Patent Publication Number: US-9903353-B2

Title: Variable displacement swash plate compressor

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a variable displacement swash plate compressor. 
     Japanese Laid-Out Patent Publication No. 5-172052 describes a conventional variable displacement swash plate compressor (hereafter simply referred to as the compressor). The compressor has a housing including a front housing member, a cylinder block, and a rear housing member. The front housing member and the rear housing member each includes a suction chamber and a discharge chamber. The cylinder block includes a swash plate chamber and cylinder bores. A rotatable drive shaft is supported in the housing. A swash plate that is rotatable together with the drive shaft is arranged in the swash plate chamber. A link mechanism is located between the drive shaft and the swash plate to allow the inclination angle of the swash plate to change. The inclination angle refers to an angle of the swash plate relative to a plane orthogonal to the rotation axis of the drive shaft. Each cylinder bore accommodates a reciprocal piston. Two shoes are provided for each piston to serve as a conversion mechanism that uses the rotation of the swash plate to reciprocate the piston in the corresponding cylinder bore with a stroke that is in accordance with the inclination angle of the swash plate. An actuator, which includes a movable body and a control pressure chamber, changes the inclination angle of the swash plate. A control mechanism regulates the pressure of the control pressure chamber to control the actuator. 
     The link mechanism includes a lug arm, first and second arms, and a movable body. The lug arm is fixed to the drive shaft and located in front of the swash plate chamber. The first arm is located on the front surface of the swash plate, and the second arm is located on the rear surface of the swash plate. The first arm pivotally couples the lug arm and the swash plate. The second arm pivotally couples the movable body and the swash plate. 
     In the compressor, the control mechanism increases the pressure of the control pressure chamber with the pressure of the refrigerant in the discharge chamber to move the movable body toward the swash plate along the axis of the drive shaft. As a result, the movable body pushes the swash plate and increases the inclination angle of the swash plate. The swash plate comes into contact with the lug arm when the inclination angle of the swash plate becomes maximal. This allows the compressor displacement to be maximized for each rotation of the drive shaft. 
     In the conventional compressor described above, contact of the swash plate and the lug arm restricts the swash plate at the maximum inclination angle. The lug arm is fixed to the drive shaft. Thus, contact of the swash plate and the lug arm may produce an impact that generates vibration and lowers the durability of the compressor. Further, contact of the swash plate and the lug arm produces noise. Such situations become further noticeable when quickly increasing the compressor displacement to the maximum amount. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a durable compressor with noise reduced. 
     One aspect of the present invention is a variable displacement swash plate compressor provided with a housing including a suction chamber, a discharge chamber, a swash plate chamber, and a cylinder bore. A drive shaft is rotationally supported by the housing. A swash plate is rotatable together with the drive shaft in the swash plate chamber. A link mechanism is arranged between the drive shaft and the swash plate. The link mechanism includes a supporting portion that pivotally supports the swash plate, and the link mechanism allows for changes in an inclination angle of the swash plate relative to a plane orthogonal to an axis of the drive shaft. A piston is reciprocally accommodated in the cylinder bore. A conversion mechanism is configured to reciprocate the piston in the cylinder bore with a stroke that is in accordance with the inclination angle of the swash plate when the swash plate rotates. An actuator is located in the swash plate chamber. The actuator is capable of changing the inclination angle of the swash plate. A control mechanism is configured to control the actuator. The actuator includes a partitioning body arranged on the drive shaft. The partitioning body is movable along the axis of the drive shaft. A movable body is arranged on the drive shaft. The movable body includes a coupling portion coupled to the swash plate, and the movable body moves in contact with the partitioning body along the axis of the drive shaft to change the inclination angle of the swash plate. A control pressure chamber is defined by the partitioning body and the movable body. The movable body is moved by drawing refrigerant in the control pressure chamber from the discharge chamber. The swash plate is configured to contact and move the partitioning body as the inclination angle increases. 
     Other aspects and advantages of the present 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 cross-sectional view showing a compressor of a first embodiment when the displacement is maximal; 
         FIG. 2  is a schematic diagram showing a control mechanism in the compressor of  FIG. 1 ; 
         FIG. 3A  is a front view of a swash plate in the compressor of  FIG. 1 ; 
         FIG. 3B  is a cross-sectional view of the swash plate in the compressor of  FIG. 1 ; 
         FIG. 4  is a cross-sectional view showing the compressor of  FIG. 1  when the displacement is minimal; 
         FIG. 5  is a partially enlarged cross-sectional view showing an abutment portion pushing a partitioning body in the compressor of  FIG. 1 ; 
         FIG. 6  is a partially enlarged cross-sectional view showing a compressor of a second embodiment when the inclination angle of the swash plate is minimal; 
         FIG. 7A  is a front view of the swash plate in the compressor of  FIG. 6 ; 
         FIG. 7B  is a cross-sectional view of the swash plate in the compressor of  FIG. 6 ; 
         FIG. 8  is a partially enlarged cross-sectional view showing the swash plate at a predetermined second inclination angle in the compressor of  FIG. 6 ; 
         FIG. 9  is a partially enlarged cross-sectional view showing the compressor of  FIG. 6  when the inclination angle of the swash plate is maximal; and 
         FIG. 10  is a graph showing the relationship of the swash plate inclination angle and the variable pressure difference. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     First and second embodiments of the present invention will now be described with reference to the drawings. Each compressor of the first and second embodiments is a variable displacement compressor that employs double-headed pistons and a swash plate. The compressor is installed in a vehicle to form a refrigeration circuit of a vehicle air conditioner. 
