U.S. patent application number 14/317041 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 LG ELECTRONICS INC.. Invention is credited to Sangsub JEONG, Wonhyun JUNG, Kyoungseok KANG, Jookon KIM, Chulgi ROH, Kiwook SONG.
Application Number | 20150004025 14/317041 |
Document ID | / |
Family ID | 50771168 |
Filed Date | 2015-01-01 |
United States Patent
Application |
20150004025 |
Kind Code |
A1 |
KANG; Kyoungseok ; et
al. |
January 1, 2015 |
LINEAR COMPRESSOR
Abstract
A linear compressor is provided that may include a shell
provided with a refrigerant inlet; a cylinder provided inside of
the shell to form a compression space; a piston that reciprocates
inside of the cylinder to compress a refrigerant in the compression
space; and a motor assembly that provides a drive force to the
piston and provided with a permanent magnet. The piston may include
a piston body having a cylindrical outer circumferential surface
and a surface-treated area, which may be processed with a material
having a predetermined hardness value, and a valve support provided
at an end of the piston body and having a suctioning hole be in
communication with the compression space. The valve support may
form a first non-surface-treated area, which is not
surface-treated.
Inventors: |
KANG; Kyoungseok; (Seoul,
KR) ; JUNG; Wonhyun; (Seoul, KR) ; ROH;
Chulgi; (Seoul, KR) ; JEONG; Sangsub; (Seoul,
KR) ; SONG; Kiwook; (Seoul, KR) ; KIM;
Jookon; (Seoul, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
LG ELECTRONICS INC. |
Seoul |
|
KR |
|
|
Assignee: |
LG ELECTRONICS INC.
Seoul
KR
|
Family ID: |
50771168 |
Appl. No.: |
14/317041 |
Filed: |
June 27, 2014 |
Current U.S.
Class: |
417/415 |
Current CPC
Class: |
F04B 39/0215 20130101;
F04B 39/0016 20130101; F05C 2251/048 20130101; F04B 35/045
20130101; F04B 39/0005 20130101; F04B 39/0276 20130101; F05C
2253/12 20130101 |
Class at
Publication: |
417/415 |
International
Class: |
F04B 35/04 20060101
F04B035/04; F04B 53/14 20060101 F04B053/14; F04B 53/16 20060101
F04B053/16; F04B 49/22 20060101 F04B049/22 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 28, 2013 |
KR |
10-2013-0075512 |
Jun 28, 2013 |
KR |
10-2013-0075514 |
Oct 4, 2013 |
KR |
10-2013-0118464 |
Claims
1. A linear compressor, comprising: a shell provided with a
refrigerant inlet; a cylinder provided inside of the shell to form
a compression space; a piston that reciprocates inside the cylinder
to compress a refrigerant in the compression space; and a motor
assembly that provides a drive force to the piston and provided
with a permanent magnet, wherein the piston comprises: a piston
body having a cylindrical outer circumferential surface including a
first surface-treated area comprising a material having a
predetermined hardness value; and a valve support provided at a
first end of the piston body and having a suction hole in
communication with the compression space, the valve support having
a first non-surface-treated area.
2. The linear compressor of claim 1, wherein the valve support
includes a surface that faces the compression space, and the first
non-surface-treated area is formed on the surface.
3. The linear compressor of claim 1, wherein the first
non-surface-treated area comprises a nonmagnetic material that
delivers heat, during the compression to the piston body.
4. The linear compressor of claim 1, further comprising a flange
coupled to a second end of the piston body that extends in a radial
direction of the piston body, wherein the cylindrical outer
circumferential surface comprises: a first outer circumferential
surface area that forms the first surface-treated area; and a
second outer circumferential surface area that forms a second
non-surface-treated area.
5. The linear compressor of claim 4, wherein the first outer
circumferential surface area is an outer circumferential surface
area that extends from the first end of the piston body toward the
flange.
6. The linear compressor of claim 4, wherein the second outer
circumferential surface area is an outer circumferential surface
area that extends from the second end of the piston body to which
the flange is coupled, toward the valve support.
7. The linear compressor of claim 1, wherein the first
non-surface-treated portion of the valve support is spaced from a
second non-surface-treated area.
