Gasoline direct-injection engine

A gasoline direct-injection engine for causing a self-ignition of a fuel injected into a cylinder by an injector and at least containing gasoline, comprising:

• a controller for controlling a fuel injection by the injector,
• wherein a geometric compression ratio of the engine is 15:1 or higher;
• wherein the controller causes the injector to perform a pre-injection for keeping a variation of an in-cylinder temperature after a compression top dead center within a predetermined temperature range by injecting an amount of the fuel that causes an oxidative reaction without resulting in a hot flame reaction;
• wherein the controller causes the injector to perform a main injection for causing self-ignition combustion of the fuel after the compression top dead center and while the variation of the in-cylinder temperature is kept within the predetermined temperature range, by injecting the fuel after the pre-injection;
• wherein the pre-injection is at least divided into a first pre-injection and a second pre-injection for injecting the fuel after the first pre-injection;
• wherein the first pre-injection is performed in an early stage of a compression stroke, and the second pre-injection is performed in an early stage of an expansion stroke before the main injection;
• wherein the self-ignition is caused when an engine load reaches or exceeds a predetermined threshold value in a high load range;
• wherein the in-cylinder temperature is between 1,000K and 1,100K while the variation of the in-cylinder temperature is kept within the predetermined temperature range;
• and
• wherein with respect to a total injection amount of the fuel including the pre-injection and the main injection, a ratio of the injection amount of the fuel injected in the main injection is ¾ or higher.