Patent Publication Number: US-8117959-B2

Title: Swash plate type compressor

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a swash plate type compressor, which is equipped with a rotary valve for connecting a cylinder bore that is in a suction stroke to a swash plate chamber. 
     Japanese Laid-Open Patent Publication No. 5-306680 discloses a swash plate type variable displacement compressor equipped with a rotary valve. The rotary valve is mounted on the circumferential surface of a drive shaft. The outer circumferential surface of the rotary valve includes a variable suction passage. The rotary valve is accommodated in a shaft bore of a cylinder block such that the rotary valve rotates with respect to the cylinder block and moves in the axial direction of the drive shaft. The surface of the cylinder block facing the swash plate chamber includes an inlet groove for drawing in refrigerant gas from the swash plate chamber. The inlet groove communicates with the shaft bore. The cylinder block has cut-out grooves, which connect the shaft bore to the cylinder bores. When any of the cylinder bores is in a suction stroke, refrigerant gas in the swash plate chamber is drawn into the cylinder bore via the inlet groove, the shaft bore, the variable suction passage, and the associated cut-out groove. 
     In the compressor of the above publication, the inlet groove is open toward a boss of a swash plate, which rotates integrally with the drive shaft. The distance between the boss and the inlet groove is always constant even when the swash plate is rotating. Therefore, during operation of the compressor, rotation of the boss generates stationary vortices in refrigerant between the boss and the inlet groove, which hinders refrigerant gas from being drawn into the inlet groove. As a result, the amount of refrigerant gas drawn into the cylinder bore is suppressed. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an objective of the present invention to provide a swash plate type compressor that has improved suction efficiency of refrigerant gas from a swash plate chamber to a cylinder bore. 
     According to one aspect of the invention, a swash plate type compressor is provided. The compressor includes a housing, which defines a swash plate chamber inside the housing. The swash plate chamber contains refrigerant gas. A drive shaft is rotatably supported by the housing. The drive shaft defines an axial direction and a radial direction. A cylinder block is included in the housing. The cylinder block has a shaft bore, through which the drive shaft extends. A plurality of cylinder bores are arranged about the shaft bore at intervals from one another. A plurality of guide passages each connects the associated cylinder bore to the shaft bore. A plurality of pistons each is disposed in the corresponding cylinder bore. A swash plate is accommodated in the swash plate chamber. The swash plate includes a boss, which is mounted on the drive shaft, and a plate portion, which extends from the circumferential surface of the boss to be inclined with respect to the drive shaft. The plate portion is coupled to the pistons. The swash plate rotates integrally with the drive shaft causing each piston to reciprocate in the corresponding cylinder bore. A rotary valve rotates in synchronization with the drive shaft. The rotary valve includes a suction passage, which sequentially connects the cylinder bores in a suction stroke via the associated guide passage. An introduction guide communicates with the shaft bore to introduce the refrigerant gas in the swash plate chamber to the rotary valve. The introduction guide faces the boss and extends in the radial direction from the shaft bore beyond the boss. 
     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 longitudinal cross-sectional view illustrating a double-headed piston swash plate type compressor according to a first embodiment of the present invention; 
         FIG. 2  is a perspective view illustrating the cylinder block shown in  FIG. 1 ; 
         FIG. 3  is a perspective view illustrating the drive shaft and the suction passage of the compressor shown in  FIG. 1 ; 
         FIG. 4  is a transverse cross-sectional view illustrating an assembled state of the cylinder block of  FIG. 2  and the drive shaft of  FIG. 3 ; 
         FIG. 5  is a partially enlarged view of  FIG. 1  illustrating bolt holes and suction recesses; 
         FIG. 6  is a longitudinal cross-sectional view illustrating a compressor according to a second embodiment of the present invention; 
         FIG. 7  is a partially enlarged view of a bolt hole and a suction recess according to a modified embodiment of the present invention; 
         FIG. 8  is a transverse cross-sectional view illustrating an assembled state of a cylinder block and a drive shaft according to another modified embodiment; 
         FIG. 9  is a partially enlarged view of a bolt hole and a suction recess according to another modified embodiment; and 
         FIG. 10  is a partially enlarged view of a bolt hole and a suction recess according to another modified embodiment. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A first embodiment of the present invention will now be described with reference to  FIGS. 1 to 5 .  FIG. 1  shows a swash plate type compressor  10  according to the first embodiment. The compressor  10  is a double-headed piston swash plate type compressor. Arrow Y 1  of  FIG. 1  represents the front and rear direction of the compressor  10 . The front and rear direction is parallel to the direction of an axis L, that is, the axial direction of the compressor  10 . 
     As shown in  FIG. 1 , a housing of the compressor  10  includes, in order from the left to the right in  FIG. 1 , a front housing member  13 , a front cylinder block  11 , a rear cylinder block  12 , and a rear housing member  14 , which are coupled to one another. The front housing member  13  and the rear housing member  14  are components of the housing. A front valve plate assembly  15  is located between the front cylinder block  11  and the front housing member  13 . A rear valve plate assembly  19  is located between the rear cylinder block  12  and the rear housing member  14 . 
     Several, for example, five through bolts B tightly secure the front cylinder block  11 , the rear cylinder block  12 , the front housing member  13 , and the rear housing member  14 . The front cylinder block  11 , the rear cylinder block  12 , the front housing member  13 , and the rear housing member  14  have several, for example, five bolt holes BH, which extend in the axial direction. The five bolt holes BH are located at equal angular intervals in the circumferential direction. Each through bolt B is inserted in the corresponding one of the bolt holes BH. A threaded portion N is formed at the distal end of each through bolt B to be screwed to the rear housing member  14 . The diameter of the bolt holes BH is greater than that of the through bolts B.  FIG. 1  shows one of the bolt holes BH and one of the through bolts B. 
