Glow Plug Heat Element Positioning for Offset Prevention
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Solution Overview
Problem
Glow plugs with tungsten-based heat generation elements face issues with proper fixation due to tensile stress during solidification, leading to potential offset and reduced durability, especially with smaller wire diameters, which affects temperature distribution and engine startability.
Innovation Solution
The glow plug design ensures the heat generation element is positioned in the fusion zone's periphery, where it solidifies early, with specific radial distance constraints between cross-sections and the base metal portion, maintaining contiguity and preventing offset, thereby stabilizing engine startability and reducing short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the heat generation element is fixed in the center of the fusion zone, then the fixation process is simpler, but the heat generation element moves or offsets during solidification due to tensile stress
Solution Approach 1:
The heat generation element is preliminarily positioned in the periphery region of the fusion zone before solidification occurs. This preliminary positioning in a region that solidifies early prevents subsequent movement during the solidification process, resolving the contradiction between simple fixation and precise positioning.
2Power
If the wire diameter of the heat generation element is reduced to increase heat generation efficiency, then the heating performance improves, but the element becomes more susceptible to offset due to lower rigidity
Solution Approach 1:
The heat generation element is placed in a specific local region (periphery of the fusion zone) that has different solidification characteristics. This local positioning compensates for the reduced rigidity of thinner wire by utilizing the early solidification of the periphery region to provide immediate structural support and prevent offset.
3Ease of manufacture
If the heat generation element offsets from the center during solidification, then the manufacturing process is simpler, but the temperature distribution becomes non-uniform and durability decreases
Solution Approach 1:
The invention utilizes the natural tensile stress and early solidification of the periphery region of the fusion zone, which would normally be considered a challenge, as a beneficial mechanism to automatically secure the heat generation element in position. The periphery solidification acts as a natural fixing mechanism that prevents offset and ensures uniform temperature distribution.
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 ensures the heat generation element is fixed at the desired position without offset, enhancing temperature distribution uniformity, improving engine startability, and increasing durability by reducing short circuit occurrences.
Implementation Method 1
the forward end of the tubular member in which the forward end of the heat generation element is disposed is melted; then, the melted forward end is solidified, thereby forming the fusion zone into which the forward end of the heat generation element is inserted. In the course of solidification, the fusion zone is solidified such that solidification starts from its periphery and gradually proceeds toward the center.
Implementation Method 2
a glow plug having a heat generation element which contains tungsten (W) as a main component is proposed
Data Source
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AI summary
To provide a glow plug having a heat generation element fixed at a desired position in a forward end of a tubular member. A radial distance F between the radially outermost end of a first heat-generation-element cross section 901 which is a rearmost one of the cross sections of a heat generation coil 820 appearing in a fusion zone 891 and disposed on one side of an axial line and the radially innermost end of a base metal portion 893 is 0.200 mm or less. Specifically, the distance F between a straight line L1 extending along the axial line from the radially outermost end of the first heat-generation-element cross section 901 and a straight line L2 extending along the axial line from the radially innermost end of the base metal portion 893 is 0.200 mm or less. Further, a radial distance G between the radially outermost end of a second heat-generation-element cross section 902 which is a rearmost one of the cross sections of the heat generation coil 820 appearing in the fusion zone 891 and disposed on the other side of the axial line and the radially innermost end of the base metal portion 893 is 0.200 mm or less. Specifically, the distance G between a straight line L3 extending along the axial line from the radially outermost end of the second heat-generation-element cross section 902 and a straight line L4 extending along the axial line from the radially innermost end of the base metal portion 893 is 0.200 mm or less.