Abstract: An improved combustion chamber of a subchamber type of internal combustion engine defines a space extending contiguously to a subchamber injection port within a subchamber mouthpiece. A subchamber injection port control rod is disposed in the space adjacent the injection port. Remote from the subchamber injection port is an actuator within the space. A working substance such as wax, rubber, alcohol, etc. that expands and contracts to a large degree when subjected to temperature changes is sealingly enclosed within the actuator by an expansible member made of rubber or the like. One end of the subchamber injection port control rod is inserted into the expansible member.

Abstract: A combustion chamber of a sub-chamber type internal combustion engine is improved so as to operate efficiently at an excellent fuel consumption with low smoke density, either upon partial loading or upon heavy loading. The combustion chamber includes a sub-chamber port communicating a main combustion chamber with a subsidiary combustion chamber formed within a cylinder head. A space portion is formed in a cylinder head member on the side of the sub-chamber port located farthest from a cylinder center line on a cross-sectional plane of the sub-chamber port defined as a plane including a center line of the subsidiary combustion chamber and the center line of a cylinder and opening into the sub-chamber port. An expansible/contractible tube is contained within the space portion. A sub-chamber port control rod is connected to the expansible/contractible tube and slidably extends into the opening of the space portion.

Abstract: An auxiliary chamber injection port providing communication between a main combustion chamber and an auxiliary combustion chamber has its axis composed of a combination of a straight line and an arc in a manner to satisfy the following relationships: .theta..sub.1 <.theta..sub.2 ; 20.degree..ltoreq..theta..sub.1 .ltoreq.45.degree.; and 35.degree..ltoreq..theta..sub.2 .ltoreq.67.5.degree., if the outflow angle of the axis of said auxiliary chamber injection port at the open end at the side of said auxiliary combustion chamber is designated at .theta..sub.2 with respect to a plane normal to the center line of said auxiliary combustion chamber and if the outflow angle of the axis of said auxiliary chamber injection port at the open end at the side of said main combustion chamber with respect to a plane normal to the center line of said auxiliary combustion chamber is designated at .theta..sub.1.