Spark Plug Degradation Detection via Misfire-Preignition Correlation
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Solution Overview
Problem
Existing methods for detecting pre-ignition in engines, particularly those with high compression ratios or boosted engines, often inaccurately attribute pre-ignition events to spark plug degradation, leading to inappropriate mitigating actions that can damage the engine.
Innovation Solution
A system and method that differentiate between pre-ignition caused by excessive boost or compression ratio and that caused by spark plug degradation by correlating cylinder misfire history with pre-ignition events, using an engine controller to indicate spark plug degradation and limit combustion in affected cylinders at high engine loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing methods detect pre-ignition based on ion currents and leakage currents, then pre-ignition detection capability is improved, but measurement precision deteriorates due to inaccurate attribution of pre-ignition causes
Solution Approach 1:
The patent segments the pre-ignition detection process into two distinct detection paths: one for detecting pre-ignition caused by excessive boost/compression (using only pre-ignition event detection) and another for detecting pre-ignition caused by spark plug degradation (using correlated misfire and pre-ignition detection). This segmentation allows each detection path to use appropriate detection criteria, improving overall measurement precision while maintaining reliable detection capability.
2Device complexity
If existing methods attribute all pre-ignition events to excessive boost or compression ratio, then device complexity is reduced, but reliability deteriorates due to missed spark plug degradation detection
Solution Approach 1:
The patent implements a dynamic detection approach where the system adapts its detection strategy based on operating conditions and historical data. The engine controller dynamically correlates misfire history with pre-ignition events to determine the likely cause, switching between different detection modes as needed. This dynamic approach maintains reliability for detecting spark plug degradation while avoiding unnecessary system complexity.
3Reliability
If existing methods take aggressive mitigating actions for all pre-ignition events, then pre-ignition prevention is improved, but object-generated harmful factors worsen due to unnecessary engine damage from incorrect mitigation
Solution Approach 1:
The patent implements a feedback-based mitigation system where the engine controller continuously monitors pre-ignition events and misfire history, then adjusts mitigation actions accordingly. When spark plug degradation is detected through correlation analysis, the system applies targeted mitigation such as retarding ignition timing or enriching the air-fuel mixture specifically for affected cylinders. This feedback approach ensures effective pre-ignition prevention while avoiding harmful aggressive mitigation actions when they are not needed.
Data Source
AI summary
Methods and systems are provided for identifying and indicating degradation of an engine cylinder spark plug. In response to a cylinder misfire event during selected engine operating conditions, followed by an occurrence of a threshold number and/or rate of pre-ignition events in the same cylinder, a controller may determine that the spark plug is degraded. The controller may limit combustion in the cylinder in response to the degradation. Additionally, cylinder pre-ignition mitigating steps may be taken.