Ignition Plug Insulator Protrusion for Pre-ignition Prevention
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Solution Overview
Problem
The existing ignition plugs face challenges in maintaining ignition performance while preventing pre-ignition, as increased surface area of the insulator's front end portion leads to susceptibility to heat, causing pre-ignition, and a larger volume results in carbon deposition, reducing plasma generation.
Innovation Solution
An ignition plug design with a protruding portion of the insulator having a specific surface-to-volume ratio, axial length, and diameter differences, along with a configuration that includes regions with varying diameters and a tapered shape, ensures effective heat dissipation and plasma generation, preventing pre-ignition and maintaining ignition performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the surface area of the front end portion of the insulator is increased to improve ignition performance, then the amount of non-equilibrium plasma generation is increased, but the front end portion becomes more susceptible to heat from combustion gas causing pre-ignition
Solution Approach 1:
The insulator is designed with non-uniform thickness: the front end portion has a smaller outer diameter (creating a protruding portion) while the rear portion has a larger outer diameter. This local variation in geometry allows the front end to have sufficient surface area for plasma generation while the larger rear volume provides enhanced heat dissipation capacity, preventing excessive temperature rise and pre-ignition.
Solution Approach 2:
The patent specifies precise dimensional parameters: the difference between outer diameter of center electrode and inner diameter of insulator is 0.01mm or more, the axial length of protruding portion is 6.7-12.7mm, and the surface-to-volume ratio S/V1 is controlled within 1.07-1.35. These parameter optimizations balance plasma generation surface area with heat dissipation volume, resolving the contradiction between ignition performance and pre-ignition prevention.
2Temperature
If the volume of the insulator is increased to improve heat dissipation, then heat can be radiated more easily from the front end portion, but the surface temperature becomes low causing carbon deposition on the front end portion
Solution Approach 1:
The insulator features a protruding front end portion with smaller outer diameter that extends forward of the metal shell. This localized geometry creates a region with appropriate surface-to-volume ratio (S/V1 = 1.07-1.35) that maintains sufficient temperature for preventing carbon deposition while the overall larger insulator volume provides heat dissipation capacity.
Solution Approach 2:
The insulator is designed with a tapered shape where the outer diameter gradually changes from the front end to the rear end. This curved, non-uniform geometry optimizes both heat dissipation (through increased volume) and temperature maintenance at the front end (through appropriate surface area and shape), preventing carbon deposition while enabling effective heat radiation.
3Reliability
If the surface area of the front end portion is increased to enhance plasma generation, then ignition performance is improved, but the amount of heat dissipation through the insulator is reduced
Solution Approach 1:
The insulator design transitions from a uniform cylindrical shape to a tapered three-dimensional form with varying outer diameter along the axial direction. This dimensional variation creates a protruding front end portion that increases surface area for plasma generation while the extended rear portion increases volume for heat dissipation, achieving both objectives simultaneously through spatial optimization.
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
The design effectively prevents pre-ignition and improves ignition performance by balancing heat dissipation and plasma generation, ensuring stable operation and reduced carbon deposition.
Implementation Method 1
the more easily the heat can be radiated (dissipated) from the front end portion of the insulator through the insulator
Implementation Method 2
non-equilibrium plasma is generated in a space around the insulator for ignition of air-fuel mixture
Data Source
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AI summary
Disclosed is an ignition plug capable of improving ignition performance while preventing pre-ignition. The ignition plug includes a center electrode, a bottomed cylindrical insulator enclosing a front end portion of the center electrode and a cylindrical metal shell holding therein the insulator. The insulator has, on a front end side thereof, a protruding portion protruding from and located frontward of a front end of the metal shell. In the ignition plug, a difference between an outer diameter of the center electrode and an inner diameter of the insulator is 0.01 mm or more; an axial length of the protruding portion is 6.7 mm to 12.7 mm; and the following condition is satisfied: 1.07 ≤ S/V1 ≤ 1.35 where S is an outer surface area of the protruding portion; and V1 is a volume of the protruding portion.