     The front cylinder block  11  includes a columnar front block body  11 A and a front circumferential wall  11 B, which extends from the periphery of the front block body  11 A. The rear cylinder block  12  includes a columnar rear block body  12 A and a rear circumferential wall  12 B, which extends from the periphery of the rear block body  12 A. The bolt holes BH are adjacent to the circumferential walls  11 B,  12 B. 
     The front block body  11 A has the front opposing surface  11   d , which faces the rear block body  12 A. The rear block body  12 A has the rear opposing surface  12   d , which faces the front opposing surface  11   d . The front circumferential wall  11 B has a front inner circumferential surface  11   e . The rear circumferential wall  12 B has a rear inner circumferential surface  12   e . The front circumferential wall  11 B is joined to the rear circumferential wall  12 B. The opposing surfaces  11   d ,  12   d  and the inner circumferential surfaces  11   e ,  12   e  define a swash plate chamber  25 . 
     As shown in  FIGS. 1 and 5 , a front inclined surface R is formed between a front opposing surface  11   d  and the front circumferential wall  11 B. The front inclined surface R is also located between the circumferential surface of the bolt holes BH and the front circumferential wall  11 B. The front inclined surface R faces the swash plate chamber  25 . The front inclined surface R prevents the front opposing surface  11   d  from intersecting the front circumferential wall  11 B at a right angle. That is, the front inclined surface R makes the angle between the front opposing surface  11   d  and the front circumferential wall  11 B gentle. 
     A rear inclined surface R is formed between a rear opposing surface  12   d  and the rear circumferential wall  12 B. The rear inclined surface R is also located between the circumferential surface of the bolt holes BH and the rear circumferential wall  12 B. The rear inclined surface R faces the swash plate chamber  25 . The rear inclined surface R prevents the rear opposing surface  12   d  from intersecting the rear circumferential wall  12 B at a right angle. The rear inclined surface R makes the angle between the rear opposing surface  12   d  and the rear circumferential wall  12 B gentle. 
     At the center portion of the front block body  11 A is formed a through hole, which is a front shaft bore  11   a  in the first embodiment. At the center portion of the rear block body  12 A is formed a through hole, which is a rear shaft bore  12   a  in the first embodiment. The drive shaft  22  extends through the shaft bores  11   a ,  12   a . The inner circumferential surface of the front shaft bore  11   a  functions as a front slide bearing  11   f . The inner circumferential surface of the rear shaft bore  12   a  functions as a rear slide bearing  12   f . The slide bearings  11   f ,  12   f  rotatably support the drive shaft  22 . The through bolts B and the bolt holes BH extend through the swash plate chamber  25 . 
     Between the front housing member  13  and the drive shaft  22  is located a lip seal  23 . The drive shaft  22  protrudes outside the compressor  10 . A power transmission mechanism PT located outside the compressor  10  selectively connects the drive shaft  22  to a drive source of the vehicle, which is an internal combustion engine E. 
     The swash plate chamber  25  accommodates a swash plate  24 . The swash plate  24  is mounted on the drive shaft  22  to rotate integrally with the drive shaft  22 . The swash plate  24  has a disk-like plate portion  24   b  and a cylindrical boss  24   a , which protrudes from the plate portion  24   b . The drive shaft  22  is fitted to a through hole of the boss  24   a . That is, the boss  24   a  permits the plate portion  24   b  to be attached to the circumferential surface of the drive shaft  22 . In other words, the plate portion  24   b  extends from the circumferential surface of the boss  24   a . The plate portion  24   b  is integrated with the boss  24   a . The plate portion  24   b  is inclined with respect to the drive shaft  22 . Several, for example, five double-headed pistons  30  are coupled to the periphery of the plate portion  24   b . A pair of hemispherical shoes  31  are located between each double-headed piston  30  and the plate portion  24   b.    
     A front thrust bearing  26  is arranged between the front block body  11 A and the boss  24   a . The front block body  11 A has a front seat  11   c , which receives the front thrust bearing  26 . The front seat  11   c  is formed to have an annular shape to surround the front shaft bore  11   a  and faces the boss  24   a.    
     A rear thrust bearing  27  is arranged between the rear block body  12 A and the boss  24   a . The rear block body  12 A has a rear seat  12   c , which receives the rear thrust bearing  27 . The rear seat  12   c  is formed to have an annular shape to surround the rear shaft bore  12   a  and faces the boss  24   a . The thrust bearings  26 ,  27  receive thrust load that acts on the double-headed pistons  30  and the swash plate  24 . The thrust bearings  26 ,  27 , which sandwich the swash plate  24 , restrict the drive shaft  22  from moving in the direction of the axis L. 
     As shown in  FIG. 2 , the front block body  11 A has several, for example, five front cylinder bores  28 . The five front cylinder bores  28  are arranged about the drive shaft  22 . The rear block body  12 A has several, for example, five rear cylinder bores  29 . The five rear cylinder bores  29  are arranged about the drive shaft  22 . Each of the front cylinder bores  28  faces the associated rear cylinder bore  29 . The five bolt holes BH and the five front cylinder bores  28  are arranged alternately one by one in the circumferential direction. That is, the five bolt holes BH and the five rear cylinder bores  29  are arranged alternately one by one in the circumferential direction. 
