FORM 2
THE PATENTS ACT 1970
(39 of 1970)
&
The Patent Rules, 2003
Complete Specification
(See section 10 and rule 13)
Direct Mounting Exhaust Silencer For Internal Combustion Engines
Mahindra and Mahindra Ltd.
An Indian company registered under the Indian Companies Act, 1956,
Gateway Building, Apollo Bunder, Mumbai - 400001, Maharashtra, India.
The following specification particularly describes the invention and the manner in which it is to be performed:

DIRECT MOUNTING EXHAUST SILENCER FOR INTERNAL COMBUSTION ENGINES
FIELD OF INVENTION:
The present invention generally relates to an exhaust system of internal combustion engine used with applications in the field of generator sets and telecommunications. It particularly relates to an exhaust silencer that is directly mounted on the engine cylinder head, thereby ridding the engine exhaust system of the exhaust manifold which is conventionally used to direct passage of exhaust gas to the atmosphere through a silencer.
BACKGROUND OF INVENTION:
The conventional arrangement of the exhaust system for internal combustion engines generally includes an exhaust manifold and an exhaust silencer. Exhaust manifold vary in design depending on the engines on which they are fitted, based on parameters such as the number of inlet ports, location of the exhaust port, selection material to withstand the high temperatures of the exhaust gases. Moreover, as there are multiple flows of exhaust gas in operation, the design has to ensure that these flows do not obstruct each other thereby creating back pressure in the exhaust manifold. Furthermore, there's typically a pipe provided between the manifold and the silencer, all of which takes up valuable space in the

engine compartment, which could be used towards the engine placement itself and other associated units.
There have been many developments in the field of exhaust manifold design to cater to different engine applications and engine types. In the case of generator sets where the engine runs at constant speed there are existing manifold designs that meet the performance requirement. However, even these are limited by the space constraints mentioned earlier.
There some inventions which discloses exhaust muffler directly mounted on the engine cylinder head. However, most of these inventions are useful only in the case of single cylinder engines, motor cycle engines and low horse power engines. Some of them are now described.
US patent 7389853 discloses a muffler suited for discharging exhaust gas from an engine. This muffler comprises a housing defining an interior, an inlet aperture, and an outlet aperture. A baffle plate is provided in the muffler interior to define an inlet space to receive exhaust gas and an intermediate space. A first aperture is provided in the baffle plate for fluid communication between the inlet space and the intermediate space and a second aperture is provided in the baffle plate for fluid communication between intermediate space and outlet aperture. A drawback of this system is that even though the aforesaid muffler is directly mounted on engine to receive the exhaust gas, this particular configuration cannot not be

adapted to use with higher HP engine having more than two cylinders engine as it can develop back pressure in the exhaust system.
US patent 4854417 discloses an exhaust muffler for internal combustion engine which comprises a casing defining a hollow space therein, an exhaust inlet port having its one end directly mounted on to the engine exhaust port and the other end that is connected to the hollow space of the casing. It also comprises an exhaust outlet passage which releases the exhaust gas to the atmosphere from the hollow space of the casing. US patent 6044926 discloses a muffler for small general purpose engine. The muffler comprises a case having a pair of case halves defined to form to a first chamber and a second chamber, an exhaust inlet for communicating the gas with the first chamber and an exhaust outlet for releasing the exhaust gas to the atmosphere from the second chamber. Both these invention are intended to work only with small horse power engines or single cylinder engines. When catering to higher horse power engines or engines that incorporate two or more cylinders, there would be more than a single exhaust inlet ports. In these situations, utmost care would need to be exercised in order to overcome a possible build-up of back pressure. A drawback of the '417 and '926 patents is that the configurations disclosed therein are not able to efficiently attenuate fundamental frequencies of sound waves associated with the exhaust gas coming from the individual cylinders.

