CA2072947A1

CA2072947A1 - Method for producing a device for muffling sound or catalytic treatment of exhaust

Info

Publication number: CA2072947A1
Application number: CA002072947A
Authority: CA
Inventors: Willem Denis Maria Stuer
Original assignee: Willem Denis Maria Stuer; Scambia Industrial Developments Aktiengesellschaft
Current assignee: Scambia Industrial Developments AG
Priority date: 1991-07-08
Filing date: 1992-07-02
Publication date: 1993-01-09
Also published as: ES2092665T3; DK0523008T3; EP0523008A1; GR3021076T3; DE59207166D1; ATE143094T1; EP0523008B1

Abstract

Abstract The invention is directed to a method for producing a device forming a muffler 1 or a catalytic converter comprising a casing having an outer wall part 4 and an inner wall part 5. The two wall parts 4, 5 are connected with one another at least at the ends of the casing and are constructed in such a way that there is an intermediate space 16 between them at least in some places.
This intermediate space 16 is produced in that a pressure is generated between the inner wall part 5 and the outer wall part 4 by a substance in order to bend one wall part 4, 5 away from the other wall part 4, 5 at least in some places.

Description

2~7~

METHOD FOR PRODUCING A DEYICE FOR MUFFLING SOUND OR CATALYTIC
TREATMENT OF EXHAUST

Description The invention is directed to a method for producing a device for muffling sound or for the ca~alytic treatment of exhaust.
The device comprises an elongated casing having an outer wall part and an inner wall part. The two wall parts are connected with one another at both ends of the casing, each wall part being connected in every instance with a terminating or closing wall.

The method can be used e.g. for producing a device forming a muffler or catalytic converter which serves as part of an exhaust system of an internal combustion engine and is connected with the exhaust outlet of such an engine.

A known muffler provided for installation in the exhaust line of an internal combustion engine has an elongated double-walled casing which is generally cylindrical and circular in cross section, its two wall parts contacting one another so as to be approximately free of play. The pulsating flows of gas contained in the exhaust flow are smoothed in ~he mu~fler so that the intake and exhaust noises of the internal combustion engine are deadened. This is achieved in that the exhaust flow is guided through at least one chamber and/or at least one perforated exhaust pipe enveloped by a sound absorbing material.
In the method for producing such a muffler, two sheet metal pieces having a thickness of 0.5 mm are placed one upon the other and bent toward the longitudinal wall. During or after the bending, at least one exhaust pipe and the sound absorbing material are inserted into the casing. Following this, the edges of the two wall parts extending along a generating or surface line are turned up to form a longitudinal flange and are connected with one another at their ends and with a closing wall in each instance.

Since the two snugly contactiny metallic wall parts have a relatively high sound and heat conductivity, this muffler has poor sound and heat insulation.

A second known muffler which differs only slightly from the muffler described above and is manufactured according to the same method comprises an intermediate space between the two wall parts. The wall parts are held at a distance from one another by a fiberglass layer located between them. The radial distance between the outer surface of the inner wall part and the inner surface of the outer wall part is normally approximately 1 mm to 2 mm.

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The fiberglass layer improves the sound and heat insulation of the muffler. But this improvement is only slight, since the fiberglass layer used for improving the insulation is very thin and has a relatively high thermal conductivity. In addition to this, the fiberglass layer is relatively expensive.

Similar problems are also posed in the production of catalytic converters.

The object of the present invention is to develop a method by which a device forming a muffler or catalytic converter can be produced without the disadvantages of the described mufflers.

This object is met by a method with the characteristic features of claim 1.

The invention is further directed to a device produced according ~o this method which is defined by the characteristic features of claim 10.

Advantageous arrangements of the method and the device produced according to the method are defined in the dependent claims.

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The subject matter of the invention is now explained with reference to three embodiment examples shown in the drawing:

Figure 1 shows a longitudinal section through a muffler having an outer wall part and an inner wall part prior to the indentation of the latter;

Figure 2 shows a longitudinal section through the muffler shown in Figure 1, but with an inner wall part which is indented in some places;

Figure 3 shows a section through the muffler according to line III-IIl of Figure 2;

Figure 4 shows a longitudinal section through another muffler according to line IV-IV of Figure 5;

Figure 5 shows a section according to line V-V of the muffler shown in Figure 4;

Figure 6 shows a plan view of another muffler whose casing comprises half~shells;

~igure 7 shows a longitudinal section through the muffler shown in Figure 6 according to line VII-VII of Figure 8;

_b 7~7 Figure 8 shows a section according to line VIII-VIII of the muffler shown in Figure 7.

