Patent Publication Number: US-8118568-B2

Title: Hermetic compressor

Description:
This application is a U.S. national phase application of PCT international application PCT/JP2005/022725, filed Dec. 6, 2005. 
     TECHNICAL FIELD 
     The present invention relates to a hermetic compressor used in a refrigerating cycle of an electric refrigerator for household and professional uses, and the like. 
     BACKGROUND ART 
     In recent years, demand for global environmental protection has become increasingly strong. For this reason, in refrigerators, other refrigerating cycle apparatus and the like, it is especially strongly desired to increase efficiency. 
     Hitherto, in the hermetic compressor utilized in refrigerators, refrigerating cycle apparatus and the like, there has been used a resin suction muffler. These conventional hermetic compressors are disclosed in, for example, Japanese Patent Unexamined Publication No. H05-195953 and the like. 
     Hereunder, the conventional hermetic compressor is explained with reference to the drawings. 
       FIG. 9  shows a longitudinal sectional view of the conventional hermetic compressor.  FIG. 10  shows a perspective view of a suction muffler used in the conventional hermetic compressor. 
     In  FIG. 9  and  FIG. 10 , oil  202  is stored in a bottom part of hermetic container  201  (hereafter referred to as “container  201 ”). Compressing member  204  (hereafter referred to as “member  204 ”) is supported elastically with respect to container  201  by suspension spring  206 . 
     Member  204  is constituted by motor element  210 , and compressing element  220  disposed above motor element  210 . Motor element  210  is constituted by stator  212  and rotor  214 . 
     Compressing element  220  has crank shaft  221  (hereafter referred to as “shaft  221 ”). Shaft  221  is constituted by main shaft  222  and eccentric shaft  224 . Main shaft  222  is supported rotatably with respect to bearing  227  provided in block  226 . Rotor  214  is fixed to main shaft  222 . Additionally, shaft  221  has oil supplying mechanism  225 . 
     Further, piston  228  is inserted so as to be capable of reciprocating with respect to cylinder  230  monolithically formed in block  226 . Cylinder  230  forms, together with valve plate  232  (hereafter referred to as “plate  232 ”), compression chamber  234 . 
     A piston pin (not shown in the drawing) attached to piston  228  is inserted rotatably with respect to coupling part  236  to constitute a coupling means. Eccentric shaft  224  is inserted rotatably with respect to coupling part  236 . By this construction, coupling part  236  couples eccentric shaft  224  and piston  228 . 
     Cylinder head  238  covers plate  232 . Suction muffler  240  (hereafter referred to as “muffler  240 ”) is retained by cylinder head  238  and plate  232  while being nipped. Muffler  240  is molded and formed by a resin such as poly-butylene terephthalate. Inside muffler  240 , there is provided sound deadening space  242  whose inside face has been formed approximately like a circular cone. In a lower end of muffler  240 , there is provided oil discharge opening  246  (hereafter referred to as “opening  246 ”). In this manner, hermetic compressor  200  (hereafter referred to as “compressor  200 ”) is constituted. 
     Next, operation of compressor  200  is explained. 
     When an electric current is applied to motor element  210 , stator  212  generates a rotating magnetic field. By this rotating magnetic field, rotor  214  rotates together with main shaft  222 . By the rotation of main shaft  222 , eccentric shaft  224  eccentrically moves. An eccentric motion of eccentric shaft  224  is transmitted to piston  228  through coupling part  236 . As a result, piston  228  reciprocates in cylinder  230 . A refrigerant gas (not shown in the drawing) having returned from a refrigerating cycle (not shown in the drawing) outside container  201  is introduced into compression chamber  234  through muffler  240 . The refrigerant gas introduced into compression chamber  234  is compressed in compression chamber  234  by piston  228 . The compressed refrigerant gas is sent again to the refrigerating cycle outside container  201 . 
     On the occasion of this refrigerant compression, noise is generated by an intermittent suction of the refrigerant gas. Muffler  240  serves to reduce the generated noise. Additionally, by the fact that muffler  240  is formed by the resin whose heat transfer is small, heating of the refrigerant gas is prevented. By this fact, a decrease in performance of compressor  200  is prevented. 
