Exhaust purification apparatus for internal combustion engine

An exhaust purification apparatus for an internal combustion engine comprising:

• a heated gas generation apparatus configured to generate heated gas utilizing part of exhaust gas flowing through an exhaust passage in the internal combustion engine, the heated gas generation apparatus including a catalyst configured to provide an oxidation function, a fuel supply nozzle configured to supply fuel to the catalyst, and a heater;
• an exhaust purification unit provided downstream of the heated gas generation apparatus so as to be heated by the heated gas;
• an incoming gas temperature sensor configured to detect an actual incoming gas temperature of the exhaust purification unit;
• an incoming gas temperature estimation unit configured to estimate the incoming gas temperature of the exhaust purification unit;
• and
• a diagnosis unit configured to acquire the actual incoming gas temperature detected by the incoming gas temperature sensor and the estimated incoming gas temperature estimated by the incoming gas temperature estimation unit, when at least the fuel supply nozzle of the heated gas generation apparatus is actuated, and detecting one of poisoning of the catalyst with HC and degradation of the catalyst in the heated gas generation apparatus based on a result of comparison of the actual incoming gas temperature and the estimated incoming gas temperature acquired,
• wherein the diagnosis unit first detects that one of the poisoning of the catalyst with HC and the degradation of the catalyst is occurring and then carries out a predetermined poisoning recovery process for recovering the catalyst from being poisoned with HC, and thereafter determines which of the poisoning with HC and the degradation is occurring, and
• wherein the diagnosis unit detects that one of the poisoning of the catalyst with HC and the degradation of the catalyst is occurring if a difference between the actual incoming gas temperature and the estimated incoming gas temperature both acquired at a first timing when at least the fuel supply nozzle of the heated gas generation apparatus is actuated is greater than a predetermined value, and then the diagnosis unit carries out the poisoning recovery process by stopping the fuel supply nozzle while actuating the heater, and thereafter the diagnosis unit actuates at least the fuel supply nozzle again and detects degradation of the catalyst if the difference between the actual incoming gas temperature and the estimated incoming gas temperature both acquired at a second timing when the fuel supply nozzle is actuated is greater than a predetermined value.