| 摘要 |
PURPOSE:To provide a lean burning internal combustion engine which can avoid deterioration in ignitability, performance under a full-load condition, and emission with a four-valve structure, and enables adaption of an inexpensive oxygen sensor. CONSTITUTION:In an internal combustion engine having four valves, a fuel injection valve 18 is arranged in one intake flow passage 112, while an oxygen sensor 19 is arranged in a corresponding exhaust passage 152. The upper surface of the piston on the side where the fuel injection valve and the oxygen sensor are provided is higher than that of the other side, so that air-fuel mixture is pressed to the portion near an ignition plug 16 when intake is compressed. Thus, ignitability is secured even under a lean condition. It is possible to keep lean burning as a whole by controlling exhaust gas characteristics detected by the oxygen sensor 19 to be a theoretical air-fuel ratio. |
