Ceramic Heater Resistor Element with Tapered Cross Section
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Solution Overview
Problem
Ceramic heaters and glow plugs face challenges in achieving quick heating performance, reducing power consumption, and maintaining durability, especially when used for super quick temperature raising, which puts a large load on the devices and can be affected by variations in power supply voltage.
Innovation Solution
A ceramic heater design featuring a substrate with a resistor element having a U-shaped heat-generating portion and intermediate portions between the heat-generating and lead portions, where the cross-sectional areas and diameters of the circumscribed circles at different points satisfy specific relations, reducing stress concentration and optimizing heat generation efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the resistance of the glow plug is reduced to enable quick heating performance, then the heating speed is improved, but a large rush current flows at startup causing durability problems
Solution Approach 1:
The resistor element is designed with non-uniform resistance distribution along its length. The front end portion (heat-generating portion) has higher resistance to limit rush current, while the rear end portion (lead portions) has lower resistance to enable quick heating. This local differentiation of resistance properties resolves the contradiction between heating speed and durability.
2Use of energy by moving object
If the cross-sectional area ratio of heat-generating portion to lead portions is increased to reduce power consumption, then energy efficiency is improved, but temperature uniformity across the support member surface deteriorates
Solution Approach 1:
The resistor element features local differentiation in cross-sectional area: the heat-generating portion has smaller cross-sectional area to reduce power consumption, while the lead portions have larger cross-sectional area to maintain temperature uniformity. This spatial variation in geometry allows simultaneous optimization of energy efficiency and thermal uniformity.
3Temperature
If the temperature at the surface of the support member is increased to heat low-temperature surfaces, then heating performance is improved, but energization durability drops due to excessive thermal stress
Solution Approach 1:
The resistor element is designed with non-uniform cross-sectional area along its length. The lead portions have larger cross-sectional area to distribute thermal stress and prevent excessive temperature rise, while the heat-generating portion has smaller cross-sectional area to concentrate heating where needed. This local geometric differentiation enables improved heating performance while maintaining energization durability.
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 design achieves excellent quick heating performance, reduces power consumption, and enhances durability by distributing heat generation efficiently and minimizing stress on the heat-generating portion, allowing the ceramic heater to reach high temperatures with minimal power consumption and maintain performance even at lower voltage levels.
Implementation Method 1
a heating resistor element formed of, for example, an electrically conductive ceramic is embedded in an electrically insulative ceramic substrate
Data Source
Figure 1
Figure 2
Figure 3(a)~3(c)
AI summary
[Objective] To provide a ceramic heater which has excellent quick heating performance, can reduce power consumption, and is excellent in durability, and a glow plug which can realize quick heating performance, low power consumption, and durability in the case of quick temperature rising, all being realized at high levels. [Means for Solution] A ceramic heater 12 includes a substrate 60 and a resistor element 30 buried in the substrate 60. The resistor element 30 includes a heat-generating portion 33 formed of an electrically conductive ceramic and folded into a U-like shape, lead portions 31 joined to end portions of the heat-generating portion 33, and intermediate portions 40 located between the heat-generating portion 33 and the lead portions 31. The intermediate portions 40 are formed such that, when cross sections at arbitrary two points P1 and P2 along the axis XA direction are compared, both the diameter CL of an imaginary circumscribed circle CG containing cross sections of the resistor element 30 and the total cross sectional area HS of the cross sections become small in the front end side cross section as compared with those in the rear end side cross section.