extracted from wipo:
formulas and tables are not copied:
FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
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 motor, a fan, and an
air conditioner.
BACKGROUND ART
[0002]
10 Conventionally, a motor in which a permanent magnet is
attached to a rotor and a coil is attached to a stator is
widely used (see, for example, Patent Reference 1). In such a
motor, demagnetization of the permanent magnet may be caused by
a magnetic flux generated in the coil of the stator.
15 PRIOR ART REFERENCE
PATENT REFERENCE
[0003]
[PATENT REFERENCE 1]
Japanese Patent Application Publication No. 2001-178046
20 (see FIGS. 1 and 2)
SUMMARY OF THE INVENTION
PROBLEM TO BE SOLVED BY THE INVENTION
[0004]
In general, as the thickness of the permanent magnet
25 increases, the demagnetization of the permanent magnet is less
likely to occur, but a use amount of permanent magnet material
increases and thus the manufacturing cost increases. On the
other hand, when the thickness of the permanent magnet is made
extremely thin, the use amount of permanent magnet material is
30 reduced, but the price per unit weight of the permanent magnet
increases due to an increase in the processing cost. This
results in an increase in manufacturing cost.
[0005]
The present invention is intended to solve the above3
described problems, and an object of the present invention is
to suppress the demagnetization of a permanent magnet while
reducing the manufacturing cost.
MEANS OF SOLVING THE PROBLEM
5 [0006]
A motor of the present invention includes a rotor having
a rotor core having a magnet insertion hole, and a permanent
magnet disposed in the magnet insertion hole, the rotor being
rotatable about a rotation axis, and a stator provided so as to
10 surround the rotor, the stator having a stator core having a
tooth facing the rotor, and a coil wound around the tooth. The
permanent magnet has a thickness thicker than or equal to 2.1
mm in a direction in which the permanent magnet faces the
stator and is magnetized in a direction of the thickness. A
15 minimum gap AG (mm) between the rotor and the stator, a winding
number Nt of the coil around the tooth, an overcurrent
threshold Ip (A) for a current flowing through the coil, and a
lower limit Hct (kA/m) of a coercive force of the permanent
magnet satisfy Hct ≥ 0.4 × (Ip × Nt/AG) + 410.
20 [0007]
A motor of the present invention includes a rotor having
a rotor core having a magnet insertion hole, and a permanent
magnet disposed in the magnet insertion hole, the rotor being
rotatable about a rotation axis, and a stator provided so as to
25 surround the rotor, the stator having a stator core having a
tooth facing the rotor, and a coil wound around the tooth. The
permanent magnet has a thickness thicker than or equal to 3 mm
in a direction in which the permanent magnet faces the stator
and is magnetized in a direction of the thickness. The
30 thickness of the permanent magnet is thicker than or equal to 3
mm. A minimum gap AG (mm) between the rotor and the stator, a
winding number Nt of the coil around the tooth, an overcurrent
threshold Ip (A) for a current flowing through the coil, and a
lower limit Hct (kA/m) of a coercive force of the permanent
4
magnet satisfy Hct ≥ 0.32 × (Ip × Nt/AG) + 350.
EFFECTS OF THE INVENTION
[0008]
According to the present invention, the demagnetization
of the permanent magnet can be suppressed 5 while reducing the
manufacturing cost by reducing the price per unit weight of the
permanent magnet.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009]
10 FIG. 1 is a cross-sectional view illustrating a motor of
a first embodiment.
FIG. 2 is a cross-sectional view illustrating a rotor of
the first embodiment.
FIG. 3 is an enlarged cross-sectional view illustrating a
15 part of the motor of the first embodiment.
FIG. 4 is an enlarged schematic diagram illustrating a
portion including an inter-pole portion of the rotor of the
first embodiment.
FIG. 5 is an enlarged cross-sectional view illustrating a
20 part of the rotor of the first embodiment.
FIG. 6 is a graph illustrating a relationship between a
thickness of a permanent magnet and a price per unit weight of
the permanent magnet.
FIG. 7 is a graph illustrating a relationship between Ip
25 × Nt/AG and a lower limit of a coercive force of the permanent
magnet.
FIG. 8 is a graph illustrating a relationship between Ip
× Nt/AG and the lower limit of the coercive force of the
permanent magnet.
30 FIG. 9 is a schematic diagram for explaining the flow of
a magnetization magnetic flux in the rotor.
FIG. 10 is a block diagram illustrating a control system
of the motor of the first embodiment.
FIG. 11 is a cross-sectional view illustrating a rotor of
5
a second embodiment.
FIG. 12 is a cross-sectional view illustrating a part of
the rotor of the second embodiment.
FIG. 13 is a schematic diagram for explaining a position
of an end surface of the permanent magnet in 5 the rotor of the
second embodiment.
FIG. 14 is a longitudinal sectional view illustrating a
motor of the second embodiment.
FIG. 15 is a graph illustrating a relationship between
10 demagnetization current and a demagnetization ratio in the
motor of the second embodiment.
FIG. 16(A) is a front view illustrating an air
conditioner to which the motor of each embodiment is applied,
and FIG. 16(B) is a cross-sectional view illustrating an
15 outdoor unit of the air conditioner.
FIG. 17 is a schematic diagram illustrating a refrigerant
circuit of the air conditioner illustrated in FIG. 16(A).
MODE FOR CARRYING OUT THE INVENTION
[0010]
20 FIRST EMBODIMENT
(Configuration of Motor)
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
25 provided so as to surround the rotor 2. The motor 1 is also a
permanent magnet embedded motor in which permanent magnets 25
are embedded in the rotor 2. An air gap (clearance) 10 of, for
example, 0.4 mm is provided between the rotor 2 and the stator
5.
30 [0011]
Hereinafter, an axis serving as a rotational center of
the rotor 2 is referred to as a rotation axis C1, and a
direction of the rotation axis C1 is referred to as an “axial
direction”. A circumferential direction about the rotation
6
axis C1 (indicated by the arrow R1 in FIG. 1) is referred to as
a “circumferential direction”, and a radial direction about the
rotation axis C1 is referred to as a “radial direction”. FIG.
1 is a cross-sectional view of the motor at a plane
perpendicular to the rotation axis 5 C1 of the rotor 2.
[0012]
(Configuration of Stator)
The stator 5 includes a stator core 50 and a coil 55
wound on the stator core 50. The stator core 50 is formed of a
10 plurality of magnetic stack elements each having a thickness of,
for example, 0.2 mm to 0.5 mm, which are stacked in the axial
direction and fixed 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.
15 [0013]
The stator core 50 has a yoke 52 having an annular shape
about the rotation axis C1 and a plurality of teeth 51
extending inward in the radial direction (i.e., toward the
rotation axis C1) from the yoke 52. The teeth 51 are arranged
20 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 a space for accommodating the coil 55
is formed between adjacent teeth 51.
[0014]
25 A tip end of the tooth 51 on the inner side in the radial
direction has a wider width in the circumferential direction
than other portions of the tooth 51. The tip end of the tooth
51 faces an outer circumference of the rotor 2 via the air gap
10 described above. Each of an outer circumference 50a of the
30 stator core 50 (i.e., an outer circumference of the yoke 52)
and an inner circumference 50b of the stator core 50 (i.e., the
tip end of the tooth 51) has a circular annular shape.
