Vehicle development field is currently dominated by the tightening of CO_2-emission targets. Future targets are achievable with conventional diesel technologies in the small and medium vehicle classes, but not in the larger vehicle classes. They also cannot be met with current gasoline engines. For small vehicles, naturally aspirated engines will be used because of the high cost sensitivity in this segment. Basic engine optimization measures, such as friction reduction and thermal management, will be adopted for all engine and vehicle classes. In the larger vehicle classes, engines will be designed with cylinder deactivation technology or as downsized engines. Since both of these measures tend to increase the crankshaft torque fluctuations, effective decoupling elements are needed to reduce the gearbox input torque fluctuations to a tolerable level. The higher specific torque produced by the engines, especially downsized engines and the accompanying downspeeding will require higher gear ratios. This will be partly accomplished by a smaller first gear ratio and an increased gear ratio spread or, potentially, even a higher number of gears. When the requirements for the gearbox increase, so does its complexity. Further reductions in fuel consumption can be realized through hybridization and electrification, especially for higher inertia weight classes and gasoline engines. The level of hybridization and, hence, the installed electrical power have a direct impact on the gearbox complexity. The complexity of the gearbox increases, whereas the combustion engine design can be simplified by reducing variabilities and costly technologies. For electric vehicles, the gearbox complexity can be reduced by providing only one- or two-speed gearboxes. Nevertheless, future gearbox design and development will face increased challenges.
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