FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
ELECTRIC MOTOR, COMPRESSOR, FAN, AND REFRIGERATING AND AIR
CONDITIONING APPARATUS;
MITSUBISHI ELECTRIC CORPORATION, A CORPORATION ORGANISED AND
EXISTING UNDER THE LAWS OF JAPAN, WHOSE ADDRESS IS 7-3, MARUNOUCHI
2-CHOME, CHIYODA-KU, TOKYO 1008310, JAPAN
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION
AND THE MANNER IN WHICH IT IS TO BE PERFORMED.
2
DESCRIPTION
TECHNICAL FIELD
[0001]
The present invention relates to 5 an electric motor
including a permanent magnet.
BACKGROUND ART
[0002]
As an electric motor in a highly efficient closed
10 compressor used for a refrigeration cycle apparatus, a
permanent magnet synchronous motor (also called a brushless DC
motor) such as an interior permanent magnet motor is generally
used. A permanent magnet or permanent magnets are disposed in
a rotor core of a rotor of the permanent magnet synchronous
15 motor. Heat is normally generated on the rotor core upon
driving of the permanent magnet synchronous motor. When the
heat generated on the rotor core is conducted to the permanent
magnet, the temperature of the permanent magnet rises, and the
permanent magnet thus demagnetizes. As a result, the torque
20 and the efficiency of the electric motor problematically lower.
Under the circumstances, a rotor that reduces the rise in
temperature of a permanent magnet or permanent magnets by
passing a refrigerant through the periphery of the permanent
magnet has been proposed (see, for example, patent reference 1).
25 PRIOR ART REFERENCE
PATENT REFERENCE
[0003]
Patent Reference 1: Japanese Patent Application
Publication No. 2016-86462
30 SUMMARY OF THE INVENTION
PROBLEM TO BE SOLVED BY THE INVENTION
[0004]
In the conventional technique, however, since the
permanent magnet of the rotor is cooled using the refrigerant,
3
when a path through which the refrigerant passes is clogged,
the permanent magnet cannot be sufficiently cooled. The rise
in temperature of the permanent magnet of the rotor
demagnetizes the permanent magnet. As a result, the efficiency
of the electric motor problematically 5 lowers.
[0005]
The present invention has been made to solve the abovedescribed
problem, and has as its object to improve the
efficiency of the electric motor by reducing the rise in
10 temperature of the permanent magnet of the rotor.
MEANS OF SOLVING THE PROBLEM
[0006]
An electric motor according to the present invention
includes a stator including a first stator end located on a
15 first side in an axial direction, a second stator end located
on a second side opposite to the first side in the axial
direction, a tooth extending in a radial direction, and a
winding wound around the tooth, and a rotor including a rotor
core including a plurality of electrical steel sheets laminated
20 in the axial direction, a magnet insertion hole, a first rotor
end located on the first side, and a second rotor end located
on the second side, a permanent magnet inserted in the magnet
insertion hole, a shaft fixed to the rotor core and supported
only on the second side, a first end plate covering the first
25 side of the magnet insertion hole, and a second end plate
covering the second side of the magnet insertion hole, wherein
the first rotor end is located apart from the first stator end
toward the first side in the axial direction, the second rotor
end is located apart from the second stator end toward the
30 first side in the axial direction, a relationship between a
distance D1 and a distance D2 satisfies D1 > D2 ≥ 0, where D1
is a distance from the permanent magnet to the first end plate,
and D2 is a distance from the permanent magnet to the second
end plate, and a thickness of each of the plurality of
4
electrical steel sheets is not less than 0.1 mm and not more
than 0.25 mm.
EFFECTS OF THE INVENTION
[0007]
According to the present invention, the 5 efficiency of the
electric motor can be improved by reducing the rise in
temperature of the permanent magnet of the rotor.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008]
10 FIG. 1 is a plan view schematically illustrating a
structure of an electric motor according to Embodiment 1 of the
present invention.
FIG. 2 is a partial sectional view schematically
illustrating the structure of the electric motor.
15 FIG. 3 is a side view schematically illustrating a
structure of a rotor.
FIG. 4 is a sectional view schematically illustrating the
structure of the rotor.
FIG. 5 is a diagram illustrating a positional
20 relationship between the rotor and a stator in an x-z plane.
FIG. 6 is a diagram illustrating a positional
relationship between the rotor and a stator core in an x-y
plane.
FIG. 7 is a plan view schematically illustrating a
25 structure of a first end plate.
FIG. 8 is a plan view schematically illustrating the
structure of the rotor 2.
FIG. 9 is a sectional view taken along a line C9 - C9 in
FIG. 8.
30 FIG. 10 is a diagram illustrating another example of a
second end plate.
FIG. 11 is a block diagram illustrating an exemplary
configuration of a driving system in the electric motor.
FIG. 12 is a diagram illustrating an exemplary state of
5
the rotor during driving of the electric motor.
FIG. 13 is a graph representing a relationship between
the thickness of an electrical steel sheet and the magnitude of
iron loss generated on the rotor in the electric motor.
FIG. 14 is a sectional view schematically 5 illustrating a
structure of a compressor according to Embodiment 2 of the
present invention.
FIG. 15 is a diagram schematically illustrating a
structure of an air conditioner according to Embodiment 3 of
10 the present invention.
MODE FOR CARRYING OUT THE INVENTION
[0009]
Embodiments of the present invention will be described in
detail below with reference to the drawings.
15 In an x-y-z orthogonal coordinate system illustrated in
each drawing, the z-axis direction (z-axis) indicates a
direction parallel to an axis line A1 of a shaft 26 of an
electric motor 1, the x-axis direction (x-axis) indicates a
direction perpendicular to the z-axis direction (z-axis), and
20 the y-axis direction (y-axis) indicates a direction
perpendicular to both the z-axis direction and x-axis direction.
The axis line A1 serves as the center of rotation of a rotor 2.
The direction parallel to the axis line A1 will also be
referred to as the "axial direction of the rotor 2" or simply
25 as the "axial direction" hereinafter. A radial direction
indicates a direction perpendicular to the axis line A1.
[0010]
EMBODIMENT 1.
FIG. 1 is a plan view schematically illustrating a
30 structure of the electric motor 1 according to Embodiment 1 of
the present invention. An arrow C1 indicates the
circumferential direction of a stator 3 about the axis line A1.
The arrow C1 also indicates the circumferential direction of
the rotor 2 about the axis line A1. The circumferential
6
direction of each of the rotor 2 and the stator 3 will also be
simply referred to as the “circumferential direction”
hereinafter.
FIG. 2 is a partial sectional view schematically
illustrating the structure of the electric 5 motor 1. FIG. 2
illustrates the outer appearance of the rotor 2, and a crosssection
of the stator 3 in the x-z plane. The upper side (that
is, the +z side) in FIG. 2 will be referred to as a first side
hereinafter, and the lower side (that is, the -z side) in FIG.
10 2 will be referred to as a second side hereinafter.
[0011]
The electric motor 1 includes the rotor 2, the stator 3,
and a bearing 4. The electric motor 1 is, for example, an
interior permanent magnet motor.