[0015]
Crimping portions for integrally fixing the stack
7
elements of the stator core 50 are formed in the yoke 52 and
the teeth 51 of the stator core 50, as indicated by reference
characters 56 and 57. The crimping portions may be formed in
any other position as long as the stack elements are integrally
fixed by the 5 crimping portions.
[0016]
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
10 stator core 50 and the coil 55 from each other. The insulator
54 is formed by integrally molding a resin with the stator core
50 or assembling a resin molded body which is molded as a
separate component, to the stator core 50.
[0017]
15 The insulator 54 is formed of an insulating resin such as
polybutylene terephthalate (PBT), polyphenylene sulfide (PPS),
liquid crystal polymer (LCP), or polyethylene terephthalate
(PET). The insulator 54 may be formed of an insulating resin
film that has a thickness of 0.035 to 0.4 mm.
20 [0018]
The coil 55 is wound around the tooth 51 via the
insulator 54. The coil 55 is formed of a material that
contains copper or aluminum as a main component. The coil 55
is wound around each tooth 51 (concentrated winding). It is
25 also possible to fill the slot 53 with a resin (for example,
the same resin as that of the insulator 54) so as to surround
the coil 55.
[0019]
(Configuration of Rotor)
30 FIG. 2 is a cross-sectional view illustrating the rotor 2.
The rotor 2 has a rotor core 20 having a cylindrical shape
about the rotation axis C1. The rotor core 20 is formed of a
plurality of magnetic stack elements each having a thickness of
0.2 to 0.5 mm, which are stacked in the axial direction and
8
fixed together by crimping or the like. In this example, the
stack element is an electromagnetic steel sheet 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 5 2 is 50 mm in
this example.
[0020]
The rotor core 20 has a central hole 23 at its center in
the radial direction. The central hole 23 is a shaft insertion
10 hole that passes through the rotor core 20 in the axial
direction and has a circular cross section. A rotation shaft
11 is fixed inside the central hole 23 and is rotatably
supported by bearings 12 and 13 (FIG. 14). The rotation axis
C1 is a central axis of the rotation shaft 11. The rotation
15 shaft 11 is formed of metal such as iron (Fe), nickel (Ni),
chromium (Cr) or the like.
[0021]
A plurality of magnet insertion holes 21 are formed along
an outer circumferential surface of the rotor core 20. The
20 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 through the rotor core 20 in the axial direction. The
number of magnet insertion holes 21 is ten in this example, but
25 is not limited to ten.
[0022]
The magnet insertion hole 21 extends linearly in a
direction perpendicular to a straight line (also referred to as
a magnetic pole center line) that passes through the rotation
30 axis C1 and a pole center M1 to be described later. The magnet
insertion hole 21 has an outer-side end portion 21a which is an
end portion on the outer side in the radial direction, an
inner-side end portion 21b which is an end portion on the inner
side in the radial direction, and side end portions 21c which
9
are both end portions in the circumferential direction.
[0023]
A 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 5 in a direction in
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 formed of, for example, a rare earth
magnet that contains neodymium (Nd) or samarium (Sm), as a main
10 component. The permanent magnet may be formed of a ferrite
magnet that contains iron as a main component, in place of the
rare earth magnet.
[0024]
The permanent magnet 25 is magnetized (in other words,
15 has anisotropy) in a thickness direction. The permanent
magnets 25 adjacent to each other in the circumferential
direction are arranged so that pole-faces of opposite
polarities face the outer circumferential side of the rotor
core 20.
20 [0025]
The permanent magnet 25 disposed in each magnet insertion
hole 21 constitutes a magnetic pole. Thus, the number of
magnetic poles of the rotor 2 is ten. However, the number of
magnetic poles of the rotor 2 is not limited to ten. A center
25 of the magnet insertion hole 21 in the circumferential
direction is the pole center M1. A boundary between the
adjacent magnet insertion holes 21 is an inter-pole portion M2.
[0026]
The permanent magnet 25 has an outer-side end portion 25a
30 which is an end portion on the outer side in the radial
direction, an inner-side end portion 25b which is an end
portion on the inner side in the radial direction, and side end
portions 25c which are both end portions in the circumferential
direction. The outer-side end portion 25a of the permanent
10
magnet 25 faces the outer-side end portion 21a of the magnet
insertion hole 21, while the inner-side end portion 25b of the
permanent magnet 25 faces the inner-side end portion 21b of the
magnet insertion hole 21. The side end portions 25c of the
permanent magnet 25 face the side end portions 5 21c of the
magnet insertion hole 21.
[0027]
Although one permanent magnet 25 is disposed in each
magnet insertion hole 21 in this example, a plurality of
10 permanent magnets 25 may be disposed side by side in the
circumferential direction in each magnet insertion hole 21. In
this case, the magnet insertion hole 21 may be formed in a V
shape so that its center in the circumferential direction
protrudes inward in the radial direction.
15 [0028]
A flux barrier (i.e., a leakage magnetic flux suppression
hole) 22 is formed on each of both sides of the magnet
insertion hole 21 in the circumferential direction. Each flux
barrier 22 has a first portion 22a (FIG. 4) extending from the
20 outer-side end portion 21a of the magnet insertion hole 21
outward in the radial direction, and a second portion 22b (FIG.
4) extending from the side end portion 21c of the magnet
insertion hole 21 toward the inter-pole portion M2 side.
[0029]
25 A core portion between the flux barrier 22 and the outer
circumference of the rotor core 20 is a thin-walled portion
(also referred to as a bridge portion). A thickness of the
thin-walled portion is desirably the same as the thickness of
each of the stack elements constituting the rotor core 20.
30 This makes it possible to suppress the leakage magnetic flux
between the adjacent magnetic poles. The flux barrier 22 is
disposed on each of both sides of the magnet insertion hole 21
in the circumferential direction, but may be disposed only on
one side of the magnet insertion hole 21 in the circumferential
11
direction.
[0030]
FIG. 3 is an enlarged cross-sectional view illustrating a
part of the motor 1. The rotor core 20 has a flower shape
whose outer diameter is maximum at the pole 5 center M1 and is
minimum at the inter-pole portion M2. Meanwhile, the inner
circumference 50b of the stator core 50 has a circular annular
shape. Thus, a gap between the rotor 2 and the stator 5 (i.e.,
a width of the air gap 10) has a minimum value G1 at the pole
10 center M1 and a maximum value G2 at the inter-pole portion M2.
The minimum value G1 of the gap between the rotor 2 and the
stator 5 is referred to as a minimum gap AG between the rotor 2
and the stator 5.
[0031]
15 FIG. 4 is an enlarged diagram illustrating a portion
including the inter-pole portion M2 of the rotor 2. The outer
circumference of the rotor core 20 has an outer circumferential
portion 20a including the pole center M1 and an outer
circumferential portion 20b including the inter-pole portion M2.
20 Both of the outer circumferential portions 20a and 20b are arcshaped
portions having centers of curvature on the rotation
axis C1 side, but have different radii of curvature. In this
example, a border E between the outer circumferential portion
20a and the outer circumferential portion 20b is located on the
25 outer side of the flux barrier 22 in the radial direction.
