Patent Publication Number: US-8991296-B2

Title: Compressor

Description:
FIELD OF THE INVENTION 
     The present invention relates to a compressor which separates, for example, oil contained in discharged gas and returns the separated oil to a low pressure zone. 
     BACKGROUND OF THE INVENTION 
     Patent Document 1 discloses a compressor equipped with an oil reservoir chamber. An oil separation chamber is formed in the rear housing member of the compressor so as to extend in the radial direction of the rear housing member, and the oil reservoir chamber is provided below the oil separation chamber and also at the rear end of the rear housing member so as to project outwardly. A through hole connecting the oil separation chamber with the oil reservoir chamber is formed in the rear housing member. Further, the rear housing member is provided with a discharge chamber for discharging compressed refrigerant gas including misted oil and an inflow passage for connecting the discharge chamber with the oil separation chamber. The oil separation chamber is connected to a discharge hole, and a check valve unit for preventing the refrigerant gas from reversely flowing from the oil separation chamber to the discharge chamber is provided in the discharge hole. 
     The check valve unit has a pipe portion projecting to the oil separation chamber, and the pipe portion and the oil separation chamber constitute oil separating means. A gas return passage, which connects an annular port in a base portion provided in the check valve unit with an oil reservoir chamber, is formed in the rear housing member. The gas return passage is smaller (about 1 mm) in diameter than the through hole and functions as a passage for returning the refrigerant gas which has entered the oil reservoir chamber to a discharge path including the annular port. 
     In the above-described compressor, compressed refrigerant gas in the discharge chamber flows into the oil separation chamber by way of the inflow passage. The refrigerant gas, which has entered the oil separation chamber, collides with the outer circumferential surface of the pipe portion and swirls around the outer circumferential surface, by which misted oil contained in the refrigerant gas is separated from the refrigerant gas. The thus separated oil collects at the bottom of the oil separation chamber and flows into the oil reservoir chamber from an inlet of the through hole. 
     Oil contained in the oil reservoir chamber is returned through the oil return passage to a crank chamber and others. Refrigerant gas, from which oil has been separated, is supplied to an external refrigerant circuit through a discharge pipe by way of a pipe portion, a check valve and others. Since the gas return passage is formed between the discharge path and the oil reservoir chamber of refrigerant gas, a flow of refrigerant gas is created due to a pressure difference ΔP between the oil separation chamber and the discharge path. Oil, which has been separated from refrigerant gas in the oil separation chamber, joins with the flow and immediately flows into the oil reservoir chamber through the through hole. 
     Patent Document 2 discloses a swash-plate type compressor equipped with an oil separation chamber. A projected portion is provided in an upper part of the rear cylinder block of the compressor, and a cyclone-type oil separation chamber is formed in the projected portion. Further, the compressor is provided with a connecting hole adjacent to the oil separation chamber and the connecting hole is connected to a muffler chamber formed in the rear cylinder block. A primary oil reservoir for collecting separated oil is formed below the oil separation chamber. A main oil reservoir is provided on the side of the oil separation chamber and the primary oil reservoir. An oil return hole connected to a swash plate chamber, which is a low pressure zone, is opened in a valve seat face at the bottom of the main oil reservoir. A reed valve made of a spring steel plate is provided in the opening of the oil return hole, and the reed valve is deformed depending on a pressure difference between a high pressure zone and a low pressure zone and capable of controlling the flow rate of oil flowing through the oil return hole. 
     In the above-described compressor, high-pressure compressed refrigerant gas flowing from the discharge chamber into the muffler chamber is introduced into an oil separation chamber via the connecting hole. The refrigerant gas introduced into the oil separation chamber swirls along the circumferential wall of the oil separation chamber, by which misted oil contained in the refrigerant gas is separated from the refrigerant gas by the actions of centrifugal force. The thus separated oil is collected in the primary oil reservoir and reserved in the main oil reservoir through the connecting hole due to a pressure difference between the high pressure zone and the low pressure zone. 
     The opening degree of the reed valve is controlled depending on a pressure difference between the high pressure zone and the low pressure zone. For example, when the pressure difference is small, the reed valve is opened to a great degree. Therefore, a greater amount of oil is returned from the main oil reservoir to the swash plate chamber through the oil return hole. When the pressure difference is great, the reed valve is opened to a small degree, and a small amount of oil is returned from the main oil reservoir to the swash plate chamber by way of the oil return hole. 
     However in the compressor disclosed in Patent Document 1, refrigerant gas is allowed to flow due to the pressure difference ΔP, by which oil separated from the oil separation chamber can be directly fed to the oil reservoir chamber. However, when machining constraints such as breakage of cutting tools are taken into account, the oil reservoir chamber must be arranged at a place proximate to the oil separation chamber due to the necessity for providing a small-diameter through hole (about 1 mm). On arrangement of the oil reservoir chamber at a place proximate to the oil separation chamber, the rear housing member is larger in dimension to result in a larger compressor. 
     In the compressor disclosed in Patent Document 2, a reed valve is provided, by which there is provided a structure to feed oil from the primary oil reservoir to the main oil reservoir due to a pressure difference between the oil separation chamber, which is a high pressure zone, and the swash plate chamber, which is a low pressure zone. However, it is quite difficult to control the opening degree of the reed valve depending on the pressure difference, when consideration is given to variations in the spring constant of a raw material of the reed valve and others in the manufacturing process. Therefore, there is a concern that the opening degree of the reed valve might not be appropriately controlled depending on the pressure difference. Specifically, the reed valve can be opened greatly when there is no intension to feed high-pressure refrigerant gas from the high pressure zone to the low pressure zone. In order to solve this problem, there is proposed an idea that a connecting hole is narrowed in such a manner that high-pressure refrigerant gas is not allowed to enter the swash plate chamber by way of the connecting hole connecting the primary oil reservoir with a main oil reservoir. However, due to the machining constraints, the main oil reservoir needs to be located at a place proximate to the primary oil reservoir. As a result, as in Patent Document 1, the compressor is made large in dimension. 
     As described above, the compressors disclosed in Patent Document 1 and Patent Document 2 have a problem that the flexibility of the design in arranging an oil separator and a reservoir of separated oil is reduced.
     Patent Document 1: Japanese Laid-Open Patent Publication No. 2004-218610   Patent Document 2: Japanese Laid-Open Patent Publication No. 5-240158   

     SUMMARY OF THE INVENTION 
     Accordingly, it is an objective of the present invention to provide a compressor that can be made compact. 
