JPH0444082B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an exhaust device for exhausting combustion gas from an internal combustion engine, and more particularly to an exhaust device for exhausting combustion gas from an internal combustion engine of a vehicle. Exhaust gas produced by an internal combustion engine, such as that installed in a vehicle, is discharged through an exhaust system. The exhaust system includes a relatively small diameter tube extending from the exhaust manifold to an opening to the atmosphere and having one or more silencers along it. The silencer is a heavy, bulky device that is much larger in diameter than the rest of the exhaust system. Silencers are used to cancel, within a relatively short distance, the acoustic shock waves created by the explosive release of the combusted air-fuel mixture from the cylinder. This shock wave includes sound waves of various frequencies. The silencer is
Structures well known in the art are used to attenuate sound waves of various frequencies. Large silencers are extremely susceptible to road damage and are limited by the space that must be accommodated in the vehicle. When the exhaust system cools, moisture condenses in the large partitioned space inside the muffler, causing rust and deterioration of the muffler. Silencers are relatively complex in construction and require a plurality of different metal pieces that must be treated in different ways. Silencers are therefore relatively expensive and heavy. In recent years, exhaust systems have also been required to eliminate unburned hydrocarbons from the exhaust gas. This function is performed by a separate catalytic converter. Converters are additions to conventional exhaust systems and form relatively bulky containers. Exhaust containing unburned hydrocarbons is
It flows into the converter and passes through a catalyst from precious metals of the platinum group, including platinum, palladium and rhodium, all plated on alumina. The alumina is pelletized or coated onto an extruded ceramic substrate. The converter acts to reduce pollutants in the atmosphere by oxidizing hydrocarbons. The volume of the converter also requires that the structure of the vehicle be particularly adapted to receive the converter. The oxidation of unburned hydrocarbons generates significant heat and the converter is at high temperatures. Vehicles must also be constructed to ensure that they do not suffer damage from particularly high temperatures. Conventional mufflers, converters, interconnect pipes, exhaust pipes and end tail pipes are connected by clamps and attached to the vehicle through mounting brackets. These devices have a relatively complex structure, which requires time and effort to assemble and increases costs. There is a need for an improved exhaust system that retains the muffling and oxidizing properties of conventional mufflers and converters, yet reduces its size, cost and weight. In this case, the flexibility of the vehicle structure increases. There is also a need to develop new exhaust systems that have equal or increased durability in use and reduced assembly time and material costs. Recent proposals that seek to achieve some of these goals include de Cardenas.
There is an apparatus described in US Pat. According to the present invention, an exhaust system for exhausting gas from an internal combustion engine having an exhaust manifold of a vehicle is obtained. The exhaust system includes a uniform diameter tube section extending from an engine exhaust manifold to an opening to the atmosphere. This tube section carries exhaust gases from the engine to the atmosphere. A plurality of porous filters are positioned within the tube section along its length to muffle exhaust noise. The porous filter is formed from at least one section of expanded metal. Each section is folded along its length at selected locations to form individual filters between each fold, each filter being spaced a predetermined distance from the filter formed by the common fold. In accordance with the present invention, the predetermined distance between each filter is varied along the tube section to enhance muffling in a range of acoustic frequencies. The exhaust system also includes at least one section along the tube section that is unfiltered to form a mixing chamber in which isolated portions of the shock waves cancel each other out. Each filter has a rectangular (including square) cross section and forms four arcuate passages between each filter and the inner wall of the tube section that serve to dissipate shock waves. Each filter may have an oval (including circular) cross-section between each fold to allow each filter to contact the inner wall of the tube section about approximately its inner circumference. The filter piece may be twisted in a helical manner with the edge of the filter piece contacting the inner surface of the tube piece to form a filter. According to the invention, the porous material can be selected from the group consisting of metal, ceramic material or heat-resistant plastic material. Each hole in the porous material can be sized to enhance sound deadening over a range of acoustic frequencies, and can have an airfoil cross-section to enhance sound deadening. Each hole is
It can be produced by expanding the material, by interweaving linear materials, or by other suitable dimensions. According to the invention, each section of porous material is coated with alumina and also a metal from the platinum group and positioned along its length within the tube section to oxidize unburned hydrocarbons in the exhaust gas. The tube segment is continuous along its entire length;
