NOx Sensor Control Apparatus Temperature Gradient Compensation
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Solution Overview
Problem
The existing NOx sensor control apparatuses face accuracy issues in detecting oxygen and NOx concentrations due to temperature gradients between cells in the NOx sensor element, which are exacerbated by changes in the use environment, leading to errors in output measurements.
Innovation Solution
The NOx sensor control apparatus includes impedance detection means for the first and second cells, a heater control mechanism to set target impedance values, and an output correction mechanism that compensates for temperature gradients by estimating the temperature of the third cell based on impedance deviations between the first and second cells, thereby correcting the output and enhancing detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the heater energization control is performed to maintain a fixed temperature for one cell, then the detection function is activated, but temperature gradients between cells cause measurement errors
Solution Approach 1:
The patent applies local quality by independently controlling the temperature of each cell through separate heater energization control. Instead of maintaining a uniform temperature across all cells, the system adjusts the temperature of the first cell, second cell, and third cell individually to compensate for local temperature gradients, thereby eliminating measurement errors while maintaining the necessary activation temperature for detection functionality.
2Adaptability or versatility
If the NOx sensor element is elongated with three cells arranged sequentially, then the sensor can perform multiple detection functions, but temperature gradients arise between the cells
Solution Approach 1:
The patent addresses the temperature gradient issue in multi-cell elongated sensors by implementing local temperature control for each cell. The first cell, second cell, and third cell are individually monitored and heated to their respective optimal temperatures, allowing the elongated sensor structure to maintain both its multi-functional capability and temperature uniformity across different locations.
Solution Approach 2:
The system dynamically adjusts the heater energization for each cell based on real-time temperature monitoring. The control apparatus continuously monitors the temperature of each cell and adjusts the heater output accordingly, enabling the sensor to adapt to changing thermal conditions while maintaining optimal operating temperatures for all three cells despite the elongated structure.
3Adaptability or versatility
If the temperature gradient changes due to environmental factors, then the sensor responds to environmental variations, but detection accuracy deteriorates
Solution Approach 1:
The patent implements feedback control by continuously monitoring the temperature of each cell and adjusting the heater energization accordingly. When environmental factors cause temperature gradient changes, the control apparatus detects these variations through temperature monitoring and automatically adjusts the heating to maintain optimal temperatures, thereby compensating for environmental effects and preserving detection accuracy.
Solution Approach 2:
The system compensates for environmental variations by dynamically changing the temperature parameters of each cell through adjusted heater energization. Instead of maintaining fixed temperatures, the control apparatus adapts the temperature of the first, second, and third cells based on real-time conditions, allowing the sensor to respond to environmental changes while maintaining measurement precision through parameter adjustment.
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 solution effectively compensates for temperature gradient-induced errors, improving the accuracy of oxygen and NOx concentration detection without complicating the circuit structure, ensuring stable and precise gas concentration measurements.
Implementation Method 1
a NOx sensor element which includes: an oxygen concentration detection cell which has an oxygen ion conductive solid electrolyte and a pair of electrodes
Implementation Method 2
it is necessary to activate each cell by heating the NOx sensor to a predetermined activation temperature (for example, a predetermined temperature of 750° C. or above) and hence, a heater is provided to the NOx sensor as an integral part of each cell
Implementation Method 3
the first pumping cell is driven so as to pump out oxygen from the first measuring chamber or to pump oxygen into the first measuring chamber from the outside
Implementation Method 4
A voltage (electric motive force) corresponding to the oxygen concentration in the first measuring chamber is outputted by the oxygen concentration detection cell
Implementation Method 5
By applying a fixed voltage to the second pumping cell which faces the NOx measuring chamber, NOx in the gas to be measured is decomposed so that an electric current corresponding to the NOx concentration flows between a pair of electrodes of the second pumping cell
Data Source
AI summary
In a NOx sensor control apparatus (1), a NOx sensor includes a heater (164), and an oxygen concentration detection cell (130), a first pumping cell (110) and a second pumping cell (120) which are arranged sequentially in the axis O direction. The NOx sensor control apparatus 1 includes a first impedance detection means (59a, 60) which detects the first impedance of the first cell (oxygen concentration detection cell), a heater control means (60) which performs an energization control of a heater such that the first impedance becomes a target value, a second impedance detection means (59b, 60) which detects the second impedance of the second cell (second pumping cell), and an output correction means (60) which corrects an output of at least the third cell (first pumping cell) based on the deviation between the first impedance and the second impedance.