     Additionally, by utilizing actions of a centrifugal force generated by the rotation of shaft  221 , and the like, oil supplying mechanism  225  supplies oil  202  stored in the bottom part of container  201  to upper compressing element  220 . Oil  202  supplied to compressing element  220  lubricates some sliding portions of bearing  227  and the like. Thereafter, oil  202  is dispersed from an upper end of shaft  221  to the environment by the centrifugal force of main shaft  222 . Dispersed oil  202  lubricates members such as piston  228  and cylinder  230 . Additionally, oil  202  adheres to inside wall surface  250  of container  201 , and flows down to the bottom part of container  201  along inside wall surface  250 . As oil  202  flows down along inside wall surface  250 , heat is conducted from oil  202  to container  201 . The heat conducted to container  201  is radiated to the outside of hermetic compressor  200  through a wall surface material of container  201 . By this fact, a cooling of compressor  200  is performed. 
     Further, oil  202  having dispersed from the upper end of shaft  221  is sucked also into muffler  240  with a flow of the refrigerant gas. The flow of the refrigerant gas is released into sound deadening space  242  in muffler  240 , and its velocity decreases. When the flow velocity of the refrigerant gas decreases, oil  202  drops to a lower part of sound deadening space  242 . Oil  202  having dropped into sound deadening space  242  flows down along inside wall surface  252  of sound deadening space  242 . Oil  202  having flowed down collects to a lower end of sound deadening space  242 . Thereafter, oil  202  having collected to the lower end of sound deadening space  242  is discharged from opening  246  to the outside of muffler  240 . 
     However, in the above configuration of conventional compressor  200 , it is difficult to contrive a miniaturization of muffler  240  with an inside shape of sound deadening space  242  maintained in a shape like the circular cone. This fact hinders the miniaturization of compressor  200 . 
     That is, in order for muffler  240  to achieve a sound deadening function, sound deadening space  242  necessitates a spatial volume (width or depth of sound deadening space  242 ) larger than a certain value. Further, in order for oil  202  to flow to opening  246  along inside wall surface  252 , sound deadening space  242  is shaped like the circular cone having an angle of a certain degree. Thereupon, for muffler  240 , a height of a certain degree becomes necessary, so that opening  246  approaches a liquid level of oil  202  stored in the bottom part of container  201 . 
     However, the liquid level of oil  202  stored in the bottom part of container  201  changes by an operating state of compressor  200 . Especially, at start-up of compressor  200 , a refrigerant gas having dissolved in oil  202  bubbles out due to a pressure drop in container  201 . For this reason, the liquid level of oil  202  ascends, so that opening  246  is immersed in oil  202 . Additionally, an average pressure in sound deadening space  242  is low in comparison with that in container  201 . As a result, a large quantity of oil  202  enters through opening  246  into sound deadening space  242 , so that oil  202  is liable to remain in muffler  240 . 
     Further, it is considered to dispose opening  246  while being separated from oil  202  in the bottom part of container  201  by reducing an incline of inner wall surface  252  to thereby suppress a height of muffler  240  to a low level. However, a dropping velocity of oil  202  flowing down along inner wall surface  252  becomes slow, so the oil  202  is not discharged sufficiently from sound deadening space  242 . As a result, similarly, oil  202  is liable to remain in muffler  240 . 
     Like this, if the large quantity of oil  202  remains in muffler  240 , when the refrigerant gas is sucked into compressing chamber  234 , oil  202  is raised, so that the large quantity of oil  202  is sucked into compressing chamber  234 . 
     If the large quantity of oil  202  flows into compressing chamber  234 , a load during compressing becomes large. As a result, an input energy of compressor  200  increases. Or, the refrigerant gas is not compressed sufficiently, so that a refrigerating ability of compressor  200  decreases. Further, by the fact that a compressing load and the like abruptly fluctuate, the noise of the compressor  200  becomes larger. Additionally, heat exchanger performance is influenced by the fact that the large quantity of oil  202  is discharged to the refrigerating cycle. 
