The main obstacle in the development of hybrid vehicles is economic: fuel savings pain to compensate for additional investment costs. A new hybrid series-parallel architecture should improve this situation, by lowering the power of the electrical equipment, thus their costs and by reducing the energy conversions, thus the energy losses.
The basic idea is to associate two planetary gear mechanisms for power derivation. These mechanisms have two different gear ratios, one dedicated for low speeds and the other for high speeds of the vehicle. Some arrangements make the permutation smooth without friction or jolt. They give the opportunity to choose the mechanism which derives the less power. Consequently, the whole electric propulsion chain can be downsized, generating major cost cuts.
At the same time, we reduce the energy to be multi converted into (mechanical-electrical-chemical-electrical-mechanical+daily leakages) which means a better global efficiency and less CO2. In addition high and low speed working conditions are improved, and sport or economic driving can be offered.
With the double planetary gear mechanism (also called Dual Power Split Device: DPSD), the unavoidable inertia of the electric generator can be used to store some kinetic energy of the vehicle at low speed. The effect is similar to an ultra-capacitor. It can be increased in industrial vehicles by adding a relatively small flywheel (less than 1% of the vehicle mass). It can also be punctually used to increase vehicle performances such as acceleration or ICE start up. To decrease the electric power allows lower voltage that goes towards more safety also.
Note: In the known multi-mode architectures, one planetary gear mechanism for power derivation (3 rotating shafts) is associated to one or more planetary gear mechanisms for power transmission (2 rotating shafts, same as in a gear box) without impacting the derived power. The present device alternatively used two planetary gear mechanisms of different and negative gear ratios to obtain two different levels of derived power.
The figure shows a cross-section of an alternative of the device. Here, the selection of the planetary gear mechanism in operation has been replaced by a two speeds gearbox in order to increase the GENERATOR speed at the same time and get more inertia. The GENERATOR already runs high speed for economic reasons. The sliding pinion on the GENERATOR shaft can gear earthier the gear on the pilot shaft dedicated to the low speeds either the gear on the pilot shaft dedicated to the high speeds. While geared, the sliding pinion can also move a little further to engage also some fixed teeth in order to lock the corresponding pilot shaft obviously when its speed is null. So we can have 5 positions corresponding to five modes: A= neutral or pure electric mode, B= hybrid mode for low speed, C= hybrid mode for high speed, E= parking mode or thermal mode at low speed, D= thermal mode at high spee