Patent Publication Number: US-9850886-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-Open Patent Publication No. 52-131204 discloses a conventional variable displacement swash-plate compressor (hereinafter, referred to as a compressor). The compressor includes a swash plate chamber, cylinder bores, a suction chamber, and a discharge chamber, which are provided in the housing. A drive shaft is rotationally supported in the housing. The swash plate chamber accommodates a swash plate, which is rotational through rotation of the drive shaft. The swash plate has a through hole. A link mechanism is located between the drive shaft and the swash plate. The link mechanism allows the inclination angle of the swash plate to be changed. The inclination angle is the angle of the swash plate in relation to a direction perpendicular to the axis of the drive shaft. Each cylinder bore reciprocally accommodates a piston. A conversion mechanism reciprocates each of the pistons in the associated one of the cylinder bores by the stroke corresponding to the inclination angle through rotation of the swash plate. A top dead center associated part for positioning each piston at the top dead center is defined on the swash plate. The inclination angle of the swash plate is changed by an actuator. The actuator is controlled by a control mechanism. The control mechanism includes a pressure regulation valve. 
     The link mechanism includes a lug member, a hinge ball, and a link. The lug member is located in the swash plate chamber and is fixed to the drive shaft. The hinge ball is fitted about the drive shaft to be arranged in the through hole of the swash plate. This causes the outer circumferential surface of the hinge ball to contact the through hole. The link is provided between the lug member and the swash plate. The link connects the swash plate to the lug member, so that the swash plate is permitted to pivot. 
     The actuator includes the lug member, a movable body, and a control pressure chamber. The movable body has a cylindrical shape. The movable body is fitted about the drive shaft to be arranged between the lug member and the hinge ball. When the movable body and the hinge ball contact each other, the movable body is engaged with the swash plate via the hinge ball. When moving along the drive shaft axis, the movable body changes the inclination angle of the swash plate. The control pressure chamber, which is defined by the lug member and the movable body, uses its internal pressure to move the movable body. 
     In this compressor, when the control mechanism connects the discharge chamber and the control pressure chamber with each other using the pressure regulation valve, the pressure in the control pressure chamber is increased. This moves the movable body along the axis of the drive shaft and pushes the hinge ball along the axis of the drive shaft. Accordingly, the hinge ball is moved along the axis of the drive shaft, and the swash plate slides on the hinge ball in the direction reducing the inclination angle. This allows the displacement of the compressor per rotation of the drive shaft to be reduced. 
     However, in the above described compressor, the movable body of the actuator and the swash plate are engaged with each other via the hinge ball. Thus, the size of the entire compressor needs to be increased to increase the size of the movable body so that the movable body is easily moved with a great thrust. 
     When decreasing the inclination angle of the swash plate in the compressor, the movable body pushes the swash plate via the hinge ball. The tolerance during manufacture is likely to vary contacting positions between the outer circumferential surface of the hinge ball and the swash plate. Accordingly, when the movable body pushes the hinge ball, the direction of the load acting on the swash plate is likely to change. Thus, the movable body cannot smoothly move the hinge ball along the axis of the drive shaft, and the movable body cannot stably decrease the inclination angle of the swash plate. Also, the orientation of the movable body tends to be unstable, which can result in pressure leakage in the control pressure chamber. In this case, the displacement cannot be quickly changed in response to changes in the driving state of machinery on which the compressor is mounted, such as a vehicle, and high controllability cannot be achieved. 
     SUMMARY OF THE INVENTION 
     An objective of the present invention is to provide a variable displacement swash-plate compressor that achieves a sufficient controllability while minimizing the size. 
     To achieve the foregoing objective and in accordance with one aspect of the present invention, a variable displacement swash-plate compressor is provided that includes a housing having a swash plate chamber and a cylinder bore, a drive shaft that is rotationally supported by the housing, a swash plate that is supported in the swash plate chamber and is rotational by rotation of the drive shaft, a link mechanism, a piston, a conversion mechanism, an actuator, and a control mechanism. The link mechanism is arranged between the drive shaft and the swash plate, and allows an inclination angle of the swash plate to be changed with respect to a direction perpendicular to a drive shaft axis of the drive shaft. The piston is reciprocally received in the cylinder bore. The conversion mechanism causes the piston to reciprocate in the cylinder bore by a stroke corresponding to the inclination angle of the swash plate through rotation of the swash plate. The actuator is configured to change the inclination angle. The control mechanism controls the actuator. The link mechanism includes a lug member that is located in the swash plate chamber and is fixed to the drive shaft and a transmitting member that transmits rotation of the lug member to the swash plate. The swash plate has a through hole, which slides on an outer circumference of the drive shaft in response to changes in the inclination angle. The swash plate is guided by the link mechanism and the through hole along the drive shaft axis and in a direction of the inclination angle, thereby changing the inclination angle. The actuator includes the lug member, a movable body, and a control pressure chamber. The movable body is located between the lug member and the swash plate and is configured to rotate integrally with the swash plate and to move along the drive shaft axis, thereby changing the inclination angle. The control pressure chamber is defined by the lug member and the movable body and is configured such that pressure in the control pressure chamber is changed by the control mechanism to move the movable body. The movable body includes an acting portion that is configured to push the swash plate with the pressure in the control pressure chamber. The swash plate includes a receiving portion that contacts and is pushed by the acting portion. The acting portion and the receiving portion contact each other at an acting position. A top dead center associated part for positioning the piston at a top dead center is defined on the swash plate. When the drive shaft and the acting position are viewed from a direction that is perpendicular to a top dead center plane containing the top dead center associated part and the drive shaft axis, the acting position is defined at a position overlapping with the drive shaft regardless of the inclination angle. 
     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 of a compressor according to a first embodiment at the minimum displacement; 
         FIG. 2  is a schematic diagram showing the control mechanism of the compressor according to the first embodiment; 
         FIG. 3  is a schematic front view of the swash plate of the compressor according to the first embodiment; 
         FIG. 4  is a rear view of the lug plate of the compressor according to the first embodiment; 
         FIG. 5  is an enlarged partial cross-sectional view showing the lug plate and the movable body of the compressor according to the first embodiment; 
         FIG. 6  is a side view of the movable body of the compressor according to the first embodiment; 
         FIG. 7  is a rear view of the movable body of the compressor according to the first embodiment; 
         FIG. 8  is an enlarged partial cross-sectional view of the compressor according to the first embodiment in a state of the maximum displacement, in which the drive shaft and the first and second acting positions are viewed from a D 1  direction in  FIG. 7 ; 
         FIG. 9  is an enlarged partial cross-sectional view of the compressor according to the first embodiment in a state of the minimum displacement, in which the drive shaft and the first and second acting positions are viewed from a D 1  direction in  FIG. 7 ; 
         FIG. 10  is a schematic front view of the swash plate of a compressor according to a second embodiment; 
         FIG. 11  is a side view of the movable body of the compressor according to the second embodiment; 
         FIG. 12  is a rear view of the movable body of the compressor according to the second embodiment; 
         FIG. 13  is an enlarged partial cross-sectional view of the compressor according to the second embodiment in a state of the minimum displacement, in which the drive shaft and the first and second acting positions are viewed from a D 1  direction in  FIG. 12 ; 
         FIG. 14  is a schematic front view of the swash plate of a compressor according to a third embodiment; 
         FIG. 15  is a side view of the movable body of the compressor according to the third embodiment; 
         FIG. 16  is a rear view of the movable body of the compressor according to the third embodiment; and 
         FIG. 17  is an enlarged partial cross-sectional view of the compressor according to the third embodiment in a state of the minimum displacement, in which the drive shaft and the first and second acting positions are viewed from a D 1  direction in  FIG. 16 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     First to third embodiments of the present invention will now be described with reference to the drawings. Compressors according to the first to third embodiments are variable displacement swash-plate compressors with single-headed pistons. These compressors are installed in vehicles and are each included in the refrigeration circuit in the air conditioner for the vehicle. 
