Spark Plug Welding: Laser Output Variation for Join Strength
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Solution Overview
Problem
In spark plugs, the joining quality between the front end member and the metal shell is not adequately ensured, leading to issues like significant expansion of the weld bead and fouling due to spattering during the weld-joining process.
Innovation Solution
A spark plug design with a weld portion that includes melt extending parts along the outer circumference of the front end member, where the melting depth is adjusted to improve joining quality, and a manufacturing method using laser irradiation to form the weld portion with specific output variations to minimize appearance degradation and enhance strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the front end member is weld-joined to the metal shell, then the joining strength is improved, but the appearance degrades due to weld bead expansion and spattering
Solution Approach 1:
The invention applies different laser output levels to different circumferential positions during welding. Specifically, the laser output is set to a first level for a first circumferential range and a second level (different from the first) for a second circumferential range. This local variation in welding parameters creates a weld portion with non-uniform melt extending parts, where some portions have smaller melting depths, thereby suppressing weld bead expansion and spattering in critical areas while maintaining overall joining strength.
2Reliability
If the laser output is increased to ensure joining strength, then the welding reliability is improved, but the weld bead expansion and spattering increase
Solution Approach 1:
The invention changes the laser output parameter during the welding process. By setting the laser output to different levels (first output level and second output level) for different circumferential ranges, the welding process achieves reliable joining without excessive weld bead expansion. The variation in laser output parameters allows the melt extending parts to have different melting depths, with some portions having smaller melting depths that suppress harmful effects while maintaining overall weld integrity.
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 effectively improves the joining strength between the front end member and the metal shell while suppressing the occurrence of weld bead expansion and fouling, ensuring a higher quality and reliable spark plug.
Implementation Method 1
a manufacturing method using laser irradiation to form the weld portion
Implementation Method 2
in which the front end member and the metal shell have been mutually melted
Data Source
AI summary
A spark plug includes a center electrode, a ground electrode, and a cylindrical metal shell. The ground electrode is welded to the metal shell via a weld portion. The weld portion is formed along the outer circumference end part of an annular part in the ground electrode. The weld portion has a plurality of melt extending parts extending toward the inner circumference side from the outer circumference end part of the annular part and aligned such that adjacent ones are connected to each other at the end part. The plurality of melt extending parts partially include smaller melt extending parts whose melting depth is smaller than others.