| 摘要 |
PROBLEM TO BE SOLVED: To prevent the lowering of the bearing of an intersecting part of beads and to prevent penetration by curvedly forming skirt parts at a combustion chamber hole side for smoothly connecting a straight part between the combustion chamber holes and circular arc-shaped parts around the combustion chamber holes. SOLUTION: In an intersecting part 5C of beads 5, 5 around adjacent combustion chamber holes 7, 7, and skirt parts at combustion chamber 7 sides of the beads 5, 5 smoothly connect a straight part 5A between the combustion chamber holes 7, 7 and circular arc-shaped parts 5B around the combustion chamber holes excluding the straight part. That is, by connecting beads in such manner that a radius of curvature is gradually changed, a curved shape is formed. A radius of curvature Ra of the skirt parts at the combustion chamber 7 side of the beads 5 on the intersecting part 5C is smaller than a radius of curvature Rb of the beads 5 of the circular arc-shaped parts 5B around the other combustion chamber 7. Whereby a region where the rigidity of the bead is extremely changed can not be found near the intersecting part 5C of the beads 5, which prevent penetration at this part.
|