     To achieve the foregoing objective, and in accordance with one aspect of the present invention, a compressor for compressing oil-containing refrigerant gas is proposed. The compressor is provided with a discharge chamber, a discharge passage, a lid, an oil separator, an introduction passage, an oil reservoir, an oil reservoir chamber, and an oil passage. Compressed refrigerant gas is discharged to the discharge chamber. The discharge passage is formed in the discharge chamber. The lid is located in the discharge passage to partition the discharge chamber from the discharge passage. The oil separator is located in the discharge passage, and a separation chamber is formed between the oil separator and the lid. The oil separator separates oil from the refrigerant gas introduced into the separation chamber. The introduction passage introduces the refrigerant gas into the separation chamber from the discharge chamber. The oil reservoir is located around the lid to reserve oil separated from the refrigerant gas. The reservoir chamber reserves the separated oil and is connected to a low pressure zone in the compressor, the pressure of which is lower than the discharge chamber. The oil passage connects the oil reservoir with the reservoir chamber. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view illustrating a compressor according to a first embodiment of the present invention; 
         FIG. 2  is an enlarged view of a main portion of the compressor shown in  FIG. 1 ; 
         FIG. 3  is a schematic cross-sectional view taken along line  3 - 3  shown in  FIG. 2 ; 
         FIG. 4  is an enlarged view of a main portion of a compressor according to a second embodiment of the present invention; 
         FIG. 5  is an enlarged view of a main portion of a compressor according to a third embodiment of the present invention; 
         FIG. 6  is an enlarged view of a main portion of a compressor according to a fourth embodiment of the present invention; 
         FIG. 7  is an enlarged view of a main portion of a compressor according to a fifth embodiment of the present invention; 
         FIG. 8  is an enlarged view of a main portion of a compressor according to a sixth embodiment of the present invention; 
         FIG. 9  is an enlarged view of a main portion of a compressor according to a seventh embodiment of the present invention; 
         FIG. 10  is an enlarged view of a main portion of a compressor according to an eighth embodiment of the present invention; 
         FIG. 11  is an enlarged view of a main portion of a compressor according to a ninth embodiment of the present invention; 
         FIG. 12  is a perspective view of a lid according to a ninth embodiment of the present invention; 
         FIG. 13  is an enlarged view of a main portion of a compressor according to a tenth embodiment of the present invention; 
         FIG. 14  is a perspective view of a lid according to a an eleventh embodiment of the present invention; 
         FIG. 15(   a ) is a schematic cross-sectional view of a compressor according to a modification of the ninth through eleventh embodiments; 
         FIG. 15(   b ) is an enlarged view of a main portion of a compressor according to another modification; 
         FIG. 16  is an enlarged view of a main portion of a compressor according to a first modified embodiment; and 
         FIG. 17  is an enlarged view of a main portion of a compressor according to a second modified embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, a variable displacement swash plate type compressor (hereinafter, simply referred to as a compressor) according to a first embodiment will be described with reference to  FIGS. 1 to 3 . 
     As shown in  FIG. 1 , the housing of the compressor is provided with a front housing member  12  joined to the front end of a cylinder block  11  and a rear housing member  14  joined to the rear end of the cylinder block  11  via a valve/port forming member  13 . A crank chamber  15  is defined in a zone enclosed by the cylinder block  11  and the front housing member  12 . A drive shaft  16  is disposed in the crank chamber  15  in a rotatable manner. The drive shaft  16  is coupled to an engine  17  mounted on a vehicle and rotated by energy supplied from the engine  17 . 
     In the crank chamber  15 , a lug plate  18  is fixed to the drive shaft  16  so as to make an integrated rotation with the drive shaft  16 . Further, a swash plate  19  is accommodated in the crank chamber  15 . The swash plate  19  is supported by the drive shaft  16  and capable of sliding on the drive shaft  16  along the axial line of the drive shaft  16  and also capable of tilting with respect to the drive shaft  16 . A hinge mechanism  20  is located between the lug plate  18  and the swash plate  19 . The swash plate  19  is capable of rotating in synchronization with the lug plate  18  and the drive shaft  16  via the hinge mechanism  20  and also capable of tilting while moving in the axial direction of the drive shaft  16 . Further, the inclination angle of the swash plate  19  is controlled by a displacement control valve  21  as described below. 
     A plurality of cylinder bores  11   a  (only one of them is shown in  FIG. 1 ) are formed in the cylinder block  11 , and a single headed piston  22  is accommodated in each of the cylinder bores  11   a  so as to reciprocate. Each of the pistons  22  is anchored on the outer circumference of the swash plate  19  with shoes  23 . Therefore, the rotational movement of the swash plate  19  in association with the rotation of the drive shaft  16  is converted to linear reciprocation of the piston  22  with the shoe  23 . 
     Compression chambers  24  each enclosed by one of the pistons  22  and the valve/port forming member  13  are defined on the back face (on the right in  FIG. 1 ) of the cylinder bores  11   a.    
     A suction chamber  25  is defined in the rear housing member  14 , and a discharge chamber  26  is defined around the suction chamber  25 . 
     Refrigerant gas in the suction chamber  25  is drawn into the compression chamber  24  via a suction port  27  and an inlet valve  28  formed in the valve/port forming member  13  due to the movement of the piston  22  from a position of the top dead center to a position of the bottom dead center. The refrigerant gas drawn into the compression chamber  24  is compressed to a predetermined pressure due to the movement of the piston  22  from a position of the bottom dead center to a position of the top dead center, and then discharged to the discharge chamber  26  via a discharge port  29  and a discharge valve  30  formed in the valve/port forming member  13 . 
     A bleed passage  31  and a supply passage  32  are provided in the housing. The bleed passage  31  is used to exhaust refrigerant gas from the crank chamber  15  to the suction chamber  25 . The supply passage  32  is used to introduce the discharged refrigerant gas in the discharge chamber  26  to the crank chamber  15 . A displacement control valve  21  is located in the supply passage  32 . 
     The opening degree of the displacement control valve  21  is adjusted, by which the amount of high-pressure refrigerant gas introduced into the crank chamber  15  via the supply passage  32  to the amount of refrigerant gas exhausted from the crank chamber  15  via the bleed passage  31  is controlled to determine a pressure in the crank chamber  15 . 
     Thereby, a difference between the pressure in the crank chamber  15  behind the piston  22  and the pressure in the compression chamber  24  is changed, and an inclination angle of the swash plate  19  with respect to the drive shaft  16  is accordingly changed. As a result, changed is the stroke of each piston  22 , that is, the displacement of the compressor. 
     For example, when the internal pressure of the crank chamber  15  is decreased, the inclination angle of the swash plate  19  is increased, and the compressor displacement is increased. The swash plate  19  indicated by the chain double-dashed line in  FIG. 1  is in a state that the inclination angle is maximum. In contrast, when the internal pressure of the crank chamber  15  is increased, the inclination angle of the swash plate  19  is decreased, and the compressor displacement is decreased. The swash plate  19  indicated by the solid line in  FIG. 1  is in a state that the inclination angle is minimum. 
     As shown in  FIGS. 1 and 2 , a cylindrical hole  33  is formed in the upper part of the rear housing member  14  so as to be connected to the discharge chamber  26 . The cylindrical hole  33  is provided with a discharge passage located in the discharge chamber  26 . The cylindrical hole  33  extends parallel with the axial line of the drive shaft  16 . A cylindrical oil separator  35  is disposed at the center of the cylindrical hole  33  in the axial direction. The oil separator  35  is fixed to the cylindrical hole  33  by orienting a cylindrical portion  35   a  forward and fitting a base portion  35   b  greater in diameter than the cylindrical portion  35   a  into the cylindrical hole  33 . Further, a check valve  36  is accommodated adjacent to the oil separator  35  further behind (on the right in  FIG. 2 ) the center of the cylindrical hole  33  axial direction. A check valve  36  is used to prevent a refrigerant from reversely flowing from an external refrigerant circuit  48  to the discharge chamber  26 . 
     A diameter-enlarged hole  33   a , which is greater in diameter than the cylindrical hole  33 , is formed at the inlet portion of the cylindrical hole  33  (on the left in  FIG. 2 ). Thereby, a step portion is formed on the inner wall surface  33   b  of the cylindrical hole  33 . A lid  34  for partitioning the discharge chamber  26  from the cylindrical hole  33  is attached to the inlet portion of the cylindrical hole  33 . The lid  34  is provided with a flange portion  34   a  and an outer ring portion  34   b , and a step portion is formed on the outer circumferential surface of the lid  34  by the flange portion  34   a  and the outer ring portion  34   b . The lid  34  is fixed to the cylindrical hole  33  by fitting the outer ring portion  34   b  into the inner wall surface  33   b  of the cylindrical hole  33  and also fitting the flange portion  34   a  into the diameter-enlarged hole  33   a . The thickness dimension e of the flange portion  34   a  in the axial direction is set to be smaller than the depth dimension f of the diameter-enlarged hole  33   a  in the axial direction (e&lt;f). 
     A separation chamber  42  is formed in a space enclosed by the lid  34 , the oil separator  35  and the inner wall surface  33   b  of the cylindrical hole  33 . The discharge chamber  26  and the separation chamber  42  are connected via an introduction passage  40 , and discharged refrigerant gas is introduced from the discharge chamber  26  to the separation chamber  42  through the introduction passage  40 . 
