| 摘要 |
PURPOSE: To improve the volumetric efficiency of intake air by a method where in even when a relative position error between an intake port and a valve seat is produced due to the deviation of a core position during casting, an edge part and a stepped part are prevented from occurring to the inside of the curve of the intake port without needing separate machining. CONSTITUTION: In the intake port 14 of an internal combustion engine having an inclination passage 6 inclined toward the vicinity of the valve port 3 of a combustion chamber 2 based on the axis of the valve port 3 and extending approximately straight, a curved part 8 having a given curvature of radius R is formed at a connection part between the inclination passage 6 and the valve port 3. The curvature of radius R is obtained according to a formulas of R=K.2X/ 1-cos(180 deg.-α)}, and (1<K<=4), provided a position tolerance (x) between he intake port 4 and a valve seat 7 is 0.3-1mm and the angle of the inclination passage 6 with the axis of the valve port 3 isα.
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