(19)
(11)EP 2 818 709 A1

(12)EUROPEAN PATENT APPLICATION

(43)Date of publication:
31.12.2014 Bulletin 2015/01

(21)Application number: 14168916.6

(22)Date of filing:  20.05.2014
(51)International Patent Classification (IPC): 
F04B 35/04(2006.01)
F04B 39/12(2006.01)
(84)Designated Contracting States:
AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR
Designated Extension States:
BA ME

(30)Priority: 28.06.2013 KR 20130075512
28.06.2013 KR 20130075514
04.10.2013 KR 20130118580

(71)Applicant: LG Electronics, Inc.
Seoul 150-721 (KR)

(72)Inventors:
  • Kang, Kyoungseok
    153-802 Seoul (KR)
  • Jung, Wonhyun
    153-802 Seoul (KR)
  • Roh, Chulgi
    153-802 Seoul (KR)
  • Song, Kiwook
    153-802 Seoul (KR)
  • Kim, Jookon
    153-802 Seoul (KR)
  • Jeong, Sangsub
    153-802 Seoul (KR)

(74)Representative: Vossius & Partner 
Siebertstrasse 4
81675 München
81675 München (DE)

  


(54)Linear compressor


(57) A linear compressor is provided. The linear compressor includes a shell having a refrigerant inlet, a cylinder arranged in the shell, a piston reciprocating in the cylinder, a motor assembly providing a driving force to the piston and having a permanent magnet, and a frame arranged on one side of the motor assembly, wherein the cylinder includes a first outer circumferential part with which an inner stator of the motor assembly is combined, and a second outer circumferential part extended from the first outer circumferential part and forcibly press-fit into the frame.




Description

BACKGROUND



[0001] The present disclosure relates to a linear compressor.

[0002] 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 being widely used in home appliances or industrial machineries such as refrigerators and air-conditioners.

[0003] Compressors may be largely classified into reciprocating compressors in which a compression space for suctioning or discharging a working gas is defined between a piston and a cylinder to compress a refrigerant while the piston is linearly reciprocated within the cylinder, rotary compressors in which a compression space for suctioning or discharging a working gas is defined between a roller that is eccentrically rotated and a cylinder to compress a refrigerant while the roller is eccentrically rotated along an inner wall of the cylinder, and scroll compressors in which a compression space for suctioning or discharging is defined between an orbiting scroll and a fixed scroll to compress a refrigerant while the orbiting scroll is rotated along the fixed scroll.

[0004] In recent years, among the reciprocating compressors, linear compressors having a simple structure in which the piston is directly connected to a driving motor, which is linearly reciprocated, to improve compression efficiency without mechanical loss due to switching in moving are being actively developed.

[0005] 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.

[0006] The linear motor has a structure in which a permanent magnet is disposed between an inner stator and an outer stator. Here, the permanent magnet may be linearly reciprocated by a mutual electromagnetic force between the permanent magnet and the inner (or outer) stator. Also, since the permanent magnet is operated in a state where 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.

[0007] The linear compressor according to the related art is disclosed in Korean Patent Publication No. 10-2010-0112474, proposed by this applicant.

[0008] Referring to Figs. 1 and 2 of the Korean Patent Application, in the case of a typical linear compressor, a frame 2 and a cylinder 3 are integrally formed in a closed container.

[0009] Specifically, the cylinder 3 is manufactured through magnetic casting, and then aluminum, a non-magnetic material is insert-molded onto the outer circumferential surface of the cylinder to manufacture the frame 2.

[0010] The frame 2 integrally formed with the cylinder 3 may be coupled to a peripheral component, e.g., a discharge valve assembly 6 or a motor cover 7. In this case, a force (coupling force) applied when the frame 2 is coupled to the discharge valve assembly 6 or the motor cover 7 may be applied to the cylinder 3.

[0011] When the coupling force is applied to the cylinder 3, the cylinder 3 is deformed. In addition, when the deformation of the cylinder 3 is significant, interference may occur due to the friction between the cylinder and the piston reciprocating in the cylinder.

[0012] As such, since interference occurs between the cylinder and the piston, there is a limitation in that interference occurs among a permanent magnet connected to the piston, an inner stator and an outer stator and thus there is damage to a part.

[0013] In addition, there are limitations in that due to the deformation of the cylinder, there may be a crack in a combination of the piston and the cylinder and a compression gas is externally leaked through the crack.