     As shown in  FIG. 3 , the introduction passage  40  is constituted in such a manner that a streamline of discharged refrigerant gas introduced into the separation chamber  42  is given an approximate tangent of the transverse cross-section circle on the inner wall surface  33   b  of the separation chamber  42 . Therefore, the discharged refrigerant gas introduced to the separation chamber  42  through the introduction passage  40  swirls along the inner wall surface  33   b  in a clockwise direction. 
     In the separation chamber  42 , the discharged refrigerant gas swirls along the inner wall surface  33   b  in a space between the inner wall surface  33   b  and the cylindrical portion  35   a  of the oil separator  35 , by which oil contained in the discharged refrigerant gas is centrifuged from the discharged refrigerant gas. The discharged refrigerant gas, from which oil has been separated, is introduced from the separation chamber  42  into the check valve  36  through a conduit  35   c  in the oil separator  35 , and drained to the discharge flange  43  through a drain passage  41 . The conduit  35   c  extends through the oil separator  35  in the longitudinal direction and is opened in the separation chamber  42  at a position of the front end, which is opposed to the lid  34 . The thus separated oil collects in the vicinity below the lid  34  at the bottom of the separation chamber  42 . 
     In a state that the lid  34  is fitted into the cylindrical hole  33 , there is formed an annular space  37  between a step portion on the outer circumferential surface of the lid  34  and a step portion on the inner wall surface  33   b  of the separation chamber  42 . The annular space  37  is an annular groove formed around the lid  34 , the cross section of which is rectangular. The annular space  37  functions as an oil reservoir connected to the separation chamber  42 . 
     Further, a step  33   c  having a constant width is formed on the inner wall surface  33   b  of the separation chamber  42 , which is located below the lid  34  and fitted into the outer ring portion  34   b  of the lid  34 . This step  33   c  is used to form a constriction passage  38  which connects the separation chamber  42  with the annular space  37 . Therefore, oil G separated from discharged refrigerant gas to collect at the bottom of the separation chamber  42  flows to the annular space  37  through the constriction passage  38 . 
     In  FIG. 1 , a discharge flange  43  is provided on the upper face of the cylinder block  11  so as to project outwardly. A high pressure fluid chamber  44  and a low pressure fluid chamber  45  are formed in the discharge flange  43 , and a constriction portion  46  is provided between the fluid chambers  44 ,  45 . A reservoir chamber  47  for reserving oil is provided below the low pressure fluid chamber  45 . 
     The high pressure fluid chamber  44  is connected to the separation chamber  42  via the drain passage  41 , and the low pressure fluid chamber  45  is connected to the external refrigerant circuit  48  via a port (not shown). Therefore, discharged refrigerant gas drained from the separation chamber  42  is introduced into the high pressure fluid chamber  44  through the drain passage  41 . The refrigerant gas flows into the low pressure fluid chamber  45  by way of the constriction portion  46 . 
     The reservoir chamber  47  and the annular space  37  are connected via the oil passage  39 . Therefore, the separation chamber  42  and the reservoir chamber  47  are connected via the constriction passage  38 , the annular space  37  and the oil passage  39 . The reservoir chamber  47  is connected to the crank chamber  15 , which is a low pressure zone, and others via an oil return passage (not shown). 
     Next, an explanation will be made for the actions of the above described compressor. 
     First, when compressed refrigerant gas is discharged from the discharge chamber  26 , the discharge refrigerant gas is introduced into the separation chamber  42  through the introduction passage  40 . The discharge refrigerant gas introduced into the separation chamber  42  flows toward the front end of the cylindrical portion  35   a , while swirling along the inner wall surface  33   b  in a space between the inner wall surface  33   b  and the cylindrical portion  35   a  of the oil separator  35 . At this time, misted oil contained in the discharged refrigerant gas is separated from the refrigerant gas by the actions of centrifugal force. The thus separated oil swirls inside the separation chamber  42  due to the influence of the swirling refrigerant gas, a part of which drops along the inner wall surface  33   b  of the separation chamber  42  due to its own weight and collects in the vicinity below the lid  34  at the bottom of the separation chamber  42 . 
     Discharged refrigerant gas, from which oil has been separated, is introduced into the check valve  36  from the front end of the cylindrical portion  35   a  of the oil separator  35  through the conduit  35   c . The discharged refrigerant gas, from which oil has been separated, is drained to the discharge flange  43  through the drain passage  41  after being introduced into the check valve  36 . Then, the discharge refrigerant gas introduced into the high pressure fluid chamber  44  of the discharge flange  43  flows into the low pressure fluid chamber  45  and then is supplied to the external refrigerant circuit  48  via the discharge port. 
     Oil G, which collects at the bottom of the separation chamber  42 , flows to the annular space  37  through the constriction passage  38 . The annular space  37  and the reservoir chamber  47  are connected, and the reservoir chamber  47  is connected to the crank chamber  15 , which is a low pressure zone of a pressure lower than the discharge chamber  26 , and others. Therefore, developed is a pressure difference ΔP between the separation chamber  42  and the reservoir chamber  47 . That is, the pressure in the separation chamber  42  connected to the discharge chamber  26  is greater than that in the reservoir chamber  47 . Oil, which flows from the separation chamber  42  to the annular space  37 , elevates along the annular space  37  and flows into the reservoir chamber  47  through the oil passage  39  due to the actions of the pressure difference ΔP. 
     The oil reserved in the reservoir chamber  47  is returned to the crank chamber  15  and others through an oil return passage (not shown) and used in lubricating sliding parts of the compressor. 
     As so far described in detail, according to the present embodiment, the following advantages are obtained. 
     (1) The oil separator  35  is arranged in the cylindrical hole (discharge passage)  33  in the discharge chamber  26 , and the lid  34  is used to close the inlet portion of the cylindrical hole  33  to form a separation chamber  42 . Then, an annular space  37  is formed around the lid  34 , and a constriction passage  38  is provided for connecting the annular space  37  with the separation chamber  42 . Thereby, oil G, which collects in the separation chamber  42 , is allowed to flow to the reservoir chamber  47  further above the separation chamber  42  through the annular space  37  by utilizing a pressure difference ΔP between the separation chamber  42  and the reservoir chamber  47 . Therefore, the annular space  37  and an oil passage  39  for connecting the annular space  37  with the reservoir chamber  47  can be processed by setting the diameter arbitrarily. As a result, the flexibility of the design in arranging the reservoir chamber  47  is improved, which allows the compressor to be miniaturized. 
     (2) The constriction passage  38  for connecting the annular space  37  with the separation chamber  42  is provided to prevent high-pressure discharge refrigerant gas from reversely flowing from the separation chamber  42  to the reservoir chamber  47 , thus allowing only oil G to pass. 
     (3) The lid  34  is attached between the discharge chamber  26  and the separation chamber  42 , by which the separated oil G is reserved in the vicinity below the lid  34  at the bottom of the separation chamber  42 , without allowing the gas to flow to the discharge chamber  26 . As a result, the thus reserved oil G is effectively drained to the reservoir chamber  47 . 
     (4) Since a step portion provided on the outer circumferential surface of the lid  34  and the inner wall surface of the separation chamber  42  is used to form an annular space  37 , no special processing for forming the annular space  37  is needed. Therefore, the annular space  37  is made easily in a reduced number of processing steps. 
     (5) Only the step portion  33   c  is provided on the inner wall surface  33   b  of the separation chamber  42 , thereby forming the constriction passage  38  which connects the separation chamber  42  with the annular space  37 . Therefore, the constriction passage  38  can be made easily in a reduced number of processing steps. 
     Next, an explanation will be made for a compressor of a second embodiment by referring to  FIG. 4 . 
     The present embodiment is constituted in the same way as the first embodiment except that the configuration of the constriction passage connecting the separation chamber  42  with the annular space  37 . Therefore, some of the symbols or numerals used in the previous explanation are used commonly here for the sake of convenience. An explanation will be omitted from common constitutions and made only for changed constitutions. 
