U.S. patent application number 14/316908 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 Wonhyun JUNG, Kyoungseok KANG, Chulgi ROH. Invention is credited to Wonhyun JUNG, Kyoungseok KANG, Chulgi ROH.
Application Number | 20150004021 14/316908 |
Document ID | / |
Family ID | 50732021 |
Filed Date | 2015-01-01 |
United States Patent
Application |
20150004021 |
Kind Code |
A1 |
KANG; Kyoungseok ; et
al. |
January 1, 2015 |
LINEAR COMPRESSOR
Abstract
A linear compressor is provided that may include a shell
including a refrigerant inlet, an outer stator provided in the
shell and including a coil, an inner stator disposed to be spaced
apart from the outer stator, a permanent magnet disposed to be
movable between the outer stator and the inner stator, a cylinder
including a compression space, in which a refrigerant sucked in
through refrigerant inlet may be compressed, a piston coupled to
the permanent magnet so as to be reciprocated in the cylinder, a
first surface area provided on the piston and having a first
hardness value, and a second surface area provided on the cylinder
and having a second hardness value, such that a difference value
between the first and second hardness values is more than a preset
value.
Inventors: |
KANG; Kyoungseok; (Seoul,
KR) ; JUNG; Wonhyun; (Seoul, KR) ; ROH;
Chulgi; (Seoul, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KANG; Kyoungseok
JUNG; Wonhyun
ROH; Chulgi |
Seoul
Seoul
Seoul |
|
KR
KR
KR |
|
|
Assignee: |
LG ELECTRONICS INC.
Seoul
KR
|
Family ID: |
50732021 |
Appl. No.: |
14/316908 |
Filed: |
June 27, 2014 |
Current U.S.
Class: |
417/410.1 |
Current CPC
Class: |
F04B 39/122 20130101;
F04B 39/0005 20130101; F05C 2253/12 20130101; F04B 35/045
20130101 |
Class at
Publication: |
417/410.1 |
International
Class: |
F04B 35/04 20060101
F04B035/04 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 28, 2013 |
KR |
10-2013-075514 |
Claims
1. A linear compressor, comprising: a shell comprising a
refrigerant inlet; an outer stator provided in the shell and
comprising a coil; an inner stator disposed to be spaced apart from
the outer stator; a permanent magnet disposed movable between the
outer stator and the inner stator; a cylinder comprising a
compression space in which a refrigerant sucked in through the
refrigerant inlet is compressed; a piston coupled to the permanent
magnet to be reciprocated in the cylinder; a first surface area
provided on the piston, the first surface area having a first
hardness value; and a second surface area provided on the cylinder,
the second surface area having a second hardness value, so that a
difference in value between the first and second hardness values is
more than a predetermined value.
2. The linear compressor according to claim 1, wherein the
predetermined value is at least approximately 150Hv or more based
on Vickers hardness.
3. The linear compressor according to claim 1, wherein the
predetermined value is determined so that an abrasion amount
generated at the piston or the cylinder, while the piston is
repeatedly reciprocated for a predetermined period of time, is
approximately 3 .mu.m or less.
4. The linear compressor according to claim 2, wherein the first
surface area or the second surface area is made of one of polytetra
fluoroethylene (PTFE), diamond like carbon (DLC), an Ni--P alloy,
or an anodizing layer.
5. The linear compressor according to claim 4, wherein the first
surface area comprises one of PTFE, DLC, Ni--P alloy, or an
anodizing layer, and wherein the second surface area comprises
another one of PTFE, DLC, Ni--P alloy, or an anodizing layer, which
is different from the first surface area.
6. The linear compressor according to claim 5, wherein the first
surface area is made of PTFE, and the second surface area is made
of the anodizing layer.
7. The linear compressor according to claim 1, wherein the piston
and the cylinder are made of a non-magnetic material.
8. The linear compressor according to claim 7, wherein the piston
and the cylinder are made of aluminum or an aluminum alloy.
9. The linear compressor according to claim 8, wherein the aluminum
or the aluminum alloy of the piston and the cylinder are the same
material.
10. The linear compressor according to claim 1, wherein the first
surface area is provided on an outer circumferential surface of the
piston, and the second surface area is provided on an inner
circumferential surface of the cylinder, which is disposed opposite
to the outer circumferential surface of the piston.
11. The linear compressor according to claim 1, wherein the piston
comprises: a piston body received in the cylinder; and a flange
that extends in a radial direction of the piston body and coupled
to the permanent magnet, and wherein the first surface area is
provided on an outer circumferential surface of the piston
body.
