Evaluation of a motor vehicle oxygen sensor performance
First Claim
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1. A method for evaluating the performance of an oxygen sensor that detects an oxygen concentration level in an exhaust gas from an internal combustion engine, the method comprising:
- cutting off a fuel supply to the internal combustion engine and allowing the detected oxygen concentration level of the exhaust gas to rise;
reinstating said fuel supply after the detected oxygen concentration level has risen above a pre-determined upper threshold;
measuring a fall time for the detected oxygen concentration level to fall to a pre-determined lower threshold from the moment said fuel supply is reinstated; and
producing an oxygen sensor degradation signal if said measured fall time exceeds a pre-set time.
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Abstract
The invention relates to the performance evaluation of an oxygen gas sensor in a motor vehicle, where the oxygen gas sensor is used to measure the oxygen content of the combusted air fuel mixture of a motor vehicle exhaust. The method involves measuring the fall time for the detected oxygen level to fall to a pre-determined lower threshold after the fuel supply to the engine has been cut off, and if the measured fall time exceeds a pre-set time, producing an oxygen sensor degradation signal.
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Citations
18 Claims
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1. A method for evaluating the performance of an oxygen sensor that detects an oxygen concentration level in an exhaust gas from an internal combustion engine, the method comprising:
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cutting off a fuel supply to the internal combustion engine and allowing the detected oxygen concentration level of the exhaust gas to rise;
reinstating said fuel supply after the detected oxygen concentration level has risen above a pre-determined upper threshold;
measuring a fall time for the detected oxygen concentration level to fall to a pre-determined lower threshold from the moment said fuel supply is reinstated; and
producing an oxygen sensor degradation signal if said measured fall time exceeds a pre-set time. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. A performance evaluating system for detecting a degradation in an oxygen sensor that detects an oxygen concentration level of an exhaust gas of an internal combustion engine, the performance evaluator comprising:
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means for cutting off a fuel supply to the internal combustion engine and allowing the detected oxygen concentration level of the exhaust gas to rise;
means for reinstating a fuel supply after the detected oxygen concentration level has risen above a pre-determined upper threshold;
means for measuring a fall time from the moment said fuel supply is reinstated for the detected oxygen concentration level to fall to a pre-determined lower threshold; and
means for producing an oxygen sensor degradation signal if said measured fall time exceeds a pre-set time.
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18. A fault detector for detecting a fault in an oxygen sensor that senses the oxygen concentration of the exhaust gas of an internal combustion engine with an engine management system, the fault detector comprising:
- a microprocessor, responsive to signals from the engine management system and the oxygen sensor, such microprocessor having a counter-timer, wherein if the microprocessor receives a command signal from the engine management system indicating that fuel to the engine has been cut off, followed by a signal from the oxygen sensor indicating that the sensed oxygen level has reached an upper threshold, the microprocessor measures the elapsed time from the moment the engine management system issues a command for fuel reinstatement until the sensed oxygen has fallen to a lower threshold value, and if the elapsed time is greater than a pre-set time, to issue an oxygen sensor fault signal.
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