Spark Plug Electrode Composition for Oxidation Resistance
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Solution Overview
Problem
Spark plugs face challenges with high-temperature oxidation and spark-induced erosion due to the formation of Al nitride and low-melting-point compounds when exposed to high-temperature environments, leading to reduced durability and reliability of noble metal tips.
Innovation Solution
Incorporating specific elements such as C, Si, Mn, Cr, Fe, and adjusting their concentrations in the electrode materials to form carbides and oxides that enhance resistance to high-temperature oxidation and spark-induced erosion, while maintaining workability and joining reliability by using a noble metal tip with a weight of 1.5 mg or more.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Al is contained in electrode material to improve resistance to high-temperature oxidation, then oxidation resistance is improved, but Al nitride deposits form causing embrittlement and reducing durability
Solution Approach 1:
The patent removes Al from the electrode material composition entirely, extracting the harmful element that causes Al nitride deposition and embrittlement, while seeking alternative oxidation resistance mechanisms through other alloying elements
Solution Approach 2:
The patent changes the chemical composition parameters of the electrode material by specifying precise ranges for Ni (75-85 mass%), Cr (10-20 mass%), and Fe (3-10 mass%), eliminating Al to prevent nitride formation while maintaining oxidation resistance through optimized alloy composition
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 significantly improves resistance to high-temperature oxidation and spark-induced erosion, as well as the reliability of the noble metal tip's joining, ensuring enhanced durability and performance in severe engine environments.
Implementation Method 1
C combines with Cr, etc., to form carbide
Implementation Method 2
yields, at a temperature near a solid solution formation temperature, the effect of improving resistance to high-temperature oxidation through prevention of coarsening of crystal grains
Implementation Method 3
Si combines with O to form oxide, and yields the effect of improving resistance to high-temperature oxidation
Implementation Method 4
Mn combines with S to form compound, and yields the effect of improving resistance to spark-induced erosion
Implementation Method 5
Cr combines with O to form oxide, and yields the effect of improving resistance to high-temperature oxidation
Implementation Method 6
Fe combines with O to form oxide, and yields the effect of improving resistance to high-temperature oxidation
Data Source
Figure 1
Figure 2
AI summary
There is provided a spark plug which exhibits improved resistance to high-temperature oxidation of an electrode, and improved resistance to spark-induced erosion of, improved resistance to oxidation of, and improved joining reliability of a tip joined to the electrode. A spark plug (1) has spark members (31) and (41); each of the spark members (31) and (41) has a weight of 1.5 mg or more; and a center electrode (5) and a ground electrode (27) contain Ni as a main component, C in an amount of 0.005% by mass to 0.10% by mass, Si in an amount of 1.05% by mass to 3.0% by mass, Mn in an amount of 2.0% by mass or less, Cr in an amount of 20% by mass to 32% by mass, and Fe in an amount of 6% by mass to 16% by mass.