Corona Igniter Insulator Compression Design
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Solution Overview
Problem
The reverse-assembly method of corona igniters leads to operational and manufacturing compromises, particularly in internal combustion engines, where the insulator is often under tension, making it difficult to retain and resulting in reduced strength and stability.
Innovation Solution
A corona igniter design where the insulator is not under tension during assembly or installation, featuring an increased outer diameter at the lower shoulder and a shell with a smaller inner diameter at the same location, allowing for compression instead of tension, and an intermediate conductive part between the insulator and shell to enhance strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the insulator outer diameter is increased to improve electrical performance, then the insulator cannot be retained in the shell without tension, but tension reduces insulator strength and reliability
Solution Approach 1:
Instead of increasing the insulator outer diameter to improve electrical performance (which would create tension), the patent inverts the approach by decreasing the shell inner diameter at the firing end. This allows the insulator to be retained without tension while maintaining or improving electrical performance through the optimized diameter profile.
Solution Approach 2:
The patent applies local quality by creating a specific diameter profile where the shell inner diameter is decreased only at the firing end (local area) rather than uniformly throughout. This localized modification allows the insulator to be retained without tension while maintaining the overall electrical performance benefits of a larger insulator diameter in other regions.
2Reliability
If reverse-assembly method is used to accommodate larger insulator diameter, then electrical performance is improved, but manufacturing and installation complexity increases
Solution Approach 1:
The patent inverts the traditional reverse-assembly approach by modifying the shell geometry (decreasing inner diameter at firing end) rather than relying on the insulator being larger than the shell. This inversion simplifies the assembly process while maintaining the electrical performance benefits.
Solution Approach 2:
The patent changes the geometric parameters of the shell (specifically the inner diameter at the firing end) to enable simplified assembly. By adjusting this parameter, the shell can accommodate the insulator without requiring complex reverse-assembly procedures, thus reducing manufacturing and installation complexity.
3Strength
If the shell inner diameter is decreased to retain insulator without tension, then insulator strength is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies local quality by decreasing the shell inner diameter only at the firing end rather than uniformly throughout the entire shell. This localized modification reduces the overall manufacturing precision requirements compared to a uniform diameter reduction, as only a specific region requires tight tolerances.
Solution Approach 2:
The patent changes the shell inner diameter parameter in a localized manner, creating a diameter profile that transitions from a larger diameter in the upper portion to a smaller diameter at the firing end. This parameter variation allows for relaxed manufacturing precision in non-critical areas while maintaining the necessary precision only where needed for insulator retention.
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 achieves exceptional electrical performance and increased mechanical strength by avoiding tension in the insulator, maintaining strength even after installation in an engine, with the insulator being either in compression or not under stress, thus overcoming the limitations of traditional reverse-assembly methods.
Implementation Method 1
a corona igniter for emitting a radio frequency electric field to ionize a fuel-air mixture and provide a corona discharge
Implementation Method 2
The electric field causes a portion of a mixture of fuel and air in the combustion chamber to ionize and begin dielectric breakdown, facilitating combustion of the fuel-air mixture
Implementation Method 3
an insulator formed of an electrically insulating material surrounds a central electrode
Data Source
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AI summary
A reversed-assembled corona igniter including an insulator, central electrode, and metal shell, wherein an outer diameter of the insulator increases adjacent a lower end of the metal shell to achieve an electrical advantage is provided. In addition, the insulator maintains strength because is not placed under tension during or after assembly, or once disposed in an engine. To achieve the increase in insulator outer diameter, the insulator includes a lower shoulder adjacent the shell firing end. An intermediate part, such as braze and/or a metal ring, is disposed between the insulator outer surface and the shell adjacent the shell firing end. To prevent tension in the insulator, the insulator can be supported at only one location between the insulator upper end and the insulator lower end, for example along the intermediate part.