KR102148260B1 - A linear compressor - Google Patents

Abstract

The present invention relates to a linear compressor.
A linear compressor according to an embodiment of the present invention includes a shell provided with a refrigerant suction unit; A cylinder provided inside the shell and forming a compression space; A piston reciprocating within the cylinder and compressing a refrigerant in the compression space; And a motor assembly providing a driving force to the piston and having a permanent magnet, wherein the piston has a cylindrical outer circumferential surface and a piston body forming a surface treatment unit processed from a material having a set hardness value; A valve support part forming one end of the piston body and having a suction hole for sucking refrigerant into the compression space; And a flange portion coupled to the other end of the piston body and extending in a radial direction of the piston body, and wherein the valve support portion forms a first non-processed surface-treated portion.

Description

Linear compressor {A linear compressor}

The present invention relates to a linear compressor.

In general, a compressor is a mechanical device that receives power from a power generating device such as an electric motor or a turbine and compresses air, refrigerant or other various operating gases to increase the pressure. It is widely used throughout.

If these compressors are classified largely, a reciprocating compressor that compresses the refrigerant while the piston linearly reciprocates inside the cylinder by forming a compression space through which the working gas is sucked and discharged between the piston and the cylinder. ), and a compression space in which working gas is sucked and discharged between the eccentrically rotated roller and the cylinder is formed, and the roller is rotated eccentrically along the inner wall of the cylinder to compress the refrigerant, and a rotary compressor and orbiting scroll A compressed space through which the working gas is sucked and discharged is formed between the scroll and the fixed scroll, and the orbiting scroll may be divided into a scroll compressor that compresses the refrigerant while rotating along the fixed scroll.

Recently, among the reciprocating compressors, a number of linear compressors having a simple structure have been developed, in particular, by allowing a piston to be directly connected to a driving motor for reciprocating linear motion, thereby improving compression efficiency without mechanical loss due to motion conversion.

In general, a linear compressor is configured to suck a refrigerant, compress it, and discharge it while the piston moves in a reciprocating linear motion inside a cylinder by a linear motor in a sealed shell.

The linear motor is configured such that a permanent magnet is positioned between the inner stator and the outer stator, and the permanent magnet is driven to linearly reciprocate by mutual electromagnetic force between the permanent magnet and the inner (or outer) stator. In addition, as the permanent magnet is driven while being connected to the piston, the piston sucks and compresses the refrigerant while reciprocating and linearly moving inside the cylinder, and then discharged.

With respect to the conventional linear compressor, the present applicant has filed a patent application (hereinafter, referred to as a conventional application) (Publication No. 10-2010-0010421).

The linear compressor according to the conventional application includes an outer stator 240, an inner stator 220 and a permanent magnet 260 as a linear motor, and one end of the piston 130 is connected to the permanent magnet 260.

When the permanent magnet 260 reciprocates and linearly moves by mutual electromagnetic force between the permanent magnet 260 and the inner stator 220 and the outer stator 240, the piston 130 is a cylinder together with the permanent magnet 260 Reciprocating and linear motion in the interior of (130)

According to this prior art, in the course of the piston repeatedly moving inside the cylinder, interference may occur between the cylinder and the piston, thereby causing wear on the cylinder or the piston.

In particular, when a predetermined pressure (fastening pressure) acts on the piston while the piston is fastened with the surrounding configuration, and the piston is deformed by the pressure, more interference between the cylinder and the piston may occur.

In addition, when a slight error occurs in the process of assembling the piston and the cylinder, there is a problem that the compressed gas leaks to the outside, and accordingly, the wear occurs more.

In this way, while interference occurs between the cylinder and the piston, there is a problem in that the permanent magnet connected to the piston and the inner stator and the outer stator interfere with each other, causing damage to the component.

And, in the case of a conventional linear compressor, a cylinder or a piston is composed of a magnetic material, so that the amount of flux generated in the linear motor leaks out to the outside through the cylinder or piston, thereby reducing the efficiency of the compressor. There was a problem.

