Ignition Plug Welding Geometry for Thermal Stress Reduction
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Solution Overview
Problem
Ignition plugs in internal combustion engines face increased thermal stress due to higher engine output, leading to peeling of the electrode tip from the electrode body, which reduces durability and performance.
Innovation Solution
The design of the ignition plug includes a specific geometry for the welding portion between the electrode tip and body, where the length of the welding portion is sufficient to reduce thermal stress, with a ratio of welding portion length to electrode tip length (L2/L1) ≥ 0.25 in critical areas, and a far-side protruding length of the welding portion ≥ 0.1 mm, ensuring increased anti-peeling performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the electrode tip is joined to the electrode body using welding methods, then the electrode durability is improved, but thermal stress causes cracks at the boundaries and peeling occurs
Solution Approach 1:
The patent changes the geometric parameters of the welding portion, specifically setting the length L2 of the welding portion and controlling the ratio L2/L1 ≥ 0.25 in the 1/4 range from the second end. This parameter optimization reduces thermal stress concentration and prevents peeling while maintaining the strength benefits of welding.
Solution Approach 2:
The patent applies different structural characteristics to different parts of the welding portion. The welding portion has specific local geometric features (length L2, ratio L2/L1) in the critical 1/4 range from the second end, creating local quality variations that reduce thermal stress at the most vulnerable boundaries while maintaining overall joint strength.
2Power
If the engine output is increased, then the power performance is improved, but the thermal stress on the ignition plug increases leading to peeling
Solution Approach 1:
The patent optimizes the geometric parameters of the welding portion (length L2, ratio L2/L1) to reduce thermal stress concentration. This allows the ignition plug to withstand the higher thermal stresses generated by increased engine output without experiencing peeling or cracking.
Solution Approach 2:
The patent designs the welding portion with sufficient length L2 and appropriate ratio L2/L1 ≥ 0.25 in advance, creating a structural buffer that cushions against thermal stress before it causes damage. This preemptive design allows the system to handle higher power outputs without failure.
3Reliability
If the welding portion length is increased, then the anti-peeling performance is improved, but the device complexity increases
Solution Approach 1:
The patent identifies specific parameter ranges (L2/L1 ≥ 0.25 in the 1/4 range from the second end) that provide optimal anti-peeling performance. By defining clear parameter boundaries, the patent achieves high reliability without excessive complexity, as the manufacturing process only needs to control these specific dimensional ratios.
Solution Approach 2:
The patent applies the welding portion length optimization specifically to the critical 1/4 range from the second end, rather than uniformly throughout the entire welding portion. This partial action approach focuses resources on the most stress-prone area, achieving high anti-peeling performance with minimal additional complexity.
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 configuration effectively reduces thermal stress and enhances the anti-peeling performance of the electrode tip, preventing peeling and maintaining the integrity of the electrode assembly under high-temperature conditions.
Implementation Method 1
When an ignition plug is used in an internal combustion engine, thermal stress occurs in the welding portion due to combustion heat
Data Source
Figure 1
Figure 2A~2B
Figure 3A~3C
AI summary
An ignition plug includes an insulator that includes a through hole; a center electrode; a metal shell that holds the insulator; a bar-shaped ground electrode body 31; an electrode tip 39 that is disposed along a side surface of the ground electrode body opposing a discharge surface of the center electrode; and a welding portion 35 that is disposed between the ground electrode tip and the ground electrode body. Over a sub-range RA2 which is 1/4 of a range RA1 from a first end P1 to a second end 392 of the ground electrode tip, a length L1 of the ground electrode tip and a length L2 of the welding portion in a direction perpendicular to a direction D1 satisfy (L2/L1) ≥ 0.25.