Patent Publication Number: US-2009223244-A1

Title: Swash plate type compressor

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a swash plate type compressor. 
     A conventional swash plate type compressor is disclosed in Japanese Patent Application Publication No. 10-54350. The swash plate type compressor has a housing assembly including a front housing, a cylinder block, and a rear housing. The housing assembly defines therein a plurality of cylinder bores, a suction chamber, a discharge chamber, and a crank chamber. A drive shaft is rotatably supported by the front housing. One end of the drive shaft extends out of the front housing through the crank chamber. The cylinder block defines therein an accommodation chamber in which the other end of the drive shaft is located. A valve unit is arranged between the cylinder block and the rear housing. The accommodation chamber communicates with the suction chamber through a hole of the valve unit. 
     A swash plate is inclinably and slidably supported by the drive shaft in the crank chamber. Each cylinder bore accommodates therein a piston so that the piston is reciprocally slidable therein. A pair of front and rear shoes are disposed between the swash plate and the pistons. Wobbling motion of the swash plate is converted into reciprocating motion of the pistons through the shoes. The discharge chamber is connected to the crank chamber through a supply passage. A displacement control valve is disposed in the supply passage for adjusting the pressure in the crank chamber. 
     In this swash plate type compressor, the drive shaft has a bleed passage formed therein for communication between the crank chamber and the suction chamber. The bleed passage has a hole extending radially in the drive shaft, and a passage extending axially in the drive shaft for connecting the hole to the suction chamber. 
     In this swash plate type compressor, the drive shaft has at the end thereof in the accommodation chamber a valve. The valve is operable to reduce the opening of the bleed passage in response to an increase of the rotational speed of the drive shaft, and to increase the opening of the bleed passage in response to a decrease of the rotational speed of the drive shaft. 
     The swash plate type compressor constitutes a refrigeration circuit with a condenser, an expansion valve, and an evaporator for a vehicle air conditioning system. Refrigerant gas containing lubricating oil is sealed in the refrigeration circuit. The displacement control valve is operable to adjust the pressure in the crank chamber in accordance with the pressure in the suction chamber and the flow rate of refrigerant gas. Thus, the inclination angle of the swash plate with respect to the drive shaft is changed for controlling the displacement of the swash plate type compressor. 
     While a vehicle is running at a high speed, the opening of the bleed passage of the swash plate type compressor is decreased due to the increased rotational speed of the drive shaft. Especially, while the compressor is driven at a high speed and operating with a high displacement, the pressure in the crank chamber is gradually increased thereby to reduce the displacement of the compressor. Thus, the compression load of the compressor may be reduced. While a vehicle is running at a low speed, on the other hand, the opening of the bleed passage is increased due to the decreased rotational speed of the drive shaft. Thus, in accordance with the required refrigeration performance, the pressure in the crank chamber is gradually decreased thereby to increase the displacement of the compressor. Therefore, the compressor can improve the refrigeration performance. 
     The swash plate type compressor, especially when the drive shaft is driven to rotate at a high speed, requires improved sliding characteristics between the swash plate and the shoes, and also between the cylinder bores and the pistons. When the drive shaft is driven to rotate at a low speed, it is required that the amount of lubricating oil contained in refrigerant gas discharged into external refrigeration circuit outside the compressor should be decreased, and the compressor should provide a high refrigeration performance. 
