Spark Coil Lead Terminal Layout for Thermal Stress Relief
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Solution Overview
Problem
Conventional spark coils have high costs due to multiple components and are prone to lead terminal separation and bobbin cracking caused by thermal expansion and shrinkage in internal-combustion engines.
Innovation Solution
A spark coil design featuring a tubular secondary bobbin with flanges and a long-sheet-shaped secondary lead terminal that is surface-contacted between the flanges, preventing direct contact with the bobbin's side surfaces, thereby reducing thermal stress and component count.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If two lead terminals are used (one on output terminal side and one on secondary conductive wire side) to ensure electrical connection, then electrical connection reliability is improved, but the number of components increases leading to high cost
Solution Approach 1:
The patent merges the two separate lead terminals into a single integrated secondary lead terminal that directly connects the secondary conductive wire to the output terminal. This single lead terminal structure eliminates the need for two separate terminals while maintaining reliable electrical connection, thereby reducing component count and manufacturing cost.
2Stability of the object's composition
If the bent portion of the lead terminal is press-fitted into the secondary bobbin to secure connection, then connection stability is improved, but repetitive thermal expansion and shrinkage cause lead terminal separation and bobbin cracking
Solution Approach 1:
The patent extracts the secondary lead terminal from the press-fitted configuration and repositions it to be disposed between the flanges of the secondary bobbin without press-fitting into the bobbin body. This extraction eliminates the harmful interaction between the lead terminal and the bobbin structure during thermal cycling, preventing both lead terminal separation and bobbin cracking while maintaining connection stability through the flange-supported configuration.
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 design reduces the risk of lead terminal separation from the bobbin and inhibits crack generation in the bobbin, while maintaining low costs and ensuring reliable electrical connections.
Implementation Method 1
the lead terminals of the spark coil repetitively undergo thermal expansion and thermal shrinkage owing to repetitive changes in the temperature of the internal-combustion engine
Implementation Method 2
the lead terminals of the spark coil repetitively undergo thermal expansion and thermal shrinkage owing to repetitive changes in the temperature of the internal-combustion engine
Data Source
AI summary
A spark coil includes: a center core; a primary coil disposed on an outer periphery of the center core; a secondary coil disposed on an outer periphery of the primary coil; and an output terminal electrically connected to the secondary coil. The secondary coil includes a tubular secondary bobbin having a plurality of flanges on an outer peripheral side thereof, a secondary conductive wire wound around the secondary bobbin, and a long-sheet-shaped secondary lead terminal having one and another end portions electrically connected to the secondary conductive wire and the output terminal, respectively. The secondary lead terminal is disposed, between corresponding ones of the flanges, in surface contact with none of side surfaces of the flanges.