Glow Plug Terminal Sealing for Corrosion Prevention
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Solution Overview
Problem
Conventional glow plugs for diesel engines experience corrosion of connecting surfaces due to exposure to external moisture and corrosive gases, leading to increased resistance and reduced starting ability, as the gap between the main metal shell and the center wire is not fully sealed at the rear end, allowing external air to access the connecting surfaces.
Innovation Solution
A glow plug design that uses a sealing member, such as an O-ring made of rubber-like elastic material, to airtightly seal the rear end portion of the conductive member within the terminal member, preventing contact with external air and thus suppressing corrosion, along with an insulating spacer to ensure reliable insulation and prevent moisture or corrosive gas ingress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the gap between the main metal shell and the center wire is sealed with an O-ring and insulating member, then airtightness is maintained, but the connecting surfaces of the center wire and terminal member remain exposed to external air and moisture
Solution Approach 1:
The terminal member is designed with an enclosing portion that forms a nested structure around the rear end portion of the center wire. This nested configuration creates an inner chamber that houses the connecting surfaces, effectively shielding them from external corrosive environments while maintaining a compact overall structure.
Solution Approach 2:
A sealing member is introduced as an intermediary element between the terminal member and the main metal shell. This sealing member extends along the inner peripheral surface of the main metal shell and seals the shaft hole, creating a barrier that prevents external air and moisture from reaching the connecting surfaces inside the terminal member.
2Object-affected harmful factors
If the terminal member encloses the rear end portion of the center wire, then connecting surfaces are protected from corrosion, but the structure becomes more complex
Solution Approach 1:
The terminal member is designed to perform multiple functions simultaneously: it provides electrical connection through the center wire, encloses and protects the connecting surfaces from corrosion, and works with the sealing member to maintain the airtight environment. This multi-functionality reduces the need for additional separate protective components.
Solution Approach 2:
The enclosing portion of the terminal member is integrated directly with the connection structure, merging the protective enclosure function with the existing electrical connection components. This integration avoids adding separate protective housings or chambers, thereby simplifying the overall structure while still achieving corrosion protection.
3Object-affected harmful factors
If a sealing member is used to seal the shaft hole, then the rear end portion is protected from external air, but the insulating property between main metal shell and terminal member must be ensured
Solution Approach 1:
The sealing member is constructed from composite material that combines rubber-like elastic properties for sealing with insulating properties to prevent electrical conduction. This composite material allows the sealing member to simultaneously provide both the sealing function and the insulation function, eliminating the need for separate insulating components.
Solution Approach 2:
The material properties of the sealing member are specifically selected and engineered to change or adjust parameters such as elasticity, hardness, and electrical resistivity. By optimizing these material parameters, the sealing member can effectively seal the shaft hole while maintaining sufficient electrical insulation between the main metal shell and the terminal member.
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 seals the connecting surfaces from external air, preventing corrosion and maintaining the desired resistance values, ensuring reliable and efficient starting of diesel engines by maintaining the intended temperature characteristics.
Implementation Method 1
a sealing member, such as an O-ring made of rubber-like elastic material, to airtightly seal the rear end portion of the conductive member within the terminal member
Implementation Method 2
an insulating spacer to ensure reliable insulation and prevent moisture or corrosive gas ingress
Implementation Method 3
A glow plug used for assisting the starting of a diesel engine includes a heater that generates heat by conduction
Data Source
Figure 1
Figure 2
Figure 3
AI summary
[Object] To provide a glow plug such that corrosion of connecting surfaces of a conductive member and a terminal member is suppressed, and a method for manufacturing the same. [Means for Solution] A glow plug 1 is provided with: a heater 2; a tubular main metal shell 4 with a shaft hole 43; a conductive member 3 extending in the shaft hole 43 of the main metal shell 4 toward a rear end side GK in an axial direction HJ; a metal terminal member 5 with one part 55 positioned in the shaft hole 43 and another part 56 protruding from a rear end 48 of the main metal shell 4 toward the rear end GK in the axial direction HJ, the terminal member 5 including an enclosing portion 51 opened toward a front end side GS in the axial direction HJ, the enclosing portion 51 housing a rear end portion 32 of the conductive member 3 and having electrical continuity with the rear end portion 32, the terminal member 5 being disposed in the shaft hole 43 while spaced apart from an inner peripheral surface 43m of the main metal shell 4 forming the shaft hole 43; and a sealing member 7 made of an insulator and airtightly sealing and insulating between the inner peripheral surface 43m and the terminal member 5 in the shaft hole 43.