Patent Publication Number: US-2022220953-A1

Title: Linear compressor

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to and the benefit of Korean Patent Application No. 10-2021-0003339 filed in the Korean Intellectual Property Office on Jan. 11, 2021. 
     TECHNICAL FIELD 
     The present disclosure relates to a compressor. More specifically, the present disclosure relates to a linear compressor for compressing a refrigerant by a linear reciprocating motion of a piston. 
     BACKGROUND 
     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, and is widely used in the whole industry and home appliances. 
     The compressors may be classified into a reciprocating compressor, a rotary compressor, and a scroll compressor according to a method of compressing the refrigerant. 
     The reciprocating compressor uses a method in which a compression chamber is formed between a piston and a cylinder to suction or discharge a working gas, and the piston linearly reciprocates in the cylinder to compress a refrigerant. 
     The rotary compressor uses a method in which a compression chamber is formed between a roller that eccentrically rotates and a cylinder to suction or discharge a working gas, and the roller eccentrically rotates along an inner wall of the cylinder to compress a refrigerant. 
     The scroll compressor uses a method in which a compression chamber is formed between an orbiting scroll and a fixed scroll to suction or discharge a working gas, and the orbiting scroll rotates along the fixed scroll to compress a refrigerant. 
     Recently, among the reciprocating compressors, the use of linear compressors is gradually increasing since these linear compressors can improve compression efficiency without a mechanical loss due to motion switch by directly connecting a piston to a drive motor linearly reciprocating and have a simple structure. 
     The linear compressor is configured such that a piston in a casing forming a sealed space suctions and compresses a refrigerant and then discharges the refrigerant while linearly reciprocating along an axial direction (or axially) in a cylinder by a linear motor. 
     Here, “axial direction” refers to a direction in which the piston reciprocates. 
     Thus, a noise occurs in a process in which the piston continues to suction, compress, and discharge the refrigerant while reciprocating in the cylinder along the axial direction. 
     In order to reduce the noise generated thus, a linear compressor provided with an intake muffler is disclosed in Korean Patent Application Publication No. 10-2018-0079026 (hereinafter, referred to as “prior art”). 
     With reference to  FIGS. 1 to 5 , an intake muffler included in a linear compressor according to the prior patent is described below. 
       FIG. 1  is a perspective view illustrating configuration of an intake muffler included in a linear compressor according to the prior patent.  FIG. 2  is a cross-sectional view taken along II-IF of  FIG. 1 . 
     An intake muffler  2000  disclosed in the prior patent includes a first muffler  2100  disposed inside a piston body  1300 , a second muffler  2300  disposed behind the first muffler  2100 , and a third muffler  2500  accommodating at least a portion of the first muffler  2100  and the second muffler  2300 . 
     The first muffler  2100  includes a body  2110  that forms a refrigerant flow passage and extends along the axial direction, a flange  2120  extending from the body  2110  along a radial direction (or radially), and a flange extension  2130  extending rearward in the axial direction from a flange connection portion of the flange  2120 . 
     The first muffler  2100  is coupled to the third muffler  2500  by press-fitting the flange extension  2130  to the inside of the third muffler  2500 . 
     The second muffler  2300  is coupled to the third muffler  2500  by press-fitting the second muffler  2300  to the inside of the third muffler  2500  at the rear of the first muffler  2100 . 
     In the intake muffler  2000  having the above-described configuration, the body  2110  of the first muffler  2100  is formed to have a smaller outer diameter than an inner diameter of the piston body  1300 , and the flange  2120  of the first muffler  2100  is coupled to a flange  1320  of the piston. 
     Thus, a discharge space  2100   e  is formed between the piston body  1300  and the body  2110  of the first muffler  2100 . 
     The flange  2120  of the first muffler  2100  includes a plurality of communication holes  2150  communicating with the discharge space  2100   e.    
     When an intake of a refrigerant into a compression chamber P is performed, the communication holes  2150  may guide a refrigerant pressure of an intake space  2600  to rapidly increase. 
     More specifically, when the refrigerant compressed in the compression chamber P is discharged to a discharge cover, a piston  1300  moves from top dead center to bottom dead center, and the refrigerant suctioned by the compressor in this process flows into the piston  1300  through the intake muffler  2000 . 
     In this instance, as the refrigerant pressure in the intake space  2600  is high and this state continues for a long time, an intake valve  1350  opens faster and remains open for a long time, and thus a large amount of refrigerant may be introduced into the compression chamber P. 
     However, when a pressure in the intake space  2600  is relatively low at a time at which the intake valve  1350  is opened, an amount of refrigerant introduced into the compression chamber P through the opened intake valve  1350  is reduced. Thus, it is necessary to rapidly increase the pressure in the intake space  2600  according to the time at which the intake valve  1350  is opened. 
     After the refrigerant is discharged from the compression chamber P, when the piston  1300  moves rearward, that is, toward the bottom dead center, a phenomenon in which the refrigerant is not rapidly introduced into the first muffler  2100  may occur by a volume of the refrigerant remaining between the piston  1300  and the first muffler  2100 . 
     Accordingly, the communication holes  2150  of the first muffler flange  2120  allow the remaining refrigerant to flow rearward and to be discharged from the piston  1300 . Hence, when the piston  1300  moves toward the bottom dead center, the communication holes  2150  allow the refrigerant to be rapidly introduced into the first muffler  2100 . 
       FIG. 3  is a cross-sectional view illustrating a flow of a refrigerant suctioned in an intake port of a piston through an intake muffler in a linear compressor according to the prior patent.  FIG. 4  is an experimental graph illustrating an increase in an intake flow amount in a linear compressor according to the prior patent, compared to a linear compressor according to a related art. 
     In  FIG. 4 , the linear compressor according to the related art refers to a linear compressor in which a communication hole  210  is not included in a first flange  2120 . 
     A refrigerant suctioned by the compressor may flow into the intake muffler  2000  through a through hole  2520  of the third muffler  2500 , may sequentially pass through an inlet hole  2320   a  of the second muffler  2300  and an inlet hole  2110   a  of the first muffler  2100 , and may be then introduced into the body  2110  of the first muffler  2100 . 
     The refrigerant in the body  2110  of the first muffler  2100  flows into the intake space  2600 , and the refrigerant flowing into the intake space  2600  is suctioned into the compression chamber P through an intake port  1330  of the piston  1300  when the intake valve  1350  is opened. 
     Here, the intake space  2600  may be understood as a space between a body front portion of the piston  1300  and a front end of the first muffler  2100 . 
     When a pressure of the compression chamber P is higher than a pressure of the intake space  2600 , the intake valve  1350  is closed, and a volume of the compression chamber P decreases while the piston  1300  moves forward. Hence, the compression of the refrigerant is fulfilled. 
     Afterwards, when the pressure of the compression chamber P increases and is higher than a pressure of the discharge space, the discharge of the refrigerant is fulfilled while a discharge valve (not shown) is opened. 
     In this case, a position of the piston  1300  forms top dead center (P 1  in  FIG. 4 ) at time to. 