The device shown in Figures 1 to 3 forms a muffler 1 and comprises a casing with a horizontal axis 2. The muffler 1 is provided for installation in the exhaust system of an internal combustion engine and can be connected, e.g. directly or via a catalytic converter, with the exhaust outlet of an internal combustion engine. The casing of the muffler 1 has walls comprising an elongated, sleeve-like longitudinal wall 3 which is generally cylindrical and more or less circular in cross section and has an outer wall part 4 as well as an inner wall part 5.
The walls are further made up of two closing walls 6 arranged at the two ends of the longitudinal wall 3. One closing wall comprises an exhaust inlet 7 feeding in the exhaust and the other closing wall comprises an exhaust outlet 8 serving to guide away the exhaust.

The interior 9 of the muffler 1 is divided into three regions by two intermediate walls 10. The middle interior region which is constructed as a hollow chamber is connected with the inlet 7 and the outlet 8 via perfora~ed exhaust pipes 11. Each of the two exhaust pipes 11 penetrates an intermediate wall 10 and a closing wall 6 and i5 enveloped in the two outer regions of the interior 9 by a sound absorbing material 12 which comprises - 2~729~7 e.g. rock wool and/or basalt wool. The two wall parts 4 and 5 of the muffler 1 are securely connected with one another along a surface line by a longitudinal flange 14 and are likewise securely connected with one another at their ends as well as with the closing walls 6 by means of an end flange 15.

It is noted here that the walls in Figures 1 to 3, as well as in the other described figures, are drawn with overproportionate thickness for reasons relating to graphic depiction.

In producing the muffler 1 shown in Figure 1, two planar sheet metal pieces are first cut to the desire~d dimensions of the longitudinal wall 3. These sheet metal pieces which serve to form the two wall parts 4 and 5 have a thickness between 0.5 mm and 1.5 mm. Two sheet metal pieces of identical thickness are preferably used to produce a muffler 1. However, it is also possible that the sheet metal piece servin~ to form the inner wall part 5 can be somewhat thinner than the sheet metal piece serving to form the outer wall part 4.

In the next method step, an expanding agent 13 in a more or less free-flowing or at least pasty state is applied to the outer surface of the sheet metal piece forming the inner wall part 5 and/or to the inner surface of the sheet metal piece forming the 2(,~4r, outer wall part 4. This can be effected e.g. by spraying or brushing on. It is preferable that no expanding agent 13 be applied to the edge zones of the sheet metal pieces serving to produce the longitudinal flange 14 and end flange 15. The expanding agent 13 can be made up, for example, of a dispersion with a dispersion medium and a plastic-containing material, available under the name of "Mikroperlen" from the firm LEHMANN &
FOSS ~ CO., Hamburg, Germany, which is dispersed in the latter and expands when heated and in so doing increases by 40 to 70 times its volume. The expanding agent contains 5 percent by weight to 20 percent by weight of the dispersed material and is applied in a coating thickness of at least 0.1 mm.

The two sheet metal pieces are then placed one upon the other and bent toward the longitudinal wall 3. The intermediate walls 10, exhaust pipes 11 and sound absorbing material 12 are inserted during or after bending. The intermediate walls 10 are constructed as disks or plates and comprise an outer angled edge region and an angled edge region at the holes 10a. These edge regions contact the inner wall part 5 and the exhaust pipes 11 and can form a pressure connection with the latter and/or be spot welded for example. The ends of the two wall parts 4 and 5 extending along a surEace line are then pressed together and turned up to form a longitudinal flange 14, shown in a simplified manner in Figure 3, and possibly also spot welded together. In 2 ~ '{

so doing, the two wall parts 4 and 5 contack one another via the expanding agent 13 located between them preferably with, at most, slight play and, if possible, none at all and so as to fit snugly. Finally, the closing walls 6 are placed on the exhaust pipes 11 which partially project out. The closing walls 6, like the intermediate walls 10, are constructed as plates and have an outer angled edge region and an angled edge region at the holes 6a. The outer edge region is then folded with the wall ~arts 4 and 5 to form an end flange 15 and pressed together with the latter and possibly spot welded in addition. The closing walls 6 and the intermediate walls 10 comprise metal pieces which preferably have a thickness o~ 1.5 to 2.5 mm.

