Patent Publication Number: US-11047373-B2

Title: Piston compressor including a suction throttle

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to Japanese Patent Application No. 2018-068570 filed on Mar. 30, 2018 and Japanese Patent Application No. 2019-054599 filed on Mar. 22, 2019, the entire disclosure of which is incorporated herein by reference. 
     BACKGROUND ART 
     The present disclosure relates to a piston compressor. 
     Japanese Patent Application Publication No. 5-306680 discloses a conventional piston compressor (hereinafter referred to merely as “compressor”) in the drawings of No. 1 and No. 10 in the above Publication. The compressor includes a housing, a drive shaft, a fixed swash plate, a plurality of pistons, a discharge valve, a control valve, and a rotating body. 
     The housing includes a cylinder block. The cylinder block has a plurality of cylinder bores and a first communication passage communicating with the cylinder bores. The housing has a discharge chamber, a swash plate chamber, an axial hole, and a control pressure chamber. The swash plate chamber also serves as a suction chamber for introducing refrigerant from the outside of the compressor. The swash plate chamber communicates with the axial hole. 
     The drive shaft is rotatably supported in the axial hole. The fixed swash plate is rotatable by the rotation of the drive shaft in the swash plate chamber. The inclination angle of the fixed swash plate is constant with respect to the plane perpendicular to the drive shaft. Each piston forms a compression chamber in the cylinder bore and coupled to the fixed swash plate. A reed type discharge valve is provided between the compression chamber and the discharge chamber to discharge refrigerant in the compression chamber into the discharge chamber. The control valve controls the pressure of refrigerant so as to serve as control pressure. 
     The rotating body is provided on the outer peripheral surface of the drive shaft and disposed in the axial hole. The rotating body partitions the suction chamber and the control pressure chamber. The rotating body is rotatable integrally with the drive shaft in the axial hole and movable based on the control pressure in the axial direction of the drive shaft with respect to the drive shaft. A second communication passage is formed on the outer peripheral surface of the rotating body. The second communication passage intermittently communicates with the first communication passage in accordance with the rotation of the drive shaft. The second communication passage has a small formed portion and a large formed portion on the outer circumferential surface of the rotating body in the circumferential direction of the rotating body. 
     As each piston of the compressor reciprocates in the cylinder bore, an intake stroke for sucking the refrigerant, a compression stroke for compressing the sucked refrigerant, and a discharge stroke for discharging the compressed refrigerant are performed in the compression chamber. In accordance with the position in the axial direction of the rotating body of the compressor, the compressor can change the communication angle around the axis through which the first communication passage and the second communication passage communicate with each other per one rotation of the drive shaft. Thus, in the compressor, the flow rate of the refrigerant discharged from the compression chamber to the discharge chamber can be changed. 
     Specifically, when the rotating body moves in the axial hole in the axial direction and a portion of the second communicating passage, which is formed small in the circumferential direction on the outer circumferential surface of the rotating body, communicates with the first communicating passage, the communication angle becomes small. In the case, when the piston moves from the top dead center to the bottom dead center, refrigerant in the swash plate chamber is sucked into the compression chamber from the second communication passage through the first communication passage. When the piston moves from the bottom dead center to the top dead center, the second communication passage and the first communication passage are disconnected from each other. As a result, the sucked refrigerant is compressed in the compression chamber. Then, the compressed refrigerant is discharged to the discharge chamber. 
     On the other hand, when a portion of the second communicating passage, which is formed large in the circumferential direction on the outer circumferential surface of the rotating body, communicates with the first communication passage, the communication angle becomes large. In the case, not only while the piston moves from the top dead center to the bottom dead center, but also while the piston moves to a certain extent from the bottom dead center to the top dead center, the first communication passage and the second communication passage communicate with each other. For the reason, part of the refrigerant sucked into the compression chamber while the piston moves from the top dead center to the bottom dead center is discharged from the compression chamber to the upstream side of the compression chamber when the piston moves from the bottom dead center to the top dead center. When the piston approaches the top dead center, the first communication passage and the second communication passage are disconnected from each other. Thus, the flow rate of refrigerant compressed in the compression chamber decreases, so that the flow rate of refrigerant discharged from the compression chamber to the discharge chamber decreases as compared to the case in which the communication angle is small. 
     However, in the above-described conventional compressor, when the rotating body moves in the axial direction to change the communication angle around the axis between the first communication passage and the second communication passage from a small state to a large state, the flow rate of the refrigerant discharged from the compression chamber to the discharge chamber hardly decreases. Thus, the controllability of the compressor hardly increases. In particular, in an operating state in which the fixed swash plate rotates at a high speed, the first communication passage and the second communication passage are disconnected from each other before the refrigerant sucked into the compression chamber is sufficiently discharged to the upstream side of the compression chamber and the refrigerant is compressed in the compression chamber. Therefore, when the communication angle is changed from the small state to the large state, the flow rate of the refrigerant discharged from the compression chamber to the discharge chamber becomes hardly decreases more prominently. 
     The present disclosure, which has been made in light of such circumstances, is directed to providing a piston compressor that has excellent controllability. 
     SUMMARY 
     In accordance with an aspect of the present invention, there is provided a piston compressor including a housing including a cylinder block having a plurality of cylinder bores, having a discharge chamber, a swash plate chamber, and an axial hole, a drive shaft rotatably inserted into the axial hole and supported in the axial hole, a fixed swash plate rotatable together with the drive shaft in the swash plate chamber, wherein an inclination angle of the fixed swash plate with respect to a plane perpendicular to an axis of the drive shaft is constant, a piston forming a compression chamber in each cylinder bore and coupled to the fixed swash plate, a discharge valve discharging refrigerant gas in each compression chamber into the discharge chamber, a rotating body provided on the drive shaft and rotatable integrally with the drive shaft and movable in a direction of the axis of the drive shaft with respect to the drive shaft based on a control pressure, and a control valve configured to control the control pressure. The cylinder block has a plurality of first communication passages communicating with the respective cylinder bores. The rotating body has a second communication passage that communicates with the respective first communication passages intermittently by rotation of the drive shaft. A flow rate of refrigerant gas discharged from the compression chambers into the discharge chamber decreases when a communication angle around the axis, at which the second communication passage communicates with the respective first communication passages, becomes large per a rotation of the drive shaft depending on a position of the rotating body in the direction of the axis. The piston compressor includes a suction throttle that decreases the flow rate of refrigerant gas in the compression chamber when the communication angle becomes large based on the control pressure. 
     Other aspects and advantages of the disclosure will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which: 
         FIG. 1  is a longitudinal sectional view showing a piston compressor at a maximum flow rate, according to a first embodiment of the present disclosure; 
         FIG. 2  is a longitudinal sectional view showing the piston compressor of  FIG. 1  at a minimum flow rate; 
         FIG. 3  is a partially enlarged longitudinal sectional view showing the piston compressor of  FIG. 1  at a maximum flow rate; 
         FIG. 4  is a partially enlarged longitudinal sectional view showing a suction throttle and its surroundings of the piston compressor of  FIG. 1  at a maximum flow rate; 
         FIG. 5  is a partially enlarged longitudinal sectional view showing the piston compressor and its surroundings of  FIG. 1  at a minimum flow rate; 
         FIG. 6  is a graph showing the relationship between the change of communication angle and the change of discharge flow rate in the piston compressor of  FIG. 1  at a high-speed rotation; 
         FIG. 7  is a graph showing the relationship between the change of communication angle and the change of discharge flow rate in the piston compressor of  FIG. 1  at a low-speed rotation; 
         FIG. 8  is a longitudinal sectional view showing a piston compressor at a maximum flow rate, according to a second embodiment of the present disclosure; 
         FIG. 9  is a partially enlarged longitudinal sectional view showing a suction throttle and its surroundings of the piston compressor of  FIG. 8  at a maximum flow rate; 
         FIG. 10  is a partially enlarged longitudinal sectional view showing the suction throttle and its surroundings of the piston compressor of  FIG. 8  at a minimum flow rate; 
         FIG. 11  is a longitudinal sectional view showing a piston compressor at a maximum flow rate, according to a third embodiment of the present disclosure; 
         FIG. 12  is a partially enlarged longitudinal sectional view showing a suction throttle and its surroundings of the piston compressor of  FIG. 11  at a maximum flow rate; 
         FIG. 13  is a partially enlarged longitudinal sectional view showing the suction throttle and its surroundings of the piston compressor of  FIG. 11  at a minimum flow rate; 
         FIG. 14  is a longitudinal sectional view showing a piston compressor at a maximum flow rate, according to a fourth embodiment of the present disclosure; 
         FIG. 15  is a partially enlarged longitudinal sectional view showing the suction throttle and its surroundings of the piston compressor of  FIG. 14  at a maximum flow rate; 
         FIG. 16  is a partially enlarged longitudinal sectional view showing the suction throttle and its surroundings of the piston compressor of  FIG. 14  at a minimum flow rate; 
         FIG. 17  is a longitudinal sectional view showing a piston compressor at a maximum flow rate, according to a fifth embodiment of the present disclosure; 
         FIG. 18  is a partially enlarged longitudinal sectional view showing the suction throttle and its surroundings of the piston compressor of  FIG. 17  at a maximum flow rate; and 
         FIG. 19  is a partially enlarged longitudinal sectional view showing the suction throttle and its surroundings of the piston compressor of  FIG. 17  at a minimum flow rate. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     The following will describe piston compressors according to a first embodiment through a fifth embodiment of the present disclosure with reference to the drawings. The compressors have a single headed piston. The compressors are mounted in a vehicle and constitute part of a refrigeration circuit of an air conditioner. 
     First Embodiment 
     Referring to  FIGS. 1 and 2 , a compressor according to a first embodiment of the present disclosure includes a housing  1 , a drive shaft  3 , a fixed swash plate  5 , a plurality of pistons  7 , a valve forming plate  9 , a rotating body  11 , a control valve  13 , a suction unit  15   a , and a suction throttle  43   a . The valve forming plate  9  is an example of a discharge valve of the present disclosure. 
     The housing  1  has a front housing  17 , a rear housing  19 , and a cylinder block  21 . In the present embodiment, the front housing  17  is located on the front side of the compressor and the rear housing  19  is located on the rear side of the compressor to define the front and rear direction of the compressor. The upper sides of the planes of  FIGS. 1 and 2  are defined as the upper side of the compressor and the lower sides of the planes are defined as the lower side of the compressor to define the upper and lower direction of the compressor. In  FIG. 3  and the following drawings, the front and rear direction and the upper and lower direction are displayed corresponding to  FIGS. 1 and 2 . The front and rear direction in the embodiment is merely examples. The position of the compressor according to embodiments in the present disclosure may be appropriately modified in accordance with a vehicle to be mounted. 
