Procedure and device to monitor an exhaust gas after-treatment system

Abstract

The invention concerns a procedure to monitor an exhaust gas after-treatment system of an internal combustion engine with a motor block and an exhaust gas duct, which has at least one catalytic converter, upstream from which a reagent substance necessary for the NOx reduction in the catalytic converter is introduced by means of an introduction device, whereby the reduction agent rate is increased to such an extent at defined reference operating points until an ammonia breach is detected in direction of flow behind the catalytic converter by means of an ammonia sensitive sensor in the exhaust gas duct.

Description

The invention is more closely explained in the following description using one of the examples of embodiment depicted in the figure.

FIG. 1 shows a schematic depiction of an exhaust gas after-treatment system of an internal combustion engine

Claims

1. A method of monitoring an exhaust gas after-treatment system of an internal combustion engine with a motor block and an exhaust gas duct, which has at least one catalytic converter, upstream from which a reagent substance necessary for NOx reduction in the catalytic converter is introduced by means of an introduction device, the method comprising increasing a reduction agent rate at defined reference operating points to such a degree until an ammonia breach is detected by an ammonia sensitive sensor in an exhaust gas tract in the direction of flow behind the catalytic converter.

2. A method according to claim 1, wherein increasing includes increasing the reduction agent rate up to the ammonia breach and with the aid of additional operating parameters of the exhaust gas after-treatment system, and further comprising calculating a current maximum ammonia storage capability for a particular operating point.

3. A method according to claim 2, wherein calculating the ammonia storage capability includes calculating based on a temperature progression at the catalytic converter, a NOx amount calculated from an air mass and a NOx concentration, a NOx conversion in the catalytic converter, an ammonia level at the beginning of the test, or an amount of the reduction agent supplied during the regeneration, which is determined by means of a measuring device attached to the introduction device.

4. A method according to claim 1, further comprising ascertaining a correction of a liquid level characteristic curve from a current ammonia storage capability.

5. A method according to claim 1, further comprising testing of the ammonia storage capability in regular intervals or at favorable operating points.

6. An application of the procedure according to claim 1, further comprising determining an ammonia storage capability of the catalytic converter by deploying a procedure in combined or integrated exhaust gas systems, in which a sooty particle filtering is additionally implemented by means of a particle filter.

7. An application according to claim 6, further comprising emptying the ammonia storage prior to the regeneration of the particle filter and filling the ammonia storage at the conclusion of the regeneration.

8. A device to monitor an exhaust gas after-treatment system of an internal combustion engine with a motor block and at least one exhaust gas duct, which has at least one NOx sensor to determine a NOx content in an exhaust gas and at least one catalytic converter upstream from which a reagent substance necessary for NOx reduction in the catalytic converter can be introduced by means of an introduction device, whereby the NOx sensor as well as additional sensors to measure a temperature at the catalytic converter and to measure an air in a delivery air duct as well as an ammonia sensitive sensor in a direction of flow behind the catalytic converter maintain an active connection to a monitoring unit, wherein in the monitoring unit an excess metering of the reagent substance can be initiated, an ammonia breach can be detected by means of the ammonia sensitive sensor and an ammonia storage capability for the catalytic converter can be determined.

9. A device according to claim 8, wherein the exhaust gas duct has a particle filter in the direction of flow behind the catalytic converter.

10. A device according to claim 8, wherein within the monitoring unit, the current ammonia storage capability of the catalytic converter can be stored in a characteristic curve/engine characteristic map-unit of the monitoring unit.

11. A device according to claim 8, wherein a function to determine the ammonia storage capability of the catalytic converter in the monitoring unit is designed as software and/or hardware and is at least partially a component of a larger engine management system.