[0032]
FIG. 5 is an enlarged cross-sectional view illustrating a
part of the rotor 2. In the outer circumference of the rotor
core 20, a distance from the inner circumference 50b of the
30 stator 5 (FIG. 3) to the outer circumferential portion 20b
including the inter-pole portion M2 is longer than a distance
from the inner circumference 50b to the outer circumferential
portion 20a including the pole center M1. That is, the outer
circumferential portion 20b faces the air gap 10 which is wider
12
than that the outer circumferential portion 20a faces.
[0033]
A point A1 as a first point is defined on the outer
circumferential portion 20b. The side end portion 25c of the
permanent magnet 25 (i.e., the 5 end portion in the
circumferential direction) is disposed on a straight line L1
connecting the point A1 and the rotation axis C1. The outer
circumferential portion 20b of the rotor core 20 is at a longer
distance from the stator 5. Thus, by disposing the side end
10 portion 25c of the permanent magnet 25 on the straight line L1,
a magnetic flux from the stator 5 (also referred to as a stator
magnetic flux) is less likely to flow to the side end portion
25c of the permanent magnet 25. Although the side end portion
25c of the permanent magnet 25 is a portion which is more
15 likely to be demagnetized, the demagnetization of the side end
portion 25c can be made less likely to occur by disposing the
side end portion 25c of the permanent magnet 25 as above.
[0034]
An outer corner 25e, which is the corner of the side end
20 portion 25c of the permanent magnet 25 on the outer side in the
radial direction, is more desirably disposed on the straight
line L1 connecting the point A1 and the rotation axis C1.
Although the outer corner 25e of the permanent magnet 25 is a
portion which is most likely to be demagnetized, the
25 demagnetization of the outer corner 25e is less likely to occur
by disposing the outer corner 25e of the permanent magnet 25 as
above.
[0035]
As illustrated in FIG. 4, the outer corner 25e of the
30 permanent magnet 25 is disposed inside the flux barrier 22 and
is not in contact with the rotor core 20. Thus, the magnetic
flux flowing through of the rotor core 20 is not likely to
reach the outer corner 25e of the permanent magnet 25. As a
result, the demagnetization of the outer corner 25e of the
13
permanent magnet 25 is further less likely to occur.
[0036]
(Reduction of Manufacturing Cost and Suppression of
Demagnetization of Permanent Magnet)
Next, the manufacturing cost 5 and suppression of
demagnetization of the permanent magnet 25 will be described.
The demagnetization characteristic of the permanent magnet 25
has a correlation to the thickness T1 of the permanent magnet
25. In general, as the thickness T1 of the permanent magnet 25
10 increases, the demagnetization is less likely to occur (in
other words, resistance to demagnetization increases). As the
thickness T1 of the permanent magnet 25 decreases, the
demagnetization is more likely to occur (in other words, the
resistance to demagnetization decreases).
15 [0037]
On the other hand, as the thickness T1 of the permanent
magnet 25 increases, the use amount of material increases, and
thus the manufacturing cost increases. When the thickness T1
of the permanent magnet 25 is extremely thin, the use amount of
20 material is reduced, but the processing cost increases. The
increase in the processing cost exceeds the reduction in the
material cost, which leads to an increase in the manufacturing
cost.
[0038]
25 FIG. 6 is a graph illustrating a relationship between the
thickness T1 (mm) of the permanent magnet 25 and a price per
unit weight (Yen/g) of the permanent magnet 25. From FIG. 6,
it is understood that, when the thickness T1 of the permanent
magnet 25 is thinner than 2.1 mm, the price per unit weight
30 (Yen/g) of the permanent magnet 25 increases dramatically due
to an increase in the processing cost. Thus, it is desirable
to suppress the demagnetization of the permanent magnet 25
while setting the thickness T1 of the permanent magnet 25 to be
thicker than or equal to 2.1 mm.
14
[0039]
The demagnetization of the permanent magnet 25 is caused
by the magnetic flux from the stator 5, i.e., the magnetic flux
generated by the current flowing through the coil 55. This
magnetic flux is proportional to the product 5 of the current
flowing through the coil 55 and a winding number (the number of
turns) Nt of the coil 55 wound around one tooth 51.
[0040]
As the minimum gap AG between the rotor 2 and the stator
10 5 decreases, the magnetic flux from the stator 5 reaching the
rotor 2 increases. As the minimum gap AG between the rotor 2
and the stator 5 increases, the magnetic flux from the stator 5
reaching the rotor 2 decreases.
[0041]
15 Here, focus is placed on a value (Ip × Nt/AG), which is
obtained by dividing the product Ip × Nt of an overcurrent
threshold Ip (A) and the winding number Nt of the coil 55 for
one tooth 51, by the minimum gap AG (mm) between the rotor 2
and the stator 5. The overcurrent threshold Ip (A) is the
20 maximum value of the current flowing through the coil 55. The
unit of Ip × Nt/AG is A/mm.
[0042]
The motor 1 is controlled by a drive device 101 (FIG. 10)
to be described later so that the current flowing through the
25 coil 55 does not exceed the overcurrent threshold (i.e., an
overcurrent protection level). This overcurrent threshold is
the above-described overcurrent threshold Ip. The overcurrent
threshold is also referred to as an overcurrent cutoff value.
[0043]
30 FIG. 7 is a graph illustrating a relationship between Ip
× Nt/AG and a lower limit Hct (kA/m) of a coercive force of the
permanent magnet 25. The coercive force refers to an intensity
of the magnetic field at which the magnetic polarization of the
permanent magnet 25 is zero in a magnetization curve (J-H
15
curve).
[0044]
The permanent magnet 25 formed of a rare earth magnet has
characteristic such that its coercive force decreases as a
temperature increases. When the motor 1 is used 5 in a fan of an
air conditioner, the temperature of the permanent magnet 25
increases to 100°C. Thus, the lower limit Hct of the coercive
force is defined as the coercive force of the permanent magnet
25 when the temperature of the permanent magnet 25 is 100°C
10 (i.e., the highest temperature in an operating temperature
range).
[0045]
FIG. 7 shows data obtained when the thickness T1 of the
permanent magnet 25 is changed to five different values, namely,
15 1.5 mm, 2.1 mm, 3 mm, 5 mm, and 6 mm. For example, in a case
where the thickness T1 of the permanent magnet 25 is 2.1 mm,
when the coordinates (Ip × Nt/AG, Hct) are on or above a curve
for T1 = 2.1 mm, the demagnetization of the permanent magnet 25
does not occur. As the thickness T1 of the permanent magnet 25
20 increases, the demagnetization is less likely to occur. Thus,
as the thickness T1 increases, the curve is located on the
lower side.
[0046]
From FIG. 7, it is understood that, in a region where Ip
25 × Nt/AG is higher than or equal to 750 (A/mm), there is a
linear functional relationship between Ip × Nt/AG and the lower
limit Hct of the coercive force. In particular, the curve
indicative of the data for the thickness T1 of 2.1 mm can be
approximated by a straight line of Hct = 0.4 × (Ip × Nt/AG +
30 410 (indicated by a dashed line in FIG. 7).
