Ignition Coil Assembly Layout to Reduce Stray Capacitance
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Solution Overview
Problem
Long high voltage extensions in spark plug wells create stray capacitance, leading to high current peaks, spark plug wear, and electromagnetic interference, which are particularly problematic in SI-ICE engines using alternative fuels like hydrogen, affecting performance and maintenance costs.
Innovation Solution
An ignition coil assembly with an elongated connection portion positioned within the spark plug well, reducing stray capacitance by keeping the ignition coil close to the spark plug, and incorporating a rigid tubular extension for mechanical stability and a ventilation arrangement to evacuate gases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If a long high voltage extension cable is used to connect the ignition coil to the spark plug, then the ignition system can reach the spark plug in deep spark plug wells, but the stray capacitance increases leading to high current peaks and spark plug wear
Solution Approach 1:
The patent extracts the high voltage generation function from a separate ignition coil located outside the spark plug well and places it directly at the spark plug tip. This eliminates the need for a long high voltage extension cable by integrating the ignition coil with the spark plug, thereby removing the source of stray capacitance problems while maintaining the ability to reach deep spark plug wells.
2Area of stationary object
If the spark plug well is designed to be narrow to accommodate limited space, then the engine remains compact, but the stray capacitance increases due to closer proximity between the extension and the well
Solution Approach 1:
The patent removes the problematic high voltage extension cable from the system by integrating the ignition coil directly with the spark plug. This eliminates the harmful interaction between the extension cable and the narrow spark plug well, allowing the well to maintain its narrow dimensions for compact engine design without suffering from increased stray capacitance.
3Power
If high voltage is applied to generate a spark, then combustion is initiated, but high current peaks occur due to stray capacitance discharge affecting spark plug life
Solution Approach 1:
The patent merges the ignition coil and spark plug into a single integrated unit called a spark generator. This combination eliminates the high current peaks caused by stray capacitance discharge in separate cable connections, thereby protecting the spark plug from excessive current stress and extending its operational life while maintaining the necessary high voltage for spark generation.
4Length of moving object
If a long high voltage extension cable is used, then the ignition coil can be positioned away from the spark plug, but electromagnetic radiation increases making it difficult to meet EMC requirements
Solution Approach 1:
The patent eliminates the long high voltage extension cable that acts as an antenna for electromagnetic radiation by integrating the ignition coil with the spark plug. This removal of the radiating element directly addresses EMC concerns while maintaining the necessary electrical connection for spark generation.
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 spark plug wear, and decreases electromagnetic interference, enhancing engine performance and reducing maintenance costs while supporting efficient ignition with lower energy consumption.
Implementation Method 1
The ignition coil typically includes a transformer, having a primary and secondary coil winding around a soft magnetic core. To the primary side of the transformer, a low voltage is applied when a spark is to be released. The low voltage is then transformed to a high voltage on the secondary side of the transformer.
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. The high voltage pulse charges the stray capacitance in parallel with increasing the voltage over the spark plug gap. Finally, 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. The current and energy during the flash-over and shortly thereafter may be very high, and it increases with increased stray capacitance because the charge that has been built up in the stray capacitance is then almost instantaneously released
Data Source
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AI summary
An ignition coil assembly (100) for installation in a spark plug well (400) of a combustion engine (200) and for enabling a spark of a spark plug (500) installed in a distal end (410) of the spark plug well (400) is disclosed. The ignition coil assembly (100) comprises an ignition coil (125) adapted to transform a first voltage to a second voltage for enabling the spark, and an elongated connection portion (110) extending in the spark plug well (400) when the ignition coil assembly (100) is installed in the spark plug well (400). The ignition coil (125) is connected to a first end (111) of the elongated connection portion (110). The first end (111) of the elongated connection portion (110) is closer to the spark plug (500) than a second end (112) of the elongated connection portion (110) when the ignition coil assembly (100) is installed in the spark plug well (400), whereby the ignition coil assembly (100) is adapted to provide the first voltage to the ignition coil (125) by means of the elongated connection portion (110).