Ignition Coil Magnetic Return Path Using Wound Ferritic Wire
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Solution Overview
Problem
Conventional ignition coils require significant amounts of copper wire and generate scrap during manufacturing, with increasing copper costs and costly tooling for magnetic return path structures.
Innovation Solution
A magnetic return path structure using a loop-shaped, magnetically-permeable core with a circular or rectangular cross-section, formed from strip steel or ferritic wire, allowing direct winding of primary and secondary windings without scrap and costly tooling, reducing copper usage and production waste.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a rectangular cross-section magnetic core with C-I or E-I shape is used, then magnetic permeability is improved, but mean length per turn of windings increases
Solution Approach 1:
The patent applies curvature by using a circular cross-section magnetic core instead of a rectangular one. This allows the primary winding to be wound directly onto the core in a spiral pattern, reducing the mean length per turn while maintaining effective magnetic coupling. The circular geometry eliminates the need for a primary spool and reduces the path length of the winding turns.
2Length of moving object
If a round magnetic core with direct primary winding is used, then mean length per turn is reduced, but magnetic permeability decreases
Solution Approach 1:
The patent merges the functions of the magnetic core and the magnetic return path into a single integrated structure. The U-shaped magnetic return path is formed from the same magnetic material as the core, creating a continuous magnetic circuit that maintains high permeability while allowing direct winding on the circular core. This integration ensures efficient magnetic flux closure without requiring separate high-permeability components.
Solution Approach 2:
The patent incorporates air gaps into the magnetic return path during the molding process itself, before assembly. These pre-formed air gaps control the magnetic flux distribution and prevent core saturation, maintaining optimal magnetic permeability in the circular core configuration without requiring subsequent machining or adjustment.
3Reliability
If a C-shaped laminated steel core is used, then magnetic permeability is improved, but manufacturing scrap is generated
Solution Approach 1:
The patent changes the manufacturing parameter from stamping (which generates scrap) to injection molding (which is scrap-free). The magnetic return path is molded as a single piece from magnetic powder and binder, eliminating the need for stamping operations that produce scrap material. This parameter change maintains the U-shaped geometry and magnetic properties while achieving zero scrap production.
4Reliability
If a stamped magnetic return path is used, then magnetic circuit is completed, but costly tooling is required
Solution Approach 1:
The patent replaces the mechanical stamping process with injection molding. Instead of using expensive stamping dies to form the magnetic return path, the component is molded from magnetic powder and binder using injection molding technology. This substitution eliminates the need for costly tooling while completing the magnetic circuit effectively.
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 reduces copper wire usage, eliminates scrap and costly tooling, while maintaining comparable performance to conventional ignition coils, and provides a cost-effective and efficient manufacturing process.
Implementation Method 1
providing a magnetic return path that eliminates scrap, can be made without costly tooling and which also permits the use of a circular-shaped magnetic core
Implementation Method 2
an ignition apparatus that utilizes a high-voltage transformer that includes a magnetically-permeable core and primary and secondary windings
Data Source
AI summary
An ignition apparatus includes a core, primary and secondary windings and a loop-shaped magnetic return path structure. The structure includes layers of wound strip steel or wound ferritic wire stacked in an outward fashion. The core is placed in an interior of the loop forming at least one air gap between a core end surfaces and the structure. A combined core and magnetic return path structure includes a continuous loop formed by winding ferritic wire either on a spool or on a mandrel and is then bonded. The bonded winding is cut to form two C-shaped portions. Each C-shaped portion has a central yoke that extends into a pair of parallel legs. The C-shaped portions are re-assembled over primary and second windings so that the legs form a pair of parallel branches. One branch acts as the core and the other branch acts as the magnetic return path.