     First Embodiment 
     As shown in  FIG. 1 , the compressor according to the first embodiment includes a housing  1 , a drive shaft  3 , a swash plate  5 , a link mechanism  7 , pistons  9 , pairs of shoes  11   a,    11   b,  an actuator  13 , and a control mechanism  15 , which is illustrated in  FIG. 2 . 
     As shown in  FIG. 1 , the housing  1  has a front housing member  17  at a front position in the compressor, a rear housing member  19  at a rear position in the compressor, and a cylinder block  21  and a valve assembly plate  23 , which are arranged between the front housing member  17  and the rear housing member  19 . 
     The front housing member  17  includes a front wall  17   a,  which extends in the vertical direction of the compressor on the front side, and a circumferential wall  17   b,  which is integrated with the front wall  17   a  and extends rearward from the front of the compressor. The front housing member  17  has a substantially cylindrical cup shape with the front wall  17   a  and the circumferential wall  17   b.  Furthermore, the front wall  17   a  and the circumferential wall  17   b  define a swash plate chamber  25  in the front housing member  17 . 
     The front wall  17   a  has a boss  17   c,  which projects forward. The boss  17   c  accommodates a shaft sealing device  27 . The boss  17   c  has a first shaft hole  17   d,  which extends in the front-rear direction of the compressor. The first shaft hole  17   d  accommodates a first slide bearing  29   a.    
     The circumferential wall  17   b  has an inlet  250 , which communicates with the swash plate chamber  25 . The swash plate chamber  25  is connected to a non-illustrated evaporator through the inlet  250 . Since low-pressure refrigerant gas that has passed through the evaporator flows into the swash plate chamber  25  via the inlet  250 , the pressures in the swash plate chamber  25  is lower than the pressure in a discharge chamber  35 , which will be discussed below. 
     A part of the control mechanism  15  is received in the rear housing member  19 . The rear housing member  19  includes a first pressure regulation chamber  31   a,  a suction chamber  33 , and the discharge chamber  35 . The first pressure regulation chamber  31   a  is located in the central part of the rear housing member  19 . The discharge chamber  35  has an annular shape and is located in a radially outer part of the rear housing member  19 . Also, the suction chamber  33  has an annular shape between the first pressure regulation chamber  31   a  and the discharge chamber  35  in the rear housing member  19 . The discharge chamber  35  is connected to a non-illustrated outlet. 
     The cylinder block  21  includes cylinder bores  21   a,  the number of which is the same as that of the pistons  9 . The cylinder bores  21   a  are arranged at equal angular intervals in the circumferential direction. The front end of the each cylinder bore  21   a  communicates with the swash plate chamber  25 . The cylinder block  21  also includes retainer grooves  21   b,  which limit the lift of suction reed valves  41   a,  which will be discussed below. 
     The cylinder block  21  further includes a second shaft hole  21   c,  which communicates with the swash plate chamber  25  and extends in the front-rear direction of the compressor. The second shaft hole  21   c  accommodates a second slide bearing  29   b.  The first slide bearing  29   a  and the second slide bearing  29   b  may be replaced by rolling-element bearings. 
     The cylinder block  21  further has a spring chamber  21   d.  The spring chamber  21   d  is located between the swash plate chamber  25  and the second shaft hole  21   c.  The spring chamber  21   d  accommodates a restoration spring  37 . The restoration spring  37  urges the swash plate  5  forward of the swash plate chamber  25  when the inclination angle is minimized. The cylinder block  21  also includes a suction passage  39 , which communicates with the swash plate chamber  25 . 
     The valve assembly plate  23  is located between the rear housing member  19  and the cylinder block  21 . The valve assembly plate  23  includes a valve base plate  40 , a suction valve plate  41 , a discharge valve plate  43 , and a retainer plate  45 . 
     The valve base plate  40 , the discharge valve plate  43 , and the retainer plate  45  include suction ports  40   a,  the number of which is equal to that of the cylinder bores  21   a.  Furthermore, the valve base plate  40  and the suction valve plate  41  include discharge ports  40   b,  the number of which is equal to that of the cylinder bores  21   a.  The cylinder bores  21   a  communicate with the suction chamber  33  through the suction ports  40   a  and communicate with the discharge chamber  35  through the discharge ports  40   b.  Furthermore, the valve base plate  40 , the suction valve plate  41 , the discharge valve plate  43 , and the retainer plate  45  include a first communication hole  40   c  and a second communication hole  40   d.  The first communication hole  40   c  connects the suction chamber  33  to the suction passage  39 . This causes the swash plate chamber  25  to communicate with the suction chamber  33 . 
     The suction valve plate  41  is provided on the front surface of the valve base plate  40 . The suction valve plate  41  includes suction reed valves  41   a,  which are allowed to selectively open and close the suction ports  40   a  by elastic deformation. The discharge valve plate  43  is located on the rear surface of the valve base plate  40 . The discharge valve plate  43  includes discharge reed valves  43   a,  which are allowed to selectively open and close the discharge ports  40   b  by elastic deformation. The retainer plate  45  is provided on the rear surface of the discharge valve plate  43 . The retainer plate  45  limits the maximum opening degree of the discharge reed valves  43   a.    
     The drive shaft  3  has a cylindrical outer circumferential surface  30 . The drive shaft  3  is inserted in the boss  17   c  toward the rear of the housing  1 . The front portion of the drive shaft  3  is supported by the shaft sealing device  27  in the boss  17   c  and is supported by the first slide bearing  29   a  in the first shaft hole  17   d.  The rear portion of the drive shaft  3  is supported by the second slide bearing  29   b  in the second shaft hole  21   c.  In this manner, the drive shaft  3  is supported by the housing  1  to be rotational about the drive shaft axis O. The second shaft hole  21   c  and the rear end of the drive shaft  3  define a second pressure regulation chamber  31   b.  The second pressure regulation chamber  31   b  communicates with the first pressure regulation chamber  31   a  through the second communication hole  40   d.  The first and second pressure regulation chambers  31   a,    31   b  constitute a pressure regulation chamber  31 . 
