Capacity control system for variable capacity compressor and display device for the system

A capacity control system for a variable capacity compressor whose capacity varies with change in control pressure, the variable capacity compressor being inserted, together with a heat radiator, an expansion device and an evaporator, in a circulation path for circulating a refrigerant, to constitute a refrigeration cycle of an air conditioning system, the capacity control system comprising:

• a capacity control valve having a valve element applied with a discharge pressure, which is a pressure of the refrigerant at any portion in a discharge pressure region of the refrigeration cycle, with a suction pressure, which is a pressure of the refrigerant at any portion in a suction pressure region of the refrigeration cycle, and with an electromagnetic force of a solenoid in such a manner that the discharge pressure is countered by the suction pressure and the electromagnetic force, the valve element being capable of opening and closing a valve hole to vary the control pressure and thereby adjust the capacity of the variable capacity compressor;
• external information detection means for detecting one or more items of external information related to the refrigeration cycle;
• and
• target suction pressure setting means for setting, based on the external information detected by the external information detection means, a target suction pressure for controlling the pressure in the suction pressure region as a control target;
• wherein an opening of the capacity control valve is varied in accordance with the external information detected by the external information detection means, to vary the control pressure and thereby adjust the refrigerant discharge capacity of the variable capacity compressor;
• discharge pressure calculation means for calculating, based on the external information detected by the external information detection means, the pressure in the discharge pressure region of the variable capacity compressor;
• control signal calculation means for calculating a discharge capacity control signal based on the pressure of the discharge pressure region calculated by the discharge pressure calculation means and the target suction pressure set by the target suction pressure setting means;
• solenoid driving means for supplying an electric current to the solenoid of the capacity control valve in accordance with the discharge capacity control signal calculated by the control signal calculation means;
• a suction pressure estimation means for estimating, based on the external information detected by the external information means, a pressure that is estimated to prevail in the suction pressure region if the variable capacity compressor is operated with a maximum discharge capacity;
• discharge capacity determination means for determining, based on the estimated pressure of the suction pressure region estimated by the suction pressure estimation means and the target suction pressure set by the target suction pressure setting means, whether the variable capacity compressor is operating with the maximum discharge capacity or with a controlled discharge capacity;
• and
• drive load calculation means for calculating a drive load of the variable capacity compressor.