Capacity control device for controlling a variable displacement

Abstract

A capacity control device for a variable displacement compressor in a refrigerating or air conditioning system is disclosed. The capacity control device controls the operation of a variable displacement device having two variable displacement valves for changing the capacity of the compressor as a function of the required refrigerating capacity of the air conditioning system. The capacity control device determines whether the compressor should operate at a high, medium or low capacity. If the required refrigerating capacity is smaller than the current capacity of the compressor, the capacity control device actuates the variable displacement device to enable the compressor to operate at a lower capacity. If the required refrigerating capacity is larger than the current capacity of the compressor, the capacity control device actuates the variable displacement device to enable the compressor to operate at a larger capacity. The capacity control device includes a temperature detector and a timing circuit responsive to the current temperature of the air generated by the air conditioning system to generate a plurality of output signals which ultimately control the two varible displacement valves to change the capacity of the compressor from high to medium to low and vice versa.