Patent Description:
A compressor refers to a device that is configured to receive power from a power generator such as a motor or a turbine and compress a working fluid such as air or refrigerant. The compressors may be used in industry or home appliances to perform a steam compression refrigeration cycle (hereinafter, referred to as "refrigeration cycle").

The compressors may be classified into a reciprocating compressor, a rotary compressor, and a scroll compressor depending on a method of compressing the refrigerant.

The reciprocating compressor may define a compression space between a piston and a cylinder, and the piston linearly reciprocates to compress a fluid. The rotary compressor may compress a fluid by a roller that eccentrically rotates inside a cylinder. The scroll compressor may compress a fluid by engaging and rotating a pair of spiral scrolls.

In some cases, among the reciprocating compressors, linear compressors may use a linear reciprocating motion without using a crank shaft is gradually increasing. The linear compressor may have advantages in that it has less mechanical loss resulting from switching a rotary motion to the linear reciprocating motion and thus can improve the efficiency, and has a relatively simple structure.

In some cases, a linear compressor may include a cylinder positioned in a casing forming a sealed space to form a compression chamber, and a piston covering the compression chamber that reciprocates in the cylinder. The linear compressor repeats a process in which a fluid in the sealed space is suctioned into the compression chamber while the piston is positioned at a bottom dead center (BDC), and the fluid of the compression chamber is compressed and discharged while the piston is positioned at a top dead center (TDC).

The linear compressor may include a compression unit and a drive unit installed inside the linear compressor. The compression unit performs a process of compressing and discharging a refrigerant while performing a resonant motion by a resonant spring through a movement generated in the drive unit.

The piston of the linear compressor repeatedly performs a series of processes of suctioning the refrigerant into the casing through an intake pipe while reciprocating at high speed inside the cylinder by the resonant spring, and then discharging the refrigerant from a compression space through a forward movement of the piston to move it to a condenser through a discharge pipe.

The linear compressor may be classified into an oil lubricated linear compressor and a gas lubricated linear compressor according to a lubrication method. The oil lubricated linear compressor is configured to store a predetermined amount of oil in the casing and lubricate between the cylinder and the piston using the oil. The gas lubricated linear compressor is configured not to store an oil in the casing, induce a part of the refrigerant discharged from the compression space between the cylinder and the piston, and lubricate between the cylinder and the piston by a gas force of the refrigerant.

The oil lubricated linear compressor supplies the oil of a relatively low temperature between the cylinder and the piston and thus can suppress the cylinder and the piston from being overheated by motor heat or compression heat, etc. Hence, the oil lubricated linear compressor suppresses specific volume from increasing as the refrigerant passing through an intake flow path of the piston is suctioned into the compression chamber of the cylinder and is heated, and thus can prevent in advance an intake loss from occurring.

In some cases, when the refrigerant and an oil discharged to a refrigeration cycle device are not smoothly returned to the compressor, the oil lubricated linear compressor may experience an oil shortage in the casing of the compressor. The oil shortage in the casing may lead to a reduction in reliability of the compressor.

In some cases, the gas lubricated linear compressor may have advantages in that it can be made smaller than the oil lubricated linear compressor, and there is less reduction in the reliability of the compressor due to the oil shortage because it lubricates between the cylinder and the piston using the refrigerant.

A muffler unit for noise reduction may be coupled to the piston. In some cases, the noise reduction effect may be lowered due to a limited space.

<CIT> discloses a linear compressor having a suction muffler for reducing noise. <CIT> discloses a linear compressor having a muffler assembly which not only guides a suction flow of the refrigerant but also attenuates noise generated when the refrigerant is sucked into a compression space through a suction valve. <CIT> discloses a linear compressor in which refrigerant is sucked into a compression space via a suction muffler.

The present disclosure describes a linear compressor configured to reduce noise in a low frequency or mid-frequency band.

The present disclosure further describes a linear compressor configured to improve noise reduction characteristics of a second muffler unit.

The present disclosure further describes a linear compressor configured to improve space efficiency.

The present disclosure further describes a linear compressor that couples a second muffler unit and a back cover, each including a different material, without a separate process.

The present disclosure further describes a linear compressor including a second muffler unit press-fitted to a back cover.

The present disclosure further describes a linear compressor having a resonator defined between a muffler body and a muffler cover.

The present disclosure further describes a linear compressor configured to reduce or eliminate interference between a second muffler unit and a spring supporter.

According to the present invention defined in the appended independent claim, a linear compressor includes a cylinder, a piston configured to axially reciprocate in the cylinder, a back cover disposed at a rear of the piston, the back cover defining an opening at a central region around an axial centerline thereof, a first muffler unit coupled to the piston, the first muffler unit including (i) an inner guide disposed in the piston and (ii) a first intake muffler disposed between the inner guide and the back cover, and a second muffler unit including (i) a second intake muffler that is in fluid communication with the first intake muffler and is coupled to the back cover (<NUM>) adjacent to the opening, (ii) a muffler body surrounding the second intake muffler, and (iii) a muffler cover disposed between the muffler body and the back cover. An outer circumferential surface of the second intake muffler defines a first communication hole that fluidly communicates an inside of the second intake muffler with a first space that is defined between the second intake muffler and the muffler body, and the muffler body defines a resonance communication hole that fluidly communicates the first space with a second space that is defined between the muffler body and the muffler cover.

Through this, since a resonator that is the space between the muffler body and the muffler cover is additionally provided, noise in a low or mid-frequency band can be reduced.

A diameter of an inner circumferential surface of the second intake muffler may be greater than a diameter of an outer circumferential surface of the first intake muffler, such that the first intake muffler is axially movable with respect to the second intake muffler.

The space between the second intake muffler and the muffler body does not axially overlap the first intake muffler, and only a part of the space between the second intake muffler and the muffler body may radially overlaps the piston.

Through this, since an additional expansion space is provided, noise reduction characteristics of the second muffler unit can be improved.

The second intake muffler may include a first cylindrical portion, a first flange that extends radially outward from a front portion of the first cylindrical portion and radially overlaps a front end of the muffler body, a second flange extending radially outward from a central portion of the first cylindrical portion, and a coupling portion that extends radially outward from a rear portion of the first cylindrical portion and is coupled to the back cover.

In this case, the first communication hole may be disposed between the first flange and the second flange.

Through this, the present invention can improve space efficiency while improving noise reduction characteristics of the second muffler unit.

The muffler body may include a second cylindrical portion disposed radially outside of the second intake muffler, and in which a front and a rear of a central area are opened, a front of a space between an inner surface and an outer surface is closed, and a rear of the space between the inner surface and the outer surface is opened, and a third flange extending inward from the inner surface of the second cylindrical portion. A rear surface of the second flange may contact a front surface of the third flange.

Through this, when the second intake muffler is coupled to the back cover, the muffler cover can be press-fitted to the back cover.

The resonance communication hole may be disposed adjacent to the third flange.

Through this, noise generated in the piston can be easily introduced into the resonator via the resonance communication hole.

The muffler cover may include a ring portion that extends in a circumferential direction and seals a rear opened between the inner surface and the outer surface of the second cylindrical portion, a first extension extending rearward from an outer end of the ring portion, and a second extension extending forward from an inner end of the ring portion. An outer surface of the first extension and an inner surface of the second extension may contact the second cylindrical portion.

In addition, a space between the inner surface of the second cylindrical portion, the outer surface of the second cylindrical portion, a front surface of the second cylindrical portion, and the ring portion may be sealed except for the resonance communication hole.

Through this, the present invention can form a resonator that is the space between the muffler body and the muffler cover.

The muffler body may include a plurality of grooves that are concavely formed inward from the outer surface of the second cylindrical portion and are spaced apart in a circumferential direction. Each of the plurality of grooves may include a base surface, a first stepped portion that connects the base surface and the outer surface of the second cylindrical portion and extends in the circumferential direction, and a second stepped portion and a third stepped portion that connect the base surface and the outer surface of the second cylindrical portion and extend axially. A rear surface of the first stepped portion may include a rib extending rearward, and the muffler cover may be seated on the rib.

In this case, the space between the muffler body and the muffler cover may be disposed between the plurality of grooves in the circumferential direction.

Further, the resonance communication hole may include a plurality of resonance communication holes disposed between the plurality of grooves in the circumferential direction.

Through this, the present invention can improve the space efficiency.

The linear compressor may further comprise a spring supporter including a second coupling portion coupled to the piston, a body portion connected to the second coupling portion and surrounding the first muffler unit, and a support portion bent radially outward from a rear of the body portion, and a spring disposed between the spring supporter and the back cover. The plurality of grooves may axially overlap the support portion.

Through this, the present invention can prevent interference between the muffler body and the spring supporter.

In another aspect of the present disclosure, a linear compressor includes a cylinder, a piston configured to axially reciprocate in the cylinder, a back cover disposed at a rear of the piston, the back cover defining an opening at a central area thereof in a radial direction, and a muffler unit including (i) an intake muffler coupled to the opening, (ii) a muffler body surrounding the intake muffler, and (iii) a muffler cover disposed between the muffler body and the back cover. An outer circumferential surface of the intake muffler defines a first communication hole that fluidly communicates an inside of the intake muffler with a first space that is defined between the intake muffler and the muffler body, and the muffler body defines a resonance communication hole that fluidly communicates the first space with a second space that is defined between the muffler body and the muffler cover.

An axial length of the space between the muffler body and the muffler cover may be greater than a radial length of the space between the muffler body and the muffler cover.

In addition, the space between the muffler body and the muffler cover may not axially overlap the piston.

Through this, since an additional expansion space is provided, noise reduction characteristics of the muffler unit can be improved.

The intake muffler may include a first cylindrical portion, a first flange that extends radially outward from a front of the first cylindrical portion and radially overlaps a front end of the muffler body, a second flange extending radially outward from a central area of the first cylindrical portion, and a first coupling portion that extends radially outward from a rear area of the first cylindrical portion and is coupled to the opening.

Through this, the linear compressor can improve space efficiency while improving noise reduction characteristics of the muffler unit.