     First Embodiment 
     Referring to  FIG. 1 , a compressor of the first embodiment includes a housing  1 , a drive shaft  3 , a swash plate  5 , a link mechanism  7 , pistons  9 , front and rear shoes  11   a  and  11   b , an actuator  13 , and a control mechanism  15 , which is shown in  FIG. 2 . Each piston  9  is provided with a pair of the shoes  11   a  and  11   b.    
     As shown in  FIG. 1 , the housing  1  includes a front housing member  17 , which is located at the front of the compressor, a rear housing member  19 , which is located at the rear of the compressor, first and second cylinder blocks  21  and  23 , which are located between the front housing member  17  and the rear housing member  19 , and first and second valve formation plates  39  and  41 . 
     The front housing member  17  includes a boss  17   a , which projects toward the front. A sealing device  25  is arranged in the boss  17   a . Further, the front housing member  17  includes a first suction chamber  27   a  and a first discharge chamber  29   a . The first suction chamber  27   a  is located in a radially inner portion of the front housing member  17 , and the first discharge chamber  29   a  is annular and is located in a radially outer portion of the front housing member  17 . 
     The front housing member  17  includes a first front communication passage  18   a . The first front communication passage  18   a  includes a front end that is in communication with the first discharge chamber  29   a  and a rear end that opens at the rear end of the front housing member  17 . 
     The rear housing member  19  includes the control mechanism  15  shown in  FIG. 2 . The rear housing member  19  includes a second suction chamber  27   b , a second discharge chamber  29   b , and a pressure regulation chamber  31 . The pressure regulation chamber  31  is located in a radially central portion of the rear housing member  19 . The second suction chamber  27   b  is annular and located at a radially outer side of the pressure regulation chamber  31  in the rear housing member  19 . The second discharge chamber  29   b  is also annular and located at a radially outer side of the second suction chamber  27   b  in the rear housing member  19 . 
     The rear housing member  19  includes a first rear communication passage  20   a . The first rear communication passage  20   a  includes a rear end that is in communication with the second discharge chamber  29   b  and a front end that opens at the front end of the rear housing member  19 . 
     A swash plate chamber  33  is defined in the first cylinder block  21  and the second cylinder block  23 . The swash plate chamber  33  is located in an axially middle portion of the housing  1 . 
     The first cylinder block  21  includes first cylinder bores  21   a , which are arranged at equal angular intervals in the circumferential direction and which extend parallel to one another. Further, the first cylinder block  21  includes a first shaft bore  21   b . The drive shaft  3  extends through the first shaft bore  21   b . A first plain bearing  22   a  is arranged in the first shaft bore  21   b.    
     The first cylinder block  21  also includes a first recess  21   c , which is in communication and coaxial with the first shaft bore  21   b . The first recess  21   c  is in communication with the swash plate chamber  33  and forms a portion of the swash plate chamber  33 . A first thrust bearing  35   a  is arranged in a front portion of the first recess  21   c . Further, the first cylinder block  21  includes a first communication passage  37   a  that communicates the swash plate chamber  33  with the first suction chamber  27   a . The first cylinder block  21  also includes a first retainer groove  21   e , which restricts the maximum open degree of first suction reed valves  391   a , which will be described later. 
     The first cylinder block  21  includes a second front communication passage  18   b . The second front communication passage  18   b  includes a front end that opens at the front end of the first cylinder block  21  and a rear end that opens at the rear end of the first cylinder block  21 . 
     In the same manner as the first cylinder block  21 , the second cylinder block  23  includes second cylinder bores  23   a . Each second cylinder bore  23   a  is paired and axially aligned with one of the first cylinder bores  21   a . The first cylinder bores  21   a  and the second cylinder bores  23   a  have the same diameter. 
     The second cylinder block  23  includes a second shaft bore  23   b . The drive shaft  3  extends through the second shaft bore  23   b . The second shaft bore  23   b  includes a second plain bearing  22   b . The first and second plain bearings  22   a  and  22   b  may be replaced by ball bearings. 
     The second cylinder block  23  also includes a second recess  23   c , which is in communication and coaxial with the second shaft bore  23   b . Further, the second recess  23   c  is also in communication with the swash plate chamber  33  and forms a portion of the swash plate chamber  33 . A second thrust bearing  35   b  is arranged in a rear portion of the second recess  23   c . The second cylinder block  23  includes a second communication passage  37   b  that communicates the swash plate chamber  33  with the second suction chamber  27   b . The second cylinder block  23  also includes a second retainer groove  23   e , which restricts the maximum open degree of first suction reed valves  411   a , which will be described later. 
     The second cylinder block  23  includes a discharge port  230 , a converging discharge chamber  231 , a third front communication passage  18   c , a second rear communication passage  20   b , and a suction port  330 . The discharge port  230  is in communication with the converging discharge chamber  231 . The discharge port  230  connects the converging discharge chamber  231  to a condenser (not shown), which is included in the refrigeration circuit. The suction port  330  connects the swash plate chamber  33  to an evaporator (not shown), which is included in the refrigeration circuit. 
     The third front communication passage  18   c  includes a front end that opens at a front end of the second cylinder block  23  and a rear end that is in communication with the converging discharge chamber  231 . When the first cylinder block  21  is joined with the second cylinder block  23 , the third front communication passage  18   c  is connected to the rear end of the second front communication passage  18   b.    
     The second rear communication passage  20   b  includes a front end that is in communication with the converging discharge chamber  231  and a rear end that opens at the rear end of the second cylinder block  23 . 
     The first valve formation plate  39  is arranged between the front housing member  17  and the first cylinder block  21 . The second valve formation plate  41  is arranged between the rear housing member  19  and the second cylinder block  23 . 
