| 摘要 |
On a piston top surface 10, a cavity 12 and two valve recesses 14 are formed. On the piston top surface 10, a first heat insulating film is formed. However, on edge portions 10a, 12a and 14a, a second heat insulating film different from the first heat insulating film is formed. The second heat insulating film is formed along the edge portions 10a, 12a and 14a. The first heat insulating film is composed of porous alumina and a sealer. The second heat insulating film is composed of only porous alumina. |
