Ceramic Heater Brazed Joint Structure for Thermal Stress Durability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Ceramic heaters face challenges in maintaining adequate joining strength between the ceramic body and the cylindrical metal member due to repetitive thermal stresses and vibrations, which complicates miniaturization and durability, especially under rapid temperature cycles or high-temperature conditions.
Innovation Solution
A ceramic heater design featuring a brazing material restraining portion on the cylindrical metal member with reduced wettability, combined with a plating layer, rough-finished exposed metal surfaces, and circumferential protrusions or grooves, enhances the joining strength by preventing brazing material flow and maintaining adhesion under thermal stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the cylindrical metal member is made larger to increase the joining area with the ceramic body, then the joining strength between the cylindrical metal member and the ceramic body is improved, but the miniaturization of the ceramic heater becomes difficult
Solution Approach 1:
The end face of the cylindrical metal member is designed with non-uniform wettability, creating regions of high wettability and low wettability. This local differentiation allows the brazing material to be selectively restrained in specific areas, enhancing joining strength without requiring an overall increase in the cylindrical metal member's size.
Solution Approach 2:
The wettability parameter of the cylindrical metal member's end face is modified through surface treatment or material composition changes. By creating areas with different wettability characteristics, the brazing material's flow and distribution are controlled, achieving strong joining while maintaining a compact heater structure.
2Reliability
If the cylindrical metal member is made larger to increase the joining area, then the durability under thermal stress and vibrations is improved, but the miniaturization requirement cannot be met
Solution Approach 1:
By creating local variations in wettability on the end face, the brazing material forms a differentiated distribution pattern that enhances structural integrity. This local optimization provides improved resistance to thermal stress and vibrations without requiring a larger overall structure.
Solution Approach 2:
The brazing material restraining portion is pre-formed on the cylindrical metal member before the joining process. This preliminary structure guides the brazing material during assembly, ensuring optimal distribution and bonding strength from the start, which enhances durability under subsequent thermal cycling and vibrational stresses.
3Ease of manufacture
If the brazing material is allowed to flow freely during joining, then the joining process is simpler, but the joining strength deteriorates under repetitive thermal hysteresis and vibrations
Solution Approach 1:
The end face of the cylindrical metal member incorporates a brazing material restraining portion with low wettability that naturally limits brazing material flow during the joining process. This passive restraint mechanism maintains joining strength under thermal and mechanical stress while requiring minimal modification to the manufacturing process.
Solution Approach 2:
The brazing material restraining portion acts as an intermediary structure between the cylindrical metal member and the brazing material. It controls the brazing material's behavior during joining, preventing excessive flow while maintaining adequate bonding, thus preserving joining strength without complicating the manufacturing process.
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 enhanced design significantly increases the joining strength and durability of the ceramic heater, ensuring reliable performance even under rapid temperature fluctuations and high-stress conditions, thereby improving the overall durability and stability of the ceramic heater.
Implementation Method 1
the brazing material restraining portion having lower wettability to the brazing material than that of other portions of the end face of the one end
Implementation Method 2
a surface of the exposed metal portion is rough-finished
Implementation Method 3
the cylindrical metal member further comprises a plurality of protrusions or a plurality of grooves which are on a surface of the exposed metal portion, the protrusions and grooves configured to extend in a circumferential direction
Data Source
AI summary
Provided is a ceramic heater having enhanced joining strength between a heater section and a cylindrical metal member and having enhanced durability. A ceramic heater includes a heater section including a ceramic body and a heat-generating resistor configured to be buried in the ceramic body, a metal layer which is on part of a surface of the ceramic body and is configured to apply electric current to the heater section, and a cylindrical metal member, and inner surface of one end thereof being joined to the metal layer with a brazing material interposed therebetween, wherein the cylindrical metal member includes a brazing material restraining portion in an end face of the one end thereof, the brazing material restraining portion having lower wettability to the brazing material than that of other portions of the end face of the one end.