| 摘要 |
<p>PROBLEM TO BE SOLVED: To reduce unbalance of a weight of a piston 1 around a piston pin, and to effectively cool a part at an exhaust valve-side, of a crown portion of high heat load.SOLUTION: A cavity 28 is formed on a crown surface of a piston 1 eccentrically to an intake valve 6 side to receive fuel spray from a fuel injection valve positioned at an intake valve side, and a bulging portion 25 raised like a mountain, remains mainly in a region near an exhaust valve 8. A cooling channel 31 to which an oil is guided by oil jet, is formed inside of a thick portion 30 inside of a piston ring groove 21. The cooling channel 31 has an intake valve-side part 31a having a small path cross-sectional area and an exhaust valve-side part 31b having a large path cross-sectional area. An oil inlet of a lower face is positioned at the exhaust valve-side part 31b. The unbalance of a weight of the piston 1 can be reduced by the difference in cross-sectional areas of the paths. Further the exhaust valve-side part can be effectively cooled.</p> |