The muffler body may include a second cylindrical portion disposed at a radially outside of the intake muffler, and in which a front and a rear of a central area are opened, a front of a space between an inner surface and an outer surface is closed, and a rear of the space between the inner surface and the outer surface is opened, and a third flange extending inward from the inner surface of the second cylindrical portion. A rear surface of the second flange may contact a front surface of the third flange.

Through this, when the intake muffler is coupled to the back cover, the muffler cover can be press-fitted to the back cover.

Further, a space between the inner surface of the second cylindrical portion, the outer surface of the second cylindrical portion, a front surface of the second cylindrical portion, and the ring portion may be sealed except for the resonance communication hole.

Through this, the linear compressor can form a resonator that is the space between the muffler body and the muffler cover.

The space between the muffler body and the muffler cover may be disposed between the plurality of grooves in the circumferential direction. The resonance communication hole may include a plurality of resonance communication holes disposed between the plurality of grooves in the circumferential direction.

Through this, the linear compressor can improve the space efficiency.

The linear compressor may further comprise a spring supporter including a second coupling portion coupled to the piston, a body portion connected to the second coupling portion and surrounding a space between the piston and the muffler unit, and a support portion bent radially outward from a rear of the body portion, and a spring disposed between the spring supporter and the back cover. The plurality of grooves may axially overlap the support portion.

Through this, the linear compressor can prevent interference between the muffler body and the spring supporter.

The present invention can provide a linear compressor capable of reducing noise in a low frequency or mid-frequency band.

The present invention can provide a linear compressor configured to improve noise reduction characteristics of a second muffler unit.

The present invention can provide a linear compressor configured to improve space efficiency.

The present invention can provide a linear compressor capable of coupling a second muffler unit and a back cover each including a different material without a separate process.

The present invention can provide a linear compressor capable of press-fitting a detailed configuration of a second muffler unit to a back cover.

The present invention can provide a linear compressor capable of additionally forming a resonator between a muffler body and a muffler cover.

The present invention can provide a linear compressor capable of preventing interference between a second muffler unit and a spring supporter.

The accompanying drawings, which are included to provide a further understanding of the present invention and constitute a part of the detailed description, illustrate implementations of the present invention and serve to explain technical features of the present invention together with the description.

Reference will now be made in detail to implementations of the present disclosure, examples of which are illustrated in the accompanying drawings.

<FIG> is a perspective view showing an example of a linear compressor.

Referring to <FIG>, in some implementations, a linear compressor <NUM> can include a shell <NUM> and shell covers <NUM> and <NUM> coupled to the shell <NUM>. In a broad sense, the shell covers <NUM> and <NUM> can be understood as one configuration of the shell <NUM>.

In some examples, legs <NUM> can be coupled to a lower side of the shell <NUM>. The legs <NUM> can be coupled to a base of a product on which the linear compressor <NUM> is mounted. For example, the product can include a refrigerator, and the base can include a machine room base of the refrigerator. As another example, the product can include an outdoor unit of an air conditioner, and the base can include a base of the outdoor unit.

The shell <NUM> can have a substantially cylindrical shape and can be disposed to lie in a horizontal direction or an axial direction. <FIG> illustrates that the shell <NUM> is extended in the horizontal direction and has a slightly low height in a radial direction, by way of example. That is, since the linear compressor <NUM> can have a low height, there is an advantage in that a height of the machine room can decrease when the linear compressor <NUM> is installed in, for example, the machine room base of the refrigerator.

A longitudinal central axis of the shell <NUM> coincides with a central axis of a main body of the linear compressor <NUM> to be described below, and the central axis of the main body of the linear compressor <NUM> can coincide with a central axis of a cylinder <NUM> and a piston <NUM> that constitute the main body of the linear compressor <NUM>.

A terminal <NUM> can be installed on an outer surface of the shell <NUM>. The terminal <NUM> can transmit external electric power to a drive unit <NUM> of the linear compressor <NUM>. More specifically, the terminal <NUM> can be connected to a lead line of a coil 132b.

A bracket <NUM> can be installed on the outside of the terminal <NUM>. The bracket <NUM> can include a plurality of brackets surrounding the terminal <NUM>. The bracket <NUM> can perform a function of protecting the terminal <NUM> from an external impact, etc..

Both sides of the shell <NUM> can be opened. The shell covers <NUM> and <NUM> can be coupled to both sides of the opened shell <NUM>. More specifically, the shell covers <NUM> and <NUM> can include a first shell cover <NUM> coupled to one opened side of the shell <NUM> and a second shell cover <NUM> coupled to the other opened side of the shell <NUM>. An inner space of the shell <NUM> can be sealed by the shell covers <NUM> and <NUM>.

<FIG> illustrates that the first shell cover <NUM> is positioned on the right side of the linear compressor <NUM>, and the second shell cover <NUM> is positioned on the left side of the linear compressor <NUM>, by way of example. In other words, the first and second shell covers <NUM> and <NUM> can be disposed to face each other. It can be understood that the first shell cover <NUM> is positioned on an intake side of a refrigerant, and the second shell cover <NUM> is positioned on a discharge side of the refrigerant.

The linear compressor <NUM> can include a plurality of pipes <NUM>, <NUM>, and <NUM> that are included in the shell <NUM> or the shell covers <NUM> and <NUM> and can suction, discharge, or inject the refrigerant.

The plurality of pipes <NUM>, <NUM>, and <NUM> can include an intake pipe <NUM> that allows the refrigerant to be suctioned into the linear compressor <NUM>, a discharge pipe <NUM> that allows the compressed refrigerant to be discharged from the linear compressor <NUM>, and a supplementary pipe <NUM> for supplementing the refrigerant in the linear compressor <NUM>.

For example, the intake pipe <NUM> can be coupled to the first shell cover <NUM>. The refrigerant can be suctioned into the linear compressor <NUM> along the axial direction through the intake pipe <NUM>.

The discharge pipe <NUM> can be coupled to an outer circumferential surface of the shell <NUM>. The refrigerant suctioned through the intake pipe <NUM> can be compressed while flowing in the axial direction. The compressed refrigerant can be discharged through the discharge pipe <NUM>. The discharge pipe <NUM> can be disposed closer to the second shell cover <NUM> than to the first shell cover <NUM>.

The supplementary pipe <NUM> can be coupled to the outer circumferential surface of the shell <NUM>. A worker can inject the refrigerant into the linear compressor <NUM> through the supplementary pipe <NUM>.

The supplementary pipe <NUM> can be coupled to the shell <NUM> at a different height from the discharge pipe <NUM> in order to prevent interference with the discharge pipe <NUM>. Herein, the height can be understood as a distance measured from the leg <NUM> in a vertical direction. Because the discharge pipe <NUM> and the supplementary pipe <NUM> are coupled to the outer circumferential surface of the shell <NUM> at different heights, the work convenience can be attained.

On an inner circumferential surface of the shell <NUM> corresponding to a location at which the supplementary pipe <NUM> is coupled, at least a portion of the second shell cover <NUM> can be positioned adjacently. In other words, at least a portion of the second shell cover <NUM> can act as a resistance of the refrigerant injected through the supplementary pipe <NUM>.

Thus, with respect to a flow path of the refrigerant, a size of the flow path of the refrigerant introduced through the supplementary pipe <NUM> can be configured to decrease by the second shell cover <NUM> while the refrigerant enters into the inner space of the shell <NUM>, and to increase again while the refrigerant passes through the second shell cover <NUM>. In this process, a pressure of the refrigerant can be reduced to vaporize the refrigerant, and an oil contained in the refrigerant can be separated. Thus, while the refrigerant, from which the oil is separated, is introduced into the piston <NUM>, a compression performance of the refrigerant can be improved. The oil can be understood as a working oil present in a cooling system.

<FIG> is a cross-sectional view illustrating an example structure of the linear compressor <NUM>.

Hereinafter, the linear compressor will be described taking, as an example, a linear compressor that suctions and compresses a fluid while a piston linearly reciprocates, and discharges the compressed fluid.

A linear compressor can be a component of a refrigeration cycle, and a fluid compressed in the linear compressor can be a refrigerant circulating the refrigeration cycle. The refrigeration cycle can include a condenser, an expander, an evaporator, etc., in addition to the linear compressor. The linear compressor can be used as a component of a cooling system of a refrigerator, but is not limited thereto. The linear compressor can be widely used in the whole industry.

Referring to <FIG>, the linear compressor <NUM> can include a casing <NUM> and a main body received in the casing <NUM>. The main body of the linear compressor <NUM> can include a frame <NUM>, the cylinder <NUM> fixed to the frame <NUM>, the piston <NUM> that linearly reciprocates inside the cylinder <NUM>, the drive unit <NUM> that is fixed to the frame <NUM> and gives a driving force to the piston <NUM>, and the like. For example, the cylinder <NUM> and the piston <NUM> can be referred to as compression units <NUM> and <NUM>.

The linear compressor <NUM> can include a bearing for reducing a friction between the cylinder <NUM> and the piston <NUM>. For instance, the bearing can include an oil bearing or a gas bearing. Alternatively, a mechanical bearing can be used as the bearing.

The main body of the linear compressor <NUM> can be elastically supported by support springs <NUM> and <NUM> installed at both ends in the casing <NUM>. The support springs <NUM> and <NUM> can include a first support spring <NUM> for supporting the rear of the main body and a second support spring <NUM> for supporting a front of the main body. The support springs <NUM> and <NUM> can include a leaf spring. The support springs <NUM> and <NUM> can absorb vibrations and impacts generated by a reciprocating motion of the piston <NUM> while supporting the internal components of the main body of the linear compressor <NUM>.

The casing <NUM> can define a sealed space. The sealed space can include an accommodation space <NUM> in which the suctioned refrigerant is received, an intake space <NUM> which is filled with the refrigerant before the compression, a compression space <NUM> in which the refrigerant is compressed, and a discharge space <NUM> which is filled with the compressed refrigerant.

The refrigerant suctioned from the intake pipe <NUM> connected to the rear side of the casing <NUM> can be filled in the accommodation space <NUM>, and the refrigerant in the intake space <NUM> communicating with the accommodation space <NUM> can be compressed in the compression space <NUM>, discharged into the discharge space <NUM>, and discharged to the outside through the discharge pipe <NUM> connected to the front side of the casing <NUM>.