SUMMARY



[0014] Embodiments provide a linear compressor that prevents the deformation of a cylinder.

[0015] In one embodiment, a linear compressor includes: a shell having a refrigerant inlet; a cylinder arranged in the shell; a piston reciprocating in the cylinder; a motor assembly providing a driving force to the piston and having a permanent magnet; and a frame arranged on one side of the motor assembly, wherein the cylinder includes a first outer circumferential part with which an inner stator of the motor assembly is combined; and a second outer circumferential part extended from the first outer circumferential part and forcibly press-fit into the frame.

[0016] The frame may include a frame body having an insertion part into which the cylinder is inserted; and a press-fit part extended from the frame body and into which the second outer circumferential part of the cylinder is forcibly press-fit.

[0017] A slope may be formed on a side of the press-fit part that is connected to the frame body, wherein the slope may be formed to enable an internal diameter to become small as the press-fit part is away from the frame body.

[0018] The frame may further include a hook part on an inner circumferential surface of the slope, wherein the hook part may be hooked on a protrusion of the cylinder.

[0019] A space may be formed between a hook part of the frame and the second outer circumferential part.

[0020] The cylinder may further include a stepped part, wherein the stepped part may be formed on an interface between the first outer circumferential part and the second outer circumferential part and support the inner stator.

[0021] An external diameter of the second outer circumferential part may be formed to be larger than an external diameter of the first outer circumferential part.

[0022] An end of the press-fit part of the cylinder may be spaced from the inner stator.

[0023] The cylinder may further include a third outer circumferential part extended from the second outer circumferential part, and the protrusion may be formed on an interface between the second outer circumferential part and the third outer circumferential part.

[0024] An external diameter of the third outer circumferential part may be formed to be larger than an external diameter of the second outer circumferential part.

[0025] The second outer circumferential part may further include a press-fit corresponding part combined with the press-fit part, and a thickness of the press-fit corresponding part may be formed to be thicker than a thickness of the press-fit part.

[0026] The thickness of the press-fit corresponding part may be formed to be five times to eight times the thickness of the press-fit part.

[0027] The motor assembly may further include an outer stator and a state cover supporting the outer stator, and the frame may be coupled to the stator cover.

[0028] The linear compressor may further include a discharge value selectively opened to enable refrigerant compressed in the cylinder to be externally discharged; and a discharge muffler surrounding the discharge value, wherein the frame may be coupled to the discharge muffler.

[0029] The frame and the cylinder may be made of aluminum or an aluminum alloy.

BRIEF DESCRIPTION OF THE DRAWINGS



[0030] 

Fig. 1 is a cross-sectional view illustrating an inner configuration of a linear compressor according to an embodiment.

Fig. 2 is an exploded perspective view of a linear compressor and a frame assembly of a linear compressor according to an embodiment.

Fig. 3 is a cross-sectional view of a combination of a frame and a cylinder according to an embodiment.

Fig. 4 is a cross-sectional view of a combination of a frame assembly and a discharge muffler according to an embodiment.

Fig. 5 is an enlarged view of circled part "A" of Fig. 4.

Figs. 6 and 7 show, before combination, a frame and a cylinder according to an embodiment.

Fig. 8 shows how forces are applied on a frame assembly according to an embodiment.


DETAILED DESCRIPTION OF THE EMBODIMENTS



[0031] Hereinafter, specific embodiments will be described with reference to accompanying drawings. However, the scope of the present disclosure is not limited to the embodiments herein, and thus a person skilled in the art, who understood the scope of the present disclosure, would easily suggest other embodiments within the same scope thereof.

[0032] Fig. 1 is a cross-sectional view illustrating an inner configuration of a linear compressor according to an embodiment.

[0033] Referring to Fig. 1, the linear compressor 10 according to an embodiment includes a cylinder 120 disposed in a shell 100, a piston 130 linearly reciprocating inside the cylinder 120, and a motor assembly 200 which is a linear motor exerting a driving force on the piston 130. The shell 100 may be configured by combination of an upper shell and a lower shell.

[0034] The cylinder 120 may be made of a nonmagnetic material such as an aluminum-based material (aluminum or aluminum alloy).

[0035] Since the cylinder 120 is made of the aluminum-based material, the magnetic flux generated in the motor assembly 200 is 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.

