Crank Angle Misfire Detection Under Engine Disturbances
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Solution Overview
Problem
Existing misfire detection systems in internal combustion engines face challenges in accurately distinguishing misfires from disturbances such as acceleration, deceleration, clutch operations, and road surface variations, leading to costly and inaccurate misfire detection.
Innovation Solution
A misfire detection method that utilizes a crank position sensor to detect crank angle signals, calculates inter-signal times only in the combustion process, and determines presence/absence of a misfire by least squares, and determines presence/absence of a misfire based on the inclination of the regression line.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If misfire detection is performed by observing rotation speed difference or inter-signal time in all processes (intake, compression, combustion, exhaust), then misfire detection coverage is improved, but detection accuracy deteriorates due to disturbances such as acceleration, deceleration, clutch operation, and road surface variations
Solution Approach 1:
The patent divides the engine cycle into four distinct processes (intake, compression, combustion, exhaust) and selectively applies misfire detection only to the combustion process. This segmentation allows the system to focus on the most critical phase where misfire has the greatest impact, while avoiding false detections caused by disturbances in other processes.
Solution Approach 2:
The patent applies different detection strategies to different processes: inter-signal time is measured in all processes for comprehensive monitoring, but misfire determination is made specifically based on inter-signal time characteristics in the combustion process only. This local quality approach optimizes detection accuracy by focusing analysis on the most informative phase.
2Measurement precision
If control for prohibiting misfire detection is performed during disturbances, then false detection is reduced, but misfire detection responsiveness deteriorates due to delayed detection when disturbances occur
Solution Approach 1:
The patent dynamically adjusts the detection strategy based on the engine operating phase. By continuously monitoring which process the engine is in and applying appropriate detection thresholds and methods for each phase, the system maintains high accuracy without unnecessary prohibitions during disturbances, thereby reducing detection delays.
3Reliability
If misfire detection is performed in all processes, then detection thoroughness is improved, but system complexity and computational load increase
Solution Approach 1:
The patent extracts and isolates the combustion process from the other engine cycles for dedicated misfire analysis. By taking out only the combustion phase inter-signal time data for misfire determination, the system reduces computational complexity and processing requirements while maintaining thorough detection capability for the most critical misfire scenarios.
Data Source
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AI summary
A misfire detection device detects presence/absence of a misfire in an internal combustion engine (1) in which respective processes of intake, compression, combustion, and exhaust are performed in a cylinder (3) due to rotation of a crank shaft (6), and includes a crank position sensor (32) that detects a crank angle signal (Sn) synchronized with a rotation angle of the crank shaft (6), and a control unit (31) that calculates, based on a plurality of the crank angle signals (Sn) detected by the crank position sensor (32), a plurality of inter-signal times (Xn) as reception intervals of the crank angle signals (Sn). The control unit (31) detects presence/absence of a misfire based on each of the inter-signal times (Xn) in the combustion process.