Method For Protecting An Exhaust Aftertreatment System

Abstract

The method of the present invention is adapted to protect an exhaust aftertreatment system by preventing the system from becoming clogged and/or damaged during periods of light engine load. According to a preferred embodiment, the present invention protects the exhaust aftertreatment system by increasing the load on the engine during periods of light engine load and/or low exhaust temperature.

1 . A method for protecting an exhaust aftertreatment system for a vehicle having an engine operatively connected to a transmission, comprising:
 establishing a predetermined engine load limit;   monitoring a current engine load;   determining whether the current engine load is less than the predetermined engine load limit;   determining whether the aftertreatment system requires regeneration if the engine load is less than the predetermined engine load limit; and   increasing the current engine load if regeneration is required and the engine load is less than the predetermined engine load limit;   wherein said increasing the current engine load includes applying a brake torque at a transmission input between the engine and the transmission.   
     
     
         2 . The method of  claim 1 , wherein said increasing the current engine load includes applying a retarder device. 
     
     
         3 . The method of  claim 2 , wherein said increasing the current engine load includes calculating a desired engine load increase required to regenerate the exhaust aftertreatment device. 
     
     
         4 . The method of  claim 3 , wherein said increasing the current engine load includes calculating a desired retarder load configured to induce the desired engine load increase. 
     
     
         5 . The method of  claim 4 , wherein said increasing the current engine load includes applying the desired retarder load. 
     
     
         6 . The method of  claim 5 , wherein said increasing the current engine load includes calculating a transmission output torque reduction caused by applying the desired retarder load. 
     
     
         7 . The method of  claim 6 , wherein said increasing the current engine load includes commanding the engine to increase engine output torque by an amount necessary to offset the transmission output torque reduction caused by the retarder. 
     
     
         8 . The method of  claim 7 , further comprising:
 establishing a predetermined exhaust temperature limit;   monitoring a current exhaust temperature;   determining whether the current exhaust temperature is less than the predetermined exhaust temperature limit;   determining whether the aftertreatment system requires regeneration if the exhaust temperature is less than the predetermined exhaust temperature limit; and   increasing the current engine load if regeneration is required and the exhaust temperature is less than the predetermined exhaust temperature.   
     
     
         9 . A method for protecting an exhaust aftertreatment system, comprising:
 establishing a predetermined exhaust temperature limit;   monitoring a current exhaust temperature;   determining whether the current exhaust temperature is less than the predetermined exhaust temperature limit;   determining whether the aftertreatment system requires regeneration if the exhaust temperature is less than the predetermined exhaust temperature limit; and   increasing a current engine load if regeneration is required and the exhaust temperature is less than the predetermined exhaust temperature limit.   
     
     
         10 . The method of  claim 9 , wherein increasing the current engine load includes:
 applying a retarder device;   calculating a desired engine load increase required to regenerate the exhaust aftertreatment device;   calculating a desired retarder load configured to induce the desired engine load increase; and   applying the desired retarder load.   
     
     
         11 . The method of  claim 10 , wherein said increasing the current engine load includes calculating a transmission output torque reduction caused by applying the desired retarder load. 
     
     
         12 . The method of  claim 11 , wherein said increasing the current engine load includes commanding the engine to increase engine output torque by an amount necessary to offset the transmission output torque reduction caused by the retarder. 
     
     
         13 . The method of  claim 12 , further comprising:
 establishing a predetermined engine load limit;   monitoring the current engine load;   determining whether the current engine load is less than the predetermined engine load limit;   determining whether the aftertreatment system requires regeneration if the engine load is less than the predetermined engine load limit; and   increasing the current engine load if regeneration is required and the engine load is less than the predetermined engine load limit.   
     
     
         14 . The method of  claim 13 , wherein increasing the current engine load includes applying the retarder device at a transmission input. 
     
     
         15 . The method of  claim 13 , wherein increasing the current engine load includes applying the retarder device at a transmission output.