1 to 3, further
comprising:
at least one third permanent magnet forming part of the
outer peripheral surface of the rotor and magnetized to have
25 polar anisotropy; and
at least one fourth permanent magnet that is a different
type from the at least one third permanent magnet, is adjacent
to the at least one third permanent magnet in the
circumferential direction, has lower magnetic force than
30 magnetic force of the at least one third permanent magnet, and
is magnetized to have polar anisotropy, wherein
the at least one first permanent magnet includes a first
ring-shaped portion covering an end portion of the second
permanent magnet in an axial direction of the rotor,
45
the at least one third permanent magnet includes a second
ring-shaped portion covering an end portion of the fourth
permanent magnet in the axial direction of the rotor, and
in the axial direction of the rotor, the first ring5 shaped portion faces the second ring-shaped portion.
9. The rotor according to claim 8, wherein in a plane
orthogonal to the axial direction of the rotor, a magnetic pole
center position of the at least one first permanent magnet
10 coincides with a magnetic pole center position of the at least
one third permanent magnet.
10. The rotor according to any one of claims 1 to 3, further
comprising:
15 at least one third permanent magnet forming part of the
outer peripheral surface of the rotor and magnetized to have
polar anisotropy; and
at least one fourth permanent magnet that is a different
type from the at least one third permanent magnet, is adjacent
20 to the at least one third permanent magnet in the
circumferential direction, has lower magnetic force than
magnetic force of the at least one third permanent magnet, and
is magnetized to have polar anisotropy, wherein
in a plane orthogonal to an axial direction of the rotor,
25 a magnetic pole center position of the at least one first
permanent magnet coincides with a magnetic pole center position
of the at least one third permanent magnet.
11. The rotor according to any one of claims 1 to 3, wherein
30 both ends of the at least one first permanent magnet in
an axial direction overlap each other by an angle w1 [degrees]
in a plane orthogonal to the axial direction of the rotor, and
the angle w1 satisfies 0 < w1 < 0.2 × 2n/360.
46
12. The rotor according to claim 1 or 2, wherein
in a plane orthogonal to an axial direction of the rotor,
both ends of the at least one first permanent magnet in the
axial direction overlap each other by an angle w2 [degrees] in
5 an inter-pole part of the rotor, and
the angle w2 satisfies 0 < w2 < 0.2 × 2n/360.
13. The rotor according to any one of claims 1 to 3, wherein
a width of the first permanent magnet in the circumferential
10 direction is largest at a center of the rotor in an axial
direction of the rotor.
14. A rotor having 2n (n is a natural number) magnetic poles
and including a plurality of layered magnets composed of two to
15 m (m is a natural number and a divisor for n) layers that are
stacked in an axial direction, wherein
each layered magnet of the plurality of layered magnets
includes
at least one first permanent magnet forming part of an
20 outer peripheral surface of the rotor and magnetized to have
polar anisotropy, and
at least one second permanent magnet that is a different
type from the at least one first permanent magnet, is adjacent
to the at least one first permanent magnet in a circumferential
25 direction of the rotor, has lower magnetic force than magnetic
force of the at least one first permanent magnet, and is
magnetized to have polar anisotropy, and
in each first permanent magnet of the plurality of
layered magnets, supposing one cycle is an angle formed by
30 adjacent north poles in a plane orthogonal to the axial
direction of the rotor, positions of north poles of two first
permanent magnets adjacent to each other in the axial direction
are shifted from each other by n/m cycles in the
circumferential direction.
47
15. The rotor according to any one of claims 1 to 14, wherein
the at least one first permanent magnet is a rare earth magnet.
5 16. The rotor according to any one of claims 1 to 15, wherein
the second permanent magnet is a ferrite magnet.
17. An electric motor comprising:
a stator; and
10 the rotor according to any one of claims 1 to 16
rotatably disposed inside the stator.
18. An air blower comprising:
the electric motor according to claim 17; and
15 a blade to be driven by the electric motor.
19. An air conditioner comprising:
an indoor unit; and
an outdoor unit connected to the indoor unit, wherein
20 at least one of the indoor unit or the outdoor unit
includes the electric motor according to claim 17.
20. A method for fabricating a rotor including a first
permanent magnet and a second permanent magnet, the second
permanent magnet being adjacent to the first permanent magnet
in a circumferential direction and having lower magnetic force
than magnetic force of the first permanent magnet, the method
comprising:
generating a magnetic field having polar anisotropy
inside a mold for the second permanent magnet, by using a
magnet for magnetization;
molding the second permanent magnet magnetized to have
polar anisotropy, by injection molding;
generating a magnetic field having polar anisotropy
inside a mold for the first permanent magnet, by using a magnet
for magnetization; and
molding the first permanent magnet by injection molding
on an outer peripheral surface of the second permanent magnet
so that the first permanent magnet forms part of an outer
peripheral surface of the rotor, in a state where the second
permanent magnet is disposed inside the mold for the first
permanent magnet.