The porous material may extend along substantially the entire length of the tube section and within it, or may be concentrated in one or more locations. Further, according to the present invention, there is provided an exhaust system for discharging gas from an internal combustion engine having an exhaust manifold of a vehicle. The exhaust system has a uniform diameter tube section extending from an engine exhaust manifold to an opening to the atmosphere. This tube section conveys the exhaust gas therein to the opening. At least one section of liner is positioned within the tube section during formation of the tube section. This section includes a plurality of airfoil baffles extending into the gas stream to muffle the exhaust air. According to the invention, the airfoil baffle is selected from the group consisting of metal, heat-resistant plastic and ceramic. The liner is constructed from a continuous strip, the airfoil baffle is stamped from the strip, and the edges of the strip are folded and welded to form the tube section itself within the exhaust pipe section. During this process, a cylindrical body to be welded is formed. The airfoil baffle plate can vary in length, cross-section, thickness, suppression angle, and frequency along the length of the liner to enhance the muffling effect of the exhaust system. In accordance with the invention, an exhaust system is provided which includes a tube section of uniform diameter containing a wire fabric to muffle the exhaust gas. The wire may have various diameters and cross-sections, and the resulting fabric extends along the length of the tube section to provide enhanced muffling in the range of acoustic frequencies of the exhaust air. Embodiments of the exhaust system of the present invention will be described in detail below with reference to the accompanying drawings. Like reference numerals represent similar or corresponding parts throughout the accompanying drawings. FIG. 1 shows a vehicle 10 with associated internal combustion engine 12 for propulsion. Engine 12 includes an exhaust manifold 14 that collects combustion exhaust from engine 12 from one or more cylinders for disposal to the atmosphere. The parts shown in dashed lines represent a conventional muffler 20, a conventional converter 18 and a conventional clamp 21. Converter 18 and silencer 20 are connected to tube section 22
They are interconnected by. It is clear that the structure of the vehicle 10 must be particularly able to accommodate the relatively bulky converter 18 and muffler 20. It is also clear that a typical exhaust system is comprised of many parts that must be assembled at the same time or prior to assembling the vehicle on the assembly line. The exhaust device 24 illustrated in FIG.
constitutes an example. As shown, the exhaust system 24 of the present invention includes a continuous tube section 26 having a uniform outer diameter and a flange 28 at one end for connection to the exhaust manifold 14. Pipe piece 26
The opposite end includes an opening 3 near the rear of the vehicle 10 for exhausting combustion gases from the engine 12 to the atmosphere.
0 is set. The tube piece 26 has bends 32, 34, 36, 38, 40, 42, 43 along its length.
Vehicle 1, including the rear axle and other components
It is adapted to the structure of 0. As will be discussed in more detail below, the exhaust system 24 serves to muffle the exhaust of the engine 12 and also includes catalytic conversion elements to oxidize unburned hydrocarbons and reduce air pollution. Details of the interior of the exhaust system 24 will be described with reference to FIGS. 2, 3, and 4. FIG. 2 shows a piece 44 of expanded porous material 46. FIG. Piece 44
The individual spaced apart rectangular filters 50 may be folded sufficiently to form square filters as shown. The mesh piece 52 of each filter 50 defines a plurality of holes 54 through which exhaust gas can pass through each filter 50. The mesh 52 attenuates and destroys the acoustic frequency shock waves created in the exhaust by the explosive release of the combusted air-fuel mixture from the engine 12. The bending angle 56 of the fold line 48 is selected to provide an optimum cross section for the filter 50. Second
In the embodiments of FIGS. 3 and 4, the material 46 is
It is bent at an angle 56 close to 180° to form a square filter 50 transverse to the exhaust flow as indicated by arrow 58. In a second variant, shown in FIGS. 6A, 6B and 6C, the bend angle 56 is less than 180° and the folded and stretched piece is placed in a rectangular filter 60.
to form. Filter 60 is not transverse to the direction of gas flow. The bend angle 56 can be varied along the length of the section to enhance the muffling effect in the range of acoustic frequencies of the exhaust flow. Steel would be a preferred material to form the expanded material. However, heat-resistant plastics, ceramics or other materials may also be used. An exhaust system constructed in accordance with the present invention using a hole 54 having dimensions of approximately 6.35 mm by approximately 3.175 mm (1/4 in. by 1/8 in.) satisfactorily muffles exhaust gas with acceptable back pressure. I understood. In a rectangular filter 50 (including the square filter 50 shown), there are four arcuate passages 6 between the inner wall 70 of the tube piece 26 and the outer edge 72 of the filter 50.
