Compressor torque estimate device, engine controller and method of estimating compressor torque

A compressor torque estimate device is used for a variable displacement compressor whose displacement is variable based on a compressor control signal for estimating a compressor torque of the compressor. The compressor torque estimate device includes a torque calculator and a corrector. The torque calculator calculates a torque required for driving the compressor based on the compressor control signal, thereby obtaining a calculated torque. The corrector corrects the calculated torque by a procedure of first-order lag, thereby obtaining a corrected torque. The corrector also estimates the corrected torque to be the compressor torque.