Patent ID: 6389802
Filing Date: 2002-05-21
Classification: B01D,F01N,F02D

Abstract:
A method for changing the mixture composition of the exhaust gas supplied from a combustion process to a NOx storage catalytic converter, the method comprising the steps of:providing an NOx sensor mounted rearward of said NOx storage viewed in flow direction; changing said exhaust gas composition in a first phase so as to cause said exhaust gas to contain more NOx than in a second phase; forming an ancillary signal by considering the signal of said NOx sensor and said ancillary signal defining the degree of conversion (q) of said NOx storage catalytic converter; changing said exhaust gas composition in said second phase so as to cause said exhaust gas to contain a reducing agent; changing over from the first phase into said second phase when said degree of conversion (q) drops below a threshold; and, wherein said degree of conversion is given by q={(d(mNO)/dt)forwâˆ’(d(mNO)/dt)rear}/(d(mNO)/dt)forw where: d(mNO)/dt is the NOx mass flow forward of said NOx storage catalytic converter and d(mNO)/dt is the NOx mass flow rearward of said NOx storage catalytic converter.