1
FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
STATOR AND ELECTRIC MOTOR INCLUDING THE SAME;
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 stator and an electric motor including the
5 stator.
Background Art
[0002]
An electric motor for use in, for example, a compressor includes a ring-shaped
stator and a rotor that is rotatably provided inward of the stator, as described in, for
10 example, Patent Literature 1. The stator includes a stator core and coils. The
stator core includes back yoke portions circularly arranged and teeth that protrude
inwardly from the back yoke portions. The coils are wound around the teeth of the
stator core. The stator core is made up of ring-shaped core sheets that are stacked
on each other. Each of the core sheets includes divided core pieces arranged in a
15 circumferential direction. Ends of back yoke portions of adjacent ones of the core
pieces are joined to each other, whereby the core pieces are circularly arranged.
Citation List
Patent Literature
[0003]
20 Patent Literature 1: Japanese Unexamined Patent Application Publication No.
2013-42620
Summary of Invention
Technical Problem
[0004]
25 In the case where an electric motor is incorporated into a compressor, a stator
is shrink-fitted to an inner surface of a hermetic container that forms an outer
peripheral portion of the compressor. In the case where the stator is configured such
that ends of adjacent back yoke portions are joined to each other in close contact with
each other from an inner surface side to an outer surface side of the stator in the
30 radial direction thereof, the ends of the back yoke portions strike each other when the
3
stator is shrink-fitted to the inner surface of the hermetic container, and a stress is
increased. There is a risk that the increase of the stress will be a cause of an
increase of an iron loss.
[0005]
By contrast, in the case where the stator is configured such 5 that between ends
of adjacent back yoke portions, an opening is provided from the inner surface side to
the outer surface side of the stator in the radial direction thereof, it is possible to
reduce the probability that the ends of the back yoke portions will strike each other
when the stator is shrink-fitted to the inner surface of the hermetic container, and thus
10 also possible to reduce an iron loss that is assumed to occur. However, because of
provision of the opening from the inner surface side to the outer surface side of the
stator in the radial direction, the stiffness of the stator is reduced, and the degree of
the fixation between the stator and the hermetic container is reduced, as a result of
which noise may be more frequently made at the compressor. The above fixation
15 corresponds to a fall-out load and a holding torque.
[0006]
The present disclosure is applied to solve the above problems. It should be
noted that when the stator is shrink-fitted to an inner surface of a hermetic container,
ends of back yoke portions strikes each other, and this may be a cause of an increase
20 of an iron loss. The present disclosure thus relates to a stator and an electric motor
including the stator, which can reduce an iron loss that is assumed to occur, and can
also prevent the stiffness of the stator from being reduced, thereby reducing an
increase in the frequency of occurrence of noise at a compressor.
Solution to Problem
25 [0007]
A stator according to an embodiment of the present disclosure includes: a
stator core including back yoke portions circularly arranged and teeth that protrude
inwardly from the back yoke portions; and coils wound around the teeth of the stator
core. The stator core is made up of first core sheets and second core sheets that
30 are circularly formed and stacked together. The first core sheets and the second
4
core sheets each include divided core pieces arranged in a circumferential direction,
and ends of the back yoke portions of any adjacent two of the core pieces are joined
to each other, whereby the core pieces are circularly arranged. In each of the first
core sheets, between the ends of the back yoke portions of any adjacent two of the
core pieces of the first core sheet, a cutout portion is provided 5 to have an opening
that extends from an inner surface side to an intermediate portion of the first core
sheet in a radial direction thereof, and a close contact portion is provided by joining
the ends of the back yoke portions to each other, such that the close contact portion
extends from the intermediate portion to an outer surface side of the first core sheet.
10 In each of the second core sheets, a close contact portion is provided by joining the
ends of the back yoke portions of any adjacent two of the core pieces of the second
core sheet to each other, such that the close contact portion extends from an inner
surface side to an outer surface side of the second core sheet in a radial direction
thereof.
15 Advantageous Effects of Invention
[0008]
According to the embodiment of the present disclosure, in each first core sheet,
the cutout portions are each provided to extend from the inner surface side to the
intermediate portion of the first core sheet in the radial direction thereof, that is, each
20 cutout portion is provided in a region to which a magnetic flux is assumed to be
concentratedly applied. Because of provision of the cutout portions, it is possible to
reduce an increase in a stress which occurs when the stator is shrink-fitted to an inner
surface of a hermetic container, and also reduce an iron loss that is assumed to
occur. Furthermore, since the cutout portions are provided in the first core sheet, an
25 outer portion of each of the first core sheets can be contracted. It is therefore
possible to increase the stress on the close contact portions, and thus also increase
the stiffness of the close contact portions. Since the Young's modulus of the close
contact portions is increased in accordance with the increase in the stiffness of the
close contact portions, the degree of the fixation between the stator and the hermetic
5
container is also increased. It is therefore possible to reduce the frequency of
occurrence of noise at a compressor.
