| 摘要 |
Provided is a technique, which can suppress that a fuel added from a fuel adding valve sticks to an exhaust passage, and that the fuel weaves out of an exhaust emission purifying device. The fuel adding instant, at which the fuel is added from fuel adding valves (11, 12), is switched, according to a running condition, to the instant, at which the instantaneous exhaust emission flow rates in exhaust pipes (7, 8) are different. In the case of a running condition, under which the fuel may seriously stick to the exhaust pipes (7, 8), therefore, the fuel is added at the instant when the instantaneous exhaust emissions through the exhaust pipes (7, 8) are high, so that the fuel may be easily entrained by the exhaust emissions to the vicinities of exhaust emission purifying devices (9, 10), thereby to suppress the stick of the fuel to the exhaust pipes (7, 8). In the case of a running condition, under which the fuel may seriously weave out of the exhaust emission purifying devices (9, 10), on the other hand, the fuel is added at the instant when the instantaneous exhaust emissions through the exhaust pipes (7, 8) are low, so that the fuel may be hardly entrained by the exhaust emissions and slowed down in its movement, thereby to suppress the weave of the fuel out of the exhaust emission purifying devices (9, 10).
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