FIELD OF THE INVENSION.
[0001] The present invention relates to a compressor.
Background
[0002] A compressor in which a motor is mounted and an
10 eccentric hole is formed in a rotor core of a rotor of the
motor to reduce eccentricity of a rotating body that is
arranged in a compression mechanism to thereby prevent a
defect, such as vibration, due to the eccentricity of the
rotating body is known (Patent Literatures 1 to 3). The
15 compressor as described above does not include a balance
weight that is separated from the rotor core, so that it is
possible to reduce a manufacturing cost and prevent
deterioration of compression efficiency due to stirring of
the refrigerant.
20 Citation List
Patent Literature
[0003] Patent Literature 1: Japanese Laid-open Patent
Publication No. H04-112652
Patent Literature 2: Japanese Laid-open Patent
25 Publication No. 2003-219616
Patent Literature 3: Japanese Laid-open Patent
Publication No. 2018-17201
Summary
Technical Problem
30 [0004] However, when what is called an Interior
Permanent Magnet (IPM) type rotator, in which a permanent
magnet is embedded in a rotor core, is used, and if a size
of an eccentric hole that is formed in the rotor core is
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increased in order to reduce eccentricity of a rotating
body (a structural body that integrally rotates inside a
compressor: for example, a shaft, an annular piston of a
compression unit, and a rotor core of a rotator), a flow of
5 a magnetic flux that passes through the rotor core may be
disturbed, and efficiency of the motor may be reduced.
[0005] The disclosed technology has been conceived in
view of the foregoing situations, and an object of the
disclosed technology is to provide a compressor that
10 reduces eccentricity of a rotating body and prevents
reduction in efficiency of a motor.
Solution to Problem
[0006] According to an aspect of an embodiment, a
compressor includes a shaft that is arranged along a
15 rotation axis, a compression unit that drives along with
rotation of the shaft, a rotor core that is fixed to the
shaft, a plurality of permanent magnets that are embedded
inside the rotor core, and a stator that causes the rotor
core to rotate about the rotation axis, wherein a plurality
20 of eccentric holes for adjusting balance when the shaft
rotates are formed in the rotor core, and the plurality of
eccentric holes are formed on an inner side of a polygonal
region for which midpoints of sides at a side of the
rotation axis among sides formed by side surfaces of the
25 plurality of permanent magnets in a cross section
perpendicular to the rotation axis serve as vertices.
Advantageous Effects of Invention
[0007] The disclosed compressor is able to reduce
30 eccentricity of a rotating body that is arranged inside the
compressor and prevent reduction in efficiency of a motor.
Brief Description of Drawings
[0008] FIG. 1 is a vertical cross-sectional view of a
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compressor of a first embodiment.
FIG. 2 is a top view of a rotor core of the compressor
of the first embodiment.
FIG. 3 is a cross-sectional view of the rotor core of
5 the compressor of the first embodiment.
FIG. 4 is a diagram illustrating a flow of a magnetic
flux that passes through the rotor core.
FIG. 5 is a cross-sectional view of a rotor core of a
compressor of a second embodiment.
10 FIG. 6 is a top view of the rotor core of the
compressor of the second embodiment.
FIG. 7 is a top view of a rotor core of a compressor
of a third embodiment.
FIG. 8 is a top view of a rotor core of a compressor
15 of a fourth embodiment.
FIG. 9 is a top view of a rotor core of a compressor
of a fifth embodiment.
Description of Embodiments
[0009] A compressor according to embodiments disclosed
20 in the present application will be described below with
reference to the drawings. The technology of the present
disclosure is not limited by the description below. In
addition, in the following description, the same components
are denoted by the same reference symbols, and repeated
25 explanation will be omitted.
[0010] First Embodiment
A compressor 1 of a first embodiment includes, as
illustrated in FIG. 1, a container 2, a shaft 3, a
compression unit 5, and a motor unit 6. FIG. 1 is a
30 vertical cross-sectional view of the compressor 1 of the
first embodiment. A sealed internal space 21 is formed in
the container 2. The internal space 21 is formed in an
approximately cylindrical shape. The container 2 is formed
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such that a central axis of a cylinder formed by the
internal space 21 is parallel to a vertical direction when
the container 2 is vertically installed on a horizontal
plane. The container 2 includes suction pipes 22 and a
5 discharge pipe 23. Channels 221 are formed inside the
suction pipes 22 and the suction pipes 22 are bonded to the
container 2 such that the channels 221 are connected to a
lower part of the internal space 21. A channel 231 is
formed inside the discharge pipe 23 and the discharge pipe
10 23 is bonded to the container 2 such that the channel 231
is connected to an upper part of the internal space 21.
[0011] The shaft 3 is formed in a rod shape, and
includes a first eccentric portion 32 and a second
eccentric portion 33. The shaft 3 is arranged in the
15 internal space 21 such that the shaft 3 extends along a
rotation axis 31 that overlaps with the central axis of the
cylinder formed by the internal space 21 and such that the
first eccentric portion 32 and the second eccentric portion
33 are arranged in a lower portion of the internal space
20 21, and is supported by the container 2 so as to be
rotatable about the rotation axis 31.
[0012] The compression unit 5 is arranged in a lower
portion of the internal space 21 so as to surround the
first eccentric portion 32 and the second eccentric portion
25 33 of the shaft 3. The compression unit 5 is what is
called a rotary type compression mechanism and includes a
first annular piston 51 and a second annular piston 52.
The first annular piston 51 is fitted to the first
eccentric portion 32 and revolves with rotation of the
30 shaft 3. The second annular piston 52 is fitted to the
second eccentric portion 33 and revolves with rotation of
the shaft 3. With the revolution of the first annular
piston 51 and the second annular piston 52, the compression
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unit 5 compresses a refrigerant that is supplied from the
suction pipes 22, and supplies the compressed refrigerant
to a space above the compression unit 5 in the internal
space 21. In other words, the compression unit 5 drives
5 along with the rotation of the shaft 3.
[0013] The motor unit 6 is arranged in a space above the
compression unit 5 in the internal space 21. The motor
unit 6 includes a rotor 61 and a stator 62. The rotor 61
includes a rotor core 611, an upper end plate 612, a lower
10 end plate 613, and a plurality of rivets 614. The rotor
core 611 is formed in an approximately cylindrical shape.
