Patent Publication Number: US-2022213877-A1

Title: Capacity control valve

Description:
TECHNICAL FIELD 
     The present invention relates to a capacity control valve that variably controls capacity of a working fluid, for example, a capacity control valve that controls a discharge amount of a variable displacement compressor used for an air conditioning system of an automobile in accordance with pressure. 
     BACKGROUND ART 
     A variable displacement compressor used for an air conditioning system of an automobile, etc. includes a rotating shaft to be driven and rotated by an engine, a swash plate coupled to the rotating shaft in such a manner that a tilt angle is variable, compressing pistons coupled to the swash plate, etc., and by changing the tilt angle of the swash plate, changes a stroke amount of the pistons to control a discharge amount of a fluid. This tilt angle of the swash plate can be continuously changed by appropriately controlling pressure in a control chamber while utilizing suction pressure Ps of a suction chamber that suctions the fluid, discharge pressure Pd of a discharge chamber that discharges the fluid pressurized by the pistons, and control pressure Pc of the control chamber that houses the swash plate, with using a capacity control valve to be driven to open and close by electromagnetic force. 
     At the time of continuously driving the variable displacement compressor, the capacity control valve performs normal control in which energization is controlled by a control computer, a valve element is moved in the axial direction by electromagnetic force generated in a solenoid, and a CS valve provided between a control port through which a control fluid of the control pressure Pc passes and a suction port through which a suction fluid of the suction pressure Ps passes is opened and closed to adjust the control pressure Pc of the control chamber of the variable displacement compressor. 
     At the time of normal control of the capacity control valve, the pressure of the control chamber in the variable displacement compressor is appropriately controlled, and by continuously changing the tilt angle of the swash plate with respect to the rotating shaft, the stroke amount of the pistons is changed to control the discharge amount of the fluid to the discharge chamber. Thus, the air conditioning system is adjusted to have a target cooling ability. 
     In a capacity control valve of Patent Citation 1, by opening and closing a CS valve to control a fluid of control pressure Pc running from a control chamber of a variable displacement compressor to a suction chamber and bringing a pressure difference between discharge pressure Pd of a discharge chamber and the control pressure Pc of the control chamber respectively applied in the stroke direction of pistons close to a target value, a discharge amount of the fluid discharged from the discharge chamber is changed. A valve opening degree of the CS valve is changed in accordance with electromagnetic force by an electric current applied to a solenoid, and in response to this, the target value of the pressure difference is changed, so that the discharge amount of the fluid discharged from the discharge chamber is changed. 
     In Patent Citation 1, a pressure sensitive portion having a diaphragm is provided in a pressure sensitive chamber of the capacity control valve, and the valve opening degree of the CS valve is adjusted by changing force of the pressure sensitive portion to move a valve element in accordance with suction pressure Ps. The suction fluid of the suction pressure Ps supplied to the pressure sensitive chamber is guided to the back surface side of the valve element via the valve element and a communication passage formed in a shaft and a plunger forming the solenoid, so that an influence of the suction pressure Ps applied on both the sides in the moving direction of the valve element is cancelled. 
     CITATION LIST 
     Patent Literature 
     
         
         Patent Citation 1: JP 2011-94554 A (PAGE 10, FIG. 2) 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     However, in Patent Citation 1, since the influence of the suction pressure Ps is cancelled, a control property of the CS valve is excellent but at the time of opening the CS valve, a pressure receiving area for the control pressure Pc in the valve element is large on the pressure receiving surface side where the control pressure Pc is applied in the valve opening direction. Thus, the control pressure Pc which is higher than the suction pressure Ps is applied to bias the valve element in the valve opening direction, and there is a problem that responsiveness of the capacity control valve is deteriorated. At the time of opening the CS valve, the fluid of the control pressure sometimes runs round to the back surface side of the valve element, and energy efficiency is poor. 
     The present invention is achieved focusing on such problems, and an object thereof is to provide a capacity control valve with which responsiveness can be enhanced. 
     Solution to Problem 
     In order to solve the foregoing problem, a capacity control valve according to the present invention is a capacity control valve including: a valve housing provided with a suction port through which a suction fluid of suction pressure passes, and a control port through which a control fluid of control pressure passes; a valve element configured to be driven by a solenoid; a spring that biases the valve element in a direction opposite to a driving direction of the solenoid; and a CS valve formed by a CS valve seat and the valve element, the CS valve being configured for opening and closing a communication between the control port and the suction port in accordance with a movement of the valve element, wherein the control pressure is controlled in accordance with opening and closing operation of the CS valve, and the capacity control valve further includes communication control means that controls a communication between the control port and a space on a back surface side of the valve element. According to the aforesaid feature of the present invention, by providing communication between the control port and the back surface side of the valve element by the communication control means and supplying the control fluid of the control pressure to the back surface side of the valve element, it is possible to reduce an influence of the control pressure applied to the valve element. Thus, it is possible to enhance responsiveness with respect to control at the time of high output of a variable displacement compressor. Since the communication control means is to control a communication amount of the fluid in accordance with needs, it is possible to reduce a leakage amount of the control fluid. 
