Schaeffl er SYMPOSIUM 201012 Acti ve diff erenti al 178 Schaeffl er SYMPOSIUM 2010 17912 Acti ve diff erenti al 12 12 Ac ti ve diff erenti al 179 Schaeffl er SYMPOSIUM 2010 Schaeffl er SYMPOSIUM 2010 178 Schaeffl er acti ve eDiff erenti al The acti ve diff erenti al for future drive trains Dr. Tomas Smetana Thorsten Biermann Prof. Dr. Bernd-Robert Höhn, FZG Munich Franz Kurth, FZG Munich Dr. Christi an Wirth, ZG GmbH GarchingSchaeffl er SYMPOSIUM 201012 Acti ve diff erenti al 180 Schaeffl er SYMPOSIUM 2010 18112 Acti ve diff erenti al 12Preface The development of drives for electric vehicles is coming increasingly to the fore in the search for new mobility concepts, motivated by global warming and the scarcity of fossil fuels. The Federal Government wants to make Germany a leading market for electromobility in the com-ing 10 years. One million electric vehicles ca-pable of being recharged from the electricity supply system and so-called, plug-in hybrid ve-hicles should be driving on German roads by 2020. Because development work in the last few de- cades, above all in terms of individual mobility, was primarily focused on drive concepts based on internal combustion engines, there is cur-rently an enormous lot of catching up to do in the development of electric drive trains. Not only the technical aspects must be highlighted, the industrial structure and supply chains must also be created in order to enable the manufac-ture of electric drive trains for large-scale pro-duction. A wide range of existing expertise at suppliers, research associations and universi-ties must be bundled and further developed in a network. This interlinking will enable efficient and effective use of existing resources, which will benefit all involved, as they develop future-proof systems technology for vehicle drives. Irrespective of the topic electromobility, the number of registrations for road vehicles is ris-ing continuously and the density of traffic is also increasing as a result. Nevertheless, in or-der to reduce the number of accidents, the eS-afety Campaign was started with the ambitious target of halving the number of road deaths in the European Union within only 10 years by 2010. This task cannot be achieved just by im-proved road conditions. The drive train of the vehicle with its corresponding control system must be so intelligently designed that human error in road traffic can be corrected. The de-velopment of relevant driver assistance sys-tems has already been initiated. The actual hardware, which also enables the use of such systems in electric drive trains, is, however, new territory that holds opportunities for inno-vation.Introducti on History The idea of arranging the differential coaxially in relation to an electric motor arose at a very early stage during development of the spur gear dif-ferential at Schaeffler. The very first designs indi-cated that an extremely compact drive train could be produced in this way. It was solely the innovative, Schaeffler-specific idea that was lacking, because prototypes with similar ar-rangements had already been built by other companies. The idea was finally developed in cooperation with the FZG Munich to combine the transmis-sion with a superimposing stage, in order to also integrate the electric, lateral distribution of torque within the range of functions. Along with the significantly improved drive per- formance and higher energy efficiency, a funda-mental advantage of this innovative drive sys-tem, which was given the name “active electric Differential” (active eDifferential), is the possi- bility of integrating a driver assistance system in order to prevent accidents and to actively inter-vene in the control of the vehicle. The drive axle is, therefore, the actual tool with which lateral and longitudinal control of drive torques can be realized in a purely, electrically-driven vehicle. Emergency avoidance and braking maneuvers can be realized later using these func-ti ons in test vehicles. Stat