| 摘要 |
PURPOSE:To perform a high accurate air-fuel ratio control eliminating an output error in an air-fuel ratio sensor by detecting temperature of an oxygen concentration detecting element by a temperature detecting means and feedback controlling a power feed to a heater so as to obtain a target value of the temperature. CONSTITUTION:An air-fuel ratio sensor 8 generates in its oxygen concentration cell part 23 electromotive force in accordance with a difference of oxygen concentration between the atmosphere and exhaust gas. This electromotive force is compared with reference voltage in an operational amplifier 27, and in accordance with the difference, a pump current Ip is fed to an oxygen pump part 22 through a voltage current converter 28. This current Ip is output as an air-fuel ratio voltage signal by a current voltage converter 29, and an air-fuel ratio feedback control is performed. Here a temperature sensor 26 detects temperature of an oxygen concentration detecting element to be output to a CPU16 through an amplifier 21, and by the difference from the target temperature, a heater 24 is electrified through a heater voltage control circuit 14, feedback controlling the element temperature. Thus generating no error in an output of the air-fuel ratio sensor, a high accurate air-fuel ratio control can be performed. |