     The first valve formation plate  39  includes a first valve plate  390 , a first suction valve plate  391 , a first discharge valve plate  392 , and a first retainer plate  393 . First suction holes  390   a  extend through the first valve plate  390 , the first discharge valve plate  392 , and the first retainer plate  393 . The number of the first suction holes  390   a  is the same as the number of the first cylinder bores  21   a . First discharge holes  390   b  extend through the first valve plate  390  and the first suction valve plate  391 . The number of the first discharge holes  390   b  is the same as the number of the first cylinder bores  21   a . A first suction communication hole  390   c  extends through the first valve plate  390 , the first suction valve plate  391 , the first discharge valve plate  392 , and the first retainer plate  393 . A first discharge communication hole  390   d  extends through the first valve plate  390  and the first suction valve plate  391 . 
     Each first cylinder bore  21   a  is in communication with the first suction chamber  27   a  through the corresponding first suction hole  390   a . Further, each first cylinder bore  21   a  is in communication with the first discharge chamber  29   a  through the corresponding first discharge hole  390   b . The first suction chamber  27   a  is in communication with the first communication passage  37   a  through the first suction communication hole  390   c . The first front communication passage  18   a  is in communication with the second front communication passage  18   b  through the first discharge communication hole  390   d.    
     The first suction valve plate  391  is arranged on the rear surface of the first valve plate  390 . The first suction valve plate  391  includes first suction reed valves  391   a , which may be elastically deformed to open and close the corresponding first suction holes  390   a . The first discharge valve plate  392  is arranged on the front surface of the first valve plate  390 . The first discharge valve plate  392  includes first discharge reed valves  392   a , which may be elastically deformed to open and close the corresponding first discharge holes  390   b . The first retainer plate  393  is arranged on the front surface of the first discharge valve plate  392 . The first retainer plate  393  restricts the maximum open degree of each first discharge reed valve  392   a.    
     The second valve formation plate  41  includes a second valve plate  410 , a second suction valve plate  411 , a second discharge valve plate  412 , and a second retainer plate  413 . Second suction holes  410   a  extend through the second valve plate  410 , the second discharge valve plate  412 , and the second retainer plate  413 . The number of the second suction holes  410   a  is the same as the number of the second cylinder bores  23   a . Second discharge holes  410   b  extend through the second valve plate  410  and the second suction valve plate  411 . The number of the second discharge holes  410   b  is the same as the number of the second cylinder bores  23   a . A second suction communication hole  410   c  extends through the second valve plate  410 , the second suction valve plate  411 , the second discharge valve plate  412 , and the second retainer plate  413 . A second discharge communication hole  410   d  extends through the second valve plate  410  and the second suction valve plate  411 . 
     Each second cylinder bore  23   a  is in communication with the second suction chamber  27   b  through the corresponding second suction hole  410   a . Further, each second cylinder bore  23   a  is in communication with the second discharge chamber  29   b  through the corresponding second discharge hole  410   b . The second suction chamber  27   b  is in communication with the second communication passage  37   b  through the second suction communication hole  410   c . The first rear communication passage  20   a  is in communication with the second rear communication passage  20   b  through the second discharge communication hole  410   d.    
     The second suction valve plate  411  is arranged on the front surface of the second valve plate  410 . The second suction valve plate  411  includes the second suction reed valves  411   a , which may be elastically deformed to open and close the corresponding second suction holes  410   a . The second discharge valve plate  412  is arranged on the rear surface of the second valve plate  410 . The second discharge valve plate  412  includes second discharge reed valves  412   a , which may be elastically deformed to open and close the corresponding second discharge holes  410   b . The second retainer plate  413  is arranged on the rear surface of the second discharge valve plate  412 . The second retainer plate  413  restricts the maximum open degree of each second discharge reed valve  412   a.    
     In the compressor, the first front communication passage  18   a , the first discharge communication hole  390   d , the second front communication passage  18   b , and the third front communication passage  18   c  form a first discharge communication passage  18 . Further, the first rear communication passage  20   a , the second discharge communication hole  410   d , and the second rear communication passage  20   b  form a second discharge communication passage  20 . 
     In the compressor, the first and second suction chambers  27   a  and  27   b  are in communication with the swash plate chamber  33  through the first and second communication passages  37   a  and  37   b  and the first and second suction communication holes  390   c  and  410   c . Thus, the pressure of the first and second suction chambers  27   a  and  27   b  is substantially equal to the pressure of the swash plate chamber  33 . Low-pressure refrigerant gas from the evaporator flows into the swash plate chamber  33  through the suction port  330 . Thus, the pressure of the swash plate chamber  33  and the first and second suction chambers  27   a  and  27   b  is lower than the pressure of the first and second discharge chambers  29   a  and  29   b.    
     The drive shaft  3  includes a shaft body  30 , a first support member  43   a , and a second support member  43   b . The shaft body  30  includes a front portion defining a first small diameter portion  30   a  and a rear portion defining a second small diameter portion  30   b . The shaft body  30 , which extends from the front to the rear of the housing  1 , extends through the sealing device  25  and the first and second plain bearings  22   a  and  22   b . Thus, the shaft body  30  and, consequently, the drive shaft  3  are supported by the housing  1  rotationally about the axis O of the drive shaft  3 . The shaft body  30  has a front end located in the boss  17   a  and a rear end projecting into the pressure regulation chamber  31 . 
     The swash plate  5 , the link mechanism  7 , and an actuator  13  are arranged on the shaft body  30 . The swash plate  5 , the link mechanism  7 , and the actuator  13  are each located in the swash plate chamber  33 . 
     The first support member  43   a  is fitted to the first small diameter portion  30   a  of the shaft body  30 . Further, the first support member  43   a  is located between the first small diameter portion  30   a  and the first plain bearing  22   a  in the first shaft bore  21   b . The first support member  43   a  includes a flange  430 , which contacts the first thrust bearing  35   a , and a coupling portion (not shown), through which a second pin  47   b  is inserted. The front end of a recovery spring  44   a  is fitted to the first support member  43   a . The recovery spring  44   a  extends from the flange  430  toward the swash plate  5  along the axis O of the drive shaft  3 . 
