Honeycomb Structure Bonding Layer Voids for Crack Suppression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional diesel particulate filters (DPFs) with segmented honeycomb structures face issues with crack formation in bonding layers due to thermal stress and temperature differences, leading to reduced durability and increased risk of breakage, especially when loaded with oxidation catalysts and high-porosity materials like SiC.
Innovation Solution
A honeycomb structure featuring prismatic columnar segments bonded with layers that include bottomed-hollow voids at intersections, where the voids extend inward from the end faces and are strategically positioned to suppress crack extension, with a void depth ratio of 5% or more and a bonding layer width of 0.5 to 2.0 mm, effectively managing thermal stress and temperature variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a segmented-structure honeycomb structure is used to prevent breakage, then the total thermal stress can be absorbed, but cracks easily occur in the bonding layers of the circumferential portion
Solution Approach 1:
The bonding layer is designed with different properties at different locations: the circumferential portion has enhanced crack resistance through specific structural features, while the longitudinal portion maintains bonding function. This local differentiation allows the bonding layer to simultaneously absorb thermal stress and resist cracks in the circumferential direction.
Solution Approach 2:
The bonding layer is divided into a circumferential portion and a longitudinal portion, with the longitudinal portion further segmented into multiple regions. This segmentation allows each portion to be optimized for its specific function: the circumferential portion for crack resistance and the longitudinal portion for bonding and stress absorption.
2Volume of moving object
If high-porosity materials like SiC are used to reduce DPF size, then downsizing is achieved, but temperature difference between inside and outside increases leading to cracks
Solution Approach 1:
The DPF uses a composite structure combining SiC material with a specifically designed bonding layer that has different thermal properties. The bonding layer acts as a thermal management component, reducing the temperature difference between the inside and outside of the DPF while maintaining the downsized volume enabled by high-porosity SiC material.
3Productivity
If oxidation catalyst is loaded on the honeycomb structure, then PM combustion is promoted, but cracks occur in the bonding layers during heat treatment
Solution Approach 1:
The bonding layer is designed with local quality differentiation where the circumferential portion has enhanced crack resistance to withstand the thermal stress from catalyst loading heat treatment, while the longitudinal portion maintains the bonding function necessary for structural integrity during operation.
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 crack extension in the bonding layers, enhancing the durability and reliability of DPFs by maintaining bonding strength and reducing pressure loss, even under conditions of high thermal stress and temperature fluctuations.
Implementation Method 1
Because a high thermal stress is generated in the DPF due to the combustion heat of the PM, measures to prevent the breakage of the DPF are necessary.
Implementation Method 2
a purification device that purifies exhaust gas emitted from an automobile that uses a diesel engine as a power source employs a diesel particulate filter (DPF)
Implementation Method 3
the honeycomb structure is coated with slurry including the oxidation catalyst and then is subject to heat treatment at high temperature to be baked
Implementation Method 4
a reproduction process of combusting the deposited PM by using high-temperature exhaust gas generated from the diesel engine
Implementation Method 5
materials having low heat conduction with high porosity tend to be used as the materials of the DPF. Because the high-porosity materials have characteristically low heat conduction, using the high-porosity materials as the material of DPF leads to a problem that a temperature difference between the inside and outside of DPF easily occurs
Data Source
AI summary
A honeycomb structure includes honeycomb segments, bonding layers and a circumferential wall. The bonding layers include bottomed-hollow voids which extend toward an internal side in an axial direction from an end face of the honeycomb structure and which are formed at at least one of intersections, and a ratio of a depth of each void in the axial direction to a length of each honeycomb segment in the axial direction is 5% or more.