After the two wall parts 4 and 5 are connected with one another and with the closing walls 6 as well as with the intermediate walls 10, the expanding agent 13 is heated to a temperature of at least 80C, preferably at least 100C, e.g.
120C to 140C. The expanding agent 13 accordingly foams and expands. In so doing, it generates a pressure which causes an indentation of the inner wall part 5 in some places so that the latter assumes the approximate shape shown in Figures 2 and 3.
That is, an intermediate space 16 is formed between the wall parts 4 and 5 in every region between two ad~acent walls 6 and lO
and 10 and 10, respectively, wherein the inner wall part 5 still contacts the outer wall part 4 at the closing walls 6, 2~72~47 intermediate walls 10 and longitudinal flange 14. The greatest radial distance h between the outer surface of the inner wall part 5 and the inner surface of the outer wall part 4 is at least 3 mm, e.g. 6 mm. The intermediate spaces 16 are first filled by foamed expanding agent 13. After the indentation of the inner wall part 5, the muffler 1 can now be heated to a temperature of at least 300C, e.g. 400C . The expanding agent 13 is at least partially burnt by this additional heating. After the burning of the expanding agent 13, the intermediate spaces 16 contain, at most, small quantities of the ashes caused by the burning, i.e.
they no longer contain practically any solid material.

The heating of the muffler serving to indent the inner wall part 5 , particularly the heating of the expanding agent 13 located between its wall parts 4 and 5, is effected e.g. in a workshop of the production plant. However, it is also possible to install the muffler in the exhaust system of an internal combustion engine in the state shown in Figure 1 - that is, with an inner wall part 5 which is not indented. The indentation of the inner wall part 5 and the burning of the expanding agent 13 will then be triggered by the hot exhaust.

The construction of the muffler shown in Figures 4 and 5 and designated in its entirety by 17 is similar, in part, to that of the muffler 1 described with reference to Figures 1 to 3. The 2 ~ J ~ 7 casing of the muffler 17 comprises two wall parts, likewise designated by 4 and 5. However, the muffler 17 is oval in cross section and has oval closing and intermedia~e walls, likewise designated by 6 and 10, respectively. Its two perforated exhaust pipes, designated by 18 and 19, are offset relative to one another in cross section. Further, a connection piece 20 which opens between the two wall parts 4 and 5 i5 inserted in the outer wall part 4.

The production of the muffler 17 is effected in a manner partly similar to that of the production of the muffler 1 shown in Figure 1. However, a substantial difference is to be noted in that no expanding agent ls applied between the two wall parts 4 and 5.

In this case, a fluid, namely water 21, is injected through the connection piece 20 between the two wall parts 4 and 5 of the longitudinal wall by means of a pump 22 to form the intermediate spaces 16 of the muffler 17. The inner wall part 5 is then indented in the region between every two adjacent walls 6 and 10 and 10 and 10, respectively, by the generated pressure. The fluid pressure re~uired for this is dependent on the cross-sectional dimensioning of the wall par~s 4 and 5 and on their thickness and can be e.g. 10 to 50 MPa. After the indentation of the inner wall part 5 and the removal of the pump 22, the water ~7~7 21 can escape via the connection piece 20 and/or possibly the longitudinal flange 14 and end flange 15 so that the muffler 17 comprises intermediate spaces ~6, as shown in Figure 5, which no longer contain water 21.

Of course, a gas, e.g. air, can also be used instead of water 21 as fluid for indenting the inner wall part 5.

The muffler shown in Figures 6, 7 and 8 and designated in its entirety by 23 likewise has an elongated form and comprises a casing which is formed by two identical shells, namely a first, lower shell 24 and a second, upper shell 25, each of which has an outer wall part 26 and an inner wall part 27. The shells 24 and 25 comprise two semicircular, outwardly projecting portions 24a and 25a at their ends. These portions 24a and 25a, respectively, form a collar-shaped and a circular opening 28 in pairs. The shells 24 and 25 and their wall parts 26 and 27 additionally comprise edge portions 30 at their elongated edge regions, which edge portions 30 likewise project out, contact one another and are welded together.

