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]
ELECTRIC MOTOR, COMPRESSOR, AIR BLOWER, 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 an electric motor 5 including a permanent magnet.
BACKGROUND ART
[0002]
In general, an electric motor including a rotor whose 10 shaft is supported only on one side in an axial direction. In
such an electric motor, while the electric motor is being
driven, a bearing supporting the shaft serves as a fulcrum, and
the shaft is warped in some cases. When the shaft is warped,
the position of the rotor moves in a radial direction, and 15 accordingly, the rotor may contact a stator. In view of this,
proposed is an electric motor in which an air gap on a free end
side is set large and an air gap at a support side is set
smaller than the air gap on the free end side (e.g., Patent
Reference 1). 20
PRIOR ART REFERENCE
PATENT REFERENCE
[0003]
Patent Reference 1: Japanese Unexamined Utility Model 25 Registration Application Publication No. H02-68645
SUMMARY OF THE INVENTION
PROBLEM TO BE SOLVED BY THE INVENTION
[0004] 30 In a conventional technique, if the outer diameter of a
rotor core is increased in order to reduce the size of an air
gap, the width of an inter-pole part, for example, a thin-wall
part, of the rotor core increases in size. Accordingly,
3
leakage of magnetic fluxes easily occurs near the inter-pole
part. On the other hand, if the outer diameter of the rotor
core is reduced in order to reduce leakage of magnetic fluxes
near the inter-pole part, the air gap is enlarged, and a
magnetic force in the electric motor decreases, 5 disadvantageously.
[0005]
It is therefore an object of the present invention to
reduce leakage of magnetic fluxes in a rotor and enhance a
magnetic force in an electric motor. 10 [0006]
An electric motor according to the present invention
includes: a stator; and a rotor including a shaft, a first
rotor core fixed on a first side of the shaft in an axial
direction, and a second rotor core fixed on a second side of 15 the shaft, the second side being opposite to the first side in
the axial direction, the rotor being disposed inside the stator,
wherein the shaft is supported only on the first side, a
minimum distance from the first rotor core to the stator in a
radial direction is shorter than a minimum distance from the 20 second rotor core to the stator in the radial direction, a
maximum radius of the first rotor core is longer than a maximum
radius of the second rotor core, the first rotor core includes
a first hole and a first thin-wall part, the first thin-wall
part being located outside the first hole in the radial 25 direction, the second rotor core includes a second hole and a
second thin-wall part, the second thin-wall part being located
outside the second hole in the radial direction, and a shape of
the first thin-wall part and a shape of the second thin-wall
part are the same. 30
EFFECTS OF THE INVENTION
[0007]
According to the present invention, leakage of magnetic
4
fluxes in the rotor is reduced, and a magnetic force is
enhanced in the electric motor.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] 5 FIG. 1 is a plan view schematically illustrating a
structure of a first side of an electric motor according to a
first embodiment of the present invention.
FIG. 2 is a plan view schematically illustrating the
structure of a second side of the electric motor. 10 FIG. 3 is a cross-sectional view schematically
illustrating the structure of the electric motor.
FIG. 4 is a cross-sectional view schematically
illustrating a structure of a first side of a rotor.
FIG. 5 is a cross-sectional view schematically 15 illustrating the structure of a second side of the rotor.
FIG. 6 is a diagram illustrating a positional
relationship between a first rotor core and a stator core in an
xy plane.
FIG. 7 is a diagram illustrating an example of a state of 20 the rotor while the electric motor is being driven.
FIG. 8 is a plan view illustrating another example of the
structure of the first rotor core.
FIG. 9 is a plan view illustrating yet another example of
the structure of the first rotor core. 25 FIG. 10 is a plan view illustrating still another example
of the structure of the first rotor core.
FIG. 11 is a graph showing a relationship between an
angle [degree] formed by two lines passing through both ends of
an outer peripheral surface in a circumferential direction and 30 a rotation center of the first rotor core and an increase rate
[%] of an induced voltage.
FIG. 12 is a cross-sectional view schematically
illustrating a structure of a compressor according to a second
5
embodiment.
FIG. 13 is a diagram schematically illustrating a
configuration of an air conditioner according to a third
embodiment.
5 MODE FOR CARRYING OUT THE INVENTION
[0009]
FIRST EMBODIMENT
An embodiment of the present invention will be described
in detail with reference to the drawings. 10 In an xyz orthogonal coordinate system shown in each
drawing, a z axis direction (z axis) represents a direction
parallel to an axis line Ax of an electric motor 1, an x axis
direction (x axis) represents a direction perpendicular to the
z axis direction (z axis), and a y axis direction (y axis) 15 represents a direction perpendicular to both of the z axial
direction and the x axial direction. The axis line Ax is a
rotation center of a rotor 2. The direction parallel to the
axis line Ax will be also referred to as an “axial direction of
the rotor 2” or simply an “axial direction.” A radial 20 direction is a direction perpendicular to the axis line Ax.
[0010]
FIG. 1 is a plan view schematically illustrating a
structure of a first side of an electric motor 1 according to a
first embodiment of the present invention. In the electric 25 motor 1 illustrated in FIG. 1, a bearing 4 is detached from a
shaft 26. An arrow C1 represents a circumferential direction
of a stator 3 about the axis line Ax. The arrow C1 also
represents a circumferential direction of the rotor 2 about the
axis line Ax. The circumferential directions of the rotor 2 30 and the stator 3 will be also simply referred to as a
“circumferential direction.”
FIG. 2 is a plan view schematically illustrating the
structure of a second side of the electric motor 1.
6
FIG. 3 is a cross-sectional view schematically
illustrating the structure of the electric motor 1. In FIG. 3,
the lower side (i.e., +z side) is the first side, and the upper
side (i.e., −z side) is the second side. In this embodiment,
the first side will be also referred to as a bearing side, and 5 a second side will be also referred to as a counter bearing
side.
[0011]
The electric motor 1 includes the rotor 2, the stator 3,
and the bearing 4. The electric motor 1 is, for example, a 10 permanent magnet synchronous motor (also called a brushless DC
motor) such as an interior permanent magnet electric motor.
The electric motor 1 is used as an electric motor in a highefficiency
hermetic compressor for use in a refrigeration cycle
apparatus, for example. 15 [0012]
As illustrated in FIGS. 1 and 2, the stator 3 includes a
stator core 31. As illustrated in FIG. 3, the stator 3 also
includes a winding 32 wound around the stator core 31. In the
stator 3 illustrated in FIGS. 1 and 2, the winding 32 is 20 detached from the stator core 31. For example, an insulator is
disposed between the stator core 31 and the winding 32. In the
case where the electric motor 1 is driven, a current is
supplied to the winding 32 and thus the rotor 2 rotates.
