GB2056558A - Silencer, particularly for a motor vehicle - Google Patents

Abstract

A casing 31 provided with an outlet 35 includes a flow tube 10 having an inlet 11, at least part of the flow tube 10 within the casing 31 being partly or wholly surrounded by a chamber 19 of non-circular cross-section. The flow tube 10 may be circular or non-circular, e.g. triangular and is provided with perforations 26. The chamber 19 is also perforated and is divided by baffles 15, 17 having holes 27, 29. The silencer is relatively easy and inexpensive to manufacture as the triangular section tubes are produced merely by bending flat sheet metal into the appropriate non-circular configuration. <IMAGE>

Description

SPECIFICATION Silencer, particularly for a motor vehicle This invention relates to a silencer, in particular an exhaust silencer for a conventional motor vehicle having an internal combustion engine and also relates to a method for the manufacture of such a silencer.

The object of the invention is to produce a silencer in a convenient and relatively inexpensive manner.

According to the invention a silencer comprises a casing, an outlet from the casing, a flow tube within said casing, an inlet to the flow tube, at least part of said flow tube being surrounded by a chamber of non-circular cross-section, gases flowing, in use, through said flow tube and said chamber.

According to a further aspect of the invention, a method of manufacturing a silencer comprising providing a flow tube with an inlet thereto, surrounding at least part of said flow tube with a chamber defined by a pair of plates at the respective ends of a larger section tube, and providing an outer casing of the silencer, characterised in that the larger section tube is formed by bending flat sheet metal into a tube of non-circular cross-section.

The invention will now be described by way of example, with reference to the accompanying drawings, in which; Figure 1 is a schematic, fragmentary side view of a silencerofthe invention; and Figure 2 is an enlarged cross-sectional view on the line 2-2 of Figure 1, with an outer casing ofthe silencer not being shown, but showing the position of a circular inlet end of a flow tube of the silencer.

The silencer shown in the drawings is a reverse flow exhaust silencer for a motor vehicle having a conventional internal combustion engine. The silencer has a central exhaust gas flow tube 10, an inlet end 11 of which is circular and, in use, is connected in a conventional manner two a manifold pipe from the engine to receive exhaust gases. The remainder of the length of the flow tube 10 is of equilateral triangular cross-section as shown in Figure 2. A transition part of the tube between the two different cross-sections is denoted by the numeral 12 in Figure 1. The position of the circular end 11 is shown in dashed lines in Figure 2.

At the axial position of the flow tube where the transition from circular to triangular section begins, the flow tube is surrounded by a fixed circular end plate 13 having an axially directed peripheral annular flange extending from one side thereof towards said end 11 of the tube. To the other side of the plate 13 is secured a circular reinforcement plate 14. A further plate in the form of a circular baffle plate 15 is--fixed to the triangular section part of the tube 10 ata position a short way beyond the end of the transition part 12. The baffle plate 15, like the end plate 13, has an axially directed, peripheral annular flange 16, directed towards the end 11 ofthe tube 10.A further, identical baffle plate 17 with flange 18 is fixed on the tube 10 art a position spaced axially from the baffle plate 15 and extending between and secured to the two baffle plates 15, 17 is an equilateral triangular section tube 19. The tube 19 is considerably largerthan the triangular portion of the flow tube 10 and external surfaces of the corners of the triangular tube 19 engage with and are secured, preferably welded, to the interior surface of the flange 18 of the baffle plate 17 as shown in Figure 2, these corners thus lying on a circle of diameter substantially equal to that of baffle plates 15 and 17. The baffle plates 15, 17 and the tube 19 thus form a chamber surrounding part of the tube 10.

The triangular section of the tube 10 is inverted with respect to that of the tube 19 and the relative sizes of the triangular tubes 10 and 19 are such that the corners of the triangular tube 10 engaged with and are secured, preferably welded, to respective internal side surfaces ofthetube 19, again as shown in Figure 2. With this arrangement, a side 20 of the triangular part of the tube 10, which is opposite a corner 21 of the tube 10 is parallel to a side 22 of the tube 19 which the corners 21 engages. Thus the other two sides of the tube 10 are parallel to the opposite two sides of the tube 19 and accordingly three separated spaces 23, 24, 25 of equilateral triangular section are defined between the tubes 10 and 19. The space 23 communicates with the interior of the tube 10 by way of perforations 26 in the side 20 of the tube 10.Similar perforations (not shown) are provided in the other two sides of the tube 10 within the chamber. As used herein the term "perforation" includes a hole of any shape and also includes a semi-pierced or a louvred hole.

