U.S. patent application number 14/280825 was filed with the patent office on 2015-01-01 for linear compressor.
This patent application is currently assigned to LG ELECTRONICS INC.. The applicant listed for this patent is Sangsub JEONG. Invention is credited to Sangsub JEONG.
Application Number | 20150004030 14/280825 |
Document ID | / |
Family ID | 51176050 |
Filed Date | 2015-01-01 |
United States Patent
Application |
20150004030 |
Kind Code |
A1 |
JEONG; Sangsub |
January 1, 2015 |
LINEAR COMPRESSOR
Abstract
A linear compressor is provided. The linear compressor may
include a cylinder that forms a compression space for a
refrigerant, a piston that reciprocates in an axial direction
inside of the cylinder, and a linear motor that supplies power to
the piston. The linear motor may include an outer stator including
a first stator magnetic pole, a second stator magnetic pole, and an
opening defined between the first stator magnetic pole and the
second stator magnetic pole; an inner stator disposed apart from
the outer stator to form an air gap therebetween; and a permanent
magnet movably disposed in the air gap between the outer stator and
the inner stator and having three poles. The three poles may
include two end magnetic poles, and a central magnetic pole
disposed between the two end magnetic poles. The piston may be
moveable by a stroke between a top dead center position and a
bottom dead center position, and a length of the first stator
magnetic pole or the second stator magnetic pole may be greater
than a length of the stroke.
Inventors: |
JEONG; Sangsub; (Seoul,
KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
JEONG; Sangsub |
Seoul |
|
KR |
|
|
Assignee: |
LG ELECTRONICS INC.
Seoul
KR
|
Family ID: |
51176050 |
Appl. No.: |
14/280825 |
Filed: |
May 19, 2014 |
Current U.S.
Class: |
417/420 |
Current CPC
Class: |
H02K 33/16 20130101;
F04D 25/06 20130101; F04B 35/045 20130101; H02K 7/14 20130101 |
Class at
Publication: |
417/420 |
International
Class: |
F04D 25/06 20060101
F04D025/06 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 28, 2013 |
KR |
10-2013-075512 |
Claims
1. A linear compressor, comprising: a cylinder that forms a
compression space for a refrigerant; a piston that reciprocates in
an axial direction inside of the cylinder; and a linear motor that
supplies power to the piston, wherein the linear motor comprises:
an outer stator comprising a first stator magnetic pole, a second
stator magnetic pole, and an opening defined between the first
stator magnetic pole and the second stator magnetic pole; an inner
stator disposed apart from the outer stator to form an air gap
therebetween; and a permanent magnet movably disposed in the air
gap between the outer stator and the inner stator and having three
poles, wherein the three poles include: two end magnetic poles; and
a central magnetic pole disposed between the two end magnetic
poles, wherein the piston is moveable by a stroke between a top
dead center position and a bottom dead center position, and wherein
a length of the first stator magnetic pole or the second stator
magnetic pole is greater than a length of the stroke.
2. The linear compressor according to claim 1, wherein the central
magnetic pole has a length greater than a length of any one of the
two end magnetic poles.
3. The linear compressor according to claim 2, wherein the length
of the central magnetic pole is twice or less than the length of
the any one of the two end magnetic poles.
4. The linear compressor according to claim 1, wherein a length of
the central magnetic pole is equal to or less than a sum of lengths
of the two end magnetic poles.
5. The linear compressor according to claim 1, wherein an axial
direction length of the opening is equal to or greater than a
radial direction height of the air gap.
6. The linear compressor according to claim 1, wherein a length of
any one of the two end magnetic poles is approximately 90% or more
of a length of the first stator magnetic pole or the second stator
magnetic pole.
7. The linear compressor according to claim 1, wherein the two end
magnetic poles comprise: a first pole coupled to the central
magnetic pole at a first interface; and a second pole coupled to
the central magnetic pole at a second interface.
8. The linear compressor according to claim 7, wherein the first
interface reciprocates in an axial direction between both ends of
the first stator magnetic pole, based on a center of the first
stator magnetic pole, and the second interface reciprocates in an
axial direction between both ends of the second stator magnetic
pole, based on a center of the second stator magnetic pole.
9. The linear compressor according to claim 7, wherein the first
pole comprises an end at a position that faces the first interface,
and wherein the end of the first pole is positioned outside of the
outer stator when the piston is positioned at the bottom dead
center position.
10. The linear compressor according to claim 9, wherein the end of
the first pole is positioned at an end of or outside of the first
stator magnetic pole when the piston is positioned at the top dead
center position.
11. The linear compressor according to claim 1, wherein the two end
magnetic poles comprise a first pole coupled to a first side of the
central magnetic pole, and wherein at least a portion of the first
pole is positioned in the air gap between the first stator magnetic
pole and the inner stator.
12. The linear compressor according to claim 11, wherein the two
end magnetic poles comprise a second pole coupled to a second side
of the central magnetic pole, and wherein at least a portion of the
second pole is positioned in the air gap between the second stator
magnetic pole and the inner stator.
13. The linear compressor according to claim 1, wherein the opening
is defined between a tip of the first stator magnetic pole and a
tip of the second stator magnetic pole, at a side of an
accommodation space that accommodates a coil.
14. The linear compressor according to claim 1, wherein the piston
and the cylinder are made of aluminum or aluminum alloy.
15. A linear compressor, comprising: a cylinder that forms a
compression space for a refrigerant; a piston that reciprocates in
an axial direction inside of the cylinder; and a linear motor that
supplies power to the piston, wherein the linear motor comprises:
an outer stator comprising a first stator magnetic pole, a second
stator magnetic pole, and an opening defined between the first
stator magnetic pole and the second stator magnetic pole; an inner
stator disposed apart from the outer stator to form an air gap
therebetween; and a permanent magnet movably disposed in the air
gap between the outer stator and the inner stator and having three
poles, wherein the three poles include: two end magnetic poles; and
a central magnetic pole disposed between the two end magnetic
poles, wherein the piston is moveable by a stroke between a top
dead center position and a bottom dead center position, wherein a
length of the first stator magnetic pole or the second stator
magnetic pole is greater than a length of the stroke, and wherein
the permanent magnet is made of a ferrite material.
16. The linear compressor according to claim 15, wherein the
central magnetic pole has a length greater than a length of any one
of the two end magnetic poles.
17. The linear compressor according to claim 15, wherein a length
of the central magnetic pole is equal to or less than a sum of
lengths of the two end magnetic poles.
18. The linear compressor according to claim 15, wherein an axial
direction length of the opening is equal to or greater than a
radial direction height of the air gap.
