Straddled Vehicle Misfire Detection Using Crankshaft Fluctuation Patterns
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Solution Overview
Problem
In straddled vehicle engine units with two or more cylinders, accurately distinguishing misfires is challenging due to overlapping crankshaft rotation speed fluctuation distributions in normal and misfire situations, especially in low load and low rotation speed regions, and when traveling on rough roads.
Innovation Solution
A misfire detection system with a crankshaft rotation speed fluctuation physical quantity acquisition unit and a misfire determination unit that includes first, second, and third determination units to differentiate between normal and misfire conditions by setting physical quantity determination references and analyzing fluctuation patterns, effectively reducing erroneous misfire detections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the internal combustion engine is configured with lower moment of inertia to operate at higher rotation speeds, then the rotation speed capability is improved, but the crankshaft rotation speed fluctuation distribution widens in low load and low rotation speed regions, causing overlap between normal and misfire situations
Solution Approach 1:
The patent transitions from single-dimension misfire detection (using only crankshaft rotation speed fluctuation) to multi-dimensional detection by introducing vibration sensor data as an additional dimension. This allows the system to distinguish between normal operation fluctuations and actual misfires by analyzing both rotation speed and vibration characteristics simultaneously, resolving the detection accuracy problem in low load/low speed regions.
Solution Approach 2:
The patent dynamically changes detection parameters based on operating conditions. It sets different determination thresholds for crankshaft rotation speed fluctuation physical quantities depending on whether the engine is in normal operation or rough road traveling state. This adaptive parameter adjustment allows accurate misfire detection across the entire operation range, including the problematic low load and low rotation speed region where distribution overlap occurs.
2Loss of energy
If the engine operates in low load and low rotation speed region, then fuel economy is improved, but the crankshaft rotation speed fluctuation distribution widens causing overlap between normal and misfire situations
Solution Approach 1:
The patent implements dynamic detection strategies that adapt to changing operating conditions. The system continuously monitors crankshaft rotation speed fluctuation physical quantities and dynamically adjusts determination thresholds based on the current operating state (normal vs. rough road). This dynamic adaptation ensures accurate misfire detection even in low load and low rotation speed regions where fuel economy is prioritized but detection accuracy is compromised.
Solution Approach 2:
The patent introduces vibration sensor data as an intermediary element that helps distinguish between normal operation fluctuations and actual misfires in low load conditions. By combining vibration characteristics with rotation speed data, the system can accurately detect misfires during fuel-efficient operating modes without sacrificing detection accuracy.
3Reliability
If the engine operates on rough roads, then vehicle durability is improved through robust operation, but the crankshaft rotation speed fluctuation distribution widens causing overlap between normal and misfire situations
Solution Approach 1:
The patent segments the detection process into distinct analysis stages: acquiring crankshaft rotation speed fluctuation physical quantities, determining whether the vehicle is in rough road traveling state, and applying appropriate determination thresholds. This segmented approach allows the system to handle rough road conditions separately from normal operation, maintaining accurate misfire detection despite the widened fluctuation distribution caused by rough road vibrations.
Solution Approach 2:
The patent implements feedback mechanisms where the system continuously monitors operating conditions and adjusts detection parameters accordingly. By using feedback from vibration sensors and rotation speed data to dynamically adjust determination thresholds, the system maintains high misfire detection accuracy even when operating on rough roads that cause increased crankshaft rotation speed fluctuations.
4Measurement precision
If multiple determination methods are used to improve misfire detection accuracy, then detection precision is improved, but device complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-establishing determination thresholds for different operating conditions (normal operation vs. rough road traveling state). These thresholds are set in advance based on characteristic data from each state, allowing the system to quickly and accurately determine misfires without complex real-time calculations. This preliminary preparation simplifies the detection process while maintaining high accuracy.
Data Source
Figure 1(a)~1(d)
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AI summary
Provided is a straddled vehicle engine unit including two or more cylinders and mounted to a straddled vehicle, the straddled vehicle engine unit capable of detecting a misfire in an internal combustion engine with high accuracy over a wide operation range. The straddled vehicle engine unit includes an internal combustion engine and a misfire detection device. The misfire detection device includes a crankshaft rotation speed fluctuation physical quantity acquisition unit and a misfire determination unit that determines a misfire state. The misfire determination unit includes a first determination unit, a second determination unit, and a third determination unit. The first determination unit determines whether or not the crankshaft rotation speed fluctuation physical quantity acquired by the crankshaft rotation speed fluctuation physical quantity acquisition unit is greater than a set physical quantity determination reference. The second determination unit determines whether or not a fluctuation pattern constituted by a physical quantity and the crankshaft rotation speed fluctuation physical quantity acquired at least before or after the physical quantity falls within a set misfire pattern range. The third determination unit determines whether a misfire determination is to be set as effective or not, based on a result of the determination by the first determination unit and a result of the determination by the second determination unit.