FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
ROTOR, MOTOR, COMPRESSOR, AND REFRIGERATION CYCLE APPARATUS
MITSUBISHI ELECTRIC CORPORATION, A CORPORATION
ORGANISED AND EXISTING UNDER THE LAWS OF JAPAN, WHOSE ADDRESS IS
7-3, MARUNOUCHI 2-CHOME, CHIYODA-KU, TOKYO 1008310, JAPAN
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE
INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED
2
DESCRIPTION
TECHNICAL FIELD
[0001]
The present disclosure relates to a rotor, a motor, a5
compressor, and a refrigeration cycle apparatus.
BACKGROUND ART
[0002]
In a rotor of a motor, a shaft is fixed in a center hole
of a rotor core by shrink fitting. In the shrink fitting, the10
rotor core is heated to expand the center hole. Patent
Reference 1, for example, discloses that cutout portions are
formed along the inner periphery of a center hole in order to
facilitate insertion of a shaft into the center hole.
PRIOR ART REFERENCE15
PATENT REFERENCE
[0003]
Patent Reference 1: Japanese Patent Application
Publication No. 2006-254662 (see FIG. 2)
SUMMARY OF THE INVENTION20
PROBLEM TO BE SOLVED BY THE INVENTION
[0004]
However, if the cutout portions are formed along the
center hole of the rotor core, the contact area between the
rotor core and the shaft decreases, and fitting strength25
between the rotor core and the shaft decreases accordingly. If
a shrink fitting margin is increased in order to increase the
fitting strength, the time necessary for shrink fitting
increases, and a fabrication process increases.
[0005]30
The present disclosure is made to solve the foregoing
problem, and an object of the present disclosure is to increase
fitting strength between a rotor core and a shaft.
MEANS TO SOLVE THE PROBLEM
3
[0006]
A rotor according to the present disclosure includes a
shaft, an annular rotor core fixed to the shaft and having a
magnet insertion hole, and a permanent magnet disposed in the
magnet insertion hole. The rotor core has a center hole which5
is formed at a center of the rotor core in a radial direction
and into which the shaft is fitted, a plurality of slits formed
around the center hole and each elongated in a circumferential
direction of the rotor core, a rib formed between two of the
plurality of slits, which are adjacent to each other in the10
circumferential direction, of the plurality of slits, and a
groove portion formed to extend outward in the radial direction
from the center hole. The groove portion is located on an
inner side of the rib in the radial direction. A width T of
the rib in the circumferential direction and a width W of the15
groove portion in the circumferential direction satisfy T > W.
The width T of the rib in the circumferential direction
increases as a distance to the center hole decreases.
EFFECTS OF THE INVENTION
[0007]20
In the present disclosure, since the groove portion is
formed on the inner side of the rib in the radial direction,
the center hole can be uniformly expanded during heating of the
rotor, and thus the shaft can be easily inserted in the center
hole. In addition, since the width T of the rib and the width25
W of the groove portion satisfy T > W, a sufficient contact
area is obtained between the shaft and the center hole, and
thus fitting strength between the rotor core and the shaft can
be increased.
BRIEF DESCRIPTION OF THE DRAWINGS30
[0008]
FIG. 1 is a cross-sectional view illustrating a motor
according to a first embodiment.
FIG. 2 is a cross-sectional view illustrating a rotor
4
according to the first embodiment.
FIG. 3 is an enlarged view illustrating a portion
including slits of a rotor core according to the first
embodiment.
FIG. 4 is an enlarged view illustrating a portion5
including a rib of the rotor core according to the first
embodiment.
FIGS. 5(A) and 5(B) are diagrams for explaining a shrink
fitting process of a comparative example.
FIGS. 6(A) and 6(B) are diagrams for explaining a shrink10
fitting process of the first embodiment.
FIG. 7 is a longitudinal sectional view illustrating a
compressor to which the motor according to the first embodiment
is applicable.
FIG. 8 is a diagram illustrating a refrigeration cycle15
apparatus including the compressor of FIG. 7.
MODE FOR CARRYING OUT THE INVENTION
[0009]
FIRST EMBODIMENT
(Configuration of Motor 100)20
FIG. 1 is a transverse cross-sectional view illustrating
a motor 100 according to a first embodiment. The motor 100 is
an inner rotor type motor including a rotor 1 and an annular
stator 3 surrounding the rotor 1. An air gap is formed between
the stator 3 and the rotor 1.25
[0010]
In the following description, a rotation center axis of
the rotor 1 is referred to as an axis Ax. A direction of the
axis Ax is referred to as an “axial direction.” A
circumferential direction about the axis Ax is referred to as a30
“circumferential direction,” and a radial direction about the
axis Ax is referred to as a “radial direction.”
[0011]
(Configuration of Stator 3)
5
The stator 3 includes an annular stator core 30 and a
coil 35 wound on the stator core 30. The stator core 30 is
constituted by a plurality of electromagnetic steel sheets
stacked in the axial direction. The thickness of each
electromagnetic steel sheet is, for example, 0.1 mm or more and5
1.0 mm or less.
[0012]
The stator core 30 includes a yoke 31 extending in the
circumferential direction and a plurality of teeth 32 extending
inward from the yoke 31 in the radial direction. A slot 3310
that is a space for accommodating the coil 35 is formed between
adjacent ones of the teeth 32.
