Control system for variable displacement compressor

A control system for use in a variable displacement compressor of a refrigerant circuit in an air conditioner, the compressor compressing refrigerant by rotation of a drive shaft of the compressor, while displacement of the compressor is variable, the control system comprising:

• a control valve including:
• a valve body;
• a pressure sensing means for mechanically detecting at least one pressure of plural kinds of pressure in the refrigerant circuit, the pressure sensing means moving the valve body in such a manner that the displacement of the compressor is varied to cancel variation of a detected pressure detected by the pressure sensing means;
• and
• a varying means for varying a reference value for positioning the valve body by the pressure sensing means;
• a pressure detector for electrically detecting the pressure detected by the pressure sensing means in the refrigerant circuit and/or physical quantity which correlates with the pressure detected by the pressure sensing means in the refrigerant circuit;
• a calculator for calculating a limit value based upon information detected by the pressure detector, wherein the limit value is a variation limit of urging force applied to the valve body by the varying means toward an increasing side of the displacement of the compressor;
• and
• a controller for controlling the varying means in such a manner that the urging force applied to the valve body does not exceed the limit value toward the increasing side of the displacement of the compressor, wherein the displacement of the compressor is maximized by the pressure sensing means under the pressure when the varying means applies urging force of the limit value to the valve body.