The rotor core 611 is arranged such that a central axis of
the cylinder overlaps with the rotation axis 31 and is
fixed to the shaft 3. In other words, the rotor core 611
15 is supported by the container 2 so as to be rotatable about
the rotation axis 31 via the shaft 3. The upper end plate
612 is formed in an approximately disc shape, and arranged
so as to cover an upper end surface 615 of the rotor core
611. The lower end plate 613 is formed in an approximately
20 disc shape, and arranged so as to cover a lower end surface
616 of the rotor core 611. The plurality of rivets 614 are
made of magnetic materials and formed in rod shapes. The
plurality of rivets 614 penetrate through the rotor core
611 in a top-bottom direction that is parallel to the
25 rotation axis 31 and are caulked to fix the upper end plate
612 and the lower end plate 613 to the rotor core 611.
[0014] The stator 62 is formed in an approximately
cylindrical shape. The stator 62 is arranged so as to
surround the cylindrical rotor 61 and fixed to the
30 container 2. The rotor 61 and the stator 62 are coaxially
arranged such that respective central axes coincide with
each other. The stator 62 includes a stator core 63, an
upper insulator 671, a lower insulator 672, and a plurality
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of windings 68.
[0015] FIG. 2 is a top view of the rotor core 611 of the
compressor 1 of the first embodiment. In the rotor core
611, directions of magnetic fluxes that pass through
5 centers in cross sections of a plurality of permanent
magnets 655 (655-1 to 655-6) perpendicular to the rotation
axis 31 are denoted by d axes d1 to d6. Further,
directions magnetically perpendicular to the plurality of d
axes d1 to d6 are denoted by a plurality of q axes q1 to
10 q6. The plurality of d axes d1 to d6 are perpendicular to
the rotation axis 31 and radially extend from the rotation
axis 31 at regular intervals in a circumferential direction
of the rotor core 611 so as to pass through the centers in
the cross sections of the permanent magnets 655-1 to 655-6
15 perpendicular to the rotation axis 31. The plurality of q
axes q1 to q6 pass through positions between the adjacent
two permanent magnets (between the adjacent two d axes
among the plurality of d axes d1 to d6). Specifically, the
plurality of d axes d1 to d6 and the plurality of q axes q1
20 to q6 are perpendicular to the rotation axis 31, are
alternately arranged at regular intervals in the
circumferential direction of the rotor core 611, and
radially extend from the rotation axis 31.
[0016] The rotor core 611 includes a shaft hole 641, a
25 plurality of magnet holes 642, a plurality of rivet holes
643, a plurality of upper-end-side eccentric holes 644, and
a plurality of lower-end-side eccentric holes 645. The
shaft hole 641 is formed along the rotation axis 31 so as
to overlap with the rotation axis 31 and so as to penetrate
30 through the upper end surface 615 and the lower end surface
616 of the rotor core 611. The shaft 3 penetrates through
the shaft hole 641 and is shrunk fit, so that the rotor
core 611 is fixed to the shaft 3.
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[0017] The plurality of magnet holes 642 are formed at
positions corresponding to the plurality of d axes d1 to d6
in the circumferential direction of a circle formed by the
rotor core 611 (such that the d axes d1 to d6 pass through
5 centers of the corresponding magnet holes 642 in a cross
section perpendicular to the rotation axis 31). Each of
the magnet holes 642 is formed so as to penetrate through
the upper end surface 615 and the lower end surface 616 of
the rotor core 611. For example, as for a first magnet
10 hole 642-1 that is one of the magnet holes 642, an innerperipheral-
side inner wall surface 647 that is located on
an inner peripheral side close to the rotation axis 31
among inner wall surfaces of the first magnet hole 642-1 is
formed in the first magnet hole 642-1. The inner15
peripheral-side inner wall surface 647 is formed in an
approximately flat shape. The first magnet hole 642-1 is
formed such that a side 648 along the inner-peripheral-side
inner wall surface 647 is perpendicular to the first d axis
d1 in the cross section perpendicular to the rotation axis
20 31. The first magnet hole 642-1 is formed such that the
first d axis d1 passes through a midpoint 649 (a center
point 657) that is a midpoint of the side 648 (the innerperipheral-
side inner wall surface 647). In other words,
the midpoint 649 (the center point 657) overlaps with a
25 foot of a perpendicular line that is extended from the
rotation axis 31 to the side 648 in the cross section
perpendicular to the rotation axis 31.
[0018] The first magnet hole 642-1 is arranged between a
second magnet hole 642-2 and a sixth magnet hole 642-6
30 among the plurality of magnet holes 642 in the
circumferential direction of the rotor core 611, that is,
the first magnet hole 642-1 is adjacent to the second
magnet hole 642-2 and adjacent to the sixth magnet hole
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642-6. Here, the q axes q1 to q6 are half lines for which
the rotation axis 31 of the rotor 61 serve as start points
and which pass through positions between the two adjacent
permanent magnets 655 in the circumferential direction of
5 the rotor core 611. The q axes q1 to q6 are aligned at
regular intervals in the circumferential direction of the
rotor core 611. For example, the first magnet hole 642-1
is formed between the first q axis q1 and the sixth q axis
q6 that are adjacent to each other in the circumferential
10 direction of the rotor core 611 among the plurality of q
axes q1 to q6. The magnet holes other than the first
magnet hole 642-1 among the plurality of magnet holes 642
are formed in the same manner as the first magnet hole 642-
1.
15 [0019] Each of the rivet holes 643 is formed parallel to
the rotation axis 31 and so as to penetrate through the
upper end surface 615 and the lower end surface 616 of the
rotor core 611. Each of the rivet holes 643 is formed in
the vicinity of a position between the two adjacent magnet
20 holes among the plurality of magnet holes 642, and formed
on an inner peripheral side closer to the rotation axis 31
than the plurality of magnet holes 642. In other words,
each of the rivet holes 643 is formed so as to intersect
with the corresponding q axis among the plurality of q axes
25 q1 to q6. Furthermore, a distance from each of the rivet
holes 643 to the rotation axis 31 is shorter than a
distance from each of the magnet holes 642 to the rotation
axis 31.
[0020] A first upper-end-side eccentric hole 644-1 that
30 is one of the upper-end-side eccentric holes 644 is formed
so as to have a larger cross-sectional area than a crosssectional
area of a single (each) rivet hole among the
plurality of rivet holes 643 and so as to be located on an
Docket No. PFGA-22316-PCT: FINAL
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inner peripheral side of the first magnet hole 642-1.