[0013] 25 As illustrated in FIGS. 1 and 2, the stator core 31
includes at least one tooth 311 extending in the radial
direction, and a yoke 312 extending in the circumferential
direction. In the example illustrated in FIG. 1, the stator
core 31 includes a plurality of teeth 311 (specifically six 30 teeth 311).
[0014]
The stator core 31 is formed annularly. The stator core
31 is formed by stacking a plurality of electromagnetic steel
7
sheets in the axial direction. Each of the plurality of
electromagnetic steel sheets is stamped into a predetermined
shape. The inner peripheral surface of the stator 3
(specifically the inner peripheral surface of the stator core
31) has a uniform curvature radius. That is, in an xy plane, 5 the distance from the axis line Ax to the teeth 311 is uniform
in the circumferential direction.
[0015]
The rotor 2 is rotatably disposed inside the stator 3 in
the radial direction. The rotor 2 includes a first rotor core 10 21, a second rotor core 22, at least one permanent magnet 220,
and a shaft 26. In the example illustrated in FIGS. 1 through
3, the rotation axis of the rotor 2 coincides with the axis
line Ax.
[0016] 15 As illustrated in FIG. 3, the first rotor core 21 is
fixed to the first side of the shaft 26 in the axial direction.
The second rotor core 22 is fixed to the second side of the
shaft 26, and the second side is opposite to the first side in
the axial direction. 20 [0017]
The bearing 4 supports the first side of the shaft 26.
Accordingly, the shaft 26 is supported only on the first side.
[0018]
A distance L1 is a minimum distance from an end of the 25 shaft 26 on the second side in the axial direction to the
bearing 4. A distance D1 is a minimum distance from the first
rotor core 21 to the bearing 4. A thickness T1 is a thickness
of the first rotor core 21 in the axial direction. A distance
G1 is a minimum distance from the first rotor core 21 to the 30 stator 3 in a case where the rotation axis of the rotor 2
coincides with the center of the stator 3 in a plane
perpendicular to the axial direction. A distance G2 is a
minimum distance from the second rotor core 22 to the stator 3
8
in a case where the rotation center of the rotor 2 coincides
with the center of the stator 3 in the xy plane. In the case
where the rotation center of the rotor 2 coincides with the
center of the stator 3 in a plane perpendicular to the axial
direction, the rotation center of the rotor 2 coincides with 5 the axis line Ax. That is, the axis line Ax is also a line
indicating the center of the stator 3.
[0019]
When the shaft 26 tilts in a zx plane, the maximum travel
distance of the first side of the rotor 2, specifically, the 10 first rotor core 21, in the radial direction is approximated at
G2 × (D1 + T1)/L1. Thus, an air gap between the first side of
the rotor 2, specifically, the first rotor core 21, and the
stator 3, needs to be larger than G2 × (D1 + T1)/L1. Thus, the
distance G1 needs to be larger than G2 × (D1 + T1)/L1. 15 Accordingly, in the example illustrated in FIG. 3, the electric
motor 1 satisfies G1 > G2 × (D1 + T1)/L1.
[0020]
FIG. 4 is a cross-sectional view schematically
illustrating a structure of the first side of the rotor 2. 20 The first rotor core 21 includes a plurality of
electromagnetic steel sheets 201a stacked in the axial
direction, at least one hole 202a (also referred to as a first
hole), a shaft hole 203a, at least one hole 204a, and at least
one first thin-wall part 205a. The first rotor core 21 has a 25 substantially cylindrical shape.
[0021]
Each of the plurality of electromagnetic steel sheets
201a has a thickness of 0.1 mm or more and 0.25 mm or less.
Each of the electromagnetic steel sheets 201a is formed by 30 stamping into a predetermined shape. The at least one hole
202a, the shaft hole 203a, the at least one hole 204a, and the
at least one first thin-wall part 205a are formed in each of
the plurality of electromagnetic steel sheets 201a. The shaft
9
hole 203a is formed in a plane perpendicular to the axial
direction, that is, at the center of the electromagnetic steel
sheets 201a in the xy plane.
[0022]
In this embodiment, the hole 202a is a hole closest to 5 the inter-pole part among holes formed in the electromagnetic
steel sheets 201a (except for the shaft hole 203a) in the plane
perpendicular to the axial direction, that is, in the xy plane.
[0023]
In the example illustrated in FIG. 4, a plurality of 10 holes 202a (specifically four holes 202a) are arranged in the
circumferential direction. In the example illustrated in FIG.
4, the number of holes 202a is equal to the number of magnetic
poles of the rotor 2.
[0024] 15 In the example illustrated in FIG. 4, the permanent
magnets 220 are inserted in the holes 202a. The permanent
magnets 220 are, for example, rare earth magnets. The
permanent magnets 220, however, are not limited to rare earth
magnets. The width of each permanent magnet 220 in the radial 20 direction is smaller than the width of each hole 202a in the
radial direction.
[0025]
As illustrated in FIG. 4, each of the permanent magnets
220 is located on the inner side in a corresponding one of the 25 holes 202a in the radial direction. Thus, a gap is formed
between the inner wall defining the hole 202a and the outer
surface of the permanent magnet 220 in the radial direction.
In the gap, oil or a refrigerant may be present.
[0026] 30 The at least one first thin-wall part 205a is located
outside the holes 202a in the radial direction. Specifically,
the at least one first thin-wall part 205a is formed between
the holes 202a and the outer edge of the first rotor core 21.
10
In the example illustrated in FIG. 4, a plurality of first
thin-wall parts 205a (specifically eight first thin-wall parts
205a) are formed in the first rotor core 21. Each of the first
thin-wall parts 205a extends along the circumferential
direction. 5 [0027]
As illustrated in FIG. 4, the first rotor core 21 also
includes first portions 21a located at magnetic pole center
parts of the rotor 2, second portions 22a located at inter-pole
parts of the rotor 2, outer peripheral surfaces 23a (also 10 referred to as first outer peripheral surfaces) including the
first portions 21a, and outer peripheral surfaces 24a (also
referred to as second outer peripheral surfaces) including the
second portions 22a.
[0028] 15 In the xy plane, the first portions 21a are end portions
of the first rotor core 21 in the radial direction. Similarly,
in the xy plane, the second portions 22a are end portions of
the first rotor core 21 in the radial direction. The first
portions 21a and the second portions 22a form part of the outer 20 edge of the first rotor core 21.
[0029]
The magnetic pole center parts of the rotor 2 are parts
of the rotor 2 through which magnetic pole center lines B1 pass.
Each of the magnetic pole center lines B1 indicated by a broken 25 line is a line passing through the center of the permanent
magnet 220 and the rotation center of the rotor 2 in the xy
plane.
[0030]
The inter-pole parts of the rotor 2 are parts of the 30 rotor 2 through which inter-pole lines B2 pass. Each of the
inter-pole lines B2 indicated by a broken line is a line
passing through an intermediate point between two adjacent
permanent magnets 220 and the rotation center of the rotor 2 in
11
the xy plane.
