Direct injection internal combustion engine and controlling method therefor

摘要

A direct injection internal combustion engine comprises: catalysts for purifying exhaust gases, the catalysts being disposed in an exhaust passage of the engine; a control device for controlling the engine so as to warm up or activate the catalysts when the catalysts are required to be warmed up or activated; wherein the control device includes a first control part for control part control the engine with an air-fuel ratio of the engine being set at a value in proximity to a stoichiometric air-fuel ratio, an ignition timing being set at a point after a top dead center and a fuel injection timing being set within a compression stroke: and a second control part for controlling the engine with an air-fuel ratio of the engine being set at a value in proximity to a stoichiometric air-fuel ratio, with an ignition timing being set before a top dead center and a fuel injection timing being set within a compression stroke after the first control part controls the engine. The controlling operation performed by the first control part enables stable afterburning and raises the exhaust temperature, and it is therefore possible to efficiently warm up the catalysts while controlling the emission of unburned HC. The following controlling operation of the second control part enables CO and O2 to coexist in the exhaust gases and react on the catalysts. The resulting heat of reaction further warms up the catalysts and accelerates the activation of the catalysts while preventing the deterioration in the fuel economy.