     It may be preferable that the space on the back surface side of the valve element communicates with the suction port. According to this preferable configuration, it is possible to let the control fluid of the control pressure supplied to the back surface side of the valve element by the communication control means go to the suction port. 
     It may be preferable that the space on the back surface side of the valve element communicates with the suction port via a throttle. According to this preferable configuration, it is possible to maintain the back surface side of the valve element at pressure which is close to the control pressure. 
     It may be preferable that a guide hole through which the valve element is inserted is formed in the valve housing on the back surface side of the valve element with respect to the suction port. According to this preferable configuration, it is possible to form the throttle by a clearance formed between the valve element and the guide hole of the valve housing. Thus, a structure of the capacity control valve is simplified. 
     It may be preferable that the communication control means is configured to provide communication between the control port and the space on the back surface side of the valve element by an electromagnetic force generated in the solenoid. According to this preferable configuration, by providing communication between the control port and the back surface side of the valve element at the time of applying a high electric current to the solenoid, it is possible to reduce the influence of the control pressure applied to the valve element. Thus, it is possible to enhance the responsiveness with respect to the control at the time of high output of the variable displacement compressor. 
     It may be preferable that the solenoid includes a coil, a plunger, a center post, and a spring arranged between the plunger and the center post, the communication control means is formed by the valve housing in which a through hole passing through in the axial direction is formed, the center post capable of closing an opening end of the through hole, and the plunger, and the center post is be movable toward the plunger by the electromagnetic force generated in the solenoid. According to this preferable configuration, by moving the center post toward the plunger at the time of applying a high electric current to the solenoid, it is possible to open the opening end of the valve housing to provide communication between the control port and the back surface side of the valve element via the through hole. Thus, since it is possible to form the communication control means by utilizing a structure of the solenoid itself, it is possible to simplify the structure of the capacity control valve. 
     It may be preferable that the center post is pushed onto the valve housing by bias means, and the bias means has larger bias force than the spring. According to this preferable configuration, it is possible to move the center post toward the plunger at the time of applying a high electric current to the solenoid, and to stably operate the plunger and the valve element by the electromagnetic force of the solenoid. 
     It may be preferable that the communication control means is a control pressure operated valve that controls the communication between the control port and the space on the back surface side of the valve element by bias means arranged in a through hole which passes through the valve housing in the axial direction, and an operated valve element to be biased in a valve closing direction of the control pressure operated valve by the bias means. According to this preferable configuration, when the control pressure is increased, by opening the control pressure operated valve against bias force of the bias means and providing communication between the control port and the back surface side of the valve element, it is possible to reduce the influence of the control pressure applied to the valve element. Thus, it is possible to enhance the responsiveness with respect to the control at the time of high output of the variable displacement compressor. 
     It may be preferable that a supplementary spring arranged in a control fluid supply chamber which is formed in the valve housing and to which the control fluid is supplied, is provided, the supplementary spring being interlockingly coupled to the valve element. According to this preferable configuration, it is possible to stabilize an action of the valve element. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic configuration diagram showing a swash plate type variable displacement compressor into which a capacity control valve according to a first embodiment of the present invention is assembled. 
         FIG. 2  is a sectional view showing a structure of the capacity control valve according to the first embodiment of the present invention. 
         FIG. 3  is a sectional view in which a major part is enlarged, showing a state where a CS valve is opened in a non-energized state of the capacity control valve according to the first embodiment of the present invention. 
         FIG. 4  is a sectional view showing pressure distribution in  FIG. 3 . In order to show the pressure distribution, sections of members are not shown in the figure. 
         FIG. 5  is a sectional view in which a major part is enlarged, showing a state at the time of applying a high electric current to a solenoid in a case where control pressure in the first embodiment of the present invention is high. 
         FIG. 6  is a view showing pressure distribution in  FIG. 5 . In order to show the pressure distribution, the sections of the members are not shown in the figure. 
         FIG. 7  is a sectional view in which a major part is enlarged, showing a state where the CS valve in the first embodiment of the present invention is closed. 
         FIG. 8  is a view showing pressure distribution in  FIG. 7 . In order to show the pressure distribution, the sections of the members are not shown in the figure. 
         FIG. 9  is a sectional view showing a structure of a capacity control valve according to a second embodiment of the present invention. 
         FIG. 10  is a view showing pressure distribution in a state where a CS valve is opened in a non-energized state of the capacity control valve according to the second embodiment of the present invention. In order to show the pressure distribution, sections of members are not shown in the figure. 
         FIG. 11  is a view showing pressure distribution in a state where the CS valve in the second embodiment of the present invention is closed. In order to show the pressure distribution, the sections of the members are not shown in the figure. 
         FIG. 12  is a sectional view showing a modified example of the capacity control valve according to the first embodiment of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Modes for carrying out a capacity control valve according to the present invention will be described below based on embodiments. 
