Vehicle having a nitrogen oxides storage converter and on-board method for monitoring and diagnosing the nitrogen oxides storage converter

Abstract

A vehicle includes a NOx storage converter to receive exhaust gases from a diesel engine, store at least a minimum amount of the NOx at a temperature below a storage threshold, release the NOx at a temperature above a releasing threshold, oxidize hydrocarbon, and oxidize carbon monoxide. An input temperature sensor at an entrance to the NOx storage converter determines an input temperature of the exhaust gases. An output temperature sensor is at an output of the NOx storage converter to determine an output temperature of the exhaust gases. A control module receives the input temperature and the output temperature, determines a magnitude of an exotherm in the NOx storage converter, and stores an electronic fault code in a computer memory in response to the magnitude of the exotherm being below a minimum temperature. The fault code indicates a reduction in a NOx storage capacity of the NOx storage converter.

1 . A vehicle, comprising:
 a Nitrogen Oxides (NOx) storage converter to receive exhaust gases including NOx from a diesel engine, store at least a minimum amount of the NOx at a temperature below a storage threshold, release the NOx at a temperature above a releasing threshold, oxidize hydrocarbon (HC), and oxidize carbon monoxide;   an input temperature sensor disposed at an entrance to the NOx storage converter to determine an input temperature of the exhaust gases;   an output temperature sensor disposed at an output of the NOx storage converter to determine an output temperature of the exhaust gases; and   a control module to:
 receive the input temperature and the output temperature; 
 determine a magnitude of an exotherm in the NOx storage converter; and 
 store an electronic fault code in a computer memory in response to the magnitude of the exotherm being below a minimum temperature, wherein the fault code indicates a reduction in a NOx storage capacity of the NOx storage converter. 
   
     
     
         2 . The vehicle as defined in  claim 1  wherein the NOx storage converter is further to store the HC when a monolith temperature in the NOx storage converter is below the storage threshold. 
     
     
         3 . The vehicle as defined in  claim 1  wherein the at least the minimum amount of the NOx stored is 10 percent of the NOx received from the diesel engine. 
     
     
         4 . The vehicle as defined in  claim 1  wherein the storage threshold temperature is above 160 degrees Celsius. 
     
     
         5 . The vehicle as defined in  claim 1  wherein the releasing threshold temperature is above 140 degrees Celsius. 
     
     
         6 . The vehicle as defined in  claim 1  wherein the storage threshold temperature is within 20 degrees Celsius of the releasing threshold temperature. 
     
     
         7 . The vehicle as defined in  claim 1 , further comprising a Selective Catalyst Reduction (SCR) converter, or a Selective Catalyst Reduction in Filter (SCRF) converter, disposed downstream from the NOx storage converter in an exhaust gas treatment system to reduce the NOx in the exhaust gases. 
     
     
         8 . A method for monitoring and diagnosing a Nitrogen Oxides (NOx) storage converter on a vehicle comprising:
 starting a diesel engine at a start time and operating the diesel engine thereby generating exhaust gases including NOx;   conducting the exhaust gases via an exhaust system through the NOx storage converter;   measuring an input temperature of the exhaust gases flowing into the NOx storage converter;   measuring an output temperature of the exhaust gases flowing out of the NOx storage converter;   determining an exothermic activity value indicative of an exothermic activity of the NOx storage converter by comparing the input temperature and the output temperature;   determining a diagnostic value by comparing the exothermic activity value to a predetermined exothermic activity threshold, the diagnostic value being indicative of an operational state of both a NOx storage function and a hydrocarbon (HC) oxidation function of the NOx storage converter; and   storing the diagnostic value in a computer memory.   
     
     
         9 . The method as defined in  claim 8  wherein:
 the determining the exothermic activity value indicative of exothermic activity of the NOx storage converter includes determining a temperature change by subtracting the input temperature from the output temperature; 
 the exothermic activity value is the temperature change; and 
 a positive temperature change is indicative of the exothermic activity of the NOx storage converter. 
 
     
     
         10 . The method as defined in  claim 9  wherein:
 the determining the diagnostic value includes subtracting a predetermined temperature threshold from the temperature change; and 
 a positive diagnostic value indicates the operational state of both the NOx storage function and the HC oxidation function of the NOx storage converter. 
 
     
     
         11 . The method as defined in  claim 8  wherein the input temperature is below a diagnostic start temperature at the start time. 
     
     
         12 . The method as defined in  claim 11  wherein the diagnostic start temperature is under 150 degrees Celsius. 
     
     
         13 . The method as defined in  claim 8 , further comprising:
 storing at least a minimum amount of the NOx by adsorption in the NOx storage converter at a monolith temperature below a storage threshold temperature;   releasing the NOx when the monolith temperature is above a releasing threshold temperature;   oxidizing hydrocarbon in the NOx storage converter; and   oxidizing carbon monoxide in the NOx storage converter.   
     
     
         14 . The method as defined in  claim 13  wherein the minimum amount of the NOx stored is 10 percent of NOx received from the diesel engine. 
     
     
         15 . The method as defined in  claim 13  wherein the storage threshold temperature is above 160 degrees Celsius. 
     
     
         16 . The method as defined in  claim 13  wherein the releasing threshold temperature is above 140 degrees Celsius. 
     
     
         17 . The method as defined in  claim 13  wherein the storage threshold temperature is within 20 degrees Celsius of the releasing threshold temperature. 
     
     
         18 . The method as defined in  claim 8 , further comprising injecting a predetermined amount of the HC into the exhaust gases to chemically react in the NOx storage converter.