     The present invention is directed to providing a swash plate type compressor that can provide excellent sliding characteristics when the drive shaft is driven to rotate at a high speed, and provide high refrigeration performance when the drive shaft is driven to rotate at a low speed. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, a swash plate type compressor has a housing assembly, a drive shaft, a swash plate, a piston, a motion converter, a bleed passage, and an oil separator. The housing assembly includes a cylinder bore, a suction chamber, a discharge chamber, and a crank chamber. The drive shaft is rotatably supported by the housing assembly, and extends through the crank chamber. The swash plate is supported by the drive shaft in the crank chamber. The piston is accommodated in the cylinder bore so as to be reciprocally slidable therein. The motion converter is disposed between the swash plate and the piston, and converts wobbling motion of the swash plate into reciprocating motion of the piston. The bleed passage communicates between the crank chamber and the suction chamber. The oil separator is disposed in the housing assembly. The oil separator separates no or less amount of lubricating oil from the refrigerant gas in the increased rotational speed of the drive shaft than that in the decreased rotational speed of the drive shaft. The refrigerant gas passed through the oil separator is introduced into the suction chamber, and the separated lubricating oil is returned to the crank 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 
         FIG. 1  is a longitudinal cross-sectional view showing a swash plate type compressor according to a first preferred embodiment of the present invention; 
         FIG. 2  is a partially enlarged longitudinal cross-sectional view showing the swash plate type compressor of  FIG. 1  when the drive shaft is driven to rotate at a low speed; 
         FIG. 3  is a partially enlarged longitudinal cross-sectional view showing the swash plate type compressor of  FIG. 1  when the drive shaft is driven to rotate at a high speed; 
         FIG. 4  is a perspective view showing a valve of the swash plate type compressor of  FIG. 1 ; 
         FIG. 5  is a partially enlarged longitudinal cross-sectional view showing the swash plate type compressor according to a second preferred embodiment of the present invention when the drive shaft is driven to rotate at a low speed; 
         FIG. 6  is a partially enlarged longitudinal cross-sectional view showing the swash plate type compressor of  FIG. 5  when the drive shaft is driven to rotate at a high speed; 
         FIG. 7  is a partially enlarged longitudinal cross-sectional view showing the swash plate type compressor according to a third preferred embodiment of the present invention when the drive shaft is driven to rotate at a low speed; 
         FIG. 8  is a partially enlarged longitudinal cross-sectional view showing the swash plate type compressor of  FIG. 7  when the drive shaft is driven to rotate at a high speed; 
         FIG. 9  is a partially enlarged longitudinal cross-sectional view showing the swash plate type compressor according to a fourth preferred embodiment of the present invention when the drive shaft is driven to rotate at a low speed; and 
         FIG. 10  is a partially enlarged longitudinal cross-sectional view showing the swash plate type compressor of  FIG. 9  when the drive shaft is driven to rotate at a high speed. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following will describe a swash plate type compressor according to the first through fourth preferred embodiments of the present invention with reference to  FIGS. 1 through 10 . 
     The swash plate type compressor of the first preferred embodiment is a variable displacement type compressor used for a vehicle air conditioning system. Referring to  FIG. 1 , the compressor has a drive shaft  7  and a housing assembly including a cylinder block  1 , a front housing  3 , and a rear housing  5 . The cylinder block  1  has a plurality of cylinder bores  1 A extending parallel to the axis of the drive shaft  7 . The left side of the drawing corresponds to the front side of the compressor, and the right side of the drawing corresponds to the rear side of the compressor. 
     A suction chamber  11  and a discharge chamber  13  are defined in the rear housing  5  for communication with the cylinder bores  1 A through a valve unit  9 . A crank chamber  15  is defined by the front housing  3  and the cylinder block  1 . The front housing  3  and the cylinder block  1  have shaft holes  3 A,  1 B formed therein, respectively. A shaft seal  17  made of a rubber material is arranged between the front housing  3  and the drive shaft  7  in the shaft hole  3 A for sealing the drive shaft  7 . A plane bearing  19  is arranged in the shaft hole  1 B. An accommodation chamber  1 C is defined in the cylinder block  1  at the rear center thereof so as to face the valve unit  9  and for communication with the shaft hole  1 B. 
     The drive shaft  7  is rotatably supported by the front housing  3  and the cylinder block  1  in such a manner that the center part thereof extends through the crank chamber  15 , and one end thereof extends out of the front housing  3 . The drive shaft  7  is connected to a pulley (not shown) and an electromagnetic clutch on which a belt is wounded, and driven to rotate by a drive source such as an engine or the like through the belt. Each cylinder bore  1 A accommodates therein a piston  21  so that the piston  21  is reciprocally slidable therein. Each piston  21  defines a compression chamber with the corresponding cylinder bore  1 A. 
     A lug plate  23  is fixed to the drive shaft  7  in the crank chamber  15  for rotation therewith and for receiving compression force, and a thrust bearing  25  and a plane bearing  27  are arranged between the lug plate  23  and the front housing  3 . A swash plate  29  is mounted on and supported by the drive shaft  7  so as to be tiltable with a variable inclination angle with respect to a plane extending perpendicularly to the axis of the drive shaft  7  in the crank chamber  15 . The lug plate  23  has a hinge portion  23 A extending toward the swash plate  29 . The swash plate  29  has a hinge portion  29 A extending toward the lug plate  23 . The hinge portions  23 A,  29 A form a link mechanism  31 . A coil spring  33  is arranged between the lug plate  23  and the swash plate  29  for urging the lug plate  23  and the swash plate  29  away from each other. 
