Patent ID: 6971379

Claim:
A combustion chamber structure in an internal combustion engine having a combustion chamber that is vertically defined by a lower face of a cylinder head and an upper face of a piston fitted in a cylinder, the lower face of the cylinder head being substantially circular in plain shape, comprising: at least one intake valve provided on one side of the cylinder head with respect to a predetermined chord having both ends thereof crossing a curve that defines the plain shape of the lower face of the cylinder head; at least one exhaust valve provided on another side of the cylinder head with respect to the predetermined chord; a tapered portion formed substantially conical in shape at a peripheral portion of the upper face of the piston; and a recessed portion formed at near a center of the upper face of the piston, wherein a gap between said tapered portion and a peripheral portion of the lower face of the cylinder head opposed thereto is formed to increase toward vicinity of said chord.