Influences of Torsional Damper Temperature and Vibration Amplitude on the Tree-Dimensional Vibrations of the Crankshaft-Cylinder Block System under Firing Conditions

By applying the dynamic stiffness matrix method, three-dimensional vibrations of the crankshaft system under firing conditions were investigated for an automobile engine, taking account of the vibration behavior of the torsional damper and the cylinder block. To simplify the analyses, the crankshaft was idealized by a set of jointed structures consisting of simple round rods and simple beam blocks of rectangular cross-section; the main journal bearings were idealized by a set of linear springs and dash-pots.

For the flywheel of flexible structure, the dynamic stiffness matrix was derived from FEM. However, for the cylinder block, the dynamic stiffness matrix was constructed from the experimental values of the modal parameters obtained from the experimental modal analysis (EMA), because of the complicated structure. For the torsional damper, the influences of the damper temperature and the damper vibration amplitude on the damper vibration behavior were investigated by a series of shaker tests in a thermostatic chamber. Then the dynamic stiffness matrix was constructed for the total crankshaft-cylinder block system by the principle of superposition. The three-dimensional vibrations of the crankshaft system were analyzed for the two cases in which a solid pulley and a torsional damper were attached to the crankshaft, to investigate such influence on the vibrations of the crankshaft-cylinder block system under firing conditions. The calculated results were compared with the experimental ones.