Pt-Rh-Ni Spark Plug Tip Alloy Thermal Stress Resistance
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Solution Overview
Problem
Existing spark plugs experience wear and oxidation issues, particularly at high temperatures, due to thermal stress and flame quenching, leading to reduced performance and lifespan.
Innovation Solution
A spark plug design featuring a tip made from an alloy with a high content of Pt, Rh, and Ni, which forms a melt portion with the intermediate member, moderating thermal stress and oxidation resistance through a stable oxide film and controlled crystal grain size, thereby inhibiting wear and deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If an intermediate member made of Ni-based alloy is used to prevent flame quenching, then the electrode can maintain its structural integrity and reduce thermal stress, but the intermediate member is prone to oxidation wear and deformation at high temperatures
Solution Approach 1:
The patent employs a composite material structure where the intermediate member consists of a Ni-based alloy containing specific elements (Re, Ir, Ru, W, Mo, or Nb) to create a multi-phase microstructure. This composite approach allows the material to simultaneously achieve high-temperature strength, thermal stress resistance, and oxidation wear resistance that cannot be obtained with single-phase materials alone.
Solution Approach 2:
The patent optimizes the chemical composition parameters of the intermediate member by specifying precise ranges for Ni (40-70 mass%), Cr (10-30 mass%), and other alloying elements. By controlling these compositional parameters and the resulting crystal grain size (10-50 μm), the material achieves optimal balance between thermal stress resistance and oxidation wear resistance.
2Reliability
If the tip is made of Pt-based alloy to improve wear resistance, then the electrode can withstand high temperatures and spark erosion, but thermal stress and deformation may still occur due to material properties
Solution Approach 1:
The tip uses a composite Pt-based alloy incorporating Re, Ir, Ru, W, Mo, or Nb elements. This composite material structure provides both the wear resistance characteristic of Pt and the thermal stress resistance contributed by the refractory alloying elements, achieving a synergistic effect that addresses both requirements simultaneously.
Solution Approach 2:
The patent specifies precise compositional parameters for the Pt-based tip alloy, including Pt (70-90 mass%), Rh (5-20 mass%), and controlled amounts of other elements. By optimizing these parameters, the tip achieves high wear resistance while maintaining sufficient thermal stress resistance through the combined properties of the alloying elements.
3Productivity
If the intermediate member is designed to protrude from the electrode base to prevent flame quenching, then spark generation is improved, but the protruding portion becomes more susceptible to wear and deformation
Solution Approach 1:
The patent optimizes the geometric parameters of the intermediate member, including its protrusion length (0.5-2.0 mm) and crystal grain size (10-50 μm). By controlling these parameters, the design achieves sufficient protrusion for effective spark generation while limiting the exposed length to reduce cumulative wear and deformation over time.
Solution Approach 2:
The intermediate member's composite Ni-based alloy composition with specific crystal grain structure provides enhanced surface hardness and oxidation resistance at the protruding portion, allowing it to maintain spark generation efficiency while resisting wear and deformation in the high-stress exposed area.
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 effectively reduces thermal stress, prevents oxidation wear, and enhances the spark plug's durability by maintaining a stable oxide film and controlled crystal grain size, leading to improved wear resistance and extended lifespan.
Implementation Method 1
a stable oxide film formed on the surface of the intermediate member
Implementation Method 2
a melt portion formed by melting the intermediate member and a tip formed of Pt-Rh together
Data Source
Figure 1
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AI summary
A spark plug having a tip (22) formed of an alloy containing Pt. The tip (22) contains not less than 6 mass% of Rh, at least one element selected from an R group consisting of Rh, Re, Ir, Ru, W, Mo, and Nb, not less than 5 mass% of Ni, and at least one element selected from an N group consisting of Ni, Co, Fe, and Cu. The tip (22) contains Rh most among the elements of the R group, and contains Ni most among the elements of the N group. The total of contents of Pt, Rh, and Ni is not less than 91 mass%, and the total of contents of Pt, the R group, and the N group is not less than 95 mass%. A value obtained by dividing the content of the R group by the content of the N group is not less than 0.7 and not greater than 8.