Claims:I/We claim:
1. An exhaust system (200) for a vehicle (100), said exhaust system (200) connected to a power unit (125) of said saddled vehicle (100), the exhaust system (200) comprising:
an exhaust pipe (205), said exhaust pipe (205) formed by an upstream end portion (U), and a downstream end portion (D),
said upstream end portion (U) includes a first axis (VV`) passing centrally and said downstream end portion (D) includes a second axis (CC`) passing centrally therethrough,
said first axis (VV`) intersecting said second axis (CC`) at an angle.
2. An exhaust system (200) for a vehicle (100), said exhaust system (200) connected to a power unit (125) of said saddled vehicle (100), the exhaust system (200) comprising:
an exhaust pipe (205), said exhaust pipe (205) formed by an upstream end portion (U), and a downstream end portion (D),
a cover member (201) attached to a second downstream end portion (215) of a second downstream portion (207), said cover member is configured to annularly cover a treatment device (211); and
a diffuser (202), said diffuser (202) disposed upstream to said treatment device (211) inside said cover member (201).
3. An exhaust system (200) for a vehicle (100), said exhaust system (200) connected to a power unit (125) of said saddled vehicle (100), the exhaust system (200) comprising:
an exhaust pipe (205), said exhaust pipe (205) formed by an upstream end portion (U), and a downstream end portion (D),
said upstream end portion (U) includes a first axis (VV`) passing centrally and said downstream end portion (D) includes a second axis (CC`) passing centrally therethrough,
said first axis (VV`) intersecting said second axis (CC`) at an angle;
a cover member (201) attached to a second downstream end portion (215) of a second downstream portion (207); and
a diffuser (202), said diffuser (202) disposed in said cover member (201).
4. An exhaust system (200) for a vehicle (100), said exhaust system (200) connected to a power unit (125) of said saddled vehicle (100), the exhaust system (200) comprising:
an exhaust pipe (205), said exhaust pipe (205) formed by an upstream end portion (U), and a downstream end portion (D),
a cover member (201) disposed circumferentially around a treatment device (211), a cover second end portion (201d) of said cover member (201) is attached to a second downstream end portion (215), said cover member (201) comprising a fitting portion (TF) detachably attached to a portion of said treatment device (211).
5. The exhaust system (200) for a saddled vehicle (100) as claimed in claim 2, wherein said cover member (201) is disposed at a close proximity to at least one-cylinder head cover (183a) of said power unit (125).
6. The exhaust system (200) for a saddled vehicle (100) as claimed in claim 2, wherein said diffuser (202) includes one or more perforations (202a), said one or more perforations (202a) are disposed within an outer circumferential surface (202o) of said diffuser (202).
7. The exhaust system (200) for a saddled vehicle (100) as claimed in claim 2, wherein said diffuser (202) is disposed adjoiningly and upstream to a sensor mounting portion (204).
8. The exhaust system (200) for a saddled vehicle (100) as claimed in claim 2, wherein said diffuser (202) is attached to an inner circumferential surface (201i) of said cover member (201) and said diffuser (202) is disposed upstream of said treatment device (211).
9. The exhaust system (200) for a saddled vehicle (100) as claimed in claim 2, wherein said treatment device (211) is disposed in a second position (P2) in said cover member (201).
10. The exhaust system (200) for a vehicle (100) as claimed in claim 4, wherein said cover member (201) is configured to extend beyond said treatment device (211) longitudinally.
11. The exhaust system (200) as claimed in claim 4, wherein said second-downstream end portion (215) is configured to support a treatment device (211).
12. The exhaust system (200) as claimed in claim 4, wherein said treatment device (211) includes one end (219) being supported by said second-downstream end portion (215) and a second portion (218) of said treatment device (211) projects outwards therefrom, said second portion (218) is disposed with an annular gap (230) between said inner circumferential surface (201i) of said cover member (201).
13. The exhaust system (200) for a saddled vehicle (100) as claimed in claim 9, wherein said second position (P2) enables difference in a distance (d).
14. The exhaust system (200) for a saddled vehicle (100) as claimed in claim 13, wherein said distance (d) is in range of 10 mm to 50 mm.
Dated this 28th day of April 2020 , Description:TECHNICAL FIELD
[0001] The present subject matter, in general, relates to a vehicle with two or more wheels including an internal combustion engine and, in particular relates to a combustion gas-exhaust system for the internal combustion engine of the vehicle.
BACKGROUND
[0002] Generally, motor vehicles like two or three wheeled type vehicles which are compact are provided with an internal combustion (IC) engine unit. These types of vehicles have gained popularity due to their compact layout and their ability to carry an additional passenger and/or to carry loads on them. These vehicles may constitute two-wheels or three-wheels depending on application, engine layout etc. Some of these vehicles are provided with a swinging-type engine, and a connecting link, like a toggle link, is provided to swingably support the IC engine unit. Some other type of vehicles has the IC engine fixedly mounted to the frame. In these vehicles the IC engine may be forwardly inclined. The vehicles have an exhaust system that is extending at a lower portion of the vehicle and extending towards a muffler positioned on one of the sides of the vehicle or may be at a center. The vehicle is to be provided with sufficient ground clearance to securely accommodate the exhaust system, which is one of many packaging and, layout challenges in such vehicles.
[0003] Additionally, these saddle ride-type motor vehicles are operated in different terrains and with different driving patterns as those are dependent on the location of operation or user, which are beyond control of the manufacturer. These vehicles when operated in such different terrains and with different driving patterns are subjected to jerks and the resultant impact may be transferred to various systems of the vehicle.
[0004] Moreover, the exhaust system has to perform optimally in order to treat exhaust gases without any failure of the system even under severe usage conditions. For example, a poor ground clearance may damage the exhaust system, which is substantially at a lower portion on the vehicle resulting in adversely affecting the performance of the exhaust system.

BRIEF DESCRIPTION OF THE DRAWINGS
[0005] The detailed description is described with reference to an embodiment of a scooter type two wheeled vehicle along with the accompanying figures. The same numbers are used throughout the drawings to reference like features and components.
