Spark Plug Cover Geometry for Machining Inclined Nozzle Holes
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Solution Overview
Problem
Existing spark plug designs that form swirl flows in auxiliary combustion chambers face productivity issues due to the difficulty in forming inclined nozzle holes with convex curved surfaces, requiring advanced machining techniques like laser beam machining, which lowers manufacturing efficiency.
Innovation Solution
The spark plug design incorporates a plug cover with concave portions adjacent to the outer openings of the nozzle holes, allowing for easier formation of inclined nozzle holes through conventional cutting work, such as drilling, by creating a surface orthogonal to the nozzle hole axis, thereby simplifying the manufacturing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional cutting work is used to form inclined nozzle holes, then productivity is improved, but the nozzle holes cannot be formed with the required inclination and precision
Solution Approach 1:
The patent applies preliminary action by forming a concave portion on the plug cover before creating the inclined nozzle hole. This pre-prepared concave surface provides a proper machining surface that allows conventional cutting tools to accurately form the inclined nozzle hole at the desired angle (e.g., 45 degrees) without requiring advanced machining techniques. The concave portion is formed in advance to enable subsequent precise inclined hole formation through simple cutting work.
2Manufacturing precision
If laser beam machining is used to form inclined nozzle holes, then manufacturing precision is improved, but productivity deteriorates
Solution Approach 1:
The patent replaces complex mechanical machining systems (like laser beam machining) with simpler mechanical cutting operations. By providing the concave portion as a pre-prepared surface, conventional cutting tools can achieve the same precision as advanced machining methods, thereby substituting high-precision but low-productivity processes with high-productivity conventional machining.
3Shape
If the plug cover surface is made convex, then the aesthetic appearance is improved, but the ease of manufacture deteriorates
Solution Approach 1:
The patent applies local quality by making only the specific region where the nozzle hole will be formed (the local area) concave, while the rest of the plug cover outer surface can remain convex for aesthetic purposes. This localized concave portion provides the necessary machining surface for easy inclined hole formation without compromising the overall aesthetic appearance of the plug cover.
Data Source
AI summary
A spark plug for an internal combustion engine includes a cylindrical insulator, a center electrode, a cylindrical housing, and a plug cover. On a tip side of the insulator, an auxiliary combustion chamber is formed which is surrounded by at least the plug cover. The plug cover is provided with nozzle holes that communicate between the auxiliary combustion chamber and the outside of the auxiliary combustion chamber. A central axis of the nozzle hole is inclined with respect to a plug radial direction when viewed in a plug axial direction. At least a part around an outer opening of the nozzle hole is provided with a concave portion that is adjacent to the outer opening. The concave portion is recessed from the outside to the inside of the plug cover.