Spark Plug Auxiliary Combustion Space Volume Ratio Optimization
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Solution Overview
Problem
Conventional spark plugs with auxiliary combustion chambers face excessive heat and pressure losses, leading to inadequate ignition ability and combustion stability.
Innovation Solution
A spark plug design with a center electrode, insulator, cylindrical metal shell, ground electrode, and cap forming an auxiliary combustion space, where the volume of the electrodes relative to the combustion space is minimized to reduce heat and pressure losses, ensuring the condition (B/A) ≤ 0.25, and a gap length of 0.2 mm or larger to enhance ignition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the auxiliary combustion chamber is designed with conventional dimensions, then the structure is simple, but heat and pressure losses become excessive leading to inadequate ignition ability
Solution Approach 1:
The patent applies parameter changes by optimizing the ratio of electrode volume to auxiliary combustion space volume (B/A ≤ 0.25) and setting specific gap length (0.2 mm or larger). These parameter adjustments reduce heat and pressure losses while improving ignition ability, resolving the contradiction between reliability and energy loss.
2Reliability
If the gap between center electrode and ground electrode is increased, then ignition ability is improved, but the volume occupied by electrodes increases leading to higher heat losses
Solution Approach 1:
The patent resolves this contradiction by optimizing the gap length parameter to be 0.2 mm or larger for improved ignition, while simultaneously controlling the overall electrode volume ratio (B/A ≤ 0.25) to minimize heat losses. This balanced parameter optimization allows both ignition ability and heat loss reduction to be achieved.
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 improves ignition ability by reducing heat and pressure losses, enhancing combustion stability and burning speed while maintaining wear resistance.
Implementation Method 1
When a spark discharge is generated in a gap between the center electrode and the ground electrode, the air-fuel mixture introduced into the auxiliary combustion chamber is ignited by the spark discharge
Implementation Method 2
A flame is developed upon the ignition, and propagates to the outside, that is, to the combustion chamber of the internal combustion chamber through the hole of the cap. By such flame propagation, the air-fuel mixture in the combustion chamber is burned
Data Source
AI summary
A spark plug includes: an insulator with an axial hole; a center electrode held in a front end side of the axial hole; a cylindrical metal shell disposed around the insulator and having a seal part brought into contact with an outer circumferential surface of the insulator; a ground electrode arranged to form a gap with the center electrode; and a cap connected to a front end part of the metal shell to define therein an auxiliary combustion space in which the gap is formed, the cap having at least one through hole formed to provide communication between the auxiliary combustion space and the outside, wherein the condition (B/A)≤0.25 is satisfied where A represents a volume of an imaginary space defined at a position frontward of the seal part; and B represents a volume of parts of the ground and center electrodes located in the imaginary space.