Diagnosis of sensor failure in airflow-based engine control system
First Claim
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1. A method of diagnosing failure in connection with a mass airflow sensor used in an airflow-based engine control system for an internal combustion engine, the engine having one or more cylinders and an exhaust gas recirculation (EGR) system that recirculates exhaust at a variable EGR rate, comprising:
- obtaining a measured airflow mass value from the mass airflow sensor;
obtaining a measured intake oxygen concentration value;
obtaining a measured exhaust oxygen concentration value;
calculating an EGR rate based on the relationship between the intake oxygen concentration value and the exhaust oxygen concentration value;
obtaining a measured intake manifold pressure value;
obtaining a measured intake manifold temperature value;
calculating a total gas flow rate into the cylinders, based on the measured intake pressure value and the measured intake manifold temperature value;
subtracting the EGR rate from the total gas flow rate, thereby obtaining a calculated value for a mass air flow rate, which is not based on the measured airflow mass value;
comparing the measured airflow mass value to the calculated airflow mass value; and
generating airflow mass sensor failure data if the comparing step does not result in a match.
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Abstract
An air-flow based control system for an internal combustion engine has various sensors that are used to calculate various control commands. By comparing pairs of values calculated from different sensors, errors in connection with the sensors can be detected.
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Citations
4 Claims
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1. A method of diagnosing failure in connection with a mass airflow sensor used in an airflow-based engine control system for an internal combustion engine, the engine having one or more cylinders and an exhaust gas recirculation (EGR) system that recirculates exhaust at a variable EGR rate, comprising:
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obtaining a measured airflow mass value from the mass airflow sensor; obtaining a measured intake oxygen concentration value; obtaining a measured exhaust oxygen concentration value; calculating an EGR rate based on the relationship between the intake oxygen concentration value and the exhaust oxygen concentration value; obtaining a measured intake manifold pressure value; obtaining a measured intake manifold temperature value; calculating a total gas flow rate into the cylinders, based on the measured intake pressure value and the measured intake manifold temperature value; subtracting the EGR rate from the total gas flow rate, thereby obtaining a calculated value for a mass air flow rate, which is not based on the measured airflow mass value; comparing the measured airflow mass value to the calculated airflow mass value; and generating airflow mass sensor failure data if the comparing step does not result in a match. - View Dependent Claims (2, 3)
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4. A method of diagnosing failure in connection with an intake oxygen sensor or exhaust oxygen sensor of an engine having an exhaust gas recirculation (EGR) system that recirculates exhaust at a variable EGR rate, and having a control system that uses an EGR base map to determine the EGR rate, comprising:
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calculating a first calculated EGR rate by subtracting a measured intake air flow rate from a total as flow rate into the cylinders; obtaining a measured intake oxygen concentration value using the intake oxygen sensor; obtaining a measured exhaust oxygen concentration value using the exhaust oxygen sensor; calculating a second calculated EGR rate based on the relationship between the intake oxygen concentration value and the exhaust oxygen concentration value; accessing the EGR base map stored in memory of the control system, the map providing EGR rates for given engine operating conditions, such that for a current operating condition the EGR rate provided by the map is the EGR rate used to control the EGR rate of the engine; and comparing the first calculated EGR rate and the second calculated EGR rate with the EGR rate provided by the EGR base map for the same engine speed and intake O2 mass value; and if the first calculated EGR rate and EGR rate provided by the EGR base map match each other but do not match the second calculated EGR rate, generating data indicating failure of the intake oxygen sensor or the exhaust oxygen sensor.
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Specification