Selection of the Optimum Damping Coefficient for Torsional Vibration Dampers for Crankshafts of Reciprocating Internal Combustion Engine

Abstract

The paper presents the free oscillation analysis of the reduced torsional system in the crankshaft of a six-cylinder piston internal combustion engine with a liquid or rubber (internal friction) damper mounted on the toe. Installing a torsional vibration damper on the sock of the crankshaft changes the frequency of free oscillations, and in addition, when installing a rubber damper, another mass of the torsional system is added with the coefficient of rigidity of the rubber layer and the moment of inertia of the damper flywheel. At the same time, for liquid torsional vibration damper, the flywheel which has no direct connection with the toe of the crankshaft, for the calculation of free oscillations to the moment of inertia of the sock it is necessary to add a half the moment of inertia of the flywheel. The order of selection of optimal damping coefficients, namely the moments of inertia of the damper flywheel and damping coefficients of silicone fluid, is considered. For the rubber (internal friction) damper, the necessary parameters include the moment of inertia of the flywheel, the stiffness coefficient of the rubber layer and the damping coefficient. The free oscillations are considered in a complex form, which allows obtaining a function after the transition to real values that can be taken as a function of optimizing the parameters of the liquid or rubber damper. In this case, at the optimum damping or maximum energy dissipated in the damper, the amplitude of torsional oscillations of the crankshaft toe is reduced as much as possible. Using this approach allows for a significant reduction in the number of calculations with different damping coefficients and chooses the most optimal results.