Spark Plug Intermediate Member Corrosion Resistance
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Solution Overview
Problem
The durability and corrosion resistance of spark plugs with a noble metal tip attached via an intermediate member, particularly in the vicinity of the discharge gap, are compromised due to corrosion from cooling-heating cycles, affecting both ground and center electrodes.
Innovation Solution
Incorporating a nickel alloy intermediate member with specific compositions of chromium, silicon, and aluminum, and optimizing the surface area ratios and dimensions of the tip-bonding and electrode-bonding portions to enhance corrosion resistance and heat transfer, thereby reducing metal diffusion and temperature elevation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If an intermediate member is provided between the ground electrode and noble metal tip, then the amount of noble metal employed can be reduced and a sufficient distance can be secured between the ground electrode and the discharge gap, but the intermediate member may corrode to an unacceptable extent when employed for a long period of time, particularly due to cooling-heating cycles
Solution Approach 1:
The invention changes the chemical composition parameters of the intermediate member by specifying precise ranges for chromium (15-25 wt.%), silicon (0.03-0.06 mg/mm³), and aluminum (0.03-0.06 mg/mm³) content. These parameter changes create a material with optimized corrosion resistance while maintaining electrical conductivity and structural integrity under thermal cycling conditions.
Solution Approach 2:
The invention employs a composite material approach by creating a multi-element alloy system (nickel-chromium-silicon-aluminum) that combines the beneficial properties of each element: nickel provides base strength and conductivity, chromium provides corrosion resistance, silicon and aluminum provide surface oxidation resistance. This composite material structure resolves the contradiction between using less noble metal and maintaining durability.
2Reliability
If the intermediate member contains nickel as a main component with chromium, silicon, and aluminum, then corrosion resistance is improved, but the structural complexity and manufacturing precision requirements increase
Solution Approach 1:
The invention establishes specific parameter ranges for each alloying element to achieve the desired corrosion resistance. By defining chromium at 15-25 wt.%, silicon at 0.03-0.06 mg/mm³, and aluminum at 0.03-0.06 mg/mm³, the patent creates a manufacturable specification that balances performance requirements with production feasibility, reducing the need for extreme precision while maintaining effectiveness.
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 improved intermediate member design significantly enhances the durability and corrosion resistance of the spark plug, preventing deterioration and maintaining performance even under repeated cooling-heating cycles.
Implementation Method 1
heat transfer, thereby reducing metal diffusion and temperature elevation
Implementation Method 2
corrosion resistance, and the spark plug, which includes the intermediate member, also exhibits improved durability and corrosion resistance
Data Source
Figure 1
Figure 2
Figure 3(A)~4
AI summary
A spark plug including a center electrode; an insulator; a metallic shell; and a ground electrode, wherein at least one of the center electrode and the ground electrode has thereon an intermediate member which connects the center electrode or the ground electrode to a noble metal tip. The intermediate member has a tip-bonding portion to which the noble metal tip is bonded, and an electrode-bonding portion which has a diameter greater than that of the tip-bonding portion, and which is bonded to the center electrode or the ground electrode. The intermediate member contains nickel (Ni) as a main component, and also contains chromium (Cr) in an amount of 15 to 25 wt.%. The intermediate member contains, in a surface portion thereof, silicon (Si) in an amount per unit volume of 0.04 mg/mm3 to 0.12 mg/mm3, and aluminum (Al) in an amount per unit volume of 0.03 mg/mm3 to 0.10 mg/mm3.