Patent Publication Number: US-6699017-B2

Title: Restriction structure in variable displacement compressor

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a restriction structure in a variable displacement compressor. 
     In a conventional variable displacement compressor as disclosed in, for example, Japanese Unexamined Patent Publication No. 2001-3860, a low-pressure chamber is formed in a front head in order to improve the reliability of a shaft sealing unit arranged between the housing and the rotary shaft. The low-pressure chamber is shut off from a crank chamber by a first seal member. A second seal member which constitutes the shaft sealing unit is retained in the low-pressure chamber. Refrigerant that reaches the compressor from the outlet of an evaporator flows into the low-pressure chamber. Therefore, the suction pressure of the low-pressure chamber alone is applied to the second seal member, thereby reducing the load on the second seal member as compared with a case where the pressure in the crank chamber is applied to the second seal member. 
     The structure that uses a pair of seal members to define the low-pressure chamber increases the cost. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an objective of the present invention to ensure the high reliability of a shaft sealing unit located between the housing and the rotary shaft of a compressor to seal the housing while reducing the cost. 
     To achieve the foregoing and other objectives and in accordance with the purpose of the present invention, a variable displacement compressor having a housing assembly, a rotary shaft, a swash plate, pistons, seal means, a retaining chamber, a refrigerant passage, and a restricting member is provided. The housing assembly has a suction chamber, a discharge chamber, a control pressure chamber, and a cylinder block having a plurality of cylinder bores. The rotary shaft extends in the control pressure chamber and protrudes outside from the housing assembly. The rotary shaft is rotatably supported by the housing assembly. The swash plate is supported on the rotary shaft in a tiltable manner and rotatable together with the rotary shaft and is placed in the control pressure chamber. Pistons are retained in the cylinder bores and define compression chambers in the cylinder bores, so that as the pistons reciprocate in the respective cylinder bores based on rotation of the swash plate, a refrigerant is drawn into the compression chambers from the suction chamber, the refrigerant is discharged from the compression chambers to the discharge chamber. An inclination angle of the swash plate is changed by adjusting a pressure in the control pressure chamber. The seal means is provided between the housing assembly and the rotary shaft, for sealing inside the housing assembly. The retaining chamber retains the seal means. The retaining chamber is separated from the suction chamber and the control pressure chamber. The refrigerant passage extends from outside the housing assembly to the suction chamber through the retaining chamber. The refrigerant passage supplies the refrigerant to the seal means. The restricting member restricts the refrigerant from the control pressure chamber to the retaining chamber and releases an internal pressure of the control pressure chamber. 
     Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention, together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which: 
     FIG. 1 is a side cross-sectional view of an entire compressor according to a first embodiment of the present invention; 
     FIG.  2 ( a ) is an enlarged side cross-sectional view of essential portions of the invention in FIG. 1; 
     FIG.  2 ( b ) is a cross-sectional view taken along line  2   b — 2   b  in FIG.  2 ( a ); 
     FIG. 3 is a cross-sectional view taken along line  3 — 3  in FIG. 1; 
     FIG. 4 is a cross-sectional view taken along line  4 — 4  in FIG. 1; 
     FIG.  5 ( a ) is an enlarged side cross-sectional view of essential portions of a compressor according to a second embodiment of the present invention; 
     FIG.  5 ( b ) is a cross-sectional view taken along line  5   b — 5   b  in FIG.  5 ( a ); 
     FIG.  6 ( a ) is an enlarged side cross-sectional view of essential portions of a compressor according to a third embodiment of the present invention; 
     FIG.  6 ( b ) is a cross-sectional view taken along line  6   b — 6   b  in FIG.  6 ( a ); 
     FIG.  7 ( a ) is an enlarged side cross-sectional view of essential portions of a compressor according to a fourth embodiment of the present invention; 
     FIG.  7 ( b ) is a cross-sectional view taken along line  7   b — 7   b  in FIG.  7 ( a ); 
     FIG. 8 is a side cross-sectional view showing a compressor according to a fifth embodiment of the present invention; 
     FIG. 9 is a side cross-sectional view of essential portions showing a compressor according to a sixth embodiment of the present invention; and 
     FIG. 10 is a cross-sectional view taken along line  10 — 10  in FIG.  9 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A first embodiment of the present invention will be described below referring to FIGS. 1 to  4 . 