12. A linear compressor comprising a piston reciprocated in a
cylinder by a force generated by an interaction between a magnetic
flux generated by a current applied to a coil and a magnetic flux
of a permanent magnet, the linear compressor comprising: a first
surface area provided on an outer circumferential surface of the
piston; and a second surface area provided on an inner
circumferential surface of the cylinder, wherein a predetermined
difference in hardness value is provided between a hardness value
of the first surface area and a hardness value of the second
surface area.
13. The linear compressor according to claim 12, wherein the
predetermined difference in hardness value is at least
approximately 150Hv or more based on Vickers hardness.
14. The linear compressor according to claim 12, wherein the first
surface area comprises one of polytetra fluoroethylene (PTFE),
diamond like carbon (DLC), an Ni--P alloy, or an anodizing layer,
and the second surface area comprises another one of PTFE, DLC,
Ni--P alloy, or an anodizing layer, which is different from the
first surface area.
15. A linear compressor, comprising: a shell comprising a
refrigerant inlet; an outer stator provided in the shell and
comprising a coil; an inner stator disposed to be spaced apart from
the outer stator; a permanent magnet disposed movable between the
outer stator and the inner stator; a cylinder comprising a
compression space in which a refrigerant sucked in through the
refrigerant inlet is compressed; a piston coupled to the permanent
magnet to be reciprocated in the cylinder; a polytera fluroethylene
(PTFE) layer provided on an outer circumferential surface of the
piston; and an anodizing layer provided on an inner circumferential
surface of the cylinder.
16. A linear compressor, comprising: a shell comprising a
refrigerant inlet; an outer stator provided in the shell and
comprising a coil; an inner stator disposed to be spaced apart from
the outer stator; a permanent magnet disposed movable between the
outer stator and the inner stator; a cylinder comprising a
compression space in which a refrigerant sucked in through the
refrigerant inlet is compressed and having a first surface area
having a first hardness value; and a piston coupled to the
permanent magnet to be reciprocated in the cylinder and having a
second surface area having a second hardness value, wherein a
difference in value between the first hardness value and the second
hardness value allows slippage between the cylinder and the
piston.
17. The linear compressor according to claim 16, wherein the
predetermined value is at least approximately 150Hv or more based
on Vickers hardness.
18. The linear compressor according to claim 16, wherein the
predetermined value is determined so that an abrasion amount
generated at the piston or the cylinder, while the piston is
repeatedly reciprocated for a predetermined period of time, is
approximately 3 .mu.m or less.
19. The linear compressor according to claim 16, wherein the first
surface area or the second surface area is made of one of polytetra
fluoroethylene (PTFE), diamond like carbon (DLC), an Ni--P alloy,
or an anodizing layer.
20. The linear compressor according to claim 19, wherein the first
surface area comprises one of PTFE, DLC, Ni--P alloy, or an
anodizing layer, and wherein the second surface area comprises
another one of PTFE, DLC, Ni--P alloy, or an anodizing layer, which
is different from the first surface area.
21. The linear compressor according to claim 20, wherein the first
surface area is made of PTFE, and the second surface area is made
of the anodizing layer.
22. The linear compressor according to claim 16, wherein the piston
and the cylinder are made of a non-magnetic material.
23. The linear compressor according to claim 22, wherein the piston
and the cylinder are made of aluminum or an aluminum alloy.
24. The linear compressor according to claim 23, wherein the
aluminum or the aluminum alloy of the piston and the cylinder are
the same material.
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. 10-2013-0075514,
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.
According to the related art, while the piston repeatedly moves
within the cylinder, interference between the cylinder and the
piston may occur causing abrasion of the cylinder or piston. More
particularly, when a predetermined pressure (a coupling pressure)
acts on the piston causing deformation of the piston due to the
pressure, interference between the cylinder and the piston may
occur. Also, if a slight error occurs when the piston is assembled
with the cylinder, a compression gas may leak to the outside, and
thus, abrasion between the cylinder and the piston may occur.
[0009] As described above, the interference between the cylinder
and the piston may occur causing interference between the permanent
magnet and the inner and outer stators, thereby damaging
components. Also, in the case of the linear compressor according to
the related art, the cylinder and/or the piston may be formed of a
magnetic material. Thus, a large amount of flux generated in the
linear motor may leak to the outside through the cylinder and the
piston, deteriorating efficiency of the compressor.
