Internal combustion engine

An internal combustion engine in which a tumble flow is generated inside a combustion chamber, comprising:

• a spark plug arranged at a central part of a wall surface of the combustion chamber on a cylinder head side;
• an in-cylinder injection valve configured to inject fuel at a specific timing so that, when stratified charge combustion operation is performed, a fuel spray proceeds towards a vortex center of the tumble flow;
• and
• a control device configured to calculate a size of a combustion fluctuation during stratified charge combustion operation, and in a case where the size of the combustion fluctuation that is calculated is greater than a determination value, change a spray penetration force of fuel injection that is performed at the specific timing so that a plug-periphery air-fuel ratio that is an air-fuel ratio of an air-fuel mixture at a periphery of the spark plug at an spark timing changes to a rich side,
• wherein the control device is configured to calculate an air-fuel ratio index value that has a correlation with the plug-periphery air-fuel ratio, and
• wherein changing of the spray penetration force by the control device is performed by performing any one operation among an operation that increases the spray penetration force and an operation that decreases the spray penetration force, and in a case where the air-fuel ratio index value exhibits a change to a rich side as a result of performing the one operation a first time, the one operation is continued, while in a case where the air-fuel ratio index value exhibits a change to a lean side as a result of performing the one operation the first time, the other operation among the operation that increases the spray penetration force and the operation that decreases the spray penetration force is performed.