Claims:WE CLAIM:
1. An exhaust system (100) for a motor vehicle (10), comprising:
a first exhaust pipe (110) extending between a receiving end (112) and a releasing end (114), the receiving end (112) being coupled to an exhaust port (12a) of an engine (12);
a muffler (120) having an inlet (122) and an outlet (124);
a first catalytic converter (130) for treating exhaust gas released from the engine (12); and
a second catalytic converter (140) for further treating exhaust gas exiting the first catalytic converter (130);
wherein, the first catalytic converter (130) and the second catalytic converter (140) being disposed between the releasing end (114) of the first exhaust pipe (110) and the inlet (122) of the muffler (120).

2. The exhaust system (100) as claimed in claim 1, comprising a housing (160) extending between the releasing end (114) of the first exhaust pipe (110) and the inlet (122) of the muffler (120), the first catalytic converter (130) and the second catalytic converter (140) being disposed inside the housing (160).

3. The exhaust system (100) as claimed in claim 2, wherein the housing (160) extends between a first end (162) and a second end (164), the first end (162) of the housing (160) being attached at the releasing end (114) of the first exhaust pipe (110) and the second end (164) of the housing (160) being attached at the inlet (122) of the muffler (120).

4. The exhaust system (100) as claimed in claim 3, wherein an intake end (132) of the first catalytic converter (130) is attached to the first end (162) of the housing (160), and an egress end (144) of the second catalytic converter (140) is attached to the second end (164) of the housing (160).

5. The exhaust system (100) as claimed in claim 3, comprising an oxygen sensor (170) for determining whether air-fuel ratio in the engine (12) is rich or lean, the oxygen sensor (170) being disposed at the first end (162) of the housing (160), and being disposed upstream of the first catalytic converter (130) in the direction of flow of exhaust gases.

6. The exhaust system (100) as claimed in claim 2, wherein the housing (160) has a bent profile in a vehicle side view such that a neutral axis (X-X’) of the first catalytic converter (130) is not in-line with a neutral axis (Y-Y’) of the second catalytic converter (140).

7. The exhaust system (100) as claimed in claim 1, wherein the distance between an egress end (134) of the first catalytic converter (130) and an intake end (142) of the second catalytic converter (140) is between one to three times of diameter of the first catalytic converter (130).

Dated this 25th day of June 2021

TVS MOTOR COMPANY LIMITED
By their Agent & Attorney

(Nikhil Ranjan)
of Khaitan & Co
Reg No IN/PA-1471 , Description:FIELD OF THE INVENTION
[001] The present invention relates to an exhaust system for motor vehicles.

BACKGROUND OF THE INVENTION
[002] The emission norms that have to be met by motor vehicles are becoming increasingly stringent. To meet these stringent emission norms, a typical motor vehicle such as a saddle-type vehicle employs a secondary catalytic converter in addition to a primary catalytic converter. Conventionally, the primary catalytic converter is located near the exhaust port of the engine of the motor vehicle, and the secondary catalytic converter is located away from the primary catalytic converter and inside a muffler of the motor vehicle.
[003] Catalytic converters get activated and start reducing the emissions only after they reach the light-off temperature, which happens normally around 250-300°C. The time period at which the catalyst becomes active is referred to as light-off time. The temperature of the exhaust gases decreases as the exhaust gas move from the exhaust port of the engine further into the exhaust pipe. Hence, although the light-off time of the primary catalytic converter remains low as the primary catalytic converter can take benefits from the high temperature of the exhaust gases exiting the exhaust port, the light-off time for the secondary catalytic converter is relatively large as the secondary catalytic converter is located far from the exhaust port, and the temperature of the exhaust gases reduces substantially by the time they reach the secondary catalytic converter. Farther is the secondary catalytic converter from the exhaust port, greater will the light-off time for the secondary catalytic converter. A greater light-off time also leads to greater emissions from the vehicle, as the secondary catalytic converter remains inactive for a portion of the time for which the motor vehicle runs.
[004] This conventional configuration of the primary and the secondary catalytic converters as explained above also requires catalytic converters of a larger size to be used, which not only makes them largely expensive due to the limited presence of precious metals in the catalytic converters, but also makes the exhaust bulky, leading to further design complications.
[005] Thus, there is a need in the art for an exhaust system for a motor vehicle which addresses at least the aforementioned problems.