The present invention has been proposed to solve such a problem, and an object of the present invention is to provide a linear compressor that prevents friction or interference between a piston and a cylinder.

A linear compressor according to an embodiment of the present invention includes a shell provided with a refrigerant suction unit; A cylinder provided inside the shell and forming a compression space; A piston reciprocating within the cylinder and compressing a refrigerant in the compression space; And a motor assembly providing a driving force to the piston and having a permanent magnet, wherein the piston has a cylindrical outer circumferential surface, and a piston body forming a surface treatment unit processed from a material having a set hardness value; A valve support part forming one end of the piston body and having a suction hole for sucking refrigerant into the compression space; And a flange portion coupled to the other end of the piston body and extending in a radial direction of the piston body, and wherein the valve support portion forms a first non-processed surface-treated portion.

In the linear compressor according to another aspect, the shell is provided with a refrigerant suction unit; A cylinder provided inside the shell and forming a compression space; A piston reciprocating within the cylinder and compressing a refrigerant in the compression space; And a motor assembly providing a driving force to the piston and having a permanent magnet, wherein the piston body comprises: a piston body forming a surface-treated portion processed from a set material and a second non-processed portion not processed; A valve support part coupled to one end of the piston body and having a suction hole for sucking refrigerant into the compression space; A suction valve selectively shielding the suction hole; And a first non-surface treatment part formed on the outer surface of the valve support part and made of a non-magnetic material that is not processed.

According to the present invention, a surface treatment unit is provided on the outer surface of the piston to increase wear resistance, thereby improving the reliability of the compressor component.

In addition, since surface treatment is not performed on the valve support portion of the piston, the compression heat existing in the compression space or cylinder can be transferred to the piston, and accordingly, the thermal expansion coefficients of the cylinder and the piston are similarly formed, so that the inner peripheral surface of the cylinder and the piston are It is possible to prevent the clearance between the outer circumferential surfaces from becoming too large.

In addition, since the outer circumferential surface of the piston body includes a surface treatment part and a non-surface treatment part, and heat transfer from the cylinder through the non-surface treatment part is formed, the thermal expansion coefficients of the cylinder and the piston are similarly formed to prevent the clearance from becoming too large. You will be able to.

In particular, the valve support part is provided at one end of the piston body, and the non-surface treatment part is provided at the other end of the piston body, and heat is transferred from both ends to increase the temperature of the entire piston, so that the temperature of the cylinder and the piston is uniformly formed. Can be.

Therefore, since the degree of thermal expansion of the cylinder and the piston becomes similar, the distance can be maintained within an appropriate range, and accordingly, abrasion due to friction between the piston or the cylinder can be prevented.

In addition, since the cylinder and the piston are made of a non-magnetic material, especially aluminum, it is possible to prevent the magnetic flux generated from the motor assembly from leaking to the outside of the cylinder, thereby improving the efficiency of the compressor.

In addition, there is an advantage that the manufacturing cost of the compressor can be reduced by configuring the permanent magnet provided in the motor assembly with an inexpensive ferrite material.

1 is a cross-sectional view showing an internal configuration of a linear compressor according to an embodiment of the present invention.
2 is a cross-sectional view showing a coupling state of a cylinder and a piston according to an embodiment of the present invention.
3 is a cross-sectional view showing a state in which the piston moves in one direction in the state of FIG. 2.
4 is a view showing the configuration of a piston according to an embodiment of the present invention.
5A is a cross-sectional view showing a state of a combination of a cylinder and a piston when the entire outer surface of the piston is surface-treated according to an embodiment of the present invention.
5B is a cross-sectional view illustrating a combination of a cylinder and a piston when a plurality of non-surface treatment units are formed on a piston according to an embodiment of the present invention.

Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. However, the spirit of the present invention is not limited to the presented embodiments, and those skilled in the art who understand the spirit of the present invention will be able to easily propose other embodiments within the scope of the same idea.

1 is a cross-sectional view showing an internal configuration of a linear compressor according to an embodiment of the present invention.

