| 摘要 |
<p>For combustion engines with a three way catalyst it is necessary to implement an air/fuel ratio control to keep the air/fuel ration within a rather narrow range for best catalyst efficiency. The present invention describes an air/fuel ratio controller (6) and a method that uses an upstream control loop to maintain a given optimum air/fuel ratio (» opt ), whereas the optimum air/fuel ratio (» opt ) is determined in the controller (6) in an downstream control loop by adding incremental offset (”») to the air/fuel ratio set-point (» SP ) of an upstream control loop whilst monitoring a NOx sensor (10) output. The air/fuel ratio set-points (» SP ) at two turning points (SP1, SP2) in the NOx sensor (10) output are used to calculate a new optimum air/fuel ratio set-point (» opt ) as mean value of the air/fuel ratio set-points (» SP1 , » SP2 ) at the turning points (SP1, SP2).</p> |
