Spark Plug Ground Electrode Resistance Welding Joint
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Solution Overview
Problem
Existing spark plugs experience a lack of mechanical strength in the joint between the ground electrode and the metal shell due to limited weld area, which can lead to solidification cracking and separation under high engine temperatures, failing to meet modern automotive requirements for high power, low fuel consumption, and low emissions.
Innovation Solution
A spark plug design that uses resistance welding to create a larger weld interface between the ground electrode and the metal shell, with a sinking depth of 0.4 mm or more, and a ratio of sinking depth to ground electrode thickness within 0.2 to 0.7, ensuring a strong joint while minimizing the length of the ground electrode to enhance heat dissipation and reduce thermal resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If laser welding is used to join the ground electrode to the metal shell, then the welding process is efficient and automated, but the weld area is small resulting in insufficient joint strength
Solution Approach 1:
The patent transitions from conventional laser welding (which creates a small focal weld area) to resistance welding with an extension structure that increases the weld interface area by utilizing both the end surface and inner peripheral surface of the metal shell. This dimensional expansion of the weld area resolves the contradiction between welding efficiency and joint strength.
2Productivity
If laser welding is used to join the ground electrode to the metal shell, then the welding process is fast, but the rapid heating and cooling causes solidification cracking
Solution Approach 1:
The patent replaces laser welding (which uses optical energy causing rapid thermal cycles) with resistance welding (which uses electrical resistance heating). This substitution changes the heating mechanism, allowing for more controlled thermal processes that reduce solidification cracking while maintaining welding efficiency.
3Power
If the ground electrode is made longer to improve spark performance, then the spark generation is enhanced, but the heat accumulation increases causing higher temperature
Solution Approach 1:
The patent extracts the welding function from the main body of the ground electrode by adding a separate extension structure. This allows the ground electrode to be shortened in the combustion chamber while the extension provides the necessary weld interface, thereby reducing heat accumulation in the spark-generating portion while maintaining adequate joint strength.
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
The enhanced joint strength and reduced thermal resistance improve the reliability and durability of the spark plug, preventing separation and maintaining performance under high engine temperatures, thus meeting modern automotive standards.
Implementation Method 1
The ground electrode is joined to the metal shell by resistance welding
Data Source
AI summary
An improved structure of a spark plug is provided to ensure a high strength of joint between a ground electrode and a metal shell. The ground electrode is resistance-welded to the metal shell so that it is embedded partially in an end surface of the metal shell to create a weld interface extending from the end surface to an inner periphery of the metal shell, thus resulting in an increased size of the weld interface to increase the joint strength. The resistance welding keeps the temperature of a weld between the ground electrode and the metal shell at a lower level during welding as compared with laser welding, thus minimizing solidification cracking in the weld.