In each of the baffle plates 15, 17, three holes 27, 28, 29 are provided. The holes are arranged in the plates so that relative to the tube 19, they are disposed adjacent the corners of the tube 19 as shown in Figure 2. The holes 27, 28, and 29 thus allow communications between the spaces 23, 24, 25 and the outside ofthe chamber at the opposite ends thereof.

As shown best in Figure 2, each side of the triangular tube 19 has perforations 30 therein, these perforations, like the perforations in the side 20 of the flow tube 10, extending for the full length of the chamber.

At the other end of the tube 10 from the end 11,a further chamber of almost identical form to that formed by the baffle plates 15, 17 and the tube 19 is provided. The same numerals have thus been used for identical components. The only differences are that the peripheral flanges 16, on the baffle plates 15,17 face away from the end 11 of the flow tube and that the flow tube terminates at the baffle 17, as can be seen in Figure 1. Although in Figure 1 the chamber nearest the end 11 is shown shorter than the other chamber, the lengths of the chambers can be selected as required. Although in this described embodiment there are two chambers, any suitable number from one upwards could be provided. Between chambers the tube 10 is unperforated.

Acylindrical outer casing 31 is provided overthe chambers and flow tube 10, only part of this casing being shown in Figure 1. The peripheral flanges 16, 18 of the baffle plates 15,17 and the peripheral flange of the end plate 13 are all secured to the internal surface of the cylindrical casing 31. This casing could instead be of non-circular cross-section. At its end remote from the end 11 of the flow tube 10, the casing 31 is closed by an end plate 32, to a peripheral flange of which it is secured. A reinforce ment plate 33 is secured to the side of the end plate facing the adjacent end of the flow tube 10. A space 34 between the end of the flow tube 10 at the baffle plate 17 and the closed end of the casing is relatively long, longer in fact than either chamber, although this is not shown in Figure 1 for convenience.This space 34 forms an expansion chamberforgas reach ing the end of the flowtube 10. The casing 31 is closed at its other end by the plate 13, so that the circular section end 11 ofthe flow tube protrudes from the casing. As is well known in the art, the vol ume ofthe expansion chamber should be greater than the swept volume ofthe engine cylinders.

At an axial position corresponding to the transition between the circular and triangular sections of the tube 10, a circular cross-section outlet pipe 35 is provided. The pipe 35 extends normally from the tube 10 to which it is secured and is open towards the hole 27 in the baffle plate 15 disposed adjacent thereto.

All the components of the silencer are made of sheet metal and could, for example, be of stainless steel.

The triangular section part of the flow tube 10 is manufactured from flat steel plate by bending it into an equilateral triangularconfiguration, as shown in Figure 2, adjacent edges of the plate being secured together by welding or other suitable process. Simi larly the tube 19 is likewise produced by bending flat steel plate into the triangular configuration of Figure 2, with the plate edges being secured together. The plate is preferably perforated before bending.

The tube 10 is then received in the tube 19 and the two tubes welded together at their three points of contact Baffle plates 15 and 17 received on the tube 10 at opposite ends of the tube 19 are brought to engage the ends ofthe tube 19 to define the chamber around the tube 10. The baffle plates, which thus have respective holes therein to match the triangular section of the tube 10, are then securged to the tube 19.

When all the chambers have been so formed, the tube 10 with surrounding chambers is received in the casing 31 and secured thereto by way of the end plates 13 and 32 and outlet35.The circular section inlet end 11 of the flow tube 10, which is also formed from the flat sheet metal extends outwardly from the end plate 13.

In use, exhaust gases pass through the inlet end 11 and into the triangular section of the tube 10. At the first chamber, a proportion of the gases pass through the tube 10, as shown by the arrows on Figure 1, with the remainder ofthe gases entering the spaces 23 to 25 through the perforations in the sides of the tube 10. Such gases can also pass through the perforations 30. The gases in the tube 10 then pass from the first chamber along the tube to the second chamber, where again a proportion ofthe gases enterthe spaces 23 to 35 and can pass through the perforations 30. The gases then flow from the tube 10 into the expansion chamber 34.After expansion, the direction of flow of the gases is reversed and they flow through the holes 27 to 29 in the baffle plate 17 of said second chamber, into the spaces 23 to 25 in the second chamber, as well as around the tube 19. After leaving the second chamber through the holes 27 to 29 the gases flow, as indicated, within the casing and then into the first chamber. Gases leaving the first chamberthrough the holes 27 to 29 in the baffle plate 15 then flow to the outlet pipe 35, and thence to a conventional exhaust pipe of the motor vehicle. Thus the exhaust gases are slowed down as they pass through the silencer andthe energy and thus the pressure of the gases is reduced, particularly in the expansion chamber.