8. The linear compressor of claim 7, wherein the first
non-surface-treated area is formed at a first end of the piston
body, and the second non-surface-treated area is formed at a second
end of the piston body.
9. The linear compressor of claim 7, wherein the second
non-surface-treated area comprises a nonmagnetic material that
delivers heat of the cylinder to the piston body.
10. The linear compressor of claim 1, further comprising a suction
valve coupled to the valve support to selectively open the suction
hole.
11. The linear compressor of claim 1, wherein the piston and the
cylinder are made of a nonmagnetic material.
12. The linear compressor of claim 11, wherein the piston and the
cylinder are made of aluminum or an aluminum alloy.
13. A linear compressor, comprising: a shell provided with a
refrigerant inlet; a cylinder provided inside of the shell to form
a compression space; a piston that reciprocates inside the cylinder
to compress a refrigerant in the compression space; and a motor
assembly that provides a drive force to the piston and provided
with a permanent magnet, wherein the piston comprises: a piston
body having a cylindrical outer circumferential surface including a
first surface-treated area, and a first non-surface-treated area; a
valve support provided at a first end of the piston body and having
a suction hole in communication with the compression space; a
suction valve that selectively opens the suction hole; and a second
non-surface-treated area comprising a non-magnetic material on an
outer surface of the valve support.
14. The linear compressor of claim 13, wherein the first
non-surface-treated area comprises a nonmagnetic material that
delivers heat, during the compression to the piston body.
15. The linear compressor of claim 13, further comprising a flange
coupled to a second end of the piston body that extends in a radial
direction of the piston body, wherein the cylindrical outer
circumferential surface comprises: a first outer circumferential
surface area that forms the first surface-treated area; and a
second outer circumferential surface area that forms a second
non-surface-treated area.
16. The linear compressor of claim 13, wherein the piston and the
cylinder are made of a nonmagnetic material.
17. The linear compressor of claim 16, wherein the piston and the
cylinder are made of aluminum or an aluminum alloy.
18. A linear compressor, comprising: a shell provided with a
refrigerant inlet; a cylinder provided inside of the shell to form
a compression space; a piston that reciprocates inside the cylinder
to compress a refrigerant in the compression space; and a motor
assembly that provides a drive force to the piston and provided
with a permanent magnet, wherein the piston comprises: a piston
body having a cylindrical outer circumferential surface including a
first surface area comprising a material having a predetermined
hardness value; and a valve support provided at a first end of the
piston body and having a suction hole in communication with the
compression space, the valve support having a surface that faces
the compression space, at least a portion of the surface comprising
a nonmagnetic material that delivers heat, during the compression
to the piston body.
19. The linear compressor of claim 18, wherein the cylindrical
outer circumferential surface comprises: a first outer
circumferential surface area that forms the first surface area; and
a second outer circumferential surface area that forms a second
surface area having a different hardness value from the
predetermined hardness value.
20. The linear compressor of claim 19, wherein the first outer
circumferential surface area is surface-treated to provide the
predetermined hardness and the second outer circumferential surface
area is not surface treated.
21. The linear compressor of claim 18, wherein the piston and the
cylinder are made of a nonmagnetic material.
22. The linear compressor of claim 21, wherein the piston and the
cylinder are made of aluminum or an 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, No. 10-2013-0075514, filed in
Korea on Jun. 28, 2013, and No. 10-2013-0118464, filed in Korea on
Oct. 4, 2013, which are hereby incorporated by reference in their
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 which 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 may include an outer
stator, an inner stator, and a permanent magnet, which form a
linear motor. The permanent magnet may be connected to an end of a
piston. When the permanent magnet linearly reciprocates due to a
mutual electromagnetic force between the inner stator and the outer
stator, the piston linearly reciprocates in a cylinder along with
the permanent magnet.
[0009] 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 pressure, interference between the cylinder and the piston may
occur. Also, if a slight error occurs while 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.
