Gas Sensor Deterioration Judgment via Output Increase Rate
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Solution Overview
Problem
Existing gas concentration detection apparatuses face accuracy issues in deterioration judgment due to individual sensor differences, leading to delayed and inaccurate detection of sensor degradation, as element resistance, power, and heater resistance vary among sensors.
Innovation Solution
The apparatus forms a deterioration judgment based on the cell output of the gas concentration detection cell, specifically using the inflection point in the cell output to determine sensor activity and degradation, comparing correlation values with reference values to assess the oxygen decomposition capability and excess oxygen discharge capacity, thereby reducing the influence of individual sensor differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heater energization control is exercised to activate the sensor, then the sensor becomes active, but the element temperature must be raised excessively and maintained in consideration of individual sensor differences, delaying deterioration judgment
Solution Approach 1:
The patent performs deterioration judgment before the sensor is fully activated. By evaluating the sensor's response characteristics during the warm-up phase (before excessive temperature raising is needed), the system can detect sensor degradation early without waiting for full activation, thus resolving the time loss while ensuring sensor reliability
Solution Approach 2:
Instead of requiring full sensor activation with excessive temperature raising, the patent uses partial action by evaluating sensor response during the initial warm-up phase. This partial evaluation is sufficient to detect deterioration without the need for complete activation, reducing the time penalty while maintaining judgment accuracy
2Measurement precision
If element resistance, power supplied to heater, or heater resistance are used for deterioration judgment, then sensor status can be assessed, but accuracy decreases due to individual sensor differences
Solution Approach 1:
The patent changes the evaluation parameter from physical properties (element resistance, heater resistance, power) that vary between sensors to functional response characteristics (cell output changes over time) that are consistent across sensors. This parameter transformation maintains measurement precision while eliminating the impact of individual sensor differences
Solution Approach 2:
The patent uses feedback by monitoring the cell output response during warm-up and comparing it against expected patterns. This feedback mechanism allows the system to assess sensor health based on functional performance rather than fixed physical parameters, accommodating individual sensor variations while maintaining judgment accuracy
3Reliability
If heater energization control is exercised, then sensor activation is achieved, but impedance varies when attempting to raise element temperature excessively, decreasing deterioration judgment accuracy
Solution Approach 1:
The patent performs deterioration judgment during the preliminary warm-up phase before excessive heater energization causes impedance variations. By evaluating sensor response early in the activation process, the system maintains measurement precision while still achieving sensor activation, avoiding the impedance variability problem
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 allows for early and accurate deterioration judgment of the gas sensor, preventing the use of degraded sensors in control operations and distinguishing between permanent and temporary deterioration, thus maintaining sensor performance.
Implementation Method 1
a solid electrolyte body (21), which is oxygen ion conductive
Implementation Method 2
heater (6)... heater energization control
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
The present invention relates to a gas concentration detection apparatus for detecting the concentration of a specific gas component in an exhaust gas emitted from an engine, and forms a deterioration judgment about the gas concentration detection apparatus accurately and immediately. After excess oxygen is discharged by an oxygen pump cell 2, a NOx concentration detection apparatus, which uses a NOx sensor cell 4 to detect the concentration of NOx, judges whether a NOx sensor 1 is activated, that is, whether an inflection point has appeared in the NOx sensor cell output of the NOx sensor 1. If the NOx sensor 1 is not activated yet, an output increase rate Vu (t) of the NOx sensor cell output during an increase process of the NOx sensor cell output is acquired. It is then judged whether the output increase rate Vu (t) is lower than a predetermined reference value Vthl. If the obtained judgment result indicates that Vu (t) < Vthl, it is concluded that the NOx sensor cell 4 is deteriorated.