     As shown in  FIG. 4 , the constriction passage  51  of the present embodiment is formed by a through hole  52  provided in the lowest part of the outer ring portion  34   b  of the lid  34  so as to extend in a perpendicular direction (vertical direction in  FIG. 4 ) with respect to the axial line of the lid  34 . The separation chamber  42  is connected to the annular space  37  by the constriction passage  51 . Therefore, oil G separated by the discharge refrigerant gas and reserved at the bottom of the separation chamber  42  flows into the annular space  37  through the constriction passage  51 . 
     According to the present embodiment, the following advantage are obtained in addition to the advantages of (1) through (4) described in the first embodiment. 
     (1) The through hole  52  is formed in the outer ring portion  34   b  of the lid  34 , thereby forming the constriction passage  51  which connects the separation chamber  42  with the annular space  37 . It is not necessary to process the housing of the compressor but sufficient to process only the lid  34  for forming the constriction passage  51 . That is, the constriction passage  51  can be made easily. 
     Next, an explanation will be made for a compressor of a third embodiment by referring to  FIG. 5 . 
     The present embodiment is constituted in the same way as the first embodiment except that the configuration of the lid  34  and the oil separator  35 . Therefore, some of the symbols and numerals used in the previous explanation will be used commonly here for the sake of convenience. An explanation will be omitted from common constitutions and made only for changed constitutions. 
     As shown in  FIG. 5 , in the compressor of the present embodiment, a lid  62 , which partitions the separation chamber  42  from the discharge chamber  26 , is integrally formed with the oil separator  35 . Specifically, a member  61  is constituted by the lid  62 , which partitions the separation chamber  42  from the discharge chamber  26 , a cylindrical portion  63  functioning as the oil separator  35 , and a base portion  64  for reserving the cylindrical portion  63 . A conduit  65  is provided in the member  61 , and the conduit  65  is opened at the back (in the lateral direction in  FIG. 5 ). 
     In a state that a check valve  36  is attached to the opening of the conduit  65 , as shown in  FIG. 5 , the base portion  64  of the member  61  is inserted into the cylindrical hole  33 . The base portion  64  is fitted into an inner wall surface  33   b , the outer ring portion  62   b  of the lid  62  is fitted into the inner wall surface  33   b , and the flange portion  62   a  is fitted into the diameter-enlarged hole  33   a , by which the member  61  is fixed to the cylindrical hole  33 . The thickness dimension e of the flange portion  62   a  in the axial direction is set to be smaller than the depth dimension f of the diameter-enlarged hole  33   a  in the axial direction (e&lt;f). 
     A separation chamber  42  is formed in a donut-shaped space enclosed by the lid  62 , the cylindrical portion  63 , the base portion  64  and the inner wall surface  33   b . The discharge chamber  26  is connected to the separation chamber  42  via the introduction passage  40 . A gas passage hole  63   a , which connects the separation chamber  42  with the conduit  65 , is formed in the cylindrical portion  63  of the member  61  so as to extend in a direction orthogonal with the center axial line of the conduit  65 , and opened in the separation chamber  42 . In the present embodiment, the gas passage hole  63   a  extends in a direction orthogonal with the center axial line of the conduit  65 . 
     A step portion is formed by the flange portion  62   a  and the outer ring portion  62   b  on the outer circumferential surface of the lid  62 . In a state that the member  61  is fixed to the cylindrical hole  33 , an annular space  37  is formed as an oil reservoir between a step portion on the outer circumferential surface of the lid  62  and a step portion on the inner wall surface  33   b  of the cylindrical hole  33 . The annular space  37  is an annular groove formed around the lid  62 , the cross section of which is rectangular. The annular space  37  functions as an oil reservoir connected to the separation chamber  42 . 
     In the above described compressor, refrigerant gas discharged from the discharge chamber  26  is introduced into the separation chamber  42  through the introduction passage  40 . The discharged refrigerant gas introduced into the separation chamber  42  flows toward the front of the cylindrical portion  63 , while swirling in a space between the inner wall surface  33   b  and the cylindrical portion  63  along the inner wall surface  33   b . At this time, misted oil contained in the discharged refrigerant gas is separated from the refrigerant gas by the actions of centrifugal force. The thus separated oil swirls inside the separation chamber  42  due to the influence of the swirling refrigerant gas, a part of which drops along the inner wall surface  33   b  of the separation chamber  42  due to its own weight and collects in the vicinity below the lid  62  at the bottom of the separation chamber  42 . 
     Discharged refrigerant gas, from which oil has been separated, is introduced into the check valve  36  after flowing into the conduit  65  through the gas passage hole  63   a  formed in front of the cylindrical portion  63 . The discharged refrigerant gas introduced into the check valve  36  is drained to the discharge flange  43  through the drain passage  41 . 
     Oil G, which collects at the bottom of the separation chamber  42 , flows to an annular space  37  through the constriction passage  38  and elevates the annular space  37  to flow quickly into the reservoir chamber  47  due to a pressure difference ΔP between the separation chamber  42  and the reservoir chamber  47 . 
     According to the present embodiment, the following advantages are obtained in addition to the advantages of (1) through (5) described in the first embodiment. 
     (1) The lid  62 , which partitions the separation chamber  42  from the discharge chamber  26 , the cylindrical portion  63  functioning as the oil separator  35  and the base portion  64  are formed in an integrated manner so as to constitute the single member  61 , thus making it possible to reduce the number of components and also simplify the assembly. 
     The compressor of the fourth embodiment shown in  FIG. 6  is the same as the compressor of the first embodiment except for the method for forming an annular space. Constitutions, which are the same as those of the compressor of the first embodiment, will be given the same symbols or numerals, and detailed explanations thereof are omitted. 
     In  FIG. 6 , an annular groove  71 , the cross section of which is rectangular, is formed on the inner wall surface  33   b  in the inlet portion of the cylindrical hole  33  formed in the rear housing member  14 . The annular groove  71  is provided in a position connected to the oil passage  39 . A lid  72  is provided with a tubular outer ring portion  72   a  having a constant outer diameter in the axial direction but devoid of a flange portion. 
     Therefore, the outer ring portion  72   a  of the lid  72  is fitted into the inner wall surface  33   b , thereby forming an annular space  37  as an oil reservoir between the annular groove  71  and the outer circumferential surface of the outer ring portion  72   a . The annular space  37  functions as an oil reservoir connected to the separation chamber  42 . 
     The annular groove  71  may be formed on the outer circumferential surface of the outer ring portion  72   a  in place of the rear housing member  14 . 
     In forming the annular space  37  used in the compressor of the fourth embodiment, the annular groove  71  may be formed only on one of the rear housing member  14  and the lid  72 . It is, therefore, expected to reduce the number of processing steps. 
     The compressor of the fifth embodiment shown in  FIG. 7  is the same as compressor of the third embodiment except for the configuration of the annular space as an oil reservoir of the compressor. Constitutions, which are the same as those of the compressor of the third embodiment, will be given the same symbols or numerals, and detailed explanations thereof are omitted. 
     In  FIG. 7 , the lid  74  and the oil separator  35  made up of a cylindrical portion  75  and a base portion  76  are constituted as an integrally formed member  73 . The member  73  is arranged in the cylindrical hole  33  in a state that the check valve  36  is attached to the side of an opening (on the right in the drawing) of a conduit  77  formed in the oil separator  35 . The lid  74  is formed in a flange shape and the cylindrical portion  75  is provided with a large diameter portion  75   a  and a small diameter portion  75   b . The small diameter portion  75   b  is arranged between the lid  74  and the large diameter portion  75   a.    
