Multi-Cylinder Engine Misfire Detection from Startup Speed Changes
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Solution Overview
Problem
Existing misfire detection methods for multi-cylinder engines, particularly those using catalysts, struggle to detect misfires early enough to prevent degradation of the catalyst due to high temperatures, as they rely solely on monitoring exhaust gas temperature which is insufficient for timely detection.
Innovation Solution
A misfire detection apparatus for multi-cylinder engines that utilizes a rotation sensor to detect instantaneous changes in engine rotational speed during startup, combined with an electronic control unit to determine misfires based on rotational speed patterns, allowing for early detection and prevention of catalyst damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If exhaust gas temperature monitoring is used for misfire detection, then the catalyst purification function is maintained, but misfire detection timing is delayed and cannot prevent catalyst degradation
Solution Approach 1:
The patent applies preliminary action by detecting misfires during the startup period through rotational speed monitoring before the engine reaches normal operating temperature. This early detection prevents unburned gas from reaching the catalyst in misfiring conditions, avoiding catalyst degradation before it occurs. The system proactively identifies misfires rather than reacting after temperature rise is detected.
Solution Approach 2:
The patent uses rotational speed as an intermediary parameter to detect misfires indirectly. Instead of directly monitoring catalyst temperature or exhaust composition, the system measures engine rotational speed fluctuations caused by misfiring cylinders. This intermediary measurement enables early misfire detection without requiring direct catalyst condition monitoring.
2Loss of time
If rotational speed monitoring is used for early misfire detection, then misfire detection timing is improved, but the system cannot directly assess catalyst temperature conditions
Solution Approach 1:
The patent segments the misfire detection process into two distinct phases: startup period detection using rotational speed monitoring, and normal operation detection using exhaust temperature monitoring. This segmentation allows the system to use the most appropriate detection method for each operational phase, maintaining early detection capability during startup while assessing catalyst conditions during normal operation.
Solution Approach 2:
The system implements feedback by continuously monitoring engine operational parameters and adjusting detection strategies based on engine state. The ECU analyzes rotational speed patterns during startup and provides feedback on misfire conditions, enabling real-time detection and response. This feedback mechanism ensures the system adapts to changing engine conditions while maintaining early detection capability.
Data Source
AI summary
A misfire detection apparatus for multi-cylinder engine is configured to detect a misfiring state in which any of a plurality of cylinders in an engine is misfiring, the engine including: the plurality of cylinders, and a catalyst device configured to purify exhaust gas from the plurality of cylinders. The apparatus includes: a rotation sensor configured to detect a rotational speed of the engine, and an electronic control unit including a processor and a memory coupled to the processor and configured to control operation of the engine. The processor detects the misfiring state of the engine based on the rotational speed of the engine detected by the rotation sensor.