ABSTRACT In view of legal requirements and measures for climate protection, fuel efficient vehicles have become increasingly important. Against this background, transmissions are a key factor for two main reasons: Energy consumption and emissions can be reduced by optimization of conventional transmissions. The “ideal” transmission has a potential of contributing to this goal by about 10%. Between 4 and 5% out of this 10% can realistically be achieved. Driveline electrification constitutes another necessary step for CO 2 savings. To this end, an ideal option is integrating the electric components into the transmission. In view of the uncertain market development for hybrid car demand, a modular approach to electrification in transmissions is essential. This article outlines the electrification approach. MOTIVATION In an effort to strike a balance between increasing fuel prices due to diminishing resources and the necessity to reduce CO 2 emissions to slow down the rate of global warming, the automotive industry is exploring various alternatives. The consistent pursuit of optimization measures concerning combustion engines and transmissions as well as the broader application of hybrid technology are one option for realizing short and medium term goals for the reduction of CO 2 emissions. While the improvement of conventional technologies will still play a decisive role in the future [ 1], measures such as the development of alternative fuels and hybrid vehicles will affect the market in the medium term. These measures complement each other and are thus not competing (Figure 1). Figure 1. CO2 Savings Potential Passenger Cars in Germany I In a fictional world, where only electric drivelines are used, the other technologies would be replaced, even if some components of hybrid technology (electric motors, batteries) could be re-used. On that score, hybrid technology used in different solutions such as full and plug-in hybrid, is often labeled a “transitional” solution. Many experts currently agree however, that the replacement of electric vehicles will either occur in the distant future, or possibly never ( Figure 2). It is rather anticipated that all of the aforementioned technologies will exist in parallel. Symptomatic of hybrid drivelines is the fact that this is the only technology suitable for operation with all energy sources that are presently favored (liquid fuels, hydrogen, electric power) [ 3]. The Modular Hybrid Transmission Kit from ZF2013-01-1446 Published 04/08/2013 Ralf Kubalczyk ZF Friedrichshafen AG doi:10.4271/2013-01-1446Downloaded from SAE International by Tsinghua University, Friday, June 08, 2018Figure 2. CO2 Savings Potential Passenger Cars in Germany II Consequently, the development of highly efficient conventional technology, including hybrids and new driveline concepts, such as drivelines for pure electric mobility, will have to be advanced to cope with global megatrends, such as globalization, demographic change, urbanization, mobility, and new ecology. HYBRID DRIVE AND ELECTRIFICATION Since the emergence of electric vehicle drives, it is increasingly important to differentiate between and have clear definitions of terms such as hybrid drives, EV drives, and range extender options. The difference between the two types of drives should be defined by the power source that is designed for all driving specifications of the driveline. In a hybrid electric vehicle (HEV), 100% of the spec will be fulfilled by the ICE; in an EV the whole spec will be fulfilled by the EM. Range- extended electric vehicles are a special variant of EVs, to which the aforementioned facts are also applicable; in addition, these vehicles can also be assisted intermittently with input from the range extender device, such as an ICE, if this device is connected to the drive axle. The range extender, by definition, simply extends the range and does not meet other drive specification requirements (e.g. top speed, performance, etc.) li