Further, the first upper-end-side eccentric hole 644-1 is
formed so as to be located on an inner side of a polygonal
region 653 for which the midpoints 649 of the above-
5 described sides 648 of all of the magnet holes 642 serve as
vertices. Each of sides (653-1 to 653-6) that form the
polygonal region 653 is a line segment that connects the
center points 657 (the midpoints 649) of the two adjacent
magnet holes among the plurality of magnet holes 642. For
10 example, the first side 653-1 among the sides 653-1 to 653-
6 that form the polygonal region 653 is a line segment that
connects the center point 657 (the midpoint 649) of the
first magnet hole 642-1 and the center point 657 (the
midpoint 649) of the second magnet hole 642-2. The sixth
15 side 653-6 among the sides 653-1 to 653-6 is a line segment
that connects the center point 657 (the midpoint 649) of
the first magnet hole 642-1 and the center point 657 (the
midpoint 649) of the sixth magnet hole 642-6. With the six
line segments (the sides 653-1 to 653-6) that are connected
20 as described above, the polygonal (a regular hexagon in the
embodiment) region 653 is formed on an inner diameter side
relative to a region that is enclosed by the plurality of
permanent magnets 655 of the rotor core 611 in the cross
section perpendicular to the rotation axis 31.
25 [0021] In this case, the first upper-end-side eccentric
hole 644-1 is arranged on an inner peripheral side closer
to the rotation axis 31 than the first side 653-1 and is
arranged on an inner peripheral side closer to the rotation
axis 31 than the sixth side 653-6. Further, the first
30 upper-end-side eccentric hole 644-1 is formed so as not to
be located on an outer peripheral side farther away from
the rotation axis 31 than the first side 653-1, and so as
not to be located on an outer peripheral side farther away
Docket No. PFGA-22316-PCT: FINAL
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from the rotation axis 31 than the sixth side 653-6. In
other words, the first upper-end-side eccentric hole 644-1
is arranged on the inner side of the polygonal (a regular
hexagon in the embodiment) region 653 for which the
5 midpoints 649 (the center points 657) of the sides 648 of
the plurality of permanent magnets 655 serve as vertices.
Furthermore, the first upper-end-side eccentric hole 644-1
is formed so as to intersect with the first d axis d1 and
so as to be plane symmetric with respect to a first d-axis
10 plane 652-1 that is a plane passing through the first d
axis d1 and the rotation axis 31. In other words, the
first upper-end-side eccentric hole 644-1 is formed so as
to be line symmetric with respect to the first d axis d1 in
the cross section perpendicular to the central axis. A
15 second upper-end-side eccentric hole 644-2 among the
plurality of upper-end-side eccentric holes 644 is formed
on the inner peripheral side of the region 653 so as not to
be located on the outer peripheral side relative to the
polygonal region 653, similarly to the first upper-end-side
20 eccentric hole 644-1.
[0022] A first lower-end-side eccentric hole 645-1 among
the plurality of lower-end-side eccentric holes 645 is
formed on an inner peripheral side of a fourth magnet hole
642-4 so as not to be located on the outer peripheral side
25 relative to the polygonal region 653, similarly to each of
the upper-end-side eccentric holes 644. Further, the first
lower-end-side eccentric hole 645-1 is formed such that the
first lower-end-side eccentric hole 645-1 and the first
upper-end-side eccentric hole 644-1 are point symmetric
30 with respect to a center point of the rotor core 611 in the
top-bottom direction on the rotation axis 31. A second
lower-end-side eccentric hole 645-2 among the plurality of
lower-end-side eccentric holes 645 is formed on an inner
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peripheral side of a third magnet hole 642-3 so as not to
be located on the outer peripheral side relative to the
polygonal region 653, similarly to the first lower-end-side
eccentric hole 645-1. Furthermore, the second lower-end-
5 side eccentric hole 645-2 is formed such that the second
lower-end-side eccentric hole 645-2 and the second upperend-
side eccentric hole 644-2 are point symmetric with
respect to the center point of the rotor core 611 on the
rotation axis 31.
10 [0023] FIG. 3 is a cross-sectional view of the rotor
core 611 of the compressor 1 of the first embodiment. Each
of the upper-end-side eccentric holes 644 is formed
parallel to the rotation axis 31 and formed in a hole that
is recessed from the upper end surface 615 so as not to
15 penetrate through the lower end surface 616. Each of the
lower-end-side eccentric holes 645 is formed parallel to
the rotation axis 31 and formed in a hole that is recessed
from the lower end surface 616 so as not to penetrate
through the upper end surface 615.
20 [0024] FIG. 4 is a diagram illustrating a flow of a
magnetic flux that passes through the rotor core 611. The
rotor 61 further includes the plurality of permanent
magnets 655. Each of the permanent magnets 655 is formed
in a plate shape (rectangular solid shape) such that an N25
pole appears on one surface of the plate and an S-pole
appears on the other surface of the plate. In the
plurality of permanent magnets 655, magnetic fluxes
generated by the respective permanent magnets 655 flow
along the plurality of d axes d1 to d6.
30 [0025] An inner-peripheral-side surface 658 is formed at
a side close to the rotation axis 31 in the first permanent
magnet 655-1 that is arranged inside the first magnet hole
642-1 among the plurality of permanent magnets 655. The
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first magnet hole 642-1 is arranged such that the innerperipheral-
side surface 658 extends along the side 648 and
the center point 657 of the inner-peripheral-side surface
658 overlaps with the midpoint 649 of the side 653-1. In
5 this case, in the first permanent magnet 655-1, a direction
of a magnetic flux that is generated by the first permanent
magnet 655-1 goes along the first d axis d1. The permanent
magnets other than the first permanent magnet 655-1 among
the plurality of permanent magnets 655 are arranged in the
10 same manner as the first permanent magnet 655-1.
[0026] Further, the plurality of permanent magnets 655
are arranged such that orientations of magnetic poles of
the two permanent magnets that are arranged inside the two
adjacent magnet holes are different from each other.
15 Specifically, the plurality of permanent magnets 655 are
arranged such that the magnetic pole on an inner peripheral
side of the sixth permanent magnet 655-6 that is adjacent
to the first permanent magnet 655-1 is different from the
magnetic pole on an inner peripheral side of the first
20 permanent magnet 655-1. The upper end plate 612 covering
the upper end surface 615 and the lower end plate 613
covering the lower end surface 616 are fixed to the rotor
core 611, so that the plurality of permanent magnets 655
are fixed to the rotor core 611 such that the plurality of
25 permanent magnets 655 do not come off from the plurality of
magnet holes 642.
