Patent ID: 7509801
Filing Date: 2009-03-31
Classification: F01N,Y02T

Abstract:
1. An exhaust gas control method for an internal combustion engine, comprising: performing a poisoning recovery process that controls an operating state of an internal combustion engine such that sulfur oxide is released from a NOx storage reduction catalyst provided in an exhaust passage for the internal combustion engine, detecting a total concentration of sulfur oxide and hydrogen sulfide in exhaust gas that has passed through the NOx storage reduction catalyst during the poisoning recovery process; detecting a concentration of the sulfur oxide in the exhaust gas that has passed through the NOx storage reduction catalyst during the poisoning recovery process; calculating a concentration of the hydrogen sulfide based on the total concentration and the concentration of the sulfur oxide that are detected; controlling at least one exhaust gas that flows into the NOx storage reduction catalyst and a state of the NOx storage reduction catalyst such that the sulfur oxide is released from the NOx storage reduction catalyst, an amount of the released sulfur oxide is in a predetermined range, and the concentration of the hydrogen sulfide is reduced when the concentration of the hydrogen sulfide exceeds a permissible limit, and controlling the operating state of the internal combustion engine such that, when the concentration of the hydrogen sulfide exceeds the permissible limit, the amount of the sulfur oxide released from the NOx storage reduction catalyst is equal to or larger than a lower limit value of the predetermined range, and the concentration of the hydrogen sulfide is equal to or lower than the permissible limit.