WO2001011210A1

WO2001011210A1 - Exhaust volume made of polymer material

Info

Publication number: WO2001011210A1
Application number: PCT/FR2000/002227
Authority: WO
Inventors: Christian Sarda; Sylvain Pelissard; Jean Lagier; Frédéric Abadie; Alain Tournier
Original assignee: Faurecia Systemes D'echappement
Priority date: 1999-08-10
Filing date: 2000-08-02
Publication date: 2001-02-15
Also published as: DE10084885T1; FR2797467A1; FR2797467B1; AU6849100A

Abstract

The invention concerns an exhaust volume (10) comprising a casing whereof at least one wall (12, 14) is made of a polymer material. The or each wall (12, 14) comprises, at least in a located zone of said wall, two layers (22, 24) of polymer material and a separating barrier (26, 40) interposed between the two layers (22, 24). The barrier is not chemically or physically bound to the two layers (22, 24).

Description

Exhaust volume in polymer material.

The present invention relates to an exhaust volume, of the type comprising an envelope, at least one wall of which is made of a material comprising a polymer.

It further relates to several methods of manufacturing such an exhaust volume.

It has already been envisaged to manufacture certain exhaust volumes of an exhaust line of an internal combustion engine from polymer materials. In particular, casings of exhaust silencers made of composite material are already known, such as polymers reinforced by fibers.

The use of such exhaust volumes is particularly suitable in an automobile since they are very light. In addition, since the materials used for manufacturing are easy to shape, the exhaust volumes can have complex shapes on the outside.

However, the use of polymeric materials only slightly reduces the noise emissions due to the pulsed circulation of gases in the exhaust line.

Thus, the invention aims to provide an exhaust volume allowing improved sound isolation of the exhaust line, and whose manufacture is simple.

To this end, the invention relates to an exhaust volume of the aforementioned type, characterized in that the or each wall comprises, at least in a region marked with said wall, two layers of material comprising a polymer and, a barrier separator interposed between the two layers which barrier has no physical or chemical bond with the two layers.

According to particular embodiments, the exhaust volume comprises one or more of the following characteristics: - the two layers of material comprising a polymer each comprise a polymer chosen from the group consisting of a thermoplastic polymer, a thermosetting polymer and a photocrosslinkable polymer; - At least one of the two layers of material comprising a polymer comprises reinforcing elements coated in the polymer;

- Said barrier comprises a film of a material incompatible with the two layers of material comprising a polymer; - Said barrier comprises a gas plate maintained in an enclosed space delimited by the two layers of material comprising a polymer; and

- The volume includes means for connecting the or each wall of material comprising a polymer ensuring the cohesion of the exhaust volume, which connection means are applied to the periphery of the or each wall in at least one connection area , and the or each bond pad has no barrier, the two layers being joined by physical or chemical bonds in the or each bond pad.

The subject of the invention is also a method of manufacturing an exhaust volume as defined above, comprising the steps of:

A - hot forming in a mold, a wall of material comprising a polymer; and

B - after cooling, place the wall of material comprising a polymer in said exhaust volume, characterized in that the formation of said wall of material comprising a polymer comprises the steps of: a - initially placing a film in a mold forming a barrier; and b - injecting on either side of the barrier film a material comprising a thermoplastic polymer. As a variant, the formation of the wall of material comprising a polymer comprises one or other of the following successive stages: a - superimposing between the two forms of a mold a first layer of material comprising a thermosetting polymer, a barrier film and a second layer of a material comprising a thermosetting polymer; b - heat; and c - apply compression; or a - introducing into a mold a material comprising a polymer for the manufacture of the two layers of said wall; and b - while the materials comprising polymers are hot, injecting, into the mold, a separation gas immiscible with the materials comprising polymers to ensure the creation of a pocket between the two layers; or a - introduce a blowing agent into the material comprising a polymer intended to form the two layers; and b - placing in the mold the material comprising a polymer and said blowing agent, under the conditions of activation of said blowing agent; or a - hot placing in a variable-volume mold a material comprising a polymer and fibers, the material being intended to form the two layers; and b - increase the volume of the mold to ensure the formation of the gas layer under the action of the relaxation of the fibers. The invention will be better understood on reading the description which follows, given solely by way of example and made with reference to the drawings, in which:

FIG. 1 is a section view of an exhaust volume according to the invention consisting of two assembled half-shells each containing a separating film,

- Figure 2 is a view similar to that of Figure 1 of an alternative embodiment where the separating film is replaced by a gas slide.

