Patent ID: 6826902
Filing Date: 2004-12-07
Classification: F01N,F02D,Y02T

Abstract:
A method for estimating oxygen storage capacity of a lean NOx trap (LNT) used in an internal combustion engine, such engine having a sensor disposed downstream of the LNT, such sensor producing an output signal time history indicating an air-fuel ratio time history of such exhaust, such method comprising:integrating the output signal over time to determine the amount of oxygen stored in the LNT as function of time; evaluating the integrated output signal at a time the voltage indicates the exhaust has switched from a condition rich of stoichiometry to a condition lean of stoichiometry; calculating a relative amount of oxygen stored in the LNT at the switch time, such calculation being a function of the air-fuel ratio of the exhaust and an air-fuel ratio of exhaust leaving the LNT; and calculating the oxygen storage capacity as a function of the calculated relative amount of oxygen stored in the LNT at the switch time and the evaluated integrated output signal at the time the voltage indicates the exhaust has switched from rich of stoichiometry to lean of stoichiometry.