| 摘要 |
PURPOSE:To suppress the increase in the temperature of the exhaust side to lower the temperature of the full part of the piston head and to prevent the seizure of the piston by forming the piston head into a deviated thickness structure in which the exhaust side is relatively thinner than the other parts. CONSTITUTION:A two-cycle internal combustion engine A for an outboard motor is accommodated in a cowling B, for example, and the head part C1 of the piston C is heated in accordance with the combustion in a combustion chamber 7. With respect to the temperature in the piston head C1, the temperature at the exhaust side S1 facing an exhaust hole 1 is higher than that at the scanvenging side S2 facing a scanvenging hole 2. Therefore, the thickness of the piston head C1 is made into a deviated thickness and the thickness of the exhaust side S1 is made relatively thinner than the thickness of the scanvenging side S2. Accordingly, the propagation of heat from the exhaust side S1 where it is apt to become high temperatures to the scanvenging side S2 where it is apt to be cooled, is promoted, and the exhaust side S1 is indirectly cooled. |
