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Crankshaft torsional dampers are increasingly being used for the gasoline engines of compact cars as well as for ordinary high speed diesel and gasoline engines. Recently, so-called bending dampers are sometimes attached to the torsional dampers to reduce the bending and axial vibrations. To investigate the influence of such crankshaft torsional and bending dampers on the crankshaft vibrations, we first designed three kinds of dampers, each for the reduction of the crankshaft vibration, in the torsional, axial, and radial directions. Next, we developed two kinds of dampers for the simultaneous reduction in the torsional and axial modes, and in the torsional and radial direction modes. We measured the three-dimensional vibrations for both the dampers and the crankshaft, under engine operating conditions, A four-cylinder in-line diesel engine (4 - ϕ 115 x 110) was used for the experiments.

Torsional dampers have been attached to engine crankshafts only for the control of the crankshaft torsional vibrations. However, a torsional damper is a mass-spring system of three-dimensions, so the torsional damper could exert some influence on the three-dimensional vibrations of the crankshaft system. Since the inertia ring of the torsional damper has moments of inertia and it rotates with the crankshaft, gyroscopic vibrations of the inertia ring can also be generated. For a V-type ten-cylinder diesel engine (V- 10, ϕ119 × 150), the three-dimensional vibrations of the crankshaft system were calculated by the dynamic stiffness matrix method, taking account of the influence of the gyroscopic vibrations of the inertia ring of the torsional damper. The dynamic bending stresses were measured at the fillets of both the No.1 crank journal and the No.1 crank pin in the No.1 crank throw plane.