Patent ID: 7287371
Filing Date: 2007-10-30
Classification: F01N,F02D

Abstract:
1. A system for an engine, comprising: an upstream catalyst with a washcoat having a predetermined amount of precious metal physically segregated from NOx storage material; said catalyst closely coupled to said engine that can store oxidants when the engine is operating lean and release and reduce said stored oxidants when operating the engine stoichiometric or rich; a downstream catalyst that can store oxidants when the engine is operating lean and release and reduce said stored oxidants when operating the engine stoichiometric or rich; a controller for operating the engine lean, and after said lean operation, operating the engine stoichiometric or rich to reduce stored oxidants in said upstream catalyst without necessarily reducing stored oxidants in said downstream catalyst; a first exhaust gas sensor coupled upstream of said upstream catalyst; a second exhaust gas sensor coupled between said upstream and downstream catalysts; and a third exhaust gas sensor coupled downstream of said downstream catalyst; and wherein said controller adjusts injected fuel to maintain a desired air-fuel ratio based on at least each of said first, second, and third exhaust gas oxygen sensors.