     O-rings  49   a,    49   b  are provided on the rear end of the drive shaft  3 . The O-rings  49   a,    49   b  are located between the drive shaft  3  and the second shaft hole  21   c  to seal off the swash plate chamber  25  and the pressure regulation chamber  31  from each other. 
     The link mechanism  7 , the swash plate  5 , and the actuator  13  are mounted on the drive shaft  3 . The link mechanism  7  includes first and second swash plate arms  5   e,    5   f  provided on the swash plate  5  shown in  FIG. 3 , a lug plate  51  shown in  FIG. 4 , and first and second lug arms  53   a,    53   b  provided on the lug plate  51 . The first and second swash plate arms  5   e,    5   f  correspond to transmitting members. The lug plate  51  corresponds to a lug member. For illustrative purposes, part of the second swash plate arm  5   f  is omitted by using a break line. 
     As shown in  FIG. 3 , the swash plate  5  has a swash plate main portion  50 , a swash plate weight  5   c,  and the first and second swash plate arms  5   e,    5   f.    
     The swash plate main portion  50  is shaped as a flat annular plate and has a front surface  5   a  and a rear surface  5   b.  A top dead center associated part T for positioning each piston  9  at the top dead center and a bottom dead center associated part U for positioning each piston  9  at the bottom dead center are defined on the swash plate main portion  50 . Also, as shown in  FIG. 3 , an imaginary top dead center plane D is defined in this compressor. The top dead center plane D includes the top dead center associated part T, the bottom dead center associated part U, and the drive shaft axis O. Further, as shown in  FIG. 8 , the swash plate main portion  50  includes an imaginary swash plate reference plane S for determining the inclination angle of the swash plate  5  in relation to a direction perpendicular to the drive shaft axis O. The swash plate reference plane S is parallel with the front surface  5   a  and the rear surface  5   b.    
     As shown in  FIG. 3 , the swash plate main portion  50  includes a through hole  5   d.  The drive shaft  3  is inserted in the through hole  5   d.  Two flat guide surfaces  52   a,    52   b  are provided in the through hole  5   d.  When the drive shaft  3  is inserted in the through hole  5   d,  the guide surfaces  52   a,    52   b  contact the outer circumferential surface  30  of the drive shaft  3 . 
     First and second receiving surfaces  54   a,    54   b  are provided on the front surface of the swash plate main portion  50  about the through hole  5   d.  The first and second receiving surfaces  54   a,    54   b  each correspond to a receiving surface. As shown in  FIG. 8 , the first receiving surface  54   a  is a flat surface parallel with the swash plate reference plane S. The second receiving surface  54   b,  which is shown in  FIG. 3 , has the same structure as the first receiving surface  54   a.  The first receiving surface  54   a  and the second receiving surface  54   b  are arranged on the front surface  5   a  at positions on opposite sides of the top dead center plane D. When the drive shaft  3  is passed through the through hole  5   d,  the drive shaft  3  is located between the first receiving surface  54   a  and the second receiving surface  54   b.    
     A part of the first receiving surface  54   a  that makes line contact with a first acting portion  14   a  at a first acting position F 1 , which will be discussed below, is a first receiving portion  6   a.  Likewise, a part of the second receiving surface  54   b  that makes line contact with a second acting portion  14   b  at a second acting position F 2 , which will be discussed below, is a second receiving portion  6   b.  As described above, the first receiving surface  54   a  and the second receiving surface  54   b  are arranged on the front surface  5   a  at positions on opposite sides of the top dead center plane D. Thus, the first receiving portion  6   a  and the second receiving portion  6   b  are also located on opposite sides of the top dead center plane D. Since the first and second receiving surfaces  54   a,    54   b  are flat, the first and second receiving portions  6   a,    6   b  are flat. 
     The swash plate weight  5   c  is provided on the front surface  5   a  at a position closer to the bottom dead center associated part U than the drive shaft axis O. That is, the swash plate weight  5   c  is located between the drive shaft axis O and the bottom dead center associated part U. As shown in  FIG. 1 , the swash plate weight  5   c  has a substantially semi-circular cylindrical shape and extends from the front surface  5   a  toward a movable body  13   a,  which will be discussed below. 
     The first and second swash plate arms  5   e,    5   f  are arranged on the front surface  5   a  at positions closer to the top dead center associated part T than the drive shaft axis O. Specifically, the first and second swash plate arms  5   e,    5   f  are located between the drive shaft axis O and the top dead center associated part T. The first swash plate arm  5   e  and the second swash plate arm  5   f  are arranged on the front surface  5   a  at positions on opposite sides of the top dead center plane D. As shown in  FIG. 1 , the first and second swash plate arms  5   e,    5   f  extend from the front surface  5   a  toward the lug plate  51 . For illustrative purposes, the shapes of the swash plate weight  5   c  and the first and second swash plate arms  5   e,    5   f  are simplified in  FIG. 3 . The same applies to  FIGS. 10 and 14 , which will be discussed below. 
     As shown in  FIG. 4 , the lug plate  51  has a substantially annular shape with a through hole  510 . The drive shaft  3  is press-fitted in the through hole  510 , so that the lug plate  51  rotates integrally with the drive shaft  3 . As shown in  FIG. 1 , a thrust bearing  55  is located between the lug plate  51  and the front wall  17   a.    
     As shown in  FIG. 5 , the lug plate  51  has a recessed cylinder chamber  51   a.  The cylinder chamber  51   a  has a cylindrical shape coaxial with and extending along the drive shaft axis O. The cylinder chamber  51   a  communicates with the swash plate chamber  25  at the rear. 
     As shown in  FIG. 4 , the first lug arm  53   a  and the second lug arm  53   b  are provided on the lug plate  51  at positions on opposite sides of the top dead center plane D. On the lug plate  51 , the first and second lug arms  53   a,    53   b  are located at positions closer to the top dead center associated part T on the swash plate main portion  50  than the drive shaft axis O and extend from the lug plate  51  toward the swash plate  5 . That is, the first and second lug arms  53   a,    53   b  are located between the drive shaft axis O and the top dead center associated part T on the lug plate  51 . 
     The lug plate  51  has first and second guide surfaces  57   a,    57   b  between the first and second lug arms  53   a,    53   b.  The first guide surface  57   a  and the second guide surface  57   b  are also located on opposite sides of the top dead center plane D. As shown in  FIG. 1 , the first guide surface  57   a  is inclined such that the distance from the swash plate  5  gradually decreases from the outer circumference of the lug plate  51  toward the cylinder chamber  51   a.  The second guide surface  57   b  has the same shape as the first guide surface  57   a.    
