Spark Plug Electrode Geometry for Ignitability and Wear
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Solution Overview
Problem
There is a need for improved ignitability and wear resistance in spark plugs due to higher compression of air-fuel mixtures in internal combustion engines, as existing designs often compromise between these two performance metrics.
Innovation Solution
The spark plug design optimizes the dimensions of the center electrode tip, ground electrode tip, gap length, and edge-to-edge distance to achieve a balance between ignitability and wear resistance by setting specific ratios and ranges for these parameters, including R1 < R2, 0.5 mm ≤ R1 ≤ 1.1 mm, 0.7 mm ≤ R2 ≤ 1.2 mm, 0.6 mm ≤ G1 ≤ 1.3 mm, and 1.4 ≤ (R2 / R1) × (G2 / G1) ≤ 1.8, with a focus on the thermal conductivity of the ground electrode body and its core part.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the ground electrode tip outer diameter R2 is increased to improve wear resistance, then wear resistance is improved, but ignitability deteriorates
Solution Approach 1:
The patent applies parameter changes by establishing specific mathematical relationships between multiple parameters (R1, R2, G1, G2) rather than changing a single parameter. The condition (R2/R1)×(G2/G1)≥1.4 creates an optimized balance where the ground electrode tip diameter R2 is increased for wear resistance while the ratios are controlled to maintain ignitability. This multi-parameter optimization resolves the contradiction by finding the optimal combination point.
2Reliability
If the edge-to-edge distance G2 is increased to improve wear resistance, then wear resistance is improved, but ignitability deteriorates
Solution Approach 1:
The patent uses parameter changes by defining the optimal range for the ratio G2/G1 within the composite condition (R2/R1)×(G2/G1)≥1.4. By controlling the edge-to-edge distance G2 relative to gap length G1 through this ratio, the patent achieves wear resistance improvement while preventing ignitability deterioration. The mathematical relationship provides a systematic way to balance these conflicting requirements.
3Productivity
If the center electrode tip outer diameter R1 is decreased to improve ignitability, then ignitability is improved, but wear resistance deteriorates
Solution Approach 1:
The patent applies parameter changes by establishing the relationship R1 < R2 and incorporating R1 into the composite condition (R2/R1)×(G2/G1)≥1.4. This creates an optimized balance where R1 is decreased for better ignitability while the ratio R2/R1 is controlled to ensure adequate wear resistance. The multi-parameter approach allows simultaneous optimization of both conflicting properties.
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 configuration enhances both ignitability and wear resistance of the spark plug, as demonstrated by evaluation tests showing improved performance across various samples, with further optimization possible by adjusting the projection length T and core part length ratio.
Implementation Method 1
a core part buried in the base material and having a higher thermal conductivity than the base material
Implementation Method 2
a voltage is applied between a center electrode and a ground electrode that are insulated from each other by an insulator, and thereby a spark occurs at a gap formed between the front end part of the center electrode and the front end part of the ground electrode
Data Source
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AI summary
Objective: To improve ignitability and wear resistance of a spark plug. Means for Solution: In a particular cross section including a center axis of the center electrode tip, when two directions that are orthogonal to a center axis of the center electrode tip and opposed to each other are denoted as a first direction and a second direction, an outer diameter of a first face that is a gap forming face of the center electrode tip is denoted as R1, an outer diameter of a second face that is a gap forming face of the ground electrode tip is denoted as R2, a length of the gap is denoted as G1, and an average distance of a distance between an end in the first direction of the first face and an end in the first direction of the second face and a distance between an end in the second direction of the first face and an end in the second direction of the second face is denoted as G2, R1 < R2, 0.5 mm ≤ G1 ≤ 1.1 mm, 0.7 mm ≤ G2 ≤ 1.2 mm, 0.6 mm ≤ G1 ≤ 1.3 mm, and 1.4 ≤ (R2/R1) x (G2/G1) ≤ 1.8 are satisfied.