Hence, there remains a need in the field of exhaust systems to design and develop an exhaust silencer which can be directly mounted on the exhaust ports of higher Horse Power engine having more than two cylinders thereby to work away with the exhaust manifold. The present invention is also intended to make the exhaust system of internal combustion engine very compact and cost effective in respect of complexity of design and manufacturing of multiple components.
OBJECTIVES AND ADVANTAGES OF INVENTION:
The principal objective of the present invention is to develop an exhaust system for internal combustion engine, which is void of exhaust manifold. This is expected to result in direct cost savings.
Another objective of the present invention is to provide an exhaust silencer which is directly mounted on the engine exhaust ports so as to make the exhaust system very compact and cost effective.
Yet another objective of the present invention is to provide an exhaust silencer which minimises or eliminates back pressure & at the same time effectively attenuates frequencies of sound waves associated with the exhaust gas generated from the multiple cylinders.
Still another objective of the present invention is to provide an exhaust silencer system which is simple in design and manufacture yet without compromising the engine performance and noise level associated with the exhaust gas.

A still further objective of the present invention is to reduce the time consumed in assembling the exhaust system.
A further objective of the present invention is to provide an exhaust system which has less number of parts than the conventional systems, which ensures a simpler exhaust system.
Yet another object of the present invention is to provide an integrated exhaust system that is easily serviceable and maintainable thus leading to saving in resources.
SUMMARY OF THE INVENTION:
The present invention provides a direct mounting exhaust silencer which is devoid of exhaust manifold for internal combustion engines. The inlet passages of the silencer are corrected directly to the exhaust ports of the engine. A number of resonating chambers are provided which are separated with baffle plates and connected with perforated communication tubes. It has been found that the resultant system very compact as compared to the existing exhaust systems. It has also been found that the silencer lowers back pressure in the exhaust system and attenuates the noise levels.
BRIEF DESCRIPTION OF DRAWINGS:
FIGURE 1 is perspective of engine assembly incorporating the exhaust silencer
according to the present invention.
FIGURE 2 is perspective of the exhaust silencer of FIG. 1.
FIGURE 3 is enlarged longitudinal sectional view along the line A-A of Figure 2.
FIGURE 4 shows a perspective view of an embodiment of the present invention

FIGURE 5 shows a longitudinal section of the embodiment shown in Figure 4.
List of parts:
Engine assembly 100 Second end of the inlet passage 111
Fly wheel 101 Upstream end 112
Crank case 102 Downstream end 113
Cylinder head 104 First resonator chamber 114
Radiator assembly 104 Second resonator chamber 115
Exhaust silencer 105 Third resonator chamber 116
Housing 106, Hollow space 106a First baffle plate 117
Inlet Passage 107 Seconcl baffle plate 118
Outlet passage 108 First communicating tube 119
First end of the inlet passage 109 Seconcl communicating tube 120
Flange 110 Perforations 121
DETAILED DESCRIPTION:
Referring to FIG. 1, an engine assembly 100 comprises a fly wheel 101, a crank case 102, a cylinder head 103, air intake system (not shown), a radiator assembly 104 and an exhaust silencer 105. The crank case includes cylinder and piston arrangement, wherein the piston moves reciprocally within the cylinder. Bottom end of the piston is rotatabaly connected with a crank shaft which in turn rigidly connected to the fly wheel 101. Inlet valve and exhaust valve arrangements and