[0013]
In this example, six teeth 32 are arranged at equal
intervals in the circumferential direction. The number of15
teeth 32 is not limited to six, and any number of teeth 32 may
be provided. An insulating portion is provided between the
stator core 30 and the coil 35. The insulating portion is, for
example, an insulator 34 illustrated in FIG. 7, an insulating
film, or the like.20
[0014]
The coil 35 includes a conductor of copper or aluminum
and an insulating film covering the conductor. The coil 35 is
wound around the teeth 32 via the insulating portion. The
method for winding the coil 35 may be concentrated winding or25
distributed winding.
[0015]
(Configuration of Rotor 1)
FIG. 2 is a transverse cross-sectional view illustrating
the rotor 1. The rotor 1 includes a rotor core 10, permanent30
magnets 20, and a shaft 25 (FIG. 1). The rotor core 10 is
constituted by a plurality of electromagnetic steel sheets
stacked in the axial direction. The thickness of each
electromagnetic steel sheet is, for example, 0.1 mm or more and
6
1.0 mm or less.
[0016]
A plurality of magnet insertion holes 11 are formed along
an outer periphery 18 of the rotor core 10 at equal intervals
in the circumferential direction. One permanent magnet 20 is5
inserted in each of the magnet insertion holes 11. Each
permanent magnet 20 has a thickness in the radial direction of
the rotor core 10 and is magnetized in the thickness direction.
[0017]
Each permanent magnet 20 is made of a rare earth magnet.10
The rare-earth magnet is, for example, a neodymium magnet
containing neodymium (Nd), iron (Fe), and boron (B), a
samarium-iron-nitrogen magnet containing samarium (Sm), iron
(Fe), and nitrogen (N), or the like.
[0018]15
The permanent magnet 20 in each of the magnet insertion
holes 11 constitutes one magnetic pole. The center of the
magnet insertion hole 11 in the circumferential direction
serves as a magnetic pole center P. An inter-pole portion M is
formed between adjacent ones of the magnet insertion holes 11.20
[0019]
In this example, the number of the magnet insertion holes
11 is four, and the number of the permanent magnets 20 is also
four. Thus, the number of poles of the rotor 1 is four.
However, the number of poles of the rotor 1, is not limited to25
four, and only needs to be two or more.
[0020]
Although one permanent magnet 20 is disposed in each
magnet insertion hole 11 in this example, two or more permanent
magnets 20 may be disposed in each magnet insertion hole 11.30
Each magnet insertion hole 11 extends linearly in this example,
but may extend in a V shape, for example,
[0021]
The rotor core 10 has a center hole 14 at a center in the
7
radial direction thereof. The center hole 14 is a circular
hole to which the shaft 25 (FIG. 1) is fixed by shrink fitting.
The shaft 25 is constituted by, for example, a metal.
[0022]
A plurality of slits 12 each elongated in the5
circumferential direction are formed around the center hole 14
of the rotor core 10. The slits 12 extend in an arc shape in
the circumferential direction and are arranged at equal
intervals in the circumferential direction. The slits 12 are
formed to make heat, which is applied from the center hole 1410
side, less likely to transfer to the magnet insertion holes 11
during shrink fitting of the shaft 25 described later.
[0023]
The number of the slits 12 is equal to the number of the
magnet insertion holes 11, that is, four. The center of each15
slit 12 in the circumferential direction is aligned with the
corresponding magnetic pole center P. The slits 12 are not
limited to this arrangement, and the number of the slits 12 may
be different from the number of the magnet insertion holes 11.
[0024]20
A rib 13 is formed between each two of the slits 12
adjacent to each other in the circumferential direction. The
rib 13 is a core region extending in the radial direction. The
number of the ribs 13 is equal to the number of the slits 12.
[0025]25
Groove portions 15 are formed to extend outward in the
radial direction from the center hole 14. The groove portions
15 are formed on the inner side of the ribs 13 in the radial
direction.
[0026]30
A width W of each groove portion 15 in the
circumferential direction and a width T of each rib 13 in the
circumferential direction satisfy W < T. In other words, the
width W of the groove portion 15 in the circumferential
8
direction is narrower than the width T of the rib 13 in the
circumferential direction. This is for the purpose of
increasing fitting strength between the center hole 14 of the
rotor core 10 and the shaft 25, as will be described later.
[0027]5
An inner peripheral core portion 16 that is an annular
core portion is formed between the center hole 14 of the rotor
core 10 and the slits 12 and the ribs 13 of the rotor core 10.
The inner peripheral core portion 16 is a portion that is
heated in a shrink fitting process described later to be10
expanded outward in the radial direction.
[0028]
FIG. 3 is an enlarged view illustrating a portion
including the slits 12 of the rotor core 10. Each of the slits
12 includes an inner edge 12a facing the center hole 14 of the15
rotor core 10, an outer edge 12b located on the outer side of
the inner edge 12a in the radial direction, and side edges 12c
each facing the corresponding rib 13.
[0029]
Each of the inner edge 12a and the outer edge 12b of the20
slit 12 extends to form an arc shape in the circumferential
direction about the axis Ax. Each slit 12 has a width L in the
radial direction. The width L is a distance between the inner
edge 12a and the outer edge 12b.
