Patent ID: 6477831
Filing Date: 2002-11-12
Classification: F01N,Y02T

Abstract:
An engine producing exhaust gas containing CO, H2 and hydrocarbon, the engine having:(a) exhaust apparatus through which the exhaust flows; (b) means to supply air to the exhaust apparatus; and (c) engine management means; the exhaust apparatus containing:(a) an electrical heater; (b) a CO and H2 oxidation catalyst for oxidising CO and H2 in the exhaust gas, the CO and H2 oxidation catalyst being positioned on or downstream of the electrical heater; (c) a hydrocarbon oxidation catalyst for oxidising hydrocarbon in the exhaust gas, the hydrocarbon oxidation catalyst being also the CO and H2 oxidation catalyst or being positioned downstream thereof; (d) an inlet from the means to supply air, the inlet positioned upstream of the CO and H2 oxidation catalyst and the hydrocarbon oxidation catalyst; and (e) a three-way catalyst for oxidising CO and HC to form CO2 and H2O and for reducing NOx to form nitrogen, said three-way catalyst positioned upstream of the inlet, wherein all of said air supplied to the exhaust apparatus is introduced to the exhaust apparatus at a point downstream of said three-way catalyst; the engine being adapted so that on starting it at ambient temperature, the engine management means is effective to produce heat electrically by the electrical heater, and so that on or after the start of the engine and extending into a time at least 5 seconds after the start of the engine, the engine management means is effective to decrease the air/fuel ratio to the engine so as to increase the amount of CO and H2 supplied to the CO and H2 oxidation catalyst and to supply sufficient air to the CO and H2 oxidation catalyst by the means to supply air so as to increase the amount of CO and H2 oxidised by the CO and H2 oxidation catalyst and hence increase the heat produced chemically by the CO and H2 oxidation catalyst, whereby the heat produced electrically by the electrical heater and the increase in heat produced chemically by the CO and H2 oxidation catalyst heat the CO and H2 oxidation catalyst to speed up its reaching the hydrocarbon light-off temperature of the hydrocarbon oxidation catalyst and hence speed up the hydrocarbon oxidation catalyst reaching its light-off temperature.