     SUMMARY OF THE INVENTION 
     A hermetic compressor of the present invention has a hermetic container storing oil, and a compressing element accommodated in the hermetic container and compressing a refrigerant gas; the compressing element has a compression chamber, a cylinder forming the compressing chamber, a piston inserted into the cylinder and reciprocating, and a suction muffler whose one end communicates with the compression chamber; and the suction muffler has a sound deadening space, a gas flow forming part forming a gas flow flowing in a constant direction in the sound deadening space, and an oil discharge opening provided in a downstream side of the gas flow in a lower part of the sound deadening space. By this construction, there is realized a hermetic compressor in which the oil does not readily remain in the suction muffler, whose noise is lower, and whose performance is stabilized. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a longitudinal sectional view of a hermetic compressor in an embodiment of the present invention. 
         FIG. 2  is a sectional view along a line  2 - 2  line of the hermetic compressor shown in  FIG. 1 . 
         FIG. 3  is a sectional view of a suction muffler used in the hermetic compressor shown in  FIG. 1 . 
         FIG. 4  is a perspective view of the suction muffler shown in  FIG. 3 . 
         FIG. 5  is a sectional view of a suction muffler used in the hermetic compressor shown in  FIG. 1 . 
         FIG. 6  is a sectional view of a suction muffler used in the hermetic compressor shown in  FIG. 1 . 
         FIG. 7  is a sectional view of a suction muffler used in the hermetic compressor shown in  FIG. 1 . 
         FIG. 8  is a sectional view of a suction muffler used in the hermetic compressor shown in  FIG. 1 . 
         FIG. 9  is a longitudinal sectional view of a conventional hermetic compressor. 
         FIG. 10  is a perspective view of a suction muffler used in the conventional hermetic compressor. 
     
    
    
     DETAILS DESCRIPTION OF THE INVENTION 
     Hereunder, there is explained about an embodiment of the present invention is explained with reference to the drawings. 
       FIG. 1  is a longitudinal sectional view of a hermetic compressor in an embodiment of the present invention.  FIG. 2  is a sectional view along line  2 - 2  of the hermetic compressor shown in  FIG. 1 .  FIG. 3  is a sectional view of a suction muffler used in the hermetic compressor shown in  FIG. 1 .  FIG. 4  is a perspective view of the suction muffler shown in  FIG. 3 . 
     In  FIG. 1  to  FIG. 4 , oil  102  is stored in a bottom part inside hermetic container  101  (hereafter referred to as “container  101 ”). Additionally, there is accommodated compressing member  104  (hereafter referred to as “member  104 ”) inside container  101 . Member  104  is constituted by motor element  110  and compressing element  120  driven by motor element  110 . Member  104  is supported elastically with respect to container  101  by suspension spring  106 . Further, inside container  101 , there is filled a hydrocarbon refrigerant gas, such as R600a for instance, whose global warming potential is low. Further, power source terminal  108  is attached to container  101  for supplying power from a power source to motor element  110 . In this manner, hermetic compressor  100  (hereafter referred to as “compressor  100 ”) is constituted. 
     First, motor element  110  is described. 
     Motor element  110  forms a salient pole concentrated winding-type DC brushless motor. Motor element  110  has stator  112  and rotor  114 . Motor element  110  is connected to an inverter drive circuit (not shown in the drawings) by lead wire  109  through power source terminal  108 . 
     Stator  112  is formed with a winding being wound around magnetic pole teeth of an iron core of stator  112  through an insulating material. The iron core of stator  112  is formed by so-called flat-rolled electromagnetic steel sheets and strip (silicon steel plate), such as non-oriented magnetic sheets and strip (JIS C2552) for instance, whose iron loss is low. For the iron core of stator  112 , it is desirable to use the flat-rolled electromagnetic steel sheets and strip whose thickness is 0.7 mm or less, and whose iron loss is 7 W/kg or less. Additionally, for the iron core of stator  112 , it is desirable to use the flat-rolled magnetic steel sheets and strip whose thickness is 0.35 mm, and whose iron loss is as low as 0.4 W/kg or less. 
