Patent ID: 8332129

Claim:
An internal combustion engine exhaust gas system comprising: an exhaust gas control apparatus which is arranged in an exhaust passage of the internal combustion engine and purifies exhaust gas; a fuel supply device which is arranged upstream of the exhaust gas control apparatus and supplies fuel into the exhaust passage; an exhaust gas recirculation apparatus that removes some of the exhaust gas from downstream of the exhaust gas control apparatus as EGR gas and introduces that removed exhaust gas into an intake passage of the internal combustion engine; and an exhaust gas recirculation control apparatus which, taking into account the amount of fuel supplied by the fuel supply device, controls an EGR rate, which is the percentage of EGR gas in intake gas that is drawn into a cylinder of the internal combustion engine in a state in which the EGR gas introduced by the exhaust gas recirculation apparatus is mixed with air introduced into the intake passage, such that an oxygen concentration of the intake gas is constant before and after fuel is supplied by the fuel supply device.