[0031]
The outer peripheral surfaces 23a project outward in the
radial direction compared with the outer peripheral surfaces
24a. In the xy plane, a distance Ra (also referred to as a 5 radius Ra) from the rotation center of the rotor 2 to the first
portions 21a is larger than a distance Wa (also referred to as
a radius Wa) from the rotation center of the rotor 2 to the
second portions 22a. In other words, the radius Ra of the
first rotor core 21 at the magnetic pole center parts is larger 10 than the radius Wa of the first rotor core 21 at the inter-pole
parts. Thus, a minimum distance from the second portions 22a
to the stator core 31 is larger than a minimum distance from
the first portions 21a to the stator core 31. In other words,
an air gap between the first rotor core 21 and the stator core 15 31 in the inter-pole parts is larger than an air gap between
the first rotor core 21 and the stator core 31 in the magnetic
pole center parts.
[0032]
FIG. 5 is a cross-sectional view schematically 20 illustrating a structure of the second side of the rotor 2.
The second rotor core 22 includes a plurality of
electromagnetic steel sheets 201b stacked in the axial
direction, at least one hole 202b (also referred to as a second
hole), a shaft hole 203b, at least one hole 204b, and at least 25 one second thin-wall part 205b. The second rotor core 22 has a
substantially cylindrical shape.
[0033]
Each of the plurality of electromagnetic steel sheets
201b has a thickness of 0.1 mm or more and 1 mm or less in many 30 cases. Each of the electromagnetic steel sheets 201b is formed
by stamping into a predetermined shape. The at least one hole
202b, the shaft hole 203b, the at least one hole 204b, and the
at least one second thin-wall part 205b are formed in each of
12
the plurality of electromagnetic steel sheets 201b. The shaft
hole 203b is formed at the center of the electromagnetic steel
sheet 201b in a plane perpendicular to the axial direction,
that is, the xy plane.
[0034] 5 In this embodiment, the hole 202b is a hole closest to
the inter-pole part among holes formed in the electromagnetic
steel sheet 201b (except for the shaft hole 203b) in the plane
perpendicular to the axial direction, that is, in the xy plane.
In the example illustrated in FIG. 5, the permanent magnets 220 10 are inserted in the holes 202b. The shape of the holes 202b is
the same as the shape of the holes 202a. The shape of the
holes 202b may be different from the shape of the holes 202a.
[0035]
In the example illustrated in FIG. 5, a plurality of 15 holes 202b (specifically four holes 202b) are arranged in the
circumferential direction. In the example illustrated in FIG.
5, the number of holes 202b is equal to the number of magnetic
poles of the rotor 2.
[0036] 20 In the example illustrated in FIG. 5, the permanent
magnets 220 are inserted in the holes 202b. That is, one
permanent magnet 220 is inserted in the hole 202a of the first
rotor core 21 and the hole 202b of the second rotor core 22.
That is, the hole 202b communicates with the hole 202a. The 25 width of each permanent magnet 220 in the radial direction is
smaller than the width of each hole 202b in the radial
direction.
[0037]
As illustrated in FIG. 5, the permanent magnet 220 is 30 located on the inner side in the hole 202b in the radial
direction. Thus, a gap is formed between the inner wall
defining hole 202b and the outer surface of the permanent
magnet 220 in the radial direction. In the gap, oil or a
13
refrigerant may be present.
[0038]
The at least one second thin-wall part 205b is located
outside the hole 202b in the radial direction. Specifically,
the at least one second thin-wall part 205b is formed between 5 the hole 202b and the outer edge of the second rotor core 22.
In the example illustrated in FIG. 5, a plurality of second
thin-wall parts 205b (specifically eight second thin-wall parts
205b) are formed in the second rotor core 22. Each of the
second thin-wall parts 205b extends along the circumferential 10 direction.
[0039]
The shape of the first thin-wall part 205a and the shape
of the second thin-wall part 205b are the same. For example,
in the xy plane, the first thin-wall part 205a and the second 15 thin-wall part 205b have the same width in the radial direction.
In addition, in the xy plane, the first thin-wall part 205a and
the second thin-wall part 205b have the same length in the
circumferential direction.
[0040] 20 A distance from the rotation center of the rotor 2 (axis
line Ax in FIG. 4) to the first thin-wall part 205a is equal to
a distance from the rotation center of the rotor 2 (axis line
Ax in FIG. 5) to the second thin-wall part 205b. In addition,
an angle formed by a line passing through the rotation center 25 of the rotor 2 and the first thin-wall part 205a (e.g., the
barycenter of the first thin-wall part 205a) to the magnetic
pole center part (e.g., a line passing through the rotation
center of the rotor 2 and the first portion 21a in FIG. 4) in
the xy plane is equal to an angle formed by a line passing 30 through the rotation center of the rotor 2 and the second thinwall
part 205b (e.g., the barycenter of the second thin-wall
part 205b) to the magnetic pole center part (e.g., a line
passing through the rotation center of the rotor 2 and the
14
first portion 21b in FIG. 5) in the xy plane. That is, in the
xy plane, the position of the first thin-wall part 205a and the
position of the second thin-wall part 205b in the rotor 2 are
the same. In other words, in the xy plane, the position of the
first thin-wall part 205a and the position of the second thin- 5 wall part 205b overlap each other.
[0041]
The shaft hole 203b of the second rotor core 22
communicates with the shaft hole 203a of the first rotor core
21. The shaft 26 is inserted in the shaft holes 203a and 203b 10 formed in a center portion of the rotor 2 in the xy plane. The
shaft 26 is fixed to the first rotor core 21 (specifically the
shaft hole 203a) and the second rotor core 22 (specifically the
shaft hole 203b), and rotatably supported only on the first
side. Specifically, the shaft 26 is rotatably supported by the 15 bearing 4 on the first side.
[0042]
As illustrated in FIG. 5, the second rotor core 22 also
includes first portions 21b located at the magnetic pole center
parts of the rotor 2, second portions 22b located at the inter- 20 pole parts of the rotor 2, outer peripheral surfaces 23b (also
referred to as first outer peripheral surfaces) including the
first portions 21b, and outer peripheral surfaces 24b (also
referred to as second outer peripheral surfaces) including the
second portions 22b. 25 [0043]
In the xy plane, the first portions 21b are end portions
of the second rotor core 22 in the radial direction. Similarly,
in the xy plane, the second portions 22b are end portions of
the second rotor core 22 in the radial direction. The first 30 portions 21b and the second portions 22b form part of the outer
edge of the second rotor core 22.
[0044]
The outer peripheral surface of the second rotor core 22,
15
that is, the outer peripheral surfaces 23b and 24b, has a
curvature equal to that of the outer peripheral surface 24a of
the first rotor core 21.
