Patent ID: 8028518

Claim:
A method for controlling a sulfur purge in an internal combustion engine provided with a NOX catalytic converter in an exhaust passage thereof, comprising: estimating an extent of sulfur deposition in the NOX catalytic converter; changing operating parameters of the engine from normal values so as to produce a reducing agent from exhaust gas in the exhaust passage and thereby carry out a sulfur purge in the NOX catalytic converter; detecting an upstream air fuel ratio value corresponding to an air fuel ratio in an upstream part of the NOX catalytic converter; detecting a downstream air fuel ratio value corresponding to an air fuel ratio in a downstream part of the NOX catalytic converter; computing a difference between the upstream air fuel ratio detected by the first detector and a stoichiometric air fuel ratio; detecting a temperature of the NOX catalytic converter; detecting a CO consumption rate in the NOX catalytic converter according to the detected temperature of he NOX catalytic converter; and ending the sulfur purge based on one of the computed difference between the upstream air fuel ratio and stoichiometric air fuel ratio, and outputs of the upstream and downstream air fuel ratios.