     In this compressor, the first and second swash plate arms  5   e,    5   f  are inserted between the first and second lug arms  53   a,    53   b  to mount the swash plate  5  to the drive shaft  3 . The lug plate  51  and the swash plate  5  are thus coupled to each other with the first and second swash plate arms  5   e,    5   f  located between the first and second lug arms  53   a,    53   b.  When rotation of the lug plate  51  is transmitted from the first and second lug arms  53   a,    53   b  to the first and second swash plate arms  5   e,    5   f,  the swash plate  5  rotates with the lug plate  51  in the swash plate chamber  25 . 
     Since the first and second swash plate arms  5   e,    5   f  are located between the first and second lug arms  53   a,    53   b,  the distal end of the first swash plate arm  5   e  contacts the first guide surface  57   a,  and the distal end of the second swash plate arm  5   f  contacts the second guide surface  57   b.  The first and second swash plate arms  5   e,    5   f  slide on the first and second guide surfaces  57   a,    57   b,  respectively. Accordingly, the swash plate  5  is allowed to change its inclination angle, which is defined by the swash plate reference plane S, between the minimum inclination angle shown in  FIGS. 1 and 9  and the maximum inclination angle shown in  FIG. 8 , while substantially maintaining the position of the top dead center associated part T. 
     As shown in  FIG. 5 , the actuator  13  includes the lug plate  51 , a movable body  13   a,  and a control pressure chamber  13   b.    
     As shown in  FIG. 6 , the movable body  13   a  is fitted about the drive shaft  3 . The movable body  13   a  is thus located between the lug plate  51  and the swash plate  5  to move along the drive shaft axis O while sliding on the drive shaft  3 . The movable body  13   a  has a substantially cylindrical shape coaxial with the drive shaft  3 . Specifically, the movable body  13   a  has a movable body main portion  130 . 
     The movable body main portion  130  includes a first cylindrical portion  131 , a second cylindrical portion  132 , and a coupling portion  133 . The first cylindrical portion  131  is located at a position facing the swash plate  5  in the movable body  13   a  and extends along the drive shaft axis O. The first cylindrical portion  131  has the smallest outer diameter in the movable body main portion  130 . As shown in  FIG. 5 , a ring groove  131   a  is provided in the inner circumferential surface of the first cylindrical portion  131 . An O-ring  49   c  is fitted in the ring groove  131   a.  The second cylindrical portion  132  is located at a position on the movable body main portion  130  that faces the lug plate  51 , that is, on in a front portion of the movable body  13   a.  The second cylindrical portion  132  has a diameter larger than that of the first cylindrical portion  131  and has the largest outer diameter in the movable body main portion  130 . The second cylindrical portion  132  has a ring groove  132   a  in the outer circumferential surface. An O-ring  49   d  is fitted in the ring groove  132   a.  The coupling portion  133  has an outer diameter that gradually increases from the first cylindrical portion  131  toward the second cylindrical portion  132  and couples the first cylindrical portion  131  and the second cylindrical portion  132  to each other. 
     As shown in  FIG. 6 , the first cylindrical portion  131  has an acting surface  134  at the rear end, that is, at a position that faces the swash plate  5 . The acting surface  134  has a shape like a truncated cone, the diameter of which decreases from the outer circumference of the first cylindrical portion  131  toward the drive shaft axis O. 
     As shown in  FIG. 7 , the first and second acting portions  14   a,    14   b  are provided on the acting surface  134 . As shown in  FIG. 8 , the first acting portion  14   a  extends along the drive shaft axis O in a direction from the acting surface  134  toward the first receiving surface  54   a  the swash plate main portion  50 . As in the case of the first acting portion  14   a,  the second acting portion  14   b  extends along the drive shaft axis O in a direction from the acting surface  134  toward the second receiving surface  54   b.    
     As shown in  FIG. 7 , the first acting portion  14   a  and the second acting portion  14   b  are located on the acting surface  134  at positions on opposite sides of the top dead center plane D. Further, the first acting portion  14   a  and the second acting portion  14   b  are located on the acting surface  134  to be plane-symmetrical with respect to the top dead center plane D. Accordingly, the distance from the first acting portion  14   a  to the drive shaft axis O is equal to the distance from the second acting portion  14   b  to the drive shaft axis O. When the drive shaft  3  is passed through the movable body  13   a,  the drive shaft  3  is located between the first acting portion  14   a  and the second acting portion  14   b.    
     As shown in  FIG. 8 , the rear end of the first acting portion  14   a  has a cylindrical shape protruding toward the swash plate  5 . Thus, the first acting portion  14   a  makes line contact with a part of the first receiving surface  54   a,  that is, with the first receiving portion  6   a,  at the first acting position F 1 . For the illustrative purposes, the drive shaft  3  is illustrated with long dashed double-short dashed lines in  FIG. 8 . The same applies to  FIGS. 9, 13, and 17  which will be discussed below. 
     Likewise, the rear end of the second acting portion  14   b  has a cylindrical shape protruding toward the swash plate  5 . Thus, the second acting portion  14   b  makes line contact with a part of the second receiving surface  54   b,  that is, with the second receiving portion  6   b,  at the second acting position F 2 . Accordingly, the acting surface  134  contacts the first and second receiving surfaces  54   a,    54   b  via the first and second acting portions  14   a,    14   b  and the first and second receiving portions  6   a,    6   b.    
     As described above, the first and second acting portions  14   a,    14   b  are located on the acting surface  134  at positions on opposite sides of the top dead center plane D, the first and second receiving surfaces  54   a,    54   b  are arranged on the front surface of the swash plate main portion  50  at positions on opposite sides of the top dead center plane D. Thus, as shown in  FIG. 7 , the first acting position F 1  and the second acting position F 2  are located at positions on opposite sides of the top dead center plane D. 
     When the drive shaft  3  and the first and second acting positions F 1 , F 2  are viewed from a D 1  direction, which is perpendicular to the top dead center plane D, as indicated by the arrow in  FIG. 7 , the first acting position F 1  is defined at a position overlapping with the drive shaft axis O as shown in  FIGS. 8 and 9  regardless of the inclination angle of the swash plate  5 . As in the case of the first acting position F 1 , the second acting position F 2 , which is shown in  FIG. 1 , is defined at a position overlapping with the drive shaft axis O regardless of the inclination angle of the swash plate  5 . That is, when the drive shaft  3  and the first and second acting positions F 1 , F 2  are viewed from the D 1  direction of  FIG. 7 , the first and second acting portions  14   a,    14   b  are each located on the acting surface  134  to overlap with the drive shaft axis O regardless of the inclination angle of the swash plate  5 . 
