PISTON FOR INTERNAL COMBUSTION ENGINE, AND INTERNAL COMBUSTION ENGINE

According to the present invention, a piston for an internal combustion engine is configured so as to allow reciprocal motion along an axial direction inside a cylinder, the piston comprising a cavity formed, so as to be recessed, at a central section of a piston top surface, and an outer circumferential edge section located radially outward of the cavity on the piston top surface, wherein: the cavity includes a lip section having an inclined surface which extends diagonally downward towards a radially inward side from the outer circumferential edge section, a ridge section which protrudes upward from a bottom section of the cavity, and a curved section which connects the ridge section and the lip section; and the curved section includes an outer-circumferential-side curved surface which has a curved surface that is continuous with the lip section, an inner-circumferential-side recessed surface which includes a deepest section of the cavity, and which has a surface that is located further radially inward than the outer-circumferential-side curved surface and that is continuous with the ridge section, and a protruding surface which protrudes upward and is formed between the outer-circumferential-side curved surface and the inner-circumferential-side recessed surface.