ON BOARD DIAGNOSTIC MONITOR OF NOX CONVERSION EFFICIENCY FOR AFTERTREATMENT DEVICE

• US 20100043397A1
• Filed: 08/07/2009
• Published: 02/25/2010
• Est. Priority Date: 08/19/2008
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations Incorporated (Motors Liquidation Co. GUC Trust)
• Inventors: Wang, Yue-Yun, Solbrig, Charles E., Yanakiev, Ognyan N.
• Granted Patent: US 8,245,567 B2
• Time in Patent Office: Days
• US Class Current: 60/273
• CPC Class Codes: F01N 11/007 the diagnostic devices measuring oxygen or air concentration downstream of the exhaust apparatus
• CPC Class Codes: F01N 2550/02 Catalytic activity of catalytic converters
• 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 2900/1622 Catalyst reducing agent absorption capacity or consumption amount
• CPC Class Codes: F01N 3/0814 combined with catalytic converters, e.g. NOx absorption/storage reduction catalysts
• CPC Class Codes: F01N 3/208 Control of selective catalytic reduction [SCR], e.g. dosing of reducing agent
• CPC Class Codes: Y02T 10/12 Improving ICE efficiencies
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

A method for indicating a malfunctioning catalyst in a powertrain including an internal combustion engine and an aftertreatment system including an aftertreatment device utilizing a catalyst to convert NOx includes monitoring a NOx content entering the aftertreatment system, monitoring a NOx content exiting the aftertreatment system, determining an actual conversion efficiency based upon the NOx content entering the aftertreatment system and the NOx content exiting the aftertreatment system, monitoring factors affecting conversion efficiency within the aftertreatment device, determining a malfunction conversion efficiency indicative of the malfunctioning catalyst based upon the factors affecting conversion efficiency within the aftertreatment device, and indicating the malfunctioning catalyst based upon comparing the actual conversion efficiency to the malfunction conversion efficiency.

Claims

1. Method for indicating a malfunctioning catalyst in a powertrain including an internal combustion engine and an aftertreatment system comprising an aftertreatment device utilizing a catalyst to convert NOx, the method comprising:

monitoring a NOx content entering the aftertreatment system;

monitoring a NOx content exiting the aftertreatment system;

determining an actual conversion efficiency based upon the NOx content entering the aftertreatment system and the NOx content exiting the aftertreatment system;

monitoring factors affecting conversion efficiency within the aftertreatment device;

determining a malfunction conversion efficiency indicative of the malfunctioning catalyst based upon the factors affecting conversion efficiency within the aftertreatment device; and

indicating the malfunctioning catalyst based upon comparing the actual conversion efficiency to the malfunction conversion efficiency.

2. The method of claim 1, wherein monitoring factors affecting conversion efficiency within the aftertreatment device comprises:

monitoring a bed temperature within the aftertreatment device;

monitoring a space velocity within the aftertreatment device; and

monitoring an amount of ammonia storage within the aftertreatment device.

3. The method of claim 1, wherein monitoring the NOx content entering the aftertreatment system comprises determining an engine out NOX content with a virtual NOx sensor.

4. The method of claim 1, wherein determining the actual conversion efficiency comprises utilizing a low pass filter to determine the actual conversion efficiency.

5. The method of claim 4, wherein utilizing the low pass filter to determine the actual conversion efficiency comprises:

integrating the NOx content entering the aftertreatment system through a time span;

integrating the NOx content exiting the aftertreatment system through the time span;

determining a ratio of the integrated NOx content exiting the aftertreatment system to the integrated NOx content entering the aftertreatment system; and

determining the actual conversion efficiency based upon the determined ratio.

6. The method of claim 1, further comprising monitoring an amount of urea injected into the aftertreatment system;

and

wherein monitoring an amount of ammonia storage within the aftertreatment device is based upon the monitored amount of urea injected.

7. The method of claim 2, wherein determining the malfunction conversion efficiency comprises utilizing a calibrated functional relationship of the bed temperature, the space velocity, and the amount of ammonia storage to the malfunction conversion efficiency.

8. The method of claim 7, wherein the calibrated functional relationship is utilized from a look-up table.

9. The method of claim 7, wherein the calibrated functional relationship is utilized from a computerized model.

10. The method of claim 1, further comprising selecting a calibratable threshold factor;

and

wherein determining the malfunction conversion efficiency is based upon the selected calibratable threshold factor and a nominal conversion efficiency.

11. The method of claim 2, wherein monitoring the bed temperature comprises monitoring a temperature sensor coupled to the catalyst.

12. The method of claim 2, wherein monitoring the bed temperature comprises:

monitoring properties of an exhaust gas flow entering the aftertreatment system; and

determining the bed temperature based upon the monitored properties.

13. The method of claim 1, wherein determining the actual conversion efficiency comprises integrating an instantaneous actual conversion efficiency values through a time period;

and

wherein determining the malfunction conversion efficiency indicative of the malfunctioning catalyst comprises integrating an instantaneous malfunction conversion efficiency through the time period.

14. The method of claim 1, further comprising warning an operator of the powertrain based upon the indicating.

15. The method of claim 1, further comprising modulating operation of the powertrain based upon the indicating.

16. The method of claim 15, wherein modulating operation of the powertrain comprises commanding operation of the engine to create less NOx.

17. The method of claim 15, wherein modulating operation of the powertrain comprises operating the aftertreatment system assuming decreased performance from the malfunctioning catalyst.

18. Method for indicating a selective catalytic reduction device with a malfunctioning catalyst in an aftertreatment system of a powertrain, the catalyst treating NOx with an ammonia reactant, the method comprising:

monitoring a NOx content entering the aftertreatment system;

monitoring a NOx content exiting the aftertreatment system;

determining an actual conversion efficiency of the catalyst based upon the NOx content entering the aftertreatment system and the NOx content exiting the aftertreatment system;

monitoring a bed temperature within the selective catalytic reduction device;

monitoring a space velocity within the selective catalytic reduction device;

monitoring an amount of ammonia storage within the selective catalytic reduction device;

determining a predicted nominal conversion efficiency of the catalyst based upon the bed temperature, the space velocity, and the amount of ammonia storage;

determining a drop in conversion efficiency of the catalyst from the predicted nominal conversion efficiency indicative of the malfunctioning catalyst based upon the bed temperature, the space velocity, and the amount of ammonia storage;

indicating the malfunctioning catalyst based upon comparing the actual conversion efficiency to the predicted nominal conversion efficiency minus the drop in conversion efficiency; and

generating an alert based upon the indicating.

19. System for indicating a malfunctioning catalyst in a selective catalytic reduction device in an aftertreatment system, the catalyst treating NOx with an ammonia reactant, the method comprising:

the selective catalytic reduction device comprising the catalyst;

a control module

monitoring an actual conversion efficiency of the selective catalytic reduction device,

monitoring factors affecting conversion efficiency of the selective catalytic reduction device,

determining a malfunction conversion efficiency indicative of the malfunctioning catalyst based upon the factors affecting conversion efficiency of the selective catalytic reduction device, and

generating a signal indicating the malfunctioning catalyst based upon comparing the actual conversion efficiency to the malfunction conversion efficiency.

20. The system of claim 19, wherein the control module monitoring factors affecting conversion efficiency of the selective catalytic reduction device comprises:

the control module

monitoring a bed temperature within the selective catalytic reduction device,

monitoring a space velocity within the selective catalytic reduction device, and

monitoring an amount of ammonia storage within the selective catalytic reduction device.