Glow Plug Heater Bent Lead Aspect Ratio
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Solution Overview
Problem
Heaters, such as glow plug heaters, face micro-crack issues due to stress concentration at the interface between the lead and insulating base when high inrush power is applied, leading to thermal expansion and reduced durability.
Innovation Solution
A heater design with bent lead portions having a larger aspect ratio than the terminal portion, dispersing the load of inrush power and reducing stress concentration, combined with a metallic holding member to enhance durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If inrush power is increased to achieve rapid heating, then heating speed is improved, but stress concentration occurs at the bent portion of the lead causing micro-cracks
Solution Approach 1:
The bent portions of the lead are designed with a specific cross-sectional aspect ratio (larger than the terminal portion) to create localized structural characteristics that disperse stress concentration. This local geometric modification allows the lead to withstand inrush power while preventing micro-cracks at the bent portions.
2Power
If large current is applied to the resistor for rapid heating, then power output is improved, but thermal expansion causes micro-cracks at the lead-interface
Solution Approach 1:
The cross-sectional aspect ratio of the bent portions is specifically designed to be larger than that of the terminal portion. This parameter change in the lead geometry modifies the stress distribution pattern, allowing the system to handle high inrush power while preventing thermal expansion-induced micro-cracks at the interface between the lead and insulating base.
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 effectively suppresses micro-cracks and enhances the reliability and durability of the heater by dispersing the inrush power load, allowing for reliable rapid heating without local expansion-induced damage.
Implementation Method 1
a resistor (3) embedded in the insulating base (2)
Implementation Method 2
the load of inrush power placed on the two bent portions (41, 42) is dispersed from the outer sides of the curves of the bent portions
Implementation Method 3
a heater capable of more rapid heating has been desired, and accordingly, a need has occurred for increasing the electric power (inrush power) supplied through the terminal portion so that a large current is applied to the resistor at the start
Data Source
Figure 1~2(b)
Figure 3(a)~3(e)
Figure 4
AI summary
[Object] To provide a highly reliable, durable heater in which micro-cracks caused by stress concentration resulting from local expansion is suppressed even when a large current flows through a bent portion of the lead, for example, for rapid heating, and a glow plug including the heater. [Solution] A heater 1 of the present invention includes an insulating base 2, a resistor 3 embedded in the insulating base 2, a lead 4 embedded in the insulating base 2. One end of the lead 1 is joined to the resistor 3, and the other end is led out as a terminal portion 5 on the surface of the insulating base 2. The lead 4 in longitudinal section has at least two bent portions 41. The bent portions 41 in cross-section each have an aspect ratio larger than the aspect ratio of the terminal portion 5.