     The second support member  43   b  is fitted to the rear of the second small diameter portion  30   b  of the shaft body  30  and located in the second shaft bore  23   b . The front portion of the second support member  43   b  includes a flange  431 , which contacts the second thrust bearing  35   b . O-rings  51   a  and  51   b  are arranged on the second support member  43   b  at the rear side of the flange  431 . 
     Referring to  FIG. 1 , the swash plate  5  is an annular plate and includes a front surface  5   a  and a rear surface  5   b . The front surface  5   a  faces the front side of the compressor in the swash plate chamber  33 . The rear surface  5   b  faces the rear side of the compressor in the swash plate chamber  33 . 
     The swash plate  5  includes a ring plate  45 . The ring plate  45  is an annular plate. An insertion hole  45   a  extends through the center of the ring plate  45 . The shaft body  30  is inserted through the insertion hole  45   a  in the swash plate chamber  33  to couple the swash plate  5  to the drive shaft  3 . 
     Referring to  FIG. 3A , the surface of the ring plate  45  located at the same side as the rear surface  5   b  of the swash plate  5  includes two abutment portions  53   a  and  53   b . The abutment portions  53   a  and  53   b  are separated from the center C of the swash plate  5  toward the lower end U of the swash plate  5 . Further, the abutment portions  53   a  and  53   b  are arranged symmetrically relative to the center line L that extends through the center C of the swash plate  5 . 
     The abutment portions  53   a  and  53   b  are identically shaped, triangular in cross-section, and project toward the rear from the ring plate  45  as shown in  FIG. 3B . Referring to  FIG. 1 , when the swash plate  5  is inclined at a first predetermined inclination angle, the abutment portions  53   a  and  53   b  contact a partitioning body  13   b , which will be described later. The abutment portions  53   a  and  53   b  may be designed to have any suitable shape. 
     The ring plate  45  includes a coupler (not shown) coupled to pulling arms  132 , which will be described later. 
     As shown in  FIG. 1 , the link mechanism  7  includes a lug arm  49 . The lug arm  49  is arranged at the front side of the swash plate  5  in the swash plate chamber  33  and located between the swash plate  5  and the first support member  43   a . The lug arm  49  is generally L-shaped. The rear end of the lug arm  49  includes a weight  49   a . The weight  49   a  extends over one half of the circumference of the actuator  13 . The weight  49   a  may be designed to have a suitable shape. 
     A first pin  47   a  couples the rear end of the lug arm  49  to an upper portion of the ring plate  45 . The first pin  47   a  corresponds to a supporting portion of the present invention. Thus, the lug arm  49  is supported by the ring plate  45 , or the swash plate  5 , so that the lug arm  49  is pivotal about the axis of the first pin  47   a , namely, a first pivot axis M 1 . The first pivot axis M 1  extends in a direction perpendicular to the axis O of the drive shaft  3 . The drive shaft  3  is located between abutment portions  53   a  and  53   b  and the first pin  47   a , or the first pivot axis M 1 . 
     A second pin  47   b  couples the front end of the lug arm  49  to the first support member  43   a . Thus, the lug arm  49  is supported by the support member  43   a , or the drive shaft  3 , so that the lug arm  49  is pivotal about the axis of the second pin  47   b , namely, a second pivot axis M 2 . The second pivot axis M 2  extends parallel to the first pivot axis M 1 . The lug arm  49  and the first and second pins  47   a  and  47   b  are elements forming the link mechanism  7  of the present invention. 
     The weight  49   a  extends toward the rear of the lug arm  49 , that is, the side opposite to the second pivot axis M 2  as viewed from the first pivot axis M 1 . The lug arm  49  is supported by the first pin  47   a  on the ring plate  45  so that the weight  49   a  is inserted through a groove  45   b  in the ring plate  45  and is located at the rear side of the ring plate  45 , that is, the same side as the rear surface  5   b  of the swash plate  5 . Rotation of the swash plate  5  around the axis O of the drive shaft  3  generates centrifugal force that acts on the weight  49   a  at the rear side of the swash plate  5 . 
     In the compressor, the link mechanism  7  couples the swash plate  5  and the drive shaft  3  so that the swash plate  5  is able to rotate together with the drive shaft  3 . Further, the pivoting of two ends of the lug arm  49  about the first pivot axis M 1  and the second pivot axis M 2  enables the inclination angle of the swash plate  5  to be changed from the maximum inclination angle to the minimum inclination angle shown in  FIG. 4 . 
     Referring to  FIG. 1 , each piston  9  includes a front end that defines a first piston head  9   a  and a rear end that defines a second piston head  9   b . The first piston head  9   a  is reciprocally accommodated in the corresponding first cylinder bore  21   a . The first piston head  9   a  defines a first compression chamber  21   d  with the first valve formation plate  39  in the first cylinder bore  21   a . The second piston head  9   b  is reciprocally accommodated in the corresponding second cylinder bore  23   a . The second piston head  9   b  defines a second compression chamber  23   d  with the second valve formation plate  41  in the second cylinder bore  23   a.    
     The middle of each piston  9  includes an engagement portion  9   c , which accommodates the semispherical shoes  11   a  and  11   b . The shoes  11   a  and  11   b  convert the rotation of the swash plate  5  to the reciprocation of the piston  9 . The shoes  11   a  and  11   b  correspond to a conversion mechanism of the present invention. In this manner, the first and second piston heads  9   a  and  9   b  are reciprocated in the first and second cylinder bores  21   a  and  23   a  with a stroke that is in accordance with the inclination angle of the swash plate  5 . 