[0045]
As illustrated in FIG. 3, the minimum distance G1 from 5 the first rotor core 21 to the stator 3 in the radial direction
is shorter than the minimum distance G2 from the second rotor
core 22 to the stator 3 in the radial direction. The minimum
distance G1 is a minimum distance of an air gap between the
first rotor core 21 and the stator 3. The minimum distance G2 10 is a minimum distance of an air gap between the second rotor
core 22 and the stator 3.
[0046]
As illustrated in FIG. 4, a maximum radius of the first
rotor core 21 is a distance Ra from the rotation center of the 15 rotor 2 to the first portion 21a in the xy plane. That is, the
maximum radius of the first rotor core 21 is the radius Ra of
the first rotor core 21 in the magnetic pole center parts in
the xy plane. The distance Wa from the rotation center of the
rotor 2 to the second portions 22a in the xy plane is the 20 radius Wa of the first rotor core 21 in the inter-pole parts.
[0047]
As illustrated in FIG. 5, the maximum radius of the
second rotor core 22 is a distance Rb (also referred to as a
radius Rb) from the rotation center of the rotor 2 to the first 25 portions 21b in the xy plane, and is also a radius of the
second rotor core 22 in the magnetic pole center parts in the
xy plane. In addition, the maximum radius of the second rotor
core 22 is also the distance Rb from the rotation center of the
rotor 2 to the second portions 22b in the xy plane. That is, 30 in the xy plane, the radius of the second rotor core 22 in the
magnetic pole center parts is equal to the radius of the second
rotor core 22 in the inter-pole parts.
[0048]
16
As illustrated in FIG. 3, the maximum radius Ra of the
first rotor core 21 is larger than the maximum radius Rb of the
second rotor core 22. That is, the maximum outer diameter of
the first rotor core 21 (i.e., 2 × Ra) is larger than the
maximum diameter of the second rotor core 22 (i.e., 2 × Rb). 5 [0049]
The radius Wa of the first rotor core 21 in the interpole
parts of the first rotor core 21 is equal to the radius Rb
of the second rotor core 22 in the inter-pole parts of the
second rotor core 22 (i.e., Wa = Rb). That is, the outer 10 diameter of the first rotor core 21 in the inter-pole parts of
the first rotor core 21 (i.e., 2 × Wa) is equal to the outer
diameter of the second rotor core 22 in the inter-pole parts of
the second rotor core 22 (i.e., 2 × Rb).
[0050] 15 The number of magnetic poles of the first rotor core 21
is N2 (N2 > 2), and the number of magnetic poles of the second
rotor core 22 is also N2. That is, the number of magnetic
poles of the rotor 2 is also N2. In this embodiment, N2 = 4.
Supposing the number of pole pairs of the first rotor core 21 20 is N1, N1 = N2/2 is established, and the number of pole pairs
of the second rotor core 22 is also N2/2. That is, the number
of pole pairs of the rotor 2 is also N2/2.
[0051]
FIG. 6 is a diagram illustrating a positional 25 relationship between the first rotor core 21 and the stator
core 31 in the xy plane. FIG. 6 illustrates a portion of the
first rotor core 21 and a portion of the stator core 31.
[0052]
Each of the teeth 311 includes a main body 311a and a 30 tooth front end 311b. The main body 311a extends in the radial
direction. The tooth front end 311b extends in the
circumferential direction, and faces the rotor 2 (specifically
the first rotor core 21).
17
[0053]
In a plane perpendicular to the axial direction,
supposing an angle (mechanical angle) formed by two lines L2
passing through both ends of the outer peripheral surface 23a
in the circumferential direction and the rotation center of the 5 first rotor core 21 is A1 [degree], the electric motor 1
satisfies 87 < A1 × N1 < 130. In other words, the angle formed
by two lines L2 is larger than 87 degrees and smaller than 130
degrees, in terms of electrical angles.
[0054] 10 FIG. 7 is a diagram illustrating an example of a state of
the rotor 2 while the electric motor 1 is being driven. The
axis line Ax’ represents the center of the shaft 26 illustrated
in FIG. 7. In the example illustrated in FIG. 7, the axis line
Ax’, which is the rotation center of the rotor 2, is shifted 15 from the axis line Ax that is originally set.
[0055]
In the zx plane, supposing a tilt of the shaft 26 is θ1,
the first side of the rotor 2, specifically, the maximum travel
distance of the first rotor core 21 in the radial direction is 20 expressed as (D1 + T1) × sinθ1. Thus, the distance G1 (FIG. 3)
needs to be larger than (D1 + T1) × sinθ1. Thus, the electric
motor 1 satisfies G1 > (D1 + T1) × sinθ1. Accordingly, it is
possible to prevent the first side of the rotor 2, specifically,
the first rotor core 21, from contacting the stator 3. 25 [0056]
A distance D1 is a minimum distance from the first rotor
core 21 to the bearing 4. A thickness T1 is a thickness of the
first rotor core 21 in the axial direction. The tilt θ1 is a
maximum tilt of the shaft 26 in a plane parallel to the axial 30 direction, that is, the zx plane. Specifically, the tilt θ1 is
a maximum tilt of the shaft 26 from the axis line Ax in the zx
plane. In other words, the tilt θ1 is an angle in a case where
the second side of the rotor 2, specifically, the second rotor
18
core, contacts the stator 3. The distance G1 is a minimum
distance from the first rotor core 21 to the stator 3 in a case
where the rotation center of the rotor 2 and the stator 3
coincide with each other in the xy plane.
[0057] 5 VARIATIONS
FIGS. 8, 9, and 10 are plan views illustrating other
examples of the structure of the first rotor core 21. In the
second rotor core 22, the structure except for the outer edge
can be formed similarly to the structure of the first rotor 10 core 21 shown in FIGS. 8, 9, and 10.
[0058]
In the example illustrated in FIG. 8, the shape of the
hole 202a is different from the hole 202a described in the
first embodiment. Specifically, both ends of the hole 202a 15 illustrated in FIG. 8, specifically, both ends of the hole 202a
in the longitudinal direction in the xy plane, extend in the
radial direction. The longitudinal direction of the hole 202a
is a direction perpendicular to the magnetic pole center line
B1 in the xy plane. In this case, the shape of the hole 202b 20 of the second rotor core 22 is also the same as that of the
hole 202a. The position and shape of the thin-wall part of the
second rotor core 22 are the same as those of the first thinwall
part 205a.
[0059] 25 In the example illustrated in FIG. 9, the first rotor
core 21 also includes at least one hole 206a. In the xy plane,
the hole 206a is formed outside the hole 202a in the
longitudinal direction. The longitudinal direction of the hole
202a is a direction perpendicular to the magnetic pole center 30 line B1 in the xy plane. In the example illustrated in FIG. 9,
the hole 206a is a hole closest to an inter-pole part among
holes formed in the electromagnetic steel sheet 201a (except
for the shaft hole 203a) in a plane perpendicular to the axial
19
direction, that is, in the xy plane. In the example
illustrated in FIG. 9, the first thin-wall part 205a is formed
between the hole 206a and the outer edge of the first rotor
core 21. In this case, the second rotor core 22 also has a
hole similar to the hole 206a of the first rotor core 21. The 5 position and shape of the thin-wall part of the second rotor
core 22 are the same as those of the first thin-wall part 205a.
