Spark Plug Stepped Metal Shell Insulator Airtightness
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Solution Overview
Problem
Existing spark plug technologies face challenges in maintaining airtightness between the metal shell and insulator without excessively increasing the load, which can lead to insulator cracking due to excessive deformation of the packing material.
Innovation Solution
A spark plug design featuring a metal shell with a stepped portion that includes a first convex portion, a second convex portion, and a connection portion, where the connection portion is positioned to allow for elastic deformation and distribute load effectively, reducing the need for additional packing and minimizing the risk of insulator cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a load that the metal shell and the insulator apply to the packing is increased to improve airtightness, then the airtightness is increased, but the excessively deformed packing strongly compresses the insulator causing it to break
Solution Approach 1:
The stepped portion is divided into multiple convex portions (first convex portion, second convex portion, third convex portion) with connection portions between them. This segmentation allows the structure to distribute the compressive load across multiple segments, preventing excessive deformation of any single packing region and reducing the risk of insulator cracking while maintaining airtightness.
Solution Approach 2:
Different convex portions are designed with different dimensions and positions to create localized variations in packing compression. The first convex portion has a larger diameter than the second, and the third has a smaller diameter, creating a gradient compression pattern that optimizes airtightness at different locations while preventing excessive stress concentration that would damage the insulator.
2Strength
If the shape of a gap between the metal shell and the insulator is adjusted to suppress excessive deformation of the packing, then occurrence of cracking of the insulator is suppressed, but airtightness may be compromised
Solution Approach 1:
The stepped portion creates multiple segmented gaps between convex portions, each with controlled dimensions. The connection portions bridge these gaps while maintaining packing compression, ensuring airtightness is achieved across the entire interface without requiring excessive gap adjustment that would cause insulator cracking.
Solution Approach 2:
The connection portions act as intermediary elements between the convex portions, providing a transition zone that maintains packing compression and ensures airtightness while preventing excessive stress transmission to the insulator. The connection portions mediate between the need for airtightness and the need to protect the insulator from excessive deformation.
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 ensures airtightness between the metal shell and insulator while preventing insulator cracking by utilizing elastic deformation to apply opposing forces, reducing the number of components and minimizing buckling risks, thus enhancing the overall performance and reliability of the spark plug.
Implementation Method 1
a tensile stress is produced at the first convex portion along the rear-end-side facing surface, and a compression stress is produced at the first convex portion along a connection-portion-side surface adjacent to the second convex portion. As a result, it is possible to closely contact the rear-end-side facing surface with the insulator either directly or via the other member by an opposing force that is produced by elastic deformation of the first convex portion.
Data Source
AI summary
A spark plug having a metal shell and an insulator, wherein a stepped portion that includes a rear-end-side facing surface that retains an insulator either directly or via another member is provided at an inner periphery of a metal shell. The stepped portion includes a first convex portion that includes the rear-end-side facing surface, a second convex portion that is disposed on a front end side of the first convex portion and that is adjacent to the first convex portion, and a connection portion that connects the first convex portion and the second convex portion to each other.