Referring to FIG. 1, in a linear compressor 10 according to an embodiment of the present invention, a cylinder 120 provided inside the shell 110 and a piston 130 reciprocating and linearly moving inside the cylinder 120 ) And a motor assembly 200 for imparting a driving force to the piston 130. The shell 110 may be configured by combining an upper shell and a lower shell.

The shell 110 includes a suction unit 101 through which the refrigerant is introduced and a discharge unit 105 through which the refrigerant compressed in the cylinder 120 is discharged. The refrigerant sucked through the suction part 101 flows into the piston 130 through the suction muffler 140. During the process of the refrigerant passing through the suction muffler 140, noise may be reduced.

Inside the cylinder 120, a compression space P in which the refrigerant is compressed by the piston 130 is formed. In addition, in the piston 130, a suction hole 133b for introducing a refrigerant into the compression space P is formed, and at one side of the suction hole 133b, a suction hole 133b is selectively opened. A valve 132 is provided. The suction valve 132 may be formed of a steel plate.

At one side of the compression space P, discharge valve assemblies 170, 172, and 174 for discharging the refrigerant compressed in the compression space P are provided. That is, the compression space P is understood as a space formed between one end of the piston 130 and the discharge valve assemblies 170, 172, and 174.

The discharge valve assemblies 170, 172, 174 include a discharge cover 172 that forms a discharge space of the refrigerant, and a discharge valve that opens when the pressure of the compression space P is equal to or higher than the discharge pressure to introduce the refrigerant into the discharge space. 170) and a valve spring 174 provided between the discharge valve 170 and the discharge cover 172 to impart an elastic force in the axial direction.

Here, the "axial direction" may be understood as a direction in which the piston 130 reciprocates, that is, a horizontal direction in FIG. 1.

The suction valve 132 may be formed on one side of the compression space P, and the discharge valve 170 may be provided on the other side of the compression space P, that is, on the opposite side of the suction valve 132.

In the course of the piston 130 reciprocating and linear movement inside the cylinder 120, when the pressure in the compression space P is lower than the discharge pressure and less than the suction pressure, the suction valve 132 is opened and the refrigerant Is sucked into the compression space (P). On the other hand, when the pressure in the compression space P is equal to or higher than the suction pressure, the refrigerant in the compression space P is compressed while the suction valve 132 is closed.

On the other hand, when the pressure in the compression space (P) becomes more than the discharge pressure, the valve spring 174 is deformed to open the discharge valve 170, and the refrigerant is discharged from the compression space (P) and discharged. It is discharged to the discharge space of the cover 172.

In addition, the refrigerant in the discharge space flows into the roof pipe 178 through the discharge muffler 176. The discharge muffler 176 may reduce the flow noise of the compressed refrigerant, and the loop pipe 178 guides the compressed refrigerant to the discharge part 105. The roof pipe 178 is coupled to the discharge muffler 176 and extends to be bent, and is coupled to the discharge part 105.

The linear compressor 10 further includes a frame 110. The frame 110 is configured to fix the cylinder 120, and may be configured integrally with the cylinder 120 or may be fastened by a separate fastening member. In addition, the discharge cover 172 and the discharge muffler 176 may be coupled to the frame 110.

The motor assembly 200 includes an outer stator 210 fixed to the frame 110 and disposed to surround the cylinder 120, and an inner stator 220 disposed to be spaced apart from the inner stator 210. ) And a permanent magnet 230 positioned in a space between the outer stator 210 and the inner stator 220.

The permanent magnet 230 may linearly reciprocate by mutual electromagnetic force between the outer stator 210 and the inner stator 220. In addition, the permanent magnet 230 may be composed of a single magnet having one pole, or may be configured by combining a plurality of magnets having three poles.

In addition, the permanent magnet 230 may be made of a relatively inexpensive ferrite material.

The permanent magnet 230 may be coupled to the piston 130 by a connecting member 138. The connecting member 138 may extend from the other end of the piston 130 to the permanent magnet 130. As the permanent magnet 230 moves linearly, the piston 130 may linearly reciprocate together with the permanent magnet 230 in the axial direction.