     A shoe  35  is arranged between the swash plate  29  and each piston  21 . The shoe  35  includes a pair of front and rear shoes  35 A,  35 B. The front shoe  35 A is arranged between the front surface of the swash plate  29  and the front seat surface of the piston  21 , and the rear shoe  35 B is arranged between the rear surface of the swash plate  29  and the rear seat surface of the piston  21 . Each of the front and rear shoes  35 A,  35 B has a substantially hemispherical shape, and serves as a motion converter. 
     The drive shaft  7  has a radial hole  37 , an axial passage  39 , and a discharge hole  41  formed therein. The axial passage  39  extends along the axial direction of the drive shaft  7  to the rear end of the drive shaft  7 , the radial hole  37  extends radially from the axial passage  39 , and the discharge hole  41  extends radially from the axial passage  39  at a position adjacent to the rear end of the drive shaft  7 . 
     The radial hole  37  is formed in the drive shaft  7  at a position between the lug plate  23  and the front housing  3  so as to extend across the diameter of the drive shaft  7  from the axis to the outer peripheral surfaces thereof. An oil guide passage  3 B is formed in the front housing  3  so as to extend from the outer region of the crank chamber  15  to a space between the front housing  3  and the lug plate  23  in facing relation to the thrust bearing  25 . The front housing  3  also has formed therein an oil guide passage  3 C connected to the oil guide passage  3 B, and extending in facing relation to the plane bearing  27  and the shaft seal  17 . The oil guide passage  3 C communicates with the radial hole  37  through the shaft seal  17  in the shaft hole  3 A. The oil guide passage  3 B and the oil guide passage  3 C form the oil guide passage of the first preferred embodiment of the present invention. 
     Referring to  FIGS. 2 and 3 , the rear end of the drive shaft  7  extends into the accommodation chamber  1 C which is in communication with the discharge hole  41 . The discharge hole  41  is formed in the drive shaft  7  so as to extend across the diameter of the drive shaft  7  from the axis to the outer peripheral surfaces thereof. An oil separating member  43  is mounted to the rear end of the drive shaft  7 , and a valve  45  is inserted into the rear end of the axial passage  39  of the drive shaft  7 . 
     The oil separating member  43  has a cylindrical portion  43 A, a tapered portion  43 B, and a flange portion  43 C. The cylindrical portion  43 A is fitted over the rear end of the drive shaft  7 . The tapered portion  43 B is formed integrally with the cylindrical portion  43 A so as to taper from the valve unit  9  toward the rear end portion of the cylindrical portion  43 A. The flange portion  43 C is flanged outwardly from the rear end portion of the tapered portion  43 B and extends in facing relation to the valve unit  9 . The accommodation chamber  1 C is partitioned into a first chamber  47  and a second chamber  49  with a clearance therebetween by the oil separating member  43 . The first chamber  47  is located outside the cylindrical portion  43 A, the tapered portion  43 B, and the flange portion  43 C, and in indirect communication with the throttle hole  9 A. The second chamber  49  is located inside the cylindrical portion  43 A, the tapered portion  43 B, and the flange portion  43 C, and in direct communication with the throttle hole  9 A. 
     The front end portion of the valve  45  having a cylindrical shape is inserted into the axial passage  39  of the drive shaft  7 , while the rear end portion of the valve  45  has a spherical cap shape. As shown in  FIG. 4 , the rear end portion of the valve  45  is divided into four segments to the radial direction. The four segments move to radial direction, or move away one another against its own elastic force under the influence of centrifugal force so as to open the valve  45 . As shown in  FIGS. 2 and 3 , a weight  45 A is fixed on the inner surface of each segment of the valve  45 . 
     The valve unit  9  has a throttle hole  9 A formed therethrough for communication between the second chamber  49  in the accommodation chamber  1 C and the suction chamber  11 . As shown in  FIG. 1 , the cylinder block  1  has a return passage  51  formed therein for connecting the first chamber  47  in the accommodation chamber  1 C to the inner region of the crank chamber  15  adjacent to the drive shaft  7 . With the compressor installed in the vehicle, the return passage  51  connects the lower region of the first chamber  47 , as seen in  FIG. 1 , to the crank chamber  15 . The oil guide passage  3 B, the oil guide passage  3 C, the radial hole  37 , the axial passage  39 , the discharge hole  41 , the first chamber  47 , the second chamber  49  and the throttle hole  9 A form the bleed passage of the first preferred embodiment of the present invention. The oil guide passage  3 B, the oil guide passage  3 C, the radial hole  37 , and the axial passage  39  form the upstream passage of the first preferred embodiment of the present invention. The accommodation chamber  1 C, the oil separating member  43 , the return passage  51  and the valve  45  form the oil separator of the first preferred embodiment of the present invention. 
