Ignition Coil Thermal Expansion Decoupling
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Solution Overview
Problem
The variation in thermal expansion properties of materials in independent ignition coils causes stresses and strains, leading to component breakdowns due to the continual heating and cooling cycle, resulting in reliability issues.
Innovation Solution
Incorporation of a resilient thermal expansion de-coupling means, such as a radially expanding and contracting sheath buffer with a protrusion, between the primary support spool and primary coil, allowing for axial movement and alleviating stresses caused by differential expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If co-axially arranged materials are used in the ignition coil, then the coil structure is compact and functional, but differential thermal expansion causes stresses and strains leading to component breakdown
Solution Approach 1:
A resilient buffer member is introduced as an intermediary component between the primary support spool and the primary coil. This buffer member absorbs differential thermal expansion through elastic deformation, preventing stress transmission between the spool and coil windings, thereby maintaining component reliability while preserving the compact co-axial structure.
Solution Approach 2:
The resilient buffer member is designed with specific material properties (elastic modulus, damping characteristics) that allow it to change its mechanical parameters in response to thermal conditions. The buffer's elasticity enables it to expand and contract radially, accommodating thermal growth of the co-axial materials without generating damaging stresses.
2Ease of manufacture
If rigid support spools are used to hold coils in place, then assembly is simplified, but thermal expansion differences cause component breakage over time
Solution Approach 1:
The resilient buffer member functions as a flexible element that radially expands and contracts to absorb thermal expansion differences. This flexible component is positioned between the rigid primary support spool and the primary coil, allowing the rigid spool structure to remain for assembly simplicity while the flexible buffer protects against thermal stress-induced breakage.
3Reliability
If resilient thermal expansion de-coupling means is added between support spool and coil, then thermal expansion differences are accommodated, but device complexity increases
Solution Approach 1:
The resilient buffer member is designed as a simple cylindrical component with a radial protrusion, making it structurally straightforward despite its functional complexity. The buffer's simple geometry minimizes the increase in device complexity while effectively accommodating thermal expansion differences between the support spool and coil windings.
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 significantly increases the longevity and reliability of the ignition coil by accommodating thermal expansion differences between components, reducing the likelihood of component failure.
Implementation Method 1
The variation in the thermal expansion properties of the co-axially arranged materials in the ignition coil can cause stresses and strains within the coil
Implementation Method 2
resilient sheath buffer capable of expanding and contracting in a radial direction
Data Source
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AI summary
This invention relates to an ignition coil for the engine of a vehicle. The ignition coil comprises a core member (18) having a number of layers wrapped around it. The formation of these layers from the core member outward comprises a secondary support spool (22), a secondary coil (24), a primary support spool (28) and a primary coil (32). Resilient thermal expansion de-coupling means (30) is provided between at least one of the primary and secondary coils (32, 24) and its or their corresponding support spool or spools (28, 22). The thermal expansion de-coupling means (30) allows each layer to expand and contract substantially independently of one another. This reduces the stress exerted on each layer as it is heated/cooled which increases the overall lifetime of the ignition coil.