Oxygen Sensor Control Device Eliminates Diffusion Layer Hysteresis
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Solution Overview
Problem
The responsiveness of existing oxygen concentration sensors for internal combustion engines is reduced due to a diffusion rate controlling layer, leading to hysteretic output voltage changes when the air-fuel ratio approaches the stoichiometric ratio, resulting in inaccurate air-fuel ratio detection and control.
Innovation Solution
A control device for internal combustion engines that eliminates the diffusion rate controlling layer, applying a reference voltage between the electrodes to promote reaction and increase responsiveness, allowing for accurate air-fuel ratio detection by maintaining a linear relationship between inter-electrode voltage and output current without a limiting current region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a diffusion rate controlling layer is added to the exhaust gas side electrode, then the exhaust gas diffusion rate is controlled, but the responsiveness of the oxygen concentration sensor is reduced and hysteresis occurs in the output voltage
Solution Approach 1:
The patent removes the diffusion rate controlling layer from the exhaust gas side electrode, extracting the problematic component that caused hysteresis. This extraction eliminates the diffusion limitation while maintaining sensor functionality through the alternative approach of applying a positive voltage to promote oxygen ion migration.
Solution Approach 2:
The patent changes the electrical parameter by applying a positive voltage (0.1-0.5V) between the exhaust gas side electrode and reference gas side electrode. This voltage application fundamentally alters the sensor operation mode from passive diffusion-based detection to active electrochemically-enhanced detection, improving responsiveness without needing a diffusion controlling layer.
2Device complexity
If no voltage is applied between electrodes, then the sensor structure is simple, but the output voltage becomes hysteretic and air-fuel ratio detection becomes inaccurate
Solution Approach 1:
The patent introduces a small positive voltage (0.1-0.5V) between the electrodes, changing the electrical parameter from zero to a controlled positive value. This parameter change eliminates hysteresis and improves measurement precision while maintaining relatively simple sensor structure and control logic.
Solution Approach 2:
The patent implements feedback control by continuously monitoring the output voltage and comparing it with reference voltages to determine air-fuel ratio status. The system adjusts fuel injection based on this feedback, creating a closed-loop control system that achieves accurate air-fuel ratio detection and control.
3Reliability
If a diffusion rate controlling layer is used, then exhaust gas diffusion is regulated, but complex configurations and controls are required to address hysteresis
Solution Approach 1:
The patent extracts and removes the diffusion rate controlling layer, eliminating the need for complex control mechanisms to compensate for hysteresis. The simplification extends to the control system, which only needs to interpret output voltage relative to reference voltages without dealing with hysteresis compensation.
Solution Approach 2:
By changing the electrical parameter (applying positive voltage), the patent simplifies the overall system configuration. The voltage application naturally promotes oxygen ion migration and eliminates hysteresis, reducing the need for complex control algorithms or additional components.
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 configuration enables accurate air-fuel ratio control with a simple setup, reducing hysteretic effects and improving detection precision by ensuring a linear output current response to air-fuel ratio changes.
Implementation Method 1
a solid electrolyte body, an exhaust gas side electrode being disposed on one side of the solid electrolyte body and being in contact with the exhaust gas
Implementation Method 2
an oxygen concentration sensor that is provided with a solid electrolyte body, an exhaust gas side electrode being disposed on one side of the solid electrolyte body and being in contact with the exhaust gas
Data Source
Figure 1
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AI summary
A sensor for detecting oxygen concentration in exhaust gas or an air-fuel ratio provided with a solid electrolyte body, an exhaust gas side electrode being disposed on one side of the solid electrolyte body and being in contact with the exhaust gas, an atmosphere side electrode being disposed on the other side of the solid electrolyte body and being in contact with the atmosphere, and an electric circuit applying a reference voltage between these electrodes is arranged in an engine exhaust passage. The sensor for detecting the oxygen concentration in the exhaust gas or the air-fuel ratio has a characteristic in which an output current (Ip) continues to increase without having a limiting current region when the voltage (Vs) applied between the electrodes is increased while the air-fuel ratio is constant. The air-fuel ratio is controlled based on the output current (Ip) of the sensor for detecting the oxygen concentration in the exhaust gas or the air-fuel ratio.