     The front housing  17  has a front wall  17   a  extending in the radial direction thereof and a substantially cylindrical-shaped circumferential wall  17   b  integrally formed with the front wall  17   a  and extending rearward in a direction of an axis O of the drive shaft  3  from the front wall  17   a . The front wall  17   a  has a first boss portion  171 , a second boss portion  172 , and a first axial hole  173 . The first boss portion  171  protrudes forward in the direction of the axis O. A shaft seal device  25  is provided in the first boss portion  171 . The second boss portion  172  protrudes rearward in the direction of the axis O in the swash plate chamber  31  that is described later. The first axial hole  173  passes through the front wall  17   a  in the direction of the axis O. 
     The rear housing  19  has a suction chamber  27 , a discharge chamber  29 , a suction port  27   a , and a discharge port  29   a . The suction chamber  27  is located on the center side of the rear housing  19 . The discharge chamber  29  is annularly formed and is located adjacent to the outer circumferential surface of the suction chamber  27 . The suction port  27   a  communicates with the suction chamber  27  and extends in the rear housing  19  in the direction of the axis O and opens to the outside of the rear housing  19 . The suction port  27   a  is connected to an evaporator via a pipe. Thus, low-pressure refrigerant gas passing through the evaporator is sucked into the suction chamber  27  through the suction port  27   a . The discharge port  29   a  communicates with the discharge chamber  29  and extends in the radial direction of the rear housing  19  and opens to the outside of the rear housing  19 . The discharge port  29   a  is connected to a condenser via a pipe. The illustration of the pipes, the evaporator, and the condenser is omitted. 
     The cylinder block  21  is located between the front housing  17  and the rear housing  19 . The cylinder block  21  has a plurality of cylinder bores  21   a  extending in the direction of the axis O. Each of the cylinder bores  21   a  is arranged at equal angular intervals in the circumferential direction. The cylinder block  21  is joined to the front housing  17  to form a swash plate chamber  31  between the front wall  17   a  and the circumferential wall  17   b  of the front housing  17 . The swash plate chamber  31  is in communication with the suction chamber  27  through an access passage (not shown). The number of the cylinder bores  21   a  may be appropriately modified. 
     The cylinder block  21  has a second axial hole  21   b , a support wall  21   c , and first communication passages  21   d  having the same number as the number of the cylinder bores  21   a . The second axial hole  21   b  is located on the center side of the cylinder block  21  and extends in the direction of the axis O. The rear side of the second axial hole  21   b  is located in the suction chamber  27  by joining the cylinder block  21  to the rear housing  19  via the valve forming plate  9 . As a result, the second axial hole  21   b  communicates with the suction chamber  27 . 
     The support wall  21   c  is located on the center side of the cylinder block  21  and in front of the second axial hole  21   b . The support wall  21   c  partitions the second axial hole  21   b  from the swash plate chamber  31 . The support wall  21   c  has a third axial hole  210 . The third axial hole  210  is coaxial with the first axial hole  173  and penetrates the support wall  21   c  in the direction of the axis O. The first to third axial holes  173 ,  21   b , and  210  are examples of the axial hole of the present disclosure. 
     The first communication passages  21   d  communicate with the respective cylinder bores  21   a . The first communication passages  21   d  extend in the radial direction of the cylinder block  21  and communicate with the cylinder bores  21   a  and the second axial holes  21   b , respectively. 
     The valve forming plate  9  is provided between the rear housing  19  and the cylinder block  21 . The rear housing  19  and the cylinder block  21  are joined via the valve forming plate  9 . 
     The valve forming plate  9  is constituted by a valve plate  91 , a discharge valve plate  92 , and a retainer plate  93 . The valve plate  91  has discharge holes  910  having the same number as the number of the cylinder bores  21   a . The cylinder bores  21   a  communicate with the discharge chamber  29  through the respective discharge hole  910 . 
     The discharge valve plate  92  is provided on the rear surface of the valve plate  91 . The discharge valve plate  92  is provided with a plurality of discharge reed valves  92   a  that open and close the discharge holes  910  by elastic deformation. The retainer plate  93  is provided on the rear surface of the discharge valve plate  92 . The retainer plate  93  regulates the maximum opening degree of the discharge reed valve  92   a.    
     The drive shaft  3  extends from the front side toward the rear side of the housing  1  in the direction of the axis O. The drive shaft  3  has a threaded portion  3   a , a first diameter portion  3   b , and a second diameter portion  3   c . The threaded portion  3   a  is located at the front end of the drive shaft  3 . The drive shaft  3  is connected to a pulley and an electromagnetic clutch that are not shown in the drawing via the threaded portion  3   a.    
     The first diameter portion  3   b  is continuously formed with the rear end of the threaded portion  3   a  and extends in the direction of the axis O. The second diameter portion  3   c  is continuously formed with the rear end of the first diameter portion  3   b  and extends in the direction of the axis O. The second diameter portion  3   c  has a smaller diameter than the first diameter portion  3   b . Thus, the drive shaft  3  has a stepped portion  3   d  formed between the first diameter portion  3   b  and the second diameter portion  3   c.    
     Referring to  FIG. 3 , the second diameter portion  3   c  has an axial passage  30   a  and a second radial passage  30   b . The axial passage  30   a  extends in the direction of the axis O in the second diameter portion  3   c . The rear end of the axial passage  30   a  opens to the rear surface of the second diameter portion  3   c , or the rear surface of the drive shaft  3 . The second radial passage  30   b  communicates with the axial passage  30   a . The second radial passage  30   b  extends in the radial direction of the drive shaft  3  in the second diameter portion  3   c  and opens to the outer circumferential surface of the second diameter portion  3   c.    
     A support part  33  is press-fitted to the rear side of the second diameter portion  3   c . Thus, the support part  33  is rotatable together with the drive shaft  3  in the second axial hole  21   b . The support part  33  is constituted by a flange portion  33   a  and a cylindrical portion  33   b . The flange portion  33   a  is formed to have substantially the same diameter as the second axial hole  21   b . The cylindrical portion  33   b  is formed to be slightly smaller in diameter than the flange portion  33   a . The cylindrical portion  33   b  is integrally formed with the flange portion  33   a  and extends forward from the flange portion  33   a  in the direction of the axis O. 
     As shown in  FIGS. 1 and 2 , the first diameter portion  3   b  of the drive shaft  3  is inserted into the first axial hole  173  of the front housing  17  and the third axial hole  210  and rotatably supported in the first axial hole  173  and the third axial hole  210 . That is the drive shaft  3  is inserted into the housing  1  and rotatably supported in the housing  1 . The first diameter portion  3   b  is rotatable in the swash plate chamber  31 . The second diameter portion  3   c  is located in the second axial hole  21   b  and is rotatable in the second axial hole  21   b . The rear end of the second diameter portion  3   c  protrudes from the inside of the second axial hole  21   b  and extends into the suction chamber  27 , so that the axial passage  30   a  is connected to the suction chamber  27  at the rear end. The support part  33  is disposed on the rear side of the second axial hole  21   b , so that the flange portion  33   a  partitions the inside of the second axial hole  21   b  from the suction chamber  27 . 
     In the first boss portion  171 , the drive shaft  3  is inserted into the shaft seal device  25 , so that the shaft seal device  25  seals the inside of the housing  1  from the outside of the housing  1 . 
     The fixed swash plate  5  is press-fitted to the first diameter portion  3   b  of the drive shaft  3  and is disposed in the swash plate chamber  31 . The fixed swash plate  5  is rotatable by the rotation of the drive shaft  3  in the swash plate chamber  31 . The inclination angle of the fixed swash plate  5  with respect to the plane perpendicular to the axis of the drive shaft  3  is constant. In the swash plate chamber  31 , a thrust bearing  35  is provided between the second boss portion  172  and the fixed swash plate  5 . 
     The pistons  7  are accommodated in the respective cylinder bores  21   a . Each piston  7  and the valve forming plate  9  form a compression chamber  45  in the cylinder bore  21   a . An engaging portion  7   a  is formed in each piston  7 . Semispherical shoes  8   a  and  8   b  are provided in the engaging portion  7   a . The pistons  7  are coupled to the fixed swash plate  5  by the shoes  8   a  and  8   b . The shoes  8   a  and  8   b  serve as a conversion unit for converting the rotation of the fixed swash plate  5  into the reciprocating motion of each piston  7 . Each piston  7  can reciprocate in the cylinder bore  21   a  between the top dead center and the bottom dead center of the piston  7 . Hereinafter, the top dead center and the bottom dead center of the piston  7  will be referred to as the top dead center and the bottom dead center, respectively. 
     As shown in  FIG. 3 , the rotating body  11  is provided in the second axial hole  21   b . The rotating body  11  is formed in a substantially cylindrical shape and has an outer circumferential surface  11   a  and an inner circumferential surface  11   b . The rotating body  11  is formed to have substantially the same outer diameter as the inner diameter of the second axial hole  21   b . The inner circumferential surface  11   b  is insertable through the second diameter portion  3   c  of the drive shaft  3 . The rotating body  11  is disposed in the second axial hole  21   b , so that a control pressure chamber  37  is formed between the support wall  21   c  and the rotating body  11  in the second axial hole  21   b.    
     The rotating body  11  is splined to the second diameter portion  3   c  on the inner circumferential surface  11   b . That is, the rotating body  11  is provided on the outer circumferential surface of the drive shaft  3 . The rotating body  11  is rotatable integrally with the drive shaft  3  in the second axial hole  21   b . As shown in  FIGS. 4 and 5 , the rotating body  11  is movable in the direction of the axis O in the second axial hole  21   b  with respect to the drive shaft  3 , or in the front-rear direction within the second axial hole  21   b  based on the differential pressure between suction pressure and control pressure. The suction pressure and the control pressure will be described later. 
     As shown in  FIGS. 3 and 4 , when the rotating body  11  moves to a most rearward position in the direction of the axis O in the second axial hole  21   b , the rotating body  11  is brought into contact with the cylindrical portion  33   b  of the support part  33 . As shown in  FIG. 5 , when the rotating body  11  moves at a most forward position in the direction of the axis O in the second axial hole  21   b , the rotating body  11  is brought into contact with the stepped portion  3   d  of the drive shaft  3 . Thus, the cylindrical portion  33   b  serves as a first regulating portion that regulates the amount of movement of the rotating body  11  in the rearward direction. The stepped portion  3   d  serves as a second regulating portion that regulates the amount of movement of the rotating body  11  in the forward direction. 