     As shown in  FIG. 1 , the rear housing  5  accommodates therein a displacement control valve  53 . The displacement control valve  53  communicates with the suction chamber  11  through a detecting passage  55 , and connects the discharge chamber  13  to the crank chamber  15  through the supply passage  57 . The displacement control valve  53  is operable to change the opening of the supply passage  57  depending on the detected pressure in the suction chamber  11 , thus varying the displacement of the compressor. 
     As shown in  FIG. 1 , the discharge chamber  13  of the compressor is connected to the suction chamber  11  by a tube  59  by way of a check valve  61 , a condenser  63 , an expansion valve  65 , and an evaporator  67 . The compressor, the check valve  61 , the condenser  63 , the expansion valve  65  and the evaporator  67  and the tube  59  form the refrigeration circuit. Refrigerant gas containing lubricating oil is sealed and circulated in the refrigeration circuit. 
     In the above-described compressor, the displacement control valve  53  adjusts the pressure in the crank chamber  15  in accordance with the pressure in the suction chamber  11  and the flow rate of the refrigerant gas. Thus, the inclination angle of the swash plate  29  is changed with respect to the drive shaft  7 , with the result that the displacement of the compressor is varied. 
     While a vehicle is running at a high speed, the drive shaft  7  is driven to rotate at a high speed, accordingly. The valve  45  is then opened by centrifugal force against its own elastic force, as shown in  FIG. 3 . Thus, the effective opening of the axial passage  39  of the drive shaft  7  is increased. Therefore, the axial passage  39  is connected to the second chamber  49 , so that refrigerant gas in the axial passage  39  is flowed into the suction chamber  11  through the second chamber  49  inside the oil separating member  43  and the throttle hole  9 A without separating lubricating oil therefrom. The cross-section of the opening of the valve  45  is set greater than at least one of the cross-sections of the opening of the discharge hole  41  and the opening of a passage formed by a clearance between the flange portion  43 C and the valve unit  9  or between the first chamber  47  and the second chamber  49 . 
     The crank chamber  15  has regions having a relatively large amount of lubricating oil, and having a relatively small amount of lubricating oil. The region having a relatively large amount of lubricating oil includes the outer region of the crank chamber  15 , and the region having a relatively small amount of lubricating oil includes the inner region away from the outer surface of the crank chamber  15 . In the crank chamber  15 , the swash plate  29  is driven to rotate by the drive shaft  7 , and lubricating oil is brought to the outer region of the crank chamber  15  due to a centrifugal force. The region having a relatively large amount of lubricating oil further includes the lower region of the crank chamber  15 , and the region around the outer surface of the cylinder bore  1 A. The region having a relatively large amount of lubricating oil further includes the upper region of the crank chamber  15 . 
     The outer region of the crank chamber  15  has a relatively large amount of lubricating oil. Lubricating oil in the crank chamber  15  is introduced into the radial hole  37  through the oil guide passage  3 B that extends from such outer region of the crank chamber  15  and also through the oil guide passage  3 C. Thus, refrigerant gas containing a relatively large amount of lubricating oil is introduced into the suction chamber  11 . Therefore, the amount of lubricating oil in the crank chamber  15  is adequate, and the lubricating oil is not subjected excessive agitation by the swash plate  29 , so that the lubrication oil is not heated excessively due to the shearing of the swash plate  29 , and the viscosity of lubricating oil is not decreased. Therefore, sliding surfaces of the shoes  35  and the swash plate  29  and the like are lubricated properly. Since refrigerant gas from the suction chamber  11  contains a relatively large amount of lubricating oil, the sliding surfaces of the cylinder bores  1 A and the pistons  21  are also lubricated properly. 
     The amount of lubricating oil in refrigerant gas discharged out of the compressor into the external refrigeration circuit is increased. However, the refrigeration performance of the compressor is not affected since the pistons  21  are then reciprocating at a high speed. 
     Since lubricating oil is introduced into the radial hole  37  through the shaft seal  17 , a relatively large amount of lubricating oil is supplied to the shaft seal  17  made of a rubber material, so that the durability of the shaft seal  17  is improved. 