19. The linear compressor according to claim 15, wherein a length
of any one of the two end magnetic poles is approximately 90% or
more of a length of the first stator magnetic pole or the second
stator magnetic pole.
20. The linear compressor according to claim 15, wherein the two
end magnetic poles comprise: a first pole coupled to the central
magnetic pole at a first interface; and a second pole coupled to
the central magnetic pole at a second interface.
21. The linear compressor according to claim 20, wherein the first
interface reciprocates in an axial direction between both ends of
the first stator magnetic pole, based on a center of the first
stator magnetic pole, and the second interface reciprocates in an
axial direction between both ends of the second stator magnetic
pole, based on a center of the second stator magnetic pole.
22. The linear compressor according to claim 20, wherein the first
pole comprises an end at a position that faces the first interface,
and wherein the end of the first pole is positioned outside of the
outer stator when the piston is positioned at the bottom dead
center position.
23. The linear compressor according to claim 22, wherein the end of
the first pole is positioned at an end of or outside of the first
stator magnetic pole when the piston is positioned at the top dead
center position.
24. The linear compressor according to claim 15, wherein the two
end magnetic poles comprise a first pole coupled to a first side of
the central magnetic pole, wherein at least a portion of the first
pole is positioned in the air gap between the first stator magnetic
pole and the inner stator, and wherein the two end magnetic poles
comprise a second pole coupled to a second side of the central
magnetic pole, and wherein at least a portion of the second pole is
positioned in the air gap between the second stator magnetic pole
and the inner stator.
25. The linear compressor according to claim 24, wherein the piston
and the cylinder are made of aluminum or aluminum alloy.
Description
CROSS-REFERENCE TO RELATED APPLICATION(S)
[0001] The present application claims priority under 35 U.S.C. 119
and 35 U.S.C. 365 to Korean Patent Application No. 10-2013-0075512,
filed in Korea on Jun. 28, 2013, which is hereby incorporated by
reference in its entirety.
BACKGROUND
[0002] 1. Field
[0003] A linear compressor is disclosed herein.
[0004] 2. Background
[0005] In general, compressors may be mechanisms that receive power
from power generation devices, such as electric motors or turbines,
to compress air, refrigerants, or other working gases, thereby
increasing a pressure of the working gas. Compressors are widely
used in home appliances or industrial machineries, such as
refrigerators and air-conditioners.
[0006] Compressors may be largely classified into reciprocating
compressors, in which a compression space, into and from which a
working gas, such as a refrigerant, is suctioned and discharged, is
defined between a piston and a cylinder to compress the refrigerant
while the piston is linearly reciprocated within the cylinder;
rotary compressors, in which a compression space, into and from
which a working gas, such as a refrigerant, is suctioned and
discharged, is defined between a roller, which is eccentrically
rotated, and a cylinder to compress the refrigerant while the
roller is eccentrically rotated along an inner wall of the
cylinder; and scroll compressors in which a compression space, into
and from which a working gas, such as a refrigerant, is suctioned
and discharged, is defined between an orbiting scroll and a fixed
scroll to compress the refrigerant while the orbiting scroll is
rotated along the fixed scroll. In recent years, among the
reciprocating compressors, linear compressors having a simple
structure in which a piston is directly connected to a drive motor,
which is linearly reciprocated, to improve compression efficiency
without mechanical loss due to switching in moving, are being
actively developed. Generally, such a linear compressor is
configured to suction and compress a refrigerant while a piston is
linearly reciprocated within a cylinder by a linear motor in a
sealed shell, thereby discharging the compressed refrigerant.
[0007] The linear motor has a structure in which a permanent magnet
is disposed between an inner stator and an outer stator. The
permanent magnet may be linearly reciprocated by a mutual
electromagnetic force between the permanent magnet and the inner
(or outer) stator. Also, as the permanent magnet is operated in a
state in which the permanent magnet is connected to the piston, the
refrigerant may be suctioned and compressed while the piston is
linearly reciprocated within the cylinder and then be
discharged.
[0008] A linear compressor according to the related art is
disclosed in Korean Patent Publication No. 10-2010-0010421. The
linear compressor according to the related art includes a linear
motor, which is provided with an outer stator having a core and a
coil-wound body, an inner stator, and a permanent magnet. One end
of a piston is connected to the permanent magnet. The permanent
magnet may include one magnet having a single polarity, and may be
a rare-earth magnet.
[0009] When the permanent magnet is linearly reciprocated by mutual
electromagnetic force between the inner stator and the outer
stator, the piston linearly reciprocates in a cylinder along with
the permanent magnet. However, rare earth metals are expensive.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] Embodiments will be described in detail with reference to
the following drawings in which like reference numerals refer to
like elements, and wherein:
[0011] FIG. 1 is a cross-sectional view of a linear compressor
according to an embodiment;
[0012] FIG. 2 is an enlarged view of a portion "A" of the linear
compressor of FIG. 1;
[0013] FIGS. 3 and 4 are cross-sectional views illustrating a
reciprocating motion of a permanent magnet in an axial direction
according to operation a linear motor of the linear compressor of
FIG. 1;
[0014] FIGS. 5 and 6 are cross-sectional views schematically
illustrating the linear motor of FIGS. 3-4;
[0015] FIG. 7A illustrates magnetic flux in a linear motor having a
magnetic pole tip distance of T1, FIG. 7B illustrates magnetic flux
in a linear motor having a magnetic pole tip distance of T2, and
FIG. 7C illustrates a magnitude of leakage magnetic flux in the
linear motors of FIGS. 7A and 7B;
[0016] FIG. 8 is a cross-sectional view of a linear motor
illustrating a position of a permanent magnet when a piston is
positioned at a bottom dead center (BDC) position, according to an
embodiment;
[0017] FIG. 9 is a cross-sectional view of a linear motor
illustrating a position of a permanent magnet when a piston is
positioned at a top dead center (TDC) position, according to an
embodiment;
[0018] FIG. 10 is a graph showing a magnitude of a thrust generated
according to lengths of magnetic poles at both ends, in a permanent
magnet according to an embodiment;
[0019] FIG. 11 is a graph showing variations in a cogging force
according to lengths of magnetic poles at both ends, in a permanent
magnet according to an embodiment;
[0020] FIG. 12 is a graph showing a magnitude of a thrust generated
according to a length of a central magnetic pole, in a permanent
magnet according to an embodiment; and
[0021] FIG. 13 is a graph showing variations in a cogging force
according to a length of a central magnetic pole, in a permanent
magnet according to an embodiment.
