Vehicle Implementation of a GM RWD Six-Speed Integrated-Friction-Launch Automatic Transmission 2007-01-3747
Friction Launch transmissions use a wet multi-plate clutch to replace the torque converter in an automatic transmission. By using one of the range clutches inside the transmission, the benefits of this integrated friction launch technology (IFL), such as reduction in mass, packaging, and cost, can be enhanced. The availability of new automatic transmissions with higher number of speeds and wider ratio spreads makes IFL technology more viable than ever before. The new GM Rear-Wheel-Drive (RWD) six-speed transmission has paved the way for a full implementation of integrated friction launch technology in a GM full size Sport-Utility Vehicle (SUV). This project focuses on both hardware and control issues with the friction launch clutch. The hardware issues include designing the clutch for launch energy, cooling, and durability. The control issues 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 design of the clutch and the cooling system, and the development of the launch and creep control algorithms. Vehicle test data presented in this report show that High-Energy-Capacity Clutch (HECC) design as a friction-launch device can handle a wide-open throttle launch for a full-size truck application. 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. Also, vehicle fuel economy tests revealed promising fuel economy improvements over production intent 6-speed RWD transmission.