Abstract: A gasoline engine of four-cycle spark ignition type comprises a piston-cylinder assembly having a piston including a partition and a combustion chamber separated into two compartments by the partition in the forward portion of the piston reciprocation, and an ignition plug set in one of the compartments in which the first combustion occurs. In this case, the ignition timing is determined in a period in which the ignited flames are retained by the partition so as not to contact the mixture in the other compartments, and the flames in the first combustion compartment are in contact with the combustible mixture in the next compartment when the compartments communicate with each other by releasing the separation of the chamber in the back portion of the piston reciprocation stroke.

Abstract: A heat insulation construction for gasoline engines comprising a piston, a sub-piston projecting on the top of the piston. A cylinder head is secured to the top of a cylinder and has a recess into which the sub-piston may be inserted at a position near the top dead center of the piston stroke to form two independent combustion chambers. An ignition plug is provided in one of the combustion chambers in the cylinder head. An intake passage and exhaust passage are provided in the cylinder head. A heat insulating air layer is provided in the top portion of the piston and sub-piston, and a heat insulating air layer is provided on the inner wall of the cylinder head, which is formed by casting hollow structures made of steel plates in the cylinder head.

Abstract: An internal combustion engine in which a cylinder head is formed with a pocket and a main piston is formed with an auxiliary piston slidable in the pocket. A combustion chamber is defined between the cylinder head and the main piston. The combustion chamber includes first and second combustion spaces defined between the pocket and the auxiliary piston and between the cylinder head and the main piston when the piston is substantially at a position near a top dead center of a piston stroke. Homogeneous air-fuel mixtures are compressed in the first and second combustion spaces and are ignited by first and second spark plugs disposed in the first and second combustion spaces, respectively, at different times, such that the combustions will be effected at different flame propagation speeds.