The casing <NUM> can include the shell <NUM> formed in a substantially cylindrical shape that is open at both ends and is long in a transverse direction, the first shell cover <NUM> coupled to the rear side of the shell <NUM>, and the second shell cover <NUM> coupled to the front side of the shell <NUM>. For instance, the front side is the left side of the figure and is a direction in which the compressed refrigerant is discharged, and the rear side is the right side of the figure and is a direction in which the refrigerant is introduced. Further, the first shell cover <NUM> and the second shell cover <NUM> can be formed as one body with the shell <NUM>.

The casing <NUM> can be formed of a thermally conductive material. Hence, heat generated in the inner space of the casing <NUM> can be quickly dissipated to the outside.

The first shell cover <NUM> can be coupled to the shell <NUM> in order to seal the rear side of the shell <NUM>, and the intake pipe <NUM> can be inserted and coupled to the center of the first shell cover <NUM>.

The rear side of the main body of the linear compressor <NUM> can be elastically supported by the first support spring <NUM> in the radial direction of the first shell cover <NUM>.

The first support spring <NUM> can include a circular leaf spring. An edge portion of the first support spring <NUM> can be elastically supported by a support bracket 123a in a forward direction with respect to a back cover <NUM>. An opened center portion of the first support spring <NUM> can be supported by an intake guide 116a in a rearward direction with respect to the first shell cover <NUM>.

The intake guide 116a can have a through passage formed therein. The intake guide 116a can be formed in a cylindrical shape. A front outer circumferential surface of the intake guide 116a can be coupled to a central opening of the first support spring <NUM>, and a rear end of the intake guide 116a can be supported by the first shell cover <NUM>. In this instance, a separate intake support member 116b can be interposed between the intake guide 116a and an inner surface of the first shell cover <NUM>.

A rear side of the intake guide 116a can communicate with the intake pipe <NUM>, and the refrigerant suctioned through the intake pipe <NUM> can pass through the intake guide 116a and can be smoothly introduced into a first muffler unit <NUM> to be described below.

A damping member 116c can be disposed between the intake guide 116a and the intake support member 116b. The damping member 116c can be formed of a rubber material or the like. Hence, a vibration that can occur in the process of suctioning the refrigerant through the intake pipe <NUM> can be prevented from being transmitted to the first shell cover <NUM>.

The second shell cover <NUM> can be coupled to the shell <NUM> to seal the front side of the shell <NUM>, and the discharge pipe <NUM> can be inserted and coupled through a loop pipe 115a. The refrigerant discharged from the compression space <NUM> can pass through a discharge cover assembly <NUM> and then can be discharged into the refrigeration cycle through the loop pipe 115a and the discharge pipe <NUM>.

A front side of the main body of the compressor <NUM> can be elastically supported by the second support spring <NUM> in the radial direction of the shell <NUM> or the second shell cover <NUM>.

The second support spring <NUM> can include a circular leaf spring. An opened center portion of the second support spring <NUM> can be supported by a first support guide 117b in a rearward direction with respect to the discharge cover assembly <NUM>. An edge of the second support spring <NUM> can be supported by a support bracket 117a in a forward direction with respect to an inner surface of the shell <NUM> or the inner circumferential surface of the shell <NUM> adjacent to the second shell cover <NUM>.

In some examples, unlike <FIG>, the edge of the second support spring <NUM> can be supported in the forward direction with respect to the inner surface of the shell <NUM> or the inner circumferential surface of the shell <NUM> adjacent to the second shell cover <NUM> through a separate bracket coupled to the second shell cover <NUM>.

The first support guide 117b can be formed in a cylindrical shape. A cross section of the first support guide 117b can have a plurality of diameters. A front side of the first support guide 117b can be inserted into a central opening of the second support spring <NUM>, and a rear side of the first support guide 117b can be connected to the discharge cover assembly <NUM>. A support cover 117c can be coupled to the front side of the first support guide 117b with the second support spring <NUM> interposed therebetween. A cup-shaped second support guide 117d that is recessed rearward can be coupled to the front side of the support cover 117c. A cup-shaped third support guide 117e that corresponds to the second support guide 117d and is recessed forward can be coupled to the inside of the second shell cover <NUM>. The second support guide 117d can be inserted into the third support guide 117e and can be supported in the axial direction and/or the radial direction. In this instance, a gap can be formed between the second support guide 117d and the third support guide 117e.

The frame <NUM> can include a body portion <NUM> supporting the outer circumferential surface of the cylinder <NUM>, and a first flange portion <NUM> that is connected to one side of the body portion <NUM> and supports the drive unit <NUM>. The frame <NUM> can be elastically supported with respect to the casing <NUM> by the first and second support springs <NUM> and <NUM> together with the drive unit <NUM> and the cylinder <NUM>.

The body portion <NUM> can wrap the outer circumferential surface of the cylinder <NUM>. The body portion <NUM> can be formed in a cylindrical shape. The first flange portion <NUM> can extend from a front end of the body portion <NUM> in the radial direction.

The cylinder <NUM> can be coupled to an inner circumferential surface of the body portion <NUM>. An inner stator <NUM> can be coupled to an outer circumferential surface of the body portion <NUM>. For example, the cylinder <NUM> can be pressed and fitted to the inner circumferential surface of the body portion <NUM>, and the inner stator <NUM> can be fixed using a separate fixing ring.

An outer stator <NUM> can be coupled to a rear surface of the first flange portion <NUM>, and the discharge cover assembly <NUM> can be coupled to a front surface of the first flange portion <NUM>. For example, the outer stator <NUM> and the discharge cover assembly <NUM> can be fixed through a mechanical coupling member.

On one side of the front surface of the first flange portion <NUM>, a bearing inlet groove 125a forming a part of the gas bearing can be formed, a bearing communication hole 125b penetrating from the bearing inlet groove 125a to the inner circumferential surface of the body portion <NUM> can be formed, and a gas groove 125c communicating with the bearing communication hole 125b can be formed on the inner circumferential surface of the body portion <NUM>.

The bearing inlet groove 125a can be recessed to a predetermined depth along the axial direction. The bearing communication hole 125b is a hole having a smaller cross-sectional area than the bearing inlet groove 125a and can be inclined toward the inner circumferential surface or the inside surface of the body portion <NUM>. The gas groove 125c can be formed in an annular shape having a predetermined depth and an axial length on the inner circumferential surface of the body portion <NUM>. Alternatively, the gas groove 125c can be formed on the outer circumferential surface of the cylinder <NUM> in contact with the inner circumferential surface of the body portion <NUM>, or formed on both the inner circumferential surface of the body portion <NUM> and the outer circumferential surface of the cylinder <NUM>.

In addition, a gas inlet <NUM> corresponding to the gas groove 125c can be formed on the outer circumferential surface of the cylinder <NUM>. The gas inlet <NUM> forms a kind of nozzle in the gas bearing.

The frame <NUM> and the cylinder <NUM> can be formed of aluminum or an aluminum alloy material.

The cylinder <NUM> can be formed in a cylindrical shape in which both ends are opened. The piston <NUM> can be inserted through a rear end of the cylinder <NUM>. A front end of the cylinder <NUM> can be closed via a discharge valve assembly <NUM>. The compression space <NUM> can be formed between the cylinder <NUM>, a front end of the piston <NUM>, and the discharge valve assembly <NUM>. For example, the front end of the piston <NUM> can be referred to as a head portion <NUM>. The volume of the compression space <NUM> increases when the piston <NUM> moves backward, and decreases as the piston <NUM> moves forward. That is, the refrigerant introduced into the compression space <NUM> can be compressed while the piston <NUM> moves forward, and can be discharged through the discharge valve assembly <NUM>.

The cylinder <NUM> can include a second flange portion <NUM> disposed at the front end. The second flange portion <NUM> can bend to the outside of the cylinder <NUM>. The second flange portion <NUM> can extend in an outer circumferential direction of the cylinder <NUM>. The second flange portion <NUM> of the cylinder <NUM> can be coupled to the frame <NUM>. For example, the front end of the frame <NUM> can include a flange groove corresponding to the second flange portion <NUM> of the cylinder <NUM>, and the second flange portion <NUM> of the cylinder <NUM> can be inserted into the flange groove and coupled through a coupling member.

In some implementations, a gas bearing can be provided to supply a discharge gas to a gap between the outer circumferential surface of the piston <NUM> and the outer circumferential surface of the cylinder <NUM> and lubricate between the cylinder <NUM> and the piston <NUM> with gas. The discharge gas supplied between the cylinder <NUM> and the piston <NUM> can provide a levitation force to the piston <NUM> to reduce a friction generated between the piston <NUM> and the cylinder <NUM>.

For example, the cylinder <NUM> can include the gas inlet <NUM>. The gas inlet <NUM> can communicate with the gas groove 125c formed on the inner circumferential surface of the body portion <NUM>. The gas inlet <NUM> can pass through the cylinder <NUM> in the radial direction. The gas inlet <NUM> can guide the compressed refrigerant introduced in the gas groove 125c between the inner circumferential surface of the cylinder <NUM> and the outer circumferential surface of the piston <NUM>. Alternatively, the gas groove 125c can be formed on the outer circumferential surface of the cylinder <NUM> in consideration of the convenience of processing.

An entrance of the gas inlet <NUM> can be formed relatively widely, and an exit of the gas inlet <NUM> can be formed as a fine through hole to serve as a nozzle. The entrance of the gas inlet <NUM> can further include a filter blocking the inflow of foreign matter. The filter can be a metal mesh filter, or can be formed by winding a member such as fine thread.

The plurality of gas inlets <NUM> can be independently formed. Alternatively, the entrance of the gas inlet <NUM> can be formed as an annular groove, and a plurality of exits can be formed along the annular groove at regular intervals. The gas inlet <NUM> can be formed only at the front side based on the axial direction center of the cylinder <NUM>. On the contrary, the gas inlet <NUM> can be formed at the rear side based on the axial direction center of the cylinder <NUM> in consideration of the sagging of the piston <NUM>.

The piston <NUM> is inserted into the opened rear end of the cylinder <NUM> and is provided to seal the rear of the compression space <NUM>.