     A coil spring  39  is provided between the rotating body  11  and the support part  33 . As shown in  FIG. 3 , the rear end of the coil spring  39  is accommodated in the cylindrical portion  33   b  of the support part  33 . The coil spring  39  urges the rotating body  11  toward the front of the second axial hole  21   b.    
     The rotating body  11  has a second communication passage  41 . The second communication passage  41  has a first radial passage  41   a  and a main body passage  41   b . The first radial passage  41   a  opens to the inner circumferential surface  11   b  of the rotating body  11  and extends in the radial direction of the rotating body  11 . The first radial passage  41   a  communicates with the second radial passage  30   b  when the rotating body  11  is inserted through the second diameter portion  3   c . The first radial passage  41   a  is formed to have substantially the same diameter as the second radial passage  30   b.    
     The main body passage  41   b  is recessed on the outer circumferential surface  11   a  and communicates with the first radial passage  41   a . Specifically, as shown in  FIGS. 1 and 2 , the main body passage  41   b  is formed so as to extend from the approximate center of the rear end of the rotating body  11  to the rear end of the rotating body  11  on the outer circumferential surface  11   a  in the front-back direction. The main body passage  41   b  gradually increases in the circumferential direction of the outer circumferential surface  11   a  from the front end of the rotating body  11  toward the rear end of the rotating body  11 . That is, a first portion  411  is formed small in the circumferential direction of the outer circumferential surface  11   a  and is located on the front end side of the main body passage  41   b . A second portion  412  is formed large in the circumferential direction of the outer circumferential surface  11   a  and is located on the rear end side of the main body passage  41   b . The shape of the main body passage  41   b  may be modified. In  FIGS. 1 and 2 , the rotating body  11  is displaced from a position of the rotating body  11  shown in  FIGS. 3 to 5  with respect to the axis O, for explanation. As shown in  FIGS. 3 to 5 , the shape of the main body passage  41   b  is simplified for ease of explanation. The shape of the main body passage  41   b  is simplified in  FIGS. 8 to 19  described later. 
     As shown in  FIGS. 3 to 5 , the main body passage  41   b  of the second communication passage  41  communicates with each first communication passages  21   d  intermittently by the rotation of the rotating body  11  rotated by the drive shaft  3  in the second axial hole  21   b . The main body passage  41   b  changes the communication angle around the axis O, at which the main body passage  41   b  communicates with each first communication passage  21  per one rotation of the drive shaft  3  depending on a position of the rotating body  11  in the second axial hole  21   b , i.e., a position of the rotating body  11  with respect to the drive shaft  3  in the direction of the axis O of the drive shaft  3 . Hereinafter, the communication angle around the axis O, at which the main body passage  41   b  communicates with each first communication passage  21  per one rotation of the drive shaft  3  is merely referred to as a communication angle. 
     As shown in  FIG. 3 , the control valve  13  is provided in the rear housing  19 . The rear housing  19  has a detection passage  13   a  and a first supply passage  13   b . The rear housing  19  cooperates with the cylinder block  21  to have a second supply passage  13   c . The control valve  13  is connected to the suction chamber  27  through a detection passage  13   a . The control valve  13  is connected to the discharge chamber  29  through the first supply passage  13   b . The control valve  13  is connected to the control pressure chamber  37  through the second supply passage  13   c . The refrigerant gas in the discharge chamber  29  is partly introduced into the control pressure chamber  37  through the first supply passage  13   b , the second supply passage  13   c , and the control valve  13 . The control pressure chamber  37  is connected to the suction chamber  27  through a bleed passage (not shown) to introduce the refrigerant gas in the control pressure chamber  37  into the suction chamber  27  though the bleed passage. The control valve  13  adjusts its opening degree by monitoring and detecting the suction pressure, which is the pressure of refrigerant gas in the suction chamber  27 , with the detection passage  13   a . Consequently, the control valve  13  controls the flow rate of the refrigerant gas introduced from the discharge chamber  29  into the control pressure chamber  37 . More specifically, the control valve  13  increases its valve opening degree to increase the flow rate of the refrigerant gas introduced from the discharge chamber  29  into the control pressure chamber  37  through the first supply passage  13   b  and the second supply passage  13   c , and decreases its valve opening degree to decrease the flow rate of the refrigerant gas introduced from the discharge chamber  29  into the control pressure chamber  37  through the first supply passage  13   b  and the second supply passage  13   c . The control valve  13  changes the flow rate of the refrigerant gas introduced from the discharge chamber  29  into the control pressure chamber  37  against the flow rate of the refrigerant gas introduced from the control pressure chamber  37  into the suction chamber  27  to control the control pressure, which is a pressure of refrigerant gas in the control pressure chamber  37 . The control pressure chamber  37  may be connected to the swash plate chamber  31  through the bleed passage. 
     The suction unit  15   a  is constituted by the first communication passage  21   d , the second communication passage  41 , the axial passage  30   a , and the second radial passage  30   b . The suction unit  15   a  sucks refrigerant gas in the suction chamber  27  into each of the compression chambers  45 . Specifically, refrigerant gas in the suction chamber  27  flows from the axial passage  30   a  into the second radial passage  30   b  and reaches the first radial passage  41   a  of the second communication passage  41 . The refrigerant gas that reaches the first radial passage  41   a  flows from the first radial passage  41   a  into the main body passage  41   b  and flows from the main body passage  41   b  through the first communication passage  21   d  to be sucked into each compression chamber  45 . 
     The suction throttle  43   a  is constituted by the first radial passage  41   a  and the second radial passage  30   b . The movement of the rotating body  11  in the direction of the axis O in the second axial hole  21   b  changes the communicating area of the first radial passage  41   a  and the second radial passage  30   b . As a result, the suction throttle  43   a  can change the flow rate of refrigerant gas into each compression chamber  45 , or the flow rate of refrigerant gas sucked into each compression chamber  45 , based on the movement of the rotating body  11  in the direction of the axis O. 
     In the compressor configured as described above, the drive shaft  3  rotates and then the fixed swash plate  5  rotates in the swash plate chamber  31 . As a result, each piston  7  reciprocates in the cylinder bore  21   a  between the top dead center and the bottom dead center, so that in the compression chamber  45 , an intake stroke for sucking refrigerant gas from the suction chamber  27 , a compression stroke for compressing sucked refrigerant gas, and a discharge stroke for discharging compressed refrigerant gas are repeatedly performed. In the discharge stroke, the valve forming plate  9  discharges refrigerant gas in the compression chamber  45  into the discharge chamber  29  therethrough. Then, the refrigerant gas in the discharge chamber  29  is discharged to a condenser via the discharge port  29   a.    
     In the compressor according to the present embodiment, when the rotating body  11  moves in the direction of the axis O in the second axial hole  21   b  during the intake stroke, the flow rate of refrigerant gas discharged from each compression chamber  45  into the discharge chamber  29  per one rotation of the drive shaft  3  can be changed. 
     Specifically, to increase the flow rate of the refrigerant gas discharged from each compression chamber  45  into the discharge chamber  29 , the control valve  13  increases its valve opening degree to increase the flow rate of the refrigerant gas introduced from the discharge chamber  29  into the control pressure chamber  37 , thereby increasing the control pressure in the control pressure chamber  37 . This increases the variable differential pressure that is the differential pressure between the control pressure and the suction pressure. 
     Thus, the rotating body  11  starts to move rearward in the direction of the axis O from the position shown in  FIG. 2  in the second axial hole  21   b  against the urging force of the coil spring  39 . As a result, the main body passage  41   b  relatively moves rearward relative to each of the first communication passages  21   d . As a result, in the portion formed small in the circumferential direction of the outer circumferential surface  11   a , the main body passage  41   b  comes to communicate with each of the first communication passages  21   d . Thus, in the compressor according to the present embodiment, the communication angle gradually decreases. As the rotating body  11  moves, the first radial passage  41   a  starts to relatively move rearward relative to the second radial passage  30   b , so that the communicating area between the first radial passage  41   a  and the second radial passage  30   b  gradually increases. As a result, the suction throttle  43   a  gradually increases the flow rate of refrigerant gas into each compression chamber  45 . 
     When the variable differential pressure becomes maximum, as shown in  FIGS. 3 and 4 , the rotating body  11  moves to the most rearward position in the second axial hole  21   b  and is in contact with the cylindrical portion  33   b . Then, in the main body passage  41   b , the first portion  411  communicates with each of the first communication passages  21   d . Thus, in the compressor according to the present embodiment, the communication angle becomes minimum. 
     Therefore, when the rotating body  11  rotates, the main body passage  41   b  of the second communication passage  41  communicates with each of the first communication passages  21   d  only while each piston  7  moves from the top dead center to the bottom dead center in the compression chamber  45 . 
     When the variable differential pressure becomes maximum, as shown in  FIG. 4 , the first radial passage  41   a  relatively moves rearward relative to the second radial passage  30   b , so that the first radial passage  41   a  communicates with the second radial passage  30   b  over the whole area thereof. The communication area between the first radial passage  41   a  and the second radial passage  30   b  becomes the area S 1 . The suction throttle  43   a  maximizes the flow rate of refrigerant gas flowing into each compression chamber  45 . 
     Thus, when each piston  7  moves from the top dead center to the bottom dead center, the flow rate of refrigerant gas sucked into the compression chamber becomes maximum. In the compressor according to the present embodiment, when each compression chamber  45  is in the compression stroke, the flow rate of refrigerant gas compressed in the compression chamber  45  becomes maximum, so that when the compression chamber  45  is in the discharge stroke, the flow rate of the refrigerant gas discharged from the compression chamber  45  into the discharge chamber  29  becomes maximum. 
     On the other hand, to decrease the flow rate of the refrigerant gas discharged from each compression chamber  45  into the discharge chamber  29 , the control valve  13  decreases its valve opening degree to decrease the flow rate of the refrigerant gas introduced from the discharge chamber  29  into the control pressure chamber  37 , thereby decreasing the control pressure in the control pressure chamber  37 . This decreases the variable differential pressure. 
     Then, the rotating body  11  moves forward from the state shown in  FIG. 3  in the forward direction of the axis O in the second axial hole  21   b  due to the urging force of the coil spring  39 . As a result, the main body passage  41   b  relatively moves forward relative to each of the first communication passages  21   d , and is in a state of communicating with each of the first communication passages  21   d  at a portion formed large in the circumferential direction of the outer circumferential surface  11   a . Therefore, the communication angle gradually increases. 
