Investigation of the Driving Comfort of the DE-REX Powertrain Based on Vehicle Measurements

Abstract

The “Two-Drive-Transmission with Range-Extender” (DE-REX) is a parallel-series powertrain concept, which was developed and set up in a demonstrator vehicle in the course of a publicly funded project. The powertrain concept is characterized by using two electric motors and an internal combustion engine. The transmission consists of two parallel two-speed subtransmissions and couples the aggregates with the drive shafts. While hybrid driving, the operation of the internal combustion engine with two mechanical gears only is challenging regarding the acoustic comfort. Therefore, virtual gear ratios using the series hybrid driving mode are introduced. The acoustic comfort in the demonstrator vehicle for parallel and series modes is measured and compared to the one of a conventionally driven vehicle with a 7-speed dual clutch transmission. The results of the comparative measurements show that despite of the strictly reduced number of gear ratios in the DE-REX powertrain, the acoustic comfort while hybrid driving can be as good as in a conventionally driven vehicle when virtual gear ratios are used. Since the overall power of the DE-REX powertrain is limited while driving in the series hybrid mode, a fast mode change to a full power parallel hybrid mode is essential. Based on measurement results of a mode change from series to parallel operating mode in the DE-REX demonstrator vehicle, it is shown that the mode change feels very responsive, sporty and comfortable for the driver. The results of the DE-REX demonstrator vehicle measurements approve the high driving comfort in the hybrid driving modes.