Motor Vehicle Acoustic-Thermal Shield With Foam-Blocking Porous Shell
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Solution Overview
Problem
Existing acoustic and thermal protective shields for motor vehicles face issues with foam penetration into the shell, leading to reduced acoustic absorption properties, increased weight, and higher costs due to excessive foam consumption.
Innovation Solution
Incorporating a combination of thick and fine fibers, along with a specific bonding agent, to create a porous shell that minimizes foam penetration, thereby maximizing acoustic absorption and reducing weight and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thick fibers are used in the shell, then the shell provides good acoustic absorption properties, but foam penetrates deeply into the shell reducing acoustic absorption
Solution Approach 1:
The shell uses a composite fiber structure combining thick reinforcing fibers (25-40% by weight) with fine bonding fibers (15-35% by weight). The fine fibers create a dense network that blocks foam penetration while the thick fibers maintain acoustic absorption properties. This composite approach resolves the contradiction by preventing foam from reaching the thick fibers.
Solution Approach 2:
Different regions of the shell have different fiber densities and compositions. The fine fibers are distributed throughout to block foam, while thick fibers are positioned to provide acoustic absorption where needed. This local differentiation allows the shell to simultaneously resist foam penetration and maintain acoustic performance.
2Temperature
If foam penetration is allowed to create sealed skin, then thermal insulation is improved, but acoustic absorption properties decrease and weight increases
Solution Approach 1:
The shell maintains its porous structure with fine fibers creating a foam-blocking barrier. The porosity is controlled to allow minimal foam penetration just enough to create a sealed skin for thermal insulation, while preserving sufficient porous thickness for acoustic absorption. The fine fiber network provides this selective permeability.
3Temperature
If more foam is used to ensure complete sealing, then thermal insulation improves, but cost and weight increase
Solution Approach 1:
The fine fibers are pre-positioned in the shell to create a foam-blocking barrier before foam injection. This preliminary arrangement of fine fibers prevents excessive foam penetration, ensuring that foam is used only where necessary for sealing rather than being consumed by deep penetration into the shell 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 solution effectively blocks foam penetration, enhancing acoustic absorption properties and reducing the weight and cost of the shield, particularly at higher frequencies, while maintaining effective thermal insulation.
Implementation Method 1
said shell has a porosity intended to enable said foam to create a sealed skin on the side of said face, by foam penetration into a fraction of the thickness of said shell
Implementation Method 2
said shield is acoustically insulating, according to a 'mass-spring' principle-implementing a mass layer, formed by said shell provided with said sealed skin, and said spring layer
Implementation Method 3
said shield further having acoustic absorption properties conferred by the fraction of the thickness of said shell not penetrated by said foam and remaining porous
Implementation Method 4
the bonding agent is formed by fusible bonding fibers in an amount from 35 to 50% by weight of said shell
Data Source
AI summary
An acoustic and thermal shield for a motor vehicle, including a porous shell based on fibers bound together by a binding agent and a spring layer based on elastically compressible polyurethane foam, the porosity of the shell being such that the foam is able to create a sealed skin on the underside of the shell, which fibers consist of two types: thick reinforcing fibers in an amount of 25 to 40% by weight of the shell and fine fibers in an amount of 15 to 35% by weight of the shell, the bonding agent being formed by fusible bonding fibers in an amount of 35 to 50% by weight of the shell, so that substantially no foam penetrates the thickness of the shell.