Abstract: A mixture-compressing internal combustion engine with a combustion space arranged either in the piston or in the cylinder head and with an ignition source located in the cylinder head; the main volume of the combustion space is thereby delimited by circular arcs, as viewed in plan view, of which the circular arc located closest to the ignition source is arranged at least approximately concentrically about the ignition source; a part of the piston which is matched within this area of the cylinder head adjoins the ignition source so closely that at first a smaller portion of the charge is ignited in the gap which is formed between the cylinder head and this piston part shortly prior to the end of the compression stroke while the main portion of the charge is combusted, at the earliest, beginning with the upper dead-center position of the piston.

Abstract: A spark-ignited reciprocating-piston internal combustion engine is provided with a combustion chamber subdivided in the top dead center zone into two chambers. These two chambers are separated from one another by overlapping parts of the piston and cylinder and cylinder head when in the top dead center zone, such that when in this position a cross-connection between the chambers exist only at one position along the circumference of the piston. An ignition source is provided adjacent one circumferential end of a first of the chambers which forms a combustion duct between the ignition source and the cross connection. The ignition is controlled so as to take place only after the piston and cylinder are in respective positions separating the combustion chamber into the two chambers.