FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
ELECTRIC MOTOR, COMPRESSOR, AND AIR CONDITIONER;
MITSUBISHI ELECTRIC CORPORATION, A CORPORATION
ORGANISED AND EXISTING UNDER THE LAWS OF JAPAN, WHOSE ADDRESS IS
7-3, MARUNOUCHI 2-CHOME, CHIYODA-KU, TOKYO 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 disclosure relates to an electric motor, a5
compressor, and an air conditioner.
BACKGROUND ART
[0002]
In general, an electric motor with a permanent magnet which10
is shorter than the stator core in the axial direction has been
proposed (e.g., Patent Reference 1).
PRIOR ART REFERENCE
PATENT REFERENCE15
[0003]
Patent Reference 1: Japanese Patent Application Publication
No. 2003-274591
SUMMARY OF THE INVENTION20
PROBLEM TO BE SOLVED BY THE INVENTION
[0004]
However, if the permanent magnet is shorter than the stator
core in the axial direction, the magnetic attractive force between
the stator and the rotor becomes unstable depending on the center25
position in the axial direction of the permanent magnet with
respect to the center of the stator core in the axial direction,
and thus the noise in the electric motor increases due to a rotor
vibration.
30
[0005]
It is an object of the present disclosure to reduce noise in
an electric motor.
3
MEANS OF SOLVING THE PROBLEM
[0006]
An electric motor according to an aspect of the present
disclosure includes:
a stator including a stator core and a coil provided on5
the stator core; and
a rotor disposed inside the stator and including a rotor
core and a permanent magnet, the rotor core including a magnet
insertion hole, the permanent magnet being disposed in the
magnet insertion hole,10
wherein an end of the stator core on a first side in an
axial direction is located away from the rotor core to the
first side,
the electric motor satisfies Ls/2 > Lb + Lm/2 and Ls/2
< Lb + La15
where Ls is a length of the stator core in the axial
direction, Lb is a distance in the axial direction between
the end of the stator core on the first side and an end of the
rotor core on the first side, Lm is a length of the permanent
magnet in the axial direction, and La is a distance in the20
axial direction from the end of the rotor core on the first
side to a center of the permanent magnet in the axial direction.
A compressor according to another aspect of the present
disclosure includes:
a sealed container;25
a compression device disposed in the sealed container; and
the electric motor to drive the compression device.
An air conditioner according to another aspect of the
present disclosure includes:
the compressor; and30
a heat exchanger.
EFFECTS OF THE INVENTION
[0007]
4
According to the present disclosure, noise in the electric
motor can be reduced.
[0008]
FIG. 1 is a side view schematically showing an electric
motor according to a first embodiment.5
FIG. 2 is a cross-sectional view schematically showing the
inside of the electric motor.
FIG. 3 is a cross-sectional view showing another example of
a rotor.
FIG. 4 is a cross-sectional view showing a still another10
example of the rotor.
FIG. 5 is a cross-sectional view showing a still another
example of the rotor.
FIG. 6 is a cross-sectional view of the rotor in FIG. 5
taken along line A6-A6.15
FIG. 7 is a cross-sectional view of the rotor in FIG. 5
taken along line A7-A7.
FIG. 8 is a cross-sectional view showing another example of
a rotor core shown in FIG. 5.
FIG. 9 is a cross-sectional view showing still another20
example of the rotor core shown in FIG. 5.
FIG. 10A and FIG. 10B are cross-sectional views showing
still another example of the rotor core shown in FIG. 5.
FIG. 11 is a cross-sectional view schematically showing an
electric motor as a comparative example.25
FIG. 12 is a cross-sectional view showing the structure of a
compressor according to a second embodiment.
FIG. 13 is a diagram schematically showing the structure of
a refrigerating and air conditioning apparatus according to a
third embodiment.30
MODE FOR CARRYING OUT THE INVENTION
[0009]
First Embodiment
5
In an xyz orthogonal coordinate system shown in each drawing,
a z-axis direction (z-axis) represents a direction parallel to the
axis Ax of the electric motor 1, an x-axis direction (x-axis)
represents a direction orthogonal to the z-axis direction, and a
y-axis direction (y-axis) represents a direction orthogonal to5
both the z-axis direction and the x-axis direction. The axis Ax
refers to the rotation center of a rotor 2, that is, the rotation
axis of the rotor 2. The direction parallel to the axis Ax is
also referred to as the “axis direction of the rotor 2” or simply
the “axis direction.” A radial direction refers to a direction10
along a radius of the rotor 2 or a stator 3, and refers to a
direction orthogonal to the axis Ax. An xy plane refers to a
plane orthogonal to the axial direction. An arrow D1 represents a
circumferential direction about the axis Ax. A circumferential
direction of the rotor 2 or the stator 3 is also simply referred15
to as the “circumferential direction.”
