Spark Plug Insulator Buffer Member for Shock Absorption
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Solution Overview
Problem
Spark plugs for internal combustion engines face durability issues due to stress concentration and potential cracking of the insulator when abnormal combustion events like pre-ignition or knocking occur, causing supersonic shock waves that lead to vibration and stress concentration at the boundary between the enlarged diameter portion and the long leg portion.
Innovation Solution
A spark plug design incorporating a buffer member made of a ductile material, which is disposed at the distal end side of the engaging part to restrain the insulator's enlarged diameter part, reducing stress concentration and preventing cracking by absorbing vibrations and shock waves.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the insulator has a long leg portion with an enlarged diameter portion crimped by the housing, then the insulator is supported and positioned, but stress concentration occurs at the boundary between the enlarged diameter portion and the long leg portion causing cracking
Solution Approach 1:
A buffer member made of ductile material is introduced as an intermediary component between the insulator and the housing. This buffer member absorbs vibration energy and reduces stress concentration at the critical boundary region, preventing cracking while maintaining support stability. The buffer member acts as a mediator that decouples the rigid connection between the insulator and housing, allowing relative movement and stress absorption.
Solution Approach 2:
The buffer member is positioned in advance at the location where stress concentration is most likely to occur (at the boundary between the enlarged diameter portion and the long leg portion). This beforehand cushioning arrangement ensures that when vibration or shock occurs during engine operation, the stress is already absorbed and distributed by the buffer member, preventing cracking before it can initiate.
2Manufacturing precision
If the insulator is rigidly fixed by crimping the enlarged diameter portion, then positioning accuracy is improved, but vibration from shock waves causes stress concentration and cracking
Solution Approach 1:
The buffer member changes the mechanical parameters of the connection between the insulator and housing. By introducing a compliant element, the rigidity of the connection is reduced while maintaining positioning accuracy. The buffer member allows for controlled deformation under vibration, changing the stress distribution parameters to prevent cracking while preserving the insulator's positioned stability.
3Volume of moving object
If the insulator diameter is reduced to allow smaller spark plug size, then compactness is improved, but the insulator becomes more susceptible to vibration-induced cracking
Solution Approach 1:
The buffer member serves as a protective intermediary that compensates for the reduced structural margin in smaller insulators. By absorbing vibration energy before it reaches the insulator, the buffer member allows the use of smaller insulator dimensions without proportionally reducing the cracking resistance, effectively decoupling the size reduction from the strength degradation.
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 buffer member effectively reduces the degree of vibration and stress concentration on the insulator, enhancing the spark plug's durability and preventing breakage, allowing it to withstand significantly higher shockwave pressures without cracking, achieving at least three times the durability of conventional designs.
Implementation Method 1
a buffer member that restrains the distal end side exposed part by pressing a part of the distal end side exposed part toward the center and a part of the inner peripheral surface of the lateral electrode in a radial direction
Implementation Method 2
When abnormal combustion of the internal combustion engine such as a pre-ignition or knocking occurs, a supersonic shock wave is produced by sudden pressure changes, and may be propagated to the spark plug
Data Source
AI summary
A spark plug 5 for an internal combustion engine includes a center electrode 1, an insulator 2, and a housing 3. The insulator 2 includes a distal end side exposed part and an insulator enlarged diameter part 21. The housing 3 includes a lateral electrode 32, an engaging part 33, and a crimping portion 35. A buffer member 4 that restrains the distal end side exposed part 20 by pressing a part of the distal end side exposed part 20 toward the center and a part of the inner peripheral surface of the lateral electrode 32 in a radial direction at a distal end side of the engaging part 33 is disposed at a base end side of the gas pocket 230.