     In the compressor, a change in the inclination angle of the swash plate  5  changes the stroke of the pistons  9 . This, in turn, moves the top dead center of each of the first and second piston heads  9   a  and  9   b . More specifically, a decrease in the inclination angle of the swash plate  5  moves the top dead center of the second piston head  9   b  more than the top dead center of the first piston head  9   a.    
     Referring to  FIG. 5 , the actuator  13  is arranged in the swash plate chamber  33 . The actuator  13  is located at the rear of the swash plate  5  in the swash plate chamber  33  and is movable into the second recess  23   c . The actuator  13  includes a movable body  13   a , the partitioning body  13   b , and the control pressure chamber  13   c . The control pressure chamber  13   c  is defined between the movable body  13   a  and the partitioning body  13   b.    
     The movable body  13   a  includes a rear wall  130 , a circumferential wall  131 , and two pulling arms  132 . Each pulling arm  132  corresponds to a coupling portion of the present invention. The rear wall  130  is located at the rear of the movable body  13   a  and extends in the radial direction toward the outer side from the axis O of the drive shaft  3 . An insertion hole  130   a  extends through the rear wall  130 . The second small diameter portion  30   b  of the shaft body  30  is inserted through the insertion hole  130   a . An O-ring Sic is arranged in the wall of the insertion hole  130   a . The circumferential wall  131  is continuous with the outer circumference of the rear wall  130  and extends toward the front of the movable body  13   a . Each pulling arm  132  is formed on the front end of the circumferential wall  131  and projects toward the front of the movable body  13   a . The rear wall  130 , the circumferential wall  131 , and the pulling arms  132  are arranged so that the movable body  13   a  has the form of a cylinder that has a closed end. 
     The partitioning body  13   b  is disk-shaped and has a diameter that is substantially the same as the inner diameter of the movable body  13   a . An insertion hole  133  extends through the center of the partitioning body  13   b . An O-ring  51   d  is arranged in the wall of the insertion hole  133 . Further, an O-ring  51   e  is arranged on the outer circumferential surface of the partitioning body  13   b.    
     An inclination angle reduction spring  44   b  is located between the partitioning body  13   b  and the ring plate  45 . More specifically, the rear end of the inclination angle reduction spring  44   b  contacts the partitioning body  13   b , and the front end of the inclination angle reduction spring  44   b  contacts the ring plate  45 . 
     The second small diameter portion  30   b  of the drive shaft  3  is inserted through the insertion hole  130   a  of the movable body  13   a  and the insertion hole  133  of the partitioning body  13   b . Thus, when the movable body  13   a  is accommodated in the second recess  23   c , the movable body  13   a  and the link mechanism  7  are located at opposite sides of the swash plate  5 . 
     The partitioning body  13   b  is located in the movable body  13   a  at the rear of the swash plate  5  and surrounded by the circumferential wall  131 . The partitioning body  13   b  is rotatable together with the drive shaft  3  and movable along the axis O of the drive shaft  3  in the swash plate chamber  33 . In this manner, when the movable body  13   a  and the partitioning body  13   b  move along the axis O of the drive shaft  3 , the inner circumferential surface of the circumferential wall  131  of the movable body  13   a  moves along the outer circumferential surface of the partitioning body  13   b.    
     By surrounding the partitioning body  13   b  with the circumferential wall  131 , the control pressure chamber  13   c  is formed between the movable body  13   a  and the partitioning body  13   b . The control pressure chamber  13   c  is partitioned from the swash plate chamber  33  by the rear wall  130 , the circumferential wall  131 , and the partitioning body  13   b.    
     A snap ring  55  is fitted to the second small diameter portion  30   b . The snap ring  55  is located in the control pressure chamber  13   c  on the second small diameter portion  30   b  near a radial passage  3   b , which will be described later. The snap ring  55  corresponds to a movement amount restriction portion of the present invention. Instead of the snap ring  55 , for example, a flange may be arranged on the second small diameter portion  30   b  to serve as the movement amount restriction portion of the present invention. 
     A third pin  47   c  couples the pulling arms  132  to the lower end, which is indicated by “U” in the drawings, of the ring plate  45 . The third pin  47   c  corresponds to the coupling portion of the present invention. Thus, the swash plate  5  is supported by the movable body  13   a  so as to be pivotal about the axis of the third pin  47   c , namely, an action axis M 3 . The action axis M 3  extends parallel to the first and second pivot axes M 1  and M 2 . In this manner, the movable body  13   a  is coupled to the swash plate  5  so that the partitioning body  13   b  is opposed to the swash plate  5 . In the compressor, the pulling arms  132  and the third pin  47   c , which form the coupling portion, are opposed to the first pin  47   a , which serves as the supporting portion, with the abutment portions  53   a  and  53   b  disposed in between. More specifically, the coupling portion (pulling arms  132  and third pin  47   c ) is located at the opposite side of the supporting portion (first pin  47   a ) as viewed from the center C of the swash plate  5 . The abutment portions  53   a  and  53   b  are located between the coupling portion (pulling arms  132  and third pin  47   c ) and the supporting portion (first pin  47   a ) near the coupling portion (pulling arms  132  and third pin  47   c ). In other words, the abutment portions  53   a  and  53   b  are located closer to the coupling portion than the center C of the swash plate  5 . 
