New Launch Devices for Automatic Transmissions 2013-01-0233
Hydrodynamic launch elements, from the Foettinger principle of the torque converter to the first series production HCC wet clutch, are becoming more relied on in the transmission world for their high power density, launch comfort, and vibrational isolation capability. In order to attain the ambitious fuel economy objectives of the future, engine vibrations have to be successfully isolated from the driveline at low engine speed ranges without the use of the hydrodynamic circuit. This is now all the more challenging as new combustion engines are producing higher torsional vibrations as a result of fewer cylinders, higher combustion pressures, cylinder deactivation, and lower critical speeds.
This paper will describe the next generation of powertrain vibrational isolation, dampening via powersplit. Additionally, a next generation wet launch element, the Hydrodynamically Cooled Clutch will be discussed. A brief description of the current state of the art dampening technologies will be reviewed, highlighting the limitations of these solutions which pave the way for the new generations.
The challenge with front wheel drive or hybrid layouts is to reduce the dimensions of the hydrodynamic and clutch systems, while sustaining high thermal capacity in order to improve vibrational isolation, and ensure protection against judder in a challenging packaging environment.