A Dual Clutch Torque Converter for Dual Input Shaft Transmissions

This paper presents an alternative launch device for layshaft dual clutch transmissions (DCT's). The launch device incorporates a hydrodynamic torque converter, a lockup clutch with controlled slip capability and two wet multi-plate clutches to engage the input shafts of the transmission. The device is intended to overcome the deficiencies associated with using conventional dry or wet launch clutches in DCT's, such as limited torque capacity at vehicle launch, clutch thermal capacity and cooling, launch shudder, lubricant quality and requirement for interval oil changes. The alternative device enhances drive quality and performance at vehicle launch and adds the capability of controlled capacity slip to attenuate gear rattle without early downshifting. Parasitic torque loss will increase but is shown not to drastically influence fuel consumption compared to a dry clutch system, however synchronizer engagement can become a concern at cold operating temperatures. The performance of the dual clutch torque converter is assessed in a 7 speed front wheel drive DCT application and compared against the dry clutch system in the areas of launch, start/stop, driveline torsional isolation, gear rattle mitigation and fuel consumption. The dual clutch torque converter is shown to overcome the shortcomings of a dry friction launch system and deliver equivalent fuel economy performance.