     When the discharge of the refrigerant is fulfilled, the piston  1300  and the intake muffler  2000  move to the rear, and the refrigerant is suctioned into the intake muffler  2000  as described above. In this instance, since the refrigerant remaining in the inside of the piston  1300 , i.e., a space between the piston  1300  and the first muffler  2100  or the intake space  2600  is discharged to the rear through the communication holes  2150  included in the flange  2120  of the first muffler  2100 , the refrigerant is rapidly suctioned into the intake muffler  2000 . 
     Accordingly, the decompression of the refrigerant in the intake space  2600  may be reduced. 
     A discharge space  2110   e  having a flow passage, through which the remaining refrigerant is discharged, is formed between an inner peripheral surface of a piston body  1310  and an outer peripheral surface of the body  2110  of the first muffler  2100 . 
     The refrigerant flows from the intake space  2600  to the rear through the discharge space  2110   e  and is discharged from the first muffler  2100  through the communication holes  2150  provided in the flange  2120  of the first muffler  2100 . 
     As above, in the process in which the piston  1300  moves from top dead center to bottom dead center, a circulation of the refrigerant flow may occur while the discharge and the intake of the refrigerant in the piston  1300  are fulfilled together. 
       FIG. 4  illustrates a distribution of pressures measured in the intake space in a case of the linear compressor according to the prior patent (indicated by the thick dotted line) and a case of the related art linear compressor in which the communication hole is not provided in the flange of the first muffler in the structure of the intake muffler of the linear compressor according to the prior patent (indicated by the thin dotted line). 
     When the piston  1300  moves from top dead center P 1  toward bottom dead center P 2  (at time t 3 ), the pressure in the intake space in the case of the related art linear compressor decreases and then increases again. On the other hand, in the case of the linear compressor according to the prior patent, the pressure in the intake space  2600  at the top dead center P 1  is almost kept. 
     That is, it can be seen from  FIG. 4  that the pressure in the intake space  2600  is kept higher by an area ‘A’ in the linear compressor according to the prior patent than in the related art linear compressor. 
     In addition, as the pressure in the intake space  2600  is kept relatively high, an amount of refrigerant suctioned into the compression chamber P may increase when the intake valve  1350  is opened. 
     That is, it can be seen from  FIG. 4  that an amount of refrigerant suctioned into the compression chamber P in the linear compressor according to the prior patent (indicated by the thick dotted line) is more than that in the related art linear compressor (indicated by the thin dotted line) by an area ‘B’. 
     In  FIG. 4 , a time duration from time t 1  to time t 2  indicates an open duration of the intake valve  1350 . 
     Accordingly, if the communication hole  2150  is provided in the flange  2120  of the first muffler  2100 , the refrigerant may be rapidly suctioned through the intake muffler  2000 . Hence, since the pressure in the intake space  2600  can be kept relatively high, an amount of refrigerant suctioned in the compression chamber P can increase. 
     With reference to the pressure distribution of each portion of the muffler illustrated in  FIG. 5 , since the pressure reduction in the inlet portion of the first muffler  2100  in the prior patent is more improved than that in the related art linear compressor, the pressure reductions in the inlet portion of the first muffler  2100 , the outlet portion of the first muffler  2100 , and the inlet portion of the intake port  1330  in the prior patent can be more improved than those in the related art linear compressor. However, since a pressure from an inlet guide portion  1560  connected to an inlet of the third muffler  2500 , specifically, an intake pipe (not shown) to an inlet of the second muffler  2300  in the prior patent is similar to that in the related art linear compressor, there is a problem in that the overall improvement effect of the pressure reduction is low, and the compression efficiency of the linear motor cannot be effectively improved. 
     SUMMARY 
     An object of the present disclosure is to provide a linear compressor capable of effectively improving a pressure reduction at an inlet side of an intake muffler. 
     Another object of the present disclosure is to provide a linear compressor capable of generating a high pressure at an outlet side of an intake muffler. 
     Another object of the present disclosure is to provide a linear compressor capable of effectively improving a compression efficiency. 
     To achieve the above-described and other objects of the present disclosure, in one aspect, there is provided a linear compressor comprising a first muffler disposed in a piston body, a second muffler disposed below the first muffler and configured to communicate with the first muffler, and a third muffler configured to accommodate a portion of a rear end of the first muffler and the second muffler, wherein each of the first muffler and the second muffler includes (i) a body that defines a refrigerant flow passage and extends in an axial direction, and (ii) a flange that extends radially from the body, and wherein the flange of the first muffler and the flange of the second muffler each include a communication portion. 
     Accordingly, the refrigerant remaining in a discharge space formed between the piston body and the body of the first muffler flows into an inner space of the third muffler through the communication portions of the first muffler and the second muffler, when a piston moves from top dead center to bottom dead center. 
     The communication portion of the first muffler and the communication portion of the second muffler each may include a communication hole provided in the corresponding flange, and may further include a communication pipe communicating with the corresponding communication hole. 
     The linear compressor including the intake muffler according to embodiments of the present disclosure provides a communication portion communicating with the communication portion (communication hole) provided in the flange of the first muffler to the flange of the second muffler, and can further improve a pressure reduction at an inlet portion of the third muffler compared to the prior patent. 
     As the pressure reduction at the inlet portion of the third muffler is improved, a pressure reduction at an inlet portion of the first muffler, an outlet portion of the first muffler, and an inlet portion of an intake port can be further improved compared to the prior patent. 
     Accordingly, since a pressure reduction at an inlet end of the intake muffler can be further improved compared to the prior patent, and a pressure at an outlet end of the intake muffler can be generated higher than the prior patent, the present disclosure can efficiently improve compression efficiency compared to the prior patent. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the present disclosure and constitute a part of the detailed description, illustrate embodiments of the present disclosure and serve to explain technical features of the present disclosure together with the description. 
         FIG. 1  is a perspective view illustrating configuration of an intake muffler according to the prior patent. 
         FIG. 2  is a cross-sectional view taken along II-IF of  FIG. 1 . 
         FIG. 3  is a cross-sectional view illustrating a flow of a refrigerant suctioned into an intake port of a piston through an intake muffler according to a prior patent. 
         FIG. 4  is an experimental graph illustrating an increase in an intake flow amount in a linear compressor adopting an intake muffler according to a prior patent, compared to a linear compressor according to a related art. 
         FIG. 5  is an experimental graph illustrating an improvement in a pressure reduction in a linear compressor adopting an intake muffler according to a prior patent, compared to a linear compressor according to a related art. 
         FIG. 6  is an appearance perspective view illustrating configuration of a linear compressor according to an embodiment of the present disclosure. 
         FIG. 7  is an exploded perspective view of a shell and a shell cover of a linear compressor according to an embodiment of the present disclosure. 
         FIG. 8  is a cross-sectional view taken along VI-VI′ of  FIG. 6 . 
         FIG. 9  is an exploded perspective view illustrating configuration of a piston assembly according to an embodiment of the present disclosure. 
         FIG. 10  is a cross-sectional view of an intake muffler according to a first embodiment of the present disclosure. 
