Internal-combustion engine i.e. diesel engine, operating method for motor vehicle, involves determining characteristic of feed ratio and measuring signal, and determining operating condition of selective catalytic reduction system

• Main Authors: RODATZ, PAUL, SACK, CHRISTIAN, ARLT, TINO
• Format: Patent
• Language: English; German
• Published: 09.10.2008
• Subjects: BLASTING; ENGINE PLANTS IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNALCOMBUSTION ENGINES; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES ORENGINES IN GENERAL; HEATING; LIGHTING; MACHINES OR ENGINES IN GENERAL; MECHANICAL ENGINEERING; STEAM ENGINES; WEAPONS

The method involves determining a characteristic of a feed ratio of nitrogen oxides to a reducing agent. A characteristic of a measuring signal of an exhaust gas probe (38) is determined, where the probe is downstream to a selective catalytic reduction (SCR) catalyst (23) of a SCR system. An operating condition of the SCR system is determined based on gradients of both the characteristics. A temporal correlation of positive gradients of the characteristic of the measuring signal is detected by the SCR catalyst. An independent claim is also included for a device for operating an internal-combustion engine. Zum Betreiben einer Brennkraftmaschine mit einem SCR-System wird ein Verlauf eines Feed-Verhältnisses (ALPHA) ermittelt, das ein Verhältnis aus Stickoxiden zu einem Reduktionsmittel repräsentiert. Ein Verlauf eines Messsignals (EG_SIG) einer Abgassonde stromabwärts eines SCR-Katalysators des SCR-Systems wird ermittelt. Abhängig von je einem Gradienten (ALPHA_GRD; EG_GRD) der beiden Verläufe wird ein Betriebszustand des SCR-Systems festgestellt.