Until now engine downsizing was mainly used to increase vehicle performance and to compensate vehicle weight increase. Real downsizing in terms of actually reducing engine displacement per vehicle weight has only just begun. These modern boosted engines show high power and torque levels, also at relatively low engine speeds. To really exploit the benefits of the downsized powertrain very long last gear ratios are required. The high low end torque is generated by boost pressure. Studies have shown that no significant boost pressure can be achieved in the first second after vehicle launch, even with sophisticated charge systems. To achieve good perceived performance the responsiveness within this first second is extremely important. To achieve or maintain acceptable levels of vehicle response the total first gear ratio must be significantly increased to values >20. The resulting torque ratio demand of around 10 will be relatively easy to achieve with torque converter transmissions. Here the gap to todays technology is relatively small. For non-converter transmissions this will require 9 to 10 forward gears. To achieve this without increasing package space, mechanical complexity and costs the current gear set structure of DCTs (Dual Clutch Transmission) will no longer work. A possible solution is shown by the X-DCT concept from FEV Motorentechnik Aachen. With an intelligent gear set structure this 10-speed DCT achieves a ratio spread of around 10.3 with a mechanical complexity equal to todays 6- or 7-speed DCTs. Current DCT architectures uses a gear set with one pair of gears per ratio. For a typical 7-speed DCT this results in about 19 gears and 4 full shift forks. The solution is a multiple usage of gears, similar to FEVs 7H-AMT. In this transmission the additional required gear ratios for the electric motor are generated by using unused gears in the combustion engine path.
Future automatic transmission requirements
2011
14 Seiten, 5 Bilder, 5 Tabellen, 2 Quellen
Aufsatz (Konferenz)
Englisch
Future Automatic Transmission Requirements
British Library Conference Proceedings | 2011
|Future automatic transmission requirements
Kraftfahrwesen | 2011
|Future automatic transmission fluids - performance requirements
Kraftfahrwesen | 1986
|Future automatic transmission fluids-performance requirements
Tema Archiv | 1986
|Future Requirements to Transmission Layout
British Library Online Contents | 1992
|