Excessive sulfur poisoning recovery control method and apparatus for exhaust gas control catalyst

摘要

When sulfur components accumulate on an exhaust gas control catalyst (36a, 38a), a PM accumulation amount PMsm is increased and the frequency with which a lean-burn temperature increase routine is executed under fine particle regeneration control is increased (step S102). As a result, the sulfur components accumulated on the exhaust gas control catalyst (36a, 38a) are released using the lean-burn temperature increase routine of the fine particle regeneration control. Therefore, even when sulfur poisoning is so excessive that the engine operating state does not come into the sulfur poisoning recovery control execution range, the lean-burn temperature increase routine of the fine particle regeneration control can be executed so that the excessive sulfur components on the exhaust gas control catalyst (36a, 38a) can be released by executing this lean-burn temperature increase routine. Because the sulfur components released by executing the lean-burn temperature increase routine are excessive sulfur components that have accumulated on the exhaust gas control catalyst (36a, 38a) and the frequency with which the lean-burn temperature increase routine is executed is high, it is possible to keep down the concentration of sulfur components that are released.