Composite Inorganic Fiber Insulation Mat for Exhaust Systems
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Solution Overview
Problem
Conventional insulation mats for automotive exhaust systems face challenges such as high cost, limited temperature resistance, and significant shrinkage, which affect their efficiency in retaining heat and reducing pollutant emissions during the light-off period of exhaust gas treatment devices.
Innovation Solution
A method of forming an insulation mat using a mixture of first and second inorganic fibers, where the first fibers shrink by no more than 2% and the second fibers shrink between 5-15% when heat-treated, entangled to form a mat with enhanced tensile strength and thermal resistance, without the use of non-fibrous binders prior to heat treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If silica fiber mats or glass fiber mats are used for insulation, then the mat can be manufactured at lower cost, but the mat exhibits significant shrinkage and limited temperature resistance
Solution Approach 1:
The patent combines two different inorganic fiber types with complementary properties: alumina-silica fibers (low shrinkage, high temperature resistance) and silica fibers (cost-effective, good insulative properties). This composite approach allows the mat to achieve both cost-effectiveness and high-temperature stability, resolving the contradiction between manufacturing cost and reliability.
2Reliability
If polycrystalline alumina fiber mats are used for insulation, then the mat exhibits excellent temperature resistance and low shrinkage, but the mat becomes much more expensive
Solution Approach 1:
Instead of using expensive polycrystalline alumina fibers alone, the patent creates a composite mat combining alumina-silica fibers (which provide the necessary low shrinkage and temperature resistance) with more cost-effective silica fibers. This composite structure achieves the reliability of alumina-based materials at a lower cost by leveraging the synergistic properties of both fiber types.
Solution Approach 2:
The patent applies different fiber types in a distributed manner throughout the mat structure, with alumina-silica fibers strategically positioned to provide structural stability and shrinkage resistance, while silica fibers fill other spaces to provide insulative properties and cost-effectiveness. This local differentiation of material quality optimizes both performance and cost.
3Device complexity
If conventional single-fiber-type insulation mats are used, then the mat structure is simple and cost-effective, but the mat exhibits poor basis weight and thickness tolerances
Solution Approach 1:
The composite fiber structure inherently improves manufacturing precision through self-regulation. The two fiber types have different physical properties that complement each other, allowing the mat to maintain consistent basis weight and thickness even with normal manufacturing variations. The entanglement of different fiber types creates a more uniform and stable structure.
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 resulting insulation mat provides improved thermal management, reduced pollutant emissions, and lower production costs, maintaining heat within the exhaust system to facilitate faster light-off of exhaust gas treatment devices while withstanding high temperatures with minimal shrinkage.
Implementation Method 1
the first inorganic fibers shrink by no more than 2 percent when the mixture of fibers is heat treated at a temperature of 500°C to 800°C
Implementation Method 2
the second inorganic fibers shrink from 5 to 15 percent when the mixture of fibers is heat treated at a temperature of 500°C to 800°C
Implementation Method 3
The resulting insulation mat provides improved thermal management, reduced pollutant emissions, and lower production costs, maintaining heat within the exhaust system
Data Source
Figure 1
AI summary
Methods of forming insulation mats including: providing a mixture of fibers comprising first inorganic fibers and second inorganic fibers, wherein the first inorganic fibers shrink by no more than about 2 percent and the second fibers shrink by about 5 to about 15 percent when the mixture of fibers is heat treated; wet-forming a web of fibers from the mixture of fibers; entangling the web of fibers to form an insulation mat; heat-treating the insulation mat; and drying the web of fibers and/or the insulation mat after said wet-forming and prior to or during said heat treating; and wherein the insulation mat includes substantially no non-fibrous binder material prior to said heat treating the insulation mat at a temperature of from about 500°C to about 800°C, optionally for at least about 3 minutes. Insulation mats manufactured according to the above methods.