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 in
accordance with an embodiment;
[0012] FIG. 2 is a cross-sectional view illustrating a coupling
state between a cylinder and a piston according to an
embodiment;
[0013] FIG. 3 is a cross-sectional view illustrating a state in
which the piston of FIG. 2 is moved in one direction;
[0014] FIG. 4 is a cross-sectional view illustrating a state in
which a piston and a cylinder are coupled with each other according
to an embodiment; and
[0015] FIG. 5 is a graph illustrating change in abrasion ratio of
the cylinder or the piston according to a difference in hardness
between first and second surface areas according to an
embodiment.
DETAILED DESCRIPTION
[0016] Hereinafter, embodiments will be described in detail with
reference to the accompanying drawings. Embodiments may, however,
be embodied in many different forms and should not be construed as
being limited to the embodiments set forth herein; rather,
alternate embodiments included in other retrogressive inventions or
falling within the spirit and scope of the present disclosure can
easily be derived through adding, altering, and changing, and will
fully convey the concept of the invention to those skilled in the
art.
[0017] FIG. 1 is a cross-sectional view of a linear compressor in
accordance with 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 in the cylinder 120, and a
motor assembly 200 that provides a drive force to the piston 130.
The shell 100 may include an upper shell and a lower shell.
[0018] The shell 100 may further include an inlet 101, through
which a refrigerant may flow into the shell 100, and an outlet 105,
through which the refrigerant compressed in the cylinder 120 may be
discharged from the shell 100. The refrigerant sucked in through
the inlet 101 may flow into the piston 130 through a suction
muffler 140. While the refrigerant passes through the suction
muffler 140, noise may be reduced.
[0019] A compression space P, in which the refrigerant may be
compressed by the piston 130, may be provided in the cylinder 120.
A suction hole 131a, through which the refrigerant may be
introduced to the compression space P, may be provided at the
piston 130, and a suction valve 132 may be provided at a side of
the suction hole 131a to selectively open the suction hole
131a.
[0020] A discharge valve assembly 170, 172, and 174 may be provided
at a side of the compression space P to discharge the refrigerant
compressed in the compression space P. That is, the compression
space P may be defined between an end of the piston 130 and the
discharge valve assembly 170, 172, and 174.
[0021] The discharge valve assembly 170, 172, 174 may include a
discharge cover 172, which may define a discharge space for the
refrigerant, a discharge valve 170, which may be opened so that the
refrigerant may be introduced into the discharge space when a
pressure of the compression space P is more than a discharge
pressure, and a valve spring 174, which may be provided between the
discharge valve 170 and the discharge cover 172 so as to provide an
elastic force in an axial direction. The term "axial direction" may
refer to a reciprocating direction of the piston 130, that is, a
transverse direction in FIG. 1. The suction valve 132 may be
provided at a first side of the compression space P, and the
discharge valve 170 may be provided at a second side of the
compression space P, that is, at an opposite side to the suction
valve 132.
[0022] While the piston 130 is reciprocated in the cylinder 120, if
the pressure of the compression space P is lower than the discharge
pressure and also less than a suction pressure, the suction valve
132 may be opened, and the refrigerant may be suctioned into the
compression space P. On the other hand, if the pressure of the
compression space P is more than the suction pressure, the suction
valve 132 may be closed and the refrigerant in the compression
space P compressed. If the pressure of the compression space P is
more than the discharge pressure, the valve spring 174 may be
deformed so as to open the discharge valve 170, and the refrigerant
discharged from the compression space P to the discharge space of
the discharge cover 172.
[0023] The refrigerant in the discharge space may be introduced
into a loop pipe 178 through a discharge muffler 176. The discharge
muffler 176 may reduce a 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 extended to be coupled to the outlet
105.
[0024] The linear compressor 10 may further include a frame 110.
The frame 110 may serve to fix the cylinder 200 within the shell
100. The frame 110 may be integrally provided with the cylinder 200
or may be fastened to the cylinder 200 by a separated fastening
member, for example. The discharge cover 172 and the discharge
muffler 176 may be coupled to the frame 110.
[0025] The motor assembly 200 may include an outer stator 210,
which may be fixed to the frame 110 and disposed to enclose or
surround the cylinder 120, an inner stator 220, which may be
disposed inside the outer stator 210 to be spaced apart from the
outer stator 210, and a permanent magnet 230, which may be disposed
at or in a space between the outer and inner stators 210 and 220.
The permanent magnet 230 may be linearly reciprocated by an
electromagnetic force between the outer and inner stators 210 and
220. Further, the permanent magnet 230 may be a single magnet
having one pole, or may be formed by coupling a plurality of
magnets having three poles. More specifically, in a case of the
permanent magnet 230 having three poles, one surface thereof may
have a polar distribution of a N-S-N type, and the other surface
thereof may have a polar distribution of a S-N-S type.