DETAILED DESCRIPTION
[0022] Hereinafter, embodiments will be described with reference to
accompanying drawings. However, the scope is not limited to
embodiments disclosed herein, and thus, a person skilled in the
art, who understood the scope, would easily suggest other
embodiments within the same scope thereof.
[0023] FIG. 1 is a cross-sectional view of a linear compressor
according to an embodiment. Referring to FIG. 1, the linear
compressor 10 may include a cylinder 120 disposed in a shell 100, a
piston 130 that linearly reciprocates inside the cylinder 120, and
a motor assembly 200, which may be in the form of a linear motor,
that exerts a drive force on the piston 130. The shell 100 may
include an upper shell and a lower shell.
[0024] The shell 100 may further include an inlet 110, through
which a refrigerant may flow into the shell 100, and an outlet 105,
through which the refrigerant compressed inside the cylinder 120
may be discharged from the shell 100. The refrigerant suctioned in
through the inlet 101 may flow into the piston 130 via a suction
muffler 140. While the refrigerant is passing through the suction
muffler 140, noise may be reduced.
[0025] The piston 130 may be made of a nonmagnetic material, such
as an aluminum-based material, for example, aluminum or aluminum
alloy. As the piston 130 may be made of the aluminum-based
material, magnetic flux generated in the motor assembly 200 may be
delivered to the piston 130, thereby preventing the magnetic flux
from being leaked outside of the piston 130. The piston 130 may be
formed by forging, for example.
[0026] The cylinder 120 may be made of a nonmagnetic material, such
as an aluminum-based material, for example, aluminum or aluminum
alloy. The cylinder 120 and the piston 130 may have a same material
composition ratio, that is, type and composition ratio.
[0027] As the cylinder 120 may be made of the aluminum-based
material, magnetic flux generated in the motor assembly 200 may be
delivered to the cylinder 120, thereby preventing the magnetic flux
from being leaked outside of the cylinder 120. The cylinder 120 may
be formed by extruded rod processing, for example.
[0028] The piston 130 and the cylinder 120 may be made of the same
material, for example, aluminum, and thus, may have a same thermal
expansion coefficient. During operation of the linear compressor
10, a high-temperature environment (about 100 ) may be created in
the shell 100. At this time, the piston 130 and the cylinder 120
may have the same thermal expansion coefficient, and thus, may have
a same amount of thermal deformation. As the piston 130 and the
cylinder 120 may be thermally deformed in different amounts or
directions, it is possible to prevent interference with the
cylinder 120 during movement of the piston 130.
[0029] A compression space P to compress the refrigerant by the
piston 130 may be defined in the cylinder 120. A suction hole 131a,
through which the refrigerant may be introduced into the
compression space P, may be defined in the piston 130, and a
suction valve 132 to selectively open the suction hole 131a may be
disposed at a side of the suction hole 131a.
[0030] A discharge valve assembly 170, 172, and 174 to discharge
the refrigerant compressed in the compression space P may be
disposed at a side of the compression space P. That is, the
compression space P may be formed between an end of the piston 130
and the discharge valve assembly 170, 172, and 174.
[0031] The discharge valve assembly 170, 172, and 174 may include a
discharge cover 172, in which a discharge space of the refrigerant
may be defined; a discharge valve 170, which may be opened and
introduce the refrigerant into the discharge space when the
pressure of the compression space P is not less than a discharge
pressure; and a valve spring 174, which may be disposed between the
discharge valve 170 and the discharge cover 172 to exert an elastic
force in an axial direction. The term "axial direction" used herein
may refer to a direction in which the piston linearly reciprocates,
that is, a substantially horizontal direction in FIG. 1, while the
term "radial direction" may refer to a direction substantially
perpendicular to the reciprocating direction of the piston 130,
that is, a substantially vertical direction in FIG. 1.
[0032] The suction valve 132 may be disposed at a first side of the
compression space P, and the discharge valve 170 may be disposed at
a second side of the compression space P, that is, at an opposite
side to the suction valve 132. While the piston 130 linearly
reciprocates inside the cylinder 120, the suction valve 132 may be
opened to allow the refrigerant to be introduced into the
compression space P when the pressure of the compression space P is
lower than the discharge pressure and not greater than a suction
pressure. In contrast, when the pressure of the compression space P
is not less than the suction pressure, the refrigerant of the
compression space P may be compressed in a state in which the
suction valve 132 is closed.
[0033] If the pressure of the compression space P is the discharge
pressure or greater, the valve spring 174 may be deformed to open
the discharge valve 170, and the refrigerant may be discharged from
the compression space P into a discharge space of the discharge
cover 172. The refrigerant of the discharge space may flow into a
loop pipe 178 via a discharge muffler 176. The discharge muffler
176 may reduce flow noise of the compressed refrigerant, and the
loop pipe 178 may guide the compressed refrigerant to the outlet
105. The loop pipe 178 may be coupled to the discharge muffler 176
and curvedly extend to be coupled to the outlet 105.
[0034] The linear compressor 10 may further include a frame 110.
The frame 110, which may fix the cylinder 120 within the shell 100,
may be integrally formed with the cylinder 120 or may be coupled to
the cylinder 120 by means of a separate fastening member, for
example. The discharge cover 172 and the discharge muffler 176 may
be coupled to the frame 110.
[0035] The motor assembly 200 may include an outer stator 210,
which may be fixed to the frame 110 and disposed so as to surround
the cylinder 120, an inner stator 220 disposed apart from an inside
of the outer stator 210, and a permanent magnet 230 disposed in a
space between the outer stator 210 and the inner stator 220. The
permanent magnet 230 may linearly reciprocate due to a mutual
electromagnetic force between the outer stator 210 and the inner
stator 220. The permanent magnet 230 may include a single magnet
having one pole facing the outer stator 210, or multiple magnets
having three poles facing the outer stator 210. In the case of the
permanent magnet 230 having three poles, one surface there may have
a polar distribution of N-S-N, and the other surface thereof may
have a polar distribution of S-N-S
[0036] The permanent magnet 230 may be coupled to the piston 130 by
a connection member 138. The connection member 138 may extend to
the permanent magnet 230 from an end of the piston 130. As the
permanent magnet 230 linearly moves, the piston 130 may linearly
reciprocate in an axial direction along with the permanent magnet
230.
[0037] The outer stator 210 may include a bobbin 213, a coil 215,
and a stator core 211. The coil 215 may be wound in a
circumferential direction of the bobbin 213. The coil 215 may have
a polygonal section, for example, a hexagonal section. The stator
core 211 may be formed by stacking a plurality of laminations in a
circumferential direction, and may be disposed to surround the
bobbin 213 and the coil 215.