15 [0012]
The stator 3 includes a stator core 31, a first stator
end 31a located on the first side in the axial direction, a
second stator end 31b located on the second side in the axial
direction, and windings 32 wound on the stator core 31 (more
20 specifically, teeth 311), as illustrated in FIG. 2. An
insulator, for example, are interposed between the stator core
31 and the windings 32. In the stator 3 illustrated in FIG. 1,
the windings 32 are omitted from the stator core 31.
[0013]
25 The first stator end 31a is the end of the stator core 31
on the first side, and the second stator end 31b is the end of
the stator core 31 on the second side.
[0014]
The stator core 31 includes at least one tooth 311
30 extending in the radial direction, and a yoke 312 extending in
the circumferential direction, as illustrated in FIG. 1. In
the example illustrated in FIG. 1, the stator core 31 includes
a plurality of teeth 311 (more specifically, six teeth 311).
[0015]
7
The stator core 31 is formed annularly. The stator core
31 is formed by a plurality of electrical steel sheets
laminated in the axial direction. Each of the plurality of
electrical steel sheets is stamped into a predetermined shape.
5 [0016]
FIG. 3 is a side view schematically illustrating a
structure of the rotor 2. The broken lines represented in FIG.
3 indicate inner walls defining fixing holes 206 and 274.
FIG. 4 is a sectional view schematically illustrating the
10 structure of the rotor 2. Referring to FIG. 4, a first end
plate 27a is omitted from a rotor core 20.
The rotor 2 is rotatably disposed inside the stator 3 in
the radial direction. The rotor 2 includes the rotor core 20,
at least one permanent magnet 220, the shaft 26, the first end
15 plate 27a, a second end plate 27b, and at least one fixing
member 28. The axis of rotation of the rotor 2 coincides with
the axis line A1.
[0017]
The rotor core 20 includes a plurality of electrical
20 steel sheets 201 laminated in the axial direction, at least one
magnet insertion hole 202, a shaft hole 203, at least one hole
204, at least one thin-wall portion 205, at least one fixing
hole 206 (to be also referred to as a second fixing hole), a
first rotor end 21a located on the first side, and a second
25 rotor end 21b located on the second side. The rotor core 20
has a substantially cylindrical shape.
[0018]
The first rotor end 21a is the end of the rotor core 20
on the first side in the axial direction, and the second rotor
30 end 21b is the end of the rotor core 20 on the second side in
the axial direction.
[0019]
As illustrated in FIG. 3, the first end plate 27a covers
the first side of the magnet insertion hole 202. The second
8
end plate 27b covers the second side of the magnet insertion
hole 202. The fixing members 28 are inserted in the fixing
holes 206 of the rotor core 20 and the fixing holes 274 of the
first end plate 27a and the second end plate 27b. The fixing
members 28 fix the first end plate 27a and the 5 second end plate
27b to the rotor core 20. With this configuration, the first
end plate 27a and the second end plate 27b are fixed to the
rotor core 20.
[0020]
10 The thickness of each of the plurality of electrical
steel sheets 201 is not less than 0.1 mm and not more than 0.25
mm. Each electrical steel sheet 201 is formed into a
predetermined shape by stamping. The at least one magnet
insertion hole 202, the shaft hole 203, the at least one hole
15 204, the at least one thin-wall portion 205, and the at least
one fixing hole 206 are formed in the plurality of electrical
steel sheets 201. The shaft hole 203 is formed at the centers
of the electrical steel sheets 201, each in a plane
perpendicular to the axial direction, that is, in the x-y plane.
20 [0021]
In the example illustrated in FIG. 4, a plurality of
magnet insertion holes 202 (more specifically, four magnet
insertion holes 202) are arranged in the circumferential
direction. Again in the example illustrated in FIG. 4, the
25 number of magnet insertion holes 202 is equal to that of
magnetic poles on the rotor 2.
[0022]
The permanent magnets 220 are inserted in the magnet
insertion holes 202. The permanent magnets 220 use, for
30 example, rare-earth magnets. However, the permanent magnets
220 are not limited to the rare-earth magnets. The width of
the permanent magnet 220 in the radial direction is smaller
than the width of the magnet insertion hole 202 in the radial
direction.
9
[0023]
The permanent magnets 220 are located on an inner side
with respect to the radial direction in the magnet insertion
holes 202, as illustrated in FIG. 4. Therefore, voids are
formed between the inner walls of the magnet 5 insertion holes
202 and the outer surfaces of the permanent magnets 220 in the
radial direction. Oil or a refrigerant may be present in these
voids.
[0024]
10 The at least one hole 204 is formed outside the magnet
insertion hole 202 in the radial direction. In the example
illustrated in FIG. 4, a plurality of holes 204 (more
specifically, eight holes 204) are formed in the rotor core 20.
Each hole 204 extends in the circumferential direction. Holes
15 other than the holes 204 may be formed in the rotor core 20.
In this case, the holes 204 are holes closest to inter-pole
portions.
[0025]
The at least one thin-wall portion 205 is formed between
20 the hole 204 and the outer edge of the rotor core 20. In the
example illustrated in FIG. 4, a plurality of thin-wall
portions 205 (more specifically, eight thin-wall portions 205)
are formed on the rotor core 20. Each thin-wall portion 205
extends in the circumferential direction.
25 [0026]
The shaft 26 is inserted in the shaft hole 203 formed at
the center of the rotor 2 in the x-y plane. The shaft 26 is
fixed to the rotor core 20 (more specifically, the shaft hole
203) and rotatably supported only on the second side. More
30 specifically, the shaft 26 is rotatably supported by the
bearing 4 on the second side.
[0027]
The rotor core 20 further includes first portions 20a
located in magnetic pole center portions of the rotor 2, second
10
portions 20b located in the inter-pole portions of the rotor 2,
outer peripheral surfaces 20c (to be also referred to as first
outer peripheral surfaces) including the first portions 20a,
and outer peripheral surfaces 20d (to be also referred to as
second outer peripheral surfaces hereinafter) 5 including the
second portions 20b.
[0028]
In the x-y plane, the first portions 20a are ends of the
rotor core 20 in the radial direction. Similarly, in the x-y
10 plane, the second portions 20b are some other ends of the rotor
core 20 in the radial direction. The first portions 20a and
the second portions 20b form part of the outer edge of the
rotor core 20.
[0029]
15 The magnetic pole center portions are portions through
which magnetic pole center lines B1 pass in the rotor 2. The
magnetic pole center lines B1 indicated by broken lines are
straight lines passing through the centers of the permanent
magnets 220 and the center of rotation of the rotor 2 in the x20
y plane.
[0030]
The inter-pole portions are portions through which interpole
lines B2 pass in the rotor 2. The inter-pole lines B2
indicated by broken lines are straight lines each passing
25 through the midpoint between two permanent magnets 220 adjacent
to each other and the center of rotation of the rotor 2 in the
x-y plane.
[0031]
The outer peripheral surfaces 20c project outward in the
30 radial direction compared with the outer peripheral surfaces
20d. In the x-y plane, the distance from the center of
rotation of the rotor 2 to the first portion 20a is larger than
the distance from the center of rotation of the rotor 2 to the
second portion 20b. In other words, the radius M1 of the rotor
11
core 20 in the magnetic pole center portion is larger than the
radius M2 of the rotor core 20 in the inter-pole portion.