     FIG. 1 shows the internal structure of a variable displacement compressor. A housing assembly  10  of the compressor is constructed by connecting a front housing member  11 , a rear housing member  12 , and a cylinder block  19  together. The front housing member  11  comprises a supporting piece  30  and a chamber defining piece  31 . The supporting piece  30 , the chamber defining piece  31 , the cylinder block  19  and the rear housing member  12  are secured by fastening bolts  32 , which are screwed into the rear housing member  12  through the supporting piece  30 , the chamber defining piece  31  and the cylinder block  19 . 
     A rotary shaft  13  extends through the chamber defining piece  31  and the cylinder block  19 , which define a control pressure chamber  111 . A rotor  14  is fixed to the rotary shaft  13  in the control pressure chamber  111 . A radial bearing  33  and a thrust bearing  42  are located between the rotor  14  and the chamber defining piece  31 . A radial bearing  34  is located between the end portion of the rotary shaft  13  that is inserted in a support hole  195 , formed in the cylinder block  19 , and the surface of the support hole  195 . The chamber defining piece  31  supports the rotor  14  and the rotary shaft  13  through the radial bearing  33  such that the rotor  14  and the rotary shaft  13  rotate integrally. The cylinder block  19  rotatably supports the rotary shaft  13  through the radial bearing  34 . 
     The rotary shaft  13  protrudes outside the compressor via a through hole  40  in the supporting piece  30  and receives the rotational drive power from an external drive source, such as the engine of a vehicle. A mechanical seal  35  and a shut-off ring  36  are located in the through hole  40  apart from each other in the axial direction of the rotary shaft  13 . The mechanical seal  35  serves as shaft sealing means intervened between the housing assembly  10  and the rotary shaft  13  in order to seal inside the housing assembly  10 . The shut-off ring  36  is formed of a synthetic resin, such as polytetrafluoroethylene. The movement of the shut-off ring  36  toward the mechanical seal  35  from the radial bearing  33  is restricted by a flange  404  formed on an inner surface  401  of the through hole  40 . 
     As shown in FIGS.  2 ( a ) and  2 ( b ), an outer surface  361  of the shut-off ring  36  is in close contact with the inner surface  401  of the through hole  40  in a slidable manner, and an inner surface  362  of the restriction ring  36  is in close contact with an outer surface  131  of the rotary shaft  13 . As the rotary shaft  13  rotates, the restriction ring  36  slides on the outer surface  131  of the rotary shaft  13  or the inner surface  401  of the through hole  40  or both of the outer surface  131  of the rotary shaft  13  and the inner surface  401  of the through hole  40 . 
     A restriction groove  37  is formed in the inner surface  362  of the restriction ring  36  in the axial direction of the rotary shaft  13 . The restriction groove  37  communicates with the through hole  40 , at the position between the mechanical seal  35  and the restriction ring  36 , and the control pressure chamber  111 . In other words, through hole  40  between the mechanical seal  35  and the restriction ring  36  communicates with the control pressure chamber  111  via the restriction groove  37  serving as a restriction passage. The restriction ring  36  connects the through hole  40  with the control pressure chamber  111  through a restricting groove  37 . The through hole  40  becomes a retaining chamber of the mechanical seal  35  as the shaft sealing means. The restriction ring  36  and the restriction groove  37  constitute pressure release means which has a restriction function to release pressure into the retaining chamber from the control pressure chamber  111 . 
     As shown in FIG. 1, a swash plate  15  is supported on the rotary shaft  13  to slide in the axial direction of the rotary shaft  13  and to tilt with respect to the rotary shaft  13 . A pair of guide pins  16  (shown in FIG. 3) is fixed to the swash plate  15 . The guide pins  16  are slidably fitted in guide holes  141  formed in the rotor  14 . The engagement of the guide pins  16  with the guide holes  141  allows the swash plate  15  to be tiltable with respect to the rotary shaft  13  and rotatable together with the rotary shaft  13 . The inclination of the swash plate  15  is guided by the guide holes  141 , the guide pins  16 , and the rotary shaft  13 . 
