Glow Plug Graphite Seal Insulating Layer
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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, necessitating a more reliable and durable sealing solution.
Innovation Solution
A graphite sealing element is used in conjunction with an insulating layer on the connecting bolt or glow tube, where the graphite ring is pressed between the glow tube and the connecting bolt, with the glow tube diameter reduced to secure the seal, avoiding additional material connections and enhancing temperature resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If an elastomer sealing element is used between the glow tube and connection bolt, then the sealing function is achieved, but the maximum temperature is limited to 200°C in long-term use
Solution Approach 1:
The patent changes the material parameter from elastomer to graphite, which fundamentally alters the temperature resistance capability. Graphite can withstand temperatures exceeding 200°C while maintaining sealing properties, directly resolving the temperature limitation of elastomer seals in glow plug applications
Solution Approach 2:
The invention creates a composite sealing structure by combining graphite sealing element with an electrical insulating layer. This composite approach simultaneously achieves high-temperature resistance from graphite and electrical insulation to prevent short circuits, while the metallic housing provides structural support and thermal management
2Temperature
If a metallic sealing ring is used instead of elastomer, then temperature resistance is improved, but electrical insulation requires additional insulating layer and complex connection
Solution Approach 1:
The patent changes the material parameter from metal to graphite for the sealing element. Graphite inherently provides both the required temperature resistance and electrical insulation properties, eliminating the need for additional insulating layers and simplifying the overall device structure while maintaining sealing effectiveness at elevated temperatures
3Temperature
If a graphite sealing element is used, then temperature resistance and electrical insulation are improved, but the sealing pressure and fit precision must be optimized
Solution Approach 1:
The patent applies preliminary action by pre-compressing the graphite sealing element before installation into the sealing groove. This pre-compression ensures that the graphite element maintains adequate contact pressure with both the glow tube and connection bolt, compensating for any dimensional variations and ensuring reliable sealing without requiring extremely tight manufacturing tolerances
Solution Approach 2:
The invention optimizes the geometric parameters of the graphite sealing element, including its cross-sectional area, thickness, and compression ratio. By carefully selecting these parameters, the seal achieves optimal fit precision and contact pressure under operating conditions, ensuring reliable sealing performance across temperature cycles
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 configuration provides a reliable, cost-effective, and durable heating element seal capable of withstanding higher temperatures without electrical short circuits, suitable for applications beyond cooled engine environments.
Implementation Method 1
The sealing element made of graphite is arranged in an electrically insulated manner in a sealing section between the glow tube and the connecting bolt
Implementation Method 2
The sealing element made of graphite is pressed between the glow tube and the connecting bolt
Implementation Method 3
the glow tube has a diameter reduction at least in the area of the sealing section, by means of which the sealing element is pressed as a graphite ring between glow tube and connecting bolt
Data Source
Figure 1
Figure 2~3
AI summary
The invention relates to a glow plug comprising a sheathed element 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 (18) is in electrical contact with the glow tube (16) and the other end is in electrical contact with a connecting pin (17). The connecting pin (17) protrudes into an axial opening (22) of the glow tube (16) where it is connected in a sealing section (23) to the glow tube (16) in an electrically insulating manner by means of a heating body seal (30). The heating body seal (30) is embodied with a sealing element (31) made of graphite and at least one electric insulating layer (32), wherein the glow tube (16) is pressed with the sealing element (31) made of graphite on the connecting pin (17). In order to produce the heating body seal (30), a pre-pressed graphite ring (31) is pressed in the opening (22) of the glow tube (16) in the sealing section (23) between glow tube (16) and connecting pin (17).