Ceramic Heater Central Section Resistance for Thermal Stress Reduction
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Solution Overview
Problem
Ceramic heaters used in gas sensors deteriorate quickly due to repeated on-off cycles, leading to reduced product life, as they expand and contract, affecting the heating section's integrity.
Innovation Solution
A ceramic heater design with a conductive layer featuring central linear sections with a lower resistance value per unit length than the outer sections, which reduces peak temperatures and minimizes expansion and contraction, thereby extending the heater's lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the ceramic heater is repeatedly turned on and off to meet emissions control requirements, then the heating function is maintained, but the heating section deteriorates due to repeated expansion and contraction, reducing product life
Solution Approach 1:
The patent applies local quality by creating different resistance values in different sections of the heating pattern. The central section has a first resistance value while the end sections have a second resistance value, allowing each section to have different thermal characteristics that reduce overall stress during thermal cycling
Solution Approach 2:
The patent changes the resistance parameter along the heating pattern to control temperature distribution. By making the central section resistance different from the end sections, the patent creates a temperature profile that reduces thermal stress and expansion/contraction damage during repeated on-off cycles
2Ease of manufacture
If the heating resistance pattern uses uniform line width and thickness, then the manufacturing is simple, but the temperature distribution is non-uniform with end sections being cooler, reducing heating efficiency
Solution Approach 1:
The patent applies local quality by creating different resistance values in different sections of the heating pattern. The central section has a first resistance value while the end sections have a second resistance value, allowing each section to have different thermal characteristics that reduce overall stress during thermal cycling
Solution Approach 2:
The patent changes the resistance parameter along the heating pattern to control temperature distribution. By making the central section resistance different from the end sections, the patent creates a temperature profile that reduces thermal stress and expansion/contraction damage during repeated on-off cycles
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 improved design effectively decreases peak temperatures at the central sections, reducing deterioration and extending the ceramic heater's life, and consequently, the gas sensor element's life as well.
Implementation Method 1
a conductive layer configured to generate heat when receiving electric power
Implementation Method 2
the ceramic heater is repeatedly expanded and contracted
Data Source
AI summary
A ceramic heater has a plate substrate made of ceramic and a conductive layer. The conductive layer has a heating section and a pair of lead sections. When receiving electric power, the conductive layer generates heat. The lead sections are formed at one section on the plate substrate adjacent to each other in a width direction and formed along a longitudinal direction on the plate substrate. The heating section is formed to meander on the other section in the plate substrate and both ends of the heating section are connected to the lead sections, respectively. In particular, central sections formed at a central area of the heating section in the width direction and the longitudinal direction have a resistance value which is lower per unit length than a resistance value of other linear shaped sections of the heating section.