WO2021210020A1

WO2021210020A1 - A noise processing unit for a motor vehicle

Info

Publication number: WO2021210020A1
Application number: PCT/IN2021/050376
Authority: WO
Inventors: Bharaniram Senthilkumar; Mani Boobalan
Original assignee: Tvs Motor Company Limited
Priority date: 2020-04-15
Filing date: 2021-04-15
Publication date: 2021-10-21
Also published as: EP4136330A4; CN115461530A; WO2021210020A4; EP4136330A1

Abstract

The present subject matter relates to an exhaust system with a noise processing unit (225) like a muffler for a motor vehicle. The noise processing unit (225) is part of an exhaust system (102) connected to an internal combustionengine (101). The noise processing unit (225) comprises one or more intermediatechamber(s) (311) that are selectively disposed physically between plurality of firstchamber(s) (301, 302). One or more second chamber(s) (321) are disposedsubsequent to the plurality of first chambers (301, 302). The noise processing unit(225) is configured to direct exhaust gases to flow through the plurality of firstchambers (301, 302), subsequently through the one or more intermediatechambers (311) and then through the one or more second chambers (321). Thenoise processing unit (225) occupies less space and performs effective attenuationof noise.

Description

A NOISE PROCESSING UNIT FOR A MOTOR VEHICLE

TECHNICAL FIELD

[0001] The present subject matter relates to a noise processing unit for a motor vehicle and more particularly but not exclusively to the noise processing unit for two-wheeled or three-wheeled motor vehicles.

BACKGROUND [0002] Generally, a motor vehicle, powered by an internal combustion (IC) engine, is provided with an exhaust system, which is connected to an exhaust port of the IC engine. The exhaust system is used for expelling exhaust gases, produced due to the combustion of air-fuel mixture in one or more combustion chambers of the IC engine of the motor vehicle, into the atmosphere as the exhaust gases comprise carbon monoxide, hydrocarbons, nitrous oxides etc. The exhaust system, in addition to being used for treating the exhaust gases, is also used for attenuating noise produced due to the combustion process.

[0003] Generally, in certain fun and adventurous applications like racing, a noisy motor vehicle may be preferred, where attenuation of noise is not critical. However, in commuter applications, noise emanated from the motor vehicle is unsuitable considering noise pollution and other requirements to be maintained in public places.

BRIEF DESCRIPTION OF DRAWINGS

[0004] The detailed description is described with reference to the accompanying figures, which is related to a two-wheeled motor vehicle being one embodiment of the present invention. However, the preset invention is not limited to the depicted embodiment(s). In the figures, the same or similar numbers are used throughout to reference features and components.

[0005] Fig. 1 illustrates a left-side view of an exemplary motor vehicle, in accordance with an embodiment of the present subject matter.

[0006] Fig. 2 depicts a right-side view of an exemplary internal combustion engine with an exhaust system, in accordance with an embodiment of the present subject matter. [0007] Fig. 3 (a) illustrates a schematic view of a noise processing unit, in accordance with an embodiment of the present subject matter.

[0008] Fig. 3 (b) illustrates a schematic sectional view of the noise processing unit, in accordance with an embodiment of the present subject matter.

[0009] Fig. 3 (c) depicts another sectional view of the noise processing unit, in accordance with an embodiment of the present subject matter.

[00010] Fig. 3 (d) illustrates an enlarged view of a portion of the noise processing unit, in accordance with an embodiment of the present subject matter as depicted in Fig. 3 (c).

DETAILED DESCRIPTION

[00011] Generally, in order to get low exhaust sound, motor vehicles employ methods such as increasing a surface area/ volume of a portion of the exhaust system where exhaust gases expand, typically, inside a muffler. In certain other solutions known in the art, multiple tail pipes or split type exhaust system are used. All these methods increase the overall size of the exhaust system including the muffler. Typically, such solutions are implemented in large capacity motor vehicles like four-wheeled motor vehicles or multi-wheeled motor vehicles having more than four wheels. Such motor vehicles have larger bodies and have scope for accommodating longer and larger even split type exhaust systems. Attempts have been made to adapt similar solutions in two-wheeled or three-wheeled motor vehicles with large capacity, which typically have a larger vehicle area or with a longer wheel base. However, such solutions cannot be implemented in smaller capacity commuter vehicles with compact vehicle layout or with relatively smaller wheel base. Moreover, the aforementioned solutions add up to manufacturing cost of the vehicle, making it impractical to be implemented in low-cost smaller capacity motor vehicles.

