Glow Plug Heating Rod Pre-Tension Assembly
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Solution Overview
Problem
The production of ceramic glow plugs is complicated by the need for precise axial alignment and soldering of the glow element, which can lead to misalignment issues due to uneven solder application.
Innovation Solution
A pre-tension method is used to connect the contact element to the glow element by pressing it against the glow element, eliminating the need for soldering and ensuring precise alignment, where the sheath is compressed axially or radially indented to create tensile stress that maintains the contact, and a press-fit assembly is formed to secure the glow element within the sheath.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If soldering is used to connect the contact element to the glow element, then electrical contact is achieved, but axial misalignment occurs due to uneven solder application
Solution Approach 1:
The patent replaces the soldering process (thermal/chemical joining) with a mechanical press-fit system. The contact element is inserted into the glow element and retained through elastic deformation of the glow element's connector portion, eliminating the need for solder and its associated misalignment problems.
Solution Approach 2:
The patent utilizes elastic deformation as a key parameter to create a press-fit connection. The connector portion of the glow element is elastically deformed during assembly to secure the contact element, and this elastic recovery provides the retaining force without requiring soldering.
2Force
If the glow element is inserted into the sheath and compressed axially, then pre-tension is created to press components together, but the sheath requires additional processing steps
Solution Approach 1:
The patent applies local quality by creating a conical interior surface at a specific location within the sheath. This localized geometric feature works with the cylindrical glow element to generate radial contact forces when axial compression is applied, providing pre-tension without requiring complex processing of the entire sheath.
Solution Approach 2:
The patent transforms the one-dimensional axial compression force into two-dimensional radial contact forces through the conical surface geometry. The axial compression on the conical surface generates radial outward forces that press the contact element against the glow element, effectively creating pre-tension through dimensional transformation.
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 simplifies the production process, avoids misalignment, and ensures a reliable electrical contact without soldering, reducing the number of components and allowing for versatile glow plug designs.
Implementation Method 1
Axially compressing the sheath or radially indenting the same creates a tensile stress in the sheath, which is exerted in the longitudinal direction of the sheath. This tensile stress pushes the components arranged inside the sheath against each other, namely the contact element against the connector portion of the glow element.
Implementation Method 2
finally retracting (e.g., by bending the circumferential wall radially inwards) or beading the sheath at its rear end facing away from the glow tip, after which the sheath is compressed axially.
Implementation Method 3
It is preferable to compress the sheath axially while at least a section of the sheath is heated.
Data Source
AI summary
This document describes a heating rod for a glow plug with a ceramic glow element having a glow tip at its front end and a connector portion at its rear end, a contact element making electrical contact with the connector portion of the glow element, and a sheath, from which the front end of the glow element protrudes. According to this disclosure, the contact element is pressed against the glow element under pre-tension. Furthermore, this document describes a method for producing such a heating rod and a glow plug with such a heating rod.