Ion Current Feedback for Spark Plug Fouling Control
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Solution Overview
Problem
Short engine start and restart cycles lead to spark plug deposit formation, causing fouling and undesirable engine performance, with existing strategies either ineffective or objectionable to customers, and there is a need for a more controlled approach to manage ignition energy and prevent plug fouling.
Innovation Solution
A system and method using ionization current sensing to detect plug fouling, employing progressive corrective actions such as repetitive sparking, advancing spark timing, and adjusting air/fuel ratio, which can be more aggressive for assembly plant conditions or less noticeable for customer use, to effectively remove spark plug deposits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an alternate engine calibration with lean air/fuel ratio, advanced spark timing, and elevated idle speed is employed to prevent spark plug fouling, then spark plug deposit formation is reduced or prevented, but engine stalling occurs particularly during cold starts and higher idle speed is objectionable to customers
Solution Approach 1:
The system dynamically adjusts engine calibration parameters based on detected plug fouling conditions and operating context (assembly plant vs. customer use). The controller switches between different calibration strategies - aggressive corrective actions during assembly plant operations and more conservative actions during customer use - allowing the system to adapt its behavior to different operational phases and environmental conditions.
Solution Approach 2:
The system changes key operating parameters (air/fuel ratio, spark timing, idle speed) based on the detected fouling condition and operational context. During assembly plant operations, parameters are adjusted more aggressively to eliminate deposits, while during customer use, parameter changes are more conservative to maintain normal engine performance and avoid customer notice.
2Reliability
If aggressive corrective actions are employed to eliminate spark plug deposits, then plug fouling is effectively prevented, but noticeable changes in engine operation and performance occur that may be objectionable to customers
Solution Approach 1:
The system segments corrective actions into different levels of aggressiveness based on the operational context. During assembly plant operations, aggressive corrective actions are applied to all cylinders. During customer use, the system applies only necessary corrective actions to specific affected cylinders with less aggressive parameter changes, segmenting the response based on both spatial (cylinder-specific) and contextual (operational phase) factors.
Solution Approach 2:
The system applies partial corrective actions during customer use - only to the extent necessary to address detected fouling conditions without implementing full aggressive corrective measures. This partial action approach eliminates deposits while minimizing noticeable changes in engine operation, applying just enough correction to solve the problem without excess that would be perceived by customers.
3Measurement precision
If ionization current sensing is used to detect plug fouling conditions, then early detection and corrective action are enabled, but system complexity increases
Solution Approach 1:
The ionization sensing system serves multiple functions: it detects plug fouling conditions, monitors combustion quality, and provides feedback for corrective control actions. By making the sensing system multi-functional, the patent reduces overall system complexity as a single sensing mechanism performs multiple detection and control functions rather than requiring separate systems for each function.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides effective and customer-friendly strategies to reduce or eliminate spark plug fouling by using ion current feedback to manage ignition energy, ensuring improved engine performance and customer satisfaction by employing aggressive corrective actions when necessary and less noticeable strategies when required.
Implementation Method 1
ionization current sensing (or ion sense) uses a bias voltage applied across a sensor positioned within the combustion chamber to generate a current signal indicative of the combustion quality and timing
Data Source
AI summary
A system and method for operating an engine having ionization signal sensing include detecting plug fouling and controlling the engine using progressively more aggressive control strategies if the fouling condition persists. A first control strategy may be used when the number of engine starts or running time are below corresponding thresholds and a second strategy otherwise. The first strategy may employ progressively more aggressive control procedures to eliminate spark plug deposits that may include repetitive sparking, exhaust cycle sparking, increasing engine loading, advancing spark timing, increasing air/fuel ratio, and increasing idle speed, for example. The second strategy may include similar corrective actions employed in a different order and/or to a lesser degree in an attempt to eliminate plug fouling without any noticeable change in engine operation or performance as perceived by the vehicle operator. The control strategies may be applied to individual cylinders, cylinder banks, or all cylinders.