Honeycomb Filter Wall Gradient for Strength and Low Back Pressure
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Solution Overview
Problem
High-porosity particulate filters, such as gasoline particulate filters, face challenges with insufficient strength, leading to defects during production, transportation, and packaging, which complicates the production process and reduces efficiency.
Innovation Solution
A honeycomb structure body with a specific radial wall thickness distribution and a skin layer, where the inner porous walls have a smaller average wall thickness than the outer porous walls, and the skin layer thickness is optimized to enhance strength, thermal shock resistance, and reduce back pressure, achieved through integral molding and controlled extrusion molding die design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the porosity of the particulate filter is increased to meet emission regulations, then the filtering performance is improved, but the strength of the filter decreases leading to defects during production and transportation
Solution Approach 1:
The patent applies local quality by creating a skin layer with different properties than the inner honeycomb structure. The skin layer has higher strength and lower porosity compared to the inner porous walls, providing enhanced mechanical protection where needed while maintaining high porosity in the bulk structure for filtering performance. This is achieved through controlled extrusion molding that forms a denser outer layer during the molding process.
2Strength
If a secondary coating or outer coating process is applied to strengthen the peripheral wall, then the structural strength is improved, but the production process complexity increases and production efficiency decreases
Solution Approach 1:
The patent merges the skin layer formation with the main extrusion molding process, eliminating the need for separate secondary coating or outer coating steps. The skin layer is formed integrally during the extrusion molding process through controlled material flow and density gradients, combining what were previously separate operations into one unified manufacturing step, thereby improving production efficiency.
Solution Approach 2:
The skin layer is formed preliminarily during the extrusion molding process itself, before any post-processing steps. The controlled extrusion creates the denser outer layer as part of the initial forming operation, so the strengthening function is built in advance rather than requiring subsequent coating or reinforcement operations.
3Strength
If the wall thickness of the porous walls is increased to improve strength, then the structural strength is improved, but the back pressure of the filter increases
Solution Approach 1:
The patent applies local quality by concentrating the increased wall thickness in the skin layer at the outer periphery, while the inner porous walls maintain thinner walls to minimize flow resistance. This localized thickening provides strength where structurally needed (at the outer surface) without significantly increasing back pressure, as the internal flow channels retain their original thin-wall configuration.
Data Source
AI summary
A honeycomb structure body, which includes a honeycomb body and a skin layer, the honeycomb body including axially extending channels defined by a porous wall, wherein a radial path of a radial section of the honeycomb body from a central axis to the skin layer consists of a porous wall inner section and a porous wall outer section in sequence, an average wall thickness of inner porous walls provided in the porous wall inner section is smaller than an average wall thickness of outer porous walls provided in the porous wall outer section, and a length of the porous wall inner section in the radial path accounts for 71%-95%. The specific structure of the honeycomb structure body not only increases the strength of the honeycomb structure body, but also ensures good thermal shock resistance and small back pressure.