Patent Publication Number: US-2017350623-A1

Title: Refrigeration cycle device and compressor used in same

Description:
TECHNICAL FIELD 
     The present invention relates to a refrigeration cycle device and a compressor used in the same. 
     BACKGROUND ART 
       FIG. 6  is a diagram illustrating a refrigeration cycle configured by compressor  101 , condenser  102 , evaporator  103 , decompressors  104 , injection pipe  105 , and gas-liquid separator  106 . In the refrigeration cycle, a gas phase component and a liquid phase component of intermediate pressure refrigerant are separated by using gas-liquid separator  106  to perform gas injection. Conventionally, in order to reduce power consumption and improve capability of the refrigeration cycle, a refrigeration cycle device has been proposed that injects intermediate pressure gas refrigerant into a compressor. For example, Patent Literature 1 discloses a rotary compressor equipped with back flow suppressive means for suppressing back flow of gas refrigerant in a compression chamber when gas refrigerant that has taken out from gas-liquid separator  106  is injected in the working compression chamber. Furthermore, Patent Literature 2 discloses a rotary type two-stage compressor that performs gas injection with respect to an intermediate pressure region of two-stage compression. 
     However, like Patent Literature 1, when gas injection is performed with respect to the working compression chamber, the pressure in the compression chamber is largely fluctuated from low pressure to high pressure at the cycle of an operation frequency, causing a problem to be described below. That is, when the pressure of an injection pipe outlet becomes higher than an injection gas pressure, the refrigerant in the compression chamber may disadvantageously flow back from an injection port. To solve the problem, Patent Literature 1 discloses provisions such as providing a check valve to prevent back flow, but the check valve can block original flow of the injection. Furthermore, even when back flow itself can be suppressed, injection to the compression chamber whose pressure fluctuates becomes intermittent, so that pulsation of refrigerant pressure in the injection pipe becomes large, disadvantageously causing noise or vibration. 
     On the other hand, like Patent Literature 2, when injection is performed in the intermediate pressure region of the two-stage compression, injection is performed to a stable pressure region, which solves the above problems, making it possible to perform gas injection of a continuously stable amount. In the tow-stage compression system, under the operating condition in which the pressure difference between low pressure and high pressure is large, leakage or the like of refrigerant due to the pressure difference becomes small as compared with a single-stage compression system, making it possible to exert high efficiency capability. However, under the operation condition with a low load in which the pressure difference is small, the two-stage compression system has a problem in that its efficiency is lowered as compared with the single-stage compression system due to slide loss or the like. Furthermore, substantive compressor suction volume is limited to the volume of the compression chamber on the side on which low pressure refrigerant is suctioned, requiring grow in size of the compressor in order to exert a desired refrigerating or heating capability under low differential pressure operation conditions in which injection effect is small. 
     CITATION LIST 
     Patent Literature 
     PTL 1: Japanese Patent No. 3718964 
     PTL 2: Japanese Patent No. 4719432 
     SUMMARY OF THE INVENTION 
     The present invention is to solve the above problems, and provides a refrigeration cycle device that switches to injection operation of a two-stage compression system during high load operation, for example, during low outdoor air temperature while employing a single-stage compression system that exerts high efficiency capability during normal operation. This provides a refrigeration cycle device that exerts a high capability. 
     That is, a refrigeration cycle device according to the present invention includes a compressor including a first compression chamber and a second compression chamber that are independent, a condenser, a decompressor, an evaporator, an injection path configured to introduce intermediate pressure refrigerant decompressed by the decompressor, a first suction path configured to introduce low pressure refrigerant from the evaporator to the first compression chamber, and a second suction path configured to introduce low pressure refrigerant from the evaporator to the second compression chamber. The refrigeration cycle device further includes a communication passage configured to introduce intermediate pressure refrigerant compressed in the first compression chamber to the second compression chamber, and a switch element configured to selectively make the second compression chamber communicate with the evaporator or make the second compression chamber communicate with the communication passage. The injection path introduces the intermediate pressure refrigerant to the second compression chamber. The refrigerant is compressed in the first compression chamber and the second compression chamber independently when the second compression chamber is communicated with the evaporator, and refrigerant compressed in the first compression chamber is further compressed in the second compression chamber when the second compression chamber is communicated with the communication passage. 