[0010]
Electric Motor 1
FIG. 1 is a side view schematically showing the electric
motor 1 according to the first embodiment. In FIG. 1, the lower20
side (i.e., +z side) is the first side, and the upper side (i.e.,
-z side) is the second side. In other words, the second side is
opposite the first side in the axial direction.
FIG. 2 is a cross-sectional view schematically showing the
inside of the electric motor 1. In FIG. 2, the shaft 23 is25
removed from the rotor 2 to show the dimensions of the components
of the rotor 2.
[0011]
The electric motor 1 includes the rotor 2 and the stator 3.
The electric motor 1 is a permanent magnet synchronous motor (also30
referred to as a brushless DC motor), such as a permanent magnet
embedded motor. The electric motor 1 may include at least one
bearing that rotatably supports the shaft 23 of the rotor 2.
[0012]
6
Stator 3
The stator 3 is located outside the rotor 2. As shown in
FIG. 1, the stator 3 includes a stator core 31 and at least one
coil 32. Each coil 32 is provided in the stator core 31. An
insulator may be disposed between the stator core 31 and the coil5
32.
[0013]
The stator core 31 is an annular core that includes a yoke
extending in the circumferential direction and a plurality of
teeth each extending from the yoke in the radial direction. As10
shown in FIG. 2, a length Ls is the length of the stator core 31
in the axial direction.
[0014]
The stator core 31, for example, is composed of a plurality
of thin sheets of iron with magnetic properties. In the first15
embodiment, the stator core 31 is composed of a plurality of
electrical steel sheets laminated in the axial direction.
[0015]
The coil 32 (i.e., winding) is wound around, for example, an
insulator attached to the stator core 31. In this case, the coil20
32 is insulated by the insulator. The coil 32 is made, for
example, of a material including copper or aluminum.
[0016]
The stator core 31 may be fixed by a cylindrical shell made,
for example, of a material including iron. In this case, the25
stator 3 is covered by the cylindrical shell with, for example,
shrinkage fit.
[0017]
The stator core 31 includes a first stator core end 311 and
a second stator core end 312. The first stator core end 311 is30
the end of the stator core 31 on the first side in the axial
direction. The second stator core end 312 is the end of the
stator core 31 on the second side in the axial direction.
[0018]
7
The first stator core end 311 is located away from the
rotor core 21 of the rotor 2 to the first side in the axial
direction.
[0019]
Rotor 25
The rotor 2 is rotatably disposed inside the stator 3. The
rotor 2 includes the rotor core 21, at least one permanent magnet
22, and the shaft 23. In the present embodiment, the rotor 2
includes a plurality of permanent magnets 22. The rotor core 21
is fixed to the shaft 23. The rotor core 21 is a cylindrical10
shape. The rotor core 21 is composed of a plurality of electrical
steel sheets, for example. As shown in FIG. 1, the rotor 2 may
include at least one end plate 24.
[0020]
The rotor core 21 includes a first rotor core end 211, a15
second rotor core end 212, and at least one magnet insertion hole
213. The first rotor core end 211 is the end of the rotor core 21
on the first side in the axial direction. The second rotor core
end 212 is the end of the rotor core 21 on the second side in the
axial direction.20
[0021]
The end plate 24 provided at the first rotor core end 211 is
also referred to as a “first end plate 241.” The end plate 24
provided at the second rotor core end 212 is also referred to as a
“second end plate 242.”25
[0022]
The shaft 23 is inserted into a shaft hole formed in the
center portion of the rotor 2 in the xy plane, for example.
[0023]
In the present embodiment, the rotor core 21 includes a30
plurality of magnet insertion holes 213. Each permanent magnet 22
is disposed in the magnet insertion hole 213. A length Lm is the
length of the permanent magnet 22 in the axial direction.
[0024]
8
As shown in FIG. 2, a distance La is the distance in the
axial direction from the first rotor core end 211 to the center of
the permanent magnet 22 in the axial direction. A distance Lb is
the distance in the axial direction between the first stator core
end 311 and the first rotor core end 211.5
[0025]
In the example shown in FIG. 2, the electric motor 1
satisfies Ls/2 > Lb + Lm/2 and Ls/2 < Lb + La.
[0026]
First Modification10
FIG. 3 is a cross-sectional view showing another example of
the rotor 2.