[0030]25
The width of the slit 12 in the radial direction is
preferably uniform except for end portions of the slit 12 in
the circumferential direction. However, the slit 12 is not
limited to this example. In a case where the width of the slit
12 in the radial direction varies depending on the position in30
the circumferential direction, the width of a portion closest
to the rib 13 is defined as the width L. Although corners of
end portions of the slit 12 in the circumferential direction
are rounded as described later, the width L corresponds to an
9
interval between an intersection point of an extension line of
the inner edge 12a and an extension line of the side edge 12c
and an intersection point of an extension line of the outer
edge 12b and the extension line of the side edge 12c.
[0031]5
A curved corner 121 is formed on the center hole 14 side
of the side edge 12c of each slit 12. A curved corner 122 is
formed on the outer periphery 18 (FIG. 2) side of the side edge
12c. The curved corner 121 is also referred to as a first
curved corner, and the curved corner 122 is also referred to as10
a second curved corner.
[0032]
The curved corner 121 has a radius of curvature R1, and
the curved corner 122 has a radius of curvature R2. The radius
of curvature R1 of the curved corner 121 and the radius of15
curvature R2 of the curved corner 122 satisfy R1 > R2. The
width L of the slit 12 in the radial direction and the radius
of curvature R1 of the curved corner 121 satisfy R1 > L/2.
[0033]
FIG. 4 is an enlarged view illustrating a portion20
including the rib 13. The rib 13 is a portion sandwiched
between two slits 12 in the circumferential direction. A
boundary point between the curved corner 121 and the inner edge
12a of the slit 12 is defined as A1. A boundary point between
the side edge 12c and the curved corner 121 is defined as A2.25
A boundary point between the side edge 12c and the curved
corner 122 is defined as A3.
[0034]
An interval between the boundary points A1 of two slits
12 in the circumferential direction is defined as T1. An30
interval between the boundary points A2 of two slits 12 in the
circumferential direction is defined as T2. An interval
between the boundary points A3 of two slits 12 in the
circumferential direction is defined as T3. These intervals T1,
10
T2, and T3 satisfy T1 > T2 ≥ T3. That is, the rib 13 has such
a shape that the width T in the circumferential direction
increases as the distance to the center hole 14 decreases.
[0035]
The intervals T1, T2, and T3 preferably satisfy T1 > T2 ≥5
T3 > W, in a relationship with the width W of the groove
portion 15 in the circumferential direction.
[0036]
As illustrated in FIGS. 3 and 4, a distance D1 from the
center hole 14 to the center of the slit 12 in the10
circumferential direction and a distance D2 from the center
hole 14 to an end portion of the slit 12 in the circumferential
direction satisfy D1 < D2. The distance D1 is a distance from
the center hole 14 to the center of the inner edge 12a of the
slit 12 in the circumferential direction. The distance D2 is a15
distance from the center hole 14 to the boundary point A1
between the inner edge 12a and the curved corner 121 (FIG. 4).
[0037]
(Function)
Next, function of the first embodiment will be described.20
FIGS. 5(A) and 5(B) are diagrams illustrating a shrink fitting
process of a rotor 1C in a comparative example. The rotor 1C
of the comparative example is different from the rotor 1 of the
first embodiment in that no groove portion 15 is formed around
the center hole 14.25
[0038]
In shrink fitting of the shaft 25 in the rotor 1C, the
rotor core 10 is heated in a state where the permanent magnets
20 are attached to the rotor core 10 as illustrated in FIG.
5(A) so as to increase the inner diameter of the center hole 1430
by thermal expansion. Examples of the heating method include a
method of placing the rotor core 10 in a heating furnace to
heat the entire rotor core 10 and a method of heating the rotor
core 10 from the center hole 14 side by high-frequency
11
induction heating.
[0039]
In a state where the inner diameter of the center hole 14
is increased, the shaft 25 at a lower temperature than the
rotor core 10 is inserted in the center hole 14. After the5
shaft 25 is inserted in the center hole 14, the rotor core 10
is cooled at normal temperature or low-temperature environment.
Accordingly, the inner diameter of the center hole 14 of the
rotor core 10 decreases, and the shaft 25 is fitted in the
center hole 14 as illustrated in FIG. 5(B).10
[0040]
In the case of using the heating furnace as a heating
method, heat is transferred to the rotor core 10 from both of
the center hole 14 and the outer periphery 18. On the other
hand, in the case of using high-frequency induction heating,15
heat is supplied from the center hole 14, and thus heat is
transferred from the center hole 14 toward the outer periphery
18 of the rotor core 10.
[0041]
The temperature difference in the rotor core 10 occurs in20
either heating method, but tends to be larger in the high-
frequency induction heating. Thus, before the temperature of
the entire rotor core 10 increases, the temperature of the
inner peripheral core portion 16 around the center hole 14
increases, and the inner peripheral core portion 16 is about to25
thermally expand.
[0042]
The slits 12 are formed around the center hole 14, and
the ribs 13 are each formed between adjacent ones of the slits
12. The inner peripheral core portion 16 can be considered to30
be divided into a first portion 16a located on the inner side
of each slit 12 in the radial direction and a second portion
16b located on the inner side of each rib 13 in the radial
direction.
12
[0043]
The slit 12 is filled with a gas such as air, oil, or the
like, and thus rigidity of the slit 12 is significantly lower
than that of the rotor core 10. Accordingly, the first portion
16a of the inner peripheral core portion 16, which is located5
on the inner side of the slit 12 in the radial direction, is
easily deformed outward in the radial direction.
