Porous Ru Electrode Tips for Vibration-Resistant Spark Plugs
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Solution Overview
Problem
Spark plugs with Ru or Ru alloy tips suffer from cracking due to lack of ductility under engine vibration.
Innovation Solution
The spark plug design incorporates Ru tips with a porosity of 0.1 ppm to 100000 ppm, hydrogen content of 0.1 ppm to 4 ppm, and Pt content of 0.1% to 30%, along with a Vickers hardness of 190 HV, to reduce stress and prevent cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a tip made simply of Ru or Ru alloy is used, then the tip has high durability and resistance to thermal expansion, but the tip lacks ductility and may crack due to engine vibration
Solution Approach 1:
The tip is constructed as a composite material combining Ru (providing durability and thermal expansion resistance) with other metals or alloys (providing ductility and crack resistance). This composite structure allows the tip to simultaneously achieve high durability and adequate ductility to withstand engine vibrations without cracking.
Solution Approach 2:
The chemical composition parameters of the tip material are modified by adding specific elements or alloys to the Ru base material. This changes the material properties to achieve an optimal balance between durability and ductility, preventing crack formation while maintaining resistance to thermal expansion.
2Strength
If the tip porosity is increased to reduce stress and prevent cracking, then the tip ductility improves, but the structural integrity may be compromised
Solution Approach 1:
The tip is designed with a controlled porous structure where pores are intentionally introduced at specific levels (0.1-100000 ppm) to reduce stress concentration and improve ductility. The porous structure acts as stress relief zones that prevent crack propagation while maintaining sufficient structural integrity for spark plug operation.
Solution Approach 2:
The porosity parameter is precisely controlled within the range of 0.1-100000 ppm to achieve the optimal balance between stress reduction and structural integrity. This parameter optimization allows the tip to have adequate ductility to prevent cracking while maintaining the strength needed for reliable operation.
Data Source
AI summary
A spark plug includes an insulator that has an axial hole extending along an axial line; a center electrode that is disposed in the axial hole; a metal shell that is disposed at an outer periphery of the insulator; and a ground electrode that is connected to the metal shell. At least one of the center electrode and the ground electrode has a tip whose main component is Ru, and a porosity of the tip is greater than or equal to 0.1 ppm and less than or equal to 100000 ppm.