ZF New 8-speed Automatic Transmission 8HP70 - Basic Design and Hybridization- 2009-01-0510
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 2nd generation offers significantly improved customer-relevant features such as reduced fuel consumption, response time and shifting speed. With regard to the increasing requirements especially in reduction of CO2 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 meet 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.