     Rotor  114  is disposed inside stator  112 . Rotor  114  is constituted by an iron core of rotor  114 , and a permanent magnet disposed inside the iron core of rotor  114 . As the permanent magnet, there is used a rare earth magnet such as neodymium for instance. Further, rotor  114  is fixed to main shaft  122  constituting crank shaft  121  (hereafter referred to as “shaft  121 ”). Similarly to the iron core of stator  112 , the iron core of rotor  114  is also formed with the flat-rolled electromagnetic steel sheets and strip, such as non-oriented electromagnetic sheets and strip (JIS C2552), being laminated. 
     Further, motor element  110  is operated at various frequencies between 15 r/sec (revolutions per second) and 75 r/sec by an inverter drive. 
     Next, details of compressing element  120  are explained. 
     Compressing element  120  is disposed above motor element  110 . 
     Shaft  121  constituting compressing element  120  has main shaft  122  and eccentric shaft  124 . A lower end part of main shaft  122  is immersed in oil  102  stored in the bottom part of container  101 . In shaft  121 , there is provided oil supplying mechanism  125  which communicates from the lower end part of main shaft  122  to an upper end part of eccentric shaft  124  and which is for supplying oil  102  to an upper part of compressing element  120 . In block  126 , there are provided bearing  127  and cylinder  130 . Bearing  127  rotatably supports main shaft  122 . 
     Piston  128  is fitted to and inserted into cylinder  130  so as to be capable of reciprocating therein. Valve plate  132  (hereafter referred to as “plate  132 ”) is disposed at an end face of cylinder  130 . Compression chamber  134  is formed by cylinder  130  and plate  132 . Piston  128  and eccentric shaft  124  are connected by coupling part  136  that constitutes a coupling means. 
     Suction muffler  140  (hereafter referred to as “muffler  140 ”) is fixed by the fact that it is supported while being nipped by plate  132  and cylinder head  138 . Muffler  140  is formed by a synthetic resin, such as poly-butylene terephthalate, that is a crystalline resin to which glass fibers have been mainly added. 
     Additionally, sound deadening space  142  is formed inside muffler  140 . Muffler  140  has inlet pipe  150  and outlet pipe  152 . One end of pipe  150  opens into sound deadening space  142 , and the other end of inlet pipe  150  opens into container  101 . One end of pipe  152  opens into sound deadening space  142 , and the other end of outlet pipe  152  opens into compression chamber  134 . 
     A back face side of muffler  140  adjoins stator  112  and block  126 . Muffler  140  has an external shape extending along stator  112  and block  126 . 
     Further, as shown in  FIG. 1  and  FIG. 4 , lower portion  140 B in a front face side of muffler  140  is thinner in its thickness than upper portion  140 A in order to secure a distance from power source terminal  108 . Lower portion  140 B has a shape which is thinner in its center part in comparison with its left and right parts. Additionally, lower surface  140 C of muffler  140  is formed by a substantially horizontal face. Lower surface  140 C is disposed a certain distance from oil  102  stored in the bottom part of container  101 . 
     As shown in  FIG. 3  and  FIG. 4 , outlet pipe  152  extends in an approximately horizontal direction along a wall surface in an upper end of sound deadening space  142 . A tip of outlet pipe  152  opens in the vicinity of the wall surface in the upper end of sound deadening space  142 . 
     The refrigerant gas flows out as gas flows  152 A,  152 B which are indicated by arrows of alternate long and short dash lines while passing through outlet pipe  152  from sound deadening space  142 . By the flow of the flowing-out refrigerant gas, annular gas flow  143  is generated in a clockwise direction along an outer periphery in sound deadening space  142 . In other words, gas flow forming part  144  forming gas flow  143  is formed by outlet pipe  152 . 
     Next, annular gas flow  143  formed inside sound deadening space  142  is explained in detail with reference to  FIG. 4 . 