The piston <NUM> can include a head portion <NUM> and a guide portion <NUM>. The head portion <NUM> can be formed in a disc shape. The head portion <NUM> can be partially open. The head portion <NUM> can partition the compression space <NUM>. The guide portion <NUM> can extend rearward from an outer circumferential surface of the head portion <NUM>. The guide portion <NUM> can be formed in a cylindrical shape. The inside of the guide portion <NUM> can be empty, and a front of the guide portion <NUM> can be partially sealed by the head portion <NUM>. A rear of the guide portion <NUM> can be opened and connected to the first muffler unit <NUM>. The head portion <NUM> can be provided as a separate member coupled to the guide portion <NUM>. Alternatively, the head portion <NUM> and the guide portion <NUM> can be formed as one body.

The piston <NUM> can include an intake port <NUM>. The intake port <NUM> can pass through the head portion <NUM>. The intake port <NUM> can communicate with the intake space <NUM> and the compression space <NUM> inside the piston <NUM>. For example, the refrigerant flowing from the accommodation space <NUM> to the intake space <NUM> in the piston <NUM> can pass through the intake port <NUM> and can be suctioned into the compression space <NUM> between the piston <NUM> and the cylinder <NUM>.

The intake port <NUM> can extend in the axial direction of the piston <NUM>. The intake port <NUM> can be inclined in the axial direction of the piston <NUM>. For example, the intake port <NUM> can extend to be inclined in a direction away from the central axis as it goes to the rear of the piston <NUM>.

A cross section of the intake port <NUM> can be formed in a circular shape. The intake port <NUM> can have a constant inner diameter. In contrast, the intake port <NUM> can be formed as a long hole in which an opening extends in the radial direction of the head portion <NUM>, or can be formed such that the inner diameter becomes larger as it goes to the rear.

The plurality of intake ports <NUM> can be formed in at least one of the radial direction and the circumferential direction of the head portion <NUM>.

The head portion <NUM> of the piston <NUM> adjacent to the compression space <NUM> can be equipped with an intake valve <NUM> for selectively opening and closing the intake port <NUM>. The intake valve <NUM> can operate by elastic deformation to open or close the intake port <NUM>. That is, the intake valve <NUM> can be elastically deformed to open the intake port <NUM> by the pressure of the refrigerant flowing into the compression space <NUM> through the intake port <NUM>. The intake valve <NUM> can be a lead valve, but is not limited thereto and can be variously changed.

The piston <NUM> can be connected to a mover <NUM>. The mover <NUM> can reciprocate forward and backward according to the movement of the piston <NUM>. The inner stator <NUM> and the cylinder <NUM> can be disposed between the mover <NUM> and the piston <NUM>. The mover <NUM> and the piston <NUM> can be connected to each other by a magnet frame <NUM> that is formed by detouring the cylinder <NUM> and the inner stator <NUM> to the rear.

The first muffler unit <NUM> can be coupled to the rear of the piston <NUM> to reduce a noise generated in the process of suctioning the refrigerant into the piston <NUM>. The refrigerant suctioned through the intake pipe <NUM> can flow into the intake space <NUM> in the piston <NUM> via the first muffler unit <NUM>.

The first muffler unit <NUM> can include a first intake muffler <NUM> communicating with the accommodation space <NUM> of the casing <NUM>, and an inner guide <NUM> that is connected to a front of the first intake muffler <NUM> and guides the refrigerant to the intake port <NUM>.

The first intake muffler <NUM> can be positioned behind the piston <NUM>. A rear opening of the first intake muffler <NUM> can be disposed adjacent to the intake pipe <NUM>, and a front end of the first intake muffler <NUM> can be coupled to the rear of the piston <NUM>. The first intake muffler <NUM> can have a flow path formed in the axial direction to guide the refrigerant in the accommodation space <NUM> to the intake space <NUM> inside the piston <NUM>.

The inside of the first intake muffler <NUM> can include a plurality of noise spaces partitioned by a baffle. The first intake muffler <NUM> can be formed by combining two or more members. For example, a second intake muffler can be press-coupled to the inside of a first intake muffler to form a plurality of noise spaces. In addition, the first intake muffler <NUM> can be formed of a plastic material in consideration of weight or insulation property.

One side of the inner guide <NUM> can communicate with the noise space of the first intake muffler <NUM>, and other side can be deeply inserted into the piston <NUM>. The inner guide <NUM> can be formed in a pipe shape. Both ends of the inner guide <NUM> can have the same inner diameter. The inner guide <NUM> can be formed in a cylindrical shape. Alternatively, an inner diameter of a front end that is a discharge side of the inner guide <NUM> can be greater than an inner diameter of a rear end opposite the front end.

The first intake muffler <NUM> and the inner guide <NUM> can be provided in various shapes and can adjust the pressure of the refrigerant passing through the first muffler unit <NUM>. The first intake muffler <NUM> and the inner guide <NUM> can be formed as one body.

The discharge valve assembly <NUM> can include a discharge valve <NUM> and a valve spring <NUM> that is provided on a front side of the discharge valve <NUM> to elastically support the discharge valve <NUM>. The discharge valve assembly <NUM> can selectively discharge the compressed refrigerant in the compression space <NUM>. For instance, the compression space <NUM> refers to a space defined between the intake valve <NUM> and the discharge valve <NUM>.

The discharge valve <NUM> can be disposed to be supportable on the front surface of the cylinder <NUM>. The discharge valve <NUM> can selectively open and close the front opening of the cylinder <NUM>. The discharge valve <NUM> can operate by elastic deformation to open or close the compression space <NUM>. The discharge valve <NUM> can be elastically deformed to open the compression space <NUM> by the pressure of the refrigerant flowing into the discharge space <NUM> through the compression space <NUM>. For example, the compression space <NUM> can maintain a sealed state while the discharge valve <NUM> is supported on the front surface of the cylinder <NUM>, and the compressed refrigerant of the compression space <NUM> can be discharged into an opened space in a state where the discharge valve <NUM> is spaced apart from the front surface of the cylinder <NUM>. The discharge valve <NUM> can be a lead valve, but is not limited thereto and can be variously changed.

The valve spring <NUM> can be provided between the discharge valve <NUM> and the discharge cover assembly <NUM> to provide an elastic force in the axial direction. The valve spring <NUM> can be provided as a compression coil spring, or can be provided as a leaf spring in consideration of an occupied space or reliability.

When the pressure of the compression space <NUM> is equal to or greater than a discharge pressure, the valve spring <NUM> can open the discharge valve <NUM> while deforming forward, and the refrigerant can be discharged from the compression space <NUM> and discharged into a first discharge space 104a of the discharge cover assembly <NUM>. When the discharge of the refrigerant is completed, the valve spring <NUM> provides a restoring force to the discharge valve <NUM> and thus can allow the discharge valve <NUM> to be closed.

A process of introducing the refrigerant into the compression space <NUM> through the intake valve <NUM> and discharging the refrigerant of the compression space <NUM> into the discharge space <NUM> through the discharge valve <NUM> is described as follows.

In the process in which the piston <NUM> linearly reciprocates in the cylinder <NUM>, when the pressure of the compression space <NUM> is equal to or less than a predetermined intake pressure, the intake valve <NUM> is opened and thus the refrigerant is suctioned into a compression space <NUM>. On the other hand, when the pressure of the compression space <NUM> exceeds the predetermined intake pressure, the refrigerant of the compression space <NUM> is compressed in a state in which the intake valve <NUM> is closed.

When the pressure of the compression space <NUM> is equal to or greater than the predetermined intake pressure, the valve spring <NUM> deforms forward and opens the discharge valve <NUM> connected to the valve spring <NUM>, and the refrigerant is discharged from the compression space <NUM> to the discharge space <NUM> of the discharge cover assembly <NUM>. When the discharge of the refrigerant is completed, the valve spring <NUM> provides a restoring force to the discharge valve <NUM> and allows the discharge valve <NUM> to be closed, thereby sealing a front of the compression space <NUM>.

The discharge cover assembly <NUM> is installed at the front of the compression space <NUM>, forms a discharge space <NUM> for receiving the refrigerant discharged from the compression space <NUM>, and is coupled to a front of the frame <NUM> to thereby reduce a noise generated in the process of discharging the refrigerant from the compression space <NUM>. The discharge cover assembly <NUM> can be coupled to a front of the first flange portion <NUM> of the frame <NUM> while receiving the discharge valve assembly <NUM>. For example, the discharge cover assembly <NUM> can be coupled to the first flange portion <NUM> through a mechanical coupling member.

An O-ring <NUM> can be provided between the discharge cover assembly <NUM> and the frame <NUM> to prevent the refrigerant in a gasket <NUM> for thermal insulation and the discharge space <NUM> from leaking.

The discharge cover assembly <NUM> can be formed of a thermally conductive material. Therefore, when a high temperature refrigerant is introduced into the discharge cover assembly <NUM>, heat of the refrigerant can be transferred to the casing <NUM> through the discharge cover assembly <NUM> and dissipated to the outside of the compressor.

The discharge cover assembly <NUM> can include one discharge cover, or can be arranged so that a plurality of discharge covers sequentially communicate with each other. When the discharge cover assembly <NUM> is provided with the plurality of discharge covers, the discharge space <NUM> can include a plurality of spaces partitioned by the respective discharge covers. The plurality of spaces can be disposed in a front-rear direction and can communicate with each other.

For example, when there are three discharge covers, the discharge space <NUM> can include a first discharge space 104a between the frame <NUM> and a first discharge cover <NUM> coupled to the front side of the frame <NUM>, a second discharge space 104b between the first discharge cover <NUM> and a second discharge cover <NUM> that communicates with the first discharge space 104a and is coupled to a front side of the first discharge cover <NUM>, and a third discharge space 104c between the second discharge cover <NUM> and a third discharge cover <NUM> that communicates with the second discharge space 104b and is coupled to a front side of the second discharge cover <NUM>.

