Misfire Detection Device for Internal Combustion Engine
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Solution Overview
Problem
Existing misfire detection systems face challenges in achieving high accuracy at high load and high rotation speed conditions while maintaining accuracy at low load and low rotation speed conditions, due to the overlap of crankshaft rotation speed fluctuation distributions during rough road travel, which complicates distinguishing between normal and misfire states.
Innovation Solution
The system reduces the moment of inertia of the internal combustion engine to enhance misfire detection accuracy in high load and high rotation speed regions by widening the interval between adjacent tails of crankshaft rotation speed fluctuation distributions, and incorporates a rough road traveling determination unit to suspend misfire determinations in low load and low rotation speed regions where distributions overlap, using techniques like distribution state comparison and vehicle state detection to differentiate between normal and misfire conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the moment of inertia of the internal combustion engine is reduced, then misfire detection accuracy in high load and high rotation speed region is enhanced, but misfire detection accuracy in low load and low rotation speed region deteriorates when traveling on a rough road
Solution Approach 1:
The patent applies dynamics by making the misfire determination section position variable rather than fixed. The position of the misfire determination section is dynamically adjusted based on the crankshaft rotation speed, allowing the system to adapt to different operating conditions. This resolves the contradiction by enabling optimal misfire detection across both high load/high speed and low load/low speed regions without compromising reliability on rough roads.
Solution Approach 2:
The patent changes the parameter of the misfire determination section position based on crankshaft rotation speed. By adjusting this parameter dynamically, the system achieves high misfire detection accuracy in high load and high rotation speed regions while maintaining reliability in low load and low rotation speed regions, even when traveling on rough roads.
2Device complexity
If a fixed position misfire determination section is used, then device complexity is reduced, but misfire detection accuracy deteriorates due to nadir position deviation in different rotation regions
Solution Approach 1:
The patent implements dynamics by making the misfire determination section position variable according to crankshaft rotation speed. This dynamic adjustment ensures that the nadir position of crankshaft rotation speed decrease remains within the misfire determination section across different rotation regions, maintaining high detection accuracy without significantly increasing system complexity.
Data Source
AI summary
An engine unit includes an internal combustion engine and a misfire detection device. The misfire detection device includes a rough road traveling determination unit that: (a) determines a rough road traveling state based on a distribution state of a crankshaft rotation speed fluctuation physical quantity acquired by a crankshaft rotation speed fluctuation physical quantity acquisition unit, or (b) includes a vehicle traveling state detection unit for detecting a physical quantity in relation to a vehicle traveling state except the crankshaft rotation speed fluctuation physical quantity, and determines a rough road traveling state based on a detection result obtained by the vehicle traveling state detection unit; and suspends a determination of a misfire in the internal combustion engine based on a determination result obtained by the rough road traveling determination unit.