SUMMARY OF THE INVENTION
[006] The present invention is directed towards an exhaust system for a motor vehicle. The exhaust system has a first exhaust pipe extending between a receiving end and a releasing end. The receiving end is coupled to an exhaust port of an engine. The exhaust system further has a muffler having an inlet and an outlet, a first catalytic converter for treating exhaust gas released from the engine and a second catalytic converter for further treating exhaust gas exiting the first catalytic converter. Herein, the first catalytic converter and the second catalytic converter are disposed between the releasing end of the first exhaust pipe and the inlet of the muffler.
[007] In an embodiment of the invention, the exhaust system further has a housing extending between the releasing end of the first exhaust pipe and the inlet of the muffler. The first catalytic converter and the second catalytic converter are disposed inside the housing. In an embodiment, the housing extends between a first end and a second end. The first end of the housing is attached at the releasing end of the first exhaust pipe and the second end of the housing is attached at the inlet of the muffler.
[008] In another embodiment of the invention, an intake end of the first catalytic converter is attached to the first end of the housing, and an egress end of the second catalytic converter is attached to the second end of the housing.
[009] In a further embodiment of the invention, the exhaust system has an oxygen sensor for determining whether air-fuel ratio in the engine is rich or lean. The oxygen sensor is disposed at the first end of the housing, and is disposed upstream of the first catalytic converter in the direction of flow of exhaust gases.
[010] In a further embodiment of the invention, the housing has a bent profile in a vehicle side view such that a neutral axis of the first catalytic converter is not in-line with a neutral axis of the second catalytic converter.
[011] In a further embodiment of the invention, the distance between an egress end of the first catalytic converter and an intake end of the second catalytic converter is between one to three times of diameter of the first catalytic converter.