The rotor 2 shown in FIG. 3 can be applied to the electric
motor 1 shown in FIG. 1. In the first modification, the rotor 2
includes at least one non-magnetic material 25A. In the example15
shown in FIG. 3, the rotor 2 includes a plurality of non-magnetic
materials 25A. Each non-magnetic material 25A is disposed on the
first side in the axial direction with respect to the permanent
magnet 22 in the magnet insertion hole 213. Each non-magnetic
material 25A is made of, for example, resin, aluminum, or copper.20
[0027]
The length in the axial direction between the end of the
permanent magnet 22 on the first side and the first rotor core end
211 is greater than or equal to Lt1, where Lt1 is the length of
the non-magnetic material 25A in the axial direction. In this25
case, the electric motor 1 satisfies Ls/2 < Lb + La1, where Lm/2 +
Lt1 = La1.
[0028]
Second Modification
FIG. 4 is a cross-sectional view showing a still another30
example of the rotor 2.
The rotor 2 shown in FIG. 4 can be applied to the electric
motor 1 shown in FIG. 1.
In the second modification, the rotor 2 includes the end
9
plate 24 (specifically, first end plate 241) provided at the first
rotor core end 211 of the rotor core 21. The first end plate 241
includes at least one protruding portion 25B. In the example
shown in FIG. 4, the first end plate 241 includes a plurality of
protruding portions 25B. Each protruding portion 25B protrudes in5
the magnet insertion hole 213 toward the second side that is
opposite the first side in the axial direction.
[0029]
The length in the axial direction between the end of the
permanent magnet 22 on the first side and the first rotor core end10
211 is greater than or equal to Lt2, where Lt2 is the length of
the protruding portion 25B in the axial direction. In this case,
the electric motor 1 satisfies Ls/2 < Lb + La2, where Lm/2 + Lt2 =
La2.
[0030]15
Third Modification
FIG. 5 is a cross-sectional view showing a still another
example of the rotor 2.
FIG. 6 is a cross-sectional view of the rotor 2 in FIG. 5
taken along line A6-A6.20
FIG. 7 is a cross-sectional view of the rotor 2 in FIG. 5
taken along line A7-A7.
The rotor 2 shown in FIG. 5 can be applied to the electric
motor 1 shown in FIG. 1.
In third modification, at least a part of each magnet25
insertion hole 213 on the first side is covered by a cover 25C.
The cover 25C is a part of the rotor core 21. As shown in FIG. 7,
all of each magnet insertion hole 213 on the first side may be
covered by the cover 25C.
[0031]30
The electric motor 1 satisfies Ls/2 < Lb + La3, where Lt3 is
the length in the axial direction between a surface, which faces
the permanent magnet 22, of the cover 25C and the first rotor core
end 211 and Lm/2 + Lt3 = La3.
10
[0032]
Fourth Modification
FIG. 8 is a cross-sectional view showing another example of
the rotor core 21 shown in FIG. 5. The location of the cross
section shown in FIG. 8 corresponds to the location of the cross5
section of the rotor 2 taken along line A7-A7 in FIG. 5.
The rotor core 21 shown in FIG. 8 can be applied to the
rotor 2 shown in FIG. 5. That is, the rotor core 21 shown in FIG.
8 can be applied to the electric motor 1 shown in FIG. 1.
In the fourth modification, a part of each magnet insertion10
hole 213 on the first side is covered by a part of the rotor core
21. In other words, a part of each magnet insertion hole 213 on
the first side is covered by the cover 25C. The other part of
each magnet insertion hole 213 on the first side is not covered by
the rotor core 21.15
[0033]
Fifth Modification
FIG. 9 is a cross-sectional view showing still another
example of the rotor core 21 shown in FIG. 5. The location of the
cross section shown in FIG. 9 corresponds to the location of the20
cross section of the rotor 2 taken along line A7-A7 in FIG. 5.
The rotor core 21 shown in FIG. 9 can be applied to the
rotor 2 shown in FIG. 5. That is, the rotor core 21 shown in FIG.
9 can be applied to the electric motor 1 shown in FIG. 1.
In the fifth modification, a part of each magnet insertion25
hole 213 on the first side is covered by a part of the rotor core
21. In other words, a part of each magnet insertion hole 213 on
the first side is covered by the plurality of covers 25C. In the
example shown in Fig. 9, a part of each magnet insertion hole 213
on the first side is covered by the two covers 25C. The other30
part of each magnet insertion hole 213 on the first side is not
covered by the rotor core 21.
[0034]
Sixth Modification
11
FIG. 10A and FIG. 10B are cross-sectional views showing
still another example of the rotor core 21 shown in FIG. 5. The
location of the cross section shown in FIG. 10A and FIG. 10B
corresponds to the location of the cross section of the rotor 2
taken along line A7-A7 in FIG. 5. In FIG. 10B, a part of the5
rotor core 21 is shown.