The first discharge space 104a can selectively communicate with the compression space <NUM> by the discharge valve <NUM>, the second discharge space 104b can communicate with the first discharge space 104a, and the third discharge space 104c can communicate with the second discharge space 104b. Hence, as the refrigerant discharged from the compression space <NUM> sequentially passes through the first discharge space 104a, the second discharge space 104b, and the third discharge space 104c, a discharge noise can be reduced, and the refrigerant can be discharged to the outside of the casing <NUM> through the loop pipe 115a and the discharge pipe <NUM> communicating with the third discharge cover <NUM>.

The drive unit <NUM> can include the outer stator <NUM> that is disposed between the shell <NUM> and the frame <NUM> and surrounds the body portion <NUM> of the frame <NUM>, the inner stator <NUM> that is disposed between the outer stator <NUM> and the cylinder <NUM> and surrounds the cylinder <NUM>, and the mover <NUM> disposed between the outer stator <NUM> and the inner stator <NUM>.

The outer stator <NUM> can be coupled to the rear of the first flange portion <NUM> of the frame <NUM>, and the inner stator <NUM> can be coupled to the outer circumferential surface of the body portion <NUM> of the frame <NUM>. The inner stator <NUM> can be spaced apart from the inside of the outer stator <NUM>, and the mover <NUM> can be disposed in a space between the outer stator <NUM> and the inner stator <NUM>.

The outer stator <NUM> can be equipped with a winding coil, and the mover <NUM> can include a permanent magnet. The permanent magnet can be comprised of a single magnet with one pole or configured by combining a plurality of magnets with three poles.

The outer stator <NUM> can include a coil winding body <NUM> surrounding the axial direction in the circumferential direction, and a stator core <NUM> stacked while surrounding the coil winding body <NUM>. The coil winding body <NUM> can include a hollow cylindrical bobbin 132a and a coil 132b wound in a circumferential direction of the bobbin 132a. A cross section of the coil 132b can be formed in a circular or polygonal shape and, for example, can have a hexagonal shape. In the stator core <NUM>, a plurality of lamination sheets can be laminated radially, or a plurality of lamination blocks can be laminated along the circumferential direction.

The front side of the outer stator <NUM> can be supported by the first flange portion <NUM> of the frame <NUM>, and the rear side thereof can be supported by a stator cover <NUM>. For example, the stator cover <NUM> can be provided in a hollow disc shape, a front surface of the stator cover <NUM> can be supported by the outer stator <NUM>, and a rear surface thereof can be supported by a resonant spring <NUM>.

The inner stator <NUM> can be configured by stacking a plurality of laminations on the outer circumferential surface of the body portion <NUM> of the frame <NUM> in the circumferential direction.

One side of the mover <NUM> can be coupled to and supported by the magnet frame <NUM>. The magnet frame <NUM> has a substantially cylindrical shape and can be disposed to be inserted into a space between the outer stator <NUM> and the inner stator <NUM>. The magnet frame <NUM> can be coupled to the rear side of the piston <NUM> to move together with the piston <NUM>.

As an example, a rear end of the magnet frame <NUM> is bent and extended inward in the radial direction to form a first coupling portion 136a, and the first coupling portion 136a can be coupled to a third flange portion <NUM> formed behind the piston <NUM>. The first coupling portion 136a of the magnet frame <NUM> and the third flange portion <NUM> of the piston <NUM> can be coupled through a mechanical coupling member.

A fourth flange portion 161a formed in front of the first intake muffler <NUM> and a fifth flange portion 162a formed in rear of the inner guide <NUM> can be interposed between the third flange portion <NUM> of the piston <NUM> and the first coupling portion 136a of the magnet frame <NUM>. Thus, the piston <NUM>, the first muffler unit <NUM>, and the mover <NUM> can linearly reciprocate together in a combined state.

When a current is applied to the drive unit <NUM>, a magnetic flux can be formed in the winding coil, and an electromagnetic force can occur by an interaction between the magnetic flux formed in the winding coil of the outer stator <NUM> and a magnetic flux formed by the permanent magnet of the mover <NUM> to move the mover <NUM>. At the same time as the reciprocating movement of the mover <NUM> in the axial direction, the piston <NUM> connected to the magnet frame <NUM> can also reciprocate integrally with the mover <NUM> in the axial direction.

The drive unit <NUM> and the compression units <NUM> and <NUM> can be supported by the support springs <NUM> and <NUM> and the resonant spring <NUM> in the axial direction.

The resonant spring <NUM> amplifies the vibration implemented by the reciprocating motion of the mover <NUM> and the piston <NUM> and thus can achieve an effective compression of the refrigerant. More specifically, the resonant spring <NUM> can be adjusted to a frequency corresponding to a natural frequency of the piston <NUM> and can allow the piston <NUM> to perform a resonant motion. Further, the resonant spring <NUM> generates a stable movement of the piston <NUM> and thus can reduce the generation of vibration and noise.

The resonant spring <NUM> can be a coil spring extending in the axial direction. Both ends of the resonant spring <NUM> can be connected to a vibrating body and a fixed body, respectively. For example, one end of the resonant spring <NUM> can be connected to the magnet frame <NUM>, and the other end can be connected to the back cover <NUM>. Therefore, the resonant spring <NUM> can be elastically deformed between the vibrating body vibrating at one end and the fixed body fixed to the other end.

A natural frequency of the resonant spring <NUM> can be designed to match a resonant frequency of the mover <NUM> and the piston <NUM> during the operation of the compressor <NUM>, thereby amplifying the reciprocating motion of the piston <NUM>. However, because the back cover <NUM> provided as the fixing body is elastically supported by the first support spring <NUM> in the casing <NUM>, the back cover <NUM> may not be strictly fixed.

The resonant spring <NUM> can include a first resonant spring 118a supported on the rear side and a second resonant spring 118b supported on the front side based on a spring supporter <NUM>.

The spring supporter <NUM> can include a body portion 119a surrounding the first intake muffler <NUM>, a second coupling portion 119b that is bent from a front of the body portion 119a in the inward radial direction, and a support portion 119c that is bent from the rear of the body portion 119a in the outward radial direction.

A front surface of the second coupling portion 119b of the spring supporter <NUM> can be supported by the first coupling portion 136a of the magnet frame <NUM>. The second coupling portion 119b of the spring supporter <NUM> can be coupled to the piston <NUM>. An inner diameter of the second coupling portion 119b of the spring supporter <NUM> can cover an outer diameter of the first intake muffler <NUM>. For example, the second coupling portion 119b of the spring supporter <NUM>, the first coupling portion 136a of the magnet frame <NUM>, and the third flange portion <NUM> of the piston <NUM> can be sequentially disposed and then integrally coupled through a mechanical member. In this instance, the description, that the fourth flange portion 161a and the fifth flange portion 162a of the first intake muffler <NUM> can be interposed between the third flange portion <NUM> of the piston <NUM> and the first coupling portion 136a of the magnet frame <NUM> and they can be fixed together, is the same as that described above.

The first resonant spring 118a can be disposed between a front surface of the back cover <NUM> and a rear surface of the spring supporter <NUM>. The second resonant spring 118b can be disposed between a rear surface of the stator cover <NUM> and a front surface of the spring supporter <NUM>.

A plurality of first and second resonant springs 118a and 118b can be disposed in the circumferential direction of the central axis. The first resonant springs 118a and the second resonant springs 118b can be disposed parallel to each other in the axial direction, or can be alternately disposed. The first and second resonant springs 118a and 118b can be disposed at regular intervals in the radial direction of the central axis. For example, three first resonant springs 118a and three second resonant springs 118b can be provided and can be disposed at intervals of <NUM> degrees in the radial direction of the central axis.

The compressor <NUM> can include a plurality of sealing members that can increase a coupling force between the frame <NUM> and the components around the frame <NUM>.

For example, the plurality of sealing members can include a first sealing member that is interposed at a portion where the frame <NUM> and the discharge cover assembly <NUM> are coupled and is inserted into an installation groove provided at the front end of the frame <NUM>, and a second sealing member that is provided at a portion at which the frame <NUM> and the cylinder <NUM> are coupled and is inserted into an installation groove provided at an outer surface of the cylinder <NUM>. The second sealing member can prevent the refrigerant of the gas groove 125c between the inner circumferential surface of the frame <NUM> and the outer circumferential surface of the cylinder <NUM> from leaking to the outside, and can increase a coupling force between the frame <NUM> and the cylinder <NUM>. The plurality of sealing members can further include a third sealing member that is provided at a portion at which the frame <NUM> and the inner stator <NUM> are coupled and is inserted into an installation groove provided at the outer surface of the frame <NUM>. In some examples, the first to third sealing members can have a ring shape.

An operation of the linear compressor <NUM> described above is as follows.

First, when a current is applied to the drive unit <NUM>, a magnetic flux can be formed in the outer stator <NUM> by the current flowing in the coil 132b. The magnetic flux formed in the outer stator <NUM> can generate an electromagnetic force, and the mover <NUM> including the permanent magnet can linearly reciprocate by the generated electromagnetic force. The electromagnetic force can be alternately generated in a direction (forward direction) in which the piston <NUM> is directed toward a top dead center (TDC) during a compression stroke, and in a direction (rearward direction) in which the piston <NUM> is directed toward a bottom dead center (BDC) during an intake stroke. That is, the drive unit <NUM> can generate a thrust which is a force for pushing the mover <NUM> and the piston <NUM> in a moving direction.

The piston <NUM> linearly reciprocating inside the cylinder <NUM> can repeatedly increase or reduce the volume of the compression space <NUM>.

When the piston <NUM> moves in a direction (rearward direction) of increasing the volume of the compression space <NUM>, a pressure of the compression space <NUM> can decrease. Hence, the intake valve <NUM> mounted in front of the piston <NUM> is opened, and the refrigerant remaining in the intake space <NUM> can be suctioned into the compression space <NUM> along the intake port <NUM>. The intake stroke can be performed until the piston <NUM> is positioned in the bottom dead center by maximally increasing the volume of the compression space <NUM>.