[0044]
On the other hand, the second portion 16b of the inner
peripheral core portion 16, which is located on the inner side10
of the rib 13 in the radial direction, is restricted from being
deformed outward in the radial direction by the presence of the
rib 13, and thus the second portion 16b is not easily deformed
outward in the radial direction.
[0045]15
Consequently, when the rotor core 10 is heated from the
center hole 14 side, the first portion 16a is expanded in the
radial direction more greatly than the second portion 16b in
the inner peripheral core portion 16. As a result, in the
center hole 14, a first portion 14a located on the inner side20
of each slit 12 in the radial direction is expanded outward in
the radial direction more greatly than a second portion 14b
located on the inner side of each rib 13 in the radial
direction. In other words, the center hole 14 is nonuniformly
expanded, and circularity of the center hole 14 decreases.25
[0046]
In order to insert the shaft 25 in the center hole 14,
the outer diameter of the shaft 25 needs to be smaller than a
minimum inner diameter of the center hole 14. Thus, it is
necessary to continue heating until the inner diameter of the30
second portions 14b of the center hole 14 becomes larger than
the outer diameter of the shaft 25. That is, there is a
problem that the heating time increases.
[0047]
13
FIGS. 6(A) and 6(B) are diagrams showing a shrink fitting
process of the rotor 1 according to the first embodiment. In
the rotor 1 according to the first embodiment, the groove
portions 15 are formed to be continuous with the center hole 14
on the inner side of the ribs 13 in the radial direction.5
[0048]
In the first embodiment, the rotor core 10 is heated as
illustrated in FIG. 6(A) to increase the inner diameter of the
center hole 14 by thermal expansion using the heating method
similar to the comparative example. In a state where the inner10
diameter of the center hole 14 is increased, the shaft 25 at a
lower temperature than the rotor core 10 is inserted in the
center hole 14. When the temperature of the rotor core 10
returns to normal temperature, the inner diameter of the center
hole 14 decreases and the center hole 14 and the shaft 25 are15
fixed to each other as illustrated in FIG. 6(B).
[0049]
During heating, a temperature difference occurs in the
rotor core 10 as in the comparative example. In particular, in
high-frequency induction heating in which the rotor core 10 is20
heated from the center hole 14 side, the temperature difference
in the rotor core 10 tends to be large.
[0050]
The first portions 16a of the inner peripheral core
portion 16 are easily expanded in the radial direction, whereas25
the second portions 16b are not easily expanded outward in the
radial direction. Accordingly, the first portions 14a of the
center hole 14 are expanded outward in the radial direction
more greatly than the second portions 14b.
[0051]30
However, in the first embodiment, the groove portion 15
is formed to be continuous with the center hole 14 on the inner
side of each rib 13 in the radial direction. In other words,
the second portions 14b of the center hole 14 are expanded
14
outward in the radial direction beforehand. Thus, the shaft 25
can be inserted in the center hole 14 as long as the inner
diameter of the first portions 14a of the center hole 14 is
larger than the outer diameter of the shaft 25.
[0052]5
Since the first portions 14a of the center hole 14 are
easily expanded outward in the radial direction as described
above, the time for heating the rotor core 10 can be shortened.
Accordingly, the time necessary for shrink fitting can be
shortened. That is, the fabrication process of the rotor 1 can10
be shortened.
[0053]
Here, in a case where the groove portions 15 are formed
in the center hole 14, as the circumferential width (i.e., the
width W in FIG. 2) of each groove portion 15 increases, the15
contact area between the center hole 14 and the shaft 25
decreases. As the contact area between the center hole 14 and
the shaft 25 decreases, fitting strength between the rotor core
10 and the shaft 25 decreases. The decrease in fitting
strength between the rotor core 10 and the shaft 25 can be20
suppressed by increasing a shrink fitting margin. However, in
such a case, the heating time increases.
[0054]
For this reason, in the first embodiment, as illustrated
in FIG. 2, the width W of each groove portion 15 in the25
circumferential direction is made narrower than the width T of
each rib 13 in the circumferential direction. Since the width
W of the groove portion 15 is narrower than the width T of the
rib 13 as described above, only portions (i.e., the second
portions 14b) of the center hole 14 that are less likely to be30
expanded by thermal expansion can be expanded in the radial
direction, and the other portions (i.e., the first portions
14a) can be in contact with the shaft 25. Accordingly,
sufficient fitting strength can be obtained between the rotor
15
core 10 and the shaft 25.
[0055]
Since the first portions 16a of the inner peripheral core
portion 16 are easily deformed outward in the radial direction
and the second portions 16b are not easily deformed outward in5
the radial direction as described above, stress tends to be
concentrated on portions each between the first portion 16a and
the second portion 16b (i.e., portions corresponding to end
portions of the slits 12 in the circumferential direction).
Consequently, due to plastic deformation of the inner10
peripheral core portion 16, inner diameter distortion of the
center hole 14 may remain.
[0056]
This affects work in the case of redoing shrink fitting.
In general, when the rotor core 10 is insufficiently heated or15
when the temperature of the rotor core 10 decreases with the
lapse of time after heating of the rotor core 10 until
insertion of the shaft 25, there are cases where shrink fitting
is redone by heating the rotor core 10 again.
