Electrically Heated Catalyst Case for Soot-Resistant Insulation
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Solution Overview
Problem
Insulation properties of electrically heated catalysts (EHCs) in vehicles degrade due to soot buildup, particularly on the downstream side of the exhaust system, which is not effectively addressed by existing insulation measures.
Innovation Solution
A vehicle configuration with a constricted part in the exhaust passage and an EGR passage connected to this part, redirecting high-temperature exhaust gas to gaps between the case and insulation coat, thereby reducing soot adhesion and maintaining insulation performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an insulation coat is applied to the outer circumferential side of the EHC, then insulation between the EHC and case is improved, but insulation properties degrade due to soot buildup on the insulation coat
Solution Approach 1:
The patent redirects high-temperature exhaust gas through a constricted part and EGR passage to flow over the insulation coat. The harmful hot exhaust gas that would normally cause soot accumulation is instead used to burn off and remove soot from the insulation coat surface, converting the harmful thermal energy into a cleaning mechanism that maintains insulation properties
Solution Approach 2:
The patent introduces a constricted part that reduces the inside diameter of the case, creating a localized region where exhaust gas velocity and temperature parameters change. This parameter change enables the exhaust gas to effectively contact and clean the insulation coat surface, transforming the thermal environment from a soot-generation condition to a soot-removal condition
2Object-affected harmful factors
If the case inside diameter is reduced to redirect exhaust gas flow, then soot removal effectiveness is improved, but the compactness of the catalytic converter is reduced
Solution Approach 1:
The patent segments the case into different sections with different inside diameters - a constricted part with reduced diameter and other portions with normal diameter. This segmentation allows the exhaust gas flow to be redirected and accelerated only in the specific region where soot removal is needed, while maintaining the overall compactness of the catalytic converter by not reducing the entire case diameter
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 configuration inhibits soot buildup on the insulation coat, preserving the insulation properties of the EHC and promoting efficient heat transfer to downstream catalysts, while allowing for a compact catalytic converter design.
Implementation Method 1
redirecting high-temperature exhaust gas to gaps between the case and insulation coat, thereby reducing soot adhesion
Implementation Method 2
redirecting high-temperature exhaust gas to gaps between the case and insulation coat
Data Source
AI summary
A vehicle includes: an EHC which is provided in an exhaust passage of an internal combustion engine and of which the temperature can be raised by application of a current; a tubular first case housing the EHC; an insulation coat disposed between an inner wall of the first case and an outer circumference of the EHC so as to surround the outer circumference of the EHC; a constricted part that is provided at an end portion of the first case on a downstream side in a flow direction of an exhaust gas to reduce the inside diameter of the first case along the flow direction; and an EGR passage connected to the constricted part.