| 摘要 |
PROBLEM TO BE SOLVED: To enable to restrain air pollutant in exhaust gas and to bring forth high output and high efficiency in 4-stroke cycle internal combustion engine in which one of the pair of intake valves pauses. SOLUTION: With this 4-stroke cycle internal combustion engine, a common intake port 10 is branched at its downstream end into a pair of branch intake ports 12, 24 through partition wall 11, each of which has an intake valve 16, 17 for separately opening and closing each of the intake ports 12, 24. In area of low air-intake operation, one intake valve 16 of the pair 16, 17 opens and closes while the other valve stops, and in the area of high air-intake operation, both of the pair valves open and close together. In this case, a helical notch 57c is formed at width-wise center of partition wall 11 dividing the pair of branch intake ports 12, 14, to downstream direction from upstream end edge of the partition wall 11.
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