Influence of dynamic behaviour on elastohydrodynamic lubrication of spur gears

In this study, the elastohydrodynamic lubrication (EHL) behaviour of high-speed spur gear contacts is investigated under dynamic conditions. A non-linear time-varying vibratory model of spur gear pairs is introduced to predict the instantaneous tooth forces under dynamic conditions within both the linear and non-linear operating regimes. In this model, the periodically time-varying gear mesh stiffness and the motion transmission error are used as excitations and a constant damping ratio is employed. This model allows the prediction of steady-state nonlinear response in the form of tooth separation (contact loss). An earlier gear mixed EHL model [1] is adapted to simulate the lubrication behaviour of spur gear contacts under these dynamic loading conditions, considering the variations of the basic contact parameters, such as radii of curvature, sliding and rolling velocities, and measured roughness profiles, as the contact moves along the tooth from the start of active profile to the tip. The EHL predictions under dynamic loading conditions are compared to those assuming quasi-static contact loads for gear sets having smooth and rough surfaces to demonstrate the important influence of dynamic loading on gear lubrication. The unique, transient EHL behaviour under the non-linear (intermittent contact loss) condition is also illustrated.