Operating and diagnostic method for an SCR exhaust-gas aftertreatment system

US8499545B2 · kind B2 · utility

Assignee

• Daimler AG · DE

Inventors

• Michael-Rainer Busch · Großenhain, DE
• Dirk Herbstritt · Durmersheim, DE
• Uwe Hofmann · Würzburg, DE

Key dates

• Filing date: Aug 13, 2008
• Grant date: Aug 6, 2013
• Expiry date: Feb 1, 2030

Classification

• Technology area (CPC Y): Emerging Cross-Sectional Technologies
• CPC primary: Y02T10/40
• WIPO field: Environmental technology
• WIPO sector: Chemistry

Abstract

In an operating and diagnostic method for an SCR exhaust gas aftertreatment system which has an SCR catalytic converter with ammonia storage capacity, a signal of an exhaust gas sensor that is sensitive to nitrogen oxide and ammonia and is arranged downstream of the SCR catalytic converter, is measured. In a normal operating mode, ammonia is supplied to the SCR catalytic converter corresponding to a filling level model for ammonia stored in the SCR catalytic converter, in such a way that the ammonia filling level of the SCR catalytic converter is held at least approximately at a predefinable nominal value (or value range). The normal operating mode is interrupted if an exhaust gas sensor signal that exceeds a predefinable first limit value, is registered, and the set urea dosing rate is increased by a predefinable degree in relation to the value provided in the normal operating mode. Thereafter, a return is made to the normal operating mode, or a switch is made to a diagnostic operating mode, as a function of the profile of the signal of the exhaust gas sensor.