Challenges of Engine Starts and Drivability in a Parallel Hybrid-Electric System

The concept of the Modular Hybrid Transmission (MHT) is to use a production transmission design with modifications to create a new low investment cost parallel hybrid-electric powertrain. In the MHT system to be discussed, the torque converter has been replaced with a 40-kilowatt electric induction machine, which is coupled to a 300 volt - 3.6 Ah Lithium-Ion battery in a 1450 kg vehicle. Also, an added wet clutch system allows the engine to be disconnected from the electric machine enabling “electric only” driving.

The drivability problems occur when the driver's desire to accelerate changes quickly and the engine is still shut down. This situation can occur both from rest and while already moving.