Exhaust Gas Sensor Response Diagnosis via Output Estimation
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Solution Overview
Problem
Existing exhaust gas sensor diagnostic systems cannot accurately diagnose the degree of response lowering in exhaust gas sensors, leading to potential errors in engine control and emission deterioration when sensors are blocked or degrade, as they only compare actual outputs with normal outputs without accounting for varying response levels.
Innovation Solution
A diagnostic device that estimates normal and lowered outputs based on engine operation states, gas flow velocities, and sensor characteristics, allowing for comparison of actual outputs with both normal and lowered outputs to determine the response lowering degree, using integration values and change rates to reduce noise influence and prevent erroneous diagnoses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the output of the exhaust gas sensor is corrected based on the deviation between the estimated output and the actual output, then the measurement precision is improved, but the reliability deteriorates when the response of the exhaust gas sensor is lowered
Solution Approach 1:
The patent segments the response characteristic into multiple levels by introducing a lowered response characteristic alongside the normal response characteristic. This allows the system to distinguish between different degrees of sensor degradation and apply appropriate correction strategies, thereby improving both measurement precision and diagnosis accuracy.
Solution Approach 2:
The patent changes the response characteristic parameter from a single fixed value to multiple possible values (normal response characteristic and lowered response characteristic). This enables the system to adapt to different sensor states and make more accurate diagnoses, resolving the contradiction between correction precision and diagnosis reliability.
2Productivity
If the fuel injection quantity and EGR gas quantity are controlled based on the output of the exhaust gas sensor, then the emission control is improved, but the reliability deteriorates when the sensor response is blocked or degraded
Solution Approach 1:
The patent implements a feedback mechanism where the system continuously monitors the exhaust gas sensor output and compares it with estimated outputs based on different response characteristics. This feedback loop allows the system to detect sensor degradation and adjust control strategies accordingly, maintaining both emission control efficiency and control stability.
Solution Approach 2:
The patent prepares multiple response characteristics (normal and lowered) in advance to cushion against potential sensor failures or degradations. By having pre-established correction strategies, the system can maintain reliable control even when the sensor response is blocked or degraded, preventing sudden control failures.
3Device complexity
If the response of the exhaust gas sensor is lowered due to blockage or degradation, then the device complexity is reduced, but the measurement precision deteriorates
Solution Approach 1:
The patent creates a copy of the normal response characteristic to represent the lowered response characteristic. This virtual copy allows the system to simulate and account for sensor degradation without physically modifying the sensor structure, thereby maintaining device simplicity while improving measurement precision through computational methods.
Data Source
AI summary
In a transient state caused by fuel cut, a normal output of an A/F sensor having normal response and a lowered output having response lowered by a predetermined value as compared to the normal output are estimated, and an actual output of the A/F sensor is sensed. S1 as an integration value of a deviation between the normal output and the lowered output and S2 as an integration value of a deviation between the normal output and the actual output are calculated respectively until the normal output and the lowered output converge to an oxygen concentration equivalent to an atmosphere. S2 changes in accordance with a lowering degree of the response of the actual output. Therefore, the lowering degree of the response of the A/F sensor can be diagnosed based on S2/S1.