[00012] For example, the two-wheeled motor vehicle, typically, has a naked appearance, at least a rearward portion of the motor vehicle. On such vehicles, various critical components like the IC engine are compactly packaged between the two wheels. Some two-wheeled motor vehicle may even have a storage space for carrying loads or goods that requires additional utility space on the vehicle which cannot be compromised or reduced. In these vehicles, the exhaust system is routed carefully keeping it away from the critical components of the motor vehicle and away from rider, typically being disposed towards a rearward portion of the vehicle, to limit dissipation of heat towards the critical components or the rider and / or pillion. In some other attempts to solve the problem, a control valve is provided within the muffler in order to direct air through various pipes or chambers. Accommodation of such valves require additional volume in the muffler along with such plural passages and also, requiring actuators, mechanical or electronic, to control the valve thereby increasing cost of the system. Creation of additional volume on the already compact motor vehicle increases size of the exhaust system, which may result in interfering with other components of the motor vehicle or with pillion rider. Also, increasing size of the exhaust system creates a challenge of appearance and disproportionate appearance, which is undesired.

[00013] Thus, in motor vehicles with exhaust system design confronted with aforementioned space related and layout contradictions, there exists a challenge to provide an effective noise processing unit like a muffler. Curve A, depicted in Fig. 4, illustrates an exemplary attenuation curve at various frequencies for a typical small capacity motor vehicle. As can be seen, there are certain impulses and sharp-raise and falls in the attenuation at various frequencies and at other portions, the noise attenuation is almost negligible. This makes an exhaust note very disturbing due to improper attenuation making it noisy for the rider and for passersby.

[00014] Further, exhaust system or the muffler in the two-wheeled or three wheeled motor vehicles have one or two mounting portions thereof thereby leading to a major challenge of mounting such complex exhaust systems. For example, the mounting portion like a mounting bracket acts as a connecting member between the muffler and a frame assembly or chassis of the motor vehicle. There may be a material failures around welded zone of mounting bracket to the muffler making that portion of the muffler a heat affected zone & vulnerable to durability failure. Additionally, welding temperatures typically shoot up to 1000°C thereby affecting mechanical property of the heat affected zone resulting in undesirable failure eventually, rendering the damaged or deteriorated exhaust system, a noisy one.

[00015] Therefore, there is a need for an exhaust system that can provide noise attenuation at almost all operating conditions of the IC engine. The exhaust system should be compact in order to implemented even in a motor vehicle with a smaller wheel base. Further, the exhaust system should be cost-effective and should easy to install with rigid mounting without any modification of existing frame assembly or chassis.

[00016] The exhaust system as per the present invention comprises a noise processing unit with a compact configuration to be accommodated on a compact motor vehicle. In one embodiment, the noise processing unit comprises multiple chambers configured to effectively attenuate noise across various frequencies without occupying much space.

[00017] In one embodiment, the noise processing unit comprises plurality of first chambers, one or more second chambers and one or more intermediate chambers. The plurality of first chambers substantially form upstream chambers. The one or more intermediate chambers are selectively disposed physically between the plurality of first chambers. The one or more second chambers form the downstream chambers. The noise processing unit is configured to direct exhaust gases to flow through the plurality of first chambers, subsequently through the one or more intermediate chambers and through the one or more second chambers for effective noise attenuation across a large frequency range.

[00018] In one embodiment, the exhaust gases pass through a substantial number of first chambers and then passes through the intermediate chambers. For example, in case of two first chambers, the noise reduction unit or noise processing unit can be configured such that the exhaust gas is made to pass through both the first chambers and then through the intermediate chamber(s). [00019] In one embodiment, one or more intermediate chambers comprises of cumulative volume which is less than a cumulative volume any one of said plurality of first chambers, plus said one or more second chambers. Thus, the first chambers with larger volume, enables expansion of exhaust gases which enter the noise processing unit with higher velocity. The larger first chambers enable reduction of energy and correspondingly noise due to effective expansion.

[00020] In one embodiment, the intermediate chambers with smaller volume is configured to act upon large frequencies of waves that get attenuated thereat due to a substantial change in area and volume. The chambers are configured to create internally reflecting opposite-phase sound waves of various frequencies, which get selectively cancelled out across the chambers resulting in desired sound effect. [00021] In one embodiment of the present invention, the one or more intermediate chambers are selectively disposed between the plurality of first chambers in a predetermined layout. Said one or more intermediate chambers are configured to change direction of flow of exhaust gases in two or more directions. This increases the travel path of the exhaust gases leading to enhanced dissipation of the heat energy.

