Development of a Clutch Assisted Engine Start

Environmental protection and ecient energy utilization have been always important issues in the automotive industry, but have gained signicant momentum with the growing demand for mobility around the world and its impact on the global environment. For this purpose, many improvements in automobile technology have been accomplished over the past decades. However fuel economy with improvements in vehicle powertrain technology has been penalized by customer preferences. Automotive industry faces the challenge of producing vehicles that meet future fuel economy and emissions requirements which are priced to meet the desired customer value. As hybrid vehicles, due to the high cost of the electrication they introduce, in next years will not impact the OEM eet-averaged CO2 gures in a signicant way, it is benecial to introduce new cost-oriented CO2 features able to optimize engine operations, as they oer a very favorable cost/benet ratio. According to market trend, the increasing interest on automated transmission (i.e. AMT, DCT) plays a key-role towards the optimization of engine operation. The basic principle of shutting the engine o at idle to remove engineâs drag torque could be adopted at vehicle in motion, extending the distance covered by the vehicle coasting, when no traction is required, by opening the clutch automatically. Literature calls such operation âsailingâ: represents a low cost control feature, as it does not introduce new components, able to enhance Start & Stop technology. Turning o the combustion engine during coasting conditions increases the number of engine starts over vehicle lifetime, impacting the whole vehicle. Today starter motors are typically designed for Start&Stop applications for up to 300:000 engine crank over vehicle lifetime. This number can double for Start&Stop Sailing applications. However, the number of load cycles for the starter motor can be reduced signicantly if the engine is revved up via clutch. The work focuses on the development clutch assisted start by applying a new methodology based on modeling and simulation. In general, starting the engine through clutch engagement consists in spending a certain amount of the traveling vehicle kinetic energy to spin up the engine. The consequent deceleration of the vehicle, due to this maneuver, must be mitigated by an appropriate clutch closing strategy. Moreover, vibrations induced in the powertrain during the maneuver can generate uncomfortable feelings for the passenger. Hence a powertrain and driveline modeling that allows to investigate the impact on drivability for dierent clutch engagement in dierent operating conditions in order to fulll drivability requirements.