GB2265569A

GB2265569A - A cowling for internal-combustion engines of motor vehicles

Info

Publication number: GB2265569A
Application number: GB9306047A
Authority: GB
Inventors: Helmut Stober
Original assignee: Daimler Benz AG; Mercedes Benz AG
Current assignee: Daimler Benz AG; Mercedes Benz AG
Priority date: 1992-04-04
Filing date: 1993-03-23
Publication date: 1993-10-06
Anticipated expiration: 2013-03-23
Also published as: GB9306047D0; IT1261418B; DE4211409A1; SE507286C2; SE9300884D0; FR2689935B1; ITRM930165A1; FR2689935A1; ITRM930165A0; SE9300884L; GB2265569B

Abstract

A self-supporting, heat and sound insulating cowling for internal-combustion engines of motor vehicles comprises a plurality of layers which have been compression-moulded under the effect of pressure and heat to form zones of defined- predetermined compaction. The cowling comprises, on the engine side, a thicker, heat insulating and sound insulating layer (2) of an inorganic fibrous material, which is covered by a layer (4) of carbon-fibre material. A thicker layer (3) of inorganic fibrous material, facing away from the engine, cures to form a self-supporting support layer. 25 to 35% by volume of it consists of 25 to 50 mm long glass fibres and the rest consists of either a high temperature resistant polyester resin and mineral filler or polypropylene. This support layer may be covered on the bodywork side by a layer (5) of non-woven polyester or polyacrylonitrile fibres. <IMAGE>

Description

2265569 1 A cowling for internal-combustion engine of motor vehicles The

invention relates to a self -supporting, heat and sound insulating cowling for internal-combustion engines of motor vehicles, as is known from commercial vehicles massproduced by the applicant.

In the known construction, the cowling is fitted on both sides of the engine, mounted underneath the driver's cab, in the region between the frame side member and the underside of the driver's cab.

German Offenlegungsschrift. 3,601,204 discloses an absorption moulding which comprises a plurality of nonwoven layers and may serve for such sound insulating cowlings for the engine compartment of motor vehicles, but which is not dimensionally stable. The already known absorption moulding comprises a top layer, on the engine side, of synthetic fibres, an adjoining heat insulating and sound absorbing layer of inorganic fibrous material which can be subjected to high thermal loads, and a further absorbing layer of organic fibres. This moulding is unsuitable in cases where there is high thermal loading, since both the synthetic fibrous material of the top layer and the organic fibres are in the long term damaged or destroyed by the high temperatures in the engine compartment. As mentioned, the absorption moulding itself is also not dimensionally stable and has to be installed together with a dimensionally adapted support shell, to be produced separately. Thus, a cowling produced in this way obtains the self-supporting characteristic mentioned at the beginning only by having the separate support shell, as a result of which the effort involved in producing the cowling itself, as well as the effort involved in installation, that is, ultimately the costs for the ready-fitted cowling, are relatively high.

In German Patent Specification 3,818,301 there is likewise described a noise insulating moulding for the engine compartment of motor vehicles in which inorganic

2 f ibrous material, which can be subjected to high thermal loads and is bonded by a binder, is covered on the engine side by a carbon-fibre material by means of a joining mediumcontaining melamine resin. This moulding is intended to have good noise insulation and also is suitable for use as a thermal insulation up to a temperature range of about 500'C. It is in this case also envisaged that the moulding is provided with a layer of carbon fibres towards the bodywork. This layer of carbon fibres is intended to provide certain mechanical protection for the sensitive layer of inorganic fibrous material. Altogether, the moulding described there also does not constitute a dimensionally stable cowling for the engine compartment of motor vehicles, but has to be paired with a dimensionally adapted support shell in order for it to be able to form a self-supporting cowling; thus, a self-supporting cowling formed by the pliant absorption moulding just described would also be relatively expensive.

The present invention seeks to develop a cowling in such a way that, while retaining the noise insulating and heat insulating effect and the self-supporting characteristic, the cowling is easier to produce and install.

According to the present invention there is provided a self-supporting, heat and sound insulating cowling for internal-combustion engines of motor vehicles, comprising an absorption moulding adapted to be on an engine side within the cowling and formed by a plurality of nonwoven layers, and a dimensionally adapted support shell, arranged on the side facing away from the engine within the cowling and stabilising the absorption moulding in its intended shape and installed position, the nonwoven layers of the absorption moulding being compressed to form zones of predetermined compaction and the absorption layer of the absorption moulding which serves for sound absorption and thermal shielding of the engine heat containing inorganic fibres, wherein the support shell is structurally integrated with the absorption moulding to form a single compression- 4 3 moulded part by there being moulded on the side facing away from the engine of the effectively absorbing nonwoven layers of the cowling a very substantially pore-free, about 1 to 5 mm thick support layer compressible together with the effectively absorbing nonwoven layers of the cowling to form a uniform moulding and of which - 25 to 35% by volume consists of 25 to 50mm long glass fibres and otherwise either a) contains 25 to 35% by volume of a high temperature resistant polyester resin and 35 to 45% by volume of mineral fillers or b) contains 65 to 75% by volume of polypropylene.

