Patent ID: 7421333
Filing Date: 2008-09-02
Classification: F01N,F02D,Y02T

Abstract:
1. A malfunction detection system for an internal combustion engine comprising: an air fuel ratio detection section that detects the air fuel ratio of an exhaust gas of an internal combustion engine; an EGR device that connects an intake system and an exhaust system of said internal combustion engine for recirculating a part of the exhaust gas to the intake system; an exhaust gas air fuel ratio feedback control section that controls, in a feedback manner, the air fuel ratio of the exhaust gas to a predetermined air fuel ratio based on the air fuel ratio of the exhaust gas detected by said air fuel ratio detection section; an intake air amount feedback control section that changes the amount of the exhaust gas recirculated by said EGR device in such a manner that the amount of fresh air sucked to said internal combustion engine is adjusted to a target amount; a state value detection section that detects the state values of a plurality of items, respectively, related to a change in the air fuel ratio of the exhaust gas in individual operating states including when said engine is in a first operating state in which feedback control according to said exhaust gas air fuel ratio feedback control section is not performed but feedback control according to said intake air amount feedback control section is performed, and when said engine is in a second operating state in which both feedback control according to said exhaust gas air fuel ratio feedback control section and feedback control according to said intake air amount feedback control section are performed; a first item identification section that identifies items whose state values detected by said state value detection section in said first operating state are outside of a normal value range that is set with respect to the state value of each item in said first operating state; a second item identification section that identifies items whose state values detected by said state value detection section in said second operating state are outside of a normal value range that is set with respect to the state value of each item in said second operating state; and a malfunction item identification section that identifies which item is malfunction, from the items specified by said first item identification section and from the items identified by said second item identification section.