Spark Plug Resistor Seal Geometry for Noise Reduction
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Solution Overview
Problem
The existing spark plug designs with a resistor inside the insulator suffer from reduced radio-wave noise reduction performance due to the shorter effective length of the resistor, which also leads to increased sealing failures between the conductive seal and the resistor.
Innovation Solution
The spark plug configuration includes a resistor positioned between the center electrode and the metal terminal nut, with a conductive seal contacting both, featuring a contact surface with varying distances along the central axis, including local maxima and minima, to increase the contact area without shortening the resistor's effective length, thereby reducing sealing failures and maintaining radio-wave noise reduction performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the contact portion between the conductive seal and the resistor is formed in a bowl shape that projects toward the tip end side, then sealing failure is reduced, but the effective length of the resistor decreases
Solution Approach 1:
The contact surface is designed with three-dimensional undulating features including ridges and grooves that extend in the axial direction. This dimensional transformation from a simple planar or bowl-shaped contact surface to a multi-level undulating surface increases the contact area between the conductive seal and resistor without sacrificing the axial effective length of the resistor, thereby improving sealing reliability while maintaining noise reduction performance
Solution Approach 2:
The contact surface incorporates curved undulating features with ridges and grooves instead of flat or simple bowl-shaped surfaces. These curved geometric features increase the contact area between the conductive seal and resistor, improving sealing reliability while preserving the resistor's effective length for maintaining radio-wave noise reduction performance
2Reliability
If the contact area between the conductive seal and the resistor is expanded, then sealing failure is reduced, but the effective length of the resistor is shortened
Solution Approach 1:
The contact surface is designed with three-dimensional undulating features including ridges and grooves that extend in the axial direction. This dimensional transformation from a simple planar or bowl-shaped contact surface to a multi-level undulating surface increases the contact area between the conductive seal and resistor without sacrificing the axial effective length of the resistor, thereby improving sealing reliability while maintaining noise reduction performance
Data Source
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AI summary
Sealing failure between a conductive seal and a resistor is reduced while a decrease in radio-wave noise reduction performance is suppressed. A spark plug includes an insulator with a through hole, a center electrode disposed at a tip end side of the through hole, a metal terminal nut disposed at a rear end side of the through hole, a resistor disposed in a position between the center electrode and the metal terminal nut inside of the through hole and apart from the center electrode, and a conductive seal that is disposed between the resistor and the center electrode inside of the through hole and contacts both the center electrode and the resistor. Here, in an adoptable configuration, a contact surface between the resistor and the conductive seal may include at least one point where a distance in the central axis direction from a virtual plane that includes a rear end of the resistor and is vertical to the central axis is local maximum, and include at least one point where the distance is local minimum, in at least one cross section including a central axis. A configuration where at least a part of the resistor is positioned at the tip end side with respect to a rear end of the center electrode may be adopted.