2, 64, 66, 68 are formed. Some of the shock waves in the exhaust enter these passages. The turbulent imbalance between the gas flow between each passage and the gas filtering through filter 50 enhances the decomposition of acoustic frequency shock waves and enhances the muffling effect. Although the segment 44 spans the entire length of the tube segment 26, the preferred construction incorporates one or more mixing chambers 74 along the length of the tube segment 26, as shown in FIG. The mixing chamber 74 consists of two pieces 44,44
A mixing chamber 74 formed between or in a single continuous piece as shown in the first variant of the invention according to FIG.
There may also be a section 76 that is linear along.
Each mixing chamber 74 mixes separate portions of the decomposed shock wave so that these portions cancel each other out and further enhance the muffling effect. By providing the straight section 76,
Section 44 extends in a continuous strip over the length of tube section 26 to facilitate manufacturing. Ideally, the exhaust system 24 includes a series of filters and mixing chambers with holes of various sizes in each filter to attenuate the shock waves, ideally to attenuate a maximum range of acoustic frequencies.
This pattern repeats along the length of the exhaust system to create a targeted multistage acoustic decomposition effect for each frequency. The mesh piece 52 is also formed with various airfoil cross-sectional shapes to move gas within the tube piece 26 and enhance damping. Exhaust system 24 also acts as a catalytic converter. Common catalytic converters are constructed in two basic ways. One method involves preparing a number of alumina pellets coated with a platinum group metal. The platinum group includes platinum, palladium and rhodium. In the second method, the ceramic material is coated with alumina and then coated with a catalyst from the platinum group. The catalyst facilitates the oxidation of unburned hydrocarbons in the exhaust gas. The mesh piece 52 is made of alumina 7 as shown in FIG. 3A.
8 and platinum group metal 80, and performs a catalytic conversion function in an exhaust system 24. When steel is used as the wrought material 46, it is desirable to coat the steel with a ceramic material before coating the alumina 78 and platinum group metal 80. A third modification of the exhaust device 24 is shown in FIGS. 7A and 7B.
An example is shown in FIG. This variant of the exhaust system includes a piece 82 formed from expanded material 46 with a circular filter 84 .
The fold line 48 between each filter 34 is folded approximately 180 degrees so that each circular filter 84 is generally transverse to the gas flow. Periphery 86 of circular filter 84
are in contact with the inner wall 70 and each filter 84 is connected to the tube section 26.
extends over the entire internal cross-section of. The arcuate passages 62, 64, 66, 68 are therefore eliminated. A fourth variant of the exhaust system 24 is shown in FIGS. 8A and 8.
As shown in FIGS. B and 8C, pieces 88 are obtained which are formed from wrought metal 46 and which partition oval filters 90. The material at each fold 48 stretches the folded piece 88 at an angle of less than 180 degrees. However, the oval shape of the filters 90 allows each oval filter 90 to contact the inner wall 70 of the tube piece 26 along the inner circumference obliquely to the length of the tube piece 26.
Each filter 90 is therefore not transverse to the direction of flow. Passages 62, 64, 66, 68 are eliminated so that the entire gas flow must pass through each filter 90. The distance between each filter 90 can also be adjusted according to the length of the oval. A fifth modification of the exhaust system 24 is illustrated in FIGS. 9A, 9B, and 9C, and in FIGS. 15 and 16. In this variant, a piece 94 of the continuous strip of wrought material 46 of uniform width is twisted in a helical manner, and the outer edge 96 of the piece 94 has a helical winding 9
8,100 to contact the inner wall 70 of the tube section 26. Gas flows through each filter 102 formed by a helical piece 94 . Each filter 102 presents a plurality of porous cross-sections extending around the entire circumference of the inner wall 70 to the gas flow. FIG. 15 shows the placement of a portion of section 94 within tube section 26. FIG. FIG. 16 is an end view of exhaust system 24 having one filter 102 formed by a length of section 94 sufficient to span the entire circumference of the inner wall.
This exhaust system 24 has many advantages. The tube section 26 of the exhaust device 24 forms a continuous muffling tube. Experiments have shown that a conventional exhaust system 16 can be removed by a tube section 26 that has approximately the same outer diameter as the connecting pipe 22 in the conventional exhaust system 16 and extends the length of the conventional exhaust system 16.