[0036] The piston 130 may be made of an aluminum material (aluminum or aluminum alloy), a non-magnetic material. Since the piston 130 is made of the aluminum material, it is possible to prevent magnetic flux generated from a motor assembly 200 from becoming delivered and leaked to the outside of the piston 130. In addition, the piston 130 may be formed by using a forging method.

[0037] In addition, the component ratios of the materials of the cylinder 120 and the piston 130, i.e., types and composition ratios thereof may be the same. The piston 130 and the cylinder 120 are made of the same material (aluminum), and thus have the same thermal expansion coefficient. During operation of the linear compressor 10, a high-temperature environment (about 100°C) is created in the shell 100. At this time, the piston 130 and the cylinder 120 have the same thermal expansion coefficient, and may thus have the same amount of thermal deformation.

[0038] As a result, since the piston 130 and the cylinder 120 are thermally deformed by different amounts or in different directions, it is possible to prevent interference with the cylinder 120 during movement of the piston 130.

[0039] The shell 100 includes a suction unit 101 suctioning refrigerant and a discharge unit 105 discharging refrigerant compressed in the cylinder 120. The refrigerant suctioned through the suction unit 101 flows into the piston 130 via a suction muffler 140. While the refrigerant passes through the suction muffler 140, noise may decrease.

[0040] A compression space P for compressing the refrigerant by the piston 130 is defined in the cylinder 120. A suction hole 131a through which the refrigerant is introduced into the compression space P is defined in the piston 130, and a suction valve 132 selectively opening the suction hole 131a is disposed at one side of the suction hole 131a.

[0041] A discharge valve assembly 170, 172 and 174 for discharging the refrigerant compressed in the compression space P is disposed at one side of the compression space P. That is, it is understood that the compression space P is formed between one end of the piston 130 and the discharge valve assembly 170, 172 and 174.

[0042] The discharge valve assembly 170, 172 and 174 includes a discharge cover 172 in which a discharge space of the refrigerant is defined; a discharge valve 170 which is opened and introduces 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 is disposed between the discharge valve 170 and the discharge cover 172 to exert an elastic force in an axial direction. In this example, it can be understood that the "axial direction" used herein is a direction in which the piston linearly reciprocates, that is, a horizontal direction in Fig. 1.

[0043] The suction valve 132 may be disposed at one side of the compression space P, and the discharge valve 170 may be disposed at the other side of the compression space P, that is, at an opposite side of the suction valve 132.

[0044] While the piston 130 linearly reciprocates inside the cylinder 120, the suction valve 132 is 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. On the contrary, when the pressure of the compression space P is not less than the suction pressure, the refrigerant of the compression space P is compressed in a state where the suction valve 132 is closed.

[0045] If the pressure of the compression space P is the discharge pressure or more, the valve spring 174 is deformed to open the discharge valve 170 and the refrigerant is discharged from the compression space P into the discharge space of the discharge cover 172.

[0046] The refrigerant of the discharge space flows into a loop pipe 178 via the discharge muffler 176. The discharge muffler 176 may reduce flow noise of the compressed refrigerant, and the loop pipe 178 guides the compressed refrigerant to a discharge part 105. The loop pipe 178 is coupled to the discharge muffler 176 and curvedly extends to be coupled to the discharge part 105.

[0047] The linear compressor 10 further includes a frame 110. The frame 110 is a component to fix the cylinder 120. As an example, the cylinder 120 may be press-fit (or press-fit coupled) into the frame 110.

[0048] The press-fit or press-fit coupling is understood as a technique that when a first object is inserted into a second object, at least one of the first object and the second object is deformed by a certain force for combination if the size or diameter of the first object is larger than that of the second object.

[0049] While the cylinder 120 and the frame 110 are combined, the frame 110 may be coupled to the discharge muffler 176 or the discharge cover 172 by a coupling member. In addition, the frame 110 may be coupled to the stator cover 240. As an example, the coupling member may be a bolt.

[0050] On the other hand, the frame 110 may be made of an aluminum-based material (aluminum or aluminum alloy), a non-magnetic material. Since the frame 110 is made of the aluminum-based material, it is possible to prevent magnetic flux generated from a motor assembly 200 from becoming delivered to the frame 110 and leaked to the outside of the frame 110.

[0051] The motor assembly 200 includes an outer stator 210 fixed to the frame 110 and disposed so as to surround the cylinder 120, an inner stator 220 disposed apart from the 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.

