Ignition Coil Resistor Coating for Hermetic Sealing
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Solution Overview
Problem
Existing ignition coils face challenges in hermetically sealing the gap between the resistor and the case, leading to potential resin leakage and mechanical stress due to inaccuracies in machining or press-fitting, which can result in damage to the case.
Innovation Solution
The ignition coil design includes a high-voltage tower with a resinous coating on the resistor, allowing for precise fitting and minimizing mechanical stress, ensuring a stable seal without increasing the case size by absorbing stress through the coating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the resistor is press-fit directly into the open end of the case, then the number of parts is reduced, but the mechanical stress increases and may cause damage to the case
Solution Approach 1:
A resinous coating is applied to the outer periphery of the resistor as an intermediary layer between the resistor and the case. This coating reduces mechanical stress during press-fitting by providing a compliant interface that absorbs fitting forces, preventing damage to the case while maintaining the integrated design approach.
Solution Approach 2:
The resinous coating changes the physical parameters of the resistor surface, providing a material layer with different mechanical properties (softer, more compliant) than the rigid resistor body. This parameter change allows the resistor to be fitted into the case with reduced stress transmission to the case structure.
2Device complexity
If the resistor is press-fit directly into the open end of the case, then the assembly is simplified, but machining accuracy requirements increase
Solution Approach 1:
The resinous coating serves as a compensating intermediary that masks dimensional variations and machining tolerances. By providing a conformal layer between the resistor and case, it reduces the impact of machining inaccuracies on the overall fit and sealing performance.
Solution Approach 2:
The coating modifies the dimensional parameters of the resistor outer surface, allowing for greater tolerance in the base resistor manufacturing while achieving the required final dimensions after coating application. This relaxes the machining accuracy requirements for the resistor and case mating surfaces.
3Ease of manufacture
If the gap between resistor and case is not hermetically sealed, then the assembly process is simpler, but resin leakage occurs
Solution Approach 1:
The resinous coating acts as an intermediary sealing layer that fills and seals the gap between the resistor and case. This coating provides a hermetic barrier that prevents resin leakage while maintaining a simple assembly process, as the coating itself forms the seal rather than requiring additional sealing components or complex assembly steps.
4Strength
If the high-voltage tower thickness is increased to ensure structural stiffness, then the case strength improves, but the case size increases
Solution Approach 1:
The resinous coating serves as a stress-absorbing intermediary that protects the high-voltage tower from excessive mechanical stress during assembly. This stress absorption allows the high-voltage tower to maintain adequate structural stiffness with reduced thickness, thereby minimizing the overall case size while preserving structural integrity.
Data Source
AI summary
An ignition coil for internal combustion engines is provided which includes a primary and a secondary coils magnetically coupled with each other, a case, a resistor, and a resinous filler. The case includes a case body in which the primary and secondary coils are disposed and a tubular high-voltage tower extending from the case body toward a head of the ignition coil. The resistor 3 is press-fitted into the high-voltage tower and electrically connected to the secondary coil. The resinous filler is packed in the case body to hermetically seal the primary coil and the secondary coil. The resistor includes a resinous coating which covers an outer circumference of the resistor and is press-fit in the high-voltage tower through the resinous coating. This facilitates hermetically sealing a gap between the resistor body and the case and ensures the stability of the sealing.