fuel injector is provided in the cylinder head 103. Air inlet ports for receiving filtered air from the atmosphere into the combustion chamber and exhaust gas outlet ports for releasing combusted gas in to the atmosphere are also provided in the cylinder head 103 at both the longitudinal sides thereof. An air intake manifold (not shown) is mounted on to the cylinder head 103 at one of the longitudinal sides where air inlet ports are provided. The exhaust silencer 105 according to the present invention is mounted onto the cylinder head 103 at the other longitudinal side where exhaust gas outlet ports are provided.
During the combustion process, the air and the fuel received inside the combustion chamber is getting combusted and the gas coming out from the combustion chamber is passing through the exhaust gas outlet port and then through the exhaust silencer 105 to the atmosphere. The exhaust silencer according to the present invention ensures least backpressure in the exhaust system and thereby achieves desired engine performance and at the same time achieves desired noise level reduction. The detailed construction details of interior of the exhaust silencer and mounting thereof with the exhaust gas outlet port provided in the cylinder head 3 03 are described herein below with reference to the FIG. 2 to FIG. 3.
Referring to FIG. 2, the exhaust silencer 105 comprises an substantially elongated housing 106 which defines a hollow space at the interior thereof. Two inlet passages 107 for" directing the exhaust gas coming out from the exhaust gas outlet

ports are provided in the cylinder head to the interior of the housing 106. Also provided is one outlet passage 108 for releasing the exhaust gas from the interior of the housing 106 to the atmosphere through an extended pipe (not shown). One end 109 of the of the inlet passages 107 is provided with flanges 110, which in turn is provided with plurality of holes for mounting with the exhaust gas outlet port provided in the cylinder head 103. The other end 111 of the inlet passages 107 is connected to the apertures provided at the lateral surface of the elongated housing 106, which will facilitate the mounting of the exhaust silencer 105 lateral to the engine cylinder head 103. This will also ensure compact packing of the entire engine assembly. Even though the present invention discloses exhaust silencer with two inlet passages, a person skilled in art should be able to decide number of inlet passages according to the number of cylinders of the engine and thus it should not limit the scope of the present invention.
The ends 109 of the two inlet passages 107 are mounted on the respective exhaust gas outlet ports and the ends 111 tapers towards each other and connected with housing 106 near its upstream end 112 through two apertures This particular design is surprisingly found to produce a surprisingly low level of back pressure in the exhaust system and provide robust construction to the silencer. The outlet passage 108 is provided at the downstream end 113 of the housing 106 radially at 90 degree apart from the plane of inlet passages 107 so that when the exhaust silencer 105 is getting mounted onto the engine 100, the outlet passage 108 will project upwardly.

Referring to FIG. 3, the hollow space at the interior of the housing 106 is divided into plurality of resonator chambers to attenuate different frequencies of sound waves associated with the exhaust gas. The hollow space is divided into a first resonator chamber 114, a second resonator chamber 115 and a third resonator chamber 116 with the help of a first baffle plate 117 and a second baffle plate 118. The first resonator chamber 114 is defined by the first end 112 of the housing 106 and the first baffle plate 117 to receive the exhaust gas coming out from the combustion chamber through the inlet passages 107. Volume of the first resonator chamber 114 is substantially made large enough to receive the exhaust gas and thereby to achieve least back pressure in the exhaust system. The second resonator chamber 115 is defined by the first baffle plate 117 and the second baffle plate 118. The first baffle plate 117 is provided with an aperture to receive a first communicating tube 119 through which the exhaust gas is communicated between the first resonator chamber 114 and the second resonator chamber 115. The third resonator chamber 116 is defined between the second baffle plate 118 and the second end 113 of the housing 106. The second baffle plate 118 is provided with an aperture to receive a second communicating tube 120 through which the exhaust gas is communicated between the second resonator chamber 115 and the third resonator chamber 116. The third resonator chamber is communicated with outlet passage 108 for exiting the exhaust gas to the atmosphere. Both the first communicating tube 319 and the second communicating tube 120 are provided with perforations 121 for effectively attenuating the sound level.

