In this article we have introduced the Auto Start Stop Function as part of the BMW EfficientDynamics. We gave a brief introduction into the ASSF functionality and focused on two aspects, the ASSF Operating Strategy and the key engine functions (Quick Start and Comfort Stop). The Operating Strategy appears to have four major tasks to take care of. First is to evaluate the vehicle's current state. This turns out to be a challenging task due to the restricted ensemble of sensors within large scale volume models. Second, the driver's intuition needs to be evaluated exactly, especially taking into account a quickly changing environment. The third aspect covers the finding of an optimal solution to all trade-offs as to derive the best decision whether to start or stop the engine automatically. Finally, the Operating Strategy controls the engine functions and coordinates the functional interaction to other systems. The Quick Start is realized by a bunch of steps. The conventional synchronisation is replaced by saving the exact position already at engine stop. The key to that is a crankshaft sensor with backward rotation detection and appropriate software functions. Enabled by a load prediction the first reasonable combustion is fired. Finally we optimise the start process with respect to dynamics (fast order of combustions) and emission applying a DoE. The Comfort Stop relies primarily on a stop prediction. The stop prediction considers only a designated set of shut-off conditions as trigger the start of the evacuation of the air intake system. Thereby the shut-off delay can be reduced and the engine vibrations can be suppressed effectively. As to keep the system behaviour comprehensible the time for evacuation of the air intake system is upper bounded thus providing a compromise between shut-down comfort and system response. The ASSF is realized at a neutral emissions behaviour enabled by an engine start request initiated by the readiness of the catalyst system. ASSF ensures that all emission related diagnostics are executed appropriately within the NEDC and that all emission related sensors work reliable during all runtime. Finally all adaptations have been decoupled from Automatic Starts and Stops.
Operating strategy and engine functions for an automatic start stop function - an intelligent contribution to the BMW efficient dynamics
Betriebsstrategie und Motorfunktionen für die Auto Start Stopp Funktion - ein intelligenter Beitrag zur effizienten Dynamik der BMW Group
2007
37 Seiten, 7 Bilder, 5 Quellen
Folienbeitrag
Conference paper
English