Honeycomb Structure Unbonded Portions Crack Prevention
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Solution Overview
Problem
Conventional segmented-honeycomb structures for diesel particulate filters face issues with crack formation in bonding layers due to thermal stress and temperature differences, leading to reduced durability and increased risk of breakage.
Innovation Solution
The honeycomb structure incorporates bottomed-hollow unbonded portions in the circumferential bonding layers, which suppress the extension of cracks by providing voids that prevent further crack propagation when they occur, thereby enhancing the structural integrity and durability of the bonding layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a segmented-structure honeycomb structure is used to prevent breakage under thermal stress, then the overall structural strength is improved, but cracks easily occur in the bonding layers of the circumferential portion
Solution Approach 1:
The invention divides the bonding layer into bonded portions and unbonded portions, creating a segmented structure within the bonding layer itself. This allows the bonding layer to accommodate thermal stress by having intentional unbonded regions that can expand and contract independently, preventing crack propagation while maintaining overall structural strength.
Solution Approach 2:
The invention applies different bonding characteristics to different regions of the bonding layer. The circumferential bonding layers have unbonded portions at specific positions while other regions remain fully bonded. This local differentiation allows stress concentration points to be strategically managed, preventing cracks in critical areas while maintaining bond strength where needed.
2Reliability
If high-porosity materials are used for DPF to achieve high filtration efficiency, then the purification performance is improved, but heat conduction decreases causing temperature differences and cracks
Solution Approach 1:
The invention utilizes porous materials for the honeycomb structure to achieve high filtration efficiency through effective PM trapping. The porous partition walls provide high surface area for filtration while the segmented bonding structure compensates for the low heat conduction by allowing thermal stress accommodation.
3Productivity
If catalyst loading is performed at high temperature to promote PM combustion, then the reproduction process effectiveness is improved, but thermal stress increases causing bonding layer cracks
Solution Approach 1:
The invention incorporates unbonded portions in advance within the bonding layers before catalyst loading and high-temperature operation. These pre-designed unbonded regions act as cushioning zones that absorb and distribute thermal stress during subsequent high-temperature reproduction processes, preventing crack formation even when catalyst combustion generates intense heat.
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 implementation of unbonded portions effectively reduces the maximum crack length and maintains bond strength, ensuring the honeycomb structure's reliability under thermal stress and temperature fluctuations, thus preventing breakage and maintaining filtration efficiency.
Implementation Method 1
the total thermal stress of the honeycomb structure can be absorbed but cracks etc. are easy to occur in the bonding layers of the circumferential portion of the honeycomb structure
Data Source
AI summary
A honeycomb structure includes plugged honeycomb segments, bonding layers and a circumferential wall. The bonding layers includes bottomed-hollow unbonded portions, which extend toward an internal side in an axial direction from an end face of the honeycomb structure, in portions of circumferential bonding layers bonding the honeycomb segments on an outermost circumference. The unbonded portions exist on respective extended lines extending from an intersection of the bonding layers which is closest to a centroid of the end face. An opening length of the unbonded portion is 1 to 10 mm, a ratio of an opening depth of the unbonded portion to a length of the honeycomb segment is 10 to 45%, and a ratio of a distance from the circumferential wall to a point at which an open end of the unbonded portion ends to a length of the circumferential bonding layer is 5 to 100%.