     Thus, as the rotating body  11  rotates, the main body passage  41   b  of the second communication passage  41  communicates with each of the first communication passages  21   d  not only while each piston  7  moves from the top dead center to the bottom dead center in each compression chamber  45 , but also while each piston  7  moves from the bottom dead center to the top dead center by a certain degree. As a result, while each piston  7  moves from the top dead center to the bottom dead center, part of refrigerant gas sucked into each compression chamber  45  passes through the first communication passage  21   d  and the main body passage  41   b  and is discharged to the upstream side of the compression chamber  45 , or to the outside of the compression chamber  45 . 
     As the variable differential pressure decreases and the rotating body  11  moves forward, the first radial passage  41   a  relatively moves forward relative to the second radial passage  30   b . Then, the communicating area between the first radial passage  41   a  and the second radial passage  30   b  gradually decreases. As a result, the suction throttle  43   a  decreases the flow rate of refrigerant gas into each compression chamber  45 . While each piston  7  moves from the top dead center to the bottom dead center, the flow rate of refrigerant gas sucked into each compression chamber  45  decreases. Thus, in the compressor according to the present embodiment, when the compression chamber  45  is in the compression stroke, the flow rate of refrigerant compressed in each compression chamber  45  decreases, so that when the compression chamber  45  is in the discharge stroke, the flow rate of refrigerant gas discharged from the compression chamber  45  into the discharge chamber  29  decreases. 
     When the variable differential pressure becomes minimum, as shown in  FIG. 5 , the rotating body  11  moves at the most forward position in the second axial hole  21   b  and comes into contact with the stepped portion  3   d . As a result, the second portion  412  of the main body passage  41   b  communicates with the respective first communication passages  21   d  and the communication angle becomes maximum. Since the variable differential pressure becomes minimum, the first radial passage  41   a  relatively moves forward relative to the second radial passage  30   b , so that the first radial passage  41   a  communicates only with a small part of the second radial passage  30   b . As a result, the communicating area between the first radial passage  41   a  and the second radial passage  30   b  becomes the minimum area S 2  and the flow rate of refrigerant gas flowing from the second radial passage  30   b  into the first radial passage  41   a  becomes minimum. 
     Thus, when the communication angle becomes maximum, the main body passage  41   b  comes to communicate with the respective first communication passages  21   d  until the respective pistons  7  come closer to the top dead center. Then, a large amount of refrigerant gas is discharged to the outside of the compression chambers  45  through each of the first communication passages  21   d  and main body passage  41   b . Since the communicating area between the first radial passage  41   a  and the second radial passage  30   b  becomes minimum area S 2 , the suction throttle  43   a  minimizes the flow rate of refrigerant gas to each compression chamber  45 . While each piston  7  moves from the top dead center to the bottom dead center, the flow rate of refrigerant gas sucked into the compression chamber  45  becomes minimum. Thus, in the compressor according to the present embodiment, the flow rate of refrigerant gas compressed in each compression chamber  45  becomes minimum when the compression chamber  45  is in the compression stroke, so that when the compression chamber  45  is in the discharge stroke, the flow rate of refrigerant gas discharged from the compression chamber  45  into the discharge chamber  29  becomes minimum. 
     Thus, in the compressor according to the present embodiment, the flow rate of refrigerant gas discharged to the outside of each compression chamber  45  through the first communication passage  21   d  and the main body passage  41   b  and the flow rate of refrigerant sucked into each compression chamber  45  through the suction unit  15   a  can change the flow rate of refrigerant gas discharged from the compression chamber  45  into the discharge chamber  29 . As a result, the compressor according to the present embodiment can perform excellent controllability. 
     The following will describe the function of the compressor according to the present embodiment in comparison with a compressor of a comparative example. 
     In the compressor according to the comparative example not shown in the drawing, the drive shaft  3  does not have the axial passage  30   a  and the second radial passage  30   b . The second communication passage  41  is constituted only by the main body passage  41   b . Accordingly, in the compressor of the comparative example, the suction unit  15   a  does not have the suction throttle  43   a . The other configuration of the compressor according to the comparative example is the same as that of the compressor according to the first embodiment. 
     In the compressor according to the comparative example, refrigerant gas in the suction chamber  27  is sucked through the main body passage  41   b  and each of the first communication passages  21   d  into the compression chamber  45 . Then, since the compressor according to the comparative example does not have the suction throttle  43   a , the compressor is configured to change only the flow rate of refrigerant gas discharged to the outside of each compression chamber  45  so that the flow rate of refrigerant gas in the compression chamber  45  changes. 
     As shown in  FIGS. 6 and 7 , in the compressor according to the comparative example, if the communication angle changes from a small state to a large state, the flow rate of refrigerant discharged from each compression chamber into the discharge chamber  29  is difficult to decrease. For the reason, the controllability of the compressor according to the comparative example cannot be increased. In particular, as shown in  FIG. 6 , in an operating state in which the drive shaft  3  rotates at a high speed and the fixed swash plate  5  rotates at a high speed, the main body passage  41   b  becomes disconnected from each of the first communication passages  21   d  by the rotation of the rotating body  11  before refrigerant gas sucked into each compression chamber  45  is sufficiently discharged to the outside of the compression chamber  45  through the main body passage  41   b  and the first communication passage  21   d . Therefore, in the compressor according to the comparative example, the flow rate of refrigerant gas present in each compression chamber  45  is difficult to decrease. Since the refrigerant gas is compressed, in the compressor according to the comparative example, the flow rate of refrigerant gas discharged from each compression chamber  45  into the discharge chamber  29  is remarkably difficult to decrease when the communication angle changes from a small state to a large state. 
     On the other hand, in the compressor according to the first embodiment, the suction throttle  43   a  decreases the flow rate of refrigerant gas into each compression chamber  45  when the communication angle becomes large based on the control pressure. Thus, in the compressor according to the first embodiment including the case where the communication angle is the maximum based on the control pressure, when the communication angle is large, the flow rate of refrigerant gas sucked into each compression chamber  45  decreases. 
     As a result, in the compressor according to the first embodiment as compared to the compressor according to the comparative example, as shown in  FIG. 6 , not only in the case where the fixed swash plate  5  rotates at a high speed, but also when the fixed swash plate  5  rotates at a low speed, the flow rate of refrigerant gas discharged from each compression chamber  45  into the discharge chamber  29  suitably decreases when the communication angle changes from the small state to the large state. Thus, in the compressor according to the first embodiment, the flow rate of refrigerant gas discharged from each compression chamber  45  into the discharge chamber  29  can suitably decrease as the communication angle increases. In the compressor according to the first embodiment, when the communication angle is small, including the case where the communication angle is the minimum, the flow rate of refrigerant gas discharged from each compression chamber  45  after refrigerant gas is sucked into the compression chamber  45  decreases while the flow rate of refrigerant gas sucked into each compression chamber  45  increases. Thus, the flow rate of refrigerant gas discharged from each compression chamber  45  into the discharge chamber  29  can suitably increase. 
     Accordingly, the compressor according to the first embodiment is excellent in controllability. 
     In particular, in the compressor according to the first embodiment, the communication area between the first radial passage  41   a  and the second radial passage  30   b  changes in the suction throttle  43   a  based on the movement of the rotating body  11  in the direction of the axis O. Since the communication angle increases, the communication area between the first radial passage  41   a  and the second radial passage  30   b  decreases, so that the flow area of refrigerant gas into each compression chamber  45  decreases. Accordingly, in the compressor according to the first embodiment, the suction throttle  43   a  can suitably adjust the flow rate of refrigerant gas into each compression chamber  45  in accordance with the position of the rotating body  11  in the second axial hole  21   b . The suction throttle  43   a  decreases the flow rate of refrigerant gas into each compression chamber  45  when the communication angle becomes large based on the movement of the rotating body  11  in the direction of the axis O. 
     Further, this compressor performs an inlet-side control such that the control valve  13  changes a flow rate of the refrigerant gas introduced from the discharge chamber  29  into the control pressure chamber  37  through the first supply passage  13   b  and the second supply passage  13   c . This enables a pressure in the control pressure chamber  37  to become higher quickly, thereby increasing the flow rate of the refrigerant gas discharged from each compression chamber  45  into the discharge chamber  29  quickly. 
     Second Embodiment 
     As shown in  FIG. 8 , in the compressor according to a second embodiment, the suction port  27   a  is formed in the circumferential wall  17   b  of the front housing  17 . In the compressor according to the second embodiment, low pressure refrigerant gas passing through the evaporator is sucked into the swash plate chamber  31  through the suction port  27   a . That is, the swash plate chamber  31  also serves as a suction chamber. Thus, the suction pressure is maintained in the swash plate chamber  31 . The control valve  13  is connected to the swash plate chamber  31  through the detection passage  13   a . The control pressure chamber  37  is formed on the center side of the rear housing  19 . As a result, the rear end of the second axial hole  21   b  communicates with the control pressure chamber  37  and control pressure applies to the rear end of the second axial hole  21   b  as well as the control pressure chamber  37 . In this compressor, the control pressure chamber  37  is connected to the swash plate chamber  31  through the bleed passage (not shown). 
     The cylinder block  21  has a suction passage  21   e  formed in the second axial hole  21   b . The suction passage  21   e  is constituted by a suction space  47  formed in the second axial hole  21   b  and a through hole  49  formed in the support wall  21   c . The through hole  49  passes through the support wall  21   c  in the direction of the axis O so that the swash plate chamber  31  communicates with the suction space  47 . The through hole  49  and the suction space  47  are applied by suction pressure as well as the swash plate chamber  31 . The suction space  47  will be described later. 
     The drive shaft  3  includes a threaded portion  3   a  and a first diameter portion  3   b . The length of the drive shaft  3  in the direction of the axis O is shorter than that of the compressor according to the first embodiment. As shown in  FIGS. 9 and 10 , the first diameter portion  3   b  has a recess  3   e  extending forward from the rear surface thereof in the direction of the axis O. 
     In the compressor according to the second embodiment, a rotating body  51  is provided. The rotating body  51  has a first valve body  53  and a second valve body  55 . The first valve body  53  and the second valve body  55  are disposed in the second axial hole  21   b.    
     The first valve body  53  has a shaft portion  53   a , a tapered portion  53   b , a spring seat  53   c , and a connecting portion  53   d . The shaft portion  53   a  extends in the direction of the axis O. The front side of the shaft portion  53   a  is press-fitted into the recess  3   e . Thus, the first valve body  53  is fixed to the drive shaft  3  and is integrally rotatable with the drive shaft  3  in the second axial hole  21   b . The tapered portion  53   b  is connected to the rear end of the shaft portion  53   a . The tapered portion  53   b  has a conical shape that gradually increases in diameter as the tapered portion  53   b  extends rearward in the direction of the axis O. The spring seat  53   c  is connected to the rear end of the tapered portion  53   b . The diameter of the spring seat  53   c  is larger than that of the rear end of the tapered portion  53   b , which is the portion having the maximum diameter in the tapered portion  53   b . The connecting portion  53   d  is formed to be smaller in diameter than the spring seat  53   c  and is connected to the spring seat  53   c . The connecting portion  53   d  extends from the spring seat  53   c  rearward in the direction of the axis O. 
