Überwachungsverfahren für NOx-Speicherkatalysatoren und Abgasreinigungsvorrichtung zur Durchführung dieses Verfahrens

摘要

The invention relates to a method for monitoring a NOx storage catalytic converter (14) positioned downstream of an internal combustion engine (12) run on a lean mixture. According to said method the NOx storage efficiency of the catalytic converter (14) is determined from the NOx exhaust gas concentrations upstream and downstream of the NOx storage catalytic converter (14) and compared with a defined threshold value. Execution of the method requires compliance with defined operating conditions, such as a lambda value > 1 and a catalytic converter temperature between 200 and 600 DEG C. According to the invention an exhaust-gas purification device suitable for carrying out the method comprises a NOx storage catalytic converter (14) having a lambda sensor (16) positioned upstream and a lambda sensor (18) positioned downstream for determining oxygen concentrations in the exhaust gas and to ensure that the catalytic converter is monitored only during lean-mixture operations. A NOx probe (20) positioned upstream and a further NOx probe (22) positioned downstream measure NOx concentrations in the exhaust gas upstream and downstream of the catalytic converter (14), the desired NOx storage efficiency being determined from said concentrations. However, the exhaust gas NOx concentration upstream of the catalytic converter (14) can also be calculated using modeling. The exhaust-gas purification device can also comprise a temperature probe, positioned upstream and/or downstream of the catalytic converter, for determining catalytic converter temperature.