The rotor core 21 shown in FIG. 10A or FIG. 10B can be
applied to the rotor 2 shown in FIG. 5. That is, the rotor core
21 shown in FIG. 10A or FIG. 10B can be applied to the electric
motor 1 shown in FIG. 1.10
In the sixth modification, a part of the magnet insertion
hole 213 on the first side and on an end side in the radial
direction is covered by a part of the rotor core 21, and the other
part of the magnet insertion hole 213 on the first side is not
covered by the rotor core 21.15
[0035]
A part of the rotor core 21 is, for example, a projection
21A projecting in the radial direction of the rotor core 21. In
the example shown in FIG. 10A and FIG. 10B, the rotor core 21
includes a plurality of projections 21A. Each projection 21A20
covers a part of the magnet insertion hole 213 on the first side.
In the example shown in FIG. 10A and FIG. 10B, each projection 21A
projects outward in the radial direction, but each projection 21A
may project inward in the radial direction. Also, in order to
hold the permanent magnet 22 by the plurality of projections 21A,25
it is preferable that the width in the radial direction of the
magnet insertion hole 213 between the projections 21A and the
inner wall, which faces the tips of the projections 21A, of the
magnet insertion hole 213 be smaller than the width in the radial
direction of the permanent magnet 22.30
[0036]
Each projection 21A may be in contact with the permanent
magnet 22. In this case, each permanent magnet is supported by at
least one projection 21A. In the example shown in FIG. 10A, each
12
projection 21A is in contact with the surface, which faces in the
radial direction, of the permanent magnet 22. The example shown
in FIG. 10A shows a state where the permanent magnet 22 is pressed
and supported by the projections 21A. For example, the permanent
magnet 22 is fixed by the protrusions 21A with press fitting.5
When each projection 21A fixes the permanent magnet 22 with press
fitting, the corner of the permanent magnet 22 may be chipped, so
it is preferable that each permanent magnet 22 be chamfered.
[0037]
In the example shown in FIG. 10B, each projection 21A is in10
contact with the end of the permanent magnet 22 on the first side.
In this case, each permanent magnet 22 is supported in the axial
direction by at least one projection 21A.
[0038]
Advantages of Present Embodiment15
Normally, when the first stator core end 311 is located away
from the rotor core 21 of the rotor 2 to the first side in the
axial direction, the magnetic attractive force between the stator
3 and the rotor 2 occurs in the positive direction of the z-axis
(downward in FIG. 1). The magnetic attractive force in the axial20
direction can preload the bearing that rotatably supports the
shaft 23. When a mechanical bearing is used in which the shaft 23
can move freely in the axial direction (z-axis direction) to some
extent, the rotor 2 can be held to one side by applying force in
one direction to the rotor 2, thereby suppressing the vibration of25
the rotor 2.
[0039]
FIG. 11 is a cross-sectional view schematically showing an
electric motor 1A as a comparative example.
In the electric motor 1A according to the comparative30
example, as in the present embodiment, the first stator core end
311 is located away from the rotor core 21 of the rotor 2 to the
first side in the axial direction. That is, the distance in the
axial direction between the first stator core end 311 and the
13
first rotor core end 211 is a distance Lb. In the comparative
example according to the electric motor 1A, the rotor 2A is
different from the rotor 2 of the electric motor 1 according to
the present embodiment. Specifically, in the axial direction, the
position of the end of each permanent magnet 22 on the first side5
is the same as the position of the first rotor core end 211 of the
rotor core 21. Therefore, the electric motor 1A according to the
comparative example satisfies Ls/2 > Lb + Lm/2. That is, the
center of each permanent magnet 22 in the axial direction is
shifted to the first side with respect to the center of the stator10
core 31 in the axial direction. In this case, the magnetic
attractive force in the axial direction between the stator 3 and
the rotor 2A becomes unstable, and thus the preload given to the
bearing that rotatably supports the shaft 23 becomes unstable. As
a result, the vibration of the rotor 2A and the noise in the15
electric motor 1A increase, and thus the equipment used to control
the electric motor 1A malfunctions.
[0040]
In the electric motor 1 according to the present embodiment,
the first stator core end 311 is located away from the rotor core20
21 of the rotor 2 to the first side in the axial direction. That
is, the distance in the axial direction between the first stator
core end 311 and the first rotor core end 211 is the distance Lb.
In this case, the electric motor 1 satisfies Ls/2 > Lb + Lm/2 and
Ls/2 < Lb + La. Therefore, the center of each permanent magnet 2225
in the axial direction is shifted to the second side with respect
to the center of the stator core 31 in the axial direction. With
this configuration, the magnetic attractive force in the axial
direction between the stator 3 and the rotor 2 is properly
adjusted. Specifically, the magnetic attractive force acting on30
the rotor core 21 due to the magnetic flux from the stator 3
occurs in the positive direction of the z-axis (downward in FIG.
