Combustion chamber of an internal combustion engine

Claim 1

An internal combustion engine comprising: a cylinder block having a cylinder bore therein; a cylinder head having an inner wall mounted on said cylinder block; a first raised portion formed on the periphery of the inner wall of said cylinder head, having a flat bottom face and projecting downwardly; a piston reciprocally movable in said cylinder bore and having a top face with a flat peripheral portion approachable to said flat bottom face, creating a first squish area therebetween at the end of the compression stroke for spouting out a first squish flow along the top face of said piston, said first squish area comprising an annular area between the flat peripheral portion of the top face of the piston and the flat bottom face of the cylinder head, said first squish area extending substantially along the entire periphery of the top face of said piston; a combustion chamber defined by the inner wall of the cylinder head and the top face of said piston; an intake valve movably mounted on said cylinder head in fluid communication with said combustion chamber; an exhaust valve movably mounted on said cylinder head in fluid communication with said combustion chamber; 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, 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 compression stroke for spouting out a second squish flow which moves forward in the upper interior of said combustion chamber in a 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; a third raised portion formed on the inner wall of said cylinder head above said second raised portion having a bottom wall which cooperates with said rear face of said second raised portion for creating said second squish area; and a pair of spark plugs located in said combustion chamber, comprising a first spark plug located near said first raised portion in a recess formed on the inner wall of said combustion chamber, said recess being located on an extension of said second squish area and extending outwardly beyond a straight line extending between the peripheries of said intake and exhaust valves, and a second spark plug located near said third raised portion, said first squish area extending inwardly from the periphery of the top face of the piston to a continuous, sinuous inner periphery which extends around and is almost vertically under the intake valve, the exhaust valve, and said spark plug recess and adjacent to said second raised portion, the surface area ratio of the sum of the first and second squish areas formed on the inner wall of the cylinder head and the first and second squish areas formed on the top face of the piston to the sum of the cross-sectional area of the cylinder bore and the surface area of the inner wall of the cylinder head, excluding the surface area of the vertical side wall of said first raised portion, is in the range of from 30 to 50 percent.