[0052] 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 be composed of a single magnet having one pole, or may be formed by combination of multiple magnets having three poles.

[0053] In addition, the permanent magnet 230 may be made of a ferrite material that is relatively cheap.

[0054] 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 from one 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.

[0055] The outer stator 210 includes a coil-wound body 213 and 215 and a stator core 211.

[0056] The coil-wound body 213 and 215 includes a bobbin 213 and a coil 215 wound in a circumferential direction of the bobbin 213. The coil 215 may have a polygonal section, for example, a hexagonal section.

[0057] The stator core 211 is provided such that a plurality of laminations is stacked in a circumferential direction, and may be disposed to surround the coil-wound body 213 and 215.

[0058] If a current is applied to the motor assembly 200, the current flows to the coil 215, flux is formed around the coil 215 by the current flowing through the coil 215, and the flux flows forming a closed loop along the outer stator 210 and the inner stator 220.

[0059] Flux flowing along the outer stator 210 and the inner stator 220 and flux in the permanent magnet 230 interact, so a force to move the permanent magnet 230 may be generated.

[0060] A state cover 240 is disposed at one side of the outer stator 210. One end of the outer stator 210 may be supported by the frame 110, and the other end thereof may be supported by the stator cover 240. The frame 110 and the stator cover 240 may be coupled by a coupling member (not shown).

[0061] The inner stator 220 is fixed to the outer circumference of the cylinder 120. The inner stator 220 is configured such that a plurality of laminations is stacked at an outer side of the cylinder 120 in a circumferential direction.

[0062] The linear compressor 10 further includes a supporter 135 supporting the piston 130, and a back cover 180 extending toward the inlet 101 from the piston 130. The back cover 180 may be disposed to cover at least a portion of the suction muffler 140.

[0063] The linear compressor 10 includes a plurality of springs 151 and 155 which of each natural frequency is adjusted so as to allow the piston 130 to perform resonant motion, the springs being elastic members.

[0064] The plurality of springs 151 and 155 include a first spring 151 supported between the supporter 135 and the stator cover 240, and a second spring 155 supported between the supporter 135 and the back cover 180. The elastic modulus of the first spring 151 and the second spring 155 may be equally formed.

[0065] The first spring 151 may be provided in plurality at both sides of the cylinder 120 or piston 130, and the second spring 155 may be provided in plurality at the front of the cylinder 120 or piston 130.

[0066] In this example, it can be understood that the term "front" used herein means a direction oriented toward the inlet 101 from the piston 130. That is, it can be understood that 'rear' means a direction oriented toward the discharge valve assembly 170, 172 and 174 from the inlet 101. This term may also be equally used in the following description.

[0067] Predetermined amount oil may be stored on an inner bottom surface of the shell 100. An oil supply device 160 for pumping oil may be provided in a lower portion of the shell 100. The oil supply device 160 is operated by vibration generated according to linear reciprocating motion of the piston 130 to thereby pump the oil upward.

[0068] The linear compressor 10 further includes an oil supply pipe 165 guiding the flow of the oil from the oil supply device 160. The oily supply pipe 165 may extend from the oil supply device 160 to a space between the cylinder 120 and the piston 130.

[0069] The oil pumped from the oil supply device 160 is supplied to the space between the cylinder 120 and the piston 130 via the oil supply pipe 165, and performs cooling and lubricating operations.

[0070] Fig. 2 is an exploded perspective view of a linear compressor and a frame assembly of a linear compressor according to an embodiment, Fig. 3 is a cross-sectional view of a combination of a frame and a cylinder according to an embodiment, and Fig. 4 is a cross-sectional view of a combination of a frame assembly and a discharge muffler according to an embodiment.

[0071] Referring to Figs. 2 to 4, a frame assembly according to an embodiment includes a frame 110 including a frame body 110a forming an insertion part, a cylinder 120 inserted into the insertion part 111, and an inner stator 220 combined with the outer circumferential surface of the cylinder 120.

[0072] The frame body 110a has an approximate circle or plate shape. In addition, the insertion part 111 is formed in a manner that at least a portion of the frame body 110a is removed, and the cylinder 120 is inserted in one direction through the insertion part 111. The frame includes combinations 112 to 114 that are arranged on one side of the insertion part 111 and combined with the cylinder 120.