         FIG. 11  is a perspective view of a second muffler included in an intake muffler according to a first embodiment of the present disclosure. 
         FIG. 12  is an experimental graph illustrating an improvement in a pressure reduction in a linear compressor adopting an intake muffler according to a first embodiment illustrated in  FIG. 10 , compared to a linear compressor according to a prior patent. 
         FIG. 13  is a cross-sectional perspective view of an intake muffler according to a second embodiment of the present disclosure. 
         FIG. 14  is a perspective view of a second muffler included in an intake muffler according to a second embodiment of the present disclosure. 
         FIG. 15  is a cross-sectional perspective view of an intake muffler according to a third embodiment of the present disclosure. 
         FIG. 16  is a perspective view of a second muffler included in an intake muffler according to a third embodiment of the present disclosure. 
         FIG. 17  is a cross-sectional perspective view of an intake muffler according to a fourth embodiment of the present disclosure. 
         FIG. 18  is a perspective view of a first muffler included in an intake muffler according to a fourth embodiment of the present disclosure. 
         FIG. 19  is a perspective view of a second muffler included in an intake muffler according to a fourth embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
     It should be understood that when a component is described as being “connected to” or “coupled to” other component, it may be directly connected or coupled to the other component or intervening component(s) may be present. 
     It will be noted that a detailed description of known arts will be omitted if it is determined that the detailed description of the known arts can obscure embodiments of the present disclosure. The accompanying drawings are used to help easily understand various technical features and it should be understood that embodiments presented herein are not limited by the accompanying drawings. As such, the present disclosure should be understood to extend to any alterations, equivalents and substitutes in addition to those which are particularly set out in the accompanying drawings. 
     In addition, a term of “disclosure” may be replaced by document, specification, description, etc. 
       FIG. 6  is an appearance perspective view illustrating configuration of a linear compressor according to an embodiment of the present disclosure.  FIG. 7  is an exploded perspective view of a shell and a shell cover of a linear compressor according to an embodiment of the present disclosure.  FIG. 8  is a cross-sectional view taken along VI-VI′ of  FIG. 6 . 
     Referring to the figures, a linear compressor  10  according to an embodiment of the present disclosure includes a shell  101  and shell covers  102  and  103  coupled to the shell  101 . In a broad sense, the first shell cover  102  and the second shell cover  103  can be understood as one configuration of the shell  101 . 
     Legs  50  may be coupled to a lower side of the shell  101 . The legs  50  may be coupled to a base of a product in which the linear compressor  10  is installed. Examples of the product may include a refrigerator, and the base may include a machine room base of the refrigerator. As another example, the product may include an outdoor unit of an air conditioner, and the base may include a base of the outdoor unit. 
     The shell  101  may have a substantially cylindrical shape and may be disposed in a transverse direction or a horizontal direction or an axial direction.  FIG. 6  illustrates that the shell  101  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  10  can have a low height, there is an advantage in that a height of the machine room can decrease when the linear compressor  10  is installed in the machine room base of the refrigerator. 
     A terminal  108  may be installed on an outer surface of the shell  101 . The terminal  108  is understood as configuration to transmit external electric power to a motor assembly of the linear compressor  10 . The terminal  108  may be connected to a lead line of a coil  141   c  (see  FIG. 8 ). 
     A bracket  109  is installed outside the terminal  108 . The bracket  109  may include a plurality of brackets surrounding the terminal  108 . The bracket  109  can perform a function of protecting the terminal  108  from an external impact, etc. 
     Both sides of the shell  101  are configured to be opened. The shell covers  102  and  103  may be coupled to both sides of the opened shell  101 . 
     The shell covers  102  and  103  include the first shell cover  102  coupled to one opened side of the shell  101  and the second shell cover  103  coupled to the other opened side of the shell  101 . An inner space of the shell  101  may be sealed by the shell covers  102  and  103 . 
       FIG. 6  illustrates that the first shell cover  102  is positioned on the right side of the linear compressor  10 , and the second shell cover  103  is positioned on the left side of the linear compressor  10 , by way of example. Thus, the first and second shell covers  102  and  103  may be disposed to face each other. 
     The linear compressor  10  further includes a plurality of pipes  104 ,  105 , and  106  that are included in the shell  101  or the shell covers  102  and  103  and may suction, discharge, or inject the refrigerant. 
     The plurality of pipes  104 ,  105 , and  106  include an intake pipe  104  that allows the refrigerant to be suctioned into the linear compressor  10 , a discharge pipe  105  that allows the compressed refrigerant to be discharged from the linear compressor  10 , and a process pipe  106  for supplementing the refrigerant in the linear compressor  10 . 
     The intake pipe  104  may be coupled to the first shell cover  102 . The refrigerant may be suctioned into the linear compressor  10  along the axial direction through the intake pipe  104 . 
     The discharge pipe  105  may be coupled to an outer peripheral surface of the shell  101 . The refrigerant suctioned through the intake pipe  104  may be compressed while flowing in the axial direction. The compressed refrigerant may be discharged through the discharge pipe  105 . The discharge pipe  105  may be disposed closer to the second shell cover  103  than to the first shell cover  102 . 
     The process pipe  106  may be coupled to the outer peripheral surface of the shell  101 . A worker may inject the refrigerant into the linear compressor  10  through the process pipe  106 . 
     The process pipe  106  may be coupled to the shell  101  at a different height from the discharge pipe  105  in order to prevent interference with the discharge pipe  105 . Herein, the “height” may be understood as a distance measured from the leg  50  in a vertical direction (or a radial direction). 
     On an inner peripheral surface of the shell  101  corresponding to a location at which the process pipe  106  is coupled, at least a portion of the second shell cover  103  may be positioned adjacently. In other words, at least a portion of the second shell cover  103  may act as a resistance of the refrigerant injected through the process pipe  106 . 
     Thus, with respect to a flow passage of the refrigerant, a size of the flow passage of the refrigerant introduced through the process pipe  106  may be configured to decrease while the refrigerant enters into the inner space of the shell  101 . 
     In this process, a pressure of the refrigerant may be reduced to vaporize the refrigerant, and an oil contained in the refrigerant may be separated. Thus, while the refrigerant, from which the oil is separated, is introduced into a piston  130 , a compression performance of the refrigerant can be improved. The oil may be understood as a working oil present in a cooling system. 
     A cover support portion  102   a  is provided at the inner surface of the first shell cover  102 . A second support device  185  to be described later may be coupled to the cover support portion  102   a . The cover support portion  102   a  and the second support device  185  may be understood as devices for supporting the main body of the linear compressor  10 . 
     Here, the main body of the compressor refers to a component provided inside the shell  101 , and may include, for example, a driver that reciprocates forward and rearward and a support portion supporting the driver. 
     The driver may include a piston  130 , a magnet frame  138 , a permanent magnet  146 , a supporter  137 , an intake muffler  200 , and the like. The support portion may include resonance springs  176   a  and  176   b , a rear cover  170 , a stator cover  149 , a first support device  165 , and a second support device  185 , and the like. 