     While the vehicle is running at a low speed, the drive shaft  7  is driven to rotate at a low speed, accordingly. As shown in  FIG. 2 , the valve  45  is closed due to a relatively small centrifugal force against the elastic force of the valve  45 . Thus, the effective opening of the axial passage  39  of the drive shaft  7  is decreased. Then, the fluid communication between the axial passage  39  and the second chamber  49  is blocked, so that refrigerant gas in the axial passage  39  is introduced into the first chamber  47  through the discharge hole  41 , and then into the second chamber  49 . Lubrication oil is separated from refrigerant gas when the refrigerant gas in the first chamber  47  is passed through the clearance between the valve unit  9  and the flange portion  43 C or between the first chamber  47  and the second chamber  49 . Subsequently, refrigerant gas in the second chamber  49  is introduced into the suction chamber  11  through the throttle hole  9 A. Meanwhile, lubricating oil separated from refrigerant gas is retained in the first chamber  47 , and then returned to the crank chamber  15  through the return passage  51 . The return passage  51  connects the lower region of the first chamber  47  to the region of the crank chamber  15  having the relatively small amount of lubricating oil. Thus, the separated lubricating oil from the refrigerant gas retained in the first chamber  47  is easily returned to the crank chamber  15 . In other words, the oil separator separates no or less amount of lubricating oil from the refrigerant gas in the increased rotational speed of the drive shaft  7  than that in the decreased rotational speed of the drive shaft  7 , the refrigerant gas passed through the oil separator is introduced into the suction chamber  11 , and the separated lubricating oil is returned to the crank chamber  15 . 
     Thus, the amount of lubricating oil in refrigerant gas discharged out of the compressor and into the external refrigeration circuit is decreased, so that the compressor can provide high refrigeration performance. 
     The amount of lubricating oil in the crank chamber  15  is increased during the low-speed operation of the compressor. However, the swash plate  29  agitates lubricating oil only at a low speed, so that the viscosity of lubricating oil is hardly decreased, and lubrication oil is hardly heated. Therefore, the sliding surfaces are lubricated properly. 
     The compressor according to the first preferred embodiment of the present invention can provide excellent sliding characteristics when the drive shaft  7  is driven to rotate at a high speed, and high refrigeration performance when the drive shaft  7  is driven to rotate at a low speed. 
     The swash plate type compressor according to the second preferred embodiment of the present invention shown in  FIGS. 5 and 6  differs from the compressor according to the first preferred embodiment in terms of the structure of the valve and the oil separating member. 
     The drive shaft  7  has a discharge hole  73  formed therein so as to extend in the radial direction thereof for connecting the axial passage  39  to the first chamber  47 . The drive shaft  7  also has a valve hole  7 A and a guide hole  7 B formed therein behind the discharge hole  73  so as to extend in the radial direction thereof and in parallel with the discharge hole  73  for connecting with the axial passage  39 . The valve hole  7 A has a larger diameter than the guide hole  7 B, and the valve hole  7 A and the guide hole  7 B are formed coaxially. A valve body  69 A and a connecting bar  69 B are received slidably in the valve hole  7 A and the guide hole  7 B, respectively. The valve body  69 A is movable into the axial passage  39  so as to close the axial passage  39 . One end of the connecting bar  69 B is fixed to the valve body  69 A, and the other end of the connecting bar  69 B is fixed to a spring seat  69 C disposed in the accommodation chamber  1 C. A spring  69 D is disposed between the outer peripheral surface of the drive shaft  7  and the spring seat  69 C for urging the valve body  69 A in the direction that closes the axial passage  39 . The valve body  69 A, the connecting bar  69 B, the spring seat  69 C and the spring  69 D form a valve  69 . The valve body  69 A serves also as a weight. 
     An oil separating member  71  has a cylindrical portion  71 A and a flange portion  71 B. The cylindrical portion  71 A is fitted over the rear end of the drive shaft  7 . The flange portion  71 B is formed integrally with the cylindrical portion  71 A and flanged outwardly from the rear end of the cylindrical portion  71 A in facing relation to the valve unit  9 . The oil guide passage  3 B, the oil guide passage  3 C, the radial hole  37 , the axial passage  39 , the discharge hole  73 , the first chamber  47 , the second chamber  49 , and the throttle hole  9 A form the bleed passage of the second preferred embodiment of the present invention. The oil guide passage  3 B, the oil guide passage  3 C, the radial hole  37 , and the axial passage  39  form the upstream passage of the second preferred embodiment of the present invention. The accommodation chamber  1 C, the oil separating member  71 , the return passage  51  and the valve  69  form the oil separator of the second preferred embodiment of the present invention. The rest of the structure of the second preferred embodiment of the present invention are substantially the same as the first preferred embodiment. 