[0073] An opening 120a combined with the discharge value 170 is formed in the cylinder 120. The opening 120a is understood as an open part of one end of the cylinder 120. If the discharge value 170 opens, the refrigerant compressed in the compression space P flows into the discharge cover 172 via the opening 120a.

[0074] A discharge muffler 176 is provided on one side of the frame 110. In addition, a bracket 350 is provided between the frame 110 and the discharge muffler 176.

[0075] A first coupling hole 176a is formed in the discharge muffler 176 and a third coupling hole 118 is formed in the frame 110. In addition, a second coupling hole 352 is formed in the bracket 350. A certain coupling member is arranged to pass through the first to the third coupling holes 176a, 352 and 118 and combines the frame 110, the bracket 350 and the discharge muffler 176. The bracket 350 helps the frame 110 and the discharge muffler 176 to be closely combined.

[0076] A sealer 360 is provided around the opening 120a. While the frame 110 and the discharge muffler 176 are combined, the sealer 360 may be arranged where the opening 120a of the cylinder 120 and the discharge muffler 176 are combined. While refrigerant flows from the cylinder 120 to the discharged cover 172, the sealer 360 may prevent the refrigerant from becoming leaked.

[0077] A fourth coupling hole 119 is formed in the frame 110. The fourth coupling hole 119 may be combined with the stator cover 240 by a certain coupling member. The outer stator 210 may be held on one side of the frame 110 on which the fourth coupling hole 119 is formed.

[0078] The cylinder 120 includes a plurality of outer circumferential parts 121, 123 and 125 that form the outer circumferential surface of the cylinder 120 and have different external diameters.

[0079] The outer circumferential parts 121, 123 and 125 include a first outer circumferential part 121 combined with the inner stator 220. The inner stator 220 is press-fit coupled onto the outer circumferential surface of the first outer circumferential part 121, 121. The inner stator 220 may have a hollow cylindrical shape to be able to surround the first outer circumferential part 121.

[0080] A second outer circumferential part 123 is extended to one side of the first outer circumferential part 121. The second outer circumferential part 123 may be extended from the first outer circumferential part 121 toward the opening 120a.

[0081] The external diameter of the second outer circumferential part 123 is formed to be larger than that of the first outer circumferential part 121. A stepped part 122 externally extended in a radial direction is formed on the interface between the first outer circumferential part 121 and the second outer circumferential part 123. Due to the stepped part 122, the external diameter of the second outer circumferential part 123 is formed to be larger than that of the first outer circumferential part 121.

[0082] The second outer circumferential part 123 provides a surface that is in contact with the frame 110. In this example, the term "contact" is understood as a contact for the press-fitting into the frame 110.

[0083] A third outer circumferential part 125 is extended to one side of the second outer circumferential part 123. The third outer circumferential part 125 may be extended from the second outer circumferential part 123 toward the opening 120a.

[0084] The external diameter of the third outer circumferential part 125 is formed to be larger than that of the second outer circumferential part 123. A protrusion 124 externally extended in a radial direction is formed on the interface between the second outer circumferential part 123 and the third outer circumferential part 125. Due to the hook part 124, the external diameter of the third outer circumferential part 125 is formed to be larger than that of the second outer circumferential part 123.

[0085] The hook part 124 provides a surface that is in contact with the frame 110. In this example, the term "contact" is understood as a contact for being hooked on the frame 110.

[0086] The frame 110 includes a press-fit part 112 into which the cylinder 120 is press-fit while the cylinder is inserted into the frame 110. The press-fit part 112 has an approximate cylindrical shape and is combined to surround the outer circumferential surface of the second outer circumferential part 123.

[0087] That is, the internal diameter of the press-fit part 112 may be formed to be slightly smaller than the external diameter of the second outer circumferential part 123. When the second outer circumferential part 123 is press-fit into the press-fit part 112, at least one of the second outer circumferential part 123 and the press-fit part 112 may be deformed. That is, deformation may be made in a manner that the internal diameter of the second outer circumferential part 123 is reduced or the external diameter of the press-fit part 112 is expanded.

[0088] A slope 113 is formed on a side of the press-fit part 112 that is connected to the frame body 110a. The slope 113 is formed so that an internal diameter becomes small as the press-fit part 112 becomes far away from the frame body 110a. The slope 113 may have a cylindrical shape having a sloping outer circumferential surface to surround the cylinder 120.

