Oxygen Sensor Constant Current Circuit Abnormality Diagnosis
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Solution Overview
Problem
Existing gas sensors, such as oxygen sensors in internal-combustion engine vehicles, face challenges in detecting abnormalities in the constant current supply portion, leading to prolonged diagnosis times and potential adverse effects on other control systems.
Innovation Solution
A gas sensor control device with a constant current supply portion that changes output characteristics by controlling a constant current between sensor electrodes, allowing for rapid abnormality diagnosis by determining the presence of abnormalities based on sensor output when the current is stopped or maintained at a predetermined value, without the need to switch current values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the current value is switched to execute abnormality diagnosis, then the abnormality detection capability is improved, but the diagnosis time is extended
Solution Approach 1:
The patent applies preliminary action by storing multiple constant current values in advance within the constant current supply portion. This allows the system to quickly switch between pre-prepared current values during abnormality diagnosis without requiring time-consuming current generation or adjustment processes, thereby reducing diagnosis time while maintaining reliable abnormality detection
Solution Approach 2:
The patent implements dynamics by enabling the constant current supply portion to dynamically switch between different stored current values based on diagnostic needs. This dynamic switching capability allows the system to adapt current levels during diagnosis without extending the diagnostic process, resolving the contradiction between detection reliability and diagnosis speed
2Productivity
If the abnormality diagnosis is executed during fuel cut, then the diagnosis can be performed, but it may adversely affect other controls such as rich injection control
Solution Approach 1:
The patent applies parameter changes by modifying the constant current parameter during diagnosis while the ECU maintains other control parameters (such as fuel injection timing and amount) at their normal operating values. This selective parameter adjustment allows abnormality diagnosis to proceed without disrupting other control functions, eliminating the adverse effects mentioned in the contradiction
3Adaptability or versatility
If the current supply portion is used to change output characteristics, then the sensor adaptability is improved, but the complexity of detecting abnormalities increases
Solution Approach 1:
The patent applies universality by designing the constant current supply portion to serve multiple functions: it not only provides the constant current needed for normal sensor operation but also stores multiple current values for abnormality diagnosis purposes. This multi-functionality reduces the need for separate diagnostic equipment, simplifying the overall system while maintaining adaptability in output characteristics 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
This approach enables prompt detection of abnormalities in the constant current circuit, reducing diagnosis time and minimizing interference with other control systems, thus improving the reliability and efficiency of gas sensor feedback control.
Implementation Method 1
a sensor element in which a solid electrolyte body is disposed between a pair of sensor electrodes
Data Source
AI summary
A constant current circuit is controlled to stop a constant current Ics (Ics=0) flowing between sensor electrodes of an oxygen sensor, in a period before the oxygen sensor becomes active, during a fuel cut of an engine, and after the engine stops. When an abnormality (for example, a failure) occurs in the constant current circuit, a sensor output equivalent to an output of the oxygen sensor of when the constant current circuit is controlled to stop the constant current Ics is different from a normal sensor output. An abnormality diagnosis is executed to determine a presence or absence of the abnormality in the constant current circuit depending on whether the output of the oxygen sensor is out of a predetermined normal range, in a period before the oxygen sensor becomes active, during a fuel cut of an engine, and after the engine stops (when the constant current circuit is controlled to stop the constant current Ics).