O.sup.2 -sensor fault diagnosis method and apparatus
First Claim
1. A fault diagnosis apparatus for an O2 -sensor employed in a fuel supply control system of an internal combustion engine, comprising:
- an O2 -sensor for detecting concentration of oxygen contained in an exhaust gas of an internal combustion engine;
feedback control means for controlling a quantity of fuel supplied to said internal combustion engine through feedback control in dependence on an output signal of said O2 -sensor; and
a microcomputer;
wherein said microcomputer is preprogrammed to perform;
a first means comprising an enforcive fuel quantity correcting control circuit for computing if said O2 -sensor exhibits an abnormality on the basis of the output signal state of said O2 -sensor for forcibly changing the amount of said fuel supplied to the engine during said feedback control; and
a second computation means comprising an input resistance changing circuit for detecting an abnormality of said O2 -sensor in accordance with an abnormality computation process which bears a stronger correlation to the abnormality than the commutation performed by said first computation means, said second computation being performed when said feedback control based on the output of said O2 -sensor is not being performed.
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Abstract
An O2 -sensor fault diagnosis method and apparatus for detecting a fault of an O2 -sensor when a feedback control of a fuel supply to an engine is performed by making use of the output of an O2 -sensor and detecting and identifying a fault of the O2 -sensor even in the case where the feedback control is invalidated. A microcomputer (24) receives an output of an O2 -sensor (19) for detecting concentration of oxygen contained in an exhaust gas of an internal combustion engine (1). An ECU (20) controls a quantity of fuel supplied to the internal combustion engine (1) through feedback control in dependence on an output signal of the O2 -sensor (19). A first decision circuit is provided for deciding whether or not the O2 -sensor (19) exhibits abnormality on the basis of the output signal state of the O2 -sensor (19) by forcibly changing the amount of the fuel supplied to the engine during the feedback control, and a second decision circuit is provided for deciding abnormality of the O2 -sensor (19) in accordance with an abnormality decision process which bears a stronger correlation to the abnormality than the decision performed by the first decision circuit. Fault detection of the O2 -sensor is possible not only during the feedback control of the fuel supply but also in the state where the feedback control is not performed.
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Citations
7 Claims
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1. A fault diagnosis apparatus for an O2 -sensor employed in a fuel supply control system of an internal combustion engine, comprising:
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an O2 -sensor for detecting concentration of oxygen contained in an exhaust gas of an internal combustion engine; feedback control means for controlling a quantity of fuel supplied to said internal combustion engine through feedback control in dependence on an output signal of said O2 -sensor; and a microcomputer; wherein said microcomputer is preprogrammed to perform; a first means comprising an enforcive fuel quantity correcting control circuit for computing if said O2 -sensor exhibits an abnormality on the basis of the output signal state of said O2 -sensor for forcibly changing the amount of said fuel supplied to the engine during said feedback control; and a second computation means comprising an input resistance changing circuit for detecting an abnormality of said O2 -sensor in accordance with an abnormality computation process which bears a stronger correlation to the abnormality than the commutation performed by said first computation means, said second computation being performed when said feedback control based on the output of said O2 -sensor is not being performed. - View Dependent Claims (2, 3, 4)
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5. A fault diagnosis method for an O2 -sensor employed in a fuel supply control system of an internal combustion engine, comprising:
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a first operation of forcibly varying an amount of fuel supplied to said internal combustion engine during a feedback control of the fuel supply to said engine in dependence upon an output signal supplied from an O2 -sensor for detecting concentration of oxygen contained in an exhaust gas of an internal combustion engine, to thereby compute if said O2 -sensor suffers an abnormality on the basis of an output signal state of said O2 -sensor; and a second operation of computing if an abnormality of the O2 -sensor exists in accordance with a second computation method which bears a stronger correlation to the abnormality of the O2 -sensor when the feedback control of the fuel supply to the engine is not performed. - View Dependent Claims (6, 7)
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Specification
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- Resources
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Current AssigneeMitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
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Original AssigneeMitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
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InventorsNakamichi, Masaki
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Primary Examiner(s)Nelli, Raymond A.
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Application NumberUS08/615,411Time in Patent Office607 DaysField of Search123/688, 123/481, 123/479, 123/691, 123/703, 60/276, 73/118.1, 340/438, 364/431.05US Class Current123/688CPC Class CodesF02D 41/1474 by detecting the commutatio...F02D 41/1495 Detection of abnormalities ...F02D 41/2458 with an additional dither s...
