GB2070688A

GB2070688A - A fan shroud

Info

Publication number: GB2070688A
Application number: GB8105838A
Authority: GB
Original assignee: Nissan Motor Co Ltd
Current assignee: Nissan Motor Co Ltd
Priority date: 1980-02-29
Filing date: 1981-02-24
Publication date: 1981-09-09
Also published as: JPS56127899U; GB2070688B

Abstract

A shroud 13 for an internal combustion engine cooling fan is made from a fibrous substrate (23), Fig. 2b (not shown), impregnated with an organic resin and shaped by heating and pressing. The fibrous substrate has a high damping capacity and exhibits a high sound absorbing characteristic. The substrate is embraced by fabric outer layers (21). Reinforcing plates may be provided at the mounting flange 11. <IMAGE>

Description

SPECIFICATION A fan shroud The present invention relates to a fan shroud for a fan for cooling an internal combustion engine.

A conventional shroud for a fan of this type is shown in, for example, Fig. 1.

In general, such a fan shroud has been formed integrally or separably of steel or synthetic resin. The shroud shown in Fig. 1 consists of a flange 1 for mounting the shroud onto a radiator (not shown) and formed with several apertures 2 to receive set screws for the mounting, a cylindrical duct 3 covering the rotating fan blades to improve the cooling effect of the fan, and surrounding walls 4 connecting the mounting flange 1 to the cylindrical duct 3.

The fan shroud of this type, however, has the disadvantage that it tends to transmit vibration of associated moving parts. In addition, as it is a formed or molded part of a metal of synthetic resin whose damping capacity or sound absorption is low, noise caused by rotation of the fan is not sufficiently absorbed, and variation in the pressure of the air flow produced by the fan causes the shroud itself to vibrate so as to generate noise.

It is an object of the invention to provide an improved fan shroud which eliminates the above disadvantages of the prior art by forming the shroud from a fibrous substrate which is soft and has a high damping capacity to exhibit a high sound absorbing characteristic.

It is a further object of the invention to provide an improved fan shroud which is formed from a fibrous substrate comprising portions of high density and portions of relatively low density, thereby improving its rigidity and sound absorption.

In order that the invention may be more clearly understood, preferred embodiments will be described, by way of example, with reference to the accompanying drawings.

Figure 1 is a prior art fan shroud integrally made of a synthetic resin as described above; Figure 2a is a fan shroud integrally formed according to the invention; Figure 2b is a sectional view of a fibrous substrate of the fan shroud shown in Fig. 2a; Figure 3 is an explanatory graph illustrating a sound absorbing coefficient curve of the fibrous substrate used in the fan shroud according to the invention; Figure 4 is a sectional view of a fibrous substrate of a fan shroud of another embodiment of the invention; Figures 5a and 5b are partial sectional views of fan shrouds having flanges provided with reinforcing plates; Figure 6 is a graph illustrating the noise reducing effect of a fan shroud according to the invention in comparison with the prior art;; Figure 7 is a perspective view of the fan shroud according to the invention manufactured for a test to obtain the graph of Fig. 6; and Figure 8 is a partial sectional view taken along the line VIII-VIII in Fig. 7.

Fig. 2a illustrates one example of the integrally formed fan shroud according to the invention and Fig. 2b shows a general crosssection of the shroud. The shroud comprises a mounting flange 11 formed at its corners with several mounting apertures 1 2 which, in use, align with apertures formed in a radiator (not shown), a cylindrical duct 1 3 surrounding the blades of a fan, and surrounding walls 14 connecting the mounting flange 11 to the cylindrical duct 1 3.

In forming the shroud according to embodiments of the invention, organic or inorganic fiber is added with phenol or acrylic resin and its crosslinking agent, for example, formaldehyde and heated and formed by pressing to obtain a desired shape. As shown in Fig. 2b, the fiber layer 23 is embraced by fabric layers 21 adhered thereto.

The fan shroud according to the invention accomplishes the following function. As the conventional fan shrouds are made of steel of plastics material, they have a lower sound absorbing coefficient and a poor damping capacity, so that vibration from vehicle bodies is transmitted to the shrouds which themselves also cause noise by variation in pressure of air flow produced by the fans, which noise is difficult to reduce.

In contrast herewith, according to the invention, the fiber layer 23 which is superior in sound absorption is used as a substrate and coated on both its sides with fabric 21, thereby reducing the noise cause by the vibration of the shroud itself and effectively absorbing part of the pitch noise due to the rotation of the fan and noise caused by the fluid.

