Patent GB-1363332-A (GB)
Title: Method and apparatus for reducing the concentrations of toxic compounds in exhaust gases from an internal combustion engine
IPC: F02D41/14
Filed: 1972-08-16
Abstract: 1363332 Treating exhaust gas NISSAN MOTOR CO Ltd 16 Aug 1972 [28 Dec 1971] 38243/72 Heading F1B A method for reducing noxious compounds contained in I.C. engine exhaust gas, comprising detecting the temperature of an exhaust gas treating device associated with the engine, or of the gas therein and controlling the air-fuel ratio of the mixture supplied to the engine in dependence on the detected temperature to maintain optimum efficiency of the treatment device. An apparatus for carrying out the method consists of an engine 10 supplied with an air-fuel mixture by a carburettor 12 through an induction manifold 18. An exhaust manifold 20 leads to an exhaust gas treating device 42. Warm air can be supplied to the engine by opening a valve 34 so that the induced air entering a pipe 38 passes over the manifold 20. The valve 34 is actuated by intake manifold vacuum acting on a diaphragm 36 through a conduit 38, a temperature responsive valve 40 being fitted in the conduit. The air-fuel ratio is controlled by varying the position of a choke valve 22, which is connected by a rod 56 to a diaphragm 52, acted on by a compression spring 54 which tends to close the valve 22. One side 50a of the diaphragm is connected by a duct 70 to a chamber 64 which is connected by a pipe 66 to the inlet manifold, so that when manifold vacuum is high, the choke valve 22 is opened. A partition wall 72 in the chamber has an opening 72a which is opened or closed by a thermostatic valve 76, responsive to the temperature of the water in the cooling jacket 78. When the water temperature is low, the valve 76 is open and atmospheric air enters by a vent 74 to break the vacuum on the diaphragm 52. A further pipe 80 communicates with the chamber 64 and through a restrictor 82 with an atmospheric vent. A solenoid-actuated valve member 84a controls the admission of air to the pipe 80, the solenoid circuit including a temperature responsive switch 86, connected in series with the ignition switch 88 to a battery 90. The switch 86 energizes the solenoid 84b when the exhaust gas temperature is low so that the valve member 84a is withdrawn, air enters the pipe 80 to reduce the vacuum acting on the diaphragm 54 and the choke valve 22 partially closes to enrich the mixture, so that more unburnt compounds reach the treating device and its operating temperature is increased to the optimum value. A further embodiment of the apparatus modifies the air-fuel ratio by making use of a power valve assembly provided in the carburetter, Fig. 2. The main nozzle of the carburetter draws fuel from a float chamber 112 through a main jet 120, emulsifying air being metered by a jet 122b. Idling and slow-running mixture issues from a port 114, the fuel being metered by a jet 126a and air being metered by jets 126, 126b and 126c. A power jet 134 supplies additional fuel to the main nozzle passage 108, when the valve 136 is open. The valve 136 is connected by a rod 140 to a vacuum piston 142 which slides in a vacuum cylinder 144, connected by a duct 154 to a point in the intake manifold downstream of the throttle valve 102. When the manifold pressure is high, valve 136 is opened by spring 148. The vacuum cylinder is also connected by a pipe 156 and through a restrictor 156a to a two-way solenoid-actuated valve 164, which is energized via a temperature responsive switch 86. When the treating device 42 is operating at low temperature, the solenoid is energized and pipe 156 is connected to an atmospheric vent 158, so that the pressure in cylinder 144 rises, the valve 136 opens and additional fuel is supplied to the main nozzle. When the device 42 is at too high a temperature the solenoid is de-energized and moves the valve so that vent 158 is only connected to pipe 160, and air is admitted to the engine through the slow running port 114. At the same time, the valve 136 is closed by the intake manifold vacuum acting on the piston 144.