operating condition determining method for a variable capacity compressor in an air conditioning system for vehicles and vehicle air-conditioning system

摘要

PROBLEM TO BE SOLVED: To accurately discriminate whether or not a variable displacement compressor is operated at maximum discharge capacity.SOLUTION: Volumetric efficiency &eegr;v of a refrigerant sucked in a cylinder is calculated based on a rotation speed Nc of the variable displacement compressor (S101), refrigerant density &ngr;' of a compressor inlet is calculated based on a set value Ps' of suction pressure Ps, a flow rate threshold value Gsl for accurately discriminating whether or not the variable displacement compressor is operated at the maximum discharge capacity, is calculated in the following expression by using these volumetric efficiency and refrigerant density (S103), the compressor is operated at the maximum discharge capacity when a detected actual refrigerant flow rate Gr is the flow rate threshold value Gsl or more, and discrimination is made that the compressor is operated in less than the maximum discharge capacity when the detected actual refrigerant flow rate Gr is less than the Gsl. Gsl=(&pgr;D/4)×L'×n×(Nc/60)×&eegr;v×&ngr;'. D: a diameter of respective pistons, L': a stroke in maximum discharge capacity operation of the pistons, n: the number (n) of cylinders, and Nc: a rotation speed of a rotation mechanism.