Glow Plug Metallic Seal Insulating Layer High Temp
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Solution Overview
Problem
Existing glow plugs face limitations in high-temperature applications due to the temperature constraints of elastomer sealing elements, which are not suitable when used outside cooled engine blocks, leading to potential short circuits and reduced reliability.
Innovation Solution
A metallic sealing ring with an electrical insulating layer is used between the glow tube and the connection bolt, where the insulating layer is applied to prevent electrical shorts and the press connection ensures a gas-tight seal, with the insulating layer's properties determining the operating temperature resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an elastomer sealing element is used to seal between the glow tube and connection bolt, then the sealing function is achieved, but the maximum operating temperature is limited to 200°C
Solution Approach 1:
The patent changes the material parameter of the sealing element from elastomer to metallic sealing ring, which fundamentally alters the temperature resistance parameter. The metallic sealing ring can withstand temperatures up to 1000°C, compared to the elastomer's 200°C limit, while maintaining sealing functionality through the press connection between the glow tube and connection bolt.
Solution Approach 2:
The patent creates a composite sealing structure combining the metallic sealing ring with an electrical insulating layer. This composite design simultaneously achieves thermal resistance (through the metal), electrical insulation (through the coating layer), and sealing functionality (through the press connection), resolving multiple contradictory requirements.
2Temperature
If a metallic sealing ring is used instead of elastomer, then temperature resistance is improved, but electrical insulation between connection bolt and glow tube deteriorates
Solution Approach 1:
The patent introduces an electrical insulating layer as an intermediary substance between the metallic sealing ring and the electrical components. This insulating layer acts as a mediator that prevents direct electrical contact between the conductive metallic sealing ring and the connection bolt or glow tube, thereby eliminating the short circuit risk while preserving the high-temperature resistance of the metal.
Solution Approach 2:
The sealing structure becomes a composite of metallic sealing ring plus electrical insulating layer, where each material contributes its superior property: the metal provides thermal resistance and mechanical sealing, while the insulating layer provides electrical isolation. This composite approach resolves the contradiction between conductivity and insulation.
3Object-affected harmful factors
If the connection bolt is provided with an electrical insulating layer, then electrical insulation is achieved, but the sealing reliability may deteriorate
Solution Approach 1:
The patent applies the electrical insulating layer locally only in the sealing area of the connection bolt, rather than coating the entire component. This localized application ensures that electrical insulation is provided precisely where needed (at the sealing interface), while the rest of the connection bolt maintains its original properties for mechanical fastening and electrical conduction elsewhere in the circuit.
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
This solution provides a reliable and cost-effective heater seal with high temperature resistance, allowing the connection-side area of the glow plug to withstand extreme temperatures similar to the glow area, enhancing durability and preventing electrical shorts.
Implementation Method 1
the insulating layer is applied to prevent electrical shorts
Implementation Method 2
the press connection ensures a gas-tight seal
Data Source
Figure 1~2
AI summary
Disclosed is a glow plug comprising a sheathed element (14) which is accommodated in a metallic housing. The sheathed element comprises a glow tube (16) and a coiled element (18) arranged in the glow tube (16), wherein one end of the coiled element is in electrical contact with the glow tube and the other end is in electrical contact with a connecting pin (17). The connecting pin protrudes into an axial opening (22) of the glow tube where it is connected in a sealing section (23) to the glow tube in an electrically insulating manner by means of a heating body seal. An electric insulating layer (33) is formed at least in the sealing section on the glow tube and/or the connecting pin. In order to provide a heating body seal, the glow tube is pressed in the region of the electric insulating layer onto the connecting pin.