Method and apparatus for diagnosing exhaust gas aftertreatment component degradation

• US 20060242945A1
• Filed: 05/02/2005
• Published: 11/02/2006
• Est. Priority Date: 05/02/2005
• Status: Active Grant

• Current Assignee: Cummins Incorporated
• Original Assignee: Cummins Incorporated
• Inventors: Huang, Shyan, Wang, Yue Yun, Tsai, Jerilyn
• Granted Patent: US 8,215,098 B2
• Time in Patent Office: Days
• US Class Current: 60/277
• CPC Class Codes: F01N 11/002 the diagnostic devices measuring or estimating temperature or pressure in, or downstream of the exhaust apparatus
• CPC Class Codes: F01N 13/009 having two or more separate purifying devices arranged in series
• CPC Class Codes: F01N 13/0097 the purifying devices are arranged in a single housing
• CPC Class Codes: F01N 2550/03 of sorbing activity of adsorbents or absorbents
• CPC Class Codes: F01N 2560/026 for measuring or detecting NOx
• CPC Class Codes: F01N 2560/06 the means being a temperature sensor
• CPC Class Codes: F01N 2560/14 having more than one sensor of one kind
• CPC Class Codes: F01N 2900/0422 measuring the elapsed time
• CPC Class Codes: F01N 3/0821 combined with particulate filters catalysed diesel particulate filters F01N3/035
• CPC Class Codes: F01N 3/0842 Nitrogen oxides
• CPC Class Codes: F01N 3/106 Auxiliary oxidation catalysts
• CPC Class Codes: F02B 29/0406 Layout of the intake air cooling or coolant circuit
• CPC Class Codes: F02B 37/00 Engines characterised by provision of pumps driven at least for part of the time by exhaust
• CPC Class Codes: F02D 2200/0802 Temperature of the exhaust gas treatment apparatus
• CPC Class Codes: F02D 2200/0806 NOx storage amount, i.e. amount of NOx stored on NOx trap
• CPC Class Codes: F02D 2200/0811 NOx storage efficiency
• CPC Class Codes: F02D 41/0072 Estimating, calculating or determining the EGR rate, amount or flow sensors in EGR systems F02M26/45
• CPC Class Codes: F02D 41/0275 the exhaust gas treating apparatus being a NOx trap or adsorbent
• CPC Class Codes: F02D 41/146 the characteristics being an NOx content or concentration
• CPC Class Codes: F02D 41/1465 with determination means using an estimation
• CPC Class Codes: F02D 41/187 : using a hot wire flow sensor
• CPC Class Codes: F02D 41/22 : Safety or indicating devices for abnormal conditions in air/fuel ratio feedback systems F02D41/1495, in electric control linkage F02D11/107, in purge control systems F02M25/0809
• CPC Class Codes: F02M 26/05 : High pressure loops, i.e. wherein recirculated exhaust gas is taken out from the exhaust system upstream of the turbine and reintroduced into the intake system downstream of the compressor
• CPC Class Codes: F02M 26/23 : Layout, e.g. schematics
• CPC Class Codes: F02M 26/45 : Sensors specially adapted for EGR systems
• CPC Class Codes: Y02T 10/40 : Engine management systems

Abstract

A system is provided for diagnosing operation of an exhaust gas aftertreatment component for an internal combustion engine. The system includes a NOx sensor producing a NOx signal indicative of NOx content of exhaust gas exiting the aftertreatment component, and a control circuit configured to estimate as a function of a number of engine operating conditions a NOx inlet content corresponding to a NOx content of exhaust gas produced by the engine and entering the aftertreatment component. The control circuit is configured to determine a NOx conversion efficiency of the aftertreatment component as a function of the NOx signal and of the NOx inlet content, and to determine that the aftertreatment component is degraded if the NOx conversion efficiency is below a threshold value for at least a first predefined time period.