Thanks to the special composition of the material for the base layer, the latter can be moulded together with the other effectively absorbing nonwoven layers in one and the same compression moulding operation to form a uniform dimensionally stable workpiece, that is to form a uniform self-supporting cowling, whereby not only the production of the cowling, but also its installation is made significantly easier and cheaper. Due to the different composition of the individual layers, a different characteristic of the layers is achieved in spite of the same pressures and temperatures for all the layers. The nonwoven layers remain adequately loose for the required absorption effect, whereas the support layer is pore-free, hard and rigid. Of the two alternatives for the support layer, the design according to alternative a) is intended for high temperature loading of the support layer up to, for example, about 500'C, whereas the design of the support layer according to alternative b) is intended for cases of lower temperature loading, for example up to about 2000C, and/or the requirement for good noise insulation.

Preferably, when the support layer contains 25 to 35% by volume of a high temperature resistant polyester resin and 35 to 45% by volume of mineral fillers, the mineral filler for the support layer contains quartz sand.

The effectively absorbing nonwoven layer of the cowling may 4 contain about 85 to 96%, preferably 94%, by volume of basalt wool and otherwise phenolic resin binder. The effectively absorbing nonwoven layer of the cowling may be provided on the surface facing the engine compartment with a top layer consisting of a carbon-fibre material.

Preferably, the support layer contains 65 to 75% by volume of polypropylene, the effectively absorbing nonwoven layers of the cowling containing a nonwoven layer or consisting completely of a nonwoven layer of which about 70 to 80%, preferably 75%, by volume is composed of synthetic and/or textile f ibres and the rest is composed of phenolic resin binder.

Preferably, the surf ace of the support layer is provided with a 0.5 to 2 mm thick covering layer of cotton fibres, polyester fibres or polyacrylonitrile fibres.

Two exemplary embodiments of the invention are described below by way of example and represented in a drawing, in which:

Fig. I shows a partial cross-section through a first embodiment of a onepart self-supporting cowling part and Fig. 2 shows a partial cross-section through a second embodiment of a cowling part.

Figure 1 shows the self-supporting cowling 1 which can be subjected to relatively high thermal loads, comprising the absorption layer 2, compression-moulded from a nonwoven layer of inorganic fibres, and the support layer 3, consisting of glass fibres, mineral filler and binder, compress ion-moulded together with the absorption layer 2 and thereby compacted pore-free and cured. The heat-resistant absorption layer 2 consists to a great extent, for example 94% by volume, of mineral fibres, in particular basalt wool, which are mixed with a binder, f or example with 6 % by volume of phenolic resin binder. Thanks to the relatively low binder content in the absorption layer, this layer apart from the edge zones with extremely high pressure per unit area - continues to contain pores even after the joint hot press moulding operation and, because of this, has a good heat insulating and sound insulating effect. In the support layer 3, on the other hand, the fibre content is considerably lower than in the absorption layer 2; to be precise, only a quarter to about a third of the support layer consists of inorganic fibres, in particular of glass fibres. The remaining, greater part of the constituents of the support layer is predominantly made up of inorganic filler and otherwise resin binder. In order to obtain in the hot press moulding of the cowling part a stable, cured support layer 3 which can be subjected to high thermal loads, a high temperature resistant polyester resin is used as binder. Quartz sand has proved to be particularly suitable as mineral filler for the support layer.

The absorption layer 2 facing the engine is provided with a top layer 4 of carbon fibres. This top layer on the engine side preferably has a thickness of 1 to 2 mm and a weight per unit area of 100 to 150 g/m:2. In the case of the exemplary embodiment represented, for visual reasons the support layer 3 is also provided on the outside with a top layer 5 having a layer thickness of about 1 mm and a weight per unit area of 100 to 150 g/m:-', which consists of a polyester nonwoven or of polyacrylonitrile fibres. This top layer may also be bonded to the surface of the support layer 3 by an interposed, heat-activatable adhesive film.

Reference 6 denotes the edge zones of the support layer 3, which have a particularly high density and consequently also a high mechanical stability; to be precise, on account of an appropriate shaping of the compression mould, the fibres of the absorption layer are compacted porefree in this region as well. This is achieved on the one hand by an appropriate shaping of the compression mould and a correspondingly high compressing pressure in the edge zones. In addition, in the edge zone the binder content can also be increased specifically in this location by spraying on binder resin. The openings required for fitting the cowling in the motor vehicle, for example screw through- 6 holes, can be punched out in these edge zones.

The moulding is produced in one operation. First of all the material mixture for the support layer 3, made up in a prefabricated nonwoven, is laid in the lower half of an opened compression mould and the material for the absorption layer 2, likewise prepared in nonwoven form, is placed thereupon. A carbon-fibre nonwoven is also placed onto the absorption material. The compression mould filled in this way is then closed and pressed together under the effect of heat, the cowling receiving its shape and the material of the support layer being compacted pore-free and compressed to form a cured, self-supporting layer having a thickness of 1 to 5 mm. After the compressing operation, the thickness of the support layer in the centre of the moulding is normally 3 to 5 mm and decreases towards the edge layers down to about 1 mm. Depending on the configuration of the cowling, during the compressing operation this material layer is compressed to a layer of about 50 mm thickness in the centre of the moulding and to about 5 mm in the edge zones, with a weight per unit area of 1500 to 3000 kg/m-'. Since the support layer 3 and the absorption layer 2 contain binder dispersed within their fibres, this results in a good cohesion of the various layers in the hot press moulding of the cowling.