[0038] A stator cover 240 may be disposed at a side of the outer
stator 210. A first end of the outer stator 210 may be supported by
the frame 110, and a second end of the outer stator 210 may be
supported by the stator cover 240.
[0039] The inner stator 220 may be fixed to an outer circumference
of the cylinder 120. The inner stator 220 may be formed by stacking
a plurality of laminations at an outer side of the cylinder 120 in
a circumferential direction.
[0040] The linear compressor 10 may further include a supporter 135
that supports the piston 130, and a back cover 115 that extends
toward the inlet 101 from the piston 130. The back cover 115 may be
disposed to cover at least a portion of the suction muffler
140.
[0041] The linear compressor 10 may include a plurality of springs
151 and 155, a natural frequency of each of which may be adjusted
so as to allow the piston 130 to perform resonant motion. The
plurality of springs 151 and 155 may include a plurality of first
springs 151 supported between the supporter 135 and the stator
cover 240, and a plurality of second springs 155 supported between
the supporter 135 and the back cover 115.
[0042] The plurality of first springs 151 may be provided at both
sides of the cylinder 120 or the piston 130, and the plurality of
second springs 155 may be provided at a front of the cylinder 120
or the piston 130. The term "front" used herein may refer to a
direction oriented toward the inlet 101 from the piston 130. The
term "rear" may refer to a direction oriented toward the discharge
valve assembly 170, 172, and 174 from the inlet 101. These terms
may also be equally used in the following description.
[0043] A predetermined amount of oil may be stored on an inner
bottom surface of the shell 100. An oil supply device 160 to pump
oil may be provided in a lower portion of the shell 100. The oil
supply device 160 may be operated by vibration generated according
to the linear reciprocating motion of the piston 130 to thereby
pump the oil upward.
[0044] The linear compressor 10 may further include an oil supply
pipe 165 that guides flow of the oil from the oil supply device
160. The oil supply pipe 165 may extend from the oil supply device
160 to a space between the cylinder 120 and the piston 130. The oil
pumped from the oil supply device 160 may be supplied to the space
between the cylinder 120 and the piston 130 via the oil supply pipe
165, and perform cooling and lubricating operations.
[0045] FIG. 2 is an enlarged view of a portion "A" of the linear
compressor of FIG. 1. FIGS. 3 and 4 are cross-sectional views
illustrating a reciprocating motion of the permanent magnet in an
axial direction according to operation of a linear motor of the
linear compressor of FIG. 1.
[0046] Referring to FIGS. 2 to 4, the outer stator 210 according to
embodiments may include the stator core 211, in which the plurality
of laminations may be stacked in the circumferential direction. The
stator core 211 may be configured such that a first core 211a and a
second core 211b are coupled at a coupling portion 211c.
[0047] An accommodation space, in which the bobbin 213 and the coil
215 may be disposed, may be defined in the stator core 211, and an
opening 219 may be provided at a side of the accommodation space.
That is, the first core 211a and the second core 211b may be
coupled, such that the stator core 211 has the opening 219 at a
central portion thereof to thereby have a C-shape.
[0048] The first core 211a may include a first stator magnetic pole
217 that acts with the permanent magnet 230. The second core 211b
may include a second stator magnetic pole 218 that acts with the
permanent magnet 230. The first stator magnetic pole 217 and the
second stator magnetic pole 218 may be portions of the first and
second cores 211a and 211b, respectively. The opening 219 may be a
space between the first stator magnetic pole 217 and the second
magnetic pole 218.
[0049] The permanent magnet 230 may be formed of a ferrite
material, which may be relatively inexpensive. The permanent magnet
230 may include multiple poles 231, 232 and 233, polarities of
which may be alternately arranged. The multiple poles 231, 232, and
233 may include a first pole 231, a second pole 232, and a third
pole 233, which may be coupled to each other.
[0050] When a current is applied to the motor assembly 200, a
current may flow through the coil 215, a magnetic flux may be
formed around the coil 215 by the current flowing through the coil
215, and the magnetic flux may flow along the outer stator 210 and
the inner stator 220 while forming a closed circuit. The first
stator magnetic pole 217 may form one of an N-pole or a S-pole, and
the second stator magnetic pole 218 may form the other one of the
N-pole or the S-pole (see solid line arrow A in FIG. 5).
[0051] The multiple poles 231, 232, and 233 (permanent magnet 230)
may linearly reciprocate in an axial direction between the outer
stator 210 and the inner stator 220 by means of an interaction
force of the magnetic flux flowing through the outer stator 210 and
the inner stator 220 and the magnetic flux formed by the multiple
poles 231, 232, and 233 (permanent magnet 230). The piston 130 may
move inside the cylinder 120 by motions of the multiple poles 231,
232, and 233 (permanent magnet 230).
[0052] When the current flowing through the coil 215 changes its
direction, a direction of the magnetic flux passing through the
outer stator 210 and the inner stator 220 may be changed. That is,
in the above-described example, polarities of the first and second
stators 217 and 218 may be interchanged. Therefore, a movement
direction of the multiple poles 231, 232, and 233 (permanent magnet
230) may be reversed, and therefore, a movement direction of the
piston 130 may also be changed. In this way, as the direction of
the magnetic flux is changed repetitively, the piston 130 may
linearly reciprocate.
[0053] FIG. 3 illustrates a mode in which first spring 151 is
elongated when the multiple poles 231, 232, and 233 (permanent
magnet 230) move in a first direction. FIG. 4 illustrates a mode in
which the second spring 151 is compressed when the multiple poles
231, 232, and 233 (permanent magnet 230) move in a second
direction.
[0054] The multiple poles 231, 232, and 233 (permanent magnet 230)
and the piston 130 may linearly reciprocate by repeating the modes
of FIGS. 3 and 4. For example, when the permanent magnet 230 is at
a position shown in FIG. 3, the piston 130 is positioned at a
bottom dead center (BDC) position, and when the permanent magnet
230 is at a position shown in FIG. 4, the piston 130 is positioned
at a top dead center (TDC) position.
[0055] The term BDC may refer to a position when the piston 130 is
at a lowest position inside the cylinder 120, that is, a position
when the piston 130 is disposed farthest away from the compression
space P. The term TDC may refer to a position when the piston 130
is at a highest position inside the cylinder 120, that is, a
position when the piston 130 is disposed closest to the compression
space P.
[0056] Hereinafter, a structure of the motor assembly 200 will be
more fully described with reference to the drawings.
[0057] FIGS. 5 and 6 are cross-sectional views schematically
illustrating the linear motor of FIGS. 3-4. Referring to FIG. 5,
according to an embodiment, the first stator magnetic pole 217 of
the first core 211a and the second stator magnetic pole 218 of the
second core 211b may be disposed apart from each other with respect
to the opening 219.
