Cantilevered Ground Electrode Spark Plug Gap Adjustment
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Solution Overview
Problem
Conventional prechamber ignition plugs face challenges in adjusting the spark discharge gap between the center electrode and ground electrodes within a prescribed range due to their structural design, leading to variations in gap size during manufacturing, affecting ignition performance.
Innovation Solution
The ignition plug design features a rod-shaped ground electrode cantilevered and fixed to the metallic shell, allowing for adjustable gap settings through load application, with a metal fitting enhancing joint strength and durability, and a manufacturing method that includes a gap adjustment step using a rotatable adjustment jig to ensure precise gap control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the center electrode and ground electrodes are located within the ignition chamber, then ignition performance is improved, but gap adjustment becomes structurally difficult
Solution Approach 1:
The ground electrode is designed as a cantilever structure that can be dynamically adjusted by applying load to its proximal end portion, allowing the gap to be modified after assembly. This dynamic adjustment capability resolves the contradiction by enabling gap tuning while maintaining the electrodes within the ignition chamber for good ignition performance.
Solution Approach 2:
The ground electrode is segmented into a proximal end portion for fixing and a distal end portion for facing the center electrode. This segmentation allows the proximal end to be fixed to the metallic shell while the distal end can be positioned to achieve the desired gap, enabling adjustment while keeping both electrodes within the ignition chamber.
2Manufacturing precision
If accurate assembly of metallic shell, insulator, and center electrode is performed during manufacturing, then gap size is brought into prescribed range, but manufacturing complexity increases
Solution Approach 1:
The ground electrode serves a dual function: it is both a functional component for spark discharge and an adjustment mechanism for gap control. By applying load to the proximal end portion, the gap can be self-adjusted to the prescribed range without requiring highly accurate assembly of other components, thereby reducing manufacturing complexity.
Solution Approach 2:
The gap size is controlled by changing the physical state or position of the ground electrode through load application rather than relying on precise assembly parameters. This parameter change approach allows gap adjustment after assembly, reducing the stringency of manufacturing precision requirements.
3Stability of the object's composition
If ground electrode is fixed to metallic shell, then structural stability is improved, but gap adjustability is reduced
Solution Approach 1:
The ground electrode is fixed at its proximal end portion to provide structural stability, while the distal end portion remains adjustable through load application. This creates a system that is stable at the fixed end but adaptable at the gap-forming end, resolving the contradiction between fixation and adjustability.
Solution Approach 2:
The ground electrode is divided into a proximal end portion for fixing to the metallic shell and a distal end portion for forming the gap. This segmentation allows the proximal end to provide stable fixation while the distal end maintains adjustability, simultaneously achieving both stability and adaptability.
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 design enables easy and precise adjustment of the spark discharge gap, improving durability and ignition performance by maintaining gap consistency, facilitating mass production, and enhancing the prechamber plug's ability to handle heat loads effectively.
Implementation Method 1
a proximal end portion of the ground electrode is fixed to the metallic shell in such a manner that the ground electrode is cantilevered and extends in a chord direction of the ignition chamber; a distal end portion of the ground electrode faces a circumferential surface of the center electrode directly or indirectly, with a gap therebetween
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
An ignition plug having an ignition chamber at the front end of a metallic shell has a problem in that adjustment of a gap for spark discharge is difficult because a center electrode and a ground electrode are located within the ignition chamber. An ignition plug of the present invention includes a metallic shell 1 having a through hole 7 extending therethrough in an axial direction, an insulator 2 fitted into the through hole 7 of the metallic shell 1 and having an axial hole 5 extending in the axial direction, and a center electrode 3 fitted into the axial hole 5 of the insulator 2. The ignition plug further includes a cap member 11 which covers a front end opening of the metallic shell 1, provided on a front end side thereof where the center electrode 3 is disposed, to thereby form an ignition chamber 4 at the front end portion of the metallic shell 1, and a ground electrode 6 disposed within the ignition chamber 4 and facing a circumferential surface of the center electrode 3 directly or indirectly. The ground electrode 6 has a rod-like shape, a proximal end portion 6a of the ground electrode 6 is fixed to the metallic shell 1 such that the ground electrode 6 is cantilevered and extends in a chord direction of the ignition chamber 4, and a distal end portion of the ground electrode 6 faces the circumferential surface of the center electrode 3 directly or indirectly.