Power transmission system for use in vehicle

The power transmission system for use in a vehicle includes a power split device (24) to perform power distribution among a flywheel (30) for storing rotational energy as mechanical energy, an internal combustion engine (10) and an electric rotating machine (32). The power transmission system is provided with an interrupting device (20) configured to interrupt power transmission between a group of the flywheel (30) and the electric rotating machine (32) and a group of the internal combustion engine (10) and drive wheels (16) of the vehicle when rotational energy stored in the flywheel (30) is transmitted to the electric rotating machine (32) through the power split device (24) under condition that power is transmitted between the internal combustion engine (10) and the drive wheels (16). A further embodiment (Figure 8A) is disclosed showing two power split devices (54,58) as well as two motor-generators (50a,50b).