     In  FIG. 4 , a tip of inlet pipe  150  opens in a horizontal direction in an approximate center inside sound deadening space  142 . Inlet pipe  150  is constituted such that there is formed gas flow  150 A in which the refrigerant gas flows in a direction from right to left. Further, outlet pipe  152  is disposed in a front side of an upper end part of sound deadening space  142 . Outlet pipe  152  is constituted such that there is formed gas flow  152 A in which the refrigerant gas flows in a direction from left to right. 
     Above inlet pipe  150 , sound deadening space  142  has a space in a back face side of outlet pipe  152 . Further, also below inlet pipe  150 , sound deadening space  142  has a space whose depth is small. Further, at a height approximately the same as inlet pipe  150 , sound deadening space  142  has a space extending in front sides of left and right. These spaces of four places in upper end, lower end, left end and right end respectively communicate with each other. 
     Further, inlet pipe  150  is formed monolithically with a wall surface in its back face side. Still further, in the vicinity of an opening part of inlet pipe  150  with respect to sound deadening space  142 , an interstice scarcely exists between inlet pipe  150  and the wall surface in front side. Accordingly, an internal structure of sound deadening space  142  becomes a doughnut-like space in which the above-mentioned upper, lower, left and right spaces have communicated so as to surround the opening part of inlet pipe  150 . Accordingly, sound deadening space  142  forms in its inside annular gas passage  148 . 
     Additionally, sound deadening space  142  has a shape whose lateral width is wide in comparison with its height. Further, lower surface  140 C of sound deadening space  142  is constituted by the approximately horizontal face. In the vicinity of a bottom part of muffler  140 , in other words, in a lower part of sound deadening space  142  and in a side face in a downstream side of gas flow  143 , there is provided oil discharge opening  146  (hereafter referred to as “opening  146 ”). 
     Operations and actions of hermetic compressor  100 , constituted as described above, are explained below. 
     When the electric current is applied to motor element  110  by the inverter drive circuit, rotor  114  rotates together with main shaft  122  due to a magnetic field occurring in stator  112 . With a rotation of main shaft  122 , eccentric shaft  124  eccentrically rotates. An eccentric motion of eccentric shaft  124  is converted into a reciprocating motion through coupling part  136 . By this fact, piston  128  reciprocates in cylinder  130 . By the fact that piston  128  reciprocates in cylinder  130 , the refrigerant gas in container  101  is sucked into compression chamber  134 . Additionally, the refrigerant gas is compressed in compression chamber  134 . In other words, a suction operation and a compression operation of the refrigerant gas are performed. 
     In a suction process of the refrigerant gas with the compression operation, the refrigerant gas in container  101  is intermittently sucked into compression chamber  134  through muffler  140 . After being compressed, the sucked refrigerant gas is sent to the refrigerating cycle (not shown in the drawings) provided outside container  101  through discharge piping (not shown in the drawings) and the like. 
     Muffler  140  constitutes an expansion type muffler including inlet pipe  150 , outlet pipe  152  and sound deadening space  142 . Muffler  140  has a function of reducing the noise which occurs by the intermittent suction of the refrigerant gas. Further, muffler  140  is formed by poly-butylene terephthalate resin etc. whose heat transfer is extremely small in comparison with metal and the like. By this fact, there is prevented a temperature rise of the refrigerant gas which returns to compression chamber  134  from the refrigerating cycle through muffler  140 . The refrigerant gas which returns to compression chamber  134  from the refrigerating cycle through muffler  140  has comparatively low temperature, so that the refrigerant gas maintains a low temperature. As a result, a decrease in performance of compressor  100  is prevented. 
