Field of the Invention

The invention generally relates to a muffler for automotive vehicles, and more particularly, to a muffler for automotive vehicles having integrated DOC/POC (oxidation catalysts in tandem with EGR-exhaust gas re-circulation) unit within the muffler body and the muffler for automotive vehicles meets the BSIV emission norms.

Background of the Invention

The conventional automotive mufflers come in all different shapes, styles and size depending on the desired application. Generally automotive mufflers usually have a circular or elliptical cross section. A circular shaped cross section is best suited in a vehicle as it delays the onset of higher order modes. These types of mufflers have been widely tested and the general observations from such tests are described. The mufflers which employ the principle of both reflective and absorptive techniques to reduce the noise level gas of automotive vehicles to a pre-determined range with additionally accommodate various after treatment device systems.

Commercial vehicles are the major contributors for noise pollution by automobiles. The main contributor of noise in a commercial vehicle, per se, is the exhaust system. The control of noise from the exhaust system depends on the design of the muffler, the layout of the exhaust system, the piping and also the after treatment devices. However, the specific focus is towards the design of the muffler. Design of mufflers is a complex function that affects the noise characteristics and the fuel efficiency of the vehicle. So, a good design of the muffler should give the best noise reduction and offer optimum back pressure for the engine. Moreover, for a given internal configuration, mufflers have to work for a broad range of internal combustion engine speed. Mufflers can have a number of elements inside which need to be chosen as per the level of attenuation required and recommended internal combustion engine back pressure. Any muffler is qualified by the amount of insertion loss (IL) that takes place within the muffler. Insertion loss can be defined as the difference in sound pressure levels (SPL) at the exhaust outlet, with and without the muffler. Based on the required insertion loss, mufflers with different internal configurations can be designed and tested for muffled noise spectrum and vehicle noise.

In addition to these, there is a need for exhaust systems to meet stricter emission norms. In such cases when the migration from BSIV norms is effected, there is a need to have additional after-treatment devices. The common ones used are SCR (selective catalytic reduction) and DOC/POC (oxidation catalysts in tandem with EGR-exhaust gas re-circulation).

Summary of the Invention

In order to solve the above-described problem, the present invention provides a muffler for automotive vehicles. The advantages of the muffler for automotive vehicles are as follows:

a) Consistent performance,
b) Reduced cost,
c) Reduced weight,
d) Decreased variety,
e) Ease in vehicle assembly,
f) Reduced components assembly time, and
g) To meet BSIV emission norms.

The object of the present invention is to provide a muffler for automotive vehicles providing reduced noise generation and offer optimum back pressure for the internal combustion engine, which in turn lead to optimum fuel efficiency of the vehicles.

A further object of the present invention is to provide a muffler for automotive vehicles having integrated DOC/POC unit within the muffler body and as such there is no need for packaging the DOC/POC unit separately.

Another object of the present invention is to provide a muffler for automotive vehicles which is simple in construction and less costly.

Yet another object of the present invention is to provide a muffler for automotive vehicles having one coated DOC, a coated POC and an uncoated POC wherein these devices work in tandem to achieve the optimum emission performance.

Yet a further object of the present invention is to provide a muffler for automotive vehicles which blends the performance characteristics of the exhaust system for automotive vehicles.

Accordingly, the present invention provides a muffler for automotive vehicles connected at rear end of the inlet pipe assembly extending from an internal combustion engine of automotive vehicles and an outlet pipe assembly connected at rear end of the muffler so that the treated exhaust gases from the muffler flows to the atmosphere, wherein the muffler comprising: an inlet flared tube for connecting the inlet pipe assembly and the muffler; an inlet cone connected at the front end of the muffler; a DOC/POC assembly welded at the rear end of the inlet cone and having one DOC and two POC, wherein the DOC and the first POC are coated with precious metal and the second POC is uncoated; a jacket for encasing all the components of the muffler; a first end cover for supporting the inlet flared tube and the inlet cone; perforated baffles for supporting the DOC/POC assembly; an exponential connector for compressing the gases coming out of the DOC/POC assembly; a perforated baffle for supporting a perforated outlet pipe which is packed with glasswool; and a second end cover (9) for supporting the perforated outlet pipe.

