Honeycomb Filter Outer Surface Irregularities for Thermal Shock Resistance
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Solution Overview
Problem
Conventional honeycomb filters for exhaust gas purification face issues with displacement and reduced efficiency due to pressure changes and thermal expansion, leading to reduced particulate collection and potential cracking, as the sealing material's holding power is compromised.
Innovation Solution
A honeycomb structural body with irregularities on its outer peripheral face, determined by specific geometric criteria, is used, where the center-of-gravity of concentric curves is intentionally offset, and the ceramic block is formed by combining porous ceramic members through a sealing material layer, enhancing thermal shock resistance and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional honeycomb filter is installed in a casing through mat-like holding sealing material, then the filter can be held in position, but the filter may displace when pressure increases or thermal expansion occurs
Solution Approach 1:
The patent introduces asymmetry by forming irregularities (protrusions and recesses) on the outer peripheral face of the honeycomb structural body. This asymmetric surface structure allows the mat-like holding sealing material to mechanically interlock with the honeycomb body, creating anchoring effects that prevent displacement under pressure and thermal expansion conditions.
Solution Approach 2:
The irregularities are pre-formed on the outer peripheral face of the honeycomb structural body before installation. This preliminary structuring of the surface enables the sealing material to effectively grip and hold the honeycomb body in place, preventing displacement before it can occur during operation.
2Ease of manufacture
If the honeycomb filter is held by mat-like sealing material, then installation is simple, but the sealing material may droop and close through holes reducing efficiency
Solution Approach 1:
The irregularities create an asymmetric profile where protrusions extend toward the exhaust gas inlet side. This asymmetric geometry physically prevents the mat-like sealing material from drooping onto the end face and closing the through holes, while still allowing simple installation through the interlocking mechanism.
3Temperature
If the honeycomb filter operates at high temperature, then exhaust gas purification is effective, but thermal expansion may reduce holding power
Solution Approach 1:
The irregularities are pre-formed on the outer peripheral face to create a mechanical interlocking structure. This preliminary structuring ensures that even when thermal expansion occurs at high operating temperatures, the sealing material maintains its gripping force through the interlocked profile, preventing displacement and maintaining holding power.
4Quantity of substance
If pressure on the exhaust gas inlet side increases, then particulate collection increases, but the honeycomb filter may displace or crack
Solution Approach 1:
The irregularities create asymmetric stress distribution patterns. The protrusions and recesses act as stress relief features that distribute the increased pressure loads more evenly throughout the structure, preventing concentration of stresses that would lead to cracking or displacement under high particulate collection conditions.
Data Source
AI summary
A honeycomb structural body comprising: a pillar-shaped ceramic block and a sealing material provided on an outer peripheral portion of said ceramic block, each of them having irregularities formed on an outer peripheral face wherein: when a least square curve is determined by a least square method on the basis of points constituting the contour of a cross-section, a center-of-gravity is defined as c1, a distance between a minimum concentric circumscribed curve having c1 and the center-of-gravity c1 is defined as D1, a distance between a maximum concentric inscribed curve having c1 and the center-of-gravity c1 is defined as D2, and the following inequality is satisfied: about 0.3 mm≦(D1-D2); same definition is applied to said ceramic block, a center-of-gravity thereof is defined as c2, a distance between a minimum concentric circumscribed curve having c2 and the center-of-gravity c2 is defined as D3, a distance between a maximum concentric inscribed curve having c2 and the center-of-gravity c2 is defined as D4, and the following inequality is satisfied: about 0.5 mm≦(D3-D4)≦about 7.0 mm.