Brief Description of Drawings
[0009]
[Fig. 1] Fig. 1 is a vertical sectional view schematically 5 illustrating a
configuration of a hermetic compressor provided with an electric motor including a
stator according to an embodiment of the present disclosure.
[Fig. 2] Fig. 2 is a plan view illustrating a stator core of the stator according to
the embodiment of the present disclosure.
10 [Fig. 3] Fig. 3 is a vertical sectional view schematically illustrating part of the
stator core of the stator according to the embodiment of the present disclosure, where
cutout portions are provided in first core sheets.
[Fig. 4] Fig. 4 is a vertical sectional view schematically illustrating part of the
stator core of the stator according to the embodiment of the present disclosure, where
15 close contact portions are provided in the first core sheets.
[Fig. 5] Fig. 5 is an enlarged view illustrating a connection portion of a first core
sheet in the stator according to the embodiment of the present disclosure.
[Fig. 6] Fig. 6 is an enlarged view illustrating a connection portion of a second
core sheet of the stator according to the embodiment of the present disclosure.
20 [Fig. 7] Fig. 7 is an enlarged view illustrating a connection part of a first core
sheet in an existing stator core.
[Fig. 8] Fig. 8 is an enlarged view illustrating a connection portion of a second
core sheet in the existing stator core.
Description of Embodiments
25 [0010]
The embodiment of the present disclosure will be described below with
reference to the above figures. In each of the figures, components that are the same
as or correspond to those in a previous figure are denoted by the same reference
signs, their descriptions will be omitted or simplified as appropriate. Furthermore,
6
the shapes, sizes, positions, etc. of components as illustrated in the figures can be
changed as appropriate within the scope of the embodiment of the present disclosure.
[0011]
Embodiment
Fig. 1 is a vertical sectional view schematically illustrating a 5 configuration of a
hermetic compressor provided with an electric motor including a stator according to
an embodiment of the present disclosure. Fig. 2 is a plan view illustrating a stator
core of the stator according to the embodiment of the present disclosure. Fig. 3 is a
vertical sectional view schematically illustrating part of the stator core of the stator
10 according to the embodiment of the present disclosure, where cutout portions are
provided in first core sheets. Fig. 4 is a vertical sectional view schematically
illustrating part of the stator core of the stator according to the embodiment of the
present disclosure, where close contact portions are provided in the first core sheets.
Fig. 1 illustrates a cylinder type rotary compressor as an example of a hermetic
15 compressor 100. In the hermetic compressor 100, a compression element 2 that
compresses refrigerant gas and an electric element 3 that drives the compression
element 2 are provided in a hermetic container 1.
[0012]
The hermetic container 1 is made up of a lower container 10 formed in the
20 shape of a cylinder having a bottom portion and an upper container 11 that
hermetically covers an upper opening of the lower container 10. In the lower
container 10, the compression element 2 is provided on a lower side of the lower
container 10, and the electric element 3 is provided on an upper side of the lower
container 10. The compression element 2 and the electric element 3 are coupled to
25 each other by a crankshaft 12, and a rotary motion of the electric element 3 is
transmitted to the compression element 2. The compression element 2 compresses
refrigerant gas using the transmitted rotational power and then discharges the
compressed refrigerant gas into the hermetic container 1. That is, the hermetic
container 1 is filled with the compressed refrigerant gas, that is, high-temperature,
30 high-pressure refrigerant gas obtained by the above compression. Refrigerating
7
machine oil for lubricating the compression element 2 is stored in a lower portion of
the hermetic container 1, that is, in the bottom portion of the lower container 10.
[0013]
The compression element 2 includes a cylinder 20, a rolling piston 21, a main
bearing 22, a sub bearing 23, a discharge muffler 24, and a vane 5 (not illustrated).
[0014]
The cylinder 20 is provided with a cylinder chamber in which a compression
chamber and a suction chamber are provided. To the cylinder 20, a suction
connection pipe 25 is connected. In the suction connection pipe 25, suction gas
10 supplied from a refrigeration cycle circuit via a suction muffler 26 flows. The cylinder
chamber is open at both ends in an axial direction of the cylinder chamber.
