Reducing torsional vibrations by means of a kinematically driven flywheel — Theory and experiment

Abstract

Modern turbocharged combustion engines induce high fluctuating torques at the crankshaft. They result in torsional crankshaft vibrations that are transferred both to the gearbox and the auxiliary engine systems. To reduce the torsional crankshaft vibrations, a kinematically driven flywheel (KDF) for compensating fluctuating engine torques has been developed. It comprises a flywheel that is coupled to the crankshaft by means of a non-uniformly transmitting mechanism. The kinematical transfer behaviour of the mechanism is synthesised in such a manner that the inertial flywheel torque compensates at least one harmonic of the fluctuating engine torque. The degree of non-uniformity of the mechanism has to be adapted to the actual speed and load of the engine. A novel geared double-crank mechanism with cycloidal-crank input and adjustable crank length is proposed and analysed. Parameter synthesis is achieved by means of a simplified mechanical model that calculates the required transfer function for a given engine torque. A multibody simulation of a three-cylinder engine equipped with the KDF demonstrates the efficacy of the system. A functional prototype has been built up and tested on an electrically driven test stand. Measurements confirm the simulated behaviour of the KDF thus demonstrating the potential of the device.