Claims

1. A system for diagnosing operation of an exhaust gas aftertreatment component for an internal combustion engine, the system comprising:

a NOx sensor producing a NOx signal indicative of NOx content of exhaust gas exiting the aftertreatment component, and

a control circuit estimating as a function of a number of engine operating conditions a NOx inlet content corresponding to a NOx content of exhaust gas produced by the engine and entering the aftertreatment component, the control circuit determining a NOx conversion efficiency of the aftertreatment component as a function of the NOx signal and of the NOx inlet content and determining that the aftertreatment component is degraded if the NOx conversion efficiency is below a threshold value.

2. The system of claim 1 further including:

an engine speed sensor producing an engine speed signal indicative of rotational speed of the engine,

a mass air flow sensor producing a mass air flow signal indicative of a mass flow of fresh air entering the engine,

an intake manifold coupled to the engine,

an exhaust manifold coupled to the engine, and

an EGR conduit fluidly coupled between the exhaust manifold and the intake manifold,

wherein the control circuit is configured to estimate the NOx inlet content as a function of the engine speed signal, the mass air flow signal, a flow rate of fuel supplied to the engine, a fuel timing value and an EGR flow rate value indicative of a flow rate of recirculated exhaust gas through the EGR conduit.

3. The system of claim 1 further including:

an engine speed sensor producing an engine speed signal indicative of rotational speed of the engine,

a mass air flow sensor producing a mass air flow signal indicative of a mass flow of fresh air entering the engine, and

a pressure sensor producing a pressure signal indicative of ambient air pressure,

wherein the control circuit is configured to estimate the NOx inlet content as a function of the engine speed signal, the mass air flow signal, the pressure signal, a flow rate of fuel supplied to the engine, and a fuel timing signal.

4. The system of claim 1 wherein the control circuit is configured to determine the NOx conversion efficiency further as a function of a flow rate of the exhaust gas entering the aftertreatment component.

5. The system of claim 4 further including:

an engine speed sensor producing an engine speed signal indicative of rotational speed of the engine, and

a mass air flow sensor producing a mass air flow signal indicative of a mass flow of fresh air entering the engine,

wherein the control circuit is configured to determine the flow rate of the exhaust gas entering the aftertreatment component as a function of the engine speed signal, the mass air flow signal and a flow rate of fuel supplied to the engine.

6. The system of claim 1 wherein the control circuit is configured to determine that the aftertreatment component is degraded only if the NOx conversion efficiency is below the threshold value for at least a first predefined time period

7. The system of claim 6 wherein the control circuit is configured to determine the NOx conversion efficiency of the aftertreatment component by determining from the NOx signal an accumulated aftertreatment component outlet NOx quantity over a second predefined time period, determining from the NOx inlet content an accumulated aftertreatment component inlet NOx quantity over the second predefined time period, and determining the NOx conversion efficiency as a function of a ratio of the accumulated aftertreatment component outlet NOx quantity and the accumulated aftertreatment component inlet NOx quantity.

8. The system of claim 7 wherein the control circuit is configured to determine the accumulated aftertreatment component outlet NOx quantity as a function of the NOx signal and of a flow rate of exhaust gas entering the aftertreatment component over the second predefined time period, and to determine the accumulated aftertreatment component inlet NOx quantity as a function of the NOx inlet content and of the flow rate of exhaust gas entering the aftertreatment component over the second predefined time period.

9. The system of claim 8 further including:

an engine speed sensor producing an engine speed signal indicative of rotational speed of the engine, and

a mass air flow sensor producing a mass air flow signal indicative of a mass flow of fresh air entering the engine,

wherein the control circuit is configured to determine the flow rate of the exhaust gas entering the aftertreatment component as a function of the engine speed signal, the mass air flow signal and a flow rate of fuel supplied to the engine.

