| 摘要 |
PURPOSE:To increase or decrease an exhaust gas recirculation ratio in accordance with the heavy or light load of an engine by a method wherein an EGR valve, meausring the amount of the recirculation of the exhaust gas, is controlled by an EGR control valve so as to make the pressure difference between the fore part and the hind part of the EGR valve constant. CONSTITUTION:The exhaust gas, taken out of an exhaust pipe 3, is recirculated to a suction pipe 2 through an introducing passage 5, a choking section 6, a pressure chamber 7 and the EGR (exhaust gas recirculation) valve 8. The amount of the recirculation thereof is determined by the opening area of the valve 8 and the pressure difference between the fore part and the hind part of the valve while the amount of suction air is determined by the opening area of a throttle valve 4 and the pressure difference between the fore part and the hind part of the valve. On the other hand, in the EGR control valve 11 controlling the flow amount of the choked section 6, the valve element 18 thereof is moved to control the pressure in the pressure chamber 7 so that the pressure difference between an EGR gas chamber 13 and a vacuum chamber 14 is balanced with a constant value determined by the effective area of a diaphragm 12 and the initial load of a spring 15. When the negative pressure of the suction air becomes lower than the predetermined value thereof, a check valve 25 is closed to shut off the EGR gas and thereby preventing the reduction of the output of the engine. |