[0047]
From this, it is understood that the demagnetization of
the permanent magnet 25 having the thickness T1 thicker than or
equal to 2.1 mm can be suppressed when Hct  0.4 × (Ip × Nt/AG)
16
+ 410 is satisfied. That is, by setting the thickness T1 of
the permanent magnet 25 to be thicker than or equal to 2.1 mm,
the demagnetization of the permanent magnet 25 can be
suppressed while reducing the manufacturing cost.
5 [0048]
As illustrated in FIG. 6 described above, when the
thickness T1 of the permanent magnet 25 is thicker than or
equal to 3 mm, the price per unit weight (yen/g) of the
permanent magnet 25 is constant. Thus, it is more desirable to
10 suppress demagnetization of the permanent magnet 25 while
setting the thickness T1 of the permanent magnet 25 to be
thicker than or equal to 3 mm.
[0049]
FIG. 8 is a graph in which the curve for the thickness T1
15 of 3 mm is approximated by a straight line in the same graph as
FIG. 7. The respective curves indicating data when the
thickness T1 of the permanent magnet 25 is 1.5 mm, 2.1 mm, 3 mm,
5 mm, and 6 mm are the same as those in FIG. 7. As illustrated
in FIG. 8, the curve indicating the data for the thickness T1
20 of 3 mm can be approximated by a straight line of Hct = 0.32 ×
(Ip × Nt/AG) + 350 in the region where Ip × Nt/AG is greater
than or equal to 750 (A/mm).
[0050]
From this, it is understood that the demagnetization of
25 the permanent magnet 25 having the thickness T1 thicker than or
equal to 3 mm can be suppressed when Hct  0.32 × (Ip × Nt/AG)
+ 350 is satisfied. That is, by setting the thickness T1 of
the permanent magnet 25 to be thicker than or equal to 3 mm,
the manufacturing cost can be further reduced and the
30 demagnetization of the permanent magnet 25 can be suppressed.
[0051]
A portion of the permanent magnet 25 that is relatively
likely to be demagnetized is the side end portions 25c where
the magnetic flux is likely to concentrate. For this reason,
17
as illustrated in FIG. 5, the side end portion 25c of the
permanent magnet 25 is disposed on the straight line L1
connecting the point A1 on the outer circumferential portion
20b of the rotor core 20 and the rotation axis C1.
5 [0052]
The air gap 10 between the rotor 2 and the stator 5 is a
space and has a high magnetic resistance compared to the rotor
core 20 formed of a magnetic material. Thus, the side end
portion 25c of the permanent magnet 25 is disposed on the inner
10 side of the outer circumferential portion 20b in the radial
direction (i.e., on the straight line L1) via a wide space from
the stator 5. This makes it difficult for the stator magnetic
flux to flow to the side end portion 25c, so that the
demagnetization of the side end portion 25c of the permanent
15 magnet 25 can be made less likely to occur.
[0053]
In particular, a portion of the permanent magnet 25 that
is most likely to be demagnetized is the outer corner 25e of
the side end portions 25c. For this reason, as illustrated in
20 FIG. 4, the outer corner 25e of the permanent magnet 25 is
desirably disposed on the straight line L1 connecting the point
A1 on the outer circumferential portion 20b of the rotor core
20 and the rotation axis C1. This makes it difficult for the
stator magnetic flux to flow to the outer corner 25e, so that
25 the demagnetization of the outer corner 25e of the permanent
magnet 25 can be made less likely to occur.
[0054]
As illustrated in FIG. 4, the outer corner 25e of the
permanent magnet 25 is disposed inside the flux barrier 22 and
30 is not in contact with the rotor core 20. The flux barrier 22
is an opening and has a high magnetic resistance. Since the
outer corner 25e of the permanent magnet 25 is surrounded by
the opening, the magnetic flux flowing through the rotor core
20 is less likely to reach the outer corner 25e. As a result,
18
the demagnetization of the outer corner 25e of the permanent
magnet 25 can be made further less likely to occur.
[0055]
(Thickness of Permanent Magnet)
As described above, the thickness T1 5 of the permanent
magnet 25 is desirably thicker than or equal to 2.1 mm in order
to reduce the manufacturing cost. Meanwhile, the permanent
magnet 25 is generally magnetized in a state where the
permanent magnet 25 is inserted into the magnet insertion hole
10 21 of the rotor core 20.
[0056]
FIG. 9 is a schematic diagram illustrating a magnetizing
step of the permanent magnet 25. A magnetization magnetic flux
F which is generated in a magnetization device disposed on the
15 outer circumferential side of the rotor core 20 flows to the
permanent magnet 25 in the magnet insertion hole 21 through the
outer circumferential portion of the rotor core 20.
[0057]
The magnetization direction D of the permanent magnet 25
20 is the thickness direction. Thus, only a component of the
magnetization magnetic flux F in the thickness direction of the
permanent magnet 25 contributes to the magnetization of the
permanent magnet 25. In a case where the diameter of the rotor
2 is 50 mm, when the thickness of the permanent magnet 25
25 exceeds 4 mm (a thickness T2 illustrated in FIG. 9), the
magnetization magnetic flux F passing through an inner region
of the permanent magnet 25 in the radial direction is largely
inclined with respect to the thickness direction, and thus
magnetization of the inner side of the permanent magnet 25 in
30 the radial direction is insufficient.
[0058]
Thus, in order to sufficiently magnetize the permanent
magnet 25, the thickness T1 of the permanent magnet 25 is
desirably thinner than or equal to 4 mm.
19
[0059]
(Drive Device of Motor)
Next, the drive device 101 that drives the motor 1 will
be described. FIG. 10 is a block diagram illustrating a
configuration of the drive device 101. The 5 drive device 101
may be mounted on a board 7 (FIG. 14) incorporated in the motor
1 or may be provided outside the motor 1.
[0060]
The drive device 101 has a converter 102 that rectifies
10 an output of a power source 110, an inverter 103 that outputs
an AC voltage to the coil 55 of the motor 1, and a controller
105 that controls these components. The power source 110 is,
for example, an AC power source of 200 V (effective voltage).
[0061]
15 The controller 105 has a current detection circuit 108
that detects a current value of the inverter 103, an inverter
drive circuit 107 that drives the inverter 103, and a CPU 106
that serves as an inverter control unit.
[0062]
20 The converter 102 is a rectifier circuit that receives an
AC voltage from the power source 110, rectifies and smooths the
voltage, and outputs the voltage through bus lines 111 and 112.
The converter 102 has bridge diodes 102a, 102b, 102c, and 102d
that rectify the AC voltage, and a smoothing capacitor 102e
25 that smooths the output voltage. The voltage output from the
converter 102 is referred to as a bus line voltage. The output
voltage of the converter 102 is controlled by the controller
105.
[0063]
30 The input terminals of the inverter 103 are connected to
the bus lines 111 and 112 of the converter 102. Meanwhile, the
output terminals of the inverter 103 are connected to threephase
coil portions of the motor 1 via U-phase, V-phase, and Wphase
wirings (output wires) 104U, 104V, and 104W.
