Impedance Detector for Oxygen Sensor with Dynamic Current Timing
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Solution Overview
Problem
Existing impedance detection methods for oxygen concentration sensors are inefficient as they apply a fixed current duration, which can be too short or too long, leading to inaccurate impedance measurement and prolonged air fuel ratio detection times, depending on the sensor's electrical characteristics.
Innovation Solution
An impedance detector with a current application portion that adjusts the duration of applied currents based on the sensor's characteristics, using a first current and a second current of opposite polarity, to optimize impedance detection in oxygen concentration sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a fixed period of time is used to apply constant current for impedance measurement, then the measurement process is simple and consistent, but the impedance detection accuracy deteriorates when sensor characteristics change
Solution Approach 1:
The patent implements dynamic adjustment of the constant current application period based on sensor characteristics. The control device determines sensor type (e.g., planar vs. tubular) and electrochemical characteristics, then dynamically sets the current application period accordingly. This resolves the contradiction by making the measurement process adaptive rather than fixed, ensuring accuracy across different sensor types while maintaining operational simplicity through automated determination.
Solution Approach 2:
The patent changes the time parameter (current application period) based on sensor characteristics. Different sensor types have different optimal measurement periods - for example, planar sensors may require longer periods than tubular sensors. The system adjusts this parameter automatically based on sensor identification, resolving the contradiction between fixed-process simplicity and adaptive precision.
2Measurement precision
If the current application period is extended to ensure accurate impedance detection, then impedance measurement accuracy improves, but the air fuel ratio detection time increases
Solution Approach 1:
The system dynamically optimizes the current application period by determining sensor characteristics first, then setting the minimum necessary measurement time for that specific sensor type. This prevents unnecessary time extension while ensuring adequate measurement duration for accurate impedance detection, resolving the time-accuracy tradeoff.
Solution Approach 2:
The patent applies the principle of partial action by determining the precise minimum current application period needed for each sensor type rather than using a uniformly excessive time period. This ensures sufficient measurement time for accuracy while avoiding unnecessary time loss in air fuel ratio detection cycles.
3Productivity
If the current application period is reduced to maintain fast air fuel ratio detection, then response time improves, but impedance measurement accuracy deteriorates
Solution Approach 1:
The system dynamically adjusts the current application period based on sensor characteristics to achieve the minimum necessary measurement time for each sensor type. This prevents excessive measurement time while ensuring sufficient duration for accurate impedance detection, resolving the contradiction between speed and accuracy.
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 approach allows for accurate impedance detection by adjusting current application time according to the sensor's electrical characteristics, minimizing detection time and ensuring precise air fuel ratio measurement.
Implementation Method 1
an oxygen concentration sensor element which generates an electromotive force in accordance with a concentration difference of oxygen
Implementation Method 2
a constant current for measuring an impedance... is applied to a cell as the element... A difference between a both-end voltage of the element before being applied with the constant current and a both-end voltage of the element when being applied with the constant current is detected as a value that is correlated with the impedance
Data Source
AI summary
In an impedance detector, a current application portion applies a first current and a second current, directions of which are opposite to each other, to an element of an oxygen concentration sensor. A detection portion detects a difference between a current application prior voltage and a current application subsequent voltage. The current application prior voltage is a voltage between both of ends of the element before being applied with the first current, and the current application subsequent voltage is a voltage between both of the ends of the element when being applied with the first current. An impedance calculation portion calculates an impedance of the element based on the difference detected by the detection portion and a value of the first current. The current application portion is configured to change a current application time to apply the first current and the second current according to a command provided thereto.