Spark Plug Ground Electrode Width and Position for Ignition Stability
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Solution Overview
Problem
Spark plugs for internal combustion engines face instability in ignition due to varying mounting orientations, which obstruct mixture flow and lead to deteriorated ignition performance, especially in lean-burn engines, as the ground electrode can obstruct the air-fuel mixture flow, causing stalling and mechanical strength issues.
Innovation Solution
A spark plug design with a ground electrode having a maximum dimension of 1.3 to 2.0 mm and a specific distance relation between the center and intersection centers, ensuring a stable flow velocity around the spark gap regardless of mounting orientation, thereby minimizing ignition deterioration and simplifying the installation process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the ground electrode is made thicker to ensure mechanical strength, then the mechanical strength is improved, but the mixture flow obstruction is worsened
Solution Approach 1:
The patent applies parameter changes by precisely controlling the width dimension of the ground electrode within the range of 1.3mm to 2.0mm. This dimensional parameter optimization allows the ground electrode to maintain sufficient mechanical strength while minimizing its obstruction to mixture flow, thereby resolving the contradiction between strength and flow resistance.
2Reliability
If the ground electrode is positioned upstream to improve ignition, then the ignition ability is improved, but the mounting orientation control becomes more difficult
Solution Approach 1:
The patent implements universality by designing the ground electrode with specific dimensional parameters (width: 1.3-2.0mm, distance from center: W+0.525 to W+0.66) that enable it to function effectively across multiple mounting orientations. This design allows the spark plug to maintain reliable ignition performance regardless of whether the ground electrode is positioned upstream, downstream, or at the same level as the center electrode, thereby eliminating the need for precise orientation control during installation.
3Object-generated harmful factors
If a hole is formed in the ground electrode to reduce flow obstruction, then the mixture flow is improved, but the mechanical strength decreases
Solution Approach 1:
Instead of forming holes in the ground electrode, the patent applies parameter changes by optimizing the width dimension of the solid ground electrode structure to 1.3-2.0mm. This dimensional optimization reduces flow obstruction without compromising mechanical strength, as the electrode maintains its structural integrity while presenting a smaller profile to the mixture flow.
4Object-generated harmful factors
If thin plates are used to weld the ground electrode to the housing, then the flow obstruction is reduced, but the device complexity increases
Solution Approach 1:
The patent applies parameter changes by optimizing the ground electrode as a solid structure with controlled width (1.3-2.0mm) rather than using thin plates with holes. This approach reduces flow obstruction through dimensional optimization while maintaining structural simplicity, avoiding the need for complex welding processes with multiple thin plates.
Data Source
AI summary
A spark plug for an internal combustion engine includes a cylindrical metal shell, a center electrode, and a ground electrode. The center electrode has an end portion which protrudes outside an end of the metal shell. The ground electrode is joined at an end thereof to the metal shell and has an inner surface facing the end portion of the center electrode. The ground electrode has a maximum width W meeting a relation of 1.3≤W≤2.0. A distance d between the center of an end surface of the center electrode and the inner surface of the ground electrode on a plane extending through the center of the center electrode perpendicular to an axis of the spark plug is selected to meet a relation of W+0.525≤d≤1.07W+0.66. This ensures the stability of ignitability of the spark plug.