Intake Oxygen Sensor Degradation Detection via Time Constant Comparison
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Solution Overview
Problem
Existing intake oxygen sensors in engine systems can degrade, leading to inaccurate EGR flow estimates and compromised engine control due to altered time constants, making it difficult to accurately correct for pressure fluctuations in the air intake system.
Innovation Solution
A method is implemented to detect oxygen sensor degradation by comparing the time constants of the intake oxygen sensor and throttle inlet pressure sensor, allowing for notification of necessary replacement and alternative EGR flow estimation methods when degradation is detected.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the intake oxygen sensor is used to estimate EGR flow based on oxygen concentration changes, then EGR control can be achieved, but sensor degradation alters the time constant and reduces measurement accuracy
Solution Approach 1:
The system performs preliminary diagnostics by comparing the time constant of the oxygen sensor output with the expected time constant before using the sensor for EGR estimation. This advance check prevents degraded sensor data from compromising measurement accuracy.
Solution Approach 2:
The system continuously monitors the time constant of the oxygen sensor output and uses this feedback to determine whether the sensor is functioning properly. When the time constant deviates from expected values, the system adjusts its operation to avoid using unreliable sensor data.
2Measurement precision
If pressure correction is applied to the oxygen sensor output using TIP signal, then compensation for pressure fluctuations is achieved, but sensor degradation reduces the correlation between TIP and oxygen sensor signals
Solution Approach 1:
The system checks the time constant of the oxygen sensor before applying pressure correction. This preliminary verification ensures that the sensor signal is still reliable and correlated with the TIP signal, preventing loss of information through incorrect correction.
Solution Approach 2:
The system uses the oxygen sensor's time constant as feedback to determine whether pressure correction should be applied. When the time constant indicates sensor degradation, the system stops applying correction to avoid introducing errors from uncorrelated signals.
3Productivity
If the oxygen sensor output is used for EGR estimation during boosted conditions, then EGR control is maintained, but time constant variations reduce the accuracy of EGR flow estimates
Solution Approach 1:
Before using the oxygen sensor for EGR estimation during boosted conditions, the system performs a preliminary check of the sensor's time constant. This ensures that only accurate sensor data is used, maintaining EGR control continuity without sacrificing precision.
Solution Approach 2:
The system continuously monitors the oxygen sensor's time constant during boosted conditions and uses this feedback to determine when EGR estimation should be performed. This feedback mechanism maintains productivity while ensuring measurement precision through conditional operation.
Data Source
AI summary
Methods and systems are provided for diagnosing an intake oxygen sensor. In one example, a method may include indicating degradation of an intake oxygen sensor based on a first time constant of an output of the intake oxygen sensor and a second time constant of an output of a throttle inlet pressure sensor. The method may further include adjusting EGR flow based on the output of the intake oxygen sensor and the output of the throttle inlet pressure sensor when the intake oxygen sensor is not degraded.