The piston <NUM> reaching the bottom dead center can perform the compression stroke while switching its motion direction and moving in a direction (forward direction) of reducing the volume of the compression space <NUM>. As the pressure of the compression space <NUM> increases during the compression stroke, the suctioned refrigerant can be compressed. When the pressure of the compression space <NUM> reaches a setting pressure, the discharge valve <NUM> is pushed out by the pressure of the compression space <NUM> and is opened from the cylinder <NUM>, and the refrigerant can be discharged into the discharge space <NUM> through a separation space. The compression stroke can continue while the piston <NUM> moves to the top dead center at which the volume of the compression space <NUM> is minimized.

As the intake stroke and the compression stroke of the piston <NUM> are repeated, the refrigerant introduced into the accommodation space <NUM> inside the compressor <NUM> through the intake pipe <NUM> can be introduced into the intake space <NUM> in the piston <NUM> by sequentially passing the intake guide 116a, the first intake muffler <NUM>, and the inner guide <NUM>, and the refrigerant of the intake space <NUM> can be introduced into the compression space <NUM> in the cylinder <NUM> during the intake stroke of the piston <NUM>. After the refrigerant of the compression space <NUM> is compressed and discharged into the discharge space <NUM> during the compression stroke of the piston <NUM>, the refrigerant can be discharged to the outside of the compressor <NUM> via the loop pipe 115a and the discharge pipe <NUM>.

<FIG> are a perspective view showing an example of a muffler unit. <FIG> is an exploded perspective view of the muffler unit. <FIG> is a perspective view showing an example of a second intake muffler. <FIG> is a side view of the second intake muffler. <FIG> is a cross-sectional view of the second intake muffler. <FIG> is a front view of the second intake muffler. <FIG> is a rear view of the second intake muffler. <FIG> and <FIG> are a perspective view showing an example of a muffler body. <FIG> is a front view of the muffler body. <FIG> is a rear view of the muffler body. <FIG> and <FIG> are a perspective view showing an example of a muffler cover. <FIG> is a cross-sectional view showing an example of a piston, a muffler unit, and a back cover. <FIG> is a perspective view of the muffler unit and the back cover. <FIG> is a cross-sectional exploded perspective view of the muffler unit and the back cover. <FIG> is a rear view of the back cover. <FIG> and <FIG> are a rear view of the back cover and the muffler unit. <FIG> is a perspective view showing an example of the piston, a spring supporter, a first resonant spring, the muffler unit, and the back cover. <FIG> is a block diagram showing an example of multiple resonators. <FIG> is a graph illustrating an example of a transmission loss (TL) per frequency in multiple resonators. <FIG> is a graph illustrating an example of an insertion loss (IL) depending on a frequency in a muffler unit according to a related art and a muffler unit.

Referring to <FIG>, muffler units <NUM> and <NUM> of the linear compressor <NUM> include a first muffler unit <NUM> and a second muffler unit <NUM>, but can be implemented except some of these components and does not exclude additional components.

In the present disclosure, the front refers to an axially front and the rear refers to an axially rear. More specifically, in <FIG>, the front can refer to a downward direction, and the rear can refer to an upward direction. In <FIG>, the front can refer to a left direction, and the rear can refer to a right direction. For example, the refrigerant in the cylinder is compressed in a direction from a rear side of the cylinder to a front side of the cylinder.

In some implementations, the first muffler unit <NUM> includes the first intake muffler <NUM> and the inner guide <NUM>.

The second muffler unit <NUM> is coupled to an opening <NUM> formed in a radially central area of the back cover <NUM>. The second muffler unit <NUM> can provide an expansion space in which noise is attenuated between the piston <NUM> and the back cover <NUM>. Through this, noise of the linear compressor <NUM> can be reduced by improving a performance of the muffler units <NUM> and <NUM>.

The second muffler unit <NUM> can include ribs <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> protruding from an outer surface or an inner surface. It can be understood here that the outer surface includes a radially outer circumferential surface, a front surface, and a rear surface. Through this, the rigidity of the second muffler unit <NUM> can be improved.

The second muffler unit <NUM> includes a second intake muffler <NUM>, a muffler body <NUM>, and a muffler cover <NUM>, but can be implemented except some of these components and does not exclude additional components.

The second intake muffler <NUM> communicates with the first intake muffler <NUM>. A diameter of a front end of the second intake muffler <NUM> can be larger than a diameter of a rear end of the first intake muffler <NUM>. As the piston <NUM> reciprocates axially, a rear area of the first intake muffler <NUM> coupled to the piston <NUM> can move axially inside the second intake muffler <NUM>.

The second intake muffler <NUM> is coupled to the back cover <NUM>. More specifically, the second intake muffler <NUM> can be coupled to the opening <NUM>.

The second intake muffler <NUM> can include a first cylindrical portion <NUM>. The first cylindrical portion <NUM> can be formed in a cylindrical shape in which both the front and the rear are opened. A first communication hole <NUM> can be formed in an outer circumferential surface of the first cylindrical portion <NUM>. The front of the first cylindrical portion <NUM> can communicate with the first intake muffler <NUM>. A diameter of a front end of the first cylindrical portion <NUM> can be larger than the diameter of the rear end of the first intake muffler <NUM>. The first intake muffler <NUM> can be positioned inside the front end of the first cylindrical portion <NUM>. The first cylindrical portion <NUM> can be coupled to the back cover <NUM>.

In the first cylindrical portion <NUM>, a first flange <NUM>, a second flange <NUM>, a third coupling portion <NUM>, first ribs <NUM> and <NUM>, and a first communication hole <NUM>, a second rib <NUM>, a second communication hole <NUM>, a partition wall <NUM>, a protrusion <NUM>, and third ribs <NUM> and <NUM> can be formed.

The second intake muffler <NUM> can include the first flange <NUM>. The first flange <NUM> can extend radially outward from the front of the first cylindrical portion <NUM>. The first flange <NUM> can radially overlap a front end of the muffler body <NUM>. The protrusion <NUM> disposed adjacent to an internal flow path and protruding forward can be formed on a front surface of the first flange <NUM>. A radially protruding length of the first flange <NUM> can be greater than a radially protruding length of the second flange <NUM>.

The second intake muffler <NUM> can include the second flange <NUM>. The second flange <NUM> can extend radially outward from a central area of the first cylindrical portion <NUM>. The second flange <NUM> can be disposed between the first flange <NUM> and the third coupling portion <NUM>. The second flange <NUM> can contact a third flange <NUM> of the muffler body <NUM>. Specifically, a rear surface of the second flange <NUM> can contact a front surface of the third flange <NUM> of the muffler body <NUM>. An elastic member <NUM> can be disposed between the second flange <NUM> and the third flange <NUM>. The drawings illustrate that a third groove <NUM> is formed only in the third flange <NUM>, by way of example. However, unlike this, a groove in which the elastic member <NUM> is disposed can also be formed in the second flange <NUM>.

The second intake muffler <NUM> can include the third coupling portion <NUM>. The third coupling portion <NUM> can be formed at the rear of the second intake muffler <NUM>. The third coupling portion <NUM> can protrude radially outward from the rear end of the first cylindrical portion <NUM>. The third coupling portion <NUM> can be formed in a shape corresponding to the opening <NUM> of the back cover <NUM>. The third coupling portion <NUM> can pass through the opening <NUM> of the back cover <NUM>, rotate, and be seated on the rear surface of the back cover <NUM>. In this case, the third coupling portion <NUM> and the opening <NUM> of the back cover <NUM> can be formed in an oval or polygonal shape.

Through this, it is possible to firmly couple the back cover <NUM> made of a metal material and the second muffler unit <NUM> made of a non-metal material. In addition, the second intake muffler <NUM> can be coupled to the opening <NUM> of the back cover <NUM> without a separate welding process.

The second intake muffler <NUM> includes the first communication hole <NUM> formed in its outer circumferential surface. The first communication hole <NUM> can be formed in the first cylindrical portion <NUM>. The first communication hole <NUM> can be formed between the first flange <NUM> and the second flange <NUM>. The first communication hole <NUM> can communicate an inside of the second intake muffler <NUM> with a space between the second intake muffler <NUM> and the muffler body <NUM>. The space between the second intake muffler <NUM> and the muffler body <NUM> in which the first communication hole <NUM> is formed can be referred to as a "first expansion space. " The first communication hole <NUM> can include a plurality of first communication holes <NUM> that are spaced apart in a circumferential direction. Through this, the linear compressor can improve noise filtering characteristics through an additional expansion room of the second muffler unit <NUM>.

In some implementations, the first communication hole <NUM> is described as having a rectangular shape by way of example, but the shape of the first communication hole <NUM> can be variously changed.

The space between the second intake muffler <NUM> and the muffler body <NUM> may not axially overlap the first intake muffler <NUM>. Only a part of the space between the second intake muffler <NUM> and the muffler body <NUM> can axially overlap the piston <NUM>. Through this, the linear compressor can improve space efficiency while improving noise filtering characteristics of the muffler units <NUM> and <NUM>.

The second intake muffler <NUM> can include the second communication hole <NUM> formed in its outer circumferential surface. The second communication hole <NUM> can be formed in the first cylindrical portion <NUM>. The second communication hole <NUM> can be formed between the second flange <NUM> and the third coupling portion <NUM>. The second communication hole <NUM> can communicate the inside of the second intake muffler <NUM> with a space between the second intake muffler <NUM>, the muffler body <NUM>, the muffler cover <NUM>, and the back cover <NUM>. The space between the second intake muffler <NUM>, the muffler body <NUM>, the muffler cover <NUM>, and the back cover <NUM> can be referred to as a "second expansion space. " The second communication hole <NUM> can include a plurality of second communication holes <NUM> that are spaced apart in a circumferential direction. Through this, the linear compressor can improve noise filtering characteristics through an additional expansion room of the second muffler unit <NUM>.

In some implementations, the second communication hole <NUM> is described as having a rectangular shape by way of example, but the shape of the second communication hole <NUM> can be variously changed.

A diameter of the space between the second intake muffler <NUM>, the muffler body <NUM>, the muffler cover <NUM>, and the back cover <NUM> can be greater than a diameter of the space between the second intake muffler <NUM> and the muffler body <NUM>. Through this, the linear compressor can improve noise reduction efficiency of the second muffler unit.

