INTERNAL COMBUSTION ENGINE WITH SUBSIDIARY CHAMBER

PROBLEM TO BE SOLVED: To stabilize self ignition combustion by canceling a shortage of oxygen in a subsidiary chamber, and enlarge self ignition operation region by suitably controlling the self ignition timing corresponding to load. SOLUTION: In a state in which an opening/closing valve 27 which opens/closes a communicating hole in which a combustion chamber 9 and the subsidiary chamber 21 communicate with each other is opened near a compression top dead center, an air-fuel mixture inside the combustion chamber 9 enters the subsidiary chamber 21 from an intake stroke to a compression stroke which are performed later, and the opening/closing valve 27 is closed in the compression stroke. Inside the subsidiary chamber 21 where the air-fuel mixture enters, an subsidiary fuel injection valve 31 injects fuel, and temperature rises due to an influence of such as a high temperature wall part 25 in which heat is insulated, whereby reforming of thermal decomposition, oxidation and the like is advanced. Thereafter, the opening/closing valve 27 is opened near the compression top dead center whereby the compressed high temperature air-fuel mixture enters the subsidiary chamber 21, and the self ignition combustion occurs in the subsidiary chamber 21 first in which the reforming is advanced. Temperature and pressure of the combustion chamber 9 are increased by heat generation due to the self ignition combustion, whereby the air-fuel mixture inside the combustion chamber 9 sequentially moves to a state of self ignition combustion.