The interior of the casing is constructed so as to be exactly identical to the interior of the muffler 1 shown in Figures 1 and 3 and comprises two exhaust pipes 29 which -2~72~7 penetrate the circular openings 28 and are possibly welded ~ith the outwardly projecting portions 24a, 2sa of the casing.

The intermediate spaces 31 in the walls of the muffler 23 can be produced either according to the method described with reference to Figures 1 to 3 or the method described with reference to Figures 4 and 5.

The method for producing a muffler shown in ~igures 1 to 7 can be changed in various ways. It is noted first that the wall parts or walls of the muffler, those which are visible as well as those which are not visible, comprise stainless steel and can possibly ~e provided with a thin aluminum coat.

Further, it should be noted that the magnitude and the number of chambers and also the lengths and opening cross sections of the exhaust pipes can be selected as desixed so that it is possible to produce mufflers of the described type which can be optimally adapted to the intended use, i.e. to the stroke volume of the corresponding internal combustion engine.

If a device serving as a catalytic converter is to be produced, this device can comprise casings similar to those described in the preceding with reference to Figures 1 to 8. For a device serving as a catalytic converter, a casing of the type 2~72~,~7 ~13-shown in Figures 6 to 8 comprising two half-shells is particularly advisable. Together, the two half-shells can form a substantially cylindrical outer surface area which is circular, oval or elliptical in cross section. Then, instead of the exhaust pipes 11, 18 and 29 and instead of the sound absorbing material 12, the casing can contain at least one catalytic converter body comprising passages whose defining surfaces are coated with a catalytically active material.

Claims

1. Method for producing a device for muffling sound or for the catalytic treatment of exhaust, wherein the device comprises a casing having an outer wall part 4, 26 and an inner wall part 5, 27 and wherein the two wall parts 4, 5; 26, 27 are connected with one another at least at the two ends of the casing and are at a distance from one another at least in some places, characterized in that a pressure is generated between the outer wall part 4, 2 and the inner wall part 5, 27 by a substance in order to bend on wall part 4, 5; 26, 27 away from the other wall part 4, 5; 26, 2 at least in some places.

2. Method according to claim 1, characterized in that the inner wall part 5, 27 is indented in the interior 9 of the casing.

3. Method according to claim 1 or 2, characterized in that an expanding agent 13 is arranged between the two wall parts 4, 5 and is heated in such a way that it expands and generates the pressure for bending at least one wall part 4, 5.

4. Method according to claim 3, characterized in that prior to connecting the two wall parts 4, 5 the expanding agent 13 is applied to the surface of at least one wall part 4, 5 which surface is to face the other wall part 4, 5.

5. Method according to claim 3 or 4, characterized in that the muffler 1 or the catalytic converter is connected with the exhaust outlet of an internal combustion engine with the expanding agent 13 in the unexpanded state, and the expanding agent 13 is heated by the exhaust of the internal combustion engine and made to expand.

6. Method according to one of claims 3 to 5 r characterized in that the expanding agent 13 is heated and burnt after the indentation of the inner wall part 5.

7. Method according to claim 1 or 2, characterized in that the pressure for bending at least one wall part 4, 5 is generated in that a fluid is injected between the two wall parts 4, 5.

8. Method according to claim 7, characterized in that a liquid, e.g. water 21, is used as fluid.

9. Method according to claim 7, characterized in that a gas, e.g. air, is used as fluid.

10. Device for muffling sound or for the catalytic treatment of exhaust produced according to the method according to one of claims 1 to 9, characterized in that one of the two wall parts 4, 5; 26, 27 between said ends is bent away from the other wall part 4, 5; 26, 27 at least in some places.

11. Device according to claim 10, characterized in that the distance between the two wall parts 4, 5; 26, 27 is at least 3 mm, e.g. 6 mm, in some places.

12. Device according to claim 10 or 11, characterized in that the intermediate space 16, 31 between the two wall parts 4, 5;
26, 27 is substantially free of solid material.