Dynamic Threshold Adjustment for Engine Misfire Detection
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Solution Overview
Problem
Existing determination methods for internal combustion engine exhaust gas characteristics fail to accurately assess deterioration beyond allowable ranges, as they rely solely on misfire rates, which can be misleading due to varying operation modes and increased unburned fuel during partial fuel cut-off processes.
Innovation Solution
A determination device and method that execute a partial fuel cut-off process, misfire detection, and dynamic threshold adjustment based on misfire rates during both regular and partial fuel cut-off operations, setting a lower threshold during partial fuel cut-off to prevent false negatives and accurately determine exhaust gas characteristic deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a partial fuel cut-off process is executed to increase fuel supply to remaining cylinders, then the amount of unburned fuel in the exhaust system increases, but the misfire rate threshold becomes less reliable for determining exhaust gas characteristic deterioration
Solution Approach 1:
The determination threshold is dynamically adjusted based on the execution state of the partial fuel cut-off process. When the process is executing, a lower second determination threshold is used; when not executing, a higher first determination threshold is used. This dynamic adaptation resolves the contradiction by making the measurement criterion flexible rather than fixed, allowing accurate determination under varying operational conditions.
Solution Approach 2:
The patent changes the determination threshold parameter according to the operational mode (execution or non-execution of partial fuel cut-off). This parameter change approach directly addresses the contradiction by adjusting the evaluation standard to match the current fuel supply conditions, ensuring reliable exhaust gas characteristic determination regardless of the unburned fuel amount.
2Device complexity
If a fixed determination threshold is used for misfire rate, then the determination method is simple, but it cannot accurately determine exhaust gas characteristic deterioration during partial fuel cut-off operations
Solution Approach 1:
The system transitions from a static fixed threshold to a dynamic adaptive threshold that automatically adjusts based on operational mode. This maintains relative simplicity while significantly improving reliability, as the threshold adaptation is based on straightforward detection of whether partial fuel cut-off is executing, without requiring complex algorithms.
Solution Approach 2:
The determination process incorporates feedback from the execution state of the partial fuel cut-off process. The system continuously monitors whether the process is executing and adjusts the determination threshold accordingly, creating a closed-loop control that improves reliability while maintaining simplicity through automated feedback-based adjustment.
Data Source
AI summary
A determination device for an internal combustion engine executes a partial fuel cut-off process. The determination device determines that exhaust gas characteristics have deteriorated when the misfire rate of the internal combustion engine is greater than or equal to a determination threshold. The determination device sets the determination threshold to a first determination threshold when the calculated misfire rate is a misfire rate in a period of non-execution of the partial fuel cut-off process. Also, the determination device sets the determination threshold to a second determination threshold, which is less than the first determination threshold, when the calculated misfire rate is a misfire rate in a period of execution of the partial fuel cut-off process.