Spark Plug Sealing Disc Knurling for Overtightening Resistance
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Solution Overview
Problem
Existing spark plugs are prone to damage due to excessive forces and stresses during assembly and operation, particularly in the thread base, leading to potential overtightening issues and inadequate sealing between the spark plug and cylinder head.
Innovation Solution
A solid annular sealing disk with knurling on the radially outer region is used to increase friction between the sealing ring and the spark plug housing or shaft, reducing axial forces and allowing for a tolerance against high torques, while maintaining a flat sealing region for precise positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the sealing disc is made with a smooth flat surface, then the manufacturing is simple and positioning is precise, but the friction is insufficient leading to excessive axial forces and potential damage to the spark plug housing
Solution Approach 1:
The sealing disc is designed with knurling only in the radially outer region while maintaining a smooth flat surface in the radially inner region. This local differentiation allows the outer region to provide high friction for force reduction while the inner region ensures precise positioning and sealing, resolving the contradiction between strength and device complexity.
2Force
If the knurling extends across the entire sealing disc, then the friction is maximized and axial forces are reduced, but the sealing area is compromised and positioning precision is lost
Solution Approach 1:
The knurling is localized to the radially outer region of the sealing disc, leaving the radially inner region as a smooth flat sealing area. This spatial differentiation ensures that the knurled region provides high friction to reduce axial forces while the smooth inner region maintains precise positioning and sealing contact with the cylinder head.
3Quantity of substance
If the sealing disc is made as a folded seal, then the material usage is reduced, but the positioning and orientation precision is insufficient
Solution Approach 1:
The sealing disc is designed as a solid, homogeneous annular structure rather than a folded seal. This homogeneous solid construction provides superior positioning and orientation precision while maintaining reasonable material usage, resolving the contradiction between material efficiency and positioning accuracy.
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 reduces the risk of spark plug damage by distributing stresses evenly, enhancing the sealing effect and improving overtightening resistance, ensuring secure assembly and operation without excessive loads on the housing.
Implementation Method 1
The inventive measure of providing the sealing washer with knurling on the side facing the end face and/or on the side facing the spark plug shaft increases the coefficient of friction between the sealing ring and the spark plug housing, or between the sealing ring and the spark plug shaft.
Data Source
Figure 1
Figure 2a~2c
Figure 3
AI summary
The invention relates to a spark plug (1) comprising a spark plug housing (2) comprising an annular end face (10) facing the combustion chamber and a thread (8) arranged on the combustion-chamber side of the end face for screwing the spark plug (1) into a spark plug shaft of an internal combustion engine and comprising an annular solid sealing disc (11) which is plugged or can be plugged onto the spark plug housing (2) for sealingly resting between the end face (10) and the spark plug shaft. The sealing disc (11) has a knurling (17) solely radially outwards on the side (11u) facing the end face (10) and/or solely radially outwards on the side (11o) facing the spark plug shaft.