Patent ID: 8001953

Claim:
An exhaust gas recirculation system for an internal combustion engine, comprising: 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 an EGR control unit that controls an amount of exhaust gas recirculated back to the internal combustion engine by adjusting an opening amount of the high-pressure EGR valve to a reference high-pressure EGR valve opening amount determined in advance 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 in advance based on the operation mode of the internal combustion engine during a steady operation of the internal combustion engine, wherein, in a transitional operation period in which the operation mode of the internal combustion engine is changing, the EGR control unit first controls the opening amount of the high-pressure EGR valve, and then controls the opening amount of the low-pressure EGR valve in a feedback manner after a predetermined condition is satisfied, so that an amount of air taken in the internal combustion engine matches a predetermined target intake air amount.