Gas Sensor Control Apparatus Oxygen Pumping Stability
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Solution Overview
Problem
Conventional sensor control systems for gas sensors, such as NOX sensors, face challenges in accurately detecting gas concentrations due to individual differences among detection elements, leading to deviations in timing and stability, especially when starting the detection process after preliminary control.
Innovation Solution
A sensor control apparatus and method that applies output correction based on individual differences among detection elements, using drive control, preliminary control, calculation, storage, determination, and correction means to adjust oxygen concentration and apply correction data for accurate gas concentration detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If preliminary control is performed to rapidly pump oxygen out of the second measurement chamber, then the detection timing of NOX concentration can be advanced, but the oxygen concentration at the end of preliminary control becomes unstable due to H2O dissociation, causing time course changes in detection output
Solution Approach 1:
The patent applies preliminary control before drive control to rapidly reduce oxygen concentration in the second measurement chamber, advancing the detection timing. This preliminary action prepares the system for earlier NOX detection while the subsequent drive control with corrected voltage ensures stable output by compensating for H2O dissociation effects.
Solution Approach 2:
The patent changes the voltage application parameter from constant voltage to corrected voltage based on H2O concentration. By adjusting the voltage applied to the second oxygen pump cell according to H2O levels, the system maintains stable oxygen pumping despite H2O dissociation, thereby stabilizing the detection output while enabling early detection through preliminary control.
2Speed
If high voltage is applied to the second oxygen pump cell during preliminary control to rapidly pump out oxygen, then the oxygen concentration can be reduced to detection level, but H2O dissociation occurs on the electrode, causing current increase and oxygen concentration variability
Solution Approach 1:
The patent dynamically adjusts the voltage parameter applied to the second oxygen pump cell based on H2O concentration measurements. During preliminary control, high voltage is applied for rapid oxygen pumping, but the voltage is then corrected based on H2O levels to prevent excessive dissociation. This parameter adjustment maintains fast pumping speed while improving oxygen concentration control precision.
3Reliability
If constant voltage is applied to the second oxygen pump cell during drive control, then the detection element output can stabilize, but individual differences among detection elements cause timing deviations in reaching stable output
Solution Approach 1:
The patent adjusts the voltage parameter applied to the second oxygen pump cell based on individual detection element characteristics and H2O concentration. By customizing the voltage for each sensor unit, the system achieves stable output faster, reducing the stabilization time caused by individual differences while maintaining output reliability through the H2O-based correction mechanism.
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 earlier and more accurate detection of gas concentrations by correcting for individual differences, ensuring consistent patterns in concentration correspondence values and reducing variations, thus improving the reliability of gas sensor systems.
Implementation Method 1
The first oxygen pump cell pumps oxygen out of a first measurement chamber into which an object gas is introduced, or pumps oxygen into the first measurement chamber
Implementation Method 2
As a result of applying the constant voltage, NOX within the gas is decomposed, and oxygen ions originating from the NOX flow through the second oxygen pump cell
Implementation Method 3
The control apparatus detects the concentration of NOX within the object gas on the basis of the current flowing through the second oxygen pump cell
Implementation Method 4
some control apparatuses are configured to perform, at the time of startup of the internal combustion engine, preliminary control so as to temporarily and rapidly pump oxygen out of the second measurement chamber
Implementation Method 5
oxygen is pumped back into the second measurement chamber such that the voltage applied to the second oxygen pump cell becomes the above-mentioned constant voltage
Data Source
AI summary
A sensor control apparatus is disclosed, including a preliminary control for supplying a constant current to a second oxygen pump cell of a gas sensor for a constant period of time so as to control to a constant level the amount of oxygen pumped out from a second measurement chamber (S40 to S50). At the beginning of drive control (S55 to S80), oxygen is pumped back into the second measurement chamber. During the pumping back operation, an NOX concentration correspondence value has a large time course change and is not stable. The NOX concentration correspondence value is corrected using correction data common among gas sensors, wherein the timing for applying the correction data is adjusted by making use of an application time determined in accordance with individual differences of each gas sensor.