Although in the embodiment described the crosssection ofthetubes 10 and 19 is triangular, any other suitable non-circular or polygonal section could be used. Such non-circular or polygonal sections need not be the same for the tube 10 and the tube 19.

Moreover the tube 10 could possibly beof circularsection.

Manufacture of the silencerofthe invention is facilitated by the fact that the tube 19 is of noncircular cross-section. The tube 19 is thus easily formed from flat sheet metal by bending such material into the required non-circular configuration. With the embodiment illustrated the flat sheet metal can easily be bent into a triangular configuration and it will be appreciated that this is much easierthan forming circular section tube. The flat sheet metal would preferably be appropriately perforated before the bending thereof is carried out.

Thus the silencer can be manufactured relatively easily and inexpensively as compared to silencers having circular section components, particularly if subsfantially all the tube 10, and possibly also the casing 31, in addition to the tube 19 is of non-circular cross-section, and thus producible from flat sheet metal.

In addition to the manufacturing advantages, it is thoughtthatthe silencerofthe invention may produce a reduction in noise levels as compared to known conventional silencers. The silencer may also possibly produce better heat dissipation and reduce back pressure on the engine as compared to known silencers, thereby resulting in more efficientpower transfer and increased fuel; economy.

Although only a reverse flow silencer is described and illustrated, the invention is equally applicable to so-called "straight-through" silencers

Claims (20)

1. Asilencercomprising casing, areoutletfrom said casing, a flow tube within said casing, an inlet to the flow tube, at least part of sa id flovw tube with in the casing being surrounded by a chamber of noncircular cross-section, gases flowing, in use, through said flow tube and said chamber.

2. A silencer as claimed in claIm 1, wherein said chamber is defined by a pair of plates through which said flpw tube extends, and a larger, non-circular section tube extending between said end plates to surround said flow tube.

3. A silencer as claimed in claim 2, wherein each plate is a baffle plate having holes therein, each hole communicating the exterior of the chamber with a space in the chamber between the larger section tube and the flow tube.

4. A silencer as claimed in claim 2 or claim 3, wherein the portion of the flow tube within the larger section tube is perforated to allow communication between the interior of the flow tube and the interior of the chamber defined around said flow tube between the end plates and said larger section tube.

5. A silencer as claimed in any one of claims 2 to 4, wherein said larger section tube is perforated to allow communication between the interior of said larger section tube and the interior of the casing around it.

6. A silencer as claimed in any one of claims 2 to 4, wherein said casing is cylindrical and each plate is circular, the periphery of each plate being provided with an axially directed annular flange, which is secured to an inner surface of the casing.

7. A silencer as claimed in any one of claims 2 to 6, wherein the flow tube is of non-circular crosssection within the casing.

8. A silencer as claimed in claim 7, wherein the flow tube is of triangular cross-section within the casing.

9. A silencer as claimed in claim 8, wherein the flow tube is of circular cross-section at its inlet end and at the axial position where the flow tube changes from circular to triangular section, said casing outlet is provided.

10. A silencer as claimed in claim 8 or claim 9, wherein said larger section tube is oftriangular cross-section.

11. A silencer as claimed in claim 10, wherein the corners of the triangular flow tube are secured to respective internal sides of said larger triangular section tube.

12. A silencer as claimed in claim 10 or claim 11, wherein the corners of said larger triangular section tube lie on a circle having a diameter no greater than that of each plate, so that the larger section tube is disposed within the area of each plate.

13. A silencer as claimed in any one of claims 1 to 12, wherein a plurality of chambers each surrounding partofthe flow tube is provided.

14. A method of manufacturing a silencercom- prising providing a flow tube with an inlet thereto, surrounding at least part of said flow tube with a chamber defined by a pair of plates atthe respective ends of a larger section tube, and providing an outer casing of the silencer, characterised in that the larger section tube is formed by bending flat sheet metal into a tube of non-circular cross-section.

15. A method as claimed in claim 14, wherein said flow tube is formed by bending flat sheet metal into a tube of non-circular cross-section.

16. A method as claimed in claim 15, wherein said flow tube is received within said larger section tube and the corners of said flow tube engage and are secured to interior flat sides of the larger section tube thereby forming a number of separated spaces between the two tubes.

17. A method as claimed in claim 16, wherein both said tubes are of equilateral triangular crosssection and the corners of the flow tube are secured to the centres of said interior sides of the larger section tube respectively so that the spaces are of equilateral triangular cross-section.

18. A method as claimed in claim 17, wherein each of the plates at the ends of the chamber is provided with three holes allowing communication between said spaces and the exterior of the chamber.

19. A silencer substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

20. A method of manufacturing a silencer substantially as hereinbefore described with reference to and as shown in the accompanying drawings.