Piston structure with a combustion chamber

Abstract

The combustion chamber structure having a combustion chamber almost at the center of the piston is installed in a cavity formed in the piston body with a heat insulating layer interposed therebetween. The combustion chamber structure and the piston body are joined by a joining member. The combustion chamber structure is formed with a nozzle insertion hole and communication holes. The joining member is made of a material with a thermal expansion coefficient intermediate between those of the piston body and the combustion chamber structure, or of almost the same kind of material as the piston body. Alternatively, the combustion chamber structure forms a piston head portion and the piston body forms a piston skirt portion. The lower surface of the piston head portion is formed as a tapered surface that is inclined toward the periphery. The upper surface of the piston skirt portion is also formed as a tapered surface that extends along the opposing tapered surface of the piston head portion. The lower surface of the outer periphery of the piston head portion and the upper surface of the outer periphery of the piston skirt portion are in firm contact with each other. The combustion chamber structure of this invention is so constructed that a rich air-fuel mixture is generated in the upper part of the combustion chamber and that the mixture is quickly ejected into the cylinder chamber to reduce the combustion period.