Spark Plug Ground Electrode Inclined Surface Design
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Solution Overview
Problem
Spark plugs face challenges in maintaining ignitability and durability, especially in lean fuel and supercharged internal combustion engines, where existing designs struggle to ensure reliable ignition and prevent flame quenching.
Innovation Solution
A spark plug design featuring a ground electrode with an inclined surface where a noble metal tip is buried, allowing for increased ignitability by reducing flame quenching and enhancing durability through specific geometric configurations and welding techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If a noble metal tip protrudes from the end of the ground electrode, then the sparking location can be concentrated and durability can be increased, but flame quenching occurs and ignitability decreases
Solution Approach 1:
The patent applies local quality by creating an inclined surface at a specific location on the ground electrode where the noble metal tip is joined. This inclined surface is positioned at the distal end of the ground electrode, forming a localized region with different geometric properties (inclined rather than flat) that prevents flame quenching while maintaining the durability benefits of the protruding noble metal tip.
2Ease of manufacture
If the ground electrode has a flat distal end surface, then manufacturing is simple, but flame kernel growth is hampered and ignitability decreases
Solution Approach 1:
The patent applies asymmetry by replacing the conventional flat distal end surface of the ground electrode with an inclined surface. This asymmetric geometry creates a favorable orientation for flame kernel development, allowing the flame to propagate more effectively away from the electrode surface and preventing flame quenching, thereby improving ignitability.
3Stability of the object's composition
If the noble metal tip is joined flush with the ground electrode surface, then structural integrity is maintained, but the tip may fall off and durability decreases
Solution Approach 1:
The patent applies the nesting principle by having the noble metal tip partially embedded in the ground electrode at the inclined surface. The tip is joined such that it is nested within the ground electrode structure, with part of the tip buried in the inclined surface. This nesting configuration provides mechanical anchoring that prevents tip fallout while maintaining structural integrity.
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 effectively increases ignitability and durability by suppressing flame quenching and preventing noble metal tip fallout, as demonstrated by improved limit air/fuel ratios and anti-peeling performance in various tests.
Implementation Method 1
since the ground electrode has the inclined surface, the hampering of the growth of a flame kernel produced by a discharge between the center electrode and the noble metal tip (flame quenching) can be suppressed
Implementation Method 2
A noble metal tip is joined to the inclined surface such that part of the noble metal tip is buried in the inclined surface
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
A spark plug (100) includes an insulator (10) having an axial hole (12) along an axial line (O); a center electrode (20) that is provided in the axial hole (12); a cylindrical metal shell (50) that is disposed around an outer periphery of the insulator (10); and a ground electrode (30) whose base end is fixed to the metal shell (50). A distal end portion (33) of the ground electrode (30) includes a first surface (34) that faces a side of the center electrode (20), a second surface (37) that faces a side that is opposite to the first surface (34), and an inclined surface (36) that is formed continuously with a distal end of the first surface (34) and is inclined with respect to the second surface (37) such that a thickness of the ground electrode (30) decreases towards a distal end side of the ground electrode (30). A noble metal tip (31) is joined to the inclined surface (36) such that part of the noble metal tip (31) is buried in the inclined surface (36). A width (D) of the inclined surface (36) is larger than a width (G) of the noble metal tip (31). When a distance from a distal end of the ground electrode (30) to a proximal-end-side end portion of the inclined surface (36) is A and a distance from the distal end of the ground electrode (30) to a proximal-end-side end portion of the noble metal (31) tip is B, A ≥ B.