Therefore, the shortest distance from the second portion 20b to
the stator core 31 is larger than the shortest distance from
the first portion 20a to the stator core 31. 5 In other words,
an air gap between the rotor core 20 and the stator core 31 in
the inter-pole portion is larger than an air gap between the
rotor core 20 and the stator core 31 in the magnetic pole
center portion.
10 [0032]
FIG. 5 is a diagram illustrating a positional
relationship between the rotor 2 and the stator 3 in the x-z
plane. FIG. 5 illustrates cross-sectional structures of the
rotor 2 and the stator 3.
15 As illustrated in FIG. 5, the first rotor end 21a is
located apart from the first stator end 31a toward the first
side in the axial direction, and the second rotor end 21b is
located apart from the second stator end 31b toward the first
side in the axial direction.
20 [0033]
Letting D1 be the distance from the permanent magnet 220
to the first end plate 27a in the axial direction, and D2 be
the distance from the permanent magnet 220 to the second end
plate 27b in the axial direction, the relationship between the
25 distances D1 and D2 satisfies D1 > D2 ≥ 0. When the distance
from the permanent magnet 220 to the first end plate 27a is not
uniform, the distance D1 is the shortest distance from the
permanent magnet 220 to the first end plate 27a. Similarly,
when the distance from the permanent magnet 220 to the second
30 end plate 27b is not uniform, the distance D2 is the shortest
distance from the permanent magnet 220 to the second end plate
27b.
[0034]
FIG. 6 is a diagram illustrating a positional
12
relationship between the rotor 2 and the stator core 31 in the
x-y plane. FIG. 6 illustrates a part of the rotor 2 and a part
of the stator core 31.
[0035]
The tooth 311 includes a main body 5 311a and a tooth
distal end 311b. Ends 311c are the ends of the tooth distal
end 311b in the circumferential direction. The main body 311a
extends in the radial direction. The tooth distal end 311b
extends in the circumferential direction, and faces the rotor 2
10 (more specifically, the rotor core 20).
[0036]
Each hole 204 is located on a straight line L1 passing
through the axis line A1 (that is, the center of rotation of
the rotor 2) and the end 311c of the tooth distal end 311b.
15 Similarly, each thin-wall portion 205 is located on the
straight line L1 passing through the axis line A1 and the end
311c of the tooth distal end 311b in the circumferential
direction.
[0037]
20 The electric motor 1 satisfies θ1 ≥ θ2, where θ1 is the
angle formed by two straight lines L1 passing through the both
ends 311c of the tooth distal end 311b and the center of
rotation of the rotor 2 in a plane perpendicular to the axial
direction, that is, in the x-y plane, and θ2 is the angle
25 formed by two straight lines L2 passing through the both ends
of the outer peripheral surface 20c in the circumferential
direction and the center of rotation of the rotor 2 in the x-y
plane.
[0038]
30 FIG. 7 is a plan view schematically illustrating a
structure of the first end plate 27a. The structure of the
second end plate 27b is the same as that of the first end plate
27a illustrated in FIG. 7.
The first end plate 27a includes outer edges 271 (to be
13
also referred to as first outer edges) forming part of the
outer edge of the first end plate 27a in the x-y plane, outer
edges 272 (to be also referred to as second outer edges)
adjacent to the outer edges 271 in the circumferential
direction, a shaft hole 273 to pass the shaft 5 26 through it, at
least one fixing hole 274 (to be also referred to as a first
fixing hole), and at least one magnet fixing portion 275.
[0039]
In the example illustrated in FIG. 7, a plurality of
10 outer edges 271 (more specifically, four outer edges 271), a
plurality of outer edges 272 (more specifically, four outer
edges 272), a plurality of fixing holes 274 (more specifically,
four fixing holes 274), and a plurality of magnet fixing
portions 275 (more specifically, five magnet fixing portions
15 275) are formed on the first end plate 27a. The radius T1 of
the first end plate 27a on the magnetic pole center portion of
the rotor 2 is larger than the radius T2 of the first end plate
27a on the inter-pole portion of the rotor 2. The first end
plate 27a and the second end plate 27b are made of, for example,
20 nonmagnetic bodies.
[0040]
FIG. 8 is a plan view schematically illustrating the
structure of the rotor 2. In FIG. 8, the structure of the
rotor core 20 is indicated by broken lines, and the structure
25 of the first end plate 27a is indicated by solid lines.
Part of the outer edges 271 of the first end plate 27a
are located on the magnetic pole center portions of the rotor 2,
and part of the outer edges 272 of the first end plate 27a are
located on the inter-pole portions of the rotor 2.
30 [0041]
The outer edges 271 of the first end plate 27a are
located apart from the outer peripheral surfaces 20c of the
rotor core 20 inward in the radial direction. The outer edges
272 of the first end plate 27a are located apart from the outer
14
peripheral surfaces 20d of the rotor core 20 outward in the
radial direction. More specifically, on the magnetic pole
center portions, the outer edges 271 of the first end plate 27a
are located apart from the first portions 20a of the rotor core
20 inward in the radial direction. On the inter-5 pole portions,
the outer edges 272 of the first end plate 27a are located
apart from the second portions 20b of the rotor core 20 outward
in the radial direction.
[0042]
10 FIG. 9 is a sectional view taken along a line C9 - C9 in
FIG. 8.
The magnet fixing portions 275 fix the positions of the
permanent magnets 220. The magnet fixing portions 275 are, for
example, projections having spring properties. The projections
15 having spring properties can be formed by bending part of the
first end plate 27a toward the permanent magnets 220, as
illustrated in, for example, FIG. 9. In the example
illustrated in FIG. 9, the positions of the permanent magnets
220 are fixed by the magnet fixing portions 275. In this case,
20 the relationship between the distances D1 and D2 satisfies D1 >
D2 and D2 = 0.
[0043]
FIG. 10 is a diagram illustrating another example of the
second end plate 27b.
25 The second end plate 27b may include the magnet fixing
portions 275 to fix the positions of the permanent magnets 220.
In the example illustrated in FIG. 10, the positions of the
permanent magnets 220 are fixed by the magnet fixing portions
275 of the first end plate 27a and the magnet fixing portions
30 275 of the second end plate 27b. In this case, the length of
the magnet fixing portion 275 of the first end plate 27a in the
axial direction is larger than the length of the magnet fixing
portion 275 of the second end plate 27b in the axial direction.
Hence, the relationship between the distances D1 and D2
15
satisfies D1 > D2 > 0.
[0044]
Since the permanent magnets 220 are fixed in position in
the axial direction by the magnet fixing portions 275, it is
possible to prevent the permanent magnets 220 5 from shifting in
the axial direction during driving of the electric motor 1 and
to reduce variations in magnetic flux in the axial direction
flowing into the stator 3. This makes it possible to improve
the efficiency of the electric motor 1. Furthermore, even if
10 the magnet insertion holes 202 or the permanent magnets 220
have dimensional errors in the axial direction, the magnet
fixing portions 275 can absorb the errors because of their
spring properties.
[0045]
15 The fixing holes 206 of the rotor core 20, the fixing
holes 274 of the first end plate 27a, and the fixing members 28
have circular shapes in the x-y plane. In the x-y plane,
letting r1 be the radius of the fixing member 28, r2 be the
radius of the fixing hole 274, r3 be the radius of the fixing
20 hole 206, M1 be the radius of the rotor core 20 in the magnetic
pole center portion, and T1 be the radius of the first end
plate 27a on the magnetic pole center portion, their
relationship satisfies r1 < r2, r1 < r3, and M1 > T1.
