Spark Plug Ground Electrode Gap Structure Against Vibration Cracks
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing spark plugs with a ground electrode press-fitted into a tubular metallic shell are prone to cracking due to vehicle vibrations, as the edge of the hole in the metallic shell contacts the outer surface of the ground electrode.
Innovation Solution
A spark plug design featuring a tubular metallic member with a penetration hole intersecting the axial direction, where the ground electrode has a fixing portion, a projecting portion, and an insertion portion, forming a space between the insertion portion and the inner surface of the penetration hole, with an angle between the inner and outer surfaces ranging from 0° to 90°, preventing direct contact and potential cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the ground electrode tip is press-fitted into the hole of the tubular metallic shell in such a manner that the ground electrode tip projects toward the inner side of the metallic shell, then the ground electrode is securely fixed and projects for proper function, but a crack is generated in a region where the edge of the hole of the metallic shell is in contact with the outer surface of the ground electrode tip due to vehicle vibration
Solution Approach 1:
A resin layer is introduced as an intermediary substance between the ground electrode tip and the penetration hole edge of the metallic shell. This resin layer absorbs vibration stresses and prevents direct contact between the rigid metal surfaces, thereby eliminating crack generation while maintaining secure fixation of the ground electrode
Solution Approach 2:
The resin layer is applied in advance between the ground electrode tip and the penetration hole edge to cushion against upcoming vibration stresses. This preventive measure ensures that when vehicle vibrations occur, the cushioning layer already in place absorbs the stress before it can cause cracks at the contact region
Data Source
AI summary
A spark plug includes a center electrode, a tubular metallic shell which holds the center electrode therein in an insulated state, and a ground electrode which faces a forward end portion of the center electrode. The metallic shell has a penetration hole which penetrates the metallic shell in a direction intersecting an axial direction. The ground electrode has a press-fitted portion inserted into the penetration hole and fixed to the metallic shell, a projecting portion projecting toward an inner side of the metallic shell, and an insertion portion disposed between the press-fitted portion and the projecting portion, inserted into the penetration hole, and forming a space between the insertion portion and an inner surface of the penetration hole. An angle α formed between the inner surface of the penetration hole and an outer surface of the insertion portion falls within a range of 0°<α<90°.