It was found that almost the same silencing effect can be obtained. A bulky silencer is therefore unnecessary. Exhaust device 24
If the converter has a catalytic converter function, the catalytic converter 18 would also be unnecessary. Therefore, the exhaust device 24
This reduces the size and weight of the exhaust system body and increases flexibility in vehicle construction, including lower profile, more streamlined and lighter vehicles. In this case, fuel can be saved.
The smoother and less bulky profile of the exhaust device 24 means that it is also less susceptible to road damage. Furthermore, the continuous tubing section 26 does not require the clamps normally used with conventional evacuation systems 16. Exhaust device 24
This simplicity saves material costs on the assembly line and allows for lower back pressures for the desired level of sound deadening. When configured with a catalytic converter function, the exhaust system 24 further has the advantage of dissipating heat generation from the contact action along the length of the catalytic converter function of the exhaust system 24. In this case, heat generation in any particular part of the vehicle is reduced and greater flexibility in the construction of the vehicle is obtained. Although the exhaust system 24 can perform three functions within a given length and minimum diameter, the tube section 22 of a conventional exhaust system 16 of similar diameter only passes gas. The tube section 26 not only carries away the gas, but also muffles exhaust noise and removes contaminants. The presence of passages 62, 64, 66, 68 enhances ventilation within exhaust system 24 when it is not activated. In this way, the degree of corrosion is lower than that observed in ordinary mufflers,
The durability of the exhaust device 24 during operation can be further increased. Exhaust system 24 also provides great flexibility in bending to fit the structure of the vehicle. For example, FIG. 14 shows an internal longitudinal section of exhaust system 24 at bends 40,42. Exhaust device 2 is responsible for silencing.
4, limited distortion or disassembly of each filter at a particular bend will not significantly affect the operation of the exhaust system. The distortion of a small number of filters 60 pressed more closely together at the inner diameter of the bend and fanned out at the outer diameter of this bend has virtually no effect on the exhaust system. A small number of filters 59 are pressed closer together due to the shortening of the tube sections when forming the flange 53, but again there is no practical negative effect. Material 46 can be formed from extruded ceramic material having a variety of pores and shapes that can be sized and configured to fit into tube section 26 prior to forming tube section 26 and welding the tube section seams. When bending the tube section 26, the ceramic section breaks at the flange and can be bent without appreciably reducing the muffling ability of the exhaust system. The exhaust system 24 is adapted to suit the displacement of the internal combustion engine for which it is to be used, the length of the pipe section to be installed, the desired muffling characteristics, the degree of acceptable backpressure, and the level of pollution control required. Can be made into various grades. Since the muffling and catalytic converter functions are separate, the exhaust system 24 can be used solely for muffling or for pollution control only. However, the functions of silencing and catalytic conversion can be combined in the same exhaust system 24. Further, it is desirable that the exhaust device 24 is configured in a plurality of sections. This is desirable for ease of assembly. Furthermore, it is possible in this case to combine an exhaust system section that is used exclusively for noise reduction with a further section that is used exclusively as a catalytic converter. In this case, the silencing section and the conversion section can be replaced independently of each other. Also, the muffling section and the catalytic conversion section do not occupy the entire length of the tube section 26. The weight of the exhaust device 24 is
This can be reduced by eliminating unnecessary materials within 6. It is also possible to use an evacuation device expansion material made of multiple types of materials. For example, steel is used for the sound deadening section, while ceramic is used for the catalytic converter section. The ideal production system would be to make the pipe sections that perform the functions of sound deadening and catalytic conversion in a continuous continuous configuration, or in a series of continuously repeating configurations, and in which all parts would be made at the end of their service life. can be designed to reach simultaneously. A sound level test was conducted using a normal exhaust system and a de-air exhaust system.
An exhaust system constructed in accordance with the present invention was compared with an exhaust system incorporating a muffler, such as that described in U.S. Pat. Sound level tests were also conducted on a single 5 ft. length of tube section and with no silencer or tube section. All tests were conducted using a General Motors V8 with an exhaust volume of approximately 4638.37 cm (283 in ³ ).
I went there using a mold engine. A Genrad 1983 sound level meter with a rapid response method was used for all measurements. All tests were conducted in a home garage under the same conditions. The sound level meter was mounted on a tripod approximately midway between the side of the vehicle and one wall of the garage and approximately 4 feet away from the open end of the exhaust system.
