Patent ID: 7587891

Claim:
A method for regenerating a NOx absorbing catalyst, comprising: a) detecting a first NOx value in an exhaust gas by a NOx sensor; b) determining whether to perform a regeneration mode or not based on a comparison of the detected value and a predetermined upper limit UL; c) performing a first regeneration mode of the NOx absorbing catalyst for a predetermined time period T 1 , if it is determined that the regeneration mode needs to be performed; d) detecting a second NOx value by the NOx sensor after the performing of the first regeneration mode; e) determining a time period T 2 for performing a second regeneration mode in a predetermined method after performing the first regeneration mode; f) performing the second regeneration mode of the NOx absorbing catalyst for the determined time period T 2 ; g) detecting a third NOx value by the NOx sensor after the performing of the second regeneration mode; h) determining whether to perform a poisoning recovery mode or not based on a determination of whether a performance of the NOx absorbing catalyst has been deteriorated using an amount of exhausted NOx detected after the performing of the second regeneration mode; and i) performing the poisoning recovery mode if it is determined that the poisoning recovery mode needs to be performed, wherein the time period T 2 is determined based on the predetermined time period T 1 and a difference between amounts of exhausted NOx by the performing of the first regeneration mode, wherein the determining of whether to perform the poisoning recovery mode or not determines whether a difference between the third NOx value sensed after the performing of the second regeneration mode and a predetermined fresh level, which is an intended criterion as a result of the performing of the regeneration mode, is greater than a predetermined level SPL and thereby determines whether a performance of the NOx absorbing catalyst has been deteriorated, and wherein the time period T 2 is determined as shown in the following equation: T 2 =T 1 *(b−FL)/(a−b), where a is an initial sensed value of NOx, b is a sensed value of NOx after performing the first regeneration, T 1 is the predetermined time period, and FL is a predetermined fresh level.