[0058] In more detail, a first tip 217a may be provided at an end
of the first stator magnetic pole 217, and a second tip 218a may be
provided at or on the second stator magnetic pole 218. The opening
219 may be formed by a separation between the first tip 217a and
the second tip 218a. An axial direction length of the opening 219
may be defined as "T", which may be a distance between the first
tip 217a and the second tip 218a.
[0059] A gap between the outer stator 210 and the inner stator 220
may be an air gap. More specifically, the air gap may be a portion
at which the magnetic flux generated in the outer stator 210 and
the magnetic flux generated in the permanent magnet 230 meet, and
thus, a thrust for the permanent magnet 230 may be formed by
interaction of the magnetic fluxes. A height of the air gap may be
defined as "G". As the permanent magnet 230 reciprocates in the air
gap, a thickness MT of the permanent magnet 230 may be formed
smaller than the height G of the air gap.
[0060] As described in FIG. 5, when a current is applied to the
coil 215 so as to form the magnetic flux in a clockwise direction,
a portion of the magnetic flux may pass through the first stator
magnetic pole 217, the second stator magnetic pole 218, the
permanent magnet 230, and the inner stator 220. A first portion of
the magnetic flux may be referred to as an "air gap magnetic flux".
The air gap magnetic flux may generate a thrust for the permanent
magnet 230.
[0061] A second portion of the magnetic flux may be formed to pass
through the first stator magnetic pole 217 from the second stator
magnetic pole 218. The other portion of the magnetic flux is not
helpful for generating a thrust to act on the permanent magnet 230,
and thus, may be referred to as "leakage magnetic flux (dotted
arrow).
[0062] A relationship between the height G of the air gap and the
axial direction length T of the opening 219 is provided
hereinbelow.
[0063] As described above, the magnetic flux may include the air
gap magnetic flux and the leakage magnetic flux. When one of the
air gap magnetic flux or the leakage magnetic flux increases, the
other magnetic flux may decrease, relatively.
[0064] A ratio between the air gap magnetic flux and the leakage
magnetic flux may vary with a ratio between the height G of the air
gap and the axial direction length T of the opening 219. In more
detail, as the gap between the outer stator 210 and the inner
stator 220 increases as the height G of the air gap increases, a
magnitude of the magnetic flux flowing into the inner stator 220
from the outer stator 210 decreases. That is, the magnitude of the
air gap magnetic flux decreases.
[0065] As the gap between the outer stator 210 and the inner stator
220 decreases as the axial direction length T of the opening 219
decreases, a magnitude of the magnetic flux flowing from one of the
inner stator 220 or the outer stator 210 into the other stator
increases. That is, the magnitude of the air gap magnetic flux
increases.
[0066] Therefore, to reduce the leakage magnetic flux and increase
the air gap magnetic flux relatively, the axial direction length T
of the opening 219 may be equal to or greater than the height G of
the air gap. That is, T.gtoreq.G may be established. Related
effects may be confirmed in FIGS. 7A to 7C.
[0067] FIG. 7A illustrates magnetic flux in a linear motor having a
magnetic pole tip distance of T1. FIG. 7B illustrates magnetic flux
in a linear motor having a magnetic pole tip distance of T2. FIG.
7C illustrates a magnitude of a leakage magnetic flux in the linear
motor of FIGS. 7A and 7B.
[0068] FIG. 7A illustrates a flow of the magnetic flux generated in
the motor assembly 200 when the axial direction length of the
opening 219 is T1, and FIG. 7B illustrates a flow of the magnetic
flux generated in the motor assembly 200 when the axial direction
length of the opening 219 is T2. T2 is greater than T1. For
example, T1 may be approximately 3 mm and T2 may be approximately 9
mm. The air gaps in FIGS. 7A and 7B may have a same height G.
[0069] In FIGS. 7A and 7B, when a point where a first line in a
radial direction, which penetrates through a center of the opening
219, meets the inner stator 220 is defined as a zero point (O), a
point intersecting with a second line that connects the first and
second stator magnetic poles 217 and 218 may be defined as a first
point (P1). A distance between the zero point O and the first point
P1 may correspond to the height of the air gap. Also, when a point
on the bobbin 213 at which the first line intersects with the
coupling part 211c is defined in as a second point (P2), FIG. 7C
illustrates a magnetic flux that leaks from the motor assembly
200.
[0070] In more detail, as illustrated in FIG. 7A, in the height G
of the air gap, if the opening 219 has a relatively small axial
length, a leakage magnetic flux of the magnetic flux generated in
the outer stator 210, for example, a leakage magnetic flux of a
positive (+) pole may significantly increase from the zero point O
to the first point P1 to form a maximum leakage magnetic flux at
the point P1. The leakage magnetic flux may gradually decrease from
the first point P1 to the second point P2.
[0071] Also, the leakage magnetic flux of the positive (+) pole may
be switched in direction to a negative (-) pole to significantly
increase. Away from the second point P2, the magnitude of the
leakage magnetic flux may have an approximately constant value (a
constant magnetic flux). Herein, the terms "positive (+) pole" and
"negative (-) pole" may denote leakage magnetic flux directions
opposite to each other. Also, the constant magnetic flux may be a
maximum magnetic flux of the negative (-) pole.
[0072] On the other hand, as illustrated in FIG. 7B, in the height
G of the air gap, if the opening 219 has a relatively large axial
length, a leakage magnetic flux of the magnetic flux generated in
the outer stator 210, for example, a leakage magnetic flux of a
positive (+) pole may smoothly increase from the zero point O to
the first point P1 to form a maximum leakage magnetic flux at the
first point P1. The maximum magnetic flux in FIG. 7B may have a
value relatively less than that in FIG. 7A. The leakage magnetic
flux may gradually decrease from the first point P1 to the second
point P2.
[0073] The leakage magnetic flux of the positive (+) pole may be
switched in direction to the negative (-) pole to significantly
increase. Away from the first point P2, the magnitude of the
leakage magnetic flux may have an approximately constant value (a
constant magnetic flux). However, the constant magnetic flux in
FIG. 7B may have a value relatively greater than that in FIG.
7A.
[0074] As illustrated in FIG. 7C, with respect to the height G of
the predetermined air gap, the more the opening increases in length
T, the more the maximum leakage magnetic flux, that is, the maximum
magnetic fluxes of the positive (+) and negative (-) poles
decrease. Thus, a larger amount of thrust may be provided to the
permanent magnet 230 to improve the operation efficiency of the
motor assembly 200.
