Oxidation catalyst burn threshold adjustment to avoid quenching

Abstract

A method of controlling an exhaust gas treatment system for an engine includes relating the usage of an oxidation catalyst to a temperature offset value, and increasing a current burn threshold temperature by the temperature offset value to define an adjusted burn threshold temperature. Hydrocarbons may be injected into a flow of exhaust gas when the temperature of the oxidation catalyst is equal to or greater than the adjusted burn threshold temperature. The temperature at which the hydrocarbons are injected into the exhaust gas is thereby increased to accommodate performance degradation in the oxidation catalyst, which extends the life of the oxidation catalyst.

1 . A method of operating a vehicle, the method comprising:
 tracking a usage of an oxidation catalyst;   relating the tracked usage of the oxidation catalyst to a temperature offset value;   adjusting a current burn threshold temperature by the temperature offset value to define an adjusted burn threshold temperature; and   injecting hydrocarbons into a flow of exhaust gas when a temperature of the oxidation catalyst is equal to or greater than the adjusted burn threshold temperature to regenerate the oxidation catalyst.   
     
     
         2 . A method as set forth in  claim 1  further comprising detecting a request to regenerate the oxidation catalyst. 
     
     
         3 . A method as set forth in  claim 1  wherein tracking the usage of the oxidation catalyst includes tracking a total mileage of the vehicle. 
     
     
         4 . A method as set forth in  claim 3  wherein tracking the usage of the oxidation catalyst includes tracking an operating temperature history of the oxidation catalyst during the usage of the vehicle. 
     
     
         5 . A method as set forth in  claim 4  wherein tracking the usage of the oxidation catalyst includes tracking a period of time the oxidation catalyst is operating within each of a plurality of pre-defined temperature ranges. 
     
     
         6 . A method as set forth in  claim 5  wherein relating the tracked usage of the oxidation catalyst to the temperature offset value includes referencing a relationship relating the temperature offset value to at least one of the total mileage of the vehicle, the operating temperature history of the oxidation catalyst or the time the oxidation catalyst is operated within the pre-defined temperature ranges. 
     
     
         7 . A method as set forth in  claim 6  wherein relating the tracked usage of the oxidation catalyst to the temperature offset value includes referencing a look-up table relating the temperature offset value to at least one of the total mileage of the vehicle, the operating temperature history of the oxidation catalyst or the time the oxidation catalyst is operated within the pre-defined temperature ranges. 
     
     
         8 . A method as set forth in  claim 6  wherein relating the tracked usage of the oxidation catalyst to the temperature offset value includes solving an equation relating the temperature offset value to at least one of the total mileage of the vehicle, the operating temperature history of the oxidation catalyst or the time the oxidation catalyst is operated within the pre-defined temperature ranges. 
     
     
         9 . A method as set forth in  claim 1  wherein adjusting the current burn threshold temperature by the temperature offset value includes adding the temperature offset value to the current burn threshold temperature. 
     
     
         10 . A method as set forth in  claim 1  further comprising sensing a temperature of the flow of exhaust gas to determine if the temperature of the flow of exhaust gas is equal to or greater than the adjusted burn threshold temperature. 
     
     
         11 . A method as set forth in  claim 10  wherein sensing a temperature of the flow of exhaust gas includes sensing a temperature of the flow of exhaust gas upstream of the oxidation catalyst and sensing a temperature of the flow of exhaust gas downstream of the oxidation catalyst. 
     
     
         12 . A method as set forth in  claim 1  further comprising detecting when the oxidation catalyst is quenched. 
     
     
         13 . A method as set forth in  claim 12  wherein detecting when the oxidation catalyst is quenched includes identifying when the temperature of the oxidation catalyst drops below the adjusted burn threshold temperature. 
     
     
         14 . A method as set forth in  claim 13  further including stopping the injection of hydrocarbons into the flow of the exhaust gas when the oxidation catalyst is quenched. 
     
     
         15 . A method as set forth in  claim 12  further comprising comparing the adjusted burn threshold temperature to a maximum burn threshold temperature to determine if the adjusted burn threshold temperature is less than or equal to the maximum burn threshold temperature. 
     
     
         16 . A method as set forth in  claim 15  further comprising temporarily increasing the adjusted burn threshold temperature when the oxidation catalyst is quenched to complete regeneration of the oxidation catalyst. 
     
     
         17 . A method as set forth in  claim 15  further comprising tracking a number of occurrences the oxidation catalyst is determined to be quenched at the adjusted burn threshold temperature. 
     
     
         18 . A method as set forth in  claim 16  further comprising permanently increasing the adjusted burn threshold temperature when the number of occurrences is greater than a pre-defined limit. 
     
     
         19 . A method as set forth in  claim 1  further comprising:
 defining the adjusted burn threshold temperature as a revised current burn threshold temperature; 
 re-adjusting the revised current burn threshold temperature by the temperature offset value to define a re-adjusted burn threshold temperature; and 
 injecting hydrocarbons into a flow of exhaust gas when a temperature of the oxidation catalyst is equal to or greater than the re-adjusted burn threshold temperature to regenerate the oxidation catalyst. 
 
     
     
         20 . A method of controlling an exhaust gas treatment system of a vehicle having an engine, the method comprising:
 tracking a usage of an oxidation catalyst;   relating the tracked usage of the oxidation catalyst to a temperature offset value;   adjusting a current burn threshold temperature by the temperature offset value to define an adjusted burn threshold temperature;   detecting a request to regenerate the oxidation catalyst;   sensing a temperature of the flow of exhaust gas to determine if the temperature of the flow of exhaust gas is equal to or greater than the adjusted burn threshold temperature;   injecting hydrocarbons into a flow of exhaust gas when a temperature of the oxidation catalyst is equal to or greater than the adjusted burn threshold temperature to regenerate the oxidation catalyst;   identifying when the temperature of the oxidation catalyst drops below the adjusted burn threshold temperature to detect when the oxidation catalyst is quenched;   stopping the injection of hydrocarbons into the flow of the exhaust gas when the oxidation catalyst is quenched;   comparing the adjusted burn threshold temperature to a maximum burn threshold temperature to determine if the adjusted burn threshold temperature is less than or equal to the maximum burn threshold temperature;   tracking a number of occurrences the oxidation catalyst is determined to be quenched at the adjusted burn threshold temperature; and   permanently increasing the adjusted burn threshold temperature when the number of occurrences is greater than a pre-defined limit and the adjusted burn threshold temperature is less than the maximum burn threshold temperature.