Reduction of Friction Losses in Journal Bearings of Valve Train Shaft by Application of Running-in Profile

摘要

Increasing requirements for improved efficiency of internal combustion engines necessitate the reduction of friction losses. 10 to 30% of the total friction of the engine occur in the valve train varying with load and speed. The journal bearings of the camshaft create up to 40% of these losses and are therefore a good target for optimisation. ThyssenKrupp Presta, leading manufacturer of assembled camshafts, sees raised interest from customers for surface treatments like super-finishing, nitrating or different coatings. A special test stand to produce precise friction measurements of camshaft bearings under realistic conditions has been developed and successfully used to show that running in with initial wear is of similar significance for optimal camshaft bearings as e.g. surface quality when new. IST GmbH have extended their multi-body and hydrodynamics program FIRST with the energy based wear-model from Fleischer, to be able to simulate changes in roughness and contour due to running-in in hydrodynamic bearings. The numerical results will be validated using the measured data and it will be shown that friction reduction due to wear and running-in times can be predicted.