APPARATUS AND METHOD FOR DETECTING VARIATION ABNORMALITY IN AIR-FUEL RATIO BETWEEN CYLINDERS
First Claim
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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Abstract
According to a first aspect of the present invention, there is provided an apparatus for detecting variation abnormality in an air-fuel ratio between cylinders comprising a wide-range air-fuel ratio sensor and an O2 sensor 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, air-fuel ratio controlling unit 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 a stoichiometric air-fuel ratio based upon output from the wide-range air-fuel ratio sensor, and abnormality detecting unit for detecting variation abnormality in an air-fuel ratio between cylinders based upon output from the O2 sensor for the predetermined period when the air-fuel ratio control is performed.
35 Citations
13 Claims
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1. An apparatus for detecting variation abnormality in an air-fuel ratio between cylinders comprising:
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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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method for detecting variation abnormality in an air-fuel ratio between cylinders in an internal combustion engine having a plurality of cylinders, comprising:
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a step 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 a predetermined air-fuel ratio region based upon output from first air-fuel ratio detecting means provided in an exhaust passage upstream of an exhaust gas purifying apparatus; and a step for detecting variation abnormality in an air-fuel ratio between cylinders based upon output from second air-fuel ratio detecting means for the predetermined period when the air-fuel ratio control is performed, the second air-fuel ratio detecting means being 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 the predetermined air-fuel ratio region is larger as compared to an output characteristic of the first air-fuel ratio detecting means. - View Dependent Claims (11, 12, 13)
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Specification