Combustion system for internal combustion engines

A combustion system for internal combustion engines, comprising

• a cylinder,
• a piston reciprocatingly disposed in said cylinder undergoing a stroke movement.
• a sub-piston projecting from a top of said piston, said sub-piston having a side wall,
• a cylinder head secured to a top of said cylinder defining a space between said cylinder head and top surface of said piston and sub-piston, and said cylinder head having an inner wall defining a recess into which said sub-piston is insertable at a position near top dead center of the stroke of said piston so that the space between said cylinder head and said top surfaces of said piston and sub-piston is dividable into a first combustion chamber on top of said piston and a second combustion chamber on top of said sub-piston, respectively, with a clearance being defined between said side wall of said sub-piston and said inner wall of said recess,
• each of said first and second combustion chambers having a different compression ratio from each other, p1 an ignition plug means provided in one of said combustion chambers having a lower compression ratio for being energized after said sub-piston has engaged in said recess,
• said first combustion chamber and said clearance between said side wall of said sub-piston and said inner wall of said recess being cooperatively formed such that a part of air-fuel mixture compressed in the other of said combustion chambers having a higher compression ratio injects into said one combustion chamber having the lower compression ratio at a beginning of the division period of said space into said first and second combustion chambers to effect turbulence in said one combustion chamber.
• an intake passage opening into either of said combustion chambers,
• an exhaust passage opening into either of said combustion chambers,
• an exhaust gas recirculation passage communicating said exhaust passage to said intake passage,
• a carburetor means for supplying a lean air-fuel mixture to said intake passage, whereby mixture in the other of said combustion chambers having the higher compression ratio is injected into said one combustion chamber having the lower compression ratio at the beginning of the division period which causes a turbulence flow of the air-fuel mixture in said one combustion chamber having the lower compression ratio, whereby the lean air-fuel mixture may be surely ignited, and the mixture in said other combustion chamber having the higher compression ratio may subsequently be ignited as torch ignition by flame injected from said one combustion chamber having the lower compression ratio when said sub-piston is separated from said recess thereby to perform a two-stage combustion,
• said inner wall and said side wall of said sub-piston define said clearance when said sub-piston is inserted in said recess at the beginning of the division period, the part of said mixture in said other combustion chamber is injected into said one combustion chamber and through said clearance, and
• said first and second combustion chambers are completely separated and openly communicate in an expansion stroke of said piston when said sub-piston is withdrawn from said recess for the subsequent torch ignition, the latter constituting the second stage of the two-stage combustion,