     When the drive shaft  7  is driven to rotate at a high speed, the valve  69  is moved due to a relatively large centrifugal force so that the valve body  69 A is moved away from the axis of the drive shaft  7  against the urging force of the spring  69 D. As a result, the effective opening of the axial passage  39  is increased by the valve body  69 A, as shown in  FIG. 6 . Thus, refrigerant gas in the crank chamber  15  containing a relatively large amount of the lubricating oil is introduced into the second chamber  49  through the oil guide passage  3 B, the oil guide passage  3 C, the radial hole  37  and the axial passage  39 . Refrigerant gas in the second chamber  49  is drawn into the suction chamber  11  through the throttle hole  9 A. The cross-section of the opening of the axial passage  39  is set greater than at least one of the cross-sections of the opening of the discharge hole  73  and the opening of a passage formed by a clearance between the flange portion  71 B and the valve unit  9 , or between the first chamber  47  and the second chamber  49 . 
     When the drive shaft  7  is driven to rotate at a low speed, on the other hand, the valve  69  is moved due to a relatively small centrifugal force so that the valve body  69 A is moved toward the axis of the drive shaft  7  by the urging force of the spring  69 D, as shown in  FIG. 5 . Thus, the effective opening of the axial passage  39  is decreased by the valve body  69 A. Therefore, refrigerant gas in the crank chamber  15  containing a relatively large amount of lubricating oil is introduced into the first chamber  47  through the oil guide passage  3 B, the oil guide passage  3 C, the radial hole  37 , the axial passage  39  and the discharge hole  73 . Then, lubricating oil is separated from refrigerant gas when refrigerant gas in the first chamber  47  is flowed into the second chamber  49 . Subsequently, refrigerant gas in the second chamber  49  is flowed into the suction chamber  11  through the throttle hole  9 A. Meanwhile, lubricating oil retained in the first chamber  47  separated from refrigerant gas is returned to the crank chamber  15  through the return passage  51 . 
     As is obvious from the foregoing, the compressor according to the second preferred embodiment of the present invention can provide the same advantageous effects as the first preferred embodiment. 
     The swash plate type compressor according to the third preferred embodiment of the present invention differs from the compressors according to the first and second preferred embodiments in terms of the structure of the valve and the oil separating member. 
     The drive shaft  7  has a discharge hole  79  formed therein so as to extend in the radial direction for connecting the axial passage  39  to the first chamber  47 . The drive shaft  7  also has a valve hole  7 C and a guide hole  7 D formed coaxially therein behind the discharge hole  79  so as to extend in the radial direction thereof and in parallel with the discharge hole  79 , and connect to the axial passage  39 . The valve hole  7 C and the guide hole  7 D are in communication with the axial passage  39  and the second chamber  49 , respectively. The valve hole  7 C has a larger diameter than the guide hole  7 D. A connecting bar  75 B is slidably inserted through the valve hole  7 C and the guide hole  7 D. A valve body  75 A is disposed in the accommodation chamber  1 C or movably disposed on the outer end of the valve hole  7 C. One end of the connecting bar  75 B is fixed to the valve body  75 A, and the other end of the connecting bar  75 B is fixed to a spring seat  75 C disposed in the accommodation chamber  1 C. A spring  75 D is disposed between the outer peripheral surface of the drive shaft  7  and the spring seat  75 C for urging the valve body  75 A against the outer peripheral surface of the drive shaft  7  thereby to close the valve hole  7 C. The valve body  75 A, the connecting bar  75 B, the spring seat  75 C and the spring  75 D form a valve  75 . The valve body  75 A serves also as a weight. The valve body  75 A is made of a material having a larger specific gravity than the materials of the connecting bar  75 B and the spring seat  75 C. The rear end of the axial passage  39  is closed by a plug  78 . 
     An oil separating member  77  has a cylindrical portion  77 A, a tapered portion  77 B, and a flange portion  77 C. The cylindrical portion  77 A is fitted over the rear end of the drive shaft  7 . The tapered portion  77 B is formed integrally with the cylindrical portion  77 A so as to taper from the valve unit  9  toward the end of the cylindrical portion  77 A. The flange portion  77 C is flanged outwardly from the rear end of the tapered portion  77 B and extends in facing relation to the valve unit  9 . The oil guide passage  3 B, the oil guide passage  3 C, the radial hole  37 , the axial passage  39 , the discharge hole  79 , the first chamber  47 , the valve hole  7 C, the second chamber  49  and the throttle hole  9 A form the bleed passage of the third preferred embodiment of the present invention. The oil guide passage  3 B, the oil guide passage  3 C, the radial hole  37 , and the axial passage  39  form the upstream passage of the third preferred embodiment of the present invention. The accommodation chamber  1 C, the oil separating member  77 , the return passage  51  and the valve  75  form the oil separator of the third preferred embodiment of the present invention. The rest of the structure of the third preferred embodiment of the present invention is substantially the same as the first preferred embodiment of the present invention. 