     As shown in  FIG. 6 , the first cylindrical portion  131  has a rotation stopper  135 , which restricts the movable body  13   a  from rotating about the drive shaft axis O. The rotation stopper  135  has a rectangular shape as shown in  FIG. 7  and extends from the outer circumferential surface of the first cylindrical portion  131  toward the top dead center associated part T of the swash plate main portion  50 . The rotation stopper  135  is located between the movable body main portion  130  and the swash plate main portion  50 , more specifically, between the first swash plate arm  5   e  and the second swash plate arm  5   f,  which are shown in  FIG. 3 . Thus, as the swash plate  5  rotates, the rotation stopper  135  contacts the first swash plate arm  5   e  or the second swash plate arm  5   f  to restrict the movable body  13   a  from rotating about the drive shaft axis O. This allows the movable body  13   a  to be rotated integrally with the lug plate  51  and the swash plate  5  by rotation of the drive shaft  3 . 
     As shown in  FIG. 5 , the control pressure chamber  13   b  is defined by the second cylindrical portion  132 , the coupling portion  133 , the cylinder chamber  51   a,  and the drive shaft  3 . The control pressure chamber  13   b  and the swash plate chamber  25  are sealed off from each other by the O-rings  49   c,    49   d.    
     The drive shaft  3  has an axial passage  3   a  and a radial passage  3   b.  The axial passage  3   a  extends from the rear end of the drive shaft  3  toward the front end along the drive shaft axis O. The radial passage  3   b  extends in a radial direction from the front end of the axial passage  3   a  and opens in the outer circumferential surface of the drive shaft  3 . As shown in  FIG. 1 , the rear end of the axial passage  3   a  communicates with the pressure regulation chamber  31 . The radial passage  3   b  communicates with control pressure chamber  13   b  as shown in  FIG. 5 . The axial passage  3   a  and the radial passage  3   b  connect the pressure regulation chamber  31  to the control pressure chamber  13   b.    
     As shown in  FIG. 1 , the drive shaft  3  has, at the front end, a threaded portion  3   c.  The drive shaft  3  is connected to a non-illustrated pulley or a non-illustrated electromagnetic clutch through the threaded portion  3   c.    
     Each piston  9  is accommodated in the corresponding one of the cylinder bores  21   a  and is allowed to reciprocate in the cylinder bore  21   a.  Each piston  9  and the valve assembly plate  23  define a compression chamber  57  in the corresponding cylinder bore  21   a.    
     Each piston  9  has an engaging portion  9   a.  Each engaging portion  9   a  accommodates a pair of hemispherical shoes  11   a,    11   b.  The shoes  11   a,    11   b  correspond to a conversion mechanism. Each shoe  11   a  slides on the front surface  5   a  of the swash plate main portion  50 . In contrast, each shoe  11   b  slides on the rear surface  5   b  of the swash plate main portion  50 . The swash plate main portion  50  thus actuates the shoes  11   a,    11   b.  Accordingly, the shoes  11   a,    11   b  convert rotation of the swash plate  5  into reciprocation of the pistons  9 , and the pistons  9  reciprocate in the cylinder bores  21   a  by a stroke corresponding to the inclination angle defied by the swash plate reference plane S. Instead of providing the shoes  11   a,    11   b,  a wobble plate type conversion mechanism may be employed in which a wobble plate is provided on the rear surface  5   b  of the swash plate main portion  50  via a thrust bearing, and the wobble plate and the pistons  9  are connected to each other with connecting rods. 
     As shown in  FIG. 2 , the control mechanism  15  includes a low-pressure passage  15   a,  a high-pressure passage  15   b,  a control valve  15   c,  an orifice  15   d,  the axial passage  3   a,  and the radial passage  3   b.    
     The low-pressure passage  15   a  is connected to the pressure regulation chamber  31  and the suction chamber  33 . The low-pressure passage  15   a,  the axial passage  3   a,  and the radial passage  3   b  connect the control pressure chamber  13   b,  the pressure regulation chamber  31 , and the suction chamber  33  to one another. The high-pressure passage  15   b  is connected to the pressure regulation chamber  31  and the discharge chamber  35 . The high-pressure passage  15   b,  the axial passage  3   a,  and the radial passage  3   b  connect the control pressure chamber  13   b,  the pressure regulation chamber  31 , and the discharge chamber  35  to one another. 
     The control valve  15   c  is arranged in the low-pressure passage  15   a.  The low-pressure control valve  15   c  is allowed to adjust the opening degree of the low-pressure passage  15   a  based on the pressure in the suction chamber  33 . The high-pressure passage  15   b  also has the orifice  15   d.    
     In this compressor, a pipe connected to the evaporator is connected to the inlet  250  shown in  FIG. 1 , and a pipe connected to the condenser is connected to the outlet. The condenser is connected to the evaporator via a pipe and an expansion valve. These components, which include the compressor, the evaporator, the expansion valve, and the condenser, constitute the refrigeration circuit in the air conditioner for a vehicle. The illustration of the evaporator, the expansion valve, the condenser, and the pipes is omitted. 
     In the compressor having the above-described configuration, the drive shaft  3  rotates to rotate the swash plate  5 , thus reciprocating each piston  9  in the corresponding cylinder bore  21   a.  This varies the volume of each compression chamber  57  in accordance with the piston stroke. Thus, the refrigerant that has been drawn from the evaporator into the swash plate chamber  25  through the inlet  250  flows through the suction passage  39  and the suction chamber  33  and is compressed in the compression chambers  57 . The refrigerant that is compressed in the compression chambers  57  is discharged to the discharge chamber  35  and is discharged to the condenser through the outlet. 
     The actuator  13  changes the inclination angle of the swash plate  5  to increase or decrease the stroke of the pistons  9 , thereby varying the displacement of the compressor. 
     Specifically, when the control valve  15   c  of the control mechanism  15  shown in  FIG. 2  reduces the opening degree of the low-pressure passage  15   a,  the pressure in the pressure regulation chamber  31  is increased, and the pressure in the control pressure chamber  13   b  is increased. This causes the movable body  13   a  to move along the drive shaft axis O toward the swash plate  5  as shown in  FIG. 9 , while moving away from the lug plate  51 . 
     Accordingly, at the first acting position F 1 , the first acting portion  14   a  pushes the first receiving portion  6   a  along the drive shaft axis O toward the rear of the swash plate chamber  25 . Likewise, at the second acting position F 2 , the second acting portion  14   b  pushes the second receiving portion  6   b  along the drive shaft axis O toward the rear of the swash plate chamber  25 . Therefore, the first and second swash plate arms  5   e,    5   f  slide on the first and second guide surfaces  57   a,    57   b,  respectively, toward the drive shaft axis O. 
     Thus, the swash plate  5  decreases the inclination angle while substantially maintaining the position of the top dead center associated part T. This reduces the stroke of the pistons  9  and the displacement of the compressor per rotation of the drive shaft  3 . When reaching the minimum inclination angle shown in the drawing, the swash plate  5  contacts the restoration spring  37 . 
