Analysis of crankshaft three-dimensional vibrations in a rotating coordinate system

摘要

To decrease the noise and vibration of an engine powerplant, the three-dimensional vibration behavior of the crankshaft system must be clarified precisely. However, the description of dynamic behavior in fixed coordinates would be extremely complex, since many time-variable parameters must be introduced in the equation of motion for the rotating crankshaft. In this research, the vibration behavior of a rotating crankshaft system was analyzed by a rotating coordinate system attached to the crankshaft system: (1) by deriving the time-invariable characteristic matrices of multi-degrees-of-freedom for the crankshaft system, and (2) by calculating the forced vibration behavior of the crankshaft system under operating conditions. To investigate the validity of this approach, we calculated the crankshaft vibration behavior under different operating conditions for the cases when different types of crank-pulleys were attached step-by-step to the crankshaft of a four-cylinder in-line diesel engine. These calculated results were compared with the experimental ones. From the calculated and measured results, instructive knowledge could be obtained about the vibration behavior of the rotating crankshaft systems under operating conditions.