To prevent unstable generation of tumble flow due to influence of intake pulsations when generating tumble flow in a combustion chamber by partially cutting off intake supplied to the inside of a combustion chamber through an intake passage.
A flow control valve 20 having a shape in which the upper side is cut away, is arranged on an independent intake passage 16. When an intake amount in a lean burn operation area is low, the flow control valve 20 is closed. When the intake amount in the lean burn operation area is high, the flow control valve 20 is opened. A high-speed passage 17 and a low-speed passage 18 are formed between a surge tank 19 and the independent intake passage 16. In the high-speed passage 17, a natural vibration frequency control valve is arranged. When the flow control valve 20 is closed, the natural vibration frequency control valve is totally closed, whereby intake supply is executed by the low-speed passage 18.
FUJIMOTO MASAHIKO
IWAI KOHEI
KUWABARA TAKAYUKI
MURAKAMI YASUSHI
NOOI YOSHIHISA
YAMAGATA NAOYUKI
YANO YASUHIDE