     The cylindrical hole  33  is provided with a large diameter-enlarged hole  33   a  on the side opened in the discharge chamber  26 . The diameter-enlarged hole  33   a  is extended axially up to the vicinity of the large diameter portion  75   a  in the cylindrical portion  75 . Therefore, a zone on the lid  74  in the separation chamber  78  defined by the member  73 , the diameter-enlarged hole  33   a  of the cylindrical hole  33  and the inner wall surface  33   b  forms an annular space  79  which is expanded to a greater extent than others. The annular space  79  acts as an oil reservoir connected to the separation chamber  78 . 
     The base portion  76  and the lid  74  are press-fitted respectively into the inner wall surface  33   b  and the diameter-enlarged hole  33   a , by which the member  73  is fixed to the cylindrical hole  33 . A gas passage hole  75   c  extending in a direction crossing at a right angle with the center axial line of the conduit  77  is disposed at four positions of the small diameter portion  75   b  and opened in the separation chamber  78 . It is preferable that the gas passage hole  75   c  is disposed at a position which is as close to the large diameter portion  75   a  as possible. The oil passage  39  is directly opened in the uppermost part of an annular passage  79 , which is an oil reservoir, and set to be of such a dimension that a certain constriction is given to prevent high-pressure refrigerant gas in the separation chamber  78  from flowing into the reservoir chamber  47 . The introduction passage  40  for refrigerant gas, which connects the discharge chamber  26  with the separation chamber  78 , is provided in the rear housing member  14  forming the cylindrical hole  33  so as to tilt against the center axial line of the conduit  77  and is opened toward the large diameter portion  75   a  of the cylindrical portion  75 . 
     In the thus constituted compressor of the fifth embodiment, high-pressure refrigerant gas introduced from the discharge chamber  26  into the separation chamber  78  via the introduction passage  40  swirls around the large diameter portion  75   a , as in the first embodiment, by which oil contained in the refrigerant gas is centrifuged. The thus separated oil swirls in the annular space  79  to gather around the lid  74  and the wall face of the diameter-enlarged hole  33   a . A part of the oil drops due to its own weight and collects in the lower part of the annular space  79  (bottom in  FIG. 7 ) as well. 
     Oil G which swirls and gathers around the upper wall face (above in  FIG. 7 ) of the annular space  79  flows into the reservoir chamber  47  through the oil passage  39  due to a pressure difference. The oil G, which collects on the lower wall face of the annular space  79 , gradually swirls upwardly by a swirling flow inside the annular space  79  and sequentially drained from the oil passage  39  to the reservoir chamber  47 . 
     Refrigerant gas, from which oil has been separated in the separation chamber  78 , flows from the gas passage hole  75   c  into the conduit  77 , opening up the check valve  36  to the right as shown in  FIG. 7  depending on the pressure of the refrigerant gas, thus flowing from the drain passage  41  to the external refrigerant circuit  48  (refer to  FIG. 1 ). 
     The compressor of the fifth embodiment has the following advantages in addition to the advantages described in the third embodiment. 
     (1) The annular space  79  is expanded in the radial direction of the cylindrical hole  33 , by which the lid  74  and the wall face of the diameter-enlarged hole  33   a  on which oil G collects are positioned away from the gas passage hole  75   c . Therefore, prevented is a phenomenon where the centrifuged oil G is taken into the conduit  77  by refrigerant gas, thus making it possible to reduce the oil concentration of the refrigerant gas flowing into the external refrigerant circuit  48 . 
     (2) Since the gas passage hole  75   c  is formed in the small diameter portion  75   b  of the cylindrical portion  75  constituting the oil separator  35 , it is possible to make the gas passage hole  75   c  short in length and to reduce the pressure loss of refrigerant gas flowing into the conduit  77 . 
     (3) Since the member  73  is press-fitted and fixed to the cylindrical hole  33 , the lid  74  and the base portion  76  are fixed stably even when they are made thin. Therefore, it is possible to form the separation chamber  78  long to separate oil more effectively. Further, no seal member is needed to reduce the number of components. 
     The compressor of the sixth embodiment shown in  FIG. 8  is the same as the first embodiment except for the configuration of the constitution of the lid  34 . The constitutions, which are the same as those of the compressor of the first embodiment, will be given the same symbols or numerals, and detailed explanations thereof are omitted. 
     In  FIG. 8 , the inner wall surface  33   b  of the cylindrical hole  33  is constant in diameter in the axial direction and opened in the discharge chamber  26 . A lid  80  is made of an iron plate obtained by pressing a thin iron plate. The lid  80  has a cylindrical outer ring portion  81 . The lid  80  is not restricted to the iron plate as a material but may be formed by using other rigid materials and also formed by a molding method. An outer ring portion  81  is provided with a constriction passage  82  at a position corresponding to the oil passage  39  disposed in the upper part (above in  FIG. 8 ) of the rear housing member  14  and constituted so that the oil passage  39  coincides with the constriction passage  82  when the lid  80  is press-fitted and fixed to the inner wall surface  33   b.    
     In  FIG. 8 , the constriction passage  82  and the oil passage  39  are formed identical in diameter. However, as long as the constriction passage  82  is large enough to give a sufficient constriction effect, the oil passage  39  may be larger in diameter than the constriction passage  82  so that it can be worked easily and oil is allowed to flow easily. The lid  80  extending from the side end face of the discharge chamber  26  up to the constriction passage  82  must be long enough in sealing a space between the discharge chamber  26  and the separation chamber  83  to be described below. However, it is preferable that the length is made as short as possible and the inlet of the constriction passage  82  is positioned away from the inlet  35   d  of the conduit  35   c  as much as possible. 
     The base portion  35   b  of the oil separator  35  to which the check valve  36  is attached is press-fitted into the cylindrical hole  33  and the outer ring portion  81  of the lid  80  is also press-fitted into the cylindrical hole  33 , by which a separation chamber  83  is formed between the oil separator  35  and the lid  80 , and an oil reservoir  84  is also formed along the inner circumferential surface of the outer ring portion  81  of the lid  80 . The oil reservoir  84  functions as an oil reservoir connected to the separation chamber  83 . 
     In the compressor of the sixth embodiment, high-pressure refrigerant gas in the discharge chamber  26  is supplied to the cylindrical portion  35   a  of the oil separator  35  through the introduction passage  40  and moved to the lid  80 , while swirling therearound, by which oil is centrifuged. The refrigerant gas, from which oil has been separated, flows into the conduit  35   c  from the inlet  35   d , opening up the check valve  36  due to its own pressure, thereby flowing into the drain passage  41 . Oil G separated from the refrigerant gas is influenced by a swirling flow of the refrigerant gas to swirl around the oil reservoir  84 , and a part of the oil collects in the lower part (bottom in  FIG. 8 ) of the oil reservoir  84  due to its own weight. Therefore, of swirling oil, oil G existing in the upper part shown in  FIG. 8  flows to the oil passage  39  through the constriction passage  82  due to a pressure difference and is drained to the reservoir chamber  47  (refer to  FIG. 1 ). 
     The compressor of the sixth embodiment has the following advantages. 
     (1) Since the oil G swirling around the oil reservoir  84  is drained to the oil passage  39  due to a pressure difference, the reservoir chamber  47  is arranged with an improved flexibility of the design. This allows the compressor to be miniaturized. 
     (2) Since the lid  80  is made thin, it is possible to make the separation chamber  83  long and prevent a phenomenon that the separated oil is taken to the conduit  35   c  together with refrigerant gas. 
     The compressor of the seventh embodiment shown in  FIG. 9  is the same as the compressors of the first and sixth embodiment except for the configuration of the lid. Constitutions, which are the same as those of the compressor of the first and sixth embodiments, will be given the same symbols or numerals, and detailed explanations thereof are omitted. 
     In  FIG. 9 , a step is formed by the diameter-enlarged hole  33   a  front to the inner wall surface  33   b  of the cylindrical hole  33  constituting a discharge passage, and the oil passage  39  connected to the reservoir chamber  47  (refer to  FIG. 1 ) is opened near the step portion of the diameter-enlarged hole  33   a , the constitution of which is similar to that of the compressor of the first embodiment. The lid  85  is a plate material formed by pressing an iron plate, as in the compressor of the sixth embodiment. The lid may be formed by using other materials or by a different working method. The lid  85  is formed as a cylinder with a bottom and provided with a large-diameter flange portion  85   a  and an outer ring portion  85   b , the outer diameter of which is equal to the inner diameter of the inner wall surface  33   b.    