[0015]
The rolling piston 21 is eccentrically rotated in the cylinder chamber. The
rolling piston 21 is ring-shaped, and an inner periphery of the rolling position 21 is
15 fitted to an eccentric shaft 12a of the crankshaft 12 such that the eccentric shaft 12a
can be slid. That is, the compression element 2 is configured such that the rolling
piston 21 fitted to the eccentric shaft 12a of the crankshaft 12 is provided in the
cylinder chamber, and an end of a vane that is reciprocated radially in a groove
provided in the cylinder 20 is in contact with an outer periphery of the rolling piston 21
20 to define the compression chamber.
[0016]
The main bearing 22 is fitted to a main shaft 12b of the crankshaft 12 in such a
manner as to allow the main shaft 12b to be slid, and closes one of the openings of
the cylinder chamber of the cylinder 20. To the main bearing 22, the discharge
25 muffler 24 is attached. High-temperature, high-pressure gas discharged from a
discharge valve of the main bearing 22 flows into the discharge muffler 24 and is then
discharged from a discharge hole 24a of the discharge muffler 24 into the hermetic
container 1. The sub bearing 23 is fitted to a sub shaft 12c of the crankshaft 12 in
such a manner as to allow the sub shaft 12c to be slid, and closes the other opening
30 of the cylinder chamber of the cylinder 20.
8
[0017]
The electric element 3 is an electric motor including a ring-shaped stator 4 and
a rotor 8 that is rotatably provided inward of the stator 4. The electric element 3 is,
for example, a brushless DC motor.
5 [0018]
The stator 4 includes a stator core 5 and coils 7. As illustrated in Fig. 2, the
stator core 5 has a plurality of back yoke portions 50 circularly arranged and a
plurality of teeth 51 that protrude inwardly from the back yoke portions 50. As
illustrated in Figs. 3 and 4, the stator core 5 is made up of first and second core
10 sheets 5A and 5B that are alternately stacked together. The first and second core
sheets 5A and 5B are each formed by performing punching processing on a thin
magnetic steel sheet. The stator core 5 has an outside diameter greater than an
inside diameter of an intermediate portion of the lower container 10, and is fixed to an
inner surface of the lower container 10 by shrink fitting.
15 [0019]
The first core sheets 5A each include a plurality of divided core pieces 6
arranged in a circumferential direction, and ends of back yoke portions 50 of any
adjacent two of the core pieces 6 are joined to each other, whereby the core pieces 6
are circularly arranged. Similarly, the second core sheets 5B each include a plurality
20 of divided core pieces 6 arranged in a circumferential direction, and ends of back
yoke portions 50 of any adjacent two of the core pieces 6 are joined to each other,
whereby the core pieces 6 are circularly arranged. The core pieces 6 of the first
core sheets 5A and the core pieces 6 of the second core sheets 5B are rotatably
connected by rotation shafts 52.
25 [0020]
Fig. 5 is an enlarged view illustrating a connection portion of a first core sheet
in the stator according to the embodiment of the present disclosure. Fig. 6 is an
enlarged view illustrating a connection portion of a second core sheet in the stator
according to the embodiment of the present disclosure. As illustrated in Fig. 5,
30 between ends of any two adjacent back yoke portions 50 of a first core sheet 5A, a
9
cutout portion 60 and a close contact portion 61 are provided. The cutout portion 60
includes an opening which extends from an inner surface side to an intermediate
portion of the first core sheet 5A in a radiation direction thereof. The close contact
portion 61 is located from the intermediate portion to an outer surface side of the first
core sheet 5A. At the close contact portion 61, the ends of the 5 adjacent back yoke
portions 50 are jointed to each other. By contrast, as illustrated in Fig. 6, between
any two adjacent back yoke portions 50 of a second core sheet 5B, a close contact
portion 62 is provided to extend from an inner surface side to an outer surface side of
the second core sheet 5B in a radial direction thereof.
10 [0021]
In the stator 4 shrink-fitted to the hermetic container 1, in a region which
extends from the inner surface side to the intermediate portion in the radial direction
and in which a magnetic flux is assumed to be concentratedly applied, the cutout
portion 60 is provided; and on the other hand, in a region which extends from the
15 intermediate portion to the outer surface side and in which a magnetic flux is not
assumed to be concentratedly applied, a close contact portion 61 is provided. It
should be noted that the region in which a magnetic flux is not assumed to be
concentratedly applied is, for example, a region that is located from the outer surface
side of the stator 4 to a position that is separated from the outer surface side of the
20 stator 4 by approximately 2 mm in the radial direction. The region in which a
magnetic flux is assumed to be concentratedly applied is, for example, a region that is
located from a position that is separated from the outer surface side by more than
approximately 2 mm to the inner surface side.