[0026] The permanent magnet 230 may be coupled to the piston 130 by
a connection member 138. The connection member 138 may extend from
an end of the piston 130 to the permanent magnet 130. As the
permanent magnet 230 is linearly moved, the piston 130 may be
linearly reciprocated together with the permanent magnet 230 in the
axial direction.
[0027] 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 shape, for example, a hexagonal shape. The stator core
211 may be configured by stacking a plurality of laminations in the
circumferential direction, and may be disposed so as to enclose the
bobbin 213 and the coil 215.
[0028] If a current is applied to the motor assembly 200, the
current may flow through the coil 215, and a magnetic flux may be
generated around the coil 215. The magnetic flux may form a closed
circuit and flow along the outer and inner stators 210 and 220. The
magnetic flux flowing along the outer and inner stators 210 and 220
may interact with a magnetic flux of the permanent magnet 230, and
thus, a force to move the permanent magnet 230 may be
generated.
[0029] A stator cover 240 may be provided at a side of the outer
stator 210. A first side end of the outer stator 210 may be
supported by the frame 110, and a second side end thereof may be
supported by the stator cover 240.
[0030] The inner stator 220 may be fixed to an outer circumference
of the cylinder 120. The inner stator 220 may be configured by
stacking a plurality of laminations in a circumferential direction
at an outside of the cylinder 120.
[0031] The linear compressor 10 may further include a supporter 135
that supports the piston 130, and a back cover 115 that extends
from the piston 130 toward the inlet 101. The back cover 115 may be
disposed so as to cover at least a portion of the suction muffler
140.
[0032] The linear compressor 10 may include a plurality of springs
151 and 155, a natural frequency of which may be controlled so as
to enable a resonant motion of the piston 130. The plurality of
springs 151 and 155 may include a plurality of first springs 151,
which may be disposed between the supporter 135 and the stator
cover 240, and a plurality of second springs 155, which may be
disposed between the supporter 135 and the back cover 115.
[0033] 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 side of the cylinder
120 or the piston 130. The term a "front side" may refer to a
direction from the piston 130 toward the inlet 101. The term a
"rear side" may refer to a direction from the inlet 101 toward the
discharge valve assembly 170, 172, and 174. These terms may also be
used in the below description.
[0034] A predetermined amount of oil may be stored at or in an
internal bottom surface of the shell 100, and an oil supplying
device 160 may be provided at a lower side of the shell 100 to pump
the oil. The oil supplying device 160 may be operated by vibration
generated when the piston 130 is linearly reciprocated, so as to
pump the oil upwardly.
[0035] The linear compressor 10 may further include an oil supply
pipe 165 that guides oil flow from the oil supplying device 160.
The oil supply pipe 165 may extend from the oil supplying device
160 to a space between the cylinder 120 and the piston 130. The oil
pumped from the oil supplying device 160 may be supplied to the
space between the cylinder 120 and the piston through the oil
supply pipe 165, and perform cooling and lubricating functions.
[0036] FIG. 2 is a cross-sectional view illustrating a coupling
state between a cylinder and a piston according to an embodiment.
FIG. 3 is a cross-sectional view illustrating a state in which the
piston of FIG. 2 is moved in one direction. FIG. 4 is a
cross-sectional view illustrating a state in which a piston and a
cylinder are coupled with each other according to an
embodiment.
[0037] Referring to FIGS. 2 to 4, the piston 130 according to this
embodiment may be provided in the cylinder 120 to be reciprocated.
The piston 130 may be made of an aluminum material, for example,
aluminum or an aluminum alloy, which is a non-magnetic material. As
the piston 130 may be made of the aluminum material, magnetic flux
generated at the motor assembly 200 may be prevented from being
transferred to the piston 130 and then leaked to an outside of the
piston 130. The piston 130 may be formed by forging, for
example.
[0038] The piston 130 may include a piston body 131, which may have
an approximately cylindrical shape and may be disposed in the
cylinder 120, and a flange 136, which may be radially expanded from
a side end of the piston body 131 and coupled to the permanent
magnet 230.
[0039] The inlet 131a may be provided at a first surface of the
piston body 131. The first surface of the piston body 131 may be a
surface facing the discharge valve 170, for example, a rear surface
thereof.
