| 摘要 |
PURPOSE:To evade an excess of the current of an oxygen pump element and to prevent the element from deterioration suddenly by deciding an air-fuel ratio a specific time after the start of current supply to the oxygen pump element. CONSTITUTION:When deciding that air-fuel ratio feedback control condition based upon an engine rotating speed is satisfied, an air-fuel ratio control circuit 20 sets a pump current value IP the specific counted time later, and supplies a constant current to electrode plates 5 and 6 of the oxygen pump element 1 through a programmable voltage generating circuit 19 and a constant current circuit 11. Then, the output VS' obtained by amplifying the voltage between electrodes 7 and 8 of a battery element 2 by a noninverting amplifier 25 is compared with the standard limiter voltage of a limiter circuit 26 further a specific time later to decide the air-fuel ratio. A solenoid valve 35 is opened or closed according to the comparison result to adjust the supply of secondary air to the engine, controlling the air-fuel ratio. |
