Spark Plug Cap Orifices for Combustion Stability
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Solution Overview
Problem
Existing spark plugs experience pre-ignition issues due to excessive heating of the insulator, which causes fuel gas to ignite prematurely within the cap, leading to instability in fuel combustion.
Innovation Solution
A spark plug design featuring a tubular metal shell with a ledge for the insulator, a cap with orifices of varying cross-sectional areas, and a reduced length of the insulator's front end portion to enhance fuel gas flow and cooling, thereby reducing overheating and improving combustion stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the insulator front end portion is made longer to improve structural stability, then the insulator can be securely locked onto the ledge, but the surface area exposed to heat increases causing excessive heating and pre-ignition of fuel gas
Solution Approach 1:
The patent applies parameter changes by optimizing the length of the insulator front end portion to be 12mm or less, and by varying the cross-sectional areas of multiple orifices in the cap. This creates different fuel gas flow rates through the orifices, enhancing cooling effectiveness while maintaining structural stability through the locking portion design.
2Ease of manufacture
If uniform orifices are used in the cap, then manufacturing is simpler, but fuel gas flow rate is uniform resulting in reduced cooling effectiveness and increased pre-ignition risk
Solution Approach 1:
The patent applies local quality by making the orifices have different cross-sectional areas rather than uniform sizes. This creates localized variations in fuel gas flow rates through different orifices, with some orifices providing higher flow rates for better cooling effectiveness, while others provide stable ignition. This resolves the contradiction by prioritizing performance over manufacturing simplicity.
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 stabilizes fuel ignition and combustion by varying the fuel gas flow rates, cooling the insulator, and evenly distributing heat transfer, resulting in reduced pre-ignition and improved combustion performance.
Implementation Method 1
the fuel gas can cool the front end portion of the insulator. This structure can thus reduce overheating of the front end portion
Data Source
AI summary
A spark plug includes a tubular metal shell; an insulator including a locking portion locked onto the metal shell; and a cap disposed at a front end side of the metal shell, the cap having a plurality of orifices. The plurality of orifices include orifices with different cross-sectional areas. A sum of the number of one or more largest orifices and the number of one or more large orifices that have a cross-sectional area of larger than or equal to 90% of the one or more largest orifices is smaller than the number of orifices that are other than the one or more largest orifices and the one or more large orifices. A length of the front end portion in an axial direction between a front end of the insulator and a front end of the locking portion is smaller than or equal to 12 mm.