Exhaust Gas Sensor Crack Detection via Impedance Correction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing failure detection systems for exhaust gas sensors struggle to accurately detect cracks due to variations in impedance, which can lead to incorrect assessments regardless of temperature fluctuations.
Innovation Solution
A failure detection apparatus and method that applies a reverse voltage between the atmosphere-side and exhaust-side electrodes, detects the reverse current, and corrects it using an impedance correlation value to filter out impedance influences, ensuring accurate detection of cracks in the sensor element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the electric current value is used to detect cracks in the sensor element, then crack detection is enabled, but detection accuracy deteriorates due to impedance variations caused by temperature changes
Solution Approach 1:
The patent introduces an impedance correlation value as an intermediary parameter to mediate between the measured electric current and the crack detection decision. This intermediary captures the impedance influence separately, allowing the system to distinguish between current changes caused by impedance variations versus those caused by actual cracks, thereby resolving the contradiction between detection capability and measurement precision
Solution Approach 2:
The patent changes the parameter used for detection from raw electric current to a corrected current value that compensates for impedance effects. By transforming the measurement parameter to account for temperature-induced impedance changes, the system maintains detection accuracy across varying operating conditions while preserving crack detection capability
2Adaptability or versatility
If the sensor element operates at different temperatures, then operational flexibility is improved, but detection reliability deteriorates due to impedance variations
Solution Approach 1:
The patent dynamically adjusts the detection parameters by introducing temperature-compensated impedance correlation values. This allows the sensor to adapt to different temperature conditions while maintaining reliable crack detection, as the impedance compensation mechanism ensures that detection reliability is preserved across the full operating temperature range
Solution Approach 2:
The patent implements a dynamic detection system where the impedance correlation value is continuously updated based on operating conditions. This dynamic approach allows the system to maintain detection reliability across varying temperatures by adapting the detection criteria to current impedance characteristics rather than using fixed thresholds
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables reliable crack detection in exhaust gas sensors, unaffected by impedance variations, providing stable and accurate results across different temperature conditions.
Implementation Method 1
an electrolyte layer that is disposed between the exhaust-side electrode and the atmosphere-side electrode and that allows movement of oxygen ions between the exhaust-side electrode and the atmosphere-side electrode
Implementation Method 2
a reverse voltage application device that applies a reverse voltage between the atmosphere-side electrode and the exhaust-side electrode so that the electric potential of the exhaust-side electrode becomes higher than the electric potential of the atmosphere-side electrode
Data Source
AI summary
An air-fuel ratio sensor has an exhaust-side electrode and an atmosphere-side electrode. The atmosphere-side electrode is disposed in an atmosphere layer that communicates with the atmosphere. Since the air-fuel ratio sensor is disposed in an exhaust passage, exhaust gas enters the atmosphere layer if a sensor crack occurs. Ordinarily, forward voltage is applied to the air-fuel ratio sensor to obtain an output thereof in accordance with the air-fuel ratio. Immediately after the applied voltage is switched to reverse voltage, sensor current i1 in accordance with the impedance flows, regardless of the presence/absence of a sensor crack. After that, the sensor current converges to a value i2 that is in accordance with the oxygen concentration in the atmosphere layer. The presence/absence of a sensor crack is determined by comparing the value obtained by correcting i2 by i1, with a criterion value.