CONTROL DEVICE FOR ENGINE, ENGINE, METHOD OF CONTROLLING ENGINE, AND COMPUTER PROGRAM PRODUCT

A control device for controlling an engine provided with a fuel pump including a pressurizing chamber, a plunger inserted into the pressurizing chamber and which changes a volume of the pressurizing chamber, and an on-off valve configured to open and close a suction port, is provided. When a pressurizing cycle consists of a period of pressurizing stroke in which the volume of the pressurizing chamber is reduced to allow fuel to be pressurized and a period of suction stroke in which the volume of the pressurizing chamber is increased to allow fuel to be drawn into the pressurizing chamber, , a closing cycle of the on-off valve is controlled so that a ratio of the closing cycle to the pressurizing cycle becomes smaller in a second combustion mode where a partial compression-ignition combustion is performed than in a first combustion mode where SI combustion is performed.