Hydropneumatic storage technology for hybrid passenger cars

The development of today´s powertrains focusses on the reduction of vehicles´ CO₂-emissions. Therefore several new technologies for internal combustion engines have been established. A further tendency is the advancing hybridization and electrification of powertrains vehicles. However, these trends lead to increasing system costs, which are a very important aspect at the market segment of compact cars. At the Institute of Internal Combustion Engines of the Technische Universitaet Muenchen a drivetrain concept for urban and commuter traffic is under development. It is based on a lean burn air cooled two-cylinder natural gas engine, which is combined with a hydraulic hybrid system. The paper contains detailed information about the hydraulic hybrid drivetrain and especially about the hydropneumatic storage technology. Particular characteristics and innovations of the hydraulic hybrid system compared to systems known so far are presented and discussed.