Insulating Isolator for Exhaust Heat Shield Thermal Expansion
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Solution Overview
Problem
Heat shields for internal combustion engine exhaust manifolds face challenges in accommodating thermal expansion differences between the manifold and the heat shield, requiring a solution that also addresses mechanical vibration isolation and allows for the use of lower-cost, lower-melting-point materials.
Innovation Solution
An insulating isolator design featuring a first land with a fastener aperture, embossed bead portions, and multiple apertures that can be tuned for specific applications to manage thermal and mechanical stresses, allowing for the use of lower-cost materials and effective vibration isolation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the entire heat shield is constructed of high-temperature material to withstand severe conditions at the connection point, then the heat shield can endure high temperatures, but the cost increases and the mass increases
Solution Approach 1:
The heat shield uses different materials for different regions: high-temperature material only at the connection point where severe thermal conditions exist, and lower-cost, lower-melting-point material for the majority of the shield that is insulated from extreme temperatures. This localized material differentiation resolves the contradiction by applying high-temperature resistance only where necessary.
Solution Approach 2:
The heat shield is divided into distinct zones with different thermal exposure levels. The connection point area is segmented as a high-temperature zone requiring specialized material, while the bulk of the shield is segmented as a lower-temperature zone that can use more economical materials, thus reducing overall mass and cost while maintaining temperature resistance where needed.
2Strength
If the heat shield is rigidly connected to the exhaust manifold, then the mounting is secure, but the different thermal expansion of the manifold and heat shield causes alignment difficulties and stress
Solution Approach 1:
The isolator incorporates flexible elements including a bead portion with circumferential gaps and petals that can flex and deform. This flexibility allows the mounting structure to accommodate differential thermal expansion between the rigid exhaust manifold and the heat shield while maintaining secure attachment, resolving the contradiction between mounting strength and thermal adaptability.
Solution Approach 2:
The isolator transitions from a rigid connection to a dynamic, flexible connection that can adapt its shape and position in response to thermal expansion differences. The flexible bead and petal structures allow relative movement and alignment adjustment as temperatures change, maintaining secure mounting while accommodating dimensional changes.
3Ease of manufacture
If the connection points are directly bolted to the manifold, then the mounting is simple, but the fasteners are exposed to severe temperatures causing material degradation
Solution Approach 1:
The isolator acts as an intermediary component between the fasteners and the exhaust manifold. It provides thermal insulation to the fastener openings, creating a thermal barrier that protects the fasteners from severe manifold temperatures while maintaining the simple bolted mounting configuration. This resolves the contradiction by mediating the thermal exposure while preserving manufacturing simplicity.
4Strength
If the isolator uses a solid structure for strength, then the mounting is robust, but the vibration transmission from the engine increases
Solution Approach 1:
The isolator incorporates a porous or cellular internal structure within the bead portion and petal structures. This porous configuration reduces the isolator's natural frequency and dampens vibration transmission from the engine while maintaining sufficient structural strength for mounting. The porous structure acts as a vibration isolator, resolving the contradiction between structural integrity and vibration reduction.
Solution Approach 2:
The isolator is designed with specific geometric features including circumferential gaps and petal structures that create vibration-damping characteristics. These features are tuned to reduce the transmission of engine vibrations to the heat shield while maintaining the necessary mechanical strength for secure mounting, addressing the contradiction between strength and vibration isolation.
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 design effectively isolates thermal and mechanical stresses, enabling the use of lower-cost materials while maintaining structural integrity and vibration isolation, thus protecting components from extreme temperatures and vibrations.
Implementation Method 1
In addition, it would be advantageous to develop a mounting configuration that simultaneously functioned as an isolator for mechanical vibration from the engine.
Implementation Method 2
the temperature in the heat shield can be at its greatest due to heat conducting from the manifold directly into the heat shield. Thus, the connection points between the heat shield and the exhaust manifold must be able to withstand severe temperature conditions.
Data Source
AI summary
An insulating isolator for a heat shield has a unitary first land, a bead portion, a second land and a half bead. The first land defines a fastener aperture. In one case, a plurality of circumferentially spaced apart petals is formed in the isolator. The petals may be separated by gaps. In another case, a set of circumferentially spaced apart apertures are formed in the isolator.The heat shield may have at least two disk apertures. Two metallic disks are located in the area of at least one of the two disk apertures. The metallic disks are connected to each other, have aligned fastener openings that are smaller than the disk apertures and they are smaller than the metallic sheet. One of the metallic disks may have a bead.