1), and the magnetic attractive force between the stator 3 and
rotor 2 due to the magnetic flux from each permanent magnet 22
14
also occurs in the positive direction of the z-axis (downward in
FIG. 1), and thus the preload given to the bearing can be in the
same one direction. As a result, the vibration of the rotor 2 and
the noise in the electric motor 1 can be reduced, and it is
possible to prevent the equipment used to control the electric5
motor 1 from malfunctioning.
[0041]
As described in the first modification, the rotor 2 may
include at least one non-magnetic material 25A. In this case, the
non-magnetic material 25A is disposed on the first side in the10
axial direction with respect to the permanent magnet 22 in the
magnet insertion hole 213. The length of the non-magnetic
material 25A in the axial direction is indicated by Lt1. With
this configuration, the position of the permanent magnet 22 in the
axial direction is regulated by the non-magnetic material 25A.15
That is, the length in the axial direction between the end of the
permanent magnet 22 on the first side and the first rotor core end
211 is regulated by the nonmagnetic material 25A to be greater
than or equal to Lt1. In this case, the electric motor 1
satisfies Ls/2 < Lb + La1, where Lm/2 + Lt1 = La1. Therefore, in20
the first modification, the position of the permanent magnet 22 in
the axial direction can be easily regulated, and the preload given
to the bearing by the magnetic attractive force can be in one
direction. As a result, the vibration of the rotor 2 and the
noise in the electric motor 1 can be reduced, and it is possible25
to prevent the equipment used to control the electric motor 1 from
malfunctioning.
[0042]
As described in the second modification, the rotor 2 may
include the end plate 24 (specifically, first end plate 241)30
provided at the first rotor core end 211 of the rotor core 21.
The first end plate 241 includes at least one protruding portion
25B. The length of the protruding portion 25B in the axial
direction is indicated by Lt2. The protruding portion 25B
15
protruding portion protrudes in the magnet insertion hole 213
toward the second side that is opposite the first side in the
axial direction. With this configuration, the position of the
permanent magnet 22 in the axial direction is regulated by the
protruding portion 25B. That is, the length in the axial5
direction between the end of the permanent magnet 22 on the first
side and the first rotor core end 211 is regulated to be greater
than or equal to Lt2 by the protruding portion 25B. In this case,
the electric motor 1 satisfies Ls/2 < Lb + La2, where Lm/2 + Lt2 =
La2.10
[0043]
In the second modification, the position of the permanent
magnet 22 in the axial direction can be easily regulated in the
process of manufacturing the electric motor 1. Therefore, in the
second modification, the position of the permanent magnet 22 in15
the axial direction can be easily regulated, and the preload given
to the bearing by the magnetic attractive force can be in one
direction. As a result, the vibration of the rotor 2 and the
noise in the electric motor 1 can be reduced, and it is possible
to prevent the equipment used to control the electric motor 1 from20
malfunctioning.
[0044]
In addition, in the second modification, no additional parts
are needed to regulate the position of the permanent magnet.
Therefore, the cost of the electric motor 1 can be reduced25
compared to the first modification.
[0045]
As described in the first modification, the first side of
each magnet insertion hole 213 may be covered by a part of the
rotor core 21. The part of the rotor core 21 is the cover 25C.30
The length in the axial direction between the surface of the cover
25C facing the permanent magnet 22 and the first rotor core end
211 is indicated by Lt3. With this configuration, the position of
the permanent magnet 22 in the axial direction is regulated by the
16
cover 25C. That is, the length in the axial direction between the
end of the permanent magnet 22 on the first side and the first
rotor core end 211 is regulated by the cover 25C to be greater
than or equal to Lt3. In this case, the electric motor 1
satisfies Ls/2 < Lb + La3, where Lm/2 + Lt3 = La3.5
[0046]
In the third modification, the position of the permanent
magnet 22 in the axial direction can be easily regulated.
Therefore, in the third modification, the position of the
permanent magnet 22 in the axial direction can be easily regulated,10
and thus the preload given to the bearing by the magnetic
attractive force can be in one direction. As a result, the
vibration of the rotor 2 and the noise in the electric motor 1 can
be reduced, and it is possible to prevent the equipment used to
control the electric motor 1 from malfunctioning.15
[0047]
In addition, in the third modification, a part of the
electrical steel sheet that constitutes the rotor core 21 only has
to include the cover 25C. Therefore, the position of the
permanent magnet 22 in the axial direction can be controlled with20
the number of electrical steel sheets. In other words, the
position of the permanent magnet 22 in the axial direction can be
controlled with the position of the electrical steel sheet that
includes the cover 25C. For that reason, the accuracy of the
position of the permanent magnet 22 in the axial direction can be25
enhanced.