The second intake muffler <NUM> can include the partition wall <NUM>. The partition wall <NUM> can partition an inner space <NUM> of the first cylindrical portion <NUM>. The partition wall <NUM> can be formed only in a rear area of the first cylindrical portion <NUM>. The partition wall <NUM> can radially overlap the second communication hole <NUM>. The partition wall <NUM> can radially overlap the space between the second intake muffler <NUM>, the muffler body <NUM>, the muffler cover <NUM>, and the back cover <NUM>. Through this, the linear compressor can improve the space efficiency while improving the intake efficiency of the refrigerant.

The second intake muffler <NUM> can include the first ribs <NUM> and <NUM>. The first ribs <NUM> and <NUM> can protrude radially outward from the outer circumferential surface of the second intake muffler <NUM>. The first ribs <NUM> and <NUM> can protrude radially outward from the outer circumferential surface of the first cylindrical portion <NUM>. The first ribs <NUM> and <NUM> can extend in the circumferential direction. A part of the first ribs <NUM> and <NUM> can be disposed between the first flange <NUM> and the second flange <NUM>, and other part can be disposed between the second flange <NUM> and the third coupling portion <NUM>.

A part of the first ribs <NUM> and <NUM> can overlap the first communication hole <NUM> in the circumferential direction. Through this, the linear compressor can improve the rigidity of the second intake muffler <NUM> without affecting the flow of the refrigerant flowing inside the second intake muffler <NUM>.

The first ribs <NUM> and <NUM> can include a plurality of first ribs <NUM> and <NUM> that are axially spaced apart from each other. In some implementations, the plurality of first ribs <NUM> and <NUM> can be configured such that the three first ribs are disposed between the first flange <NUM> and the second flange <NUM>, and the two first ribs are disposed between the second flange <NUM> and the third coupling portion <NUM>, by way of example. However, the present disclosure is not limited thereto, and the number of first ribs <NUM> and <NUM> can be variously changed.

The second intake muffler <NUM> can include the second rib <NUM>. The second rib <NUM> can extend axially between the first flange <NUM> and the second flange <NUM>. The second rib <NUM> can include a first area 2128b extending axially from the outer circumferential surface of the first cylindrical portion <NUM>; a second area 2128a that is connected to the first area 2128b, protrudes rearward from the rear surface of the first flange <NUM>, and extends radially; and a third area 2128c that is connected to the first area 2128b, protrudes forward from the front surface of the second flange <NUM>, and extends radially.

The second rib <NUM> can overlap a part (e.g., <NUM>) of the first ribs <NUM> and <NUM>. A radially protruding length of the second rib <NUM> can be greater than radially protruding lengths of the first ribs <NUM> and <NUM>.

Through this, the linear compressor can prepare for vibration applied to the second intake muffler <NUM> by improving the rigidity of the second intake muffler <NUM> in a plurality of directions.

The second intake muffler <NUM> can include the third ribs <NUM> and <NUM>. The third ribs <NUM> and <NUM> can be formed on the first flange <NUM>. The third ribs <NUM> and <NUM> can protrude forward from the front surface of the first flange <NUM>. The third ribs <NUM> and <NUM> can protrude radially. Through this, the rigidity of the first flange <NUM> can be improved.

The third ribs <NUM> and <NUM> can include a plurality of third ribs <NUM> and <NUM> spaced apart in the circumferential direction. The plurality of third ribs <NUM> and <NUM> can be radially disposed based on a central area of the first flange <NUM>. A part (e.g., <NUM>) of the plurality of third ribs <NUM> and <NUM> can be formed in a different shape from a shape of other part (e.g., <NUM>). Through this, the coupling direction of the second intake muffler <NUM> including the first flange <NUM> can be guided.

The third ribs <NUM> and <NUM> may not axially overlap the second rib <NUM>. Through this, the linear compressor can improve the space efficiency while improving the rigidity of the second intake muffler <NUM>.

An area where the third ribs <NUM> and <NUM> and the protrusion <NUM> are connected can be formed as a curved surface <NUM>.

The muffler body <NUM> can surround the second intake muffler <NUM>. When the second intake muffler <NUM> is coupled to the opening <NUM>, the muffler body <NUM> can be press-fitted to the back cover <NUM>. The muffler body <NUM> can include a second cylindrical portion <NUM> and the third flange <NUM>.

The second cylindrical portion <NUM> can be disposed at a radially outside of the second intake muffler <NUM>. The second cylindrical portion <NUM> can be formed in a cylindrical shape with an opened rear. Specifically, the second cylindrical portion <NUM> can have a shape in which a front and a rear of a central area are opened, a front of a space between an inner surface 222b and an outer surface 222c is closed, and a rear of the space between the inner surface 222b and the outer surface 222c is opened.

The third flange <NUM> can extend inward from the inner surface 222b of the second cylindrical portion <NUM>. An inner area of the third flange <NUM> can axially overlap an outer area of the second flange <NUM>. The third flange <NUM> can contact the second flange <NUM>. Specifically, the front surface of the third flange <NUM> can contact the rear surface of the second flange <NUM>. Through this, when the third coupling portion <NUM> of the second intake muffler <NUM> is coupled to the opening <NUM> of the back cover <NUM>, the muffler body <NUM> can be press-fitted between the second intake muffler <NUM> and the back cover <NUM>.

The elastic member <NUM> can be disposed between the third flange <NUM> and the second flange <NUM>. The third flange <NUM> can include the third groove <NUM> in which the elastic member <NUM> is seated. The present disclosure describes that the third groove <NUM> is formed only in the third flange <NUM>, by way of example, but the third groove <NUM> can be formed in at least one of the front surface of the third flange <NUM> and the rear surface of the second flange <NUM>. The third groove <NUM> can extend in the circumferential direction. Through this, the present disclosure can guide a position of the elastic member <NUM> disposed between the second intake muffler <NUM> and the muffler body <NUM>, and can improve the coupling stability by allowing the second muffler unit <NUM> to be press-fitted to the back cover <NUM> while removing a gap between the second intake muffler <NUM> and the muffler body <NUM>.

A hole <NUM> can be formed in the central area of the third flange <NUM>. The first cylindrical portion <NUM> of the second intake muffler <NUM> can be disposed in the hole <NUM>.

The muffler body <NUM> includes a resonance communication hole <NUM>. The resonance communication hole <NUM> can be formed in the inner surface 222b of the second cylindrical portion <NUM>. The resonance communication hole <NUM> communicates a space between the second intake muffler <NUM> and the second cylindrical portion <NUM> with a space between the muffler body <NUM> and the muffler cover <NUM>. The resonance communication hole <NUM> can communicate a space between the second intake muffler <NUM> and the second cylindrical portion <NUM> with a space between the second cylindrical portion <NUM> and a ring portion <NUM>.

The resonance communication hole <NUM> can be disposed adjacent to the third flange <NUM>. Through this, noise generated in the piston <NUM> can be easily introduced into the resonator via the resonance communication hole <NUM>.

The space between the second cylindrical portion <NUM> and the ring portion <NUM> can be understood as a space between the inner surface 222b, the outer surface 222c, and a front surface 222a of the second cylindrical portion <NUM> and the ring portion <NUM>. The space between the second cylindrical portion <NUM> and the ring portion <NUM> can be referred to as a "resonator.

The resonator that is the space between the inner surface 222b, the outer surface 222c, and the front surface 222a of the second cylindrical portion <NUM> and the ring portion <NUM> can form a closed space by the second cylindrical portion <NUM> and the ring portion <NUM> except for the resonance communication hole <NUM>.

An axial length of the space between the muffler body <NUM> and the muffler cover <NUM> can be greater than a radial length of the space between the muffler body <NUM> and the muffler cover <NUM>. The space between the muffler body <NUM> and the muffler cover <NUM> may not axially overlap the piston <NUM>.

Due to the additional resonator, it is possible to reduce noise of a low frequency or mid-frequency in the <NUM> frequency band.

The muffler body <NUM> can include a fourth rib <NUM>. The fourth rib <NUM> can protrude radially outward from the outer surface 222c or the outer circumferential surface of the second cylindrical portion <NUM>. The fourth rib <NUM> can extend axially. Through this, the rigidity of the muffler body <NUM> can be improved.

The fourth rib <NUM> can contact a leg portion <NUM> of the back cover <NUM>. The back cover <NUM> can include a support member <NUM> in which the opening <NUM> is formed, a plurality of leg portions <NUM> that extend forward from a radially outside of the support member <NUM> and are spaced apart in the circumferential direction, and a plurality of extension members <NUM> that extend radially from the support member <NUM> and are spaced apart in the circumferential direction. The fourth rib <NUM> can include a plurality of fourth ribs <NUM> spaced apart in the circumferential direction. Each of the plurality of fourth ribs <NUM> can contact each of the plurality of leg portions <NUM>. Through this, the linear compressor can guide the position of the muffler body <NUM> relative to the back cover <NUM> and press-fit the muffler body <NUM> to the back cover <NUM>.

The muffler body <NUM> can include a fifth rib <NUM>. The fifth rib <NUM> can be formed in an area between the inner surface 222b of the second cylindrical portion <NUM> and the front surface of the third flange <NUM>. Specifically, the fifth rib <NUM> can extend from the inner surface 222b of the second cylindrical portion <NUM> to the front surface of the third flange <NUM>. Through this, the rigidity of the area connecting the second cylindrical portion <NUM> and the third flange <NUM> can be improved.

The fifth rib <NUM> can be closer to the inner surface 222b of the second cylindrical portion <NUM> as the fifth rib <NUM> becomes distant from the front surface of the third flange <NUM>. Specifically, as the fifth rib <NUM> becomes distant from the front surface of the third flange <NUM>, a length of the fifth rib <NUM> from the inner surface 222b of the second cylindrical portion <NUM> can decrease. Through this, the position of the second flange <NUM> relative to the third flange <NUM> can be guided.

The muffler body <NUM> can include a plurality of first grooves <NUM>. The plurality of first grooves <NUM> can be concave inward from the outer surface 222c of the second cylindrical portion <NUM>. The plurality of first grooves <NUM> can be concavely formed rearward from the front surface 222a of the second cylindrical portion <NUM>. The plurality of first grooves <NUM> can be spaced apart from each other in the circumferential direction. In some implementations three first grooves <NUM> may be defined, by way of example, but other implementations are not limited thereto. For example, the number of first grooves <NUM> can be variously changed.