     Oil supplying mechanism  125  carries oil  102  stored in the bottom part of container  101  to the upper part of compressing element  120  by utilizing the centrifugal force obtained by a rotation of shaft  121 , a viscous, frictional force occurring in a sliding part, and the like. Oil  102  carried to compressing element  120  performs lubrication of each of the sliding parts of main shaft  122  and eccentric shaft  124 . Additionally, it is dispersed into container  101  from an upper end part of shaft  121 . Dispersed oil  102  showers down on each of the sliding parts of piston  128  and cylinder  130 , thereby performing the lubrication. The temperature of oil  102  rises as the oil  102  lubricates the sliding parts due to the influence of frictional heat of the sliding parts, and the like. Oil  102  having risen in temperature adheres to inside wall surface  160  of container  101 . Oil  102  having adhered to inside wall surface  160  flows down to a lower part of container  101  along inside wall surface  160 . As oil  102  flows down to the lower part of container  101 , thermal energy of oil  102  is radiated to the outside of container  101  through container  101 , in other words, with container  101  as a heat transfer material. This causes cooling of an inside of compressor  100 . 
     Additionally, one part of oil  102  having dispersed into container  101  is sucked into muffler  140  via inlet pipe  150  that opens into container  101 . Oil  102  having entered into muffler  140  is sucked to sound deadening space  142  through inlet pipe  150 . When the refrigerant gas is sucked to sound deadening space  142  and its pressure is released, oil  102  drops to the bottom part of sound deadening space by gravity. 
     As shown in  FIG. 3  and  FIG. 4 , by the velocity of the refrigerant gas flowing to outlet pipe  152 , the refrigerant gas in sound deadening space  142  is energized and, in the back face side of outlet pipe  152 , gas flow  143 A flows from left to right. Further, annular gas passage  148  is formed in sound deadening space  142 . By these facts, there occur gas flow  143 B, gas flow  143 C and gas flow  143 D, so that annular gas flow  143  cycling in sound deadening space  142  is formed. Gas flow  143 B is a gas flow which flows, in a right side of sound deadening space  142 , downwardly at a front side of inlet pipe  150 . Further, gas flow  143 C is a gas flow which flows, in a lower end of sound deadening space  142 , from right to left. Additionally, gas flow  143 D is a gas flow which flows upwardly in a left side of sound deadening space  142 . 
     Oil  102  having dropped to the bottom part of sound deadening space  142  is conveyed to a vicinity of opening  146  by gas flow  143 C. Oil  102  conveyed to the vicinity of opening  146  becomes oil pool  102 A which seals opening  146 . As shown by broken line  146 A in  FIG. 3 , a liquid level of oil pool  102 A attains an oblique slanting face due to gas flow  143 C. 
     As to a pressure in muffler  140 , a negative pressure and a positive pressure alternately occur with respect to a pressure in container  101 . In other words, muffler  140  is respiring. For this reason, through opening  146 , there are alternately repeated a process in which oil  102  is discharged from muffler  140  to container  101  and a process in which the refrigerant gas is sucked from container  101  into muffler  140 . By this fact, oil  102  having collected in the vicinity of opening  146  is intermittently discharged into container  101 . 
     As a result, oil  102  does not readily remain in muffler  140 , so that there is no fact that a large quantity of oil  102  remains in muffler  140 . The large quantity of oil  102  is prevented from being sucked to compressing chamber  134 . 
     The refrigerant gas in sound deadening space  142  is energized by gas flow  152 A of the refrigerant gas flowing out through outlet pipe  152 , so that annular gas flow  143  is formed in the inner circumference of sound deadening space  142 . In other words, gas flow forming part  144  forming gas flow  143  is constituted by outlet pipe  152  which opens in the approximately horizontal direction along the wall surface in the upper end of sound deadening space  142 . Accordingly, there is no necessity to add such a particular component as to provide, e.g., a special fan for generating gas flow  143 C. In other words, gas flow forming part  144  is constituted without an accompanying increase in cost. 
     Further, at start-up of compressor  100 , it may occur that a non-gasified liquid-like refrigerant flows into compressor  100  from the refrigerating cycle. Further, it may also occur that the pressure in container  101  abruptly decreases and thus the refrigerant gas having dissolved in oil  102  bubbles out. By these facts, it may occur that oil  102  and the liquid-like refrigerant flow into muffler  140 , drop into sound deadening space  142  by gravity, and remain in the bottom part of sound deadening space  142 . 