     This makes it possible to exert high heating capability utilizing injection effect by two-stage injection operation that does not cause pulsation of the injection pipe under the operating conditions in which pressure difference is large such as operation at a low outdoor air temperature as a refrigeration cycle device that injects intermediate pressure gas refrigerant. This also enables power consumption suppressed high efficient operation by making each of the two compression chambers perform single-stage compression from a low pressure to a high pressure during low load and low differential pressure operation. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a diagram illustrating a compressor and a refrigeration cycle during single-stage compressing operation in a refrigeration cycle according to the present invention. 
         FIG. 2  is a diagram illustrating the compressor and the refrigeration cycle during two-stage compressing operation in the refrigeration cycle according to the present invention. 
         FIG. 3  is an enlarged view of a compression mechanism portion structuring the refrigeration cycle according to the present invention. 
         FIG. 4  is a plan view of a compression chamber of a rotary compressor structuring the refrigeration cycle according to the present invention. 
         FIG. 5  is a diagram illustrating a relation between a compression chamber volume ratio and an injection ratio in the refrigeration cycle according to the present invention. 
         FIG. 6  is a diagram illustrating a conventional injection refrigeration cycle using a gas-liquid separator. 
     
    
    
     DESCRIPTION OF EMBODIMENT 
     A first aspect of the present disclosure includes a compressor including a first compression chamber and a second compression chamber that are independent, a condenser, a decompressor, an evaporator, an injection path configured to introduce intermediate pressure refrigerant decompressed by the decompressor, a first suction path configured to introduce low pressure refrigerant from the evaporator to the first compression chamber, and a second suction path configured to introduce low pressure refrigerant from the evaporator to the second compression chamber. The refrigeration cycle device further includes a communication passage configured to introduce intermediate pressure refrigerant compressed in the first compression chamber to the second compression chamber, and a switch element configured to selectively make the second compression chamber communicate with the evaporator or make the second compression chamber communicate with the communication passage. The injection path introduces the intermediate pressure refrigerant to the second compression chamber. The refrigerant is compressed in the first compression chamber and the second compression chamber independently when the second compression chamber is communicated with the evaporator, and refrigerant compressed in the first compression chamber is further compressed in the second compression chamber when the second compression chamber is communicated with the communication passage. 
     This makes it possible to exert high heating capability utilizing injection effect by two-stage injection operation that does not cause pulsation of the injection pipe under the operating conditions in which pressure difference is large such as operation at a low outdoor air temperature. This also enables power consumption suppressed high efficient operation by making each of the two compression chambers perform single-stage compression from a low pressure to a high pressure during low load and low differential pressure operation. 
     In a second aspect, in the refrigeration cycle device according to the first aspect, the second suction path has a connection part connecting with the injection path on a downstream side of the switch element. 
     This makes overheated refrigerant compressed in the first compression chamber be mixed with intermediate pressure refrigerant, which is small in degree of superheat, transmitted from injection pipe till the overheated refrigerant is introduced in the second compression chamber, when two-stage compressing operation is performed. This makes it possible to reduce degree of superheat of the refrigerant introduced in the second compression chamber, making it possible to improve compression efficiency in the second compression chamber. Furthermore, when single-stage compressing operation is performed, making the pressure of the refrigerant flowing in the injection pipe be a substantively low pressure state and using the injection pipe as a bypass circuit of the refrigerant passing through the evaporator become possible, making it possible to reduce the gas refrigerant flowing in the evaporator. This makes it possible to yield efficiency improvement effect of the evaporator, making it possible to improve refrigeration cycle efficiency and capability. 
     In a third aspect, in the refrigeration cycle device according to the first aspect, a volume of the first compression chamber and a volume of the second compression chamber are equal. Note that a volume ratio only needs to be substantially equal and may have a difference of about ±10%. 
