Platinum Alloy Spark Plug Electrode CTE Matching
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Solution Overview
Problem
Current platinum alloys used in spark plug electrodes are expensive due to high platinum content and fail to effectively match the coefficient of thermal expansion (CTE) of nickel-based electrodes, leading to thermal stress and wear, especially in oxidizing conditions at elevated temperatures.
Innovation Solution
A platinum-based alloy with 20-35% palladium and up to 15% iridium, with the balance being platinum, is used to reduce platinum content while maintaining a CTE close to nickel, thereby minimizing thermal expansion rate stresses and providing cost-effectiveness and oxidation resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high percentage platinum content is used in the alloy, then oxidation resistance and electrode durability are improved, but cost increases significantly
Solution Approach 1:
The patent changes the compositional parameters of the alloy by reducing platinum content from traditional high percentages (90-95%) to a lower range (5-40%), while compensating with other precious metals like palladium (10-60%) and iridium (5-30%) to maintain the required oxidation resistance and mechanical properties
Solution Approach 2:
The patent creates a composite precious metal alloy system combining platinum with palladium and iridium, where each metal contributes specific properties: platinum provides oxidation resistance, palladium reduces cost and improves CTE matching, and iridium enhances strength and thermal stability
2Quantity of substance
If platinum content is reduced to lower cost, then manufacturing cost decreases, but oxidation resistance and electrode durability worsen
Solution Approach 1:
The patent adjusts the alloy composition parameters to include palladium (10-60%) and iridium (5-30%) in specific ranges that compensate for reduced platinum, maintaining oxidation resistance while achieving cost reduction through optimized metal ratios
Solution Approach 2:
The patent substitutes expensive platinum with relatively cheaper palladium and iridium metals that can provide similar or superior performance characteristics, effectively replacing high-cost material with lower-cost alternatives that meet the same functional requirements
3Stability of the object's composition
If nickel content is increased to match CTE of nickel base electrode, then thermal expansion matching is improved, but thermal stress at weld junction increases under severe thermal conditions
Solution Approach 1:
The patent creates a multi-metal composite alloy where palladium and iridium are combined with platinum and nickel to achieve a balanced CTE that matches the nickel base electrode while the iridium component provides thermal stability and strength to reduce thermal stress at the weld junction
Solution Approach 2:
The patent optimizes the local composition at the weld junction area by including iridium (5-30%) which provides localized strength and thermal stability, allowing the alloy to better withstand thermal stresses at the critical weld interface between the precious metal enhancement and nickel base 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 alloy reduces the cost of spark plug electrodes while maintaining durability and thermal expansion matching, thus extending the lifespan of spark plugs by minimizing thermal stress and wear.
Implementation Method 1
the platinum alloy should include metals that help reduce thermal stress on the weld junction between the precious metal and the nickel alloy base electrode. Current platinum alloys have 10% nickel to better match the coefficient of thermal expansion (CTE) of the nickel base electrode
Data Source
AI summary
A spark plug and an alloy for an electrode tip of a spark plug is disclosed herein. The spark plug having: an insulator shell; a center electrode inside the insulator shell such that one end of the center electrode protrudes from the insulator shell; a metal shell exterior to the insulator shell; a side ground electrode having one end coupled to the metal shell and the other end facing the protruding end of the center electrode to form a spark discharge gap between the center electrode and the side ground electrode; and an electrode tip secured to at least one of the side ground electrode or the center electrode, located at the spark discharge gap, the electrode tip comprising a platinum-based alloy comprising 20 to 35% by weight of palladium, from greater than 0 to 15% by weight iridium, and the balance of the alloy being platinum, all % by weight being based on the total weight of the alloy.