Abstract
The automotive vehicle market has seen an increase in the number of hybrid electric vehicles (HEVs), and forecasts predict additional growth. In HEVs, the hybrid drivetrain hardware can combine electric motor, clutches, gearbox, electro-hydraulics and its control unit. In HEV hardware the transmission fluid can be designed to be in contact with an integrated electric motor. One transmission type that is well-suited to such hybridization is the dual clutch transmission (DCT), where a lubricating fluid is in contact with the complete motor assembly as well as the DCT driveline architecture. This includes its electrics, and therefore raises questions around the suitability of standard transmission fluids in such an application. In turn this drives the need for further understanding of fluid electrical properties in addition to the more usually studied engineering hardware electrical properties. New understanding for the behaviour of transmission fluids in electric fields has been gained and this knowledge has been applied to designing a fluid with the appropriate electrical characteristics. In addition to this the other essential performance characteristics for DCT fluids of this type have also been addressed, such as oxidation resistance, corrosion protection and clutch friction. A finished fluid containing this new additive technology that’s suitable for a hybrid electric DCT unit, an e-DCT, is described here, as well as some of the more fundamental investigations underpinning its overall development.