The muffler is divided into four chambers, the first chamber consists of the inlet cone and connects the DOC/POC assembly, the second chamber having two perforated baffles which supports the DOC/POC assembly, the third chamber consists of baffle and the perforated outlet pipe fitted with the exponential connector, and the fourth chamber consists of perforated baffle and a second end cover which support the perforated outlet pipe.

The inlet pipe assembly is inserted into the inlet flared tube and thus establishes connection with muffler. The DOC/POC is about 300 to 400 cells per square inch of area. The jacket supports perforated baffles, and the jacket and the first end cover prevents exhaust gases from leaking out.

The perforated baffles having atleast 12 holes of 12.5mm diameter scattered evenly which helps gases to flow from the third chamber into the first chamber and second chamber so that the gases lose energy thereby reducing overall noise.

The DOC/POC assembly, exponential connector, perforated baffle, perforated outlet pipe and inlet cone aids in reducing noise. The DOC/POC assembly and inlet cone aids in reduction of emissions.

The muffler construction of the glasswool is in the form of a continuous fiber so that when the sound waves pass through the perforated outlet pipe, they pass through the perforations in the perforated outlet pipe and into the fourth chamber which is packed with glasswool for absorbing the energy and vibrations of the sound waves and thereby reduces sound intensity and gives better acoustic performance.

The invention also relates to an exhaust system having a muffler as described herein, wherein exhaust system comprising a inlet pipe assembly connected at one end of the muffler so that exhaust gases from the internal combustion engine flows through the inlet pipe assembly to the muffler, and outlet pipe assembly connected at other end of the muffler so that the treated exhaust gases from the muffler flows to the atmosphere.

Emission device in integrated muffler:

BSIV emissions in diesel engines are achieved through two routes:

■ The EGR Route
■ The SCR Route

As far as diesel engines are concerned, the main pollutants in the exhaust gases are NOx (oxides of nitrogen) and PM (particulate matter). Due to the NOx-PM trade off characteristic of an internal combustion engine where each component increases or decreases inversely with respect to each other, it is possible to control only one of them at a time in the engine. The present invention make use of the SCR route to control PM in the internal combustion engine itself and then control NOx in an after treatment system. The present invention make use of the EGR route to control NOx in the internal combustion engine and then control PM in the after treatment system.

The present invention is a solution for BSIV through EGR Route and the emission device used in the present invention to achieve BSIV emissions is a DOC/POC assembly.

The DOC converts the harmful NOx into N02 in order for the POC to convert it further. There is also effective reduction of CO and HC. There is usually a 30% reduction in PM.

The POC converts the N02 into N2 and 02. This oxygen is utilized to oxidize the particulate matter. The PM reduction achieved is up to 50%. The DOC and POC assembly give a combined PM reduction of up to 80%.

In addition to this, special purpose absorptive material is added in the flow path which inhibits the passage of any spark through the flow chambers.

Brief Description of the Accompanying Drawings

The advantages and features of the invention will become more clearly apparent from the following description which refers to the accompanying drawings given as non-restrictive examples only and in which:

Figure 1 illustrates the perspective view of the exhaust system for automotive vehicle having the muffler of the present invention; and

Figure 2 demonstrates the front view of the muffler for automotive vehicles according to the invention.

Detailed Description of the Preferred Embodiments

Referring to Figure 1, the exhaust system X for automotive vehicle of the present invention comprises an inlet pipe assembly W, a muffler Y and an outlet pipe assembly Z. The exhaust gases from the internal combustion engine flows through the inlet pipe assembly W and arrive at the muffler Y. Once the gases enter into the muffler Y, the gases are treated for emissions and noise reduction by means of features incorporated inside the muffler. The gases then exit through the outlet pipe assembly Z.

Referring to Figure 2, the muffler Y of the present invention comprises of jacket 3 which is covered at both end by end covers 4 & 9. The jacket 3 is divided into four chambers A, B, C & D with a help of the perforated baffles 5 and a perforated baffle 7. The two numbers of 12 holes perforated baffles 5 has been mounted to divide the first, second and third chambers A, B & C and the perforated baffle 7 has been mounted to divide the third and fourth chambers C & D on the end of jacket 3. The exponential connector 6 is fixed to one end of the perforated outlet pipe 8. The inlet flared tube 1 is inserted from the first end cover 4 and extends up to the shell unit 2 on the first chamber A. The integrated DOC and POC assembly 2 is placed on the perforated baffles 5 up to the third chamber C. The perforated baffle 7 is comprised one set of perforation of predetermined size to kill certain frequencies. Each row of perforation is staggered compared to adjacent row of perforation. In a preferred embodiment, the diameter of the perforation diameter can be 3.18mm and the pitch distance between corresponding points of consecutive rows can be make 15% open area of the baffle. The two perforated baffles 5, 7 which support the shell unit 2 each have 12 holes of diameter 12.5mm.