[0046]
25 The electric motor 1 further satisfies (r2 + r3) - 2 × r1
≤ M1 - T1.
[0047]
FIG. 11 is a block diagram illustrating an exemplary
configuration of a driving system in the electric motor 1.
30 The electric motor 1 further includes an inverter 7 to
apply a voltage to the windings 32, and a booster circuit 8
(also called a converter) to boost the voltage applied to the
windings 32. When the electric motor 1 is driven, the carrier
frequency for adjusting the voltage applied to the windings 32
16
is, for example, 1 kHz to 8 kHz. The carrier frequency may be
controlled by the inverter 7, or may be controlled by a
controller external to the inverter 7.
[0048]
The effects of the electric motor 1 5 according to this
Embodiment will be described below.
Generally, when a permanent magnet synchronous motor is
driven, a voltage is applied to a stator (more specifically,
windings), and a magnetic force is generated by the stator.
10 Since the magnetic force from the stator contains harmonics
(also called harmonic components), harmonics that are not
synchronized with rotation of a rotor are present. These
harmonics include a harmonic generated due to a current
distortion generated in energizing the windings, and a harmonic
15 generated due to slots that are spaces formed between teeth of
the stator. The harmonics that are not synchronized with
rotation of the rotor change magnetic flux in the rotor (more
specifically, permanent magnets), and iron losses thus occur on
the rotor. These iron losses occur on the surface of the rotor
20 and then generate heat. When this heat is conducted to the
permanent magnets through a rotor core, the temperature of the
permanent magnets rises.
[0049]
Generally, to increase the output of the electric motor,
25 rare-earth magnets are used as the permanent magnets of the
rotor. A rise in temperature of the rare-earth magnets causes
reduction in the magnetic force and the coercive force, and
thus causes reduction in the output and the efficiency of the
electric motor. It is, therefore, desired to set the
30 temperature of the permanent magnets as low as possible.
[0050]
Since rare-earth magnets containing a low content of
dysprosium are susceptible to heat, it is necessary to reduce
the rise in temperature in a rotor in an electric motor using
17
rare-earth magnets containing a low content of dysprosium. In
particular, since the coercive force of permanent magnets
containing no dysprosium is low, it is necessary to reduce the
rise in temperature in the electric motor using rare-earth
magnets containing a low content of 5 dysprosium. When,
therefore, the content of dysprosium in the permanent magnets
is 4% or less by weight, it is important to reduce the rise in
temperature of the permanent magnets. Conversely, using a
technique capable of reducing the temperature of the permanent
10 magnets, permanent magnets containing dysprosium at a content
of 0% to 4% by weight can be used as the permanent magnets of
the rotor.
[0051]
FIG. 12 is a diagram illustrating an exemplary state of
15 the rotor 2 during driving of the electric motor 1. In FIG. 12,
arrows illustrated in the air gap between the rotor 2 and the
stator 3 indicate flows of magnetic flux from the stator 3.
[0052]
Generally, when the shaft of the rotor is rotatably
20 supported on one side in the axial direction, the shaft readily
tilts during driving of the electric motor. When the shaft of
the rotor tilts, a region in which the air gap between the
rotor and the stator becomes narrow is generated. When the air
gap between the rotor and the stator is narrow, since the
25 density of magnetic flux flowing into the rotor core is high,
the rotor core tends to be affected by the harmonics of the
magnetic force from the stator. As a result, the iron loss on
the surface of the rotor core increases. When, therefore, the
shaft of the rotor is rotatably supported on one side in the
30 axial direction, a large amount of heat is generated by the
rotor core due to the iron loss.
[0053]
In the electric motor 1, the shaft 26 of the rotor 2 is
supported only on one end side in the axial direction, the
18
first rotor end 21a is located apart from the first stator end
31a toward the first side in the axial direction, and the
second rotor end 21b is located apart from the second stator
end 31b toward the first side in the axial direction. The
electric motor 1 having this structure is used 5 as, for example,
an electric motor for a rotary compressor.
[0054]
When the electric motor 1 is applied to an electric motor
for a rotary compressor, since the first rotor end 21a and the
10 second rotor end 21b are located apart from the first stator
end 31a and the second stator end 31b, respectively, toward the
first side in the axial direction, an attractive force is
produced in the axial direction in the electric motor 1. This
makes it possible to control a clearance for compressing a
15 refrigerant in the compressor.
[0055]
As illustrated in FIG. 12, when the first rotor end 21a
and the second rotor end 21b are located apart from the first
stator end 31a and the second stator end 31b, respectively,
20 toward the first side in the axial direction, magnetic flux
from the stator 3 flowing into one end side of the rotor 2 in
the axial direction increases. In the example illustrated in
FIG. 12, magnetic flux from the stator 3 flowing into the
second side of the rotor 2 increases. In this case, since the
25 harmonic components of the magnetic force from the stator 3 are
dominant, and the magnetic flux density of the rotor 2 on the
second side increases, the iron loss of the rotor 2 on the
second side increases. As a result, the temperature of the
rotor 2 problematically rises. There is particularly a problem
30 in that the temperature of the rotor 2 on the second side
readily rises.
[0056]
In the electric motor 1 according to this Embodiment, the
relationship between the distances D1 and D2 satisfies D1 > D2
19
≥ 0. This makes it possible to reduce the volume of the
permanent magnets 220 on the first side and to increase the
area of the permanent magnets 220 facing the stator 3. As a
result, the magnetic force of the permanent magnets 220 can be
efficiently used, and the magnetic force 5 of the rotor 2 can
thus be strengthened.
[0057]
When the permanent magnets 220 are in contact with the
second end plate 27b (that is, D2 = 0), since the area of the
10 permanent magnets 220 facing the stator 3 is largest, the
magnetic force of the rotor 2 can be most effectively used.
However, when the volume of the permanent magnets 220 on the
second side of the rotor 2 is large, the temperature of the
permanent magnets 220 on the second side readily rises. It is,
15 therefore, desired to increase the volume of the permanent
magnets 220 on the second side of the rotor 2, and to keep down
the rise in temperature of the permanent magnets 220.
[0058]
FIG. 13 is a graph representing a relationship between
20 the thickness of the electrical steel sheet 201 and the
magnitude of iron loss generated on the rotor 2 in the electric
motor 1.
As illustrated in FIG. 13, when the thickness of the
electrical steel sheet 201 is larger than 0.25 mm, the iron
25 loss remarkably increases. Generally, the iron loss of an
electrical steel sheet includes a hysteresis loss and an eddy
current loss. To reduce the iron loss due to the harmonics of
the magnetic force from the stator 3, it is effective to reduce
the eddy current loss. When the thickness of the electrical
30 steel sheet 201 is 0.25 mm or less, the iron loss, especially
the eddy current loss, can be reduced. However, when the
thickness of the electrical steel sheet 201 is smaller than 0.1
mm, it is difficult to stamp the electrical steel sheet 201.
Therefore, the thickness of the electrical steel sheet 201 is
20
desirably not less than 0.1 mm and not more than 0.25 mm.
