Honeycomb Structure Uniform Heating via Height Variation
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Solution Overview
Problem
Conventional honeycomb structures for catalyst-supported exhaust gas purification face challenges in achieving uniform heating, leading to inadequate purification performance, especially in plug-in hybrid and hybrid vehicles where engine starting frequency is low, resulting in catalyst temperatures not reaching activation temperatures promptly.
Innovation Solution
A columnar honeycomb structure with improved bottom surface shape, featuring specific height ratios and concave portions, allows for uniform heat generation without joining parts with different volume resistivities, enhancing heating uniformity while maintaining structural reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the honeycomb structure uses a single material with uniform volume resistivity, then the manufacturing process is simple and structural reliability is maintained, but the heating uniformity is poor leading to inadequate catalyst activation
Solution Approach 1:
The invention applies local quality by creating a non-uniform height distribution across the honeycomb structure. The center portion has a different height than the peripheral portions, which results in different electrical resistance values in different regions. This local variation in geometric dimensions creates the desired non-uniform heating pattern without requiring different materials or joining operations, thus maintaining structural reliability while improving heating uniformity.
2Temperature
If the honeycomb structure is joined from multiple parts with different volume resistivity, then the heating uniformity is improved, but the structural reliability deteriorates due to breakage at joint parts
Solution Approach 1:
The invention merges multiple functional requirements into a single monolithic honeycomb structure. By varying the height of different portions within one continuous structure rather than joining separate parts, the invention achieves both the desired non-uniform heating pattern and maintains structural reliability. The single-piece construction eliminates weak joint areas while the geometric variation provides the necessary electrical resistance differences for uniform heating.
3Productivity
If the catalyst temperature is increased to activation temperature rapidly, then the exhaust gas purification performance is improved, but the energy consumption increases due to electric heating requirements
Solution Approach 1:
The invention changes the electrical resistance parameter spatially across the honeycomb structure by varying the height of different portions. This parameter variation allows the structure to generate heat more efficiently and uniformly when electric current is applied, enabling rapid catalyst activation. The optimized resistance distribution ensures that energy is distributed effectively throughout the structure, reducing overall energy consumption compared to uniform heating approaches while achieving fast activation.
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 improved honeycomb structure achieves significant heat generation uniformity, ensuring effective catalyst activation and exhaust gas purification without compromising structural integrity.
Implementation Method 1
The EHC is configured to be capable of heating the catalyst to the activation temperature before starting of the engine by connecting a pair of terminals to a columnar honeycomb structure made of conductive ceramics and causing the honeycomb structure itself to generate heat by applying electric current
Data Source
AI summary
A columnar honeycomb structure comprising an outer peripheral side wall having an outer peripheral side surface; a plurality of partition walls that partition and form a plurality of cells penetrating from one bottom surface to another bottom surface to form flow paths, the plurality of partition walls being disposed inside the outer peripheral side wall; and a pair of terminal connection portions arranged on the outer peripheral side wall, wherein the honeycomb structure satisfies a relationship of H1>H2 in which: H1 represents an average height of the entire honeycomb structure; and H2 represents an average height of a portion of the honeycomb structure surrounded by a straight line M1 parallel to a line segment M and located at a distance of 0.1×L1 from the line segment M toward a first direction and a straight line M2 parallel to the line segment M and located at a distance of 0.1×L2 from the line segment M toward a second direction, wherein when viewing the honeycomb structure from its bottom, the line segment M represents a line segment connecting circumferential centers of the pair of terminal connection portions and extending from one outer peripheral side surface to the other outer peripheral side surface, and L1 and L2 represent length in the first direction and the second direction perpendicular to the line segment M from a middle point O of the line segment M to the outer peripheral side surface, respectively.