     This makes it possible to make the sizes and weights of eccentric rotation series members such as a shaft eccentric shaft and a piston equal, making it possible to manufacture the compressor with a low price. 
     In a fourth aspect, in the refrigeration cycle device according to the first aspect, the compressor is provided around a shaft and has two eccentric shafts each performing eccentric rotation, and phases of the two eccentric shafts are deviated by 180 degrees. 
     This makes it possible to structure two compression mechanisms without deviating the gravity center of the rotation member with respect to a shaft axis direction, making it possible to suppress vibration of the compressor. Furthermore, allocation ratios of compression power become equal, making it possible to perform efficient compressing operation. Note that “deviation by 180 degrees” includes the case of “deviation by substantially 180 degrees”. 
     In a fifth aspect, in the refrigeration cycle device according to the second aspect, the second suction path has an upward gradient part between the connection part and the second compression chamber. 
     This makes the intermediate pressure overheated gas refrigerant introduced from the first compression chamber be preferentially introduced to the second compression chamber even when liquid refrigerant is flown from the injection pipe when the two-stage injection operation is performed. Liquid component refrigerant that is large in its specific gravity is evaporated by heat exchange with overheated gas refrigerant without being introduced in the second compression chamber. This makes it possible to keep lubrication of the compressor good and efficiently perform the two-stage compressing operation. 
     In a sixth aspect, in the refrigeration cycle device according to the first aspect, inverter operation to arbitrarily change a rotation number of the compressor is performed. 
     This makes it possible to perform continuous high efficiency operation with respect to a wide range capability zone from small capability to large capability, and to provide a large capability operation in which the injection effect and high speed operation are combined during a low outside air temperature. 
     A seventh aspect provides the compressor used in the refrigeration cycle device according to any one of the first aspect to the sixth aspect. 
     Hereinafter, an exemplary embodiment of the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited by the following exemplary embodiment. 
     First Exemplary Embodiment 
       FIG. 1  is a refrigeration cycle diagram during single-stage compressing operation according to an exemplary embodiment of the present invention.  FIG. 2  is a refrigeration cycle diagram during two-stage compressing operation according to the exemplary embodiment.  FIG. 3  is an enlarged view of a compression mechanism portion according to the exemplary embodiment.  FIG. 4  is a plan view of a compression chamber of a rotary compression mechanism according to the exemplary embodiment. 
     As illustrated in  FIGS. 1 and 2 , a refrigeration cycle device of the exemplary embodiment includes compressor  1 , condenser  2 , evaporator  3 , decompressors  4 , injection pipe  5 , and gas-liquid separator  6 . 
     A main body of compressor  1  includes, in sealed vessel  11 , motor  12 , first compression mechanism  20  structuring first compression chamber  21 , second compression mechanism  30  structuring second compression chamber  31 , and shaft  13 . Motor  12  is disposed above first compression mechanism  20  and second compression mechanism  30 . First compression mechanism  20 , second compression mechanism  30 , and motor  12  are coupled with shaft  13 . Terminal  14  for supplying electric power to motor  12  is provided at an upper portion of sealed vessel  11 . Oil storage part  15  for retaining lubricant is formed at the bottom of sealed vessel  11 . The main body of the compressor has a structure of a so-called hermetic compressor. 
     Each of first compression mechanism  20  and second compression mechanism  30  is a positive displacement fluid mechanism. 
     First compression mechanism  20  includes first cylinder  25 , first piston  26 , first vane  27 , first spring  29 , first frame  60 , and partition plate  40 . First piston  26  is disposed inside first cylinder  25 . First piston  26  is fitted with first eccentric shaft  13   a  of shaft  13 . First compression chamber  21  is formed between the outer periphery of first piston  26  and the inner periphery of first cylinder  25 . First vane groove  28  is formed in first cylinder  25 . First vane  27  and first spring  29  are housed in first vane groove  28 . The tip of first vane  27  is in contact with the outer periphery of the first piston. First vane  27  is pushed toward first piston  26  by first spring  29 . 
