Spark Plug Housing Pressure Contact Surface Design
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Solution Overview
Problem
Conventional spark plugs experience reduced airtightness due to dents on the pressure contact surface caused by barrel metal plating, leading to engine malfunctions, as the angular corners of the spark plug housing interfere with other housings during the plating process.
Innovation Solution
The spark plug design features a tubular housing with a pressure contact surface tapered towards the tip and a connection surface formed by deforming substrate corners during the manufacturing process, ensuring the pressure contact surface is radially inward and avoiding interference, thus preventing dents and maintaining airtightness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If barrel metal plating is applied to the housing, then productivity is improved and cost is reduced, but dents are made on the housing surfaces due to collision between housings in the barrel
Solution Approach 1:
The patent applies preliminary action by performing barrel metal plating before forming the pressure contact surface. The housing is plated first, then the pressure contact surface is formed by machining or deformation processes that remove or repair the dents caused during plating. This sequence allows the harmful dents to be created and then eliminated in a subsequent step, ensuring both high productivity from plating and high manufacturing precision for the pressure contact surface.
2Manufacturing precision
If the angular portion of the pressure contact surface is positioned closer to the outer periphery of the housing, then the pressure contact surface can be formed, but the corner is likely to interfere with other objects during manufacturing, causing dents
Solution Approach 1:
The patent applies preliminary action by completing the pressure contact surface formation before the barrel metal plating process. The pressure contact surface is machined or deformed to its final shape and position, then the entire housing undergoes metal plating. This sequence ensures the pressure contact surface is already formed and protected, eliminating the risk of dents on this critical surface during the plating process while maintaining manufacturing precision.
Solution Approach 2:
The patent applies beforehand cushioning by designing the housing structure with sufficient material thickness and structural support around the pressure contact surface area. This structural cushioning prevents dents from propagating to the pressure contact surface even if some occur during barrel plating, and allows for easy repair or removal of dents in non-critical areas without affecting the pressure contact surface quality.
3Reliability
If the pressure contact surface is pressed against the cylinder head, then adhesion and airtightness are ensured, but dents on the pressure contact surface reduce adhesion and airtightness
Solution Approach 1:
The patent applies preliminary action by forming the pressure contact surface to its final precise geometry and surface quality before the barrel metal plating process. The pressure contact surface is machined or deformed to eliminate any dents, then the housing undergoes plating. This sequence ensures the pressure contact surface maintains its integrity and smoothness, guaranteeing reliable adhesion and airtightness when pressed against the cylinder head, while still allowing the productivity benefits of barrel plating.
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 prevents dents on the pressure contact surface, ensuring reliable adhesion and airtightness between the spark plug and cylinder head, enhancing engine performance and reducing manufacturing complexities.
Implementation Method 1
screwing a mounting screw into a female screw provided in the plug hole of the cylinder head thereby generating longitudinal force
Implementation Method 2
adhesion between the pressure contact surface and the seat surface
Implementation Method 3
the barrel is rotated to apply metal plating to surfaces of respective housings
Implementation Method 4
due to collision between the housings in the barrel, dents can be made on the housing surfaces
Data Source
AI summary
An outer periphery of the tubular housing includes a parallel surface, a pressure contact surface and a connection surface. The parallel surface is formed parallel to an axial direction of the spark plug. The pressure contact surface is located closer to a tip of the spark plug and more radially inward than the parallel surface. The pressure contact surface has a tapered shape in that a diameter decreases toward the tip. The pressure contact surface is pressed against a cylinder head when installed in the internal combustion engine. The connection surface is located closer to a base of the spark plug than an extension line in a longitudinal cross-section of the spark plug parallel to the axial direction including a plug central axis. The connection surface connects an outer peripheral end of the pressure contact surface with a longitudinal end of the parallel surface.