Spark Plug Insulator Design for Side Spark Prevention
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Solution Overview
Problem
Conventional spark plugs with compact structures experience reduced ignition capability due to the occurrence of side sparks, which are caused by carbon deposition on the insulator surface, leading to decreased insulation distance and unreliable ignition of the air-fuel mixture.
Innovation Solution
The spark plug design includes specific dimensional parameters such as increasing the outer diameter of the insulator, defining volumes and distances, and using Ir-based and Pt-based alloys for the center and ground electrodes, respectively, to prevent side sparks and maintain high ignition capability without prolonging the insulator's protrusion into the combustion chamber.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the insulator outer diameter is increased to prevent side sparks, then side spark prevention is improved, but the spark plug compactness deteriorates
Solution Approach 1:
The insulator outer diameter is not uniformly increased but varies locally - the end portion has a larger diameter while the middle portion maintains a smaller diameter. This local quality approach prevents side sparks at the critical end region while keeping the overall spark plug dimensions compact for modern engine installations.
2Volume of moving object
If the insulation distance is reduced to achieve compact spark plug structure, then spark plug compactness is improved, but side spark occurrence increases
Solution Approach 1:
The insulator design features a localized increase in outer diameter at the end portion, creating different insulation characteristics at different positions. This allows the spark plug to maintain compact overall dimensions while the enlarged end portion provides sufficient insulation distance to prevent side sparks.
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 specified dimensions and materials ensure effective prevention of side sparks, maintaining a high ignition capability by controlling carbon deposition and ensuring sufficient space for flame propagation, thus enhancing the spark plug's performance in compact engine installations.
Implementation Method 1
the insulator has a function of preventing carbon from being deposited on a surface thereof
Implementation Method 2
a tip portion 52 that faces an end 39 of the center electrode 3 through a spark gap G
Data Source
AI summary
A spark plug according to the invention includes a metal shell, a hollow insulator, a center electrode, and a ground electrode. The insulator has a first end protruding into a combustion chamber of an engine and a second end opposite to the first end in the lengthwise direction of the insulator. The insulator increases in outer diameter from the edge of the inner surface thereof at the first end to a reference plane that is defined to extend perpendicular to the lengthwise direction of the insulator and away 0.1 mm from the edge of the inner surface of the insulator toward the second end of the same in the lengthwise direction. Further, a first volume V1, which is the volume of a portion of the insulator between the edge of the inner surface of the insulator and the reference plane, is in the range of 0.15 to 0.38 mm3.