Patent ID: 7013214
Filing Date: 2006-03-14
Classification: F02D

Abstract:
1. An air-fuel ratio feedback control apparatus for an internal combustion engine, comprising: an air-fuel ratio sensor disposed in an exhaust pipe of said engine, to output a detection signal of an air-fuel ratio; a control section that receives the detection signal from said air-fuel ratio sensor, and that outputs an air-fuel ratio feedback control signal so that the air-fuel ratio detected based on the detection signal is brought into a target air-fuel ratio; a diagnosing section that forcibly changes said target air-fuel ratio during an air-fuel ratio feedback control by said control section, that diagnoses a response characteristic of said air-fuel ratio sensor based on a change in detection signal from said air-fuel ratio sensor to the change in said target air-fuel ratio, and that outputs a signal indicating a diagnosis result; a storing section that stores a value of the air-fuel ratio feedback control signal immediately before the starting of diagnosis by said diagnosing section; and a reset section that returns said target air-fuel ratio to a normal value when the diagnosis by said diagnosing section is finished, and that simultaneously resets said air-fuel ratio feedback control signal to said value stored in said storing section immediately before the starting of the diagnosis.