Device for judging deterioration of catalyst of engine

• Main Author: NAGAI; TOSHINARI
• Format: Patent
• Language: English
• Published: 28.04.1998
• Edition: 6
• Subjects: BLASTING; CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TOTRANSPORTATION; 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; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; HEATING; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS; LIGHTING; MACHINES OR ENGINES IN GENERAL; MECHANICAL ENGINEERING; STEAM ENGINES; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS; TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINSTCLIMATE CHANGE; WEAPONS

A device for judging the deterioration of a three-way catalyst comprising an upstream O2 sensor and a downstream O2 sensor which are arranged in the exhaust passage upstream and downstream of the three-way catalyst respectively. When the ratio of length of the output signal response curve of the downstream O2 sensor and the length of the output signal response curve of the upstream O2 sensor is over a threshold level, it is judged that the three-way catalyst has deteriorated. The threshold value is reduced as the mean value of the air-fuel ratio becomes off from the stoichiometric air-fuel ratio.