| 摘要 |
PROBLEM TO BE SOLVED: To provide an EGR device capable of accomplishing a high efficiency NOx reduction by performing the opening and closing operations of an EGR passage based on proper conditions. SOLUTION: The EGR device has a shutter valve to open and close the EGR passage and performs the opening and closing operations based on the conditions of the excess air ratio. Concretely the excess air ratio λ is sensed in the shutter valve control routine (Step S2), and if judgement is passed that the sensed value is below the specified limit excess air ratio λv (Step S3=Yes), an instruction is given to full close the shutter valve (Step S5). Thereby the excess air ratio is judged as the condition for generation of black smokes in the exhaust gas irrespective of the degree of accelerator opening or the size of time change of the fuel injection amount, and the EGR introduction is stopped or started on the basis of the comparison with the lower limit value. |