     The front block body  11 A has several, for example, five front guide passages  41 , which extend in the radial direction. Each front guide passage  41  connects the corresponding front cylinder bore  28  to the front shaft bore  11   a . Each front guide passage  41  has a front inlet  41   a , which opens in the circumferential surface of the front shaft bore  11   a , and a front outlet  41   b , which opens in the circumferential surface of the front cylinder bore  28 . 
     The rear block body  12 A has several, for example, five rear guide passages  42 , which extend in the radial direction. Each of the rear guide passages  42  connects the corresponding rear cylinder bore  29  to the rear shaft bore  12   a . Each rear guide passage  42  has a rear inlet  42   a , which opens in the circumferential surface of the rear shaft bore  12   a , and a rear outlet  42   b , which opens in the circumferential surface of the rear cylinder bore  29 . 
     The compressor  10  has five double-headed pistons  30 . A pair of one of the front cylinder bores  28  and the associated rear cylinder bore  29  accommodates one of the double-headed pistons  30 . As the drive shaft  22  rotates, the swash plate  24  is rotated, which causes the double-headed piston  30  to reciprocate in the associated cylinder bores  28 ,  29 . The front valve plate assembly  15  closes the front openings of the front cylinder bores  28 , and the double-headed pistons  30  close the rear openings of the front cylinder bores  28 . As a result, a front compression chamber  28   a  is defined in each front cylinder bore  28 . The volume of each front compression chamber  28   a  changes in accordance with reciprocation of the associated double-headed piston  30 . The double-headed pistons  30  close the front openings of the rear cylinder bores  29 . The rear valve plate assembly  19  closes the rear openings of the rear cylinder bores  29 . As a result, a rear compression chamber  29   a  is defined in each rear cylinder bore  29 . The volume of each rear compression chamber  29   a  changes in accordance with reciprocation of the associated double-headed piston  30 . 
     A discharge pressure zone, which is a front discharge chamber  13   a  in the first embodiment, is formed in the front housing member  13 . Discharge ports  15   a , which correspond to the front compression chambers  28   a , and front discharge valve flaps  15   b , which selectively open and close the discharge ports  15   a , are formed in the front valve plate assembly  15 . 
     A discharge pressure zone, which is a rear discharge chamber  14   a  in the first embodiment, is formed in the rear housing member  14 . Discharge ports  19   a , which correspond to the rear compression chambers  29   a , and rear discharge valve flaps  19   b , which selectively open and close the discharge ports  19   a , are formed in the rear valve plate assembly  19 . 
     The front circumferential wall  11 B has a suction port P, which connects the swash plate chamber  25  to the outside of the compressor  10 . The front housing member  13  has a front outlet (not shown), which selectively connects the front discharge chamber  13   a  to the outside of the compressor  10 . The rear housing member  14  has a rear outlet (not shown), which selectively connects the rear discharge chamber  14   a  to the outside of the compressor  10 . 
     The suction port P is connected to an external refrigerant circuit (not shown). The external refrigerant circuit includes a gas cooler, an expansion valve, and an evaporator. The suction port P is connected to an outlet of the evaporator. The discharge chambers  13   a ,  14   a  are connected to inlets of the gas cooler. The compressor  10  introduces refrigerant gas of the evaporator to the swash plate chamber  25  via the suction port P. The compression chambers  28   a ,  29   a draw in refrigerant gas from the swash plate chamber  25 , compress the refrigerant gas, and discharge the compressed refrigerant gas to the discharge chambers  13   a ,  14   a.    
     Next, a refrigerant gas suction system of the compressor  10  will now be described. 
     As shown in  FIGS. 1 and 4 , the drive shaft  22  has a front rotary valve  35 A corresponding to the front block body  11 A and a rear rotary valve  35 B corresponding to the rear block body  12 A. In other words, the rotary valves  35 A,  35 B are formed integrally with the drive shaft  22 , and rotate in synchronization with the drive shaft  22 . The front rotary valve  35 A permits the front cylinder bores  28  to sequentially draw in refrigerant gas from the swash plate chamber  25 . The rear rotary valve  35 B permits the rear cylinder bores  29  to sequentially draw in refrigerant gas from the swash plate chamber  25 . In other words, parts of a circumferential surface  22   a  of the drive shaft  22  that face the slide bearings  11   f ,  12   f  function as the rotary valves  35 A,  35 B. 
     As shown in  FIGS. 1 ,  2  and  4 , the front block body  11 A has a front introduction guide  53  facing the swash plate chamber  25 . The front introduction guide  53  introduces refrigerant gas in the swash plate chamber  25  to the front rotary valve  35 A. The front introduction guide  53  is formed in the front opposing surface  11   d.    
     The rear block body  12 A has a rear introduction guide  63  facing the swash-plate chamber  25 . The rear introduction guide  63  introduces refrigerant gas in the swash plate chamber  25  to the rear rotary valve  35 B. The rear introduction guide  63  is formed in the rear opposing surface  12   d.    
     The front introduction guide  53  includes a front annular groove  50 , several front suction recesses  60 , and part of the bolt holes BH. The front annular groove  50  and the front suction recesses  60  are formed in the front opposing surface  11   d . The front annular groove  50  surrounds the front shaft bore  11   a  and the front rotary valve  35 A. In this embodiment, five front suction recesses  60  extend in the radial direction from the front annular groove  50 . 
