Spark Plug Ground Electrode Nickel Layer Thickness Gradient
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Solution Overview
Problem
The existing spark plug designs face issues with nickel layer separation due to abrupt thickness changes in the boundary region, leading to stress differences between the nickel layer and the ground electrode, which can cause abnormal spark discharge and deterioration in ignition performance.
Innovation Solution
A spark plug configuration where the nickel layer on the ground electrode has a gradual thickness decrease towards the base material exposed region, with specific length conditions (LA ≥ 25 μm, LA ≥ 50 μm, or LA ≥ 90 μm) to ensure the nickel layer can deform with the ground electrode during heating/cooling cycles and bending, reducing stress differences and preventing separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the nickel layer is removed from the distal end portion for tip bonding, then bondability is improved, but the boundary region separates due to stress difference
Solution Approach 1:
The patent controls the thickness of the nickel layer in the boundary region to be between 1 μm and 10 μm, which is thinner than the outer lateral surface but thicker than the tip bonding region. This parameter optimization allows the boundary region to follow deformation during heating/cooling cycles and bending, reducing stress difference and preventing separation while maintaining adequate adhesion.
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 configuration effectively reduces stress differences and prevents nickel layer separation, ensuring stable spark discharge and improved ignition performance by allowing the nickel layer to follow the ground electrode's deformation, thereby enhancing the spark plug's durability and reliability.
Implementation Method 1
the boundary region of the outer-lateral-side nickel layer cannot follow deformation (expansion or contraction) of the ground electrode caused due to heating/cooling cycles during operation of the internal combustion engine
Implementation Method 2
the nickel layer may be separated when the ground electrode coated with the nickel layer is subjected to bending
Data Source
AI summary
A spark plug includes a metal shell, a ground electrode joined to a front end portion of the metal shell and a nickel layer formed on the ground electrode, wherein the ground electrode has a base material exposed region in which a base material of the ground electrode is exposed; and wherein the nickel layer includes an outer-lateral-side nickel layer located on an outer lateral surface of the ground electrode at a position adjacent to the base material exposed region and satisfies a condition of LA≧25 μm, where LA is a length from a first part of the outer-lateral-side nickel layer having a thickness equal to 80% of a maximum thickness of the outer-lateral-side nickel layer to a second part of the outer-lateral-side nickel layer having a thickness equal to 20% of the maximum thickness of the outer-lateral-side nickel layer in a longitudinal direction of the ground electrode.