Patent ID: 8756922

Claim:
An apparatus for evaluating the condition of a NOx adsorber catalyst (NAC) of an internal combustion engine system, comprising: a NOx adsorber catalyst (NAC) through which an exhaust gas stream is flowable; an oxygen sensor positioned proximate an outlet of the NAC, the oxygen sensor device being capable of detecting an amount of oxygen in the exhaust gas exiting the NAC; a controller in electronic communication with the oxygen sensor to receive detected oxygen amounts from the oxygen sensor, the controller configured to convert the detected oxygen amounts to lambda values, and wherein the controller comprises: a rich condition timing module configured to accumulate the total time during which exhaust gas exiting the NAC has a lambda value less than 1.0; a NAC outlet lambda module configured to store NAC outlet lambda values of the exhaust gas while the exhaust gas exiting the NAC has a lambda value less than 1.0; and a NAC condition module configured to evaluate the condition of the NAC based on the total time during which exhaust gas exiting the NAC has a lambda value less than 1.0 and an accumulation of the stored NAC outlet lambda values; wherein the NAC condition module evaluates the condition of the NAC based on a ratio of the total time during which exhaust gas exiting the NAC has a lambda value less than 1.0 and the accumulation of the stored NAC outlet lambda values; and wherein the accumulation of the stored NAC outlet lambda values comprises an accumulation of modified NAC outlet lambda values each comprising a lambda value acquisition time interval multiplied by the difference between one and a respective stored NAC outlet lambda value.