[0010] As described above, 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 a case of the related art linear compressor,
each of the cylinder 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 piston,
deteriorating efficiency in the compressor.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] Embodiments will be described in detail with reference to
the following drawings in which like reference numerals refer to
like elements, and wherein:
[0012] FIG. 1 is a cross-sectional view of a linear compressor
according to an embodiment;
[0013] FIG. 2 is a partial cross-sectional perspective view of a
coupled state between a cylinder and a piston according to an
embodiment;
[0014] FIG. 3 is a partial cross-sectional perspective view of the
cylinder and the piston of FIG. 2 illustrating movement;
[0015] FIG. 4 is a perspective view of a piston according to an
embodiment;
[0016] FIG. 5A is a cross-sectional view illustrating a coupled
state between a cylinder and a piston when an outer surface of the
piston is all surface-treated according to an embodiment; and
[0017] FIG. 5B is a cross-sectional view illustrating a coupled
state between a cylinder and a piston when the piston has a
plurality of non-surface-treated portions according to an
embodiment.
DETAILED DESCRIPTION
[0018] 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. Where possible, like
reference numerals have been used to indicate like elements and
repetitive disclosure has been omitted.
[0019] 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 that exerts a drive force on the piston 130.
The shell 100 may include an upper shell and a lower shell.
[0020] 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 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 passes through the suction
muffler 140, noise may be reduced.
[0021] A compression space P to compress the refrigerant by the
piston 130 may be defined in the cylinder 120. A suction hole 133b,
through which the refrigerant may be introduced into the
compression space P, may be defined in the piston 130, and a
suction valve 132 that selectively opens the suction hole 133b may
be disposed at a side of the suction hole 133b. The suction valve
132 may be formed of a steel plate.
[0022] 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.
[0023] 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 horizontal direction in FIG. 1.
[0024] 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 of 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 in the
compression space P may be compressed in a state in which the
suction valve 132 is closed.
[0025] When 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 in 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.
[0026] 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 coupling member, for
example. The discharge cover 172 and the discharge muffler 176 may
be coupled to the frame 110.
[0027] 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 by 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 more detail, in
a magnet having three poles, when poles of a first surface are
arranged in the form of N-S-N, the poles of a second surface may be
arranged in the form of S-N-S. The permanent magnet 230 may be
composed of a ferrite material, which is relatively
inexpensive.
[0028] 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.
[0029] 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 211. 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.
[0030] When a current is applied to the motor assembly 200, 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. When the magnetic flux
flowing along the outer stator 210 and the inner stator 220
interacts with the magnetic flux of the permanent magnet 230, a
force to move the permanent magnet 230 may be generated.
[0031] A state 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.
[0032] 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.
[0033] 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.
[0034] 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. The plurality of first
springs 151 and the plurality of second springs 155 may have a same
elastic coefficient.
[0035] The plurality of first springs 151 may be provided at upper
and lower sides of the cylinder 120 or piston 130, and the
plurality of second springs 155 may be provided at a front of the
cylinder 120 or 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.
[0036] 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.
[0037] The linear compressor 10 may further include an oil supply
pipe 165 that guides the 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.
[0038] FIG. 2 is a partial cross-sectional perspective view of a
coupled state between a cylinder and a piston according to an
embodiment. FIG. 3 is a partial cross-sectional perspective view of
the cylinder and the piston of FIG. 2 illustrating movement. FIG. 4
is a perspective view of a piston according to an embodiment.
[0039] Referring to FIGS. 2 through 4, the piston 130 according to
an embodiment is provided to reciprocate inside the cylinder 120.
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, the
magnetic flux generated in the motor assembly 200 may be delivered
to the piston 130, thereby preventing the magnetic flux from being
leaked to the outside of the piston 130. The piston 130 may be
formed by forging, for example.
[0040] The piston 130 may include a piston body 131 having an
approximately cylindrical shape and disposed inside the cylinder
120, and a flange 136 that extends in a radial direction from a
first end of the piston body 131 and coupled to the connection
member 138. The piston 130 may reciprocate along with the permanent
magnet 230.
[0041] A valve support 133 that forms one or more suction holes
133b may be provided to a second end of the piston body 131. A
refrigerant flowing in the piston body 131 may flow into the
compression space P through the one or more suction hole 133b.
[0042] In summary, the flange 136 coupled to the permanent magnet
230 may be provided to or at the first end of the piston body 131,
and the valve support 133 having a surface that faces the
compression space P may be provided to or at the second end of the
piston body 131. The valve support 133 may be made of a nonmagnetic
material, for example, aluminum.