[0075] FIG. 8 is a cross-sectional view of a linear motor
illustrating a position of a permanent magnet when a piston is
positioned at the BDC position, according to an embodiment. FIG. 9
is a cross-sectional view of a linear motor illustrating a position
of a permanent magnet when a piston is positioned at the TDC
position, according to an embodiment.
[0076] Referring to FIGS. 5, 6, 8, and 9, the permanent magnet
according to embodiments may include the plurality of poles 231,
232, and 233, which may be alternately arranged in polarity. The
plurality of poles 231, 232, and 233 may include the first pole
231, the second pole 232 coupled to the first pole 231, and the
third pole 233 coupled to the second pole 232.
[0077] The second pole 232 may be referred to as a "central
magnetic pole", and the first and third poles 231 and 233 may be
referred to as "both end magnetic poles" in that the second pole
232 is disposed between the first and third poles 231 and 233.
[0078] The central magnetic pole 232 may have a length greater than
a length of each of the both end magnetic poles 231. 233. A length
of the central magnetic pole 232 may be defined as a length "MC", a
length of the first pole 231 may be defined as a length "MF", and a
length of the third pole 233 may be defined as a length "MR". The
lengths MF and MR may have the same value. On the other hand, the
lengths MF and MR may have values different from each other so as
to increase the thrust according to a design of the compressor.
[0079] A first interface surface 235 may be disposed between the
first pole 231 and the second pole 232, and a second interface
surface 236 may be disposed between the second pole 232 and the
third pole 233. The first interface surface 235 may be reciprocated
within a range which is not out of a range of the first stator
magnetic pole 217 with respect to a center of the first stator
magnetic pole 217, and the second interface surface 236 may be
reciprocated within a range which is not out of a range of the
second stator magnetic pole 218 with respect to a center of the
second stator magnetic pole 218.
[0080] That is, the first interface surface 235 may be reciprocated
in an axial direction between both ends of the first stator
magnetic pole 217 with respect to the center of the first stator
magnetic pole 217. Also, the second interface surface 236 may be
reciprocated in the axial direction between both ends of the second
stator magnetic pole 218 with respect to the center of the second
stator magnetic pole 218.
[0081] A force (thrust) pulled and pushed between polarities (an N
pole or an S pole) of the first stator magnetic pole 217 and
polarities of the first and second poles 231 and 232 may occur.
Also, as the force pulled and pushed between polarities (an N pole
or an S pole) of the second stator magnetic pole 217 and polarities
of the second and third poles 231 and 232 may occur, the permanent
magnet may be reciprocated.
[0082] The first and second poles 231 and 233 may have the same
polarity. The second pole 232 disposed between the first and third
poles 231 and 233 may have a polarity opposite to a polarity of
each of the first and second poles 231 and 233. For example, if
each of the first and third poles 231 and 233 is a N pole, the
second pole 232 may be a S pole. If each of the first and third
poles 231 and 233 is a S pole, the second pole 232 may be a N
pole.
[0083] A structure, in which two poles acting on each other with
respect to the first stator magnetic pole 217 are disposed, and the
other two poles acting on each other with respect to the second
stator magnetic pole 218 are disposed, may be provided to generate
a larger amount of thrust on the permanent magnet 230. The two
poles acting on each other may have the same length, and also, the
other two poles may have the same length. However, when considering
the limited inner space of the compressor 10, a permanent magnet
having four poles may be limited in arrangement. That is, if the
four poles are arranged, the permanent magnet may increase in
length, and thus, the linear motor may increase in length.
[0084] Thus, the permanent magnet 230 according to embodiments may
have two poles positioned at a central portion to serve as one pole
and three poles that are alternately arranged. Thus, the pole
disposed at the central portion, that is, the central magnetic pole
may have a length greater than a length of each of both end
magnetic poles. Thus, when compared to a case in which four poles
are arranged, a compact structure may be realized. In addition,
both end magnetic poles may be reduced by a half or less in length.
That is, the following relational expression may be defined.
MF or MR.ltoreq.MC.ltoreq.2*MF or 2*MR
[0085] Also, the central magnetic pole may have a length MC less
than a sum of the length MF of the first pole 231 and the length MR
of the second pole 232.
[0086] In summary, the greater the length of the central magnetic
pole increases, the more the mutual acting force with the first
stator magnetic pole 217 or the second stator magnetic pole 218
increases. Thus, the thrust may increase.
[0087] However, when considering a whole size of the linear motor,
that is, when considering miniaturization or compactification, if
the forgoing relational expression is satisfied, the two effects,
that is, increase of the thrust and the compactification of the
compressor may be achieved.
[0088] The length P of the first stator magnetic pole 217 or the
second stator magnetic pole 218 in the axial direction may be
determined on the basis of stroke S of the piston 130 when a
maximum load is applied to the compressor 10. The stroke S of the
piston 130 may be a distance between the TDC position and the BDC
position.
[0089] When the piston 130 is positioned at the BDC position, a
first end (a left end in FIG. 8) of the first pole 231 may be
disposed outside the first core 211a. The first end of the first
pole 231 may be defined as an end opposite the first interface
surface 235, which defines a second end of the first pole 231.
[0090] Also, outside of the first core 211a may be understood as an
area defined as outside of a virtual line in a radius direction,
which passes through an outer end of the first core 211s. Also, the
terms "outside" or "outward direction" may refer to a direction
extending away from the center of the opening 219, and "inside or
inward direction" may refer to a direction toward or closer to the
center of the opening 219.
[0091] Also, when the piston 130 is positioned at the TDC position,
the first end of the first pole 231 may be disposed inside the
first core 211a. That is, the first end of the first pole 231 may
be disposed within a region, in which the first core 211a is
disposed, with respect to the axial direction.
[0092] However, the first end of the first pole 231 may not move
inside of the first stator magnetic pole 217. That is, the first
end of the first pole 231 may be disposed at a position
corresponding to an end of the first stator magnetic pole 217 or
disposed outside of the first stator magnetic pole 217. Herein, the
phrase inside of the first stator magnetic pole 217 may be refer to
a space between virtual lines in the radial direction, which pass
through both ends of the first stator magnetic pole 217.
[0093] The first stator magnetic pole 217 may have the same axial
length as the second stator magnetic pole 218. In more detail, an
axial length P of the first or second stator magnetic pole 217 or
218 may be determined by adding a control error or mechanical error
to the stroke S of the piston 130. For example, if the stroke S is
about 16 mm, the length P may be set to about 18 mm.
