ON-BOARD DIAGNOSTICS OF TEMPERATURE SENSORS FOR SELECTIVE CATALYST REDUCTION SYSTEM

• US 20100235141A1
• Filed: 03/16/2009
• Published: 09/16/2010
• Est. Priority Date: 03/16/2009
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations Incorporated (General Motors Company)
• Inventors: Wang, Yue-Yun, He, Yongsheng
• Granted Patent: US 8,515,710 B2
• Time in Patent Office: Days
• US Class Current: 702/183
• CPC Class Codes: F01N 2550/00 Monitoring or diagnosing the deterioration of exhaust systems
• CPC Class Codes: F01N 3/2066 Selective catalytic reduction [SCR]
• CPC Class Codes: F02D 41/1441 Plural sensors
• CPC Class Codes: F02D 41/1446 the characteristics being exhaust temperatures
• CPC Class Codes: F02D 41/222 relating to the failure of sensors or parameter detection devices
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

Methods and systems for detecting faults in temperature sensors on engine systems provided with equipment for treatment of combustion products of an exhaust effluent stream during engine operation include determining sensor faults from differences in temperature between sensors present in such systems over time. Estimated exhaust gas temperatures may be compared against real time temperature measurements to arrive at a diagnostic residual value representing the difference between a modeled value and measured value, and deviation of the measured value from the modeled value is used to indicate a sensor fault.

Claims

1. Method for identifying a fault in a temperature sensor present in a combination comprising a combustion engine having an exhaust gas treatment system that includes a catalyst chamber, said system including an upstream temperature sensor disposed in effective sensing contact with engine exhaust gases present prior to their entry into said catalyst chamber, and a downstream temperature sensor disposed in effective sensing contact with treated engine exhaust gases exiting said catalyst chamber, said method comprising:

providing a first specified temperature and a second specified temperature;

providing a diagnostic time period;

providing a critical difference value;

providing a timeout value;

operating said engine;

determining a first point in time that the temperature of said upstream temperature sensor reaches said first specified temperature;

determining a second point in time that the temperature of said upstream temperature sensor reaches said second specified temperature;

determining a third point in time at which the temperature reading provided by said downstream temperature sensor reaches said first specified temperature;

determining a time interval, representing the amount of time elapsed between said first point in time and said third point in time;

determining the difference between said time interval and said diagnostic time period; and

indicating a fault condition for said downstream temperature sensor upon occurrence of at least one of the events selected from the group consisting of;

the difference between said time interval and said diagnostic time period is greater than said critical difference value; and

said downstream temperature sensor does not reach said first specified temperature prior to the elapse of an amount of time equal to said timeout value, as measured from said first point in time.

2. Method according to claim 1 wherein said first specified temperature is any temperature in the range of between about 100°

centigrade and about 200°

centigrade, including all temperatures and ranges of temperatures therebetween.

3. Method according to claim 2 wherein said first specified temperature is about 150°

centigrade.

4. Method according to claim 1 wherein said second specified temperature is any temperature in the range of between about 200°

centigrade and about 300°

centigrade, including all temperatures and ranges of temperatures therebetween.

5. Method according to claim 4 wherein said second specified temperature is about 250°

centigrade.

6. Method according to claim 1 wherein said timeout value is any amount of time between about three minutes and about ten minutes, including all amounts of time and ranges of times therebetween

7. Method according to claim 1 wherein the temperature of said upstream temperature sensor is at any temperature that is less than about 100°

centigrade prior to carrying out said method.

8. Method for identifying a fault in a temperature sensor present in a combination comprising a combustion engine having an exhaust gas treatment system that includes a catalyst chamber, said system including an upstream temperature sensor disposed in effective sensing contact with engine exhaust gases present prior to their entry into said catalyst chamber, and a downstream temperature sensor disposed in effective sensing contact with treated engine exhaust gases exiting said catalyst chamber, said method comprising:

providing a first predetermined temperature and a second predetermined temperature;

operating said engine;

determining the temperatures sensed by said downstream temperature sensor and said upstream temperature sensor;

comparing the temperature sensed by said downstream temperature sensor with said first predetermined temperature;

comparing the temperature sensed by said upstream temperature sensor with said second predetermined temperature;

determining a failure condition to be present in said upstream temperature sensor when the temperature sensed by said downstream temperature sensor is above said first predetermined temperature and the temperature sensed by said upstream temperature sensor is below said second predetermined temperature.

9. Method according to claim 8 wherein said first predetermined temperature and said second predetermined temperature are each independently any temperature in the range of between about 150°

centigrade and about 300°

centigrade, including all temperatures and ranges of temperatures therebetween.

10. Method according to claim 8 wherein said method is conducted when said engine is operating at an r.p.m. that is at least above about 500 r.p.m.

11. Method according to claim 8 wherein said method is conducted when said engine is operating at an r.p.m. that is at least above about 900 r.p.m.

12. Method according to claim 8 wherein said method is conducted when said engine is not decelerating.

13. Method according to claim 12 wherein said method is conducted when said engine has not been decelerating for at least any amount of time in the range of between about 15 seconds and about two minutes, including all amounts of time and all ranges of times therebetween.

14. Method according to claim 8 wherein said first predetermined temperature is about 250°

centigrade and wherein said second predetermined temperature is about 250°

centigrade.

15. Method for identifying a fault in a temperature sensor present in a combination comprising a combustion engine having an exhaust gas treatment system that includes a catalyst chamber, said system including an upstream temperature sensor disposed in effective sensing contact with engine exhaust gases present prior to their entry into said catalyst chamber, and a downstream temperature sensor disposed in effective sensing contact with treated engine exhaust gases exiting said catalyst chamber, said method comprising:

providing an estimated temperature of the engine exhaust gases on the downstream side of said catalyst chamber, based on data including a temperature of the engine exhaust gases on the upstream side of the catalyst, a flow rate of the engine exhaust gases, an ambient temperature, and a catalyst geometry;

determining an actual temperature of the engine exhaust gases on the downstream side of said catalyst chamber from said downstream temperature sensor;

calculating a diagnostic residual value based on the difference between said actual temperature and said estimated temperature;

comparing said diagnostic residual value to a diagnostic value; and

determining a fault condition to be present in a temperature sensor in the event that the magnitude of the diagnostic residual value exceeds said diagnostic value.

16. Method according to claim 15 wherein said diagnostic residual value is a measurement of temperature difference and is less than about 20°

centigrade.

17. Method according to claim 15 wherein said determining and calculating are carried out in a control module.

18. Apparatus for identifying a fault in a temperature sensor present in a combination comprising a combustion engine having an exhaust gas treatment system that includes a catalyst chamber, said system including an upstream temperature sensor disposed in effective sensing contact with engine exhaust gases present prior to their entry into said catalyst chamber, and a downstream temperature sensor disposed in effective sensing contact with treated engine exhaust gases exiting said catalyst chamber, said apparatus comprising:

a plurality of sensors disposed in effective sensing contact on said combination, said sensors including at least one temperature sensor; and

at least one control module configured to receive inputs from said plurality of sensors and to

monitor sensor-derived first temperature data concerning exhaust gases present at a first location in said system over time,

generate data concerning a second temperature value relating to said system,

compare said first temperature data with said second temperature data, and

indicate a fault in a temperature sensor when said first temperature data and said second temperature data differ by more than a predetermined critical difference value.

19. Apparatus according to claim 18 wherein said second temperature value is provided by a second temperature sensor disposed at a second location in said system.

20. Apparatus according to claim 18 wherein said second temperature value is provided by a computer model that generates virtual sensor temperature data as a function of monitored engine operating parameters.