[0027] As for the flow of the magnetic flux that passes
through a region corresponding to the sixth q axis q6 in
the rotor core 611, in other words, the flow of the
30 magnetic flux that passes through the region 656 in the
vicinity of the sixth q axis q6 as illustrated in FIG. 4, a
magnetic flux line that passes through the first permanent
magnet 655-1 extends so as to intersect with the side 648
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corresponding to the first permanent magnet 655-1, and a
magnetic flux line that passes through the sixth permanent
magnet 655-6 adjacent to the first permanent magnet 655-1
extends so as to intersect with the side 648 corresponding
5 to the sixth permanent magnet 655-6. Furthermore, a
magnetic flux line passes through the inside of the rotor
core 611 in a circular arc shape so as to moderately
connect the magnetic flux line that passes through the
first permanent magnet 655-1 and the magnetic flux line
10 that passes through the sixth permanent magnet 655-6. In
this case, the magnetic flux line passes a path that avoids
the upper-end-side eccentric holes 644 that are openings,
but all of the upper-end-side eccentric holes 644 are
formed on the inner side (inner peripheral side) of the
15 polygonal region 653, so that the path of the circular arc
magnetic flux line that passes through the inside of the
rotor core 611 as described above is not largely distorted.
With this configuration, a magnetic flux path in the
vicinity of the upper-end-side eccentric holes 644 in the
20 rotor core 611 can be made similar to a flow of a magnetic
flux that passes through a region in the vicinity of the q
axis that is not located close to the upper-end-side
eccentric holes 644 among the plurality of q axes q1 to q6,
so that it is possible to prevent reduction in efficiency
25 of a motor due to distortion of the flow of the magnetic
flux. Furthermore, similarly to the plurality of upperend-
side eccentric holes 644, all of the lower-end-side
eccentric holes 645 are formed on the inner side (inner
peripheral side) of the polygonal region 653, so that a
30 path of the circular arc magnetic flux line that passes
through the inside of the rotor core 611 is not largely
distorted. Therefore, the lower-end-side eccentric holes
645 are able to prevent reduction in the efficiency of the
Docket No. PFGA-22316-PCT: FINAL
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motor due to distortion of the flow of the magnetic flux.
Consequently, the rotor core 611 is rotated by a rotary
magnetic field that is generated by the stator 62, and is
able to realize the same magnetic flux path as in a case in
5 which the upper-end-side eccentric holes or the lower-endside
eccentric holes are not formed, so that it is possible
to prevent reduction in the efficiency of the motor unit 6.
Furthermore, the upper-end-side eccentric holes 644 that
are formed so as to be located close to one end side of the
10 rotor core 611 and the lower-end-side eccentric holes 645
that are formed so as to be located close to the other end
side of the rotor core 611 are arranged in a point
symmetric manner (separated by 180 degrees) in the
circumferential direction in the cross section
15 perpendicular to the rotation axis 31, so that the rotor 61
is made eccentric with respect to the rotation axis 31, and
the eccentric holes function as a balancer of the rotating
body. As a result, the compressor 1 is able to reduce
eccentricity of the rotating body and prevent reduction in
20 the efficiency of the motor unit 6, so that it is possible
to highly efficiently compress the refrigerant.
Furthermore, the compressor 1 need not include a balance
weight for reducing vibration separately from the rotor
core 611, so that it is possible to reduce a manufacturing
25 cost.
[0028] Operation of compressor 1
The compressor 1 is arranged in a refrigeration cycle
device (not illustrated) and is used to compress a
refrigerant and circulate the refrigerant in the
30 refrigeration cycle device. The motor unit 6 generates a
rotating magnetic field in an internal space of the stator
62 by appropriately applying three phase voltage to the
plurality of windings 68. The rotor 61 rotates with the
Docket No. PFGA-22316-PCT: FINAL
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aid of the rotating magnetic field that is generated by the
stator 62. The shaft 3 transmits the rotation of the rotor
61 to the compression unit 5.
[0029] The shaft 3 relatively largely vibrates when
5 rotating about the rotation axis 31 without the rotor 61
because of arrangement of the first eccentric portion 32
and the second eccentric portion 33 that are fitted to the
first annular piston 51 and the second annular piston 52.
In the compressor 1, the plurality of upper-end-side
10 eccentric holes 644 are formed so as to be located close to
one end side of the rotor core 611 that is fixed to the
shaft 3 and the plurality of lower-end-side eccentric holes
645 are formed so as to be located close to the other end
side of the rotor core 611. Further, the plurality of
15 upper-end-side eccentric holes 644 and the plurality of
lower-end-side eccentric holes 645 are arranged so as to be
point symmetric with each other (separated from each other
by 180 degrees) in the circumferential direction in the
cross section perpendicular to the rotation axis 31, so
20 that a center of gravity of an upper half of the rotor core
611 is located close to the lower-end-side eccentric holes
645, and a center of gravity of a lower half of the rotor
core 611 is located close to the upper-end-side eccentric
holes 644. Furthermore, due to inclination of the center
25 of gravity of the rotor core 611 as described above, it is
possible to keep balance of the rotating body formed of the
shaft 3, the first annular piston 51, the second annular
piston 52, and the rotor 61. The compressor 1 is able to
reduce the vibration by keeping balance of the rotating
30 body.
[0030] The first annular piston 51 and the second
annular piston 52 revolve with the rotation of the rotor
61. Due to the revolution of the first annular piston 51
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and the second annular piston 52, the compression unit 5
sucks a low pressure gas refrigerant via the suction pipes
22, and compresses the sucked low pressure gas refrigerant
to generate a high pressure gas refrigerant. The generated
5 high pressure gas refrigerant is supplied to a space
between the compression unit 5 and the motor unit 6 in the
internal space 21. The high pressure gas refrigerant that
is supplied to the space between the compression unit 5 and
the motor unit 6 in the internal space 21 passes through a
10 gap that is formed in the motor unit 6, and is then
supplied to a space above the motor unit 6 in the internal
space 21. The high pressure gas refrigerant that is
supplied to the space above the motor unit 6 in the
internal space 21 is discharged to a device in the
15 subsequent stage of the compressor 1 in the refrigeration
cycle device via the discharge pipe 23.