     First Embodiment 
     A capacity control valve according to a first embodiment of the present invention will be described with reference to  FIGS. 1 to 8 . Hereinafter, description will be given with the left and right sides seen from the front side of  FIG. 2  being the left and right sides of the capacity control valve. 
     A capacity control valve V of the present invention is assembled into a variable displacement compressor M used for an air conditioning system of an automobile, etc. By variably controlling pressure of a working fluid (hereinafter, simply referred to as the “fluid”) serving as a coolant, a discharge amount of the variable displacement compressor M is controlled and the air conditioning system is adjusted to have a target cooling ability. 
     First, the variable displacement compressor M will be described. As shown in  FIG. 1 , the variable displacement compressor M has a casing  1  including a discharge chamber  2 , a suction chamber  3 , a control chamber  4 , and plural cylinders  4   a . A communication passage providing direct communication between the discharge chamber  2  and the control chamber  4  is provided in the variable displacement compressor M. A fixed orifice  9  for adjusting and balancing pressure between the discharge chamber  2  and the control chamber  4  is provided in this communication passage (see  FIG. 2 ). 
     The variable displacement compressor M also includes a rotating shaft  5  to be driven and rotated by an engine (not shown) installed outside the casing  1 , a swash plate  6  coupled to the rotating shaft  5  in an eccentric state by a hinge mechanism  8  in the control chamber  4 , and plural pistons  7  coupled to the swash plate  6  and fitted reciprocatably in the respective cylinders  4   a . With using the capacity control valve V to be driven to open and close by electromagnetic force, a tilt angle of the swash plate  6  is continuously changed by appropriately controlling pressure in the control chamber  4  while utilizing suction pressure Ps of the suction chamber  3  that suctions the fluid, discharge pressure Pd of the discharge chamber  2  that discharges the fluid pressurized by the pistons  7 , and control pressure Pc of the control chamber  4  that houses the swash plate  6 . Thereby, a stroke amount of the pistons  7  is changed to control a discharge amount of the fluid. For convenience of description, the capacity control valve V assembled into the variable displacement compressor M is not shown in  FIG. 1 . 
     Specifically, the higher the control pressure Pc in the control chamber  4  is, the smaller the tilt angle of the swash plate  6  with respect to the rotating shaft  5  becomes, and the more the stroke amount of the pistons  7  is reduced. However, when the pressure becomes fixed pressure or more, the swash plate  6  is brought into a substantially perpendicular state with respect to the rotating shaft  5 , that is, a state where the swash plate  6  is slightly tilted from the exactly perpendicular state. At this time, the stroke amount of the pistons  7  becomes minimum, and pressurization of the fluid in the cylinders  4   a  by the pistons  7  becomes minimum. Therefore, the discharge amount of the fluid to the discharge chamber  2  is reduced, and the cooling ability of the air conditioning system becomes minimum. Meanwhile, the lower the control pressure Pc in the control chamber  4  is, the larger the tilt angle of the swash plate  6  with respect to the rotating shaft  5  becomes, and the more the stroke amount of the pistons  7  is increased. However, when the pressure becomes fixed pressure or less, the tilt angle of the swash plate  6  with respect to the rotating shaft  5  becomes maximum. At this time, the stroke amount of the pistons  7  becomes maximum, and the pressurization of the fluid in the cylinders  4   a  by the pistons  7  becomes maximum. Therefore, the discharge amount of the fluid to the discharge chamber  2  is increased, and the cooling ability of the air conditioning system becomes maximum. 
     As shown in  FIGS. 2 and 3 , the capacity control valve V assembled into the variable displacement compressor M adjusts an electric current energized in a coil  86  forming a solenoid  80  and performs open/close control of a CS valve  50  in the capacity control valve V, so that by controlling the fluid flowing out to the suction chamber  3  from the control chamber  4 , the control pressure Pc in the control chamber  4  is variably controlled. A discharge fluid of the discharge pressure Pd of the discharge chamber  2  is always supplied to the control chamber  4  via the fixed orifice  9 , and the control pressure Pc in the control chamber  4  is increased by closing the CS valve  50  in the capacity control valve V. 
     In the present embodiment, the CS valve  50  is formed by a CS valve element  51  serving as a valve element and a CS valve seat  10   a  formed on an inner peripheral surface of a valve housing  10 . By bringing and separating an axially left end  52   a  of a large diameter portion  52  of the CS valve element  51  into contact with and from the CS valve seat  10   a , the CS valve  50  is opened and closed. 
     Next, a structure of the capacity control valve V will be described. As shown in  FIGS. 2 and 3 , the capacity control valve V is mainly formed by the valve housing  10  made of a metal material or a resin material, the CS valve element  51  whose axially left end portion is arranged in the valve housing  10 , and the solenoid  80  connected to the valve housing  10 , the solenoid that applies drive force to the CS valve element  51 . 
     As shown in  FIGS. 2 and 3 , the CS valve element  51  is formed by the large diameter portion  52  which is a pillar-shaped body having a constant section, a small diameter portion  53  having a smaller diameter than the large diameter portion  52  and extending on the axially left side, and a small diameter portion  54  having a smaller diameter than the large diameter portion  52  and extending on the axially right side, and also serves as a rod arranged to pass through the coil  86  of the solenoid  80 . 
