| 摘要 |
In response to a torque demand decreasing to or below a reference value, the value of a virtual air-fuel ratio used in calculating a target air volume for achieving the torque demand is changed from a first air-fuel ratio to a second air-fuel ratio that is leaner than the first air-fuel ratio. The target air volume is back calculated from the torque demand using the virtual air-fuel ratio. In addition, after the virtual air-fuel ratio value is changed from the first air-fuel ratio to the second air-fuel ratio, the target air-fuel ratio switches from the first air-fuel ratio to the second air-fuel ratio. A target EGR rate is calculated using the virtual air-fuel ratio. Preferably, the target EGR rate is determined by selecting the lesser value of a first target value for the EGR rate calculated by using the virtual air-fuel ratio and a second target value for the EGR rate calculated by using the target air-fuel ratio. |
