Spark Plug Gasket Inclined Surface for Accurate Electrode Positioning
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Solution Overview
Problem
The existing spark plug mounting system fails to accurately position the ground electrode relative to the combustion chamber due to frictional forces, leading to potential deterioration in ignition performance and airtightness.
Innovation Solution
A spark plug design featuring a metal annular gasket with an inclined forward end surface and a curved surface portion, which provides a wedge effect and stabilizes friction, allowing for accurate positioning of the ground electrode when mounted to the combustion apparatus, and a thickness and hardness that prevent deformation and thermal loosening.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a solid annular gasket is attached to the screw neck to provide airtightness, then sealing performance is improved, but the relative position of the ground electrode cannot be accurately controlled due to frictional forces during mounting
Solution Approach 1:
The forward end surface of the gasket is designed with a curved surface portion having a specific radius of curvature (0.05mm to 0.2mm). This curvature creates a point contact or line contact with the combustion apparatus seat, reducing the frictional force that causes positioning deviation during mounting, while still maintaining effective sealing.
Solution Approach 2:
The gasket's forward end surface is designed with an inclined portion that slopes from the radially outer side toward the radially inner side. This inclination angle and the specific geometry parameters (distance between outermost and innermost edges of 0.02mm to 0.12mm) are optimized to control the mounting friction and enable accurate positioning of the ground electrode.
2Reliability
If the gasket thickness is increased to improve sealing, then airtightness is enhanced, but the gasket becomes more prone to deformation and thermal loosening
Solution Approach 1:
The gasket thickness is precisely controlled within the range of 1.5mm to 2.5mm. This optimized thickness parameter provides sufficient sealing capability while maintaining dimensional stability and resistance to thermal loosening. The specific thickness range balances sealing effectiveness with structural stability under thermal conditions.
3Stability of the object's composition
If the gasket hardness is increased to prevent deformation, then dimensional stability is improved, but the gasket becomes more difficult to install and may damage the combustion apparatus
Solution Approach 1:
The gasket hardness is controlled within the range of 30 Hv to 70 Hv. This optimized hardness range provides sufficient dimensional stability to prevent excessive deformation during mounting, while remaining soft enough to be easily installed without damaging the combustion apparatus seat or causing gasket breakage.
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 solution ensures reliable and accurate positioning of the ground electrode, preventing ignition performance deterioration and maintaining airtightness over time by stabilizing friction and resisting thermal deformation.
Implementation Method 1
a forward end surface of the gasket has an inclined portion which inclines rearward with respect to a direction of the axis from a radially outer side toward a radially inner side
Implementation Method 2
the friction between the gasket and the combustion apparatus can be stabilized, and, consequently, when the spark plug is mounted to the combustion apparatus with a predetermined tightening torque, the forward end portion of the metallic shell (ground electrode) can be accurately disposed at a predetermined position in relation to the combustion chamber
Implementation Method 3
a curved surface portion which is formed between the forward end surface and an outer side surface of the gasket, and as viewed in a section which contains the axis, a radius of curvature of the curved surface portion is 0.2 mm or less
Implementation Method 4
a thickness of the gasket along the axis is 1.0 mm to 2.0 mm, and a Vickers hardness of the gasket is 60 Hv to 150 Hv. Accordingly, when the spark plug is mounted to the combustion apparatus, thermal loosening of the gasket can be restrained
Implementation Method 5
a Vickers hardness of the gasket is 60 Hv to 150 Hv
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
A spark plug (1) includes a metallic shell (3) extending along an axis (CL1) and a solid annular gasket (18). The metallic shell 3 has an externally threaded portion (15) and a seat portion (16), and the gasket (18) has an inside diameter smaller than the thread diameter of the externally threaded portion (15) and is provided between the externally threaded portion (15) and the seat portion (16). The forward end surface (18F) of the gasket (18) has an inclined portion (18A) which inclines rearward with respect to the direction of the axis (CL1) from the radially outer side toward the raidally inner side. The thickness of the gasket (18) along the axis (CL1) is 2.0 mm or less; the distance along the axis (CL1) between the outermost circumferential edge and the innermost circumferential edge of inclined portion (18A) is 0.02 mm to 0.12 mm; and the Vickers hardness of the gasket (18) is 60 Hv or more. Thus, when the spark plug is mounted to a combustion apparatus, the position of a forward end portion of the metallic shell (ground electrode) in relation to a combustion chamber can be accurately set.