Spark Plug Ground Electrode Convex Fusion Joint
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Solution Overview
Problem
The existing spark plugs for internal combustion engines face issues with durability and reliability due to heat stress causing cracks and oxidization in the joint between the precious-metal-chip and the base material of the ground electrode, leading to increased demand voltage and manufacturing costs.
Innovation Solution
A spark plug design featuring a ground electrode with a convex portion made of a fusion solidification part, where precious metals and base materials are melted and solidified together, forming a single metallic crystal alloy with an average precious metal content of 80% or less, enhancing thermal conductivity and reducing wear, while using a smaller amount of precious metals to lower manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If precious-metal-chip is welded to base material of ground electrode only at joint part, then manufacturing cost is reduced, but reliability of joint deteriorates due to cracks and oxidization under heat stress
Solution Approach 1:
The invention applies local quality by creating a convex portion with fusion solidification part (precious metals melted and solidified with base material) at the electric discharge surface, while the rest of the ground electrode remains as base material. This localized fusion treatment enhances reliability at the critical joint area without requiring precious metals throughout the entire electrode, thus resolving the contradiction between manufacturing cost and joint reliability.
Solution Approach 2:
The invention uses composite materials by forming a fusion solidification part where precious metals and base material are melted together and solidified, creating a composite structure with average precious metal content of 80% or less. This composite approach improves joint reliability through better thermal conductivity and crack resistance, while controlling precious metal usage to maintain cost-effectiveness.
2Ease of manufacture
If precious-metal-chip is welded only on circumference of contacting surfaces, then manufacturing cost is reduced, but thermal conductivity deteriorates causing temperature rise and increased wear
Solution Approach 1:
The convex portion with fusion solidification part is created locally at the electric discharge surface where thermal conductivity is most critical. This localized treatment improves heat dissipation at the hottest area without requiring expensive precious metals throughout the entire ground electrode, thus resolving the contradiction between manufacturing cost and temperature control.
Solution Approach 2:
The fusion solidification part creates a composite material structure with enhanced thermal conductivity at the critical discharge surface. By concentrating precious metals in this specific region with average content of 80% or less, the invention improves temperature management while controlling manufacturing costs.
3Use of energy by moving object
If spark discharge gap is made small to lower demand voltage, then electrical performance is improved, but amount of precious metals used increases raising manufacturing cost
Solution Approach 1:
The invention creates a convex portion that projects toward the center electrode, locally enhancing the electric field at the discharge surface. This allows for effective spark discharge with reduced demand voltage without requiring a uniformly small gap throughout, thus maintaining lower precious metal usage and controlling manufacturing costs.
Solution Approach 2:
The convex portion adds a dimensional feature to the ground electrode, creating a three-dimensional structure that concentrates the electric field at the discharge surface. This dimensional change enables lower demand voltage without proportionally increasing precious metal usage, as the enhancement is localized to the convex portion rather than requiring uniform gap reduction across the entire electrode.
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 spark plug achieves improved durability and reliability in the joint portion with enhanced thermal conductivity, reduced wear, and lower demand voltage, while minimizing the use of precious metals to lower production costs.
Implementation Method 1
precious metals and the part of the base materials of the ground electrode are melted together by arc welding on at least a part of the electric discharge surface
Implementation Method 2
melted together by arc welding
Implementation Method 3
the melted portion is solidified
Implementation Method 4
The crystal of the mixture that forms the domain is a domain where the portion of a single metallic crystal and the portion alloyed in part come to be intermingled
Implementation Method 5
since the thermal conductivity of the joint part 954 is smaller than that of the precious-metal-chip 953, heat radiation of the precious-metal-chip 953 worsens
Data Source
AI summary
A spark plug for internal-combustion engines equipped with a center electrode and a ground electrode is provided. In the spark plug, the ground electrode is fixed to a mount fitting, while the ground electrode has a convex portion. The convex portion is made of a part of base materials of the ground electrode where the part is facing the center electrode, and is projected toward the center electrode. The convex portion has a fusion solidification part made of precious metal materials and a part of the base materials melted together and solidified at least on part of an electric discharge surface facing the center electrode.