     A stopper  102   b  may be provided at the inner surface of the first shell cover  102 . The stopper  102   b  is understood as configuration to prevent the main body of the compressor  10 , in particular, a motor assembly (not shown) from being damaged by colliding with the shell  101  due to a vibration or an impact, etc. generated during transportation of the linear compressor  10 . 
     The stopper  102   b  is positioned adjacent to the rear cover  170  to be described later. The stopper  102   b  can prevent an impact from being transferred to the motor assembly (not shown) since the rear cover  170  interferes with the stopper  102   b  when shaking occurs in the linear compressor  10 . 
     A spring fastening portion  101   a  may be provided on the inner peripheral surface of the shell  101 . The spring fastening portion  101   a  may be disposed adjacent to the second shell cover  103 . The spring fastening portion  101   a  may be coupled to a first support spring  166  of a first support device  165  to be described later. As the spring fastening portion  101   a  and the first support device  165  are coupled, the main body of the compressor may be stably supported inside the shell  101 . 
       FIG. 8  is a cross-sectional view taken along VI-VI′ of  FIG. 6 .  FIG. 9  is an exploded perspective view illustrating configuration of a piston assembly according to an embodiment of the present disclosure. 
     Referring to  FIGS. 8 and 9 , the linear compressor  10  according to an embodiment of the present disclosure includes a cylinder  120  provided in the shell  101 , a piston  130  that linearly reciprocates in the cylinder  120 , and a motor assembly (not shown) including a linear motor that gives a driving force to the piston  130 . 
     When the motor assembly (not shown) drives, the piston  130  may reciprocate in the axial direction. 
     The linear compressor  10  further includes an intake muffler  200  coupled to the piston  130 . The intake muffler  200  can reduce a noise generated from a refrigerant suctioned through an intake pipe  104 . 
     The refrigerant suctioned through the intake pipe  104  passes through the intake muffler  200  and flows into the piston  130 . For example, in a process in which the refrigerant passes through the intake muffler  200 , the flow noise of the refrigerant can be reduced. 
     The intake muffler  200  includes a plurality of mufflers  210 ,  230 , and  250 . The plurality of mufflers  210 ,  230 , and  250  include a first muffler  210 , a second muffler  230 , and a third muffler  250  that are coupled to each other. 
     The first muffler  210  is positioned in the piston  130 , and the second muffler  230  is coupled to the rear of the first muffler  210 . The third muffler  250  may accommodate the second muffler  230  therein and may extend to the rear of the first muffler  210 . 
     From a perspective of the flow direction of the refrigerant, the refrigerant suctioned through the intake pipe  104  may sequentially pass through the third muffler  250 , the second muffler  230 , and the first muffler  210 . In this process, the flow noise of the refrigerant can be reduced. 
     The intake muffler  200  further includes a muffler filter  280 . The muffler filter  280  may be positioned at an interface where the first muffler  210  and the second muffler  230  are coupled. For example, the muffler filter  280  may have a circular shape, and an outer peripheral portion of the muffler filter  280  may be supported between the first and second mufflers  210  and  230 . 
     In the present disclosure, “axial direction (or axially)” may be understood as a direction in which the piston  130  reciprocates, i.e., a longitudinal direction in  FIG. 8 . In the “axial direction”, a direction directed from the intake pipe  104  to a compression chamber P, i.e., a direction in which the refrigerant flows may be understood as “front”, and the opposite direction thereof may be understood as “rear”. 
     On the other hand, “radial direction (or radially)” may be understood as a direction perpendicular to the direction in which the piston  130  reciprocates, i.e., a transverse direction in  FIG. 8 . 
     The piston  130  includes a piston body  131  having a substantially cylindrical shape and a piston flange  132  extending radially from the piston body  131 . 
     The piston body  131  may reciprocate axially inside the cylinder  120 , and the piston flange  132  may reciprocate axially outside the cylinder  120 . 
     The cylinder  120  is configured to accommodate at least a portion of the first muffler  210  and at least a portion of the piston body  131 . 
     The compression chamber P in which the refrigerant is compressed by the piston  130  is formed in the cylinder  120 . An intake port  133  that introduces the refrigerant into the compression chamber P is formed at a front surface of the piston body  131 , and an intake valve  135  that selectively opens the intake port  133  is provided at the front of the intake port  133 . A second fastening hole  135   a  to which a valve fastening member  134  is coupled is formed at approximately the center of the intake valve  135 . 
     The valve fastening member  134  may be understood as configuration to couple the intake valve  135  to a first fastening hole  131   b  of the piston  130 . The first fastening hole  131   b  is formed at approximately the center of a front end surface of the piston  130 . The valve fastening member  134  may pass through the second fastening hole  135   a  of the intake valve  135  and may be coupled to the first fastening hole  131   b.    
     The piston  130  includes the piston body  131  that has a substantially cylindrical shape and extends forward and rearward, and the piston flange  132  extending radially outwardly from the piston body  131 . 
     A body front portion  131   a  in which the first fastening hole  131   b  is formed is provided at the front of the piston body  131 . The intake port  133  selectively shielded by the intake valve  135  is formed at the body front portion  131   a . The intake port  133  includes a plurality of intake ports, and the plurality of intake ports  133  are formed outside the first fastening hole  131   b.    
     The plurality of intake ports  133  may be disposed to surround the first fastening hole  131   b . For example, the eight intake ports  133  may be provided. 
     A rear portion of the piston body  131  is opened so that the intake of the refrigerant is fulfilled. At least a portion of the intake muffler  200 , i.e., the first muffler  210  may be inserted into the piston body  131  through the opened rear portion of the piston body  131 . 
     The piston flange  132  includes a flange body  132   a  extending radially outwardly from the rear portion of the piston body  131 , and a piston fastening portion  132   b  further extending radially outwardly from the flange body  132   a.    
     The piston fastening portion  132   b  includes a piston fastening hole  132   c  to which a predetermined fastening member is coupled. The fastening member may pass through the piston fastening hole  132   c  and may be coupled to a magnet frame  138  and a supporter  137 . The piston fastening portion  132   b  may include a plurality of piston fastening portions  132   b , and the plurality of piston fastening portions  132   b  may be spaced apart from each other and disposed at an outer peripheral surface of the flange body  132   a.    
     At the front of the compression chamber P, a discharge cover  160  forming a discharge space  160   a  of the refrigerant discharged from the compression chamber P, and discharge valve assemblies  161  and  163  that are coupled to the discharge cover  160  and selectively discharge the refrigerant compressed in the compression chamber P are provided. The discharge space  160   a  includes a plurality of spaces partitioned by an inner wall of the discharge cover  160 . The plurality of spaces may be disposed forward and rearward and may communicate with each other. 
     The discharge valve assemblies  161  and  163  include a discharge valve  161  that is opened when a pressure of the compression chamber P is greater than or equal to a discharge pressure, and introduces the refrigerant into the discharge space  160   a  of the discharge cover  160 , and a spring assembly  163  that is provided between the discharge valve  161  and the discharge cover  160  and provides axially an elastic force. 
