Exhaust Gas Muffler

Mufflers, for example for motor vehicles, often include inserts for dividing and silencing the pulsating flow of exhaust gas. Generally, to provide appropriate silencing, and at the same time a reasonably low pressure drop, such inserts have to be relatively complex and large. To be able to reduce the dimensions of the muffler while maintaining its silencing capacity, fiber inserts, usually constituted of mineral fibers, can be provided in the muffler. The life of such mineral fiber inserts, however, is too short in relation to the life-expectancy of the structure of the muffler itself, especially if it is made of stainless steel, or other corrosion-resistant material. Another drawback of known mufflers is that, normally, different constructions and dimensions of the mufflers have to be available for different engine types.

This invention relates to an exhaust gas muffler, particularly for combustion engines, comprising a tubular envelope, a gas inlet at one end of the envelope, a gas outlet at the other end of the envelope, and between these ends, at least one muffler insert which includes two, or several, spaced apart cones of sheet metal, whose edges substantially closely contact the envelope, and whose axes of symmetry are substantially coaxial to the axis of the envelope.

An object of the present invention is to provide a muffler of simple construction, which without fiber inserts, and without causing unfavorable pressure drop of the exhaust gases, can be manufactured with relatively small dimensions, and at the same time have excellent silencing capacity.

Another object of the present invention is to provide a muffler which can be manufactured of only a few parts, and produced largely automatically, or at least with a simplified assembling procedure.

Still another object of the present invention is to provide a muffler of standard construction, which in a simple manner, by small modifications of its components, can be adapted to different types of engines.

The above-mentioned objects are achieved in mufflers of the above-described type by the fact that at least one sheet metal cone of each insert has at least one or a small number of relatively large gas flow passages, and that the centers of the passages adjacent cones are angularly separated, and that each insert is disposed with the apices of the cones directed toward the muffler outlet, and that adjacent cones of an insert are disposed at a distance from one another such that the apex of the rear cone, as viewed in the direction of the the gas flow, lies downstream of a plane perpendicular to the direction of the axis through the surface of abutment to the envelope of the front cone.

In order that the invention will be more clearly understood, it will now be disclosed in greater detail with reference to the accompanying drawings, wherein:

FIG. 1 is a part sectional and a part elevational view of an exhaust gas muffler constructed according to the teachings of the present invention;

FIG. 2 is a sectional view taken along the lines II--II of FIG. 1;

FIG. 3 is a partial sectional view showing a part of a sheet metal cone insert;

FIG. 4 is a sectional view of another embodiment of the present invention;

FIG. 5 is a sectional view taken along the lines V--V of FIG. 4;

FIG. 6 is a sectional view taken along the lines VI--VI of FIG. 4; and

FIG. 7 is a sectional view of a muffler intended principally to be combined with the muffler shown in FIG. 4.

FIG. 1 shows a muffler which is well-suited for combustion engines, for example motor vehicle engines. The muffler comprises a tubular envelope 10 each end of which is defined and closed by end walls 11 and 12. A perforated baffle 13 forms, together with the end wall 11 and the envelope 10, a gas diffusing chamber 14. A muffler gas inlet tube 15 extends through the end wall 11 to the baffle 13. The part of the tube 15 which is between the end wall 11 and the baffle 13 is provided with a large number of perforations 16.

A first insert 17 in the right hand side of the envelope 10 comprises sheet metal cones 18, in which one is inserted in the other, and are arranged in the envelope 10 inside of and adjacent to the baffle 13, the cones 18 being disposed with their bases facing the baffle 13.

Each sheet metal cone 18 has three gas flow passages Moreover, each passage 19 can include a portion which is perforated in a certain pattern, or is preferably one single port, as seen in the figures. The ports are arranged relative to one another at an angular distance of 120.degree. with respect to the axis 20 of the cone 18, and of the envelope 10. The angle width of the ports is preferably less than 45.degree., with respect to the axis. Preferably, the ports are in the form of circle sectors, or triangles, with the apex directed to the axis of symmetry 20 of the cone 18 and the envelope 10, the ports being symmetrical relative to a plane through the axis of symmetry of the cone 18.

Adjacent cones 18 are angularly displaced relative to one another through 60.degree. with respect to their ports. The peripheral edges of the cones 18 are substantially closely fixed to the inner wall of the envelope 10. The envelope 10 as well as the cones 18 are suitably circular in cross section, the axes coinciding with the axis of envelope 10.

A perforated second baffle 21 forms a second gas diffusing chamber together with the end wall 12 and the envelope 10. A gas outlet pipe 23 for the muffler extends through the end wall 12 to the baffle 21. The part of the pipe 23 which is between the end wall 12 and the baffle 21 is provided with a large number of perforations 24. A second insert 25 comprising sheet metal cones 18 and inserted one in the other are disposed in the envelope 10 inside of and adjacent to the baffle 21, with the apices of the cones 18 facing the baffle 21. In other respects, the insert 25 is arranged and constructed like the insert 17. However, if desired, the number of cones 18 of each insert can be different. Suitably, the number of cones 18 of an insert is two, but three or even four cones can be used in the assembly.

