SAE International Development of Innovative Toyota 10-Speed Longitudinal Automatic Transmission 2017-01-1099

Toyota Motor Corporation has developed an innovative 10-speed longitudinal automatic transmission called the Direct Shift-10AT. The Direct Shift-10AT is a significant contributor to the excellent dynamic performance of the Lexus LC500. A wide gear spread with close gear ratios allows for rhythmical shifting, smooth and powerful acceleration from a standing start, along with quiet and relaxed high- speed driving due to low engine speeds. The lock-up area is expanded to a wider range of vehicle speeds (excluding low-speed regions such as when starting off), by the adoption of a multi-plate lock-up clutch, a newly developed torque converter, and a high-precision controller. As a result, the shift control can match the driver's intended operation more directly because the main cause of the response delay (transient changes in engine speed (flare)) is eliminated. Furthermore, fuel economy is improved due to the adoption of low friction clutches. Emotional driving performance is achieved using a support control that responds to the driver's intention and the driving situation, cooperative control with the powertrain, and one of the world's quickest shifting automatic transmissions. This support control adopts an individual driving force control for each driver by estimating the driver's intention based on the accelerator operation and vehicle state to seamlessly select a shift pattern. This paper describes the gear ratio design method, new control technology, and vehicle performance of the Direct Shift-10AT.