[0059]
In the electric motor 1 according to this Embodiment,
since the magnetic flux from the stator 3 flowing into the
second side of the rotor 2 increases, the 5 temperature of the
permanent magnets 220 on the second side readily rises, and
their demagnetization characteristics are therefore prone to
degradation. The use of magnets possessing high coercive force
as the permanent magnets 220 makes it possible to improve the
10 demagnetization characteristics. In the electric motor 1
according to this Embodiment, instead of using magnets
possessing high coercive force, setting the thickness of the
electrical steel sheet 201 to not less than 0.1 mm and not more
than 0.25 mm makes it possible to reduce the iron loss
15 generated on the rotor 2 and to reduce heat generated due to
the iron loss. As a result, the rise in temperature of the
permanent magnets 220 can be reduced.
[0060]
The larger the angle θ2 (FIG. 6), the longer the region
20 in which the air gap between the rotor 2 and the stator 3 is
narrow can be formed to be in the circumferential direction,
and thus magnetic flux from the permanent magnets 220 can
efficiently flow into the stator 3. However, when the distance
from the stator core 31 to the rotor core 20 is short, since
25 the harmonics of the magnetic force from the stator core 31
exert a great influence, the iron loss on the rotor core 20
increases. In the electric motor 1 according to this
Embodiment, the relationship between the angles θ1 and θ2
satisfies θ1 ≥ θ2. This makes it possible to lessen the
30 influence of the harmonics of the magnetic force from the
stator 3. As a result, the magnetic force of the permanent
magnets 220 can efficiently flow into the stator 3, and the
iron loss generated on the surface of the rotor core 20 can
thus be reduced.
21
[0061]
The holes 204 (FIG. 4) of the rotor core 20 extend in the
circumferential direction. This makes it possible to elongate
the paths from the outer peripheral surface of the rotor core
20 to the permanent magnets 220 through the 5 electrical steel
sheets 201. As a result, since heat generated on the outer
peripheral surface of the rotor core 20 is hard to be conducted
to the permanent magnets 220, the rise in temperature of the
permanent magnets 220 can be reduced. Furthermore, since the
10 holes 204 are formed in the rotor core 20, the surface area of
the rotor core 20 can be increased, and heat generated by the
rotor core 20 and the permanent magnets 220 can be dissipated
through the holes 204 to the exterior of the rotor 2.
[0062]
15 The holes 204 of the rotor core 20 are located on the
straight lines L1 passing through the axis line A1 (that is,
the center of rotation of the rotor 2) and the ends 311c of the
tooth distal end 311b in the circumferential direction. This
makes it possible to reduce the harmonics of the magnetic force
20 due to the structure of the tooth distal end 311b and the
structure of the slot between two teeth 311, and to reduce the
iron loss on the rotor 2.
[0063]
The permanent magnets 220 are located on an inner side
25 with respect to the radial direction in the magnet insertion
holes 202. Therefore, voids are formed between the inner walls
of the magnet insertion holes 202 and the outer surfaces of the
permanent magnets 220 in the radial direction. With this
configuration, heat generated on the outer peripheral surface
30 of the rotor core 20 is hard to be conducted to the permanent
magnets 220. As a result, the rise in temperature of the
permanent magnets 220 can be reduced.
[0064]
The radius T2 of the first end plate 27a on the inter22
pole portion is larger than the radius M2 of the rotor core 20
in the inter-pole portion. In other words, the outer edges 272
are located apart from the second portions 20b of the rotor
core 20 outward in the radial direction. This means that the
volume of the first end plate 27a projecting 5 outward from the
second portions 20b of the rotor core 20 can be increased.
This makes it possible to dissipate, through the first end
plate 27a, heat generated by the rotor core 20 in the interpole
portions. As a result, heat conducted from the rotor core
10 20 in the inter-pole portions to the permanent magnets 220 can
be reduced.
[0065]
The radius T1 of the first end plate 27a on the magnetic
pole center portion is smaller than the radius M1 of the rotor
15 core 20 in the magnetic pole center portion. In other words,
the outer edges 271 are located apart from the first portions
20a of the rotor core 20 inward in the radial direction. This
makes it possible to prevent the first end plate 27a from
coming into contact with the stator core 31 and to reduce the
20 distance from the rotor core 20 to the stator core 31 in the
magnetic pole center portion. As a result, magnetic flux from
the rotor 2 can efficiently flow into the stator core 31.
[0066]
In the x-y plane, the amount of shift of the first end
25 plate 27a with respect to the rotor core 20 is expressed as (r2
- r1) + (r3 - r1) = (r2 + r3) - 2 × r1. Note that the maximum
amount of movement between the fixing member 28 and the fixing
hole 274 of the first end plate 27a is expressed as r2 - r1,
and the maximum amount of movement between the fixing member 28
30 and the fixing hole 206 of the rotor core 20 is expressed as r3
- r1.
[0067]
When, therefore, the electric motor 1 satisfies (r2 + r3)
- 2 × r1 ≤ M1 - T1, even if the first end plate 27a shifts due
23
to the voids between the fixing members 28 and the fixing holes
206 and 274, the first end plate 27a can be mounted on the
rotor core 20 so that the outer edges 271 of the first end
plate 27a are located apart from the first portions 20a of the
rotor core 20 inward in the radial direction. 5 This shape
prevents the first end plate 27a from falling outward in the
radial direction of the rotor 2. With this configuration, the
width of the space between the stator 3 and the rotor 2 in the
radial direction can be determined by the outer peripheral
10 surfaces 20c and 20d of the rotor 2. Therefore, the width of
the space between the stator 3 and the rotor 2 in the radial
direction can be set to a minimum dimension in consideration of,
for example, decentering of the rotor 2, flexure of the shaft
26, and variations in shape. Under this condition, setting the
15 radius T2 of the first end plate 27a on the inter-pole portion
larger than the radius M2 of the rotor core 20 in the interpole
portion makes it possible to increase the volume of the
first end plate 27a projecting outward from the second portions
20b of the rotor core 20. This makes it possible to dissipate
20 heat generated by the rotor core 20 in the inter-pole portions
to the exterior of the rotor 2 through the first end plate 27a.
As a result, heat conducted from the rotor core 20 in the
inter-pole portions to the permanent magnets 220 can be reduced.
[0068]
25 The air gap between the stator core 31 and the rotor core
20 in the inter-pole portions is larger than the air gap
between the stator core 31 and the rotor core 20 in the
magnetic pole center portions. With this arrangement, since
the spatial harmonics of the stator 3 can be reduced, the iron
30 loss generated on the surface of the rotor core 20 in the
inter-pole portions can also be reduced. As a result, the rise
in temperature of the permanent magnets 220 on the sides of the
inter-pole portions can be reduced.
[0069]
24
When the carrier frequency for adjusting a voltage
applied to the windings 32 is high, the voltage applied to the
windings 32, that is, a voltage for driving the electric motor
1 can be precisely adjusted, and the harmonic components of the
magnetic force can thus be reduced. In the 5 electric motor 1,
the carrier frequency of the voltage applied to the windings 32
is, for example, 1 kHz to 8 kHz. This makes it possible to
precisely adjust the voltage for driving the electric motor 1
and to reduce the harmonic components of the magnetic force.