20
[0064]
The inverter 103 has a U-phase switching element 1Ua
corresponding to a U-phase upper arm, a U-phase switching
element 1Ub corresponding to a U-phase lower arm, a V-phase
switching element 1Va corresponding to a V-5 phase upper arm, a
V-phase switching element 1Vb corresponding to a V-phase lower
arm, a W-phase switching element 1Wa corresponding to a W-phase
upper arm, and a W-phase switching element 1Wb corresponding to
a W-phase lower arm.
10 [0065]
The U-phase switching elements 1Ua and 1Ub are connected
to the U-phase wiring 104U. A U-phase diode 2Ua is connected
in parallel to the U-phase switching element 1Ua. A U-phase
diode 2Ub is connected in parallel to the U-phase switching
15 element 1Ub.
[0066]
The V-phase switching elements 1Va and 1Vb are connected
to the V-phase wiring 104V. A V-phase diode 2Va is connected
in parallel to the V-phase switching element 1Va. A V-phase
20 diode 2Vb is connected in parallel to the V-phase switching
element 1Vb.
[0067]
The W-phase switching elements 1Wa and 1Wb are connected
to the W-phase wiring 104W. A W-phase diode 2Wa is connected
25 in parallel to the W-phase switching element 1Wa. A W-phase
diode 2Wb is connected in parallel to the W-phase switching
element 1Wb.
[0068]
Each of the switching elements 1Ua to 1Wb can be
30 constituted by, for example, a transistor such as an Insulated-
Gate Bipolar Transistor (IGBT). Switching of each of the
switching elements 1Ua to 1Wb is controlled by a drive signal
from the inverter drive circuit 107.
[0069]
21
The inverter drive circuit 107 generates a drive signal
for switching on and off each of the switching elements 1Ua to
1Wb of the inverter 103 based on a Pulse Width Modulation (PWM)
signal input from the CPU 106, and outputs the drive signal to
5 the inverter 103.
[0070]
A resistor 109 is connected to an input side of the
inverter 103 (for example, the bus line 112 from the converter
102), and the current detection circuit 108 is connected to the
10 resistor 109. The current detection circuit 108 is a current
detector that detects a current value of the current on the
input side of the inverter 103 (i.e., the bus line current of
the converter 102). In this example, a shunt resistor is used
as the current detection circuit 108.
15 [0071]
The CPU 106 as the inverter control unit controls the
inverter 103. The CPU 106 outputs an inverter drive signal (a
PWM signal) to the inverter 103 based on an operation
instruction signal or the like from a remote controller of the
20 air conditioner 500 or the like.
[0072]
The CPU 106 detects the current value of the inverter 103
using the current detection circuit 108 and compares the
detected current value with an overcurrent threshold stored in
25 advance. When the detected current value is greater than or
equal to the overcurrent threshold, a stopping signal is output
to the inverter 103 to thereby stop the inverter 103 (that is,
to stop the rotation of the motor 1). This overcurrent
threshold is the overcurrent threshold Ip described above.
30 [0073]
(Effects of Embodiment)
As described above, in the first embodiment, the
permanent magnet 25 has the thickness T1 thicker than or equal
to 2.1 mm, and the minimum gap AG between the rotor 2 and the
22
stator 5, the winding number Nt of the coil 55 wound around the
tooth 51, the overcurrent threshold Ip for the current flowing
through the coil 55, and the lower limit Hct of the coercive
force of the permanent magnet 25 satisfy Hct ≥ 0.4 × (Ip ×
Nt/AG) + 410. This makes it possible 5 to suppress
demagnetization of the permanent magnet 25 while reducing the
price per unit weight of the permanent magnet 25 to reduce the
manufacturing cost.
[0074]
10 Further, the permanent magnet 25 has the thickness T1
thicker than or equal to 3 mm, and the minimum gap AG between
the rotor 2 and the stator 5, the winding number Nt of the coil
55 wound around the tooth 51, the overcurrent threshold Ip for
the current flowing through the coil 55, and the lower limit
15 Hct of the coercive force of the permanent magnet 25 satisfy
Hct ≥ 0.32 × (Ip × Nt/AG) + 350. This makes it possible to
suppress demagnetization of the permanent magnet 25 while
reducing the price per unit weight of the permanent magnet 25
to a further lower level to reduce the manufacturing cost.
20 [0075]
By setting the thickness T1 of the permanent magnet 25 to
be made less than or equal to 4 mm, the entire permanent magnet
25 can be sufficiently magnetized in a state where the
permanent magnet 25 is inserted into the magnet insertion hole
25 21.
[0076]
The outer circumference of the rotor core 20 has the
outer circumferential portion 20a (i.e., the first outer
circumferential portion) located at a shorter distance from the
30 stator 5 and the outer circumferential portion 20b (i.e., the
second outer circumferential portion) located at a longer
distance from the stator 5, and the side end portion 25c of the
permanent magnet 25 is disposed on the straight line connecting
the point A1 (i.e., the first point) on the outer
23
circumferential portion 20b and the rotation axis C1. This
makes it difficult for the stator magnetic flux to flow to the
side end portion 25c of the permanent magnet 25, and thus the
demagnetization can be suppressed.
5 [0077]
The corner (the outer corner 25e) on the outer side in
the radial direction of the side end portion 25c of the
permanent magnet 25 is disposed on the straight line connecting
the point A1 on the outer circumferential portion 20b of the
10 rotor core 20 and the rotation axis C1. This makes it
difficult for the stator magnetic flux to flow to the outer
corner 25e of the permanent magnet 25, and thus the effect of
suppressing the demagnetization can be enhanced.
[0078]
15 The outer corner 25e of the permanent magnet 25 is formed
in the flux barrier 22 formed continuously with the magnet
insertion hole 21, and is not in contact with the rotor core 20.
This makes it difficult for the magnetic flux in the rotor core
20 to reach the outer corner 25e of the permanent magnet 25.
20 Thus, the effect of suppressing the demagnetization can be
further enhanced.
[0079]
Second Embodiment
Next, a second embodiment of the present invention will
25 be described. A motor 1A of the second embodiment differs from
the motor 1 of the first embodiment in a configuration of the
rotor 3. A stator of the motor 1A of the second embodiment has
a configuration similar to that of the stator 5 of the motor 1
of the first embodiment.
30 [0080]
(Configuration of Rotor)
FIG. 11 is a cross-sectional view illustrating a rotor 3
of the second embodiment. The rotor 3 has a rotor core 30
having a cylindrical shape about the rotation axis C1. The
24
rotor core 30 is composed of a plurality of magnetic stack
elements each having a thickness of 0.2 to 0.5 mm, which are
stacked in the axial direction and fixed together by crimping
or the like. A structure of the stack element is as described
in the 5 first embodiment.
[0081]
A plurality of magnet insertion holes 31 are formed along
an outer circumferential surface of the rotor core 30. The
magnet insertion holes 31 are arranged at equal intervals in
10 the circumferential direction. Each magnet insertion hole 31
has an elongated shape in the circumferential direction and
passes through the rotor core 30 in the axial direction. The
number of magnet insertion holes 31 is five in this example. A
permanent magnet 35 is disposed in each magnet insertion hole
15 31.