[00022] In one embodiment, the plurality of first chambers, the one or more intermediate chambers and the one or more second chambers are disposed adjoiningly along an axis of the noise processing unit. Since each chamber is disposed adjacent to another chamber along the axis any expansion of size, say in vertical direction, is avoided thereby not affecting current position of a pillion foot-rest and position of other critical components. Thus, the present subject matter achieves effective noise attenuation by even creating at least two directional changes of flow of exhaust gases by substantially retaining the cross- sectional area of the unit.

[00023] In one embodiment, the one or more intermediate chambers of the noise processing unit comprises at least one intermediate chamber disposed substantially at a mid-portion of the noise processing unit. In one embodiment, the at least one intermediate chamber is formed by a first baffle plate and a second baffle plate, and the baffle plates are to be disposed in proximity to each other to form the smaller volume and the baffle plates at the mid-portion enable retention of structural integrity during welding of a mounting member or the like due to large surface area at that region. Further, configuration of the noise processing unit eliminates need for providing perforations on the baffle plate itself which would have affected the structural integrity of the baffle plates.

[00024] In one embodiment, the noise processing unit comprises a mounting member and the mounting member is secured to an outer casing of the noise processing unit at a portion in proximity to the intermediate chamber. Even though welding happens on the outer casing, the baffle plates disposed in proximity provide additional area to accommodate higher heat during welding or the like.

[00025] In one embodiment, the noise processing unit comprises plurality of connectors, configured to bypass an immediately disposed chamber, to provide a longer flow path and also enable a change in direction of flow by bypassing an immediate chamber. The connectors are provided with optimal length for establishing connection between chambers without need for extension of connectors along entire length of the noise processing unit.

[00026] In one embodiment, at least two connectors, passing through a baffle plate, are disposed at an offset from an axis of the noise processing unit for optimal accommodation of components without occupying large space. For example, in one implementation, three connectors are accommodated on the baffle plate and three connectors are disposed at an offset from the axis of the noise processing unit, which is typically taken at a center of the noise processing unit. [00027] In one embodiment, the noise processing unit is configured for a compact vehicle comprising a wheel base in range of 1200 - 1400 millimeters.

[00028] In one embodiment, the exhaust system comprises an exhaust pipe with an outlet portion. The outlet portion comprises an extended portion that at least partially extends into one of the plurality of first chambers. The one or more second chambers comprises an out-pipe for expelling gases into atmosphere. The at least one of the outlet portion and the out-pipe is provided with perforations that are configured to diffuse exhaust gases during entry and during exit from the noise processing unit.

[00029] In one implementation, the intermediate chamber is configured to attenuate high frequency waves in exhaust gases, which are greater than 4000 Hz that are unpleasant to human ear. In one implementation, the second chamber with a cumulative volume greater than the first chambers is configured to attenuate frequency waves in range of 1500 Hz to 3000 Hz, which typically create a metallic sound, with at least two directional changes or flow reversals. Thus, the exhaust gases expelled from the noise processing unit are pleasant to rider and passers by creating a requisite exhaust noise that is desired.

[00030] Thus, the exhaust gases that are released from the IC engine at a high speed, and through a narrow exhaust pipe are effectively attenuated of noise/ sound before expelling into atmosphere.

[00031] The exhaust system may be implemented in any two-wheeled vehicle or a three-wheeled motor vehicle. However, for the purpose of explanation and by no limitation, the exhaust system, corresponding additional advantages and features are described through the following embodiment. Arrows wherever provided on top right comer of the figure represent direction with respect to motor vehicle. Arrow F represents forward direction, arrow R represents rearward direction, arrow UW represents upward direction and arrow DW represents downward direction.

[0001] Fig. 1 illustrates a left-side view of an exemplary motor vehicle 100, in accordance with an embodiment of the present subject matter. The motor vehicle 100 comprises of a frame assembly 105 acting as a structural member of the motor vehicle 100. The frame assembly 105 comprises a head tube 111, a main tube 105 (schematically shown with dotted line) extending rearwardly downward from the head tube 111. The motor vehicle comprises a front wheel 110, a rear wheel 103, a fuel tank 121 and seat 106. In one embodiment, the frame assembly 105 includes a main tube 112, a down tube (not shown), and one or more seat rails (not shown) extending rearward from the main tube 112. The head pipe 111 supports a steering shaft (not shown) and a front suspension 114 (only one visible) that is attached to the steering shaft through a lower bracket (not shown). The front suspension 114 supports the front wheel 110. The upper portion of the front wheel 110 is covered by a front fender 115 mounted to the front suspension 114 at the end of the steering shaft. A handlebar assembly 108 is fixed to upper bracket (not shown) and can rotate in both directions for maneuvering the motor vehicle 100. A head light 109, a visor guard (not shown) and instrument cluster (not shown) is arranged on an upper portion of the head pipe 111. The down tube may be located in front of the IC engine 101 and extends slantingly downward from head pipe 111. The main tube 112 is located above the IC engine 101 and extends rearward from head pipe 111. The IC engine 101 is mounted at the front by the down tube and rear of the IC engine 101 at the rear portion is connected to the main tube 112.