     The flange portion  85   a  of the lid  85  and the outer ring portion  85   b  are press-fitted and fixed respectively to the diameter-enlarged hole  33   a  of the separation chamber  83  and the inner wall surface  33   b  of the separation chamber  83 , by which an annular space  86  is formed between the outer circumferential surface of the outer ring portion  85   b  and the inner circumferential surface of the diameter-enlarged hole  33   b . A constriction passage  87  is drilled in a longitudinal wall, which is in the lower part (bottom in  FIG. 9 ) of the lid  85  and connects the flange portion  85   a  with the outer ring portion  85   b . The separation chamber  83  is connected to the annular space  86  by the constriction passage  87 . The annular space  86  functions as an oil reservoir connected to the separation chamber  83 . 
     In the seventh embodiment, high-pressure refrigerant gas in the discharge chamber  26  is supplied to the cylindrical portion  35   a  of the oil separator  35  through the introduction passage  40  and moved to the lid  85 , while swirling therearound, by which oil is centrifuged. The refrigerant gas, from which oil has been separated, flows in a similar manner as described in the first and sixth embodiments. 
     Oil G separated from the refrigerant gas receives a swirling flow of the refrigerant gas, swirling around the inner circumference of the outer ring portion  85   b . A part of the oil drops due to its own weight and tends to collect in the lower part of the outer ring portion  85   b  (bottom in  FIG. 8 ). The oil G, which collects in the lower part of the outer ring portion  85   b , flows into the annular space  86  via the constriction passage  87  and is drained to the reservoir chamber  47  (refer to  FIG. 1 ) from the annular space  86  through the oil passage  39  due to a pressure difference. Therefore, the compressor of the seventh embodiment is capable of exhibiting a synergistic effect in combination with the advantages of the compressor described in the first embodiment and those of the compressor described in the sixth embodiment. 
     The compressor of the eighth embodiment as shown in  FIG. 10  is the same as the compressor of the first embodiment except for the points shown below. Constitutions, which are the same as those of the compressor of the first embodiment, will be given the same symbols or numerals, and detailed explanations thereof are omitted. 
     In the compressor of the eighth embodiment, the oil separator  90  is integrally formed with the rear housing member  14 . 
     In  FIG. 10 , an inner wall  89  of the discharge passage  88  extending in the axial direction of the drive shaft of the compressor is constant in diameter in the axial direction. A cylindrical oil separator  90  is integrally formed with the rear housing member  14  so as to project into the discharge passage  88 . The rear housing member  14  is provided with a drain passage  91 , which connects a separation chamber  93  with the high pressure fluid chamber  44 , and the drain passage  91  is formed by a through hole bending in a V-letter shape. The drain passage  91  is provided with a conduit  90   b  extending horizontally from the front end of the oil separator  90  to the back of the rear housing member  14  along the axial line of the oil separator  90  and a part extending in an obliquely upward direction from the conduit  90   b  to the rear housing member  14 . The conduit  90   b  is provided with an inlet  90   a  opened on the front end of the oil separator  90 . An oil passage  39  having an appropriate constriction function is opened on the upper part of the inner wall  89  (above in  FIG. 10 ). 
     A plate-like lid  92  is press-fitted and fixed to the inner wall  89  of the discharge passage  88 . The lid  92  is arranged in such a position that the inner end face coincides with an opening of the oil passage  39 . A space between the lid  92  and the oil separator  90  is formed as the separation chamber  93 . Also formed is an oil reservoir  94 , which is defined by the inner end face of the lid  92  and the inner wall  89 . The oil reservoir  94  functions as an oil reservoir connected to the separation chamber  93 . The check valve  36  given in the first embodiment may be provided appropriately in a passage leading to the drain passage  91  or to the external refrigerant circuit  48 . 
     In the eighth embodiment, high-pressure refrigerant gas in the discharge chamber  26  is supplied from the introduction passage  40  to the outer circumferential surface of the oil separator  90  and moved to the lid  92  while swirling in a spiral, by which oil is centrifuged. The refrigerant gas, from which oil has been removed, is drained from the inlet  90   a  to the external refrigerant circuit  48  through the conduit  90   b  and the drain passage  91 . Oil G, which swirls in the oil reservoir  94  to exist in the upper part, is drained from the oil passage  39  to the reservoir chamber  47  due to a pressure difference. 
     In addition to the advantages described in the compressor of the first embodiment, the compressor of the eighth embodiment has an advantage that the number of parts for constituting an oil separator and the number of assembly steps are reduced to a great extent to simplify the constitution. 
     The compressor of the ninth embodiment shown in  FIGS. 11 and 12  is the same as the compressor of the first embodiment except for a part of the compressor. Therefore, constitutions, which are the same as those of the compressor, will be given the same symbols or numerals, and detailed explanations thereof are omitted. In the compressor of the first embodiment, the step  33   c  for forming the constriction passage  38  is formed on the cylindrical hole  33 , and the oil passage  39  is connected to the side face of the lid  34  facing an annular space. In the compressor of the ninth embodiment, provided is an oil return passage for supplying oil from the reservoir chamber  47  to the suction chamber  25 , which is a low pressure zone. 
     In  FIG. 11 , the inner wall surface  33   b  of the cylindrical hole  33  is constant in diameter in the axial direction and opened to the discharge chamber  26 . The lid  95  is made of a cylindrical metal member corresponding to the diameter of the cylindrical hole  33 . As shown in  FIG. 12 , an annular groove  96  is formed on the outer circumferential surface  95   a  of the lid  95 . The groove  96  constitutes an intermediate oil passage  100 , which is a part of an oil return passage  97 , corresponding to an oil constriction portion in the oil return passage  97 . The groove  96  is easily formed by cutting or pressing by means of a lathe or a pressing machine. The lid  95  is press-fitted and fixed to the cylindrical hole  33  to define the separation chamber  42 . In a state that the lid  95  is fixed, there is formed a hermetic intermediate oil passage  100  enclosed by the groove  96  and the inner wall surface  33   b  of the separation chamber  42 . 
     The oil return passage  97  includes the hermetic intermediate oil passage  100  formed by the groove  96  and the inner wall surface  33   b , an oil upstream passage  98 , which connects the reservoir chamber  47  with the groove  96 , and an oil downstream passage  99 , which connects the groove  96  with the suction chamber  25 . Although only partially shown in  FIG. 11 , the oil upstream passage  98  and the oil downstream passage  99  are formed in the rear housing member  14 . The oil upstream passage  98  and the oil downstream passage  99  are set to be greater in the flow passage area than the intermediate oil passage  100 . Therefore, the intermediate oil passage  100  functions as an oil constriction portion in the oil return passage  97 . Since a constriction effect in the oil constriction portion is dependent on the flow passage area of the groove  96 , the flow passage area of the groove  96  is determined by the performance of the compressor. The flow passage area of the oil upstream passage  98  and the oil downstream passage  99  may be set, with production engineering factors taken into account. Oil passing through the oil return passage  97  flows along the inner wall surface  33   b  covering the groove  96  in the intermediate oil passage  100 . 
     The ninth embodiment has the following advantages. 
     (1) Since there is provided the oil return passage  97  for supplying oil from the reservoir chamber  47  to the suction chamber  25 , it is possible to easily form the intermediate oil passage  100 , which is a part of the oil return passage  97  only by processing the groove  96  on the outer circumferential surface  95   a  of the lid  95 . It is possible to form the oil return passage  97  passing through the lid  95 . It is also possible to easily route the oil return passage  97 . 
