Patent ID: 7237542

Claim:
A combustion engine, the engine comprising: a cylinder, said cylinder having a concave annular recess in an axially central portion thereof; a first piston displaceably guided in said cylinder, said first piston having a concave first piston bottom; a first crankshaft; a first connecting rod connected between said first piston and said first crankshaft; a second piston disposed opposite to said first piston and displaceably guided in said cylinder, said second piston having a concave second piston bottom, wherein said first and said second piston bottoms face and define, together with said cylinder, a combustion chamber within said cylinder; a second crankshaft; and a second connecting rod connected between said second piston and said second crankshaft, wherein at upper dead center positions of said first piston and of said second piston, said first piston bottom, said second piston bottom, and said concave annular recess define a spherical combustion chamber.