Fuel injection control device for direct injection engine

A fuel injection control device for a direct injection engine, the control device comprising:

• an engine body including a combustion chamber defined by a cylinder head ceiling portion, a cylinder provided for a cylinder block, and a piston reciprocating inside the cylinder;
• a fuel injection control unit which includes a fuel injection valve, provided inside the combustion chamber to inject a liquid fuel, and which is configured to inject the fuel into the combustion chamber at a predetermined timing;
• and
• a catalyst device arranged on an exhaust passage of the engine body and configured to purify an exhaust gas exhausted from the combustion chamber, wherein
• the fuel injection control unit is configured to
• inject the fuel in a predetermined injection mode into the combustion chamber such that while the engine body is in a warm state where the temperature of the engine body has reached or exceeded a predetermined temperature, an air-fuel mixture layer and a heat-insulating gas layer, surrounding the air-fuel mixture layer, are formed in the combustion chamber at a point in time when an air-fuel mixture ignites,
• change the injection mode of the fuel into the combustion chamber such that while the engine body is in a cold state where the temperature of the engine body is less than the predetermined temperature, the lower the temperature of the engine body is, the thinner the heat-insulating gas layer becomes,
• retard an injection start timing of the fuel to a predetermined timing such that while the catalyst device is inactive and the engine body is cold, the heat-insulating gas layer thickens, and
• advance the injection start timing of the fuel while the catalyst device is active and the engine body is cold with respect to the injection start timing while the catalyst device is inactive and the engine body is cold.

A fuel injection control device for a direct injection engine, the control device comprising:

• an engine body including a combustion chamber defined by a cylinder head ceiling portion, a cylinder provided for a cylinder block, and a piston reciprocating inside the cylinder;
• and
• a fuel injection control unit which includes a fuel injection valve, provided inside the combustion chamber to inject a liquid fuel, and which is configured to inject the fuel into the combustion chamber at a predetermined timing, wherein
• the fuel injection control unit is configured to
• inject the fuel in a predetermined injection mode into the combustion chamber such that while the engine body is in a warm state where the temperature of the engine body has reached or exceeded a predetermined temperature, an air-fuel mixture layer and a heat-insulating gas layer, surrounding the air-fuel mixture layer, are formed in the combustion chamber at a point in time when an air-fuel mixture ignites, and
• change the injection mode of the fuel into the combustion chamber such that while the engine body is in a cold state where the temperature of the engine body is less than the predetermined temperature, the lower the temperature of the engine body is, the thinner the heat-insulating gas layer becomes,
• the fuel injection control unit performs discrete injections including a plurality of fuel injections, and
• sets an interval between two successive injections of the discrete injections to be shorter while the engine body is cold than while the engine body is warm.