Glow Plug Sheath Tube Forward End Design
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Solution Overview
Problem
Glow plugs face challenges in securing both durability and rapid heat-up performance, as a short distance between the heat generation coil and sheath tube leads to exposure and durability issues, while a long distance increases heat capacity, making rapid heating difficult.
Innovation Solution
The glow plug design allows for adjustable length of the forward end portion, with a rectilinear or spiral heat generation coil, reducing the thickness of the sheath tube's forward end portion to enhance durability and rapid heat-up performance by optimizing the thickness ratio and welding process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the distance between the forward end of the heat generation coil and the forward end of the sheath tube is short, then rapid heat-up performance is improved, but durability deteriorates due to exposure of the heat generation coil
Solution Approach 1:
The invention optimizes the distance parameter B between the forward end of the heat generation coil and the forward end of the sheath tube, establishing a specific range (0.5mm to 2.0mm) that balances rapid heat-up performance with durability. This parameter optimization prevents coil exposure while maintaining fast heating capability.
Solution Approach 2:
The invention applies different thickness values to different portions of the sheath tube. The forward end portion has a thickness C that is 0.95 to 1.05 times the thickness A of the side portion, creating a localized reinforcement zone that enhances durability at the critical forward end without compromising overall heat-up performance.
2Reliability
If the distance between the forward end of the heat generation coil and the forward end of the sheath tube is long, then durability is improved, but rapid heat-up performance deteriorates due to increased heat capacity
Solution Approach 1:
The invention establishes an optimal distance range (0.5mm to 2.0mm) that prevents excessive heat capacity accumulation while ensuring the heat generation coil remains protected. This parameter optimization resolves the contradiction between durability and heat-up speed.
Solution Approach 2:
By making the forward end portion thickness C equal to 0.95 to 1.05 times the side portion thickness A, the invention creates a localized structural feature that provides durability enhancement without significantly increasing overall heat capacity, thus maintaining rapid heat-up performance.
3Reliability
If the thickness of the forward end portion of the sheath tube is increased, then durability is improved, but heat capacity increases making rapid heating difficult
Solution Approach 1:
The invention optimizes the thickness ratio between the forward end portion (thickness C) and the side portion (thickness A), establishing that C should be 0.95 to 1.05 times A. This parameter control ensures durability is maintained while heat capacity is kept low for rapid heating.
Solution Approach 2:
The invention applies a localized thickness adjustment at the forward end portion, making it slightly thicker than or equal to the side portion. This local reinforcement provides durability where needed without significantly increasing overall heat capacity.
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 design secures both durability and rapid heat-up performance by restraining exposure of the heat generation coil and reducing heat capacity, allowing the glow plug to reach high temperatures quickly while maintaining longevity.
Implementation Method 1
a heat generation coil disposed in the sheath tube and whose forward end is connected to a forward end portion of the sheath tube
Data Source
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AI summary
To secure durability and rapid heat-up performance of a glow plug. A glow plug includes a sheath tube having a side portion extending in the axial direction and a forward end portion connected to the forward end of the side portion and closing the forward end of the side portion, and a heat generation coil disposed in the sheath tube in such a manner as to extend in the axial direction and whose forward end portion is connected to the forward end portion of the sheath tube. The forward end portion of the heat generation coil is surrounded by and embedded in the forward end portion of the sheath tube. An alloy portion located between the heat generation coil and the forward end portion of the sheath tube and formed of an alloy of a metal used to form the sheath tube and a metal used to form the heat generation coil has a thickness of 10 µm or less. The minimum thickness A of the side portion of the sheath tube as measured in a region along the axial direction where the heat generation coil is disposed, the distance B along the axial direction from the forward end of the sheath tube to the forward end of the heat generation coil, and the maximum thickness C of the forward end portion of the sheath tube along the axial direction meet the relational expressions B > A and C/A ≤ 2.5.