[0006] Fig 1 depicts a right-side view of an exemplary motor vehicle, in accordance with an embodiment of the present subject matter.
[0007] Fig. 2 illustrates a front perspective view of the power unit, in accordance with an embodiment of the present subject matter.
[0008] Fig. 3 depicts a right-side perspective view of the exhaust system 200, in accordance with the embodiment of Fig. 2.
[0009] Fig. 4 illustrates a right-side view of an engine assembly along with position of the treatment device with respect to the ground plane.
[00010] Fig. 5 illustrates a sectional view of a portion of the exhaust system, in accordance with the embodiment as depicted in Fig. 3.
[00011] Fig. 6 illustrates a front view of a portion of the exhaust pipe of the exhaust system of the vehicle.
[00012] Fig. 7 shows the conversion efficiency of the treatment device versus time.
[00013] Fig. 8 illustrates a comparative study of the graphical representation of the ground clearance attained due to various position of the treatment device in the exhaust pipe.
[00014] Fig. 9 illustrates a comparative study of the graphical representation of the durability of the treatment device and the sensor unit during different conditions.
[00015] Fig. 10 illustrates a comparative study of the graphical representation of the temperature at which the treatment device attains thermal equilibrium at various conditions is provided.
DETAILED DESCRIPTION
[00016] Conventionally, motor vehicles are provided with drive means including the internal combustion (IC) engine and/or a traction motor. Also, the vehicle includes various sub-systems like the air induction system that works in conjunction with the fuel supply system like carburetor or fuel injector. Air-fuel mixture is supplied to the IC engine for combustion, which produces desired power and torque that is transferred to at least one wheel of the vehicle. Further, the gas exhaust system includes exhaust pipe that transmits the gases generated during combustion process to a muffler. Generally, the gases that are produced may include various harmful components including total hydrocarbons (THC), carbon monoxide (CO), and nitrogen oxides (NOx). There is a need for treating the harmful components prior to emitting the gases into the atmosphere through the muffler. Typically, a gas treatment device is used for treatment of the aforementioned harmful components before emitting to the atmosphere. The known exhaust pipe/discharge pipe has to accommodate the treatment device securely. The exhaust pipe should also be capable of accommodating a sensor unit for detecting the amount of oxygen content in the emitted exhaust gases.
[00017] Generally, the gas treatment device is disposed within the exhaust system. The treatment device has a light-off or operating temperature that has to be attained in shortest possible time for the treatment device to be optimally functional at best efficiency. To achieve early light-off, the treatment device may be disposed in close proximity to the exhaust port. However, disposing the treatment device in close proximity to the exhaust port may damage or burn the treatment device itself thereby leading to poor durability which is primarily owing to its exposure to the extremely high temperature of the exhaust gases closer to the exit portion. In known art, overheating the treatment device occurs owing to direct heat transfer, by conduction process, from the exhaust pipe to the treatment device on account of the physical mounting contact of the treatment device and the exhaust pipe which acts like a heat source by being continuously heated by the exhaust gases. On the other hand, if the treatment device is disposed away from the exhaust port, the treatment device would not achieve early light-off by which the exhaust gases would go untreated or ineffectively treated for a longer duration until the optimum equilibrium temperature is attained for light off of the treatment device is attained. Fig. 7 shows a graphical representation of conversion efficiency of a treatment device versus time in conventional systems. Line-A (dotted line) depicts the conversion efficiency of the treatment device from the time of engine start and till it reaches a maximum point or optimal point. As depicted, the conventional treatment device takes more time to reach its maximum efficiency for treatment of exhaust gas. In other words, the treatment device takes more time to reach its light-off temperature. Within this time large amount of exhaust gases go untreated which is undesirable. Thus, the challenge is to provide an exhaust system with early light-off without damaging it or compromising on its durability.
[00018] Conventionally, a heating coil may be provided for heating the treatment device since the high level of untreated gases are primarily emitted during the first few minutes of starting the engine operation, that is before the treatment device becomes sufficiently operational. Some solutions in the art suggest provision of additional components like heating coil that help in bringing the treatment device to operating temperature or light-off temperature quickly after engine start. However, such a system is not cost effective and at the same time the system is not efficient as it consumes more energy from power source(s) for heating. The provision of heating coil or such electrical/electronic heating system may act as a deterrence to function of other electronic systems of the vehicle. This is because, the high-power required by the heating coils, cannot be delivered by the alternator during engine start, since the engine operates in lower RPM close to start condition. Therefore, the engine gets loaded due to the above power requirements or the battery is used. Additionally, packaging the additional heating system within layout with good ground clearance is a challenge.
[00019] Moreover, the IC engine is provided with a lambda sensor or oxygen sensor, which is used to measure and monitor the amount of residual oxygen in the exhaust gas. The data provided by the lambda sensor is used by a control unit to alter/regulate the air-fuel mixture being supplied to the IC engine. Thus, the lambda sensor is required to be mounted on the exhaust system to measure a precise quantity of oxygen for effective control of the combustion mixture.
[00020] Furthermore, the exhaust gases that exit the exhaust port are travelling at high velocity and these gases funnel down towards the treatment device to only certain region leaving the other region of the treatment device underutilized. As available in most layouts of the IC engines, the presence of curved portion of the exhaust pipe, being disposed immediately after an upstream end of the exhaust pipe, causes the high velocity exhaust gases to flow along one side, which is outer peripheral side owing to the inertia around the bend trajectory. In particular, the gases flow to the side opposite to the exhaust port, of the exhaust pipe. As a result, the exhaust gases reach the treatment device utilizing only a partial portion of the treatment device resulting in poor utilization of the treatment device. Additionally, only partial portion of the treatment device gets over utilized leading to early failure of the treatment device, which is undesired. Additionally, treatment device failure may require replacement of entire exhaust system which is a costly affair.