[0082]
The permanent magnet 35 disposed in each magnet insertion
hole 31 constitutes a magnet magnetic pole P1. The permanent
magnets 35 are arranged in such a manner that pole-faces of the
20 same polarity (for example, N pole) face the outer
circumferential side of the rotor core 30. Thus, a portion
through which the magnetic flux flows in the radial direction
is formed between adjacent permanent magnets 35 in the rotor
core 30. That is, a pseudo-magnetic pole P2 whose polarity is
25 opposite to that of the permanent magnet 35 is formed.
[0083]
That is, the rotor 3 has five magnet magnetic poles P1
and five pseudo-magnetic poles P2, which are alternately
arranged in the circumferential direction. Thus, the number of
30 poles of the rotor 3 is ten. The motor having such a rotor
configuration is referred to as a consequent pole type. The
number of poles of the rotor 3 is not limited to ten.
[0084]
The rotor core 30 has an inner circumference 33 of an
25
annular shape. A resin portion 4 is provided on an inner side
the rotor core 30, and serves as a supporting portion that
supports the rotor core 30. The resin portion 4 supports the
rotor core 30 with respect to the rotation shaft 11 and is
formed of a non-magnetic material, more 5 specifically, a
thermoplastic resin such as polybutylene terephthalate (PBT).
The resin portion 4 can be obtained by molding the rotor core
30 and the rotation shaft 11 with resin.
[0085]
10 The resin portion 4 includes an inner cylindrical portion
41 fixed to the outer circumferential surface of the rotation
shaft 11, an annular outer cylindrical portion 43 fixed to the
inner circumference 33 of the rotor core 30, and a plurality of
ribs (connecting portions) 42 connecting the inner cylindrical
15 portion 41 and the outer cylindrical portion 43.
[0086]
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
20 and radially extend from the inner cylindrical portion 41
toward the outer side in the radial direction. The position of
each rib 42 in the circumferential direction corresponds to the
center of the permanent magnet 35 in the circumferential
direction (i.e., the pole center of the magnet magnetic pole
25 P1). A hollow portion 44 is formed between ribs 42 adjacent to
each other in the circumferential direction. The outer
cylindrical portion 43 is formed to be continuous to outer ends
in the radial direction of the ribs 42.
[0087]
30 In the consequent pole type rotor 3, there is no
permanent magnet in the pseudo-magnetic pole P2, and thus the
magnetic flux passing through the pseudo-magnetic pole P2 is
more likely to flow toward the rotation shaft 11. By providing
the resin portion 4 between the rotor core 30 and the rotation
26
shaft 11, the leakage magnetic flux to the rotation shaft 11
can be suppressed.
[0088]
FIG. 12 is a cross-sectional view showing the rotor core
30 and the permanent magnet 35. In FIG. 12, 5 the resin portion
4 and the rotation shaft 11 are omitted. The outer
circumference of the rotor core 30 has outer circumferential
portions 30a (i.e., first center circumferential portions)
whose centers are located at the pole centers of the magnetic
10 poles (the magnet poles P1 and the pseudo-magnetic poles P2),
and outer circumferential portions 30b (i.e., second outer
circumferential portions) whose centers are located at the
inter-pole portions. The outer circumferential portions 30a
and 30b have the same shapes as the outer circumferential
15 portions 20a and 20b described in the first embodiment,
respectively.
[0089]
The magnet insertion hole 31 has the same shape as the
magnet insertion hole 21 of the first embodiment. Flux
20 barriers 32 are formed on both sides of the magnet insertion
hole 31 in the circumferential direction. The flux barrier 32
is provided for suppressing the leakage magnetic flux between
the magnetic pole P1 and the pseudo-magnetic pole P2. The flux
barrier 32 has the same shape as the flux barrier 22 of the
25 first embodiment.
[0090]
The permanent magnet 35 has the same structure as the
permanent magnet 25 of the first embodiment. That is, the
thickness of the permanent magnet 35 is thicker than or equal
30 to 2.1 mm. The overcurrent threshold Ip (A) for the current
flowing through the coil 55, the winding number Nt of the coil
55 for one tooth 51, the minimum gap AG (mm) between the rotor
2 and the stator 5, and the lower limit Hct of the coercive
force of the permanent magnet 35 satisfy Hct ≥ 0.4 × (Ip ×
27
Nt/AG) + 410.
[0091]
The thickness of the permanent magnet 35 may be thicker
than or equal to 3 mm. In this case, the overcurrent threshold
Ip (A) for the current flowing through the coil 5 55, the winding
number Nt of the coil 55 for one tooth 51, the minimum gap AG
(mm) between the rotor 2 and the stator 5, and the lower limit
Hct of the coercive force of the permanent magnet 35 satisfy
Hct ≥ 0.32 × (Ip × Nt/AG) + 350.
10 [0092]
Thus, by setting the thickness T1 of the permanent magnet
35 to be thicker than or equal to 2.1 mm (or thicker than or
equal to 3 mm), demagnetization of the permanent magnet 25 can
be suppressed while reducing the manufacturing cost.
15 [0093]
FIG. 13 is an enlarged diagram for explaining the
position of a side end portion 35c of the permanent magnet 35.
In FIG. 13, a straight line L1 is defined as a straight line
connecting a point A1 on the outer circumferential portion 30b
20 of the rotor core 30 and the rotation axis C1 (FIG. 12). The
side end portion 35c of the permanent magnet 35 is located on
the straight line L1. This makes it difficult for the stator
magnetic flux to flow to the side end portions 35c of the
permanent magnet 35, which is a portion where demagnetization
25 is more likely to occur. Thus, the demagnetization can be
suppressed.
[0094]
More desirably, an outer corner 35e which is an outer
corner in the radial direction of the side end portion 35c of
30 the permanent magnet 35 is located on the straight line L1.
This makes it difficult for the stator magnetic flux to flow to
the outer corner 35e of the permanent magnet 35, which is a
portion where the demagnetization is most likely to occur.
Thus, the effect of suppressing the demagnetization is enhanced.
28
[0095]
The outer corner 35e of the permanent magnet 35 is
located inside the flux barrier 32 and is not in contact with
the rotor core 30. Thus, the magnetic flux flowing through the
rotor core 30 is less likely to reach the outer 5 corner 35e of
the permanent magnet 35. Thus, the effect of suppressing the
demagnetization is enhanced.
[0096]
(Configuration of Motor)
10 FIG. 14 is a side cross-sectional view showing a motor 1
of a second embodiment. The stator 5 is covered with a mold
resin portion 60 to configure a mold stator 6.
[0097]
The mold resin portion 60 is formed of, for example, a
15 thermosetting resin such as a bulk molding compound (BMC). The
mold resin portion 60 has an opening 62 on the left side (a
load side to be described later) in FIG. 14 and a bearing
supporting portion 61 located on the side opposite to the
opening 62 (a counter-load side to be described later). The
20 rotor 3 is inserted through the opening 62 into a hollow
portion inside the stator 5.
[0098]
A metal bracket 15 is mounted to the opening 62 of the
mold resin portion 60. One bearing 12 that supports the
25 rotation shaft 11 is held by the bracket 15. A cap 14 that
prevents water or the like from intruding into the bearing 12
is attached to the outside of the bracket 15. The other
bearing 13 that supports the rotation shaft 11 is held by the
bearing supporting portion 61.
