Electrically-Heated Catalytic Converter Terminal Thermal Expansion Gradient
Solution Overview
Problem
The existing electrically-heated catalytic converters face reliability issues due to thermal stress and damage at interfaces caused by differences in thermal expansion coefficients between components, leading to potential cracks and decreased electric connection performance.
Innovation Solution
The design incorporates a ceramic substrate with electrode films and terminals, where the thermal expansion coefficient of the electrode terminals decreases from the brazing filler metal side to the electrode film side, matching the expansion coefficients of adjacent components to minimize interface damage, using a Ti-based brazing filler metal with a multi-layer structure and specific thermal expansion coefficients to ensure compatibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional single-material electrode terminals are used, then manufacturing is simple, but thermal stress and interface damage occur due to thermal expansion coefficient mismatches
Solution Approach 1:
The electrode terminal is constructed as a composite structure with a ceramic base material and a ceramic coating layer having different thermal expansion coefficients. This composite design allows the terminal to match thermal expansion characteristics of both the brazing filler metal (higher expansion) and electrode film (lower expansion), reducing thermal stress and interface damage while maintaining manufacturing feasibility through established coating technologies.
Solution Approach 2:
The electrode terminal exhibits spatial variation in thermal expansion properties, with the coating layer providing locally optimized thermal expansion matching at different interfaces. The ceramic coating layer specifically addresses the thermal expansion mismatch at the brazing interface, while the base material maintains structural integrity, creating locally adapted properties throughout the terminal structure.
2Adaptability or versatility
If ceramic substrates are used in hybrid and plug-in hybrid vehicles, then usability improves, but thermal expansion coefficient mismatches cause interface damage
Solution Approach 1:
The electrode terminal uses a composite ceramic structure where the coating layer's thermal expansion coefficient is specifically selected to match the brazing filler metal, while the base material maintains compatibility with the ceramic substrate. This enables reliable operation across different vehicle types (gasoline, hybrid, plug-in hybrid) while preventing interface damage through optimized thermal expansion matching.
Solution Approach 2:
The thermal expansion coefficient parameter is optimized through material composition control in the ceramic coating layer. By adjusting the chemical composition and microstructure of the coating, the thermal expansion coefficient is tuned to match the brazing filler metal, enabling the system to maintain reliability across varying operational conditions and vehicle applications.
3Ease of manufacture
If electrode terminals with uniform thermal expansion coefficient are used, then manufacturing is easier, but thermal stress causes cracks at interfaces
Solution Approach 1:
The electrode terminal employs a composite ceramic structure with distinct base material and coating layer, each optimized for specific functions. The coating layer provides thermal expansion matching at the brazing interface through controlled composition, while the base material ensures structural strength. This composite approach maintains manufacturing feasibility using established ceramic coating processes while significantly improving interface strength and crack resistance.
Solution Approach 2:
The electrode terminal is segmented into functionally distinct regions: the base material provides structural support and electrical conductivity, while the coating layer specifically addresses thermal expansion matching at the brazing interface. This segmentation allows each region to be optimized independently for its specific function, improving overall interface strength without compromising manufacturability.
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
This configuration effectively reduces interface damage and enhances the reliability of electric connections by minimizing thermal expansion coefficient differences, resulting in a more durable and efficient electrically-heated catalytic converter.
Implementation Method 1
external electrodes (5) attached to both sides of the electrode terminal (3) via brazing filler metals (4)
Implementation Method 2
electrode terminals (3) made of ceramic, each of the electrode terminals being secured to a corresponding one of the electrode films; and external electrodes (5) attached to both sides of the electrode terminal (3)
Implementation Method 3
the thermal expansion coefficient of each of the electrode terminals decreases from a portion at which the electrode terminal is joined to the brazing filler metal toward a portion at which the electrode terminal is joined to the corresponding electrode film
Implementation Method 4
the honeycomb catalyst is heated by supplying electric current to the electrode to increase the activity of the honeycomb catalyst
Data Source
AI summary
An electrically-heated catalytic converter includes: a substrate made of ceramic, the substrate including a catalyst coated layer; electrode films made of ceramic, the electrode films being disposed on a surface of the substrate; electrode terminals made of ceramic, each of the electrode terminals being secured to a corresponding one of the electrode films; and external electrodes each attached to a corresponding one of the electrode terminals via a brazing filler metal. A thermal expansion coefficient of the brazing filler metal is equal to or higher than a thermal expansion coefficient of the electrode terminals, and is equal to or lower than a thermal expansion coefficient of the external electrodes. The thermal expansion coefficient of each of the electrode terminals decreases from a portion at which the electrode terminal is joined to the brazing filler metal toward a portion at which the electrode terminal is joined to the corresponding electrode film.