Spark Plug Packing Hardness for Crimp Alignment
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Solution Overview
Problem
Conventional spark plugs face challenges in maintaining airtightness and alignment between center and ground electrodes, especially in smaller diameters, due to deformation of low-hardness packings during crimping, leading to eccentricity and reduced ignitability.
Innovation Solution
A spark plug design with an annular packing having a hardness greater than or equal to the metal shell's stepped portion, typically not less than 300 Hv, to minimize packing deformation and ensure proper alignment, while allowing for correction of off-centered assembly states during crimping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a low-hardness plate packing is used to ensure airtightness through deformation, then the packing can be brought into close contact with the metal shell and insulator, but the packing is deformed nonuniformly during crimping, causing eccentricity and alignment deterioration
Solution Approach 1:
The patent changes the key parameter of the packing from low hardness to high hardness (not less than 300 Hv). This parameter change allows the packing to resist deformation during crimping while still achieving adequate contact, thereby preventing nonuniform deformation and maintaining alignment precision without sacrificing airtightness
Solution Approach 2:
The patent applies different hardness requirements to different components: the packing is made with high hardness (not less than 300 Hv) to resist deformation, while the metal shell maintains its structural integrity. This local differentiation of material properties allows the packing to maintain its shape and positioning function during crimping
2Volume of moving object
If a small-diameter spark plug is fabricated to achieve miniaturization, then the spark plug size is reduced, but the wall thickness of the metal shell becomes thin, causing the stepped portion to become excessively deformed under crimping load
Solution Approach 1:
The patent changes the hardness parameter of the packing to be not less than 300 Hv, making it harder than conventional packings. This allows the packing to serve as a rigid positioning element that prevents the thin-walled metal shell from deforming excessively during crimping, thereby maintaining manufacturing precision in miniaturized spark plugs
Solution Approach 2:
The high-hardness packing acts as an intermediary element between the insulator and the thin-walled metal shell. During crimping, this packing maintains its shape and provides a stable interface, preventing the transfer of excessive deformation to the metal shell and insulator assembly
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 design maintains airtightness and improves alignment between electrodes, reducing eccentricity and enhancing ignitability, particularly in smaller diameter spark plugs where misalignment effects are greater.
Implementation Method 1
When the metal shell is crimped as described above, the plate packing undergoes crush deformation and assumes a state in which it is in close contact with both the metal shell and the insulator
Implementation Method 2
the packing has a hardness greater than or equal to a hardness of the stepped portion of the metal shell, or has a Vickers hardness of not less than 300 Hv
Data Source
Figure 1
Figure 2
AI summary
A spark plug including a center electrode; an insulator; a metal shell; a ground electrode; and an annular packing, all as defined herein, wherein the packing has a hardness greater than or equal to a hardness of the stepped portion of the metal shell or has a Vickers hardness of not less than 300 Hv. Preferably, a difference between the hardness of the packing and the hardness of the stepped portion of the metal shell is from 120 Hv to 160 Hv, and the packing has a Vickers hardness of not more than 500 Hv.