Patent ID: 7779620
Filing Date: 2010-08-24
Classification: F01N,Y02T

Abstract:
1. An air-fuel ratio feedback control device for use in a fuel injection control system for controlling a fuel injection amount for an internal combustion engine comprises: a downstream air-fuel ratio sensor disposed at the downstream side of a catalyst set in an exhaust system of the internal combustion engine and outputs a downstream air-fuel ratio detection output; downstream air-fuel ratio feedback control means having PI calculating means for calculating a downstream air-fuel ratio feedback amount on the basis of the downstream air-fuel ratio detection output and a target downstream air-fuel ratio; an upstream air-fuel ratio sensor disposed at the upstream side of the catalyst and outputs an upstream air-fuel ratio detection output; upstream air-fuel ratio feedback control means for generating a correction amount to the fuel injection amount on the basis of the upstream air-fuel ratio detection output, and generating a target upstream air-fuel ratio; and catalyst deterioration diagnosing means for carrying out deterioration diagnosis of the catalyst, wherein the catalyst deterioration diagnosing means has diagnosis permission judging means for judging permission of the deterioration diagnosis of the catalyst on the basis of a driving area of the internal combustion engine, air-fuel ratio varying means for outputting an air-fuel ratio variation output at a catalyst deterioration diagnosis time by the catalyst deterioration diagnosis means, catalyst deterioration judging means for judging the deterioration of the catalyst on the basis of the downstream air-fuel ratio detection output at the catalyst deterioration diagnosis time, and catalyst deterioration diagnosis prohibiting means for setting a deterioration diagnosis prohibition time for the catalyst after the catalyst deterioration diagnosis, and wherein the upstream air-fuel ratio feedback control means has upstream air-fuel ratio learning calculating means and target upstream air-fuel ratio calculating means, the upstream air-fuel ratio learning calculating means calculates an upstream air-fuel ratio learning calculation amount on the basis of the integration value shifted from the PI calculating means to the upstream air-fuel ratio learning calculating means under the state that the catalyst deterioration diagnosis is not carried out by the catalyst deterioration diagnosis means, the target upstream air-fuel ratio calculating means, at the catalyst deterioration diagnosis time, outputs the target upstream air-fuel ratio on the basis of the downstream air-fuel ratio feedback amount and the air-fuel ratio variation output, and the target upstream air-fuel ratio calculating means, at the state that the catalyst deterioration diagnosis is not carried out, outputs the target upstream air-fuel ratio on the basis of the downstream air-fuel ratio feedback amount and the upstream air-fuel ratio learning calculation amount.