     As shown in  FIG. 1 , an axial passage  3   a  extends through the second small diameter portion  30   b  from the rear end toward the front along the axis O of the drive shaft  3 . The radial passage  3   b  extends through the second small diameter portion  30   b  from the front end of the axial passage  3   a  in the radial direction and opens in the outer surface of the shaft body  30 . The rear end of the axial passage  3   a  is in communication with the pressure regulation chamber  31 . The radial passage  3   b  is in communication with the control pressure chamber  13   c . Thus, the control pressure chamber  13   c  is in communication with the pressure regulation chamber  31  through the radial passage  3   b  and the axial passage  3   a.    
     The front end of the shaft body  30  includes a threaded portion  3   c . The threaded portion  3   c  couples the drive shaft  3  to a pulley or an electromagnetic clutch (neither shown). 
     As shown in  FIG. 2 , the control mechanism  15  includes a bleed passage  15   a , a gas supplying passage  15   b , a control valve  15   c , an orifice  15   d , the axial passage  3   a , and the radial passage  3   b.    
     The bleed passage  15   a  is connected to the pressure regulation chamber  31  and the second suction chamber  27   b . The control pressure chamber  13   c , the pressure regulation chamber  31 , and the second suction chamber  27   b  are in communication with one another through the bleed passage  15   a , the axial passage  3   a , and the radial passage  3   b . The gas supplying passage  15   b  is connected to the pressure regulation chamber  31  and the second discharge chamber  29   b . The control pressure chamber  13   c , the pressure regulation chamber  31 , and the second discharge chamber  29   b  are in communication with one another through the gas supplying passage  15   b , the axial passage  3   a , and the radial passage  3   b . The gas supplying passage  15   b  includes the orifice  15   d.    
     The control valve  15   c  is arranged in the bleed passage  15   a . The control valve  15   c  is able to adjust the open degree of the bleed passage  15   a  based on the pressure of the second suction chamber  27   b.    
     In the compressor, a pipe leading to the evaporator is connected to the suction port  330 . A pipe leading to a condenser is connected to the discharge port  230 . The condenser is connected to the evaporator by a pipe and an expansion valve. The compressor, the evaporator, an expansion valve, the condenser, and the like form the refrigeration circuit of the vehicle air conditioner. The evaporator, the expansion valve, the condenser, and the pipes are not shown in the drawings. 
     In the compressor, the rotation of the drive shaft  3  rotates the swash plate  5  and reciprocates each piston  9  in the corresponding first and second cylinder bores  21   a  and  23   a . Thus, the volumes of the first and second compression chambers  21   d  and  23   d  change in accordance with the piston stroke. This repeats a suction phase that draws refrigerant gas into the first and second compression chambers  21   d  and  23   d , a compression phase that compresses the refrigerant gas in the first and second compression chambers  21   d  and  23   d , and a discharge phase that discharges the compressed refrigerant gas to the first and second discharge chambers  29   a  and  29   b.    
     The refrigerant gas discharged to the first discharge chamber  29   a  flows through the first discharge communication passage  18  to the converging discharge chamber  231 . In the same manner, the refrigerant gas discharged to the second discharge chamber  29   b  flows through the second discharge communication passage  20  to the converging discharge chamber  231 . The refrigerant gas is discharged from the converging discharge chamber  231  through the discharge port  230  and delivered through a pipe to the condenser. 
     During the phases such as the suction phase, a compression reaction that acts to decrease the inclination angle of the swash plate  5  acts on rotational members including the swash plate  5 , the ring plate  45 , the lug arm  49 , and the first pin  47   a . A change in the inclination angle of the swash plate would increase or decrease the stroke of the pistons  9  that control the compressor displacement. 
     More specifically, when the control valve  15   c  in the control mechanism  15  shown in  FIG. 2  increases the open degree of the bleed passage  15   a , the pressure of the pressure regulation chamber  31  and, consequently, the pressure of the control pressure chamber  13   c  become substantially equal to the pressure of the second suction chamber  27   b . Namely, the variable pressure difference between the control pressure chamber  13   c  and the swash plate chamber  33  is decreased. Thus, referring to  FIG. 4 , the piston compression force acting on the swash plate  5  moves the movable body  13   a  of the actuator  13  toward the front in the swash plate chamber  33 . 
     As a result, in the compressor, compression reaction, which acts on the swash plate  5  through the pistons  9 , urges the swash plate  5  in the direction that decreases the inclination angle. This pulls the movable body  13   a  toward the front of the swash plate chamber  33  with the pulling arms  132  at the action axis M 3 . Thus, in the compressor, the lower end U of the swash plate  5  is pivoted in the clockwise direction about the action axis M 3  against the urging force of the recovery spring  44   a . Further, the rear end of the lug arm  49  pivots in the counterclockwise direction about the first pivot axis M 1 , and the front end of the lug arm  49  pivots in the counterclockwise direction about the second pivot axis M 2 . Thus, the lug arm  49  moves toward the flange  430  of the first support member  43   a . Consequently, the swash plate  5  is pivoted using the action axis M 3  as an action point and the first pivot axis M 1  as a fulcrum point. In this manner, the inclination angle of the swash plate  5  relative to a plane orthogonal to the rotation axis O of the drive shaft  3  decreases and shortens the stroke of the pistons  9  thereby decreasing the compressor displacement for each rotation of the drive shaft  3 . The inclination angle of the swash plate  5  in  FIG. 4  is the minimum inclination angle of the compressor. 
     In the compressor, the centrifugal force acting on the weight  49   a  is applied to the swash plate  5 . Thus, in the compressor, the swash plate  5  may easily be moved in the direction that decreases the inclination angle. 
     When the inclination angle of the swash plate  5  decreases, the ring plate  45  comes into contact with the rear end of the recovery spring  44   a . This elastically deforms the recovery spring  44   a  and moves the rear end of the recovery spring  44   a  toward the flange  430 . 