[0002] In one embodiment, the fuel tank 121 is mounted on a horizontal portion of the main tube 112. Seat rails are joined to main tube 112 and extend rearward to support the seat 106. A rear swing arm (not shown) is connected to the frame assembly 105 to swing vertically, and a rear wheel 103 is connected to rear end of the rear swing arm. Generally, the rear swing arm is supported by a mono rear suspension or two suspensions 11 (as illustrated in the present embodiment) disposed on either side of the motor vehicle 100. A tail light unit (not shown) is disposed at the end of the motor vehicle at the rear of the seat 106. The rear wheel 103 is arranged substantially below the seat 106 and rotates by a driving force of the IC engine 101 transmitted through a chain drive (not shown) from the IC engine 101. In another embodiment, a belt drive, a continuously variable transmission or an automatic transmission may be used. Further, an electric motor may be provided to assist the IC engine 101 or to independently drive the motor vehicle 100 in conjunction with an IC engine. An exhaust system 102 is connected to the IC engine 101 for expelling exhaust gases generated due to combustion of air-fuel mixture. In one embodiment, at least a portion of the exhaust system 102 extends towards one lateral side of the motor vehicle 100 and is disposed adjacent to the rear wheel 103 (a portion of the exhaust system 102 disposed adjacent to the rear wheel 103 and is schematically shown in dotted line).

[00032] Fig. 2 depicts a right-side view of the IC engine 101 provided with an exhaust system 102, in accordance with an embodiment of the present subject matter. The IC engine 101 comprises a cylinder head assembly 210 having a cylinder head 203 and a cylinder head cover 202 mounted atop the cylinder head 203. In an embodiment, the internal combustion engine 101 is a single cylinder engine. More particularly, in one embodiment, the internal combustion engine 101 is a four-stroke internal combustion engine 101. In other alternative embodiment, the internal combustion engine 101 can include more than one cylinder head, say a plurality of cylinders. In an embodiment, the cylinder head 203 of the present subject matter includes one or more ports (not shown in this figure). For example, an exhaust port (not seen in this figure) of the internal combustion engine 101 enables exiting/expelling out the exhaust gases arising out of the combustion of the air-fuel mixture that occurs inside the combustion chamber (not shown) of the internal combustion engine 101. The gases exiting from the exhaust port are transported through an exhaust pipe 215 of the exhaust system 102 of the internal combustion engine 101. In an embodiment, the exhaust pipe 215 includes an inlet opening 201 which is connected to the exhaust port (not seen in this figure) of the internal combustion engine 101 for enabling smooth travel of the exiting exhaust gases. In one embodiment, the exhaust pipe 215 is connected to the cylinder head 203 through a flange member (not shown).

[0003] In one embodiment, the cylinder head 203 of the internal combustion engine 101 is mounted atop a cylinder block 204. The cylinder block 204 is supported by a crankcase 20. The cylinder head 203 and the cylinder block 204 define a combustion chamber (not shown) and a piston (not shown) which is slidable within the combustion chamber resulting in the four-strokes. In an embodiment, the exhaust pipe 215 of the present subject matter includes a first bend 208 adjacent to the inlet opening 201 and a second bend 209 farther from the first bend 208. A distance between the first bend 208 and the second bend 209 depends on one or more parameters including a diameter of wheel(s), wheel base, ground clearance of the second bend from a road / ground surface etc. In an embodiment, the engine 101 includes at least one spark plug (not shown). In an embodiment, the vehicle 100 is a saddle-ride type vehicle. In another embodiment, the vehicle 100 is a step-through type vehicle. A diameter of wheel and a layout of the vehicle is subject to alter depending on the aforementioned type and other type of vehicles. [0004] In one embodiment, an air-fuel supply device 220 is connected to intake port 206 for regulated supply of air and fuel. The air-fuel supply device can be a carburetor, a combination of throttle body and fuel-injector, an electronic carburetor or the like. In an embodiment, the cylinder head assembly 210 can include more than one exhaust port 205. In an embodiment, the cylinder head assembly 210 of the present subject matter has at least one intake port 206 that allows entry of air-fuel mixture into the combustion chamber (not shown). In an embodiment, the cylinder head assembly 210 includes at least one exhaust port 205 disposed on the other side of the intake port 206. In the depicted embodiment, the intake port 206 is disposed on rearward facing side of the cylinder head 203 and the exhaust port 205 is disposed on a front facing side of the cylinder head 203. In other implementations, the exhaust port 205 can be disposed on a rear facing side or a downward facing side of the cylinder head and the intake port is disposed substantially opposite to the exhaust port.

