| 摘要 |
An addition valve is provided upstream of an exhaust gas purifying catalyst (NOx catalyst) in an exhaust pipe and in the vicinity of a water jacket in a cylinder head, in addition to a fuel injection valve injecting fuel for combustion in a combustion chamber. The addition valve injects a reducing agent in an addition amount in accordance with an operation state of an engine. Using an engine coolant temperature correlated to a temperature of the addition valve, a target addition interval of the addition valve is made shorter with increase in the engine coolant temperature, so that the addition amount is increased (step 130). The temperature of the exhaust gas purifying catalyst (catalyst bed temperature) is raised as a result of increase in the addition amount. Here, a target injection amount of fuel, representing one of parameters other than the addition amount that affect the catalyst bed temperature, is restricted by using an injection amount upper limit, such that the catalyst bed temperature does not exceed an upper limit of an allowable range (steps 240, 250).
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