     As shown in  FIGS. 2 and 3 , in the valve housing  10 , a Ps port  11  serving as a suction port which passes through in the radial direction and communicates with the suction chamber  3  of the variable displacement compressor M is formed. On the radially inner side of an axially left end of the valve housing  10 , a recessed portion  10   d  recessed to the axially right side is formed, and by inserting a case body  13  into the recessed portion  10   d  from the axially left side, integrally connected and fixed in a substantially sealed state. A Pc port  12  serving as a control port which communicates with the control chamber  4  of the variable displacement compressor M is formed in this case body  13 , and the inside of the case body  13  serves as a control fluid supply chamber  14  to which a control fluid is supplied via the Pc port  12 . 
     In an axially left end portion of the case body  13 , an axially left end of a supplementary spring  18  that biases in the axial direction is secured, and in an axially right end of the supplementary spring  18 , a ring member  19  to which the small diameter portion  53  of the CS valve element  51  is inserted and fixed is secured. 
     Inside the valve housing  10 , a valve chamber  20  is formed. In the valve chamber  20 , the axially left end  52   a  of the large diameter portion  52  of the CS valve element  51  is arranged reciprocatably in the axial direction. The Ps port  11  extends in the radially inward direction from an outer peripheral surface of the valve housing  10 , and communicates with the valve chamber  20 . The Pc port  12  communicates with the valve chamber  20  via the control fluid supply chamber  14  and a communication passage  15  to be described later. 
     On the inner peripheral surface of the valve housing  10 , the CS valve seat  10   a  is formed at an opening end edge of the communication passage  15  on the valve chamber  20  side, the communication passage providing communication between the control fluid supply chamber  14  and the valve chamber  20 . On the inner peripheral surface of the valve housing  10 , a guide hole  10   b  with which an outer peripheral surface of the CS valve element  51  is slidable is formed on the solenoid  80  side of the CS valve seat  10   a  and the valve chamber  20 . That is, in the valve housing  10 , the CS valve seat  10   a  and the guide hole  10   b  are integrally formed on the inner peripheral surface. Between an inner peripheral surface of the guide hole  10   b  and the outer peripheral surface of the CS valve element  51 , a minute gap is formed by slightly separating in the radial direction. The CS valve element  51  is smoothly movable with respect to the valve housing  10  in the axial direction. 
     In the valve housing  10 , a recessed portion  10   c  in which the radially inner side of an axially right end is recessed to the axially left side is formed, and integrally connected by inserting a flange portion  82   d  of a center post  82  from the axially right side and further fixing a casing  81  from the axially right side. On the radially inner side of a bottom surface of the recessed portion  10   c  of the valve housing  10 , an opening end of the guide hole  10   b  on the solenoid  80  side is formed. 
     In the valve housing  10 , a through hole  21  extending in the axial direction is formed between bottom portions of the recessed portions  10   c ,  10   d  in both axial ends. The valve housing  10  is formed to be capable of providing communication between the control fluid supply chamber  14  and a space S inside the casing  81  of the solenoid  80 , for example, at the time of applying a high electric current. The space S inside the casing  81  communicates with a space in the center post  82 . 
     As shown in  FIGS. 2 and 3 , the solenoid  80  is mainly formed by the casing  81  having an opening portion  81   a  which is open on the axially left side, the substantially cylindrical center post  82  inserted into the opening portion  81   a  of the casing  81  from the axially left side and arranged between the radially inner side of the casing  81  and the radially inner side of the valve housing  10 , the CS valve element  51  inserted into the center post  82  reciprocatably in the axial direction, the CS valve element whose axially left end portion is arranged in the valve housing  10 , a movable iron core  84  serving as a plunger to which an axially right end portion of the CS valve element  51  is inserted and fixed, a coil spring  85  provided between the center post  82  and the movable iron core  84 , the coil spring serving as a spring that biases the movable iron core  84  to the axially right side which is the valve opening direction of the CS valve  50 , and the excitation coil  86  wound on the outside of the center post  82  via a bobbin. 
     A recessed portion  81   b  in which the radially inner side of an axially left end is recessed to the axially right side is formed in the casing  81 , and a wave spring  16  serving as bias means that biases in the axial direction is arranged in this recessed portion  81   b . An annular plate  17  made of a rigid material such as metal is fixed to an axially left end of the wave spring  16 , and the radially inner side of the annular plate  17  extends to the flange portion  82   d  of the center post  82 . Preferably, regarding the center post  82 , the flange portion  82   d  is sandwiched by the annular plate  17  and the bottom portion of the recessed portion  10   c  of the valve housing  10  in a substantially sealed manner in the axial direction. 
     The wave spring  16  has a higher spring constant than the coil spring  85 . Specifically, the wave spring  16  is a spring having a higher spring constant K16 than a spring constant K85 of the coil spring  85  (K16&gt;K85). 
