Spark Plug Insulator Inclined Surface for Ignition
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Solution Overview
Problem
Existing spark plugs for internal combustion engines face challenges in increasing the ignitability of the air-fuel mixture while minimizing the occurrence of lateral sparks, which are caused by carbon accumulation on the insulator surface, leading to inefficient ignition and potential short circuits.
Innovation Solution
The design includes an insulator protrusion with an inclined surface on the outer peripheral surface, guiding airflow diagonally into the discharge gap, reducing carbon accumulation and enhancing the stretch of the electric spark towards the combustion chamber center, thereby increasing ignitability and preventing heat from being drawn by the engine head.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the insulator surface is made smooth and flat, then manufacturing is easier, but carbon accumulation occurs leading to lateral sparks
Solution Approach 1:
The insulator surface is designed with an asymmetric inclined surface rather than a symmetric flat surface. The inclined surface has a specific angle (30-60 degrees) relative to the axial direction, creating an asymmetric geometry that prevents carbon accumulation by directing carbon particles away from the discharge gap area, thereby eliminating lateral sparks while maintaining manufacturing feasibility.
Solution Approach 2:
The design transitions from a two-dimensional flat insulator surface to a three-dimensional inclined surface structure. By introducing the inclination angle in the radial direction while maintaining axial extension, the surface gains dimensional complexity that enables carbon particle diversion without complicating the manufacturing process excessively.
2Reliability
If the electric spark is contained close to the spark plug, then the ignition is more controlled, but the ignitability of the air-fuel mixture is reduced
Solution Approach 1:
The inclined insulator surface acts as an intermediary structure between the contained spark and the combustion chamber. It guides the electric spark along its inclined surface toward the center of the combustion chamber, mediating between the need for spark containment near the plug and the need for spark propagation throughout the combustion chamber to achieve good ignitability.
3Device complexity
If the insulator protrusion has a vertical outer surface, then the structure is simpler, but airflow does not guide the spark effectively
Solution Approach 1:
The design changes the geometric parameter of the insulator outer surface from vertical (90-degree angle to axial direction) to inclined (30-60-degree angle to axial direction). This parameter change enables the surface to guide airflow and electric spark effectively toward the combustion chamber center, improving ignitability without significantly increasing structural 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 design effectively increases the ignitability of the air-fuel mixture by reducing lateral sparks and ensuring the electric spark is stretched towards the combustion chamber center, promoting efficient combustion and minimizing the risk of short circuits.
Implementation Method 1
an outer peripheral surface of the insulator protrusion includes an insulator inclined surface extending inward toward a tip in a plug axial direction
Implementation Method 2
an electric discharge is induced in the discharge gap, and an air-fuel mixture in a combustion chamber is ignited by this electric discharge
Data Source
AI summary
A spark plug includes a housing, an insulator, a center electrode, and an earth electrode. The earth electrode has a gap-forming surface which forms a discharge gap between the gap-forming surface and a tip surface of the center electrode. The insulator includes an insulator protrusion protruding on the tip side of the housing in a plug axial direction. At least one of cross-sections passing through a plug center axis and parallel to the plug axial direction is referred to as an axial parallel cross-section. The outer peripheral surface of the insulator protrusion includes an insulator inclined surface extending inward toward the tip in the plug axial direction, in a straight line or a curve that is convex inward, in the axial parallel cross-section. In the axial parallel cross-section, a virtual straight line passing through both ends of the insulator inclined surface passes through the gap-forming surface.