Patent ID: 7152392
Filing Date: 2006-12-26
Classification: F01N,Y02T

Abstract:
1. An exhaust gas cleaning system for an internal combustion engine, the system comprising: an exhaust gas after-treatment device disposed in an exhaust passage of the engine; an outlet gas temperature sensing means for sensing outlet gas temperature of exhaust gas downstream of the exhaust gas after-treatment device; temperature estimating means for calculating estimated temperature of the exhaust gas after-treatment device from an output of the outlet gas temperature sensing means with the use of an inverse transfer function of a change in the outlet gas temperature with respect to a change in the temperature of the exhaust gas after-treatment device; and state detecting means for determining whether the exhaust gas after-treatment device is in a predetermined state, based on the estimated temperature calculated by the temperature estimating means; wherein the temperature estimating means uses the inverse transfer function expressed with first-order lag and dead time; wherein the temperature estimating means changes a time constant of the first-order lag and the dead time respectively in accordance with a flow rate of the exhaust gas.