[0094] If the length P is less than the stroke S, the first or
second interface surface 235 or 236 may move outward from the first
or second stator magnetic pole 217 or 218. Thus, the force pushed
and pulled between the magnetic poles 217 and 218 and the permanent
magnet 230 may be reduced. Thus, the length P may be determined to
be greater than the stroke S.
[0095] A relational expression between the length P and the length
of the first pole 231 or the second pole 233 is defined. When each
of the first and second interface surfaces 235 and 236 is
reciprocated with respect to the center of each of the first and
second stator magnetic poles 217 and 218, if both ends of both end
magnetic poles 231 and 233 move into both ends of the first and
second stator magnetic poles 217 and 218, the thrust applied to the
permanent magnet may be reduced. That is, if at least a portion of
both end magnetic poles 231 and 233 is not disposed outside both
ends of the first and second stator magnetic poles 217 and 218, the
mutual acting force between the magnetic fluxes of the outer stator
210 and the permanent magnet 230 may be weakened.
[0096] Thus, when considering the thrust for generating the
reciprocating motion of the permanent magnet 230, the length MF of
the first pole 231 and the length MR of the third pole 233 may be
greater than the length P of each of the first and second stator
magnetic poles 217 and 218.
[0097] However, the length MF of the first pole 231 and the length
MR of the third pole 233 are factors that have an influence on a
whole length of the permanent magnet 230. Thus, the lengths MF and
MR may be used as a limiting factor to realize miniaturization of
the linear compressor 10.
[0098] Thus, the current embodiment proposes the following
relational expression.
MF or MR.gtoreq.0.9*P
[0099] According to the above-described relational expression, if
the length MF of the first pole 231 and the length MR of the third
pole 233 are within a range similar to the length P of each of the
first and second stator magnetic poles 217 and 218, the thrust may
be reduced, and the linear compressor 10 may be compact.
[0100] FIG. 10 is a graph showing a magnitude of a thrust generated
according to lengths of magnetic poles at both ends, in the
permanent magnet according to an embodiment. FIG. 11 is a graph
showing a magnitude of a cogging force according to lengths of
magnetic poles at both ends, in a permanent magnet according to an
embodiment.
[0101] Referring to FIG. 10, a change in thrust with respect to a
same input current according to a length of each of both end
magnetic poles 231 and 233 according to embodiments is illustrated.
The horizontal axis in FIG. 10 illustrates a position of the
permanent magnet 230. A zero point (O) on the horizontal axis may
be defined as a state in which each of the first and second
interface surfaces 235 and 236 is disposed at the center of each of
the first and second stator magnetic poles 217 and 218. This state
may be understood as a state in which the permanent magnet is
disposed at the zero point.
[0102] Also, a negative (-) position may be defined as a case in
which the permanent magnet 230 moves from the zero point in a first
direction, and a positive (+) position may be defined as a case in
which the permanent magnet 230 moves from the zero point in a
second direction. Along the horizontal axis, the more a critical
value in position increases, the greater a distance from the zero
point.
[0103] Referring to FIG. 10, when the permanent magnet 230 is
disposed at the zero point, the thrust may be maximally generated.
Also, the more each of both end magnetic poles 231 and 233
increases in length, the more the maximum thrust may increase.
[0104] For example, under a same condition in which the central
magnetic pole 232 has a length of about 24 mm, if each of both end
magnetic poles 231 and 233 has a length of about 19 mm, the maximum
thrust may be F1 N. Also, if each of both end magnetic poles 231
and 233 has a length of about 17 mm, the maximum thrust may be F2
N. Here, the maximum thrusts may be defined as follow:
F1>F2>F3
[0105] Also, the more each of both end magnetic poles 231 and 233
increases in length, the more a magnitude of the thrust may
significantly increase on the whole. That is, as the more each of
both end magnetic poles 231 and 233 increase in length, the more
the magnitude of the thrust applied to the permanent magnet 230
increases, operation efficiency of the compressor may be
improved.
[0106] FIG. 11 illustrates variations or a change in peak value of
a force due to magnetic reluctance of the permanent magnet 230,
that is, a cogging force according to length of each of both end
magnetic poles 231 and 233 according to an embodiment.
[0107] The magnetic reluctance or cogging force of the permanent
magnet 230 may be understood as electrical resistance with respect
to an mutual acting force between the magnetic flux generated in
the outer stator 210 and the magnetic flux of the permanent magnet
230. The cogging force may increase to a peak value according to a
position (position (+) or negative (-) position) of the permanent
magnet or vary in a direction in which the peak value decreases. In
more detail, when the permanent magnet 230 is disposed at the
positive (+) position, the cogging force may be formed in a
positive (+) direction and have a peak value at a predetermined
position. On the other hand, when the permanent magnet 230 is
disposed at the negative (-) position, the cogging force may be
formed in a negative (-) direction and have a peak value at a
predetermined position. Here, the positive (+) and negative (-)
directions of the cogging force may denote forces acting in
directions opposite to each other.
[0108] The more the peak value increases, the more the force
applied to the springs 151 and 155 may increase. Thus, it may be
difficult to control the linear motor 200.
[0109] Referring to FIG. 11, the more each of both end magnetic
poles 231 and 233 increases in length, the more the positive (+)
and negative (-) peak value of the cogging force may decrease.
Thus, the linear motor 200 may be easily controlled.
[0110] For example, under the same condition in which the central
magnetic pole 232 has a length of about 24 mm, if each of both end
magnetic poles 231 and 233 has a length of about 19 mm, a peak
value of the cogging force may be about 15 N. Also, if each of both
end magnetic poles 231 and 233 has a length of about 18 mm, a peak
value of the cogging force may be about 20 N. Also, if each of both
end magnetic poles 231 and 233 has a length of about 17 mm, a peak
value of the cogging force may be about 27 N.
[0111] FIG. 12 is a graph showing a magnitude of a thrust generated
according to a length of a central magnetic pole, in the permanent
magnet according to an embodiment. FIG. 13 is a graph showing
variations in a cogging force according to a length of a central
magnetic pole, in the permanent magnet according to an
embodiment.
[0112] Referring to FIGS. 12 and 13, the more each of both end
magnetic poles increase in length, the more the thrust may
increase, and the peak value of the cogging force may decrease. As
described with reference to FIGS. 10 and 11, as the thrust
increases, operation efficiency of the linear motor may be
improved. Also, as the peak value of the cogging force decreases,
the control reliability of the linear motor may be improved.
