| 摘要 |
PURPOSE:To enable to prevent an oxygen sensor from breakage by a method wherein a current increasing control for the oxygen sensor upon acceleration is delayed by a predetermined time in the air to fuel control system controllng the electric current for the oxygen sensor in accordance with an operation condition signal. CONSTITUTION:The air to fuel ratio control system controls the input electric current to a sensor 4a and the voltage of a heater in accordance with the variation of the operation condition signal P. Now, when a car is being moved from a low speed to a high speed running, that means the operation condition signal P showing a sudden decrease of a suction vacuum is outputted, a control circuit 18 selects a resistor 21 having the minimum value in order to make the electric current inputted into the sensor 4a the maximum value. However, a delay circuit 27 is provided at the input side of the resistor 21, therefore, the increase of the input current is effected with a predetermined time delay due to the CR time constant of this circuit 27 that means it is effected in accordance with the increase of the running speed of the car. Accordingly, the transfer of an actual exhaust temperature into a high area agrees with the increase of the input current and thereby preventing the breakage of the oxygen sensor. |