     First frame  60  is disposed at the lower face of first cylinder  25 , and partition plate  40  is disposed at the upper face of first cylinder  25 . First cylinder  25  is sandwiched between first frame  60  and partition plate  40 . In first compression chamber  21 , a first suction chamber and a first compression-discharge chamber are formed by being partitioned by first vane  27 . 
     Second compression mechanism  30  includes second cylinder  35 , second piston  36 , a second vane (not shown), a second spring (not shown), second frame  70 , and partition plate  40 . Second cylinder  35  is concentrically arranged with respect to first cylinder  25 . Second piston  36  is disposed inside second cylinder  35 . Second piston  36  is fitted with a second eccentric shaft (not shown) of shaft  13 . Second compression chamber  31  is formed between the outer periphery of second piston  36  and the inner periphery of second cylinder  35 . A second vane groove is formed in second cylinder  35 . A second vane and a second spring are housed in the second vane groove. The tip of the second vane is in contact with the outer periphery of the second piston. The second vane is pushed toward second piston  36  by the second spring. Second frame  70  is disposed at the upper face of second cylinder  35 , and partition plate  40  is disposed at the lower face of the second cylinder  35 . Second cylinder  35  is sandwiched between second frame  70  and partition plate  40 . In second compression chamber  31 , a second suction chamber and a second compression-discharge chamber are formed by being partitioned by the second vane. 
     Furthermore, the eccentricity direction of first eccentric shaft  13   a  is deviated from the eccentricity direction of second eccentric shaft  13   b  by 180 degrees. That is, the phase of first piston  26  is deviated from the phase of second piston  36  by 180 degrees in a rotation angle of shaft  13 . 
     Furthermore, first discharge space  24  in which the refrigerant compressed by first compression chamber  21  is discharged is provided in first frame  60 . The refrigerant (working fluid) compressed by first compression chamber  21  is introduced into first suction chamber  21   a  of first compression chamber  21  through first suction path  96 . The refrigerant discharged from first compression-discharge chamber  21   b  of first compression chamber  21  is flown into first discharge space  24  from first discharge hole  22  formed in first frame  60 . 
     Furthermore, first check valve  23  is provided at first discharge hole  22 . First check valve  23  prevents refrigerant from being flown from first discharge space  24  to first compression chamber  21 . Furthermore, single-stage compression communication passage  91  and single-stage compression discharge hole  92  are formed between first discharge space  24  and sealed vessel  11 . Single-stage compression discharge hole  92  is formed at second frame  70 . Single-stage compression communication passage  91  and single-stage compression discharge hole  92  make first discharge space  24  communicate with an inside of sealed vessel  11 . Furthermore, third check valve  93  is provided at single-stage compression discharge hole  92 . Third check valve  93  prevents refrigerant from being flown from the inside of sealed vessel  11  to first ejection space  24 . 
     The refrigerant compressed in second compression chamber  31  is introduced into a second suction chamber (not shown) of second compression chamber  31  through second suction path  97 . The refrigerant discharged from the second compression-discharge chamber (not shown) of a second compression chamber  31  is introduced inside sealed vessel  11  from second discharge hole  32 . Second discharge hole  32  is formed at second frame  70 . 
     Second check valve  33  is provided at second discharge hole  32 . Second check valve  33  prevents refrigerant from being flown from the inside of sealed vessel  11  to second compression chamber  31 . 
     Two-stage compression communication passage  94  makes first discharge space  24  connect with switch valve  95  (control element), and makes first discharge space  24  communicate with second suction path  97  ( FIG. 2 ) or blocks the communication ( FIG. 1 ) depending on the state of switch valve  95 . 
     Discharge path  90  penetrates an upper portion of sealed vessel  11 . Discharge path  90  introduces compressed refrigerant outside sealed vessel  11 . Discharge path  90  is connected to condenser  2  to supply high-pressure refrigerant to condenser  2 . 
     First suction path  96  (first connection pipe  53 ) connects first compression mechanism  20  and accumulator  50  and introduces refrigerant to be compressed from accumulator  50  to first compression chamber  21  of first compression mechanism  20 . 