In actual use, the muffler is intended normally to have gas flowing in the direction of the arrow 26. While the gas diffusing chambers 14 and 22 serve to broaden the gas flow through the envelope.

In a preferred embodiment of the present invention, the sheet metal cones 18 have an outer diameter of 128 mm. and an apex angle of 90.degree.. The ports in the passage 19 are in the form of equilateral triangles with a side length of 36 mm. In mufflers for larger gas flows, ports with a side length of 42 mm. have been tested. The distance between the cones of an insert, as measured at right angles between the surfaces of the cones, amounts to 10-15 mm.

Adjacent cones 18 of an insert are arranged at such relative distances that the apex of the rear cone, as seen in the direction of the gas flow, lies downstream of a plane through the front limitation of the gas flow passages of the front cone, the passages being disposed at equal distances from the apex of the cone.

Each insert can comprise two sheet metal cones 18. If desired, a larger number of each insert can be chosen, but then the increased pressure drop must be considered. Normally, an insert comprises a maximum of four cones 18. The diameter of the envelope, as well as the outer diameter of the cones, can be chosen according to given conditions, but for ordinary motor vehicles, an envelope diameter of 100-150 mm. would be appropriate. Once a certain diameter has been chosen for the envelope of the muffler, the gas pressure drop can be determined by the number of cones 18 included in each insert, and/or by the size of the port area, or the number of ports in each cone.

In a preferred embodiment the distance between the inserts 17 and 25 is 200 mm.

It should be evident, however, that it is also possible to make the muffler with more than two inserts, which are suitably disposed at equal distance relative to one another.

As seen in FIG. 3, the ports in the passage 19 are preferably arranged near the base of the cone 18, so that the axial distance between the apex 27 of a cone 18 and a plane P through the front edge of the ports in the passage 19 is greater than the axial distance T between adjacent cones 18.

The perpendicular distance S between the surfaces of two adjacent cones 18 is preferably such that it corresponds to half the gas flow area of a passage 19 divided by the height of this passage, as measured along the generatrix of a cone 18.

Referring now to the embodiment shown in FIG. 4, the muffler has an envelope 10a with an end wall 11a through which extends a gas inlet pipe 15a. The pipe 15a also extends through a perforated baffle 13a so that a gas diffusing chamber 14a is formed between the baffle 13a, end wall 11a and envelope 10a. The envelope enclosed two sheet metal cones 18a, which are coaxial with the axis of the envelope and of which one cone has its apex inside a plane which is perpendicular to the axis of the envelope, and has its extension through the abutment surface to the envelope of the second sheet metal cone. Each cone has a circular gas flow passage or passages 19a with an area of substantially the same size as that of the inlet pipe 15a. As seen in FIG. 5, the centers of the gas flow passages 19a are placed about 90.degree. relative to one another. The envelope further encloses two frustro-cones 28, which with their peripheries, are connected to the envelope 10a, and to one another by a central pipe 29 in such a manner that the pipe forms a passage for the gas through the muffler. The pipe 29 has an opening 30 so that a chamber 31 is formed between the cones 28, envelope 10a and the pipe 29. The envelope 10a furthermore has a sheet metal end cone 32. The latter cone is also frustro-conical, with its smaller end directed toward the outlet, and merges into an outlet pipe 23a. In addition, the envelope has an end wall 12a at the outlet side. Between this end wall, the outlet pipe 23a and the cone 32 a chamber 33 is formed which via two ports 34 in the cone 32 communicates with the part of the muffler, through which the gas flows.

The embodiment shown in FIG. 7, which is mainly intended to co-act with the muffler shown in FIG. 4, comprises, like the above-described embodiments of the invention, an envelope 10b with end walls 11b and 12b and an inlet pipe 15b as well as a baffle 13b, defining a rear gas diffusing chamber 14b. As in the embodiment shown in FIG. 7, a sheet metal end cone 32b with ports 34b is provided, which together with the envelope and the end wall 12b forms a front gas diffusing chamber 33b. The embodiment of FIG. 7 is further provided with an outlet pipe 23b. In this case, the insert comprises two sheet metal cones 18b and 18c, the rear cone as seen in the direction of flow, having a gas flow passage 19b, and the front cone being perforated.

It should be pointed out that it is possible within the scope of the present invention, for example in the embodiments shown in FIGS. 1 and 4, to divide the envelope into two separate, substantially equal large parts connected to one another via a pipe, in order to make it possible to install the various parts of the muffler at locations which are most suitable with respect to accessibility.