Ru-Chip Spark Plug Structure for Thermal Stress Crack Resistance
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Solution Overview
Problem
The mechanical strength of spark plugs containing Ru decreases due to thermal stress, leading to potential chip cracks.
Innovation Solution
The spark plug design includes an insulator, center electrode, and ground electrode with Ru-containing chips, where the average crystal grain diameter is between 1 μm and 50 μm, and the aspect ratio is between 0.8 and 2.0, ensuring the chip's mechanical strength and reducing crack generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Ru is used as the main constituent of the chip, then electrical conductivity and anti-corrosion properties are improved, but mechanical strength decreases and cracks may be generated by thermal stress
Solution Approach 1:
The invention changes the physical parameters of the Ru-containing chip by controlling the average crystal grain diameter to be 1 μm or more and 50 μm or less, and the aspect ratio to be 0.8 or more and 2.0 or less. This parameter optimization resolves the contradiction by maintaining the electrical conductivity and anti-corrosion properties of Ru while improving mechanical strength and crack resistance through refined grain structure.
Solution Approach 2:
The invention uses composite material structure by combining Ru with other materials to form a chip that contains Ru as main constituent but with controlled crystal grain structure. The composite nature of the material allows achieving both the electrical/anti-corrosion properties of Ru and the mechanical strength provided by the optimized grain structure.
2Reliability
If Ru-containing chips are used in spark plugs, then electrical performance is improved, but crack generation occurs under thermal stress
Solution Approach 1:
The invention changes the physical parameters of the chip by controlling crystal grain diameter (1-50 μm) and aspect ratio (0.8-2.0), which fundamentally alters the material's response to thermal stress. These parameter changes maintain electrical performance while preventing crack generation by creating a grain structure that can better accommodate thermal expansion and stress distribution.
Data Source
AI summary
A spark plug includes a center electrode and a ground electrode that are electrically insulated from each other. At least one of the center electrode and the ground electrode includes a base material and a chip that is sealed to the base material. The chip contains Ru as a main constituent, faces the other one of the center electrode and the ground electrode, and includes a front end surface at a tip in the thickness direction of the chip, and, in a cross-section passing through the center of gravity of the front end surface and being parallel to the thickness direction of the chip, an average of crystal grain diameters obtained by dividing the length of a test line drawn perpendicularly to the thickness direction of the chip by the number of crystal grains intersected by the test line is 1 μm or more and 50 μm or less.