     However, outlet pipe  152  is provided near an upper end face of sound deadening space  142  and sufficiently separated from lower surface  140 C. For this reason, even if certain quantities of oil  102  and the liquid-like refrigerant are accumulated in the bottom part of sound deadening space  142 , oil  102  and the liquid-like refrigerant are prevented from being sucked in large quantities into compression chamber  134  through outlet pipe  152 . As a result, there are prevented an occurrence of noise from compressor  100 , and breakage of components of compressor  100 , such as a valve (not shown in the drawings). 
     Further, lower surface  140 C of sound deadening space  142  is constituted by the approximately horizontal face. Additionally, opening  146  is disposed near an end part in a downstream side of gas flow  143 C in the vicinity of lower surface  140 C. By these facts, a dimension in a height direction is suppressed to a small value and, also in muffler  140 , a volume of sound deadening space  142  is secured and a certain distance is secured between opening  146  and oil  102  stored in the bottom part of container  101 . 
     The pressure in container  101  abruptly decreases at the start-up of compressor  100 , and the refrigerant gas having dissolved in oil  102  bubbles out, so that the liquid level of oil  102  may be raised. Even if the liquid level of oil  102  has raised, oil  102  and the liquid-like refrigerant are prevented from flowing into muffler  140  via inlet pipe  150  and opening  146 . For this reason, oil  102  and the liquid-like refrigerant are prevented from being sucked in large quantity into compression chamber  134 . By this fact, the occurrence of the noise is prevented and, at the same time, a performance of compressor  100  is stabilized. 
     Further, motor element  110  is the salient pole concentrated winding-type DC brushless motor, and is smaller in dimension in the height direction than a distributed winding induction motor. Accordingly, the dimension in the height direction is suppressed to a small value while a certain content volume of muffler  140  is secured. Additionally, oil  102  is prevented from remaining inside muffler  140 . By this fact, the noise of compressor  100  is reduced, and the performance of compressor  100  is stabilized, while miniaturization of compressor  100  is achieved. 
     Especially, with motor element  110  in which a rare earth magnet capable of obtaining a strong magnetic force is used, there is realized compressor  100  in which the dimension in the height direction is additionally suppressed to a small value. Accordingly, even if the height of muffler  140  is low, there remarkably appears an advantage that residence of oil  102  in muffler  140  is prevented. As a result, the height of compressor  100  is additionally suppressed to the small value. 
     Further, the centrifugal force acts on annular gas flow  143  formed in sound deadening space  142 . By this fact, oil  102  contained in the refrigerant gas is centrifugally separated. Oil  102  centrifugally separated adheres to inside wall surface  162  of sound deadening space  142  and flows down to the bottom part of sound deadening space  142  along inside wall surface  162 . For this reason, an inflow of oil  102  into compression chamber  134  is additionally suppressed. As a result, noise is additionally reduced, and the performance of compressor  100  becomes additionally stable. 
     Further, annular gas flow  143  is formed in sound deadening space  142 . By this fact, gas flow  143 C is not readily disturbed, and stable, strong gas flow  143 C in a constant direction is formed. Stable and strong gas flow  143 C in the constant direction additionally ensures the flow of oil  102  discharged from muffler  140  through opening  146 . 
     There is provided a visor  156  protruding like an eaves, in an upper side of opening  146 . If a large quantity of oil  102  adheres to an outer surface of muffler  140  near opening  146 , oil  102  could be sucked into muffler  140  from opening  146 . By this fact, there is a possibility that a large quantity of oil  102  accumulates in muffler  140 . However, by the fact that visor  156  is provided, oil  102  flowing down along the outer surface of muffler  140  is prevented from accumulating around opening  146 . As a result, there is avoided the suction of oil  102  from an outside to an inside of muffler  140  through opening  146 . 