10 [0070]
Generally, the higher the carrier frequency, the higher
the switching loss, and the lower the efficiency of the
electric motor. When the carrier frequency in the electric
motor 1 is 1 kHz to 8 kHz, the voltage for driving the electric
15 motor 1 can be precisely adjusted in the state where the
harmonics of the magnetic force from the stator 3 and the
switching loss of the stator 3 are reduced. However, when the
carrier frequency ranges from 1 kHz to 8 kHz, the iron loss
generated due to the presence of the harmonics of the magnetic
20 force from the stator 3 cannot be sufficiently kept low.
Nevertheless, in the electric motor 1 according to this
Embodiment, even when the carrier frequency ranges from 1 kHz
to 8 kHz, since the structure described in this Embodiment is
provided, the iron loss generated on the surface of the rotor
25 core 20 can be reduced.
[0071]
The electric motor 1 further includes a booster circuit 8
to boost the voltage applied to the windings 32. Generally,
since the use of a booster circuit results in a high voltage,
30 the modulation rate of the voltage is low when the electric
motor is driven at a low rotation speed. When the modulation
rate is low, the distortion of a current for driving the
electric motor is large, and the harmonic components of the
magnetic force caused by the current increase. As a result,
25
the iron loss generated on the rotor increases. In the
electric motor 1 according to this Embodiment, however, even
when the booster circuit 8 is used, since the above-mentioned
structure is provided, the iron loss generated on the surface
of the rotor core 5 20 can be reduced.
[0072]
In an electric motor in which the pulsation of the load
is strong and equipped with no sensor to detect the position of
a rotor, the features of the electric motor 1 according to this
10 Embodiment are more effective. Generally, since an electric
motor using a sensor to detect the position of a rotor can
obtain the position of the rotor, the rotor can be controlled
to be driven at a constant rotation speed even if the pulsation
of the load on the electric motor is strong. In an electric
15 motor equipped with no sensor to detect the position of a rotor,
however, it is difficult to control the rotor to be driven at a
constant rotation speed.
[0073]
In an electric motor equipped with no sensor to detect
20 the position of a rotor, for example, since a state occurs in
which the fundamental wave of a magnetic force from a stator is
not synchronized with the rotor, iron losses occur on the
surface of a rotor core due to the fundamental wave of the
magnetic force from the stator. As a result, the temperature
25 of the rotor rises, and the temperature of permanent magnets
rises. Since the electric motor 1 according to this Embodiment
has the structure described in this Embodiment, even when the
electric motor 1 is equipped with no sensor to detect the
position of the rotor, the rise in temperature of the permanent
30 magnets 220 can be reduced.
[0074]
Regarding the pulsation of the load on the electric motor,
when the ratio between the minimum value and the maximum value
of the torque of the electric motor is 20% or more, a state is
26
more likely to occur in which magnetic flux from the stator
does not flow to an appropriate position with respect to the
phase of the rotor. This phenomenon more remarkably occurs
when the ratio between the minimum value and the maximum value
of the torque of the electric motor is 50% or 5 more. Generally,
in an electric motor provided in a compressor for an air
conditioner, the pulsation of the load is strong. In, for
example, an electric motor provided in a rotary compressor, a
ratio between the minimum value and the maximum value of the
10 torque of 50% or more may occur. When, therefore, the electric
motor 1 is used as an electric motor in a compressor, the
features of the electric motor 1 according to this Embodiment
are more effective.
[0075]
15 As described above, in the electric motor 1, the first
rotor end 21a is located apart from the first stator end 31a
toward the first side in the axial direction, and the second
rotor end 21b is located apart from the second stator end 31b
toward the first side in the axial direction. Furthermore, the
20 shaft 26 is fixed to the rotor core 20 (more specifically, the
shaft hole 203), and rotatably supported only on the second
side. Under these conditions, since the electric motor 1 has
the structure described in this Embodiment, the rise in
temperature of the permanent magnets 220 of the rotor 2 can be
25 reduced, and the efficiency of the electric motor can thus be
improved.
[0076]
EMBODIMENT 2.
A compressor 6 according to Embodiment 2 of the present
30 invention will be described below.
FIG. 14 is a sectional view schematically illustrating a
structure of the compressor 6 according to Embodiment 2.
[0077]
The compressor 6 includes an electric motor 60 as an
27
electric power element, a closed container 61 as a housing, and
a compression mechanism 62 as a compression element. In this
Embodiment, the compressor 6 is a rotary compressor. However,
the compressor 6 is not limited to the rotary compressor.
5 [0078]
The electric motor 60 is the electric motor 1 according
to Embodiment 1. In this Embodiment, the electric motor 60 is
designed as an interior permanent magnet motor, but it is not
limited to this.
10 [0079]
The closed container 61 covers the electric motor 60 and
the compression mechanism 62. Freezer oil to lubricate the
sliding portions of the compression mechanism 62 is stored at
the bottom of the closed container 61.
15 [0080]
The compressor 6 further includes a glass terminal 63
fixed to the closed container 61, an accumulator 64, a suction
pipe 65, and a discharge pipe 66.
[0081]
20 The compression mechanism 62 includes a cylinder 62a, a
piston 62b, an upper frame 62c (first frame), a lower frame 62d
(second frame), and a plurality of mufflers 62e respectively
mounted on the upper frame 62c and the lower frame 62d. The
compression mechanism 62 further includes a vane to separate
25 the cylinder 62a into the suction and compression sides. The
compression mechanism 62 is driven by the electric motor 60.
[0082]
The electric motor 60 is fixed in the closed container 61
by press fitting or shrink fitting. The stator 3 may be
30 directly mounted in the closed container 61 by welding instead
of press fitting and shrink fitting.
[0083]
Power is supplied to the windings of the stator 3 of the
electric motor 60 via the glass terminal 63.
28
[0084]
The rotor (more specifically, one end side of the shaft
26) of the electric motor 60 is rotatably supported by a
bearing provided on the upper frame 62c and a bearing provided
on the 5 lower frame 62d.
[0085]
The shaft 26 is inserted in the piston 62b. The shaft 26
is rotatably inserted in the upper frame 62c and the lower
frame 62d. The upper frame 62c and the lower frame 62d close
10 the end faces of the cylinder 62a. The accumulator 64 supplies
a refrigerant (for example, a refrigerant gas) to the cylinder
62a via the suction pipe 65.
[0086]
The operation of the compressor 6 will be described below.
15 The refrigerant supplied from the accumulator 64 is drawn by
suction into the cylinder 62a through the suction pipe 65 fixed
to the closed container 61. The electric motor 60 rotates
through applying an electric current to an inverter, and thus
the piston 62b fitted to the shaft 26 rotates in the cylinder
20 62a. With this operation, the refrigerant is compressed in the
cylinder 62a.
[0087]
The refrigerant ascends in the closed container 61
through the mufflers 62e. The compressed refrigerant is mixed
25 with the freezer oil. When the mixture of the refrigerant and
the freezer oil passes through an air hole 36 formed in the
rotor core, separation between the refrigerant and the freezer
oil is accelerated and thus the freezer oil can be prevented
from flowing into the discharge pipe 66. In this way, the
30 compressed refrigerant is supplied to the high-pressure side of
a refrigeration cycle through the discharge pipe 66.
[0088]
As the refrigerant for the compressor 6, R410A, R407C,
R22, or the like, can be used. However, the refrigerant for
29
the compressor 6 is not limited to these examples. As the
refrigerant for the compressor 6, a low-GWP (Global Warming
Potential) refrigerant, or the like, can be used.
