| 摘要 |
PURPOSE:To keep up temperature in a groove part as high as possible and prevent moisture from getting dewed as well as to keep off any corrosive wear on sulfuric aicd, by sticking a porous molded body close to an inner side of a cylindrical surface having a piston-ring groove of a piston which installs a cavity part leading a cooling fluid therein. CONSTITUTION:Cooling oil is fed to a head part of a piston 1 and each of cavity parts 1a and 1b for cooling a cylindrical surface having a piston-ring groove 2a. A porous molded body 6 is closely set up in an inner side of the cavity part 1a. With this constitution, the back of the ring groove 2a is prevented from being directly cooled by the cooling oil without increasing piston weight so much and, what is more, formation of sulfuric acid due to dew condensation inside the groove is kept back, thus corrosive wear is prevented from occurring. |
