NOx trapping catalytic converter diagnostic apparatus

A method of determining deterioration of a NOx trapping catalytic converter comprising:

• estimating an estimated amount of particulate matter accumulated in a particulate matter filter that is positioned downstream of the NOx trapping catalytic converter based on at least the particulate matter flowing into the particulate matter filter;
• detecting a detected amount of particulate matter accumulated in the particulate matter filter;
• and
• determining deterioration of the NOx trapping catalytic converter based on the estimated amount of accumulated particulate matter and the detected amount of accumulated particulate matter,
• the estimating of the estimated amount of particulate matter including estimating the estimated amount of particulate matter that flows into and accumulates in the particulate matter filter during a prescribed amount of time based on an engine operating condition, the estimated amount of particulate matter corresponding to an increased amount of particulate matter increased in the particulate matter filter during the prescribed amount of time, and
• the detecting of the detected amount of particulate matter including detecting the detected amount of particulate matter that flows into and accumulates in the particulate matter filter during the prescribed amount of time based on a detected pressure difference across the particulate matter filter, the detected amount of particulate matter corresponding to an increased amount of particulate matter increased in the particulate matter filter during the prescribed amount of time.

A NOx trapping catalytic converter diagnostic apparatus comprising:

• a NOx trapping catalytic converter arranged in an exhaust passage of an engine;
• a particulate matter filter arranged downstream of the NOx trapping catalytic converter;
• and
• a controller for controlling an operational state of the engine, the controller further comprising
• particulate matter accumulation estimating means for estimating an estimated amount of particulate matter that flows into and accumulates in the particulate matter filter during a prescribed amount of time based on the operational state of the engine, the estimated amount of particulate matter corresponding to an increased amount of particulate matter increased in the particulate matter filter during the prescribed amount of time;
• particulate matter accumulation detecting means for detecting a detected amount of particulate matter that flows into and accumulates in the particulate matter filter during the prescribed amount of time based on a detected pressure difference across the particulate matter filter, the detected amount of particulate matter corresponding to an increased amount of particulate matter increased in the particulate matter filter during the prescribed amount of time;
• and
• deterioration determining means for determining if deterioration of the NOx trapping catalytic converter has occurred based on the estimated amount of accumulated particulate matter and the detected amount of accumulated particulate matter.