Internal combustion engine of lean air-fuel mixture combustion type

Claim 1

An internal combustion engine of lean air-fuel mixture combustion type, comprising: a cylinder block; a piston reciprocably movable in the cylinder block and having a top surface; a cylinder head fixed onto the cylinder block and having an inner surface; a main combustion chamber formed between the top surface of the piston and the inner surface of the cylinder head; a subsidiary combustion chamber formed in the cylinder head; a connecting passage connecting the main combustion chamber with the subsidiary combustion chamber and opening into the main combustion chamber on the inner surface of the cylinder head for leading a lean air-fuel mixture from the main combustion chamber into the subsidiary combustion chamber and for injecting a high velocity burning jet from the subsidiary combustion chamber into the main combustion chamber; a spark plug having a spark gap located in a subsidiary combustion region consisting of the subsidiary combustion chamber and the connecting passage, and; a squish flow producing means including a raised portion formed on one side of the top surface of the piston for forming a squish area which extends from the peripheral end of the inner surface of the cylinder head to the vicinity of the opening of the connecting passage along the inner surface of the cylinder head and for creating a squish flow along the inner surface of the cylinder head when the piston reaches the vicinity of the top dead center, said connecting passage being directed away from the squish area and arranged so that the high velocity burning jet injected from the connecting passage meets with the squish flow at an angle of less than 90°.