The exhaust system tested in each case consisted of two
It was installed after a Y-shaped or cross-shaped joint that joins the individual exhaust manifolds to a common pipe just ahead of the conventional muffler location. A silencer constructed according to the de Cardenas patent specification is used for roof flashing by cutting a strip of width equal to the inside diameter of an exhaust pipe with an outside diameter of about 5.08 cm (2 inches).

Table: The acoustic readings for a silencer constructed according to the de Cardenas patent specification are recorded in Table 2.

[Table] The sound level results of the silencer constructed according to the present invention are shown in Table 3.

Table: Sound level measurements for hollow or empty tube sections approximately 152.4 cm (5 ft) in length are listed in Table 4.

Table: The measured sound levels without a pipe section or muffler after the Y-junction are given in Table 5.

[Table] The sound level measured when rapidly accelerating to 3000 RPM is shown below.

[Table] Although the exhaust device 110 illustrated in FIGS. 10, 11, 12, and 13 is not an embodiment of the present invention, it is a conventional exhaust device for attenuating acoustic shock waves created by the present inventor. The exhaust system 110 includes a tube section 26 having a substantially uniform outside diameter over its entire length. However, a liner 112 is located within the tube segment 26. The liner 112 includes a plurality of airfoil baffles 114 that project inwardly from the liner 112 into the gas flow to attenuate and break up acoustic shock waves. Liner 112 is preferably constructed from a metal such as steel. The airfoil baffle plate 114 is stamped from a continuous strip of liner material shown in FIG. 11 by cutting the material along edges 116, 118, 120.
4 is bent in one direction so that all baffles 114 extend from one side 122 of liner 112. The tube section 26 and liner 112 are then rolled into a tube shape as shown in FIG. When rolled, the tube sections 26 weld along the joint surfaces 124 to form an airtight exhaust system. Tube section 26 and liner 112 may be welded together if desired. Deflector 11 in rolled liner 112
4 extends radially inward toward the center of the exhaust system 110, as seen in FIG. Deflecting plate 1
14 can extend entirely across the inside diameter of rolled liner 112 or any shorter distance desired. The individual baffles 114 are shaped to form an airfoil surface, as seen in FIG. The airfoil surface dampens the gas flow and attenuates the acoustic frequencies of the shock waves. Each baffle plate 114 has an airfoil cross-section, a length,
The frequency along the length of the exhaust device can be varied along with the thickness and the angle of attack θ for the gas flow. If catalytic conversion function is desired, baffle plate 114 can be coated with alumina and platinum group metals to perform the conversion function. Exhaust system 110 has the advantages described above with respect to exhaust system 24. Exhaust system 110 can also be used in much the same manner as exhaust system 24 described above. The exhaust system 130 shown in FIG. 17 is a second embodiment of the present invention. In the exhaust device 130, the pipe section 2
6 is stuffed with wire fabric 132. wire fabric 13
Similar to the devices 24 and 110 described above, the device 2 acts to weaken the acoustic frequency of shock waves in the exhaust gas. The textile warp yarns may be wires with various cross sections. The weft within the fabric can also be varied as well. The open spaces between wires within fabric 132 vary in size and shape along the length of fabric 132 to increase attenuation across a range of acoustic frequencies. Exhaust system 130 also provides the benefits and uses of systems 24, 110 described above. Although the present invention has been described in detail with reference to its embodiments, it is obvious that the present invention can be modified in various ways without departing from its spirit.

[Brief explanation of the drawing]

FIG. 1 is a bottom view of a vehicle with a first embodiment of the exhaust system according to the invention, shown in solid lines, and a conventional exhaust system with a conventional muffler, a conventional catalytic converter and a clamp, shown in broken lines; FIG. . Fig. 2 is a partial perspective view showing the exhaust system of the present invention shown in Fig. 1 with a part cut away and enlarged, Fig. 3 is a sectional view taken along line 3-3 in Fig. 2, and Fig. 3A is FIG. 4 is an enlarged sectional view taken along line 3A-3A of FIG. 2, and FIG. 4 is a reduced horizontal sectional view taken along line 4-4 of FIG. 5 is a horizontal sectional view of the first variant of FIG. 4, FIGS. 6A, 6B and 6.
