Reliability and Efficiency of Electric Vehicle Transmissions

Electric vehicle (EV) design imposes particularly harsh tribological conditions on EV gearboxes. This includes the combination of high torque and low gear speed at one extreme and very high speeds with relatively low torques at another. In addition, cooling requirement call for unconventional lubricating fluids, with some of the latest lubricants developed specifically for this application containing significant amounts of water. This results in harsh tribological conditions in transmission elements such as bearings and gears while also increasing oil churning losses.

This project is concerned with optimising efficiency and reliability of EV transmissions. It proposes to devise a model which is able to predict the tribological conditions and the overall power losses in transmissions suitable for use in electric vehicles. Crucially, the approach will include a detailed treatment of gear and bearing operation in order to accurately predict operational lifetimes and friction losses in these components. This will include the use of measured rheological properties of lubricants currently used or being developed for use in EV transmissions.

The overall aims of this project are:
- To improve the efficiency and hence increase the range of EVs through optimising transmission architecture (number of ratios, ratio split, weight) required to provide adequate input-output matching for a given vehicle duty.
- To optimise EV lubricant formulation to minimise gearbox power losses (and hence extend vehicle range) while maintaining durability. Lubricant considerations will address tribological performance, cooling, electrical properties and material compatibility.