Control valve for clutch type variable displacement compressor

Abstract

A control valve for a clutch type variable displacement compressor includes a liquid-discharge passage for connecting a second port in communication with a control-pressure chamber of the compressor to a third port in communication with the suction-pressure region of the compressor. Opening and closing the liquid-discharge passage are controlled by movement of a pressure-sensing member of a pressure-sensing mechanism. The pressure-sensing member is placed such that the liquid-discharge passage is opened while pressure equalization inside the compressor at a stop of the compressor is maintained in starting the compressor from its stop state. The pressure-sensing member is moved in a direction which causes the liquid-discharge passage to be closed when a pressure in the suction-pressure region is lowered and reaches a predetermined pressure as the compressor is started.

1 . A control valve for a clutch type variable displacement compressor having a control-pressure chamber, a discharge-pressure region and a suction-pressure region, comprising: 
 a first port in communication with the discharge-pressure region;    a second port in communication with the control-pressure chamber;    a third port in communication with the suction-pressure region;    a refrigerant-supply passage for connecting the first port to the second port;    a valve body operable to open and close the refrigerant-supply passage;    a pressure-sensing mechanism operable to control the valve body according to a pressure in the suction-pressure region, the pressure-sensing mechanism including a pressure-sensing member;    a rod operable to move the valve body for opening and closing the refrigerant-supply passage; and    a liquid-discharge passage for connecting the second port to the third port, opening and closing the liquid-discharge passage being controlled by movement of the pressure-sensing member,    wherein the pressure-sensing member is placed such that the liquid-discharge passage is opened while pressure equalization inside the compressor at a stop of the compressor is maintained in starting the compressor from its stop state, the pressure-sensing member being moved in a direction which causes the liquid-discharge passage to be closed when a pressure in the suction-pressure region is lowered and reaches a predetermined pressure as the compressor is started.    
   
   
       2 . The control valve according to  claim 1 , wherein the liquid-discharge passage includes a recess formed in a lateral surface of the rod.  
   
   
       3 . The control valve according to  claim 1 , wherein the liquid-discharge passage includes a through hole extending through the rod.  
   
   
       4 . The control valve according to  claim 1 , wherein the pressure-sensing member is a bellows expandable and contractible according to the pressure in the suction-pressure region.  
   
   
       5 . The control valve according to  claim 1 , further comprising a valve housing that defines therein a valve chamber in communication with the first port, a communication chamber in communication with one of the second and third ports and a pressure-sensing chamber in communication with the other of the second and third ports.  
   
   
       6 . The control valve according to  claim 5 , wherein the pressure-sensing mechanism is disposed in the pressure-sensing chamber.  
   
   
       7 . The control valve according to  claim 5 , wherein the valve body is disposed in the valve chamber.  
   
   
       8 . The control valve according to  claim 5 , wherein the liquid-discharge passage includes the communication chamber and the pressure-sensing chamber.  
   
   
       9 . The control valve according to  claim 5 , wherein the communication chamber is located between the valve chamber and the pressure-sensing chamber.  
   
   
       10 . The control valve according to  claim 5 , wherein the valve chamber is located between the communication chamber and the pressure-sensing chamber.  
   
   
       11 . The control valve according to  claim 1 , wherein the rod has a large-diameter portion and a small-diameter portion, the valve body being provided by a step formed between the large-diameter portion and the small-diameter portion.