[0089]
As typical examples of the low-GWP 5 refrigerant, the
following refrigerants are given.
[0090]
(1) An exemplary halogenated hydrocarbon having a carboncarbon
double bond in its composition is HFO-1234yf (CF3CF=CH2).
10 HFO is an abbreviation of Hydro-Fluoro-Olefin. Olefin is an
unsaturated hydrocarbon having only one double bond. The GWP
of HFO-1234yf is 4.
[0091]
(2) An example of hydrocarbon having a carbon-carbon double
15 bond in its composition is R1270 (propylene). R1270 has the
GWP of 3, which is lower than the GWP of HFO-1234yf, but R1270
is more flammable than HFO-1234yf.
[0092]
(3) An example of a mixture containing at least one of a
20 halogenated hydrocarbon having a carbon-carbon double bond in
its composition or a hydrocarbon having a carbon-carbon double
bond in its composition is a mixture of HFO-1234yf and R32.
Since HFO-1234yf is a low-pressure refrigerant and therefore
causes a considerable pressure loss, it readily degrades the
25 performance of the refrigeration cycle (especially in an
evaporator). It is, therefore, desired to use a mixture with,
for example, R32 or R41, which is a high-pressure refrigerant.
[0093]
The compressor 6 according to Embodiment 2 has the
30 effects described in Embodiment 1.
[0094]
Using the electric motor 1 according to Embodiment 1 as
the electric motor 60, the efficiency of the electric motor 60
can be improved, and consequently the efficiency of the
30
compressor 6 can be improved.
[0095]
EMBODIMENT 3.
An air conditioner 50 (also called a refrigerating and
air conditioning apparatus or a refrigeration 5 cycle apparatus)
according to Embodiment 3 of the present invention will be
described below.
FIG. 15 is a diagram schematically illustrating a
structure of the air conditioner 50 according to Embodiment 3
10 of the present invention.
[0096]
The air conditioner 50 according to Embodiment 3 includes
an indoor unit 51 as a fan (first fan), refrigerant piping 52,
and an outdoor unit 53 as a fan (second fan) connected to the
15 indoor unit 51 via the refrigerant piping 52.
[0097]
The indoor unit 51 includes an electric motor 51a (for
example, the electric motor 1 according to Embodiment 1), an
air blower 51b driven by the electric motor 51a to blow air,
20 and a housing 51c that covers the electric motor 51a and the
air blower 51b. The air blower 51b includes, for example,
blades 51d driven by the electric motor 51a. The blades 51d,
for example, are fixed to a shaft (for example, the shaft 26)
of the electric motor 51a and generate an air current.
25 [0098]
The outdoor unit 53 includes an electric motor 53a (for
example, the electric motor 1 according to Embodiment 1), an
air blower 53b, a compressor 54, and a heat exchanger (not
illustrated). The air blower 53b is driven by the electric
30 motor 53a to blow air. The air blower 53b includes, for
example, blades 53d driven by the electric motor 53a. The
blades 53d, for example, are fixed to a shaft (for example, the
shaft 26) of the electric motor 53a and generate an air current.
The compressor 54 includes an electric motor 54a (for example,
31
the electric motor 1 according to Embodiment 1), a compression
mechanism 54b (for example, a refrigerant circuit) driven by
the electric motor 54a, and a housing 54c that covers the
electric motor 54a and the compression mechanism 54b. The
compressor 54 is, for example, the compressor 5 6 described in
Embodiment 2.
[0099]
In the air conditioner 50, at least one of the indoor
unit 51 or the outdoor unit 53 includes the electric motor 1
10 described in Embodiment 1. More specifically, as a driving
source for the air blower, the electric motor 1 described in
Embodiment 1 is applied to at least one of the electric motors
51a or 53a. As the electric motor 54a of the compressor 54,
the electric motor 1 described in Embodiment 1 may be used.
15 [0100]
The air conditioner 50 can perform an operation such as a
cooling operation for blowing cold air from the indoor unit 51,
or a heating operation for blowing hot air from the indoor unit
51. In the indoor unit 51, the electric motor 51a serves as a
20 driving source for driving the air blower 51b. The air blower
51b can blow conditioned air.
[0101]
With the air conditioner 50 according to Embodiment 3,
since the electric motor 1 described in Embodiment 1 is applied
25 to at least one of the electric motors 51a or 53a, the same
effects as those described in Embodiment 1 can be obtained.
This makes it possible to improve the efficiency of the air
conditioner 50.
[0102]
30 Using the electric motor 1 according to Embodiment 1 as a
driving source for a fan (for example, the indoor unit 51), the
same effects as those described in Embodiment 1 can be obtained.
This makes it possible to improve the efficiency of the fan. A
fan including the electric motor 1 according to Embodiment 1
32
and blades (for example, the blades 51d or 53d) driven by the
electric motor 1 can be solely used as apparatus for blowing
air. The fan is also applicable to apparatus other than the
air conditioner 50.
5 [0103]
Using the electric motor 1 according to Embodiment 1 as a
driving source for the compressor 54, the same effects as those
described in Embodiment 1 can be obtained. This makes it
possible to improve the efficiency of the compressor 54.
10 [0104]
The electric motor 1 described in Embodiment 1 can be
mounted not only in the air conditioner 50, but also in
apparatus including a driving source, such as a ventilating fan,
a household electrical appliance, or a machine tool.
15 [0105]
The features in the above-described Embodiments can be
combined together as appropriate.
DESCRIPTION OF REFERENCE CHARACTERS
[0106]
20 1, 51a, 53a, 54a, 60 electric motor; 2 rotor; 3 stator; 4
bearing; 6 compressor; 8 booster circuit; 20 rotor core; 20a
first portion; 20b second portion; 20c outer peripheral surface
(first outer peripheral surface); 20d outer peripheral surface
(second outer peripheral surface); 21a first rotor end; 21b
25 second rotor end; 26 shaft; 27a first end plate; 27b second end
plate; 31 stator core; 31a first stator end; 31b second stator
end; 50 air conditioner; 51 indoor unit (fan); 53 outdoor unit
(fan); 201 electrical steel sheet; 202 magnet insertion hole;
220 permanent magnet; 311 tooth; 311a main body; 311b tooth
30 distal end.
33
We Claim:
1. An electric motor comprising:
a stator including a first stator end located on a first
side in an axial direction, a second stator 5 end located on a
second side opposite to the first side in the axial direction,
a tooth extending in a radial direction, and a winding wound
around the tooth; and
a rotor including a rotor core including a plurality of
10 electrical steel sheets laminated in the axial direction, a
magnet insertion hole, a first rotor end located on the first
side, and a second rotor end located on the second side, a
permanent magnet inserted in the magnet insertion hole, a shaft
fixed to the rotor core and supported only on the second side,
15 a first end plate covering the first side of the magnet
insertion hole, and a second end plate covering the second side
of the magnet insertion hole,
wherein the first rotor end is located apart from the
first stator end toward the first side in the axial direction,
20 the second rotor end is located apart from the second
stator end toward the first side in the axial direction,
a relationship between a distance D1 and a distance D2
satisfies D1 > D2 ≥ 0, where D1 is a distance from the
permanent magnet to the first end plate, and D2 is a distance
25 from the permanent magnet to the second end plate, and
a thickness of each of the plurality of electrical steel
sheets is not less than 0.1 mm and not more than 0.25 mm.
