Sheathed Glow Plug Contact Element Design
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Solution Overview
Problem
Existing glow plugs with ceramic heating pins require insulating powder to prevent short circuits and mechanical stabilization, which complicates production and increases costs, while the electrical connection is not robust enough to withstand thermal and mechanical stress.
Innovation Solution
A glow plug design featuring a stable contact element connection between the ceramic heating pin and connecting bolt, eliminating the need for insulating powder, with a radially resilient contact sleeve and axially displaceable contact element to compensate for thermal expansion, and a reduced diameter section for increased radial distance and reduced risk of short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If insulating powder is filled into the housing to insulate the electrically conductive wire, then short circuit prevention is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent removes the insulating powder filling step from the manufacturing process by redesigning the electrical connection system. The contact element with integrated insulation and the reduced diameter connection-side section eliminate the need for additional insulating material, thereby simplifying manufacturing while maintaining short circuit prevention
Solution Approach 2:
The contact element serves as an intermediary component that provides both electrical connection and insulation functions. By integrating the insulating function into the contact element structure itself rather than relying on separate insulating powder, the patent achieves reliable short circuit prevention without adding manufacturing complexity
2Ease of manufacture
If a wire connection is used between the connecting bolt and ceramic heating pin, then electrical contacting is achieved, but mechanical stability and thermal stress resistance deteriorate
Solution Approach 1:
The contact element is designed with axial displacability, allowing it to move dynamically in response to thermal expansion and contraction of the ceramic heating pin. This dynamic capability maintains reliable electrical contact and mechanical stability throughout the operating temperature range, overcoming the rigidity limitations of fixed wire connections
Solution Approach 2:
The contact element combines conductive and insulating materials in a single integrated component. This composite structure provides both electrical connection and insulation functions while maintaining mechanical stability under thermal stress, eliminating the need for separate wire and insulating powder components
3Ease of manufacture
If the ceramic heating pin has a uniform diameter, then manufacturing is simpler, but space for lateral contacting and electrical insulation is insufficient
Solution Approach 1:
The ceramic heating pin features a reduced diameter connection-side section at the connection end, creating local radial space for the contact element while maintaining the standard diameter elsewhere. This localized modification provides necessary clearance for electrical contacting and insulation without requiring complete redesign of the entire heating pin geometry
Solution Approach 2:
By reducing the diameter in the connection-side section, the patent creates radial space that enables lateral contacting of the second electrical contact point on the peripheral surface. This dimensional modification in the radial direction solves the space constraint problem without affecting the axial length of the heating pin
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 provides a cost-effective, robust, and reliable electrical connection that maintains contact stability under thermal and mechanical stress, simplifying production and reducing the risk of short circuits and contact failure.
Implementation Method 1
The contact element has a radially resilient contact sleeve and a connecting conductor. The radially resilient contact sleeve produces a reliable sliding contact between the contact element and the second contact point on the connection-side section of the heating pin.
Implementation Method 2
The arrangement of the second electrical contact point on a peripheral surface of the ceramic heating pin in combination with an axially displaceable electrical contact of the contact element on the ceramic heating pin forms a sliding contact of the contact element on the second contact point, which enables length compensation through different thermal expansion of the connecting bolt and ceramic heating pin
Implementation Method 3
no transverse forces act on the contact element, so that there is no risk of the contact element being lifted off or bent away from the second electrical contact point, even in the event of thermal relaxation during operation of the glow plug
Data Source
Figure 1
Figure 2
Figure 3a~3b
AI summary
The invention relates to a glow plug for an internal combustion engine, comprising a housing (1) in which a connecting bolt (4) is arranged, and comprising a ceramic heating rod (2), said ceramic heating rod (2) having a first electrical contact point (6) and a second electrical contact point (7). The first electrical contact point (6) of the heating rod (2) is at least indirectly connected to the housing (1) of the glow plug. The second electrical contact point (7) is electrically connected to the connecting bolt (4) by means of a contact element (8). The second electrical contact point (7) is arranged on a circumferential surface of a section (5) of the ceramic heating rod (2) on a connecting side. The contact element (8) has a section allowing an axially moveable electrical contact with the second contact point (7), on the circumferential surface of the connecting-side section (5).