PREMIXING COMPRESSION IGNITION TYPE ENGINE

PROBLEM TO BE SOLVED: To suppress combustion noise while performing proper premixing compression ignition combustion.SOLUTION: A water injector 24 for injecting water into a combustion chamber 6 is arranged. Then, in a part of an operation region, the water injector is controlled so that SI+CI combustion in which a second air-fuel mixture G2 in a second region R2 is self-ignited occurs after a first air-fuel mixture G1 in a first region R1 including an electrode part 23a of an ignitor 23 is combusted by receiving ignition energy. In a low-load side SI+CI region A2 in an execution region of the SI+CI combustion, an air-fuel ratio of the first air-fuel mixture G1 is set leaner than an air-fuel ratio of the second air-fuel mixture G2, and also leaner than a theoretical air-fuel ratio, and in a high-load side SI+CI region A3 in the execution region of the SI+CI combustion, the air-fuel ratio of the first air-fuel mixture G1 is set leaner than the air-fuel ratio of the second air-fuel mixture G2, and richer than that at an operation in the low-load side SI+CI region A2, and injection water is made to exist in the second region R2.SELECTED DRAWING: Figure 1 【課題】適切な予混合圧縮着火燃焼を実現しつつ燃焼騒音を小さく抑える。【解決手段】燃焼室６に水を噴射する水噴射装置２４を設ける。そして、一部の運転領域において、点火装置２３の電極部２３ａを含む第１領域Ｒ１の第１混合気Ｇ１が点火エネルギーを受けて燃焼した後第２領域Ｒ２の第２混合気Ｇ２が自着火するＳＩ＋ＣＩ燃焼が起きるように制御するとともに、ＳＩ＋ＣＩ燃焼の実行領域のうち低負荷側ＳＩ＋ＣＩ領域Ａ２では、第１混合気Ｇ１の空燃比を第２混合気Ｇ２の空燃比よりもリーンかつ理論空燃比よりもリーンにし、ＳＩ＋ＣＩ燃焼の実行領域のうち高負荷側ＳＩ＋ＣＩ領域Ａ３では、第１混合気Ｇ１の空燃比を第２混合気Ｇ２の空燃比よりもリーンかつ低負荷側ＳＩ＋ＣＩ領域Ａ２での運転時よりもリッチにし、かつ、第２領域Ｒ２に噴射水が存在するように制御する。【選択図】図１