The shell unit 2 has the DOC substrate material Cordierite used with cell density of 200cpsi and POC cell density 330cpsi.The overall shell length 574mm and diameter 183mm. The outlet pipe 8 is inserted from the hole of the perforated baffle 7 on the fourth chamber D and passes through the second end cover 9. The perforated outlet pipe 8 comprises set of perforations to kill certain frequencies. Each row of perforations is staggered compared to adjacent row of perforations for a given set. Preferably, the diameter of the perforation can be 2.8mm and the pitch can be about 5.6mm. The perforation contains 34 rows and 48 holes per row. The outlet pipe 8 is fixed between the perforated baffle 7 and the second end cover 9 at a distance of around from 210mm to 218mm, preferably 215mm. The Glass wool has spreader across the whole of the region around the perforated outlet pipe 8 and inside the fourth chamber D.

In a preferred embodiment, the four chambers A, B, C, and D of the jacket 3 could be having specific dimensions of 231mm, 158mm, 246mm, and 215mm. The shape of the jacket 3 is preferably constructed from a plane sheet with ends of overlapped and welded across the whole length or crimped across the whole length.

The exhaust system X consists of an inlet pipe assembly W, a muffler Y, and an outlet pipe assembly Z through which exhaust gases flow from the internal combustion internal combustion engine and into the atmosphere.

The inlet pipe assembly W connects the internal combustion engine to the muffler Y through which exhaust gases flow from the internal combustion engine to the muffler Y.

The muffler Y is an envelope which consists of the elements assisting in reducing noise and also emissions. The muffler Y is divided into four chambers A, B, C and D.

The outlet pipe assembly Z connects the muffler Y to the atmosphere through which exhaust gases which has been treated for noise and emissions flow from the muffler Y into the atmosphere.

The first chamber A consists of the inlet cone 10 and connects the DOC/POC assembly 2.

The second chamber B is formed by the two perforated baffles 5 which supports the DOC/POC assembly 2.

The third chamber C is where the treated gases come out of the DOC/POC assembly 2. It also consists of a perforated outlet pipe 8 fitted with an exponential connector 6.

The fourth chamber D is formed by a perforated baffle 7 and a second end cover 9 which support the perforated outlet pipe 8. The region around the perforated outlet pipe 8 in the fourth chamber D is filled with glasswool 11 which helps in noise reduction.
The inlet flared tube 1 serves in establishing a connection between the inlet pipe assembly W and the muffler Y. The inlet pipe assembly W is inserted into the inlet flared tube 1 and thus establishes connection with muffler Y.

The DOC/POC assembly 2 is a combination of one DOC and two POCs. The DOC and the first POC are coated with precious metal while the second POC is uncoated. The combination of these three is very important in achieving the emission targets of BS4. An additional function performed by this combination is reducing noise. When the exhaust gases flow through the DOC/POC assembly, they are forced to flow through its tiny holes/cells. The construction of the DOC/POC is such that there are about 300 to 400 cells per square inch of area. When the gases pass through such tiny spaces, they lose energy by virtue of friction with the inner walls and this helps reduce noise.

The jacket 3 is the outer shell which encloses all the components of the muffler Y and performs the function of supporting the perforated baffles 5 and preventing exhaust gases from leaking out.

The first end cover 4 serves as a support for the inlet flared tube 1 and the inlet cone 10 and performs the function of preventing exhaust gases from leaking out.

The two perforated baffles (5) supports the DOC/POC assembly 2. The perforated baffles are holes (atleastl2 numbers of 12.5mm diameter scattered evenly) which help gases to flow from the third chamber C into the first chamber A and second chamber B. The two perforated baffles (5) help in making use of this additional flow volume which ultimately help the gases lose energy thereby reducing overall noise.