[0060]
In the example illustrated in FIG. 10, the first rotor
core 21 also includes at least one hole 206a. In the xy plane, 10 the hole 206a is formed outside the hole 202a in the
longitudinal direction and between the hole 202a and the outer
edge of the first rotor core 21. The longitudinal direction of
the hole 202a is a direction perpendicular to the magnetic pole
center line B1 in the xy plane. In the example illustrated in 15 FIG. 10, the hole 206a is a hole closest to an inter-pole part
among holes formed in the electromagnetic steel sheet 201a
(except for the shaft hole 203a) in a plane perpendicular to
the axial direction, that is, in the xy plane. In the example
illustrated in FIG. 10, the first thin-wall part 205a is formed 20 between the hole 206a and the outer edge of the first rotor
core 21. In this case, the second rotor core 22 also has a
hole similar to the hole 206a of the first rotor core 21. The
position and shape of the thin-wall part of the second rotor
core 22 are the same as those of the first thin-wall part 205a. 25 [0061]
Advantages of the electric motor 1 according to this
embodiment will be described hereinafter.
In general, an air gap between a stator and a rotor is
designed narrow. This can reduce magnetic resistance in an 30 electric motor and avoid a decrease in a magnetic force.
However, in a case where the shaft of the rotor is rotatably
supported only on one side in the axial direction, the rotor is
subjected to a magnetic force in the radial direction so that
20
the shaft of the rotor might be warped. In view of this, in
the case where the shaft of the rotor is rotatably supported
only on one end in the axial direction, an air gap between the
stator and the rotor is preferably designed wide. However, as
the size of the air gap increases, the magnetic force decreases. 5 [0062]
In an electric motor using a permanent magnet, a magnetic
force of the permanent magnet is large in the radial direction,
and thus, the shaft of the rotor is easily warped. Thus, in
the case where the shaft of the rotor is rotatably supported by 10 the bearing only on one side in the axial direction, the
bearing side of the shaft serves as a fulcrum, and the shaft
might be warped. In this case, an air gap on the counter
bearing side is narrower than an air gap on the bearing side.
Thus, in a conventional electric motor, to prevent contact of 15 the counter bearing side of the rotor core with the stator, the
outer diameter of the rotor core needs to be small. However,
if the outer diameter of the rotor core is small, an air gap
becomes wide in some portions, and as a result, a magnetic
force decreases. 20 [0063]
In the electric motor 1 according to this embodiment, the
minimum distance G1 from the first rotor core 21 to the stator
3 in the radial direction is smaller than the minimum distance
G2 from the second rotor core 22 to the stator 3 in the radial 25 direction. Accordingly, in consideration of warpage of the
shaft 26, an air gap between the stator 3 and the rotor 2 can
be appropriately set. That is, in the electric motor 1 using
the permanent magnet 220, since a magnetic force of the
permanent magnet 220 is large in the radial direction, the 30 shaft 26 of the rotor 2 is easily warped. Even in a case where
the shaft 26 of the rotor 2 is warped, the second side of the
rotor 2 does not contact the stator 3, and a narrow air gap on
the second side (e.g., the minimum distance G2) is maintained.
21
In addition, since the minimum distance G1 on the first side is
smaller than the minimum distance G2 on the second side, the
air gap on the first side (e.g., the minimum distance G1) can
be also maintained narrow. Consequently, a decrease in a
magnetic force in the electric motor 1 can be prevented. 5 [0064]
The electric motor 1 includes the first rotor core 21 and
the second rotor core 22 having different maximum outer
diameters. That is, the rotor 2 includes two types of rotor
cores. Specifically, to set an air gap on the first side 10 smaller than an air gap on the second side, it is preferable to
appropriately maintain air gaps in the electric motor 1 with a
minimum configuration. In general, electromagnetic steel
sheets constituting a rotor core are formed by press work. If
design of the rotor core, for example, the shapes of the first 15 rotor core 21 and the second rotor core 22, is different in
many portions, molds are individually needed for processing
electromagnetic steel sheets of the first rotor core 21 and the
second rotor core 22, and thus, costs increase. On the other
hand, in the electric motor 1 according to this embodiment, it 20 is sufficient to change the shapes of the two types of rotor
cores, that is, the first rotor core 21 and the second rotor
core 22, only for portions where the air gap on the first side
is set smaller than the air gap on the second side. Thus,
processing costs and mold costs can be reduced. 25 [0065]
The stator 3 (specifically the stator core 31) has a
uniform curvature radius of the inner peripheral surface. That
is, in the xy plane, the distance from the axis line Ax to the
teeth 311 is uniform in the circumferential direction. 30 Accordingly, by setting the radii of the first rotor core 21
and the second rotor core 22 individually, the sizes of the two
types of air gaps (i.e., the minimum distances G1 and G2) can
be adjusted. In addition, since the inner peripheral surface
22
of the stator 3 has a uniform curvature radius, the winding 32
can be easily wound. Moreover, in the process of fabricating
the electric motor 1, the stator 3 can be conveyed by using the
inner peripheral surface of the stator 3 (e.g., the surface of
the tooth front end 311b). 5 [0066]
In the electric motor 1 according to this embodiment, the
maximum radius of the first rotor core 21 (specifically the
radius Ra) is larger than the maximum radius of the second
rotor core 22 (specifically the radius Rb). Accordingly, the 10 size of the air gap on the first side of the rotor 2 can be
reduced. In general, when the outer diameter of a rotor core
is increased in order to reduce the size of an air gap, the
width of a thin-wall part in the radial direction increases.
If the width of the thin-wall part increases, the strength to a 15 centrifugal force generated in the rotor core increases. On
the other hand, if the width of the thin-wall part increases,
leakage of magnetic fluxes near the inter-pole part easily
occurs.
[0067] 20 In the electric motor 1, the shape of the first thin-wall
part 205a and the shape of the second thin-wall part 205b are
the same. A distance from the rotation center of the rotor 2
(axis line Ax in FIG. 4) to the first thin-wall part 205a is
equal to a distance from the rotation center of the rotor 2 25 (axis line Ax in FIG. 5) to the second thin-wall part 205b. In
addition, an angle formed by a line passing through the
rotation center of the rotor 2 and the first thin-wall part
205a to the magnetic pole center part in the xy plane is equal
to an angle formed by a line passing through the rotation 30 center of the rotor 2 and the second thin-wall part 205b to the
magnetic pole center part in the xy plane. That is, in the xy
plane, the position of the first thin-wall part 205a and the
position of the second thin-wall part 205b in the rotor 2 are
23
the same. Accordingly, in a manner similar to the second thinwall
part 205b, the width of the first thin-wall part 205a in
the radial direction can be reduced, and thus, leakage of
magnetic fluxes near the inter-pole part can be reduced.
