Electrically Heated Honeycomb Structure for Thermal Shock Stability
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Solution Overview
Problem
Honeycomb structures used in electrically heated catalyst systems experience cracks and positional displacement due to thermal shock and vibrations, compromising heat generation and mechanical strength.
Innovation Solution
A honeycomb structure with a specific coefficient of linear expansion range (4.1×10−6/°C to 4.8×10−6/°C) and a silicon carbide-silicon composite material composition, combined with electrode layers and metal terminals, to enhance thermal shock resistance and reduce cracking and displacement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a honeycomb structure made of ceramics with a coefficient of linear expansion within the range taught in prior art documents (3.5 to 6.0 ppm/K or 2.0×10−6/K to 4.6×10−6/K) is used, then thermal shock resistance is improved, but cracks still occur in practical applications
Solution Approach 1:
The patent applies parameter changes by precisely controlling the coefficient of linear expansion within a specific range (4.1×10−6/°C to 4.8×10−6/°C) and adjusting the silicon carbide particle size distribution (D10: 2-10 μm, D50: 15-30 μm, D90: 40-70 μm) to optimize both thermal shock resistance and mechanical strength, resolving the contradiction between these two properties
Solution Approach 2:
The patent uses composite materials by creating a silicon carbide-silicon composite where silicon carbide particles are dispersed in a silicon matrix, with specific particle size distribution and composition ratios (SiC: 60-90 wt%, Si: 10-40 wt%) to simultaneously achieve high thermal shock resistance and mechanical strength
2Ease of operation
If the honeycomb structure is housed in a metal pipe for practical installation, then ease of operation is improved, but positional displacement occurs due to vibrations
Solution Approach 1:
The patent applies parameter changes by optimizing the outer surface roughness of the honeycomb structure (Ra: 0.1-10 μm) to enhance friction and prevent displacement while maintaining ease of installation, resolving the contradiction between installability and positional stability
3Manufacturing precision
If cracks occur in the honeycomb structure, then manufacturing precision is maintained, but heat generation performance decreases
Solution Approach 1:
The patent uses composite materials with silicon carbide particles in a silicon matrix, where the silicon phase provides crack bridging and energy dissipation mechanisms that prevent crack propagation, thereby maintaining both structural integrity and heat generation performance under thermal stress
Solution Approach 2:
The patent applies parameter changes by optimizing the silicon carbide particle size distribution (D10: 2-10 μm, D50: 15-30 μm, D90: 40-70 μm) to create a hierarchical structure that effectively prevents crack initiation and propagation, maintaining heat generation performance while ensuring structural integrity
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 solution provides a honeycomb structure that maintains structural integrity under temperature changes and vibrations, ensuring consistent heat generation and mechanical stability, thereby improving the performance of electrically heated catalyst systems.
Implementation Method 1
a silicon carbide-silicon composite material composition, combined with electrode layers and metal terminals, to enhance thermal shock resistance and reduce cracking and displacement
Implementation Method 2
energizing the honeycomb structure itself to generate heat
Data Source
AI summary
A honeycomb structure including an electrically conductive honeycomb structure portion, comprising an outer peripheral wall, and partition walls disposed inside the outer peripheral wall and partitioning a plurality of cells forming flow paths from one end surface to the other end surface; and a pair of electrode layers provided on an outer surface of the outer peripheral wall so as to face each other across a central axis of the honeycomb structure portion; wherein a coefficient of linear expansion of the honeycomb structure portion measured according to JIS R1618:2002 when temperature is changed from 40° C. to 300° C. is 4.1×10−6/° C. or more, and the coefficient of linear expansion of the honeycomb structure portion measured according to JIS R1618:2002 when the temperature is changed from 300° C. to 800° C. is 4.2×10−6/° C. or more and 4.8×10−6/° C. or less.