BUILT-UP PISTON STRUCTURE

PROBLEM TO BE SOLVED: To provide a built-up piston structure for further improving cooling performance with a simple structure. SOLUTION: This built-up piston structure is assembled by screw joining an upper piston 51 including a first spherical surface 85, and a lower piston 58 including a second spherical surface 91, and includes a spherical surface connecting structure of slidingly fitting these first spherical surface 85 and second spherical surface 91 to a spherical small end part 24 of a connecting rod 16. A lower part opened annular upper space 63 is formed on the lower side of a reverse surface 53 of a crown part 50 in the upper piston 51 and around the first spherical surface 85. An upper part of the lower piston 58 is formed with a disk-like ceiling part 99 reaching a lower skirt part 97 positioned outside in the radial direction from the second spherical surface 91 side, and an upper part opened annular lower space 90 on the upper side of this ceiling part 99 and on the outer peripheral side more than the second spherical surface 91. A cooling channel 100 for cooling a piston 13 by lubricating oil, is formed of the upper space 63 and the lower space 90. COPYRIGHT: (C)2010,JPO&INPIT