Misfire Detection Using Integrated Rotational Deviation
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Solution Overview
Problem
Existing misfire determination devices for multi-cylinder four-cycle engines inaccurately detect misfires due to failure to account for normal periodic fluctuations in engine rotation, leading to reduced reliability and potential false alarms.
Innovation Solution
A misfire determination device that calculates deviations in elapsed time between pulses corresponding to specific rotational angles, integrates these deviations over a predetermined angle, and compares the integrated value to a threshold to accurately determine misfires, while also counting repeated occurrences to confirm misfire events.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the rotational deviation is calculated by comparing the average rotation number in the current cycle with that in the previous cycle, then the misfire determination device can detect misfire events, but the periodical increase and decrease of engine rotations may be mistakenly determined as misfire (misdetection)
Solution Approach 1:
The patent segments the rotational deviation calculation into two distinct components: (1) the cycle-to-cycle variation component that captures misfire events, and (2) the periodic variation component that accounts for normal engine operation fluctuations. By separating these components and processing them differently, the system achieves accurate misfire detection without false alarms from periodic variations.
Solution Approach 2:
The patent introduces an intermediary mechanism - a correction value that mediates between the raw rotational deviation and the final misfire determination. This correction value compensates for periodic variations before the final comparison, acting as a buffer that prevents normal fluctuations from triggering false misfire alerts while preserving genuine misfire signals.
2Device complexity
If the rotational deviation is calculated without considering the normal periodical increase and decrease of engine rotation, then the calculation is simple, but the reliability of misfire determination is reduced due to false detections
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing the periodic variation characteristics of the engine during normal operation. These pre-computed reference values are then used to correct the rotational deviation in real-time, eliminating the need for complex real-time analysis while maintaining high detection reliability.
Solution Approach 2:
The patent changes the parameter being measured from the raw rotational deviation to a corrected rotational deviation that has been adjusted by the periodic variation compensation. This parameter transformation converts a noisy, unreliable signal into a clean, reliable indicator of actual misfire events.
3Ease of operation
If the misfire determination is based on a single rotational deviation threshold, then the determination process is simple, but false alarms occur due to normal rotation fluctuations
Solution Approach 1:
The patent adds another dimension to the determination process by introducing a correction value that operates in parallel with the threshold comparison. Instead of relying solely on a single threshold, the system uses a two-dimensional approach: the corrected rotational deviation (original deviation minus periodic variation) is compared against the threshold, creating a more robust decision boundary that reduces false alarms.
Data Source
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AI summary
A misfire determination device for a multi-cylinder four-cycle engine (11), which determines a misfire based on a pulse (P) outputted each time when a crankshaft (15) rotates by a predetermined rotational angle, includes a timing device (30) for timing an elapsed time (T) until a number of pulses in a stroke (TN) are counted at each pulse output timing, a deviation calculating device (30) for calculating a deviation (DT) between a first time (TR) and a second time (TL), an integrated value calculating device (30) for calculating an integrated value (RC) by integrating the calculated deviation by the predetermined rotational angle of the crankshaft, and a determining device (30) for determining whether or not the misfire occurs at any one of the plurality of the cylinders (12) based on a magnitude relationship between the integrated value and a predetermined threshold value (DR).