Toyota New TNGA High-Efficiency Eight-Speed Automatic Transmission Direct Shift-8AT for FWD Vehicles

Paper #:
  • 2017-01-1093

Published:
  • 2017-03-28
Abstract:
Because of environmental issues such as reducing carbon dioxide and tightening fuel economy regulations for automobiles, it has become essential to develop vehicles with superior fuel efficiency and cleaner emissions. At the same time, the demand of the basic performance characteristics such as driving performance and NVH is increasing. Toyota Motor Corporation has developed a new eight-speed automatic transaxle (UA80) which has realized these requirements at a high level, and is adopted into the new Siena and Highlander. UA80 is the first Toyota transaxle which incorporates the TNGA concept. It has high level competitiveness in wide torque range from L4 engine to V6 engine by using both optimization and standardization of main components. Additionally it has a superior installation performance by optimizing the transaxle size and arrangement and achieved a low gravity center. It contributes to vehicle’s attractiveness by improving driving performance, NVH and design. UA80 adopts compact and highly efficient geartrain which has 2 planetary gear sets, 4 clutches and 2 brakes. As a result we have achieved both “increased number of gear speeds and multiple plate lock-up clutch” and “reduced length and weight” which are obviously conflicting features. By incorporating new technologies such as larger lock-up range, off axis oil pump and low drag clutch discs, UA80 achieves an outstanding fuel consumption among the equivalent automatic transaxles. The fuel economy of the vehicle is improved drastically compared to the conventional 6-speed transaxle. Also it contributes to spectacular level up of acceleration performance by optimizing the gear ratio arrangement to match the characteristics of the vehicle and the engine. Additionally direct feeling and smooth gear shifting is achieved by new shifting control system with lock-up condition. This paper describes the major features, adopted techniques and performance of this transaxle.
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