Honeycomb Structure with Variable Resistivity Electrodes
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Solution Overview
Problem
Existing honeycomb structures with metal heaters face issues of excessive current flow when using high-voltage power sources, leading to potential damage to the power source circuit and difficulties in integrating the heater and catalyst, while also experiencing challenges in temperature distribution uniformity and catalyst loading.
Innovation Solution
A honeycomb structure with electrode sections having varying electrical resistivity, where the center portion has a lower resistivity than the expanded portions, and a band-like shape extending in the cell direction, to manage current flow and temperature distribution, while maintaining structural integrity and catalyst loading efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a metal heater is used in the honeycomb structure, then the heating function is improved, but the electric resistance is too low causing excessive current flow
Solution Approach 1:
The invention changes the electrical resistivity parameter of the honeycomb structure itself by selecting specific materials (silicon carbide, silicon nitride, or cordierite with specific compositions) to achieve a resistivity between 1-200 Ω·cm. This allows the structure to function as both catalyst carrier and heater while controlling current flow to prevent circuit damage.
2Temperature
If a metal heater is disposed on the upstream side of the honeycomb structure, then the exhaust gas temperature is raised, but the heater and catalyst cannot be integrated
Solution Approach 1:
The invention merges the heater and catalyst into a single integrated honeycomb structure. The heating elements are formed as integral parts of the honeycomb walls themselves, allowing the structure to simultaneously perform catalytic conversion and heating functions without requiring separate components.
Solution Approach 2:
The honeycomb structure is designed to perform multiple functions: it serves as the catalyst carrier, the heating element, and the structural support all in one component. This multi-functionality eliminates the need for separate metal heaters and simplifies the overall system.
3Ease of manufacture
If the honeycomb structure is made of cordierite or sintered silicon carbide, then the catalyst can be loaded, but the heating efficiency is insufficient when using high voltage power sources
Solution Approach 1:
The invention optimizes the electrical resistivity parameter of the honeycomb material to fall within 1-200 Ω·cm, which is higher than traditional cordierite or sintered silicon carbide. This parameter change enables efficient heating when using high voltage power sources while maintaining catalyst loading capability.
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 honeycomb structure effectively suppresses excessive current flow and temperature distribution bias, ensuring safe and efficient operation when using high-voltage power sources, while allowing for effective catalyst loading and uniform heat generation.
Implementation Method 1
the heater made of a metal has a low electric resistance, and hence when such a power source having the high voltage is used, there is the problem that a current excessively flows
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
There is disclosed a honeycomb structure including a honeycomb structure section 4, and a pair of band-like electrode sections 21 arranged on a side surface 5 of the honeycomb structure section, an electrical resistivity of the honeycomb structure section 4 is from 1 to 200 Ωcm, in a cross section which is perpendicular to a cell extending direction, the one electrode section 21 is disposed on an opposite side of the other electrode section 21 via the center O, an angle which is 0.5 time as large as a central angle of the electrode section 21 is from 15 to 65°, and each of the electrode sections 21 is formed so as to become thinner from a center portion 21a in a peripheral direction toward both ends in the peripheral direction, and in the cross section which is perpendicular to the extending direction of the cells 2, the whole outer peripheral shape is a round shape.