[0043] The suction valve 132, which may selectively open the
suction hole 133b, may be provided to the valve support 133. When
the pressure of the compression space P is less than a suction
pressure, that is, the inner pressure of the piston body 131, the
suction valve 132 may be opened, and when the pressure of the
compression space P is larger than the suction pressure, the
suction valve 132 may be closed.
[0044] The piston body 131 may include an outer circumference
provided with a surface-treated portion 310 and a (first)
non-surface-treated portion 320. The outer circumferential surface,
on which the surface-treated portion 310 may be formed, may be
referred to as a "first outer circumferential surface", and the
outer circumferential surface, on which the non-surface-treated
portion 320 may be formed, may be referred to as a "second outer
circumferential surface".
[0045] The surface-treated portion 310 may be a portion of the
outer circumferential surface of the piston body 131, which is
surface-treated, and the non-surface-treated portion 320 may be an
aluminum surface, which is not surface-treated. The surface-treated
portion 310 may be formed to extend in a direction oriented toward
the flange 136 from the second end of the piston body 130 coupled
to the valve support 133. The surface-treated portion 310 may be
provided to improve abrasion resistance, lubrication, or heat
resistance of the piston body 131. For example, the surface-treated
portion 310 may be a "first coating layer". The surface-treated
portion 310 may be made of one of Teflon (PTFE), diamond like
carbon (DLC), Nickel (Ni)-phosphorous (P) alloy, or an anodizing
layer. The above-described materials will be described
hereinbelow.
[0046] PTFE is a fluorine-based polymer and is generally referred
to as "Teflon". The PTFE may be partially sprayed on the outer
circumferential surface of the piston body 131 in a state in which
a fluorene resin is configured to paint, is heated, and plasticized
at a constant temperature to form an inert coating layer. As the
PTFE has a low friction coefficient, when the PTFE is coated on the
outer circumferential surface of the piston body 131, surface
lubrication may be enhanced and abrasion resistance improved.
[0047] The PTFE has a relatively very low hardness, and measurement
of hardness of the PTFE may be performed by the pencil hardness
test. For example, the hardness of the PTFE may be the pencil
hardness HB or higher. When the hardness of the PTFE is converted
to a Vickers hardness (Hv), the PTFE may have a Vickers hardness in
a range of approximately 0-30 Hv.
[0048] The anodizing layer may be an aluminum oxide layer, which
may be formed when a current is applied to an aluminum anode, and
an aluminum surface is oxidized by oxygen generated in the aluminum
anode. The anodizing layer may have superior corrosion resistance
and insulation resistance. The hardness of the anodizing layer may
be varied with a state or component of a base material (mother
material) to be coated, and may have a range of approximately
300-500 Hv.
[0049] DLC is a non-crystalline carbon-based new material, and may
be provided in the form of a thin film by electrically accelerating
carbon ions in plasma or activated hydrocarbon molecules and
allowing the electrically accelerated carbon ions or activated
hydrocarbon molecules to a surface. The DLC may have physical
properties similar to diamond, that is, high hardness and abrasion
resistance, superior electrical insulation, and a low friction
coefficient, which leads to superior lubrication. The DLC may have
a hardness in a range of approximately 1,500-1,800 Hv.
[0050] The Ni--P alloy may be coated on the outer circumferential
surface of the piston body 131 by an electroless nickel plating,
for example, and may be formed when Ni and P components are
surface-precipitated at a uniform thickness. The Ni--P alloy may
have a composition including Ni: .about.90-92% and P: .about.9-10%.
The Ni--P alloy may improve corrosion resistance and abrasion
resistance of a surface to provide superior lubrication. The Ni--P
alloy may have a hardness in a range of approximately 500-600
Hv.
[0051] Aluminum materials have good heat transfer properties.
However, when the surface-treated portion 310 is provided to the
piston body 131 made of an aluminum material, the heat transfer
property in the piston body 131 may be reduced compared to a case
in which the piston body 131 is made of only the aluminum material.
Therefore, while the piston 130 reciprocates inside the cylinder
120, a temperature of the inner space of the cylinder 120 may be
elevated to a high temperature, the heat expansion rate in the
portion, among the piston body 131, where the surface-treated
portion 310 is provided may be different from that in the portion
where the non-surface-treated portion 320 is provided.
