Exhaust-gas temperature rising system for an in-cylinder injection type internal combustion engine

摘要

An exhaust-gas temperature rising system for a spark-ignition, in-cylinder injection type internal combustion engine includes an electronic control unit. In case that the engine is in an operating condition where the exhaust-gas temperature is required to rise, on an occasion of a main-fuel injection in a compression stroke, the electronic control unit controls engine control parameters such as ignition timing and air-fuel ratio so as to cause a cool-flame-reaction product, which remains in a combustion chamber in a middle stage of or a subsequent stage of an expansion stroke, to have a concentration close to an inflammable concentration limit, and then causes an additional fuel to be injected into the combustion chamber from the fuel injection valve in the middle stage of or the subsequent stage of the expansion stroke. The cool-flame reaction of the additional fuel quickly occurs, and the concentration of the cool-flame-reaction product exceeds the inflammable concentration limit, so that the additional fuel is enflamed by self-inflammation. The energy produced by the combustion of the additional fuel is effectively utilized for a rise in the exhaust-gas temperature.