Patent ID: 7716917
Filing Date: 2010-05-18
Classification: F02D,Y02T

Abstract:
1. An apparatus for controlling air-fuel ratio of an internal combustion engine being equipped with a catalytic converter having a three-way function; an oxygen sensor, which is installed at the upstream side of said catalytic converter in respect to exhaust gas flow direction, for generating a switching signal showing rich/lean relative to a certain air-fuel ratio; and an air-fuel ratio sensor, which is installed at the downstream side of said catalytic converter in respect to exhaust gas flow direction, for generating a linear output signal corresponding to the air-fuel ratio, at an exhaust gas passage, wherein said apparatus comprises: a deviation calculation means for calculating deviation between the air-fuel ratio measured by said air-fuel ratio sensor, and target air-fuel ratio; and a feedback control means of the air-fuel ratio for carrying out feedback control of the air-fuel ratio based on the deviation calculated by said deviation calculation means, and the output signal of said oxygen sensor, wherein said feedback control means of the air-fuel ratio includes a control variable calculation means for calculating a variable for feedback control of the air-fuel ratio by deviation calculated by said deviation calculation means; a comparison means for comparing whether the output voltage of said oxygen sensor is larger than a threshold value set responsive to deviation calculated by said deviation calculation means, or not; and a reflection judgment means for judging whether the control variable by said control variable calculation means should be reflected to feedback control of the air-fuel ratio or not, based on the comparison result of said comparison means and the control variable by said control variable calculation means.