Gas Sensor Common Wire Malfunction Diagnosis
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Solution Overview
Problem
Existing methods for diagnosing a break in the common wire of a gas concentration detecting unit, used in air-fuel ratio feedback control of internal combustion engines, are complex and prone to errors, as they require analysis of output signals from multiple terminals.
Innovation Solution
A method that diagnoses a malfunction in the common wire by monitoring voltage variations at connecting points other than the common wire, using oscillations and threshold values to determine the presence of a malfunction, allowing for simple and accurate diagnosis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If output signals from three output terminals are used to diagnose common wire break, then diagnostic capability is provided, but device complexity increases
Solution Approach 1:
The invention extracts the diagnostic function from complex multi-terminal signal analysis and implements it through a simple voltage comparison operation at a single terminal. By monitoring voltage variations at one connecting point and comparing against a predetermined threshold, the system achieves reliable common wire break detection without requiring analysis of multiple terminal signals, thus reducing diagnostic complexity while maintaining reliability
Solution Approach 2:
Instead of actively injecting test signals and analyzing complex responses from multiple terminals, the invention inverts the approach by passively monitoring natural voltage variations at a single terminal. This inversion simplifies the diagnostic mechanism from active multi-point testing to passive single-point voltage comparison
2Reliability
If combination of three output signals is used for diagnosis, then common wire break can be detected, but error in diagnostic result may occur
Solution Approach 1:
The invention implements a feedback mechanism where the monitored voltage is continuously compared against a predetermined threshold value. When the voltage variation exceeds this threshold, the system immediately identifies a common wire break condition. This feedback-based threshold comparison ensures accurate and reliable diagnostic results by clearly distinguishing between normal voltage fluctuations and actual malfunction conditions
Solution Approach 2:
The invention changes the diagnostic parameter from complex multi-terminal signal combinations to a simple single-terminal voltage variation parameter. By monitoring voltage changes at one terminal and comparing against a predetermined threshold, the system achieves accurate common wire break detection while eliminating errors associated with complex signal combination analysis
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 simplifies the diagnosis of common wire malfunctions by detecting voltage variations and oscillations, providing reliable and accurate results with improved noise resistance.
Implementation Method 1
an oxygen pump cell including a first solid electrolytic layer and a pair of electrodes interposing the first solid electrolytic layer therebetween
Implementation Method 2
an oxygen concentration detection cell including a second solid electrolytic layer and a pair of electrodes interposing the second solid electrolytic layer therebetween
Data Source
AI summary
To provide a malfunction diagnosing method and apparatus capable of reliably determining a malfunction even where the malfunction occurs in a common wire connecting a gas sensor and a control circuit for driving it. In a gas concentration measurement unit 1 having a sensor control circuit 50 which is connected to a sensor element 10 including an oxygen pump cell 14 and an oxygen concentration detection cell 24 and controls and drives this sensor element 10, a variation state of a terminal voltage at one connecting point (specifically, a Vs+ terminal) other than connecting points between electrodes facing a measurement chamber of each cell 14 and 24 and a common wire 24 is detected by a malfunction detection circuit 53 and an arithmetic processor 54. Based on this variation state of the terminal voltage, diagnosis of malfunction in the common wire 42 is executed. When the common wire 42 is broken, the terminal voltage at the Vs+ terminal varies with oscillations. Therefore, the malfunction detection circuit 53 and the arithmetic processor 54 detect this voltage variation with oscillations to output a malfunction determination signal to a CPU.