Spark Plug Heat Dissipation via Sheet Packing Geometry
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Solution Overview
Problem
Existing spark plugs face challenges in heat dissipation, particularly when the center electrode temperature exceeds 950°C, leading to pre-ignition, and there is a need for improved heat dissipation to accommodate increased combustion chamber temperatures and reduced spark plug size without sufficient studies on heat dissipation through the insulator, sheet packing, and metallic shell path.
Innovation Solution
The spark plug design ensures sufficient contact areas between the insulator and sheet packing and the sheet packing and metallic shell, with specific thickness and Vickers hardness values for the sheet packing and metallic shell, along with a male thread diameter of M14 or less, to enhance heat dissipation. The sheet packing's thickness is between 0.15 mm and 0.20 mm, and the metallic shell's Vickers hardness is 240 HV or more, while the sheet packing's hardness is 100 HV or more but less than the metallic shell's, to prevent excessive deformation and maintain accurate installation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the center electrode temperature is increased to improve combustion chamber temperature, then the output power and fuel economy are improved, but pre-ignition occurs when the temperature exceeds 950°C
Solution Approach 1:
The patent changes the thermal parameters of the spark plug by optimizing the heat dissipation path. Specifically, it controls the thickness and hardness of the sheet packing to regulate heat flow from the center electrode through the insulator to the metallic shell, maintaining the center electrode temperature below 950°C while still achieving improved combustion chamber temperature for better power output and fuel economy.
2Adaptability or versatility
If the spark plug size is reduced to improve design flexibility, then the device complexity is reduced, but heat accumulation in the spark plug increases
Solution Approach 1:
The patent optimizes the dimensional parameters of the sheet packing (thickness between 0.15-0.20 mm) and the hardness parameters (Vickers hardness between 100-240 HV) to enhance heat dissipation efficiency. This allows the spark plug to maintain effective heat dissipation even with reduced size, preventing heat accumulation while preserving design flexibility.
3Area of stationary object
If the sheet packing thickness is increased to ensure sufficient contact area, then the heat dissipation is improved, but the deformation allowance is reduced
Solution Approach 1:
The patent identifies an optimal thickness range for the sheet packing (0.15-0.20 mm) that balances two competing requirements: sufficient contact area for effective heat dissipation and adequate deformation allowance for maintaining installation accuracy. This optimized parameter range ensures both thermal performance and mechanical reliability.
Solution Approach 2:
The patent employs a composite structure involving the sheet packing with specific material properties (controlled hardness and thickness) that combines thermal conduction functionality with mechanical deformation capability. The sheet packing acts as an intermediate layer that simultaneously manages heat transfer and accommodates dimensional variations.
4Temperature
If the contact area between insulator and sheet packing is increased to improve heat dissipation, then the heat dissipation is improved, but the manufacturing precision requirements are increased
Solution Approach 1:
The patent controls the sheet packing thickness within a specific range (0.15-0.20 mm) to optimize the balance between heat dissipation performance and manufacturing feasibility. This parameter control ensures sufficient contact area for effective thermal conduction while maintaining tolerance levels that are achievable with standard manufacturing processes.
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 heat dissipation from the insulator through the sheet packing to the metallic shell, reducing pre-ignition occurrences and maintaining the accuracy of the insulator's installation, thereby enhancing the spark plug's heat dissipation properties and preventing excessive displacement.
Implementation Method 1
heat dissipation through a path from the insulator through the sheet packing to the metallic shell
Data Source
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AI summary
In a spark plug, heat dissipation through a path from an insulator through a sheet packing to a metallic shell is improved. The spark plug satisfies the relation 2.8 ≤ (A + B)/M. Here, A is the sum of a length A1 of contact between the sheet packing and the metallic shell in one half section and a length A2 of contact between the sheet packing and the insulator in the one half section. B is the sum of a length B1 of contact between the sheet packing and the metallic shell in the other half section and a length B2 of contact between the sheet packing and the insulator in the other half section. M is the difference obtained by subtracting the inner diameter D of a ledge from the inner diameter C of a middle hole portion.