| 摘要 |
PURPOSE:To prevent carbon from accumulating on recessed portions in the recessed portions provided on top of a piston to avoid interference between intake and exhaust valves and the piston by setting the curvature radius of the inner face corner portions of the recessed portion on the exhaust valve side larger. CONSTITUTION:A total of four recessed portions 4b, 4c are formed in positions opposite to each of two intake valves 7 and two exhaust valves 8 respectively on top of a piston 4. Each recessed portion 4b, 4c is provided so as to avoid interference between each valve 7, 8 and the piston 4 when the piston 4 is positioned on the top dead center in a condition that each valve 7, 8 is in a valve opening position. In this case, each recessed portion 4b opposite to each intake valve 7 is formed into a cylindrical shape so as to be a necessary minimum capacity, i.e., the curvature radius of the inner face corner portions is set small. On the other hand, the curvature radius of the inner face corner portions of each recessed portion 4c opposite to each exhaust valve 8 is set large forming its sectional form into a circular arc shape. |