The exhaust volume 10 shown in Figure 1 comprises two identical half-shells 12, 14 linked to one another by connecting means 16 such as glue, rivets, bolts or staples.

Each half-shell 12, 14 essentially has the form of a half-cylinder 18 extended laterally on either side by two external connecting pads 20 constituting assembly zones. The areas assembly are glued one on the other to ensure the joining of the two half-shells.

According to the invention, each half-shell comprises, in at least one region identified, two layers of polymer material and a separating barrier interposed between the two layers, this barrier being devoid of physico-chemical bond with the two layers.

Thus, the half-shells 12 and 14 each have an outer layer 22 and an inner layer 24 between which is interposed a film 26 forming the separating barrier. Advantageously, the separating barrier extends only over most of the semi-cylindrical part 18 of each half-shell. Thus, the bonding pads 20 are devoid of a barrier, the two layers 22, 24 being physically or chemically bonded to each other along these pads.

The thickness of each layer 22 and 24 is between 0.2 mm and 4 mm and is preferably between 0.05 and 1.5 mm. The thickness of the film 26 is between 0.05 mm and 1 mm. It is advantageously between 0.1 and 0.5 mm.

According to a first embodiment, the layers 22 and 24 are made of the same thermoplastic material. This is preferably chosen from one of the families of thermoplastic materials from polyethylene, polypropylene, polyamide, polysulfones, polyether sulfones, polyphenylene sulfide (PPS), polyether ketone (PEEK) , liquid crystal polymers, polytetrafluoroethylene (PTFE), polyimides, as well as hybrid compounds based on mixtures of the aforementioned products.

As a variant, the layers 22 and 24 are made of thermosetting and / or photo-crosslinkable materials, in particular crosslinkable under the action of ultraviolet. These materials are preferably one of the following types of resin: unsaturated polyester, epoxy, vinyl ester, phenolic, isophthalic, polyurethane, as well as the hybrid compounds based on mixtures of the abovementioned resins.

Whatever the nature of the polymer material used for layers 22 and 24, these may include embedded reinforcing elements in the polymer material. These reinforcing elements comprise for example short or long fibers of glass or carbon. They may also include a fabric or a lattice of glass, carbon or stainless steel. The polymer material can also be used alone without reinforcing elements.

The intermediate barrier film is made of a material incompatible with the polymer material used to make the layers 22 and 24. In particular, the material is chosen so that no, or practically no chemical or physical bond is established at the interfaces between the barrier film 26 and one or other of the layers 22 and 24. This barrier film is formed for example of polyvinyl acrilate (PVA), Halar ^®, Teflon ^® or an aluminum sheet.

In the alternative embodiment shown in FIG. 2, the film 26 constituting the separating barrier is replaced by a gas blade 40 held in an enclosed space 42 forming a pocket delimited between the layers 22 and 24. This gas blade 40 is obtained either by injection gas during the molding of the half-shell, either by reaction of an expanding or porogenic agent during molding. The manufacturing process will be described in the following description. The gas blade 40 is limited outside the connecting regions of the half-shell.

It is noted, by using an exhaust volume delimited by an envelope produced from a polymer sheet as described above, that the acoustic emissions, during a vibratory excitation of the structure are reduced.

Table 1 which follows shows the emission levels obtained during a vibratory excitation and during an acoustic excitation, on the one hand from a monolayer polymer structure as known in the state of the art and, d On the other hand, a polymer structure with two layers separated by a mechanically independent barrier.