[0089] The slope 113 may be combined with a portion of the frame body 110a on which the insertion part 111 is formed. Since the slope 113 is extended upwardly, it may not be in contact with the cylinder 120. That is, the frame 110 is combined with the cylinder 120 on a portion of the press-fit part 112 other than the slope 113, and it is arranged on the slope 113 to be spaced outwardly from the cylinder 120.

[0090] As such, since an area or region where the frame 110 is in contact with the cylinder 120 is not wide, the magnitude of a force delivered to the cylinder 120 among forces applied to the frame 110 may not be great.

[0091] Thus, it is possible to reduce the deformation of the cylinder 120. In particular, when considering that the frame 110 and the cylinder 120 are made of a soft aluminum based material, the deformation level of the cylinder 120 may significantly depend on the force and thus, it may be very meaningful to decrease force delivered to the cylinder 120.

[0092] A hook part 114 is provided under the slope 113. The hook part 114 is hooked on the hook part 124. The cylinder 120 is inserted in one direction (right direction in Fig. 4) through the insertion part 111 and the first outer circumferential part 121 is first inserted. In addition, the cylinder 120 may be inserted until there is interference between the hook part 114 and the hook part 124.

[0093] Fig. 5 is an enlarged view of circled part "A" of Fig. 4, and Figs. 6 and 7 show, before combination, a frame and a cylinder according to an embodiment.

[0094] Referring to Figs. 5 to 7, a portion of the press-fit part 112 of the frame 110 according to an embodiment other than the slope 113 is press-fit coupled to at least a portion of the second outer circumferential part 123 of the cylinder 120. The second outer circumferential part 123 includes a press-fit corresponding part 123a combined with the press-fit part 112. The press-fit corresponding part 123a forms the outer circumferential surface of at least a portion of the second outer circumferential part 123.

[0095] The thickness of the press-fit part 112, i.e. height t1 is formed to be smaller than the thickness t2 of the press-fit corresponding part 123a.

[0096] As an example, the thickness t2 may have a value that is five times to eight times the thickness t1.



[0097] Due to a thickness difference between the press-fit part 112 and the press-fit corresponding part 123a, while the second outer circumferential part 123 is press-fit into the press-fit part 112, there may be a deformation difference between the press-fit part 112 and the second outer circumferential part 123. That is, the deformation of the cylinder 120 having a thick thickness may be less than that of the press-fit part 112 having a relatively thin thickness.

[0098] In particular, since the frame 110 and the cylinder 120 each are made of an aluminum-based material, when a certain force is applied to the frame 110 or the cylinder 120, the deformation level of the frame 110 or the cylinder 120 may significantly depend on the force.

[0099] As an example, by the ratio of the thickness t1 and the thickness t2, the deformation of the press-fit part 112 may have a value that is 250 times to 350 times the deformation of the second outer circumferential part 123. Since the deformation is in inverse proportion to the elastic modulus of an aluminum-based material, the elastic modulus of the press-fit part 112 may have a value that is 1/350 to 1/250 the elastic modulus of the second outer circumferential part 123.

[0100] The inner stator 220 is press-fit into the first outer circumferential part 121 of the cylinder 120. In addition, the stepped part 122 is in contact with the external surface of the inner stator 220. On the contrary, the external surface of the inner stator 220 is spaced from the frame 110.

[0101] Specifically, a virtual first line formed by extending the stepped part 122 in a radial direction is W1 spaced from a virtual second line formed by extending the end of the press-fit part 112 in a radial direction. Thus, the inner stator 220 is in contact with the stepped part 122, while not in contact with the press-fit part 112.

[0102] According to such a configuration, while the inner stator 220 is press-fit into the outside of the cylinder 120, the inner stator 220 does not apply a force (pressing force) to the frame 110.

[0103] Thus, it is possible to prevent a force from the inner stator 220 from becoming delivered to the second outer circumferential part 123 through the press-fit part 112. As a result, it is possible to prevent the deformation of the cylinder 120.

[0104] On the other hand, the hook part 114 arranged on the frame 110 may be hooked on the hook part 124 of the cylinder 120. In this case, a contact surface on which hooking is performed is vertically extended in a radial direction with respect to the outer circumferential surface of the second outer circumferential part 123.

[0105] In addition, a space 127 is formed between the hook part 114 and the second outer circumferential part 123. The space 127 defines a space between the hook part and the second outer circumferential part 123.