Moreover, in this state, the radius of the first rotor core 21 5 in the magnetic pole center part is larger than the radius of
the second rotor core 22 in the magnetic pole center part.
Thus, the air gap on the first side of the rotor 2 can be made
small. Consequently, leakage of magnetic fluxes near the
inter-pole part of the rotor 2 can be reduced, and a magnetic 10 force in the electric motor 1, especially a magnetic force on
the first side of the rotor 2, can be enhanced.
[0068]
The shape of the hole 202a of the first rotor core 21 is
preferably the same as the shape of the hole 202b of the second 15 rotor core 22, and the curvature of the outer peripheral
surface 24a of the first rotor core 21 is preferably equal to
the curvature of the outer peripheral surfaces 23b and the 24b
of the second rotor core 22. Accordingly, the first thin-wall
part 205a can be formed to have the same shape as that of the 20 second thin-wall part 205b.
[0069]
When the shape of the hole 202a of the first rotor core
21 is the same as that of the hole 202b of the second rotor
core 22, the shape on the first side of the permanent magnet 25 220 and the shape on the second side of the permanent magnet
220 can be made the same. Thus, one permanent magnet 220 can
be disposed on the first side and the second side of the rotor
2, that is, in the holes 202a and 202b, and thus, the number of
permanent magnets 220 can be reduced, the process of inserting 30 the permanent magnet 220 can be easily performed, and costs for
fabricating the electric motor 1 can be reduced.
[0070]
In the case where the shape of the hole 202a of the first
24
rotor core 21 is the same as the shape of the hole 202b of the
second rotor core 22, the holes 202a and 202b can be formed
with a common mold. Thus, mold costs can be reduced.
[0071]
FIG. 11 is a graph showing a relationship between an 5 angle [degree] formed by two lines L2 passing both ends of the
outer peripheral surface 23a in the circumferential direction
and the rotation center of the first rotor core 21 and an
increase rate [%] of an induced voltage. The vertical axis
represents an increase rate of an induced voltage in the 10 electric motor 1 with reference to an electric motor including
a rotor in which the outer edge of a rotor core in the xy plane
is a complete circle. The horizontal axis represents an
electrical angle.
[0072] 15 As illustrated in FIG. 11, if the angle formed by the two
lines L2 is from 0 degrees to 87 degrees, the induced voltage
increases. If the angle formed by the two lines L2 exceeds 130
degrees, the induced voltage decreases. Specifically, if the
angle formed by the two lines L2 is from 0 degrees to 87 20 degrees, an induced voltage increases as the outer peripheral
surface 23a becomes longer in the circumferential direction.
That is, as a region where the air gap is small is longer in
the circumferential direction, the induced voltage increases.
If the angle formed by the two lines L2 exceeds 130 degrees, 25 the outer peripheral surface 23a reaches the first thin-wall
part 205a. That is, the width of the first thin-wall part 205a
increases by the width of the outer peripheral surface 23a in
the radial direction, and leakage of magnetic fluxes increases.
[0073] 30 Thus, when the electric motor 1 satisfies 87 < A1 × N1 <
130, leakage of magnetic fluxes can be reduced and the induced
voltage can be increased. In addition, when the electric motor
1 satisfies 90 < A1 × N1 < 130, the induced voltage can be
25
effectively increased. Furthermore, when the electric motor 1
satisfies 106 < A1 × N1 < 111, the induced voltage can be more
effectively increased.
[0074]
The electric motor 1 preferably satisfies G1 > (D1 + T1) 5 × sinθ1 and G2 > G1. Similarly, the electric motor 1
preferably satisfies G1 > G2 × (D1 + T1)/L1 and G2 > G1.
Accordingly, even when the rotor 2 tilts, it is possible to
prevent contact of the first side of the rotor 2, specifically
the first rotor core 21, with the stator 3. 10 [0075]
As described above, since the electric motor 1 has the
structure described above, leakage of magnetic fluxes in the
rotor 2 can be reduced, and a magnetic force in the electric
motor 1 can be enhanced. 15 [0076]
SECOND EMBODIMENT
A compressor 6 according to a second embodiment of the
present invention will be described.
FIG. 12 is a cross-sectional view schematically 20 illustrating a structure of the compressor 6 according to the
second embodiment.
[0077]
The compressor 6 includes an electric motor 60 serving as
an electric element, a closed container 61 serving as a housing, 25 and a compression mechanism 62 serving 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.
[0078] 30 The electric motor 60 is the electric motor 1 according
to the first embodiment. In this embodiment, the electric
motor 60 is an interior permanent magnet electric motor, but is
not limited to this type.
26
[0079]
The closed container 61 covers the electric motor 60 and
the compression mechanism 62. In a bottom portion of the
closed container 61, refrigerating machine oil for lubricating
a sliding portion of the compression mechanism 62 is stored. 5 [0080]
The compressor 6 also includes a glass terminal 63 fixed
to the closed container 61, an accumulator 64, a suction pipe
65, and a discharge pipe 66.
[0081] 10 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 individually
attached to the upper frame 62c and the lower frame 62d. The
compression mechanism 62 also includes a vane that divides the 15 inside of the cylinder 62a into a suction side and a
compression side. The compression mechanism 62 is driven by
the electric motor 60.
[0082]
The electric motor 60 is fixed in the closed container 61 20 by press fitting or shrink fitting. A stator 3 may be directly
attached to the closed container 61 by welding, instead of
press fitting or shrink fitting.
[0083]
Electric power is supplied to a winding of the stator 3 25 of the electric motor 60 through the glass terminal 63.
[0084]
A rotor (specifically one end of a shaft 26) of the
electric motor 60 is rotatably supported by a bearing provided
on each of the upper frame 62c and the lower frame 62d. 30 [0085]
The shaft 26 is inserted in a 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
27
an end face of the cylinder 62a. The accumulator 64 supplies a
refrigerant (e.g., refrigerant gas) to the cylinder 62a through
the suction pipe 65.
[0086]
Next, an operation of the compressor 6 will be described. 5 Refrigerant supplied from the accumulator 64 is sucked into the
cylinder 62a from the suction pipe 65 fixed to the closed
container 61. The electric motor 60 rotates by electrification
of an inverter so that the piston 62b fitted to the shaft 26
rotates in the cylinder 62a. In this manner, the refrigerant 10 is compressed in the cylinder 62a.