     In the compressor, when the inclination angle of the swash plate  5  decreases and shortens the stroke of the pistons  9 , the top dead center of each second piston head  9   b  is moved away from the second valve formation plate  41 . Thus, in the compressor, the inclination angle of the swash plate  5  becomes close to zero degrees. As a result, the first compression chambers  21   d  slightly compress refrigerant gas, while the second compression chambers  23   d  do not perform compression at all. 
     When the control valve  15   c  shown in  FIG. 2  decreases the open degree of the bleed passage  15   a , the pressure of the refrigerant gas in the second discharge chamber  29   b  raises the pressure of the pressure regulation chamber  31  thereby raising the pressure of the control pressure chamber  13   c . As a result, the variable pressure difference is increased. Thus, referring to  FIG. 1 , in the actuator  13 , the movable body  13   a  moves toward the rear of the swash plate chamber  33  against the piston compression force acting on the swash plate  5 . 
     As a result, in the compressor, the movable body  13   a  pulls rearward the section of the swash plate  5  near the lower end U with the pulling arms  132  at the action axis M 3 . Thus, in the compressor, the lower end U of the swash plate  5  is pivoted in the counterclockwise direction about the action axis M 3 . Further, the rear end of the lug arm  49  pivots in the clockwise direction about the first pivot axis M 1 , and the front end of the lug arm  49  pivots in the clockwise direction about the second pivot axis M 2 . Thus, the lug arm  49  moves away from the flange  430  of the first support member  43   a . Consequently, using the action axis M 3  as an action point and the first pivot axis M 1  as a fulcrum point, the swash plate  5  is pivoted in a direction opposite to the direction that decreases the inclination angle, and the section at the lower end U of the swash plate  5  moves toward the partitioning body  13   b . In this manner, the inclination angle of the swash plate  5  increases and lengthens the stroke of the pistons  9  thereby increasing the compressor displacement for each rotation of the drive shaft  3 . The inclination angle of the swash plate  5  in  FIG. 1  is the first predetermined inclination angle of the compressor. The first predetermined inclination angle is set in the compressor and smaller than the maximum inclination angle, which is mechanically set. 
     In this manner, when the swash plate  5  of the compressor is inclined at the first predetermined inclination angle, the abutment portions  53   a  and  53   b  contact the partitioning body  13   b . This restricts the inclination angle to the first predetermined angle in the compressor. 
     The abutment portions  53   a  and  53   b  are separated from the center C toward the lower end U of the swash plate  5 . Thus, the abutment portions  53   a  and  53   b  contact a peripheral portion of the partitioning body  13   b , that is, a location separated from the insertion hole  133 . 
     Referring to  FIG. 5 , when suddenly increasing the compressor displacement to the maximum, the swash plate  5  may overshoot the first predetermined inclination angle and reach the maximum inclination angle. In this case, the abutment portions  53   a  and  53   b  would come to contact and push the partitioning body  13   b  with a strong force. 
     In the compressor, however, the partitioning body  13   b  is movable along the axis O of the drive shaft  3 . Accordingly, even if the abutment portions  53   a  contact or push the partitioning body  13   b  with a strong force, the partitioning body  13   b  is moved toward the rear along the axis O of the drive shaft  3  in a direction opposite to the abutment portions  53   a  and  53   b . That is, when the inclination angle of the swash plate  5  goes beyond the first predetermined inclination angle and reaches the maximum inclination angle, the abutment portions  53   a  and  53   b  move the partitioning body  13   b . When moved toward the rear, the partitioning body  13   b  comes into contact with the snap ring  55 . This restricts further rearward movement of the partitioning body  13   b.    
     In this manner, the compressor suppresses the shock and the pressing force of the abutment portions  53   a  and  53   b  when coming to contact or pushing the partitioning body  13   b . Thus, the compressor reduces vibration when the abutment portions  53   a  and  53   b  come to contact the partitioning body  13   b  and limits damage to the swash plate  5 , the partitioning body  13   b , and the abutment portions  53   a  and  53   b . Further, the compressor reduces noise. 
     Accordingly, the compressor of the first embodiment has high durability and superior quietness. 
     In the compressor, the partitioning body  13   b  is moved along the axis O of the drive shaft  3 . Thus, even though the swash plate  5  and the partitioning body  13   b  are located near each other, open space for the abutment portions  53   a  and  53   b  may be obtained between the swash plate  5  and the partitioning body  13   b . This allows the compressor to be reduced in length in the axial direction. 
     Further, the compressor includes the snap ring  55  on the small diameter portion  30   b  of the shaft body  30 . Thus, contact of the partitioning body  13   b  with the snap ring  55  restricts the movement amount of the partitioning body  13   b  along the axis O of the drive shaft  3 . This limits unnecessary rearward movement of the partitioning body  13   b  along the axis O of the drive shaft  3  and keeps the radial passage  3   b  unexposed to the outside of the control pressure chamber  13   c , that is, unexposed to the swash plate chamber  33 . 
     The snap ring  55  is located in the control pressure chamber  13   c  near the radial passage  3   b . Thus, there is no need to obtain open space dedicated for the snap ring  55  in the control pressure chamber  13   c , and the control pressure chamber  13   c  may be reduced in size. This also allows the compressor to be reduced in length in the axial direction. 
     In the compressor, the partitioning body  13   b  is movable along the axis O of the drive shaft  3 . This allows the movable body  13   a  to easily move relative to the partitioning body  13   b  when changing the inclination angle of the swash plate  5 . Thus, the compressor is able to smoothly change the inclination angle of the swash plate  5 . 