[00021] For example, in a forwardly inclined engine, the exhaust gases exiting the downward facing side of the exhaust port get funneled down flowing towards the treatment device. Nevertheless, the exhaust gases get concentrated to certain portion of the exhaust pipe causing only some portion of the treatment to be utilized. This occurs due to the high velocity exhaust gas passing through only certain region of the exhaust passage, whereas other portions of the exhaust gas travel with poor velocity and also results in turbulence affecting flow. Additionally, the exhaust gases flowing at high velocity will be passing quickly through the treatment device leaving minimal time for the conversion/treatment to take place. This results in poor conversion treatment of the exhaust gases.
[00022] Further, an additional challenge is to accommodate a treatment device in an exhaust system in vehicles having a forwardly inclined engine. In such vehicles, ground clearance of the vehicle with reference to the position of the exhaust port is substantially low for accommodating and routing the exhaust pipe at such compact ground clearance. In the art, some solutions were proposed to address the problem of accommodation of treatment device, for example the treatment device is disposed at a split portion of the exhaust pipe by using two holders on either sides of the treatment device. Such systems involve multiple welding points, which are considered weak points in terms of leaks or even in terms of structural strength, as the exhaust system is rigidly connected the IC engine. In the aforementioned systems, the exhaust pipe is to be split co-axially, two device-holding members are to be provided on either sides of the treatment device, and the treatment device is disposed in a casing resulting in increase in number of components, which implies increase in number of joints which is challenging. The exhaust pipe provided with the treatment device gets suspended and such aforementioned multiple parts increases weight of the system that makes the joints vulnerable for failure owing to own weight of the system, resonance forces, fatigue loads and due to external parameters like jerks or vibrations.
[00023] At this outset, additional challenge is to accommodate such aforementioned exhaust systems in compact type vehicle by maintaining sufficient ground clearance and to optimally dispose the exhaust system. In order to maintain ground clearance, the exhaust pipe requires sharp bending, which is complicated in tubular parts. Also, the treatment device cannot be accommodated close to the bend in such systems. Thus, the light-off of the treatment device is poor offering compromised performance of the powertrain as a whole.
[00024] Similar to the conversion device, the lambda sensor also needs to be disposed at an optimum distance from the exhaust port. Generally, the lambda sensor being disposed on the exhaust pipe is known in the art, wherein the lambda sensor is disposed at a point where the information provided by the sensor is not absolute. However, such a design requires separate provision for sensor on the exhaust pipe, which increases the size of the exhaust pipe. Moreover, for optimum functioning of the exhaust pipe, it is to be disposed in proximity to the exhaust port, specifically it is to be disposed in the proximity to a curved portion of the exhaust pipe, which is a major challenge due to the complexity in mounting the sensor on a curved surface. Additionally, provision of the lambda sensor on the exhaust pipe may lead to leakage of exhaust gases whereby the lambda sensor would not be able to provide accurate exhaust gas related data, say the oxygen content. Thus, the control unit tends to alter/regulate the air-fuel mixture depending on the inaccurate data. This affects the performance of the engine resulting in rich mixture or lean mixture at undesired engine operating conditions. Moreover, an additional plate/ casing may be provided to provide a tight seal from escape of exhaust gases that increases size of the exhaust system especially that of the exhaust pipe, which is generally tubular member, affecting the layout of the vehicle. For example, in a vehicle having a forwardly inclined engine, the ground clearance of the vehicle is affected.
[00025] Besides, the lambda sensor should be able to provide the oxygen content related data prior to treatment and in some cases an additional lambda sensor may be used to get the data post conversion. Thus, there is design conundrum to accommodate the treatment device and the lambda sensor optimally in proximity to the exhaust port.
[00026] Therefore, there is a need for providing an improved solution while addressing the aforementioned and other shorts comings in the prior art. Consequently, the exhaust system should be capable of offering reduced weak points like joints offering structural rigidity to the system. Also, the exhaust system should be capable of providing optimum performance.
[00027] Hence, the present subject matter provides an improved exhaust system for a motor vehicle. The motor vehicle comprises a power unit including an internal combustion (IC) engine. A cylinder head of the IC engine includes an exhaust port provided on one of side walls thereof. The exhaust system includes an exhaust pipe having one end connected to the exhaust port and other end connected to a muffler. In one embodiment, a treatment device is provided in the exhaust pipe in proximity to the exhaust port.
[00028] It is a feature of the present subject matter that the exhaust pipe includes a first portion a second portion, wherein the second portion is disposed downstream to the first portion with respect to exhaust gas flow direction. The exhaust pipe is connected to the exhaust port through the first portion and the second portion gets connected to the muffler. Thus, the exhaust pipe of the present subject matter is a compact unit with primarily two parts viz. a first portion and a second portion, which are minimal in size as compared to similar conventional systems.
[00029] It is a feature of the present subject matter that a treatment device is at least partially enclosed/accommodated in the first portion, which is in proximity to the exhaust port offering early light-off thereof. It is an aspect that the first portion defines an accommodation space capable of configuring the treatment device in proximity to the exhaust port and still offers sufficient ground clearance.
[00030] It is another feature of the present subject matter that the treatment device is not intermediately disposed, which would typically require multiple welding or connections. Thus, the number of weak points is reduced as the number of joints (welds) are reduced.
[00031] It is yet another aspect of the present subject matter that the treatment device is cantilevered/cantilever mounted to one of a first portion and a second portion thereby minimizing any thermal conduction of heat from the exhaust pipe to the treatment device while still enabling configuring the disposition of the treatment device closer to the exhaust port. In one embodiment, an upstream end portion of the second portion is adapted to cantilever support the treatment device. The term ‘cantilever mounted’ used herein infers that one end (downstream end) of the treatment device is upstream end portion of the second portion, and other end portion of the treatment device is suspended within the first portion without any direct contact therewith.
