System and method to minimize the amount of NOx released from a NOx trap

摘要

A method is described for controlling lean and rich operation of an internal combustion engine coupled to a lean NOx trap. In one example, the termination of the lean air-fuel mixture is based on an oxygen storage capacity and temperature of the NOx trap. In another example, the level and duration of rich air-fuel ratio purging operation is also controlled based on the oxygen storage capacity of the NOx trap.