[0040] The piston body 131 may include an outer circumferential
surface on which a first surface area 310, which may be in the form
of a predetermined layer or film, may be provided. The first
surface area 310 may be provided on the outer circumferential
surface of the piston body 131 in a surface treatment manner. By
providing the first surface area 310, it is possible to improve
abrasion resistance, lubricity, and heat resistance of the piston
body 131. For example, the first surface area 310 may be a "first
coating layer". For example, the first surface area 310 may be made
of one of polytera fluoroethylene (PTFE), diamond like carbon
(DLC), a nickel-phosphorus alloy, or an anodizing layer.
[0041] The flange 136 may include a plurality of holes 137a and
137b. The plurality of holes 137a and 137b may include one or more
coupling holes 137a, in which a fastening member coupled with the
supporter 135 and the connection member 138 may be inserted, and
one or more through-holes 137b, which may reduce flow resistance
generated around the piston 130.
[0042] The cylinder 120 may be made of an aluminum material, for
example, aluminum or an aluminum alloy, which is a non-magnetic
material. A material composition ratio, that is, a kind and
composition of the material in each of the cylinder 120 and the
piston 130 may be the same.
[0043] As the cylinder 120 may be made of the aluminum material,
magnetic flux generated at the motor assembly 200 may be prevented
from being transferred to the cylinder 120 and then leaked to an
outside of the cylinder 120. Further, the cylinder 120 may be
formed by extruded rod processing, for example.
[0044] As the piston 130 and the cylinder 120 may be made of the
same material, for example, aluminum, the piston 130 and the
cylinder 120 may have a same thermal expansion coefficient. While
the linear compressor 10 is operated, a high temperature
environment approximately (100.degree. C.) is created in the shell
100. As the piston 130 and the cylinder 120 have the same thermal
expansion coefficient, the piston 130 and the cylinder 120 may be
equally thermally deformed. As the piston 130 and the cylinder 120
may be thermally deformed in different sizes or directions, the
piston 130 may be prevented from interfering with the cylinder 120,
while the piston 130 is reciprocated.
[0045] The cylinder 120 may have the hollow cylindrical shape, and
the piston body 131 may be movably received therein. The cylinder
120 may include an inner circumferential surface disposed opposite
to an outer circumferential surface of the piston body 131. A
second surface area 320, which may be in the form of a
predetermined layer or film, may be provided on the inner
circumferential surface of the cylinder 120.
[0046] The second surface area 320 may be provided using a
different surface treatment from that of the first surface area
310. By providing the second surface area 320, it is possible to
improve abrasion resistance, lubricity, and heat resistance of the
piston body 131. For example, the second surface area 320 may be a
"second coating layer". For example, the second surface area 320
may be made of one of Teflon (PTFE), diamond like carbon (DLC), a
nickel-phosphorus alloy, or a anodizing layer.
[0047] A certain difference in hardness between the outer
circumferential surface of the piston 130 and the inner
circumferential surface of the cylinder 120 may be generated. If
the difference in hardness therebetween is too small, one of the
piston 130 or the cylinder 120 may be stuck to the other one, that
is, the surface thereof may be worn, while the piston 130 is
reciprocated in the cylinder 120.
[0048] Therefore, in this embodiment, each of the piston 130 having
the first surface area 310 and the cylinder 120 having the second
surface area 320 may have a hardness greater than a predetermined
value, and thus, the abrasion resistance of the piston 130 and the
cylinder 120 may be improved.
[0049] Hereinafter, a surface area treatment method for the first
surface area 310 or the second surface area 320 will be
described.
[0050] The first surface area 310 or the second surface area 320
may include polytera fluoroethylene (PTFE). PTFE is a fluorinate
polymer, which is referred to as "Teflon".
[0051] In a state in which the fluorinate polymer is formed into a
paint, the PTFE may be sprayed on the outer circumferential surface
of the piston 130 or the inner circumferential surface of the
cylinder 120, and treated by heating and plastic working at a
predetermined temperature, thereby providing an inactive coating
layer. As the PTFE has a low frictional coefficient, the PTFE may
be coated on the outer circumferential surface of the piston 130 or
the inner circumferential surface of the cylinder 120, to enhance
lubricity and abrasion resistance of the surface.
[0052] The hardness of the PTFE is very small, and may be measured
by a measuring method of pencil hardness. For example, the hardness
of the PTFE may be more than a pencil hardness of HB. However, when
the hardness of the PTFE is converted into Vickers hardness (Hv),
the PTFE may have approximately 0 to approximately 30Hv (referring
to Table 1).
[0053] For example, the first surface area 310 or the second
surface area 320 may include a film prepared by an anodizing
technique, that is, an anodizing layer. The anodizing technique is
a kind of aluminum painting, in which, when current is applied in a
state in which aluminum is used as an anode, an aluminum surface is
oxidized by oxygen generated at the anode, and thus, an oxidized
aluminum layer is provided.
