CLOSED-LOOP MIXTURE CONTROL SYSTEM FOR AN INTERNAL COMBUSTION ENGINE WITH EXHAUST GAS CIRCULATION

摘要

1510405 Automatic control of engine exhaust NISSAN MOTOR CO Ltd 9 June 1976 [ 9 June 1975] 23822/76 Heading G3R [Also in Division F 1] An I.C. engine in a road vehicle has a three-way catalytic converter 7 for its exhaust, a proportion of exhaust gas is recirculated, and the air/fuel ratio is controlled in response to an exhaust component sensor 3. The signal from the latter is compared with a reference and the result applied to a proportioned and integral controller 4 to adjust a carburetter 5. Exhaust recirculation is controlled by Venturi depression and is via a conduit 9 which may be closed by a valve 10b at low engine temperature, measured at 13. The ratio control signal is clamped at a rich value when the engine temperature is low, the engine is idling (detected by gear neutral switch 14 and throttle closed switch 15a) or at full throttle (switch 15b). Also at low temperature the ignition is retarded by blocking the normal vacuum advance device. To prevent excessive vacuum when the throttle is "snapped shut" a device 20 provides some opening, under the control of vacuum and engine speed detector 22. Fuel evaporated from tank 24 is collected at 25 and stored in a carbon filled canister 27, from which it is fed to the engine under vacuum control. The air/fuel ratio is also adjusted in response to an altitude detector 33. The catalytic converter may be externally heated from the exhaust pipe. In a modification, Figs. 2 and 3 (not shown) an "abnormallity detector" cuts out the proportional channel, disables the integrating channel (to produce a "rich" control signal) and blocks the exhaust recirculation if (i) the converter temperature is too high, (ii) the exhaust gas temperature is too low for the oxygen sensor to operate, (iii) speed is high and throttle is closed for (iv) the oxygen sensor output is high or low for longer than a prescribed time. In another modification, Figs 4 and 6 (not shown) the mixture is enriched and the recirculation is blocked at low engine temperatures by transistor circuits which modify the reference value for the oxygen sensor inversely as the temperature until a set value is reached.