     Each front suction recess  60  includes an inner end  60   a , which communicates with the front annular groove  50 , and an outer end  60   b , which communicates with the associated bolt hole BH. That is, the outer ends  60   b  of the front suction recesses  60  are opening ends located at radially outer end of the front opposing surface  11   d . In other words, part of the bolt holes BH configure part of the front introduction guide  53  so as to be connected to the front suction recesses  60  to function together as the front introduction guide  53 . The front suction recesses  60  are narrow grooves, which extend in the radial direction of the drive shaft  22 . The front suction recesses  60  are arranged at equal angular intervals in the circumferential direction of the drive shaft  22 . The five front suction recesses  60  and the five front cylinder bores  28  are arranged alternately one by one in the circumferential direction. That is, each front suction recess  60  is arranged between an adjacent pair of the front cylinder bores  28 . 
     The rear introduction guide  63  includes a rear annular groove  51 , several rear suction recesses  61 , and part of the bolt holes BH. The rear annular groove  51  and the rear suction recesses  61  are formed in the rear opposing surface  12   d . The rear annular groove  51  surrounds the rear shaft bore  12   a  and the rear rotary valve  35 B. In this embodiment, five rear suction recesses  61  extend in the radial direction of the rear annular groove  51 . 
     Each rear suction recess  61  includes an inner end  61   a , which communicates with the rear annular groove  51 , and an outer end  61   b , which communicates with the associated bolt hole BH. That is, the outer ends  61   b  of the rear suction recesses  61  are opening ends located at radially outer end of the rear opposing surface  12   d . In other words, part of the bolt holes BH configure part of the rear introduction guide  63  so as to be connected to the rear suction recesses  61  to function together as the rear introduction guide  63 . The rear suction recesses  61  are narrow grooves, which extend in the radial direction of the drive shaft  22 . The rear suction recesses  61  are arranged at equal angular intervals in the circumferential direction of the drive shaft  22 . The five rear suction recesses  61  and the five rear cylinder bores  29  are arranged alternately one by one in the circumferential direction. That is, each rear suction recess  61  is arranged between an adjacent pair of the rear cylinder bores  29 . 
     The suction recesses  60 ,  61  extend radially outward from the annular grooves  50 ,  51  over the seats  11   c ,  12   c  to the circumferential walls  11 B,  12 B. That is, the suction recesses  60 ,  61  extend radially outward than the boss  24   a . The outer ends  60   b ,  61   b  of the suction recesses  60 ,  61  are not covered by the boss  24   a , and faces the plate portion  24   b . That is, the outer ends  60   b ,  61   b  are freely open to the swash plate chamber  25 . As described above, the thrust bearings  26 ,  27  and the boss  24   a  do not cover the entire suction recesses  60 ,  61 . 
       FIG. 2  shows the cross-sectional area α of the suction recesses  60 ,  61  and the opening area β of the suction recesses  60 ,  61  with two kinds of shades. The cross-sectional area α represents the cross-sectional area of the suction recesses  60 ,  61  along a plane perpendicular to the radial direction. The opening area β represents the opening area of part of the suction recesses  60 ,  61  that is radially outward of the seats  11   c ,  12   c  along a plane perpendicular to the axial direction. That is, the opening area β shows the opening area of part of the suction recesses  60 ,  61  that face the plate portion  24   b . In other words, the opening area β represents the area of the suction recesses  60 ,  61  that does not face the boss  24   a  and is open to the swash plate chamber  25 . The opening area β is greater than the cross-sectional area α. 
     As shown in  FIGS. 1 and 3 , the circumferential surface  22   a  of the drive shaft  22  has a front suction passage  70 A, which corresponds to the front rotary valve  35 A, and a rear suction passage  70 B, which corresponds to the rear rotary valve  35 B. The front suction passage  70 A and the rear suction passage  70 B are located at intervals of 180 degrees in the circumferential direction of the drive shaft  22 . The front suction passage  70 A corresponds to the front shaft bore  11   a . The rear suction passage  70 B corresponds to the rear shaft bore  12   a . Refrigerant gas in the swash plate chamber  25  is drawn into the front cylinder bores  28  via the front introduction guide  53 , the front suction passage  70 A, and the front guide passages  41 . Refrigerant gas in the swash plate chamber  25  is drawn into the rear cylinder bores  29  via the rear introduction guide  63 , the rear suction passage  70 B, and the rear guide passages  42 . 
     The suction passages  70 A,  70 B are defined by grooves formed in the circumferential surface  22   a  of the drive shaft  22 . The suction passages  70 A,  70 B are formed in the shape of steps. That is, each suction passage  70 A,  70 B includes a first communication section  70   a  and a second communication section  70   b . Both of the first communication sections  70   a  are located between the both of the second communication sections  70   b  in the axial direction. The dimension of the first communication section  70   a  in the circumferential direction is greater than that of the second communication section  70   b . That is, the cut-out depth of the drive shaft  22  at the suction passages  70 A,  70 B changes stepwise. 
     The first communication sections  70   a  correspond to the introduction guides  53 ,  63 . The second communication sections  70   b  correspond to the guide passages  41 ,  42 . That is, the first communication section  70   a  of the front rotary valve  35 A constantly communicates with the five front suction recesses  60  via the front annular groove  50 . During operation of the compressor  10 , the second communication section  70   b  of the front rotary valve  35 A constantly connects the first communication section  70   a  to at least one of the front guide passages  41 . That is, one of the front cylinder bores  28  constantly draws in refrigerant gas from the swash plate chamber  25  via the front rotary valve  35 A and the five front suction recesses  60 . 