[0005] In an embodiment, the exhaust pipe 215 includes at least one catalytic converter unit optimally disposed at a pre-determined distance from the exhaust port 205 of the cylinder head 203. In one embodiment, the catalytic converter unit is disposed between the first bend 208 and the second bend 209 of the exhaust pipe 215. In an embodiment, the at least one catalytic converter unit is a pre- catalytic converter or an auxiliary catalytic converter, which is provided upstream of a main catalytic converter (not shown) in the exhaust system of the present subject matter. In an alternative embodiment, the main catalytic converter (not shown) is disposed within a noise reduction device 225 of the exhaust system 102 of the present subject matter. In an embodiment, closer the catalytic converter unit to the exhaust port, higher is the efficiency of the catalytic converter unit.

[0006] In one embodiment, the exhaust pipe 215 comprises an outlet portion 211 that is connected to the noise processing unit 225. The outlet portion 211 may extend in to at least a portion of the noise processing unit 225. Further, a sealing member 204 is provided to act as a seal between the outlet portion 211 and noise processing unit 225 to eliminate any leak of exhaust gases into atmosphere. In one embodiment, the sealing member 204 is disposed to annularly cover at least a portion of the noise processing unit 225 and the outlet portion 211. The sealing member 204 is preferably welded. The noise processing unit 225 extends substantially in a rearward direction from the outlet portion 211. As depicted in Fig. 1, the noise processing unit 225, in one implementation, would be disposed adjacent to at least a portion of the rear wheel 103 and below a pillion foot-rest (not shown) of the motor vehicle 100.

[00033] Fig. 3 (a) illustrates a schematic view of a noise processing unit 225, in accordance with an embodiment of the present subject matter. The noise processing unit 225, which is part of the exhaust system 102, is configured to expel exhaust gases produced during the combustion of air-fuel mixture and is configured to perform reduction/ attenuation of noise generated during release of the exhaust gases from the IC engine before expelling into the atmosphere.

[00034] The noise processing unit 225 comprises an outer casing 360 (schematically shown in dotted lines) and a plurality of chambers (expansion chambers) that are formed by plurality of baffle plates disposed within the noise processing unit 225. In the depicted embodiment, plurality of first chamber(s), one or more second chamber(s) and one or more intermediate chamber(s) are provided. In depicted implementation, two first chambers 301, 302 are provided and the outlet portion 211 of the exhaust pipe 215 is connected such that its downstream extended portion (365) opens into one of the two first chamber 301, 302. The outlet portion 211 is provided with an extended portion 365 and the extended portion 365 may be a solid tube or a perforated tube. Further, an intermediate chamber 311 is provided and the intermediate chamber 311 is formed adjacent to at least one of the first chambers 301, 302. A second chamber 321 is provided subsequent to the plurality of the first chambers 301, 302. In one implementation, the second chambers 321 is disposed at a downstream portion of the noise processing unit 225. The first chamber 301 is formed by a first baffle plate 331 (between the first baffle plate and an upstream enclosure of the noise processing unit 225), the intermediate chamber 311 is formed between the first baffle plate 331 and a second baffle plate 332. The first chamber 302 disposed subsequent to the intermediate chamber 311 is formed between the second baffle plate 332 and a third baffle plate 333. Hereinafter, the first chamber 301 is referred to as a primary-first chamber and the first chamber 302 is referred to as a secondary-first chamber. In the current embodiment, the intermediate chamber 311 is disposed physically between the primary-first chamber 301 and the secondary-first chamber 302 or generally referring, the intermediate chamber 311 is selectively disposed between plurality of first chambers 301, 302. Further, the second chamber 321 is formed between the third baffle plate 333 and an end- baffle plate 335.

