Spark Plug Auxiliary Chamber Tapered Hole Design
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Solution Overview
Problem
The existing spark plugs with auxiliary chambers suffer from pre-ignition due to excessive temperature at the outer open end of through holes and inefficient flame spread, leading to decreased fuel economy.
Innovation Solution
A spark plug design featuring a through hole with a diameter reduction portion within 0.1 mm from the outer open end, where the diameter decreases gradually towards the inner end, and a configuration where the distance from the central axis to the frontmost portion of the outer open end is larger than to the rearmost portion, inhibiting excessive temperature increase and ensuring adequate flame spread.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the outer open end of the through hole is exposed to flame continuously, then the flame can ignite the fuel gas in the combustion chamber, but the temperature of the outer open end is excessively increased causing pre-ignition
Solution Approach 1:
The through hole is designed with non-uniform cross-sectional area, where the cross-sectional area at the outer open end is smaller than that at the inner open end. This local variation in geometry creates different flow resistance characteristics at different locations, allowing the flame to be restricted at the outer open end while maintaining adequate flow through the hole, thus preventing excessive temperature increase and pre-ignition
Solution Approach 2:
The patent changes the geometric parameters of the through hole, specifically making the cross-sectional area at the outer open end smaller than at the inner open end. This parameter change modifies the flame flow characteristics, reducing the exposure of the outer open end to flame and thereby controlling the temperature rise to prevent pre-ignition
2Temperature
If the flame density is reduced to prevent pre-ignition, then the outer open end temperature is controlled, but the flame spread in the combustion chamber may be insufficient
Solution Approach 1:
The through hole features different cross-sectional areas at different locations: a smaller area at the outer open end to restrict flame and control temperature, and a larger area at the inner open end to maintain flame density and jetting speed. This local quality differentiation allows simultaneous achievement of pre-ignition prevention and adequate flame spread
Solution Approach 2:
The patent addresses the contradiction by introducing a dimensional variation along the length of the through hole, creating a tapered or stepped structure where the cross-sectional area changes from outer end to inner end. This dimensional change enables the system to achieve both temperature control at the outer end and sufficient flame propagation through the combustion chamber
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 prevents pre-ignition and enhances fuel economy by reducing flame density and maintaining sufficient jetting speed, allowing the flame to spread effectively in the combustion chamber.
Implementation Method 1
a gap for spark discharge is formed between the center electrode and the ground electrode
Implementation Method 2
the pressure in the auxiliary chamber is increased by the flame, and the flame jets out from the interior of the auxiliary chamber through a through hole to the outside of a plug cover due to the pressure
Data Source
AI summary
A spark plug includes: a center electrode; a ground electrode that is provided such that a gap for spark discharge is formed between the center electrode and the ground electrode; and a plug cover covering the center electrode and the ground electrode from a front side. The plug cover has a through hole, wherein the plug cover includes a diameter reduction portion formed in a range of 0.1 mm or less from an outer open end of the through hole in a direction along a central axis of the through hole and having a diameter gradually decreasing from the outer open end toward an inner open end of the through hole. A relationship of 0 mm<x−y<0.2 mm is satisfied, where x is a diameter at the outer open end, and y is a diameter at an inner end of the diameter reduction portion.