EXHAUST GAS RECIRCULATION SYSTEM
PURPOSE: To increase or decrease an EGR ratio in accordance with the heavy or light load of an engine by a method wherein an EGR valve, measuring the recirculating amount of the exhaust gas, is controlled by an EGR control valve so that a pressure difference between an EGR gas chamber and a vacuum chamber for the EGR control valve will become 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 a suction pressure becomes lower than the predetermined value thereof , a check valve 28 shuts off the atmosphere and closes the EGR control valve 11 to stop the exhaust gas recirculation. COPYRIGHT: (C)1982,JPO&Japio