     The spring assembly  163  may include a valve spring (not shown) and a spring support portion (not shown) for supporting the valve spring (not shown) to the discharge cover  160 . 
     For example, the valve spring (not shown) may be formed as a leaf spring. The spring support portion (not shown) may be integrally injection-molded with the valve spring (not shown) by an injection process. 
     The discharge valve  161  is coupled to the valve spring (not shown), and a rear portion or a rear surface of the discharge valve  161  is positioned so that it is supportable to the front surface of the cylinder  120 . 
     When the discharge valve  161  is supported to the front surface of the cylinder  120 , the compression chamber P may maintain a sealed state. When the discharge valve  161  is spaced apart from the front surface of the cylinder  120 , the compression chamber P may be opened, and the compressed refrigerant inside the compression chamber P may be discharged. 
     The compression chamber P may be defined as a space between the intake valve  135  and the discharge valve  161 . 
     The intake valve  135  may be formed on one side of the compression chamber P, and the discharge valve  161  may be provided on other side of the compression chamber P, that is, on the opposite side of the intake valve  135 . 
     In the process in which the piston  130  reciprocates linearly in the axial direction inside the cylinder  120 , when the pressure of the compression chamber P is lower than the discharge pressure and is less than or equal to an intake pressure, the discharge valve  161  is closed and the intake valve  135  is opened. Hence, the refrigerant is suctioned into the compression chamber P. 
     On the other hand, when the pressure of the compression chamber P is greater than or equal to the intake pressure, the refrigerant in the compression chamber P is compressed in the closed state of the intake valve  135 . 
     When the pressure of the compression chamber P is greater than or equal to the intake pressure, the valve spring (not shown) is deformed forward to open the discharge valve  161 , and the refrigerant is discharged from the compression chamber P and is discharged into the discharge space  160   a  of the discharge cover  160 . 
     When the discharge of the refrigerant is completed, the valve spring (not shown) provides a restoring force to the discharge valve  161 , and thus the discharge valve  161  is closed. 
     The linear compressor  10  further includes a cover pipe  162   a  that is coupled to the discharge cover  160  and discharges the refrigerant flowing in the discharge space  160   a  of the discharge cover  160 . For example, the cover pipe  162   a  may be made of a metal material. 
     The linear compressor  10  further includes a loop pipe  162   b  that is coupled to the cover pipe  162   a  and transfers the refrigerant flowing through the cover pipe  162   a  to the discharge pipe  105 . One side of the loop pipe  162   b  may be coupled to the cover pipe  162   a , and other side may be coupled to the discharge pipe  105 . 
     The loop pipe  162   b  may be made of a flexible material. The loop pipe  162   b  may roundly extend from the cover pipe  162   a  along the inner peripheral surface of the shell  101  and may be coupled to the discharge pipe  105 . For example, the loop pipe  162   b  may have a wound shape. 
     The linear compressor  10  further includes a frame  110  fixing the cylinder  120 . For example, the cylinder  120  may be press-fitted to the inside of the frame  110 . The cylinder  120  and the frame  110  may be made of aluminum or an aluminum alloy material. 
     The frame  110  is disposed to surround the cylinder  120 . That is, the cylinder  120  may be positioned to be accommodated inside the frame  110 . The discharge cover  160  may be coupled to a front surface of the frame  110  by a fastening member. 
     The motor assembly (not shown) includes an outer stator  141  that is fixed to the frame  110  and is disposed to surround the cylinder  120 , an inner stator  148  that is disposed to be spaced apart from the inside of the outer stator  141 , and a permanent magnet  146  positioned in a space between the outer stator  141  and the inner stator  148 . 
     The permanent magnet  146  may reciprocate linearly by a mutual electromagnetic force between the permanent magnet  146  and the outer stator  141  and the inner stator  148 . The permanent magnet  146  may be composed of a single magnet having one pole, or may be configured by combining a plurality of magnets having three poles. 
     The permanent magnet  146  may be installed in the magnet frame  138 . The magnet frame  138  has a substantially cylindrical shape and may be inserted into a space between the outer stator  141  and the inner stator  148 . 
     Based on the cross-sectional view of  FIG. 8 , the magnet frame  138  may be coupled to the piston flange  132 , extended outward in the radial direction, and bent forward. The permanent magnet  146  may be installed in a front portion of the magnet frame  138 . 
     When the permanent magnet  146  reciprocates, the piston  130  may reciprocate axially along with the permanent magnet  146 . 
     The outer stator  141  includes coil winding bodies  141   b ,  141   c , and  141   d  and a stator core  141   a . The coil winding bodies  141   b ,  141   c , and  141   d  include a bobbin  141   b  and a coil  141   c  wound in a circumferential direction of the bobbin  141   b.    
     The coil winding bodies  141   b ,  141   c , and  141   d  further include a terminal portion  141   d  for guiding a power supply line connected to the coil  141   c  to be withdrawn or exposed to the outside of the outer stator  141 . The terminal portion  141   d  may be disposed to be inserted into a terminal insertion portion of the frame  110 . 
     The stator core  141   a  includes a plurality of core blocks that is configured such that a plurality of laminations is stacked in a circumferential direction. The plurality of core blocks may be disposed to surround at least a portion of the coil winding bodies  141   b  and  141   c.    
     The stator cover  149  is provided on one side of the outer stator  141 . That is, one side of the outer stator  141  may be supported by the frame  110 , and other side may be supported by the stator cover  149 . 
     The linear compressor  10  further includes a cover fastening member (not shown) for fastening the stator cover  149  to the frame  110 . The cover fastening member (not shown) may pass through the stator cover  149 , extend forward toward the frame  110 , and may be coupled to a first fastening hole of the frame  110 . 
     The inner stator  148  is fixed to the outer periphery of the frame  110 . Further, the inner stator  148  is configured such that a plurality of laminations is stacked in a circumferential direction from the outside of the frame  110 . 
     The linear compressor  10  further includes a supporter  137  supporting the piston  130 . The supporter  137  is coupled to the rear side of the piston  130 , and the intake muffler  200  may be disposed inside the supporter  137  to pass therethrough. 
     The piston flange  132 , the magnet frame  138 , and the supporter  137  may be fastened by a fastening member. 
     A balance weight (not shown) may be coupled to the supporter  137 . A weight of the balance weight (not shown) may be determined based on an operating frequency range of the compressor body. 
     The linear compressor  10  further includes a rear cover  170  that is coupled to the stator cover  149 , extends rearward, and is supported by the second support device  185 . 
     The rear cover  170  includes three support legs, and the three support legs may be coupled to the rear surface of the stator cover  149 . A spacer (not shown) may be interposed between the three support legs and the rear surface of the stator cover  149 . 
     A distance from the stator cover  149  to a rear end of the rear cover  170  may be determined by adjusting a thickness of the spacer (not shown). The rear cover  170  may be elastically supported by the supporter  137 . 
     The linear compressor  10  further includes an inlet guide portion  156  that is coupled to the rear cover  170  and guides the introduction of the refrigerant into the intake muffler  200 . At least a portion of the inlet guide portion  156  may be inserted into the inside of the intake muffler  200 . 
