Combustion chamber of an internal combustion engine

An internal combustion engine comprising:

• a cylinder block having a cylinder bore therein;
• a cylinder head mounted on said cylinder block and having an inner wall;
• a first raised portion having on its lower end a flat bottom face and being formed on the periphery of the inner wall of said cylinder head so as to project downwards;
• a piston reciprocally movable in said cylinder bore and having a top face which has a flat peripheral portion approachable to said flat bottom face, the inner wall of said cylinder head and the top face of said piston defining a combustion chamber therebetween;
• an intake valve movably mounted on said cylinder head for leading a combustible mixture into said combustion chamber;
• an exhaust valve movably mounted on said cylinder head for discharging exhaust gas into the atmosphere;
• a spark plug having a spark plug recess located in said combustion chamber on the inner wall of said cylinder head, said recess extending outwardly beyond a straight line extending between the peripheries of the intake and exhaust valves;
• a first squish area spouting out a first squish flow as said piston reaches the end of its compression stroke, said first squish area comprising an annular area between said flat peripheral portion of the top face of said piston and the flat bottom face of said cylinder head, said first squish area extending substantially along the entire periphery of said top face of said piston;
• a second raised portion formed on the top face of said piston at a position opposite to said first raised portion with respect to an axis of said piston and having a rear face and a front face exposed to said combustion chamber, said rear face being approachable to the inner wall of said cylinder head so as to create a second squish area therebetween at the end of the compression stroke for spouting out a second squish flow which moves forward in the upper interior of said combustion chamber in the direction opposite to the spouting direction of said first squish flow;
• said first and second squish flows cooperating with each other to create a strong swirl motion rotating about a horizontal axis in said combustion chamber, said first squish area extending inward from the periphery of said top face of said piston to a continuous sinuous periphery which extends around and is almost vertically under said intake valve, said exhaust valve, and said spark plug recess and adjacent to said second raised portion;
• and
• a third raised portion formed on the inner wall of said cylinder head above said second raised portion and having a bottom wall which cooperates with said rear face of said second raised portion for creating said second squish area therebetween.