Parallel hybrid powertrain for an automotive vehicle

Abstract

A hybrid powertrain for an automotive vehicle comprising an internal combustion engine and transmission assembly providing a first selectably shiftable geared torque flow path to vehicle traction wheels and an electric motor-generator unit defining a second geared torque flow path that is located between the output of the first geared torque flow path and the traction wheels. Through the deployment of an appropriate control system, including the necessary control algorithms, the electric motor-generator unit can be operated to supply torque to the traction wheels while the torque flow in the first torque flow path is interrupted during the occurrence of a ratio change in the transmission assembly and during disengagement of a clutch. Because of this interactive control of two power sources, the vehicle driveability can be enhanced along with an improvement of the engine exhaust gas emissions. In addition, the electric motor-generator unit in the second torque flow path can be used to launch the vehicle electrically immediately upon request of the operator. This ability of the powertrain permits engine-off operation during vehicle coast-down and standstill periods without any loss of driveability. During electric launch of the vehicle, the interactive control of the two power sources permits the internal combustion engine to be restarted and then gradually take over the propulsion task from the electric motor-generator unit.