A method of testing a proper functioning of a selective catalytic reduction system

Abstract

A method is disclosed to test for a proper functioning of a selective catalytic reduction system of an internal combustion engine. A selective catalytic reduction system includes a catalyst disposed in an exhaust pipe of the engine, an injector disposed in the exhaust pipe upstream of the catalyst for injecting a reducing agent, a pump for providing the reducing agent from a tank to the injector via a supply conduit and a pressure sensor for measuring a pressure within the supply conduit. The engine is operated at idle speed and a functionality check of the pressure sensor is executed. The engine is operated to increase an exhaust gas temperature in the exhaust pipe upstream of the catalyst and a functionality check of the pump is executed. A functionality check of the injector is executed after the functionality check of the pump and once the exhaust gas temperature has reached a predetermined target value thereof. A functionality check of the supply conduit is executed after the functionality check of the injector. The selective catalytic reduction system is identified as functioning properly when all of the functionality checks yields a positive result or malfunctioning when any one of the functionality checks yields a negative result.

Description

technical field [0001] The present invention relates to a method of testing the correct functioning of a selective catalytic reduction (SCR) system of an internal combustion engine, in particular an internal combustion engine of a motor vehicle (eg a gasoline engine or a diesel engine). Background technique [0002] SCR systems are known as aftertreatment devices designed to reduce nitrogen oxides (NOx) emitted by an internal combustion engine. The SCR system includes a catalyst that is placed in the engine's exhaust pipe to convert nitrogen oxides into natural nitrogen and water with the aid of a reducing agent. The reducing agent can be injected in liquid state to the exhaust pipe by a dedicated injector arranged upstream of the catalyst. The injector receives reductant from the tank through a pump that is in fluid communication with the injector via a supply conduit. [0003] The SCR system may also include a pressure sensor for measuring the pressure of the reductant i...

AI Technical Summary

Problems solved by technology

However, each functional test is only performed in the predetermined operating state of the internal combustion engine, so that the warning process can remain activated for a relatively long time after maintenance without providing any immediate evidence that the maintenance has been successful

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