Plugged Honeycomb Structure End-Surface Polishing
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Solution Overview
Problem
Conventional plugged honeycomb structures used in diesel particulate filters face issues with soot deposition at the ends of plugged portions, leading to increased pressure loss and fuel inefficiency, as well as end-surface cracks during regeneration, due to recess portions generated during firing, which also complicate the canning process.
Innovation Solution
A plugged honeycomb structure with a smoothing treatment by end-surface polishing in a region at least 20 mm wide from the outer periphery of each end surface, reducing the depth of recess portions to less than 0.02 mm, prevents soot deposition and thermal stress concentration, thereby maintaining filter layer area and preventing structural damage during canning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the plugged honeycomb structure is used continuously for a long period of time, then the filter performs soot removal function, but the soot is easily deposited at the ends of the plugged portions due to recess portions, leading to rapid pressure loss increase
Solution Approach 1:
The patent applies a smoothing treatment to the end surfaces of the plugged portions before the filter is put into service. This preliminary action removes the recess portions that would otherwise cause soot deposition, thereby preventing the harmful effect before it occurs during filter operation.
Solution Approach 2:
The smoothing treatment is applied locally only to the end surfaces of the plugged portions where recess portions exist, rather than treating the entire filter structure. This localized treatment addresses the specific problem area without affecting other parts of the filter.
2Object-generated harmful factors
If spray coating with densifying material is applied to suppress soot deposition, then soot deposition is reduced, but the densifying material adheres to partition walls and decreases filter layer area
Solution Approach 1:
The smoothing treatment is performed before the filter is assembled and before any coating operations. By eliminating the recess portions in advance, the need for subsequent spray coating with densifying material is removed, thereby preventing the densifying material from adhering to the partition walls and maintaining full filter layer area.
3Productivity
If the plugged honeycomb structure undergoes regeneration, then deposited soot is burnt and removed, but thermal stress concentrates on recess portions causing end-surface cracks
Solution Approach 1:
The smoothing treatment removes recess portions before the filter is put into service, eliminating the stress concentration points that would form during regeneration. This preliminary structural modification prevents crack initiation while allowing the regeneration process to proceed efficiently.
Solution Approach 2:
By eliminating the recess portions through smoothing treatment, the patent removes the vulnerable points where thermal stress would concentrate during regeneration. This beforehand modification cushions against the development of end-surface cracks that would otherwise occur during the thermal cycling of regeneration.
4Object-generated harmful factors
If densifying material is spray coated on end surfaces, then the total length of the plugged honeycomb structure increases, complicating the canning process
Solution Approach 1:
The smoothing treatment is applied to the end surfaces of the plugged portions before assembly, eliminating the need for subsequent spray coating with densifying material. This preliminary action prevents the additional length increase that would complicate the canning process.
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
This approach effectively suppresses soot deposition and thermal stress, preventing rapid pressure loss increases and end-surface cracks, while ensuring the structural integrity and efficiency of the filter, thus maintaining fuel efficiency and preventing damage during the canning process.
Implementation Method 1
a smoothing treatment by end-surface polishing is performed so that a depth of a recess portion generated at an end of each of the plugged portions during the firing becomes small
Implementation Method 2
the partition walls 7 become filter layers, and the soot in the exhaust gas is caught by the partition walls 7, and deposited on the partition walls 7
Implementation Method 3
the cells are first charged with the constituent material of the plugged portions, followed by firing
Data Source
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Figure 5
AI summary
There is disclosed a plugged honeycomb structure which does not decrease an area of a filter layer or does not increase the total length thereof, but can suppress the deposition of soot at ends of plugged portions on an inlet end surface side or the generation of end-surface cracks on an outlet end surface side during regeneration, when the structure is used as a filter such as a DPF. A plugged honeycomb structure 1 includes a honeycomb structured body where a plurality of cells communicating between an inlet end surface and an outlet end surface are partitioned by porous partition walls; and plugged portions to plug open frontal areas of the predetermined cells on the side of the inlet end surface and open frontal areas of the remaining cells on the side of the outlet end surface. The plugged portions are formed by charging the cells with a constituent material of the plugged portions, followed by firing, and in a region A having a width of at least 20 mm from an outer periphery of each of the inlet end surface and the outlet end surface, a smoothing treatment by end-surface polishing is performed so that a depth of a recess portion generated at an end of each of the plugged portions during the firing becomes small.