     A plurality of cylinder bores  191  is formed in the cylinder block  19  at equal angular intervals around the rotary shaft  13 . Although only one cylinder bore  191  is shown in FIG. 1, five cylinder bores  191  are provided according to the embodiment as shown in FIG. 4. A piston  17  is retained in each cylinder bore  191 . 
     Each piston  17  defines a compression chamber  192  in the associated cylinder bore  191 . The rotational motion of the swash plate  15  is converted to the forward and backward reciprocating motion of the associated piston  17  via shoes  18  so that the piston  17  moves forward and backward in the cylinder bore  191 . 
     A first plate  20 , a second plate  21 , a third plate  22 , and a fourth plate  23  are intervened between the cylinder block  19  and the rear housing member  12  to form a valve plate assembly. A suction chamber  121  and a discharge chamber  122  are defined in the rear housing member  12 . A partition  41  separates the suction chamber  121  from the discharge chamber  122  which is surrounded by the suction chamber  121 . 
     The motion of the piston  17  (the leftward movement from the right-hand side in FIG. 1) causes a refrigerant in the suction chamber  121 , which is a suction pressure zone, to push a suction valve  211  on the second plate  21  away from a suction port  201  in the first plate  20  and flow into the compression chambers  192 . The motion of the piston  17  (the rightward movement from the left-hand side in FIG. 1) causes the refrigerant flowed into the compression chambers  192  to push a discharge valve  221  on the third plate  22  away from a discharge suction port  202  in the first plate  20  and flow into the discharge chamber  122 , which is a discharge pressure zone. As the discharge valve  221  abuts on a retainer  231  on the fourth plate  23 , its degree of opening is restricted. The compression reactive force that acts on each piston  17  at the time of discharging the refrigerant to the discharge chamber  122  from each compression chamber  192 , is received at an end wall of the chamber defining piece  31  via the shoes  18 , the swash plate  15 , the guide pins  16 , the rotor  14 , and the thrust bearing  42 . 
     A pressure supply passage  38 , which connects the discharge chamber  122  to the control pressure chamber  111 , feeds the refrigerant in the discharge chamber  122  to the control pressure chamber  111 . The refrigerant in the control pressure chamber  111  flows to the through hole  40  through the thrust bearing  42 , a clearance in the radial bearing  33 , and the restriction groove  37 . That is, the pressure in the control pressure chamber  111  is released into the through hole  40  via the restriction groove  37 . 
     An electromagnetic displacement control valve  25  is intervened in the pressure supply passage  38 . The displacement control valve  25  is excited and de-excited by a controller (not shown). The controller excites and de-excites the displacement control valve  25  based on a detected room temperature acquired by a room temperature detector (not shown), which detects the room temperature in a vehicle, and a target temperature, which has been set by a room temperature setting unit (not shown). The displacement control valve  25  is open in a de-energized state and is closed in an energized state. That is, the refrigerant in the discharge chamber  122  is fed to the control pressure chamber  111  when the displacement control valve  25  is de-excited, while the refrigerant in the discharge chamber  122  is not fed to the control pressure chamber  111  when the displacement control valve  25  is excited. The displacement control valve  25  controls the supply of the refrigerant to the control pressure chamber  111  from the discharge chamber  122 . 
     The inclination angle of the swash plate  15  is changed by the control of the pressure in the control pressure chamber  111 . The inclination angle of the swash plate  15  becomes smaller as the pressure in the control pressure chamber  111  increases, whereas the inclination angle of the swash plate  15  becomes larger as the pressure in the control pressure chamber  111  decreases. The pressure in the control pressure chamber  111  rises as the refrigerant is supplied to the control pressure chamber  111  from the discharge chamber  122 , whereas the pressure in the control pressure chamber  111  falls as the supply of the refrigerant to the control pressure chamber  111  from the discharge chamber  122  is stopped. That is, the inclination angle of the swash plate  15  is controlled by the displacement control valve  25 . 
     The maximum inclination angle of the swash plate  15  is defined by the abutment of the swash plate  15  against the rotor  14 . The minimum inclination angle of the swash plate  15  is defined by the abutment of a snap ring  24  on the rotary shaft  13  against the swash plate  15 . 