     The linear compressor  10  further includes a plurality of resonance springs  176   a  and  176   b  in which each natural frequency is adjusted so that the piston  130  can perform a resonant motion. 
     The plurality of resonance springs  176   a  and  176   b  include a first resonance spring  176   a  supported between the supporter  137  and the stator cover  149  and a second resonance spring  176   b  supported between the supporter  137  and the rear cover  170 . 
     By the action of the plurality of resonance springs  176   a  and  176   b , a stable movement of the driver reciprocating in the linear compressor  10  can be performed, and generation of vibration or noise caused by the movement of the driver can be reduced. 
     The supporter  137  includes a first spring support portion (not shown) coupled to the first resonance spring  176   a.    
     The linear compressor  10  further includes a first support device  165  that is coupled to the discharge cover  160  and supports one side of the main body of the compressor  10 . The first support device  165  may be disposed adjacent to the second shell cover  103  to elastically support the main body of the compressor  10 . 
     The first support device  165  includes a first support spring  166 . The first support spring  166  may be coupled to the spring fastening portion  101   a.    
     The linear compressor  10  further includes a second support device  185  that is coupled to the rear cover  170  and supports other side of the main body of the compressor  10 . The second support device  185  may be coupled to the first shell cover  102  to elastically support the main body of the compressor  10 . 
     The second support device  185  includes a second support spring  186 . 
     The second support spring  186  may be coupled to the cover support portion  102   a.    
       FIG. 10  is a cross-sectional view of an intake muffler according to a first embodiment of the present disclosure.  FIG. 11  is a perspective view of a second muffler illustrated in  FIG. 10 .  FIG. 12  is an experimental graph illustrating an improvement in a pressure reduction in a linear compressor adopting an intake muffler according to a first embodiment illustrated in  FIG. 10 , compared to a linear compressor according to a prior patent. 
     Referring to  FIGS. 10 to 12 , an intake muffler  200  according to an embodiment of the present disclosure includes a plurality of mufflers  210 ,  230 , and  250 . The plurality of mufflers  210 ,  230 , and  250  may be press-fitted and coupled to each other. 
     The plurality of mufflers  210 ,  230 , and  250  may be made of a plastic material and easily press-fitted and coupled to each other. Hence, and a heat loss through the plurality of mufflers  210 ,  230 , and  250  in the flow process of the refrigerant can be reduced. 
     The intake muffler  200  includes a first muffler  210 , a second muffler  230  coupled to the rear of the first muffler  210 , a muffler filter  280  supported by the first muffler  210  and the second muffler  230 , and a third muffler  250  that is coupled to the first and second mufflers  210  and  230  and into which the inlet guide portion  156  is inserted. The third muffler  250  extends to the rear of the second muffler  230 . 
     The third muffler  250  includes a body  251  having a cylindrical shape with an empty interior. The body  251  of the third muffler  250  extends forward and rearward. A through hole  252 , into which the inlet guide portion  156  is inserted, is formed in a rear surface of the third muffler  250 . The through hole  252  may be defined as an “inlet hole” guiding the introduction of the refrigerant into the intake muffler  200 . 
     The third muffler  250  further includes a protrusion  253  extending forward from the rear surface of the third muffler  250 . The protrusion  253  extends forward from an outer peripheral portion of the through hole  252 , and the inlet guide portion  156  may be inserted into the inside of the protrusion  253 . 
     The first and second mufflers  210  and  230  may be coupled to each other inside the third muffler  250 . For example, the first and second mufflers  210  and  230  may be press-fitted and coupled to an inner peripheral surface of the third muffler  250 . A stepped portion  254 , to which the second muffler  230  is coupled, is formed at the inner peripheral surface of the third muffler  250 . 
     When the second muffler  230  moves into the third muffler  250  and is press-fitted to the third muffler  250 , the second muffler  230  may be caught in the stepped portion  254 . Thus, the stepped portion  254  may be understood as a stopper for limiting the rearward movement of the second muffler  230 . 
     The first muffler  210  is coupled to a front end of the second muffler  230  and is press-fitted to the inner peripheral surface of the third muffler  250 . The muffler filter  280  may be interposed at a boundary where the first and second mufflers  210  and  230  are coupled. 
     The second muffler  230  includes a body  231  that is configured such that a cross-sectional area of a flow passage of the refrigerant changes as it goes from the upstream to the downstream of the refrigerant flow based on a flow direction of the refrigerant. An inlet hole  232   a , through which the refrigerant discharged from the inlet guide portion  156  is introduced, is formed at a rear end of the body  231  of the second muffler  230 . 
     The body  231  of the second muffler  230  includes a first part  231   a  that extends from the inlet hole  232   a  toward the front to have a predetermined inner diameter, and a second part  231   b  that extends from the first part  231   a  to the front and has an inner diameter less than the inner diameter of the first part  231   a . The inlet hole  232   a  of the second muffler  230  is formed at a rear end of the first part  231   a.    
     According to the configuration described above, the refrigerant introduced into the second muffler  230  through the inlet hole  232   a  of the second muffler  230  passes through a flow passage that has a reduced cross-sectional area in a process of flowing from the first part  231   a  to the second part  231   b.    
     A discharge hole  232   b  discharging the refrigerant passing through the second part  231   b  is formed at a front end of the body  231  of the second muffler  230 . The discharge hole  232   b  of the second muffler  230  may be formed at a front end of the second part  231   b.    
     The second muffler  230  includes a flange  233  that extends radially from an outer peripheral surface of a front portion of the body  231 , and a flange extension  234  extending forward from the flange  233 . The flange extension  234  may be press-fitted to the inner peripheral surface of the third muffler  250 . 
     A boundary between the flange  233  and the flange extension  234  of the second muffler  230 , i.e., a portion bent from the radial direction to the axial direction may form a “catching jaw” that allows the second muffler  230  to be caught in the stepped portion  254  of the third muffler  250 . 
     A cross-sectional area of a flow passage formed inside the flange extension  234  may be formed to be greater than a cross-sectional area of a flow passage of the second part  231   b . Thus, the refrigerant discharged from the body  231  of the second muffler  230  may be diffused while flowing into the flange extension  234 . Since a flow rate of the refrigerant is reduced by the diffusion of the refrigerant, a noise reduction effect can be obtained. 
     For example, the second muffler  230  can reduce a noise of a high frequency band of 4 to 5 kHz. The refrigerant discharged from the second muffler  230  may pass through the muffler filter  280  and may be introduced into the first muffler  210 . 
     The first muffler  210  includes a body  211  positioned in front of the muffler filter  280 , i.e., positioned on the downstream side of the refrigerant flow. The body  211  of the first muffler  210  has a cylindrical shape with an empty interior and may extend forward. An inner space of the first muffler body  211  forms a refrigerant flow passage. 