[0057]20
When shrink fitting is redone, if the inner diameter
distortion of the center hole 14 that has occurred in the
previous heating remains, insertion of the shaft 25 in the
center hole 14 is difficult, and it is necessary to perform
change25
in conditions such as increase in the heating time for
expanding the center hole 14. Thus, the inner diameter
distortion of the center hole 14 is preferably as small as
possible.
[0058]30
In order to suppress the inner diameter distortion of the
center hole 14, it is effective to reduce stress concentration
on portions corresponding to end portions of the slits 12 in
the circumferential direction. For this reason, in the first
16
embodiment, as illustrated in FIG. 3, the radius of curvature
R1 of the curved corner 121 on the center hole 14 side of the
side edge 12c of the slit 12 and the radius of curvature R2 of
the curved corner 122 on the outer periphery 18 side of the
side edge 12c satisfy R1 > R2.5
[0059]
By making the radius of curvature R1 of the curved corner
121 of the slit 12 large, stress can be dispersed, and inner
diameter distortion of the center hole 14 can be suppressed.
Accordingly, in redoing the shrink fitting described above, the10
shaft 25 can be easily inserted in the center hole 14.
[0060]
In order to increase the radius of curvature R1 of the
curved corner 121 as much as possible, in addition to
satisfying R1 > R2 as described above, it is preferable that15
the radius of curvature R1 of the curved corner 121 and the
width L of the slit 12 in the radial direction satisfy R1 > L/2.
Accordingly, stress concentration in the inner peripheral core
portion 16 can be further reduced.
[0061]20
In a case where an angle formed by the side edge 12c and
the inner edge 12a of the slit 12 is an acute angle, stress
tends to be concentrated on the curved corner 121 between the
side edge 12c and the inner edge 12a. For this reason, in
order to increase the angle formed by the side edge 12c and the25
inner edge 12a of the slit 12 as much as possible, the rib 13
is formed so that the width T of the rib 13 in the
circumferential direction increases as the distance to the
center hole 14 decreases.
[0062]30
That is, as described with reference to FIG. 4, the
interval T1 between the boundary points A1, the interval T2
between the boundary points A2, and the interval T3 between the
boundary points A3 of two slits 12 on both sides of the rib 13
17
satisfy T1 > T2 ≥ T3. Accordingly, stress concentration on the
curved corner 121 can be reduced.
[0063]
In addition, in the first embodiment, the distance D2
from the center hole 14 to the end portion of the slit 12 in5
the circumferential direction and the distance D1 from the
center hole 14 to the center of the slit 12 in the
circumferential direction satisfy D1 < D2.
[0064]
As described above, in the inner peripheral core portion10
16, a portion on which stress tends to be concentrated most is
a portion corresponding to the end portion of the slit 12 in
the circumferential direction. When the distance D2 from the
center hole 14 to the end portion of the slit 12 in the
circumferential direction is increased, the width of a portion15
of the inner peripheral core portion 16 on which stress tends
to be concentrated most can be increased, and thus stress
concentration can be reduced.
[0065]
Next, suppression of demagnetization of the permanent20
magnets 20 will be described. Each permanent magnet 20 is
constituted by, for example, a rare earth magnet. The rare
earth magnet has high magnetic force, and thus is advantageous
for enhancing motor efficiency. On the other hand, the rare
earth magnet has the property of susceptibility to25
demagnetization at high temperature, as compared to permanent
magnets of other types (for example, ferrite magnets).
[0066]
Thus, when the permanent magnets 20 are heated during
heating of the rotor core 10, demagnetization of the permanent30
magnets 20 may occur. In particular, when heat applied to the
center hole 14 of the rotor core 10 is transferred to the
permanent magnets 20 in the magnet insertion holes 11,
demagnetization of the permanent magnets 20 may occur.
18
[0067]
In some cases, shrink fitting of the shaft 25 can be
performed at a stage before magnetization of the permanent
magnets 20. Even in such cases, when the permanent magnets 20
are heated, performance and quality of the permanent magnets 205
may degrade.
[0068]
For this reason, in the first embodiment, the slits 12
are formed around the center hole 14, and heat transfer paths
from the center hole 14 to the magnet insertion holes 11 are10
made longer, so that a temperature rise of the permanent magnet
20 is suppressed. In particular, in a case where the ribs 13
are located on the inner side of the inter-pole portions M in
the radial direction, the heat transfer paths from the rib 13
to the magnet insertion holes 11 are the longest, and15
demagnetization of the permanent magnets 20 can be effectively
suppressed.
[0069]
The width T of the rib 13 in the circumferential
direction represents the width at which heat is transferred,20
and the width L of the slit 12 in the radial direction
represents a length in which heat is transferred. As the width
T of the rib 13 in the circumferential direction decreases,
heat is less likely to be transferred. As the width L of the
slit 12 in the radial direction increases, heat is less likely25
to be transferred. Thus, it is preferable that the width T of
the rib 13 in the circumferential direction is as small as
possible and the width L of the slit 12 in the radial direction
is as large as possible. For this reason, the width T of the
rib 13 in the circumferential direction and the width L of the30
slit 12 in the radial direction preferably satisfy T ≤ L.
[0070]
In this example, the number of the ribs 13 is equal to
the number of the magnet insertion holes 11 (i.e., the number
19
of poles). However, as long as the heat transfer path from the
center hole 14 to each magnet insertion hole 11 can be made
long, the number of the ribs 13 may be larger or smaller than
the number of the magnet insertion holes 11. For example, one
to three of the four ribs 13 illustrated in FIG. 2 may be5
provided. Also in such a case, the groove portion 15 is
preferably formed on the inner side of each rib 13 in the
radial direction.
