Control valve for variable displacement compressor

Abstract

To provide a control valve for a variable displacement compressor, based on a Pd−Ps differential pressure control method, which is capable of setting characteristics concerning the degree of influence of crank pressure on a change in the differential pressure between discharge pressure and suction pressure, to desired characteristics with ease. A control valve for a variable displacement compressor adjusts the difference between an effective pressure-receiving area A on a discharge pressure side of an intermediate in which a valve element and a shaft are integral with each other and an effective pressure-receiving area B on a suction pressure side of the intermediate, as required. This makes it possible to obtain desired differential pressure·crank pressure characteristics according to the specifications of the control valve. Changes in the effective pressure-receiving areas have almost no influence on electric current·differential pressure characteristics, i.e. the relationship between the value of electric current supplied to a solenoid and the differential pressure between discharge pressure and suction pressure, and hence it is possible to realize the changes in the effective pressure-receiving areas with ease.

1 . A control valve for a variable displacement compressor, the control valve being mounted in the variable displacement compressor, for controlling pressure in a crankcase of the compressor to thereby vary a discharge capacity of refrigerant, comprising: 
 a body that has a discharge pressure port for introducing discharge pressure of the compressor, a crank pressure port for delivering crank pressure generated in the control valve to the crankcase, and a suction pressure port for introducing suction pressure, the discharge pressure port, the crank pressure port, and the suction pressure port being sequentially arranged from one end of the body;    a valve element that is moved to and away from a valve seat provided between the discharge pressure port and the crank pressure port, for reducing the discharge pressure introduced from the discharge pressure port by a restriction passage formed between the valve element and the valve seat to generate the crank pressure;    a shaft that supports the valve element in a valve-opening or valve-closing direction and is capable of operating in unison with the valve element; and    a solenoid that is connected to an end of the body opposite to the discharge pressure port, and comprises a core, a plunger capable of being made integral with the valve element via the shaft, and a solenoid coil for being energized to generate a magnetic circuit including the plunger and the core,    wherein a degree of influence of the crank pressure on a change in differential pressure between the discharge pressure and the suction pressure is adjusted by adjusting a difference between an effective pressure-receiving area of an intermediate for receiving the discharge pressure, the intermediate being formed by making the valve element and the shaft integral with each other, and an effective pressure-receiving area of the intermediate for receiving the suction pressure.    
   
   
       2 . The control valve according to  claim 1 , wherein a crankcase-communicating chamber filled with the generated crank pressure and having the valve element disposed therein is defined between the valve seat and the crank pressure port of the body, 
 wherein a guide hole is formed in the body on a side opposite to the discharge pressure port in a manner coaxial with a valve hole defining the valve seat, the guide hole opening into the crankcase-communicating chamber and having the shaft inserted therein for guiding the shaft,    wherein the shaft is configured to receive the suction pressure on a side of the guide hole opposite to the crankcase-communicating chamber,    wherein the effective pressure-receiving area of the intermediate for receiving the discharge pressure is adjusted by a size of a cross-sectional area of the valve hole, and    wherein the effective pressure-receiving area of the intermediate for receiving the suction pressure is adjusted by a size of a cross-sectional area of the guide hole.    
   
   
       3 . The control valve according to  claim 2 , wherein the effective pressure-receiving area of the intermediate for receiving the discharge pressure is configured to be larger than the effective pressure-receiving area of the intermediate for receiving the suction pressure, whereby the degree of the influence of the crank pressure on the change in the differential pressure between the discharge pressure and the suction pressure is made larger than when the two effective pressure-receiving areas are equal to each other.  
   
   
       4 . The control valve according to  claim 2 , wherein the effective pressure-receiving area of the intermediate for receiving the discharge pressure is configured to be smaller than the effective pressure-receiving area of the intermediate for receiving the suction pressure, whereby the degree of the influence of the crank pressure on the change in the differential pressure between the discharge pressure and the suction pressure is made smaller than when the two effective pressure-receiving areas are equal to each other.