The first groove <NUM> can include a base surface 2222a, a first stepped portion 2222b that connects the base surface 2222a and the outer surface 222c of the second cylindrical portion <NUM> and extends in the circumferential direction, and second and third stepped portions 2222c that connect the base surface 2222a and the outer surface 222c of the second cylindrical portion <NUM> and extend axially.

The plurality of first grooves <NUM> can axially overlap the support portion 119c of the spring supporter <NUM>. Through this, the linear compressor can prevent interference between the muffler body <NUM> and the spring supporter <NUM> and improve the space efficiency.

A resonator can be formed between the plurality of first grooves <NUM> in the circumferential direction. Specifically, a space between the muffler body <NUM> and the muffler cover <NUM> can be formed between the plurality of first grooves <NUM> in the circumferential direction. More specifically, the space between the inner surface 222b, the outer surface 222c, and the front surface 222a of the second cylindrical portion <NUM> and the ring portion <NUM> can be formed each between the plurality of first grooves <NUM> in the circumferential direction. The plurality of resonance communication holes <NUM> can be disposed between the plurality of first grooves <NUM> in the circumferential direction. Through this, it is possible to improve space efficiency while preventing interference with other configurations.

The muffler body <NUM> can include sixth ribs <NUM> and <NUM>. The sixth ribs <NUM> and <NUM> can extend rearward from a rear surface of the first stepped portion 2222b of the first groove <NUM>. Through this, the rigidity of the plurality of first grooves <NUM> can be improved.

The sixth ribs <NUM> and <NUM> can include an inner rib <NUM> formed at the inside and an outer rib <NUM> disposed at a radially outside of the inner rib <NUM>. An axial length of the outer rib <NUM> can be greater than an axial length of the inner rib <NUM>. Specifically, a protruding length of the outer rib <NUM> from the first stepped portion 2222b can be greater than a protruding length of the inner rib <NUM>. Through this, the position of the muffler cover <NUM> relative to the muffler body <NUM> can be guided.

The muffler cover <NUM> can be seated on the sixth ribs <NUM> and <NUM>. The ring portion <NUM> can be seated on the outer rib <NUM>, and a second extension <NUM> can be seated on the inner rib <NUM>.

The muffler body <NUM> can include a guide groove <NUM>. The guide groove <NUM> can be formed in the front surface 222a of the second cylindrical portion <NUM>. The guide groove <NUM> can include a plurality of guide grooves <NUM> spaced apart in the circumferential direction. The guide groove <NUM> can radially overlap the fourth rib <NUM>. Through this, when the second muffler unit <NUM> is coupled to the back cover <NUM>, a correct coupling direction can be guided to a user.

An area <NUM> which is opened rearward between the inner surface 222b and the outer surface 222c in the muffler body <NUM> can be referred to as a "resonator. " The area <NUM> which is opened rearward between the inner surface 222b and the outer surface 222c in the muffler body <NUM> can be sealed by the muffler cover <NUM>. That is, this can be understood as the same meaning as the space between the muffler body <NUM> and the muffler cover <NUM>.

The muffler body <NUM> can include an eighth rib <NUM>. The eighth rib <NUM> can be formed in the area <NUM> which is opened rearward between the inner surface 222b and the outer surface 222c in the muffler body <NUM>. The eighth rib <NUM> can be formed in a space between the plurality of first grooves <NUM>. Specifically, the eighth rib <NUM> can be formed in a space between the second and third stepped portions 2222c. The eighth rib <NUM> can protrude inward from the outer surface 222c of the muffler body <NUM>. Through this, it is possible to improve the rigidity of the resonator of the muffler body <NUM> while improving the space efficiency.

The muffler cover <NUM> can be disposed between the muffler body <NUM> and the back cover <NUM>. The muffler cover <NUM> can be seated on the sixth ribs <NUM> and <NUM>. When the second intake muffler <NUM> is coupled to the opening <NUM>, the muffler cover <NUM> can be press-fitted to the back cover <NUM>. The muffler cover <NUM> can be entirely formed in a ring shape or a circular band shape.

The muffler cover <NUM> can include the ring portion <NUM>, a first extension <NUM>, and the second extension <NUM>. The central area of the ring portion <NUM> can be opened. The ring portion <NUM> can extend in the circumferential direction. The ring portion <NUM> can be formed in a ring shape or a circular band shape. The first extension <NUM> can extend rearward from the outer surface or the outer end of the ring portion <NUM>. The second extension <NUM> can extend forward from the inner surface or the inner end of the ring portion <NUM>.

The ring portion <NUM> and the second extension <NUM> can contact the muffler body <NUM>. The second extension <NUM> can be seated on the inner rib <NUM>. The ring portion <NUM> can be seated on the outer rib <NUM>. The first extension <NUM> can contact the back cover <NUM>. An outer surface of the first extension <NUM> and an inner surface of the second extension <NUM> can contact the second cylindrical portion <NUM>. Through this, when the third coupling portion <NUM> of the second intake muffler <NUM> is coupled to the opening <NUM> of the back cover <NUM>, the muffler cover <NUM> can be press-fitted between the muffler body <NUM> and the back cover <NUM>.

The ring portion <NUM> can seal a rear opened between the inner surface 222b and the outer surface 222c of the second cylindrical portion <NUM>. The outer surface of the first extension <NUM> can contact the second cylindrical portion <NUM>.

The muffler cover <NUM> can include a seventh rib <NUM>. The seventh rib <NUM> can be formed between the rear surface of the ring portion <NUM> and the inner surface of the first extension <NUM>. The seventh rib <NUM> can include a plurality of seventh rib units <NUM> and <NUM> spaced apart in the circumferential direction. The plurality of seventh rib units <NUM> and <NUM> can face each other. The support bracket 123a can be disposed between the plurality of seventh rib units <NUM> and <NUM>. Through this, the linear compressor can guide the position of the muffler cover <NUM> and improve the rigidity of the muffler cover <NUM>.

The muffler cover <NUM> can include a fourth coupling portion <NUM>. The fourth coupling portion <NUM> can protrude radially outward from the first extension <NUM>. A straight line extending the fourth coupling portion <NUM> can be disposed between the plurality of seventh rib units <NUM> and <NUM>. The fourth coupling portion <NUM> can be seated in a second groove <NUM> concavely formed from the inside to the outside of the fourth rib <NUM>. The fourth coupling portion <NUM> can include a plurality of fourth coupling portions <NUM> spaced apart in the circumferential direction. Through this, the linear compressor can guide the position of the muffler cover <NUM> relative to the muffler body <NUM> while improving the rigidity of the muffler cover <NUM> and the muffler body <NUM>.

<FIG> is a block diagram of multiple resonators. A space between the inner guide <NUM> and the piston <NUM> can be described as a first resonator HR1, and an additional resonator that is the space between the second cylindrical portion <NUM> and the ring portion <NUM> can be described as a second resonator HR2.

Referring to <FIG>, when only the first resonator HR1 is present, only the transmission loss in the <NUM> band is improved, and when only the second resonator HR2 is present, only the transmission loss in the <NUM> band is improved. Compared to this, when the first resonator HR1 and the second resonator HR2 are linearly arranged, the transmission loss in both the <NUM> and <NUM> bands can be improved, and the transmission loss in a frequency band (e.g., <NUM>) between the respective resonators HR1 and HR2 can also be improved.

When the resonators HR1 and HR2 are applied to the linear compressor <NUM>, the first resonator HR1 can improve the transmission loss in the <NUM> band, the second resonator HR2 can improve the transmission loss in the <NUM> band, and the resonators HR1 and HR2 can improve the transmission loss in the <NUM> and <NUM> bands.

Referring to <FIG>, noise reduction characteristics of the muffler units <NUM> and <NUM> of the linear compressor <NUM> can be further improved compared to the related art. Specifically, noise in a low or mid-frequency band between <NUM> and <NUM> can be reduced, and noise in a high-frequency band between <NUM> and <NUM> can also be reduced. The insertion loss (IL) can be understood as expressing a difference in a sound level before and after mounting the muffler units <NUM> and <NUM> on a dB scale.

Some implementations or other implementations of the present invention described above are not exclusive or distinct from each other. Some implementations or other implementations of the present disclosure described above can be used together or combined in configuration or function.

For example, configuration "A" described in an implementation and/or the drawings and configuration "B" described in another implementation and/or the drawings can be combined with each other. That is, even if the combination between the configurations is not directly described, the combination is possible except in cases where it is described that it is impossible to combine.

Claim 1:
A linear compressor comprising:
a cylinder (<NUM>);
a piston (<NUM>) configured to axially reciprocate in the cylinder (<NUM>);
a back cover (<NUM>) disposed at a rear of the piston (<NUM>), the back cover (<NUM>) defining an opening at a central region around an axial centerline thereof;
a first muffler unit (<NUM>) coupled to the piston (<NUM>), the first muffler unit (<NUM>) comprising (i) an inner guide (<NUM>) disposed in the piston (<NUM>) and (ii) a first intake muffler (<NUM>) disposed between the inner guide (<NUM>) and the back cover (<NUM>); and
a second muffler unit (<NUM>) comprising (i) a second intake muffler (<NUM>) that is in fluid communication with the first intake muffler (<NUM>) and (ii) a muffler body (<NUM>) surrounding the second intake muffler (<NUM>),
characterized in that:
the second intake muffler (<NUM>) is coupled to the back cover (<NUM>) adjacent to the opening,
the second muffler unit (<NUM>) further comprises (iii) a muffler cover (<NUM>) disposed between the muffler body (<NUM>) and the back cover (<NUM>),
an outer circumferential surface of the second intake muffler (<NUM>) defines a first communication hole (<NUM>) that fluidly communicates an inside of the second intake muffler (<NUM>) with a first space that is defined between the second intake muffler (<NUM>) and the muffler body (<NUM>), and
the muffler body (<NUM>) defines a resonance communication hole (<NUM>) that fluidly communicates the first space with a second space that is defined between the muffler body (<NUM>) and the muffler cover (<NUM>).