[0071]
The groove portion 15 only needs to be formed from the10
center hole 14 outward in the radial direction and on the inner
side of the rib 13 in the radial direction. The shape of each
groove portion 15 is semicircular in this example, but may be
other shapes. In order to reduce stress concentration around
the groove portion 15, the inner periphery of the groove15
portion 15 is preferably curved.
[0072]
(Advantages of Embodiment)
As described above, the rotor 1 according to the first
embodiment includes the shaft 25, the annular rotor core 1020
fixed to the shaft 25 and having the magnet insertion hole 11,
and the permanent magnet 20 disposed in the magnet insertion
hole 11. The rotor core 10 includes the center hole 14 which
is formed at the center of the rotor core 10 in the radial
direction and in which the shaft 25 is fitted, the plurality of25
slits 12 formed around the center hole 14 and each elongated in
the circumferential direction, the rib 13 formed between
adjacent two of the slits 12, and the groove portion 15 formed
to extend outward in the radial direction from the center hole
14. The groove portion 15 is located on the inner side of the30
rib 13 in the radial direction. The width T of the rib 13 in
the circumferential direction and the width W of the groove
portion 15 in the circumferential direction satisfy T > W.
[0073]
20
Since the groove portion 15 is formed on the inner side
of the rib 13 in the radial direction as above, the center hole
14 can be uniformly expanded during heating of the rotor core
10 so that the shaft 25 can be easily inserted in the center
hole 14. In addition, since the width T of the rib 13 and the5
width W of the groove portion 15 satisfy T > W, a sufficient
contact area is obtained between the shaft 25 and the center
hole 14, and thus fitting strength between the rotor core 10
and the shaft 25 can be increased.
[0074]10
Each slit 12 includes the side edge 12c facing the rib 13,
the curved corner 121 formed on the inner side of the side edge
12c in the radial direction, and the curved corner 122 formed
on the outer side of the side edge 12c in the radial direction,
and the radii of curvatures R1 and R2 of the curved corners 12115
and 122 satisfy R1 > R2. Thus, stress concentration on the
inner peripheral core portion 16 during heating of the rotor
core 10 can be reduced.
[0075]
Further, since the radius of curvature R1 of the curved20
corner 121 and the width L of the slit 12 satisfy R1 > L/2,
stress concentration on the inner peripheral core portion 16
during heating of the rotor core 10 can be further reduced.
[0076]
Moreover, since the distance D1 from the center hole 1425
to the center of the inner edge 12a of the slit 12 in the
circumferential direction and the distance D2 from the center
hole 14 to the end of the inner edge 12a of the slit 12 in the
circumferential direction satisfy D1 < D2, the width of a
portion of the inner peripheral core portion 16 on which stress30
tends to be concentrated most can be increased, and thus stress
concentration can be reduced.
[0077]
Since the rib 13 and the groove portion 15 are located on
21
the inner side of the inter-pole portion M in the radial
direction, the heat transfer path from the center hole 14 to
the magnet insertion hole 11 can be made the longest, and thus
the effect of suppressing demagnetization of the permanent
magnet 20 can be enhanced.5
[0078]
The width T of the rib 13 in the circumferential
direction increases as the distance to the center hole 14
decreases, and thus stress concentration around the curved
corner 121 of the slit 12 in the rotor core 10 can be reduced.10
[0079]
(Compressor)
Next, a compressor 300 to which the motor 100 is
applicable will be described. FIG. 7 is a longitudinal
sectional view illustrating the compressor 300 including the15
motor 100. The compressor 300 is a rotary compressor in this
example, but may be a scroll compressor.
[0080]
The compressor 300 includes a closed container 307, a
compression mechanism 301 disposed in the closed container 307,20
and the motor 100 that drives the compression mechanism 301.
[0081]
The compression mechanism 301 includes a cylinder 302
including a cylinder chamber 303, a rolling piston 304 fixed to
the shaft 25 of the motor 100, a vane dividing the inside of25
the cylinder chamber 303 into a suction side and a compression
side, and an upper frame 305 and a lower frame 306 through
which the shaft 25 is inserted and which close end faces of the
cylinder chamber 303 in the axial direction. An upper
discharge muffler 308 and a lower discharge muffler 309 are30
respectively attached to the upper frame 305 and the lower
frame 306.
[0082]
The closed container 307 is a cylindrical container. A
22
bottom portion of the closed container 307 stores refrigerating
machine oil (not shown) for lubricating sliding portions of the
compression mechanism 301. The shaft 25 is rotatably held by
the upper frame 305 and the lower frame 306 serving as bearing
portions.5
[0083]
The cylinder 302 includes the cylinder chamber 303
therein, and the rolling piston 304 eccentrically rotates in
the cylinder chamber 303. The shaft 25 includes an eccentric
shaft part, and the rolling piston 304 is fitted to the10
eccentric shaft part.
[0084]
The stator 3 of the motor 100 is incorporated in the
closed container 307 by a method such as shrink fitting, press
fitting, or welding. The coil 35 of the stator 3 is supplied15
with electric power from a glass terminal 311 fixed to the
closed container 307. The shaft 25 is fixed to the rotor core
10 as described above.
