Method for determining nitrogen oxide concentration in exhaust flow path of diesel engine of motor car, involves determining nitrogen oxide concentration depending on nitrogen oxide sensor signal and modeled value

摘要

The method involves detecting nitrogen oxide concentration based on a signal of a nitrogen oxide sensor (40). A modeled value of an adjusting ratio of nitrogen dioxide to nitrogen oxide is determined from operational parameters of an internal combustion engine (11) and/or an exhaust tube (23). Nitrogen oxide concentration is determined depending on the signal of the nitrogen oxide sensor and the modeled value, where the ratio of the nitrogen dioxide to the nitrogen oxide in an exhaust gas flow is determined before entering a selective catalytic reduction (SCR) catalyzer (35). An independent claim is also included for a controlling and/or regulating device for determining nitrogen oxide concentration in a flow path behind a selective catalytic reduction (SCR) catalyzer arranged in an exhaust system of a combustion engine.