     In contrast, when the control valve  15   c  of the control mechanism  15  shown in  FIG. 2  increases the opening degree of the low-pressure passage  15   a,  the pressure in the pressure regulation chamber  31  and thus the pressure in the control pressure chamber  13   b  become substantially equal to the pressure in the suction chamber  33 . Thus, reaction force that acts on the swash plate  5  from components such as the pistons  9  causes the movable body  13   a  to move along the drive shaft axis O from the swash plate  5  toward the lug plate  51  as shown in  FIG. 8 . 
     The reaction force acting on the swash plate  5  and the urging force of the restoration spring  37  cause the first and second swash plate arms  5   e,    5   f  to slide on the first and second guide surfaces  57   a,    57   b,  respectively, to move away from the drive shaft axis O. 
     Accordingly, the swash plate  5  thus increases the inclination angle while substantially maintaining the position of the top dead center associated part T. This increases the stroke of the pistons  9  and thus increases the displacement of the compressor per rotation of the drive shaft  3 . When the inclination angle of the swash plate  5  is maximized in the drawing, the displacement per rotation of the drive shaft  3  is maximized. 
     As described above, a part of the first receiving surface  54   a  on the front surface  5   a  of the swash plate main portion  50  serves as the first receiving portion  6   a.  The first receiving portion  6   a  is pushed while making line contact with the first acting portion  14   a  provided on the movable body  13   a  at the first acting position F 1 . Likewise, a part of the second receiving surface  54   b  on the front surface  5   a  serves as the second receiving portion  6   b.  The second receiving portion  6   b  is pushed while making line contact with the second acting portion  14   b  provided on the movable body  13   a  at the second acting position F 2 . Accordingly, the inclination angle of the swash plate  5  is reduced. That is, when reducing the inclination angle of the swash plate  5 , the movable body  13   a  pushes the swash plate  5  along the drive shaft axis O, while making line contact with the swash plate  5  via the first and second acting positions F 1 , F 2 . Since the compressor has no sleeve such as a conventional hinge ball between the movable body  13   a  and the swash plate  5 , the size of the compressor is reduced, accordingly. Thus, it is possible to increase the size of the movable body  13   a  so that the movable body  13   a  is moved by a greater thrust without increasing the overall size of the compressor. 
     Since the movable body  13   a  pushes the swash plate  5  while directly contacting the swash plate  5 , the direction of the load acting on the swash plate  5  resists change. That is, the movable body  13   a  is not easily inclined in any direction other than the direction in which the drive shaft axis O extends, and resists warping. Therefore, the movable body  13   a  is reliably allowed to push the swash plate  5  along the drive shaft axis O, so that the movable body  13   a  stably reduces the inclination angle of the swash plate  5 . Since the orientation of the movable body  13   a  is stabilized, pressure leakage in the control pressure chamber  13   b  is unlikely to occur. 
     Then, with reference to the top dead center plane D, the first acting portion  14   a  pushes the first receiving portion  6   a  at the first acting position F 1 , and the second acting portion  14   b  pushes the second receiving portion  6   b  at the second acting position F 2 . Accordingly, when the inclination angle of the swash plate  5  is reduced, the movable body  13   a  pushes the swash plate  5  at two positions, or the first acting position F 1  and the second acting position F 2 , which are on opposite sides of the top dead center plane D. 
     Particularly, when the drive shaft  3  and the first and second acting positions F 1 , F 2  are viewed from the D 1  direction, which is perpendicular to the top dead center plane D, the first and second acting positions F 1 , F 2  overlap with the drive shaft axis O as shown in  FIGS. 8 and 9  regardless of the inclination angle of the swash plate  5 . Thus, when the inclination angle of the swash plate  5  is reduced, the first and second acting portions  14   a,    14   b  are allowed to push the first and second receiving portions  6   a,    6   b  at positions close to the drive shaft axis O, respectively. 
     Therefore, even if the movable body  13   a  pushes the swash plate  5  via the first and second acting positions F 1 , F 2 , the swash plate  5  is not easily inclined in a direction other than the direction in which the inclination angle is changed and thus resists warping. Thus, when the inclination angle of the swash plate  5  is changed, the movable body  13   a  is allowed to smoothly move along the drive shaft axis O. 
     Therefore, the compressor according to the first embodiment achieves a sufficient controllability, while minimizing the size. 
     Further, the reaction force that acts from the pistons  9  to the swash plate  5  during operation of the compressor generates moment that acts to rotate the swash plate  5  in a direction other than the direction in which the inclination angle is changed. In this respect, the guide surfaces  52   a,    52   b  in the through hole  5   d  of the compressor slide on the outer circumferential surface  30  of the drive shaft  3  in response to changes in the inclination angle of the swash plate  5 . Then, the swash plate  5  is guided by the link mechanism  7  and the drive shaft  3  along the drive shaft axis O and in the direction of the inclination angle, so that the inclination angle is changed as described above. At this time, the guide surfaces  52   a,    52   b  allow the swash plate  5  to easily contact the outer circumferential surface  30  of the drive shaft  3  at two points on opposite sides of the drive shaft axis O. Therefore, the compressor reliably prevents the swash plate  5  from being warped by the moment. Since the compressor has no sleeve, the number of components is reduced, and the manufacturing costs are reduced, accordingly. 
     The first and second acting portions  14   a,    14   b  are provided on the acting surface  134 , and the first and second acting portions  14   a,    14   b  protrude toward the first and second receiving surfaces  54   a,    54   b,  respectively. This allows the first and second receiving surfaces  54   a,    54   b,  and thus the first and second receiving portions  6   a,    6   b,  to be flat and parallel with the swash plate reference plane S, facilitating the production of the swash plate  5 . In this respect also, the production costs for the compressor are reduced. 
     Further, the rotation stopper  135  restricts the movable body  13   a  from rotating about the drive shaft axis O. Thus, when the inclination angle of the swash plate  5  is reduced, the first and second acting portions  14   a,    14   b  are prevented from pushing the first and second receiving portions  6   a,    6   b  at positions offset from positions overlapping with the drive shaft axis O, respectively. 
     Second Embodiment 
     In the compressor according to the second embodiment, the first and second receiving surfaces  54   a,    54   b  of the compressor according to the first embodiment are replaced by a receiving surface  54   c  as shown in  FIG. 10 . The receiving surface  54   c  is also arranged on the front surface  5   a  of the swash plate main portion  50  and about the through hole  5   d.  The receiving surface  54   c  has a flat section  540  and first and second protrusions  6   c,    6   d.  As shown in  FIG. 13 , the flat section  540  is a flat surface parallel with the swash plate reference plane S. 