     Second suction path  97  connects second compression mechanism  30  and switch valve  95  serving as a control element. To switch valve  95 , an end of second suction path  97 , an end of second connection pipe  54  connected with accumulator  50 , and an end of two-stage compression communication passage  94  are connected. Switch valve  95  selectively makes one of second connection pipe  54  and two-stage compression communication passage  94  communicate with second suction path  97  and blocks the path between the other one and second suction path  97 . In other words, switch valve  95  selectively makes second compression chamber  31  communicate with evaporator  3  or makes second compression chamber  31  communicate with two-stage compression communication passage  94 . 
     Injection pipe  5  is connected at an upper portion of second suction path  97  connecting second compression mechanism  30  and switch valve  95 . Second suction path  97  is equipped with connection part  80  with injection pipe  5  on the downstream side of switch valve  95 . Second suction path  97  joins the gas refrigerant introduced from gas-liquid separator  6  through injection pipe  5  and the refrigerant introduced from switch valve  95  and introduces the gas refrigerant and the refrigerant to second compression mechanism  30 . Second suction path  97  has upward gradient part  97   a  between connection part  80  of injection pipe  5  and second compression mechanism  30 . This preferentially introduces gas refrigerant relatively light in specific gravity to second compression mechanism  30  when the joined refrigerant is watery refrigerant including liquid component. Moreover, liquid storage part  97   b  may be provided so that liquid refrigerant exchanges heat with overheated gas refrigerant to be evaporated. 
     The refrigerant condensed in condenser  2  is decompressed in decompressor  4 . Gas-liquid separator  6  separates some evaporated gas refrigerant and liquid refrigerant. The separated liquid refrigerant further passes through decompressor  4  and is introduced to evaporator  3  as low-pressure refrigerant. In contrast, gas refrigerant separated by gas-liquid separator  6  passes through injection pipe  5  and is joined with the refrigerant introduced from any one of second connection pipe  54  and two-stage compression communication passage  94  at second suction path  97 , and is introduced to second compression mechanism  30 . In the present invention, since injection gas is introduced to a stable pressure region, back flow does not occur in injection pipe  5 . However, means for adjusting or stopping injection pressure may be provided by providing a close valve or a metering valve at injection pipe  5 . 
     To evaporator  3 , the refrigerant decompressed to a low pressure by decompressor  4  is introduced, and liquid refrigerant is evaporated by thermal exchange to be discharged as gas refrigerant. The discharged refrigerant is introduced to accumulator  50  with liquid refrigerant that has failed to be evaporated in evaporator  3 . 
     Accumulator  50  includes accumulation vessel  51 , introduction pipe  52 , first connection pipe  53 , and second connection pipe  54 . Accumulation vessel  51  has an internal space capable of retaining liquid refrigerant and gas refrigerant. Introduction pipe  52  is provided at an upper portion of accumulation vessel  51 . Introduction pipe  52  is connected with evaporator  3  to supply low pressure refrigerant. First connection pipe  53  and second connection pipe  54  penetrate bottom portions of accumulation vessel  51  and are opened to the inner space of accumulation vessel  51 . Note that another member such as a baffle may be provided inside accumulation vessel  51  to prevent liquid refrigerant from being flown into first connection pipe  53  and second connection pipe  54  from introduction pipe  52 . Alternatively, first connection pipe  53  and the second connection pipe may be directly connected with introduction pipe  52  depending on the type of compressor  1 . 
     The exemplary embodiment makes it possible to switch between the refrigeration cycle operation in which the single-stage compressing operation is simultaneously performed by the two compression mechanisms and the refrigeration cycle operation in which the two-stage compressing operation is performed by the two compression mechanisms with the injection of an intermediate pressure, by using switch valve  95 . Hereinafter, the description will be specifically described. 
     First, the case of performing the single-stage compressing operation during low differential pressure in which pressure difference between high pressure and low pressure is small will be described. 
     As illustrated in  FIG. 1 , second suction path  97  and second connection pipe  54  are connected by switch valve  95 . In contrast, second suction path  97  and two-stage compression communication passage  94  are blocked. In this case, first compression mechanism  20  and second compression mechanism  30  are connected to accumulator  50 , so that first compression mechanism  20  and second compression mechanism  30  are connected in parallel. 
