Abstract To meet increasing driveability expectation and government stringent fuel economy regulations reducing CO2 emissions of passenger cars; Toyota developed a new 8-speed automatic transmission "Direct Shift-8AT". Direct Shift-8AT is the first stepped automatic transmission model based on “TNGA” philosophy. New models which received Direct Shift-8AT are the new Camry, Highlander and Sienna. Direct Shift-8AT has an innovative control method with gear train and torque converter models, providing enhanced driveability and fuel economy performance through high efficiency transmission technology. This paper describes details of the new technology and vehicle performance. 1. Introduction The innovative 8-speed automatic transmission “Direct Shift-8AT” is the first stepped automatic transmission model based on “TNGA” philosophy. It helps to achieve good vehicle fuel economy and driveability. The new Camry, Highlander and Sienna received Direct Shift-8AT. The Direct Shift-8AT adopted the following newly developed technologies to achieve a good driveability. • A gear train with a wide gear spread and a lower gear ratio, enhancing standing start and acceleration performance ( Fig. 1). • A shift control and lock-up (L/U) control that achieves a more natural and direct response dynamic performance with respect to gas pedal inputs.The transmission efficiency in transient states, during acceleration, is one of the most important factors to improve driveability. New shift and L/U control are then developed to reduce energy losses which create heat on the friction plates or in the torque converter. Figure 1. Lower gear ratio of 8-speed AT (UA80) Figure 2. Fuel economy performance and regulations for four-cylinder Camry The new shift and L/U controls used by the Direct Shift-8AT were developed by focusing on the details of the functional requirements for efficient transmission of torque. As a result, it was necessary to add many functions to the original control method. Instead, a new control design, using gear train and torque converter models, was adopted to satisfy these requirements without overcomplicating the controls.Driveability Improvement with Innovative Toyota 8 Speed Automatic Transmission Control2017-01-1109 Published 03/28/2017 Keisuke Ota, Masami Kondo, Shuntaro Shinohara, Norihiro Tsukamoto, Seiji Masunaga, and Ayumu Sagawa Toyota Motor Corporation CITATION: Ota, K., Kondo, M., Shinohara, S., Tsukamoto, N. et al., "Driveability Improvement with Innovative Toyota 8 Speed Automatic Transmission Control," SAE Technical Paper 2017-01-1109, 2017, doi:10.4271/2017-01-1109. Copyright © 2017 SAE InternationalDownloaded from SAE International by University of Edinburgh, Saturday, August 25, 2018Combining these new control methods, with the lightweight, compact, and highly efficient automatic transmissions (ATs), helps to achieve excellent vehicle fuel economy, while enabling a more natural and responsive dynamic performance. For example, the fuel economy of the new Camry equipped with these transmissions is world-leading for a vehicle in its class. 2. System Configuration 2.1 Description of Vehicles Installed with Direct Shift- 8AT The Direct Shift-8AT (UA80) is installed in the 2017 Highlander, and 2017 Sienna, and is paired with a V6 engine generating a maximum torque of 263 lb.-ft. ( Table 1 ). This transmission replaces a 6-speed AT (6AT) in these vehicles. In specific terms, the UA80 replaces the U660 transmission. Table 1. Description of vehicles installed with Direct Shift-8AT 2.2 Configuration of Automatic Transmissions Table 2 shows the technical data for the newly developed UA80 and the previous U660 transmissions. Each gear of these transmissions is demonstrated as the systems shown in figure 3, 4 and 5. The eight speeds of the new transmissions are achieved without increasing weight or length from the 6AT. In addition, although the maximum torque capacity of the UA80 has increased from 2