10. The system of claim 1 wherein the control circuit is responsive to an indicator indicating that regeneration of the aftertreatment component is occurring to determine whether the aftertreatment component is saturated as a function of the NOx signal and of the NOx inlet content, and to thereafter determine the NOx conversion efficiency of the aftertreatment component and determine whether the aftertreatment component is degraded only if the aftertreatment component is not saturated.

11. The system of claim 10 wherein the control circuit is configured to determine whether the aftertreatment component is saturated by determining a lean NOx conversion efficiency of the aftertreatment component as a function of the NOx signal and of the NOx inlet content, and determining that the aftertreatment component is not saturated if the lean NOx conversion efficiency is greater than a first minimum efficiency value and the lean NOx conversion efficiency does not drop below a second minimum efficiency value for more than a predefined time period.

12. The system of claim 10 wherein the control circuit is configured to determine whether the NOx sensor is faulty and to determine whether any sensor producing sensory information from which the NOx inlet content is estimated is faulty, and to thereafter determine the NOx conversion efficiency of the aftertreatment component and determine whether the aftertreatment component is degraded only if the NOx sensor is not faulty and no sensor producing sensory information from which the NOx inlet content is estimated is faulty.

13. The system of claim 1 further including a temperature sensor producing a temperature signal indicative of a temperature of exhaust gas exiting the aftertreatment component,

and wherein the control circuit is configured to determine the NOx conversion efficiency of the aftertreatment component and determine whether the aftertreatment component is degraded only if the temperature signal indicates that the temperature of the exhaust gas exiting the aftertreatment component is within a predefined temperature range and a flow rate of exhaust gas entering the aftertreatment component is within a predefined flow rate range.

14. The system of claim 13 further including:

an engine speed sensor producing an engine speed signal indicative of rotational speed of the engine, and

a mass air flow sensor producing a mass air flow signal indicative of a mass flow of fresh air entering the engine,

wherein the control circuit is configured to determine the flow rate of the exhaust gas entering the aftertreatment component as a function of the engine speed signal, the mass air flow signal and a flow rate of fuel supplied to the engine.

15. The system of claim 13 wherein the control circuit is responsive to an indicator indicating that regeneration of the aftertreatment component is occurring to determine whether the aftertreatment component is saturated as a function of the NOx signal and of the NOx inlet content, and to thereafter determine the NOx conversion efficiency of the aftertreatment component and determine whether the aftertreatment component is degraded only if the aftertreatment component is not saturated.

16. The system of claim 15 wherein the control circuit is configured to determine the NOx conversion efficiency of the aftertreatment component and determine whether the aftertreatment component is degraded only if the temperature of the exhaust gas exiting the aftertreatment component has been within a predefined temperature range, the flow rate of exhaust gas entering the aftertreatment component has been within the predefined flow rate range and the aftertreatment component has not been saturated for at least a predefined time period.

17. The system of claim 15 further including a key switch having at least an on position and an off position,

and wherein the control circuit is configured to determine the NOx conversion efficiency of the aftertreatment component and determine whether the aftertreatment component is degraded only if the temperature of the exhaust gas exiting the aftertreatment component has been within a predefined temperature range, the flow rate of exhaust gas entering the aftertreatment component has been within the predefined flow rate range and the aftertreatment component has not been saturated for at least a predefined time period, and the key switch is in the on position.

18. The system of claim 1 wherein the control circuit is configured to determine the threshold value as a function of a bed temperature of the aftertreatment component and of a flow rate of exhaust gas entering the aftertreatment component.

19. The system of claim 18 further including:

an aftertreatment component inlet temperature sensor producing an inlet temperature signal indicative of a temperature of exhaust gas entering the aftertreatment component, and

an aftertreatment component outlet temperature sensor producing an outlet temperature signal indicative of a temperature of exhaust gas exiting the aftertreatment component,

wherein the control circuit is configured to determine the bed temperature of the aftertreatment component as a function of the temperature inlet signal and of the temperature outlet signal.

