Control system for use in exhaust gas recirculation system

In a fuel system for use in an exhaust gas recirculation system of an internal combustion engine, wherein part of the exhaust gases from the exhaust system is recirculated to the engine intake system to reduce the amount of harmful components contained in the exhaust gases, as well as to prevent lowering in the running performance of the engine by controlling the recirculation of exhaust gases, the improvements comprising:

• a vacuum operated recirculation control valve means connected between the engine intake and exhaust systems to control recirculation of exhaust gases between said exhaust system and said intake system;
• a vacuum operated fuel control mechanism to increase the open, cross-sectional area of a fuel metering member in the engine carburetor, to compensate for the running performance of the engine, which has been lowered due to exhaust gas recirculation;
• a negative-pressure switching valve to selectively communicate negative pressure to said recirculation control valve means as well as to fuel control mechanism, said negative-pressure switching valve including a valve body having at least one inlet and two outlets defining two communication paths therebetween, a valve stem, a diaphragm and a diaphragm chamber positioned so that a negative pressure supplied to a compartment of said diaphragm chamber effects switching of communication from one path to the other;
• means connecting said fuel control mechanism with one outlet of said negative-pressure switching valve;
• means connecting said recirculation control valve with the other said outlet;
• means connecting the diaphragm compartment of said negative-pressure switching valve to at least one of a delay element or a delay by-pass valve;
• means to actuate said delay by-pass valve comprising means to sense at least one of the following:
• an acceleration-transient condition;
• a change gear position;
• cooling water temperature;
• vehicle speed;
• or exhaust gas temperature;
• means connecting said delay element and said delay by-pass to the engine carburetor air intake so that the operation of the switching valve is controlled commensurate to the running condition of the engine, the engine vacuum being commensurate with the opening of the throttle valve in the engine carburetor;
• whereby when said negative-pressure switching valve is actuated, a recirculating path for exhaust gases is closed, and concurrently an additional fuel passage for said fuel control mechanism is closed, thereby controlling both the recirculation of exhaust gases and the concentration of the mixture charge.