Control apparatus for engine exhaust gas purification system

Claim 1

Control apparatus for a fluid cooled engine of a vehicle including an exhaust gas purification system having an exhaust gas recirculation system including a negative pressure source, an exhaust gas oxidation reactor, and a secondary air supply system including a positive pressure source, comprising: a. first means for detecting the temperature of engine cooling fluid and providing a first pneumatic signal when the fluid temperature exceeds a predetermined level; b. second means for detecting ambient temperature and providing a second pneumatic signal when the ambient temperature exceeds a predetermined level; c. third means for detecting the internal temperature of the gas oxidation reactor and providing a third pneumatic signal when the internal temperature exceeds a predetermined level; d. fourth means for detecting the speed of the vehicle and providing a fourth pneumatic signal when the vehicle speed is lower than a predetermined speed; and e. selective actuating means for logically processing said first, second, third and fourth pneumatic signals to produce fifth, sixth and seventh pneumatic signals which control the exhaust gas recirculation system, the exhaust gas oxidation reactor and the secondary air supply system, said selective actuating means including a first inlet having a first one-way valve for receiving said second pneumatic signal, a second inlet including a second oneway valve for receiving said fourth pneumatic signal, said first and second valves being closed in response to the pressure of said second and fourth pneumatic signals, a first passage connecting said first and second inlets via said first and second valves, a third inlet including a third one-way valve for receiving said first pneumatic signal, a second passage including a fourth one-way valve connected to said third inlet via said third valve and to said first passage via said fourth valve, said fourth valve allowing gas to flow only from said second passage to said first passage, said second passage including a first outlet for said fifth pneumatic signal, a third passage having a pair of orifices and connecting said first and second passages, a gas vent formed in said third passage, a first three-way changeover valve including a first diaphragm and first and second compartments located on either side of said first diaphragm, said second compartment communicating with said first passage, a first valve member, connected to said first diaphragm, for changing communication between first, second and third gas chambers, a first spring, connected within said first compartment, for applying a spring force to said first diaphragm, a second three-way change-over valve including a second diaphragm and third and fourth compartments located on either side of said second diaphragm, a second valve member, connected to said second diaphragm, for changing communication between fourth, fifth and sixth gas chambers, a second spring, connected within said fourth compartment, for applying a spring force to said second diaphragm, a fourth passage connecting said second and third compartments, a fifth passage connecting said first and fourth compartments, a fourth inlet connected to said first compartment and receiving said third pneumatic signal, a second outlet, connected to said second gas chamber, for said sixth pneumatic signal, a third outlet, connected to said fifth gas chamber, for said seventh pneumatic signal, a sixth passage connecting the positive pressure source to said third and fourth gas chambers, and a seventh passage connecting the negative pressure source to said first and sixth gas chamber.