Cylindrical Core Ignition Coil Copper Reduction
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Solution Overview
Problem
The increasing cost of copper wire due to its high price has made it a significant portion of the total bill of materials in ignition coils for internal combustion engines, necessitating a reduction in copper wire usage without compromising performance.
Innovation Solution
A circular-shaped magnetic core with a high permeance magnetic return path is used, allowing the primary winding to be wound directly on the core, reducing the mean length per turn and the number of turns required, thereby minimizing copper wire usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper wire is used for primary and secondary windings in conventional ignition coils, then reliable electrical insulation and conductivity are achieved, but the cost becomes significantly high due to increased copper prices
Solution Approach 1:
The patent changes the material parameter from copper wire to copper-free alternatives (such as aluminum or copper-clad aluminum wire). This substitution maintains the essential electrical properties (conductivity and insulation) while significantly reducing the quantity and cost of copper material used in the ignition coil windings
Solution Approach 2:
The patent employs cheaper alternative materials (aluminum or copper-clad aluminum) to replace expensive copper wire. These alternative materials provide comparable electrical performance at lower cost, effectively reducing the bill of materials without sacrificing reliability
2Reliability
If a rectangular cross-section magnetic core with C-I or E-I shape is used, then high magnetic permeability is achieved, but the mean length per turn of windings increases requiring a primary spool
Solution Approach 1:
The patent transitions from asymmetric rectangular cross-section cores (C-I or E-I shapes) to a symmetric circular cross-section core. This geometric change allows the windings to be wrapped directly around the core without requiring a primary spool, thereby reducing the mean length per turn while maintaining effective magnetic coupling and permeability
3Length of stationary object
If a round magnetic core with open magnetic path configuration is used, then the primary winding can be wound directly onto the core reducing mean length per turn, but the magnetic circuit has large air gaps reducing magnetic permeability
Solution Approach 1:
The patent combines the advantages of both core configurations by using a round cross-section core (enabling direct winding) with a closed magnetic path structure. This integration eliminates large air gaps in the magnetic circuit, maintaining high magnetic permeability while allowing the windings to be wrapped directly around the core for reduced mean length per turn
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
This approach effectively reduces the amount of copper wire used while maintaining comparable performance to conventional ignition coils, thereby controlling costs.
Implementation Method 1
an ignition apparatus that utilizes a high-voltage transformer that includes a magnetically-permeable core and primary and secondary windings
Implementation Method 2
a magnetically-permeable structure defining a high permeance magnetic return path
Data Source
AI summary
An ignition apparatus includes a cylindrical core made from magnetically-permeable material and a C-shaped magnetic return path structure that is made from a stack of silicon steel laminations. A tightly controlled air gap is provided between one leg of the C-shaped structure and an end face of the core, forming a magnetic circuit having a high magnetic permeability, which overall reduces the number of primary winding turns needed, thereby reducing the amount of copper wire. In addition, the circular cross-section of the core reduces the mean length per turn (MLT) of the primary winding because the primary winding can be wound directly on the core, which in turn also reduces the MLT of the secondary winding. The reduced MLT also reduces the amount of copper wire. The structure may be replaced using a magnetically-permeable, U-shaped shield.