Due to rotating inertias within the engine and transmission, the response of a vehicle during large engine speed transients may appear reluctant or even counteracting. Reminiscent of comparable behaviour in aircraft jet-propulsion, this phenomenon is also referred to as jet-start. To overcome this behaviour, a CVT powertrain is augmented with a plenetary gear set and a compact steel flywheel. The new transmission seamlessly combines two contradictory features: the driveability in terms of the pedal-to-wheel response is greatly improved and a large leap towards optimal fuel economy can be made. This is achieved by cruising the vehicle at extremely low engine speeds, using the large ratiocoverage of the CVT. The flywheel acts as a "peak shaver" during speed shifts: it delivers power during engine acceleration and absorbs kinetic energy during engine decelerations. In this paper, system dynamics and control aspects of the new powertrain are discussed.
|Publication status||Published - 2001|