[0054] The anodizing layer has excellent corrosion resistance and
electrical breakdown resistance. The hardness of the anodizing
layer may be changed according to a state or a composition of a
material (a basic material) to be coated, and may be approximately
300 to 500Hv (referring to Table 1).
[0055] As another example, the first surface area 310 or the second
surface area 320 may include diamond-like carbon (DLC). DLC is an
amorphous carbon-based new material which is a thin film-shaped
material prepared by electrically accelerating carbon ions in
plasma or activated hydrocarbon molecules and smashing them on the
surface. DLC has similar physical properties to diamond, and thus,
has high hardness and abrasion resistance, excellent electrical
breakdown resistance, a low frictional coefficient, and excellent
lubricity. The hardness of the DLC may be approximately 1,500 to
1,800 (referring to Table 1).
[0056] As still another example, the first surface area 310 or the
second surface area 320 may include a nickel-phosphorus alloy
material. The nickel-phosphorus alloy material may be provided on
the outer circumferential surface of the piston 130 or the inner
circumferential surface of the cylinder 120 by an electroless
nickel plating manner, such that nickel and phosphorus are
surface-segregated in a uniform thickness. The nickel-phosphorus
alloy material may have a chemical composition in which nickel
content is approximately 90 to 92%, phosphorus content is
approximately 9 to 10%.
[0057] The nickel-phosphorus alloy material may improve corrosion
resistance and abrasion resistance of the surface and also provide
excellent lubricity. The hardness of the nickel-phosphorus alloy
material may be approximately 500 to 600Hv. (referring to Table
1).
TABLE-US-00001 TABLE 1 Coating material (method) Hardness (Hv,
Vickers hardness) PTFE (Teflon) 0~30 (average: 15) Anodizing layer
300~500 (average: 400) DLC (Diamond-Like Carbon) 1,500~1,800
(average: 1,650) Ni--P alloy 500~600 (average: 550)
[0058] As described above, the first surface area 310 or the second
surface area 320 may be provided by one of the four coating
materials (methods), for example.
[0059] However, the first surface area 310 and the second surface
area 320 may be provided by different coating materials (methods)
from each other. Therefore, the outer circumferential surface of
the piston 130 and the inner circumferential surface of the
cylinder 120 may have a hardness difference, which is more than a
predetermined value. For convenience of explanation, a hardness
valve of the first surface area 310 may be referred to as a "first
hardness value", and a hardness value of the second surface area
320 may be referred to as a "second hardness value".
[0060] In this embodiment, the above four materials (methods) may
be selected to provide the hardness difference which is more than
the predetermined value. Hereinafter, referring to an experimental
graph, a change in an abrasion ratio of the cylinder or the piston
according to the hardness difference between the first and second
surface areas will be described.
[0061] FIG. 5 is a graph illustrating change in abrasion ratio of
the cylinder or the piston according to a hardness difference
between first and second surface areas in accordance with an
embodiment. In FIG. 5, a predetermined surface area was provided on
each of the outer circumferential surface of the piston 130 and the
inner circumferential surface of the cylinder 120, and an abrasion
ratio occurring at the piston or the cylinder according to a
hardness difference between surface area was experimentally
measured and organized. The predetermined surface area was prepared
using various materials or methods other than the four methods
described in Table 1. While the piston 130 was repeatedly
reciprocated in the cylinder 120, it was targeted to maintain the
abrasion ratio of the surface of the piston 130 or the cylinder 120
at approximately 3 .mu.m or less in order to prevent damage to the
piston 130 and the cylinder 120 and to secure operation
reliability.
[0062] Referring to FIG. 5, the surface areas were provided so that
the hardness difference between the first surface area 310 of the
piston 130 and the second surface area 320 of the cylinder 120 was
approximately 50Hv, and then, for example, reciprocation of the
piston 130 was performed for approximately 100 hours or more. In
this case, the abrasion ratio of the piston 130 or the cylinder 120
was approximately 5 .mu.m
[0063] When the hardness difference between the first surface area
310 and the second surface area 320 was approximately 80Hv, the
abrasion ratio of the piston 130 or the cylinder 120 was
approximately 4 .mu.m. When the hardness difference between the
first surface area 310 and the second surface area 320 was P1, the
abrasion ratio of the piston 130 or the cylinder 120 was
approximately 3 .mu.m. P1 is formed around approximately 150Hv. In
a range in which the hardness difference is P1 or more, the
abrasion ratio is maintained at 3 .mu.m or less. As the hardness
difference is increased, the abrasion ratio may be gradually
decreased. In other words, in order to secure operation reliability
of the piston 130 and the cylinder 120, each surface treatment or
area may be selected so that the hardness difference between the
first surface area 310 of the piston 130 and the second surface
area 320 of the cylinder 120 is approximately 150Hv or more.
