APPARATUS AND METHOD FOR DETECTING VARIATION ABNORMALITY IN AIR-FUEL RATIO BETWEEN CYLINDERS

  • US 20120174900A1
  • Filed: 12/24/2010
  • Published: 07/12/2012
  • Est. Priority Date: 12/24/2010
  • Status: Abandoned Application
First Claim
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1. An apparatus for detecting variation abnormality in an air-fuel ratio between cylinders comprising:

  • first air-fuel ratio detecting means provided in an exhaust passage upstream of an exhaust gas purifying apparatus arranged in the exhaust passage for an internal combustion engine having a plurality of cylinders;

    second air-fuel ratio detecting means provided in the exhaust passage upstream of the exhaust gas purifying apparatus and having an output characteristic that an output variation to an air-fuel ratio change in a predetermined air-fuel ratio region is larger as compared to an output characteristic of the first air-fuel ratio detecting means;

    air-fuel ratio controlling means for performing air-fuel ratio control for a predetermined period in such a manner as to make an exhaust air-fuel ratio be equal to an air-fuel ratio in the predetermined air-fuel ratio region based upon output from the first air-fuel ratio detecting means; and

    abnormality detecting means for detecting variation abnormality in an air-fuel ratio between cylinders based upon output from the second air-fuel ratio detecting means for the predetermined period when the air-fuel ratio control is performed by the air-fuel ratio controlling means.

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