Patent attributes
An HCCI engine operated in HCCI and SI combustion modes. The engine includes an external EGR apparatus for performing external EGR. A control unit executes combustion control by specifying either one of HCCI and SI combustion ranges based on the driving state of the engine and a combustion range map for specifying the combustion range in accordance with the driving state. The map includes the HCCI and SI combustion ranges and a switch preparation combustion range, which is included in the SI combustion range and extends along a boundary between the SI combustion range and the HCCI combustion range. The control unit lowers the temperature in the combustion chamber when the switch preparation combustion range is specified by reducing the amount of internal EGR or performing the external EGR.
