Spark Plug Electrode Manufacturing Using MIM Composite Parts
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Solution Overview
Problem
The high cost of using precious metal alloys like iridium for spark plug electrodes limits the cost-effectiveness of spark plug manufacturing, and the welding of these alloys to base-metal sections can be problematic due to thermal expansion differences.
Innovation Solution
The use of metal injection molded (MIM) composite parts with a base metal or alloy core and a precious metal or alloy coating, where the coating is applied selectively to the spark gap surface and forms islands to enhance ignition, and the core is welded to the base-metal section without the coating, creating a positive mechanical interlock and metallurgical bond.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If precious metal alloys like iridium are used for spark plug electrodes, then the service life of spark plugs is extended, but the manufacturing cost increases significantly
Solution Approach 1:
The patent applies local quality by coating only the spark gap surface of the electrode core with precious metal, while leaving other surfaces uncoated. This selective coating ensures that precious metal is present where it is most needed for extending service life (at the spark gap), while reducing overall precious metal usage and manufacturing cost.
Solution Approach 2:
The patent uses composite materials by combining a base metal core (such as nickel or iron) with a precious metal coating (such as iridium or platinum). This composite structure provides the mechanical strength and electrical conductivity of the base metal core, along with the durability and spark performance of the precious metal coating, thereby extending service life while reducing cost compared to using solid precious metal throughout.
2Ease of manufacture
If precious metal alloys are welded to base-metal sections, then the electrode structure is formed, but thermal expansion differences cause welding problems
Solution Approach 1:
The patent uses the base metal core as an intermediary between the welding process and the precious metal coating. The base metal core is welded to the spark plug body, and then the precious metal is coated onto the core. This intermediary approach avoids direct welding of precious metal to the spark plug body, eliminating thermal expansion mismatch issues during welding while still achieving a reliable electrode structure.
3Duration of action of stationary object
If the entire electrode is made of precious metal, then service life is maximized, but the amount of precious metal required is excessive
Solution Approach 1:
The patent applies local quality by coating only the spark gap surface of the electrode core with precious metal, while leaving other surfaces uncoated. This selective coating ensures that precious metal is present where it is most needed for extending service life (at the spark gap), while reducing overall precious metal usage and manufacturing cost.
Solution Approach 2:
The patent applies partial action by coating only the necessary portion of the electrode (the spark gap surface) with precious metal, rather than coating the entire electrode. This partial coating provides sufficient precious metal where it is most needed for durability and spark performance, while significantly reducing the total quantity of precious metal required.
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
This approach reduces the amount of precious metal required, minimizes thermal expansion issues during welding, and maintains or improves the service life of spark plugs by forming intermetallic compounds that enhance bonding.
Implementation Method 1
The plurality of islands are located at least partially in a plurality of pores formed in the base metal or the base metal alloy and project above the base metal or the base metal alloy at the surface so as to promote ignition sparks according to a point effect
Implementation Method 2
the precious metal-based coating connected to the nickel-based electrode core by both a positive mechanical interlock and a metallurgical bond
Implementation Method 3
the precious metal-based coating connected to the nickel-based electrode core by both a positive mechanical interlock and a metallurgical bond
Implementation Method 4
sintering the debound and coated core to form a composite part
Implementation Method 5
forming intermetallic compounds that enhance bonding
Data Source
AI summary
A method for manufacturing an ignition electrode for spark plugs for internal combustion engines and spark plug manufactured therewith. The method includes producing by powder metallurgy a green part or brown part containing the base metal or the base metal alloy, coating of a part of the surface of the green part or brown part with a mixture that contains the precious metal or the precious metal alloy in the form of a powder and a binder, removing the binder from the layer that was formed by the coating and that contains the precious metal or the precious metal alloy, and sintering the coated green part or brown part to form a composite part. The composite part can be welded as an end piece to the one end of the base-metal section of the ignition electrode.