| 摘要 |
PURPOSE: To restrain such inconvenience as the worsening of a fuel consumption and an output shock by selecting a smaller exhaust gas recirculation rate after comparing a basic exhaust gas recirculation rate with a limit exhaust gas recirculation rate and setting this as a target exhaust gas recirculation rate and controlling an exhaust gas recirculation valve. CONSTITUTION: EGR amount (rate, exhaust gas recirculation amount/fresh air intake amount) is controlled in response to the lift amount of a valve element 206 by the size of the negative pressure in an operation room 205A acting on a diaphragm 205 by EGR valve (exhaust gas recirculation valve) 204. The lift amount of EGR valve 204 is controlled by an atmosphere side control solenoid valve 208 and a negative pressure side control solenoid valve 209 provided in an atmosphere introducing passage 208A communicating one end side to the atmosphere and the other end side to the operation room 205A. An air surplus rate is controlled most suitably by controlling the EGR valve 204 so as to be the limit EGR rate when the limit EGR rate is smaller than the basic EGR rate set in advance and the basic EGR rate when it is larger after calculating based on a limitλset at every fuel injection amount and an operation condition and a cylinder gas amount.
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