     The second valve body  55  is disposed in the second axial hole  21   b , so that the second valve body  55  partitions the suction space  47  from the control pressure chamber  37  in the second axial hole  21   b . Thus, the space between the second valve body  55  and the support wall  21   c  serves as the suction space  47  in the second axial hole  21   b.    
     The second valve body  55  has a valve main body  55   a , a valve hole  55   b , a support part  55   c , and a coil spring  55   d . The valve main body  55   a  is formed in a cylindrical shape that has substantially the same diameter as the second axial hole  21   b . The valve main body  55   a  has an annular passage  551 . The valve main body  55   a  has the second communication passage  41  constituted by the first radial passage  41   a  and the main body passage  41   b . In the compressor according to the second embodiment, the main body passage  41   b  is recessed on the outer circumferential surface of the valve main body  55   a  in a state in which the direction of the main body passage  41   b  is reversed from that in the compressor according to the first embodiment in the front-rear direction. Thus, in the compressor according to the second embodiment, the first portion  411  is located on the rear end side of the main body passage  41   b  and the second portion  412  is located on the front end side of the main body passage  41   b . The first radial passage  41   a  communicates with the annular passage  551 . As a result, the annular passage  551  communicates with the second communication passage  41 . 
     The valve hole  55   b  is located in front of the valve main body  55   a  and formed integrally with the valve main body  55   a . The periphery of the valve hole  55   b , or the front surface of the valve main body  55   a  is a valve seat  552 . The valve hole  55   b  extends in the direction of the axis O and communicates with the annular passage  551 . As a result, the annular passage  551  communicates with the suction space  47  through the valve hole  55   b . The shaft portion  53   a  and the tapered portion  53   b  of the first valve body  53  are inserted through the valve hole  55   b . The valve hole  55   b  is formed slightly larger in diameter than the tapered portion  53   b.    
     The support part  55   c  has a flange portion  553  and a connected portion  554 . The flange portion  553  is press-fitted into the valve main body  55   a . As a result, the support part  55   c  is fixed to the valve main body  55   a  in a state that the support part  55   c  is located behind the first valve body  53  in the annular passage  551 . The connected portion  554  is integrally formed with the flange portion  553  and extends from the flange portion  553  toward the first valve body  53 . The connected portion  554  has a connecting hole  555 . The connecting portion  53   d  of the first valve body  53  is inserted into the connecting hole  555 . 
     The connecting portion  53   d  is splined to the connected portion  554  in the connecting hole  555 . As a result, the rotation of the drive shaft  3  and the first valve body  53  is transmitted to the valve main body  55   a . Thus, in the second axial hole  21   b , the second valve body  55  including the valve main body  55   a  is rotatable integrally with the drive shaft  3  and the first valve body  53 . In the second valve body  55 , the connected portion  554  slides relative to the connecting portion  53   d  in the direction of the axis O due to the differential pressure between the suction pressure and the control pressure. Thus, the second valve body  55  is movable in the second axial hole  21   b  with respect to the drive shaft  3  and the first valve body  53  in the direction of the axis O based on the control pressure. 
     The coil spring  55   d  is provided between the spring seat  53   c  and the flange portion  553 . The coil spring  55   d  urges the second valve body  55  toward the rear of the second axial hole  21   b.    
     A circlip  59  is provided in the second axial hole  21   b . The circlip  59  is located on the rear side of the second axial hole  21   b  and comes in contact with the second valve body  55  when the second valve body  55  moves in the second axial hole  21   b  furthest rearward in the direction of the axis O. As a result, the circlip  59  regulates the amount of movement of the second valve body  55  in the rearward direction. When the second valve body  55  moves in the second axial hole  21   b  furthest forward in the direction of the axis O, the connected portion  554  comes into contact with the spring seat  53   c  of the first valve body  53 . As a result, the connected portion  554  and the spring seat  53   c  regulate the forward movement amount of the second valve body  55 . 
     In the compressor according to the present embodiment, the suction unit  15   b  is constituted by the first communication passage  21   d , the second communication passage  41 , the suction passage  21   e , the valve hole  55   b , and the annular passage  551 . In the compressor according to the present embodiment, refrigerant gas sucked into the swash plate chamber  31  reaches the first radial passage  41   a  through the suction passage  21   e , the valve hole  55   b , and the annular passage  551 . The refrigerant gas that reaches the first radial passage  41   a  flows from the main body passage  41   b  through the first communication passage  21   d  and is sucked into each compression chamber  45 . 
     The compressor according to the present embodiment, has the suction throttle  43   b . The suction throttle  43   b  is constituted by the shaft portion  53   a , the tapered portion  53   b  of the first valve body  53 , and the valve hole  55   b . Other configurations of the compressor are the same as those of the compressor according to the first embodiment, and the same components are denoted by the same reference numerals, and a detailed description thereof will be omitted. 
     In the compressor according to the present embodiment, the control valve  13  increases the control pressure of the control pressure chamber  37  to increase the variable differential pressure so that the second valve body  55  resists the urging force of the coil spring  55   d  and starts to move in the second axial hole  21   b  from the state shown in  FIG. 1  forward in the direction of the axis O. Then, the tapered portion  53   b  starts to move rearward relative to the annular passage  551 . As a result, in the suction throttle  43   b , the opening degree of the valve hole  55   b  gradually increases. Thus, the flow rate of refrigerant gas flowing through the valve hole  55   b  gradually increases. As a result, the suction throttle  43   b  gradually increases the flow rate of refrigerant gas into each compression chamber  45 . As the second valve body  55  moves in the second axial hole  21   b  forward in the direction of the axis O, the communication angle gradually decreases. Thus, the flow rate of refrigerant gas discharged from each compression chamber  45  into the discharge chamber  29  gradually increases. 
     When the variable differential pressure becomes maximum, the tapered portion  53   b  moves further rearward relative to the valve hole  55   b , so that as shown in  FIG. 9 , only the shaft portion  53   a  enters in the valve hole  55   b . In the suction throttle  43   b , the opening degree of the valve hole  55   b  becomes maximum, so that the flow rate of refrigerant gas flowing through the valve hole  55   b  becomes maximum. As a result, the suction throttle  43   b  maximizes the flow rate of refrigerant gas into each compression chamber  45 . In the main body passage  41   b , when the first portion  411  communicates with each of the first communication passages  21   d , the communication angle with the first portion  411  becomes minimum. Thus, in the compressor according to the present embodiment, the flow rate of refrigerant gas discharged from each compression chamber  45  into the discharge chamber  29  becomes maximum. 
     On the other hand, the control valve  13  reduces the control pressure of the control pressure chamber  37  to reduce the variable differential pressure, so that the second valve body  55  moves in the second axial hole  21   b  rearward in the direction of the axis O due to the urging force of the coil spring  55   d . Then, the tapered portion  53   b  relatively moves forward relative to the valve hole  55   b  and starts to enter the valve hole  55   b . As a result, in the suction throttle  43   b , the opening degree of the valve hole  55   b  gradually decreases. Thus, the suction throttle  43   b  gradually decreases the flow rate of refrigerant gas into each compression chamber  45 . As the second valve body  55  moves rearward in the second axial hole  21   b  in the direction of the axis O, the communication angle gradually decreases. Thus, the flow rate of refrigerant gas discharged from each compression chamber  45  into the discharge chamber  29  gradually decreases. 
     When the variable differential pressure becomes minimum, the tapered portion  53   b  enters deeper into the valve hole  55   b . As a result, in the suction throttle  43   b , the opening degree of the valve hole  55   b  becomes minimum, so that refrigerant gas flows from the suction passage  21   e  into the annular passage  551  through a slight gap between the valve hole  55   b  and the tapered portion  53   b . That is, the flow rate of refrigerant gas flowing through the valve hole  55   b  becomes minimum. As a result, the suction throttle  43   b  minimizes the flow rate of refrigerant gas into each compression chamber  45 . The main body passage  41   b  communicates with the first communication passage  21   d  in the second portion  412 , so that the communication angle becomes maximum. Thus, in the compressor according to the present embodiment, the flow rate of refrigerant gas discharged from each compression chamber  45  into the discharge chamber  29  becomes minimum. 
     Third Embodiment 
     As shown in  FIG. 11 , in the compressor according to the third embodiment, the suction port  27   a  is formed in the circumferential wall  17   b  of the front housing  17 . Accordingly, as in the case of the compressor according to the second embodiment, since the swash plate chamber  31  also serves as the suction chamber in the compressor according to the third embodiment, the suction pressure is maintained in the swash plate chamber  31 . The control valve  13  is connected to the swash plate chamber  31  through the detection passage  13   a . The swash plate chamber  31  and the inside of the second axial hole  21   b  communicate with each other through the through hole  49  formed in the support wall  21   c . On the other hand, the control pressure chamber  37  is formed on the center side of the rear housing  19 . Accordingly, the second axial hole  21   b  also communicates with the control pressure chamber  37 . The fixed swash plate  5  has the introduction passage  5   a  extending in the radial direction and opening into the swash plate chamber  31 . 
     The drive shaft  3  is constituted by the threaded portion  3   a  and the first diameter portion  3   b . The rear end of the first diameter portion  3   b  protrudes from the inside of the second axial hole  21   b  and extends into the control pressure chamber  37 . The first diameter portion  3   b  has a supply passage  71  and a connecting passage  73 . The supply passage  71  includes a first supply passage  71   a , a second supply passage  71   b , a third supply passage  71   c , and a fourth supply passage  71   d . The first supply passage  71   a  is located on the front side of the first diameter portion  3   b . The first supply passage  71   a  extends in the radial direction and opens to the outer peripheral surface of the first diameter portion  3   b  and communicates with the introduction passage  5   a . As a result, the supply passage  71  is connected to the swash plate chamber  31  through the introduction passage  5   a.    