The sound absorbing coefficient of the material of the shroud made of the fiber layer 23 is very high as shown in Fig. 3 which effectively serves to reduce the noise caused by the fan. The sound absorbing characteristic depends upon the thickness of the fiber layer 23 and is varied by controliing pressure applied in pressing, so that any sound absorbing coefficient can be selected at will. The vibration damping capacity is also high, so that the shroud according to the invention does not form a source of noise due to vibration.

With the embodiment of the invention shown in Fig. 4, a fiber layer 23 is provided on both its surfaces with film layers, 22 of rubber or synthetic resin for waterproofing or oilproofing, onto which are bonded fabrics 21.

Figs. 5a and 5b illustrate further embodiments of the invention, wherein a reinforcing plate 1 spa or 1 sub of steel, aluminium, plastics material or the like is circumferentially bonded to a fiber layer of a mounting flange 11 of a shroud to reinforce the rigidity of the mounting flange 11. In Fig. 5a, the L-shaped reinforcing plate 15a is secured to the outer surface of the flange and in Fig. 5b, the flat reinforcing plate 1 5b is secured to the surface of the flange on the side of a radiator. These reinforcing plates f5a and 15b may be embedded in the fiber layer 23.

Fig. 6 is a graph illustrating a noise reducing effect of the shroud according to the invention in comparison with the prior art.

Fig. 7 shows a fan shroud 30 according to the invention used for the test whose result is shown in Fig. 6. A cylindrical duct 33 of the shroud 30 has a diameter of 390 mm. As shown in Fig. 8, in forming a fiber layer 34, portions of different density are provided to improve its rigidity and sound absorbing performance. The thinner portion 34a is of a higher density for the rigidity and the thicker portion 34b is of a lower density for the sound absorption. This fiber layer 34 is provided on either surface with a fabric layer 35 having a film on its inner side, and a rubber layer 36 adhered to the surface of the layer 34.

As can be seen from the above description, according to the invention the shroud for a fan is formed of the material consisting of organic or inorganic fiber and phenoi or acrylic resin subjected to the crosslinking reaction, thereby reducing noise caused by it's vibration and effectively absorbing noise resulting from fluid flowing by rotation of the fan.

Moreover, as the specific gravity of the material is about 0.6, the shroud according to the invention is about 30% lighter than those of the prior art. The fibers used for this purpose may be pieces of general garments and, therefore, effect very low cost in manufacture.

With the embodiments shown in Figs. 5a and Sb, furthermore, the reinforcing plates are arranged substantially all over the mounting flanges of the shrouds to improve the rigidity of the flanges for mounting them to radiators by means of set screws or the like with improved durability of the shroud.

Claims

1. A fan shroud for a fan for a radiator of an internal combustion engine, said shroud being made of a fibrous substrate impregnated with an organic resin and formed in a desired shape by heating and pressing.

2. A fan shroud as set forth in claim f, wherein said fibrous substrate is organic.

3. A fan shroud as set forth in claim 1, wherein said fibrous substrate is inorganic.

4. A fan shroud as set forth in claim 1, wherein said organic resin is phenol resin.

5. A fan shroud as set forth in claim 1, wherein said organic resin is acrylic resin.

6. A fan shroud as set forth in claim 1 wherein said fibrous substrate includes a crosslinking agent such as formaldehyde before heating and forming.

7. A fan shroud as set forth in claim 1, wherein said fibrous- substrate is provided orl both surfaces with fabric layers adhered thereto.

8. A fan shroud as set forth in claim 1, wherein said fibrous substrate is provided one both its surfaces with film layers of a material selected from rubber and synthetic resin for fluidproofing, onto which are bonded fabrics layers.

9. A fan shroud as set forth in claim 1, wherein said fibrous substrate is provided on one side with a rubber layer adhered thereto and on the other side with a fabric layer adhered thereto having on its inner surface a rubber film layer.

10. A fan shroud as set forth in claim 1, wherein said fibrous substrate comprises thinner portions of high density and thicker portions of relatively lower density, thereby improving its rigidity and sound absorption, respectively.

11. A fan shroud substantially as described with reference to, and as illustrated in, Figs. 2a and 2b, or Fig. 4, or Figs. 7 and 8, of the accompanying drawings.