System and method for diagnosing deterioration of NOx-occluded catalyst

• Main Authors: ISHIHARA, KOUJI, ITOU, YASUYUKI
• Format: Patent
• Language: English; French; German
• Published: 26.03.2003
• Edition: 7
• Subjects: BLASTING; COMBUSTION ENGINES; CONTROLLING COMBUSTION ENGINES; ENGINE PLANTS IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNALCOMBUSTION ENGINES; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES ORENGINES IN GENERAL; HEATING; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS; LIGHTING; MACHINES OR ENGINES IN GENERAL; MECHANICAL ENGINEERING; PERFORMING OPERATIONS; PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL; SEPARATION; STEAM ENGINES; TRANSPORTING; WEAPONS

A deterioration diagnosing system for a NOx-occluded catalyst comprises an inlet NOx concentration estimating unit which estimates NOx concentration at an inlet part of the catalyst; an outlet NOx concentration detecting unit which detects NOx concentration at an outlet part of the catalyst; and a deterioration degree judging unit which judges a deterioration degree of the catalyst in accordance with a rate of the minimum value of NOx concentration detected by the detecting unit for a predetermined period to a value of NOx concentration estimated by the estimating unit at the time when the minimum value of NOx concentration is detected. The predetermined period is a period between a time when the engine exhaust gas shows the stoichiometric and/or richer air/fuel ratio and a subsequent time when the engine exhaust gas shows the stoichiometric and/or richer air/fuel ratio.