30 [0099]
The rotation shaft 11 protrudes from the stator 5 to the
left side in FIG. 14. For example, an impeller of a fan is
attached to a tip end 11a of the rotation shaft 11. Thus, the
protruding side (the left side in FIG. 14) of the rotation
29
shaft 11 is referred to as the “load side”, whereas the side
opposite to the load side (the right side in FIG. 14) is
referred to as the “counter-load side”.
[0100]
The board 7 is disposed on the counter-5 load side of the
stator 5. A drive circuit 72 for driving the motor 1 and a
magnetic sensor 71 are mounted on the board 7. The magnetic
sensor 71 is disposed so as to face a sensor magnet 36 attached
to the rotor 3. The drive circuit 72 is the drive device 101
10 illustrated in FIG. 10. Alternatively, the drive circuit 72
can be provided outside the motor 1, instead of being provided
on the board 7.
[0101]
Lead wires 73 are wired on the board 7. The lead wires
15 73 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 74 for drawing out the lead wires 73 to the outside
is attached to an outer circumferential portion of the mold
20 resin portion 60.
[0102]
The resin portion 4 described above is provided on an
inner circumferential side of the rotor core 30, and also
covers both end surfaces of the rotor core 30 in the axial
25 direction. A part of the resin portion 4 is desirably inserted
into the magnet insertion hole 31. This prevents the permanent
magnet 35 from dropping out of the magnet insertion hole 31.
[0103]
The sensor magnet (i.e., a position detecting magnet) 36
30 having an annular shape is attached to the rotor core 30. The
sensor magnet 36 is disposed on the side of the rotor core 30
that faces the board 7 in the axial direction and held so as to
be surrounded by the resin portion 4. The sensor magnet 36 has
magnetic poles the number of which is the same as the number of
30
poles of the rotors 3, and the magnetic poles are arranged at
equal intervals in the circumferential direction. The
magnetization direction of the sensor magnet 36 is the axial
direction, but is not limited thereto.
5 [0104]
The magnetic sensor 71 is constituted by, for example, a
Hall IC and disposed so as to face the sensor magnet 36 of the
rotor 3. The magnetic sensor 71 detects a position (i.e., a
rotational position) of the rotor 3 in the circumferential
10 direction based on a change in the magnetic flux (N/S) from the
sensor magnet 36, and outputs a detection signal. The magnetic
sensor 71 is not limited to the Hall IC, but may also be a
Magneto-Resistive (MR) device, a Giant-Magneto-Resistive (GMR)
device, or a magnetic impedance device.
15 [0105]
The detection signal of the magnetic sensor 71 is output
to the drive circuit 72. When 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 sensor lead
20 wires. The drive circuit 72 controls the current flowing
through 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.
[0106]
25 Here, description has been made of an example in which
the sensor magnet 36 and the magnetic sensor 71 are used to
detect the rotational position of the rotor 3, but it is
possible to perform sensor-less control in which the rotational
position of the rotor 3 is detected based on the current
30 flowing through the coil 55 or the like.
[0107]
Here, description has been made of a configuration in
which the stator 5 is covered with the mold resin portion 60,
but it is also possible to employ a configuration in which the
31
stator 5 is fixed by shrink-fitting into the inside of a shell.
The configuration of the motor 1A described with reference to
FIG. 14 is also applied to the motor 1 of the first embodiment
except for the rotor 3 and the resin portion 4.
5 [0108]
FIG. 15 is a graph illustrating changes in the
demagnetization ratio with respect to the demagnetization
current in the motor 1 of the first embodiment and the motor 1A
of the second embodiment in comparison to each other. In FIG.
10 15, a curve S1 indicates data for the motor 1 of the first
embodiment, and a curve S2 indicates data for the motor 1A of
the second embodiment. The demagnetization current refers to a
current which flows through the coil 55 to generate a stator
magnetic flux.
15 [0109]
Since the motor 1A of the second embodiment has the
consequent pole type rotor 3, the number of permanent magnets
35 is smaller than that of the motor 1 in the first embodiment.
Thus, portions demagnetized by the stator magnetic flux are
20 small in number, and therefore the demagnetization of the
permanent magnets 35 is less likely to occur. As a result, in
the motor 1A of the second embodiment, an increase in the
demagnetization ratio with an increase in the demagnetization
current is reduced to a lower level than that in the motor 1 of
25 the first embodiment.
[0110]
(Effects of Embodiment)
As described above, in the motor 1A of the second
embodiment, the rotor 3 is of the consequent pole type and the
30 permanent magnets 35 are small in number, and portions where
demagnetization occurs are small in number. Therefore,
demagnetization of the permanent magnets 35 can be effectively
prevented, in addition to the effects described in the first
embodiment.
32
[0111]
The resin portion 4 (i.e., the supporting portion) formed
of non-magnetic material is provided between the rotor core 30
and the rotation shaft 11, and thus it is possible to suppress
the leakage magnetic flux to the rotation shaft 5 11 which tends
to occur in the consequent pole type rotor.
[0112]
Although the resin portion 4 is provided between the
rotor core 30 and the rotation shaft 11 in this example, it is
10 also possible to directly fix the rotation shaft 11 to the
rotor core 30 without providing the resin portion 4, like the
rotor core 20 (FIG. 2) of the first embodiment. The resin
portion 4 as in the second embodiment may be provided between
the rotor core 20 and the rotation shaft 11 of the first
15 embodiment.
[0113]
(Air Conditioner)
Next, an air conditioner to which the motor of each of
the embodiments described above is applied will be described.
20 FIG. 16(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
501, an indoor unit 502, and a refrigerant pipe 503 connecting
these units. The outdoor unit 501 has a fan (i.e., an outdoor
25 fan) 510.
[0114]
FIG. 16(B) is a cross-sectional view taken along the line
16B-16B illustrated in FIG. 16(A). The outdoor unit 501 has a
housing 508 and a frame 509 fixed within the housing 508. The
30 motor 1 serving as a drive source of the fan 510 is fixed to
the frame 509 by screws or the like. An impeller (blade
portion) 511 is attached to the rotation shaft 11 of the motor
1 via a hub 512.
[0115]
33
FIG. 17 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
compressor 504, the condenser 505, the throttle 5 device 506, and
the evaporator 507 are connected by the refrigerant pipe 503 to
constitute a refrigeration cycle. That is, the refrigerant
circulates through the compressor 504, the condenser 505, the
throttle device 506, and the evaporator 507 in this order.
10 [0116]
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 (i.e.,
an indoor fan) 520 that supplies indoor air to the evaporator
15 507 is provided in the indoor unit 502.
[0117]
The operation of the air conditioner 500 is as follows.
The compressor 504 compresses sucked refrigerant and sends out
the compressed refrigerant. The condenser 505 exchanges heat
20 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.
The fan 510 of the outdoor unit 501 releases heat dissipated
when the refrigerant is condensed in the condenser 505, to the
25 outside of a room. The throttle device 506 adjusts the
pressure or the like of the refrigerant flowing through the
refrigerant pipe 503.
