Patent ID: 8196404

Claim:
A method for controlling an exhaust gas recirculation system for an internal combustion engine, the exhaust gas recirculation system including: a turbocharger that includes a compressor arranged in an intake passage of the internal combustion engine, and a turbine arranged in an exhaust passage of the internal combustion engine; a high-pressure EGR unit that recirculates a portion of exhaust gas back to the internal combustion engine through a high-pressure EGR passage that provides communication between the exhaust passage, at a portion upstream of the turbine, and the intake passage, at a portion downstream of the compressor; a low-pressure EGR unit that recirculates a portion of exhaust gas back to the internal combustion engine through a low-pressure EGR passage that provides communication between the exhaust passage, at a portion downstream of the turbine, and the intake passage, at a portion upstream of the compressor; a high-pressure EGR valve that is provided in the high-pressure EGR passage and that changes a flow passage area of the high-pressure EGR passage; a low-pressure EGR valve that is provided in the low-pressure EGR passage and that changes a flow passage area of the low-pressure EGR passage; and a control unit, the method comprising: adjusting an opening amount of the high-pressure EGR valve to a reference high-pressure EGR valve opening amount determined based on an operation mode of the internal combustion engine, and adjusting an opening amount of the low-pressure EGR valve to a reference low-pressure EGR valve opening amount determined based on the operation mode of the internal combustion engine; and correcting the reference high-pressure EGR valve opening amount based on characteristics of exhaust gas present in the low-pressure EGR passage immediately before the operation mode of the internal combustion engine is changed to a mode where a fuel supply cut-off operation mode of the internal combustion engine ends, and maintaining the opening amount of the high-pressure EGR valve at the corrected reference high-pressure EGR valve opening amount during a predetermined period after the operation mode of the internal combustion engine is changed, in a case where the operation mode of the internal combustion engine is changed.