Spark Plug Ground Electrode Projecting Portion Design
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Solution Overview
Problem
Internal combustion engines face challenges in igniting the air-fuel mixture due to high compression and supercharging, leading to reduced ignitability, especially in engines generating tumble flow, which affects both ignitability and durability of spark plugs.
Innovation Solution
A spark plug design featuring a tubular insulator, center electrode, and a rod-shaped ground electrode with a projecting portion that satisfies specific geometric and angular relationships, ensuring a wider spark discharge area and improved durability by dispersing spark discharge consumption across the ground electrode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high compression and supercharging are applied to internal combustion engines, then engine power and efficiency are improved, but ignitability of the air-fuel mixture deteriorates
Solution Approach 1:
The ground electrode is segmented into a main body portion and a projecting portion that extends toward the center electrode. This segmentation creates multiple discharge points and distributes the spark discharge consumption across different regions, improving ignitability under high compression conditions while maintaining engine power
Solution Approach 2:
The ground electrode transitions from a conventional planar configuration to a three-dimensional structure with a projecting portion that extends in the axial direction toward the center electrode. This dimensional change increases the spark discharge area and improves ignitability without compromising engine performance
2Reliability
If a chip is bonded to the front end surface of the ground electrode to reduce flame quenching, then ignitability is improved, but the structure becomes more complex and manufacturing more difficult
Solution Approach 1:
The invention extracts the flame quenching reduction function from a separate bonded chip and integrates it directly into the ground electrode structure through the projecting portion. This eliminates the need for additional components and simplifies both the structure and manufacturing process while maintaining improved ignitability
3Reliability
If the ground electrode projects further toward the center electrode to increase spark discharge area, then ignitability is improved, but durability deteriorates due to increased consumption
Solution Approach 1:
The ground electrode is divided into a main body portion and a projecting portion, with the spark discharge occurring primarily at the projecting portion. This segmentation protects the main body from direct discharge consumption, extending the service life and improving durability while maintaining enhanced ignitability through the extended discharge area
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
Enhances ignitability by maintaining a stable spark discharge over a longer period and improves durability by reducing flame quenching and consumption, particularly in engines with tumble flow, while maintaining performance in both ignitability and durability.
Implementation Method 1
When a voltage is applied to the spark discharge gap, a spark discharge is generated
Data Source
AI summary
A ground electrode includes a main body portion and a projecting portion having a width smaller than a width of the main body portion. A spark discharge gap is formed between a discharging surface of the projecting portion and a front end surface of a center electrode. When the front end surface and the ground electrode are projected on a first plane, at least a part of the projection region of the projecting portion overlaps the projection region of the front end surface. A width Le (mm), a width Lc (mm), a cross-sectional area Sg (mm2), a cross-sectional area Sc (mm2), an angle θ1(°), an angle θ2(°), an angle θ3(°), and an angle θ4(°) satisfy expressions Le < Lc, 2.9 ≤ Sc + Sg ≤ 4.25, and 0.30 ≤ (θ1/θ2) × (θ3/θ4) ≤ 0.67.