[0087]
The refrigerant passes through the mufflers 62e and rises
in the closed container 61. Refrigerating machine oil is mixed
in the compressed refrigerant. While the mixture of the 15 refrigerant and the refrigerating machine oil is passing
through an air hole 36 formed in a rotor core, separation
between the refrigerant and the refrigerating machine oil is
promoted, and accordingly, a flow of the refrigerating machine
oil into the discharge pipe 66 can be prevented. In this 20 manner, the compressed refrigerant is supplied to a highpressure
side of a refrigerant cycle through the discharge pipe
66.
[0088]
As a refrigerant for the compressor 6, R410A, R407C, or 25 R22, for example, can be used. However, the refrigerant for
the compressor 6 is not limited to these examples. For example,
as a refrigerant for the compressor 6, a refrigerant having a
small global warming potential (GWP) or the like can be used.
[0089] 30 Typical examples of the refrigerant having a small GWP
includes the following refrigerants.
[0090]
(1) Halogenated hydrocarbon including a carbon double
28
bond in a composition is, for example, HFO-1234yf (CF3CF=CH2).
HFO stands for Hydro-Fluoro-Olefin. Olefin is unsaturated
hydrocarbon having one double bond. The GWP of HFO-1234yf is 4.
[0091]
(2) Hydrocarbon having a carbon double bond in a 5 composition is, for example, R1270 (propylene). The GWP of the
R1270 is 3, which is smaller than the GWP of HFO-1234yf, but
flammability of R1270 is higher than flammability of HFO-1234yf.
[0092]
(3) A mixture including at least one of halogenated 10 hydrocarbon having a carbon double bond in a composition or
hydrocarbon having a carbon double bond in a composition is,
for example, a mixture of HFO-1234yf and R32. Since HFO-1234yf
is a low-pressure refrigerant, a pressure loss is large, and
performance in a refrigeration cycle (especially in an 15 evaporator) tends to degrade. Thus, it is preferable to use a
mixture with, for example, R32 or R41, which is a high-pressure
refrigerant.
[0093]
The compressor 6 according to the second embodiment has 20 advantages described in the first embodiment.
[0094]
In addition, the use of the electric motor 1 according to
the first embodiment as the electric motor 60 can enhance
efficiency of the electric motor 60, and as a result, 25 efficiency of the compressor 6 can be enhanced.
[0095]
THIRD EMBODIMENT
An air conditioner 50 (also referred to as a
refrigerating and air conditioning apparatus or a refrigeration 30 cycle device) according to a third embodiment of the present
invention will be described.
FIG. 13 is a diagram schematically illustrating a
configuration of the air conditioner 50 according to the third
29
embodiment.
[0096]
The air conditioner 50 according to the third embodiment
includes an indoor unit 51 serving as an air blower (first air
blower), a refrigerant pipe 52, and an outdoor unit 53 serving 5 as an air blower (second air blower) connected to the indoor
unit 51 through the refrigerant pipe 52.
[0097]
The indoor unit 51 includes an electric motor 51a (e.g.,
the electric motor 1 according to the first embodiment), an air 10 blow unit 51b that is driven by the air electric motor 51a to
thereby send air, and a housing 51c covering the electric motor
51a and the air blow unit 51b. The air blow unit 51b includes
a blade 51d that is driven by the electric motor 51a, for
example. For example, the blade 51d is fixed to a shaft (e.g., 15 a shaft 26) of the electric motor 51a, and generates an airflow.
[0098]
The outdoor unit 53 includes an electric motor 53a (e.g.,
the electric motor 1 according to the first embodiment), an air
blow unit 53b, a compressor 54, and a heat exchanger (not 20 shown). The air blow unit 53b is driven by the electric motor
53a to thereby send air. The air blow unit 53b includes a
blade 53d that is driven by the electric motor 53a, for example.
For example, the blade 53d is fixed to a shaft (e.g., a shaft
26) of the electric motor 53a, and generates an airflow. The 25 compressor 54 includes an electric motor 54a (e.g., the
electric motor 1 according to the first embodiment), a
compression mechanism 54b (e.g., a refrigerant circuit) that is
driven by the electric motor 54a, and a housing 54c covering
the electric motor 54a and the compression mechanism 54b. The 30 compressor 54 is, for example, the compressor 6 described in
the second embodiment.
[0099]
In the air conditioner 50, at least one of the indoor
30
unit 51 or the outdoor unit 53 includes the electric motor 1
described in the first embodiment. Specifically, as a driving
source of the air blow unit, the electric motor 1 described in
the first embodiment is applied to at least one of the electric
motors 51a or 53a. As an electric motor 54a of the compressor 5 54, the electric motor 1 described in the first embodiment may
be used.
[0100]
The air conditioner 50 can perform operations such as a
cooling operation of sending cold air from the indoor unit 51 10 or a heating operation of sending warm air from the indoor unit
51, for example. In the indoor unit 51, the electric motor 51a
is a driving source for driving the air blow unit 51b. The air
blow unit 51b can send conditioned air.
[0101] 15 In the air conditioner 50 according to the third
embodiment, since the electric motor 1 described in the first
embodiment is applied to at least one of the electric motors
51a or 53a, the same advantages as those described in the first
embodiment can be obtained. Accordingly, efficiency of the air 20 conditioner 50 can be enhanced.
[0102]
In addition, as a driving source of an air blower (e.g.,
the indoor unit 51), the electric motor 1 according to the
first embodiment is used. Thus, the same advantages as those 25 described in the first embodiment can be obtained. In this
manner, efficiency of the air blower can be enhanced. An air
blower including the electric motor 1 according to the first
embodiment and the blade (e.g., the blade 51d or 53d) driven by
the electric motor 1 can be used singly as a device for sending 30 air. This air blower is also applicable to devices other than
the air conditioner 50.
[0103]
The use of the electric motor 1 according to the first
31
embodiment as a driving source of the compressor 54 can obtain
the same advantages as those described in the first embodiment.
Accordingly, efficiency of the compressor 54 can be enhanced.
[0104]
The electric motor 1 described in the first embodiment 5 can be mounted on equipment including a driving source, such as
a ventilator, household electrical appliance, or a machine tool,
other than the air conditioner 50.
[0105]
Features of the embodiments described above may be 10 combined as appropriate.
DESCRIPTION OF REFERENCE CHARACTERS
[0106]
1, 51a, 53a, 54a, 60 electric motor, 2 rotor, 3 stator, 4 15 bearing, 6 compressor, 21 first rotor core, 21a, 21b first
portion, 22a, 22b second portion, 23a, 23b outer peripheral
surface (first outer peripheral surface), 24a, 24b outer
peripheral surface (second outer peripheral surface), 22 second
rotor core, 26 shaft, 31 stator core, 50 air conditioner, 51 20 indoor unit (air blower), 53 outdoor unit (air blower), 201a,
201b electromagnetic steel sheet, 202a, 202b hole, 205a first
thin-wall part, 205b second thin-wall part, 220 permanent
magnet, 311 tooth.