[00035] In one embodiment, a volume of the intermediate chamber 311 (or a cumulative volume of intermediate chambers in case of more than one intermediate chamber) is substantially smaller than a cumulative volume of the first chambers 301, 302. The volume of the intermediate chamber(s) 311 is also substantially smaller than a volume (or cumulative volume) of second chambers 321. The exhaust gases EG entering the noise processing unit 225 passes through the first chambers 301, 302, then to the intermediate chamber(s) 311 and then to the second chamber(s) 321. The plurality of chambers 301, 302, 311, 321 are configured to effectively reduce momentum of the exhaust gases entering the muffler 235. In one embodiment, the intermediate chamber 311 with the lesser volume disposed between the primary-first chamber 301 and the secondary-first chamber 302 is selectively bypassed while travelling therethrough and the exhaust gases enter the intermediate chamber 311 after flowing through all the first chambers 301, 302. The flow of exhaust gases in the noise processing unit 225 is discussed in subsequent description. In one embodiment, the first chamber 301, 302 are configured to accommodate an additional catalytic converter unit (not shown). The additional catalytic converter unit can act as a primary catalytic converter or a secondary catalytic converter unit. As the first chambers 301, 302 are provided with larger volume, the noise processing unit can accommodate even a larger primary converter thereat.

[00036] Fig. 3 (b) illustrates a schematic sectional view of a noise processing unit 225, in accordance with an embodiment of the present subject matter. The outlet portion 211 extending into the noise processing unit 225 is provided with an extended portion 366 which is provided with plurality of perforations, configured to diffuse exhaust gases EG entering the noise processing unit 225. The diffused exhaust gases expand in the primary-first chamber 301 thereby experiencing reduction in momentum and resulting in exhaust gases EG1 with reduced energy. For example, the chambers that are separated by the baffle plates and the baffle plates are assumed to have infinite impedance, in one implementation. The reduction in energy of exhaust gases occurs due to dissipation of heat (by conduction or convention) in the first chamber and due to reduction of momentum due to expansion.

[00037] Further, a first connector 341 connects the primary-first chamber 301 and the secondary-first chamber 302. The term ‘connector’ may include any means for transferring exhaust gases from one chamber to another. In one embodiment, similar to the depicted embodiment, the connector is a cylindrical member. The first connector 341 is disposed at an offset from an axis A-A’ of the noise processing unit 225 and from the extended portion 365 to avoid direct entry of exhaust gases EG into the first connector 341 and to enable entry after expansion. The first connector 341 passes through the intermediate chamber 311, bypassing flow of any exhaust gases into the intermediate chamber 311 from the primary- first chamber 301. The first connector 341 passes through the first baffle plate 331 and the second baffle plate 332 and is supported by them. The exhaust gases EG1 after reaching the secondary-first chamber 302, further undergoes expansion due to larger volume of the secondary-first chamber 302. In one implementation, the secondary-first chamber 302 is provided with a volume larger than the primary- first chamber 301. The exhaust gases EG1 in the secondary-expansion chamber 302 experience a further reduction in momentum, especially due to change in direction of flow resulting in exhaust gases EG2 with reduced energy. In the secondary-first chamber 302 of the current embodiment, the exhaust gases are directed to flow in a direction opposite to a direction of entry of the exhaust gases into the noise processing unit 225.

[00038] The noise processing unit 225 is provided with a second connector 342 for connecting the secondary-first chamber 302 to the intermediate chamber 311. The second connector 342 and first connector 341 are disposed at an offset from an axis A-A’ of the noise processing unit 225 for optimal packaging. The exhaust gases EG2 entering the intermediate chamber 311 has already passed through two large expansion chambers and the intermediate chamber 311 with the smaller volume is configured to attenuate any high frequency waves of the exhaust gas resulting into exhaust gas EG3 with further reduced energy. Subsequently, the exhaust gases EG3 experiences a change in flow direction due to a third connector 343 connecting the intermediate chamber 311 and the second chamber 321, which is physically disposed subsequent to secondary-first chamber 302. The third connector 343 is supported by the second baffle plate 332 and the third baffle plate 343. Flow of the exhaust gases into the second chamber 321 causes the exhaust gases to realign into the original flow direction.

[00039] The third connector 343 bypasses the secondary-first chamber 302 thereby enabling passage of gases into the second chamber 321 for attenuation of any remaining higher frequency waves thereby resulting in exhaust gases EG4 with further noise attenuation. In one embodiment, the third connector 343, the second connector 342, and the first connector 341 are disposed at an offset from the axis A-A’ of the noise processing unit 225. This enables the connectors 341, 342, 343 to be efficiently or optimally packaged on the second baffle plate 332. The second chamber 321 is provided with an out-pipe 345 configured to expel the exhaust gases EG5 from the exhaust system 102 into the atmosphere. In one embodiment, the exhaust out-pipe 345 is provided with perforation for a final diffusing of exhaust gases. Thus, the exhaust gases EG5 exiting the noise processing unit 225 have an attenuation substantially across all frequencies as depicted in Curve B of Fig. 4. The Curve B represents an exemplary graph plotted for noise attention across various frequencies, in accordance with an embodiment of the present subject matter. As can see, curve B does not comprise any sudden spikes or sudden rise and falls and a relatively substantial attenuation of noise across various frequencies.