     The first communication section  70   a  of the rear rotary valve  35 B constantly communicates with the five rear suction recesses  61  via the rear annular groove  51 . During operation of the compressor  10 , the second communication section  70   b  of the rear rotary valve  35 B constantly connects the first communication section  70   a  to at least one of the rear guide passages  42 . That is, one of the rear cylinder bores  29  constantly draws in refrigerant gas from the swash plate chamber  25  via the rear rotary valve  35 B and the five rear suction recesses  61 . 
     As shown in  FIG. 4 , the first communication section  70   a  has a first circumferential end  70   c , which is the end in the circumferential direction, and a second circumferential end  70   d , which is opposite to the first circumferential end  70   c . When the first circumferential end  70   c  of the front rotary valve  35 A faces the inner end  60   a  of one of the front suction recesses  60 , the second circumferential end  70   d  faces the inner end  60   a  of the front suction recess  60  that is spaced from the first one with another suction recess  60  in between. More specifically, when the first circumferential end  70   c  faces half of the cross-sectional area α of one of the suction recesses  60 , the second circumferential end  70   d  faces half of the cross-sectional area α of the suction recess  60  that is spaced from the first one with another suction recess  60  in between. In other words, one suction recess  60  exists between the suction recess  60  that faces the first circumferential end  70   c  and the suction recess  60  that faces the second circumferential end  70   d . In this manner, during operation of the compressor  10 , the first communication section  70   a  constantly face at least two suction recesses  60 . 
     As shown in  FIG. 4 , during operation of the compressor  10 , the second communication section  70   b  of the front rotary valve  35 A communicates with at least one of the front guide passages  41 . That is, the second communication section  70   b  of the front rotary valve  35 A sequentially communicates with the front inlets  41   a  of the five front guide passages  41  intermittently. During operation of the compressor  10 , there are times during which the second communication section  70   b  of the front rotary valve  35 A simultaneously communicates with the front inlets  41   a  of two of the front guide passages  41 . Therefore, the circumferential surface  22   a  of the drive shaft  22  selectively blocks the front guide passages  41 . In the same way, the second communication section  70   b  of the rear rotary valve  35 B communicates with at least one of the rear guide passages  42 . 
     The operations of the compressor  10  will now be described. 
     In the case where one of the front cylinder bores  28  shown in  FIG. 1  is in a suction stroke, that is, when one of the double-headed pistons  30  shown in  FIG. 1  moves from the left to the right in  FIG. 1 , the second communication section  70   b  of the front rotary valve  35 A is connected to the front inlet  41   a  of one of the front guide passages  41  shown in  FIG. 1 . Refrigerant gas in the swash plate chamber  25  is drawn into one of the front cylinder bores  28  shown in  FIG. 1  via the five front suction recesses  60 , the front annular groove  50 , the first communication section  70   a  and the second communication section  70   b  of the front rotary valve  35 A, and the associated front guide passage  41  shown in  FIG. 1 . 
     When one of the rear cylinder bores  29  shown in  FIG. 1  is in a suction stroke, that is, when one of the double-headed pistons  30  moves from the right to the left of  FIG. 1 , the second communication section  70   b  of the rear rotary valve  35 B is connected to the rear inlet  42   a  of one of the rear guide passages  42  shown in  FIG. 1 . Refrigerant gas in the swash plate chamber  25  is drawn into one of the rear cylinder bores  29  shown in  FIG. 1  via the five rear suction recesses  61 , the rear annular groove  51 , the first communication section  70   a  and the second communication section  70   b  of the rear rotary valve  35 B, and the associated rear guide passage  42  shown in  FIG. 1 . 
     When one of the front cylinder bores  28  shown in  FIG. 1  is in a discharge stroke, that is, when one of the double-headed pistons  30  moves from the right to the left in  FIG. 1 , the circumferential surface  22   a  of the front rotary valve  35 A disconnects the front cylinder bore  28  shown in  FIG. 1  from the swash plate chamber  25 . Refrigerant gas in the associated front compression chamber  28   a  passes through the corresponding front discharge port  15   a , presses open the associated front discharge valve flap  15   b , and is discharged to the front discharge chamber  13   a . Refrigerant gas in the front discharge chamber  13   a  flows out to the external refrigerant circuit. 
     When one of the rear cylinder bores  29  shown in  FIG. 1  is in a discharge stroke, that is, when one of the double-headed pistons  30  shown in  FIG. 1  moves from the left to the right in  FIG. 1 , the circumferential surface  22   a  of the rear rotary valve  35 B disconnects the rear cylinder bore  29  shown in  FIG. 1  from the swash plate chamber  25 . Refrigerant gas in the associated rear compression chamber  29   a  passes through the corresponding rear discharge port  19   a , presses open the associated rear discharge valve flap  19   b , and is discharged to the rear discharge chamber  14   a . Refrigerant gas in the rear discharge chamber  14   a  flows out to the external refrigerant circuit. 
     The outer ends  60   b ,  61   b  of the suction recesses  60 ,  61  are located radially outward of the boss  24   a . The outer ends  60   b ,  61   b  are directly open to the swash plate chamber  25 . The outer ends  60   b ,  61   b  face the plate portion  24   b.    
     When the swash plate  24  is rotating, the distance between the plate portion  24   b  and the suction recesses  60 ,  61  continuously changes. That is, the plate portion  24   b  constantly stirs refrigerant gas in the vicinity of the suction recesses  60 ,  61 . As a result, stationary vortices are prevented from being generated between the plate portion  24   b  and the suction recesses  60 ,  61 . Thus, the suction recesses  60 ,  61  are prevented from being affected by vortices in refrigerant gas, and promptly draw in refrigerant gas from the swash plate chamber  25 . 
