| 摘要 |
PURPOSE: To improve exhaustion efficiency by providing an exhaustion recessed part in a piston head formed so as to spread including an exhaust valve and two intake valves when a piston is seen from a cylinder head on a plane. CONSTITUTION: A roughly triangular shape exhaustion recessed part 8, a roughly fan shaped guiding groove 25 and one valve recess 19 are formed in a piston head 7, the exhaustion recessed part 8 and the guiding groove 25 are arranged opposite to each other so as to communicate these with each other and the valve recess 19 is laid over the exhaustion recessed part 8. Two valve recesses 17 and 18 are formed for a combined use by the exhaustion recessed part 8 and this exhaustion recessed part 8 is formed to be triangular spreading so as to include an exhaust valve 5 and two intake valves 4 and 4. The guiding groove 25 is formed with a fan shaped pivot (a) facing the jetting hole 15 of an overcurrent room 11 from the lower side and the tip part 25b of the guiding groove 25 spreading toward the exhaustion recessed part 8 and the exhaustion recessed part 8 is set with its capacity center displaced from the center of a piston 6 to the exhaust valve 5 side.
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