Patent ID: 7392797

Claim:
An EGR failure determination system for an internal combustion engine including an external EGR device that recirculates exhaust gases emitted from a cylinder into the cylinder and changes a recirculation amount of the exhaust gases, and an internal EGR device that causes combustion gases generated in the cylinder to remain as a high-temperature gas higher in temperature than the exhaust gases and changes a remaining amount of the combustion gases, the EGR failure determination system determining failures of the external EGR device and the internal EGR device, comprising: EGR rate parameter-calculating means for calculating an EGR rate parameter indicative of a ratio of a total EGR amount which is a sum of an amount of the exhaust gases recirculated into the cylinder and an amount of the combustion gases remaining in the cylinder, to a total gas amount which is a sum of the total EGR amount and an amount of fresh air drawn into the cylinder, according to a first operating condition parameter indicative of an operating condition of the engine; target value-setting means for setting a target value as a target of the EGR rate parameter; EGR control value-calculating means for calculating an EGR control value according to the EGR rate parameter and the target value; control means for controlling the external EGR device and the internal EGR device according to the EGR control value; and failure determination means for determining that at least one of the external EGR device and the internal EGR device is faulty when the EGR control value is not within a predetermined range.