     Refrigerant gas includes lubricant for lubricating various sliding portions of the compressor  10 . The lubricant is separated from refrigerant gas and thrown to the periphery of the swash plate chamber  25  by centrifugal force caused by rotation of the drive shaft  22  and the swash plate  24 , and adheres to the circumferential walls  11 B,  12 B of the swash plate chamber  25  and the through bolts B. As refrigerant gas in the swash plate chamber  25  is drawn into the suction recesses  60 ,  61 , the lubricant on the circumferential walls  11 B,  12 B is transferred along the inclined surfaces R and flows into the bolt holes BH and the suction recesses  60 ,  61 . The lubricant on the through bolts B moves along the through bolts B, and subsequently flows into the suction recesses  60 ,  61 . The lubricant that has flowed into the suction recesses  60 ,  61  is drawn into the cylinder bores  28 ,  29  via the annular grooves  50 ,  51 , the suction passages  70 A,  70 B, and the guide passages  41 ,  42 . In this manner, the lubricant circulates within the compressor  10 . 
     The first embodiment has the following advantages. 
     (1) The opposing surfaces  11   d ,  12   d  of the cylinder blocks  11 ,  12  facing the swash plate chamber  25  have the suction recesses  60 ,  61 . The suction recesses  60 ,  61  introduce refrigerant gas in the swash plate chamber  25  to the front and rear rotary valves  35 A,  35 B. The outer ends  60   b ,  61   b  of the suction recesses  60 ,  61  are located radially outward than the boss  24   a  of the swash plate  24 . That is, the suction recesses  60 ,  61  face the boss  24   a  and extend in the radial direction from the shaft bores  11   a ,  12   a  beyond the boss  24   a . The outer ends  60   b ,  61   b  are not disconnected by the swash plate  24 , and are open to the swash plate chamber  25 . Therefore, the outer ends  60   b ,  61   b  of the suction recesses  60 ,  61  easily draw in refrigerant gas from the swash plate chamber  25  without being affected by rotation of the swash plate  24 . 
     Thus, the front and rear rotary valves  35 A,  35 B draw in refrigerant gas from the swash plate chamber  25  without being inhibited by the swash plate  24 . In other words, the boss  24   a  does not inhibit the flow of refrigerant gas into the cylinder bores  28 ,  29 . Therefore, for example, as compared to a case where the outer ends  60   b ,  61   b  of the suction recesses  60 ,  61  face the boss  24   a , the suction efficiency of refrigerant gas drawn into the cylinder bores  28 ,  29  is improved. This improves the compression efficiency of the compressor  10 . 
     (2) The cylinder blocks  11 ,  12  have the annular grooves  50 ,  51  located between the suction recesses  60 ,  61  and the front and rear rotary valves  35 A,  35 B. Refrigerant gas in the suction recesses  60 ,  61  is stored in the annular grooves  50 ,  51 . Thus, the cylinder bores  28 ,  29  in the suction stroke draw in refrigerant gas from the suction recesses  60 ,  61  via the annular grooves  50 ,  51 . Therefore, the cylinder bores  28 ,  29  easily draw in sufficient amount of refrigerant gas. 
     (3) The opening area β of the suction recesses  60 ,  61  is greater than the cross-sectional area α of the suction recesses  60 ,  61 . For example, when the opening area β is smaller than the cross-sectional area α, the suction recesses  60 ,  61  undesirably serve as restrictors restricting the flow of refrigerant gas. That is, the smaller opening area β makes it difficult to ensure the sufficient amount of refrigerant gas drawn into the suction recesses  60 ,  61  from the swash plate chamber  25 . That is, the sufficient amount of refrigerant gas is not introduced to the front and rear rotary valves  35 A,  35 B. Only securing the cross-sectional area α does not eliminate such disadvantage. 
     According to the first embodiment, a large amount of refrigerant gas in the suction recesses  60 ,  61  is easily and efficiently introduced to the front and rear rotary valves  35 A,  35 B. That is, a large amount of refrigerant gas is easily and efficiently drawn into the cylinder bores  28 ,  29 . 
     (4) The outer ends  60   b ,  61   b  of the suction recesses  60 ,  61  do not face the boss  24   a , and are directly open to the swash plate chamber  25 . Therefore, the outer ends  60   b ,  61   b  easily draw in refrigerant gas and lubricant without being affected by rotation of the swash plate  24 . That is, the boss  24   a  does not inhibit introduction of lubricant to the suction recesses  60 ,  61 . Thus, lubricant easily flows into the front and rear rotary valves  35 A,  35 B, the guide passages  41 ,  42 , and the cylinder bores  28 ,  29 . Therefore, sliding performance of the drive shaft  22  and the front and rear rotary valves  35 A,  35 B with respect to the cylinder blocks  11 ,  12  is improved. This also improves the sliding performance of the double-headed pistons  30 . 
     (5) The inclined surfaces R are formed between the circumferential walls  11 B,  12 B and the bolt holes BH. The lubricant on the circumferential walls  11 B,  12 B easily flows into the suction recesses  60 ,  61  via the inclined surfaces R. The lubricant that has flowed into the suction recesses  60 ,  61  circulates within the compressor  10  with the flow of refrigerant gas. Therefore, the sliding portions of the compressor  10  are easily lubricated. 
     In particular, in the first embodiment, the circumferential surface of the bearings  11   f ,  12   f  function as the slide bearings  11   f ,  12   f , which rotatably support the drive shaft  22 . That is, the cylinder blocks  11 ,  12  do not include additional radial bearings, and directly support the drive shaft  22  and the front and rear rotary valves  35 A,  35 B. Therefore, the inclined surfaces R, which easily circulate the lubricant are suitable for lubricating the slide bearings  11   f ,  12   f.    
