| 摘要 |
PURPOSE:To accurately detect stoichiometric point (point) by regarding a pump current value when a pump voltage varies abruptly owing to the point as a reference value and calculating an air fuel ratio from the deviation between the reference value and a normal pump current value. CONSTITUTION:An oxygen sensor (a), the point detecting means (b), a current detecting means (c), and an air fuel ratio calculating means (d) are provided. Then the pump current value when the pump voltage varies abruptly owing to the point is regarded as a reference value and the air fuel ratio is calculated from the deviation between the reference value and normal pump current value. In this case, the pump voltage varies abruptly coincidently with the point, so the pump current value at this time accurately corresponds to an ideal air fuel ratio. Therefore, while the point is accurately detected regardless of fluctuation in temperature and source voltage and variation in circuit constant, the air fuel ratio is accurately detected over a wide range. |