     The center post  82  is formed by a rigid body which is a magnetic material such as iron or silicon steel, and includes a cylindrical portion  82   b  extending in the axial direction, the cylindrical portion where an insertion hole  82   c  into which the CS valve element  51  is inserted is formed, and the annular flange portion  82   d  extending in the radially outward direction from an outer peripheral surface of an axially left end portion of the cylindrical portion  82   b.    
     Next, actions of the capacity control valve V, mainly actions of opening and closing the CS valve  50  will be described. 
     First, a non-energized state of the capacity control valve V will be described. As shown in  FIGS. 2 and 3 , in the capacity control valve V, in a non-energized state, by pressing the movable iron core  84  to the axially right side by bias force of the coil spring  85  and bias force of the supplementary spring  18 , the CS valve element  51  is moved to the axially right side and the axially left end  52   a  of the large diameter portion  52  of the CS valve element  51  is separated from the CS valve seat  10   a , and the CS valve  50  is opened. 
     At this time, to the CS valve element  51 , the bias force F sp1  of the coil spring  85 , the bias force F sp2  of the supplementary spring  18 , and force F P1  by pressure of the fluid to an axially left end surface of the CS valve element  51  are applied to the axially right side, and force F P2  by pressure of the fluid to an axially right end surface of the CS valve element  51  is applied to the axially left side. That is, given that the right side is the positive side, force F rod =F sp1 +F sp2 +F P1 −F P2  is applied to the CS valve element  51 . At the time of opening the CS valve  50 , the force F P1  by the pressure of the fluid to the axially left end surface of the CS valve element  51  is force by the control pressure Pc in the control fluid supply chamber  14  applied to an axially left end of the small diameter portion  53  of the CS valve element  51  and force by pressure of the fluid in the valve chamber  20  applied to the axially left end  52   a  of the large diameter portion  52  of the CS valve element  51 . Meanwhile, the force F P2  by the pressure of the fluid to the axially right end surface of the CS valve element  51  is force by pressure of the fluid running round from the valve chamber  20  to the back surface side of the CS valve element  51  via the gap between the inner peripheral surface of the guide hole  10   b  of the valve housing  10  and the outer peripheral surface of the CS valve element  51 , that is, the fluid existing in the space S of the casing  81 . The force F P1  by the pressure of the fluid to the axially left end surface of this CS valve element  51  is higher than the force F P2  by the pressure of the fluid to the axially right end surface of the CS valve element  51  (i.e., F P1 &gt;F P2 ). 
     As shown in  FIG. 4 , in a non-energized state of the capacity control valve V, the bias force F sp3  of the wave spring  16  and the force F P2  by the pressure of the fluid to the axially right end surface of the CS valve element  51  are applied to the annular plate  17 . By the bias force F sp3  of the wave spring  16  and the force F P2  by the pressure of the fluid to the axially right end surface of the CS valve element  51 , the center post  82  is pushed onto the valve housing  10 , and by this center post  82 , an opening end  21   a  on the axially right side of the through hole  21  of the valve housing  10  (see  FIG. 5 ) is closed in a substantially sealed manner.  FIG. 4  shows pressure distribution immediately after an energized state is turned into a non-energized state by dots, and it is needless to say that the pressure in the capacity control valve V becomes uniform over time. 
     Next, an energized state of the capacity control valve V will be schematically described with reference to  FIG. 7 . As shown in  FIG. 7 , in the capacity control valve V, in an energized state, that is, at the time of normal control, at the time of so-called duty control, when electromagnetic force F sol  generated by applying an electric current to the solenoid  80  exceeds the force F rod  (i.e., F sol &gt;F rod ), by pulling the movable iron core  84  to the axially left side, that is, toward the center post  82 , and moving the CS valve element  51  fixed to the movable iron core  84  to the axially left side together, the axially left end  52   a  of the CS valve element  51  is seated on the CS valve seat  10   a  of the valve housing  10 , and the CS valve  50  is closed. 
     At this time, to the CS valve element  51 , the electromagnetic force F sol  is applied on the axially left side, and the force F rod  is applied on the axially right side. That is, given that the right side is the positive side, force F rod −F sol  is applied to the CS valve element  51 . At the time of closing the CS valve  50 , the force F P1  by the pressure of the fluid to the axially left end surface of the CS valve element  51  is the force by the control pressure Pc of the control fluid of the Pc port  12 . 
     Next, a fully-opened state of the CS valve  50  in a case where the control pressure Pc is high or a case where the control pressure Pc is to be radially increased, that is, a state before a non-energized state of the capacity control valve V is turned into a fully-closed state of the CS valve  50  will be described. Hereinafter, for convenience of description, the force F P1  by the pressure of the fluid to the axially left end surface of the CS valve element  51  will be called as the force F P1  by the pressure of the fluid in the control fluid supply chamber  14  and the valve chamber  20 , and the force F P2  by the pressure of the fluid to the axially right end surface of the CS valve element  51  will be called as the force F P2  by the pressure of the fluid in the space S. 
