Friction torque reduction due to laser surface texturing in Cam tappet contact - A Mathematical modeling approach

Higher efficiency and lower emissions of modern IC engines are still a challenge for all components of the valve train. One of the most critical tribological interfaces, the cam–tappet operates under severe mixed lubrication under high contact stress and sliding velocities. Surface texturing techniques have been developed based on the laser method and are considered to be a promising micro-tribological modification to obtain lubrication behavior improvement and energy saving. The frictional torque characteristics of a flat-faced tappet with laser made micro-texture patterns on its surface in a cam mechanism. One-dimensional mathematical modelling and integration of the 3D transverse leakage compensation are developed, which include the hydrodynamic, asperity and thermal/shear-thinning effects and trace the contact behavior across the cam cycle. Asperity interactions, flow factors, viscosity response, temperature dependent material properties are included in the modelling approach. The influence of the modification of the micro-texture geometry and its distribution on the film thickness, pressure distribution and lubricant rheology is demonstrated, affecting the frictional torque. The results show that a suitably designed laser texture can indeed greatly reduce the friction under certain operating conditions. This research offers insights of relevance for advanced surface engineering in automotive valve trains and can be used to further advance mechanical efficiency in internal combustion engines.