Figure C is a cross-sectional view, a plan view and a side view of a filter section, and Figure 7A is a cross-sectional view, respectively, of the second modification of the present exhaust system;
FIGS. 7B and 7C are a cross-sectional view, a plan view of a filter section, and a side view, respectively, of a third modification of the present exhaust system, and FIGS. 8A, 8B, and 8C are a fourth modification of the present exhaust system. Figures 9A, 9B and 9C are a cross-sectional view, a filter piece plan view and a side view, respectively, of the fifth variant of the present exhaust system; It is.
FIG. 10 is a side view showing a conventional exhaust system by the present inventor together with an unbent part to illustrate the inside, FIG. 11 is a perspective view of a liner used in the exhaust system shown in FIG. 12, and FIG. An enlarged sectional view taken along line 12-12 in Fig. 10, and Fig. 13 is an enlarged sectional view taken along line 12-12 in Fig. 12.
13 is an enlarged sectional view taken along line 13. FIG. FIG. 14 is a horizontal cross-sectional view showing the first embodiment of the present exhaust system as it is attached to an exhaust manifold, and FIG. 15 is a partially cutaway diagram showing a fifth modification of the first embodiment of the present exhaust system. The side view, FIG. 16, is a sectional view taken along line 16-16 in FIG. 15. FIG. 17 is a partially cutaway perspective view of the second embodiment of the present exhaust system. DESCRIPTION OF SYMBOLS 10... Vehicle, 12... Internal combustion engine, 14... Exhaust manifold, 26... Pipe piece, 30... Opening,
44...piece, 48...fold, 50...filter.

Claims (1)

[Scope of Claims] 1. In an exhaust device 24 for discharging gas from an internal combustion engine 12 having an exhaust manifold 14 of a vehicle 10, (a) extending from the exhaust manifold 14 to an opening 30 to the atmosphere and discharging gas from the internal combustion engine; (b) at least one piece 44, 82, 88, 94 of expanded porous material 46, with a tube section 26 of uniform diameter for conveying exhaust gases to the atmosphere; The sections 44, 82, 88, 94 are provided with a plurality of expanded porous material filters 50, 60, 84, 90, 102 positioned along the length to muffle exhaust noise. The filters 5 are folded at selected positions along the front edge, and the individual filters 5 are folded between these folds 48.
0, 60, 84, 90, 102, and each of these filters 50, 60, 84, 90, 102
are spaced a predetermined distance from adjacent filters. 2 The adjacent filters 50, 60, 84, 9
1. The predetermined distance between 0 and 102 is varied along the length of the tube section 26 to enhance the silencing effect in the range of acoustic frequencies inside the exhaust device 24. exhaust system. 3. The tube section 26 is provided with at least one section along its length which is not provided with the filters 50, 60, 84, 90, 102, so that shock waves of the acoustic frequency subdivided by each preceding filter are provided. 2. The exhaust system according to claim 1, wherein a mixing chamber 74 is formed in which portions of . 4. The filters 50, 60 have a rectangular cross section and their inner walls 70 along the length of the tube section 26.
and the edge 72 of the filters 50, 60.
An exhaust system as claimed in claim 1, characterized in that the arcuate passages (62, 64, 66, 68) are formed to aid in the dissipation of acoustic frequency shock waves. 5. The filters 84, 90 have an oval cross section so that they can contact the inner wall 70 of the tube piece 26 around their entire circumference. Exhaust device as described in section. 6 the at least one section 94 comprising the expanded porous material 46 and the tube section 26;
Claim 1: The tube piece 94 is twisted into a spiral shape and inserted into the tube piece 26 to form the filter 102. Exhaust system as described. 7. The exhaust system of claim 1, wherein the expanded porous material 46 is made of a material selected from the group consisting of metal, ceramic, and heat-resistant plastic. 8 Approximately 6.35 mm x as the expanded porous material
The exhaust device according to claim 1, which uses expanded steel with a hole of about 12.7 mm (about 1/4 inch x about 1/2 inch). 9. The exhaust system of claim 1, wherein the expanded porous material 46 comprises a mesh piece 52 having an airfoil shape to alter gas flow and attenuate acoustic frequency shock waves. 10. The exhaust system of claim 1, wherein said uniform diameter tube segment 26 has a continuous length extending from said exhaust manifold 14 to an opening 30 to atmosphere. 11. The exhaust system of claim 1, wherein the holes (54) in the expanded porous material (46) vary in size along the length of the tube section (26) to attenuate a range of acoustic frequency shock waves. 12. The expanded porous material 46 is comprised of a reticulated piece 52 plated with alumina 78 and a platinum group metal 80 to form a catalytic converter inside the exhaust device 24. exhaust system. 13. The exhaust system of claim 1, wherein the expanded porous material 46 is plated with a material selected from the group consisting of alumina and platinum group metals. 14 In an exhaust device 24 for discharging gas from an internal combustion engine 12 having an exhaust manifold 14 of a vehicle 10, (a) extending from the exhaust manifold 14 to an opening 30 to the atmosphere, and discharging exhaust gas from the internal combustion engine 12 to the atmosphere; (b) at least one piece 44 of porous material 46;
a plurality of porous material filters 50, 60, 84, 90 formed from 82, 88, 94 and having through-holes 54 located within said tube section along its length to muffle exhaust noise; 102 , the pieces 44 , 82 , 88 , 94 are folded along their length at selected positions, and the individual filters 50 , 6 are folded between adjacent folds 48 .
