Patent ID: 8555665

Claim:
A method for operating a variable-displacement compressor, wherein a volume of a compression chamber of at least one cylinder is varied during a compression cycle, wherein during the cycle the at least one cylinder is alternately coupled to a low pressure side and a high pressure side of the compressor, comprising estimating a first thermodynamic state of the low pressure side using a temperature (T evap )characteristic of a temperature (T in ) of a fluid at an inlet of the compressor and estimating a second thermodynamic state of the high pressure side using a pressure value (P out ) of the fluid at an outlet on high pressure side of the compressor, estimating a current compression ratio (specific volume in/specific volume out ( v in v out ) ) of the compressor, calculating a compressor displacement (D) as a function of the compression ratio ( v in v out ) , estimating a compressor torque (M) depending on the calculated displacement (D) and the estimated first and second thermodynamic states, providing the estimated compressor torque (M) to a control unit for operating the compressor or an engine coupled to the compressor , and controlling operation of the compressor or the engine coupled to the compressor as a function of the estimated compressor torque (M).