     In a fully-opened state of the CS valve  50 , when the control pressure Pc is high, force generated by a pressure difference between the force F P1  by the pressure of the fluid in the control fluid supply chamber  14  and the valve chamber  20  and the force F P2  by the pressure of the fluid in the space S is increased, and the force F P1  by the pressure of the fluid in the control fluid supply chamber  14  and the valve chamber  20  is largely applied to the CS valve element  51  to bias to the axially right side, that is, in the valve opening direction. Thus, in order to move the CS valve element  51  to the axially left side, a large electric current to be applied is required. Even in a case where the control pressure Pc is to be radically lowered, in order to move the CS valve element  51  to the axially left side, a large electric current to be applied is also required. 
     As shown in  FIGS. 5 and 6 , when a large electric current is applied to the solenoid  80 , that is, at the time of applying a high electric current to the solenoid  80 , large electromagnetic force F sol  that pulls the center post  82  and the movable iron core  84  to each other is generated between the center post  82  and the movable iron core  84 . When this electromagnetic force F sol  exceeds the bias force F sp3  of the wave spring  16  and the force F P2  by the pressure of the fluid existing in the space S of the casing  81  (i.e., F sol &gt;F sp3 +F P2 ), the center post  82  is moved to the axially right side by the electromagnetic force F sol , and a gap is formed between the bottom portion of the recessed portion  10   c  of the valve housing  10  and an axially left end of the center post  82 . Thereby, the control fluid supply chamber  14  and the space S of the casing  81  communicate with each other via the through hole  21 , the fluid is supplied from the control fluid supply chamber  14  into the space S of the casing  81  through the through hole  21 , and the force generated by the pressure difference between the force F P1  by the pressure of the fluid in the control fluid supply chamber  14  and the valve chamber  20  and the force F P2  by the pressure of the fluid in the space S is reduced. In such a way, the opening end  21   a  on the axially right side of the through hole  21 , the center post  82 , and the movable iron core  84  function as communication control means that control communication between the Pc port  12  and the back surface side of the CS valve element  51 . 
     When the force generated by the pressure difference between the force F P1  by the pressure of the fluid in the control fluid supply chamber  14  and the valve chamber  20  and the force F P2  by the pressure of the fluid in the space S is reduced, and since, as described above, the wave spring  16  is the spring having the higher spring constant K16 than the spring constant K85 of the coil spring  85  (i.e., K16&gt;K85), the bias force F sp3  of the wave spring  16  is dominantly applied. As shown in  FIGS. 7 and 8 , the center post  82  is pushed back to the axially left side, the coil spring  85  is contracted, the movable iron core  84  and the CS valve element  51  are moved to the axially left side together, the axially left end  52   a  of the large diameter portion  52  of the CS valve element  51  is seated on the CS valve seat  10   a , and the CS valve  50  is closed. Since the force generated by the pressure difference between the force F P1  by the pressure of the fluid in the control fluid supply chamber  14  and the valve chamber  20  and the force F P2  by the pressure of the fluid in the space S is small, an influence on the CS valve element  51  by the force F P1  by the pressure of the fluid in the control fluid supply chamber  14  and the valve chamber  20  is reduced, and it is possible to smoothly operate the CS valve element  51  to the axially left side, that is, in the valve closing direction. 
     According to this, by moving the center post  82  in the axial direction, it is possible to provide communication between the Pc port  12  and the back surface side of the CS valve element  51 , that is, the space S of the casing  81 , supply the control fluid in the control fluid supply chamber  14  to the back surface side of the CS valve element  51 , and reduce an influence of the pressure of the fluid applied in the valve opening direction of the CS valve element  51 . Thus, it is possible to smoothly operate the CS valve element  51  in the valve closing direction, and enhance responsiveness with respect to control at the time of high output of the variable displacement compressor M. 
     The center post  82  is operated to open the through hole  21  in accordance with the pressure difference between the pressure of the fluid in the space S and the pressure of the fluid in the valve chamber  20 . Thus, it is possible to supply the control fluid in the control fluid supply chamber  14  into the space S of the casing  81  in accordance with needs, and adjust an opening degree of the CS valve  50  with high precision. In other words, when a pressure difference between the control pressure and the suction pressure is small, the force generated by the pressure difference applied to the CS valve element  51  is permitted. Meanwhile, in a case where the pressure difference between the control pressure and the suction pressure is large, it is possible to cancel the force generated by the pressure difference applied to the CS valve element  51 . Thus, it is possible to obtain both control precision of the CS valve element  51  and reduction in a leakage amount of the fluid. 
     The space S of the casing  81  communicates with the Ps port  11 , and it is possible to let the control fluid in the control fluid supply chamber  14  supplied to the space S of the casing  81  through the through hole  21  go to the Ps port  11 . In such a way, it is possible to let the fluid go by utilizing the existing Ps port  11 . Thus, it is possible to simplify the structure of the capacity control valve V. 