     (2) The oil constriction portion determines the amount of oil supplied from the reservoir chamber  47  to the suction chamber  25  due to the constriction effect, thus making it possible to prevent refrigerant gas from passing from the reservoir chamber  47  to the suction chamber  25  by using an oil constriction portion. 
     (3) Since the oil constriction portion is formed in the intermediate oil passage  100 , not only the intermediate oil passage  100  but also the oil constriction portion is easily formed. When there is formed an oil constriction portion with a small flow passage area, the oil constriction portion is easily set for accuracy. 
     (4) Since the intermediate oil passage  100  is the groove  96 , the intermediate oil passage  100  corresponds to the oil constriction portion and a flow passage area of the oil constriction portion is set with high accuracy. Further, since there is formed the oil constriction portion along the inner wall surface  33   b , it is possible to sufficiently secure a distance of the oil constriction portion in the oil return passage  97 . 
     The compressor of the tenth embodiment shown in  FIG. 13  is the same as the compressor of the ninth embodiment except for the configurations of the lid and the intermediate oil passage. The constitutions, which are the same as those of the compressor described in the first and ninth embodiments, will be given the same symbols or numerals, and detailed explanations thereof are omitted. 
     As shown in  FIG. 13 , a lid  101  of the compressor described in the present embodiment is press-fitted into the cylindrical hole  33 , but no groove is formed on the outer circumferential surface  101   a  of the lid  101 . Of the inner wall surface  33   b  of the separation chamber  42 , an annular groove  102  is formed at a site at which the outer circumferential surface  101   a  is in contact. That is, the annular groove  102  is formed in the rear housing member  14 . The groove  102  constitutes the intermediate oil passage  100 , which is a part of the oil return passage  97 , corresponding to the oil constriction portion in the oil return passage  97 . The groove  102  can be easily formed by cutting with the use of a lathe. In a state that the lid  101  is fixed, there is formed a hermetic intermediate oil passage  100  enclosed with the groove  102  and the outer circumferential surface  101   a  of the lid  101 . 
     The oil return passage  97  includes the intermediate oil passage  100 , the oil upstream passage  98  connecting the reservoir chamber  47  with the groove  102 , and the oil downstream passage  99  connecting the groove  102  with the suction chamber  25 , which is a low pressure zone. The oil upstream passage  98  and the oil downstream passage  99  are shown only partially in  FIG. 13 . The groove  102  is smaller in flow passage area than the oil upstream passage  98  and the oil downstream passage  99 . The intermediate oil passage  100  functions as an oil constriction portion in the oil return passage  97 . Oil passing through the oil return passage  97  flows along the outer circumferential surface  101   a  of the lid  101 , which covers the groove  102  in the intermediate oil passage  100 . 
     The compressor of the tenth embodiment has advantages similar to the advantages (2) and (3) of the compressor described in the ninth embodiment. Further, since there is provided the oil return passage  97  for supplying oil from the reservoir chamber  47  to the suction chamber  25 , it is possible to easily form the intermediate oil passage  100  only by providing the groove  102  on the inner wall surface  33   b . Further, since the intermediate oil passage  100  can be easily formed, the oil return passage  97  is easily routed. 
     Further, since the intermediate oil passage  100  as an oil constriction portion is formed by the groove  102 , it is possible to set a flow passage area of the oil constriction portion with higher accuracy. The oil constriction portion is formed along the outer circumferential surface  101   a , thereby making it possible to sufficiently secure a distance of the oil constriction portion in the oil return passage  97 . 
     The lid  105  of the compressor described in the eleventh embodiment shown in  FIG. 14  is the same as the lid of the compressor of the ninth embodiment except for the configuration of the lid and the intermediate oil passage. The constitutions, which are the same as those of the compressor described in the first and ninth embodiments, will be given the same symbols or numerals, and detailed explanations thereof are omitted. 
     The lid  105  shown in  FIG. 14  is provided with a through hole  106 , which extends across the lid  105  in the radial direction. The through hole  106  is formed linearly to constitute the intermediate oil passage  100 , which is a part of the oil return passage  97 , corresponding to a hermetic oil constriction portion in the oil return passage  97 . Openings on both ends of the through hole  106  are respectively arranged on the outer circumferential surface  105   a  of the lid  105 . These openings are located at positions corresponding to opening positions of the oil upstream passage  98  and the oil downstream passage  99  on the inner wall surface  33   b . Therefore, when the lid  105  is press-fitted into the cylindrical hole  33 , the direction of the through hole  106  is allowed to coincide with the opening positions of the oil upstream passage  98  and the oil downstream passage  99  and the lid  105  is then press-fitted into the cylindrical hole  33 . The through hole  106  is easily formed, for example, by drilling. 
     The through hole  106  is smaller in the flow passage area than the oil upstream passage  98  and the oil downstream passage  99 . This is because the through hole  106  is allowed to function as an oil constriction portion in the oil return passage  97 . Oil passing through the oil return passage  97  flows in the through hole  106  in the intermediate oil passage  100 . 
     The compressor of the eleventh embodiment has advantages similar to the advantages (2), (3) of the compressor described in the ninth embodiment. Further, since there is provided the oil return passage  97  for supplying oil from the reservoir chamber  47  to the suction chamber  25 , which is a low pressure zone, it is possible to easily form the intermediate oil passage  100  only by providing the through hole  106  on the lid  105 . Therefore, the oil return passage  97  is easily routed. 
     Further, since the intermediate oil passage  100  as an oil constriction portion is formed by the through hole  106 , it is possible to set a flow passage area of the oil constriction portion with high accuracy. Further, since there is provided an oil constriction portion passing through the lid  105 , the lid  105  can be press-fitted and fixed to the rear housing member  14  more strongly than a case where the oil constriction portion is formed on the outer circumferential surface  105   a  of the lid  105 . Still further, oil in the oil return passage  97  is less likely to leak into the separation chamber  72  or the discharge chamber  25 . 
     Next, an explanation will be made for modifications of the compressors given in the ninth to eleventh embodiments by referring to  FIGS. 15(   a ) and  15 ( b ). For the sake of convenience in making an explanation, the constitutions, which are the same as those of the compressors given in the first and ninth embodiments, will be given the same symbols or numerals, and detailed explanations thereof are omitted. The lid  110  shown in  FIG. 15(   a ) is provided with a cylindrical outer ring portion  111 , and the outer ring portion  111  is formed, for example, by pressing a metal plate. A small diameter portion bent toward the center in the radial direction is formed at a midpoint of the outer ring portion  111  in the axial direction. A groove  112  is formed on the outer circumferential surface of the outer ring portion  111  corresponding to the small diameter portion. Constituted is the oil return passage  97  when the hermetic groove  112  is positioned so as to coincide with the oil upstream passage  98  and the oil downstream passage  99  in a state that the lid  110  is press-fitted into the cylindrical hole  33 . 
     The lid  115  shown in  FIG. 15(   b ) is not press-fitted into but fixed to a cylindrical hole  33  by using a snap spring. The cylindrical hole  33  is provided with a large diameter portion  331  corresponding to the diameter of the lid  115  and a small diameter portion  332  smaller in diameter than the lid  115 . A step  333  is formed between the large diameter portion  331  and the small diameter portion  332 . The lid  115  is in a cylindrical shape, and a sealing groove  117  is formed at both ends on the outer circumferential surface  115   a  of the lid  115  in the axial direction. A groove  116  as the intermediate oil passage  100  is formed between the sealing grooves  117 . 
     Contrastingly, a snap-ring annular groove  334  is formed at a place close to the opening on the inner wall surface  331   a  of the large diameter portion  331 . A seal member  118  is attached to the sealing groove  117  of lid  115 , and the lid  115  is inserted into the large diameter portion  331  until it hits against the step  333 . Then, a snap ring  119  is attached to the annular groove  334 , by which the lid  115  is prevented from coming off the cylindrical hole  33 . The seal member  118  is provided, by which oil in the oil return passage  97  hardly leaks to the separation chamber  42  or the discharge chamber  26 . 