[0031] In a compressor of a comparative example, in
which a balance weight for keeping balance of a rotating
body (a rotator or a shaft) is arranged in the rotor 61,
20 the balance weight stirs a refrigerant in the internal
space 21, so that flow resistance occurs when the
refrigerant passes inside the compressor and compression
efficiency may be reduced. The compressor 1 of the first
embodiment, because the balance weight is not arranged in
25 the rotor 61, is able to reduce stirring of the refrigerant
in the internal space 21, and is able to prevent reduction
in compression efficiency for the refrigerant as compared
to the compressor of the comparative example.
[0032] Effect of compressor 1 of first embodiment
30 The compressor 1 of the first embodiment includes the
compression unit 5, the rotor core 611, the plurality of
permanent magnets 655, and the stator 62. The compression
unit 5 compresses a refrigerant along with rotation of the
Docket No. PFGA-22316-PCT: FINAL
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shaft 3 about the rotation axis 31. The rotor core 611 is
fixed to the shaft 3. The plurality of permanent magnets
655 are embedded inside the rotor core 611. The stator 62
causes the rotor core 611 to rotate about the rotation axis
5 31. The plurality of upper-end-side eccentric holes 644
and the plurality of lower-end-side eccentric holes 645 for
adjusting balance at the time of rotation of the shaft 3
are formed in the rotor core 611. The plurality of upperend-
side eccentric holes 644 and the plurality of lower10
end-side eccentric holes 645 are formed on an inner side of
a second region (the polygonal region 653) that is smaller
than a first region that is enclosed by the plurality of
permanent magnets 655 in the rotor core 611. The center
points 657 (the midpoints 649) that serve as vertices of a
15 polygon that forms the second region (the polygonal region
653) are the center points 657 (the midpoints 649) of the
inner-peripheral-side surfaces 658 (the sides 648) of the
permanent magnets 655-1 to 655-6. Furthermore, each of the
sides of the polygon that forms the region 653 is a line
20 segment that connects the center point 657 (the midpoint
649) of the inner-peripheral-side surface 658 (the side
648) of one (for example, the permanent magnet 655-1) of
the two adjacent permanent magnets and the center point 657
(the midpoint 649) of the inner-peripheral-side surface 658
25 (the side 648) of the other one (for example, the permanent
magnet 655-6) of the two adjacent permanent magnets.
[0033] The compressor 1 need not include a balance
weight for reducing eccentricity of the rotating body
separately from the rotor core 611, so that it is possible
30 to reduce a manufacturing cost, and prevent deterioration
of compression efficiency due to stirring of the
refrigerant. Further, the compressor 1 is able to prevent
the plurality of upper-end-side eccentric holes 644 and the
Docket No. PFGA-22316-PCT: FINAL
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plurality of lower-end-side eccentric holes 645 from
disturbing the flow of the magnetic flux that passes
through the rotor core 611. The compressor 1 prevents
disturbance of the flow of the magnetic flux, so that it is
5 possible to highly efficiently rotate the shaft 3 and
highly efficiently compress the refrigerant.
[0034] Furthermore, the compressor 1 of the first
embodiment further includes the upper end plate 612 and the
lower end plate 613 that cover the upper end surface 615 of
10 the rotor core 611 to fix the plurality of permanent
magnets 655 to the rotor core 611, and the plurality of
rivets 614 that fix the upper end plate 612 and the lower
end plate 613 to the rotor core 611. The plurality of
rivet holes 643, through which the plurality of rivets 614
15 penetrate, are formed in the rotor core 611. In a plane
perpendicular to the rotation axis 31, a cross-sectional
area of one eccentric hole among the plurality of upperend-
side eccentric holes 644 and the plurality of lowerend-
side eccentric holes 645 is larger than a cross20
sectional area of each of the rivet holes 643. In the
compressor 1, the rivet holes 643 with small crosssectional
areas are arranged above the q axes, so that it
is possible to prevent the plurality of rivet holes 643
from disturbing the flow of the magnetic flux that passes
25 through the rotor core 611.
[0035] Meanwhile, the cross-sectional area of each of
the rivet holes 643 in the compressor 1 of the first
embodiment as described above may be larger than a crosssectional
area of one eccentric hole among the plurality of
30 upper-end-side eccentric holes 644 and the plurality of
lower-end-side eccentric holes 645. A magnetic flux that
passes through the rotor core 611 can more easily pass
through the plurality of rivet holes 643 as compared to the
Docket No. PFGA-22316-PCT: FINAL
19
eccentric holes because the plurality of rivets 614 are
inserted in the plurality of rivet holes 643. Therefore,
the compressor 1 is able to reduce disturbance of the flow
of the magnetic flux even if the cross-sectional areas of
5 the plurality of rivet holes 643 are larger than the crosssectional
areas of the eccentric holes.
[0036] Second Embodiment
A compressor of a second embodiment is configured such
that, as illustrated in FIG. 5, the rotor core 611 of the
10 compressor 1 of the first embodiment as described above is
replaced with a different rotor core 701, and other
components are the same as those of the compressor 1 as
described above. FIG. 5 is a cross-sectional view of the
rotor core 701 of the compressor of the second embodiment.
15 The rotor core 701 is configured by replacing the plurality
of upper-end-side eccentric holes 644 and the plurality of
lower-end-side eccentric holes 645 of the rotor core 611 as
described above with a plurality of different upper-endside
eccentric holes 702 and a plurality of different
20 lower-end-side eccentric holes 703, and other components
are the same as those of the rotor core 611 as described
above. Each of the upper-end-side eccentric holes 702 is
formed parallel to the rotation axis 31 and formed in a
hole that is recessed from the upper end surface 615 so as
25 not to penetrate through the lower end surface 616,
similarly to the plurality of upper-end-side eccentric
holes 644. The plurality of lower-end-side eccentric holes
703 are formed such that the plurality of lower-end-side
eccentric holes 703 and the plurality of upper-end-side
30 eccentric holes 702 are point symmetric with respect to a
center point of the rotor core 701 in the top-bottom
direction on the rotation axis 31. In other words, each of
the lower-end-side eccentric holes 703 is formed parallel
Docket No. PFGA-22316-PCT: FINAL
20
to the rotation axis 31 and formed in a hole that is
recessed from the lower end surface 616 so as not to
penetrate through the upper end surface 615, similarly to
the plurality of lower-end-side eccentric holes 645.
