Control process for an internal combustion engine operating with a poor mixture at least some of the time as a function of operating parameters of the exhaust gases and an NOx storage catalyzer

摘要

An operating zone for a poor mixture with two or more dimensions is defined by operating points which can be preset. These include the minimum requirements which can be preset for the operating parameter(s) combined with the exhaust gas parameter(s). The operating zone is subdivided into segments. Segments are blocked if one or more of the operating points do not reach the minimum requirements. The process uses a measurement and control unit to determine the operating parameter and the exhaust gas parameter. The exhaust gas parameter is the mass flow of NOx upstream of the NOx storage catalyzer and the operating parameter is the temperature of the NOx storage catalyzer, with the operating zone designed in the form of a NOx mass flow/NOx storage catalyzer temperature diagram subdivided into segments. The segments give defined increments for the temperature and/or the NOx mass flow rate, with the temperature increments between 5 and 50 K, preferably between 5 and 25K, and the mass flow rate increments between 0.25 and 5 mg NOx/s, preferably between 0.5 and 2.1 mg NOx/s. Supplementary segments, which deviate slightly from the operating point at which the minimum requirements are given, are blocked from use with a poor mixture. In particular, the segments where the deviations are at most 0.5mg NOx/s and/or 5K. The favorable operating range for the catalyzer predetermined for the vehicle, is used as the initialization values and adapted using an predetermined algorithm. A temperature threshold is preset, preferably in the range 320 to 400 deg. C. In the case where the catalyzer temperature is high and near the upper threshold value and the NOx mass flow rate is several orders of magnitude below the threshold, the operating zone is adapted to allow a temperature above that of the upper threshold (and vice versa). If the temperature is low and near the lower threshold value, and the NOx mass flow rate is also low, the operating zone is adapted to allow a temperature below the threshold until it reaches a defined minimum, preferably 200 to 250 deg. C. The extent of the adaptation is defined as a function of the operating points at the minimum values. The parameters of the catalyzer are determined and/or calculated continuously or after a certain flow for a specific period. Other parameters are also incorporated to optimize the storage capacity of the NOx catalyzer. The upper threshold values are selected as a function of the material used to coat the catalyzer.