| 摘要 |
PURPOSE:To make possible to reduce the discharge amount of NOx, by providing such an arrangement that exhaust gas recirculation is stopped ruing low load operation but is not stopped during speed shift manipulation in an acceleration condition. CONSTITUTION:A controller 27 receives various operating condition signals of an engine, such as, for example, an intake-air amount output from an air flow sensor 18, a throttle valve opening degree output from a throttle valve opening degree sensor 28 and an engine rotational speed output from a rotational speed sensor 29, and when it is determined in accordance with these detection signals that the engine 1 falls in a condition in which the rotational speed of the engine 1 is below a set rotational speed and a variation rate of throttle valve opening degree is below a set value, an EGR valve is closed to stop exhaust gas recirculation. At this time if it is judged that the operating condition is at first shifted into a low load condition, and if a clutch switch 32 is turned on during speed change manipulation, a negative pressure holding valve 31 is operated to sustain exhaust gas circulation until the count value of a timer reaches a predetermined time value. |