     As shown in FIG.  2 ( a ), suction passages  301  and  304  are formed in the supporting piece  30  to communicate with the through hole  40 . An inlet  101  of the suction passage  301  in the housing assembly  10  is provided in the outer surface of the supporting piece  30  at the topmost position. An inlet port  402  of the suction passage  301  opens to the through hole  40  and is provided at the topmost position in the inner surface  401  of the through hole  40 . An outlet port  403  of the suction passage  304  opens to the through hole  40 , and is provided at the lowermost position in the inner surface  401  of the through hole  40 . That is, the inlet port  402  is located directly above the rotary shaft  13 , and the outlet port  403  directly below the rotary shaft  13 . 
     As shown in FIG. 1, suction passages  312  and  193  are formed in the vicinity of the lowermost position of a peripheral wall  311  of the chamber defining piece  31  and in the vicinity of the lowermost position of the cylinder block  19 . The suction passage  312  communicates with the suction passage  304  at the junction of the supporting piece  30  and the chamber defining piece  31 , and communicates with the suction passage  193  at the junction of the chamber defining piece  31  and the cylinder block  19 . 
     A through hole  203  is formed in the vicinity of the lowermost positions of the first plate  20 , the second and third plates  21  and  22 , and the fourth plate  23 . The through hole  203  communicates with the suction passage  193  and the suction chamber  121 . The suction passage  301  constitutes a refrigerant passage upstream of the through hole  40 , while the suction passages  304 ,  312  and  193  and the through hole  203  constitute a refrigerant passage downstream of the through hole  40 . 
     The discharge chamber  122  and the suction chamber  121  are connected via an external refrigerant circuit  26 , the suction passage  301 , the through hole  40 , the suction passages  304 ,  312  and  193  and the through hole  203 . The refrigerant that has flowed to the external refrigerant circuit  26  from the discharge chamber  122  passes through a condenser  27 , an expansion valve  28  and an evaporator  29  and returns to the suction chamber  121  through the suction passage  301 , the through hole  40 , the suction passages  304 ,  312  and  193  and the through hole  203 . 
     The first embodiment has the following advantages. 
     (1-1) A passage  261  (shown in FIG.  1 ), which is part of the external refrigerant circuit  26  and which extends to the inlet  101  of the suction passage  301  from the evaporator  29 , is the suction pressure zone outside the compressor. The temperature of the refrigerant that has undergone heat exchange in the evaporator  29  has become low and the refrigerant that has flowed to the suction passage  301  from the external refrigerant circuit  26  passes through the through hole  40  and flows to the suction chamber  121  via the suction passages  304 ,  312  and  193 . The pressure in the through hole  40  is low, a level equivalent to the suction pressure. Therefore, the load on the mechanical seal  35  is reduced as compared with the case where the pressure in the control pressure chamber  111  is applied to the mechanical seal  35 . 
     The refrigerant that passes the through hole  40  cools the mechanical seal  35  directly or indirectly. Part of the lubrication oil of a low temperature that flows together with the refrigerant sticks on the mechanical seal  35  to lubricate and cool down the mechanical seal  35 . Part of the low-temperature lubrication oil contacts the outer surface of the rotary shaft  13  to cool down the part of the rotary shaft  13  near the through hole  40 . Therefore, the mechanical seal  35  is efficiently cooled down. The reduction in load on the mechanical seal  35  and the efficient cooling of the mechanical seal  35  improves the reliability of the mechanical seal  35 . 
     The pressure in the control pressure chamber  111  is adjusted by the pressure release via the restriction groove  37  of the restriction ring  36  as the pressure release means. The restriction groove  37  connects the interior of the through hole  40  between the mechanical seal  35  and the restriction ring  36  with the control pressure chamber  111  through a restriction passage. Therefore, the interior of the through hole  40  between the mechanical seal  35  and the restriction ring  36  is kept as the suction pressure zone. 
