Spark Plug Weld Portion Geometry for Joining Reliability
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Solution Overview
Problem
The reliability of the joining between noble-metal chips and base material electrodes in spark plugs is compromised by inadequate weld quality, leading to durability issues and increased manufacturing costs due to excessive use of noble-metal materials.
Innovation Solution
A spark plug design featuring a columnar noble-metal chip joined to a base material electrode via a weld portion with specific geometric and thermal stress management, utilizing a pulsed laser beam application method that adjusts energy emission and angle to ensure robust bonding while minimizing material usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If welding is used to join noble-metal chip to base material electrode, then joining reliability is improved, but thermal stress in weld portion increases leading to durability issues
Solution Approach 1:
The patent applies parameter changes by controlling the weld portion thickness B to be within a specific range (0.05D ≤ B ≤ 0.2D where D is the noble-metal chip diameter) and positioning the weld portion at a specific distance from the center axis (0.3D ≤ radial distance ≤ 0.7D). These parameter optimizations reduce thermal stress concentration while maintaining joining reliability, directly resolving the contradiction between reliable joining and thermal stress management.
2Reliability
If more noble-metal material is used to improve durability, then joining reliability is improved, but manufacturing cost increases
Solution Approach 1:
The patent optimizes the weld portion thickness B to be within 0.05D ≤ B ≤ 0.2D (where D is the noble-metal chip diameter), which minimizes the amount of noble-metal material required while ensuring sufficient joining reliability. This parameter optimization directly addresses the contradiction by reducing material consumption without compromising durability.
Solution Approach 2:
The patent applies local quality by concentrating the weld portion at a specific radial distance from the center axis (0.3D ≤ radial distance ≤ 0.7D) rather than distributing it uniformly. This localized welding approach ensures reliable joining at the critical interface while minimizing overall noble-metal material usage, resolving the contradiction between reliability and material quantity.
3Strength
If weld portion thickness is increased to improve joining strength, then joining reliability is improved, but thermal stress concentration increases
Solution Approach 1:
The patent identifies an optimal parameter range for weld portion thickness B (0.05D ≤ B ≤ 0.2D where D is the noble-metal chip diameter) that balances joining strength and thermal stress. Within this range, the weld portion is thick enough to provide sufficient strength but thin enough to avoid excessive thermal stress concentration, directly resolving the contradiction between strength and thermal stress.
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 solution enhances the reliability of the noble-metal chip to base material electrode joining, reduces thermal stress, and lowers manufacturing costs by optimizing the weld portion's geometry and energy application, resulting in a durable and cost-effective spark plug.
Implementation Method 1
applying a pulsed laser beam to a boundary portion between the base material electrode and the noble-metal chip
Implementation Method 2
applying a pulsed laser beam to a boundary portion between the base material electrode and the noble-metal chip while shifting a point of application of the pulsed laser beam in a circumferential direction
Implementation Method 3
emission energy of the pulsed laser beam is maximum at a first pulse emission, and thereafter is gradually decreased with the increase of the number of times of pulse emission
Data Source
AI summary
The spark plug has a configuration satisfying the relationships of B≧0.7A and 0.3 mm≦A≦0.6 mm, where B is an axial thickness along the central axis line Q of the weld portion formed between the base material electrode and the noble-metal chip, and A is an axial distance along the central axis line Q between the intersection points P3 and X. The intersection point P3 is a point at which a phantom axis line radially distant from the central axis line Q by D/2 (D being a diameter of the noble-metal chip) intersects with the boundary line between the weld portion and the noble-metal chip. The intersection point X is a point at which an extension of the contour line of the base material electrode in the vicinity of the weld portion intersects with a boundary line between the weld portion and the base material electrode.