     The density of the lubricant adhered to the circumferential walls  11 B,  12 B is relatively high in the compressor  10 . The inclined surfaces R are advantageous for introducing the high-density lubricant into the suction recesses  60 ,  61 . Therefore, the sliding performance of the drive shaft  22  and the front and rear rotary valves  35 A,  35 B is easily improved. 
     (6) The outer ends  60   b ,  61   b  of the suction recesses  60 ,  61  communicate with the bolt holes BH. That is, part of the bolt holes BH function as part of the introduction guides  53 ,  63 . Therefore, for example, as compared to a case where the suction recesses  60 ,  61  are formed adjacent to the circumferential walls  11 B,  12 B and do not communicate with the bolt holes BH, the first embodiment suppresses decrease in the strength of the cylinder blocks  11 ,  12 . 
     The lubricant included in the refrigerant gas is separated from the refrigerant gas by centrifugal force, and adheres to the circumferential walls  11 B,  12 B or the through bolts B. The lubricant adhered to the through bolts B is transferred along the through bolts B, and is subsequently drawn into the suction recesses  60 ,  61 . Since the bolt holes BH of the first embodiment communicate with the suction recesses  60 ,  61 , lubricant on the through bolts B is easily drawn into the suction recesses  60 ,  61 . Therefore, as compared to a case where, for example, the suction recesses  60 ,  61  are separate from the bolt holes BH, the first embodiment easily ensures an adequate amount of lubricant introduced to the suction recesses  60 ,  61 . That is, an adequate amount of lubricant introduced to the cylinder bores  28 ,  29  is easily ensured. 
     (7) Each of the cylinder blocks  11 ,  12  has several, that is, five suction recesses  60 ,  61 . Therefore, as compared to a case where, for example, each of the cylinder blocks  11 ,  12  has a single suction recess  60 ,  61 , an adequate amount of refrigerant gas drawn into the front and rear rotary valves  35 A,  35 B is easily ensured. 
     (8) The suction recesses  60 ,  61  and the cylinder bores  28 ,  29  are arranged alternately one by one in the circumferential direction. Thus, the suction recesses  60 ,  61  are arranged in a well-balanced manner at equal intervals in the entire circumferential direction of the swash plate chamber  25 . This prevents, for example, the suction recesses  60 ,  61  from being arranged unevenly. The front and rear rotary valves  35 A,  35 B of the first embodiment efficiently draw in refrigerant gas from the swash plate chamber  25 . 
     (9) The front and rear rotary valves  35 A,  35 B are formed integrally with the drive shaft  22 . That is, the suction passages  70 A,  70 B are directly formed in the circumferential surface  22   a  of the drive shaft  22 . Thus, as compared to a case where, for example, separate rotary valves are mounted on the drive shaft  22 , the first embodiment reduces the number of components of the compressor  10 . Furthermore, the first embodiment prevents enlargement of the shaft bores  11   a ,  12   a , which accommodate the front and rear rotary valves  35 A,  35 B. That is, enlargement of the compressor  10  is suppressed. 
     (10) The front housing member  13  and the rear housing member  14  of the first embodiment eliminate a suction chamber of refrigerant gas. Instead, the swash plate chamber  25  serves as the suction chamber. Therefore, the first embodiment suppresses increase in the axial dimension of the compressor  10 . 
     (11) The drive shaft  22  is a solid body and does not have an internal passage. The suction passages  70 A,  70 B of the front and rear rotary valves  35 A,  35 B are formed in the circumferential surface  22   a  of the drive shaft  22 . This improves the rigidity of the drive shaft  22 . 
     (12) The front and rear rotary valves  35 A,  35 B draw in refrigerant gas from the swash plate chamber  25 , which is located between the front cylinder block  11  and the rear cylinder block  12 , and transfer the refrigerant gas to the associated cylinder bores  28 ,  29 . Therefore, unlike a compressor that, for example, defines a suction chamber only between the rear housing member  14  and the rear valve plate assembly  19  so as to transfer refrigerant gas in the suction chamber to the front cylinder bores  28 , the compressor of the first embodiment easily draws in refrigerant gas to the cylinder bores  28 ,  29  evenly. 
     (13) As shown in  FIG. 4 , the first communication section  70   a  of the front rotary valve  35 A constantly faces the inner end  60   a  of at least one of the suction recesses  60  when the front rotary valve  35 A is at any rotational position. Likewise, the first communication section  70   a  of the rear rotary valve  35 B constantly faces the inner end  61   a  of at least one of the suction recesses  61  when the rear rotary valve  35 B is at any rotational position. Thus, the suction passages  70 A,  70 B easily draw in refrigerant gas from the suction recesses  60 ,  61 . Therefore, refrigerant gas is promptly and efficiently drawn into the cylinder bores  28 ,  29 . 
     (14) The suction passages  70 A,  70 B each include the first communication section  70   a , which faces the corresponding one of the annular grooves  50 ,  51 , and the second communication section  70   b , which faces the guide passages  41 ,  42 . The dimension of the first communication section  70   a  in the circumferential direction is greater than that of the second communication section  70   b . Thus, the opening area of the suction passages  70 A,  70 B with respect to the suction recesses  60 ,  61  is easily increased. That is, refrigerant gas is easily drawn into the suction passages  70 A,  70 B. Therefore, refrigerant gas is easily drawn into the cylinder bores  28 ,  29 . 