[00040] The noise processing unit 225 comprises the intermediate chamber 311, with the baffle plates 331, 332 that are substantially closer, and disposed at a substantial mid-portion of the noise processing unit 225 thereby providing requisite structural rigidity at the mid-portion to support the entire noise processing unit 225. In one embodiment, the mid-portion is a portion of the noise processing unit 225 forming a 50% mid-region thereof. In one embodiment, a mounting member 350 is disposed in proximity to the intermediate chamber 311. Thus, during welding of the mounting member 350 to the outer casing 360, a total surface area in that region is larger due to the presence of the baffle plates 331,

332 thereby reducing affect of heat on the noise processing unit 225. Thus, any adverse effect on material properties of the noise processing unit is minimal making the structure rigid. The noise processing unit can be mounted using a single mounted member 350. However, in another implementation, more than one mounting member may be used if required. As depicted in Fig. 3 (b), the chambers 301, 302, 311, 321 are disposed adjoining each other along an axis A- A’ of the noise processing unit 225 without increasing width of the noise processing unit 225 (overall cross-sectional area and especially in vertical direction, when viewed from side) so as to be mounted on motor vehicles having smaller wheel base say a wheelbase in the range of 1200 to 1400 millimeters. Further, the noise processing unit 225 would not be interfering with the compact layout and with required position of a pillion foot-rest thereby avoiding any layout or design change.

[00041] Fig. 3 (c) depicts another sectional perspective view of the noise processing unit 225, in accordance with an embodiment of the present subject matter. Fig. 3 (d) illustrates an enlarged view of a portion of the noise processing unit 225, in accordance with an embodiment of the present subject matter as depicted in Fig. 3 (c). The exhaust gases flow initially into larger first chamber 301, 302 that enable expansion of exhaust gases which enter at high velocity and initially suppressing certain frequency waves. Further, the baffle plates 331, 332,

333 are configured to provide destructive interference to cancel out unwanted frequencies of sound generated during combustion process. Further, the first chambers 301, 302 with the intermediate chambers 311 selectively provided between the first chambers 301, 302 provide longer travel path for the exhaust gases within the first chambers 301, 302 and through the first connector 341 with longer length whereby longer flow path is obtained thereby enabling absorption of energy by dissipation of heat and attenuation of sound. The noise processing unit 225 with the lengthier flow path eliminates unwanted noise/ sound. Further, the intermediate chamber 331 disposed selectively physically between the first chambers 301, 302 and with a flow entering the intermediate chamber 311 after passing through all the first chambers 301, 302 enables at least a double reversal of flow direction thereby further slowing down the exhaust gases and enabling higher transmission losses, which results in reduced noise. The change in the surface area provides a resistance to the flow of the exhaust gases, and the exhaust gases reflect a portion of their strength in the form of sound waves in a direction opposite to their travel direction, i.e., sound waves of an opposite phase are created. The reflected opposite-phase sound waves cancel out initial sound waves of the exhaust gases, thereby reducing the exhaust sound to a desired exhaust sound. In one embodiment, to further enable diffusing of exhaust gases, the connector 341, 342, 343 can be provided with perforations that in conjunction with the configuration of the muffler enable effective attenuation of noise.

[00042] The muffler of the exhaust system with the muffler is designed such that minimum space is occupied on the motor vehicle, thereby eliminating need for a layout change. The number of expansion chambers can be varied as per requirement. The exhaust system can be used in any type of vehicle including two-or three-wheeled motor vehicles or even in multi-wheeled vehicle with compact layout.