[0052] The non-surface-treated portion 320 may be formed at or on
only an area equal to a region extending from the first end of the
piston body 131 toward the second end of the piston body 131. That
is, the non-surface-treated portion 320 may be formed to extend in
a direction oriented toward the valve support 133 from the flange
136. The surface-treated portion 310 may be coupled to the
non-surface-treated portion 320.
[0053] The valve support 133 may include a (second)
non-surface-treated portion 133a. The non-surface-treated portion
133a may be a portion which is not subject to a separate surface
treatment, and may be formed of only the nonmagnetic material, for
example, aluminum, forming the valve support 133. As aluminum has a
superior heat transfer rate, compression heat formed in the
compression space P may be easily delivered to the piston through
the valve support 133.
[0054] The flange 136 may include a plurality of holes 137a and
137b. The plurality of holes 137a and 137b may include at least one
coupling hole 137a, into which a coupling member coupled to the
supporter 135 and the connection member 138 may be inserted, and at
least one through hole 137b to reduce flow resistance generated
around the piston 130.
[0055] 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.
[0056] As the cylinder 120 may be made of the aluminum-based
material, the magnetic flux generated in the motor assembly 200 may
be delivered to the cylinder 120, thereby preventing the magnetic
flux from being leaked to the outside of the cylinder 120. The
cylinder 120 may be formed by extruded rod processing, for
example.
[0057] The cylinder 120 and the piston 130 may have a same material
composition ratio, that is, type and composition ratio. The piston
130 and the cylinder 120 may be made of a same material, for
example, aluminum, and thus, may have a same thermal expansion
coefficient.
[0058] The cylinder 120 may have a hollow cylindrical shape, and
may movably receive the piston body 131 therein. The cylinder 120
may include an inner circumferential surface 121 that faces the
outer circumferential surface of the piston body 131.
[0059] The inner circumferential surface of the cylinder 120 may
include a (third) non-surface-treated portion 121a. The
non-surface-treated portion 121a may be a portion which is not
subject to a separate surface treatment, and may be formed of an
aluminum material. For example, the non-surface-treated portion
121a may be made of a material corresponding to the
non-surface-treated portion 133a of the piston 130 and the
non-surface-treated portion 320, and may have a same heat expansion
coefficient as the non-surface-treated portion 133a and the
non-surface-treated portion 320.
[0060] Additional embodiments are discussed hereinbelow.
[0061] The inner circumferential surface 121 of the cylinder may
include a surface-treated portion. The surface-treated portion of
the inner circumferential surface 121 may be made of one of Teflon
(PTFE), diamond like carbon (DLC), Nickel (Ni)-phosphorous (P)
alloy, or an anodizing layer.
[0062] It is, however, noted that the surface-treated portion of
the inner circumferential surface 121 may be made of a material
different from the material forming the surface-treated portion 310
of the piston 130. This is because only when a hardness difference
between the surface-treated portion of the inner circumferential
surface 121 and the surface-treated portion of the piston 130 is
not less than a predetermined hardness value, abrasion of the
cylinder 120 or the piston 130 may be prevented.
[0063] For example, the surface-treated portion of the inner
circumferential surface 121 may be made of an anodizing layer which
does not have a relatively great influence on heat transfer rate,
and the surface-treated portion 310 of the piston 130 may be made
of PTFE (Teflon), which has a great influence on the heat transfer
rate.
[0064] FIG. 5A is a cross-sectional view illustrating a coupled
state between a cylinder and a piston when an outer surface of the
piston is all surface-treated according to an embodiment, and FIG.
5B is a cross-sectional view illustrating a coupled state between a
cylinder and a piston when the piston has a plurality of
non-surface-treated portions according to an embodiment. Unlike the
previous embodiments, with this embodiment, a surface-treated
portion may be formed on an entire outer surface of the piston 130.
That is, the surface-treated portion may be provided to the outer
circumferential surface of the piston body 131 and the outer
surface of the valve support 133.
[0065] In a state in which the piston 130 is received inside the
cylinder 120, the outer circumferential surface of the piston body
131 may be formed to be spaced a predetermined distance (clearance)
apart from the inner circumferential surface 121 of the cylinder
120. Oil supplied from the oil supply device 160 may be introduced
into the space to flow in the space via the oil supply pipe
165.
