Small-Diameter Spark Plug Resistive Seal Design
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Solution Overview
Problem
Existing spark plug designs face challenges in suppressing electromagnetic interference (EMI) in small diameter applications, where internal resistor integration weakens ceramic insulation, leads to structural integrity issues, and heating of the upper terminal stud causes oxidation and connector installation problems.
Innovation Solution
A spark plug assembly with a tubular insulator and a conductive shell, featuring an intermediate tapered section in the central passage to self-center the connecting pin and increase insulator wall thickness, along with a fired-in suppressor seal that eliminates the need for heating the upper terminal stud, using a conductive glass seal and a connecting pin with a tapered head to ensure proper assembly and electrical connectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If an internal resistor element is placed within the ceramic insulator to suppress EMI, then electromagnetic interference suppression is improved, but the structural integrity of the ceramic insulation is weakened due to thin wall sections
Solution Approach 1:
The resistor element is divided into multiple segments or beads arranged in series along the central passage, rather than a single large continuous resistor. This segmentation allows the resistor to occupy less cross-sectional area while maintaining the required resistance value, thereby preserving the ceramic insulator wall thickness and structural integrity.
Solution Approach 2:
The resistor element is nested within the hollow central passage of the ceramic insulator, utilizing the existing internal space. This nesting approach allows the resistor to be contained within the insulator without requiring additional space that would thin the insulator walls, maintaining both EMI suppression functionality and structural strength.
2Strength
If the cross-sectional area of the resistor is reduced to maintain insulator strength, then structural integrity is improved, but the diameter of the upper terminal stud must be reduced which causes buckling during cold pressing and hot pressing operations
Solution Approach 1:
The resistor is segmented into multiple smaller beads that can be individually pressed into place. This segmentation allows the use of a standard-diameter terminal stud for the cold pressing operation, as each resistor bead is small and can be compacted independently without requiring a large stud diameter, thereby preventing buckling while maintaining insulator strength.
3Ease of manufacture
If the upper terminal stud is heated along with the sealing glasses in a furnace, then the sealing process is completed, but the terminal stud undergoes oxidation and discoloration which requires more force to connect the spark plug wire lead
Solution Approach 1:
The upper terminal stud is extracted from the furnace heating process and protected from oxidation by being removed before the high-temperature sealing operation. The sealing glasses are heated and bonded without the terminal stud present, eliminating the oxidation and discoloration problems while still achieving the required seal integrity.
Solution Approach 2:
A protective coating or atmosphere control mechanism is used as an intermediary during the furnace heating process to prevent oxidation of the terminal stud. This allows the terminal stud to remain in the furnace for the sealing operation without suffering from oxidation and discoloration, maintaining both the sealing quality and the terminal's aesthetic appearance and ease of connection.
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 solution effectively suppresses EMI, enhances dielectric capacity and structural integrity, and prevents oxidation of the terminal stud, improving the reliability and aesthetics of small diameter spark plugs by ensuring proper assembly and electrical performance.
Implementation Method 1
A spark plug assembly for a spark-ignited combustion event... A fired-in suppressor seal electrically interconnects the electrode head and the shank of the connecting pin... resistive seal
Implementation Method 2
The central passage includes an intermediate tapered section... increase insulator wall thickness... enhances dielectric capacity
Implementation Method 3
the connecting pin has a tapered pin head that is seated in the tapered section of the central passageway... self-center the connecting pin
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
A spark plug (10) includes an intermediate connecting pin (54) disposed in the central passage (28) of an the insulator body (12). The connecting pin (54) seats in an intermediate taper section (72) within the central passage (28), which is generally frustoconical and establishes a transition between a first larger diameter of the central passage (28) and a second smaller diameter. The intermediate tapered section (72) is located longitudinally above a filleted transition (26) feature of the insulator body (12) exterior. A pin head (53) of the connecting pin (54) has a complementary tapered under-cut and seats against the intermediate tapered section (72) to provide self-centering of the connecting pin (54) without trapping gas during the assembly process. The intermediate taper section (72) also provides an increase in insulator wall thickness which improves dielectric capacity and structural integrity of the insulator (12).