0, 84, 90, 102, and each of these filters has a common fold 48 formed on each side thereof.
Each portion of the porous material 46 is coated with alumina 78 and a platinum group metal 80 at a predetermined distance from the filter that shares the porous material 46 to form a catalytic converter portion that oxidizes unburned hydrocarbons in the exhaust gas. An exhaust system characterized by: 15 The filter 50, 60, 84, 90, 1
15. The exhaust system according to claim 14, wherein a predetermined distance between the exhaust systems 24 and 24 is changed to strengthen the silencing effect in the range of acoustic frequency shock waves inside the exhaust system 24. 16 The filters 50, 60, 84, 90, 10 are disposed inside at least a portion of the tube section 26.
15. The exhaust system according to claim 14, wherein a mixing chamber 74 is formed without providing a mixing chamber 74 for mixing and canceling out separate parts of shock waves therein. 17 The pieces 44 are made generally uniform in width and bent at an angle 56 not exceeding 180° at the fold line 48 to form filters 50, 60 of rectangular cross section, with the pieces 44 5
0.60 edge 72 and inner wall 70 of said tube piece 26
4 arcuate passages 62, 64, 66, 6 between
8 and allow exhaust gas to flow through these passages, further attenuating acoustic frequency shock waves due to pressure and imbalance between the flow through said filters 50, 60 and said passages 62, 64, 66, 68. An exhaust system according to claim 14, wherein the exhaust system is configured to: 18 By varying the width of the pieces 82, 88 and varying the angle 56 of the fold line 48 to form filters 84, 90 of oval cross-section, the edges of each of these filters 84, 90 are aligned with the tube. 15. The exhaust device according to claim 14, wherein the exhaust device contacts the inner wall 70 of the piece 26 along an elliptical curve. 19. The exhaust system of claim 14, wherein said piece (94) has a uniform width and is twisted to form a spiral contained within said tube piece (26). 20. The exhaust system of claim 14, wherein said porous material 46 is selected from the group of materials consisting of metals, ceramics and high temperature plastics. 21 The filter 50, 60, 84, 90, 1
02 is formed by a net-like piece 52, and this net-like piece 52
Claim 14 having an airfoil-shaped cross section exposed to the gas flow so as to alter the gas flow, further attenuating acoustic frequency shock waves.
Exhaust device as described in section. 22 Expanded steel is used as the expanded porous material 46, and the holes 54 of the expanded steel are about 6.35 mm x about 12.7 mm (about 1/4 inch x about 1/2 inch).
15. The exhaust device according to claim 14, having dimensions of . 23. The exhaust system of claim 14, wherein said uniform diameter tube section 26 has a continuous length from said exhaust manifold 14 to an opening 30 to atmosphere. 24. The exhaust system of claim 14, wherein the holes 54 in the porous material 46 vary in size along the length of the tube section 26 to attenuate target frequencies over a range of acoustic frequency shock waves. . 25. The tube piece 26 is provided with at least two sections, the first section primarily muffling the exhaust,
15. The exhaust system of claim 14, wherein the second portion primarily reduces hydrocarbons in the exhaust gas. 26. The exhaust device according to claim 17, wherein said piece 44 is bent to form a filter 50 having a square cross section. 27. The exhaust device according to claim 18, wherein the piece 82 is bent to form a filter 84 having a circular cross section.