Spark Plug Laminated Sealing Layer Vibration Resistance
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Solution Overview
Problem
Conventional spark plugs have insufficient shock resistance and gas-tightness due to inadequate sealing structures, which are compromised by increased engine vibrations, leading to poor fixation of the center electrode and connecting terminal.
Innovation Solution
A spark plug design featuring a laminated sealing layer with a higher metallic content for shock resistance and a lower metallic content for fluidity, where the glass sealing material in the second sealing layer has a lower viscosity and softer point than the first, ensuring reliable fixation and gas-tightness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the metallic component content in the sealing member is increased to enhance shock resistance, then the shock resistance is improved, but the fluidity of the sealing member is lowered causing inadequate fixation of the connecting terminal
Solution Approach 1:
The sealing member is divided into two distinct sealing layers: a lower sealing layer with higher metallic component content (50-70 wt%) for shock resistance, and an upper sealing layer with lower metallic component content (20-50 wt%) for fluidity and fixation reliability. This segmentation allows each layer to optimize its composition for its specific function without compromising the other.
Solution Approach 2:
Different regions of the sealing member are assigned different material compositions tailored to local requirements. The lower sealing layer near the center electrode uses high metallic content for shock absorption, while the upper sealing layer near the connecting terminal uses low metallic content for better fluidity and sealing performance, creating local quality optimization throughout the structure.
2Ease of manufacture
If a single sealing member composition is used, then the manufacturing process is simplified, but the gas-tightness and fixation adequacy are insufficient under engine vibrations
Solution Approach 1:
The sealing member is segmented into two layers with different compositions to simultaneously achieve gas-tightness and vibration resistance. The lower layer provides structural stability and shock resistance, while the upper layer ensures proper fluidity for gas-tight sealing, resolving the reliability issue without significantly complicating the manufacturing process.
Solution Approach 2:
The sealing member uses a composite structure with two different glass-based sealing materials having distinct metallic component contents. This composite approach combines the advantages of both high-metallic-content materials (shock resistance) and low-metallic-content materials (fluidity and sealing performance) into a single integrated component.
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 enhances shock resistance and gas-tightness by maintaining the center electrode's fixation and ensuring the connecting terminal's secure attachment, even under engine vibrations, while maintaining electrical conductivity.
Implementation Method 1
glass sealing material contained in the second sealing layer has a fluidity higher than that of glass sealing material contained in the first sealing layer at a temperature higher than the softening point of the glass component constituting the sealing layer
Implementation Method 2
at a glass sealing step, the insulator is inserted into a heating furnace so that the sealing member is softened
Implementation Method 3
Vibration shocks thus applied to the spark plug which is mounted in the engine are also applied to the sealing member through the center electrode
Data Source
AI summary
A spark plug including a cylindrical insulator having an axial hole extending in an axial direction; a center electrode held in the axial hole on a leading end side; a connecting terminal held in the axial hole on a trailing end side; and a sealing layer provided in the axial hole and including a glass sealing material containing a glass component and a metallic component, the sealing layer including a first sealing layer containing a first glass sealing material and a second sealing layer containing a second glass sealing material laminated in an axial direction of the axial hole, the first sealing layer contacting the center electrode, and the second sealing layer contacting the connecting terminal, wherein the second glass sealing material has a fluidity higher than that of the first glass sealing material at a temperature higher than a softening point of a glass component in the sealing layer.