2009-01-0510 ZF New 8-speed Automatic Transmission 8HP70 - Basic Design and Hybridization- Heribert Scherer and Manfred Bek ZF Getriebe GmbH Stefan Kilian ZF Friedrichshafen AG Copyright © 2009 SAE International ABSTRACT The world’s first six-speed automatic transmission for passenger cars was introduced to the market by ZF in 2001. The 6HP-family is based on a Lepelletier planetary gear set. An advanced version of these transmissions was launched in 2006. The 2 nd generation offers significantly improved custom er-relevant features such as reduced fuel consumption, response time and shifting speed. With regard to the increasing requirements especially in reduction of CO 2 emissions, a new eight- speed transmission is now under development. The main targets for this transmission family are a further significant reduction in fuel consumption and emissions, good driving performance and state of the art driving comfort. The paper describes the transmission 8HP70, the schematic, main features and major design components. Key figures like transmission weight and size, fuel efficiency benefits and driving performance are shown compared to the 6-speed transmission of the 2nd generation. The 8HP70 transmission offers the possibility of implementing several start-up devices and of integrating different all-wheel drive configurations. Based on a modular system, the 8-speed transmission can be equipped with a variety of hybrid functions. Micro, mild and full hybrid solutions can be implemented without the need of additional installation space. The described technical features m eet the demands of future requirements. The new 8HP-family shows that the technology of “conventional” automatic transmissions with torque converter and planetary gear sets still contain a lot of potential. In combination with the known advantages such as market acceptance, cost-benefit ratio, and comfort, this new transmission generation of ZF will mark a milestone in the history of automatic transmission technology for cars, which will serve as a benchmark for other transmission systems. INTRODUCTION After introduction of the first generation of ZF automatic 6-speed transmissions for RWD in 2001 and the launch in 2006 of a reengineered second generation providing significant benefits [1], the question arose as to how the further stiffening requir ements regarding fuel consumption and CO 2 emission reduction could be satisfied. The result of seve ral studies was that further optimization of the Lepelletier-based 6-speed transmission would not make sense but that new transmission concepts based on the proven planetary transmission technology did harbor potentials for achievement of the development goals. This transmission system must on the one hand allow greater spreading and more gears and at the same time improvement of internal efficiency. Fig. 1 shows the triangle of goals for this project. SAE Int. J. Engines | Volume 2 | Issue 1 314Downloaded from SAE International by Univ of California Berkeley, Sunday, July 29, 2018 Figure 1 Project targets The main emphasis was naturally on making a big step forward regarding consumpt ion and emission reduction. As Fig. 2 shows, with 6% savings compared to the already optimized 2nd generation of 6-speed transmissions, the goal was ambitious. In order to also meet the requirements of various vehicles and drivelines, the basic transmission needed to be variably designed for modular equipment with diverse starting elements and AWD system s. Furthermore, the transmission was required to permit realization of various levels of hybridization. Figure 2 Fuel efficiency ZF transmissions TRANSMISSION CONCEPT SCHEMATIC - Within a comprehensive search field matrix, transmission systems with several shifting components and gearsets were systematically analyzed, the challenge being to find a system which would on the one hand permit more than 6 gears with a