[0113] Referring to FIG. 12, it can be seen that the thrust
increases as the central magnetic pole increases in length MC under
the condition in which both end magnetic poles have the same
length. For example, under the condition in which the lengths MF
and MR are about 18 mm, it is seen that the thrust (the maximum
thrust: 85 V/m/s) when the length MC is about 26 mm may be greater
than that (the maximum thrust: 83 V/m/s) when the length MC is
about 24 mm.
[0114] Referring to FIG. 13, it is seen that the peak value of the
cogging force decreases as the central magnetic pole increases in
length MC under the condition in which both end magnetic poles may
have the same length. For example, under a condition in which the
lengths MF and MR are about 18 mm, it is seen that the peak value
(about 13 N) of the cogging force when the length MC is about 26 mm
may be less than that (about 20 N) of the cogging force when the
length MC is about 24 mm.
[0115] According to embodiments, as the permanent magnet may
include a magnet having three polarities, an amount of a magnetic
flux generated may be increased. Also, the increased magnetic flux
of the permanent magnet may interact with a magnetic flux generated
from the outer stator, thereby increasing a thrust exerted on the
piston.
[0116] Further, as a length of the opening between the magnetic
poles disposed in the outer stator may be maintained equal to or
greater than the air gap between the outer stator and the inner
stator, it is possible to reduce a leaked magnetic flux and
increase a magnitude of the magnetic flux generated from the outer
stator and oriented toward the inner stator. Accordingly, the air
gap magnetic flux and the magnetic flux of the permanent magnet may
interact with each other, thereby generating higher thrust.
[0117] Moreover, in the permanent magnet having three poles, a
length of the both-end magnetic pole may be a predetermined
proportion of a length of magnetic pole of the outer stator, thus
making it possible to increase a generated thrust in comparison
with a current applied to the linear motor and also reduce a
cogging force (or torque).
[0118] Additionally, in the permanent magnet having three poles, a
length of the central magnetic pole may be greater than lengths of
the both-end magnetic poles, and may be twice or less than the
lengths of the both-end magnetic poles. This also enables a
generated thrust to be increased and a cogging force (or torque) to
be reduced.
[0119] Also, the piston and the cylinder may be made of a
nonmagnetic material, such as aluminum or aluminum alloy, and thus,
magnetic flux may be prevented from being leaked to the outside
through the piston or cylinder. In addition, the permanent magnet
may be made of an inexpensive ferrite material, thereby reducing a
manufacturing cost for the motor assembly.
[0120] Embodiments disclosed herein provide a linear compressor
provided with a linear motor capable of generating a sufficient
force (a thrust).
[0121] Embodiments disclosed herein provide a linear compressor
that may include a cylinder that forms a compression space for a
refrigerant; a piston that reciprocatably moves in an axial
direction inside the cylinder; and a linear motor that supplies a
power to the piston. The linear motor may include an outer stator
including a first stator magnetic pole, a second stator magnetic
pole, and an opening defined between the first stator magnetic pole
and the second stator magnetic pole; an inner stator disposed apart
from the outer stator; and a permanent magnet movably disposed in
an air gap between the outer stator and the inner stator, and
having three poles. The three poles may include two both-end
magnetic poles, and a central magnetic pole disposed between the
two both-end magnetic poles. The central magnetic pole may have a
length greater than the both-end magnetic poles.
[0122] A length of the central magnetic pole may be twice or less
than that of any one of the two both-end magnetic poles. A length
of the central magnetic pole may be equal to or less than a sum of,
lengths of the two both-end magnetic poles. An axial direction
length of the opening may be equal to or greater than a radial
direction height of the air gap.
[0123] The piston may be moveable by a stroke between a top dead
center (TDC) and a bottom dead center (BDC), and a length of the
first stator magnetic pole or the second stator magnetic pole may
be equal to or less than the stroke. A length of any one of the two
both-end magnetic poles may be approximately 90% or more of a
length of the first stator magnetic pole or second stator magnetic
pole.
[0124] The two both-end magnetic poles may include a first pole
coupled to the central magnetic pole at a first interface, and a
second pole coupled to the central magnetic pole at a second
interface. The first interface may reciprocate in an axial
direction between both ends of the first stator magnetic pole,
based on a center of the first stator magnetic pole, and the second
interface may reciprocate in an axial direction between both ends
of the second stator magnetic pole, based on a center of the second
stator magnetic pole.
[0125] The first pole may include an end at a position facing the
first interface, and the end of the first pole may be positioned
outside the outer stator when the piston is positioned at the BDC.
The end of the first pole may be positioned at an end of or outside
the first stator magnetic pole when the piston is positioned at the
TDC.
[0126] The two both-end magnetic poles may include a first pole
coupled to one side of the central magnetic pole, and at least a
portion of the first pole may be positioned in an air gap between
the first stator magnetic pole and the inner stator. The two
both-end magnetic poles may include a second pole coupled to the
other side of the central magnetic pole, and at least a portion of
the second pole may be positioned in an air gap between the second
stator magnetic pole and the inner stator.
[0127] The opening may be defined between a tip of the first stator
magnetic pole and a tip of the second stator magnetic pole, at one
side of an accommodation space for accommodating a coil.
[0128] The permanent magnet may be made of a ferrite material. The
piston and the cylinder may be made of aluminum or aluminum
alloy.
[0129] Although embodiments have been described with reference to a
number of illustrative embodiments thereof, it should be understood
that numerous other modifications and embodiments can be devised by
those skilled in the art that will fall within the spirit and scope
of the principles of this disclosure. More particularly, various
variations and modifications are possible in the component parts
and/or arrangements of the subject combination arrangement within
the scope of the disclosure, the drawings and the appended claims.
In addition to variations and modifications in the component parts
and/or arrangements, alternative uses will also be apparent to
those skilled in the art.
[0130] Any reference in this specification to "one embodiment," "an
embodiment," "example embodiment," etc., means that a particular
feature, structure, or characteristic described in connection with
the embodiment is included in at least one embodiment of the
invention. The appearances of such phrases in various places in the
specification are not necessarily all referring to the same
embodiment. Further, when a particular feature, structure, or
characteristic is described in connection with any embodiment, it
is submitted that it is within the purview of one skilled in the
art to effect such feature, structure, or characteristic in
connection with other ones of the embodiments.
[0131] Although embodiments have been described with reference to a
number of illustrative embodiments thereof, it should be understood
that numerous other modifications and embodiments can be devised by
those skilled in the art that will fall within the spirit and scope
of the principles of this disclosure. More particularly, various
variations and modifications are possible in the component parts
and/or arrangements of the subject combination arrangement within
the scope of the disclosure, the drawings and the appended claims.
In addition to variations and modifications in the component parts
and/or arrangements, alternative uses will also be apparent to
those skilled in the art.
* * * * *