     When the drive shaft  7  is driven to rotate at a high speed, the valve  75  is moved due to a relatively large centrifugal force so that the valve body  75 A is moved away from the axis of the drive shaft  7  against the urging force of the spring  75 D. Accordingly, the valve hole  7 C is opened by the valve body  75 A. Refrigerant gas in the crank chamber  15  containing a relatively large amount of lubricating oil is introduced into the second chamber  49  through the oil guide passage  3 B, the oil guide passage  3 C, the radial hole  37 , the axial passage  39  and the valve hole  7 C. Refrigerant gas thus introduced in the second chamber  49  is then flowed into the suction chamber  11  through the throttle hole  9 A. 
     When the drive shaft  7  is driven to rotate at a low speed, the valve  75  is moved due to a relatively small centrifugal force so that the valve body  75 A is moved toward the axis of the drive shaft  7  by the urging force of the spring  75 D. Accordingly, the opening of the valve hole  7 C is closed by the valve body  75 A, as shown in  FIG. 7 . Thus, refrigerant gas in the crank chamber  15  containing a relatively large amount of lubricating oil is introduced into the first chamber  47  through the oil guide passage  3 B, the oil guide passage  3 C, the radial hole  37 , the axial passage  39  and the discharge hole  79 . Lubricating oil is separated from refrigerant gas when the refrigerant gas in the first chamber  47  is introduced into the second chamber  49 . Subsequently, refrigerant gas is drawn into the suction chamber  11  through the throttle hole  9 A. Meanwhile, lubricating oil retained in the first chamber  47  separated from the refrigerant gas is returned to the crank chamber  15  through the return passage  51 . 
     Therefore, the compressor according to the third preferred embodiment of the present invention can provide the same advantageous effects as the first and second preferred embodiments of the present invention. 
     The swash plate type compressor according to the fourth preferred embodiment of the present invention differs from the compressors according to the first through third preferred embodiments of the present invention in terms of the structure of the valve, the oil separating member, and the axial passage. 
     Referring to  FIGS. 9 and 10 , an assembly  80  includes a valve  81  and an oil separating member  82 . The valve  81  is formed integrally with an oil separating member  82 , and fitted on the rear end of the drive shaft  7 . The assembly  80  has a first valve hole  7 E and a second valve hole  7 F formed coaxially therein in the radial direction of the assembly  80  with the same diameter. A valve seat  7 G is formed at the end of the first valve hole  7 E. The valve  81  includes a second valve body  81 A slidably received in the second valve hole  7 F. According to the fourth preferred embodiment of the present invention, the first valve hole  7 E and the valve seat  7 G form a discharge hole  83 . The valve  81  further includes a first valve body  81 C and a connecting bar  81 B. One end of the connecting bar  81 B is fixed to the first valve body  81 C, and the other end of the connecting bar  81 B is fixed to the second valve body  81 A, as shown in  FIG. 9 . A spring seat  81 D is formed between the first valve hole  7 E and the second valve hole  7 F with a diameter that is smaller than that of the first valve hole  7 E and the second valve hole  7 F. A spring  81 E is disposed between the first valve body  81 C and the spring seat  81 D for urging the first valve body  81 C in the direction that disengages from the valve seat  7 G for opening the discharge hole  83 , and the second valve body  81 A in the direction that closes the axial passage  39 . The second valve body  81 A, the connecting bar  81 B, the first valve body  81 C, the spring seat  81 D, and the spring  81 E form the valve  81 . The second valve body  81 A serves also as a weight. 
     The axial passage  39  of the fourth embodiment includes a front passage  39 A formed in the drive shaft  7  and a rear passage  39 B formed in the assembly  80  for fluid communication with each other. The rear passage  39 B is formed in such a manner that the effective diameter of the rear passage  39 B is variable. The first valve hole  7 E and the second valve hole  7 F are connected to the rear passage  39 B, respectively. The valve  81  is arranged at a position adjacent to the rear end of the rear passage  39 B. The second valve body  81 A is movable into the rear passage  39 B so as to close the rear passage  39 B. 
