| 摘要 |
<p>PURPOSE:To prevent any balance between NOx and HC, CO in exhaust gases from varying by making an air-fuel ratio leaner than the theoretical one when an overlap period is longer, and richer than that when it is shorter, respectively. CONSTITUTION:An engine body 1 is provided with a value timing variable mechanism 5, changing valve timing according to a driving state, and a means regulating an air-fuel ratio with a control unit 20. Here, this control unit 20 sets the air-fuel ratio to the more lean side than the theoretical one when an overlap period is largely changed by the valve timing variable mechanism 5. Conversely, when this overlap period is changed to smallness, the air-fuel ratio is set to the more rich side than the theoretical one. With this constitution, a variation in balance between NOx and HC, CO in exhaust gases due to increase or decrease of internal exhaust recirculation with the change of the overlap period is checked by regulation of the air-fuel ratio.</p> |
