Patent ID: 6453685
Filing Date: 2002-09-24
Classification: F04B

Abstract:
A control apparatus for controlling discharge capacity of a variable displacement compressor included in a refrigeration circuit of an air conditioner, said refrigeration circuit including an evaporator, said control apparatus comprising:a differential pressure detector for detecting a differential pressure between two pressure monitoring points set to said refrigeration circuit, on which the discharge capacity of the variable displacement compressor is reflected; a temperature sensor for detecting a cooling state of said evaporator as temperature information; a set differential pressure calculator for calculating a set differential pressure which becomes a control target of a differential pressure between the two pressure monitoring points, based on a temperature detected by the temperature sensor of said evaporator and a target temperature which is a control target of the temperature of said evaporator; a limit value setting device for setting a limit value to the differential pressure between the two pressure monitoring points when the temperature detected by the temperature sensor of said evaporator is lowered from the state higher than a threshold temperature which is set to higher than the target temperature to the state lower than the threshold temperature, and for releasing the setting of the limit value when the temperature detected by the temperature sensor of said evaporator is raised from the state lower than the threshold temperature to the state higher than the threshold temperature; a set differential pressure setting device for comparing the set differential pressure calculated by said set differential pressure calculator with the limit value set by said limit value setting device, for dealing with the set differential pressure in itself if the discharge capacity of the variable displacement compressor which the set differential pressure represents is less than that of the variable displacement compressor which the limit value represents, and for dealing with the limit value as a new set differential pressure if the discharge capacity of the variable displacement compressor which the set differential pressure represents is greater than that of the variable displacement compressor which the limit value represents; and a compressor control mechanism for controlling the discharge capacity of the variable displacement compressor so that the differential pressure detected by the differential pressure detector approaches to the set differential pressure from said set differential pressure setting device.