Spark Plug Nugget Welding Strength
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Solution Overview
Problem
The increasing severity of the working environment in internal combustion engines due to higher engine outputs leads to potential separation of the intermediate member from the electrode base metal in spark plugs, resulting from inadequate welding strength between the intermediate member and the electrode base metal.
Innovation Solution
A spark plug design where a nugget is formed through fusion and solidification at the boundary between the intermediate member and the electrode base metal, with specific geometrical parameters such as S1/(D1 × H1) ≥ 0.005, ensuring improved welding strength, and the nugget is strategically positioned to enhance attachment area and resistance to erosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the intermediate member is attached directly to the electrode base metal via welding, then the area of joining is increased and noble metal usage is reduced, but the welding strength fails to endure severe working environments resulting in separation
Solution Approach 1:
The invention changes the geometric parameters of the welding structure by forming a nugget with specific dimensions. The nugget has a width W1 and length L1 that satisfy the relational expression W1 × L1 ≥ 0.005 × D1², where D1 is the outer diameter of the noble metal tip. This parameter change ensures adequate welding strength while maintaining the joining area benefits.
Solution Approach 2:
The invention creates a composite structure consisting of three materials: the electrode base metal, the intermediate member, and the nugget. This composite construction combines the advantages of each material - the electrode base metal provides structural support, the intermediate member reduces noble metal usage, and the nugget provides strong welding attachment - to achieve both adequate joining area and welding strength.
2Strength
If a nugget is formed through welding at the boundary between the intermediate member and electrode base metal, then welding strength is improved, but the structural complexity increases
Solution Approach 1:
The invention manages structural complexity by controlling the nugget dimensions through specific relational expressions. The nugget width W1 and length L1 are constrained by W1 × L1 ≥ 0.005 × D1², and additional constraints W1 ≤ 0.5 × D1 and L1 ≤ 1.5 × D1. These parameter changes ensure the nugget provides sufficient strength without excessive complexity.
Solution Approach 2:
The invention applies local quality by concentrating the welding reinforcement (nugget) only at the critical boundary between the intermediate member and electrode base metal, rather than uniformly throughout the entire structure. This localized approach improves welding strength where needed while minimizing overall structural 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 described spark plug design significantly improves the welding strength between the intermediate member and the electrode base metal, reducing the risk of separation and enhancing the durability of the spark plug under harsh engine conditions.
Implementation Method 1
a nugget is formed through fusion and solidification resulting from welding at at least a portion of a boundary between the intermediate member and the electrode base metal
Data Source
Figure 1
Figure 2(A)~2(B)
Figure 3
AI summary
An object is to provide a technique for improving welding strength between an intermediate member and an electrode member. In a section of a spark plug cut by a plane which passes through the center of gravity of the intermediate member and is in parallel with the facing direction between a center electrode and an extending portion of a ground electrode, the spark plug satisfies the relational expression S1/(D1 × H1) ≥ 0.005, where S1 is the total area of nuggets, H1 is the height of the end surface of a noble metal tip from the disposition surface of an electrode base metal, and D1 is the maximum width of the noble metal tip.