Hybrid propulsion system and method for conjoint application of propulsion torque

The system has a mechanically coupled internal combustion engine and electrical machine and short- and long-term storage devices. The storage devices are coupled via an electric valve so that when supplying the electrical machine it is first supplied only from the short-term device and the valve connects the storage devices in parallel with the voltage from the short-term device falls to or below that of the long-term device. The system has an internal combustion engine and an electrical machine (15) that are mechanically coupled and apply drive torque to the drive together when the power demanded is high and short- and long-term storage devices charged with different higher and lower charging voltages respectively. The storage devices are coupled via an electric valve so that when supplying the electrical machine it is first supplied only from the short-term device and the valve connects the storage devices in parallel with the voltage from the short-term device falls to or below that of the long-term device. AN Independent claim is also included for the following: (a) a method of common application of drive torque with an internal combustion engine and an electric machine in a hybrid drive system.