5 [0037] FIG. 6 is a top view of the rotor core 701 of the
compressor of the second embodiment. The plurality of
upper-end-side eccentric holes 702 are formed on the inner
side of the polygonal (a regular hexagon in the embodiment)
region 653, similarly to the plurality of upper-end-side
10 eccentric holes 644 as described above. A first upper-endside
eccentric hole 702-1 among the plurality of upper-endside
eccentric holes 702 is formed on the inner peripheral
side of the first magnet hole 642-1. The first upper-endside
eccentric hole 702-1 is formed such that a cross
15 section perpendicular to the rotation axis 31 has an
approximately pentagonal shape. An outer-peripheral-side
inner wall surface 704, which is located on an outer
peripheral side among inner wall surfaces of the first
upper-end-side eccentric hole 702-1, is formed in the first
20 upper-end-side eccentric hole 702-1. The outer-peripheralside
inner wall surface 704 is bent such that a portion
(portion overlapping with the first d axis d1) that
intersects with the first d-axis plane 652-1 that is a
plane passing through the first d axis d1 and the rotation
25 axis 31 in the outer-peripheral-side inner wall surface 704
is located closest to the side 648. Furthermore, the
outer-peripheral-side inner wall surface 704 is bent so as
to be located farther away from the side 648 with an
increase in a distance from the center point 657 of the
30 first permanent magnet 655-1 along the polygonal region
653. A second upper-end-side eccentric hole 702-2 among
the plurality of upper-end-side eccentric holes 702 is
formed on the inner peripheral side of the sixth magnet
Docket No. PFGA-22316-PCT: FINAL
21
hole 642-6, and is formed in the same manner as the first
upper-end-side eccentric hole 702-1.
[0038] The plurality of lower-end-side eccentric holes
703 are formed such that the plurality of lower-end-side
5 eccentric holes 703 and the plurality of upper-end-side
eccentric holes 702 are point symmetric with respect to the
center point of the rotor core 701 in the top-bottom
direction on the rotation axis 31. In other words, a first
lower-end-side eccentric hole 703-1 among the plurality of
10 lower-end-side eccentric holes 703 is formed on the inner
peripheral side of the fourth magnet hole 642-4. The first
lower-end-side eccentric hole 703-1 is formed such that a
cross section perpendicular to the rotation axis 31 has an
approximately pentagonal shape. An outer-peripheral-side
15 inner wall surface 705, which is located on an outer
peripheral side among inner wall surfaces of the first
lower-end-side eccentric hole 703-1, is formed in the first
lower-end-side eccentric hole 703-1. The outer-peripheralside
inner wall surface 705 is bent such that a portion
20 (portion overlapping with the fourth d axis d4) that
intersects with a fourth d-axis plane 652-4 in the outerperipheral-
side inner wall surface 705 is located closest
to the side 648 (located on the most outer diameter side).
Furthermore, the outer-peripheral-side inner wall surface
25 705 is bent so as to be located farther away from the side
648 with an increase in a distance from the center point
657 of the forth permanent magnet 655-4 along the polygonal
region 653. A second lower-end-side eccentric hole 703-2
among the plurality of lower-end-side eccentric holes 703
30 is formed on the inner peripheral side of the third magnet
hole 642-3, and formed in the same manner as the first
lower-end-side eccentric hole 703-1.
[0039] The outer-peripheral-side inner wall surface 704
Docket No. PFGA-22316-PCT: FINAL
22
is bent so as to extend along the plurality of polygonal
regions 653, so that the plurality of upper-end-side
eccentric holes 702 can be formed such that inner volumes
of the plurality of upper-end-side eccentric holes 702 are
5 increased as compared to the plurality of upper-end-side
eccentric holes 644 as described above. The outerperipheral-
side inner wall surface 705 is bent so as to
extend along the plurality of sides 648, so that the
plurality of lower-end-side eccentric holes 703 can be
10 formed such that inner volumes of the plurality of lowerend-
side eccentric holes 703 are increased as compared to
the plurality of lower-end-side eccentric holes 645 as
described above.
[0040] In the compressor of the second embodiment,
15 because the plurality of upper-end-side eccentric holes 702
and the plurality of lower-end-side eccentric holes 703 are
arranged on the inner peripheral side of the polygonal
region 653, it is possible to reduce eccentricity of the
rotating body and prevent reduction in the efficiency of
20 the motor unit 6, similarly to the compressor 1 of the
first embodiment as described above. Furthermore, in the
compressor of the second embodiment, because the volumes of
the plurality of upper-end-side eccentric holes 702 and the
plurality of lower-end-side eccentric holes 703 are
25 increased, it is possible to increase the function of
reducing eccentricity of the rotating body as compared to
the compressor 1 of the first embodiment as described
above.
[0041] Third Embodiment
30 While the outer-peripheral-side inner wall surfaces
704 and 705 of the compressor of the second embodiment are
bent so as to extend along the polygonal region 653, the
outer-peripheral-side inner wall surfaces 704 and 705 need
Docket No. PFGA-22316-PCT: FINAL
23
not always extend along the polygonal region 653. A
compressor of a third embodiment is configured such that,
as illustrated in FIG. 7, the rotor core 701 of the
compressor of the second embodiment as described above is
5 replaced with a different rotor core 711, and other
components are the same as those of the compressor of the
second embodiment as described above. FIG. 7 is a top view
of the rotor core 711 of the compressor of the third
embodiment. The rotor core 711 is configured by replacing
10 the plurality of upper-end-side eccentric holes 702 and the
plurality of lower-end-side eccentric holes 703 of the
rotor core 701 as described above with a plurality of
different upper-end-side eccentric holes 712 and a
plurality of lower-end-side eccentric holes 713, and other
15 components are the same as those of the rotor core 701 as
described above.