     The second supply passage  71   b  communicates with the first supply passage  71   a  and extends rearward in the direction of the axis O in the first diameter portion  3   b . As shown in  FIGS. 12 and 13 , the third supply passage  71   c  communicates with the second supply passage  71   b  and extends rearward in the direction of the axis O in the first diameter portion  3   b . The third supply passage  71   c  is formed to have a larger diameter than the second supply passage  71   b  in the direction of the axis O. Thus, a first step portion  711  is formed between the second supply passage  71   b  and the third supply passage  71   c . The fourth supply passage  71   d  communicates with the third supply passage  71   c . The fourth supply passage  71   d  extends rearward in the direction of the axis O in the first diameter portion  3   b  and opens to the rear surface of the first diameter portion  3   b . As a result, the supply passage  71  is also connected to the control pressure chamber  37 . In addition, the fourth supply passage  71   d  is formed to have a diameter larger than that of the third supply passages  71   c . As a result, a second step portion  712  is formed between the third supply passage  71   c  and the fourth supply passage  71   d . The connecting passage  73  communicates with the fourth supply passage  71   d . The connecting passage  73  extends in the radial direction and opens to the outer peripheral surface of the first diameter portion  3   b.    
     A moving body  75  is provided in the fourth supply passage  71   d . The moving body  75  is formed to have substantially the same diameter as the fourth supply passage  71   d  and splined to the fourth supply passage  71   d . As a result, the moving body  75  can rotate integrally with the drive shaft  3 . The moving body  75  is movable in the fourth supply passage  71   d  in the direction of the axis O. Since the moving body  75  is provided in the fourth supply passage  71   d , suction pressure applies to the front face of the moving body  75  through the first to third supply passages  71   a  to  71   c . Control pressure applies to the rear face of the moving body  75  through the fourth supply passage  71   d . The moving body  75  is movable based on the control pressure in the direction of the axis O. 
     The moving body  75  has a through passage  75   a . The through passage  75   a  has a substantially crank shape and extends in the direction of the axis O and in the radial direction. The through passage  75   a  has a first opening  751  that opens toward the second and third supply passages  71   b  and  71   c  and a second opening  752  that opens toward the connecting passage  73 . As a result, the through passage  75   a  communicates with the swash plate chamber  31  through the first to third supply passages  71   a  to  71   c , and communicates with the connecting passage  73 . 
     A circlip  74  is provided in the fourth supply passage  71   d . As shown in  FIG. 13 , the moving body  75  comes in contact with the circlip  74  when the moving body  75  moves in the fourth supply passage  71   d  furthest rearward in the direction of the axis O. As a result, the circlip  74  regulates the amount of movement of the moving body  75  in the rearward direction. On the other hand, as shown in  FIG. 12 , the moving body  75  comes in contact with the second step portion  712  when the moving body  75  moves in the fourth supply passage  71   d  furthest forward in the direction of the axis O. As a result, the second step portion  712  regulates the amount of movement of the moving body  75  in the forward direction. 
     In the third supply passage  71   c , a coil spring  76   a  is provided between the first step portion  711  and the moving body  75 . The coil spring  76   a  urges the moving body  75  toward the rear of the fourth supply passage  71   d.    
     The compressor according to the present embodiment, includes a rotating body  77 . The rotating body  77  is formed in a cylindrical shape having substantially the same diameter as the second axial hole  21   b  and is disposed in the second axial hole  21   b . That is, the rotating body  77  is provided on the outer circumferential surface of the drive shaft  3 . As a result, suction pressure applies to the front face of the rotating body  77  through the through hole  49 . Control pressure applies to the rear face of the rotating body  77 . 
     The rotating body  77  is splined to the first diameter portion  3   b  of the drive shaft  3 . As a result, the rotating body  77  is integrally rotatable with the drive shaft  3  in the second axial hole  21   b . The rotating body  77  is movable in the second axial hole  21   b  with respect to the drive shaft  3  in the direction of the axis O due to the differential pressure between the suction pressure and the control pressure. 
     Circlips  78  and  79  are provided on the first diameter portion  3   b . The circlip  78  is provided on the front side of the second axial hole  21   b  in the first diameter portion  3   b  so that when the rotating body  77  moves to the most forward position in the second axial hole  21   b  in the direction of the axis O, the rotating body  77  comes in contact with the circlip  78 . As a result, the circlip  78  regulates the amount of the forward movement of the rotating body  77 . The circlip  79  is provided on the rear side in the second axial hole  21   b  in the first diameter portion  3   b  so that when the rotating body  77  moves to the most rearward position in the second axial hole  21   b  in the direction of the axis O, the rotating body  77  comes in contact with the circlip  79 . As a result, the circlip  79  regulates the amount of the rearward movement of the rotating body  77 . 
     In the second axial hole  21   b , a coil spring  76   b  is provided between the rotating body  77  and the support wall  21   c . The coil spring  76   b  urges the rotating body  77  toward the rear of the second axial hole  21   b.    
     The rotating body  77  has the main body passage  41   b  and the third radial passage  41   c . The main body passage  41   b  and the third radial passage  41   c  constitute the second communication passage  42 . In the compressor according to the present embodiment, as in the case of the compressor according to the second embodiment, the main body passage  41   b  is recessed on the outer peripheral surface of the rotating body  77  in a state in which the direction of the main body passage  41   b  is reversed from that in the compressor according to the first embodiment in the front-rear direction. The third radial passage  41   c  extends radially and communicates with the main body passage  41   b  and the connecting passage  73 . That is, the second communication passage  42  communicates with the connecting passage  73 . The third radial passage  41   c  is formed longer in the direction of the axis O than the first radial passage  41   a  of the compressor according to the first embodiment. Thus, even when the rotating body  77  moves in the second axial hole  21   b  in the direction of the axis O, the communicating area between the third radial passage  41   c  and the connecting passage  73  is constant. 
     In the compressor according to the third embodiment, a suction unit  15   c  is constituted by each of the first communication passages  21   d , the second communication passage  42 , the supply passage  71 , the connecting passage  73 , and the through passage  75   a . As a result, in the compressor according to the present embodiment, refrigerant gas sucked into the swash plate chamber  31  reaches the third radial passage  41   c  from the connecting passage  73  through the supply passage  71  and the through passage  75   a . That is, the connecting passage  73  communicates with the second communication passage  42 . The refrigerant gas that reaches the third radial passage  41   c  flows from the main body passage  41   b  through each of the first communication passages  21   d  and is sucked into each compression chamber  45 . 
     The compressor according to the third embodiment includes the suction throttle  43   c . The suction throttle  43   c  is constituted by the connecting passage  73  and the through passage  75   a . In this compressor according to the third embodiment, as in the case of the compressor according to the second embodiment, the control pressure chamber  37  is connected to the swash plate chamber  31  through the bleed passage (not shown). The other configuration of the compressor according to the third embodiment is the same as that of the compressor according to the first embodiment. 
     In the compressor according to the third embodiment, the control valve  13  increases the control pressure of the control pressure chamber  37  to increase the variable differential pressure, so that the rotating body  77  starts to move in the second axial hole  21   b  from the state shown in  FIG. 13  against the urging force of the coil spring  76   b  in the direction of the axis O. At the same time, the moving body  75  starts to move in the fourth supply passage  71   d  against the urging force of the coil spring  76   a  forward in the direction of the axis O. As a result, in the suction throttle  43   c , the communicating area between the second opening  752  of the through passage  75   a  and the connecting passage  73  gradually increases. Then, the flow rate of refrigerant gas flowing from the through passage  75   a  into the connecting passage  73  gradually increases. Thus, the suction throttle  43   c  gradually increases the flow rate of refrigerant gas into each compression chamber  45 . As the rotating body  77  moves forward, the communicating angle gradually decreases. Thus, the flow rate of refrigerant gas discharged from each compression chamber  45  into the discharge chamber  29  gradually increases. 
     When the variable differential pressure becomes maximum, as shown in  FIG. 12 , the moving body  75  is located at the most forward position in the fourth supply passage  71   d . As a result, the communicating area between the second opening  752  and the connecting passage  73  becomes maximum in the suction throttle  43   c , so that the flow rate of refrigerant gas flowing from the through passage  75   a  into the connecting passage  73  becomes maximum. Thus, the suction throttle  43   c  maximizes the flow rate of refrigerant gas to each compression chamber  45 . In the case, the rotating body  77  is located at the most forward position in the second axial hole  21   b , so that the communication angle becomes minimum. Thus, in the compressor according to the third embodiment, the flow rate of refrigerant gas discharged from each compression chamber  45  into the discharge chamber  29  becomes maximum. 
     On the other hand, the control valve  13  decreases the control pressure of the control pressure chamber  37  to reduce the variable differential pressure, so that the urging force of the coil spring  76   b  causes the rotating body  77  to start to move in the second axial hole  21   b  rearward in the direction of the axis O. At the same time, the moving body  75  starts to move in the fourth supply passage  71   d  rearward in the direction of the axis O due to the urging force of the coil spring  76   a . As a result, the communicating area between the second opening  752  and the connecting passage  73  gradually decreases in the suction throttle  43   c . Thus, the flow rate of refrigerant gas flowing from the through passage  75   a  into the connecting passage  73  gradually decreases. As a result, the suction throttle  43   c  decreases the flow rate of refrigerant gas to each compression chamber  45 . As the rotating body  77  moves rearward, the communication angle gradually increases. Thus, the flow rate of refrigerant gas discharged from each compression chamber into the discharge chamber  29  decreases. 
     Then, when the variable differential pressure becomes minimum, as shown in  FIG. 13 , the moving body  75  is located at the furthest rear position in the fourth supply passage  71   d . As a result, the communicating area between the second opening  752  and the connecting passage  73  becomes minimum in the suction throttle  43   c , so that the flow rate of refrigerant gas flowing from the through passage  75   a  into the connecting passage  73  becomes minimum. Thus, the suction throttle  43   c  minimizes the flow rate of refrigerant gas to each compression chamber  45 . In the case, the rotating body  77  is located at a most rearward position in the second axial hole  21   b , so that the communication angle becomes maximum. Thus, in the compressor according to the third embodiment, the flow rate of refrigerant gas discharged from each compression chamber  45  into the discharge chamber  29  becomes minimum. 
     Fourth Embodiment 
     As shown in  FIGS. 14 to 16 , in the compressor according to a fourth embodiment, the rear housing  19  has a radial hole  61 . The radial hole  61  extends from the center side of the rear housing  19  in the radially outward direction of the rear housing  19  and opens to the outside of the rear housing  19 . A partition part  63  is fixed in the radial hole  61 . The partition part  63  partitions the radial hole  61  into a first suction passage  271  and the control pressure chamber  37 . The end portion of the first suction passage  271  in the radially outward direction of the rear housing  19  serves as a suction port  27   a.    