The outer stator 210 includes coil winding bodies 213 and 215 and a stator core 211.

The coil winding bodies 213 and 215 include a bobbin 213 and a coil 215 wound in the circumferential direction of the bobbin 213. The cross section of the coil 215 may have a polygonal shape, and for example, may have a hexagonal shape.

The stator core 211 is configured by stacking a plurality of laminations in a circumferential direction, and may be disposed to surround the coil winding bodies 213 and 215.

When a current is applied to the motor assembly 200, a current flows through the coil 215, and a flux is formed around the coil 215 by the current flowing through the coil 215, and the magnetic flux Is flowed along the outer stator 210 and the inner stator 220 while forming a closed circuit.

A magnetic flux flowing along the outer stator 210 and the inner stator 220 and the magnetic flux of the permanent magnet 230 interact, so that a force for moving the permanent magnet 230 may be generated.

A stator cover 240 is provided on 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 may be supported by the stator cover 240.

The inner stator 220 is fixed to the outer periphery of the cylinder 120. In addition, the inner stator 220 is configured by stacking a plurality of laminations from the outside of the cylinder 120 in the circumferential direction.

The linear compressor 10 further includes a supporter 135 supporting the piston 130 and a back cover 115 extending from the piston 130 toward the suction unit 101. The back cover 115 may be disposed to cover at least a portion of the suction muffler 140.

The linear compressor 10 includes a plurality of springs 151 and 155, which are elastic members, whose natural frequencies are adjusted so that the piston 130 can perform resonant motion.

In the plurality of springs 151 and 155, a first spring 151 supported between the supporter 135 and the stator cover 240, and a second spring supported between the supporter 135 and the back cover 115 A spring 155 is included. The first spring 151 and the second spring 155 may have the same elastic modulus.

A plurality of the first springs 151 may be provided on the upper and lower sides of the cylinder 120 or the piston 130, and the second spring 155 is a front side of the cylinder 120 or the piston 130 As a result, a plurality of pieces may be provided.

Here, the "forward" may be understood as a direction from the piston 130 toward the suction part 101. That is, a direction from the suction unit 101 toward the discharge valve assemblies 170, 172, and 174 may be understood as "rear". This term may be used equally in the following description.

A predetermined oil may be stored on the inner bottom surface of the shell 100. In addition, an oil supply device 160 for pumping oil may be provided under the shell 100. The oil supply device 160 may be operated by vibration generated as the piston 130 reciprocates and linearly moves to pump oil upward.

The linear compressor 10 further includes an oil supply pipe 165 for guiding the flow of 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 is supplied to the space between the cylinder 120 and the piston 130 via the oil supply pipe 165 to perform cooling and lubrication.

2 is a cross-sectional view showing a combination of a cylinder and a piston according to an embodiment of the present invention, FIG. 3 is a cross-sectional view showing a state in which the piston moves in one direction in the state of FIG. 2, and FIG. 4 is an implementation of the present invention. It is a cross-sectional view showing an example of a combination of a cylinder and a piston.

2 to 4, the piston 130 according to the embodiment of the present invention is provided to enable a reciprocating motion inside the cylinder 120.

The piston 130 may be made of a non-magnetic aluminum material (aluminum or aluminum alloy). Since the piston 130 is made of an aluminum material, the magnetic flux generated by the motor assembly 200 is transmitted to the piston 130 to prevent leakage to the outside of the piston 130. In addition, the piston 130 may be formed by a forging method.

The piston 130 has a substantially cylindrical shape and extends in a radial direction from the other end of the piston body 131 and the piston body 131 disposed inside the cylinder 120 to the connecting member 138. It includes a flange portion 136 to be coupled. The piston 130 may reciprocate together with the permanent magnet 230.

In addition, at one end of the piston body 131, a valve support part 133 forming one or more suction holes 133b is provided. The refrigerant flowing inside the piston body 131 may flow into the compression space P through the suction hole 133b.

