Engine Misfire Detection Using Dual Threshold Speed Analysis
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Solution Overview
Problem
Existing misfire determination systems for internal combustion engines with multiple cylinders struggle to accurately distinguish between single-cylinder and multi-cylinder misfires due to similar changes in rotational speed, especially during weak combustion, leading to potential misclassification.
Innovation Solution
A misfire determination apparatus that utilizes a microprocessor to calculate a misfire parameter based on rotational speed changes in each cylinder, employing multiple thresholds to differentiate between single-cylinder and multi-cylinder misfires by analyzing the misfire parameter's correlation with rotational speed changes, and determining the type of misfire through a series of flag signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single threshold is used to determine misfire based on rotational speed changes, then the determination process is simple, but the accuracy of distinguishing between single-cylinder and multi-cylinder misfires deteriorates
Solution Approach 1:
The patent applies parameter changes by introducing multiple threshold values (first threshold and second threshold) instead of a single threshold. The misfire determination unit compares the misfire parameter against these different thresholds to distinguish between single-cylinder misfire (when parameter exceeds first threshold) and multi-cylinder misfire (when parameter exceeds second threshold). This resolves the contradiction by maintaining relatively simple determination logic while significantly improving misfire type discrimination accuracy.
2Device complexity
If rotational speed change is used to detect misfire, then the detection method is simple, but the ability to accurately determine misfire during weak combustion deteriorates
Solution Approach 1:
The patent introduces a misfire parameter that integrates rotational speed changes over the combustion stroke period rather than relying on instantaneous rotational speed changes. The misfire determination unit calculates this integrated parameter and compares it against thresholds. This approach maintains simple detection methodology while improving reliability during weak combustion by accumulating evidence over the entire combustion cycle, making it more sensitive to subtle misfire conditions.
Data Source
AI summary
A misfire determination apparatus for an internal combustion engine including a rotational speed detector detecting a rotational speed of an engine and a microprocessor. The microprocessor is configured to perform calculating a misfire parameter having a correlation with a change amount of the rotational speed in a combustion stroke of each of a plurality of cylinders and increasing as an increase amount of the rotational speed is large based on the rotational speed detected by the rotational speed detector, and determining that a single-cylinder misfire has occurred when the misfire parameter is less than a first predetermined value, while determining that the single-cylinder misfire or a multi-cylinder misfire has occurred when the misfire parameter is less than a second predetermined value greater than the first predetermined value.