[0106] That is, the hook part 114 is arranged to be spaced from the second outer circumferential part 123. In summary, the hook part 114 is in contact with the cylinder 120 through the protrusion 124, while not in contact with the second outer circumferential part 123.

[0107] As such, even if hooking is performed through the hook part 114 between the frame 110 and the cylinder 120, it is possible to decrease the magnitude of a force delivered between the frame 110 and the cylinder 120 by preventing unnecessary contact except for the hook part.

[0108] A place where the press-fit part 112 is in contact with the press-fit corresponding part 123a may be referred to as "a first contact" and a place where the hook part 114 is in contact with the protrusion 124 may be referred to as "a second contact".

[0109] The first contact is extended forward and backward from a portion of the outer circumferential surface of the cylinder 120 and the second contact is extended in a radial direction from a portion of the outer circumferential surface of the cylinder 120. That is, one surface formed by the first contact may be perpendicular to another surface formed by the second contact.

[0110] Fig. 8 shows how forces are applied on a frame assembly according to an embodiment.

[0111] Referring to Figs. 6 to 8, the cylinder 120 may be inserted into the insertion part 111 of the frame 110. The cylinder 120 may be inserted in a manner that the first outer circumferential part 121 passes through the insertion part 111 and then the second outer circumferential part 123 passes through the insertion part 111.

[0112] Since the first outer circumferential part 121 is smaller than the internal diameter of the press-fit part 112, it may be inserted without interference. On the other hand, since the second outer circumferential part 123 is larger than the internal diameter of a portion of the press-fit part 112 other than the slope 113, there may be interference with the press-fit part 112. In this state, if a certain force is applied, the second outer circumferential part 123 is press-fit into the press-fit part 112.

[0113] While being press-fit, the second outer circumferential part 123 or the press-fit part 112 may be deformed. However, as described in Fig. 5, since the thickness and elastic modulus of the second outer circumferential part 123 are larger than those of the press-fit part 112, the deformation of the second outer circumferential part 123 may be relatively little.

[0114] The cylinder 120 is inserted until the protrusion 124 is hooked on the hook part 114, and the insertion is completed when the protrusion 124 interferes with the hook part 114.

[0115] While the frame 110 and the cylinder 120 are combined, the frame 110 may be coupled to the discharge muffler 176 or the stator cover 240 by a coupling member. That is, a coupling member may be combined with the third coupling hole 118 to combine the discharge muffler 176 with the frame 110, and another coupling member may be combined with the fourth coupling hole 119 to combine the stator cover 240 with the frame 110.

[0116] As such, when the frame 110 is coupled to the internal component of a linear compressor, a coupling force is applied to the frame 110. As an example, a coupling force generated through the fourth coupling hole 119 may be F1 and a coupling force generated through the third coupling hole 118 may be F2.

[0117] In addition, at least a portion F3 of the coupling forces F1 and F2 applied to the frame 110 may be delivered to the cylinder 120 through the press-fit part 112. That is, a coupling force applied to the frame 110 may be delivered to the cylinder 120 through a region where the frame 110 is press-fit coupled to the cylinder 120.

[0118] As described above, since the frame 110 is detachably combined with the cylinder 120 and a press-fit coupled region or area is narrow, the magnitude of a force delivered to the cylinder 120 may not be great. As a result, it is possible to decrease the deformation of the cylinder 120 due to the frame 110.

[0119] According to such embodiments, since the cylinder and the frame are detachably combined and an area where the cylinder is combined with the frame is narrow, the magnitude of a force delivered to the cylinder among coupling forces generated when the frame is coupled to the internal component of the compressor may be small.

[0120] As a result, since the magnitude of a force generated when the frame presses the cylinder is small, embodiments have effects in that the deformation of the cylinder may be little and thus it is possible to prevent the interference between the piston and the cylinder.

[0121] In particular, since the thickness of the press-fit part of the frame press-fit into the outer circumferential surface of the cylinder is thinner than that of the outer circumferential surface of the cylinder and the elastic modulus of the press-fit part is smaller than that of the outer circumferential surface of the cylinder, there is an advantage in that it is possible to decrease the deformation of the outer circumferential surface of the cylinder.

[0122] Moreover, since the inner stator press-fit into the outer circumferential surface of the cylinder is arranged to be spaced from the press-fit part of the frame, the coupling force of the frame is not delivered to the inner stator and thus it is possible to prevent the coupling of the frame from becoming delivered to the cylinder through the inner stator.