[0048]
As described in the fourth modification, a part of each
magnet insertion hole 213 on the first side may be covered by a
part of the rotor core 21. In other words, a part of each magnet30
insertion hole 213 on the first side is covered by the cover 25C.
The other part of the first side of each magnet insertion hole 213
is not covered by the rotor core 21. With this configuration, the
magnetic flux leaking from each permanent magnet 22 through the
17
rotor core 21 can be reduced, and the position of the permanent
magnet 22 in the axial direction can be regulated by the cover 25C.
As a result, the magnetic flux from each permanent magnet 22 can
be used effectively.
[0049]5
As described in the fifth modification, a part of each
magnet insertion hole 213 on the first side may be covered by a
plurality of covers 25C. With this configuration, the magnetic
flux leaking from each permanent magnet 22 through the rotor core
21 can be reduced, and the position of the permanent magnet 22 in10
the axial direction can be regulated by each cover 25C. As a
result, the magnetic flux from each permanent magnet 22 can be
used effectively.
[0050]
As described in the sixth modification, a part of the magnet15
insertion hole 213 on the first side and on the end side in the
radial direction may be covered by a part of the rotor core 21.
In this case, the other part of the magnet insertion hole 213 on
the first side is not covered by the rotor core 21. A part of the
rotor core 21 is, for example, the projection 21A projecting in20
the radial direction of the rotor core 21.
[0051]
The projection 21A may be in contact with the permanent
magnet 22. For example, each permanent magnet 22 is pressed and
supported in the radial direction by the projection 21A. As a25
result, the position of the permanent magnet 22 in the axial
direction can be regulated by the projection 21A. When the
projection 21A holds the permanent magnet 22, the permanent magnet
22 can be fixed at any position, and thus the magnetic attractive
force between the stator 3 and the rotor 2 due to the magnetic30
flux from each permanent magnet 22 can be determined as desired.
As a result, the magnetic attractive force between the stator 3
and the rotor 2 can be appropriate.
[0052]
18
According to the sixth modification, the magnetic flux
leaking from each permanent magnet 22 through the rotor core 21
can be reduced, and the position of the permanent magnet 22 in the
axial direction can be regulated by the projections 21A. As a
result, the magnetic flux from each permanent magnet 22 can be5
used effectively.
[0053]
In addition, according to the sixth modification, each
permanent magnet 22 can be fixed more firmly. Therefore, the
vibration of the permanent magnet 22 and the noise in the electric10
motor 1 during the rotation of the rotor 2 can be reduced.
[0054]
Second Embodiment
A compressor 6 according to a second embodiment will be
described.15
FIG. 12 is a cross-sectional view showing the structure of
the compressor 6 according to the second embodiment.
[0055]
The compressor 6 includes an electric motor 60 as an
electric element, a sealed container 61 as a housing, and a20
compression mechanism 62 as a compression element (also referred
to as a compression device). In the present embodiment, the
compressor 6 is a rotary compressor. However, the compressor 6 is
not limited to a rotary compressor.
[0056]25
The electric motor 60 is the electric motor 1 according to
the first embodiment.
[0057]
The sealed container 61 covers the electric motor 60 and the
compression mechanism 62. In the bottom portion of the sealed30
container 61, refrigerating machine oil for lubricating a
sliding portion of the compression mechanism 62 is stored.
[0058]
The compressor 6 further includes a glass terminal 63 fixed
19
to the sealed container 61, an accumulator 64, a suction pipe 65,
and a discharge pipe 66.
[0059]
The compression mechanism 62 includes a cylinder 62a, a
piston 62b, an upper frame 62c (first frame), a lower frame 62d5
(second frame), and mufflers 62e attached to the upper frame 62c
and the lower frame 62d respectively. The compression mechanism
62 further includes vanes that divide the inside of the cylinder
62a into an inlet side and a compression side. The compression
mechanism 62 is driven by the electric motor 60.10
[0060]
The electric motor 60 is fixed in the sealed container 61
with press fit or shrinkage fit. Instead of the press fit and the
shrinkage fit, the stator 3 may be attached directly to the sealed
container 61 with welding.15
[0061]
Power is supplied to the coils of the stator 3 of the
electric motor 60 via the glass terminal 63.
[0062]
The rotor 2 of the electric motor 60 (specifically, one end20
of the shaft of the rotor 2) is rotatably supported by bearings
provided in each of the upper frame 62c and the lower frame 62d.
