Abstract Increasingly stringent environmental regulations requiring lower CO2 emissions and higher fuel economy have made it essential to develop vehicles with superior fuel efficiency and cleaner emissions. At the same time, there is growing demand for even more powerful and quieter vehicles. To help satisfy these requirements, Toyota Motor Corporation has developed a new 8-speed automatic transmission for front wheel drive vehicles, incorporating its first compact torque converter with a multiple disk lock-up mechanism. This newly developed compact torque converter with a multiple disk lock-up mechanism was designed under the Toyota New Global Architecture (TNGA) development concept to achieve an excellent balance between higher efficiency through the commonization of components and stronger product appeal through installation on a whole family of transmissions. This compact torque converter is compatible with a variety of engines from inline 4-cylinder to V6 configurations. This transmission also includes a multiple disk lock-up clutch that can be used all through the torque range, which helps create a direct dynamic response and better fuel economy. A new ultra-flat torus was developed with the same stall performance as a torus for a V6 engine but with the same size as the previous inline 4-cylinder engine torus. This torus combines a maximum efficiency of at least 80% with an approximately 12% smaller flow diameter and an approximately 28% flatter design. This paper describes the main design characteristics of the new multiple disk clutch and torus. Introduction The torque converter is the main device as the starting clutch of the automatic transmission, because it provides smooth driving performance at low cost. But the vehicle needs to reduce emissions, increase power, driving performance, and NVH characteristic at the same time. As a result, the requirement for the torque converter is changing from previous model. It needs an increasingly wide lock up operating area to achieve a quick response from the pedal control, and to achieve good efficiency. The importance of the lock up clutch system and the damper are also increasing. In response, Toyota Motor Corporation has developed a new 8-speed automatic transmission for 3.5-liter front-wheel drive (FWD) vehicles called the Direct Shift-8AT UA80. The UA80 is Toyota’s first FWD transmission to incorporate a torque converter with a multiple disk lock-up mechanism. Figure 1 shows cross section of UA80. Figure 1. UA80 cross section.Development of Compact Torque Converter with New Multiple Disk Clutch for Toyota New FWD Eight-Speed Transmission Direct Shift-8AT2017-01-1118 Published 03/28/2017 Isamu Hachisuwa, Naoki Kato, Daisuke Kusamoto, Hideki Miyata, Takuya Okada, and Hitoshi Matsunaga Toyota Motor Corporation Takamitsu Kuroyanagi and Makoto nakazuru Aisin AW Co Ltd CITATION: Hachisuwa, I., Kato, N., Kusamoto, D., Miyata, H. et al., "Development of Compact Torque Converter with New Multiple Disk Clutch for Toyota New FWD Eight-Speed Transmission Direct Shift-8AT," SAE Technical Paper 2017-01-1118, 2017, doi:10.4271/2017-01-1118. Copyright © 2017 SAE InternationalDownloaded from SAE International by Univ of California Berkeley, Sunday, August 05, 2018The UA80 was designed under the Toyota New Global Architecture (TNGA) development concept to achieve an excellent balance between higher efficiency through the commonization of components and stronger product appeal through installation on the whole transmission series. Under this concept, the basic structure of the UA80 is kept unchanged, while other components are adjusted to meet customer needs and particular vehicle characteristics. This torque converter with a multiple disk lock-up mechanism adopts a high heat resistant multiple disk lock-up clutch to enable operation even under conditions that require the most frequent slip control, while maintaining compatibility with torque input from