| 摘要 |
PURPOSE:To prevent deterioration of a ternary catalyst in an internal combustion engine in which air-fuel ratio is controlled by use of ''partial lean system'', by assuming the temperature change of the ternary catalyst from the flow rate of intake air and the engine speed, and switching the characteristics of air-fuel ratio to an optimum mode on the basis of the assumed temperature change of the catalyst. CONSTITUTION:A control circuit 20 controls and calculates the opening time of fuel injection valves 5 on the basis of output signals of a sensor 8 for detecting the temperature of intake air, water temperature sensor 10, engine speed sensor 11, O2-sensor 12, etc. When a datum injection time Tp exceeds a set value Tpn in a region where a throttle valve is fully opened, the quantity of correction is determined at zero at a step 42. On the other hand, in case that Tp is smaller than Tpn but greater than the datum injection time Tpalpha at a boundary point for starting feedback control of the O2- sensor 12 and the flow rate Q of intake air is smaller than a second set value Y, feedback control of air-fuel ratio is started at a step 45. When Q is equal to or greater than Y, however, fuel supply is increased at a step 46. Further, when Q is smaller than a first set value X, Tp is so corrected that lean operation is started at a step 48. |