The simple reference structure consists of a 2 mm thick wall made of epoxy resin reinforced with glass fibers. The wall according to the invention comprises two layers of epoxy resin with a thickness of 1 mm separated by a Halar film with a thickness of 0.1 mm.

Vibration excitation is applied with a frequency range of 500-10,000 Hz.

TABLE 1

The experimental results appearing in Table 1 show a significant reduction in noise emissions during the application of vibratory excitation on a silencer having a structure according to the invention.

The methods of manufacturing the exhaust volumes produced from sheets or walls of polymer according to the invention comprising two layers separated by a physically or chemically independent barrier will now be described.

Whatever the embodiment of the exhaust volume according to the invention, it is produced in two successive phases. During a first phase, one or more walls made of polymeric materials comprising two layers separated by an independent intermediate barrier are produced hot in a mold.

After the polymer material walls have cooled, they are assembled in a second phase to form the exhaust volume.

The different embodiments of the silencer, and the various associated manufacturing processes are distinguished by the mode of implementation. vre of the first phase of hot forming of the wall of polymer material.

For the manufacture of an exhaust volume, the walls of which consist of two layers of polymer material separated from a film of an incompatible material, the polymer walls can be produced according to two distinct processes.

According to a first method, a barrier film is placed in a mold inside which it is held in the middle position by inserts. It is thus away from the opposite faces of the mold. After closing the mold, while the film is in its middle position, a thermoplastic polymeric material is injected on either side of the barrier film.

After cooling, the wall thus obtained is removed from the mold. The barrier film is thus coated between the two layers of injected thermoplastic material. Due to the incompatible natures of the material constituting the barrier film and of the plastic material injected, these are physically and chemically independent.

According to a second manufacturing process, two films of thermosetting polymers are superposed inside a mold, between which is interposed a film forming a barrier made of a polymer material which is incompatible with the thermosetting material or materials constituting the extreme layers.

The three layers thus superimposed are then heated and then a compression step is implemented while the thermosetting materials are sufficiently softened to match the shape of the mold imprint. After cooling, the wall obtained is removed from the mold.

As before, the materials being incompatible, the barrier film is mechanically and chemically independent of the extreme layers inside which it is kept.

For the manufacture of an exhaust volume wall according to the invention, internally enclosing a gaseous blade, three separate processes can be implemented.

According to a first method, a polymer material of the thermoplastic or thermosetting type is injected into a mold. As soon as the material sees its viscosity increase, in the case of a thermoplastic material, or begins to polymerize, in the case of a thermosetting material, a gas immiscible with the polymeric material, such as air, is injected directly into the mold via one or more injection nozzles. The gas thus injected is trapped inside the still fluid polymeric material. During the cooling of the wall, the trapped gas forms a gas plate maintained in a sealed pocket delimited on either side by the two layers of polymer material resulting from the separation formed by the gas plate. According to another manufacturing process, a thermoplastic polymer or a thermosetting polymer is injected into a mold to which has been added, initially, a blowing agent capable of producing a gas evolution under the action of heat. Such a blowing agent is, for example, one of the following three compounds: azodicarbonamide, oxy-bis (benzene-sulfohydrazine), dinitrosopentamethylene-tretamine.

To obtain a gaseous blade, the polymer is first maintained in compression in an initial phase. To promote the creation of the gaseous blade, the two forms of the mold are slightly separated from each other, after the initial phase of maintaining compression. The blowing agent then releases a gaseous evolution which is kept trapped between the extreme layers of the polymeric material being formed, due to the progressive cooling.

According to a final variant of the production method, a polymer material and, advantageously, a thermosetting composite material, for example based on polyester resin, are injected into a mold. This material is loaded with glass fibers or any other type of suitable fiber.

After an initial phase of compression of the composite material, the two shapes of the molds are slightly separated in order to allow a re-laxation of the glass fibers initially stressed between the two molds. The relaxation of the fibers generates a natural expansion of the composite material which creates a gas layer between the two extreme layers of the composite material. After complete cooling, a wall is obtained which internally has a gas layer separating the two extreme layers.

