Abstract
The megatrends ”reduction of emissions“ and “fuel consumption reduction” play a predominant role in the development of powertrains. For transit buses this implies both the reduction of emissions and pollutions of the intenal combustion engine, and, on the other hand, a further reduction of noise and brake dust. Also very important is the reduction of both fuel consumption and CO2 emissions. For all these targets the actual developments on the engine side have led to great improvements in the last decades, but what can be mentioned for the other components of the powertrain, especially looking for transmissions? First of all the relevant trends for transit buses have to be watched.: A large increase of the torque of the combustion engines during the last years have a big impact on the development of transmissions for buses. Furthermore, due to the higher coolant temperatures of the engine’s cooling systems to perceive a better emission behaviour because of a better efficiency of the combustion engine, coolant systems for the transmissions have to be improved as well. For transit buses powershift automatics in established markets have a share of more than 90%. The presentation will give the most recent developments for both hardware- andd function related parts of the transmissions. The function and software part demonstrate the increasing influence of electronics and their interactions within the vehicle’s electronic architecture. All the different vehicle electronics are driven collaborative to achieve best suited solutions for the different areas of customer’s requests. The development of modern Powershift transmissions today means also intensive usage of simulation tools for all fields. This exceeds by far the former strength, fatigue and vibration analyses. Practical examples, also including manufacturing simulation, will show the relevance of simulation to the development process. All the simulation results lead to a reduction of development time and a better product quality and accuracy. The presentation ends with an evaluation of different hybrid solutions. Here for the future systems are needed which combine both fuel consumption reduction and improved life cycle costs. ZF with its parallel hybrid system will offer a very attractive solution for the market.