Abnormality diagnosis for air-fuel ratio sensor system
First Claim
1. An abnormality diagnosing apparatus for an air-fuel ratio sensor system of an internal combustion engine which detects an air-fuel ratio of mixture by flowing a current of an air-fuel ratio sensor through a current detecting resistor and detecting a difference between two voltages appearing at both ends of the current detecting resistor, the abnormality diagnosing apparatus comprising:
- activation determining means for determining whether the air-fuel ratio sensor is in an active state; and
abnormality diagnosing means for diagnosing the air-fuel ratio sensor system for a presence/absence of at abnormality from a combination of results of predetermined comparison processings made separately with respect to each of the voltages appearing at the ends of the current detecting resistor, only when the air-fuel ratio sensor is determined to be in the active state.
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Accused Products
Abstract
An air-fuel ratio sensor system is diagnosed for the presence/absence of an abnormality on the basis of a reference voltage appearing at one end of a current detecting resistor and a detection voltage appearing at the other end of the current detecting resistor for detecting a current output by an air-fuel ratio sensor. If the reference voltage is outside a normal range and higher than the detection voltage, the air-fuel ratio sensor system is determined to be in a rich abnormality. If the reference voltage Vafon is outside the normal range and lower than the detection voltage, the air-fuel ratio sensor system is determined to be in a lean abnormality. If the reference voltage is within the normal range and a state of the detection voltage being close to a power supply voltage has been continuing for a predetermined period of time, the air-fuel ratio sensor system is determined to be in a circuit-shorting. If the reference voltage is within the normal range and a state of the detection voltage being equal to the reference voltage has been continuing at least for the predetermined period of time, the air-fuel ratio sensor system is determined to be in a circuit-breakage.
43 Citations
16 Claims
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1. An abnormality diagnosing apparatus for an air-fuel ratio sensor system of an internal combustion engine which detects an air-fuel ratio of mixture by flowing a current of an air-fuel ratio sensor through a current detecting resistor and detecting a difference between two voltages appearing at both ends of the current detecting resistor, the abnormality diagnosing apparatus comprising:
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activation determining means for determining whether the air-fuel ratio sensor is in an active state; and abnormality diagnosing means for diagnosing the air-fuel ratio sensor system for a presence/absence of at abnormality from a combination of results of predetermined comparison processings made separately with respect to each of the voltages appearing at the ends of the current detecting resistor, only when the air-fuel ratio sensor is determined to be in the active state. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. An abnormality diagnosing apparatus for an air-fuel ratio sensor system of an internal combustion engine which detects an air-fuel ratio of mixture by flowing a current of an air-fuel ratio sensor through a current detecting resistor and detecting a difference between voltages appearing at ends of the current detecting resistor the abnormality diagnosis apparatus comprising:
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activation determining means for detecting an active state of the air-fuel ratio sensor; and abnormality diagnosing means for diagnosing the air-fuel ratio sensor system for a presence/absence of abnormality on the basis of a voltage which appears at least one of the ends of the current detecting resistor, only when the air-fuel ratio sensor is determined to be in the active state, wherein the voltage appearing at one end of the current detecting resistor is a reference voltage and the voltage appearing at the other end of the current detecting resistor is a detection voltage varying in accordance with the current of the air-fuel ratio sensor; and the abnormality diagnosing means determines the air-fuel ratio sensor system to be abnormal when the reference voltage is outside a predetermined range.
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9. An abnormality diagnosing apparatus for an air-fuel ratio sensor system of an internal combustion engine which detects an air-fuel ratio of mixture by flowing a current of an air-fuel ratio sensor through a current detecting resistor and detecting a difference between voltages appearing at ends of the current detecting resistor the abnormality diagnosis apparatus comprising:
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activation determining means for detecting an active state of the air-fuel ratio sensor; and abnormality diagnosing means for diagnosing the air-fuel ratio sensor system for a presence/absence of abnormality on the basis of a voltage which appears at at least one of the ends of the current detecting resistor, only when the air-fuel ratio sensor is determined to be in the active state, wherein the voltage appearing at one end of the current detecting resistor is a reference voltage and the voltage appearing at the other end of the current detecting resistor is a detection voltage varying in accordance with the current of the air-fuel ratio sensor; and the abnormality diagnosing means determines the air-fuel ratio sensor system to be abnormal when a state of the detection voltage being unchanged continues for a predetermined period of time.
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10. An abnormality diagnosing apparatus for an air-fuel ratio sensor system of an internal combustion engine, comprising:
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a current detecting resistor through which a current of an air-fuel ratio sensor of said air-fuel ration sensor system flows; and a processing circuit configured to measure voltages at each end of the current detecting resistor, to separately apply abnormality diagnosis criteria with respect to each of the measured voltages and to detect a presence/absence of an abnormality of said air-fuel ratio sensor system based on the results of the applied abnormality diagnosis criteria. - View Dependent Claims (11, 12, 13, 14, 15, 16)
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Specification