Importance

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Abstract

A control device is disclosed for controlling the operation of a variable displacement compressor in an air conditioning or refrigerating system. The compressor includes a variable displacement device for changing the cooling capacity of the compressor and a magnetic clutch which operates the compressor in response to an external drive mechanism. The control device controls the operation of the magnetic clutch in response to a comparison of the temperature of the cool air generated by the evaporator of the air conditioning system and a first predetermined temperature. When the temperature is above the first predetermined temperature, the compressor is operated to lower the temperature. The control device also controls the operation of the variable displacement device in the compressor. The control device operates to increase the cooling capacity of the compressor in response to a comparison of the temperature of the cool air with a second predetermined temperature. A temperature of the cool air higher than the second predetermined temperature indicates that the cooling capacity of the compressor is insufficient to satisfy the required cooling load and cooling capacity is increased. The control operates to decrease the cooling capacity of the compressor in response to a comparison of the rate of operation of the compressor with a predetermined ideal rate of operation. As a result, the compressor operates at the minimum cooling capacity required to satisfy the cooling load.

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First Claim