     Next, a second embodiment of the present invention will be described with reference to  FIG. 6 . In a compressor  80  according to the second embodiment, the same members as the first embodiment are given the same numbers and detailed explanations are omitted. Arrow Y 2  in  FIG. 6  represents the front and rear direction of the compressor  80 . 
     As shown in  FIG. 6 , the drive shaft  22  of the second embodiment is a hollow body and has an internal passage extending in the axial direction. The internal passage is a supply passage  81  in the second embodiment. The drive shaft  22  has a front introduction hole  82 A, which connects the supply passage  81  to the front annular groove  50 , and a rear introduction hole  82 B, which connects the supply passage  81  to the rear annular groove  51 . 
     The drive shaft  22  has a front outlet hole  83 A, which connects the supply passage  81  to the front inlets  41   a  of the front guide passages  41 , and a rear outlet hole  83 B, which connects the supply passage  81  to the rear inlets  42   a  of the rear guide passages  42 . Refrigerant gas in the swash plate chamber  25  is introduced into the cylinder bores  28 ,  29  via the suction recesses  60 ,  61 , the annular grooves  50 ,  51 , the introduction holes  82 A,  82 B, the supply passage  81 , the outlet holes  83 A,  83 B, and the guide passages  41 ,  42 . The supply passage  81 , the introduction holes  82 A,  82 B, and the outlet holes  83 A,  83 B configure a suction passage, which connects the suction recesses  60 ,  61  to the guide passages  41 ,  42 . The front rotary valve  35 A of the second embodiment includes the front introduction hole  82 A and the front outlet hole  83 A. The rear rotary valve  35 B includes the rear introduction hole  82 B and the rear outlet hole  83 B. The front introduction hole  82 A and the rear introduction hole  82 B are located at an interval of 180° in the circumferential direction of the drive shaft  22 . The front outlet hole  83 A and the rear outlet hole  83 B are located at an interval of 180° in the circumferential direction of the drive shaft  22 . 
     When one of the front cylinder bores  28  is in a suction stroke, refrigerant gas in the swash plate chamber  25  is drawn into the front cylinder bore  28  via the front suction recesses  60 , the front annular groove  50 , the front introduction hole  82 A, the supply passage  81 , the front outlet hole  83 A, and the associated front guide passage  41 . 
     When one of the rear cylinder bores  29  is in a suction stroke, refrigerant gas in the swash plate chamber  25  is drawn into the rear cylinder bore  29  via the rear suction recesses  61 , the rear annular groove  51 , the rear introduction hole  82 B, the supply passage  81 , the rear outlet hole  83 B, and the associated rear guide passage  42 . 
     The above embodiments may be modified as follows. 
     The rotary valves  35 A,  35 B need not be formed integrally with the drive shaft  22 . Rotary valves  35 A,  35 B that are separate from the drive shaft  22  may be mounted on the drive shaft  22 . 
     The suction recesses  60 ,  61  and the cylinder bores  28 ,  29  need not be arranged alternately one by one in the circumferential direction. For example, the suction recesses  60 ,  61  may be arranged two by two in the circumferential direction. 
     The number of the suction recesses  60 ,  61  is not limited to five, but may be one, two, three, or four. 
     Six cylinder bores  28 ,  29  and six suction recesses  60 ,  61  may be arranged alternately one by one. 
     The length of the suction recesses  60 ,  61  may be adjusted such that the suction recesses  60 ,  61  are separate from the bolt holes BH. 
     The cross-sectional area α of the suction recesses  60 ,  61  may be the same as the opening area β of the suction recesses  60 ,  61 . 
     The length of the suction recesses  60 ,  61  may be changed as long as the outer ends  60   b ,  61   b  of the suction recesses  60 ,  61  are located radially outward than the boss  24   a.    
     As shown in  FIG. 7 , the circumferential surfaces of the bolt holes BH may be flush with the inner circumferential surfaces lie,  12   e  of the circumferential walls  11 B,  12 B. In this case, lubricant adhered to the inner circumferential surfaces  11   e ,  12   e  easily flows into the bolt holes BH without being disturbed by a step. Thus, lubricant is easily introduced to the cylinder bores  28 ,  29 . 
     As shown in  FIG. 8 , the annular grooves  50 ,  51  may be omitted. That is, only the suction recesses  60 ,  61  may configure the introduction guide. In this case, the suction recesses  60 ,  61  are directly connected to the shaft bore  11   a ,  12   a . In this case also, the first communication section  70   a  of the front rotary valve  35 A constantly faces the inner end  60   a  of at least one of the suction recesses  60 , and the first communication section  70   a  of the rear rotary valve  35 B constantly faces the inner end  61   a  of at least one of the suction recesses  61 . Therefore, the suction passages  70 A,  70 B easily ensure an adequate suction amount of refrigerant gas from the suction recesses  60 ,  61 . 
     As shown in  FIG. 9 , the outer ends  60   b ,  61   b  of the suction recesses  60 ,  61  may extend to the inner circumferential surfaces  11   e ,  12   e  of the circumferential walls  11 B,  12 B in a state separate from the bolt holes BH. 
     As shown in  FIG. 10 , the inclined surfaces R may be defined between the suction recesses  60 ,  61  and the circumferential walls  11 B,  12 B separate from the bolt holes BH. In this case, lubricant adhered to the circumferential walls  11 B,  12 B flows into the suction recesses  60 ,  61  via the inclined surfaces R. 
     The lengths of the suction recesses  60 ,  61  need not be the same. 
     The compressor need not be a double-headed piston swash plate type compressor, but may be a single-headed piston swash plate type compressor.