Research On Valve Train Dynamics Considering The Coupled Vibration Of Internal Combustion Engine System

Valve train is one of the most important parts of internal combustion(IC) engine, its performance will direct affect the fuel economy and emissions performance of IC engine. The valve train is also an important source of vibration and noise of IC engine. High speed IC engine developing with low emissions and light-weight is dominated. The fact that the vibration and noise will be serious than traditional engine, shows the strong demands in developing silent valve train. To research the dynamics of valve train, one domestic gasoline engine were studied in this paper. The main research works show as bellows:Based on concentrated mass dynamics, a centralized quality dynamics model of valve train is established. According to the structural features of double overhead camshaft(DOHC) valve train, the bending and torsional vibration analysis model of camshaft, the 3+N degrees of freedom model of valve group unit are established. According to lumped parameter modeling theory, the system parameters of valve train system were determined by the empirical formula, the FEA and experiment. The valve train dynamics such as contact stress and seat force were analyzed in detail.Based on finite element model of the engine, the valve train dynamics model considering coupled vibration of engine system dynamics is established by Power Unit module and Timing Drive module of AVL EXCITE Software which developed by AVL Corporation. The valve train dynamics at 6000 rpm of engine is calculated. Compared with the traditional dynamical analytical model without considering the coupled vibration of IC engine system, the elastic characteristic of engine parts on cam-tappet contact stress, torsional and bending vibrations of camshaft, shock and vibration of valve while opening and closing, residual vibration of valve after closing and spring flutter was researched.Considering the influence of force acting on camshaft bearing, spring force acting on cylinder head, valve train seating force and gas pressure on the vibration of cylinder head, the transient response analysis of the cylinder head was carried out. The vibration response in time domain was discussed.The valve train dynamics testing systems was built, which measure the strain response at camshaft bearing walls. The dynamic response of the cylinder head at 1000r/min of IC engine is tested. A comparative analysis was carried out between the simulated results and measured data, the comparison shows that the simulation is accordance to the experiment. The accuracy of the simulation model is verified. The necessary of taking the influence of coupled vibration of IC engine on valve train dynamics analysis is proved.