Engine down-sizing and down-speeding: A new challenge for torsional vibration filtration

摘要

Even if hybrid and electrical power-trains are expanding themselves in the market, the Internal Combustion Engine (ICE) is still very present. In order to meet the fuel consumption and CO_2 emission requirements, ambitious research programs are currently running at Valeo. These programs are mainly focused on down-sizing and down-speeding of the ICE. Down-sizing consists of reducing the number of cylinders (Typically 4 to 3 or 6 to 4) and the engine displacement. As the torque request is increased or at least kept the same, specific cylinder pressure is becoming higher and higher. As a consequence, the torque fluctuations (main NVH source in a vehicle) are more and more severe. For fuel consumption reasons, the max engine torque is available at a much lower speed. Therefore, lower excitation frequencies turn out to be more difficult to filter. For the transmission field, down-sizing and down-speeding have great consequences in terms of torque fluctuations, amplitude and frequency. Usually systems based on rotating inertia and stiffness is at a difficult limit to overcome. Therefore, major technological breakthroughs are necessary to meet the new requirements.