[00032] It is a feature of the present subject matter that the exhaust gas exiting the power unit enters first portion of the exhaust pipe. Additionally, at least a portion of the exhaust gas passes into a gap, which is formed substantially radially between the first portion and the cover member. The exhaust gas entering the gap helps in quick heating of the treatment device by which it attains early light-off. As the gap formed annularly outward of the treatment device it enables the exhaust gas to heat the treatment device from annularly outward direction.
[00033] In one embodiment, the exhaust system is secured to the power unit being forwardly-inclined type and the power unit is swingably mounted to a frame member through a toggle link.
[00034] In one embodiment, exhaust pipe is configured to support a sensor member mounted on a sensor mounting portion. In one implementation, the sensor member is mounted upstream of the first portion for providing oxygen content information for regulating engine related parameters like air-fuel mixture etc.
[00035] The sensor member is securely and rigidly supported by the cover member of the treatment device, without compromising the structural rigidity of the exhaust pipe. Further, in one implementation, the cover member that at least partially encloses the treatment device is provided with an aperture to enable a secured mounting of the sensor member. The sensor member is provided subsequent to the treatment device and the uniform flow of exhaust gas improves the sensitivity or detection of oxygen information.
[00036] These and other advantages of the present subject matter would be described in greater detail in conjunction with the figures in the following description.
[00037] Arrows wherever provided in the top right corner in the drawings depicts direction with respect to the vehicle, wherein an arrow F denotes front direction, an arrow R indicates rear direction, an arrow UP denotes upward direction, an arrow DW denotes downward direction, an arrow RH denotes right side, and an arrow LH denotes left side.
[00038] Fig. 1 depicts a side view of an exemplary motor vehicle 100, in accordance with an embodiment of the present subject matter. The vehicle 100 has a frame member 105 (schematically shown with dotted liness) that includes a head tube 106, a main frame 107 extending rearwardly downward from the head tube 106. The main frame 107 may comprise one or more main tube(s), and a pair of rear tubes 108 extending inclinedly rearward from a rear portion of the main tube. In the present embodiment, the vehicle 100 includes a step-through portion 109 defined by the frame member 105 of the vehicle 100. However, the aspects of the present subject matter are not limited to the depicted layout of the vehicle 100.
[00039] Further, a handlebar assembly 110 is connected to a front wheel 115 through one or more front suspension(s) 120. A steering shaft (not shown) connects the handlebar assembly 110 to the front suspension(s) 120 and the steering shaft is rotatably journaled about the head tube 106. A power unit 125 including an internal combustion (IC) is mounted to the frame member 105. The power unit 125 may also include a traction motor either hub mounted or mounted adjacent to the IC engine. In the depicted embodiment, the power unit 125 is disposed below at least a portion of the rear frame(s) 108. However, in an alternative embodiment, the power unit may be fixedly disposed towards front and below the main tube 107. In one implementation, the power unit 125 includes the IC engine, which is forwardly inclined type i.e. a piston axis (not shown) of the IC engine is forwardly inclined. The power unit 125 is functionally connected to a rear wheel 130 through a transmission system (not shown). The vehicle may include one or more rear wheel(s). The transmission system includes any one of a continuously variable transmission (CVT), a fixed gear ratio transmission, or automatic-manual transmission (AMT) controlled by an AMT control unit. Further, the vehicle 100 includes an air induction system (not shown) that provides air to an air-fuel mixing unit (not shown). A fuel tank (not shown) stores and supplies fuel to the air-fuel mixing unit, wherein the air-fuel mixing unit can be a carburetor or a throttle body with fuel injector. Also, the vehicle 100 includes an exhaust system 200 that helps in dissipation of exhaust gasses from the IC engine. The exhaust system 200 includes a muffler 135 mounted to the vehicle 100. In the depicted embodiment, the muffler 135 is disposed towards one lateral side of the vehicle 100.
[00040] Further, the rear wheel 130 is connected to the frame member 105 through one or more rear suspension(s) (not shown). In the depicted embodiment, the power unit 125 is swingably mounted to the frame member 105 through a toggle link 150 or the like. A seat assembly 140 is supported by the frame member 105 and is disposed rearward to the step-through portion 109.
[00041] Further, the vehicle 100 includes a front fender 155 covering at least a portion of the front wheel 115. In the present embodiment, a floorboard 145 is disposed at a step-through portion 109 and is supported by the main frame 107 and a pair of floor frames (not shown). The user can operate the vehicle 100 by resting feet on the floorboard 145, in a sitting position. In an embodiment, a fuel tank (not shown) is disposed below the seat assembly 140 and behind the utility box. A rear fender 160 is covering at least a portion of the rear wheel 135. The vehicle 100 comprises of plurality of electrical/electronic components including a headlight 165, a tail light (not shown), a battery (not shown), a transistor-controlled ignition (TCI) unit (not shown), an alternator (not shown), a starter motor (not shown). Further, the vehicle 100 may include a synchronous braking system, an anti-lock braking system.
[00042] The vehicle 100 comprises plurality of panels that include a front panel 170 disposed in an anterior portion of the head tube 106, a leg-shield 171 disposed in a posterior portion of the head tube 106. A rear panel assembly 172 includes a right side panel and a left side panel disposed below the seat assembly 140 and extending rearward from a rear portion of the floorboard 145 towards a rear portion of the vehicle 100. The rear panel assembly 172 encloses a utility box disposed below the seat assembly 140. Also, the rear panel assembly 172 partially encloses the power unit 125. Also, the muffler 135 of the exhaust system is coupled to exhaust side of the IC engine and in an implementation the muffler 135 is disposed towards one lateral side of the vehicle 100.
[00043] Fig. 2 illustrates a front perspective view of the power unit, in accordance with an embodiment of the present subject matter. The power unit 125 of the present subject matter is the IC engine that is a forwardly inclined type. Further, the IC engine is swinging type that is swingably connected to the frame member 105 the vehicle 100 through a crankcase 181. The crankcase 181 is connected to the frame member 105 using a toggle link (not shown). One end of the toggle link 150 is connected to lower portion of the crankcase 181 and another end of toggle link 150 is pivoted to the frame member (not shown).
