Method of controlling ammonia amount adsorbed in selective catalytic reduction catalyst and exhaust system using the same

Abstract

A method of controlling ammonia amount adsorbed in a selective catalytic reduction (SCR) catalyst, may include detecting current temperature of the SCR catalyst, reading predicted maximum temperature of the SCR catalyst after a predetermined time based on the current temperature of the SCR catalyst, determining a target adsorption amount of ammonia (NH3) based on the predicted maximum temperature of the SCR catalyst, and controlling amount of urea or the NH3 injected into exhaust gas based on the target adsorption amount of the NH3 and current adsorption amount of the NH3.

What is claimed is: 
     
         1 . A method of controlling ammonia amount adsorbed in a selective catalytic reduction (SCR) catalyst, comprising:
 detecting current temperature of the SCR catalyst;   reading predicted maximum temperature of the SCR catalyst after a predetermined time based on the current temperature of the SCR catalyst;   determining a target adsorption amount of ammonia (NH3) based on the predicted maximum temperature of the SCR catalyst; and   controlling amount of urea or the NH3 injected into exhaust gas based on the target adsorption amount of the NH3 and current adsorption amount of the NH3.   
     
     
         2 . The method of  claim 1 , wherein the target adsorption amount of the NH3 is a maximum NH3 amount that is adsorbed in the SCR catalyst at the predicted maximum temperature of the SCR catalyst. 
     
     
         3 . The method of  claim 1 , wherein the target adsorption amount of the NH3 is a value obtained by multiplying a predetermined safety factor to a maximum NH3 amount that is adsorbed in the SCR catalyst at the predicted maximum temperature of the SCR catalyst. 
     
     
         4 . The method of  claim 1 , wherein the reading of the predicted maximum temperature of the SCR catalyst after the predetermined time is performed when the current temperature of the SCR catalyst is higher than or equal to urea conversion temperature. 
     
     
         5 . The method of  claim 1 , wherein the predicted maximum temperature of the SCR catalyst after the predetermined time according to the current temperature of the SCR catalyst is stored in a predetermined map. 
     
     
         6 . The method of  claim 5 , wherein the predetermined map is stored in a non-volatile memory of a vehicle. 
     
     
         7 . The method of  claim 5 , further comprising:
 detecting actual maximum temperature of the SCR catalyst for the predetermined time;   determining whether the actual maximum temperature of the SCR catalyst for the predetermined time is higher than the predicted maximum temperature of the SCR catalyst after the predetermined time; and   storing the actual maximum temperature of the SCR catalyst for the predetermined time as the predicted maximum temperature of the SCR catalyst after the predetermined time in the predetermined map when the actual maximum temperature of the SCR catalyst for the predetermined time is higher than the predicted maximum temperature of the SCR catalyst after the predetermined time.   
     
     
         8 . An exhaust system comprising:
 an engine generating driving torque by burning mixture of air and fuel and exhausting exhaust gas generated at combustion process through an exhaust pipe;   a reducing agent supplier mounted on the exhaust pipe downstream of the engine and adapted to inject urea or ammonia (NH3) into the exhaust gas, wherein the urea is decomposed into the ammonia;   a selective catalytic reduction (SCR) catalyst mounted on the exhaust pipe downstream of the reducing agent supplier and adapted to absorb the ammonia and to reduce nitrogen oxide contained in the exhaust gas using adsorbed, injected or decomposed ammonia;   a temperature sensor detecting temperature of the SCR catalyst; and   a controller reading predicted maximum temperature of the SCR catalyst based on current temperature of the SCR catalyst after a predetermined time, determining a target adsorption amount of the ammonia based on the predicted maximum temperature of the SCR catalyst, and controlling amount of the urea or the NH3 injected from the reducing agent supplier based on the target adsorption amount of the NH3 and current adsorption amount of the NH3.   
     
     
         9 . The exhaust system of  claim 8 , wherein the target adsorption amount of the NH3 is maximum NH3 amount adsorbed in the SCR catalyst at the predicted maximum temperature of the SCR catalyst. 
     
     
         10 . The exhaust system of  claim 8 , wherein the target adsorption amount of the NH3 is a value obtained by multiplying a predetermined safety factor to a maximum NH3 amount adsorbed in the SCR catalyst at the predicted maximum temperature of the SCR catalyst. 
     
     
         11 . The exhaust system of  claim 8 , wherein the controller reads the predicted maximum temperature of the SCR catalyst after the predetermined time only when the current temperature of the SCR catalyst is higher than or equal to urea conversion temperature. 
     
     
         12 . The exhaust system of  claim 8 , wherein the predicted maximum temperature of the SCR catalyst after the predetermined time according to the current temperature of the SCR catalyst is stored in a predetermined map. 
     
     
         13 . The exhaust system of  claim 12 , wherein the predetermined map is stored in a non-volatile memory of a vehicle. 
     
     
         14 . The exhaust system of  claim 12 , wherein the controller stores an actual maximum temperature of the SCR catalyst for the predetermined time as the predicted maximum temperature of the SCR catalyst after the predetermined time in the predetermined map when the actual maximum temperature of the SCR catalyst for the predetermined time is higher than the predicted maximum temperature of the SCR catalyst after the predetermined time.