| 摘要 |
PROBLEM TO BE SOLVED: To enhance swirling through reducing an overlapped angle between an exhaust valve and an intake valve so as to shorten time while the induction swirl is disturbed by opening of an exhaust valve, by advancing opening and closing timing of the exhaust valve via a valve phase changing mechanism when an internal combustion engine speed is low and one of the intake valves is in operation. SOLUTION: A valve characteristics switching mechanisms Vci/Vce capable of switching valve lifting and valve opening time are provided between an intake cam shaft 7 and intake valves 12a, 12b, and between an exhaust cam shaft 8 and exhaust valves 13a, 13b. The valve characteristics switching mechanism Vci on the intake side has a single intake valve stopping mechanism for stopping one intake valve 12b. A valve phase changing mechanism Vp for advancing/delaying opening and closing timing of the exhaust valve continuously is provided on an end portion of the exhaust cam shaft 8 on which a cam sprocket 10 is fixed. With this configuration, induction swirling is enhanced by advancing opening/closing timing of the exhaust valve via the valve phase changing mechanism Vp when an internal combustion engine is operated at low speed, while one intake valve is not in operation.
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