| 摘要 |
PURPOSE:To suppress the deterioration of an O2 sensor by holding the value of a flowing-in electric current, when the inside of an exhaust pipe maintains the atmopsheric pressure and the flowing-in electric current into the O2 sensor reduces to a prescribed value or less, and suspending the feed of the flowing-in electric current after holding. CONSTITUTION:When a fuel-cut signal F/C is output from an air-fuel ratio control means 10, and the air fuel ratio shifts to the atmosphere side, the output Vi of a current-value detecting means 4 connected to an O2 sensor 1 varies. The output Vi is differentiated in the differentiation circuit 22 of a variation-rate judging means 21, and when the differentiation signal becomes nearly zero, an H signal S3 is input into a supply stop means 26, and a hold signal SH is output into a sample holding circuit 7 from a hold-signal generating circuit 27, synchronized with the initial starting-up of a signal S4, and output into an FF circuit 31 through an inverter 29. A switch 32 is turned ON by the stop signal ST supplied from the FF circuit 31, and the supply of the flowing-in current IS into the O2 sensor 1 through an operation amplifier OP3 is suspended. |
