Spark Plug Insulator Volume Ratio for Voltage Resistance
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Solution Overview
Problem
Conventional spark plugs face challenges in simultaneously improving voltage resistance, suppressing side sparking, and preventing oxidation of the center electrode, especially with increasing compression ratios in engines, where high voltage and heat management become critical issues.
Innovation Solution
The spark plug design incorporates a center electrode with a diameter not larger than 2.2 mm, a specific volume ratio of the insulator's truncated cone-shaped and second cylindrical portions, and a shelf portion on the metal shell to ensure appropriate heat dissipation and spacing, which satisfies certain volume and diameter ratios to enhance voltage resistance and prevent oxidation and side sparking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the diameter of the center electrode is reduced to improve voltage resistance and anti-side sparking characteristic, then voltage resistance improves, but the heat capacity of the center electrode decreases causing temperature rise and accelerated oxidation
Solution Approach 1:
The insulator is designed with non-uniform thickness: thinner at the front end (1.5-2.5mm) to reduce outer diameter and improve voltage resistance, and thicker at the rear end (3-5mm) to provide sufficient heat capacity and prevent center electrode oxidation. This local quality variation resolves the contradiction between voltage resistance and temperature control.
2Reliability
If the insulator outer diameter is reduced to suppress side sparking, then anti-side sparking characteristic improves, but the insulator thickness is reduced causing center electrode temperature rise and oxidation
Solution Approach 1:
The insulator employs differential thickness design where the front end portion has reduced thickness (1.5-2.5mm) to minimize outer diameter and suppress side sparking, while the rear end portion maintains greater thickness (3-5mm) to ensure adequate heat capacity and prevent center electrode oxidation.
Solution Approach 2:
The solution moves from uniform radial thickness to axial variation in thickness. By controlling insulator thickness differently at front and rear ends along the axial dimension, the patent simultaneously achieves reduced outer diameter for voltage resistance and sufficient heat capacity for temperature control.
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 improves voltage resistance, suppresses side sparking, and reduces oxidation of the center electrode, maintaining performance even in high-compression engines with stringent conditions.
Implementation Method 1
a specific volume ratio of the insulator's truncated cone-shaped and second cylindrical portions, and a shelf portion on the metal shell to ensure appropriate heat dissipation
Data Source
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AI summary
A purpose is simultaneously achieving improvement in voltage resistance, suppression of oxidation of a center electrode, and suppression of side sparking. A spark plug includes an insulator having an axial hole that extends along an axis line, and a center electrode inserted within the axial hole. The insulator includes: a first cylindrical portion; a truncated cone-shaped portion formed at a front end side of the first cylindrical portion and whose outer diameter reduces toward the front end side; and a second cylindrical portion formed at a front end side of the truncated cone-shaped portion. A diameter C of the center electrode is not larger than 2.2 mm. A total I of a volume of the truncated cone-shaped portion and a volume of the second cylindrical portion, a volume E of the center electrode from a positon at a rear end of the truncated cone-shaped portion to a position at a front end of the second cylindrical portion with respect to the direction along the axis line, and the diameter C satisfy I/E≥4.2333C2-19.79C+24.869.