| 摘要 |
PURPOSE:To lower the density of diesel smoke, by effecting recirculation of exhaust gas (ERG) only in a relatively low-load region at the time of low-speed operation of a diesel engine, and effecting EGR to a relatively high-load region at the time of high-speed operation of the engine. CONSTITUTION:To the time immediately before a low-load detecting switch 43 is turned ON as the engine load is increased from zero, a vacuum switching valve 31 continues to be deenergized since two load detecting switches 43, 47 are kept OFF, so that vacuum in a vacuum source 33 is supplied to an EGR control valve 21. Resultantly, a valve body 29 of the EGR valve 21 is opened for effecting EGR through an EGR passage 17. Thereafter, when the switch 43 is turned ON with increase of the load, current is supplied to the vacuum selecting valve 31, so that the valve 21 is closed since it is communicated to the atmosphere via an atmospheric port 34 instead of vacuum from the vacuum source 33. Here, if the engine 1 is rotated at a speed higher than a predetermined value, an engine-speed detecting switch 45 is kept OFF and the valve 21 is opened even if the switch 43 is turned ON. |
