Corona Igniter Insulator Reverse Assembly Tension Relief
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Solution Overview
Problem
The reverse-assembly method of corona igniters, which involves increasing the outer diameter of the insulator towards the high voltage electrode tip, leads to operational and manufacturing compromises, including insulator tension during assembly and installation in internal combustion engines, making it difficult to retain the insulator without applying tension.
Innovation Solution
A corona igniter design where the insulator outer diameter increases at a lower shoulder, allowing for reverse-assembly without insulator tension, featuring a conductive intermediate part between the insulator and shell to maintain compression and enhance strength, and a method of forming this configuration to ensure the insulator is not under tension during assembly or operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the insulator outer diameter is increased towards the high voltage electrode tip to improve electrical performance, then the insulator must be assembled in reverse which causes the insulator to be under tension during assembly and installation
Solution Approach 1:
The patent inverts the conventional assembly direction by assembling the insulator from the shell end rather than the electrode tip end. This reverse assembly approach, combined with a tapered bore design in the shell, allows the insulator to be installed without being under tension, thereby maintaining its mechanical strength while achieving the desired electrical performance through the increased outer diameter configuration.
Solution Approach 2:
The patent modifies the geometric parameters of the insulator and shell assembly. The insulator outer diameter is increased towards the high voltage electrode tip to improve electrical performance, while the shell bore is designed with a taper that changes from a first diameter at the shell end to a second diameter at the electrode tip end. This parameter change enables the insulator to fit properly during reverse assembly without experiencing tensile stress.
2Reliability
If the insulator outer diameter is increased to improve electrical performance, then the assembly complexity increases due to the need for reverse-assembly method
Solution Approach 1:
The patent employs parameter changes in the shell bore geometry, designing it with a specific taper that facilitates reverse assembly. The bore transitions from a first diameter at the shell end to a second diameter at the electrode tip end, creating a self-aligning and self-latching assembly mechanism that reduces operational complexity despite the inverted assembly sequence.
3Reliability
If the insulator is assembled in reverse to achieve larger outer diameter, then the manufacturing precision requirements increase to ensure proper fit and alignment
Solution Approach 1:
The patent utilizes a tapered bore design in the shell with specific diameter variations along its length. This geometric parameter change provides a gradual transition zone that accommodates manufacturing tolerances and ensures proper fit and alignment during reverse assembly, reducing the stringency of precision requirements compared to a straight-bore design.
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 insulator tension, maintaining strength comparable to or exceeding that of insulators under compression, while simplifying assembly and reducing operational stress.
Implementation Method 1
a central electrode formed of an electrically conductive material for receiving a high radio frequency voltage and emitting the radio frequency electric field
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
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.