[00044] Further, the IC engine includes a cylinder portion defined by a cylinder block 180. The cylinder block 180 is mounted to a crankcase 181 of the IC engine. The cylinder block 180 supports at least one-cylinder head 183 that includes at least one valve assembly. The valve assembly enables entry of air-fuel mixture into the cylinder portion, where the combustion of air-fuel mixture takes place. Subsequently, the valve assembly enables dissipation of the burnt exhaust gases from the cylinder. The air induction system along with air fuel supply system is connected to one side wall of the at least one-cylinder head 183 that is provided with an input port (not shown). Further, the at least one-cylinder head 183 includes an exhaust port 184 provided on other side wall of the at least one-cylinder head 183. In the present implementation, the input port is provided on the upper side wall of the at lest one-cylinder head 183 and an air fuel regulating unit, which may include a carburetor or a throttle body with fuel injector connected to the input port. Further, in the present implementation, the exhaust port 184 is provided on bottom side wall of the at least one-cylinder head 183 and the exhaust system 200 is connected to the exhaust port 184. The IC engine includes a cooling cowl assembly 185 (partially shown) that annularly encloses at least a portion of the at least one-cylinder head 183, and the cylinder block 180. The exhaust system 200 includes a exhaust pipe 205 that functionally connects the at least one-cylinder head 183 to the muffler 135. In the present implementation, the muffler 135 is disposed laterally adjacent to the rear wheel 130.
[00045] Fig. 3 depicts a right-side perspective view of the exhaust system 200, in accordance with the embodiment of Fig. 2. The exhaust system 200 includes the exhaust pipe 205 formed by an upstream end portion U and a downstream end portion D. The exhaust system 200 is connected to the exhaust port (shown in Fig. 2) through an upstream end portion of the exhaust pipe 205 thus forming a split axis exhaust pipe. The downstream end portion D is further configured with a third downstream end portion 216 through which the exhaust system 200 is connected to the muffler 135, hereinafter the downstream end portion of the exhaust pipe 205 is referred to as a third-downstream end portion 216. The exhaust system 200 includes a treatment device 211 which is disposed within a cover member 201 of the exhaust pipe 205. In the depicted embodiment, the treatment device 211 is disposed within the cover member 201, for treating the exhaust gases passing therethrough. The muffler 135 includes one or more mounting brackets 190, 191 for mounting the muffler 135 to the frame member (not shown). Thus, the exhaust gases EG exiting the at least one-cylinder head 183 (shown in Fig. 2) are treated by the treatment device thereby enabling dissipation of exhaust gases EG from the muffler 135 with minimal pollutants.
[00046] In the depicted embodiment, the second downstream portion 207 is a single tubular metallic pipe that is having one end attached to the cover member and other end secured to an inlet portion of the muffler 135. The second downstream portion 207 is secured to the cover member 201 by welding or through any other known securing mechanism. The upstream end portion U is communicatively connected to the downstream end portion D such that its axis, a first axis V-V’ forms an angle with another axis, a second axis C-C’ of the downstream portion D. Thus, the exhaust system 200 is effectively configured with a split axis design consisting of upstream portion U and downstream portion D wherein the axis of said two portions intersect each other at a angle instead of a bend as in a conventional exhaust system. As per an embodiment, the said two portions are manufactured separately and attached to each other so as to effectively communicate & allow smooth flow of the exhaust gases through them. As per as aspect of the present invention, the split axis construction of the exhaust system 200, greatly enhances the degree of freedom to decide the orientation of the downstream portion D in a given vehicle. Such design freedom helps to achieve a compact layout with good ground clearance, while at the same time enable incorporating the treatment device 211, without any adverse compromise on the layout of the engine or the vehicle.
[00047] Fig. 4 illustrates a right-side view of an engine assembly and a few peripheral parts for brevity along with position of the treatment device with respect to the ground plane. According to an embodiment of the present invention, the at least one-cylinder head 183 is protected by an at least one-cylinder head cover 183a. In particular, the at least one-cylinder head cover 183a covers the at least one-cylinder head 183 at least partially from the top of the at least one-cylinder head 183. In a conventional exhaust system (represented by dotted lines), the exhaust pipe is typically routed at first position P1. A conventional exhaust system is typically configured with a bend portion B after the joining region of the exhaust pipe to the exhaust port. A conventional exhaust system is typically configured with the axis P-P’ of the pipe portion formed after the first bend B, in such a way, that at least a portion of the said axis overlaps with the exhaust port, in a side view of the vehicle. As can be seen from Fig 4, the axis P-P’ of the pipe portion disposed at position P1 overlaps with the exhaust port 184 of the engine 125. Increasing the ground clearance would necessitate lifting the engine or vehicle as a whole from the ground level GP which has multiple disadvantages & thus undesirable. Additionally, shifting the position P1 forward & upward becomes unviable owing to the difficulty in connecting the exhaust system to the exhaust port which has manufacturing limitations restricting the bend angle to be formed at the joining region of the exhaust pipe to the exhaust port. A sharp U or V bend will be required on the exhaust pipe at the joining region, if a position P2 is to be configured making it unviable to achieve. As per an aspect of the present invention, the above problem is addressed by configuring a split axis construction of the exhaust pipe downstream of the joining region of the exhaust port to exhaust pipe. In a preferred embodiment, the treatment device 211 is disposed at a close proximity to the at least one-cylinder head cover 183a as shown by position P2. The position of the treatment device 211 in the exhaust pipe 205 is bent towards the at least one-cylinder head 183 and away from the ground plane GP. Further, as shown in figure, moving the position of the exhaust pipe from the position P1 to the position P2, from the bottom of the crankcase 181 towards the at least one-cylinder head 183, the ground clearance increase. The ground clearance, which is the distance of the engine from the ground plane GP, increases, since the engine is inclined away from the ground plane GP. In the present embodiment, the cover member 201 (not shown) including the treatment device 211 is shown by the second position P2. At the second position P2, the treatment device 211 is disposed forwardly to the exhaust port (not shown), when viewed from the vehicle rear side. Wherein, a device axis XY passing through a central axis C-C` of the downstream portion D (shown in Fig. 3) of the the treatment device 211 and oriented substantially orthogonally to the cylinder axis L-L,` is disposed forwardly of the exhaust port (not shown) and closer to the at least one-cylinder head cover 183a, at the second position P2. Further, the device axis XY is disposed normal to a cylinder axis LL` and towards the at least one-cylinder head cover. The device axis XY that is normal to the cylinder axis LL` is also away from the ground plane GP at the second position P2 and the ground clearance achieved as a result of the treatment device 211 being disposed in the second position P2 is greater than the ground clearance that was achieved in a known position P1, as shown in the figure. The difference of distance d is achieved between the position P1 and the second position P2. Thus, the vehicle is provided with sufficient ground clearance to securely accommodate the exhaust system (not shown). Further, he vehicles when operated in different terrains and with different driving patterns is not subjected to jerks and the exhaust system (not shown) is protected from the resultant impact due to the present invention.
