Marine Engine Misfire Detection With Cylinder-Specific Thresholds
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Solution Overview
Problem
Existing marine propulsion devices inaccurately determine misfires in engines due to using common angular acceleration and deviation thresholds for all cylinders, despite varying combustion states among cylinders.
Innovation Solution
Implementing a system with a controller that sets unique angular acceleration and deviation thresholds for each cylinder based on engine rotational speed and intake pressure, using sensors to detect crankshaft parameters and compare against cylinder-specific thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If common angular acceleration and deviation thresholds are applied to all cylinders, then the device complexity is reduced and ease of operation is improved, but the measurement precision of misfire detection deteriorates due to varying combustion states among cylinders
Solution Approach 1:
The patent divides the single threshold parameter into multiple cylinder-specific thresholds. Each cylinder has its own angular acceleration threshold and deviation threshold, allowing independent optimization for each cylinder's combustion characteristics. This segmentation enables accurate misfire detection for each cylinder while maintaining a unified control structure.
Solution Approach 2:
The patent implements local quality by setting thresholds specific to each cylinder's combustion state rather than using a uniform threshold for all cylinders. Each cylinder's thresholds are tailored to its local combustion characteristics, improving detection accuracy for cylinders with varying combustion states while maintaining overall system simplicity.
2Measurement precision
If cylinder-specific thresholds are set for each cylinder, then the measurement precision of misfire detection is improved, but the device complexity increases due to multiple thresholds to manage
Solution Approach 1:
The patent creates a universal threshold setting mechanism that automatically generates cylinder-specific thresholds based on a common base threshold and cylinder identification. The control device universally applies the same threshold structure across all cylinders, managing complexity through a unified approach rather than independent threshold configurations for each cylinder.
Solution Approach 2:
The system implements self-service by automatically determining cylinder-specific thresholds based on cylinder identification signals and combustion state data. The control device autonomously manages the multiple thresholds without requiring manual configuration for each cylinder, reducing operational complexity while maintaining detection precision.
Data Source
AI summary
A method of controlling a marine propulsion device including an engine including a plurality of cylinders and a crankshaft includes obtaining an angular acceleration of the crankshaft, obtaining a determination parameter to determine whether or not a misfire has occurred in the engine based on the angular acceleration of the crankshaft, and determining whether or not the misfire has occurred in the engine by comparing the determination parameter and a plurality of thresholds for each of the plurality of cylinders.