BRIEF DESCRIPTION OF THE DRAWINGS
[012] Reference will be made to embodiments of the invention, examples of which may be illustrated in accompanying figures. These figures are intended to be illustrative, not limiting. Although the invention is generally described in context of these embodiments, it should be understood that it is not intended to limit the scope of the invention to these particular embodiments.
Figure 1 illustrates a right-side view of an exemplary motor vehicle, in accordance with an embodiment of the invention.
Figure 2 illustrates a side view of an exhaust system for a motor vehicle, in accordance with an embodiment of the invention.
Figure 3 illustrates a side view of the exhaust system for the motor vehicle, in accordance with an embodiment of the invention.
Figure 4 illustrates a sectional view of an exhaust port of an engine connected to a first exhaust pipe, in accordance with an embodiment of the invention.
Figure 5 illustrates a side sectional view of the exhaust system, in accordance with an embodiment of the invention.
Figure 6 illustrates the relationship between the gas temperature and the distance from the exhaust port, in accordance with an embodiment of the invention.
Figure 7 illustrates the level of emissions of different exhaust gases in the present configuration as compared to conventional systems, in accordance with an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION
[013] The present invention relates to an exhaust system for a motor vehicle. More particularly, the present invention relates to an exhaust system with catalytic converters for treatment of exhaust gases.
[014] Figure 1 illustrates a right-side view of an exemplary motor vehicle 10, in accordance with an embodiment of the present subject matter. The vehicle 10 comprises a frame (not shown). The frame comprises a head tube, and a portion of a main tube extending rearwardly downward from the head tube to a floorboard 18. One or more front suspensions connect a front wheel 14 to a handlebar 20, which forms a steering assembly of the vehicle 10. The steering assembly is rotatably disposed about the head tube. The main tube further includes a portion extending horizontally and rearwardly from the frame. Further, the frame includes one or more rear tubes extending inclinedly rearward from a rear portion of the main tube towards a rear portion of the vehicle 10.
[015] The vehicle 10 includes a power unit comprising at least an internal combustion (IC) engine 12 (shown in Figure 2). The power unit is coupled to a rear wheel 16. In one embodiment, the engine 12 is swingably connected to the frame. In one embodiment, the engine 12 is mounted to the swing arm (not shown) and the swing arm is swingably connected to the frame. Further, the vehicle 10 includes a transmission means (not shown) coupling the rear wheel 16 to the power unit. The transmission means includes a continuously variable transmission, an automatic transmission, or a fixed ratio transmission. A seat assembly 22 is disposed above the engine 12 and is supported by the rear tubes of the frame. The seat assembly 22 is hingedly openable. The frame defines a step-through portion ahead of the seat assembly 22. The floorboard 18 is disposed at the step-through portion, wherein a rider can operate the vehicle 10 in a seated position by resting feet on the floorboard 18. Further, the floorboard 18 is capable of carrying loads.
[016] Further, the frame is covered by plurality of body panels including a front panel 30 having a front face 30A and a rear face 30B, an under-seat cover 32, and a left and a right-side panel 33 disposed on the frame and covering the frame and parts mounted thereof.
[017] In addition, a front fender 24 is covering at least a portion of the front wheel 14. A utility box is disposed below the seat assembly 22 and is supported by the frame. A rear fender 26 is covering at least a portion of the rear wheel 16 and is positioned upwardly of the rear wheel 16. One or more suspension(s) (not shown) are provided in the rear portion of the vehicle 10 for connecting the swing arm and the rear wheel 16 to the frame for damping the forces from the rear wheel 16 and the engine 12 from reaching the frame.
[018] Furthermore, the vehicle 10 comprises of plurality of electrical and electronic components including a headlight 36, a taillight 38, an alternator (not shown), and a starter motor (not shown).
[019] Figure 2 illustrates an exhaust system 100 for the motor vehicle 10. As illustrated in Figure 2, the exhaust system 100 has a first exhaust pipe 110 extending between a receiving end 112 (shown in Figure 3) and a releasing end 114 (shown in Figure 3). The receiving end 112 of the first exhaust pipe is coupled to an exhaust port 12a (shown in Figure 4) of the engine 12 and receives the exhaust gases being exited from a combustion chamber of the engine 12 via the exhaust port 12a.
[020] The exhaust system 100 further has a muffler 120 having an inlet 122 (shown in Figure 3) and an outlet 124 (shown in Figure 3). The outlet 124 releases the exhaust gases from the exhaust system 100 into the atmosphere. The exhaust system 100 further has a first catalytic converter 130 (shown in Figure 5) for treating the exhaust gases being released from the engine 12 and travelling through the first exhaust pipe 110, and a second catalytic converter 140 (shown in Figure 5) for further treating the exhaust gases exiting the first catalytic converter 130.
