Pd-Ir Alloy Spark Plug Electrode Tip Composition
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Solution Overview
Problem
Palladium (Pd) electrode tips in spark plugs suffer from low reliability due to lower melting point and susceptibility to spark-induced erosion, grain growth, and cracking at high combustion chamber temperatures, leading to separation and cracking issues.
Innovation Solution
A spark plug electrode tip composition with Pd as the main component (>40% by weight) combined with iridium (Ir), nickel (Ni), cobalt (Co), and iron (Fe) in specific weight percentages, along with optional titanium (Ti), zirconium (Zr), hafnium (Hf), and rare earth elements, to enhance resistance to spark-induced erosion and prevent separation and cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Pd is used as electrode tip material, then cost is reduced compared to Pt, but resistance to spark-induced erosion deteriorates
Solution Approach 1:
The patent applies composite materials by combining Pd with Ir, Ni, Co, and Fe to create an alloy electrode tip. This composite structure leverages the high erosion resistance of Ir and the cost-effectiveness of Pd, achieving both economic and performance goals. The specific composition ranges (Pd: 40-90%, Ir: 0.5-20%, Ni: 0.5-40%, Co: 0.5-40%, Fe: 0.5-40%) are optimized to balance cost and erosion resistance.
2Quantity of substance
If Pd is used as electrode tip material, then cost is reduced compared to Pt, but reliability deteriorates due to grain growth and cracking
Solution Approach 1:
The patent applies parameter changes by carefully controlling the composition parameters of the alloy. By adjusting the ratios of Pd, Ir, Ni, Co, and Fe within specific ranges, the material's microstructure and grain growth characteristics are modified. The presence of Ir and other alloying elements restrains grain growth at high temperatures, preventing cracking while maintaining cost advantages over pure Pt.
3Quantity of substance
If Pd is used as electrode tip material, then melting point is lower than Pt, but this leads to separation and cracking at high temperature
Solution Approach 1:
The patent uses composite materials to address the melting point issue. By creating a Pd-based alloy with Ir, Ni, Co, and Fe, the overall thermal stability is enhanced. Ir, in particular, contributes to raising the effective melting point and thermal resistance of the electrode tip, allowing it to withstand combustion chamber temperatures without separation or cracking while keeping costs lower than pure Pt.
Data Source
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AI summary
A spark plug 100 has a center electrode tip 90, 95 at an end portion of an electrode. The electrode tip 90, 95 contains Pd as a main component in an amount greater than 40% by weight and contains at least one element of Ir, Ni, Co, and Fe such that Ir, if contained, is contained in an amount of 0.5% by weight to 20% by weight inclusive and at least one element of Ni, Co, and Fe, if contained, is contained in an amount of 0.5% by weight to 40% by weight inclusive on an element basis.