Variable Displacement Compressor

Abstract

Disclosed is a variable displacement compressor provided with a displacement control valve capable of easily adjusting an optimum level the sensitivity to a rise in the pressure in a crank chamber. The variable displacement compressor is configured in such a manner that the stroke of a piston is adjusted by changing the pressure in the crank chamber, the pressure in the crank chamber being changed by adjusting the degree of opening of the displacement control valve for opening and closing a path for communicating between a discharge chamber and the crank chamber, wherein the displacement control valve is provided with a valve chamber communicating with the discharge chamber, a valve hole, a valve element for opening and closing the valve hole, a pressure sensing chamber communicating with a suction chamber, a pressure sensing member disposed in the pressure sensing chamber, and a pressure sensing rod having one end connected to the pressure sensing member and the other end connected to the valve element and driving the valve element in response to displacement of the pressure sensing member. The pressure in the crank chamber acts on the valve element from the valve hole side in the direction of opening of the valve element, and acts on the pressure sensing rod from the valve hole side in the direction of closing of the valve element. That area (Sr) of the pressure sensing rod which receives the pressure in the crank chamber is set to be greater than that area (Sv) of the valve element which receives the pressure in the crank chamber.

1 . A variable displacement compressor having a housing in which a discharge chamber, a suction chamber, a crank chamber and cylinder bores are defined therein, pistons inserted into said cylinder bores, a drive shaft supported rotatably in said housing, a motion converting mechanism including a swash plate element capable of being changed with inclination angle for converting a rotation of said drive shaft into a reciprocating motion of said pistons, a displacement control valve for opening and closing a gas supplying path communicating between said discharge chamber and said crank chamber, and a throttle element disposed in a gas bleeding path communicating between said crank chamber and said suction chamber, which adjusts a stroke of said reciprocating motion of said pistons by varying a pressure in said crank chamber by adjusting a degree of opening of said displacement control valve, and which, by said reciprocating motion of said pistons, sucks refrigerant from said suction chamber into said cylinder bores, compresses sucked refrigerant and discharges compressed refrigerant into said discharge chamber, characterized in that:
 said displacement control valve is provided with a valve chamber communicating with said discharge chamber, a valve hole having one end communicating with said valve chamber and the other end communicating with said crank chamber, a valve seat formed around said valve hole so as to be confronted to said valve chamber, a valve element disposed in said valve chamber for opening and closing said valve hole by being brought apart from and into contact with said valve seat, a pressure sensing chamber communicating with said suction chamber, a pressure sensing member disposed in said pressure sensing chamber and displaced in response to a pressure in said suction chamber, and a pressure sensing rod having one end connected to said pressure sensing member and the other end connected to said valve element from said valve hole side and driving said valve element in response to displacement of said pressure sensing member; and   a pressure in said crank chamber acts on said valve element from said valve hole side in a direction of opening of said valve element, and acts on said pressure sensing rod from said valve hole side in a direction of closing of said valve element, and when a pressure receiving area of said pressure sensing rod which receives a pressure in said crank chamber is represented by “Sr” and a pressure receiving area of said valve element which receives a pressure in said crank chamber is represented by “Sv”, Sr and Sv are set so as to satisfy Sr>Sv.   
     
     
         2 . The variable displacement compressor according to  claim 1 , wherein a pressure in said discharge chamber acts on said valve element in a direction of closing of said valve element, and when a pressure receiving area of said pressure sensing member which receives a pressure in said suction chamber is represented by “Sb”, Sr, Sv and Sb are set so as to satisfy Sb+Sv>2Sr. 
     
     
         3 . The variable displacement compressor according to  claim 1 , wherein said displacement control valve further has a pressure chamber communicating with said suction chamber, said valve element is configured so that one end of said valve element opens and closes said valve hole by being brought apart from and into contact with said valve seat, and the other end of said valve element is disposed in said pressure chamber and a pressure in said suction chamber acts thereon in a direction of closing of said valve element, and when a pressure receiving area of said pressure sensing member which receives a pressure in said suction chamber is represented by “Sb” and a pressure receiving area of said valve element which receives a pressure in said suction chamber is represented by “Sp”, Sr, Sv, Sp and Sb are set so as to satisfy Sb+Sp+Sv>2Sr. 
     
     
         4 . The variable displacement compressor according to  claim 3 , wherein Sp and Sv are set so as to satisfy Sp>Sv. 
     
     
         5 . The variable displacement compressor according to  claim 1 , wherein said throttle element disposed in said gas bleeding path is an orifice fixed with opening degree. 
     
     
         6 . The variable displacement compressor according to  claim 1 , wherein said variable displacement compressor is a compressor provided in a refrigeration circuit for an air conditioning system for vehicles.