[0022]
25 The coils 7 are wound around the teeth 51 of the stator core 5, with insulating
members 70 interposed between the coils 7 and the teeth 51. As illustrated in Fig. 1,
leads 71 through which a voltage is applied to the coils 7 to cause an electric current
to flow through the coils 7 are connected to the coils 7. The leads 71 are also
connected to a glass terminal 13 provided on the upper container 11, and are
30 supplied with power from the outside of the hermetic container 1.
10
[0023]
The rotor 8 includes a rotor core 80, a permanent magnet 81, an upper balance
weight 82, a lower balance weight 83, and a rivet 84. The rotor core 80 is made up
of stacked core sheets, each of which is formed by performing punching processing
on a thin magnetic steel sheet. The permanent magnet 81 is provided 5 in a magnet
insertion hole formed in the rotor core 80.
[0024]
The upper balance weight 82 is provided on an upper end portion of the rotor
core 80. The lower balance weight 83 is provided on a lower end portion of the rotor
10 core 80. The upper balance weight 82 and the lower balance weight 83 are provided
to correct an uneven rotary motion of the rotor 8 that is caused by displacement of a
rotation torque in compression steps such as suction, compression, and discharge of
refrigerant gas in the compression element 2. The upper balance weight 82 and the
lower balance weight 83 also serve as end plates that prevent the permanent magnet
15 81 from flying off from the position thereof. The upper balance weight 82 and the
lower balance weight 83 may be members other than the end plates.
[0025]
The rivet 84 fixes the upper balance weight 82, the lower balance weight 83,
and the rotor core 80.
20 [0026]
Fig. 7 is an enlarged view illustrating a connection portion of a first core sheet
in an existing stator core. Fig. 8 is an enlarged view illustrating a connection portion
of a second core sheet in the existing stator core. The existing stator core also
includes a plurality of back yoke portions 50 circularly arranged and a plurality of teeth
25 51 that protrude inwardly from the back yoke portions 50. The stator core is made
up of first and second core sheets 5C and 5D that are circularly formed and
alternately stacked together.
[0027]
Each first core sheet 5C and each second core sheet 5D each have a plurality
30 of divided core pieces 6 that are arranged in a circumferential direction, and ends of
11
back yoke portions 50 of any adjacent two of the core pieces 6 are joined to each
other, whereby the core pieces 6 are circularly arranged. As illustrated in Fig. 7, in
each first core sheet 5C, between ends of any two adjacent back yoke portions 50, an
opening 63 is provided to extend from an inner surface side to an outer surface side
of the first core sheet 5C in a radial direction thereof. As illustrated 5 in Fig. 8, in each
second core sheet 5D, ends of any two adjacent back yoke portions 50 are jointed to
each other to form a close contact portion 64 that extends from an inner surface side
to an outer surface side in a radial direction of the second core sheet 5D.
[0028]
10 In a stator including the stator core as illustrated in Figs. 7 and 8, because of
the provision of the opening 63 in the first core sheet 5C, it is possible to reduce the
probability that ends of back yoke portions 50 will strike each other and as a result a
stress will increase, when an outer surface of the stator is shrink-fitted to an inner
surface of the hermetic container 1, and thus possible to reduce an iron loss.
15 However, in the case where the opening 63 is provided to extend from the inner
surface side to the outer surface side as in the stator including the existing stator core
as illustrated in Figs. 7 and 8, although the iron loss can be reduced, the stiffness of
the stator may be reduced. As a result, the degree of the fixation between the stator
and the hermetic container 1 may be reduced, and as a result, nose is more
20 frequently made at a hermetic compressor.
[0029]
By contrast, in the stator 4 according to the embodiment of the present
disclosure, since the region of each first core sheet 5A to which a magnetic flux is
assumed to be concentratedly applied and which extends from the inner surface side
25 to the intermediate portion of the first core sheet 5A in the radial direction thereof is
provided as the cutout portion 60, a stress which acts when the stator 4 is shrink-fitted
to the inner surface of the hermetic container 1 can be reduced by the cutout portion
60, and an iron loss that is assumed to occur can be reduced. Furthermore, in the
stator 4, because of provision of the cutout portion 60 in the first core sheet 5A, the
30 stator 4 can be contracted, that is, the outer diameter of the stator 4 can be reduced,
12
thereby increasing the stress on the close contact portion 61. Thus, the stiffness of
the close contact portion 61 can be increased. Because the Young's modulus is
increased in accordance with the increase of the stiffness, the fixation between the
stator 4 and the hermetic container 1 is increased. It is therefore possible to reduce
the frequency of noise of the hermetic compressor 100. Furthermore, 5 the stator 4 is
configured such that the close contact portion 61 is provided to extend from the
intermediate portion, which is a portion where a magnetic flux is not assumed to be
concentratedly applied, to the outside surface side. Because of this configuration,
even if a stress acts on the close contact portion 61 during shrink fitting, it is possible
10 to reduce degradation of magnetic characteristics of the magnetic steel sheet that is
caused by the stress, and also reduce an ion loss that is assumed to occur.