     An inlet hole  211   a  into which the refrigerant passing through the muffler filter  280  is introduced is provided at the rear end of the body  211  of the first muffler  210 . A discharge hole  211   b  through which the refrigerant passing through the body  211  is discharged is provided at the front end of the body  211  of the first muffler  210 . 
     The first muffler  210  further includes a flange  212  that extends radially from an outer peripheral surface of the rear of the body  211 . The flange  212  of the first muffler  210  may be coupled to the piston flange  132  of the piston  130 . 
     A radially outer portion of the flange  212  of the first muffler  210  includes a piston coupling portion  212   a  coupled to a fastening groove (not shown) of the piston  130 . The fastening groove (not shown) may be formed in the piston flange  132 . 
     The third muffler  250  includes a piston coupling portion  251   a  coupled to the piston coupling portion  212   a.    
     The piston coupling portion  251   a  of the third muffler  250  may be configured to extend outward radially from the front portion of the third muffler body  251 . 
     The piston coupling portions  212   a  and  251   a  may be interposed between the supporter  137  and the piston flange  132 . The piston coupling portion  251   a  may extend to be inclined outward in the radial direction with respect to the third muffler body  251 . An angle θ between the body  251  of the third muffler  250  and the piston coupling portion  251   a  may be greater than 60° and less than 90°. The piston coupling portion  251   a  may be configured to be elastically deformable. 
     According to the above-described configuration, the piston coupling portions  212   a  and  251   a  can be stably supported between the supporter  137  and the piston flange  132 . In the process of moving forward or rearward the intake muffler  200 , the piston coupling portions  212   a  and  251   a  can move to be close to each other or spaced apart from each other by an inertial force. Hence, an excessive load can be prevented from being applied to the intake muffler  200 . 
     The first muffler  210  includes a flange extension  213  extending rearward from the flange  212 . The flange extension  213  may have a substantially cylindrical shape. The flange extension  213  may be press-fitted to the inner peripheral surface of the third muffler  250 . The flange  212  of the first muffler  210  may include a flange connection portion  214  connected to the flange extension  213 . 
     The flange extension  213  may support a front portion of the muffler filter  280 . In other words, the muffler filter  280  may be interposed between the flange extension  213  of the first muffler  210  and the flange extension  234  of the second muffler  230 . 
     The body  211  of the first muffler  210  may be configured such that a cross-sectional area of the flow passage of the refrigerant increases as it goes from the upstream to the downstream based on the flow direction of the refrigerant. 
     The body  211  of the first muffler  210  includes an intake guide portion  220  around the discharge hole  211   b  of the first muffler  210 , and the intake guide portion  220  guides the refrigerant discharged from the discharge hole  211   b  to the intake port  133 . 
     The intake guide portion  220  is configured to surround at least a part of the body  211  of the first muffler  210 . The intake guide portion  220  includes a first extension  221  that extends outward radially from one point of the outer peripheral surface of the body  211  of the first muffler  210 , and a second extension  223  that is spaced apart forward from the first extension  221 . 
     The flange  212  of the first muffler  210  includes a flange communication hole  215 . The communication hole  215  may be understood as configuration which guides a refrigerant pressure of an intake space  260  (see  FIG. 8 ) to rapidly increase when the intake of the refrigerant into the compression chamber P is performed. 
     More specifically, when the refrigerant compressed in the compression chamber P is discharged to the discharge cover  160 , the piston  130  moves from top dead center to bottom dead center, and the refrigerant suctioned by the compressor  10  in this process flows into the piston  130  through the intake muffler  200 . 
     In this instance, as the refrigerant pressure in the intake space  260  is high and this state continues for a long time, the intake valve  135  opens faster and remains open for a long time, and thus a large amount of refrigerant may be introduced into the compression chamber P. 
     However, when a pressure in the intake space  260  is relatively low at a time at which the intake valve  135  is opened, an amount of refrigerant introduced into the compression chamber P through the opened intake valve  135  is reduced. Thus, it is necessary to rapidly increase the pressure in the intake space  260  according to the time at which the intake valve  135  is opened. 
     After the refrigerant is discharged from the compression chamber P, when the piston  130  moves rearward, that is, toward the bottom dead center, a phenomenon in which the refrigerant is not rapidly introduced into the first muffler  210  may occur by a volume of the refrigerant remaining between the piston  130  and the first muffler  210 . Accordingly, the communication hole  215  may be understood as configuration which guides the remaining refrigerant to flow rearward and to be discharged from the piston  130 . 
     The communication hole  215  may be formed to pass through at least a portion of the flange  212  of the first muffler  210 . The plurality of communication holes  215  may be provided. 
     If the communication hole  215  is disposed to be biased at a specific position of the flange  212  of the first muffler  210 , the refrigerant may not be easily discharged. Thus, the plurality of communication holes  215  allow the refrigerant to be evenly distributed in the up-down direction and the left-right direction based on the body  211  of the first muffler  210 , and thus can allow the remaining refrigerant to be easily discharged rearward. Further, the number of flange communication holes  215  is not limited thereto. 
     The communication holes  215  may be formed between the flange connection portion  214  and the outer peripheral surface of the body  211  of the first muffler  210 . Thus, the refrigerant discharged rearward through the communication holes  215  may flow into the flange extension  213  and may be introduced into the body  211  of the first muffler  210  through the inlet hole  211   a  of the first muffler  210 , together with the refrigerant suctioned by the intake muffler  200 . 
     In order to improve the pressure reduction at the inlet side of the intake muffler  200 , the second muffler  230  includes a communication hole  235  communicating with the flange communication hole  215  of the first muffler  210  at its the flange  233 . 
     The communication hole  235  may be formed to pass through at least a portion of the flange  233  of the second muffler  230 . The plurality of communication holes  235  may be provided. 
     For example, when viewing the first muffler  210  from the front, the communication hole  235  of the second muffler  230  may be disposed to overlap the communication holes  215  of the first muffler  210 . 
     Accordingly, the refrigerant discharged rearward through the communication holes  215  of the first muffler  210  may flow into the third muffler  250  through the communication holes  235  of the second muffler  230  and may be introduced into the body  211  of the first muffler  210  through the inlet hole  211   a  of the first muffler  210 , together with the refrigerant suctioned by the intake muffler  200 . 
       FIG. 12  is an experimental graph illustrating an improvement in a pressure reduction in a linear compressor adopting an intake muffler according to the first embodiment of the present disclosure, compared to a linear compressor according to the prior patent. 
     The refrigerant suctioned by the compressor  10  flows into the intake muffler  200  through the through hole  252  of the third muffler  250 . 
     The refrigerant may pass through the second muffler  230  and may be introduced into the body  211  of the first muffler  210  through the inlet hole  211   a  of the first muffler  210 . 
     The refrigerant in the body  211  of the first muffler  210  may flow into the intake space  260 , and may be suctioned into the compression chamber P through the intake port  133  of the piston  130  when the intake valve  135  is opened. Here, the intake space  260  may be understood as a space between the body front portion  131   a  of the piston  130  and the front end of the intake muffler  200 , i.e., the front end of the first muffler  210 . 