     Next, an explanation will be made for other modified embodiments by referring to  FIGS. 16 and 17 . A first modified embodiment shown in  FIG. 16  is partially common in constitution to the compressors given in the first and ninth embodiments. Constitutions common to those of the compressors given in the first and ninth embodiments will be given the same symbols or numerals, and detailed explanations thereof are omitted. In the first modified embodiment, a step  33   c  for forming the constriction passage  38  is formed in the cylindrical hole  33 , and an oil passage  39  is connected to an annular space facing the outer circumferential surface of the lid  120 . Further, there is provided an oil return passage  97  for supplying oil from the reservoir chamber  47  to the suction chamber  25 , which is a low pressure zone. 
     A diameter-enlarged hole  33   a  greater in diameter than the cylindrical hole  33  is formed at the inlet portion (on the left in  FIG. 16 ) of the cylindrical hole  33 . A lid  120 , which partitions the discharge chamber  26  from a discharge passage formed by the cylindrical hole  33 , is attached at the inlet portion. The lid  120  is provided with a flange portion  120   a  and an outer ring portion  120   b . A step portion is formed by the flange portion  120   a  and the outer ring portion  120   b  on the outer circumferential surface  120   c  of the lid  120 . The lid  120  is fixed to the cylindrical hole  33  by fitting the outer ring portion  120   b  into the inner wall surface  33   b  of the cylindrical hole  33  and also fitting the flange portion  120   a  into the diameter-enlarged hole  33   a . An annular space  37  is formed by the outer ring portion  120   b  and the diameter-enlarged hole  33   a . An annular groove  121  is formed on the outer circumferential surface  120   c  of the lid  120  corresponding to the flange portion  120   a . The groove  121  constitutes the intermediate oil passage  100 , which is a part of the oil return passage  97 , corresponding to an oil constriction portion in the oil return passage  97 . 
     In a state that the lid  120  is fixed, there is formed a hermetic intermediate oil passage  100  enclosed by the groove  121  and the inner wall surface of the diameter-enlarged hole  33   a . The oil return passage  97  includes the hermetic intermediate oil passage  100  formed by the groove  121  and the inner wall surface, an oil upstream passage  98  connecting the reservoir chamber  47  with the groove  121 , and an oil downstream passage  99  connecting the groove  121  with a suction chamber, which is a low pressure zone. According to the first modified embodiment, oil G, which is separated from the discharge refrigerant gas to collect at the bottom of the separation chamber  42 , flows into the annular space  37  through the constriction passage  38  and is supplied to a reservoir chamber  47  through the oil passage  39 . Oil in the reservoir chamber  47  is supplied to the suction chamber  25  through the oil return passage  97 . 
     Next, an explanation will be made for a second modified embodiment shown in  FIG. 17 . The second modified embodiment is partially common in constitution to the compressor given in the second and ninth embodiments. The constitutions common to those of the compressors given in the second and ninth embodiments will be given the same symbols or numerals, and detailed explanations thereof are omitted. In the second modified embodiment, as shown in  FIG. 17 , the constriction passage  127  is formed on the lid  125 , and an oil passage  39  is connected to the annular space  37  facing the outer circumferential surface  125   c  of the lid  125 . Further, there is provided an oil return passage  97  for supplying oil from the reservoir chamber  47  to the suction chamber  25 , which is a low pressure zone. 
     The diameter-enlarged hole  33   a  greater in diameter than the cylindrical hole  33  is formed in the inlet portion (on the left in  FIG. 17 ) of the cylindrical hole  33 . As shown in  FIG. 17 , the lid  125  is provided with a flange portion  125   a  and an outer ring portion  125   b , and a step portion is formed by the flange portion  125   a  and the outer ring portion  125   b  on the outer circumferential surface  125   c  of the lid  125 . The outer ring portion  125   b  of the lid  125  is fixed into the cylindrical hole  33 . An annular groove  126  is formed on the outer circumferential surface  125   c  corresponding to the flange portion  125   a . The groove  126  constitutes the intermediate oil passage  100 , which is a part of the oil return passage  97 , corresponding to an oil constriction portion in the oil return passage  97 . 
     The constriction passage  127  of this embodiment is provided at the lowermost place of the outer ring portion  125   b  of the lid  125  and formed by a through hole  128  extending in a perpendicular direction (above in the  FIG. 17 ) with respect to the axial line of the lid  125 . The constriction passage  127  connects the separation chamber  42  with the annular space  37 . Therefore, oil G, which is separated from the discharge refrigerant gas to collect at the bottom of the separation chamber  42 , flows into the annular space  37  through the constriction passage  127  and is supplied to the reservoir chamber through the oil passage  39 . Oil in the reservoir chamber is supplied to a suction chamber through the oil return passage  97 . 
     The present invention is not limited to the above-described embodiments but may be modified in various ways within the scope of the gist of the present invention, and modified, for example, as follows. 
     The discharge passage described in the first to eighth embodiments may be arranged so as to extend obliquely with respect to the axial direction of the compressor, and an oil separator may be disposed in the discharge passage. 
     The lid described in the first to fourth embodiments may be press-fitted and fixed into a round hole as described in the fifth to eighth embodiments. 
     In the third and fifth embodiments, the base portions  64 ,  76  may be press-fitted and fixed into the cylindrical hole  33  to provide a seal member on the outer circumferential surface of the lids  62 ,  74 . This constitution makes it possible to easily assemble the members  61 ,  73 . The seal member may be provided not only on the outer circumferential surface of the lids  62 ,  74  but also between a step portion formed on the inner wall surface  33   b  of the cylindrical hole  33  and the end face of the lids  62 ,  74 . 
     In the first to eighth embodiments, the oil passage  39  may be provided below an oil reservoir. This constitution makes it possible to easily drain oil which collects at the bottom due to its own weight. 
     In the first to eighth embodiments, a reservoir chamber is provided above a separation chamber. However, the reservoir chamber may be arranged at an optimal place, for example, below the separation chamber or on the side thereof. 
     In the first to fifth and seventh embodiments, a step formed on the round inner wall surface of the discharge passage or on the outer circumferential surface of the lid and on both of them may be formed in a tapered manner. 
     The gas passage holes  63   a ,  75   c  described in the first and fifth embodiments extend at a right angle with respect to the center axial line of the conduits  65 ,  77 . However, they may extend so as to give an angle other than a right angle with respect to the center axial line, as long as they extend in a direction intersecting the center axial line. Further, gas passage holes  63   a ,  75   c  are those provided at four places but may be arranged at a plurality of places other than the four places. 
     In the first to fourth, and seventh embodiments, an annular space formed around the lid has a rectangular cross section. However, the annular space is not restricted thereto but may have a triangular, circular, or oval cross section. That is, the annular space may have any shape of the cross section, as long as it allows oil to pass through. 
     In the first, third, and fourth embodiments, a constriction passage provided below the lid is formed by providing a step portion on the inner wall surface of the separation chamber. However, it may be formed by providing a step on the outer ring portion of the lid. 
     In the eighth embodiment, the lid  92  is made thick or the lid  92  is provided with a flange portion, by which the lid  92  may partially project into an opening of the oil passage  39 . Thereby, the opening of the oil passage  39  can be made small to increase a constriction effect. 
     In the ninth to eleventh embodiments and their modifications, in order to easily form an oil constriction portion, an intermediate oil passage in the oil return passage is used to as an oil constriction portion. The intermediate oil passage does not necessarily need to function as an oil constriction portion but the oil constriction passage may be arbitrarily provided in the oil return passage. An oil constriction portion may be provided, for example, in the oil upstream passage and the oil downstream passage. 
     In the first to eleventh embodiments, the compressor is explained as a variable displacement swash plate type compressor. However, the compressor may be a fixed displacement type compressor or a wobble type compressor. Further, the compressor is not limited to a swash plate type compressor but may be a scroll type compressor and a vane type compressor.