     The space S of the casing  81  communicates the Ps port  11  via a throttle. Specifically, the minute gap between the inner peripheral surface of the guide hole  10   b  and the outer peripheral surface of the CS valve element  51  functions as a throttle OR. It is possible to let the fluid in the space S of the casing  81  slowly go to the Ps port  11 , and maintain a state where the pressure difference between the pressure of the fluid in the valve chamber  20  and the pressure of the fluid in the space S of the casing  81  is small. 
     The minute gap between the inner peripheral surface of the guide hole  10   b  and the outer peripheral surface of the CS valve element  51  is utilized as the throttle OR. Thus, there is no need for preparing a different member as a throttle, and it is possible to simplify the structure of the capacity control valve V. 
     By the electromagnetic force generated between the center post  82  and the movable iron core  84  at the time of applying a high electric current to the solenoid  80 , the center post  82  is moved to the movable iron core  84  side, and the opening end  21   a  of the through hole  21  is opened, so that the control fluid supply chamber  14  and the space S of the casing  81  communicate with each other. Thus, it is possible to form the communication control means by utilizing a structure of the solenoid  80  itself, and simplify the structure of the capacity control valve V. 
     The center post  82  is pushed onto the valve housing  10  by the wave spring  16 , and the bias force of the wave spring  16  is larger than the coil spring  85 . Thus, it is possible to move the center post  82  toward the movable iron core  84  at the time of applying a high electric current to the solenoid  80 . At the time of applying a low electric current to the solenoid  80 , or when unintended external force to the axially right side is applied to the center post  82 , it is possible to inhibit the center post  82  from moving. 
     The CS valve element  51  is biased in the axial direction by the coil spring  85  and the supplementary spring  18  on both the sides in the axial direction. Thus, an action of the CS valve element  51  in the axial direction is stabilized. Before the case body  13  is fixed to the valve housing  10 , it is possible to adjust the bias force of the supplementary spring  18  applied to the CS valve element  51 . When one of the coil spring  85  and the supplementary spring  18  is provided, the other configuration may be omitted. 
     The CS valve seat  10   a  and the guide hole  10   b  are integrally formed in the valve housing  10 . Thus, it is possible to enhance precision of an action of the CS valve element  51 . 
     In the present embodiment, the example in which the annular plate  17  has rigidity so that the annular plate is hardly deformed at the time of moving the center post  82  is described. However, the annular plate may have elasticity so that the annular plate is curved at the time of moving the center post  82 . 
     As long as the wave spring  16  can be brought into direct contact with the center post  82 , the configuration of the annular plate  17  may be omitted. 
     Second Embodiment 
     A capacity control valve according to a second embodiment of the present invention will be described with reference to  FIGS. 9 to 11 . Duplicated description for the same configurations as the first embodiment is omitted.  FIGS. 9 and 10  show states where control pressure Pc in a control fluid supply chamber  14  is low, and  FIG. 11  shows a state where the control pressure Pc in the control fluid supply chamber  14  is high. 
     As shown in  FIGS. 9 to 11 , in the second embodiment of the present embodiment, a through hole  210  formed in a valve housing  110  is formed by a small diameter hole portion  211  whose axial left end communicates with the control fluid supply chamber  14 , and a large diameter hole portion  212  continuing from an axial right end of the small diameter hole portion  211  and having a larger diameter than the small diameter hole portion  211 . An axial right end of the large diameter hole portion  212  is closed in a substantially sealed manner by a center post  821  sandwiched by the valve housing  110  and a casing  811  in the axial direction and fixed in a substantially sealed manner. In the present embodiment, the center post  821  may be fixed to the valve housing  110  or the casing  811  by bonding or welding. 
     In the large diameter hole portion  212  of the through hole  210 , a ball-shaped operated valve element  31 , and a return spring  32  serving as bias means whose axial right end is fixed to the center post  82  and whose axial left end is abutted with the operated valve element  31  are arranged. The operated valve element  31  and the return spring  32  form a control pressure operated valve  30  that controls communication between the control fluid supply chamber  14  and a space S of the casing  811 . 
     As shown in  FIG. 10 , in a state where the control pressure Pc in the control fluid supply chamber  14  is low, by biasing the operated valve element  31  to the axially left side by the return spring  32  and seating on an opening end of the small diameter hole portion  211  of the through hole  210 , the control pressure operated valve  30  is closed and the control fluid supply chamber  14  and the space S inside the casing  811  are brought into a non-communication state. 
     At this time, force F P11  by the control pressure Pc in the control fluid supply chamber  14  is applied to the axially right side, and bias force F sp11  of the return spring  32  and force F P12  by pressure of the fluid in the space S are applied to the axially left side (i.e., F P11 &lt;F sp11 +F P12 ). 
     As shown in  FIG. 11 , in a state where the control pressure Pc in the control fluid supply chamber  14  is high, by moving the operated valve element  31  to the axially right side against the bias force of the return spring  32  and the force F P12  by the pressure of the fluid in the space S, the control pressure operated valve  30  is opened, and the control fluid supply chamber  14  and the space S inside the casing  811  are brought into a communication state. 
