Three-Cylinder Engine Compression Leak Diagnosis via Crankshaft Angular Acceleration
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Solution Overview
Problem
Existing diagnosis apparatuses are ineffective in diagnosing compression leaks in in-line three-cylinder internal combustion engines, as they rely on methods developed for four-cylinder or six-cylinder engines, which do not accurately detect changes in angular acceleration during the expansion stroke due to differences in engine dynamics.
Innovation Solution
A diagnosis apparatus specifically designed for in-line three-cylinder engines, utilizing a diagnosing unit and angular acceleration derivation unit to detect changes in crankshaft angular acceleration, with criteria including the amount of change in angular acceleration per predetermined period and differences between angular accelerations at the start of expansion strokes across cylinders, to accurately diagnose compression leaks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a diagnosis process similar to that for four-cylinder or six-cylinder engines is applied to three-cylinder engines, then the device complexity is reduced, but the measurement precision of compression leak detection deteriorates
Solution Approach 1:
The patent applies local quality by creating a specialized diagnosis process tailored specifically for three-cylinder engines, recognizing that the uniform diagnosis method used for four-cylinder and six-cylinder engines is inadequate. The solution involves adjusting the diagnostic criteria to account for the unique angular acceleration characteristics of three-cylinder engines, where the angular acceleration does not significantly change during expansion strokes even when compression leaks are present.
2Ease of operation
If the diagnosis criteria for four-cylinder or six-cylinder engines is used, then the ease of operation is maintained, but the reliability of compression leak diagnosis deteriorates
Solution Approach 1:
The patent applies parameter changes by modifying the diagnostic parameters specifically for three-cylinder engines. Instead of using the criteria that angular acceleration significantly changes during expansion strokes (which works for four-cylinder and six-cylinder engines), the patent establishes new criteria where the angular acceleration amount of change is less than or equal to a predetermined threshold value. This parameter adjustment ensures reliable detection of compression leaks in three-cylinder engines while maintaining operational simplicity.
3Measurement precision
If the angular acceleration change threshold is set low, then the measurement precision improves, but the false positive rate increases
Solution Approach 1:
The patent applies feedback by using the angular acceleration data from multiple expansion strokes to establish a baseline and compare against threshold values. The diagnosing unit continuously monitors the angular acceleration amount of change during expansion strokes and compares it against the predetermined threshold, allowing for reliable detection while minimizing false positives through consistent threshold-based evaluation across multiple measurement cycles.
Data Source
AI summary
A diagnosis apparatus is applied to an in-line three-cylinder internal combustion engine, and includes a diagnosing unit and an angular acceleration derivation unit. The diagnosing unit is configured to execute a diagnosis process for diagnosing whether there is a compression leak in any one of cylinders while the internal combustion engine is in steady operation. The angular acceleration derivation unit is configured to derive an angular acceleration of a crankshaft of the internal combustion engine. The diagnosing unit is configured to, in the diagnosis process, when an amount of change in the angular acceleration per a predetermined period during an expansion stroke of any one of the cylinders is less than or equal to a threshold amount of change, diagnose that there is a compression leak in the any one of the cylinders.