[0042] Each of the upper-end-side eccentric holes 712 is
formed parallel to the rotation axis 31 and formed in a
hole that is recessed from the upper end surface 615 so as
20 not to penetrate to the lower end surface 616, similarly to
the plurality of upper-end-side eccentric holes 702. A
first upper-end-side eccentric hole 712-1 among the
plurality of upper-end-side eccentric holes 712 is formed
on the inner peripheral side of the first magnet hole 642-
25 1. The first upper-end-side eccentric hole 712-1 is formed
in an approximately triangular prism shape such that a
cross section perpendicular to the rotation axis 31 has an
approximately triangular shape. An outer-peripheral-side
inner wall surface 714, which is located on an outer
30 peripheral side among inner wall surfaces of the first
upper-end-side eccentric hole 712-1, is formed in the first
upper-end-side eccentric hole 712-1. The outer-peripheralside
inner wall surface 714 is bent such that a portion
Docket No. PFGA-22316-PCT: FINAL
24
(portion overlapping with the first d axis d1) that
intersects with the first d-axis plane 652-1 on the outerperipheral-
side inner wall surface 714 is located closest
to the side 648. Furthermore, the outer-peripheral-side
5 inner wall surface 714 is bent so as to be located farther
away from the side 648 with an increase in a distance from
the first d-axis plane 652-1. In this case, inclination of
the outer-peripheral-side inner wall surface 714 with
respect to the side 648 is larger than inclination of the
10 first side 653-1 or the sixth side 653-6 with respect to
the side 648. A second upper-end-side eccentric hole 712-2
among the plurality of upper-end-side eccentric holes 712
is formed on the inner peripheral side of the sixth magnet
hole 642-6, and is formed in the same manner as the first
15 upper-end-side eccentric hole 712-1.
[0043] The plurality of lower-end-side eccentric holes
713 are formed such that the plurality of lower-end-side
eccentric holes 713 and the plurality of upper-end-side
eccentric holes 712 are point symmetric with respect to the
20 center point of the rotor core 711 in the top-bottom
direction on the rotation axis 31. In other words, each of
the lower-end-side eccentric holes 713 is formed parallel
to the rotation axis 31 and formed in a hole that is
recessed from the lower end surface 616 so as not to
25 penetrate to the upper end surface 615. A first lower-endside
eccentric hole 713-1 among the plurality of lower-endside
eccentric holes 713 is formed on the inner peripheral
side of the fourth magnet hole 642-4. The first lower-endside
eccentric hole 713-1 is formed such that a cross
30 section perpendicular to the rotation axis 31 has an
approximately triangular shape. An outer-peripheral-side
inner wall surface 715, which is located on an outer
peripheral side among inner wall surfaces of the first
Docket No. PFGA-22316-PCT: FINAL
25
lower-end-side eccentric hole 713-1, is formed in the first
lower-end-side eccentric hole 713-1. The outer-peripheralside
inner wall surface 715 is bent such that a portion
(portion overlapping with the first d axis d1) that
5 intersects with the first d-axis plane 652-1 on the outerperipheral-
side inner wall surface 714 is located closest
to the side 648 (located on the most outer diameter side).
Furthermore, the outer-peripheral-side inner wall surface
715 is bent so as to be located farther away from the side
10 648 with an increase in a distance from the fourth d-axis
plane 652-4. In this case, inclination of the outerperipheral-
side inner wall surface 715 with respect to the
side 648 is larger than inclination of the first side 653-1
or the sixth side 653-6 with respect to the side 648. A
15 second lower-end-side eccentric hole 713-2 among the
plurality of lower-end-side eccentric holes 713 is formed
on the inner peripheral side of the sixth magnet hole 642-
6, and is formed in the same manner as the first lower-endside
eccentric hole 713-1.
20 [0044] In the compressor of the third embodiment,
because the plurality of upper-end-side eccentric holes 712
and the plurality of lower-end-side eccentric holes 713 are
surrounded by the polygonal region 653, it is possible to
reduce eccentricity of the rotating body and prevent
25 reduction in the efficiency of the motor unit 6, similarly
to the compressor 1 of the first embodiment as described
above. In the compressor of the third embodiment, because
the outer-peripheral-side inner wall surface 714 and the
outer-peripheral-side inner wall surface 715 are largely
30 inclined, it is possible to prevent distortion of the path
of the magnetic flux line by the plurality of upper-endside
eccentric holes 712 and the plurality of lower-endside
eccentric holes 713 as compared to the compressor of
Docket No. PFGA-22316-PCT: FINAL
26
the second embodiment as described above. In the
compressor of the third embodiment, because the path of the
magnetic flux line is less distorted by the plurality of
upper-end-side eccentric holes 712 and the plurality of
5 lower-end-side eccentric holes 713, it is possible further
prevent reduction in the efficiency of the motor unit 6, as
compared to the compressor of the second embodiment as
described above.
[0045] Fourth Embodiment
10 A compressor of a fourth embodiment is configured such
that, as illustrated in FIG. 8, the rotor core 701 of the
compressor of the second embodiment as described above is
replaced with a different rotor core 721, and other
components are the same as those of the compressor of the
15 second embodiment as described above. FIG. 8 is a top view
of the rotor core 721 of the compressor of the fourth
embodiment. The rotor core 721 is configured by replacing
the plurality of upper-end-side eccentric holes 702 and the
plurality of lower-end-side eccentric holes 703 of the
20 rotor core 701 as described above with a plurality of
different upper-end-side eccentric holes 722 and a
plurality of different lower-end-side eccentric holes 723,
and other components are the same as those of the rotor
core 701 as described above.
25 [0046] Each of the upper-end-side eccentric holes 722 is
formed parallel to the rotation axis 31 and formed in a
hole that is recessed from the upper end surface 615 so as
not to penetrate to the lower end surface 616, similarly to
the plurality of upper-end-side eccentric holes 702. A
30 first upper-end-side eccentric hole 722-1 among the
plurality of upper-end-side eccentric holes 722 is formed
on the inner peripheral side of the first magnet hole 642-
1. The first upper-end-side eccentric hole 722-1 is formed
Docket No. PFGA-22316-PCT: FINAL
27
such that a cross section perpendicular to the rotation
axis 31 has an approximately diamond shape. An outerperipheral-
side inner wall surface 724, which is located on
an outer peripheral side among inner wall surfaces of the
5 first upper-end-side eccentric hole 722-1, is formed in the
first upper-end-side eccentric hole 722-1. The outerperipheral-
side inner wall surface 724 is bent such that a
portion (portion overlapping with the first d axis d1) that
intersects with the first d-axis plane 652-1 on the outer10
peripheral-side inner wall surface 724 is located closest
to a plane side 8 (located on the most outer diameter
side). Furthermore, the outer-peripheral-side inner wall
surface 724 is bent so as to be located farther away from
the side 648 with an increase in a distance from the first
15 d-axis plane 652-1. A second upper-end-side eccentric hole
722-2 among the plurality of upper-end-side eccentric holes
722 is formed on the inner peripheral side of the sixth
magnet hole 642-6, and is formed in the same manner as the
first upper-end-side eccentric hole 722-1.
