Capacity control valve for variable displacement compressor

Abstract

To provide a capacity control valve for a variable displacement compressor of a Pd-Ps differential pressure-controlled type, which suppresses overshooting of the differential pressure between the discharge pressure Pd and the suction pressure Ps which can occur when the differential pressure is changed in response to a stepwise change in the solenoid current. The capacity control valve includes a valve section having a Pd-Pc valve for control of the flow rate of refrigerant flowing from a discharge chamber to a crankcase and a Pc-Ps valve for control of the flow rate of refrigerant flowing from the crankcase to a suction chamber operating in a manner interlocked with the Pd-Pc valve. A spool valve element is provided on a valve element of the Pc-Ps valve, whereby in a stroke region where the Pd-Pc valve is toward the fully-closed position, refrigerant is allowed to pass through the clearance between the spool valve element and the valve hole of the Pc-Ps valve, to cause the Pc-Ps valve to have a characteristic that the opening area thereof does not change in response to a change in stroke. This makes it possible to suppress sharp changes in the pressure Pc in the crankcase due to the existence of the clearance, even if the solenoid current is stepwise sharply changed.

1 . A capacity control valve for a variable displacement compressor, for controlling pressure in a crankcase to thereby vary discharging capacity of the variable displacement compressor such that differential pressure between pressure in a suction chamber and pressure in a discharge chamber is held at a predetermined differential pressure, comprising: 
 a first control valve for controlling a flow rate of refrigerant flowing into the crankcase from the discharge chamber;    a second control valve for controlling a flow rate of refrigerant flowing out of the crankcase into the suction chamber, the second control valve having flow rate-restricting means operable to provide an opening area which does not change in the case where the second control valve is moved more than a predetermined value of stroke amount when the second control valve is moved in an opening area-increasing direction in a manner interlocked with operation of the first control valve; and    a solenoid section for applying a solenoid force corresponding to the predetermined differential pressure to the first control valve and the second control valve.    
   
   
       2 . The capacity control valve according to  claim 1 , wherein the flow rate-restricting means comprises a spool valve element provided on a valve element of the second control valve to form a clearance between the spool valve element and a valve hole such that an opening area of the clearance does not change.  
   
   
       3 . The capacity control valve according to  claim 1 , wherein the flow rate-restricting means is an orifice provided on a downstream side of the second control valve.  
   
   
       4 . The capacity control valve according to  claim 1 , comprising a passage communicating between a space connected to the crankcase and an inside of the solenoid section, and 
 wherein the second control valve causes the pressure in the crankcase introduced via the passage into the solenoid section to be received by a valve element thereof in a valve-opening direction, to thereby cancel out the pressure in the crankcase received by the valve element in a valve-closing direction.    
   
   
       5 . The capacity control valve according to  claim 4 , wherein a pressure-receiving area of the second control valve obtained by subtracting an area where the pressure in the crankcase is received via the solenoid section from an opening area of a valve hole of the second control valve is set equal to an opening area of a valve hole of the first control valve.