2. The electric motor according to claim 1, wherein
30 the rotor core includes a first portion located at an end
of the rotor core in a radial direction and in a magnetic pole
center portion of the rotor, and a second portion located at an
end of the rotor core in a radial direction and in an interpole
portion of the rotor, and
34
in a plane perpendicular to the axial direction, a
distance from a center of rotation of the rotor to the first
portion is larger than a distance from the center of rotation
of the rotor to the second portion.
5
3. The electric motor according to claim 2, wherein
the first end plate includes a first outer edge forming a
part of an outer edge of the first end plate, and a second
outer edge adjacent to the first outer edge in a
10 circumferential direction,
the first outer edge is located apart from the first
portion inward in a radial direction, and
the second outer edge is located apart from the second
portion outward in a radial direction.
15
4. The electric motor according to claim 2 or 3, wherein
the rotor core includes a first outer peripheral surface
including the first portion, and a second outer peripheral
surface including the second portion, and
20 the first outer peripheral surface projects outward in a
radial direction compared with the second outer peripheral
surface.
5. The electric motor according to claim 4, wherein
25 the tooth includes a tooth distal end facing the rotor,
and
the electric motor satisfies θ1 ≥ θ2
where θ1 is an angle formed by two straight lines passing
through both ends of the tooth distal end in a circumferential
30 direction and the center of rotation of the rotor in the plane
perpendicular to the axial direction, and θ2 is an angle formed
by two straight lines passing through both ends of the first
outer peripheral surface in the circumferential direction and
the center of rotation of the rotor in the plane.
35
6. The electric motor according to claim 5, wherein the
rotor core includes a hole formed outside the magnet insertion
hole in a radial direction, and the hole extends in a
circumferential 5 direction.
7. The electric motor according to claim 6, wherein the hole
is located on a straight line passing through an end of the
tooth distal end in a circumferential direction and the center
10 of rotation of the rotor.
8. The electric motor according to claim 6 or 7, wherein the
rotor core includes a thin-wall portion formed between the hole
and an outer edge of the rotor core.
15
9. The electric motor according to any one of claims 1 to 8,
wherein
a width of the permanent magnet in a radial direction is
smaller than a width of the magnet insertion hole in the radial
20 direction, and
the permanent magnet is located on an inner side with
respect to the radial direction in the magnet insertion hole.
10. The electric motor according to any one of claims 1 to 9,
25 wherein
the first end plate includes a first fixing hole,
the rotor core includes a second fixing hole,
the rotor includes a fixing member to fix the first end
plate to the rotor core,
30 the fixing member is inserted in the first fixing hole
and the second fixing hole, and
the electric motor satisfies (r2 + r3) - 2 × r1 ≤ M1 - T1
where r1 is a radius of the fixing member, r2 is a radius of
the first fixing hole, r3 is a radius of the second fixing hole,
36
M1 is a radius of the rotor core in a magnetic pole center
portion of the rotor, and T1 is a radius of the first end plate
on the magnetic pole center portion.
11. The electric motor according to any one 5 of claims 1 to 10,
wherein a carrier frequency for adjusting a voltage applied to
the winding is 1kHz to 8 kHz.
12. The electric motor according to any one of claims 1 to 11,
10 further comprising a booster circuit to boost a voltage applied
to the winding.
13. A compressor comprising:
an electric motor;
15 a compression mechanism driven by the electric motor; and
a housing covering the electric motor and the compression
mechanism,
the electric motor comprising:
a stator including a first stator end located on a first
20 side in an axial direction, a second stator end located on a
second side opposite to the first side in the axial direction,
a tooth extending in a radial direction, and a winding wound
around the tooth; and
a rotor including a rotor core including a plurality of
25 electrical steel sheets laminated in the axial direction, a
magnet insertion hole, a first rotor end located on the first
side, and a second rotor end located on the second side, a
permanent magnet inserted in the magnet insertion hole, a shaft
fixed to the rotor core and supported only on the second side,
30 a first end plate covering the first side of the magnet
insertion hole, and a second end plate covering the second side
of the magnet insertion hole,
wherein the first rotor end is located apart from the
first stator end toward the first side in the axial direction,
37
the second rotor end is located apart from the second
stator end toward the first side in the axial direction,
a relationship between a distance D1 and a distance D2
satisfies D1 > D2 ≥ 0 where D1 is a distance from the permanent
magnet to the first end plate, and D2 is a 5 distance from the
permanent magnet to the second end plate, and
a thickness of each of the plurality of electrical steel
sheets is not less than 0.1 mm and not more than 0.25 mm.
10 14. A fan comprising:
an electric motor; and
a blade driven by the electric motor,
the electric motor comprising:
a stator including a first stator end located on a first
15 side in an axial direction, a second stator end located on a
second side opposite to the first side in the axial direction,
a tooth extending in a radial direction, and a winding wound
around the tooth; and
a rotor including a rotor core including a plurality of
20 electrical steel sheets laminated in the axial direction, a
magnet insertion hole, a first rotor end located on the first
side, and a second rotor end located on the second side, a
permanent magnet inserted in the magnet insertion hole, a shaft
fixed to the rotor core and supported only on the second side,
25 a first end plate covering the first side of the magnet
insertion hole, and a second end plate covering the second side
of the magnet insertion hole,
wherein the first rotor end is located apart from the
first stator end toward the first side in the axial direction,
30 the second rotor end is located apart from the second
stator end toward the first side in the axial direction,
a relationship between a distance D1 and a distance D2
satisfies D1 > D2 ≥ 0, where D1 is a distance from the
permanent magnet to the first end plate, and D2 is a distance
38
from the permanent magnet to the second end plate, and
a thickness of each of the plurality of electrical steel
sheets is not less than 0.1 mm and not more than 0.25 mm.
15. A refrigerating and air conditioning 5 apparatus
comprising:
an indoor unit; and
an outdoor unit connected to the indoor unit,
at least one of the indoor unit or the outdoor unit
10 comprising an electric motor,
the electric motor comprising:
a stator including a first stator end located on a first
side in an axial direction, a second stator end located on a
second side opposite to the first side in the axial direction,
15 a tooth extending in a radial direction, and a winding wound
around the tooth; and
a rotor including a rotor core including a plurality of
electrical steel sheets laminated in the axial direction, a
magnet insertion hole, a first rotor end located on the first
20 side, and a second rotor end located on the second side, a
permanent magnet inserted in the magnet insertion hole, a shaft
fixed to the rotor core and supported only on the second side,
a first end plate covering the first side of the magnet
insertion hole, and a second end plate covering the second side
25 of the magnet insertion hole,
wherein the first rotor end is located apart from the
first stator end toward the first side in the axial direction,
the second rotor end is located apart from the second
stator end toward the first side in the axial direction,
30 a relationship between a distance D1 and a distance D2
satisfies D1 > D2 ≥ 0, where D1 is a distance from the
permanent magnet to the first end plate, and D2 is a distance
from the permanent magnet to the second end plate, and
a thickness of each of the plurality of electrical steel
39
sheets is not less than 0.1 mm and not more than 0.25 mm.