[0063]
A shaft is inserted in the piston 62b. The shaft is
rotatably inserted in the upper frame 62c and the lower frame 62d.25
The upper frame 62c and the lower frame 62d close the end surfaces
of the cylinder 62a. The accumulator 64 supplies a refrigerant
(e.g., refrigerant gas) to the cylinder 62a via the suction pipe
65.
[0064]30
Next, an operation of the compressor 6 will be described.
A refrigerant supplied from the accumulator 64 is sucked into
the cylinder 62a from the suction pipe 65 fixed to the sealed
container 61. The electric motor 60 rotates by energizing an
20
inverter and consequently the piston 62b fitted to the shaft
rotates in the cylinder 62a. In this manner, the refrigerant
is compressed in the cylinder 62a.
[0065]
The refrigerant passes through the mufflers 62e and rises in5
the sealed container 61. Refrigerating machine oil is mixed in
the compressed refrigerant. While the mixture of the refrigerant
and the refrigerating machine oil is passing through a hole 36
formed in a rotor core, separation between the refrigerant and the
refrigerating machine oil is promoted, and accordingly, a flow of10
refrigerating machine oil into the discharge pipe 66 can be
prevented. In this manner, the compressed refrigerant is supplied
to a high-pressure side of a refrigerant cycle through the
discharge pipe 66.
[0066]15
As a refrigerant of the compressor 6, R410A, R407C, or R22,
for example, can be used. However, the refrigerant of the
compressor 6 is not limited to these materials. For example, as a
refrigerant of the compressor 6, a refrigerant having a small
global warming potential (GWP) or the like may be used.20
[0067]
Typical examples of the refrigerant having small GWPs
include refrigerants as follows:
[0068]
(1) Halogenated hydrocarbon including a carbon double25
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.
[0069]
(2) Hydrocarbon having a carbon double bond in a30
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.
[0070]
21
(3) A mixture including at least one of halogenated
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, and5
performance in a refrigeration cycle (especially in an
evaporator) tends to degrade. Thus, it is preferable to use a
mixture with R32 or R41, each of which is a high-pressure
refrigerant, for example.
[0071]10
The compressor 6 according to the second embodiment has
advantages described in the first embodiment.
[0072]
In addition, the use of the electric motor 1 according to
the first embodiment as the electric motor 60 can reduce the noise15
in the electric motor 60, and as a result, the noise in the
compressor 6 can be reduced.
[0073]
Third Embodiment
A refrigerating and air conditioning apparatus 7, including20
the compressor 6 according to the second embodiment, as an air
conditioner will be described.
FIG. 13 is a diagram schematically showing the structure of
the refrigerating and air conditioning apparatus 7 according to
the third embodiment.25
[0074]
The refrigerating and air conditioning apparatus 7 is
capable of cooling and heating operation, for example. The
refrigerant circuit diagram shown in FIG. 13 is an example of a
refrigerant circuit diagram of an air conditioner capable of30
cooling operation.
[0075]
The refrigerating and air conditioning apparatus 7 according
to the third embodiment includes an outdoor unit 71, an indoor
22
unit 72, and a refrigerant pipe 73 to connect the outdoor unit 71
and the indoor unit 72.
[0076]
The outdoor unit 71 includes the compressor 6, a condenser
74 as a heat exchanger, a throttling device 75, and an outdoor air5
blower 76 (first air blower). The condenser 74 condenses a
refrigerant compressed by the compressor 6. The throttling device
75 decompresses the refrigerant condensed by the condenser 74,
thereby adjusting a flow rate of the refrigerant. The throttling
device 75 is also referred to as a decompression device.10
[0077]
The indoor unit 72 includes an evaporator 77 as a heat
exchanger, and an indoor air blower 78 (second air blower). The
evaporator 77 evaporates the refrigerant decompressed by the
throttling device 75, thereby cooling indoor air.15
[0078]
The basic operation of the refrigerating and air
conditioning apparatus 7 in cooling operation is described
hereafter. In the cooling operation, a refrigerant is compressed
by the compressor 6, and the compressed refrigerant flows into the20
condenser 74. The condenser 74 condenses the refrigerant, and the
condensed refrigerant flows into the throttling device 75. The
throttling device 75 decompresses the refrigerant, and the
decompressed refrigerant flows into the evaporator 77. In the
evaporator 77, the refrigerant evaporates, and the refrigerant25
(specifically a refrigerant gas) flows into the compressor 6 of
the outdoor unit 71 again. When the air is sent to the condenser
74 by the outdoor air blower 76, heat moves between the
refrigerant and the air. Similarly, when the air is sent to the
evaporator 77 by the indoor air blower 78, heat moves between the30
refrigerant and the air.
[0079]
The configuration and operation of the refrigerating and air
conditioning apparatus 7 described above is an example and is not
23
limited to the examples described above.