     The first protrusion  6   c  extends along the drive shaft axis O and in a direction from the flat section  540  toward the movable body main portion  130 . The distal end of the first protrusion  6   c,  that is, the part that faces the movable body main portion  130 , has a cylindrical shape protruding toward the movable body  13   a.  The second protrusion  6   d,  which is shown in  FIG. 10 , has the same structure as the first protrusion surface  6   c.  The first and second protrusions  6   c,    6   d  correspond to first and second receiving portions. 
     As shown in  FIG. 12 , the first protrusion  6   c  and the second protrusion  6   d  are provided on the flat section  540  at positions on opposite sides of the top dead center plane D. Further, the first protrusion  6   c  and the second protrusion  6   d  are located on the flat section  540  to be plane-symmetrical with respect to the top dead center plane D. When the drive shaft  3  is passed through the through hole  5   d,  the drive shaft  3  is located between the first protrusion  6   c  and the second protrusion  6   d.  Further, the first protrusion  6   c  and the second protrusion  6   d  are located at positions slightly closer to the top dead center associated part T than the drive shaft axis O. 
     Also, as shown in  FIG. 11 , the acting surface  134  of the movable body  13   a  is a flat surface perpendicular to the drive shaft axis O. As shown in  FIG. 12 , a part of the acting surface  134  that makes line contact with the first protrusion  6   c  at the first acting position F 3  serves as a first acting portion  16   a.  A part of the acting surface  134  that makes line contact with the second protrusion  6   d  at the second acting position F 4  serves as a second acting portion  16   b.    
     When the drive shaft  3  and the first and second acting positions F 3 , F 4  are viewed from the D 1  direction in  FIG. 12 , the first acting position F 3  overlaps with the drive shaft  3  and is located at a position slightly closer to the top dead center associated part T than the drive shaft axis O as shown in  FIG. 13  regardless of the inclination angle of the swash plate  5 . The second acting position F 4 , which is shown in  FIG. 12 , has the same structure as the first acting position F 3 . 
     The movable body  13   a  of this compressor does not have the rotation stopper  135  in the first cylindrical portion  131 . Thus, as shown in  FIG. 13 , the cross-sectional shape of the movable body  13   a  along a given plane containing the drive shaft axis O is line-symmetric with respect to the drive shaft axis O. The other components of the compressor of the second embodiment are configured identically with the corresponding components of the compressor of the first embodiment. Accordingly, these components are identified by the same reference numbers, and detailed description thereof is omitted herein. 
     In this compressor also, when the inclination angle of the swash plate  5  is reduced, the first acting portion  16   a  pushes the first protrusion  6   c  toward the rear of the swash plate chamber  25  at the first acting position F 3 . Also, at the second acting position F 4 , the second acting portion  16   b  pushes the second protrusion  6   d  along the drive shaft axis O toward the rear of the swash plate chamber  25 . 
     When the drive shaft  3  and the first and second acting positions F 3 , F 4  are viewed from the D 1  direction, which is perpendicular to the top dead center plane D, the first and second acting positions F 3 , F 4  overlap with the drive shaft  3  and are located at positions slightly closer to the top dead center associated part T than the drive shaft axis O regardless of the inclination angle of the swash plate  5 . Thus, when the inclination angle of the swash plate  5  is reduced, the first and second acting portions  16   a,    16   b  are allowed to push the first and second protrusions  6   c,    6   d  at positions close to the drive shaft axis O, respectively. Therefore, even if the movable body  13   a  pushes the swash plate  5  via the first and second acting positions F 3 , F 4 , the swash plate  5  is not easily inclined in a direction other than the direction in which the inclination angle is changed and thus resists warping. Thus, when the inclination angle of the swash plate  5  is changed, the movable body  13   a  is allowed to smoothly move along the drive shaft axis O. 
     The first and second acting positions F 3 , F 4  are respectively defined at positions slightly closer to the top dead center associated part T than the drive shaft axis O. Thus, compared to the compressor according to the first embodiment, the stroke of the movable body  13   a  along the drive shaft axis O is reduced when the inclination angle of the swash plate  5  is changed in the present embodiment. 
     Further, in this compressor, parts of the acting surface  134  serve as the first acting portion  16   a  and the second acting portion  16   b.  The movable body  13   a  is permitted to rotate about the drive shaft axis O to some extent, so that there is no need to provide a member such as the rotation stopper  135  for restricting the movable body  13   a  from rotating about the drive shaft axis O. This allows the cross-sectional shape of the movable body  13   a  along a given plane containing the drive shaft axis O to be line-symmetric with respect to the drive shaft axis O, thereby facilitating the production of the movable body  13   a.  Thus, the production costs for the compressor are reduced. 
     In this compressor, as described above, a part of the acting surface  134  makes line contact with the first protrusion  6   c  at the first acting position F 3  and another part of the acting surface  134  makes line contact with the second protrusion  6   d  at the second acting position F 4  without restricting the movable body  13   a  from rotating about the drive shaft axis O by the rotation stopper  135  as in the compressor of the first embodiment. Therefore, when the inclination angle of the swash plate  5  is reduced, the first and second acting positions F 3 , F 4  are not displaced from positions overlapping with the drive shaft  3  and slightly closer to the top dead center associated part T than the drive shaft axis O regardless of the inclination angle of the swash plate  5 . The other operations of the compressor are the same as the corresponding operations of the compressor of the first embodiment. 
     Third Embodiment 
     The compressor of the third embodiment has a receiving surface  54   d  as shown in  FIG. 14 . The receiving surface  54   d  is also arranged on the front surface  5   a  of the swash plate main portion  50  and about the through hole  5   d.  The receiving surface  54   d  has a mortar portion  541  and first and second protrusions  6   e,    6   f.  As shown in  FIG. 17 , the mortar portion  541  has a decreasing diameter along the drive shaft axis O to conform to the acting surface  134  regardless of the inclination angle of the swash plate  5 . 
     The first protrusion  6   e  extends in a direction from the mortar portion  541  toward the movable body main portion  130 . The distal end of the first protrusion  6   e  has a cylindrical shape protruding toward the movable body  13   a.  The second protrusion  6   f,  which is shown in  FIG. 14 , has the same structure as the first protrusion  6   e.  The first and second protrusions  6   e,    6   f  correspond to first and second receiving portions, respectively. 
     The first protrusion  6   e  and the second protrusion  6   f  are located on the mortar portion  541  at positions on opposite sides of the top dead center plane D. Further, the first protrusion  6   e  and the second protrusion  6   f  are located on the mortar portion  541  to be plane-symmetrical with respect to the top dead center plane D. When the drive shaft  3  is passed through the through hole  5   d,  the drive shaft  3  is located between the first protrusion  6   e  and the second protrusion  6   f.  Further, the first protrusion  6   e  and the second protrusion  6   f  are located at positions slightly closer to the top dead center associated part T than the drive shaft axis O. 