[0066] In a state in which the piston does not reciprocate, that
is, in a state in which the linear compressor 10 is not operated,
the inner space of the cylinder 120 may be maintained at
atmospheric temperature, for example, at approximately 25.degree.
C. As the linear compressor 10 is operated, the piston 130 may
reciprocate, so that compression of the refrigerant in the
compression space P may occur. As the above cycles are repeated,
the temperature of the inner space of the cylinder 120 rises, so
that the cylinder 120 made of an aluminum material absorbs heat and
is thermally expanded.
[0067] At this time, as the inner circumferential surface 121 of
the cylinder 120 is provided with the non-surface-treated portion
121a, which is not surface-treated, or the surface-treated portion,
which does not have a great influence on heat transfer, the
cylinder 120 may be greatly heat-expanded. As a result, the
cylinder 120 may be greatly deformed in a direction in which an
inner diameter of the cylinder 120 is expanded.
[0068] In the meanwhile, the surface-treated portion may be
provided to the entire outer surface of the piston 130, and the
surface-treated portion of the piston 130 may be made of a material
hindering heat transfer. When the linear compressor 10 is operated,
the piston 130 reciprocates, and although the compression of the
refrigerant in the compression space P occurs and the cylinder 120
is heated, the compression heat of the compression space P or the
heat of the cylinder 120 may be blocked by the surface-treated
portion, so that the transfer of heat to the piston 130 may be
limited. Therefore, the cylinder 120 has a relatively large heat
expansion, whereas the piston 130 has a relatively small heat
expansion.
[0069] Compared with the cylinder 120, as the piston 130 is formed
at a relatively low temperature, heat expansion of the piston 130
may be limited. That is, the piston 130 may be less deformed in a
direction in which an outer diameter thereof expands.
[0070] Finally, as the cylinder 120 and the piston 130 have
different heat expansion rates due to a temperature difference
between the cylinder 120 and the piston 130, an interval between
the inner circumferential surface of the cylinder 120 and the outer
circumferential surface of the piston 130, that is, a clearance may
be relatively large (S1). When the clearance S1 is relatively
large, the piston 130 is weakly supported by the cylinder 120.
[0071] In more detail, an oil film may be formed between the piston
130 and the cylinder 120 due to oil acting as a lubricating
element. However, when the clearance S1 is large, a sufficient oil
film may not be formed between the piston 130 and the cylinder 120,
so that friction or interference may be caused between the piston
130 and the cylinder 120. Thus, the piston 130 or the cylinder 120
may be abraded.
[0072] FIG. 5B illustrates the piston 130 and the cylinder 120
according to an embodiment. Referring to FIG. 5B, the piston 130
according to an embodiment may include a surface-treated portion
310, and non-surface-treated portions 133a and 320.
[0073] In more detail, non-surface-treated portion 133a, which is
not surface-treated, may be formed on an outer surface of the valve
support 133 coupled to an end of the piston body 131. The outer
circumferential surface of the piston body 131 may include the
surface-treated portion 310 and the non-surface-treated portion
320. The non-surface-treated portion 320 may be formed on a portion
of the outer circumferential surface of the piston body 131. The
non-surface-treated portion 320 may be formed to extend in the
direction of the valve support 133 from the flange 136 coupled to
the first end of the piston body 131.
[0074] In this regard, the non-surface-treated portion 133a and the
non-surface-treated portion 320 may be formed at positions spaced
apart from each other. In other words, the non-surface-treated
portion 133a may be formed on the first end of the piston body 131,
and the non-surface-treated portion 320 may be formed on the second
end of the piston body 131.
[0075] While the piston 130 reciprocates, heat generated in the
compression space P may be delivered to the cylinder 120 and the
piston 130. As the inner circumferential surface 121 of the
cylinder 120 is provided with the non-surface-treated portion 121a,
which is not surface-treated, or the surface-treated portion, which
does not have a great influence on the heat transfer, the cylinder
120 may be greatly heat-expanded. As a result, the cylinder 120 may
be greatly deformed in a direction in which the inner diameter of
the cylinder 120 is expanded.