     At this time, to the operated valve element  31 , the force F P11  by the control pressure Pc in the control fluid supply chamber  14 , the force exceeding the bias force F sp11  of the return spring  32  and the force F P12  by the pressure of the fluid in the space S is applied to the axially right side (i.e., F P11 &gt;F sp11 +F P12 ). 
     As in the state of  FIG. 11 , when the control pressure operated valve  30  is opened and the control fluid supply chamber  14  and the space S of the casing  811  are brought into a communication state, a pressure difference of the fluid between the control fluid supply chamber  14  and the space S of the casing  811  is reduced. Thus, an influence on a CS valve element  51  by force F P1  by pressure of the fluid in the control fluid supply chamber  14  and a valve chamber  20  is reduced, and it is possible to smoothly operate the CS valve element  51  to the axially left side, that is, in the valve closing direction. 
     In such a way, when the control pressure Pc in the control fluid supply chamber  14  is increased, by operating the operated valve element  31  against the bias force of the return spring  32  and opening the control pressure operated valve  30  so as to provide communication between a Pc port  12  and the space S of the casing  811 , it is possible to reduce the influence of the pressure of the fluid in the valve chamber  20  applied to the CS valve element  51 . Thus, it is possible to enhance responsiveness with respect to control at the time of high output of a variable displacement compressor M. 
     It is possible to let the fluid in the space S of the casing  811  slowly go to a Ps port  11  from a minute gap between an inner peripheral surface of a guide hole  10   b  and an outer peripheral surface of the CS valve element  51 . Thus, it is possible to maintain a state where the control pressure operated valve  30  is opened. Specifically, it is possible to avoid that the pressure of the fluid in the space S of the casing  811  is radically increased and the control pressure operated valve  30  is immediately closed. 
     Next, a modified example of the capacity control valve according to the first embodiment of the present invention will be described. As in a capacity control valve V′ of the present modified example shown in  FIG. 12 , the configurations of the case body  13 , the supplementary spring  18 , and the ring member  19  of the first embodiment may be omitted. In this case, the recessed portion  10   d  of the valve housing  10  also serves as the Pc port and the control fluid supply chamber  14 . In such a way, even when the configurations of the case body  13 , the supplementary spring  18 , and the ring member  19  are omitted, it is possible to bias the CS valve element  51  to the axially right side by a coil spring  85 . 
     The embodiments of the present invention are described above with the drawings. However, specific configurations are not limited to these embodiments but the present invention includes changes and additions within the range not departing from the scope of the present invention. 
     For example, the first and second embodiments describe the mode that the Ps port  11  communicates with the space S which is the back surface side of the CS valve element  51  via the throttle OR which is the minute gap between the inner peripheral surface of the guide hole  10   b  and the outer peripheral surface of the CS valve element  51 . However, the present invention is not limited to this but the back surface side of the CS valve element  51  and the Ps port  11  may communicate with each other with a large opening, and a throttle member such as an orifice may be provided in the opening. Communication may be provided by not providing a throttle between the back surface side of the CS valve element  51  and the Ps port  11  but with a large opening. 
     The first embodiment describes the mode that the control fluid supply chamber  14  and the space S communicate with each other by operating the center post  82  by the electromagnetic force of the solenoid  80 . However, the present invention is not limited to this but the control fluid supply chamber  14  and the space S may communicate with each other by operating a member different from the center post  82  by the electromagnetic force of the solenoid. 
     The first and second embodiments describe the mode that the CS valve element also serves as the rod arranged to pass through the coil  86  of the solenoid  80 . However, the present invention is not limited to this but the CS valve element may be formed reciprocatably in the axial direction together with a separate rod. 
     The first and second embodiments describe that the CS valve seat and the guide hole are integrally formed on the inner peripheral surface of the valve housing. However, the present invention is not limited to this but a valve housing having a CS valve seat and a valve housing having a guide hole may be separately provided. 
     A guide portion is not limited to be formed in the valve housing but may be formed in part of the insertion hole  82   c  of the center post  82 , for example. 
     REFERENCE SIGNS LIST 
     
         
         
           
               1  Casing 
               2  Discharge chamber 
               3  Suction chamber 
               4  Control chamber 
               5  Valve housing 
               10   a  CS valve seat 
               11  Ps port 
               12  Pc port 
               13  Case body 
               14  Control fluid supply chamber 
               16  Wave spring (bias means) 
               18  Supplementary spring 
               20  Valve chamber 
               21  Through hole (communication control means) 
               21   a  Opening end 
               30  Control pressure operated valve 
               31  Operated valve element 
               32  Return spring (bias means) 
               50  CS valve 
               51  CS valve element (valve element) 
               80  Solenoid 
               81  Casing 
               82  Center post (communication control means) 
               84  Movable iron core (communication control means, plunger) 
               85  Coil spring (spring) 
               110  Valve housing 
               210  Through hole (communication control means) 
             M Variable displacement compressor 
             OR Throttle 
             Pc Control pressure 
             Pd Discharge pressure 
             Ps Suction pressure 
             S Space 
             V Capacity control valve