Engine Misfire Detection Using First-Order Crank Angle Difference
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Solution Overview
Problem
Existing engine misfire detection devices face challenges in accurately determining misfires in unequal interval combustion engines due to varying crank angles and interference from acceleration, deceleration, and other non-combustion related fluctuations, leading to reduced detection accuracy.
Innovation Solution
The engine misfire determination device calculates a first-order difference by removing rotation speed fluctuations in sections of 720×m crank angle degrees to isolate and manifest the fluctuation component attributable to unequal interval combustion, enabling accurate misfire detection without relying on second-order differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If second-order difference is used for misfire determination, then influence of acceleration and deceleration is reduced, but misfire detection accuracy deteriorates in unequal interval combustion engines
Solution Approach 1:
The patent changes the calculation parameters by using first-order difference instead of second-order difference, and introduces a correction value based on the difference between actual and average crank angle intervals. This parameter modification enables accurate misfire detection in both equal and unequal interval combustion engines while maintaining suppression of acceleration and deceleration influences.
2Measurement precision
If detection position is adjusted for unequal interval combustion, then combustion stroke alignment improves, but rotation speed deviation increases
Solution Approach 1:
The patent extracts and removes the influence of unequal interval combustion by calculating a correction value based on the difference between actual and average crank angle intervals. This correction value is then subtracted from the rotation speed difference, effectively separating the combustion-related fluctuations from the misfire signal, thereby maintaining detection alignment without being affected by interval variations.
3Reliability
If second-order difference calculation is performed, then acceleration and deceleration influence is suppressed, but detection complexity increases
Solution Approach 1:
The patent segments the misfire detection process into distinct components: calculating rotation speed at specific crank angle positions, computing first-order difference, and applying correction based on crank angle interval differences. This segmentation simplifies the overall calculation by breaking down the complex second-order difference operation into manageable steps that are easier to implement and compute.
Data Source
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AI summary
[Problem] To provide an engine misfire determination device and a vehicle applicable to a misfire determination in various types of engines. [Solution] A misfire determination device includes: a combustion fluctuation canceled value acquisition unit that acquires a first combustion fluctuation canceled value which is a rotation speed in a section of 720×m crank angle degrees including a first angle position and a second combustion fluctuation canceled value which is a rotation speed in a section of 720×m crank angle degrees including a second angle position; a combustion fluctuation manifested value calculation unit that calculates a first fluctuation manifested value by removing the first combustion fluctuation canceled value from a rotation speed at the first angle position, and calculates a second fluctuation manifested value by removing the second combustion fluctuation canceled value from a rotation speed at the second angle position; a first-order difference calculation unit that calculates a first-order difference between the first fluctuation manifested value and the second fluctuation manifested value; and a specific cylinder misfire determination unit that determines a misfire in a specific cylinder by using the first-order difference.