FR3017577A1 - THERMAL PROTECTION SCREEN FOR MOTOR VEHICLE ENGINE COMPARTMENT - Google Patents

Description

The invention relates to a thermal protection screen for motor vehicle engine compartment and a method for producing such a screen. It is known to provide a thermal protection screen for motor vehicle engine compartment, said screen comprising associated with one another: - a support structure, - a metal layer, designed to reflect the heat, recovery of all or part of a face of said structure.

The metal layer is generally based on aluminum and has a thickness of between 50 and 150 microns. The use of such a metal layer generates a heavier screen and also causes a risk of cut, due to the presence of a cutting edge on the periphery of said layer, for manufacturing operators. The invention aims to overcome these disadvantages. For this purpose, and according to a first aspect, the invention proposes a thermal protection screen for a motor vehicle engine compartment, said screen comprising, associated with one another: a support structure, a material film, thermoplastic covering all or part of a face of said structure, said film being provided on its outer surface with a thin layer of metal for reflecting heat, the thickness of said thin layer being less than or equal to 1 micron, and especially less than or equal to 200 nm. The support structure constitutes the body of the screen, giving it a certain rigidity. The film provided with a thin layer of metal - said metallized film - is intended to be turned towards a hot source when the screen is mounted in the vehicle.

The metal is in particular aluminum. The metallization of the film is in particular carried out under vacuum.

In particular, it is possible to provide for the metallization a high temperature heating step allowing passage of the metal to be deposited in the gaseous state. In the case of aluminum, it can be provided to apply a temperature of about 1500 ° C.

The aluminum then condenses on the film which is kept at low temperature, in particular by scrolling between two cooled drums. With the proposed arrangement, the screen is made lighter by involving a much thinner metal layer than that used in the prior art, the thermoplastic material having a much lower density than that of metal. In addition, it eliminates the risk of cuts for the manufacturing operator, the thin film metal deposited on the film can not form a cutting edge. It is specified that such a screen is typically used at temperatures below 350 ° C, and especially between 80 ° C and 220 ° C.

According to a second aspect, the invention proposes a method of producing such a screen. Other features and advantages of the invention will appear in the description which follows, with reference to the attached figure which is a schematic representation in partial section of a screen according to one embodiment.

With reference to the figures, a thermal protection screen 1 for a motor vehicle engine compartment is described, said screen comprising, associated with one another: a supporting structure 2, a film 3 of thermoplastic material covering a motor vehicle; all or part of a face of said structure, said face being intended to be turned towards a hot source, said film being provided on its external face - that is to say the face opposite to that facing said structure - of a thin layer 4 of metal, intended to reflect the heat, the thickness of said thin layer being less than or equal to 1 micron, and in particular less than or equal to 200 nm. In one embodiment, the thickness of the thin layer 4 is less than or equal to 100 nm.

More particularly, the thickness of the thin layer 4 is between 10 nm and 80 nm. Of course, it can be provided, not shown, that the structure 2 comprises two faces covered, in whole or in part, by a respective film 3 provided with a thin layer 4 of metal. In one embodiment, the metal is aluminum.

In one embodiment, the film 3 has a thickness of between 5 and 120 microns. According to one embodiment, the structure 2 is based on porous material, so as to allow sound absorption.

According to one embodiment, the porous material is a fiber-based felt - for example glass, rock, cotton, linen, hemp, ... - bonded together by a thermosetting resin - for example a phenolic resin, polyester, .. .

According to another embodiment, the porous material is a nonwoven fabric - for example based on polyester fibers, viscose fibers, etc. - provided with a thermosetting resin - for example a phenolic resin, polyester, etc.

In one embodiment, the porous material is based on foam, especially polyurethane. When the porous material is based on polyurethane, it is possible, in a manner not shown, for the film 3 to comprise a backing layer made of polyurethane, facing towards the structure 2, and a place layer made of polyester, the thin layer 4 of metal being deposited on said place layer. A method of producing a screen 1 is now described, said method comprising the following steps: providing a film 3 of thermoplastic material provided on one of its faces with a thin layer 4 of metal, the thickness of said layer thin being less than or equal to 1 micron, and in particular less than or equal to 200 nm, - arranging said film in a mold, said thin film being turned towards said mold, - arranging on said film a material for forming a structure 2 of support, - mold all, - unmold the screen 1 obtained. In particular, the metallization of the film 3 is carried out under vacuum. According to one embodiment, the material for forming a structure 2 is in the form of a fibrous layer provided with thermosetting resin, the molding being done by hot compression so as to densify said layer and bake said resin, leading to said structure, and to achieve the association between the film 3 and said structure, in particular by melting said film and / or because of the presence of resin. According to another embodiment, the material for forming a structure 2 is in the form of a precursor mixture of foam, in particular of polyurethane, injected into the mold on the film 3. In particular, it can be provided in this case that the injection of foam precursor mixture is accompanied by a vacuum draw performed so as to press the film 3 against the mold, in order to perfect the geometric definition of the screen 1.

Claims (10)

REVENDICATIONS1. Screen (1) for thermal protection for a motor vehicle engine compartment, said screen comprising, associated with one another: - a support structure (2), - a film (3) of thermoplastic covering material of all or part of a face of said structure, said film being provided on its outer face with a thin layer (4) of metal, intended to reflect the heat, the thickness of said thin layer being less than or equal to 1 micron, and in particular less than or equal to 200 nm. 2. Screen according to claim 1, characterized in that the metal is aluminum. 15 3. Screen according to one of claims 1 or 2, characterized in that the film (3) has a thickness between 5 and 120 microns. 4. Screen according to any one of claims 1 to 3, characterized in that the structure (2) is based on porous material, so as to allow sound absorption. 5. Screen according to claim 4, characterized in that the porous material is a felt based on fibers bonded together by a thermosetting resin. 25 6. Screen according to claim 4, characterized in that the porous material is a nonwoven provided with a thermosetting resin. 7. Screen according to claim 4, characterized in that the porous material is based on foam, especially polyurethane. 30 8. A method of producing a screen (1) according to any one of claims 1 to 7, characterized in that it comprises the following steps: - provide a film (3) of thermoplastic material provided on one of its faces a thin layer of metal, the thickness of said thin layer being less than or equal to 1 micron, and in particular less than or equal to 200 nm, - arranging said film in a mold, said thin layer being turned towards said mold; arranging on said film a material for forming a support structure (2), - molding the assembly, - demolding the screen (1) obtained. 9. The method of claim 8, when it is related to claims 5 or 6, characterized in that the material forming a structure (2) is in the form of a fibrous layer provided with thermosetting resin, the molding being done by hot compression so as to densify said layer and a firing of said resin, leading to said structure, and to achieve the association between the film (3) and said structure. The method according to claim 8, when related to claim 7, characterized in that the material for forming a structure (2) is in the form of a precursor mixture of foam injected into the mold on the film ( 3).