[00043] While certain features of the claimed subject matter have been illustrated and described herein, many modifications, substitutions, changes, and equivalents will now occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes that fall within the true spirit of the claimed subject matter. List of reference signs: 302 secondary first-chamber

100 vehicle 311 intermediate chamber

101 IC engine 321 second chamber

102 exhaust system 35 331 first baffle plate 103 rear wheel 332 second baffle plate

105 frame assembly 333 third baffle plate

106 seat 335 end-baffle plate

108 handlebar assembly 341 first connector

109 head light 40 342 second connector 110 front wheel 343 third connector

111 head pipe 345 out-pipe

112 main tube 350 mounting member

114 front suspension 360 outer casing

115 front fender 45 365 extended portion 116 chain drive 366 extended portion

11 rear suspension (perforations)

121 fuel tank EG/EG 1/EG2/EG3/EG/EG4/EG5

201 inlet portion exhaust gases

202 cylinder head-cover 50 203 cylinder head

204 sealing member

205 exhaust port

206 intake port

207 crankcase 208 first bend

209 second bend

210 cylinder head assembly

211 outlet portion

215 exhaust pipe 220 air-fuel supply device

301 primary-first chamber

Claims

We Claim:

1. A noise processing unit (225) for a motor vehicle (100), said noise processing unit (225) forming part of an exhaust system (102) functionally connected to an internal combustion engine (101) of said motor vehicle (100), said noise processing unit (225) comprising: plurality of first chambers (301, 302); one or more second chamber(s) (321); and one or more intermediate chamber(s) (311), said one or more intermediate chambers (311) selectively disposed between said plurality of first chamber(s) (301, 302), and said noise processing unit (225) configured to direct exhaust gases to flow through the plurality of first chambers (301, 302), subsequently through the one or more intermediate chambers (311) and then through the one or more second chambers (321).

2. The noise processing unit (225) for said motor vehicle (100) as claimed in claim 1, wherein said one or more intermediate chamber(s) (311) comprises a cumulative volume less than a cumulative volume of any one of said plurality of first chambers (301, 302) and said one or more second chambers (321), and wherein said one or more second chambers (321) disposed at a downstream portion of said noise processing unit (225).

3. The noise processing unit (225) for said motor vehicle (100) as claimed in claim 1, wherein said one or more intermediate chamber(s) (311) is configured to change a direction of flow of exhaust gases in two or more direction(s).

4. The noise processing unit (225) for said motor vehicle (100) as claimed in claim 1, wherein said plurality of first chambers (301, 302), said one or more intermediate chambers (311) and said one or more second chambers (321) are disposed adjoiningly along an axis (A-A’) of the noise processing unit (225).

5. The noise processing unit (225) for said motor vehicle (100) as claimed in claim 1, wherein said one or more intermediate chambers (311) comprises at least one intermediate chamber (311) disposed substantially at a mid-portion of said noise processing unit (225) and said at least one intermediate chamber (311) being formed by a first baffle plate (331) and a second baffle plate (332) disposed in proximity to each other.

6. The noise processing unit (225) for said motor vehicle (100) as claimed in claim 1, wherein noise processing unit (225) comprises a mounting member (350) and said mounting member (350) being secured to an outer casing (360) of said noise processing unit (225) at a portion in proximity to said intermediate chamber (311).

7. The noise processing unit (225) for said motor vehicle (100) as claimed in claim 1, wherein said plurality of first chambers (301, 302) comprises a primary- first chamber (301) and a secondary-first chamber (302), and a first connector (341) connects the primary-first chamber (301) and a secondary-first chamber (302) bypassing said intermediate chamber (311).

8. The noise processing unit (225) for said motor vehicle (100) as claimed in claim 1 or 6, wherein said noise processing unit (225) comprises a second connector (342) connecting said secondary-first chamber (320) to said intermediate chamber (311), and a third connector (343) connects said intermediate chamber (311) to one of said one or more second chambers (321) passing through a third baffle (333) forming one of said one or more second chambers (321).

9. The noise processing unit (225) for said motor vehicle (100) as claimed in claim 7, wherein said noise processing unit (225) comprises at least two of said first connector (341), said second connector (342) and said third connector (343) disposed at an offset from an axis (A-A’) of the noise processing unit (225).

10. The noise processing unit (225) for said motor vehicle (100) as claimed in claim 1, said motor vehicle (102) comprises a wheel base in range of 1200-1400 millimeters.

11. The noise processing unit (225) for said motor vehicle (100) as claimed in claim 1, said exhaust system (102) comprises an exhaust pipe (215) with an outlet portion (211), said outlet portion (211) comprises an extended portion (366) extending into one of said plurality of first chambers (301, 302) and said one or more second chambers (321) comprises an out-pipe (345), and wherein at least one of said outlet portion (211) and said out-pipe (345) is provided with perforations.

12. A method of processing exhaust gases by a noise processing unit (225), said method comprising steps of: passing said exhaust gases through plurality of first chambers (301, 302) of said noise processing unit (225); passing said exhaust gases through one or more intermediate chambers (311) selectively disposed between said plurality of first chambers (301, 302); and directing said exhaust gases through said one or more second chambers (321).