     The shaft sealing means demands reliable prevention of refrigerant leakage. However, the shaft sealing means need not have very high capabilities of preventing refrigerant leakage from between the inner surface  362  of the restriction ring  36  and the outer surface  131  of the rotary shaft  13  to leak the refrigerant to the through hole  40  from the control pressure chamber  111  and preventing refrigerant leakage from between the outer surface  361  of the restriction ring  36  and the inner surface  401  of the through hole  40 . The restriction ring  36  has only to be fittable over the rotary shaft  13  and in the through hole  40  to be slidable on the outer surface  131  of the rotary shaft  13  and the inner surface  401  of the through hole  40 . That is, the size precision of the restriction ring  36  can be low. 
     The restriction ring  36  can be produced cheaper and easier than the shaft sealing means. The use of the restriction ring  36  is advantageous in cost over the conventional compressor disclosed in Japanese Unexamined Patent Publication No. 2001-3860, which uses the shaft sealing means. 
     (1-2) The restriction groove  37  is formed in the inner surface  362  of the restriction ring  36 . The inner surface  362  of the restriction ring  36  is a portion where the groove can be formed easily. The inner surface  362  of the restriction ring  36  is therefore suitable as the portion where the restriction groove  37  is to be formed. 
     (1-3) The restriction ring  36  is molded of a synthetic resin. Because of a low degree of precision being sufficient for the restriction ring  36 , processing after the molding is unnecessary. Even if the outside diameter of the restriction ring  36  is set slightly larger than the diameter of the through hole  40 , particularly, the resilient deformation of the synthetic resin allows the restriction ring  36  to be fittable in the through hole  40 . Even if the inside diameter of the restriction ring  36  is set smaller than the diameter of the rotary shaft  13 , the resilient deformation of the synthetic resin allows the restriction ring  36  to be fittable over the rotary shaft  13 . Therefore, the resin restriction ring  36  is particularly easy to produce. 
     (1-4) The synthetic resin has a better slidability than metal and is thus suitable as the material for the restriction ring  36 . In particular, polytetrafluoroethylene, which has the best slidability, is most suitable as the material for the restriction ring  36 . 
     (1-5) Since the inlet port  402  and the outlet port  403  of the through hole  40  are formed apart from each other, the refrigerant flows smoothly in the through hole  40 . Therefore, the low-temperature lubrication oil which flows together with the refrigerant in the through hole  40  flows satisfactorily so that the mechanical seal  35  or the shaft sealing means retained in the through hole  40  is cooled efficiently. 
     (1-6) Part of the lubrication oil that has flowed into the through hole  40  from the inlet port  402  located directly above the rotary shaft  13  travels along the mechanical seal  35  and cools down the mechanical seal  35  while moving downward. The lubrication oil flows out from the outlet port  403  located directly under the rotary shaft  13 . Because the inlet port  402  and the outlet port  403  are respectively arranged above and below the rotary shaft  13 , the lubrication oil that travels along the mechanical seal  35  drops due to its own weight. This port arrangement contributes to the nice flow of the lubrication oil in the through hole  40 . 
     (1-7) The refrigerant in the control pressure chamber  111  flows out of the through hole  40  through the clearance in the thrust bearing  42 , the clearance in the radial bearing  33 , and the restriction groove  37 . Therefore, the lubrication oil that flows together with the refrigerant, which moves to the through hole  40  from the control pressure chamber  111 , lubricates the thrust bearing  42  and the radial bearing  33 , thereby improving the reliability of the thrust bearing  42  and the radial bearing  33 . The clearance in the thrust bearing  42  and the clearance in the radial bearing  33  are part of the refrigerant passage that extends to the through hole  40  from the control pressure chamber  111  via the restriction groove  37 . This passage structure improves the reliability of the thrust bearing  42  and the radial bearing  33 . 
     (1-8) The suction passages  301  and  304  pass through the wall of the front housing member  11  that supports the mechanical seal  35 , and the inlet  101  of the suction passage  301  in the housing assembly  10  is provided in the outer surface of the front housing member  11 . The shorter the suction passage  301  extending to the through hole  40  from the external refrigerant circuit  26  is, the more the temperature rise of the lubrication oil in the path that extends from the external refrigerant circuit  26  to the through hole  40  through the suction passage  301  is suppressed. The structure that has the inlet  101  provided in the outer surface of the front housing member  11  is preferable, as it shortens the length of the suction passage  301  that extends to the through hole  40  from the passage  261 , which is the external suction pressure zone of the housing assembly  10 . 