The cowling 11, of which a portion is represented cross-sectionally in Figure 2, is intended in particular for a thermal loading up to at most 200 to 220'C; it differs from the exemplary embodiment according to Figure 1, which can be subjected to high thermal loads, in particular by the composition of the absorption layer 21 and of the support layer 31. To be precise, here the support layer is designed virtually as a f ibre- reinf orced polypropylene moulding which is integrated in the cowling and of which about a quarter consists of inorganic fibres of about 25 to 50 mm in length, for example of glass fibres or of basalt fibres, and the rest of polypropylene. About three quarters of the absorption layer 21 is formed by synthetic and/or textile 7 fibres and the rest by phenolic resin as binder. The two top layers 4 and 5 are designed the same as in the example according to Figure 1. It is quite conceivable f or both alternative configurations of the absorption layer to be provided in one and the same cowling, to be precise at points of higher thermal loading, well in excess of 200'C; for example, in the vicinity of the exhaust pipe, a nonwoven of inorganic fibres is placed on, and in the remaining regions, less subjected to thermal loading, a nonwoven of synthetic or textile fibres is placed on.

The advantages which can be achieved by the selfsupporting, one-part cowling according to the invention are, in particular, the inexpensive producibility and installation of the cowling, a good sound absorbing effect and - in the case of the configuration which can be subjected to higher thermal loads according to Figure 1 the extremely high thermal loadability. The cowling can be fitted in all motor vehicles, both in passenger cars and in trucks, not only in the engine compartment of the vehicle but, if appropriately cut to size, anywhere where there are heat sources in a vehicle which have to be shielded off, for example exhaust pipes and turbo chargers etc.

8 claims 1. A, self -supporting, heat and sound insulating cowling f or internal- combustion engines of motor vehicles., comprising an absorption moulding adapted to be on an engine side within the cowling and formed by a plurality of nonwoven layers, and a dimensionally adapted support shell, arranged on the side facing away from the engine within the cowling and stabilising the absorption moulding in its intended shape and installed position, the nonwoven layers of the absorption moulding being compressed to f orm zones of predeterm ined compaction and the absorption layer of the absorption moulding which serves f or sound absorption and thermal shielding of the engine heat containing inorganic f ibres, wherein the support shell is structurally integrated with the absorption moulding to form a single compressionmoulded part by there being moulded on the side facing away from the engine of the effectively absorbing nonwoven layers of the cowling a very substantially pore-f ree, about 1 to 5 mm thick support layer compressible together with the effectively absorbing nonwoven layers of the cowling to form a uniform moulding and of which 25 to 35% by volume consists of 25 to 50mm long glass fibres and otherwise either a) contains 25 to 35% by volume of a high temperature resistant polyester resin and 35 to 45% by volume of mineral fillers or b) contains 65 to 75% by volume of polypropylene.

Claims

2. A cowling according to Claim 1, wherein, when the support layer

contains 25 to 35% by volume of a high temperature resistant polyester resin and 35 to 45% by volume of mineral fillers, the mineral filler for the support layer contains quartz sand.

3. A cowling according to Claim 1, wherein, when the support layer contains 25 to 35% by volume of a high 7 9 temperature resistant polyester resin and 35 to 45% by volume of mineral fillers, the effectively absorbing nonwoven layer of the cowling contains about 85 to 96% by volume of basalt wool and otherwise phenolic resin binder.

4. A cowling according to claim 3, wherein the effectively absorbing nonwoven layer of the cowling contains about 94% by volume of basalt wool and otherwise phenolic resin binder.

5. A cowling according to Claim 1, wherein when the support layer contains 25 to 35% by volume of a high temperature resistant polyester resin and 35 to 45% by volume of mineral fillers, the effectively absorbing nonwoven layer of the cowling is provided on the surface facing the engine compartment with a top layer consisting of a carbon-fibre material.

6. A cowling according to Claim 1, wherein when the support layer contains 65 to 75% by volume of polypropylene, the effectively absorbing nonwoven layers of the cowling contain a nonwoven layer or consist completely of a nonwoven layer of which about 70 to 80% by volume is composed of synthetic and/or textile fibres and the rest is composed of phenolic resin binder.

7. A cowling according to claim 6 wherein about 75% by volume of said nonwoven layer is composed of synthetic and/or textile fibres.

8. A cowling according to Claim 1, wherein the free surface of the support layer is provided with a 0.5 to 2 mm thick covering layer of cotton fibres, polyester fibres or polyacrylonitrile fibres.

9. A self-supporting, heat and sound insulating cowling for internalcombustion engines of motor vehicles, substantially as described herein with reference to and as illustrated in the accompanying drawings.