Honeycomb Structure Bonding for Diesel Particulate Filter Thermal Stress
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Solution Overview
Problem
Honeycomb structures used as diesel particulate filters face defects such as cracks due to thermal stress during use and regeneration, particularly in silicon carbide-based structures, where thermal expansion coefficients are high and thermal shock resistance is inadequate, leading to increased thermal stresses and defect generation.
Innovation Solution
A honeycomb structure with bonding material layers made of inorganic fibers, binders, and particles, where the bonding material layers are strategically placed to avoid regions of maximum thermal stress, using silicon carbide or silicon-silicon carbide composite materials for the honeycomb segments, and an outer peripheral coating layer to enhance thermal resistance and prevent crack generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If honeycomb segments are integrally bonded via bonding material layers to reduce thermal stress, then thermal stress is reduced, but the rigid bonded structure increases thermal stress from temperature gradients and the bonding material has large thermal capacity causing slow temperature response
Solution Approach 1:
The invention divides the bonding structure into segmented regions with different bonding densities. Specifically, it uses a first bonding material layer with lower bonding density and a second bonding material layer with higher bonding density at specific locations. This segmentation allows different regions to respond differently to thermal stresses, reducing the overall thermal stress while maintaining structural integrity.
Solution Approach 2:
The invention applies different bonding characteristics to different locations of the honeycomb structure. The first bonding material layer is applied to entire side faces, while the second bonding material layer is applied only to specific regions (such as corner regions or regions away from corners). This local differentiation optimizes the balance between structural strength and thermal stress resistance in each specific area.
2Temperature
If silicon carbide is used for honeycomb segments due to excellent thermal resistance, then thermal resistance is improved, but thermal expansion coefficient increases and resistance to thermal shock becomes inadequate
Solution Approach 1:
The invention uses composite bonding material layers consisting of different materials with complementary properties. The first bonding material layer and second bonding material layer are made of different materials that together provide both thermal resistance and resistance to thermal shock. This composite approach allows the structure to benefit from the high thermal resistance of silicon carbide while mitigating its poor thermal shock resistance through the complementary properties of the bonding materials.
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 strategic placement of bonding material layers reduces thermal stress and prevents crack formation, improving the thermal resistance and durability of the honeycomb structure, effectively addressing the issue of defect generation during thermal cycles.
Implementation Method 1
bond surfaces of a plurality of honeycomb segments are integrally bonded to one another via bonding material layers
Implementation Method 2
generation of defects such as cracks due to a thermal stress during use and during regeneration is effectively prevented
Data Source
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AI summary
There is disclosed a honeycomb structure which is useful as a trapping filter for an exhaust gas, above all a diesel particulate filter (DPF) for trapping particulate matters (particulates) in an exhaust gas from a diesel engine and in which internal and external temperature rises are uniformed during use and during regeneration and in which there are effectively prevented generation of defects such as cracks due to a thermal stress and generation of an adverse influence on a carried catalyst. A honeycomb structure 1 includes: a bonded honeycomb segment article 10 in which bond surfaces of a plurality of honeycomb segments 2 are integrally bonded to one another via bonding material layers 9; and an outer peripheral coating layer 4 which coats an outer peripheral surface of the bonded honeycomb segment article 10. The honeycomb structure has a structure in which a plurality of cells 5 forming fluid channels are arranged in parallel with one another in a central axis direction. The honeycomb segments 2 are bonded via the bonding material layers (partial bonding material layers) 9 disposed only in predetermined portions of the honeycomb segments 2.