     (1-9) The space in the vicinity of an outer end face  302  (see FIG. 1) of the supporting piece  30  is where there is part of the power transmission mechanism (e.g., an electromagnetic clutch) for transmitting power to the rotary shaft  13  from the external drive source. It is therefore difficult to provide the inlet  101  of the suction passage  301  in the outer end face  302 . The outer surface of the supporting piece  30 , particularly the portion of that outer surface which lies directly above the rotary shaft  13 , is suitable as the portion where the inlet  101  is provided. 
     A second embodiment shown in FIGS.  5 ( a ) and  5 ( b ) will be discussed below. Same reference symbols are used for those components which are the same as the corresponding components of the first embodiment. 
     A restriction groove  43  is formed in the outer surface  131  of the rotary shaft  13  between the radial bearing  33  and the flange  404  in the axial direction of the rotary shaft  13 . A restriction ring  44  of a synthetic resin is fitted about the rotary shaft  13  and in the through hole  40 . The length (thickness) of the restriction ring  44  is smaller than the length of the restriction groove  43  as a restriction passage. Both end portions of the restriction groove  43  are off an inner surface  441  of the restriction ring  44 . Part of the through hole  40  between the restriction ring  44  and the mechanical seal  35  communicates with the control pressure chamber  111  via the restriction groove  43 . The refrigerant in the control pressure chamber  111  flows to the through hole  40  via the restriction groove  43 . The restriction ring  44  and the restriction groove  43  constitute the pressure release means. 
     The second embodiment has the same advantages as the advantages (1-1) and (1-3) to (1-9) of the first embodiment. The outer surface  131  of the rotary shaft  13  is suitable as the portion where the restriction passage is to be formed. 
     A third embodiment shown in FIGS.  6 ( a ) and  6 ( b ) will be discussed below. Same reference symbols are used for those components which are the same as the corresponding components of the first embodiment. 
     A restriction ring  45  of a synthetic resin is fitted about the rotary shaft  13  and in the through hole  40 . The movement of the restriction ring  45  toward the mechanical seal  35  from the radial bearing  33  is restricted by a flange  132  formed on the outer surface  131  of the rotary shaft  13 . A restriction groove  46  is formed in an outer surface  451  of the restriction ring  45  in the axial direction of the rotary shaft  13 . The restriction groove  46  communicates with the through hole  40  between the mechanical seal  35  and the restriction ring  45  and with the control pressure chamber  111 . The through hole  40  between the mechanical seal  35  and the restriction ring  45  communicates with the control pressure chamber  111  via the restriction groove  46  as a restriction passage. The restriction ring  45  and the restriction groove  46  constitute the pressure release means. 
     The third embodiment has the same advantages as the advantages (1-1) and (1-3) to (1-9) of the first embodiment. 
     The restriction groove  46  is formed in the outer surface  451  of the restriction ring  45 . The outer surface  451  of the restriction ring  45  is where the groove can be formed easily. Therefore, the outer surface  451  of the restriction ring  45  is suitable as the portion where the restriction passage is to be formed. 
     A fourth embodiment shown in FIGS.  7 ( a ) and  7 ( b ) will be discussed below. Same reference symbols are used for those components which are the same as the corresponding components of the first embodiment. 
     A rubber restriction ring  47  has a U-shaped cross section and has a restriction hole  471  formed in the center of the bottom portion. The pressure on that side of the control pressure chamber  111  causes the restriction ring  47  to closely contact the outer surface  131  of the rotary shaft  13  and the inner surface  401  of the through hole  40 . The restriction hole  471  as a restriction passage and the restriction ring  47  constitute the pressure release means. 
     The fourth embodiment has the same advantages as the advantages (1-1) and (1-5) to (1-9) of the first embodiment. 
     Although the rubber restriction ring  47  is molded, the resilient deformation of the rubber permits a lower size precision than that in the case of the restriction ring of a synthetic resin. This makes the rubber restriction ring  47  easier to produce than the restriction ring of a synthetic resin. 
