Heated Catalyst Wiring Slit Design for Thermal Stress
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Solution Overview
Problem
In electrically heated catalyst devices, comb teeth-like wiring lines at the ends of the wiring line member tend to break near their bases due to repeated temperature rises and falls, caused by thermal expansion and contraction differences between metallic and ceramic materials.
Innovation Solution
Incorporating slits in the root section of the wiring line member extending in the circumferential direction of the catalyst support to prevent inward shifting of the wiring line ends, with first and second slits arranged alternately and becoming longer as they move away from the central part towards the ends, and forming an opening for the pull-out section to allow for thermal expansion and contraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If comb teeth-like wiring lines are fixed to the surface electrode without slits in the root section, then the wiring lines can be securely attached to the electrode, but the wiring lines break near their bases due to repeated thermal expansion and contraction
Solution Approach 1:
The root section of the wiring line member is divided into multiple segments by forming slits that extend from the outer edge in the circumferential direction. These slits create expansion/contraction regions that allow the root section to flex during thermal cycles, preventing stress concentration at the base of the comb teeth-like wiring lines and thereby preventing breakage while maintaining secure attachment.
2Stability of the object's composition
If the wiring line member is made rigid to maintain structural stability, then the device structure is simple, but the wiring lines cannot accommodate thermal expansion and contraction differences between metallic and ceramic materials
Solution Approach 1:
The wiring line member exhibits different mechanical properties in different regions: the comb teeth-like wiring lines and central root section maintain rigidity for stable attachment and current conduction, while the regions adjacent to the slits in the root section are designed to be flexible to accommodate thermal expansion and contraction. This local differentiation of mechanical properties allows the structure to remain stable overall while accommodating thermal stress locally.
3Reliability
If slits are added to the root section of the wiring line member to prevent breakage, then the service life is extended, but the manufacturing process becomes more complex
Solution Approach 1:
The slits in the root section are designed with specific parameters: they extend from the outer edge in the circumferential direction by a controlled length, and their width and depth are optimized to provide sufficient flexibility for thermal accommodation while maintaining structural integrity. These parameter optimizations allow the slits to be formed using standard manufacturing processes without significantly increasing manufacturing complexity, while effectively extending the service life of the wiring lines.
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
Prevents the breaking of comb teeth-like wiring lines near their bases by minimizing inward shifting due to temperature fluctuations, ensuring the device's longevity and operational efficiency.
Implementation Method 1
the catalyst support is heated by feeding a current through the surface electrode and the wiring line member
Implementation Method 2
a thermal stress occurs due to the difference between the linear expansion coefficient of the metallic material forming the surface electrodes and wiring lines and that of the ceramic material forming the catalyst support
Data Source
AI summary
An electrically heated catalyst device includes a catalyst support, a surface electrode disposed on an outer surface of the catalyst support and extending in an axis direction of the catalyst support, a wiring line member including a root section extending in the axis direction of the catalyst support and comb teeth-like wiring lines extending from the root section in a circumference direction of the catalyst support and fixed to the surface electrode, an outer cylinder covering an outer surface of the catalyst support, and a holding member holding the catalyst support and packed between the catalyst support and the outer cylinder, in which the catalyst support is heated by feeding a current through the surface electrode and the wiring line member. A slit extending from an outer edge in the circumferential direction of the catalyst support is formed in the root section of the wiring line member.