F2008-06-208
ZF´s New 8-Speed Automatic Transmission 8HP70 Transmission Concept, Design and Mechanical Components
One of the essential reasons for the development of the new generation of eight-speed transmissions is the potential for a further significant reduction of fuel consumption. This is the basic requirement in the competition with alternative transmission systems. The 8HP70 transmission for rear- and four-wheel driven pass cars with engine torques up to 700 Nm features consumption reductions of 6 % compared to the already optimized 2nd generation six-speed 6HP28. The already very high level of shift quality, response times and shifting speed of the 2nd generation of six-speed automatics is further improved. With a smart arrangement of components in the transmission and by integrating functions, a compact design was obtained. Despite an additional gear set level, no additional components are used in the 8HP transmission. The installation space of today`s six-speed transmission is not exceeded. With regard to the power-to-weight ratio a benefit of about 10 % is achieved compared to similar six-speed 6HP28. The described technical features meet the demands of future requirements. The new 8HP70 shows that the technology of "conventional" automatic transmissions with torque converter and planetary gear sets still contains a lot of potential. Thanks to its modular structure, the transmission offers the possibility of implementing several start-up devices and of integrating different four-wheel drive configurations. The key thought of an integrated four-wheel system with torque on demand clutch is to create system benefits by synergies. Instead of doubling components already existing components are employed such as the transmission-side hydraulics and control functions. Thanks to the cancellation of parts consumption benefits arise. A further reward is the reduced installation space and the significant reduction of weight. In this paper the transmission system and the transmission design of 8HP70 will be shown. Its main mechanical components will be outlined in detail and the integrated four-wheel system will be described.
This abstract is supplemented by a PDF, which can be viewed here.
Session: Transmissions