Technical Paper
Performance Analysis of the Impulse Shift CVT
2004-08-23
2004-40-0023
Due to rotating inertias within the engine and transmission, the response of a vehicle during large engine speed shifts may appear reluctant or even counteractive. To overcome this behaviour, a CVT drivetrain was augmented with a powersplitting planetary gear stage and steel flywheel in the so-called Zero Inertia (ZI) powertrain [1]. This transmission concept managed to combine two contradictive goals: the driveability in terms of the pedal-to-wheel response is greatly improved; and a large leap towards optimal fuel economy can be made. These goals were achieved by cruising the vehicle at extremely low engine speeds, enabled by the large ratiocoverage of the CVT. The flywheel acts as a 'peakshaver' during engine speed transients: it delivers power during (semi-) pedal kickdown and absorbs the engine's kinetic energy at pedal back-out.