     Additionally, compressor  100  is operated in a number of revolutions of a wide range with an inverter control used. For this reason, a quantity of the dispersion of oil  102  from shaft  121  greatly changes by the number of revolutions. However, in a high rotation operation in which the large quantity of oil  102  disperses and oil  102  is liable to be sucked into muffler  140 , gas flows  143 ,  143 C in sound deadening space  142  become strong as well. For this reason, oil  102  having accumulated in the bottom part of sound deadening space  142  is liable to collect in a vicinity of opening  146 . As a result, a discharge of oil  102  from muffler  140  through opening  146  is expedited, so that there is prevented an abnormal increase of oil pool  102 A in muffler  140 . 
     Additionally, by the fact that a flow velocity of annular gas flow  143  increases, the centrifugal force applied to the refrigerant gas in sound deadening space  142  increases. As a result, a centrifugally separating ability with respect to oil  102  contained in the refrigerant gas additionally increases as well. 
     Accordingly, even if compressor  100  is operated in a wide operation range, there is prevented the suction of oil  102  into compression chamber  134 . As a result, the performance of compressor  100  is stabilized. 
     Opening  146  has been described as being provided in a side face of muffler  140 . However, there may be a construction in which the opening is provided in the bottom part or lower surface  140 C of muffler  140 . 
     Gas flow forming part  144  has been described as being formed by outlet pipe  152  which opens into sound deadening space  142  while extending in the approximately horizontal direction along the wall surface in the upper end of sound deadening space  142 . However, the gas flow forming part  144  is not necessarily limited to outlet pipe  152  extending in the approximately horizontal direction along the wall surface in the upper end of sound deadening space  142 . 
     For example, as shown in  FIG. 5 , gas flow forming part  144  may be constituted by inlet pipe  150  which opens into sound deadening space  142  while extending in the approximately horizontal direction along the wall surface in a lower end of sound deadening space  142 . 
     Further, as shown in  FIG. 6 , gas flow forming part  144  may be constituted by outlet pipe  152  which opens into sound deadening space  142  while extending in the approximately horizontal direction along the wall surface in the lower end of sound deadening space  142 . Further, gas flow forming part  144  may be constituted by inlet pipe  150  which opens into sound deadening space  142  while extending in the approximately horizontal direction along the wall surface in the upper end of sound deadening space  142 . 
     Additionally, as shown in  FIG. 7 , gas flow forming part  144  may be constituted by outlet pipe  152  which opens into sound deadening space  142  while extending in an approximately vertical direction along the wall surface in a left end of sound deadening space  142 . Further, gas flow forming part  144  may be constituted by inlet pipe  150  which opens into sound deadening space  142  while extending in the approximately vertical direction along the wall surface in a right end of sound deadening space  142 . 
     Furthermore, as shown in  FIG. 8 , gas flow forming part  144  may be constituted by outlet pipe  152  which opens into sound deadening space  142  while extending in the approximately vertical direction along the wall surface in the right end of sound deadening space  142 . Further, gas flow forming part  144  may be constituted by inlet pipe  150  which opens into sound deadening space  142  while extending in the approximately vertical direction along the wall surface in the left end of sound deadening space  142 . 
     In other words, by the fact that gas flow forming part  144  is constituted by either one or both of outlet pipe  152  and inlet pipe  150 , the inflow of oil  102  to compression chamber  134  is suppressed without additionally providing a special member. As a result, there is provided compressor  100  whose noise is low and which realizes a stable operation. 
     Further, outlet pipe  152  and inlet pipe  150  may be provided while being respectively extended along any end face of the upper end face, the lower end face, the left end face and the right end face of sound deadening space  142 . In other words, it suffices if it is a constitution in which, in order to form annular gas flow  143  in sound deadening space  142 , an energizing force for forming gas flow  143  is given to the refrigerant gas in sound deadening space  142 . 
     As discussed above, in compressor  100 , oil  102  is certainly discharged from muffler  140 , and thus prevented from being sucked into compression chamber  134 . As a result, the performance of compressor  100  becomes stable, and noise is suppressed as well. 
     INDUSTRIAL APPLICABILITY 
     As discussed above, in the hermetic compressor, since the performance of the compressor is stable and the noise is reduced, the hermetic compressor can be widely applied to an air conditioner, a vending machine, other refrigerating apparatus and the like, and is not limited to use in a household electric refrigerator.