     The flow of refrigerant in this case will be specifically described. 
     The refrigerant suctioned from first suction path  96  is compressed by first compression mechanism  20 , and discharged in first discharge space  24  through first discharge hole  22 . On the other hand, two-stage compression communication passage  94  communicating with first discharge space  24  is blocked by switch valve  95 . Consequently, the pressure in first discharge space  24  increases to the level equal to the pressure inside sealed vessel  11 . As a result, the refrigerant discharged in first discharge space  24  passes through single-stage compression communication passage  91  and single-stage compression discharge hole  92 , opens third check valve  93 , and is discharged inside sealed vessel  11 . Furthermore, since second suction path  97  is connected with accumulator  50  via switch valve  95 , the refrigerant suctioned from second suction path  97  is compressed by second compression mechanism  30 , and is discharged inside sealed vessel  11  through second discharge hole  32 . In this context, the refrigerants compressed by respective first compression mechanism  20  and second compression mechanism  30  join inside sealed vessel  11  to be introduced outside sealed vessel  11  through discharge path  90 . 
     Herein, given that the suction volume of first compression mechanism  20  is V 1  and the suction volume of second compression mechanism  30  is V 2 , the suction volume during single-stage compressing operation becomes V 1 +V 2 . In the exemplary embodiment, by making V 1  and V 2  substantially same, workloads of the respective two compression mechanisms are equalized, enabling high efficiency compression behaviors. Furthermore, injection pipe  5  is connected to second suction path  97 , making it possible to use injection pipe  5  as a bypass of evaporator  3 . That is, by adjusting decompressor  4 , the pressure of gas-liquid separator  6  is lowered to be a low pressure to make only gas refrigerant having no latent heat be bypassed from injection pipe  5  to second compression mechanism  30 . This makes it possible to preferentially transmit the liquid refrigerant that essentially needs to be introduced to evaporator  3 , also making it possible to perform higher efficient operation by pressure loss reduction effect in evaporator  3 . 
     Next, the case of performing two-stage injection compressing operation during high differential pressure in which pressure difference between high pressure and low pressure is large will be described. 
     As illustrated in  FIG. 2 , second suction path  97  and two-stage compression communication passage  94  are connected by switch valve  95 , and connection between second suction path  97  and second connection pipe  54  is blocked. In this case, only the first suction path is connected to accumulator  50 , so that first compression mechanism  20  and second compression mechanism  30  are connected in series. 
     The flow of refrigerant in this case will be specifically described. 
     The refrigerant suctioned from first suction path  96  is compressed by first compression mechanism  20 , and discharged in first discharge space  24  through first discharge hole  22 . Herein, two-stage compression communication passage  94  communicating with first discharge space  24  is connected to second suction path  97  via switch valve  95 . Consequently, the refrigerant discharged in first discharge space  24  joins the refrigerant introduced from injection pipe  5  in second suction path  97 , and compressed by second compression mechanism  30 . The refrigerant compressed by second compression mechanism  30  is discharged inside sealed vessel  11  through second discharge hole  32 . Herein, first compression mechanism  20  and second compression mechanism  30  are connected in series, so that the pressure in first discharge space  24  becomes an intermediate pressure lower than the discharge pressure of second compression mechanism  30 . Consequently, third check valve  93  is closed by the pressure difference between first discharge space  24  and the inside of sealed vessel  11 . As a result, all of the refrigerant compressed by first compression mechanism  20  is flown into second compression mechanism  30 . Furthermore, the refrigerant compressed by second compression mechanism  30  is discharged inside sealed vessel  11 , and introduced outside the sealed vessel through discharge path  90 . 
