Govindswamy, K., Hellenbroich, G., and Ruschhaupt, J., "7-XDCT: Compact and Cost-Efficient Dual Clutch Transmission for Small and Mid-Size Vehicles," SAE Int. J. Passeng. Cars - Mech. Syst. 6(2):894-898, 2013, doi:10.4271/2013-01-1271.
The automotive industry continues to develop new powertrain technologies aimed at reducing overall vehicle level fuel consumption. The ongoing trends of “downsizing” and “down speeding” have led to the development of turbocharged engines with low displacement and high torque density. In order to meet the launch response requirements with these engines as well as fuel economy needs, transmissions with large ratio spreads will need to be developed. Due to the lack of torque amplification from the torque converter, the next generation of dual clutch transmissions (DCT) will need to have larger launch ratios and ratio spreads than currently available in production today. This paper discusses the development of a new family of DCT (called “xDCT”) for use in front wheel drive vehicles, aimed at meeting some of these challenges.The xDCT family features two innovative concepts, the idea of “gear generation” and “supported shifts”. A combination of these features results in the development of a highly compact and efficient family of DCTs. The paper will begin with a definition of the xDCT concept followed by a layout of the gear sets for 7 and 10 speed versions of this transmission. Simulation results are used to show the powershift capability as well as efficiency of the developed transmission concept. Finally, a 3D design study is utilized to demonstrate key features of the transmission concept that will result in a highly efficient and compact transmission with low mechanical complexity and full powershift capabilities.