Spark Plug Electrode Tip IrAl Cover Layer Bonding
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Solution Overview
Problem
There is a lack of sufficient studies on the application of IrAl intermetallic compound materials to electrode tips in spark plugs, leading to difficulties in ensuring separation resistance between the electrode tip and the electrode body.
Innovation Solution
A spark plug design featuring an electrode tip with a cover layer of IrAl intermetallic compound, where the tip body is bonded to the electrode body via a welded portion with a specific area ratio, enhancing the separation resistance by ensuring a large bonding area and minimizing deformation and brittleness in the welded portion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If an electrode tip formed of noble metal is bonded to an electrode body to improve wear resistance, then wear resistance is improved, but separation resistance between the electrode tip and electrode body deteriorates
Solution Approach 1:
The electrode tip is constructed as a composite structure with a tip body made of noble metal (iridium or iridium alloy) and a cover layer made of IrAl intermetallic compound. This composite structure combines the wear resistance of noble metal with the bonding compatibility of IrAl intermetallic compound, allowing both wear resistance and separation resistance to be improved simultaneously.
Solution Approach 2:
The invention changes the material parameter of the cover layer to IrAl intermetallic compound with specific thickness (5 μm to 50 μm). This parameter change enables the cover layer to form a welded portion with the nickel-based electrode body that has adequate bonding area, thereby improving separation resistance while maintaining the wear resistance provided by the noble metal tip body.
2Reliability
If a cover layer of IrAl intermetallic compound is formed on the electrode tip, then high-temperature oxidation resistance is improved, but bonding strength with the electrode body deteriorates due to insufficient bonding area
Solution Approach 1:
The invention optimizes the thickness parameter of the IrAl intermetallic compound cover layer to be between 5 μm and 50 μm. This parameter range ensures that the cover layer is thin enough to allow adequate bonding between the tip body and electrode body (achieving bonding area ratio of 35% or more), while still providing sufficient high-temperature oxidation resistance.
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 design significantly improves the separation resistance of the electrode tip by ensuring a substantial bonding area and reducing the likelihood of deformation and brittleness in the welded portion, thereby enhancing the durability and performance of the spark plug.
Implementation Method 1
a welded portion formed between the electrode body and the electrode tip and containing a component of the electrode body and a component of the electrode tip
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
At least one of a center electrode and a ground electrode of a spark plug includes an electrode body, an electrode tip, and a welded portion formed between the electrode body and the electrode tip. The electrode tip includes a cover layer that covers at least a side surface of a tip body, and the cover layer is formed of IrAl. On a section formed by cutting the electrode tip near a boundary with the welded portion, an area of the tip body is represented by Sa. An area of a projection on the section of a non-contact portion of an opposite surface of the tip body not in contact with the welded portion is represented by Sb. In this case, Sa - Sb corresponds to 35% or more of Sa.