Dynamic Behaviour of Variable Displacement Compressor for Automotive Air Conditioners

To meet the demand for improved comfort, driveability and fuel economy standards, a continuously variable displacement compressor has been developed. The compressor has a unique compression mechanism, which automatically changes displacement volume to exactly match vehicle air conditioning requirements. The compressor controls the pressure differential between the crankcase and the cylinder inlet and uses the pistons as actuators to change compressor displacement.

This paper outlines an analytical model for evaluating the dynamic behaviour of the variable displacement compression mechanism. The model gives detailed geometric and kinematic information regarding each element. It also calculates gas torque fluctuation, nutating motion of the wobble plate, constraint forces of each pair of machine elements and unbalanced forces of inertia. It calculates the pressure differential between the crankcase pressure and the cylinder inlet pressure required for displacement control.

These results can be used to estimate the effect of relevant parameters on variable displacement compressor kinematics.