25
32
We Claim:
1. An electric motor comprising:
a stator; and 5 a rotor including a shaft, a first rotor core fixed on a
first side of the shaft in an axial direction, and a second
rotor core fixed on a second side of the shaft, the second side
being opposite to the first side in the axial direction, the
rotor being disposed inside the stator, wherein 10 the shaft is supported only on the first side,
a minimum distance from the first rotor core to the
stator in a radial direction is shorter than a minimum distance
from the second rotor core to the stator in the radial
direction, 15 a maximum radius of the first rotor core is longer than a
maximum radius of the second rotor core,
the first rotor core includes a first hole and a first
thin-wall part, the first thin-wall part being located outside
the first hole in the radial direction, 20 the second rotor core includes a second hole and a second
thin-wall part, the second thin-wall part being located outside
the second hole in the radial direction, and
a shape of the first thin-wall part and a shape of the
second thin-wall part are the same. 25
2. The electric motor according to claim 1, wherein
the first rotor core includes a first portion that is an
end portion of the first rotor core in the radial direction, a
second portion that is an end portion of the first rotor core 30 in the radial direction, a first outer peripheral surface
including the first portion, and a second outer peripheral
surface including the second portion, the first portion being
located at a magnetic pole center part of the rotor, the second
33
portion being located at an inter-pole part of the rotor, and
the first outer peripheral surface projects outward in
the radial direction compared with the second outer peripheral
surface.
5 3. The electric motor according to claim 2, wherein
the electric motor satisfies
87 < A1 × N1 < 130
where N1 is the number of pole pairs in the first rotor
core, and A1 [degree] is an angle formed by two lines passing 10 through both ends of the first outer peripheral surface in the
circumferential direction and a rotation center of the first
rotor core in a plane perpendicular to the axial direction.
4. The electric motor according to any one of claims 1 to 3, 15 wherein
a radius of the first rotor core in an inter-pole part of
the first rotor core is equal to a radius of the second rotor
core in an inter-pole part of the second rotor core.
20 5. The electric motor according to any one of claims 1 to 4,
further comprising
a bearing supporting the first side of the shaft, wherein
the electric motor satisfies
G1 > G2 × (D1 + T1)/L1 25 where L1 is a minimum distance from an end of the shaft
on the second side in the axial direction to the bearing, D1 is
a minimum distance from the first rotor core to the bearing, T1
is a thickness of the first rotor core in the axial direction,
G1 is a minimum distance from the first rotor core to the 30 stator in a case where a rotation center of the rotor coincides
with a center of the stator in a plane perpendicular to the
axial direction, and G2 is a minimum distance from the second
rotor core to the stator in a case where the rotation center of
34
the rotor coincides with the center of the stator.
6. The electric motor according to any one of claims 1 to 4,
further comprising
a bearing supporting the first side of the shaft, wherein 5 the electric motor satisfies
G1 > (D1 + T1) × sinθ1
where D1 is a minimum distance from the first rotor core
to the bearing, T1 is a thickness of the first rotor core in
the axial direction, θ1 is a maximum tilt of the shaft in a 10 plane parallel to the axial direction, and G1 is a minimum
distance from the first rotor core to the stator in a case
where a rotation center of the rotor coincides with a center of
the stator in a plane perpendicular to the axial direction.
15 7. An electric motor according to any one of claims 1 to 6,
wherein
a distance from a rotation center of the rotor to the
first thin-wall part is equal to a distance from the rotation
center of the rotor to the second thin-wall part. 20
8. The electric motor according to any one of claims 1 to 7,
wherein
an angle formed by a line passing through a rotation
center of the rotor and the first thin-wall part to a magnetic 25 pole center part of the rotor in a plane perpendicular to the
axial direction is equal to an angle formed by a line passing
through the rotation center of the rotor and the second thinwall
part to a magnetic pole center part in the plane
perpendicular to the axial direction. 30
9. A compressor comprising:
an electric motor;
a compression mechanism that is driven by the electric
35
motor; and
a housing covering the electric motor and the compression
mechanism, wherein
the electric motor includes
a stator, and 5 a rotor including a shaft, a first rotor core fixed
on a first side of the shaft in an axial direction, and a
second rotor core fixed on a second side of the shaft, the
second side being opposite to the first side in the axial
direction, the rotor being disposed inside the stator, 10 the shaft is supported only on the first side,
a minimum distance from the first rotor core to the
stator in a radial direction is shorter than a minimum distance
from the second rotor core to the stator in the radial
direction, 15 a maximum radius of the first rotor core is longer than a
maximum radius of the second rotor core,
the first rotor core includes a first hole and a first
thin-wall part, the first thin-wall part being located outside
the first hole in the radial direction, 20 the second rotor core includes a second hole and a second
thin-wall part, the second thin-wall part being located outside
the second hole in the radial direction, and
a shape of the first thin-wall part and a shape of the
second thin-wall part are the same. 25
10. An air blower comprising:
an electric motor; and
a blade to be driven by the electric motor, wherein
the electric motor includes 30 a stator, and
a rotor including a shaft, a first rotor core fixed
on a first side of the shaft in an axial direction, and a
second rotor core fixed on a second side of the shaft, the
36
second side being opposite to the first side in the axial
direction, the rotor being disposed inside the stator,
the shaft is supported only on the first side,
a minimum distance from the first rotor core to the
stator in a radial direction is shorter than a minimum distance 5 from the second rotor core to the stator in the radial
direction,
a maximum radius of the first rotor core is longer than a
maximum radius of the second rotor core,
the first rotor core includes a first hole and a first 10 thin-wall part, the first thin-wall part being located outside
the first hole in the radial direction,
the second rotor core includes a second hole and a second
thin-wall part, the second thin-wall part being located outside
the second hole in the radial direction, and 15 a shape of the first thin-wall part and a shape of the
second thin-wall part are the same.
11. A refrigerating and air conditioning apparatus
comprising: 20 an indoor unit; and
an outdoor unit connected to the indoor unit, wherein
at least one of the indoor unit or the outdoor unit
includes an electric motor,
the electric motor includes 25 a stator, and
a rotor including a shaft, a first rotor core fixed
on a first side of the shaft in an axial direction, and a
second rotor core fixed on a second side of the shaft, the
second side being opposite to the first side in the axial 30 direction, the rotor being disposed inside the stator,
the shaft is supported only on the first side,
a minimum distance from the first rotor core to the
stator in a radial direction is shorter than a minimum distance
37
from the second rotor core to the stator in the radial
direction,
a maximum radius of the first rotor core is longer than a
maximum radius of the second rotor core,
the first rotor core includes a first hole and a first 5 thin-wall part, the first thin-wall part being located outside
the first hole in the radial direction,
the second rotor core includes a second hole and a second
thin-wall part, the second thin-wall part being located outside
the second hole in the radial direction, and 10 a shape of the first thin-wall part and a shape of the
second thin-wall part are the same.