[0085]
An accumulator 310 is attached to the outer side of the20
closed container 307. A refrigerant gas flows into the
accumulator 310 from a refrigerant circuit through a suction
pipe 314. In a case where liquid refrigerant flows from the
suction pipe 314 together with the refrigerant gas, the liquid
refrigerant is stored in the accumulator 310, and the25
refrigerant gas is supplied to the compressor 300.
[0086]
A suction pipe 313 is fixed to the closed container 307,
and a refrigerant gas is supplied from the accumulator 310 to
the cylinder 302 through the suction pipe 313. An upper30
portion of the closed container 307 includes a discharge pipe
312 for discharging refrigerant to the outside.
[0087]
As refrigerant of the compressor 300, R410A, R407C, R22
23
or the like may be used, for example. From the viewpoint of
preventing global warming, a refrigerant having a low global
warming potential (GWP) is preferably used. As the low-GWP
refrigerant, the following refrigerants can be used, for
example.5
[0088]
(1) First, halogenated hydrocarbon having a double bond
of carbon in its composition, such as hydro-fluoro-olefin
(HFO)-1234yf (CF3CF=CH2) can be used. HFO-1234yf has a GWP of 4.
(2) Further, hydrocarbon having a double bond of carbon10
in its composition, such as R1270 (propylene), may be used.
R1270 has a GWP of 3, which is smaller than that of HFO-1234yf,
but has flammability higher than that of HFO-1234yf.
(3) A mixture containing at least one of halogenated
hydrocarbon having a double bond of carbon in its composition15
or hydrocarbon having a double bond of carbon in its
composition, such as a mixture of HFO-1234yf and R32, may be
used. Since HFO-1234yf described above is a low-pressure
refrigerant, a pressure loss tends to increase, and performance
of a refrigeration cycle (especially an evaporator) may degrade.20
Thus, it is practically preferable to use a mixture with R32 or
R41, which is a higher-pressure refrigerant than HFO-1234yf.
[0089]
Operation of the compressor 300 is as follows. A
refrigerant gas supplied from the accumulator 310 is supplied25
to the cylinder chamber 303 of the cylinder 302 via the suction
pipe 313. When the motor 100 is driven by current supplied to
the coil 35, the shaft 25 rotates together with the rotor 1.
Then, the rolling piston 304 fitted to the shaft 25
eccentrically rotates in the cylinder chamber 303, and30
refrigerant is compressed in the cylinder chamber 303.
[0090]
The refrigerant compressed in the cylinder chamber 303
passes through the discharge mufflers 308 and 309, and further
24
passes through a gap between the rotor 1 and the stator 3 or
through holes (not shown) to flow upward in the closed
container 307. The refrigerant that has flown upward in the
closed container 307 is discharged from the discharge pipe 312
and supplied to a high-pressure side of the refrigeration cycle.5
[0091]
In the compressor 300, a torque exerted on the motor 100
pulses by a load fluctuation generated in the compression
mechanism 301. A maximum value of torque pulsation exerted on
the motor 100 of the compressor 300 is larger than that of a10
general motor. In the motor 100 according to the first
embodiment, fitting strength between the rotor 1 and the shaft
25 is high, and thus the motor 100 can withstand torque
pulsation caused by load fluctuation of the compression
mechanism 301.15
[0092]
The compressor 300 illustrated in FIG. 7 is a single
rotary compressor including a single cylinder 302, but may be a
twin rotary compressor including two cylinders with opposite
eccentric directions. Reliability of either type of compressor20
can be enhanced when the motor 100 of the first embodiment is
used therein.
[0093]
Load fluctuation in the single rotary compressor is
larger than that in the twin rotary compressor. Thus, the25
motor 100 of the first embodiment exhibits its advantages
especially in the single rotary compressor.
[0094]
(Refrigeration Cycle Apparatus)
Next, a refrigeration cycle apparatus 400 including the30
compressor 300 illustrated in FIG. 7 will be described. FIG. 8
is a diagram illustrating the refrigeration cycle apparatus 400.
The refrigeration cycle apparatus 400 is, for example, an air
conditioner, but is not limited thereto and may be, for example,
25
a refrigerator.
[0095]
The refrigeration cycle apparatus 400 illustrated in FIG.
8 includes a compressor 401, a condenser 402 that condenses
refrigerant, a decompressor 403 that decompresses refrigerant,5
and an evaporator 404 that evaporates refrigerant. The
compressor 401, the condenser 402, and the decompressor 403 are
disposed in an outdoor unit 410. The evaporator 404 is
disposed in an indoor unit 420.
[0096]10
The compressor 401, the condenser 402, the decompressor
403, and the evaporator 404 are coupled to one another by a
refrigerant pipe 407, and constitute a refrigerant circuit.
The compressor 401 is the compressor 300 illustrated in FIG. 7.
The refrigeration cycle apparatus 400 also includes an outdoor15
fan 405 facing the condenser 402, and an indoor fan 406 facing
the evaporator 404.
[0097]
Operation of the refrigeration cycle apparatus 400 is as
follows. The compressor 401 compresses sucked refrigerant and20
sends out the compressed refrigerant as a high-temperature and
high-pressure refrigerant gas. The condenser 402 performs heat
exchange between the refrigerant sent from the compressor 401
and outdoor air sent by the outdoor fan 405, condenses the
refrigerant, and sends out the condensed refrigerant as liquid25
refrigerant. The decompressor 403 causes liquid refrigerant
sent from the condenser 402 to expand, and sends out the
expanded refrigerant as low-temperature and low-pressure liquid
refrigerant.
