Development of high efficiency passenger vehicle axle

Abstract

Rising energy demand coupled with volatile fuel prices has driven the automotive industry to rebalance focus between durability and efficiency. Originally, the main target was the improvement of the internal combustion engine. After arriving at certain technological limits, all other drivetrain components were also taken into consideration. In this project, a study on a differential axle has been conducted from a lubrication point of view in order to identify efficiency enhancing routes. Initially, an axle already in production and used on a passenger vehicle was employed and the effect of lubricant viscosity on loss generation was investigated. Additionally, novel lubrication concepts, such as forced-feed lubrication and baffle implementation, were considered and tested on an in-house loss measurement rig. The quantification of loss generation, as well as, the observation of the behaviour of the axle under varying operating conditions was successfully completed. Also, the contribution of each component to overall losses was identified. Furthermore, a theoretical model was built for the prediction of axle efficiency. The model was a transient simulation of the operation of the axle, based on individual component loss generation. The thermal behaviour of the axle was also considered. The model demonstrated good correlation to available data produced from real world measurements. Finally, the benefit of the implementation of previously considered lubrication systems was investigated for the NEDC and Artemis drive cycles. It was found that significant loss reduction over the original axle design can be achieved. Overall axle losses can be reduced by up to 50% with no apparent durability compromises, which has the potential to reduce CO2 emissions by 3 g/km in a passenger vehicle.