     In the ratio between gas refrigerant and liquid refrigerant among the refrigerant separated by the gas-liquid separator, gas component increases as the pressure difference between high pressure and low pressure of the refrigeration cycle becomes larger. In the case of the conventionally proposed two-stage dedicated compressor, securing sufficient gas injection refrigerant is impossible under low load conditions where pressure difference is small, so that it is preferable to preliminarily design the heights of first cylinder  25  and second cylinder  35  to be different in order to perform the two-stage compressing operation. As a result, suction volume V 1  of first compression mechanism  20  becomes larger than suction volume V 2  of second compression mechanism  30 . However, in the exemplary embodiment, the two-stage compressing operation is limited only to a high differential pressure condition that allows injection gas to be sufficiently secured, enabling suction volume V 1  of first compression mechanism  20  to be substantially equal to suction volume V 2  of second compression mechanism  30 . 
     This enables the heights of first cylinder  25  and second cylinder  35  to be equal to thereby make the shapes and heights of first piston  26  and second piston  36  equal. Likewise, this enables the shapes and heights of first eccentric shaft  13   a  and the second eccentric shaft to be equal. As a result, deviating the phases of first eccentric shaft  13   a  and the second eccentric shaft by 180 degrees makes it possible to structure two compression mechanisms without deviating the gravity center of a rotation member from the shaft center, making it possible to provide low vibration from a low speed to a high speed. 
     Furthermore, the volume ratio of second compression mechanism  30  can be made larger than that of the conventional two-stage dedicated compressor, making it possible to cope with refrigeration recycle operation with a higher injection rate during high differential pressure operation. This makes it possible to sufficiently exert ability improvement effects during low outside air temperature operation. This point will be described below in detail. 
     In the case of the conventional two-stage dedicated compressor, the volume of the second compression chamber needs to be made smaller than the volume of the first compression chamber to keep the two-stage compressing operation in consideration of the need to perform operation with no injection during low load operation. The graph illustrated in  FIG. 5  illustrates the volume ratio of the second compression chamber with respect to the first compression chamber and the maximum ratio of gas injection refrigerant capable of being passed through the injection pipe among the refrigerant in the refrigeration cycle (called injection ratio) when outside air temperature is assumed to be −30° C. The configuration of the present invention makes it possible to increase the volume ratio of second compression mechanism  30  as compared with the configuration of the conventional two-stage dedicated compressor in which the volume ratio of the second compression chamber is small, making it possible to increase the injection ratio. This makes it possible to exert greater injection effect during low outside air temperature to provide high capability. 
     Next, separation of oil from refrigerant will be described. 
     The compressor of a high pressure type in which refrigerant is once discharged inside sealed vessel  11 , passed through discharge path  90 , and thereafter introduced outside sealed vessel  11  typically has oil storage part  15  in the sealed vessel. This is to prevent leakage of lubricant of each slide portion of the compression mechanism and refrigerant being compressed. Compressor  1  used in the refrigeration cycle device according to the exemplary embodiment also has oil storage part  15  to prevent leakage of the lubricant of each slide portion of the compression mechanism and the refrigerant being compressed. 
     Some of the oil introduced in the compression mechanism portion is mixed with refrigerant during compression and the refrigerant and the oil are discharged together inside sealed vessel  11 . Oil, which is larger in specific gravity than that of refrigerant, of the fluid that is mixture of the refrigerant and the oil discharged inside sealed vessel  11  is separated from the refrigerant by centrifugal force and gravitational force while being moved upward at the vicinity of motor  12  or inside the sealed vessel  11 . The separated oil returns to oil storage part  15  inside sealed vessel  11 . The above behavior enables the high-pressure type compressor according to the exemplary embodiment capable of separating the oil from the refrigerant in sealed vessel  11  to reduce the amount of oil introduced outside sealed vessel  11  through discharge path  90 , preventing condenser  2  and evaporator  3  from being lowered in their efficiency. This makes it possible to provide a refrigeration cycle device operable with high efficiency. 
     According to the present exemplary embodiment, in both of the single-stage compressing operation and the two-stage injection compressing operation, all refrigerant is introduced outside sealed vessel  11  through discharge path  90  after discharged inside sealed vessel  11 . This enables the refrigerant to be discharged outside sealed vessel  11  after refrigerant and oil are fully separated inside sealed vessel  11 , preventing condenser  2  and evaporator  3  from being lowered in their efficiency. This also makes it possible to reduce oil to be taken out from sealed vessel  11 , making it possible to stably secure oil in oil storage part  15  to prevent seizure and abnormal wear of the components of the compression mechanism portion. 
