Exhaust gas recirculation control device of engine

An exhaust gas recirculation (EGR) control device of an engine, comprising:

• an exhaust turbocharger having a turbine disposed in an exhaust passage of the engine and a compressor disposed in an intake passage;
• a low-pressure EGR passage connecting a part of the exhaust passage downstream of the turbine to a part of the intake passage upstream of the compressor;
• a low-pressure EGR valve disposed in the low-pressure EGR passage and for changing a cross-sectional area of the low-pressure EGR passage;
• an exhaust shutter valve disposed downstream of the connected part of the exhaust passage to the low-pressure EGR passage, and for changing a cross-sectional area of the exhaust passage;
• a valve control device for controlling openings of the low-pressure EGR valve and the exhaust shutter valve so that an amount of exhaust gas of the engine recirculated by the low-pressure EGR passage becomes a low-pressure EGR target recirculation amount that is set in advance according to an operating state of the engine;
• and
• a gear range detector for detecting a gear range of a transmission of a vehicle in which the engine is installed,
• wherein in a case where the gear range detected by the gear range detector is other than a predetermined low-speed gear range, when the low-pressure EGR target recirculation amount is smaller than a predetermined amount, the valve control device fixes the exhaust shutter valve fully opened and sets the opening of the low-pressure EGR valve to an opening that allows the recirculation amount of exhaust gas to be the low-pressure EGR target recirculation amount, and when the low-pressure EGR target recirculation amount is larger than the predetermined amount, the valve control device fixes the low-pressure EGR valve fully open and sets the opening of the exhaust shutter valve to an opening that allows the recirculation amount of exhaust gas to be the low-pressure EGR target recirculation amount, and
• wherein in a case where the gear range detected by the gear range detector is the predetermined low-speed gear range, the valve control device sets the opening of the exhaust shutter valve to a predetermined opening that is larger than fully closed but smaller than fully open according to the low-pressure EGR target recirculation amount, and sets the opening of the low-pressure EGR valve to an opening that allows the recirculation amount of the exhaust gas to be the low-pressure EGR target recirculation amount.