Future combustion strategies, driven by the need for lower emissions and increased fuel economy, require ignition systems capable of delivering high energy levels in a more flexible and intelligent manner. By monitoring the combustion process itself in real time, benefits can be achieved in performance, fuel economy, cost, and more effective packaging of the coil and associated electronics in the limited space near the spark plug. To obtain a spark event with both high current and long duration, a large, heavy coil would be required. However by using a multi-charge technique to deliver energy in 'packets' or 'pulses', it is possible to generate a comparable amount of energy in the same time using a much smaller coil. This is achieved by firing the smaller coil multiple times, with the number of additional firings determined by engine speed. In order to maximize the energy delivered in a specified time frame, the overall energy delivery rate needs to be defined and optimized. For a given set of coil and engine conditions, the discharge voltage can be related from the secondary current at the termination of the discharge. By knowing this information, the primary current at the start of next recharge cycle can be determined. The energy delivered per pulse, the recharge time to a given primary current, and the discharge time can all be calculated from the ending secondary current of the discharge. These values determine the overall rate of energy delivery. Combustion is monitored using a variation of the ion current sensing which is particularly well-suited for use with a multicharging ignition system. Multi-charging stops when a 'robust' combustion has been achieved and/or at a predetermined engine crankshaft position. This limit is typically set to a fixed number of engine degrees, and can be controlled by the engine control computer or by the multi-charge control electronics.
Dynamic ignition energy delivery with closed loop feedback control
Dynamische Zündungsenergieregelung in geschlossenem Regelkreis
1999
6 Seiten, 8 Bilder, 1 Quelle
Conference paper
English
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