Spark Plug Center Electrode Volume Increase Without Axis Deviation
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Solution Overview
Problem
Existing spark plug designs face challenges in increasing the durability of the center electrode while maintaining accurate axis alignment and withstand voltage performance, as methods to enlarge the electrode's exposed volume often result in axis deviation or reduced insulation thickness.
Innovation Solution
An electrode-attached insulator design with a large diameter portion exposed from the insulator, where the center electrode is joined to a locking member within the axial hole, allowing for increased volume without axis deviation and maintaining insulator thickness, ensuring reliable spark generation and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If the outside diameter of the exposed center electrode portion is increased to increase durability, then the volume of the center electrode to be worn is increased, but the minimum bore diameter of the axial hole must be increased causing the insulator to be made thin and reducing withstand voltage performance
Solution Approach 1:
The invention transitions from increasing the outside diameter of the exposed center electrode portion to increasing its length in the axial direction. By making the center electrode longer in the axial dimension rather than wider in radial dimension, the volume for wear resistance is increased without requiring a larger bore diameter, thus maintaining insulator thickness and withstand voltage performance.
Solution Approach 2:
The invention changes the dimensional parameters of the center electrode from radial expansion (outside diameter) to axial extension (length). This parameter transformation allows the exposed portion length to be increased while keeping the outside diameter within the original bore diameter constraints, resolving the contradiction between durability and insulator thickness.
2Duration of action of stationary object
If an annular ring member is joined to the outer circumference of the front end portion of the center electrode after insertion to increase volume, then the volume of the center electrode is increased, but the center electrode becomes inclined causing radial axis deviation and potential flashover
Solution Approach 1:
The invention performs the axis alignment action beforehand by providing a guide portion in the axial hole that guides the center electrode during insertion. This preliminary alignment prevents inclination and radial axis deviation before the center electrode is fully inserted, eliminating the need for post-insertion ring members that could cause alignment issues.
Solution Approach 2:
The guide portion acts as an intermediary element between the axial hole and the center electrode. It mediates the insertion process by providing a guiding surface that ensures the center electrode is inserted along the correct axial path, preventing inclination and maintaining precise axis alignment without requiring additional alignment components.
3Duration of action of stationary object
If the thickness of the center electrode is increased to increase the volume of the exposed portion, then the volume is increased for better durability, but the minimum bore diameter of the axial hole must be increased reducing insulator thickness
Solution Approach 1:
The invention shifts the volume increase strategy from radial thickening of the center electrode to axial lengthening. By increasing the length of the exposed center electrode portion in the axial direction while maintaining its outside diameter within the original bore constraints, the volume is increased without reducing insulator thickness.
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 enhances the durability of the spark plug by increasing the center electrode's volume without axis deviation, maintaining superior withstand voltage performance and ensuring accurate alignment of the center electrode's axis, thus preventing misfires and flashover.
Implementation Method 1
an insulator having an axial hole which extends in the direction an axis; and a center electrode disposed in the axial hole on a front-end side of the axial hole
Implementation Method 2
a locking member having a collar portion adapted to be locked on a step portion formed on an inner circumferential surface of the axial hole
Data Source
AI summary
An electrode-attached insulator having an insulator provided with an axial hole extending in the direction of an axis and a center electrode which is disposed on a distal-end side of the axial hole and has a front end portion that is exposed from a front end of the insulator. The electrode-attached insulator includes a locking member having a collar portion which is locked on a step portion. The center electrode and the locking member are joined together in the axial hole.