In summary, a flange portion 136 coupled to the permanent magnet 230 is provided at the other end of the piston body 131, and a valve support portion 133 constituting one surface facing the compression space P at one end. ) Is provided. The valve support part 133 may be made of a non-magnetic material, for example aluminum.

A suction valve 132 for selectively opening the suction hole 133b is provided in the valve support part 133. When the pressure of the compression space P is less than the suction pressure, that is, the internal pressure of the piston body 131, the suction valve 132 is opened, and when the pressure of the compression space P is greater than the suction pressure, the The intake valve 132 may be closed.

The piston body 131 includes an outer circumferential surface on which a surface treatment part 310 and a second non-surface treatment part 320 are provided. The outer circumferential surface on which the surface treatment part 310 is formed is referred to as a "first outer circumferential surface", and the outer circumferential surface on which the second non-surface treatment part 320 is formed is referred to as a "second outer circumferential surface".

The surface treatment part 310 is a part surface-treated on a part of the outer peripheral surface of the piston body 131, and the second non-surface treatment part 320 may be understood as a surface made of aluminum without surface treatment.

The surface treatment part 310 may be formed to extend in a direction toward the flange part 136 from an end of the piston body 130 to which the valve support part 133 is coupled.

By providing the surface treatment unit 310, abrasion resistance, lubricity or heat resistance of the piston body 131 may be improved. For example, the surface treatment unit 310 may be a "first coating layer".

The surface treatment unit 310 may be made of any one of PTFE (Teflon), DLC (Diamond Like Carbon), nickel-phosphorus alloy material, and anodizing layer (anodizing layer).

The above material will be described.

The PTFE is a fluorine-based polymer and is generally referred to as "Teflon". The PTFE is sprayed onto a portion of the outer peripheral surface of the piston body 131 in a state of being coated with a fluororesin, and heated and fired at a constant temperature to form an inert coating layer.

Since the PTFE has a low coefficient of friction, when coated on the outer circumferential surface of the piston body 131, it is possible to improve the lubricity of the surface and improve wear resistance.

Meanwhile, the hardness of the PTFE is very small, and the hardness is measured by a pencil hardness measurement method. For example, the hardness of the PTFE may be a pencil hardness of HB or more. However, when the hardness of the PTFE is converted to the Vickers hardness (Hv), the PTFE may have a hardness of about 0 to 30 Hv.

The anodizing film is understood as an aluminum oxide film formed by oxidizing an aluminum surface by oxygen generated at the anode when aluminum is used as an anode and energized. The anodized film has excellent corrosion resistance and insulation resistance.

Further, the hardness of the anodized film may vary depending on the state or component of the material (base material) to be coated, but may be formed at about 300 to 500 Hv.

The DLC is a new amorphous carbon-based material and is understood as a thin film-like material formed by electrically accelerating carbon ions or activated hydrocarbon molecules in plasma and colliding with the surface.

The physical properties of the DLC are similar to those of diamond, have high hardness and wear resistance, excellent electrical insulation, and low coefficient of friction, and thus have excellent lubrication properties. The hardness of the DLC may be formed at about 1,500 to 1,800 Hv.

The nickel-phosphorus alloy material may be provided on the outer circumferential surface of the piston body 131 by an electroless nickel plating method, and nickel and phosphorus components may be formed by depositing a surface with a uniform thickness. . The nickel-phosphorus alloy material may have a chemical composition ratio of 90 to 92% of nickel (Ni) and 9 to 10% of phosphorus (P).

The nickel-phosphorus alloy material improves corrosion resistance and abrasion resistance of the surface, and has excellent lubricity properties. The hardness of the nickel-phosphorus alloy material may be formed at about 500 ~ 600Hv.

On the other hand, the aluminum material itself has good heat transfer properties, but when the surface treatment unit 310 is provided on the piston body 131 made of aluminum, the heat transfer property may be reduced compared to the case where the piston body 131 is made of aluminum material itself. have.

