Method for checking the seal of a reagent injector
In a method for checking the seal of a reducing agent injector of an SCR exhaust gas aftertreatment system of an internal combustion engine comprising at least one reducing agent tank, a reducing agent pump, a reducing agent injector and an NOx sensor connected downstream from the SCR catalytic converter, the following steps are carried out: a) Generation and/or detection of a release state of the SCR system in which no reducing agent is stored in the SCR catalytic converter; b) Determining a setpoint NOx value in the exhaust gas; c) Starting the seal check with a closed reducing agent injector by increasing the reducing agent pressure; d) Detecting the NOx signal at the NOx sensor, and a) Evaluating the NOx signal.
1. A method for checking the seal of a reducing agent injector of an SCR exhaust gas aftertreatment system of an internal combustion engine comprising a least one reducing agent tank, a reducing agent pump, a reducing agent injector and an NOx sensor connected downstream from the SCR catalytic converter, the method comprising the steps of:
a) generating and/or detecting a release state of the SCR system in which no reducing agent is stored in the SCR catalytic converter,
b) determining a setpoint NOx value in the exhaust gas using either a computer model or an additional NOx sensor,
c) maintaining the reducing agent injector in a closed position while increasing the reducing agent pressure to a pressure higher than a pressure range of the reducing agent pressure during a normal operation of the SCR exhaust gas aftertreatment system,
d) detecting an NOx signal at the NOx sensor,
e) evaluating the NOx signal by:
detecting changes in the NOx signal detected at the NOx sensor,
comparing the NOx signal detected at the NOx sensor to the setpoint NOx value, and
identifying a leak in the seal of the reducing agent injector if (a) the NOx signal detected at the NOx sensor indicates a reduction in NOx value over time, and (b) the NOx signal detected at the NOx sensor deviates from the setpoint NOx value.
2. The method according to claim 1 , comprising generating the release state by regenerating a particle filter in the exhaust gas system.
3. The method according to claim 1 , comprising generating and/or detecting the release state is achieved by an ongoing high-load operation of the internal combustion engine.
4. The method according to claim 1 , wherein the release state is detected by the detection and evaluation of the exhaust gas temperature.
5. The method according to claim 1 , wherein the setpoint NOx value is determined in step b) by an NOx model and/or by a second NOx sensor connected upstream from the SCR catalytic converter and a reducing agent injector.
6. The method according to claim 1 , wherein the NOx value is defined from the NOx model by a constant operating point of the internal combustion engine.
7. The method according to claim 1 , wherein the reducing agent pressure is set in step c) to a value of 8 to 11 bar.
8. The method according to claim 1 , wherein the NOx signal is evaluated in step e) in an engine controller.
9. The method according to claim 1 , wherein the result of the evaluation of the NOx signal is transferred in step e) to a display device.
10. The method according to claim 1 , wherein the method is initiated at regular intervals and or at intervals dependent on the operating time of the internal combustion engine.
11. A facility for checking the seal of a reducing agent injector of an SCR exhaust gas aftertreatment system of an internal combustion engine comprising a least one reducing agent tank, a reducing agent pump, a reducing agent injector, an NOx sensor connected downstream from the SCR catalytic converter, means for controlling and increasing a reducing agent pressure and means for evaluating an NOx signal, wherein the facility is operable to:
a) generate and/or detect a release state of the SCR system in which no reducing agent is stored in the SCR catalytic converter,
b) determine a setpoint NOx value in the exhaust gas using either a computer model or an additional NOx sensor,
c) maintain the reducing agent injector in a closed position while increasing the reducing agent pressure to a pressure higher than a pressure range of the reducing agent pressure during a normal operation of the SCR exhaust gas aftertreatment system,
d) detect an NOx signal at the NOx sensor,
e) evaluate the NOx signal by:
detecting changes in the NOx signal detected at the NOx sensor,
comparing the NOx signal detected at the NOx sensor to the setpoint NOx value, and
identifying a leak in the seal of the reducing agent injector if (a) the NOx signal detected at the NOx sensor indicates a reduction in NOx value over time, and (b) the NOx signal detected at the NOx sensor deviates from the setpoint NOx value.
12. The facility according to claim 11 , comprising generating the release state by regenerating a particle filter in the exhaust gas system.
13. The facility according to claim 11 , comprising generating and/or detecting the release state during an ongoing high-load operation of the internal combustion engine.
14. The facility according to claim 11 , wherein the release state is detected by the detection and evaluation of the exhaust gas temperature.
15. The facility according to claim 11 , wherein the NOx value is defined from the NOx model by a constant operating point of the internal combustion engine.
16. An exhaust gas aftertreatment system comprising a facility according to claim 11 .
17. The exhaust gas aftertreatment system according to claim 16 , wherein the exhaust gas aftertreatment system is coupled to on-board diagnostics.