[00048] Further, the exhaust system, according to the invention has improved performance in order to treat exhaust gases without any failure of the system even under severe usage conditions. The improved ground clearance protects the exhaust system from any potential damage due to the inclination of the exhaust pipe towards the cylinder axis LL` and away from the ground plane GP, which is substantially at a higher inclination resulting in improving the safety of the exhaust system.
[00049] According to the present embodiment of the present invention, due to the positioning of the treatment device 211, being at an inclination to the at least one-cylinder head 183 and closer to the at least one-cylinder head 183, the exhaust gases are readily available for the treatment by the treatment device 211. The heat emitted from the exhaust gases are sufficient for activation of the treatment device 211. The activation time or the early light-off time taken for activation of the treatment device 211 is improved. As a result of which, most of the exhaust gases undergo effective and efficient treatment by the treatment device 211 before being emitted out into the environment. Therefore, the functioning of the treatment device 211 being at the second position P2 is improved along with improved ground clearance while overcoming the drawback of treatment device burnout by eliminating any heat conduction. The improvement in the ground clearance achieved is indicated by the difference in the distance from the group plane, d. The difference in the distance as per an embodiment is in range of 10 mm to 50 mm.
[00050] According to the present invention, as explained above, the technical advantage of positioning the treatment device 211 at a close proximity to the at least one-cylinder head cover 183a for early light-off without risk of burnout in parallel to being able to achieve an improved ground clearance from the ground plane GP of the treatment device 211 is being achieved.
[00051] Fig. 5 illustrates a sectional view of a portion of the exhaust system, in accordance with the embodiment as depicted in Fig. 3. The second downstream portion 207, which is a tubular metallic pipe having circular section, in the present embodiment, has a second downstream end portion 215 connected to the cover member 201.
[00052] The cover member 201 is capable of enclosing at least a portion of the treatment device 211 with minimal contact therewith. In the present embodiment, the treatment device 211 is completely enclosed, especially annularly surrounded, by the cover member 201.
[00053] In an embodiment, the treatment device 211 includes a housing 206 enclosing a substrate (not shown).
[00054] In one embodiment, the second-downstream end portion 215, the cover second end portion 201d of the cover member 201, and one end 219 of the treatment device 211 are fixedly attached to each other. In particular, all the above said portions are welded together at the second-downstream end portion 215. The cover member 201 extends from the second-downstream end portion 215, up to the length of the treatment device 211, and beyond the length of the treatment device 211.
[00055] According to an embodiment of the present invention, the second downstream end portion 215 of the second downstream portion 207 extends annularly inside the treatment device 211.
[00056] According to an embodiment of the present invention, the cover member 201 extends from the second-downstream end portion 215 along the longitudinal direction around the treatment device 211. The cover member 201 includes a transition fitting along with the treatment device 211. The transition fit 211 is established to almost half of the length of the treatment device 211 along the longitudinal direction. The transition fit of the cover member 201 enables to reduce the air gap between the cover member 201 and the treatment device 211. The reduction in air gap allows that portion of the cover member 201 having transition fit with the portion of the treatment device 211 to be closer to the treatment device 211. In this portion, the ground clearance of the portion of the treatment device being in transition fit is improved compared to other portions of the exhaust pipe. Due to the improved ground clearance, the portion of the treatment device 211 is protected from any external impacts and hence, the exhaust system has improved durability.
[00057] Further, the transition fit between the portion of the treatment device 211 and the portion of the cover member 201 provides for direct contact between the cover member 201 and the treatment device 211. This provides for improved conduction and thereby dissipation of heat.
[00058] Furthermore, the cover member 201 is extended beyond the treatment device 211 and towards the exhaust port (now shown) to a greater extent. The extended portion of the cover member 201, which is beyond the treatment device 211 is configured to get connected with the upstream portion U of the exhaust system 205. The cover member 201 is configured to function as a passage for smooth movement of the exhaust gases emerging out of the exhaust port (not shown), moving through the upstream portion U and then entering the extended portion of the cover member 201. The cover member 201 here provides smooth transition to the upstream portion U to be functionally connected with the second downstream portion 207. As a result of providing the extended cover member 201, the upstream portion U is prevented from taking sharp bends, which would affect the smooth flow of the exhaust gases therewithin.
[00059] According to an embodiment of the present invention, the treatment device 211 is cantilevered to the second-downstream end portion 215, wherein one end 219 of the treatment device is mounted to the second-downstream end portion 215. A second portion 218 of the treatment device 211 projects outwards or is suspended from the second-downstream end portion 215. Accordingly, the treatment device 211 is cantilever mounted.