20. The system of claim 18 further including:

an engine speed sensor producing an engine speed signal indicative of rotational speed of the engine, and

a mass air flow sensor producing a mass air flow signal indicative of a mass flow of fresh air entering the engine,

wherein the control circuit is configured to determine the flow rate of exhaust gas entering the aftertreatment component as a function of the engine speed signal, the mass air flow signal and a flow rate of fuel supplied to the engine.

21. The system of claim 1 further including a memory,

wherein the control circuit is configured to log a fault in the memory after determining that the aftertreatment component is degraded.

22. The system of claim 21 wherein the control circuit is configured to store the NOx conversion efficiency in the memory after determining that the aftertreatment component is degraded.

23. A method for diagnosing operation of an exhaust gas aftertreatment component for an internal combustion engine, the method comprising:

determining from information provided by a NOx sensor a NOx outlet value corresponding to a NOx content of exhaust gas exiting the aftertreatment component,

estimating as a function of a number of engine operating conditions a NOx inlet value corresponding to a NOx content of exhaust gas produced by the engine and entering the aftertreatment component,

determining a NOx conversion efficiency of the aftertreatment component as a function of the NOx outlet value and of the NOx inlet value, and

determining that the aftertreatment component is degraded if the NOx conversion efficiency is below a threshold value.

24. The method of claim 23 further including:

determining a rotational speed of the engine,

determining a mass flow rate of fresh air entering the engine,

determining a flow rate of recirculated exhaust gas supplied to an intake manifold of the engine, and

estimating the NOx inlet value as a function of the rotational speed, the mass flow rate of fresh air, the flow rate of recirculated exhaust gas, a flow rate of fuel supplied to the engine and a fuel timing value.

25. The method of claim 23 further including:

determining a rotational speed of the engine,

determining a mass flow rate of fresh air entering the engine,

determining ambient air pressure, and

estimating the NOx inlet value as a function of the rotational speed, the mass flow rate of fresh air, the ambient air pressure, a flow rate of fuel supplied to the engine and a fuel timing value.

26. The method of claim 23 wherein determining a NOx conversion efficiency of the aftertreatment component includes determining the NOx conversion efficiency further as a function of a flow rate of exhaust gas entering the aftertreatment component.

27. The method of claim 26 further including:

determining a rotational speed of the engine,

determining a mass flow rate of fresh air entering the engine, and

determining the flow rate of the exhaust gas entering the aftertreatment component as a function of the rotational speed, the mass flow rate of fresh air and a flow rate of fuel supplied to the engine.

28. The method of claim 23 further including:

determining whether the aftertreatment component is saturated as a function of the NOx outlet value and of the NOx inlet value, and

determining the NOx conversion efficiency and determining whether the aftertreatment component is degraded only if the aftertreatment component not saturated.

29. The method of claim 23 further including determining the threshold value as a function of a bed temperature of the aftertreatment component and of a flow rate of exhaust gas entering the aftertreatment component.

30. The method of claim 29 further including:

determining an inlet temperature corresponding to a temperature of exhaust gas entering the aftertreatment component,

determining an outlet temperature corresponding to a temperature of exhaust gas exiting the aftertreatment component, and

determining the bed temperature of the aftertreatment component as a function of the inlet temperature and of the outlet temperature.

31. The method of claim 29 further including:

determining a rotational speed of the engine,

determining a mass flow rate of fresh air entering the engine, and

determining the flow rate of the exhaust gas entering the aftertreatment component as a function of the rotational speed, the mass flow rate of fresh air and a flow rate of fuel supplied to the engine.

32. The method of claim 23 further including logging a fault in a memory if the aftertreatment component is degraded.

33. The method of claim 32 further including storing the NOx conversion efficiency in the memory if the aftertreatment component is degraded.

34. The method of claim 23 further including determining that the aftertreatment component is degraded only if the NOx conversion efficiency is below the threshold value for at least a predefined time period.