Spark Plug Insulator Mullite Inner Surface Thermal Expansion
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Solution Overview
Problem
Spark plug insulators are prone to breakage due to thermal expansion, which affects their durability and voltage endurance, making them less suitable for advanced internal combustion engines that require improved performance and fuel efficiency.
Innovation Solution
Incorporating mullite into the inner circumferential surface of the spark plug insulator, particularly in areas prone to higher temperatures, while maintaining alumina on the outer surface for higher voltage endurance, reduces the likelihood of breakage without compromising performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the through hole of the insulator contracts due to thermal expansion, then the insulator structure becomes more stable, but the insulator breaks due to contact with the central electrode
Solution Approach 1:
The patent applies the thermal expansion principle by selecting mullite material for the inner circumferential surface that has a coefficient of thermal expansion smaller than alumina. This prevents excessive contraction of the through hole during temperature cycles, maintaining clearance between the central electrode and insulator inner surface, thereby preventing breakage while preserving thermal stability.
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 configuration enhances the insulator's thermal stability and voltage endurance, making it less breakable and more suitable for high-performance internal combustion engines without impairing its electrical properties.
Implementation Method 1
mullite, having a coefficient of thermal expansion smaller than that of alumina. This configuration can thus prevent the through hole of the insulator from contracting due to thermal expansion of the insulator in response to a temperature rise of a distal portion of the insulator
Data Source
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AI summary
An insulator is rendered less breakable. A spark plug insulator is a tube-shaped spark plug insulator having a through hole extending in a direction of an axial line. The spark plug insulator contains alumina as a main component and mullite at at least part of the insulator. Mullite is contained in only an inner circumferential surface of the tube-shaped spark plug insulator and in at least part of the inner circumferential surface of the spark plug insulator in an area extending toward a distal end from a portion having a largest outer diameter.