[0118]
The evaporator 507 exchanges heat between the refrigerant
30 brought into a low-pressure state by the throttle device 506
and the indoor air to cause the refrigerant to take heat from
the air and evaporate (vaporize), and then sends out the
evaporated refrigerant to the refrigerant pipe 503. The fan
520 of the indoor unit 502 supplies the air (i.e., cooled air)
34
from which heat is removed by the evaporator 507, to the inside
of the room.
[0119]
The motors 1 and 1A of the respective embodiments
described above are configured to suppress 5 demagnetization of
the permanent magnets 25 and 35, respectively. Thus, by using
the motor 1 as a power source of the fan 510, the operation
efficiency of the air conditioner 500 can be enhanced for a
long time period, and the energy consumption can be reduced.
10 [0120]
Although each of the motors 1 and 1A of the embodiments
is used as the drive source of the fan (i.e., the outdoor fan)
510 of the outdoor unit 501, it may be used as a drive source
of a fan (i.e., an indoor fan) 520 of the indoor unit 502.
15 Each of the motors 1 and 1A of the embodiments is not limited
to the drive source for the fan, but may be used as a drive
source of the compressor 504, for example.
[0121]
The motors 1 and 1A of the respective embodiments are not
20 limited to the motors for the air conditioner 500, but may be
used as motors for ventilation fans, household appliances or
machine tools, for example.
[0122]
Although the desirable embodiments of the present
25 invention have been specifically described, the present
invention is not limited to the above-described embodiments,
and various modifications or changes can be made to the
embodiments without departing from the scope of the present
invention.
30 DESCRIPTION OF REFERENCE CHARACTERS
[0123]
1,1A motor; 2,3 rotor; 4 resin portion (supporting
portion); 5 stator; 6 mold stator; 7 board; 10 air gap; 11
rotation shaft; 20 rotor core; 20a outer circumferential
35
portion (first outer circumferential portion); 20b outer
circumferential portion (second outer circumferential portion);
21 magnet insertion hole; 22 flux barrier; 23 central hole;
25 permanent magnet; 25a outer end portion; 25b inner end
portion; 25c side end portion; 25e outer 5 corner; 30 rotor
core; 30a outer circumferential portion (first outer
circumferential portion); 30b outer circumferential portion
(second outer circumferential portion); 31 magnet insertion
portion; 32 flux barrier; 33 inner circumference; 35
10 permanent magnet; 35c side end portion; 35e outer corner; 36
sensor magnet; 41 inner cylindrical portion; 42 connecting
portion; 43 outer cylindrical portion; 50 stator core; 50a
outer circumference; 50b inner circumference; 51 tooth; 52
yoke; 53 slot; 54 insulating portion; 55 coil; 60 mold resin
15 portion; 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
20 (outdoor fan); 511 impeller (blade portion); 520 fan (indoor
fan).
36
We Claim :
1. A motor comprising:
a rotor having a rotor core having a magnet insertion
hole, and a permanent magnet disposed in the 5 magnet insertion
hole, the rotor being rotatable about a rotation axis; and
a stator provided so as to surround the rotor, the stator
having a stator core having a tooth facing the rotor, and a
coil wound around the tooth,
10 wherein the permanent magnet has a thickness thicker than
or equal to 2.1 mm in a direction in a direction in which the
permanent magnet faces the stator and is magnetized in a
direction of the thickness, and
wherein a minimum gap AG (mm) between the rotor and the
15 stator, a winding number Nt of the coil around the tooth, an
overcurrent threshold Ip (A) for a current flowing through the
coil, and a lower limit Hct (kA/m) of a coercive force of the
permanent magnet satisfy:
Hct ≥ 0.4 × (Ip × Nt/AG) + 410.
20
2. A motor comprising:
a rotor having a rotor core having a magnet insertion
hole, and a permanent magnet disposed in the magnet insertion
hole, the rotor being rotatable about a rotation axis; and
25 a stator provided so as to surround the rotor, the stator
having a stator core having a tooth facing the rotor, and a
coil wound around the tooth,
wherein the permanent magnet has a thickness thicker than
or equal to 3 mm in a direction in which the permanent magnet
30 faces the stator and is magnetized in a direction of the
thickness, and
wherein a minimum gap AG (mm) between the rotor and the
stator, a winding number Nt of the coil around the tooth, an
overcurrent threshold Ip (A) for a current flowing through the
37
coil, and a lower limit Hct (kA/m) of a coercive force of the
permanent magnet satisfy:
Hct ≥ 0.32 × (Ip × Nt/AG) + 350.
3. The motor according to claim 1 or 2, wherein 5 a thickness
of the permanent magnet in the radial direction is thinner than
or equal to 4 mm.
4. The motor according to any one of claims 1 to 3, wherein
10 the rotor has a pole center at a center of the magnet insertion
hole in a circumferential direction about the rotation axis and
an inter-pole portion on an outer side of the magnet insertion
hole in the circumferential direction,
wherein an outer circumference of the rotor has a first
15 outer circumferential portion extending through the pole center
and a second outer circumferential portion extending through
the inter-pole portion, and
wherein a distance from the first outer circumferential
portion to the stator is shorter than a distance from the
20 second outer circumferential portion to the stator.
5. The motor according to claim 4, wherein an end portion of
the permanent magnet in the circumferential direction is
located on a straight line connecting a first point on the
25 second outer circumferential portion and the rotation axis.
6. The motor according to claim 4 or 5, wherein an outer
corner in the radial direction of one end portion of the
permanent magnet in the circumferential direction is located on
30 a straight line connecting a first point on the second outer
circumferential portion and the rotation axis.
7. The motor according to any one of claims 1 to 6, wherein
the rotor has an opening connected to the magnet insertion hole
38
on at least one side of the magnet insertion hole in a
circumferential direction about the rotation axis, and
wherein an outer corner in the radial direction of one
end portion of the permanent magnet in the circumferential
direction is located inside the opening and 5 is not in contact
with the rotor core.
8. The motor according to any one of claims 1 to 7, wherein
a first magnetic pole is constituted by the permanent magnet,
10 and
wherein a second magnetic pole is constituted by a part
of the rotor core.
9. The motor according to claim 8, further comprising:
15 a rotation shaft; and
a supporting portion provided between the rotation shaft
and the rotor core and formed of non-magnetic material.
10. The motor according to any one of claims 1 to 9, wherein
20 the lower limit Hct of the coercive force of the permanent
magnet is a coercive force at a highest temperature in an
operating temperature range of the motor.
11. The motor according to any one of claims 1 to 10, wherein
25 a value of Ip × Nt/AG is greater than or equal to 750 A/mm.
12. The motor according to any one of claims 1 to 11, further
comprising:
an inverter supplying a current to the coil, and
30 a controller controlling the inverter,
wherein the controller stops the inverter when a current
value of the inverter exceeds the overcurrent threshold.
13. A fan comprising:
the motor according to any one of claims 1 to 12, an
a blade portion driven to rotate by the motor.
14. An air conditioner
unit, and a refrigerant pipe connecting the 5 outdoor unit and
the indoor unit,
wherein at least one of the outdoor uni
unit comprises the fan according to claim 13.
10 Dated this 17th day of
15
39
comprising an outdoor unit, an indoor
unit and the indoor