Patent GB-1356013-A (GB)
Title: Motor vehicle having an internal combustion engine and comprising air pollution reducing devices
IPC: F01N3/18
Filed: 1971-06-09
Abstract: 1356013 Purifying I C engine exhaust gases; treating charge; timing ignition NISSAN MOTOR CO Ltd 9 June 1971 [29 July 1970] 19638/71 Heading F1B A vehicle driven by an I.C. engine comprises air pollution reducing devices each adapted to be made operative under a respective engine and vehicle operating condition where a particular pollutant is emitted, sensing means for sensing the operating conditions at all times and adapted to develop corresponding electric signals, and electric control means responsive to the signals for determining each condition under which a particular pollutant is formed and for causing activation of the appropriate pollution reducing device. The vehicle speed is sensed by an A.C. generator 16 connected to the shaft of the speedometer 18, the generator output being fed to an electronic circuit contained within a controller 10 to provide three signals indicative of speeds below 10 km/h, above 10 km/h and below 80 km/h respectively. An oscillator producing an output proportional to the speedometer needle position may be used instead. The vacuum in the intake manifold 24 is sensed by a spring- loaded diaphragm 26 which actuates a switch contact 25 to disengage it from fixed contacts 29 and 28 when the vacuum rises above 150 mm Hg and falls below 350 mm Hg respectively, whereby respective signals are fed at 31 and 30 to the controller 10. Two sets of contacts operated by the diaphragm through a linear cam may be used instead. A bi-metallic element 48 sensing the temperature of the engine coolant actuates a switch arm to engage a contact 52 when the temperature has risen to 44‹ C and engage a contact 53 instead when the temperature has risen further to 100‹ C, the two resultant signals being fed at 55 and 56 to the controller 10. The exhaust gas temperature is sensed by a thermocouple or a temperature responsive resistor 58 which is connected at 59, 60 to an electronic circuit within the controller 10 to provide a signal when the temperature is not greater than 1000‹C. Further signals are fed to the controller 10 by a switch 62 which is opened when the throttle is closed to the idling position, a switch 75 which is closed when the gear next below top gear is selected, and by the starter switch 70. The signals from contact 53 and switches 70 and 75 are fed direct to conductors 251, 253 and 146 respectively, while the other signals are fed in various combinations to four AND gates having respective outputs to conductors 88, 144, 210 and 249. Fuel vapour in the fuel tank 150 passes to a canister 151 where it is absorbed by, e.g., activated carbon. In addition, when the engine is stopped, fuel vapour in the carburetter float bowl 90 is passed via a line 154, a solenoid valve 155 and a line 157' to the canister 151 and absorbed. When the ignition switch 80 is closed, the solenoid valve 155 is energized to isolate the float bowl 90 from the canister 151 and connect it to a nozzle 162 whereby fuel vapour from the float bowl is drawn into the Venturi 127 and burned in the engine. During over-run, i.e. with the throttle closed to idling position when the speed is above 10 km/h (or when, in another arrangement, a switch which is opened by depression of the clutch pedal and a switch which is opened on selection of neutral gear are both closed), the controller 10 energizes a solenoid valve 92 to open a mixture enrichment passage 89 leading from the float chamber 90 to a point downstream of the throttle valve 64. At the same time a solenoid valve 100 is energized to disconnect a line 108 from atmosphere and connect it via lines 118, 119 to the vacuum in the intake manifold 24, whereby the vacuum acts on a diaphragm 102 to rotate the stator plate 113 of the contact breaker to advance the ignition. The mixture enrichment and ignition advance both reduce the emission of CO and hydrocarbons. When the speed is 0-10 km/h with the throttle closed to idling position, the ignition is retarded. For this pupose, the controller 10 energizes a solenoid valve 110 to connect the space 109 between the diaphragm 102 and a smaller diaphragm 103 to the intake manifold vacuum, whereby the stator plate 113 is rotated to retard the ignition. At speeds of 10-80 km/h with the intake manifold vacuum between 150 and 350 mm Hg and the engine temperature above 44‹ C, the controller 10 energizes solenoid valves 173, 181. A portion of the exhaust gases is then recirculated from the silencer 172 via a filter 170, the solenoid valve 173 and a nozzle 175 to the intake manifold 24 and reburnt in the engine at a lower combustion temperature than would otherwise develop. Also, air is drawn from the air cleaner 158 into the intake manifold 24 via a line 157, the canister 151, a line 183, the solenoid valve 181 and the nozzle 175, the flow through the canister 151 desorbing the previously absorbed fuel vapour. These measures reduce the emission of nitrogen oxides. If, in addition, the second highest gear is engaged, the switch 75 energizes a relay 145 to connect a solenoid valve 135 in parallel with the solenoid valves 173, 181 so that it, too, is energized. The valve 135 then disconnects the space above a piston 130 from a line 119 subjected to the depression in the intake manifold 24 and vents it to atmosphere. The piston 130 then moves downwardly to open a valve 128 to allow fuel to pass from the fuel bowl 90 via a mixture enrichment passage 125 to a nozzle 126 discharging into the Venturi 127. The mixture enrichment reduces the emission of CO, hydrocarbons and nitrogen oxides. Even when the solenoid valve 135 is not energized, the valve 128 may open to provide mixture enrichment at high loads because the intake manifold vacuum decreases to approximately atmospheric pressure. Under light conditions of operation, with speeds up to 80 km/h, intake manifold vacuum not less than 150 mm Hg and exhaust gas temperature not greater than 1000‹ C, the controller 10 opens relay switch 206 to deenergize a solenoid valve 204 to communicate the intake manifold vacuum to a vacuum actuator 202 to close a valve 192 in a by-pass pipe 191, 196 leading from the by-pass port 195 of an exhaust gas afterburner 190 receiving exhaust gases at 194 from the exhaust manifold. Consequently, the exhaust gases now pass via openings 201 into an outer casing 197, where unburnt CO and hydrocarbons are burnt, additional air for this purpose being introduced from the air cleaner 158 via line 157, 213, air pump 212, a vacuum - operated valve 214 and a nozzle 216. The valve 214 receives its operating vacuum from the solenoid valve 204. During afterburning, the ignition is retarded to reduce the emission of nitrogen oxides, the relay switch 206 not only de-energizing the solenoid valve 204 to initiate afterburning but also de-energizing a relay 232 to switch an auxiliary contact breaker 235 into the ignition circuit to retard the ignition. The air pump 212 may continue to run when the afterburner is not in operation, the valve 214 then by-passing the pumped air to atmosphere. Preferably, the air pump 212 is instead declutched from its drive, by means of an electromagnetic clutch controlled by the relay switch 206 or a mechanical clutch operated by a vacuum piston controlled by a solenoid valve. When the engine coolant temperature exceeds 100‹ C or when the starter switch 70 is operated, the controller 10 by-passes the relay switch 206 via the conductor 251 or a relay switch 255 respectively, to prevent operation of the afterburner and the associated ignition retard.