Honeycomb Structure Protruding Walls Buffer Portions
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Solution Overview
Problem
Honeycomb structures used in diesel particulate filters (DPFs) face issues with crack generation and segmentation due to repeated heating and cooling cycles, leading to structural instability and division.
Innovation Solution
The honeycomb structure incorporates externally protruding walls in the buffer portions between segments, which provide reinforcement against tensile and compressive stresses, preventing crack formation and segmentation by maintaining the joining state between segments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a large honeycomb structure is formed by joining multiple segments together using joining material in buffer portions, then the desired size and shape can be achieved, but cracks are generated in the joining material during repeated heating and cooling cycles, leading to segmentation
Solution Approach 1:
The invention introduces protruding walls at specific locations within the buffer portions where thermal stress concentrates. These localized structural reinforcements are placed at the interfaces between segments and the joining material, providing targeted strength exactly where cracks tend to initiate during thermal cycling, without requiring reinforcement throughout the entire structure.
Solution Approach 2:
The buffer portions are formed as composite structures combining the joining material with protruding walls made of the same material as the honeycomb segments (silicon carbide or cordierite). This composite design creates a gradient structure where the protruding walls provide thermal shock resistance matching the segments, while the joining material provides bonding, resolving the contradiction between joining strength and thermal stress resistance.
2Strength
If silicon carbide is used as the aggregate material for the honeycomb structure, then excellent thermal resistance and chemical stability are achieved, but the large coefficient of thermal expansion causes defects due to thermal shock
Solution Approach 1:
The invention divides the honeycomb structure into multiple segments joined by buffer portions containing protruding walls. This segmentation allows each segment to expand and contract independently during thermal cycling, reducing the accumulation of thermal stress that would otherwise cause defects in large monolithic silicon carbide structures.
Solution Approach 2:
The protruding walls in the buffer portions act as pre-positioned cushioning elements that absorb and distribute thermal stress before it can propagate into cracks. These structural features are built into the design beforehand, providing built-in protection against thermal shock damage 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 solution effectively prevents crack development and segmentation of the honeycomb structure during regeneration cycles, enhancing its durability and maintaining structural integrity.
Implementation Method 1
each honeycomb segment has externally protruding walls on a side surface, and hence walls for reinforcement are formed in the buffer portions. Therefore, even when a tensile stress and a compressive stress are alternately applied to the buffer portions by repeating the regeneration, the protruding walls perform a reinforcement function
Implementation Method 2
Silicon carbide has a comparatively large coefficient of thermal expansion. Therefore, when a large honeycomb structure formed by using silicon carbide as an aggregate is used, a defect is generated owing to thermal shock sometimes.
Implementation Method 3
when the structure is used as the DPF and repeatedly subjected to an operation (regeneration) of burning the collected particulate matters, cracks are generated in the joining material (the buffer portions) owing to repeated heating and cooling
Data Source
Figure 1
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Figure 4
AI summary
Disclosed is a honeycomb structure capable of preventing the generation of cracks in buffer portions and preventing the honeycomb structure from being divided when an operation (regeneration) of burning collected particulate matters is repeated. A honeycomb structure 100 includes a plurality of honeycomb segments 4 having partition walls 2 separating and forming a plurality of cells functioning as fluid passages and extending from one end surface of each segment to the other end surface thereof, and protruding walls 3 which are provided so as to protrude externally from partition walls 2a forming side surfaces 5 of the segments and which extend from one end of each segment to the other end thereof in a central axis direction. The plurality of honeycomb segments 4 are arranged adjacent to one another so that the side surfaces 5 of the honeycomb segments face each other with a predetermined distance being left therebetween, each buffer portion 11 is disposed between the adjacent honeycomb segments 4 to join the honeycomb segments 4 together, and an outer peripheral portion 13 is disposed on an outermost periphery 12 of the plurality of joined honeycomb segments 4.