Therefore, in the process of reciprocating the piston 130 inside the cylinder 120, when the internal space temperature of the cylinder 120 becomes high, the portion of the piston body 131 where the surface treatment part 310 is provided and , The coefficient of thermal expansion of the portion where the second non-surface treatment part 320 is provided may vary.

The second non-surface treatment part 320 may be formed as much as an area from the other end of the piston body 131 toward one end of the piston body 131. That is, the second non-surface treatment part 320 may be formed to extend in a direction toward the valve support part 133 from a portion coupled to the flange part 136. In addition, the surface treatment unit 310 and the second non-surface treatment unit 320 may be combined.

The valve support part 133 includes a first non-surface treatment part 133a. The first non-surface treatment part 133a is a part that has not been subjected to a separate surface treatment, and is formed of a nonmagnetic material (aluminum) of the valve support part 133 itself. Since aluminum has excellent heat transfer rate, the compressed heat formed in the compression space P can be easily transferred to the piston 130 through the valve support part 133.

The flange portion 136 includes a plurality of holes 137a and 137b. In the plurality of holes (137a, 137b), at least one fastening hole (137a) into which a fastening member coupled with the supporter (135) and the connecting member (138) is inserted, and flow resistance generated around the piston (130) One or more through holes (137b) for reducing the is included.

Meanwhile, the cylinder 120 may be made of a non-magnetic aluminum material (aluminum or aluminum alloy). In addition, the material composition ratio of the cylinder 120 and the piston 130, that is, the type and composition ratio may be the same.

Since the cylinder 120 is made of an aluminum material, the magnetic flux generated by the motor assembly 200 is transmitted to the cylinder 120 to prevent leakage to the outside of the cylinder 120. In addition, the cylinder 120 may be formed by an extrusion rod processing method.

In addition, the material composition ratio of the cylinder 120 and the piston 130, that is, the type and composition ratio may be the same. Since the piston 130 and the cylinder 120 are made of the same material (aluminum), the material itself has the same coefficient of thermal expansion.

The cylinder 120 may have a hollow cylindrical shape, and the piston body 131 may be movably accommodated. The cylinder 120 includes an inner circumferential surface 121 facing the outer circumferential surface of the piston body 131.

The inner peripheral surface 121 includes a non-surface treatment portion 121a. The non-surface treatment part 121a is a part that has not been subjected to a separate surface treatment and may be formed of an aluminum material. For example, the non-surface treatment part 121a is made of a material corresponding to the first non-surface treatment part 133a and the second non-surface treatment part 320 of the piston 130, and the first non-surface treatment part 133a ) And the second non-surface treatment unit 320 may be understood to have the same coefficient of thermal expansion.

We propose another embodiment.

The inner circumferential surface 121 of the cylinder 120 may include a surface treatment unit. The surface treatment part of the inner circumferential surface 121 may be made of any one of PTFE (Teflon), DLC (Diamond Like Carbon), nickel-phosphorus alloy material, and anodizing layer (anodizing layer).

However, the surface treatment part of the inner circumferential surface 121 may be made of a material different from that of the surface treatment part 310 of the piston 130. This is, when a difference in hardness of more than a predetermined size is formed between the surface treatment part of the inner circumferential surface 121 and the surface treatment part 310 of the piston 130, the wear of the cylinder 120 or the piston 130 can be prevented. Because.

For example, the surface treatment part of the inner circumferential surface 121 is composed of an anodizing film that does not have a relatively large influence on the heat transfer rate, and the surface treatment part 310 of the piston 130 has a relatively large effect on the heat transfer rate. Teflon).

5A is a cross-sectional view showing a state of a combination of a cylinder and a piston when surface treatment is performed on the entire outer surface of a piston according to an embodiment of the present invention, and FIG. 5B is a plurality of non-surface treatments on the piston according to an embodiment of the present invention. It is a cross-sectional view showing the state of the combination of the cylinder and the piston when the part is formed.