[0098]30
The evaporator 404 performs heat exchange between indoor
air and the low-temperature and low-pressure liquid refrigerant
sent from the decompressor 403, evaporates the refrigerant, and
sends out the refrigerant as a refrigerant gas. Air from which
26
heat is taken by the evaporator 404 is supplied by the indoor
fan 406 into a room that is a space to be air-conditioned.
[0099]
The compressor 401 of the refrigeration cycle apparatus
400 includes the motor 100 according to the first embodiment,5
and fitting strength between the rotor 1 and the shaft 25 is
high. Since the motor 100 sufficiently withstand load
fluctuation in the compressor 401, reliability of the
refrigeration cycle apparatus 400 can be enhanced.
[0100]10
Although the preferred embodiments have been specifically
described above, the present disclosure is not limited to these
embodiments, and various improvements and modifications may be
made.
DESCRIPTION OF REFERENCE CHARACTERS15
[0101]
1 rotor; 3 stator; 10 rotor core; 11 magnet insertion
hole; 12 slit; 12a inner edge; 12b outer edge; 12c side
edge; 13 rib; 14 center hole; 14a first portion; 14b second
portion; 15 groove portion; 16 inner peripheral core portion;20
16a first portion; 16b second portion; 18 outer periphery; 20
permanent magnet; 25 shaft; 30 stator core; 31 yoke; 32
tooth; 33 slot; 35 coil; 100 motor; 121 curved corner (first
curved corner); 122 curved corner (second curved corner); 300
compressor; 301 compression mechanism; 307 closed container;25
400 refrigeration cycle apparatus; 401 compressor; 402
condenser; 403 decompressor; 404 evaporator; A1, A2, A3
boundary point; D1, D2 distance; R1, R2 radius of curvature.
27
We Claim:
[Claim 1]
A rotor (1) comprising:
a shaft (25);5
an annular rotor core (10) fixed to the shaft (25) and
having a magnet insertion hole (11); and
a permanent magnet (20) disposed in the magnet insertion
hole (11),
wherein the rotor core (10) has:10
a center hole (14) formed at a center of the rotor core
(10) in a radial direction, the shaft (25) being fitted into
the center hole (14);
a plurality of slits (12) formed around the center hole
(14) and each elongated in a circumferential direction of the15
rotor core (10);
a rib (13) formed between two of the plurality of slits
(12), which are adjacent to each other in the circumferential
direction, of the plurality of slits (12); and
a groove portion (15) formed to extend outward in the20
radial direction from the center hole (14),
wherein the groove portion (15) is located on an inner
side of the rib (13) in the radial direction, and
wherein a width T of the rib (13) in the circumferential
direction and a width W of the groove portion (15) in the25
circumferential direction satisfy T > W, and
wherein the width T of the rib (13) in the
circumferential direction increases as a distance to the center
hole (14) decreases.
30
[Claim 2]
The rotor (1) as claimed in claim 1, wherein each of the
plurality of slits (12) has:
a side edge (12c) facing the rib (13),
28
a first curved corner (121) formed on an inner side of
the side edge (12c) in the radial direction, and
a second curved corner (122) formed on an outer side of
the side edge (12c) in the radial direction, and
a radius of curvature R1 of the first curved corner (121)5
and a radius of curvature R2 of the second curved corner (122)
satisfy R1 > R2.
[Claim 3]
The rotor (1) as claimed in claim 2, wherein each of the10
plurality of slits (12) has a width L in the radial direction,
and
wherein the width L and the radius of curvature R1 of the
first curved corner (121) satisfy R1 > L/2.
15
[Claim 4]
The rotor (1) as claimed in any one of claims 1 to 3,
wherein each of the plurality of slits (12) has an inner edge
(12a) facing the center hole (14), and
wherein a distance D from the center hole (14) to a20
center of the inner edge (12a) in the circumferential direction
and a distance D2 from the center hole (14) to an end of the
inner edge (12a) in the circumferential direction satisfy D1 <
D2.
[Claim 5]25
The rotor (1) as claimed in any one of claims 1 to 4,
wherein the rib (13) and the groove portion (15) are located on
an inner side, in the radial direction, of an inter-pole
portion (M) between the magnet insertion hole (11) and another
magnet insertion hole (11) adjacent thereto in the30
circumferential direction.
[Claim 6]
The rotor (1) as claimed in any one of claims 1 to 5,
29
wherein each of the plurality of slits (12) has a width L in
the radial direction, and
wherein the width T of the rib (13) in the
circumferential direction is less than or equal to the width L.
5
[Claim 7]
The rotor (1) as claimed in any one of claims 1 to 6,
wherein the permanent magnet (20) is a rare earth magnet.
[Claim 8]10
A motor (100) comprising:
the rotor (1) as claimed in any one of claims 1 to 7; and
a stator (3) surrounding the rotor (1).
[Claim 9]15
A compressor (300) comprising:
the motor (100) as claimed in claim 8; and
a compression mechanism (301) driven by the motor (100).
[Claim 10]20
A refrigeration cycle apparatus (400) comprising the
compressor (300) as claimed in claim 9, a condenser (402), a
decompressor (403), and an evaporator (404).