Control system and control method for diesel engine

Abstract

A control system for a compression ignition type diesel engine includes an operating state detecting unit for detecting the operating state of the diesel engine. A combustion mode selecting unit selects, in correspondence with the output of the operating state detecting unit, a first combustion mode, wherein fuel injection is carried out in the first half of the compression stroke, or a second combustion mode, wherein fuel injection is carried out at around compression top dead center. An effective compression ratio varying unit varies the effective compression ratio of the diesel engine and a control unit controls the effective compression ratio varying unit to lower the effective compression ratio when the first combustion mode is selected by the combustion mode selecting unit compared to when the second combustion mode is selected. When the first combustion mode is selected by the combustion mode selecting unit, by fuel injection being carried out in the first half of the compression stroke and the effective compression ratio being lowered so that compression ignition occurs at around compression top dead center, a uniform highly diffuse premix combustion can be realized. When the second combustion mode is selected by the combustion mode selecting unit, by fuel injection being carried out at compression top dead center and ignition occurring at around compression top dead center substantially simultaneously with fuel injection, without the effective compression ratio being lowered, diffusion combustion is realized.

Dependencies are inferred from the claim text.