Spark Plug Metal Shell Crimp Portion Grain Size Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The challenge is to enhance the strength of a metal shell in spark plugs while maintaining workability, especially when reduced in diameter and thickness, to ensure sufficient crimping force for air tightness without increasing carbon content.
Innovation Solution
A spark plug design featuring a metal shell with a crimp portion made of carbon steel material having a grain size number equal to or greater than No. 11, with a mean lineal grain length of 0.01 mm or smaller and an intercepted grain number greater than or equal to 200, ensuring higher strength and improved workability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the metal shell is made small in diameter and thickness to reduce spark plug size, then the spark plug diameter is reduced for improved engine layout flexibility, but the crimp portion strength deteriorates and cannot be crimped with sufficient force to ensure air tightness
Solution Approach 1:
The invention changes the material parameters of the crimp portion by increasing carbon content to 0.15-0.30% and controlling alloying elements (Mn: 0.50-1.50%, Si: 0.10-0.50%, Cr: 0.10-0.50%, Mo: 0.05-0.20%, B: 0.0005-0.0050%) to achieve high strength in a thin-walled metal shell while maintaining small spark plug dimensions
Solution Approach 2:
The invention uses a composite material approach by combining carbon steel with specific alloying elements (Mn, Si, Cr, Mo, B) to create a metal shell material that achieves both high strength and small size, where the synergistic effect of multiple elements provides the necessary crimp portion strength in a reduced-diameter structure
2Strength
If the carbon content of the steel material is increased to increase the strength of the metal shell, then the strength of the steel material increases, but the steel material becomes more difficult to deform and deteriorates in workability
Solution Approach 1:
The invention optimizes the carbon content parameter to a specific range (0.15-0.30%) that provides high strength while maintaining workability, and balances multiple alloying element parameters (Mn, Si, Cr, Mo, B) to achieve both strength and deformability for successful crimping operations
Solution Approach 2:
The invention applies different material properties to different parts of the metal shell by making the crimp portion (rear end) with higher carbon content (0.15-0.30%) for strength, while the front end portion has lower carbon content (0.05-0.10%) for better workability and ease of manufacture
Data Source
AI summary
A spark plug includes an insulator having an axial hole formed therethrough in the direction of an axis of the spark plug, a center electrode disposed in a front side of the axial hole and a metal shell disposed around an outer circumference of the insulator and having a collar-shaped tool engagement portion and a crimp portion located on a rear side of the tool engagement portion and reduced in diameter toward the rear, wherein the crimp portion of the metal shell is made of a carbon steel material having a grain size number equal to or greater than No. 11 as measured according to JIS G 0551.