Stability analysis for nonlinear valve train systems in automotive engines

In the present paper, the structural stability of a valve train system is investigated. Valve trains are applied in automotive combustion engines to accomplish the alternation of load. Regarding the efficiency of the engine, a stable system is favorable since it produces less oscillations and less friction. Further, the stability behavior is important from simulative perspective since model instabilities are challenging for the numerical solvers. The system behavior is described with a simplified pendulum replacement model. The stable and unstable equilibria are calculated by means of the effective potential energy. The analysis reveals a subcritical pitchfork bifurcation which changes the stability and friction behavior depending on the cam-shaft velocity. The analytically calculated results are validated with comprehensive numerical simulations.