     Note that in the exemplary embodiment, first compression mechanism  20  is disposed on the far side of motor  12  and second compression mechanism  30  is disposed on the near side of the motor  12 . That is, motor  12 , second compression mechanism  30 , and first compression mechanism  20  are aligned in this order along the axis direction of shaft  13 . This order makes it possible to make first discharge space  24  wide without being interfered by motor  12  and the like as illustrated in  FIGS. 1 and 2 , making it possible to sufficiently yield refrigerant pulsation lowering effect in first discharge space  24 . This makes it possible to further reduce pressure pulsation in second suction path  97  connected with injection pipe  5 , making it possible to reduce vibration and noise of refrigerant pipe. 
     Note that first vane  27  and the second vane may be unified with first piston  26  and second piston  36 , respectively. That is, the vane and the piston may be a so-called swing piston. Furthermore, first piston  26  and first vane  27  may be jointed with second piston  36  and the second vane. 
     Furthermore, the effects of the present invention can be also obtained by other positive-displacement compression mechanism such as a scroll compression system, a screw compression system, and the like, non positive-displacement compression mechanism such as a turbo type, and a combination (not shown) of the different compression systems without using the rotary compression system for first compression mechanism  20  and second compression mechanism  30 . 
     Motor  12  is structured by stator  12   a  and rotor  12   b . Stator  12   a  is fixed to the inner periphery of sealed vessel  11 . Rotor  12   b  is fixed to shaft  13  and rotates with shaft  13 . By the motor  12 , first piston  26  and second piston  36  are moved inside first cylinder  25  and second cylinder  35 , respectively. As motor  12 , motors that can change rotation numbers thereof such as an interior permanent magnet synchronous motor (IPMSM) and a surface permanent magnet synchronous motor (SPMSM) can be used. 
     Controller  8  adjusts the rotation number of motor  12 , that is, a rotation number of compressor  1  by controlling inverter  7 . As controller  8 , a digital signal processor (DSP) can be used including an A/D conversion circuit, an input-output circuit, an arithmetic circuit, a storage device, and the like. 
     INDUSTRIAL APPLICABILITY 
     The present invention is useful for a refrigeration cycle device that can be used in an electrical product such as a hydronic heater, an air conditioner, and a hot water dispenser in which their evaporator is used under a low temperature environment. 
     REFERENCE MARKS IN THE DRAWINGS 
     
         
         
           
               1  compressor 
               2  condenser 
               3  evaporator 
               4  decompressor 
               5  injection pipe 
               6  gas-liquid separator 
               7  inverter 
               7  controller 
               8  sealed vessel 
               11  motor 
               12   a  stator 
               12   b  rotor 
               13  shaft 
               13   a  first eccentric shaft 
               13   b  second eccentric shaft 
               14  terminal 
               15  oil storage part 
               20  first compression mechanism 
               21  first compression chamber 
               21   a  first suction chamber 
               21   b  first compression-discharge chamber 
               22  first discharge hole 
               23  first check valve 
               24  first discharge space 
               25  first cylinder 
               26  first piston 
               27  first vane 
               28  first vane groove 
               29  first spring 
               30  second compression mechanism 
               31  second compression chamber 
               32  second discharge hole 
               33  second check valve 
               35  second cylinder 
               35  second piston 
               36  second vane groove 
               38  partition plate 
               40  accumulator 
               51  accumulation vessel 
               52  introduction pipe 
               53  first connection pipe 
               54  second connection pipe 
               60  first frame 
               70  second frame 
               80  connection part 
               90  discharge path 
               91  single-stage compression communication passage 
               92  single-stage compression discharge hole 
               93  third check valve 
               94  two-stage compression communication passage 
               95  switch valve (control element) 
               96  first suction path 
               97  second suction path 
               97   a  upward gradient part 
               97   b  liquid storage part