Control of A Friction Launch Automatic Transmission Using a Range Clutch

Abstract

Friction Launch transmissions use a wet multi-plate clutch to replace the torque converter in an automatic transmission. The main benefit of this technology is fuel economy improvement as a result of eliminating the losses in the torque converter. By using one of the range clutches inside the transmission instead of an input clutch in place of the converter, the benefits of this integrated friction launch technology, such as reduction in mass, packaging, and cost, can be enhanced. The availability of new automatic transmissions with higher number of speeds and wider overall ratio spreads makes this technology more viable than ever before. This project focuses on control issues with the friction launch clutch which include developing robust control algorithms for launch and creep, and providing damping to the driveline, when required, and ensuring acceptable vehicle drivability. This paper describes in detail the development of vehicle launch control algorithms. Vehicle test data is presented to show that the control strategy developed in this project significantly reduces the gap between the drivability of a starting clutch vehicle and a torque converter equipped vehicle.