Fuel Supply Diagnosis Using Segmented Air-Fuel Thresholds
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Solution Overview
Problem
Existing fuel supply system diagnosis devices are inadequate in accurately and efficiently detecting abnormalities in the air-fuel ratio correction factor, particularly in distinguishing between lean and rich side deviations, which can lead to inefficient fuel control and potential engine performance issues.
Innovation Solution
A diagnosis device that includes operation state detecting means, an air-fuel ratio sensor, fuel injection amount calculating means, a threshold value table, abnormality information acquiring means, and abnormality determining means, which divide operation ranges by engine speed and throttle opening to set lean and rich side threshold values, allowing for precise detection of air-fuel ratio correction factor deviations and determination of fuel supply system abnormalities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single threshold value is used for air-fuel ratio correction factor diagnosis, then the diagnosis device is simple to operate, but it cannot accurately distinguish between lean and rich side deviations across different engine operating conditions
Solution Approach 1:
The operation range of the internal combustion engine is divided into multiple segments based on engine speed and throttle opening. Each segment has its own lean side threshold value and rich side threshold value stored in the threshold value table. This segmentation allows accurate diagnosis across different operating conditions while maintaining a structured and manageable table format.
Solution Approach 2:
Different threshold values are assigned to different operation ranges (local conditions) rather than using a single universal threshold. The threshold value table provides operation-range-specific lean side threshold values and rich side threshold values, enabling locally optimized diagnosis accuracy for each operating condition.
2Measurement precision
If the operation range is divided into multiple segments with different threshold values, then diagnosis accuracy improves, but the threshold value table becomes more complex
Solution Approach 1:
The threshold value table is segmented by operation range, with each segment containing lean side and rich side threshold values. This segmentation organizes the complexity into manageable sections that correspond to specific engine operating conditions, making the table both accurate and systematically structured.
Solution Approach 2:
The threshold value table serves multiple functions simultaneously: it stores lean side threshold values, rich side threshold values, and organizes them by operation range. This multi-functionality consolidates what could be multiple separate tables into a single comprehensive structure, reducing overall system complexity.
3Reliability
If feedback control is performed continuously to maintain target air-fuel ratio, then fuel control precision is improved, but the system becomes more sensitive to temporary engine characteristics that may cause false abnormality detection
Solution Approach 1:
The diagnosis system dynamically adapts to different engine operating conditions by selecting appropriate threshold values from the threshold value table based on current engine speed and throttle opening. This dynamic adaptation allows the system to distinguish between temporary characteristics and actual abnormalities, improving detection reliability.
Solution Approach 2:
The threshold values for abnormality detection are changed according to operation range parameters (engine speed and throttle opening). By adjusting the threshold parameters to match current operating conditions, the system becomes less sensitive to temporary characteristics and more reliable in detecting actual abnormalities.
Data Source
AI summary
A diagnosis apparatus of a fuel supply system includes an operation state detector, an air-fuel ratio sensor, a fuel injection amount calculator, a threshold value table, an abnormality information acquiring device, and an abnormality determining device. In the threshold value table, operation ranges of an internal combustion engine are provided based on an engine speed and a throttle opening. In the threshold value table, a lean side threshold value and a rich side threshold value of an air-fuel ratio correction factor to determine abnormality of the fuel supply system are set beforehand for each of the operation ranges. The abnormality information acquiring device is configured to determine whether the air-fuel ratio correction factor has exceeded the lean side threshold value or the rich side threshold value extracted from the threshold value table according to an operation state so as to acquire abnormality information.