[0064] Hereinafter, referring to Table 2, when one of the four
coating materials (methods) is provided on the first surface area
310 of the piston 130 and another one is provided on the second
surface area 320 of the cylinder 120, the hardness difference of
the piston 130 and the cylinder 120 may be described as
follows.
TABLE-US-00002 TABLE 2 Hardness difference (Hv) First surface area
Second surface area between surface areas PTFE (Teflon) Anodizing
layer 385 DLC 1,635 Ni--P alloy 535 Anodizing layer PTFE 385 DLC
1,250 Ni--P alloy 150 DLC (Diamond- PTFE 1,635 Like Carbon)
Anodizing layer 1,250 Ni--P alloy 1,100 Ni--P alloy PTFE 535
Anodizing layer 150 DLC 1,100
[0065] Table 2 shows hardness difference values calculated by using
an average hardness value of each coating material. More
specifically, when the anodizing layer is provided at or on one of
the first surface area 310 or the second surface area 320, and the
Ni--P alloy is provided at or on the other one, the hardness
difference is approximately 150Hv. However, when the DLC is
provided at or on one of the first surface area 310 or the second
surface area 320, and the PTFE is provided at or on the other one,
the hardness difference is approximately 1,635Hv.
[0066] When the PTFE is provided at or on one of the first surface
area 310 or the second surface area 320, and the anodizing layer is
provided at or on the other one, the hardness difference is
approximately 385Hv. When the PTFE is provided at or on one of the
first surface area 310 or the second surface area 320, and the
Ni--P alloy is provided at or on the other one, the hardness
difference is approximately 535Hv.
[0067] When the anodizing layer is provided at or on one of the
first surface area 310 and the second surface area 320, and the DLC
is provided at the other one, the hardness difference is
approximately 1,250Hv. When the DLC is provided at or on one of the
first surface area 310 and the second surface area 320, and the
Ni--P alloy is provided at the other one, the hardness difference
is approximately 1,100Hv.
[0068] As described above, when the anodizing layer is provided at
or on one of the first surface area 310 and the second surface area
320, and the Ni--P alloy is provided at the other one, the hardness
difference value between the piston 130 and the cylinder 120 is
approximately minimum 150Hv and approximately maximum 1,635Hv. That
is, the hardness difference value may be at least approximately
150Hv or more.
[0069] When the first and second surface areas 310 and 320 are
prepared using the above-mentioned four coating materials, the
hardness difference, which is a reference for determining abrasion
resistance, may be maintained at approximately 150Hv or more. In
other words, when the surface treatment or area is provided on each
of the outer circumferential surface of the piston 130 and the
inner circumferential surface of the cylinder 120 using the four
coating materials, abrasion resistance of the piston 130 or the
cylinder 120 may be maintained at a predetermined level. Therefore,
during reciprocation of the piston 130, it is possible to secure
operation reliability of the piston 130 or the cylinder 120.
[0070] For example, when the PTFE is provided at or on the first
surface area 310 of the piston 130 and the anodizing layer is
provided at or on the second surface area 320 of the cylinder 120,
the hardness difference between the first and second surface areas
310 and 320 may be approximately 385Hv, and thus, it is possible to
satisfy the required hardness difference value.
[0071] Further, for example, the hardness difference between the
first and second surface areas 310 and 320 may be approximately 150
to 385Hv, approximately 150 to 535Hv, approximately 150 to 1,100Hv,
approximately 150 to 1250Hv, or approximately 150 to approximately
1,635Hv.
[0072] The PTFE coating layer may be provided on the piston 130
which is reciprocated, and thus, it is possible to improve
lubricity. And the anodizing layer may be provided on the cylinder
120, and thus, it is possible to improve corrosion resistance and
electrical breakdown resistance, and also, it is possible to secure
operation reliability of the piston 130 and the cylinder 120.
[0073] According to embodiments, as the cylinder and the piston may
be made of a non-magnetic material, more particularly, an aluminum
material, it is possible to prevent flux generated from the motor
assembly from being leaked to the outside of the cylinder, and
also, it is possible to improve efficiency of the compressor.
