Patent ID: 8371111
Filing Date: 2013-02-12
Classification: F01N,Y02T

Abstract:
1. An exhaust gas purification system for an internal combustion engine comprising: an exhaust gas purification apparatus provided in an exhaust passage of an internal combustion engine and configured to include a catalyst; a precatalyst provided in the exhaust passage upstream of said exhaust gas purification apparatus, having a heat capacity smaller than that of said exhaust gas purification apparatus, and having an oxidizing ability; a reducing agent addition valve provided in the exhaust passage immediately upstream of said precatalyst to add a reducing agent in a liquid state toward an upstream end surface of said precatalyst, and a controller configured to execute a routine in which when a function of said exhaust gas purification apparatus is to be recovered, the controller determines a required addition quantity or a quantity of added reducing agent needed to recover said function, and the controller controls said reducing agent addition valve to add the required addition quantity of reducing agent intermittently in multiple separate portions, and where a level of activity of said precatalyst is higher than a specific level at the time when the intermittent addition of the reducing agent through said reducing agent addition valve is performed, and during at least a portion of a period over which the intermittent addition of the reducing agent is performed, to cool said precatalyst, the controller controls said reducing agent addition valve to add a quantity of reducing agent larger than a quantity of reducing agent added in one reducing agent addition period where the level of activity of said precatalyst is equal to or lower than said specific level in a time period equal to a sum of one reducing agent addition period and one reducing agent addition suspension period subsequent thereto where the level of activity of said precatalyst is equal to or lower than said specific level.