NOx Sensor Control Apparatus Pressure Correction
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Solution Overview
Problem
Existing NOX sensors face challenges in accurately measuring NOX and oxygen concentrations due to pressure dependency variations among individual sensors, leading to measurement errors, as the diffusion resistance changes with production variations and pressure changes affect the gas flow into measurement chambers.
Innovation Solution
An NOX sensor control apparatus that includes a first pumping cell for adjusting oxygen concentration and a second pumping cell for measuring NOX concentration, with detectors for pumping currents and units for calculating concentrations, using pressure correction information to account for individual sensor variations and eliminate pressure-induced errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a gas sensor measures gas concentration based on electrode output under predetermined diffusion resistance, then the measurement is stabilized, but the gas flow amount changes with exhaust gas pressure changes, causing measurement error
Solution Approach 1:
The patent applies parameter changes by introducing pressure correction coefficients (k1 for NOX, k2 for oxygen) that adjust the measured concentrations based on detected gas pressure. The correction formulas NOX concentration = (second pumping current) × (pressure correction coefficient k1) and oxygen concentration = (first pumping current) × (pressure correction coefficient k2) dynamically change the measurement parameters according to pressure conditions, resolving the contradiction between measurement stability and accuracy under varying pressure.
2Ease of manufacture
If pressure-dependent variation in sensor output is corrected uniformly, then correction is applied, but the degree of correction varies among individual NOX sensors due to production variations in diffusion resistance, leading to inaccurate concentration information
Solution Approach 1:
The patent applies local quality by assigning unique pressure correction coefficients (k1, k2) to each individual NOX sensor based on its specific production characteristics. Instead of uniform correction, each sensor receives customized correction parameters that account for its specific diffusion resistance properties, ensuring accurate concentration measurements for each individual sensor while maintaining ease of manufacture through automated coefficient determination during production.
3Reliability
If the amount of gas flowing into the measurement chamber is controlled under predetermined diffusion resistance, then measurement is stabilized, but the diffusion resistance magnitude varies due to production conditions, causing individual sensor variations
Solution Approach 1:
The patent compensates for production variations by determining unique pressure correction coefficients (k1, k2) for each sensor during manufacturing and storing them in memory. These parameters adapt the sensor output to account for individual diffusion resistance characteristics, maintaining measurement stability while achieving consistency across different production batches through parameter customization rather than requiring identical physical diffusion resistance.
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
Enables accurate measurement of NOX and oxygen concentrations irrespective of pressure changes, reducing measurement errors by accounting for pressure dependencies specific to each NOX sensor, thus ensuring consistent results across different sensors.
Implementation Method 1
a first pumping cell which has paired first electrodes provided internally and externally, respectively, of a first measurement chamber and which pumps oxygen out of a to-be-measured gas introduced into the first measurement chamber or pumps oxygen into the first measurement chamber to thereby adjust oxygen concentration in the first measurement chamber
Implementation Method 2
NOX contained in the to-be-measured gas is decomposed by means of a second pumping cell composed of a solid electrolyte member and a pair of second electrodes, whereby a second pumping current corresponding to the NOX concentration flows between the pair of second electrodes
Implementation Method 3
the gas concentration is measured based on an output from the electrode pair of the cell, and the measurement is stabilized by limiting (controlling) the amount of the gas which flows into the measurement chamber under a predetermined diffusion resistance
Data Source
AI summary
An NOX sensor control apparatus (10) is connected to an NOX sensor (100) which includes a first pumping cell (110) and a second pumping cell (130) through which a second pumping current flows corresponding to an NOX concentration in a to-be-measured gas. The NOX sensor control apparatus (10) includes a first pumping current detection unit; a second pumping current detection unit; an oxygen concentration calculation unit (60) for calculating oxygen concentration on the basis of the first pumping current and corrected in accordance with the pressure of the to-be-measured gas, oxygen (first) pressure correction information set for the NOX sensor, and pressure information; and an NOX concentration calculation unit (60) for calculating NOX concentration on the basis of the first pumping current and corrected in accordance with pressure of the to-be-measured gas, NOX (second) pressure correction information set for the NOX sensor, and pressure information.