The exhaust gases, once they leave the DOC/POC assembly 2, are forced to flow through the exponential connector 6. The exponential connector 6 is designed such that it helps the gases coming out of the DOC/POC assembly 2 to get compressed through the exponential connector. The gases lose energy further resulting in loss of sound energy.

The perforated baffle 7 serves as a support for the perforated outlet pipe 8. In addition to this, the perforations on this perforated baffle 7 help in allowing the exhaust gases to get in contact with the glasswool 11 in the fourth chamber D, thereby reducing noise.

The perforated outlet pipe 8 helps in directing the exhaust gases out of the muffler Y. In addition to that, perforated outlet pipe 8 also helps in reducing noise by cancelling out certain frequencies when the gases pass over the perforations.

The second end cover 9 serves as a support for the perforated outlet pipe 8. It also performs the function of preventing exhaust gases from leaking out.

The construction of the muffler Y is such that there is an inlet cone 10 at the front end of the muffler Y. At the rear end of the inlet cone 10, the DOC/POC assembly 2 is welded. The design of the inlet cone 10 in terms of the cone angle and the length is such that it aids reduction of noise and also the reduction of emissions. When exhaust gases enter into the first chamber A its expanded in the region of the inlet cone 10. When this happens, they lose energy due to this expansion. The kinetic energy of the gases is reduced which benefits in reducing noise. The same gases when expand in the inlet cone 10 lead to a condition where the gases spread uniformly over the face of the DOC/POC assembly 2. This leads to a better conversion of exhaust pollutants thereby reducing emissions.

The perforated outlet pipe 8 is packed by glasswool 11. The construction of the glasswool 11 is in the form of a continuous fiber. When the sound waves pass through the perforated outlet pipe 8, they pass through the perforations in the perforated outlet pipe 8 and into the fourth chamber D which is packed with glasswool. The glasswool absorbs the energy and vibrations of the sound waves. This helps in reducing sound intensity and gives better acoustic performance.

Function of the circular muffler for automotive vehicles.

The exhaust gases from the engine, flow through the inlet pipe assembly W and arrive at the muffler Y inlet.

Once the gases enter into the muffler Y, they get expanded through the cone.

During this expansion, the gases lose energy and this helps reduce noise.

The cone is designed in such a way that the cone angle will ensure an optimum uniformity index (a parameter which specifies how efficiently the DOC/POC surface is utilized).

The gases then pass through the DOC and then the two POCs and are treated. The gases coming out of the DOC/POC assembly is treated and meets the BS4 emission norms.

The gases then pass through the exponential connector 6 which helps reduce the noise further. As it passes through the perforated outlet pipe 8, surrounded by glasswool, the high frequency noise gets absorbed and this helps in further attenuation of noise.

The gases at the outlet of the muffler Y are thus treated to meet emission norms and also, the noise is considerably reduced to meet the norms of 78dB(A).

Reference numerals:

X - Exhaust system;
W - Inlet pipe assembly;
Y - Muffler;
Z - Outlet pipe assembly;
A - First chamber;
B - Second chamber;
C - Third chamber;
D - Fourth chamber;
1 - Inlet flared tube;
2 - DOC/POC assembly;
3 - Jacket;
4 - First end cover;
5 - Two perforated baffles;

6 - Exponential connector;
7 - Perforated baffle;
8 - Perforated outlet pipe;
9 - Second end cover;

NVH Performance results: Insertion loss test:

Insertion loss is a term used to define the effectiveness of a silencer/ exhaust system. The insertion loss of an exhaust system gives the indication of how much noise reduction of the internal combustion engine is possible due to the silencer. The higher the insertion loss, the better it is from the noise perspective.

A comparative test of the invention with a silencer of older/ different concept shows that the noise performance of the AL design N4 BSIV Circular advanced integrated muffler is much better showing a considerable improvement of 1.25 to 1.6 dB over a proprietary silencer with an older design.

The below shown table gives a comparison of the mufflers tested in the same conditions on the same vehicle in terms of insertion loss.

The overall insertion loss is better for the present invention over the entire range of internal combustion engine speed. A graph showing the insertion loss curves of all the three mufflers along with the unmuffled noise is given below:

The first graph shows the insertion loss comparison for the silencers in the max power condition.

The second graph shows a similar comparison in the fly-up condition.

