Spark Plug Terminal Electrode Recess Design
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Solution Overview
Problem
Existing spark plugs face issues with insufficient compression of the glass powder mixture leading to pores in the glass seal layer and resistor, resulting in reduced density, contact area, and load life property, as well as increased resistance and vulnerability to impact.
Innovation Solution
A spark plug design featuring a terminal electrode with a recess part and a flat part at its front end, where the recess part has a depth of 0.3 mm or greater and the flat part has an area that satisfies 0.52 ≤ B/A ≤ 0.91, ensuring proper compression of the glass powder mixture and resistor composition, thereby increasing their densities and improving the fixing strength and load life property.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the glass powder mixture is insufficiently compressed during manufacturing, then the manufacturing process is simpler, but the glass seal layer contains pores and has reduced density, leading to smaller contact area and reduced fixing strength
Solution Approach 1:
The terminal electrode is designed with a recess part at its front end before the compression process. This recess part prevents the glass powder mixture from moving to the outer circumference during compression, ensuring that the mixture remains in the compression zone and achieves sufficient density without requiring complex compression equipment or procedures
Solution Approach 2:
The terminal electrode has different structural features at different locations: a recess part at the front end to concentrate the glass powder mixture, and a flat part at the outer circumference to provide sealing. This local differentiation of structure allows the compression process to be simpler while still achieving high density in the critical contact area
2Reliability
If the glass powder mixture is insufficiently compressed, then the manufacturing process is faster, but the resistor composition also remains insufficiently compressed, leading to pores and reduced load life property
Solution Approach 1:
The recess part is pre-formed on the terminal electrode before assembly. During the hot press process, this recess part automatically serves to concentrate both the glass powder mixture and the resistor composition, ensuring both materials are sufficiently compressed in a single manufacturing step without requiring additional compression operations
Solution Approach 2:
The compression of the glass powder mixture and the resistor composition is performed simultaneously in a single hot press process. The recess part of the terminal electrode serves both materials, ensuring that both achieve sufficient density and contact in one operation, thereby maintaining high reliability without sacrificing manufacturing efficiency
3Strength
If the contact area between the terminal electrode and glass seal layer is reduced, then the manufacturing is easier, but the fixing strength decreases and the terminal electrode may fall out under impact
Solution Approach 1:
The recess part is pre-formed on the terminal electrode to ensure that during assembly and compression, the glass powder mixture is concentrated in the compression zone. This preliminary structural feature ensures sufficient contact area and fixing strength without requiring complex assembly procedures or additional fastening mechanisms
Solution Approach 2:
The hot press process changes the physical state of the glass powder mixture from loose powder to dense solid, increasing the contact area and fixing strength. The recess part ensures that this parameter change occurs uniformly and effectively, achieving strong fixation through the phase change of the glass material itself
4Reliability
If the resistor composition is insufficiently compressed, then the manufacturing process is simpler, but the density of the resistor decreases, causing fewer conductive paths and increased resistance over time
Solution Approach 1:
The recess part on the terminal electrode serves as a pre-configured compression zone that automatically concentrates the resistor composition during the hot press process. This preliminary structural feature ensures sufficient compression and density of the resistor without requiring complex compression equipment or multi-step processes
Solution Approach 2:
The compression of the resistor composition is merged with the compression of the glass powder mixture in a single hot press operation. The recess part ensures both materials are compressed simultaneously to sufficient density, achieving stable resistance characteristics without adding manufacturing complexity
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 the impact resistance and load life property by ensuring a larger contact area and increased density of the glass seal layer and resistor, reducing the likelihood of gaps and oxidation, and improving the overall performance of the spark plug.
Implementation Method 1
the glass powder mixture is heated being directly compressed by the terminal electrode
Implementation Method 2
the glass powder mixture is heated being directly compressed by the terminal electrode
Implementation Method 3
the resistor composition is heated being compressed via the glass powder mixture
Implementation Method 4
the resistor composition is heated being compressed via the glass powder mixture
Implementation Method 5
a resistor for suppressing an electromagnetic wave noise... is often provided between the center electrode and the terminal electrode
Data Source
Figure 1
Figure 2A~3
Figure 4
AI summary
A spark plug (1) includes an insulator (2), a terminal electrode (6), a center electrode (5), a resistor (7), and a glass seal layer (8). The terminal electrode (6) has: a recess part (6D) opened to the front end side and having a depth in a center axis (CL2) direction of the terminal electrode (6); and a flat part (6E) neighboring the recess part (6D) at its outer circumference side. A (mm2) which represents an area of a region surrounded by an outline of an outer circumference surface of the terminal electrode (6), and B (mm2) which represents an area of a region of the terminal electrode (6) surrounded by an outline of an inner surface of the recess part (6D) in a cross section orthogonal to the center axis (CL2) and located 0.1 mm away from a front end along the center axis (CL2) to the rear end side, satisfies 0.52 ≤ B/A ≤ 0.91.