Spark Plug Insulator Support for Breakage Resistance
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Solution Overview
Problem
The challenge is to enhance the robustness of a spark plug insulator against breakage without improving its strength, particularly when downsizing the spark plug, as reducing the insulator diameter complicates securing thickness and improving durability against bending and impact.
Innovation Solution
The spark plug design includes a tubular main fitting and insulator with specific diameter and interval configurations, where the insulator is supported by a main fitting with a smaller inner diameter portions, allowing the insulator to contact the main fitting on the rear end side first when inclined, reducing the bending moment and preventing breakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the diameter of the insulator is reduced to downsize the spark plug, then the overall size of the spark plug is reduced, but it becomes difficult to secure the thickness at the intermediate body portion, making it harder to improve the strength against breakage of the insulator
Solution Approach 1:
The patent applies preliminary action by configuring the main fitting with a support portion that protrudes axially before the insulator is fully installed. This support portion is positioned to contact the insulator at a predetermined location, preventing the insulator from inclining toward the main fitting during installation. By establishing this supportive structure in advance, the patent ensures that the insulator maintains proper alignment and thickness distribution even when the insulator diameter is reduced for downsizing the spark plug.
Solution Approach 2:
The patent applies local quality by creating a support portion with specific geometric characteristics (protruding axially from the main fitting) at a localized position where it is needed most. This support portion has a specific shape and position designed to contact the insulator at a predetermined location, providing localized reinforcement exactly where the insulator is most vulnerable to inclining and breaking during installation, rather than uniformly strengthening the entire insulator.
2Ease of manufacture
If the insulator is configured with conventional dimensions, then the manufacturing is simpler, but the insulator may break when a bending moment is applied during attachment to the internal combustion engine
Solution Approach 1:
The patent introduces an intermediary element - the support portion protruding from the main fitting - that acts as a mediator between the insulator and the potential bending forces during installation. This support portion contacts the insulator at a predetermined location and prevents it from inclining toward the main fitting, thereby eliminating the bending moment that would otherwise cause the insulator to break. This intermediary structure protects the insulator without requiring changes to the insulator material or manufacturing process.
Data Source
AI summary
A spark plug includes a main fitting having a first, second, and third portions adjacent to each other. The spark plug further includes an insulator having a first opposing portion with a predetermined portion opposed to the first portion with a first interval, a second opposing portion with a second portion opposing the second portion with a second interval, and a third opposed portion opposed to the third portion. A connecting portion between the second opposing portion is supported by a support portion, and a value obtained by dividing the first interval by a length from the support portion to a rear end portion of the predetermined portion is configured to be smaller than a value obtained by dividing the second interval by a length from the support portion to a rear end portion of the second opposed portion.