20 [0047] The plurality of lower-end-side eccentric holes
723 are formed such that the plurality of lower-end-side
eccentric holes 723 and the plurality of upper-end-side
eccentric holes 722 are point symmetric with respect to the
center point of the rotor core 721 in the top-bottom
25 direction on the rotation axis 31. In other words, each of
the lower-end-side eccentric holes 723 is formed parallel
to the rotation axis 31 and formed in a hole that is
recessed from the lower end surface 616 so as not to
penetrate to the upper end surface 615. A first lower-end30
side eccentric hole 723-1 among the plurality of lower-endside
eccentric holes 723 is formed on the inner peripheral
side of the fourth magnet hole 642-4. The first lower-endside
eccentric hole 723-1 is formed such that a cross
Docket No. PFGA-22316-PCT: FINAL
28
section perpendicular to the rotation axis 31 has an
approximately diamond shape. An outer-peripheral-side
inner wall surface 725, which is located on an outer
peripheral side among inner wall surfaces of the first
5 lower-end-side eccentric hole 723-1, is formed in the first
lower-end-side eccentric hole 723-1. The outer-peripheralside
inner wall surface 725 is bent such that a portion
(portion overlapping with the first d axis d1) that
intersects with the first d-axis plane 652-1 on the outer10
peripheral-side inner wall surface 724 is located closest
to the side 648 (located on the most outer diameter side).
Furthermore, the outer-peripheral-side inner wall surface
724 is bent so as to be located farther away from the side
648 with an increase in a distance from the fourth d-axis
15 plane 652-4. A second lower-end-side eccentric hole 723-2
among the plurality of lower-end-side eccentric holes 723
is formed on the inner peripheral side of the sixth magnet
hole 642-6, and is formed in the same manner as the first
lower-end-side eccentric hole 723-1.
20 [0048] In the compressor of the fourth embodiment,
because the plurality of upper-end-side eccentric holes 722
and the plurality of lower-end-side eccentric holes 723 are
arranged on the inner peripheral side relative to the
polygonal region 653, it is possible to reduce eccentricity
25 of the rotating body and prevent reduction in the
efficiency of the motor unit 6, similarly to the
compressors of the first to the third embodiments.
[0049] Fifth Embodiment
While the outer-peripheral-side inner wall surfaces
30 704, 705, 714, 715, 724, and 725 of the plurality of upperend-
side eccentric holes and the plurality of lower-endside
eccentric holes of the compressors of the first to the
third embodiments as described above are sharpened such
Docket No. PFGA-22316-PCT: FINAL
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that the central portions are located closest to the
plurality of magnet holes 642, but the outer-peripheralside
inner wall surfaces need not always be sharpened. A
compressor of a fifth embodiment is configured such that,
5 as illustrated in FIG. 8, the rotor core 701 of the
compressor of the second embodiment as described above is
replaced with a different rotor core 731, and other
components are the same as those of the compressor of the
second embodiment as described above. FIG. 8 is a top view
10 of the rotor core 731 of the compressor of the fifth
embodiment. The rotor core 731 is configured by replacing
the plurality of upper-end-side eccentric holes 702 and the
plurality of lower-end-side eccentric holes 703 of the
rotor core 701 as described above with a plurality of
15 different upper-end-side eccentric holes 732 and a
plurality of different lower-end-side eccentric holes 733,
and other components are the same as those of the rotor
core 701 as described above.
[0050] Each of the upper-end-side eccentric holes 732 is
20 formed parallel to the rotation axis 31 and formed in a
hole that is recessed from the upper end surface 615 so as
not to penetrate to the lower end surface 616, similarly to
the plurality of upper-end-side eccentric holes 702. A
first upper-end-side eccentric hole 732-1 among the
25 plurality of upper-end-side eccentric holes 732 is formed
on the inner peripheral side of the first magnet hole 642-
1. The first upper-end-side eccentric hole 732-1 is formed
such that a cross section perpendicular to the rotation
axis 31 has an approximately hexagonal shape. An outer30
peripheral-side inner wall surface 734, which is located on
an outer peripheral side among inner wall surfaces of the
first upper-end-side eccentric hole 732-1, is formed in the
first upper-end-side eccentric hole 732-1. The outerDocket
No. PFGA-22316-PCT: FINAL
30
peripheral-side inner wall surface 734 is formed so as to
intersect with the first d-axis plane 652-1 and so as to be
parallel to the side 648. A second upper-end-side
eccentric hole 732-2 among the plurality of upper-end-side
5 eccentric holes 732 is formed on the inner peripheral side
of the sixth magnet hole 642-6, and is formed in the same
manner as the first upper-end-side eccentric hole 732-1.

WE CLAIM.
1. A compressor comprising:
a shaft that is arranged along a rotation axis;
a compression unit that drives along with rotation of
5 the shaft;
a rotor core that is fixed to the shaft;
a plurality of permanent magnets that are embedded
inside the rotor core; and
a stator that causes the rotor core to rotate about
10 the rotation axis, wherein
a plurality of eccentric holes for adjusting balance
when the shaft rotates are formed in the rotor core, and
the plurality of eccentric holes are formed on an
inner side of a polygonal region for which midpoints of
15 sides at a side of the rotation axis among sides formed by
side surfaces of the plurality of permanent magnets in a
cross section perpendicular to the rotation axis serve as
vertices.
20 2. The compressor according to claim 1, wherein
the plurality of permanent magnets are formed in
rectangular solid shapes that are arranged along the sides
at a side of the rotation axis, and
a foot of a perpendicular line that is extended from
25 the rotation axis to each of the sides at the side of the
rotation axis in the cross section passes through the
midpoint.
3. The compressor according to claim 2, wherein a first
30 eccentric hole that is located closest to the permanent
magnet among the plurality of eccentric holes is formed
such that an inner wall surface at an outer peripheral side
close to the permanent magnet is located farther away from
Docket No. PFGA-22316-PCT: FINAL
36
a side of the polygonal region with an increase in a
distance from the midpoint in a circumferential direction.
4. The compressor according to claim 3, wherein the first
5 eccentric hole is plane symmetric with respect to a plane
that passes through the perpendicular line and the rotation
axis.
5. The compressor according to claim 1, wherein
10 the plurality of eccentric holes are formed so as not
to overlap with q axes, and
the q axes passes through the rotation axis and
between permanent magnets that are adjacent to each other
in a circumferential direction.