     The rear housing  19  has a second suction passage  272 . The second suction passage  272  communicates with the first suction passage  271  and the suction chamber  27 . As a result, refrigerant gas is sucked into the suction chamber  27  through the suction port  27   a  and the first and second suction passages  271 ,  272 . The suction chamber  27  communicates with the inside of the second axial hole  21   b  through the suction communication passage  27   b  formed in the cylinder block  21 . As a result, suction pressure applies to the second axial hole  21   b  and the suction chamber  27 . 
     The rear housing  19  has a third boss portion  191 . The third boss portion  191  is an example of the boss portion of the present disclosure. The third boss portion  191  extends in the suction chamber  27  in the direction of the axis O. The rear housing  19  has a fourth axial hole  192 . The fourth axial hole  192  is an example of the shaft hole of the present disclosure. The fourth axial hole  192  passes through the third boss portion  191  in the direction of the axis O and communicates with the suction chamber  27  and the control pressure chamber  37 . 
     The drive shaft  3  has the threaded portion  3   a , the first diameter portion  3   b , and a third diameter portion  3   f . The third diameter portion  3   f  is located on the rear side of the drive shaft  3  and is continuous with the rear end of the first diameter portion  3   b . The third diameter portion  3   f  is supported in the third axial hole  210 . The third diameter portion  3   f  has a larger diameter than the first diameter portion  3   b . The third diameter portion  3   f  has a second axial passage  30   c  and a second radial passage  30   d . The second axial passage  30   c  extends in third diameter portion  3   f  in the direction of the axis O. The rear end of the second axial passage  30   c  opens to the rear surface of the third diameter portion  3   f . The second radial passage  30   d  communicates with the second axial passage  30   c . The second radial passage  30   d  extends in third diameter portion  3   f  in the radial direction and opens to the outer circumferential surface of third diameter portion  3   f.    
     As shown in  FIGS. 15 and 16 , the compressor according to the fourth embodiment includes a rotating body  65 . The rotating body  65  has a main body portion  67  and an extending portion  69 . The body portion  67  is formed to have substantially the same diameter as the second axial hole  21   b . The extending portion  69  is integrally formed with the main body portion  67  and extends from the main body portion  67  rearward in the direction of the axis O. The extending portion  69  has a smaller diameter than the main body portion  67  and is formed to have substantially the same diameter as the fourth axial hole  192 . The extending portion  69  has at the rear end thereof a protruding portion  69   a  protruding rearward. 
     The main body portion  67  of the rotating body  65  is disposed in the second axial hole  21   b . As a result, suction pressure applies to the front surface of the main body portion  67 . The extending portion  69  extends into the suction chamber  27  and is supported in the fourth axial hole  192 . As a result, the rear end of the extending portion  69  including the protruding portion  69   a  enters the control pressure chamber  37 . Accordingly, control pressure applies to the rear surface of the extending portion  69 . 
     The rotating body  65  has the first radial passage  65   a  and the first axial passage  65   b . The first radial passage  65   a  is formed in the extending portion  69  and extends in the radial direction of the rotating body  65  and opens to the outer circumferential surface of the extending portion  69 . As a result, the first radial passage  65   a  communicates with the suction chamber  27 . 
     The first axial passage  65   b  has a small diameter portion  650 , a first large diameter portion  651 , and a second large diameter portion  652 . The small diameter portion  650  is formed from the inside of the main body portion  67  to the inside of the extending portion  69 . The small diameter portion  650  extends in the direction of the axis O and communicates with the first radial passage  65   a  in the extending portion  69 . That is, the first axial passage  65   b  communicates with the first radial passage  65   a . The first large diameter portion  651  is formed in the main body portion  67 . The first large diameter portion  651  extends in the direction of the axis O and communicates with the small diameter portion  650 . The first large diameter portion  651  is formed larger in diameter than the small diameter portion  650 . Thus, in the first axial passage  65   b , a first stepped portion  653  is formed between the first large diameter portion  651  and the small diameter portion  650 . The second large diameter portion  652  is formed in the main body portion  67 . The second large diameter portion  652  extends in the direction of the axis O and the front end of the second large diameter portion  652  opens to the front surface of the main body portion  67  and the rear end of the second large diameter portion  652  communicates with the first large diameter portion  651 . The second large diameter portion  652  is formed larger in diameter than the first large diameter portion  651 . Thus, in the first axial passage  65   b , a second stepped portion  654  is formed between the second large diameter portion  652  and the first large diameter portion  651 . 
     The rotating body  65  is splined to the third diameter portion  3   f  of the drive shaft  3  in the second large diameter portion  652 . As a result, the rotating body  65  is integrally rotatable with the drive shaft  3 . In the rotating body  65 , the main body portion  67  is movable in the direction of the axis O in the second axial hole  21   b  with respect to the drive shaft  3  by the differential pressure between the suction pressure and the control pressure. Then, the extending portion  69  is movable in the fourth axial hole  192  in the direction of the axis O. The third diameter portion  3   f  is splined to the second large diameter portion  652 , so that the second axial passage  30   c  communicates with the first axial passage  65   b.    
     As shown in  FIG. 15 , when the main body portion  67  moves at the most forward position in the second axial hole  21   b  in the direction of the axis O, the second stepped portion  654  comes into contact with the rear end of the third diameter portion  3   f . As a result, the second stepped portion  654  regulates the amount of the forward movement of the rotating body  65 . As shown in  FIG. 16 , when the extending portion  69  moves in the fourth axial hole  192  to the most rearward position in the direction of the axis O, the protruding portion  69   a  comes in contact with the inner wall of the control pressure chamber  37 , or the rear housing  19 . As a result, the rear housing  19  regulates the amount of the rearward movement of the rotating body  65 . 
     In the first large diameter portion  651 , a coil spring  66  is provided between the rear end of the third diameter portion  3   f  and the first stepped portion  653 . The coil spring  66  urges the rotating body  65  toward the rear of the second axial hole  21   b.    
     The main body portion  67  has the second communication passage  42 , or, the main body passage  41   b  and the third radial passage  41   c . In the compressor according to the fourth embodiment, as in the case of the compressors according to the second and third embodiments, the main body passage  41   b  is recessed on the outer circumferential surface of the main body portion  67  in a state in which the direction of the main body passage  41   b  is reversed from that in the compressor according to the first embodiment in the front-rear direction. The third radial passage  41   c  communicates with the second radial passage  30   d . As in the case of the compressor according to the third embodiment, even when the main body portion  67  moves in the second axial hole  21   b  in the direction of the axis O, the communicating area between the third radial passage  41   c  and the second radial passage  30   d  is constant. 
     In the compressor according to the fourth embodiment, the suction unit  15   d  is constituted by the first communication passage  21   d , the second communication passage  42 , the first radial passage  65   a , the first axial passage  65   b , the second axial passage  30   c , and the second radial passage  30   d . As a result, in the compressor according to the present embodiment, refrigerant gas sucked into the suction chamber  27  reaches the third radial passage  41   c  from the first radial passage  65   a  through the first axial passage  65   b , the second axial passage  30   c , and the second radial passage  30   d . The refrigerant gas that reaches the third radial passage  41   c  flows through the first communication passage  21   d  from the main body passage  41   b  and is sucked into each compression chamber  45 . 
     The compressor according to the fourth embodiment, includes a suction throttle  43   d . The suction throttle  43   d  is constituted by the first radial passage  65   a  and the third boss portion  191 . The other configuration of the compressor according to the fourth embodiment, is the same as that of the compressor according to the first embodiment. 
     In the compressor according to the fourth embodiment, the control valve  13  increases the control pressure of the control pressure chamber  37  to increase the variable differential pressure, so that the body portion  67  of the rotating body  65  starts to move from the state shown in  FIG. 16  in the second axial hole  21   b  forward in the direction of the axis O. The extending portion  69  of the rotating body  65  starts to move in the fourth axial hole  192  forward in the direction of the axis O. Thus, the first radial passage  65   a  starts to move forward of the third boss portion  191 . As a result, in the suction throttle  43   d , the opening degree of the first radial passage  65   a  gradually increases. Thus, the flow rate of refrigerant gas flowing from the suction chamber  27  into the first radial passage  65   a  gradually increases. As a result, the suction throttle  43   d  gradually increases the flow rate of refrigerant gas to each compression chamber  45 . As the main body portion  67  moves in the second axial hole  21   b  forward in the direction of the axis O, the communication angle gradually decreases. Thus, the flow rate of refrigerant gas discharged from each compression chamber  45  into the discharge chamber  29  increases. 
     Then, when the variable differential pressure becomes maximum, as shown in  FIG. 15 , the entire first radial passage  65   a  is located in front of the third boss portion  191 . As a result, in the suction throttle  43   d , the opening degree of the first radial passage  65   a  becomes maximum, so that the flow rate of refrigerant gas flowing from the suction chamber  27  into the first radial passage  65   a  becomes maximum. Thus, the suction throttle  43   d  maximizes the flow rate of refrigerant gas to each compression chamber  45 . In the case, the communication angle becomes minimum. Thus, in the compressor according to the fourth embodiment, the flow rate of refrigerant gas discharged from each compression chamber  45  into the discharge chamber  29  becomes maximum. 
     On the other hand, the control valve  13  reduces the control pressure of the control pressure chamber  37  to reduce the variable differential pressure, so that the body portion  67  starts to move in the second axial hole  21   b  rearward in the direction of the axis O due to the urging force of the coil spring  66 . The extending portion  69  starts to move in the fourth axial hole  192  rearward in the direction of the axis O. Thus, the first radial passage  65   a  starts to move into the fourth axial hole  192  while the first radial passage  65   a  moves toward the rear of the third boss portion  191 . That is, the first radial passage  65   a  starts to be covered by the third boss portion  191 . As a result, in the suction throttle  43   d , the opening degree of the first radial passage  65   a  gradually decreases. Thus, the flow rate of refrigerant gas flowing from the suction chamber  27  into the first radial passage  65   a  gradually decreases. As a result, the suction throttle  43   d  gradually decreases the flow rate of the refrigerant gas to each compression chamber  45 . As the body portion  67  moves in the second axial hole  21   b  forward in the direction of the axis O, the communication angle gradually increases. Thus, the flow rate of refrigerant gas discharged from each compression chamber  45  into the discharge chamber  29  decreases. 
     Then, when the variable differential pressure becomes minimum, most part of the first radial passage  65   a  is covered with the third boss portion  191 , as shown in  FIG. 16 . As a result, the opening degree of the first radial passage  65   a  becomes minimum in the suction throttle  43   d , so that the flow rate of refrigerant gas flowing from the suction chamber  27  into the first radial passage  65   a  becomes minimum. Thus, the suction throttle  43   d  minimizes the flow rate of refrigerant gas into each compression chamber  45 . In the case, the communication angle becomes maximum. Thus, in the compressor according to the fourth embodiment, the flow rate of refrigerant gas discharged from each compression chamber  45  into the discharge chamber  29  becomes minimum. 
