Displacement control system for variable displacement compressor

A displacement control system for a variable displacement compressor, which is interposed in a circulation path circulating a refrigerant therethrough, together with a radiator, an expansion device, and an evaporator to configure a refrigeration cycle, and changes displacement according to a change in control pressure, comprising:

• an electromagnetic clutch that includes a coil and connects between the compressor and a power source when the coil is supplied with current;
• a displacement control valve including a valve body that is applied with pressure of a discharge pressure region of the variable displacement compressor and applied with pressure of a suction pressure region of the variable displacement compressor and an electromagnetic force of a solenoid unit in an opposite direction to the pressure of the discharge pressure region, and biasing means that biases the valve body in the same direction as the electromagnetic force, and changes the control pressure by operating the valve body;
• external-information detecting means for detecting at least one piece of external information;
• means for adjusting current for an electromagnetic clutch, which adjusts current supplied to the coil of the electromagnetic clutch according to the external information detected by the external-information detecting means;
• and
• means for adjusting current for the displacement control valve, which adjusts current supplied to a coil of the solenoid unit according to the external information detected by the external-information detecting means.