Compression capacity control device for refrigeration cycle

Abstract

In a compression capacity control device for a refrigeration cycle including a variable displacement compressor that compresses refrigerant sucked from a suction chamber communicating with a suction line, and discharges the refrigerant into a discharge chamber communicating with a discharge line, while varying the delivery quantity of the refrigerant by changing pressure in a pressure-regulating chamber which has the pressure therein controlled by an electromagnetic control valve, the electromagnetic control valve arranged between the discharge chamber and the pressure-regulating chamber is held in an open state to place the variable displacement compressor in a state with the minimum delivery quantity within a variable range, when the electromagnetic control valve is in a deenergized state. This makes it possible to dispense with a clutch for inhibiting operation of the compressor, thereby largely reducing the device cost.

What is claimed is:  
     
         1 . A compression capacity control device for a refrigeration cycle including a variable displacement compressor that compresses refrigerant sucked from a suction chamber communicating with a suction line, and discharges the refrigerant into a discharge chamber communicating with a discharge line, while varying a delivery quantity of the refrigerant by changing pressure in a pressure-regulating chamber, the pressure in the pressure-regulating chamber being controlled by an electromagnetic control valve, 
 wherein the compression capacity control device is configured to place the variable displacement compressor in a state with a minimum delivery quantity within a variable range, when the electromagnetic control valve is in a deenergized state.    
     
     
         2 . The compression capacity control device according to  claim 1 , wherein the electromagnetic control valve opens and closes communication between the pressure-regulating chamber and the discharge chamber such that differential pressure between pressure in the discharge chamber and at least one of pressure in the pressure-regulating chamber and pressure in the suction chamber is held at a predetermined differential pressure, and wherein an electromagnetic force of the electromagnetic control valve is changed to thereby change the differential pressure to change the pressure in the pressure-regulating chamber, whereby the delivery quantity of the refrigerant is controlled.  
     
     
         3 . The compression capacity control device according to  claim 1 , wherein urging means is arranged for holding the electromagnetic control valve in an open state when the electromagnetic control valve is in the deenergized state, whereby by holding the electromagnetic control valve in the open state, the variable displacement compressor is placed in the state with the minimum delivery quantity within the variable range.  
     
     
         4 . The compression capacity control device according to  claim 1 , wherein a suction line opening/closing valve is arranged for closing communication between the suction line and the suction chamber when the differential pressure between the pressure in the discharge chamber and the pressure in the suction chamber becomes equal to or smaller than a predetermined value.