Furthermore, in the stator 4, ends of any two adjacent back yoke portions 50 in each
second core sheet 5B are connected to each other, thereby forming a close contact
portion 62 that extends from the inner surface side to the outer surface side of the
15 second core sheet 5B in the radial direction thereof. In such a manner, since the
close contact portion 61 is provided, it is possible to increase the roundness of the
inner surface side of the inner diameter side of the stator 4 while increasing the
stiffness of the stator 4 in the above stacking direction. Thus, the structure can be
stabilized.
20 [0030]
In the stator 4 according to the embodiment of the present disclosure, the stator
core 5 is made up of the first and second core sheets 5A and 5B that are alternately
stacked together, whereby the function of the first core sheets 5A and that of the
second core sheets 5B can be effectively fulfilled in a well-balanced manner.
25 [0031]
The above description of the configuration of the embodiment is not restrictive.
For example, although the cylinder type rotary compressor is illustrated as an
example of the hermetic compressor 100, the hermetic compressor 100 may be a
compressor having a different structure from that of the cylinder type rotary
30 compressor. Furthermore, the configuration of the hermetic compressor 100 is not
13
limited to the configuration as illustrated in the drawings, and the hermetic
compressor 100 may include other components. Furthermore, although it is
described above that the stator core 5 is made up of the first and second core sheets
5A and 5B that are alternately stacked together, it is not restrictive. For example, it is
also possible to apply a configuration in which first and second core 5 sheets 5A and 5B
are alternately stacked such that for every two first core sheets 5A, a single second
core sheet 5B is provided. That is, various changes, applications, and uses made by
a person with ordinary skill in the art as occasion arises also fall under the subject
matter (technical scope) of the present disclosure.
10 Reference Signs List
[0032]
1 hermetic container, 2 compression element, 3 electric element
(electric motor), 4 stator, 5 stator core, 5A,5C first core sheet, 5B,5D
second core sheet, 6 core piece, 7 coil, 8 rotor, 10 lower container, 11
15 upper container, 12 crankshaft, 12a eccentric shaft, 12b main shaft, 12c
sub shaft, 13 glass terminal, 20 cylinder, 21 rolling piston, 22 main
bearing, 23 sub bearing, 24 discharge muffler, 24a discharge hole, 25
suction connection pipe, 26 suction muffler, 50 back yoke portion, 51 tooth,
52 rotation shaft, 60 cutout portion, 61,62 close contact portion, 63
20 opening, 64 close contact portion, 70 insulating member, 71 lead, 80
rotor core, 81 permanent magnet, 82 upper balance weight, 83 lower
balance weight, 84 rivet, 100 hermetic compressor
14
We Claim:
[Claim 1]
A stator comprising:
a stator core including back yoke portions circularly arranged 5 and teeth that
protrude inwardly from the back yoke portions; and
coils wound around the teeth of the stator core,
wherein the stator core is made up of first core sheets and second core sheets
that are circularly formed and stacked together,
10 wherein the first core sheets and the second core sheets each include divided
core pieces arranged in a circumferential direction, and ends of the back yoke
portions of any adjacent two of the core pieces are joined to each other, whereby the
core pieces are circularly arranged,
wherein in each of the first core sheets, between the ends of the back yoke
15 portions of any adjacent two of the core pieces of the first core sheet, a cutout portion
is provided to have an opening that extends from an inner surface side to an
intermediate portion of the first core sheet in a radial direction thereof, and a close
contact portion is provided by joining the ends of the back yoke portions to each
other, such that the close contact portion extends from the intermediate portion to an
20 outer surface side of the first core sheet, and
wherein in each of the second core sheets, a close contact portion is provided
by joining the ends of the back yoke portions of any adjacent two of the core pieces of
the second core sheet to each other, such that the close contact portion extends from
an inner surface side to an outer surface side of the second core sheet in a radial
25 direction thereof.
[Claim 2]
The stator of claim 1, wherein in the stator core, the first core sheets and the
second core sheets are alternately stacked together.
[Claim 3]
30 An electric motor comprising:
15
the stator of claim 1 or 2; and
a rotor rotatably provided inward of the stator.