Exhaust Gas Purification Filter with Segregated Pore Structure
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Solution Overview
Problem
Gasoline engines face challenges in achieving high initial particulate matter (PM) collection efficiency while minimizing pressure drop, which increases due to ash deposition over time, and existing filters struggle to balance PM collection efficiency and pressure drop reduction.
Innovation Solution
An exhaust gas purification filter with partition walls having specific pore diameter and surface opening diameter ratios, ensuring A ≥ B, where A is between 5 µm and 15 µm, and the proportion (A - B)/B is 30% or less, along with a surface opening ratio of 25% to 40%, effectively segregating and detaching ash to prevent pressure drop increase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the pores of the partition wall are made smaller to improve PM collection efficiency, then the initial PM collection efficiency is improved, but the pressure drop increases
Solution Approach 1:
The partition wall is designed with non-uniform pore distribution, creating different pore sizes in different regions. The surface layer has smaller pores (5-15 μm) for efficient PM collection, while the inner layer has larger pores to maintain low pressure drop and facilitate ash detachment. This local quality variation allows simultaneous optimization of both PM collection efficiency and pressure characteristics.
Solution Approach 2:
The partition wall is segmented into multiple layers with different pore structures. The surface layer (first region) and inner layer (second region) are functionally separated, with each layer optimized for its specific role. This segmentation enables the filter to achieve high PM collection efficiency at the surface while maintaining low pressure drop and facilitating ash removal through the inner layer.
2Stress or pressure
If the pores are made larger to reduce pressure drop, then the pressure drop is reduced, but the PM collection efficiency decreases
Solution Approach 1:
Different regions of the partition wall are assigned different pore sizes based on their functional requirements. The surface layer uses smaller pores (5-15 μm) for efficient PM collection, while the inner layer uses larger pores to reduce pressure drop and enable ash detachment, achieving both goals simultaneously through spatial differentiation.
3Object-generated harmful factors
If the catalyst is coated on the partition wall to purify exhaust gases, then the exhaust gas purification is improved, but the PM collection efficiency degrades and pressure drop increases
Solution Approach 1:
The catalyst function is extracted and separated from the PM collection function. Instead of coating the entire partition wall with catalyst, the invention uses a catalyst substrate placed in the exhaust passage that provides catalytic activity without blocking the porous structure needed for PM collection. This separation allows independent optimization of both PM collection efficiency and exhaust gas purification.
4Measurement precision
If the PM collection efficiency is improved by increasing ash deposition capacity, then the PM collection is improved, but the pressure drop increases due to accumulated ash
Solution Approach 1:
The partition wall structure is designed to dynamically adapt to ash deposition. The inner layer with larger pores and higher porosity (50-70%) provides a pathway for ash to be detached and removed from the filter. This dynamic structure allows the filter to maintain low pressure drop even after prolonged use and ash accumulation, unlike conventional filters with uniform fine pores that permanently increase in pressure drop.
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 filter ensures initial PM collection efficiency, reduces initial pressure drop, and maintains low pressure drop after ash deposition by effectively segregating and detaching ash, improving gas permeability and filter performance.
Implementation Method 1
partition walls each including a plurality of pores; a plurality of cells partitioned by the partition walls
Implementation Method 2
effectively segregating and detaching ash to prevent pressure drop increase
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
An exhaust gas purification filter (1) is configured to be disposed in an exhaust passage of a gasoline engine. The exhaust gas purification filter (1) includes partition walls (11) including a plurality of pores (110), a plurality of cells (12) partitioned by the partition walls (11), and sealing parts (13) that alternately seal ends of the plurality of cells (12) in the exhaust gas purification filter. The exhaust gas purification filter (1) is, with an average pore diameter of the partition wall (11) as A(µm) and an average surface opening diameter of the pores (110) at a surface of the partition wall as B(µm), adapted such that A ≥ B is satisfied, with A of 5 µm or more and less than 15 µm, and such that a proportion calculated from a formula of 100 × (A - B)/B is 30% or less.