Patent ID: 10487772

Abstract:
Piston has crown portion 2 having crown surface 2a defining combustion chamber, thrust-side and anti-thrust-side skirt portions 3a, 3b formed integrally with crown portion and sliding on cylinder wall surface, a pair of apron portions 4a, 4a joined to skirt portions in circumferential direction, recessed portion 6 formed on back surface that is opposite side to crown surface and extending between skirt portions along substantially longitudinal direction, and a plurality of protrusions 7 formed integrally with bottom surface of recessed portion and extending along arrangement direction of skirt portions. At least one end edge in longitudinal direction of protrusion is integrally connected to inner side surface, facing one end edge of protrusion, of recessed portion. Adequate transcription performance to molding surface can therefore be ensured while removing remains of air on bottom side of recessed portion of mold for molding protrusions on crown portion back surface during casting.