[021] As illustrated in Figure 5, the first catalytic converter 130 and the second catalytic converter 140 are disposed between the releasing end 114 of the first exhaust pipe 110 and the inlet 122 of the muffler 120. In operation, the exhaust gases exiting the engine 12 at the exhaust port 12a are received by the first exhaust pipe 110 and directed towards the first catalytic converter 130. The first catalytic converter 130 treats the exhaust gases and the second catalytic converter 140 further treats the exhaust gases or any untreated exhaust gases exiting the first catalytic converter 130. The treated exhaust gases from the second catalytic converter 140 are received by the inlet 122 of the muffler 120 and are then released into the atmosphere by the outlet 124 of the muffler 120. As has been shown in Figure 6, the exhaust gas temperatures vary linearly with respect to the distance from the exhaust port 12a. The aforesaid disposition of the second catalytic converter 140 being close to the exhaust port 12a of the engine 12 results in the temperature of the exhaust gases reaching the second catalytic converter 140 being high, which reduces in the light-off time of the second catalytic converter 140.
[022] Reference is made to Figure 2, wherein the exhaust system 100 further comprises a housing 160 that extends between the releasing end 114 of the first exhaust pipe 110 and the inlet 122 of the muffler 120. In this embodiment, the first catalytic converter 130 and the second catalytic converter 140 are disposed inside the housing 160. As further seen in Figure 3, the housing 160 extends between a first end 162 and a second end 164. The first end 162 of the housing 160 is attached at the releasing end 114 of the first exhaust pipe 110 and the second end 164 of the housing 160 is attached at the inlet 122 of the muffler 120.
[023] Reference is made to Figure 5, wherein in an embodiment, for the first catalytic converter 130 and the second catalytic converter 140 to be disposed inside the housing 160, an intake end 132 of the first catalytic converter 130 is attached to the first end 162 of the housing 160, and an egress end 144 of the second catalytic converter 140 is attached to the second end 164 of the housing 160. This means that the first catalytic converter 130 and the second catalytic converter 140 are attached to the housing 160 in a cantilever manner such that only one end of the first catalytic converter 130 and the second catalytic converter 140 are fixedly attached to the housing 160.
[024] As further illustrated in the embodiment depicted in Figure 5, the exhaust system 100 further comprises an oxygen sensor 170 for determining whether air-fuel ratio in the engine 12 is rich or lean. The oxygen sensor 170 is disposed at the first end 162 of the housing 160. Further, the oxygen sensor 170 is disposed upstream of the first catalytic converter 130 in the direction of flow of exhaust gases as shown by arrows in Figure 5, such that the oxygen sensor 170 can sense the air-fuel ratio from the untreated exhaust gases. In an embodiment, the housing 160 has a provision at the first end 162 for receiving the oxygen sensor 170.
[025] As further illustrated in Figure 5, the housing 160 has a bent profile in a vehicle side view such that a neutral axis (X-X’) of the first catalytic converter 130 is not in-line with a neutral axis (Y-Y’) of the second catalytic converter 140. This reduces the horizontal distance between the first end 162 of the housing 160 and the second end 164 of the housing 160 in a vehicle front-rear direction.
[026] It is understood that lower is the distance between the first catalytic converter 130 and the second catalytic converter 140, higher will be the temperature of the exhaust gases entering the second catalytic converter 140. To achieve this, in an embodiment, the distance between an egress end 134 of the first catalytic converter 130 and an intake end 142 of the second catalytic converter 140 is kept between one to three times of diameter of the first catalytic converter 130.
[027] Figure 7 illustrates the emission levels of various gases such as Carbon Monoxide (CO), Total Hydrocarbon Emissions (THC), Non-Methane Hydrocarbon emissions (NMHC) and Nitric Oxide (NOx) of the vehicle with the exhaust system in accordance with the present invention being substantially lower as compared to conventional exhaust systems.
[028] Advantageously, the present invention provides an exhaust system with a tandem arrangement of the first catalytic converter and the second catalytic converter. The second catalytic converter is close to the exhaust port of the engine, which ensures that the temperature of the exhaust gases entering the second catalytic converter is high, and light-off time for the second catalytic converter is low thereby reducing vehicle emissions.
[029] Further, the housing of the exhaust system having a bent profile ensures that the total length of the exhaust system in the vehicle front-rear direction is not substantially increased to accommodate the first catalytic converter and the second catalytic converter, hence requiring lower packaging space and reducing interference with other vehicle components.
[030] Furthermore, the exhaust system of the present invention with the reduced light-off time ensures that catalytic converters of a smaller size can be used. Since catalytic converters of a smaller size use a smaller amount of precious metals, they will be cheaper to manufacture and maintain.
[031] While the present invention has been described with respect to certain embodiments, it will be apparent to those skilled in the art that various changes and modification may be made without departing from the scope of the invention as defined in the following claims.