Further, as the surface treatment or area may be provided at or on
each of opposite surfaces of the piston and the cylinder, more
particularly, the outer circumferential surface of the piston and
the inner circumferential surface of the cylinder, it is possible
to increase abrasion resistance, and thus, to improve reliability
of components of the compressor.
[0074] Furthermore, as a hardness difference value between a first
surface treatment or area provided on an outer circumferential
surface of the piston and a second surface treatment or area
provided on an inner circumferential surface of the cylinder may be
provided within a predetermined range, it is possible to reduce an
abrasion ratio of the cylinder or the piston. More particularly, as
the difference value between the hardness of the first surface area
and a hardness of the second surface area may be maintained at a
predetermined value or more, it is possible to prevent the outer
circumferential surface of the piston from being stuck to the inner
circumferential surface of the cylinder, and thus, to prevent
damage to the piston or the cylinder.
[0075] Further, as the permanent magnet provided at the motor
assembly may be made of a ferrite material, which is relatively
inexpensive, it is possible to reduce manufacturing costs of the
compressor.
[0076] Embodiments disclosed herein provide a linear compressor
that prevents abrasion or damage of internal components
thereof.
[0077] Embodiments disclosed herein provide a linear compressor
that may include a shell including a refrigerant inlet, an outer
stator provided in the shell and including a coil, an inner stator
disposed to be spaced apart from the outer stator, a permanent
magnet disposed to be movable between the outer stator and the
inner stator, a cylinder including a compression space in which a
refrigerant sucked in through the refrigerant inlet is compressed,
a piston coupled to the permanent magnet so as to be reciprocated
in the cylinder, a first surface treatment part or first surface
area provided at or on the piston so as to have a first hardness
value, and a second surface area part or second surface treatment
provide at or on the cylinder so as to have a second hardness value
so that a difference value between the first and second hardness
values is more than a preset value. The preset value may be at
least approximately 150Hv or more based on Vickers hardness. The
preset value may be determined, so that an abrasion amount
generated at the piston or the cylinder, while the piston is
repeatedly reciprocated for a predetermined period of time, may be
approximately 3 .mu.m or less.
[0078] The first surface treatment part or the second treatment
part may be made of one of polytetra fluoroethylene (PTFE), diamond
like carbon (DLC), an Ni--P alloy, and an anodizing layer. The
first surface treatment part may be made of one of the PTFE, the
DLC, the Ni--P alloy, and the anodizing layer, and the second
treatment part may be made of another one of the PTFE, the DLC, the
Ni--P alloy, and the anodizing layer, which is different from the
first surface treatment part. The first surface treatment part may
be made of the PTFE, and the second surface treatment part may be
made of the anodizing layer.
[0079] The piston and the cylinder may be made of a non-magnetic
material. The piston and the cylinder may be made of aluminum or an
aluminum alloy. The aluminum or the aluminum alloy of the piston
and the cylinder may be the same material.
[0080] The first surface treatment part may be provided on an outer
circumferential surface of the piston. The second surface treatment
part may be provided on an inner circumferential surface of the
cylinder, which is opposite to the outer circumferential surface of
the piston.
[0081] The piston may include a piston body received in the
cylinder, and a flange part or flange expanded in a radial
direction of the piston body and coupled to the permanent magnet.
The first surface treatment part may be provided on an outer
circumferential surface of the piston body.
[0082] Embodiments disclosed herein provide a linear compressor
that may include a piston, which is reciprocated in a cylinder by a
force generated by an interaction between a flux generated by a
current applied to a coil and a flux of a permanent magnet, and
which includes a first surface treatment part or first surface area
provided on an outer circumferential surface of the piston, and a
second surface treatment part or second surface area provided on an
inner circumferential surface of the cylinder. A hardness value
measured at the first surface treatment part and a hardness value
measured at the second surface treatment part may make a preset
hardness difference.
[0083] Embodiments disclosed herein provide a linear compressor
that may include a shell including a refrigerant inlet, an outer
stator provided in the shell and including a coil, an inner stator
disposed to be spaced apart from the outer stator, a permanent
magnet disposed to be movable between the outer stator and the
inner stator, a cylinder including a compression space in which a
refrigerant sucked in through the refrigerant inlet may be
compressed, a piston coupled to the permanent magnet so as to be
reciprocated in the cylinder, a polytera fluroethylene (PTFE)
coating layer, which may be surface-treated on an outer
circumferential surface of the piston, and an anodizing layer which
may be surface-treated on an inner circumferential surface of the
cylinder.
[0084] 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.
[0085] 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.
[0086] 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.
* * * * *