Gas Sensor Pump Cell Startup Control to Cut Light-Off Time
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Solution Overview
Problem
Gas sensors using solid electrolytes have a long light-off time and are prone to cracking due to excessive voltage application, which is problematic for meeting stringent emission control regulations and maintaining sensor integrity.
Innovation Solution
A gas sensor design with a sensor element comprising an elongated plate-shaped base part with specific pump cells and electrodes, utilizing distinct startup and steady driving pump controls, and controlled voltage application to reduce light-off time and prevent cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If preliminary control with constant current is applied to reduce light-off time variation, then startup time consistency is improved, but light-off time remains long due to serial pump cell configuration
Solution Approach 1:
The patent divides the pump cells into two functional groups: adjustment pump cells (first and second) that control oxygen concentration, and measurement pump cells (third and fourth) that detect target gases. This segmentation allows parallel operation of adjustment and measurement functions, reducing overall light-off time compared to sequential serial configuration.
Solution Approach 2:
The control unit performs preliminary control by supplying constant current to the adjustment pump cells before drive control begins. This preliminary oxygen concentration adjustment prepares the measurement environment in advance, enabling the measurement pump cells to start detecting target gases more quickly and reducing light-off time variation.
2Productivity
If excessively high voltage is applied to pump cell to shorten light-off time, then startup speed is improved, but solid electrolyte strength reduces due to oxygen migration
Solution Approach 1:
The control unit dynamically adjusts the voltage applied to pump cells based on operational phase. During preliminary control, constant current is supplied at controlled voltage levels. During drive control, the voltage is adjusted based on detected oxygen concentration and target gas levels. This dynamic voltage adjustment enables fast startup without applying excessively high voltage that would cause oxygen migration and electrolyte degradation.
Solution Approach 2:
The control unit uses feedback from oxygen concentration detection and target gas measurement to adjust pump cell operating voltages. This feedback mechanism ensures voltage is increased only to the extent necessary for rapid startup and measurement, preventing excessive voltage application that would damage the solid electrolyte while still achieving short light-off time.
3Loss of time
If high voltage is applied to pump cell during startup, then light-off time is shortened, but cracking occurs in internal sensor structure
Solution Approach 1:
By segmenting pump cells into adjustment and measurement groups with different voltage requirements, the patent applies appropriate voltage levels to each group. Adjustment pump cells receive controlled voltage for oxygen concentration control, while measurement pump cells receive voltage based on detection needs. This prevents excessive voltage application to any single cell that would cause cracking.
Solution Approach 2:
The control unit dynamically adjusts voltage to pump cells during different operational phases. During preliminary control, moderate constant current is applied. During drive control, voltage is adjusted based on real-time gas concentration measurements. This dynamic adjustment achieves short light-off time without applying excessively high voltage that would cause internal cracking.
4Ease of operation
If multiple pump cells are configured in serial from gas inlet, then gas flow control is achieved, but light-off time increases
Solution Approach 1:
The patent segments the four pump cells into two adjustment cells (first and second) positioned near the gas inlet for oxygen concentration control, and two measurement cells (third and fourth) positioned downstream for target gas detection. This spatial segmentation enables parallel execution of gas flow adjustment and target gas measurement, reducing overall light-off time while maintaining serial configuration benefits for gas flow control.
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 achieves a short light-off time and prevents cracking in the sensor element, ensuring rapid and reliable gas concentration measurement.
Implementation Method 1
a base part in an elongated plate shape, including an oxygen-ion-conductive solid electrolyte layer
Implementation Method 2
an adjustment pump cell for adjusting an oxygen concentration in a measurement-object gas to a desired concentration
Implementation Method 3
a measurement pump cell for detecting a target gas to be measured in the measurement-object gas
Data Source
AI summary
A gas sensor includes a sensor element including an adjustment pump cell and a measurement pump cell, and a control unit including a pump control part. The pump control part performs a startup pump control at a startup of the sensor element, and a steady driving pump control at a steady drive after the startup. In the startup pump control, the pump control part applies, between an inner pump electrode and an outer pump electrode of the adjustment pump cell, a startup voltage of the adjustment pump cell that is higher than a voltage applied in the steady driving pump control; and applies, between an inner measurement electrode and an outer measurement electrode of the measurement pump cell, a startup voltage of the measurement pump cell that is higher than a voltage applied in the steady driving pump control and lower than the startup voltage of the adjustment pump cell.