Ongoing ICE development is improving the best specific fuel consumption and is enlarging the sizes of the ICE's sweet spot in the direction of higher and lower engine speeds and shifts it towards lower load operation conditions. This development reduces the fuel-consumption benefit given by a wide transmission gear ratio spread as well as the need for small ratio steps. Thus the number of transmission speeds can be reduced. Countermeas-ures to solve potential drivability deficits by the increased gear ratio steps benefit from instantaneous torque availability of an electric motor integrated into the hybrid drive train. With the "Future Hybrid" design AVL has taken a holistic development approach for all key components of the drivetrain and is able to demonstrate best fuel efficiency and cost effectiveness for outstanding vehicle customer acceptance. A shift in transmission development paradigm to also consider transient shift operations with more than two active shift elements allowed a multi-functional and compact transmission design. The Lepelletier planetary transmission with the EM integrated with the second ring gear of the modified Ravigneaux gear set provides a solution of low hardware complexity and product cost while increasing the demands on the control system to manage the transient shift operations.
展开▼
