Ignition Coil Assembly Shielding for Stray Capacitance Control
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Solution Overview
Problem
The elongated ignition coil extensions in spark plug wells of internal combustion engines create stray capacitance, leading to high current peaks, electromagnetic interference, and reduced spark plug life, especially in engines using alternative fuels like hydrogen, which can cause pre-ignition and increase maintenance costs.
Innovation Solution
An ignition coil assembly with an elongated connection portion positioned within the spark plug well, reducing stray capacitance and maintaining a short distance to the spark plug, using a rigid tubular extension for mechanical stability and incorporating a transformer to enhance efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If an elongated ignition coil extension is used to connect the transformer to the spark plug in a deep spark plug well, then the electrical connection is achieved, but the stray capacitance increases leading to high current peaks and reduced spark plug life
Solution Approach 1:
The patent introduces an intermediary shielding structure (grounded shield orFaraday cage) between the elongated ignition coil extension and the spark plug well. This intermediary element intercepts and redirects the electromagnetic field, preventing the extension from acting as an antenna and reducing stray capacitance effects, thereby protecting the spark plug from excessive current peaks while maintaining the necessary electrical connection
2Volume of moving object
If the spark plug well is designed to be narrow to accommodate limited space in the engine top, then the compact engine design is achieved, but the stray capacitance increases due to closer proximity between the extension and well walls
Solution Approach 1:
The patent introduces an intermediary shielding structure (grounded shield orFaraday cage) positioned within the narrow spark plug well. This intermediary element creates an electromagnetic barrier between the ignition coil extension and the well walls, preventing capacitive coupling despite the narrow spacing, thereby reducing stray capacitance while maintaining the compact engine design
3Adaptability or versatility
If a long extension cable is used to connect the transformer to the spark plug, then the installation flexibility is improved, but the electromagnetic radiation increases making it difficult to meet EMC requirements
Solution Approach 1:
The patent introduces an intermediary shielding structure (grounded shield orFaraday cage) that surrounds or is positioned near the extension cable. This intermediary element acts as a Faraday cage, containing the electromagnetic radiation generated by the long extension cable and preventing it from radiating outward, thereby reducing EMC issues while maintaining installation flexibility
Solution Approach 2:
The patent utilizes the grounding system as a beneficial element to convert the harmful electromagnetic radiation into a controlled path. By providing a low-impedance ground path through the shielding structure, the electromagnetic energy that would otherwise radiate is instead directed to ground, transforming a harmful effect into a controlled dissipation mechanism
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
Reduces stray capacitance, minimizes energy requirements for sparking, decreases electromagnetic interference, and extends spark plug life, while supporting efficient combustion with reduced greenhouse gas emissions.
Implementation Method 1
an ignition coil adapted to transform a first voltage to a second voltage for enabling the spark
Implementation Method 2
The elongated ignition coil extension/cable gives rise to a 'stray capacitance' i.e., a capacitance that is a result of the interaction between the extension/cable and the spark plug well
Implementation Method 3
The high voltage pulse charges the stray capacitance in parallel with increasing the voltage over the spark plug gap
Implementation Method 4
when the voltage is high enough to generate a flash-over (break down) over the spark plug electrode gap, a current is generated across the gap—i.e. the spark
Data Source
AI summary
An ignition coil assembly for installation in a spark plug well of a combustion engine and for enabling a spark of a spark plug installed in a distal end of the spark plug well. The ignition coil assembly includes an ignition coil dimensioned and configured to transform a first voltage to a second voltage for enabling the spark, and an elongated connection portion extending in the spark plug well when the ignition coil assembly is installed in the spark plug well.