NOx Sensor Control Device for Oxygen Discharge Adjustment
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Solution Overview
Problem
Existing gas sensor systems for NOx detection face challenges in accurately diagnosing deterioration and correcting output signals due to variations in oxygen discharge, leading to potential inaccuracies and structural complexity.
Innovation Solution
A gas sensor control device that temporarily changes the oxygen discharge amount by the pump cell, calculates the actual discharge amount and resulting output changes in the sensor cell, and uses these calculations to improve the accuracy of concentration detection and deterioration diagnosis without altering the sensor configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a constant voltage is applied to the pump cell, then the gas sensor operates stably, but the oxygen discharge amount may be undesired and affect deterioration diagnosis accuracy
Solution Approach 1:
The patent applies dynamics by temporarily changing the voltage applied to the pump cell from a constant value to a variable value. Specifically, the control device changes the voltage to a first value during normal operation and to a second value (different from the first) during deterioration diagnosis. This dynamic voltage adjustment allows the system to achieve both stable operation under normal conditions and accurate deterioration diagnosis when needed, resolving the contradiction between operational stability and measurement precision.
2Measurement precision
If a deterioration detection cell is added to detect sensor deterioration, then diagnosis accuracy improves, but the structure becomes complicated
Solution Approach 1:
The patent applies universality by making the existing pump cell perform multiple functions. The pump cell not only discharges oxygen during normal operation but also serves as the deterioration detection means when voltage is temporarily changed to a second value. By using the pump cell for both oxygen discharge and deterioration diagnosis, the patent eliminates the need for a separate deterioration detection cell, thus improving diagnosis accuracy without increasing structural complexity.
Solution Approach 2:
The patent applies self-service by enabling the pump cell to diagnose its own deterioration state. When the voltage is changed to the second value, the pump cell's output signal reflects its deterioration level, allowing the system to perform self-diagnosis without requiring additional dedicated detection components. This self-service capability resolves the contradiction by achieving accurate deterioration detection while maintaining a simple sensor structure.
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
The solution enables precise control and diagnosis of gas sensors, enhancing the accuracy of NOx concentration detection and deterioration assessment while maintaining a simplified sensor configuration.
Implementation Method 1
a pump cell, a monitor cell, and a sensor cell each having a solid electrolytic element and a pair of electrodes disposed on the solid electrolytic element
Data Source
AI summary
A NOx sensor includes a pump cell, a monitor cell, and a sensor cell, and the pump cell discharges an oxygen in an exhaust gas introduced into a chamber. The sensor cell outputs a detected signal depending on a concentration of a NOx according to a gas after the oxygen is discharged. A microcomputer of a sensor control circuit temporarily changes an amount of the oxygen discharged by the pump cell, and then calculates output change amounts ΔIp, ΔIs, and ΔIm of the cells. The microcomputer performs a correction of the concentration of the NOx detected by the sensor cell and a deterioration diagnosis of the sensor cell, based on the output change amounts ΔIp, ΔIs, and ΔIm of the cells. When the sensor cell current Is is smaller than the monitor cell current Im, the microcomputer determines that the NOx sensor has an abnormality.