Research On Influence Of Crankshaft And Timing Systems Dynamic Characteristics On Engine NVH Performance

Design and layout of crank and conrod mechanism and timing systems greatly impact NVH performance of engine. Based on crankshaft, conrod and various timing systems dynamics, this dissertation establishes relations between excitation characteristics of kinetic systems and structure vibration response. And it completes deep theoretical analysis and experiment research about influence of coupling dynamic characteristics between crankshaft and timing systems on engine NVH performance.Dynamic characteristics and strength issues of crankshaft and conrod are studied systematically and deeply. Muti-elastic body dynamic simulation model of crankshaft is established and it is validated by torsional vibration measurement. Dynamic stress of crankshaft fillets is studied based on modern numerical simulation technology and it is compared with traditional calculation method and fatigue test results about crankshaft strength. Results show that modern simulation analysis technology is reliable and accurate. Dynamic characteristics of conrod are anlyzed and results show that influence of conrod on excitation dynamic amplifying can be ignored in engineering application. Elastic hydrodynamic characteristics of conrod big end bearing are studied. Combination with FE nonlinear contact algorithm, conrod dynamic strength is predicted in different conditions. Coupling effects between torsional vibration excitation and engine dynamic characteristics are investigated by simulation, and it can be reduced by optimizing crankshaft torsional vibration. In addition, simulation results are validated by related measurement.Dynamic and NVH characteristics of timing systems are investigated detailedly and deeply, such as chain drive, gear drive and synchronous belt. Furthermore, coupling effects between timing system and crankshaft are analyzed. Different influence on vibration reponse of front timing cover are studied with various timing systems. Timing systems are discretized into muti-mass points using muti-rigid body dynamics. Dynamics difference bewteen silent chain and bushing chain of a gasoline engine are analyzed and compared. Additionally, both simulation and acoustic experiment results show silent chain can weaken polygon effect obviously. Meshing and impact excitation are analyzed about timing gear drives on a diesel engine. Gear meshing characteristics are compared in different conditions, such as without crankshaft speed irregularity, with crankshaft speed irregularity and using torsional vibration damper. Results indicate that dynamics optimization of gear system can reduce vibration of gear cover. Co-simulation between crankshaft and synchronous belt dynamics is implemented based on different numeric algorithms, and it shows that belt internal force has different influence on crankshaft torsional virbation. strength and lubrication of main bearings. Various timing systems are designed and arranged in a same diesel engine with combined methods of CAD and CAE. Different vibration results of timing cover are calculated and compared with same boundary conditons. It illustrates the reason that noise is larger on the front of engine equipped with timing gear drives through simulation prediction technology.This dissertation studies relation between excitation derived from kinetic systems and structure vibration response, expands application about engine structure design and analysis with numerical simulation method and gets a series of new valuable conclusions and achievement about engineering application, which provides important reference for engine design and development.