     A fifth embodiment shown in FIG. 8 will be discussed below. Same reference symbols are used for those components which are the same as the corresponding components of the first embodiment. 
     An inlet passage  123  is formed in the rear housing member  12 . The inlet passage  123  communicates with the passage  261 . A through hole  204  is formed in the first plate  20 , the second and third plates  21  and  22 , and the fourth plate  23  to communicate with the inlet passage  123 . Suction passages  194  and  313  are formed in the vicinity of the topmost positions of the outer portion of the cylinder block  19  and the peripheral wall  311  of the chamber defining piece  31 . The suction passage  194  communicates with the through hole  204 , and the suction passages  194  and  313  communicate with each other at the junction of the chamber defining piece  31  and the cylinder block  19 . A suction passage  303  in the supporting piece  30  communicates with the suction passage  313  and the through hole  40 . The inlet passage  123 , the through hole  204 , and the suction passages  194 ,  313  and  303  constitute a refrigerant passage upstream the through hole  40 . The suction passages  304 ,  312  and  193  and the through hole  203  constitute a refrigerant passage downstream the through hole  40 . A restriction ring  36 A is formed of a rubber. 
     The fifth embodiment has the same advantages as the advantages (1-1), (1-2) and (1-5) to (1-9) of the first embodiment. 
     A sixth embodiment shown in FIGS. 9 and 10 will be discussed below. Same reference symbols are used for those components which are the same as the corresponding components of the fifth embodiment. 
     As shown in FIG. 10, a first suction chamber  124  and a second suction chamber  125  are defined in the rear housing member  12  by partitions  41 ,  411  and  412 . The second suction chamber  125  communicates only with a specific one suction port  201 A in a plurality of suction ports  201 . The first suction chamber  124  communicates with the other suction ports  201  than the suction port  201 A. 
     As shown in FIG. 9, the first suction chamber  124  is connected to the external refrigerant circuit  26  via an inlet passage  126  formed in the rear housing member  12 . The suction passage  194  communicates with the inlet passage  126  via the through hole  204 , and the suction passage  193  communicates with the second suction chamber  125  via the through hole  203 . The refrigerant that has passed the evaporator  29  flows into the first suction chamber  124  and the suction passage  194  via the inlet passage  126 . The refrigerant that has flowed into the suction passage  194  flows to the suction port  201 A via the suction passages  313 ,  303 ,  304 ,  312  and  193 . 
     The sixth embodiment has the same advantages as the advantages of the fifth embodiment. Because the refrigerant flowing through the suction passages  194 ,  313 ,  303 ,  304 ,  312  and  193  is drawn into only one of a plurality of compression chambers  192 , the flow rate of the refrigerant in the suction passages  194 ,  313 ,  303 ,  304 ,  312  and  193  becomes lower than that in the fifth embodiment. It is therefore possible to make the diameters of the suction passages  194 ,  313 ,  303 ,  304 ,  312  and  193  smaller than those in the fifth embodiment. As a result, the peripheral wall  311  through which the suction passages  313  and  312  pass can be made thinner than that in the fifth embodiment, so that the compressor becomes lighter than the compressor of the fifth embodiment. 
     It should be apparent to those skilled in the art that the present invention may be embodied in many other specific forms without departing from the spirit or scope of the invention. Particularly, it should be understood that the invention may be embodied in the following forms. 
     (1) The restriction ring  36  may be formed of a metal. 
     (2) A lip seal may be used as the shaft sealing means. 
     (3) The supporting piece  30  may be formed integral with the chamber defining piece  31 . 
     (4) In each of the embodiments, the direction of the suction passage may be drastically changed before the inlet port  402  of the suction passage. 
     The rapid change in the passage direction before the inlet port  402  separates the lubrication oil from the refrigerant, thus increasing the amount of the lubrication oil that directly contacts the mechanical seal  35  or the surface of the rotary shaft  13  in the through hole  40 . In this case, the efficiency of cooling the mechanical seal  35  is improved. 
     Therefore, the present examples and embodiments are to be considered as illustrative and not restrictive and the invention is not to be limited to the details given herein, but may be modified within the scope and equivalence of the appended claims.