Spark Plug Packing for Uniform Insulator Gap
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Solution Overview
Problem
The reduction in spark plug diameter leads to increased likelihood of lateral sparking, resulting in misfires due to reduced distance between the metallic shell and insulator, causing discharge between the metallic shell and insulator.
Innovation Solution
A spark plug design featuring a tubular insulator with a leg portion and step portion, a metallic shell with cutting traces, and a packing system that ensures uniform gap between the inner and outer surfaces, preventing eccentricity and thus restraining lateral sparking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the diameter of the spark plug is reduced, then the design requirements of the internal combustion engine are met, but the distance between the metallic shell and insulator decreases, causing lateral sparking
Solution Approach 1:
A packing member is introduced as an intermediary element between the metallic shell and the insulator. This packing fills the gap created by reduced spark plug diameter, maintaining adequate spacing to prevent lateral sparking while allowing the overall spark plug diameter to be reduced to meet engine design requirements.
Solution Approach 2:
The packing is strategically placed only at specific locations where lateral sparking is most likely to occur (between the metallic shell and insulator), rather than uniformly throughout the entire spark plug structure. This localized approach prevents lateral sparking while minimizing impact on overall spark plug dimensions.
2Length of stationary object
If the distance between metallic shell and insulator is reduced, then the spark plug diameter can be smaller, but discharge between metallic shell and insulator occurs
Solution Approach 1:
The packing member serves as a dielectric intermediary between the conductive metallic shell and the insulator, preventing direct electrical discharge. It maintains electrical isolation while allowing the mechanical distance to be reduced, thus enabling smaller spark plug diameter without causing lateral sparking.
Solution Approach 2:
The packing is pre-installed between the metallic shell and insulator to cushion and prevent potential electrical discharge before it can occur. This preventive measure ensures that even when the distance is reduced, lateral sparking is blocked in advance.
Data Source
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AI summary
In a metallic shell 20, cutting traces are formed on the inner circumferential surface 30 of a trunk portion 26 and the inner circumferential surface 32 of an elongated leg portion 28. A first portion 61 of a packing 60 is in contact with and disposed between the rear end surface 31 of a ledge portion 27 of the metallic shell and the outer circumferential surface 57 of a step portion 54 of an insulator 50. A second portion 62 of the packing is in contact with and disposed between the inner circumferential surface of a trunk portion of the metallic shell and the outer circumferential surface 56 of a tubular portion 53 of the insulator. A gap between the inner circumferential surface of the elongated leg portion and the outer circumferential surface 58 of the leg portion 55 is approximately uniform along the entire circumference.