Spark Plug Ground Electrode Inclination for Joint Strength
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Solution Overview
Problem
Conventional spark plugs with noble metal tips joined through resistance welding suffer from inadequate joint strength between the noble metal tip and the ground electrode base member, leading to durability issues due to excessive oxide scale formation.
Innovation Solution
A spark plug design where the noble metal tip is embedded in the ground electrode base member through resistance welding, with a specific inclination angle (2° ≤ θ ≤ 25°) and weld configuration that extends to the boundary regions, enhancing the fusion and joint strength between the two components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If resistance welding is used to join the noble metal tip to the ground electrode base member, then the noble metal tip can be firmly attached, but excessive oxide scale forms at the joint portion leading to separation
Solution Approach 1:
The patent applies parameter changes by optimizing the inclination angle of the noble metal tip (2° ≤ θ ≤ 25°) relative to the ground electrode base member. This angular parameter modification accelerates fusion during resistance welding, enhances joint strength, and simultaneously prevents excessive oxide scale formation that would cause separation, thereby resolving the contradiction between strong attachment and long-term durability
Solution Approach 2:
The patent implements local quality by creating a weld that extends to boundary regions on the side surface of the ground electrode base member. This localized weld configuration concentrates the bonding strength at critical areas while controlling oxide scale formation at the joint portion, achieving both strong attachment and prevention of separation
2Strength
If the noble metal tip is embedded deeply into the ground electrode base member, then the joint strength increases, but oxide scale formation becomes excessive causing separation
Solution Approach 1:
The patent uses parameter changes by defining specific geometric parameters for the noble metal tip configuration, including the inclination angle (2° ≤ θ ≤ 25°) and embedment depth ratios. These parameter optimizations enable sufficient joint strength while controlling the conditions that lead to excessive oxide scale formation and subsequent separation
3Strength
If the weld extends to boundary regions, then the joint strength is sufficiently increased, but the manufacturing complexity increases
Solution Approach 1:
The patent applies local quality by directing the weld to extend specifically to boundary regions on the side surface of the ground electrode base member. This localized approach concentrates the weld material where it provides maximum bonding benefit while maintaining a relatively simple overall manufacturing process, achieving high joint strength without excessive manufacturing complexity
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 enhanced joint strength and weld configuration significantly improve the durability of the spark plug by reducing oxide scale formation and ensuring a stronger bond between the noble metal tip and the ground electrode base member.
Implementation Method 1
the noble metal tip is embedded in the ground electrode base member through resistance welding
Implementation Method 2
a weld produced through partial melting of the ground electrode base member and the noble metal tip through the resistance welding
Implementation Method 3
fusion of the ground electrode base member and the noble metal tip at the time of resistance welding is accelerated, whereby the joint strength between the ground electrode base member and the noble metal tip can be increased
Data Source
AI summary
[Objective] An object of the present invention is to provide a technique for improving durability of a spark plug. [Means for Solution] A ground electrode 40 of a spark plug 100 is composed of a ground electrode base member 41 and a noble metal tip 42. The center axis CA3 of the noble metal tip 42 slants in relation to the center axis CA2 of the ground electrode base member 41 at angle θ which satisfies a relation 2° ≤ θ ≤ 25°.