     The oil separating member  82  of the assembly  80  has a base portion  82 A, a tapered portion  82 B, and a flange portion  82 C. The tapered portion  82 B is formed so as to taper from the valve unit  9  toward the rear end of the base portion  82 A. The flange portion  82 C is flanged outwardly from the rear end of the tapered portion  82 B and extends in facing relation to the valve unit  9 . The oil guide passage  3 B, the oil guide passage  3 C, the radial hole  37 , the axial passage  39 , the discharge hole  83 , the first chamber  47 , the second chamber  49 , and the throttle hole  9 A form the bleed passage of the fourth preferred embodiment of the present invention. The oil guide passage  3 B, the oil guide passage  3 C, the radial hole  37 , and the axial passage  39  form the upstream passage of the fourth preferred embodiment of the present invention. The accommodation chamber  1 C, the oil separating member  82 , the return passage  51 , and the valve  81  form the oil separator of the fourth preferred embodiment of the present invention. The rest of the structure of the fourth preferred embodiment of the present invention is substantially the same as the first preferred embodiment of the present invention. 
     According to the compressor of the fourth preferred embodiment of the present invention, when the drive shaft  7  is driven to rotate at a high speed, the valve  81  is moved due to a relatively large centrifugal force so that the first valve body  81 C is moved toward the axis of the drive shaft  7  against the urging force of the spring  81 E. This causes the opening of the discharge hole  83  to be decreased, but the opening of the rear passage  39 B to be increased. When the first valve body  81 C is in directly contact with the valve seat  7 G, the discharge hole  83  is closed, but the cross-section of the opening of the rear passage  39 B becomes maximum. Refrigerant gas in the crank chamber  15  containing a relatively large amount of lubricating oil is introduced into the second chamber  49  through the oil guide passage  3 B, the oil guide passage  3 C, the radial hole  37 , and the axial passage  39 . Then, refrigerant gas in the second chamber  49  is drawn into the suction chamber  11  through the throttle hole  9 A. 
     When the drive shaft  7  is driven to rotate at a low speed, the valve  81  is moved due to a decreased centrifugal force so that the first valve body  81 C is moved away from the axis of the drive shaft  7  by the urging force of the spring  81 E, as shown in  FIG. 9 . Thus, the cross-section of the opening of the discharge hole  83  is increased. When the second valve body  81 A is in directly contact with the spring seat  81 D, the rear passage  39 B is closed, and the effective opening of the discharge hole  83  becomes the maximum. Thus, refrigerant gas in the crank chamber  15  containing a relatively large amount of lubricating oil is introduced into the first chamber  47  through the oil guide passage  3 B, the oil guide passage  3 C, the radial hole  37 , the axial passage  39 , and the discharge hole  83 . Lubricating oil is separated from refrigerant gas when the refrigerant gas in the first chamber  47  is introduced into the second chamber  49 . Subsequently, refrigerant gas in the second chamber  49  is drawn into the suction chamber  11  through the throttle hole  9 A. Meanwhile, lubricating oil separated from refrigerant gas is returned to the crank chamber  15  through the return passage  51 . 
     Therefore, the compressor according to the fourth preferred embodiment of the present invention can provide the same advantageous effects as the first preferred embodiment of the present invention. According to the compressor of the fourth preferred embodiment, the assembly  80  is formed in such a manner that the valve  81  is formed integrally with the oil separating member  82 . In assembling the compressor, the assembly  80  is previously made, and then the assembly  80  is only press-fitted over the rear end of the drive shaft  7 , which contribute to decreasing the processes of assembling the compressor. 
     The present invention is not limited to the above-described first through fourth embodiments, but may be modified into the various alternative embodiments as follows. 
     The link mechanism  31  is not limited to that of the above-described embodiments. Alternatively, any one of various types of link mechanisms is applicable. 
     According to the above-described embodiments, the upstream passage is in communication with the outer region of the crank chamber  15 . Alternatively the upstream passage may in communication with either region of the crank chamber  15  having a relatively large amount of lubricating oil. 
     The return passage  51  is not limited to that of the above-described embodiments. Alternatively, the return passage  51  may decline from the accommodation chamber  1 C to the crank chamber  15 . 
     The valve is not limited to that of the above-described embodiments. Alternatively, any one of the various types of valves operated in accordance with the rotational speed of the drive shaft  7  is applicable. For example, the valve may be a solenoid valve. The solenoid valve is an electromechanical valve whose state is varied in accordance with signals outputted from a rotational speed sensor or an acceleration sensor. The rotational speed sensor detects rotational speed, and the acceleration sensor detects centrifugal force. 
     The swash plate type compressor of the present invention is not limited to the variable displacement swash plate type compressor in which an inclination angle of the swash plate is variable, but it is applicable to a fixed displacement swash plate type compressor in which an inclination angle of the swash plate is not variable. 
     The swash plate type compressor of the present invention can be used for a vehicle air conditioner. 
     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 of the appended claims.