     When a pressure of the compression chamber P is higher than a pressure of the intake space  260 , the intake valve  135  is closed, and a volume of the compression chamber P decreases while the piston  130  moves forward. Hence, the compression of the refrigerant is achieved. 
     When the pressure of the compression chamber P increases and is higher than a pressure of the discharge space  160   a , the discharge of the refrigerant is achieved while the discharge valve  161  is opened. 
     When the discharge of the refrigerant is achieved, the piston  130  and the intake muffler  200  move to the rear, and the refrigerant is suctioned into the intake muffler  200  as described above. 
     In this instance, since the refrigerant remaining in the piston  130 , i.e., the space between the piston  130  and the first muffler  210  or the intake space  260  is discharged to the rear through the communication holes  215  of the first muffler  210  and the communication holes  235  of the second muffler  230 , the refrigerant can be rapidly suctioned into the intake muffler  200 . 
     Accordingly, the decompression of the refrigerant in the intake space  260  can decrease. 
     A discharge space  211   e  having a flow passage, through which the remaining refrigerant is discharged, is formed between the inner peripheral surface of the piston body  131  and the outer peripheral surface of the body  211  of the first muffler  210 . The refrigerant flows from the intake space  260  to the rear through the discharge space  211   e  and is discharged to the inner space of the third muffler  250  through the communication holes  215  of the first muffler  210  and the communication holes  235  of the second muffler  230 . 
     As above, in the process in which the piston  130  moves from top dead center to bottom dead center, a circulation of the refrigerant flow may occur while the discharge and the intake of the refrigerant in the piston  130  are fulfilled together. 
       FIG. 12  illustrates pressures measured at several points in the intake muffler according to the first embodiment of the present disclosure and the intake muffler according to the prior art. 
     As illustrated in  FIG. 12 , in the prior art, a difference between a pressure measured at the inlet guide portion  156  and a pressure measured inside the second muffler  230  is approximately 7,000 Pa. On the other hand, in the first embodiment of the present disclosure, a difference between a pressure measured at the inlet guide portion  156  and a pressure measured inside the second muffler  230  is approximately 5,000 Pa. 
     Accordingly, a pressure reduction at an inlet side of the intake muffler  200  in the first embodiment can be more efficiently improved compared to the prior art. 
     In addition, in the first embodiment, due to an improvement in the pressure reduction at the inlet side of the intake muffler  200 , a pressure at an outlet side of the intake muffler  200  can also be improved compared to the prior art. 
     Referring to  FIG. 12 , in the prior art, a difference between a pressure measured at the inlet guide portion and a pressure measured at an inlet of the intake port is approximately 9,000 Pa. On the other hand, in the first embodiment, a difference between a pressure measured at the inlet guide portion  156  and a pressure measured at an inlet of the intake port is approximately 7,000 Pa. 
     With reference to  FIGS. 13 to 19 , an intake muffler according to other embodiments of the present disclosure is described below. 
     In describing the following embodiments, the same reference numerals are given to the same components as those of the intake muffler according to the first embodiment described above, and a detailed description thereof will be omitted. 
       FIG. 13  is a cross-sectional perspective view of an intake muffler according to a second embodiment of the present disclosure.  FIG. 14  is a perspective view of a second muffler included in the intake muffler according to the second embodiment of the present disclosure. 
     As illustrated in  FIGS. 13 and 14 , the intake muffler according to the second embodiment has basically the same structure as the intake muffler according to the first embodiment described above, and they have a difference only in a structure of a second muffler. 
     More specifically, a second muffler  230 A of an intake muffler  200 A according to the second embodiment further includes a communication pipe  237 A connected to a communication hole  235 . The communication pipe  237 A extends from a flange  233  in the same direction as a flange extension  234  and is formed to be shorter than the flange extension  234 . 
     For example, an end of the communication pipe  237 A may extend to an end of a second part  231   b . That is, the end of the communication pipe  237 A and the end of the second part  231   b  may coincide with each other in the axial direction. 
     The second embodiment describes that each of the communication pipe  237 A and the communication hole  235  is provided in the same number as the number of communication holes  215  of a first muffler  210 , by way of example. However, the number of communication pipes  237 A and the number of communication holes  235  may be less than the number of communication holes  215 . 
     For example, one or two communication pipes  237 A and one or two communication holes  235  may be provided. 
     In addition, the number of communication pipes  237 A may be the same as or may be less than the number of communication holes  235 . 
     Unlike this, as illustrated in  FIGS. 15 and 16 , in a second muffler  230 B, a length of a communication pipe  237 B connected to a communication hole  235  may be greater than a length of a flange extension  234 . 
     For example, the communication pipe  237 B may be formed to have a length sufficient to contact a flange  212  of a first muffler  210 . 
     According to this, since a refrigerant flowing into a communication hole  215  of the first muffler  210  flows through the communication pipe  237 B and the communication hole  235 , the refrigerant of a discharge space  211   e  does not flow into a space formed by a rear end of the first muffler  210  and a front end of the second muffler  230 B and may flow into an inner space of a third muffler  250 . 
     This embodiment describes that the number of each of the communication hole  215 , the communication hole  235 , and the communication pipe  237 B is one, by way of example. However, each may be in plural in the same manner as the first and second embodiments described above. 
     In addition, the number of communication pipes  237 B may be the same as or may be less than the number of communication holes  235 . 
     In an intake muffler  200 B according to this embodiment, another communication hole  239  may be further provided in the communication pipe  237 B. 
     In this case, the refrigerant remaining in the space formed by the rear end of the first muffler  210  and the front end of the second muffler  230 B may flow into the third muffler  250  through the communication hole  239 . 
     Unlike this, as illustrated in  FIGS. 17 to 19 , a first muffler  210 C may include a communication pipe  217 C connected to a communication hole  215 , and a second muffler  230 C may include a communication pipe  237 C connected to a communication hole  235 . 
     The communication pipe  217 C protrudes rearward toward the second muffler  230 C, and the communication pipe  237 C protrudes forward toward the first muffler  210 C. 
     One end of the communication pipe  217 C contacts one end of the communication pipe  237 C. However, one end of the communication pipe  217 C may be spaced apart from one end of the communication pipe  237 C. 
     According to this, since a refrigerant flowing into the communication hole  215  of the first muffler  210 C flows through the communication pipe  217 C, the communication pipe  237 C, and the communication hole  235 , the refrigerant of a discharge space  211   e  does not flow into a space formed by a rear end of the first muffler  210 C and a front end of the second muffler  230 C and may flow into an inner space of a third muffler  250 . 
     This embodiment describes that the number of each of the communication hole  215 , the communication pipe  217 C, the communication hole  235 , and the communication pipe  237 C is one, by way of example. However, each may be in plural in the same manner as the first and second embodiments described above. 
     In an intake muffler  200 C according to this embodiment, a communication hole may be further provided in at least one of the communication pipe  217 C and the communication pipe  237 C, as in the third embodiment. 
     In this case, the refrigerant remaining in the space formed by the rear end of the first muffler  210 C and the front end of the second muffler  230 C may flow into the third muffler  250  through the communication hole.