An internal combustion engine, having an entire working cycle including combustion air therewith capable of being brought to a compression pressure and being suitable for various types of fuel and for single and dual piston operation, comprising in combination:
- at least one working cylinder, which includes a shell provided with a combustion chamber and a working piston having a working cycle including bottom and top dead center therewith;
- a crankshaft to which said working piston is operatively connected, said crankshaft including a bent section, which includes a crank bearing rotatably mounted on said bent section, and a crank arm connected to said working piston and to said crank bearing;
- at least one auxiliary cylinder associated with each working cylinder and provided with a wall, each of said auxiliary cylinders including an auxiliary chamber and an auxiliary piston which has a piston rod and a working cycle including a decompression phase and a compression stroke as well as having bottom and top dead center positions in which said top and bottom dead center positions of said auxiliary piston are determined by at least one stop device and which moves back and forth and is forcibly controlled in the working cycle of said working piston in which the compression stroke takes place up to approximately 45.degree. after top dead center of said working piston wherein said auxiliary piston compresses the combustion air to the compression pressure necessary for spontaneous ignition just prior to completion of the compression stroke, the combustion chamber and the auxiliary chamber having a volume ratio of approximately 6:1 to approximately 12:1 as to each other;
- said working piston being provided with an engaging piece with which a stop on the piston rod of said auxiliary piston coacts so that during at least part of the decompression phase thereof, said working piston drives said auxiliary piston;
- an intermediate space connecting each auxiliary chamber with an associated combustion chamber in which said intermediate space widens out from said auxiliary chamber toward said combustion chamber like a Venturi tube, each auxiliary chamber being in constant open communication with its associated combustion chamber via said intermediate space during the entire working cycle of said engine;
- an inlet nozzle for each of said combustion chambers for supplying fuel thereto, each inlet nozzle opening into an associated intermediate space and being controlled in the working cycle of said auxiliary piston, and
- wherein during the return in the decompression phase, said auxiliary piston is forcibly controlled by said working piston and, during the compression stroke, is moved by means of action of a spring acting on said auxiliary piston which is greater than the maximum compression pressure.