[0080]
Since the refrigerating and air conditioning apparatus 7
according to the third embodiment includes the electric motor 1
described in the first embodiment, the refrigerating and air5
conditioning apparatus 7 has the advantages described in the first
embodiment.
[0081]
Since the refrigerating and air conditioning apparatus 7
according to the third embodiment includes the compressor 610
according to the second embodiment, the refrigerating and air
conditioning apparatus 7 according to the third embodiment has the
advantages described in the second embodiment. In addition, since
the refrigerating and air conditioning apparatus 7 according to
the third embodiment includes the compressor 6 according to the15
second embodiment, the noise in the refrigerating and air
conditioning apparatus 7 can be reduced.
[0082]
The electric motor 1 described in the first embodiment
can be mounted on equipment including a driving source, such as20
a ventilator, household electrical appliance, or a machine tool,
other than the refrigerating and air conditioning apparatus 7.
[0083]
The features in each embodiment and in each modification
described above may be combined with each other.25
DESCRIPTION OF REFERENCE CHARACTERS
[0084]
1, 60 electric motor; 2 rotor; 3 stator; 6 compressor; 7
refrigerating and air conditioning apparatus; 21 rotor core; 2230
permanent magnet; 24 end plate; 25A non-magnetic material; 25B
protruding portion; 25C cover; 31 stator core; 61 sealed
container; 62 compression mechanism.
24
We Claim:
Claim 1. An electric motor comprising:
a stator including a stator core and a coil provided on
the stator core; and5
a rotor disposed inside the stator and including a rotor
core and a permanent magnet, the rotor core including a magnet
insertion hole, the permanent magnet being disposed in the
magnet insertion hole,
wherein an end of the stator core on a first side in an10
axial direction is located away from the rotor core to the
first side,
the electric motor satisfies Ls/2 > Lb + Lm/2 and Ls/2
< Lb + La
where Ls is a length of the stator core in the axial15
direction, Lb is a distance in the axial direction between
the end of the stator core on the first side and an end of the
rotor core on the first side, Lm is a length of the permanent
magnet in the axial direction, and La is a distance in the
axial direction from the end of the rotor core on the first20
side to a center of the permanent magnet in the axial direction.
Claim 2. The electric motor according to claim 1, wherein
the rotor includes a non-magnetic material,
the non-magnetic material is disposed on the first side in25
the axial direction with respect to the permanent magnet in the
magnet insertion hole,
a length in the axial direction between an end of the
permanent magnet on the first side and the end of the rotor core
on the first side is greater than or equal to Lt1, where Lt1 is a30
length of the non-magnetic material in the axial direction, and
the electric motor satisfies Ls/2 < Lb + La1, where Lm/2
+ Lt1 = La1.
25
Claim 3. The electric motor according to claim 1, wherein
the rotor includes an end plate provided at the end of the
rotor core on the first side,
the end plate includes a protruding portion protruding in
the magnet insertion hole toward the second side that is opposite5
the first side in the axial direction,
a length in the axial direction between an end of the
permanent magnet on the first side and the end of the rotor core
on the first side is greater than or equal to Lt2, where Lt2 is a
length of the protruding portion in the axial direction, and10
the electric motor satisfies Ls/2 < Lb + La2, where Lm/2
+ Lt2 = La2.
Claim 4. The electric motor according to claim 1, wherein
the first side of the magnet insertion hole is covered by a15
part of the rotor core, and
the electric motor satisfies Ls/2 < Lb + La3, where Lt3
is a length in the axial direction between a surface, which faces
the permanent magnet, of the part of the rotor core and the end of
the rotor core on the first side and Lm/2 + Lt3 = La3.20
Claim 5. The electric motor according to claim 4, wherein
a part of the magnet insertion hole on the first side is
covered by the part of the rotor core, and
the other part of the magnet insertion hole on the first25
side is not covered by the rotor core.
Claim 6. The electric motor according to claim 4, wherein
a part of the magnet insertion hole on the first side and on
an end side in a radial direction is covered by the part of the30
rotor core, and
the other part of the magnet insertion hole on the first
side is not covered by the rotor core.
26
Claim 7. The electric motor according to claim 6, wherein
the part of the rotor core is a projection projecting in the
radial direction of the rotor core,
the projection covers the part of the magnet insertion hole
on the first side, and5
the permanent magnet is pressed and supported by the
projection.
Claim 8. A compressor comprising:
a sealed container;10
a compression device disposed in the sealed container; and
the electric motor according to any one of claims 1 to 7, to
drive the compression device.
Claim 9. An air conditioner comprising:15
the compressor according to claim 8; and
a heat exchanger.