Spark Plug Insulator Root Section Volume Ratio for Heat Transfer
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Solution Overview
Problem
Existing spark plugs face challenges in maintaining both heat-resisting and contamination-resisting properties, especially with the reduction in size, leading to concerns about heat transfer efficiency and voltage-resisting capabilities.
Innovation Solution
The spark plug design includes a center electrode with a specific volume ratio between the leading end section and the root section of the insulating body, optimized to ensure effective heat transfer and contamination resistance, with configurations for different screw diameters to balance temperature and voltage-resisting properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the center electrode is reduced in size, then the productivity and compactness of the spark plug are improved, but the heat transfer efficiency from the insulating body to the metal shell is lowered
Solution Approach 1:
The invention applies local quality by creating a root section of the insulating body with specific volume characteristics (0.06 ≤ A/B ≤ 0.20) that is optimized for heat transfer, while other sections maintain different properties. This localized optimization of the root section ensures efficient heat dissipation even when the center electrode is miniaturized, resolving the contradiction between compactness and heat transfer efficiency.
2Reliability
If the surface temperature of the insulating body is raised rapidly to enhance contamination-resisting property, then the carbon deposit is burned off, but the leading end becomes overheated and generates pre-ignition
Solution Approach 1:
The invention applies local quality by creating a root section of the insulating body with specific volume characteristics (0.06 ≤ A/B ≤ 0.20) that is optimized for heat transfer, while other sections maintain different properties. This localized optimization of the root section ensures efficient heat dissipation even when the center electrode is miniaturized, resolving the contradiction between compactness and heat transfer efficiency.
Solution Approach 2:
The root section of the insulating body acts as an intermediary thermal management component between the hot leading end and the metal shell. By optimizing its volume ratio, it serves as a thermal buffer that facilitates controlled heat transfer to the metal shell, preventing both excessive heat accumulation (pre-ignition) and insufficient heat transfer (carbon deposit accumulation).
3Reliability
If the gap between the tapered section and metal shell is made small with large axial length to enhance heat-resisting and contamination-resisting properties, then heat transfer and carbon prevention are improved, but the device complexity increases
Solution Approach 1:
The invention applies local quality by creating a root section of the insulating body with specific volume characteristics (0.06 ≤ A/B ≤ 0.20) that is optimized for heat transfer, while other sections maintain different properties. This localized optimization of the root section ensures efficient heat dissipation even when the center electrode is miniaturized, resolving the contradiction between compactness and heat transfer efficiency.
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 enhances both heat-resisting and contamination-resisting properties while maintaining voltage-resisting capabilities, preventing pre-ignition and ensuring efficient operation even in smaller sizes.
Implementation Method 1
heat of the insulating body is drawn mainly to the metal shell from the center electrode that is excellent in heat conductivity
Implementation Method 2
heat of the insulating body is drawn mainly to the metal shell from the center electrode that is excellent in heat conductivity
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
In a spark plug that has a small sized center electrode, enhancement of corruption-resisting property and heat-resisting property is promoted. The spark plug 1 includes a center electrode 5, an insulator 2 and a metal shell 3, and the insulator 2 includes a foot section 13, a tapered section 14 and a middle body section 12. The maximum outer diameter of a portion, which is arranged within the foot section 13, of the center electrode 5 becomes 3.0 mm or less. A step section 21 and a leading end side inner periphery section 51 are formed in the inner periphery of the metal shell 3 and the tapered section 14 is engaged to a step section 21. When A (mm3) is a volume of a portion of 2 mm of the insulator 2 from leading end of the insulator 2 toward the rear end side along the axis CL1 and B (mm3) is a volume of a portion of the insulator 2 from the rear end of the portion of the tapered section 14 which is engaged to the step section 21 to the leading end side and the portion is 1.5 mm or less of the diameter difference between the leading end side inner periphery section 51 and its outer periphery portion, 0.12 ≤ A/B ≤ 0.24 is satisfied.