Tribology of journal bearings: Start stop operation as life-time factor

Reduction of pollutant emissions is one of the key drivers in the field of combustion engine development. In this context, in particular start stop systems are applied in order to further reduce the total fuel consumption and subsequently minimize pollutant emissions. However, this application leads to completely new operating conditions for the powertrain. In particular, hydrodynamic bearing systems are burdened by these operational changes and the increased proportion of solid friction contacts. In order to ensure safe bearing operation, in depth research in the field of start stop bearing dimensioning is required. This paper covers an extensive investigation of journal bearing systems under start stop operation conditions. With the aid of a novel component close test methodology the start stop wear characteristics of various bearing materials are investigated and compared. Furthermore, the impact of the lubricant viscosity and chemical additive formulation of engine lubricants on the start stop lifetime performance of journal bearing systems are discussed.