Center Electrode Melted Portion Geometry for Stable Spark Ignition
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Solution Overview
Problem
The generation of a flame kernel by electric discharge in existing spark plugs is unstable due to the electrical field intensity at the welded portion of the center electrode.
Innovation Solution
A spark plug design where the center electrode has a tip made of a different material than the base member, connected by a melted portion, with specific geometric relationships (0<A/B≤1, θ≤70°) that enhances the electrical field intensity and stability of the flame kernel generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the center electrode uses a welded structure with different materials for tip and base member, then the electrical field intensity at the welded portion is reduced, but the generation of flame kernel becomes unstable
Solution Approach 1:
The center electrode is divided into three distinct segments: the tip portion (discharge electrode), the melted portion (connection region), and the base member (support structure). This segmentation allows each part to have optimized properties - the tip for discharge, the melted portion for mechanical connection with reduced electrical field intensity, and the base for structural support - thereby resolving the contradiction between reducing harmful electrical field concentration and maintaining stable flame kernel generation.
Solution Approach 2:
Different portions of the center electrode are given different material compositions and geometric characteristics. The tip portion has specific material properties for optimal discharge, while the melted portion has a conical shape with controlled dimensions (A/B ratio between 0.3-0.7) to locally reduce electrical field intensity. This local differentiation allows the electrode to simultaneously achieve stable flame generation at the tip and reduced electrical field concentration at the connection region.
2Object-generated harmful factors
If the distance A between the first boundary and discharge surface is increased, then the electrical field intensity at the melted portion is reduced, but the flame kernel generation stability deteriorates
Solution Approach 1:
The patent optimizes specific geometric parameters of the melted portion, particularly the ratio A/B (distance from first boundary to discharge surface divided by distance from first to second boundary) within the range of 0.3-0.7, and controls the angle θ at the first boundary to be 30°-70°. These parameter optimizations allow the design to achieve the balance point where electrical field intensity is sufficiently reduced at the melted portion while maintaining stable flame kernel generation at the discharge surface.
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
Improves the stability of flame kernel generation by electric discharge between electrodes, allowing for efficient ignition in various engines, including gasoline, hydrogen, and gas engines.
Implementation Method 1
a melted portion that connects the tip to the base member
Implementation Method 2
generation of a flame kernel by electric discharge between electrodes
Data Source
AI summary
A spark plug includes a center electrode includes a base member, a tip and a melted portion. In a projection view formed by projecting the spark plug perpendicularly to an axial line direction, when an angle that is formed by a discharge surface of the tip and a straight line passing through a first boundary between the tip and the melted portion and a second boundary between the melted portion and the base member, the first boundary and the second boundary being located at two ends of an external shape line of the melted portion, expressed by θ, a distance between the first boundary and the discharge surface in the axial line direction expressed by A, and a distance between the first boundary and the second boundary in a direction perpendicular to the axial line expressed by B, 0<A/B≤1 and θ≤70° are satisfied.