[00060] Therefore, the exhaust gases, as indicated by the arrows, exiting the power unit (not shown) enters the exhaust pipe 205 through the upstream portion U, then through the passage provided by the cover member 201. The exhaust gases pass through the treatment device 211 where it undergoes treatment like oxidation of gases. Additionally, at least a portion of the exhaust gases pass into a gap 230, which is formed substantially around the treatment device 211 and a second upstream portion 201u of the cover member 201, due to which the gases entering the gap 230 enables quick heating and activation of the treatment device 211 through convection heating. Thus, the exhaust gases passing through the treatment device 211 as well as entering the gap 230 holistically resulting in quick heating of the preliminary treatment device 211 without the need for any additional components like heating elements, which otherwise makes the system bulkier, requiring high currents, and adding to the cost of the system. Thus, the preliminary treatment device 211 attains early light-off thereby effectively treating the exhaust gases.
[00061] Further, to enable exhaust flow to the portion of the exhaust pipe 205 prior to the treatment device 211, the cover member 201 is extended beyond the treatment device 211. The exhaust pipe 205 is laterally attached, preferably welded to the cover member 201 through a provision (not shown) in the cover member 201.
[00062] According to an additional embodiment of the present invention, the cover member 201 is configured to house a diffuser 202. In a preferred embodiment, the diffuser 202 is disposed upstream of the treatment device 211. Further, the diffuser 202 is disposed upstream to a sensor mounting portion 204. The sensor mounting portion 204 is formed on an outer surface and through the cover member 201. As shown in the Figure, the diffuser 202 is provided before the sensor mounting portion and the treatment device 211. The diffuser is fixedly attached to an inner circumferential surface 201i of the cover member 201.
[00063] The exhaust gases readily available in the cover member 201 firstly pass through the diffuser 202 and then through the treatment device 211. Since, the positioning of the cover member 201 is closer to the at least one-cylinder head cover (not shown), the sensor unit (not shown) gets to detect the exhaust gases quickly. Depending on the quick detection of the oxygen concentration in the exhaust gases by the sensor unit, further action to treat the exhaust gases can be carried out. Therefore, an efficient performance of the sensor unit is achieved. In an embodiment, the sensor mounting portion is adjoiningly disposed to a portion of the diffuser 202.
[00064] According to an embodiment of the present invention, the cover member 201 is covered at a cover second end portion 208 by a cap 203.
[00065] Fig. 6 illustrates a front view of a portion of the exhaust pipe of the exhaust system of the vehicle. The axis V-V’ of the upstream end portion U forms a predetermined angle with the axis C-C’ of the downstream end portion D. After prolonged vehicle usage, the temperature of the exhaust gas and various parts of the exhaust system will be high. This will lead to premature failure of the various parts of the exhaust system, like treatment device (not shown) and the sensor unit (not shown), the phenomenon occurs due to the deterioration and thermal fatigue.
[00066] Further, the first portion (not shown) of the treatment device being closer to the at least one-cylinder head cover (not shown) is more prone to higher heat emitted by the exhaust gases coming out of the exhaust port (not shown). However, according to the present invention, the diffuser 202 is configured to absorb the excess heat and radiate to the surrounding via the cover member 201. As a result, the life of the treatment device (not shown) and the sensor unit is increased.
[00067] Therefore, the technical advantage of having early light-off of the treatment device along with improved ground clearance of the exhaust pipe is achieved through the present invention.
[00068] According to an embodiment of the present invention, the diffuser 202 is attached to an inner circumferential surface 201i of the cover member 201. The diffuser 202 is in direct contact with the cover member 201. The excess heat received through the emitted exhaust gases is dissipated readily to the cover member 201 through direct contact. The cover member 201 is exposed to the environment on the outer surface. As a result, the excess heat is passed on to the surrounding environment. Further, according to an embodiment of the present invention, the diffuser 202 includes one or more perforations 202a. As per an embodiment, the diffuser 202 is a circular in shape. The circular diffuser 202 includes outer circumferential surface. The one or more perforations 202a are disposed within the outer circumferential surface 202o. In particular, the one or more perforations are disposed across the entire surface of the diffuser 202, when viewed from the front view, as shown in the figure. The one or more perforations 202a are configured to include smaller diameter, in other words, the one or more perforations 202a are narrow holes. The one or more perforations 202a do not allow the entire exhaust gas to pass to the treatment device. Instead, the passage of the exhaust gases is controlled, through which, the excess heat through the exhaust gases is prevented from passing further and is dissipated to the cover member 201 in direct contact therewith. Therefore, the treatment device is prevented from burning OFF or any damage that may be caused due to excess heat. The diffuser 202 also protects the sensor mounting portion 204 from getting damaged. Therefore, the functionality of the sensor mounting portion 204 and the treatment device is not affected and instead a reliable and stable functioning is achieved.
[00069] Fig. 7 shows the conversion efficiency of the treatment device versus time. The line B depicts the conversion efficiency of the treatment device in accordance with the exhaust system of the present subject matter. The conversion efficiency of the treatment device 211 reaches its maximum efficiency quickly after the start of the IC engine. The treatment device 211 reaches its maximum efficiency at a time t2, which is earlier than a time t1 required for reaching the maximum efficiency in case of an exemplary conventional system. Thus, the present subject matter offers quick heating within a time t2 offering an advantage of ?t. Further, the slope of the line B is steeper compared to the line A (conventional system) which implies that the conversion efficiency is dramatically increasing immediately after the IC engine starts and also attains early maximum conversion efficiency. The cover member 201 thereof, helps in minimizing loss of heat of the treatment device 211 as well as any damage from high temperatures and heat conduction related durability issues. Consequently, the treatment device 211 attains thermal equilibrium faster offering optimum performance thereof.