In an embodiment of the present invention (see Figures 4 and 5), each inlet passages (107) open in a separate resonating chamber rather than a single resonating chamber as with the earlier embodiment.
Example:
Tests were performed using model 3255GM (15kva, 3 cylinder.1.89 liter) Diesel Genset engine of 22.7HP power and running at 1500 rpm conventional silencer and also on using the integrated silencer of the invention where the inlet passages open into a single resonating chamber.
The existing silencer had four chambers and used connecting perforated pipes of 53mm diameter and of suitable lengths and carrying perforations placed at 12mm pitch and of 4mm diameter. The overall size of the existing silencer was 207mm diameter and 755mm length. The silencer of the invention had three resonating chambers and used two pipes of 40mm diameter with perforations of 4mm diameter pitched at 12mm spacing. The overall size of the silencer of the invention was 136mm diameter and 340mm length. Tests were carried out at different levels of load percentages.
Noise levels for the engine and the silencer, and the backpressure at a point before the silencer were measured. It shows (see Table 1) that the levels of noise generated when using the silencer of the invention were comparable with the ones

generated with the existing silencers. It also shows (see Tables 2 and 3) that the back pressures developed with the use of the silencer of the present invention (26-35 mbar) are significantly fower when compared with those developed with the use of the existing silencers (52-102 mbar).
Table 1
Average noise level (db)
Engine Silencer
Invention 91.25 90.9
Existing silencers 90.1 90.5
Table 2: Backpressure data for the silencer of the invention

Silencer of the invention
Load Percentage Positive
mm of
H20 Negative
mm of
H20 Total
mm of
H20 mbar
0 135 135 270 26
' 25 140 145 285 28
50 145 155 300 29
15 140 160 300 29
100 180 180 360 35
Table 3: Backpressure data for existing silencers

Existing silencers
Load Percentage Positive
mm of
H20 Negative
mm of
H20 Total
mm of
H20 mbar
0 270 264 534 52
25 315 305 620 61
50 360 355 715 70
75 440 440 880 86
100 520 520 1040 102

It is thus evident that the exhaust systems provided with the integrated silencer of the present invention provides a number of advantages over the existing exhaust systems. These are:
- As the exhaust system with the a silencer of the invention ate without an exhaust manifold, it thus results in direct cost savings.
- As the silencer of the invention is directly mounted on the engine exhaust ports, it makes the exhaust system very compact as compared to the existing exhaust systems.
- As the silencer of the present invention lowers back pressure & at the same time effectively attenuates frequencies of sound waves associated with the exhaust gas generated from the multiple cylinders, this helps increase the life of the exhaust systems.
- Time consumed in assembling the exhaust system is reduced with the use of the silencer of the invention.
- The exhaust system fitted with the silencer of the invention has less number of parts than the conventional systems, which ensures a simpler exhaust system.
The exhaust system fitted with the silencer of the invention is easily serviceable and maintainable thus leading to further cost savings.
It is evident from the foregoing description that the present invention has the following embodiments.

1. An exhaust silencer comprising:
a housing on which is provided at least one inlet aperture and at least one outlet aperture, - at least one inlet passage, at least one outlet passage, characterized in that said housing defines a hollow space at the interior thereof said hollow space divided into at least two zones formed using a first baffle, namely a first resonator chamber and a second resonator chamber, and wherein number of said inlet apertures is same as the number of said inlet passages, and wherein each of said inlet passages are individually connected to said housing at corresponding said inlet apertures such that the exhaust gases coming from exhaust gas outlet ports provided in the cylinder heads of an engine enter directly into respective inlet passages without presence of an exhaust manifold and get released into said first resonating chamber, from where said exhaust gases travel to said second resonating chamber through a first communication tube which is provided with perforations to attenuate noise, and wherein said exhaust gas finally leaves said silencer through said outlet passage, which is connected to said second resonator chamber.
2. An exhaust silencer as described in embodiment 1 further wherein second baffle is used to divide said hollow space into three zones comprising a third resonator chamber in addition to said first resonator chamber and said second resonator chamber, and wherein a second perforated communication tube is provided between said second resonator chamber and said third resonator

