Gas Sensor Control Apparatus for NOx Monitoring
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Solution Overview
Problem
Existing gas sensors experience delayed response to changes in air-to-fuel ratio, leading to inefficiencies in exhaust gas purification and increased NOx emissions, as they struggle to accurately monitor NOx outflows due to mismatched output characteristics with catalytic conversion efficiencies.
Innovation Solution
A gas sensor control apparatus that includes a current conduction regulating device to induce a constant electric current between electrodes of the electromotive force cell, using the electromotive force as a power source, which adjusts the sensor output characteristics to align with catalytic conversion efficiencies, ensuring accurate NOx monitoring and reduced emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If PWM control operation is used to supply constant electric current, then the sensor output characteristic can be improved, but the device complexity and cost increase
Solution Approach 1:
The patent extracts the essential function of supplying constant current from the complex PWM control system, using only a simple switch and resistor to achieve the same effect. This reduces the control structure while maintaining the improved sensor output characteristic.
Solution Approach 2:
The patent replaces expensive and complex PWM control circuitry with inexpensive passive components (resistor and switch). The simple resistor-based current limiting approach provides adequate performance without requiring sophisticated active control elements.
2Speed
If constant electric current is supplied to the gas sensor, then the response speed to air-to-fuel ratio changes is improved, but the device complexity increases
Solution Approach 1:
The patent applies periodic switching action to supply constant current pulses to the sensor during specific operating conditions (rich mixture detection). This periodic current supply improves response speed while keeping the control structure simple through timed switching rather than continuous complex control.
Solution Approach 2:
The patent changes the electrical parameter (current magnitude) by selecting different resistor values based on sensor output voltage levels. This simple parameter change approach achieves fast response without requiring complex active current control circuitry.
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 timely and accurate monitoring of NOx emissions by shifting the sensor output characteristics to correspond with NOx outflows, thereby improving exhaust gas purification and reducing NOx emissions, while simplifying the sensor control structure and reducing costs.
Implementation Method 1
an electromotive force cell, which has a solid electrolyte body and a pair of electrodes... outputs an electromotive force signal that varies depending on whether the exhaust gas is rich or lean
Implementation Method 2
a current conduction regulating device that is installed in an electric path, which is connected to the electromotive force cell, to induce a flow of a predetermined constant electric current between the exhaust side electrode and the reference side electrode through the solid electrolyte body
Data Source
AI summary
An O2 sensor has a sensor element, which includes a solid electrolyte layer and a pair of electrodes. The solid electrolyte layer is held between the electrodes, which includes an atmosphere side electrode and an exhaust side electrode. A constant current circuit is installed in an electric path, which connects between the atmosphere side electrode and a ground, to induce a flow of a predetermined constant electric current between the electrodes through the solid electrolyte layer. When the sensor element generates an electromotive force, the constant current circuit conducts an electric current, which is generated while using the electromotive force of the sensor element as an electric power source, to induce the flow of the predetermined constant electric current between the electrodes in an electromotive force range, which is equal to or larger than an electromotive force of the sensor element generated at a stoichiometric air-to-fuel ratio.