[0076] The heat may be delivered to the piston 130 through the
non-surface-treated portion 133a of the valve support 133 or the
non-surface-treated portion 320 of the outer circumferential
surface of the piston body 131 (Q1, Q2). That is, the heat may be
delivered to the piston 130 from both ends of the piston body 131.
Therefore, as time elapses, a temperature of the piston 130 may
rise to a temperature close to a temperature of the cylinder
120.
[0077] Finally, as the difference between the temperature of the
cylinder 120 and the temperature of the piston 130 may be reduced,
the cylinder 120 may have a similar heat expansion rate to the
piston 130. That is, a degree of deformation in which the inner
diameter of the cylinder 120 expands in an outer direction is
similar to a degree of deformation in which the outer diameter of
the piston 130 expands in an outer direction, so that a distance
from the inner circumferential surface 121 of the cylinder 120 to
the outer circumferential surface of the piston body 131, that is,
a clearance may be relatively small (S2). Therefore, a proper
amount of oil film may be formed between the cylinder 120 and the
piston 130 to perform a lubrication action, thereby preventing
abrasion due to friction between the cylinder 120 and the piston
130.
[0078] According to embodiments disclosed herein, a surface-treated
portion may be provided to an outer surface of a piston to increase
abrasion resistance, thus improving reliability of parts of a
compressor.
[0079] Also, as a valve support of the piston may not be
surface-treated, compression heat existing in the compression space
or the cylinder may be delivered to the piston, and thus, the
cylinder and the piston may have similar heat expansion rates,
thereby preventing a clearance between the inner circumferential
surface of the cylinder and the outer circumferential surface of
the piston from excessively increasing.
[0080] In addition, as the outer circumferential surface of the
piston body may include a surface-treated portion and a
surface-non-treated portion, and heat may be delivered from the
cylinder to the piston body through the non-surface-treated
portion, the cylinder and the piston may have similar heat
expansion rates, thus preventing the clearance from excessively
increasing.
[0081] More particularly, the valve support may be provided to or
at one end of the piston body, the non-surface-treated portion may
be provided to or at the other end of the piston body, and heat may
be delivered to the piston body from both ends of the piston body
to increase a temperature of the piston, so that the cylinder and
the piston have similar temperatures. Thus, as the cylinder and the
piston may have similar heat expansion rates, the clearance may be
maintained within a proper range, thereby preventing abrasion due
to friction of the cylinder.
[0082] Further, as the cylinder and the piston are made of a
nonmagnetic material, more particularly, an aluminum material, it
may be prevented that the magnetic flux generated from the motor
assembly is leaked to an outside, thereby improving efficiency of
the compressor. Moreover, as the permanent magnet provided to the
motor assembly may be made of an inexpensive ferrite material,
production costs of the compressor may be reduced.
[0083] Embodiments disclosed herein provide a linear compressor in
which interference between a piston and a cylinder may be
prevented.
[0084] Embodiments disclosed herein provide a linear compressor
that may include a shell provided with a refrigerant inlet; a
cylinder provided to an inside of the shell to form a compression
space; a piston that reciprocates inside the cylinder to compress a
refrigerant in the compression space; and a motor assembly that
provides a drive force to the piston and provided with a permanent
magnet. The piston may include a piston body having a cylindrical
outer circumference and a surface-treated portion, which may be
processed with a material having a set or predetermined hardness
value, and a valve support unit or support that forms an end of the
piston body and having a suction hole that suctions the refrigerant
into the compression space. The valve support unit may form a first
non-surface-treated portion, which is not surface-treated.
[0085] Embodiments disclosed herein provide a linear compressor
that may include a shell provided with a refrigerant inlet; a
cylinder provided to an inside of the shell to form a compression
space; a piston that reciprocates inside the cylinder to compress a
refrigerant in the compression space; and a motor assembly that
provides a drive force to the piston and provided with a permanent
magnet. The piston may include a piston body having a
surface-treated portion processed with a set or predetermined
material, and a second non-surface-treated portion, which is not
processed, a valve support unit or support coupled to an end of the
piston body and having a suction hole that suctions the refrigerant
into the compression space, a suction valve that selectively
shields the suction hole, and a first non-surface-treated portion,
which may be formed on an outer surface of the valve support unit
and may be formed of a non-magnetic material, which may be not
processed.
[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.
[0087] 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.
[0088] 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.
* * * * *