Claims

CLAIMS 1.- Exhaust volume (10), of the type comprising an envelope of which at least one wall (12, 14) is made of material comprising a polymer, characterized in that the or each wall (12, 14) comprises, at least in one marked region of said wall, two layers (22, 24) of material comprising a polymer and, a separating barrier (26; 40) interposed between the two layers (22, 24), which barrier has no physical bond or chemical with the two layers (22, 24).

2.- exhaust volume according to claim 1, characterized in that the two layers (22, 24) of material comprising a polymer each comprise a polymer chosen from the group consisting of a thermoplastic polymer, a thermosetting polymer and a pho polymer - toréticulable.

3.- exhaust volume according to claim 1 or 2, characterized in that at least one of the two layers (22, 24) of material comprising a polymer comprises reinforcing elements coated in the polymer.

4.- exhaust volume according to any one of claims 1 to 3, characterized in that said barrier comprises a film (26) of a material incompatible with the two layers (22, 24) of material comprising a polymer.

5.- exhaust volume according to any one of claims 1 to 3, characterized in that said barrier comprises a gas blade (40) held in an enclosed space (42) delimited by the two layers (22, 24) in material comprising a polymer.

6.- exhaust volume according to any one of the preceding claims, characterized in that it comprises means (16) for connecting the or each wall (22, 24) of material comprising a polymer ensuring the cohesion of the volume exhaust, which connection means (16) are applied to the periphery of the or each wall (22, 24) in at least one connection area (20), and in that the or each connection area (20) has no barrier (26; 40), the two layers (22, 24) being joined by physical or chemical bonds in the or each bond pad (20).

7.- A method of manufacturing an exhaust volume according to claim 4, comprising the steps of:

A - hot forming in a mold, a wall of material comprising a polymer; and B - after cooling, place the wall of material comprising a polymer in said exhaust volume, characterized in that the formation of said wall of material comprising a polymer comprises the steps of: a - initially placing in a mold a barrier film; and b - injecting on either side of the barrier film a material comprising a thermoplastic polymer.

8. A method of manufacturing an exhaust volume according to claim 4, comprising the steps of:

A - hot forming in a mold, a wall of material comprising a polymer; and

B - after cooling, place the wall of material comprising a polymer in said exhaust volume, characterized in that the formation of said wall of material comprising a polymer comprises the steps of: a - superimposing between the two forms of a mold a first layer of material comprising a thermosetting polymer, a barrier film and a second layer of a material comprising a thermosetting polymer; b - heat; and c - apply compression.

9. A method of manufacturing an exhaust volume according to claim 5, comprising the steps of:

A - hot forming in a mold, a wall of material comprising a polymer; and B - after cooling, place the wall of material comprising a polymer in said exhaust volume, characterized in that the formation of said wall of material comprising a polymer comprises the steps of: a - introducing into a mold a material comprising a polymer for the manufacture of the two layers of said wall; and b - while the materials comprising polymers are hot, inject, into the mold, a separation gas immiscible with the materials comprising polymers to ensure the creation of a pocket between the two layers.

10.- A method of manufacturing an exhaust volume according to claim 5, comprising the steps of:

A - hot forming in a mold, a wall of material comprising a polymer; and

B - after cooling, place the wall of material comprising a polymer in said exhaust volume, characterized in that the formation of said wall of material comprising a polymer comprises the steps of: a - introducing a pore-forming agent into the material comprising a polymer for forming the two layers; and b - placing in the mold the material comprising a polymer and said blowing agent, under the conditions of activation of said blowing agent.

11. A method of manufacturing an exhaust volume according to claim 5, comprising the steps of:

A - hot forming in a mold, a wall of material comprising a polymer; and

B - after cooling, set up the wall of material comprising a polymer in said exhaust volume, characterized in that the formation of said wall of material comprising a polymer comprises the steps of: a - arranging hot, in a variable volume mold, a material comprising a polymer and fibers, the material being intended to form the two layers; and b - increase the volume of the mold to ensure the formation of the gas layer under the action of the relaxation of the fibers.