In FIG. 5A, unlike the embodiment of the present invention, a surface treatment part is formed on the entire outer surface of the piston 130. That is, the surface treatment part may be provided on an outer peripheral surface of the piston body 131 and an outer surface of the valve support part 133.

When the piston 130 is accommodated in the cylinder 120, the outer circumferential surface of the piston body 131 is formed to be spaced apart by a predetermined distance from the inner circumferential surface 121 of the cylinder 120 (clearance, clearance). . Oil supplied from the oil supply device 160 may flow into the spaced apart space through the oil supply pipe 165.

In a state in which the piston 130 does not reciprocate, that is, in a state in which the linear compressor 10 is not operated, the internal space of the cylinder 120 may form an atmospheric temperature, for example, about 25°C.

When the linear compressor 10 is operated, the piston 130 reciprocates, and the refrigerant is compressed in the compression space P. As this process is repeated, the temperature of the inner space of the cylinder 120 is increased, and the cylinder 120 made of aluminum is absorbed and thermally expanded.

At this time, since the inner circumferential surface 121 of the cylinder 120 is provided with a non-surface-treated portion 121a that is not surface-treated or a surface-treated portion that does not significantly affect heat transfer, the thermal expansion phenomenon of the cylinder 120 may occur significantly. I can. Accordingly, the cylinder 120 can be greatly deformed in a direction in which the inner diameter thereof is expanded.

On the other hand, a surface treatment part is provided on the entire outer surface of the piston 130, and the surface treatment part of the piston 130 may be made of a material that interferes with heat transfer.

The linear compressor 10 is operated to cause the piston 130 to reciprocate, and even if the refrigerant is compressed in the compression space P and the cylinder 120 is heated, the compression space P is compressed. Heat or heat of the cylinder 120 is blocked by the surface treatment unit and is limited to be transferred to the piston 130. Accordingly, the cylinder 120 may have a large thermal expansion, and the piston 130 may have a relatively small thermal expansion.

Accordingly, the piston 130 is formed at a relatively low temperature compared to the cylinder 120 and is limited in thermal expansion. That is, the piston 130 may be deformed small in a direction in which its outer diameter is expanded.

As a result, the degree of thermal expansion of the cylinder 120 and the piston 130 is different due to the temperature difference between the cylinder 120 and the piston 130, so that the inner peripheral surface of the cylinder 120 and the outer peripheral surface of the piston 130 The interval, that is, the clearance is formed relatively large (S1).

When the clearance is formed relatively large, the degree to which the piston 130 is supported by the cylinder 120 is weakened.

In detail, an oil film is formed between the piston 130 and the cylinder 120 to serve as a lubrication. If the clearance is large, an oil film is sufficiently formed between the piston 130 and the cylinder 120. Since it is not formed, friction or interference occurs between the piston 130 and the cylinder 120. Accordingly, there may be a problem that abrasion occurs in the piston 130 or the cylinder 120.

In Figure 5b, the appearance of the piston 130 and the cylinder 120 according to an embodiment of the present invention is shown. Referring to FIG. 5B, the piston 130 according to the embodiment of the present invention includes a surface treatment unit 310 and a non-surface treatment unit 133a and 320.

In detail, a first non-surface-treated portion 133a is formed on the outer surface of the valve support portion 133 coupled to one end of the piston body 131 to which no surface treatment has been performed.

In addition, a surface treatment part 310 and a second non-surface treatment part 320 are included on the outer peripheral surface of the piston body 131.

The second non-surface treatment part 320 is formed on a part of the outer peripheral surface of the piston body 131. In addition, the second non-surface treatment part 320 is formed to extend in the direction of the valve support part 133 from the flange part 136 coupled to the other end of the piston body 131.

In this case, the first non-surface treatment part 133a and the second non-surface treatment part 320 may be formed at positions spaced apart from each other. In other words, the first non-surface treatment part 133a is formed at one end of the piston body 131, and the second non-surface treatment part 320 is formed at the other end of the piston body 131.

During the reciprocating motion of the piston 130, heat generated in the compression space P is transferred to the cylinder 120 and the piston 130.