chamber, from where exhaust gases finally leave said exhaust silencer through said outlet passage.
3. An exhaust silencer as described in embodiments 1 and 2 wherein volume of said first resonator chamber is substantially greater compared with said second and third resonator chambers.
4. An exhaust silencer as described in embodiments 1 to 3 wherein said housing is of substantially elongated shape such that gases released into first resonator chamber from said inlet passages have sufficient flowing room so that the build-up of back pressure inside first resonator chamber is minimized.
5. An exhaust silencer as described in embodiments 1 to 4, wherein said number of inlet passages is greater than three, and wherein corresponding number of inlet apertures are provided.
6. An exhaust silencer as described in embodiments 1 to 5, wherein the number of zones is greater than three and wherein a corresponding number of communication tubes are provided between individual zones to carry exhaust gases between resonating chambers.

7. An exhaust silencer as described in embodiments 1 to 6 wherein the ratio of
area of perforations to that of the surface of the first and second
communication tubes is between 20% to 80%, more preferably between 40 and
50%.
8. An exhaust silencer as described in embodiments 1 to 7, wherein the diameter of perforations is between 2mm to 6mm.
9. An exhaust silencer as claimed in claim 2 wherein each of said inlet passages open into a separate resonating chamber.
While the above description contains much specificity, these should not be construed as limitation in the scope of the invention, but rather as an exemplification of the preferred embodiments thereof. It must be realized that modifications and variations are possible based on the disclosure given above without departing from the spirit and scope of the invention. Accordingly, the scope of the invention should be determined not by the embodiments illustrated, but by the appended claims and their legal equivalents.

We claim:
1. A direct mounting exhaust silencer comprising:
a housing on which is provided at least one inlet aperture and at least one
outlet aperture,
- at least one inlet passage, at least one outlet passage,
characterized in that said housing defines a hollow space at the interior thereof
said hollow space divided into at least two zones formed using a first baffle,
namely a first resonator chamber and a second resonator chamber, and wherein
number of said inlet apertures is same as the number of said inlet passages, and
wherein each of said inlet passages are individually connected to said housing
at corresponding said inlet apertures such that the exhaust gases coming from
exhaust gas outlet ports provided in the cylinder heads of an engine enter
directly into respective inlet passages without presence of an exhaust manifold
and get released into said first resonating chamber, from where said exhaust
gases travel to said second resonating chamber through a first communication
tube which is provided with perforations to attenuate noise, and wherein said
exhaust gas finally leaves said silencer through said outlet passage, which is
connected to said second resonator chamber.
2. An exhaust silencer as claimed in claim 1 further wherein second baffle is used to divide said hollow space into three zones comprising a third resonator chamber in addition to said first resonator chamber and said second resonator chamber, and wherein a second perforated communication tube is provided

between said second resonator chamber and said third resonator chamber, from where exhaust gases finally leave said exhaust silencer through said outlet passage.
3. An exhaust silencer as claimed in claim 2 wherein volume of said first resonator chamber is substantially greater compared with said second and third resonator chambers.
4. An exhaust silencer as claimed in claim 3 wherein said housing is of substantially elongated shape such that gases released into first resonator chamber from said inlet passages have sufficient flowing room so that the build-up of back pressure inside first resonator chamber is minimized.
5. An exhaust silencer as claimed in claim 4, wherein said number of inlet passages is greater than three, and wherein corresponding number of inlet apertures are provided.
6. An exhaust silencer as claimed in claim 5, wherein the number of zones is greater than three and wherein a corresponding number of communication tubes are provided between individual zones to carry exhaust gases between resonating chambers.

7. An exhaust silencer as claimed in claim 6 wherein the ratio of area of perforations to that of the surface of the first and second communication tubes is between 20% to 80%, more preferably between 40 and 50%.
8. An exhaust silencer as claimed in claim 7, wherein the diameter of perforations is between 2mm to 6mm.
9. An exhaust silencer as claimed in claim 2 wherein each of said inlet passages open into a separate resonating chamber.