Though the present invention was shown and described with reference to the preferred embodiments, such are merely illustrative of the present invention and are not to be construed as limitation thereof and various modifications of the present invention will be apparent to those skilled in the art. Furthermore, all examples and conditional language recited herein are principally intended expressly to be only for pedagogical purposes to aid the reader in understanding the principles of the invention and the concepts contributed by the inventors) to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions. It is therefore not intended that the present invention be limited to the disclosed embodiments or details thereof, and the present invention includes all variations and/or alternative embodiments within the spirit and scope of the present invention as defined by the appended claims:

WE CLAIM:

1. A muffler (Y) for automotive vehicles connected at rear end of the inlet pipe assembly (W) extending from an internal combustion engine of automotive vehicles and an outlet pipe assembly (Z) connected at rear end of the muffler (Y) so that the treated exhaust gases from the muffler (Y) flows to the atmosphere, wherein the muffler (Y) comprising:

an inlet flared tube (1) for connecting the inlet pipe assembly (W) and the muffler (Y); an inlet cone (10) connected at the front end of the muffler (Y);

a DOC/POC assembly (2) welded at the rear end of the inlet cone (10) and having one DOC and two POC, wherein the DOC and the first POC are coated with precious metal and the second POC is uncoated;

a jacket (3) for encasing all the components of the muffler (Y);

a first end cover (4) for supporting the inlet flared tube (1) and the inlet cone (10); perforated baffles (5) for supporting the DOC/POC assembly (2);

an exponential connector (6) for compressing the gases coming out of the DOC/POC assembly (2); a perforated baffle (7) for supporting a perforated outlet pipe (8) which is packed with glasswool (11); and

a second end cover (9) for supporting the perforated outlet pipe (8).

2. The muffler (Y) for automotive vehicles as claimed in claim 1, wherein the muffler is divided into four chambers (A, B, C, D), the first chamber (A) consists of the inlet cone (10) and connects the DOC/POC assembly (2), the second chamber (B) having two perforated baffles (5) which supports the DOC/POC assembly (2), the third chamber (C) consists of baffle (5) and the perforated outlet pipe (8) fitted with the exponential connector (6), and the fourth chamber (D) consists of perforated baffle (7) and a second end cover (9) which support the perforated outlet pipe (8).

3. The muffler (Y) for automotive vehicles as claimed in claim 1 or 2, wherein the inlet pipe assembly (W) is inserted into the inlet flared tube (1) and thus establishes connection with muffler (Y).

4. The muffler (Y) for automotive vehicles as claimed in any one of claims 1 to 3, wherein DOC/POC is about 300 to 400 cells per square inch of area.

5. The muffler (Y) for automotive vehicles as claimed in any one of claims 1 to 4, wherein the jacket (3) supports perforated baffles (5), and the jacket (3) and the first end cover (4) prevents exhaust gases from leaking out.

6. The muffler (Y) for automotive vehicles as claimed in any one of claims 1 to 5, wherein the perforated baffles (5) having atleast 12 holes of 12.5mm diameter scattered evenly which helps gases to flow from the third chamber (C) into the first chamber (A) and second chamber (B) so that the gases lose energy thereby reducing overall noise.

7. The muffler (Y) for automotive vehicles as claimed in any one of claims 1 to 6, wherein DOC/POC assembly (2), exponential connector (6), perforated baffle (7), perforated outlet pipe (8) and inlet cone (10) aids in reducing noise.

8. The muffler (Y) for automotive vehicles as claimed in any one of claims 1 to 7, wherein DOC/POC assembly (2) and inlet cone (10) aids in reduction of emissions.

9. The muffler (Y) for automotive vehicles as claimed in any one of claims 1 to 8, wherein the construction of the glasswool (11) is in the form of a continuous fiber so that when the sound waves pass through the perforated outlet pipe (8), they pass through the perforations in the perforated outlet pipe (8) and into the fourth chamber (D) which is packed with glasswool for absorbing the energy and vibrations of the sound waves and thereby reduces sound intensity and gives better acoustic performance.

10. An exhaust system having a muffler as claimed in any one of claims 1 to 9, comprising a inlet pipe assembly (W) connected at one end of the muffler (Y) so that exhaust gases from the internal combustion engine flows through the inlet pipe assembly (W) to the muffler (Y), and outlet pipe assembly (Z) connected at other end of the muffler (Y) so that the treated exhaust gases from the muffler (Y) flows to the atmosphere.