[0123] Moreover, since the frame of the cylinder is made of a nonmagnetic material such as an aluminum-based material and it is possible to prevent flux generated from the motor assembly from becoming leaked to the outside of the cylinder, there is an advantage in that it is possible to improve the efficiency of the compressor.

[0124] Moreover, since the permanent magnet arranged in the motor assembly is made of a cheap ferrite material, there is an advantage in that it is possible to decrease the manufacturing cost of the compressor.


Claims

1. A linear compressor (10) comprising:

a shell (100) having a refrigerant inlet (101);

a cylinder (120) provided within the shell;

a piston (130) configured for reciprocating in the cylinder;

a motor assembly (200) configured for providing a driving force to the piston (130) and having a permanent magnet (230); and

a frame (110) arranged on one side of the motor assembly, wherein the cylinder (120) comprises:

a first outer circumferential part (121) with which an inner stator (220) of the motor assembly is combined; and

a second outer circumferential part (123) extended from the first outer circumferential part and forcibly press-fit into the frame(110).


 
2. The linear compressor (10) according to claim 1, wherein the frame (110) comprises:

a frame body (110a) having an insertion part (111) into which the cylinder (120) is inserted; and

a press-fit part (112) extended from the frame body (110a) and into which the second outer circumferential part (123) of the cylinder is forcibly press-fit.


 
3. The linear compressor (10) according to claim 2, wherein a slope (113) is formed on a side of the press-fit part (112) to be connected to the frame body (110a), wherein the slope (113) has an internal diameter thereof getting smaller as the slope (113) gets away from the frame body (110a) toward the press-fit part (112).
 
4. The linear compressor (10) according to claim 3, wherein the frame (110) further comprises a hook part (114) on an inner circumferential surface of the slope (113), wherein the hook part (114) is hooked on a protrusion (124) of the cylinder (120).
 
5. The linear compressor (10) according to claim 4, wherein a space (127) is provided between the hook part (114) of the frame and the second outer circumferential part (123).
 
6. The linear compressor (10) according to any of claims 2 to 5, wherein an end of the press-fit part (112) of the cylinder is spaced from the inner stator (220).
 
7. The linear compressor (10) according to any of claims 2 to 6, wherein the second outer circumferential part (123) further comprises a press-fit corresponding part (123a) combined with the press-fit part (112), and
a thickness of the press-fit corresponding part (123a) is thicker than that of the press-fit part (112).
 
8. The linear compressor (10) according to claim 7, wherein the thickness of the press-fit corresponding part (123a) is five times to eight times the thickness of the press-fit part (112).
 
9. The linear compressor (10) according to any of preceding claims, wherein the cylinder (120) further comprises a stepped part (122), wherein the stepped part is provided at an interface between the first outer circumferential part (121) and the second outer circumferential part (123) and supports the inner stator (220).
 
10. The linear compressor (10) according to claim 9, wherein an external diameter of the second outer circumferential part (123) is larger than that of the first outer circumferential part (121).
 
11. The linear compressor (10) according to any of claims 4 to 10, insofar as referring to claim 4, wherein the cylinder (120) further comprises a third outer circumferential part (125) extended from the second outer circumferential part (123), and
the protrusion (124) is provided at an interface between the second outer circumferential part (123) and the third outer circumferential part (125).
 
12. The linear compressor (10) according to claim 11, wherein an external diameter of the third outer circumferential part (125) is larger than that of the second outer circumferential part (123).
 
13. The linear compressor (10) according to any of preceding claims, wherein the motor assembly (200) further comprises an outer stator (210) and a state cover (240) supporting the outer stator, and
the frame (110) is coupled to the stator cover (240).
 
14. The linear compressor (10) according to any of preceding claims, further comprising:

a discharge valve (170, 172, 174) selectively openable to enable refrigerant compressed in the cylinder (120) to be discharged to outside; and

a discharge muffler (176) surrounding the discharge value, wherein the frame (110) is coupled to the discharge muffler.


 
15. The linear compressor (10) according to any of preceding claims, wherein the frame (110) and the cylinder (120) are made of aluminum or an aluminum alloy.
 




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Cited references

REFERENCES CITED IN THE DESCRIPTION



This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

Patent documents cited in the description