Combustion-chamber structure of engine

A combustion-chamber structure of an engine, comprising:

• a cylinder block;
• a cylinder head;
• a piston;
• and
• a combustion chamber partitioned by the cylinder block, the cylinder head, and the piston,
• wherein said piston comprises a piston body which has an upper surface facing said combustion chamber, a heat-insulation layer which is provided only in a central area, in a radial direction, of said upper surface of the piston body and has smaller heat conductivity than said piston body, a heat-diffusion layer which is provided to cover an entire part of an upper surface of said heat-insulation layer and has larger heat conductivity than the heat-insulation layer, and a heat-barrier layer which is provided to cover at least both of an entire part of an upper surface of said heat-diffusion layer and an outside area, in the radial direction, of said upper surface of the piston body and has smaller heat conductivity than said piston body, said heat-insulation layer, and said heat-diffusion layer, and
• said heat-diffusion layer comprises a contact portion which contacts with said piston body.

A combustion-chamber structure of an engine, comprising:

• a cylinder block;
• a cylinder head;
• a piston;
• and
• a combustion chamber partitioned by the cylinder block, the cylinder head, and the piston,
• wherein said piston comprises a piston body which has an upper surface facing said combustion chamber, a heat-insulation layer which is provided only in a central area, in a radial direction, of said upper surface of the piston body and has smaller heat conductivity than said piston body, a heat-diffusion layer which is provided to cover both of an entire part of an upper surface of said heat-insulation layer and an outside area, in the radial direction, of said upper surface of the piston body and has larger heat conductivity than the heat-insulation layer, and a heat-barrier layer which is provided to cover an entire part of an upper surface of said heat-diffusion layer and has smaller heat conductivity than said piston body, said heat-insulation layer, and said heat-diffusion layer, and
• said heat-diffusion layer comprises a contact portion which contacts with said piston body.