Reducing Rotational Crankshaft Oscillations by Means of a Kinematically Driven Flywheel

Modern turbo-charged internal combustion engines generate fluctuating torques with high amplitudes at the crankshaft. To reduce resultant crankshaft oscillations and their transmission to the drivetrain, flywheels and spring-damper systems like the dual-mass flywheel are commonly provided. Another concept is to couple a flywheel to the crankshaft using a non-uniformly transmitting mechanism in such a manner that the motion of the flywheel compensates the fluctuation torques. The degree of non-uniformity of the mechanism has to be adapted to the actual load and angular speed of the combustion engine. For this purpose a double-crank mechanism with cycloidal-crank input and adjustable crank length is proposed and analyzed. For a desired compensation torque the required transmission function of the mechanism is calculated using a simplified dynamic model. Parameter synthesis of the double-crank mechanism is achieved by means of a numerical optimization procedure based on a multibody model of the overall crankshaft-flywheel system.