     Second Embodiment 
     A compressor of a second embodiment includes two abutment portions  57   a  and  57   b  shown in  FIG. 6  instead of the two abutment portions  53   a  and  53   b  of the compressor in the first embodiment. Referring to  FIG. 7A , the abutment portions  57   a  and  57   b  are formed on the surface of the ring plate  45  located at the same side as the rear surface  5   b  of the swash plate  5 . The abutment portions  57   a  and  57   b  are located proximate to the center C of the swash plate  5 , that is, closer to the center C than the lower end U of the swash plate  5 . In the same manner as the abutment portions  53   a  and  53   b  in the compressor of the first embodiment, the abutment portions  57   a  and  57   b  are symmetric relative to the center line L that extends through the center C. In the compressor, the pulling arms  132  and the third pin  47   c , which form the coupling portion, and the first pin  47   a , which serves as the supporting portion, are located at opposite sides of the abutment portions  57   a  and  57   b.    
     The abutment portions  57   a  and  57   b  are identically shaped, triangular, and project toward the rear from the ring plate  45  as shown in  FIG. 7B . The abutment portions  57   a  and  57   b  are larger than the abutment portions  53   a  and  53   b  in the compressor of the first embodiment. 
     Referring to  FIG. 8 , when the swash plate  5  is inclined at a second predetermined inclination angle, the abutment portions  57   a  and  57   b  contact the partitioning body  13   b . The second predetermined inclination angle is greater than the minimum inclination angle of the swash plate  5  (refer to  FIG. 6 ) and less than the mechanically set maximum inclination angle of the swash plate  5  (refer to  FIG. 9 ). Other components of the compressor are the same as those in the compressor of the first embodiment. Same reference numerals are given to those components that are the same as the corresponding components of the first embodiment. Such components will not be described in detail. 
     In the compressor, as shown in  FIG. 8 , when the swash plate  5  is inclined at the second predetermined inclination angle, the abutment portions  57   a  and  57   b  contact the partitioning body  13   b . Referring to  FIG. 9 , when the inclination angle of the swash plate  5  changes from the second predetermined inclination angle to the maximum inclination angle, the abutment portions  57   a  and  57   b , which are in contact with the partitioning body  13   b , push the partitioning body  13   b . Thus, as the inclination angle of the swash plate  5  changes from the second predetermined inclination angle to the maximum inclination angle, the abutment portions  57   a  and  57   b  contact and push the partitioning body  13   b , and the movable body  13   a  moves toward the rear along the axis O of the drive shaft  3 . In this manner, when the inclination angle of the swash plate  5  increases from the second predetermined inclination angle to the maximum inclination angle, the abutment portions  57   a  and  57   b  push and move the partitioning body  13   b.    
     In the compressor, as described above, the inclination angle of the swash plate  5  is increased by increasing the pressure of the control pressure chamber  13   c , that is, increasing the variable pressure difference between the control pressure chamber  13   c  and the swash plate chamber  33 . As shown in the graph of  FIG. 10 , the increasing rate of the variable pressure difference from the second predetermined inclination angle to the maximum inclination angle is larger than the increasing rate of the variable pressure difference when the inclination angle comes closer to the second predetermined inclination angle from the minimum inclination angle. That is, the variable pressure difference needs to be further increased to increase the inclination angle from the second predetermined inclination angle to the maximum inclination angle. In this manner, the pressure of the control pressure chamber  13   c  needs to be further increased in order to further increase the variable pressure difference and thereby increase the inclination angle from the second predetermined inclination angle to the maximum inclination angle. 
     If the abutment portions  57   a  and  57   b  were omitted from the compressor of the present embodiment and, at the same time, the partitioning body  13   b  arranged on the second small diameter portion  30   b  were immovable along the axis O, this would lower the increasing rate of the variable pressure difference for changing the inclination angle of the swash plate  5  from the second predetermined inclination angle to the maximum inclination angle, as shown in a flat dashed line in  FIG. 10 . This means that the inclination angle may be changed in a certain range even if the variable pressure difference is substantially the same. Thus, it would be difficult to control the swash plate  5  and obtain the desired inclination angle between the compressor displacement corresponding to the second predetermined inclination angle and the compressor displacement corresponding to the maximum inclination angle. 
     In this respect, the abutment portions  57   a  and  57   b  in the compressor of the present embodiment continue to contact and push the partitioning body  13   b  from when the inclination angle of the swash plate  5  reaches the second predetermined inclination angle to when the swash plate  5  reaches the maximum inclination angle. Thus, as shown in the solid line in  FIG. 10 , the compressor of the present embodiment allows the variable pressure difference to be increased in a preferred manner for changing the inclination angle from the second predetermined inclination angle to the maximum inclination angle. That is, in the compressor, the variable pressure difference smoothly increases from the minimum inclination angle to the maximum inclination angle. This allows the compressor to easily control the torque of the vehicle engine or the like while varying the compressor displacement in a preferred manner. Other operations of the compressor are the same as the compressor of the first embodiment. 
     The present invention is not restricted to the first and second embodiments described above. It should be apparent to those skilled in the art that the present invention may be embodied in many other specific forms without departing from the spirit or scope of the invention. Particularly, it should be understood that the present invention may be embodied in the following forms. 
     The ring plate  45  of the first embodiment may include only one of the abutment portions  53   a  and  53   b . In the same manner, the ring plate  45  of the second embodiment may include only one of the abutment portions  57   a  and  57   b.    
     In the control mechanism  15 , the control valve  15   c  may be arranged in the gas supplying passage  15   b , and the orifice  15   d  may be arranged in the bleed passage  15   a . In this case, the control valve  15   c  allows for adjustment of the open degree of the gas supplying passage  15   b . This enables the control pressure chamber  13   c  to be promptly increased to a high pressure by the pressure of the refrigerant gas in the second discharge chamber thereby promptly increasing the compressor displacement. 
     The present examples and embodiments are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein, but may be modified within the scope and equivalence of the appended claims.