Since the inner circumferential surface 121 of the cylinder 120 is provided with a non-surface-treated portion 121a that is not surface-treated or a surface-treated portion that does not significantly affect heat transfer, the thermal expansion phenomenon of the cylinder 120 may occur significantly. Accordingly, the cylinder 120 can be greatly deformed in a direction in which the inner diameter thereof is expanded.

In addition, the heat is transmitted through the first non-surface treatment part 133a of the valve support part 133 of the piston 130 or the second non-surface treatment part 320 of the outer circumferential surface of the piston body 131, and the piston 130 ) Can be passed to (Q1, Q2). That is, heat may be transferred to the piston 130 from both end sides of the piston body 131. Thus, the temperature of the piston 130 may increase close to the temperature of the cylinder 120 over time.

As a result, since the temperature difference between the temperature of the cylinder 120 and the piston 130 is not large, the degree of thermal expansion of the cylinder 120 and the piston 130 is similar.

That is, the degree of deformation at which the inner diameter of the cylinder 120 is extended to the outside is similar to the degree of deformation at which the outer diameter of the piston 130 is extended to the outside, so that the piston body from the inner peripheral surface 121 of the cylinder 120 The distance to the outer circumferential surface of 131, that is, the clearance may be formed small (S2).

Therefore, an oil film of an appropriate amount is formed between the cylinder 120 and the piston 130 to perform a lubricating action, and accordingly, abrasion due to friction between the cylinder 120 and the piston 130 can be prevented. have.

10: linear compressor 100: shell
110: frame 120: cylinder
130: piston 132: suction valve
133: valve support portion 133a: first non-surface treatment portion
133b: suction hole 136: flange portion
151,155: first and second springs 160: oil supply device
170: discharge valve 200: motor assembly
210: outer stator 220: inner stator
230: permanent magnet 240: stator cover
310: surface treatment unit 320: second non-surface treatment unit

Claims (13)

A shell provided with a refrigerant suction unit;
A cylinder provided inside the shell and forming a compression space;
A piston reciprocating within the cylinder and compressing a refrigerant in the compression space; And
Provides a driving force to the piston and includes a motor assembly provided with a permanent magnet,
In the piston,
A piston body having a cylindrical outer peripheral surface; And
A valve support part forming one end of the piston body and having a suction hole for sucking refrigerant into the compression space; And
It is coupled to the other end of the piston body, and includes a flange portion extending in the radial direction of the piston body,
The cylinder includes an inner circumferential surface opposite to the outer circumferential surface of the piston body,
The outer peripheral surface of the valve support portion facing the inner peripheral surface of the cylinder includes a first non-surface-treated portion, which is not surface-treated,
In the piston body,
A first outer circumferential surface forming a surface treatment unit processed from a set material; And
It includes a second outer circumferential surface forming a second non-processed non-processed portion,
The cylinder includes an inner circumferential surface facing the first outer circumferential surface of the piston body and forming a surface treatment portion processed from a set material,
The first non-surface treatment part is composed of a non-magnetic material and is formed at one end of the piston body, the second non-surface treatment part is composed of a non-magnetic material and is formed at the other end of the piston body,
The first non-surface treatment part and the second non-surface treatment part are spaced apart from each other, and the surface treatment part is located between the first non-surface treatment part and the second non-surface treatment part. The method of claim 1,
The valve support part is a linear compressor that forms one surface of the piston facing the compression space. delete delete The method of claim 1,
The first outer circumferential surface is an outer circumferential surface extending toward the flange from one end of the piston body on which the valve support is formed. The method of claim 5,
The second outer circumferential surface is an outer circumferential surface extending toward the valve support from the other end of the piston body to which the flange portion is coupled. delete delete delete The method of claim 1,
The linear compressor further comprises a suction valve coupled to the valve support and selectively opening the suction hole. The method of claim 1,
The piston and cylinder are linear compressors composed of a non-magnetic material. The method of claim 11,
The piston and cylinder are linear compressors made of aluminum or aluminum alloy. delete

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