Spark Plug Center Electrode Structure for Vibration-Resistant Fixation
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Solution Overview
Problem
The existing spark plug designs are prone to looseness due to vibrations, caused by a small surface area contact between the center electrode and the seal member, leading to performance degradation.
Innovation Solution
A spark plug design with a center electrode having a brim portion and a connecting portion, supported by an insulator with a large and small diameter portion, where the radius ratio and length ratios are optimized to prevent excessive center of gravity separation, thereby reducing vibration and looseness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the center electrode has a small contact surface area with the seal member, then the structure is simpler, but looseness occurs due to vibrations
Solution Approach 1:
The center electrode incorporates a brim portion with a specific radial protrusion and a connecting portion with optimized dimensions, creating local structural variations that increase the contact surface area with the seal member without complicating the overall electrode design. This localized quality enhancement ensures reliable fixation while maintaining structural simplicity.
2Shape
If the center of gravity of the center electrode is located at the top end side, then the brim portion can be larger, but excessive swing or vibration occurs due to vibrations
Solution Approach 1:
The patent optimizes the dimensional parameters of the center electrode, specifically setting the ratio L2/L1 between 0.15 and 0.30 and the ratio (D1-D2)/D1 between 0.01 and 0.06. These parameter changes balance the brim portion size with the overall electrode geometry, ensuring the center of gravity remains in a stable position that prevents excessive swing or vibration during engine operation.
3Ease of manufacture
If the brim portion is short in size, then the manufacturing is easier, but the contact surface area with the seal member is small
Solution Approach 1:
The center electrode design incorporates a brim portion that protrudes in the radial direction (another dimension perpendicular to the axis direction), increasing the contact surface area with the seal member without extending the overall length of the electrode. This dimensional approach allows for easier manufacturing while achieving adequate contact area for reliable fixation.
Data Source
AI summary
Spark plug has center electrode having leg portion extending in an axis direction, brim portion located at rear end side with respect to the leg portion and protruding outwards in a radial direction with respect to the leg portion and connecting portion connecting the leg portion and the brim portion; insulator having penetration hole and supporting the center electrode; and seal member filling the penetration hole and fixing the brim portion and the insulator. The center electrode satisfies “(D1-D2)/D1≤0.06”, where a maximum value of a radius of the brim portion is D1, and a minimum value of the radius of the brim portion is D2, also satisfies “L2/L1≤0.30”, where a size of the center electrode along the axis direction is L1, and a size along the axis direction from boundary between the connecting portion and the leg portion to a center of gravity of the center electrode is L2.