[00070] In one embodiment, the power unit 125 comprising the IC engine is forwardly inclined type having a piston axis, also analogous to a cylinder axis, which is forwardly inclined. Further, the cylinder block 180 (shown in Fig. 2) is supported by the crankcase 181 which is constituted by two or more parts. Further, the at least one-cylinder head 183 mounted to the cylinder block 180 (shown in Fig. 2) includes the exhaust port 184 to which the exhaust system 200 is connected. In the present embodiment, the flange member 223 (as shown in Fig. 4) gets secured to the exhaust port 184. The exhaust pipe 205 extends towards a muffler 135 disposed either to leftward, or to rightward with respect to a lateral center of the motor vehicle 100. In one embodiment, the muffler 135 may be disposed at least partially along the lateral center. The downstream end portion of the exhaust pipe 205 includes a cover member 201 and a second downstream portion 207, and the second downstream portion 207 substantially supports the treatment device 211, which is enclosed by the cover member 201. The treatment device 211 is cantilever mounted to the second downstream portion 207. The cover member 201 enables quick heating of the treatment device 211 due to the gap 230 and the second position P2.
[00071] Fig. 8 illustrates a comparative study of the graphical representation of the ground clearance attained due to various position of the treatment device in the exhaust pipe. The graphical representations are made with treatment device placed at different positions, represented along X-axis against ground clearance as a parameter along Y-Axis. The various representations 01,02, and 03 represent the ground clearance attained when the treatment device is placed at different positions with respect to the cylinder block of the engine. It can be observed that the ground clearance attained is the lowest when the treatment device is disposed rearwardly away from and below the cylinder block of the engine, example, position P1. This results in the exhaust pipe being located closer to the ground plane. In this configuration, the treating of the exhaust gases may not happen as efficiently as in the other positions achieved by the present invention of a split axis construction of the exhaust pipe. The details will be explained in the preceding paragraphs.
[00072] The graphical representation 02 depicts the position of the treatment device provided just below the at least one-cylinder head achieved by the split axis exhaust pipe, which is the position P12. The ground clearance achieved at this position is higher than the earlier position. The performance of the treatment device is also improved accordingly. However, still the distance travelled by the exhaust gases before reaching the treatment device is not considerably reduced.
[00073] The graphical representation 03 depicts the highest ground clearance attained as compared to the other positions. This is the second position P2 where the treatment device is disposed. The treatment device is disposed below the at least one-cylinder head cover and is inclined towards the at least one-cylinder head cover and away from the ground plane. Due to which, the ground clearance is significantly improved and the exhaust gases are readily available for treatment by the treatment device. The length travelled by the exhaust gases is substantially reduced and the sensor unit and the treatment device can immediately perform their respective functionalities accordingly.
[00074] Fig. 9 illustrates a comparative study of the graphical representation of the durability of the treatment device and the sensor unit during different conditions. The graphical representations on the left-hand side illustrates the durability of the treatment device and the sensor unit when disposed at other positions 01 and 02 and does not contain the diffuser, as shown in the previous graphical representation. The graphical representation on the right-hand side is when first downstream portion of the exhaust pipe is disposed at a close proximity to the at least one-cylinder head cover and includes the diffuser disposed inside the first portion of the exhaust pipe. The life or durability of the treatment device and the sensor unit working in conjunction with the diffuser is greater as compared to the life of the treatment device and the sensor unit working without the diffuser. The same is achieved due to the dissipation of the excess heat by the diffuser into the cover member. Once, the treatment device has reached the thermal equilibrium, the remaining excess heat that is not required is dissipated and radiated by the diffuser to the cover member. Therefore, the sensor unit and the treatment device is well protected from being burnt off or any other damages caused due to the excess heat.
[00075] Fig. 10 illustrates a comparative study of the graphical representation of the temperature at which the treatment device attains thermal equilibrium at various conditions. Different conditions like, in specific, the temperature of the treatment device without diffuser, the temperature with diffuser on the treatment device directly and the temperature with diffuser on the cover member is considered. The temperature of the treatment device, without the diffuser is the maximum, as illustrated by a first curve w. At this temperature and without the diffuser, the treatment device is likely to get burnt-off due to the exposure to high heat in the exhaust gases.
[00076] Further, the second curve u is achieved with slightly lesser temperature of the treatment device, which includes the diffuser on the treatment device. The temperature is still higher and it could burn off the treatment device albeit with an improved durability over longer period of time. However, the diffuser directly provided on the treatment device may not be sufficient to dissipate the heat due to which the temperature attained is still high. Furthermore, the temperature of the treatment device with the diffuser attached to the cover member is the least represented by curve v. At this temperature, the treatment device is protected from burning off once the treatment device has reached the thermal equilibrium achieving much lighter durability over the configuration of curve u. This is because, the outer surface of the cover member is exposed to the outer environment. The diffuser being attached to the cover member, readily dissipates the excess heat from the exhaust gases to the cover member. Thereby, the cover member quickly dissipates the excess heat to the outer environment. It is observed from the graphical representation, the increment in the temperature depending upon the placement of the diffuser is increasing, as indicated by an increasing temperature T.
[00077] Therefore, the temperature of the treatment device is maintained as desired to achieve the conversion of the exhaust gases and by preventing the burning off of the treatment device.
[00078] It is to be understood that the aspects of the embodiments are not necessarily limited to the features described herein. Many modifications and variations of the present subject matter are possible in the light of above disclosure. Therefore, within the scope of claims of the present subject matter, the present disclosure may be practiced other than as specifically described.
List of reference signs:

100 vehicle
105 frame member
106 head tube
107 main frame
108 rear frame
109 step-through space
110 handlebar assembly
115 front wheel
120 front suspension
125 power unit
130 rear wheel
135 muffler
140 seat assembly
145 floorboard
150 toggle link
155 front fender
160 rear fender
165 headlight
170 front panel
171 leg shield
172 rear panel assembly
180 cylinder block
181 crankcase
182 toggle link
183 at least one-cylinder head
183a at least one-cylinder head cover
184 exhaust port
190 mounting member
200 exhaust system
201 cover member
202 diffuser
202a one or more perforations
203 cap
204 sensor mounting portion
205 exhaust pipe
206 housing
207 second downstream portion
208 cover second end portion
211 treatment device
GP ground plane
XY device axis
LL` cylinder axis
P1 position
P2 second position
201u second upstream end portion
201i inner circumferential surface
t first curve
u second curve
v third curve