     Fifth Embodiment 
     As shown in  FIGS. 17 to 19 , in the compressor according to a fifth embodiment, a suction valve  81  and circlips  82 ,  83  are provided in the radial hole  61  of the rear housing  19 . The suction valve  81  is disposed between the circlips  82  and  83 . The suction valve  81  partitions the radial hole  61  into the suction chamber  27  and the control pressure chamber  37 . As a result, suction pressure applies to the suction chamber  27  on the side of the suction valve  81  and control pressure applies to the control pressure chamber  37  on the side of the suction valve  81 . The end portion of the suction chamber  27 , located in the radially outward direction of the rear housing  19 , serves as the suction port  27   a.    
     The suction valve  81  is movable in the suction chamber  27  in the radial direction of the rear housing  19 , or in the vertical direction due to the differential pressure between the suction pressure and the control pressure in the radial hole  61 , or the variable differential pressure. That is, the suction valve  81  is movable based on the control pressure. As shown in  FIGS. 17 and 18 , the suction valve  81  comes in contact with the circlip  82  when the suction valve  81  moves to the uppermost position in the suction chamber  27 . As a result, the circlip  82  regulates the amount of the upward movement of the suction valve  81 . As shown in  FIG. 19 , the suction valve  81  comes in contact with the circlip  83  when the suction valve  81  moves to the lowermost position in the suction chamber  27 . As a result, the circlip  83  regulates the amount of the downward movement of the suction valve  81 . 
     A coil spring  84  is provided between the suction valve  81  and the circlip  82 . The coil spring  84  urges the suction valve  81  toward the lower side of the suction chamber  27 , or toward the side of the control pressure chamber  37 . 
     The suction valve  81  has a first through hole  81   a  and a second through hole  81   b . The first through hole  81   a  extends in the direction intersecting with the direction of the axis O and opens on the upper surface of the suction valve  81 . The second through hole  81   b  communicates with the first through hole  81   a  and extends in the direction of the axis O and passes through the suction valve  81 . 
     The rear housing  19  has a suction passage  85  and a communication chamber  86 . The suction passage  85  extends in the direction of the axis O and communicates with the second through hole  81   b . As a result, the suction passage  85  communicates with the suction chamber  27  through the first and second through holes  81   a  and  81   b . The communication chamber  86  is formed on the center side of the rear housing  19  and communicates with the suction passage  85 . The communication chamber  86  communicates with the control pressure chamber  37  through the fourth axial hole  192 . 
     In the compressor according to the fifth embodiment, the main body portion  67  of the rotating body  65  is disposed in the second axial hole  21   b , so that the extending portion  69  extends into the communication chamber  86  and is supported in the fourth axial hole  192 . As a result, the first radial passage  65   a  communicates with the communication chamber  86 . In the compressor according to the present embodiment, unlike the compressor according to the fourth embodiment, the third boss portion  191  is not formed in the rear housing  19 . Thus, if the extending portion  69  moves in the direction of the axis O, the communicating area between the first radial passage  65   a  and the communication chamber  86  is constant. 
     In the compressor according to the fifth embodiment, a suction unit  15   e  is constituted by the first communication passage  21   d , the second communication passage  42 , the suction valve  81 , the suction passage  85 , the communication chamber  86 , the first radial passage  65   a , the first axial passage  65   b , the second axial passage  30   c  and the second radial passage  30   d . As a result, in the compressor according to the present embodiment, refrigerant gas sucked into the suction chamber  27  reaches the communication chamber  86  through the first and second through holes  81   a ,  81   b  and the suction passage  85 . The refrigerant gas that reaches the communication chamber  86  reaches the third radial passage  41   c  from the first radial passage  65   a  through the first axial passage  65   b , the second axial passage  30   c , and the second radial passage  30   d . The refrigerant gas that reaches the third radial passage  41   c  flows through each of the first communication passages  21   d  from the main body passage  41   b  and is sucked into each compression chamber  45 . 
     The compressor according to the fifth embodiment, has a suction throttle  43   e . The suction throttle  43   e  is constituted by the suction valve  81  and the suction passage  85 . The other configuration of the compressor according to the fifth embodiment, is the same as that of the compressor according to the fourth embodiment. 
     In the compressor according to the fifth embodiment, the control valve  13  increases the control pressure of the control pressure chamber  37  to increase the variable differential pressure, so that the suction valve  81  starts to move upward in the suction chamber  27  from the state shown in  FIG. 19  against the urging force of the coil spring  84 . As a result, in the suction throttle  43   e , the suction valve  81  moves upward with respect to the suction passage  85 , so that the communicating area between the suction passage  85  and the second through hole  81   b  gradually increases. Thus, the flow rate of refrigerant gas flowing from the second through hole  81   b  through the suction passage  85  into the communication chamber  86  gradually increases. As a result, the suction throttle  43   e  gradually increases the flow rate of refrigerant gas into each compression chamber  45 . 
     When the variable differential pressure becomes maximum, as shown in  FIG. 18 , the suction valve  81  is located at the uppermost position in the suction chamber  27 . As a result, the communication area between the suction passage  85  and the second through hole  81   b  becomes maximum in the suction throttle  43   e . Thus, the flow rate of refrigerant gas flowing from the second through hole  81   b  through the suction passage  85  into the communication chamber  86  becomes maximum. As a result, the suction throttle  43   e  maximizes the flow rate of refrigerant gas into each compression chamber  45 . The movement of the main body portion  67  in the second axial hole  21   b  and the movement of the extending portion  69  in the fourth axial hole  192  when the variable differential pressure increases are the same as those of the compressor according to the fourth embodiment. Thus, in the compressor according to the fifth embodiment, the flow rate of refrigerant gas discharged from each compression chamber  45  into the discharge chamber  29  becomes maximum. 
     On the other hand, the control valve  13  decreases the control pressure of the control pressure chamber  37  to reduce the variable differential pressure, so that the suction valve  81  moves downward in the suction chamber  27  due to the urging force of the coil spring  84  in the suction chamber  27 . As a result, in the suction throttle  43   e , the suction valve  81  moves downward with respect to the suction passage  85 , so that the communicating area between the suction passage  85  and the second through hole  81   b  gradually decreases. Thus, the flow rate of refrigerant gas flowing from the second through hole  81   b  through the suction passage  85  into the communication chamber  86  gradually decreases. Thus, the suction throttle  43   e  gradually decreases the flow rate of refrigerant gas into each compression chamber  45 . 
     When the variable differential pressure becomes minimum, as shown in  FIG. 19 , the suction valve  81  is located at the lowermost position in the suction chamber  27 . As a result, in the suction throttle  43   e , the second through hole  81   b  serves as the suction passage  85  only at a small portion, so that the communicating area between the suction passage  85  and the second through hole  81   b  becomes minimum. Thus, the flow rate of refrigerant gas flowing from the second through hole  81   b  through the suction passage  85  into the communication chamber  86  becomes minimum. Thus, the suction throttle  43   e  minimizes the flow rate of refrigerant gas into each compression chamber  45 . The movement of the main body portion  67  in the second axial hole  21   b  and the movement of the extending portion  69  in the fourth axial hole  192  when the variable differential pressure decreases are the same as those of the compressor according to the fourth embodiment. Thus, in the compressor according to the fifth embodiment, the flow rate of refrigerant gas discharged from each compression chamber  45  into the discharge chamber  29  becomes minimum. 
     In the compressor according to the fifth embodiment, the communicating area between the suction passage  85  and the second through holes  81   b  changes in the suction throttle  43   e  independently of the movement of the main body portion  67  and the extending portion  69  in the direction of the axis O, or the movement of the rotating body  65  in the direction of the axis O so that the flow rate of refrigerant gas into each compression chamber  45  increases or decreases. Thus, in the compressor according to the present embodiment, the flow rate of the refrigerant gas into each compression chamber  45  is suitably adjustable. 
     Thus, the compressors according to the second to the fifth embodiments have the same function as the compressor according to the first embodiment. 
     Although the present disclosure has been described with reference to the first to the fifth embodiments, the present disclosure is not limited to the above-mentioned first to the fifth embodiments, but may be modified within the scope of the present disclosure. 
     For example, the compressors according to the second to the fifth embodiments may be configured as a double-headed piston compressor. 
     The compressor according to the first embodiment, may be configured so that the rotating body  11  moves forward in the second axial hole  21   b  in the direction of the axis O, so that the flow rate of refrigerant gas discharged from each compression chamber  45  into the discharge chamber  29  increases. 
     The compressors according to the first to the fifth embodiments, may adopt a wobble type conversion unit in which a swing plate is supported on the rear side of the fixed swash plate  5  via a thrust bearing instead of the shoes  8   a  and  8   b  and the wobble plate and each piston  7  are connected by a connecting rod. 
     In the compressors according to the first to the fifth embodiments, the control pressure may be controlled externally by on-off control of external current to the control valve  13 , or the control pressure may be controlled internally without using external current. For the external control of the control pressure, each compressor may be configured such that the opening degree of the control valve  13  is decreased by shut-off of the control valve  13  from the current. This configuration allows the opening degree of the control valve  13  to decrease and the control pressure in the control pressure chamber  37  to decrease during the stop of the compressor, thereby allowing the compressor to start in a state in which the flow rate of the refrigerant gas discharged from each compression chamber  45  to the discharge chamber  29  is minimum, and reducing a shock caused by starting the compressor. 
     The compressors according to the first to the fifth embodiments may perform an outlet-side control such that the control valve  13  changes a flow rate of the refrigerant gas introduced from the control pressure chamber  37  into the suction chamber  27  or the swash plate chamber  31  through the bleed passage. This enables the amount of the refrigerant gas in the discharge chamber  29 , which is used for changing the flow rate of the refrigerant discharged from each compression chamber  45  to the discharge chamber  29 , to be decreased, and thus increases the efficiency of the compressor. In this case, the compressor may be configured such that the opening degree of the control valve  13  is increased by shut-off of the control valve  13  from the current. This configuration allows the opening degree of the control valve  13  to increase and the control pressure in the control pressure chamber  37  to decrease during the stop of the compressor, thereby allowing the compressor to start in the state in which the flow rate of the refrigerant gas discharged from each compression chamber  45  to the discharge chamber  29  is minimum, and reducing a shock caused by starting the compressor. 
     The compressors according to the first to the fifth embodiments may include a three-way valve that adjusts the opening degrees of bleeding and supply passages, instead of the control valve  13 . 
     The present disclosure can be used for a vehicle air conditioner.