Spark Plug Center Electrode Concave Contour Bonding
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Solution Overview
Problem
The reduction in size of spark plugs has led to a decrease in the contact area between the electrode head and conductive glass, resulting in insufficient bonding strength, which can cause peeling issues when external forces are applied, especially in rotational directions.
Innovation Solution
A concave portion is formed on the base end surface of the electrode head with a closed curve contour that surrounds the center axis, featuring outward and inward protrusions, increasing the contact area and bonding strength between the center electrode and conductive glass.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the diameter of the center electrode is reduced to decrease spark plug size, then the spark plug size is reduced, but the contact area between the electrode head and conductive glass becomes small, resulting in insufficient bonding strength
Solution Approach 1:
The invention transitions from a flat bonding interface to a three-dimensional concave structure. By forming a concave portion with inward and outward portions on the electrode head, the bonding interface extends in the depth dimension, significantly increasing the contact area between the electrode head and conductive glass without increasing the radial diameter of the center electrode.
Solution Approach 2:
The concave portion features curved surfaces with inward and outward portions that create a complex three-dimensional geometry. This curved structure increases the surface area for bonding compared to a flat interface, providing enhanced bonding strength while maintaining a compact electrode head size.
2Strength
If the contact area between electrode head and conductive glass is increased to improve bonding strength, then bonding strength is improved, but the electrode head size must be increased, leading to larger spark plug size
Solution Approach 1:
Instead of increasing the radial dimensions of the electrode head, the invention utilizes the depth dimension by forming a concave portion. This allows the bonding area to extend axially into the concave structure, achieving increased bonding strength without proportionally increasing the overall volume of the electrode head.
Solution Approach 2:
The concave portion creates a nested structure where the conductive glass is positioned within the concave depression. This nesting arrangement maximizes the bonding interface area within a compact volume, as the conductive glass is embedded in the concave portion rather than requiring additional radial space.
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 concave contour design enhances the bonding strength between the center electrode and conductive glass, preventing deformation and improving resistance to rotational forces, ensuring secure engagement and increased durability.
Implementation Method 1
the conductive glass is bonded to the electrode head of the center electrode
Data Source
AI summary
A spark plug for an internal combustion engine that can improve bonding strength between a center electrode and a conductive glass is provided. The spark plug includes a housing, an insulator, a center electrode, a ground electrode, and a conductive glass. The center electrode has a locking portion that is locked from a base end side to a step portion formed on an inner peripheral surface of the insulator, and an electrode head that is closer to the base end side than the locking portion is. A concave portion is partially formed on the tip end surface of the electrode head. A concave contour, which is an outer peripheral contour of the concave portion when viewed in a plug axial direction, forms a closed curve which is spaced apart from a head contour, which is an outer peripheral contour of the base end surface of the electrode head, and surrounds a center axis (B) of the center electrode. The concave contour has an outward portion protruding toward the head contour and an inward portion protruding toward the center axis (B) of the center electrode.