     Also, as shown in  FIG. 15 , the acting surface  134  of the movable body  13   a  has a truncated conical shape with a diameter decreasing from the outer circumference of the first cylindrical portion  131  toward the drive shaft axis O. As shown in  FIG. 16 , a part of the acting surface  134  that makes line contact with the first protrusion  6   e  at the first acting position F 5  serves as a first acting portion  18   a.  A part of the acting surface  134  that makes line contact with the second protrusion  6   f  at the second acting position F 6  serves as a second acting portion  18   b.    
     As in the case of the compressor of the second embodiment, when the drive shaft  3  and the first and second acting positions F 5 , F 6  are viewed from the D 1  direction in  FIG. 16 , the first acting position F 5  overlaps with the drive shaft  3  and is located at a position slightly closer to the top dead center associated part T than the drive shaft axis O as shown in  FIG. 17  regardless of the inclination angle of the swash plate  5 . The second acting position F 6 , which is shown in  FIG. 16 , has the same structure as the first acting position F 5 . 
     The movable body  13   a  of this compressor also does not have the rotation stopper  135  in the first cylindrical portion  131 . Thus, as shown in  FIG. 17 , the cross-sectional shape of the movable body  13   a  along a given plane containing the drive shaft axis O is line-symmetric with respect to the drive shaft axis O. The other structures of the compressor are the same as the corresponding structures of the compressor of the first embodiment. 
     In this compressor, when the inclination angle of the swash plate  5  is reduced, the first and second acting portions  18   a,    18   b  push the first and second protrusions  6   e,    6   f  toward the rear of the swash plate chamber  25  at the first and second acting positions F 5 , F 6 , respectively. 
     When the drive shaft  3  and the first and second acting positions F 5 , F 6  are viewed from the D 1  direction, which is perpendicular to the top dead center plane D, the first and second acting positions F 5 , F 6  overlap with the drive shaft  3  and are located at positions slightly closer to the top dead center associated part T than the drive shaft axis O regardless of the inclination angle of the swash plate  5 . Thus, when the inclination angle of the swash plate  5  is reduced, the first and second acting portions  18   a,    18   b  are allowed to push the first and second protrusions  6   c,    6   d  at positions close to the drive shaft axis O, respectively. Thus, as in the compressor according to the second embodiment, the stroke of the movable body  13   a  along the drive shaft axis O is reduced when the inclination angle of the swash plate  5  is changed in the present embodiment. 
     Further, the acting surface  134  has a shape like a truncated cone, the diameter of which decreases from the outer circumference of the first cylindrical portion  131  toward the drive shaft axis O. The mortar portion  541  has a shape that conforms to the acting surface  134  regardless of the inclination angle. Thus, in this compressor, the swash plate  5  changes the inclination angle while being aligned with the movable body  13   a.  Therefore, when the inclination angle of the swash plate  5  is changed, no vibrations are generated in the swash plate  5 . This allows the inclination angle to be reliably changed. 
     Also, parts of the acting surface  134  serve as the first acting portion  18   a  and the second acting portion  18   b,  and there is no need to provide a member such as the rotation stopper  135  for restricting the movable body  13   a  from rotating about the drive shaft axis O. This allows the cross-sectional shape of the movable body  13   a  along a given plane containing the drive shaft axis O to be line-symmetric with respect to the drive shaft axis O, thereby facilitating the production of the movable body  13   a.    
     In this compressor also, a part of the acting surface  134  makes line contact with the first protrusion  6   e  at the first acting position F 5  and another part of the acting surface  134  makes line contact with the second protrusion  6   f  at the second acting position F 6  without restricting the movable body  13   a  from rotating about the drive shaft axis O by the rotation stopper  135  as in the compressor of the second embodiment. Therefore, when the inclination angle of the swash plate  5  is reduced, the first and second acting positions F 5 , F 6  are not displaced from positions overlapping with the drive shaft  3  and slightly closer to the top dead center associated part T than the drive shaft axis O regardless of the inclination angle of the swash plate  5 . The other operations of the compressor are the same as the corresponding operations of the compressor of the first embodiment. 
     Although only the first to third embodiments of the present invention have been described so far, the present invention is not limited to the first to third embodiments, but may be modified as necessary without departing from the scope of the invention. 
     For example, when the drive shaft  3  and the first and second acting positions F 1 , F 2  are viewed from the D 1  direction in the compressor of the first embodiment, the first and second acting positions F 1 , F 2  may be located at any positions regardless of the inclination angle of the swash plate  5  as long as these positions overlap with the drive shaft  3 . For example, the first and second acting positions F 1 , F 2  may be located at positions slightly closer to the top dead center associated part T than the drive shaft axis O or positions closer to the bottom dead center associated part U. The modification may be applied to the compressors of the first and second embodiments. 
     In the compressor according to the first embodiment, the first and second acting portions  14   a,    14   b  and the first and second receiving portions  6   a,    6   b  may be configured to make point contact with each other at the first and second acting positions F 1 , F 2 , respectively. The same modification may be applied to the first and second protrusions  6   c  to  6   f  of the compressor according to the first and second embodiments. 
     Further, the compressor according to the first embodiment may be configured such that only one of the first acting portion  14   a  and the second acting portion  14   b  is provided on the acting surface  134 , and one of the first receiving surface  54   a  and the second receiving surface  54   b,  which correspond to the first acting portion  14   a  or the second acting portion  14   b,  may be provided on the front surface  5   a  of the swash plate main portion  50 . Likewise, in the compressors according to the second and third embodiments, the first protrusions  6   c,    6   e  or the second protrusions  6   d,    6   f  may be provided on the flat section  540  or the mortar portion  541 . 
     In the compressor according to the third embodiment, the receiving surface  54   d  may be configured without the first and second protrusions  6   e,    6   f.    
     The compressor according to the first embodiment may be configured such that the inclination angle of the swash plate  5  is increased when the first and second acting portions  14   a,    14   b  push the first and second receiving portions  6   a,    6   b  along the drive shaft axis O, respectively. The same modification may be applied to the compressors of the second and third embodiments. 
     Further, regarding the control mechanism  15  of the compressor according to the first to third embodiments, the control valve  15   c  may be provided in the high-pressure passage  15   b,  and the orifice  15   d  may be provided in the low-pressure passage  15   a.  In this case, the control valve  15   c  is allowed to adjust the flow rate of high-pressure refrigerant flowing through the high-pressure passage  15   b.  This allows the high-pressure in the discharge chamber  35  to promptly increase the pressure in the control pressure chamber  13   b  and to promptly reduce the displacement. Also, the control valve  15   c  may be replaced by a three-way valve connected to the low-pressure passage  15   a  and the high-pressure passage  15   b.  In this case, the opening degree of the three-way valve is adjusted to regulate the flow rate of refrigerant flowing through the low-pressure passage  15   a  and the high-pressure passage  15   b.    
     Therefore, the present examples and embodiments are to be considered as illustrative and not restrictive and the invention is not to be limited to the details given herein, but may be modified within the scope and equivalence of the appended claims.