Gas Sensor Refresh Process for NOx Measurement Accuracy
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Solution Overview
Problem
Gas sensors experience increased undershoot and overshoot in measurement pump current over time, leading to degraded accuracy in NOx concentration measurement, particularly due to changes in moisture levels and fuel cut events in internal combustion engines.
Innovation Solution
The gas sensor incorporates a refresh process that includes adjustment and measurement pump control processes to adjust oxygen concentrations in specific chambers, determining necessity based on undershoot or overshoot, and performing these processes to maintain target oxygen levels, thereby reducing measurement errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the gas sensor is used continuously over time, then the sensor can maintain its basic detection function, but the undershoot and overshoot of the measurement pump current increase, degrading measurement accuracy
Solution Approach 1:
The patent implements a periodic refresh process that is executed at predetermined time intervals or when specific conditions are met. This periodic action restores the measurement pump cell's performance by removing accumulated substances, thereby suppressing the increase in undershoot and overshoot of the measurement pump current and maintaining measurement accuracy over extended operational periods
Solution Approach 2:
The refresh process discards accumulated substances (such as carbon deposits or moisture) from the measurement pump cell through controlled pumping operations. By removing these harmful accumulations, the measurement pump cell's performance is recovered, reducing measurement errors and restoring accurate NOx concentration detection capabilities
2Measurement precision
If a refresh process is implemented to suppress undershoot and overshoot, then measurement accuracy is maintained, but the device complexity increases due to additional control processes
Solution Approach 1:
The refresh process is designed to be automatically triggered based on predetermined conditions such as elapsed time intervals or detected sensor performance degradation. This self-service mechanism eliminates the need for complex external control systems, as the sensor autonomously determines when refresh operations are necessary, thereby maintaining measurement accuracy without proportionally increasing device complexity
Solution Approach 2:
The refresh process dynamically adjusts pumping parameters (such as pump current magnitude and duration) based on the detected state of the sensor. By changing these operational parameters adaptively, the system achieves effective restoration of measurement accuracy while avoiding unnecessarily complex control mechanisms, as the parameter adjustments are based on simple threshold comparisons or time-based logic
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 effectively suppresses the increase in undershoot and overshoot of the measurement pump current, maintaining accurate NOx concentration detection and extending the sensor's operational reliability.
Implementation Method 1
an element body which includes an oxygen-ion-conductive solid electrolyte layer
Implementation Method 2
a measurement pump cell having an outer measurement electrode provided outside the element body to come into contact with the measurement-object gas, and an inner measurement electrode disposed in a measurement chamber of the measurement-object gas flow portion, the measurement pump cell being configured to pump out oxygen from a periphery of the inner measurement electrode to a periphery of the outer measurement electrode
Implementation Method 3
an adjustment pump cell that adjusts an oxygen concentration in an oxygen concentration adjustment chamber provided upstream of the measurement chamber of the measurement-object gas flow portion
Implementation Method 4
a measurement voltage detection sensor cell that detects a voltage for measurement across the reference electrode and the inner measurement electrode
Data Source
AI summary
A gas sensor includes: a sensor element including an element body which is internally provided with a measurement-object gas flow portion that introduces a measurement-object gas and causes the measurement-object gas to flow, a measurement pump cell having an inner measurement electrode disposed in a measurement chamber and an adjustment pump cell that adjusts an oxygen concentration in an oxygen concentration adjustment chamber, a necessity determiner that performs a refresh necessity determination process of determining necessity of a refresh of the sensor element based on at least one of undershoot or overshoot at a time of rapid change in a measurement pump current; and a refresh controller that, upon a determination that the refresh is necessary in the refresh necessity determination process, performs a refresh process including at least one of an adjustment pump control process during refresh or a measurement pump control process during refresh.